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排序方式: 共有481条查询结果,搜索用时 15 毫秒
101.
Toshiya Yoshida Mikio Hasegawa Hideaki Taira Mahoko Noguchi 《Journal of Forest Research》2005,10(5):351-358
Tree retention is understood as a key practice in creating complexity, leading to heterogeneity in resources and habitats in managed stands. In this article, we clarify the long-term effects of tree retention on stand structure and tree-species composition in a 60-year-old Larix kaempferi plantation in central Japan. In our study plot (1.5 ha) there were 18 stems/ha of retained trees (determined by tree-ring analysis), mostly Quercus crispula. We conducted spatial analyses and tested the hypothesis that tree abundance, size structure, and species composition and diversity change with distance from the retained trees. Near the retained trees, L. kaempferi showed a reduction of 40%–60% in basal area, due presumably to the shading effect. In contrast, the nearby area showed greater species diversity in the canopy layer. The retained trees created patches of different species composition in the understory. The spatial gradient of shade and colonization opportunity provided by retained trees greatly affect the distribution of the colonized species, according to their shade tolerance and seed-dispersal ability, which resulted in the stand structure with a heterogeneous shrub-layer vegetation. Retention proved particularly important for the enhancement and long-term maintenance of structural and compositional complexity in L. kaempferi plantations. 相似文献
102.
Seasonal development of resinous stem canker was determined in Chamaecyparis obtusa trees wound‐inoculated with Cistella japonica in January 1996. Samples for anatomical analysis were harvested on 20 May, 9 July and 6 August in the second year of inoculation, and the sections were observed under light microscope. Resin exudation was most abundant in the second year, decreasing in the third. All new resin exudation in the second year was recognized at the May observation. New traumatic resin canal formation was observed in the August samples, and an expansion of necrotic lesions was observed mainly in summer samples in the inoculated trees and in naturally affected trees. Cistella japonica was re‐isolated from all bark lesions or inoculated wounds examined. These results suggest that the activity of Ci. japonica in the tree affects the seasonal development of resinous stem canker during the growing season of the trees. 相似文献
103.
Stress conditions produced in wood were analyzed by means of the acoustoelastic birefringence method. Bending load was applied against a wood beam specimen. Under loading, ultrasonic shear waves were propagated through the breadth direction of the wood beam specimen. The velocities of shear waves polarized in the longitudinal or tangential direction of the wood beam specimen were measured with the sing-around method. Bending stresses were determined by dividing the difference between the acoustic anisotropy and the texture anisotropy by the acoustoelastic birefringence coefficient. Shear stresses were also determined. These stress distributions of the beam specimen were in good agreement with those obtained by the strain gauge method and mechanical calculation. 相似文献
104.
Ageyama N Hanazono Y Shibata H Ono F Nagashima T Ueda Y Yoshikawa Y Hasegawa M Ozawa K Terao K 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2006,68(5):507-510
Genes and proteins of human origin are often administered to monkeys for research purposes, however, it can be difficult to obtain sufficient levels of the products in vivo due to immunological clearance. In this study, we showed that human erythropoietin (hEPO) induces generation of anti-hEPO antibody in cynomolgus macaques (n=2), although 92% of amino acid residues are common between the human and macaque EPO. The administered hEPO was thus eliminated from the animals. On the other hand, when an immunosuppressant, cyclosporin A (CyA), was administered (6 mg/kg) intramuscularly every other day in combination with hEPO (n=2), no anti-hEPO antibody was generated and high serum levels of hEPO were obtained during administration of hEPO, resulting in an increase in serum hemoglobin levels. No adverse effects associated with CyA were observed. Thus, CyA treatment is useful for prevention of immune responses associated with the administration of human proteins in monkeys. 相似文献
105.
Kano R Okabayashi K Nakamura Y Fujiwara K Hasegawa A Sasaki Y 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2006,68(1):95-96
This report deals with three additional canine cases of sterile panniculitis treated by oral administration of tacrolimus and prednisolone. The oral tacrolimus treatment was proved to be an affordable medical protocol for canine sterile panniculitis with good efficacy and without adverse effects. 相似文献
106.
Hasegawa A Yonezawa K Ohta A Mochida K Ogura A 《The Journal of reproduction and development》2012,58(1):156-161
The rapid increase in the number of genetically modified mouse strains has produced a high demand for their frozen spermatozoa from laboratories and mouse banking facilities. Historically, plastic straws have been used preferentially as containers for frozen mammalian spermatozoa because spermatozoa frozen in plastic straws have a high survival rate after thawing. However, plastic straws are more fragile and are used less often than the cryotubes used for conventional cell freezing. In this study, we sought to develop a new protocol for sperm freezing using cryotubes as the container to increase the accessibility of mouse sperm cryopreservation. Epididymal spermatozoa were collected from mature ICR or C57BL/6J (B6) males and were suspended in 18% raffinose and 3% skim milk solution. We then optimized the following conditions using the sperm survival rate as an index: 1) distance of cryotubes from the surface of the liquid nitrogen at freezing, 2) volume of the sperm suspension in the cryotube and 3) temperature of warming sperm during thawing. The best result was obtained when cryotubes containing 10 μl of sperm suspension were immersed 1 cm below the surface of the liquid nitrogen and then thawed at 50 C. The fertilization rates using spermatozoa frozen and thawed using this method were 63.1% in ICR mice and 28.2% in B6 mice. The latter rate was increased to 62.3% by adding reduced glutathione to the fertilization medium. After embryo transfer, 68% and 62% of the fertilized oocytes developed into normal offspring in the ICR and B6 strains, respectively. These results show that cryotubes can be used for cryopreservation of mouse spermatozoa under optimized conditions. This protocol is easy and reproducible, and it may be used in laboratories that do not specialize in sperm cryopreservation. 相似文献
107.
Coxa morphologically adapted to large egg in aepyornithid species compared with various palaeognaths
Endo H Akishinonomiya F Yonezawa T Hasegawa M Rakotondraparany F Sasaki M Taru H Yoshida A Yamasaki T Itou T Koie H Sakai T 《Anatomia, histologia, embryologia》2012,41(1):31-40
The coxa of palaeognaths including extinct aepyornithid species was compared by means of osteology, computed tomography (CT) imaging and macroscopic anatomy. The pre-acetabular area of the ilium was proportionally much larger in width and height in aepyornithid species than in other extant palaeognaths. The post-acetabular area of the ilium, ischium and pubis was relatively short and bilaterally extended in aepyornithid species. Although the Aepyornis species might have produced egg with a major axis exceeding 300?mm in major axis, the short post-acetabular coxa and widely opened ischium and pubis would not have been able to stably hold the eggs in the posterior space of the pelvic cavity unlike the situation in the ostrich. As aepyornithid species resembled the kiwi in measurement ratios of length and width in the pre-acetabular area, a functional-morphological model of the coxa in the aepyornithid species can be proposed based on that of the kiwi. From our data, we suggest that the extinct species of Aepyornis and Mullerornis species effectively used the anterior space of the pelvic cavity to support their extraordinary large egg. 相似文献
108.
Yamazaki M Kato A Kato C Fujii E Adachi K Miyoshi A Suzuki M 《Journal of toxicologic pathology》2009,22(2):133-137
The db/db mouse is one of the diabetes mellitus animal models and if the pathophysiological stages of diabetic changes in the mouse model could simulate the stages in human diabetes, the db/db mouse could be used to better evaluate drug candidates. Blood insulin, HbA1c levels and morphological features of pancreatic islets in db/db mice were evaluated to determine the pathophysiological stage. At 6 weeks of age, db/db mice showed the highest level of plasma insulin and lowest level of HbA1c, and histopathological examination revealed enlarged islets with a circular shape and hypertrophic islet cells. By 9 and 12 weeks of age, the plasma insulin levels had decreased to mid levels and HbA1c had increased to mid to high levels; histopathological examination at this time revealed two types of islets coexisting, enlarged circular islets and small irregular-shaped islets. By 15 and 22 weeks of age, plasma insulin had decreased further to low levels and HbA1c was at its highest level; the histopathological examination at this time revealed an increase in irregular-shaped and small islets. Based on blood insulin levels, HbA1c levels and histopathology findings in the db/db mice in this study, the clinical staging of diabetic changes were recognized. The pathophysiological stages of diabetes mellitus in this animal model were similar to the stages in humans. 相似文献
109.
Rui Kano Takayuki Yano Kota Nagamatsu Haruhiko Maruyama Hiroshi Kamata Atsuhiko Hasegawa 《Research in veterinary science》2009,87(1):64-66
The effect of down-regulation of Mcl-1 expression by small interfering RNA (siRNA) against the canine Mcl-1 gene on apoptosis was investigated by transfecting CF33 (canine mammary gland tumor cell line) with siRNA using cationic liposomes. The siRNA against canine Mcl-1 increased the rate of apoptotic cells and decreased the numbers of viable cells. Further, sequence-specific down-regulation of Mcl-1 expression was measured by real time-PCR and Western blot analysis. The siRNA directed against the Mcl-1 gene reduced both the mRNA and protein expression in the CF33. Our study suggests the importance of Mcl-1 in canine mammary tumors for inducing apoptosis and reinforces using Mcl-1 as a putative therapeutic target in canine mammary gland tumor. 相似文献
110.