A study of the structure of eggplant mottled dwarf virus

Observation of eggplant mottled dwarf virus using negatively stained particles or tissue sections subjected to different fixing and embedding procedures and to differential enzyme digestion, showed that virions have an outer envelope 100-20 Å with surface projections about 60 Å in length. The outer layer was acquired by the particles by budding at the nuclear membrane and contained lipoid material. The lipoprotein coat enveloped an internal core 45–50 nm in diameter, which was highly susceptible to pepsin but not to RNase digestion. Layers of stable material which was not removed by the manipulations of embedding occurred at the periphery and the center of the core. The peripheral layer, about 55 Å thick, which correspond to the helical nucleocapsid characteristic of rhabdoviruses, has a pitch of 45 Å in negatively stained particles.     

Electron microscopic findings in four cases of nasopharyngeal fibroma

Summary Light and electron microscopic investigations of four cases of juvenile nasopharyngeal fibroma revealed characteristic structures; a fibrous stroma, an inclination to hyalinisation and formation of scar like tissue, a lacunar thin walled vascular component, large numbers of mast cells and of fibroblasts. The tumor fibroblasts contained different nuclear bodies and particles. There existed five different types of more or less complex spherical bodies. The previously described nuclear electron dense particles with an electron lucent halo could be divided into four groups measuring 60, 90, 150 and 300 nm in diameter.In addition to the previously described ultrastructural properties of the tumors, the nuclei of the tumor fibroblasts were found to contain virus like particles. These particles were less electron dense, measuring 40 to 55 nm in diameter and arranged in groups throughout the nucleoplasm; they were different from chromatin condensations and from perichromatin granules. The structure and the size of the smallest particles was not comparable with the other nuclear inclusions.     

Ultrastructural characterization of core structures and paracrystalline inclusion bodies in L-form cells of streptomycetes

Protoplast type L-form cells of Streptomyces hygroscopicus and S. griseus contain different types of inclusion bodies. Cytoplasmic cores and paracrystalline structures are peculiar inclusions which could not be observed in normal parent bacteria. The cytoplasmic cores are 1–4 μm long and 0.05–0.25 μm broad straight and stiff non-tubular structures consisting of homogeneous moderate electron opaque material. Paracrystalline inclusions have side-lengths between 0.2 and 0.5 μm and show a characteristic pattern of 15–20 nm thick straight dark lines and electron lucent intervening spaces of 20–30 nm. Both cytoplasmic cores and paracrystalline inclusions are apparently proteins. Their occurrence in L-form cells indicates an altered synthesis of one or several proteins in these cell types.     

Utrastructural observations on <Emphasis Type="Italic">Goussia metchnikovi</Emphasis> (Laveran, 1897) in the spleen of gudgeon, <Emphasis Type="Italic">Gobio gobio</Emphasis> L.

The ultrastructure of gamonts and sporulated oocysts of Goussia metchnikovi in the spleen of gudgeon, Gobio gobio from the river Lee, England is described. In developing microgamonts, small amylopectin granules were grouped centrally and nuclei were often arranged peripherally, close to the surface membrane. Nuclear chromatin condensed into peripheral dense portions that became the nuclei of flagellated microgametes, released to the parasitophorous vacuole. The cytoplasm of macrogametes had larger, scattered amylopectin granules, lipid globules and small electron-dense bodies, but no obvious wall forming bodies; peripheral vesicular structures with the appearance of mitochondria were also present and the parasitophorous vacuole contained flocculent material, but was otherwise free of structures. Sporulated oocysts contained four sporocysts and oocyst walls appeared to consist of a single membrane. Sporocyst walls showed a dehiscence suture, characteristic of the genus Goussia, which had filamentous extensions in places. The sporocyst wall comprised a dense inner layer and a thin outer layer with a fuzzy coat, separated by an electron lucent layer. Groups of oocysts were encapsulated by fibrous layers and inflammatory cells, and many sporocysts and their contained sporozoites showed evidence of elimination by the host.     

The budding of defective human immunodeficiency virus type 1 (HIV-1) particles from cell clones persistently infected with HIV-1

Summary Three cell clones producing large numbers of infectious or noninfectious particles of human immunodeficiency virus type 1 (HIV-1), designated M 10/LAV-2, M 16/LAV-3, and MT/LAV-17, were isolated from persistently HIV-1-infected MT-4 cells. In M 10/LAV-2, the HIV-1 proteins were defective in the cleavage ofgag precursor protein, and the particles were doughnutshaped with a double-ring structure. These particles were produced by budding at the cell surface from crescentic structures followed by the formation of double-ring structures. The viral proteins in M 16/LAV-3 were defective in the cleavage ofenv precursor protein. The morphology of the virus particles was intact, and an electron dense bar-shaped core was seen inside a single-ring enveloped structure. The intact particles were released from the cell surface by a budding process in which crescent shape structures first appeared at the cell membrane, then subsequently just before release matured to a complete structure with an electron dense core. In MT/LAV-17, the synthesis of HIV-1 proteins was normal, and the particles were teardrop-shaped with an intact core structure. These particles were produced by budding with an electron dense core at the cell surface.Thus, it was suggested that the morphological maturation of HIV-1 particles was completed just before release from the cell surface in several cell clones producing HIV-1 particles of different morphology.     

Fine structure of nerves in the regenerating limb of the newt Triturus

The structural integrity of some tissues and the regeneration of extremities in some vertebrates depends upon the nervous system. To investigate the structure of nerves exhibiting trophic function, nerves in regenerating forelimbs of adult newts, Triturus viridescens, were studied with the electron microscope. Nerve fibers sprout from the transected axons, 2–3 days after amputation of the limb, and invade all portions of the blastema and epidermis in large numbers. Regenerating nerve fibers contain a greatly increased amount of smooth-surfaced channels of endoplasmic reticulum containing moderately dense material, an increased number of microtubules, and large (1000 Å) membrane-bounded dense granules. The latter were not observed normally and could be distinguished from synaptic vesicles and dense-core vesicles thought to contain catechol amines. In larger nerves, the organelles are distributed in the peripheral axoplasm around a central zone containing neurofilaments. The relationship of the fine structural changes occurring during regeneration to the trophic action of nerves and the regeneration of nerve fibers is discussed. The tortuous membranous tubules of endoplasmic reticulum could serve as channels for the transport of substances, either trophic material or materials necessary for growth of the nerve, down the axon. Microtubules may play a role in the regulation of form of the growing axon and also be related to axoplasmic flow or migration of particles (e.g., granules) along their length. The large membrane-bounded dense granules appearing during regeneration resemble neurosecretory granules, which have been associated with regeneration in some invertebrates. These structures could, therefore, contain a trophic substance or hormone that is transported down the axon, released into the intercellular spaces, and controls subsequent regeneration of the limb.     

中国流行性出血热脏器标本病毒样颗粒属性的探讨

本文应用电镜观察了12例流行性出血热(EHF)尸体标本,其中7例(58%)出现了泡状病毒样颗粒。它为圆形或椭圆形,直径72～116nm,平均92nm;有包膜,没有核样体,表面粗糙或有微突。颗粒主要分布于网织细胞及心、肝实质细胞的核膜及线粒体,偶尔见于内质网和胞浆。泡状病毒样颗粒在大小和形态上,与洪涛等在培养细胞见到的EHF病毒以及其他学者观察的汉坦病毒和布尼亚病毒基本一致,为EHF病毒在人体脏器细胞的形态表现。     

Electron microscopic observations on the development of the median eminence in perinatal rats

Summary This paper reports details of the development of the external layer of the median eminence with special reference to the appearance of the nerve terminals, containing electron dense core and electron lucent vesicles, in the outermost layer of a palisade structure (2–3 thick). Observations were made on perinatal rats of the Sprague-Dawley strain (16, 18, 20 day fetuses and rats 5 hours, one 4, and 8 days after birth). The palisade structure of the outermost layer of the median eminence was first clearly detectable 5 hours after birth. Concomitantly, there was a marked increase in the number of nerve terminals in this layer. The nerve terminals containing electron dense core and electron lucent vesicles were seen in 18 day fetuses in the outermost layer of the median eminence. These nerve terminals increased in number during development, especially from the 20th day of fetal life to the 4th day after birth. The size range of the majority of the electron lucent vesicles did not change during development, but that of the core vesicles increased from 600–800 Å from the 18th to 20th day of fetal life. The initiation of neurohemal control of the adenohypophysial function by the hypothalamus is discussed.     

Electron-dense material within sarcoplasmic reticulum apposed to transverse tubules and to the sarcolemma in dog papillary muscle fibers

The space between the sarcoplasmic reticulum (SR) apposed to the transverse (T) tubules and the sarcolemma in dog papillary muscle fibers is traversed by structures of varying densities. The distance between apposed membranes is about 70 Å at the level of densities and about 100 Å at the level of less dense areas that alternate with the densities. The apposed SR shows a marked increase in electrondense material when comparison is made with the SR not apposed. The electron-dense material is located in a dense layer parallel to and about midway between the membranes of the apposed SR and in numerous projections from the inside surface of the membranes. With appropriate staining procedures the central dense layer and the projections are as thick as membranes and they frequently show paired densities separated by a distance about equal to the distance between the outer dense layers of trilaminar membranes. The paired densities in the central dense layer and in the projections indicate that the electron-dense material within apposed SR has structure. The projections are frequently in register with scallops or serrations in the SR membranes and they also appear to contribute to a waviness in the central dense layer. The serrations and waviness are interpreted as evidence that the projections exert a holding force because they project from the SR membranes and connect with the central dense layer.     

An electron microscopic study of the mediodorsal cerebral cortex in the lizard Agama agama

Summary An electron microscopic analysis was made of the small-celled part of the mediodorsal cortex of the lizard Agama agama. This cortex consists of four layers: Superficial plexiform layer, cellular layer, deep plexiform layer and fiber layer. In the superficial plexiform layer one type of solitary neuron with smooth dendrites is present.Three types of axon terminals can be observed: terminals with a moderately electron dense matrix packed with spherical vesicles (S1 type), axon terminals with an electron lucent matrix containing fewer spherical synaptic vesicles than the S1 type (S2 type) and axon terminals with an electron lucent matrix and scattered pleomorphic synaptic vesicles (F type). F type axon terminals are larger than S terminals. At the pial surface endfeet of tanycytic processes form a limiting glial layer, contacting one another by means of gap junctions. In the cellular layer perikarya of pyramidal neurons are densely packed. The karyoplasm of these neurons shows either evenly dispersed or discretely clumped chromatin. Spiny dendrites arise from the perikarya and extend into both the superficial and deep plexiform layers. The structure of the deep plexiform layer is roughly similar to that of the superficial plexiform layer. The fiber layer contains the majority of the afferent and efferent axons of the mediodorsal cortex. The axons are myelinated and unmyelinated. Between the fibers, scattered solitary neurons are present, often accompanied by glial cells.The lateral ventricle beneath the fiber layer is lined by a single row of ependymal tanycytes. Tanycytic processes traverse the cortical layers and may form endfeet at the pial surface. Protoplasmic excresenses from some ependymal cells protrude into the ventricle.     

Fine structural modifications of the rat chromatoid body during spermiogenesis

The chromatoid body of rat spermatocytes and spermatids was studied with routine electron microscopy and the PA-silver method for detection of glycoproteins. The chromatoid body consists of a membrane-free aggregate of electron dense, finely filamentous material, in association with small vesicles. In late pachytene spermatocytes, there may be more than one chromatoid body; its dense component is diffusely reticulated. In young spermatids, there is only one chromatoid body per cell; the dense component is fairly compact, but it encloses less dense areas continuous with the cytoplasm. Within the less dense areas, as well as at the periphery of the dense component, small (400–800 Å) oval or tubular vesicular structures are observed whose contents exhibit a positive reaction for glycoprotein in PA-silver stained sections. When the spermatid nucleus begins to elongate, the chromatoid body takes the form of an arc around the axial filament proximal to the centriolar apparatus. Soon thereafter, the bulk of the chromatoid body condenses into a sphere of very dense filamentous material surrounded by a corona of enlarged glycoprotein-containing vesicles. In the later stages of spermiogenesis, the chromatoid body migrates away from the nucleus and disintegrates by fragmentation. It is noted that the chromatoid body undergoes its major morphological changes, possibly indicative of its active phase, while located in the para-centriolar region, at the time when the nucleus elongates, and the connecting piece and ring of the spermatid are formed.     

An electron-dense extracellular material in the nervous system of Aplysia

An electron dense material is found in the extracellular space of the nervous system of Aplysia, a marine mollusc whose ganglia are widely studied by neurobiologists. This material appears to consist of irregular electron-dense granules, with diameters of approximately 600 Å. This material is found between the glial cells that surround the neuronal perikarya. It is not found in other regions of the nervous system. Because it is found in the ganglion cell layer of the nervous system and because the neurons contain what may be the precursor of this substance, the electron-dense material is regarded as most probably being a neuronal product. The importance of this material is that it is one of the few examples of visible structure in the extracellular space of the nervous system.     

Observations on the structure of the eumelanosome matrix in melanosomes of the chick retinal pigment epithelium

Eumelanosomes from the developing chick pigment epithelium have been isolated, solubilized, and the residue collected. Examination of this material in the electron microscope provides evidence for new structural entities in the eumelanosome and information on the organization of the melanosome. This evidence suggests that there are (1) 190-Å fibers arranged in a zigzag fashion, surrounding 240-Å–diameter electron-lucent spaces and (2) an internal gridwork enclosing 40–50-Å-diameter spaces. These two structures are probably alternately layered and “rolled-up.”     

Ultrastructural characterization of stable L-form cells from Erysipelothrix rhusiopathiae and of accompanying artifacts

The stable L-form of Erysipelothrix rhusiopathiae is a typical protoplast type L-form. Cells are surrounded by a trilamellar cytoplasmic membrane only. They grow in form of aggregations in liquid media and their diameters vary between 0.1 and 2 μm. Always a large portion of cells undergoes lysis. It seems to be characteristic for L-form cultures of E. rhusiopathiae that always many artifact structures are formed. The artifacts are spherical particles with diameters of 0.1 μm to more than 3 μm. They can be differentiated from L-form cells only by electron microscopy. The artifacts consist of electron dense amorphous material and their surface is irregular without a clear boundary line. Obviously, these artifacts are produced from protein components of the medium and from cytoplasmatic components of the lysing L-form cells.     

Ultrastructural characterization of an iridovirus from the marine worm nereis diversicolor (O. F. Müller) Architecture of the virion and virus morphogenesis

The fine structure of a new iridovirus isolated from the marine worm Nereis diversicolor was studied both in negatively contrasted preparations and in thin sections of infected tissue. The virions were icosahedral measuring 180 × 160 nm. The virus particle was enveloped by a unit membrane covered externally by spherical subunits 60 Å in diameter. These subunits are responsible for the icosahedral structure of the virion. A layer of fibrillar material of glycoprotein nature surrounded the virus envelope. The internal extremely dense core of the virion contained the DNA genome. Virus morphogenesis occurred at the periphery of electron-dense granular viroplasms where immature forms enclosing viroplasmic material could be observed. The immature particles underwent a process of maturation giving rise to fully mature virions.     

Orderly particle arrays on the mitochondrial outer membrane in rapidly-frozen sperm

By deep-etching and rotary replication of unfixed, non-cryoprotected tissue frozen on a helium-cooled copper block, previously undemonstrable organellar surfaces and intramembranous structures can be examined. Among the more remarkable features of mammalian spermatozoa thus prepared are the highly ordered particulate arrays on the surface of the mitochondrial outer membrane. In the midpiece of the sperm, mitochondria curl around dense fibers and the axoneme. The surface of the mitochondrion that faces the plasmalemma carries closely packed rods in haphazard dispersement, composed of two to four 70-to 80-Å particles, <20 Å apart, while the concave aspect of the organelle contains rods in stepladder pattern. These ladders are parallel, with their paticles in neighboring rungs apparently in register at a 40–45° angle relative to the mitochondrial axis. This organizational disparity between the convex and concave surfaces of the organelle not only affords evidence of a new mitochondrial substructure, but represents a type of topographical heterogeneity rarely found except within specialized areas of the plasma membrane. Other novel findings in the sperm cell include the observation of “lipid” tracts flanking intramembranous particle-strands in the plasmalemma of the cytoplasmic droplet, and a gridiron design on the cytoplasmic faces of the droplet's microcisternae, as well as both within and atop its plasma membrane—a motif consistent with the presence of exocytotic or endocytotic activity in this portion of the cell. Additional recent observations are the differing internal and external periodicities of axonemal microtubules and the subunit structure of rectangles on the tail surface overlying the intramembranous particles of the zipper.     

Properties of murine intracisternal A particles: electron microscopic appearance after critical point drying and platinum shadowing.

Intracisternal A particles (IAP) are present in mouse neoplasms; morphologically they resemble certain immature forms of oncogenic RNA viruses, and they have certain biochemical markers found in known RNA tumor viruses. By combining critical point drying with uranyl acetate positive staining and shadowing, it is possible to observe whole unsectioned particles while simultaneously demonstrating internal detail. IAP exist in the isolated state as budding and intact forms, and consist of two concentric spherical shells surrounding a roughly spherical electron lucent core. The outer shell is sensitive to the detergent Na deoxycholate, but the inner shell is resistant to this agent and retains its spherical construct following treatment with it. The inner shell is not solublized by 1% Na dodecyl sulfate but it does lose its structural integrity and collapses. Exposure to 0.15% trypsin for limited time periods reveals concentric linear densities in the inner shell; such structures are faintly visible in untreated particles.     

Biochemical and electron microscopic observations of vaccinia virus morphogenesis in HeLa cells after hydroxyurea reversal

Examination of thin sections of S3 HeLa cells propagated in suspension cultures and infected with vaccinia virus in the presence of hydroxyurea (HU) showed accumulation of immature virus particles. Upon removal of the drug the typical cytoplasmic development of virions was observed, confirming the usefulness of HU for separating early and late events in the replication cycle of poxvirions in spinner cultured cells and for studying viral morphogenesis under quasisynchronous conditions.Six hours after HU reversal, cytoplasm prepared by lysis of cells in Nonidet P-40 was fractionated by sucrose density centrifugation. Particles obtained by the fractionation procedure were negatively stained and their morphology characterized as follows: fraction I contained complete virions and cores with lateral bodies; fraction II contained particles 2300 × 3000 Å in size which resembled viral cores but lacked some of the surface layers found on such subviral particles prepared in vitro; fraction III contained spherical particles 2600–2800 Å in diameter and tubular structures of varying lengths and 1300 Å in diameter; fraction IV yielded particles which morphologically resembled viral cores but had irregular surfaces and appeared damaged; their sedimentation behavior during density gradient centrifugation and subsequent isolation suggested that they may be membrane bound in the cytoplasm and were mechanically released during isolation.When cytoplasmic samples were centrifuged in velocity gradients under conditions where subviral and viral particles were pelleted, progeny DNA was found throughout the gradient. In sucrose gradients prepared in 10^?3M phosphate buffer, pH 7.2, this DNA could be resolved into three classes. A minor fraction (10% or less of the radioactivity) remained at the top of the gradient, major components sedimented at 50–100 S (about 30–40%), the third > 100 S (10–15%). The remainder of the radioactivity was in the pellet. When the 50–100 S fraction was analyzed in alkaline gradients, the denatured DNA sedimented at about 30 S.Early after HU reversal (1–3 hr), before significant assembly of viral DNA into DNase resistant structures had occurred, 85–90% of the newly synthesized viral DNA could be recovered in the form of virosomes.Thin sections of viral DNA protein complexes when examined in the electron microscope were found to be heterogeneous in composition. Irregular ovoid bodies, 0.8–1.0 μm by 0.5 to 0.7 μm in size and filamentous material often in large aggregates composed of fibrils about 20 Å in diameter comprised the major components observed in virosome preparations.     

Changes in cells' secretory organelles and extracellular matrix during endochondral ossification in the mandibular condyle of the growing rat

The mandibular condyle from 20-day-old rats was examined in the electron microscope with particular attention to intracellular secretory granules and extracellular matrix. Moreover, type II collagen was localized by an immunoperoxidase method. The condyle has been divided into five layers: (1) the most superficial, articular layer, (2) polymorphic cell layer, (3) flattened cell layer, (4) upper hypertrophic, and (5) lower hypertrophic cell layers. In the articular layer, the cells seldom divide, but in the polymorphic layer and upper part of the flattened cell layer, mitosis gives rise to new cells. In these layers, cells produce two types of secretory granules, usually in distinct stacks of the Golgi apparatus: type a, cylindrical granules, in which 300-nm-long threads are packed in bundles which appear “lucent” after formaldehyde fixation; and type b, spherical granules loaded with short, dotted filaments. The matrix is composed of thick banded “lucent” fibrils in a loose feltwork of short, dotted filaments. The cells arising from mitosis undergo endochondral differentiation, which begins in the lower part of the flattened cell layer and is completed in the upper hypertrophic cell layer; it is followed by gradual cell degeneration in the lower hypertrophic cell layer. The cells produce two main types of secretory granules: type b as above; and type c, ovoid granules containing 300-nm-long threads associated with short, dotted filaments. A possibly different secretory granule, type d, dense and cigar-shaped, is also produced. The matrix is composed of thin banded fibrils in a dense feltwork. In the matrix of the superficial layers, the “lucency” of the fibrils indicated that they were composed of collagen I, whereas the “lucency” of the cylindrical secretory granules suggested that they transported collagen I precursors to the matrix. Moreover, the use of ruthenium red indicated that the feltwork was composed of proteoglycan; the dotted filaments packed in spherical granules were similar to, and presumably the source of, the matrix feltwork. The superficial layers did not contain collagen II and were collectively referred to as perichondrium. In the deep layers, the ovoid secretory granules displayed collagen II antigenicity and were likely to transport precursors of this collagen to the matrix, where it appeared in the thin banded fibrils. That these granules also carried proteoglycan to the matrix was suggested by their content of short dotted filaments. Thus the deep layers contained collagen II and proteoglycan as in cartilage; they were collectively referred to as the hyaline cartilage region.     

Investigations on the ultrastructural cytology of branchiomeric paragangliomas (author's transl)

The paragangliomas of the jugular and carotid bodies are growth processes which show varying histological and cytological patterns. The real nature of these lesions is still a matter of discussion. In this study 6 jugular and 3 carotid body tumours were investigated using the electron microscope. The main components were irregular cells with short and long cytoplasmic processes closely packed and mostly arranged in complexes. The ultrastructural cytology of the jugular and carotid bodies showed no striking differences. The great majority of the cells exhibits a clear similarity to the cells of normal paraganglia, especially to chief cells of carotid bodies (type I cells). But there were some modifications in the cellular structure including the abnormal structure of mitochondria and a greater variation in the morphology of the dense cored granules. The cytoplasm was dominated by differing populations of mitochondria comprising such of the crista type and such showing tubulus-like structures with a dense matrix and very often intramitochondrial bodies. The characteristic feature was the occurrence of randomly distributed dense cored granules measuring 700-800 A in diameter. These granules display a homogeneous electron dense or moderately dense somewhat granular core which is separated from limiting membrane by a clear electron lucent halo. A further population of granules was of a greater dimension (3,000-4,000 A) revealing an oval or cigar-like shape. In contrast to the former type the homogeneous dense cores of these granules showed a smooth contour and the lucent halo was very narrow. In general, singular exocytotic phenomena could be supposed. More frequently, however, signs of granulolysis were encountered. Free ribosomes, arranged often as polysomes, sparse, disorderly distributed microfilaments of 60-80 A diameter, few 240 A-microtubules and some lysosomal structures are also observed. Usually the cell clusters abutted directly upon the vascular connective tissue. In other cases cytoplasmic processes are intercalated resembling sustentacular cells. Fenestrated capillaries known to be typical for the paraganglionic tissues were only seldom detected. In the interstitial tissue typical collagen fibres are found showing a periodicity of 600-700 A, but occasionally fibres with a periodicity of about 1,200 A could be seen resembling fibrous-long-spacing collagen. Synaptic junctions and nerves or axons were always lacking.