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At least 1,315 records · Page 73Linked to original sources
PubMed1989

Transfection of cloned Heliothis zea cell lines with the DNA genome of the Heliothis zea nuclear polyhedrosis virus.

Transfection conditions were optimized for the cloned UND-K derivative of the IPLB-HZ 1075 cell line using the calcium-phosphate co-precipitation technique and the DNA genome of the Heliothis zea S-type nuclear polyhedrosis virus. Optimal efficiencies were obtained using supercoiled viral DNA, and by extending the adsorption period for the diluted precipitate to 12 h. Transfection efficiencies ranging from 0.5 to 1.3 x 10(3) plaque forming units per microgram of supercoiled viral DNA were routinely obtained for UND-K cells and HzS-15 viral DNA. Transfection efficiencies were compared for 10 other cloned Heliothis cell strains and the uncloned parental IPLB-HZ 1075 cell line. The cloned cell strains UND-F, L, and U were incapable of transfection, while UND-I and G were 3 and 131 fold (respectively) less efficient than UND-K. The UND-K cells and the calcium phosphate transfection procedure permit relatively efficient in vitro manipulation of the Heliothis zea NPV virus genome.

Animals↗
PubMed1993

Pattern formation in icosahedral virus capsids: the papova viruses and Nudaurelia capensis beta virus.

The capsids of the spherical viruses all show underlying icosahedral symmetry, yet they differ markedly in capsomere shape and in capsomere position and orientation. The capsid patterns presented by the capsomere shapes, positions, and orientations of three viruses (papilloma, SV40, and N beta V) have been generated dynamically through a bottom-up procedure which provides a basis for understanding the patterns. A capsomere shape is represented in two-dimensional cross-section by a mass or charge density on the surface of a sphere, given by an expansion in spherical harmonics, and referred to herein as a morphological unit (MU). A capsid pattern is represented by an icosahedrally symmetrical superposition of such densities, determined by the positions and orientations of its MUs on the spherical surface. The fitness of an arrangement of MUs is measured by an interaction integral through which all capsid elements interact with each other via an arbitrary function of distance. A capsid pattern is generated by allowing the correct number of approximately shaped MUs to move dynamically on the sphere, positioning themselves until an extremum of the fitness function is attained. The resulting patterns are largely independent of the details of both the capsomere representation and the interaction function; thus the patterns produced are generic. The simplest useful fitness function is sigma 2, the average square of the mass (or charge) density, a minimum of which corresponds to a "uniformly spaced" MU distribution; to good approximation, the electrostatic free energy of charged capsomeres, calculated from the linearized Poisson-Boltzmann equation, is proportional to sigma 2. With disks as MUs, the model generates the coordinated lattices familiar from the quasi-equivalence theory, indexed by triangulation numbers. Using fivefold MUs, the model generates the patterns observed at different radii within the T = 7 capsid of papilloma and at the surface of SV40; threefold MUs give the T = 4 pattern of Nudaurelia capensis beta virus. In all cases examined so far, the MU orientations are correctly found.

Adenoviridae↗
PubMedDate not supplied

Purification of viruses by electrophoresis in sucrose concentration gradients. 1972.

Zone electrophoresis (ZE) in concentration gradients of sucrose proved to be a powerful technique in the purification of viruses although it is seldomly used as a single step for the separation of the infective agent from extraneous matter but usually as a final procedure. No difficulties were experienced in the purification of plant viruses with ZE possibly because of the resistance of the agents to the chloroform butanol treatment which the impure plant viruses received prior to the ZE. Likewise no difficulties were encountered during purification of human and animal picorna viruses because they also are resistant to chloroform or chloroform-butanol treatment prior to ZE. Purification of animal and possibly human reoviridae ZE as a final step is involved as they are associated with or even attached to the host cell membranes which are lipoidal in nature. Because the lipoidal material on the virus has an affinity for organic solvents the virus particles are caught in the emulsion when an extract of the crude virus material is shaken with the organic solvent. With these viruses polyethylene glycol M(r) 6000 (PEG) is often helpful as a means of displacing most of the host proteins as a step in the partial purification prior to ZE. Neurotropic African horse sickness virus which presented many problems to overcome was rendered free of extraneous proteins to the extent that electron micrographs could be made of it. Neurotropic Rift Valley fever virus was similarly difficult to purify as it was always associated with mouse brain components. This virus was finally purified from infected mouse blood in which the virus particles were not associated with host cell debris and other extraneous proteins. Zone electrophoresis experiments were not conducted on viruses with large particle sizes e.g. myxoviruses because they could be purified without a great deal of effort using polymer displacement, and thin layer centrifugation. Zone electrophoresis as a means of final purification was vividly displayed with the purification of five viruses of the larvae of the pine emperor moth, Nudaurelia cytheria cytheria.

Cell Fractionation↗
PubMed1993

A novel small RNA virus isolated from the cotton bollworm, Helicoverpa armigera.

A small RNA virus with novel characteristics has been isolated from laboratory-bred larvae of Helicoverpa armigera. Infection by the H. armigera stunt virus causes severe retardation of larval development and subsequent death. Its particles are isometric, 38 nm in diameter, and have a buoyant density of 1.296 g/ml in caesium chloride. The viral capsid has two major non-glycosylated protein components with M(r)s of 65,000 and 6000, and contains a genome composed of two non-polyadenylated single-stranded RNA molecules with lengths of 2.4 kb and 5.5 kb. The 5' termini of these RNAs are capped; their 3' termini are unblocked. In vitro translations of the viral RNAs showed synthesis of large proteins of sizes near the maximum coding capacity of each strand along with synthesis of numerous smaller proteins; no evidence for processing of precursors was seen. The physicochemical properties of the virus are most similar to those of the Nudaurelia omega virus, a provisional member of the Tetraviridae, although no antigenic relationship was observed between the two viruses. The bipartite genome and distinct capsid structure of these two viruses indicate the existence of a previously unrecognized virus group.

Amino Acid Sequence↗
PubMedDate not supplied

[Circular replicating baculovirus genome].

Free Malacosoma neustria nuclear polyhedrosis virus preparations contain nucleocapsids typical of Baculoviruses' morphology and size as well as long virus-like particles. Viral DNA is circular and covalently closed. Its preparations contain rings with single-stranded breaks, catenanes and circular dimers as well. Replicating pulse-labelled DNA preparations have been obtained from cells with the highest virus DNA synthesis. Theta-forms of replicating DNA are found in heavy fractions of sucrose gradients. Theta-forms, catenanes and circular dimers are discussed as intermediate molecules. Catenanes or (sometimes) circular dimers appear to form protein-containing complexes and long virus-like particles if the monomerization process is inhibited.

DNA Replication↗
PubMedDate not supplied

[Derivation of a transplantable cell line from oak silkworm ovarian tissue].

A continuous cell line (M. S. A. p.-1) was obtained from the ovaries of diapausing pupae of the oak silkmoth Antheraea pernyi. Active multiplication of cells was observed two months after preparing a primary culture from partly trypsinized tissues. Subcultures derived at this time were transmitted with 10 day intervals and endure over 30 passages. The cells are susceptible to the nuclear polyhedrosis viruses of Mamestra brassicae, Galleria mellonella, Malacosoma neustria and Bombyx mori.

Animals↗