[How healthy are German schools? Trends from the years 2002 to 2010]. / Wie gesund sind deutsche Schulen? Entwicklungstrends von 2002 bis 2010.

This study aims to analyse the time trends of several conditions of the school environment (satisfaction with school, school demands, quality of instruction, classmate support) in Germany that are known to affect the health of pupils.We used the national German data of the Health-Behaviour in School-aged Children (HBSC) studies conducted in the years 2002, 2006 und 2010. The time trends of these four var-iables are described by using linear and logistic regression analyses considering survey year, age group (11, 13, 15 years), gender, and school track as independent variables.We found an increase of the perceived quality of instruction and of the student's satisfaction with school from the year 2002 to the year 2010. Furthermore, pupils report slightly less support from their classmates in the present survey compared to 2002. There are no changes in the reported demands.These trend results are discussed in the light of the impact of the PISA study and the efforts to implement settings-based health promoting schools in Germany.

[Mobbing and violence at school. Trends from 2002 to 2010]. / Mobbing und Gewalt an Schulen. Entwicklungstrends von 2002 bis 2010.

The purpose of this study was to undertake an assessment and differentiated examination of the development of bullying and violence in schools between 2002 and 2010 in Germany.We examined the national German data of Health Behaviour in School-aged Children (HBSC) study in 2002, 2006 and 2010. A paper-pencil questionnaire was distributed to a representative sample (N=17 929) of 11-, 13- and 15-year-old school children. The evaluation of the data was done by descriptive statistics and logistic regression analyses, controlled by age, gender, family affluence, school type and survey year.A clear positive trend could be identified: from 2002 to 2010 the number of bullies and bully victims decreased whereas the group of the uninvolved pupils increased. There was a delay in this trend for children with low family affluence.The obvious success in the prevention of violence is shown by the decreasing rate of bullies. The paper discusses whether future prevention should focus more on victims and children with educationally deprived background.

[The HBSC Study in Germany--study design and methodology]. / Die HBSC-Studie in Deutschland--Studiendesign und Methodik.

The aim of the HBSC-Study is to collect data on the physical and mental health and health behaviour of children and adolescents and to gain a deeper insight into their situation and the specific environment they grow up in. The HBSC-study is an international school-based cross-sectional survey conducted in collaboration with the World Health Organization (WHO). The survey takes place every 4 years since 1982 and is based on a standardised protocol. In Germany the survey was first conducted in 1994 as a pilot study in North Rhine-Westphalia. The German sample is based on a random sample of classes in all public schools in Germany. 11-, 13-, and 15-year-old pupils are surveyed by means of a paper and pencil questionnaire. The questionnaire comprises a broad selection of -topics, including sociodemographics, health and risk behaviours, family, school and peers. The reported trends in the supplement are based on the data from surveys in 2002 (N=5.650), 2006 (N=7.274) and 2010 (N=5.005). The representative samples for each of the survey years are defined as follows: in 2002 the data is based on information collected in 4 Federal States (Berlin, Hesse, North Rhine-Westphalia, Saxony); in 2006 5 states define the German data file (Berlin, Hamburg, Hesse, North Rhine-Westphalia, Saxony). The data from the 2010 survey comprises data from 15 Federal States. The HBSC-data contributes towards a better understanding of the relationship between health and living conditions of young people. The papers in this supplement deliver important insights into the living context of young people and in doing this they provide important information about their health and the long-term effectiveness of public-health-measures.

[Bullying, psychosocial health and risk behaviour in adolescence]. / Bullying, psychosoziale Gesundheit und Risikoverhalten im Jugendalter.

BACKGROUND: Bullying as a subform of aggressive behaviour has not received much attention as a specific risk behaviour in adolescence. Especially the adverse health effects in relation to bullying have been barely discussed in Germany. The objective of this study is to present age- and gender-specific prevalences in bullying and to analyse the association between the different bullying roles and subjective health as well as risk behaviour. METHODS: Data were obtained from the German part of the international WHO collaborative study "Health Behaviour in School-aged Children (HBSC)" in 2002. Overall, 5,650 school children aged 11-15 years were interviewed with a standardised questionnaire. Multivariate logistic regression models were used to analyse the association between bullying, psychosocial health and risk behaviour separately for girls and boys. RESULTS: About 17% of the boys and 10% of the girls aged 11-15 years were classified as repeated bullying perpetrators. About 10% of the school children are victims of being bullied several times a month. Another 3-5% of the adolescents belonged to the group of simultaneous victims and perpetrators (bully-victims). Perpetrators as well as victims showed strong associations with psychosocial health and risk behaviour. Independently of gender, victims were significantly more likely to report repeated psychosomatic complaints, adverse mental health and negative self-reported health (boys only), than uninvolved students. Especially for male perpetrators, strong associations with regular tobacco and alcohol use and repeated drunkenness were found, while these behaviour types were significantly less prevalent among victims. The bully-victim group is characterised by high rates of psychosomatic complaints and mental health problems (boys only). CONCLUSIONS: Bullying also seems to be widespread in schools in Germany and is strongly associated with subjective health and substance-related risk behaviour. The results suggest that bullying is a critical issue that requires increasing attention in health research. The unique health problems of victims and perpetrators suggest different intervention strategies for both groups.

A possible role of the junctional face protein JP-45 in modulating Ca2+ release in skeletal muscle.

We investigated the functional role of JP-45, a recently discovered protein of the junctional face membrane (JFM) of skeletal muscle. For this purpose, we expressed JP-45 C-terminally tagged with the fluorescent protein DsRed2 by nuclear microinjection in myotubes derived from the C2C12 skeletal muscle cell line and performed whole-cell voltage-clamp experiments. We recorded in parallel cell membrane currents and Ca(2+) signals using fura-2 during step depolarization. It was found that properties of the voltage-activated Ca(2+) current were not significantly changed in JP-45-DsRed2-expressing C2C12 myotubes whereas the amplitude of depolarization-induced Ca(2+) transient was decreased compared to control myotubes expressing only DsRed2. Converting Ca(2+) transients to Ca(2+) input flux using a model fit approach to quantify Ca(2+) removal, the change could be attributed to an alteration in voltage-activated Ca(2+) permeability rather than to altered removal properties or a lower Ca(2+) content of the sarcoplasmic reticulum (SR). Determining non-linear capacitive currents revealed a reduction of Ca(2+) permeability per voltage-sensor charge. The results may be explained by a modulatory effect of JP-45 related to its reported in vitro interaction with the dihydropyridine receptor and the SR Ca(2+) binding protein calsequestrin (CSQ).

Voltage-controlled Ca2+ release and entry flux in isolated adult muscle fibres of the mouse.

The voltage-activated fluxes of Ca(2+) from the sarcoplasmic reticulum (SR) and from the extracellular space were studied in skeletal muscle fibres of adult mice. Single fibres of the interosseus muscle were enzymatically isolated and voltage clamped using a two-electrode technique. The fibres were perfused from the current-passing micropipette with a solution containing 15 mm EGTA and 0.2 mm of either fura-2 or the faster, lower affinity indicator fura-FF. Electrical recordings in parallel with the fluorescence measurements allowed the estimation of intramembrane gating charge movements and transmembrane Ca(2+) inward current exhibiting half-maximal activation at -7.60 +/- 1.29 and 3.0 +/- 1.44 mV, respectively. The rate of Ca(2+) release from the SR was calculated after fitting the relaxation phases of fluorescence ratio signals with a kinetic model to quantify overall Ca(2+) removal. Results obtained with the two indicators were similar. Ca(2+) release was 2-3 orders of magnitude larger than the flux carried by the L-type Ca(2+) current. At maximal depolarization (+50 mV), release flux peaked at about 3 ms after the onset of the voltage pulse and then decayed in two distinct phases. The slower phase, most likely resulting from SR depletion, indicated a decrease in lumenal Ca(2+) content by about 80% within 100 ms. Unlike in frog fibres, the kinetics of the rapid phase of decay showed no dependence on the filling state of the SR and the results provide little evidence for a substantial increase of SR permeability on depletion. The approach described here promises insight into excitation-contraction coupling in future studies of genetically altered mice.

Voltage-dependent Ca2+ fluxes in skeletal myotubes determined using a removal model analysis.

The purpose of this study was to quantify the Ca2+ fluxes underlying Ca2+ transients and their voltage dependence in myotubes by using the "removal model fit" approach. Myotubes obtained from the mouse C2C12 muscle cell line were voltage-clamped and loaded with a solution containing the fluorescent indicator dye fura-2 (200 microM) and a high concentration of EGTA (15 mM). Ca2+ inward currents and intracellular ratiometric fluorescence transients were recorded in parallel. The decaying phases of Ca2+-dependent fluorescence signals after repolarization were fitted by theoretical curves obtained from a model that included the indicator dye, a slow Ca2+ buffer (to represent EGTA), and a sequestration mechanism as Ca2+ removal components. For each cell, the rate constants of slow buffer and transport and the off rate constant of fura-2 were determined in the fit. The resulting characterization of the removal properties was used to extract the Ca2+ input fluxes from the measured Ca2+ transients during depolarizing pulses. In most experiments, intracellular Ca2+ release dominated the Ca2+ input flux. In these experiments, the Ca2+ flux was characterized by an initial peak followed by a lower tonic phase. The voltage dependence of peak and tonic phase could be described by sigmoidal curves that reached half-maximal activation at -16 and -20 mV, respectively, compared with -2 mV for the activation of Ca2+ conductance. The ratio of the peak to tonic phase (flux ratio) showed a gradual increase with voltage as in rat muscle fibers indicating the similarity to EC coupling in mature mammalian muscle. In a subgroup of myotubes exhibiting small fluorescence signals and in cells treated with 30 microM of the SERCA pump inhibitor cyclopiazonic acid (CPA) and 10 mM caffeine, the calculated Ca2+ input flux closely resembled the L-type Ca2+ current, consistent with the absence of SR Ca2+ release under these conditions and in support of a valid determination of the time course of myoplasmic Ca2+ input flux based on the optical indicator measurements.

Voltage-activated calcium signals in myotubes loaded with high concentrations of EGTA.

In the present study we describe the analysis of optically recorded whole cell Ca(2+) transients elicited by depolarization in cultured skeletal myotubes. Myotubes were obtained from the mouse muscle-derived cell line C2C12 and from mouse satellite cells. The cells were voltage-clamped and perfused with an artificial intracellular solution containing 15 mM EGTA to ensure that the bulk of the Ca(2+) mobilized by depolarization is bound to this extrinsic buffer. The apparent on- and off-rate constants of EGTA and the dissociation rate constant of fura-2 in the cell were estimated by investigating the Ca(2+)-dependence of kinetic components of the fluorescence decay after repolarization. These parameters were used to calculate the time course of the total voltage-controlled flux of Ca(2+) to the myoplasmic space (Ca(2+) input flux). The validity of the procedure was confirmed by model simulations using artificial Ca(2+) input fluxes. Both C2C12 and primary-cultured myotubes showed a very similar phasic-tonic time course of the Ca(2+) input flux. In most measurements, the input flux was considerably larger and showed a different time course than the estimated Ca(2+) flux carried by the L-type Ca(2+) channels, indicating that it consists mainly of voltage-controlled Ca(2+) release from the sarcoplasmic reticulum. In cells with extremely small fluorescence transients, the calculated input fluxes matched the kinetic characteristics of the Ca(2+) inward current, indicating that Ca(2+) release was absent. These measurements served as a control for the fidelity of the fluorimetric flux analysis. The procedures promise a deeper insight into alterations of Ca(2+) release gating in studies employing myotube expression systems for mutant or chimeric protein components of excitation-contraction coupling.

Excitation-contraction coupling in skeletal muscle of a mouse lacking the dihydropyridine receptor subunit gamma1.

1. In skeletal muscle, dihydropyridine (DHP) receptors control both Ca(2+) entry (L-type current) and internal Ca(2+) release in a voltage-dependent manner. Here we investigated the question of whether elimination of the skeletal muscle-specific DHP receptor subunit gamma1 affects excitation-contraction (E-C) coupling. We studied intracellular Ca(2+) release and force production in muscle preparations of a mouse deficient in the gamma1 subunit (gamma-/-). 2. The rate of internal Ca(2+) release at large depolarization (+20 mV) was determined in voltage-clamped primary-cultured myotubes derived from satellite cells of adult mice by analysing fura-2 fluorescence signals and estimating the concentration of free and bound Ca(2+). On average, gamma-/- cells showed an increase in release of about one-third of the control value and no alterations in the time course. 3. Voltage of half-maximal activation (V(1/2)) and voltage sensitivity (k) were not significantly different in gamma-/- myotubes, either for internal Ca(2+) release activation or for the simultaneously measured L-type Ca(2+) conductance. The same was true for maximal Ca(2+) inward current and conductance. 4. Contractions evoked by electrical stimuli were recorded in isolated extensor digitorum longus (EDL; fast, glycolytic) and soleus (slow, oxidative) muscles under normal conditions and during fatigue induced by repetitive tetanic stimulation. Neither time course nor amplitudes of twitches and tetani nor force-frequency relations showed significant alterations in the gamma1-deficient muscles. 5. In conclusion, the overall results show that the gamma1 subunit is not essential for voltage-controlled Ca(2+) release and force production.

Malignant hyperthermia and excitation-contraction coupling.

Malignant hyperthermia (MH) is a state of elevated skeletal muscle metabolism that may occur during general anaesthesia in genetically pre-disposed individuals. Malignant hyperthermia results from altered control of sarcoplasmic reticulum (SR) Ca2+ release. Mutations have been identified in MH-susceptible (MHS) individuals in two key proteins of excitation-contraction (EC) coupling, the Ca2+ release channel of the SR, ryanodine receptor type 1 (RyR1) and the alpha1-subunit of the dihydropyridine receptor (DHPR, L-type Ca2+ channel). During EC coupling, the DHPR senses the plasma membrane depolarization and transmits the information to the ryanodine receptor (RyR). As a consequence, Ca2+ is released from the terminal cisternae of the SR. One of the human MH-mutations of RyR1 (Arg614Cys) is also found at the homologous location in the RyR of swine (Arg615Cys). This animal model permits the investigation of physiological consequences of the homozygously expressed mutant release channel. Of particular interest is the question of whether voltage-controlled release of Ca2+ is altered by MH-mutations in the absence of MH-triggering substances. This question has recently been addressed in this laboratory by studying Ca2+ release under voltage clamp conditions in both isolated human skeletal muscle fibres and porcine myotubes.