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Shock Conditions (shock + condition)
Selected AbstractsMaterial Simulation and Damage Analysis at Thermal Shock ConditionsPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2006Franz-Barthold Gockel Thermal shock is an extreme form of thermo-mechanical loading. This detailed investigation close to reality is necessary in industrial engineering in order to get a good prediction of life expectancy for high quality and safety relevant machine components. This paper addresses on experimental investigations of deformation and damage at thermal shocked cylinders. Additionally the parameters for the Chaboche model are identified on the basis of uniaxial cyclic experiments. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Regulation of hippocampal cell adhesion molecules NCAM and L1 by contextual fear conditioning is dependent upon time and stressor intensityEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 9 2000J. Joaquín Merino Abstract Cell adhesion molecules (CAMs) of the immunoglobulin superfamily, NCAM and L1, as well as the post-translational addition of ,-2,8-linked polysialic acid (PSA) homopolymers to NCAM (PSA,NCAM), have been implicated in the neural mechanisms underlying memory formation. Given that the degree of stress elicited by the training situation is one of the key factors that influence consolidation processes, this study questioned whether training rats under different stressor intensities (0.2, 0.4, or 1 mA shock intensity) in a contextual fear conditioning task might regulate subsequent expression of NCAM, PSA,NCAM and L1 in the hippocampus, as evaluated immediately after testing rats for conditioning at 12 and 24 h after training. Behavioural inhibition (evaluated as a ,freezing' index) at testing and post-testing plasma corticosterone levels were also assessed. The results showed that 12 h post-training, conditioned animals displayed reduced NCAM, but increased L1, expression. At this time point, the group trained at the highest shock intensity (1 mA) also presented decreased PSA,NCAM expression. Analyses performed 24 h post-training indicated that the 1 mA group exhibited increased NCAM and L1 expression, but decreased expression of PSA,NCAM levels. In addition, L1 values that presented a shock intensity-dependent U-shaped pattern were also increased in the group trained at the lowest shock condition (0.2 mA) and remained unchanged in the intermediate shock condition (0.4 mA). Freezing and corticosterone values at both testing times were positively related with shock intensity experienced at training. Therefore, our results show a complex regulation of CAMs of the immunoglobulin superfamily in the hippocampus that depends upon stressor intensity and time factors. In addition, the pattern of CAMs expression found in the 1 mA group (which is the one that shows higher post-training corticosterone levels and develops the stronger and longer-lasting levels of fear conditioning) supports the view that, after a first phase of synaptic de-adherence during consolidation, NCAM and L1 might participate in the stabilization of selected synapses underlying the establishment of long-term memory for contextual fear conditioning, and suggests that glucocorticoids might play a role in the observed regulation of CAMs. [source] Small heat shock protein Hsp27 prevents heat-induced aggregation of F-actin by forming soluble complexes with denatured actinFEBS JOURNAL, Issue 22 2007Anastasia V. Pivovarova Previously, we have shown that the small heat shock protein with apparent molecular mass 27 kDa (Hsp27) does not affect the thermal unfolding of F-actin, but effectively prevents aggregation of thermally denatured F-actin [Pivovarova AV, Mikhailova VV, Chernik IS, Chebotareva NA, Levitsky DI & Gusev NB (2005) Biochem Biophys Res Commun331, 1548,1553], and supposed that Hsp27 prevents heat-induced aggregation of F-actin by forming soluble complexes with denatured actin. In the present work, we applied dynamic light scattering, analytical ultracentrifugation and size exclusion chromatography to examine the properties of complexes formed by denatured actin with a recombinant human Hsp27 mutant (Hsp27,3D) mimicking the naturally occurring phosphorylation of this protein at Ser15, Ser78, and Ser82. Our results show that formation of these complexes occurs upon heating and accompanies the F-actin thermal denaturation. All the methods show that the size of actin,Hsp27-3D complexes decreases with increasing Hsp27-3D concentration in the incubation mixture and that saturation occurs at approximately equimolar concentrations of Hsp27-3D and actin. Under these conditions, the complexes exhibit a hydrodynamic radius of ,,16 nm, a sedimentation coefficient of 17,20 S, and a molecular mass of about 2 MDa. It is supposed that Hsp27-3D binds to denatured actin monomers or short oligomers dissociated from actin filaments upon heating and protects them from aggregation by forming relatively small and highly soluble complexes. This mechanism might explain how small heat shock proteins prevent aggregation of denatured actin and by this means protect the cytoskeleton and the whole cell from damage caused by accumulation of large insoluble aggregates under heat shock conditions. [source] OH concentration time histories in n -alkane oxidationINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 12 2001D. F. Davidson OH radical concentration time histories were measured behind reflected shocks in the oxidation of four n -alkanes: propane, n -butane, n -heptane, and n -decane. Initial reflected shock conditions of these measurements were 1357,1784 K, 2.02,3.80 atm, with fuel concentrations of 300,2000 ppm, and equivalence ratios from 0.8 to 1.2. OH concentrations were measured using narrow-linewidth ring-dye laser absorption of the R1(5) line of the A,X (0,0) transition at 306.5 nm. These concentration time-history measurements were compared to the modeled predictions of eight large n -alkane oxidation mechanisms currently available in the literature and the kinetic implications of these measurements are discussed. These data, in conjunction with recent measurements of n -alkane ignition times and ethylene yields in n -alkane pyrolysis experiments, also performed in this laboratory, provide a unique database of species concentration time histories for n -alkane mechanism validation. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 775,783, 2001 [source] Diverse effects of Stat1 on the regulation of hsp90, gene under heat shock,JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 4 2007Xue-song Chen Abstract Stat1 has been known as a regulator of gene expression and a mediator of IFN, signaling in mammalian cells, while its effect in a heat shock response remains unclear. We used RNAi knockdown, point mutations, ChIP and promoter activity assays to study the effect of Stat1 on the heat-shock induction of the hsp90, gene under heat shock conditions. We found that Stat1 regulates the heat shock induction of its target genes, the hsp90, gene in a heat shock response while the constitutive activity of the gene remains unaffected. The result of Stat1 in complex with Stat3 and HSF1 that bound at the GAS to lead a moderate heat shock induction was designated as an "intrinsic" induction of the hsp90, gene. Additionally a reduced or an elevated level of heat shock induction was also controlled by the Stat1 on hsp90,. These diverse effects on the hsp90, gene were a "reduced" induction with over-expressed Stat1 elicited by transfection of wild-type Stat1 or IFN, treatment, bound at the GAS as homodimer; and an "enhanced" heat shock induction with a mutation-mediated prohibition of Stat1/GAS binding. In conclusion, the status and efficacy of Stat1 bound at the GAS of its target gene are pivotal in determining the impact of Stat1 under heat shock. The results provided the first evidence on the tumor suppressor Stat1 that it could play diverse roles on its target genes under heat shock that also shed lights on patients with fever or under thermotherapy. J. Cell. Biochem. 102: 1059,1066, 2007. © 2007 Wiley-Liss, Inc. [source] In vitro transcription of PrfA-dependent and -independent genes of Listeria monocytogenesMOLECULAR MICROBIOLOGY, Issue 1 2001M. Lalic-Mülthaler In vitro transcription starting from the promoters of the Listeria monocytogenes genes hly, plcA, actA, mpl, prfA and iap has been studied. Whereas transcription from Phly, PplcA and PactA is strictly PrfA-dependent, that from Piap, PprfA1/2 and, unexpectedly, also from Pmpl is independent. Initiation of in vitro transcription at all tested promoters except PprfA requires high concentrations of ATP but not GTP. The nucleotides required in higher concentrations for efficient in vitro transcription are always included in the first three nucleotides of the corresponding transcript. RNA polymerase prepared from L. monocytogenes cultured either in rich culture medium (RNAPBHI), exposed to heat shock conditions (RNAP48) or conditioned in minimal essential medium (RNAPMEM) shows significant differences in the transcription efficiencies when transcription is initiated at these promoters. Transcription starting from the PrfA-dependent promoters PactA and Phly is enhanced with RNAP48 and RNAPMEM (in relation to Piap,mediated transcription), while transcription from the other promoters is reduced when compared with RNAPBHI. These data suggest that in vivo transcription of the genes actA and hly may not function optimally with RNA polymerase loaded with the vegetative sigma factor 43, but may require a modified RNA polymerase, possibly loaded with an alternative sigma factor. [source] | |||||||||||||