A temperature-sensitive simian virus 40 (SV40) mutant, tsTNG-1, has been isolated from nitrosoguanidine-treated and SV40-infected African green monkey kidney (CV-1) cultures. Replication of virus at the nonpermissive temperature (38.7 C) was 3,000-fold less than at the permissive temperature (33.5 C). Plaque formation by SV40tsTNG-1 deoxyribonucleic acid (DNA) on CV-1 monolayers occurred normally at 33.5 C but was grossly inhibited at 38.7 C. The time at which virus replication was blocked at 38.7 C was determined by temperature-shift experiments. In shift-up experiments, cultures infected for various times at 33.5 C were shifted to 38.7 C. In shift-down experiments, cultures infected for various times at 38.7 C were shifted to 33.5 C. All cultures were harvested at 96 hr postinfection (PI). No virus growth occurred when the shift-up occurred before 40 hr PI. Maximum virus yields were obtained at 96 hr PI when the shift-down occurred at 66 hr, but only about 15% of the maximum yield was obtained when the shift-down occurred at 76 hr PI. These results indicate that SV40tsTNG-1 contains a conditional lethal mutation in a late viral gene function. Mutant SV40tsTNG-1 synthesized T antigen, viral capsid antigens, and viral DNA, and induced thymidine kinase activity at either 33.5 or 38.7 C. The properties of the SV40 DNA synthesized in mutant-infected CV-1 cells at 33.5 or 38.7 C were very similar to those of SV40 DNA made in parental virus-infected cells, as determined by nitrocellulose column chromatography, cesium-chloride-ethidium bromide equilibrium centrifugation, and by velocity centrifugation in neutral sucrose gradients. Mutant SV40tsTNG-1 enhanced cellular DNA synthesis in primary cultures of mouse kidney cells at 33.5 and 38.7 C and also transformed mouse kidney cultures at 36.5 C. SV40tsTNG-1 was recovered from clonal lines of transformed cells after fusion with susceptible CV-1 cells and incubation of heterokaryons at 33.5 C, but not at 38.7 C.

Animals↗

PubMed1969

The supposed role of micro-biological aerosol stabilizers as substitutes for bound water: a study of an in vitro model system.

In order to test a suggestion that inositol may take the place of water in maintaining the stability of desiccated cells, the reversible endothermic association of tobacco mosaic virus protein (TMVP) was studied turbidimetrically in presence of this substance. Its effect was to lower the temperature at which association takes place, the positive standard enthalpy and standard entropy of reaction both being increased by about 30%. The hypothesis of direct substitution of bound water by inositol at the site of macromolecular association leads to the contrary prediction that the association temperature would be raised. It is suggested that the observed effect of inositol may result from a conformation change in TMVP brought about by binding of inositol at positions adjacent to the site of reaction.

Aerosols↗

PubMedDate not supplied

Sequential genital infections by herpes simplex viruses types 1 and 2: restriction nuclease analyses of viruses from recurrent infections.

Virus isolated from a woman presenting with the first symptomatic episode of genital herpes was identified as herpes simplex virus type 1 (HSV-1) by restriction nuclease fingerprinting. Testing for IgM antibody to HSV indicated that the patient had recently contracted a new HSV infection. Virus microneutralization and the micro-solid phase radioimmunometric test for IgG, however, showed that the patient had had prior infection with herpes simplex virus type 2 (HSV-2); thus the HSV-1 infection was acquired despite the presence of antibody to HSV-2. Genital herpes recurred about four, seven, and nine months after the HSV-1 infection. Isolates from the latter three episodes all were of an identical strain of HSV-2 and were not recombinants or a mixture of the viruses. The data show that two distinctly different herpes simplex viruses can initiate genital infections in one individual and suggest that HSV-2 is more likely to recur than HSV-1.

Adult↗