AN ELECTRON MICROSCOPIC STUDY OF THE CHORIOALLANTOIC MEMBRANE FOLLOWING INFECTION WITH ROUS SARCOMA VIRUS

Infection of the chick chorioallantoic membrane (CAM) with Rous sarcoma virus (RSV) has been thought by earlier workers (12, 20) to result in the transformation of the ectoderm and then the mesoderm of that organ. In the present study, CAM were infected with 10⁴ PFU (pock-forming units) of RSV (Bryan high titre strain) and collected for electron microscopy at 2, 4, and 6 days postinfection. Observations of the fine structural changes in the CAM after RSV infection support a singular role of the mesenchyme in the initiation of the tumors. The ectodermal hyperplasia often associated with RSV tumors of the CAM appears to be a secondary response to the alteration of the underlying mesenchyme. These findings are discussed in detail, and an alternate course of RSV transformation of the CAM by way of the vascular bed is suggested.     

ELECTRON MICROSCOPIC STUDIES ON THE DEVELOPMENT OF VESICULAR STOMATITIS VIRUS IN KB CELLS

The development of vesicular stomatitis virus in KB cells was studied by electron microscopy. Sections of infected cells were made 1, 4, 7, 10, and 20 hours after inoculation of the cell cultures, and at the same intervals the supernatant fluid was assayed for virus titer by the plaque test in chick embryo cells. At 10, 14, and 20 hours after inoculation, virus rods were observed attached to cytoplasmic membranes, inside cytoplasmic vacuoles, and attached to the membranes delimiting these vacuoles; they were also found on the surface membrane of the cells. Besides the rods, spherical particles of different sizes and shapes were seen. The possibility that these structures are related to the development of virus rods is discussed. A similarity was noted between the site of maturation of vesicular stomatitis virus rods and that of some other arbor viruses.     

AN ELECTRON MICROSCOPIC STUDY OF THE DEVELOPMENT OF THE CLEAVAGE FURROW IN MAMMALIAN CELLS

The process of cytoplasmic cleavage has been studied in thin sections of rat erythroblasts and the cells of mouse leukemia and Walker 256 carcinoma of the rat. The development of the cleavage furrow begins in relation to the mid-body, which, earlier, appears on the equatorial plane in association with the continuous fibers of the spindle. The earliest evidence of a cleavage furrow is the presence of a vesicle or vesicles close to the mid-body. Subsequently, many smaller vesicles are seen in the equatorial plane. The cleavage furrow probably develops by the fusion of these vesicles so that a new plasma membrane is formed between the daughter cells, and extends from the telophase intercellular bridge to the cell margin. During the stage of formation of the vesicles, cisternae, believed to be part of the endoplasmic reticulum, assume an intimate relationship with the cleavage plane, and they may perhaps be involved in the formation of the vesicles.     

A CORRELATED HISTOCHEMICAL AND ELECTRON MICROSCOPIC STUDY OF THE INTRANUCLEAR CRYSTALLINE AGGREGATES OF ADENOVIRUS (RI-APC VIRUS) IN HELA CELLS

HeLa cells in tissue cultures infected with types 3, 4, or 7 of adenovirus (RI-APC virus) were studied in order to correlate certain histochemical and electron microscopic findings. Adjacent thin (ca. 0.05 µ) and thick (2–4 µ) sections of osmium-fixed, methacrylate-embedded cells were cut; by mapping the sections the same cells could be identified with both the electron and the light microscope. Intranuclear crystalline aggregates seen with the electron microscope to be composed of ordered arrays of viral particles were found by means of the Feulgen reaction to contain DNA. DNA is therefore assumed to be a constituent of the viral particle. The virus appeared to develop from an osmiophilic Feulgen-negative matrix. Displacement of nuclear chromatin occurred during this process. A Feulgen-azure staining method was found to permit clear distinction between viral and nuclear (host) DNA in thick sections.     

金鱼表皮的带突起细胞的扫描电镜观察

本文对60只金鱼的皮肤进行了扫描电镜研究。除观察了带有突起的诸种细胞外,尚在雄性金鱼的头盖部皮肤发现一种从未报道过的新型细胞突起,呈指状,约40×20μm。其形态大小与性结节完全不同。经喂食11-酮睾丸酮后,该突起增至近乎原来的两倍。其机能是否与性机能有关尚待进一步探讨。     

百合离体生殖细胞骨架的扫描电镜观察

从百合的花粉管分离出来的生殖细胞,经表面活化剂Ｔｒｉｔｏｎ Ｘ－１００ 及核糖核酸酶、硫酸铵离析处理。离析后的细胞经临界点干燥,扫描电镜观察显示：在离体生殖细胞的胞质内有一个非常复杂的支架网络系统。这一网络系统有内外两层：外层（靠近细胞膜）网络结构紧密,纤维束粗长;内层（靠近核）网络结构疏松,纤维束短细。一些间接证据显示,这一支架网络系统可能为微管骨架     

AN ELECTRON MICROSCOPE STUDY OF THE DEVELOPMENT OF A MOUSE HEPATITIS VIRUS IN TISSUE CULTURE CELLS

Samples taken at different intervals of time from suspension cultures of the NCTC 1469 line of mouse liver—derived (ML) cells infected with a mouse hepatitis virus have been studied with the electron microscope. The experiments revealed that the viruses are incorporated into the cells by viropexis within 1 hour after being added to the culture. An increasing number of particles are found later inside dense cytoplasmic corpuscles similar to lysosomes. In the cytoplasm of the cells from the samples taken 7 hours after inoculation, two organized structures generally associated and never seen in the controls are observed: one consists of dense material arranged in a reticular disposition (reticular inclusion); the other is formed by small tubules organized in a complex pattern (tubular body). No evidence has been found concerning their origin. Their significance is discussed. With the progression of the infection a system of membrane-bounded tubules and cisternae is differentiated in the cytoplasm of the ML cells. In the lumen of these tubules or cisternae, which are occupied by a dense material, numerous virus particles are observed. The virus particles which originate in association with the limiting membranes of tubules and cisternae are released into their lumen by a "budding" process. The virus particles are 75 mµ in diameter and possess a nucleoid constituted of dense particles or rods limiting an electron transparent core. The virus limiting membrane is sometimes covered by an outer layer of a dense material. In the cells from the samples taken 14 to 20 hours after inoculation, larger zones of the cell cytoplasm are occupied by inclusion bodies formed by channels or cisternae with their lumens containing numerous virus particles. In the samples taken 20 hours or more after the inoculation numerous cells show evident signs of degeneration.     

流感病毒感染诱导MDCK细胞凋亡的研究

用荧光染色、DNA凝胶电泳等方法检测了A型流感病毒株A1／京防86－1和B型流感病毒株B/沪防93－1诱导狗肾体代细胞(MDCKcells)的凋亡情况,并采用MTT法和流式细胞仪比较了这2株病毒对MMCK细胞的毒力和凋亡诱导能力水平。结果显示：病毒感染6h后,细胞DNA发生断裂,病毒感染12h后,可见明显的染色质凝聚;在一定范围内,细胞凋亡强度表现出明显的时间和剂量依赖关系;并且,A型流感病毒株的毒力和调亡诱导能力均强于B型流感病毒株。实验结果表明：流感病毒感染引起的细胞死亡主要是通过调亡实现的,毒力不同的流感病毒株诱导细胞调亡的能力不同。     

ELECTRON MICROSCOPIC AUTORADIOGRAPHY OF GERMINAL CENTER CELLS IN MOUSE SPLEEN

The fine structure of tritiated thymidine-labeled cells in antigen-stimulated mouse spleen germinal centers is described. In studies on the ultrastructural level, two labeled cell types found in germinal centers are observed. Large lymphocytes are characterized by their very numerous free ribosomes, a paucity of endoplasmic reticulum, relatively few mitochondria, and a poorly developed Golgi region. The nuclei are large and vesicular, and large nucleoli are present. A second labeled cell type appears to contain more mitochondria and has a higher development of the Golgi area. The nucleus contains large, numerous blocks of chromatin, indicative of a more differentiated cell type. Reticular cells, both phagocytic and non-phagocytic, were not observed to be labeled in the germinal centers.     

ELECTRON MICROSCOPIC STUDY OF THE ATPASE ACTIVITY OF THE BAI STRAIN A (MYELOBLASTOSIS) AVIAN TUMOR VIRUS

Thymus glands of chicks with leukemia induced by BAI strain A (myeloblastosis) virus were fixed in cold 4 per cent formaldehyde-sucrose. Frozen sections were incubated in the ATPase medium of Wachstein and Meisel and studied by light microscopy and electron microscopy. The ATPase activity of the virus is localized to the outermost membrane of the virus. The membrane of the blast-like cells of the thymus cortex from which the virus emerges, by budding, also possesses such activity. It appears likely that the outermost membrane of the virus is derived from the plasma membrane of these cells.     

沙冬青根瘤菌的电子显微镜研究

用透射电镜研究沙冬青根瘤中的根瘤菌。这种根瘤菌的精细结构不仅与生态环境有关,而且还随寄主细胞发育程度不同而异。在早期侵染细胞中,根瘤菌很少,一般呈圆形或椭圆形,电子密度很高,位于细胞壁附近。在成熟侵染细胞中,根瘤菌很多,布满了整个细胞,形态出现多样化。在衰老侵染细胞中,根瘤菌形状不规则,细胞质收缩,电子密度增高,内部结构模糊不清,有的甚至变成一团膜泡状结构     

大鼠海马触液神经元的分布特征及其纤维联系

本文应用ＨＲＰ追踪与电镜结合的方法研究了大白鼠海马接触脑脊液神经元的分布特征和皮质内联系。光镜观察在海马的多形细胞层和锥体细胞层等处可见散在的神经元被标记,而在室管膜层标记的细胞较多,它们分布于交织成网的阳性纤维中。透射电镜可见海马室管膜层的ＨＲＰ反应阳性的神经细胞、树突末稍及神经胶质细胞。在海马室管膜上也见到了被标记的神经纤维。同时在海马室管膜层内还发现未标记的阴性轴突与被ＨＲＰ标记的阳性树突构成的轴－树突触。上述结果提示海马为接触脑脊液神经元存在的部位之一,其接触脑脊液神经元并受到其它神经元的突触调控     

ELECTRON MICROSCOPIC LOCALIZATION OF ACID PHOSPHATASE AND THIAMINE PYROPHOSPHATASE ACTIVITY IN HYPOTHALAMIC NEUROSECRETORY CELLS OF THE RAT

Supraoptic nuclei in the hypothalamus of rats were fixed for the electron microscope by vascular perfusion with solutions of glutaraldehyde followed by post fixation with osmium tetroxide. Cytochemical methods for detection of acid phosphatase and thiamine pyrophosphatase activity have been applied to glutaraldehyde-fixed frozen sections containing the neurosecretory cells. The enzyme activities have been localized to certain Golgi cisternae. Acid phosphatase activity is present in the large (0.4 µ to 1.0 µ) granules or dense bodies which are surrounded by a single limiting membrane; both features characterize these structures as lysosomes. Smaller (0.1 µ) granules also present in the perikarya are generally unreactive towards enzyme activity and resemble in form the neurosecretory granules in the neurohypophysis.