Biomedical subjects

Thomas J Collins

Publications and source records attributed to Thomas J Collins.

2 recordsLinked to original sources

PubMed2006

Ovarian dysfunction in peripubertal hyperinsulinemia.

OBJECTIVE: Increasing evidence suggests that hyperinsulinemia plays an important role in the pathogenesis of polycystic ovary syndrome (PCOS). However, the timing for the onset of hyperinsulinemia is not clear. The objective of this study was to examine the effect of peripubertal hyperinsulinemia on the maturing female reproductive axis. METHODS: Hyperinsulinemia was induced in 28-day-old peripubertal female rats by infusing insulin (0.04 IU/d) via subcutaneously implanted Alzet minipumps (Model #2004; Durect Corp, Cupertino, CA; constant flow rate 0.25 muL/h) for 4 weeks. Control animals were administered normal saline. Estrus cyclicity was monitored regularly. Upon termination of the experimental period, the animals were killed, trunk blood and pituitaries were collected for hormone assays, and ovaries were collected for histological and immunocytochemical studies. RESULTS: In contrast to the control animals, hyperinsulinemic animals had (1) erratic estrus cycles, with prolonged (2 to 3 days) metestrus-diestrus or diestrus-proestrus stages; (2) significantly (P <.05) decreased levels of serum progesterone, and significantly (P <.05) increased levels of serum testosterone and dehydroepiandrostene sulfate; (3) prematurely luteinized ovarian follicles with prominent thecal and interfollicular stromal proliferation; and (4) markedly reduced expression of growth differentiation factor-9 (GDF-9) and activin receptors (ActR) I and IB in the ovaries. CONCLUSION: Peripubertal hyperinsulinemia in rats causes hormonal and ovarian changes similar to those in women with PCOS. Based on these novel findings, we speculate that peripubertal hyperinsulinemia may be a risk factor for the development of PCOS later in life.

Activin Receptors, Type I↗

PubMed2005

Adverse effects of methylphenidate on the reproductive axis of adolescent female rats.

OBJECTIVE: To examine the effects of chronic methylphenidate use on the reproductive axis of adolescent female rats. DESIGN: Controlled prospective study. SETTING: University research laboratory. ANIMAL(S): Twenty prepubertal female Sprague Dawley rats. INTERVENTION(S): Subcutaneous implantation of drug-filled Alzet minipumps (Durect Corporation, Cupertino, CA) for infusing methylphenidate (450 microg/d, treated) or physiological saline (control) for 4 weeks. Estrous cyclicity was checked from 3 weeks of pump implantation till the termination of the experiments. Animals were killed after 4 weeks of treatment. MAIN OUTCOME MEASURE(S): Estrous cyclicity, pituitary and peripheral FSH and LH, serum estrogen and progesterone, ovarian histology, and immunocytochemistry for localizing growth differentiation factor-9 and activin receptors-I. RESULT(S): Compared with the control group, the treated animals exhibited the following: [1] poor vaginal opening and erratic estrous cyclicity; [2] undeveloped, disrupted, or prematurely luteinized ovarian follicles; [3] absence of growth differentiation factor-9 and of activin receptors I and IB in the oocyte; and [4] high levels of LH in the pituitary. CONCLUSION(S): Chronic methylphenidate administration during adolescence perturbs pubertal onset, adversely affects maturation of the female reproductive axis by retarding pituitary LH release, and adversely affects ovarian folliculogenesis. These novel findings may have significant clinical implications in evaluating the effects of methylphenidate abuse on adolescent health.

Age Factors↗