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Effects of hypothalamic lesions upon the sexual and social behaviour of the male common marmoset (Callithrix jacchus).

The sexual and associated behaviour of 10 adult male marmosets was recorded during pair tests with ovariectomized females, before and after bilateral thermal lesions of the hypothalamus. Four sham-lesioned males served as controls. Lesions varied in volume from 1.49 to 3.28 mm3 and extended from the ventromedial hypothalamus to the diagonal band of Broca. Precopulatory behaviours (anticipatory erections, tongue flicking and anogenital investigations of the female) as well as frequencies of mounting, intromission and ejaculation decreased in lesioned males. The greatest suppression of sexual behaviour occurred after lesioning the anterior hypothalamus (AH), beneath the anterior commissure, or at the junction of the AH with the preoptic area (POA). Lesions confined to the POA had less profound behavioural effects. Treating ovariectomized females with estradiol stimulated their proceptivity but had no consistent effects upon the males' behaviour. Lesioned males did not exhibit signs of social withdrawal and frequencies of allogrooming or grooming invitations increased post-operatively. Preliminary studies on intermale aggression indicated that lesions which had the greatest effect upon sexual behaviour also tended to decrease aggressive interactions with other males. Hypothalamic lesions did not affect plasma testosterone levels, except in one male and only one animal showed signs of ill health (weight loss and hypothermia) post-operatively. These results show that damage to the AH or AH-POA junction in male marmosets causes a profound suppression of sexual 'arousal' and copulatory behaviour and that such affects are not due to androgen insufficiency or other, non-specific, side effects of neural damage.

Aggression↗

Loss of ocular dominance columns with maturity in the monkey, Callithrix jacchus.

Previous studies have shown that adult marmosets lack ocular dominance columns (ODC) in area 17, but that ODCs can be demonstrated upon visual deprivation. The present results, obtained by transneuronal transport of WGA-HRP, indicate that ODCs normally develop in juvenile marmosets but disappear before the animal reaches maturity. The findings suggest that formation of ODCs during ontogenesis, and their persistence through adulthood, are different developmental processes depending on different mechanisms.

Aging↗

Luteal deficiency caused by human ovarian follicular fluid peptide in post-partum marmosets, Callithrix jacchus.

A peptide purified from human ovarian follicular fluid (hOFFP) was administered during the follicular phase of post-partum marmosets. Four of the five animals treated with hOFFP, ovulated as evidenced by the presence of ovarian stigmata at the time of laparotomy. However, only 2 of these animals became pregnant, one had a normal delivery while the other aborted. A shortening of the luteal phase was observed in the other three animals and all animals conceived in subsequent cycles. The results indicated that treatment with the ovarian follicular fluid peptide resulted in impairment of fertility as a result of luteal insufficiency.

Animals↗

Effects of male partners upon proceptivity in ovariectomized estradiol-treated marmosets (Callithrix jacchus).

Effects of male partners upon the expression of female proceptivity were examined in two experiments using 16 ovariectomized marmosets. Experiment 1 showed that the female's proceptive tongue-flicking display (PTF) is triggered specifically by eye contact with the male. Stimulation of PTF by administration of estradiol-17 beta (E2) to ovariectomized females depends in part upon the male's responsiveness to female displays, such as "staring" and "freezing," which may serve to attract his attention and to establish eye contact. Experiment 2 provided evidence that females' proceptivity decreases if their male partners are lesioned in the preoptic area/anterior hypothalamus. Such males are sexually hypoactive and less responsive to the females' visual displays. However, E2 still activates PTF if females succeed in initiating eye contact with males. Results indicate that variability in effects of E2 upon proceptivity in marmosets may be influenced by subtle aspects of facial communication between the sexes as well as by individual differences in hormonal sensitivity. Copulatory activity in males is not essential for E2 to exert its stimulatory action upon proceptivity in female marmosets.

Animals↗

Effects of dorsal penile nerve transection upon the sexual behaviour of the male marmoset (Callithrix jacchus).

The sexual behaviour of 7 adult male marmosets and their ovariectomized partners was observed during pair-tests before and after bilateral dorsal penile nerve transection (n = 4) or a sham operation (n = 3). After transection of the dorsal penile nerves, males mounted more frequently and the initial mount of each test was more prolonged. Males continued to orientate correctly during mounts and to make rapid pelvic thrusts, with the erect penis close to the vaginal orifice. However, the deep pelvic thrust required to attain intromission was abolished. Intromission was rarely observed postoperatively and ejaculation occurred only twice, in one male. These effects were not observed in sham-operated males. The results show that afferent impulses from the penis, travelling through the dorsal penile nerves, play a vital role in the coordination of intromission and ejaculation in this primate species.

Animals↗

Sulphoxidation of S-carboxymethyl-L-cysteine in the rhesus monkey (Macaca mulatta), cynomologus monkey (Macaca fascicularis), African green monkey (Cercopithecus aethiops) and the marmoset (Callithrix jacchus).

The metabolic pathways giving rise to the urinary metabolites of S-carboxymethyl-L-cysteine have been identified for the rhesus, cynomologus, African green and marmoset species of monkey. The formation of a sulphoxide metabolite from the sulphide precursor is a reaction important in these species. The metabolic profile displayed by the marmoset was distinct from the three Old World species, with the rhesus and cynomologus being similar to man.

Animals↗

Comparison of the metabolism and disposition of [3-14C]coumarin in the rat and marmoset (Callithrix jacchus).

Male Sprague-Dawley rats and marmosets were given a single oral 25 mg/kg dose of [3-14C]coumarin and the excretion of radioactivity in the expired air, urine and faeces monitored up to 96 h. Excretion profiles were similar in both species with the bulk of the dose being excreted in the urine and faeces within 24 h. Chromatographic analysis of 0-48 h urine samples revealed similar metabolic profiles with only small amounts of unchanged coumarin and very little 7-hydroxycoumarin. Coumarin 7-hydroxylase activity was not detectable in hepatic microsomes from either species. These results demonstrate that the disposition of [3-14C]coumarin was similar in the rat and marmoset, a New World primate, and that both species, unlike man, are poor 7-hydroxylators of coumarin.

Animals↗

Plasmodium knowlesi in the marmoset (Callithrix jacchus).

Common marmosets were shown to be susceptible to Plasmodium knowlesi malaria. The morphology of the parasite was indistinguishable from the observed in the natural host (Macaca fascicularis) and the common laboratory model (Macaca mulatta). A differential susceptibility to P. knowlesi was observed in the 8 marmosets studied. Multiplication rates of parasites were variable over 24 h periods. Five animals died of a fulminating infection within 12--17 days after challenge. Three animals recovered spontaneously from infection and were subsequently resistant to challenge with homologous and heterologous variants and strains of P. knowlesi. This resistance was maintained for intervals up to 100 days between challenge infections.

Animals↗