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Query: UMLS:C0344329 (collapse)
 28,634 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The permeabilization of Trypanosoma brucei procyclic and bloodstream trypomastigotes with digitonin permitted the quantitative estimation of a mitochondrial membrane potential of the order of 130-140 mV, in both forms, using safranine O. Dependence on substrate oxidation and response of the procyclic mitochondrial membrane potential to phosphate, FCCP, valinomycin, and Ca2+ indicate that these mitochondria behave similarly to vertebrate mitochondria regarding the properties of their electrochemical proton gradient. In contrast, in bloodstream mitochondria, development of a membrane potential was independent of substrate oxidation and dependent on hydrolysis of ATP by the mitochondrial oligomycin-sensitive ATPase, as demonstrated by collapse of the membrane potential by oligomycin and its insensitivity to the respiratory chain-inhibitor antimycin A. Mitochondria of T. brucei bloodstream forms were also able to take up Ca2+ by an electrophoretic mechanism. This is the first report of the presence of a Ca2+ transport mechanism in an eukaryotic cell devoid of complete tricarboxylic acid cycle and respiratory chain, the activities of which are known to be regulated by changes in intramitochondrial calcium concentration in other cells.
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PMID:Energization-dependent Ca2+ accumulation in Trypanosoma brucei bloodstream and procyclic trypomastigotes mitochondria. 148 49

One of the proposed mechanisms of ventilator-associated lung injury is cyclic recruitment of atelectasis. Collapse of dependent lung regions with every breath should lead to large oscillations in PaO2 as shunt varies throughout the respiratory cycle. We placed a fluorescence-quenching PO2 probe in the brachiocephalic artery of six anesthetized rabbits after saline lavage. Using pressure-controlled ventilation with oxygen, ventilator settings were varied in random order over three levels of positive end-expiratory pressure (PEEP), respiratory rate (RR), and plateau pressure minus PEEP (Delta). Dependence of the amplitude of PaO2 oscillations on PEEP, RR, and Delta was modeled by multiple linear regression. Before lavage, arterial PO2 oscillations varied from 3 to 22 mm Hg. After lavage, arterial PO2 oscillations varied from 5 to 439 mm Hg. Response surfaces showed markedly nonlinear dependence of amplitude on PEEP, RR, and Delta. The large PaO2 oscillations observed provide evidence for cyclic recruitment in this model of lung injury. The important effect of RR on the magnitude of PaO2 oscillations suggests that the static behavior of atelectasis cannot be accurately extrapolated to predict dynamic behavior at realistic breathing frequencies.
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PMID:Effects of respiratory rate, plateau pressure, and positive end-expiratory pressure on PaO2 oscillations after saline lavage. 2458 6

The well-known Rayleigh-Plesset ( RP ) equation is the basis of almost all hydrodynamical descriptions of single-bubble sonoluminescence ( SBSL ). A major deficiency of the RP equation is that it accounts for viscosity of an incompressible liquid and compressibility, separately. By removing this approximation, a new modification of the RP equation is presented considering effect of compressional viscosity of the liquid. This modification leads to addition of a new viscous term to the traditional bubble boundary equation. Influence of this new term in the dynamics of a sonoluminescing bubble has numerically been studied considering effects of heat transfer at the bubble wall, nonequilibrium evaporation and condensation of water vapor, chemical reactions, and diffusion of the reactions products in the liquid. The results show that the new term has a significant damping role in the bubble motion at the end of collapse and during the rebounds, so that its consideration dramatically reduces amplitude of the afterbounces. Dependence of this new damping mechanism on the driving pressure amplitude and on the ambient radius has been investigated. The results indicate that the more intense the collapse, the more important the damping of the liquid compressional viscosity.
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PMID:Role of liquid compressional viscosity in the dynamics of a sonoluminescing bubble. 1638 84

Surface pressure-area (pi-A), surface potential-area (DeltaV-A), and dipole moment-area (mu( perpendicular)-A) isotherms were obtained for the Langmuir monolayer of two fluorinated-hydrogenated hybrid amphiphiles (sodium phenyl 1-[(4-perfluorohexyl)-phenyl]-1-hexylphosphate (F6PH5PPhNa) and (sodium phenyl 1-[(4-perfluorooctyl)-phenyl]-1-hexylphosphate (F8PH5PPhNa)), DPPC and their two-component systems at the air/water interface. Monolayers spread on 0.02 M Tris buffer solution (pH 7.4) with 0.13M NaCl at 298.2K were investigated by the Wilhelmy method, ionizing electrode method and fluorescence microscopy. Moreover, the miscibility of two components was examined by plotting the variation of the molecular area and the surface potential as a function of the molar fraction for the fluorinated-hydrogenated hybrid amphiphiles on the basis of the additivity rule. The miscibility of the monolayers was also examined by construction of two-dimensional phase diagrams. Furthermore, assuming the regular surface mixture, the Joos equation for analysis of the collapse pressure of two-component monolayers allowed calculation of the interaction parameter (xi) and the interaction energy (-Deltaepsilon) between the fluorinated-hydrogenated hybrid amphiphiles and DPPC. The observations by a fluorescence microscopy also supported our interpretation as for the miscibility in the monolayer state. Comparing the monolayer behavior between the two binary systems, no remarkable difference was found among various aspects. Among the two combinations, the mole fraction dependence in monolayer properties was commonly classified into two ranges: 0 <or= X <or= 0.3 and 0.3 < X <or = 1. Dependence of the chain length of fluorinated part was reflected for the molecular packing and surface potential.
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PMID:Langmuir monolayer properties of the fluorinated-hydrogenated hybrid amphiphiles with dipalmitoylphosphatidylcholine (DPPC). 1642 22

A systematic Langevin simulation is performed to study the crowding-induced collapse effect on a probed chain in three typical systems: hard sphere (HS), flexible polymer and rod-like polymer. Dependence of probed chain compaction on both crowder size and concentration is investigated explicitly. Particular attention is paid to examining the significant discrepancy in collapse effect associated with the crowder structure. First, we find an opposite compaction behavior in the HS and flexible polymer systems, in consistence with previous simulation and experimental observations. Compaction decreases with HS size while it increases with flexible polymer chain length. The underlying mechanism for such a contradiction is unraveled in terms of a depletion effect. For the HS system, as the crowder size increases, the ability of accommodating the probed chain enhances with a negligible depletion effect and thus results in a reduced compaction, while a polymer crowder system introduces a local depletion effect, responsible for an intensified compaction effect with increasing polymer length. Secondly, we reveal that the anisotropic feature of the rod-like polymer is a crucial factor in compaction. A novel non-monotonous behavior against the polymer length is observed under rod-like polymer crowding, which can be ascribed to the competition between anisotropy-induced stretching and crowding-induced compaction. Lastly, we present a quantitative evaluation of the crowding-induced potential, which provides a scenario for understanding compaction from a microscopic viewpoint. The potential profiles with respect to crowder size demonstrate a consistent tendency with the corresponding collapse behavior. The study in the present work provides a deeper insight into the modeling structure and dynamics of macromolecules in crowded media.
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PMID:Comparative study of the crowding-induced collapse effect in hard-sphere, flexible polymer and rod-like polymer systems. 3114 Apr 98