- Volume 1, Issue 2, 1967

Differences in symptom expression and growth curve exist between two California strains, b and c of tobacco rattle virus, each of which possesses 3 components of different particle lengths and is serologically related to two English strains. With increasing age of infection from 3 to 35 days, the particle populations of strains b and c show a shift in the middle to bottom component ratio from about 2 to 0·9. An unstable 1600 to 1700 Å fraction recovered during periods of most rapid synthesis of the strain c may be implicated in the appearance of normally present 800 to 900 Å rods.

Following SY 40 infection of monkey kidney (CV-1) cells, DNA polymerase activity was induced. Enzyme formation was inhibited by cycloheximide, but not by l- β -d-arabinofuranosylcytosine. Enhanced levels of DNA polymerase activity were also found in mouse kidney cell lines which had been transformed by SY 40.

The DNA polymerases from uninfected and SV 40-infected CV-1 cells were partially purified and compared. Both enzymes required denatured DNA as primer and were similar with respect to pH optima, amount of primer required for maximal activity, kinetics of thermal denaturation, and sensitivity to inhibition by ammonium sulphate and sodium dodecyl sulphate. However, the Michaelis constant (Km ) for [3H]thymidine 5′-triphosphate of the SV 40-induced enzyme was about half that of the enzyme from uninfected cells. The Km value of DNA polymerase partially purified from SV 40- transformed mouse cells was about the same as that of the enzyme from uninfected CV-1 cells.

A simple method is described for examining organ cultures by electron microscopy for the presence of virus particles. The method was used to detect the presence of three hitherto uncharacterized viruses. Two of these have particles resembling those of infectious bronchitis of chickens and the third morphologically resembles the parainfluenza group of viruses.

The infective process of a filamentous bacteriophage was studied in the electron microscope using thin sections of cells of Escherichia coli infected at a high multiplicity. Marked intracellular changes beginning after about 20 min. consisted of multiple layer membraneous structures and mesosomes formed by the invagination of the cell wall and the protoplasmic membrane.At the same time many particles were extruded and appeared in transverse section as small circles with a black dot, believed to be the nucleic acid core. It was difficult to see particles within the cell or being extruded from it, but some evidence suggested that bacteriophage synthesis was occurring near the cell wall. There was no abrupt lysis; the cell contents slowly leaked out leaving an intact cell envelope.

Two influenza A viruses, neurotropic nws and its recombinant nw are capable of forming plaques on BHK21 cells, nws plaques are larger than nw plaques. The small plaque size of nw virus is related to a slower rate of increase of nw than nws virus during many cycles of infection, not to inhibition by the non-cellular environwent. The slow increase could be accounted for by a delay in the formation of infectious nw virus in each cycle accompanied by a simultaneous delay in release. The synthesis of nw virus is accompanied by a large quantity of unassembled or unstable noninfectious haemagglutinin; the synthesis of nws virus yields assembled infectious haemagglutinin predominantly.

The simian adeno-satellite virus apparently cannot multiply unless host cells are co-infected with a ‘helper’ adenovirus. Following simultaneous infection of green monkey kidney cells with simian adenovirus (SV 15) and its satellite, satellite antigen was first detected by immunofluorescence in the nucleus 10 to 12 hr after inoculation, while adenovirus antigen was first detected at 16 hr. A single cycle of growth for satellite virus was completed in about 24 to 48 hr. Inoculation of satellite-free adenovirus from 10 to 15 hr before inoculation with satellite proved to be the most efficacious time for shortening the latent period of satellite. Satellite antigen could then be detected as early as 4 hr after inoculation. These results indicate that events in the adenovirus replication cycle must proceed for 10 to 12 hr before satellite can be synthesized.

An infectivity titration of satellite based on immunofluorescence was developed. The percentage of fluorescent cells in standard monolayers was determined and the infectious units were calculated from the dilution infecting 1 % of cells. Most satellite preparations had titres of 108 to 109 infectious units/ml. with one infectious unit equivalent to 30 to 100 particles.

When particles of tobacco rattle virus (TRV) were progressively degraded by alkali, detergent or urea a number of particles of specific lengths were produced. Some of the breakdown products had lengths similar to those of the naturally occurring short rods characteristic of various isolates of TRY. Loss of infectivity was associated with increasing heterogeneity of sedimentation of the long TRV particles during density gradient centrifugation. Cleavage of different strains of TRV produced relatively few fragments from 1800 to 1900 Å resembling the naturally occurring shorter rods.

An influenza virus was inactivated stepwise by ethylene iminoquinone Bayer A139; a viral product with a target size similar to that of neuraminidase was responsible for the cytopathic effect on cells grown in culture.

Particles of maize mosaic virus I are bullet-shaped, or hemispherical at both ends. Bullet-shaped particles in phosphotungstic acid measure 2550 × 900 Å, those in uranyl acetate 2410 × 730 Å. The particles appear to consist of an envelope with thread-like or knob-like protrusions, a helical structure composed of beaded units, a hollow cylinder and an inner core. The last has no visible structure but disintegrates often in somewhat spherical masses.