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Biomedical subjects

V Vonka

Publications and source records attributed to V Vonka.

At least 163 records · Page 9Linked to original sources
PubMed1976

Pathogenicity, immunogenicity and genetic stability in mice and ferrets of a cold inhibitor-resistant mutant of influenza H3N2 virus.

A cold inhibitor-resistant mutant was derived from MRC-2 virus by means of serial passages in the presence of rabbit serum and at gradually decreasing temperatures. This virus, denoted MRC-2 IRc, grew well at both 26 and 37 degree C. The pathogenicity and immunogenicity of the virus was examined in mice and ferrets. No clinical reactions were detected in either species. Both mice and ferrets developed high levels of hemagglutination inhibition and neuraminidase inhibition antibodies. The virus was reisolated from the lungs of intranasally inoculated mice; in ferrets it was recovered from nasal washing and trachea but not from lungs. The properties of the isolated viruses were examined. The viruses reisolated from mice lost their reproductive capacity at 26 degree C and were less resistant to inhibitors than the original virus. The virus isolated from the ferret nose was identical with the original virus, however the tracheal isolate exhibited a certain degree of reversion in both the markers tested.

Animals↗
PubMed1976

Ts mutant of NWS influenza virus: behaviour in vitro and in vivo.

After passaging the NWS influenza virus at increasing temperatures in the hamster embryo fibroblast (HEF) cell line, a temperature-resistant (tr) mutant which grew well at 39 degrees C was isolated. Attempts were made to isolate temperature-sensitive (ts) mutants from the tr virus. After growth in the presence of 5-fluorouracil, 233 virus clones were isolated. Among these only one was incapable of replicating at 39 degrees C. The physiological studies, the shift-up experiment and the electron microscopic investigation suggested that the genetic defect responsible for its ts character influenced a late function of the virus genome. In the lungs of intranasally infected mice, the ts mutant replicated to a lesser extent than the tr virus. During its growth in vivo, the ts virus exhibited a high degree of genetic stability.

Animals↗
PubMed1975

The nature of adenovirus persistence in human adenoid vegetations.

Ninety-seven adenoid vegetations (AV) originating from children aged 2 to 11 years were examined for the presence of adenoviruses. No infectious virus was detected in cell-free homogenates. However, adenovirus was recovered in 30 instances from either fragment or trypsinized cell cultures, or both, of the same tissues. The viruses belonged to types 1, 2, 5 and 6. It was determined by the infectious center assay that the frequency of virus-producing cells in different AV varied between 1 of every 10(5) cells to 1 of every 10(7) cells. Cells reactive with hamster sera containing antibody against the adenovirus early ("T") antigen and with rabbit sera containing antibody against the virus structural antigens were detected in cell smears from trypsinized virus-positive AV. The frequency of positive cells was very low. Nearly 80 per cent of extracts from virus-positive AV contained substances neutralizing the homotypic viruses. Adenovirus-neutralizing substances were only rarely detected in extracts from virus-negative AV. The neutralizing substances could be removed from the extracts by absorbtion with concentrates of the homotypic viruses. Most of the subjects from whom AV containing neutralizing substances were obtained, possessed high levels of homotypic serum antibodies.

Adenoids↗
PubMed1975

Sero-epidemiology of the Epstein-Barr virus: preliminary analysis of an international study - a review.

Samples of Chinese, Indian, African and Caucasian populations, randomly selected in Hong Kong, Singapore, the West Nile District of Uganda, and Nancy, France, were titrated for antibodies to EBV, viral capsid (VCA) and complement-fixing soluble (CF/S) antigens. The age-specific prevalence of infection (as reflected by the proportion of VCA-positive individuals) varied greatly up to the age of 10 years in the four populations studied, the West Nile District of Uganda being outstanding in having an early and massive infection rate. Differences were also observed between ethnic groups in Singapore, where the Chinese appeared to have a delayed infection rate compared to the Indians. Immune response, as measured by the prevalence of CF/S antibodies and by the geometric mean titres (GMT) of VCA and CF/S antibodies, differed significantly between ethnic groups, Ugandan infants (1-3-year age-groups) having a humoral response to VCA and CF/S antigens as high as or higher than that of Burkitt's lymphoma patients, decreasing thereafter to levels lower than those of any other ethnic group observed. Indians in Singapore, known to be at no risk for NPC and BL, exhibited a higher and steadier immune response to VCA in going from young to old age-groups than did the Chinese.

Adolescent↗
PubMed1974

Ribonucleotides linked to DNA of herpes simplex virus type 1.

Cells of a continuous cell line derived from rabbit embryo fibroblasts were infected with herpes simplex type 1 virus (HSV-1) and maintained in the presence of either [5-(3)H]uridine or [methyl-(3)H]thymidine or (32)PO(4) (3-). Nucleocapsids were isolated from the cytoplasmic fraction, partially purified, and treated with DNase and RNase. From the pelleted nucleocapsids, DNA was extracted and purified by centrifugation in sucrose and cesium sulfate gradients. The acid-precipitable radioactivity of [5-(3)H]uridine-labeled DNA was partially susceptible to pancreatic RNase and alkaline treatment; the susceptibility to the enzyme decreased with increasing salt concentration. No drop of activity of DNA labeled with [(3)H]thymidine was observed either after RNase or alkali treatment. Base composition analysis of [5-(3)H]uridine-labeled DNA showed that the radioactivity was recovered as uracil and cytosine. In the cesium sulfate gradient, the purified [5-(3)H]uridine-labeled DNA banded at the same position as the (32)P-labeled DNA. The present data tend to suggest that ribonucleotide sequences are present in HSV DNA, that they are covalently attached to the viral DNA, and that they can form double-stranded structures.

Alkalies↗