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Y Gazitt

Publications and source records attributed to Y Gazitt.

At least 73 records · Page 4Linked to original sources
PubMed1984

Interferon-induced cytotoxicity and (2'-5') oligo(A) synthetase activity in T cells. Differences in responsiveness among T cells from various individuals and among lymphoblastoid T-cell lines.

Peripheral blood T lymphocytes became cytotoxic toward Daudi lymphoblastoid cells when incubated in vitro with interferon (IFN). The degree and rate of response to IFN varied markedly from one blood donor to another. "Low responders," who reproducibly showed a slower response to IFN, as well as "high responders" could be identified. The rate of increase in (2'-5') oligo(A) synthetase activity in IFN-treated cells also varied and appeared to correlate to the rate of increase in cytotoxicity. Three lymphoblastoid T-cell lines (Molt 4, Peer, HPB-ALL) also became cytotoxic towards Daudi cells when incubated with IFN and in these cells too the rate of induction of cytotoxicity appeared to correlate to the rate of increase in (2'-5') oligo(A) synthetase activity. Differences in responsiveness of T cells to IFN-mediated cytotoxicity might, therefore, reflect differences in responsiveness to IFN in general. Thus, quantitation of these differences might yield useful information for assessing the dosage and frequency of IFN administration to patients undergoing therapy.

2',5'-Oligoadenylate Synthetase↗
PubMed1983

Reactivity of purified GP40 antigen with antibodies from sera of patients with colorectal cancer: a follow-up study.

A glycoprotein antigen (GP40) was previously identified as a major component of immune complexes isolated from sera of patients with Burkitt's lymphoma. Its reactivity with antibodies from sera of patients with various types of cancer was described. In this presentation we describe the methods for further purification of GP40 from Burkitt's lymphoma sera. Radioiodinated purified GP40 was used in a double antibody precipitation assay, to measure the level of free anti-GP40 antibodies in sera of patients with colorectal cancer. Follow-up studies of patients at various stages of the disease revealed a close correlation between the level of free anti-GP40 antibodies and the stage of the disease, namely, low levels in advanced stages (C-D) and high levels in early stages (A-B). Furthermore, patients in remission undergoing chemotherapy always had elevated levels of free antibodies. Similarly, patients in relapse had decreasing levels of free antibodies.

Aged↗
PubMed1982

A highly sensitive solid-phase radioimmunoassay for the assay of Plasmodium falciparum antigens and antibodies.

A highly sensitive radioimmunoassay for detection of P. falciparum antibodies and antigens is described. A partially purified P. falciparum antigen preparation is obtained from in vitro cultured parasites enriched after gelatin sedimentation by sonicating the infected red blood cells and precipitating the proteins with 50% saturated ammonium sulfate. The precipitate is dissolved in buffer, ultracentrifuged and used to coat wells of microtiter plates. Anti-P. falciparum antibodies are detected by incubating antiserum dilutions in the coated wells and detecting the bound IgG with radioiodinated staphylococcal protein A. P. falciparum antigens are detected by their ability to inhibit binding of antibodies to the coated wells. Sera of individuals with a history of P. falciparum infection contain antibodies detectable at a dilution of 1:75,000. P. falciparum RBC infected in vitro can be detected at levels of parasitemia of the order of 1 parasite or less per 10(6) RBC.

Antibodies↗
PubMed1982

Reactivity with patient antibodies of partially purified gp40 antigen from immune complexes in Burkitt's lymphoma and nasopharyngeal carcinoma.

A glycoprotein antigen (gp40) was previously identified as a major component of immune complexes isolated from sera of patients with Burkitt's lymphoma (BL) and nasopharyngeal carcinoma (NPC). In the present work gp40 was partially purified from a pool of BL/NPC sera. Sera of patients with BL and NPC as well as sera of patients with other malignant and non-malignant diseases were tested for antibodies against gp40, using a double antibody radioimmunoassay. Practically all normal sera and sera of patients with non-malignant diseases had antibodies capable of binding radioiodinated gp40. In contrast, sera of patients with BL or NPC had very low binding, while sera of patients with other malignant diseases had intermediate binding values. The low binding activity of BL/NPC sera was shown to be due to inhibition by excess gp40 present in such sera. Effusions of patients with breast or ovarian cancer also contained demonstrable amounts of gp40. The origin of gp40 is still unknown.

Antibodies↗
PubMed1981

A technique for the identification of glycoprotein antigens in immune complexes and its application to the detection of a common glycoprotein in sera of patients with Burkitt's lymphoma and nasopharyngeal carcinoma.

A new technique for the detection of glycoprotein antigens in immune complexes (IC) isolated from serum is described. The technique was developed with a model IC system consisting of ovalbumin (OVA)-rabbit anti-ovalbumin antibodies (aOVA), at 3 times antigen excess. OVA-aOVA IC added to normal human serum (NHS) were purified by absorption onto and elution from tubes coated with rheumatoid factor (RF) and were subjected to electrophoresis in polyacrylamide gels. Concanavalin A (Con A)-binding proteins were detected by treating the gels with radioiodinated Con A (125Con A), followed by autoradiography. IC isolated from sera of patients with Burkitt's lymphoma (BL) and Nasopharyngeal Carcinoma (NPC) were analyzed before and after reduction with dithiothreitol. Two closely spaced proteins of about 40 kdalton were identified in the reduced samples in 26 of 30 BL sera (86%) and in 24 of 30 NPC sera (80%) but were not seen in 30 sera of African patients with a variety of unrelated tumors nor in 12 sera of European blood bank donors.

Antigen-Antibody Complex↗
PubMed1981

An improved technique for the isolation and analysis of immune complexes.

A technique for isolating and analyzing immune complexes (IC) using rheumatoid factor (RF) as immunoadsorbent is described. It contains several modifications to a previously published original method and has given greatly improved results: a small amount of BSA-anti-BSA (aBSA) model IC was added to human serum and the mixture was filtered through a column of Sephacryl S-300, the large molecular weight fraction was concentrated and added to tubes coated with RF. The bound IC were eluted, radioiodinated and freed to the major contaminants (HSA and immunoglobulins) by adding the corresponding antisera and removing the resulting complexes by coprecipitation or with the aid of protein A-containing Staphylococci. The purified preparations were analyzed by SDS-polyacrylamide gel electrophoresis (PAGE) and autoradiography. BSA was clearly identified in the autoradiograms. An example is given of the application of this technique to the isolation and analysis of IC from an abdominal effusion obtained from a patient with ovarian cancer.

Abdomen↗
PubMed1981

Early and late changes in the glycoproteins of Friend erythroleukemia cells induced to differentiate.

Incorporation of labeled fucose and galactose into Friend virus-transformed murine erythroleukemia cells, uninduced and induced to differentiate by hexamethylene bisacetamide, was followed during the first 4 days of treatment. The plasma membrane and microsomal-mitochondrial fractions of the cells were isolated and purified. The rate of fucose and galactose incorporation into membranal proteins was markedly stimulated in the induced cells as compared to the uninduced cells. However, the total amount of the label incorporated was decreased. Binding of wheat germ agglutinin to M.W. 140,000 and 90,000 bands of the plasma membrane was increased within 24 hr of induction and occurred at the same time as increased fucose incorporation into protein bands of similar size. Stimulation of concanavalin A binding to the plasma membrane proteins within 74 hr of induction was correlated with increased galactose incorporation into M.W. 32,000 and 64,000 bands which were tentatively identified as the glycophorin bands.

Animals↗
PubMed1981

Comparative study of two groups of inducers of Friend erythroleukemia cell differentiation in a chemically defined medium.

Friend erythroleukemia cells were induced to differentiate in a chemically defined medium in which bovine serum albumin was substituted for fetal calf serum. The inducers used to induce differentiation fell into two groups. Group A included inducers such as hexamethylene bisacetamide and dimethyl sulfoxide that could not stimulate differentiation and were very toxic to the cells over a wide range of concentrations. However, addition of L-ornithine but not D-ornithine resulted in a substantial degree of differentiation approaching the degree of differentiation reached by these inducers in the presence of fetal calf serum. A second group of inducers included short-chain fatty acids, actinomycin D, and the aminonucleoside of puromycin which did induce differentiation in the absence of ornithine to a degree comparable to that reached by the same inducers in the presence of fetal calf serum. These results support our previous finding that polyamines are involved in the triggering of differentiation and the classification on this basis of the currently used inducers.

Acetamides↗
PubMed1981

Inhibition of induced L-ornithine decarboxylase stimulation and erythrodifferentiation in Friend erythroleukemia cells by 2',5'-isoadenylate trimer core.

Friend erythroleukemia cells were induced to differentiate by hexamethylene bisacetamide, dimethyl sulfoxide, and dimethylformamide. The effect of 2',5'-oligoadenosine (trimer core) on cell growth, on erythrodifferentiation, and on the level of L-ornithine decarboxylase was tested. The results indicated a dose response-inhibitory effect of the trimer core on erythrodifferentiation. The optimal dose of the trimer inhibited hexamethylene bisacetamide and dimethyl sulfoxide stimulation of L-ornithine decarboxylase activity, with no apparent effect on cell growth, resembling the effect of high doses of interferon on both erythrodifferentiation and L-ornithine decarboxylase reported previously.

Acetamides↗
PubMed1980

Polyamine biosynthesis enzymes in the induction and inhibition of differentiation in Friend erythroleukemia cells.

O-Ornithine decarboxylase (ODC) activity in cultures of Friend erythroleukemia cells induced to differentiate with various compounds was examined. Based on ability to stimulate ODC activity, the inducers tested could be divided into two categories. Inducers of the first class, among which were dimethyl sulfoxide and hexamethylene bisacetamide, stimulated ODC activity and were inhibited by dexamethasone and the phorbol diester, 12-O-tetradecanoylphorbol-13-acetate. Specific inhibitors of polyamine biosynthesis, such as methylglyoxal bis(guanylhydrazone), an inhibitor of S-adenosylmethionine decarboxylase, and the ornithine analogs, alpha-methylornithine and alpha-hydrazinoornithine, also inhibited the induction of Friend erythroleukemia cell differentiation. The inhibition of induced differentiation by this class of compounds could be abrogated by spermine, spermidine, or putrescine. Inducers of the second class, among which were sodium butyrate, actinomycin D, and aminonucleoside of puromycin, had little or no stimulatory effect on ODC and were inhibited only by bromodeoxyuridine. The effect of bromodeoxyuridine, which inhibits inducers of both classes, was not abrogated by polyamines.

Acetamides↗
PubMed1979

Early decrease of 2-deoxy glucose and alpha-amino isobutyric acid transport are among the first events in differentiating synchronized murine erythroleukemia cells.

Murine erythroleukemic cells were induced to differentiate along the erythroid pathway by Me2SO and HMBA. These inducers caused an early decrease in the transport of glucose and amino acids, both in non-synchronized and in synchronized cultures. Careful analysis of the transport parameters in synchronized cultures showed a cyclic fluctuation of the Vmax but no significant change of the Km. in the presence of the inducers, however, a modification of the Km and Vmax of both carriers was observed which was not dependent on cell cycle. This modification is very early and procedes the transient arrest of the cells in G1 reported previously. In addition, a Me2SO-resistant cell line (DR10) does not show any changes in the transport of glucose and amino acids when incubated with Me2SO. However, there is an effect on the transport when incubated with HMBA which induces differentiation of 50% of the cells. These data support the hypothesis that an early effect of the inducers on the plasma membrane may be a necessary prerequisite for initiation of differentiation in murine erythroleukemic cells.

Aminoisobutyric Acids↗
PubMed1979

Use of enzymatic and electron microscopy (freeze-etching) methods for studying ATP-dependent masking of erythrocyte membrane phospholipids.

Membrane phospholipids of ATP-depleted chicken, rat, and toad erythrocytes are more susceptible than fresh cells to hydrolysis by phospholipase C (Bacillus cereus), phospholipase A (bee venom), or the combination of these enzymes and sphingomyelinase. ATP depletion of chicken and rat erythrocytes greatly increased the membrane phospholipid fraction, which can be extracted by dry ether. Trinitrobenzene sulfonic acid attacked about 20% of the phosphatidylethanolamine of fresh chicken erythrocytes and 45% of ATP-depleted chicken erythrocytes. The intramembranous particles on the PF face of fresh chicken, rat, and toad erythrocytes are evenly distributed, while those in the same ATP-depleted erythrocytes are significantly clustered. The average distance between the intramembranous particles in the PF face of fresh chicken erythrocytes is about 13 nm, while in ATP-depleted erythrocytes it is about 30 nm. Studies with chicken erythrocytes revealed that ATP depletion is accompanied by dephosphorylation of certain membrane polypeptides. The correlation of dephosphorylation of membrane polypeptides, exposure of membrane phospholipids, and clustering of intramembranous particles is discussed.

Adenosine Triphosphate↗
PubMed1978

Inducers of erythroleukemic differentiation. Relationship of structure to activity among planar-polar compounds.

Hexamethylenebisacetamide is a potent inducer of erythroid differentiation in murine erythroleukemia cells. A series of chemical compounds structurally related to hexamethylenebisacetamide were tested for inducing activity including polymethylene chains terminally substituted with various combinations of carboxylate, amino, amide, or sulfoxide groups. Effective "dimerization" of dimethyl sulfoxide through a linear polymethylene chain increases its inducing activity by a magnitude similar to that observed when N-methylacetamide is effectively dimerized in such a manner. It was found that all potent inducing agents possess both a hydrophilic and hydrophobic portion of the molecule, as well as a planar portion. All are Lewis bases, possessing a free electron pair available for hydrogen bonding. The polymethylene chain joining functional groups must be flexible and must be 5 to 6 carbon atoms in length to achieve maximal activity. Introduction of triple or double (cis or trans) bonds into the polymethylene chain does not alter activity.

Acetamides↗
PubMed1978

Regulation of differentiation in normal and transformed erythroid cells.

Studies are described employing two erythropoietic systems to elucidate regulatory mechanisms that control both normal erythropoiesis and erythroid differentiation of transformed hemopoietic precursors. Evidence is provided suggesting that normal erythroid cell precursors require erythropoietin as a growth factor that regulates the number of precursors capable of differentiating. Murine erythroleukemia cells proliferate without need of erythropoietin; they show a variable, generally low, rate of spontaneous differentiation and a brisk rate of erythropoiesis in response to a variety of chemical agents. Present studies suggest that these chemical inducers initiate a series of events including cell surface related changes, alterations in cell cycle kinetics, and modifications of chromatin and DNA structure which result in the irreversible commitment of these leukemia cells to erythroid differentiation and the synthesis of red-cell-specific products.

Cell Cycle↗