Home-Schooling

Die vorliegende Arbeit hat das Ziel einen Vergleich zwischen den Motiven von Eltern in Österreich einerseits und Großbritannien/Australien andererseits in Bezug auf häuslichen Unterricht durchzuführen. Um einen derartigen Vergleich anzustellen, wurde zunächst ein Literaturteil mit Schwerpunkt auf internationalen Studien (vorwiegend USA und Kanada) zum Thema „Motive für häuslichen Unterricht“ erstellt. Im Anschluss daran wurde eine eigene, von den Verfasserinnen durchgeführte Erhebung zur Thematik vorgestellt. Die Untersuchung basierte auf zehn Interviews mit Müttern, die ein Kind/mehrere Kinder/alle ihre Kinder in Österreich daheim unterrichten, wobei Voraussetzung war, dass sich mindestens ein zu Hause unterrichtetes Kind im Volksschulalter befand. Dabei wurde der gesamte Themenkomplex des Home Schooling abgefragt: Alter, Geschlecht und Anzahl der zu Hause unterrichteten Kinder, Dauer des Unterrichts zu Hause, Schulbildung der Eltern, Ablauf des Unterrichts daheim, verwendete Materialien, unterrichtende Person, Auswirkungen des häuslichen Unterrichts auf die Familie, Akzeptanz des häuslichen Unterrichts seitens des Umfeldes, Änderungswünsche bezüglich häuslichem Unterricht in Österreich und schließlich der Schwerpunkt der Befragung: die Motive für den häuslichen Unterricht. Anschließend wurde eine Studie von Alan Thomas (2007) im Hinblick auf die Motive, die die 100 von Thomas befragten Familien in Großbritannien und Australien für Home Schooling angegeben hatten, analysiert. Diese Ergebnisse wurden dann mit den in Österreich erhobenen Motiven und den im Literaturteil für die USA und Kanada erhobenen Motiven verglichen. Es zeigte sich, dass die Eltern aus den genannten Ländern die gleichen Motive hatten, abgesehen von religiösen Motiven, die nur in den USA, in Großbritannien und in Kanada genannt wurden. Die am häufigsten genannten Motive waren: eine bessere und qualitativ hochwertigere Bildung durch häuslichen Unterricht, mehr Zeit, die man mit den eigenen Kindern verbringen kann, mehr Berücksichtigung der speziellen Bedürfnisse und Interessen der Kinder, Vermittlung besonderer Werte, kein Mobbing, keine Probleme mit Lehrkräften, keine Schulängste und keine anderen psychologischen Probleme.This paper aims at comparing the motives parents have in Austria and Great Britain/Australia, respectively for teaching their children at home (home schooling). In order to be able to compare those motives, the authors of this paper first analyzed the relevant literature discussing the motives parents have for educating their children at home (the studies were mainly carried out in the USA and Canada). Then they carried out their own study on home schooling in Austria by interviewing ten mothers who educated (one or more or all of) their children at home (at least one child educated at home had to be between 6 and 10 years old (elementary school age)). The questions aimed at the entire home schooling complex (number of children educated at home, age, gender, duration of home schooling so far, educational career of parents, process and organization of teaching at home, educational material used, impact of home schooling on family (life), reactions by family and others to home schooling, changes in the child due to home schooling, improvements suggested for home schooling in Austria, and most importantly: the motives for home schooling). In the next chapter, a study by Alan Thomas (2007) carried out in Great Britain and Australia based on 100 interviews with home schooling parents was analyzed. Then, those motives were compared with the motives the Austrian families had given. Finally, a comparison of the motives given in Thomas’ study, the ones mentioned in the Austrian study and those listed in all the other studies analyzed in the literature part of the paper were compared with each other. It turned out that the motives in all three countries as well as in the USA and Canada hardly differed from each other, except for religious reasons for home education that were only mentioned by American, British and Australian parents. The main motives were: higher level of education believed to be reached at home, more time spent with children, better consideration of special interests and needs of children, teaching children the “right” (social) values, no mobbing, no problems with teachers, no school anxieties, no other psychological problems

Evidence for shear-mediated Ca2+ entry through mechanosensitive cation channels in human platelets and a megakaryocytic cell line

The role of mechanosensitive (MS) Ca2+-permeable ion channels in platelets is unclear, despite the importance of shear stress in platelet function. We sought to investigate the expression and functional relevance of MS channels in human platelets. The effect of shear stress on Ca2+ entry in human platelets and Meg-01 megakaryocytic cells loaded with Fluo-3 was examined by confocal microscopy. Cells were attached to microscope slides within flow chambers that allowed application of physiological and pathological shear stress. Arterial shear (1002.6s-1) induced a sustained increase in intracellular calcium ([Ca2+]i) in Meg-01 cells and enhanced the frequency of repetitive Ca2+ transients by 80% in platelets. These Ca2+ increases were abrogated by the MS channel inhibitor GsMTx-4 or by chelation of extracellular Ca2+. Thrombus formation was studied on collagen-coated surfaces using 3,3'-dihexyloxacarbocyanine iodide (DiOC6)-stained platelets. In addition, [Ca2+]i and functional responses of washed platelet suspensions were studied with Fura-2 and light transmission aggregometry, respectively. Thrombus size was reduced 50% by GsMTx-4 independently of P2X1 receptors. In contrast, GsMTx-4 had no effect on collagen-induced aggregation and on Ca2+ influx via TRPC6 or Orai1 channels, and caused only a minor inhibition of P2X1-dependent Ca2+ entry. The Piezo1 agonist, Yoda1, potentiated shear-dependent platelet Ca2+ transients by 170%. Piezo1 mRNA transcripts and protein were detected in both platelets and Meg-01 cells using qRT-PCR and Western blotting. We conclude that platelets and Meg-01 cells express the MS cation channel Piezo1, which may contribute to Ca2+ entry and thrombus formation under arterial shear stress

Adaptive behavior of bacterial mechanosensitive channels is coupled to membrane mechanics

Mechanosensitive channel of small conductance (MscS), a tension-driven osmolyte release valve residing in the inner membrane of Escherichia coli, exhibits a complex adaptive behavior, whereas its functional counterpart, mechanosensitive channel of large conductance (MscL), was generally considered nonadaptive. In this study, we show that both channels exhibit similar adaptation in excised patches, a process that is completely separable from inactivation prominent only in MscS. When a membrane patch is held under constant pressure, adaptation of both channels is manifested as a reversible current decline. Their dose–response curves recorded with 1–10-s ramps of pressure are shifted toward higher tension relative to the curves measured with series of pulses, indicating decreased tension sensitivity. Prolonged exposure of excised patches to subthreshold tensions further shifts activation curves for both MscS and MscL toward higher tension with similar magnitude and time course. Whole spheroplast MscS recordings performed with simultaneous imaging reveal activation curves with a midpoint tension of 7.8 mN/m and the slope corresponding to ∼15-nm2 in-plane expansion. Inactivation was retained in whole spheroplast mode, but no adaptation was observed. Similarly, whole spheroplast recordings of MscL (V23T mutant) indicated no adaptation, which was present in excised patches. MscS activities tried in spheroplast-attached mode showed no adaptation when the spheroplasts were intact, but permeabilized spheroplasts showed delayed adaptation, suggesting that the presence of membrane breaks or edges causes adaptation. We interpret this in the framework of the mechanics of the bilayer couple linking adaptation of channels in excised patches to the relaxation of the inner leaflet that is not in contact with the glass pipette. Relaxation of one leaflet results in asymmetric redistribution of tension in the bilayer that is less favorable for channel opening

Molecular Biomechanics: The Molecular Basis of How Forces Regulate Cellular Function

Recent advances have led to the emergence of molecular biomechanics as an essential element of modern biology. These efforts focus on theoretical and experimental studies of the mechanics of proteins and nucleic acids, and the understanding of the molecular mechanisms of stress transmission, mechanosensing and mechanotransduction in living cells. In particular, single-molecule biomechanics studies of proteins and DNA, and mechanochemical coupling in biomolecular motors have demonstrated the critical importance of molecular mechanics as a new frontier in bioengineering and life sciences. To stimulate a more systematic study of the basic issues in molecular biomechanics, and attract a broader range of researchers to enter this emerging field, here we discuss its significance and relevance, describe the important issues to be addressed and the most critical questions to be answered, summarize both experimental and theoretical/computational challenges, and identify some short-term and long-term goals for the field. The needs to train young researchers in molecular biomechanics with a broader knowledge base, and to bridge and integrate molecular, subcellular and cellular level studies of biomechanics are articulated.National Institutes of Health (U.S.) (grant UO1HL80711-05 to GB)National Institutes of Health (U.S.) (grant R01GM076689-01)National Institutes of Health (U.S.) (grant R01AR033236-26)National Institutes of Health (U.S.) (grant R01GM087677-01A1)National Institutes of Health (U.S.) (grant R01AI44902)National Institutes of Health (U.S.) (grant R01AI38282)National Science Foundation (U.S.) (grant CMMI-0645054)National Science Foundation (U.S.) (grant CBET-0829205)National Science Foundation (U.S.) (grant CAREER-0955291

Expression and characterization of the bacterial mechanosensitive channel MscS in Xenopus laevis oocytes

We have successfully expressed and characterized mechanosensitive channel of small conductance (MscS) from Escherichia coli in oocytes of the African clawed frog, Xenopus laevis. MscS expressed in oocytes has the same single-channel conductance and voltage dependence as the channel in its native environment. Two hallmarks of MscS activity, the presence of conducting substates at high potentials and reversible adaptation to a sustained stimulus, are also exhibited by oocyte-expressed MscS. In addition to its ease of use, the oocyte system allows the user to work with relatively large patches, which could be an advantage for the visualization of membrane deformation. Furthermore, MscS can now be compared directly to its eukaryotic homologues or to other mechanosensitive channels that are not easily studied in E. coli

Expression of Stretch-Activated Two-Pore Potassium Channels in Human Myometrium in Pregnancy and Labor

Background: We tested the hypothesis that the stretch-activated, four-transmembrane domain, two pore potassium channels (K2P), TREK-1 and TRAAK are gestationally-regulated in human myometrium and contribute to uterine relaxation during pregnancy until labor. Methodology: We determined the gene and protein expression of K2P channels in non-pregnant, pregnant term and preterm laboring myometrium. We employed both molecular biological and functional studies of K2P channels in myometrial samples taken from women undergoing cesarean delivery of a fetus. Principal Findings: TREK-1, but not TREK-2, channels are expressed in human myometrium and significantly up-regulated during pregnancy. Down-regulation of TREK-1 message was seen by Q-PCR in laboring tissues consistent with a role for TREK-1 in maintaining uterine quiescence prior to labor. The TRAAK channel was unregulated in the same women. Blockade of stretch-activated channels with a channel non-specific tarantula toxin (GsMTx-4) or the more specific TREK-1 antagonist L-methionine ethyl ester altered contractile frequency in a dose-dependent manner in pregnant myometrium. Arachidonic acid treatment lowered contractile tension an effect blocked by fluphenazine. Functional studies are consistent with a role for TREK-1 in uterine quiescence. Conclusions: We provide evidence supporting a role for TREK-1 in contributing to uterine quiescence during gestation an

Surface properties of glass micropipettes and their effect on biological studies

In this paper, an investigation on surface properties of glass micropipettes and their effect on biological applications is reported. Pipettes were pulled under different pulling conditions and the effect of each pulling parameter was analyzed. SEM stereoscopic technique was used to reveal the surface roughness properties of pipette tip and pipette inner wall in 3D. More than 20 pipettes were reconstructed. Pipette heads were split open using focused ion beam (FIB) milling for access to the inner walls. It is found that surface roughness parameters are strongly related on the tip size. Bigger pipettes have higher average surface roughness and lower developed interfacial area ratio. Furthermore, the autocorrelation of roughness model of the inner surface shows that the inner surface does not have any tendency of orientation and is not affected by pulling direction. To investigate the effect of surface roughness properties on biological applications, patch-clamping tests were carried out by conventional and FIB-polished pipettes. The results of the experiments show that polished pipettes make significantly better seals. The results of this work are of important reference value for achieving pipettes with desired surface properties and can be used to explain biological phenomenon such as giga-seal formation

The core domain as the force sensor of the yeast mechanosensitive TRP channel

Stretch-activated conductances are commonly encountered in careful electric recordings. Those of known proteins (TRP, MscL, MscS, K2p, Kv, etc.) all share a core, which houses the ion pathway and the gate, but no recognizable force-sensing domain. Like animal TRPs, the yeast TRPY1 is polymodal, activated by stretch force, Ca2+, etc. To test whether its S5–S6 core senses the stretch force, we tried to uncouple it from the peripheral domains by strategic peptide insertions to block the covalent core–periphery interactions. Insertion of long unstructured peptides should distort, if not disrupt, protein structures that transmit force. Such insertions between S6 and the C-terminal tail largely removed Ca2+ activation, showing their effectiveness. However, such insertions as well as those between S5 and the N-terminal region, which includes S1–S4, did not significantly alter mechanosensitivity. Even insertions at both locations flanking the S5–S6 core did not much alter mechanosensitivity. Tryptophan scanning mutations in S5 were also constructed to perturb possible noncovalent core–periphery contacts. The testable tryptophan mutations also have little or no effects on mechanosensitivity. Boltzmann fits of the wild-type force–response curves agree with a structural homology model for a stretch-induced core expansion of ∼2 nm2 upon opening. We hypothesize that membrane tension pulls on S5–S6, expanding the core and opening the TRPY1 gate. The core being the major force sensor offers the simplest, though not the only, explanation of why so many channels of disparate designs are mechanically sensitive. Compared with the bacterial MscL, TRPY1 is much less sensitive to force, befitting a polymodal channel that relies on multiple stimuli

Molecular simulations of venom peptide-membrane interactions: Progress and challenges

Because of their wide range of biological activities venom peptides are a valuable source of lead molecules for the development of pharmaceuticals, pharmacological tools and insecticides. Many venom peptides work by modulating the activity of ion channels and receptors or by irreversibly damaging cell membranes. In many cases, the mechanism of action is intrinsically linked to the ability of the peptide to bind to or partition into membranes. Thus, understanding the biological activity of these venom peptides requires characterizing their membrane binding properties. This review presents an overview of the recent developments and challenges in using biomolecular simulations to study venom peptide‐membrane interactions. The review is focused on (i) gating modifier peptides that target voltage‐gated ion channels, (ii) venom peptides that inhibit mechanosensitive ion channels, and (iii) pore‐forming venom peptides. The methods and approaches used to study venom peptide‐membrane interactions are discussed with a particular focus on the challenges specific to these systems and the type of questions that can (and cannot) be addressed using state‐of‐the‐art simulation techniques. The review concludes with an outlook on future aims and directions in the field