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Biomedical subjects

R Brossmer

Publications and source records attributed to R Brossmer.

At least 109 records · Page 6Linked to original sources
PubMed1977

Selective isolation of Vibrio cholerae neuraminidase using an immobilized 4-(nitrophenyl)oxamic acid.

N-(4-Nitrophenyl)oxamic acid[1] (1) was coupled with Sepharose 4B containing 1,6-diaminohexane as spacer group. This material was used as a specific adsorbent in the purification of Vibrio cholerae neuraminidase. The enzyme was completely retarded and separated from the bulk of the protein when washed with 50mM sodium acetate buffer, pH 5.0. A stepwise increase of sodium chloride concentration from 1.0 to 2.0M was found to be necessary for a sharp elution of neuraminidase activity. The purification was tenfold, and a recovery of more than 90% was obtained. Neuraminidase is only weakly retarded on a column of 1,6-diaminohexane coupled with Sepharose 4B and is not adsorbed by Sepharose 4B.

Chromatography, Affinity↗
PubMed1977

Inhibition studies on Vibrio cholerae neuraminidase.

A series of viral neuraminidase inhibitors showing no structural analogy to neuraminic acids have been tested to find whether they are effective inhibitors of V. cholerae neuraminidase, too. Here we report the results obtained with the N-phenyloxamic acid derivatives 2 to 6 (R-NH-CO-COOR'; R = -C6H5NO2, -C6H5OH, -C6H5NH2; R' = -H, -C2H5; see Table 1) and with simple aromatic compounds structurally related to R, i.e. 4-nitroaniline (7), N-acetyl-4-nitroaniline (8), 4-nitrophenol (9), 2,4-dinitrophenol (10), and 4-aminophenol (11) (see Table 2). The inhibitory effects of 2 to 11 were studied according to the method of Dixon[19] in 0.1m sodium acetate buffer, pH 5.5, 2mM CaCl2, at 37 degrees C using the benzyl-alpha-ketoside of N-acetyl-D-neuraminic acid (1) as a substrate. The compounds 2 to 11 are shown to be competitive inhibitors of the enzymatic hydrolysis of the alpha-ketoside 1. The competitive inhibition kinetics are supported by the method of Lineweaver and Burk[20]. The inhibition constants (Ki) are found to be in the range of 0.03 to 5.7 mM. The simple aromatic compounds 7 to 11 show higher inhibitory activities than the phenyloxamic acid derivatives 2 to 6. In addition, significant differences in the Ki values were observed within the two series of inhibitors, whereby those containing a nitro group were most effective.

Aniline Compounds↗
PubMed1976

Inhibition of ADP-induced platelet aggregation by adenosine tetraphosphate.

In contrast to previous reports, highly purified adenosine tetraphosphate (AP4) does not induce the aggregation of platelets but inhibits the aggregation and release reaction in platelet-rich plasma promoted by ADP. The inhibitory action of AP4 on the aggregation by ADP is compared with that of AMP and ATP. The data presented suggest a competitive manner of inhibition of the ADP-induced aggregation by AP4.

Adenine Nucleotides↗
PubMed1976

[Release by agitation of constituents from cell walls of Pseudomonas aeruginosa. III. Communication: Electron microscopy (author's transl)].

A thermovariable inhibition of agglutination (EA) was demonstrated in two randomly chosen strains of Pseudomonas aeruginosa (table 1, article I). The temperature range from the loss of agglutinability to its recovery was as described in previous articles (II). The agglutination patterns were similar to those of the O-group-type strains 1 and 4, indicating that the IA is a widespread property among Pseudomonas aeruginosa strains. Shaking at moderate intensities for 20-60 hours restored the thermosensitive agglutinability (Table 2, article I), and the times necessary for restoration were somewhate dependent on the specific culture media and the strains used (table3, article I). After restoration of agglutinability the bacteria had maintained their capability to form stable suspensions in physiological saline solution (table 2, article I). Another treatment at elevated temperature did not result in an IA (table 5c, article I). During the shaking the pelleted bacteria did no longer exhibit their normal slimy stickiness, similar to what has been observed after treatment with hyaluronidase (17). When the shaking was continued after restoration of agglutinability a special serological phenomenon ("Rauh-Phänomen," cf. table 5b in article I) was noted. Suspension of the bacteria in physiological saline for 7 days did not result in the recovery from the thermovariable IA (table 4, article 1). The secondary forms of the agglutinates were similar to those of Enterobacteriaceae, the typical primary form of the agglutination into slimy networks and spheres was not observed upon the restoration of agglutinability. The hypothesis that loosely bound surface components are responsible for the thermovariable IA was examined by chemical analyses of the fractionated supernatants obtained during the shaking treatments. The first supernatant fractions obtained after relatively brief shaking periods exhibited a high viscosity, in contrast to the low viscosity of supernatants harvested later. Total acetone-precipitable material from the supernatants contained lipids, proteins and carbohydrates, however, at different ratios (tables 1, 2, 3, article II). The amounts of lipids recovered from the supernatants were similar in all fractions during the shaking treatment, whereas protein-carbohydrate complex material was maximal in the first fractions and significantly decreased in fractions harvested later (table 1 and 2, article II). The data indicated, that the restored agglutinability at elevated temperatures and the maintained suspensibility in physiological saline was due to the removal of a limited amount of material from the most superficial layer of the bacterial wall; however in the continuous presence of the cell membrane and perhaps also of the internal cell wall layers (see also 8). This concept was examined by electron microscopy. The morphology of the native bacteria is illustrated in figures 1-3 (article III)...

Agglutination↗
PubMed1975

Concanavalin A-induced aggregation of human blood platelets: Ca++-dependent and Ca++-independent effects.

Concanavalin A (CON A) causes platelets to aggregate. A Ca++-independent effect of CON A could be separated from a main effect which depends on Ca++. The main effect probably is a consequence of the CON A-induced platelet release reaction and therefore is platelet-specific. The weak residual effect observed in the presence of Na-2EDTA may be due to a similar mechanism as has been demonstrated for CON A-induced aggregations of several other normal and malignant transformed animal cells. Na-2EDTA did not inhibit the carbohydrate-specific binding capacity of CON A. Therefore, Na-2EDTA appears not to demineralize the CON A molecules under these experimental conditions. Alpha-methyl-D-glucoside inhibits the Ca++-independent as well as the Ca++-dependent effect of CON A. Pretreatment by neuraminidase stimulated the platelet aggregation induced by CON A. It is possible that removal of terminal sialic acid residues makes additional receptors accessible for the binding of CON A.

Binding Sites↗
PubMed1975

Circular dichroism studies on alpha- and beta-ketosides of 5-acetamido-3,5-dideoxy-D-glycero-D-galacto- nonulopyranosonic acid (N-acetylneuraminic acid) and of some of its derivatives.

The circular dichroism spectra of a number of N-acetylneuraminic acid derivatives in aqueous solution were studied. For all compounds, the Cotton effects were found to be in the spectral range of the acetamido and carboxyl chromophores. The c.d. curves of the methy, ethyl, and allyl alpha-D-ketosides are characterized by a broad, positive band centered at lambda similar to 195 nm with a slight skew towards the higher wavelengths and weak bands between lambda 225 and 255 nm, whereas the methyl beta-D-ketoside and the corresponding methyl ester show only an intense positive band with a broad shoulder in the same spectral range. 5-Acetamido-3,5-dideoxy-D-glycero-beta-D-galacto-nonulopyranose, its methyl beta-D-ketoside, and 5-acetamido-3,5-dideoxy-D-glycero-D-galacto-nonulopyranosonamide containing only the acetamido chromophore showed one single positive Cotton effect centered at lambda similar to 192 nm. The c.d. spectrum of 5-acetamido-3,5-dideoxy-D-glycero-D-galacto-nonulopyranosonic acid confirms the beta-D configuration of the free acid in aqueous solution, whereas the shape of the c.d. curve of O-(N-acetyl-alpha-D-neuraminopyranosyl)-(2yields3)-O-beta-D-galactopyranosyl-(1 yields 4)-D-glucopyranose resembles that of the methyl, ethyl, and allyl alpha-D-ketosides 2-4.

Carboxylic Acids↗
PubMed1975

2-phenylethanol and some of its amphiphilic derivatives as inhibitors of platelet aggregation. Structure-activity relationship.

The relationship between chemical structure and inhibitory activity of some simple water soluble phenylalkyl derivatives has been investigated. The inhibitory effect of the following analogous and homologous derivatives increases in the sequence: phenylacetic acid less than 2-phenylethanol less than 2-phenylethylamine = 4-phenylbutyric acid less than 3-phenylpropanol less than 4-phenylbutylamine, i.e., the inhibitory effect is potentiated. 1. by elongation of the alkyl chain, which is accompanied by an increase of the lipophilic character, and 2. when the polar portion is represented by the positively charged amino-group. The effect of these amphiphilic compounds on platelet aggregation appears to be mediated through polar and apolar interactions with the outer layers of the plasma membrane. The fact that the amino derivatives are the most active inhibitors suggests that negatively charged groups may be involved in the polar binding of these inhibitors. Experiments with neuraminidase-treated platelets revealed that the enzymatically removable sialic acid residues are not those negatively charged binding sites. Phentolamine and propranolol which block adrenergic alpha- and beta-receptors, respectively, do not influence the inhibitory effect of these agents.

Adenosine Diphosphate↗