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Biomedical subjects

A K Slob

Publications and source records attributed to A K Slob.

At least 109 records · Page 6Linked to original sources
PubMed1982

Testosterone induced mounting behavior in adult female rats born in litters of different female to male ratios.

Female rats can show mounting behavior towards isosexual or heterosexual conspecifics. The present experiments were designed to study whether the prenatal presence of male fetuses would affect display of this mounting behavior in adulthood. Therefore mounting behavior, after gonadectomy and during continuous treatment with testosterone propionate (TP) was studied in female rats which were born in litters without male siblings ("all female" litters) and in litters with a variable number of male siblings. Litter composition at birth did not affect display of adult mounting behavior during protracted tests (a total of 6 tests during 8 weeks of treatment with TP). The data indicate that TP induced mounting behavior in adulthood occurs independent of the prenatal presence of male fetuses. If mounting behavior in adulthood has to be "organized" by prenatally present androgen (the current way of thinking), then the present data indicate that female rat fetuses provide themselves with these hormones. It would then seem inappropriate to judge adult mounting behavior as a sign of "masculinization" of the rat brain.

Animals↗
PubMed1981

Effects of gonadectomy and exogenous gonadal steroids on sex differences in open field behaviour of adult rats.

Two experiments were carried out to investigate the contribution of gonadal hormones to the expression of sex differences in open field behaviour of adult female and male rats. In the first experiment rats were gonadectomized or sham-operated in adulthood and tested in the open field 1, 2, 3, 4, 5 or 6 weeks later (3 min/rat on 3 consecutive days during the light period of the day). It was found that following gonadectomy the well known sex difference in ambulation and rearing behaviour (females more than males), as well as in defaecation (females less than males) remained. Ovariectomy caused a decrease in ambulation and rearing, with an increase in defaecation, whereas castration had no significant effect on ambulation and rearing, but also increased defaecation. Also an overall increase in ambulation and rearing was found: animals tested 5 and 6 weeks following the operation were significantly more active than animals tested at 1-4 weeks after the operation. In the second experiment female and male rats were gonadectomized and 7 weeks later they received a silastic implant containing testosterone (T), dihydrotestosterone (DHT), oestradiol (E2), DHT plus E2, or nothing (control condition). Four weeks after the implantation the animals were tested in the open field (3 min/rat on 3 consecutive days). An overall sex difference was found for ambulation (females more than males) and for defaecation (females less than males). The only effect of hormone administration was found in DHT-treated animals: lowest ambulation and highest defaecation compared to other hormone and control animals. No differences were found between the T, E2, DHT plus E2, and control animals. From these data it was concluded that endogenous gonadal steroids seem to play a minor role in the expression of sex differences in adult open field behaviour in the rat.

Animals↗
PubMed1980

Behavioral and physiological evidence of sexual climax in the female stump-tailed macaque (Macaca arctoides).

Intense tonic/clonic uterine contractions and sudden increases in heart rate coincided with the behavioral homolog of a male ejaculatory response (minus seminal emission) in a normal female stump-tailed macaque engaged in homosexual mounting episodes. The behavioral patterns were also observed in four of ten females during 5 to 40 percent of heterosexual copulations. These observations demonstrate the existence of an orgasmic response in a nonhuman primate.

Animals↗
PubMed1980

Effect of neonatal undernutrition on serum follicle-stimulating hormone levels and ovarian development in the female rat.

1. Female rats were undernourished from birth through replacement for 12 h/d of the lactating mother by a nipple-ligated mother. This resulted in slow growth so that 22 d of age the body-weights equalled those of well-nourished animals at 14 d. 2. At 14, 17, 20 and 22 d groups of eight to ten animals each of undernourished and well-nourished rats were autopsied, serum follicle-stimulating hormone (FSH) concentration was determined by radioimmunoassay, uteruses were weighed and ovaries examined by light microscopy. 3. Undernutrition caused a 3-4 d delay in the third-week drop in serum FSH and in ovarian development as indicated by the numbers of antral follicles and by the maximal diameter of the ovaries and of the largest follicles. 4. It is postulated that the effect of undernutrition on serum FSH may be due to delayed increase in ovarian feedback effectiveness, which may be the result of either the retardation in ovarian development or a continued high level of serum oestrogen-binding protein. It remains uncertain through which mechanisms(s) undernutrition brings about delayed onset of puberty.

Age Factors↗
PubMed1980

Prenatal and early postnatal sex differences in plasma and gonadal testosterone and plasma luteinizing hormone in female and male rats.

Plasma levels of testosterone and LH were estimated in female and male rats at gestational ages of 19, 20 and 21 days and at 1, 3, 6, 12, 18 and 24 h after birth. Concentrations of testosterone in the gonads were also estimated in 20-day-old fetuses and at various times after birth. Before birth female fetuses had significantly lower levels of testosterone and higher levels of testosterone and higher levels of LH than had male fetuses. During the first 24 h after birth female rats also had lower levels of testosterone and higher levels of LH than male rats. The pattern of levels of testosterone in the hours after birth was significantly different between female and male rats in that high levels were observed 1 and 3 h after birth in male rats (3.0 and 2.2 ng/ml respectively). This finding, as well as the relatively high levels of testosterone in female fetuses (about 50% of the levels found in male womb-mates) is discussed.

Animals↗
PubMed1979

Body growth, puberty and undernutrition in the male guinea-pig.

1. Male guinea-pigs were assigned to four different groups at birth. The heaviest group of animals was severely undernourished from 21 d of age (weight gain: 1.2 g/d v. 10 g/d for normally-fed animals). 2. At 35, 45, 55 and 65 d of age in normally-fed animals, and at 45 and 55 d of age in undernourished animals, blood testosterone levels were determined by radioimmunoassay, epididymidal tissue examined for the presence of spermatozoa and testes sectioned for rating of spermatogenesis using light microscopy. 3. Sexual maturity in terms of potential fertility (spermatozoa in the epididymis) was reached by all normally-fed animals between 45 and 55 d of age. High birth-weight animals had a higher incidence of the most advanced stages of spermatogenesis than low birth-weight animals had a higher incidence of the most advanced stages of spermatogenesis than low birth-weight ones at the various ages studied. In the undernourished animals spermatogenesis was clearly delayed. 4. Plasma testosterone concentrations were already in the adult range at 35 d and independent of age and birth-weight. The undernourished animals, however, had very low levels. Maintenance of spermatogenesis seemed compatible with low plasma levels of testosterone. 5. It is concluded that the timing of testicular development seems to be determined by the time the animals are born and appears to be unaffected by severe undernutrition from 21 d of age.

Aging↗
PubMed1978

Locomotor activity and social behavior of old rats after preweaning undernutrition.

Rat pups were undernourished from birth to 25 days of age by giving them a nipple-ligated mother and a normal lactating mother for alternate periods of 12 hr/day, thus providing adequate full-time maternal care. Male and female rats undernourished neonatally had greater locomotor activity than controls in old age (16-20 months)mfemales were more activive than males, irrespective of neonatal undernutrition. At the age of 24 months, social behavior was recorded at various times of the day for pairs of male rats (1 previously undernourished and 1 control). With one minor exception, undernourished animals did not differ significantly from controls in the incidence of the various behavioral items that were scored. Neonatal social factors may compensate for possible negative effects of neonatal undernutrition on later social behavior.

Activity Cycles↗
PubMed1975

Multiple ejaculations during prolonged sexual tests and lack of resultant serum testosterone increases in Male Stumptail Macaques (M. arctoides).

The sexual behavior of four male and four female adult stumptail macaques was observed in standardized 3-hr heterosexual pair tests. The males achieved from 11 to 19 ejaculations during a single test, thus apparently exceeding any other primate studied under laboratory conditions for the ability to display multiple ejaculatory patterns in relatively short periods of time. The stage of the menstrual cycle was not found to be related to the performance of the male or female, although this variable was not analyzed in depth. Progressive increases in the interejaculatory interval (IEI) occurred for all four males for the initial two to four ejaculations of the series, and then either a plateau or a transient decrease in this measure occurred. Since the data varied considerably for IEI as well as for other quantitative measures of sexual behavior for a given pair, individual data rather than group averages are presented. Blood samples drawn immediately before and after behavioral testing as well as at comparable intervals 1 week prior to behavioral testing were analyzed for testosterone concentration by radioimmunoassay for each male. Serum testosterone values were not found to be influenced by multiple ejaculations. Instead, decreased levels of serum testosterone were encountered on the second blood sample of the day for most males, regardless of whether sexual behavior occurred. The possibility that the decreases were related to stress effects of handling is discussed. Because of this complication, it could be only tentatively concluded that repeated copulation to ejaculation over a 3-hr period did not result in appreciable changes in testosterone levels.

Animals↗