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M Castañeda

Publications and source records attributed to M Castañeda.

At least 37 records · Page 2Linked to original sources
PubMed1983

Age-dependent decrease in the activity of protein-synthesis initiation factors in rat brain.

The age-dependent reduction of brain protein synthesis was examined at the initiation step of translation in the rat. Activity of brain initiation factor 2, as well as that of other eukaryotic initiation factors that contribute to the binding of initiator aminoacyl-tRNA to ribosomes, was found to decrease with age and to decline parallel to the decrease in total protein synthesis and brain elongation factor 1 activity. Change in the activity of initiation factors was demonstrated by the results of two different assays which compared favorably with each other. Decreased activity of preparations of initiation factors derived from older animals was observed in: (1) saturating conditions; (2) mixtures of preparations from different ages; and (3) both major cell fractions, i.e. cell sap and microsomes.

Age Factors↗
PubMed1983

Small-size ribosomal RNA species in Trypanosoma cruzi.

Trypanosoma cruzi ribosomal RNA was analyzed electrophoresis. On agarose gels, where both large- and small-size species are grossly fractionable, it revealed two bands in the small-size region. These were similar in size to the mammalian 5.8 S and 5 S species. Increased resolution, however, showed these two bands to be composite. The pseudo 5.8 S band contained three, and the pseudo 5 S two, discretely sized molecules. The ribosomal binding of four of these five novel species is apparently dependent on large ribosomal subunit proteins. One species is hydrogen bonded to the beta species of 24 S ribosomal RNA. The five species were estimated to be 261, 217, 197, 141 and 110 nucleotides long.

Animals↗
PubMed1983

An endonuclease restriction analysis of the ribosomal RNA genes of Trypanosoma cruzi.

The location of ribosomal RNA genes in total-nuclear-enriched DNA preparations of Trypanosoma cruzi was analyzed by using restriction endonucleases and the eight cytoplasmic ribosomal RNA species of this organism. Two contiguous SstI DNA fragments of about 9.88 and 1.7 kilobase pairs contained the three large-size ribosomal RNA species, 18 S, beta, and alpha, and three small-size ribosomal RNA species, s1, s2 and s3. The other two small-size ribosomal species, s4 and s5, were located outside the ribosomal RNA cistron and independently of each other. Spacers of a presumed large length, about 20 kilobase pairs or more, hampered the identification of putative adjacent ribosomal RNA cistrons.

Animals↗
PubMed1981

Genome organization and ploidy number in Trypanosoma cruzi.

Trypanosoma cruzi total DNA was analyzed by DNA:DNA reassociation kinetics. The nonlinear least-squares computer solution could reasonably be fitted to three second-order kinetic components. The highly repetitive, middle repetitive, and single copy components comprised 9, 35 and 49% of the genome, respectively. The single copy sequences showed a kinetic complexity of approximately 4 times that of Escherichia coli and of some 11,000 average-sized structural genes. The repetitive sequences (about 6900) presented the long-period pattern of interspersion with a modal length of 7800 bases. The kinetic complexity of total DNA was compatible with a value of at least a diploid genome per cell.

Animals↗
PubMed1981

Trypanosoma cruzi ribosomal RNA: internal break in the large-molecular-mass species and number of genes.

The large-molecular-mass ribosomal ribonucleic acid from Trypanosoma cruzi probably contains an internal break. The molecule can be obtained in its intact form or in its two fragments depending on the denaturing agents used for its purification and/or display. This break appears to be an in vivo late processing step rather than a random nucleolytic cleavage during in vitro manipulations. Calculations of mass, from gel electrophoretograms, for the large and small main ribosomal ribonucleic acid species and for the two chains derived from the large species gave values of 1.37, 0.84, 0.70 and 0.57 X 10(6) daltons, respectively. Sedimentation velocity measurements in sucrose gradients and in the analytical ultracentrifuge indicated sedimentation coefficients of 24 and 18 S for the large and small main species, respectively. Saturation hybridization curves showed that the nuclear genome, quantified by chemical analysis, contains about 114 ribosomal ribonucleic acid gene copies.

Animals↗
PubMed1981

Role of elongation factor 1 in the translational control of rodent brain protein synthesis.

The translational control of protein synthesis during early postnatal neural development and aging was examined in the mouse and the rat. The activity of brain elongation factor 1 (bEF-1) was found to decrease exponentially with age and to decline parallel to the age-dependent decrease in total protein synthesis in both rodents. This decrement in bEF-1 activity fell within the range of reported age-related decreases in protein synthesis in in vitro systems. The factor was present in multiple forms; the lighter species predominated in older animals, whereas the young light form apparently disappeared with increasing age, and was replaced by other arising from the heavy form. Elongation factor 1 derived from young brains functioned as a rate-limiting component in polypeptide synthesis in previously saturated adult systems. The data suggest that bEF-1 has an important modulatory effect on total brain protein synthesis.

Aging↗
PubMed1980

Subunit structure of Trypanosoma cruzi chromatin.

Chromatin of Trypanosoma cruzi epimastigotes was found to be arranged in a subunit structure by the demonstration of (i) nu-bodies, (ii) monomeric and oligomeric DNA fragments, and (iii) four basic nuclear proteins which presumably correspond to the intrinsic protein component of nucleosomes. A discrete core fragment of 140 base pairs and a basic nuclear protein fraction clearly similar to most histones H1 were not detected. In contrast with vertebrate material, the nuclear preparations were physically and enzymatically fragile, the basic proteins showed different mobilities in electrophoresis, but the DNA repeat length was similar. The data are discussed in relation to histone regional charge, histone content, and chromatin condensation.

Animals↗
PubMedDate not supplied

[Consequences of heroin consumption: compartmental syndrome and rhabdomyolysis].

Compartment syndrome is a condition in which increased pressure within a limited space compromises tissue perfusion with the development of rhabdomyolysis. The causes can be physical, such as the pressure exerted on an anatomical region, or it can be associated with the consumption of illegal drugs, especially heroin. In this latter case, toxic and immunological mechanisms are involved in the physiopathology. Acute renal failure develops in 30% of cases of rhabdomyolysis. Its treatment includes efficient volume replacement, forcing urinary alkalinization and the administering of furosemide and mannitol, with certain precautions. No benefit has been shown in dopamine. When a heroin addict patient shows a clinical pattern of tumescence of his extremities, with or without a period of unconsciousness, the presence of compartment syndrome is to be suspected.

Acute Kidney Injury↗