Biomedical subjects

M D Griswold

Publications and source records attributed to M D Griswold.

112 records · Page 7Linked to original sources

PubMedDate not supplied

Expression of apolipoprotein E mRNA in the epithelium and interstitium of the testis and the epididymis.

Apolipoprotein E (apo E) is an important constituent of plasma lipoproteins and is believed to be involved in the regulation of lipid transport and distribution between tissues. The production of this apolipoprotein in extra-hepatic tissues such as the testis and epididymis could facilitate specific local functions. Apo E mRNA was detected in testis, epididymis, seminal vesicles, and prostate. In the epididymis, apo E was detected using in situ hybridization in epithelial cells and in some cells in the interstitium throughout the organ (i.e., caput, corpus, and cauda). Northern blot analysis showed that apo E mRNA is present in Sertoli cells and germ cells, but not peritubular myoid cells. Interstitial cells of the testis displayed the most intense signal for apo E message using in situ hybridization. Messenger RNA for apo E was also detected in the interstitium of rat testes at 3 and 6 days after animals were treated with ethylene dimethanesulfonate (EDS) to eliminate Leydig cells. Thus, in addition to Leydig cells, other cell types within the interstitium are capable of producing apo E message. Levels of testicular apo E mRNA increased between 30 and 60 days pc during which the germ cell population is increasing. As determined by northern blot analysis of RNA from stage synchronized testes, the levels of apo E mRNA fluctuate in relation to the cycle of the seminiferous epithelium. The cells responsible for this stage-specific variation in message could not be identified by in situ hybridization. Apolipoprotein Al (apo Al) mRNA was also found to be expressed in the epididymis but not in the testis of adult rats. The role of apolipoproteins in spermatogenesis and sperm maturation has not been elucidated. The results of this study demonstrate the specific tissues and cells types which play a role in the production and possible regulation of apo E mRNA in the male reproductive tract. These data will help in the elucidation of the function of apo E in spermatogenesis and sperm maturation.

Age Factors↗

PubMedDate not supplied

Decreased spermatogenesis as the result of an induced autoimmune reaction directed against the gonadotropin receptors in male rats.

The presence of luteinizing hormone (LH) and testosterone is considered critical for the maintenance of spermatogenesis in the rat. However, the role and importance of follicle-stimulating hormone (FSH) in the initiation and maintenance of spermatogenesis has been a subject of debate for some time. The objective of this study was to examine the role of FSH and LH in vivo in the developing and adult rat by inducing an autoimmune reaction against the receptors to these gonadotropins. Sperm numbers were reduced in animals immunized against either the FSH or LH receptor (FSHR/LHR). In animals immunized against both FSHR and LHR there was also a significant reduction in sperm number although spermatogenesis was never completely ablated. These results were seen in male rats immunized either prepubertally (18 days of age) or as adults (80 days of age). To examine the requirements for FSH in early postnatal-testicular development, pregnant females were also immunized against either FSHR, LHR, or both of the receptors, and the male offspring were examined at 30 days of age. Again, germ-cell number was decreased with the greatest effect in those pups whose mothers were immunized against both FSHR and LHR. Radioligand-receptor-binding assays revealed that the antibody produced in the rats against FSHR was able to compete with FSH for binding sites in receptor-membrane preparations. Therefore, the mechanism of disruption of spermatogenesis is probably due to suppression of hormone to receptor binding. The results of this study support a role for FSH in spermatogenesis not only during neonatal and early postnatal development but also in the adult animal.

Amino Acid Sequence↗

PubMedDate not supplied

Expression of clusterin/sulfated glycoprotein-2 under conditions of heat stress in rat Sertoli cells and a mouse Sertoli cell line.

Clusterin is the major protein produced by rat Sertoli cells and is deposited onto sperm membranes; however, its function is unknown. In order to gain insight into the regulation of clusterin in Sertoli cells, the objective of the present study was to develop a model where the expression of clusterin could be affected in Sertoli cells in vitro. Rat Sertoli cells and mouse Sertoli cells (MSC1) were cultured under heat stress conditions (41 degrees C) for up to 48 hours. The mRNA for clusterin in Sertoli cells was compared to that in human epitheliod cancer cells (A431) to determine if clusterin expression was regulated in a lestis-specific manner. The mRNA for heat shock protein 70 (HSP70) was also examined as it is a known stress-regulated gene. Expression of HSP70 mRNA was increased in all three cell types by 4 hours after the start of heat stress. Clusterin mRNA was increased over that of controls by 4 hours in heat-stressed A431 cells but did not significantly increase in MSC1 or Sertoli cells until 12 hours (P < 0.05). The induction of clusterin mRNA in MSC1 cells continued for at least 48 hours and required the sustained exposure of cells to the 41 degrees C temperature. The increase in the amount of clusterin mRNA was not due to an increase in transcript half-life, as determined by the addition of actinomycin D to the media of control vs. heat-stressed MSC1 cells. From the development of this in vitro model, we have seen that the timing of induction of clusterin by heat stress is Sertoli cell specific and is different than that of HSP70. This response in surviving cells during heat stress may be protective in that clusterin would bind to toxic compounds or solubilize cellular debris released by degenerating cells.

Animals↗

PubMedDate not supplied

Androgen regulation of the Pem homeodomain gene in mice and rat Sertoli and epididymal cells.

Although the role of homeodomain transcription factors during embryogenesis is well known, their developmental function in postnatal animals is only beginning to be understood. We examined the regulation and expression pattern of Pem, a homeodomain protein that may regulate androgen-dependent events in the testis and epididymis. Immunohistochemical analysis showed that Pem protein is expressed selectively in the nuclei of Sertoli cells during the androgen-dependent stage of the seminiferous epithelium cycle in vivo. RNase protection analysis revealed that a proximal promoter was responsible for androgen-dependent mouse Pem expression in testis and epididymis in vivo, whereas a distal promoter was used in placenta. The mouse Pem gene was expressed at approximately 10-fold higher levels in the testis than in the epididymis; conversely, the rat Pem gene was expressed at >10-fold higher levels in the epididymis than in the testis. Because androgen-binding protein has been proposed to transport androgens from the testis to the epididymis, we tested whether the > or = 20-fold higher levels of androgen-binding protein expression in the rat, compared to that of mouse, are responsible for the differential expression of Pem in these two rodent species. Studies with androgen-binding protein transgenic mice demonstrated that the species-specific difference in androgen-binding protein expression is unlikely to be responsible for the species-specific difference in Pem expression. We found that androgen is necessary but not sufficient for Pem expression, since purified Sertoli cells rapidly down-regulated Pem transcripts in culture, regardless of the presence of testosterone. We conclude that Pem gene expression in Sertoli cells requires other cell types or cellular factors in addition to androgen.

Androgen-Binding Protein↗