Network activity arising from optimal diameters of neuronal processes

Electrical coupling provides an important pathway for signal transmission between neurons. In several regions of the mammalian brain electrical synapses have been detected, and their role in the synchronization of neural networks and the generation of oscillations has been studied theoretically. Recently, it has been found that the amplitude of the postsynaptic potential is maximized for a specific diameter of the postsynaptic fiber. In this thesis, the impact of the fiber\u27s diameter on the success or failure of the action potential initiation and propagation is studied theoretically. Systems of two coupled neurons, as well as small networks, are investigated. The passive and voltage-dependent properties of the neurons are implemented using compartment modeling. The results of the simulations show that for neurons with non-branching dendrites an action potential is initiated only for a specific, optimal diameter. In contrast, for neurons with branching structures the signal transmission improves monotonically with increasing diameter. By studying a model network with a ring architecture it is demonstrated that network activity crucially depends on the diameter of the coupled fibers

Implementing a bully prevention program at the sixth grade level

The purpose of this study was to examine bully-victim behaviors and intervention strategies using case study research design in order to develop and implement a bully prevention program. Participants in this study were limited to students, parents, and teachers on one of three sixth grade teams. A program was presented including a survey for students to determine the level of bullying, questionnaires for students and teachers to evaluate program effectiveness, and interviews with teachers, the guidance counselor, and the assistant principal. Survey data was analyzed by tabulating responses and determining percentages of students experiencing bullying. Student questionnaire data was analyzed by tabulating and coding responses to determine levels of student learning as a result of the bully prevention program. Teacher questionnaire data and interviews with staff were analyzed by coding responses to determine the kinds of bullying behaviors observed before, during, and after the program. Although data indicated that the level of bullying was relatively low, several students reported being called names, being teased, and being the victim of rumors. Data collected after the program indicated students had an increased awareness of bully-victim behaviors and feelings and felt better equipped to handle themselves in bully-victim situations

Transpiration directly regulates the emissions of water-soluble short-chained OVOCs

Most plant-based emissions of volatile organic compounds are considered mainly temperature dependent. However, certain oxygenated volatile organic compounds (OVOCs) have high water solubility; thus, also stomatal conductance could regulate their emissions from shoots. Due to their water solubility and sources in stem and roots, it has also been suggested that their emissions could be affected by transport in the xylem sap. Yet further understanding on the role of transport has been lacking until present. We used shoot-scale long-term dynamic flux data from Scots pines (Pinus sylvestris) to analyse the effects of transpiration and transport in xylem sap flow on emissions of 3 water-soluble OVOCs: methanol, acetone, and acetaldehyde. We found a direct effect of transpiration on the shoot emissions of the 3 OVOCs. The emissions were best explained by a regression model that combined linear transpiration and exponential temperature effects. In addition, a structural equation model indicated that stomatal conductance affects emissions mainly indirectly, by regulating transpiration. A part of the temperature's effect is also indirect. The tight coupling of shoot emissions to transpiration clearly evidences that these OVOCs are transported in the xylem sap from their sources in roots and stem to leaves and to ambient air.Peer reviewe

Polyclonal mucosa-associated invariant T cells have unique innate functions in bacterial infection

Mucosa-associated invariant T (MAIT) cells are a unique population of αβ T cells in mammals that reside preferentially in mucosal tissues and express an invariant Vα paired with limited Vβ T-cell receptor (TCR) chains. Furthermore, MAIT cell development is dependent upon the expression of the evolutionarily conserved major histocompatibility complex (MHC) class Ib molecule MR1. Using in vitro assays, recent studies have shown that mouse and human MAIT cells are activated by antigen-presenting cells (APCs) infected with diverse microbes, including numerous bacterial strains and yeasts, but not viral pathogens. However, whether MAIT cells play an important, and perhaps unique, role in controlling microbial infection has remained unclear. To probe MAIT cell function, we show here that purified polyclonal MAIT cells potently inhibit intracellular bacterial growth of Mycobacterium bovis BCG in macrophages (MΦ) in coculture assays, and this inhibitory activity was dependent upon MAIT cell selection by MR1, secretion of gamma interferon (IFN-γ), and an innate interleukin 12 (IL-12) signal from infected MΦ. Surprisingly, however, the cognate recognition of MR1 by MAIT cells on the infected MΦ was found to play only a minor role in MAIT cell effector function. We also report that MAIT cell-deficient mice had higher bacterial loads at early times after infection compared to wild-type (WT) mice, demonstrating that MAIT cells play a unique role among innate lymphocytes in protective immunity against bacterial infection

A Lipopeptide Facilitate Induction of Mycobacterium leprae Killing in Host Cells

Little is known of the direct microbicidal activity of T cells in leprosy, so a lipopeptide consisting of the N-terminal 13 amino acids lipopeptide (LipoK) of a 33-kD lipoprotein of Mycobacterium leprae, was synthesized. LipoK activated M. leprae infected human dendritic cells (DCs) to induce the production of IL-12. These activated DCs stimulated autologous CD4+ or CD8+ T cells towards type 1 immune response by inducing interferon-gamma secretion. T cell proliferation was also evident from the CFSE labeling of target CD4+ or CD8+ T cells. The direct microbicidal activity of T cells in the control of M. leprae multiplication is not well understood. The present study showed significant production of granulysin, granzyme B and perforin from these activated CD4+ and CD8+ T cells when stimulated with LipoK activated, M. leprae infected DCs. Assessment of the viability of M. leprae in DCs indicated LipoK mediated T cell-dependent killing of M. leprae. Remarkably, granulysin as well as granzyme B could directly kill M. leprae in vitro. Our results provide evidence that LipoK could facilitate M. leprae killing through the production of effector molecules granulysin and granzyme B in T cells

A novel role of dendritic gap junction and mechanisms underlying its interaction with thalamocortical conductance in fast spiking inhibitory neurons

<p>Abstract</p> <p>Background</p> <p>Little is known about the roles of dendritic gap junctions (GJs) of inhibitory interneurons in modulating temporal properties of sensory induced responses in sensory cortices. Electrophysiological dual patch-clamp recording and computational simulation methods were used in combination to examine a novel role of GJs in sensory mediated feed-forward inhibitory responses in barrel cortex layer IV and its underlying mechanisms.</p> <p>Results</p> <p>Under physiological conditions, excitatory post-junctional potentials (EPJPs) interact with thalamocortical (TC) inputs within an unprecedented few milliseconds (i.e. over 200 Hz) to enhance the firing probability and synchrony of coupled fast-spiking (FS) cells. Dendritic GJ coupling allows fourfold increase in synchrony and a significant enhancement in spike transmission efficacy in excitatory spiny stellate cells. The model revealed the following novel mechanisms: <b><it>1) </it></b>rapid capacitive current (I_cap) underlies the activation of voltage-gated sodium channels; <b><it>2) </it></b>there was less than 2 milliseconds in which the I_capunderlying TC input and EPJP was coupled effectively; <b><it>3) </it></b>cells with dendritic GJs had larger input conductance and smaller membrane response to weaker inputs; <b><it>4) </it></b>synchrony in inhibitory networks by GJ coupling leads to reduced sporadic lateral inhibition and increased TC transmission efficacy.</p> <p>Conclusion</p> <p>Dendritic GJs of neocortical inhibitory networks can have very powerful effects in modulating the strength and the temporal properties of sensory induced feed-forward inhibitory and excitatory responses at a very high frequency band (>200 Hz). Rapid capacitive currents are identified as main mechanisms underlying interaction between two transient synaptic conductances.</p

In Vitro Analysis of the Extracellular Expression of the Renin Angiotensin System on T Lymphocyte Populations

Hypertension is a disease characterized by increased activity of the Renin Angiotensin System (RAAS) and immune related vascular dysfunction. Angiotensin II (Ang II) is the final effector molecule of the RAAS and has numerous biologic activities that perpetuates vascular remodeling and inflammation. Ang II signaling of inflammatory cells may be due the presence of RAAS components on T lymphocytes. Many studies have shown the importance of pro-inflammatory T cell phenotypes, through cytokine analysis, in hypertensive models. However, the specific characterization of the RAAS on these phenotypes has yet to be determined. We sought to establish the expression of RAAS components on naïve T cell subsets and compare that to changes in expression that may be seen with AngII treatment and anti-CD3/28 stimulation. Here we find that AngII and anti-CD3/28 treatments significantly increase the expression of RAAS components on T cell populations