A new cytoplasmic polyhedrosis virus from the salt-marsh mosquito, Aedes cantator (Diptera: Culicidae)

The ultrastructure, development, and histopathology of a new cytoplasmic polyhedrosis virus of Aedes cantator are described. Virus particles measure 70 nm in diameter, are icosahedral in shape, and consist of a central electron-dense core surrounded by a capsid with six projections. Occlusion bodies are irregular in size (0.5–3.0 μm) and shape and contain several virus particles. Virus particles are assembled within an interconnecting network of fine filaments and are occluded by the deposition of a proteinaceous crystal around groups of mature virus particles within a virogenic stroma. Infections are confined to cells of the cardia, gastric ceca, and posterior portion of the midgut, which hypertrophy and frequently lyse. Infected larvae die during the fourth larval instar or as pupae. The prevalence of infection in natural field populations is less than 1%.     

Light and electron microscopical study of Nosema eurytremae

A nuclear-polyhedrosis virus (NPV) of the silkworm, Bombyx mori, which forms an icosahedral inclusion body, was transmitted to larvae of the rice stem borer, Chilo suppressalis. Serial passages of Bombyx NPV in the alternate host by injecting the supernatant of diseased hemolymph produced inclusion bodies with cuboidal and other shapes that differed from the original shape formed in Bombyx. These different shapes increased with times of passages, and after the twelfth passage, only cuboidal inclusion bodies were formed. The icosahedral inclusion bodies in B. mori and the cuboidal inclusion bodies in C. suppressalis occluded singly enveloped virions of the same size (350 × 75 nm), but the cuboidal inclusion bodies contained only a few virions and a large number of membraneous spherical structures. The formation process of the cuboidal inclusion body differed from that of the icosahedral. At first, irregularly branched inclusion bodies containing “vacant” spaces appeared in the infected nuclei. The bodies grew larger with the deposition of protein in the spaces between the branches, and this was accompanied with the occlusion of a large number of membraneous structures formed in the vicinity of the inclusion bodies, which became cuboidal in shape.     

Electron Microscopy of Cells Infected with Adenovirus Type 2

An electron microscope study of two strains of human adenovirus type 2 revealed the production of intranuclear paracrystalline formations by one of the strains. The crystals were composed of cylindrical tubules 25.0 nm in diameter arranged in a crystalline lattice with a periodicity of 75.0 nm. They appeared at 36 hr postinfection in nuclei which contained viral particles. Prolonged treatment with proteolytic enzyme only partially digested the crystals. The relationship of these crystals to similar nonviral crystals found in association with other virus infected-cells was discussed.     

A new virus disease in the housefly, Musca domestica (Diptera)

Reovirus particles were isolated from adults in laboratory colonies of the housefly, Musca domestica. These particles were spherical in outline, 57–76 nm in diameter, and were found only in hemocyte cytoplasm, where virions have been disclosed by a new technique. Virions were present in large numbers, and viral inclusion bodies were identified. The virus particles had pentagonal and hexagonal shapes resembling a simple icosahedral structure. The virus was shown to be infectious and pathogenic to adult flies through injection or by feeding them suspensions from flies that had died of the virus. Electron micrographs of midgut sections from infected flies showed that the midgut cells were packed with dark undulating threads which were not present in uninfected flies. However, no virus particles or inclusion bodies could be seen in these cells. On the basis of their association with infected flies, and the similarity to results from other studies on reoviruses and insect viruses, it is suggested that these threads are an alternative replicative form of the reovirus. When the virus suspensions from heavily infected flies were dialyzed against weak alkaline solutions, the threads showed an inner component of coiled material, 12 nm in diameter, inside an envelope with a diameter of 50–83 nm, mean 60.3 ± 7.5, composed of subunits 7–8 nm long and 7–8 nm across.     

Fine Structure and Morphogenesis of Borna Disease Virus

Borna disease virus (BDV), a negative nonsegmented single-stranded RNA virus, has not been fully characterized morphologically. Here we present what is to our knowledge the first data on the fine ultrastructure and morphogenesis of BDV. The supernatant of MDCK cells persistently infected with BDV treated with n-butyrate contained many virus-like particles and more BDV-specific RNA than that of untreated samples. The particles were spherical, enveloped, and approximately 130 nm in diameter; had spikes 7 nm in length; and reacted with BDV p40 antibody. A thin nucleocapsid, 4 nm in width, was present peripherally in contrast to the thick nucleocapsid of hemagglutinating virus of Japan. The BDV particles reproduced by budding on the cell surface.     

Effects of Substituting Granulin or a Granulin-Polyhedrin Chimera for Polyhedrin on Virion Occlusion and Polyhedral Morphology in Autographa californica Multinucleocapsid Nuclear Polyhedrosis Virus

Substitution of granulin from the Trichoplusia ni granulosis virus (TnGV) for polyhedrin of the Autographa californica multinucleocapsid nuclear polyhedrosis virus (AcMNPV) yielded a few very large (2 to 5 μm) cuboidal inclusions in the cytoplasm and nucleus of infected cells. These polyhedra lacked the beveled edges characteristic of wild-type AcMNPV polyhedra, contained fractures, and occluded few virions. Placing a nuclear localization signal (KRKK) in granulin directed more granulin to the nucleus and resulted in more structurally uniform cuboidal inclusions in which no virions were observed. A granulin-polyhedrin chimera produced tetrahedral occlusions with more virions than granulin inclusions but many fewer than wild-type polyhedra. Despite the unusual structure of the granulin and granulin-polyhedrin inclusions, they interacted with AcMNPV p10 fibrillar structures and electron-dense spacers that are precursors of the polyhedral calyx. The change in inclusion shape obtained with the granulin-polyhedrin chimera demonstrates that the primary amino acid sequence affects occlusion body shape, but the large cuboidal inclusions formed by granulin indicate that the amino acid sequence is not the only determinant. The failure of granulin or the granulin-polyhedrin chimera to properly occlude AcMNPV virions suggests that specific interactions occur between polyhedrin and other viral proteins which facilitate normal virion occlusion and occlusion body assembly and shape in baculoviruses.     

Crystals of virus-like particles in the metacestodes of Taenia solium and T. crassiceps

Crystals of virus-like particles (VLP) are described as occurring in the nuclei of damaged tegumentary cytons from carcasses of Taenia solium metacestodes that had been stripped of their teguments. The VLP are grouped as parallel lines of round particles in an hexagonal packaging of spheroids forming small or large crystals. The individual particles have an external diameter of 36-37 nm and a wall of 5-6 nm thick, which surround a cavity of lower electron density. As identical crystals were also observed in normal tissues of T. solium and of T. crassiceps, it is suggested that both species of cysticerci are normal carriers of a similar species of virus. The possible biological implications of this condition are discussed.     

Virus Particles in Apparently Healthy Peregrinus maidis

Virus-like particles were found in apparently healthy Peregrinus maidis (Ashm.) in Venezuela. The particles were observed in the salivary gland, intestine, mycetome, adipose tissue, ovary, and hemolymph. In the cells, the particles occurred in the cytoplasm singly, in groups, free or within vesicles, and in hexagonally arranged crystals. In P. maidis from Hawaii such particles were not found. However, in these insects, single particles or crystals were observed after injecting suspensions of intestines from P. maidis from Venezuela. The particles were not observed in insects feeding on plants soiled with excretions from particle-containing P. maidis. Particles in organs of insects or in pellets of intestines were polygonal and showed a weakly contrasted envelope and a highly contrasted core. The particles had a diameter of 54 ± 9 mμ. They are believed to represent a Peregrinus virus causing latent infection.     

USE OF SERIAL SECTIONS TO DELINEATE THE STRUCTURE OF PORTHETRIA DISPAR VIRUS IN THE ELECTRON MICROSCOPE

Consecutive serial sections of polyhedra obtained from gipsy moth larvae infected with P. dispar virus revealed bundles of viral rods scattered and oriented at random within the polyhedral body. Each bundle was entirely surrounded by a dense, sharply defined membrane. The rods measured 18 to 22 mµ in diameter and averaged 280 mµ in length. No spherical viral particles were encountered. The effects of variable compression and periodic distortion of the sections on the appearance of the virus are discussed.     

Purification,electron microscopy and serology of virus isolated fromEuonymus europaea

“Euonymus mosaic virus”, purified from cucumber cotyledons by the differential and density-gradient centrifugation, shows typical nucleoprotein absorption spectrum. Electron microscopy reveals isometric virus particles of about 37 nm diameter. No reaction of purified “Euonymus mosaic virus” was observed with antisera against a raspberry ringspot virus, tobacco ringspot virus, cherry leaf roll virus, strawberry latent ringspot virus, tomato ringspot virus, elm mosaic virus, arabis mosaic virus, tomato bushy stunt virus and watermelon mosaic virus.     

Some properties of a new virus of Pieris rapae

A new insect virus of Pieris rapae was purified using a chloroform-butanol treatment followed by two differential and sucrose gradient centrifugations. The sedimentation coefficient of the purified virion was approximately 132 S, and it banded at a density of 1.39 g/cm³ in cesium chloride. The virion has a nonenveloped capsid with icosahedral symmetry. Several virions were shown to have a regular hexagonal contour about 25 nm in diameter and to be composed of many capsomeres. Full and empty viral particles, with 12 capsomeres around the periphery of the capsid, were noted. In some particles a small core has been observed which is spherical, about 15 nm in diameter. Both purified virus and partially purified virus preparations from dead, infected larvae gave only one precipitin band with a reaction of identity when tested against the antiserum to partially purified virus. When crude extracts of uninfected larvae and purified virus were tested against antiserum to partially purified virus, the pure virus produced a precipitin band. The band was formed independently and did not join to the band of the uninfected insect producing a typical reaction of nonidentity.     

Cytopathology of spotted cucumber beetle hemocytes containing virus-like particles

Spherical, virus-like particles with an average diameter of 70 nm were consistently found in the hemocytes of field-collected, spotted cucumber beetles, Diabrotica undecimpunctata. The particles and associated inclusion bodies occurred both in the cytoplasm and nucleus. Hemocytes containing the particles exhibited structural features which were indicative of virus infection. These were (1) the appearance of fibril-containing membranous vesicles, 70 to 80 nm in diameter, in the perinuclear space and in the cisternae of rough endoplasmic reticulum, (2) accumulation of vesicle-containing cisternae in certain areas of cytoplasm, (3) appearance and condensation of granular material in viroplasm-like structures, and (4) appearance of virus-like particles. The results suggest that the particles are viral in nature and occur widely in leaf-feeding beetles.     

An enzootic nuclear polyhedrosis virus of pink shrimp: Ultrastructure,prevalence, and enhancement

A nuclear polyhedrosis virus exists in pink shrimp, Penaeus duorarum, from waters of the northern Gulf of Mexico. This virus is rod-shaped, 269 nm long, and possesses an outer envelope surrounding its nucleocapsid. The nucleocapsid is 50 nm in diameter. The virus occurs in nuclei of host hepatopancreatic and midgut cells, and is both free in the nucleus and occluded within pyramidal-shaped polyhedral inclusion bodies (PIB's). Histochemically and ultrastructurally, the shrimp PIB's appear to be ribonucleoprotein and in fine structure bear close resemblance to polyhedral inclusion bodies of Baculovirus species from insects. However, the lattice line-to-line spacing is greater than that usually reported for insect PIB's. Crowding and chemical stress of shrimp in aquaria may enhance and increase the virus infection and prevalence. In limited experiments, shrimp fed heavily infected hepatopancreatic tissues had much higher mortality than controls fed only fish. The virus appears to be enzootic in pink shrimp in nature. Cytopathological changes in infected cells of shrimp appear similar to those in insects infected with certain species of Baculovirus. The name Baculovirus penaei n.sp. is proposed for the shrimp virus.     

STRUCTURE AND DEVELOPMENT OF VIRUSES OBSERVED IN THE ELECTRON MICROSCOPE : IV. VIRUSES OF THE RI-APC GROUP

Representative viruses of the RI-APC group were observed with the electron microscope in thin sections of infected HeLa cells. The viral particles varied in density, were approximately 60 mµ in diameter and had a center to center spacing when close packed of about 65 mµ. Many of the less dense particles exhibited an internal body averaging 24 mµ in diameter. It was suggested that within the nucleus the virus differentiated from dense granular and reticular material and formed crystals. Disintegration of the crystals and disruption of the nuclear membrane with release of virus into the cytoplasm appeared to occur at any stage. No evidence to suggest development of the virus in the cytoplasm was obtained. It was possible to deduce the structure of the viral crystal from the electron micrographs. The viral particles are packed in a cubic body—centered lattice. Correlative histochemical observations in the light microscope which are now in progress revealed that the crystals and non-crystalline aggregates of virus were strongly Feulgen-positive.     

Boolarra virus: Ultrastructure of intracytoplasmic virus formation in cultured Drosophila cells

Boolarra virus (BoV) is a Nodavirus isolated from Oncopera intricoides. Drosophila cell lines 1 (D1) and 2 (D2) were infected with virus and the progession of infection was followed in ultrathin sections viewed by the electron microscope. Viral morphogenesis was restricted to the cytoplasm. Virogenic stroma condensed to electron-dense areas in which were embedded electron-lucent and electron-dense particles. picornaviruslike particles 30 nm in diameter were found in membranous channels and paracrystalline arrays and were scattered throughout the cytoplasm of cells. Virus was released from cisternae and tracts which extended to the cells' periphery. Local disruption of cell membranes also released particles and aggregates of virus into the environment.     

Ultrastructural investigation on a strain of a cytoplasmic-polyhedrosis virus with nuclear inclusions

A strain of a cytoplasmic-polyhedrosis virus causes the formation of crystalline inclusions almost entirely in the nucleus, and only rarely in the cytoplasm, of the midgut epithelial cells of the silkworm Bombyx mori. It also differs from the typical strain in causing the hypertrophy of the nucleoli and the formation of dense reticulum and spherical bodies in the nucleus. The virus particles and the virogenic stromata of the new strain resemble those of the typical strain. The cytoplasmic inclusions contain virus particles, while the nuclear inclusions do not. When the infected larvae are kept at 30°C for 15 hr or at 35°C for 3–15 hr, the nuclear inclusions break up into particles of 70–250 nm in diameter. The particles are dispersed in the cells but not present in the spaces previously occupied by the decomposed inclusions.     

Copper-Containing Anti-Biofilm Nanofiber Scaffolds as a Wound Dressing Material

Copper particles were incorporated into nanofibers during the electrospinning of poly-D,L-lactide (PDLLA) and poly(ethylene oxide) (PEO). The ability of the nanofibers to prevent Pseudomonas aeruginosa PA01 and Staphylococcus aureus (strain Xen 30) to form biofilms was tested. Nanofibers containing copper particles (Cu-F) were thinner (326 ± 149 nm in diameter), compared to nanofibers without copper (CF; 445 ± 93 nm in diameter). The crystalline structure of the copper particles in Cu-F was confirmed by X-ray diffraction (XRD). Copper crystals were encapsulated, but also attached to the surface of Cu-F, as shown scanning transmission electron microscopy (STEM) and transmission electron microscopy (TEM), respectively. The copper particles had no effect on the thermal degradation and thermal behaviour of Cu-F, as shown by thermogravimetric analysis (TGA) and differential scanning calorimeter (DSC). After 48 h in the presence of Cu-F, biofilm formation by P. aeruginosa PA01 and S. aureus Xen 30 was reduced by 41% and 50%, respectively. Reduction in biofilm formation was ascribed to copper released from the nanofibers. Copper-containing nanofibers may be incorporated into wound dressings.     

Control of the bacterium Serratia marcescens in an insect host-parasite rearing program

Two occluded viruses of the Entomopoxvirus (D)/¹: ¹/¹: $\text{X}\text{X}\text{:}\text{I}\text{O}$ (= Vagoiavirus) group have been found in larvae of Dermolepida albohirtum (Scarabaeidae: Melolonthinae) and Aphodius tasmaniae (Scarabaeidae: Aphodiinae) from northern Queensland and northern Tasmania, Australia, respectively. Electron microscopical studies have been made of thin sections of occluded (mature) and nonoccluded virus particles within the fat body tissue of living diseased D. albohirtum larvae and of occluded virus particles within a dead, field-collected A. tasmaniae larva. The morphology and development of the known Australian entomopoxviruses are compared with previously known entompox or spheroidosis viruses from various insects.     

Membrane structures ofAcholeplasma laidlawii and its virus

The main types of ultrastructures found in the freeze-fracture faces ofAcholeplasma laidlawii S 2 and its virus MV-Lg-L 172 were (1) particles 7–19 nm in diameter, mostly located in the convex cytoplasmic fracture faces. (2) small bulges or aggregates, 13–25 nm in diameter. which occupied only limited areas of both inner and outer fracture faces of some mycoplasmas, (3) numerous tiny grains and/or spikes 2–6 nm in diameter, protruding from a finely structured background, especially in the outer concave mycoplasmal fracture faces, and (4) linear structures, most probably fibrils and thicker filaments, both in the fracture faces and around mycoplasmas and viruses and connected with them. There was a high degree of structural similarity between mycoplasmal and viral membranes; no obvious significant difference was found.