Analysis of By-Products of N2-SF6 Gas Mixtures Sparked under Inhomogenous Field Conditions

A vast data on formation of by-products due to arc and spark decomposition of SF6 is available in literature [1–10]. But experimental work relating to N2 - SF6 gas mixtures is limited. In view of increasing application of gas mixtures, it is essential to understand the nature of by-products formed in gas mixtures. Many recent studies have highlighted the advantages of using N2-SF6 gas mixtures as a replacement to SF6 gas for High Voltage application, with a view to reduce emission of SF6 gas into the atmosphere. Majority of these studies are aimed at determining the basic characteristics of N2-SF6 gas mixtures. However, this study attempts to understand the nature and quantum of different species formed in N2-SF6 mixtures in the presence of insulating spacers when sparked under inhomogeneous field conditions

Heat-Shock Proteins Of The Oyster Parasite Perkinsus-marinus

The susceptibility of the eastern oyster Crassostrea virginica to infection by the protozoan parasite Perkinsus marinus is influenced by temperature. Because of the crucial roles of heat shock proteins in cellular thermal tolerance and in host-parasite adaptations in other species, we compared the in vitro heat shock responses of cultured P. marin us and of oyster hemocytes. The parasite and host heat shock proteins were different in size and in immunochemical specificity. In addition, the thermal threshold for inducing the response was higher for P. marinus acclimated to the same temperature as the oysters. The results suggest that EI marinus is likely to employ heat shock proteins as part of its adaptive survival repertoire and that it may be able to function normally under conditions of hyperthermia that evoke an emergency physiological response from the oyster defense cells. Furthermore, they indicate that it is feasible to investigate the host\u27s and parasite\u27s adaptive responses to each other, since their individual responses are readily distinguishable

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2008-2009 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Human mesenchymal stem cells/multipotent stromal cells consume accumulated autophagosomes early in differentiation

Introduction: Bone marrow mesenchymal stem cells/multipotent stromal cells (MSCs) are recruited to sites of injury and subsequently support regeneration through differentiation or paracrine activity. During periods of stress such as wound site implant or differentiation, MSCs are subjected to a variety of stressors that might activate pathways to improve cell survival and generate energy. In this study, we monitored MSC autophagy in response to the process of differentiation. Methods: MSC autophagosome structures were observed by using transmission electron microscopy and a tandem green fluorescent protein-red fluorescent protein autophagic flux reporter to monitor the mammalian microtubule-associated protein-1 light chain 3 (LC3) turnover in real time. MSCs were differentiated by using standard osteogenic and adipogenic media, and autophagy was examined during short-term and long-term differentiation via immunoblots for LC3I and II. Autophagy was modulated during differentiation by using rapamycin and bafilomycin treatments to disrupt the autophagosome balance during the early stages of the differentiation process, and differentiation was monitored in the long term by using Von Kossa and Oil Red O staining as well as quantitative polymerase chain reaction analysis of typical differentiation markers. Results: We found that undifferentiated MSCs showed an accumulation of a large number of undegraded autophagic vacuoles, with little autophagic turnover. Stimulation of autophagy with rapamycin led to rapid degradation of these autophagosomes and greatly increased rough endoplasmic reticulum size. Upon induction of osteogenic differentiation, MSC expression of LC3II, a common autophagosome marker, was lost within 12 hours, consistent with increased turnover. However, during adipogenic differentiation, drug treatment to alter the autophagosome balance during early differentiation led to changes in differentiation efficiency, with inhibited adipocyte formation following rapamycin treatment and accelerated fat accumulation following autophagosome blockade by bafilomycin. Conclusions: Our findings suggest that MSCs exist in a state of arrested autophagy with high autophagosome accumulation and are poised to rapidly undergo autophagic degradation. This phenotype is highly sensitive, and a balance of autophagy appears to be key in efficient MSC differentiation and function, as evidenced by our results implicating autophagic flux in early osteogenesis and adipogenesis

Dental Care Utilization and Satisfaction of Residential University Students

Aim: The objective of this study was to provide information on the level of utilization and satisfaction of residential university students with the dental services provided by the dental clinic of a teaching hospital. Volunteers and Material: A stratified sampling technique was used to recruit volunteers from the outpatient clinic of the Obafemi Awolowo University Teaching Hospital Complex, Ile-Ife, Nigeria. Information was collected by a self-administered questionnaire composed of questions that measure the level of utilization and satisfaction with the dental services provided. Questionnaires were provided to 650 randomly chosen students residing in the University hostels. There were 39 refusals, and 6 incomplete questionnaires were discarded. This left a sample size of 605 volunteers. Results: Forty seven students (7.8%) indicated that they visited the dental hospital within the last 12 months. Males and females utilized the dental services equally, and utilization increased with age and the number of years spent on campus. Anticipation of painful dental treatment, high dental charges, long waiting times and being too busy for a dental visit were cited as the most important impediments to seeking dental treatment. Females expressed greater satisfaction with the services. Conclusion: Dental service utilization among the students was found to be low. Oral health awareness campaigns, improving the quality of the services, and shortening the waiting time are expected to increase service utilization and satisfaction. Keywords: dental care, utilization, satisfaction, young adults, Nigeria Libyan Journal of Medicine Vol. 3 (3) 2008: pp. 20-2

Mycolactone-dependent depletion of endothelial cell thrombomodulin is strongly associated with fibrin deposition in Buruli ulcer lesions

A well-known histopathological feature of diseased skin in Buruli ulcer (BU) is coagulative necrosis caused by the Mycobacterium ulcerans macrolide exotoxin mycolactone. Since the underlying mechanism is not known, we have investigated the effect of mycolactone on endothelial cells, focussing on the expression of surface anticoagulant molecules involved in the protein C anticoagulant pathway. Congenital deficiencies in this natural anticoagulant pathway are known to induce thrombotic complications such as purpura fulimans and spontaneous necrosis. Mycolactone profoundly decreased thrombomodulin (TM) expression on the surface of human dermal microvascular endothelial cells (HDMVEC) at doses as low as 2ng/ml and as early as 8hrs after exposure. TM activates protein C by altering thrombin's substrate specificity, and exposure of HDMVEC to mycolactone for 24 hours resulted in an almost complete loss of the cells' ability to produce activated protein C. Loss of TM was shown to be due to a previously described mechanism involving mycolactone-dependent blockade of Sec61 translocation that results in proteasome-dependent degradation of newly synthesised ER-transiting proteins. Indeed, depletion from cells determined by live-cell imaging of cells stably expressing a recombinant TM-GFP fusion protein occurred at the known turnover rate. In order to determine the relevance of these findings to BU disease, immunohistochemistry of punch biopsies from 40 BU lesions (31 ulcers, nine plaques) was performed. TM abundance was profoundly reduced in the subcutis of 78% of biopsies. Furthermore, it was confirmed that fibrin deposition is a common feature of BU lesions, particularly in the necrotic areas. These findings indicate that there is decreased ability to control thrombin generation in BU skin. Mycolactone's effects on normal endothelial cell function, including its ability to activate the protein C anticoagulant pathway are strongly associated with this. Fibrin-driven tisischemia could contribute to the development of the tissue necrosis seen in BU lesions

UNCLES: Method for the identification of genes differentially consistently co-expressed in a specific subset of datasets

Background: Collective analysis of the increasingly emerging gene expression datasets are required. The recently proposed binarisation of consensus partition matrices (Bi-CoPaM) method can combine clustering results from multiple datasets to identify the subsets of genes which are consistently co-expressed in all of the provided datasets in a tuneable manner. However, results validation and parameter setting are issues that complicate the design of such methods. Moreover, although it is a common practice to test methods by application to synthetic datasets, the mathematical models used to synthesise such datasets are usually based on approximations which may not always be sufficiently representative of real datasets. Results: Here, we propose an unsupervised method for the unification of clustering results from multiple datasets using external specifications (UNCLES). This method has the ability to identify the subsets of genes consistently co-expressed in a subset of datasets while being poorly co-expressed in another subset of datasets, and to identify the subsets of genes consistently co-expressed in all given datasets. We also propose the M-N scatter plots validation technique and adopt it to set the parameters of UNCLES, such as the number of clusters, automatically. Additionally, we propose an approach for the synthesis of gene expression datasets using real data profiles in a way which combines the ground-truth-knowledge of synthetic data and the realistic expression values of real data, and therefore overcomes the problem of faithfulness of synthetic expression data modelling. By application to those datasets, we validate UNCLES while comparing it with other conventional clustering methods, and of particular relevance, biclustering methods. We further validate UNCLES by application to a set of 14 real genome-wide yeast datasets as it produces focused clusters that conform well to known biological facts. Furthermore, in-silico-based hypotheses regarding the function of a few previously unknown genes in those focused clusters are drawn. Conclusions: The UNCLES method, the M-N scatter plots technique, and the expression data synthesis approach will have wide application for the comprehensive analysis of genomic and other sources of multiple complex biological datasets. Moreover, the derived in-silico-based biological hypotheses represent subjects for future functional studies.The National Institute for Health Research (NIHR) under its Programme Grants for Applied Research Programme (Grant Reference Number RP-PG-0310-1004)

E3 Ligase Subunit Fbxo15 and PINK1 Kinase Regulate Cardiolipin Synthase 1 Stability and Mitochondrial Function in Pneumonia

Acute lung injury (ALI) is linked to mitochondrial injury, resulting in impaired cellular oxygen utilization; however, it is unknown how these events are linked on the molecular level. Cardiolipin, a mitochondrial-specific lipid, is generated by cardiolipin synthase (CLS1). Here, we show that S.aureus activates a ubiquitin E3 ligase component, Fbxo15, that is sufficient to mediate proteasomal degradation of CLS1 in epithelia, resulting in decreased cardiolipin availability and disrupted mitochondrial function. CLS1 is destabilized by the phosphatase and tensin homolog (PTEN)-induced putative kinase 1 (PINK1), which binds CLS1 to phosphorylate and regulates CLS1 disposal. Like Fbxo15, PINK1 interacts with and regulates levels of CLS1 through a mechanism dependent upon Thr219. S.aureus infection upregulates this Fbxo15-PINK1 pathway to impair mitochondrial integrity, and Pink1 knockout mice are less prone to S.aureus-induced ALI. Thus, ALI-associated disruption of cellular bioenergetics involves bioeffectors that utilize a phosphodegron to elicit ubiquitin-mediated disposal of a key mitochondrial enzyme. © 2014 The Authors