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Biomedical subjects

J Olsson

Publications and source records attributed to J Olsson.

At least 109 records · Page 6Linked to original sources
PubMed1983

Hydrophobicity and adherence of oral streptococci after repeated subculture in vitro.

Fresh isolates of Streptococcus mutans, Streptococcus sanguis, and Streptococcus salivarius from human dental plaque were all highly hydrophobic. After repeated subculture in vitro on blood agar, strains of S. mutans serotype c showed decreased hydrophobicity, whereas serotype d/g strains did not. Parallel to the decreased hydrophobicity in the serotype c strains, an impaired ability to adhere to hydroxyapatite was observed. A similar but less pronounced decrease in hydrophobicity in one S. sanguis strain resulted in a marked decrease in adherence to hydroxyapatite.

Adhesiveness↗
PubMed1982

Effect of diet on the colonization of the mouth by Actinomyces viscosus (T-6) in Osborne-Mendel rats.

Oral colonization by A. viscosus, strain T-6 was studied in Osborne-Mendel rats which were fed either sucrose, glucose, starch or casein alone ad libitum by mouth. Essential nutrients were given to the rats twice daily by stomach tube. All three carbohydrates supported implantation by Actinomyces to varying degrees. Implantation did not occur when the animals were fed casein. Casein did not have any antimicrobial effect on Actinomyces already established in the rat mouth; it was impossible to eliminate an established Actinomyces flora. Feeding the animals all the dietary components through the stomach tube did not result in eradication of Actinomyces from an established flora. The Actinomyces was considerably diminished when coprophagy was prevented.

Actinomyces↗
PubMed1982

Interference of Salivary immunoglobulin A antibodies and other salivary fractions with adherence of Streptococcus mutans to hydroxyapatite.

The adherence of Streptococcus mutans to hydroxyapatite was studied in the presence of salivary fractions with varying activity of naturally occurring immunoglobulin A (IgA) antibodies. Human parotid saliva from different donors was fractionated by chromatography and compared. Salivary IgA antibodies had no decisive effect on the adherence of the S. mutans strain used. High-molecular-weight salivary components from some subjects had an adherence-promoting effect, whereas fractions collected after the void volume of a Sepharose 2B column always inhibited adherence. The data indicate that the influence of unfractionated saliva on adherence is dependent on the net effect of adherence-promoting and adherence-inhibiting components. This principle has to be considered when the effect of human saliva on microbial adherence is studied.

Adhesiveness↗
PubMed1981

Association between bacterial agglutinins and immunoglobulin A in human saliva.

Two distinct peaks were obtained when human parotid saliva was separated on a Sepharose 2B column. The bacterial agglutinating activity was concentrated to the void volume fractions whereas the IgA was found in the beginning of the second, large peak. Unfractionated saliva as well as the pooled agglutinin fractions, or a mixture of agglutinin and IgA, all induced the aggregation of KPSK2, a Streptococcus mutans serotype c strain. By adding anti-human-IgA antiserum to the whole saliva or to the mixture of agglutinin and IgA, the aggregation reaction could be eliminated. In order to achieve this effect the agglutinin and IgA had to be mixed prior to the addition of anti-IgA. Addition of anti-IgA antiserum to the agglutinin fraction only did not impair the aggregation of bacteria. The homologous reactions with anti-IgG antiserum did not give any inhibition effect. However, when human IgG was added to the saliva, or to the agglutinin, before the addition of anti-IgG, the aggregation of KPSK2 was again impaired. The data in this paper indicate that the agglutinins and the IgA antibodies in saliva may be normally associated with each other.

Agglutination↗
PubMed1980

Effect of macromolecules on adherence of Streptococcus mutans.

The influence of macromolecules on the adherence of S. mutans was studied in an in vitro incubation system using 3H-labeled bacteria and hydroxyapatite beads. The bacterial adherence was strongly inhibited by treating the beads with an extremely acidic macromolecule. An even more pronounced effect was found when this substance was present during the incubation. To the contrary no effect was discernible when the bacteria only were pretreated with the acidic macromolecule. Even the basic substance decreased the adherence of the bacteria but to a less extent. The bacterial surface has a net negative charge and attracts basic molecules while hydroxyapatite beads analogously appear to have a net positive charge and attract acidic macromolecules. This adsorption of macromolecules might be a phenomenon of importance for the microbial colonization of teeth.

Adhesiveness↗
PubMed1978

Effect of inorganic ions and surface active organic compounds on the adherence of oral streptococci.

A reduction in the adherence of oral streptococci was observed after topical application of aluminum ions to standardized dentin test pieces whereas pyrophosphate and tripolyphosphate seemed to inhibit the adherence after incorporation in the incubation solution. A pronounced effect was recorded after topical application of surfactants with the positively charged primary amino group as end group. Hydrofluorides of several such aliphatic amines effectively reduced the number of colony-forming units washed off from the test pieces. Also the free base of hexadecylamine showed a similar effect. Inhibition of adherence was also obtained with long chain esters of lysine, with an optimum at 16 carbon atoms in the alcohol group. These compounds have the advantage of being built up from molecules known to the body.

Adhesiveness↗
PubMed1977

The kinetics of reoxidation of reduced benzylamine oxidase.

1. The mechanism of reoxidation of reduced benzylamine oxidase has been investigated at different pH between 6 and 10 by steady-state and transient-state kinetic methods. 2. The reoxidation process involves minimally a second-order interaction between reduced enzyme and oxygen leading to the formation of a spectrally modified enzyme intermediate, and a subsequent first-order step converting this intermediate into free enzyme. The variation with pH of rate constants according to such a reaction scheme is reported. 3. Under aerobic conditions the oxygen-independent reaction represents the main rate-limiting step in the catalytic process at alkaline pH. At neutral or acid pH the interaction between reduced enzyme and oxygen becomes mainly rate-limiting, indicating that the concentration of oxygen may be a critical factor controlling enzyme activity under physiological conditions. 4. The spectrally modified intermediate formed during the reoxidation process exhibits a difference-absorption band centered around 290 nm in comparison to free enzyme, and an additional difference-absorption band at 470 nm in comparison to reduced enzyme. These data indicate that formation of the intermediate, besides leading to a reappearance of the 470-nm absorption band disappearing on reduction of the enzyme, results in a spectral perturbation of one or several aromatic amino-acid residues in the protein. This perturbation could possibly reflect a conformational change of the enzymes.

Benzylamine Oxidase↗
PubMed1976

Stopped-flow spectrophotometric characterization of enzymic reaction intermediates in the anaerobic reduction of pig-plasma benzylamine oxidase by amine substrates.

Reduction of benzylamine oxidase by p-methoxybenzylamine under anaerobic conditions leads to biphasic absorbance changes at 470 nm. These reflect the intermediate formation of an enzyme substrate complex with spectral properties different from those of native enzyme and fully reduced enzyme. The spectrally modified enzyme-substrate complex exhibits a broad difference absorption band centered around 360 nm. The transient accumulation of this intermediate during reaction can be conveniently followed by stopped-flow techniques at wavelengths between 320 and 360 nm, where contributions from the subsequent reduction of the enzymic 470-nm chromophore are of minor significance. 2. Analogous intermediates exhibiting similar absorption spectra seem to be formed on reduction of the enzyme by benzylamine and other amine substrates which were tested. Substitution of benzylamine as the reducing substrate by [alpha, alpha-2H]benzylamine results in a decreased accumulation of the spectrally modified intermediate. This indicates that its formation is preceded by deprotonation of the alpha-carbon of the amine substrate. 3. Circular dichroism spectra of benzylamine oxidase exhibit a positive band at 360 nm, lending support to the previous conclusion that benzylamine oxidase is a pyridoxal enzyme. Formation of the spectrally modified enzyme-substrate complex then most likely reflects the prototropic shift converting an amine-pyridoxal Schiff-base obtained by rapid pre-equilibration between enzyme and substrate into an aldehyde-pyridoxamine Schiff-base.

Amines↗
PubMed1976

Effect of pH on the transient reduction of pig-plasma benzylamine oxidase by benzylamine derivatives.

1. The transient kinetics of reduction of the 470-nm absorption band in benzylamine oxidase by substrate at different pH values between 6 and 10 have been studied by stopped-flow techniques, and substituent effects on kinetic parameters for the reduction process have been examined using a series of ring-substituted benzylamine derivatives as the substrates. 2. Reduction of the enzyme by substrate takes place in two kinetically distinguishable steps, with the intermediate formation of an enzyme-substrate complex in which the substrate appears to be covalently bound through its amino group to the prosthetic group of the enzyme, possibly in the form of an amine-pyridoxal Schiff-base. 3. The apparent stability of the enzyme-substrate complex shows no obvious dependence on the electronic properties of the amine substrates, but is strongly pH-dependent in a way suggesting that substrate-binding involves the non-protonated amines, exclusively, and requires the presence of the acid form of an ionizing group in the enzyme with apparent pKa of 8.8. 4. Reduction of the enzymatic 470-nm chromophore and release of the aldehyde product of the catalytic process are rate-limited by the same monomolecular reaction step involving the enzyme-substrate complex. Rate constants for the rate-limiting reaction exhibit no significant dependence on pH between 6 and 10, but correlate with Hammett sigma-values for the ring-substituted benzylamine derivatives tested, yielding a phi-value of + 0.3.

Amines↗
PubMed1976

Kinetic isotope effects on the catalytic activity of pig-plasma benzylamine oxidase.

1. Isotope effects on the catalytic activity of benzylamine oxidase at pH 7 and 9 have been studied by steady-state and transient-state kinetics methods, using [alpha,alpha-2H]benzylamine as the substrate. 2. Replacement of the alpha-hydrogen atoms in benzylamine by deuterium has no significant effect on substrate-binding to benzylamine oxidase, neither does it affect the rate of reoxidation of the reduced form of the enzyme. Conversion of the primarily formed enzyme-substrate complex into the reduced enzyme species, however, exhibits an isotope effect of about 3. 3. The data obtained are consistent with a mechanism in which reduction of benzylamine oxidase takes place by a rapid pre-equilibration between enzyme and substrate to form an amine-pyridoxal Schiff-base, which is then tautomerized by a comparatively slow prototropic shift to an amino aldehyde-pyridoxamine Schiff-base from which there is a rapid hydrolytic release of the aldehyde product corresponding to the amine substrate. Proton abstraction from the alpha-carbon of the amine moiety in the primary Schiff-base appears to be at least partially rate-limiting for the tautomerization step, and hence for the entire process of enzyme reduction.

Animals↗
PubMed1976

Effects of halothane on the metabolism of human adipose tissue.

The metabolism of specimens of human adipose tissue exposed to different concentrations of halothane was studied. Halothane was added to the incubation medium directly or via the gas phase above the medium. The basal lipolysis was significantly increased by low concentrations of halothane. Higher concentrations clearly diminished the lipolysis, but here, in spite of the inhibitory effect on the basal lipolysis, the lipolytic effect of noradrenaline expressed as percent increment was increased. The rate of lipid synthesis from glucose was reduced when halothane was present in the gas phase. The effect of insulin on glucose metabolism was not affected by the presence of halothane, while the antilipolytic action was abolished by high concentrations of halothane. The results show that halothane may exert dual effects on the mobilization of lipids from human adipose tissue; at low concentrations halothane enhances the basal lipolysis, while at higher concentrations it exerts inhibitory effects.

Adipose Tissue↗
PubMed1976

A method for studying adherence of oral streptococci to solid surfaces.

The adherence of different streptococci to test pieces of glass, human enamel and whale dentin carried in the mouth or immersed in saliva or bacterial suspensions was studied by examining the number and frequency of microorganisms which were selectively desorbed by a standardized washing technique. The results obtained from in vivo and in vitro experiments were similar in principle. The proportion of streptococci obtained in the first washing resembled that found in the saliva, but with more vigorous washing the proportion of S. sanguis increased while that of S. salivarius decreased. This illustrates that different microorganisms can attach to solid surfaces with different strengths. The applicability of the method was tested by treating dentin surfaces with fluoride solutions and by incorporating sucrose in the test solution. The fluoride treatment reduced while the sucrose addition increased the number of streptococci which could be removed from the surfaces.

Bacteriological Techniques↗
PubMed1976

Surface potential and adherence of oral streptococci to solid surfaces.

Strains of oral streptococci belonging to the same species but with different zeta-potential adhere with different strengths or become desorbed at different rates. However, strains of various species but with approximately the same zeta-potential also adhere differently. The adherence was found to be affected by the presence of polyvalent of counter ions in the microorganisms studied.

Adhesiveness↗