Die Inkorporation von markiertem Sauerstoff aus Wasser in die ATP-, Kreatinphosphat- und Orthophosphat-Fraktion intakter Muskeln bei Ruhe,tetanischer Reizung und Erholung

Ohne ZusammenfassungMit 7 TextabbildungenDie vorliegenden Studien am Physiologischen Institut Freiburg i. Br. wurden durch einen Bundeszuschuß des Ministeriums für Atomkernenergie und Wasserwirtschaft (Bonn) ermöglicht. Die Untersuchungen in Zürich wurden aus Mitteln des Schweizer Nationalfonds getragen. Den genannten Institutionen gilt unser besonderer Dank. Vorläufige Mitteilungen über die Methode und die hier dargestellten Ergebnisse wurden bereits früher gegeben [siehe Fleckenstein, A. E. Gerlach, u. J. Janke gemeinsam mit P. Marmier: Naturwissenschaften 46, 365 (1959); Pflügers Arch. ges. Physiol. 270, 20 (1959); P. Marmier gemeinsam mit E. Gerlach, J. Janke u. A. Fleckenstein: Pflügers Arch. ges. Physiol. 270, 19 (1959); A. Fleckenstein: University of London Special University Lectures in Physiology 26–28. Oct. 1959: The turnover rates of high energy phosphate compounds during activity and rest as indicated by the oxygen exchange with H₂O¹⁸. Bericht von E. Gerlach sowie von J. Janke vor der Freiburger Med. Ges. vom 24. 11. 1959, vgl. Klin. Wschr. 38, 341–342 (1960)].     

Mechanism of the cardioprotective effect of triamterene in the rat heart. Myocardial protection via elevation of extracellular K+ and Mg++ concentrations

1. 2,4,7-Triamino-6-phenyl-pteridine (triamterene) protects the rat heart against isoproterenol-induced myocardial lesions: Whilst cardiotoxic doses of isoproterenol produce deleterious myocardial Ca overload, simultaneous admistration of triamterene diminishes myocardial Ca incorporation considerably. 2. As to the mechanism of action, triamterene increases the plasma contents of K and Mg by inhibiting renal excretion. Accordingly, oral administration of K and Mg salts, leading to a similar rise in the K and Mg concentrations of the plasma, also prevents abundant myocardial Ca incorporation. 3. Cardioprotection by triamterene can, in fact, be simply explained by its action on the plasma K and (particularly) Mg levels. This conclusion is drawn from a quantitative comparison of the inhibitory effects of triamterene (40 mg/kg s.c.) with those of KCl or MgCl2 (10 mMol/kg p.o.) on the isoproterenol-induced increase in myocardial 45Ca uptake and absolute Ca concentration. 4. Isoproterenol induced cardiomyopathy of the rat, an experimental model of non-coronarogenic myocardial lesions, has hitherto been successfully prevented with the use of Ca-antagonists (verapamil, D 600, prenylamine, fendiline). These compounds reduce Ca influx by restricting the Ca conductivity of the myocardial sarcolemma membrane ("slow channel"). The action of triamterene, on the other hand, is based on a totally different cardioprotective principle, namely competitive inhibition of intracellular myocardial Ca accumulation via an increase in K and Mg supply. In the future treatment of cardiomyopathy it seems rather promising to try a combination of both a Ca-antagonist and triamterene, thus applying two different therapeutic principles simultaneously.     

Transendothelial migration of myeloma cells is increased by tumor necrosis factor (TNF)-alpha via TNF receptor 2 and autocrine up-regulation of MCP-1.

The proinflammatory cytokine tumor necrosis factor (TNF)-alpha has been shown to facilitate leukocyte transendothelial migration. In multiple myeloma, TNF-alpha is an important factor in the promotion of growth and survival of the malignant cells. Studies have shown that enhanced TNF-alpha levels in myeloma patients correlated with aggressive disease. Therefore, we investigated the effect of recombinant human TNF-alpha on the migrational behavior of myeloma cells across the physiological barrier of the major disease compartment, i.e., human bone marrow endothelial cells. In the presence of TNF-alpha, we observed significantly increased migration both in established myeloma cell lines and in plasma cells from myeloma patients. Expression of TNF-receptor 2 (TNF-R2) but not TNF-receptor 1 (TNF-R1) was detected in myeloma cell lines. Myeloma cells of patients also showed expression of TNF-R2 but not TNF-R1. The effect of TNF-alpha could not be explained by altered expression of adhesion molecules or metalloproteases. Instead, we found an up-regulation of monocyte chemoattractant protein (MCP)-1 and confirmed that myeloma cells express the relevant receptor C-C chemokine receptor 2. Preincubation of myeloma cells with recombinant human MCP-1 also enhanced cell migration, and this effect, as well as the effect of TNF-alpha, was abolished by treatment with anti-MCP-1 antibody. In contrast, migration of myeloma cells in the direction of an MCP-1 gradient, i.e., chemotaxis, could not be observed in the cell lines investigated. Additionally, the mRNA level of TNF-alpha was up-regulated by the cytokine treatment, which points to an autocrine loop augmenting and/or stabilizing the TNF-alpha-MCP-1 pathway. In summary, our data clearly support additional investigations using anti-MCP-1 antibodies in myeloma progression.     

Peer influence on students’ estimates of performance: social comparison in clinical rotations

Context During clinical rotations, students move from one clinical situation to another. Questions exist about students’ strategies for coping with these transitions. These strategies may include a process of social comparison because in this context it offers the student an opportunity to estimate his or her abilities to master a novel rotation. These estimates are relevant for learning and performance because they are related to self‐efficacy. We investigated whether student estimates of their own future performance are influenced by the performance level and gender of the peer with whom the student compares him‐ or herself. Methods We designed an experimental study in which participating students (n = 321) were divided into groups assigned to 12 different conditions. Each condition entailed a written comparison situation in which a peer student had completed the rotation the participant was required to undertake next. Differences between conditions were determined by the performance level (worse, similar or better) and gender of the comparison peer. The overall grade achieved by the comparison peer remained the same in all conditions. We asked participants to estimate their own future performance in that novel rotation. Differences between their estimates were analysed using analysis of variance (anova) . Results Students’ estimates of their future performance were highest when the comparison peer was presented as performing less well and lowest when the comparison peer was presented as performing better (p < 0.001). Estimates of male and female students in same‐gender comparison conditions did not differ. In two of three opposite‐gender conditions, male students’ estimates were higher than those of females (p < 0.001 and p < 0.05, respectively). Conclusions Social comparison influences students’ estimates of their future performance in a novel rotation. The effect depends on the performance level and gender of the comparison peer. This indicates that comparisons against particular peers may strengthen or diminish a student’s self‐efficacy, which, in turn, may ease or hamper the student’s learning during clinical rotations. The study is limited by its experimental design. Future research should focus on students’ comparison behaviour in real transitions.     

The influence of achievement before,during and after medical school on physician job satisfaction

In this longitudinal study, we investigated the relationship between physicians’ prior achievements (before, during and after medical school) and job satisfaction, and tested the two lines of reasoning that prior achievements influence job satisfaction positively or negatively, respectively. The participants were graduates who started their medical training in 1982 (n = 147), 1983 (n = 154), 1992 (n = 143) and 1993 (n = 153). We operationalised job satisfaction as satisfaction (on a 10-point scale) with 13 cognitive, affective and instrumental aspects of the participants’ jobs. The measures of achievement before, during and after medical school included pre-university grade point average, study progress and a residency position in the specialty of first choice, respectively. We included the effect of curriculum type (problem-based learning versus traditional), gender and years of experience as moderator variables. Higher achievers before and during medical school were more satisfied about their income (β = .152, p < .01 and β = .149, p < .05), but less satisfied with their opportunities for personal development (β = ?.159, p < .05). High achievers after medical school were more satisfied with professional accomplishments (β = .095, p < .05), with appreciation from support personnel (β = .154, p < .01) and from patients (β = .120, p < .05). Effect sizes were small. Prior achievements influenced job satisfaction. The direction of the influences depended on the job satisfaction aspect in question, which indicates that it is important to distinguish between aspects of job satisfaction. To optimize job satisfaction of high achievers, it is important for graduates to obtain their preferred specialty. Furthermore, it is vital to provide them with enough opportunities for further development.