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Biomedical subjects

M Rubinstein

Publications and source records attributed to M Rubinstein.

At least 217 records · Page 12Linked to original sources
PubMed1983

High and low potency interferon-alpha subtypes induce (2'-5') oligoadenylate synthetase with similar efficiency.

Three major subtypes of human interferon-alpha (IFN-alpha), isolated from virus-induced leukocytes, were compared for their antiviral and anticellular activities on one hand, and for their ability to induce (2'-5') oligoadenylate synthetase on the other hand. One subtype, IFN-alpha 1, was found to have low specific antiviral (6.10(6)-5.10(7) units/mg) and anticellular activities when measured on a variety of human cells. A second subtype, exhibiting an unusually high molecular weight (26,000) by SDS-polyacrylamide gel electrophoresis (IFN-alpha 26K), was found to have the highest known specific antiviral (8.10(8)-2.10(9) units/mg) and anticellular activities. Thus, these two subtypes of IFN-alpha differ by a factor of 330 and represent the two extremes in the antiviral scale on human cells. A third subtype, IFN-alpha 2, was tested as well and was found to have intermediate antiviral and anticellular activities. The ability of these three subtypes to induce (2'-5') oligoadenylate synthetase in human cells was then measured. It was found that on a weight basis, the three subtypes were equally effective in inducing the enzyme. Since the level of (2'-5') adenylate oligomers is affected also by the interferon-induced (2'-5') phosphodiesterase, the ability of these subtypes to induce this enzyme was compared as well and was found to be very similar. We therefore conclude that the differences in potency between these IFN-alpha subtypes are not related to their ability to induce (2'-5') oligoadenylate synthetase.

2',5'-Oligoadenylate Synthetase↗
PubMed1983

Spontaneous production of interferon-gamma and acid-labile interferon-alpha by subpopulations of human mononuclear cells.

A low-density subpopulation of normal human peripheral blood mononuclear leukocytes obtained by percoll gradients was found to produce significant levels (up to 10,000 units/ml) of interferon in the absence of an external inducer. The interferon (IFN) was characterized as a mixture of IFN-gamma (immune) and a pH-sensitive IFN-alpha by neutralization with specific antibodies, by lability to low pH, and by cross-reactivity on bovine cells. Significant levels of IFN were obtained only at high (greater than or equal to 5 X 10(6) cells/ml) cell densities. These levels were not affected by the presence of small T lymphocytes and sharply decreased with cell dilution in a nonlinear fashion. A release of IFN in the absence of an external inducer, indicates additional physiological roles besides its involvement in pathological conditions.

Cells, Cultured↗
PubMed1983

Effects of several species of human leukocyte interferon on cytotoxic activity of NK cells and monocytes.

Ten species of purified human leukocyte interferon were tested for their ability to modulate the cytolytic activity of natural killer (NK) cells and the cytolytic and cytostatic activities of monocytes. The interferon species were tested at several antiviral titers and examined for quantitative differences in their ability to modulate immunological function. At the higher doses of interferon (i.e., greater than 500 units) all of the interferon species demonstrated significant augmentation of cytolysis and cytostasis. However, when low levels (i.e., 10-50 units) of interferon were employed, appreciable differences between the various interferon species were seen. A similar pattern of relative potency among the various species of pure leukocyte interferon was seen for augmentation of cytolysis by monocytes and NK cells. In contrast, a different pattern of relative potency was observed for augmentation of cytostasis. These results demonstrated substantial quantitative differences (as much as 100-fold) in the ability of the various species of human leukocyte interferon to induce significant levels of augmentation of these cell-mediated functions. Such results should have significant impact in choosing a specific interferon species for appropriate clinical trials.

Cytotoxicity, Immunologic↗
PubMed1983

Influence of catecholamines on cochlear action potentials.

Catecholamines were injected intra-arterially in guinea pigs using a rheological model described elsewhere. With this method, apart from the ear, only a relatively restricted area was perfused with catecholamines, and the amount eventually entering the general circulation was insufficient to change the normal BP. The induced vasoconstriction of the labyrinthine vessels affected the cochlear blood flow and caused an increase of 11.34 dB in the mean action potential threshold. When the rate of catecholamine infusion was increased, associating vasoconstriction of the cochlear vessels with increased BP, deterioration of the action potential threshold was limited to only 2 dB. However, decrease in the normal BP under the same experimental conditions raised the threshold by 21.67 dB.

Animals↗
PubMed1983

Monoclonal antibodies to human interferon-gamma: production, affinity purification and radioimmunoassay.

Human interferon-gamma (IFN-gamma) purified to electrophoretic homogeneity by a cation exchange h.p.l.c., was used for the development of monoclonal antibodies. Following immunization, spleen lymphocytes of two mice showing the highest binding and neutralizing titers were isolated, fused with NSO mouse myeloma cells and cloned. The screening of hybridomas was based on precipitation of the immune complexes with a second antibody and recovery of the biological activity of IFN-gamma from the precipitate. Twenty nine independent hybridomas secreting antibodies specific to IFN-gamma were obtained. Twelve out of these 29 hybridomas produced antibodies that neutralized the antiviral activity of pure as well as crude IFN-gamma. Moreover, IFN-gamma obtained by various induction procedures was neutralized as well, indicating that these various IFN-gamma subtypes are immunologically cross-reactive. Immune precipitation of partially purified 125I-labelled IFN-gamma by several monoclonal antibodies revealed two protein bands of 26,000 and 21,000 daltons. Immunoaffinity chromatography of IFN-gamma gave a 50-fold purification to a specific activity > or = 4 x 10(7) units/mg. Two of the monoclonal antibodies were found suitable for a sensitive and rapid double antibody solid-phase radioimmunoassay, allowing the detection of IFN-gamma at concentrations of at least 4 ng/ml (150 units/ml) within 8 h.

Animals↗
PubMed1983

A model for research on cochlear hypoxia.

The vessels emerging from one side of the basilar artery are supplied exclusively by the homolateral vertebral artery. Since blood flow is laminar through the vertebrobasilar system, mixing between two sides does not normally occur. Based on this fact, an experimental model for research on cochlear hypoxia is proposed and described. The animal's own blood flow in the vertebral artery is completely replaced by a stream of poorly oxygenated blood injected retrogradely through the ipsilateral axillary artery. In this way, the territory supplied by the vessels emerging from this side of the basilar artery, including the ear, is rendered hypoxic. The changes in the cochlear action potentials induced by the reduced oxygen supply are recorded by a chronically implanted electrode and analyzed.

Animals↗
PubMed1983

Affinity chromatography of human fibroblast interferon (IFN-beta 1) by monoclonal antibody columns.

Eight hybridomas secreting monoclonal antibodies specific to human fibroblast interferon (IFN-beta 1) were identified by a new screening procedure based on immune precipitation with a second antibody and recovery of interferon activity from the immune precipitate. Immunoadsorbents were prepared from these monoclonal antibodies and used for purification of IFN-beta 1. Electrophoretically pure IFN-beta 1, having a specific activity of 3 X 10(8) to 6 X 10(8) units/mg was obtained by a single passage of partially purified IFN-beta 1 on these immunoadsorbents.

Animals↗
PubMed1982

Purification and structural analysis of interferon.

Studies with crude or partly purified interferon have provided a significant amount of structural information. However, complete biochemical characterization required purification to homogeneity. Earlier work on fractionation has met with many difficulties because interferon was available only in minute quantities. A scale-up of production, adaptation of multi-step purification schemes, use of high-resolution separation techniques and highly sensitive analytical methods have yielded pure interferons and hence many structural data. Specific activities, amino-acid compositions, partial sequences and structural homologies of many interferons were determined. Finally, cloned copy DNA (cDNA) fragments derived from specific interferon mRNA, as well as isolated interferon genes, have been sequenced and the data were used to elucidate complete sequences of many interferons with a high degree of confidence.

Amino Acids↗
PubMed1982

Partial improvement in negative schizophrenic symptoms after amphetamine.

In stable schizophrenic outpatients with predominantly "defect state" symptomatology amphetamine caused a reduction in negative symptoms that was statistically significant but not complete (i.e. these symptoms remained clinically discernible). The possibility that dopaminergic hypofunction contributes some elements to the schizophrenic defect state is presented, along with some limited data compatible with this concept. These findings are compared to prior studies in recently hospitalized schizophrenic subjects, and discussed with respect to recent theoretical concepts regarding the role of dopamine in schizophrenic psychopathology.

Adult↗
PubMed1982

Influence of blood viscosity on cochlear action potentials and oxygenation.

Impairment of the cochlear blood supply of guinea pigs was induced in order to study the effects of hypoxia on the cochlear action potentials. The oxygenation of the cochlear structures was decreased by perfusing the ears with polycythemic hyperviscous blood. The validity of using this model of cochlear blood flow was based on the propensity of the blood to flow in a laminar way. Because of the streamlined flow pattern, the blood supplied by the two vertebral arteries does not mix within the common trunk of the basilar artery. The retrograde injection of polycythemic hyperviscous blood into one vertebral artery will affect the ear on the injected side only. The high viscosity of the polycythemic blood decreases the rate of flow of blood through the cochlear vessels; the high oxygen content of this blood, however, avoids hypoxia of the cochlea. Therefore, in order to make the slowdown in the blood flow evident, its oxygen content was reduced to a 'precritical level' before it was infused. Injecting normoviscous blood with a 'precritical level' of oxygen caused a mild reduction in the scala media pO2 of 15.2% for the whole group of twenty animals. The hyperviscous blood with the same level of oxygenation, however, reduced the pO2 in the scala media to 53.3% of normal. These findings explain the difference in the altered click-evoked action potentials in the two groups of animals.

Action Potentials↗
PubMed1982

Interferon-dependent induction of mRNA for the major histocompatibility antigens in human fibroblasts and lymphoblastoid cells.

In human cells treated with interferons, there is an increase in the amount of HLA-A,B,C and beta 2-microglobulin exposed on the cell surface. We have used a cloned HLA-A,B,C cDNA probe to demonstrate by molecular hybridization that this effect of interferon is preceded by a large increase in the amount of HLA mRNA in the cell. This effect was found in five different human cell lines, with purified leukocyte and fibroblast interferons. The increase in HLA mRNA is comparable in its kinetics and dose-response to the induction of (2'-5') oligo(A) synthetase mRNA by interferons. Therefore, interferons seem to activate at least two cellular genes which have different biochemical functions.

Cells, Cultured↗
PubMed1982

Human interferons protect plants from virus infection.

Unfractionated human leukocyte interferon, as well as highly purified subspecies of this interferon, and a purified recombinant of human leukocyte interferon produced in bacteria are active in suppressing multiplicability of tobacco mosaic virus in tobacco leaf discs. Human fibroblast interferon exhibits diverse levels of antiviral activity against tobacco mosaic virus but becomes as active as human leukocyte interferon upon incubation with glycosidases. The effect of interferon is reversible; normal multiplication of tobacco mosaic virus resumes upon removal of interferon.

Enzyme-Linked Immunosorbent Assay↗
PubMed1982

Monoclonal antibodies to human alpha-interferon and their use for affinity chromatography.

A new screening procedure has been developed and used for the identification of three hybridomas secreting monoclonal antibodies to human leukocyte interferon (IFN-alpha). The screening procedure is based on immune precipitation with a second antibody, acid dissociation of the precipitate, and bioassay of the recovered interferon. This procedure selects for monoclonal antibodies that are suitable for affinity chromatography, as demonstrated by construction of immunoadsorbents from these monoclonal antibodies and purification to homogeneity in IFN-alpha.

Animals↗
PubMed1981

Augmentation of natural and antibody-dependent cell-mediated cytotoxicity by pure human leukocyte interferon.

Augmentation of the cytolytic activity of human natural killer cells and of antibody-dependent cell-mediated cytotoxicity has been attributed to human interferons. With the purification to homogeneity of human leukocyte interferon, it became possible to test directly whether pure interferon could increase the activity of these effector cells. Treatment of purified blood mononuclear cells with pure interferon resulted in substantial increases in natural killer cell activity and in antibody-dependent cell-mediated cytotoxicity. Concentrations of 10-100 units/ml of antiviral activity were sufficient to augment appreciably natural killer cell activity.

Antibody-Dependent Cell Cytotoxicity↗