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Biomedical subjects

D W Forrest

Publications and source records attributed to D W Forrest.

46 records · Page 3Linked to original sources
PubMed1981

Estriol- and estradiol-17 beta-induced luteinizing hormone release in ovariectomized cows and ewes.

Two studies were conducted with ovariectomized animals to compare luteinizing hormone (LH) responses during the 24-hr period following an IM injection of either estriol or estradiol-17 beta. In Exp. 1, six long-term ovariectomized (6 months) beef cows were randomly assigned to be given 1 mg of estriol or estradiol 17 beta injected in 4 ml of corn oil. Two months later, the experiment was replicated in a switch back design. In Exp. 2, eight ewes that had been ovariectomized for 1 to 4 months were randomly assigned to be given 150 micrograms of estriol or estradiol-17 beta injected in 1.5 ml of corn oil. The initial increase in serum LH concentrations occurred earlier in both cows (P less than .01) and ewes (P less than .05) in response to estriol (8 to 9 hr) than in response to estradiol 17 beta (12 to 18 hr). In addition, duration of the decrease in LH release that occurred 1 hr after estrogen injection in ewes was 3 hr shorter (P less than .05) in response to estriol than in response to estradiol-17 beta. The total area under the LH response curve was greater for both cows (P less than .05) and ewes (P less than .01) given estradiol-17 beta than for those given estriol. Administration of estradiol-17 beta induced a 10-fold increase in serum estradiol-17 beta concentrations and a two to fourfold increase in serum estrone concentrations. Both estrogens returned to basal concentrations by 24 hr after administration. Peak serum estriol exceeded 300 pg/ml within 1 hr of estriol injection, but decreased to nondetectable levels within 12 hours. We concluded that estriol can stimulate LH release from the pituitary. Furthermore, the differential LH response to the two estrogens suggests that the positive effects of estriol are mediated earlier but that estradiol-17 beta is a more potent stimulus when administered as a single IM injection.

Animals↗
PubMed1979

Effect of norgestomet on peripheral levels of progesterone and estradiol-17beta in beef cows.

Peripheral levels of progesterone and estradiol 17beta were quantified in 27 cycling cows following administration of a single Hydron ear implant (G. D. Searle and Co.) containing 2, 4 or 6 mg norgestomet or controls which received no implant. Implants were inserted subcutaneously in the ear on day 15 of the estrous cycle (day of estrus = day 0) and removed 9 days later. The 4 mg (seven of seven cows) and 6 mg (six of six cows) implants suppressed estrus; however, three of eight cows in the 2 mg group exhibited estrus prior to implant removal. The 6 mg implant group had a significantly longer interval from implant removal to estrus than either the 2 or 4 mg group. Failure to detect differences in the rate at which progesterone declined indicated norgestomet treatment did not affect normal corpus luteum regression. Estradiol levels rose at a similar rate approaching estrus in all treatments. There was no indication of increased endogenous estradiol levels due to norgestomet treatment.

Journal Article↗
PubMed1975

Coin value and perceived size: a longitudinal study.

Decimalization of the Irish currency presented an opportunity to study the perceived size of coins as they were introduced or withdrawn and to examine the accentuation of differences between coins. Estimates were obtained of the sizes of 4 coins from 478 subjects in 3 groups tested at different times: just after decimalization, 2, or 3 yr. later. A newly introduced coin was significantly underestimated in size at first but came to be significantly overestimated later, while all familiar coins were always significantly overestimated. The amount of overestimation of a coin depended on its value, not its size, leading to an accentuation of the difference between any two coins if the larger coin was also the more valuable but sometimes to the opposite if the smaller coin were of higher value than the larger member of the pair.

Adolescent↗