Search PubMed⌕ Search

Biomedical subjects

A Kohn

Publications and source records attributed to A Kohn.

At least 91 records · Page 5Linked to original sources
PubMed1980

Nature of permeability changes in membrane of HeLa cells adsorbing Sendai virus.

Adsorption of Sendai virus to HeLa cells induced in them an increased permeability to K+, Na+, Ca++, deoxyglucose, but not to fluorescein. The stimulation of uptake of 42K was temperature-dependent, did not occur below 15 degrees C, and was not inhibited by ouabain. The virus-induced increase in the uptake and release of 42K and of 3H deoxyglucose could not be mimicked by treatment of cells with linoleic acid, a procedure which increased the fluidity of the cellular membranes. The stimulatory effect of 0.5 mM ATP on the release of deoxyglucose was enhanced several fold in the presence of Sendai virus. These results seem to indicate the possible involvement of membranal enzymes such as e.g. protein kinase in the permeability changes induced by Sendai virus.

Calcium↗
PubMed1980

Unsaturated free fatty acids inactivate animal enveloped viruses.

Unsaturated free fatty acids such as oleic, arachidonic or linoleic at concentrations of 5-25 microgram/ml inactivate enveloped viruses such as herpes, influenza, Sendai, Sindbis within minutes of contact. At these concentrations the fatty acids are inocuous to animal host cells in vitro. Naked viruses, such as polio, SV40 or EMC are not affected by these acids. Saturated stearic acid does not inactivate any viruses at concentrations tested. Though the mode of action of unsaturated fatty acids is not understood, electronmicrographs of enveloped viruses treated by them indicate that the inactivation is associated with disintegration of the virus envelope.

Arachidonic Acids↗
PubMed1980

Solid-phase immune electron microscopy (SPIEM) for rapid viral diagnosis.

Immune electron microscopy (IEM) is one of the fastest and most sensitive methods for the detection and diagnosis of viruses. This technique is based on formation of immune complexes of the virus with its corresponding antibody. In IEM optimal precipitation depends on a correct ratio, and there is a prozone effect. These problems can be overcome by using the solid-phase immune electron microscopic (SPIEM) technique. In this technique the antibody is attached to a particle which is used for 'fishing' the virus to be examined out of the suspension. After low speed centrifugation the preparation is treated either for observation in the transmission electron microscope or in the scanning electron microscope. In 'positive' samples the virus is seen attached to the surface of the particle. We report here results with S. aureus as the solid phase for the detection of Sindbis virus. The anti-Sindbis gamma globulins are attached to the bacteria by means of protein A present on their surface.

Antigen-Antibody Reactions↗
PubMed1980

Interaction of polyunsaturated fatty acids with animal cells and enveloped viruses.

Essential unsaturated fatty acids such as oleic, linoleic, or arachidonic were incorporated into the phospholipids of animal cells and induced in them a change in the fluidity of their membranes. Exposure of enveloped viruses such as arbo-, myxo-, paramyxo-, or herpesviruses to micromolar concentrations of these fatty acids (which are not toxic to animal cells) caused rapid loss of infectivity of these viruses. Naked viruses such as encephalomyocarditis virus, polio virus or simian virus 40 were not affected by incubation with linoleic acid. The loss of infectivity was attributed to a disruption of the lipoprotein envelope of these virions, as observed in an electron microscope.

Animals↗
PubMed1980

Herpes simplex virus phosphoproteins. I. Phosphate cycles on and off some viral polypeptides and can alter their affinity for DNA.

We report on phosphorylation, the stability of the bound phosphate, and the properties of several phosphorylated infected-cell polypeptides (ICPs) synthesized in cells infected with herpes simplex virus 1 and 2. Our results and conclusions are as follows. (i) Phosphorylation of ICPs occurs by at least two different pathways. Thus, the 4a and 4c electrophoretic forms of ICP 4 were labeled with 32P during a pulse concurrently with their synthesis, whereas ICP 22 and ICP 27 were labeled with 32P only during a subsequent chase in the presence of unlabeled phosphate. (ii) Pulse chase studies with [35S]methionine and 32P indicate that whereas most polypeptides are stable, the bound phosphate with few exceptions cycles on and off. Of special interest is the observation that the phosphate bound to ICP 4a and 4c cycles on and off, whereas that bound to ICP 4b is stably associated. Similar cycling was observed for ICP 6, 11, 22, and 27. The observation that 4a and 4c can be phosphorylated as late as 24 h after infection, i.e., long after their synthesis ceases, suggests that all three forms may have defined functions that persist throughout the reproductive cycle. (iii) All three forms of ICP 4 can be the translational products of only one of two copies of the ICP 4 gene in the viral genome. (iv) Analyses of the distribution of the viral proteins within the cell indicate that phosphorylation is not a major determinant in the compartmentalization of most viral phosphoproteins. (v) Comparisons of the binding to DNA-cellulose of artificial mixtures of 32P- and [35S]methionine-labeled proteins from infected cells indicate that phosphorylation in some instances enhances (e.g., ICP 29) and in other instances decreases (e.g., ICP 6) binding affinity for DNA. In light of previous reports that some of the proteins identified as phosphoproteins have regulatory functions, the data suggest that phosphorylation may modify the activity of regulatory proteins in herpes simplex virus-infected cells.

Carcinoma, Squamous Cell↗
PubMed1979

Fluorescence polarization of DPH-labeled cells adsorbing viruses and its diagnostic potential.

Mammalian or avian cells were labeled with a fluorescent probe DPH (1,6-diphenyl-1,3,5-hexatriene). Within a few minutes after adsorption of various naked and enveloped viruses, the degree of fluorescence polarization (P) of the DPH embedded in the adsorbing cells as measured at 37 degrees C, was reduced, a finding indicating a decrease in the microviscosity of the lipids in the cell membrane. This change of fluidity was proportional to the concentration of the adsorbing virus and could be abolished or inhibited by homologous specific antiviral sera, but not by heterologous sera. Potential use of fluorescence polarization tests is described for titration of virus concentration, as well as for serological identification of a virus.

Adsorption↗
PubMed1979

Schistosome motility in saline media.

The authors observed the motility of 1067 worms used as a biological parameter indicating the vitality of the parasites, to define the survival time of S. mansoni males and females in 0,85% NaCl and PBS. Among the worms observed in 0,85% NaCl the mean time of survival in minutes was 204 for males and 240 for females and in PBS it was 267 min. for males and 344 min. for females. All the tested differences (media, sex; sex for saline group; sex for PBS group) were significant at a 0.0001 level.

Animals↗
PubMed1979

Oxytalan fibers in the Schistosoma mansoni tegument.

In order to elucidate the nature of the fibrous network present in Schistosoma mansoni tegument, adult worms were studied by light and electron microscopy. It was suggested that this network is formed by bundles of tubular microfibrils 10--12 nm in diameter, similar to oxytalan microfibrils present in higher animals.

Animals↗
PubMed1978

Early changes in the membrane of HeLa cells adsorbing Sendai virus under conditions of fusion.

Adsorption of Sendai virus at high multiplicity (500-1,000 HAU/10(6) cells) to HeLa cells grown in monolayers causes immediate changes in the ion barrier of the cell membrane, as well as changes in the morphology of the virus-treated cells. Within minutes of adsorption the cells begin to lose potassium and an extensive influx of ions into the cells occurs. Concomitantly with these changes, the cell membrane becomes depolarized, and the resting potential across its membrane decreases. Twenty to sixty minutes post adsorption the damage to the cell membrane is repaired, and both the potassium uptake and the resting potential return to their pre-exposure values. Scanning electron-micrographs of Sendai infected cells incubated at 37 degrees C show formation of bridging microvilli in a zipper-like fashion within two to five minutes post-adsorption; 30 to 60 minutes thereafter the majority of cells in the monolayer are fused. Biochemical changes induced by virus adsorption and the role of Ca++ ions in the observed effects are discussed.

Cell Fusion↗
PubMed1977

Picorna- and togavirus infection of cells detected by gas chromatography.

Viral infection of cells causes chemical and metabolic changes, which can be detected by gas chromatography (GC) of ether extracts of supernatant fluids and cell homogenates before any significant damage to the cells is observable microscopically. The characteristic and specific GC patterns obtained from BHK-21 and Vero cell cultures infected with encephalomyocarditis, polio, echoviruses, and a togavirus make it possible to distinguish between these infecting viruses. The appearance of 1 or 2 compounds, represented by GC peaks with TR values of 302 and 677 seconds seems to be specific for these viruses. Other peaks found in the supernatant media 1-2 hours after infection probably represent cell constituents leaking into the medium as a result of damage to the cell membrane by the invading virus.

Arboviruses↗