ORCID Profile
0000-0002-2154-4627
Current Organisation
University of Tasmania
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Central Nervous System | Biochemistry And Cell Biology Not Elsewhere Classified | Fish Pests and Diseases | Fisheries Sciences | Fish Physiology and Genetics | Fisheries Management | Neurosciences | Animal Physiology—Systems |
ANZSRC Socio-Economic Objective (SEO)
Ecosystem Assessment and Management of Fresh, Ground and Surface Water Environments | Control of Pests, Diseases and Exotic Species in Fresh, Ground and Surface Water Environments | Living resources (flora and fauna) | Nervous system and disorders | Biological sciences
Related Links
Publications
Effects of bisphenol A and fadrozole exposures on cyp19a1 expression in the murray rainbowfish, Melanotaenia fluviatilis
Publisher: Springer Science and Business Media LLC
Date: 05-06-2014
DOI: 10.1007/S00244-014-0047-1
Abstract: Several endocrine-disrupting chemicals (EDCs) have been attributed to the alteration of reproduction in fish through disrupting endogenous sex steroidogenic pathways including aromatisation of androgens to oestrogen by CYP19 aromatase. Here we investigate this hypothesis in adult male and female Melanotaenia fluviatilis by examining the mRNA expression of cyp19a1 isoforms after exposure for ≤96 h to two EDCs with contrasting modes of action: one a weak oestrogen mimic, bisphenol A [BPA (100 or 500 μg/L)], and the other a nonsteroidal aromatase inhibitor, fadrozole [FAD (10 or 50 µg/L)]. The results suggest that BPA did not affect cyp19a1a expression significantly at both concentrations, whereas 50 µg/L of FAD significantly upregulated its expression in ovary. In contrast, BPA exposures increased expression of cyp19a1b in brain of both males and females, whilst FAD had contrasting effects in brain: It increased in males but decreased in females. Similar contrasting responses of cyp19a1b were induced by BPA in gonads: upregulation in ovary and downregulation in testis. FAD did not have a significant effect on gonadal expression of cyp19a1b. Collectively, the results suggest that BPA and FAD can disrupt cyp19a1b activity more readily than can cyp19a1a, albeit with contrasting effects in either a tissue- or sex-specific context that is conceivably consistent with their (BPA and FAD) opposing modes of action. Enhanced spatial and temporal sensitivity of cyp19a1b compared with cyp19a1a suggests that brain sex of fish is more susceptible to disruption by environmental pollutants such as BPA and FAD. Therefore, we propose that the response of cyp19a1b in brain tissue of M. fluviatilis is a more suitable indicator of oestrogenic pollution in the aquatic environment.
Comparative gonad histology and semen quality of normal (XY) and neo‐males (XX) of Atlantic salmon (Salmo salar)
Publisher: Hindawi Limited
Date: 20-08-2019
DOI: 10.1111/ARE.14271
Development and evaluation of a PCR based assay for detection of the Toxic Dinoflagellate, Gymnodinium Catenatum(Graham) in ballast water and environmental samples
Publisher: Springer Science and Business Media LLC
Date: 11-2005
Effects of transgenic sterilization constructs and their repressor compounds on hatch, developmental rate and early survival of electroporated channel catfish embryos and fry
Publisher: Springer Science and Business Media LLC
Date: 04-11-2014
DOI: 10.1007/S11248-014-9846-4
Abstract: Channel catfish (Ictalurus punctatus) embryos were electroporated with sterilization constructs targeting primordial germ cell proteins or with buffer. Some embryos then were treated with repressor compounds, cadmium chloride, copper sulfate, sodium chloride or doxycycline, to prevent expression of the transgene constructs. Promoters included channel catfish nanos and vasa, salmon transferrin (TF), modified yeast Saccharomyces cerevisiae copper transport protein (MCTR) and zebrafish racemase (RM). Knock-down systems were the Tet-off (nanos and vasa constructs), MCTR, RM and TF systems. Knock-down genes included shRNAi targeting 5' nanos (N1), 3' nanos (N2) or dead end (DND), or double-stranded nanos RNA (dsRNA) for overexpression of nanos mRNA. These constructs previously were demonstrated to knock down nanos, vasa and dead end, with the repressors having variable success. Exogenous DNA affected percentage hatch (% hatch), as all 14 constructs, except for the TF dsRNA, TF N1 (T), RM DND (C), vasa DND (C), vasa N1 (C) and vasa N2 (C), had lower % hatch than the control electroporated with buffer. The MCTR and RM DND (T) constructs resulted in delayed hatch, and the vasa and nanos constructs had minimal effects on time of hatch (P < 0.05). Cadmium chloride appeared to counteract the slow development caused by the TF constructs in two TF treatments (P < 0.05). The 4 ppt sodium chloride treatment for the RM system decreased % hatch (P < 0.05) and slowed development. In the case of nanos constructs, doxycycline greatly delayed hatch (P < 0.05). Adverse effects of the transgenes and repressors continued for several treatments for the first 6 days after hatch, but only in a few treatments during the next 10 days. Repressors and gene expression impacted the yield of putative transgenic channel catfish fry, and need to be considered and accounted for in the hatchery phase of producing transgenically sterilized catfish fry and their fertile counterparts. This fry output should be considered to ensure that sufficient numbers of transgenic fish are produced for future applications and for defining repressor systems that are the most successful.
Paternal source of germ plasm determinants in the viviparous teleost, Gambusia holbrooki; dads do matter
Publisher: Elsevier BV
Date: 10-2023
Development of repressible sterility to prevent the establishment of feral populations of exotic and genetically modified animals
Publisher: Elsevier BV
Date: 05-2009
Specific amplification of mt-COI gene of the invasive gastropod Maoricolpus roseus in planktonic samples reveals a free-living larval life-history stage
Publisher: CSIRO Publishing
Date: 2005
DOI: 10.1071/MF05045
Abstract: The New Zealand screwshell Maoricolpus roseus was unintentionally introduced to south-eastern Tasmania in the 1920s. It has colonised more habitat than any other high-impact benthic marine pest in Australia and its wide temperature and depth tolerance makes further spread likely. We developed three sets of genetic probes, each targeting a unique region in the mitochondrial COI locus, for the rapid detection of this species in mixed plankton s les. In particular, we wanted to know whether this species has a planktonic life-history stage that could lead to its dispersal in ships’ ballast water. All probe sets were tested against as many closely related species as could be obtained and the reaction conditions were optimised for maximum sensitivity and specificity of M. roseus. Plankton s les collected in the Derwent Estuary between August 2003 and June 2004 were tested with the probes using a nested polymerase chain reaction. Maoricolpus roseus was detected in the plankton s les especially in the spring–summer period. The presence of M. roseus in the plankton and water available for ships’ ballast indicates that the risk of this species being spread by shipping needs to be managed.
Suppression and restoration of primordial germ cell marker gene expression in channel catfish, Ictalurus punctatus, using knockdown constructs regulated by copper transport protein gene promoters: Pot
Publisher: Elsevier BV
Date: 12-2015
DOI: 10.1016/J.THERIOGENOLOGY.2015.07.037
Abstract: Complementary DNA overexpression and short hairpin RNA interference approaches were evaluated for decreasing expression of primordial germ cell (PGC) marker genes and thereby sterilizing channel catfish, Ictalurus punctatus, by delivering knockdown constructs driven by a constitutive promoter from yeast and a copper transport protein gene into fish embryos by electroporation. Two PGC marker genes, nanos and dead end, were the target knockdown genes, and their expressions, along with that of an off-target gene, vasa, were evaluated temporally using real-time polymerase chain reaction. Copper sulfate was evaluated as a repressor compound. Some of the constructs knocked down PGC marker gene expression, and some of the constructs were partially repressed by application of 0.1-ppm copper sulfate. When the rate of sexual maturity was compared for three-year-old broodfish that had been exposed to the sterilizing constructs during embryologic development and controls that had not been exposed, several treatments had reduced sexual maturity for the exposed fish. Of two promoter systems evaluated, the one which had been designed to be less sensitive to copper generally was more effective at achieving sterilization and more responsive to repression. Knockdown constructs based on 3' nanos short hairpin RNA interference appeared to result in the best repression and restoration of normal sexual maturity. We conclude that these copper-based systems exhibited good potential for repressible transgenic sterilization. Optimization of this system could allow environmentally safe application of transgenic technology and might be applicable to other applications for aquatic organisms.
Effects of exposure to oestrogenic compounds on aromatase gene expression are gender dependent in the rainbowfish, Melanotaenia fluviatilis
Publisher: Elsevier BV
Date: 03-2013
DOI: 10.1016/J.CBPC.2012.11.004
Abstract: This study investigated the influence of two endocrine disrupting chemicals (EDCs)-an exogenous oestrogen 17β-estradiol (E2) and the oestrogen mimic 4-n-nonylphenol (NP) on the expression of aromatase transcripts in both sexes of adult Murray river rainbowfish. Reproductively active mature fish were exposed to 1, 3, and 5 μg/L E2 or 100 and 500μg/L NP for 24, 48, 72 and 96 h. The results show a significant reduction in the expression of cyp19a1a isoform in ovarian tissues with complete inhibition at the higher concentrations (3 and 5 μg/L E2 500μg/L NP between 24 and 72 h) and at all concentrations after 96 h. There was no expression of the cyp19a1a isoform in female brain, male brain or testes in any treatment. E2 significantly increased expression of cyp19a1b in female brain except at 5 μg/L after 24h exposure. In male brain tissue E2 exposure decreased cyp19a1b expression except at 1 and 5 μg/L at 24h. NP significantly upregulated cyp19a1b in the female brain (except with 500 μg/L at 72 h) and in testes tissues. NP downregulated expression of cyp19a1b in the male brain tissue. Collectively, these observations support the hypothesis that the expression of cyp19a1b is regulated via both positive and negative feedback mechanisms, with differential modulation based on the type and concentration of the exposed oestrogens, duration of exposure, fish tissue and gender of the fish. The results also imply that exogenous oestrogens can have a disruptive effect on the steroidogenic pathway and may lead to effects on sex differentiation, sexual behaviour and reproductive cycles in this fish.
Reproductive viability of paradoxically masculinised Gambusia holbrooki generated following diethylstilbestrol (DES) treatment
Publisher: Elsevier BV
Date: 10-2020
Validation of mark-recapture population estimates for invasive common carp, Cyprinus carpio, in Lake Crescent, Tasmania
Publisher: Hindawi Limited
Date: 02-11-2012
A novel testicular degenerative condition in a wild population of the common carp Cyprinus carpio (L)
Publisher: Wiley
Date: 14-07-2020
DOI: 10.1111/JFD.13216
Stages of embryonic development in the live-bearing fish, Gambusia holbrooki.
Publisher: Wiley
Date: 26-06-2022
DOI: 10.1002/DVDY.388
Abstract: Divergent morphology and placentation of Poeciliids make them suitable model for investigating how evolutionary selection has altered and conserved the developmental mechanisms. However, there is limited description of their embryonic staging, despite representing a key evolutionary node that shares developmental strategy with placental vertebrates. Here, we describe the embryonic developmental stages of Gambusia holbrooki from zygote to parturition using freshly harvested embryos. We defined 40 embryonic stages using a numbered (stages 0-39 zygote to parturition, respectively) and named (grouped into seven periods, ie, zygote, cleavage, blastula, gastrula, segmentation, pharyngula, and parturition) staging system. Two sets of quantitative (ie, egg diameter, embryonic total length, otic vesicle closure index, heart rates, the number of caudal fin rays and elements) and qualitative (ie, three-dimensional analysis of images and key morphological criteria) data were acquired and used in combination to describe each stage. All 40 stages are separated by well-defined morphological traits, revealing developmental novelties that are influenced by narrow perivitelline space, placentation, internal gestation, and sex differentiation. The principal diagnostic features described are quick, reliable, and easy to apply. This system will benefit researchers investigating molecular ontogeny, particularly sexual differentiation mechanisms in G. holbrooki.
Peripheral olfactory structures and maturity-related crypt receptor neuron kinetics in the olfactory epithelium of carp Cyprinus carpio (L.): Implications for carnal vulnerability and pest management
Publisher: CSIRO Publishing
Date: 2018
DOI: 10.1071/MF17386
Abstract: Carnal vulnerability is a powerful yet underutilised tool in integrated pest management. The lack of species-specific knowledge of underpinning sexual drivers and mechanisms for their detection has precluded efficient exploitation of the vulnerability. As a step in understanding how mature common carp Cyprinus carpio communicate and attract conspecifics, the present study undertook anatomical and histological examinations of the olfactory system, tracing changes in crypt receptor neurons (CRNs) within the olfactory rosette in relation to gonadal development, as proxy. Quantification of the density and relative position of CRNs in the lamellae revealed that their density increases significantly with sexual maturity in both males and females (P .001). In contrast, the CRNs were concentrated in the basal and surface layers of the epithelium (P .001) in females and males respectively, suggesting a sex-specific deployment and mobilisation of CRNs with the onset of maturity. This suggests that the mature males are likely equipped to detect and respond to pheromones more rapidly than females, triggering courtship behaviours such as mate pursuit that are generally associated with mature males. This maturity-driven CRN proliferation and mobilisation reveals a susceptibility, particularly of male C. carpio, to carnal lure and capture that could be exploited in pest management programs.
Ontogenic and sexually dimorphic expression of cyp19 isoforms in the rainbowfish, Melanotaenia fluviatilis (Castelnau 1878)
Publisher: Elsevier BV
Date: 02-2012
DOI: 10.1016/J.CBPA.2011.11.006
Abstract: To investigate the role of cytochrome P450 aromatase, we isolated cyp19 isoforms in the Murray River rainbowfish, M. fluviatilis. The cloned cDNA for cyp19a1a and cyp19a1b had an open reading frame (ORF) of 492 and 499 amino acid residues, with shared identity of up to 83% and 87% with the corresponding homologues of other teleosts respectively. In contrast, the cyp19a1a and cyp19a1b of the Murray River rainbowfish had a shared identity of only 61%. Not surprisingly, the phylogenetic analysis clustered the M. fluviatilis cyp19 isoforms with the corresponding isoforms of other teleosts, suggesting a shared evolutionary ancestry of the respective isoforms. We also studied the expression of cyp19 isoforms during ontogeny and in adult fish using quantitative Real-Time PCR (qPCR). Results suggest that uniquely only cyp19a1b transcripts are maternally inherited, suggesting its role in early development and growth in the species. In contrast to reports in many teleosts, the cyp19a1a was exclusively expressed in the ovarian tissue and completely absent in other tissues examined, including testis. The cyp19a1b like in most teleosts was predominantly expressed in the brain of both males and females with low level of expression in other tissues including gonads of both sexes.
Primordial Germ Cell Development in the Poeciliid, Gambusia holbrooki, Reveals Shared Features Between Lecithotrophs and Matrotrophs.
Publisher: Frontiers Media SA
Date: 03-2022
DOI: 10.3389/FCELL.2022.793498
Abstract: Metazoans exhibit two modes of primordial germ cell (PGC) specification that are interspersed across taxa. However, the evolutionary link between the two modes and the reproductive strategies of lecithotrophy and matrotrophy is poorly understood. As a first step to understand this, the spatio-temporal expression of teleostean germ plasm markers was investigated in Gambusia holbrooki , a poecilid with shared lecitho- and matrotrophy. A group of germ plasm components was detected in the ovum suggesting maternal inheritance mode of PGC specification. However, the strictly zygotic activation of dnd-β and nanos1 occurred relatively early, reminiscent of models with induction mode ( e.g., mice). The PGC clustering, migration and colonisation patterns of G. holbrooki resembled those of zebrafish, medaka and mice at blastula, gastrula and somitogenesis, respectively—recapitulating features of advancing evolutionary nodes with progressive developmental stages. Moreover, the expression domains of PGC markers in G. holbrooki were either specific to teleost ( vasa expression in developing PGCs), murine models ( dnd spliced variants) or shared between the two taxa (germline and somatic expression of piwi and nanos1 ). Collectively, the results suggest that the reproductive developmental adaptations may reflect a transition from lecithotrophy to matrotrophy.
Embryonic Onset of Sexually Dimorphic Heart Rates in the Viviparous Fish, Gambusia holbrooki
Publisher: MDPI AG
Date: 08-02-2021
DOI: 10.3390/BIOMEDICINES9020165
Abstract: In fish, little is known about sex-specific differences in physiology and performance of the heart and whether these differences manifest during development. Here for the first time, the sex-specific heart rates during embryogenesis of Gambusia holbrooki, from the onset of the heart rates (HRs) to just prior to parturition, was investigated using light cardiogram. The genetic sex of the embryos was post-verified using a sex-specific genetic marker. Results reveal that heart rates and resting time significantly increase (p 0.05) with progressive embryonic development. Furthermore, both ventricular and atrial frequencies of female embryos were significantly higher (p 0.05) than those of their male sibs at the corresponding developmental stages and remained so at all later developmental stages (p 0.05). In concurrence, the heart rate and ventricular size of the adult females were also significantly (p 0.05) higher and larger respectively than those of males. Collectively, the results suggest that the cardiac sex-dimorphism manifests as early as late-organogenesis and persists through adulthood in this species. These findings suggest that the cardiac measurements can be employed to non-invasively sex the developing embryos, well in advance of when their phenotypic sex is discernible. In addition, G. holbrooki could serve as a better model to study comparative vertebrate cardiovascular development as well as to investigate anthropogenic and climatic impacts on heart physiology of this species, that may be sex influenced.
Masculinization of Adult Gambusia holbrooki: A Case of Recapitulation of Protogyny in a Gonochorist?
Publisher: MDPI AG
Date: 30-04-2022
Abstract: 17α-Methyltestosterone (MT) is a synthetic steroid that has been widely used to masculinize many fish species when administered early during larval development, however, reports on its efficacy on adults is limited. To this end, this study investigated the efficacy of MT in the masculinization of the eastern mosquitofish (G. holbrooki) at two adult stages (maiden and repeat gravid females). The treated females were fed control or respective MT incorporated feed (0–200 mg/kg diet) for 50 days. Effects of the hormone on secondary sexual characteristics, internal gonad morphology, expression of the Anti-Müllerian Hormone (amh) gene and sexual behavior of the treated females were investigated. The results showed that MT at the dose of 50 mg/kg feed stimulated secondary sexual character development, upregulated expression of amh, formation of testicular tissue and a shift in the behavior similar to those of normal males, prominently so in treated maiden gravid females. Post-treatment, long-term observations indicated that only two masculinized females reverted back to being females and gave birth to young. Induction of masculinizing effects in most in iduals suggests that the sexual phenotype of this species appears to be highly plastic with potential to sex reverse at adulthood. This in combination with its small size and short reproductive cycle could provide an ideal system to explore the mechanisms of sequential hermaphroditism in fish and contribute to genetic control of this pest fish.
A compact cartilaginous fish model genome
Publisher: Elsevier BV
Date: 02-2005
Sex biased expression of anti-Mullerian hormone (amh) gene in a live bearing fish, Gambusia holbrooki: Evolutionary implications and potential role in sex differentiation
Publisher: Elsevier BV
Date: 05-2019
DOI: 10.1016/J.CBPB.2019.02.004
Abstract: The amh, a member of transforming growth factor-β (TGF-β) family, is known to play a critical role in vertebrate male sex differentiation, with its paralogue/s evolving to determine sex in few heterogametic (XX/XY) teleosts. However, it remains relatively unexplored in the reproductively unique live bearing teleosts. Therefore, this study comparatively examined the structure and content of G. holbrooki amh as well as characterised its expression. A paralogous Y-specific amh (amhy) was not detected, suggesting an unlikely role in sex determination. Two transcripts (1.4 and 1.5 kb) were detected in adults: the larger (1.5 kb) retaining intron 5, coding for a truncated AMH-N and no TGF-β domain. The small (1.4 kb) transcript, had both domains intact and clustered with members of Poeciliidae. In contrast to other vertebrates, a higher conservation between the N- rather than the C- terminus of amh in Poeciliidae was observed, suggesting an adaptation that may be unique to live bearing teleosts. The amh expression was 6 times higher in brain of both sexes and testis compared with ovaries (p = .001). Intriguingly, female splenic tissues showed 10 times higher expression (p = .006) and such female bias splenic expression has not been reported in any teleosts. Ontogenic expression was 25 times higher in male embryos at gastrulation stage (p = .001), much earlier than those reported in egg-laying teleosts. Such heightened expression in male embryos suggests a repressive role associated with proliferation and migration of primordial germ cells (PGCs) that are known to occur earlier at blastulation in teleosts-potentially influencing gonadal fate.
Exposure to Estrogenic Chemicals Induces Ectopic Expression of vtg in the Testis of Rainbowfish, Melanotaenia fluviatilis
Publisher: Springer Science and Business Media LLC
Date: 10-08-2013
DOI: 10.1007/S00128-013-1078-4
Abstract: Vitellogenin (Vtg) is the major egg-yolk precursor protein in oviparous organisms normally synthesised only in mature females. In males and juveniles, the vtg gene, although present, is silent, but its hepatic expression may be activated by xenoestrogens. Surprisingly, its induction and potential consequences in non-hepatic tissues remain unexplored. Here we test the hepatic and testicular response of vtg expression in adult male rainbowfish Melanotaenia fluviatilis exposed to either 1, 3, 5 μg/L 17β-estradiol or 100, 500 μg/L 4-n-nonylphenol for 24-96 h. Significant increase in the expression level of vtg mRNA in the liver and testes of exposed males was observed. The early (24 h), sensitive and reliable detection of the vtg induction using qPCR demonstrates the assay's robustness to monitor xenobiotic exposure particularly in smaller fish like rainbowfish, an emerging indicator species. Whilst, the ectopic induction of vtg mRNA in testes suggests a more complex Vtg pathway.
Daily ageing to delineate population dynamics of the invasive fish Gambusia holbrooki: implications for management and control
Publisher: Springer Science and Business Media LLC
Date: 04-2021
Development and evaluation of a PCR-based test for detection of Asterias (Echinodermata:Asteroidea) larvae in Australian plankton samples from ballast water
Publisher: CSIRO Publishing
Date: 2003
DOI: 10.1071/MF03031
Abstract: The northern Pacific seastar, Asterias amurensis, spread to Tasmania in the 1980s from its native range in the North Pacific. The seastar has subsequently established in Port Phillip Bay on mainland Australia. Transportation of larvae in ballast water is one vector for these introductions and is likely to contribute to additional range expansion of this species. Larval identification methods are critical to assess risks of further transport to uninvaded ecosystems however, morphological identification of larval asteroids is impractical and unreliable. Therefore, we have developed a sensitive PCR-based method that specifically detects Asterias DNA. The method works on isolated seastar larva, mixed plankton and ballast water s les. Trials using uninfected ballast water s les spiked with known numbers of A. amurensis larvae indicate that the technique can detect single larva in 200 mg of plankton. The test also detects other Asterias species therefore, discrimination between seastars within the genus Asterias was accomplished using denaturing gradient gel electrophoresis (DGGE). Currently, this method is being used to facilitate research on ballast water transport, distribution and the ecology of A. amurensis larvae. The general approach can be expanded to provide a rapid and cost-effective approach for detecting a suite of marine species in ballast water and environmental s les.
Use of melatonin as an inhibitor of apoptotic process for cryopreservation of zebrafish (Danio rerio) embryos
Publisher: FapUNIFESP (SciELO)
Date: 2022
Abstract: Abstract This study investigated the use of melatonin to arrest the effects of apoptosis in vitrified zebrafish (D. rerio) embryos. Dechorionated embryos at 22-24 somite-stage were ided (n = 60/treatment) into a non-vitrified (Control Group, 0 M melatonin) and vitrified treatments with 0 M (T1), 1 µM (T2) and 1 mM of melatonin (T3). For vitrified treatments, a solution methanol ropylene glycol based was used and the embryos stored in -196 °C for a week. After thaw, survival rate, scanning electron microscopy, expression of anti (bcl-2) and pro-apoptotic (bax/caspase-3) genes, reactive oxygen species (ROS) formation and DNA fragmentation analyses were performed. No live embryos were obtained from vitrified treatments, observing a rapid degeneration immediately after thawing, with the vitelline layer rupture and leakage of its content, followed by breakdown of epithelial cells and melanisation of the tissue. Regarding the apoptotic process, T3 had the highest relative gene expression, for the three genes (P 0.05) furthermore, T2 had similar expression of pro-apoptotic genes to CG (P 0.05). ROS formation revealed that CG presented lower percentage of embryo surface area affected (3.80 ± 0.40%) (P 0.05), in contrast, no differences were found among the other groups. T1 was most significantly (P 0.05) damaged by DNA fragmentation. The vitrified groups with melatonin had similar damage levels of CG (P 0.05). The inclusion of 1 µM of melatonin in the vitrifying solution, countered the effects of apoptotic process in post-thaw embryos, suggesting its utility in cryopreserving fish embryos.
Distinct cytochrome P450 aromatase isoforms in the common carp (Cyprinus carpio): Sexual dimorphism and onset of ontogenic expression
Publisher: Elsevier BV
Date: 05-2008
DOI: 10.1016/J.YGCEN.2008.03.013
Abstract: Cytochrome P450 aromatase (CYP19) is a key enzyme in the steroidogenic pathway that catalyses the conversion of testosterone to estrogen, and therefore is thought to influence gonadal sex differentiation. In an effort to understand the role of this enzyme in ovarian differentiation, we isolated cDNA encoding the two distinct isoforms, ovarian and brain (termed cyp19a and cyp19b, respectively) of adult common carp, Cyprinus carpio. The cloned cDNA for cyp19a had an open reading frame (ORF) of 518 amino acid residues, in contrast to cyp19b with an ORF of 511 amino acids. Sequence and phylogenetic analysis showed that these CYP19 isoforms were orthologous with previously described cyp19a and cyp19b from other teleosts. Quantitative real-time PCR indicated that both isoforms are expressed in adult ovary and brain, with predominant expression of cyp19a in the ovary and cyp19b in the brain. The major aromatase expressing tissue was found to be the brain, with greatest cyp19b expression in the anterior quarter (telencephalon) in both sexes. The gonad showed sexually dimorphic expression of both genes and dimorphic expression of cyp19a was observed in the cerebellum and the liver. Ontogenic expression showed that only the ovarian aromatase transcript is inherited maternally, with lower expression observed through early larval development under warmer rearing conditions. The differential and overlapping expression suggests these two aromatase genes have different roles in reproductive physiology.
Light-cardiogram, a simple technique for heart rate determination in adult zebrafish, Danio rerio
Publisher: Elsevier BV
Date: 08-2020
Part 4: Advanced life support
Publisher: Elsevier BV
Date: 10-2015
Temperature Management After Cardiac Arrest
Publisher: Elsevier BV
Date: 2016
DOI: 10.1016/J.RESUSCITATION.2015.09.396
Abstract: For more than a decade, mild induced hypothermia (32 °C-34 °C) has been standard of care for patients remaining comatose after resuscitation from out-of-hospital cardiac arrest with an initial shockable rhythm, and this has been extrapolated to survivors of cardiac arrest with initially nonshockable rhythms and to patients with in-hospital cardiac arrest. Two randomized trials published in 2002 reported a survival and neurological benefit with mild induced hypothermia. One recent randomized trial reported similar outcomes in patients treated with targeted temperature management at either 33 °C or 36 °C. In response to these new data, the International Liaison Committee on Resuscitation Advanced Life Support Task Force performed a systematic review to evaluate 3 key questions: (1) Should mild induced hypothermia (or some form of targeted temperature management) be used in comatose post-cardiac arrest patients? (2) If used, what is the ideal timing of the intervention? (3) If used, what is the ideal duration of the intervention? The task force used Grading of Recommendations Assessment, Development and Evaluation methodology to assess and summarize the evidence and to provide a consensus on science statement and treatment recommendations. The task force recommends targeted temperature management for adults with out-of-hospital cardiac arrest with an initial shockable rhythm at a constant temperature between 32 °C and 36 °C for at least 24 hours. Similar suggestions are made for out-of-hospital cardiac arrest with a nonshockable rhythm and in-hospital cardiac arrest. The task force recommends against prehospital cooling with rapid infusion of large volumes of cold intravenous fluid. Additional and specific recommendations are provided in the document.
Sterile 'Judas' carp-Surgical sterilisation does not impair growth, endocrine and behavioural responses of male carp
Publisher: Elsevier BV
Date: 09-2015
DOI: 10.1016/J.YGCEN.2015.03.005
Abstract: Use of 'Judas' fish to betray the locations of conspecifics is a powerful tool in management of invasive pest fish but poses a risk of contributing to recruitment. Our aim therefore was to generate surgically sterilised male common carp (Cyprinus carpio) and test whether they readily assimilate into wild populations, retain sexual behaviour and successfully betray the locations of feral carp. Male common carp were surgically sterilised (n=44) adopting a two-point nip technique, using either a haemoclip, suture or electro cautery to tie each of the testicular ducts about 2.5 cm cranial to urogenital sinus-retaining all of the glandular testis tissue. Observed survival (95%) and success (>70%) rates were relatively high. Plasma steroids (11-keto testosterone and 17β-estradiol) were quantified by immunoassay. A subset of sterile and control male fish (n=7 each) were implanted with radio-transmitters and released into Lake Sorell (50 km(2)) and their ability to betray the location of feral carp was assessed by radio tracking and targeted fishing. There was a statistically significant difference in 11-keto testosterone and 17β-estradiol levels over time (P 0.05), implying that surgery did not compromise the animals physiologically. The sterile Judas fish integrated well into the population-behaving similarly to control Judas males and assisted in the capture of feral carp. The study marks a significant breakthrough in the management of this pest fish with potential adoption to the management of other pest fish globally.
Gravid spot predicts developmental progress and reproductive output in a livebearing fish, Gambusia holbrooki
Publisher: Public Library of Science (PLoS)
Date: 25-01-2016
Efficacy of estradiol in feminising the eastern mosquitofish, Gambusia holbrooki: advance towards developing a genetic control option
Publisher: CSIRO Publishing
Date: 27-07-2021
DOI: 10.1071/MF21104
Abstract: As a first step towards developing genetic option to control pest populations of Gambusia holbrooki, this study investigated the efficacy of oestradiol (E2) to feminise the species. The oestrogen was administered orally via food to neonates (Experiment 1) or embryos through gravid females (Experiment 2) at dosage between 50 and 400 mg kg–1 of feed. Two control groups consisted of (C1) normal feed and (C2) feed mixed with 70% ethanol. In Experiment 1, 100% feminisation was observed at all E2 concentrations except at 400 mg kg–1 where no treated in iduals survived. There was a significantly (P 0.05) lower mean survival rate (MSR) of all E2-treated juveniles than of controls (C1: 71.73 ± 22.86% C2: 70.02 ± 18.26%), with 50 mg kg–1 showing the best MSR (66.38 ± 12.34%). In Experiment 2, 100% feminisation was achieved at E2 concentrations of 200–400 mg kg–1 food, with the best MSR (59.33 ± 12.54%) at 200 mg kg–1 concentration, which was, however, significantly lower than in control groups (C1: 79.96 ± 20.33% C2: 77.09 ± 10.32%). The reproductive output and gestation period of gravid females were not affected by E2 exposure. The outcomes provide a framework for reliable sex reversal (feminisation) in this fish, paving way for developing genetic strategies to manage and eradicate this pest fish.
Gonad Ontogeny and Sex Differentiation in a Poeciliid, Gambusia holbrooki: Transition from a Bi- to a Mono-Lobed Organ
Publisher: MDPI AG
Date: 16-05-2023
Abstract: Despite their uniqueness, the ontogeny and differentiation of the single-lobed gonads in the poeciliids are very poorly understood. To address this, we employed both cellular and molecular approaches to systematically map the development of the testes and ovary in Gambusia holbrooki from pre-parturition to adulthood, encompassing well over 19 developmental stages. The results show that putative gonads form prior to the completion of somitogenesis in this species, a comparatively early occurrence among teleosts. Remarkably, the species recapitulates the typical bi-lobed origin of the gonads during early development that later undergoes steric metamorphosis to form a single-lobed organ. Thereafter, the germ cells undergo mitotic proliferation in a sex-dependent manner before the acquisition of the sexual phenotype. The differentiation of the ovary preceded that of the testes, which occurred before parturition, where the genetic females developed meiotic primary oocytes stage I, indicating ovarian differentiation. However, genetic males showed gonial stem cells in nests with slow mitotic proliferation at the same developmental stage. Indeed, the first signs of male differentiation were obvious only post-parturition. The expression pattern of the gonadosoma markers foxl2, cyp19a1a, amh and dmrt1 in pre- and post-natal developmental stages were consistent with morphological changes in early gonad they were activated during embryogenesis, followed by the onset of gonad formation, and a sex-dimorphic expression pattern concurrent with sex differentiation of the ovary (foxl2, cyp19a1a) and testes (amh and dmrt1). In conclusion, this study documents for the first time the underlying events of gonad formation in G. holbrooki and shows that this occurs relatively earlier than those previously described for ovi- and viviparous fish species, which may contribute to its reproductive and invasive prowess.
Excess respiratory mortality and hospitalizations associated with influenza in Australia, 2007–2015
Publisher: Oxford University Press (OUP)
Date: 08-2021
DOI: 10.1093/IJE/DYAB138
Abstract: Influenza is the most common vaccine-preventable disease in Australia, causing significant morbidity and mortality. We assessed the burden of influenza across all ages in terms of influenza-associated mortality and hospitalizations using national mortality, hospital-discharge and influenza surveillance data. Influenza-associated excess respiratory mortality and hospitalization rates from 2007 to 2015 were estimated using generalized additive models with a proxy of influenza activity based on syndromic and laboratory surveillance data. Estimates were made for each age group and year. The estimated mean annual influenza-associated excess respiratory mortality was 2.6 per 100 000 population [95% confidence interval (CI): 1.8, 3.4 per 100 000 population]. The excess annual respiratory hospitalization rate was 57.4 per 100 000 population (95% CI: 32.5, 82.2 per 100 000 population). The highest mortality rates were observed among those aged ≥75 years (35.11 per 100 000 population 95% CI: 19.93, 50.29 per 100 000 population) and hospitalization rates were also highest among older adults aged ≥75 years (302.95 per 100 000 population 95% CI: 144.71, 461.19 per 100 000 population), as well as children aged & months (164.02 per 100 000 population 95% CI: –34.84, 362.88 per 100 000 population). Annual variation was apparent, ranging from 1.0 to 3.9 per 100 000 population for mortality and 24.2 to 94.28 per 100 000 population for hospitalizations. Influenza A contributed to almost 80% of the average excess respiratory hospitalizations and 60% of the average excess respiratory deaths. Influenza causes considerable burden to all Australians. Expected variation was observed among age groups, years and influenza type, with the greatest burden falling to older adults and young children. Understanding the current burden is useful for understanding the potential impact of mitigation strategies, such as vaccination.
Specific Detection of Pacific Oyster (Crassostrea Gigas) Larvae in Plankton Samples Using Nested Polymerase Chain Reaction
Publisher: Springer Science and Business Media LLC
Date: 02-2005
DOI: 10.1007/S10126-004-0034-Z
Abstract: Management of sustainable Pacific oyster fisheries would be assisted by an early, rapid, and accurate means of detecting their planktonic larvae. Reported here is an approach, based on polymerase chain reaction (PCR), for the detection of Pacific oyster larvae in plankton s les. Species-specific primers were designed by comparing partial mitochondrial cytochrome oxidase subunit I (COI) sequences from Crassostrea gigas, with other members of the family Ostreidae including those of Crassostrea angulata. Assay specificity was empirically validated through screening DNA s les obtained from several species of oysters. The assay was specific as only C. gigas s les returned PCR-positive results. A nested PCR approach could consistently detect 5 or more D-hinge-stage larvae spiked into a background of about 146 mg of plankton. The assay does not require prior sorting of larvae. We conclude that the assay could be used to screen environmental and ballast water s les, although further specificity testing against local bivalve species is recommended in new locations.
Tissue and sexually dimorphic expression of ovarian and brain aromatase mRNA in the Japanese medaka (Oryzias latipes): Implications for their preferential roles in ovarian and neural differentiation a
Publisher: Elsevier BV
Date: 08-2008
DOI: 10.1016/J.YGCEN.2008.05.016
Abstract: Cytochrome P450 aromatase (CYP19) catalyzes conversion of testosterone to estrogen, and is thought to influence neural and reproductive development in vertebrates. Unlike higher vertebrates, many teleost fish, including the medaka (Oryzias latipes) have two aromatase genes, one expressed predominantly in the ovary (cyp19a) and the other in the brain (cyp19b). However, the exact roles of the two aromatase genes in neural or ovarian development in fish are unclear. The primary objective of this study was to determine the pattern of expression of each of the genes in developing and adult medaka. Real-time PCR analysis indicated that both isoforms are expressed in adult ovary and brain, with predominant expression of cyp19a in the ovary and cyp19b in the brain. cyp19a was expressed at significantly higher levels in ovaries than in testes, whereas cyp19b was expressed at higher levels in the adult brain of females than males. Ontogenic expression showed that neither of the aromatase transcripts is inherited maternally, with onset of zygotic expression of both isoforms occurring just prior to hatching (stage 39). Also the expression of the ovarian, but not the brain, isoform was significantly higher in genetically female in iduals than in males of similar developmental stage. This coincided with the known increased proliferation of germ cells in XX genotypes, suggesting a possible role for cyp19a in ovarian differentiation. Differential expression of both isoforms in adults and during early larval development suggests that the genes have distinctly different roles: cyp19a contributing predominantly to ovarian differentiation and development and cyp19b contributing towards neural development and perhaps sexual behavior in adults.
Human liver-derived cells stably modified for regulated proinsulin secretion function as bioimplantsin vivo
Publisher: Wiley
Date: 2002
DOI: 10.1002/JGM.263
Abstract: Insulin deficiency is currently treated with pharmacological insulin secretagogues, insulin injections or islet transplants. Secondary failure of pharmacological agents is common insulin injections often fail to achieve euglycemic control and islet transplants are rare. Non-beta cells capable of regulated insulin secretion in vivo could be a functional cure for diabetes. Hepatocytes are good candidates, being naturally glucose-responsive, protein-secreting cells, while the liver is positioned to receive direct nutrient signals that regulate insulin production. Human liver-derived Chang cells were modified with a plasmid construct in which a bifunctional promoter comprising carbohydrate response elements and the human metallothionein IIA promoter controlled human proinsulin cDNA expression. Secretory responses of stable cell clones were characterized in vitro and in vivo by proinsulin radioimmunoassay. Transfected Chang cells secreted 5-8 pmol proinsulin/10(6) cells per 24 h in continuous passage for at least a year in response to 5-25 mM glucose and 10-90 microM zinc in vitro. Glucose and zinc synergistically increased proinsulin production by up to 30-fold. Non-glucose secretagogues were also active. Glucose transporter 2 (GLUT2) and glucokinase cDNA co-transfection enhanced glucose responsiveness. Intraperitoneally implanted Chang cells secreted proinsulin in scid and Balb/c mice. Serum proinsulin levels were further increased 1.3-fold (p<0.05) after glucose and 1.4- to 1.6-fold (p<0.005) after zinc administration in vivo. These results are the first to demonstrate stable proinsulin production in a human liver-derived cell line with activity in vitro and in vivo and provide a basis for engineering hepatocytes as in vivo bioimplants for future diabetes treatment.
Eradication of the Invasive Common Carp, Cyprinus carpio from a Large Lake: Lessons and Insights from the Tasmanian Experience
Publisher: MDPI AG
Date: 23-02-2021
Abstract: Common carp (Cyprinus carpio, L. 1758) are the most abundant pest fish species in Australia, detrimental to ecosystem integrity and values, and in need of suitable management solutions. In January 1995, this destructive pest was discovered in two large, connected Tasmanian lakes—Lakes Crescent (23 km2) and Sorell (54 km2). After an initial assessment, carp were immediately contained to these waters using screens to prevent their escape down-stream, followed by swift legislation to enforce closure of the lakes to the public. Assessment and evaluation of carp numbers occurred throughout the eradication program, with effort focused on Lake Crescent. Beginning with undirected removal, techniques progressively evolved to more sophisticated targeted removal with assistance from biotelemetry, in conjunction with gill netting and electro-fishing. Real-time population estimates and in situ observations resulted in a detailed cumulative understanding of carp population dynamics, behaviour and seasonal habitat choice. This allowed strategic deployment of fences to block access to marshes, and the installation of steel traps within the fences. These gears specifically prevented spawning opportunities, while concurrently capturing mature fish. Following 12 years of adaptive and integrated effort, 7797 carp (fry, juvenile and adult) were captured from Lake Crescent, with the last carp being caught in December 2007. The subsequent 14 years of monitoring has not resulted in the capture of any carp, confirming the successful eradication of carp from Lake Crescent. These management practices have been successfully replicated in the larger Lake Sorell, where 41,499 carp (fry, juvenile and adult) have been removed. It is now estimated that there are few, if any carp remaining. Collectively, the techniques and strategies described here were reliable, and can be applied as a model to control or eradicate pest populations of carp in freshwater lakes elsewhere.
Nuclear internalization of foreign DNA by zebrafish spermatozoa and its enhancement by electroporation
Publisher: Wiley
Date: 02-1996
DOI: 10.1002/(SICI)1097-010X(19960201)274:2<121::AID-JEZ5>3.0.CO;2-R
Abstract: From the socio-critical perspective of mathematical modeling, reflexive discussions about the nature, criteria, and consequences of mathematical models are not a natural consequence of modeling in school. This report is part of a larger study focused on stimulating reflexive discussions in practice employing constructivist grounded theory as a research method. Twenty-seven college algebra students engaged in a 3-week modeling project at a community college in the USA. Audio-recorded group discussions and written reflections were collected to determine how reflexive discussions were taking place. Analysis of students' actions and reflexive discussions during the modeling project produced four concepts:
Exploiting seasonal habitat use of the common carp, Cyprinus carpio, in a lacustrine system for management and eradication
Publisher: CSIRO Publishing
Date: 2012
DOI: 10.1071/MF11252
Abstract: The control of invasive species is a major challenge to the preservation of native ecosystems, both terrestrial and aquatic. A population of the invasive common carp, Cyprinus carpio, was detected in Lakes Sorell and Crescent, Tasmania, Australia, in the mid-1990s. Early detection allowed for the containment of their population to this lacustrine system. Radio-telemetry was subsequently used over a 5-year period to understand seasonal distribution of carp in relation to environmental parameters to guide efficient eradication strategies. The present study found that fish displayed increased mobility during spring–summer periods, moving into shallow habitat rich in macrophytes, particularly during years of high lake levels. During years of low lake levels, this pattern was altered with frequent use of a rocky ‘secondary’ habitat in Lake Sorell. During winter, carp congregated in deeper habitat in Lake Sorell, whereas no habitat-specific winter aggregations were found in Lake Crescent. The increased knowledge of spatio-temporal preferences of carp provided a basis for deploying barriers to facilitate the capture of fish and sabotage spawning events. The results have led to the eradication of carp from Lake Crescent and a significant reduction of their population in Lake Sorell.
Expression and knockdown of primordial germ cell genes, vasa, nanos and dead end in common carp (Cyprinus carpio) embryos for transgenic sterilization and reduced sexual maturity
Publisher: Elsevier BV
Date: 2014
Sex steroids have opposing effects on heart rate of juveniles, Gambusia holbrooki
Publisher: Bioscientifica
Date: 09-05-2023
DOI: 10.1530/JME-23-0021
Abstract: Built on our recent work that heart rates (HRs) and function in Gambusia holbrooki are sexually dimorphic, this study assessed whether the species is an appropriate model to study sex-hormone effects on heart physiology. With a hypothesis that 17β-estradiol (E 2 ) and 17α-methyltestosterone (MT) regulate the HR of juvenile G. holbrooki in a sex-specific manner, genetic males and females were treated with E 2 and MT, respectively, and the HR (bpm) was measured an hour following treatment using light-cardiogram. Results showed the HRs (bpm) of both sexes were significantly ( P 0.05) altered compared to controls. Specifically, the E 2 accelerated HR in the males and conversely MT decelerated the HR in the females. The normal expression levels of estrogen ( erα and erβ ) and G protein-coupled estrogen ( gper ) receptor genes were significantly higher ( P 0.05) in female than male hearts. Interestingly, the activity of the erβ in the heart of the MT-treated females reversed and was significantly lower ( P 0.05) than those of males while erα and gper were non-responsive. In contrast, significant down- and up-regulation of erα and gper , respectively, occurred in the liver of MT-treated females. Morphological observations suggest that MT caused hepatomegaly, somewhat resembling an inflating balloon, perhaps induced by the accumulation of unexpelled gases. E 2 -induced ventricular angiogenesis in males was likely due to an influx of blood supply caused by the increased HRs. Collectively, the results demonstrate that the juvenile G. holbrooki heart readily responds to E 2 /MT in a sex-specific manner.
Simplex PCR Assay for Positive Identification of Genetic Sex in the Japanese Medaka, Oryzias latipes
Publisher: Springer Science and Business Media LLC
Date: 28-05-2008
DOI: 10.1007/S10126-008-9106-9
Abstract: The medaka, Oryzias latipes, is a very popular model in biomedical research, particularly for elucidating sex differentiation and determination mechanisms and effects of endocrine disruptors among others. These studies require a sensitive, accurate, rapid, and reliable technique for genetic sexing of eggs, larvae, and adults. In this study, we report a simplex polymerase chain reaction approach that uses a single pair of primers for simultaneous lification of sex-specific licons. Males and females yield a single diagnostic band of 933 and 1,906 bp, respectively, in three different strains of medaka tested, permitting gender identification accurately of both immature and adult fish. This technique will be useful in both ecological and biomedical researches that employ medaka and rely on genetic sexing.
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