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排序方式: 共有572条查询结果,搜索用时 140 毫秒
101.
Toru Kobayashi Ryo Ishibashi Shinji Yamamoto Satoshi Otani Koichi Ueno Osamu Murata 《Aquaculture Research》2011,42(2):230-239
The timing of primordial germ‐cell (PGC) migration with regard to the gonadal anlagen, gonad formation and sex differentiation was examined histologically in the chub mackerel (Scomber japonicus) at 5–190 days post hatching (dph). At 5 dph, PGCs appeared on the peritoneal epithelium surface or in the mesentery, on the dorsal side of the abdominal cavity. By 10 dph, stromal cells around the PGCs proliferated. The gonadal primordium was formed by 15 dph. The gonadosomatic index was 0.01% at 30 dph and increased thereafter (0.32% in females and 0.04% in males at 160 dph). Ovarian differentiation occurred at 30–40 dph, indicated by ovarian cavity formation (elongation and fusion of the upper and lower ovarian edges). Meiosis was subsequently initiated. A few meiotic oocytes surrounded the cavity at 50 dph; most were in the perinucleolus stage at 60 dph and attained a diameter of 60–70 μm at 190 dph. Testicular differentiation occurred at 30 dph, indicated by the formation of the sperm duct primordium. Spermatogonia gradually proliferated, developing into spermatocytes at the chromatin–nucleolus stage (after 90 dph) and subsequently into spermatids and spermatozoa (160 dph). These data could aid the development of seeding and cell‐engineering technologies for scombrid fish. 相似文献
102.
This study investigated: 1) susceptibility differences to infection by Neobenedenia girellae (Capsalidae) between amberjack Seriola dumerili (Carangidae), yellowtail S. quinqueradiata and Japanese flounder Paralichthys olivaceus (Paralichthyidae); 2) growth and egg production of N. girellae on each fish species; 3) acquired protection of each fish species against this parasite. The number of N. girellae on S. dumerili was significantly higher than on S. quinqueradiata and P. olivaceus when these fishes were exposed to oncomiracidia in the same aquarium. Neobenedenia girellae growth on S. dumerili was fastest and, thus the number of eggs laid by parasites on S. dumerili was greater than on the other two species. Seriola dumerili and P. olivaceus, which were previously infected with N. girellae and treated by freshwater bath, acquired partial protection against re-infection by N. girellae. The relative re-infection of three S. dumerili individuals out of eleven individuals was markedly low compared with the initial infection, and the relative initial infection and re-infection on two P. olivaceus out of eleven individuals was markedly low. The results of this study could be useful to control N. girellae infections when cultivating S. dumerili, S. quinqueradiata and P. olivaceus. 相似文献
103.
Arata Katayama Hong-Ying Hu Mamie Nozawa Sayuri Takahashi Koichi Fujie 《Soil Science and Plant Nutrition》2013,59(6):841-846
Based on the respiratory quinone profile, changes in the structure of microbial communities in the soil samples from Nagoya University Farm were monitored after the treatment with 1% of a mixture of glucose and peptone. Samples of two soils differing in the fertilization history were examined: CF-soil with the application of only chemical fertilizers and FYM-soil with the application of only farmyard manure at a high rate. In the CF-soil, the amount of water-soluble organic carbon (WOC), indicator of the mixture of glucose and peptone, decreased to the original level after 14 d. After 7 d, the soil pH reached the maximum level, then decreased gradually. Changes in the inorganic nitrogen levels in the water extract also reflected the 14-d period of mineralization. The amount of respiratory quinones reached maximum levels after 7 d and gradually decreased, reflecting the changes in the microbial biomass. The quinone composition significantly changed during the 14-d period and returned to a profile similar to the original one after 28 d. Diversity of quinones significantly decreased during the 14-d period due to the predominance of ubiquinone with 9 isoprenoid units. In the FYM-soil, the amount of WOC decreased to the original level after 1 d, and the pH and inorganic nitrogen levels in the water extract reflected the one-day mineralization period, and nitrification started after 3 d. Although the amount of quinones indicated an increase in the microbial biomass for 14 d, the quinone composition did not change. These findings suggested that long-term application of farmyard manure resulted in stable microbial communities in response to the incorporation of organic matter in soil. 相似文献
104.
105.
Koichi Ojima 《Animal Science Journal》2019,90(7):801-807
Skeletal muscle consists of bundles of myofibers containing millions of myofibrils, each of which is formed of longitudinally aligned sarcomere structures. Sarcomeres are the minimum contractile unit, which mainly consists of four components: Z‐bands, thin filaments, thick filaments, and connectin/titin. The size and shape of the sarcomere component is strictly controlled. Surprisingly, skeletal muscle cells not only synthesize a series of myofibrillar proteins but also regulate the assembly of those proteins into the sarcomere structures. However, authentic sarcomere structures cannot be reconstituted by combining purified myofibrillar proteins in vitro, therefore there must be an elaborate mechanism ensuring the correct formation of myofibril structure in skeletal muscle cells. This review discusses the role of myosin, a main component of the thick filament, in thick filament formation and the dynamics of myosin in skeletal muscle cells. Changes in the number of myofibrils in myofibers can cause muscle hypertrophy or atrophy. Therefore, it is important to understand the fundamental mechanisms by which myofibers control myofibril formation at the molecular level to develop approaches that effectively enhance muscle growth in animals. 相似文献
106.
Occurrence of New Powdery Mildew on Greenhouse Tomato Cultivars 总被引:2,自引:0,他引:2
Yoshinori MATSUDA Koichi KASHIMOTO Yoshihiro TAKIKAWA Rika AIKAMI Teruo NONOMURA Hideyoshi TOYODA 《Journal of General Plant Pathology》2001,67(4):294-298
During a year-round survey on the occurrence of powdery mildew on greenhouse-cultivated tomato plants, the disease was most
severe in June and July. All tomato plants (45 commercial cultivars and 11 breeding lines) tested were infected with the pathogen
but had different degrees of susceptibility. The pathogen was epiphytic and produced white, round pustules mainly on leaves
of tomato plants. The pathogen produced conidia singly on conidiophores and forked appressoria on inoculated tomato leaves
and seemed to be an Oidium sp. of Erysiphe polygoni type.
Received 18 December 2000/ Accepted in revised form 22 July 2001 相似文献
107.
This study aimed to determine the load‐bearing capacity of trotting Kiso horses using gait analysis. Ten Kiso horses with a height at withers of 128 cm were included. Their riders were fitted with a marker (70 mm in diameter placed on their chest) recorded by two digital DVD cameras while trotting along a short, straight course. In total, eight tests were performed for each horse: the first with a 70 kg load; six with randomly loaded weights ranging 80–130 kg; and then a final test again with a 70 kg load. Three‐dimensional movement of the marker was analyzed using a motion capture system. The time series of vertical displacement of the marker underwent spectrum analysis by the maximum entropy method, and the autocorrelation coefficient was calculated. The first two peaks of the autocorrelation were defined as symmetry and regularity, and their sum was defined as stability. Regularity in the 120 kg test (0.54) was lower than that in the first 70 kg test (0.61), and stability in the 120 kg test (1.31) was lower than that in the first 70 kg test (1.42). We concluded that the maximum permissible load for a trotting Kiso horse is < 120 kg, which represents 31% of its bodyweight. 相似文献
108.
Osamu SASAKI Mitsuo AIHARA Koichi HAGIYA Akiko NISHIURA Kazuo ISHII Masahiro SATOH 《Animal Science Journal》2012,83(2):95-102
The objective of this study was to confirm the stability of the genetic estimation of longevity of the Holstein population in Japan. Data on the first 10 lactation periods were obtained from the Livestock Improvement Association of Japan. Longevity was defined as the number of days from first calving until culling or censoring. DATA1 and DATA2 included the survival records for the periods 1991–2003 and 1991–2005, respectively. The proportional hazard model included the effects of the region-parity-lactation stage-milk yield class, age at first calving, the herd–year–season, and sire. The heritabilities on an original scale of DATA1 and DATA2 were 0.119 and 0.123, respectively. The estimated transmitting abilities (ETAs) of young sires in DATA1 may have been underestimated, but coefficient δ, which indicated the bias of genetic trend between DATA1 and DATA2, was not significant. The regression coefficient of ETAs between DATA1 and DATA2 was very close to 1. The proportional hazard model could steadily estimate the ETA for longevity of the sires in Japan. 相似文献
109.
Bird species diversity and bird species richness were surveyed in a natural mixed forest (mature forest) and in a coniferous
plantation (30–40 years old) monthly from 1990 to 1994. These forests were 20 km apart and had similar weather conditions
and soil types. There were larch and cedar plantations, and hardwoods along streams in the coniferous plantation. In the natural
mixed forest, 55 bird species were found, whereas 40 species were recorded in the coniferous plantation. The species diversity
of bird communities was significantly higher in the natural mixed forest than in the coniferous plantation mixed with hardwood
trees. This result indicates that the coniferous plantation mixed with hardwood trees, presumed to be a more simplified environment,
is likely to be less inhabitable for many bird species than the natural mixed forest, suggesting a relationship between the
diversity of the forest environment and the diversity of the bird community. A higher number of bird species was recorded
in the small coniferous forest mixed with hardwood trees compared with those in the coniferous plantation. The mixing of broad-leaved
trees in a coniferous plantation was suggested to be effective in increasing number of bird species. These tendencies were
recorded all through the year during our study. In snow-covering periods, both the diversity and the bird species richness
fell in all study sites every year. Snow cover would have greater effect on bird species diversity in the coniferous plantation
than in other forest types probably due to diet shortages caused by the snow cover over the forest floor. 相似文献
110.
Hiroshi Matsunaga Rika Shiotari Junji Matsumura Kazuyuki Oda Yasuhiro Utsumi Koichi Yamamoto 《Journal of Wood Science》2006,52(2):95-100
This is the first report to ascertain potassium location in black heartwood of sugi (Cryptomeria japonica). The objective of this study was to understand the distribution of potassium in sugi black heartwood in connection with
anatomical morphology. Scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDXA) was used to investigate
the distribution of inorganic elements, especially potassium. In black heartwood, potassium was detected in all tissues (tracheids,
ray parenchyma, and axial parenchyma), but its concentrations were different in each xylem tissue. Potassium was particularly
accumulated in the droplets in axial parenchyma cells. In addition, calcium was also detected in all tissues. Phosphorus sometimes
existed in the granules in ray parenchyma cells. From optical microscopy, the axial parenchyma cells were observed to be arranged
in a tangential direction on transverse section and the droplets in these cells were distributed in areas of high ash and
green moisture content. For red heartwood, potassium detected by SEM-EDXA was far lower in all tissues than in the black heartwood,
while the trend for calcium was the converse. Potassium in axial parenchyma cells was more abundant in black heartwood than
in typical pale red heartwood. 相似文献