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J. CARLSON and D. L. BLACK

Summary.

Exogenous oxytocin in intact heifers shortened the oestrous cycle and decreased luteal progesterone content and in vitro synthesis both with and without the addition of lh to the incubation medium. Unilateral ovariectomy decreased the proportion of shortened oestrous cycles following oxytocin treatment. Both the removal of one ovary and oxytocin injection are thought to upset the normal hypophysial—gonadal balance of hormones leading to increased variability in cycle length.

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D. L. BLACK and JOHN DAVIS

Summary.

A mechanism is present in the oviduct of the cow that prevents the escape of oviduct fluid into the uterus. Oviducts that were ligated at the ovarian end, soon after ovulation, become greatly distended with accumulated oviducal fluid. Distension remained until about 72 hr after ovulation and then receded. The isthmic musculature, rather than the tubo-uterine junction, was responsible for blockage. Insufflation of the oviduct indicated that the uterine 3 to 4 cm of the isthmus was most influential in resisting gas passage through the tube.

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D. L. BLACK and L. V. CROWLEY

The innervation of the oviduct is primarily adrenergic although parasympathetic fibres may also be present (see Brundin (1965) for a review of the literature). While the neural control of the oviduct musculature has received much attention, little is known of the effect of the nervous system on the rate of formation or composition of oviduct fluid. Bishop (1956) reported that pilocarpine injections increased both the rate of oviduct fluid secretion and secretory pressure. He concluded from his experiments that pilocarpine stimulated fluid production by way of the cholinergic innervation of the oviduct. He further concluded that pilocarpine caused the release of secretory materials from the oviduct epithelium since oviduct fluid after pilocarpine was cloudy and contained cellular débris. The aim of this experiment was to determine
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D. C. SHARP and D. L. BLACK

Progesterone patterns in the peripheral plasma of mares have recently been reported by Smith, Bassett & Williams (1970), Stabenfeldt, Hughes & Evans (1971), and by Plotka, Witherspoon & Foley (1972). In the research reported here, progesterone levels were measured in the peripheral circulation of pony mares.

Mature pony mares of mixed breeding were checked daily for oestrus by teasing with a vigorous stallion. Blood samples were collected daily from indwelling jugular vein cannulae. After extraction of progesterone from 1- or 2-ml plasma samples with diethyl ether, the ether extract was partially concentrated by evaporation under nitrogen, and transferred to pre-coated thinlayer chromatography plates (Machery-Nagel). Progesterone was separated from other ether-soluble plasma components by one-dimensional chromatography in ether : benzene (2:1). Scraping the thin-layer plates with a razor blade to remove progesterone yielded a tight cylinder of silica gel small enough to be placed into the barrel of a Pasteur pipette, the

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D. C. SHARP III and D. L. BLACK

Summary.

Ovum transport was studied in rabbit oviducts ligated 18 hr after mating in untreated and oestrogen-treated rabbits. Essentially all ova (93·5%) were recovered from the sham-ligated oviducts up to 72 hr post coitum (p.c.). Ovum recovery from all ligated oviducts averaged 46·7%. Recovery of ova in oviducts ligated at the infundibulum and at the uterotubal junction was 100%. It is likely, therefore, that ova were transported prematurely into the uterus from ligated oviducts. Ovum transport through sham-ligated oviducts was significantly retarded by a single injection of oestradiol cyclopentylpropionate (25 or 250 μg) but remained accelerated in ligated oviducts of oestrogen-treated rabbits. The distension of ligated oviducts diminished by 60 hr p.c. in untreated rabbits, but was maintained in oestrogen-treated rabbits. Ovum transport through distended oviducts may be accelerated by the passage of oviducal fluid into the uterus.

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J. P. POLIDORO and D. L. BLACK

Summary.

Peripheral plasma progesterone levels in pregnant and superovulated pregnant rabbits at 10, 20 and 30 days post coitum were studied. No significant differences in levels of progesterone were noted throughout pregnancy in either the control or the superovulated rabbits. Although superovulation resulted in increased numbers of corpora lutea, normal foetuses and total implantations (normal and degenerate), no increase in peripheral plasma progesterone was indicated in the experimental animals.

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G. R. HOWE and D. L. BLACK

Summary.

Immotile rat, rabbit, bull and human spermatozoa, alone and in combinations, were introduced into the uteri of oestrous rats. At intervals after introduction of sperm cells, the animals were killed and the contents of each oviduct were examined for the presence of spermatozoa. The utero-tubal junction did not appear to select against the passage of foreign spermatozoa nor was motility essential for transport through the junction.

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G. R. HOWE and D. L. BLACK

Summary.

Resistance to perfusion of the oviducal isthmus in anaesthetized rabbits was enhanced by adrenaline and depressed by isoprenaline. Ovariectomy significantly decreased the response of the oviducal musculature to both autonomic drugs. The degree of response of adrenergic alpha and beta receptors was primarily dependent upon oestrogen and progesterone, respectively. Increased spontaneous activity of the tubal musculature following ovariectomy appeared to be related to oestrogen withdrawal.

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B. A. Hyde and D. L. Black

Summary. The ability of rabbit oviduct explants to incorporate radiolabelled precursors into specific secretory products was investigated. Ampullary and isthmic oviduct segments were cultured in the presence of [3H]glucosamine or [35S]sodium sulphate. Medium samples were analysed for the presence of secreted, labelled macromolecules.

Explants incorporated the [3H]glucosamine and secreted labelled glycoproteins in vitro. SDS gel electrophoresis and subsequent fluorographic analysis of culture medium demonstrated a differential secretion of glycoproteins between the ampulla and the isthmus. Although ampullary tissue secreted a greater amount of labelled glycoproteins during the sampling period, the major secretory constituent of M r ∼ 66 000 was common to both oviduct segments. Tissue incubated with [35S]sodium sulphate also secreted a labelled glycoprotein or subunit of M r ∼ 66 000.

The results indicate that rabbit oviduct explants are capable of synthesis and secretion of specific sulphated glycoproteins in vitro and that there is a difference in the type and amount of secretion produced between the two oviduct segments.

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C. A. EDDY and D. L. BLACK

Summary.

Ovum transport was studied at 48, 60 and 72 hr post coitum in rabbit oviducts perfused with 6-hydroxydopamine, contralateral control oviducts and oviducts perfused with the vehicle alone. Treatment with 6-hydroxydopamine retarded transport at 60 hr post coitum (P<0·05) but not at 48 or 72 hr. No significant difference in ovum transport was seen between control oviducts and those perfused with the vehicle. These results suggest that the influence of adrenergic innervation is time-dependent.