PubMed Health⌕ Search

Biomedical subjects

M Wirtz

Publications and source records attributed to M Wirtz.

At least 19 recordsLinked to original sources
PubMed2006

Development and first validation of the shared decision-making questionnaire (SDM-Q).

OBJECTIVE: Due to a lack of valid German instruments measuring shared decision-making (SDM), a theory-driven questionnaire (SDM-Q) to measure the process of SDM was developed and validated. METHODS: As a theoretical basis steps of the SDM process were defined in an expert panel. Item formulation was then conducted according to the Delphi method. For the first validation on a mixed sample Rasch analysis was used to eliminate items not fitting the construct thus receiving a unidimensional scale. RESULTS: After eliminating 4 items the remaining 11 form a unidimensional scale with an acceptable reliability for person measures (0.77) and very good reliability for item difficulties (0.95). Analysis of subgroups revealed a different use of items in different conditions. Furthermore the scale showed high ceiling effects. CONCLUSION: A new theory-driven instrument to measure the process of SDM has been developed and validated by use of a rigorous method revealing first promising results. Yet the ceiling effects require the addition of more discriminating items, and the different use of items in different conditions demands an in depth analysis. PRACTICE IMPLICATIONS: While the concept of SDM is constantly receiving more attention in medical practice, its valid and reliable measurement remains challenging.

Decision Making↗
PubMed2006

[Methods in health services research. The example of the evaluation of the German disease management programmes].

According to the established definition of Pfaff, health services research analyses patients' path through the institutions of the health care system. The focus is on development, evaluation and implementation of innovative measures of health care. By increasing its quality health services research strives for an improvement of efficacy and efficiency of the health care system. In order to allow for an appropriate evaluation it is essential to differentiate between structure, process and outcome quality referring to (1) the health care system in its entirety, (2) specific health care units as well as (3) processes of communication in different settings. Health services research comprises a large array of scientific disciplines like public health, medicine, social sciences and social care. For the purpose of managing its tasks adequately a special combination of instruments and methodological procedures is needed. Thus, diverse techniques of evaluation research as well as special requirements for study designs and assessment procedures are of vital importance. The example of the German disease management programmes illustrates the methodical requirements for a scientific evaluation.

Disease Management↗
PubMed2005

Risk assessment of sexual offenders in German forensic institutions.

BACKGROUND: The assessment of recidivism in sexual offenders is an urgent topic for forensic psychiatry in Germany. The call for useful predictive measures is therefore getting louder. AIMS: The present study analyses which criteria are employed by therapists in forensic hospitals to assess the dangerousness of sexual offenders. Of particular interest is whether the criteria listed in presently known prediction scores as decisive are actually used in decision-making in current forensic psychiatric practice. METHOD: Data are collected in a prospective prediction study funded by the German Research Association. RESULTS: The results reveal that therapists employ mainly clinical and less historical criteria, thus indicating substantial differences from currently known prediction scores and results of other studies. CONCLUSIONS: That therapists base their prediction of dangerousness primarily on clinical variables reveals a substantial error that has to be remedied. Further research on the extent of relevance of clinical variables is needed.

Adult↗
PubMed2005

[An empirical structural analysis of the IRES questionnaire version 2, dependent on indication, gender and age].

The patient questionnaire "Indicators of Reha Status" (IRES, Version 2) is used for assessing the need for rehabilitation and the success of rehabilitation. It is one of the most frequently used questionnaires in measuring subjective health conditions in medical rehabilitation in Germany. Based on the data of 8600 inpatient rehabilitees, the underlying structural model is examined by a confirmatory factor analysis. The model deviates in part from the original model of the questionnaire authors. The modified model was tested within 12 sub-groups. The sub-groups were divided depending on sex, age and indications (orthopaedic, cardiologic and psychosomatic) of the patients. Multi-group comparisons made between those 12 sub-groups showed specific structures within the groups of psychosomatic patients while no differences between female/male and younger/older patients were found. Furthermore, comparable structures of orthopaedic and cardiologic patients were found. Therefore the dimension values of the IRES patient questionnaire are not suited for a comparison between psychosomatic patients and patients from the somatic indications.

Age Distribution↗
PubMed2005

[Regression to the mean].

The evaluation of rehabilitation programmes may be distorted by regression to the mean: In a group of patients with extreme measurement values, these values tend to be less extreme on a following point in time due to merely random components and regardless of a "true" treatment effect. If this effect is not taken into account the effectiveness of rehabilitation programmes may be estimated wrongly. In this paper regression to the mean is explained comprehensively, and common misunderstandings are clarified. It is shown which conditions are crucial for occurrence of regression to the mean and which factors determine its strength. Furthermore it is shown how regression to the mean should be controlled in repeated measurement designs.

Artifacts↗
PubMed2004

[Duodenum-preserving pancreas head resection-an operative technique for retaining the organ in the treatment of chronic pancreatitis].

Chronic pancreatitis is an inflammatory disease characterized by the progressive conversion of pancreatic parenchyma to fibrous tissue. The most frequent causes are alcohol overconsumption and anatomic variants such as pancreas divisum, cholelithiasis, and individual genetic predisposition. The process of fibrosis with consecutive loss of pancreatic parenchyma leads to exocrine insufficiency and maldigestion and, in advanced stages of the disease, to diabetes mellitus. Beside exocrine and endocrine malfunction, mechanical complications occur such as the formation of pancreatic pseudocysts and duodenal and common bile duct obstruction. About 50% of patients with chronic pancreatitis need surgical intervention due to untreatable chronic pain. As recent investigations suggest that the head of the pancreas triggers the chronic inflammatory process, resection of this inflammatory mass must be regarded as pivotal in any surgical intervention. Radical techniques such as the Whipple procedure are undoubtedly successful regarding pain reduction but, even in its pylorus-preserving variant, associated with high postoperative morbidity due to a large loss of pancreatic parenchyma and the absence of duodenal passage. Thirty years ago, H.G. Beger described for the first time the technique of duodenum-preserving pancreatectomy, which better combines resection of the pancreatic head with low morbidity. Over the years, different variations of the original Beger technique (Frey, Izbicky, Berne modification) have been developed, and the excellent results obtained with these methods underline that organ-sparing techniques should be preferred in the surgical treatment of chronic pancreatitis.

Chronic Disease↗
PubMed2004

[On the problem of missing data: How to identify and reduce the impact of missing data on findings of data analysis].

The impact of missing data on the analysis of empirical data is a frequently unrecognized problem. Missing data may not only result in a decrease in the actual sample size but potentially biasing effects on statistical findings have to be considered as well. Two important points are made in this article: Firstly, it is shown why the identification of potential causes of missing data should be an inherent part of any data analysis; secondly, the handling of missing data should be based on appropriate assumptions in order to avoid biased results and problems concerning the interpretation of empirical findings.

Algorithms↗
PubMed2004

[Determining the quality of rater judgements using intraclass correlation, and enhancing rater judgements].

In clinical practice ratings by physicians and therapists are among the most frequently used assessment procedures. It is shown, which statistical measures should be used to assess the reliability of such ratings. Additionally, potential causes of insufficient reliability are presented. Improvement of rating quality may be achieved by rater training, which is based on an analysis of rating errors.

Algorithms↗
PubMed2003

Production of cysteine for bacterial and plant biotechnology: application of cysteine feedback-insensitive isoforms of serine acetyltransferase.

The first step of cysteine biosynthesis in bacteria and plants consists in the formation of O-acetylserine catalyzed by serine acetyltransferase (SAT). SAT is highly sensitive to feedback inhibition by cysteine as part of the regulatory circuit of cysteine biosynthesis und thus hampers over-expression and fermentation of cysteine in biotechnological production processes. Since plants contain multiple SAT isoforms with different cysteine feedback sensitivity, this resource was exploited to demonstrate the suitability of plant SATs for the production of cysteine in both bacteria and plants. Three new cDNAs encoding SATs were isolated from Nicotiana tabacum. The catalytic activity of SAT4 was insensitive up to 0.6 mM cysteine. Expression of SAT4 in a newly constructed Escherichia coli host strain without endogenous SAT activity yielded a significant accumulation of cysteine in the culture medium compared to expression of cysteine sensitive SATs in the same strain. The application of a similarly insensitive SAT isoform from A. thaliana demonstrated the suitability of this approach to increase cysteine levels in transgenic tobacco plants.

Acetyltransferases↗
PubMed2003

TIPS implantation raises leptin levels in patients with liver cirrhosis.

Increased leptin levels in patients with liver cirrhosis are postulated to result in malnutrition and increased energy expenditure. Since cirrhotic patients show improved nutritional status after a transjugular intrahepatic portosystemic stent shunt (TIPS), it was the aim of this study to evaluate plasma leptin levels and their influence on nutritional status prior to and after the TIPS procedure. We evaluated plasma leptin levels, body mass index (BMI), Child-Pugh score and pertinent biochemical parameters in 31 patients (19 men and 12 women) with severe complications of liver cirrhosis (74% ethyltoxic men, 50% ethyltoxic in women), prior to and after TIPS. Nineteen cirrhotic patients without TIPS served as controls. In women ascitic-free BMI significantly increased (from 22.8 +/- 4.6 kg/m2 to 23.9 +/- 4.9; p = 0.004 three months after TIPS), whereas in men only a tendency toward higher values (26.1 +/- 4.7 vs. 26.7 +/- 4.4; p = 0.28) was found. Analysis of peripheral venous leptin concentrations before and three months after TIPS revealed a significant increase in women (11.9 +/- 8.8 ng/ml vs. 18.6 +/- 14.9; p = 0.009) and in men (7.7 +/- 6.2 ng/ml vs. 12.2 +/- 9.0; p = 0.005). In addition, the leptin-BMI ratio increase significantly in women and men three months after TIPS implantation (women 0.49 +/- 0.29 vs. 0.73 +/- 0.52; p = 0.017; men 0.28 +/- 0.22 vs. 0.43 +/- 0.28; p = 0.002). On the other hand, patients without TIPS implantation showed no significant alterations of BMI and peripheral venous leptin concentrations. After TIPS implantation in liver cirrhotic patients, leptin levels were increased and the nutritional status improved. Therefore, our analysis suggests that in patients with predominantly ethyltoxic liver cirrhosis, elevated leptin levels are not a major reason for poorer body composition.

Adipose Tissue↗
PubMed2002

Molecular and biochemical analysis of the enzymes of cysteine biosynthesis in the plant Arabidopsis thaliana.

Among the amino acids produced by plants cysteine plays a special role as a mediator between assimilatory sulfate reduction and provision of reduced sulfur for cell metabolism. Part of this characteristic feature is the presence of cysteine synthesis in plastids, mitochondria and cytosol. Plants are the major source of reduced sulfur for human and animal nutrition. Cysteine biosynthesis deserves special attention, since reduced sulfur is channelled from cysteine into many sulfur-containing compounds in food and feed. Recent investigations are reviewed that focus on structure and regulation of cysteine synthesis in the model plant Arabidopsis thaliana. These data indicate that cysteine synthesis is not just an intermediate reaction step but that it is part of a regulatory network that mediates between inorganic sulfur supply and the demand for reduced sulfur during plant growth and in response to environmental changes.

Acetyltransferases↗
PubMed2002

The role of surgery in the prevention of familial cancer syndromes of the gastrointestinal tract.

Familial predisposition is a well-recognised risk factor in many gastrointestinal cancers. New developments in molecular genetics may contribute to the identification of cancer-prone families. Recognition of familial clustering and genetic testing can identify other members of the family with a high potential risk for cancer development. Appropriate surveillance mechanisms and management protocols may be initiated in order to prevent cancer and/or to detect cancer at an early stage. In the present article, various types of familial cancer of the gastrointestinal tract are reviewed and surgical, diagnostic and therapeutic issues for the management of esophageal, gastric, colorectal, and pancreatic cancer are emphasized.

Digestive System Neoplasms↗
PubMed2001

The cysteine synthase complex from plants. Mitochondrial serine acetyltransferase from Arabidopsis thaliana carries a bifunctional domain for catalysis and protein-protein interaction.

Serine acetyltransferase (SAT) catalyzes the rate-limiting step of cysteine biosynthesis in bacteria and plants and functions in association with O-acetylserine (thiol) lyase (OAS-TL) in the cysteine synthase complex. Very little is known about the structure and catalysis of SATs except that they share a characteristic C-terminal hexapeptide-repeat domain with a number of enzymatically unrelated acyltransferases. Computational modeling of this domain was performed for the mitochondrial SAT isoform from Arabidopsis thaliana, based on crystal structures of bacterial acyltransferases. The results indicate a left-handed parallel beta-helix consisting of beta-sheets alternating with turns, resulting in a prism-like structure. This model was challenged by site-directed mutagenesis and tested for a suspected dual function of this domain in catalysis and hetero-oligomerization. The bifunctionality of the SAT C-terminus in transferase activity and interaction with OAS-TL is demonstrated and discussed with respect to the putative role of the cysteine synthase complex in regulation of cysteine biosynthesis.

Acetyltransferases↗
PubMed2000

Genomic and functional characterization of the oas gene family encoding O-acetylserine (thiol) lyases, enzymes catalyzing the final step in cysteine biosynthesis in Arabidopsis thaliana.

The final step of cysteine biosynthesis in plants is catalyzed by O-acetylserine (thiol) lyase (OAS-TL), which occurs as several isoforms found in the cytosol, the plastids and the mitochondria. Genomic DNA blot hybridization and isolation of genomic clones indicate single copy genes (oasA1, oasA2, oasB and oasC) that encode the activities of OAS-TL A, B and C found in separate subcellular compartments in the model plant Arabidopsis thaliana. Sequence analysis reveals that the newly discovered oasA2 gene represents a pseudogene that is still transcribed, but is not functionally translated. The comparison of gene structures suggests that oasA1/oasA2 and oasB/oasC are closely related and may be derived from a common ancestor by subsequent duplications. OAS-TL A, B and C were overexpressed in an Escherichia coli mutant lacking cysteine synthesis and exhibited bifunctional OAS-TL and beta-cyanoalanine synthase (CAS) activities. However, all three proteins represent true OAS-TLs according to kinetic analysis and are unlikely to function in cyanide detoxification or secondary metabolism. In addition, it was demonstrated that the mitochondrial OAS-TL C exhibits in vivo protein-protein interaction capabilities with respect to cysteine synthase complex formation similar to cytosolic OAS-TL A and plastid OAS-TL B. Multiple database accessions for each of the A. thaliana OAS-TL isoforms can thus be attributed to a specified number of oas genes to which functionally defined gene products are assigned, and which are responsible for compartment-specific cysteine synthesis.

Arabidopsis↗
PubMed2000

Telemetry as a new concept in long term monitoring of SIDS-risk infant.

Sudden Infant Death Syndrome (SIDS) is the most frequent cause of infant death within the period of 2 to 12 months in western countries. It has been found that a suit similar to that worn by the astronauts during the execution of experiments on the Spacelab Mission D-2 is a very simple and useful means to carry the sensors required to monitor vital signs of babies at risk. A small baby-suit has been developed with the same technology used for the Spacelab Mission. The baby s suit is equipped with similar sensors to record thoracic and abdominal respiratory movements as its big -space travel brother-. This is a typical example of a successful technology transfer from medical aerospace activities into fields of daily clinical routine. In addition to the above described sensors, ECG-electrodes were integrated, as well as sensors to record vascular oxygen saturation and the corresponding pulse curve, and the baby s movements. All these vital signs are registered by a medical monitor, and permanently stored and automatically analysed online. In case of a life-threatening situation the system alerts simultaneously the personal at hospital and the parents at home. The requisite software algorithms have been developed by DLR in Cooperation with the pediatricians of the Pediatric Hospital in Köln-Porz, Cologne. When the system registers an alteration of the parameters above described -as a signal of a change in the baby s health condition- all vital signs are transfered in real-time to the supervising hospital via radio data transmission devices, mobile phone or a fixed network phone. The parents are also alerted by the device, and they can carry out the necessary reanimation procedures in case of an emergency. Parents will be trained in such actions when newborns must to be monitored. But nevertheless, they are guided and tele-assisted by an expert via telephone during the action. A clinical field trial, that will start in December 1999 at the Pediatric Hospital in Köln-Porz, Cologne, will evaluate the benefits of teleprotection by home monitoring of SIDS risk-babies.

Humans↗
PubMed2000

Modulation of redox potential in electron transfer proteins: effects of complex formation on the active site microenvironment of cytochrome b5.

The reduction potential of cytochrome b5 is modulated via the formation of a complex with polylysine at the electrode surface (Rivera et al., Biochemistry, 1998, 37, 1485). This modulation is thought to originate from the neutralization of a solvent exposed heme propionate and from dehydration of the complex interface. Although direct evidence demonstrating that neutralization of the charge on the heme propionate contributes to the modulation of the redox potential of cytochrome b5 has been obtained, evidence demonstrating that water exclusion from the complex interface plays a similar role has not been conclusive. Herein we report the preparation of the V45I/V61I double mutant of rat liver outer mitochondrial membrane (OM) cytochrome b5. This mutant has been engineered with the aim of restricting water accessibility to the exposed heme edge of cytochrome b5. The X-ray crystal structure of the V45I/V61I mutant revealed that the side chain of Ile at positions 45 and 61 restricts water accessibility to the interior of the heme cavity and protects a large section of the heme edge from the aqueous environment. Electrochemical studies performed with the V45I/V61I mutant of cytochrome b5, and with a derivative in which the heme propionates have been converted into the corresponding dimethyl ester groups, clearly demonstrate that dehydration of the heme edge contributes to the modulation of the reduction potential of cytochrome b5. In fact, these studies showed that exclusion of water from the complex interface exerts an effect (approximately 40 mV shift) that is comparable, if not larger, than the one originating from neutralization of the charge on the solvent exposed heme propionate (approximately 30 mV shift).

Binding Sites↗
PubMed2000

[Outcome predictors of intermediate-term treatments in inpatient child and adolescent psychiatry].

Purpose of this study is to identify predictors of the length of stay (LOS) in child and adolescent psychiatry (CAP) and the success of inpatient treatment. All child and adolescent inpatients that had been dismissed over a year's time from a non-university hospital after a medium-length-treatment were rated by their therapists (crisis interventions for < 2 weeks excluded). The group featured a low drop-out-rate (9.8%) and a high percentage of "problematic patients". The ICD-10 diagnoses were irrelevant for the prediction of LOS and success of treatment. The Global Assessment of Function scale (axis VI) correlated significantly with LOS, and functioning in all areas improved with a longer LOS. By the degree of initial psychopathology therapeutic success as well as LOS could be predicted fairly well. Concerning adolescents, motivation for treatment and the degree of cooperation both correlated with LOS and improvement, which implies the importance of their participation. For children under 12, cumulated psychosocial adversities (axis V) predicted a less positive outcome, cooperation of parents and patients raised the chance of success. Shortened lengths of stay will not lead to comparable success. As a system like DRGs for reimbursement of hospitalization in CAP will not prove to be efficient, other variables deserve more attention in future health economy planning. More intervening variables, such as psychosocial adversities, motivation, and cooperation have to be considered.

Adolescent↗