Biomedical subjects

W H Butler

Publications and source records attributed to W H Butler.

At least 73 records · Page 4Linked to original sources

PubMed1977

Mode of action and human health aspects of aflatoxin carcinogenesis.

The toxicity and carcinogenicity of the aflatoxins have been studied extensively in the rat. In this species these compounds are recognized as some of the most active hepatocarcinogens. The early lesions induced by the aflatoxins have been studied in an attempt to recognize the developing malignant neoplasm prior to the presence of metastasis. The relationship of focal hyperplasia to neoplasia will be discussed in comparison with other recognized carcinogens. The pattern of human hepatic neoplasia will be compared with that of neoplasia induced by the aflatoxins in order to add weight to the "mycotoxin hypothesis" of the aetiology of hepatic neoplasia. The role of dietary modification will also be discussed.

Aflatoxins↗

PubMed1976

The kinetics of methylmercury administered repeatedly to rats.

Female rats (65-75 days old) were given orally 0.84 or 3.36 mg Hg/kg as methylmercury chloride (MeHgCl) 5 times a week for 13 and 3 weeks, respectively. The proportion of inorganic to total mercury remained as low as 6% in whole animal though it increased to above 40% in the kidneys. Differences in organ half times and the negative correlation with time for blood to liver, brain and kidney mercury ratios indicated more than one compartment for MeHg+. Brain had 26 days half time with a 32% final equilibrium concentration in relation to the body concentrations. Brain concentrations of mercury reported on rats dosed repeatedly with MeHg+ agreed with these values which justifies their use when experiments are planned to give a certain brain MeHg+ concentration. Half time for the whole body was 34 days but patholgical changes-weight loss, tubular damage, slow gastrointestinal passage-disturbed the accumulation curves in the higher dose group. Blood to kidney ratio and uptake of MeHg+ by kidneys also changed significantly.

Administration, Oral↗

PubMed1976

Some effects of acute and chronic dosing with aflatoxin B1 on rat liver nuclei.

A study has been made of changes occurring in rat liver nuclei as a result of the chronic and acute administration of aflatoxin B1. This has involved resolution of the nuclei into populations of differing ploidy by means of centrifugation in a zonal rotor. Chronic feeding of the toxin to weanling rats prevents the development of the predominant tetraploid hepatocyte nuclear population, which normally takes place during maturation. Increased populations of diploid and octaploid hepatocyte nuclei are observed. Chronic feeding of the toxin to adult animals also causes a reduction in the tetraploid population already established and, again, leads to increased numbers of diploid and octaploid nuclei. Once an abnormal nuclear population has been established by feeding the toxin, it persists until the development of hepatocarcinoma (if a 6-week carcinogenic feeding regimen has been used). The hepatomas have diploid nuclei. Labeling hepatic RNA and DNA in vivo has indicated that feeding the toxin causes a reversion to the immature distribution of DNA synthesis among the nuclear population, with little effect on the pattern of distribution of RNA synthesis. Acute administration of aflatoxin to adult rats also causes a reduction in the size of the tetraploid population, with increased proportions of diploid, octaploid, and higherploidy nuclei. These results are discussed in terms of a dual action of the toxin, antimitotic and necrogenic, and the possible relationship of these to the carcinogenic process.

Aflatoxins↗

PubMed1975