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Query: UNIPROT:P50583 (asymmetrical)
 12,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effects of acute severe aortic regurgitation on the left ventricle were investigated in conscious, chronically instrumented dogs. Left ventricular dimensions and volumes were measured from biplane cineradiographs of beads positioned near the endocardium. Data were collected before and after the production of aortic regurgitation by a catheter technique. The aortic regurgitation resulted in increases in mean aortic pulse pressure from 44 to 73 mmHg (P smaller than 0.001), heart rate from 87 to 122 beats/min (P smaller than 0.02), and left ventricular end-diastolic pressure from 11 to 25 mmHg (P smaller than 0.05). Mean end-diastolic volume rose from 61 to 69 cc (P smaller than 0.001), while end-systolic volume remained unchanged at 37 cc. The end-diastolic dilatation following regurgitation was asymmetrical in that the increase in size was due principally to an increase in the septal-lateral axis. The acute volume load of aortic regurgitation was accomplished by an increase in end-diastolic volume, i.e., the Frank-Starling mechanism. The tachycardia probably reflects augmented cardiac sympathetic activity, but the constant end-systolic volume at a similar mean systolic pressure suggests that the net contractile state was unchanged.
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PMID:Dimensional analysis of the left ventricle: effects of acute aortic regurgitation. 12 19

Electron microscopic techniques are among the most important tools for obtaining structural information of biological specimens. However, the three-dimensional (3D) structural analysis of asymmetrical specimens that do not form crystalline sheets has traditionally presented serious methodological obstacles to its accomplishment. One of the fundamental questions to be addressed in this type of structural study is in what way, and to what degree, does the 3D structural conformation depend on the orientation of the specimen with respect to the electron microscopic support films. As a step in studying this problem, we have analyzed the variations of the 3D structure of the Escherichia coli 70S monosome by performing four different 3D reconstructions of the 70S monosome from subsets of images in the so-called overlap range of views. These subsets were selected according to a multivariate statistical analysis performed on the total population of overlap-range specimen images. A certain amount of structural variability exists among the 3D reconstructions, although many of the main morphological characteristics, as the relative orientation between the ribosomal subunits, remain unchanged. We have also generalized the random conical reconstruction technique (Radermacher, M., T. Wagenknecht, A. Verschoor, and J. Frank. 1987. J. Microsc. 146: 113-136) to include those cases where the specimen exhibits a rocking behavior with respect to the support. The resulting Multicone Reconstruction Technique has been applied to computer-generated images as well as the E. coli 70S monosome images from part of the overlap range of views.
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PMID:Variations of the three-dimensional structure of the Escherichia coli ribosome in the range of overlap views. An application of the methods of multicone and local single-cone three-dimensional reconstruction. 264 64

The Frank-Starling law is an important regulatory mechanism of the heart that links the end-diastolic volume with the systolic ejection fraction. This beat-to-beat regulation of the heart, underlined at the cellular level by higher myofilament calcium sensitivity at longer sarcomere length, is known as length-dependent activation or stretch sensitization of activation. However, the heart is structurally and functionally heterogeneous and asymmetrical. Specifically, contractile properties are not uniform within the left ventricle partly due to transmural differences in action potential waveforms and calcium homeostasis. The present review will focus on the role of the contractile machinery in the transmural contractile heterogeneity and its adaptation to changes in muscle strain. The expression of different myosin isoforms, the level of titin-based passive tension, and thin and thick sarcomeric regulatory proteins are considered to explain the regional cellular contractile properties. Finally, the importance of transmural heterogeneity of length-dependent activation and the consequences of its modification on the heart mechanics are discussed. Despite extensive research since the characterization of the Frank-Starling law, the molecular mechanisms by which strain information is transduced to the contractile machinery have not been fully determined yet.
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PMID:Regional variation in myofilament length-dependent activation. 2133 86