[Lectin histochemical studies on the scent gland in the Syrian hamster and Mongolian gerbil]

The scent gland and ordinary sebaceous gland of Syrian hamsters and Mongolian gerbils were studied using lectin histochemistry. Male scent glands were larger in size than those of female in both species, but in histochemistry there was no distinct difference between both sexes. Histologically, the scent gland of Syrian hamsters had a strong resemblance to ordinary sebaceous glands, compared to that of Mongolian gerbils. Since the duct of Syrian hamsters was very short, it is difficult to distinguish the duct from the infundibulum. The duct and infundibulum of Mongolian gerbils were larger in diameter than those of Syrian hamsters. The duct widely opened to dermis. Seven lectins (ConA, RCA I, PNA, SBA, UEA-I, DBA and WGA) were used in this study. All of them labelled the differentiated cells of acinus in Syrian hamsters, although SBA did not label those cells in Mongolian gerbils. The cells of the duct in Syrian hamsters and Mongolian gerbils were not labelled with SBA. Ordinary sebaceous glands in both species were labelled with all seven lectins. Lectin-binding patterns of scent glands and sebaceous glands were similar in Syrian hamsters. While, in Mongolian gerbils, SBA-binding patterns were different between scent and sebaceous glands. Histologically, the scent gland of Syrian hamsters resembles the sebaceous gland. Therefore, there is a possibility that the scent gland of Syrian hamsters still provides some properties similar to sebaceous gland.

In vitro development of two-cell embryos obtained from female mice of different ages

Female mice of the IVCS strain (ddN origin), aged 90, 180, 240, 270 and 300 days, were used in this experiment. The percentages of fertilized ova per ova collected from the oviducts, on Day 1 of pregnancy, of mice aged 90 and 180 days were 100% and 91.1%, respectively. Significantly decreased rates of fertilized ova were observed in mice aged 240 to 300 days as compared to 90-day-old controls (P < 0.05). Almost all two-cell embryos collected from 90- to 270-day-old mice developed into blastocysts or expanded blastocysts, and the developmental rate from 2-cell embryo to hatched blastocyst then decreased significantly (P < 0.05). The developmental rate from 2-cell embryo to hatched blastocyst also decreased significantly in 300-day-old mice (P < 0.05). These results demonstrate differences in the viability of mouse embryos collected from mice of different ages.

[Age-related changes in the visual function of WBN/Kob rats: a behavioral study]

Changes in visual function with increasing age were studied in male WBN/Kob rats, a new diabetic strain. In order to detect visual abnormalities in WBN/Kob rats, 5 WBN/Kob and 5 Wistar/ST (control) rats from each group were examined at 5, 9, 13, 17, 23, 27, 36, 45, 54, 67 and 80 weeks of age using dark and light distinction and open-field tests. The rates at which WBN/Kob rats selected the dark area were 85.0 to 100%, 58.8% and 52.6% at 5 to 54, 67 and 80 weeks of age, respectively, while those for Wistar/ST rats were 85.0 to 100% in each age group. Visual abnormality was obvious in WBN/Kob rats aged 67 and 80 weeks, compared with Wistar/ST rats (P < 0.05). There were no significant signs of visual abnormality in the open-field test. Detection of visual abnormality seems to be possible from 67 weeks of age.

[Differences in susceptibility of mice among various strains to oral infection with Corynebacterium kutscheri]

Differences in susceptibility of female mice among 10 strains to Corynebacterium kutscheri infection were studied pathologically and bacteriologically. Twenty mice of each strain were inoculated orally with 4 x 10(5.0) CFU of the bacteria. The gross lesions were observed in 60.0% of BALB/c-nu/nu mice, 25.0% of CBA/N mice, 10.0% of MPS mice, and 5.0% of A/J and C3H/He mice, while BALB/cCr, C57BL/6Cr, B10.BR/SgSn, ddY and ICR mice showed neither clinical signs nor gross lesions. Six BALB/c-nu/nu, two CBA/N and one MPS mice died within 15 days after inoculation. C. kutscheri was recovered from 95.0% of BALB/c-nu/nu mice, followed by 75.0% of A/J mice, 65.0% of CBA/N mice, 55.0% of MPS and BALB/cCr mice, and 30% of C3H/He mice. On the other hand, from C57BL/6Cr, B10.BR/SgSn and ddY mice, the bacteria were recovered at less than 15.0% of the mice. No bacteria were recovered from ICR mice. C. kutscheri colonized most frequently in the cecum, colon and rectum. Number of mice having agglutinating antibodies were less than 20% and their antibody titers ranged from 1:10 to 1:80. These results indicated that there were differences in susceptibility of mice among the strains to oral infection of C. kutscheri. Namely, BALB/c-nu/nu, A/J, CBA/N, MPS and BALB/cCr mice appeared to be susceptible, and C3H/He mice intermediate, while C57BL/6Cr, B10.BR/SgSn, ddY and ICR resistant. BALB/c-nu/nu mice were most susceptible and exhibited markedly severe disease by the infection.

[Copulatory behavior after ectopic pituitary grafting in male rats]

It is known that suppression of copulatory behavior observed in aged male animals is due to elevate prolactin levels, the so-called hyperprolactinemia, found in these animals. The present study was done to determine whether hyperprolactinemia can modify the copulatory behavior of young adult male rats. Hyperprolactinemia was induced by grafting one or two pituitary glands of adult males of the same strain under the kidney capsules of each sexually experienced male. Grafted animals exhibited suppressed copulatory behavior patterns when tested one month after pituitary transplantation. The animals given two pituitary grafts differed from the sham-operated controls in latency to intromit (P < 0.05), as well as in the numbers of intromission (P < 0.05) and ejaculation (P < 0.01). After tests of copulatory behavior, serum concentrations of LH, FSH, prolactin and testosterone were measured by radioimmunoassay. Serum levels of prolactin were significantly increased (P < 0.05) in the animals given 2 grafts, compared with sham-operated controls. From these results, suppression of copulatory behavior in the young adult animals grafted was similar to that in aged adults. The findings suggest that decline of copulatory behavior with increasing age results from chronic elevation of prolactin.

[Morphology of the scent gland in the vole]

The presence of the scent glands were examined macroscopically and histologically in the Japanese vole, Microtus montebelli and the Hungarian vole, Microtus arvalis. A pair of scent glands were observed on the buttocks of the Japanese vole as the oval nodules with yellowish colored skin. The size of the glands was larger in males than in females. Histologically, the glands were composed of the aggregation of many acini of sebaceous glands. The epidermis above the scent glands were thicker than that in the other areas. In the Hungarian vole, no such gland could be detected with macroscopical and histological examinations.

[Visual evoked potential from dura in rats]

Visual evoked potentials (VEPs) were recorded from 8 different points (from points A and B near the bregma to points G and H near the occipital bone) of the dura under parietal bone in rats. The study was performed with 68 adult male Slc: Wistar/ST rats weighing 259.9-298.0g. VEPs recorded from the dura had a large negative component with a peak around 45 msec (N1), a large positive component with a peak around 75 msec and a large negative component with a peak around 120 msec (N2). Points A and B were not suitable for recording of the VEPs because some rats showed no N2 peak. The amplitude of peaks N1 to P at point E, upper the left optic layer of the superior colliculus, was higher than those from other points. Point E was the best position for recording of the VEP from dura in Slc: Wistar/ST rats.

[Lectin histochemical studies on the musk gland in the house musk shrew (Suncus murinus)]

The musk gland of the adult house musk shrews (Suncus murinus) of both sexes was studied lectin histochemically. The musk gland was a kind of scent gland, consisted of congregation of branched or unbranched simple tubuloalveolar gland holocrine in nature and was attached by an apocrine gland-like structure (sweat gland) in the deeper layer of its periphery. Acinar cells of the musk gland were distinguishable into three type from basal to luminal parts of the acinus; immature cells, mature cells and degenerating cells. There was no histological difference between both sexes. Lectin-binding pattern of the musk gland was examined in comparison with that of the sweat gland and ordinary sebaceous gland by histochemical staining techniques using seven lectins: ConA, RCA I, PNA, SBA, UEA-I, DBA, WGA, WGA and PNA labelled the duct of the musk gland more intense than the acinus. Several lectins showed a tendency to label the cells situated near the luminal surface more intense than those near the basement membrane in both the acinus and duct of the musk gland. In the sweat gland and ordinary sebaceous gland, the lectin-binding pattern was different with each other and from that in the musk gland. These findings suggest that the musk gland, sweat gland, and ordinary sebaceous gland are different to each other in nature of cells and the secretion.

[Comparison of sexual behavior patterns in small laboratory animals]

It is known that in the reproductive systems, aged-related changes are prominent. Similarly, in normal nonhuman primates and other mammals such as rats, various sexual activities of male and female decline with aging. The purpose of the present study was to clarify the pattern of sexual behavior in matured mice, voles, Syrian hamsters, rats, guinea pigs, rabbits and house musk shrews of both sexes, and to select the appropriate animals for studies of aged-related changes in sexual behavior. There were species differences among laboratory animals in the pattern of sexual behavior. In summary, hamsters and rats ejaculated about three times during 30 min, while mice did once during 10 hrs. The former animals showed the intromission and ejaculation within a few min and 10 min, respectively, the latter did the ejaculation a few hrs after introduction of a heat female. In female animals, rats displayed receptive and proceptive behaviors, while hamsters and guinea pigs did only receptive behavior. From the above results, rats of both sexes may be recommended for studies of aged-related changes in sexual behavior.

[Possibility of detecting visual functional disturbance in rats by the open-field test]

In order to determine whether visual disturbance in small rodents is detectable by means of the open-field test, the ambulation scores of enucleated and intact rats in an open-field were measured. In a 30-min test of Slc:Wistar/ST rats, there were significant differences in ambulation scores between enucleated and intact rats in the first 10-min. In addition, the effects of observation times (09:00-11:00, 13:00-15:00 and 17:00-19:00 hr) and strains on the open-field test were studied using a 10-min test. Regardless of observation times, ambulation scores of enucleated rats of the Slc:Wistar/ST and F344/N Slc strains were significantly elevated as compared with those of intact rats from both strains. When tested during the 13:00-15:00 hr period, there were significant differences in the Slc:SD rats. These findings indicate that the changes in ambulation are due to visual disturbance. However, significant ambulatory changes in F344/N Slc rats were documented at the three different observation times. Based on these results, Slc:Wistar/ST rats appear to be suitable for detecting visual disturbance by the open-field test.

[Fine structure of the vomeronasal organ in the house musk shrew (Suncus murinus)]

Fine structure of the vomeronasal organ (VNO) was examined in an insectivore, house musk shrew (Suncus murinus), from a viewpoint of comparative anatomy. The VNO was a pair of tubular structure, about 6mm in length, and situated at the base of the nasal septum. The medial wall of the lumen of the VNO was lined with the sensory epithelium (SE) consisting of sensory, supporting and basal cells, while the respiratory epithelium (RE) lining the lateral wall was pseudostratified and covered with microvilli. Jacobson's glands were distributed on the dorsolateral to ventrolateral side of the VNO and opened to the lumen in the transitional region from the RE to the SE. Their secretion was PAS-positive bu talcian blue-negative. Ultrastructurally, sensory cells of the SE were bipolar neurons and covered on their free surface with conspicuously long microvilli. The other ultrastructural features in sensory, supporting and basal cells were similar to those in previously reported species. The ultrastructural features of the RE were also similar to those in previous reports except that the free surface was covered with microvilli instead of cilia. In addition, a few kinds of migrating cells were often observed in both the SE and the RE. Acinar cells of Jacobson's glands possessed a round to elliptical nucleus and many large secretory granules, about 1,000 nm in diameter. Rough endoplasmic reticulum and Golgi apparatus were well developed in their cytoplasm.(ABSTRACT TRUNCATED AT 250 WORDS)

Copulatory behavior of sexually inexperienced male guinea pigs paired with synchronized estrus females

The copulatory behavior in sexually inexperienced male guinea pigs aged 12 weeks was observed under dim red illumination. The synchronized estrus females, which were used for receptive females, received a subcutaneous implantation of progesterone-filled tubing for 2 weeks, followed by 0.5mg progesterone injection. Females given these treatment exhibited the lordosis behavior at 19:00 and 21:00 h on 4th day, and had ovulated by 09:00 h on 5th day after removal of implant. During a 2-hrs test session, standard measures of copulatory behavior were recorded. The ejaculation could be observed within the first 30 min in 6 of 7 males. The mounts, intromissions and ejaculation in male guinea pigs were shown in a lower frequency and longer latency than those of rats and hamsters.

[Comparison of the gold wire electrode with cotton wick electrode for electroretinography in small laboratory animals]

Using the gold wire and cotton wick electrodes, the electroretinograms of mice and rats were measured, and then they were compared. The results obtained were as follows: 1) There were no remarkable differences in the latencies and amplitudes of a- and b-waves, amplitudes and numbers of waves of oscillatories between two different electrodes. 2) It was easy to make and maintain the gold wire electrode as compared with the cotton wick electrode. From these results, it appears that the gold wire electrode is useful for measuring the electroretinogram of small laboratory animals.

[Fertility of male Syrian hamsters paired with one, two and four proestrous females each]

In order to improve the productivity of Syrian hamsters, we investigated whether a male could impregnate overnight more than one proestrous female. Twenty-one males and 49 females aged 8 to 10 weeks 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. Six out of 7, 7 of 14 and 4 of 28 females became pregnant and gave birth under these three systems, respectively. We conclude that it is possible for a male to impregnate overnight about one female under the above mating systems.

[On the flank gland in Syrian hamsters]

The scent gland of Syrian hamsters is named the flank gland and thought to play an important role in the communication among individuals of the same species as in a few other rodents. In the present paper, the flank gland of Syrian hamsters of both sexes was macroscopically and histologically studied with special reference to the aging. This gland reached the plateau in size at 21 days of age in females, while it continued to develop until 70 days of age in males. Its shape was circular in adult females, and elliptical in adult males, respectively. Histologically, it was identified as the developing sebaceous glands with hair follicles in both sexes at 21 days of age. Thereafter, it gradually increased in size and number of lobules. It was always better developed in males than in females at each day examined in the present study, although there were no sex differences in its histological structure.

[Diurnal rhythms in locomotor activity of the house musk shrew, Suncus murinus]

A diurnal rhythm of locomotor activity in male and female house musk shrews (Jic:SUN) aged approximately one year was observed under a schedule of 12 hr light and 12 hr darkness (light on at 07:00) over a period of 10 days. In general, the pattern of locomotor activity was similar in both sexes, with around 24-hr diurnal rhythm. A few typical patterns of locomotor activity in these animals were as follows: A. Locomotion interval was close in the light phase, while was sparse in the dark phase. B. As opposed to the pattern of A, locomotion interval was close in the dark and sparse in the light phases. C. Its interval remains stationary through a whole day.

Effects of p-chloroamphetamine (PCA) on ejaculation in aged rats

In general, sexual activity in normal animals declines with increasing age. In aged male rats, for example, no ejaculation occurs when paired with receptive females. The ejaculatory response induced by p-chloroamphetamine (PCA) in aged adult rats, 14 to 18 months of age, was observed. The animals were treated intraperitoneally with PCA. The ejaculation rates were 0.28.6, 57.1 and 100% at doses of 0.3125, 0.625, 1.25 and 2.5 mg/kg, respectively. These animals, with a few exceptions, showed an ejaculation within 2 hrs of PCA injection. These data for aged adults are similar to those for young adults.

[The change with age of the copulatory behavior of the male rats aged 67 and 104 weeks]

Changes with age in sexual fertility in male rats of the Wistar-Imamichi strain were investigated. Litter size and numbers of implantation sites in females mated with males aged 14 to 44 weeks tended to decrease with increased aging of males. These indicators in females mated with males aged over than 44 weeks decreased, compared with that aged 14 to 44 weeks (P < 0.05 to 0.001). In addition, all females mated with males aged 95 weeks were not pregnant. In male copulatory behavior with aging, incidences and numbers of mounting at 67 and 104 weeks of age were 100%, 42.6 +/- 15.3 (Mean +/- S.D.) and 42%, 1.8 +/- 2.8, respectively. The intromission and ejaculation were observed at 67 weeks, but not at 104 weeks of age. These incidences and frequencies were 86%, 10.3 +/- 10.2 for intromission, and 43%, 1.0 +/- 1.3 for ejaculation. Mount latencies (ML) at 67 and 104 weeks of age were 535.4 +/- 607.9 and 3,822.0 +/- 1,753.4 sec, respectively. There were significant differences in ML between two groups (P < 0.05). At 67 weeks of age, intromission and ejaculation latencies, and post-ejaculatory intervals were 2,563.0 +/- 2,216.3, 1,633.7 +/- 977.6, and 657.3 +/- 320.6 sec, respectively. The pregnant rate and numbers of implantation sites in females mated with males aged 67 weeks were 43% and 5.4 +/- 6.8, respectively. In females mated with males aged 104 weeks, all were not pregnant. The weights of tests, epididymides, ventral prostate and seminal vesicles at 104 weeks were light, compared with those at 67 weeks of age (P < 0.05). From these results, the copulatory behavior in male rats of the Wistar-Imamichi strain declined with aging. Sexual fertility in males aged 67 weeks decreased in less than 50%, and males aged 104 weeks showed no intromission and ejaculation.

[Diurnal rhythm of drinking activity in the house musk shrew]

A diurnal rhythm of drinking activity in 7 male and 6 female house musk shrews (Jic: SUN) aged about one year was observed over a period of 10 days under a schedule of 12 hr light and 12 hr darkness (light on at 07:00). In general, the pattern of drinking activity was similar among both sexes, with around 24-hr diurnal rhythm. A few typical drinking patterns of these animals were represented as follows: 1) Drinking interval was very close in the dark phase, while it was a little too sparse in the light phase (n = 4). 2) Its interval remains stationary through a whole day (n = 5). 3) Drinking was performed between the latter half of light and the first half of dark phases (n = 4).

[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.

[Comparison of the amounts of hCG and PMSG to induce ovulation in 50% of the animals, mice, Syrian hamsters and rats]

On the day of diestrus, female mice, syrian hamsters and rats, showing regular 4-day estrous cycles, were injected with hCG or PMSG and were inspected for the presence of ovulation the following day. The dose level expected to cause an effect in 50% of the animals (ED50) was calculated using the Van der Waerden method. When hCG was injected into i. v., i. p. and s. c., the ED50 values per animal and per body weight (kg) in parenthesis were as follows; 0.2 (7.7), 0.3 (11.5) and 0.7 (26.9) I. U. for mice, 1.0 (9.5), 1.8 (17.1) and 2.6 (24.8) I. U. for syrian hamsters and 1.3 (4.6), 3.5 (12.3) and 7.5 (26.3) I. U. for rats, respectively. In PMSG study, the ED50 values per animal and per body weight (kg) in parenthesis were as follows: i. v., 0.8 (30.8); i. p., 2.0 (76.9); s. c., 2.8 (107.7) I. U. for mice, i. v., 3.6 (34.3); i. p., 8.0 (76.2); s. c., 13.2 (125.7) I. U. for syrian hamsters and i. v., 6.0 (76.8); i. p., 20.8 (73.0); s. c., 76.8 (269.5) I. U. for rats, respectively. From these results, the intravenous ED50 value was lower than other routes in three rodents with hCG or PMSG. In all injection routes, the ED50 value for mouse was lower than others. However, there were not significant differences in the ED50 values per body weight (kg) among three rodents. In particular, subcutaneous ED50 of hCG and intraperitoneal ED50 of PMSG were almost same values among three rodents, respectively. Given that the ED50 value per body weight (kg) in one of three rodents is determined, its value may be possible to be extrapolated to remaining two rodents.

[Improvement of pituitary homograft under the kidney capsule in mice]

The model of hyperprolactinemia induced by pituitary homografts under the kidney capsule has been used mainly in the field of reproductive physiology. The authors report an improved method for pituitary grafting in mice. The procedure was as follows: 1. The male pituitary glands with normal saline were aspirated into a polyethylene tube. 2. Two incisions were made in the kidney capsule. 3. The polyethylene tube with pituitary glands was inserted via a large incision. 4. Blowing air into the tube, the pituitary glands were left under the kidney capsule and normal saline streamed out of a small incision. Using this method, all pituitary grafted mice became pseudopregnant.

[The application of industrial endoscope to observation of the ocular-fundus in small laboratory animals]

Observation and recording methods of the ocular-fundus in small laboratory animals were studied using the industrial endoscope and VTR systems, respectively. The ocular-fundus was observed widely, brightly and clearly in the usual animal facility. In addition, the ocular-fundus was recorded easily and it was possible to examine the ocular-fundus recorded by the VTR systems.