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G Klein

Publications and source records attributed to G Klein.

At least 595 records · Page 33Linked to original sources
PubMed1986

Lymphoblastoid cell lines and Burkitt-lymphoma-derived cell lines differ in the expression of a second Epstein-Barr virus encoded nuclear antigen.

Twenty-seven Epstein-Barr virus (EBV)-transformed lymphoblastoid cell lines and 27 EBV-carrying Burkitt-lymphoma-derived lines were analyzed for expression of the second EBV-encoded nuclear antigen (EBNA-2) by immunoblotting and anticomplement immunofluorescence with EBNA-2-specific sera. While all lymphoblastoid cell lines expressed EBNA-2, only 10 of the 27 BL lines were EBNA-2-positive. Comparison of the EBNA-2 coding BamHI W-, Y- and H-fragments of EBV-DNA in the different cell lines by restriction enzyme analysis suggests that EBNA-2 negativity is due either to sequence diversity or to a deletion in the BamHI WYH region.

Antigens, Viral↗
PubMed1986

Rearrangement of c-myc, pim-1 and Mlvi-1 and trisomy of chromosome 15 in MCF- and Moloney-MuLV-induced murine T-cell leukemias.

Provirus insertion near the c-myc, pim-1 or Mlvi-1 genes occurred in 7 out of 59 virally induced T-cell leukemias. C-myc was exclusively rearranged in approximately 10% of MCF247-induced tumors while Mlvi-1 was rearranged to a similar frequency in Moloney-virus-induced lymphomas. Out of 25 karyotyped tumors, 9 (36%) showed trisomy of chromosome 15. Provirus insertion near c-myc, pim-1 or Mlvi-1 occurred both in diploid lymphomas and in tumors with trisomy 15. These results suggest that the molecular and cytogenetic changes observed in murine T-cell leukemias are independent tumor-associated events and that trisomy of chromosome 15 is a common tumor-progression-related event.

Animals↗
PubMed1986

Kinetics of fluid-phase pinocytosis in Dictyostelium discoideum amoebae.

Kinetics of pinocytosis in Dictyostelium discoideum were investigated over an extended period of time (up to 6 hours) using fluorescein isothiocyanate (FITC)-dextran as a fluid-phase marker. FITC-dextran added to the medium accumulated rapidly inside the cells with a rate of influx equivalent to 9 microns3 of fluid/cell x min. After a period of about 90 min of uptake, the intracellular FITC-dextran level reached a plateau which corresponded to a strict balance between pinocytosis and exocytosis as shown both by efflux measurements and pulse experiments with (3H) dextran. At equilibrium, the amount of internalized marker reached a value equivalent to 790 microns3 of fluid taken up per amoeba, i.e. a volume paradoxically higher than the total aqueous space of the cell (520 microns3 ). FITC-dextran was thus markedly concentrated intracellularly. The endocytic compartment in which the intracellular FITC-dextran was concentrated could be completely washed out when FITC-dextran was removed from the external medium.

Dextrans↗
PubMed1986

Quantitation of Epstein-Barr virus (EBV)-determined nuclear antigen (EBNA) by a two-site enzyme immunoassay, in parallel with EBV-DNA.

A two-site enzyme (TSE) immunoassay was developed for the quantitation of the Epstein-Barr virus (EBV)-determined nuclear antigen (EBNA) using a rabbit serum raised against a synthetic peptide derived from the BamHI K region of the viral genome. Comparison of 12 EBNA-positive and 3 negative cell lines proved that the test was EBV-specific. A dot-blot assay utilizing cloned and nick translated EBV-DNA BamHI M fragment confirmed the EBV-carrier status of the EBNA-positive lines. The results obtained with both the TSE immunoassay and dot-blot assay were in agreement with published values. In contrast to earlier reports, we could not demonstrate any correlation between the content of EBNA and the number of viral genome copies.

Antigens, Viral↗
PubMed1986

Interaction between aurovertin and adenine nucleotide binding sites on mitochondrial F1-ATPase and the isolated beta subunit.

The effect of aurovertin on the binding parameters of ADP and ATP to native F1 from beef heart mitochondria in the presence of EDTA has been explored. Three exchangeable sites per F1 were titrated by ADP and ATP in the absence or presence of aurovertin. Curvilinear Scatchard plots for the binding of both ADP and ATP were obtained in the absence of aurovertin, indicating one high affinity site (Kd for ADP = 0.6-0.8 microM; Kd for ATP = 0.3-0.5 microM) and two lower affinity sites (Kd for ADP = 8-10 microM; Kd for ATP = 7-10 microM). With a saturating concentration of aurovertin capable of filling the three beta subunits of F1, the curvilinearity of the Scatchard plots was decreased for ATP binding and abolished for ADP binding, indicating homogeneity of ADP binding sites in the F1-aurovertin complex (Kd for ADP = 2 microM). When only the high affinity aurovertin site was occupied, maximal enhancement of the fluorescence of the F1-aurovertin complex was attained with 1 mol of ADP bound per mol of F1 and maximal quenching for 1 mol of ATP bound per mol of F1. When the F1-aurovertin complex was incubated with [3H]ADP followed by [14C]ATP, full fluorescence quenching was attained when ATP had displaced the previously bound ADP. In the case of the isolated beta subunit, both ADP and ATP enhanced the fluorescence of the beta subunit-aurovertin complex. The Kd values for ADP and ATP in the presence of EDTA were 0.6 mM and 3.7 mM, respectively; MgCl2 decreased the Kd values to 0.1 mM for both ADP and ATP. It is postulated that native F1 possesses three equivalent interacting nucleotide binding sites and exists in two conformations which are in equilibrium and recognize either ATP (T conformation) or ADP (D conformation). The negative interactions between the nucleotide binding sites of F1 are strongest in the D conformation. Upon addition of aurovertin, the site-site cooperativity between the beta subunits of F1 is decreased or even abolished.

Adenine Nucleotides↗
PubMed1986

Differential recognition of tumor-derived and in vitro Epstein-Barr virus-transformed B-cell lines by fetal calf serum-specific T4-positive cytotoxic T-lymphocyte clones.

Two interleukin-2 (IL-2)-dependent cytotoxic T-cell clones were obtained by limiting dilution from a lymphocyte culture stimulated in vitro with the autologous Epstein-Barr virus-transformed lymphoblastoid cell line (LCL) in the presence of fetal calf serum (FCS). Both clones uniformly had a T3+, T4+, Dr+ phenotype and lysed autologous B blasts, the autologous LCL, and allogeneic B cell lines sharing major histocompatibility complex (MHC) class II antigens. The cytotoxic function was triggered by FCS-derived components. There was no killing if the sensitive targets were cultured in serum-free medium or in medium supplemented with human serum. Sensitivity to lysis could be restored by exposing the targets to FCS for at least 6 hr at 37 degrees C. Monoclonal antibodies directed to T-cell-specific surface antigens and MHC class II antigens inhibited lysis with different efficiencies depending on the target cell origin. Killing of Burkitt's lymphoma (BL)-derived cell lines was blocked more easily than killing of LCLs. LCLs but not BL lines induced proliferation of the T-cell clones in the absence of exogenous IL-2. The differences were not related to quantitative variations in the expression of MHC class II antigens, indicating that BL lines differ from LCLs in other cell membrane properties that may influence antigen presentation. The results suggest that the affinity of effector/target binding, which is probably influenced by the concentration of antigenic determinants expressed on the target cell membrane, determines whether proliferative responses or cytotoxicity are induced in the antigen-recognizing T cells.

Antibodies, Monoclonal↗
PubMed1986

The Epstein-Barr virus determined nuclear antigen is composed of at least three different antigens.

The EBV-determined nuclear antigen, EBNA, is the only known viral product to be regularly detected in all EBV-transformed cells. The anticomplement immunofluorescence (ACIF) staining detects an EBV-specific nuclear reaction that has recently been shown to be due to at least 2 different proteins, EBNA-1 and EBNA-2, encoded by different parts of the viral genome. We now report the existence of a third antigen of the EBNA complex, designated as EBNA-3. Serum from a patient with chronic infectious mononucleosis contained no detectable antibodies to EBNA-I and had only a low EBNA-2 antibody level. Nevertheless, it gave an EBV-specific nuclear reaction of normal intensity and stained EBNA-2-positive and EBNA-2-negative EBV-carrying lines equally well. Immunoblotting with the same serum identified a new EBV-specific nuclear protein of 143-157 kDa.

Animals↗
PubMed1986

Alternative involvement of two cytogenetically distinguishable breakpoints on chromosome 8 in Burkitt's lymphoma associated translocations.

The chromosomes of 16 Burkitt's lymphoma (BL) derived cell lines were submitted to high-resolution G-band analysis. They included seven lines with t(8;14), three with t(2;8), and four with t(8;22). The translocation breakpoint in chromosome #14 was located in 14q32.3, in chromosome #2 in 2p11.1, and in chromosome #22 in 22q12.12. In chromosome #8, the translocation breakpoint was located in two cytogenetically distinct subbands: 8q24.1 in cell lines with t(8;14) and t(2;8) and 8q24.22 in cell lines with t(8;22). In the light of recent molecular findings, these results indicate that the distance between the c-myc gene, located in 8q24, and the Ig sequences might be much larger in BL lines with t(8;22) than in those with t(2;8).

Burkitt Lymphoma↗
PubMed1986

Plasma concentrations of high-density lipoprotein (HDL)-2 and HDL-3 in myocardial infarction survivors and in control subjects.

The serum concentration of several lipids, including high-density lipoprotein-cholesterol (HDL-C) and the HDL subfractions, HDL-2-C and HDL-3-C, were measured in 44 male and 26 female survivors of myocardial infarction and compared with those of a control group matched for age, sex, and body weight. Serum concentrations of total cholesterol (TC) and low-density lipoprotein (LDL-C) were significantly increased in patients as compared to control individuals. The total HDL-C concentration was lower in patients than in controls. By differential quantitation of HDL subfractions with a new precipitation method using polyethylene glycol, it was found that HDL-3-C was not significantly different between female patients and controls. The reduction of HDL-3-C in male patients was only of borderline significance. HDL-2-C in contrast was highly significantly reduced in both male and female patients. The greatest difference between patients and controls was found in the HDL-2/HDL-3-C ratio. It is therefore concluded that HDL-2-C quantitation is a valuable risk indicator for myocardial infarction yielding a better discrimination of patients from controls than total HDL-C quantitation.

Adult↗
PubMed1986

B cell activation by the nontransforming P3HR-1 substrain of the Epstein-Barr virus (EBV).

The P3HR-1 substrain of Epstein-Barr virus does not transform B cells. This defect is known to be determined by the loss of the coding sequence for the nuclear antigen EBNA-2. The virus can attach to and enter resting B cells. The initial events after EBV infection are reminiscent of those induced by polyclonal B cell activators. Similar to the effect of these, P3HR-1 virus lowers membrane IgD expression on B cells and abrogates the transient elevation of activation markers BB-1 and LB-1 induced by the culture conditions. An important event of B cell activation is the acquisition of competence to respond to specific growth factors produced by T cells. This was induced by the P3HR-1 virus. The infected B cells had elevated [3H]thymidine incorporation when exposed to the supernatant of PHA-treated T cells. The EBV receptor is identical with the complement receptor CR2. Ligand binding to CR2 has been shown both with mouse and human B cells to deliver certain activation signals. Therefore, it is possible that the early step of activation by EBV is initiated through the binding to the receptor and is thus a cell surface event.

Antigens, Surface↗
PubMed1986

Localization of the rat immunoglobulin heavy chain locus to chromosome 6.

We have previously used rat/mouse somatic cell hybrids to localize the rat c-myc gene to chromosome 7 (Sümegi et al. 1983) and the rat immunoglobulin kappa locus to chromosome 4 (Perlmann et al. 1985). We now report that by utilizing rat/mouse somatic cell hybrids, we have localized the rat immunoglobulin heavy chain locus to chromosome 6.

Animals↗