Did God make RNA?
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Biomedical subjects
Publications and source records attributed to C De Duve.
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Purified rat liver peroxisomes contain a cyanide-insensitive fatty acyl-CoA oxidizing system that uses O2 and NAD as electron acceptors. The system was detected by the ability of added palmitoyl-CoA to elicit O2 consumption, H2O2 production, and O2-dependent NAD reduction. The activity of this system is increased approximately one order of magnitude in rats treated with clofibrate, a hypolipidemic drug known to cause peroxisomal proliferation.
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Smooth muscle cells were dissociated from normal rabbit aorta by incubating the tissue in Hanks' solution containing elastase, collagenase, and hyaluronidase. The isolated cells contained significant amounts of the following acid hydrolases: N-acetyl-beta-glucosaminidase, N-acetyl-beta-galactosaminidase, beta-galactosidase, beta-glucuronidase, alpha-mannosidase, beta-glucosidase, acid phosphatase, and cathepsins C and D. The cells were disrupted and fractionated by isopycnic centrifugation on sucrose density gradients in the Beaufay automatic zonal rotor. Lysosomes with a modal density of 1.16 were identified by the distribution of these acid hydrolases and by the latency of N-acetyl-beta-glucosaminidase and beta-galactosidase. Other particulate enzymes studied in these sucrose gradients included cytochrome oxidase and monoamine oxidase (mitochondria), 5'-nucleotidase and leucyl-beta-naphthylamidase (plasma membrane), and catalase (? peroxisome). This microanalytical subcellular fractionation technique is applicable to the study of milligram quantities of many other tissues, both normal and pathological.
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Lactoferrin has been identified in rabbit heterophil leukocytes on the basis of its immunological reactivity, electrophoretic mobility, acid-resistant iron-binding properties, and spectral characteristics. Leukocyte lactoferrin was found to be exclusively localized in the specific (secondary) granules, which have been resolved from other subcellular components by zonal differential centrifugation and by isopycnic equilibration.
Rat liver peroxisomes have been separated according to size by zonal sedimentation. A method is described for calculating the size of the particles from their final position in the gradient. Peroxisomes seem biochemically homogeneous throughout their size distribution. 3 hr after injection of tritiated leucine, the specific radioactivity of catalase is the same in peroxisomes of different sizes, and it remains so for up to 1 wk after administration of the precursor. This observation rules out the possibility that peroxisomes have an extended period of independent growth. If individual particles maintain an independent existence, they must be formed very rapidly. The other possible explanation is that peroxisomes exchange material within the liver cell.
Fractionation of rabbit heterophil leukocyte homogenates by isopycnic centrifugation as well as by zonal sedimentation has helped to characterize further the particulate components of these cells. Four classes have been identified: (A) Large (0.5-0.8 microm) and dense (1.26) azurophil or primary granules, containing all the myeloperoxidase, one-third of the lysozyme, and a major proportion of the lysosomal acid hydrolase activities of the cells. (B) Smaller (0.25-0.40 microm) and less dense (1.23) specific or secondary granules, containing 90% of the alkaline phosphatase and the remainder of the lysozyme activities, but very little if any acid hydrolases. (C) Particles of low density (1.20), containing the remainder of the lysosomal acid hydrolases. This fraction was heterogeneous, but showed abundant small rod- or dumbbell-shaped particles of moderate electron opacity, surrounded by a single membrane (tertiary granules?). The possible origin of these lysosomes from contaminating macrophages could not be ruled out but appeared unlikely. (D) Slowly sedimenting material of very low density (1.14), made up of large, empty vesicular membrane structures, and containing 10% of the alkaline phosphatase, and all of a thiol-dependent acid p-nitrophenyl phosphatase, an enzyme clearly different from the lysosomal acid phosphatase.
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