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Biomedical subjects

S Pedersen

Publications and source records attributed to S Pedersen.

At least 37 records · Page 2Linked to original sources
PubMed2000

Thermodynamics of heat-shock response.

Production of heat-shock proteins is induced when a living cell is exposed to a rise in temperature. The heat-shock response of protein DnaK synthesis in E.coli for temperature shifts T-->T+DeltaT and T-->T-DeltaT is measured as a function of the initial temperature T. We observe a reversed heat shock at low T. The magnitude of the shock increases when one increases the distance to the temperature T0 approximately 23 degrees C, thereby mimicking the nonmonotonous stability of proteins at low temperature. This suggests that stability related to hot as well as cold unfolding of proteins is directly implemented in the biological control of protein folding.

Escherichia coli↗
PubMed2000

[Malignant neuroleptic syndrome. A review of epidemiology, risk factors, diagnosis, differential diagnosis and pathogenesis of MNS].

Neuroleptic malignant syndrome (NMS) is a rare, potentially life-threatening disorder that results from the use of neuroleptics. NMS was first recognised as a complication of dopamine receptor antagonists characterized by extrapyramidal disturbances, hyperthermia, muscle rigidity, autonomic instability, mental status changes and elevated serum creatine kinase levels. Concepts of NMS have changed because medications other than classic neuroleptic drugs have been implicated as triggering agents. The incidence of NMS is about 0.2% with a mortality between 4-30%, which may be diminished by treatment. The neurochemical key features in all these conditions probably result from disruption of the dopamine system in the brain and the effects of neuroleptics on muscle. Recognition of NMS is the most important step in its management by discontinuation of the causative drugs and applying supportive care and therapeutic measures. Specific therapeutic measures include the application of dopamine receptor agonists, e.g. dantrolene and use of benzodiazepines. The differential diagnosis of NMS comprises an extensive list of disorders presenting with fever and with muscle rigidity. Neuroleptics may be reintroduced in the majority of patients by using an atypical neuroleptic drug such as clozapine.

Adolescent↗
PubMed2000

Cell shrinkage is essential in lysophosphatidic acid signaling in Ehrlich ascites tumor cells.

The present study aimed at elucidating the initial intracellular lysophosphatidic acid (LPA)-induced signaling events, in order to investigate the sequence in which LPA affects the intracellular concentration of free, cytosolic Ca(2+), [Ca(2+)](i), ion channels, the F-actin cytoskeleton, cell volume and the Na(+)/H(+) exchanger. We found that stimulation of Ehrlich cells with LPA induced a transient, concentration-dependent increase in [Ca(2+)](i), which is due to Ca(2+) release from intracellular Ins(1,4,5)P(3)-sensitive stores as well as an influx of Ca(2+). The EC(50) values for LPA-induced Ca(2+) mobilization were estimated at 0.03 nm and 0.4 nm LPA in the presence and absence of extracellular Ca(2+), respectively. The LPA-induced increase in [Ca(2+)](i) resulted in (i) co-activation of Ca(2+)-activated, charybdotoxin (ChTX)-sensitive K(+) and niflumic acid-sensitive Cl(-) currents; (ii) a subsequent cell shrinkage and increased polymerization of F-actin, and (iii) activation of a Na(+)/H(+) exchange, resulting in a concentration-dependent intracellular alkalinization. The EC(50) value for the LPA-induced rate of alkalinization was estimated at 0. 37 nm LPA. When cell shrinkage was prevented, the LPA-induced activation of the Na(+)/H(+) exchanger was impaired. In conclusion, the initial signaling events induced by LPA involves activation of volume regulatory mechanisms.

Actins↗
PubMed2000

Human and mouse mitochondrial orthologs of bacterial ClpX.

We have determined the cDNA sequence and exon/intron structure of the human CLPX gene encoding a human ortholog of the E. coli ClpX chaperone and protease subunit. The CLPX gene comprises 14 exons and encodes a 633-amino acid-long precursor polypeptide. The polypeptide contains an N-terminal putative mitochondrial transit peptide, and expression of a full-length ClpX cDNA tagged at its C-terminus (Myc-His) shows that the polypeptide is transported into mitochondria. FISH analysis localized the CLPX gene to human Chromosome (Chr) 15q22.1-22.32. This localization was refined by radiation hybrid mapping placing the CLPX gene 4.6 cR distal to D15S159. Murine ClpX cDNA was sequenced, and the mouse Clpx locus was mapped to a position between 31 and 42 cM offset from the centromere on mouse Chr 9. Experimental observations indicate the presence of a pseudogene in the mouse genome and sequence variability between mouse ClpX cDNAs from different strains. Alignment of the human and mouse ClpX amino acid sequences with ClpX sequences from other organisms shows that they display the typical modular organization of domains with one AAA(+) domain common to a large group of ATPases and several other domains conserved in ClpX orthologs linked by non-conserved sequences. Notably, a C-4 zinc finger type motif is recognized in human and mouse ClpX. This motif of so far unknown function is present only in a subset of the known ClpX sequences.

ATPases Associated with Diverse Cellular Activitie↗
PubMed2000

Comparative study designs and what they show.

Normally an increase in lung deposition leads to an improved clinical effect. An increase in clinical effect should be substantial (two-fold or greater) in order to be detected even in carefully conducted clinical trials. Further studies are needed in order to define the best clinical study designs with which to detect differences between different inhalers.

Anti-Asthmatic Agents↗
PubMed2000

Hypotonic cell swelling induces translocation of the alpha isoform of cytosolic phospholipase A2 but not the gamma isoform in Ehrlich ascites tumor cells.

We demonstrate that two isoforms of the cytosolic phospholipase A2, cPLA2alpha and cPLA2gamma, are present in Ehrlich ascites tumor cells. Both enzymes are almost uniformly distributed throughout the cells under control conditions, as visualized by laser-scanning confocal microscopy. Stimulation by either hypotonic cell swelling or addition of the Ca2+ ionophore A23187 results in translocation of cPLA2alpha, but not cPLA2gamma, to the nucleus, where it forms hot-spot-like clusters. Our group previously showed that release of radioactively labeled arachidonic acid, incorporated into the phospholipids of Ehrlich cells, was immediately and transiently increased on hypotonic cell swelling [Thoroed, S.M., Lauritzen, L., Lambert, I.H., Hansen, H.S. & Hoffmann, E.K. (1997) J. Membr. Biol. 160, 47-58]. We now demonstrate that arachidonic acid is released from the nuclear fraction following hypotonic exposure. Stimulation of Ehrlich cells with A23187 also leads to an increase in arachidonic acid release from the nucleus. However, as hypotonic cell swelling is not accompanied by any detectable increase in intracellular concentration of free cytosolic Ca2+ ([Ca2+]i), stimulus-induced translocation of cPLA2alpha can also occur without elevation of [Ca2+]i. The stimulus-induced translocation of cPLA2alpha appears not to be prevented by inhibition of mitogen-activated protein (MAP) kinase activation, p38 MAP kinase, tyrosine kinases and protein kinase C, hence, phosphorylation is not crucial for the stimulus-induced translocation of cPLA2alpha. Disruption of F-actin did not affect the translocation process, thus, an intact F-actin cytoskeleton does not seem to be required for translocation of cPLA2alpha.

Animals↗
PubMed2000

Experimental infection of pigs with three dose levels of Trichuris suis.

The objective of the study was to follow the course of Trichuris suis infection in pigs given infective eggs at low (400 eggs), medium (4,000 eggs) and high inoculation dose (40,000 eggs), respectively. Interestingly, despite a 100-fold difference in dose level no significant difference was found in either blood parameters, total faecal egg excretion, fecundity or worm burdens at necropsy 12 weeks post inoculation. The highest and lowest median faecal egg output was found in the medium and high dose group, respectively. With increasing dose level, worm size, establishment and prevalence of T. suis positive pigs decreased while worms were dislocated aborally. In addition there was a highly significant correlation between female worm burden and faecal egg excretion.

Animals↗
PubMed2000

Prevalence of musculoskeletal symptoms among aluminium workers.

The aim of this study was to determine the prevalence of musculoskeletal symptoms (MSS) in workers in the aluminium industry, and to test the relationship with work by using the duration of employment as a measure of exposure. A total of 5654 workers (92%) answered a questionnaire. Operators, who were more exposed to physically demanding work, showed a greater incidence of MSS than did office workers. Among operators, the duration of employment was significantly correlated with MSS in nine out of ten areas of the body, when adjusted by multiple regression analyses for age, gender, height, weight, smoking and physical activity. Among office workers this relationship was weaker and was significant only for neck and lower back areas. The higher prevalence of MSS among operators and the association between their duration of employment and MSS suggests that a higher risk of MSS is related to the working environment.

Adolescent↗
PubMed2000

Dust in pig buildings.

It is well documented in the international scientific literature that airborne dust in pig houses can cause serious health problems for humans as well as for animals. Extensive research has been carried out in different countries during the last few decades to improve the scientific understanding of air quality issues related to intensive animal production. Research and review papers were presented at the international symposium on Dust Control in Animal Production Facilities, held in Denmark in 1999. Different techniques have been used in order to reduce dust burdens in pig confinement buildings, but up to date only the procedure of spraying oil or a mixture of oil and water has contributed to reducing the indoor dust concentrations significantly. This article summarizes the current level of understanding of dust issues in intensive animal production buildings, mainly on the basis of papers presented at the above-mentioned symposium.

Air Pollutants, Occupational↗
PubMed2000

Breath-synchronized nebulization diminishes the impact of patient-device interfaces (face mask or mouthpiece) on the inhaled mass of nebulized budesonide.

The choice of patient-device interface (face mask or mouthpiece) influences the inhaled mass and the lung deposition of nebulized drugs. The use of a mouthpiece has been shown to double the lung deposition compared with use of a face mask. We have determined the inhaled mass of budesonide using a jet nebulizer with mouthpiece in either a constant output or breath-synchronized mode in children. We have also determined the inhaled mass when the jet nebulizer is used with a nonsealing face mask in a constant output mode. The study was a 1-day, randomized, crossover, single-center study involving 158 asthmatic children (age range 5.1-15.7 years). Nebulized budesonide was administered in three single nominal doses of 1.0 mg by means of a jet nebulizer. The inhaled mass of budesonide was defined as the amount of drug deposited on filters positioned between the nebulizer and the mouthpiece or face mask. The mean inhaled mass of budesonide from different age groups ranged from 1 7.1% to 21.6% of the nominal dose with breath-synchronized nebulization with a mouthpiece. With constant output nebulization with a mouthpiece, the mean inhaled mass ranged from 8.9% to 12.2%, and with a nonsealed face mask the mean inhaled mass ranged from 5.0% to 6.9%. For children using jet nebulizers with mouthpiece, breath-synchronized nebulization appears to be superior to conventional constant output nebulization. The use of jet nebulizers with nonsealing face masks should be avoided.

Administration, Inhalation↗
PubMed1999

Localization of a human nucleoporin 155 gene (NUP155) to the 5p13 region and cloning of its cDNA.

Nucleoporins are the main components of nuclear pore complexes (NPCs) involved in nucleo-cytoplasmic transport. Starting with an expressed DNA fragment retrieved by exon trapping from pooled human BAC clones mapped to the short arm of chromosome 5, we identified a human nucleoporin cDNA sequence by PCR from a human testis cDNA library. The coding sequence showed high homology to that of the rat nucleoporin 155 (Nup155) cDNA. FISH analysis with the human BAC clone as probe localized the human NUP155 gene to chromosome band 5p13. Northern analysis showed that the human NUP155 gene was expressed at different levels in all tissues tested. Two species of transcripts were observed with estimated lengths of 5.4 and 4.7 kb, respectively, in concordance with the finding of two alternative polyadenylation sites in the cDNA. The genomic location of the human NUP155 gene suggests a possible role in the mental and developmental retardation associated with hemizygous deletions of the 5p13 region.

Amino Acid Sequence↗
PubMed1999

Chemical modification of lysine side chains of cyclodextrin glycosyltransferase from Thermoanaerobacter causes a shift from cyclodextrin glycosyltransferase to alpha-amylase specificity.

Cyclodextrin glycosyltransferases and alpha-amylases are two groups of enzymes with related secondary structures. However, cyclodextrin glycosyltransferases display transferase activities not present in alpha-amylases, probably derived from the existence of two more domains and different amino acid sequences. The hydrolytic activity of cyclodextrin glycosyltransferases is generally quite low, except for two cyclodextrin glycosyltransferases from termophiles. In this work, we have carried out the chemical modification (with acetic anhydride) of the amino groups of cyclodextrin glycosyltransferase from Thermoanaerobacter to assess their contributions to protein function. The acetylated cyclodextrin glycosyltransferase showed a significant reduction of its cyclization, coupling and disproportionation activities. Surprisingly, the hydrolytic (saccharifying) activity was slightly enhanced. These results suggest the participation of one or more lysine side chains in the interactions contributing to the transferase activity, either in any of the S11 subsites or in the acceptor binding site.

Acetic Anhydrides↗
PubMed1999

Mechanical stress induces release of ATP from Ehrlich ascites tumor cells.

The supernatant from a suspension of Ehrlich cells exposed to centrifugation at 700xg for 45 s induced a transient increase in the intracellular concentration of free, cytosolic Ca2+, [Ca2+]i, as well as activation of an outwardly rectifying whole-cell current when added to a suspension of non-stimulated cells. These effects were inhibited by suramin, a non-specific P2 receptor antagonist, and mimicked by ATP. Reversed phase HPLC analysis revealed that the supernatant from Ehrlich cells exposed to centrifugation contained 2. 6+/-0.2 microM ATP, and that the mechanical stress-induced release of ATP was inhibited by glibenclamide and verapamil, non-specific inhibitors of the cystic fibrosis transmembrane conductance regulator and P-glycoprotein, respectively. After trypan blue staining, less than 0.5% of the cells were unable to extrude the dye. Addition of extracellular ATP induced a suramin-sensitive, transient, concentration-dependent increase in [Ca2+]i, activation of an outwardly rectifying whole-cell current and a hyperpolarization of the plasma membrane. The ATP-induced hyperpolarization of the plasma membrane was strongly inhibited in the presence of charybdotoxin (ChTX), an inhibitor of several Ca2+-activated K+ channels, suggesting that stimulation of P2 receptors in Ehrlich cells evokes a Ca2+-activated K+ current. The relative potencies of several nucleotides (ATP, UTP, ADP, 2-MeSATP, alpha,beta-MeATP, bzATP) in eliciting an increase in [Ca2+]i, as well as the effect of repetitive addition of nucleotides were investigated. The results lead us to conclude that mechanical stimulation of Ehrlich cells leads to release of ATP, which in turn stimulates both P2Y1 and P2Y2 receptors, resulting in Ca2+ influx as well as release and activation of an outwardly rectifying whole-cell current.

Adenosine Triphosphate↗