ABSTRACT. Four adult Hokkaido brown bears were used as semen donors, and semen characteristics were examined before freezing and after thawing. A total of 10 electroejaculates were diluted with Tris-egg yolk extender and cooled to 4°C over 90 min. Spermatozoa were equilibrated with 4.7% glycerol for 80 min. Semen packed in 0.25 ml plastic straws were frozen with liquid nitrogen vapor. Percentages (mean ± SD) of motile and live sperm were 96 ± 2 and 86.5 ± 7.2% before freezing, and 43 ± 5 and 67.4 ± 3.9% after thawing, respectively. Although the number of progressively motile sperm after thawing varied among samples (1.8 ± 1.2 × 10 8 cells/ejaculate), frozen semen in the present study might serve for artificial insemination. KEY WORDS: brown bear, freezing, spermatozoa.J. Vet. Med. Sci. 64(4): 373-376, 2002 The Hokkaido brown bears are found only in Hokkaido Island, Japan, and their genetic diversity is known to be low [15]. An assisted reproductive technology like artificial insemination could contribute to the maintainance of their genetic diversity. We previously reported a successful semen collection of the Hokkaido brown bear by electroejaculation [7]. Semen cryopreservation is an essential procedure for assisted breeding; however, there are only a few reports on cryopreservation of the bear semen [2,9]. The objective of the present study was to examine the potential of a freezing procedure used for bull semen with a modification in glycerol concentration.Four adult males, aged 7 to 16 years and maintained at Noboribetsu Bear Park (Noboribetsu, Japan), were used as semen donors. They were kept in male groups and separated from females. A total of 10 trials of electroejaculation were conducted during the breeding season (May to July) in 1996 and 1997. Electroejaculation was conducted as described previously [7]. Briefly, bears were immobilized with tiletamine HClzolazepam HCl (Zoletil; Virbac S. A., Carros, France) in 8 trials, and with midazolam (Dormicum; F. Hoffman-La Roche Ltd., Basel, Switzerland) and ketamine HCl (Ketalar; Sankyo Co., Ltd., Tokyo, Japan) in 2 trials. After immobilization, a handmade bipolar rectal probe with two ring electrodes was inserted into the rectum. The electrical stimulation with 60 Hz alternative current, sine wave and 5 V was repeated till ejaculates were obtained. The semen was assessed by determining ejaculate volume, pH, sperm concentration and the percentage of abnormal sperm as described elsewhere [7]. The percentage of viable spermatozoa was determined by an eosin-nigrosin staining method [7] before and after freezing. Small aliquot of raw and frozen-thawed semen was taken for the assessment of sperm motility. Percentage of sperm in each type of progressive motility status was calculated under a light microscope using a scale of 0 to 4: 0, no movement; 1, slight side-to-side movement with no forward progression; 2, side-to-side movement, slow and steady forward progression; 3, steady, moderate forward progression; 4, steady, rapid forward progression. The total perce...
The vomeronasal organ (VNO) is a peripheral receptor structure that is involved in reproductive behavior and is part of the vomeronasal system. Male bears exhibit flehmen behavior that is regarded as the uptake of pheromones into the VNO to detect estrus in females. However, the morphological and histological features of the VNO in bears have not been comprehensively studied. The present study investigated the properties and degree of development of the VNO of the brown bear by histological, histochemical and ultrastructural methods. The VNO of bears was located at the same position as that of many other mammals, and it opened to the mouth like the VNO of most carnivores. The shape of the vomeronasal cartilages and the histological features of the sensory epithelium in the bear VNO were essentially similar to those of dogs. Receptor cells in the VNO of the bear possessed both cilia and microvilli like those of dogs. The dendritic knobs of receptor cells were positive for anti-G protein alpha-i2 subunit (G ) but negative for anti-G protein alpha-o subunit indicating preferential use of the V1R-G pathway in the vomeronasal system of bears, as in other carnivores. The VNO of the bear possessed three types of secretory cells (secretory cells of the vomeronasal gland, multicellular intraepithelial gland cells and goblet cells), and the present findings showed that the secretory granules in these cells also had various properties. The vomeronasal lumen at the middle region of the VNO invaginated toward the ventral region, and this invagination contained tightly packed multicellular intraepithelial gland cells. To our knowledge, this invagination and intraepithelial gland masses in the VNO are unique features of brown bears. The VNO in the brown bear, especially the secretory system, is morphologically well-developed, suggesting that this organ is significant for information transmission in this species.
Keyword:brown bear, sebaceous gland, testosterone, tree rubbing, back skin, scent gland, Ursus arctos https://mc06.manuscriptcentral.com/cjz-pubs AbstractAdult male brown bears (Ursus arctos; Linnaeus, 1758) display tree-marking behavior to chemically signalize the dominance throughout the non-denning period, and this behavior peaks during breeding season. Within the scent-marking sequence, back rub is one of a core marking postures. The present study investigated 1) seasonal changes in sebaceous glands in the back skin of brown bears and 2) the relationship between those changes and testosterone levels. Back skin tissue samples and blood were collected from captive adult intact and castrated males during pre-breeding, transitional, breeding and post-breeding seasons, which were concurrent with back skin observations. In intact males, during the transitional and breeding seasons, an oily secretion from the back skin was observed along with enlarged sebaceous glands. The plasma testosterone concentrations during the transitional and breeding seasons were increased compared with the pre-and post-breeding seasons. Secretions and enlarged sebaceous glands were not found in castrated males, and the plasma testosterone concentrations remained at baseline levels. Oily secretions of the back skin glands that appear more abundant during breeding season are rubbed against trees. Changes in size and volume of sebaceous glands, and thus their secreting capacity, are likely testosterone-regulated.
ABSTRACT. An electroejaculation technique was applied to the Hokkaido brown bear (Ursus arctos yesoensis) for semen collection and characterization of their seminal traits. Ten captive sexually mature bears were anesthetized and subjected to 21 electroejaculation trials during their mating season in 1995 and 1996. Spermic electroejaculates were recovered from 6 of the 10 bears (14 of 21 trials). The semen was characterized by serous fluid of semitransparent white color and a neutral pH. The mean values of ejaculate volume, sperm concentration, percentage of sperm motility, percentage of live spermatozoa, and percentage of pleiomorphic forms were 2.7 ml, 471.6 × 10 6 cells/ml, 80.2%, 89.7% and 21.8%, respectively. Although there was considerable variation among the seminal traits of the individual bears, the electroejaculation technique was effective in obtaining ejaculates from captive bears. -KEY WORDS: brown bear, electroejaculation, seminal trait.J. Vet. Med. Sci. 60(8): 965-968, 1998 domestic animal diets and some vegetables were provided, and the bears were housed in indoor/outdoor enclosures under the natural light cycle. All males were separated from females by a grid wall, but had visual, aural, and/or olfactory contacts during the experimental periods. A surgical plane of anesthesia was induced with an intramuscular (i.m.) injection of tiletamine HCl-zolazepam (Zoletil; 100 mg/ml, Virbac, Carros, France) at a dose of 3 mg/kg body weight by pole syringe in 19 trials. For male D (Trial no. 11), 0.01 mg/kg atropine sulfate (Atropine sulfate injection, Tanabe, Osaka, Japan) was given before the injection of tiletamine HCl-zolazepam. Male A (Trial no. 5) was preanesthetized by an i.m. injection of 0.25 mg/kg midazolam (Dormicum, Roche, Basel, Switzerland) and immobilized by an i.m. injection of 5.0 mg/kg ketamine HCl (Ketalar, Sankyo, Tokyo, Japan). With the anesthetic plane with midazolam and ketamine HCl, the animal was less immobilized than in the other trials.
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