Teacher Decisions in Classroom Management: Looking beyond the student

Student behavior can be classified as external, internal, or social, all of which can be symptoms of an Emotional-Behavioral Disorder (EBD; Cooper & Jacobs, 2001). There are a number of ways that teachers may respond to student behavior with some being considered more positive (e.g., keep the student in the classroom) and others more negative (e.g., refer the student to other school resources for permanent or temporary removal). However, it is not just the student behavior that determines how a teacher will respond. Teacher stress, self-efficacy, class size, the impact of the behavior on other students, teaching experience, and knowledge of classroom management can all impact the teacher’s decision. This study attempts to determine how much influence these factors have on a teacher’s decisions and to determine if there are differences in responses based on the type of behavior exhibited by the student. Two hundred and one teachers completed a demographic questionnaire, measures of the aforementioned areas, and indicated how they would respond to different written vignettes representing student behavior. Class size and teacher factors did not significantly impact the way teachers responded to student behavior. Concern for the behaviors exhibited by the students in the vignette were, however, impacted by knowledge, stress, self-efficacy, confidence, and training. Future directions are discussed to help clarify and go beyond the limitations found within this study

A genetic analysis of complexin function in neurotransmitter release and synaptic plasticity

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Biology, 2009.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references.Information transfer at neuronal synapses requires rapid fusion of docked synaptic vesicles in response to calcium influx during action potentials. The molecular nature of the fusion clamp machinery that prevents exocytosis of synaptic vesicles in the absence of a calcium signal is still unclear. Here we show that complexin, a small alpha-helical protein that binds fully assembled SNARE complexes, functions as the synaptic vesicle fusion clamp in vivo. Drosophila has a single complexin homolog that is abundantly expressed in presynaptic nerve terminals. Animals lacking complexin die throughout development, with adult escapers showing severe locomotion defects and a loss of visual function. Electrophysiological analysis at neuromuscular junctions in complexin null mutants reveals a dramatic increase in spontaneous synaptic vesicle fusion that is independent of nerve stimulation or extracellular calcium. High frequency stimulation at high calcium concentrations shows that the readily releasable pool in complexin mutants is severely depleted. Thus, complexin is required for maintenance of the readily releasable pool of vesicles at the synapse, and without it vesicles exocytose directly after priming. These data indicate that complexin interacts with assembled SNARE complexes to prevent premature vesicle fusion in the absence of calcium entry. In addition, a preliminary analysis of synaptotagmin 1; complexin double mutants reveals that the elevated mini frequency in complexin single mutants is dependent on synaptotagmin 1. This finding suggests that the dominant function of complexin at the synapse is to prevent synaptotagmin 1 from triggering fusion in the absence of calcium. Further analysis of synaptotagmin 1; complexin double mutants may reveal new aspects of the mechanism of the calcium-regulated vesicle fusion reaction. Minis have long been thought to represent background noise at the synapse, but there is now growing evidence that mini frequency is important in synaptic maintenance and plasticity. Complexin mutants display a substantial synaptic overgrowth phenotype. We hypothesized that the enhanced mini frequency in complexin mutants drives synaptic overgrowth and that complexin is phosphorylated by PKA to regulate mini frequency at Drosophila synapses in an activity-dependent retrograde signaling pathway that mediates a large increase in mini frequency and a concomitant induction of synaptic growth. Like complexin mutants, a syntaxin mutant with elevated mini frequency also displays enhanced synaptic growth, providing further evidence that an increase in mini frequency drives synaptic plasticity. S126 in complexin is phosphorylated by PKA in vitro. Future results may reveal that S126 is phosphorylated by PKA in vivo to regulate mini frequency in an activity-dependent manner. These results have the potential to reveal a new role for minis in local synaptic plasticity in response to neuronal activity.by Sarah Huntwork-Rodriguez.Ph.D

TitrationAnalysis: a tool for high throughput binding kinetics data analysis for multiple label-free platforms [version 1; peer review: 3 approved]

Label-free techniques including Surface Plasmon Resonance (SPR) and Biolayer Interferometry (BLI) are biophysical tools widely used to collect binding kinetics data of bimolecular interactions. To efficiently analyze SPR and BLI binding kinetics data, we have built a new high throughput analysis tool named the TitrationAnalysis. It can be used as a package in the Mathematica scripting environment and ultilize the non-linear curve-fitting module of Mathematica for its core function. This tool can fit the binding time course data and estimate association and dissociation rate constants (ka and kd respectively) for determining apparent dissociation constant (KD) values. The high throughput fitting process is automatic, requires minimal knowledge on Mathematica scripting and can be applied to data from multiple label-free platforms. We demonstrate that the TitrationAnalysis is optimal to analyze antibody-antigen binding data acquired on Biacore T200 (SPR), Carterra LSA (SPR imaging) and ForteBio Octet Red384 (BLI) platforms. The ka, kd and KD values derived using TitrationAnalysis very closely matched the results from the commercial analysis software provided specifically for these instruments. Additionally, the TitrationAnalysis tool generates user-directed customizable results output that can be readily used in downstream Data Quality Control associated with Good Clinical Laboratory Practice operations. With the versatility in source of data input source and options of analysis result output, the TitrationAnalysis high throughput analysis tool offers investigators a powerful alternative in biomolecular interaction characterization

Author response

We recently reported that the C2AB portion of Synaptotagmin 1 (Syt1) could self-assemble into Ca(2+)-sensitive ring-like oligomers on membranes, which could potentially regulate neurotransmitter release. Here we report that analogous ring-like oligomers assemble from the C2AB domains of other Syt isoforms (Syt2, Syt7, Syt9) as well as related C2 domain containing protein, Doc2B and extended Synaptotagmins (E-Syts). Evidently, circular oligomerization is a general and conserved structural aspect of many C2 domain proteins, including Synaptotagmins. Further, using electron microscopy combined with targeted mutations, we show that under physiologically relevant conditions, both the Syt1 ring assembly and its rapid disruption by Ca(2+) involve the well-established functional surfaces on the C2B domain that are important for synaptic transmission. Our data suggests that ring formation may be triggered at an early step in synaptic vesicle docking and positions Syt1 to synchronize neurotransmitter release to Ca(2+) influx. DOI: http://dx.doi.org/10.7554/eLife.17262.00

A presynaptic endosomal trafficking pathway controls synaptic growth signaling

Association of Nwk with SNX16 promotes down-regulation of synaptic growth signaling at the interface between early and recycling endosomes

Molecular Machines in the Synapse: Overlapping Protein Sets Control Distinct Steps in Neurosecretion

Activity regulated neurotransmission shapes the computational properties of a neuron and involves the concerted action of many proteins. Classical, intuitive working models often assign specific proteins to specific steps in such complex cellular processes, whereas modern systems theories emphasize more integrated functions of proteins. To test how often synaptic proteins participate in multiple steps in neurotransmission we present a novel probabilistic method to analyze complex functional data from genetic perturbation studies on neuronal secretion. Our method uses a mixture of probabilistic principal component analyzers to cluster genetic perturbations on two distinct steps in synaptic secretion, vesicle priming and fusion, and accounts for the poor standardization between different studies. Clustering data from 121 perturbations revealed that different perturbations of a given protein are often assigned to different steps in the release process. Furthermore, vesicle priming and fusion are inversely correlated for most of those perturbations where a specific protein domain was mutated to create a gain-of-function variant. Finally, two different modes of vesicle release, spontaneous and action potential evoked release, were affected similarly by most perturbations. This data suggests that the presynaptic protein network has evolved as a highly integrated supramolecular machine, which is responsible for both spontaneous and activity induced release, with a group of core proteins using different domains to act on multiple steps in the release process