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Biomedical subjects

D L Hess

Publications and source records attributed to D L Hess.

116 records · Page 7Linked to original sources
PubMed1977

The effect of luteinizing hormone releasing hormone (LHRH) antiserum administration on gonadotropin secretion in the rhesus monkey.

Single iv injections of a rabbit antiserum to synthetic LHRH promptly suppressed serum LH and FSH concentrations in ovariectomized rhesus monkeys. Gonadotropin levels remained depressed for 10-21 days, the approximate duration of enhanced LHRH binding activity in the circulation. Doses of LHRH antiserum sufficient to reduce tonic gonadotropin secretion did not modify the time course or magnitude of estrogen-induced gonadotropin surges. These negative findings, however, cannot be interpreted to signify that such surges are not caused by a release of LHRH.

Animals↗
PubMed1977

Estrogen-induced gonadotropin surges in decerebrated female rhesus monkeys with medial basal hypothalamic peninsulae.

Hypothalamic peninsulae, posteriorly continuous with the brain stem, were produced in ovariectomized rhesus monkeys by aspiration of the cerebral hemispheres and all brain structures anterior and dorsal to the optic chiasm. These preparations were sustained for 52 to 60 h postoperatively by maintaining blood gases and pH within physiological limits and by supporting arterial blood pressure, when necessary, with infusions of rhesus monkey blood and norepinephrine. The sc injection of estradiol benzoate (EB) to such animals upon completion of the ablation procedure was followed 18-24 h later by unambiguous surges of serum LH and FSH with durations in the excess of 24 h. These findings are consonant with the view that the central components of the control system that initiates the preovulatory gonadotropin surge in the rhesus monkey are resident within the medial basal hypothalamic-hypophysial apparatus.

Animals↗
PubMedDate not supplied

Neuroendocrinology of female reproduction: review, models, and potential approaches for risk assessment.

The central role of the mammalian hypothalamic-pituitary axis in regulating female reproductive cycles is reviewed. A variety of animal models and techniques that offer increased sensitivity, speed, and flexibility over traditional reproductive toxicologic approaches for short term testing or screening are discussed, including the pivotal analysis of gonadotrophin releasing hormone (GnRH) pulse generator activity in vivo and in vitro. Other neuroendocrine techniques that require further development, but provide potential approaches to demonstrate specific sites or mechanisms of action for toxic effects on the hypothalamic-pituitary axis are suggested.

Animals↗
PubMedDate not supplied

Temporary ovarian inactivity in elephants: relationship to status and time outside.

The captive elephant population in North America is in reproductive decline and, without importation from the wild, may cease to be viable within the next several decades. The estrous cycle of three captive, reproductive-age African elephants was monitored for 3 years by measuring serum progesterone concentrations. Each elephant experienced one or more episodes of extended low progesterone (>12 weeks), analogous to supposed terminal cessation of estrous cyclicity or 'flatlining' that has been described in some captive Asian and African elephants. Other studies have reported lengthy non-luteal (follicular) phases that indicate extended episodes of ovarian inactivity; however, this phenomenon has not been examined in detail. In this study, total duration of temporary ovarian inactivity or acyclicity followed a social rank pattern, with the most subordinate female having the longest and the dominant female the shortest duration. During periods of acyclicity, the number of hours the elephants spent outside was significantly less than during non-luteal or luteal phases of the cycle. Except in one instance, behavioral data recorded by elephant keepers during their interactions with the elephants showed no change in handling during periods of ovarian inactivity. Further study is necessary to distinguish the causative agent for temporary cessation of estrous cyclicity. Understanding this phenomenon is imperative for the future reproductive viability of captive elephant populations.

Animals↗
PubMedDate not supplied

Steroid production by early pregnancy human placental villi in culture.

Organ cultures prepared from human placentae obtained at 7-12 weeks of gestation were maintained for 3-13 days in Dulbecco's modified Eagle medium (DMEM). The addition of pregnenolone to the medium resulted in a dose-related increase in progesterone production and the addition of androstenedione resulted in a dose related increase in oestrogen production. More oestrone than oestradiol was measured in medium collected at the end of the first day of culture, but, on all subsequent days, oestradiol was the predominant oestrogen produced when androstenedione was added to the culture medium. When villi were incubated with [3H]androstenedione immediately after dissection most of the radiolabelled oestrogen recovered from the tissue and medium was oestrone; however, more [3H]oestradiol was recovered when villi were tested after 3 days of culture in DMEM. The addition of oestrone to the culture medium resulted in a dose related increase in oestradiol production with oestradiol accounting for a larger proportion of the total oestrogen in the day 2 and 3 medium samples than in the day 1 samples. These data demonstrate that the enzymes required for biosynthesis of progesterone and oestrogen from exogenous substrate are maintained for at least 13 days when early pregnancy placental villi are cultured in serum-free DMEM. However, a temporal change in the pattern of oestrogen synthesis does occur in culture, such that oestradiol rather than oestrone becomes the major product of androstenedione metabolism.

Androstenedione↗