Para-chloroamphetamine (PCA)-induced ejaculation in aged rats, semen analysis and artificial insemination.

The present study was undertaken to determine sperm motility and counts in semen yielded by para-chloroamphetamine (PCA)-induced ejaculation of aged rats which had lost their reproductive ability, and to attempt artificial insemination with suspensions of spermatozoa obtained in this way. The semen yielded by PCA-induced ejaculation from aged (75-week-old) rats had average sperm counts of 0.82 +/- 0.69 x 10(7), which were much lower than the average counts (9.42 +/- 1.65 x 10(7)) for semen spontaneously ejaculated by young adult rats (14 weeks old). However, 77.5% of the spermatozoa contained in the PCA-induced semen were rated as showing the most active movement. Spermatozoa collected in this way were injected into the upper parts of both uterine horns or into both ovarian bursae. Both methods made the females pregnant, but the results were better after injection into the ovarian bursae. The offspring born to these females showed no abnormalities.

A new visual method for evaluating multiple data (Diagnostic Radar Chart) in general toxicological study.

A Diagnostic Radar Chart method was devised for use in the general assessment of the toxicity of drugs on the basis of visual patterns in toxicity studies. Its usefulness was evaluated on the findings of 32 laboratory items in 3 groups of animal models with experimental pathological conditions. The chart was found to facilitate intuitive discrimination among three types of pathological animal models, evaluation of sexual differences and evaluation of individual differences among the animals for each item. Therefore, if patterns are constructed on the Diagnostic Radar Chart for each of the drugs usable for preparing animal models with typical experimental pathological conditions, the chart is thought to be useful for evaluation or identification of the toxicity of an unknown drug.

[Effect of age on the copulatory behavior of the male rat].

Fifteen male SPF Wistar-Imamichi rats, aged 10, 27 and 44 weeks, that had been raised in the authors' laboratory, were used for the observation of copulatory behavior. Each male was given the opportunity to mate with a proestrous female. During a two hour period, standard measures of copulatory behavior, e.g., mounting, intromission and ejaculation, were documented by a video recording. The following results were obtained; the number of ejaculations in 10-week-old rats, over a two hour period, was 6 to 8. Males showed a subsequent post-ejaculatory interval. The males aged 27 weeks performed 3 to 4 times during the first hour, and then refrained from sexual activity. The copulatory behavior in males aged 44 weeks declined, as compared with that of their 10 and 27 weeks old counterparts.

[Early detection of pregnancy of the rat].

A manual palpation method has been devised for early detection of pregnancy of the rat. One hand gently restrains the animal by holding it from behind in the usual manner. The thumb of the other hand is placed on the posterior abdomen and the first three fingers on the ventral midline. The three fingers were pressed gently upward and laterally. The embryos can then be palpated through the abdominal wall between the thumb and the three fingers. The number of fetuses was not affected by this palpation method. Using this technique, pregnancy was detected on the 5th day of gestation with an accuracy rate of 80% and between the 6th and 9th days with a 100% accuracy.

[Establishment of a rat strain with testicular hypoplasia and its morphological observations].

A testicular hypoplastic (T-H) rat strain, originating from the Wistar-Imamichi rat colony at the Institute for Animal Reproduction, has been maintained by full-sib matings since 1974 for eight filial generations. There were no abnormal signs in external features and growth patterns of the T-H strain. Testicular hypoplasia was detectable at about 8 weeks of age by palpation around the scrotum. Unilateral or bilateral testicular abnormalities were detected in 80 out of 391 males of this strain. The incidences were 32.5% for right side, 48.8% for left and 18.8% for both respectively. Reproductive performance of unilateral T-H males were not different from that of normal. While bilateral ones showed normal sexual behavior, they failed to produce their progenies. In adult T-H rats testicular weight was approximately two-fifth of the normal, and the accessory organs such as the seminal vesicles, epididymis and etc., especially located in the same side of the testicular hypoplasia, reduced their size and weight. Occasionally was seen lack or denaturation of the deferent duct or epididymis. At adult age, no spermatogenesis was observed in all hypoplastic testes with a few exception, and normal spermatogenesis in the testis of the normal side of unilateral T-H male.

[Variation in the number of nipples in Wistar-Imamichi rats (author's transl(].

In order to determine heritability of accessory nipples, variations in the number of nipples were investigated in 13-week old female Wistar-Imamichi rats, maintained as a closed colony in the Institute for Animal Reproduction. Most of the females examined (93.32%) had six pairs of nipples; three in the pectoral and three in the abdomino-inguinal regions. Whereas, 229 out of 3606 rats had one accessory nipple each, 9 animals had 2 accessories, and 3 females were deficient of the pectoral nipple. Most of the accessory nipples were found either in the caudal and cranial regions of the third pectoral nipples or in the regions between the second and third abdomino-inguinal nipples. The frequencies for appearance of the accessory nipples were higher in the pectoral regions than those in the abdomino-inguinal ones, and also in the left side than in the right (p < 0.01), respectively. In 208 out of 791 litters examined, 177 litters had only one sister-mate with accessory nipple, 29 litters had 2 sister-mates with accessories, and 2 litters had 3 sister-mates with accessories, respectively. The localization of accessory nipples of the sister mates within the litter was similar in most of the cases. Heritability of the appearance of accessory nipples was estimated to be 0.8074 by using the formula described by Falconer.