PubMed Health⌕ Search

Biomedical subjects

P Maurer

Publications and source records attributed to P Maurer.

At least 19 recordsLinked to original sources
PubMed1992

High-affinity and low-affinity calcium binding and stability of the multidomain extracellular 40-kDa basement membrane glycoprotein (BM-40/SPARC/osteonectin).

Reversible binding of calcium ions to a single high-affinity binding site in the 40-kDa basement membrane protein (BM-40) caused a 33% increase of alpha-helicity, an about 60% change in intrinsic fluorescence and a dramatic increase of the rate of cleavage by alpha-chymotrypsin. All these effects exhibited identical dependencies on calcium concentration from which a dissociation constant Kd = 0.6 microM was determined. Calcium release was accompanied by an increase of the frictional ratio in solution but not by denaturation which occurred at about equal guanidine.HCl concentration for both calcium-saturated and calcium-depleted protein (midpoint 1.5 M). The cleavage sites for alpha-chymotrypsin are located in or near to the EF-hand domain IV of calcium-depleted BM-40 (also known as SPARC, i.e. secreted protein acidic and rich in cysteine, and osteonectin). These and other data indicate that binding occurs in the EF-hand domain from which a large conformational change is transmitted. Low-affinity calcium-binding sites in the N-terminal glutamic-acid-rich domain I of BM-40 were identified by human leukocyte elastase which was found to cleave very specifically in the middle of this domain. From the increase of cleavage rate with increasing calcium concentration a Kd greater than or equal to 10 mM was estimated. It is suggested that variations of calcium levels in the extracellular space in this range may regulate functions of BM-40 such as collagen binding and that high-affinity binding is important for stabilization, folding and secretion during biosynthesis.

Amino Acid Sequence↗
PubMed1991

Substrate specificity and stereoselectivity of horse liver alcohol dehydrogenase. Kinetic evaluation of binding and activation parameters controlling the catalytic cycles of unbranched, acyclic secondary alcohols and ketones as substrates of the native and active-site-specific Co(II)-substituted enzyme.

1. The steady-state parameters kcat and Km and the rate constants of hydride transfer for the substrates isopropanol/acetone; (S)-2-butanol, (R)-2-butanol/2-butanone; (S)-2-pentanol, (R)-2-pentanol/2-pentanone; 3-pentanol/3-pentanone; (S)-2-octanol and (R)-2-octanol have been determined for the native Zn(II)-containing horse-liver alcohol dehydrogenase (LADH) and the specific active-site-substituted Co(II)LADH. 2. A combined evaluation of steady-state kinetic data and rate constants obtained from stopped-flow measurements, allowed the determination of all rate constants of the following ordered bi-bi mechanism: E in equilibrium E.NAD in equilibrium E.NAD.R1R2 CHOH in equilibrium E.NADH.R1R2CO in equilibrium E.NADH in equilibrium E. 3. On the basis of the different substrate specificities of LADH and yeast alcohol dehydrogenase (YADH), a procedure has been developed to evaluate the enantiomeric product composition of ketone reductions. 2-Butanone and 2-pentanone reductions revealed (S)-2-butanol (86%) and (S)-2-pentanol (95%) as the major products. 4. The observed enantioselectivity implies the existence of two productive ternary complexes; E.NADH.(pro-S) 2-butanone and E.NADH.(pro-R) 2-butanone. All rate constants describing the kinetic pathways of the system (S)-2-butanol, (R)-2-butanol/2-butanone have been determined. These data have been used to estimate the expected enantiomer product composition of 2-butanone reductions using apparent kcat/Km values for the two different ternary-complex configurations of 2-butanone. Additionally, these data have been used for computer simulations of the corresponding reaction cycles. Calculated, simulated and experimental data were found to be in good agreement. Thus, the system (S)-2-butanol, (R)-2-butanol/2-butanone is the first example of a LADH-catalyzed reaction for which the stereochemical course could be described in terms of rate constants of the underlying mechanism. 5. The effects of Co(II) substitution on the different steps of the kinetic pathway have been investigated. The free energy of activation is higher for alcohol oxidation and lower for ketone reduction when catalyzed by Co(II)LADH in comparison to Zn(II)LADH. However, the free energies of binding are affected by metal substitution in such a way that the enantioselectivity of ketone reduction is not significantly changed by the substitution of Co(II) for Zn(II). 6. Evaluation of the data shows that substrate specificity and stereoselectivity result from combination of the free energies of binding and activation, with differences in binding energies as the dominating factors. In this regard, the interactions of substrate molecules with the protein moiety are dominant over the interactions with the catalytic metal ion.

Alcohol Dehydrogenase↗
PubMed1991

Risk factors for adverse drug reactions communication of the CHDM.

In the CHDM (Comprehensive Hospital Drug Monitoring for Adverse Drug Reactions, Bern/St. Gallen), the data of the 34,838 computer registered patient admissions 1974-1988 were available for evaluation. We summarize the results of three different studies: 1. A multivariate analysis of the risk factors to developed an ADR during hospital stay, mainly the number of drugs, age, sex and renal function. 2. The occurrence rate of hyperkalemia under the treatment with diurectics, mainly potassium (K+)-losing with K+ substitution compared to the combination of K(+)-sparing with K(+)-losing preparations. 3. The occurrence-rate of exanthema in relation to amino-penicillin preparations an allopurinol. The results are presented in the communication. (Tab 7, Fig. 1, Ref. 15). Ref. 15.).

Adverse Drug Reaction Reporting Systems↗
PubMed1990

[Hyperkalemia with potassium-sparing and potassium-losing diuretics. Results from the Comprehensive Hospital Drug Monitoring Bern (CHDM)].

Of 5047 in-patients in the Division of Internal Medicine, Zieglerspital Bern (regional/teaching hospital), admitted from 1982 to 1985, 2412 were treated with at least one diuretic. The hospital records of these patients were reviewed with regard in particular to serum potassium and creatinine values as well as potassium supplementation. On the basis of this evaluation the patients were assigned to 6 different treatment groups and the relative occurrence rate of hyperkalemia probably related to drug treatment was determined. Of the 590 patients treated with only potassium losing diuretics, none was found to show a hyperkalemia event; of the 742 patients on potassium losing diuretics and potassium supplementation, 27 (3.6%) developed hyperkalemia. In the 439 patients under combined diuretics (potassium sparing with potassium losing) without potassium substitution, 76 (17.3%), and in the 381 under combined diuretics with potassium substitution 24 (6.3%), developed hyperkalemia. The further groups of patients are also described. Renal function was estimated by the formula of Cockcroft and Gault. Reduced renal function is a significant risk-factor for hyperkalemic events under combined diuretics. All hyperkalemic events were within a serum potassium range of 5.1-7.0 mmol/l.

Creatinine↗
PubMed1990

Risk of acute upper gastrointestinal bleeding in patients with ulcerative disease and treatment with non-steroidal anti-inflammatory drugs (NSAIDs). Results from the Comprehensive Hospital Drug Monitoring Berne (CHDM).

The hospital prevalence rate for upper gastrointestinal ulcerative disease in 28,531 inpatients consecutively admitted in two teaching hospitals in the Comprehensive Hospital Drug Monitoring (CHDM) in Berne, from 1974 to 1985, was 2.2% (1.8% for gastric or duodenal ulcer, and 0.4% for erosive gastritis). This was based on the evaluation of 634 patients after exclusion of the subgroup of patients with hepatic cirrhosis or upper gastrointestinal neoplasia. After exclusion of patients on anticoagulant therapy (n = 73), 561 (= 100%) patients could be further studied. Of them, 33.3% (n = 187) were found to have been exposed to non-steroidal anti-inflammatory drugs (NSAIDs), including aspirin, within 21 days prior to confirmation of the diagnosis. The observed relative risk (RR) of developing a substantial acute upper gastrointestinal bleeding (Hb less than 10 g/100 ml for men, and less than 9 g/100 ml for women, or a decrease in Hb of more than 25%) was 1.61 when patients exposed to NSAIDs (n = 187) were compared to patients not exposed to those drugs (n = 374). Although there was no significant sex difference overall, the RR for gastrointestinal bleeding differed considerably in the various age-groups; it was elevated in men under 40 years (RR = 2.86) and in women over 60 years of age (RR = 1.89), as compared to the mean RR of 1.61.

Adult↗
PubMed1990

Mastocytosis and atopy: a study of 33 patients with urticaria pigmentosa.

Thirty-three patients with histologically verified urticaria pigmentosa were studied for coexisting atopic disease by means of history, skin prick testing with five common inhalants and serological investigation for total IgE and specific IgE antibodies to five common inhalants. The prevalence of atopy in urticaria pigmentosa was similar to that observed in the normal Swiss population, both on the basis of history (7/33 = 21%) and of positive skin prick tests to common inhalants (12/33 = 36%). However, total serum IgE levels were significantly lower (geometric mean value 16.8 kU/l) than in a control group of 52 Swiss blood donors of comparable age and sex distribution (geometric mean value 43.0 kU/l, t = 2.93, P less than 0.005). Specific IgE antibodies to common inhalants were also observed less frequently in urticaria pigmentosa patients than in controls, although this difference was not statistically significant. Low total and specific IgE values in patients with urticaria pigmentosa may be explained by increased absorption of circulating IgE to abundant tissue mast cells.

Adolescent↗
PubMed1989

Effects of general anesthetics on current flow across membranes in guinea pig myocytes.

Myocytes were isolated from adult guinea pig ventricles. Whole cell, tight-seal recording was employed to investigate the electrical properties of the junctional (nexal membrane) and nonjunctional membrane (sarcolemma) under the influence of n-alkanols (heptanol, octanol) and halothane. Studies of cell pairs with a double voltage-clamp approach showed that these agents give rise to a reversible electrical uncoupling. Examination of single myocytes with a single voltage-clamp method showed that these substances modify several sarcolemmal current systems. The slope conductance was reduced over the entire voltage range examined (-90 to +50 mV). The Ca2+ inward current (Isi) showed a decreased amplitude and an accelerated inactivation. The repriming of Isi remained unchanged. The steady-state inactivation of Isi was shifted by 2-3 mV toward more negative potentials. Optical measurements demonstrated an increase in sarcomere spacing at rest and a decrease during peak systolic shortening. The results suggest that n-alkanols and halothane exert their effects on membrane currents via incorporation into the lipid bilayer.

1-Octanol↗
PubMed1988

Action potential transfer in cell pairs isolated from adult rat and guinea pig ventricles.

An enzymatic procedure was used to obtain ventricular cells from adult rat and guinea pig hearts. Isolated pairs of cells were selected to study the action potential transfer from cell to cell and determine the resistance of the nexal membrane, rn. For this purpose, each cell of a cell pair was connected to a patch pipette so as to enable whole-cell, tight-seal recording. Normal impulse transmission was observed when rn ranged from 5-265 M omega. In these cases, the action potential in both cells occurred virtually simultaneously. An occasional failure in action potential transfer was seen in cell pairs whose rn had increased to 155-375 M omega. In these cases, the impulse transfer across the nexal membrane occurred with considerable delay. Impulse transfer was completely blocked once rn was larger than 780 M omega. Assuming a single connexon conductance of 100 pS, this would mean that more than 13 connexons are necessary to allow impulse transfer from cell to cell. Two single myocytes, gently pushed together, neither showed electrotonic interaction nor impulse transfer, thus rendering unlikely the possibility of an ephaptic signal transmission.

Action Potentials↗
PubMed1987

Cell-to-cell coupling studied in isolated ventricular cell pairs.

Cell pairs isolated from adult rat and guinea pig ventricles were used to study the electrical properties of the nexal membrane. Each cell of a pair was connected to a voltage-clamp system so as to enable whole-cell, tight-seal recording. The current-voltage relationship of the nexal membrane was found to be linear, revealing a resistance rn of 2-4 M omega. rn was insensitive to the sarcolemmal membrane potential (range: -90 to +30 mV), and exerted no time-dependent gating behavior (range: 0.1 to 10 s). Lowering pHi yielded a small increase in rn. Vigorous elevations in [Ca2+]i gave rise to an increase in rn which was associated with a cell shortening. Uncoupling caused by aliphatic alcohols or halothane did not produce cell shortening. Cell pairs were also used to study action potential transfer.

Action Potentials↗
PubMed1987

Autoantibodies of various specificities encoded by genes from the VH J558 family bind to foreign antigens and share idiotopes of antibodies specific for self and foreign antigens.

We examined the binding to foreign antigens and the expression of crossreactive idiotypes by a panel of 20 murine monoclonal autoantibodies encoded by V genes from the VH J558 family. 9 of 20 antibodies bound to foreign antigens such as bacterial polysaccharides, poly(Glu50, Tyr50), poly(Glu54,Lys37,Phe9), arsonate, and lysozyme, known to interact with antibodies encoded by genes from the VH J558 family. A high proportion of our panel of autoantibodies expressed crossreactive idiotypes originally borne by monoclonal rheumatoid factors, anti-Sm, and anti-DNA antibodies, all encoded by V genes from the VH J558 family. Some of these VH J558+ autoantibodies shared crossreactive idiotypes with VH J558+ antibodies directed against foreign antigens such as influenza virus hemagglutinin, poly(Glu60,Ala30,Tyr10), arsonate, and dextran. The implications of these findings are discussed with respect to the process of activation of self-reactive clones.

Animals↗
PubMed1987

Cell pairs isolated from adult guinea pig and rat hearts: effects of [Ca2+]i on nexal membrane resistance.

Cell pairs isolated from adult rat and guinea pig ventricles were used to study the resistance of the nexal membrane, rn. Each cell of a cell pair was connected to a voltage-clamp circuit to obtain simultaneous whole-cell, tight-seal recordings. With this technique, rn was determined under experimental conditions aimed at primarily modifying [Ca2+]i. Moderate changes in [Ca2+]i (produced by trains of depolarizing voltage-clamp pulses activating the slow inward current, or alterations in [Ca2+]o from 0.5 to 10 mM), resulted in no change in rn for normally coupled cell pairs (rn = 5 M omega), but small and reversible changes in slightly uncoupled preparations (rn greater than or equal to 50 M omega). Large increases in rn developed with substantial elevations in [Ca2+]i (secondary to [Na+]o-withdrawal, exposure to strophanthidin in conjunction with isi, or Ca2+-dialysis). Increases in rn brought about via elevation in [Ca2+]i always were accompanied by cell shortening consistent with a sustained contracture. The current-voltage relationship of the nexal membrane was ohmic regardless of whether rn was low (control) or elevated (after increasing [Ca2+]i).

Animals↗
PubMed1986

The reliability of a historical interview with physically disabled respondents.

This study investigated the reliability of a historical interview with 20 respondents with physical disabilities. An existing interview, the Occupational Role History, was modified and a companion rating scale was developed. Analysis of the test-retest and interrater reliabilities suggest that a stable clinical judgment can be formed from data gathered in a historical interview.

Adolescent↗
PubMed1979

Benzylidenemalononitrile derivatives as substrates and inhibitors of a new NAD(P)H dehydrogenase of erythrocytes. Purification and crystallisation of two forms of the enzyme.

Using the powerful lachrymator (2-chlorobenzylidene)malononitrile as electron acceptor, two types of NAD(P)H dehydrogenases have been isolated from human blood. Crystallisation of the homogenous enzymes was performed in 50% polyethylene glycol solution. The enzymes (average molecular weight 18 000) are composed of only one polypeptide chain and have a very similar amino acid composition. B-side stereospecificity was determined with respect to the cofactor by gas chromatography-mass spectrometry for the reductase. Besides (2-chlorobenzylidene)malononitrile, 2,6-dichloroindophenol, methylene blue, 4-benzoquinone, FMN and FAD are also reduced using NADH or NADPH as hydrogen donor with the rates decreasing in the given order. Reduction of methemoglobin is observed only upon addition of methylene blue, FMN or FAD as carriers. (2-Chlorobenzylidene)malononitrile reduction is inhibited by most of the compounds known to be decouplers of oxidative phosphorylation.

Amino Acids↗