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D Sasaki

Publications and source records attributed to D Sasaki.

46 records · Page 3Linked to original sources
PubMed1980

Intracellular processing of procollagen induced by the action of colchicine.

Corium fragments incubated in vitro with colchicine or obtained from chick embryos 11 days old after in vivo injection of this alkaloid were studied with the electron microscope. The well known effect of colchicine in producing an accumulation of procollagen was demonstrated by electrophoretic separation of the collagenous products in polyacrylamide gels after incubation of corium fragments in vitro with labelled amino acids. Electron microscopical studies showed various types of cytoplasmic vacuoles containing collagenous fibrillar structures. Some of these vacuoles contained non-striated filaments, fibres with the periodicity of native collagen, and segment long spacing (SLS) crystallites, embedded in an electrondense substance. The central aspect of this communication is the finding of intracellular SLS in cytoplasmic vacuoles. These crystallites were morphologically intact, and had no additional bands at the NH2 or COOH ends, suggesting that they were formed by the aggregation of tropocollagen molecules. Since the presence of intact SLS in cytoplasmic vacuoles suggests that these are secretory, we believe that inhibition of the transcellular transport system by colchicine permitted the visualization of vacuoles containing the products of tropocollagen interconversions. We interpret these findings as an example of autophagocytosis, with intracellular processing of procollagen, occurring in chick embryo fibroblasts when the secretion of procollagen is inhibited by colchicine.

Animals↗
PubMed1979

Effect of dithiothreitol of the reaction of renin and angiotensinogen.

Effects of several sulfhydryl reagents on the reaction of renin and angiotensinogen were investigated by measuring the production of angiotensin I. Renin and angiotensinogen were prepared from the kidneys of dogs and from plasma of nephrectomized dogs, respectively. The amount of angiotensin I generated was increased with application of dithiothreitol, dithioerythritol and 2,3-mercapto-1-propanol. The greatest enhancement of the generation of angiotensin I was observed with dithiothreitol. Dithiothreitol had no influence on renin activity, on radioimmunoassay for angiotensin I and the recovery of synthetic angiotensin I from the incubation medium. When heterologous angiotensinogen was used, a great enhancement of generation of angiotensin I was observed. Dithiothreitol did not accelerate the reaction following replacement of the natural substrate, angiotensinogen, with the synthetic tetradecapeptide as substrate. It is postulated that dithiothreitol augments angiotensin I generation by acting on the angiotensinogen and not on the renin.

Angiotensinogen↗