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Biomedical subjects

M R Hall

Publications and source records attributed to M R Hall.

At least 55 records · Page 3Linked to original sources
PubMed1986

Plasma concentrations of prolactin during the breeding cycle in the Cape gannet (Sula capensis): a foot incubator.

Plasma prolactin was measured in the Cape gannet (Sula capensis) which differs from most other avian species in that although both sexes share equally in incubation duties, neither sex possesses an incubation patch but rather incubates a single egg with its foot webbing. Five main categories of birds were studied: nonbreeders, unmated birds which were nevertheless defending a nest site, recently mated birds, incubators, and brooders with nestlings. Prolactin titers in the plasma were 8-9 ng/ml in nonbreeding gannets, increasing to 17.7 +/- 1.6 and 16.7 +/- 1.2 ng/ml in incubating females and males, respectively. Plasma concentrations of prolactin progressively increased in nonbreeding gannets from 5.5 +/- 0.4 ng/ml in 1-year-old birds to 8.7 +/- 1.6 ng/ml in birds defending a nest site but without an egg. Blood samples taken from both incubators and nonincubators every 3 hr over 27 hr did not reveal any significant daily cycling in prolactin titers. Plasma osmolarity did not vary significantly between nonincubators and incubators, being 300.1 +/- 3.2 and 298.2 +/- 3.0 mOsm/kg, respectively. No positive correlation was found between possible osmotic stress during incubating and plasma concentrations of prolactin. Plasma concentrations of luteinizing hormone and testosterone increased while prolactin decreased, significantly, 24 hr after clutch loss. The putative inhibition of the pituitary-gonadal axis by prolactin is discussed together with other possible roles of prolactin during the breeding season in gannets.

Aging↗
PubMed1986

Characterization of Tritrichomonas foetus antigens, using bovine antiserum.

Tritrichomonas foetus antigens were identified, using the serum of an Angus heifer that had been repeatedly immunized with suspensions of 1 X 10(8) organisms in Freund's complete adjuvant. Antibody activity against T foetus was determined by dot-blot analysis, using horse-radish peroxidase-conjugated anti-bovine immunoglobulin to detect bound antibody. The antiserum contained antibodies against surface and flagellar components of live or fixed T foetus, as determined by use of immunofluorescence. The antiserum reacted with approximately 38 proteins in a pool of 55 to 60 components resolvable by polyacrylamide-gel electrophoresis of T foetus extracts.

Animals↗
PubMed1986

Use of sodium deoxycholate to extract cell wall components of virulent Mycobacterium bovis.

Mycobacterium bovis ATCC No. 19210 was grown on Middlebrook 7H-10 medium with pyruvate. Cells were harvested, and extracts were prepared, using 2% sodium deoxycholate (DOC) and 0.003M EDTA (in 0.1M Tris-HCl, 0.15M NaCl with 0.02% sodium azide [pH 8.4]). Phenylmethylsulfonyl fluoride was added, and the cells were extracted for 48 hours at 4 C. Cells were removed by centrifugation at 10,000 X g for 30 minutes. The supernatant was filter sterilized and separated into 2 fractions (peak A and peak B) by size-exclusion chromatography. The nonfractionated DOC extract and DOC peak A elicited delayed-type hypersensitivity responses at each of the protein concentrations tested (0.5, 1.5, and 4.5 micrograms) in M bovis-sensitized guinea pigs; responses were not detected, using DOC peak B. Significant differences were detected for each of the antigens when enzyme-linked immunosorbent assay values were compared, using sera from cattle before and 10 months after they were exposed to M bovis (P less than 0.01).

Animals↗
PubMed1985

In vitro and in vivo evaluation of lysozyme extracts of virulent Mycobacterium bovis in guinea pigs and calves.

Extracts of Mycobacterium bovis ATCC 19210 were prepared from cells following treatment with acetone 3 times, ethyl alcohol-ether 3 times (1:1, v/v), and chloroform 3 times. Cells were dried and suspended in 0.05M Tris-HCl (pH 7.5) containing lysozyme (1 mg/50 mg of dried cells). One aliquot of the lysozyme extract was filter-sterilized and 1 aliquot of the lysozyme extract was autoclaved. Delayed-type hypersensitivity responses elicited in sensitized guinea pigs, using the filter-sterilized lysozyme extract, were significantly greater than responses elicited using the autoclaved lysozyme extract (P less than 0.01). The filter-sterilized lysozyme extract and a purified protein derivative (PPD) of M bovis, at equal protein concentrations, elicited comparable delayed-type hypersensitivity responses in sensitized guinea pigs. Significant differences were not detected between the mean enzyme-linked immunosorbent assay (ELISA) values on sera collected from calves before exposure to M bovis, using each of the lysozyme extracts or the M bovis PPD (P greater than 0.05). Significant differences were detected when ELISA values obtained using each of the antigens on post-exposure serum were compared with ELISA values on serum collected from calves before exposure to M bovis (P less than 0.01). Differences were not detected in mean ELISA values on sera from cattle collected 12 months after exposure to M bovis, using each of the lysozyme extracts or M bovis PPD (P greater than 0.05); however, 8 of 8 calves were identified as positive on ELISA, using the filter-sterilized lysozyme extract, 7 of 8 calves were positive, using M bovis PPD, and 7 of 8 calves were positive, using the autoclaved lysozyme extract.

Animals↗
PubMed1983

Parathyroid hormone and 25-hydroxyvitamin D concentrations in sick and normal elderly people.

Serum 25-hydroxyvitamin D and immunoreactive parathyroid hormone concentrations were measured in normal elderly subjects living at home and in sick elderly patients in hospital. Normal old people tended to have high 25-hydroxyvitamin D and low parathyroid hormone concentrations; in the sick elderly this pattern was reversed. The raised serum parathyroid hormone concentrations in the sick elderly were not due to poor renal function and may have been a response to vitamin D deficiency. A high serum parathyroid hormone concentration in an elderly patient must be interpreted in the light of the patient's general health and nutritional state. Caution is needed in diagnosing primary hyperparathyroidism in this age group.

25-Hydroxyvitamin D 2↗
PubMed1983

Factors affecting prolactin secretion during breeding and incubation in the domestic duck (Anas platyrhynchos).

The plasma concentrations of prolactin were measured by radioimmunoassay throughout the breeding cycle in female domestic ducks. Prolactin levels increased significantly during egg laying from 5 to 15 ng/ml and again at the start of incubation to about 28 ng/ml. Prolactin levels remained consistently high throughout incubation and fell sharply around the time the eggs hatched. Local anaesthesia of the incubation patches of incubating females for 9 hr caused a significant decrease in plasma prolactin. It is suggested that tactile stimulation from the eggs in the nest may cause the rise in prolactin during the egg laying period and also maintain prolactin secretion during incubation.

Animals↗
PubMed1983

The effects of procaine/haematoporphyrin on age-related decline: a double-blind trial.

A randomized, double-blind study of procaine/haematoporphyrin (KH3) has been carried out over two years in a selected population of healthy elderly subjects. The period of study exceeds 500 patient years. The trial population was weighted to contain a larger proportion of subjects aged over 75 years than a standard population; those receiving active KH3 had similar characteristics on entry to those receiving placebo. Over the course of two years, KH3 was shown to be an active substance in that: (a) decrement in the consolidation of new learning was prevented in the treatment group (less than 1.0%, as against 38% in the placebo group); (b) the prevalence of incontinence increased significantly in the placebo group, but not in the active group (P less than 0.05); (c) there was a significant increase in grip strength in the active treatment group (+22%, P less than 0.01 v. placebo); (d) more adverse reactions were observed on treatment with KH3 (P less than 0.005).

Aged↗
PubMed1983

Preparation of biologically active components of Mycobacterium bovis, using Triton X-100 or potassium chloride.

Methods of producing antigen extracts of Mycobacterium bovis are described. Extraction of M bovis with a chaotropic salt, potassium chloride, or a nonionic detergent, Triton X-100, before autoclaving resulted in the production of soluble M bovis components. These antigens induced delayed-type hypersensitivity responses when injected intradermally in M bovis-sensitized guinea pigs. A comparison of the diameters of the hypersensitivity responses (on the basis of equal protein concentrations in the inocula) revealed that the potassium chloride extract and the Triton extract of M bovis induced similar responses compared to the response induced with a purified protein derivative of M bovis. These findings indicate alternative methods may be used for the production of biologically active extracts of M bovis.

Animals↗
PubMed1983

Electives in geriatric medicine.

A postal survey of medical schools in the United Kingdom has been undertaken to estimate the extent to which students undertake elective periods or topic/project work in geriatric medicine. In approximately half the schools, who completed the questionnaire (80%), at least one student had undertaken an elective in geriatric medicine in the previous year. Opportunities for topic work were available in nearly all schools and in half of these topic/project work was undertaken by all or some students.

Curriculum↗
PubMed1982

The lack of effect of intramuscular emepronium bromide for urinary incontinence.

Six elderly volunteers (4 men and 2 women), suffering from urinary incontinence due to small capacity, hyper-reflexic bladders, were assessed cystometrically 1/2 h, 1 h and 4 h after an intramuscular injection of emepronium bromide (Cetiprin). The dose given was sufficient to raise serum levels of emepronium to approximately 10 times those that could be reached with an oral dose. Analysis of the results showed that there was no significant difference in the state of the bladder at any time. The study confirms that emepronium bromide is ineffective in increasing bladder capacity in subjects with small, hyper-reflexic bladders. It has no value, therefore, in the management of urinary incontinence in elderly patients with this condition.

Aged↗
PubMed1982

Drug interactions in the elderly.

The incidence of adverse reaction to drugs and of drug interaction increases with age. The types of interaction which may occur are described. The mechanisms underlining pharmacokinetic and pharmacodynamic interactions are described and examples of common drug interactions which may occur in the elderly are given. It is emphasised that the elderly may need to take several drugs for the maintenance of good health and the potential danger of the part played by interaction must be recognised.

Aged↗
PubMed1980

Benzo[a]pyrene metabolism in cells productively infected with simian virus 40.

The metabolism of benzo[a]pyrene (BP) by cell cultures and cell-free extracts of the monkey kidney cell line CV-1 was studied in uninfected and Simian virus 40 (SV40) infected cells. Metabolites formed were separated by high-pressure liquid chromatography (HPLC) and quantified by liquid scintillation techniques. The profiles metabolites formed by uninfected and SV40 infected cells were similar except that SV40 infected cell cultures metabolized BP at an increased rate relative to uninfected cells. In addition, SV40 infected cell cultures and cell-free extracts produced an unknown compound which eluted between the 3-hydroxybenzo[a]pyrene and BP fractions. This material does not have a retention time characteristic of any of the known metabolites of BP. Labelled BP and/or its metabolites were bound to the viral DNA and histone components of intracellular viral minichromosomes as well as the viral DNA and proteins of mature virions.

Animals↗
PubMed1980

Postural hypotension in old age: is it a disorder of the nervous system or of blood vessels?

Beat to beat variation, postural changes in blood pressure and thresholds for vibration sense were measured in 10 young adults and 186 old people living at home. There was a reduction in beat to beat variation, but and increase in postural changes in blood pressure and thresholds for vibration sense in the elderly. Within age and sex groups, there was no correlation between beat to beat variation, postural changes in blood pressure and thresholds for vibration sense, but a strong positive correlation between postural changes in blood pressure and lying systolic pressures. This suggests that, in old age, a change in the structure of the vascular tree may be more important than autonomic dysfunction, as a determinant of postural hypotension.

Adult↗
PubMed1980

Is weakness in old age due to muscle wasting?

Grip strength and fat-free mass (FFM) were measured in 158 men and 112 women of 65 years and over living at home. There was a striking decline in grip strength with increasing age in both men and women. A marginal decline in FFM was not statistically significant. Multiple regression analysis suggested that age had an effect on grip strength which was independent of FFM. An explanation for this pattern might be that with ageing an increasing proportion of skeletal muscle is replaced by fibrous tissue, so that, although there is striking reduction in muscle power, there is only a marginal reduction in FFM.

Adipose Tissue↗