John C. Chapman

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BACKGROUND Female mice and rats injected with estrogen perinatally become anovulatory and develop follicular cysts. The current consensus is that this adverse response to estrogen involves the hypothalamus and occurs because of an estrogen-induced alteration in the GnRH delivery system. Whether or not this is true has yet to be firmly established. The(More)
Condensation of sperm chromatin occurs after spermatozoa have left the caput epididymis and are in transit to the cauda epididymis, during which time large numbers of disulfide bonds are formed. The formation of these disulfide bonds requires the repeated oxidation of the cofactor, NAD(P)H. To date, the means by which this oxidation is achieved has yet to(More)
3 beta-Hydroxysteroid dehydrogenase (HSD) is located in the endoplasmic reticulum and mitochondria. To determine whether the separate enzymes play different roles in steroidogenesis, the specific activity (SA) of both were measured at four different stages of the mouse estrous cycle. Microsomal HSD activity changed little throughout, averaging 8.7 +/- 0.7(More)
PROBLEM Injections of estradiol-17 beta (E2) are known to both induce anovulation and alter lymphocyte maturation in female mice. The current study examined whether the two events are related. METHOD OF STUDY Female (C3H/HeJ x 129J)F1 (C31) mice were injected with 20 micrograms of E2 from 0-3 days, or from 3-6 days, postpartum. At 8, 12, 20, 32, or 40(More)
PROBLEM Female mice injected with estradiol-17beta (E2) and testosterone during the immune adaptive period are infertile as adults. Study 1 examined the effect of the day of injection of E2 and testosterone on the incidence of infertility in two strains of mice. Study 2 examined the effect of hydrocortisone on E2-induced infertility. METHOD OF STUDY Study(More)
In mouse ovaries, the enzyme 3 beta-hydroxysteroid dehydrogenase (HSD) is distributed between microsomes and mitochondria. Throughout the follicular phase of the estrous cycle, the HSD activity in microsomes is predominant; whereas, after LH stimulation, HSD activity during the luteal phase is highest in the mitochondria. The current study examined whether(More)
The presence of nuclear androgen binding proteins measured by nuclear androgen exchange in rat spermatids and spermatozoa was re-examined. Specific binding was observed to be related to less dense contaminating particles when sonicated testes were fractionated by isopcynic centrifugation through a 40-61% Nycodenz linear gradient. No specific binding was(More)
PROBLEM Neonatal thymectomy (Tx) and estrogen (E2) administration disrupt the reproductive and immune systems of female mice. The current experiment examined the combined effects of the two procedures on ovarian function, performed in sequence, and in reverse sequence. METHOD Groups of (C57BL/6J x A/J)F1 (B6A) female mice were given four daily injections(More)
Three questions were asked in an attempt to understand how testosterone (T) concentration in the veins of the remaining testis can double within 24 h after hemicastration in the mature rat without a change in plasma luteinizing hormone (LH) levels. These three questions (and their answers) were: 1) Can the testicular hemicastration response occur in(More)
Nuclear androgen binding sites were examined in late spermatids (stages 12-19) which resisted sonication of homogenized testes of mature male rats. The measurement of unoccupied binding sites in salt extract of purified spermatid heads by nuclear exchange at -10 degrees C was developed and validated. As in the prostate, unoccupied nuclear androgen binding(More)