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At least 1,351 records · Page 75Linked to original sources
PubMed1974

Structural studies of avian myeloblastosis virus: comparison of polypeptides in virion and core component by dodecyl sulfate-polyacrylamide gel electrophoresis.

Two different systems of dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) in separate laboratories detected analogous patterns of dye bands in virions of avian myeloblastosis virus (AMV). At least 11 of the dye bands co-migrated with the major polypeptides reported in Rous sarcoma virus. Particles with the morphology of the AMV core component, obtained after exposure of AMV to the nonionic surfactant Sterox SL, contained major polypeptides p12, p27, p60, p64, p91, and p98. The polypeptide p12 has been previously shown to be the major constituent of the inner ribonucleoprotein (RNP) of the AMV core, and has been designated p12(N). Two RNP polypeptides, p64 and p91, co-electrophoresed with purified AMV DNA polymerase and have now been designated p64(P) and p91(P). The polypeptide p27 has been identified as a probable constituent of the core shell, and has accordingly now been designated p27(C). In comparison to virions of AMV, the AMV core component contained a greatly reduced amount of polypeptide p15 and appeared to lack a major polypeptide, p19. Consequently, these polypeptides may be associated either with the exterior of the core shell or the interior of the viral envelope. Glycopeptides were not detected in AMV cores, in agreement with earlier reports that they reside in external projections from the viral envelope.

Avian Leukosis Virus↗
PubMed1974

Disruptive action of potassium phosphotungstate on phiT, the temperate bacteriophage of Bacillus megaterium 899a.

Although untreated phiT may be dried on grids without damage, they were disrupted when negatively stained with potassium phosphotungstate. The potassium phosphotungstate reacted with phage suspended in phosphate buffer, and the altered but still-viable phage was disrupted only on drying. Stability of altered phage was not recovered by dialysis against 10(-3) M Mg(2+).

Bacillus megaterium↗
PubMed1974

Unusual bacteriophages in Salmonella newport.

Six phages were isolated from sewage and from a lysogenic strain. Three of them, belonging to a new morphological group, had contractile tails and elongated heads with axial ratios of 2.4:1. Two phages, possessing short tails and very long heads with axial ratios of 3.5:1, were new isolates of an extremely rare group. Phages of both groups formed polyheads of various sizes and shapes. The last phage, 61 nm in diameter, seemed to have a tail-like appendage. All phages had double-stranded DNA, were active on enterobacteria only, and differed in their host range. The first five phages seemed to be Salmonella specific.

Acridines↗
PubMed1974

Effect of ultraviolet light on mengovirus: formation of uracil dimers, instability and degradation of capsid, and covalent linkage of protein to viral RNA.

UV irradiation of purified mengovirus resulted in a very rapid inactivation of the infectivity of the virions (D(37) [37% survival dose] = 700 ergs/mm(2)) which correlated in time with the formation of uracil dimers in the viral RNA. During the first 2 min of irradiation, an average of 1.7 uracil dimers were formed per PFU of virus inactivated. Hemagglutination activity of the virions began to decrease only after a lag period of about 5 min and at a much lower rate (D(37) = 84,000 ergs/mm(2)). This decrease coincided in time with the appearance of altered proteins in the capsid and a structural change in the capsid. Although 10- to 20-min irradiated virions appeared intact in the electron microscope and sedimented at 150S in sucrose density gradients, the RNA of the virions became accessible to RNase and extractable by low concentrations of sodium dodecyl sulfate, and the virions broke down upon equilibrium centrifugation in CsCl gradients. During longer periods of irradiation (30 to 60 min), a progressively greater proportion of the virions were converted to 14S protein particles and 80S ribonucleoprotein particles composed of intact viral RNA and about 30% of the capsid proteins, alpha, beta, and gamma. Empty capsids were not detectable at any time during 60 min of irradiation, by which time disruption of the virions was complete. Irradiation of complete virions also resulted in an increased sedimentation rate of the viral RNA and in the covalent linkage to the viral RNA of about 1% of the total capsid protein in the form of heterogeneous low-molecular-weight polypeptides. The two observations seem to be causally related, since irradiation of isolated viral RNA did not result in an increase in sedimentation rate of the RNA, even though uracil dimer formation in viral RNA occurred at about the same rate and to the same extent whether intact virions or viral RNA were irradiated.

Animals↗
PubMed1974

Cold lability of Bacillus cereus bacteriophage CP-51.

Phage CP-51 was rapidly inactivated when stored at the usual refrigerator temperatures (2 to 4 C) and even more rapidly when exposed to 0 C. The loss in viability resulting from exposure to cold appeared to correlate with the increase in number of phage particles having contracted tails. High concentrations (0.01 M) of Mg(2+), Ca(2+), or Mn(2+) stabilized the phage considerably, but even in the presence of these divalent cations, it was much less stable at 0 C than at 15 C.

Bacillus cereus↗
PubMed1974

Structure of infectious bursal disease virus.

Infectious bursal disease virus of chickens was purified, and its structure was examined by the negative-staining technique in the electron microscope. The buoyant density of infectious bursal disease virus in CsCl was found to be 1.34 g/cm(3). The morphological details suggest that the capsid of the virion consists of a single layer of 32 capsomeres arranged in 5:3:2 symmetry. The virion measured about 55 nm in diameter and had no envelope.

Animals↗
PubMed1974

Diffusion constant and dimension of bacteriophage phi X174 as determined by self-beat laser light spectroscopy and electron microscopy.

The diffusion constant of bacteriophage phiX174 was determined by laser light self-beat spectroscopy. The method allows one to establish the diffusion constant in comparatively short time and with high accuracy. From the diffusion constant D(37) = 1.96 +/- 0.08 x 10(-7) cm(2)/s, the size of the virus particles within their aqueous milieu can be calculated. For phiX174, a diffusional diameter of 31.4 +/- 1.0 nm was found, in good agreement with measurements of diameters of freezeetched (32.3 +/- 1.8 nm) and negatively stained particles (33.8 +/- 2.1 nm), provided that the entire spikes of the virion are included. Other isometric viruses may show a complex interaction of the virion with the surrounding water and its ions.

Coliphages↗
PubMed1970

Characteristics of a virus isolated from a feline fibrosarcoma.

A virus was isolated from a radioresistant feline fibrosarcoma. It induced multi-nucleated giant-cell formation and lysis in a cell line derived from a canine fibro-sarcoma, which was used to characterize the virus. End-point titrations in these cells required 28 days. The virus was sensitive to ether and heat and was destroyed at pH 3. Replication was not inhibited by 5-bromodeoxyuridine. Electron microscopy revealed assembly by a budding process from the plasma membrane of infected cells. The average diameter of the virion was 106 nm. Intracisternal particles with an average diameter of 45 nm were present within infected cells. In two instances secondary monolayers of feline renal cells underwent morphological transformation after inoculation of the virus. The two strains of transformed cells are now in continuous culture and do not yield infectious virus.

Animals↗
PubMed1970

Structure and cytopathic effects of Nelson Bay virus.

A virus isolated from a flying fox (Pteropus poliocephalus) has a morphology similar to that of reoviruses. However, unlike the reoviruses, this virus has a rapid cytopathic effect, causing cell fusion, vacuolization of the cytoplasm, and an unusual nuclear degeneration. Immunofluorescence indicates that viral antigen is distributed through both nucleus and cytoplasm. Viral maturation appears to take place in discrete cytoplasmic factories, and there is no apparent involvement of spindle tubules.

Animals↗
PubMed1971

Separation and structure of components of nuclear polyhedrosis virus of the silkworm.

Morphology of structural components of nuclear polyhedrosis virus (NPV) particles of the silkworm (Bombyx mori Linné) was studied by electron microscope using negative staining. NPV particles isolated from polyhedra could be separated into five structural components by centrifugation in sucrose density gradients. The lowest band (band I) was found to consist of thick rod-shaped particles (330 by 80 nm) with knobby surfaces and with occasional protrusion at one end. The second band from the bottom (band II) was shown to consist mainly of slender rod-shaped particles (360 by 60 nm), in which internal structures were visible as a dense mass. Regular striations were also seen on the surface of these particles. By treatment with mercaptoethanol, these particles were drastically damaged, and in some cases the internal substances were partially released, producing empty inner membranes of various degrees of disintegration. In bands III and IV, both empty spherical and empty rod-shaped membranes were present. Band III was rich in empty spherical membranes which were shown to be the outer membranes of thick rod-shaped particles. The empty rod-shaped membranes, the inner membranes, were mainly located in band IV and have cross striations on the surface. It is remarkable that the uppermost band (band V) consisted purely of small spherical particles, somewhat heterogeneous in size and shape (around 20 to 25 nm in diameter), indicating the particles to be the degradation product of the virus particles. Similar particles could also be observed within the empty inner membranes.

Animals↗
PubMed1971

Interaction of Pseudomonas bacteriophage 2 with the slime polysaccharide and lipopolysaccharide of Pseudomonas aeruginosa strain B1.

Purified slime polysaccharide B and lipopolysaccharide of Pseudomonas aeruginosa strain BI were shown to possess receptor-like properties in inactivating Pseudomonas phage 2, whereas lipoprotein and glycopeptide fractions were devoid of activity. On a weight basis, slime polysaccharide B was more effective than lipopolysaccharide in inactivating phage. The specificity of the reaction with slime polysaccharide B was indicated by the fact that slime polysaccharide A of P. aeruginosa strain EI failed to inactivate phage 2. Electron micrographs showed phage 2 in typical, tail-first position of attachment on intact cells of strain BI, slime polysaccharide B, and lipopolysaccharide. Tail fibers were discernible during phage attachment.

Adsorption↗
PubMed1971

Mechanism of intranuclear crystal formation of herpes simplex virus as revealed by the negative staining of thin sections.

Structural alterations induced in HeLa cells by herpes simplex virus and the mechanism whereby the virus is formed in the nucleus in crystal arrays were studied by electron microscopy with both the usual and negatively stained sections. Aggregates of granular and filamentous material were observed in the cytoplasm of infected cells with both sections. On the other hand, no remarkable alterations in appearance of the cytoplasmic ground substance were observed with the usual sections of infected cells. However, the cytoplasmic ground substance of infected cells when negatively stained consisted of granular material which was different in appearance from the spongy material constituting the cytoplasmic matrix of uninfected cells. In the nucleus of infected cells, complexes consisting of round bodies, amorphous material, aggregates of uniform granules in rows, and viral crystals were often observed near the nuclear membrane in both types of sections. Examinations of the granular aggregates with negatively stained sections suggested that each granule represents a subunit and that the several adjoining subunits (approximately eight) constitute the requirement for formation of a single viral capsid with a core. Thus, rapid and simultaneous formation of the core and capsid within the aggregate would replace the rows of the granules with the viral crystal. The advantages of negative staining of thin sections for visualization of fine structural alterations are discussed.

Acetates↗
PubMed1971

Inactivation of polykaryocytogenic and hemolytic activities of Sendai virus by phospholipase B (lysolecithinase).

Evidence is presented that lysolecithin is involved in the fusing and hemolytic activities of Sendai virus. Treatment of the virus with phospholipase B (lysolecithinase) specifically inactivates the hemolytic and fusing abilities, without affecting the infectivity and the capability of the virus to hemagglutinate and adsorb to cells. The possible identity of lysolecithin with the "cell fusion factor" of paramyxoviruses and the mechanism of cell fusion are discussed.

Adsorption↗
PubMed1971

Spontaneous degradation of reovirus capsid into subunits.

When a plaque-purified strain of reovirus type 3 (Dearing strain) degraded during storage, electron micrographs of the degraded virion were made which clearly demonstrated the substructural components of the outer capsid.

Centrifugation, Density Gradient↗
PubMed1972

Morphogenesis of bacteriophage phi 80: identification of the cistron 13 product.

An in vitro complementation reaction leading to the assembly of bacteriophage phi80 tails from component proteins is described. Tail assembly occurs when a lysate of any mutant in cistron 13 is mixed with a second lysate of a mutant in any of the other cistrons involved in tail formation. Lysates of mutants that are blocked in tail formation contain phage heads that can unite with free tails to form infective particles. The rate of the complementation reaction shows little dependence upon temperature, suggesting that the assembly depends largely upon the kinetic encounter of the interacting components. The tail component missing in cistron 13 mutant lysates was purified approximately 55-fold and shown to be, at least in part, a protein having a molecular weight of approximately 22,000. This protein was also released from highly purified infective phi80 particles after osmotic shock followed by heattreatment, suggesting that it most probably is an integral structural protein of the phage tail. Lysates of mutants of bacteriophage lambda that are defective in tail formation were shown to contain a tail component identical with or similar to the phi80 cistron 13 product.

Ammonium Sulfate↗