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Biomedical subjects

A S Rubin

Publications and source records attributed to A S Rubin.

16 recordsLinked to original sources
PubMed1978

Suppression of the mitogen-stimulated blastogenic response during reticuloendotheliosis virus-induced tumorigenesis: investigations into the mechanism of action of the suppressor.

Splenic lymphocytes from chickens infected with reticuloendotheliosis virus (REV) are suppressed in their ability to undergo PHA-induced blastogenesis. This suppression can be detected within 72 hr after virus injection and requires active viral infection since i.p. or i.v. injection of UV-inactivated REV does not result in inhibition of the blastogenic response. Suppressor cells from the spleens of REV-infected birds severely inhibit the ability of spleen cells from uninfected chickens to respond to PHA at a ratio of 1:20, suggesting that each suppressor cell may be capable of suppressing more than one target cell. Contact between suppressor and target cells is required for the rapid inhibition of the normal PHA response. The suppressive mechanism is cytostatic in nature, and apparently of host origin since neither REV, nor REV-infected (or transformed) cells mediate the suppression. The ability of the suppressor cells to impair the blastogenic response of spleen cells is sensitive to trypsin, suggesting that an inhibitory protein is exposed on the surface of the suppressor cells.

Animals↗
PubMed1978

Isolation and partial characterization of an antibody enhancing factor from leukaemic owl monkey cell cultures.

Herpesvirus saimiri inoculated into owl monkeys (Aotus trivirgatus) causes leukaemia and lymphoma. Peripheral lymphocytes from leukaemic monkeys grown in culture are predominantly T lymphocytes. The supernatants from these cultures contain a factor which enhances the antibody response of murine B cells to sheep red blood cells (SRBC). The factor has been partially characterized by ammonium sulphate precipitation, DEAE-chromatography, gel filtration over Sephadex G-150 and disc-gel electrophoresis. The enhancing factor is a protein with a molecular weight of approximately 40,000.

Animals↗
PubMed1977

Problem-oriented approach to practice. I. Economic impact.

The problem-oriented system provides a unique management tool for medical practice. It follows basic management principles for any complex human endeavor (ie, define goals, set standards, audit performance to those standards, and assess results). The basic tool is the problem-oriented record, which demands that statements of medical action be explicit to permit audit. This concept can be extended to provide and assess care for an entire practice. Five years of cumulative data were assessed. The following changes were noted: (1) The ratio of patients to physicians doubled. (2) The total hospitalization rate fell by more than 20% and general medical portion by 60%. (3) Ambulatory use and cost decreased by approximately 20%. (4) Expenditures for services fell by 22%, while national expenditures for physician services increased by 28%.

Adult↗
PubMed1977

Non-specific suppression of the initiation of the immune response to a heterologous immunogen by supernatants from specifically stimulated, primed lymphoid cells.

In cultures of spleen cells from mice immunized with horse erythrocytes (HRBC) 7 days earlier, the simultaneous addition of sheep erythrocytes (SRBC) and the priming antigen on day 0 resulted in the suppression of the anti-SRBC plaque-forming cell (PFC) response by day 5 compared to the response of similar cultures that received only SRBC. The cell-free culture fluid from specifically-stimulated, HRBC-primed cells, but not normal cells, contained a factor that nonspecifically inhibited the anti-SRBC PFC response of cultures of normal spleen cells to which SRBC and diluted supernatant aliquots were added at the beginning of culture. Suppressor activity was not manifest unless active supernatants were added on day 0 of a 5-day culture period. Inhibition of the reference plaque response was not due to cytotoxicity of the active material, decreased immunogenicity of the SRBC, or switchover from IgM to IgG plaque formation. The soluble mediator was released slowly into the culture fluid, with linear kinetics, from specifically activated, primed cells, with maximum suppression obtained with the 120-h supernatant. When active supernatants were fractionated by gel filtration over Sephadex G-150, the inhibitory factor eluted with molecules of about 34,000 mol. wt.

Animals↗
PubMed1977

Partial characterization of a T cell-derived factor that suppresses the initiation of the humoral immune response in vitro.

Specific anamnestic stimulation of spleen cells from mice immunized 7 days earlier with horse erythrocytes (HRBC) generated the release of a soluble factor that was capable of suppressing the initiation of the in vitro primary gammaM immune response to sheep red blood cells (SRBC), as well as to the immunogen that elicited its formation. Moreover, the suppressive macromolecule (mol. wt yields to 34,000), derived from antigen-activated, HRBC-primed T lymphocytes (but not B cells), inhibited the secondary gammaM and gammaG anti-SRBC plaque-forming cell responses of SRBC-primed spleen cells. The active material was resistant to treatment with DNase and RNase, but was inactivated by protease (10 microgram/ml, 30 min) or exposure to mild heat (56 degrees, 30 min). The antibody initiation suppressor factor (AISF) was concentrated and partially purified by gel filtration, followed by poly-acrylamide gel electrophoresis.

Animals↗
PubMed1977

Transient suppression of the humoral immune response mediated by a factor derived from specifically activated, doubly primed lymphoid cells.

In cultures of sheep erythrocyte- (SRBC) stimulated spleen cells from mice immunized with tetanus toxoid (TT) and horse erythrocytes (HRBC) 30 to 90 days earlier, the addition of both HRBC (day 0) and TT (day 2) resulted in significant suppression of the anti-SRBC plaque-forming cell (PFC) response compared to the response of similar cultures maintained without the priming antigens. The observed inhibition was due to the presence of a soluble factor that was released into the supernatant fluid of the specifically stimulated, primed population of lymphoid cells between 72 and 120 hr after culture initiation. The active mediator, a macromolecule of approximately 24,000 daltons as determined by gel filtration over Sephadex G-150 and Ultrogel AcA 44, was suppressive when added within 24 hr, but not 48 hr, of assay for PFC against the reference SRBC antigen. The transiently acting soluble suppressor (TASS) was not overtly cytotoxic since total cell recovery and viability were unaffected in its presence. The results presented here are discussed in relation to a possible mechanism of action in which the negative regulation of immunoglobulin production is favored once a minimum level of immune reactivity is reached.

Animals↗
PubMed1976

Partial characterization of an immunoenhancing factor from allogeneic human lymphocyte cell lines.

The mixing of two histoincompatible human lymphocyte cell lines generated the release of a soluble factor which was capable on non-specifically enhancing the in vitro immune response of normal mouse spleen cells against sheep erythrocytes. The mediator was secreted into the supernatant of the allogeneic cell cultures within 24 h of cultuvation. The human enhancing factor (HEF) must be added to assay cultures on day 2, of a 5-day culture period, for its activity to be manifest. HEF was resistant to DNase, RNase and heating at 56 degrees for 30 min, but was inactivated by exposure to protease or elevated temperature (80 degrees for 30 min). The molecular weight of HEF, purified by ammonium sulphate fractionation, followed by Sephadex gel filtration, DEAE-cellulose chromatography and SDS-polyacrylamide gel electrophoresis, was approximately 38,000 Daltons.

Animals↗
PubMed1975

T cell products activating stem cells: further studies on the origin and action of the factor(s).

We studied the capacity of bone marrow hemopoietic stem cells to form colonies (colony forming units, CFU) in the spleens of irradiated recipient mice following incubation of the cells with T cell-derived mediators in short-term culture in vitro. The mediators were a) stem cell-activating factor (SAF) present in crude form in the supernatant from phytohemagglutinin (PHA); stimulated lymphocytes, and b) immunoenhancing factor (IEF) obtained in partially purified form from the supernatant of antigen-stimulated lymphocytes and characterized by its ability to enhance antibody formation in vitro. Both SAF and IEF increased the number of CFU in the cultured bone marrow cell suspension. However, only SAF, and not IEF, significantly stimulated DNA synthesis in the cultured cells, Furhter more, SAF appears to activate CFU in vitro, rather than merely to promote the survival of active CFU stem cells. Experiments with SAF and bone marrow from different strains of mice indicated that the biologic activity was not restricted by K and Ia regions of H complex.

Animals↗