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Biomedical subjects

P Mayr

Publications and source records attributed to P Mayr.

At least 19 recordsLinked to original sources
PubMed2005

Glycaemic control in type II diabetic tube-fed patients with a new enteral formula low in carbohydrates and high in monounsaturated fatty acids: a randomised controlled trial.

OBJECTIVES: To investigate the effects of long-term treatment with a new enteral formula low in carbohydrates and high in monounsaturated fatty acids (MUFAs), in comparison with a standard formula, on glycaemic control in tube-fed type II diabetic patients. DESIGN: Randomised, double-blind, controlled, multi-centre trial. SETTING: Early rehabilitation centres, primary care and nursing facilities. SUBJECTS: A total of 78 patients with insulin-treated type II diabetes with HbA(1C) > or =7.0% and/or fasting blood glucose >6.66 mmol/l, who required enteral tube feeding due to neurological dysphagia. INTERVENTIONS: Patients received 113 kJ (27 kcal)/kg of body weight of either test feed or an isoenergetic, isonitrogenous enteral formula (control) for 12 weeks. Glycaemic control (total daily insulin dosage (IU), fasting blood glucose, and HbA(1C)) and gastrointestinal tolerance were monitored daily. RESULTS: After 12 weeks, median values for changes from baseline were as follows (test group vs control group, 'data as available' analysis): total daily IUs -6.0 vs 0.0 (P=0.0024), fasting blood glucose (mmol/l) -1.59 vs -0.08 (P=0.0068); HbA(1C) (%) -0.8 vs 0.0 (P=0.0016). Both formulas were tolerated comparably. CONCLUSIONS: This study indicates that in tube-fed insulin-treated type II diabetic patients, the new low-carbohydrate, high MUFA formula results in a more effective glycaemic control than the standard diet, while being comparable in safety.

Adult↗
PubMed2002

Modification of diamond single crystals by chromium ion implantation with sacrificial layers.

Single-crystal diamond surfaces were implanted with chromium ions. Ion energies chosen were 120 and 180 keV. Ion doses of 1x10(17) cm(-2) were applied at a substrate temperature of 750 degrees C. Reduced lattice damage could be obtained by deposition of a titanium sacrificial layer with a thickness of 10 and 50 nm before implantation. Depth profiles of the elemental binding states were taken by photoelectron spectroscopy. The effect of the sacrificial layer thickness on diamond lattice damage was investigated by infrared spectroscopy.

Journal Article↗
PubMed2002

A randomized placebo-controlled trial of simethicone and cisapride for the treatment of patients with functional dyspepsia.

AIM: To compare the efficacy of simethicone with placebo and the prokinetic cisapride in patients with functional dyspepsia. METHODS: One hundred and eighty-five patients with functional dyspepsia were randomized and treated in a double-dummy technique with simethicone (105 mg t.d.s.), cisapride (10 mg t.d.s.) or placebo (t.d.s.). The primary outcome measure was the O'Brien global measure of the patients' rating of 10 upper gastrointestinal symptoms (graded as absent = 0, moderate = 1, severe = 2 or very severe = 3). Outcome measures were assessed at baseline and after 2, 4 and 8 weeks of treatment (intention-to-treat). RESULTS: At 2, 4 and 8 weeks, treatment with simethicone and cisapride yielded significantly (all P values < 0.0001) better improvement of symptoms compared to placebo. Simethicone was significantly better than cisapride after 2 weeks (P = 0.0007), but the differences were not statistically significant after 4 and 8 weeks. Patients treated with simethicone judged the efficacy of their treatment as very good in 46% of cases, compared to 15% and 16% receiving cisapride and placebo, respectively. CONCLUSIONS: Simethicone and cisapride were significantly better than placebo for symptom control in patients with functional dyspepsia after 2, 4 and 8 weeks of treatment. Simethicone was also superior to the prokinetic cisapride in the first 2 weeks of treatment.

Adult↗
PubMed2001

Transient-state and steady-state kinetic studies of the mechanism of NADH-dependent aldehyde reduction catalyzed by xylose reductase from the yeast Candida tenuis.

Microbial xylose reductase, a representative aldo-keto reductase of primary sugar metabolism, catalyzes the NAD(P)H-dependent reduction of D-xylose with a turnover number approximately 100 times that of human aldose reductase for the same reaction. To determine the mechanistic basis for that physiologically relevant difference and pinpoint features that are unique to the microbial enzyme among other aldo/keto reductases, we carried out stopped-flow studies with wild-type xylose reductase from the yeast Candida tenuis. Analysis of transient kinetic data for binding of NAD(+) and NADH, and reduction of D-xylose and oxidation of xylitol at pH 7.0 and 25 degrees C provided estimates of rate constants for the following mechanism: E + NADH right arrow over left arrow E.NADH right arrow over left arrow E.NADH + D-xylose right arrow over left arrow E.NADH.D-xylose right arrow over left arrow E.NAD(+).xylitol right arrow over left arrow E.NAD(+) right arrow over left arrow E.NAD(+) right arrow over left arrow E + NAD(+). The net rate constant of dissociation of NAD(+) is approximately 90% rate limiting for k(cat) of D-xylose reduction. It is controlled by the conformational change which precedes nucleotide release and whose rate constant of 40 s(-)(1) is 200 times that of completely rate-limiting E.NADP(+) --> E.NADP(+) step in aldehyde reduction catalyzed by human aldose reductase [Grimshaw, C. E., et al. (1995) Biochemistry 34, 14356-14365]. Hydride transfer from NADH occurs with a rate constant of approximately 170 s(-1). In reverse reaction, the E.NADH --> E.NADH step takes place with a rate constant of 15 s(-1), and the rate constant of ternary-complex interconversion (3.8 s(-1)) largely determines xylitol turnover (0.9 s(-1)). The bound-state equilibrium constant for C. tenuis xylose reductase is estimated to be approximately 45 (=170/3.8), thus greatly favoring aldehyde reduction. Formation of productive complexes, E.NAD(+) and E.NADH, leads to a 7- and 9-fold decrease of dissociation constants of initial binary complexes, respectively, demonstrating that 12-fold differential binding of NADH (K(i) = 16 microM) vs NAD(+) (K(i) = 195 microM) chiefly reflects difference in stabilities of E.NADH and E.NAD(+). Primary deuterium isotope effects on k(cat) and k(cat)/K(xylose) were, respectively, 1.55 +/- 0.09 and 2.09 +/- 0.31 in H(2)O, and 1.26 +/- 0.06 and 1.58 +/- 0.17 in D(2)O. No deuterium solvent isotope effect on k(cat)/K(xylose) was observed. When deuteration of coenzyme selectively slowed the hydride transfer step, (D)()2(O)(k(cat)/K(xylose)) was inverse (0.89 +/- 0.14). The isotope effect data suggest a chemical mechanism of carbonyl reduction by xylose reductase in which transfer of hydride ion is a partially rate-limiting step and precedes the proton-transfer step.

Aldehyde Reductase↗
PubMed2001

Structural and functional properties of aldose xylose reductase from the D-xylose-metabolizing yeast Candida tenuis.

The primary structure of the aldose xylose reductase from Candida tenuis (CtAR) is shown to be 39% identical to that of human aldose reductase (hAR). The catalytic tetrad of hAR is completely conserved in CtAR (Tyr51, Lys80, Asp46, His113). The amino acid residues involved in binding of NADPH by hAR (D.K. Wilson, et al., Science 257 (1992) 81-84) are 64% identical in CtAR. Like hAR the yeast enzyme is specific for transferring the 4-pro-R hydrogen of the coenzyme. These properties suggest that CtAR is a member of the aldo/keto reductase superfamily. Unlike hAR the enzyme from C. tenuis has a dual coenzyme specificity and shows similar specificity constants for NADPH and NADH. It binds NADP(+) approximately 250 times less tightly than hAR. Typical turnover numbers for aldehyde reduction by CtAR (15-20 s(-1)) are up to 100-fold higher than corresponding values for hAR, probably reflecting an overall faster dissociation of NAD(P)(+) in the reaction catalyzed by the yeast enzyme.

Aldehyde Reductase↗
PubMed2001

Probing protein stabilization by glycerol using electrospray mass spectrometry.

This study shows that electrospray ionization mass spectrometry (ESI-MS), combined with a heated turbo ion-spray interface, allows monitoring protein stabilization by glycerol in solution. Measurements obtained with the two proteins lysozyme and cytochrome c are presented. The observed mass-to-charge (m/z) distributions reveal the stabilizing effect of the additive on the protein conformations against temperature and acid-induced unfolding, as well as against denaturation by acetonitrile. The data obtained with lysozyme allow detection of minor conformational changes upon glycerol addition to the native protein, and suggest that the protein structure in the presence of the additive is slightly compressed compared with its state in water. This result corroborates previous evidence obtained by nuclear magnetic resonance. It is also shown that analysis of the m/z distributions obtained by ESI-MS can lead to detection of partially folded and partially populated states in protein samples.

Animals↗
PubMed2000

D-Xylose metabolism by Candida intermedia: isolation and characterisation of two forms of aldose reductase with different coenzyme specificities.

To study individual enzyme components responsible for the initial step of D-xylose utilisation by the yeast Candida intermedia, a two-step protocol has been developed that enables clear-cut separation and isolation of two structurally similar but functionally different aldose reductases (ALRs) in high yield. In the first step, the yeast cell extract is fractionated efficiently by biomimetic chromatography using the dye HE-3B (reactive Red 120) as pseudoaffinity ligand coupled to Sepharose CL-4B. In the second step, optimised high-resolution anion-exchange chromatography using Mono Q yields purified ALR1 and ALR2 in overall yields of 63 and 62%, respectively. ALR1 is strictly specific for NADPH (2.4 x 10(5) M(-1) s(-1)) whereas ALR2 utilises NADH and NADPH with similar specificity constants of approximately 2-4 x 10(5) M(-1) s(-1). Both enzymes are dimers with a subunit molecular mass of 36000 but they differ in pI and the number of titratable sulphydryl groups in the native protein. The chromatographic procedure identifies microheterogeneity in recombinant aldose reductase from Candida tenuis overexpressed in Escherichia coli.

Aldehyde Reductase↗
PubMed1999

Binding energy and specificity in the catalytic mechanism of yeast aldose reductases.

Derivatives of d-xylose and d-glucose, in which the hydroxy groups at C-5, and C-5 and C-6 were replaced by fluorine, hydrogen and azide, were synthesized and used as substrates of the NAD(P)H-dependent aldehyde reduction catalysed by aldose reductases isolated from the yeasts Candida tenuis, C. intermedia and Cryptococcus flavus. Steady-state kinetic analysis showed that, in comparison with the parent aldoses, the derivatives were reduced with up to 3000-fold increased catalytic efficiencies (k(cat)/K(m)), reflecting apparent substrate binding constants (K(m)) decreased to as little as 1/250 and, for d-glucose derivatives, up to 5.5-fold increased maximum initial rates (k(cat)). The effects on K(m) mirror the relative proportion of free aldehyde that is available in aqueous solution for binding to the binary complex enzyme-NAD(P)H. The effects on k(cat) reflect non-productive binding of the pyranose ring of sugars; this occurs preferentially with the NADPH-dependent enzymes. No transition-state stabilization energy seems to be derived from hydrogen-bonding interactions between enzyme-NAD(P)H and positions C-5 and C-6 of the aldose. In contrast, unfavourable interactions with the C-6 group are used together with non-productive binding to bring about specificity (6-10 kJ/mol) in a series of d-aldoses and to prevent the reaction with poor substrates such as d-glucose. Azide introduced at C-5 or C-6 destabilizes the transition state of reduction of the corresponding hydrogen-substituted aldoses by approx. 4-9 kJ/mol. The total transition state stabilization energy derived from hydrogen bonds between hydroxy groups of the substrate and enzyme-NAD(P)H is similar for all yeast aldose reductases (yALRs), at approx. 12-17 kJ/mol. Three out of four yALRs manage on only hydrophobic enzyme-substrate interactions to achieve optimal k(cat), whereas the NAD(P)H-dependent enzyme from C. intermedia requires additional, probably hydrogen-bonding, interactions with the substrate for efficient turnover.

Aldehyde Reductase↗
PubMed1999

DNA-binding activity of the transcription factor upstream stimulatory factor 1 (USF-1) is regulated by cyclin-dependent phosphorylation.

The ubiquitous transcription factor upstream stimulatory factor (USF) 1 is a member of the bzHLH (leucine zipper-basic-helix-loop-helix) family, which is structurally related to the Myc family of proteins. It plays a role in the regulation of many genes, including the cyclin B1 gene, which is active during the G2/M and M phases of the cell cycle and may also play a role in the regulation of cellular proliferation. We show that the affinity of recombinant USF-1 for DNA is greatly increased by treatment with active cyclin A2-p34(cdc2) or cyclin B1-p34(cdc2) complexes and that its interaction with DNA is dependent on p34(cdc2)-mediated phosphorylation. We have localized the phosphorylation site(s) to a region that lies outside the minimal DNA-binding domain but overlaps with the previously identified USF-specific region. Deletion studies of USF-1 suggest that amino acids 143-197 regulate DNA-binding activity in a phosphorylation-dependent manner.

Animals↗
PubMed1999

Randomised double-blind comparison of simethicone with cisapride in functional dyspepsia.

AIM: To compare the efficacy of simethicone with cisapride in patients with functional (non-ulcer) dyspepsia. METHODS: After standardized diagnostic work-up and at least 6-days wash-out of medication, 177 patients with functional dyspepsia were enrolled; 173 of them (age 19-71 years) were randomized and treated using a double-dummy technique with simethicone (84 mg t.d.s.) or cisapride (10 mg t.d.s.). At baseline and after 2 and 4 weeks, the intensity of the symptoms was scored from 0 (absent) to 3 (severe) using a standardized symptom questionnaire. Efficacy of the treatment was judged by the patients as 'very good', 'good', 'moderate' or 'no effect'. RESULTS: A total of 166 patients completed the trial. After 2 and 4 weeks, 34% and 46% (respectively), of the patients treated with simethicone judged the improvement in symptoms to be excellent compared to 13% and 22% (respectively) of patients treated with cisapride (P < 0.01). After 2 weeks the difference in the improvement in the global symptom score was significantly better (Delta30.7%, P < 0.001) for simethicone than for cisapride, while this difference failed statistical significance after 4 weeks (Delta10.2%, P=0.11). CONCLUSIONS: In patients with functional dyspepsia, simethicone relieves symptoms during the first 2 weeks of treatment significantly better than cisapride.

Cisapride↗
PubMed1996

Evaluation of a novel stable whole blood quality control material for lymphocyte subset analysis: results from the UK NEQAS immune monitoring scheme.

The UK NEQAS immune Monitoring Scheme (UK NEQAS) evaluates the performance of laboratories routinely performing T-lymphocyte subset analysis on HIV-infected individuals. The scheme originally issued fresh whole blood, but a significant problem was that of analyte stability, especially 36 h postphlebotomy. To circumvent this problem, we have developed a novel stabilisation procedure that ensures retention of leucocyte light scatter and immunological staining characteristics for up to 300 days. In addition, the stabilised whole blood preparation is fully compatible with flow cytometer technology, incorporating either whole blood lysis or "no wash, no lyse" techniques. The ranges of interlaboratory coefficient of variation for the stabilised material are now tighter than those previously obtained with fresh whole blood. Development of this novel material has enabled overseas laboratories to participate in the UK NEQAS immune Monitoring Scheme and could in the future lead to the production of reference and/or calibration reagents for leucocyte immunophenotyping.

B-Lymphocytes↗
PubMed1990

[Inhibition of spontaneous uterine contractions by magnesium. Magnesium tocolysis].

A state of magnesium deficiency has been established in the population of highly industrialized countries in the last few years. This results among other disturbancies, in increasing prematurity. Therefore the tocolytic activity of magnesium was investigated in 29 uterine strips, which were obtained during cesarean section. A highly significant (p less than 0.001) reduction of the uterine activity from 100 to 0 (0-21), 0 (0-0) and 0 (0-0) (median, 20th and 80th percentile) 10, 20 and 60 min after the application of magnesium was observed.

Culture Techniques↗
PubMed1989

[Severe bacterial infections in gynecology and obstetrics].

Within a 3-years period the presence of nosocomial bacteriaemias was analyzed retrospectively among 13.878 hospitalized patients. The incidence was 0.050%. Antibiotic prophylaxis and the operative technique play an important role in achieving a low incidence of morbidity due to infection. The management of a severe infection includes antibiotic therapy according to culture sensitivity and intensive care.

Ampicillin↗
PubMed1989

[Enamel and dentin under the ultrasonic microscope].

Ultrasonic reflection scanning microscopy is a new method for imaging the known structures of dental hard tissues on the basis of a simple specimen preparation. The specimens are scanned in a physiologic humid environment. Particularly high-contrast images are obtained from enamel tufts and lamellae, dentin tubules and interglobular dentin.

Dental Enamel↗
PubMed1988

[On the problem of the cardiotoxicity of epirubicin-cisplatin].

Cardiotoxicity is supposed to be the most important limiting factor in chemotherapy with anthracycline derivatives. The left ventricular ejection fraction was measured several times by means of radionuclid - scintigraphy in 24 patients treated with epirubicin - cisplatinum. Pathologic values have been found only in 3 patients, but no correlation with age, cumulative dose or dose/m2 of body surface could be demonstrated.

Antineoplastic Combined Chemotherapy Protocols↗