Administration of constant low doses of androgens to steers by silastic implant. Suppression of gonadotropins and peripheral conversion of androgens.

Yearling Hereford calves approximately 300 kg in weight were castrated and assigned to one of six treatment groups receiving subcutaneous implants (3 implants, 0.5 cm diameter by 10 cm length, 10% steroid by weight) of either androstenedione (D); testosterone (T); 5 alpha-androstane-3 beta, 17 beta-diol (3 beta-diol); dihydrotestosterone (DHT); androsterone (A); or control (no steroid). Blood samples were obtained at half-hour intervals for eight hours one day prior to, and one week after, castration. The castration-induced elevation in FSH secretion was suppressed or modified by the DHT, T, and 3 beta-diol implants. LH levels were not significantly suppressed. The T implants elevated serum T concentrations; DHT implants elevated serum 5 alpha-androstane-3 alpha, 17 beta-diol (3 alpha-diol) and 3 beta-diol, but not DHT concentrations; 3 beta-diol implants elevated serum 3 beta-diol concentrations. The effects of D and A implants upon serum androgen concentrations were not statistically significant, although observations in vitro suggested an adequate release rate. These data imply that T and DHT, or metabolites of DHT, suppress FSH secretion and suggest that extensive peripheral androgen metabolism occurs.

Quantitation of six androgens by combined high performance liquid chromatography and radioimmunoassay.

A technique was developed to separate six androgens (testosterone, dihydrotestosterone, androstenedione, 5 alpha-androstane-3 alpha, 17 beta-diol, 5 alpha-androstane-3 beta, 17 beta-diol, and androsterone) by high performance liquid chromatography prior to quantitation by specific radioimmunoassay systems. Methanol:water (60:40 v:v) was used as the solvent system with a C18 reversed-phase column. The method was verified and used to quantitate the androgens in serum from adult rams bled every 20 minutes for 6 hours and yearling bulls bled every 30 minutes for 8 hours. Concentrations of all 6 androgens varied in an episodic manner with testosterone being the dominant androgen.

Documentation of children's vaccination status in child care centres in Victoria.

OBJECTIVE: To assess the record-keeping of child care centres in Victoria with respect to children's vaccination status. METHODOLOGY: A random sample of 113 centres from a list of over 800 registered Victorian child care centres received a mailed questionnaire on characteristics and policies of the centre, including documentation of attending children's vaccination status. RESULTS: The response rate was 86.7%; more than 95% of centres had children under two in care. Only 85% of centres kept any record of children's immunisation status, with smaller centres and class 2 centres (occasional care centres) significantly less likely to keep records. Records were updated irregularly. Fewer than half of the centres studied kept a record of whether children had been vaccinated against Haemophilus influenzae type b. CONCLUSIONS: Despite the importance of documenting children's vaccination status, many child care centres have failed to develop adequate systems to record or update records of children's immunisation. This makes exclusion during outbreaks of a vaccine-preventable disease difficult. The ongoing process of accreditation may eventually improve performance, but both legislation and a better educational strategy to improve practice in this area are needed.

The effects of androgens and gonadotropins on testicular development in the prepubertal rat.

Treatment of male rat pups from five to 34 days of age with dihydrotestosterone or 5 alpha-androstane-3 alpha, 17 beta-diol, resulted in reduced testicular size at 35 days of age. This appeared to be due to decreased tubular diameters and reduced spermatocyte numbers, especially late pachytene cells in stages X to XIII. In rat pups treated with dihydrotestosterone or 5 alpha-androstane-3 alpha, 17 beta-diol, treatment with luteinizing hormone resulted in some restoration of tubular diameter and spermatocyte numbers. In 5 alpha-androstane-3 alpha, 17 beta-diol treated rat pups partial restoration of testes size resulted from follicle-stimulating hormone treatment, but tubular diameter and spermatocyte numbers were depressed. Single serum samples collected at 35 days of age were analysed for luteinizing and follicle-stimulating hormone concentrations. These data indicated that the effects of administered androgens were due primarily to depression of circulating gonadotropin concentrations but a direct inhibition at the level of the testis could not be ruled out.