Characterization of the T antigen and T agglutinin in inbred rats.

Treatment of rat erythrocytes with vibrio cholerae neuraminidase (VCN) exposed antigenic determinants on the cell surface membrane, and autologous rat serum contained antibodies which reacted with these determinants and with VCN-treated human erythrocytes. The antibodies were not present in sera of animals less than 8 weeks of age. Human serum also contained antibodies which reacted with the VCN-treated rat erythrocytes. Lectin isolated and purified from Arachis hypogoea agglutinated VCN-treated rat erythrocytes. This system has the characteristics of the T antigen which had been described initially in humans. Absorption studies showed that the VCN-treated rat erythrocyte membrane antigen cross-reacted with the VCN-treated human erythrocyte membrane antigen. Absorption of rat sera and the lectin solution with VCN-treated rat or human erythrocytes removed all of the molecules capable of reacting with both rat and human erythrocytes. Absorption of human sera with VCN-treated human cells removed their reactivity with both cell types, but absorption with VCN-treated rat cells did not remove completely their reactivity with VCN-treated human erythrocytes. These results indicate that the VCN-treated rat cells contain antigenic determinants which are identical to some on the VCN-treated human cells and that the human sera contain antibodies to additional antigenic specificities not shared with rat red blood cells. Haemagglutination inhibition studies with different sugars, T antigen from human erythrocyte membranes and desialylated glycoprotein from rat erythrocyte membranes showed that the T antigen, the desialylated glycoprotein and the sugars containing a terminal non-reducing beta-D-galactosyl residue inhibited the reactivity of the lectin, the rat sera and the human sera with both human and rat red blood cells. These findings show that the antigenic reactivity of the VCN-treated rat red blood cells residues in the membrane glycoproteins and that the immunodominant group is a carbohydrate. Thus, the rat has a T antigenic system very similar to that of the human.     

Beta-2-microglobulin of rat major histocompatibility complex class I antigens

Detection of the beta 2-microglobulin (beta 2m) component of the rat MHC class I antigens has been difficult. In the present report, we have addressed this issue by a systematic study of rat class I antigens from red blood cells or from lymphocytes that were freshly isolated or cultured in the presence of autologous or heterologous sera and surface-labeled with 125I or intrinsically labeled with radioactive amino acids. First, specific radioiodination of rat beta 2m in association with the antigen heavy chain on red blood cells or lymphocytes is minimal, resulting in its poor identification by SDS-PAGE. Second, labeling with radioactive methionine or lysine gives a more intense beta 2m band with respect to the heavy chain than labeling with arginine or tyrosine. Third, the beta 2m component shows a large increase in intensity compared to the heavy chain when the antigens are isolated from lymphocytes that are cultured in the presence of fetal bovine serum prior to 125I-labeling. This increase is due to exchange of endogenous rat beta 2m with bovine beta 2m and to a much higher level of radioiodination of the latter. Fourth, rat red blood cells and lymphocytes contain free surface beta 2m molecules in addition to those associated with the antigen heavy chains. The free molecules show a much higher level of radioiodination than those associated with the heavy chains, and there is little exchange between the antigen-bound and the free beta 2m after radioiodination.(ABSTRACT TRUNCATED AT 250 WORDS)     

Deletion of beta-catenin impairs T cell development

T cells encounter two main checkpoints during development in the thymus. These checkpoints are critically dependent on signals derived from the thymic microenvironment as well as from the pre-T cell receptor (pre-TCR) and the alphabeta TCR. Here we show that T cell-specific deletion of beta-catenin impaired T cell development at the beta-selection checkpoint, leading to a substantial decrease in splenic T cells. In addition, beta-catenin also seemed to be a target of TCR-CD3 signals in thymocytes and mature T cells. These data indicate that beta-catenin-mediated signals are required for normal T cell development.     

Anti-cardiolipin antibodies in infectious mononucleosis react with the membrane of activated lymphocytes

To elucidate the mechanisms of autoantibody induction in infectious mononucleosis (IM), we have studied sera from 35 patients with IM with enzyme-linked immunosorbent assays using purified antigens. In the IM group 37% had IgM antibodies to cardiolipin above the normal range (mean plus 2 standard deviations of control sera). Significantly elevated frequencies of antibodies to actin (26%) and cytoskeletal antigens (97% versus 29% in normal sera) were also found, but levels of IgM rheumatoid factors, IgM antibodies to single-stranded DNA and antibodies to ribonucleoproteins (nRNP/Sm, Sm and La) were normal. Affinity purified anti-cardiolipin antibodies reacted with the cell membrane of transformed lymphocytes but not with resting cells, suggesting that cell activation was required for the expression of antigenic epitopes. Our data suggest that the autoantibody response in IM is restricted to two classes of autoantigens: cytoskeletal and cell membrane antigens. The appearance of antigenic epitopes on EBV-transformed lymphocytes could be a mechanism for the generation of anti-cardiolipin antibodies in infectious mononucleosis. Similar mechanisms could operate in autoimmune rheumatic disease.     

The enumeration of viral genomes in murine cytomegalovirus-infected cells.

Murine cytomegalovirus (MCMV) DNA synthesis in infected cells was measured by the technique of DNA-DNA reassociation kinetics, using ¹²⁵I-labeled MCMV DNA as the probe. This method circumvented the problems inherent in thymidine incorporation studies due to the low level of thymidine kinase activity in infected cells. MCMV-DNA synthesis was detected as early as 8 hr p.i. in mouse embryo cells.     

Capacity to consent to research among patients with bipolar disorder

Experts have debated the influence of mental illness on decision-making capacity. This paper reviews concepts of decision-making capacity and existing research on the influence of mental illness on capacity to consent to research. We propose how bipolar disorder, especially mania, may have an effect on consent capacity. The current conceptualization of capacity utilizes legal standards of ‘choice’, ‘understanding’, ‘appreciation’ and ‘rational reasoning’, as well as voluntarism, or the assurance that the patient is free to agree or to decline to participate in research. Studies of patients with schizophrenia suggest impaired cognition influences ‘understanding’ and is more important than severity of psychosis in affecting decision-making abilities. There are no studies of sources and extent of impairment to consent to research among manic patients. Mania may influence a patient’s understanding of the research protocol, but also alter the patient’s views, values and level of insight, thus impairing decision-making abilities at the ‘appreciation’ standard even when the patient understands the relevant information. Mania may impact freedom to decide, yet paradoxically, manic patients may be less influenced by others and less vulnerable to coercion, undue influence and undue incentives compared to patients without mental illness. We suggest that in patients with mood disorders, the legal standard of appreciation be thoroughly probed during the consent procedure. Studies of the effect of mania and depression on consent capacity and voluntarism are needed in order to develop processes that increase safeguards in the informed consent process.     

Aqueous polymerization of acrylamide initiated by acidic permanganate/thiourea redox system

The polymerization of acrylamide, initiated by acidic permanganate/thiourea redox system, was studied in aqueous media at 30 ± 0,2 °C in nitrogen. The rate of polymerization (R_p) was found to be proportional to nearly the first power of the catalyst (KMnO₄) concentration, within the range of 0,5 · 10^?2 to 1,4 · 10^?2 mol dm^?3, and independent of the thiourea concentration. However, the rate of polymerization varies with the first power of the hydrochloric acid concentration within the range of 2,85 · 10^?2 to 11,4 · 10^?2 mol dm^?3, and increases linearly up to certain extent by varying the monomer concentration from 2,5 · 10^?2 to 12,5 · 10^?2 mol dm^?3. A deviation from the linear behaviour is observed, however, above a concentration of 12,5 · 10^?2 mol dm^?3. The initial rate of polymerization (R_i) as well as the maximum conversion increases by increasing the temperature up to 35 °C, but the maximum conversion falls as the temperature rises above 35 °C. The overall energy of activation is found to be 47,70 kJ mol^?1 (11,48 kcal/mol^?1) within the temperature range of 25–45 °C. Addition of salts, except manganous salts, was found to be associated with a depression in the R_p and maximum conversion. The effect of cationic and anionic surfactants has been found to increase and decrease the R_p respectively; non-ionic detergents, however, have no effect on the R_p.     

Aqueous polymerization of methacrylamide initiated by KMnO4/H2C2O4 redox system

The polymerization of methacrylamide initiated by potassium permanganate/oxalic acid redox system has been studied at 35 ± 0.2°C in a nitrogen atmosphere. The rate of polymerization is independent of the activator (oxalic acid) concentration within the range 5·10^?3 to 10·10^?3 mole·1^?1, except at very high (above 10·10^?3 mole·1^?1) or at very low (below 5·10^?3 mole·1^?1) concentrations of the activator. The rate varies linearly at low monomer concentration (up to 5.87·10^?2 mole·1^?1). The catalyst exponent decreases from nearly unity (0.91) to 0.66 with increase in concentration of the catalyst (KMnO₄) probably due to participation of primary radicals in the termination of the growing chain. The addition of strong acid (H₂SO₄) within the range 5 · 10^?4–15 · 10^?4 mole · l^?1, shows a constant pH of 2.7 resulting in no change in initial rate. With activator alone (H₂C₂O₄ · 2H₂O), within the pH range 2.7 to 2.9 an optimum is observed. The initial rate increases with increase in polymerization temperature. The overall energy of activation as calculated from the ARRHENIUS plot has been found to be 15.1 kcal · mole^?1 within the temperature range 30–50°C. Organic solvents (water miscible only) depress the initial rate and the maximum conversion. Small amounts of neutral salts (KCl and Na₂SO₄), however, show no appreciable effect on the polymerization rate, but small amounts of manganous salts (MnSO₄) can increase the initial rate to a considerable extent. High concentrations of MnSO₄ result in termination of the growing chain. A complexing agent, Na₂F₂, decreases the initial rate but increases the maximum conversion. Introduction of fresh catalyst at intermediate stages of polymerization increases both the rate of the reaction and the conversion.     

Kinetics of the aqueous polymerization of acrylamide initiated by the permanganate- tartaric acid redox system

The kinetics of the aqueous polymerization of acrylamide, initiated by the permanganate/tartaric acid redox system was studied at 35±0,2°C under nitrogen. The initial rate of polymerization remains independent of the tartaric acid concentration in the range 3,3.10^—3 to 9,9.10^—3mol/dm³. The order of the reaction with respect to the catalyst concentration (catalyst exponent) is found to be 0,55, indicating a bimolecular mechanism for the termination reaction. The rate of polymerization varies linearly at low monomer concentrations (1,25.10^—2 to 5,0.10^—2mol/dm³). With increase in temperature above 35°C, the initial rate increases but the conversion decreases. The overall energy of activation is found to be 18,68 kcal/mol (78,10kJ/mol) in the temperature range 30 to 50°C. Water miscible organic solvents and neutral salts depress both the rate and the conversion. Addition of MnSO₄ or the injection of more catalyst at intermediate stages raises both the initial rate and the maximum conversion. NaF decreases the rate but increases the conversion.