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Complicated Shape (complicated + shape)

Distribution by Scientific Domains

Life Sciences	50%

Selected Abstracts

Real Time Three-Dimensional Echocardiography Evaluation of Mitral Annular Characteristics in Patients with Myocardial Hypertrophy

ECHOCARDIOGRAPHY, Issue 4 2008
Fatih Yalçin M.D.
It has been shown that systolic excursion of the mitral annulus (MA) correlates well with left ventricular (LV) systolic function. Evaluation of the complicated shape and dynamics of the mitral annulus, however, may require rigorous methodology. The aim of this study was to investigate differences in MA motion between hypertrophic cardiomyopathy (HCM) and left ventricular hypertrophy (LVH) patients due to hypertension or aortic stenosis using real time three-dimensional echocardiography (RT3DE). We studied 10 HCM, 10 LVH, and 10 controls. Mean MA area changes between early and late systole were 9.5 ± 4.3% in HCM, 26 ± 15% in LVH and 19 ± 10% in normal controls. MA apicobasal motion was 5.8 ± 4 mm in HCM, 11 ± 4 mm in LVH, and 13.6 ± 6 mm in normal controls. RT3DE with digital reconstruction of MA accurately display complicated MA geometry and dynamics during a cardiac cycle. Annular function in LVH was similar to that of the normal group while annular apicobasal motion and area changes were reduced in HCM. [source]

Plasticity of death rates in stationary phase in Saccharomyces cerevisiae

AGING CELL, Issue 1 2009
Nadège Minois
Summary For the species that have been most carefully studied, mortality rises with age and then plateaus or declines at advanced ages, except for yeast. Remarkably, mortality for yeast can rise, fall and rise again. In the present study we investigated (i) if this complicated shape could be modulated by environmental conditions by measuring mortality with different food media and temperature; (ii) if it is triggered by biological heterogeneity by measuring mortality in stationary phase in populations fractionated into subpopulations of young, virgin cells, and replicatively older, non-virgin cells. We also discussed the results of a staining method to measure viability instead of measuring the number of cells able to exit stationary phase and form a colony. We showed that different shapes of age-specific death rates were observed and that their appearance depended on the environmental conditions. Furthermore, biological heterogeneity explained the shapes of mortality with homogeneous populations of young, virgin cells exhibiting a simple shape of mortality in conditions under which more heterogeneous populations of older cells or unfractionated populations displayed complicated death rates. Finally, the staining method suggested that cells lost the capacity to exit stationary phase and to divide long before they died in stationary phase. These results explain a phenomenon that was puzzling because it appeared to reflect a radical departure from mortality patterns observed for other species. [source]

Understanding the shapes of bacteria just got more complicated

MOLECULAR MICROBIOLOGY, Issue 1 2006
Terry J. Beveridge
Summary The paper by Briegel et al. in this issue of Molecular Microbiology uses advanced cryo-transmission electron microscopy (cryoTEM) techniques to reveal four separate locations of cytoplasmic filament bundles in Caulobacter crescentus. Intuitively, these filaments should be rather rigid protein structures and composed of previously identified shape-forming proteins, such as crescentin or MreB. Yet, deletion mutants lacking these proteins still possessed filaments and still possessed wild-type morphology. These results suggest that a complex combination of protein structures, including those of crescentin, MreB and these newly identified bundles, in combination with the cell envelope help maintain the complicated shape of C. crescentus. Other bacteria might have similar architectural proteins to assist in maintaining the cell contours during growth and division. [source]

Nacre in Mollusk Shells as a Multilayered Structure with Strain Gradient

ADVANCED FUNCTIONAL MATERIALS, Issue 7 2009
Boaz Pokroy
Abstract How do living organisms attain the complicated shapes of grown bio-composites? This question is answered when studying the mechanics of the nacre layer in the bivalve mollusk shells. In this study, the internal strains/stresses across the shell thickness are profiled as a function of depth by strain gauge measurements during controlled etching in the selected areas. Measurements of stress release under etching provide clear evidence that the investigated shells, in fact, are strained multilayered structures, which are elastically bent due to the forces evolving at the organic/inorganic interfaces. The stresses are mostly concentrated in the "fresh" nacre sub-layers near the inner surface of the shell adjacent to the mollusk mantle. This analysis unexpectedly shows that the elastic bending of the nacre layer is due to strain gradients which are originated in the gradual in-depth changes of the thickness of ceramic lamellae. The changes mentioned were directly observed by scanning electron microscopy. By this sophisticated design of the ultra-structure of the nacre layer, the bowed shape of the bivalve shells is apparently achieved. [source]