切断视神经对蟹视网膜电图昼夜节律的影响

在切断视神经后锯缘青蟹视网膜电图的昼夜节律发生了明显的变化,但并不完全消失,提示在中枢和眼柄中分别存在着两种起搏器。文中提出了蟹视网膜电图昼夜节律控制的模式图。     

保持培养细胞原位、原形的超薄切片制备法

本文介绍先用环氧树脂Epon812包埋剂制成丘状膜,再在膜上培养细胞,直接将膜与细胞一起包埋,制备超薄切片。此种方法不仅能克服以往培养细胞需要离心成团,容易造成细胞破碎、变形的缺点;还能避免琼脂预包埋法悬浮细胞造成的抗原封闭;并能得到为数较多的连续超薄切片。它操作简便,较好地保持了培养细胞生长的原来位置及原有形状,为培养细胞进行免疫电镜的操作和提高制备培养细胞超薄切片的数量和质量提供了一种有效的途径。     

ELECTRON MICROSCOPY OF SPORES OF BACILLUS MEGATERIUM WITH SPECIAL REFERENCE TO THE EFFECTS OF FIXATION AND THIN SECTIONING

Resting spores of Bacillus megaterium appear uniformly opaque and undifferentiated under the electron microscope. Germinated spores and spores which have lost their dipicolinic acid underwent characteristic changes in structure. Spores fixed with KMnO₄ lose their dipicolinic acid. Spores fixed with OsO₄ under certain conditions retain their dipicolinic acid. When conventional sectioning procedures are used with either method of fixation, abnormal spore structure is produced as a result of the solution of cellular constitutents. Dry sections of unfixed spores embedded in methacrylate reveal the spore structure in a more normal state. Indirect evidence has been obtained for the existence of a penetration barrier at or near the outer edge of the cortex.     

N-VINYLPYRROLIDONE AS A WATER COMPATIBLE CONSTITUENT OF EMBEDDING RESINS FOR SECTIONING IN ELECTRON MICROSCOPY

The use as an embedding resin for ultrathin sectioning of a cross-linked triple copolymer of N-vinylpyrrolidone, acrylonitrile, and ethylene glycol dimethacrylate is described. The first of these components is miscible with water, in all proportions, and can be used as a dehydrating agent, or, alternatively, ethanol may be used in the standard way. Polymerization is carried out at 37°C or even lower temperatures. This resin is unsuitable for use after osmium fixatives, but after permanganates it gives results similar to epoxy. Photographs of rye root-tip cells fixed in permanganate and sectioned in this resin are presented. Because of the water-permeable nature of the product and low polymerization temperature, this resin appears to have possibilities for histochemistry.     

THE CHANGE IN STATE OF THE PROTEINS OF MUSCLE IN RIGOR

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.     

庞泉沟保护区核心区植被景观类型特征研究

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。