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Biomedical subjects

C M Blacker

Publications and source records attributed to C M Blacker.

6 recordsLinked to original sources
PubMed1992

Ovulation stimulation and induction.

Evaluation of gonadotropins, prolactin, and thyroid function in anovulatory women directs subsequent therapy. Treatment should be initiated with the agent that is the safest and least costly for the specific indication. Except in cases of FSH elevation, pregnancy rates should approximate those of normally ovulating women. Bromocriptine, the drug of choice for hyperprolactinemia, restores ovulation in greater than 90% of women treated. Clomiphene citrate remains the drug of choice for normoestrogenic anovulation. Although drug-resistant women may respond to extended regimens, failure to ovulate or to conceive within six ovulatory cycles with clomiphene is an indication for menotropin therapy. Menotropins and pulsatile GnRH should be considered first line therapy for women with hypogonadotropic anovulation. When using hMG or pulsatile GnRH in clomiphene-resistant patients, pretreatment with GnRH analogs may normalize their response and result in higher pregnancy rates. GnRH analogs prevent premature luteinization in hMG-induced in vitro fertilization and gamete intrafallopian transfer cycles, resulting in lower cancellation rates and improved oocyte quality. Superovulation with clomiphene citrate should be attempted in patients with unexplained infertility prior to using menotropin therapy.

Bromocriptine↗
PubMed1991

The gonadotropin-releasing hormone agonist leuprolide affects the thymus and other non-reproductive systems of female rats.

To evaluate the effects of a gonadotropin-releasing hormone agonist on non-reproductive systems, we administered [D-Leu6,Des-gly10]-GnRH ethylamide (leuprolide; 5 micrograms/day) for 21 days to female Sprague-Dawley rats. In Experiment 1, continuous infusion (Alzet minipumps sc) was compared to injection. Increased thymus and body weights and decreased estradiol and uterine weights were noted for both administration methods. Spleen weight increased only in rats treated by continuous infusion. Ovary, kidney and liver weights did not change. Only leuprolide-injected rats had elevated LH with decreased corticosterone and ACTH levels, possibly related to the injection process. Glucose, insulin, progesterone, FSH and corticosterone/ACTH were not different. In Experiment 2, intact and ovariectomized rats were implanted with minipumps delivering leuprolide or 0.9% NaCl. Body and thymus weights increased, whereas uterine weight and estradiol declined in both leuprolide-treated and ovariectomized rats. No synergism between leuprolide and ovariectomy was noted. Thymosin alpha 1, but not thymosin beta 4, increased in leuprolide-treated ovariectomized rats. Peripheral white blood cell count was elevated in leuprolide-treated intact rats and ovariectomized rats. In bone marrow, non-nucleated cell count declined in leuprolide-treated intact rats, contributing to the decreased total cell count in this group. Nucleated cell count was unaffected. Therefore, thymus weight gain was accompanied only in some cases by functional changes. Our results demonstrate that leuprolide affects non-reproductive systems, in a similar manner to ovariectomy. We suggest that such alterations may be due to the hypoestrogenic environment produced by leuprolide.

Adrenocorticotropic Hormone↗
PubMed1989

Effect of GnRH agonists on the thymus in female rats.

The potential clinical applications of GnRH agonists are growing. We studied the effects of two GnRH agonists on the adult female rat thymus in 4 experiments. GnRH agonists administered sc and continuously significantly increased wet and dry thymic weights (absolute and relative). Thymic enlargement was related to the duration of treatment with GnRH agonists. The maximum increase in thymic weight occurred at approximately 18 days following initiation of treatment with GnRH agonists. Thymic enlargement does not appear to involve enhanced mitotic activity as measured by incorporation of tritiated thymidine into thymic tissue and thymic DNA. Histologic examination and computer-assisted morphometric analysis of thymuses indicated an increase in cortex to medulla ratio most pronounced at 10 and 18 days of GnRH agonist treatment. No consistent increases in splenic weight or bone marrow cell counts were observed. Thymosin alpha-1 but not thymosin beta-4 increased in GnRH agonist-treated rats. Thymic weight correlated negatively with ovarian and uterine weights, relative adrenal weight, serum estradiol, LH, and positively with thymosin alpha-1. Exogenous estrogen administration reversed GnRH agonist-induced thymic weight increase. Whether GnRH agonists have direct thymic effects remains to be determined.

Animals↗
PubMed1988

Inhibition of rat ovarian [3H]thymidine uptake by luteinizing hormone-releasing hormone agonists: a possible mechanism for preventing damage by cytotoxic agents.

To investigate the mechanism involved in luteinizing hormone-releasing hormone (LHRH) agonists' protective effects against chemotherapy-induced ovarian damage, female rats were either implanted with 1-mg pellets of LHRH agonist Zoladex (LHRHz) or sham operated. All rats were implanted with osmotic minipumps loaded with [3H]thymidine 48 h before sacrifice in diestrus. Ovaries were combusted in a biological material oxidizer. Tritiated water was recovered in a special cocktail, and ovarian tritiated thymidine uptake (3HTU) was calculated. In five experiments, LHRHz significantly reduced ovarian 3HTU. This was observed 5 days after implanting LHRHz pellets. Ovarian 3HTU correlated significantly with serum estradiol, LH, and ovarian and uterine weights. Autoradiography showed that almost all ovarian 3HTU is by granulosa cells. These data suggest that LHRHz suppresses ovarian mitotic activity. Since cytotoxic agents preferentially destroy rapidly dividing cells, our findings may represent a mechanism for ovarian protection.

Animals↗