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M Brunner

Publications and source records attributed to M Brunner.

At least 37 records · Page 2Linked to original sources
PubMed2001

Characterization of mice with a combined suppression of I(to) and I(K,slow).

Cardiac-specific expression of a truncated Kv1.1 polypeptide (Kv1DN) attenuates the slow inactivating outward K(+) current (I(K,slow)), increases action potential duration (APD) and Q-T intervals, and induces spontaneous ventricular arrhythmias. Expression of the pore mutant of Kv4.2 (Kv4DN) eliminates the fast component of the transient outward current (I(to)) and prolongs APDs and Q-T intervals markedly; however, no arrhythmias are seen in Kv4DN mice, suggesting that APD and Q-T prolongation are not per se proarrhythmic. To test this hypothesis, the Kv1DN and Kv4DN lines were crossbred to produce animals (Kv1/Kv4DN) expressing both transgenes in an identical genetic background. Whole cell voltage-clamp recordings from left ventricular apex cells confirmed that in Kv1/Kv4DN left ventricular apex cells, both components (fast and slow) of I(to) and the 4-aminopyridine-sensitive component of I(K,slow) are eliminated, resulting in marked APD prolongation compared with wild-type, Kv1DN, or Kv4DN cells. Telemetric electrocardiogram monitoring (n = 10 mice/group) revealed a significant prolongation of Q-Tc and P-R intervals in Kv1/Kv4DN animals compared with Kv1DN or Kv4DN animals. Spontaneous arrhythmias were observed mainly in Kv1DN mice. Thus the attenuation of fast I(to) in addition to I(K,slow) in Kv1/Kv4DN mice causes significant prolongation of APD and Q-T intervals and attenuation of spontaneous arrhythmias.

4-Aminopyridine↗
PubMed2001

SAP97 interacts with Kv1.5 in heterologous expression systems.

PDZ domain-containing proteins such as SAP97 and ZO-1 have been implicated in the targeting and clustering of ion channels. We have explored the interactions of these polypeptides with a cardiac voltage-gated potassium channel. Immunocytochemistry in cardiac myocytes revealed colocalization of SAP97 and Kv1.5, both at the intercalated disks and the lateral membranes. Transient transfection experiments in COS-7 cells revealed that SAP97 and Kv1.5 polypeptides formed perinuclear clustered complexes that could be coimmunoprecipitated. Mutation of the three COOH-terminal amino acid residues of Kv1.5 (T-D-L to A-A-A) abolished these interactions. Whereas in most COS-7 cells the SAP97-Kv1.5 complexes were retained in the ER, functional analyses in Xenopus oocytes showed that Kv1.5-encoded outward potassium currents were augmented by coexpression with SAP97. By contrast, cotransfected ZO-1 and Kv1.5 polypeptides in COS-7 cells could not be coprecipitated nor did the coinjection of ZO-1 augment the Kv1.5-encoded currents in oocytes. Collectively, our results suggest that SAP97 may play an important role in the modulation of Kv1.5 channel function in cardiac myocytes.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Testosterone inhibits expression of inducible nitric oxide synthase in murine macrophages.

We investigated the effect of testosterone, the main sexual steroid hormone in men, upon inducible nitric oxide synthesis in murine macrophages. Incubation of murine macrophages (RAW 264.7 cells) stimulated by bacterial lipopolysaccharide (2 microg/ml) with increasing amounts of testosterone (0.1-40 microM) showed a dose dependent inhibition of inducible nitric oxide synthesis. Inducible nitric oxide synthase protein expression was reduced in a dose dependent manner as revealed by immunoblotting when cells were incubated with increasing amounts of testosterone. This was associated with a decline in iNOS mRNA-levels as determined by competitive semiquantitative PCR. As nitric oxide plays an important role in immune defense and atherosclerosis prevention, testosterone-induced iNOS inhibition could lead to an elevated risk of infection as well as to the development of atherosclerotic lesions.

Animals↗
PubMed2000

The role of the TIM8-13 complex in the import of Tim23 into mitochondria.

Tim8 and Tim13 are non-essential, conserved proteins of the mitochondrial intermembrane space, which are organized in a hetero-oligomeric complex. They are structurally related to Tim9 and Tim10, essential components of the import machinery for mitochondrial carrier proteins. Here we show that the TIM8-13 complex interacts with translocation intermediates of Tim23, which are partially translocated across the outer membrane but not with fully imported or assembled Tim23. The TIM8-13 complex binds to the N-terminal or intermediate domain of Tim23. It traps the incoming precursor in the intermembrane space thereby preventing retrograde translocation. The TIM8-13 complex is strictly required for import of Tim23 under conditions when a low membrane potential exists in the mitochondria. The human homologue of Tim8 is encoded by the DDP1 (deafness/dystonia peptide 1) gene, which is associated with the Mohr-Tranebjaerg syndrome (MTS), a progressive neurodegenerative disorder leading to deafness. It is demonstrated that import of human Tim23 is dependent on a high membrane potential. A mechanism to explain the pathology of MTS is discussed.

Animals↗
PubMed2000

Termination of recent-onset atrial fibrillation/flutter in the emergency department: a sequential approach with intravenous ibutilide and external electrical cardioversion.

Safety and effectiveness are the goals in treating patients with arrhythmias. In an open prospective study, we observed the efficacy and safety of up to 2 mg intravenous ibutilide, a new class III antiarrhythmic agent in haemodynamically stable patients presenting in the emergency department (ED) with symptoms of recent-onset (<48 h) atrial fibrillation/flutter. Arrhythmia termination within 90 min, haemodynamic parameters and proarrhythmic effects were assessed. Non-responders to the ibutilide infusion underwent external electrical cardioversion. We included 51 patients. In 31 patients therapeutic intervention with intravenous ibutilide was successful within 90 min (61%). In another seven patients conversion to sinus rhythm occurred after 90 min without any other intervention (14%). Blood pressure remained stable and no relevant proarrhythmic effects were observed. The 13 patients who did not respond to ibutilide treatment underwent successful external electrical cardioversion. The overall conversion rate was 100%. Forty-seven patients (92%) were discharged within a median of 9 h and managed as outpatients. In conclusion, in haemodynamically stable patients with recent-onset atrial fibrillation/flutter intravenous ibutilide and external electrical cardioversion for conversion to sinus rhythm turned out to be effective and safe. The short duration of admission makes this strategy attractive for use in the ED.

Adult↗
PubMed2000

Inhibition of inducible nitric oxide synthesis by oxidized lipoprotein(a) in a murine macrophage cell line.

Increased plasma levels of human lipoprotein(a) (Lp(a)) are highly correlated with the development of atherosclerotic lesions. During our study, we investigated the effects of native and hypochlorite oxidized lipoprotein(a) (ox-Lp(a)) on nitric oxide production by the inducible nitric oxide synthase (iNOS) in lipopolysaccharide/interferon stimulated mouse macrophages (J774A.1). Ox-Lp(a) (0-2 microg/ml) induces a dose dependent inhibition of inducible nitric oxide synthesis. iNOS protein expression showed a dose dependent reduction as revealed by immunoblotting when cells were incubated with increasing amounts of ox-Lp(a). Ox-Lp(a) decreases iNOS mRNA synthesis as shown by reverse transcription-polymerase chain reaction. Ox-Lp(a) induced iNOS inhibition might contribute to the development of atherosclerotic lesions by reducing the anti-atherogenic effects of nitric oxide.

Animals↗
PubMed2000

Immune complexes from serum of patients with lyme disease contain Borrelia burgdorferi antigen and antigen-specific antibodies: potential use for improved testing.

We report sequestration of specific IgM anti-Borrelia burgdorferi (Bb) and Bb antigens within immune complexes (ICs) isolated from serum of patients with Lyme disease (LD). The relative enrichment in specific IgM measured by ELISA was apparent, even after correcting for differences in total IgM concentration in serum versus ICs. Immunoblot demonstrated that ICs contained antibodies against specific Bb proteins, whereas reactivity was absent or significantly lessened in unprocessed serum. This is the first study to show ICs containing Bb antigen identified by immunoblot with anti-Bb monoclonal antibody. ICs may be a useful source of antigen and antibody for development of more-accurate testing for LD.

Antibodies, Bacterial↗
PubMed2000

Validation of urea as an endogenous reference compound for the in vivo calibration of microdialysis probes.

Microdialysis is a widely used experimental technique, which offers the opportunity to measure drug and metabolite concentrations in the interstitial space fluid in animals and humans. However, microdialysis probes need to be calibrated in vivo to obtain a recovery factor, which describes the relative drug transfer across the membrane. Recently, novel time-saving calibration techniques, based on the use of reference compounds, have been developed. In particular, the use of endogenous urea levels has been advocated. In the present study we set out to validate the use of the urea reference technique for microdialysis probe calibration in healthy volunteers, employing glucose and paracetamol as model analytes. Urea calibration was compared with the results of two standard calibration techniques, i.e. the no net flux technique and the retrodialysis technique. For glucose, recovery values, calculated by the urea reference technique differed significantly from those values, which were assessed by the no net flux technique (p < 0.05), whereas for paracetamol recovery values did not differ significantly, albeit a high intramethod variability was observed (CV=66%). As a conclusion, we could not confirm the hypothesis that recovery values calculated by the urea reference technique provide equivalent results compared with standard calibration techniques.

Acetaminophen↗
PubMed2000

Usefulness of carvedilol in unstable angina pectoris.

The safety and efficacy of adding oral carvedilol (25 mg twice daily) to standardized treatment of unstable angina was assessed in a multicenter, randomized, double-blind, placebo- controlled trial on 116 patients with acute unstable angina. Patients were monitored in an intensive care unit and underwent 48-hour Holter monitoring to assess transient ischemia. Carvedilol as adjunctive therapy resulted in a significant reduction of median heart rate (65 vs 75 beats/min, p <0.05), mean systolic blood pressure (133 vs 130 mm Hg, p <0.05), and mean rate-pressure product (8,337 vs 10,042, p <0.05). Carvedilol reduced the ischemic burden during 48 hours of treatment by 75% (49 vs 204 minutes), including a 36% reduction of patients with ischemic episodes (p <0.05), a 66% reduction of the mean number of ischemic episodes (8 vs 24, p <0.05), and a 76% reduction in the mean duration of ischemic episodes (50 vs 205 minutes, p <0.05). Side effects occurred in 8 of 59 patients (13.6%) in the carvedilol group and in 5 of 54 patients (8.8%) given placebo. Although not significant, the early onset of maximal blood pressure reduction and the delayed effect on heart rate were closely correlated to drug-induced hypotension and bradycardia in the carvedilol group. Thus, carvedilol as an adjunctive to standardized treatment effectively reduces heart rate and blood pressure, and thus the ischemic burden in patients with unstable angina pectoris, but requires close monitoring of patients at risk for bradycardia or hypotension.

Acute Disease↗
PubMed2000

Tim23 links the inner and outer mitochondrial membranes.

Tim23, a key component of the mitochondrial preprotein translocase, is anchored in the inner membrane by its C-terminal domain and exposes an intermediate domain in the intermembrane space that functions as a presequence receptor. We show that the N-terminal domain of Tim23 is exposed on the surface of the outer membrane. The two-membrane-spanning topology of Tim23 is a novel characteristic in membrane biology. By the simultaneous integration into two membranes, Tim23 forms contacts between the outer and inner mitochondrial membranes. Tethering the inner membrane translocase to the outer membrane facilitates the transfer of precursor proteins from the TOM complex to the TIM23 complex and increases the efficiency of protein import.

Animals↗
PubMed2000

[SIDS prevention program in Tyrol].

In April 1994, an intervention campaign to reduce the incidence of sudden infant death syndrome (SIDS) was established in the Tyrol. The campaign was intended to increase knowledge concerning risk factors for SIDS in the general community and to improve individual care for infants at risk. In contrast to interventional programmes in other federal states of Austria (i.e. Vorarlberg, Styria), this programme did not utilise polysomnography for identifying infants at risk. A part of the intervention programme was the "Styrian risk questionnaire", a standardised questionnaire concerning risk factors for SIDS. Individual instructions for health care of children at risk (risk score > or = 7) were provided and, if necessary, subscription of home monitoring was performed at the out-patient department (SIDS out-patient service) of the Department of Paediatrics in Innsbruck and other paediatric departments throughout the Tyrol. The educational programme also included information concerning basic life support. Psychological support was offered to parents of SIDS infants. Risk factors for SIDS in the Tyrol before the campaign were assessed in a retrospective case-control study (time period 1984-1994; 99 SIDS infants, 136 controls). The risk of SIDS was markedly reduced when parents had detailed knowledge of the risk factors of SIDS (odds ratio (OR) 0.03; p < 0.001), which emphasises the importance of information and educational programmes. The incidence of SIDS declined after the beginning of the intervention campaign from 1.83/1000 live births (average incidence from 1984-1994) to 0.4/1000 live births and remained at this level thereafter. Post-neonatal mortality also declined from 3.9 to 1.3/1000 live births. The prevalence of the prone sleeping position declined immediately after the campaign (53.7% vs. 5.4%, p < 0.001), as did the frequency of maternal smoking during pregnancy (22.9% vs. 14.5%, p < 0.01). Breast feeding became more popular. In all, the low-cost intervention programme in the Tyrol proved to be highly efficient in reducing the risk of SIDS and in maintaining this effect for several years.

Adult↗
PubMed2000

Micellar electrokinetic chromatography for the analysis of cefpirome in microdialysis and plasma samples obtained in vivo from human volunteers.

Pharmacokinetics of drugs in the human interstitial space fluid can be monitored by means of microdialysis. However, the small-volume microdialysis samples containing low drug concentrations require a sensitive analytical method. In the present study, micellar electrokinetic chromatography (MEKC) is described for the quantification of cefpirome in human microdialysis and plasma samples. Sample preparation of human plasma samples by ultracentrifugation was suitable for comparison of plasma and microdialysate concentrations. Limits of quantification were 2 microg/mL and 0.3 microg/mL for plasma and microdialysate samples, respectively. The limit of detection (LOD) was estimated at 0.2 microg/mL for the plasma and microdialysate samples. In conclusion, MEKC is a reliable and reproducible technique for measuring cefpirome concentrations in microdialysates as well as centrifuged plasma samples.

Adsorption↗
PubMed2000

Selection of continuous epitope sequences and their incorporation into poly(ethylene glycol)-peptide conjugates for use in serodiagnostic immunoassays: application to Lyme disease.

Continuous epitope sequences were selected from immunogenic Bb proteins by epitope mapping. The identified epitope sequences were synthesized by solid phase peptide synthesis and purified by high performance liquid chromatography. Each epitope was conjugated individually to a multifunctional poly(ethylene glycol) (PEG) carrier. The result PEG-peptide conjugates were used as antigens in ELISA for diagnosis of Lyme disease. The results showed that the defined epitope peptides were Lyme disease specific and could be used in a format of PEG-peptide conjugate as the antigen to achieve improved sensitivity and specificity.

Amino Acid Sequence↗
PubMed2000

Protein translocation into mitochondria: the role of TIM complexes.

Import of nuclear-encoded mitochondrial preproteins is mediated by a general translocase in the outer membrane, the TOM complex, and by two distinct translocases in the mitochondrial inner membrane, the TIM23 complex and the TIM22 complex. Both TIM complexes cooperate with the TOM complex but facilitate import of different classes of precursor proteins. Precursors with an N-terminal presequence are imported via the TIM23 complex, whereas mitochondrial carrier proteins require the TIM22 complex for insertion into the inner membrane. This review discusses recent advances in understanding the structure and function of the translocases of the inner membrane and the possible role of Tim proteins in the development of the Mohr-Tranebjaerg syndrome, a mitochondrial disorder leading to neurodegeneration.

Animals↗
PubMed2000

Target site concentrations after continuous infusion and bolus injection of cefpirome to healthy volunteers.

BACKGROUND: Recent data indicate a higher level of effectivity of beta-lactam antibiotics if serum concentrations are kept above the minimal inhibitory concentration (MIC) of the pathogen. This concept would favor continuous infusion over bolus dosing. However, it is usually not the serum concentration but the free interstitial concentration in the target tissue that determines antibiotic activity. We therefore set out to measure effective drug concentrations in the interstitial space of muscle and subcutaneous adipose tissue and to compare trough levels and times above the MIC after bolus versus continuous infusion of cefpirome. METHODS: Twelve healthy volunteers received a single dose of 2 g cefpirome as an intravenous bolus or as a continuous infusion over 8 hours in a crossover design, and the resulting free interstitial tissue concentrations were measured with use of microdialysis. RESULTS: After bolus injection, mean interstitial trough concentrations were 3.0 +/- 1.9 microg/mL and 2.1 +/-1.0 microg/mL for muscle and subcutaneous tissue, respectively; continuous infusion resulted in trough levels of 10.1 +/- 6.8 microg/mL and 10.1 +/- 4.6 microg/mL for muscle and subcutaneous tissue, respectively. This resulted in significantly longer times above the MIC with continuous infusion for Staphylococcus epidermidis and Enterobacter cloacae. Bacteria with an MIC < or =1 would be covered by either method, whereas higher doses seem to be necessary for Pseudomonas aeruginosa. CONCLUSION: Although susceptible organisms will usually be covered sufficiently with standard dosing regimens, soft tissue infections with bacteria that have MIC values of 2 to 8 may profit from continuous application. Coverage of P aeruginosa, however, would be inadequate with conventional daily doses of 4 g cefpirome regardless of the method of application.

Adult↗