Morphometric analysis of the development of sexual dimorphism of the mouse pelvis.

Sex differences in the innominate bone of C57BL/Tw mice were studied morphometrically from the day of birth to 120 days of age. In neonatal male and female mice, a small cartilaginous spine was found on the basal part of ischium. This process disappeared in males within 24 hours after birth, whereas in females it remained until at least 30 days. Other sexual differences in the pubis and the ischium appeared at 30 and 120 days, respectively. The pubis in female mice was longer and thinner than that in the males, and the ischium in male mice was shorter and thicker than that in the females. Thirty-day-old female mice treated neonatally with testosterone or 5 alpha-dihydrotestosterone possessed pubic bones shorter and thicker than those of the age-matched untreated females. Pubes in male mice castrated at the day of birth were thinner than those in intact males. These findings suggest that the shape of the innominate bone is transformed to the male type under the influence of early postnatal androgen.

Toxicological studies on a new macrolide antibiotic, midecamycin acetate (miokamycin). Part II-1. Subacute toxicity in rats.

Miokamycin (MOM) is a derivative of midecamycin, a macrolide antibiotic isolated from a culture broth of Streptomyces mycarofaciens. The objective of this study was to determine the subacute toxicity in male and female rats (Wistar, SPF, 5-week-old) after repeated oral administration of MOM, non-crystalline solid, for 5 weeks at selected dosage levels of 1,000, 2,000 and 4,000 mg/kg/day. It is concluded that the maximum non-toxic dosage level of MOM, non-crystalline solid, was 1,000 mg/kg/day but without specific toxic effects with rats when it was orally administered once daily for 5 weeks.

Effect of porcine relaxin on cervical dilatation, pelvic area and parturition in beef heifers.

Purified porcine relaxin (3,000 U/mg) was administered either into the cervical os or by intra-muscular injection to crossbred beef heifers beginning 4 days before expected parturition, in an attempt to elucidate the physiological roles of relaxin in cervical dilatation, the pelvic area, and parturition. Relaxin (3,000 U in a gel vehicle), when administered into the cervical os during late pregnancy, induced significant dilatation of the cervix 8 and 16 h later, as compared to vehicle-treated controls. This induced cervical dilatation did not cause premature parturition in relaxin-treated heifers and was similar to controls. Exogenous relaxin during late gestation elicited an increased growth rate of the pelvic area, as determined by sequential measurements of height and width of the pelvic canal. These results indicate that, before parturition, pelvic width increased more rapidly than pelvic height and that exogenous relaxin elicited a greater response in both parameters. Highly significant nocturnal elevations in concentrations of progesterone in peripheral blood serum occurred in vehicle-treated control heifers during late pregnancy. These nocturnal elevations in serum levels of progesterone were significantly reduced after 8 and 16 h of relaxin treatment in experimental animals as compared to control heifers. The mechanisms by which porcine relaxin reduces ovarian progesterone secretion in beef heifers remain undefined.