Characterization of Translocation Contact Sites Involved in the Import of Mitochondrial Proteins

Import of proteins into the mitochondrial matrix requires translocation across two membranes. Translocational intermediates of mitochondrial proteins, which span the outer and inner membrane simultaneously and thus suggest that translocation occurs in one step, have recently been described (Schleyer, M., and W. Neupert, 1985, Cell, 43:339-350). In this study we present evidence that distinct membrane areas are involved in the translocation process. Mitochondria that had lost most of their outer membrane by digitonin treatment (mitoplasts) still had the ability to import proteins. Import depended on proteinaceous structures of the residual outer membrane and on a factor that is located between the outer and inner membranes and that could be extracted with detergent plus salt. Translocational intermediates, which had been preformed before fractionation, remained with the mitoplasts under conditions where most of the outer membrane was subsequently removed. Submitochondrial vesicles were isolated in which translocational intermediates were enriched. Immunocytochemical studies also suggested that the translocational intermediates are located in areas where outer and inner membranes are in close proximity. We conclude that the membrane-potential-dependent import of precursor proteins involves translocation contact sites where the two membranes are closely apposed and are linked in a stable manner

Manfred Lüders/Jochen Wissinger (Hrsg.): Forschung zur Lehrerbildung. Kompetenzentwicklung und Programmevaluation. Münster u.a.: Waxmann 2007. 193 S., EUR 27,90. Michaela Gläser-Zikuda/Jürgen Seifried (Hrsg.): Lehrerexpertise. Analyse und Bedeutung unterrichtlichen Handelns. Münster u.a.: Waxmann 2008. 263 S. [Rezension]

Sammelrezension zu: Manfred Lüders/Jochen Wissinger (Hrsg.): Forschung zur Lehrerbildung. Kompetenzentwicklung und Programmevaluation. Münster/New York/Berlin/München: Waxmann 2007. 193 S., EUR 27,90. Michaela Gläser-Zikuda/Jürgen Seifried (Hrsg.): Lehrerexpertise. Analyse und Bedeutung unterrichtlichen Handelns. Münster/ New York/Berlin/München: Waxmann 2008. 263 S

The ideology of feasibility. How psychology lends plausibility to an efficiency-oriented educational policy

Anhand des amerikanischen Bildungswesens wird aufgezeigt, wie eine Reformpolitik, die sich an ökonomischen Zielen und Konzepten orientiert, von Teilen der akademischen Psychologie ideologische Unterstützung erfährt. Sowohl im Behaviorismus wie im Kognitivismus ist ein wissenschaftliches Selbstverständnis auszumachen, das die Disziplin auf Kriterien der technologischen Formung und Umformung von Verhalten verpflichtet. Psychologisches Wissen gilt als Kontroll- und Herstellungswissen, was einer Bildungsreform, die auf Produktivitäts- und Effizienzsteigerung setzt, Plausibilität und Machbarkeit in Aussicht stellt. Die These wird an ausgewählten Beispielen aus der Geschichte der amerikanischen Psychologie belegt. (DIPF/Orig.)Based on the example of the US-American educational system, the author shows how some parts of the academic psychology give ideological support to a reform policy oriented by economic objectives and concepts. In both behaviorism and cognitivism, a scientific self-awareness is to be discerned which commits the discipline to criteria of the technological shaping and reshaping of behavior. Psychological knowledge is considered control- and production knowledge, which, in turn, holds the promise of plausibility and feasibility for an educational reform seeking an increase in productivity and efficiency. This thesis is substantiated by select examples from the history of American psychology. (DIPF/Orig.

FROM MEDALS TO MUSCLES TO MOLECULES AND BACK AGAIN (DYSON LECTURE)

The purpose of this abstract is to provide an overview over my career activities in the areas of muscle and sport biomechanics. I started in the area of sport biomechanics as an undergraduate student at the Federal Technical Institute in Zurich with the intention of becoming a track and field coach. During my graduate studies, I realized that the science of human motion was more fascinating to me than the possibility to coach athletes, and so I pursued a career that led me to do work on the cellular and molecular mechanisms of muscle contraction. For the past decade, I have tried to apply the knowledge gained on the molecular and cellular level to practical problems in sport and rehabilitation. One of the lessons learnt in these endeavours was that intuition is good in science, but reliance on intuition alone often leads to incorrect conclusions. Therefore, checking your intuition at all times is essential. Another lesson I learnt was that, particularly in sport science, the dramatic breakthroughs in technique and material development (Fosbury flop, skate skiing, etc.) often come from athletes and coaches rather than scientists, thus working with athletes and coaches, rather than merely using them as subjects of your studies is essential

UNDERSTANDING MUSCLE PROPERTIES IN SPORTS PERFORMANCEOPTIMIZATION

Understanding muscle properties in the context of sports movements is crucial for maximizing power output, minimizing the cost of transport, or delaying fatigue. Here, we review the three basic properties of skeletal muscles that affect optimal working performance: the force-length, the force (power)-velocity, and the time-dependent force properties. We demonstrate on two examples (cycling and cross-country skiing) how knowledge of muscle properties can help maximize sport performance

MUSCLE SERIES ELASTICITY: THEORETICAL AND EXPERIMENTAL CONSIDERATIONS

Muscle series elasticity is easy to measure, but hard to associate with specific structures. It affects the length and rate of change in length of the contractile elements, provides possibilities for storage of elastic energy, and has been associated with energy saving mechanisms during movement. External tendons are clearly in series with the contractile machinery of the muscle, while aponeuroses are not. Aponeuroses have been implicitly or explicitly modeled as, or associated with, series elastic elements of the muscle’s contractile machinery. However, theoretical models that enforce isovolumetricity clearly reveal that aponeuroses cannot be considered in series with muscles or tendons. Experimental results confirm the theoretical conclusions and show that assuming aponeuroses to be part of the series elasticity of muscles over-estimates energy storage and metabolic cost savings

In situ titin properties at long lengths when Ig domain folding/unfolding is prevented

Titin, also known as connectin, is the largest known protein and was discovered in the mid-1970s and consists of Immunoglobulin (Ig) domains that flank N2A and PEVK segments. At long lengths and high force these Ig domains unfold. There is growing evidence that titin may change its stiffness by attaching its proximal portion to actin upon activation. If so folding/unfolding of Ig domains may become physiologically relevant. This is of interest because Ig domain folding/unfolding is associated with a great loss of energy, but preventing such folding/unfolding has been shown to result in a virtually elastic behaviour with no energy loss in isolated titin molecules.  Therefore, the purpose of this study was to test titin properties in situ within sarcomeres at lengths where Ig domain unfolding has occurred while preventing folding/unfolding of Ig domains during small stretch shortening cycles