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Biomedical subjects

D L Walker

Publications and source records attributed to D L Walker.

At least 109 records · Page 6Linked to original sources
PubMed1977

Modification of hydroxyindole-O-methyltransferase activity in experimental pineocytomas induced in hamsters by a human papovavirus (JC).

Hydroxyindole-O-methyltransferase (HIOMT) (HIOMT) activity was studied and compared in 7 pineal tumors (pineocytomas) induced in vivo in Syrian hamsters after postnatal inoculation with strains of human papovavirus (JC). Levels of tumor HIOMT activity were correlated with degree of cytologic differentiation of the pineocytes of each neoplasm, as judged from electrom micrographs. The relative capacities of the HIOMT in the tumors to methylate three related substrates gave similar ratios in the individual tumors and were not different from those of HIOMT in normal hamster pineal glands.

Acetylserotonin O-Methyltransferase↗
PubMed1977

JC virus, a human polyomavirus associated with progressive multifocal leukoencephalopathy: additional biological characteristics and antigenic relationships.

JC virus, a human polyomavirus, failed to grow or produce cytopathic effects in any of a variety of cells tested other than primary human fetal glial (PHFG) cells. Cells tested included other primary human cells and glial cells from other animals. Only a rare cell in inoculated insusceptible human cell cultures produced T or virion antigen. In PHFG cell cultures JC virus produced subtle cytopathic effects, and the majority of progeny remained cell associated. Only a few cells in the heterogenous PHFG cell cultures contained T antigen at 24 h postinoculation, and virion antigen was not detected until 48 h postinoculation. The infectivity of JC virus was resistant to inactivation by ether and by heating at 50 degrees C for 1 h. A three-way minor antigenic relationship was demonstrated among the virion antigens of JC virus, BK virus, and simian virus 40 by neurtralization and/or hemagglutination inhibition tests. Serological evidence is presented for the existence of JC virus as a distinct entity before the use of simian virus 40-contaminated poliovirus vaccines and for the nonexistence of an animal reservoir for JC virus infection.

Animals↗
PubMed1977

Specificity of the Tumor-specific transplantation antigen induced by JC virus, a human polyomavirus.

The specificity of the tumor-specific transplantation antigen (TSTA) induced by JC virus was investigated by cross protection tests in weanling hamsters. Hamsters immunized with JC virus, BK virus, or SV40 were challenged 5 weeks later with known numbers of JC virus- or SV40-induced hamster tumor cells. Both the JC virus-immune and the SV40-immune hamsters showed resistance to challenge with homologous but not heterologous tumor cells, and the BK virus-immune hamsters were not resistant to either heterologous tumor cell. The TSTA induced by JC virus did not cross-react with that induced by SV40.

Animals↗
PubMed1977

Differential neurooncogenicity of strains of JC virus, a human polyoma virus, in newborn Syrian hamsters.

The neurooncogenicity recently isolated strains of the human polyoma virus, JC virus, was determined by intracerebral inoculation of newborn Syrian golden hamsters. All three strains produced malignant brain tumors in a majority of inoculated animals during a 6.5-month observation period. The results obtained with the MAD-2 strain, 19 of 20 animals with cerebellar medulloblastomas and 0 of 20 animals with pineal gland tumors, were quite similar to those observed previously with the prototypic strain of JC virus, MAD-1. Inoculation of the MAD-4 strain, however, resulted in 10 of 22 animals with pineal gland tumors and only 10 of 22 animals with tumors in the cerebellum. The MAD-3 strain was neurooncogenic, but too few animals lived to be weaned to provide significant additional information. The basis for the apparent predilection of the MAD-4 strain for the pineal gland is unknown. Two hamsters in the experiment developed extracranial neuroblastomas.

Abdominal Neoplasms↗
PubMed1976

JC Papovavirus in progressive multifocal leukoencephalopathy.

Brain tissue from seven patients with progressive multifocal leukoencephalopathy was tested for the presence of papovaviruses. JC virus, ahuman papovavirus, was identified in all seven cases. Virus was isolated in tissue culture from extracts from each of four patients and was detected by immunofluorescence in sections from the other three. The new osolates were indistinguishable from the prototypical JC strain serologically and in all biological characteristics examined. Thus JC virus has, to date, been associated with 20 cases of progressive multifocal leukoencephalopathy.

Adult↗
PubMed1976

Comparison of JC and BK human papovaviruses with simian virus 40: DNA homology studies.

Studies were performed to ascertain the relationship of human papovavirus JC to BK virus and to simian virus 40 (SV40) by further restriction endonuclease analysis and by DNA-DNA competition hybridization on membrane filters. Form I DNA extracted from two new isolates from cases of progressive multifocal leukoencephalopathy of human papovaviruses that were JC-like in their antigenic properties were found to yield restriction endonuclease fragmentation patterns similar to those of prototypic JC virus DNA and different from those of BK or SV40. Form I DNA preparations of JC and BK viruses were found to be related to each other and to SV40 DNA to a similar extent, with JC and BK virus DNAs containing sequences homologous to both early and late regions of the SV40 genome. The relatedness in each comparison was less than 50%, and heterologous hybrids between either JC or BK and SV40 DNAs were found to be less stable than homologous SV40-SV40 hybrids in high concentrations of formamide, suggesting substantial mismatch within homologous regions, to the extent of 15 to 30%. The new JC-like isolates were also studied in competition hybridization reactions with SV40 DNA and yielded results similar to those obtained with JC virus.

BK Virus↗
PubMed1974

Comparison of JC and BK human papovaviruses with simian virus 40: restriction endonuclease digestion and gel electrophoresis of resultant fragments.

JC virus was found to have a buoyant density of 1.20 g/cm(3) in linear sucrose-D(2)O and 1.35 g/cm(3) in cesium chloride isopycnic gradients. DNA extracted either from JC-infected cultures or from gradient-purified virions occupied a dense position relative to linear DNA in cesium chloride/ethidium bromide gradients, and the circular configuration of the extracted DNA was confirmed by electron microscopy, with a measured molecular weight of 2.93 x 10(6). DNA from BK virus was similarly prepared and compared to JC and to an SV40 DNA standard by digestion with restriction endonuclease preparations from Haemophilus influenzae, Haemophilus parainfluenzae, and Escherichia coli. Digests were electrophoretically analyzed on gradient polyacrylamide slab gels or agarose gels, and the three viruses were found to have distinctly different cleavage patterns by this form of analysis: JC and BK viruses were almost entirely different from SV40 and significantly different from each other. Thus, JC and BK human papovaviruses appear to be discrete new members of the papovavirus group, rather than SV40 variants.

Centrifugation, Density Gradient↗
PubMed1973

Human papovavirus (JC): induction of brain tumors in hamsters.

Eighty-three percent of hamsters inoculated at birth with JC virus, a human papovavirus isolated from brain tissue of a case of progressive multifocal leukoencephalopathy, developed malignant gliomas within 6 months. Three brain tumors have been serially transplanted as subcutaneous tumors. JC virus was isolated from five of seven tumors tested. Cells from four tumors were cultivated in vitro. These cells contained an intranuclear antigen with the characteristics of a T antigen, and this antigen was antigenically related to SV40 T antigen. Although virus was not recovered from extracts of serially cultured tumor cells, JC virus was rescued when one tumor cell line was fused with permissive cells.

Animals↗
PubMed1971

Virulence and attenuation of murine cytomegalovirus.

Murine cytomegalovirus (MCMV) was rapidly and regularly attenuated by passage through mouse embryo cell culture. This attenuation was manifested by alteration of lethality for suckling mice and by a striking loss of capacity to multiply in liver and spleen of weanling mice. The attenuation was selective in that the passaged virus multiplied vigorously in other organs and established high titer infections in submaxillary glands and pancreas comparable to those seen with wild virus. Furthermore, attenuated virus no longer induced transient suppression of antibody and interferon responsiveness which was a regular feature of wild MCMV infection. Wild and attenuated MCMV shared the property of being poor immunogens. They induced anti-CMV complement-fixing or neutralizing antibody very slowly with barely detectable levels present at the end of the first 2 weeks of infection. The close antigenic relationship between wild and attenuated agents was demonstrated by nearly identical neutralization by a rabbit antiserum induced with wild MCMV. Furthermore, survivors of neonatal infection with attenuated virus were fully protected against subsequent challenge with potentially lethal doses of wild MCMV. Virulence could be rapidly restored by back passage in mice.

Journal Article↗