A Demonstration of the Role ofhetGenes in Heterokaryon Formation inNeurosporaunder Simulated Field Conditions

An experimental system was developed for assessing the role ofhetgenes in heterokaryon formation inNeurosporain nature. Burned sugar cane segments planted in soil were infected using a mixture of mutant ascospores of two genotypes.Neurosporaramified in the cane and erupted as distinct pustules of conidia. When ascospores carried identicalhetalleles, the (macro) conidial pustules which formed were heterokaryotic. On the other hand, when ascospores carried dissimilarhetalleles, the pustules were homokaryotic. These results showed that stable heterokaryons between compatible strains can form in nature. When two strains are growing together on a natural substrate, heterozygosity athetloci serves to maintain their individuality.

On the relationship of thermodynamic parameters with the buried surface area in protein-ligand complex formation

Prediction of thermodynamic parameters of protein-protein and antigen-antibody complex formation from high resolution structural parameters has recently received much attention, since an understanding of the contributions of different fundamental processes like hydrophobic interactions, hydrogen bonding, salt bridge formation, solvent reorganization etc. to the overall thermodynamic parameters and their relations with the structural parameters would lead to rational drug design. Using the results of the dissolution of hydrocarbons and other model compounds the changes in heat capacity (DeltaCp), enthalpy (DeltaH) and entropy (DeltaS) have been empirically correlated with the polar and apolar surface areas buried during the process of protein folding/unfolding and protein-ligand complex formation. In this regard, the polar and apolar surfaces removed from the solvent in a protein-ligand complex have been calculated from the experimentally observed values of changes in heat capacity (DeltaCp) and enthalpy (DeltaH) for protein-ligand complexes for which accurate thermodynamic and high resolution structural data are available, and the results have been compared with the x-ray crystallographic observations. Analyses of the available results show poor correlation between the thermodynamic and structural parameters. Probable reasons for this discrepancy are mostly related with the reorganization of water accompanying the reaction which is indeed proven by the analyses of the energetics of the binding of the wheat germ agglutinin to oligosaccharides.

Social processes of health and physical education teachers’ identity formation: Reproducing and changing culture

This paper examines Initial Teacher Education students’ experiences of participation in health and physical education (HPE) subject department offices and the impact on their understandings and identity formation. Pierre Bourdieu’s concepts of habitus, field, and practice along with Wenger’s communities of practice form the theoretical frame used in the paper. Data were collected using surveys and interviews with student‐teachers following their teaching practicum and analysed using coding and constant comparison. Emergent themes revealed students’ participation in masculine‐dominated sports, gendered body constructions, and repertoires of masculine domination. Findings are discussed in relation to their impact on student‐teachers’ learning, identity formation, and marginalizing practices in the department offices. Implications for teacher education and HPE are explored.

Lymphatic vascular maturation : Roles of FOXC2, NFATc1 and liprin ß1

The blood vascular system is a closed circulatory system, responsible for delivering oxygen and nutrients to the tissues. In contrast, the lymphatic vascular system is a blind-ended transport system that collects the extravasated tissue fluid from the capillary beds, and transports it back to the blood circulation. Failure in collecting or transporting the lymph, due to defects in the lymphatic vasculature, leads to accumulation of extra fluid in the tissues, and consequently to tissue swelling lymphedema. The two vascular systems function in concert. They are structurally related, but their development is regulated by separate, however overlapping, molecular mechanisms. During embryonic development, blood vessels are formed by vasculogenesis and angiogenesis, processes largely mediated by members of the vascular endothelial growth factor (VEGF) family and their tyrosine kinase receptors. The lymphatic vessels are formed after the cardiovascular system is already functional. This process, called lymphangiogenesis, is controlled by distinct members of the VEGF family, together with the transcription factors Prox1 and Sox18. After the primary formation of the vessels, the vasculature needs to mature and remodel into a functional network of hierarchically organized vessels: the blood vasculature into arteries, capillaries and veins; and the lymphatic vasculature into lymphatic capillaries, responsible for the uptake of the extravasated fluid from the tissues, and collecting vessels, responsible for the transport of the lymph back to the blood circulation. A major event in the maturation of the lymphatic vasculature is the formation of collecting lymphatic vessels. These vessels are characterized by the presence of intraluminal valves, preventing backflow of the lymph, and a sparse coverage of smooth muscle cells, which help in pumping the lymph forward. In our study, we have characterized the molecular and morphological events leading to formation of collecting lymphatic vessels. We found that this process is regulated cooperatively by the transcription factors Foxc2 and NFATc1. Mice lacking either Foxc2 or active NFATc1 fail to remodel the primary lymphatic plexus into functional lymphatic capillaries and collecting vessels. The resulting vessels lack valves, display abnormal expression of lymphatic molecules, and are hyperplastic. Moreover, the lymphatic capillaries show aberrant sprouting, and are abnormally covered with smooth muscle cells. In humans, mutations in FOXC2 lead to Lymphedema-Distichiasis (LD), a disabling disease characterized by swelling of the limbs due to insufficient lymphatic function. Our results from Foxc2 mutant mice and LD patients indicate that the underlying cause for lymphatic failure in LD is agenesis of collecting lymphatic valves and aberrant recruitment of periendothelial cells and basal lamina components to lymphatic capillaries. Furthermore, we show that liprin β1, a poorly characterized member of the liprin family of cytoplasmic proteins, is highly expressed in lymphatic endothelial cells in vivo, and is required for lymphatic vessel integrity. These data highlight the important role of FOXC2, NFATc1 and liprin β1 in the regulation of lymphatic development, specifically in the maturation and formation of the collecting lymphatic vessels. As damage to collecting vessels is a major cause of lymphatic dysfunction in humans, our results also suggest that FOXC2 and NFATc1 are potential targets for therapeutic intervention.

Hybrid Sol-Gel Combustion Synthesis of Nanoporous Anatase

Nanoporous anatase with a thin interconnected filmlike morphology has been synthesized in a single step by coupling a nonhydrolytic condensation reaction of a Ti precursor with a hybrid sol-gel combustion reaction. The method combines the advantages of a conventional sol-gel method for the formation of porous structures with the high crystallinity of the products obtained by combustion methods to yield highly crystalline, phase-pure nanoporous anatase. The generation of pores is initiated by the formation of reverse micelles in a polymeric polycondensation product, which expand during heating, leading to larger pores. A reaction scheme involving a complex formation and nonhydrolytic polycondensation reaction with ester elimination leads to the formation of ail extended Ti-O-Ti network. The effect of process parameters, such as temperature and relative ratio of cosurfactants, on phase formation has been studied. The possibility of band gap engineering by controlled doping during synthesis and the possibility of attachment of molecular/nanoparticle sensitizers provide opportunities for easy preparation of photoanodes for solar cell applications.

Structure, function and intracellular dynamics of alphavirus replication complexes

Intracellular membrane alterations are hallmarks of positive-sense RNA (+RNA) virus replication. Strong evidence indicates that within these exotic compartments, viral replicase proteins engage in RNA genome replication and transcription. To date, fundamental questions such as the origin of altered membranes, mechanisms of membrane deformation and topological distribution and function of viral components, are still waiting for comprehensive answers. This study addressed some of the above mentioned questions for the membrane alterations induced during Semliki Forest virus (SFV) infection of mammalian cells. With the aid of electron and fluorescence microscopy coupled with radioactive labelling and immuno-cytochemistry techniques, our group and others showed that few hours after infection the four non structural proteins (nsP1-4) and newly synthesized RNAs of SFV colocalized in close proximity of small membrane invaginations, designated as spherules . These 50-70 nm structures were mainly detected in the perinuclear area, at the limiting membrane of modified endosomes and lysosomes, named CPV-I (cytopathic vacuoles type I). More rarely, spherules were also found at the plasma membrane (PM). In the first part of this study I present the first three-dimensional reconstruction of the CPV-I and the spherules, obtained by electron tomography after chemical or cryo-fixation. Different approaches for imaging these macromolecular assemblies to obtain better structure preservation and higher resolution are presented as unpublished data. This study provides insights into spherule organization and distribution of viral components. The results of this and other experiments presented in this thesis will challenge currently accepted models for virus replication complex formation and function. In a revisitation of our previous models, the second part of this work provides the first complete description of the biogenesis of the CPV-I. The results demonstrate that these virus-induced vacuoles, where hundreds of spherules accumulate at late stages during infection, represent the final phase of a journey initiated at the PM, which apparently serves as a platform for spherule formation. From the PM spherules were internalized by an endocytic event that required the activity of the class I PI3K, caveolin-1, cellular cholesterol and functional actin-myosin network. The resulting neutral endocytic carrier vesicle delivered the spherules to the membrane of pre-existing acidic endosomes via multiple fusion events. Microtubule based transport supported the vectorial transfer of these intermediates to the pericentriolar area where further fusions generated the CPV-I. A signal for spherule internalization was identified in one of the replicase proteins, nsP3. Infections of cells with viruses harbouring a deletion in a highly phosphorylated region of nsP3 did not result in the formation of CPV-Is. Instead, thousands of spherules remained at the PM throughout the infection cycle. Finally, the role of the replicase protein nsP2 during viral RNA replication and transcription was investigated. Three enzymatic activities, protease, NTPase and RNA-triphosphatase were studied with the aid of temperature sensitive mutants in vitro and, when possible, in vivo. The results highlighted the interplay of the different nsP2 functions during different steps of RNA replication and sub-genomic promoter regulation, and suggest that the protein could have different activities when participating in the replication complex or as a free enzyme.

Co-Signaling by Neurotrophic Factors and the Extracellular Matrix for Axonal Growth and Neuronal Survival

Neurotrophic factors (NTFs) and the extracellular matrix (ECM) are important regulators of axonal growth and neuronal survival in mammalian nervous system. Understanding of the mechanisms of this regulation is crucial for the development of posttraumatic therapies and drug intervention in the injured nervous system. NTFs act as soluble, target-derived extracellular regulatory molecules for a wide range of physiological functions including axonal guidance and the regulation of programmed cell death in the nervous system. The ECM determines cell adhesion and regulates multiple physiological functions via short range cell-matrix interactions. The present work focuses on the mechanisms of the action of NTFs and the ECM on axonal growth and survival of cultured sensory neurons from dorsal root ganglia (DRG). We first examined signaling mechanisms of the action of the glial cell line-derived neurotrophic factor (GDNF) family ligands (GFLs) on axonal growth. GDNF, neurturin (NRTN) and artemin (ART) but not persephin (PSPN) promoted axonal initiation in cultured DRG neurons from young adult mice. This effect required Src family kinase (SFK) activity. In neurons from GFRalpha2-deficient mice, NRTN did not significantly promote axonal initiation. GDNF and NRTN induced extensive lamellipodia formation on neuronal somata and growth cones. This study suggested that GDNF, NRTN and ARTN may serve as stimulators of nerve regeneration under posttraumatic conditions. Consequently we studied the convergence of signaling pathways induced by NTFs and the ECM molecule laminin in the intracellular signaling network that regulates axonal growth. We demonstrated that co-stimulation of DRG neurons with NTFs (GDNF, NRTN or nerve growth factor (NGF)) and laminin leads to axonal growth that requires activation of SFKs. A different, SFK-independent signaling pathway evoked axonal growth on laminin in the absence of the NTFs. In contrast, axonal branching was regulated by SFKs both in the presence and in the absence of NGF. We proposed and experimentally verified a Boolean model of the signaling network triggered by NTFs and laminin. Our results put forward an approach for predictable, Boolean logics-driven pharmacological manipulation of a complex signaling network. Finally we found that N-syndecan, the receptor for the ECM component HB-GAM was required for the survival of neonatal sensory neurons in vitro. We demonstrated massive cell death of cultured DRG neurons from mice deficient in the N-syndecan gene as compared to wild type controls. Importantly, this cell death could not be prevented by NGF the neurotrophin which activates multiple anti-apoptotic cascades in DRG neurons. The survival deficit was observed during first postnatal week. By contrast, DRG neurons from young adult N-syndecan knock-out mice exhibited normal survival. This study identifies a completely new syndecan-dependent type of signaling that regulates cell death in neurons.

Formation of an unusual copper(II) complex from the degradation of a novel tricopper(II) carbohydrazone complex

An unusual copper(II) complex [Cu(L-1a)(2)Cl-2] CH3OH center dot H2O center dot H3O+Cl- (1a) was isolated from a solution of a novel tricopper(II) complex [Cu-3(HL1)Cl-2]Cl-3 center dot 2H(2)O (1) in methanol. where L-1a is 3-(2-pyridyl)triazolo [1,5-a]-pyridine, and characterized with single crystal X-ray diffraction study. The tricopper(II) complex of potential ligand 1,5-bis(di-2-pyridyl ketone) carbohydrazone (H2L1) was synthesized and physicochemically characterized, while the formation of the complex la was followed by time-dependant monitoring of the UV-visible spectra. which reveals degradation of ligand backbone as intensity loss of bands corresponding to O -> Cu(II) charge transfer.

Structural-stratigraphic reconstruction of the lower Whakataki formation, north island, New Zealand

This thesis details a Miocene aged sedimentary rock formation located in north island New Zealand. Mapping, stratigraphic logging and petrographic analysis of the rock formation ascertained that it was deposited in a deep-marine, tectonically active region. The work details the make-up of the sedimentary rocks using geochemistry and microscopy to define their origin. This definition was used to interpret the depositional model of the sediments detailing how they were transported and how they were emplaced.

Strategies for efficient disruption of metabolism in Mycobacterium tuberculosis from network analysis

Tuberculosis continues to be a major health challenge, warranting the need for newer strategies for therapeutic intervention and newer approaches to discover them. Here, we report the identification of efficient metabolism disruption strategies by analysis of a reactome network. Protein-protein dependencies at a genome scale are derived from the curated metabolic network, from which insights into the nature and extent of inter-protein and inter-pathway dependencies have been obtained. A functional distance matrix and a subsequent nearness index derived from this information, helps in understanding how the influence of a given protein can pervade to the metabolic network. Thus, the nearness index can be viewed as a metabolic disruptability index, which suggests possible strategies for achieving maximal metabolic disruption by inhibition of the least number of proteins. A greedy approach has been used to identify the most influential singleton, and its combination with the other most pervasive proteins to obtain highly influential pairs, triplets and quadruplets. The effect of deletion of these combinations on cellular metabolism has been studied by flux balance analysis. An obvious outcome of this study is a rational identification of drug targets, to efficiently bring down mycobacterial metabolism.

Relative electrical distance concept for evaluation of network reactive power and loss contributions in a deregulated system

With the liberalisation of electricity market it has become very important to determine the participants making use of the transmission network.Transmission line usage computation requires information of generator to load contributions and the path used by various generators to meet loads and losses. In this study relative electrical distance (RED) concept is used to compute reactive power contributions from various sources like generators, switchable volt-amperes reactive(VAR) sources and line charging susceptances that are scattered throughout the network, to meet the system demands. The transmission line charge susceptances contribution to the system reactive flows and its aid extended in reducing the reactive generation at the generator buses are discussed in this paper. Reactive power transmission cost evaluation is carried out in this study. The proposed approach is also compared with other approaches viz.,proportional sharing and modified Y-bus.Detailed case studies with base case and optimised results are carried out on a sample 8-bus system. IEEE 39-bus system and a practical 72-bus system, an equivalent of Indian Southern grid are also considered for illustration and results are discussed.

Inferring neuronal network connectivity from spike data: A temporal data mining approach

Understanding the functioning of a neural system in terms of its underlying circuitry is an important problem in neuroscience. Recent d evelopments in electrophysiology and imaging allow one to simultaneously record activities of hundreds of neurons. Inferring the underlying neuronal connectivity patterns from such multi-neuronal spike train data streams is a challenging statistical and computational problem. This task involves finding significant temporal patterns from vast amounts of symbolic time series data. In this paper we show that the frequent episode mining methods from the field of temporal data mining can be very useful in this context. In the frequent episode discovery framework, the data is viewed as a sequence of events, each of which is characterized by an event type and its time of occurrence and episodes are certain types of temporal patterns in such data. Here we show that, using the set of discovered frequent episodes from multi-neuronal data, one can infer different types of connectivity patterns in the neural system that generated it. For this purpose, we introduce the notion of mining for frequent episodes under certain temporal constraints; the structure of these temporal constraints is motivated by the application. We present algorithms for discovering serial and parallel episodes under these temporal constraints. Through extensive simulation studies we demonstrate that these methods are useful for unearthing patterns of neuronal network connectivity.