Showing papers in "Comparative Biochemistry and Physiology B in 2001"
TL;DR: By altering peripheral glucose utilization fish could become more glucose tolerant, costs to the aquaculture industry may be substantially reduced, and future experimental directions are suggested.
Abstract: Teleost fish are generally considered to be glucose intolerant. This mini-review examines some of the background and the possible mechanistic bases for this statement. Glucose intolerance is a clinical mammalian term meaning that a glucose load results in persistent hyperglycemia. Teleost fish show persistent hyperglycemia that is generally coincident with transient hyperinsulinemia. The fact that teleost generally have high plasma insulin compared with mammals implies insulin-deficiency is not a suitable explanation for this persistent hyperglycemia. Instead, peripheral utilization of glucose is probably the principle cause of hyperglycemia. Recent evidence for muscle insulin receptors, glucose transporters and hexokinase/glucokinase is reviewed and future experimental directions are suggested. If by altering peripheral glucose utilization fish could become more glucose tolerant, costs to the aquaculture industry may be substantially reduced.
464 citations
TL;DR: This work focuses chiefly on animal anhydrobiosis, achieved by the reversible loss of almost all the organism's water, and the adaptive biochemical and biophysical mechanisms allowing this to take place involve the participation of large concentrations of polyhydroxy compounds, chiefly the disaccharides trehalose or sucrose.
Abstract: David Keilin (Proc. Roy. Soc. Lond. B, 150, 1959, 149–191) coined the term ‘cryptobiosis’ (hidden life) and defined it as ‘the state of an organism when it shows no visible signs of life and when its metabolic activity becomes hardly measurable, or comes reversibly to a standstill.’ I consider selected aspects of the 300 year history of research on this unusual state of biological organization. Cryptobiosis is peculiar in the sense that organisms capable of achieving it exhibit characteristics that differ dramatically from those of living ones, yet they are not dead either, so one may propose that cryptobiosis is a unique state of biological organization. I focus chiefly on animal anhydrobiosis, achieved by the reversible loss of almost all the organism's water. The adaptive biochemical and biophysical mechanisms allowing this to take place involve the participation of large concentrations of polyhydroxy compounds, chiefly the disaccharides trehalose or sucrose. Stress (heat shock) proteins might also be involved, although the details are poorly understood and seem to be organism-specific. Whether the removal of molecular oxygen (anoxybiosis) results in the reversible cessation of metabolism in adapted organisms is considered, with the result being ‘yes and no’, depending on how one defines metabolism. Basic research on cryptobiosis has resulted in unpredicted applications that are of substantial benefit to the human condition and a few of these are described briefly.
403 citations
TL;DR: In this article, the authors discuss the role of myofibrillar proteins in fish muscle growth and their role in protein synthesis, showing that the myofibillar fraction accounts for almost two-thirds of protein synthetic activity, implying that it is the accretion of my-of-branch proteins that makes the single most important contribution to fish growth.
Abstract: Most fish are indeterminate growers with white muscle making up the majority of the acquired bulk. Within the muscle, the myofibrillar fraction accounts for almost two-thirds of the protein synthetic activity, implying that it is accretion of myofibrillar proteins that makes the single most important contribution to fish growth. Fish muscle growth itself is not linear and occurs through a combination of hyperplasia and hypertrophy in post-juvenile stages. Superimposed on periodicity of growth in length and mass can be other phases governed by lunar, reproductive or circannual cycles. Data on fish growth are discussed in the framework of site-specific muscle abundance, metabolic and functional zonation of muscle, proliferation and differentiation of satellite cells and the contribution of myofibrillar proteins. Hormonal control of muscle growth is described against the backdrop of plasma availability of myogens (insulin, IGF-I, growth hormone), distribution and dynamics of their respective receptors, and their interactions. Important contributions of the ‘supply side’ are discussed with hormones regulating amino acid resorption from the intestine, intestinal growth, liver processing and amino acid uptake by the muscle. Data are also interpreted from metabolic angles, to explain lipolytic and nitrogen-sparing effects of growth hormones, and lipogenic effects of insulin and high protein diets. Finally, special attention is devoted to the multifaceted roles of arginine in fish growth, as precursor, intermediate and hormone secretagogue.
332 citations
TL;DR: All of the widely used control genes are evaluated, dissecting different methodological approaches and issues regarding the experimental context to generate a procedure that will help to discern the best control for novel experiments.
Abstract: The measurement of transcript levels constitutes the foundation of today's molecular genetics. Independent of the techniques used, quantifications are generally normalised using invariant control genes to account for sample handling, loading and experimental variation. All of the widely used control genes are evaluated, dissecting different methodological approaches and issues regarding the experimental context (e.g. development and tissue type). Furthermore, the major sources of error are highlighted when applying these techniques. Finally, different approaches undertaken to assess the invariance of control genes are critically analysed to generate a procedure that will help to discern the best control for novel experiments.
280 citations
TL;DR: While elements of the HPI axis may mediate some of the appetite-suppressing effects of stress, it is undetermined how either CRF-related peptides, cortisol, or other Elements of the stress response interact with the complex circuitry of the hypothalamic feeding center.
Abstract: Although environmental, social and physical stressors have been shown to inhibit food intake and feeding behavior in fish, little is known about the mechanisms that mediate the appetite-suppressing effects of stress. Since the hypothalamic-pituitary-interrenal (HPI) axis is activated in response to most forms of stress in fish, components of this axis may be involved in mediating the food intake reductions elicited by stress. Recent investigations into the brain regulation of food intake in fish have identified several signals with orexigenic and anorexigenic properties. Among these appetite-regulating signals are related neuropeptides that can activate the HPI axis, namely corticotropin-releasing factor (CRF) and urotensin I (UI). Central injections of CRF or UI, or treatments that result in an increase in hypothalamic CRF and UI gene expression, can elicit dose-dependent decreases in food intake that can be reversed by pre-treatment with a CRF-receptor antagonist. Evidence also suggests that cortisol, the end product of HPI activation in most fishes (i.e. Osteichthyes), may be involved in the regulation of food intake. Overall, while elements of the HPI axis may mediate some of the appetite-suppressing effects of stress, it is undetermined how either CRF-related peptides, cortisol, or other elements of the stress response interact with the complex circuitry of the hypothalamic feeding center.
190 citations
TL;DR: It is concluded that P450aromB mRNA is a sensitive marker of XE effect during embryogenesis, but further studies are required to determine whether changes in neural aromatase expression and estrogen biosynthesis have consequences for CNS development.
Abstract: Estrogen synthesized in the brain itself by the action of cytochrome P450 aromatase (P450arom) is known to have permanent organizing effects on the developing CNS. In fish, estrogen upregulates the predominant brain isoform (P450aromB), implying that xenoestrogens (XE) could act as neurodevelopmental toxicants by altering P450aromB. To test this hypothesis, zebrafish embryos were exposed to 17beta-estradiol (E(2)), diethylstilbestrol (DES, a potent agonist), and bisphenol A (BPA, a weak agonist). RT-PCR/Southern transfer analysis showed that E(2) (0.01-10 microM) upregulated P450aromB in a dose-response manner. The effect of DES (0.01 microM) was similar to 1 microM E(2) (three- to four-fold higher than control), but BPA was less effective (
190 citations
TL;DR: There were significant differences in liver PUFA metabolism between Arctic charr and the other salmonids, which could have important consequences, both physiologically and in their ability to be successfully cultured on diets containing vegetable oils.
Abstract: The desaturation and elongation of [1- 14 C]18:3n-3 was investigated in hepatocytes from different populations and three different species of salmonids indigenous to Scotland, brown trout, Atlantic salmon and Arctic charr. Two groups of fish were sampled, before and after they were fed two experimental diets, a control diet containing fish oil and a diet containing vegetable oil (a 1:1 blend of linseed and rapeseed oils) for 12 weeks. At each sampling time, fatty acyl desaturation and elongation activity was determined in isolated hepatocytes, and samples of liver were also collected for lipid compositional analysis. At the initiation of the dietary trial, the liver polar-lipid fatty acid compositions of salmon and brown trout were very similar to each other, and the two charr populations were similar to each other, having lower total n-3 polyunsaturated fatty acids (PUFA) and 22:6n-3, but higher 20:5n-3 than the other salmonids. Initially, hepatocyte desaturation activity varied, with the highest activity in brown trout, followed by salmon and then charr. Production of 20:5n-3 was particularly high in brown trout. Desaturation of [1- 14 C]18:3n-3 was significantly greater in all fish fed the diet containing vegetable oil compared to fish fed the diet containing fish oil. The increase in activity was less in brown trout compared to the other groups of fish. Feeding the vegetable oil diet increased the levels of 18:2n-6, 20:3n-6, total n-6 PUFA, 18:3n-3, 18:4n-3, 20:3n-3 and 20:4n-3, and decreased 22:6n-3 and the n-3/n-6 ratio in salmon and brown trout. By contrast, in charr fed the vegetable oil diet, there was no increase in 18:3n-3, 18:4n-3, 20:3n-3 or 20:4n-3 in liver polar lipids and the level of 22:6n-3 was not decreased. In addition, there was only a modest increase in the levels of 18:2n-6 and total n-6 PUFA, and so the n-3/n-6 ratio was only slightly decreased. The percentage of 20:4n-6, which was not increased in salmon and brown trout fed vegetable oil, was increased in charr fed the vegetable oil diet. Overall, the results indicated that there were significant differences in liver PUFA metabolism between Arctic charr and the other salmonids, which could have important consequences, both physiologically and in their ability to be successfully cultured on diets containing vegetable oils.
171 citations
TL;DR: The term, ovarian follicle (or oocyte) maturation be used for teleosts without qualifiers such as 'final' to define the first and second stages of follicular maturation.
Abstract: Most research on the control of oocyte maturation by luteinizing hormone (LH) in teleosts and amphibians has focused on the production and action of maturation-inducing hormone (MIH), the follicular hormone that directly triggers the resumption of oocyte meiosis. However, current information indicates that LH regulates maturation in two stages, and that ‘oocyte maturation’ can be appropriately described within the broader context of ‘ovarian follicle maturation’. During the first stage of maturation the follicle (somatic) cells acquire the ability to produce MIH and the oocyte to respond to MIH (i.e. oocyte maturational competence, OMC), whereas in the second stage the follicle cells produce MIH and, consequently, the oocyte is released from meiotic arrest. A number of factors such as insulin-like growth factor-I, serotonin, and others may mediate or modulate the OMC-inducing action of LH. Like the acquisition of MIH-producing ability, the acquisition of OMC requires activation of the protein kinase A pathway. Two major cellular events associated with OMC acquisition are increases in homologous and heterologous gap junction contacts and in oocyte MIH receptor activity. The increased oocyte MIH receptor activity is presumably associated with OMC acquisition, but the significance of changes in gap junction contacts is at present uncertain. To eliminate inconsistency and ambiguity associated with current terminology we propose that the term, ovarian follicle (or oocyte) maturation be used for teleosts without qualifiers such as ‘final’ to define the first and second stages of follicular maturation.
167 citations
TL;DR: This review traces the evolution of ion channels, with particular emphasis on the factors and evolutionary pathways that may have given rise to voltage-gated potassium (K+), calcium (Ca2+), and sodium (Na+) channels.
Abstract: Voltage-gated ion channels are responsible for the electrical activity in a variety of cell types in modern-day animals. However, they represent the result of many millions of years of evolution of a family of ion channel proteins that are also found in prokaryotes and diverse eukaryotes, and probably exist in all life forms. This review traces the evolution of ion channels, with particular emphasis on the factors and evolutionary pathways that may have given rise to voltage-gated potassium (K+), calcium (Ca2+), and sodium (Na+) channels. The review also highlights the utility of comparing phylogenetically distinct versions of the same protein as a means to better understand the structure and function of proteins.
150 citations
TL;DR: It is found that there is no indication in adult male African catfish for a direct, GnRH-mediated stimulation of LH synthesis, and the role of GnRH as LH secretagogue is evident, but the limited available information at present precludes a generalized view on the testicular feedback on FSH.
Abstract: The pituitary gonadotropins luteinizing hormone (LH) and follicle-stimulating hormone (FSH) regulate steroidogenesis and spermatogenesis by activating receptors expressed by Leydig cells (LH receptor) and Sertoli cells (FSH receptor), respectively. This concept is also valid in fish, although the piscine receptors may be less discriminatory than their mammalian counterparts. The main biological activity of LH is to regulate Leydig-cell steroid production. Steroidogenesis is moreover modulated in an autoregulatory manner by androgens. The male sex steroids (testosterone in higher vertebrates, 11-ketotestosterone in fish) are required for spermatogenesis, but their mode of action has remained obscure. While piscine FSH also appears to have steroidogenic activity, specific roles have not been described yet in the testis. The feedback of androgens on gonadotrophs presents a complex pattern. Aromatizable androgens/estrogens stimulate LH synthesis in juvenile fish; this effect fades out during maturation. This positive feedback on LH synthesis is balanced by a negative feedback on LH release, which may involve GnRH neurones. While the role of GnRH as LH secretagogue is evident, we have found no indication in adult male African catfish for a direct, GnRH-mediated stimulation of LH synthesis. The limited available information at present precludes a generalized view on the testicular feedback on FSH.
150 citations
TL;DR: It is found that even a single meal containing 24% of glucose is sufficient to induce the GK expression (mRNA and activity) as in mammals, and suggests that in carnivorous rainbow trout, the liver is capable to strongly regulate the utilisation of glucose but not the synthesis of glucose.
Abstract: The low dietary starch utilisation by rainbow trout (Oncorhynchus mykiss) may be attributed to a dysfunction of the nutritional regulation of the hepatic glucose/glucose-6-phosphate cycle. The present study was initiated to analyse the regulation of activity and gene expression of hepatic glucokinase (GK) and glucose-6-phosphatase (G6Pase) by dietary carbohydrates in this species. We found that even a single meal containing 24% of glucose is sufficient to induce the GK expression (mRNA and activity) as in mammals. In contrast, although the inhibitory effect of dietary glucose on G6Pase expression is observed at the molecular level, the G6Pase activity is not significantly inhibited by dietary glucose. Thus, in contrast to the gluconeogenic G6Pase enzyme, a rapid adaptation of the hepatic glycolytic GK enzyme to dietary glucose seems effective in rainbow trout. These results suggest that in carnivorous rainbow trout, the liver is capable to strongly regulate the utilisation of glucose but not the synthesis of glucose.
TL;DR: The results suggest the Bmdsx would also regulate sexual differentiation, as does the Drosophila dsx gene.
Abstract: The doublesex (dsx) gene is known as the final gene of the sex-determining cascade in Drosophila melanogaster. We have isolated a homologue of dsx in the silkworm, Bombyx mori, which has an epistatic feminizing gene located on the W chromosome. RT-PCR analysis indicated that B. mori dsx (Bmdsx) was transcribed in all the examined tissues, and the size of the amplified products was different between males and females. In Northern blot hybridization of poly(A)(+) RNA, the Bmdsx probe also detected a band with a sex-specific size difference. The male-specific cDNA lacked the sequence between 713 and 961nt of the female-specific cDNA. An RNase protection assay indicated that this sequence was male-specifically removed from the Bmdsx pre-mRNA. Southern blot analysis showed that Bmdsx is present at a single copy in the genome. These results suggested that the primary Bmdsx transcript is alternatively spliced to yield male- and female-specific mRNA isoforms. These sex-specific isoforms encode polypeptides with a common amino-terminal sequence but sex-specific carboxyl termini. DNA binding domain (DM domain) of BmDSX has 80% identity with D. melanogaster DSX proteins. These results suggest the Bmdsx would also regulate sexual differentiation, as does the Drosophila dsx gene.
TL;DR: Results further support that NPY is a physiological brain transducer involved in the regulation of daily appetite and feeding in goldfish.
Abstract: In mammals, NPY is a key factor in the regulation of feeding behavior. In the present study, the effects of refeeding for 1–3 h in 72–75-h food deprived (FD) goldfish on the levels of NPY mRNA in telencephalon-preoptic (TEL-POA), hypothalamus (HYP) and optic tectum-thalamus (OT-THAL) were examined, using Northern blot analysis. Goldfish FD for 72 h exhibited a significant increase in NPY mRNA levels in all brain regions. At 1 h after 72-h FD (73-h FD), NPY mRNA was significantly increased in TEL-POA and OT-THAL, but remained the same as 72-h FD fish in HYP. At 3 h after 72-h FD (75 h), all brain regions exhibited a significant increase in NPY mRNA levels. However, subsequent refeeding for 1–3 h rapidly and completely reversed the effects of FD in all brain regions, reaching fed levels within 1–3 h of refeeding. Serum GH levels were highest in 72-h FD fish, but decreased significantly over 1–3 h after 72-h FD; whereas, refeeding reversed the increase in serum GH levels only at 3 h after refeeding. Taken together, these results further support that NPY is a physiological brain transducer involved in the regulation of daily appetite and feeding in goldfish.
TL;DR: Three different experimentally-induced catabolic states in fishes are compared in this paper: fasting; insulin-dependent diabetes mellitus (IDDM); and stress, and the utility of serum IGFBP measurement to serve as an effective indicator of catabolic condition in fishes is discussed.
Abstract: In fishes as well as in all vertebrates in which it has been assessed, physiological shifts toward catabolism (e.g. such as during food deprivation) are consistently associated with elevations in the serum levels of at least one (often two in fishes) IGFBP in the ≤31-kDa size range. In mammals, 30-kDa IGFBP-1 is strongly up-regulated under catabolic circumstances, and it plays an important physiological role by sequestering IGF peptides to inhibit energy-expensive growth until conditions are more favorable (e.g. with resumed feeding). Similarly in fishes, it has been found that when the ≤31-kDa IGFBPs are elevated in serum, somatic growth is inhibited, suggesting a similar growth-inhibitory role of these proteins to that of mammalian IGFBP-1. Three different experimentally-induced catabolic states in fishes are compared in this paper: fasting; insulin-dependent diabetes mellitus (IDDM); and stress. A strong relationship between elevated serum cortisol concentrations and the presence of IGFBPs in each case is noted, and the utility of serum IGFBP measurement to serve as an effective indicator (marker) of catabolic condition in fishes is discussed.
TL;DR: This overview will summarise both the conserved and the divergent aspects of the various immune systems of metazoans throughout their history ultimately revealing the unique characteristics of the immune system in vertebrates.
Abstract: All metazoans protect themselves from invasion of microorganisms, parasites, viruses and even cells from individuals of the same species. In all phyla, precise mechanisms of recognition allow for discrimination between self and non-self avoiding the danger of contamination. In that sense, all metazoans have an ‘immune system’. This does not mean that the recognition events and the resulting effector reactions are mediated by homologous systems across metazoans. Some features may be conserved while some will be specific to one phylum or even one class within a Ž phylum Fig. 1 and review in Du Pasquier and . Flajnik, 1999 . This overview will summarise both the conserved and the divergent aspects of the various immune systems of metazoans throughout their history ultimately revealing the unique characteristics of the immune system in vertebrates.
TL;DR: The sequence alignments between the predicted protein sequence of rainbow trout desaturase-like and other Delta6- and Delta5-desaturases revealed a high percentage identity withDelta6- Desaturases (64-66% identity with vertebrate Delta6s).
Abstract: This report describes the cloning, nutritional regulation and tissue distribution of a desaturase-like enzyme in rainbow trout (Oncorhynchus mykiss). The open reading frame of the trout desaturase-like cDNA encodes a 454-amino acid peptide that contains two membrane-spanning domains, three histidine-rich regions and a cytochrome b5 domain, which all align perfectly with the same domains located in other recently identified vertebrate Delta5- and Delta6-desaturases. Nutritional regulation of trout desaturase-like gene expression, as well as the tissue expression profile, are also similar to those observed in other vertebrate Delta5- and Delta6-desaturases. Finally, the sequence alignments between the predicted protein sequence of rainbow trout desaturase-like and other Delta6- and Delta5-desaturases revealed a high percentage identity with Delta6-desaturases (64-66% identity with vertebrate Delta6-desaturases). These results demonstrate for the first time the presence and nutritional modulation of a Delta6-desaturase-like cDNA in rainbow trout.
TL;DR: Chicken liver mitochondria consumed O2 at an accelerated rate when supplied with low concentrations of hydrogen sulfide, suggesting that this may be a widespread mitochondrial trait, and that it is consistent with the hypothesis that mitochondria originated from sulfide-oxidizing symbionts.
Abstract: Chicken liver mitochondria consumed O2 at an accelerated rate when supplied with low concentrations of hydrogen sulfide. Maximum respiration occurred in 10 μM sulfide, and continued more slowly up to concentrations as high as 60 μM. Sulfide oxidation was coupled to adenosine triphosphate (ATP) synthesis, as shown by firefly luciferase luminescence and by measurement of the mitochondrial membrane electrochemical gradient. Synthesis of ATP required low, steady-state concentrations of sulfide (<5 μM), which were maintained by use of a syringe pump. The ratio of consumed O2 to sulfide changed at low sulfide and O2 concentrations, indicating alternative metabolic reactions and products. In low concentrations of sulfide, presumably most similar to physiological, the O2/sulfide ratio was 0.75. This is the first report of sulfide oxidation linked to ATP synthesis in any organism not specifically adapted to a sulfide-rich environment. We suggest that this may be a widespread mitochondrial trait, and that it is consistent with the hypothesis that mitochondria originated from sulfide-oxidizing symbionts.
TL;DR: It is shown that IGF-I responds to changed rations within 2-4 weeks in salmonids, and was strongly correlated with specific growth rate in weight in terminally sampled fish after 4 weeks.
Abstract: We examined the response of growth hormone (GH), total plasma insulin-like growth-factor I (IGF-I), and growth rate to a change in ration in coho salmon. Tanks of individually tagged fish were placed on high, medium, or low ration, and sampled every 2 weeks for 8 weeks to create a range of growth rates. Some fish received non-lethal blood draws, while others were sampled terminally. Plasma IGF-I levels were higher in high ration fish than in low ration fish from 4 weeks after the beginning of experimental diets to the end of the experiment. GH levels were low and similar in all fish after changing rations, except for the fish in the low ration group at week 2. IGF-I was strongly correlated with specific growth rate in weight in terminally sampled fish after 4 weeks. GH did not correlate with growth rate or IGF-I levels. Growth parameters (length, weight, specific growth rates in weight and length, and condition factor) responded to ration. Serial sampling reduced growth rates and hematocrit, but did not change hormone levels. This study shows that IGF-I responds to changed rations within 2-4 weeks in salmonids.
TL;DR: The study confirms the structural relationship of collagen to habitat and function and revealed interesting differences in the frog skin collagen when compared to the hitherto known vertebrate collagens.
Abstract: The current paper pertains to the study of frog skin, more specifically Rana tigerina skin collagen, which is a major extracellular matrix protein known to play an important role in the wound-healing process. This study revealed interesting differences in the frog skin collagen when compared to the hitherto known vertebrate collagens. This could probably be attributed to the position of the amphibians in the vertebrate hierarchy. Therefore, detailed investigations on the various physico-chemical properties, such as reconstitution, redissolution, viscosity and denaturation were carried out. The study confirms the structural relationship of collagen to habitat and function.
TL;DR: Evidence is now accumulating that many of the co-factors that regulate MRF activity in mammals are also present in lower vertebrates, and the inductive signals controlling the initial expression of MRFs within the developing somite of lower vertebrate proteins are currently being elucidated.
Abstract: The transcription factors of the MyoD family have essential functions in myogenic lineage determination and muscle differentiation. These myogenic regulatory factors (MRFs) activate muscle-specific transcription through binding to a DNA consensus sequence known as the E-box present in the promoter of numerous muscle genes. Four members, MyoD, myogenin, myf5 and MRF4/herculin/myf6, have been identified in higher vertebrates and have been shown to exhibit distinct but overlapping functions. Homologues of these four MRFs have also been isolated in a variety of lower vertebrates, including amphibians and fish. Differences have been observed, however, in both the expression patterns of MRFs during muscle development and the function of individual MRFs between lower and higher vertebrates. These differences reflect the variety of body muscle formation patterns among vertebrates. Furthermore, as a result of an additional polyploidy that occurred during the evolution of some amphibians and fish, MyoD, myogenin, myf5 and MRF4 may exist in lower vertebrates in two distinct copies that have evolved separately, acquiring specific roles and resulting in increased complexity of the myogenic regulatory network. Evidence is now accumulating that many of the co-factors (E12, Id, MEF2 and CRP proteins) that regulate MRF activity in mammals are also present in lower vertebrates. The inductive signals controlling the initial expression of MRFs within the developing somite of lower vertebrate proteins are currently being elucidated.
TL;DR: The results of the study suggest that the two s-triazine pesticides have an additive and not a synergistic impact on olfactory-mediated endocrine function in mature male salmon parr.
Abstract: Short-term exposure of the olfactory epithelium of mature male Atlantic salmon parr to either the pesticide simazine (concentrations 1.0 and 2.0 microg l(-1)) or the pesticide atrazine (concentration 1.0 microg l(-1)) significantly reduced the olfactory response to the female priming pheromone, prostaglandin F(2alpha). In addition, the reproductive priming effect of the pheromone on the levels of expressible milt was also reduced after exposure to the individual pesticides (simazine 0.1, 0.5, 1.0 and 2.0 microg l(-1) and atrazine 0.5 and 2.0 microg l(-1)). When the olfactory epithelium was exposed to a mixture of simazine and atrazine, (concentrations of 0.5:0.5 and 1.0:1.0 microg l(-1)), there was no significant reduction in the olfactory response when compared to the single pesticides at equivalent concentrations. In addition, exposure to a mixture of simazine and atrazine had no synergistic effect on the priming response, and plasma levels of testosterone, 11-ketotestosterone and 17,20beta-dihydroxy-4-pregnen-3-one were similar in the groups of male parr exposed to the individual pesticides. Although the levels of expressible milt were reduced in all groups, there were no significant differences between the different pesticide treatments. The results of the study suggest that the two s-triazine pesticides have an additive and not a synergistic impact on olfactory-mediated endocrine function in mature male salmon parr.
TL;DR: This review summarizes the current research on human exo -α-sialidase (sIALidase, neuraminidase).
Abstract: This review summarizes the current research on human exo-alpha-sialidase (sialidase, neuraminidase). Where appropriate, the properties of viral, bacterial, and human sialidases have been compared. Sialic acids are implicated in diverse physiological processes. Sialidases, as enzymes acting upon sialic acids, assume importance as well. Sialidases hydrolyze the terminal, non-reducing, sialic acid linkage in glycoproteins, glycolipids, gangliosides, polysaccharides, and synthetic molecules. Therefore, a variety of assays are available to measure sialidase activity. Human sialidase is present in several organs and cells. Its cellular distribution could be cytosolic, lysosomal, or in the membrane. Human sialidase occurs in a high molecular-mass complex with several other proteins, including cathepsin A and beta-galactosidase. Multi-protein complexation is important for the in vivo integrity and catalytic activity of the sialidase. However, multi-protein complexation, the occurrence of isoenzymes, diverse subcellular localization, thermal instability, and membrane association have all contributed to difficulties in purifying and characterizing human sialidases. Human sialidase isoenzymes have recently been cloned and sequenced. Even though crystal structures for the human sialidases are not available, the highly conserved regions of the sialidase from various organisms have facilitated molecular modeling of the human enzyme and raise interesting evolutionary questions. While the molecular mechanisms vary, genetic defects leading to human sialidase deficiency are closely associated with at least two well-known human diseases, namely sialidosis and galactosialidosis. No therapy is currently available for either disease. A thorough investigation of human sialidases is therefore crucial to human health.
TL;DR: It is concluded that MAP kinases are important components of salinity adaptation and participate in osmosensory signaling pathways in gill epithelium of euryhaline fishes.
Abstract: The abundance and activity of three subgroups of mitogen-activated protein (MAP) kinases, the extracellular signal regulated kinase 1 (ERK1), stress-activated protein kinase 1/ Jun N-terminal kinase (SAPK1), and stress-activated protein kinase 2/ p38 (SAPK2), were measured in gill epithelium of the euryhaline teleost Fundulus heteroclitus exposed for 1 h to 4 weeks to hyper- and hyposmotic stress. The abundance of ERK1, SAPK1 and SAPK2 was analyzed by standard Western immunodetection. MAP kinase activity is a function of phosphorylation and was measured using phospho-specific and MAP kinase subgroup-specific antibodies. The abundance of the 63 kDa fish isoform of SAPK2 increases significantly during hyper- but not hyposmotic stress while ERK1 and SAPK1 protein levels remain unchanged during both types of osmotic stress. In contrast to this small effect of osmotic stress on MAP kinase abundance, the activity of all MAP kinases decreases significantly in response to hyperosmotic stress and increases significantly during hyposmotic stress. These results demonstrate for the first time that the activity of all major MAP kinases is osmoregulated in gill epithelium of euryhaline fish. Based on these results we conclude that MAP kinases are important components of salinity adaptation and participate in osmosensory signaling pathways in gill epithelium of euryhaline fishes.
TL;DR: The results indicate that avian embryos discriminate between different carotenoids during their distribution from the yolk to various tissues as mentioned in this paper, and β-carotene was a significant component in the yolks of these three wild species, forming 25-29% by wt.
Abstract: The concentrations (μg/g wet yolk) of total carotenoids in eggs of the common moorhen ( Gallinula chloropus ), American coot ( Fulica americana ) and lesser black-backed gull ( Larus fuscus ), collected in the wild, were 47.5, 131.0 and 71.6, respectively. In contrast to data for eggs of the domestic chicken, β-carotene was a significant component in the yolks of these three wild species, forming 25–29% by wt. of the total carotenoids present. The concentration of total carotenoids in the livers of the newly-hatched chicks was 5–10 times higher than in the other tissues and β-carotene was again a major component, forming 37–58% of the hepatic carotenoids. In the newly-hatched gull, the proportions of both lutein and zeaxanthin were very low in the liver but high in the heart and muscle when compared with the yolk. By contrast canthaxanthin, echinenone and β-carotene were very minor constituents of heart and muscle when compared with their proportions in the yolk of the gull. The proportions of lutein and zeaxanthin in the liver of the newly-hatched coot and moorhen were also far lower than in the yolk whereas the liver was relatively enriched with β-cryptoxanthin, β-carotene and (in the moorhen) echinenone. The results indicate that avian embryos discriminate between different carotenoids during their distribution from the yolk to the various tissues.
TL;DR: The results suggest that enough PUFA, especially n-3PUFA, should be supplied to the crab during ovarian maturation, as both triacylglycerol and phosphatidylcholine were responsible for the increase in ovarian lipid concentration during sexual maturation.
Abstract: This experiment was conducted to investigate the variation in lipid composition during the ovarian maturation of the crab Eriocheir sinensis . The Chinese mitten-handed crab broodstock was divided into six different maturation periods according to the size and color of ovary. Ovary, hepatopancreas, muscle, and hemolymph of broodstock in different maturation periods were analyzed for total lipid and fatty acids using gas chromatography, and lipid classes by thin-layer chromatography. The ovarian lipid concentration (expressed as percent wet ovarian weight) increased steadily from stage II (5.4%) to stage IV (19.1%), and decreased to the lowest levels after spawning (stage V, 6.6%). The hepatopancreatic lipid concentration (expressed as percent wet hepatopancreatic weight) increased with maturity of the ovaries, reached a maximum at stage III 2 (29.9%), and decreased during the subsequent period to spawning (16.7%). The muscular and hemolymph lipid concentration did not change markedly during the ovarian development. These results suggest the possible movement of hepatopancreatic lipids to the ovaries during the ovarian maturation. Both triacylglycerol and phosphatidylcholine were responsible for the increase in ovarian lipid concentration during sexual maturation. The fatty acids of total lipid, triacylglycerol, and phosphatidylcholine of the ovaries did not vary systematically during the ovarian maturation, but the ratio between n-3PUFA (polyunsaturated fatty acid) and n-6PUFA did change regularly with the ovarian lipid. These suggest that enough PUFA, especially n-3PUFA, should be supplied to the crab during ovarian maturation.
TL;DR: In vitro experiments showed that recombinant human activin-A leads to higher levels of GPalpha, FSHbeta and LHbeta mRNAs in pituitary cell culture, and evidence for their differential regulation, and insight into their mode of action is provided.
Abstract: A steroidogenic tilapia gonadotropin (taGtH=LH) was purified from pituitaries of hybrid tilapia (Oreochromis niloticus x O. aureus) and a homologous RIA was established. This RIA enabled the study of the endocrine regulation of GtH release, the transduction pathways involved in its secretion and its profile during the spawning cycle. Discrepancies between steroid and taGtH peaks during the cycle led to the conclusion that an additional gonadotropin similar to salmonid FSH operates early in the cycle. In order to identify this hormone and to study the endocrine control of synthesis of all gonadotropin (GtH) subunits, a molecular approach was taken. The cDNA sequences and the entire gene sequences encoding the FSHbeta and LHbeta subunits, as well as an incomplete sequence of the glycoprotein hormone alpha subunit (GPalpha), were cloned. Salmon gonadotropin-releasing hormone (sGnRH) elevated mRNA steady-state levels of all three GtH subunits in cultured pituitary cells. Pituitary adenylate cyclase-activating polypeptide (PACAP) and neuropeptide Y (NPY) also stimulated the expression of these subunits and potentiated the effect of GnRH, except that NPY did not affect FSHbeta. The GnRH and NPY effects were found to be mediated mainly through protein kinase C (PKC), while protein kinase A (PKA) cascade was involved to a lesser extent. Mitogen-activated protein kinase (MAPK) cascade takes part in mediating GnRH effects, possibly via PKC. Testosterone (T) and estradiol (E2), but not 11-ketotestosterone (KT), are able to elevate GPalpha and LHbeta mRNAs in pituitary cells of early maturing or regressing males. Low levels of T exposure are associated with elevated FSHbeta mRNA in cells of mature fish, while higher levels suppress it, but elevate LHbeta mRNA. In vivo observations also showed the association of low T levels with increased FSHbeta mRNA and high T levels with elevated LHbeta mRNA. In accordance with these findings, analysis of LHbeta and FSHbeta 5' gene-flanking regions revealed on both gene promoters a GtH-specific element (GSE), half site estrogen response elements (ERE), cAMP response element (CRE) and AP1. In vitro experiments showed that recombinant human activin-A leads to higher levels of GPalpha, FSHbeta and LHbeta mRNAs in pituitary cell culture. Porcine inhibin marginally decreased the mRNA levels of GPalpha and FSHbeta, but at a low level (1 ng/ml) it stimulated that of LHbeta. These results shed some light on certain hypothalamic and gonadal hormones regulating the expression of GtH subunit genes in tilapia. In addition, they provide evidence for their differential regulation, and insight into their mode of action.
TL;DR: This work successfully extracted and purified a sufficient quantity of pigment from the red plumage of the Scarlet Macaw (Ara macao) for a partial chemical analysis, and proposes a linear polyenal structure comparable with the molecules tetradecahexenal, hexadecaheptanal, octadecaoctenal and eicosanonenal.
Abstract: Parrots (Psittaciformes) harbor unusually bright, non-carotenoid, feather pigments. We successfully extracted and purified a sufficient quantity of pigment from the red plumage of the Scarlet Macaw ( Ara macao) for a partial chemical analysis. The extracts were analyzed by HPLC coupled with UV–VIS and mass spectroscopy before and after total hydrogenation. We found at least four pigment components. We propose a linear polyenal structure comparable with the molecules tetradecahexenal, hexadecaheptenal, octadecaoctenal and eicosanonenal.
TL;DR: The data suggest that, in the presence of PI-containing food, H. virescens larvae express new trypsin molecules that form oligomers and are apparently less affected by PIs because of tighter binding to the substrate (lower K(m) values) and a putative decreased affinity for PIs.
Abstract: The tobacco budworm Heliothis virescens is adapted to feed on tobacco leaves that have proteinase protein inhibitors (PIs). To study this adaptation, the midgut proteinases of Heliothis virescens larvae reared on artificial PI-free diet and on tobacco leaves were compared using ion exchange chromatography, hydrophobic chromatography, gel filtration and polyacrylamide gel electrophoresis at different conditions. SDS polyacrylamide-gradient gel electrophoresis (SDS-PAGE) and kinetic studies shown that leaf-fed larvae have a chymotrypsin ( M r 26 000) and four trypsins (T1–T4) with the following properties: T1, K m 0.3 μM, M r 70 000 ; T2, K m 0.4 μM, M r 67 000; T3, K m 2.4 μM, M r 29 000; T4, K m 15 μM, M r 17 000. Diet-fed larvae have a chymotrypsin ( M r 26 000) and a major trypsin ( K m 2.9 μM, M r 29 000). Native PAGE at different gel concentrations showed that in these conditions, only T1 and T2 occur in leaf-fed larvae, whereas gel filtration in the absence and presence of SDS revealed that T1 and T2 might arise by polymerization of T3 and T4, respectively. The data suggest that, in the presence of PI-containing food, H. virescens larvae express new trypsin molecules that form oligomers and are apparently less affected by PIs because of tighter binding to the substrate (lower K m values) and a putative decreased affinity for PIs.
TL;DR: Behavior responses of male goldfish to three steroidal components of the female preovulatory pheromone are examined, suggesting that goldfish, and likely other fish species, may employ blends of hormonal products as phersomones.
Abstract: The goldfish sex pheromone system is the best understood among the teleost fishes. Pheromones in this species are unspecialized hormonal products, which are released in ratios that vary with reproductive status. This study examined behavioral responses of male goldfish to three steroidal components of the female preovulatory pheromone: 17,20beta-dihydroxy-4-pregnen-3-one (1720betaP); 17,20beta-dihydroxy-4-pregnen-3-one-20-sulfate (1720betaP-S); and androstenedione (AD). Males were observed during exposure to nanomolar concentrations of each steroid over a 2-h period. We observed chasing, nudging (courtship behaviors) and pushing (an aggressive behavior). Each steroid elicited a different set of behaviors. 1720betaP, which is released by ovulatory females, elicited a low level of chasing and nudging that persisted throughout the experiment. Exposure to 1720betaP-S, which is released primarily by ovulatory females, triggered a large increase in nudging and chasing that lasted for only 5 min. In contrast, AD, which is released by females early in the ovulatory cycle and by mature males, elicited increases in aggressive behavior. 1720betaP and 1720betaP-S both caused increases in GtH-II release while AD did not. These results demonstrate that goldfish can discriminate components found in the female pheromone blend, suggesting that goldfish, and likely other fish species, may employ blends of hormonal products as pheromones.
TL;DR: This study is the first report of a death-domain-containing TNF receptor and the first publication of a TNF ligand in fish.
Abstract: Using degenerative primers, partial cDNAs of a TNF (tumor necrosis factor) receptor and two TNF ligands were obtained by PCR of zebrafish and trout cDNAs, or cDNA libraries. These fragments were then used to screen cDNA libraries of appropriate tissues to obtain clones containing full coding sequences. A zebrafish cDNA was obtained that presumably codes for a 438 amino acid ovarian TNF receptor (OTR) that was identified as a death-domain-containing member of the TNF receptor family. On Northern blots, the OTR cDNA hybridized with a 3.4-kb transcript that is abundant in the zebrafish ovary but lightly detected in all other tissues tested. A zebrafish cDNA presumably coding for a 214 amino acid protein with sequence similarity to mammalian TRAIL (TNF-related apoptosis inducing ligand), was also isolated. In addition, a fragment of the brook trout TRAIL homologue was obtained. Finally, a full-length brook trout cDNA, that presumably codes for a 255 amino acid protein with sequence similarity to mammalian TNF-alpha and lymphotoxin-alpha, was isolated. This study is the first report of a death-domain-containing TNF receptor and the first published report of a TNF ligand in fish.