Improvement of hyperglycemia and sexual dysfunction in diabetic female rats by an artificial endocrine pancreas developed from mouse beta cells.

We investigated the effects of a bioartificial endocrine pancreas (Bio-AEP) produced by mouse beta cells on sexual dysfunction of streptozotocin (STZ)-induced diabetic female rats. Female rats were administered STZ (60 mg/kg BW, i.v.) at the age of 10 weeks and transplanted with a Bio-AEP including mouse beta cells at the age of 14 weeks (STZ+Bio-AEP group). Lordosis and proceptive sexual behavior of female rats were observed. The results showed that after the Bio-AEP transplant blood glucose recovered from 380-450 mg/dl induced by streptozotocin to 140-230 mg/dl and suppressed lordosis and proceptive behavior also recovered. These results suggest that it is possible to reverse sexual dysfunction by continuous administration of mouse insulin.

Correlation between body weight (epididymal fat) and permeation rate of serum leptin through the blood-brain barrier (BBB) in male rats aged 8 months.

In this study, in order to clarify the kinetics of leptin, we focused on the ratio of leptin concentrations in cerebrospinal fluid and serum in aged male rats, and examined the weight of epididymal fat, and the passage rate of leptin through the blood-brain barrier. In the lighter animals, the epididymal fat weight was low, while leptin concentrations in the serum and cerebrospinal fluid were also low. Conversely, in the heavier animals, the weight of epididymal fat and leptin concentrations in the serum and cerebrospinal fluid were higher. With regard to the ratio of leptin in the cerebrospinal fluid and serum, the passage rate of leptin through the blood-brain barrier was lower in the heavier animals than in the lighter animals.

Ontogenetic changes of ultrasonic vocalizations emitted from infant rats.

Ontogenetic changes of USVs were investigated to establish an index of stress in infant rats. The USVs were obtained by exposing infant rats to cold stress and were analyzed by real-time spectrography. USV waveforms consisted of four types, R-I, II, III and IV. These USVs were closely monitored at the age of 3-7 days in both sexes. From day 14, the frequency and incidence of USVs gradually decreased and had disappeared completely at the age of 21 days. Therefore, USVs should be useful in estimating the stress of infant rats between the ages of 3-7 days.

Comparison of ultrasonic vocalizations emitted by rodent pups.

Ultrasonic vocalizations (USVs) emitted by rodent pups, mouse, rat, Syrian hamster, vole, and Mongolian gerbil, were compared as a basic study for a screening test of anti-panic drugs. USVs of rodent pups, separated from their mother under a low temperature condition, were collected by Real-Time Spectrogram (RTS) apparatus, and transformed into spectrograms and power spectra by SIGNAL software. Waveforms of USVs emitted by the rodent pups showed several characteristic features, and species specificity of USVs was shown. We think that the species specificity might be due to differences of the anatomical structures in the respiratory tract and respiratory patterns in rodent pups.

Comparative study on circadian rhythms of body temperature, heart rate, and locomotor activity in three species hamsters.

Circadian rhythms of body temperature, heart rate, and locomotor activity were observed in the unanesthetized and unrestrained Syrian hamsters, Djungarian hamsters and Chinese hamsters, and the differences in these biological characters among the three species of hamster were investigated. In each species, body temperature, heart rate, and locomotor activity in the dark period were higher than those in the light period. Heart rate of Chinese hamsters was higher than that of the others in both the light and dark periods. In addition, it was found that the body temperature of Djungarian hamsters decreased rapidly one time a day. These results show species differences in body temperature, heart rate and locomotor activity of Syrian, Djungarian and Chinese hamsters.

Copulatory behavior and fertility of male house musk shrews (Suncus murinus) paired with one, two and four females each.

In order to improve the productivity of house musk shrews, we investigated whether a male could impregnate more than one female within 24 h. Eighteen males and 40 females aged one year were used in this experiment. The mating systems were as follows: one male was paired with one female, one male was paired with two females, and one male was paired with four females. In the fertility rate, six out of 6, 4 of 12 and 4 of 20 females became pregnant and gave birth under three systems, respectively. In the copulatory behavior, numbers of intromissions and ejaculations were more in the 1:1 mating group as compared with the 1:2 and 1:4 groups. We conclude that it is possible for a male to impregnate about one female within 24 h.

Developmental expression of penile reflexes and copulatory behavior in male rats.

First, pubertal development of the penile reflexes, e.g., erections, cups and flips in Wistar-Imamichi male rats was investigated following sheath retraction. Second, the penile reflexes and copulatory behavior in the above males were compared between 10 and 44 weeks of age. The penile reflexes in Wistar-Imamichi rats began to appear from day 26, and all males displayed full components of the reflexes on day 47. The occurrence rates and mean numbers of erections, cups and flips in aged adults were significantly low, compared with the young adults. Also, in the observation of copulatory behavior the occurrence rate of ejaculations, and mean numbers of intromissions and ejaculations in aged adults were significantly lower than that in young adults. These results of the present study may suggest that the decrease of copulatory behavior in male rats with age results from the dysfunction of the penile reflexes with age.