PubMed Health⌕ Search

Biomedical subjects

M Grieshaber

Publications and source records attributed to M Grieshaber.

14 recordsLinked to original sources
PubMed2001

Binding of urate and caffeine to haemocyanin analysed by isothermal titration calorimetry.

Haemocyanin serves as an oxygen carrier in the haemolymph of decapod crustaceans. The oxygen-binding behaviour of the pigment is modulated by the two major anaerobic metabolites, l-lactate and urate. The binding of these two metabolites to haemocyanin has been investigated mainly indirectly by following the effector-induced changes in the oxygen-binding properties of the respiratory pigment. Only a few direct investigations of effector binding, employing ultracentrifugation techniques and equilibrium dialysis, have been carried out. No evidence for cooperative binding for either effector was detected using these methods. However, isothermal titration calorimetry (ITC) offers a useful tool to gain additional insight into the binding of effectors to these highly allosterically regulated macromolecules. By applying the ITC method to the fully oxygenated dodecameric haemocyanin of the lobster Homarus vulgaris, cooperativity in binding has been found for the urate analogue caffeine but not for urate itself: using urate and the urate analogue caffeine as ligands, two conformations of the oxygenated pigment were detected.

Allosteric Regulation↗
PubMed1998

[Diagnostic and therapeutic procedures by doctors for patients in a hypertensive crisis. An inquiry in 56 internal medicine clinics].

BACKGROUND AND OBJECTIVE: Despite official guidelines on the diagnosis and treatment of hypertensive crisis, the extent to which they are being followed in routine medical practice is unknown. This study was undertaken to discover how hospital doctors were handling cases of hypertensive crisis (HC). MATERIALS AND METHODS: Physicians were requested to participate in a multiple-choice questionnaire study, relating to the diagnosis of HC, any emergency diagnosis and choice of antihypertensive drugs, these questionnaires to be distributed among the medical staff. Ultimately 463 questionnaires (one per doctor) were sent out and 325 were completed (response rate of 70%). RESULTS: The most frequently mentioned blood pressure values characteristics for HC were > 200 systolic and > 120 diastolic. 160/90 was given most often as the therapeutic goal, which most doctors wanted to reach in an HC within 30 to 60 min. The calcium-antagonist nifedipine was the drug of first choice for almost all clinical presentations. Second was intravenously urapidil, an alpha-agonist. Nitroglycerin was named as first choice only for pulmonary oedema or myocardial infarction. In everyone of the stated conditions most doctors were eager to avoid using beta-blockers. As for the drug of first choice in associated myocardial infarction, 111 doctors named nifedipine, 28 wanted to avoid it and 45 considered it contraindicated. CONCLUSION: These data show a marked discrepancy between recommended guidelines and actual practice in the management of hypertensive crisis.

Acute Disease↗
PubMed1997

Sulphide oxidation and oxidative phosphorylation in the mitochondria of the lugworm

Oxygen consumption, ATP production and cytochrome c oxidase activity of isolated mitochondria from body-wall tissue of Arenicola marina were measured as a function of sulphide concentration, and the effect of inhibitors of the respiratory complexes on these processes was determined. Concentrations of sulphide between 6 and 9 µmol l-1 induced oxygen consumption with a respiratory control ratio of 1.7. Production of ATP was stimulated by the addition of sulphide, reaching a maximal value of 67 nmol min-1 mg-1 protein at a sulphide concentration of 8 µmol l-1. Under these conditions, 1 mole of ATP was formed per mole of sulphide consumed. Higher concentrations of sulphide led to a decrease in ATP production until complete inhibition occurred at approximately 50 µmol l-1. The production of ATP with malate and succinate was stimulated by approximately 15 % in the presence of 4 µmol l-1 sulphide, but decreased at sulphide concentrations higher than 15­20 µmol l-1. Cytochrome c oxidase was also inhibited by sulphide, showing half-maximal inhibition at 1.5 µmol l-1 sulphide. Sulphide-induced ATP production was inhibited by antimycin, cyanide and oligomycin but not by rotenone or salicylhydroxamic acid. The present data indicate that sulphide oxidation is coupled to oxidative phosphorylation solely by electron flow through cytochrome c oxidase, whereas the alternative oxidase does not serve as a coupling site. At sulphide concentrations higher than 20 µmol l-1, oxidation of sulphide serves mainly as a detoxification process rather than as a source of energy.

Journal Article↗
PubMed1996

Tissue swelling and intracellular pH in the CA1 region of anoxic rat hippocampus.

The fluorescent dye BCECF was used to simultaneously determine the intracellular pH (ratio 495 : 450 nm) and changes in relative tissue volume (fluorescence at the 450 nm isosbestic wavelength) in rat hippocampal slices. Anoxia in the presence of glucose caused tissue swelling and subsequent intracellular acidosis after a short and small transient alkaline peak. Reoxygenation reversed tissue swelling only partly and ended in persistent tissue swelling. The intracellular pH was initially further acidified before restoration to the normoxic intracellular pH occurred. Omitting glucose during anoxia caused similar but more marked changes of relative tissue volume. However, acidosis during anoxia was less marked and subsequently converted to alkalosis. Reoxygenation also caused initial acidification but the intracellular pH was not completely restored afterwards.

Acidosis↗
PubMed1996

Renal tubular damage: an extraintestinal manifestation of chronic inflammatory bowel disease.

OBJECTIVE: To investigate whether treatment of inflammatory bowel disease (IBD) with 5-aminosalicylate or sulphasalazine in IBD may induce renal tubular damage. DESIGN AND METHODS: The urinary enzymes beta-N-acetyl-D-glucosaminidase ( beta-NAG), dipeptidylpeptidase 4 (DPP4) and alanine aminopeptidase (AAP) were measured as markers of renal tubular damage in 104 consecutive patients with Crohn's disease and in 43 consecutive patients with ulcerative colitis (all with normal serum creatinine values). Control values were gained from 65 healthy persons. RESULTS: The normal values (mean +/- SD) for the urinary enzymes investigated (U/g creatinine in the urine) were: DPP4 4.5 +/- 2.2, beta-NAG 1.6 +/- 1.4, AAP 11.4 +/- 6.5. In 28% of the patients with ulcerative colitis elevated beta-NAG levels of more than the mean + 2 x SD were measured. This pathological enzymuria was nearly exclusively found in patients with active disease (CAI > 6): DPP4 15.6 +/- 25.3, beta-NAG 8.3 +/- 10.1, AAP 24.7 +/- 50.1 (all three enzymes were significantly elevated). The highest values were measured in patients with active ulcerative colitis before start of therapy. Nineteen per cent of the patients with Crohn's disease had elevated beta-NAG levels of more than the mean + 2 x SD. There was no significant difference in enzymuria between patients with active (CDAI > 150) and patients with inactive Crohn's disease (CDAI < or = 150). DPP4 and AAP were normal in both groups. A correlation between the enzymuria and the cumulative doses of 5-aminosalicylic acid, sulphasalazine or prednisolone could not be found. The courses of enzymuria in three patients who presented with the first severe manifestation of IBD are described. They were treated with either corticosteroids and 5-aminosalicylic acid or corticosteroids and sulphasalazine. Before onset of therapy, very high urine enzyme values were measured. They almost normalized in the course of successful medical therapy despite increasing cumulative doses of 5-aminosalicylic acid or sulphasalazine. CONCLUSIONS: Renal tubular damage can frequently be observed in IBD. Our results suggest that this is an extraintestinal manifestation of the disease and not a toxic side-effect of anti-inflammatory therapy using 5-aminosalicylic acid or sulphasalazine.

Adolescent↗
PubMed1987

Evidence for succinate production by reduction of fumarate during hypoxia in isolated adult rat heart cells.

It has been demonstrated that perfusion of myocardium with glutamic acid or tricarboxylic acid cycle intermediates during hypoxia or ischemia, improves cardiac function, increases ATP levels, and stimulates succinate production. In this study isolated adult rat heart cells were used to investigate the mechanism of anaerobic succinate formation and examine beneficial effects attributed to ATP generated by this pathway. Myocytes incubated for 60 min under hypoxic conditions showed a slight loss of ATP from an initial value of 21 +/- 1 nmol/mg protein, a decline of CP from 42 to 17 nmol/mg protein and a fourfold increase in lactic acid production to 1.8 +/- 0.2 mumol/mg protein/h. These metabolite contents were not altered by the addition of malate and 2-oxoglutarate to the incubation medium nor were differences in cell viability observed; however, succinate release was substantially accelerated to 241 +/- 53 nmol/mg protein. Incubation of cells with [U-14C]malate or [2-U-14C]oxoglutarate indicates that succinate is formed directly from malate but not from 2-oxoglutarate. Moreover, anaerobic succinate formation was rotenone sensitive. We conclude that malate reduction to succinate occurs via the reverse action of succinate dehydrogenase in a coupled reaction where NADH is oxidized (and FAD reduced) and ADP is phosphorylated. Furthermore, by transaminating with aspartate to produce oxaloacetate, 2-oxoglutarate stimulates cytosolic malic dehydrogenase activity, whereby malate is formed and NADH is oxidized. In the form of malate, reducing equivalents and substrate are transported into the mitochondria where they are utilized for succinate synthesis.

Adenosine Triphosphate↗
PubMed1983

The pre-employment interview in the hospital pharmacy.

The personal interview is generally used as a pre-employment screening technique by hospital pharmacy directors. The effectiveness of this interaction can be maximized by explicitly identifying the objectives to be accomplished by the interview, carefully preparing a collection of questions through which the objectives are achieved, and creating an environment which promotes a free-flowing exchange of information. Some sample objectives and questions are offered. Different types of questions and their appropriate use are presented. Thoroughly planning and carefully conducting the pre-employment interview will optimize the time spent in this valuable activity.

Interviews as Topic↗
PubMed1976

Anaerobic metabolism of the common cockle, Cardium edule. II. Partial purification and properties of lactate dehydrogenase and octopine dehydrogenase. A comparative study.

1. Octopine dehydrogenase and lactate dehydrogenase were purified 190-fold and 10-fold respectively from the adductor muscle of the marine bivalve Cardium edule by gel filtration on Sephadex G-100 and chromatography on DEAE-Sephadex A-50. 2. Lactate dehydrogenase was capable to convert D- and L-lactate, had a molecular weight of about 70 000 and 280 000 daltons, exhibits no distinct pH optimum and was not inhibited by lactate. The enzyme showed apparent Km values of 0.16 mM for pyruvate and 16 mM and 48 mM for D- and L-lactate respectively. 3. In comparison to the purified enzymes from other species, octopine dehydrogenase from Cardium edule showed similar biochemical properties : pH optima of 6.8 and 8.7 respectively, Km values of 0.9 mM (for pyruvate) and 2.0 mM (for arginine), a molecular weight of 37 000 daltons and inhibition by octopine. Electrophoretic studies on standard polyacrylamide gels showed five isoenzymes. 4. The biochemical properties of both dehydrogenases are compared to the conditions in vivo of these animals and the biological role of the octopine dehydrogenase is discussed.

Amino Acid Oxidoreductases↗
PubMedDate not supplied

On the evolution of an oligocephalic enzyme. glutamine-chorismate-amidotransferase-free anthranilate phosphoribosyltransferases from mutant strains of Salmonella typhimurium.

(1) A procedure has been described for the purification of two glutamine-chorismate-amidotransferase-free anthranilate phosphoribosyltransferases from mutant strains TAX6trpR782 and trpAB1653trpR782 of Salmonella typhimurium. (2) The native enzymes tend to aggregate forming polymers of molecular weights 333,000 in the case of TAXtrpR782 and 220,000 and larger than 1X10(6) in the case of trpAB1653trpR782. In the presence of sodium dodecyl sulfate the polymer of trpAB1653trpR782 dissociates into a single component with molecular weight of 72,000. (3) In contrast to anthranilate phosphoribosyltransferase of the wild type component II, the glutamine-chorismate-amidotransferase-free proteins do not complex with component I. They do however show catalytical similarities with the wild type with respect to anthranilate phosphoribosyltransferase activity.

Anthranilate Phosphoribosyltransferase↗