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Biomedical subjects

A R Austin

Publications and source records attributed to A R Austin.

18 recordsLinked to original sources
PubMed1998

Preliminary observations on the pathogenesis of experimental bovine spongiform encephalopathy (BSE): an update.

Further preliminary observations are reported of an experiment to examine the spread of infectivity and the occurrence of pathological changes in cattle exposed orally to infection with bovine spongiform encephalopathy. Calves were dosed at four months of age and clinically monitored groups were killed sequentially from two to 40 months after inoculation. Tissues were collected for bioassay, for histopathological examinations and for the detection of PrP. Previous reported observations have included the presence of infectivity in the distal ileum of cattle killed after six to 18 months, the earliest onset of clinical signs in an exposed animal after 35 months, and diagnostic histopathological changes in the brain, in association with clinical disease, after 36, 38 and 40 months. In spite of the relative inefficiency of the bioassay of scrapie-like agents across a species barrier the new observations confirm that the onset of clinical signs and pathological changes in the central nervous system (CNS) occur at approximately the same time. The earliest pathological change, the presence of abnormal PrP 32 months after inoculation, coincided with the earliest detected infectivity in the CNS and occurred shortly before there was evidence of typical spongiform changes in the brain 36 months after inoculation. Infectivity has now been demonstrated in the peripheral nervous system, in the cervical and thoracic dorsal root ganglia 32 to 40 months after inoculation and in the trigeminal ganglion 36 and 38 months after inoculation. At the time of writing evidence of infectivity in other tissues is confined to the distal ileum, not only after six to 18 months but also after 38 and 40 months, but these findings may be supplemented by the results of further mouse assays. Nevertheless, they are in general agreement with current knowledge of the pathogenesis of scrapie.

Animals↗
PubMed1997

Abnormalities of heart rate and rhythm in bovine spongiform encephalopathy.

Heart rates of healthy cows and cows suspected of having bovine spongiform encephalopathy were measured by auscultation and by a portable cardiac monitor. Bradycardia was demonstrated in suspect cases which were confirmed histopathologically. Disturbances in cardiac rhythm were also evident in some cases. Healthy cows deprived of food exhibited bradycardia. The administration of pharmacological doses of atropine indicated that bradycardia in BSE was mediated by increased vagal influence, suggesting that the cardioinhibitory reflexes in the caudal brainstem were functionally altered by the disease.

Animals↗
PubMed1996

Transmission dynamics and epidemiology of BSE in British cattle.

A comprehensive analysis of the bovine spongiform encephalopathy (BSE) epidemic in cattle in Great Britain assesses past, present and future patterns in the incidence of infection and disease, and allows a critical appraisal of different culling policies for eradication of the disease.

Age Factors↗
PubMed1996

Simple method for the perfusion-fixation of adult bovine brain.

It is widely accepted that the vascular perfusion of a tissue leads to its optimal fixation for ultrastructural examination, but the technique has been applied with little success in large animals such as cattle. This paper describes a simple and highly reproducible method for the perfusion-fixation of adult bovine brain. The carotid arteries are cannulated and the perfusate is introduced by means of a peristaltic pump. The inclusion of toluidine blue in the fixative makes it possible to assess the success of the technique, and prevents the costly and time-consuming processing of material which is suboptimally fixed. The method is potentially valuable for the examination of a wide range of neurological conditions in large domestic animals at an ultrastructural level in optimally fixed material.

Animals↗
PubMed1986

Positive predictive value of cholescintigraphy in common bile duct obstruction.

Technetium-99m DISIDA imaging was employed in 400 patients to differentiate obstruction of the common bile duct from medical and other surgical causes of hyperbilirubinemia. Sequential anterior images demonstrated variable degrees of liver uptake, yet there was no evidence of intrabiliary or extrabiliary radioactivity for at least 4 hr after injection in 25 patients. Twenty-three patients were surgically documented to have complete obstruction of the common bile duct. One patient had hepatitis, and another had sickle cell crisis without bile duct obstruction. The remaining patients had either partial or no obstruction of the common bile duct. We conclude that the presence of liver uptake without evident biliary excretion by 4 hr on cholescintigraphy is highly sensitive and predictive of total obstruction of the common bile duct.

Adult↗
PubMed1981

The digestion by cattle of grass silage made with formic acid and formic acid-formaldehyde.

1. A primary growth crop of perennial ryegrass (Lolium perenne L., cv. S23) was partially wilted and ensiled after the application of either formic acid-water (1:3, w/v; 7.11 l/t fresh herbage; control diet C) or formic acid-formaldehyde (1:1, w/w; 8.8 l/t fresh herbage; formaldehyde treated diet F) which supplied 50 g HCHO/kg crude protein (nitrogen (N) x 6.25). The two silages were fed separately and a third diet comprising formaldehyde-treated silage, supplemented with urea (20 g/kg dry matter DM) at the time of feeding was also examined (diet FU). 2. The three diets were fed at a level of 16 g DM/kg live weight to six 3- to six-month-old cattle fitted with rumen and re-entrant duodenal cannulas in two 3 x 3 Latin Square experiments, and measurements were made of the digestion of energy, carbohydrate and N. 3. The formaldehyde-treated silage had a lower content of fermentation acids and ammonia-N, and a higher content of water-soluble carbohydrate and total amino acids. The apparent digestibility of organic matter, energy and N were depressed (P less than 0.05, P less than 0.05 and P less than 0.01 respectively) by treatment with formaldehyde, but cellulose and neutral-detergent fibre digestibility were unaffected. 4. Within the rumen the digestion of organic matter, cellulose and neutral-detergent fibre were unaffected by formaldehyde treatment or supplementation with urea. Microbial protein synthesis in the rumen was similar for the three diets (average 131 g/kg apparently digested organic matter in the rumen). 5. The application of formic acid-formaldehyde increased (P less than 0.05) the amount of food protein escaping degradation in the rumen (4.76 diet C, 6.89 diet F; 7.07 diet FU g/kg protein intake). The contribution of amino acids of dietary origin at the duodenum increased (P less than 0.05) from 50 (diet C) to 80 (diet F) and 82 (diet FU) g/kg DM intake, and the flow of total amino acids at the duodenum was 33% higher (P less than 0.001) in cattle fed formic acid-formaldehyde silage diets compared with the control silage due to the reduction in degradation of protein at ensiling and in the rumen.

Amino Acids↗
PubMed1980

The influence of dietary iodine on iodine in the blood serum of cows and calves in the perinatal period.

Concentrations of total iodine (TI) and protein-bound iodine (PBI) in the blood serum of both cows and their neonatal calves were related to the iodine content of the diet fed to the cows. A group of six cows (group 1) fed a diet containing 0.6 ppm iodine had mean concentrations of TI and PBI of 4.1 and 3.4 microgram/100 ml respectively. A second group (group 2), fed a diet containing 4.6 ppm iodine, had concentrations of 33.8 and 7.6 microgram/100 ml of TI and PBI respectively. Calves of groups 1 and 2 had mean concentrations of TI of 21 microgram/100 ml and 96 microgram/100 ml respectively within 24 h of birth, but these concentrations declined markedly over a period of eight days. Evidence was obtained that the high concentrations of TI, and also of PBI, in neonatal calves relative to the concentrations in their dams resulted mainly from placental transfer rather than from the ingestion of colostrum.

Administration, Oral↗
PubMed1977

The effect of shearing pregnant ewes on lamb birth weights.

Shearing housed pregnant ewes at about the 11th week of pregnancy resulted in increased ewe liveweight gain (P greater than 0-01) and heavier twin litter weights (P greater than 0-01). The lambs from the shorn ewes also grew faster when put out to pasture. Unshorn pregnant ewes had a faster and more variable respiration rate, probably due to their being too hot in the prevailing conditions. The effect of this apparent heat stress on fetal nutrition is discussed.

Animals↗