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T Larsson

Publications and source records attributed to T Larsson.

At least 19 recordsLinked to original sources
PubMed1994

Spin trapping of methyl radicals by the acyl nitroso compound Ph--C(= O)NO formed in the photochemical reaction between benzohydroxamic acid, dimethyl sulfoxide and hydrogen peroxide. An EPR study.

By the use of EPR spectroscopy, it has been shown that acyl nitroso compounds can act as spin traps for short-lived radicals with the formation of acyl aminoxyl radicals. The reaction was studied for the system benzohydroxamic acid [Ph--C(= O)N(H)]-dimethyl sulfoxide-hydrogen peroxide. The acyl aminoxyl radicals appeared almost immediately when the reaction mixture was irradiated in situ in the EPR cavity with UV light. The trapping reaction involved two photochemical reactions, i.e. the oxidation of the hydroxamic acid to the acyl nitroso compound Ph--C(= O)NO, and the formation of methyl radicals from dimethyl sulfoxide. The EPR spectra are superpositions of the spectra of two species of acyl aminoxyl radicals, i.e. the radicals Ph--C(= O)N(O.)H formed by oxidation of the parent benzohydroxamic acid, and the radical Ph--C(= O)N(O.)CH3, formed by trapping of methyl radicals.

Dimethyl Sulfoxide↗
PubMed1991

Cartilage matrix proteins. A basic 36-kDa protein with a restricted distribution to cartilage and bone.

A non-collagenous quantitatively prominent protein was purified from guanidine hydrochloride extracts of bovine tracheal cartilage. Purification was achieved by cesium chloride density gradient centrifugation and chromatography on DEAE-cellulose at pH 7.0 followed by CM-cellulose at pH 5.0. The protein has a marked tendency to form aggregates in denaturing solutions of high ionic strength, e.g. 6 M guanidine hydrochloride. The purified protein contains a single, Mr 36,000 polypeptide chain, with a particularly high content of leucine. It contains about 1% carbohydrate with a remarkable absence of hexosamines and sialic acid, whereas xylose, galactose, mannose, and fucose were identified in the preparation. The protein was identified in extracts of cartilage and bone and could be shown to be primarily extracellular. Tendon may contain trace amounts of the protein, whereas extracts of several other tissues showed no immunoreactivity in enzyme-linked immunosorbent assay.

Animals↗
PubMed1991

Computer-controlled mechanical testing machine for small samples of biological viscoelastic materials.

Time dependency in the mechanical properties of viscoelastic materials means that a variety of tests is often required to fully characterize their properties. Computer control is the best way of controlling loads and displacements and the rate at which they are applied, as well as recording and analysing the data produced. This paper describes apparatus for measuring the viscoelastic properties of articular cartilage in compression which is readily adaptable to any small sample in which accurate strain measurements require small, carefully controlled displacements. An IBM-type microcomputer is used to control a stepper motor driving a ball screw with a positional accuracy of about 1 micron.

Biomechanical Phenomena↗
PubMed1991

Effects of mechanical load on cartilage matrix biosynthesis in vitro.

Cultured bovine articular cartilage full thickness explants were mechanically loaded, both statically and cyclically, at high frequency (2s of load with 2s intervals of no load) and low frequency (60s of load with 60s intervals of no load), at 1 MPa. Metabolic effects of the load were studied by radiolabeling and compared with non-loaded cartilage explants. High frequency load had a stimulatory effect on protein and proteoglycan synthesis while low frequency and static load showed decreased synthesis. Removing the load from the cultures restored synthesis to non-loaded control culture levels. No major differences in protein biosynthetic pattern were revealed, as determined by SDS-PAGE and fluorography, showing the generalized nature of the response.

Animals↗
PubMed1989

Chondrocyte-matrix interactions. Attachment to proteins isolated from cartilage.

Interactions between bovine chondrocytes and cartilage extracellular matrix proteins and proteoglycans were demonstrated by cell attachment to plastic surfaces coated with the macromolecules. Chondrocytes, which had been maintained in suspension culture, attached to fibronectin, bone sialoprotein, collagen II, and two novel 36- and 58-kDa proteins isolated from cartilage. Attachment to fibronectin and bone sialoprotein was inhibited by competition with an Arg-Gly-Asp containing peptide, whereas attachment to the 36- and the 58-kDa proteins was not affected. The chondrocytes attached but did not spread on 36- and 58-kDa proteins. Other matrix proteins tested gave little or no binding of the chondrocytes. These include a 59-kDa protein, a 100-kDa subunit protein, and a 148-kDa protein. Freshly isolated chondrocytes also attached to proteoglycans, while attachment to the other matrix constituents was the same as for cells maintained in spinner culture prior to assay.

Animals↗
PubMed1989

Large cartilage proteoglycan (PG-LA) influences the biosynthesis of macromolecules by isolated chondrocytes.

Bovine articular and tracheal chondrocytes were cultured at high density in multilayers. Intact or fragmented large aggregating proteoglycans (PG-LA) from cartilage were added to the cultures and the biosynthetic response studied by the incorporation of [3H]-leucine and [35S]-sulfate for proteins and proteoglycans respectively. Incorporated radiolabel and patterns of synthesized macromolecules were compared with control cultures without additives and cultures containing either of the synthetic polymers dextran or dextran sulfate. All proteoglycans and derivatives containing globular protein structures had a stimulatory effect on the biosynthesis of both proteins and proteoglycans as did the highly polyanionic polymer dextran sulfate. Distribution of the radiolabeled material between the cell- and medium pools were however different in the various cultures. A radiolabeled protein, migrating as a triplet band at a position of approximately 140 kDa after reduction, was detected by SDS-PAGE and fluorography. The protein was present in all cell extracts and in the media of cultures stimulated with proteoglycans and proteoglycan fragments, except chondroitin sulfate side chains. The protein was shown to be collagenous in nature by collagenase digestion and identified as procollagen II by immunoprecipitation.

Animals↗
PubMed1988

Hyposmolar entrapping of a spin label into aged red cells.

The aging of human erythrocytes stored in vitro at 4 degrees C was studied by the entrapping method. Erythrocytes were subjected to a sudden hyposmolar stress by suspension in solutions of varying osmolarity in the presence of the spin label tempocholine. The curves obtained when the amount of the spin label entrapped in the ghosts after resealing was plotted against the osmolarity of the buffer solutions exhibited an entrapping which increased with time of the in vitro storage of the erythrocytes (40-60 and 80-100 days). Rejuvenation of the aged erythrocytes by addition of glucose-adenine restored the entrapping curves to shapes nearly similar to those obtained with erythrocytes collected 30-35 days earlier.

Cells, Cultured↗
PubMed1986

Two novel matrix proteins isolated from articular cartilage show wide distributions among connective tissues.

Two proteins of Mr = 58,000 and 59,000, respectively, were purified from 4 M guanidinium chloride extracts of articular cartilage by dissociative CsCl-density gradient centrifugation followed by gel chromatography on Sephadex G-200 and ion exchange chromatography on DEAE-cellulose. The two proteins differ in ionic properties and only the one with Mr = 59,000 bound to the ion exchanger. Although the two proteins showed dissimilar peptide patterns after proteolysis, their amino acid composition was similar, with very high contents of leucine and aspartic acid/asparagine. The two proteins showed no cross-reactivity in radioimmunoassays. By use of these assays, the proteins were demonstrated in extracts of most connective tissues, with high contents of about 0.1% of tissue wet weight determined in several types of cartilage. Among the non-cartilage connective tissues, tendon and sclera had the highest contents of the proteins, i.e. about 0.1% of the tissue wet weight. Bone extracts, on the other hand, contained insignificant amounts of the proteins. Only the Mr = 59,000 protein was detected in serum, its concentration being about 33 micrograms/l. Both proteins were shown to be localized in the extracellular matrix of cartilage, predominantly in the territorial matrix, by using indirect immunofluorescence.

Amino Acids↗
PubMed1986

Stereoselective binding of 3-acetoxy-, and 3-hydroxy-1,4-benzodiazepine-2-ones to human serum albumin. Selective allosteric interaction with warfarin enantiomers.

Stereoselective binding of oxazepam, lorazepam, temazepam and methyl lorazepam as well as of their acetates to human serum albumin was investigated by different techniques. The 2'-chlorine and the N(1)-methyl substitution exert opposite effects on the antipodes. Enantiomers of oxazepam acetate (OAc) and lorazepam acetate (LAc) displace diazepam. Allosteric interactions with warfarin were manifested by either mutually increased or decreased binding depending on the structure of benzodiazepine and on the configuration of both benzodiazepine and warfarin. The most remarkable effect could be observed in the simultaneous binding of (S)-lorazepam acetate and (S)-warfarin.

Benzodiazepines↗
PubMed1985

Entrapping of the spin label tempocholine into human erythrocytes by resealing after hyposmolar stress. Comparison with haemolysis. The effects of some membrane-active substances.

Human erythrocytes were subjected to a sudden hyposmolar stress by suspension in solutions of varying salt concentrations in the presence of the spin label tempocholine. The enlarged pores in the erythrocyte membranes produced by the influx of water, followed by stretching, allowed the passage of the spin label, so that a certain amount of tempocholine was entrapped when the erythrocytes spontaneously resealed with closing of the pores. The excess of spin label in the external solution was then reduced to a diamagnetic species by the addition of ascorbic acid. The positively charged tempocholine and the ascorbic acid did not penetrate properly resealed erythrocytes, so that the electron spin resonance (ESR) signal from the entrapped spin label constituted a measure of the effective resealing of the pores and rifts in the membrane subsequent to hyposmolar stress. Some drug substances were found to influence the entrapping curves obtained when the amount of entrapped spin label was plotted against the osmolarity. Chlorpromazine, trifluoperazine, nicardipine, amperozide and haloperidol gave rise to a dose-dependent decrease of the entrapping of tempocholine, especially at low osmolarities. The exclusion of Ca2+ and Mg2+ ions from the solutions increased the action of chlorpromazine. The protective action against haemolysis brought about by a number of membrane-active substances at low concentrations [2] had its counterpart in the entrapping curve observed with chlorpromazine at 0.1 mM. It is suggested that the substances in this series exerted their action on the resealing process by interaction with the calmodulin system.

Calcium↗
PubMed1984

The efflux of spin label entrapped in human erythrocyte ghosts when suspended in hyposmolar solutions. The effect of chlorpromazine, trifluoperazine, nicardipine and some other membrane active substances.

Human erythrocyte ghosts were loaded with the spin label tempocholine . Once entrapped in the ghosts, this spin label, carrying a positive charge, is not able to penetrate through intact ghost membranes. The ghosts were loaded with spin label to a concentration high enough to introduce exchange broadening of the electron spin resonance (ESR) signal with a relatively small signal amplitude. The efflux of the spin label brought about by hyposmolar stress was studied. The appearance of the label in the relatively large external volume gave rise to an increase of the ESR signal amplitude since the concentration of the spin label outside the ghosts was in the range in which exchange broadening can be excluded. The duration of the efflux following hyposmolar stress was less than half a minute. After this time, the ghosts resealed spontaneously and without restoration of the normal osmolarity. A number of membrane active substances were studied for possible influence on the efflux of spin label induced by hyposmolar stress. The drug substances chlorpromazine, trifluoperazine and nicardipine were found to increase the hyposmolar efflux of spin label. It was suggested that these substances, classified as calcium-antagonists and inhibitors of the calmodulin system, exert their action on the efflux of spin label by interaction with membrane proteins which maintain shape and tension of the erythrocytes.

Calcium Channel Blockers↗
PubMed1983

Comparative studies of the binding of some ligands to human serum albumin non-covalently attached to immobilized Cibacron Blue, or covalently immobilized on Sepharose, by column affinity chromatography.

A comparative study of the ligand-binding properties of human serum albumin was performed by the technique of affinity chromatography with the protein attached to immobilized Cibacron Blue F3GA (Blue Sepharose), or covalently immobilized on Sepharose. The binding strength of octanoate, decanoate and dodecanoate is much weaker when human serum albumin is attached to immobilized Cibacron Blue, indicating that the binding sites for fatty acids are involved in the attachment of human serum albumin to immobilized Cibacron Blue. The results revealed additional alterations of the ligand binding when human serum albumin was attached to immobilized Cibacron Blue, involving sites outside of the binding domains of fatty acids. Thus the stereoselective binding of L-tryptophan was abolished, and the resolution of the warfarin enantiomers was impaired. However, the binding strength of warfarin and salicylic acid was rather close to the values observed with human serum albumin covalently immobilized on Sepharose. It is suggested that the availability of the binding sites for L-tryptophan, warfarin and salicylic acid is partially blocked by the complex between albumin and the dye without direct participation in the complex-formation. An alternative interpretation involves an allosteric mechanism brought about by complex-formation between serum albumin and the immobilized Cibacron Blue.

Anthracenes↗
PubMed1981

Synthesis and binding to tubulin of an allocolchicine spin probe.

A spin probe for the colchicine binding site on tubulin has been synthesized from allocolchicine. The probe is competitive to colchicine with an apparent inhibition constant of 11 microM while allocolchicine has an inhibition constant of 2 microM. Microtubule assembly is inhibited to 50% by 7 microM of the spin probe. As a mitotic poison the spin probe is less potent than colchicine. These data suggest that the probe binds to the same site on tubulin as colchicine and in spite of the somewhat lower efficiency, it seems to be a valuable tool for the study of the microtubule system.

Animals↗
PubMed1978

Quantitative studies on competitive ligand binding to bovine serum albumin by use of the spin label 5-doxyl dodecanoic acid.

The binding of the spin label 5-doxyl dodecanoic acid to bovine serum albumin in phosphate buffer at pH 7.4 was studied by electron spin resonance spectroscopy. Free label and label bound to serum albumin could be quantitatively measured and evaluated from the superposition spectra of these two species with no previous separation. The efficiency relative to the spin label as competitors for binding to serum albumin was studied with salicylic acid and some fatty acids of medium length. The results were represented both by the stoichiometric model involving equilibrium constants Ki, by binding isotherms constructed from the Ki values, and by a purely graphical representation of the experimental data points without connection with any special binding model.

Binding, Competitive↗
PubMed1977

The value of thermography and the determination of fibrin-fibrinogen degradation products in the diagnosis of deep venous thrombosis.

Fifty-one patients with leg symptoms indicating deep venous thrombosis (DVT) were investigated concomitantly with thermography and phlebography. Altogether 26 legs with phlebographically proven DVT exhibited a thermographic picture typical of DVT. So, however, did 3 out of 25 legs with no DVT. A 94 percent agreement was found between phlebography and thermography when applied to legs with suspect DVT. The serum levels of fibrin-fibrinogen degradation products (FDP) were assayed in 58 patients attending hospital for suspect DVT. These patients were free from other diseases known to be followed by raised FDP levels. With borderline significance, the DVT group had higher FDP values. The usefulness of this laboratory test in the diagnosis of DVT is, however, questioned.

Adult↗