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M C Stephens

Publications and source records attributed to M C Stephens.

13 recordsLinked to original sources

Premedical program effective in increasing admissions to health professional schools.

The Special Premedical Studies Program (SPSP) has been successful in preparing Aboriginal students in Canada for admission to medicine, dentistry, medical rehabilitation, and pharmacy at the University of Manitoba. The success rate for admission to these faculties is 20%. There is a higher failure rate in the basic years of medical/dental education, but remediation has been 100% successful. Failure rates in the clinical years do not differ from those of the mainstream population. Grade point averages and MCAT scores are given less weight in the special consideration category of application at the University of Manitoba. SPSP students can and do apply to this category. The higher rate of first unsuccessful attempt in the basic years of medical education specifically can be attributed to a variety of factors, including reading skills. Although the numbers are small, we show that there is a correlation between the comprehension score of the Nelson-Denny test and the verbal score of MCAT. But there was no difference on the average between verbal score in MCAT and pass/fail in basic medical years. Students who scored above the 80th percentile on the comprehension portion of the Nelson-Denny test were successful in their first attempt at examinations in medical school.

American Indian or Alaska Native↗

The Gaucher mouse.

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Acid Phosphatase↗

Distribution of conduritol B epoxide in the animal model for Gaucher's disease (Gaucher mouse).

The time course of the distribution of the beta-glucosidase inhibitor [3H]conduritol B epoxide was determined in various organs of mice, which had received a single interperitoneal dose of the inhibitor. The epoxide is rapidly distributed over all tissues except brain where its concentration is only one-tenth of the average. This is considered an indication that the epoxide can pass the blood/brain barrier only with difficulty. A 4-fold enrichment is seen in the kidney. The inhibitor is excreted with a half-life of about 7 h; it is not metabolized. A parallel determination of beta-glucosidase activity in the tissues showed greater than 90% inhibition within 1 and 2 h and a beginning recovery between 4 and 12 h. The only exception was brain, where no effects could be seen after 1 h and where a subsequent decrease to 37% of normal was observed after 12 h.

Animals↗

Development of glycolipids and gangliosides in lead treated neonatal rats.

Lead (0.01% or 0.1% in the diet) was given to rats from conception to an age of 14, 21 or 32 days, and the development of brain cerebrosides, sulfatides and gangliosides was followed. Animals which had received 0.1% lead displayed a marked retardation in the onset and a reduction in the final level (at 32 days) of the lipids characteristic for the myelination process (cerebrosides and sulfatides). A slight decrease was also seen in the level of gangliosides at 32 days. It is suggested that certain aspects of lead encephalopathy might be explained by the toxic effects of lead on the glia population and the consequent interference with normal formation of myelin.

Animals↗

Studies on the possible identity of particulate beta-glucosidase and beta-xylosidase of mouse liver.

Mouse liver beta-glucosidase (beta-D-glucosidase glucohydrolase, EC 3.2.1.21) and beta-xylosidase (1,4-beta-D-xylan xylohydrolase, EC 3.2.1.37) activities were studied under different conditions of incubation in an attempt to determine whether these two activities are due to a single enzyme or two separate enzymes. The results showed that: (a) Particle-bound beta-glucosidase and beta-xylosidase activities exhibit similar characteristics with different buffers and at various pH values, in the presence or absence of taurocholate. (b) Both activities are inhibited by gluconolactone and conduritol B eposice. beta-Glucosidase activity is inhibited competitively by the two inhibitors, but beta-xylosidase activity is inhibited non-competitively. (c) Xylonolactone was a very poor inhibitor of both activities, but the inhibition of beta-xylosidase activity was more pronounced than that of beta-glucosidase. (d) The presence of glucosides or xylosides simultaneously in the incubation medium suggested the presence of one enzyme with both activities. These results, together with the mode of inhibition produced by gluconolactone and conduritol B epoxide also suggest the presence of two different binding sites for the beta-D-glucoside and beta-D-xyloside, respectively.

Animals↗

Brain lipids in pyridoxine-deficient young rats.

Pyridoxine deficiency produced in rats during the period of development of the central nervous system resulted in a decreased incorporation of (1-14C) acetate into total lipid extracts of brain. It also resulted in a uniform decrease in the incorporation of the labeled precursor into the cholesterol, glycolipid and phospholipid fractions of brain. The specific radioactivity of purified cerebrosides and sulfatides was decreased by 78% in pyridoxine-deficient rats with respect to controls. The decreased incorporation of labeled precursor in the deficient rats was not due to the labeled precursor, since the specific radioactivity of brain acetate and the brain concentrations of acetyl coenzyme A and acetate were similar in both deficient and control rats. The results indicate that in pyridoxine deficiency established in the young rat there is an impaired formation of myelin.

Acetates↗