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Biomedical subjects

S Lindskog

Publications and source records attributed to S Lindskog.

At least 163 records · Page 9Linked to original sources
PubMed1985

The inhibition of human carbonic anhydrase II by some organic compounds.

The inhibition of human carbonic anhydrase II (carbonate hydro-lyase, EC 4.2.1.1) by tetrazole, 1,2,4-triazole, 2-nitrophenol, and chloral hydrate has been investigated. These inhibitors, together with phenol which has been studied previously (Simonsson, I., Jonsson, B.-H. and Lindskog, S. (1982) Biochem. Biophys. Res. Commun. 108, 1406-1412), can be classified in three groups depending upon the kinetic patterns of inhibition of CO2 hydration at pH near 9. The first group, represented by tetrazole and 2-nitrophenol, yields predominantly uncompetitive inhibition under these conditions in analogy with simple, inorganic anions. The second group, represented by 1,2,4-triazole and chloral hydrate gives rise to essentially noncompetitive inhibition patterns, whereas phenol, representing the third group, is a competitive inhibitor of CO2 hydration. These diverse inhibition patterns are discussed in terms of the kinetic mechanism scheme originally proposed by Steiner et al. (Steiner, H., Jonsson, B.-H. and Lindskog, S. (1975) Eur. J. Biochem. 59, 253-259.

Binding, Competitive↗
PubMed1985

Purification and some properties of carbonic anhydrase from bovine skeletal muscle.

Procedures for the purification of bovine muscle carbonic anhydrase (isoenzyme III) are described. The purified enzyme has a molecular weight near 29,000 and contains one Zn2+ ion per molecule. The sedimentation coefficient, s(0)20,w, is 2.8 X 10(-13) s, the isoelectric pH is 8.5, and A280(0.1%) = 2.07 cm-1. The CO2 hydration activity, expressed as kcat/Km, is about 1.5% of that of human isoenzyme I (or B) and about 0.3% of that of human isoenzyme II (or C) at pH 8 and 25 degrees C. The activity is nearly independent of pH between pH 6.0 and 8.6. The muscle enzyme is weakly inhibited by the sulfonamide inhibitor, acetazolamide, whereas some anions, particularly sulfide and cyanate, are efficient inhibitors. Bovine carbonic anhydrase III contains five thiol groups, two of which react readily with Ellman's reagent without effect on the catalytic activity. A reinvestigation of the amino acid sequences of cysteine-containing tryptic peptides has shown that cysteine residues occur at sequence positions 66, 183, 188, 203, and 206.

Amino Acid Sequence↗
PubMed1985

Fibrous dysplasia of bone and concomitant dysplastic changes in the dentin.

Fibrous dysplasia of bone and dentinal dysplasia have not been classified as related conditions. However, the present report describes a patient with both polyostotic fibrous dysplasia and dysplastic changes in the dentin. One bone lesion was first discovered on the right side of the mandible on a routine roentgenogram. There was an atypical radiolucency apical to a short-rooted molar with an obliterated pulp. Additional lesions were found on the left side of the mandible in the maxilla, in the frontal and occipital bones, in the ilium, in the proximal ulnae, and in the ribs. All lesions demonstrated an increased uptake of Tc99. A biopsy specimen of bone from the right side of the mandible showed small calcified islands in a cell-rich connective tissue. Microscopic analysis of the right first molar showed irregularly shaped dentin with the dentinal tubules arranged in a whorl-like fashion surrounding an almost completely obliterated pulp chamber and canal. Healing after tooth extraction and after the bone biopsy was unremarkable. After 6 months the alveolus was reorganized and the bone patterns appeared normal, although the radiolucent areas inferior to the teeth remained unchanged. The concomitant occurrence of dysplastic changes in bone and teeth may be a sign of a generalized defect in the mesenchymal hard-tissue-forming cells.

Adult↗
PubMed1985

Activity of gamma-glutamyl transferase in developing teeth of the rat.

gamma-Glutamyl transferase activity was studied with an enzyme histochemical technique in rat molar teeth at different stages of development. The odontoblasts showed an increasing activity during formation of the crown. The secretory ameloblasts did not show any activity, while activity was intense in the postsecretory ameloblasts. This activity was confined to the apical part of the cell. In the reduced ameloblasts at the enamel free cusp tips a similar activity was noted. Since gamma-glutamyl transferase has been shown to be involved in endocytosis and transport of amino acids, the localization of the enzyme in developing teeth suggests an active uptake of amino acids from the enamel matrix of the ameloblasts during enamel maturation.

Ameloblasts↗
PubMed1984

The reaction between NADPH and mercuric reductase from Pseudomonas aeruginosa.

The reaction between the FAD-containing enzyme, mercuric reductase, and its reducing substrate, NADPH, has been studied at 5 degrees C, pH 7.3, by rapid-scan and fixed-wavelength stopped-flow techniques with the aim to characterize reaction intermediates. With an excess of NADPH the spectral changes observed in rapid-scan experiments can be described by a simple kinetic model, A----B----C----D, where A, B, C, and D represent distinct spectral species. The first step is virtually complete within the dead time of the apparatus. It is associated with a 16% bleaching of flavin absorbance and the appearance of a very broad charge-transfer band (epsilon max = 1.9 mM-1 cm-1) centered near 600 nm. The second step (k = 43 s-1) involves a further small bleaching of flavin absorbance and intensification of the charge-transfer band (epsilon max = 3.3 mM-1 cm-1) which becomes centered near 580 nm. The third step (k = 8 s-1) involves an intensification and a blue shift of the main FAD absorption band. Concurrently, the charge-transfer band increases in intensity and becomes centered near 530 nm (epsilon 530 = 5.0 mM-1 cm-1). While the first two steps involve 1 mol of NADPH per mol of FAD, the third step requires a second equivalent of NADPH. A 2-electron-reduced enzyme (EH2) can be obtained by treatment of the oxidized enzyme (E) with dithioerythritol. Addition of 1 eq of NADP+ to dithioerythritol-generated EH2 gives rise to a spectral species similar to the kinetic intermediate C, while the addition of 1 eq of NADPH gives rise to a spectral species similar to D. It is proposed that B largely corresponds to an E-NADPH complex, C to an EH2-NADP+ complex, and D to an EH2-NADPH complex.

Hydrogen-Ion Concentration↗
PubMed1984

Anion inhibition of CO2 hydration catalyzed by human carbonic anhydrase II. Mechanistic implications.

Five monovalent anions, I-, N3-, SCN-, NCO- and Au(CN)2-, were investigated as inhibitors of CO2 hydration catalyzed by human carbonic anhydrase II (carbonate hydro-lyase, EC 4.2.1.1). Predominantly uncompetitive inhibition patterns were observed at pH near 9 in all cases. While Dixon plots of Km/V vs. inhibitor concentration were linear, all the investigated anions except NCO- gave nonlinear Dixon plots of 1/V vs. inhibitor concentration. The anion SCN- was also tested at pH 7.4 and 6.4. Essentially noncompetitive patterns of inhibition of CO2 hydration were obtained at both these pH values. These results are analyzed in terms of two rivaling mechanism models, a kinetic scheme originally proposed by Steiner et al. (Steiner, H., Jonsson, B.-H. and Lindskog, S. (1975) Eur. J. Biochem. 59, 253-259) and a rapid-equilibrium kinetic scheme proposed by Pocker and Deits (Pocker, Y. and Deits, T.L. (1982) J. Am. Chem. Soc. 104, 2424-2434). It is concluded that the observed steady-state inhibition patterns are compatible with both models, but that discriminatory data, strongly favouring the model of Steiner et al., are available in the literature.

Anions↗
PubMed1984

Catalytic properties and inhibition of Cd2+-carbonic anhydrases.

Cd2+ derivatives of human carbonic anhydrases I and II and bovine red cell carbonic anhydrase (carbonate hydro-lyase, EC 4.2.1.1) have been prepared. The metal ion in these derivatives is readily displaced by Zn2+. The Cd2+-carbonic anhydrases have appreciable 4-nitrophenyl acetate hydrolase activities. These activities increase with pH as if dependent on the basic form of a group with pKa near 10. The Cd2+-carbonic anhydrases also have significant CO2 hydration activities. The Cd2+ derivatives are strongly inhibited by monovalent anions. In particular, I- is a much more potent inhibitor of the Cd2+ enzymes than of the native enzymes. Acetazolamide (5-acetylamido-1,3,4-thiadiazole 2-sulfonamide) is also a strong inhibitor although its affinity for the Cd2+ enzyme is less than its affinity for the native enzyme.

Acetazolamide↗
PubMed1984

Effects of pH and inhibitors on the absorption spectrum of cobalt(II)-substituted carbonic anhydrase III from bovine skeletal muscle.

Bovine apocarbonic anhydrase III has been prepared by incubation with 2-carboxy-1,10-phenanthroline at pH 5.5. The Co(II)-substituted enzyme has been prepared and its absorption spectrum has been studied. The spectrum is nearly pH-independent above pH 6. It is very similar to the high pH spectral forms of Co(II)-carbonic anhydrases I and II. The spectra of complexes with the sulfonamide inhibitor, acetazolamide, and with CN- and NCO - are virtually identical to the spectra of the corresponding complexes with Co(II)-isoenzymes I and II. The spectrum of the N-3 complex indicates that this anion is bound somewhat differently in Co(II) isoenzyme III than in the other Co(II)-substituted isoenzymes.

Animals↗
PubMed1984

Tooth ankylosis. Clinical, radiographic and histological assessments.

Ankylosis is a serious condition for the affected teeth as such teeth form part of the remodelling process of the alveolar bone and are therefore progressively resorbed. There are, however, very few clinical studies on tooth ankylosis and the reason for this may be due to the difficulties that are encountered in the diagnosis of minor areas of ankylosis. In the present study, the radiographs, percussion sound and mobility of experimentally extracted and replanted monkey incisors were compared with a morphometric histological study of ankylosis. Ankylotic areas were evident radiographically when the ankylosis was located on the proximal surfaces of the root, but were not evident when the ankylosis occurred on the lingual and labial surfaces. The percussion sound was dull and the mobility normal in all non-ankylotic teeth as well as in those teeth which histologically demonstrated ankylosis on less than 10% of the root surface. When the ankylosis affected 10-20% of the root surface, 2 out of 4 teeth changed their percussion sound from dull to high and these teeth no longer possessed normal mobility. When more than 20% of the root surface was affected with ankylosis, the percussion sound was characteristically high in all teeth and no mobility was present.

Animals↗
PubMed1984

Scanning electron microscopic study of orthodontically induced injuries to the periodontal membrane.

Scanning electron microscopy was used to study vascular and cellular changes in the periodontal membrane (PDM) in rats after orthodontic treatment ranging from 3 h to 9 days. The orthodontic forces ranged between 200 mN and 400 mN. Within the first hours of treatment extravasated erythrocytes, eichinocytes and platelets in various stages of degeneration were found in the pressure zones. The connective tissue of the pressure zones developed an amorphous appearance lacking discernible fibers and blood vessels following treatment for 24 h. These areas are known as hyaline zones, an area of local aseptic necorsis. Three days after the application of an orthodontic force macrophage-like cells were abundant close to the hyaline zone. They adhered to the hyaline zone with filopods radiating from pseudopods. Large osteoclast-like cells with several projections towards the bone surface were found around the hyaline zone and in the marrow spaces close to the pressure zones. The results indicated that the tissue reactions leading to remodeling of the PDM in the pressure zones are closely related to vascular injuries and subsequent formation of coagulated blood. Furthermore, macrophages seem to be the cells which play the most important role during degradation of the hyaline zone.

Animals↗
PubMed1984

Kinetics and mechanism of carbonic anhydrase isoenzymes.

A mechanism model has been presented that can describe most known kinetic properties of carbonic anhydrase isoenzymes I, II, and III. The essential features of this model include: Nucleophilic attack of metal-bound OH- on CO2 to form metal-bound HCO-3. Formation of metal-bound OH- from metal-bound H2O. In isoenzyme II, and probably also in isoenzyme I, this reaction step involves an intramolecular transfer of H+ between the metal site and a titratable histidine residue via a number of hydrogen-bonded H2O molecules. In isoenzyme II, this step limits the maximal rate of catalysis. Also in isoenzyme III, the H2O-splitting step may be rate limiting, but since this isoenzyme has no titratable active-site histidine, H+ transfer may take place directly with components of the solvent. In isoenzymes I and II, rapid H+ transfer between active site and solution proceeds in a reaction between the titratable histidine residue and buffer molecules. The model can also rationalize a variety of observed inhibition patterns.

Carbonic Anhydrases↗
PubMed1984

Enamel hypoplasia in permanent teeth induced by periodontal ligament anesthesia of primary teeth.

Periodontal ligament anesthesia was applied to 16 primary teeth in jaw quadrants of two monkeys. The teeth in the contralateral positions were not injected and the permanent teeth in this area served as controls. The animals were killed after 22 months when the permanent incisors began to erupt. In total, enamel hypoplasia or hypomineralization (or both) was noticed in 15 permanent teeth in the experimental quadrants but in none of the controls. The results strongly emphasized that periodontal ligament anesthesia should be used with great care on primary teeth close to developing permanent teeth.

Anesthesia, Dental↗