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Biomedical subjects

D E Walters

Publications and source records attributed to D E Walters.

At least 73 records · Page 4Linked to original sources
PubMed1986

Changes in brain catecholamine mechanisms following perinatal exposure to marihuana.

Adult female rats received daily oral doses of a crude marihuana extract (CME; equivalent to 20 mg/kg delta 9-THC) throughout gestation and lactation. The offspring were sacrificed at 10, 20, 40 or 60 days postpartum and tissue samples of cerebral cortex and striatum were dissected and assayed for alpha 1-adrenergic and D2-dopaminergic receptors, respectively, and tyrosine hydroxylase activity. The body weight at birth and 10 days of age was reduced as was brain weight at 10 and 60 days of age in offspring exposed to CME. Perinatal exposure to CME reduced the binding capacity (Bmax) of D2 receptors in the striatum of 10 and 20-day-old offspring. The Bmax for alpha 1 receptors in the cerebral cortex was not altered at any age. Tyrosine hydroxylase activity was significantly decreased in the striatum of 20 and 40-day-old offspring exposed to CME. The results indicate that chronic perinatal exposure to CME can selectively alter the development of specific catecholamine mechanisms in rat brain.

Animals↗
PubMed1986

Residual milk in Friesland sheep and the galactopoietic effect associated with oxytocin treatment.

Mature lactating Friesland ewes had a mean lactation yield of 293 +/- 26 kg during a lactation period of 35 +/- 2 weeks giving an average daily milk yield of 1.2 kg/d. Ewes were injected intravenously after normal milking with either saline (sham) or oxytocin and then remilked to determine the volume of residual (alveolar) milk. After a long milking interval of 16 h oxytocin treatment gave a significantly greater total daily milk yield than the sham treatment (oxytocin minus saline, morning milking, 0.199 +/- 0.038 kg, mean +/- s.e.m., P less than 0.01) Oxytocin had a small significant reverse effect after a short milking interval of 8 h (afternoon milking, -0.065 +/- 0.022 kg, P less than 0.05). The average increase in total daily yield over four stages of lactation was 0.133 +/- 0.029 kg (P less than 0.01), or 11% of the average daily milk yield. The galactopoietic effect of oxytocin was associated with the efficient removal of residual (alveolar) milk. Residual milk accounted for 7.4 and 27.2% of the total daily milk yield in ewes treated with saline or oxytocin respectively. Residual milk expressed as a proportion of daily total milk yield remained steady in ewes studied between April and July, but declined in September when yields were less than 1 kg/d.

Animals↗
PubMed1986

An investigation of the prevalence of intestinal parasites in pre-school children in Ghana.

Evidence for the presence of 11 intestinal parasites in pre-school children from 4 rural villages in Ghana was obtained from an examination of stool samples. Striking differences were detected between the prevalence of some of the 6 common infections in the 4 villages. The prevalence of Ascaris lumbricoides varied from about 76% in one village (Oshiyie, coastal savanna) to apparently 0% in another (Akuma, forest zone). No differences in prevalence for any infection were observed to be sex dependent. Investigation of the relationship between age of the children and prevalence showed that the degree of prevalence of both A. lumbricoides and Trichuris trichiura had essentially levelled off by the time the children were 4 years old. There was no evidence to suggest that the prevalence of either Entamoeba sp. or spp. or hookworm was approaching a maximum value, even in the oldest children. These trends applied across the villages regardless of the differences in prevalence values for the infections. On average, the children of Oshiyie were found to harbour twice as many infections as the children of the other villages. The investigation of the prevalence data revealed evidence of associations between pairs of infections, particularly those involving hookworm and T. trichiura.

Age Factors↗
PubMed1986

Observations on 767 clinical pregnancies and 500 births after human in-vitro fertilization.

Details of 767 clinical pregnancies and 500 births from Bourn Hall are reported. All treated patients included some over 40 years old, many with ovarian or uterine defects, male infertility, etc. Patients were treated during their natural cycle or stimulated with clomiphene or clomiphene and human menopausal gonadotrophin. Follicular maturation was induced by an endogenous luteinizing hormone surge or human chorionic gonadotrophin. A maximum of three embryos were replaced, except in a few patients receiving four. Twenty-eight percent of pregnancies aborted, occurring more frequently in patients who were over 40, with a complicated obstetric history, and given clomiphene alone. Approximately 18% of fetuses 'vanished' in multi-pregnancies. Seventy-one sets of binovular twins and nine sets of triplets have been born, and seven twins and three triplets are ongoing. Seventeen and a half per cent of patients aged 39 and less with one or more replaced embryos delivered one or more children, rising to almost 25% with three replaced embryos. A mean of 1.3 children were born per delivery when three embryos were replaced. Most deliveries were by Caesarean section. There were two cases of placenta praevia, one stillbirth, four major and eight minor anomalies. All the triplets, and some twins and singletons had low birth weights and were born prematurely. The sex ratio was 247 males to 253 females.

Abortion, Spontaneous↗
PubMed1986

The effect of day length on the duration of pregnancy and the onset of parturition in the rat.

Rats mated under normal lighting conditions of a 24 h day were transferred to a sound-proof room with period lengths (T) of 24 h (12 h light and 12 h dark, 12L:12D), or 22 h (11L:11D). During the first 15 d of pregnancy the rats were kept together in a large enclosure and the locomotor activity of the group was recorded. From day 15 they were kept separately, in cages, and from day 21 the number of litters born was noted every 3 h. On 12L:12D, rats displayed well defined periods of activity which were closely related to photoperiod. Mean activity was greatest in the dark, and overall activity declined after day 13 of gestation. On 11L:11D, coupling of locomotor activity to the dark phase was retained initially, but was not sustained throughout the period of study. Activity in the light was comparable to that in the dark at the time when the light:dark cycles of 11L:11D became reversed relative to those of 12L:12D. Rats on a 24 h day had a peak time of delivery at 519 h after mating (21.6 cycles of 12L:12D) and those on a 22 h day at 527 h (24.0 cycles of 11L:11D; difference, P less than 0.002). The 11L:11D cycle therefore increased rather than decreased the duration of pregnancy, implying that elapsed time rather than the number of light:dark cycles experienced has the greater influence on the length of gestation. Of the animals on a 24 h day 76% had their litters in the light phase of the cycle, whereas only 36% of those on a 22 h day gave birth in the light (P less than 0.02).

Activity Cycles↗
PubMed1985

In vitro fertilization using cryopreserved donor semen in cases where both partners are infertile.

The incidence of pregnancy after in vitro fertilization (IVF) was studied in a group of 38 couples (55 cycles) where both partners were infertile. Cryopreserved donor semen (IVF-D) was used in all cycles. Results were compared with those in a control group of couples where the husband's semen was considered normal and only the wife was infertile. No significant differences were found between the IVF-D and control groups in the incidence of fertilization (80% versus 72%), pregnancy per cycle (33% versus 29%), and abortion (18% versus 20%), despite the considerably lower percentage of motile spermatozoa in the IVF-D group. Forty percent of patients, each treated unsuccessfully with at least 12 artificial inseminations with donor semen, became pregnant after one or two IVF-D cycles. It is concluded that IVF with frozen donor semen is a beneficial treatment for couples where both partners are infertile.

Female↗
PubMed1985

Prolonged storage of human spermatozoa at room temperature or in a refrigerator.

Spermatozoa from patients who underwent in vitro fertilization (IVF) therapy were prepared free from seminal plasma with the use of IVF culture medium supplemented with 8% human serum. Samples were then stored either at room temperature or in a refrigerator, and their motility and ability to penetrate zona-free hamster eggs were assessed every second day. With storage at room temperature, motility declined by less than half over the first 14 days, with some samples still active 20 days after preparation. The ability of the samples to penetrate hamster eggs was unchanged during the first 6 days of storage, and most of the samples still had positive tests after 14 days. Some spermatozoa could still penetrate after 17 days. Room-temperature-stored spermatozoa were still able to fertilize human oocytes 5 days after preparation. With storage in a refrigerator motility declined rapidly, and few sperm were motile after 14 days. However, these samples penetrated relatively more hamster eggs after 14 days' storage than room-temperature-stored samples did. Spermatozoa stored overnight in a refrigerator had significantly higher hamster egg penetration rates than spermatozoa stored overnight at room temperature. After storage overnight at room temperature, false-positive and false-negative results of hamster egg penetration tests were common in relation to IVF outcome; after refrigerated storage, no false-negative results were found.

Animals↗
PubMed1985

Treatment of idiopathic infertility, cervical mucus hostility, and male infertility: artificial insemination with husband's semen or in vitro fertilization?

Couples with male infertility (n = 86), idiopathic infertility (n = 68), and cervical mucus hostility (n = 48) of a long duration were treated either by in vitro fertilization (IVF) or artificial insemination with husband's semen (AIH). The incidence of pregnancy per cycle in couples in whom the male partner was infertile was significantly (P less than 0.01) higher after IVF, compared with AIH (21% versus 5%, respectively). The differences were most apparent in couples with asthenospermia (47% versus 0%, respectively); no significant difference was found when the infertility was caused by oligospermia only (11% versus 9%, respectively). More patients with idiopathic infertility became pregnant after one cycle with IVF, compared with AIH (20% versus 8%, respectively); but, because of intragroup disparity in size, this difference was not significant. A highly significant difference (P less than 0.01) was found after one attempt with IVF, compared with AIH, in patients with cervical mucus hostility (38% versus 3%, respectively).

Cervix Mucus↗
PubMed1985

Food intake and body weight changes in mice infected with metacestodes of Taenia crassiceps.

General nutritional effects on female CFLP mice harbouring larval Taenia crassiceps were investigated using groups of mice fed ad libitum on purified diets containing 2%, 4%, 8% and 16% (w/w) protein respectively. When uninfected and infected mice were compared over an experimental period of 20 weeks, it was established that a significantly higher proportion of uninfected mice survived the course of the experiment than infected mice. There was no evidence of the presence of the parasites having any effect on the overall food intake of the mice. Infected mice, however, were found to be significantly heavier, on a fresh weight basis, than their uninfected partners, but the pattern was reversed when the dry weights of mouse carcasses were compared following the removal of parasites. In general, more parasite tissue was recovered from mice feeding on the higher protein diets (8% and 16%).

Animals↗
PubMed1985

A statistical evaluation of implantation after replacing one or more human embryos.

All the available data relating to pregnancy and multiple implantations from Bourn Hall Clinic are used to assess the accuracy of two statistical models of implantation. The simple binomial model was found to be incapable of describing both the pregnancy rates and the incidence of multiple implantations, whereas a two-parameter model, incorporating both patient and embryo variability, provided a good fit to the data. The estimates obtained for the two parameters in the second model suggested that 36% of the embryos could implant, and that 43% of patients were capable of sustaining implantation. The Maximum Likelihood method of constructing 95% confidence limits on the estimates of the parameter values is demonstrated.

Embryo Implantation↗
PubMed1983

On some useful statistical techniques in the analysis of hormone data.

Three multivariate statistical techniques, which have been found very useful in the analysis of hormone data, are demonstrated. The value of these techniques as a means of compressing the information contained in a complex array of experimental units and variates into a few "dimensions" is emphasised.

Analysis of Variance↗
PubMed1983

Nippostrongylus (Nematoda) in protein-malnourished rats: host mortality, morbidity and rehabilitation.

The synergistic relationship between host nutrition and the effects of Nippostrongylus was investigated experimentally in rats fed a diet containing 1% (w/w) protein. Rats were infected with 10 doses of N. brasiliensis varying from 0.35 to 99 larvae/g and their daily food intake and weekly body mass were compared with those uninfected rats fed the same diet for a period of 9 weeks. The deterioration of the uninfected rats observed as a result of protein-energy malnutrition was found to be accelerated in a dose-dependent manner in the rats infected with N. brasiliensis. Analysis of food intake and body mass measurements demonstrated that this acceleration was related to a decrease in food intake and indicated a likely alteration in nutrient utilization, both of which were established by the end of the first week of the infection. Remission from the combined effects of malnutrition and infection was achieved by offering the rats a high-protein diet (20% w/w), whereupon rehabilitation was found to be complete within a period of 9 days. The implications of the results and the possible mechanisms involved in their generation are discussed in relation to the frequent coexistence of helminthiasis and malnutrition.

Animals↗
PubMed1983

Parasite population biology and host nutrition: dietary fructose and Moniliformis (Acanthocephala).

Experiments were carried out to investigate the possible influence of host-dietary fructose concentration on the relationship between worm burden and the fecundity of Moniliformis dubius. Worm length was found to be dependent both on the fructose concentration of the host's diet and on worm burden. The number of free ovaries/female worm was found to increase linearly with increasing dietary fructose concentration but was independent of worm burden. The length of the ovaries increased with increasing dietary fructose concentration and decreased in response to increases in worm density. The magnitude of the density-dependent reduction in the volume of ovarian tissue/female was decreased in worms from rats fed on diets containing low concentrations of fructose. The numbers of eggs present in the body cavities of the female worms was found to be positively correlated with dietary fructose concentration. At 5 weeks post-infection, mature eggs (containing fully developed acanthor larvae) were found in the body cavities of female worms from rats whose diets contained 3 and 12% fructose, but not in those from rats whose diets contained 1 and 2% fructose (w/w). The experimental results are discussed in the wider context of the influence of host nutrition on parasite population biology.

Acanthocephala↗
PubMed1983

Oestrogen metabolism in the endometrium, corpus luteum and ovarian residual tissue of the rabbit.

Reproductive tissues (uterine endometrium, corpus luteum and ovarian residual tissues) from pregnant and pseudopregnant rabbits were incubated with equimolar concentrations of [3H]oestrone and [3H]oestrone sulphate (0.375 pmol) to monitor the changes in oestrogen metabolism during the early stages of pregnancy (days 0, and 3-8 post coitum) and to investigate the embyonic effect upon maternal oestrogen metabolism. Oestradiol-17 beta was the major metabolite formed from oestrone and sulphoconjugation occurred in all tissues studied. Oestrone sulphate was converted primarily to oestradiol-17 beta-3-monosulphate. Endometrial 17 beta-oxidoreductase significantly decreased and sulphotransferase increased in activity during the preimplantation period, but no differences were noted between gravid and non-gravid horns in unilaterally pregnant animals, nor between pregnant or pseudopregnant animals. Significant decreases occurred in 17 beta-oxidoreductase and sulphotransferase activity in luteal tissue, but these were more than offset by increases in tissue weight. No differences in the activities in luteal tissues were detected between pregnant or pseudopregnant animals, nor between ovarian tissue adjacent to gravid or non-gravid uterine horns. The results show that significant changes occur in oestrogen metabolism in the rabbit endometrium and corpus luteum within 8 days after ovulation, and that these changes result from maternal factors expressed systemically rather than by the effects of the developing conceptus expressed locally.

Animals↗
PubMed1983

Mammary uptake and metabolism of progesterone in goats and its effect on milk progesterone concentrations during the oestrous cycle and early pregnancy.

Following the observation that the concentration of progesterone in goats' milk differs appreciably according to the specificity of the antiserum used in a non-extraction (direct) radioimmunoassay, experiments were carried out to find an explanation for these results. Milk and plasma samples were collected during the oestrous cycle and during an equivalent period of pregnancy after a fertile mating. Samples were analyzed by a direct radioimmunoassay using two antisera, 18/3 which is highly specific for progesterone and 465/6 which is less specific, and by radioimmunoassay of fractions isolated by thin-layer chromatography (TLC). Values obtained for milk and plasma samples collected during the oestrous cycle and early pregnancy were similar, except that values for milk samples measured with antiserum 465/6 were higher in pregnancy compared to those obtained during the oestrous cycle. Values obtained for milk and plasma with antiserum 465/6 were significantly higher than those obtained with 18/3 (P less than 0.001). After TLC this difference was found to be due principally to the presence of compound(s) with chromatographic properties identical to 5-pregnanedione(s). A comparison of the concentration measured in arterial and mammary venous plasma and in milk showed that about 25% of progesterone (5.7 nmol/min) was extracted by the mammary gland, and that substantial amounts of immunoreactive metabolites of progesterone are secreted into milk with only small quantities being transferred into mammary vein plasma.

Animals↗
PubMed1983

Follicular steroids as a prognosticator of successful fertilization of human oocytes in vitro.

Oocytes were collected by aspiration of preovulatory follicles from 55 women. The preovulatory rise in LH was monitored in urine using the Hi-Gonavis (Mochida Pharmaceuticals) technique. Patients were treated either during the natural cycle or after the induction of ovulation with clomiphene citrate. After collection and culture, the oocytes were inseminated with the spermatozoa of the husband. The levels of progesterone, oestradiol-17 beta and androstenedione in the clear follicular fluid were measured by radioimmunoassay. A multivariate analysis containing these three hormone levels together with two ratios of progesterone with each of the other hormones indicated reasonable discrimination between the oocytes which fertilized and those which remained unfertilized after insemination. The discriminant analysis suggested that the fertilization of the oocytes could have been predicted on the basis of these hormonal profiles with a success rate which exceeded 90%.

Androstenedione↗