共查询到20条相似文献,搜索用时 46 毫秒
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庞泉沟保护区核心区植被景观类型特征研究 总被引:3,自引:0,他引:3
利用植被景观类型图,获得面积、周长、景观斑块的长、宽等信息,对庞泉沟保护区核心区的植被景观特征进行分析。结果表明,核心区景观及斑块分布具有明显的地带性;核心区景观多样性较小,均匀度较低。另外,本文尝试用长宽比、伸张度、圆环度和周长与长轴的比这四种指数对景观斑块的特征进行了分析。结果表明,这四种指数在景观特征分析中具有一定的生态学意义。 相似文献
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A. E. Mirsky 《The Journal of general physiology》1936,19(4):571-575
1. When myosin is exposed to a typical denaturing agent (acid) it becomes insoluble and its SH groups are activated. 2. The same number of active SH groups is found in the soluble myosin of resting muscle as in the insoluble myosin of muscle in rigor. No activation of SH groups accompanies the formation of insoluble protein in rigor. 3. When the insoluble myosin of muscle in rigor is treated with a denaturing agent its SH groups are activated. 4. Protein coagulation as brought about by denaturing agents (heat, acid, alkali, alcohol, urea, salicylate, surface forces, ultraviolet light) is a distinctly different change from the coagulation of myosin brought about by the unknown agent in muscle. 相似文献
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Cirrhosis of the liver has no effect upon the incidence of carcinoma of the prostate. 相似文献
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THE ROLE OF THE PIGMENT EPITHELIUM IN THE ETIOLOGY OF INHERITED RETINAL DYSTROPHY IN THE RAT 总被引:17,自引:6,他引:11
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Visual cell outer segment renewal was studied in eyes of mutant Royal College of Surgeons (RCS) and Sprague-Dawley (control) rats by a combination of microscopy and radioautography with the light and electron microscopes. RCS and control rats were injected with amino acids-3H at 11 days of age. Radioactive rod outer segment discs were assembled at the outer segment base from radioactive proteins synthesized in the rod inner segments. In controls, all radioactive discs assembled at 11 days of age were displaced the length of the outer segments, removed from outer segment tips, and phagocytized by the pigment epithelium by 8 days after injection. In the RCS rats, disc assembly and displacement resembled controls for the first 3 days after injection. However, as disc assembly continued for some time thereafter, a layer of labeled, disorganized, lamellar debris accumulated between the outer segment tips and the pigment epithelium. The buildup of debris was accompanied by visual cell death. At no time during the study was there evidence for phagocytic activity by the pigment epithelium. 61 days after injection, the layer of debris was the only heavily radioactive component in the retina. In the retina of RCS rats, the outer segment renewal mechanism malfunctions because the pigment epithelium does not fulfill its normal phagocytic role. The end result is visual cell death and blindness. 相似文献
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FINE STRUCTURAL CHANGES IN THE FLAGELLUM OF THE SPERMATID IN EXPERIMENTAL CRYPTORCHIDISM OF THE RAT 总被引:2,自引:1,他引:1
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Toshio Nagano 《The Journal of cell biology》1963,18(2):337-344
Rat testes were confined to the abdominal cavity by operation. After 1 to 26 days they were excised, fixed with osmium tetroxide, sectioned, and examined with the electron microscope. Changes in the axial filament complex of the spermatid flagellum appeared 2 days after operation, and the arrangement of filaments in the middle- and main pieces of some spermatid tails was disordered as compared to the 9 + 2 filament arrangement in the tails of the control spermatids and in other flagella and cilia. In cross-sections, the filaments in the experimental material were nine or less in number, and each of them was single and dense. Occasionally some were double, and in those instances one filament was dense and the other was light and tubular. The central filaments were obscure. In longitudinal sections,the filaments were not parallel to the main axis of the flagella or to each other. It was assumed that the central filaments were more sensitive to the experimental conditions than the peripheral pairs of filaments. Furthermore, the light filaments of the peripheral pairs were more sensitive than the dense filaments. Besides the axial filament complex, the fibrous sheath which surrounds it in the main piece was also changed. The plasma membrane of the changed flagella disappeared or became fragmented. 相似文献
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THE CAUSATION OF THE DIURNAL CHANGES IN NITROGEN FIXATION IN THE NODULES OF ALNUS GLUTINOSA 总被引:5,自引:5,他引:0
C. T. WHEELER 《The New phytologist》1971,70(3):487-495