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Anna Marchlewska-Koj

Summary. After fractionation of the urine of male mice on Sephadex G-75 followed by thin-layer electrophoresis pheromonal activity (i.e. pregnancy blocking) was found in the peptide fraction. The pregnancy-blocking pheromone is therefore a peptide or a substance bound with the peptide fraction.

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Fructose was determined in ejaculates of normal and vasectomized male mice, after recovery of the ejaculates from mated females. Approximately 70% of the total fructose remained in the copulatory plug and only 30% was present in the fluid portion of the seminal plasma. When the fluid portion of the ejaculate was left in the uterus for 2 hr without contact with the plug (the uterine horn having been ligated), a statistically significant decrease of fructose occurred in relation to the initial value. When, however, such semen was left in the uterus in contact with the plug, this decrease was counterbalanced by an influx of fructose released from the plug.

No clear difference in the decrease of fructose content was found between the fluid portion of ejaculates from normal and vasectomized males after 2 hr in the uterus.

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Anna Marchlewska-Koj, B. Jemioło, J. Woźniacka and K. Kozłowski

Summary. Outbred female mice were exposed during 3 oestrous cycles and mated to outbred or C57BL/kw males. Although ovulation number (CL and flushed eggs) was similar in all females, there were significantly fewer (P < 0·01) fertilized eggs and implantations in females exposed and mated to C57BL/kw males. Exposure to outbred males and mating with C57BL/kw males led to some improvement but the best results were obtained with females mated to outbred males. The activity of uterine dehydrogenases on Day 4 of pregnancy was also greatest in females mated to outbred males. It is concluded that the pheromonal stimulation leads to hormone concentration differences which affect implantation.