42 research outputs found

    Protein kinase Cζ regulates phospholipase D activity in rat-1 fibroblasts expressing the α(1A )adrenergic receptor

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    BACKGROUND: Phenylephrine (PHE), an α(1 )adrenergic receptor agonist, increases phospholipase D (PLD) activity, independent of classical and novel protein kinase C (PKC) isoforms, in rat-1 fibroblasts expressing α(1A )adrenergic receptors. The aim of this study was to determine the contribution of atypical PKCζ to PLD activation in response to PHE in these cells. RESULTS: PHE stimulated a PLD activity as demonstrated by phosphatidylethanol production. PHE increased PKCζ translocation to the particulate cell fraction in parallel with a time-dependent decrease in its activity. PKCζ activity was reduced at 2 and 5 min and returned to a sub-basal level within 10–15 min. Ectopic expression of kinase-dead PKCζ, but not constitutively active PKCζ, potentiated PLD activation elicited by PHE. A cell-permeable pseudosubstrate inhibitor of PKCζ reduced basal PKCζ activity and abolished PHE-induced PLD activation. CONCLUSION: α(1A )adrenergic receptor stimulation promotes the activation of a PLD activity by a mechanism dependent on PKCζ; Our data also suggest that catalytic activation of PKCζ is not required for PLD stimulation

    Hyperglycaemia and diabetes impair gap junctional communication among astrocytes

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    Sensory and cognitive impairments have been documented in diabetic humans and animals, but the pathophysiology of diabetes in the central nervous system is poorly understood. Because a high glucose level disrupts gap junctional communication in various cell types and astrocytes are extensively coupled by gap junctions to form large syncytia, the influence of experimental diabetes on gap junction channel-mediated dye transfer was assessed in astrocytes in tissue culture and in brain slices from diabetic rats. Astrocytes grown in 15–25 mmol/l glucose had a slow-onset, poorly reversible decrement in gap junctional communication compared with those grown in 5.5 mmol/l glucose. Astrocytes in brain slices from adult STZ (streptozotocin)-treated rats at 20–24 weeks after the onset of diabetes also exhibited reduced dye transfer. In cultured astrocytes grown in high glucose, increased oxidative stress preceded the decrement in dye transfer by several days, and gap junctional impairment was prevented, but not rescued, after its manifestation by compounds that can block or reduce oxidative stress. In sharp contrast with these findings, chaperone molecules known to facilitate protein folding could prevent and rescue gap junctional impairment, even in the presence of elevated glucose level and oxidative stress. Immunostaining of Cx (connexin) 43 and 30, but not Cx26, was altered by growth in high glucose. Disruption of astrocytic trafficking of metabolites and signalling molecules may alter interactions among astrocytes, neurons and endothelial cells and contribute to changes in brain function in diabetes. Involvement of the microvasculature may contribute to diabetic complications in the brain, the cardiovascular system and other organs

    Chemical composition and isotopic signatures of ice and snow over a Himalayan Glacier (Satopanth) in India

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    This study reports the chemical composition and isotopic signatures of snow and ice over a Himalayan Glacier in India. An observational campaign was carried out from September 22, 2016, to October 2, 2016, over Satopanth in central Himalaya. The pH value of ice and snow, respectively, was 5.6 ± 0.4 and 5.9 ± 0.35 over the glacier, indicating moderate acidity of the glacier components. Calcium (Ca2+) was the dominant component in snow (35.2%), while sulfate (SO42−) was dominant in ice samples (52.7%). The neutralization factor was estimated to find the extent of neutralization of acidic fractions by basic components. It is found that Ca2+ was the prominent neutralizing factor both in snow and ice over the region. Oxygen and hydrogen isotopic analyses of snow, surface layer ice and debris-covered ice suggest that the moisture source is common for all three components. δD and d-excess values of snow at Satopanth are different than that of those for Chorabari, Dokriani and Tiprabank Glacier, indicating the plausibility of different sources of moisture for these glaciers. Limited observations suggest that the interaction of ice with the debris has no impact on the isotopic signatures of the ice over the region; such non-alteration of isotopic signatures makes the region important for ice core-based paleoclimatic studies

    Physics Potential of the ICAL detector at the India-based Neutrino Observatory (INO)

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    The upcoming 50 kt magnetized iron calorimeter (ICAL) detector at the India-based Neutrino Observatory (INO) is designed to study the atmospheric neutrinos and antineutrinos separately over a wide range of energies and path lengths. The primary focus of this experiment is to explore the Earth matter effects by observing the energy and zenith angle dependence of the atmospheric neutrinos in the multi-GeV range. This study will be crucial to address some of the outstanding issues in neutrino oscillation physics, including the fundamental issue of neutrino mass hierarchy. In this document, we present the physics potential of the detector as obtained from realistic detector simulations. We describe the simulation framework, the neutrino interactions in the detector, and the expected response of the detector to particles traversing it. The ICAL detector can determine the energy and direction of the muons to a high precision, and in addition, its sensitivity to multi-GeV hadrons increases its physics reach substantially. Its charge identification capability, and hence its ability to distinguish neutrinos from antineutrinos, makes it an efficient detector for determining the neutrino mass hierarchy. In this report, we outline the analyses carried out for the determination of neutrino mass hierarchy and precision measurements of atmospheric neutrino mixing parameters at ICAL, and give the expected physics reach of the detector with 10 years of runtime. We also explore the potential of ICAL for probing new physics scenarios like CPT violation and the presence of magnetic monopoles.Comment: 139 pages, Physics White Paper of the ICAL (INO) Collaboration, Contents identical with the version published in Pramana - J. Physic

    Moving from contractor to owner operator: Impact on safety culture; a case study

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    Purpose – The purpose of this paper is to investigate whether a change in staffing contractual arrangements, specific training in hazard identification, mentoring of supervisors and the introduction of a robust safety system could improve an organisation\u27s safety culture. How safety conditions change under contracted out labour compared to direct labour and the influence that contracting out has on organisational safety culture is explored. Design/methodology/approach – The study used a case study methodology to detail how the change occurred over a six month period in 2011. As part of the analysis a model of the change process and push-pull factors is offered. Findings – As a result of the change, all areas saw some improvement. Work-related injury statistics dropped significantly, supervisors were clear of their roles, actively monitoring their crews to ensure they worked in a safer manner than before, and staff were actively addressing work-place hazards. With the safety system in place the organisation should be deemed compliant and diligent by the state auditing authorities. This study has also shown that using contractor workers together with in-house workers that are managed under different safety regimes is problematic. The problems don’t occur due to the contractor\u27s safety systems being less robust than the parent company\u27s or that contract workers are themselves less safe; it is the added complexity of managing multiple safety regimes and the lack of trust of the robustness of each system that create conflict. Research limitations/implications – The paper reports on the change process of one mining organisation in Western Australia as a case study from a managerial sample and is thereby limited. Practical implications – This study demonstrates the difficulties in changing safety culture in an underground mining organisation. The paper argues the need for specialised training in identifying hazards by the staff, the mentoring of supervisory staff and the adoption of a robust safety system to support improved safety culture. Originality/value – There is little research conducted in the resources sector researching changes in human resource supply and OHS management, in particular moving from contracted labour to hiring in-house. This case provides an insight into how a change in staffing hiring arrangements, together with specific safety initiatives, has a positive impact on safety performance
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