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Biomedical subjects

F Ramirez

Publications and source records attributed to F Ramirez.

At least 181 records · Page 10Linked to original sources
PubMed1982

Effects of hemodialysis and dimercaprol in acute dichromate poisoning.

A 22-month-old infant died after ingesting sodium dichromate his father had brought from work. Treatment included folic acid and dimercaprol administration, hemodialysis, and exchange transfusion. To evaluate this treatment, four dogs were hemodialyzed after receiving intravenous sodium dichromate: their dialyzer chromate clearance was similar to their renal chromate clearance and their dialyzer chromate clearance was not significantly different before or after dimercaprol administration. This and other cases in the literature indicate that although chromate poisoning is often fatal, supportive care, forced diuresis, and chelating agents may be helpful. Hemodialysis may be required if renal failure occurs. Awareness of toxicity and prevention remain the most important approaches.

Acute Disease↗
PubMed1982

Antenatal diagnosis of sickle cell disease: amniotic fluid cell DNA analysis.

Using recombinant DNA methods and amniocentesis, the antenatal diagnosis of sickle cell disorders can be accomplished. This article presents the authors' experiences with 21 pregnancies at risk using HpaI and Hind III restriction enzyme digestions of adult leukocytic and fetal amniotic fluid cell DNA. The authors were able to establish direct beta A- and beta S-globin gene linkages to the restricted fragments in 9 families. In 8 families no direct linkages could be determined and estimates of exclusion of fetal beta S homozygosity were used. These estimates were made on the basis of the frequencies of association of the HpaI fragments with the beta S and beta A genes in the Afro-American population. In 4 families, no estimates or linkages could be established, and the patients were counseled in reference to fetoscopy. The data also indicated the frequencies of association of the HpaI fragments with the beta A and beta S gene in the New Jersey-New York population. These studies did not seem to indicate any exclusive preferential segregation of the HpaI and Hind III polymorphisms.

Amniotic Fluid↗
PubMed1982

Assignment of the human pro alpha 2(I) collagen structural gene (COLIA2) to chromosome 7 by molecular hybridization.

A cDNA for the pro alpha 2 chain of human type I collagen has been recently cloned and amplified. We have used this specific probe to identify the human chromosome carrying the pro alpha 2(I) collagen gene. The DNA from 17 independent human/hamster and human/mouse somatic cell hybrids was digested by Eco RI and the restriction pattern analyzed in Southern blot experiments, using the 32P-labeled cDNA as a hybridization probe. The gene coding for the pro alpha 2 collagen subunit could be unambiguously assigned to human chromosome 7. All the other chromosomes, including chromosome 17, were excluded.

Animals↗
PubMed1982

Focal segmental glomerulosclerosis, crescent, and rapidly progressive renal failure.

The usual clinical course of focal segmental glomerulosclerosis is marked by progressive decrease in renal functional and sclerosis on biopsy over a period of months to years. We report a variant exemplified by 2 children who developed chronic renal failure within 12 weeks of the onset of nephrotic syndrome; repeat renal biopsies demonstrated extensive extracapillary glomerular proliferation and crescent formation. Both were males, less than 5 years of age, presenting with nephrotic syndrome resistant to steroid therapy and normal renal function. Renal biopsies done after 8 weeks of therapy, demonstrated findings compatible with focal segmental glomerulosclerosis. Within 12 weeks of onset of nephrotic syndrome, both patients experienced a decrease in renal function requiring dialysis. Repeat renal biopsies revealed extensive extracapillary glomerular proliferation with crescent formation. These patients represent a variant of focal segmental glomerulosclerosis characterized by rapid progression to renal failure with extensive extracapillary glomerular proliferation and crescent formation.

Biopsy↗
PubMed1981

Cloning a cDNA for the pro-alpha 2 chain of human type I collagen.

Poly(A)-RNA enriched for type I procollagen sequences was isolated from normal human fibroblasts and used as template to synthesize double-stranded cDNA with avian myeloblastosis virus (AMV) reverse transcriptase. After the ends had been blunted with nuclease S1 and dGMP tails had been added with terminal deoxynucleotidyltransferase, the double-stranded cDNA was annealed with pBR322 DNA that had previously been cleaved with EcoRI, blunted with AMV reverse transcriptase, and dCMP-tailed with terminal deoxynucleotidyltransferase. The chimeric molecule was used to transform Escherichia coli strain HB101. Ninety-five recombinant clones were obtained and screened by dot hybridization analysis using 32P-labeled cDNA synthesized from the original poly(A)-RNA collagen-enriched population. Three positive clones were isolated and further characterized by blot hybridization techniques and by EcoRII digestion. One clone with an insert of 2.2 kilobases was shown to contain sequences encoding for the pro-alpha 2 chain of human type I procollagen. DNA sequence analysis of a 172-nucleotide fragment demonstrated that the cloned cDNA extends from amino acid position 450 of the alpha 2 chain to the middle of the COOH-terminal propeptide.

Base Sequence↗
PubMed1981

A nucleotide change at a splice junction in the human beta-globin gene is associated with beta 0-thalassemia.

beta 0-Thalassemia is a heterogeneous group of disorders associated with absence of beta-globin. In a survey of DNAs from patients with beta 0-thalassemia of diverse ethnic origins, a change at the splice junction at the 5' end of the large intervening sequence (IVS 2) of the human beta-globin gene has been found in one patient of Italian and another two of Iranian ethnic origins. The enzyme Hph I recognizes a change at this site and generates a large-than-normal fragment of DNA, which hybridizes specifically to a beta-globin IVS 2 probe. No other changes in beta-globin gene DNA structure or organization are detectable by extensive restriction endonuclease analysis. The enzyme HinfI which recognizes a sequence beginning three nucleotides from the 5' end of the IVS 2 splice junction, produces normal fragments and localizes the defect to a G-G-T sequence at the 5'-end IVS 2 splice junction. This sequence is known to be remarkably conserved in all globin genes from many species and in most other genes examined to date. Thus, in at least some beta 0-thalassemia patients, the beta 0-thalassemia defect is associated with a nucleotide change at a splice junction. These patients provide unique examples of naturally occurring defects in splice junctions of eukaryotic genes associated with absence of specific gene function.

Base Sequence↗
PubMed1981

Inhibition of the links between electron transfer and proton translocation in mitochondria.

The mechanism by which proton extrusion is linked to electron transfer in mitochondria was investigated by means of the primary amine-specific reagent fluorescamine, and of compounds obtained from the reaction of fluorescamine with simple amines (e.g. benzylamine) and with the mycosamine-containing antibiotic amphotericin B. The effect of these 'modifiers' (i.e. fluorescamine transfer chain were assayed separately using specific inhibitors to block the action associated with the other site. Both types of modifiers inhibited the proton extrusion across the membrane to a significantly greater extent than the electron transfer process in both sites II and III. In contrast, the lactone derivative (or cyclic form) of the amine-fluorescamine compounds had no significant inhibitory effect on the proton extrusion and its associated electron transfer. These results are consistent with the hypothesis that the link between proton extrusion and electron transfer in mitochondria is indirect in nature. The results show that: (a) the links involved in sites II and III are identical or very similar in nature; (b) a covalent modification of primary amino groups in the inner membrane is not essential for the expression of these differential inhibitory effects; (c) specific structural features in the amine-fluorescamine compounds, and in the mitochondria-fluorescamine derivatives, are crucial for the expression of the inhibitory effects. Our results contradict the 'redox loop' model of Mitchell, and are compatible with the proton pump concept for the linked proton translocation in oxidative phosphorylation.

Animals↗
PubMed1981

Isolation and characterization of cloned DNA: the delta and beta globin genes in homozygous beta + thalassemia.

We have isolated and characterized a clone of human DNA from a patient with beta+ thalassemia containing the entire delta and beta structural genes and their flanking sequences. Partial Eco RI digestion of spleen DNA was used to obtain 15 to 20 kilobase (kb) pieces of human DNA that were then ligated to charon 4A lambda phage DNA. The 8 x 10(5) recombinants obtained were grown and screened for their content of beta gene sequences. Four positive clones were found, and one (beta T1-1) has been extensively analyzed. Subclones containing the entire beta gene and the large beta intervening sequence (IVS 2) have been isolated in the plasmid pBR 322. The fragments generated by restriction enzyme digestion in these subclones have been compared to those in similar subclones from normal beta genes. No differences have been found indication no significant rearrangements of deletions of the delta and beta genes. With the enzymes used, 11.2% of IVS 2 have been compared, and thus far no differences between the thalassemic and normal genes have been detected. The 24 enzymes used include Hph I, which recognizes the 5' end of IVS 2, and AIu I that cleaves at the 3' end. Thus, there appears to be conservation of nucleotide sequences at the ends of IVS 2 in this beta + thalassemia patient, although RNA metabolism studies suggest a possible defect in RNA processing.

Adult↗
PubMed1980

The molecular basis of disorders of human hemoglobin synthesis.

The structure and organization of the human globin genes at the nucleotide level has been established by restriction endonuclease digestion of cellular DNA, and by the isolation and purification of these genes in phage vectors. With this approach it has been possible to define alterations at the DNA level resulting in a group of inherited diseases of man known as the thalassemia syndromes, and related disorders. Combined with other known genetic and biochemical data, these studies provide a framework for understanding the pathogenesis of these disorders at the molecular level.

Base Sequence↗
PubMed1980

Phosphatidylcholesterol bilayers. A model for phospholipid-cholesterol interaction.

Aqueous dispersions of monovalent and divalent cations salts of O-(1,2-dipalmitosyl-sn-glycero-3-phosphoryl)cholesterol form multilamellar vesicles as shown by freeze-fracture electron microscopy, by electron micrographs of the negatively stained liposomes, and by swelling curves of liposomes in hypo-osmotic medium. Differential scanning calorimetry reveals that aqueous dispersions of divalent metal salts of O-(1,2-dipalmitoyl-sn-glycero-3-phosphoryl)cholesterol undergo a characteristic thermotropic phase transition with a relatively large cooperative unit (n greater than 250 for the calcium salt). In contrast, monovalent cation salts of O-(1,2-dipalmitoyl-sn-glycero-3-phosphoryl)cholesterol do not show a thermotropic phase transition under comparable conditions. The molecular area of 0-(1,2-dipalmitoyl-sn-glycero-3-phosphoryl)cholesterol in a monolayer is the same in the presence and absence of Ca2+, and is virtually equal to the area of an equimolar mixture of dipalmitoyl phosphatidic acid and cholesterol. To account for the novel state induced by Ca2+, on aqueous dispersions of O-(1,2-dipalmitoyl-sn-glycero-3-phosphoryl)cholesterol (i.e., bilayer organization and highly cooperative phase transition), a linear array model is proposed in which Ca2+ bridges adjacent arrays of O-(1,2-dipalmitoyl-sn-glycero-3-phosphoryl)cholesterol molecules, thus freezing the acyl chains in their normal state. One of the main corollaries of the model is that the cooperative unit for a thermotropic phase transition is essentially one-dimensional, rather than a two-dimensional matrix. O-(1,2-Dipalmitoyl-sn-glycero-3-phosphoryl)cholesterol is proposed as an orientationally and conformationally restricted analog of glycerophospholipid plus cholesterol in bilayers.

Cholesterol↗
PubMed1980

Differential effects on energy transduction processes by fluorescamine derivatives in rat liver mitochondria.

Intact rat liver mitochondria were treated with compounds derived from the reaction of fluorescamine with various types of primary amines, including the mycosamine-containing antibiotics amphotericin B and nystatin. The effect of varying amounts of these compounds on ATPase-linked inorganic phosphate (Pi) formation on oxygen consumption, and on MgATP-linked and succinate-linked proton movements was examined. The antibiotic-fluorescamine compounds did not affect the Pi formation rate but strongly inhibited both the ATPase-linked and the succinate-linked H+ extrusion rates to approximately the same extent. The antibiotic derivatives decreased the oxygen consumption rate, but this effect was much smaller than the decrease in the respiration-dependent proton extrusion rate. The benzylamine-fluorescamine compound significantly increased the Pi formation rate, in contrast to the antibiotic analogues. The benzylamine derivative, like the antibiotic derivatives, inhibited both types of proton extrusion rates. The slight decrease in the oxygen consumption rate caused by the benzylamine derivative was significantly smaller than the corresponding decrease observed with the antibiotic derivatives. These studies, in which fluorescamine derivatives bind reversibly to mitochondria, are compared with previous studies in which fluorescamine itself binds irreversibly to mitochondria and results in a Pi formation rate increase and MgATP- and succinate-linked proton extrusion rate inhibition but has no effect on the oxygen consumption rate.

Adenosine Triphosphatases↗
PubMed1980

Association of lysophosphatidylcholine with fatty acids in aqueous phase to form bilayers.

Lysophospholipids have been implicated in a variety of physiological process. In vivo lysophospholipids are invariably produced with fatty acids as the product of hydrolysis by phospholipase A2 (ref. 2). Therefore, it is of considerable interest to examine the properties of the mixture of these lipids in aqueous suspensions. Results presented here demonstrate that a mixture of fatty acid and lysophosphatidylcholine forms a bilayer type of organisation even though the individual components form micelles when dispersed in an aqueous phase.

Chemical Phenomena↗
PubMed1980

Disorders of human hemoglobin.

Studies of the human hemoglobin system have provided new insights into the regulation of expression of a group of linked human genes, the gamma-delta-beta-globin gene complex in man. In particular, the thalassemia syndromes and related disorders of man are inherited anemias that provide mutations for the study of the regulation of globin gene expression. New methods, including restriction enzyme analysis and cloning of cellular DNA, have made it feasible to define more precisely the structure and organization of the globin genes in cellular DNA. Deletions of specific globin gene fragments have already been found in certain of these disorders and have been applied in prenatal diagnosis.

Chromosome Aberrations↗