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Vascular reactivity (VR) denotes changes in volumetric blood flow in response to arterial occlusion. Current techniques to study VR rely on monitoring blood flow parameters and serve to predict the risk of future cardiovascular complications. Because tissue temperature is directly impacted by blood flow, a simplified thermal model was developed to study the alterations in fingertip temperature during arterial occlusion and subsequent reperfusion (hyperemia). This work shows that fingertip temperature variation during VR test can be used as a cost-effective alternative to blood perfusion monitoring. The model developed introduces a function to approximate the temporal alterations in blood volume during VR tests. Parametric studies are performed to analyze the effects of blood perfusion alterations, as well as any environmental contribution to fingertip temperature. Experiments were performed on eight healthy volunteers to study the thermal effect of 3 min of arterial occlusion and subsequent reperfusion (hyperemia). Fingertip temperature and heat flux were measured at the occluded and control fingers, and the finger blood perfusion was determined using venous occlusion plethysmography (VOP). The model was able to phenomenologically reproduce the experimental measurements. Significant variability was observed in the starting fingertip temperature and heat flux measurements among subjects. Difficulty in achieving thermal equilibration was observed, which indicates the important effect of initial temperature and thermal trend (i.e., vasoconstriction, vasodilatation, and oscillations). 相似文献
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Phycoferritin from the nutritionally important blue-green alga Arthrospira platensis has been isolated, by application of conventional biochemical techniques. The molecular mass, yield, iron and total neutral
carbohydrate contents of the purified protein were 470 kDa, 0.044 mg g−1 of Arthrospira, 1.4 and 20%, respectively. The iron content was much lower when compared to bacterial and mammalian ferritins. The P: Fe
ratio of Arthrospira phycoferritin was 1: 3.5, a value akin to bacterioferritins. Native gel-electrophoresis revealed the presence of isoforms.
Subunit analysis by SDS-PAGE and Western blotting showed a protein subunit with an apparent molecular mass of 18 kDa. Oligomeric
forms of the protein subunit were also present. The phycoferritin exhibited cross-reactivity with anti-pea seed ferritin suggesting
phylogenetic relationship with that of higher plants. Carbohydrate analysis of phycoferritin by GC-MS revealed the presence
of sugars such as galactose, glucose and mannose similar to that of mammalian ferritins. Interestingly, the analysis also
revealed sugars such as rhamnose, xylose and talose, which has not been reported in the structure of ferritins. Except for
very low histidine content in phycoferritin, the rest of the amino acid composition resembled to ferritins of other species.
UV-visible spectral analysis of the phycoferritin revealed the presence of haem groups, a property characteristic of bacterioferritins.
The fluorescence intensity of phycoferritin was higher than equine spleen ferritin. Circular dichroic spectra revealed a lower
degree of helicity. 相似文献
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Summary An investigation was carried out in order to study the effect of salts namely NaC1 and Na2SO4 on the rate of translocation of photosynthates in pigeonpea, at the pod filling stage. At the concentration of 10 EC NaC1
only 17% of the14C assimilates are translocated from the source leaf to the other parts of the plant. Out of this pods receive about 8%. On
the other hand even at a concentration of 15 EC Na2SO4 about 30% of the total14C assimilates get translocated and out of this pods receive about 12%. From this it may be concluded that under salt-stress
conditions the rate of translocation of photosynthates is adversely affected and between the two salts, NaC1 was discovered
to have a marked inhibitory effect. 相似文献
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S. S. Shishvan A. Vigliotti V. S. Deshpande 《Biomechanics and modeling in mechanobiology》2018,17(6):1631-1662
Cells are quintessential examples of out-of-equilibrium systems, but they maintain a homeostatic state over a timescale of hours to days. As a consequence, the statistics of all observables is remarkably consistent. Here, we develop a statistical mechanics framework for living cells by including the homeostatic constraint that exists over the interphase period of the cell cycle. The consequence is the introduction of the concept of a homeostatic ensemble and an associated homeostatic temperature, along with a formalism for the (dynamic) homeostatic equilibrium that intervenes to allow living cells to evade thermodynamic decay. As a first application, the framework is shown to accurately predict the observed effect of the mechanical environment on the in vitro response of smooth muscle cells. This includes predictions that both the mean values and diversity/variability in the measured values of observables such as cell area, shape and tractions decrease with decreasing stiffness of the environment. Thus, we argue that the observed variabilities are inherent to the entropic nature of the homeostatic equilibrium of cells and not a result of in vitro experimental errors. 相似文献
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Medha Raina Adil Moghal Amanda Kano Mathew Jerums Paul D. Schnier Shun Luo Rohini Deshpande Pavel V. Bondarenko Henry Lin Michael Ibba 《The Journal of biological chemistry》2014,289(25):17780-17790
Quality control operates at different steps in translation to limit errors to approximately one mistranslated codon per 10,000 codons during mRNA-directed protein synthesis. Recent studies have suggested that error rates may actually vary considerably during translation under different growth conditions. Here we examined the misincorporation of Phe at Tyr codons during synthesis of a recombinant antibody produced in tyrosine-limited Chinese hamster ovary (CHO) cells. Tyr to Phe replacements were previously found to occur throughout the antibody at a rate of up to 0.7% irrespective of the identity or context of the Tyr codon translated. Despite this comparatively high mistranslation rate, no significant change in cellular viability was observed. Monitoring of Phe and Tyr levels revealed that changes in error rates correlated with changes in amino acid pools, suggesting that mischarging of tRNATyr with noncognate Phe by tyrosyl-tRNA synthetase was responsible for mistranslation. Steady-state kinetic analyses of CHO cytoplasmic tyrosyl-tRNA synthetase revealed a 25-fold lower specificity for Tyr over Phe as compared with previously characterized bacterial enzymes, consistent with the observed increase in translation error rates during tyrosine limitation. Functional comparisons of mammalian and bacterial tyrosyl-tRNA synthetase revealed key differences at residues responsible for amino acid recognition, highlighting differences in evolutionary constraints for translation quality control. 相似文献
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