Publications by authors named "Erin L Damsteegt"

16 Publications

  • Page 1 of 1

An in vitro ovarian explant culture system to examine sex change in a hermaphroditic fish.

PeerJ 2020 11;8:e10323. Epub 2020 Nov 11.

Department of Zoology, University of Otago, Dunedin, New Zealand.

Many teleost fishes undergo natural sex change, and elucidating the physiological and molecular controls of this process offers unique opportunities not only to develop methods of controlling sex in aquaculture settings, but to better understand vertebrate sexual development more broadly. Induction of sex change in some sequentially hermaphroditic or gonochoristic fish can be achieved in vivo through social manipulation, inhibition of aromatase activity, or steroid treatment. However, the induction of sex change in vitro has been largely unexplored. In this study, we established an in vitro culture system for ovarian explants in serum-free medium for a model sequential hermaphrodite, the New Zealand spotty wrasse (). This culture technique enabled evaluating the effect of various treatments with 17-estradiol (E), 11-ketotestosterone (11KT) or cortisol (CORT) on spotty wrasse ovarian architecture for 21 days. A quantitative approach to measuring the degree of ovarian atresia within histological images was also developed, using pixel-based machine learning software. Ovarian atresia likely due to culture was observed across all treatments including no-hormone controls, but was minimised with treatment of at least 10 ng/mL E. Neither 11KT nor CORT administration induced proliferation of spermatogonia (i.e., sex change) in the cultured ovaries indicating culture beyond 21 days may be needed to induce sex change in vitro. The in vitro gonadal culture and analysis systems established here enable future studies investigating the paracrine role of sex steroids, glucocorticoids and a variety of other factors during gonadal sex change in fish.
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http://dx.doi.org/10.7717/peerj.10323DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7666549PMC
November 2020

Spatiotemporal expression of activin receptor-like kinase-5 and bone morphogenetic protein receptor type II in the ovary of shortfinned eel, Anguilla australis.

Comp Biochem Physiol B Biochem Mol Biol 2021 Jan 28;251:110509. Epub 2020 Sep 28.

Department of Zoology, University of Otago, PO Box 56, Dunedin 9054, New Zealand.

In the eel ovary, the expression of growth differentiation factor-9 (Gdf9) appears to be largely confined to the germ cell in early stages of oogenesis. However, both the target tissue and the function of Gdf9 in fish remain unknown. This study aimed to describe the abundance and localization of activin receptor-like kinase-5 (Alk5) and bone morphogenetic protein receptor type II (Bmpr2), which together mediate the Gdf9 signal, in the ovary of a basal teleost, the shortfinned eel, Anguilla australis, during early folliculogenesis. The cDNA encoding eel alk5 and bmpr2 genes were cloned, characterized and the transcript abundances of these receptors quantified by quantitative real-time PCR. Ovarian transcript abundance for both receptors, along with that of gdf9 and of its paralogue bmp15, increased from the previtellogenic to early vitellogenic stage. Localization of receptor mRNAs by in situ hybridization revealed that these receptors are located in the somatic cells surrounding the oocyte. Furthermore, tissue distribution analysis showed that the expression of alk5 and bmpr2 were highest in ovary and thyroid, respectively. Unexpectedly, however, bmpr2 mRNA levels were lower in the ovary than in any of the other 17 tissues examined, and indeed, lower than ovarian gdf9 transcript abundance. These findings, together with the ovarian expression pattern of Gdf9, suggest that Gdf9, and conceivably, Bmp15, from the oocyte can signal through receptors that are located on the somatic cells surrounding the oocyte; this, in turn, facilitates elucidation of the function of these growth factors during oogenesis in teleost fish.
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http://dx.doi.org/10.1016/j.cbpb.2020.110509DOI Listing
January 2021

Effects of estradiol and 11-ketotestosterone pre-treatment on artificial induction of maturation in silver female shortfinned eels (Anguilla australis).

PLoS One 2020 24;15(2):e0229391. Epub 2020 Feb 24.

Department of Zoology, University of Otago, Dunedin, New Zealand.

Our previous work documented significant advancements in steroid-induced progression of oogenesis, demonstrating that co-treatment of female eels with 11-ketotestosterone (11KT) and estradiol-17β (E2) successfully induced uptake of vitellogenin by oocytes. Here we evaluate the effects of this steroid co-treatment on subsequent time to ovulation and egg quality in shortfinned eels artificially matured by hypophysation. Co-treatment with 11KT (1 mg) and E2 (0.2 or 2 mg) significantly reduced time to ovulation and therefore, the amount of pituitary homogenate required, without any detrimental effects on gonadosomatic index, oocyte diameter or the total weight of stripped eggs. E2 treatment resulted in promising increases in fertilization rates. These indicators suggest that co-treatment with 11KT and E2 holds promise for future artificial maturation practices in terms of minimising fish handling and stress, and of reducing the need for expensive pituitary preparations.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0229391PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7039463PMC
May 2020

Conservation and diversity in expression of candidate genes regulating socially-induced female-male sex change in wrasses.

PeerJ 2019 11;7:e7032. Epub 2019 Jun 11.

Department of Anatomy, University of Otago, Dunedin, Otago, New Zealand.

Fishes exhibit remarkably diverse, and plastic, patterns of sexual development, most striking of which is sequential hermaphroditism, where individuals readily reverse sex in adulthood. How this stunning example of phenotypic plasticity is controlled at a genetic level remains poorly understood. Several genes have been implicated in regulating sex change, yet the degree to which a conserved genetic machinery orchestrates this process has not yet been addressed. Using captive and in-the-field social manipulations to initiate sex change, combined with a comparative qPCR approach, we compared expression patterns of four candidate regulatory genes among three species of wrasses (Labridae)-a large and diverse teleost family where female-to-male sex change is pervasive, socially-cued, and likely ancestral. Expression in brain and gonadal tissues were compared among the iconic tropical bluehead wrasse () and the temperate spotty () and kyusen () wrasses. In all three species, gonadal sex change was preceded by downregulation of (encoding gonadal aromatase that converts androgens to oestrogens) and accompanied by upregulation of (encoding anti-müllerian hormone that primarily regulates male germ cell development), and these genes may act concurrently to orchestrate ovary-testis transformation. In the brain, our data argue against a role for brain aromatase () in initiating behavioural sex change, as its expression trailed behavioural changes. However, we find that isotocin (, that regulates teleost socio-sexual behaviours) expression correlated with dominant male-specific behaviours in the bluehead wrasse, suggesting upregulation mediates the rapid behavioural sex change characteristic of blueheads and other tropical wrasses. However, expression was not sex-biased in temperate spotty and kyusen wrasses, where sex change is more protracted and social groups may be less tightly-structured. Together, these findings suggest that while key components of the molecular machinery controlling gonadal sex change are phylogenetically conserved among wrasses, neural pathways governing behavioural sex change may be more variable.
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http://dx.doi.org/10.7717/peerj.7032DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6568253PMC
June 2019

Expressional regulation of gonadotropin receptor genes and androgen receptor genes in the eel testis.

Gen Comp Endocrinol 2019 09 19;280:123-133. Epub 2019 Apr 19.

Department of Zoology, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand.

Receptors for follicle-stimulating hormone (Fshr), luteinizing hormone (Lhcgr1 and Lhcgr2) and androgens (Ara and Arb) transduce the hormonal signals that coordinate spermatogenesis, but the factors that regulate the abundance of these transducers in fish testes remain little-understood. To mend this paucity of information, we first determined changes in transcript abundance for these receptors (fshr, lhcgr1, ara and arb) during spermatogenesis induced by human chorionic gonadotropin (hCG) injection in the eel, Anguilla australis. We related our findings to testicular production of the fish androgen, 11-ketotestosterone (11-KT), and to the levels of the transcripts encoding steroidogenic acute regulatory protein (star) and 11β-hydroxylase (cyp11b), and subsequently evaluated the effects of hCG or 11-KT on mRNA levels of these target genes in vitro. Testicular 11-KT production was greatly increased by hCG treatment, both in vivo and in vitro, and associated with up-regulation of star and cyp11b transcripts. In situ hybridization indicated that testicular fshr mRNA levels were higher in the early stages of hCG-induced spermatogenesis, while lhcgr1 transcripts were most abundant later, once spermatids were observed. In vitro experiments further showed that hCG and its steroidal mediator 11-KT significantly increased fshr transcript abundance. These data provide new angles on the interactions between gonadotropin and androgen signaling during early spermatogenesis. Increases in levels of 11-KT following hCG injection elevated testicular fshr mRNA levels augmenting Fsh sensitivity in the testis. This evidence is suggestive of a positive feedback loop between gonadotropins and 11-KT that may be key to regulating early spermatogenesis in fish.
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http://dx.doi.org/10.1016/j.ygcen.2019.04.020DOI Listing
September 2019

A Novel Role for Somatostatin in the Survival of Mouse Pancreatic Beta Cells.

Cell Physiol Biochem 2019 15;52(3):486-502. Epub 2019 Mar 15.

Health Science Research Group, Department of Life Sciences, University of Roehampton, London, UK,

Background/aims: Cross-talk between different pancreatic islet cell types regulates islet function and somatostatin (SST) released from pancreatic delta cells inhibits insulin secretion from pancreatic beta cells. In other tissues SST exhibits both protective and pro-apoptotic properties in a tissue-specific manner, but little is known about the impact of the peptide on beta cell survival. Here we investigate the specific role of SST in the regulation of beta cell survival in response to physiologically relevant inducers of cellular stress including palmitate, cytokines and glucose.

Methods: Pancreatic MIN6 beta cells and primary mouse islet cells were pre-treated with SST with or without the G signalling inhibitor, pertussis toxin, and exposed to different cellular stress factors. Apoptosis and proliferation were assessed by measurement of caspase 3/7 activity, TUNEL and BrdU incorporation, respectively, and expression of target genes was measured by qPCR.

Results: SST partly alleviated upregulation of cellular stress markers (Hspa1a and Ddit3) and beta cell apoptosis in response to factors such as lipotoxicity (palmitate), pro-inflammatory cytokines (IL1β and TNFα) and low glucose levels. This effect was mediated via a G protein-dependent pathway, but did not modify transcriptional upregulation of the specific NFκB-dependent genes, Nos2 and Ccl2, nor was it associated with transcriptional changes in SST receptor expression.

Conclusion: Our results suggest an underlying protective effect of SST which modulates the beta cell response to ER stress and apoptosis induced by a range of cellular stressors associated with type 2 diabetes.
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http://dx.doi.org/10.33594/000000035DOI Listing
March 2019

Synergistic effects of estradiol and 11-ketotestosterone on vitellogenin physiology in the shortfinned eel (Anguilla australis).

Biol Reprod 2019 05;100(5):1319-1332

Department of Zoology, University of Otago, Dunedin, New Zealand.

Estradiol-17β (E2) and 11-ketotestosterone (11KT) have been implicated in vitellogenesis and in regulating expression of the follicle-stimulating hormone receptor (fshr), respectively. To override the captivity-induced reproductive block in shortfinned eel, Anguilla australis, we hypothesized that in combination, 11KT and E2 would stimulate ovarian uptake of vitellogenin (Vtg). Early pubertal eels received hormone implants containing varying concentrations of E2 (0, 0.2, 2, 5 mg) with or without 11KT (1 mg). Vtg levels were determined in plasma, liver, and ovarian tissues by histological examination, qPCR, immunoblotting, or single radial immunodiffusion. The expression of gonadotropin-beta subunits and gonadotropin receptors in the pituitary and ovary, respectively, were analyzed to determine mechanisms by which steroid effects may be exerted. When administered alone, E2 increased hepatic production and plasma levels of Vtg. In contrast, 11KT decreased plasma levels of Vtg, seemingly reducing its production. Neither 11KT nor E2 could induce uptake of Vtg into oocytes, although E2 treatment appeared necessary for uptake to occur. This was the case despite 11KT dramatically increasing both oocyte size and fshr mRNA levels. Astonishingly, the uptake of Vtg was successfully induced by co-treatment with 11KT and E2, suggesting that 11KT might facilitate the incorporation of Vtg into the developing oocyte. These results highlight the potential of sex steroid co-treatment, an approach aimed at mimicking oogenesis in wild eels, to induce vitellogenesis, specifically ovarian yolk deposition, even in the absence of exogenous gonadotropin treatment.
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http://dx.doi.org/10.1093/biolre/ioz007DOI Listing
May 2019

Does silvering or 11-ketotestosterone affect osmoregulatory ability in the New Zealand short-finned eel (Anguilla australis)?

J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2018 12 29;204(12):1017-1028. Epub 2018 Oct 29.

Department of Zoology, University of Otago, P.O. Box 56, Dunedin, New Zealand.

Silvering has been associated with advancing osmoregulatory ability. Given the demonstrated role of 11-ketotestosterone (11KT) in mediating many of the silvering-related changes, we investigated the role of 11KT in driving this advanced osmoregulatory ability in the New Zealand short-finned eel (Anguilla australis). Yellow (non-migratory) eels with or without 11KT implants and blank-implanted silver (migratory) eels, either held in freshwater or subjected to seawater challenge, were sampled to determine serum [Na] and [Cl], pituitary prolactin mRNA levels, gill Na/K-ATPase activity and gill mRNA levels for Na/K-ATPase-α1 subunit and for Na/K/2Cl co-transporter-1α-subunit. Developmental stage and 11KT treatment advanced the eels' osmoregulatory ability. Thus, serum [Na] and [Cl] were affected by developmental stage and 11KT treatment upon seawater challenge. However, seawater challenge, not 11KT treatment or developmental stage, produced the strongest and the most consistent effects on A. australis osmoregulatory processes, inducing significant effects in all the relevant parameters we measured. In light of our results and in view of the eel's marine ancestry, we contend that A. australis, or freshwater eels in general, are highly tolerant and able to adapt quickly to changing salinities even at the yellow stage, which may preclude a critical need for an advanced osmoregulatory ability at silvering.
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http://dx.doi.org/10.1007/s00359-018-1300-2DOI Listing
December 2018

The evolution of apolipoprotein B and its mRNA editing complex. Does the lack of editing contribute to hypertriglyceridemia?

Gene 2018 Jan 12;641:46-54. Epub 2017 Oct 12.

Department of Zoology, University of Otago, 340 Great King Street, PO Box 56, Dunedin 9054, New Zealand.

The evolution of apolipoprotein B (Apob) has been intensely researched due to its importance during lipid transport. Mammalian full-length apob100 can be post-transcriptionally edited by the enzyme apolipoprotein B mRNA editing enzyme, catalytic polypeptide-like complex-one (Apobec1) resulting in a truncated Apob, known as Apob48. Whilst both full-length and truncated forms of Apob are important for normal lipid homeostasis in mammals, there is no evidence for the presence of apob mRNA editing prior to the divergence of the mammals, yet, non-mammalian vertebrates appear to function normally with only Apob100. To date, the majority of the research carried out in non-mammalian vertebrates has focused on chickens with only a very limited number examining apob mRNA editing in fish. This study focused on the molecular evolution of Apobec1 and Apob in order to ascertain if apob mRNA editing occurs in eels, a basal teleost which represents an evolutionarily important animal group. No evidence for the presence of Apobec1 or the ability for eel apob to be edited was found. However, an important link between mutant mice and the evident hypertriglyceridemia in the plasma of non-mammalian vertebrates was made. This study has provided imperative evidence to help bridge the evolutionary gap between fish and mammals and provides further support for the lack of apob mRNA editing in non-mammalian vertebrates.
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http://dx.doi.org/10.1016/j.gene.2017.10.024DOI Listing
January 2018

Storage by lyophilization - Resulting RNA quality is tissue dependent.

Anal Biochem 2016 10 8;511:92-6. Epub 2016 Aug 8.

Department of Zoology, University of Otago, PO Box 56, Dunedin 9054, New Zealand.

In today's highly collaborative scientific community there is a growing need to transport biological samples across the globe. Lyophilization is a cost-effective preservation method which avoids the use of hazardous chemicals, creating an appealing, yet essentially unexplored, prospect for the long-range transport of animal tissue samples. This study examined the integrity of RNA following its extraction from eel tissue (liver, spleen and ovary) that had been subjected to i) freezing only; ii) freezing and lyophilization, and iii) freezing, lyophilization and subsequent storage at ambient temperature for one week. Only small reductions in RNA integrity were identified in lyophilized, stored sample compared to that of flash-frozen or lyophilized sample not subjected to storage. Reductions in RNA integrity were most profound in ovary tissue, which has a notably higher lipid content (∼35% of dry weight) than liver (∼17%) or spleen (∼15%). However, lowered RNA integrity numbers did not affect qPCR-estimated relative or absolute transcript copy numbers of two arbitrary target genes. These findings confirm that this method is a viable option for shipping animal tissue samples world-wide and could open up numerous benefits for the biological sciences as a whole.
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http://dx.doi.org/10.1016/j.ab.2016.08.005DOI Listing
October 2016

A comparative study of vitellogenesis in Echinodermata: Lessons from the sea star.

Comp Biochem Physiol A Mol Integr Physiol 2016 08 13;198:72-86. Epub 2016 Apr 13.

Department of Zoology, University of Otago, 340 Great King Street, Dunedin 9016, New Zealand.

The provision of yolk precursor proteins to the oviparous egg is crucial for normal embryo development. In Echinodermata, a transferrin-like yolk component termed major yolk protein (MYP) is a major precursor protein in Echinoidea and Holothuroidea. In contrast, in Asteroidea a single vitellogenin (Vtg) was recently identified, but its role as primary yolk protein remains unclear. To resolve the apparent MYP-Vtg dichotomy in sea stars and to understand the dynamics of candidate yolk protein gene expression during the reproductive cycle, we investigated the molecular structures of sea star Vtg and MYP and quantified their transcript levels during oogenesis. By combining protein sequencing of the predominant proteins in ovulated eggs of Patiriella regularis with ovarian transcriptome sequencing and molecular cloning, we characterized two cDNAs encoding two bona fide Vtgs (PrVtg1 and PrVtg2) and a partial cDNA encoding MYP (PrMYP). PrMYP mRNA was found in low abundance in growing oocytes, possibly as maternal transcripts for translation after ovulation. In contrast, PrVtg transcripts, whose levels varied during the reproductive cycle, were not found in developing oocytes - rather, they were detected in ovarian follicle cells and pyloric caeca, indicating an extra-oocytic origin. Vtg accumulating in oocytes was stored in the form of cleaved products, which constituted the most abundant yolk polypeptides in ovulated sea star eggs; their levels decreased during early embryonic and larval development. Together, these traits are the hallmarks of a classical yolk protein - and hence, we contend that Vtg, and not MYP, is the main yolk protein in asteroids.
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http://dx.doi.org/10.1016/j.cbpa.2016.04.013DOI Listing
August 2016

Triacylglyceride physiology in the short-finned eel, Anguilla australis--the effects of androgen.

Am J Physiol Regul Integr Comp Physiol 2016 Mar 13;310(5):R422-31. Epub 2016 Jan 13.

Department of Zoology, University of Otago, Dunedin, New Zealand; and.

The importance of androgens (especially 11-ketotestosterone) during previtellogenesis in eels is well established. In wild pubertal migrants, circulating 11-ketotestosterone levels correlate with a number of morphological and molecular changes. Here, we test the prediction that this correlation represents a causal relationship by artificially raising the levels of circulating 11-ketotestosterone in prepubertal nonmigratory female and pubertal, migratory male short-finned eels (Anguilla australis) using sustained-release hormone implants. In females, increases in hepatosomatic index and transcript copy numbers of hepatic apolipoprotein B and microsomal triacylglyceride transfer protein indicated increased repackaging of endogenously sourced triacylglycerides. These changes in liver measures were reflected in increased concentrations of serum triacylglycerides. However, despite a small increase in gonadosomatic index, ovarian lipoprotein receptor transcript abundances were not affected by 11-ketotestosterone. Interestingly, no such changes in hepatic gene expression were detected in a dose-response experiment using males. We propose that the androgens are inducing the observed changes in previtellogenic females, although it remains unclear to what extent these effects are direct or indirect.
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http://dx.doi.org/10.1152/ajpregu.00149.2015DOI Listing
March 2016

Effects of 11-ketotestosterone and temperature on inhibin subunit mRNA levels in the ovary of the shortfinned eel, Anguilla australis.

Comp Biochem Physiol B Biochem Mol Biol 2015 Sep 7;187:14-21. Epub 2015 May 7.

Department of Zoology, University of Otago, 340 Great King Street, Dunedin 9016, New Zealand. Electronic address:

Members of the transforming growth factor-b (TGFb) superfamily are important during early oogenesis in mammals. In this study, we tested whether documented effects of 11-ketotestosterone (11KT) on previtellogenic eel ovaries are mediated through affecting the expression of key ovarian TGFb genes. Furthermore, we investigated whether 11KT effects interacted with temperature. Accordingly, three thermal regimes were compared and their interaction with 11KT-mediated actions on expression of TGFb superfamily genes (chiefly inhibin subunits) evaluated in the eel (Anguilla australis). Inhibin subunit mRNA levels were also measured in ovarian explants cultured in vitro with 11KT and in ovaries from eels collected from the wild. In wild eels, inhibin-bA mRNA levels were higher in early than in previtellogenic eels; inhibin-a expression did not differ between stages, whereas that of inhibin-bB first decreased, then recovered with advanced developmental stage. Temperature was ineffective in modulating any of the end points, at least as long as a Q10 adjustment was made to correct for 'metabolic dose'. However, 11KT affected the expression of inhibin-a compared to control fish, while those of inhibin-b subunit genes remained unaffected. In contrast, 11KT dramatically reduced mRNA levels of inhibin-b subunits in vitro, but had inconsistent effects on inhibin-a transcript abundance. We conclude that 11KT affects ovarian inhibin subunit gene expression, but effects are not in keeping with the changes seen during early oogenesis in eels from the wild. We further contend that in vivo temperature experiments are easily biased and that Q10 corrections may be required to identify 'true' temperature effects.
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http://dx.doi.org/10.1016/j.cbpb.2015.04.012DOI Listing
September 2015

Triacylglyceride physiology in the short-finned eel, Anguilla australis—changes throughout early oogenesis.

Am J Physiol Regul Integr Comp Physiol 2015 Jun 25;308(11):R935-44. Epub 2015 Mar 25.

Department of Zoology, University of Otago, Dunedin, New Zealand; and.

During certain stages in an animal's life cycle, energy requirements may exceed energy intake from the diet. The spawning migration of temperate eels is a textbook example of negative energy balance, forcing these fish to rely on stored fats (triacylglycerides) to provide their muscles with energy for swimming and their growing oocytes with the nutrients needed to develop and support healthy offspring. We predicted broad implications of this great need for endogenous triacylglycerides in terms of their packaging, transport, and ovarian uptake. To test this, serum lipid concentrations and transcript abundances of intestinal and hepatic triacylglyceride packagers and ovarian triacylglyceride modifiers and receivers were investigated throughout previtellogenesis (feeding phase) and into early vitellogenesis (fasting phase) in short-finned eels. A switch from exogenous to endogenous triacylglyceride packaging was seen as the liver upregulated transcript levels of apolipoprotein B and microsomal triacylglyceride transport protein and downregulated those of apolipoprotein E and lipoprotein lipase. In the intestine, the reverse response was observed. Furthermore, ovarian transcript abundances of triacylglyceride modifiers and receivers increased (apolipoprotein E, lipoprotein lipase, and vitellogenin receptor), indicative of increased triacylglyceride uptake during previtellogenesis. We propose that increased hepatic apolipoprotein B production is a conserved vertebrate response to prolonged periods of negative energy balance.
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http://dx.doi.org/10.1152/ajpregu.00436.2014DOI Listing
June 2015

How do eggs get fat? Insights into ovarian fatty acid accumulation in the shortfinned eel, Anguilla australis.

Gen Comp Endocrinol 2015 Sep 7;221:94-100. Epub 2015 Feb 7.

Department of Zoology, University of Otago, 340 Great King Street, PO Box 56, Dunedin 9054, New Zealand.

Previous research using eels has shown that 11-ketotestosterone can induce ovarian triacylglyceride accumulation both in vivo and in vitro. Further, accumulation is dramatically enhanced in the presence of very-low density lipoprotein. This study examined the involvement of the low density lipoprotein receptor and vitellogenin receptor in oocyte lipid accumulation. Specific antisera were used in an attempt to block the vitellogenin receptor and/or the low density lipoprotein receptor. Accordingly, incubation with the low density lipoprotein receptor antiserum clearly reduced the oocyte diameter and the amount of oil present within the oocyte. In contrast, blocking the vitellogenin receptor had little effect on either oocyte surface area or the abundance of oil droplets in the cytosol. In keeping with birds, we conclude that the low density lipoprotein receptor is a major player involved in mediating ovarian fatty acid accumulation in the eel. However, lipoprotein lipase-mediated fatty acid accumulation also remains conceivable, for example through interactions between this enzyme and the low density lipoprotein receptor.
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http://dx.doi.org/10.1016/j.ygcen.2014.12.019DOI Listing
September 2015

Development and partial characterisation of an antiserum against apolipoprotein B of the short-finned eel, Anguilla australis.

J Comp Physiol B 2014 Jul 11;184(5):589-99. Epub 2014 Mar 11.

Department of Zoology, University of Otago, 340 Great King Street, PO Box 56, Dunedin, 9054, New Zealand,

Despite its key role in transportation of triacylglycerides in blood, the distribution, localisation and molecular weight variants of apolipoprotein B (Apob) in teleost fish have essentially escaped study. To address this, a specific short-finned eel (Anguilla australis) Apob antiserum was produced by an immunised rabbit, purified and partially characterised. Localisation of Apob at both the mRNA (in situ hybridisation) and protein (immunohistochemistry) levels mirrored that of mammals; thus immunostaining was confined to the interstitial spaces of the liver and the vascular core of the intestinal villi. Immunostaining of proteins by Western blotting, followed by high-resolution LC-MS, indicated that peptide sequence coverage of Apob in low-density lipoproteins spanned the full-length protein. We conclude that only full-length Apob is produced by eels and that both liver and intestine are key sites for its synthesis.
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http://dx.doi.org/10.1007/s00360-014-0821-4DOI Listing
July 2014