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A C Vasconcelos

Publications and source records attributed to A C Vasconcelos.

28 records · Page 2Linked to original sources
PubMed1981

Euploidy in Ricinus: EUPLOIDY EFFECTS ON PHOTOSYNTHETIC ACTIVITY AND CONTENT OF CHLOROPHYLL-PROTEINS.

The effects of nuclear genome duplication on the chlorophyll-protein content and photochemical activity of chloroplasts, and photosynthetic rates in leaf tissue, have been evaluated in haploid, diploid, and tetraploid individuals of the castor bean, Ricinus communis L. Analysis of this euploid series revealed that both photosystem II (2,6-dichlorophenolindophenol reduction) and photosystem I oxygen uptake (N,N,N',N'-tetramethyl-p-phenylenediamine to methyl viologen) decrease in plastids isolated from cells with increasingly larger nuclear complement sizes. Photosynthetic O(2)-evolution and (14)CO(2)-fixation rates in leaf tissue from haploid, diploid, and tetraploid individuals were also found to decrease with the increase in size of the nuclear genome. Six chlorophyll-protein complexes, in addition to a zone of detergent complexed free pigment, were resolved from sodium dodecyl sulfate-solubilized thylakoid membranes from cells of all three ploidy levels. In addition to the P700-chlorophyll a-protein complex and the light-harvesting chlorophyll a/b-protein complex, four minor complexes were revealed, two containing only chlorophyll a and two containing both chlorophyll a and b. The relative distribution of chlorophyll among the resolved chlorophyll-protein complexes and free pigment was found to be similar for all three ploidy levels.

Journal Article↗
PubMed1981

Freeze-fracture architecture and polypeptide composition of thylakoid membranes from euploid Ricinus cells.

The freeze-fracture architecture and polypeptide composition of thylakoid membranes of euploid cells of Ricinus communis L. were examined. Electron microscopic examination of the chloroplasts of 1N 2N and 4N cells revealed little variation in the size of chloroplasts, lamellar structure and internal organization of plastids, despite increases in plastid numbers per cell observed to accompany the increase in nuclear ploidy. Thylakoid membranes from euploid cells were also similar in their freeze-fracture morphology. Two basic types of intramembranous particles were observed on the fracture faces of thylakoid membranes of euploid cells. The endoplasmic fracture (EF) face of experimentally unstacked thylakoid membranes of 1N, 2N and 4N cells contain 2 size categories of particles (115-121 A and 164-166 A), whereas the protoplasmic fracture (PF) face of these membranes contain a single size category of particles (85-88 A). The distribution and size of the EF- and PF-face particles were found to be similar among membranes from cells of the 3 ploidy levels. Analysis of the polypeptide composition of thylakoid membranes from 1N, 2N and 4N cells revealed no difference in the relative proportion of the constituent polypeptides of these membranes. The possible factors involved in the regulation of the development of thylakoid structure and composition in the presence of altered nuclear genome size are discussed.

Ricinus communis↗
PubMed1980

Euploidy in Ricinus. I. Euploidy and gene dosage effects on cellular proteins.

Investigations of an euploid series of castor bean, Ricinus communis L., Consisting of haploid, diploid, and tetraploid individuals, was performed to determine the value of such a series in studying the biochemical consequences of genome multiplication. The effects of euploidization of the nuclear genome on the biosynthesis of cellular proteins were examined. Extracts of total soluble proteins from 10-day-old leaves of all three ploidy levels examined by electrophoresis on polyacrylamide gels revealed no difference in the complement of proteins present; however, differences in intensity of several protein bands were detected. Analysis of esterases isozyme activity by isoelectric focusing revealed both increases and decreases in the activity levels of individual isozyme variants in responses to changes in ploidy levels. Results from this analysis are discussed in terms of possible regulatory mechanisms active in the regulation of duplicated genes.

DNA Replication↗
PubMed1976

Fractionation and Analysis of Polypeptides of Euglena gracilis Chloroplasts.

Intact Euglena gracilis chloroplasts, purified on gradients of silica sol, were lysed osmotically and fractionated by centrifugation on discontinuous gradients of sucrose into their soluble, envelope membrane, and thylakoid membrane components. The proteins of the different subchloroplast fractions, as well as those of whole chloroplasts, were analyzed by electrophoresis on sodium dodecyl sulfate polyacrylamide gels. The polypeptide profile of each fraction was distinctive and was in general similar to the profile obtained for analogous fractions of the chloroplasts of higher plants.The envelope membranes were separated into two fractions in the gradients according to their banding densities. Electron micrographs showed that the light envelope fraction consisted mostly of single-membrane vesicles, whereas the heavy envelope fraction consisted of multiple layers of folded membranes. Both envelope fractions were ultrastructurally distinct from the thylakoid membranes.

Journal Article↗
PubMed1976

Synthesis of Proteins by Isolated Euglena gracilis Chloroplasts.

Intact Euglena gracilis chloroplasts, which had been purified on gradients of silica sol, incorporated [(35)S]methionine or [(3)H]leucine into soluble and membrane-bound products, using light as the only source of energy. The chloroplasts were osmotically shocked, fractionated on discontinuous gradients of sucrose, and the products of protein synthesis of the different fractions characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The soluble fraction resolved into three zones of radioactivity, the major one corresponding to the large subunit or ribulose diphosphate carboxylase. The thylakoid membrane fraction contained nine labeled polypeptides, the two most prominent in the region of 31 and 42 kilodaltons. The envelope fraction contained a major radioactive peak of about 48 kilodaltons and four other minor peaks. The patterns of protein synthesis by isolated Euglena chloroplasts are broadly similar to those observed with chloroplasts of spinach and pea.

Journal Article↗
PubMed1975

Isolation of Intact Chloroplasts of Euglena gracilis by Isopycnic Sedimentation in Gradients of Silica.

A technique is described for the isolation of structurally intact and partially active chloroplasts from photoheterotrophically grown Euglena gracilis. The separation of intact chloroplasts from stripped chloroplast membranes and other subcellular particles was achieved by sedimentation in continuous, isosmotic density gradients of Ludox AM, a silica sol.The final preparations contained an average of 93% intact chloroplasts and corresponded to approximately 10% of the the chlorophyll of the original cell suspension and 20 to 30% of the chlorophyll layered on the gradients.The chloroplasts obtained were intact by the criteria of ultrastructure, their content of ribulose diphosphate carboxylase, and their activity in a modified Hill reaction assay (U. Heber and K. A. Santarius. 1970. Z. Naturforsch. 25b: 718-727). In addition, the isolated chloroplasts were capable of incorporating amino acids into protein in the light.

Journal Article↗
PubMedDate not supplied

[Reactivation of Trypanosoma cruzi infection in patients with acquired immunodeficiency syndrome].

A patient with AIDS and asymptomatic Chagas's disease and positive xenodiagnosis was taking ketoconazole in order to suppress parasitemia and prevent reactivation of Chagas's disease. Ketoconazole was unplanned suspended after 6 months, and the patient was admitted with fever, headache, vomiting, tachycardia, postural hypotension, hepatosplenomegaly, and positive xenodiagnosis one month later. Treatment with benzonidazole was begun leading to suppression of parasitemia. The patient had probability a neurotoxoplasmosis associated and progressed to coma and death with sepsis. No parasite was found in autopsy.

AIDS-Related Opportunistic Infections↗