Biomedical subjects

Daniel G Cyr

Publications and source records attributed to Daniel G Cyr.

At least 19 recordsLinked to original sources

PubMed2007

Proliferation of adult sertoli cells following conditional knockout of the Gap junctional protein GJA1 (connexin 43) in mice.

GJA1 (also known and referred to here as connexin 43 and abbreviated CX43) is the predominant testicular gap junction protein, and CX43 may regulate Sertoli cell maturation and spermatogenesis. We hypothesized that lack of CX43 would inhibit Sertoli cell differentiation and extend proliferation. To test this, a Sertoli cell-specific Cx43 knockout (SC-Cx43 KO) mouse was generated using Cre-lox technology. Immunohistochemistry indicated that CX43 was not expressed in the Sertoli cells of SC-Cx43 KO mice, but was normal in organs such as the heart. Testicular weight was reduced by 41% and 76% in SC-Cx43 KO mice at 20 and 60 days, respectively, vs. wild-type (wt) mice. Seminiferous tubules of SC-Cx43 KO mice contained only Sertoli cells and actively proliferating early spermatogonia. Sertoli cells normally cease proliferation at 2 wk of age in mice and become terminally differentiated. However, proliferating Sertoli cells were present in SC-Cx43 KO but not wt mice at 20 and 60 days of age. Thyroid hormone receptor alpha (THRA) is high in proliferating Sertoli cells, then declines sharply in adulthood. Thra mRNA expression was increased in 20-day SC-Cx43 KO vs. wt mice, and it showed a trend toward an increase in 60-day mice, indicating that loss of CX43 in Sertoli cells inhibited their maturation. In conclusion, we have generated mice lacking CX43 in Sertoli cells but not other tissues. Our data indicate that CX43 in Sertoli cells is essential for spermatogenesis but not spermatogonial maintenance/proliferation. SC-Cx43 KO mice showed continued Sertoli cell proliferation and delayed maturation in adulthood, indicating that CX43 plays key roles in Sertoli cell development.

Animals↗

PubMed2007

In utero exposure to tributyltin alters the expression of E-cadherin and localization of claudin-1 in intercellular junctions of the rat ventral prostate.

Tributyltin (TBT) is an environmental contaminant, exhibiting well-established toxicity to reproductive systems in aquatic organisms. Little information exists regarding the effects of TBT on mammalian reproduction. Cellular junctions are crucial for sperm development and maturation. Intercellular tight junctions are formed by transmembrane proteins such as claudins (Cldns), while the formation of tight junctions involves signaling components of adhering junctions, comprised of cadherins. The objectives of this study were to determine the effects of in utero exposure to TBT on the rat ventral prostate. Pregnant Sprague-Dawley rats were given doses of TBT (2.5, 10, or 20 mg/kg) throughout gestation and sacrificed at Day 91. Ventral prostate weights of TBT-treated rats were decreased in all treatment groups. Results of gene expression macro-array analysis indicated that numerous genes related to cellular adhesion and cell polarity were affected. Cldn-1 mRNA levels decreased after exposure to TBT. Cldn-1 was immunolocalized to the apical lateral margins of adjacent prostatic epithelial cells in controls, but was increasingly dispersed along the lateral plasma membrane with increasing TBT dose, suggesting that the targeting of Cldn-1 or its localization to tight junctions was altered as a result of fetal TBT exposure. E-cadherin mRNA levels and immunolocalization were decreased in a dose-dependent manner. These data indicate that in utero TBT exposure results in permanent alterations in ventral prostate and that these are associated with alterations in the expression and distribution of cell adhesion and tight junctional proteins.

Animals↗

PubMed2007

Structural abnormalities in spermatids together with reduced sperm counts and motility underlie the reproductive defect in HIP1-/- mice.

Huntingtin interacting protein 1 (HIP1) is an endocytic adaptor protein with clathrin assembly activity that binds to cytoplasmic proteins, such as F-actin, tubulin, and huntingtin (htt). To gain insight into diverse functions of HIP1, we characterized the male reproductive defect of HIP1(-/-) mice from 7 to 30 weeks of age. High levels of HIP1 protein were expressed in the testis of wild-type mice as seen by Western blots and as a reaction over Sertoli cells and elongating spermatids as visualized by immunocytochemistry. Accordingly, major structural abnormalities were evident in HIP1(-/-) mice with vacuolation of seminiferous tubules caused by an apparent loss of postmeiotic spermatids and a significant reduction in mean profile area. Remaining spermatids revealed deformations of their heads, flagella, and/or acrosomes. In some Sertoli cells, ectoplasmic specializations (ES) were absent or altered in appearance accounting for the presence of spherical germ cells in the epididymal lumen. Quantitative analyses of sperm counts from the cauda epididymidis demonstrated a significant decrease in HIP1(-/-) mice compared to wild-type littermates. In addition, computer-assisted sperm analyses indicated that velocities, amplitude of lateral head displacements (ALH), and numbers and percentages of sperm in the motile, rapid, and progressive categories were all significantly reduced in HIP1(-/-) mice, while the numbers and percentages of sperm in the static category were greatly increased. Taken together, these various abnormalities corroborate reduced fertility levels in HIP1(-/-) mice and suggest a role for HIP1 in stabilizing actin and microtubules, which are important cytoskeletal elements enabling normal spermatid and Sertoli cell morphology and function.

Animals↗

PubMed2006

Sexual dimorphism in the regulation of liver connexin32 transcription in hexachlorobenzene-treated rats.

Hexachlorobenzene (HCB), an epigenetic carcinogen, causes female rats to be more susceptible to liver tumor formation than males. HCB exposure in females downregulates the expression of Cx32, a gap junction protein, through the activation of Akt. The objectives of this study were to determine (1) the implication of different regions of the hepatic Cx32 promoter in the observed sexual dimorphism in the expression of Cx32, (2) the implication of different regions of the hepatic Cx32 promoter in the HCB-induced downregulation of Cx32 in female rat liver, and (3) if HCB exposure modulates the binding of transcription factors on the Cx32 promoter through Akt activation. Male and female rats were exposed to HCB during 5 consecutive days and sampled 45 days later. Electrophoresis mobility shift assays showed that the intensity of only one nuclear protein-DNA complex differed between males and females. The formation of this complex requires two binding sites to be intact in a fragment of the basal promoter (Fr26). Following HCB exposure, the intensity of two complexes (Fr26 and Fr110) was decreased in females, but not in males, consistent with the decrease in Cx32 expression observed only in HCB-treated females. In vitro studies using a rat hepatocyte cell line (MH1C1) showed that the formation of the Fr110 protein-DNA complex appears to be controlled by Akt and requires the integrity of a Myb site. Overall, results suggest that both the sexual dimorphism and the downregulation of Cx32 in HCB-treated female rats are mediated by a reduction in the binding of activating transcription factors on the Cx32 promoter.

Animals↗

PubMed2006

In utero exposure to tributyltin chloride differentially alters male and female fetal gonad morphology and gene expression profiles in the Sprague-Dawley rat.

Tributyltin (TBT) is an environmental contaminant commonly used in anti-fouling agents for boats, as well as a by-product from several industrial processes. It has been shown to accumulate in organisms living in areas with heavy maritime traffic thereby entering the food chain. Here, we determined the consequences of in utero exposure to TBT on the developing fetal gonads in the Sprague-Dawley rat. Timed pregnant rats were gavaged either with vehicle or TBT (0.25, 2.5, 10 or 20 mg/kg) from days 0 to 19 or 8 to 19 of gestation. On gestational day 20, dams were sacrificed; fetal testes and ovaries were processed for light (LM) or electron microscopic (EM) evaluation and RNA was prepared for gene expression profiling. At the highest doses of TBT the number of Sertoli cells and gonocytes was reduced, there were large intracellular spaces between Sertoli cells and gonocytes and there was an increased abundance of lipid droplets in the Sertoli cells; EM studies revealed abnormally dilated endoplasmic reticulum in Sertoli cells and gonocytes. In the intertubular region between adjacent interstitial cells, immunostaining for the gap junctional protein connexin 43 was strong in controls, whereas it was reduced or completely absent in treated rats. In the ovaries, TBT (20 mg/kg, days 0-19; 10 mg/kg, days 8-19) reduced the number of germ cells by 44% and 46%, respectively. On examining gene expression profiles in the testis, 40 genes out of 1176 tested were upregulated more than two-fold over control. While no genes were upregulated in the TBT exposed fetal ovary, eight genes were downregulated. In conclusion, in utero exposure to TBT resulted in gender-specific alterations in gonadal development and gene expression profiles suggesting that there may be different adaptive changes to toxicity in developing male and female rats.

Abnormalities, Drug-Induced↗

PubMed2006

The expression of multiple connexins throughout spermatogenesis in the rainbow trout testis suggests a role for complex intercellular communication.

Certain fish, such as rainbow trout (Oncorhynchus mykiss), are seasonal breeders. Spermatogenesis in rainbow trout is synchronous; therefore, at any time point during this process, germ cells are predominantly at the same stage of development. As such, rainbow trout represent an excellent model in which to study spermatogenesis. Gap junctions are composed of connexons, which are themselves formed by six transmembrane proteins termed connexins (Cxs). The objectives of this study were to assess which Cxs are expressed in the rainbow trout testis, and if their expression was stage specific during gonadal maturation. Rainbow trout were killed at various stages of maturation, and total cellular RNA was isolated from the testes. RT-PCR using degenerate primers recognizing all vertebrate Cxs indicates that there are several different Cxs in trout testes. Amplicons were cloned and sequenced. Homology comparisons indicate that these were cx43, cx43.4, cx31, and cx30. Immunolocalization of these Cxs indicate that Cx43 was localized primarily to Sertoli cells, while Cx43.4 was localized along the lateral plasma membranes between adjacent spermatocytes. Cx30 was localized to the interstitial Leydig cells, and Cx31 was localized primarily to the endothelium of interstitial blood vessels. The expression of each Cx varied as a function of the stage of spermatogenesis, suggesting that the expression of these proteins is highly regulated. Together, these results indicate that intercellular communication in the testis is complex, involves several different Cxs, and is a highly regulated process.

Amino Acid Sequence↗

PubMed2006

Activation of the integrin-linked kinase pathway downregulates hepatic connexin32 via nuclear Akt.

Gap junctions mediate intercellular communication through channels composed of proteins termed connexins (Cxs). We have shown that Cx32 is downregulated in the liver of female rats exposed to hexachlorobenzene (HCB), an epigenetic environmental carcinogen. This is concomitant with the activation of the integrin-linked kinase (ILK) pathway, leading to the activation and nuclear translocation of Akt and the inactivation of glycogen synthase kinase-3beta (GSK3beta). E-cadherin, an adhering junction protein, is also downregulated in the liver of these female rats, owing to the inactivation of GSK3beta. Using an in vitro model, the aim of this study was to determine the role of the ILK pathway in the regulation of Cx32. In order to mimic the activation of the ILK pathway, a well-differentiated rat hepatoma cell line, MH1C1, was transiently transfected with an expression vector for ILK (ILK+ cells). ILK+ cells displayed significantly lower Cx32 mRNA levels and Akt was also activated and translocated into the nucleus. Using a constitutively active Akt expression vector, we showed that Akt transfected cells had lower Cx32 mRNA levels, indicating a role for Akt in Cx32 regulation. Finally, using an Akt-NES vector, a nuclear-active form of Akt, we showed that Cx32 protein levels were reduced in transfected cells as compared with cell transfected with the wild-type inactive Akt vector, suggesting that the nuclear form of Akt is responsible for the downregulation of Cx32. Overall, these data indicate that Cx32 is downregulated by the ILK pathway activation in rat hepatocytes and that this is mediated via the activation and nuclear translocation of Akt.

Active Transport, Cell Nucleus↗

PubMed2006

Immunomodulatory effects of estradiol and cadmium in adult female rats.

A wide range of toxic effects has been associated with cadmium (Cd) exposure in mammals. However, the physiological factors that modulate these effects have received limited attention. We have previously demonstrated that neonatal exposure of rats to Cd during lactation results in sex-specific immunotoxic effects in both juvenile and adult rats. The objectives of this study were to determine the effects of 17beta-estradiol (E(2)) on the immunotoxicity of Cd in female rats. We compared the effects of 28 days of exposure to 0, 5, and 25 ppm cadmium chloride (CdCl(2)) through drinking water on ovariectomized Sprague-Dawley rats and on ovariectomized rats with E(2) implant which mimicked the physiological level of E(2) in female rat. Our results clarify the control of important immune functions by E(2) at physiological level and demonstrate significant interactions between Cd and E(2) effects on the cytotoxic activity of natural killer cells and phagocytosis of splenic cells as well as on the total number of thymocytes and of the four subpopulations of the thymocytes as defined by the expression of the cell-surface markers CD4 and CD8. Cd and E(2) share several mechanisms of action that may account for these interactions. The estrogenic potential of Cd could also account for some of the observed effects. These interactions have to be taken into consideration in evaluating the risk of Cd immunotoxicity and the possible interactions with hormonal treatments.

Animals↗

PubMed2006

Expression of aquaporins in the efferent ductules, sperm counts, and sperm motility in estrogen receptor-alpha deficient mice fed lab chow versus casein.

Estrogens play an important role in the male reproductive tract, and this is especially so for the efferent ductules, where alpha-estrogen receptors (ERalpha) have been localized. Mice deficient in ERalpha (alphaERKO mice) are infertile, and the effect appears to be due in part to retention of water at the level of the efferent ductules. In the present study, we examined the consequences of ERalpha deletion on the distribution of certain aquaporins (AQPs), water protein channels, in the efferent ductules and on sperm numbers and motility. In addition, the effects of feeding mice a regular lab chow diet, which contains phytoestrogens, known to affect male reproductive tract functions, and a casein diet, which lacks phytoestrogens, were also assessed. Light microscope immunolocalizations of AQP-1 and AQP-9 revealed dramatic reduction and patchier staining in alphaERKO mice with distal areas of the efferent ductules being more affected than proximal areas. No other changes in immunolocalizations were noted as a consequence of diet. Computer-assisted sperm analyses demonstrated a 62% reduction in cauda epididymal sperm/ml in alphaERKO mice fed lab chow, whereas 87% fewer sperm/ml were observed in alphaERKO mice fed casein, suggesting an enhanced role for sperm production and concentration in a diet containing phytoestrogens. All sperm motility parameters were altered to some degree in alphaERKO mice fed lab chow. Alterations in sperm motility parameters were also detected, but were less dramatic in alphaERKO mice fed casein. These data suggest that the decrease in AQP expression in the efferent ductules of alphaERKO mice contributes in part to water retention in this tissue, eventually leading to backflow of water into the testis, with subsequent decreases in sperm concentration and motility. The data also suggest that phytoestrogens, which are present in regular lab chow, can influence the male reproductive tract with and without the presence of ERalpha, promoting efferent ductule and epididymal functions when ERalpha is expressed, but inhibiting these same functions when ERalpha is missing. Taken together the data underscore the importance of estrogens and ERalpha in maintaining sperm maturation and preventing male infertility.

Animals↗

PubMed2006

Identification of multiple claudins in the rat epididymis.

The luminal environment of the epididymis is highly specialized with specific proteins, ions, pH, etc. required for sperm maturation. Tight junctions between epididymal principal cells are responsible for the formation of the blood-epididymal barrier, which regulates this luminal environment. Claudins (Cldns) are a recently discovered family of transmembrane proteins and are essential components of tight junctions. Previous work from our laboratory has demonstrated the presence and localization of Cldn-1 in all regions of the rat epididymis. The objective of this study was to determine the presence and localization of other Cldns in the epididymis. Using RT-PCR we have identified mRNA transcripts for Cldn-3 through -9 in each region of the adult rat epididymis. Immunolocalization of Cldn-3, Cldn-4, and Cldn-5 were done in adult as well as in 42- and 14-day-old rats. Cldn-5 in adult rats was localized exclusively in blood vessels of the interstitium. Cldn-3 was localized apically in the epididymal epithelium between adjacent principal cells throughout the epididymis, where tight junctions have been reported histologically. There were no differences in the localization of Cldn-3 in epididymides of rats at the different ages. In 14-day-old rats, Cldn-4 was localized all along the lateral plasma membrane between adjacent principal cells. The immunostaining was more pronounced in the proximal regions of the epididymis. In both 42-day-old rats and adults, Cldn-4 was localized primarily to apical tight junctions between principal cells and staining was more pronounced in the proximal region of the epididymis. Cldn-16 transcripts were also identified by RT-PCR. These transcripts were present in both proximal and distal regions of the epididymis of young (Day 14 and 21) animals, but only in the proximal (initial segment) region of the adult epididymis. These data indicate that epididymal tight junctions are composed of several Cldns, suggestive of a complex regulation of the blood-epididymal barrier.

Aging↗

PubMed2005

Involvement of the integrin-linked kinase pathway in hexachlorobenzene-induced gender-specific rat hepatocarcinogenesis.

Overexpression of the integrin-linked kinase (ILK) pathway disrupts cell-cell interactions, an epigenetic event leading to epithelial cell transformation. Female rats exposed to hexachlorobenzene (HCB) for 5 consecutive days and sampled 45 days later show a decrease in liver gap junctional intercellular communication. We hypothesized that HCB also alters E-cadherin expression and that this alteration is mediated by the ILK pathway. Hepatic ILK levels were markedly increased in HCB-treated female rats. Cytoplasmic/membrane levels of protein kinase B (Akt), a target of ILK, and its phosphorylated active form were decreased in treated female rats. Flow cytometric analysis showed a concomitant increase in nuclear Akt levels. Both ILK and Akt can phosphorylate glycogen synthetase kinase-3beta (GSK3beta), rendering it inactive. Phosphorylated-GSK3beta levels were higher in treated females and resulted in a twofold decrease in the activity of GSK3beta. The inactivation of GSK3beta in HCB-treated female rats resulted in the nuclear translocation of beta-catenin, as demonstrated by both immunocytochemistry and flow cytometric analyses. Western blot analysis showed an 84% decrease in E-cadherin levels in HCB-treated rats as compared to controls, and this decrease was not mediated by Snail activation. Mimicking the activation of ILK with specific GSK3beta inhibitors resulted in downregulation of E-cadherin levels but had no effect on Cx32 expression in the MH(1)C(1) cells. Overall, these results indicate that hepatic E-cadherin is downregulated as a result of an overexpression of the ILK pathway. The concomitant HCB-induced downregulation of intercellular communication does not occur as a result of either E-cadherin downregulation or GSK3beta inactivation.

Administration, Oral↗

PubMed2005

Characterization of a novel rat epididymal cell line to study epididymal function.

The epididymis is an androgen-dependent organ that allows spermatozoa to become fully functional as they pass through this tissue. The specialized functions of the epididymis are mediated by interactions between epididymal epithelial cells and between epididymal cells and spermatozoa. Although the critical role of the epididymis in sperm maturation is well established, the mechanisms regulating cell-cell interactions remain poorly understood because of the lack of appropriate cell line models. We now report the characterization of a novel rat caput epididymal cell line (RCE) that was immortalized by transfecting primary cultures of rat epididymal cells with the simian virus 40 large T antigen. At the electron microscope level, the cell line was composed of epithelial principal cells with characteristics of in vivo cells; principal cells had well-developed Golgi apparatus, abundant endoplasmic reticulum cisternae, and few endosomes. RCE cells expressed the mRNAs coding for the androgen receptor, estrogen receptor alpha, and 4-ene-steroid-5-alpha-reductase types 1 and 2 as well as epididymal-specific markers Crisp-1 and epididymal retinoic acid binding protein. Epididymal retinoic acid binding protein expression was significantly induced with dihydrotestosterone, although this effect was not blocked by flutamide, suggesting that RCE cells are not androgen responsive. Neighboring cells formed tight and gap junctions characteristic of epididymal cells in vivo and expressed tight (occludin and claudin-1, -3, and -4) and gap junctional proteins (connexin-26, -30.3, -32, and -43). The RCE cell line displays many characteristics of epithelial principal cells, thus providing a model for studying epididymal cell functions.

Androgens↗

PubMed2005

Sex-specific effects of neonatal exposures to low levels of cadmium through maternal milk on development and immune functions of juvenile and adult rats.

Cadmium (Cd) is a major environmental contaminant. Although immunotoxic effects have been associated with Cd exposure, the inconsistency of experimental results underlines the need of an experimental approach more closely related to environmental conditions. We investigated the effects of exposing neonatal Sprague-Dawley rats to environmentally relevant doses of Cd through maternal milk. Dams received 10 parts per billion (ppb) or 5 parts per million (ppm) Cd chloride (CdCl2) in drinking water from parturition until the weaning of the pups. Half of the offspring was sampled at weaning time. The remaining juvenile rats received water without addition of Cd until adulthood. Cd accumulation in kidneys of juvenile rats fed from dams exposed to Cd indicated the transfer of the metal from mother to pups through maternal milk. This neonatal exposure resulted in decreased body, kidney and spleen weights of just weaned females but not of males. This effect was more pronounced in the less exposed females fed from dams exposed to 10 ppb Cd, which also displayed lower hepatic metallothionein-1 (MT-1) mRNA levels. The effect of Cd exposure on body and organ weights did not persist to adulthood. In contrast, we observed gender-specific effects of neonatal Cd exposure on the cytotoxic activity of splenic NK-cells of both juvenile and adult rats. Cd also strongly inhibited the proliferative response of Con A-stimulated thymocytes in both male and female adult rats 5 weeks after the cessation of Cd exposure. These immunotoxic effects were observed at doses much lower than those reported to produce similar effects when exposure occurred during adulthood. In conclusion, neonatal exposures to environmentally relevant levels of Cd through maternal milk represent a critical hazard liable to lead to both transitory and persistent immunotoxic effects.

Animals↗

PubMed2005

Nonylphenol alters connexin 43 levels and connexin 43 phosphorylation via an inhibition of the p38-mitogen-activated protein kinase pathway.

Endocrine-disrupting chemicals are exogenous compounds that mimic or inhibit the action of estrogens or other hormones. Nonylphenol, an environmental contaminant distributed along the St. Lawrence River, has been reported to act as a weak estrogen. Previous studies from our laboratory have shown that rats that were fed fish taken from nonylphenol contaminated sites have altered spermatogenesis and decreased sperm count. The mechanism responsible for this effect is unknown. Gap junctional intercellular communication (GJIC) in the testis is critical for coordinating spermatogenesis. The objectives of the study were to determine the effects of nonylphenol on GJIC and connexin 43 (Cx43) in a murine Sertoli cell line, TM4. Cells were exposed for 24 h to different concentrations (1 to 50 microM) of either nonylphenol or 17beta-estradiol. GJIC was determined using a microinjection approach in which Lucifer yellow was injected directly into a single cell, and GJIC was assessed 3 min postinjection. Nonylphenol exposure decreased GJIC between adjacent cells by almost 80% relative to controls. A significant concentration-dependent reduction in GJIC was observed at nonylphenol concentrations between 1 and 50 microM. Cx43 immunofluorescent staining was reduced at both 10 and 50 microM doses of nonylphenol. Cx43 phosphorylation, as determined by Western blot analysis, was reduced at both 10 and 50 microM concentrations, which may explain, at least in part, the inhibition of GJIC. In contrast, no effect on GJIC or Cx43 protein was observed in cells exposed to 17beta-estradiol at these concentrations. Cx43 has been reported to be phosphorylated via the p38-mitogen-activated protein kinase (MAPK) pathway. P38-MAPK activity was assessed in both control and nonylphenol-exposed cells. A dose-dependent decrease in p38-MAPK activity was observed in nonylphenol-exposed Sertoli cells. Protein kinase C activity was also measured and was not influenced by nonylphenol. These results suggest that nonylphenol inhibits GJIC between Sertoli cells and that this is modulated via nonestrogenic pathways.

Animals↗

PubMed2005

Effects of FSH receptor deletion on epididymal tubules and sperm morphology, numbers, and motility.

Follicle stimulating hormone (FSH) interacts with its cognate receptor (R) on Sertoli cells within the testis and plays an important role in the maintenance of spermatogenesis. Male FSH-R knockout (FORKO) mice show fewer Sertoli cells and many that are structurally abnormal and as a consequence fewer germ cells. Lower levels of serum testosterone (T) and androgen binding protein (ABP) also occur, along with reduced fertility. To assess the effects of FSH-R depletion as an outcome of testicular abnormalities, sperm from the cauda epididymidis were counted and examined ultrastructurally. As reduced fertility may also reflect changes to the epididymis, the secondary responses of the epididymis to lower T and ABP levels were also examined by comparing differences in sizes of epididymal tubules in various regions of FORKO and wild type (WT) mice. Sperm motility was evaluated in FORKO mice and compared to that of WT mice by computer assisted sperm analysis (CASA). Quantitatively, the data revealed that epithelial areas of the caput and corpus epididymidis were significantly smaller in FORKO mice compared to WT mice. Cauda epididymal sperm counts in FORKO mice were also much lower than in WT mice. This resulted in changes to 9 out of 14 sperm motility parameters, related mostly to velocity measures, which were significantly lower in the FORKO mice. The greatest change was observed relative to the percent static sperm, which was elevated by 20% in FORKO mice compared to controls. EM analyses revealed major changes to the structure of the heads and tails of cauda luminal sperm in FORKO mice. Taken together these data suggest a key role for the FSH receptor in maintaining Sertoli cells to sustain normal sperm numbers and proper shapes of their heads and tails. In addition, the shrinkage in epididymal epithelial areas observed in FORKO mice likely reflect direct and/or indirect changes in the functions of these cells and their role in promoting sperm motility, which is noticeably altered in FORKO mice.

Animals↗

PubMed2004

Consumption of xenoestrogen-contaminated fish during lactation alters adult male reproductive function.

Little information exists on the transfer of endocrine-disrupting effects through the food chain. The transfer of chemicals, particularly from the aquatic ecosystem, that can cause such effects on fish-eating predators must be established. Fish from the St. Lawrence River are exposed to xenoestrogens causing male reproductive dysfunction. The objective of this study was to determine if lactational exposure to contaminated fish could alter the development of the male reproductive system in rats. Three experimental groups were used: rats (dams) gavaged with (a) distilled water (control), or (b) homogenized fish from a reference site (Iles de la Paix) or (c) homogenized fish from a xenoestrogen-contaminated site (Ilet Vert). Pups were exposed via lactation and sampled on either day 21 (weaning) or day 91 (adults). There was no effect on the body weights or in the male reproductive organ weights between groups except for adult epididymal weight, which was significantly decreased in the xenoestrogen group. Adult sperm concentrations and sperm motility parameters were all significantly decreased in the xeonestrogen group as compared to the reference and control groups. Furthermore, the distribution of stages of spermatogenesis was altered in the xenoestrogen group, indicating an effect on the kinetics of spermatogenesis. Immunoreactivity of connexin43 (Cx43), a gap-junctional protein, was markedly decreased in the seminiferous epithelium of the xenoestrogen group, suggesting that the intercellular coordination of testicular function may be affected. These data indicate that contaminants from xenoestrogen environments may pass through the food chain and exert effects on male reproductive functions.

Animals↗

PubMed2004

Contaminant effects on the teleost fish thyroid.

Numerous environmentally relevant chemicals, including polychlorinated hydrocarbons, polycyclic aromatic hydrocarbons, organochlorine pesticides, chlorinated paraffins, organophosphorous pesticides, carbamate pesticides, cyanide compounds, methyl bromide, phenols, ammonia, metals, acid loads, sex steroids, and pharmaceuticals, exert acute or chronic effects on the thyroid cascade in the approximately 40 teleost fish species tested to date. Thyroid endpoints, therefore, serve as biomarkers of exposure to environmental pollutants. However, the mechanisms underlying thyroid changes and their physiological consequences are poorly understood because the thyroid cascade may respond indirectly and it has considerable capacity to compensate for abuses that otherwise would disrupt thyroid hormone homeostasis. Indeed, a xenobiotic-induced change in fish thyroid function has yet to be conclusively causally linked to decreased fitness or survival. Other complications in interpretation arise from the diversity of test conditions employed and the often indiscriminate use of numerous thyroid endpoints. Future work should be directed toward standardizing test conditions and thyroid endpoints and investigating causal links between thyroid changes and fish growth, reproduction, and development. Development may be particularly susceptible to thyroid disruption, and thyroid endpoints appropriate for early life stages need to be applied.

Animals↗

PubMed2003

Consequences of xenoestrogen exposure on male reproductive function in spottail shiners (Notropis hudsonius).

There is limited information on the physiological consequences associated with exposure to xenoestrogens under field conditions. The objectives of this study were to determine the presence of estrogenic chemicals in the St. Lawrence River and their effects on male reproduction in the spottail shiner (Notropis hudsonius). Hepatic vitellogenin (VTG) mRNA levels in immature shiners indicate extensive estrogenic contamination spanning almost 50 km both upstream and downstream from the island of Montreal. Stages of spermatogenesis were assessed in fish captured at sites having varying levels of estrogenic contamination. In control fish, 95% had testis of either stage IV (50%) or stage V (45%) of spermatogenesis. At Ile Dorval, where VTG mRNA levels are moderate, fish had testes of stage III (38%) and IV (45%) and only 15% of fish were at spermatogenic stage V. In contrast, at Ilet Vert and Ile Beauregard, located in the sewage effluent plume from the City of Montreal and where hepatic VTG mRNA levels are high in fish, none of the fish were at stage V and 8% of fish at Ilet Vert were at stage II of development. Sperm concentration and various motility parameters were significantly lower in shiners from Ilet Vert as compared with those from Iles de la Paix (reference). Histological analyses of testes revealed that more than one-third of the fish captured at sites with the highest estrogenic contamination displayed intersex, a condition in which ovarian follicles were developing within the testis. These data indicate that there is significant estrogenic contamination in the St. Lawrence River that is associated with impaired reproductive function in male fish.

Animals↗