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T Behrens

Publications and source records attributed to T Behrens.

14 recordsLinked to original sources
PubMed2006

[Epidemiological studies in the HTA evaluation process].

Results of epidemiological studies should be considered as part of the available evidence when evaluating drug treatment benefits in health technology assessment (HTA). Pharmaco-epidemiological databases can provide a broader understanding of the effectiveness of drugs in populations that are frequently underrepresented in clinical trials. Such databases are also useful to investigate drug safety with regard to socio-demographic and medical care-related indicators and hereby contribute to an optimal and targeted pharmacological therapy. Using examples from pharmaco-epidemiological asthma studies, the present article discusses associated difficulties in interpreting database results against the background of various sources of bias and proposes possibilities for integrating observational data into the HTA evaluation process. Researchers are challenged to engage in considerable efforts to develop a standardized inventory of epidemiological methods, e.g. for the pooled analysis of epidemiological data.

Biomedical Technology↗
PubMed2005

"Safe" Coulomb excitation of 30Mg.

We report on the first radioactive beam experiment performed at the recently commissioned REX-ISOLDE facility at CERN in conjunction with the highly efficient gamma spectrometer MINIBALL. Using 30Mg ions accelerated to an energy of 2.25 MeV/u together with a thin (nat)Ni target, Coulomb excitation of the first excited 2+ states of the projectile and target nuclei well below the Coulomb barrier was observed. From the measured relative deexcitation gamma-ray yields the B(E2;0(+)gs-->2(+)1) value of 30Mg was determined to be 241(31)e2 fm4. Our result is lower than values obtained at projectile fragmentation facilities using the intermediate-energy Coulomb excitation method, and confirms the theoretical conjecture that the neutron-rich magnesium isotope 30Mg resides outside the "island of inversion."

Journal Article↗
PubMed2005

Symptoms of asthma and the home environment. The ISAAC I and III cross-sectional surveys in Münster, Germany.

BACKGROUND: The indoor home environment has been shown to be associated with the presence of respiratory symptoms and atopic disease. METHODS: Two cross-sectional surveys (1995-2000) were conducted, using data from the ISAAC phase I and III surveys, collected in Münster, Germany (n = 6,996, response 81.8%). We analyzed the prevalence ratio (PR) for several indoor exposures and asthma-related outcomes in 6- to 7-year-old children, adjusting for potential confounders. RESULTS: Positive associations were observed regarding exposure to molds, environmental tobacco smoke, cooking with gas and space heating with fossil fuels, but most associations were not statistically significant. Surprisingly, presence of a carpet was negatively associated with most respiratory conditions. When restricting the analysis to participants without avoidance of a carpet due to a history of atopic disease, the protective associations disappeared. Mostly, present pet ownership did not show positive associations with respiratory symptoms. However, ownership at different times in life revealed positive associations, particularly in regard to birds owned in the first year of life (PR 1.51, 95% CI 1.11-2.06, for sleep disturbance due to wheeze and PR 1.28, 95% CI 1.01-1.63, for wheeze during the last 12 months, respectively). CONCLUSIONS: Only few indoor factors were positively associated with the studied outcomes. The change of associations in participants that reported allergy-related avoidance of carpets suggests that the observed effects are a result of asthmatics' changed behavior. The effect of allergy-related change in behavior and the results observed concerning the ownership of pets at different ages underline the need of establishing a precise temporal relationship between disease and exposure.

Animals↗
PubMed2005

[Association between classic cardiovascular risk factors and age-related maculopathy (ARM). Results of the baseline examination of the Münster Aging and Retina Study (MARS)].

BACKGROUND: Epidemiological studies have reported inconsistent associations between cardiovascular risk factors and the occurrence of age-related maculopathy (ARM). METHODS: In the baseline examination of the Muenster Aging and Retina Study (MARS), we assessed this potential relationship in 1060 subjects who underwent clinical and ophthalmologic examinations. The ARM status was graded according to international standardized classifications. RESULTS: There were 974 eye pairs available for analysis. Smoking, hypertension, hypercholesterolemia, and a history of myocardial infarction or stroke were found significantly more often in patients with ARM. There were no statistically significant multivariate associations between overweight, diabetes, or a history of myocardial infarction or stroke. CONCLUSIONS: Our results confirm previous epidemiological studies pointing to a potential role of atherosclerotic processes in the development of ARM.

Aged↗
PubMed2005

[Visual function and quality of life in patients with age-related maculopathy: results of the Münster Age and Retina Study (MARS)].

BACKGROUND: The aim of this study was to examine the association between increasing severity of age-related maculopathy (ARM) stages, visual function and quality of life. METHODS: Using the 25-item version of the National Eye Institute Visual Function Questionnaire (NEI VFQ) in the Münster age and retina study (MARS), 974 patients (normal fundus: n = 208; early ARM: n = 466; late ARM: n = 300) with bilateral gradable fundus photographs were asked about their visual function and quality of life. The NEI VFQ scales with regard to general health, general vision, near vision, distance vision and peripheral vision were assessed. According to the ARM stages, age- and gender-adjusted mean scores were calculated and tested for statistically significant differences. RESULTS: The perception of general health, general vision, near vision, distance vision and peripheral vision was getting worse with increasing severity of ARM stages. Comparing the maculopathy groups, significant differences in age- and gender-adjusted mean scores were found between patients with late ARM and healthy subjects and patients with late and early ARM. Furthermore, we observed for the dimension general vision a significant difference of the mean score between early ARM and healthy control group [mean score; early ARM: 68.7 (0.7) vs. control group: 72.2 (1.1); p = 0.005]. CONCLUSIONS: The results of the NEI VFQ reflect the clinical expectation of an inverse relation between increasing severity of ARM stages and visual function and quality of life.

Age Factors↗
PubMed2004

Different methods to calculate effect estimates in cross-sectional studies. A comparison between prevalence odds ratio and prevalence ratio.

OBJECTIVES: According to results from the epidemiological literature, it can be expected that the prevalence odds ratio (POR) and the prevalence ratio (PR) differ with increasing disease prevalence. We illustrate different concepts to calculate these effect measures in cross-sectional studies and discuss their advantages and weaknesses, using actual data from the ISAAC Phase III cross-sectional survey in Münster, Germany. METHODS: We analyzed data on the association between self-reported traffic density and wheeze and asthma by means of the POR, obtained from a logistic regression, and the PR, which was estimated from a log-linear binomial model and from different variants of a Poisson regression. RESULTS: The analysis based on the less frequent disease, i.e. asthma with an overall prevalence of 7.8%, yielded similar results for all estimates. When wheezing with a prevalence of 17.5% was analyzed, the POR produced the highest estimates with the widest confidence intervals. While the point estimates were similar in the log-binomial model and Poisson regression, the latter showed wider confidence intervals. When we calculated the Poisson regression with robust variances, confidence intervals narrowed. CONCLUSIONS: Since cross-sectional studies often deal with frequent diseases, we encourage analyzing cross-sectional data based on log-linear binomial models, which is the 'natural method' for estimating prevalence ratios. If algorithms fail to converge, a useful alternative is to define appropriate starting values or, if models still do not converge, to calculate a Poisson regression with robust estimates to control for overestimation of errors in the binomial data.

Adolescent↗
PubMed2003

Are asthma and allergies in children and adolescents increasing? Results from ISAAC phase I and phase III surveys in Münster, Germany.

OBJECTIVE: To assess time trends in symptoms of asthma, allergic rhinitis, and atopic eczema among children in Münster, Germany. METHODS: Two cross-sectional surveys 5-years apart (1994/1995, 1999/2000) using ISAAC core written and video questionnaires and applying the ISAAC protocol. Two main age groups (6-7 and 13-14 year olds) were designated with information collected by parental and self-report for both age groups, respectively. A school-based sample of 7744 participants in the 1994/1995 survey and 7962 participants in the 1999/2000 survey was recruited. In the first and second surveys, response rates for the 6-7 year olds were 81 and 82%, respectively, while for the 13-14 year olds response rates were 94% in both. Analyses focus on the change in 12-month prevalence of symptoms of asthma, rhinitis, and eczema. RESULTS: There is a tendency towards an increase in current symptoms for all three conditions and in both age groups, but more so among girls. Indices of diagnosis either remained the same or increased in parallel to the increase in symptoms. Indices of severity also showed a homogenous increase in the 5-year study period. CONCLUSIONS: Our study shows that symptoms of asthma, rhinitis, and eczema are increasing, reflecting a change in the morbidity of these conditions in our population.

Adolescent↗
PubMed2001

The role of nitrogen-efficient cultivars in sustainable agriculture.

To improve nitrogen (N) efficiency in agriculture, integrated N management strategies that take into consideration improved fertilizer, soil, and crop management practices are necessary. This paper reports results of field experiments in which maize (Zea mays L.) and oilseed rape (Brassica napus L.) cultivars were compared with respect to their agronomic N efficiency (yield at a given N supply), N uptake efficiency (N accumulation at a given N supply), and N utilization efficiency (dry matter yield per unit N taken up by the plant). Under conditions of high N supply, significant differences among maize cultivars were found in shoot N uptake, soil nitrate depletion during the growing season, and the related losses of nitrate through leaching after the growing season. Experiments under conditions of reduced N supply indicated a considerable genotypic variation in reproductive yield formation of both maize and oilseed rape. High agronomic efficiency was achieved by a combination of high uptake and utilization efficiency (maize), or exclusively by high uptake efficiency (rape). N-efficient cultivars of both crops were characterized by maintenance of a relatively high N-uptake activity during the reproductive growth phase. In rape this trait was linked with leaf area and photosynthetic activity of leaves. We conclude that growing of N-efficient cultivars may serve as an important element of integrated nutrient management strategies in both low- and high-input agriculture.

Agriculture↗
PubMed1993

Ly-GDI, a GDP-dissociation inhibitor of the RhoA GTP-binding protein, is expressed preferentially in lymphocytes.

The Ras-related small GTP-binding proteins are involved in diverse cellular events, including cell signaling, proliferation, cytoskeletal organization, and secretion. The interconversion of the active, GTP-bound form of the protein to the inactive, GDP-bound form is influenced by two types of regulatory proteins, those that alter the intrinsic GTPase activity of the GTP-binding protein and those that affect the rate of GDP/GTP exchange. By utilizing a subtractive hybridization approach, we have isolated a human gene encoding Ly-GDI, a protein that has striking homology to the product of a previously cloned gene, Rho-GDI, which inhibits GDP/GTP exchange on the Rho family of GTPases. In contrast to Rho-GDI, which is ubiquitously expressed, Ly-GDI is expressed only in hematopoietic tissues and predominantly in B- and T-lymphocyte cell lines. The full-length Ly-GDI cDNA encodes a 27-kDa protein which binds to RhoA and inhibits GDP dissociation from RhoA. Stimulation of T lymphocytes with phorbol ester leads to phosphorylation of Ly-GDI, suggesting an involvement of Ly-GDI in lymphocyte activation pathways. Cell type-specific regulators of the Ras-like GTP-binding proteins may provide one mechanism by which different cell types respond uniquely to signals transduced through the same cell surface receptor or may provide a way by which the GTP-binding proteins can be uniquely engaged by tissue-restricted receptors.

Amino Acid Sequence↗