Glucose catabolism during aging and differentiation in hypocotyls ofPhaseolus mungo seedlings

Changes in activities of the glycolytic and pentose phosphate (PP) pathways in glucose catabolism in various parts of the hypocotyls obtained from 4-day-old etiolatedPhaseolus mungo seedlings were investigated by measuring the inhibition rates of respiration by iodoacetate and malonate, and the release of¹⁴CO₂ from [1-¹⁴C]- and [6-¹⁴C]glucose. The relative activity of the PP pathway in glucose catabolism was higher in the immature part (Part I) and the aged part (Part V) of the hypocotyls than in the intermediary one (Part III), while the activity of the glycolytic pathway decreased with aging. On a fresh weight basis, the enzyme activities of the glycolytic and PP pathways were higher in Part I than in Parts III and V. On a protein content basis, however, activities of the enzymes of the PP pathway increased with aging and differentiation of the hypocotyls whereas those of the glycolytic pathway decreased. Levels of nicotinamide adenine nucleotides were found to be in the following order: Part I>Part III> Part V for NAD⁺+NADH; Part I>Part V>Part III for NADP⁺+NADPH. The stimulative effect of methylene blue on decreasing the C₆/C₁ ratio was greater in Part III than in Part I, and No effect was observed in Part V. These data suggest that a decrease in the activity of the glycolytic pathway with aging and differentiation may be due to the decreasing glycolytic enzyme activities and NAD(H) content. The higher activity of the PP pathway in the immature part is attributable to larger amounts of NADP(H) and enzymes of the PP pathway. The greater contribution of the PP pathway to glucose catabolism in the aged part than in the intermediary part seems to results from a more active turnover of NADP and the relatively higher activity of the enzymes of the PP pathway than those of the glycolytic pathway.     

Clinical Use of a New Mitral Disc Valve

A disc valve of new design was used successfully for the replacement of the mitral valve in patients with rheumatic mitral valve disease. This valve would appear to have the following advantages over the mitral ball valve prosthesis:• Lower left atrial pressure after replacement.• Elimination of the hazard of left ventricular outflow tract obstruction with mitral valve replacement.• Decreased incidence of thromboembolization.• Abolition of possibility of ventricular septal irritation.Despite the better outlook for this valve compared with the ball valve for mitral valve substitution, the mitral valve should always be repaired whenever feasible. Repair is possible in the majority of patients.     

Fine Structure of Bacillus subtilis : I. Fixation

The fine structure of Bacillus subtilis has been studied by observing sections fixed in KMnO₄, OsO₄, or a combination of both. The majority of examinations were made in samples fixed in 2.0 per cent KMnO₄ in tap water. Samples were embedded in butyl methacrylate for sectioning. In general, KMnO₄ fixation appeared to provide much better definition of the boundaries of various structures than did OsO₄. With either type of fixation, however, the surface structure of the cell appeared to consist of two components: cell wall and cytoplasmic membrane. Each of these, in turn, was observed to have a double aspect. The cell wall appeared to be composed of an outer part, broad and light, and an inner part, thin and dense. The cytoplasmic membrane appeared (at times, under KMnO₄ fixation) as two thin lines. In cells fixed first with OsO₄ solution, and then refixed with a mixture of KMnO₄ and OsO₄ solutions, the features revealed were more or less a mixture of those revealed by each fixation alone. A homogeneous, smooth structure, lacking a vacuole-like space, was identified as the nuclear structure in a form relatively free of artifacts. Two unidentified structures were observed in the cytoplasm when B. subtilis was fixed with KMnO₄. One a tortuous, fine filamentous element associated with a narrow light space, was often found near the ends of cells, or attached to one end of the pre-spore. The other showed a special inner structure somewhat similar to cristae mitochondriales.