Browsing by keyword "Sodium Chloride"
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Blood flow and functional responses correlate in the ovine neural lobeRegional neurohypophyseal and cerebral blood flow were measured in 5 awake unstressed female sheep with radiolabelled microspheres before and after the intracarotid infusion of a 3% NaCl solution. Plasma arginine vasopressin (AVP) levels were concurrently measured by radioimmunoassay. Following intracarotid sodium chloride infusion, neural lobe (but not median eminence) blood flow significantly increased, as did plasma AVP levels. Directed thirst and water-seeking behavior was observed, accompanied by a global increase in cortical blood flow. We conclude that the neuroendocrine response and the behavioral display induced by intracarotid sodium chloride infusion are accompanied by increases in blood flow in selected brain regions.
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Conformational changes of lysozyme refolding intermediates and implications for aggregation and renaturationIt is believed that denatured-reduced lysozyme rapidly forms aggregates during refolding process, which is often worked around by operating at low protein concentrations or in the presence of aggregation inhibitors. However, we found that low concentration buffer alone could efficiently suppress aggregation. Based on this finding, stable equilibrium intermediate states of denatured-reduced lysozyme containing eight free SH groups were obtained in the absence of redox reagents in buffer of low concentrations alone at neutral or mildly alkaline pH. Transition in the secondary structure of the intermediate from native-like to beta-sheet was observed by circular dichroism (CD) as conditions were varied. Dynamic light scattering and ANS-binding studies showed that the self-association accompanied the conformational change and the structure rich in beta-sheet was the intermediate state for aggregation, which could form either amyloid protofibril or amorphous aggregates under different conditions as detected by Electron Microscopy. Combining the results obtained from activity analysis, RP-HPLC and CD, we show that the activity recovery was closely related to the conformation of the refolding intermediate, and buffer of very low concentration (e.g. 10mM) alone could efficiently promote correct refolding by maintaining the native-like secondary structure of the intermediate state. This study reveals reasons for lysozyme aggregation and puts new insights into protein and inclusion body refolding.
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Regulation of Drosophila p38 activation by specific MAP2 kinase and MAP3 kinase in response to different stimuliThe p38 mitogen-activated protein kinase (MAPK) signaling pathway plays an important role in cellular responses to inflammatory stimuli and environmental stress. Activation of p38 is mediated through phosphorylation by upstream MAPKK, which in turn is activated by MAPKKK. However, the mechanism of how different upstream MAP2Ks and MAP3Ks specifically contribute to p38 activation in response to different stimuli is still not clearly understood. By using double-stranded RNA-mediated interference (RNAi) in Drosophila cells, we demonstrate that D-MKK3 is a major MAP2K responsible for D-p38 activation by UV, heat shock, NaCl or peptiodglycan (PGN). Stimulation of UV and PGN activates D-p38 through D-MEKK1, heat shock-induced activation of D-p38 signals through both D-MEKK1 and D-ASK1. On the other hand, maximal activation of D-p38 by NaCl requires the expression of four MAP3Ks.
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Spreading waves of decreased diffusion coefficient after cortical stimulation in the rat brainA method is demonstrated for the noninvasive detection and study of spreading cortical depression. Spreading depression (SD) was elicited in rats by topical application of potassium chloride to the exposed cortex. The apparent diffusion coefficient (Dapp) of water in a region of the cortex, measured using a PFG-NMR spin echo sequence with an observation time of 40 ms, declines 35% within 30 s and recovers to the normal value within the next 30 s. The region of decreased Dapp was shown to be 2 mm in size and to move in the cortex, away from the point of application, with a uniform velocity of 3.3 +/- 0.5 mm/min. The behavior of the affected region is consistent with other reports of the behavior of SD as monitored by electrophysiological means. The technique can be implemented on currently available MRI equipment and makes possible the noninvasive study of SD in animal models of neurological disorders, their therapeutic intervention, and possibly the study of SD in humans.