STAGES IN THE DEVELOPMENT OF TWO INSECT VIRUSES

1954 ◽  
Vol 1 (3) ◽  
pp. 170-174 ◽  
Author(s):  
F. T. Bird ◽  
Mary M. Whalen
Keyword(s):  
Electron Micrographs ◽  
Free Virus ◽  
Insect Virus ◽  
Thin Sections ◽  
Virus Particles ◽  
Nuclear Membranes ◽  
Small Holes ◽  
Insect Viruses

Stages in the development of viruses of two Hymenopterous insects, Diprion hercyniae (Htg.) and Neodiprion americanus banksianae Roh., are shown in electron micrographs of thin sections. Following swelling of the nuclei and nucleoli and coagulation of the chromatin, rod-shaped virus particles appear chiefly on the exposed surfaces of the chromatin. The chromatin of D. hercyniae often coagulates into separate lumps that suggest small polyhedra. These first produce rod-shaped particles on their exposed surfaces and later transform into recognizable polyhedra. The chromatin of N. a. banksianae is more uniformly dispersed, and polyhedra arise as thickenings within the chromatin. In the latter insect, virus particles are frequently observed within the developing polyhedra, suggesting that polyhedra are formed by the accumulation of protein around groups of virus particles. Both polyhedra and free virus particles are larger and denser in the nuclear sap than in the chromatin. Their formation continues in remnants of chromatin in nuclei otherwise filled with large polyhedra. An incidental observation is that the nuclear membranes of some nuclei are pitted with small holes.

scholarly journals THE STRUCTURE OF INSECT VIRUS PARTICLES

1956 ◽  
Vol 2 (3) ◽  
pp. 301-306 ◽  
Author(s):  
Kenneth M. Smith
Keyword(s):  
Inclusion Bodies ◽  
Virus Disease ◽  
Composite Particles ◽  
Insect Virus ◽  
Virus Diseases ◽  
Thin Sections ◽  
Virus Particles ◽  
Nuclear Polyhedrosis

Thin sections have been cut of the virus particles from four types of insect virus diseases: cytoplasmic polyhedroses of lepidopterous larvae, a nuclear polyhedrosis of Tipula paludosa (Diptera), a granulosis from Melanchra persicariae (Lepidoptera), and a new virus disease without polyhedra from T. paludosa. The cytoplasmic polyhedral viruses are thought to have composite particles in some cases. The shape and enveloping membranes of the different virus particles are compared. In the new virus disease of T. paludosa some of the virus particles appear to be empty; inclusion bodies surrounded by complicated membranes are also demonstrated.

Intranuclear changes in the polyhedrosis of Tipula paludosa (Meig.)

Parasitology ◽  
1955 ◽  
Vol 45 (3-4) ◽  
pp. 482-487 ◽  
Author(s):  
Kenneth M. Smith
Keyword(s):  
Electron Microscopy ◽  
Nuclear Membrane ◽  
Blood Cells ◽  
Free Virus ◽  
Inner Membrane ◽  
Thin Sections ◽  
Virus Particles ◽  
Nuclear Changes ◽  
Thin Walled

By means of ultra-thin sections for electron microscopy it has been possible to observe intra-nuclear changes in the polyhedrosis of larvae of Tipula paludosa. The virus rods arise in the centres of the greatly enlarged nuclei of blood cells. Thin-walled vesicles, apparently filled with fluid, form round individual virus rods and collect in masses on the inner wall of the nuclear membrane. Crystallization then begins, starting at the edge against the nuclear membrane. The vesicles are gradually compressed round the rods, eventually forming a capsule. Sections through free virus particles show them to be enclosed in a membrane, a second inner membrane round the substance of the rod may also be present.There appears to be no capsule round the free virus particles such as encloses the virus particles inside the polyhedral crystal.

Periodic Structure in the Matrix Protein of an Insect Virus

1982 ◽  
Vol 40 ◽  
pp. 302-303
Author(s):  
H.M. Mazzone ◽  
W.F. Engler ◽  
R. Zerillo ◽  
G.F. Bahr
Keyword(s):  
Inclusion Body ◽  
Periodic Structure ◽  
Matrix Protein ◽  
Malacosoma Disstria ◽  
Insect Virus ◽  
Virus Particles ◽  
The Matrix ◽  
Nucleopolyhedrosis Virus

The nucleopolyhedrosis virus (NPV) of the forest tent cater - pillar (Malacosoma disstria Hubner) has been analyzed in our laboratories. As a representative of the Baculovirus class, the NPV has virus particles enclosed with in a proteinaceous structure, the inclusion body.

Studies of a Defective Measles Virus

1968 ◽  
Vol 26 ◽  
pp. 208-209
Author(s):  
R. M. McCombs ◽  
M. Benyesh-Melnick ◽  
J. P. Brunschwig
Keyword(s):  
Inclusion Bodies ◽  
Measles Virus ◽  
Giant Cells ◽  
Helical Structures ◽  
Thin Sections ◽  
Virus Particles ◽  
Extracellular Virus ◽  
Culture Cells ◽  
Infected Cells ◽  
Eosinophilic Inclusions

Measles virus is an agent that is capable of replicating in a number of different culture cells and generally causes the formation of multinucleated giant cells. As a result of infection, virus is released from the cells into the culture fluids and reinfection can be initiated by this cell-free virus. The extracellular virus has been examined by negative staining with phosphotungstic acid and has been shown to be a rather pleomorphic particle with a diameter of about 140 mμ. However, no such virus particles have been detected in thin sections of the infected cells. Rather, the only virus-induced structures present in the giant cells are eosinophilic inclusions (intracytoplasmic or intranuclear). These inclusion bodies have been shown to contain helical structures, resembling the nucleocapsid observed in negatively stained preparations.

The restoration of blurred electron micrographs

1986 ◽  
Vol 44 ◽  
pp. 180-181
Author(s):  
Bridget Carragher ◽  
David A. Bluemke ◽  
Michael J. Potel ◽  
Robert Josephs
Keyword(s):  
Cross Section ◽  
Electron Micrographs ◽  
Relative Motion ◽  
Finite Thickness ◽  
Image Plane ◽  
Helical Axis ◽  
Thin Sections ◽  
Structural Details

We have investigated the feasibility of restoring blurred electron micrographs. Two related problems have been considered; the restoration of images blurred as a result of relative motion between the specimen and the image plane, and the restoration of images which are rotationally blurred about an axis. Micrographs taken while the specimen is drifting result in images which are blurred in the direction of motion. An example of rotational blurring arises in micrographs of thin sections of helical particles viewed in cross section. The twist of the particle within the finite thickness of the section causes the image to appear rotationally blurred about the helical axis. As a result, structural details, particularly at large distances from the helical axis, will be obscured.

scholarly journals INTRACELLULAR FORMS OF POX VIRUSES AS SHOWN BY THE ELECTRON MICROSCOPE (VACCINIA, ECTROMELIA, MOLLUSCUM CONTAGIOSUM)

1953 ◽  
Vol 98 (2) ◽  
pp. 157-172 ◽  
Author(s):  
William H. Gaylord ◽  
Joseph L. Melnick
Keyword(s):  
Electron Microscope ◽  
Hollow Spheres ◽  
Molluscum Contagiosum ◽  
Dense Granule ◽  
Homogeneous Material ◽  
Dense Matrix ◽  
Thin Sections ◽  
Virus Particles ◽  
Typical Inclusion ◽  
Mature Virus

The intracellular development of three pox viruses has been studied with the electron microscope using thin sections of infected tissue. Cells infected with vaccinia, ectromelia, and molluscum contagiosum viruses all form developmental bodies preliminary to the production of mature virus. Developmental bodies, believed to be virus precursors, are round to oval, slightly larger than mature virus particles, less dense to electrons, and have a more varied morphology. It is suggested as a working hypothesis that the process of maturation of a virus particle takes place as follows. In the earliest form the developmental bodies appear as hollow spheres, imbedded in a very dense cytoplasmic mass constituting an inclusion body, or in a less dense matrix near the nucleus in cells without typical inclusion bodies. The spheres become filled with a homogeneous material of low electron density. A small, dense granule appears in each developmental body and grows in size at the expense of the low density material. Following growth of the granule, particles are found with the dimensions of mature virus and having complex internal structure resembling bars or dumbells. Mature virus is ovoid and very dense to electrons. An "empty" interior may be found within its thick walls.

A Massive System of Microtubules Associated with Cytoplasmic Movement in Telotrophic Ovarioles

1970 ◽  
Vol 6 (2) ◽  
pp. 431-449
Author(s):  
H. C. MACGREGOR ◽  
H. STEBBINGS
Keyword(s):  
Electron Micrographs ◽  
Thin Sections ◽  
Positive Form ◽  
Form Birefringence ◽  
Terminal Filament ◽  
Telotrophic Ovary ◽  
Oocyte Cytoplasm ◽  
Heavy Labelling

The telotrophic ovary of Notonecta glauca glauca consists of 7 ovarioles. Each ovariole comprises, from front to rear, a terminal filament, a trophic region, a prefollicular region, and a series of 10-15 follicles of progressively increasing size The trophic region is largely syncytial and is made up of polyploid trophic nuclei packed around a central trophic core The cytoplasm of the trophic core is continuous with the cytoplasm of each oocyte through a system of trophic tubes. There is one trophic tube per oocyte. The trophic nuclei have large nucleoli. There are a few small nucleoli in the oocyte nuclei The cytoplasm of the trophic core, the trophic tubes, and the oocytes is rich in RNA. Autoradiographs of sections of ovarioles fixed 2 h after injection of [3H]uridine into animals show label over the trophic nuclei only. Eight-hour autoradiographs show heavy labelling of the trophic region and label over the front ends of the trophic tubes, but little label over the posterior regions of the tubes or the oocyte cytoplasm. Later autoradiographs mdicate that label gradually spreads backwards from the trophic core, along the trophic tubes, and progressively builds up in the oocyte cytoplasm These observations are thought to indicate synthesis of RNA in the trophic region and movement of RNA from the trophic core along the trophic tubes to the oocytes The trophic core and tubes show brilliant positive form birefringence with respect to their lengths. This birefringence can be reduced by keeping animals at 2 °C for 12 h, and eliminated by placing ovarioles in 1 % colchicine for 6 h. Electron micrographs of thin sections of ovarioles show that trophic core and tubes are densely and uniformly packed with ribosomes and microtubules The latter are lined up along the trophic tubes. There are about 30000 microtubules evident in a TS through a trophic tube 15µm wide. Lengths of microtubules up to 2µm have been observed. Ribosomes are packed between the microtubules but are excluded from regions where the spacing between adjacent microtubules is less than 25 nm The contribution of the trophic region to the oocytes and the role of the microtubules in maintaining or facilitating the movement of ribosomes along the trophic tubes is discussed

Structural cross-bridges between microtubules and mitochondria in central axons of an insect (Periplaneta americana)

1977 ◽  
Vol 27 (1) ◽  
pp. 255-272
Author(s):  
D.S. Smith ◽  
U. Jarlfors ◽  
M.L. Cayer
Keyword(s):  
Electron Micrographs ◽  
Mitochondrial Membrane ◽  
Periplaneta Americana ◽  
Freeze Fracture ◽  
Outer Mitochondrial Membrane ◽  
Thin Sections ◽  
Cross Bridge ◽  
Multiple Association ◽  
Random Models ◽  
Cross Bridges

The distribution of microtubules and mitochondria in central axons of an insect (Periplaneta americana) is assessed by comparison between counts on micrographs and computed axon random ‘models’. These studies show that the observed multiple association of microtubules with individual mitochondria is statistically highly significant. Electron micrographs of thin sections show that linkage is effected by physical cross-bridge, possibly comprising components from the microtubule and mitochondrion. Linear particle arrays are described on the outer mitochondrial membrane in freeze-fracture replicas, and tentatively related to the bridges seen in thin sections. The results are discussed in terms of proposed roles of microtubules in neurons and other cells.

scholarly journals A non-enveloped arbovirus released in lysosome-derived extracellular vesicles induces super-infection exclusion

2020 ◽  
Author(s):  
Thomas Labadie ◽  
Polly Roy
Keyword(s):  
Extracellular Vesicles ◽  
Defense Mechanism ◽  
Degradation Process ◽  
Free Virus ◽  
Enveloped Viruses ◽  
Virus Particles ◽  
Enveloped Virus ◽  
Super Infection

AbstractRecent developments on extracellular vesicles (EVs) containing multiple virus particles challenge the rigid definition of non-enveloped viruses. However, how non-enveloped viruses hijack cell machinery to promote non-lytic release in EVs, and their functional roles, remain to be clarified. Here we used Bluetongue virus (BTV) as a model of a non-enveloped arthropod-borne virus and observed that the majority of viruses are released in EVs, both in vitro and in the blood of infected animals. Based on the cellular proteins detected in these EVs, and use of inhibitors targeting the cellular degradation process, we demonstrated that these extracellular vesicles are derived from secretory lysosomes, in which the acidic pH is neutralized upon the infection. Moreover, we report that secreted EVs are more efficient than free-viruses for initiating infections, but that they trigger super-infection exclusion that only free-viruses can overcome.Author summaryRecent discoveries of non-enveloped virus secreted in EVs opened the door to new developments in our understanding of the transmission and pathogenicity of these viruses. In particular, how these viruses hijack the host cellular secretion machinery, and the role of these EVs compared with free-virus particles remained to be explored. Here, we tackled these two aspects, by studying BTV, an emerging arthropod-borne virus causing epidemics worldwide. We showed that this virus is mainly released in EVs, in vivo and in the blood of infected animals, and that inhibition of the cell degradation machinery decreases the release of infectious EVs, but not free-virus particles. We found that BTV must neutralize the pH of lysosomes, which are important organelles of the cell degradation machinery, for efficient virus release in EVs. Our results highlight unique features for a virus released in EVs, explaining how BTV transits in lysosomes without being degraded. Interestingly, we observed that EVs are more infectious than free-virus particles, but only free-viruses are able to overcome the super-infection exclusion, which is a common cellular defense mechanism. In conclusion, our study stresses the dual role played by both forms, free and vesicular, in the virus life cycle.

scholarly journals ELECTRON MICROSCOPE OBSERVATIONS ON THE SURFACE ADENOSINE TRIPHOSPHATASE-LIKE ENZYMES OF HELA CELLS INFECTED WITH HERPES VIRUS

1963 ◽  
Vol 19 (2) ◽  
pp. 337-347 ◽  
Author(s):  
M. A. Epstein ◽  
S. J. Holt
Keyword(s):  
Enzyme Activity ◽  
Hela Cells ◽  
Adenosine Triphosphatase ◽  
Plasma Membranes ◽  
Enzyme Reaction ◽  
Thin Sections ◽  
Virus Particles ◽  
Extracellular Virus ◽  
Simplex Virus ◽  
Vacuolar Membranes

HeLa cells infected with herpes simplex virus have been examined in thin sections by electron microscopy after cytochemical staining for the presence of surface enzymes splitting adenosine triphosphate. As with uninfected HeLa cultures (18), the opaque enzyme reaction product was localized at the plasma membranes of about half the cells, tending to be present where there were microvilli and absent on smooth surfaces. Where mature extracellular herpes particles were found in association with cell membranes showing the enzyme activity, they were invariably likewise stained, and conversely, those mature particles which lay close against cells without reaction product at the surface were themselves free of it. Particles found budding into cytoplasmic vacuoles were also always without opaque deposit since this was never seen at vacuolar membranes, even in cells having the activity at the surface. The enzyme reaction product thus provided a marker indicating the manner in which the particles escape from cells and mature by budding out through cellular membranes, carrying, in the process, a portion of the latter on to themselves to form the outer viral limiting membrane. In some instances, virus particles were observed with more opaque material covering them than was present at the cell membrane with which they were associated. This finding has been taken as evidence for a physiological waxing and waning of surface enzyme activity of adenosine triphosphatase type. The fine structure of the mature extracellular virus as prepared here, using glutaraldehyde fixation, is also recorded. The observations and interpretations are discussed in full.

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