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D G Cyr

Publications and source records attributed to D G Cyr.

At least 19 recordsLinked to original sources
PubMed2001

Phagocytic response of macrophages from the pronephros of American plaice (Hipoglossoides platessoides) exposed to contaminated sediments from Baie des Anglais, Quebec.

Sediments of Baie des Anglais on the St. Lawrence estuary have a history of environmental contamination, but little information exists regarding their toxicity. The purpose of the present study was to determine the effects of contaminated Baie des Anglais sediments on American plaice (Hippoglossoides platessoides) immune function. Three sites in Baie des Anglais were selected which vary in proximity to local industries and in their sediment contaminant load. Sites 1 and 2 (within the bay) are the closest to shore and most heavily contaminated while sediments at Site 3, which is outside the bay, are the least contaminated. In the first experiment, American plaice were placed in cages at each site for three weeks and immune function was assessed by measuring the phagocytic activity of pronephric macrophages. At the time of sampling, plaice displayed pronephros cell immune response disturbances indicating that Site 1 and 2 were most toxic and Site 3 the least toxic. The results obtained for phagocytosis revealed that contaminants present in the sediments are bioavailable to fish, which came in contact with them and significantly affected their immune system. In the second experiment, sediments from the most toxic site, Site 1, were collected for a laboratory controlled experiment in which plaice were exposed for up to 3 months to these contaminated marine sediments, while the control group was exposed to relatively uncontaminated beach sand. At the end of the exposure period, plaice were transferred from contaminated sediment to beach sand and sampled one month later in order to determine if immune function had returned to control levels. The total number of macrophages decreased following three months of exposure, while the active macrophages had already decreased after the first month of exposure. Following the rehabilitation period a significant trend toward normal response was noted. Sediments from Baie des Anglais contain primarily less highly chlorinated PCBs and lower concentrations of the intermediate and highly chlorinated PCBs. The total concentration of PCBs (sum of 20 congeners) in the contaminated sediments was 1500 ng/g while in the beach sand, the levels were 13.6 ng/g dry weight. Only the low chlorinated PCB congeners were efficiently transferred from the sediments to the plaice liver. Together, these results suggest that the effect of chemical exposure on the phagocytosis of plaice macrophages may be reversible if the fish are returned to a non-contaminated habitat.

Adaptation, Physiological↗
PubMed2000

Thyroid hormone deiodination in tissues of American plaice, Hippoglossoides platessoides: characterization and short-term responses to polychlorinated biphenyls (PCBs) 77 and 126.

We have described the tissue distribution and properties of thyroid hormone (TH) deiodination activities of the marine American plaice, Hippoglossoides platessoides. We then studied the 1- or 4-week responses of the plaice liver and brain deiodination activities and the plasma thyroxine (T4) and 3,5,3'-triiodothyronine (T3) levels to an intraperitoneal injection (5-500 ng/g) of the polychlorinated biphenyl (PCB) congeners 77 (3,3'-4,4'-tetrachlorobiphenyl) or 126 (3,3',4,4',5-pentachlorobiphenyl). T4 and 3,3'5'-triiodothyronine (rT3) outer-ring deiodination (ORD) activities were greater in liver than in kidney, gill, heart, brain, intestine or muscle; inner-ring deiodination (IRD) activity occurred in all tissues but was consistently higher in brain. Deiodination characteristics (optimal pH, optimal dithiothreitol concentration, responses to inhibitors and apparent Km values of 0.6-4 nM) fell in the same rage as those of low-Km deiodinases in other teleosts. Deiodination activities were maximal when assayed at 25 degrees C but uniformly low over the natural range of 0-9 degrees C. Neither PCB 77 nor PCB 126 altered brain T4ORD activity or plasma T4 levels (P < 0.05). However, at 1 week post injection hepatic T4ORD activity was increased and plasma T3 levels lowered by PCB 77 (5 and 25 ng/g), while hepatic IRD activity was increased by PCB 126 (50 and 500 ng/g). Neither PCB 77, PCB 126 nor selected hydroxylated. PCBs given in vitro compared with T4 for binding sites on plasma proteins or altered hepatic deiodination activity, indicating no direct action on plasma proteins or deiodinases We conclude that plaice TH deiodination tissue distribution and characteristics resemble those of other teleosts. Deiodination activities are low at natural assay temperatures but at 1 week show some responses to PCBs 77 and 126.

Animals↗
PubMed2000

Quantification of rainbow trout (Oncorhynchus mykiss) estrogen receptor-alpha messenger RNA and its expression in the ovary during the reproductive cycle.

This study developed a quantitative reverse transcription-polymerase chain reaction (RT-PCR) method to measure estrogen receptor-alpha (ERalpha) mRNA in the rainbow trout (Oncorhynchus mykiss). Using RT-PCR, and primers based on the known ERalpha DNA sequence in this species, cDNA sequences representing most of the protein coding region were obtained from ovary poly A(+) RNA. Using these DNA sequences as probes in Northern blot hybridizations confirmed that a single transcript of 4.2 kilobases in poly A(+) RNA could be detected in liver and ovary RNA. For the quantitative RT-PCR assay an internal standard RNA molecule was produced to control for inherent inter-tube differences in amplification efficiency and permit accurate quantification of ERalpha mRNAs. The quantitative RT-PCR assay proved to be highly specific for ERalpha mRNA with a detection limit of 6.9 fg, which corresponds to 273 fg ERalpha mRNA/microg total RNA. The quantitative RT-PCR assay was used to measure the levels of ERalpha mRNA in ovaries of rainbow trout at different stages of reproductive development. Ovarian ERalpha mRNA expression was found during two distinct periods of reproductive development, in pre-vitellogenic ovaries of fish with ovarian follicle diameters (OFDs) </=100 microm and in mid-vitellogenic ovaries with OFDs >1000 microm. ERalpha mRNA could not be detected in the ovaries of fish with OFDs >100 microm but </=1000 microm. The highest levels of ERalpha mRNA were found in late vitellogenic ovaries of fish with OFDs >2000 microm.

Animals↗
PubMed1999

Toxicological characterization of sediments from Baie des Anglais on the St. Lawrence Estuary.

The sediments of Baie des Anglais on the St. Lawrence Estuary have a history of environmental contamination, but no information exists relating to their toxicity. The purpose of the present study was to characterize three sites in and near Baie des Anglais, in terms of sediment toxicity and contaminants. Sites 1 and 2 within the Baie des Anglais are relatively close to local industry and municipal sewage discharge points, while Site 3 is outside the bay. Three microscale bioassays, Microtox, echinoderm fertilization and Toxi-ChromoPad, showed that sediments from Site 1 were the most toxic, followed by Site 2. Site 3 was non-toxic. While the solid phase Microtox test did indicate that Site 1 was most toxic, the absolute response was weak. Liver cytochrome P450 1A1 mRNA in American plaice (Hippoglossoides platessoides), captured at Site 1 in the bay was significantly induced compared to the P450 system of plaice captured at Sites 2 and 3. Hepatic metallothionein mRNA levels were not significantly different between plaice captured at all three sites. Sediment chemical analyses revealed a gradient in polycyclic aromatic hydrocarbons, polychlorinated biphenyls and dibenzofurans (PCDF) with the highest levels recorded at Site 1, about 10-fold less at Site 2 and 100-fold less at Site 3. Amongst the organochlorines the PCDF group were deemed the most important due to their prevalence and known toxicity. Heavy metal concentrations were low and representative of background levels for the St. Lawrence Estuary.

Animals↗
PubMed1999

Cellular immunolocalization of occludin during embryonic and postnatal development of the mouse testis and epididymis.

Cellular junctions in the testis and epididymis play crucial roles for the development and maturation of spermatozoa. In the testis, tight junctions between Sertoli cells form a functional blood testis barrier between 10 and 16 days of age, whereas the tight junctional blood epididymal barrier between adjacent epithelial cells is formed between days 18 and 21. In the present study, occludin, a constituent integral membrane protein of tight junctions, was localized by immunofluorescent confocal microscopy in embryonic (days 13.5-18.5), postnatal (days 5-23) and adult (day 70) mouse testes and epididymides to correlate its expression with the onset of tight junctions and eventual formation of these barriers. At embryonic days 13.5 and 16.5, low diffuse cytoplasmic levels of occludin were observed in cells of the testicular cords. By embryonic day 18.5, the level of occludin was still low but appeared as a filiform-like network streaming toward the center of the cord. At postnatal days 5 and 7 immunostaining became more intense and appeared to outline the periphery of Sertoli cells of seminiferous tubules. Postnatal day 14 marked the appearance of an intense, focal band-like localization of occludin at the base of the tubules, correlating with the appearance of a functional blood-testis barrier. By day 23 and in adults, expression of occludin was noted at the base of the tubule appearing as intense, wavy, discontinuous bands similar in appearance irrespective of the stage of the seminiferous epithelium cycle. In the developing epididymis, intense cytoplasmic immunostaining was present in epithelial cells of many epididymal tubules at embryonic day 13.5. By embryonic day 16.5, intense occludin immunostaining appeared along the lateral plasma membranes of epithelial cells, whereas at embryonic day 18.5, immunostaining was punctate and apically located, suggesting the presence of tight junctions by this age; similar immunostaining was noted at postnatal days 5 and 7. In the adult epididymis, distinct punctate apical staining was observed between adjacent principal cells of all epididymal regions except the proximal initial segment, where occludin was found only in association with narrow cells. These results indicate that in the epididymis, the appearance of occludin at apical sites between adjacent epithelial cells occurs during embryonic development suggesting that tight junctions form earlier than in the testis. While occludin was expressed in a similar pattern between Sertoli cells at all stages of the cycle in the adult testis, its expression in the adult epididymis was cell- and region-specific. Taken together these data suggest that different factors regulate occludin expression in the testis and epididymis.

Aging↗
PubMed1998

Effects of long-term temperature acclimation on thyroid hormone deiodinase function, plasma thyroid hormone levels, growth, and reproductive status of male Atlantic cod, Gadus morhua.

The recent collapse of the Northwestern Atlantic cod fisheries has coincided with a cooling of water temperatures. During this time the condition factor of cod has been poor. The objective of the present study was to determine the effects of long-term temperature acclimation on growth reproduction and thyroid function in laboratory held Atlantic cod (Gadus morhua). One of the key parameters used to assess thyroid function is the peripheral metabolism of L-thyroxine (T4) by microsomal deiodinase enzymes. Deiodinase function has not been described for gadid fish. T4 outer-ring deiodinating activity (apparent K(m) 1-2 nM) was confined primarily to liver. Its properties resembled those for hepatic T4ORD activity of other teleosts and the mammalian type II deiodinase. The T4ORD activity of cod liver exceeded that of salmonids and could explain the high plasma T3 levels (10-18 ng/ml), which were 2-5 times greater than T4 levels. T4 and T3 inner-ring deiodination was confined mainly to brain. In order to determine the effects of long-term temperature acclimation on cod, somatic growth, reproduction, and thyroidal status were assessed monthly in 400-900-g satiation-fed male Atlantic cod captured in June from the St. Lawrence Estuary and then acclimated from August to the following June under a natural photoperiod at 2-4 degrees C (LT) or 6-10 degrees C (HT). Reproductive status was determined from the gonadosomatic index (GSI), plasma testosterone (T) and 11-ketotestosterone (11-KT) levels, and the appearance of milt; thyroidal status was determined from plasma T4 and 3,5,3'-triiodo-L-thyronine (T3) levels and hepatic T4ORD activity to produce biologically active T3. Testis maturation (high levels of 1 and 11-KT, and milt release) occurred in April and May and was uninfluenced by acclimation temperature. LT cod grew more slowly than HT cod. Differences in body weight were particularly evident from December to February. In conclusion, (i) cod possess outer- and inner-ring deiodinase activities, predominating respectively in liver and brain, and with properties resembling those of other teleosts, (ii) T4ORD activity of liver is unusually high and may account for the high plasma T3 levels in this species, (iii) T4ORD activity tends to increase during periods of increased somatic growth, and (iv) chronic acclimation of male cod to 2-4 degrees C, as opposed to 6-10 degrees C, decreases somatic growth but does alter circulating levels of thyroid hormones and androgens and it does not change the time of sexual maturation.

Acclimatization↗
PubMed1996

Immunocytochemical localization and regulation of connexin43 in the adult rat epididymis.

Connexin43 (Cx43) is one of the most predominant gap junction proteins found in vivo, and although present in the testis, it has not been examined in the epididymis. Immunocytochemistry using an anti-Cx43 antibody revealed a punctate immunoperoxidase reaction at the apical margins between adjacent epithelial cells of the efferent ducts. In the epididymis, punctate reactive sites were observed at the base of the epithelium between basal and principal cells. There was no staining between adjacent principal cells at their apical or lateral margins. Cx43 immunostaining was also seen between myoid cells surrounding the tubules but only in the cauda epididymidis. Using a Cx43 cDNA probe, Northern blot analysis of total cellular RNA revealed a single hybridizing band of approximately 3.0 kb in all regions of the epididymis. Throughout the epididymis of bilaterally orchidectomized rats at 7 or 14 days, an immunoperoxidase reaction for Cx43 persisted at the base of the epithelium between principal and basal cells. However, in the initial segment only, immunolocalization of Cx43 was also observed apically between adjacent principal cells. This apical staining was lost in rats that received testosterone replacement. Myoid cells in the cauda epididymidis of control rats expressed Cx43, however, orchidectomized rats did not express Cx43 in this cell layer. Western blots revealed the presence of a major protein band at 43 kDa corresponding to unphosphorylated Cx43 as well as Cx43 species at 44 and 46 kDa, which were more prominent in orchidectomized rats. Together these data represent one of the first examples of Cx43 gap junctions between heterologous cell types (i.e. principal and basal cells). Moreover, Cx43 expression in myoid cells of the cauda epididymidis is androgen-dependent and in the initial segment of the epididymis only, the intracellular targeting of Cx43 towards the principal-principal cell interface under normal conditions is regulated by androgens.

Aging↗
PubMed1995

Structure and turnover of junctional complexes between principal cells of the rat epididymis.

The epididymal junctional complex between adjacent principal cells is composed of apically located gap, adherens and tight junctions. Tight junctions between adjacent epithelial cells lead to the formation of the blood-epididymal barrier. The objectives of this study were to examine the structure of the epididymal junctional complex in the different regions of the epididymis and to review the regulation of epithelial cadherin in the rat epididymis. Changes in the structure of the junctional complex, at the level of the electron microscope, were evident when comparing the initial segment to other regions of the epididymis. In the initial segment, the tight junction spanned a considerable length of the apical plasma membrane but had few desmosomes. In the other regions of the epididymis, the span of merging plasma membranes was considerably reduced, but in these regions, numerous desmosomes were present in the apical region. Several examples of what appeared to be a loss of portions of the plasma membrane of adjacent principal cells were evident along the entire epididymis. Such images as the invagination of a portion of the lateral plasma membrane of one principal cell into another, constriction of the invaginated area and eventual detachment leading to the formation of annular junctions suggest that there is a turnover of plasma membranes. The formation of cellular junctions involves the interactions of cell adhesion proteins followed by the addition of junctional proteins which assemble into tight and gap junctions. Epithelial cadherin (E-Cad), a calcium-dependent cell adhesion protein, was localized to the principal cells of the epididymis. Immunocytochemistry at the level of the electron microscope showed that E-Cad was present between the lateral plasma membranes of adjacent principal cells, both in the region of the junctional complex and in the deeper lying areas. E-Cad was also present in annular junctions located in close proximity to the junctional complex, indicating that these structures were related to the plasma membrane. E-Cad mRNA levels are regulated during postnatal epididymal development. In the caput-corpus epididymidis, E-Cad mRNA concentrations increase to peak at 42 days of age. This is well correlated with the conversion of testosterone to dihydrotestosterone in the epididymis. In the cauda epididymidis, however, E-Cad mRNA concentrations do not increase as a function of age, indicating that this protein is regulated in a segment-specific manner.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

Role of apoptosis in mediating phosphoramide mustard-induced rat embryo malformations in vitro.

Phosphoramide mustard, an active metabolite of the anticancer drug cyclophosphamide, causes malformations in rat embryos undergoing organogenesis in vitro. The purpose of the present study was to investigate the hypothesis that apoptosis plays an important role in mediating the teratogenicity of phosphoramide mustard. Apoptosis is a process of active or programmed cell death which is characterized by internucleosomal DNA fragmentation and de novo RNA and protein synthesis. Sulphated glycoprotein-2 (SGP-2) or clusterin is induced in some models of apoptosis and is one of the proteins likely to be involved in the maintenance of cell integrity. In the present study, day 10 rat embryos were cultured for 6, 12, 24, and 45 hr, with or without the addition of 10 microM phosphoramide mustard. After culture for 24 or 45 hr with exposure to 10 microM phosphoramide mustard, the embryos were both growth-retarded and malformed. Exposure to phosphoramide mustard for 6 or 12 hr did not significantly alter the relative amounts of either the mRNA or protein for SGP-2; this treatment also had no effect on DNA fragmentation in embryos or their yolk sacs. After 24 hr in culture, the relative amounts of SGP-2 protein, but not mRNA, were increased 2-fold in the yolk sacs of the phosphoramide mustard-exposed embryos, but not in the embryos themselves. At this time, DNA fragmentation was detected in phosphoramide mustard-exposed embryos, but not in their yolk sacs or in control embryos. After 45 hr in culture, SGP-2 protein and mRNA levels were increased 2-4-fold above the controls in the phosphoramide mustard-exposed embryos and their yolk sacs. Immunohistochemical analysis revealed that in control embryos cultured for 45 hr, the SGP-2 reaction product was localized in the heart, hindgut, and yolk sac. In contrast, in phosphoramide mustard-treated embryos cultured for 45 hr, SGP-2 immunostaining was found throughout the embryo, with a strong immunoreaction in the mesenchyme and ectoplacental cone. DNA fragmentation in the embryos exposed to phosphoramide mustard for 45 hr was more extensive than that found after 24 hr, but fragmentation was still not detected in the yolk sac. Thus exposure in vitro to a teratogenic concentration of phosphoramide mustard resulted in DNA fragmentation and an increased expression of SGP-2 in the embryo. These data suggest that apoptosis is involved in mediating the teratogenicity of phosphoramide mustard.

Abnormalities, Drug-Induced↗
PubMed1994

Mechanism of trimethylamine-induced inhibition of macromolecular synthesis by mouse embryos in culture.

The effects of trimethylamine (TMA) on uptake mechanisms and lysosomal function were studied in mouse embryos, isolated yolk sacs and limb buds. TMA at 0.75 mM did not inhibit uptake of [14C]sucrose by yolk sacs of day 9 embryos or by day 15 isolated yolk sacs but did inhibit uptake of 125I-labelled bovine serum albumin ([125I]BSA) by day 15 isolated yolk sacs. Concentrations of TMA up to 2.5 mM did not inhibit lysosomal degradation of [125I]BSA by isolated yolk sacs, as judged by the release of trichloroacetic acid (TCA)-soluble radioactivity into the culture media. The inhibition of [125I]BSA uptake induced by TMA was reversible on removal of TMA. When day 8 embryos were cultured in serum containing [3H]leucine-labelled proteins, uptake and incorporation of radioactivity in 0.75 mM TMA-treated embryos was 47 and 44%, respectively, of that in untreated controls. TMA at 0.75 mM did not inhibit the uptake and incorporation of free [3H]leucine into embryonic protein nor the amount of free [3H]leucine taken up or incorporated into protein by day 12 isolated limb buds. It is concluded that the reduced macromolecular synthesis in embryos exposed to TMA is due to an inhibition of receptor-mediated uptake of nutrients by the yolk sac.

Animals↗
PubMed1993

Developmental changes in epithelial cadherin messenger ribonucleic acid and immunocytochemical localization of epithelial cadherin during postnatal epididymal development in the rat.

The formation of junctional complexes between adjacent epithelial principal cells leads to formation of the blood-epididymal barrier; this barrier is complete by 21 days of postnatal age. Cadherins are cell surface proteins that mediate intercellular adhesion and are involved in the formation of adherence, gap, and tight junctions between epithelial cells. In the adult rat epididymis, epithelial cadherin (E-Cad) is localized in principal cells; E-Cad mRNA concentrations are androgen dependent in this tissue. The objectives of this study were to determine the regulation of E-Cad mRNA concentrations and the pattern of immunocytochemical localization of E-Cad during epididymal development. Using Northern blot analysis, we noted that in the caput-corpus epididymidis, there was a 3-fold increase in E-Cad mRNA concentrations between 7-14 days; an additional 3-fold increase between days 35-42, when E-Cad mRNA concentrations reached their peak, was noted. A dramatic decrease in E-Cad mRNA was observed between 42-49 days of age. This effect was transitory as E-Cad mRNA concentrations returned to almost 80% of peak concentrations on day 56 and remained constant thereafter. In the cauda epididymidis, E-Cad mRNA concentrations increased by only 1.6-fold between days 7-21. E-Cad mRNA concentrations then decreased by 70% to their lowest concentrations on day 56. There was a 2-fold increase in E-Cad mRNA concentrations between postnatal ages 56-91 days. These results suggest that the developmental regulation of E-Cad mRNA concentrations is segment specific. A subsequent study on the longitudinal distribution of E-Cad mRNA levels in six epididymal segments at 21, 42, and 56 days of age revealed that the relative proportion of E-Cad mRNA along the epididymis changes as a function of age. An immunocytochemical study with the light microscope, using an anti-E-Cad antibody, demonstrated that the localization and relative concentrations of E-Cad varied as a function of age. On day 15, the immunoperoxidase staining of the entire epididymal epithelium was apical, with the weakest staining in the cauda epididymidis. By day 21, the reaction spread to cover the supranuclear region of the principal cells in all segments, while on day 39, it covered the entire cytoplasm of these cells, suggesting a high rate of synthesis or storage of the protein. At later time intervals, the intensity of staining over the principal cells appeared to increase with age.(ABSTRACT TRUNCATED AT 400 WORDS)

Aging↗
PubMed1992

Effects of short-term 17 beta-estradiol treatment on the properties of T4-binding proteins in the plasma of immature rainbow trout, Oncorhynchus mykiss.

To determine the effects of 17 beta-estradiol (E2) on the properties of the plasma proteins that bind L-thyroxine (T4) immature rainbow trout, Oncorhynchus mykiss, were injected intraperitoneally on days 0 and 3 with 0.5 mg E2-3-benzoate/100 g body weight, and plasma was sampled on days 4, 7, or 12. Control trout received peanut oil alone. E2 caused a small but significant decrease in the free T4 index. Saturation analysis on miniature G-25 Sephadex columns revealed at least two major T4-binding sites. Filtration on agarose Bio-gel A 1.5 also indicated two major T4-binding protein fractions with molecular weights of 150 and 55 kDa with a small proportion of T4 binding to a 1,500-kDa site presumed to be lipoprotein. Addition of unlabeled T4 displaced [125I]T4 from the 55-kDa site and unmasked an adjacent site of higher molecular weight. E2 increased the proportion of T4 bound to the low-affinity (150 kDa) site relative to that bound to the high-affinity (55 kDa) site, increased the level of protein associated with the 1,500-kDa site and its T4 binding, and also initiated the production of presumed vitellogenin (VTG), which bound a small amount of T4. It is concluded that the E2-induced depression in FT4 is caused by a shift in T4 binding between high-affinity and low-affinity sites, and also by binding of small amounts of T4 to presumed lipoprotein and VTG.

Animals↗
PubMed1992

Clinical significance of type 5 patterns in platform posturography.

Several abnormal patterns have been identified on the sensory portion of the computerized dynamic posturography test. The vestibular deficit pattern, also known as the "5-6" pattern, is frequently seen in patients with either uncompensated unilateral vestibular lesions, severe bilateral peripheral vestibular loss, or dysfunction involving the vestibular pathways in the brain stem and/or cerebellum. In both sensory conditions 5 and 6, the patient's balance/equilibrium is determined primarily by the vestibular system. A subgroup of the vestibular deficit pattern has been identified, in which only sensory condition 5 is abnormal. This article presents findings in several cases identified with the 5 pattern. Implications for diagnosis and for monitoring the recovery phase after treatment are discussed.

Adolescent↗
PubMed1992

Distribution and regulation of epithelial cadherin messenger ribonucleic acid and immunocytochemical localization of epithelial cadherin in the rat epididymis.

The epithelium of the epididymis possesses an elaborate network of tight junctions between principal cells which is altered as a function of postnatal age. Cadherins are implicated in the formation of tight junctions. The objective of the present study was to determine whether RNA transcripts for cadherins were present in the epididymis, and if so, how they were hormonally regulated. Using specific cDNA probes for epithelial cadherin (E-Cad) and neural cadherin (N-Cad), Northern blot analysis was used to study steady state levels of cadherin mRNAs. A major E-Cad mRNA species of 4.7 kilobases and a weaker 4.3-kilobase species were observed in the epididymis. No signal for N-Cad was detected. Steady state mRNA levels for E-Cad were highest in the caput and corpus epididymidis and were almost 4 times higher than those in the initial segments and cauda epididymidis; no signal was detected in the vas deferens. Light microscopic immunocytochemical localization of E-Cad revealed a reaction over the principal cells of the entire epididymis. The relative intensities of the immunoreactivity suggested that the E-Cad protein concentration was highest in the corpus, followed by the caput, cauda, and initial segments of the epididymis. There was no reaction over the epithelial basal and clear cells or intraepithelial halo cells. Three days after bilateral orchidectomy, E-cad mRNA was decreased by 75% in the caput epididymidis. A dose-dependent maintenance of mRNA concentration for E-Cad was observed throughout the epididymis of orchidectomized rats after replacement with testosterone. Fourteen days after unilateral orchidectomy, no differences were observed in the concentrations of epididymal E-Cad mRNA between control and unilaterally orchidectomized rats. Together, these data demonstrate that mRNA for E-Cad is present and translated in the rat epididymis, is differentially distributed along this tissue, and can be regulated by circulating androgens.

Animals↗
PubMed1992

Regulation of sulfated glycoprotein-2 (clusterin) messenger ribonucleic acid in the rat epididymis.

Sulfated glycoprotein-2 (SGP-2) is secreted by the principal cells of the caput epididymidis and binds to spermatozoa as they transit through this segment. The regulation of SGP-2 in the epididymis is poorly understood. The objectives of these studies were to determine if SGP-2 messenger RNA (mRNA) concentrations in the epididymis are regulated by testosterone or during postnatal development. Northern blot analysis was done using denatured plasmid containing a complementary DNA insert for rat SGP-2. A single 2.1-kilobase transcript was present throughout the epididymis. SGP-2 mRNA concentrations were highest in the caput followed by the initial segment, the cauda, and the corpus epididymidis. To determine if androgens regulate SGP-2 mRNA concentrations, adult rats were bilaterally orchidectomized and testosterone was replaced for 7 days using steroid-filled capsules measuring 2.5 or 18.6 cm. In the initial segment and the caput epididymidis, neither orchidectomy nor testosterone replacement, at either dose, had any effect on SGP-2 mRNA concentrations. In the corpus and cauda epididymidis, bilateral orchidectomy resulted in a 3.5- and 9.4-fold increase, respectively, in SGP-2 mRNA concentrations, whereas testosterone replacement caused a dose-dependent decrease in SGP-2 mRNA concentrations. Unilateral orchidectomy was done to determine if SGP-2 mRNA concentrations are dependent on testicular factors released in the lumen of the epididymis. In the corpus and the cauda epididymidis, unilateral orchidectomy resulted in elevated SGP-2 mRNA concentrations in the ipsilateral epididymis. There were no changes in SGP-2 mRNA concentrations in the initial segment and caput epididymidis. These results provide complementary evidence that the message for SGP-2 is differentially regulated along the epididymis. During postnatal development SGP-2 mRNA concentrations in the caput-corpus epididymidis increased dramatically between 14 and 21 days as well as between 49 and 63 days. Interestingly, between 28 and 42 days, when serum testosterone concentrations are increasing, there was no change in the concentration of SGP-2 mRNA in the caput-corpus epididymidis. Similar results were observed in the cauda epididymidis with the exception that between 28 and 42 days, there was a dramatic decrease in SGP-2 mRNA in the cauda epididymidis. Together these experiments demonstrate that the regulation of SGP-2 mRNA concentrations is segment specific. In the initial segment and caput epididymidis there is no apparent regulation of SGP-2 by testicular factors,whereas in the corpus and cauda epididymidis testosterone can repress SGP-2 mRNA concentrations.

Animals↗
PubMed1992

Identification and developmental regulation of cadherin messenger ribonucleic acids in the rat testis.

Cellular interactions in the rat testis are suggested by the presence of gap junctions between developing germ cells and Sertoli cells as well as tight junctions between adjacent Sertoli cells. Cadherins are cell surface proteins that mediate calcium-dependent intercellular adhesion. In these experiments the presence and developmental regulation of three cadherins have been examined: epithelial cadherin (E-Cad), neural cadherin (N-Cad), and placental cadherin (P-Cad). Northern blot analysis of testicular RNA indicates the presence of N-Cad [4.3 and 3.5 kilobases (kb)] and P-Cad (3.5 kb) transcripts. No E-Cad message was detected. To determine whether mRNA concentrations for P-Cad and N-Cad are regulated during postnatal rat testicular development, testes from rats ranging in age from 7-91 days were subjected to Northern blot analysis. Relative P-Cad mRNA levels were highest at 7 days of age and decreased to almost half of these levels by day 14. P-Cad mRNA levels subsequently decreased to low levels and remained constant thereafter. This contrasted with the developmental pattern observed for the 4.3-kb N-Cad transcript, which was low early in testicular development but increased to peak levels on day 42, coincident with the shedding of the first sperm. N-Cad mRNA concentrations decreased from 42 to 56 days and then remained constant until 91 days. While mouse P-Cad antibody did not cross-react with rat P-Cad, immunoblots of testicular membrane protein preparations identified the presence of immunoreactive N-Cad protein in the testis. The presence of N-Cad protein confirms that N-Cad mRNA is translated in this tissue. The developmental patterns of P-Cad and N-Cad mRNA suggest a role for P-Cad early in testicular development, while N-Cad appears to play a role in later stages of spermatogenesis.

Aging↗