SOME OBSERVATIONS ON THE FINE STRUCTURE OF THE SYMPATHETIC GANGLION OF BULLFROG

Electron microscope observations of abdominal sympathetic ganglia of American bullfrogs, Rana catesbiana, have demonstrated the presence of specific areas of cytoplasm in the superficial zone of the perikaryon which are devoid of granulated endoplasmic reticulum. These areas are occupied almost exclusively by granules 200 to 400 A in diameter which can be stained intensely with lead hydroxide but faintly with uranyl acetate. Each granule shows subgranular internal structure after the lead staining. Granules of similar properties are found in synapses also, and may be glycogen. From the satellite cell there extends a number of leaf- or finger-like cytoplasmic projections around the root portion of the nerve process. Some of these projections directly cover the surface of the nerve process. Many others, however, are separated from the neuron by a fairly wide interspace. Multivesicular bodies of the neuron are occasionally observed in a configuration which suggests that they are being extruded from the root of the nerve process into the interspace. Filaments about 100 A in thickness are found in the satellite cell cytoplasm. They are arranged more or less parallel to each other and are especially well developed around synapses and nerve fibers.     

SOME OBSERVATIONS ON THE FINE STRUCTURE OF THE LUTEIN CELLS OF X-IRRADIATED RAT OVARY

The ovaries of 10- to 13-week-old rats were exteriorized and irradiated with sterilizing doses of X-rays. Following treatment, the animals entered a phase of constant vaginal cornification. Animals were killed 8 to 12 wk after the onset of this phase, and their ovaries were prepared for electron microscopy. Tissue was fixed in glutaraldehyde, postfixed in osmium tetroxide (Millonig's, phosphate-buffered), and embedded in Epon. Lutein cells from these ovaries were compared with those from sham-irradiated controls. The cytoplasm of lutein cells from experimental animals was characterized by an increase in the amount of agranular endoplasmic reticulum and by an increase in the number of mitochondria. These mitochondria are more variable in external form and often possess increased numbers of villiform cristae. Other features noted were a decrease in the amount of cytoplasmic lipid granules and an increase in cell size and surface irregularity. The significance of the morphological findings is discussed in relation to ovarian hormone production in animals sterilized by X-irradiation.     

青藏高原东缘岷江冷杉天然群落的种群结构和空间分布格局

 岷江冷杉(Abies faxoniana)是青藏高原东缘亚高山顶极森林植被的优势种之一,主要分布于岷江、大渡河和白龙江的上游地区。该文研究了岷江冷杉天然原始群落的种群结构和空间分布格局。样方大小为100 m ×60 m。测定了所有个体的坐标及其胸径、高度和冠幅。将岷江冷杉按大小级分为5级,即幼苗：H（高度）<0.33 m; 幼树: H≥0.33 m, 且 DBH（胸径）<2.5 cm; 小树: 2.5 cm≤DBH<7.5 cm; 中树: 7.5 cm≤DBH <22.5 cm和大树: DBH≥22.5 cm。采用了Morisita 指数 (Iδ)、方差均值比 (V/m), 聚块度指标(m*/m)和空间点格局分析方法 (SPPA) (采用了Ripley二次分析法)4种方法分析岷江冷杉的空间分布格局。结果表明： 1) 岷江冷杉种群结构稳定。因为其年龄结构表现为增长型, 幼苗幼树储备丰富,密度分别为2 217·hm-2和2 683·hm-2,可见岷江冷杉天然更新良好,进而通过其“移动镶嵌循环”更新维持其种群的稳定性。在大小级结构图中的一些缺刻和年龄结构图中的“断代”现象,是干扰的时空异质性在采样的时间和空间断面上的反映。 2) 幼苗、幼树和小树在所有的研究尺度（从 1 m×1m 到 30 m×30 m）下都呈聚集分布。但中树和大树基本上呈随机分布。3) 聚集强度随尺度的变化而变化。上述的前3种方法表明,聚集强度随尺度的增加而减弱。但是,空间点格局分析法表明,岷江冷杉幼苗、幼树和小树的聚集强度首先随尺度的增加而增强,达到一定高峰后,随尺度的增加而减弱。 4) 岷江冷杉的空间分布格局是它与其自然环境长期作用的结果,同时也反映了其种群天然更新的格局和机制。 5) 4种分析方法对格局的判别基本一致, 但空间点格局分析法更能反映出格局强度随尺度的变化的关系,是值得推荐的一种分析空间分布格局的方法。使用空间点格局分析法的限制主要在于其计算和采样比较复杂。另外,由于Ripley 二次分析法对于“空白”的探测不敏感,需要进一步做一些方法上的改进。     

OBSERVATIONS ON THE STRUCTURE OF SOME FORMS OF GOMPHONEMA PARVULUM KÜTZ. II. THE INTERNAL ORGANIZATION1

The diatom species Gomphonema parvulum Kütz. was isolated, grown in culture, and the details of the internal organization studied by light and electron microscopy. The organism is usually identified from its frustular morphology, but members of the genus Gomphonema can be separated from other naviculoid forms by the H-shaped chromatophore, whose lobes are connected on 3 sides across the center of the cell, and also from the position of the pyrenoid. This is situated, on the inner side of the chromatophore and is not embedded in the center of the chromatophore. New observations of this pennate diatom include details of the periplastidial network, of the Golgi vesicular activity, and of the storage products.     

OBSERVATIONS ON THE STRUCTURE OF RHODOSPIRILLUM RUBRUM

Sections of Rhodospirillum rubrum cells from cultures of different ages have been examined to obtain information on the development of chromatophores in this organism. Cells from the 12-hour cultures studied contain neither distinct invaginations of the cytoplasmic membrane nor distinct chromatophores. The first structures that can be related to chromatophore development occur peripherally in the cells, are relatively few in number, relatively high in density, and have an indistinct membrane. In cells from 26-hour cultures numerous distinct invaginations of the cytoplasmic membrane are present, and all layers of the cytoplasmic membrane are involved in the formation of each invagination. As the invaginations become more numerous, the ends of the invaginations become constricted to form one or more structures similar to the chromatophores previously described in this organism. Cells of R. rubrum, therefore, develop a structural continuum which initially consists of invaginations of the cytoplasmic membrane, and later of the chromatophores produced by and attached to these invaginations. The presence of this continuum, however, does not necessarily exclude the existence of discrete chromatophores within these cells. Several other structures previously reported in this organism are described in greater detail.     

OBSERVATIONS ON THE STRUCTURE OF RHODOSPIRILLUM MOLISCHIANUM

The lamellae of the bacterium Rhodospirillum molischianum originate as extensions of the cytoplasmic membrane into the cytoplasm of the cell. Initially, these extensions are narrow folds and occur independently of one another. The first lamellae to appear average about 80 A in width, representing one side of the infolded cytoplasmic membrane, or 160 A when the two sides of the fold are closely appressed. The 160-A lamellae increase in number and may associate to form larger lamellae, which represent varying degrees of association between adjacent folds. Later, the space within each fold increases; the two appressed regions of the cytoplasmic membrane in each fold separate to form distinct invaginations, and the lamellae observed at this stage are formed by an association of the sides of adjacent invaginations.     

A MICRO DISSECTION OF THE PACHYTENE THREADS OF TRADESCANTIA VIRGINICA L. WITH OBSERVATIONS ON SOME ASPECTS OF MITOSIS

A micro dissection of the pachytene threads of Tradescantia virginica L. shows that the relation of the chromosomes is a matter of continuous linkage in a chain and that, undoubtedly, division and segregation are everywhere processes of abstriction with subsequent mechanical distribution of the elements.