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Transabdominal palpation was used to determine maturity, course of pregnancy and post-partum changes in marmosets throughout seventy-four full-term pregnancies. The accuracy of the technique is compared with that of other methods of studying the course of pregnancy in this species.
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Subcutaneous injections of oestradiol benzoate in oil, resulting in a sustained elevation of circulating oestradiol levels, induced an initial suppression of LH secretion, followed by a positive discharge of LH in castrated male and female and in intact male marmosets. Oestrogen-induced LH release (producing maximum LH concentrations 24 h after the injection) was observed in 75% of castrated males and females. A positive discharge of LH occurred in 50% of intact males 28-36 h after oestrogen administration.
Measurements of growth, plasma progesterone and testosterone levels, and copulatory behaviour were obtained from captive marmosets from birth until 600-800 days of age. Body weight and knee-to-heel length were similar for both sexes. Males exhibited a neonatal testosterone surge from 15-100 days and testosterone levels began to rise again, coincident with the growth of the testis, at about 250 days. The males were copulating by 400-500 days of age. Paired females were apparently ovulating and able to conceive from about 400 days. In peer groups, only the dominant female became pregnant, because subordinate females failed to ovulate.
Concentrations of LH/CG, androstenedione and testosterone rose in early pregnancy to maximum values at 6--10 weeks. Thereafter LH/CG levels declined and androstenedione and testosterone levels remained at plateau values or declined until term. Progesterone, oestradiol-17 beta and oestrone increased after ovulation and remained high throughout pregnancy. At 12 weeks, when LH/CG levels were falling, progesterone and oestradiol rose well above the luteal-phase levels which were maintained for the first 12 weeks. Progesterone declined in the 2 weeks before birth, while oestradiol and oestrone remained high. Pregnancies of an unknown stage were dated by reference to a graph of uterine diameter, measured by abdominal palpation, in animals at known times after conception. Measurement of progesterone concentrations during the conception cycle gave more accurate dating and showed that the gestation length was 144 days.
The positive-feedback action of oestradiol-17 beta on LH release was studied in gonadectomized male and female and intact male marmoset monkeys. Positive feedback was observed in normal intact males in response to a single subcutaneous injection of 35 micrograms oestradiol benzoate. The sustained elevation in oestradiol-17 beta levels achieved by the injections resulted in a marked suppression of circulating testosterone concentrations. Subcutaneous injections (0.5 mg/injection) of testosterone or dihydrotestosterone to gonadectomized males and females immediately following and 8 h after oestradiol benzoate failed to inhibit positive feedback. Similar treatment with progesterone (1.0 mg/injection) tended to standardize both positive and negative components of the feedback response. In contrast, progesterone implants (achieving progesterone concentrations similar to those obtained with the injections), maintained during and for 8 days before the oestradiol benzoate treatment, effectively inhibited positive feedback. LH responses to the various treatments were similar in gonadectomized males and females. These data suggest a relative unimportance of testicular secretions in suppressing oestrogen-induced LH release in the adult marmoset and indicate similarities between the control of positive feedback in male and female primates.
The levels of immunoreactive oestrone, oestradiol-17 beta and oestriol in plasma and urine were measured during early, mid- and late pregnancy in the marmoset monkey. In plasma, unconjugated oestrone remained less than 2% of total (conjugated plus unconjugated) oestrone throughout gestation, whereas unconjugated oestradiol-17 beta increased from 3% of the total value in early and mid-pregnancy to 35% in late pregnancy. The reversal in the unconjugated oestrone: oestradiol-17 beta concentration ratio from early (12:1) to late (0 . 15:1) pregnancy occurred despite the continuing predominance of oestrone in terms of total hormone. Total oestriol was measurable but in relatively low concentrations. Oestradiol conjugate was the predominant urinary oestrogen metabolite measured at each stage of pregnancy. The pattern of urinary oestrone and oestradiol-17 beta reflected plasma levels of total hormone, rather than unconjugated hormone, showing no further increase after mid-pregnancy. In contrast, oestriol increased throughout pregnancy and to a proportionately greater extent than oestrone or oestradiol-17 beta, but at lower absolute levels. High-pressure liquid chromatography of urine extract indicated the presence of considerable amounts of oestrogen immunoreactivity not accounted for by oestrone, oestradiol-17 beta and oestriol and with a retention time similar to that of 16 alpha-hydroxyoestrone. Gas chromatography and mass spectroscopy provided further evidence to suggest that 16 alpha-hydroxyoestrone is an abundant urinary oestrogen metabolite during pregnancy in the marmoset monkey.
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A heterologous double-antibody radioimmunoassay for marmoset LH is described in detail. The system uses NIAMDD rat LH-I-1 for iodination, NIAMDD rat LH-RP-1 as standard and anti-ovine rabbit LH 610V serum. The assay measures the level of marmoset LH in plasma and shows a maximum cross-reaction (B/Bo = 50%) of 0.3% with other rat, human or bovine pituitary hormones. The heterologous assay has been applied to the measurement of the level of LH in the marmoset after gonadectomy and after the subsequent implantation of oestradiol-17beta capsules. A clear increase in the concentration of LH in the plasma was observed by day 3 after gonadectomy and in most animals the level reached a plateau by day 9. The rates of increase in the concentration of LH and the maximum levels attained after gonadectomy were similar in male and female marmosets. The secretion of LH in long-term gonadectomized marmosets was episodic. In four of the marmosets studied, the frequency of the pulsatile discharges of LH was circhoral, whereas in the remaining five animals the frequency could not be determined. Subcutaneous implants containing oestradiol-17beta were seen to have a biphasic effect on the secretion of LH in all gonadectomized marmosets. After a transient increase in the concentration of LH (positive feedback) on day 1, levels fell markedly by day 4 and were undetectable 8 days after the implants were introduced (negative feedback).
The metabolism of the fungicide zineb, (zinc ethylenebisdithiocarbamate), has been studied in the rat and the marmoset. 2. It was found in both species that a relatively large proportion (21-22%) of the original zineb administered was detectable in the excreta as ethylenethiourea (ETU) a known mutagen, teratogen and carcinogen. 3. A further proportion (2-5%) was determined to be ethyleneurea which is a metabolite of ETU. 4. Results of comparative experiments in marmosets revealed that ETU was photolabile in the presence of excreta, thus showing the importance of conducting the studies in the dark.
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Adult common marmosets, inoculated with either of 2 oncogenic Herpesvirus saimiri (HVS) strains, developed fatal lymphoproliferative disease within 23-25 days post inoculation (PI). The disease was identical to HVS-induced lymphoma in cotton-topped and white-lipped marmosets. Common marmosets inoculated with an attenuated HVS strain developed persistent infection; virus has been recovered from cocultivated lymphocytes of these animals for more than 384 days PI.
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In marmosets, the clinical signs of poisoning following the administration of sarin and the effects of sarin upon performance in three behavioral test models were investigated. The sensitivity of marmosets to the lethal action of sarin was shown to be greater than that of rodent species and rabbits but very similar to that of the rhesus monkey. Doses of sarin ranging from 33 to 55% LD50, resulting in erythrocyte acetylcholinesterase inhibitions of 88% or more, were shown to disrupt the performance of a food-reinforced visually guided reaching response. However, the pattern of disruption did not suggest a specific action of sarin upon visuomotor coordination and could not be explained on the basis of an indirect effect of this agent upon either feeding motivation or changes in gross mobility. It was suggested that possible changes in animals' perception of the reaching task and/or their own drugged ability may be relevant to any interpretation of sarin-induced changes in visuomotor coordination in this species.
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