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Biomedical subjects

J Ramírez

Publications and source records attributed to J Ramírez.

At least 19 recordsLinked to original sources
PubMed1995

Nucleotide sequence and chromosomal localization of the gene encoding the Old Yellow Enzyme from Kluyveromyces lactis.

A 6.6 kb genomic DNA fragment from the yeast Kluyveromyces lactis was isolated. Sequence analysis of this fragment revealed the presence of two incomplete open reading frames (ORFs) in one strand, one coding for the carboxyl terminus of the plasma membrane H(+)-ATPase and the other for the amino terminus of an unidentified product. In the complementary strand, a full-length ORF which encodes for a protein homologous to the yeast NADPH-dependent Old Yellow Enzyme was found. The deduced amino acid sequence of this ORF predicts a protein of 398 residues with 84% similarity in its full length to OYE1 from Saccharomyces carlsbergensis and OYE2 from Saccharomyces cerevisiae. In addition, an internal region showed considerable similarity to the bile acid-inducible polypeptide from Eubacterium sp., to the NADH oxidase from Thermoanaerobium brockii, to the trimethylamino dehydrogenase from bacterium W3A1 and to the estrogen-binding protein from Candida albicans, suggesting a functional or structural relationship between them. Inactivation of the KYE1 (Kluyveromyces Yellow Enzyme) gene by deletion of 0.6 kb fragment between positions +358 and +936 produced viable cells with a slight increase in their generation time. Haploid cells carrying the disrupted allele showed one-third of the NADPH oxidase activity, compared to wild-type cells. Southern blotting analysis of digested DNA and chromosomes separated by contour-clamped homogeneous electric field electrophoresis from K. lactis indicated that this is a single-copy gene and it is localized on chromosome II, whose molecular size has been estimated to be approximately 1.3 Mb.

Amino Acid Sequence↗
PubMed1995

Iron bioavailability from diets consumed by different socioeconomic strata of the Venezuelan population.

The iron bioavailability from three typical diets consumed by socioeconomic stratum IV (SES IV--working class) of the Venezuelan population was determined by the extrinsic label method. Although the iron content of the SES IV diets was about the same (250 mumol/d) as that of upper (SES I-III) and lower (SES V) socioeconomic strata diets, iron-replete subjects absorbed 43 and 61% more iron from the SES I-III diets than from the SES IV and V diets, respectively, and absorption from the main meal of the SES I-III diets was 100% greater. However, iron deficient subjects absorbed about the same amount of iron (45 mumol/d) from the SES IV diets as from the SES I-III diets. The SES I-III diets contained more iron absorption enhancers (ascorbic acid and meat protein) and less of the inhibitor phytate, than the SES IV and V diets. Iron absorption from the meals of four diets consumed at different times during the day was also measured. There was no significant difference in the percentage iron absorption from the same meals eaten in the morning after an overnight fast, and when eaten at the customary time of day.

Absorption↗
PubMed1995

A NADP-glutamate dehydrogenase mutant of the petit-negative yeast Kluyveromyces lactis uses the glutamine synthetase-glutamate synthase pathway for glutamate biosynthesis.

The activities of the enzymes involved in ammonium assimilation and glutamate biosynthesis were determined in wild-type and NADP-glutamate dehydrogenase (GDH) null mutant strains of Kluyveromyces lactis. The specific NADP-GDH activity from K. lactis was fivefold lower than that found in Saccharomyces cerevisiae. The glutamine synthetase (GS) and glutamate synthase (GOGAT) activities were similar to those reported in S. cerevisiae. The NADP-GDH null mutant was obtained by transforming the uraA strain MD2/1 with a linearized integrative yeast vector harbouring a 390 bp fragment of the NADP-GDH structural gene. This mutant grew as well as the parent strain on ammonium, but showed GS and GOGAT activities higher that those found in the wild-type strain, implying that the GS-GOGAT pathway could play a leading role in glutamate biosynthesis in K. lactis. Southern blotting analysis of K. lactis chromosomes separated by contour-clamped homogeneous electric field electrophoresis, indicated that the NADP-GDH structural gene is localized on chromosome VI.

Amino Acid Sequence↗
PubMed1991

An energy-dependent efflux system for potassium ions in yeast.

An efflux of potassium ions was demonstrated in mutants of yeast cells lacking a functional high affinity carrier system for monovalent cations. This efflux showed the following characteristics: (a) It was stimulated by the presence of a substrate, either glucose or ethanol. (b) It was stimulated by several cationic organic molecules, such as ethidium bromide, dihydrostreptomycin, diethylaminoethyldextran, and also by trivalent cations, such as Al3+ and lanthanides; this stimulation also depended on the presence of a substrate. (c) K+ efflux was decreased in yeast mutants with decreased ATPase activity, which generated a lower membrane potential. (d) Although the efflux appeared to be of an electrogenic nature, producing hyperpolarization of cells, it was accompanied by the efflux of phosphate, probably as an anion partially compensating for the large amount of cations leaving the cell. (e) K+ efflux was also accompanied by an uptake of protons. (f) The efflux appeared more clearly in cells grown in YPD medium, and not in more complex media nor in the same YPD medium if supplemented with Ca2+ or Mg2+. Efflux of monovalent cations produced by Tb3+ and organic cationic agents was also demonstrated in wild type strains. This efflux system appears to be, at least partially, electrogenic, but seems to be also an exchange system for protons and to function as a symport with phosphate; it may be involved in the regulation of the internal pH of the cell, and appears to be regulated by its link to the energetic status of the cell, probably through the membrane potential.

Calcium↗
PubMed1991

[Round atelectasis: infrequent cause of solitary pulmonary nodule].

Two cases of round atelectasis are reported. One had an asbestiform origin, with lingular localization and pathological confirmation. The other was located in the posterobasal segment of the left lower lobe, and it was presumably caused by pleural tuberculosis. In both patients the characteristic radiological findings were present, with an outstanding "comet's tail" sing. The outcome of both patients was satisfactory. Emphasis is made on the usefulness of noninvasive diagnostic investigations, such as conventional pulmonary and computed tomography (CT) of the torax, which, in conjunction with an adequate anamnesis, permit the correct diagnosis and may prevent surgical exploration.

Aged↗
PubMed1991

Calcium transport sensitive to ruthenium red in cytochrome oxidase vesicles reconstituted with mitochondrial proteins.

We describe a calcium transport that is sensitive to ruthenium red in liposomes reconstituted with mitochondrial extracts. This system is able to build an internally negative membrane potential, which allows the electrogenic influx of Ca2+ and Sr2+. Proteins with molecular weights higher than 35 kDa were incorporated to the vesicles, and enhanced the accumulation of the cation in an energy-dependent fashion.

Animals↗
PubMed1991

Liposomes as carriers for allergy immunotherapy.

With the aim of obtaining an efficient but safer vaccine for allergy immunotherapy, the possibility of using liposomes as adjuvants has been considered given their proven low toxicity, adjuvant properties and ability to maintain the encapsulated substance in their interior for some time in vivo. Different methods of encapsulating allergenic extracts into neutral, positively, and negatively charged DPPC: cholesterol liposomes have been investigated and the immune response provoked by these in mice was studied and compared to the immune response to free allergen or other adjuvants such as aluminium hydroxide. The results obtained show that allergen encapsulated in all three types of liposomes elicit an increase in specific IgG levels higher than that provoked by free allergen, however, both encapsulation efficiency and specific IgG titre were higher when positively charged (DPPC: cholesterol stearylamine) liposomes were used. Specific IgE levels to allergen in positive and neutral liposomes was lower than to allergen in negative liposomes or adsorbed to Al(OH)3. No difference were found in the behaviour of liposomes prepared by different methods (the results were obtained from pooled sera from different groups of mice so there is no statistical data). These results confirm the immunoadjuvant effect of liposomes for allergy immunotherapy. Further studies to determine their lack of toxicity, pharmacokinetic studies and human clinical studies are necessary to confirm their adequacy for human use and advantage over current immunotherapy methods.

Allergens↗
PubMed1991

[Disseminated mucormycosis in a hemodialyzed female patient treated with deferoxamine].

A case is presented of a patient affected of chronic renal failure caused by multiple myeloma who was under a chelating treatment with Depreroxamine as a consequence of iron intoxication and suffered a disseminated mucormycosis. We performed a literature search of previous cases and discuss the probable relation between this opportunistic infection and depheroxamine treatment.

Deferoxamine↗
PubMed1990

Cholesterol side-chain cleavage and 11 beta-hydroxylation are inhibited by gossypol in adrenal cortex mitochondria.

Cholesterol side-chain cleavage and 11 beta-hydroxylation were assessed in isolated adrenal cortex mitochondria by formation of pregnenolone and corticosterone, respectively, in the presence and absence of gossypol. Pregnenolone biosynthesis was inhibited when increasing concentrations of gossypol were added. The control value of 4 nmol min-1 mg-1 dropped to 2 nmol min-1 mg-1 with 30 microM of the drug in the incubation medium. A more pronounced inhibitory effect was observed upon 11 beta-hydroxylation of steroids; I50 was 11 microM. Seventy-five percent of corticosterone production was impaired when 30 microM of gossypol were present. Bovine serum albumin prevented and reversed the inhibitory action of the drug. Kinetic studies showed a linear mixed type inhibition, suggesting a direct action of the drug upon the enzymatic complex. This study demonstrates a direct inhibitory effect of gossypol upon the steroidogenic enzymes located in the inner mitochondrial membrane of the adrenal cortex.

Adrenal Cortex↗
PubMed1990

Experimental reconstruction of the canine trachea with a free revascularized small bowel graft.

Extensive tracheal stenotic lesions caused by tracheomalacia or neoplasms represent a surgical challenge. Segmental tracheal substitution is sometimes required to obtain radical cure. We present an experimental study of 27 dogs undergoing replacement of the cervical trachea using a vascularized small bowel segment as a tubular graft. A silicone stent was placed in the lumen of the intestinal fragment and was removed the second week after operation. Endoscopic and histological examinations were performed between the first week and second month after operation, and rigidity of the graft was assessed in all cases. No evidence of anastomotic stricture or mucous formation was found. Microscopic examination showed the substitution of bowel mucosa by squamous epithelium as well as the development of connective tissue favoring the fixation of the skeletal muscular structures of the neck to the serous layer of the graft, thus avoiding collapse of the new airway.

Anastomosis, Surgical↗
PubMed1990

Histological types of laryngotracheal tumors induced in Syrian golden hamsters by nitrosomorpholine and nitrosopiperidine.

The chronic oral administration of nitrosomorpholine (NM) and nitrosopiperidine (NP) to 360 adult Syrian golden hamsters of both sexes resulted in the induction of a high incidence of laryngo-tracheal tumors, which in the group treated with 0.01% solution of NM affected up to 80% of the males. A total of 232 different laryngo-tracheal tumors were found. 36 of these were located within the supraglottic and glottic larynx, 62 were within the subglottic and glottic larynx, and 134 arose within the trachea. Among the laryngeal supraglottic and glottic tumors there were 18 squamous cell carcinomas, 16 squamous cell papillomas and only 2 mixed cell mucoepidermoid papillomas. All the subglottic laryngeal tumors and tracheal tumors were mixed cell mucoepidermoid papillomas. In this study, the squamous cell carcinomas observed within the larynx of hamsters bear morphological and biological similarities to their tumor counterpart found in the larynx of adult man. The laryngeal squamous papillomas observed in this experiment are not similar to the squamous papillomas occurring in man during infancy and childhood. The mixed cell mucoepidermoid papillomas of the hamster trachea and subglottis are a peculiar neoplasm of this species, which morphologically and biologically differs from the cases of tracheal papillomatosis described in man, as well as from the mucoepidermoid tumors of major and minor salivary gland origin also seen in this latter species.

Administration, Oral↗
PubMed1990

Primary intrapulmonary benign schwannoma. A case with ultrastructural and immunohistochemical confirmation.

Neurogenic pulmonary tumours are rare. Neurofibromas are the most common variety and tend to occur in patients with generalized neurofibromatosis, whereas schwannomas arise sporadically in patients who have no evidence of this disorder. A case of solitary benign schwannoma arising in a segmental bronchus is presented, and the published cases reviewed. Microscopically, the tumour had a spindle-shaped cell proliferation with palisade formation in several fields and low cellularity in other areas. The diagnosis was supported by positive immunostaining for S-100 protein and by ultrastructural examination which showed elongated cells surrounded by well-preserved basal lamina and numerous cytoplasmic processes also possessing a basal lamina.

Aged↗
PubMed1989

Aurovertin fluorescence changes of the mitochondrial F1-ATPase during multi- and uni-site ATP hydrolysis.

The aurovertin-F1 complex was used to monitor fluorescence changes of the mitochondrial adenosine triphosphatase during multi- and uni-site ATP hydrolysis. It is known that the fluorescence intensity of the complex is partially quenched by addition of ATP or Mg2+ and enhanced by ADP (Chang, T., and Penefsky, H. S. (1973) J. Biol. Chem. 248, 2746-2754). In the present study low concentrations of ATP (0.03 mM) induced a marked fluorescence quenching which was followed by a fast fluorescence recovery. This recovery could be prevented by EDTA or an ATP regenerating system. The rate of ATP hydrolysis by the aurovertin-F1 complex and the reversal of the ATP-induced fluorescence quenching were determined in these various conditions. ITP hydrolysis also resulted in fluorescence quenching that was followed by a recovery of fluorescence intensity. Under conditions for single site catalysis, fluorescence quenching was observed upon the addition of ATP. This strongly indicates that fluorescence changes in the aurovertin-F1 complex are due to the binding and hydrolysis of ATP at a catalytic site. Therefore the resulting ADP molecule bound at this catalytic site possibly induces the fluorescence recovery observed.

Adenosine Diphosphate↗
PubMed1989

Measurement of casein digestion by a fluorometric method.

A qualitative and quantitative method to assay proteolytic degradation of casein with a spectrofluorometer was developed. Proteolysis produced by different pure or mixed proteinases in a pH range 2 to 7.4 quenches the fluorescence emitted at a wavelength of 350 nm by casein excited at 300 nm in less than 5 min. This method is very sensitive, fast, and requires minimal sample preparation. Proteinases that do not generate peptides appropriate for fluorescence quenching cannot be detected with this assay and proteinases with intrinsic fluorescence may require special adjustments of the spectrofluorometer. This method monitors the disappearance of intact substrate proteins continuously, omitting the separation step necessary in other methods to measure product peptides.

Animals↗