Search PubMed⌕ Search

Biomedical subjects

E Silva

Publications and source records attributed to E Silva.

At least 55 records · Page 3Linked to original sources
PubMed2000

Isolation of mesophilic solvent-producing clostridia from Colombian sources: physiological characterization, solvent production and polysaccharide hydrolysis.

One hundred and seventy-eight new butanol-acetone producing bacteria related to saccharolytic clostridia were isolated from agricultural sources in Colombia and their fermentation potential was evaluated. Thirteen isolates produced more total solvents from glucose than Clostridium acetobutylicum ATCC 824. The isolates with the highest single solvent production were IBUN 125C and IBUN 18A with 0.46 mol butanol and 0.96 mol ethanol formed from 1 mol glucose, yielding 25. 2 and 29.1 g l(-1) total solvents, respectively, which is close to the maximum values described to date. Most of the new isolates produced exoenzymes for the hydrolysis of starch, carboxymethyl cellulose, xylan, polygalacturonic acid, inulin and chitosan. Together with the high efficiency of solvent production, these hydrolytic isolates may be useful for the direct fermentation of biomass. According to their physiological profile, the most solvent-productive isolates could be classified as strains of C. acetobutylicum, Clostridium beijerinckii, and Clostridium NCP262.

Clostridium↗
PubMed2000

Cloning and characterization of a new theta-class glutathione-S-transferase (GST) gene, gst-3, from Drosophila melanogaster.

We report here on the cloning and characterization of a new theta-class glutathione-S-transferase (GST) gene, gst-3, from Drosophila melanogaster. Its sequence is distinct from previously characterized Drosophila GST genes, and Southern blotting shows no other closely related genes in the genome. In-situ hybridization localizes the gene to chromosome 2 (55D), near gst-2 (53F), and clearly separate from the gst-D cluster at 87B. The gene is intronless and appears to possess conventional 5' TATA, Cap and 3' polyadenylation signals. A single transcript, approximately 1kb in size, appears to be expressed at high levels in all developmental stages examined. When this gene is overexpressed using various upstream GAL4 driver systems, no striking phenotypes are observed; however, we detect bristle morphology defects in some progeny. The gst-3 gene does not appear to be essential, based upon our observation that mutant flies homozygous for an EP element insertion 5' to the TATA box produce little or no detectable gst-3 mRNA; these flies are viable and fertile at 25 and 29 degrees C. Nevertheless, the gst-3 gene appears to be evolutionarily conserved in other Drosophila species, suggesting that it may be functionally important.

Amino Acid Sequence↗
PubMed2000

The N-terminal tandem repeat region of human prion protein reduces copper: role of tryptophan residues.

Prion protein (PrP) has attracted considerable attention, mainly due to its involvement in transmissible spongiform encephalopathies. Toward its N-terminal region, PrP bears an octapeptide repeat which has been shown to bind copper. We found that a human synthetic peptide (PrP(59-91)), corresponding to the four repeats of Pro-His-Gly-Gly-Gly-Trp-Gly-Gln has the ability to reduce copper. A mutant peptide lacking tryptophan displayed only 24% of the wild-type copper-reducing activity. Experiments performed in a N(2) environment confirmed that O(2) is not involved in the reaction. Our results indicated that cell surface PrP, besides its ability to bind copper, bears the capacity to reduce copper in vitro. The potential physiological role of copper reduction by PrP is discussed.

Copper↗
PubMed2000

Reactivity of monoclonal antibodies against a tryptophan-riboflavin adduct toward irradiated and non-irradiated bovine-eye-lens protein fractions: an indicator of in vivo visible-light-mediated phototransformations.

We describe here the reactivity toward the soluble protein of bovine eye lens of anti-tryptophan-riboflavin (anti-Trp-RF) adduct monoclonal antibodies, which recognize the hapten tryptophan-riboflavin generated by irradiation of a solution of bovine serum albumin in the presence of riboflavin. It is demonstrated that five different anti-Trp-RF adduct monoclonal antibodies, all belonging to the IgG1 isotype, react with the total soluble proteins of bovine eye lens. The components of the soluble protein are separated by Sephadex G-200 chromatography and the isolated fractions analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). All the separated protein fractions also react by a direct ELISA with the monoclonal antibodies; this reaction is more intense when the isolated fractions have been previously irradiated with visible light in the presence of riboflavin under an atmosphere of oxygen or nitrogen. Irradiation of the total soluble protein with visible light in the presence of riboflavin produces the appearance of new bands, corresponding to compounds of higher molecular weight. Riboflavin-sensitized irradiation of the protein fractions with visible light under an oxygen or nitrogen atmosphere is accompanied by a concomitant decrease of the tryptophan fluorescence. It is postulated that the action of visible light in the presence of either the endogenous riboflavin or its derivatives could be partly responsible for the protein aggregation observed during aging.

Animals↗
PubMed2000

Essential genes in autosomal heterochromatin of Drosophila melanogaster.

We are taking two approaches to understanding the structure, function and regulation of essential genes within Drosophila heterochromatin. In the first, we have undertaken a genetic and molecular characterization of essential genes within proximal 3L heterochromatin. The expression of such 'resident' genes within a heterochromatic environment is paradoxical and poorly understood, given that the same environment can inactivate euchromatic sequences (position effect variegation, or PEV). A second approach involves the study of the local chromosomal environment of heterochromatic (het) genes, as assayed both biochemically, and via the effects of genetic modifiers of PEV, the latter being putative components important for het gene expression. Our results to date suggest that the three most proximal genes in 3L heterochromatin have key roles in development, and indicate strong effects of combinations of genetic modifiers of PEV on het gene expression.

Animals↗
PubMed2000

Epidemiologic aspects of arterial hypertension in Maracaibo, Venezuela.

The purpose of this study was to determine the prevalence of arterial hypertension (HT) awareness and the influence of age, sex and body mass index on the degree of control of HT in the population of Maracaibo, State of Zulia, Venezuela. It included 7424 subjects, 3640 males (M) and 3784 females (F). Information was collected through domiciliary visits with a questionnaire designed for this purpose. Hypertension was defined as such when values were > or =140 mm Hg for systolic blood pressure (SBP) and > or =90 mm Hg for diastolic blood pressure (DBP). In the total sample, 36.9% were hypertensive. A higher prevalence in M (45.2%) than in F (28.9%), was observed. The percentage of HT increased with age in both genders. There was a high percentage of hypertensives with obesity (73.5%) which did not vary when discriminating for gender and age. Obese subjects were more prone to have HT until age 50. Those younger than 40 took less medication but were proportionally better controlled. Of the hypertensive population 54.3% were not aware of their condition, of 45.7% remaining, 22.8% did not have regular control visits, 18.4% inspite of medication were not controlled and only 4.5% were well controlled. Better control was observed in F (6.2%) than in M (3.3%), P < 0.001. It is concluded that HT is a serious public health problem because of its high prevalence and lack of control, and it is necessary to implement educational and medical programmes for the detection and control of this disease.

Adult↗
PubMed2000

Riboflavin photodegradation and photosensitizing effects are highly dependent on oxygen and ascorbate concentrations.

Riboflavin (RF) is a normal component of the eye lens which triggers a strong photosensitizing activity when exposed to light. Upon irradiation with short wavelength radiations below 400 nm, RF-photosensitized damage may occur. However, vitamin C is present at high concentrations in the normal lens and plays an important role in inhibiting these photosensitization processes. An in vitro simple model was used with the objective of understanding better the relationships between vitamin C and oxygen concentrations on the mechanisms of RF-mediated photodegradation of tryptophan (Trp), a target particularly sensitive to photo-oxidation. Under nitrogen, the RF decomposition reached its maximal value, and vitamin C and Trp photo-oxidation was negligible. When increasing oxygen pressure, RF photodegradation dropped and vitamin C photo-oxidation strongly increased and was maximal at 100% O2. RF-induced photodegradation of Trp first increased with oxygen concentration, up to 40 microM O2, and then decreased. RF and Trp degradation were significantly protected by vitamin C so that no more than 20% of the substrates concentration were oxidized in the presence of vitamin C higher than 0.8 mM. From our results we conclude that in the specific conditions of the normal lens, the high vitamin C concentration (2 mM) is compatible with the UVA radiation hazard, despite the presence of RF. However, if lenticular vitamin C decreases below 0.8 mM, photodegradation of RF may occur and Trp may therefore be photo-oxidized by a Type-I mechanism.

Ascorbic Acid↗
PubMed2000

A CRX null mutation is associated with both Leber congenital amaurosis and a normal ocular phenotype.

PURPOSE: To identify and characterize new cone rod homeobox (CRX) mutations associated with the Leber congenital amaurosis phenotype. METHODS: The human CRX gene was sequenced in 74 consecutive patients carrying the diagnosis of Leber congenital amaurosis. RESULTS: Two mutations were identified in CRX that cause frameshifts and predict severe truncations of the encoded protein. One of these, a 1-bp insertion, spares only nine N-terminal amino acids, removing the homeodomain, WSP motif, and conserved OTX domain at the C terminus. Of the CRX mutations described in the literature, this is the first that convincingly represents a null allele of the gene. Although the patient heterozygous for this null allele is affected with Leber congenital amaurosis, it was surprising that her father, who had normal vision, was heterozygous for the same mutation. CONCLUSIONS: These results strongly suggest that haploinsufficiency of CRX is not sufficient to cause a retinal disorder. Loss of function alleles of CRX appear to cause Leber congenital amaurosis through a recessive or multigenic mechanism.

Base Sequence↗
PubMed2000

Lactic acidosis and antiretroviral therapy: a case report and literature review.

Antiretrovirals, particularly nucleoside analogue reverse transcriptase inhibitors (RTIs) - DDI, 3TC and D4T, are widely used to effectively control human immunodeficiency virus (HIV) infection. These drugs have several adverse effects including anemia, peripheral neuropathy, pancreatitis and, on rare occasions, lactic acidosis. We describe the case of a 39 year old patient who had severe lactic acidosis after receiving stavudine (D4T) and didanosine (DDI) for an 8 month period. She had never manifested an opportunistic infection and presented a CD4 count of 378 cells/mm3 and an undetectable viral load (< 400 copies/ml). The purpose of the following report is to alert clinicians and infectious diseases specialists to the occurrence of lactic acidosis in asymptomatic HIV patients receiving antiretrovirals for long periods of time.

Acidosis, Lactic↗
PubMed2000

Guess what! Porokeratosis of Mibelli.

A 72-year-old man had noticed, in his early forties, the appearance of well-defined papulous hyperkeratotic lesions, with increasing growth, located on both sides of his feet. After twenty-five years he consulted a dermatologist for the first time. Physical examination showed annular papules and rose-coloured plaques with atrophic centres, some of them hypopigmented, with higher and irregular borders, separated from the surrounding skin by longitudinal and well-defined furrows. The lesions presented variable sizes and shapes, some of them punctate, involving exclusively and in a bilateral form, both sides, back and sole of the feet (Figs. 1 and 2). The patient did not report any subjective symptoms. He was immunocompetent and did not remember that any relative had the same disease, nor had he been subjected to radiation treatment.

Aged↗
PubMed1999

Visible light-induced photooxidation of glucose sensitized by riboflavin.

We conducted this study to evaluate the oxidation of glucose induced by visible light in the presence of sensitizers such as methylene blue and flavins (i.e., flavin mononucleotide and riboflavin). The concentration of the sensitizers was similar to that of flavin in parenteral nutrients. The photooxidation of glucose sensitized by flavin mononucleotide or riboflavin was greater than that which was observed in the presence of methylene blue, whereas the isotopic effect of deuterium oxide (D(2)O) was enhanced more substantially in the presence of methylene blue than in the presence of flavins. These results show that methylene blue exerts its action through singlet oxygen and that at a high substrate concentration (as was used in this work) flavin mononucleotide and riboflavin act preferentially as type I sensitizers. In the flavin photosensitized processes, the presence of hydrogen peroxide, superoxide anion, and hydroxyl radical was demonstrated. The photooxidation of glucose is favored by an increase in pH, and it also depends on the energy absorbed by the system. By using a specific reagent for glucose (i.e., o-toluidine), it was possible to quantify the photoconversion of glucose. The results obtained in this work should be considered in the management of glucose-containing parenteral nutrients that are exposed to visible light in the presence of a multivitamin complex containing flavin mononucleotide.

Journal Article↗
PubMed1999

Photochemical and pharmacokinetic properties of selected flavins.

Some photochemical and pharmacokinetic properties of riboflavin, lumiflavin and the 2',3',4',5' tetraacetyl, tetrapropionyl, tetrabutiryl and tetrapalmitoyl esters of riboflavin have been studied. The esters are considerably more photostable than riboflavin but less so than lumiflavin, and appear to be photosensitizers with a behaviour similar to that of riboflavin, promoting photoreactions of biological targets even in the absence of molecular oxygen. The various flavins display important differences in their pharmacokinetic behaviour. Riboflavin, lumiflavin and the short-chain esters (the acetyl and propionyl esters) are rapidly cleared from serum, and recovered in comparable amounts from the liver and kidneys. These results are in agreement with their hydrophilic or moderately hydrophobic character. In contrast, the longer-chain butiryl and palmitoyl esters exhibit a prolonged retention in serum and undergo a significantly larger accumulation in the liver as compared with the kidneys; they are also found in the spleen. In all cases the tissue uptake of these esters becomes appreciable only after 24 h. These results are coherent with the highly hydrophobic character of these esters, which induce a slow release from serum lipoproteins and have a preferential clearance via the bile-gut pathway, showing affinity for the components of the reticuloendothelial system. These long-chain riboflavin esters will probably have a greater and more persistent risk of photoinduced hepatotoxicity than riboflavin, lumiflavin and the short-chain esters.

Animals↗
PubMed1999

Procalcitonin used as a marker of infection in the intensive care unit.

OBJECTIVE: To determine the value of procalcitonin (ProCT) as a marker of infection in critically ill patients. DESIGN: Prospective, observational study. SETTING: Medicosurgical department of intensive care (31 beds). PATIENTS: One hundred eleven infected and 79 noninfected patients. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: ProCT and C-reactive protein (CRP) concentrations were monitored daily. The best cutoff values for ProCT and CRP were 0.6 ng/mL and 7.9 mg/dL, respectively. Compared with CRP, ProCT had a lower sensitivity (67.6 vs. 71.8), specificity (61.3 vs. 66.6), and area under the receiver operating characteristic curve (0.66 vs. 0.78, p < .05). The combination of ProCT and CRP increased the specificity for infection to 82.3%. In the infected patients, plasma ProCT, but not CRP, values were higher in nonsurvivors than in survivors. Infected patients with bacteremia had higher ProCT concentrations than those without bacteremia, but similar CRP concentrations. ProCT levels were particularly high in septic shock patients. CONCLUSIONS: ProCT is not a better marker of infection than CRP in critically ill patients, but it can represent a useful adjunctive parameter to identify infection and is a useful marker of the severity of infection.

Adolescent↗
PubMed1999

Evaluation of electromyographic activity and heart rate responses to isometric exercise. The role played by muscular mass and type.

The purpose of the present study was to examine the relationship between the electromyographic (EMG) activity and heart rate (HR) responses induced by isometric exercise performed by knee extension (KE) and flexion (KF) in men. Fifteen healthy male subjects, 21 +/- 1.3 years (mean +/- SD), were submitted to KE and KF isometric exercise tests at 100% of maximal voluntary contraction (MVC). The exercises were performed with one leg (right or left) and with two legs simultaneously, for 10 s in the sitting position with the hip and knee flexed at 90 degrees. EMG activity (root mean square values) and HR (beats/min) were recorded simultaneously both at rest and throughout the sustained contraction. The HR responses to isometric exercise in KE and KF were similar when performed with one and two legs. However, the HR increase was always significantly higher in KE than KF (P < 0.05), whereas the EMG activity was higher in KE than in KF (P < 0.05), regardless of the muscle mass (one or two legs) involved in the effort. The correlation coefficients between HR response and the EMG activity during KE (r = 0.33, P > 0.05) and KF (r = 0.15, P > 0.05) contractions were not significant. These results suggest that the predominant mechanism responsible for the larger increase in HR response to KE as compared to KF in our study could be dependent on qualitative and quantitative differences in the fiber type composition found in each muscle group. This mechanism seems to demand a higher activation of motor units with a corresponding increase in central command to the cardiovascular centers that modulate HR control.

Adult↗
PubMed1999

Decreased expression of retinoic acid receptors, transforming growth factor beta, involucrin, and cornifin in cervical intraepithelial neoplasia.

Cervical intraepithelial neoplasia (CIN) I, II, and III represent a spectrum of premalignant epithelial changes and are ideal targets for application of chemoprevention strategies. Intermediate end point biomarkers are increasingly being used as surrogate end points to monitor clinical chemoprevention trials. To identify potential biomarkers in cervical epithelium, we analyzed the expression of nuclear retinoic acid receptor (RAR) mRNA by in situ hybridization, involucrin, cornifin, and transforming growth factors (TGFs) beta1 and beta2 by immunohistochemistry in cervical specimens, which contained adjacent normal epithelium and CIN lesions from 52 patients. These biomarkers were expressed in all adjacent normal cervical epithelia, whereas all CIN lesions including CIN I, CIN II, and CIN III exhibited decreased expression of RAR-alpha by 55.8%, RAR-beta by 64.7%, RAR-gamma by 54.9%, involucrin by 80.8%, cornifin by 88.5%, TGF-beta1 by 89.7%, and TGF-beta2 by 85.7%. Viewed as a whole, these biomarkers were down-regulated in 100% of the CIN lesions. Because all of these biomarkers can be modulated in vitro by retinoids, they may serve as intermediate biomarkers for retinoid chemoprevention trials in the patients with CIN lesions.

Biomarkers, Tumor↗