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Biomedical subjects

A D Dayan

Publications and source records attributed to A D Dayan.

At least 19 recordsLinked to original sources
PubMed1991

Effects of a cholecystokinin receptor antagonist on rat exocrine pancreatic response to raw soya flour.

1 Raw soya flour (RSF) in the diet induces pancreatic hypertrophy and hyperplasia in the rat, changes ascribed to production of a high circulating level of cholecystokinin (CCK) due to inhibition of trypsin in the duodenum. Prolonged ingestion results in pancreatic adenomas and carcinomas. 2 L-364, 718, a potent, highly specific CCK antagonist was used to investigate the short-term role of CCK. 3 In rats fed 50% RSF and L-364, 718 5 mg kg-1 p.o. twice daily for 4 d, there was inhibition of pancreatic hypertrophy and hyperplasia, which is further evidence that peripherally-acting CCK plays a major role in the generation of RSF-mediated changes in the pancreas.

Animals↗
PubMed1991

A comparison of spongiosis induced in the brain by hexachlorophene, cuprizone and triethyl tin in the Sprague-Dawley rat.

The effect of hexachlorophene (HCP; 2,2'-methylenebis(3,4,6-trichlorophenol), cuprizone (CPZ; bicyclohexone oxaldihydrazone) and triethyl tin (TET; triethyl tin sulphate) in producing vacuoles in the brain of the Sprague-Dawley rat has been quantified by image analysis of the extent of the spongy change in the white matter. The state of the astrocytes was assessed by immunocytochemical staining for glial fibrillary acidic protein (GFAP). HCP and TET caused a dose-related spongiosis, but cuprizone had no significant effect on the brain. With chronic HCP treatment, the spongiosis was accompanied by astrocyte hypertrophy and proliferation, and the extent of the gliotic reaction was related to the dose of HCP. The results demonstrate that HCP can produce and maintain astrocyte proliferation in the rat brain. Such an agent was required for use in an investigation of a putative tumour promoter in the rat.

Animals↗
PubMed1990

Death of the LD50.

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Animal Testing Alternatives↗
PubMed1990

Strength of meaning--strong words and a certain message?

The ability to convey specific meanings is important to scientists in their writing. However, difficulties arise when the ideas to be portrayed are judgmental. While extreme terms expressing strength of meaning are readily understood, more subtle ones appear not to be.

Humans↗
PubMed1989

Who needs toxicology?

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Education, Medical, Undergraduate↗
PubMed1988

Histopathological classification of nonantral gastric endocrine growths in man.

Recently, the gastric endocrine system has been recognized as the origin of benign and malignant tumors in pernicious anemia. It has also been found that the gastric endocrine cells respond to permanent elevation of serum gastrin levels induced by changes in acid secretion in response to surgical procedures, drug therapy and age. Therefore, a definition of nonantral gastric endocrine hyperplasia (simple or diffuse, linear or chain-forming, micronodular, adenomatoid), dysplasia (enlarging or fusing micronodules, microinvasion, nodular growth) and neoplasia (intramucosal carcinoid, invasive carcinoid) is presented. The individual entities are illustrated, together with the literature discussed and the techniques for their identification presented.

Endocrine System Diseases↗
PubMed1987

Alterations in crypt cell populations in the small intestine as an early toxic response to sub-acute ethanol administration.

Crypt cell production was examined in young male rats (Sprague-Dawley) given 1, 5 or 15% ethanol in their drinking water for up to 14 days. Ethanol 1 and 5% did not influence food and liquid consumption and growth was similar to that seen in control animals given tap water only to drink. Animals given 15% ethanol exhibited a significant reduction in food and liquid intake and showed a marked diminution in weight gain within 7 days. Ethanol consumption did not affect the length of the small bowel, but 5 and 15% concentrations inhibited cell production in the jejunum and in the distal aspect of the ileum. The relative position of the proliferative compartment, as assessed by the 50% total mitosis level, was unaltered as a result of the treatment. 1% Ethanol led to an increased mitotic rate in the jejunum after 14 days, treatment. Crypt cell production returned to normal in animals given 5% ethanol for 7 days and then a recovery period of 7 days. Mitotic inhibition resulting from ethanol ingestion is probably due to a direct effect (jejunum and proximal ileum) but systemic changes possibly contribute to changes seen in the distal ileum. The nutritional and toxicological implications of ethanol consumption are discussed.

Animals↗
PubMed1987

Dominant lethal study of ribavirin in male rats.

Ribavirin, a new synthetic antiviral agent, was studied for dominant lethal effects in male CD rats. The drug was administered intraperitoneally at doses of 50, 100 and 200 mg/kg/day for 5 days. Males were mated weekly with 8 consecutive batches of female rats. Marginal increase in early foetal death detected in Assessment Weeks 3 and 8 in females mated with the low-dose and high-dose males were not dose-related and were most probably chance events caused by the particularly low vehicle control frequencies for these 2 weeks. Also, the slightly reduced pregnancy proportion among females mated with the high-dose treated males was to a substantial extent the effect of a single male rate which failed to fertilize any females. Ribavirin was, therefore, regarded as being devoid of any mutagenic potential demonstrable by a rat dominant lethal assay.

Animals↗
PubMed1987

Comparative subacute effects of dietary raw soya flour on the pancreas of three species, the marmoset, mouse and rat.

Subacute changes induced in the pancreas by raw soya flour have been studied in three species. The raw soya flour was fed to male Sprague-Dawley rats and male CD-1 mice for 2, 4 or 8 days at a level of 50% (w/w) in the diet, and to male and female marmosets for 2 or 7 days at 20% (w/w) in the diet. The stathmokinetic method was used to study mitotic activity in the pancreas, and mean acinar cell area was calculated using an image analysis system. The relative weight of the pancreas in the rat and mouse increased during dosing, but that of the marmoset did not. No proliferative or trophic effects were observed in marmoset pancreas, but in both the mouse and rat a transient increase in mitotic activity was followed by a steady increase in acinar cell size.

Animals↗
PubMed1987

Evaluation of the BTS approach to the testing of substances and preparations for their acute toxicity.

This study has shown that the new approach to acute oral toxicity testing proposed by the British Toxicology Society: provides the information on the toxic effects of materials necessary for human risk assessment, can be used to rank materials for regulatory purposes on the basis of their acute toxicity, provides advantages for animal welfare by requiring the use of fewer animals than conventional acute oral toxicity tests and by subjecting those animals used to less chance of experiencing pain or distress.

Administration, Oral↗