Recent years have seen a steady decline in the number of new physician-investigators (Association of American Medical Colleges, 2000). To encourage medical students to select research careers, the Queen's University Faculty of Health Sciences curriculum includes a mandatory Critical Enquiry elective in the 2nd year. An anonymous written survey was administered to medical students before and after the elective to determine their perceptions of the value of the elective and its impact on their decision to pursue a career in medical research. There was a significant increase in the number of students expressing an interest in pursuing a research career following the elective (35-42%, p = 0.029). Students recognized other benefits including the development of critical appraisal, information literacy, and critical thinking skills; and the opportunity to select an area of and form contacts for postgraduate training. Even students who choose not to pursue careers in medical research perceive benefits to a mandatory undergraduate research elective.

Our investigations on acid phosphatase (AP) were aimed at finding a biochemical assay marker for androgen actions in the rat prostrate. We quantitatively examined the effects of l-tartrate or formaldehyde on AP activity in tissue filtrates from nine adult male rat tissues, plasma and hemolysed red blood cells (HRBC). There was significant inhibition of AP activity in all instances with the exception of HRBC with tartrate. The prostate inhibition results were not different from those for seminal vesicles and adrenals but were different from the other tissues studied. Ten days following castration the inhibition by tartrate was less in all tissues studied except plasma and HRBC; the formaldehyde inhibition percentages were not altered.

The single injection and constant infusion techniques were utilized to study the kinetics of dehydroepiandrosterone (DHEA) metabolism and its peripheral conversion to several other C19-steroids including C19-steroid sulfates. The MCRs (mean +/- SEM) for normal men and normal women were 1866 +/- 144 and 1901 +/- 87 liters/24 h, respectively. The single injection technique yielded values for rate constants (units) and volumes of distribution (1) as follows: K1, 42.6 +/- 7.7 for men and 37.1 +/- 5.0 for women; K2, 64.3 +/- 11.2 for men and 55.5 +/- 5.0 for women; K2, 64.3 +/- 11.2 for men and 55.5 +/- 5.0 for women; V1, 38.5 +/- 6.0 for men and 33.7 +/- 2.5 for women; V2, 30.4 +/- 7.3 for men and 27.5 +/- 9.9 for women. The constant infusion technique yielded values for the conversion ratios for the transformation of DHEA to several products: delta 5-androstene-3 beta, 17 beta-diol to DHEA of 0.10 +/- 0.01 for men and 0.16 +/- 0.03 for women, delta 4-androstenedione to DHEA of 0.04 +/- 0.01 for men and 0.07 +/- 0.02 for women, DHEA sulfate (DHEAS) to DHEA of 6.36 +/- 0.81 for men and 10.09 +/- 0.87 for women, delta 5-androstene-3 beta, 17 beta-diol sulfate to DHEA of 0.42 +/- 0.06 for men and 0.50 +/- 0.04 for women, and androsterone sulfate to DHEA of 1.11 +/- 0.13 for men and 2.06 +/- 0.18 for women. The ratios for the conversion to DHEA sulfate and androsterone sulfate were significantly higher for women than men. The plasma concentrations of DHEA were 8.50 +/- 0.95 and 8.75 +/- 1.01 ng/ml for men and women, respectively. The calculated production rates for DHEA were 16.34 +/- 2.66 and 16.19 +/- 1.78 mg/24 h for men and women, respectively. There was no sex difference in the binding of DHEA to plasma proteins and this is reflected in the lack of sex difference in the MCRs. Calculations indicate that DHEA is a major precursor of circulating delta 5-diol.

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Acid phosphatase (EC 3.1.3.2) activity was examined for its possible utilization as a biochemical marker for the profound changes that occur in the prostate gland after castration. Tissue filtrates were prepared from the prostate glands of mature male rats at various times after castration. The acid phosphatase activity was characterized by polyacrylamide gel electrophoresis and the percentage inhibition in the presence of tartrate. Prostatic acid phosphatase from mature rats has been shown to have two bands of activity, a lysosomal acid phosphatase and a secretory acid phosphatase. After castration, there was a loss of the secretory acid phosphatase from gel electrophoresis patterns by day 5 and a corresponding rise in the percentage inhibition by tartrate from the normal value of 43·2% to a maximum of 55·4% on day 7. Between days 7 and 15 there was a linear decrease in the percentage inhibition by tartrate, but after day 15 the value did not change significantly from 31·1% After castration, the specific activity of the uninhibited enzyme increased from a normal basal level of 2·16 μmol h−1 mg protein−1 to a maximum on day 7 of 8·10 μmol h−1 mg protein−1. After this time, the specific activity decreased slowly until it reached a normal level on day 21. Intraperitoneal administration of testosterone, 5α-dihydrotestosterone or 5α-androstane-3α,17β-diol at a dose of 2 mg/day and starting immediately after castration prevented the changes in percentage inhibition by tartrate and the loss of the secretory band of acid phosphatase. Administration of these androgens from day 7 after castration led to a decrease in the percentage inhibition from 50·1% to a minimum of 31·5% before the level returned to the normal value found in the mature rat. The secretory band of acid phosphatase, which was not present in gels at day 7, reappeared after 8–11 days of treatment with androgens. Of the androgens used,5α- androstane-3α,17β-diol was the most potent.

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