Biomedical subjects

H Amao

Publications and source records attributed to H Amao.

At least 19 recordsLinked to original sources

PubMed2000

Functional natural killer T cells in experimental mouse strains, including NK1.1- strains.

Natural killer T (NKT) cells are a newly discovered subset of lymphocytes. It appears that this subset has potential as important regulators of immune responses. But because there are relatively few NKT cells in lymphoid organs and because of technical difficulties in detecting NKT cells in most mouse strains, the roles of NKT cells have not been fully identified and little attention has been paid to the roles of NKT cells in immunological experiments in which NK1.1- strains were used. To examine the existence of functional NKT cells in various strains of experimental mice, including NK1.1- strains, we utilized alpha-galactosylceramide (KRN7000) which is thought to react specifically with NKT cells. Indeed, we could confirm that early cytokine (IL-4 and IFN-gamma) secretion at 2 h after the injection of KRN7000 was dependent on NKT cells. With this in vivo system, we have successfully detected the presence of functional NKT cells in various mouse strains, including AKR/N, BALB/c, C3H/HeJ, C3H/HeN, C57BL/6, C.B-17, CBA/N, NC, NOD, SJL, W/Wv, aly/aly and aly/+. Notable increases of serum IL-4 were detected in W/Wv and aly/+ strains, and defective response of IFN-gamma in SJL mice and that of IL-4 in NOD mice were observed. This is the first report to show the functional significance of NKT cells in cytokine secretion in various mouse strains in response to a ligand for the T cell receptor of NKT cells.

Adjuvants, Immunologic↗

PubMed2000

Marking behavior is innate and not learned in the Mongolian gerbil.

We studied whether marking behavior in Mongolian gerbils would be innate or learned behavior. The marking behavior was defined as "animals rubbing their abdominal scent glands on small protruding objects". Between 21 and 90 days of age, Mongolian gerbils, which were kept under such conditions that they would be unable to learn this behavior, were observed at intervals of 5-15 days to find out if there were signs of the behavior or not. Six male and four female Mongolian gerbils were used for observing. Neonate Mongolian gerbils during the age of 3 to 28 days were fostered by ICR mother mice. Weaning Mongolian gerbils were then individually kept away from the others. Marking behavior was observed in 2 out of 6 males at 50 days of age and 2 of 4 females at 60 days and the mean frequency of the marking behavior for 10 min was 3.5 in the males and 5.0 in the females. These results suggest that marking behavior was innate and not learned behavior in Mongolian gerbils.

Animals↗

PubMed1999

Observation of marking-like behavior, marking behavior, and growth of the scent gland in young Mongolian gerbils (Meriones unguiculatus) of an inbred strain.

A marking-like behavior (defined by authors), a marking behavior, and growth of the scent glands were observed in young Mongolian gerbils of an inbred strain. In males and females, a marking-like behavior, in which animals rub their abdominal scent glands on the floor, began to be seen at the age of 19 days and could be seen in almost all the gerbils at 22 days of age during the suckling period. The frequency of this behavior was highest at 60 days of age (males: 17.9/10 min, females: 15.4/10 min) and there was no sex difference. Marking behavior, in which animals rub their abdominal scent glands on small protruding objects, began to be seen at the age of 40 days in males and 50 days in females. The frequency of this behavior tended to increase until 90 days of age in males (13.7/10 min), but the levels were low (2.5-5.0/10 min) in females. The values in the male group therefore tended to be higher than that in the female group. Macroscopic scent gland pads were clearly observed at the age of 30 days in males, but not until 45 days of age in females. At the age of 45-90 days, the length of the scent gland pad in males and females was 2.1-2.8 and 1.6-1.7 cm, respectively and the width was 0.3-0.5 in males and 0.2-0.3 cm in females. During this period, the length and depth of the pads in males were significantly greater than those in females (p < 0.05). Histological examination of the structure of the scent glands after the age of 45 days showed that the development of clusters of acinar cells in females occurred much later than that in males, but the basic structure of these glands was similar in both sexes. These results suggest that the marking-like behavior was manifested although during the period when the scent glands had not yet developed, whereas true marking behavior first occurred when the glands were moderately well developed.

Aging↗

PubMed1999

Sex differences in susceptibility of ICR mice to oral infection with Corynebacterium kutscheri.

Sex difference in susceptibility to oral infection with Corynebacterium (C.) kutscheri was experimentally studied in ICR mice. Immature (4-week-old) and adult (14-week-old) mice were inoculated with two infecting doses of C. kutscheri, and necropsied for bacteriological and serological survey 4 weeks after the bacterial infection. No macroscopic lesions at necropsy were demonstrated, except for one adult male given 10(9) bacteria. In immature mice, C. Kutscheri isolated from the oral cavity and cecum with FNC agar, were recovered in only 40.0% of female mice but in 90.0% of male mice given 10(6) bacteria (p < 0.05), and in only 55.6% of female mice but in 80.0% male mice given 10(8) bacteria. In adult mice given 10(9) bacteria, the organism were recovered in only 45.5% of female mice but in 90.9% of male mice (p < 0.05), furthermore, the mean number of organisms in the cecum of male mice harboring the organism was significantly higher than that in females (p < 0.01). Castration caused an increase in host resistance in adult male mice. These results indicated that ICR male mice were more susceptible than females, in terms of bacterial colonization in the cecum and the oral cavity, to oral infection with C. kutscheri.

Aging↗

PubMed1995

Pathogenicity of Corynebacterium kutscheri in the Syrian hamster.

The pathogenicity of Corynebacterium kutscheri isolated for the first time from Syrian hamster was experimentally studied in hamsters. In hamsters given intramuscular (i.m.) or subcutaneous (s.c.) inoculation with 10 or 10(3) bacteria, neither clinical signs nor gross lesions were found. In those given 10(5) bacteria i.m., moderate proliferation of granulation tissue was found in the muscle of the inoculation region at necropsy. In the animals given 10(5) bacteria s.c., a nodular lesion was observed at the inoculation site 2 days post-inoculation (p.i.), but the nodules subsided gradually from 6 days p.i. and were unclear 10 days p.i. At necropsy, small abscesses were found in all the animals in this group. In those given 10(7) bacteria either i.m. or s.c., lesions were clearly observed at the inoculation site 1 to 10 days p.i., and a large abscess was noted at necropsy. The organisms were isolated only from the lesions in the groups. Agglutinating antibody in the sera was detected only in the animals given 10(5) or 10(7) bacteria. This suggests that 10(5) of C. kutscheri are needed to form localized nodular abscesses in Syrian hamsters.

Animals↗

PubMed1995

Natural and subclinical Corynebacterium kutscheri infection in rats.

Distribution of Corynebacterium kutscheri was determined in 41 rats housed in a conventionally managed colony that were infected naturally and subclinically. At 2, 5, 10, 20 and 25 months after initial isolation of C. kutscheri, attempts were made to isolate C. kutscheri from 17 sites, with a new selective medium, FNC agar. In total, the prevalence (97.6%) of C. kutscheri isolation was significantly (P < 0.001) higher than the frequency (70.7%) of antibody detection. None of the rats manifested any distinct clinical signs of disease and macroscopic lesions caused by C. kutscheri were not detected. In 40 rats with subclinical infection, the organisms were most frequently isolated from the oral cavity, esophagus, cecal contents, and colon and rectum (> 95.0%). The isolation rate was next highest in the trachea, submaxillary lymph nodes, and nasal cavity (47.5 to 52.5%). The organisms hardly colonized the lung, liver, and kidney. Mean numbers of organisms found in the esophagus, cecal contents, and colon and rectum ranged from 10(3.9) to 10(4.2) CFU/g, and were significantly (P < 0.05, P < 0.01) high in comparison with those in the lung. These results indicated that many healthy rats in the naturally infected colony harbored C. kutscheri, and the organisms colonized the oral cavity, esophagus, cecal contents, and colon and rectum most frequently.

Animals↗

PubMed1995

Natural habitats of Corynebacterium kutscheri in subclinically infected ICGN and DBA/2 strains of mice.

Subclinically infected mice of ICGN and DBA/2 strains housed in a conventionally managed colony were examined to determine natural habitats of Corynebacterium kutscheri. At 5, 7, 9, 12 and 13 months after initial isolation of the organism from oral cavity and cecal contents of five ICGN mice, attempts were made to isolate C. kutscheri from 19 sites using a new selective medium, furazolidone-nalidixic acid-colimycin agar. From the initial survey to 13 months, C. kutscheri was isolated from 27 of 29 ICGN mice (93.1%) and 9 of 10 DBA/2 mice (90%). In contrast, antibody against C. kutscheri was detected in only 3 of 29 ICGN mice (10.3%). None of the mice manifested distinct clinical signs of infection, and only 1 ICGN mouse had macroscopic lesions such as hepatic abscess and large spleen. In 21 ICGN and 9 DBA/2 mice that harbored the organism without macroscopic lesions, the organisms were most frequently isolated from the oral cavity (ICGN:100%, DBA/2:66.7%), cecum (ICGN:95.2%, DBA/2:100%), and colon and rectum (ICGN:95.2%, DBA/2:100%). Remarkable differences between the two mouse strains were observed in colonization of the nasal cavity (ICGN:85.7%, DBA/2:0%) and trachea (ICGN:71.4%, DBA/2:33.3%). In mice of both strains, the organisms rarely colonized the lung, liver, and kidney. Mean numbers of organisms in the cecum, and colon and rectum ranged from 10(4.1) to 10(4.6) colony-forming units/g and were significantly higher in comparison with those in the small intestine (P < 0.01, P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

[Investigation of the development of dermatitis in hypotrichotic rats--microbiological study].

The hereditary hypotrichotic (WBN/IIa-Ht) rat is affected by dermatitis characterized by erosions and crust formation on dorsal skin areas. The bacterial flora of this dermatitis and the normal skin of the hypotrichotic rat was examined. As controls the cutaneous flora of atrichotic and Wistar rats was examined, and the results compared with those in hypotrichotic rats. The total number of bacterial colonies from the lesions and normal skin of hypotrichotic rats were 3.9 x 10(5) to 1.16 x 10(8) CFU/cm2 and 1.6 x 10(3) to 1.8 x 10(4) CFU/cm2, respectively. In the lesions, overwhelming numbers of S. aureus were detected as almost pure cultures. In the normal skin, S. aureus was predominant, accounting for about 90% of all bacteria. The total number of bacterial colonies in the atrichotic rats was the same as in the hypotrichotic rats. The majority of the isolates were Staphylococcus sp., and about half of them were identified as S. aureus. The total number of bacterial colonies from the skin of individual Wistar rats varied extremely, ranging from 64 to 2.98 x 10(5) CFU/cm2. The flora mainly consisted of coagulase-negative Staphylococcus (CNS), S. aureus, and alpha-hemolytic Streptococcus sp., and CNS was isolated most frequently. Histopathological examination of the eroded portions in hypotrichotic rats revealed many clusters of coccoid bacteria and neutrophilic cell infiltration of the epidermis. These findings suggest that the dermatitis in hypotrichotic rats was caused by S. aureus and affected by unknown traits of these rats.

Animals↗

PubMed1993

Comparison of etiological and immunological characteristics of two attenuated Erysipelothrix rhusiopathiae strains of serotypes 1a and 2.

Two acriflavine-fast attenuated Erysipelothrix rhusiopathiae strains Koganei 65-0.15 of serotype 1a (strain Kg-1a) and 2 (strain Kg-2) were comparatively characterized. Biochemical characterization showed the similar reactions with slight variation between the strains. Strain Kg-2 was more resistant to acriflavine dye than strain Kg-1a. Pathogenicity of strain Kg-2 was higher than strain Kg-1a in mice of strains ddY. C3H/He and A/J. Significant differences of clinical signs between strains Kg-1a and Kg-2 were observed in occurrence of arthritis (P < 0.05) and systemic signs (P < 0.01) of only ddY mice. C3H/He mice was more resistant than ddY and A/J mice to the infection of strains Kg-1a and Kg-2. Three culture fractions, whole culture: WC, culture filtrate: CF and killed cells: KC, of strain Kg-2 were more protective than those of strain Kg-1a in ddY mice. CF of strain Kg-2 was most protective in all fractions. Heating at 56 degrees C and 100 degrees C or treatment with trypsin completely reduced the protective activity of WC of the two strains, indicating that major protective antigens of WC were protein. The present results demonstrated that immunogenicity and pathogenicity for mice were different between the two attenuated strains.

Acriflavine↗

PubMed1993

[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.

Animals↗

PubMed1993

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.

Aging↗

PubMed1992

Effects of naloxone and naltrexone on receptive and proceptive behaviors in female rats.

The sexual receptive and proceptive behaviors induced by opiate antagonists, naloxone and naltrexone in estrogen-primed ovariectomized rats were observed under the presence of sexually active males. The females were treated intraperitoneally with naloxone or naltrexone at doses ranging from 0.5 to 4.0 mg/kg and the sexual behavior of females was tested before and after the injection of drug. The results obtained suggest that the opiate antagonists play a role in the regulation of lordosis behavior, but not proceptive behavior in female rats.

Animals↗

PubMed1992

[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.

Animals↗

PubMed1991

Copulatory behavior of sexually inexperienced male voles paired with proestrous females.

The copulatory behavior in sexually inexperienced male voles aged 9-13 weeks old was observed under dim red illumination. Proestrous females were used as stimulus voles in copulatory behavior tests. A 30-min test session was recorded. All males showed at least one ejaculation within 30 min. In addition, the pattern of copulatory behavior in male voles was compared to that reported previously in male hamsters. The frequencies of mount, intromission and ejaculation in male voles were similar to that in male hamsters but there were significant differences in the latencies of mounting, intromission, ejaculation and post-ejaculation between the two species.

Animals↗

PubMed1991

p-Chloroamphetamine-induced ejaculation and the 22-kHz vocalization of the male rat.

It is well known that the male rats paired with receptive females emit the 22-kHz vocalization after ejaculation. The question addressed is whether after ejaculation injected with PCA without receptive females the 22-kHz call would be emitted. Emission of the 22-kHz call in males injected by PCA was not observed after ejaculation.

Animals↗

PubMed1991

Pre- and post-implantation losses of embryos in aging female IVCS mice.

Mated female mice of the IVCS strain, aged 90 (control group), 180, 210, 240, 270, 300, 330, 360 and 420 days old, were studied for pre- and post-implantation loss of embryos. The percentage of pre-implantation loss in mice aged 90 to 210 days was 1.7/11.8 (14.4%) to 2.7/11.7 (23.1%). In mice aged 240 to 300 days it increased significantly as compared to the controls (46.5-90.2% versus 14.4%). It reached 100% in 300-days-old mice. The post-implantation loss of embryos and/or fetuses in mice aged 90 to 240 days was 1.0/10.2 (9.8%) to 2.5/9.0 (27.8%). In mice aged 270 to 300 days it increased significantly compared to the controls (100% versus 9.8%). The decrease in reproductive activity appeared first in a decrease in litter size, followed by a decrease in the number of blastocyst and implantation sites, and finally by anovulation during the process of aging in IVCS mice.

Aging↗

PubMed1991

Central effects of yohimbine on copulatory behavior in aged male rats.

It is well known that yohimbine has a history of popular use because of its supposed aphrodisiac properties. The present study was done to determine whether yohimbine can modify the copulatory behavior of aged male rats. Adult male rats of the Wistar-Imamichi strain, 52 weeks of age and weighing 600-650g, were injected intracerebroventricularly with yohimbine hydrochloride (5, 10 micrograms/10 microliters/rat) or vehicle. Each male was then given the opportunity to mate with a receptive female for 30 min after administration of yohimbine or vehicle. Yohimbine produced significant decreases in the latency to initial mounting and significant increases in the number of mountings. However, there was no ejaculation in the yohimbine-and vehicle-treated males. This study is the first to clearly establish an important modulator of sexual arousal for yohimbine in aged male rats.

Aging↗

PubMed1991

Effects of methamphetamine on copulatory behavior in male rats.

Many papers have reported the effect of amphetamine and its close relative, methamphetamine on sexual activity in humans. The effect of these drugs on animal sexual behavior is unknown. The present study was done to determine whether methamphetamine modifies the copulatory behavior of male rats. Sexually experienced rats of the Wistar-Imamichi strain, 10 weeks of age, were singly injected intraperitoneally with methamphetamine hydrochloride at doses of 0, 1, 2 or 4 mg/kg body weight. Tests were initiated at 19: 30 in the dark period. Observations were conducted for 90 min. At dosages of 1 or 2 mg/kg there were no changes in copulatory behavior ascribed to the administration of methamphetamine. At 4 mg/kg the frequencies of mounting, intromission and ejaculation were greatly decreased but the spontaneous motor activity and stereotypic behavior increased in all males. In a further experiment, males were given methamphetamine by intraperitoneal injection once a week for 8 weeks. The copulatory behavior was tested 5 times at two weeks intervals. In the 4th testing, the percentage showing ejaculation decreased. In the 5th testing, there was no ejaculation and the incidence of intromission decreased. No stereotypic behavior was displayed in any of the males during the testing. From these results, it was concluded that methamphetamine inhibits the intromitting and ejaculating behavior in male rats.

Animals↗