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161.
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Keisuke Yamano Kazuharu Nomura Hideki Tanaka 《Aquaculture (Amsterdam, Netherlands)》2007,270(1-4):499-504
Development of the thyroid gland of the Japanese eel (Anguilla japonica) was studied with the use of tank-reared fish. A single thyroid follicle was first found in larvae at 29 days post hatching (dph), total length (TL) 12 mm. Until reaching 25 mm in TL (100 dph), leptocephali had one or two follicles per individual. The inner colloid of the follicles was weakly immuno-positive against the anti-thyroxine (T4) antibody. The number of thyroid follicles and the immunoreactivity later increased as the larvae grew. Thyroid hormones (TH) T4 and triiodothyronine (T3) were not detected in premetamorphic larvae by radioimmunoassays, but became detectable during metamorphosis. The maximum level of T4 was seen in fish at the end of metamorphosis and in just-metamorphosed juveniles, whereas T3 reached the highest level during metamorphosis and declined toward the end of metamorphosis. The results indicated that the thyroid gland first became active during metamorphosis in the development of eel. 相似文献
163.
Hiroshi Ashida Toshiyuki Tanabe Keisuke Satoh Atsushi Fukui Sho Tanaka Nobuhiro Suzuki 《Fisheries Science》2010,76(5):785-793
The reproductive biology of male skipjack tuna Katsuwonus pelamis was examined from May 2005 to December 2007 in the tropical western and central Pacific Ocean. Testis maturity was classified
into five stages (i.e., immature, early maturation, mid maturation, late maturation, and regression) on the basis of morphological
changes in the germinal epithelium. The testis duct system (TS), which was characterized by lobules that lack spermatocysts,
store only sperm, and form an anastomosing network, was located under the main sperm duct. The TS was observed at all stages
of maturity except the immature stage, and first appeared in individuals with a fork length (FL) of 38–40 cm. The estimated
minimum size at first maturity was 35.5 cm FL and the size at 0.5 maturity was 40.7 cm in FL. It was difficult to clearly
differentiate the testis maturity stage based solely on the gonad index (GI) class because each GI class contained mature
fish. Monthly changes in testis height index and GI did not follow a seasonal cycle. Mature individuals dominated throughout
the year. These results imply that male skipjack tuna in this area showed evidence of spawning activity throughout the year
without a clear seasonal pattern. 相似文献
164.
We developed both a cryopreservation method for Japanese sea cucumber spermatozoa and an artificial fertilization method using post‐thaw spermatozoa. Twenty per cent dimethyl sulfoxide (DMSO), 16% foetal bovine serum, and 64% artificial seawater were suitable cryodiluent, and the diluent was pre‐cooled to 0°C. Semen was diluted with the solution and enclosed in a 250 μl straw, cooled to ?50°C at 10.4 ± 0.4°C/min, and immediately immersed in liquid nitrogen. Although this method showed the highest post‐thaw motility in all the conditions we examined, its post‐thaw motility was still less than approximately 15%. Artificial fertilization was carried out by adding post‐thaw semen with a cryodiluent to the oocytes. The fertilization rate of 200 oocytes/ml seawater increased with the amount of post‐thaw semen from 1 to 5 μl but showed a significant decrease at 25 μl. This decrease was considered to be due to DMSO in the cryodiluent, because the fertilization rate of the fresh semen decreased sharply when the DMSO concentration around the oocytes was 1.0% or more. Further improvement in increasing post‐thaw motility and lowering the cryoprotectant concentration is necessary for commercial‐scale artificial fertilization. 相似文献
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167.
Keisuke Tomioka Toyozo Sato Jouji Moriwaki Yuichi Terasawa Hiroki Koganezawa 《Journal of General Plant Pathology》2012,78(2):133-135
Severe spotting and blighting of leaves were found on bacopa (Sutera cordata), a scrophulariaceous ornamental, in greenhouses in Gunma Prefecture, Japan, from January through February 2007. After we
isolated and identified the causal fungus as Colletotrichum destructivum and inoculated host plants with the isolate to confirm pathogenicity, we named this new disease anthracnose of bacopa. 相似文献
168.
Kozai K Hojo T Takahashi M Acosta TJ Nambo Y Okuda K 《The Journal of reproduction and development》2012,58(4):393-397
Although circulating progesterone (P(4)) levels tend to change with the season, little is known about the seasonal changes of P(4) synthesis-related proteins in the corpus luteum (CL) of mares. To examine these changes, seventy-four ovaries containing a CL were collected from Anglo-Norman mares at a local abattoir in Kumamoto, Japan (~N32°), five times during one year. The stages of the CLs were classified as early, mid and regressed by macroscopic observation of the CL and follicles. The mid CL, which had the highest P(4) concentration, was used to evaluate the seasonal changes in P(4) synthesis. The luteal P(4) concentration and mRNA expression of luteinizing hormone receptor (LHCGR) were lowest during early winter and highest during late winter. The mRNA expressions of steroidogenic acute regulatory protein (StAR), P450 cholesterol side-chain cleavage enzyme (P450scc) and 3β-hydroxysteroid dehydrogenase/Δ5-Δ4 isomerase (3β-HSD) were lowest during early winter and increased during late winter. These results suggest that P(4) synthesis in the CL is affected by the seasonal changes in the mRNA expressions of P(4) synthesis-related proteins in mares. 相似文献
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