Search PubMed⌕ Search

Biomedical subjects

L A Falk

Publications and source records attributed to L A Falk.

At least 55 records · Page 3Linked to original sources
PubMed1981

Herpesvirus tamarinus and its relation to herpes simplex virus.

We have characterized Herpesvirus tamarinus (HT), a virus of New World primates related to herpes simplex virus. HT virion DNA cross-hybridized appreciably with herpes simplex virus type 1 (HSV-1) DNA. The HT-HSV-1 cross-hybridizing DNA sequences were distributed over the length of the genome; some DNA sequences, however, were apparently more homologous than others. HT virion DNA was estimated from the sum of restriction endonuclease fragments to have a mol. wt. 98 X 10(6). Only 1 molar fragments were found with some restriction endonucleases and 0.5 and 1 molar fragments were found with other restriction endonucleases but no evidence was found for 0.25 molar fragments. Independent isolates of HT from different species of South American primates gave nearly identical restriction endonuclease cleavage patterns of virion DNA. Although cross-reacting antigenic proteins of HT and HSV-1 were not detected by neutralization or immunofluorescence tests, cross-reacting antigenic proteins were detected by SDS-polyacrylamide gel electrophoresis of immunoprecipitates of 35S-labelled infected cell extracts.

Antigens, Viral↗
PubMed1980

Herpesvirus saimiri: protective effect of attenuated strain against lymphoma induction.

An attenuated strain of Herpesvirus saimiri (A-HVS) induced a persistent, latent infection in common marmosets. Virus was recovered from circulating lymphocytes of infected animals and antibody response to virus-specified antigens was demonstrated over 3-12 months PI. A-HVS-infected common marmosets and animals without previous A-HVS exposure were challenged with oncogenic HVS (125-825 PFU); marmosets without A-HVS infection developed malignant lymphoproliferative disease and died 3 weeks PI whereas all persistently-infected animals have survived 38-43 months post challenge.

Animals↗
PubMed1980

Comparative studies of interferon and three antiviral agents on neurotropic and oncogenic herpesviruses.

The antiviral effects of four compounds, phosphonoacetate, phosphonoformate, acycloguanosine, and purified human lymphoblastic interferon, were tested against two neurotropic herpesviruses, herpesvirus platyrrhine and herpes simplex virus, and two oncogenic herpesviruses, herpesvirus saimiri and herpesvirus ateles. All four compounds induced different degrees of inhibition of these herpesviruses. Phosphonoacetate and phosphonoformate at concentrations of 50 micrograms/ml or greater showed powerful antiviral activities. Interferon was more effective against herpesvirus saimiri and herpesvirus ateles, the two oncogenic viruses. Herpes simplex virus and the oncogenic herpesviruses were effectively inhibited by acycloguanosine, whereas herpesvirus platyrrhine proved to be resistant. The simian herpesviruses required a higher concentration of phosphonoformate, phosphonoacetate, and acycloguanosine for antiviral action. The antiviral action of all four compounds was contingent on the continued presence of the compounds in the infected cell culture medium.

Antigens, Viral↗
PubMed1979

Isolation of a cytomegalovirus from salivary glands of white-lipped marmosets (Saguinus fuscicollis).

Minced salivary glands from seven white-lipped marmosets (Saguinus fuscicollis and Saguinus nigricollis) and one cotton-topped marmoset (Saguinus oedipus) were cocultivated with marmoset cell cultures. A viral agent, designated SSG, was isolated from two Saguinus fuscicollis. Slowly progressing foci of rounded, vacuolated, refractile cells were first observed at 40-43 days incubation. Electron microscopy revealed intranuclear herpesvirus nucleocapsids and intracytoplasmic and extracellular enveloped particles. Infected cells stained with hematoxylin and eosin contained eosinophilic intranuclear and cytoplasmic inclusion bodies. SSG could be passaged in cell cultures only using viable whole cells; infectious cell-free virus was not detected in either culture supernatants or cell lysates. SSG replicated in marmoset fibroblastic but not in marmoset epithelioid or human fibroblastic cell cultures. Plasma antibodies to SSG were detected by indirect immunofluorescence assays in 16 of 56 (28.6%) adult wild-caught marmosets but were absent in 40 colony-born, hand-reared marmosets. Antigenic cross-reactivity of SSG with a rhesus monkey (Macaca mulatta) cytomegalovirus (bidirectional) and with a human cytomegalovirus (unidirectional) was also demonstrated by indirect immunofluorescence assays. SSG was identified as a herpesvirus by morphology and was classified as a cytomegalovirus by its site of isolation, biologic properties in vitro, and antigenic characteristics.

Animals↗
PubMed1978

Herpesvirus ateles DNA and its homology with Herpesvirus saimiri nucleic acid.

Analysis of the structural organization of Herpesvirus ateles DNA shows that two types of viral DNA molecules are encapsidated in virions: (i) M-genomes, which contain 74% light sequences (L-DNA, 38% guanine plus cytosine) and 26% highly repetitive heavy sequences (H-DNA, 75% guanine plus cytosine), and (ii) defective H-genomes, which consist exclusively of repetitive H-DNA. The structure of M-genomes from H. ateles consists of an L-DNA region of about 70 x 10(6) daltons inserted between H-DNA termini of variable length. M-genomes with a shorter H-DNA region at one end of the molecule have a long stretch of H-DNA at the other end, resulting in a total molecular weight of 89.8 +/- 8.5 x 10(6). Thus it resembles the structure of M-genomes of H. saimiri. H-DNA of the two independent H. ateles isolates, strains 810 and 73, reveals different patterns after cleavage with restriction endonuclease Sma I. H-DNA of H. ateles 810 appears to consist of identical tandem repeat units with a molecular weight of 1,035,000; the H-DNA repeat unit of strain 73 is shorter (930,000 molecular weight). Corresponding DNA sequences of the two H. ateles strains (810 and 73) are completely homologous in cross-hybridizations. However, a discrete nucleotide sequence divergence between these virus strains is detected by measuring melting temperatures (T(m)) of DNA hybrid molecules. Some homology exists between H. ateles and H. saimiri DNA. Hybridization of L-DNA from H. ateles with L-DNA from H. saimiri shows about a 35% homology between the respective L-DNA sequences; the resulting heteroduplex molecules show a decrease of T(m) by 13.5 degrees C, corresponding to about a 9% mismatching in cross-hybridizing parts of L-regions. Very little homology is found between H-DNA of H. ateles and H. saimiri.

Base Sequence↗
PubMed1977

Transformation of lymphocytes by Herpesvirus papio.

Cotton-topped (CT) or white-lipped (WL) marmoset lymphocytes were transformed in vitro with herpesvirus papio (HVP) into permanently growing lymphoblastoid cell lines (LCL). Five of 9 HVP-transformed CT cell lines contained cells with antigens reacting with antibodies to Epstein-Barr virus (EBV) capsid antigen (VCA) and/or to EBV-induced early antigens (EA). None of 12 WL LCL revealed such antigen-producing cells. Cells from both groups of cultures failed to react with antibodies to the EBV-specified nuclear antigen (EBNA). Exposure of baboon circulating lymphocytes to X-irradiated HVP or EBV-carring cells, or to suspensions of EBV resulted in establishment of LCL which all contained VCA and/or EA-positive, but no EBNA-positive cells. Nuclear antigens were undetectable also with anti-VCA-positive sera from baboons, chimpanzees, or other non-human primates. DNA-complementary RNA (cRNA) filter hybridization with EBV cRNA showed that with one exception transformed CT or WL marmoset cells contained at least 1-2 virus genome equivalents per cell, while at least 12-25 virus genome equivalents per cell were detected in transformed baboon cells. These data need confirmation by DNA-DNA reassociation kinetics.

Animals↗
PubMed1977

Susceptibility of common marmosets (Callithrix jacchus) to oncogenic and attenuated strains of Herpesvirus saimiri.

Adult common marmosets, inoculated with either of 2 oncogenic Herpesvirus saimiri (HVS) strains, developed fatal lymphoproliferative disease within 23-25 days post inoculation (PI). The disease was identical to HVS-induced lymphoma in cotton-topped and white-lipped marmosets. Common marmosets inoculated with an attenuated HVS strain developed persistent infection; virus has been recovered from cocultivated lymphocytes of these animals for more than 384 days PI.

Animals↗
PubMed1976

Mononuclear cell fraction carrying Herpesvirus saimiri in persistently infected squirrel monkeys.

Circulating lymphocytes from squirrel monkeys persistently infected with Herpesvirus saimiri (HVS) were separated into B- and T-lymphocyte fractions by a rosette-enrichment technique. HVS was isolated only from lymphocyte fractions forming rosettes or from unseparated lymphocytes; this indicated that T-lymphocytes were the target cells for HVS in the natural host, squirrel monkeys.

Animals↗