An Electron Microscopic Study of Erythrophagocytosis

The present study describes a submicroscopic surface fragmentation of erythrocytes which occurs in the ascitic fluid of rats bearing the Novikoff ascites hepatoma. The resulting fragments attach to the surface of macrophages and are phagocytized by pseudopod formation. Plasma membrane in the region of these phagocytosis vacuoles appears to condense into electron-opaque material, suggesting an alteration in its physicochemical state. Stages in intracellular digestion of intact erythrocytes or small fragments within the phagocytosis vacuoles are illustrated; no particles resembling ferritin are observed. The phagocytosis vacuoles possess high levels of acid phosphatase activity. They may be called phagosomes, a type of lysosome. There is no indication of a connection between phagosomes and other formed cytoplasmic organelles. Small vacuoles of the order of 80 mµ in diameter, which may represent pinocytosis vacuoles, are present in the cytoplasm and some appear to be in contact with the phagosome membrane, reminiscent of observations of Rose with HeLa cells.     

Electron Microscopic Study of the Phagocytosis Process in Lung

Diluted India ink was instilled into the nasal cavity of mice and the lungs of some animals were fixed with osmium tetroxide at various intervals after one instillation. The lungs of other animals were fixed after 4, 7, 9, 16, or 18 daily instillations. The India ink was found to be phagocytized almost exclusively by the free alveolar macrophages. A few particles are occasionally seen within thin portions of alveolar epithelium, within the "small" alveolar epithelial cells, or within occasional leukocytes in the lumina of alveoli. The particles are ingested by an invagination process of the plasma membrane resulting in the formation of intracellular vesicles and vacuoles. Ultimately large amounts of India ink accumulate in the cell, occupying substantial portions of the cytoplasm. The surfaces of phagocytizing macrophages show signs of intense motility. Their cytoplasm contains numerous particles, resembling Palade particles, and a large amount of rough surfaced endoplasmic reticulum. These structures are interpreted as indicative of protein synthesis. At the level of resolution achieved in this study the membranes of this reticulum appear as single dense "lines." On the other hand, the plasma membrane and the limiting membranes of vesicles and of vacuoles often exhibit the double-line structure typical of unit membranes (Robertson, 37). The inclusion bodies appear to be the product of phagocytosis. It is believed that some of them derive from the vacuoles mentioned above, and that they correspond to similar structures seen in phase contrast cinemicrographs of culture cells. Their matrix represents phagocytized material. Certain structures within this matrix are considered as secondary and some of these structures possess an ordered form probably indicative of the presence of lipid. The possible origin and the fate of alveolar macrophages are briefly discussed.     

Ruthenium Red Stain Able Surface Layer on Lung Alveolar Cells; Electron Microscopic Interpretation

Luft's ruthenium red (RR) method was applied to lung tissue. Small blocks of mouse lung were fixed for 1 hr with 1.2% glutaraldehyde at 0-4 C, buffered with 0.067 M cacodylate, pH 7.3 and containing RR, 1 mg/ml. Following fixation, lung blocks were immersed in 0.15 M cacodylate for 10 min and postfixed for 3 hr at room temperature with 2% OsO₄ buffered with 0.067 M cacodylate, pH 7.3, and containing RR, 1 mg/ml. Blocks were dehydrated with ethanol, embedded in Araldite, and ultrathin sections treated with uranyl acetate and lead citrate solutions to enhance contrast of cell structures. Electron micrographs revealed an electron-dense layer coating the exposed surfaces of alveolar cells. This layer corresponded in location and appearance to that observed by other investigators who used colloidal iron techniques.     

Electron Microscopic Analysis of a Spherical Mitochondrial Structure

Mitochondria undergo dynamic structural alterations to meet changing needs and to maintain homeostasis. We report here a novel mitochondrial structure. Conventional transmission electron microscopic examination of murine embryonic fibroblasts treated with carbonyl cyanide m-chlorophenylhydrazone (CCCP), a mitochondrial uncoupler, found that more than half of the mitochondria presented a ring-shaped or C-shaped morphology. Many of these mitochondria seemed to have engulfed various cytosolic components. Serial sections through individual mitochondria indicated that they formed a ball-like structure with an internal lumen surrounded by the membranes and containing cytosolic materials. Notably, the lumen was connected to the external cytoplasm through a small opening. Electron tomographic reconstruction of the mitochondrial spheroids demonstrated the membrane topology and confirmed the vesicular configuration of this mitochondrial structure. The outside periphery and the lumen were defined by the outer membranes, which were lined with the inner membranes. Matrix and cristae were retained but distributed unevenly with less being kept near the luminal opening. Mitochondrial spheroids seem to form in response to oxidative mitochondrial damage independently of mitophagy. The structural features of the mitochondrial spheroids thus represent a novel mitochondrial dynamics.     

An Electron Microscopic Study on Spermatogenesis in Golfingia ikedai

The process of spermatogenesis in Golfingia ikedai was observed with electron microscope. Clusters of primary spermatocytes continued spermatogenesis while floating in the body fluid. No direct connections were found between the cells and no cytophore formation was observed. Preacrosomal vesicles were formed from small Golgi-bodies just after the meiosis. Subacrosomal substances were aggregated just under the acrosomal vesicle in the middle stage of spermiogenesis and changed into fibrous structures in the completed spermatozoon. A peculiar annulus structure developed around the base of the flagellum. The phylogenetic position of this worm was also discussed in relation to the polychaetes and other worms.     

Electron Microscopic Study of the Morphogenesis of Vesicular Stomatitis Virus

Except for the rate, vesicular stomatitis virus (VSV) grows as well at 25 C as at 37 C in primary chick embryo fibroblast cells and in a pig kidney cell line [PK(H13)]. Maximal yields were reached at about 28 hr at 25 C and 10 hr at 37 C in these cells. Morphogenesis, as observed by electron microscopy, was similar at the two temperatures. The main feature was accumulation of virus in intracytoplasmic vacuoles. Mode of release of VSV has been controversial; both budding (as displayed by myxoviruses) and maturation at membranes of cytoplasmic vacuoles (as with arboviruses) have been claimed. Our observations support the latter view, and the apparent dichotomy in interpretation is discussed.     

Electron Microscopic Study of Hemadsorption on Vaccinia Virus Infected Cells

Hemadsorption (HAD) induced in HEp-2 cells infected with vaccinia virus was observed. In ultrathin sections, binding of 36 red blood cells (RBCs) was examined in detail and 3 types of HAD were observed: (1) direct and close binding of RBCs to infected HEp-2 cells (cyto-HAD) was observed in cross sections of 27 RBCs, (2) binding of RBCs through microvilli of infected cells was found in 11 RBCs, and (3) five RBCs were distorted to form tentacle-like projections by which they were bound to the HEp-2 cell surface. Scanning electron microscopy revealed that more than 30% of the RBCs were bound to microvilli of vaccinia virus-infected HEp-2 cells, and that the number of microvilli twined round each RBC was over ten. RBCs were attached to certain microvilli through swollen sucker-like tips which were not observable in non-infected HEp-2 cells. RBCs sometimes revealed a polygonal shape at regions of binding to microvilli. Virion-mediated RBC-HEp-2 cell binding could not be observed.     

A Light and Electron Microscopic Study of Anabaena volzii Lemm

Anabaena volzii Lemm. is a rare species of Cyanophyta. It possesses characteristics of prokary0tes. Young filaments of A. volzii consist of only vegetative cells. The filament leng- thens by the increase of its cell number owing to amitosis. A mature filament contains vegetative cells, heterocysts and akinetes; the latter two differentiate from the vegetative cells. Vegetative cells and heterocysts are short-cylindric shaped. An akinete in longitudinal sections of appear to be elliptical. Viewed with a transmission electron microscope, an electron-dense cell wall, plasmolemma, thylakoids (photosynthetic lamellae), nucleo-plasmic region and polyhedral bodies can be seen in the vegetative cell. The nucleo-plasmic region, which lacks a nuclear envelope, is surrounded or dissected, but often connected with the thylakoids. There are also some extremely electron-dense (if samples were post-fixed in osmic acid) cyanophycin granules in its cytoplasm. Heterocyst is larger than vegetative cells. Its remarkable features are a thick envelope, an electron-transparent cell wall and a distinctive plug-like body at both ends of the cell respectively. In the plug-like body is seen an irregular narrow channel. Somewhat dilated thylakoids in the heterocyst appear to be more winding and contorted (than those in vegetative cells), making a dedicate pattern. A long ellipticring-shaped membrane structure is formed in a heterocyst ,composed, of an electron-dense rod core surrounded by 14 concentric layers of lamellae. Akinete forms thick cell wall. A nucleo-plasmic region, fine and contorted thylakoids, many cyanophycin granules, and abundant ribosomes are found in akinetes.     

Electron Microscopic Analysis of the Inner Synaptic Layer in the River Lamprey (Lampetra fluviatilis)

Abstract Different types of synaptic contacts between bipolar, amacrine and ganglion cells were scored on random electron micrographs and on montages comprising the entire thickness of the inner synaptic layer. Currently accepted criteria were used when classifying the different cell processes. The percental distribution of dyads was estimated to 56 % amacrine-amacrine dyads, 34 % amacrine-ganglion dyads and 10 % ganglion-ganglion dyads. The ratio of amacrine conventional synapses to bipolar ribbon synapses was 6.8 : 1. The density per unit area of conventional synapses (0.035/μm²) and ribbon synapses (0.005/ μm²) was found markedly low as compared with other vertebrate species except the carp. The inner synaptic layer of the river lamprey is suggested to be of the intermediate type in which both simple and complex ganglion cell receptive fields may be expected.     

Electron Microscopy of Solitary and Aggregated Slime Mould Cells

Polysphondylium violaceum and Dictyostelium discoideum myxamoebae have simple double-layered nuclear membranes, a cytoplasmic reticulum of particle-covered membranes, and small mitochondria consisting of convoluted tubules tightly packed in double membranes. In addition to objects still recognisable as bacteria, their food vacuoles contain concentric (or spiral) membranes, apparently formed secondarily from undigested material; these are ultimately ejected. Where the triple-layered plasma membranes (~70 A wide) of cells in the early aggregates are apposed to one another, they run parallel but separated by a layer of rather constant thickness (~200 A), as in many unspecialised metazoan tissues. Thus studies on slime moulds may well increase our understanding of cell adhesion and tissue formation in metazoa.     

An Electron Microscopic Study of the Bipolar Bodies in Crithidia oncopelti

SYNOPSIS. An electron microscopic study of the structure of the flagellate Crithidia oncopelti was carried out with particular reference to the nature of the bipolar body which occurs in the organism. Apart from the bipolar body, the fine structure of C. oncopelti is similar to that of the related flagellate, C. fasciculata. The bipolar body is typically a sausage-shaped organelle limited by 2 unit membranes. Outpouchings of these membranes into the cytoplasm of C. oncopelti were found, along with a constant absence of (a) ribosomes on the outer aspect of the external of the 2 membranes, (b) structures analogous to nuclear pores and (c) an internal structure analogous to a nucleolus. It is concluded that the balance of structural and biochemical evidence favors the idea that the bipolar body is a bacterial protoplast rather than a 2nd nucleus.     

Electron Microscopic Examination of Corynebacterium ovis

Corynebacterium ovis (C. pseudotuberculosis) was examined by electron microscopy after being subjected to various methods of fixation. The organism exhibited a fine structure similar to other corynebacterial species in the appearance of its cell wall, plasma membrane, nuclear apparatus, cytoplasmic matrix, wealth and complexity of intracytoplasmic membrane systems, and polyphosphate granules. An outstanding structural feature was the existence of an electron-dense, floccular layer external to the cell wall which both ligroin and acetone-methanol extractions demonstrated to be the previously postulated surface lipid of this organism. The only variations in structure evident between virulent and attenuated strains was a quantitative difference in the thickness and appearance of the surface lipid. The observation of this layer provided a basis for explaining the surface properties of C. ovis, with particular respect to its clumping capacity in suspension, the waxiness of its growth on solid media, and its ability to grow as a pellicle on suitable liquid media. The variation in the visible amount of surface lipid between the virulent and avirulent strains adequately explained the divergence of these three surface properties between the strains.     

Electron Microscopic Observations of Rabbit Antibodies

Electron micrographs were obtained showing the individual, shadow-cast macromolecules from solutions of purified anti-p-azobenzoate rabbit antibody and of normal γ-globulin. The two materials look alike and consist mainly of asymmetrical rod-like particles about 30 to 40 A in diameter. Lengths are not constant but the weight average is about 250 A for the antibodies and about 200 A for the γ-globulin. The average observed dimensions are reasonably consistent with values deduced from physical-chemical methods, although the shape is more nearly that of a cylindrical rod rather than the ellipsoid employed in hydrodynamical theory. Mixtures of antibody and specific dihaptenic dye were examined in attempts to establish the mode of the specific aggregation. At the high dilutions necessary for electron microscopy (0.1 mg./ml.), the effect of the dye was small and tended to be masked by non-specific aggregation on drying. The evidence suggests that under these conditions the specific reaction involves an end-to-end aggregation of the elementary particles to produce a weight average length about twice that of the pure antibody.     

浮游病毒的电镜观察

直接用戊二醛固定水样中的浮游病毒,通过超速离心使已固定的浮游病毒沉淀到覆有Formvar膜和碳支持膜的铜网上,经醋酸双氧铀染色后,利用透射电镜对湖水中的浮游病毒进行观察．结果可观察到球形、杆状和蝌蚪状等形态各异的浮游病毒颗粒及球形病毒的囊膜子粒、杆状病毒的核衣壳、具有不同尾部的蝌蚪状病毒等的精细超微结构．从而建立了一种简便、快捷和高效研究浮游病毒的电镜方法．     

Scanning Electron Microscopic Study of Cytoskeleton in Isolated Generative Cells of Lily

Isolated generative cells of lily were extracted with Triton X-100, ammonium sulphate and RNase. The exposed contents were then viewed in the scanning electron microscope after critical point drying. The treatments revealed that in the cytoplasm of the generative cell there was a reticulate network of cytoskeleton. This reticulate network of cytoskeletal scaffold had two layers: (1) an outer layer (near the membrane) consisting of long and thick fibres that were tightly knitted together, and (2) an inner layer (near the nucleus) consisting of thin and short fibres that were loosely knitted together. Indirect evidence using immunofluorescence techniques for labelling microtubules and TRITC-phalloidin staining of actin microfilaments indicated that the cytoskeleton seen in the scanning electron microscope appeared likely to be a microtubule cytoskeleton rather than a microfilament cytoskeleton.     

粘质沙雷氏菌的电镜观察

用扫描电镜和透射电镜对粘质沙雷氏菌(Serratia marcescens)的临界点干燥标本和负染标本作了观察,均可见到细胞表面常有一至二个直径为0.12～0.24μm的颗粒。在超薄切片中颗粒则有两种不同的结构:一种是外膜泡(Outer membrane vesicle);另一种是致密体(Dense body)。致密体可能是一种分泌性颗粒,它既不是内部的贮存物,也不似外部进来的异物。它们看来形成于细胞质内后分泌到细胞外。在细菌中这是一种罕见现象。有关致密体的化学性质和功能尚不清楚。文中指出粘质沙雷氏菌的纲胞表面也具有茂密的菌毛(Pili)。     

Scanning Electron Microscopic Studies of Candida albicans

A scanning electron microscopic study of selected morphological stages of Candida albicans is presented. Stages represented are budding yeast cells, mycelial-like forms, chlamydospores, germ tube formation, and an unusual rough cell type.