Stress sensitization

Janzen, W., and Ehrenstein, G. W., Hysteresis Measurements for Characterizing the Cyclic Strain and Stress Sensitivity of Glass Fiber Reinforced PBT, SPEANTEC, May 1989. 

For bio-transformation processes, immobilised enzymes are often used because their activity persists over a longer period of time than that of free enzymes. The reduction of enzyme activity in enzymatic reactors is a consequence of energy dissipation by sparging and stirring, which is required for instance for oxygen transport or realisation of constant reaction conditions as regards temperature and pH. In the other hand low and high pH-values leads also to a decrease of enzyme activity and increase the stress sensitivity. 

Static leak-off experiments with borate-crosslinked and zirconate-cross-Unked hydroxypropylguar fluids showed practically the same leak-off coefficients [1883]. An investigation of the stress-sensitive properties showed that zirconate filter-cakes have viscoelastic properties, but borate filter-cakes are merely elastic. Noncrosslinked fluids show no filter-cake-type behavior for a large range of core permeabilities, but rather a viscous flow dependent on porous medium characteristics. 

Ishida With respect to Ufespan, work by Paul Shaw on cjfi mutant flies showed that they became very sensitive to desiccation and sleep stress (Shaw et al 2002). cjfi flies died early after sleep deprivation. So the molecular mechanism of lifespan might be related to that of the circadian system. But another possibility is that BMALl and CLOCK regulate many other output factors, such as stress-sensitive proteins. 

Tic disorders have long been identified as stress-sensitive conditions (Silva et al., 1995). Typically,... 

Vathy, L, He, H.J., lodice, M., Hnatczuk, O.C., and Rimanoczy, A. (2000) Prenatal morphine exposure differentially alters TH-immunoreactivity in the stress-sensitive brain circuitry of adult male and female rats. Brain Res Bull 51 267—273. 

These results are a remarkable achievement. They were obtained at 670MFIz, with a spatial resolution of 5-10 pm. The total velocity changes involved were of the order of 0.5 per cent, and the stress sensitivity achieved was 0.3 MPa. 

The discussion thus far has emphasized sensitivity of the frequency of C02 s v3 mode to local stress, sensitivity of its absorption intensity to IR polarization, and sensitivity of both properties to resonant coupling of dimers. For the type of crystals under consideration, which consist mostly of simple hydrocarbon groups, these factors probably dominate in determining the IR spectral characteristics. Other factors can be involved, however, and although they can make simple interpretation of the spectra more problematic, they can also provide additional information about the environment of the C02 probe molecule. The following examples illustrate how one can track the motion of C02 over distances of 1-15 A by observing its proximity to free radical centers or to halogen or deuterium substituents in the crystal lattice. This information complements the previously discussed structural studies, which related to structure within the dimer rather than to the location of the C02 in the crystal matrix. 

Non-destructive methods include holographic interferometry, resistance transducers, stress-sensitive covers, and other similar techniques. In practice, the following physical methods of non-destructive monitoring of residual stresses are commonly used X-ray diffraction, measurement of dielectric properties, and ultrasonic control. The main purpose of these methods is to monitor the structural transformations or distortions taking place as a result of residual stresses and local deformations. However, the application of methods such as X-ray diffraction to measure distortions in unit cel dimensions, ultrasonics to measure elastic wave propagation velocities, etc., all encounter numerous experimental problems. Therefore, in ordinary laboratory conditions only quantitative estimations of residual stresses can be obtained. 

Mukheijee P. K., DeCoster M. A., Campbell F. Z., Davis R. J., and BazanN. G. (1999). Glutamate receptor signaling interplay modulates stress-sensitive mitogen-activated protein kinases and neuronal cell death. J. Biol. Chem. 274 6493-6498. 

Zou, J., Guo, Y., Guettouche, T., Smith, D.F. and Voellmy, R. (1998) Repression of heat shock transcription factor HSF1 activation by FISP90 (HSP90 complex) that forms a stress-sensitive complex with FISF1. Cell, 94, 471 —480. Zuo, J., Rungger, D. and Voellmy R. (1995) Multiple layers of regulation of human heat shock transcription factor 1. Mol Cell. Biol., 15, 4319 1330. 

The best system for aeration and stirring of culture medium in a bioreactor must minimize shear stress without significantly reducing the oxygen transfer (KLa) and yet avoiding the generation of foam. In some systems, protectors such as serum, Pluronic F68, PEG, dextrans, lipids, and cholesterol, may have to be used to prevent shear stress. Sensitivity to shear depends on the cell line, and fortunately the lines most often utilized industrially for the production of mAbs, such as hybridomas, CHO, and BHK-21, are among the most resistant animal cells in relation to these hydrodynamic forces (Chisti, 2000 Chu and Robinson, 2001 Wu, 1995). 

PC shows either craze or shear behavior, with no mixed behavior, i.e., successively regenerated localized DCG zones. There is a sharp transition between the craze and the shear branches, as seen in Fig. 35. The competition between crazing and shear is temperature and stress sensitive. The mode, once determined, persists as the barrier is high between these two modes. At 75 °C and above, no craze-crack growth is observed, although shear fracture does persist down to —25 °C, albeit only at high stresses. 

In equation (1), Tocto corresponds to the shear yield stress under zero pressure and a is a pressure coefficient, which quantifies the yield stress sensitivity to pressure. Such a yield criterion has previously been shown to hold for epoxy resins under a wide range of pressure, temperature and strain rate conditions [10, 11]. The two parameters, Tocto and a were found to be 44 MPa and 0.173 respectively from the uniaxial and plane strain compression results reported in table I. 

The concept of stress sensitization , whereby early hfe stressors can induce an enhanced reactivity to later environmental adversities (reviewed in Read et al., 2005), may also be relevant to the etiology of schizophrenia This phenomenon, which results in abnormal activation of the HPA axis, is thought to involve alterations in the mesolimbic dopamine system (reviewed in Laruelle, 2000) resulting in excessive release of dopamine, a hallmark of psychotic episodes (Laruelle et al., 1996). Taken together, it appears likely that prenatal developmental abnormalities in limbic structures that regulate the HPA axis predispose this system to sensitivity to stressors in early childhood and adolescent maturation. This predisposition may then play a key role in the precipitation of psychotic episodes, as well as the deterioration of brain function that accompanies the progression of the disease. 

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