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Biomedical subjects

A Marx

Publications and source records attributed to A Marx.

At least 217 records · Page 12Linked to original sources
PubMed1987

Dependence of the electrogenic pump current of Xenopus oocytes on external potassium.

The membrane potential of Xenopus oocytes showed a variable response to an increase of the K+ concentration in the bathing solution, [K+]e, from 2.5 mM to 20 mM. In 54% of the cases (n = 52) the cells hyperpolarized (by max. 70 mV). In the presence of 10(-5) M ouabain, all cells depolarized suggesting that the hyperpolarization was caused by an electrogenic Na+/K+ pump. In cells stored overnight in a Na+-free solution the transition from 2.5 to 20 mM [K+]e always caused depolarization indicating that the stimulation of the pump requires high internal sodium, [Na+]i. Cells stored overnight in a Na+-rich solution had a [Na+]i of 30.7 +/- 7 mM, i.e. the Na+/K+ pump was saturated with sodium (Lafaire and Schwarz 1986). With 9 such cells we determined the K+ activation of the Na+/K+ pump. The activation follows Hill kinetics with Imax = 90.5 nA, Ks = 2.3 mM, and n = 1.68.

Animals↗
PubMed1987

Specific and nonspecific protection of mice by Pseudomonas aeruginosa lipopolysaccharides.

The role of lipopolysaccharide (LPS) in eliciting a predominant cellular or humoral protection of mice is determined by the amount administered and the immunization schedule. Three basically different experimental conditions could be characterized. Five days after immunization with 100 micrograms of LPS, a nonspecific protection was observed due to the immunomodulatory capacity of lipid A. After 14 days, the same amount of LPS results in an O-specific humoral protection. On the other hand, 0.1 micrograms of LPS lead to a specific protection within 5 days after immunization due to a synergistic action of a specific humoral response (induced by the O-side chain) and a nonspecific signal modulated by lipid A. In order to study the role of each LPS region for protection, the free side chain was conjugated to albumin, followed by complexation with lipid A. To induce a nonspecific protection 5 days after immunization, the presence of lipid A was mandatory, in either the conjugated or free form. Removal of ester-linked fatty acids from free lipid A reduced its protective and mitogenic capacities by 50, and 25%, respectively.

Animals↗
PubMed1987

Ion transport systems in erythrocytes from paramyotonia patients.

To test the hypothesis of a general defect in the ion transport systems in the cell membranes of patients with paramyotonia congenita, we measured the ouabain-inhibitable and the furosemide-inhibitable K+ influxes in erythrocytes from two patients. In the temperature range examined (15-40 degrees C), the ouabain-inhibitable flux did not differ significantly from control. Also the furosemide-inhibitable flux was well in the rather large control range. The dependence of these fluxes on the external K+ concentration was normal. Energy depletion of the erythrocytes by preincubation with desoxy-glucose led to reduced K+ influxes that were not significantly different in patients and controls. The results do not support the hypothesis of a general defect in the ion transport systems in paramyotonia; they do, however, not rule out the possibility that the ion transport systems in paramyotonic skeletal muscle are defect.

Adult↗
PubMed1986

The lipid composition of erythrocyte ghosts from a patient with congenital paramyotonia.

The membrane lipid and fatty acid compositions of red blood cells from a paramyotonia patient were investigated. Cholesterol and total phospholipid contents in paramyotonia were not different from control. Only the sphingomyelin content was lower, and thus the molar ratio of phosphatidylcholine/sphingomyelin was higher than normal. The major abnormality concerned the fatty acid pattern. In all the phospholipid classes saturated fatty acids were increased and unsaturated fatty acids were decreased. The overall ratio of saturated/unsaturated fatty acids was 2.1 vs 1.6 in controls. Similar findings have been reported for the sarcolemma from paramyotonia patients. Thus, the results indicate that the membrane defect in this disease may be generalized.

Erythrocyte Membrane↗
PubMed1983

Isolation of a rabbit IgG fraction with cytophilic properties.

About 15% of rabbit IgG loaded on a column of Con A-Sepharose 4B was found to be specifically bound to the column due to a structural variation in its carbohydrate moiety. The Con A-retained rabbit IgG contained a higher amount of neutral hexoses than the initial IgG but its molecular weight, antigenic structure and half-life were identical or similar. The Con A-retained rabbit IgG has an affinity for the Fc receptor-bearing homologous macrophages which is 10 times higher than that of the initial IgG. The IgG fraction not retained on Con A-Sepharose is practically devoid of binding ability. These results suggest that the Con A-bound IgG may represent the cytophilic fraction of monomeric IgG responsible for the binding of IgG to Fc receptor-bearing cells.

Animals↗
PubMed1983

Immunochemical studies on Brucella abortus lipopolysaccharides.

The antigenic-toxic complex of B. abortus isolated in the phenol phase of phenol/water system, is a lipopolysaccharide (LPS)-protein macromolecule. The specific side chain was isolated from this complex by means of pronase treatment and mild HCl cleavage, followed by fractionation on Sephadex. The side chain thus isolated lost its capacity to coat erythrocytes but not that of neutralizing antibodies, as shown in the hemagglutination inhibition test. Esterification of the side chain with lauryl sulfat restored its erythrocyte coating capacity. In view of transforming this haptene into an immunogen, it was attached to S. minnesota Re cells. Immunization of rabbits with this conjugate engendered the formation of antibodies that agglutinated B. abortus and B. melitensis cells as well. As the side chain could only be isolated from the smooth strain, it proves that a defect in the synthesis of this moiety gave rise to the rough Brucella mutant. In the latter fraction glucose, mannose and quinovosamine were identified. Fraction II separated on Sephadex was identified as the core polysaccharide, present in the preparation obtained from smooth and rough strain. In the core region 2-keto-3-deoxy-octonate, glucose, glucosamine (from the smooth but not from the rough strain) and protein were identified. Following the mild HCl hydrolysis, the lipid-protein moiety i.e. region 3, is also split off but without precipitating and, during the fractionation on Sephadex, it adsorbs onto the gel. The absence of beta-hydroxymyristic acid and glucosamine in Brucella lipid dissociates it from the enteric lipid A. In the LPS-protein's toxicity a major role has the protein present only in the smooth strain.

Animals↗
PubMed1982

Immunological activities of purified preparations of enterobacterial common antigen.

The immunological activities of three purified preparations of enterobacterial common antigen (ECA) obtained by different procedures were studied. ECA-Ma (method of A. Marx) was from Salmonella typhimurium TV149 (Ra mutant), ECA-My (method of H. Mayer) was from S. montevideo, and ECA-Ro (method of E. Romanowska) was from Shigella sonnei phase I. These preparations, on a weight basis, neutralized similar amounts of ECA antibodies, indicating that the serological activities were comparable. Neither ECA-My nor ECA-Ro elicited specific delayed-type hypersensitivity skin reactions at 24 or 48 h in immunized guinea pigs. ECA-Ma, as well as the nonpurified preparations of the antigens used for immunization, elicited reactions at 24 h but not at 48 h. Thus, ECA-specific delayed-type hypersensitivity was not detected in immunized guinea pigs. Striking differences were noted in the immunogenicity of these antigens, ECA-Ma being highly immunogenic in the rabbit in contrast to ECA-My and ECA-Ro. ECA-Ma was a potent mitogen for guinea pig spleen cells, stimulating high levels of DNA synthesis; ECA-My was only slightly active. The three antigens were mitogenic to spleen cells from both CBA/J and C3H/HeJ mice, although not to the same degree, indicating that this effect is not due to contaminating lipopolysaccharide, since the latter strain of mice is resistant to endotoxin. Since an ECA-Ma extract made from an ECA-negative mutant proved to be mitogenic to murine spleen cells, the mitogenicity is not due to the ECA haptenic determinant. The mitogenic effect is polyclonal in nature, ECA-Ma producing a maximum response on day 3. Thus, the ECA preparations are both B-cell mitogens and polyclonal activators in murine spleen cells. From these studies it is evident that the biological and immunological activities of these purified antigens depend not only on the haptenic determinant but also on associated or bound components of the preparations.

Animals↗
PubMed1982

Isolation and characterization of a cross-reacting antigen in strains of Bacteroidaceae.

A Bacteroidaceae cross-reacting antigen (BCA) was isolated from several strains belonging to species in the genera Fusobacterium and Bacteroides. We showed that each of the 28 strains examined synthesized either BCA or the O-specific lipopolysaccharide (LPS). The structural difference between the two antigens was demonstrated by passive hemagglutination. BCA coated erythrocytes spontaneously and reacted with equal intensity to all bacterial antisera of BCA+ strains, whereas LPS was species specific and also coated erythrocytes after the antigen was treated with NaOH. BCA is an acid polysaccharide as proven by immunoelectrophoresis and by its capacity to form a salt linkage with lysozyme. Chemical analysis demonstrated the presence of galactosamine, glucosamine, galactose, glucose, mannose, and N-acetyl. BCA was nontoxic and did not contain lipid A in its molecule. The small particle size of BCA determined its hapten character. When attached to acid-treated Salmonella minnesota Re cells, it acted as an immunogen. By immunizing rabbits with this hapten-bacterial cell suspension, we obtained a highly potent antiserum that agglutinated all BCA+ strains.

Antigens, Bacterial↗
PubMed1978

Immunochemical studies on a Yersinia enterocolitica O:9 lipopolysaccharide cross-reacting with Brucella abortus and Vibrio cholerae extracts.

The presence of two distinct lipopolysaccharides in Yersinia enterocolitica O:9 is described: one isolated from the aqueous phase and one from the phenol phase (Westphal system). The sugar moiety of the phenol phase lipopolysaccharide has been identified as being responsible for the serologic cross-reaction of Y. enterocolitica O:9, Brucella abortus and Vibrio cholerae. The phenol phase antigen consists of glucose, galactose, glucosamine, 2-keto-3-deoxyoctonic acid, heptose, lipid A and a protein moiety. Haemagglutination experiments revealed two different structures: one that readily coats erythrocytes and another that requires alkali treatment. The former may be separated by repeated adsorptions on erythrocytes. Serologically, the two structures behave like a single antigen. The action of normal rabbit serum on the erythrocyte-containg capacity of the two structures was studied.

Animals↗
PubMed1977

Demonstration of enterobacterial common antigen by bacterial agglutination.

Potent antisera against the enterobacterial common antigen (ECA) agglutinate R bacteria of the Enterobacteriaceae family that possess unimpaired R-core structures of the Escherichia coli R1 or E. coli R4 core type. In these strains, known to be ECA immunogenic, ECA is most probably linked to the lipopolysaccharide R core. R mutants of other core types (e.g., Salmonella Ra, E. coli R2 or R3) or R mutants with incomplete core structures of the E. coli R1 type, as well as an rfaL mutant deficient in the O-translocase system, agglutinate to a much lesser extent or not at all. All the later mutants are nonimmunogenic; they possess the ECA in a free form, not linked to the R core. None of the S forms tested from many different enterobacterial genera was found to be agglutinable with the ECA antiserum. The dynamics of the ECA agglutinin formation in rabbits parallels the ECA hemagglutinin formation, indicating that the same antibody class might be involved in bacterial agglutination and hemagglutination.

Agglutination↗
PubMed1976

Role of the rfa locus in the immunogenicity of common enterobacterial antigen.

Escherichia coli O14 is one of the few strains of Enterobacteriaceae which in the rabbit engender antibodies in high titers against the common enterobacterial antigen (CA). It is a rough strain that does not possess a specific side chain in its lipopolysaccharide structure (rfa+rfb-). An rfa mutant (rfa-rfb-) was isolated from this parental strain. Chemical analysis revealed the absence of one glucose and of one galactose molecule in the core polysaccharide of the mutant. The incomplete synthesis of the core was accompanied by loss of immunogenicity of CA. In the mutant, in contrast to the wild type, CA was not bound to the core; hence, the core lipopolysaccharide might exert immunosuppressive activity on CA. A protein fraction of normal rabbit serum was shown to destroy the erythrocyte-coating capacity of CA. This fraction also displayed immunosuppressive activity on free CA but not on CA bound to the core polysaccharide.

Animals↗
PubMed1975

Immunochemical studies on purified common enterobacterial antigen (KUNIN).

A common antigen (KUNIN) purification method is described. The preparation obtained was highly antigenic, as proved by hemagglutination and its inhibition, and immunogenic in rabbits. Chemical analysis demonstrated the presence of an L-phosphoglycerid of the cephalin type, of protein, glucosamine, acetyl and glucose. The antigen had the character of an acidic polymer. It readily forms salt linkages with lysozyme. Phospholipase A induced the release of myristic, palmitic and stearic acids. It also destroyed both the antigenicity and immunogenicity of common antigen.

Animals↗