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Biomedical subjects

R H Peters

Publications and source records attributed to R H Peters.

At least 55 records · Page 3Linked to original sources
PubMed1987

Suppression of adult copulatory behaviors following LiCl-induced aversive contingencies in juvenile male rats.

Sexually immature juvenile male rats received an injection of .3 M (20 ml/kg) lithium chloride (LiCl) during each of 8-10 pairings (spaced at 2-3-day intervals) with an estrous female. Approximately seven weeks later, these males displayed fewer copulatory behaviors in pairings with estrous females than saline control rats. Noncontingent .3 M LiCl injections administered to juvenile males did not affect adult copulatory behaviors. Males that were either group or individually housed during the retention interval displayed comparable suppression, which suggests that copulatory suppression does not represent a generalized aversion to social interactions with another animal. Males housed during the retention interval in an environment that contained the odors of estrous females also displayed suppression comparable to that of males housed in the absence of such odors. This suggests that the associations that mediate copulatory suppression are not elicited solely by the odor cues of estrous females. These data demonstrate that LiCl-induced aversive contingencies in juvenile male rats subsequently suppress adult copulatory behaviors.

Animals↗
PubMed1987

Steroidal silicon side-chain analogues as potential antifertility agents.

A number of silicon-substituted analogues of ethynylestradiol that exhibit modified and enhanced biological activities have been synthesized. Particularly noteworthy are a group of [(trialkylsilyl)ethynyl]estradiol analogues that exhibit high antifertility potency and markedly reduced estrogenic activity. The best compounds synthesized are 17 alpha-[(triethylsilyl)ethynyl]estradiol (5) and 17 alpha-[(tert-butyldimethylsilyl)ethynyl]estradiol (33), which show a separation of antifertility from estrogenic activity in the rat. The results of structure-activity studies indicate a good correlation between the observed biological activities and the calculated van der Waals volumes of the three variable silicon substituents.

Animals↗
PubMed1987

Automated determination of angiotensin-converting enzyme in serum.

This is an adaptation of the Fujirebio "ACEcolor" kit for automated measurement of angiotensin-converting enzyme (EC 3.4.15.1) in serum with the Cobas Fara centrifugal analyzer. The linear range extends to an activity of 110 U/L. Results obtained by the present method and by the manual method were identical, and correlated closely (r = 0.983) with those by Cushman's modified method. The reference interval for 77 adult blood-bank donors was 9-25 U/L (mean 17, SD 4 U/L). Within-run and between-run CVs are 1.7 and 4.0%, respectively. The present method permits rapid, precise, and economical measurement of the enzyme and allows users of a Cobas Fara centrifugal analyzer to introduce a fully automated assay for angiotensin-converting enzyme into their clinical laboratory.

Adolescent↗
PubMed1985

Electrolytic current parameters in the dorsolateral tegmental obesity syndrome in rats.

Female rats received lesions in the dorsolateral tegmentum formed by the 20 sec passage of 0.25, 0.5, or 0.75 mA anodal or 0.5, 0.75, 1.0, 1.25, or 1.5 mA cathodal current. Although all lesion parameters induced roughly comparable body weight gains, the largest effect was seen with 1.25 mA cathodal current. Anodal lesions were much larger and induced transient periods of hyperactivity that confounded the effects of the lesions on body weight gain.

Animals↗
PubMed1983

Dietary quinine has a nongustatory effect on food intake in rats.

Recent data suggests that quinine adulteration of rats' maintenance diets may suppress food intake by postingestional (i.e., pharmacological or toxicological) mechanisms. This possibility was tested by increasing rats' rates of drug excretion prior to presentation of quinine maintenance diets. This treatment increased consumption of 3 concentrations (0.1, 0.2, 0.4%) of quinine diet in 2 separate experiments. In a third experiment, the same treatment did not alter consumption of quinine water in a 2 bottle test, suggesting that the increased consumption of quinine adulterated food was not due to a generalized decrease in the gustatory aversiveness of quinine. The data directly support the idea that quinine has postingestional effects which account for at least part of the suppression of food intake seen with quinine adulterated diets. The data further suggest that at least some of these effects occur postabsorptively.

Animals↗
PubMed1983

Learned aversions to copulatory behaviors in male rats.

When male rats received an injection of lithium chloride immediately after an encounter with an estrous female, the vigor of subsequent copulatory responding was initially unaffected. After 5 to 10 such pairings, however, male rats displayed an aversion to copulatory behaviors; they ceased to copulate entirely. These aversions persisted when the rats were tested in a novel environment and extinguished after four nonreinforced trials. This multiple-trial adaptation of the conditioned taste aversion paradigm provides a new approach to the aversive control of sexual behavior.

Animals↗
PubMed1981

Unimpaired quinine metabolism in rats with ventromedial hypothalamic lesions.

Rats with lesions of the ventromedial hypothalamus (VMH) show a greater decrease in food intake than normal rats if fed diets adulterated with quinine. To determine if this hyperresponsivity is due to impaired quinine metabolism, in vitro rates of drug metabolism of female hooded rats with VMH lesions were measured. Determinations were made both under basal conditions and under conditions known to cause induction of drug metabolizing enzymes. VMH rats showed rates of drug metabolism virtually identical to controls under all conditions tested. These data suggest that VMH lesioned rats are not more sensitive to quinine dietary adulteration because of impaired quinine metabolism.

Animals↗
PubMed1981

Pituitary beta-endorphin, naloxone, and feeding in several experimental obesities.

The role of beta-endorphin in the development of several obesity syndromes was examined. Adult female hooded rats received ventromedial hypothalamic lesions, dorsolateral tegmental lesions, parasagittal hypothalamic knife cuts, intraventricular 5,7-dihydroxytryptamine, ovariectomy, control surgery, or were deprived to 75% of normal body weight. Dose-dependent suppression of food intake by the opiate antagonist naloxone (0.5, 1.8, 6.8, or 25.0 mg/kg, ip) was measured during once-daily 4-h food access periods. No difference was found among the groups at any dose. Pituitary beta-endorphinlike immunoreactivity (BELI) was substantially decreased in knife-cut rats, but was unaltered by other treatments. Obesity had no effect on BELI. In another experiment, rats made obese by prolonged maintenance on palatable foods had elevated pituitary BELI levels. Feeding mechanisms involving opioid peptides do not appear to be of etiological significance in the syndromes examined.

5,7-Dihydroxytryptamine↗
PubMed1978

Naloxone interactions with morphine-and shock-potentiated tonic immobility in chickens.

Opiate receptor involvement in tonic immobility was examined by administering various does of the opiate antagonist naloxone before measuring morphine-potentiated, shock-poteniated or unpotentiated tonic immobility in chickens. Naloxone attenuated morphine-potentiated, but not shock-potentiated or unpotentiated tonic immobility. Morphine-potentiated tonic immobility appears to be opiate specific.

Animals↗