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Biomedical subjects

R M Hoar

Publications and source records attributed to R M Hoar.

5 recordsLinked to original sources

Interlaboratory comparison of behavioral testing.

New requirements by several regulatory agencies for testing the psychotoxic potential of new drugs, chemicals, and environmental contaminants raise unique problems. In order to assess intra- and interlaboratory reliability of behavioral tests a model animal maze learning procedure was designed and run in 3 cooperating laboratories. Uniform procedures were written and identical mazes were constructed. Normal control animals of identical age and sex, but of different strains, were used by the participants. A positive control group of neurologically impaired rats was run by one laboratory. Significant differences in test results among the laboratories were found. Data obtained from the positive control animals (mean errors=28.3) indicated a learning impairment statistically significant compared to the negative control data (mean errors=12.7) from any of the participating laboratories. Based on the results of this study, a reasonable standard of interlaboratory reliability in behavioral testing appears an attainable goal.

Animals

Potentiation of methotrexate embryolethality by aspirin in rats.

The augmentation of methotrexate-induced embryotoxicity by aspirin was studied. Pregnant Charles River CD rats were given methotrexate or aspirin alone or in combination on gestation day 9 or 12. The frequency of fetal abnormalities was not affected and fetal body weight loss was not additive in the combined treatment. However, pretreatment with aspirin (200 mg/kg) significantly enhanced the embryolethality of methotrexate given at soes of 0.2 mg/kg on day 9 and 1.5 mg/kg on day 12. Studies with tritiated methotrexate in pregnant rats demonstrated that aspirin delayed the renal excretion of methotrexate and increased the concentrations of methotrexate in maternal plasma and the embryos. It is suggested that these effects are responsible for the observed potentiation of embryolethality.

Abnormalities, Drug-Induced

Comparative developmental aspects of selected organ systems. II. Gastrointestinal and urogenital systems.

A brief description of the basic patterns of mammalian organogenesis of the gastrointestinal and urogenital systems is presented based on events as they occur in human beings. The emphasis is not on the details of this development, but rather on its organization and timing, with tables of comparative development providing a comparison of similar events in man, rat, mouse, and chick.

Animals

An improved technic for thyroidectomy in guinea pigs.

A technic for thyroidectomy in the guinea pig was presented. After anesthetizing the guinea pig with methoxyflurane, the thyroid was removed by electric cautery. The step-by-step procedure was described. Possible complications such as recurrent laryngeal nerve damage and the stimulation of aberrant thyroid tissue were discussed.

Anesthesia, Inhalation