Biomedical subjects
Publications and source records attributed to G W Litman.
Explore the source record for details and available documents.
A histone-like protein that is rich in alanine and lysine (protein AK) has been obtained in homogeneous form by high-resolution gel filtration of H2SO4 extracts of calf thymus chromatin. Protein AK: (i) migrates as a single band in polyacrylamide gel electrophoresis in both acetic acid/urea and sodium dodecyl sulfate; (ii) is a basic protein; (iii) lacks tryptophan; (iv) is not extracted from chromatin with 0.35 M NaCl; and (v) is not soluble in 0.75 M HClO4. Protein AK is distinguished from the high-mobility group (HMG) proteins on the basis of these latter solubility characteristics and from the histones and protein A24 on the basis of amino acid composition and distribution of tryptic peptides in two-dimensional chromato-electrophoresis. In addition, protein AK is distinguished from the HMG proteins, the histones, and protein A24 on the basis of its mobility in two polyacrylamide gel electrophoresis systems. The amino acid composition of protein AK resembles that of HU, a basic DNA-binding protein found in Escherichia coli.
A two-step procedure employing gel filtration and anion exchange chromatography has been utilized to isolate LMW immunoglobulin from the horned shark, Heterodontus francisci. Light chains obtained by complete reduction and alkylation of the parent protein have been compared by several analytical techniques. Amino acid composition data implies a limited degree of variation in the light chains isolated from individual animals. Polyacrylamide gel electrophoresis of the CNBr digests of the light chains reveal indistinguishable banding profiles of the major peptides. Isoelectric focusing indicates limited heterogeneity in the light chain spectrotype and identity in the pI of the majority of bands detectable by staining. The suggested degree of structural similarity in the light chains of this phylogenetically primitive shark is discussed in terms of the evolutionary position of the species and current theories concerning the origins of structural diversity in immunoglobulins.
The alteration of two erythrocyte plasma membrane functions, acetylcholine hydrolysis and glucose exchange, by a series of structurally related small lipophilic compounds which exhibit antihemolytic behavior was studied. 2-Methyldimethylaminoazobenzene is a more potent inhibitor of acetylcholinesterase than the 3'-methyl analogue, while the unsubstituted compound fails to inhibit. Esterase inhibition by the 2-methyl compound is non-competitive and dependent on the anion composition of the assay buffer. The temperature dependence of acetylcholinesterase activity in the presence of the 2-methyl compound suggests that interaction with inhibitor is influenced by the state of lipids tightly bound to the enzyme. Glucose exchange is inhibited to the same extent by both methyl derivatives but not by the unsubstituted dye, and the temperature dependence in the presence of inhibitor is not grossly altered. The lack of correlation between inhibition of membrane function adn stabilization of erythrocytes against osmotic hemolysis is discussed.
Raman spectra have been obtained on aqueous solutions of the following human immunoglobulins: IgM-kappa McE, IgG-kappa Ger, IgM-kappa WSm and IgG-lambda Gui. The former two species exhibit the property of cryoprecipitation. Comparison of the spectra shows that all immunoglobulins have similar secondary structures, predominantly of the beta-sheet type. Fab mu and (Fc)5 mu fragments of IgM-kappa McE also yield Raman spectra which indicate closely similar secondary structures. Minor differences among the spectra can be explained by differences in amino acid compositions of the respective proteins.
Explore the source record for details and available documents.
The acrylamide-quenching patterns of the intrinsic tryptophan fluorescence of six cold-soluble monoclonal immunoglobulin M (IgM) and two monoclonal IgM proteins possessing cryoglobulin properties (abnormal cold insolubility) have been compared. Static and dynamic components of quenching have been resolved by a modified form of the Stern-Volmer relationship. The unusual observation of static quenching seen with the multitryptophan containing IgM is determined to be a consequence of essentially homogeneous indole fluorescence arising from conserved tryptophan residues within each homologous immunoglobulin domain. Although the static component of the quenching of the two IgM cryoimmunoglobulins examined is similar to that of the non-cryoimmunoglobulin, IgM, some of the cryoglobulin's tryptophan residues appear to be more kinetically exposed to acrylamide than the tryptophans in the non-cryoglobulin IgM. An unusually large negative entropy of activation observed for the quenching process of both cryoimmunoglobulins suggests some abnormality in the dynamic (flexibility) properties of these proteins.
A new antigenic determinant was discovered with a hemagglutination-inhibition assay system. Designated Hv(1), it is located in the variable region of human immunoglobulin heavy chains of the G, M, and A classes. Pedigree and population analyses suggest that it has an autosomal dominant mode of inheritance. This represents the first description of an allotypic determinant in the variable region of human immunoglobulins.
Explore the source record for details and available documents.
The physical and chemical properties of five human and one canine monoclonal cryoimmunoglobulin have been compared. By many criteria, the proteins cannot be distinguished from the noncryoglobulin reference proteins analyzed in parallel; however, certain hydrodynamic and spectroscopic properties of the proteins indicate that cryoimmunoglobulins differ in tertiary structure relative to their cold-soluble counterparts. These differences seem to favor low-temperature-induced association between cryoglobulin molecules as an immediate consequence of increased intermolecular ionic or van der Waals forces. No evidence was found for the formation of cold-dependent antigen-antibody complexes or the ubiquitous presence of low-temperature-dependent conformation changes as a component of cryoprecipitation. Rather, the anomalous solution behavior of monoclonal cryoimmunoglobulins can be considered a direct result of the individual solubility properties of these proteins.
The hydrodynamic (gel filtration and sedimentation) properties of an isolated monoclonal IgM-K cryoglobulin (McE.) and five non-cryoglobulin cold-soluble proteins, as well as their constituent monomeric subunits and (Fc)5mu and Fabmu fragments, are compared under both native and partially denaturing conditions. It is concluded that the cryoimmunoglobulin exhibits a significantly greater Stokes radius than the non-cryoglobulin reference proteins, and that this difference arises in the Fabmu region of the McE. molecule. When the proteins and their fragments are analysed by circular dichroism in the far u.v. region, an atypical conformation is again detected in the Fabmu region of the cryoglobulin. These findings are the first demonstration and partial structural localization of a conformation anomaly in a monoclonal cryoimmunoglobulin.
The effects of a variety of compounds upon the cold-induced insolubility of the IgM-K cryoglobulin McE have been examined. Cryoprecipitation was found to be inhibited by certain neutral salts, ureas, amides, tetraalkylammonium salts, long chain sodium alkyl sulfates, sugars, and a number of other agents. Cryoprecipitation was enhanced by increasing the hydrophobicity of alcohols, ureas, amides, and tetraalkylammonium salts, as well as by low concentrations of many solutes. With the exception of the alkyl sulfates, inhibition was not accompanied by detectable changes in conformation of the cryoimmunoglobulin. These inhibitions and enhancements were also associated with changes in the temperature at which cryoprecipitation was initiated as well as the temperature at which a low temperature-induced conformation change occurs in the McE protein. The effects of solutes on McE are compared to results obtained with five other (two IgG, three IgM) cryoimmunoglobulins, and it is hypothesized that electrostatic and dispersion forces are primarily responsible for the cold insolubility of monoclonal cryoimmunoglobulins.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
A 9-year old female Doberman Pinscher had a 5-month history of epistaxis. On routine testing of the dog's serum, blockage of the intake tubes of the equipment resulted. At this point, cryoglobulinemia was suspected and was later confirmed to be due to a monoclonal cryoglobulin (IgM), by means of immunochemical studies. Clinical recovery was achieved by use of cytotoxic drugs.
The GIX antigen expressed on the thymocytes of GIX+ mice is a type-specific constituent of glycoprotein gp70, which forms the major envelope component of murine leukemia virus. In the prototype GIX+ mouse strain 129, this glycoprotein is a Mendelian character expressed independently of virus production. In the intact thymocyte plasma membrane, part of this glycoprotein, bearing group-specific (gs) antigen, is inaccessible to antibody. The moiety bearing the type-specific GIX determinant is accessible to GIX antibody, which may be an important factor in determining the consequences of autoimmune responses involving GIX. Previously, all attempts to induce GIX antibody in mice had failed. We now find that the hybrid mouse (B6-GIX+ X 129) spontaneously produces substantial amounts of GIX antibody, presumably of the IgM class appearing as early as 2 mo of age. The specificity of the GIX natural mouse antibody is the same as that recognized by the conventional GIX typing serum produced in rats ("anti-NTD"). As neither parent strain produces appreciable GIX antibody, we surmise that this autoimmune response requires two dominant genes, each parent contributing a high-response allele to the hybrid. These can be envisaged as two immune response loci, controlling different immunocompetent cells which must cooperate to produce GIX antibody. Production of GIX antibody by the hybrids increases progressively with age. This is accompanied by decreased expression of GIX antigen on their thymocytes. We attribute this to antigenic modulation. Antibody to gs antigen of gp70 is also found in autoimmune (B6-GIX+ X 129) hybrids but not in either parent strain. We are investigating evidence of a pathological autoimmune syndrome in these hybrids. The special interest of this syndrome is that it presumably signifies the consequences of autoimmunization to a single C-type virus component, expressed without significant virus production, in a mouse with no evident genetic predisposition to such disease in the absence of that antigen.
Explore the source record for details and available documents.
Human erythrocytes have been used as a model for evaluating the chemical carcinogen-plasma membrane interaction. The carcinogenic aromatic amines 2-acetylaminofluorene, dimethylaminoazobenzene, and 3'-methyldimethylaminoazobene stabilize erythrocytes against lysis in hypotonic solution. In general, the stabilization potential of these compounds reflects their oil:water partition coefficients and may be related to both their extracellular distribution and ultimate capacity for penetration of target cells. The polycyclic aromatic hydrocarbons, 3-methylcholanthrene and benz[a]anthracene, confer little protection against hemolysis and simultaneous incubation of nonprotective 3-methylcholanthrene and protective 3'-methyldimethylaminoazobenzene slightly alters the stabilization afforded by the latter. 7,12-dimethylbenz[a]anthracene exhibits greater protective capacity than does benz[a]anthracene. Polycyclic aromatic hydrocarbons manifested considerably higher degrees of absolute binding to erythrocytes in isotonic solution than did aromatic amines. The difference in erythrocyte binding and stabilization exhibited by the 2 classes of carcinogens suggest distinct mechanisms of membrane association that may relate to their metabolic disposition.