Biomedical subjects

Susanne Fischer

Publications and source records attributed to Susanne Fischer.

14 recordsLinked to original sources

PubMed2006

In planta AKT2 subunits constitute a pH- and Ca2+-sensitive inward rectifying K+ channel.

Heterologous expression of plant genes in yeast and animal cells represents a common approach to study plant ion channels. When expressed in Xenopus oocytes and COS cells the Arabidopsis Shaker-like K+ channel, AKT2 forms a weakly voltage-dependent channel, blocked by Ca2+ and protons. Channels with these characteristics, however, were not found in AKT2-expressing Arabidopsis cell types. To understand this phenomenon, we employed Agrobacterium-mediated transient transformation to functionally characterise Arabidopsis thaliana channels in Nicotiana benthamiana mesophyll cells. In this expression system we used AtTPK4 as a control for voltage-independent A. thaliana channels. Agrobacteria harbouring GFP-tagged constructs with the coding sequences of AKT2 and AtTPK4 were infiltrated into intact tobacco leaves. With quantitative RT-PCR analyses channel transcripts of AKT2 and AtTPK4 were determined in transformed leaves. These results were confirmed by Western blots with V5 epitope-tagged AKT2 and AtTPK4 proteins, showing that the channel protein was indeed synthesised. For functional analysis of these channels, mesophyll protoplasts were isolated from infiltrated leaf sections. Patch-clamp studies revealed that AKT2 channels in mesophyll protoplasts retained Ca2+ and pH sensitivity, characteristics of the heterologously expressed protein, but displayed pronounced differences in voltage-dependence and kinetics. AKT2-transformed mesophyll cells, displayed inward-rectifying, rather than voltage-independent K+ channels, initially characterised in AKT2-expressing animal cells. In contrast, AtTPK4 showed the same electrophysiological characteristics both, in oocytes and plant cells. Our data suggest that heterologous systems do not always possess all regulatory components for functional expression of plant channels. Therefore, transient expression of plant proteins in planta provides an additional research tool for rapid biophysical analysis of plant ion channels.

Arabidopsis↗

PubMed2006

Swiss doctors' attitudes towards end-of-life decisions and their determinants: a comparison of three language regions.

OBJECTIVES: To investigate attitudes to end-of-life decisions, and the influence of cultural factors and of doctors' personal characteristics on these attitudes. METHOD: As part of a European research project (EURELD), a study on attitudes towards medical end-of-life decisions was conducted among doctors in the German-, French- and Italian-speaking areas of Switzerland. A written questionnaire was sent to a random sample of nine different types of specialist; it presented 14 statements on end-of-life decisions and doctors were asked whether they agreed or disagreed with them. RESULTS: The response rate was 64%. 1360 questionnaires were studied. The results show general agreement with statements on the alleviation of pain and other symptoms with possible life-shortening effect, as well as on non-treatment decisions. The language region was a strong determinant of agreement on some attitudes towards end-of-life decisions. Agreement on the use of lethal drugs and alleviation of pain and other symptoms with possible life-shortening effect was higher among French-speaking than among German- and Italian-speaking doctors. For nontreatment decisions, agreement was higher in the German-speaking region than in the French- and Italian-speaking regions of the country. Italian-speaking doctors were strongly opposed to any kind of end-of-life decision. Religious believers and those who attended a larger number of terminal patients tended to disagree more often with end-of-life decisions than the other doctors. CONCLUSIONS: In end-of-life decision-making, Switzerland represents "Europe in miniature". The impact on end-of-life decisions of cultural factors and the number of terminal patients attended needs further consideration.

Adult↗

PubMed2006

Responders and non-responders in a study on medical end-of-life decisions in Denmark, the Netherlands, Sweden and Switzerland.

OBJECTIVES: To determine the direction and magnitude of participation bias in end-of-life research. METHODS: Within the framework of a European survey on medical end-of-life decisions, a non-response study was conducted among physicians in Denmark, the Netherlands, Sweden and Switzerland. People were asked about their attitudes and experiences in the area of medial end-of-life decision. The response rates ranged from 12.8% (Netherlands) to 39.4% (Switzerland). The responders (n = 5403) and the non-responders (n = 866) were compared regarding socio-demographic characteristics, experiences with terminal patients and agreement with attitudes towards "end-of-life decisions". The reasons for non-participation to the study were analyzed. RESULTS: Non-response did not cause socio-demographic distortion, but non-responders had statistically significantly fewer terminal patients than responders. Agreement rates were statistically significantly higher among responders than among non-responders for euthanasia, non-treatment decision and life-preserving statements. Neutral answers were statistically significantly more frequent among non-responders than among responders for life-preserving and euthanasia statements. The most commonly mentioned reason for non-participation was "lack of time". CONCLUSION: Non-participation does cause an overestimation of proponents of life-shortening, as well as of life-preserving end-of-life decisions. Non-responders more often have ambiguous attitudes towards end-of-life decisions than responders.

Adult↗

PubMed2006

Intentionally hastening death by withholding or withdrawing treatment.

PURPOSE: This study aims to provide empirical data on physicians' intentions in withholding and withdrawing treatment, and to discuss possible implications for the ethical debate. BASIC PROCEDURES: The data presented come from EURELD, a large research project designed to investigate medical end-of-life decisions in six European countries. A continuous random sample of death certificates formed the basis for contacting doctors who had attended the deceased; the doctors were asked to complete, strictly anonymously, mail questionnaires on the decisions taken at the end of their patients' lives. MAIN FINDINGS: In the six countries studied, physicians reported they had the explicit intention of hastening the end of life in 45% of all treatments that were withheld/ withdrawn. The highest numbers of cases with an underlying intention of hastening the end of life were found in Switzerland and Sweden (52% and 51%, respectively); the lowest figures came from Denmark and Belgium (36% and 38%). Middle-ranking countries were Italy (42%) and the Netherlands (45%). Overall, dialysis and respiration were comparatively more often forgone with the explicit intent to hasten the end of life (57% and 54%, respectively), whereas a particularly low percentage of cases with such an explicit intention was found for oncotherapy (34%). PRINCIPAL CONCLUSIONS: In almost every second case, a medical decision to withhold or withdraw treatment is taken with the explicit intention of hastening the end of the patient's life. No clear association can be found between the intent to hasten the end of life and features of the treatment forgone that can be determined objectively, such as the likelihood and extent of a life-shortening effect, the immediacy of death, or the expected burden of any potential life-sustaining measure. The findings of the study challenge the usefulness of doctors' intentions with regard to hastening the end of life as criteria for moral judgements on decisions to withhold or withdraw medical treatment.

Critical Care↗

PubMed2005

Elucidation of the stator organization in the V-ATPase of Neurospora crassa.

V-ATPases are membrane protein complexes that pump protons in the lumen of various subcellular compartments at the expense of ATP. Proton pumping is done by a rotary mechanism that requires a static connection between the membrane pumping domain (V(0)) and the extrinsic catalytic head (V(1)). This static connection is composed of several known subunits of the V-ATPase, but their location and topological relationships are still a matter of controversy. Here, we propose a model for the V-ATPase of Neurospora crassa on the basis of single-particle analysis by electron microscopy. Comparison of the resulting map to that of the A-ATPase from Thermus thermophilus allows the positioning of two subunits in the static connecting region that are unique to eukaryotic V-ATPases (C and H). These two subunits seem to be located on opposite sides of a semicircular arrangement of the peripheral connecting elements, suggesting a role in stabilizing the stator in V-ATPases.

Intracellular Membranes↗

PubMed2005

Access to death certificates: what should research ethics committees require for approval?

PURPOSE: To present and discuss the reactions of research ethics committees (RECs) in a number of countries when asked for approval of a study requiring access to death certificates to identify the physicians signing the certificates and to send them a four-page questionnaire about medical decisions made at the patient's end-of-life that could possibly have hastened death. METHODS: A simple questionnaire were sent to the responsible national investigator in an international study (Australia, Belgium, Denmark, Italy, the Netherlands, Sweden, Switzerland) asking about the interactions between the national research group and the national/regional REC(s). RESULTS: Different laws or guidelines were used by the RECs. Denmark, the Netherlands, and Switzerland did not require an application to a REC. In Australia and Sweden, the RECs wanted changes in the research protocol, and one national research group had to refrain from publishing its results because the attrition rate became too high, probably due to the required changes in the protocol. RECOMMENDATIONS: Generally, similar demands from all RECs in relation to one project are strongly desirable. In epidemiological research, in which voluntary completion of an anonymous questionnaire demonstrates consent, additional prior informed consent about being approached should not be required.

Death Certificates↗

PubMed2005

AKT2/3 subunits render guard cell K+ channels Ca2+ sensitive.

Inward-rectifying K+ channels serve as a major pathway for Ca2+-sensitive K+ influx into guard cells. Arabidopsis thaliana guard cell inward-rectifying K+ channels are assembled from multiple K+ channel subunits. Following the recent isolation and characterization of an akt2/3-1 knockout mutant, we examined whether the AKT2/3 subunit carries the Ca2+ sensitivity of the guard cell inward rectifier. Quantification of RT-PCR products showed that despite the absence of AKT2 transcripts in guard cells of the knockout plant, expression levels of the other K+ channel subunits (KAT1, KAT2, AKT1, and AtKC1) remained largely unaffected. Patch-clamp experiments with guard cell protoplasts from wild type and akt2/3-1 mutant, however, revealed pronounced differences in Ca2+ sensitivity of the K+ inward rectifier. Wild-type channels were blocked by extracellular Ca2+ in a concentration- and voltage-dependent manner. Akt2/3-1 mutants lacked the voltage-dependent Ca2+ block, characteristic for the K+ inward rectifier. To confirm the akt2/3-1 phenotype, two independent knockout mutants, akt2-1 and akt2::En-1 were tested, demonstrating that the loss of AKT2/3 indeed affects the Ca2+ dependence of guard cell inward rectifier. In contrast to AKT2 knockout plants, AKT1, AtKC1, and KAT1 loss-of-function mutants retained Ca2+ block of the guard cell inward rectifier. When expressed in HEK293 cells, AKT2 channel displayed a pronounced susceptibility toward extracellular Ca2+, while the dominant guard cell K+ channel KAT2 was Ca2+ insensitive. Thus, we conclude that the AKT2/3 subunit constitutes the Ca2+ sensitivity of the guard cell K+ uptake channel.

Arabidopsis↗

PubMed2005

Influence of patient symptoms and physical findings on general practitioners' treatment of respiratory tract infections: a direct observation study.

BACKGROUND: The high rate of antibiotic prescriptions general practitioners (GPs) make for respiratory tract infections (RTI) are often explained by non-medical reasons e.g. an effort to meet patient expectations. Additionally, it is known that GPs to some extent believe in the necessity of antibiotic treatment in patients with assumed bacterial infections and therefore attempt to distinguish between viral and bacterial infections by history taking and physical examination. The influence of patient complaints and physical examination findings on GPs' prescribing behaviour was mostly investigated by indirect methods such as questionnaires. METHODS: Direct, structured observation during a winter "cough an cold period" in 30 (single handed) general practices. All 273 patients with symptoms of RTI (age above 14, median 37 years, 51% female) were included. RESULTS: The most frequent diagnoses were 'uncomplicated upper RTI/common cold' (43%) followed by 'bronchitis' (26%). On average, 1.8 (95%-confidence interval (CI): 1.7-2.0) medicines per patient were prescribed (cough-and-cold preparations in 88% of the patients, antibiotics in 49%). Medical predictors of antibiotic prescribing were pathological findings in physical examination such as coated tonsils (odds ratio (OR) 15.4, 95%-CI: 3.6-66.2) and unspecific symptoms like fatigue (OR 3.1, 95%-CI 1.4-6.7), fever (OR 2.2, 95%-CI: 1.1-4.5) and yellow sputum (OR 2.1, 95%-CI: 1.1-4.1). Analysed predictors explained 70% of the variance of antibiotic prescribing (R2 = 0,696). Efforts to reduce antibiotic prescribing, e.g. recommendations for self-medication, counselling on home remedies or delayed antibiotic prescribing were rare. CONCLUSIONS: Patient complaints and pathological results in physical examination were strong predictors of antibiotic prescribing. Efforts to reduce antibiotic prescribing should account for GPs' beliefs in those (non evidence based) predictors. The method of direct observation was shown to be accepted both by patients and GPs and offered detailed insights into the GP-patient-interaction.

Adolescent↗

PubMed2004

Physicians' attitudes towards end-of-life decisions: a comparison between seven countries.

In the context of an European collaborative research project (EURELD), a study on attitudes towards medical end-of-life decisions was conducted among physicians in Belgium, Denmark, Italy, the Netherlands, Sweden and Switzerland. Australia also joined the consortium. A written questionnaire with structured questions was sent to practising physicians from specialties frequently involved in the care of dying patients. 10,139 questionnaires were studied. Response rate was equal to or larger than 50% in all countries except Italy (39%). Apart from general agreement with respect to the alleviation of pain and symptoms with possible life-shortening effect, there was large variation in support--between and within countries--for medical decision that may result in the hastening of death. A principal component factor analysis found that 58% of the variance of the responses is explained by four factors. 'Country' explained the largest part of the variation of the standardized factor scores.

Adult↗

PubMed2004

Structure-based assembly of protein complexes in yeast.

Images of entire cells are preceding atomic structures of the separate molecular machines that they contain. The resulting gap in knowledge can be partly bridged by protein-protein interactions, bioinformatics, and electron microscopy. Here we use interactions of known three-dimensional structure to model a large set of yeast complexes, which we also screen by electron microscopy. For 54 of 102 complexes, we obtain at least partial models of interacting subunits. For 29, including the exosome, the chaperonin containing TCP-1, a 3'-messenger RNA degradation complex, and RNA polymerase II, the process suggests atomic details not easily seen by homology, involving the combination of two or more known structures. We also consider interactions between complexes (cross-talk) and use these to construct a structure-based network of molecular machines in the cell.

Chaperonins↗

PubMed2003

Sevoflurane provides greater protection of the myocardium than propofol in patients undergoing off-pump coronary artery bypass surgery.

BACKGROUND: Sevoflurane, like other halogenated anesthetics, has been shown to have a protective effect on the myocardium at risk after an ischemic injury. The current study tested the hypothesis that such beneficial effects, so far mainly seen in the laboratory, are reproducible in humans. METHODS: After institutional review board approval, 20 patients scheduled to undergo elective off-pump coronary artery bypass surgery were randomized to receive general anesthesia with either sevoflurane or propofol. Except for this, anesthetic and surgical management was the same in both groups. For assessing myocardial injury, troponin I and myocardial fraction of creatine kinase were determined during the first 24 postoperative hours. Systemic hemodynamic variables were measured before, during, and after completion of coronary artery bypass. RESULTS: Troponin I concentrations increased significantly more in propofol-anesthetized patients than in patients anesthetized with sevoflurane. CONCLUSION: Patients receiving sevoflurane for off-pump coronary artery surgery had less myocardial injury during the first 24 postoperative hours than patients receiving propofol. The results further support cardioprotective effects of sevoflurane.

Aged↗

PubMed2002

[Patterns of risk behavior and aspects of authoritarianism: results of an empirical study of 20-year-old men].

OBJECTIVES: As possible explanations for risk behaviour in young men past strains, lack of resources, social individualization processes and genderspecific aspects are discussed. For this study the concept of authoritarianism was used as the model for analysis. METHODS: 4,235 recruits from the German-speaking part of Switzerland were surveyed with regard to risk behaviours in sexuality, alcohol consumption, suicide tendency, and violence. The predicting variables for non-risk behaviours and for different risk behaviour patterns were identified by means of logistic regression analysis. The main predicting variables included authoritarianism, disposition to discriminate, stressful life events, and personal and social resources. RESULTS: The results show that the different aspects of authoritarianism not only influence prejudice and aggression towards dissenters as has been shown in other studies, but risk behaviours in general. Between the aspects of authoritarianism and risk behaviour patterns positive as well as negative correlations were found. CONCLUSION: We conclude that there are different types of authoritarian men who differ with regard to risk behaviours.

Adult↗

PubMedDate not supplied

In vitro cultivation of an insect Microsporidian Tubulinosema ratisbonensis in mammalian cells.

Tubulinosema ratisbonensis is a microsporidian pathogen of Drosophila melanogaster belonging to the family Tubulinosematidae. The microsporidia in this family mainly cause infections in invertebrate hosts, but two members of this family, Brachiola vesicularum and Brachiola algerae, have been found to cause infections in humans as well. Moreover, B. algerae can be transmitted to immunodeficient mice and grows in mammalian cell cultures. Thus, the examination of the opportunistic properties of other members of the family Tubulinosematidae is important. Spores of T. ratisbonensis, isolated from infected fruit flies, were used to inoculate mammalian and insect cell cultures. Parasite growth was only seen in human lung fibroblasts. No growth was seen in Vero cells or insect cell cultures. Comparison of growth kinetics at 31 degrees C and 37 degrees C showed that there were fewer and smaller parasitic foci in cultures incubated at 37 degrees C. Transmission electron microscopy revealed the typical ultrastructure of T. ratisbonensis, and scanning electron microscopy showed oval or slightly pyriform spores, with some spores having extruded their polar tubes. The PCR-amplified sequences of rDNA fragments from infected cell cultures were 100% identical to the original T. ratisbonensis rRNA sequence. As T. ratisbonensis is able to proliferate in mammalian cell cultures, it may have the opportunistic properties of other members of the family Tubulinosematidae.

Animals↗

PubMedDate not supplied

Morphological and molecular investigations of Tubulinosema ratisbonensis gen. nov., sp. nov. (Microsporidia: Tubulinosematidae fam. nov.), a parasite infecting a laboratory colony of Drosophila melanogaster (Diptera: Drosophilidae).

A new species of microsporidia from Drosophila melanogaster was investigated by light and electron microscopy and by ribosomal RNA (rRNA) sequencing. This microsporidium and the previously described Nosema kingi and Nosema acridophagus have been transferred to the new genus Tubulinosema gen. nov. with the following characters: nuclei are in diplokaryotic arrangement during the life cycle. All stages are in direct contact with the host cell cytoplasm, slightly anisofilar polar tube with the last coils being smaller in diameter arranged in one or two rows on both sides of the diplokaryon and small tubuli on the surface of late meronts. Spores are oval or slightly pyriform. Thick endospore wall, thinner over anchoring disc. This new genus and the genus Brachiola have been placed in a new family Tubulinosematidae fam. nov. Phylogenetic analysis of small subunit rRNA sequences by different methods placed Tubulinosema spp. in one clade with the genus Brachiola forming its sister clade, which is distant from the clade containing the true Nosema spp. including Nosema bombycis.

Animals↗