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Biomedical subjects

T Kagawa

Publications and source records attributed to T Kagawa.

At least 181 records · Page 10Linked to original sources
PubMed1977

The use of the Björk-Shiley prosthetic valve in children under 10 years of age.

Five children under 10 years of age were operated on with a Björk-Shiley disc valve. The mitral valve was replaced in four patients and the tricuspid valve in one. No hospital death, late death or thromboembolic episode was observed during the 155 patient-months of the follow-up. Moreover, a marked reduction in cardiomegaly was demonstrated to parallel the clinical improvement and low risk seen in adults. We feel that our experience might justify a more aggressive approach in the management of valvular disease in children of the younger age group.

Child↗
PubMed1976

Total rupture of the left main bronchus successfully repaired nine years after injury.

A patient who sustained a traumatic rupture of the left main bronchus that was successfully repaired nine years later is presented, and reference is made to reports of similar instances in which operation has been performed more than five years after injury. Pulmonary function following operation improved progressively and proved the delayed repair to have been a reasonable decision.

Adult↗
PubMed1975

The development of microbodies (glyoxysomes and leaf peroxisomes) in cotyledons of germinating watermelon seedlings.

The ontogeny of glyoxysomes and leaf peroxisomes has been examined in the cotyledons of germinating watermelon (Citrullus vulgaris) seedlings. Organelles from the cotyledons were extracted by razor blade homogenization and microbodies were separated by sucrose density gradient fractionation. Both kinds of microbodies have the same mean equilibrium density on sucrose gradients.The development of leaf peroxisomes was examined in seedlings transferred to light at 4 days and 10 to 12 days. In seedlings maintained in darkness to the age of 10 to 12 days, glyoxysomal enzymes virtually disappeared, and the losses were paralleled by a corresponding loss in microbody protein. During this period peroxisomal activity was low and changed only slightly. On transfer to light at this stage, the activity of peroxisomal enzymes rose strikingly. The residual glyoxysomal activity disappeared completely, and the developmental pattern of microbody catalase and microbody protein paralleled the light-induced glyoxysomal disappearance.Similar patterns of microbody development were observed when 4-day-old dark-grown seedlings with maximum glyoxysomal activities were exposed to light. The activity of the peroxisomal enzymes increased and the glyoxysomal enzymes disappeared at a faster rate than in darkness. These changes were again paralleled by the accelerated demise of microbody catalase and microbody protein. Thus under both conditions glyoxysomes were selectively destroyed during peroxisomal development, and the amount of peroxisomes produced was insufficient to offset the loss of glyoxysomal protein. The results do not support the contention that glyoxysomes are transformed to leaf peroxisomes in developing cucurbit cotyledons and favor the view that the two kinds of microbody arise independently of each other.

Journal Article↗
PubMed1973

Endoplasmic reticulum as the site of lecithin formation in castor bean endosperm.

The properties of a discrete membranous fraction isolated on sucrose gradients from castor bean endosperm have been examined. This fraction was previously shown to be the exclusive site of phosphorylcholine-glyceride transferase. The distribution of NADPH-cytochrome c reductase and antimycin insensitive NADH-cytochrome c reductase across the gradient followed closely that of the phosphorylcholine-glyceride transferase. This fraction also had NADH diaphorase activity and contained cytochromes b(5) and P 450. On sucrose gradients containing 1 mM EDTA this fraction had a mean isopycnic density of 1.12 g/cm(3) and sedimented separately from the ribosomes; electron micrographs showed that it was comprised of smooth membranes. When magnesium was included in the gradients to prevent the dissociation of membrane-bound ribosomes, the isopycnic density of the membrane fraction with its associated enzymes was increased to 1.16 g/cm(3) and under these conditions the electron micrographs showed that the membranes had the typical appearance of rough endoplasmic reticulum. Together these data show that the endoplasmic reticulum is the exclusive site of lecithin formation in the castor bean endosperm and establish a central role for this cytoplasmic component in the biogenesis of cell membranes.

Cell Fractionation↗
PubMed1973

The origin and turnover of organelle membranes in castor bean endosperm.

The origin and turnover of organelle membranes in castor bean (Ricinus communis L. var. Hale) endosperm was examined using choline-(14)C as a phospholipid precursor. On sucrose gradients three major particulate fractions were separated; a light membranous fraction (density 1.11-1.13 gram per cm(3)), the mitochondria (1.18 gram per cm(3)), and the glyoxysomes (1.24 gram per cm(3)). Choline-(14)C was readily incorporated into lecithin in all three particulate fractions, but the light membranous fraction became labeled first. Incorporation continued into all three fractions for 6 hours, at which time the available choline-(14)C had been completely used. Subsequently, (14)C was lost from the three components at distinctly different rates. When an excess of unlabeled choline was added after 1 hour (pulse-chase experiment), incorporation of choline-(14)C into glyoxysomes and mitochondria continued for three hours, but at a diminishing rate. This was followed by a period in which the (14)C content of the mitochondria declined at a rate expected, if the half life of lecithin in the membrane were about 50 hours and that of the glyoxysomes 10 hours. These values are close to those calculated from the experiments in which no chase was used. The labeling in the light membrane fraction behaved differently from that of the mitochondria and glyoxysomes following the chase of unlabeled choline. Incorporation continued for only 1 additional hour, and then the (14)C content declined sharply in the subsequent 4 hours. The early kinetics and subsequent interrelationships are those expected if the lecithin in the membranes of mitochondria and glyoxysomes originates in components of the light membrane fraction.

Journal Article↗
PubMed1973

Development of enzymes in the cotyledons of watermelon seedlings.

Changes in hypocotyl length, cotyledon weight, lipid content, chlorophyll content, and capacity for photosynthesis have been described in seedlings of Citrullus vulgaris, Schrad. (watermelon) growing at 30 C under various light treatments. Corresponding changes in the levels of 19 enzymes in the cotyledons are described, with particular emphasis on enzymes of microbodies, since during normal greening, enzymes of the glyoxysomes are lost and those of leaf peroxisomes appear. In complete darkness enzymes of the glyoxysomes reach a peak at 4 days and decline as the fat is depleted. Enzymes of mitochondria and of glycolytic pathways also peak at 4 to 5 days and either remain unchanged or decline to a lesser extent. Exposure to light at 4 days, when the cotyledons emerge, results in a selectively greater destruction of enzymes of the glyoxylate cycle; chlorophyll synthesis and capacity for photosynthesis increase in parallel, and there is a striking increase in the activities of chloroplast enzymes and in those of the leaf peroxisomes, hydroxypyruvate reductase and glycolate oxidase. The reciprocal changes in enzymes of the glyoxysomes and of leaf peroxisomes can be temporally dissociated, since even after 10 days in darkness, when malate synthetase and isocitrate lyase have reached very low levels, hydroxypyruvate reductase and glycolate oxidase increase strikingly on exposure to light and the cotyledons become photosynthetic. Furthermore, the parallel development of enzymes of leaf peroxisomes and functional chloroplasts is not immutable, since hydroxypyruvate reductase and glycolate oxidase activity can be elicited in darkness following a 5-minute exposure to light at day 4 while chlorophyll does not develop under these conditions.

Journal Article↗