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Biomedical subjects

M Berggren

Publications and source records attributed to M Berggren.

At least 37 records · Page 2Linked to original sources
PubMed1994

Site-directed mutagenesis of active site cysteines in human thioredoxin produces competitive inhibitors of human thioredoxin reductase and elimination of mitogenic properties of thioredoxin.

Thioredoxin and thioredoxin reductase comprise a redox system ubiquitous in all organisms. To better understand the thiol chemistry of the mammalian thioredoxin-thioredoxin reductase redox system, mutants of human thioredoxin were produced by site-directed mutagenesis in which the two active site cysteines were replaced by serine residues, individually (C32S and C35S) and in combination (C32S/C35S). C35S and C32S/C35S were found to be competitive inhibitors of the reduction of human thioredoxin by human thioredoxin reductase with Ki values of 1.8 and 6.7 microM, respectively. C32S did not inhibit thioredoxin reductase, apparently due to aggregation of the oxidized C32S species. Examination of the three mutant forms of thioredoxin by circular dichroism spectroscopy indicated that there were significant differences in the secondary structures when compared with thioredoxin. There were detectable changes in the circular dichroism spectra when thioredoxin, C35S, and C32S/C35S were bound to thioredoxin reductase, whereas C32S with thioredoxin reductase underwent only a small spectral change. Recombinant human thioredoxin stimulated DNA synthesis and the proliferation of murine fibroblasts. The ability of thioredoxin to stimulate cell proliferation could not be duplicated by either dithiothreitol or glutathione. C32S, C35S, and C32S/C35S failed to stimulate cell proliferation, showing that the redox active form of thioredoxin is necessary for eliciting growth stimulation.

3T3 Cells↗
PubMed1994

Biochemical, structural, and biological properties of human thioredoxin active site peptides.

The human redox protein thioredoxin is an autocrine growth factor for some cancer cells. Redox activity is essential for this function but other required structural features of thioredoxin are not known. Two 8-mer peptides (I and II) and one 14-mer peptide (III) were designed based on the amino acid sequence of the redox active site of thioredoxin. Peptide I and peptide III contained the wild-type sequence of thioredoxin while peptide II contained serine residues in place of the catalytically active cysteines. Circular dichroism spectroscopy indicated that all three peptides were comprised mainly of random coil, with peptide III containing slightly more ordered secondary structure. Peptides I and III were substrates for thioredoxin reductase with KM values of 890 and 265 microM, respectively. The redox inactive peptide II could not compete with thioredoxin for reduction by thioredoxin reductase in a coupled insulin reduction assay. However, peptide II was a competitive inhibitor for the reduction of 5, 5'-dithiobis-(2-nitrobenzoic acid) by thioredoxin reductase. All three peptides gave only background levels of stimulation of the proliferation of Swiss 3T3 murine fibroblasts when compared to the stimulation caused by thioredoxin. These results suggest that while the ability of thioredoxin to stimulate cellular proliferation is redox-dependent, more information than that contained in the redox active site domain alone defined by 14 amino acids is required.

3T3 Cells↗
PubMed1994

The thioredoxin/thioredoxin reductase redox system and control of cell growth.

Thioredoxin is a redox protein that is important for a variety of intracellular functions, possibly including regulation of transcription factor activity. We have shown that human thioredoxin has the same predicted amino acid sequence as adult T-cell-derived leukemic cell growth factor. Recombinant human thioredoxin stimulates the proliferation of Swiss murine 3T3 fibroblasts with an EC50 of 100 nM and the proliferation of a number of human cancer cells. Site-directed mutagenesis of the active-site cysteines of thioredoxin has shown that redox activity is necessary for the stimulation of cell proliferation. Added 125I-thioredoxin is taken up by cells in culture and could have intracellular action. A series of alkyl 2-imidazolyl disulfides have been shown to be competitive inhibitors of human thioredoxin reductase with Ki values of 3.3 to 8.6 microM. The compounds inhibited Swiss 3T3 serum-dependent proliferation with IC50 values of 2.0 to 4.0 microM, and one compound inhibited Swiss 3T3 thioredoxin-dependent proliferation with an IC50 value of 60 nM.

3T3 Cells↗
PubMed1993

Improved results in zone 2 flexor tendon injuries with a modified technique of immediate controlled mobilization.

The results following primary and delayed primary repair in zone 2 flexor tendon injuries were evaluated in 85 fingers of 79 patients using immediate controlled mobilization post-operatively. In 31 patients a conventional Kleinert technique was used. In the remaining 48 patients a modified technique was used with rubber band traction to all fingers instead of only to the injured one. Also a shorter dorsal splint was used in order to secure extension of the PIP and DIP joints. The results were improved and the time of treatment was reduced.

Adult↗
PubMed1993

Biodegradation of 4-nonylphenol in seawater and sediment.

Biodegradation of 14C-labelled nonylphenol at the concentration 11 microg litre (-1) in seawater has been estimated by collection and quantification of the formed labelled carbon dioxide. Initially degradation was very slow but when the microorganisms had become adapted, after four weeks at 11 degrees C, the degradation rate increased rapidly and after 58 days about 50% of 14C from NP was found in the CO2 fraction. In the presence of sediment the initial degradation rate was high and did not increase after longer incubation. Lack of oxygen reduced the degradation rate by half in the presence of sediment.

Journal Article↗
PubMed1992

Ultrasonic characterization of mycelial morphology as a fractal structure.

Preliminary measurements of scattering of ultrasound from filamentous microorganisms in aqueous-medium suspensions are reported. The data are used to characterize the structuring (morphology) between the organisms quantitatively by modelling the morphology in terms of fractal structures and obtaining the fractal dimension as the characteristic parameter. The fractal dimension is calculated from the slope of a log-log plot of scattered intensity versus the scattering vector magnitude. The intensity is measured over a range of magnitudes of the scattering vector by varying the scattering angle as well as the ultrasonic frequency. Results from microbial suspensions of different species and different morphologies indicate that the fractal dimension can be used to quantify the morphological state of a suspension. The fractal dimension ranges from around 1.5 for suspensions with pelletous morphology to around 2.5 for suspensions with filamentous morphology.

Fourier Analysis↗
PubMed1991

Platelet-derived growth factor blocks the increase in intracellular free Ca2+ caused by calcium ionophores and a volatile anesthetic agent in Swiss 3T3 fibroblasts without altering toxicity.

Platelet-derived growth factor (PDGF) produced an almost complete block of the increase in intracellular free Ca2+ concentration ([Ca2+]i) in Swiss 3T3 fibroblasts caused by the Ca2(+)-selective ionophores 4-bromo-A23187 and ionomycin, and by the volatile anesthetic agent halothane. The effect of PDGF was similar to the decreased [Ca2+]i response to Ca2(+)-ionophores produced by phorbol 12-myristate 13-acetate, an activator of protein kinase C. There was no effect of PDGF or PMA on the acute or delayed toxicity of the Ca2(+)-ionophores to Swiss 3T3 cells, suggesting that the increase in [Ca2+]i is not the direct cause of toxicity of these agents.

Aequorin↗
PubMed1991

Enhanced mobilization of intracellular Ca2+ induced by halothane in hepatocytes isolated from swine susceptible to malignant hyperthermia.

Halothane, in a dose-dependent manner, induced the release of intracellular Ca2+ in hepatocytes prepared from swine. The magnitude of the release induced by halothane was greater for hepatocytes prepared from animals susceptible to malignant hyperthermia (MH) than for those from normal swine. Two different methods were used to ascertain the release of Ca2+ induced by halothane: 1) the release of 45Ca2+ from nonmitochondrial stores of saponin-permeabilized hepatocytes was measured; and 2) changes in luminescence from intact hepatocytes loaded with the Ca2(+)-sensitive photoprotein aequorin were recorded. It was also observed that, although 1,4,5-inositol trisphosphate (IP3), guanosine-5-triphosphate, and arachidonic acid all induced a significant release of 45Ca2+ from permeabilized swine hepatocytes, only the quantities of 45Ca2+ released by IP3 were significantly greater for the hepatocytes prepared from the animals susceptible to MH. These data indicate an abnormal Ca2+ homeostasis in hepatocytes isolated from swine susceptible to MH, which supports the hypothesis that membrane systems from multiple organs may be affected in this genetic disorder.

Animals↗
PubMed1991

Mechanisms of hydroperoxide-induced broncho- and vasoconstriction in isolated and perfused rat lung.

The mechanisms of hydroperoxide-induced broncho- and vasoconstriction were investigated in the perfused and ventilated rat lung. Hydrogen peroxide (500 microM), tertiary butylhydroperoxide (500 microM) and arachidonic acid (100 microM) induced similar profiles of broncho- and vasoconstriction which could be prevented by the inhibitor of cyclooxygenase, diclofenac (100 microM) but not by nordihydroguaiaretic acid (5 and 25 microM), an inhibitor of lipoxygenase. The hydroperoxides also caused a time-dependent increase in the levels of thromboxane and prostacycline, products of cyclooxygenase. Furthermore, the thromboxane agonist, U44069 (100 pmoles), caused a very rapid broncho- and vasoconstriction that was preventable by the thromboxane antagonist L655.240 (1 microM). L655.240 also inhibited hydrogen peroxide-induced broncho- and vasoconstriction. The phospholipase A2 inhibitors, quinacrine (100 microM) and dibucaine (100 microM), did not prevent hydroperoxide-induced broncho- and vasoconstriction. The Ca2+ chelator, EGTA, prevented hydroperoxide and arachidonic acid-induced lung constriction, although it did not inhibit the release of thromboxane. The infusion of arachidonic acid and hydroperoxides resulted in edema in the lung which was prevented by prior administration of diclofenac, indomethacin or L655.240. These results indicate that hydroperoxide-induced broncho- and vasoconstriction and lung edema are mediated by thromboxane, a product of cyclooxygenase. The mechanism of hydroperoxide-induced release of arachidonic acid is not clear but does not seem to involve Ca2+ nor the activation of phospholipase A2.

Animals↗
PubMed1990

Bioaccumulation of 4-nonylphenol in marine animals--a re-evaluation.

The bioaccumulation of 4-nonylphenol (NP) has been studied in shrimps (Crangon grangon L.), mussels (Mytilus edulis L.) and sticklebacks (Gasterosteus aculeatus L.) exposed to (14)C-NP in running seawater. NP was extracted with high recovery from tissues which were pretreated with pancreatic enzymes. The bioconcentration factor determined of NP in fish was 1300 and in mussels, 3400. These values are 5 and 340 times higher, respectively, than values reported earlier.

Journal Article↗
PubMed1990

Effects of some autacoids on breathing and perfusion flow in the isolated perfused rat lung.

The effects of three autacoids [5-hydroxytryptamine (5-HT), bradykinin and acetylcholine (Ach)) on breathing and pulmonary circulation were studied in the isolated perfused and ventilated rat lung after intravascular injection or intrabronchial instillation. 5-HT, bradykinin and Ach all caused a dose related reduction in breathing, after injection into the pulmonary artery, with Ach being the most potent. With regard to effects on the pulmonary circulation, a dose-related reduction in perfusate flow was noted with bradykinin and 5-HT with bradykinin being about 10 times more potent than 5-HT. Ach did not reduce or increase perfusate flow. After intrabronchial instillation only 5-HT caused reduced perfusate flow. Effects on breathing were difficult to evaluate with this route of administration. The isolated perfused and ventilated lung seems to be a usable model to simultaneously study effects on respiration and pulmonary circulation.

Acetylcholine↗
PubMed1989

Lethal and sublethal toxicity of 4-nonylphenol to the common mussel (Mytilus edulis L.).

The toxicity of nonylphenol to the common mussel (Mytilus edulis L.) has been determined in both semistatic and continuous flow test systems. The LC50 values obtained were for 96 h, 30 mg litre(-1); 360 h, 0.5 mg litre(-1); and 850 h, 0.14 mg litre(-1). Sublethal effects, manifested as decreased byssus strength and change of scope for growth, were obtained at a concentration as low as 0.056 mg litre(-1). Fertilization and early developmental success were not affected at the highest concentration tested (0.2 mg litre(-1)).

Journal Article↗
PubMed1988

Hydroperoxide and cigarette smoke induced effects on lung mechanics and glutathione status in rat isolated perfused and ventilated lungs.

The effects of t-butylhydroperoxide (TBH) and cigarette smoke on lung mechanics (CDYN and RL) and glutathione status (GSH) were studied using an isolated perfused and ventilated rat lung preparation. TBH (200, 400, 1000 microM) infused via the pulmonary circulation caused a dose-related bronchoconstriction. The lung GSH-levels were also significantly reduced. Pretreatment of rats with diethylmaleate (DEM) potentiated the TBH elicited bronchoconstriction. DEM (1 mM) infused into the pulmonary circulation caused an almost complete depletion of GSH-content but no effects on lung mechanics were seen. Indomethacin (2.8 and 28 microM) infusion attenuated TBH (400 microM) induced bronchoconstriction. These findings suggest that the TBH induced bronchoconstriction is at least partly mediated via arachidonic acid metabolites. When TBH was administered intratracheally, weak and not dose-related bronchoconstriction was observed even though doses higher than those given intravascularly were used. However, the GSH-content of the lungs was markedly decreased. Cigarette smoke caused weak if any effects on lung mechanics but significantly decreased lung GSH-content.

Animals↗
PubMed1988

Determination of the intracellular protein thiol distribution of hepatocytes using monobromobimane derivatisation of intact cells and isolated subcellular fractions.

The derivatisation of intact rat hepatocytes with monobromobimane resulted in rapid labelling of accessible protein thiols in several subcellular fractions. The derivatisation procedure did not cause acute cytotoxicity, nor did it alter the buoyant densities of the fractions or their gross protein compositions. Quantitation of the fluorescence irreversibly associated with the fractions demonstrated considerable intracellular heterogeneity in this pool of thiols. Values were highest in cytosol (ca. 90 nmol/mg protein), intermediate in microsomes (ca. 65 nmol/mg protein) and mitochondria (ca. 45 nmol/mg protein) and lowest in a crude fraction containing both nuclei and plasma membrane (ca. 35 nmol/mg protein). Similar values were obtained from microsomes and cytosol derivatised after fractionation but there were significant increases of ca. 100% in corresponding values from isolated mitochondria and the nuclear/plasma membrane fraction. These results are discussed in terms of the dynamic fluxes in monobromobimane protein thiols during fractionation and the applicability of this noninvasive method to studies of the mechanism(s) of toxicity of reactive xenobiotics and the role(s) of protein thiols in normal cellular function.

Animals↗
PubMed1987

N-acetylcysteine and glutathione-dependent protective effect of PZ51 (Ebselen) against diquat-induced cytotoxicity in isolated hepatocytes.

The glutathione peroxidase (GSH-Px)-like reduction of H2O2 by the selenoorganic compound 2-phenyl-1,2-benzoisoselenazol-3(H)-one (PZ51: Ebselen) was studied using glutathione (GSH) and the therapeutic agent N-acetylcysteine (NAC) to provide reducing equivalents. In a purely chemical system containing H2O2 and in an enzymatic system of glucose/glucose oxidase-generated H2O2 Ebselen alone did not reduce H2O2. Ebselen in combination with either GSH (1 mM) or NAC (1 mM) was capable of reducing H2O2 in both systems. In these non-cellular systems GSH was a more effective source of reducing equivalents than NAC. The GSH-Px-like activity of Ebselen was further investigated in a cellular system. The redox-cycling bipyridylium compound diquat generates active oxygen species, depletes intracellular glutathione, and is cytotoxic in isolated hepatocytes pretreated with the glutathione reductase inhibitor 1,3-bis(Z-chloro-ethyl)-1-nitrosourea (BCNU). Ebselen alone did not ameliorate diquat cytotoxicity, but in combination with either GSH (1 mM) or NAC (1 mM) it produced a significant delay in diquat-induced cytotoxicity. Further additions of either GSH (0.5 mM) or NAC (0.5 mM) at 30 min intervals provided significantly more protection against diquat-induced cytotoxicity and intracellular GSH depletion than the single 1 mM addition. Thus, the combination of Ebselen and NAC may provide an effective antidote in cases of overexposure to bipyridylium herbicides, such as diquat and paraquat.

Acetylcysteine↗
PubMed1986

Lung protection by a thiol-containing antioxidant: N-acetylcysteine.

N-acetylcysteine (NAC) is a thiol-containing compound which nonenzymatically interacts and detoxifies reactive electrophiles and free radicals. NAC was shown to effectively protect human bronchial fibroblasts against the toxic effects of tobacco smoke condensates and the isolated perfused lung against the glutathione (GSH)-depleting effect of tobacco smoke. NAC was also shown to reduce the reactive oxygen intermediate hydrogen peroxide (H2O2) and protect against the toxic effects of H2O2. In vivo studies, however, demonstrated that NAC when administered orally has very low bioavailability due to rapid metabolism to GSH among other metabolites. Thus, even though NAC is very effective in protecting cells of different origins from the toxicity of reactive components in tobacco smoke and reactive oxygen species, a direct scavenging effect by NAC in vivo, particularly when administered orally, does not seem likely. The bioavailability of NAC itself is very low when given this route. A more relevant mechanism in vivo for any protective effect NAC may exert against toxic species may be due to NAC acting as a precursor of GSH and facilitating its biosynthesis. GSH will then serve as the protective agent and detoxify reactive species both enzymatically and nonenzymatically.

Acetylcysteine↗
PubMed1985

N-acetylcysteine protection against the toxicity of cigarette smoke and cigarette smoke condensates in various tissues and cells in vitro.

The protective effect of N-acetylcysteine on the toxicity of tobacco smoke condensates was investigated using different cellular in vitro systems. Cigarette smoke condensates, and the non-volatile and semi-volatile fractions separated from the condensate were used. All three smoke condensate fractions were toxic to isolated rat hepatocytes and lung cells and caused a loss of cell membrane integrity. A rapid depletion of cellular reduced glutathione (GSH) preceded the toxicity. The loss of GSH was due to conjugation of reactive compounds in the condensate fractions and not to oxidation since no increase in oxidized glutathione (GSSG) could be observed. N-acetylcysteine at a concentration of 1 mM protected both from the GSH loss and cell toxicity caused by the condensate fractions. The effect of the tobacco smoke condensate on the colony forming efficiency (CFE) of cultured human bronchial cells was also investigated. Already at concentrations of 50 micrograms/ml the survival decreased to 40% of control and at 100 micrograms/ml almost no cells formed colonies. N-acetylcysteine substantially increased survival when added at 10 mM concentration.

Acetylcysteine↗