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Biomedical subjects

R C Carroll

Publications and source records attributed to R C Carroll.

64 records · Page 4Linked to original sources
PubMed1980

Phosphorus nuclear magnetic resonance of bovine platelets.

31P nuclear magnetic resonance (NMR) spectra of bovine platelets at 28 degrees C display prominent peaks from adenine nucleotides in two different environments, the metabolic and storage pools. Addition of 20 mM 2-deoxy-D-glucose and 0.1 mM 2,4-dinitrophenol depletes metabolic ATP, resulting in loss of nucleotide signals at 5, 10, and 19 ppm and leaving peaks at 6.5, 10.5, and 19 ppm that are assigned primarily to the dense granule storage pool. The ATP/ADP concentration ratio of the remaining pools is 1.9 +/- 0.2, with chemical shifts which reflect a more acidic environment for the intragranular nucleotides than for the cytosol. Isolated bovine dense granules give spectra with similar peak positions to those ascribed to the storage pool after metabolic depletion of whole cells. Storage pool nucleotide spectra are highly temperature dependent. Below 20 degrees C, the beta-ATP peak broadens and decreases in area to the point that it is almost undetectable at 0 degrees C, probably reflecting formation of progressively higher molecular weight aggregates at the lower temperatures. The release reaction was followed by 31P NMR after addition of thrombin at 28 degrees C. Spectra of the cell suspension taken at 5-min intervals were compared to spectra of perchloric acid extracts produced in parallel. A new finding of these experiments is that the released nucleotides rapidly undergo a transition to a "NMR silent" form as part of the bovine platelet release reacton. Metabolic breadkdown and external paramagnetic ion interactions did not explain the loss of signal from the storage pool. During release reaction, the nucleotides may be broadened out beyond detection due to immobilization by divalent cation and/or platelet membrane binding.

Adenine Nucleotides↗
PubMed1978

Reversion of transformed glycolysis to normal by inhibition of protein synthesis in rat kidney cells infected with temperature-sensitive mutant of Rous sarcoma virus.

Normal rat kidney cells infected with a temperature-sensitive mutant (LA23) of Rous sarcoma virus exhibit the transformed phenotype when grown at 33 degrees and the normal phenotype at 39 degrees. We have previously shown [Ash, J.F., Vogt, P.K. & Singer, S.J. (1976) Proc. Natl. Acad. Sci. USA 73, 3603-3607] that the addition of protein synthesis inhibitors to LA23-infected cells grown at 33 degrees causes them to revert, over a period of 12 hr, to the normal phenotype with respect to morphological and cytoskeletal characteristics. We now show that reversion of the metabolic characteristics of the transformed phenotype to those of the normal also occurs under these conditions. LA23-infected cells show an increased rate of aerobic glycolysis at 33 degrees compared to that at 39 degrees. They also show a different sensitivity of that rate to dinitrophenol and oligomycin at 33 degrees compared to 39 degrees. Such cells grown at 33 degrees in the presence of cycloheximide or abrin rapidly recover the aerobic glycolysis characteristics of the normal phenotype. These results support the thesis that transformation by the src gene of the Rous sarcoma virus is a pleiotypic and reversible process, such as is involved in a pleiotypic enzymic modification reaction and its reversal.

Aerobiosis↗
PubMed1976

Identification and transmembranous localization of active cytochrome oxidase in reconstituted membranes of purified phospholipids by electron microscopy.

Cytochrome oxidase vesicles with high oxidase activity and respiratory control ratio (greater than 3.5) were characterized by the freeze-etch technique for electron microscopy. By the use of this technique, cytochrome oxidase is shown to be an inner membrane particle. By locating cross-fractured vesicles in the same preparation, cytochrome oxidase particles are shown to extend across the phospholipid bilayer membranes. When cytochrome oxidase is added to preformed liposomes respiratory control is not observed, but high oxidase activity is maintained. In this preparation the cytochrome oxidase particles are located on the outer vesicle membrane surface. These observations provide direct evidence that cytochrome oxidase is found in a transmembranous position in closed, activecytochrome oxidase vesicles having respiratory control.

Electron Transport Complex IV↗
PubMed1975

Arrangement of the subunits in solubilized and membrane-bound cytochrome c oxidase from bovine heart.

The arrangement of the six cytochrome c oxidase subunits in the inner membrane of bovine heart mitochondria was investigated. The experiments were carried out in three steps. In the first step, exposed subunits were coupled to the membrane-impermeant reagent p-diazonium benzene [32S]sulfonate. In the second step, the membranes were lysed with cholate anc cytochrome c oxidase was isolated by immunoprecipitation. In the third step, the six cytochrome c oxidase subunits were separated from each other by dodecyl sulfate-acrylamide gel electrophoresis and scanned for radioactivity. Exposed subunits on the outer side of the mitochondrial inner membrane were identified by labeling intact mitochondria. Exposed subunits on the matrix side of the inner membrane were identified by labeling sonically prepared submitochondrial particles in which the matrix side of the inner membrane is exposed to the suspending medium. Since sonic irradiation leads to a rearrangement of cytochrome c oxidase in a large fraction of the resulting submitochondrial particles, an immunochemical procedure was developed for isolating particles with a low content of displaced cytochrome c oxidase. With mitochondria, subunits II, V, and VI were labeled, whereas in purified submitochondrial particles most of the label was in subunit III. The arrangement of cytochrome c oxidase in the mitochondrial inner membrane is thus transmembraneous and asymmetric; subunits II, V, and VI are situated on the outer side, subunit III is situated on the matrix side, and subunits I and IV are buried in the interior of the membrane. In a study of purified cytochrome c oxidase labeled with p-diazonium benzene [32S]sulfonate, the results were similar to those obtained with the membrane-bound enzyme. Subunits I and IV were inaccessible to the reagent, whereas the other four subunits were accessible. In contrast, all six subunits became labeled if the enzyme was dissociated with dodecyl sulfate before being exposed to the labeling reagent.

Animals↗