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D Martínez

Publications and source records attributed to D Martínez.

At least 19 recordsLinked to original sources
PubMed2003

Comparison of pore-forming ability in membranes of a native and a recombinant variant of Sticholysin II from Stichodactyla helianthus.

Sticholysin II (St II) a potent cytolysin from the sea anemone Stichodactyla helianthus was obtained by recombinant procedures exhibiting six histidine residues in its N-terminus (St IIn6H). The functional comparison between St II and St IIn6H showed a lesser pore-forming ability for the recombinant than for the native in human or rat red blood cells (RBC) and in large unilamellar vesicles (LUV) of different phospholipid composition. However, binding of St IIn6H to small unilamellar vesicles (SUV) was higher with regard to St II. The explanation to the different permeabilizing capacity of both protein variants is not clear, but a different anchoring of St IIn6H to the lipid bilayer could delay the organization of the competent pore into membrane.

Amino Acid Substitution↗
PubMed2002

Molecular epidemiology of hepatitis B virus in Afro-Venezuelan populations.

Hepatitis B virus (HBV) infection among Venezuelan populations of African origin was analyzed. These populations exhibited lower HBV prevalence than the one found in the African continent. Sequence analysis of 6 isolates showed that 3 belonged to genotype F, while the 3 others were HBV genotype A. HBV genotype A was more common in the Afro-Venezuelan groups than in the general Venezuelan population. This might reflect the introduction of genotype A during the slavery period. The absence of the African genotype E among these isolates supports the hypothesis of a recent origin for this HBV genotype. HBV genotype F has already been introduced to these relatively isolated communities.

Africa↗
PubMed2001

Primary structure of two cytolysin isoforms from Stichodactyla helianthus differing in their hemolytic activity.

Sticholysin I (St-I) and sticholysin II (St-II) are cytolysins purified from the sea anemone Stichodactyla helianthus with a high degree of sequence identity (93%) but clearly differenced in their hemolytic activity. In order to go further into the structural determinants for the different behavior of St-I and St-II, we report here the complete amino acid sequences and the consensus secondary structure prediction of both proteins. The complete determination of St-II primary structure confirms the partial revision of cytolysin III amino acid sequence. All nonconservative changes between St-I and St-II are located at the N-terminal. According to our prediction these changes could be located at the same face of an alpha-helix during pore formation events and could account for the observed differences in hemolytic activity between St-I and St-II.

Amino Acid Sequence↗
PubMed2000

Solid-phase extraction coupling to capillary electrophoresis with emphasis on environmental analysis.

This article reviews the status of solid-phase extraction (SPE) coupled with capillary electrophoresis (CE). It focuses on some of the organic pollutants which have captured the interest of analytical chemists--phenols, surfactants, dyes, polynuclear aromatic hydrocarbons (PAHs), aromatic and aliphatic amines, aromatic acids and aromatic sulfonic acids--and, in particular, on monitoring pesticides from different sources. It shows that the coupling of SPE to CE has considerable potential in the analysis of environmental pollutants.

Amines↗
PubMed1999

Evaluation of different electrolyte systems and on-line preconcentrations for the analysis of haloacetic acids by capillary zone electrophoresis.

This study compares the sodium chromate, potassium hydrogenphthalate, 2,6-naphthalenedicarboxylic acid dipotassium and sodium tetraborate electrolyte systems, for determining haloacetic acids using capillary zone electrophoresis with and without modified electroosmotic flow. In order to detect low concentrations of these compounds, an on-line preconcentration step was carried out. Results were good when standard solutions were analysed, but when the method was applied to real samples, the sample had to be pretreated to decrease the interference of the matrix. For this reason, a solid-phase extraction process with LiChrolut EN cartridges was applied to clean up the sample before the injection.

Acetates↗
PubMed1999

Pheromone-triggered orientation flight of male moths can be disrupted by trifluoromethyl ketones.

In a wind tunnel trifluoromethyl ketones (TFMKs) have been found to disrupt the orientation flight of male moths to pheromone sources (virgin females or synthetic pheromone). This is demonstrated by comparison of the flight parameters of the Egyptian armyworm Spodoptera littoralis and the Mediterranean corn borer Sesamia nonagrioides, which had been topically treated with TFMKs, with those calculated for untreated insects. Inhibition occurred in all types of behavior and that of the source contact has been quantified and found to be dose-dependent. The same effect has also been noticed in Mediterranean corn borer males flying to an attraction source consisting of mixtures of (Z)-11-hexadecenyl trifluoromethyl ketone (8), a closely related analogue of the major component of the pheromone, and the natural pheromone blend. The most active TFMKs are those closest in structure to the natural pheromone, along with those chemicals which easily hydrate in solution, such as the beta-thiosubstituted derivatives. Along with the previously reported reduction of catches in the field, our results suggest the possible application of these chemicals in future new pest control strategies.

Animals↗
PubMed1999

Vagus nerve prolonged stimulation in cats: effects on epileptogenesis (amygdala electrical kindling): behavioral and electrographic changes.

PURPOSE: To analyze the effect of prolonged (daily) electrical vagus nerve stimulation (VNS) on daily amygdaloid kindling (AK) in freely moving cats. METHODS: Fifteen adult male cats were implanted in both temporal lobe amygdalae, both lateral geniculate bodies, and prefrontal cortices. A bipolar hook (5-mm separation) stainless steel electrode also was implanted in the unsectioned left vagus nerve. AK only was performed on five of the cats as a control. The remaining 10 cats were recorded under the following experimental conditions: VNS (1.2-2.0 mA, 0.5-ms pulses, 30 Hz) for 1 min along with AK (1-s train, 1-ms pulses, 60 Hz, 300-600 microA), followed by VNS alone for 1 min, four times between 11:00 a.m. and 2 p.m. At different times, VNS was arrested, and AK was continued until stage VI kindling was reached. RESULTS: The behavioral changes evoked by VNS were as follows: left miosis, blinking, licking, abdominal contractions, swallowing, and eventually yawning, meowing, upward gaze, and short head movements. Compulsive eating also was present with a variable latency. Outstanding polygraphic changes consisted of augmentation of eye movements and visual evoked potentials while the animal was awake and quiet, with immobility and upward gaze. An increase of the pontogeniculooccipital (PGO) wave density in rapid eye movement (REM) sleep also was noticeable. AK was completed (to stage VI) in the control animals without a vagus nerve implantation in 23.4+/-3.7 trials. In animals with VNS, the AK was significantly delayed, remaining for a long time in the behavioral stages I-III and showing a reduction of afterdischarge duration and frequency. Stage VI was never reached despite 50 AK trials, except when the vagus nerve electrodes were accidentally broken or vagal stimulation was intentionally arrested. Under these circumstances, 24.4+/-8.16 AK trials alone were necessary to reach stage VI of kindling. CONCLUSIONS: Our results indicate that left, electrical VNS interferes with AK epileptogenesis. This anticonvulsant effect could be related to the increase of REM sleep.

Amygdala↗
PubMed1998

Comparative study of a solid-phase extraction system coupled to capillary electrophoresis in the determination of haloacetic compounds in tap water.

This study compares four different commercial sorbents, LC-SAX (a quaternary ammonium anion exchanger), LiChrolut EN (a highly crosslinked styrene-divinylbenzene), Envi-Carb (a graphitized carbon black) and Oasis HLB [a macroporous poly(divinylbenzene-co-N-vinylpyrrolidone) copolymer], for the solid-phase extraction (SPE) of various haloacetic compounds from aqueous samples. The recoveries with the different sorbents were studied by coupling an off-line SPE system to capillary electrophoresis with indirect photometric detection. The recoveries were highest when LiChrolut EN was used. The limits of detection for the compounds are in the low microgram per litre range and the recovery values are over 80% for dichloroacetic acid and trichloroacetic acid, two of the most habitual haloacetic acids in chlorinated water, when 500 ml of standard solution was preconcentrated using this sorbent. Finally, the performance of the method with different water samples, the effect of chlorination in a treatment plant and the evolution of the haloacetic acids in the water distribution system were tested and the results were compared with those obtained using liquid-liquid extraction and gas chromatography-mass spectrometry.

Dichloroacetic Acid↗
PubMed1998

Capillary zone electrophoresis with indirect UV detection of haloacetic acids in water.

A capillary zone electrophoresis (CZE) system for determining haloacetic acids in water was optimized with indirect photometric detection. Two different carrier electrolytes, potassium hydrogenphthalate and sodium 2,6-naphthalenedicarboxylate, were evaluated in terms of sensitivity and two different electroosmotic flow modifiers, tetradecyltrimethylammonium bromide and hexadecyltrimethylammonium bromide, were tested. Parameters such as electrolyte concentration and pH, and the concentration of the electroosmotic flow modifiers, which affect the CZE separations, were investigated. The method was used to determine haloacetic acids in chlorine tap water using the liquid-liquid extraction process.

Acetates↗
PubMed1998

The role of ionic strength on the enhancement of the hemolytic activity of sticholysin I, a cytolysin from Stichodactyla helianthus.

Sticholysin I (St I) is a potent cytolytic polypeptide purified from the Caribbean sea anemone Stichodactyla helianthus. The hemolytic activity of sticholysin is potentiated by its preincubation at high ionic strengths. In the present work the mechanism of the potentiating action of the medium ionic strength on the toxin hemolytic capacity is investigated. It is suggested that preincubation with high saline concentration induces a transition of St I to a more relaxed conformation that facilitates the lytic process.

Animals↗
PubMed1996

[Intramuscular myxoma. Apropos of a case].

Intramuscular myxoma is a relatively unusual benign tumor of soft tissues. Clinical examination is non specific and the definitive diagnosis can only be established on histology. The treatment consists of excision of the tumor. The prognosis is very good and recurrence is very rare. No cases of metastasis have been described.

Aged↗
PubMed1995

Experimental model for local administration of nerve growth factor in microsurgical nerve reconnections.

An experimental model for local administration of neuronotrophic substances at the site of peripheral nerve lesion is presented. The model consists of a subcutaneously located silicone reservoir and a connecting tube with its distal end fixed in the proximity of the severed and repaired nerve. The results of the preliminary tests of the model are presented. Sixty Sprague-Dawley rats were divided into two groups: control (saline-treated) (n = 30) and NGF-treated (n = 30). After axotomy of the sciatic nerve, an epineurial repair is performed. NGF or saline is injected daily into the subcutaneous reservoir during the first 3 weeks after axotomy and a single dose in the fourth week. The regenerated nerve observed in the NGF-treated group after four weeks of treatment presents a greater percentage of myelinated axons, thicker myeline sheaths, and more mature endoneurial layers. This experimental model provides a reliable and quantitative way to deliver neuronotrophic substances in site and at different administration rates.

Animals↗
PubMed1995

[Blood insulin in fasting conditions as a simple marker of insulin resistance in hypertensive patients].

Insulin resistance is associated to hypertension, obesity and diabetes and may be an independent cardiovascular risk factor. The exact assessment of insulin resistance requires complex metabolic studies. However, there is a good correlation between this parameter and fasting serum insulin levels. The aim of this work was to study fasting serum insulin levels by radio immuno analysis in 43 hypertensive patients aged 56 +/- 5.5 years old (27 male, 17 obese and 8 diabetics) and 20 normotensive controls aged 50 +/- 4.8 years old (13 male). Insulin levels were 3.8 UI/L in controls, 12.1 UI/L in normal weight, 15.5 UI/L in obese and 18.3 UI/L in diabetic hypertensives (ANOVA p < 0.001). These levels were above two standard deviations of control values in 50% of normal weight, 66% of obese and 62% of diabetic hypertensives. It is concluded that normal weight, obese and diabetic hypertensive subjects have high fasting insulin levels.

Adult↗
PubMed1995

[Epidemiology of exocrine pancreatic cancer in the Principality of Asturias, 1973-1992].

Pancreatic adenocarcinoma continues increasing in frequency, its diagnosis is usually realized very late and the results of the surgery, that is the only possibility of cure, gives often a feeling of frustration. During the period between 1973 and 1992, 1032 patients were diagnosed of pancreatic carcinoma at the different hospital institutions of our region. The incidence has increased from 1.28 to 6.42 cases/100,000. The proportion male/female was 1.5/1. Mean age of the patients was 67.5 +/- 11.35 and the median age was 65 years. In relation with the sex, the women age was higher: 70.2 +/- 11.81 (p < 0.01). The best diagnostic test was the CAT scan with 87.5 sensitivity. The overall resectability rate was low (11%), but there is a large difference between the beginning and the end of the period (6.8% and 14.1% respectively). Staging of the disease was stage IV in 36.4% of the cases. The 66.5% of the patients underwent palliative surgery. Cholecystojejunostomy was the most frequent operation. It wasn't possible any surgical management at the 3.5% of the cases cause of the disease was very extended; laparotomy was the only method used in 18.7%. The average survival rate with exeresis surgery was 18 months; with palliative surgery, it was only of eight months. The natural history of pancreatic carcinoma was situated at 5.57 +/- 2.63.

Adenocarcinoma↗