Learn More
Activation of the Ca2+/Mg2+ ATPase associated with highly purified Torpedo synaptic vesicles results in 45Ca2+ uptake. The accumulated 45Ca2+ is released by hypoosmotic buffer and by the Ca2+ ionophore A23187. Density-gradient centrifugation and permeation chromatography reveal that vesicular acetylcholine and the membrane-bound 45Ca2+ co-migrate, thus(More)
Dark-grownEuglena cells were exposed to light at both their late stationary phase of growth (“old cells”), and at their late exponential phase (“young cells”). Chlorophyll accumulation was faster and photosynthetic oxygen evolution was detected earlier in the “young” cells. Photosystem I activity was measured at early stages of greening in both “young” and(More)
A procedure for the separation of proplastids free of mitochondria from dark-grown Euglena cells has been developed. A fraction enriched in proplastids was used for freeze-etching study of proplastid structure. The prolamellar body in freeze-etched replicas appeared sponge-like, with thylakoids, often vesicular, emerging from it. The prolamellar body and(More)
Dark-grownEuglena cells were exposed to light for 0, 6, 12, 24 and 48 hours. At each of these periods samples were taken for chlorophyll determination, measurements of O2 evolution and thin sectioning. For freeze-etching studies, plastids at the various developmental stages were separated on Urografin gradients. The prolamellar body (PLB) in proplastids of(More)
The human colon adenocarcinoma cell line HT29 displays an undifferentiated phenotype under standard growth conditions. When these cells were cultured for 21 days and then treated with forskolin, most of the cells formed brush borders on their apical surfaces. Brush border formation was inhibited by cytochalasin D but not by colchicine. Colchicine,(More)
The human colon adenocarcinoma cell line HT 29 grows in DMEM virtually without tight junctions (TJ). Fascia occludens type TJ can be induced in these cells by treatment with a variety of proteases or with hypertonic ammonium sulfate solution. The induced formation of TJ is not affected by pretreatment of the cells with cycloheximide or puromycin. The(More)
Retina tissue from 6-day chick embryos was organ-cultured for 3 days in the presence of antibodies to R-cognin, a surface antigen of retina cells. The antibodies which are known to bind to this antigen caused a striking malformation: interruption of the outer limiting membrane and extensive cell disorganization resulting in exteriorization of many cells and(More)
The non-polar human adenocarcinoma cells (HT29) when grown as monolayers or aggregates, have no tight junctions and no brush border. When these cells are treated with forskolin (15-100 microM) or cholera toxin (1 nM) intercellular lumina appear between the cells and about 30% of the cells facing the medium or the lumina are fully covered with a brush(More)