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Query: UMLS:C0033377 (prolapse)
 11,717 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Straited membranous structures (SMS), which consisted of sheets or ribbons of 130 to 220 A in thickness, showed variable patterns of periodic substructure, and resembled SMS described in renal and ocular tissues in various diseases, were found in extracellular locations in a) mitral valve (2 patients) and tricuspid valve (1 patient) of 2 patients with mitral valvular prolapse, b) mitral valve and femoral artery of 1 patient with Marfan's syndrome and prolapsed mitral valve, and c) myocardium (2 patients) and thickened endocardium (3 patients) of 3 patients with congenital heart disease associated with muscular obstruction to right ventricular outflow. Striated membranous structures measured up to several microns in diameter, often were highly folded and convoluted, and sometimes appeared circular in outline. Some SMS measured from 130 to 150 A in thickness and had indistinct edges and poorly defined periodicity. The majority of SMS, however, had greater thicknesses, in the range of 200 A, and a periodicity characterized by alternating light and dark bands with a spacing that varied from 100 to 160 A. The structures were associated with thickened basement membranes, elastic fibers, and membrane-bound bodies of the type thought to be involved in elastogenesis. Evidence available suggests that SMS results from an unusual pattern of arrangement of a component, possibly Type IV collagen, of basement membrane material.
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PMID:Striated membranous structures in human hearts. An ultrastructural study. 97 Apr 44

Bcl-2, Bcl-XL, and Bax are members of the Bcl-2 family that play important roles in apoptosis regulation. These proteins are believed to be membrane-bound and to regulate apoptosis through formation of homo- and heterodimers. However, we recently found by subcellular fractionation that whereas Bcl-2 is predominantly a membrane protein as previously reported, Bax and a significant fraction of Bcl-XL are soluble in thymocyte and splenocyte extracts. In addition, we have demonstrated that the ability of Bax to form dimers appears to be a detergent-induced phenomenon that coincides with a detergent-induced conformational change. We have further investigated the tertiary and quaternary states of Bax in the presence of various detergents. Detergents such as Triton X-100 and Triton X-114 readily enable Bax hetero- and homodimerization. However, other detergents such as polydocanol, W-1, octyl glucoside, dodecyl maltoside, Tween 20, and sodium cholate allow varying degrees of Bax hetero- and homodimerization. Detergents such as 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonic acid (Chaps) and Brij 35 allow neither hetero- nor homodimer formation. Immunoprecipitation analysis with the conformation-sensitive antibody uBax 6A7 revealed that whereas Triton X-100 readily exposes the N-terminal Bax epitope (amino acid 13-19), only limited exposure of the epitope occurs in Triton X-114, polydocanol, dodecyl maltoside, and sodium cholate, and no exposure of this epitope was observed in W-1, Chaps, octyl glucoside, Tween 20, and Brij 35. Moreover, we could not detect any proteins associated with the cytosolic form of Bax based on immunopurification of this protein. Sephacryl S-100 gel filtration chromatography analysis of the cytosolic Bax indicated that this protein is monomeric and displays an apparent molecular mass of 25 kDa. Induction of apo-ptosis which causes the insertion of the soluble form of Bax into membranes did not result in appreciable Bax/Bcl-XL, Bax/Bcl-2 or Bax/Bax dimer formation as determined by cross-linking studies. Further analysis of Bax after apoptosis induction by immunoprecipitation in the presence of Chaps also revealed no significant heterodimer formation. In conclusion, Bax displays several distinct states in different detergents that expose defined regions of the protein. In addition, these results suggest that mechanisms other than the simple dimerization among members of the Bcl-2 family may be required for the regulation of apoptosis.
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PMID:Bax in murine thymus is a soluble monomeric protein that displays differential detergent-induced conformations. 955 44

Through the action of its membrane-bound type I receptor, transforming growth factor-beta (TGF-beta) elicits a wide range of cellular responses that regulate cell proliferation, differentiation, and apo ptosis. Many of these signaling responses are mediated by Smad proteins. As such, controlling Smad activity is crucial for proper signaling by TGF-beta and its related factors. Here, we show that TGF-beta induces phosphorylation at three sites in the Smad3 linker region in addition to the two C-terminal residues, and glycogen synthase kinase 3 is responsible for phosphorylation at one of these sites, namely Ser-204. Alanine substitution at Ser-204 and/or the neighboring Ser-208, the priming site for glycogen synthase kinase 3 in vivo activity, strengthened the affinity of Smad3 to CREB-binding protein, suggesting that linker phosphorylation may be part of a negative feedback loop that modulates Smad3 transcriptional activity. Thus, our findings reveal a novel aspect of the Smad3 signaling mechanism that controls the final amplitude of cellular responses to TGF-beta.
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PMID:A negative feedback control of transforming growth factor-beta signaling by glycogen synthase kinase 3-mediated Smad3 linker phosphorylation at Ser-204. 1945 83