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Biomedical subjects

M Shinitzky

Publications and source records attributed to M Shinitzky.

At least 55 records · Page 3Linked to original sources
PubMed1988

Possible correlation between tumor invasiveness and low serum cholesterol.

The predisposition to solid tumor of individuals with low serum cholesterol may correlate with membrane properties of the emerging neoplastic cells. Evidence is presented to indicate that cholesterol content in the membrane of tumor cells is adjusted with respect to the serum cholesterol. Upon incorporation of cholesterol, tumor cells, which are exemplified here by colon and gastric carcinoma cells, become substantially more immunogenic and therefore more susceptible to clearance by the immune system.

Cholesterol↗
PubMed1987

Augmentation of mitogen responsiveness in the aged by a special lipid diet AL 721.

Diminished immune responses in aging may be partially due to alteration of the lipid composition of membrane and a decrease in membrane fluidity. The effect of a daily diet of 10 g active lipid (AL 721) on the mitogen responsiveness of peripheral blood mononuclear cells (PBMC) from aged volunteers was studied. AL 721 is a mixture of lipids from hen egg yolk which was formulated for in vivo rectification of rigidified cell membranes in an attempt to restore proper physiological function. After 3 weeks on the diet, six aged participants displayed a significant increase in lymphocyte responsiveness to mitogens, while in four the responsiveness was unaffected, or increased insignificantly. In all six participants, a decline in lymphocyte responsiveness was observed a week after termination of the diet. Our preliminary results indicate that improvement of immune functions in the aged may be achieved by dietary manipulation of lipids. This innocuous approach seems to be of potential value and merits further studies.

Aged↗
PubMed1987

AL721, a novel membrane fluidizer.

AL721, which is a novel lipid mixture extracted from egg yolks, is believed to be a therapeutic pharmacologic agent. AL721 interacts with membranes of various types of cells with a common mode of action. AL721 modifies cellular membrane composition and fluidity through passive extraction and/or exchange of cholesterol. Physiologically diminished cell function due to rigidification of its membrane is reversible both in vitro and in vivo by AL721. Fluidization of aged membranes with AL721 has been shown to restore brain serotonin receptor function both in vitro and in vivo. AL721 can also successfully restore deficient immune responsiveness of lymphocytes to mitogen stimulation in aged subjects. Drug tolerance to morphine and ethanol develops upon elevation of the viscosity of neuronal cell membranes in order to counteract the fluidization effect of the drug. Treatment of rigidified cellular membranes with AL721 in vivo can markedly reduce withdrawal symptoms. The virucidal effect of AL721 on the human immunodeficiency virus is believed to operate by lowering of viral membrane cholesterol thus interfering with the binding of the viral antigen to the host cell. Non-toxicity of AL721 is clearly demonstrated in animal and human safety studies.

Aged↗
PubMed1987

Therapeutic vaccination against adjuvant arthritis using autoimmune T cells treated with hydrostatic pressure.

An ideal treatment for autoimmune diseases would be a nontoxic means of specifically neutralizing the autoreactive lymphocytes responsible for the disease. This goal has been realized in experimental autoimmunity models by immunizing rats or mice against their own autoimmune cells such that the animals generate an immune response specifically repressive to the disease-producing lymphocytes. This maneuver, termed lymphocyte vaccination, was demonstrated to be effective using some, but not all, autoimmune helper T-lymphocyte lines. We now report that T lymphocytes, otherwise incapable of triggering an immune response, can be transformed into effective immunogens by treating the cells in vitro with hydrostatic pressure. Clone A2b, as effector clone that recognized cartilage proteoglycan and caused adjuvant arthritis in Lewis rats, is such a cell. Untreated A2b could not trigger an immune response, but inoculating rats with pressure-treated A2b induced early remission of established adjuvant arthritis as well as resistance to subsequent disease. Specific resistance to arthritis was associated with anti-idiotypic T-cell reactivity to clone A2b and could be transferred from vaccinated rats to naive recipients using donor lymphoid cells. Aggregation of T-lymphocyte membrane components appeared to be important for an immune response because the effects of hydrostatic pressure could be reproduced by treatment of A2b with chemical cross-linkers or with agents disrupting the cytoskeleton. Populations of lymph node cells from antigen-primed rats, when treated with hydrostatic pressure, could also induce suppression of disease. Thus, effective vaccines can be developed without having to isolate the autoimmune T lymphocytes as lines or clones. These results demonstrate that effector T lymphocytes suitably treated may serve as agents for specifically controlling the immune system.

Animals↗
PubMed1987

Patterns of lipid changes in membranes of the aged brain.

The lipid composition of cell plasma membranes reflects a steady-state between accumulation of serum lipids, predominantly cholesterol, and intracellular lipid synthesis and degradation. In the aging tissue this subtle balance is impaired with a net accumulation of cholesterol and other rigidifying lipids such as sphingomyelin in the membrane. As a consequence, most membrane processes, including ion transports in neuronal tissues, are slowed down. In principle, it is possible to rectify such adversative processes in vivo by increasing the level of specific phospholipids and glycerides in the serum.

Aging↗
PubMed1986

Inhibition of IL-2 secretion and IL-2 receptor appearance of activated lymphocytes pretreated with hydroxylated sterols.

When murine BALB/c splenocytes are pretreated for 2 h with different concentrations of 25-hydroxycholesterol (25-HC) or 7 beta-hydroxycholesterol (7-HC), washed and stimulated either with irradiated C57BL/6 splenocytes or with Con A, IL-2 secretion is inhibited in a dose-dependent way as well as the subsequent cell proliferation. Using the same treatment and stimulation conditions, IL-2 receptor appearance on human T lymphocytes, as characterized by anti-Tac antibody binding, is also inhibited in a dose-dependent way. In contrast, the hydrophilic derivative of 7 beta-hydroxycholesterol, the 3.7 bishemisuccinate sodium salt (7-HC BHS), did not influence any of the 3 tested parameters.

Animals↗
PubMed1986

Active immunotherapy of human solid tumor with autologous cells treated with cholesteryl hemisuccinate. A Phase I study.

A marked increase in specific immunogenicity of tumor cells is induced upon incorporation of cholesteryl hemisuccinate (CHS) into the cell membrane, which presumably promotes the expression of latent tumor-associated antigens. Immunotherapy with CHS-treated and irradiated tumor cells as vaccine was found to be very effective in various murine experimental tumors and in eliciting delayed-type hypersensitivity in cancer patients. Based on these findings, we have carried out a Phase I study on 21 patients with solid tumor who had exhausted standard therapeutic options. All participating patients were examined by conventional physical and clinical tests prior and during the study. The immunotherapy regimen for most patients consisted of an intramuscular injection of 2 X 10(7) CHS treated and irradiated autologous tumor cells given at 2-week intervals. Variations on this regimen were mostly due to the lack of sufficient number of cells. None of the patients displayed evidence of toxicity or any other local or systemic adverse effects. In seven patients, regression of tumor mass was observed. In six of nine patients who were tested for delayed-type hypersensitivity against their CHS treated tumor cells, a significant increase in skin reaction was observed after immunotherapy. The lack of any adverse reaction in this treatment, in addition to the observed positive clinical and immunologic response in advanced cancer patients, indicate a safe therapeutic potency which is planned to be investigated in the subsequent clinical studies.

Cholesterol Esters↗
PubMed1986

Promotion of tumor antigenicity in EL-4 leukemia cells by hydrostatic pressure.

Subjection of EL-4-leukemia cells to hydrostatic pressure of 1200-1500 atm for 15 min increased their weak basal immunogenicity to a potent practical level. Injection of such pressure-treated and irradiated EL-4 cells into syngeneic naive C57Bl/6 mice significantly delayed tumor development and increased survival after subsequent challenge with untreated EL-4 cells. Application of pressure of 1500 atm for a longer period of time (e.g., 120 min) resulted in cell death and a smaller increase in tumor immunogenicity which could be partially accounted for by passive shedding of membrane material. Unlike previously studied tumor cells, incorporation of cholesteryl hemisuccinate (CHS) into the plasma membrane of EL-4 cells increased their apparent tumor immunogenicity only slightly. In addition, isolated EL-4 plasma membranes, untreated, CHS-treated or pressure-treated, as well as the material shed thereof by hydrostatic pressure, were all of weak immunogenicity. Modulation in the projection of surface antigens upon pressure treatment could account for the observed increase in tumor immunogenicity and was monitored via the Thy 1.2 antigen. Fluorescence cell sorting analysis indicated that upon application of 1500 atm for different periods of time the projection of Thy 1.2 progressively and irreversibly increased to a maximal level of about 140% at 15 min. At longer pressurization the availability of Thy 1.2 to antibody binding decreased sharply to levels below that of the untreated cells. It is suggested that pressure promotion of tumor immunogenicity is induced by changes in projection and surface distribution of the relevant antigens.

Animals↗
PubMed1985

Selective release of integral proteins from human erythrocyte membranes by hydrostatic pressure.

The overt effect of pressure on biological membranes is mediated predominantly through lipid condensation and disintegration of cytoskeletal polymers. These may lead to selective shedding of integral proteins, which could then be isolated by conventional means. In this study we have used the well characterised human erythrocyte membrane in order to establish the technical requirements for future use of pressure, as an alternative to detergents, in isolation of membrane proteins. Pressure of varying magnitude (300-1640 bar) and duration (5-60 min) was applied on human erythrocyte ghost membranes in suspension at different temperatures (4, 24 and 37 degrees C) and in the presence of various solutes. After ultracentrifugation protein and lipids remaining in the supernatant were quantified and analysed. It is indicated that selective integral membrane proteins can be shed off under defined conditions and presumably remain in solution by the support of strongly associated phospholipids and specific solutes. On the basis of our findings a series of technical recommendations for the isolation of specific membrane proteins is outlined.

Electrophoresis, Polyacrylamide Gel↗
PubMed1985

The effect of pressure on the lipid microviscosity and phase transition of lung surfactant.

The effect of pressure on the lipid dynamics of the rat lung surfactant was studied in liposomes made of the natural lung surfactant of the rat and of model phospholipid mixture. The determined parameter was the lipid microviscosity, monitored by the fluorescence polarization of the probe 1,6-diphenyl-1,3,5-hexatriene. Osmotic pressure of up to 47 atm, as well as hydrostatic pressure of up to 1.4 kbar, were applied at a constant temperature. The effect of pressure was monitored by the change in the lipid microviscosity of the system. The maximal change achieved with osmotic pressure at a constant temperature was only 30%. This suggests that the conversion of melted lipid to its solid phase above the lipid critical temperature requires several hundred atmospheres. Similarly, measurements of lipid microviscosity under increased hydrostatic pressure revealed transitions which occurred at above 400 atm. Since such pressures are far beyond the physiological scale, it excludes the possibility that pressure alone can be responsible for a full phase transition of the lung surfactant during respiration. Upon decompression, microviscosity of the examined lipid system was found to return to its original values, confirming the reversibility of the process.

Animals↗
PubMed1985

A special lipid mixture for membrane fluidization.

The potency for membrane fluidization of mixtures containing neutral lipids (NL), phosphatidylcholine (PC) and phosphatidylethanolamine (PE) from hen egg yolk was tested on human erythrocytes and lymphocytes. A specific mixture consisting of 70% NL, 20% PC and 10% PE was found to be a potent membrane fluidizer operating almost exclusively by extracting membrane cholesterol. Spectral results and electron micrographs indicate that aqueous dispersion of this mixture consists of chylomicron-like assemblies where the neutral lipids provide the hydrophobic core on the surface of which phospholipids are spread as a monolayer.

Drug Combinations↗
PubMed1985

Lipid fluidity of the outer segment membranes from cephalopod retina.

Membranes from the retina outer segments of squid (Loligo sp.) were isolated by sucrose continuous gradient. In these membranes, phosphatidylcholine and phosphatidylethanolamine were shown to be the most abundant lipids, while rhodopsin was the predominant protein. Steady-state fluorescence depolarization of the probe 1,6 diphenyl-1,3,5-hexatriene was employed to characterize the microviscosity of the photosensitive membranes and of the vesicles prepared from their lipid extract. The lipid fluidity parameter (r0/r-1)-1 in these membranes ranged between approximately 3.8 and approximately 0.95 (0-38 degrees C), while the value of the lipid extract vesicles ranged between approximately 3 and approximately 0.6. No phase transition was observed in the membrane and vesicle preparation in the range of temperatures under study [0-38 degrees C). Photosensitive membranes from cuttlefish (sepia officinalis) gave similar results. The (r0/r-1)-1 value in this species varied between approximately 4 and approximately 1.2 (0-38 degrees C) with a linear dependence on temperature. In these outer segments the bleaching of rhodopsin did not cause any change of the membrane lipid fluidity value. The present results are compared with those obtained in bovine rod outer segments.

Animals↗
PubMed1984

Inhibition of growth and metastases in mice by immunization with cholesterol hemisuccinate-enriched tumor cells.

Incorporation of cholesterol hemisuccinate (CHS) into the membrane of tumor cell rigidifies the lipid layer, exposes cryptic antigens, and enhances immunogenicity. The local growth and metastatic spread of the 3LL Lewis lung carcinoma were studied in conjunction with immunizations by CHS-enriched 3LL cells. C57BL/6J mice received 2 consecutive immunizations with 10(7) CHS-treated, irradiated (10,000 rad) 3LL cells. Two control groups were immunized with MCA-102 sarcoma cells or CHS-enriched syngeneic spleen cells. All groups were challenged with viable 3LL cells after immunizations. Mice pre-immunized with CHS-enriched 3LL cells showed a delayed tumor growth after subsequent challenge with 3LL. Effect of immunization on the growth of established tumors was examined in 3LL-bearing mice which were treated with 10(7) CHS-enriched tumor cells on days 1-12 after initial tumor implantation. A second identical immunotherapy was given 6 days after the first immunization. Tumor growth was significantly inhibited in mice which received the first immunization 1 day after tumor implantation, while immunization on day 3 or after inhibited the growth rate to a lesser extent. Suppression of pulmonary metastases was assessed after excision of a primary 3LL tumor growing in the foot pad which had reached 8 mm in diameter. Immunization consisted of intraperitoneal injection of 10(7) irradiated CHS-enriched tumor cells following excision and repeated after 6 days. This immunization resulted in a significant decrease in pulmonary metastasis as scored by direct counts of metastatic nodules, by [125I]iododeoxyuridine (125IUdR) incorporation, and by lung weight. Metastatic 3LL cells from nodules which survived immune elimination were isolated and implanted into mice which were pre-immunized with primary 3LL cells enriched with CHS. For comparison, a group of mice was immunized and challenged with primary 3LL cells. Inhibition of tumor growth and pulmonary metastasis formation was observed only in the mice which were challenged with the primary tumor.

Animals↗
PubMed1983

Changes in cell-surface expression of MHC and Thy-1.2 determinants following treatment with lipid modulating agents.

Treatment of normal mouse spleen cells with lipid fluidity modulators changes the expression of cell-surface H-2 determinants. BALB/c spleen cells treated for 1 to 2 hr with cholesteryl hemisuccinate (CHS) displayed reduced levels of all tested H-2 determinants (H-2L, H-2K, and H-2D) as evaluated by flow microfluorometry and increased membrane lipid packing density as determined by 1,6-diphenyl-1,3,5-hexatriene (DPH) fluorescence polarization. In contrast, decreasing membrane lipid packing density by phosphatidylcholine treatment decreased DPH fluorescence polarization and increased the expression of MHC determinants. The effects were selective in that expression of Thy-1.2 determinants was decreased by the latter treatment and not increased by CHS. The results are discussed in terms of passive modulation of antigenic expression.

Animals↗
PubMed1983

Regulation of membrane function by lipids; implications for tumor development.

Increase in the lipid fluidity of membranes increases the turnover number of each diffusible unit, but in general decreases its accessibility to ligand binding. As a result, many membranal functions reach a maximal activity at a specific lipid fluidity. These effects of membrane fluidity bear direct implications on tumor development with significant clinical potential. Two main avenues, by which lipid manipulation could be applied in cancer treatment are now being studied in experimental animals and cancer patients. In the first, the immunogenicity of tumor cells in syngeneic and autologous systems increase upon increase of the membrane microviscosity which is in line with the findings that membrane antigens become more exposed upon such treatment. Irradiated tumor cells with increased membrane microviscosity (e.g. by incorporation of cholesteryl hemisuccinate, CHS) thus act as strong and specific vaccine against the viable untreated tumor cells of the same kind. The second lipid manipulation relates to restoration of suppressed immune competence. A special mixture of lipids (Active Lipid, AL) designed to efficiently fluidize cell membranes was found to restore various immunological functions of leukocytes from cancer patients. The combination of augmentation of tumor immunogenicity and restoration of immune functions by such lipid manipulations is expected to constitute an innocuous active immunotherapy regimen for cancer treatment.

Animals↗
PubMed1983

Amniotic fluid fluorescence polarization value at physiological temperature: a marked improvement in assessing fetal lung maturity.

Determination of fetal lung maturity by measurement of the fluorescence polarization (P) value of the amniotic fluid at room temperature has become the method of choice in an increasing number of perinatal units because of its simplicity and relatively high predictive value. Nevertheless, its power to discriminate between cases with and without hyaline membrane disease (HMD) needs improvement. To this end, we assessed the discriminative power of the P value at the physiological temperature of 37 degrees C (P37) as compared with the power at 25 degrees C (P25). The study group consisted of 288 consecutive cases at risk for preterm delivery. Samples from all 288 cases were measured at 25 degrees C and samples from 112 of these were measured concurrently at 37 degrees C as well. HMD occurred in 27 infants of the total group, nine of whom belonged to the subgroup tested at both temperatures. When sensitivity was fixed at 100% the specificity of P37 was 97% as compared to 79% for P25 (p less than 0.001). The percentage of cases with infants free of HMD who had borderline P values was also significantly smaller: 1% vs 21%, respectively (p less than 0.001). Although data on more HMD cases are needed to establish the precise threshold of lung maturity for P37, we conclude that P37 is a considerably better discriminator for fetal lung maturity determination than P25.

Amniotic Fluid↗