Toshio Tsubota

American black bears, Ursus americanus, are seasonal breeders with a mating season in late spring to early summer. The objectives of this study were to determine whether there are seasonal changes in spermatogenesis and immunolocalization of testicular steroidogenic enzymes, and to correlate these changes with peripheral steroid concentrations. Three captive mature bears were maintained in open cages during the summer season and provided with chambers for denning during the winter. Testicular bi

Toshio Tsubota, Yoshiyuki Takahashi, Hiroshi Kanagawa, Changes in Serum Progesterone Levels and Growth of Fetuses in Hokkaido Brown Bears, Bears: Their Biology and Management, Vol. 7, A Selection of Papers from the Seventh International Conference on Bear Research and Management, Williamsburg, Virginia, USA, and Plitvice Lakes, Yugoslavia, February and March 1986 (1987), pp. 355-358

We examined changes in the concentrations of serum progesterone (P4), estradiol-17beta (E2), FSH, LH, prolactin (PRL), and inhibin to determine their interaction and their effect on the reproductive endocrine controls of pregnant and nonpregnant female Japanese black bears. Fourteen female bears were used in this study over a 2-yr period. In the first year, six of the bears were divided into two groups; a pseudopregnant group and a nonpregnant group. In the second year, the remaining eight bears

The Japanese black bear, Ursus thibetanus japonicus, is a seasonal breeder and shows delayed implantation for several months during pregnancy. The objective of this study was to clarify the steroidogenic capability of the corpus luteum and placenta during pregnancy, including both delayed implantation and fetal development, by immunolocalization of steroidogenic enzymes in these organs of the Japanese black bear. Ovaries and placentae from 15 wild Japanese black bears, which had been killed lega

Ovaries having corpora lutea and uteri of 6 female Hokkaido brown bears (Ursus arctos yesoensis), which were legally killed by hunters from October to December in Hokkaido, Japan, were examined macroscopically and histologically. Four of the 6 female bears had unimplanted embryos in the uterine lumen during the period of delayed implantation between October 19 and November 20. Ovaries of bears which had unimplanted embryos contained the corpora lutea with extensive vacuolation or numerous granul

To clarify how Borrelia miyamotoi is maintained in the environment in Hokkaido, we examined Ixodes persulcatus for its prevalence among wild rodents and its tick vector by detecting a portion of the borrelial flaB gene in rodent urinary bladder and blood samples, and from whole ticks. We compared B. miyamotoi infection rates to Borrelia garinii and Borrelia afzelii, which are human Lyme disease pathogens also carried by wild rodents, and which are transmitted by the same vector tick. Whereas B.

Asiatic black bears (Ursus thibetanus) have a widespread distribution in mountain landscapes, and are considered vulnerable globally, but are low-priority species for conservation in Nepal. Habitat fragmentation, illegal hunting, and human-bear conflict are the major threats to Asiatic black bears across their global range. Having an adequate level of genetic variation in a population helps with adapting to rapidly changing environments, and thus is important for the long-term health of bear pop

In the present study, assay of the serum leptin concentration of the Japanese black bear (Ursus thibetanus japonicus) was attempted using a canine-leptin-specific sandwich enzyme-linked immunosorbent assay (ELISA). The dose-response curve of the bear serum was linear and parallel to the canine leptin standard curve. In mated and unmated bears, the serum leptin concentration was stable at low levels from May to August or September, gradually increased from September or October, and then remarkabl