ORCID Profile
0000-0001-8288-6068
Current Organisation
University of South Australia
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Publisher: Elsevier BV
Date: 11-1991
DOI: 10.1016/0034-5687(91)90085-W
Abstract: The effect of temperature upon ventilation and metabolism was measured on a breath by breath basis in the lizard Ctenophorus nuchalis. This species displayed a typical reptilian breathing pattern groups of breaths separated by periods of breath holding. The lengths of the non-ventilatory periods (NVP) decreased as temperature increased. As a result, overall breathing frequency (f) displayed a thermal dependence. Outside the preferred temperature range (27-37 degrees C) f was also affected by changes in the frequency of breathing that occurred during periods of ventilation (f'). On the other hand, tidal volume (VT) was maintained constant at all temperatures except 42 degrees C ('panting' threshold). Thus, due to the thermal dependency of f, ventilation (VE) displayed a significant increase between 18 and 37 degrees C. Metabolism (VO2 and VCO2) also increased within this temperature range. However, as a result of a lower Q10 for ventilation, ventilatory requirement (VE/VO2 and VE/VCO2) decreased. In addition, lung volume (LV) increased with temperature. Examination of the alveolar ventilation-PCO2 relationship revealed that as a result of the increase in LV the level of intrapulmonary CO2 at the end of an NVP was maintained irrespective of temperature. This implies a temperature-independent chemical threshold for the onset of breathing. It is postulated that with temperature the observed increase in LV could offset the increase in metabolism by slowing the rise of intrapulmonary CO2 levels. This would delay the onset of breathing which in turn would lower VE/VCO2 (and VE/VO2) by preventing an effectual hyperventilation. This supports the notion, at least in C. nuchalis, that relative alkalinity is maintained.
Publisher: Informa UK Limited
Date: 31-10-2008
Publisher: Informa UK Limited
Date: 1990
DOI: 10.3109/01902149009068819
Abstract: In any 24-h period the body temperature (Tb) of the central Australian agamid lizard, Ctenophorus nuchalis, may vary from 13 to 45 degrees C the mean preferred Tb is 37 degrees C. We have analyzed surfactant-type lipids in lizards that underwent rapid changes in Tb from 37 degrees C to 14, 19, 27, or 44 degrees C. Lipids were extracted from lung lavage and lamellar body fractions, and phospholipids and cholesterol components were measured. There was no change in either the total amount or relative proportions of the different classes of phospholipids, but cooling increased the cholesterol content of lavage. An increase in the cholesterol: phospholipid ratio was evident within 2 h of cooling to 19 degrees C and was maintained for at least 48 h. The ratio increased from 8% at 37 degrees C, to 15% after 4 h at 19 degrees C, and 18% after 4 h at 14 degrees C. Possibly the increase in cholesterol promotes fluidity and absorption of surfactant within the alveoli of lizards with low Tb. Cold lizards collapse their lungs during prolonged periods of apnea and the surfactant may prevent the epithelial walls from adhering.
Publisher: Springer Science and Business Media LLC
Date: 26-03-2001
Abstract: Pulmonary surfactant is synthesised in alveolar type II cells and secreted into the lining of the lung in response to ventilation, temperature changes and autonomic neurotransmitters. Type II cells were isolated from the heterothermic marsupial, Sminthopsis crassicaudata. The neurotransmitters, isoproterenol and carbamylcholine chloride significantly increased phosphatidylcholine secretion at 37 degrees C (basal: 14.2%, isoproterenol: 20.1%, carbamylcholine: 17.0%). Temperature reduced the rate of secretion from dunnart type II cells (e.g. basal: 14.2% at 37 degrees C 7.2% at 18 degrees C). However, the change in secretory rate between 37 degrees C and 18 degrees C was less than expected if due to temperature alone (Q10= 1.4). The surfactant secretory pathway is therefore modulated by factors other than and in addition to, temperature. The response of dunnart type II cells to the agonists remained the same at both temperatures. Basal secretion was higher in dunnart type II cells (14.2% in 4 h) than has been reported in rat type II cells (1.9% in 3 h) and consequently, the agonist-stimulated increases in secretion from dunnart type II cells (41% above basal in 4 h) were much lower than observed for rat type II cells (200% above basal in 1.5 h).
Publisher: Informa UK Limited
Date: 28-09-2017
Publisher: Elsevier BV
Date: 1992
Publisher: Elsevier BV
Date: 11-2002
DOI: 10.1016/S1095-6433(02)00187-3
Abstract: Pulmonary surfactant is a mixture of lipids and proteins that is secreted by alveolar type II cells in the lungs of all air-breathing vertebrates. Pulmonary surfactant functions to reduce the surface tension in the lungs and, therefore, reduce the work of breathing. In mammals, the embryonic maturation of the surfactant system is controlled by a host of factors, including glucocorticoids, thyroid hormones and autonomic neurotransmitters. We have used a co-culture system of embryonic type II cells and lung fibroblasts to investigate the ability of dexamethasone, tri-iodothyronine (T(3)), adrenaline and carbamylcholine (carbachol) to stimulate the cellular secretion of phosphatidylcholine in the bearded dragon (Pogona vitticeps) at day 55 (approx. 92%) of incubation and following hatching. Adrenaline stimulated surfactant secretion both before and after hatching, whereas carbachol stimulated secretion only at day 55. Glucocorticoids and triiodothyronine together stimulated secretion at day 55 but did not after hatching. Therefore, adrenaline, carbachol, dexamethasone and T(3), are all involved in the development of the surfactant system in the bearded dragon. However, the efficacy of the hormones is attenuated during the developmental process. These differences probably relate to the changes in the cellular environment during development and the specific biology of the bearded dragon.
Publisher: Elsevier BV
Date: 1987
Publisher: Informa UK Limited
Date: 02-01-2015
Publisher: Public Library of Science (PLoS)
Date: 03-03-2016
Publisher: Informa UK Limited
Date: 02-01-2015
Publisher: Canadian Center of Science and Education
Date: 19-12-2014
DOI: 10.5539/JSD.V7N1P1
Publisher: Frontiers Media SA
Date: 12-2017
Publisher: University of Chicago Press
Date: 2007
DOI: 10.1086/508823
Abstract: We determined the effects of high gestational loads on ventilation and the rate of oxygen consumption (VO2) in the scincid lizard Tiliqua rugosa. Tiliqua rugosa is a large viviparous lizard that gives birth to one to four young after 6-7 mo gestation. Pregnant females gave birth to large young, weighing 89.5+/-5.9 g, which represents 21.6%+/-2.6% of maternal body mass. As the embryos developed, they occupied an increasingly large proportion of the body cavity, decreasing food consumption and compressing the gastrointestinal tract. Computerized axial tomography scans demonstrated that the lungs were compressed and/or regionally collapsed by the developing embryos, potentially compromising ventilation. Both minute ventilation (VE) and tidal volume decreased as gestation progressed, but no compensatory changes in breathing frequency or in the duration of the nonventilatory period were observed. The total rate of VO2, consisting of contributions from both maternal and fetal tissues, did not change during gestation, suggesting that maternal VO2 decreases as fetal VO2 increases. Pregnant females demonstrated a decreased ventilatory response to increased respiratory drive (triggered via inhalation of hypoxic hypercapnic gas), which may be associated with the increased energetic cost of ventilating a compressed lung or the desensitization of chemoreceptors during gestation. The decreased ability of the respiratory system to respond to increased respiratory drive may have important consequences for locomotor performance and predator avoidance in pregnant lizards.
Publisher: Elsevier BV
Date: 2002
DOI: 10.1016/S1388-1981(01)00185-8
Abstract: The primary function of pulmonary surfactant is to reduce the surface tension (ST) created at the air-liquid interface in the lung. Surfactant is a complex mixture of lipids and proteins and its function is influenced by physiological parameters such as metabolic rate, body temperature and breathing. In the microchiropteran bat Chalinolobus gouldii these parameters fluctuate throughout a 24 h period. Here we examine the surface activity of surfactant from warm-active and torpid bats at both 24 degrees C and 37 degrees C to establish whether alterations in surfactant composition correlate with changes in surface activity. Bats were housed in a specially constructed bat room at Adelaide University, at 24 degrees C and on a 8:16 h light:dark cycle. Surfactant was collected from bats s led during torpor (25<T(b) 35 degrees C). Alterations in the lipid composition of surfactant occur with changes in the activity cycle. Most notable is an increase in surfactant cholesterol (Chol) with decreases in body temperature [Codd et al., Physiol. Biochem. Zool. 73 (2000) 605-612]. Surfactant from active bats was more surface active at higher temperatures, indicated by lower ST(min) and less film area compression required to reach ST(min) at 37 degrees C than at 24 degrees C. Conversely, surfactant from torpid bats was more active at lower temperatures, indicated by lower ST(min) and less area compression required to reach ST(min) at 24 degrees C than at 37 degrees C. Alterations in the Chol content of bat surfactant appear to be crucial to allow it to achieve low STs during torpor.
Publisher: University of Chicago Press
Date: 05-2003
DOI: 10.1086/375434
Publisher: American Thoracic Society
Date: 08-1995
DOI: 10.1165/AJRCMB.13.2.7626285
Abstract: In this study, we characterized surfactant lipids from the lungs of the lungfish, Protopterus annectens, Lepidosiren paradoxa, and Neoceratodus fosteri (Sarcopterygiia: Dipnoi). We quantified the types of phospholipids present, the amounts of total phospholipid, disaturated phospholipid (DSP)--purported to be the primary surface tension-controlling agent--and cholesterol (CHOL), an important fluidizer. The surfactant phospholipid profiles of all three lungfish were very similar to each other and those of many other animals reported previously. Phosphatidylcholine was the dominant phospholipid (60% to 80%) phosphatidylglycerol was virtually absent and there was a significant proportion of the combination of phosphatidylserine and phosphatidylinositol (10%). The Australian lungfish N. forsteri possessed a surfactant 5 times richer in CHOL and 2 and 3 times poorer in DSP than the surfactant of the African lungfish P. annectens and the South American lungfish L. paradoxa, respectively. Hence, the CHOL/DSP mass ratio of N. forsteri was 12 and 20 times greater than that of P. annectens and L. paradoxa, respectively. Therefore, the surfactant composition of the two derived species of lungfish (P. annectens and L. paradoxa) very closely resembles that of hibians, whereas surfactant from the primitive lungfish (N. forsteri) is almost identical to that of the primitive air-breathing actinopterygiian fish. Thus, it is likely that pulmonary surfactant had only a single origin, coinciding with that of the vertebrates. As with most nonmammalian vertebrates, it is possible that lungfish surfactant functions as an antiglue at low lung volumes or when the lungs are completely collapsed. Furthermore, it appears that within a species, an increase in lung development correlates with an increase in the relative amount of surfactant cholesterol and a decrease in the phospholipid saturation level.
Publisher: Wiley
Date: 15-12-2016
DOI: 10.1002/CPHY.C150003
Abstract: Surfactant lipids and proteins form a surface active film at the air‐liquid interface of internal gas exchange organs, including swim bladders and lungs. The system is uniquely positioned to meet both the physical challenges associated with a dynamically changing internal air‐liquid interface, and the environmental challenges associated with the foreign pathogens and particles to which the internal surface is exposed. Lungs range from simple, transparent, bag‐like units to complex, multilobed, compartmentalized structures. Despite this anatomical variability, the surfactant system is remarkably conserved. Here, we discuss the evolutionary origin of the surfactant system, which likely predates lungs. We describe the evolution of surfactant structure and function in invertebrates and vertebrates. We focus on changes in lipid and protein composition and surfactant function from its antiadhesive and innate immune to its alveolar stability and structural integrity functions. We discuss the biochemical, hormonal, autonomic, and mechanical factors that regulate normal surfactant secretion in mature animals. We present an analysis of the ontogeny of surfactant development among the vertebrates and the contribution of different regulatory mechanisms that control this development. We also discuss environmental (oxygen), hormonal and biochemical (glucocorticoids and glucose) and pollutant (maternal smoking, alcohol, and common “recreational” drugs) effects that impact surfactant development. On the adult surfactant system, we focus on environmental variables including temperature, pressure, and hypoxia that have shaped its evolution and we discuss the resultant biochemical, biophysical, and cellular adaptations. Finally, we discuss the effect of major modern gaseous and particulate pollutants on the lung and surfactant system. © 2016 American Physiological Society. Compr Physiol 6:363‐422, 2016.
Publisher: JSTOR
Date: 03-1985
DOI: 10.2307/1564431
Publisher: American Physiological Society
Date: 11-2005
DOI: 10.1152/AJPREGU.00496.2004
Abstract: Pulmonary surfactant, a complex mixture of lipids and proteins, lowers the surface tension in terminal air spaces and is crucial for lung function. Within an animal species, surfactant composition can be influenced by development, disease, respiratory rate, and/or body temperature. Here, we analyzed the composition of surfactant in three heterothermic mammals (dunnart, bat, squirrel), displaying different torpor patterns, to determine: 1) whether increases in surfactant cholesterol (Chol) and phospholipid (PL) saturation occur during long-term torpor in squirrels, as in bats and dunnarts 2) whether surfactant proteins change during torpor and 3) whether PL molecular species (molsp) composition is altered. In addition, we analyzed the molsp composition of a further nine mammals (including placental/marsupial and hetero-/homeothermic contrasts) to determine whether phylogeny or thermal behavior determines molsp composition in mammals. We discovered that like bats and dunnarts, surfactant Chol increases during torpor in squirrels. However, changes in PL saturation during torpor may not be universal. Torpor was accompanied by a decrease in surfactant protein A in dunnarts and squirrels, but not in bats, whereas surfactant protein B did not change in any species. Phosphatidylcholine (PC)16:0/16:0 is highly variable between mammals and is not the major PL in the wombat, dunnart, shrew, or Tasmanian devil. An inverse relationship exists between PC16:0/16:0 and two of the major fluidizing components, PC16:0/16:1 and PC16:0/14:0. The PL molsp profile of an animal species is not determined by phylogeny or thermal behavior. We conclude that there is no single PL molsp composition that functions optimally in all mammals rather, surfactant from each animal is unique and tailored to the biology of that animal.
Publisher: Elsevier BV
Date: 06-2006
DOI: 10.1016/J.RESP.2005.08.001
Abstract: Maintaining a functional pulmonary surfactant system at depth is critical for ing mammals to ensure that inspiration is possible upon re-emergence. The lipid and protein composition of lavage extracts from three pinniped species (California sea lion, Northern elephant seal and Ringed seal) were compared to several terrestrial species. Lavage s les were purified using a NaBr discontinuous gradient. Concentrations of phospholipid classes and molecular species were measured using electrospray ionisation mass spectrometry, cholesterol was measured using high-performance liquid chromatography, surfactant protein A (SP-A) and SP-B were measured using enzyme-linked immunosorbent assays. There were small differences in phospholipid classes, with a lower level of anionic surfactant phospholipids, PG and PI, between ing and terrestrial mammals. There were no differences in PL saturation or SP-A levels between species. PC16:0/14:0, PC16:0/16:1, PC16:0/16:0, long chain PI species and the total concentrations of alkyl-acyl species of PC and PG as a ratio of diacyl species were increased in ing mammals, whereas concentrations of PC16:0/18:1, PG16:0/16:0 and PG16:0/18:1 were decreased. Cholesterol levels were very variable between species and SP-B was very low in ing mammals. These differences may explain the very poor surface activity of pinniped surfactant that we have previously described [Miller, N.J., Daniels, C.B., Schürch, S., Schoel, W.M., Orgeig, S., 2005. The surface activity of pulmonary surfactant from ing mammals. Respir. Physiol. Neurobiol. 150 (2006) 220-232], supporting the hypothesis that pinniped surfactant has primarily an anti-adhesive function to meet the challenges of regularly collapsing lungs.
Publisher: Wiley
Date: 28-04-2014
DOI: 10.1002/ECE3.1094
Publisher: Springer Science and Business Media LLC
Date: 02-1998
DOI: 10.1007/PL00006287
Abstract: Surface tension is reduced at the air-liquid interface in the lung by a mixture of lipids and proteins termed pulmonary surfactant. This study is the first to provide evidence for the presence of a surfactant-specific protein (Surfactant Protein A-SP-A) in the gas-holding structures of representatives of all the major vertebrate groups. Western blot analysis demonstrated cross-reactivity between an antihuman SP-A antibody and material lavaged from lungs or swimbladders of members from all vertebrate groups. Immunocytochemistry localized this SP-A-like protein to the air spaces of lungs from the actinopterygiian fish and lungfish. Northern blot analysis indicated that regions of the mouse SP-A cDNA sequence are complementary to lung mRNA from all species examined. The presence of an SP-A-like protein and SP-A mRNA in members of all the major vertebrate groups implies that the surfactant system had a single evolutionary origin in the vertebrates. Moreover, the evolution of the surfactant system must have been a prerequisite for the evolution of airbreathing. The presence of SP-A in the goldfish swimbladder demonstrates a role for the surfactant system in an organ that is no longer used for airbreathing.
Publisher: Elsevier BV
Date: 02-1996
DOI: 10.1016/0034-5687(95)00078-X
Abstract: We have previously reported that levels of pulmonary surfactant in the lungs of the lizard Pogona vitticeps increase with increasing body temperature. Static lung compliance decreases with increasing body temperature, and is only marginally affected by the presence of surfactant. Here, we examined the effects of surfactant, temperature, ventilatory pattern and autonomic neurotransmitters on opening and filling pressures. Isolated lungs were ventilated at either 18 or 37 degrees C at low, intermediate and high ventilatory regimes. The effects of acetylcholine and adrenaline were examined using an isolated perfused lung preparation at 27 degrees C. Changing ventilatory pattern or experimental temperature had no effect on either filling or opening pressures. Removal of surfactant increased both opening and filling pressures. Adrenaline administration reduced opening and filling pressures. Normal variations in surfactant levels, which occur with changes in body temperature, do not affect either opening or filling pressures. A critical amount of surfactant may be necessary to prevent adhesion of epithelial surfaces in the lungs of Pogona vitticeps. The anti-glue function of pulmonary surfactant may be more important at 18 than at 37 degrees C.
Publisher: University of Chicago Press
Date: 11-1999
DOI: 10.1086/316712
Abstract: Surfactant occurs in cyclically inflating and deflating, gas-holding structures of vertebrates to reduce the surface tension of the inner fluid lining, thereby preventing collapse and decreasing the work of inflation. Here we determined the presence of surfactant in material lavaged from the airspace in the gas mantle of the pulmonate snail Helix aspersa. Surfactant is characterized by the presence of disaturated phospholipid (DSP), especially disaturated phosphatidylcholine (PC), lavaged from the airspace, by the presence of lamellated osmiophilic bodies (LBs) in the airspaces and epithelial tissue, and by the ability of the lavage to reduce surface tension of fluid in a surface balance. Lavage had a DSP hospholipid (PL) ratio of 0.085, compared to 0.011 in membranes, with the major PL being PC (45.3%). Cholesterol, the primary fluidizer for pulmonary surfactant, was similar in lavage and in lipids extracted from cell homogenates (cholesterol/PL: 0.04 and 0. 03, respectively). LBs were found in the tissues and airspaces. The surface activity of the lavage material is defined as the ability to reduce surface tension under compression to values much lower than that of water. In addition, surface-active lipids will vary surface tension, increasing it upon inspiration as the surface area expands. By these criteria, the surface activity of lavaged material was poor and most similar to that shown by pulmonary lavage of fish and toads. Snail surfactant displays structures, a biochemical PL profile, and biophysical properties similar to surfactant obtained from primitive fish, teleost swim bladders, the lung of the Dipnoan Neoceratodus forsteri, and the hibian Bufo marinus. However, the cholesterol/PL and cholesterol/DSP ratios are more similar to the hibian B. marinus than to the fish, and this similarity may indicate a crucial physicochemical relationship for these lipids.
Publisher: Elsevier
Date: 2014
Publisher: Springer Science and Business Media LLC
Date: 12-06-2007
DOI: 10.1007/S00239-006-0083-1
Abstract: Maximum-likelihood models of codon and amino acid substitution were used to analyze the lung-specific surfactant protein C (SP-C) from terrestrial, semi-aquatic, and ing mammals to identify lineages and amino acid sites under positive selection. Site models used the nonsynonymous/synonymous rate ratio (omega) as an indicator of selection pressure. Mechanistic models used physicochemical distances between amino acid substitutions to specify nonsynonymous substitution rates. Site models strongly identified positive selection at different sites in the polar N-terminal extramembrane domain of SP-C in the three ing lineages: site 2 in the cetaceans (whales and dolphins), sites 7, 9, and 10 in the pinnipeds (seals and sea lions), and sites 2, 9, and 10 in the sirenians (dugongs and manatees). The only semi-aquatic contrast to indicate positive selection at site 10 was that including the polar bear, which had the largest body mass of the semi-aquatic species. Analysis of the biophysical properties that were influential in determining the amino acid substitutions showed that isoelectric point, chemical composition of the side chain, polarity, and hydrophobicity were the crucial determinants. Amino acid substitutions at these sites may lead to stronger binding of the N-terminal domain to the surfactant phospholipid film and to increased adsorption of the protein to the air-liquid interface. Both properties are advantageous for the repeated collapse and reinflation of the lung upon ing and resurfacing and may reflect adaptations to the high hydrostatic pressures experienced during ing.
Publisher: Wiley
Date: 02-2005
DOI: 10.1890/04-0920
Publisher: Wiley
Date: 09-1998
Publisher: Oxford University Press (OUP)
Date: 04-1998
DOI: 10.1093/ICB/38.2.305
Publisher: Springer Science and Business Media LLC
Date: 16-06-2016
Publisher: CSIRO Publishing
Date: 2003
DOI: 10.1071/RD02087
Abstract: Pulmonary surfactant is a complex mixture of phospholipids (PLs), neutral lipids and proteins that lines the inner surface of the lung. Here it modulates surface tension, thereby increasing lung compliance and preventing the transudation of fluid. In humans, pulmonary surfactant is comprised of approximately 80% PLs, 12% neutral lipids and 8% protein. In most eutherian (i.e. placental) mammals, cholesterol (Chol) comprises approximately 8–10% by weight or 14–20 mol% of both alveolar and lamellar body surfactant. It is regarded as an integral component of pulmonary surfactant, yet few studies have concentrated on its function or control. The lipid composition is highly conserved within the vertebrates, except that surfactant of teleost fish is dominated by cholesterol, whereas tetrapod pulmonary surfactant contains a high proportion of disaturated phospholipids (DSPs). The primitive Australian dipnoan lungfish Neoceratodus forsterii demonstrates a ‘fish-type’ surfactant profile, whereas the other derived dipnoans demonstrate a surfactant profile similar to that of tetrapods. Homology of the surfactant proteins within the vertebrates points to a single evolutionary origin for the system and indicates that fish surfactant is a ‘protosurfactant’. Among the terrestrial tetrapods, the relative proportions of DSPs and cholesterol vary in response to lung structure, habitat and body temperature (T b), but not in relation to phylogeny. The cholesterol content of surfactant is elevated in species with simple saccular lungs or in aquatic species or in species with low T b. The DSP content is highest in complex lungs, particularly of aquatic species or species with high T b. Cholesterol is controlled separately from the PL component in surfactant. For ex le, in heterothermic mammals (i.e. mammals that vary their body temperature), the relative amount of cholesterol increases in cold animals. The rapid changes in the Chol to PL ratio in response to various physiological stimuli suggest that these two components have different turnover rates and may be packaged and processed differently. In mammals, the pulmonary surfactant system develops towards the end of gestation and is characterized by an increase in the saturation of PLs in lung washings and the appearance of surfactant proteins in amniotic fluid. In general, the pattern of surfactant development is highly conserved among the amniotes. This conservation of process is demonstrated by an increase in the amount and saturation of the surfactant PLs in the final stages ( %) of development. Although the ratios of surfactant components (Chol, PL and DSP) are remarkably similar at the time of hatching/birth, the relative timing of the maturation of the lipid profiles differs dramatically between species. The uniformity of composition between species, despite differences in lung morphology, birthing strategy and relationship to each other, implies that the ratios are critical for the onset of pulmonary ventilation. The differences in the timing, on the other hand, appear to relate primarily to birthing strategy and the onset of air breathing. As the amount of cholesterol relative to the phospholipids is highly elevated in immature lungs, the pattern of cholesterol during development and evolution represents an ex le of ontogeny recapitulating phylogeny. The fact that cholesterol is an important component of respiratory structures that are primitive, when they are not in use or developing in an embryo, demonstrates that this substance has important and exciting roles in surfactant. These roles still remain to be explored.
Publisher: CSIRO Publishing
Date: 1987
DOI: 10.1071/ZO9870253
Abstract: The riparian skink Sphenomorphus quoyii can catch aquatic prey. Aquatic animals represent 26.4% of prey items, and occur in 18% of stomachs. This frequency is much higher than previously recorded for S. quoyii but is similar to that of other small riparian lizards. In laboratory experiments, S. quoyii captured aquatic prey items as they rose to the surface of water-filled containers. The skinks did not forage under water. Damselfly larvae, water beetles and tadpoles, that often swam slowly and near the surface, were easily captured. Snails that remained on the bottom, and mosquito-fish that were too fast, were not often eaten. There was no apparent size selection for either small or large tadpoles.
Publisher: MDPI AG
Date: 17-03-2013
DOI: 10.3390/ANI4010119
Publisher: Elsevier BV
Date: 12-1995
DOI: 10.1016/0034-5687(95)00039-9
Abstract: In mammals, the surface tension of the fluid lining the inner lung greatly contributes to the work of breathing. Surface tension is modified by the secretion of a mixture of surface active lipids and proteins (termed pulmonary surfactant). A disaturated phospholipid (DSP), predominantly dipalmitoylphosphatidylcholine (DPPC), can eliminate surface tension under high dynamic compression. Cholesterol (CHOL) and unsaturated phospholipids (USP) promote respreading upon inflation by converting DPPC to the disordered liquid-crystalline state. It appeared to us that a surfactant rich in DPPC, which has a high phase transition temperature of 41 degrees C, is likely to be of only limited use in the lungs of reptiles, many of which have preferred body temperatures between 20 and 30 degrees C. We review here the presence and composition of surfactant in species from the three subclasses of the Reptilia and relate these to lung structure and function, phylogeny and environmental selection pressures such as body temperature. We also discuss the function of reptilian surfactant and the factors which control surfactant turnover. Large amounts of pulmonary surfactant have been found in all reptiles so far examined. In general, warmer reptiles have greater amounts of surfactant which is also relatively enriched in DSP. Cold lizards (18 degrees C) have significantly elevated levels of surfactant cholesterol. As in all vertebrates, PC is always the dominant phospholipid (60-80%). Unlike mammals, phosphatidylglycerol (PG) is absent, with the exception of one species. The remaining phospholipid groups are present to varying degrees. The saturated fatty acid, palmitic acid (16:0) is the dominant acyl group, oleic acid (18:1) is the dominant mono-unsaturated fatty acid, and polyunsaturates comprise only about 20% of the total fatty acid profile. For two species of dragon lizards, short term changes in temperature do not affect the fatty acids, but protracted periods of cold significantly decrease the presence of 16:0 in turtle lavage (Lau and Keough, Can.J. Biochem. 59: 208-219, 1981). Surfactant appears to function as an antiglue in most reptiles, serving to lower opening pressure, and decrease the work of breathing. However, surface tension forces generally do not influence reptilian lung compliance, suggesting that the primary functions of mammalian surfactant are not necessarily relevant to reptiles.
Publisher: Elsevier
Date: 2014
Publisher: Wiley
Date: 25-03-2020
DOI: 10.1111/AEC.12883
Publisher: University of Chicago Press
Date: 07-2001
DOI: 10.1086/322158
Abstract: Pulmonary surfactant, consisting predominantly of phosphatidylcholine (PC), is secreted from Type II cells into the lungs of all air-breathing vertebrates, where it functions to reduce surface tension. In mammals, glucocorticoids and thyroid hormones contribute to the maturation of the surfactant system. It is possible that phylogeny, lung structure, and the environment may influence the development of the surfactant system. Here, we investigate the ontogeny of PC secretion from cocultured Type II cells and fibroblasts in the sea turtle, Chelonia mydas, following 58, 62, and 73 d of incubation and after hatching. The influence of glucocorticoids and thyroid hormones on PC secretion was also examined. Basal PC secretion was lowest at day 58 (3%) and reached a maximal secretion rate of 10% posthatch. Dexamethasone (Dex) alone stimulated PC secretion only at day 58. Triiodothyronine (T(3)) stimulated PC secretion in cells isolated from days 58 and 73 embryos and from hatchling turtles. A combination of Dex and T(3) stimulated PC secretion at all time points.
Publisher: Springer Science and Business Media LLC
Date: 10-1994
DOI: 10.1007/BF00302547
Abstract: To analyze the relationship between complement component 3 (C3) and the prevalence of cardiometabolic risk factors and disease activity in the rheumatic diseases having the highest rates of cardiovascular morbidity and mortality: rheumatoid arthritis (RA), psoriatic arthritis (PsA) and axial spondyloarthritis (axSpA). This is a cross-sectional study including 200 RA, 80 PsA, 150 axSpA patients and 100 healthy donors. The prevalence of cardiometabolic risk factors [obesity, insulin resistance, type 2 diabetes mellitus, hyperlipidemia, apolipoprotein B/apolipoprotein A (apoB/apoA) and atherogenic risks and hypertension] was analyzed. Serum complement C3 levels, inflammatory markers and disease activity were evaluated. Cluster analysis was performed to identify different phenotypes. Receiver operating characteristic (ROC) curve analysis to assess the accuracy of complement C3 as biomarker of insulin resistance and disease activity was carried out. Levels of complement C3, significantly elevated in RA, axSpA and PsA patients, were associated with the prevalence of cardiometabolic risk factors. Hard clustering analysis identified two distinctive phenotypes of patients depending on the complement C3 levels and insulin sensitivity state. Patients from cluster 1, characterized by high levels of complement C3 displayed increased prevalence of cardiometabolic risk factors and high disease activity. ROC curve analysis showed that non-obesity related complement C3 levels allowed to identify insulin resistant patients. Complement C3 is associated with the concomitant increased prevalence of cardiometabolic risk factors in rheumatoid arthritis and spondyloarthritis. Thus, complement C3 should be considered a useful marker of insulin resistance and disease activity in these rheumatic disorders.
Publisher: American Physiological Society
Date: 06-1999
DOI: 10.1152/JAPPL.1999.86.6.1959
Abstract: Torpor in the dunnart, Sminthopsis crassicaudata, alters surfactant lipid composition and surface activity. Here we investigated changes in surfactant composition and surface activity over 1 h after rapid arousal from torpor (15–30°C at 1°C/min). We measured total phospholipid (PL), disaturated PL (DSP), and cholesterol (Chol) content of surfactant lavage and surface activity (measured at both 15 and 37°C in the captive bubble surfactometer). Immediately after arousal, Chol decreased (from 4.1 ± 0.05 to 2.8 ± 0.3 mg/g dry lung) and reached warm-active levels by 60 min after arousal. The Chol/DSP and Chol/PL ratios both decreased to warm-active levels 5 min after arousal because PL, DSP, and the DSP/PL ratio remained elevated over the 60 min after arousal. Minimal surface tension and film compressibility at 17 mN/m at 37°C both decreased 5 min after arousal, correlating with rapid changes in surfactant Chol. Therefore, changes in lipids matched changes in surface activity during the postarousal period.
Publisher: Elsevier BV
Date: 09-2022
Publisher: Springer Science and Business Media LLC
Date: 05-1990
DOI: 10.1007/BF01954257
Publisher: Elsevier BV
Date: 06-2008
DOI: 10.1016/J.CBPA.2007.09.004
Abstract: Elasmosaurs were extremely long-necked, aquatic reptiles that used four flippers for locomotion. Their distinctive long neck distinguishes them from all other Mesozoic forms, yet the potential uses and constraints of this structure are poorly understood, particularly with regard to feeding. Several associated series of elasmosaurian cervical vertebrae were used to measure ranges of potential flexion. Two-dimensional models, based on a complete specimen of the Late Cretaceous elasmosaur Aphrosaurus furlongi, were created to measure mobility in both vertical and horizontal planes. Accuracy of the models was assessed through comparative analyses with currently extant vertebrate analogues (e.g. snake, turtle, seal). Results suggest that the elasmosaurian neck was capable of a 75-177 degrees ventral, 87-155 degrees dorsal, and 94-176 degrees lateral range of movement depending upon the thickness of cartilage reconstructed between each vertebra. Neck postures such as a 'swan-like' S-shape are shown to be implausible because they require >360 degrees vertical flexion. However, maintenance of a straight neck while swimming, together with considerable lateral and/or ventral movement during prey capture and feeding are feasible.
Publisher: Elsevier BV
Date: 05-2001
DOI: 10.1016/S1095-6433(01)00307-5
Abstract: In most eutherian mammals, cholesterol (Chol) comprises approximately 8-10 wt.% or 14-20 mol.% of both alveolar and lamellar body surfactant. It is regarded as an integral component of pulmonary surfactant, yet few studies have concentrated on its function or control. Throughout the evolution of the vertebrates, the contribution of cholesterol relative to surfactant phospholipids decreases, while that of the disaturated phospholipids (DSP) increases. Chol generally appears to dominate in animals with primitive bag-like lungs that lack septation, in the saccular lung of snakes or swimbladders which are not used predominantly for respiration, and also in immature lungs. It is possible that in these systems, cholesterol represents a protosurfactant. Cholesterol is controlled separately from the phospholipid (PL) component in surfactant. For ex le, in heterothermic mammals such as the fat-tailed dunnart, Sminthopsis crassicaudata, and the microchiropteran bat, Chalinolobus gouldii, and also in the lizard, Ctenophorus nuchalis, the relative amount of Chol increases in cold animals. During the late stages of embryonic development in chickens and lizards, the Chol to PL and Chol to DSP ratios decrease dramatically. While in isolated lizard lungs, adrenaline and acetylcholine stimulate the secretion of surfactant PL, Chol secretion remains unaffected. This is also supported in isolated cell studies of lizards and dunnarts. The rapid changes in the Chol to PL ratio in response to various physiological stimuli suggest that these two components have different turnover rates and may be packaged and processed differently. Infusion of [3H]cholesterol into the rat tail vein resulted in a large increase in Chol specific activity within 30 min in the lamellar body (LB) fraction, but over a 48-h period, failed to appear in the alveolar surfactant fraction. Analysis of the limiting membrane of the lamellar bodies revealed a high (76%) concentration of LB cholesterol. The majority of lamellar body Chol is, therefore, not released into the alveolar compartment, as the limiting membrane fuses with the cell membrane upon exocytosis. It appears unlikely, therefore, that lamellar bodies are the major source of alveolar Chol. It is possible that the majority of alveolar Chol is synthesised endogenously within the lung and stored independently from surfactant phospholipids. The role of cholesterol in the limiting membrane of the lamellar body may be to enable fast and easy processing by maintaining the membrane in a relatively fluid state.
Publisher: Elsevier BV
Date: 05-2001
DOI: 10.1016/S1095-6433(01)00303-8
Abstract: Richard E. Pattle contributed enormously to the biology of the pulmonary surfactant system. However, Pattle can also be regarded as the founding father of comparative and evolutionary research of the surfactant system. He contributed eight seminal papers of the 167 publications we have located on this topic. In particular, Pattle produced a synthesis interpreting the evolution of the surfactant system that formed the foundation for the area. Prepared 25 years ago this synthesis spawned the three great discoveries in the comparative biology of the surfactant system: (1) that the surfactant system has been highly conserved throughout the enormous radiation of the air breathing vertebrates (2) that temperature is the major selective condition that influences surfactant composition (3) that acting as an anti-adhesive is one primitive and ubiquitous function of vertebrate surfactant. Here we review the literature and history of the comparative and evolutionary biology of the surfactant system and highlight the areas of comparative physiology that will contribute to our understanding of the surfactant system in the future. In our view the surfactant system is a neatly packaged system, located in a single cell and highly conserved, yet spectacularly complex. The surfactant system is one of the best systems we know to examine evolutionary processes in physiology as well as gain important insights into gas transfer by complex organisms.
Publisher: CSIRO Publishing
Date: 1998
DOI: 10.1071/ZO98022
Abstract: The fat-tailed dunnart (Sminthopsis crassicaudata) is a small carnivorous marsupial with detectable brown adipose tissue. In order to determine whether catecholamines and food intake increase thermogenesis in this species, we measured the response of oxygen consumption (Vo2) to (i) intraperitoneal noradrenaline (0.25–4.0 mg kg-1), and (ii) food intake. The effect of nutritional status and macronutrient composition of the diet on the Vo2 response to food intake was determined by feeding both non-deprived and 24-h-food-deprived animals with either laboratory diet (1.01 Kcal g-1 (4.2 KJ g-1), 20% fat) or live mealworms (Tenebrio molitor larvae) (2.99 Kcal g-1 (12.5 KJ g-1), 30% fat). Intraperitoneal injection of noradrenaline at doses of 0.25 and 0.5 mg kg-1 increased Vo2 by 14% and 31% respectively at 30 min (P ≤ 0.05), whereas noradrenaline at 2 and 4 mg kg-1 decreased Vo2 by 10% and 31% respectively (P ≤ 0.05). Following food intake, Vo2 increased in both non-deprived (P 0.05) and 24-h-food-deprived (P 0.05) animals. While the magnitude of the increase in Vo2 was similar in animals fed with either laboratory diet or mealworms, both diets increased Vo2 more in non-deprived than in 24-h-food-deprived animals (P 0.05). These results suggest that in S. crassicaudata (i) catecholamines increase thermogenesis and (ii) the magnitude of diet-induced thermogenesis is dependent on both the nutritional status of the animal and the macronutrient composition of the diet.
Publisher: Elsevier BV
Date: 1987
Publisher: CSIRO Publishing
Date: 1995
DOI: 10.1071/ZO9950165
Abstract: The effect of altering body temperature and the oxygen and carbon dioxide composition of inspired air on the respiratory pattern of the unrestrained lizard Pogona vitticeps was determined using pneumotachometry that did not require restraining the animal. P. vitticeps demonstrated a typical reptilian breathing pattern of groups of breaths separated by periods of breath-holding. Respiratory patterns were measured at 18 degrees C and at 37 degrees C. Minute ventilation decreased at the lower temperature as a result of a decrease in average frequency. Tidal volume was temperature independent. The change in average frequency resulted from both a decrease in the instantaneous inspiratory time and an increase in the time spent in a non-ventilatory period. As a result, the work of breathing was less at 18 degrees C than at 37 degrees C. With the exception of tidal volume, breathing patterns were independent of changes to the composition of inspired air. At both 18 degrees C and 37 degrees C, inspiring a 5% CO2/13% O-2/82% N-2 gas mixture increased tidal volume but did not increase minute ventilation.
Publisher: The Company of Biologists
Date: 09-2003
DOI: 10.1242/JEB.00519
Abstract: Homeothermic mammals experience pulmonary surfactant dysfunction with relatively small fluctuations in body temperature. However, ground squirrels survive dramatic changes in body temperature during hibernation, when body temperature drops from 37°C to 0-5°C during prolonged torpor bouts. Using type II cells isolated from both warm-active and torpid squirrels, we determined the effect of assay temperature, autonomic agonists and torpor on surfactant secretion. Basal secretion was significantly higher in type II cells isolated from torpid squirrels compared with warm-active squirrels when assayed at the body temperature of the animal from which they were isolated(4°C and 37°C, respectively). A change in assay temperature significantly decreased surfactant secretion. However, the change in secretory rate between 37°C and 4°C was less than expected if due to temperature alone (Q10 range=0.8-1.2). Therefore, the surfactant secretory pathway in squirrel type II cells demonstrates some temperature insensitivity. When incubated at the body temperature of the animal from which the cells were isolated, the adrenergic agonist, isoproterenol, significantly increased surfactant secretion in both warm-active and torpid squirrel type II cells. However, the cholinergic agonist, carbamylcholine chloride, only increased secretion in torpid squirrel type II cells when incubated at 4°C. Torpor did not affect basal cAMP production from isolated type II cells. However, the production of cAMP appears to be upregulated in response to isoproterenol in torpid squirrel type II cells. Thus, at the cellular level, both the secretory and regulatory pathways involved in surfactant secretion are thermally insensitive. Upregulating basal secretion and increasing the sensitivity of type II cells to cholinergic stimulation may be adaptative characteristics of torpor that enable type II cells to function effectively at 0-5°C.
Publisher: Elsevier BV
Date: 05-2001
DOI: 10.1016/S1095-6433(01)00305-1
Abstract: Pulmonary surfactant (PS) is a complex mixture of phospholipids, neutral lipids and proteins that lines the inner surface of the lung. Here, it modulates surface tension thereby increasing lung compliance and preventing the transudation of fluid. In mammals, the PS system develops towards the end of gestation, characterized by an increase in the saturation of phospholipids in lung washings and the appearance of surfactant proteins in amniotic fluid. Birth, the transition from in utero to the external environment, is a rapid process. At this time, the PS system is important in opening and clearing the lung of fluid in order to initiate pulmonary ventilation. In oviparous vertebrates, escape from an egg can be a long and exhausting process. The young commence pulmonary ventilation and hatching by 'pipping' through the eggshell, where they remain for some time, presumably clearing their lungs. This paper relates changes in the development of the pulmonary surfactant system within the non-mammalian amniotes in response to birth strategy, lung morphology and phylogeny in order to determine the conservatism of this developmental process. Total phospholipid (PL), disaturated phospholipid (DSP) and cholesterol (Chol) were quantified from lung washings of embryonic and hatchling chickens, bearded dragons (oviparous), sleepy lizards (viviparous), snapping turtles and green sea turtles throughout the final stages of incubation and gestation. In all cases, the pattern of development of the pulmonary surfactant lipids was consistent with that of mammals. PL and DSP increased throughout the latter stages of development and Chol was differentially regulated from the PLs. Maximal secretion of both PL and DSP occurred at 'pipping' in oviparous reptiles, coincident with the onset of airbreathing. Similarly, the amount of DSP relative to total PL was maximal immediately after the initiation of airbreathing in chickens. The relative timing of the appearance of the lipids differed between groups. In the oviparous lizard, surfactant lipids were released over a relatively shorter time than that of the sleepy lizard, turtles, birds and mammals. Thus, despite temporal differences and vastly different lung morphologies, birth strategies and phylogenies, the overall development and maturation of the PS system is highly conserved amongst the amniotes.
Publisher: Elsevier BV
Date: 05-2001
Publisher: Wiley
Date: 03-03-2006
Publisher: University of Chicago Press
Date: 09-2004
DOI: 10.1086/422058
Abstract: Several times throughout their radiation fish have evolved either lungs or swim bladders as gas-holding structures. Lungs and swim bladders have different ontogenetic origins and can be used either for buoyancy or as an accessory respiratory organ. Therefore, the presence of air-filled bladders or lungs in different groups of fishes is an ex le of convergent evolution. We propose that air breathing could not occur without the presence of a surfactant system and suggest that this system may have originated in epithelial cells lining the pharynx. Here we present new data on the surfactant system in swim bladders of three teleost fish (the air-breathing pirarucu Arapaima gigas and tarpon Megalops cyprinoides and the non-air-breathing New Zealand snapper Pagrus auratus). We determined the presence of surfactant using biochemical, biophysical, and morphological analyses and determined homology using immunohistochemical analysis of the surfactant proteins (SPs). We relate the presence and structure of the surfactant system to those previously described in the swim bladders of another teleost, the goldfish, and those of the air-breathing organs of the other members of the Osteichthyes, the more primitive air-breathing Actinopterygii and the Sarcopterygii. Snapper and tarpon swim bladders are lined with squamous and cuboidal epithelial cells, respectively, containing membrane-bound lamellar bodies. Phosphatidylcholine dominates the phospholipid (PL) profile of lavage material from all fish analyzed to date. The presence of the characteristic surfactant lipids in pirarucu and tarpon, lamellar bodies in tarpon and snapper, SP-B in tarpon and pirarucu lavage, and SPs (A, B, and D) in swim bladder tissue of the tarpon provide strong evidence that the surfactant system of teleosts is homologous with that of other fish and of tetrapods. This study is the first demonstration of the presence of SP-D in the air-breathing organs of nonmammalian species and SP-B in actinopterygian fishes. The extremely high cholesterol/disaturated PL and cholesterol/PL ratios of surfactant extracted from tarpon and pirarucu bladders and the poor surface activity of tarpon surfactant are characteristics of the surfactant system in other fishes. Despite the paraphyletic phylogeny of the Osteichthyes, their surfactant is uniform in composition and may represent the vertebrate protosurfactant.
Publisher: Elsevier BV
Date: 05-2001
DOI: 10.1016/S0034-5687(00)00225-5
Abstract: This study describes the developmental changes in pulmonary surfactant (PS) lipids throughout incubation in the sea turtle, Chelonia mydas. Total phospholipid (PL), disaturated phospholipid (DSP) and cholesterol (Chol) harvested from lung washings increased with advancing incubation, where secretion was maximal at pipping, coincident with the onset of pulmonary ventilation. The DSP/PL ratio increased, whereas the Chol/PL and the Chol/DSP ratio declined throughout development. The phospholipids, therefore, are independently regulated from Chol and their development matches that of mammals. To explore whether hypoxia could elicit an effect on the development of the PS system, embryos were exposed to a chronic dose of 17% O2 for the final approximately 40% of incubation. Hypoxia did not affect incubation time, absolute, nor relative abundance of the surfactant lipids, demonstrating that the development of the system is robust and that embryonic development continues unabated under mild hypoxia. Hypoxia-incubated hatchlings had lighter wet lung weights than those from normoxia, inferring that mild hypoxia facilitates lung clearance in this species.
Publisher: Elsevier BV
Date: 2004
DOI: 10.1016/J.BBRC.2003.12.012
Abstract: Marine mammals have a spectacular suite of respiratory adaptations to deal with the extreme pressures associated with deep ing. In particular, maintaining a functional pulmonary surfactant system at depth is critical for marine mammals to ensure that inspiration is possible upon re-emergence. Pulmonary surfactant is secreted from alveolar type II (ATII) cells and is crucial for normal lung function. It is not known whether ATII cells have the ability to continue to secrete pulmonary surfactant under pressure, or how secretion is maintained and controlled. We show here that surfactant secretion in California sea lions (Zalophus californianus) was increased after high pressures (25 and 50 atm) of short duration (30 min), but was unaffected by high pressures of long duration (2 h). This is in contrast to a similar sized terrestrial mammal (sheep), where surfactant secretion was increased after high pressures of both long and short duration. Z. californianus and terrestrial mammals also show similar responses to stimulatory hormones and autonomic neurotransmitters. It therefore seems that an increase in the quantity of surfactant in seal lungs after ing is most likely caused by mechanostimulation induced by pressure and volume changes, and that seals are adapted to maintain constant levels of surfactant under long periods of high pressure.
Publisher: University of Chicago Press
Date: 07-1997
DOI: 10.1086/515847
Abstract: An increase in body temperature in the bearded dragon, Pogona vitticeps, is accompanied by an increase in the amount of pulmonary surfactant, a mixture of proteins and lipids, with the latter consisting predominantly of phospholipid and cholesterol. This increase may result from a temperature-induced change in autonomic input to the lungs, as perfusing the isolated lungs of P. vitticeps with either acetylcholine or adrenaline increases surfactant phospholipid release. However, whether acetylcholine acts via intrapulmonary sympathetic ganglia or directly on alveolar Type II cells is unknown. Moreover, the relative importance of circulating catecholamines and pulmonary sympathetic nerves on the control of the surfactant system is also obscure. Here, we describe the mechanism of the modulation of the surfactant system and the effect of this modulation on lung compliance. The role of acetylcholine was determined by perfusing isolated lungs with acetylcholine, acetylcholine and the ganglionic antagonist hexamethonium, or acetylcholine, hexamethonium, and the muscarinic antagonist atropine. Perfusing with acetylcholine significantly increased phospholipid release but did not affect cholesterol release. While histological examination of the lung revealed the presence of a large autonomic ganglion at the apex, blocking sympathetic ganglia with hexamethonium did not prevent the acetylcholine-mediated increase in phospholipid. However, the increase was inhibited by blocking muscarinic receptors with atropine, which indicates that acetylcholine acts on muscarinic receptors to stimulate phospholipid release. By increasing pulmonary smooth muscle tone, acetylcholine decreased opening pressure and increased static inflation pressures. Plasma levels of noradrenaline and adrenaline increased with increasing temperature and were accompanied by a greater surfactant content in the lungs. While surfactant content was also higher in animals that exercised, plasma levels of adrenaline, noradrenaline, and dopamine were not elevated following exercise. Hence, surfactant release in the lizard lung may increase in response to an increase in plasma catecholamine levels. Acetylcholine, and hence the parasympathetic nervous system, may act to stimulate surfactant release but does not act via pulmonary sympathetic ganglia. We conclude that promoting surfactant secretion via an increase in circulating catecholamines may be inappropriate for a cold lizard with a requirement to conserve energy. As body temperature decreases, release of surfactant via nonadrenergic mechanisms, including cholinergic stimulation, may become increasingly important.
Publisher: Elsevier BV
Date: 03-1989
DOI: 10.1016/0034-5687(89)90042-X
Abstract: The lungs of the central netted dragon Ctenophorus nuchalis are bag-like, with most of the gas exchange region located in the anterior third. Although the faveoli are much larger than the mammalian alveoli, the lizard at 37 degrees C has approximately 70 times more surfactant phospholipid per unit area of respiratory surface than does a similar sized mammal. However, when expressed as per wet lung weight, lizards and rats possessed similar amounts of phospholipids. Dipalmitoylphosphatidylcholine was the principal phospholipid in both species. However, major differences existed in the phospholipid, neutral lipid and fatty acid profiles. Whereas the lizard contained neither phosphatidylglycerol nor phosphatidylethanolamine it had more cholesterol, esterified cholesterol, acylglycerides and unsaturated fatty acids. Although the ratio of saturated:unsaturated fatty acids was similar in rats and lizards, palmitic acid predominated in the former. The composition of lizard surfactant suggests that it would adsorb rapidly at reduced body temperature.
Publisher: Elsevier BV
Date: 10-1993
DOI: 10.1016/0034-5687(93)90053-D
Abstract: We previously showed that the lung of the central Australian lizard, Ctenophorus nuchalis, contains a large amount of surfactant, the composition of which varies with body temperature. We now show that the specific compliance of the lungs of these lizards remains constant regardless of whether they were maintained at 10, 18, 27, 37 or 43 degrees C for 4 hours. In contrast, the opening pressure was constant up to 27 degrees C, but decreased at 37 and 43 degrees C. When we lavaged the lungs in situ to remove the majority of surfactant, specific compliance decreased while opening pressure increased. The lungs of C. nuchalis are essentially two bubbles, with the left one larger at low and intermediate volumes. After collapsing both lungs, the larger left lung always inflated first. However, following lavage the smaller right lung inflated first. As the larger lung, when collapsed, would have a much greater area of epithelial contact, this result is consistent with surfactant acting as an 'antiglue'. During deflation the smaller lung collapsed first, consistent with the law of Laplace. Compliance did not change in the saline-filled lung suggesting that the gas-liquid interface does not play a major role. We conclude that in the lungs of these lizards, surfactant is acting as an antiglue. This might be important during periods of apnea at low body temperatures, when residual volume is small and epithelial surfaces may come into contact.
Publisher: Elsevier BV
Date: 06-2005
DOI: 10.1016/J.CBPB.2005.05.035
Abstract: Pulmonary surfactant has previously been shown to change during development, both in composition and function. Adult pinnipeds, unlike adult terrestrial mammals, have an altered lung physiology to cope with the high pressures associated with deep ing. Here, we investigated how surfactant composition and function develop in California sea lions (Zalophus californianus). Phosphatidylinositol was the major anionic phospholipid in the newborn, whereas phosphatidylglycerol was increased in the adult. This increase in phosphatidylglycerol occurred at the expense of phosphatidylinositol and phosphatidylserine. There was a shift from long chain and polyunsaturated phospholipid molecular species in the newborn to shorter chain and mono- and disaturated molecular species in the adult. Cholesterol and SP-B concentrations were also higher in the adult. Adult surfactant could reach a lower equilibrium surface tension, but newborn surfactant could reach a lower minimum surface tension. The composition and function of surfactant from newborn California sea lions suggest that this age group is similar to terrestrial newborn mammals, whereas the adult has a " ing mammal" surfactant that can aid the lung during deep es. The onset of ing is probably a trigger for surfactant development in these animals.
Publisher: Elsevier BV
Date: 10-2003
DOI: 10.1016/J.BBRC.2003.08.152
Abstract: Fat-tailed dunnarts, Sminthopsis crassicaudata, survive dramatic changes in body temperature during torpor without experiencing surfactant dysfunction. Adrenergic factors regulate surfactant secretion through beta(2)-adrenergic receptors on alveolar type II cells. Temperature has no effect on the secretory response of dunnart type II cells to adrenergic stimulation. We hypothesise that during torpor, dunnart type II cells up-regulate the number of adrenergic receptors present on type II cells to enable stimulation at lower concentrations of agonist. Here, we isolated type II cells from warm-active (35 degrees C) and torpid (15 degrees C) dunnarts and examined the effects of an in vitro temperature change on the number and activity of adrenergic receptors. Torpor did not affect the beta-adrenergic receptor number. However, we observed a significant decrease in adrenergic receptor number when cells from warm-active animals were incubated at 15 degrees C and when cells from torpid animals were incubated at 37 degrees C. cAMP production was significantly higher in type II cells from torpid dunnarts than warm-active dunnarts and this may contribute, in part, to the temperature insensitivity we have previously observed in the adrenergic regulation of surfactant secretion.
Publisher: JSTOR
Date: 03-1986
DOI: 10.2307/1564134
Publisher: American Physiological Society
Date: 08-2004
DOI: 10.1152/AJPREGU.00399.2003
Abstract: The surfactant system, a complex mixture of lipids and proteins, controls surface tension in the lung and is crucial for the first breath at birth, and thereafter. Heterokairy is defined as plasticity of a developmental process within an in idual. Here, we provide experimental evidence for the concept of heterokairy, as hypoxia induces a change in the onset and rate of development of surfactant, probably via endogenous glucocorticoids, to produce in iduals capable of surviving early hatching. Chicken eggs were incubated under normoxic (21% O 2 ) conditions throughout or under hypoxic (17% O 2 ) conditions from day 10 of incubation. Embryos were s led at days 16, 18, and 20 and also 24 h after hatching. In a second experiment, dexamethasone (Dex), tri-iodothyronine (T 3 ), or a combination (Dex + T 3 ) was administered 24 and 48 h before each time point. Both hypoxia and Dex accelerated maturation of the surfactant lipids by increasing total phospholipid (PL), disaturated phospholipid (DSP), and cholesterol (Chol) in lavage at days 16 and 18. Maturation of surfactant lipid composition was accelerated, with day 16 %DSP/PL, Chol/DSP, and Chol/PL resembling the ratios of day 20 control animals. The effect of Dex + T 3 was similar to that of Dex alone. Hypoxia increased plasma corticosterone levels at day 16, while plasma T 3 levels were not affected. Hence, exposure to hypoxia during critical developmental windows accelerates surfactant maturation, probably by increasing corticosterone production. This internal modulation of the developmental response to an external stimulus is a demonstration of physiological heterokairy.
Publisher: Elsevier BV
Date: 02-2006
DOI: 10.1016/J.RESP.2005.03.002
Abstract: Pinnipeds (seals and sea lions) have developed a specialised respiratory system to cope with living in a marine environment. They have a highly reinforced lung that can completely collapse and reinflate during ing without any apparent side effects. These animals may also have a specialised surfactant system to augment the morphological adaptations. The surface activity of surfactant from four species of pinniped (California sea lion, Northern elephant seal, Northern fur seal and Ringed seal) was measured using a captive bubble surfactometer (CBS), and compared to two terrestrial species (sheep and cow). The surfactant of Northern elephant seal, Northern fur seal and Ringed seal was unable to reduce surface tension (gamma) to normal levels after 5 min adsorption (61.2, 36.7, and 46.2 +/- 1.7 mN/m, respectively), but California sea lion was able to reach the levels of the cow and sheep (23.4 mN/m for California sea lion, 21.6 +/- 0.3 and 23.0 +/- 1.5 mN/m for cow and sheep, respectively). All pinnipeds were also unable to obtain the very low gamma(min) achieved by cow (1.4 +/- 0.1 mN/m) and sheep (1.5 +/- 0.4 mN/m). These results suggest that reducing surface tension to very low values is not the primary function of surfactant in pinnipeds as it is in terrestrial mammals, but that an anti-adhesive surfactant is more important to enable the lungs to reopen following collapse during deep ing.
Publisher: Springer Berlin Heidelberg
Date: 2009
Publisher: Wiley
Date: 20-06-2007
Publisher: Wiley
Date: 09-1998
DOI: 10.1111/J.1440-1681.1998.TB02283.X
Abstract: 1. Pulmonary surfactant is a mixture of lipids and proteins that lines the air-liquid interface of the lungs of all vertebrates. In mammals, it functions to reduce and vary surface tension, which helps to decrease the work of breathing, provide alveolar stability and prevent alveolar oedema. The present review examines the evolution and relative importance of these surface activity related functions in the lungs of vertebrates. 2. The surface activity of surfactant from fish, hibians, birds and most reptiles is generally very low, correlating with a low body temperature and a low disaturated phosholipid content of their surfactant. In contrast, the surfactant of those reptiles with a higher preferred body temperature, as well as that of birds and mammals, has a much higher surface activity. 3. The two main functions of surfactant in mammals are to provide alveolar stability and to increase compliance of the relatively stiff bronchoalveolar lung. As the respiratory units of most non-mammalian vertebrates are up to 1000-fold larger and up to 100-fold more compliant, surfactant is not required for these functions. 4. In non-mammals, surfactant appears to act as an anti-glue preventing the adhesion of respiratory surfaces that may occur when the lungs collapse (e.g. during ing, swallowing of prey or on expiration). Surfactant also controls lung fluid balance. These functions can be fulfilled by a surfactant with relatively low surface activity and may represent the primitive functions of surface active material in vertebrate lungs.
Publisher: Elsevier BV
Date: 08-2011
DOI: 10.1016/J.RESP.2011.05.015
Abstract: Pulmonary surfactant fulfils erse functions at the lung air-liquid interface of all air-breathing vertebrates. Neurohormonal regulation of surfactant synthesis and secretion is highly conserved among non-mammalian amniotes. Although the pattern of surfactant lipid maturation is similar among species, the onset and completion differ dramatically. These differences are apparently not determined by phylogeny, but may relate to the timing of development of relative hypoxia as an embryo develops, which is related to birthing strategy. We have proposed that hypoxia is an evolutionary drive for differential surfactant development among species. In mammalian and non-mammalian models, hypoxia induces fetal growth restriction. Depending on the timing of the insult, this may be associated with an acceleration or deceleration of surfactant development. The hypoxic effect may be mediated via hormonal and growth factors, such as glucocorticoids and VEGF. However, the multifactorial nature of mammalian growth restriction models complicates the mechanistic interpretations. Hence, less complex oviparous animal models are required, in which hypoxia can be isolated from maternal influences.
Publisher: Elsevier BV
Date: 08-2003
DOI: 10.1016/S0006-291X(03)01427-X
Abstract: The small microchiropteran bat, Chalinolobus gouldii, undergoes large daily fluctuations in metabolic rate, body temperature, and breathing pattern. These alterations are accompanied by changes in surfactant composition, predominantly an increase in cholesterol relative to phospholipid during torpor. Furthermore, the surface activity changes, such that the surfactant functions most effectively at that temperature which matches the animal's activity state. Here, we examine the surface activity of surfactant from bats during arousal from torpor. Bats were housed at 24 degrees C on an 8:16h light:dark cycle and their surfactant was collected during arousal (28<T(b)<32 degrees C). Surface activity was examined with a Captive Bubble Surfactometer at 24 and 37 degrees C. Surfactant from arousing bats was more active at 37 degrees C than at 24 degrees C, indicated by a lower ST(min) and reduced film area compression required to reach ST(min). It appears that the arousal-induced changes in surfactant composition, i.e., lower levels of cholesterol, inhibit adsorption of surfactant at 24 degrees C. Furthermore, the alterations in surfactant composition during arousal are very rapid, such that the mixture behaves more like surfactant from warm-active bats, and therefore, functions more effectively at 37 degrees C.
Publisher: University of Chicago Press
Date: 09-2000
DOI: 10.1086/317745
Abstract: Pulmonary surfactant is a mixture of phospholipids, neutral lipids, and proteins that controls the surface tension of the fluid lining the lung. Surfactant amounts and composition are influenced by such physiological parameters as metabolic rate, activity, body temperature, and ventilation. Microchiropteran bats experience fluctuations in these parameters throughout their natural daily cycle of activity and torpor. The activity cycle of the microchiropteran bat Chalinolobus gouldii was studied over a 24-h period. Bats were maintained in a room at constant ambient temperature (24 degrees C) on an 8L : 16D cycle. Diurnal changes in the amount and composition of surfactant were measured at 4-h intervals throughout a 24-h period. The C. gouldii were most active at 2 a.m. and were torpid at 2 p.m. Alveolar surfactant increased 1.5-fold immediately after arousal. The proportion of disaturated phospholipid remained constant, while surfactant cholesterol levels increased 1.5-fold during torpor. Alveolar cholesterol in C. gouldii was six times lower than in other mammals. Cholesterol appears to function in maintaining surfactant fluidity during torpor in this species of bat.
Publisher: Wiley
Date: 2007
DOI: 10.1002/AR.20410
Abstract: Rational treatment of lymphoedema may be improved in the future with a better understanding of the physiological processes involved in the regeneration of new lymphatic vessels (lymphangiogenesis). Many lizard species undergo tail autotomy as a predator escape response and subsequently regenerate nonlymphoedematous tails. Such species may offer novel models for examining lymphangiogenesis. In this lymphoscintigraphic evaluation, three radioactive tracers were employed, (99m)Tc-antimony trisulphide colloid (approximately 10 nm diameter), (99m)Tc-tin fluoride colloid (approximately 2,000 nm (99m)Tc-TFC), and (99m)Tc-diethylenetriaminepentaacetic acid (soluble (99m)Tc-DTPA), to examine lymphatic function in regenerating tails of the Australian marbled gecko, Christinus marmoratus. Rate of local clearance and velocity of migration were determined in geckos with original tails and at 6, 9, 12, and >24 weeks after autotomy. In original-tailed geckos, the smaller radiocolloid was cleared to a greater extent and had a faster lymph velocity than in geckos with regenerated tails. The same parameters measured for larger particles were greater in early regeneration than later. (99m)Tc-TFC did not migrate from the injection site in fully regenerated and original gecko tails, which indicates that larger particles are increasingly impeded as tail regeneration progresses. Soluble (99m)Tc-DTPA diffused from the injection site extremely rapidly via venous capillaries in all tails, confirming that the slower clearance of the colloids is solely via the lymphatics. Differences in clearance and lymph velocity between differently sized colloids throughout tail regeneration may be influenced by changes in surrounding tissue structure density and the lymphatic vessel porosity.
Publisher: Elsevier BV
Date: 03-2015
Publisher: Elsevier
Date: 2003
Publisher: Elsevier BV
Date: 06-2007
DOI: 10.1016/J.CBD.2007.02.003
Abstract: The pulmonary surfactant system of heterothermic mammals must be capable of dealing with the effect of low body temperatures on the physical state of the lipid components. We have shown previously that there is a modest increase in surfactant cholesterol during periods of torpor, however these changes do not fully explain the capacity of surfactant to function under the wide range of physical conditions imposed by torpor. Here we examine indirectly the role of surfactant protein C (SP-C) in adapting to variable body temperatures by testing for the presence of positive (adaptive) selection during evolutionary transitions between heterothermy and homeothermy. We sequenced SP-C from genomic DNA of 32 mammalian species from groups of closely related heterothermic and homeothermic species (contrasts). We used phylogenetic analysis by maximum likelihood estimates of rates of non-synonymous to synonymous substitutions and fully Bayesian inference of these sequences to determine whether the mode of body temperature regulation exerts a selection pressure driving the molecular adaptation of SP-C. The protein sequence of SP-C is highly conserved with synonymous or highly conservative amino acid substitutions being predominant. The evolution of SP-C among mammals is characterised by high codon usage bias and high rates of transition/transversion. The only contrast to show evidence of positive selection was that of the bears (Ursus americanus and U. maritimus). The significance of this result is unclear. We show that SP-C is under strong evolutionary constraints, driven by purifying selection, presumably to maintain protein function despite variation in the mode of body temperature regulation.
Publisher: Elsevier
Date: 2003
Publisher: Informa UK Limited
Date: 1996
DOI: 10.3109/01902149609031775
Abstract: The lungs of all air-breathing vertebrates contain a form of pulmonary surfactant that lines the alveolar air-water interface where it modifies the interfacial surface tension. These pulmonary surfactants all consist of varying amounts of phospholipids (saturated and unsaturated) and cholesterol. The extent of variation between vertebrate groups and between species within a vertebrate group has been attributed to differences in factors such as phylogeny, body temperature, habitat, and lung structure. The influence of these factors on hibian surfactant composition and function has been studied, but the reptiles, which comprise a polyphyletic group of vertebrates, have never been critically examined. The surfactant lipid composition from species belonging to the three groups of reptiles, the Archosauria (crocodiles), Lepidosauria (snakes and lizards), and Anapsida (turtles), has been determined. New data is presented in conjunction with already published data to create an evolutionary framework that concentrates particularly on the influence of phylogeny, body temperature, and lung structure on the composition of the surfactant lipids. Large amounts of pulmonary surfactant were found in all species of reptiles. All species lavaged at 23 degrees C (except C. atrox) demonstrated DSP/PL ratios of 23-33%. Animals with multicameral lungs exhibited an elevated CHOL/DSP ratio compared with species with unicameral lungs. In all groups, phosphatidylcholine (PC) was the dominant (60-80%) phospholipid. Phosphatidylserine and phosphatidylinositol (PS/PI) and sphingomyelin (S) represented the other phospholipids, while phosphatidylglycerol (PG), lysophosphatidylcholine (LPC), and phosphatidylethanolamine (PE) were occasionally observed. In two species of lizards (C. nuchalis and P. vitticeps), the saturated fatty acid, palmitic acid (16:0), was the dominant tail group on the phospholipids. Oleic acid (18:1) was the dominant monounsaturated fatty acid, whereas polyunsaturates comprised about a fifth of the total fatty acid profile. Short-term (4 h) changes in temperature did not affect the relative proportions of the fatty acids in either species. Comparison of the current data with previously published literature suggests that phylogeny and habitat do not significantly influence surfactant lipid composition, but body temperature and to a lesser extent lung structure are important determinants of reptilian surfactant lipid composition.
Publisher: Springer Science and Business Media LLC
Date: 15-06-2017
DOI: 10.1007/S11120-017-0409-4
Abstract: Ferredoxins are soluble iron sulphur proteins which function as electron donors in a number of metabolic pathways in a broad range of organisms. In photosynthetic organisms, PETF, or ferredoxin 1 (FDX1), is the most studied ferredoxin due to its essential role in photosynthesis, where it transfers electrons from photosystem I to ferredoxin-NADP
Publisher: Elsevier BV
Date: 11-2006
DOI: 10.1016/J.RESP.2006.04.012
Abstract: Pulmonary surfactant lines the alveolar air-water interface, varying surface tension with lung volume to increase compliance and prevent adhesion of respiratory surfaces. We examined whether the surfactant system of ing mammals exhibits adaptations for more efficient lung function during ing, to complement other respiratory adaptations. Here we review adaptations at the molecular, compositional, functional and cellular levels and during development for animals beginning life on land and progressing to an aquatic environment. Molecular adaptations to ing were examined in surfactant protein C (SP-C) from terrestrial, semi-aquatic and ing mammals using phylogenetic analyses. Diving species exhibited sites under positive selection in the polar N-terminal domain. These amino acid substitutions may lead to stronger binding of SP-C to the phospholipid film and increased adsorption to the air-liquid interface. The concentration of shorter chain phospholipid molecular species was greater and SP-B levels were lower in ing than terrestrial mammals. This may lead to a greater fluidity and explain the relatively poor surface activity of ing mammal surfactant. There were no consistent differences in cholesterol between ing and terrestrial mammals. Surfactant from newborn California sea lions was similar to that of terrestrial mammals. Secretory activity of alveolar type II epithelial cells of sea lions demonstrated an insensitivity to pressure relative to sheep cells. The poor surface activity of ing mammal surfactant is consistent with the hypothesis that it has an anti-adhesive function that develops after the first entry into the water, with a surfactant film that is better suited to repeated collapse and respreading.
Publisher: Elsevier BV
Date: 07-2023
Publisher: Oxford University Press (OUP)
Date: 10-2007
DOI: 10.1093/ICB/ICM079
Abstract: (Orgeig and Daniels) This surfactant symposium reflects the integrative and multidisciplinary aims of the 1st ICRB, by encompassing in vitro and in vivo research, studies of vertebrates and invertebrates, and research across multiple disciplines. We explore the physical and structural challenges that face gas exchange surfaces in vertebrates and insects, by focusing on the role of the surfactant system. Pulmonary surfactant is a complex mixture of lipids and proteins that lines the air-liquid interface of the lungs of all air-breathing vertebrates, where it functions to vary surface tension with changing lung volume. We begin with a discussion of the extraordinary conservation of the blood-gas barrier among vertebrate respiratory organs, which has evolved to be extremely thin, thereby maximizing gas exchange, but simultaneously strong enough to withstand significant distension forces. The principal components of pulmonary surfactant are highly conserved, with a mixed phospholipid and neutral lipid interfacial film that is established, maintained and dynamically regulated by surfactant proteins (SP). A wide variation in the concentrations of in idual components exists, however, and highlights lipidomic as well as proteomic adaptations to different physiological needs. As SP-B deficiency in mammals is lethal, oxidative stress to SP-B is detrimental to the biophysical function of pulmonary surfactant and SP-B is evolutionarily conserved across the vertebrates. It is likely that SP-B was essential for the evolutionary origin of pulmonary surfactant. We discuss three specific issues of the surfactant system to illustrate the ersity of function in animal respiratory structures. (1) Temperature: In vitro analyses of the behavior of different model surfactant films under dynamic conditions of surface tension and temperature suggest that, contrary to previous beliefs, the alveolar film may not have to be substantially enriched in the disaturated phospholipid, dipalmitoylphosphatidylcholine (DPPC), but that similar properties of rate of film formation can be achieved with more fluid films. Using an in vivo model of temperature change, a mammal that enters torpor, we show that film structure and function varies between surfactants isolated from torpid and active animals. (2) Spheres versus tubes: Surfactant is essential for lung stabilization in vertebrates, but its function is not restricted to the spherical alveolus. Instead, surfactant is also important in narrow tubular respiratory structures such as the terminal airways of mammals and the air capillaries of birds. (3). Insect tracheoles: We investigate the structure and function of the insect tracheal system and ask whether pulmonary surfactant also has a role in stabilizing these minute tubules. Our theoretical analysis suggests that a surfactant system may be required, in order to cope with surface tension during processes, such as molting, when the tracheae collapse and fill with water. Hence, despite observations by Wigglesworth in the 1930s of fluid-filled tracheoles, the challenge persists into the 21st century to determine whether this fluid is associated with a pulmonary-type surfactant system. Finally, we summarize the current status of the field and provide ideas for future research.
Publisher: Informa UK Limited
Date: 23-05-2017
Publisher: Elsevier BV
Date: 03-1994
DOI: 10.1016/0034-5687(94)90088-4
Abstract: We examined the composition and function of pulmonary surfactants in hibians inhabiting aquatic and terrestrial habitats with particular regard to the influences of (1) variations in body temperature, (2) external hydrostatic pressure and (3) breathing pattern. Two fully aquatic salamanders, and the completely terrestrial cane toad Bufo marinus (all maintained at 21-23 degrees C) were selected. Whereas one of the salamanders (Siren intermedia) possessed gills and lungs, Amphiuma tridactylum only possessed lungs. We determined the amounts of cholesterol (Chol), disaturated phospholipids (DSP) and total phospholipid (PL) in lavage of all three species, and also determined the types of phospholipids of B. marinus and A. tridactylum. DSP lowers surface tension at the air-water interface in the lung, while Chol and unsaturated phospholipids assist spreading and maintain the DSP in its disordered, liquid-crystalline state at high lung volumes. All three species had significant amounts of pulmonary-type surfactant. The two aquatic salamanders had identical ratios of both Chol/PL and DSP/PL both of which in turn were nearly twice those of B. marinus. All three species had similar Chol/DSP ratios. Aquatic salamanders sustain high external hydrostatic pressures exerted by the aquatic environment and tend to collapse their lungs during expiration. We hypothesize that these salamanders might require a DSP-rich surfactant to prevent the epithelial surfaces from adhering and large amounts of Chol to keep the DSP fluid. The terrestrial B. marinus has less DSP, suggesting a surfactant which is fluid over a large range of temperatures. Possibly, cane toads do not require a DSP rich surfactant as they neither collapse their lungs on deflation, nor experience external hydrostatic pressures promoting lung collapse. The PL profile of B. marinus lavage was similar to that of other frogs and mammals, containing phosphatidylcholine (PC) as the predominant phospholipid together with substantial amounts of phosphatidylglycerol (PG). On the other hand, although A. tridactylum exhibited high levels of PC, it contained phosphatidylinositol (PI) in place of PG, a pattern typical of reptiles and birds.
Publisher: University of Chicago Press
Date: 05-2002
DOI: 10.1086/341999
Abstract: The antioxidant enzyme (AOE) system protects the lung from oxidative damage. The pulmonary surfactant (PS) system lowers the interfacial pressure within the lung, improving lung compliance and aiding lung clearance. In mammals, the AOE and PS systems develop in tandem during the final 10%-20% of gestation. Here, we investigated the development of these systems in the viviparous skink, Tiliqua rugosa. The content of total phospholipid (PL), disaturated phospholipid (DSP), and cholesterol (Chol) increased in lung washings from foetal lizards with advancing gestational age. Similarly, the relative saturation of the PLs increased throughout gestation, with mid-stage 40 foetuses having a DSP/PL equivalent to newborns and adults. Maternal lizards had significantly less total PL, DSP, and Chol than nongravid and newborn lizards however, the relative composition did not differ from nongravid animals. This presumably results from compression of the lungs under the bulk of the developing foetus. The Chol/PL and Chol/DSP ratios declined early in development such that mid-stage 40 embryos had comparable ratios to both newborns and adults. Thus, it appears that the PS system matures in a similar manner in skinks and in mammals. However, the composition of surfactant is complete some weeks before parturition, probably to enable improved survivorship of the precocial young in the event of premature birth. Unlike the surfactant lipids, the AOEs, catalase, superoxide dismutase, and glutathione peroxidase did not differ appreciably throughout gestation. It appears therefore that like the surfactant lipids the AOE system is in readiness for air breathing throughout the latter stages of gestation, possibly in preparation for premature birth. Unlike mammals, the PS and AOE systems develop independently from one another.
No related grants have been discovered for Christopher Daniels.