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Biomedical subjects

M B Brown

Publications and source records attributed to M B Brown.

At least 163 records · Page 9Linked to original sources
PubMed1981

Transfer effects in feature-positive and feature-negative learning by adult humans.

In two experiments, college students performed a feature-positive or a feature-negative discrimination task based on colors or symbols and were then transferred to a feature-positive or feature-negative discrimination based on the other stimulus dimension (symbols-colors, colors-symbols). Initial task results yielded a substantial feature-positive effect and indicated that the color task was easier than the symbol task. Transfer task results indicated that the feature-positive effect was maintained and showed that consistent transfer (positive-positive, negative-negative) led to superior performance on the transfer task. These results were obtained when the correct solution to the initial task was provided to the subject prior to transfer (Experiment 1) and when it was not (Experiment 2). These results systematically replicated the existence of the feature-positive effect in adult humans and showed that both feature-positive and feature-negative discrimination learning were facilitated by consistent examples of these problems.

Discrimination Learning↗
PubMed1978

Strategies for the selection of log-linear models.

In a multidimensional contingency table strategies have been proposed to build log-linear models using either stepwise methods or standardized estimates of the parameters of the saturated model. Brown (1976) proposed a two-step procedure to screen effects and then test a subset of models. Alternate methods of model building are discussed with respect to the final choice of model and with respect to intermediate information available to the data analyst during the selection process.

Depression↗
PubMed1975

Accumulation of some secretory enzymes in venom glands of Vipera palaestinae.

Secretion of venom in the venom glands of Vipera palaestinae was studied by measuring the protein content and enzymatic activities of L-amino acid oxidase (LAO), phosphodiesterase (PDE), and benzoylarginine ethyl esterase (BAEE). These were tested in the accumulating venom and gland homogenates at 0, 2, 3, 4,6, and 15 days after an intitial emptying of the venom glands by milking. Changes in the total activities of the enzymes and in the protein concentration were found in the venom samples, but not in the homogenates, at the different intervals after milking. In the venom the total activities of LAO, PDE, and BAEE were higher the longer the time intervals from the initial milking. When the data were fit by a straight line, the fluctuations from the line were of opposite signs for LAO and PDE at the 3- and the 4-day intervals. There were no significant correlations between the specific activities or between the changes in the specific activities of any two of the enzymes at any time interval. It is concluded that each of the enzymes is secreted at a rate independent of the other two; this pattern of secretion can best be described as nonparallel.

Amino Acid Oxidoreductases↗
PubMedDate not supplied

Effect of hyperglycemia and the aldose reductase inhibitor tolrestat on sural nerve biochemistry and morphometry in advanced diabetic peripheral polyneuropathy. The Tolrestat Study Group.

Tolrestat is a well tolerated nonhydantoin aldose reductase inhibitor that has been reported to improve nerve conduction in diabetic animals and humans. Its effects on nerve biochemistry and structure have not been studied in patients with diabetic neuropathy. Patients with advanced diabetic neuropathy treated with long-term open-label tolrestat were randomly assigned to continuation on drug treatment or to placebo-controlled drug withdrawal for 12 months. At the end of this period, sural nerve biopsies were obtained for measurement of glucose, sorbitol, and fructose content, and for detailed morphometric analysis. Tolrestat ameliorated the glucose-mediated increase in sorbitol and fructose in sural nerve tissue. No statistically significant differences in nerve morphometry emerged between the two groups; however, both treatment groups exhibited increased nerve-fiber regeneration and normalization of axo-glial dysfunction and segmental demyelination following long-term tolrestat treatment. These findings are similar to those previously reported in a placebo-controlled sequential nerve biopsy study with the aldose reductase inhibitor sorbinil. Thus tolrestat is a biochemically effective aldose reductase inhibitor in human diabetic nerve with potential therapeutic efficacy for diabetic neuropathy.

Aldehyde Reductase↗