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G A Cornwall

Publications and source records attributed to G A Cornwall.

23 records · Page 2Linked to original sources
PubMed1986

Induction and enhancement of progressive motility in hamster caput epididymal spermatozoa.

Progressive motility was induced in hamster caput epididymal spermatozoa incubated in Tyrodes medium containing 50 mM theophylline, 1.0% Fraction V bovine serum albumin, and 15% (v/v) heat-treated human seminal plasma. Under these induction conditions, however, the maximum percent of caput spermatozoa exhibiting progressive motility (21%) and the time during which motility was sustained (120 min) were significantly less (p less than 0.05) than that of controls from the cauda epididymidis. Moreover, in contrast to caudal spermatozoa, the majority of the induced caput spermatozoa exhibited some degree of flagellar bending at the neck or midpiece. In subsequent experiments the procedure for motility induction was modified to achieve levels of motility in caput spermatozoa equivalent to those observed for caudal spermatozoa. The addition of 5 microM diamide, a sulfhydryl oxidant, to the induction medium prevented the flagellar angularity observed in induced caput sperm preparations. The percentage of caput spermatozoa induced to progressive motility was increased to levels characteristic of caudal spermatozoa (48%) by the addition of hamster caudal epididymal fluid (CEF) to the induction medium. Finally, the viability of the induced caput spermatozoa was significantly enhanced (p less than 0.05) by the removal of Fraction V albumin from the induction medium. In the presence of CEF and in the absence of albumin, 50% of the caput spermatozoa acquired progressive motility and sustained this motility for 4 h. Moreover, when fatty acid-free, charcoal-extracted albumin instead of Fraction V albumin was utilized in the induction procedure, a maximum of 43% of the caput spermatozoa acquired progressive motility and maintained this motility for 4 h, suggesting that the decreased sperm viability observed in the presence of Fraction V albumin was due to a contaminant of albumin, possibly fatty acids. The studies described herein demonstrate for the first time that immature quiescent caput epididymal spermatozoa can be induced to acquire progressive and sustained motility equivalent to that observed in mature caudal epididymal spermatozoa.

Animals↗
PubMed1984

The relationship between prenatal lethality or fetal weight and intrauterine position in rats exposed to diethylstilbestrol, zeranol, 3,4,3',4'-tetrachlorobiphenyl, or cadmium.

When administered orally during gestation, diethylstilbestrol (DES), zeranol (ZN), and 3,4,3',4'-tetrachlorobiphenyl (4CB) but not cadmium (Cd) exhibited significant developmental toxicity, including elevated embryo- and fetolethality and reduced fetal weight, in Sprague-Dawley rats. An analysis was performed to determine the effect of intrauterine position on these parameters. In control dams sacrificed after day 18, the general pattern was that fetuses at the ovarian end of the uterine horns were significantly lighter in weight, while the heavier fetuses were located in middle positions. Treatment with each of the chemicals reduced fetal weight equally across all uterine positions. An inverse of the weight pattern was observed for prenatal mortality in controls. Embryonic resorptions were relatively more frequent at both ovarian and cervical ends, while conceptuses at intermediate positions were less vulnerable. No significant alterations in this pattern were observed in treated litters. The frequency of late fetal deaths in 4CB-treated litters was significantly higher at the cervical end of the horn, however. No differences between horns or between sexes were observed in the relative position patterns for either weight or mortality.

Animals↗
PubMedDate not supplied

Characterization of sulfhydryl proteins involved in the maintenance of flagellar straightness in hamster spermatozoa.

Hamster caput epididymal spermatozoa exhibit a marked 90-180 degree bend when induced to acquire progressive motility in vitro (Cornwall et al, 1988). Flagellar bending is prevented by oxidizing sperm sulfhydryl (SH) groups with diamide. In the present study, the authors examined the SH proteins involved in sperm flagellar bending using two-dimensional polyacrylamide gel electrophoresis and monobromobimane, an SH-specific fluorescent dye. Proteins extracted from samples containing bent caput spermatozoa contained more reduced SH than the same proteins extracted from straight caput spermatozoa. To further characterize these sperm SH proteins, caudal epididymal spermatozoa that exhibited straight flagella were induced to undergo flagellar bending by treatment with the SH reductant dithiothreitol. Specific proteins of 85-94 kDa, 50-55 kDa and 35-40 kDa, which were rich in SH groups when extracted from samples containing bent caput spermatozoa, were also SH-rich in samples containing bent cauda spermatozoa. These studies suggest that oxidation of specific SH proteins may be important for maintaining sperm flagellar morphology.

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↗