PubMed Health⌕ Search

Biomedical subjects

L C McLAREN

Publications and source records attributed to L C McLAREN.

17 recordsLinked to original sources
PubMed1961

The location and nature of enterovirus receptors in susceptible cells.

It is shown that enterovirus receptors are found mainly in the microsomal fraction of disrupted primate cells. Greater virus adsorption was exhibited by disrupted cells than by intact cells, indicating that enterovinis receptor may be present on intracellular membranes as well as on the surface of the cell. Polio-virus receptor is an integral part of, or is firmly attached to, the insoluble lipoproteins of the cell. All attempts to solubilize receptor have either destroyed virus-adsorbing activity, or have failed to separate it from sedimentable lipoproteins. The destruction of poliovirus receptor activity by proteolytic enzymes, surface active agents, organic solvents, concentrated urea solutions, phenol, formaldehyde, etc., all strongly indicate that this receptor function depends upon integrity of a protein portion of the membrane lipoproteins.

Enterovirus↗
PubMed1960

Enteroviral ribonucleic acid. I. Recovery from virus and assimilation by cells.

A relatively sensitive and adequately reproducible assay of infectious enteroviral RNA was obtained by exposing calf serum-grown HeLa cells to RNA suspended in 2 M magnesium sulfate solution. Highly purified enteroviral preparations yielded RNA exhibiting more than 0.1 per cent of the infectivity of whole original virus and infectivity regressed linearly with dilution. Radioisotope experiments with P(32)-labeled RNA and spectrophotometric studies demonstrated that Gierer-Schramm phenol extraction permits almost quantitative recovery of high molecular weight RNA from poliovirus. Intact chromatography-purified type 2 poliovirus in the analytical ultracentrifuge showed a sharp boundary and a sedimentation coefficient of S(20, w) = 147 +/- 5S. Phenol-extracted poliovirus RNA exhibited a heterodisperse sedimentation pattern with a large proportion of homogeneous, rapidly sedimenting material having a coefficient of S(20, w) = 37 +/- 2S. Although the bulk of extracted poliovirus RNA as measured by radiophosphorus labeling was not taken up by cells, the infectious fraction of RNA was adsorbed rapidly by HeLa-cell or L strain mouse fibroblast monolayers, indicating a possible dissimilarity between the bulk of extracted virus RNA and a relatively small fraction responsible for infectivity. Enhancement of poliovirus RNA infectivity for HeLa cells by high ionic-strength magnesium sulfate solution appeared due partly to an effect of hypertonicity on cells, and partly to an effect of high-concentration divalent cation on RNA itself, but not to enhancement of adsorption. Poliovirus RNA adsorbed by HeLa cells apparently was rapidly received within the cells since it became quickly insusceptible to ribonuclease. Heterologous nucleic acids and degradation products to the level of oligoribonucleotides inhibited infectivity of poliovirus RNA for HeLa cells. This inhibitory activity appeared due to intermolecular complexing, since exposure of cells to heterologous RNA immediately before or after exposure to virus RNA failed to reduce infectivity. Ultraviolet absorption spectra demonstrated that the RNA within intact poliovirus is more hypochromic (and thus more extensively hydrogen-bonded) than is the same RNA isolated by phenol extraction, and suspended in 0.02 M phosphate buffer.

HeLa Cells↗
PubMed1960

Enteroviral ribonucleic acid. II. Biological, physical, and chemical studies.

Chromatographic behavior of whole type 1 poliovirus and phenol-extracted viral RNA on diethylaminoethyl cellulose columns, as revealed by assay of plaque-forming capacity, indicated that infectious RNA had surface properties markedly different from those of the intact virus. Infectious RNA of type 1 poliovirus and Coxsackie B1 virus was relatively resistant to heat inactivation as compared to intact virus. Kinetics of inactivation at elevated temperatures were multi-hit in character. The structure of infectious enterovirus RNA was investigated by treatment with chemical inactivating agents. Urea and guanidine as hydrogen bond-disrupting agents, and mercaptoethanol and thioglycolate as disulfide bond-disrupting agents, and combinations of these did not destroy RNA infectivity whereas hydrogen bond-disrupting treatment inactivated intact virus rapidly. RNA infectivity was not reduced by chloroform extraction alone, or by octanol extraction alone, but was reduced by chloroform-octanol extraction which failed to depolymerize RNA to an extent detectable by ultracentrifugal analysis. Infectivity of type 1 poliovirus and Coxsackie B1 virus RNA was destroyed in accordance with first order kinetics by very dilute solutions of pancreatic ribonuclease, and by purified snake venom phosphodiesterase, but not at all by bacterial alkaline phosphatase. Inactivation by venom diesterase was not accelerated by prior treatment of RNA with bacterial alkaline phosphatase. These results indicated that infectivity of enteroviral RNA resided in a single stranded structure, that a single break of a phosphodiester bond anywhere along the structure was sufficient to destroy infectivity, and that infectivity did not require a terminal phosphate group. Hydroxylamine, but not other carbonyl reagents, rapidly destroyed infectivity of intact type 1 poliovirus viral RNA without depolymerization of RNA-detectable by behavior in the analytical ultracentrifuge. With S(35)-methionine-labeled poliovirus a very small fraction of radioactivity remained in RNA preparations following phenol extraction. No evidence could be obtained to indicate that infectious enteroviral RNA was composed of subunits. RNA extracted with phenol during the course of infection of HeLa cells with type 1 poliovirus resembled RNA obtained from purified whole virus with respect to heat inactivation, hydroxylamine inactivation, chromatographic separation, susceptibility to protein denaturing agents, and ability to infect productively both naturally susceptible HeLa cells and naturally insusceptible L strain mouse cells. Intracellular production of infectious RNA paralleled intracellular maturation of whole virus and preceded it by a very short interval.

Animals↗
PubMed1959

The mammalian cell-virus relationship. IV. Infection of naturally insusceptible cells with enterovirus ribonucleic acid.

Ribonucleic acid extracted with phenol from Type 1 poliovirus, Coxsackie A-9, Coxsackie B-1, and ECHO 8 viruses infected non-primate cells and animals insusceptible to whole virus as such. Viral RNA was proved infectious for insusceptible cells in test systems of established cell lines, primary monolayer cultures, Maitland type cultures, and living animals inoculated intracerebrally. Cells of rabbit, swine, mouse, guinea pig, chicken, and hamster were infected. Each virus produced was identical with the virus donating RNA, in (a) neutralization by homotypic antiserum, (b) resistance to ribonuclease treatment, and (c) failure to be adsorbed or replicated by nonprimate cells, even of the strain producing the virus from RNA. Produced virus was adsorbed and replicated by susceptible primate cells as usual. Virus in RNA-infected cell cultures was produced in a single cycle unaccompanied by overt cytopathic effect on non-primate cells or disease of intracerebrally inoculated animals. By drastic elution of infective poliovirus associated with rabbit cells exposed to massive inocula of intact virus, intact poliovirus was shown to infect insusceptible non-primate cells to produce progeny indistinguishable from the parent virus population. Under these conditions, infection was accomplished by about 10 virus plaque-forming units per billion inoculated.

Animals↗
PubMed1959

The mammalian cell-virus relationship. I. Attachment of poliovirus to cultivated cells of primate and non-primate origin.

Primary or established strain cultures of a variety of primate cells that were susceptible to cytopathic infection strongly adsorbed poliovirus. Insusceptible non-primate cells in primary or established-strain culture did not so adsorb virus (or propagate it), with exception of the ERK-1 embryo rabbit kidney strain. All tested cells, regardless of type or susceptibility, adsorbed about 1 per cent of input virus, which became cell-associated (CAV) without loss of infectivity. In combination with susceptible or insusceptible cells, CAV was only about 90 per cent neutralized by homotypic antiserum. CAV eluted continuously from non-susceptible cells with continued incubation; eluted virus gave rise to infection and new CAV to the same degree in susceptible cells as did original virus.

Animals↗
PubMed1959

The mammalian cell-virus relationship. II. Adsorption, reception, and eclipse of poliovirus by HeLa cells.

Phases of attachment, reception or penetration, and eclipse of Type 1 poliovirus infecting HeLa cells in monolayer were studied. Firm attachment was not completely dependent on salt concentration, and was sensitive to temperature change. Like attachment, progressive resistance of adsorbed virus to inactivation by externally applied antibody was temperature-sensitive. Penetration was shown to be independent of physiologic integrity of cells. Virus in process of penetration was not affected by ribonuclease. Eclipse of adsorbed virus was not dependent on metabolic activity or physical integrity of HeLa cells. Debris from poliovirus-susceptible cells inactivated the virus in a manner similar to the kinetic course of virus adsorption by intact cells, and released cell-associated infective virus in similar amounts. All cells insusceptible to poliovirus infection failed to yield active debris. Virus inactivation by debris, like virus reception by intact cells, was temperature-sensitive. Debris could not inactivate virus adsorbed to cells, or alter the progressive incapacity of antibody to neutralize penetrating virus. The active debris factor was insoluble, was not associated with cell nuclei, was inactivated by fat solvents and trypsin treatment, and was destroyed by beat inactivation or sonic disruption. Anti-HeLa serum applied to cells before exposure to virus reduced the rate of virus adsorption, while antiserum treatment immediately following virus adsorption was ineffective. These findings suggested that the capacity of HeLa and other susceptible cells to adsorb, receive, and eclipse poliovirus was associated with organized cytoplasmic lipoprotein structures not possessed by insusceptible cells. The reaction of virus with receptor substance contained in debris was not readily reversed by treatment shown not to affect virus and to destroy activity of uncombined debris. Sensitivity of poliovirus adsorption by HeLa cells to change in environmental salt concentration or temperature was dependent on the method of measurement.

Adsorption↗