Search PubMed⌕ Search

Biomedical subjects

W R Allen

Publications and source records attributed to W R Allen.

At least 181 records · Page 10Linked to original sources
PubMed1979

Serum-dependent regulation of alpha-aminoisobutyric acid uptake in bovine granulosa cells.

The removal of serum from the medium of ovarian granulosa cells in exponential or confluent stages of growth results in a rapid and pronounced decrease in the rate of transport of the non-metabolizable amino acid, alpha-aminoisobutyric acid. This decrease is rapidly and completely reversed by the addition of serum. The decrease and its reversal are insensitive to inhibitors of RNA and protein syntheisis and are unaffected by a number of other metabolic inhibitors. The serum requirement cannot be replaced by peptide hormones known to stimulate cell division and secretion by these cells. These data are consistent with a model of post-translational control of AIB transport by a high-molecular-weight component of serum.

Aminoisobutyric Acids↗
PubMed1979

Septic arthritis after ureteroneocystostomy.

Acute infectious arthritis is an uncommon disease that is most commonly caused by Neisseria gonorrhoeae or gram-positive cocci. Gram-negative bacteria are an infrequent and highly virulent cause of septic arthritis and most commonly enter the circulation through the urinary tract, as in this case after ureteroneocystostomy. The resulting arthritis carries a mortality of 25% and a morbidity of 80%. Early recognition and treatment with appropriate antibiotics and mechanical drainage is imperative. Needle drainage of the affected joint has been shown superior to open surgical drainage.

Acute Disease↗
PubMed1979

In-vivo myometrial electrical activity in the cyclic mare.

Uterine electromyography was performed by means of chronically implanted surface electrodes in 3 Pony mares during spontaneous oestrous cycles and following luteolysis induced by a prostaglandin analogue (fluprostenol). Three distinct patterns were recognized during the oestrous cycle. (1) During oestrus well defined phases of activity with closely grouped high-amplitude spikes were separated by long periods (10-45 min) of complete inactivity. (2) During dioestrus more diffuse phases of activity with low-amplitude spikes were separated by variable periods of relative inactivity. (3) During luteolysis, short and frequently occurring phases of activity were propagated between the two electrodes on one uterine horn; a similar pattern also occurred between 1 and 3 h after injection of fluprostenol. Peripheral plasma progesterone, but not total inconjugated oestrogen, concentrations were closely related to characteristics of the myographic activity during the cycle. Insemination during oestrus and injection of fluprostenol during dioestrus caused a marked and prolonged increase in myometrial electrical activity. Almost any non-specific environmental stimulus, including entry by palpation of the genital tract per rectum and vaginoscopic examination, but these were of brief duration and the normal resting pattern of activity was quickly re-established after completion of the manipulations.

Action Potentials↗
PubMed1979

The binding of FSH, LH and PMSG to equine gonadal tissues.

Gonadotrophin-receptor binding studies involving the use of 125I-labelled highly purified FSH and LH have shown that equine gonadal tissues possess similar numbers of specific FSH and LH receptors per cell as the gonadal tissues of other mammals. However, while rat, cow and pig gonadal tissues were shown to bind as much 125I-labelled PMSG as 125I-labelled LH on a molar basis, the equivalent equine tissues bound only less than or equal to 4% as much of the labelled PMSG as LH. Competitive binding studies involving the use of radioreceptor assay techniques have further demonstrated that the small but significant degree of PMSG binding which does take place to equine tissues occurs at LH receptors and not at receptors specific for PMSG. The binding of PMSG to equine FSH receptors was negligible. These results suggest that PMSG (1) binds to equine LH receptors with about one-tenth the affinity of that observed with LH receptors of other species and (2) does not appear to bind specifically to equine FSH receptors. This would possibly explain the apparent refractoriness of mares' ovaries to exogenous and endogenous OMSG.

Animals↗
PubMed1979

The role of the fetal gonads and placenta in steroid production, maintenance of pregnancy and parturition in the mare.

The effects of fetal gonadectomy on steroid production and the maintenance of pregnancy in the mare were studied. Removal of the fetal gonads resulted in an immediate fall in maternal plasma concentrations of conjugated and unconjugated oestrogens whereas progestagen levels remained unchanged. Hormone profiles in mares carrying sham-operated fetuses remained similar to those in unoperated control mares. Plasma levels of 13,14-dihydro-15-oxo-PGF-2 alpha (PGFM) were much lower, and uterine contractions weaker, during labour in mares carrying gonadectomized foals than in control mares. Pregnancy was maintained until parturition at term in the mares carrying gonadectomized fetuses. However, 3 of the 4 gonadectomized foals were dysmature and died during or soon after birth. The biosynthetic pathways involved in the production of oestrogens by the feto-placental unit and the possible role of oestrogens in fetal development in the pregnant mare are discussed.

Animals↗
PubMed1978

Maternal recognition of pregnancy and immunological implications of trophoblast-endometrium interactions in equids.

Fertilized eggs reach the uterus of the mare by the sixth day after ovulation whereas unfertilized eggs remain lodged in the fallopian tubes for many months. However, embryo removal studies indicate that the fetal message for luteal maintenance in the pregnant mare is not transmitted until Days 14-16. The equine endometrial cups comprise a series of small, ulcer-like endometrial outgrowths which are present in the pregnant horn of the uterus between 40 and 150 days of gestation. Each cup consists of a discrete colony of large, gonadotropin-secreting, trophoblast cells derived from a specialized region of the fetal membranes which invade the maternal endometrium around Day 37 after ovulation. Histological examination of endometrial cups from horses and donkeys, carrying intra- and interspecific conceptuses and after reciprocal transfer of hybrid zygotes, indicates maternal recognition of paternal transplantation antigens on the endometrial cup cells. This leads to a successful cell-mediated immune reaction which destroys the cups. The development of the local immune response is paralled by a rapid rise in the titre of paterno-specific cytotoxic antibodies in maternal serum. The precise function of endometrial cups in the maintenance of equine pregnancy remains to be elucidated.

Animals↗
PubMed1977

Studies on the equine placenta. III. Ultrastructure of the uterine glands and the overlying trophoblast.

Ultrastructural studies of the uterine glands at intervals during pregnancy in the mare show that secretory activity continues after formation of the placental exchange units. The nature of the glandular secretion appeared initially to be proteinaceous, but cellular debris was also present during the last third of gestation. These secretions were absorbed by the trophoblast overlying the mouths of the glands. The fate secretions and their significance for the fetus and placenta are unknown.

Animals↗
PubMed1977

Influence of foetal genotype on the follicle-stimulating hormone:luteinizing hormone ratio of pregnant mare serum gonadotrophin.

Rat testicular radioreceptor assays specific for FSH and LH were used to determine the FSH:LH ratio of PMSG produced by horse, donkey, mule and hinny conceptuses. Measurements of FSH and LH activities in PMSG produced both in vivo and in vitro by the four types of conceptuses showed that the genotype of the foetus markedly influences the FSH:LH ratio of PMSG. The FSH:LH ratio of PMSG produced by the horse conceptus was around unity whereas the ratio of PMSG produced by the donkey conceptus was as low as 0-2. Furthermore, the hybrid mule and hinny conceptuses both produced PMSG with an FSH:LH ratio which was approximately midway between those of the horse and donkey.

Animals↗
PubMed1976

The use of synthetic prostaglandin analogue to induce oestrus in mares.

A clinical trial involving 359 mares was conducted to ascertain the clinical value of a synthetic prostaglandin analogue (fluprostenol, ICI-81,008) structurally related to PGF2oc for treating mares in prolonged dioestrus. Some 263 mares (73.3%) displayed oestrus within 5 days of a first intramuscular injection of 250 mug fluprostenol and, of those mares later examined for pregnancy, 108 (40%) were found to have conceived during the first induced oestrus. A further 21 mares (8%) cycled normally and conceived to services during the second oestrus. Most (80.3%) of the plasma samples obtained from 242 mares prior to treatment showed a progesterone concentration greater than 1 ng/ml, thereby indicating the presence of functional luteal tissue in the ovaries. The results support earlier observations that most non-pregnant mares which fail to cycle during the breeding season are in a state of prolonged dioestrus rather than anoesturs.

Animals↗
PubMed1976

The current position of A.I. in horse breeding.

This short review article describes the various techniques currently available for artificial insemination in the horse. The collection and use of raw and extended semen is discussed together with the more recent developments in freezing semen. The expected conception rates with both fresh and frozen semen are quoted. The possible benefits in disease control and stud management are discussed, as well as the difficulties in controlling the use of A.I. from the Breed Registration Authorities point of view.

Animals↗