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Biomedical subjects

M Posch

Publications and source records attributed to M Posch.

At least 19 recordsLinked to original sources
PubMed2006

Diuretic potential of energy drinks.

Recent literature suggests that both caffeine and taurine can induce diuresis and natriuresis in rat and man. Although they act via different cellular mechanisms, their diuretic actions might be additive. This is of considerable interest, as several commercially available energy drinks contain both substances. In this study we examined the possible diuretic effects of caffeine and taurine in a cross-over-design in which 12 healthy male volunteers received each of 4 different test drinks (750 ml of energy drink containing 240 mg caffeine and 3 g taurine, the three other test drinks either lacked caffeine, taurine or both) after restraining from fluids for 12 h. Mixed model analyses demonstrated that urinary output and natriuresis were significantly increased by caffeine (mean differences 243 ml and 27 mmol; both p < 0.001) and that there were no such effects of taurine (mean differences 59 ml and -4 mmol). Additionally, urinary osmolarity at baseline was significantly related to the urinary output (p < 0.001). Urine osmolarity values at baseline and in the 6 h urine collection did not differ significantly between treatments. Taken together, our study demonstrates that diuretic and natriuretic effects of the tested energy drink were largely mediated by caffeine. Taurine played no significant role in the fluid balance in moderately dehydrated healthy young consumers. Consequently, the diuretic potential of energy drinks will not differ significantly from other caffeine containing beverages.

Adolescent↗
PubMed2006

Modelling the effect of climate change on recovery of acidified freshwaters: relative sensitivity of individual processes in the MAGIC model.

The MAGIC model was used to evaluate the relative sensitivity of several possible climate-induced effects on the recovery of soil and surface water from acidification. A common protocol was used at 14 intensively studied sites in Europe and eastern North America. The results show that several of the factors are of only minor importance (increase in pCO(2) in soil air and runoff, for example), several are important at only a few sites (seasalts at near-coastal sites, for example) and several are important at nearly all sites (increased concentrations of organic acids in soil solution and runoff, for example). In addition changes in forest growth and decomposition of soil organic matter are important at forested sites and sites at risk of nitrogen saturation. The trials suggest that in future modelling of recovery from acidification should take into account possible concurrent climate changes and focus specially on the climate-induced changes in organic acids and nitrogen retention.

Climate↗
PubMed2006

Clinical features, classification and prognosis of migraine and tension-type headache in children and adolescents: a long-term follow-up study.

We performed a long-term follow-up examination in children and adolescents with migraine and tension-type headache (TTH) in order to investigate the evolution of clinical features and headache diagnoses, to compare International Classification of Headache Disorders (ICHD)-I and ICHD-II criteria and to identify prognostic factors. We re-examined 227 patients (52.4% female, age 17.6 +/- 3.1 years) 6.6 +/- 1.6 years after their first presentation to a headache centre using identical semistructured questionnaires. Of 140 patients initially diagnosed with migraine, 25.7% were headache free, 48.6% still had migraine and 25.7% had TTH at follow-up. Of 87 patients with TTH, 37.9% were headache free, 41.4% still had TTH and 20.7% had migraine. The number of subjects with definite migraine was higher in ICHD-II than in ICHD-I at baseline and at follow-up. The likelihood of a decrease in headache frequency decreased with a changing headache location at baseline (P < 0.0001), with the time between baseline and follow-up (P = 0.0019), and with an initial diagnosis of migraine (P = 0.014). Female gender and a longer time between headache onset and first examination tended to have an unfavourable impact. In conclusion, 30% of the children and adolescents presenting to a headache centre because of migraine or TTH become headache-free in the long-term. Another 20-25% shift from migraine to TTH or vice versa. ICHD-II criteria are superior to those of ICHD-I in identifying definite migraine in children and adolescents presenting to a headache centre. The prognosis is adversely affected by an initial diagnosis of migraine and by changing headache location, and it tends to be affected by an increasing time between headache onset and first presentation.

Adolescent↗
PubMed2005

[Translation and psychometric testing of the Rotator Cuff Quality-of-Life Measure (RC-QOL) for use in German-speaking regions].

The evaluation of quality of life is an established criterion for evaluation of therapeutic measures. Starting from the English-speaking area a great number of different patient-based outcomes measures were developed to specifically question disorders of the musculoskeletal system and the results of treatment. Because of the lack of a German measurement tool for patients with rotator cuff disease the translation and the psychometric testing following international guidelines of the 34-item, multidimensional, English Rotator Cuff Quality-of-Life Measure (RC-QOL) was undertaken. Reliability (test-retest reliability, internal consistency), validity, practicability and acceptance of the German version of the RC-QOL were tested by 102 patients with an impingement syndrome after translation and cross-culture adaptation of the English original questionnaire. In addition, the SF-36, the Constant and UCLA scores were evaluated. Between the evaluations there was no significant difference; the Pearson correlation coefficient was 0.89 for the test-retest reliability. The internal consistency showed a high homogeneity with a Cronbach Alpha-coefficient of 0.98. A Pearson correlation coefficient between 0.67-0.76 registered a high correlation with the physical subscales of the SF-36, the Constant and the UCLA scores. The mean time required for completing the RC-QOL was 12 minutes; mean time required for evaluation was 10 minutes. The questionnaire was incompletely answered by 16 patients (15.6%). A total of 120 items (3.5%) were left unanswered. After successful translation and psychometric testing of the German version of the Rotator Cuff Quality-of-Life Measure (RC-QOL) a multidimensional measurement tool for evaluating the quality of life of German-speaking patients with pathology of the rotator cuff is available.

Female↗
PubMed2004

Red blood cell deformability and aggregation behaviour in different animal species.

Comparative animal studies showed the wide variation of whole blood and plasma viscosity, and erythrocyte aggregation among mammalian species. Whole blood viscosity and red blood cell aggregation is influenced by red cell fluidity. To evaluate differences in erythrocyte deformability in mammals, three species were investigated, whose erythrocytes have a different aggregation property: horse, as a species with high, dog with medium, and sheep with almost unmeasurable aggregation tendency. Erythrocyte deformability was tested ektacytometrically (Elongation Index [EI], LORCA, Mechatronics, Hoorn, Netherlands) at shear stresses from 0.30 to 53.06 Pa. Equine erythrocytes showed EI-values from 0.047 at low shear stress to 0.541 at high shear stress. The EI from dog's erythrocytes ranged from 0.035 to 0.595. Sheep's erythrocytes had an EI of 0.005 at low and 0.400 at high shear stress. Although it might be presumed from the aggregation property that horse had the highest EI among the three species, the EI of canine erythrocytes exceeded the value in horses by 10% at high shear stress. Further, equine erythrocytes started to deform at higher shear stresses (1.69 Pa) than did canine and ovine cells, whose EI increased continuously with increasing shear stress. At moderate shear stress (1-5 Pa) deformability was even higher in the sheep than in the horse. However, at shear stresses higher than 5.34 Pa, equine red cell elongation clearly exceeded the values of sheep. We conclude that erythrocyte elongation is different between the animal species, not clearly linked with the aggregation property, and that the degree of deformability at various shear stresses is species-specific.

Animals↗
PubMed2003

Muscle fatigue and fatigue-related biomechanical changes during a cyclic lifting task.

STUDY DESIGN: Electromyographic and biomechanical methods were utilized to investigate correlations between indexes of localized muscle fatigue and changes in the kinematics and kinetics of motion during a cyclic lifting task. SUMMARY OF BACKGROUND DATA: Recent advances in time-frequency analysis procedures for electromyographicic signal processing provide a new way of studying localized muscle fatigue during dynamic contractions. These methods provide a means to investigate fatigue-related functional impairments in patients with low back pain. OBJECTIVES: To study the relationship between localized muscle fatigue and the biomechanics of lifting and lowering a weighted box. Fatigue-related changes in the electromyographicic signal of trunk and limb muscles were evaluated and compared to kinematic and kinetic measures in order to determine whether lifting strategy is modified with fatigue. METHODS: A total of 14 healthy male subjects (26 +/- 5 years) cyclically lifted and lowered a 13 kg box (12 lifts/min) for 4.5 minutes. A 5-second static maximum lifting task was included immediately before and after the cyclic lifting task to measure changes in lifting strength and static electromyographicic fatigue indexes. Electromyographic signals from 14 muscle sites (including paravertebral and limb muscles) were measured. Changes in the electromyographicic Instantaneous Median Frequency, a fatigue index, were computed using time-frequency analysis methods. This index was compared with more standardized measures of fatigue, such as those based on electromyographicic median frequency acquired during a static trunk extension test, subjective fatigue measures, and maximal static lifting strength. Biomechanical measures were gathered using a motion analysis system to study kinematic and kinetic changes during the lifting task. RESULTS: During the cyclic lifting task, the electromyographic Instantaneous Median Frequency significantly decreased over time in the paravertebral muscles, but not in the limb muscles. Paravertebral electromyographicic Instantaneous Median Frequency changes were consistent with self-reports of fatigue as well as decreases in trunk extension strength. The magnitude of muscle-specific changes in electromyographicic Instantaneous Median Frequency was not significantly correlated with electromyographicic median frequency changes from the static trunk extension task. The load of the box relative to the maximal static lifting strength significantly affected the electromyographicic Instantaneous Median Frequency changes of paravertebral back muscles. Significant changes with fatigue during the task were found in the angular displacements at the knee, hip, trunk, and elbow. These biomechanical changes were associated with increased peak torque and forces at the L4-L5 vertebral segment. CONCLUSIONS: Our results demonstrate correlation between localized muscle fatigue and biomechanical adaptations that occur during a cyclic lifting task. This new technique may provide researchers and clinicians with a means to investigate fatigue-related effects of repetitive work tasks or assessment procedures that might be useful in improving education, lifting ergonomy, and back school programs. Although both the dynamic and static tasks resulted in spectral shifts in the electromyographicic data, the fact that these methods led to different muscle-specific findings indicates that they should not be considered as equivalent assessment procedures.

Adult↗
PubMed2003

Sequential tests for noninferiority and superiority.

The problem of simultaneous sequential tests for noninferiority and superiority of a treatment, as compared to an active control, is considered in terms of continuous hierarchical families of one-sided null hypotheses, in the framework of group sequential and adaptive two-stage designs. The crucial point is that the decision boundaries for the individual null hypotheses may vary over the parameter space. This allows one to construct designs where, e.g., a rigid stopping criterion is chosen, rejecting or accepting all individual null hypotheses simultaneously. Another possibility is to use monitoring type stopping boundaries, which leave some flexibility to the experimenter: he can decide, at the interim analysis, whether he is satisfied with the noninferiority margin achieved at this stage, or wants to go for more at the second stage. In the case where he proceeds to the second stage, he may perform midtrial design modifications (e.g., reassess the sample size). The proposed approach allows one to "spend," e.g., less of alpha for an early proof of noninferiority than for an early proof of superiority, and is illustrated by typical examples.

Humans↗
PubMed2002

The SCARF osteotomy for the correction of hallux valgus deformities.

The authors report their experience with a modified SCARF osteotomy with three years follow-up. Correction of moderate to severe hallux valgus deformities was achieved using a Z step osteotomy cut to realign the first metatarsal bone. A retrospective analysis was undertaken in 89 consecutive patients (111 feet). Results were analyzed by clinical examination, a questionnaire including the AOFAS forefoot score, and plain roentgenograms. Hallux valgus and intermetatarsal angle improved at mean 19.1 degrees and 6.6 degrees, respectively. Mean forefoot score improved from 50.1 to 91 points out of 100 possible points. Satisfactory healing time was expressed by an average return back to work of 5.8 weeks and back to sport of 8.3 weeks. Persistence or recurrence of hallux valgus was seen in seven patients (6%). The complication rate was 5.4% including superficial wound infection, traumatic dislocation of the distal fragment, and hallux limitus. The presented technique provides predictable correction of moderate to severe hallux valgus deformities.

Adult↗
PubMed2001

Past and future exceedances of nitrogen critical loads in Europe.

Critical loads of acidity and nutrient nitrogen--simple measures of the sensitivity of ecosystems to deposition--have been widely used for setting emission reduction targets in Europe. In contrast to sulfur, the emissions of nitrogen compounds remain high in the future. This is also true for the exceedances of critical loads until 2010. Looking further into the future, climate change is likely to influence ecosystem sensitivity, and thus critical loads. It is shown that higher temperatures, changed precipitation patterns, and modified net primary production mainly increase critical loads, except in mountainous and arid regions. Using consistent scenarios of climate change and air pollution from a recently completed European study (AIR-CLIM), it is shown that the exceedances in 2100 of the critical loads are declining in comparison to 2010. However, exceedances of critical loads of nutrient nitrogen remain substantial, even under the most stringent scenario. This confirms the increasing role nitrogen plays in environmental problems in comparison to sulfur. Thus research should focus on the effects of nitrogen in the environment, especially under conditions of climate change, to support nitrogen-emission mitigating policies. This not only reduces acidification and eutrophication, but also helps curb the formation of tropospheric ozone.

Environmental Monitoring↗
PubMed2001

Homo-oligomerisation and nuclear localisation of mouse histone deacetylase 1.

Reversible histone acetylation changes the chromatin structure and can modulate gene transcription. Mammalian histone deacetylase 1 (HDAC1) is a nuclear protein that belongs to a growing family of evolutionarily conserved enzymes catalysing the removal of acetyl residues from core histones and other proteins. Previously, we have identified murine HDAC1 as a growth factor-inducible protein in murine T-cells. Here, we characterise the molecular function of mouse HDAC1 in more detail. Co-immunoprecipitation experiments with epitope-tagged HDAC1 protein reveal the association with endogenous HDAC1 enzyme. We show that HDAC1 can homo-oligomerise and that this interaction is dependent on the N-terminal HDAC association domain of the protein. Furthermore, the same HDAC1 domain is also necessary for in vitro binding of HDAC2 and HDAC3, association with RbAp48 and for catalytic activity of the enzyme. A lysine-rich sequence within the carboxy terminus of HDAC1 is crucial for nuclear localisation of the enzyme. We identify a C-terminal nuclear localisation domain, which is sufficient for the transport of HDAC1 and of reporter fusion proteins into the nucleus. Alternatively, HDAC1 can be shuttled into the nucleus by association with another HDAC1 molecule via its N-terminal HDAC association domain. Our results define two domains, which are essential for the oligomerisation and nuclear localisation of mouse HDAC1.

Active Transport, Cell Nucleus↗
PubMed2001

Short segment stimulation of the anterior transposed ulnar nerve at the elbow.

OBJECTIVE: To determine whether short segment stimulation after anterior subcutaneous transposition of the ulnar nerve reaches normal values and correlates with postoperative clinical findings. DESIGN: Comparative cross-sectional study. SETTING: Outpatient clinic of a university department of physical medicine and rehabilitation. PATIENTS: Nineteen patients (15 men, 4 women) with 21 surgically treated ulnar neuropathies at the elbow; and 19 healthy controls (11 men, 8 women) with 24 measured nerves. INTERVENTIONS: Assessed motor function of ulnar innervated muscles and staged into 4 categories; used questionnaire to assess clinical course of the nerve lesion and graded into 5 categories; took electrophysiologic recordings to measure motor conduction velocity and compound muscle action potentials; and studied short segment stimulation across elbow and lower arm. MAIN OUTCOME MEASURES: Mean +/- standard deviation of ulnar short segment conduction time across the elbow, amplitude and motor conduction velocity; grading of ulnar nerve lesions; grading of the course of disease after surgery; and logistic regression and correlation (Spearman's correlation coefficient) for electrophysiologic and clinical parameters. RESULTS: Sixteen nerves showed focal conduction slowing in patients. No significant correlation between the course of disease and electrophysiologic parameters was seen. For stepwise logistic regression, there was a significant effect between grade of nerve lesion and amplitude, but no significant effect between the course of disease and electrophysiologic parameters. CONCLUSION: A focal conduction slowing across the elbow after anterior subcutaneous transposition does not correlate with postoperative clinical findings.

Adolescent↗
PubMed2001

Cross-cultural adaptation of the Minnesota Living with Heart Failure Questionnaire for German-speaking patients.

We performed a cross-cultural adaptation of the "Minnesota Living with Heart Failure Questionnaire" (LHFQ) for use in German-speaking chronic heart failure patients. The instrument was translated and back translated, pre-tested and reviewed by a committee. The German version was tested in 114 patients with chronic heart failure. Reliability was assessed by a test-retest procedure and Cronbach's coefficient alpha of internal consistency (0.94). To assess concurrent validity, we compared the LHFQ sum scores with the New York Heart Association classification rating (r = 0.53; p < 0.0001), the 6-minute walk (r = -0.39; p < 0.0001), the left ventricular ejection fraction (r = -0.24; p = 0.011) and big-endothelin (r = 0.27; p = 0.004). Construct validity on the LHFQ scores in comparison with the Medical Outcomes Study SF-36 Health Survey (MOS SF-36) was significant (-0.41 to -0.74; all p < 0.0001). The reliability and validity of the German version of the LHFQ was proved; the questionnaire can be recommended for use in future clinical trials.

Aged↗
PubMed2001

Flexible two-stage designs: an overview.

In this overview we introduce the basic ideas behind a new flexible approach in sequential designs. The different concepts based on two-stage combination tests and conditional error functions are brought together. We sketch the construction of p-values, confidence intervals, and median unbiased estimates. Finally, recursive combination tests are introduced which extend the flexibility to the choice of the number of interim analyses.

Clinical Trials as Topic↗
PubMed2000

Substrate binding is a prerequisite for stabilisation of mouse thymidine kinase in proliferating fibroblasts.

Thymidine kinase (TK) expression in mammalian cells is strictly growth regulated, with high levels of the enzyme present in proliferating cells and low levels in resting cells. We have shown that mouse TK expressed from a constitutive promoter is still subject to this regulation. The drastic decline in TK enzyme levels in resting cells is largely due to a pronounced reduction in the half-life of the protein. Deletion of the 30 C-terminal amino acid residues from TK abrogates growth regulation, rendering the enzyme very stable. Moreover, the substrate thymidine was sufficient to stabilise the labile TK protein in quiescent cells. Here, we report that the ability of TK to bind substrates is essential for both growth-dependent regulation and stabilisation by the substrate. By mutation or elimination of the binding sites for either of the two substrates, ATP and thymidine, we expressed TK proteins lacking enzymatic activity which abolished growth-regulated expression in both cases. Mutant TK proteins impaired in substrate binding were subject to rapid degradation in exponentially growing cells and thymidine was no longer sufficient to inhibit this rapid decay. A C-terminal truncation known to stabilise the TK wild-type protein in resting cells did not affect the rapid turnover of enzymatically inactive TK proteins. Proteasome inhibitors also failed to stabilise these substrate-binding mutants. By cross-linking experiments, we show that TK proteins with mutated substrate-binding sites exist only as monomers, whereas active TK enzyme forms dimers and tetramers. Our data indicate that, In addition to the C terminus intact substrate-binding sites are required for growth-dependent regulation of TK protein stability.

Adenosine Triphosphate↗
PubMed2000

Phenological weighting of ozone exposures in the calculation of critical levels for wheat, bean and plantain.

This paper presents phenological weighting factors to be applied to AOT40 (accumulated ozone exposure above a threshold of 40 nl l(-1)) ozone exposure-response relationships for crops at different growth stages. The quantification of such factors represents a step-forward in the derivation of Level II critical levels for ozone. The weighting factors presented are derived from published literature on the sensitivity of wheat (Triticum aestivum), bean (Phaseolus vulgaris) and plantain (Plantago major) to ozone at different growth stages. Weighting functions were calculated using either multiple linear regression or the reciprocal residual mean square (RMS(-1)). The resulting weights were transformed into multiplication factors to be applied to the monthly AOT40 during the 3-month assessment period of critical level exceedance. Interspecific differences were too large to allow for the development of a unified weighting function for the three species considered. For wheat grain yield, the derived multiplication factors varied by almost four-fold (0.40, 1.06, 1.54), while those for bean pod yield varied by only about 25% (0.85, 1.01, 1.14). The available data for plantain were restricted to short-term studies conducted under controlled conditions. These data were not suitable for the derivation of weighting factors comparable to those derived for bean and wheat. Based on known differences in wheat development and phenology across Europe, the need for a geographic differentiation of the time period for the calculation of the critical level exceedances is also discussed and examples provided of the adoption of the derived weightings in the mapping of critical level exceedances. Differences between critical level exceedance maps using weighted and unweighted AOT40 calculations are discussed.

Journal Article↗
PubMed2000

Load-dependence of fatigue related changes in tremor around 10 Hz.

OBJECTIVES: The aim of the study was to investigate the effects of different loads on tremor around 10 Hz during fatiguing contractions. METHODS: Eighteen healthy volunteers performed sustained isometric knee extensions at 30%, 50% and 70% maximum voluntary contraction (MVC). During the fatiguing contractions, mechanical recordings were made with a high-resolution force sensor. Tremor-power was calculated for the 6-20 Hz frequency window as a function of time normalized to endurance time. RESULTS: Initial tremor power was different between the high and low load tasks. Changes of tremor with contraction time differed between the three tasks, in that tremor of the 30% MVC contraction showed the least decrease throughout the sustained contraction, whilst that of the 50% and 70% MVC showed progressively higher decreases. At failure, all 3 contractions merged to the same tremor level. CONCLUSION: Load-dependent, fatigue-related 6-20 Hz tremor changes during sustained submaximum voluntary contractions seem mainly the consequence of recruitment of new units and fatigue-related properties of the high threshold motor units of muscles.

Adult↗