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Summary.

The reaction sites of acetyl and non-specific cholinesterases were located in the electron microscope in spermatogenic tissue and mature spermatozoa of the white mouse. A variety of substrates and inhibitors were used to distinguish between the two groups of enzymes. The shifting distribution of the cholinesterases during sperm cell development and maturation indicates that the origin and fate of the acetylcholine-cholinesterase system may be correlated with the initiation and control of sperm motility. During spermiogenesis, the cholinesterases first appeared in the plasma membrane of the early spermatid. With the gradual development of the spermatids, the reactivity increased; a large amount of reaction product appeared in the neck region, in the fibrillar components and in the cytoplasm of the maturing spermatozoa. As the spermatozoa were liberated into the lumen, much of the enzyme was discarded through the residual bodies. The smooth-surfaced endoplasmic reticulum of Sertoli cells, sub-surface cisternae and the filament bundle of the `mantle' always reacted strongly. In mature spermatozoa, the main reaction sites shifted to the fibrillar components. Some reactivity might also be noticed at the plasma membrane and mitochondrial surfaces. During maturation in the epididymis, the spermatozoa discarded an additional amount of enzyme along with the cytoplasmic droplet.

Summary.

The effects of potassium, sodium, chloride and calcium on the percentage progressive motility of samples of chimpanzee and bull spermatozoa were investigated. Inhibitors and stimulatory of motility were identified. Three parameters of chimpanzee sperm motility, velocity, frequency and amplitude, were measured. There was no consistent change related to ion concentration. The ionic constituents of chimpanzee and bull seminal plasma were also analysed.

Summary. The influence of neonatal androgenization on behavioural receptivity was tested by treating female voles on the 3rd day of life with testosterone propionate or with the oil vehicle. After treatment in adulthood with urine or with oestradiol benzoate, androgenized voles were less likely than normal females to display behavioural oestrus and were more likely to engage in agonistic behaviour in tests with stud males. Uteri of androgenized and control females treated with oestradiol benzoate in adulthood manifested similar increases in weight; however, only normal females treated with male urine showed increased uterine weights. Males castrated in adulthood did not display lordosis after treatment with oestradiol benzoate. Sexual differentiation induced by neonatal testicular secretions appears to limit responsiveness of the adult neuroendocrine axis to chemosensory stimuli in male urine.

Summary.

Boar spermatozoa accumulated zinc when stored in vitro in contact with boar seminal plasma. Zinc uptake was much more rapid when the spermatozoa were stored at 5° C than when stored at 30° C. Freezing or the addition of the membrane-damaging agents, filipin or digitonin, before storage at 30° C, caused rapid zinc uptake, but addition of the metabolic inhibitors, fluoride or iodoacetate did not accelerate zinc uptake. It is concluded that when membrane damage occurs spermatozoa accumulate zinc from the seminal plasma and that zinc content of spermatozoa is dependent on time of sampling after ejaculation, conditions of storage and membrane integrity.

Prolactin may be involved in the regulation of reproduction in black bears (Ursus americanus) as it is a mediator of photoperiodic changes in a number of species. The objectives of this study were to validate a radioimmunoassay to measure prolactin in bear serum and to describe seasonal changes in serum prolactin concentrations in captive male bears. Serum samples were obtained nine times during a year from three captive male black bears that were denning between November and March and active during the other months. The heterologous prolactin radioimmunoassay, using pig¹²⁵I-labelled prolactin and goat anti-pig prolactin as a primary antibody, was validated. Injection of thyrotrophin-releasing hormone into the three male bears in June resulted in a rapid increase in serum concentrations of prolactin (t = 0, 11.4–14.8 ng ml⁻¹; t = 15–30 min, 18.4–28.7 ng ml⁻¹). The sensitivity of the assay was 0.08 ng per tube. Intra- and interassay coefficients of variation were 5.5% (n = 6) and 5.7% (n = 6), respectively. Serum concentrations of prolactin changed seasonally, with the lowest concentrations in December (mean ± sd = 1.1 ± 0.1 ng ml⁻¹); this was followed by a gradual increase between January (2.6 ± 0.6 ng ml⁻¹) and April (6.4 ± 1.2 ng ml⁻¹) and the highest concentrations in May (17.6 ± 4.7 ng ml⁻¹), preceding peak testosterone concentrations in June. The observation that prolactin secretion increased with increasing daylength suggests that photoperiod may be an external regulator. The presence of high concentrations of prolactin before peak testosterone concentrations suggests that prolactin may play a role in regulating seasonal changes in the testes.

Summary. Holstein–Friesian cattle heterozygous for the deficiency of uridine monophosphate (UMP) synthase have half-normal activity of UMP synthase. The homozygous recessive genotype would result in little or no activity, has not been observed among live animals and apparently leads to embryonic mortality at ∼Day 40 of gestation. Activity of UMP synthase averaged 2·74 ± 0·61 units/mg protein for 19 obligatory normal embryos (from normal × normal matings). Activity for 18 embryos from heterozygote × heterozygote matings yielded three non-overlapping groups as follows: (i) five presumed normals with > two-thirds normal activity, (ii) ten apparent heterozygotes with one-third to two-thirds normal activity and (iii) three putative homozygous recessive embryos with < one-third normal activity. The distribution among these groups was consistent with the 1:2:1 ratio expected for autosomal inheritance. Conception of embryos homozygous recessive for this disorder was demonstrated.

Keywords: embryonic mortality; inherited disorder; uridine monophosphate synthase; embryo; cow

Summary. Studies in C57BL/6J, DBA/2J and C3H/HeJ mice and in two F₁ hybrid strains (B6D2F₁ and B6C3HF₁) 2–5 months old revealed marked genotypic differences among inbred strains. C57 mice had three times as many regular (3–6 days) cycles as DBA and C3H mice, due largely to fewer pseudopregnant-like (7–14 day) cycles. C57 had longer regular cycles than DBA and C3H mice. Although the frequencies of regular cycles of DBA and C3H mice were similar, the cycles of C3H mice were shorter than those of DBA mice. The results indicated that the genetic determinants of the frequency of regular cycles differ from those specifying cycle length. Frequency of regular cycles of F₁ hybrids was either intermediate between the parent strains (B6D2F₁) or similar to the C57 strain (B6C3HF₁), suggesting that regular cycle frequency shows additive genetic variation in the former crosses, but mostly dominant variance in the latter background. Regular cycles were either shorter than in both parent strains (B6D2F₁) or similar to one of them (B6C3HF₁), indicating heterosis and dominance for genes specifying short cycles. Although the lack of reciprocal crosses meant that maternal effects and possible genomic imprinting effects could not be assessed, these results reveal marked genetic influences on cycle length and frequency and suggest that some of the genes specifying these two traits differ.

Keywords: genotype; oestrous cycle; pregnancy; mouse

Summary. Musk shrews (Suncus murinus) were maintained for 8 weeks in long (16 h light:8 h darkness) or short (8 h light:16 h darkness) daylengths. Males housed in short daylengths had significantly lighter androgen-dependent sex accessory organs than did males kept in long daylengths. This same trend was noted in male sexual behaviour. However, the weights of the testes and epididymides and sperm numbers did not differ. Females housed in short daylengths had significantly lighter cervices and were less likely to demonstrate sex behaviour than animals kept in under long daylengths. Ovarian and uterine weights did not differ. These results suggest that the ability to respond to photoperiod can exist in tropical mammals, even if it is not used as a cue to time seasonal breeding.

Summary. Progesterone concentrations in systemic blood were determined by radioimmunoassay in crossbred cattle used as recipients in an embryo transfer programme. An embryo was transferred surgically to the uterine horn of 528 females which were in oestrus within one half-day of the donor. Jugular blood was obtained at the time embryos were transferred (3–7 days after oestrus) and again from most females between Days 9 and 14. Pregnancy was determined by rectal palpation 45– 65 days after oestrus. There were no significant differences between serum progesterone levels of females which remained pregnant and those which did not. Out of 177 pregnant recipients, none had serum progesterone levels <0·5 ng/ml on Days 10, 11, or 12 but in 8, values were <1·0 ng/ml. Blood samples were also taken on Days 20, 21, or 22 from 113 of these recipients. The mean ± s.e.m. concentration of progesterone in the pregnant females (5·14 ± 0·34 ng/ml) was significantly higher (P < 0·001) than in the non-pregnant females (1·17 ± 0·25 ng/ml). The correlation coefficients between progesterone levels on Days 3, 4, 5 or 6 and 10–12 ranged from 0·18 to 0·37 (all P < 0·02). Progesterone levels were not related to length of the previous cycle, the time of day an animal was first noticed in oestrus or the side of the corpus luteum. However, cows with a short oestrus had higher progesterone levels on Days 3–7 (P < 0·01) than those in oestrus for a longer time.