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Biomedical subjects

M Vaara

Publications and source records attributed to M Vaara.

101 records · Page 6Linked to original sources
PubMed1983

Polycations sensitize enteric bacteria to antibiotics.

Polymyxin B nonapeptide, a polymyxin B derivative which lacks the fatty acyl part and the bactericidal activity of polymyxin, was shown to sensitize smooth encapsulated Escherichia coli (O18:K1) and smooth Salmonella typhimurium to hydrophobic antibiotics (novobiocin, fusidic acid, erythromycin, clindamycin, nafcillin, and cloxacillin). The polymyxin B nonapeptide-treated bacteria were as sensitive to these antibiotics as are deep rough mutants. A lysine polymer with 20 lysine residues (lysine 20) had a largely similar effect. Larger lysine polymers and the protamine salmine were bactericidal but, at sublethal concentrations, sensitized the strains to the antibiotics mentioned above, whereas lysine4, streptomycin, cytochrome c, lysozyme, and the polyamines cadaverine, spermidine, and spermine had neither bactericidal nor sensitizing activity.

Anti-Bacterial Agents↗
PubMed1983

Polycations as outer membrane-disorganizing agents.

The outer membrane-disorganizing effect of a short (10-min) treatment with polycationic agents was studied with smooth Salmonella typhimurium used as a test organism. The polycationic agents were the protamine salmine, a lysine polymer with 20 lysine residues (lysine20), and the deacylated polymyxin B derivative polymyxin B nonapeptide. Two different types of outer membrane-disorganizing were found. Protamine and lysine20 released 20 to 30% of the lipopolysaccharide from the outer membrane and sensitized the bacteria to the anionic detergent sodium dodecyl sulfate but did not (under these conditions) make the bacteria permeable to the hydrophobic probes fusidic acid and actinomycin D. In contrast, polymyxin B nonapeptide did not release lipopolysaccharide or sensitize the bacteria to sodium dodecyl sulfate but made the outer membrane permeable to the hydrophobic probes. None of the agents was bactericidal under the conditions used or caused any leakage of periplasmic beta-lactamase. Polymyxin B was used as a reference and showed characteristic outer membrane-disorganizing action. In thin-section electron microscopy, polymyxin B nonapeptide caused the appearance of long, narrow, finger-like projections on the outer membrane. Protamine and lysine20 caused a distinctly wrinkled appearance of the outer membrane but no projections.

Bacterial Proteins↗
PubMed1981

Outer membrane permeability barrier disruption by polymyxin in polymyxin-susceptible and -resistant Salmonella typhimurium.

In contrast to their polymyxin-susceptible parent strains, polymyxin-resistant Salmonella typhimurium mutants (pmrA strains) did not lose their outer membrane permeability barrier to macromolecules such as lysozyme and periplasmic proteins upon polymyxin treatment. The sensitization of pmrA strains to deoxycholate-induced lysis required 10-times-higher polymyxin concentrations than did the sensitization of the parent strains. These findings indicate that the pmrA mutation affects the outer membrane and decreases its susceptibility to polymyxin. By contrast, the pmrA mutants did not differ from their parents in the uptake of gentian violet after treatment with polymyxin, suggesting a degree of specificity in the pmrA effect in the outer membrane.

Bacterial Proteins↗
PubMed1981

Increased outer membrane resistance to ethylenediaminetetraacetate and cations in novel lipid A mutants.

Polymyxin-resistant pmrA mutants of Salmonella typhimurium differed from their parents in that they were resistant to tris(hydroxymethyl)aminomethane-ethylenediaminetetraacetate-lysozyme, tris(hydroxymethyl)aminomethane-ethylenediaminetetraacetate-deoxycholate, and tris(hydroxymethyl)aminomethane-ethylenediaminetetraacetate-bacitracin. Tris(hydroxymethyl)aminomethane-ethylenediaminetetraacetate released about 50% less lipopolysaccharide from the pmrA strains than from the parental strains when the bacteria were grown in L-broth containing 2 mM Ca2+. Protamine, polylysine, octapeptin, benzalkonium chloride, cold NaCl, cold MgCl2, or cold tris(hydroxymethyl)aminomethane hydrochloride (pH 7.2) caused no leakage or markedly less leakage of periplasmic beta-lactamase from a pmrA mutant than from its parent strain. pmrA mutants were more resistant than their parent strains to protamine and polylysine but not to octapeptin or benzalkonium chloride, as measured by the ability of these agents to kill the bacteria or to sensitize them to deoxycholate-induced lysis. The pmrA strains did not differ from their parent strains in sensitivity to several antibiotics, in porin function (as measured by cephaloridine diffusion across the outer membrane), or in outer membrane-associated phospholipase A activity.

Anti-Bacterial Agents↗
PubMed1980

Ultrastructure of the cell wall of a Synechocystis strain.

The ultrastructure of the cell wall of a Synechocystis strain, isolated from the Gulf of Finland, was studied using several electron microscopic techniques. This cyanobacterium has numerous projections which were observed to penetrate the cell wall complex. An additional layer (AL) was associated with the outer membrane. An additional external wall layer (EL) was connected to the outer membrane complex by thin fibers as revealed by ruthenium red staining. A hexagonal arrangement of the subunits in the additional external wall layer with a lattice constant of 15.5 nm was found.

Cell Wall↗
PubMed1979

Two improved methods for obtaining axenic cultures of cyanobacteria.

Scoring the agar plate before incubation under unidirectional light led to a rapid separation of gliding filamentous cyanobacteria from their contaminating bacteria. Twenty strains were purified by the method. Additionally, 13 axenic cyanobacterial strains were isolated from pour plates made after treatment of cyanobacterial cultures in tryptone-yeast extract-glucose broth with cycloserine in darkness to select for obligate photoautotrophs.

Journal Article↗
PubMedDate not supplied

LPS greatly enhances the antibody response to hapten-polysaccharide conjugates, but not to hapten-protein conjugates.

In confirmation of earlier findings, we observed that an injection of bacterial lipopolysaccharide (LPS) into mice caused a considerable increase in the serum concentrations of IgM and IgG (total Ig rose three- to four-fold in 7 days), and a corresponding increase in the concentrations of "natural" anti-(3-iodo-4-hydroxy-5-nitrophenyl) acetyl (NIP) and anti-trinitrophenol (TNP) antibodies. Our main purpose was to determine what effect LPS had on antigen-dependent responses. Hapten conjugates of a polysaccharide and of proteins were used as antigens. Hapten-protein conjugates induced a strong anti-hapten antibody response (up to 1 mg/ml of anti-hapten antibodies on day 7). Hapten-polysaccharide conjugates induced only a meagre increase in anti-hapten antibodies from the pre-immunization level (maximal concentration 65 micrograms/ml on day 7). LPS, when injected with the antigen, greatly enhanced the antibody response to the hapten-polysaccharide conjugates (up to 2.6 mg/ml of anti-hapten antibodies on day 7). It had little effect on antibody responses to hapten-protein conjugates. The combination treatment had the same effect on immunoglobulin concentrations as LPS alone.

Animals↗
PubMedDate not supplied

Sensitization of Gram-negative bacteria to antibiotics and complement by a nontoxic oligopeptide.

A major virulence factor of bacteria that cause generalized infections is their resistance to the lytic action of the complement cascade, an important defence mechanism of the host. Invasive Gram-negative enteric bacteria, which cause about one-third of all bacteraemic infections, are completely resistant to lysis by complement, even in the presence of hyperimmune serum. The same bacteria are also resistant to many antibiotics that are effective therapeutic agents against other bacteria, as the outermost surface layer (the outer membrane) of the bacteria functions as a permeability barrier. Here we show that it is possible to sensitize such bacteria to both complement and antibiotics by using an agent that binds to the outer membrane. This agent is a nontoxic derivative of polymyxin which by itself has no bactericidal action.

Animals↗
PubMedDate not supplied

An empirical investigation of the 'Biopsychosocial Disease Consequence model': psychological impairment, disability and handicap in chronic pain patients.

The purpose of this study is to emphasize the meaningfulness of a global, functional rather than a narrow medical view in the efficacy evaluation of chronic pain treatment. Therefore, the 'Biopsychosocial Disease Consequence (BPSDC) model' to assess function more globally than before, is presented in this article. The model is based on two theories: (1) the biopsychosocial approach and (2) WHO's classification of impairments, disabilities and handicaps. In addition to the presentation of the conceptual model, the development of the hypothetical criteria and assessment models for psychological impairments, disabilities and handicaps, and the validity testing of the psychological assessment axis are described. Within each of the three classes, i.e. psychological impairments, disabilities and handicaps, the results supported the independence of the hypothetical criteria from each other. On the other hand, results suggested that some changes to the hypothetical assessment models for some of the criteria might be valuable. It was concluded that although the most adequate psychological assessment models for function, found in this study, can be considered as robust and recommendable as one set of tools for functional assessment, the main aim of this article is to encourage multidisciplinary team efforts to develop and systematize the assessment procedures of function in patients suffering from chronic diseases.

Adult↗