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Biomedical subjects

L Lindqvist

Publications and source records attributed to L Lindqvist.

At least 55 records · Page 3Linked to original sources
PubMed1989

Purification and characterization of a new beta-lactamase from Clostridium butyricum.

A highly penicillin-resistant beta-lactamase-producing strain of Clostridium butyricum, strain NBL 3, was isolated. The specific activity of the unpurified beta-lactamase was 0.29 U/mg of protein. The enzyme was purified 1,130-fold by QAE Zetaprep, Sephacryl S-300, and Mono Q column passages. The purified enzyme was judged homogeneous by sodium dodecyl sulfate gradient gel electrophoresis and fast protein liquid chromatography. The enzyme hydrolyzed phenoxymethylpenicillin, benzylpenicillin, ampicillin, and carbenicillin more rapidly than piperacillin and cephaloridine. Cephalothin, cephalexin, cefoxitin, moxalactam, cefotaxime, and imipenem were only slightly hydrolyzed, at less than 1% the rate for phenoxymethylpenicillin. The enzyme was inhibited by clavulanic acid, sulbactam, tazobactam, and p-chloromercuribenzoate. The molecular weight was determined by gel filtration and sodium dodecyl sulfate gradient gel electrophoresis to be 32,000. The isoelectric point was 4.4. Aspartic acid-asparagine, glutamic acid-glutamine, leucine, lysine, alanine, and serine dominated the amino acid composition.

Amino Acids↗
PubMed1989

Effects of dietary polyamine precursors on the metabolism and tissue concentrations of amino acids in the rat.

Experiments were conducted to determine the effects of dietary supplements of amino acid precursors of polyamines on amino acid metabolism in the rat in order to better understand comparative aspects of polyamine metabolism. Rats were fed isonitrogenous combinations of methionine, ornithine, arginine and 2-difluoromethylornithine in casein-based diets. It was observed that hepatic concentrations of methionine, 5'-deoxy-5'-methylthioadenosine and decarboxylated S-adenosylmethionine were more easily influenced by diet than were arginine and metabolites. It was concluded that rats may be more refractory to exogenous polyamine precursor amino acids than are chicks because of the presence of a functional urea cycle.

Adenosine↗
PubMed1988

Effects of buffer salt on the geminate recombination of photodissociated carboxyhemoglobin and its isolated subunits.

The geminate recombination of photodissociated carboxyhemoglobin (human adult) and its isolated subunits was studied by nanosecond laser photolysis. The rebinding kinetics were found not to depend upon the kind of buffer used or on pH but changed appreciably with the buffer concentration. The results are compared to oxygenation properties under the same conditions.

Buffers↗
PubMed1988

Influence of the gel-liquid phase transition on hematoporphyrin triplet deactivation in liposomes.

The deactivation of the triplet state of hematoporphyrin and its dimethyl ester in unilamellar liposomes of dipalmitoyl phosphatidylcholine was studied by nanosecond laser flash photolysis. It was found that the rate of deactivation increases abruptly on raising the temperature in the region of the gel-liquid phase transition of the lipid bilayer (41 degrees C). The rate of change has its maximum at 38.4 +/- 0.5 degree C for both porphyrins. This variation is due to the high lateral mobility of the porphyrins in the liquid-crystal bilayer, which enhances the rates of concentration triplet quenching and triplet-triplet annihilation.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1988

Norfloxacin binds to human fecal material.

Earlier studies have reported very high (120 to 2,700 mg/kg) concentrations of norfloxacin in feces after therapeutic doses. MICs for fecal microorganisms are with few exceptions far below these levels. Nevertheless, clinical investigations show that the main part of the aerobic gram-positive and the anaerobic microflora remains unaffected after norfloxacin administration. In this study, the binding of [14C]norfloxacin to fecal material was analyzed. The binding of a group of nonlabeled quinolones to feces and the interactions between Enterococcus faecium, Bacteroides fragilis, and norfloxacin were also investigated. The results showed that norfloxacin has the ability to bind to feces. The specific binding was reversible, saturated after 90 min of incubation at 37 degrees C, and increased linearly with fecal concentration. Scatchard plots and nonlinear regression computer analyses revealed two different binding classes. The primary specific binding had a dissociation constant (KD) of 1.0 microM and a maximal binding capacity (Bmax) of 0.12 mumol/g of feces. The KD and Bmax of the secondary, more unspecific binding were 450 microM and 11.8 mumol/g of feces, respectively. The binding of unlabeled ciprofloxacin, enoxacin, ofloxacin, pefloxacin, and norfloxacin to feces was comparable to that of [14C]norfloxacin. The results of norfloxacin binding to suspensions of B. fragilis suggested that the main part of the binding is to the bacterial fraction of feces. In the presence of 8.0 g (dry weight) of B. fragilis per liter, the MBC of norfloxacin for E. faecium increased from 8 to 256 micrograms/ml. The finding of the present study indicated that binding of norfloxacin to feces may explain the paradox of high fecal concentrations of norfloxacin versus the actual effect on the normal gastrointestinal microflora.

Adult↗
PubMed1988

Increased (L+)-lactic acid production in lysozyme-inactivated suspensions of human dental plaque.

The effect of lysozyme-inactivation on L(+)-lactic acid (LA) production in dental plaque suspensions was evaluated. From 10 children 24-h plaque was collected and lysozyme activity inhibited by addition of goat antiserum to human lysozyme. Acid production was stimulated by addition of glucose. The results showed significantly increased LA levels (50-150%) in lysozyme-inactivated plaque suspensions from 8 of the subjects compared to untreated controls. The increase in acid production activity was not related to plaque lysozyme levels. The findings indicate that the presence of lysozyme may be limiting on acid production in the early dental plaque.

Adolescent↗
PubMed1987

Metabolic responses to exercise in the racehorse: changes in plasma alanine concentration.

Previous studies in humans have shown that alanine is released from the skeletal muscle in proportion to the work load. We have measured plasma alanine and urea concentrations in well-trained Standardbred and Finnish-bred (cold-blooded) trotters after a graded-intensity exercise and during recovery to study metabolic responses to exercise in this animal model. As controls we measured blood lactate, pyruvate, and glucose concentrations as well as hematocrit values. Metabolic responses to exercise were closely reflected in all these parameters. Plasma alanine increased relatively more than plasma lactate at moderate-intensity exercise near anaerobic threshold. The linear correlation between the intensity of exercise and plasma alanine was similar to that observed earlier in humans. Interestingly, plasma alanine concentrations remained elevated long after the submaximal exercise, whereas the concentration of lactate, pyruvate, and glucose decreased more rapidly. No significant changes were found in plasma urea concentration under these conditions. The most significant differences in the metabolic responses to exercise of the two breeds studied were the higher lactate-to-pyruvate ratios achieved during the high-intensity exercise and the more sensitive increases of plasma alanine even during low-intensity exercise in the Finnish-bred horses. These differences probably reflect different compositions of muscle fiber types in the two breeds. The findings together indicate that plasma alanine is greatly increased in the racehorse during and after a high-intensity exercise and thus is an important vehicle in transporting ammonia and carbon skeletons of products of anaerobic glycolysis out of the muscle tissue.

Alanine↗
PubMed1987

Effect of inactivated salivary lysozyme on L(+)-lactic acid production in saliva and in cultures of Streptococcus mutans BHT.

The aim of this study was to evaluate the antimicrobial contribution of human lysozyme in saliva. In one series of experiments, L(+)-lactic acid (LA) production in exponential phase cultures of Streptococcus mutans BHT treated with lysozyme-deficient salivary supernatant was determined. In other experiments, LA concentration was measured in whole saliva samples from 22 school-children where the lysozyme activity had been inhibited by the addition of goat antiserum to human lysozyme (GAsL). LA production in both S. mutants cultures and saliva samples was stimulated by D-glucose addition. The results indicated a time dependent increase (approximately 30%) in LA production in lysozyme-deficient reaction-mixtures compared to untreated controls. The mean LA concentration in lysozyme-inactivated whole saliva samples was significantly higher (p less than 0.01) compared to untreated saliva. However, in 4 out of 22 children the GAsL-treatment did not affect LA production. The individual differences could not be related to salivary secretion rate, lysozyme activity or the number of S. mutans and lactobacilli in saliva. The findings of this study suggest a protective role for lysozyme in limiting acid production in saliva, but individual differences exist.

Enzyme Activation↗
PubMed1985

Characterization of a new beta-lactamase from Fusobacterium nucleatum by substrate profiles and chromatofocusing patterns.

Seven beta-lactamase-producing Fusobacterium nucleatum strains were isolated from patients with recurrent tonsillitis. The isolates were highly resistant to phenoxymethylpenicillin, benzylpenicillin, ampicillin, piperacillin and cloxacillin. They were all sensitive to cefaclor, cephaloridine, cefotaxime, cefoxitin, latamoxef (moxalactam) and imipenem. Penicillinase activity was found intracellularly after 20 h incubation. Specific activity of the unpurified penicillinase varied among the strains between 0.24-9.3 U/mg protein. The enzyme hydrolysed ampicillin and benzylpenicillin more rapidly than piperacillin. Cephalothin and imipenem were hydrolysed at rates less than 1% of benzylpenicillin. Chromatofocusing experiments eluted the beta-lactamases from all strains at a single peak between pH 5.1-5.2.

Anti-Bacterial Agents↗
PubMed1985

Purification and properties of a novel beta-lactamase from Fusobacterium nucleatum.

A strain of Fusobacterium nucleatum which produced high levels of beta-lactamase was isolated. The specific activity of the unpurified beta-lactamase was 7.8 U/mg of protein. By Sephacryl S-300 and S-200 column passage and chromatofocusing, the enzyme was purified 450-fold. Sodium dodecyl sulfate-gradient gel electrophoresis revealed a single band. The enzyme hydrolyzed phenoxymethylpenicillin, benzylpenicillin, and ampicillin more rapidly than carbenicillin and piperacillin. Cephaloridine, cefaclor, cephalothin, imipenem, and SCH 34343 had hydrolysis rates of less than or equal to 1% that of phenoxymethylpenicillin. The enzyme was inhibited by clavulanic acid and RO-15-1903/001 but not by p-mercuribenzoate or cefoxitin. Molecular weight by gel filtration was determined to be 21,000 and by sodium dodecyl sulfate-gradient gel electrophoresis was determined to be 26,000. The amino acids aspartic acid-asparagine, glutamic acid-glutamine, serine, glycine, and lysine dominated the amino acid composition.

Amino Acids↗
PubMed1985

Beta-lactamases in anaerobic bacteria.

The known mechanisms of beta-lactam resistance in anaerobic bacteria involve production of beta-lactamases, alteration of penicillin-binding proteins and blocked penetration of beta-lactams through the outer membranes. The most important factor in beta-lactam resistance is production of beta-lactamase. Beta-lactamases in various Bacteroides, Fusobacterium and Clostridium species have been described. Beta-lactam resistance in Bacteroides fragilis is most commonly mediated by beta-lactamase production mainly of cephalosporinase character. Recent studies have also shown that B. fragilis can produce a penicillinase which inactivates piperacillin and carbenicillin. Enzymes inactivating cefoxitin and imipenem have also been isolated from B. fragilis. The Bacteroides non-fragilis species produce beta-lactamases of mainly penicillinase character. Recently a penicillinase from Fusobacterium nucleatum has been characterized. Among the clostridia, Clostridium butyricum, C. clostridiiformis and C. ramosum have been shown to produce penicillinases.

Bacteria, Anaerobic↗
PubMed1985

Masticatory movements in patients treated with fixed prosthesis on osseointegrated dental implants in the mandible.

Mandibular movements were recorded by means of an optoelectronic system (Sel spot) in 16 complete denture wearers before and after insertion of tissue integrated prostheses in the mandible. Analysis of the single chewing cycle revealed an obvious increase in mandibular velocity and displacement after rehabilitation. The duration of the occlusion phase was also significantly shortened, probably due to the stabilization of the occlusion provided by the fixed implant bridge.

Computers↗
PubMed1983

Quantitative changes in aminoacylation of transfer RNA and in free amino acids during fructose-induced depletion of adenine nucleotides in rat liver.

Fructose induces depletion of adenine nucleotides in liver and also strongly inhibits incorporation of radioactive amino acids into protein (Mäenpää, P.H., Raivio, K.O. and Kekomäki, M.P. (1968) Science 161, 1253-1254). In this study we have investigated the effects of fructose on aminoacylation of tRNA and on free amino acids in rat liver. 30 min after D-fructose (30 mmol/kg) was injected intraperitoneally into rats, liver ATP was reduced by 58%, ADP by 42%, AMP by 13%, the ATP/ADP ratio by 30%, and total adenine nucleotides by 48%. Using gas chromatography, the aminoacylation of tRNA was determined by quantifying the endogenous amino acids attached to tRNA in vivo. Aminoacylation was reduced by 31%. With different amino acids, reduction varied from 4% (asparagine plus aspartic acid) to 58% (arginine). On the other hand, the amount of free amino acids in the liver was increased by 24%. The most marked individual change was in alanine, which increased 5.7-times. This may have resulted from a combination of effects involving an increased production of alanine in muscle and liver and decreased hepatic gluconeogenesis from alanine caused by the ATP depletion.

Adenine Nucleotides↗
PubMed1983

Neuraminidase in Bacteroides fragilis.

A neuraminidase from Bacteroides fragilis was purified 542-fold by isoelectric focusing, adsorption chromatography on Affi-Gel 202, and gel filtration chromatography on Sephadex G-200. On isoelectric focusing the neuraminidase was resolved into three differently charged fractions with pI values of 6.8, 7.1, and 7.4. The major component of pI 7.1 was used for further purification. The purified enzyme had optimal activity at pH 6.4 with N-acetylneuraminlactose as the substrate. Its molecular weight, determined by Sephadex G-200 gel filtration chromatography, was 92,000. The neuraminidase hydrolyzed terminal neuraminic acid residues from N-acetylneuraminlactose, fetuin, bovine submaxillary mucin, and porcine stomach lining mucin. A new method for the detection of neuraminidase activity is described which is based on rocket affinoelectrophoresis. It utilizes the differences in the interaction of sialylated and desialylated mucin with Helix pomatia lectin, enzymatic activity being detected by formation of affinorockets after incubation of the neuraminidase with bovine submaxillary mucin.

Bacteroides fragilis↗
PubMed1982

Gas chromatographic determination of free amino acids and amino acids attached to transfer RNA in biological samples.

A method was developed to analyze quantitatively free amino acids and amino acids attached to transfer RNA (tRNA) in tissue samples by gas chromatography. Free amino acids were purified by ion-exchange chromatography after deproteinization. Total cellular aminoacyl-tRNA was extracted from rabbit reticulocytes and liver by a modified phenol extraction method under conditions which were designed to prevent deacylation of the attached amino acids. After deacylation and separation from tRNA by pressure ultrafiltration, eighteen amino acids were determined by gas chromatography as their N-heptafluorobutyryl isobutyl derivatives.

Amino Acids↗