ORCID Profile
0000-0002-5915-5416
Current Organisations
Bureau of Meteorology
,
University of Tasmania Institute for Marine and Antarctic Studies
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Publisher: Elsevier BV
Date: 04-2001
Abstract: In a group of 12 normal-weight, normotensive, nondiabetic adult females, the intramyocellular lipid (IMCL) to creatine ratio of the soleus muscle was determined using localized (1)H-magnetic resonance spectroscopy ((1)H-MRS) and related to skeletal muscle blood (and oxygen) supply (as assessed by near infrared spectroscopy [NIRS] of the forearm). A significant positive association was found between IMCL content and reoxygenation rate of forearm muscle hemoglobin (Hb) after 1 minute of ischemic exercise (r = .70, P = .01). The relative efficiency of skeletal muscle oxygen supply may be a determining factor of IMCL content in skeletal muscle.
Publisher: Elsevier BV
Date: 09-2016
Publisher: Wiley
Date: 12-2001
DOI: 10.1046/J.1440-1754.2001.00753.X
Abstract: To examine the prevalence of small dense low density lipoprotein (LDL) in a cohort of children under 10 years of age and to investigate the relationship to other biochemical variables and to measures of fatness. A preponderance of small dense LDL (pattern B), is associated with obesity, abdominal fat accumulation, insulin resistance and risk of heart disease in adults. LDL peak particle diameter (PPD) was determined by gel electrophoresis in 53 children under 10 years of age and in 65 of their parents: apoproteins A1 and B were determined by turbidimetry. Anthropometric variables, basic lipid profiles, insulin and leptin had been determined previously. Differences between patterns A (large light particles > 25.5 nm diameter) and B were examined by t-test, Chi-square, or Mann-Whitney test. Relationships between the variables were reported as Pearson correlation coefficients. Pattern B (PPD of < or = 25.5 nm) prevalence was 7.5% in children and 11% in parents (17% in men and 5% in women). Most of the children (86%) who had PPD < or = 26.0 nm also had parents with PPD in this range. A strong association was found between children's and mother's PPD (r=0.60, P < 0.001), but this was somewhat less with fathers (r=0.40, P=0.02). Children in the lowest tertile of PPD had a tendency towards a higher body mass index, waist, fat mass and insulin. The prevalence of small dense LDL is lower in children under 10 years of age than in their parents fathers had a higher prevalence of pattern B than mothers and there is some evidence of a familial effect in the inheritance of pattern B.
Publisher: Copernicus GmbH
Date: 16-07-2015
DOI: 10.5194/ACPD-15-19477-2015
Abstract: Abstract. Aerosol observations above the Southern Ocean and Antarctic sea ice are scarce. Measurements of aerosols and atmospheric composition were made in East Antarctic pack ice on-board the Australian icebreaker Aurora Australis during the spring of 2012. One particle formation event was observed during the 32 days of observations. This event occurred on the only day to exhibit extended periods of global irradiance in excess of 600 W m−2. Within the single air-mass influencing the measurements, number concentrations of particles larger than 3 nm (CN3) reached almost 7700 cm−3 within a few hours of clouds clearing, and grew at rates of 5.6 nm h−1. Formation rates of 3 nm particles were in the range of those measured at other Antarctic locations at 0.2–1.1 ± 0.1 cm−3 s−1. Our investigations into the nucleation chemistry found that there were insufficient precursor concentrations for known halogen or organic chemistry to explain the nucleation event. Modelling studies utilising known sulfuric acid nucleation schemes could not simultaneously reproduce both particle formation or growth rates. Surprising correlations with Total Gaseous Mercury (TGM) were found that, together with other data, suggest a mercury driven photochemical nucleation mechanism may be responsible for aerosol nucleation. Given the very low vapour pressures of the mercury species involved, this nucleation chemistry is likely only possible where pre-existing aerosol concentrations are low and both TGM concentrations and solar radiation levels are relatively high (~ 1.5 ng m−3 and & geq 600 W m−2, respectively), such as those observed in the Antarctic sea ice boundary layer in this study or in the global free-troposphere, particularly in the Northern Hemisphere.
Publisher: Wiley
Date: 09-1997
Publisher: Informa UK Limited
Date: 1998
Publisher: American Geophysical Union (AGU)
Date: 30-03-2022
DOI: 10.1029/2021GB007121
Abstract: The equatorial Pacific is the largest oceanic source of carbon dioxide to the atmosphere. This outgassing varies depending on the El Niño‐Southern Oscillation (ENSO) and decadal climate variability. New production, the amount of phytoplankton net primary production driven by upwelled nitrate, plays a significant role in modulating air‐sea CO 2 fluxes as the biological carbon pump removes carbon from the surface ocean. We aim to understand how the physical drivers of sea surface temperature and wind speed influence interannual and decadal variability of the equatorial Pacific carbon cycle. In the equatorial Pacific, there are three biogeochemical regimes: the upwelling cold tongue east of 140°W and south of the equator (3°N–15°S) the eastern Pacific warm pool north of the equator (3°–15°N) and the 28.5°C western Pacific warm pool, west of 140°W. We find that between 2000 and 2020, air‐sea CO 2 flux and Δ p CO 2 increased in the cold tongue (45 mmolC m −2 yr −2 , 1.5 μatm yr −1 , respectively) but decreased elsewhere, while new production decreased everywhere. The western Pacific occasionally became a weak carbon sink, depending on ENSO and this sink was strongest at 165°E during central Pacific “Modoki” El Niño events. We find that changes in wind speed, temperature and ENSO frequency have altered the surface carbon budget. The mean basin‐wide (150°E−90°W and 15°N–15°S) new production for 2000–2020 was 1.2 ± 0.1 PgC yr −1 and air‐sea CO 2 flux was 0.5 ± 0.1 PgC yr −1 . New production decreased at −7.7 ± 1.6 TgC yr −2 , compared to the CO 2 flux trend of −1.7 ± 1.4 TgC yr −2 .
Publisher: American Geophysical Union (AGU)
Date: 12-2019
DOI: 10.1029/2019JC015498
Publisher: Elsevier BV
Date: 1998
DOI: 10.1016/S0026-0495(98)90202-5
Abstract: Long-chain polyunsaturated fatty acids (LCPUFAs), including docosahexaenoic acid ([DHA] 22:6 n-3), are important components of cell membranes. Low levels of DHA and other LCPUFAs in skeletal muscle membrane phospholipid are associated with insulin resistance and obesity in adults. These findings may be influenced by both dietary and genetic factors. This study aimed to investigate the interrelationships between the type of infant feeding, skeletal muscle phospholipid fatty acid (FA) composition, and glucoregulation in young children. Skeletal muscle biopsies and fasting blood s les were obtained from 56 normally nourished young children (35 males and 21 females) aged less than 2 years (mean +/- SE, 0.76 +/- 0.06) undergoing elective surgery. The dietary history was taken, and muscle phospholipid FA composition was analyzed. Subgroups of totally breast-fed and age-matched formula-fed infants were compared. Breast-fed infants (n = 13 age, 0.54 +/- 0.06 years) had a significantly higher percentage of DHA (3.63% +/- 0.22% v 1.84% +/- 0.11%, P < .0001) and total percentage of LCPUFAs (30.24 +/- 0.87% v 25.17% +/- 0.86, P < .0001) in muscle phospholipids compared with the formula-fed group (n = 12 age, 0.59 +/- 0.08 years). The totally breast-fed group had lower plasma glucose levels than the formula-fed group (4.7 +/- 0.2 v 5.4 +/- 0.2 mmol/L, P < .02). Consistent with these findings, further analysis of a group of 39 children who had either never or not recently been breast-fed showed significant inverse correlations between fasting plasma glucose and the percentage of both DHA (r = -.47, P < .003) and total LCPUFAs (r = -.38, P < .05). The results of this study show that (1) breast-feeding increases LCPUFA levels in skeletal muscle membrane and (2) early development of relatively higher levels of LCPUFAs in the phospholipid of skeletal muscle, influenced both by type of feeding and by genetic predisposition, is associated with lower fasting plasma glucose. Early changes in skeletal muscle membrane phospholipid FA saturation may play a role in the subsequent development of diseases associated with insulin resistance.
Publisher: American Geophysical Union (AGU)
Date: 07-2013
DOI: 10.1002/JGRC.20270
Publisher: Inter-Research Science Center
Date: 23-06-2016
DOI: 10.3354/MEPS11742
Publisher: American Diabetes Association
Date: 1999
DOI: 10.2337/DIABETES.48.1.112
Abstract: In adult humans, insulin resistance is associated with relatively low proportions of polyunsaturated fatty acids (PUFAs) in muscle membrane structural lipid. The aim of the present study was to determine the relationship between young children's muscle membrane fatty acid (FA) composition and indices of insulin resistance in their mothers. Muscle biopsy specimens obtained at the time of elective surgery from 83 children (54 boys), aged 0.78 +/- 0.05 year (mean +/- SE), were analyzed for phospholipid FA composition. Fasting blood s les were collected from the mothers of the children, and maternal BMIs were calculated. Stepwise multiple regression analysis showed that after accounting for the effect of breast-feeding, log maternal insulin levels were inversely associated with the child's muscle membrane docosahexaenoic acid (22:6 n-3 R2 = 0.29, P = 0.0006) and the sum of the n-3 PUFAs (R2 = 0.23, P = 0.0016) but positively associated with the sum of the n-6 PUFAs (R2 = 0.05, P = 0.03) and the n-6/n-3 PUFA ratio (R2 = 0.20, P = 0.007). Independent of breast-feeding, log maternal triglyceride levels were inversely associated with the child's muscle membrane unsaturation index (a measure of unsaturation) (R2 = 0.08, P = 0.005). Maternal BMI total, LDL, and HDL cholesterol and the child's age, sex, and birth weight were not significant predictors of the child's muscle membrane FA composition. Thus, maternal fasting insulin and triglyceride levels are significant predictors of the FA composition of the child's muscle membrane. The less unsaturated muscle membranes in children whose mothers have higher fasting insulin and triglyceride levels may reflect a genetic reluctance to incorporate PUFAs into membranes, thus predisposing them to insulin resistance syndromes.
Publisher: Wiley
Date: 13-01-2011
DOI: 10.1111/J.1529-8817.2010.00944.X
Abstract: All photosynthetic organisms endeavor to balance energy supply with demand. For sea-ice diatoms, as with all marine photoautotrophs, light is the most important factor for determining growth and carbon-fixation rates. Light varies from extremely low to often relatively high irradiances within the sea-ice environment, meaning that sea-ice algae require moderate physiological plasticity that is necessary for rapid light acclimation and photoprotection. This study investigated photoprotective mechanisms employed by bottom Antarctic sea-ice algae in response to relatively high irradiances to understand how they acclimate to the environmental conditions presented during early spring, as the light climate begins to intensify and snow and sea-ice thinning commences. The sea-ice microalgae displayed high photosynthetic plasticity to increased irradiance, with a rapid decline in photochemical efficiency that was completely reversible when placed under low light. Similarly, the photoprotective xanthophyll pigment diatoxanthin (Dt) was immediately activated but reversed during recovery under low light. The xanthophyll inhibitor dithiothreitol (DTT) and state transition inhibitor sodium fluoride (NaF) were used in under-ice in situ incubations and revealed that nonphotochemical quenching (NPQ) via xanthophyll-cycle activation was the preferred method for light acclimation and photoprotection by bottom sea-ice algae. This study showed that bottom sea-ice algae from the east Antarctic possess a high level of plasticity in their light-acclimation capabilities and identified the xanthophyll cycle as a critical mechanism in photoprotection and the preferred means by which sea-ice diatoms regulate energy flow to PSII.
Publisher: Wiley
Date: 11-02-2001
DOI: 10.1046/J.1440-1754.2001.00568.X
Abstract: We report the first described case of a first rib fracture secondary to pertussis infection. An 11-year-old boy presented with sudden onset of severe right-sided pleuritic chest pain on a background of a 6 week history of a coughing illness and considerable weight loss. Pertussis was clinically suspected and proven on serology. A cause for the severe pain was initially difficult to confirm, causing some concern regarding possible underlying pathology, but was later demonstrated to be due to a first rib fracture. The anatomy of the first rib, and the biomechanical forces placed upon it that are exacerbated during a coughing illness are described.
Publisher: Cambridge University Press (CUP)
Date: 21-10-2016
DOI: 10.1017/S0954102016000390
Abstract: This review represents the Southern Ocean community’s satellite data needs for the coming decade. Developed through widespread engagement and incorporating perspectives from a range of stakeholders (both research and operational), it is designed as an important community-driven strategy paper that provides the rationale and information required for future planning and investment. The Southern Ocean is vast but globally connected, and the communities that require satellite-derived data in the region are erse. This review includes many observable variables, including sea ice properties, sea surface temperature, sea surface height, atmospheric parameters, marine biology (both micro and macro) and related activities, terrestrial cryospheric connections, sea surface salinity, and a discussion of coincident and in situ data collection. Recommendations include commitment to data continuity, increases in particular capabilities (sensor types, spatial, temporal), improvements in dissemination of data roducts/uncertainties, and innovation in calibration/validation capabilities. Full recommendations are detailed by variable as well as summarized. This review provides a starting point for scientists to understand more about Southern Ocean processes and their global roles, for funders to understand the desires of the community, for commercial operators to safely conduct their activities in the Southern Ocean, and for space agencies to gain greater impact from Southern Ocean-related acquisitions and missions.
Publisher: Springer Science and Business Media LLC
Date: 08-04-2020
DOI: 10.1038/S41598-020-62800-7
Abstract: Antarctic krill ( Euphausia superba ) are a key component of the Antarctic food web with considerable lipid reserves that are vital for their health and higher predator survival. Krill lipids are primarily derived from their diet of plankton, in particular diatoms and flagellates. Few attempts have been made to link the spatial and temporal variations in krill lipids to those in their food supply. Remotely-sensed environmental parameters provide large-scale information on the potential availability of krill food, although relating this to physiological and biochemical differences has only been performed on small scales and with limited s les. Our study utilised remotely-sensed data (chlorophyll a and sea surface temperature) coupled with krill lipid data obtained from 3 years of fishery-derived s les. We examined within and between year variation of trends in both the environment and krill biochemistry data. Chlorophyll a levels were positively related to krill lipid levels, particularly triacylglycerol. Plankton fatty acid biomarkers analysed in krill (such as n-3 polyunsaturated fatty acids) increased with decreasing sea surface temperature and increasing chlorophyll a levels. Our study demonstrates the utility of combining remote-sensing and biochemical data in examining biological and physiological relationships between Antarctic krill and the Southern Ocean environment.
Location: Australia
No related grants have been discovered for Robert Johnson.