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Biomedical subjects

G T Taylor

Publications and source records attributed to G T Taylor.

At least 55 records · Page 3Linked to original sources
PubMed1983

Sexual experience, androgens and female choice of a mate in laboratory rats.

Sexual experience produces long-lasting changes in both the behaviour and reproductive system of a male rat. The response of the female rat to an area that had recently housed a previously mated male was investigated in three experiments. In experiments 1 and 2 females preferentially urine marked in an area vacated by a sexually experienced (SE) male relative to areas vacated by a sexually inexperienced (SI) or castrated (C) male. The density of female marks were ranked SE greater than SI greater than C greater than empty area. In experiment 3 female preference of an SE male with varied and multiple mating experiences was magnified when compared with an SI male. There was the suggestion that the multiple SE male was even preferred to a male with only a single mating experience. A fourth experiment demonstrated an acute increase in circulating testosterone in multiple SE males exposed to oestrous or non-oestrous females, and the increase was observable for up to 7 days after exposure to an oestrous female. The conclusion is that chronic changes in androgen-dependent urinary by-products released by the SE male mediate the discrimination and choice of a mate by the female rat.

Animals↗
PubMed1983

Reproductive physiology and penile papillae morphology of rats after sexual experience.

Research which examined acute and chronic changes in the reproductive physiology and morphology of male rats after mating is reported. A group of sexually experienced (SE) and a group of sexually inexperienced (SI) animals were castrated on day 110 of age. Those animals and a group of SE and a group of SI gonadally intact males were left undisturbed for 30 days, and all animals were killed on day 140 of age. Testes, epididymides, penes and levator ani muscles were heavier in SE males, and those males had increased titres of circulating testosterone. Moreover, testicular sperm production was higher in SE than SI males immediately after the weekly copulatory sessions. Scanning electron microscopic examination of the surfaces of the glans penes revealed that sexual experience slowed the decay of penile papillae. More importantly, SE-intact males possessed uniformly large penile papillae, while the large papillae on penes from SI-intact males were interspersed with smaller papillae in various stages of development. The results suggest that mating provokes substantial changes in the endocrine integrity, fecundity and penile morphology of male rats.

Animals↗
PubMed1982

Urinary odors and size protect juvenile laboratory mice from adult male attack.

For the portion of their ontogeny, the juveniles of many mammalian species appear resistant to aggressive attack by adult male conspecifics. The possibility that urinary odors and small size contribute to this immunity from attack was investigated with C57/Bl, A/J, and DW/J laboratory mice. The results of the 1st of 6 experiments were that juvenile mice of both genders evoked great curiosity from aggressive resident male adults, but juveniles were rarely attacked. In Experiments II and III, exchanging urine between juveniles and adult males suggested that juveniles possess a distinctive odor, In Experiments, IV-VI, dwarf adult, normal-size adults, and juveniles were placed with aggressive adult male residents. The dwarf males were attacked, but not as severely as normal-sized male intruders (Experiment IV). The dwarf males, however, evoked more aggressive behavior than juveniles (Experiment V), and juveniles with the odors from either normal-sized or dwarf adult males were attacked more readily than non-odorized juveniles (Experiment VI). These data suggest that both odor and size contribute to the juveniles' immunity from attack.

Aggression↗
PubMed1982

Female rats prefer an area vacated by a high testosterone male.

In each of 4 experiments, female rats were observed as they moved freely about an apparatus that had recently housed 2 males. The androgen levels of the males were manipulated with castrations and exogenous injections of testosterone propionate (TP). For the most part, female exploration times in the areas vacated by the 2 males did not differ. The urinary markings over the urine from the males, however, did differ. The female exhibited a decided marking preference for the area that had housed the male with higher titers of androgens. The preferences were for intact vis-a-vis castrated males, though injections of TP restored the castrates' attractiveness to the females. When both males possessed reproductive levels of TP, the females preferred to mark over the urine of the male with the higher levels of the androgen. The reproductive advantage for the female may be the choice of a mate with more viable sperm, because androgens are intimately involved in spermatogenesis.

Animals↗
PubMed1982

Presence of intact and gonadectomized juveniles and the reduction of fighting between adult male rats.

Research is reported which investigated the aggressive interactions between adult male rats in the presence of 17-27 day old juvenile conspecifics. Following a brief exposure to an inaccessible juvenile male, juvenile female, estrous adult female, or empty compartment, the males of Experiment 1 were allowed to interact with another adult male. Results were that the presence of both genders of juveniles reduced fighting between the adult males, and pre-pubertal females were particularly effective as an aggression-inhibitor. The hormonal bases for those sex differences were examined in Experiment 2 using juveniles gonadectomized on Postnatal Day 10. Adult males were more aggressive following exposure to intact juvenile males than to castrated juvenile males; the latter males, intact juvenile females, and ovariectomized juvenile females provoked similar and low rates of fighting between adult males. These data suggest that the sexual dimorphism is a function of testicular hormones present during the juvenile stage which modify the stimulus characteristics of a pre-pubertal male rat.

Aggression↗
PubMed1980

Solvent extracts of carbon black--determination of total extractables and analysis for benzo(alpha)pyrene.

The efficiency of three organic solvents for extraction of adsorbates, including polycyclic aromatic hydrocarbons (PAH), on five rubber-grade oil furnace blacks was studied. Measurement of both the percent total extractables and the specific PAH, benzo(alpha)pyrene (B alpha P), showed toluene to be a better extractant than benzene and both to be superior to cyclohexane. Spectral analysis for B alpha P was preceded by chromatographic separation. A thin layer technique was shown to be a rapid and reliable replacement for paper chromatography.

Benzopyrenes↗
PubMed1977

Nutrition and factors limiting the growth of a methanogenic bacterium (Methanobacterium thermoautotrophicum).

The purification of Methanobacterium thermoautotrophicum from a culture contaminated with a heterotrophic organism is described. A defined inorganic medium under H2/CO2 (80:20 v/v) has been developed to support growth of M. thermoautotrophicum up to a concentration of at least 1.7 g dry weight/l. In a conventional medium iron and nitrogen sources were found to be growth-limiting factors. Throughout most of the culture period the rate of transfer of hydrogen or carbon dioxide from gas to liquid was the factor which controlled the growth rate. The growth yields of bacteria were in the range of 0.6-1.6 g dry weight/mole CH4.

Anaerobiosis↗
PubMed1976

Influence of female's sexual cycle on aggressiveness in male rats.

Two experiments examined the relationship between the female's stage of estrus and agonistic behavior among males. Socially subordinate male albino rats were exposed to an inaccessible female and then given equal numbers of free-choice and forced-choice trials to a more aggressive "target" male or to an empty compartment. The submissive males were more aggressive following exposure to an estrous female than following exposure to a diestrous female. Furthermore, the probability of approaching the more aggressive male increased. This heightened level of aggressiveness was accompanied by a comparable increase in hostile behaviors by the dominant target males of Experiment 1. However, in the second experiment the increase in submissive-male aggressiveness was sufficient to reduce the social distance between the submissive subjects and their moderately aggressive target males.

Aggression↗
PubMed1976

Properties and physiological effects of thermal carbon black.

Studies have been carried out to determine the possible physiological effects of contact with carbon black made by the thermal process. Contact was made by ingestion, skin application and/or inhalation. Ingestion and/or skin application do not appear to lead to any changes from the normal. Inhalation exposures do not produce pulmonary function changes (antemortem or postmortem studies) but may lead to moderate to severe "perifocal" emphysema in Rhesus monkeys (not observed in guinea pigs). Inhalation studies also suggest right ventricular septal and to a degree, left ventricular hypertrophy in Rhesus monkeys as an effect. Additional studies are necessary to support these finding and consideration must be given to the variability among exposed subjects as compared to controls.

Animals↗
PubMed1975

Discriminability and the contrafreeloading phenomenon.

According to previous reports of the "contrafreeloading phenomenon," animals will work for a reward, and sometimes work quite hard, in the presence of the same reward available freely. With rats as the subjects two experiments are presented which suggest that the contrafreeloading data are explainable with a basic learning principle, discriminability and its accompanying response decrement. For some animals the change in stimulus conditions with introduction of free water was made more highly discriminable by a change in earned reinforcement conditions. The other animals remained on the same earned reinforcement conditions under which all the animals had been trained. The results demonstrated that the discriminability between the conditions of working and freeloading is a most important factor contributing to the continued responding in the presence of free rewards.

Animals↗
PubMed1975

Social position and competition in laboratory rats.

Two experiments with rats as subjects are described, which control for social position, i.e., relative dominance/submission, in an appetitive social learning-performance setting. The results indicate that animals that perform quite effectively when alone exhibit significantly reduced levels of responding when placed into a social environment. The severity of the response decrement is, at least in part, a function of the relative social position of the subjects involved. A dominant male made few responses when paired with another dominant male. Yet, a dominant subject made even fewer responses when paired with a submissive subject, which bar pressed at approximately half the individual level. These findings are interpreted as suggesting that social position, with its accompanying characteristic form of aggression, is an important determinant of performance in a social learning environment.

Adaptation, Psychological↗
PubMed1975

Male aggression in the presence of an estrous female.

The relationship between male rat aggressiveness and the presence of a female was studied. Twenty 100-day-old dominant male albino rats were individually exposed to an inaccessible female rat in a specially constructed apparatus. The males were then given free-forced trials to an empty compartment or a compartment housing a submissive male. The results indicate that following exposure to an estrous female, dominant males increased their percentage of choices to the submissive male. Moreover, the incidences of aggressions by the dominant animal toward the submissive animal increased sharply after prior exposure to the estrous female. These data suggest that one antecedent source of aggression among male rodents may be the presence of a sexually receptive female.

Aggression↗