Metabolism of lysosomal enzymes in the protein-deficient weanling rat.

We have shown that the protein-deficient weanling rat fed a 3% casein diet, within 2 to 4 wk, exhibits marked changes in serum lysosomal hydrolases similar to those observed in children suffering from protein-calorie malnutrition: serum hexosaminidase, alpha-mannosidase, and beta-glucuronidase activities increase 3-fold, 2-fold, and 50%, respectively, whereas the acid phosphatase levels decrease by 50%. Rehabilitation of the protein-deficient animals with a diet containing 25% protein (i.e., casein) results in a rapid restoration of the plasma lysosomal hydrolase profiles to normal in less than 1 wk. The specific activities of various tissue lysosomal enzymes change significantly in the protein-deficient animals; however, no overall consistent pattern of change is apparent. In general, the greatest number of changes in lysosomal enzymes occurs in the kidney, whereas the brain exhibits the smallest differences between experimental and control animals in this regard. Perfusion experiments have shown that the rate of release of lysosomal enzymes from livers of rats fed the protein-deficient diet is profoundly altered when compared to that of control animals. Studies of the variation of enzyme secretion with time have demonstrated that the rate of secretion of hexosaminidase by the liver remains low and then rises markedly (3-fold) after the animals have been consuming the 3% casein diet for 16 days. In contrast, the secretion of both acid phosphatase and beta-glucuronidase is markedly depressed in the early phase of protein malnutrition (i.e., 7 to 16 days), and then increases greatly by the 3rd wk. These results demonstrate that changes occur in the rate of secretion of lysosomal enzymes by the liver during the course of experimental protein malnutrition.

Factors related to medical school application and acceptance in minority summer enrichment program students.

Baylor College of Medicine has conducted a summer enrichment program for minority/disadvantaged premedical students since 1969. Follow-up data on medical school application and acceptance for participants from 1980 through 1984 were analyzed in relation to selected preprogram variables--cumulative college grade point average, total Scholastic Aptitude Test score, competitiveness of undergraduate college, sex, and ethnicity. Results of univariate and multivariate analyses indicated that: 1) females were significantly less likely to apply to medical school than males, 2) females had significantly lower mean MCAT scores (5.9 vs 7.2) even though their preprogram academic performance was comparable to that of the males, and 3) after controlling for MCAT scores, none of the preprogram variables were significant in predicting medical school acceptance. These findings suggest the need for research to explain the discrepancy between male and female MCAT performance and frequency of medical school application in summer program participants. The findings also have implications for the type of counseling provided to female participants in summer enrichment programs.

Rat renal peritubular transport and metabolism of plasma [35S]glutathione.

More than 80% of the plasma glutathione is extracted during a single pass through the kidney. The peritubular component of this extraction was characterized by in situ arterial infusion of [35S]glutathione and [3H]inulin. The peak of 35S-labeled material recovered in the renal venous effluent was delayed approximately 10 S compared with the peak of [3H]inulin. As a result, the initial fractions exhibited a decreased 35S/3H ratio, indicating that 35S-labeled material is transported out of the postglomerular peritubular capillaries. Later fractions exhibited a normalized 35S/3H ratio greater than 1, consistent with the subsequent addition of a 35S-labeled metabolite to the venous circulation. An identical profile was observed when perfusion experiments were repeated using gamma-[35S]glutamyl-S-methylcysteine and [3H]inulin. Renal venous plasma samples obtained from a rat perfused with [35S]glutathione were reduced with sodium borohydride, reacted with monobromobimane, and analyzed by high-pressure liquid chromatography. More than 70% of the recovered 35S-labeled material was identified as cysteine and 20% was recovered as unmetabolized glutathione. Pretreatment of rats with a single injection of AT-125 resulted in 96% inactivation of renal gamma-glutamyltranspeptidase. Under these conditions, the percent of glutathione converted to cysteine (35%) was significantly less than the observed level of renal extraction (61%). Two injections of AT-125 caused a complete inhibition of cysteine formation. However, the residual level of renal extraction (41%) was still significantly greater than the filtration fraction (26%). The peritubular transport of glutathione is stimulated by prior depletion of renal glutathione with buthionine-L-sulfoximine and is competitively inhibited by simultaneous infusion of gamma-glutamylcysteine.(ABSTRACT TRUNCATED AT 250 WORDS)

A computer-assisted admission matching system for the University of Texas medical schools.

The feasibility of a computer-assisted admission matching system was investigated in 1973-74 at the Medical and Dental Application Center at the request of the four University of Texas medical schools. Preference data were gathered from applicants and from schools, and matching simulation was conducted concurrently with actual admission action for 1974 entering classes. Implementation of a matching system for admission of the 1975 entering classes was demonstrated to be feasible, and a decision to implement such a system was made. Data indicating the need for a matching system are briefly reviewed, and the matching concept is discussed. Results of the 1974 feasibility study are presented, and the first year of implementation for the 1975 entering classes is described. Admission matching improved the efficiency of the admission process by reducing the number of unproductive offers of admission and by providing more applicants earlier decisions from participating schools regarding their applications.