Genotype, uterine position, and testosterone sensitivity in older female mice.

CF-1 and CK (C57BL/6J x AKr) female mice that developed in utero between two males (2M), adjacent to one male (1M), or between two females (0M) were tested for their sensitivity to the aggression-promoting property of testosterone (T) beginning at 9 months of age. Comparisons between the strains showed that a higher proportion of CF-1 females fought in response to T and that the period of hormone exposure required to induce aggression also was shorter in this strain. Within each of the genotypes, there were no systematic differences in responsiveness to T related to contiguity to males during fetal development. While the results provide further evidence for genotype as a major influence on neural sensitivity to androgen, they do not support uterine position of females relative to males as a source of phenotypic variation in responsiveness.

The intrauterine position phenomenon and precopulatory behaviors of house mice.

The effects of intrauterine position on two sexually dimorphic, precopulatory, reproductive behaviors, were investigated in male and female mice of three different genetic strains. The two behaviors were: (i) urinary odor preference and (ii) ultrasonic mating vocalizations. In addition, anogenital distance was measured both at birth and later in adulthood as a morphological index of masculinization. The intrauterine positions of individual mice relative to male and female siblings were classified according to two different classification schemes based upon hypotheses of interfetal steroid transfer: (i) the contiguity hypothesis which is based on diffusion of steroids within the uterus and (ii) the transvasculature hypothesis which posits the movement of fetal steroids via the maternal vasculature. In contrast to expectations, intrauterine position defined by either the contiguity hypothesis or the transvasculature hypothesis, did not have a consistent effect on urinary odor preferences, ultrasonic mating vocalizations, or anogenital distance in male and female house mice.

Failure to detect a putative oestrus-indicating pheromone in the urine or vaginal secretions of female sheep.

Extensive use of gas chromatographic analysis of the volatile and non-volatile components of sheep urine and sheep vulvovaginal secretions at different stages of the oestrous cycle has not succeeded in identifying the putative oestrus-indicating pheromone produced by the ewe. However the putative pheromone is probably not a low molecular weight alcohol, diol, phenol, amine, amide, aldehyde, ketone, fatty acid or steroid.