Do increases in enzyme activities during muscle differentiation reflect expression of new genes?
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Biomedical subjects
Publications and source records attributed to R Cole.
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Mitral regurgiation with atrial fibrillation in a 3-year-old St. Bernard dog was corrected by digitalization, placement of a mitral valve prosthesis, and direct current cardioversion. The atrial fibrillation eventually returned and became refractory to cardioversion.
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Disabling pain of pancreatic origin can be relieved by drugs, by direct surgery to the pancreas, or by denervation of the pancreas. The place of each is discussed in the management of pancreatic pain. The special role of a coeliac plexus block in these cases is emphasized and the technique of its performance is described in detail.
When Escherichia coli B cells were labelled with [14-C] glycerol and chased, there was a marked sparing of the phosphatidyl moiety compared to the nonacylated glycerol moiety of phosphatidylglycerol. When energy-depleted cells were restored to an energy-rich medium there resulted a conversion of 32-P-labelled cardiolipin to phosphatidylglycerol, a lack of phosphatidic acid accumulation and no loss in total polyglycerophosphatide counts. In cell-free extracts, phosphatidic acid produced from 32-P-labelled cardiolipin by the action of Escherichia coli phosphalipase D, was readily recycled to form poly-glycerophosphatide. In the presence of glycerol, such extracts displayed traansphosphatidylase activity by degrading cardiolipin to phosphatidyglycerol mainly. The results as a whole indicate that the enzyme synthesizing cardiolipin together with cardiolipin-hydrolyzing phospholipase D constitute a cycle which is normally involved in the turnover of polyglycerophosphatides in Escherichia coli.
A phospholipase hydrolyzing cardiolipin to phosphatidic acid and phosphatidyl glycerol was characterized in gram-negative bacteria but was absent in preparations of gram-positive bacteria, Saccharomyces cerevisiae, and rat liver mitochondria. In cell-free extracts of Escherichia coli, Salmonella typhimurium, Proteus vulgaris, and Pseudomonase aeruginosa, this cardiolipin-hydrolyzing enzyme had similar pH and Mg2+ requirements and displayed a specificity which excluded phosphatidyl glycerol and phosphatidyl ethanolamine as substrates.
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We have investigated three classes of small bacteriophage T4 particles which differ from normal T4 particles in length of their deoxyribonucleic acid (DNA), in head length, in protein content, and in density. The different particles contain DNA molecules measuring 0.90, 0.77, or 0.67, respectively, of the normal T4 length. An additional class of viable particles contains DNA molecules of 1.1 unit length. These discrete differences in DNA length correspond to discrete differences in length (but not width) of the respective heads and are roughly proportional to the resulting differences in head volumes. The measured relative dimensions of the different heads fit best the relative dimensions predicted by a quasi-icosahedral model in which the smallest T4 head corresponds to an icosahedron with a triangulation number T = 21. The mid-portion of this structure is thought to be elongated by adding successive rows of gene 23 protein hexamers, the normal T4 head having three added rows. Different mutants produce small particles of the three classes in varying proportions, but no mutant produces exclusively particles of a single class. Particles of each class, with indistinguishable DNA content, show additional minor differences in protein content, as measured by differences in buoyant density and in the relative ratio of (32)P to (35)S.
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