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Initial Diameter (initial + diameter)
Selected AbstractsFibroblast elongation and dendritic extensions in constrained versus unconstrained microtissuesCYTOSKELETON, Issue 3 2009Dylan M. Dean Abstract Cytoskeletal tension is fundamental to many biological processes, including germ layer sorting during embryogenesis [Krieg et al., 2008]. In vitro, such tension influences cell sorting in self-assembled, 3D microtissues and can be of sufficient magnitude to cause complex-shaped microtissue failure [Dean et al., 2007]. To examine the process of failure under cell-derived tension, we subjected normal human fibroblasts (NHFs) to directed self-assembly [Dean et al., 2007] in micro-molds designed to yield self-constraining microtissues. As cells contracted in this assay, the constrained microtissues narrowed, thinned and ultimately failed at their midpoints. By adding small numbers of GFP+ cells, changes in cell movement and morphology were assessed and compared to those of unconstrained microtissues. We found that cells formed numerous dendritic extensions within an hour of self-assembly and retracted these extensions as they elongated up to 30 times their initial diameter (,600 ,m) just prior to failure. Surprisingly, significant coordination in cell motility was observed over large distances within microtissues. Pharmacologic interventions showed that failure was myosin II and Rho kinase dependent and inhibition of failure resulted in shorter cells with greater numbers of extensions. These findings further our understanding of cellular self-assembly and introduce the use of GFP+ cells with directed self-assembly as a scaffold-free analogue to fibroblast-populated collagen gels (FPCGs). Cell Motil. Cytoskeleton 2009. © 2009 Wiley-Liss, Inc. [source] Some questions on dispersion of human exhaled droplets in ventilation room: answers from numerical investigationINDOOR AIR, Issue 2 2010C. Chen Abstract, This study employs a numerical model to investigate the dispersion characteristics of human exhaled droplets in ventilation rooms. The numerical model is validated by two different experiments prior to the application for the studied cases. Some typical questions on studying dispersion of human exhaled droplets indoors are reviewed and numerical study using the normalized evaporation time and normalized gravitational sedimentation time was performed to obtain the answers. It was found that modeling the transient process from a droplet to a droplet nucleus due to evaporation can be neglected when the normalized evaporation time is <0.051. When the normalized gravitational sedimentation time is <0.005, the influence of ventilation rate could be neglected. However, the influence of ventilation pattern and initial exhaled velocity on the exhaled droplets dispersion is dominant as the airflow decides the droplets dispersion significantly. Besides, the influence of temperature and relative humidity on the dispersion of droplets can be neglected for the droplet with initial diameter <200 ,m; while droplet nuclei size plays an important role only for the droplets with initial diameter within the range of 10 ,m,100 ,m. Practical Implications Dispersion of human exhaled droplets indoor is a key issue when evaluating human exposure to infectious droplets. Results from detailed numerical studies in this study reveal how the evaporation of droplets, ventilation rate, airflow pattern, initial exhaled velocity, and particle component decide the droplet dispersion indoor. The detailed analysis of these main influencing factors on droplet dispersion in ventilation rooms may help to guide (1) the selection of numerical approach, e.g., if the transient process from a droplet to a droplet nucleus due to evaporation should be incorporated to study droplet dispersion, and (2) the selection of ventilation system to minimize the spread of pathogen-laden droplets in an indoor environment. [source] Tree mortality and effects of release from competition in an old-growth Fagus-Abies-Picea standJOURNAL OF VEGETATION SCIENCE, Issue 5 2001Jerzy Szwagrzyk Abstract. In a montane mixed Fagus-Abies-Picea forest in Babia Gora National Park (southern Poland), the dynamics of an old-growth stand were studied by combining an 8-yr annual census of trees in a 1-ha permanent sample plot with radial increments of Abies and Picea growing in the central part of the plot. The mortality among the canopy trees was relatively high (10% in 8 yr), but the basal area increment of surviving trees slightly exceeded the losses caused by tree death. DBH increment was positively correlated with initial diameter in Abies and Picea, but not in Fagus. For individual trees smaller than the median height, basal area increment was positively related to the basal area of old snags and the basal area of recently deceased trees in their neighbourhood, but negatively related to the basal area of live trees. Dendrochronological analysis of the past growth patterns revealed numerous periods of release and suppression, which were usually not synchronized among the trees within a 0.3 ha plot. The almost normal distribution of canopy tree DBH and the small number of young individuals in the plot indicated that stand dynamics were synchronized over a relatively large area and, hence, were consistent with the developmental phase concept. On the other hand, the lack of synchronization among periods of growth acceleration in individual mature Abies and Picea trees conforms more closely to the gap-dynamics paradigm. [source] Recommendations for screening intervals for small aortic aneurysms,BRITISH JOURNAL OF SURGERY (NOW INCLUDES EUROPEAN JOURNAL OF SURGERY), Issue 7 2003R. J. McCarthy Background: The aim was to determine the optimum rescreening interval for small abdominal aortic aneurysms (AAAs). Methods: Data from 12 years of population screening of 65-year-old men were analysed and 1121 small AAAs (less than 4·0 cm in initial diameter) were divided into groups: group 1 (2·6,2·9 cm; n = 625), group 2 (3·0,3·4 cm; n = 330) and group 3 (3·5,3·9 cm; n = 166). Expansion rate and the cumulative proportions to expand to over 5·5 cm, or require surgery, or rupture were calculated. Results: Expansion rate was related to initial aortic diameter: 0·09 cm per year in group 1, 0·16 cm per year in group 2 and 0·32 cm per year in group 3 (P < 0·001). Aneurysms in 2·4 per cent of patients in group 1 exceeded a diameter of 5·5 cm or required surgery within 5 years; there were no ruptures. In group 2, no aorta exceeded 5·5 cm but at 3 years 2·1 per cent had reached 5·5 cm and 2·9 per cent had required surgery. The rupture rate at 3 years was zero. In group 3, the aneurysm diameter exceeded 5·5 cm in 1·2 per cent of patients, but no patient required surgery or experienced rupture within 1 year; at 2 years 10·5 per cent of aneurysms had exceeded 5·5 cm in diameter or required surgery and 1·4 per cent had ruptured. Conclusion: The appropriate rescreening interval can be determined by initial aortic diameter in screened 65-year-old men. AAAs of initial diameter 2·6,2·9 cm should be rescanned at 5 years, those of 3·0,3·4 cm at 3 years and those of 3·5,3·9 cm at 1 year. Copyright © 2003 British Journal of Surgery Society Ltd. Published by John Wiley & Sons, Ltd. [source] Morphological mechanisms for regulating blood flow through hepatic sinusoidsLIVER INTERNATIONAL, Issue 1 2000Robert S. McCuskey Abstract: This review summarizes what is known about the various morphological sites that regulate the distribution of blood flow to and from the sinusoids in the hepatic microvascular system. These sites potentially include the various segments of the afferent portal venules and hepatic arterioles, the sinusoids themselves, and central and hepatic venules. Given the paucity of smooth muscle in the walls of these vessels, various sinusoidal lining cells have been suggested to play a role in regulating the diameters of sinusoids and influencing the distribution and velocity of blood flow in these vessels. While sinusoidal endothelial cells have been demonstrated to be contractile and to exhibit sphincter function, attention has recently focused on the perisinusoidal stellate cell as the cell responsible for controlling the sinusoidal diameter. A very recent study, however, suggested that the principal site of vasoconstriction elicited by ET-1 was the pre-terminal portal venule. This raised the question of whether or not the diameters of sinusoids might decrease due to passive recoil when inflow is reduced or eliminated and intra-sinusoidal pressure falls. In more recent in vivo microscopic studies, clamping of the portal vein dramatically reduced sinusoidal blood flow as well as the diameters of sinusoids. The sinusoidal lumens rapidly returned to their initial diameters upon restoration of portal blood flow suggesting that sinusoidal blood pressure normally distends the sinusoidal wall which can recoil when the pressure drops. Stellate cells may be responsible for this reaction given the nature of their attachment to parenchymal cells by obliquely oriented microprojections from the lateral edges of their subendothelial processes. This suggests that care must be exercised when interpreting the mechanism for the reduction of sinusoidal diameters following drug administration without knowledge of changes occurring to the portal venous and hepatic inflow. [source] | ||||||||||