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

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

The role of the cytoskeleton in volume regulation and beading transitions in PC12 neurites

We present investigations on volume regulation and beading shape transitions in PC12 neurites conducted using a flow-chamber technique. By disrupting the cell cytoskeleton with specific drugs we investigate the role of its individual components in the volume regulation response. We find that microtubule disruption increases both swelling rate and maximum volume attained, but does not affect the ability of the neurite to recover its initial volume. In addition, investigation of axonal beading --also known as pearling instability-- provides additional clues on the mechanical state of the neurite. We conclude that the initial swelling phase is mechanically slowed down by microtubules, while the volume recovery is driven by passive diffusion of osmolites. Our experiments provide a framework to investigate the role of cytoskeletal mechanics in volume homeostasis

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

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

Conformational changes in a pore-forming region underlie voltage-dependent “loop gating” of an unapposed connexin hemichannel

The structure of the pore is critical to understanding the molecular mechanisms underlying selective permeation and voltage-dependent gating of channels formed by the connexin gene family. Here, we describe a portion of the pore structure of unapposed hemichannels formed by a Cx32 chimera, Cx32*Cx43E1, in which the first extracellular loop (E1) of Cx32 is replaced with the E1 of Cx43. Cysteine substitutions of two residues, V38 and G45, located in the vicinity of the border of the first transmembrane (TM) domain (TM1) and E1 are shown to react with the thiol modification reagent, MTSEA–biotin-X, when the channel resides in the open state. Cysteine substitutions of flanking residues A40 and A43 do not react with MTSEA–biotin-X when the channel resides in the open state, but they react with dibromobimane when the unapposed hemichannels are closed by the voltage-dependent “loop-gating” mechanism. Cysteine substitutions of residues V37 and A39 do not appear to be modified in either state. Furthermore, we demonstrate that A43C channels form a high affinity Cd2+ site that locks the channel in the loop-gated closed state. Biochemical assays demonstrate that A43C can also form disulfide bonds when oocytes are cultured under conditions that favor channel closure. A40C channels are also sensitive to micromolar Cd2+ concentrations when closed by loop gating, but with substantially lower affinity than A43C. We propose that the voltage-dependent loop-gating mechanism for Cx32*Cx43E1 unapposed hemichannels involves a conformational change in the TM1/E1 region that involves a rotation of TM1 and an inward tilt of either each of the six connexin subunits or TM1 domains

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