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S Hurtado

Publications and source records attributed to S Hurtado.

13 recordsLinked to original sources
PubMed2006

Optimized background reduction in low-level gamma-ray spectrometry at a surface laboratory.

The background of a coaxial Ge detector placed at a surface laboratory has been reduced by means of a background reduction setup consisting of a passive shield of low-activity lead, a simple radon suppression system and an active shield with a plastic scintillation plate. In particular, we have devoted our efforts to in-depth optimization of each parameter associated with different anticoincidence setups and to their subsequent intercomparison. The overall performance of the active shield was improved by using the optimum time parameters for each setup. The final objective is to decrease the cosmic-ray background and, by this way, to reduce the detection limits of gamma-ray spectrometers at conventional laboratories, and consequently make them competitive for different measurements like (210)Pb dating.

Background Radiation↗
PubMed2004

Ambulatory blood pressure monitoring in renal transplant patients: modifiable parameters after active antihypertensive treatment.

BACKGROUND: Hypertension (HT) accounts for nearly 60% to 80% of renal transplant patients (RT). It is one of the most important risk factors for cardiovascular diseases and may cause chronic graft dysfunction. Therefore, it is important to accurately detect and treat HT. We aimed to evaluate the changes in ambulatory blood pressure monitoring (ABPM) parameters among hypertensive RT after active treatment compared with baseline values. METHODS: Thirty seven RT (25 men, 12 women, aged 49.4 +/- 11.2 year) diagnosed with mild to moderate HT underwent 24-hour ABPM after a 4-week washout period (W0). For the 23 RT with confirmed HT of a second 24-hour ABPM was recorded after 4 weeks of treatment with doxazosin GITS (-4 mg once daily in the morning), a new formulation of an alpha1-receptor inhibitor (W4). Nondippers were considered when mean blood pressure (BP) showed a < or = 10% reduction during sleep. Statistical analyses included Saphiro-Wilks test, Student t test, and ANOVA. RESULTS: After active treatment systolic, diastolic, and mean BP (SBP, DBP, MBP) significantly decreased during diurnal and 24 hours but not the nocturnal period. No significant change was observed for heart rate nor for pulse pressure during any period. The prevalence dippers increased from 0% to 17% after treatment. After placebo administration 8 among 37 RT with HT diagnosed according to casual BP remained hypertensive at nighttime (but not at daytime) according to 24-hour ABPM. CONCLUSIONS: Diurnal and 24-hour periods of ABPM showed significant changes in SBP, DBP, and MBP after active treatment with doxazosin GITS. No significant BP changes were observed in the nocturnal period or in dipper status. Further studies using ABPM must be undertaken to determine the optimal dosage and time of administration of antihypertensive drugs in RT.

Antihypertensive Agents↗
PubMed2003

Efficacy and safety of doxazosin GITS in hypertensive renal transplant patients: comparison of 8 and 4 mg.

BACKGROUND: Hypertension (HT), a prevalent complication in renal transplant patient (RT), must be accurately treated because cardiovascular disease is the leading cause of death and of chronic graft dysfunction. Sympathetic activity may contribute to HT in RT, yielding the rationale to suspect that doxazosin, an alpha1-adrenergic receptor inhibitor, may lower blood pressure (BP). The aim of this study was to evaluate the efficacy and safety of doxazosin GITS (4 and 8 mg) in RT. METHODS: Twenty-three hypertensive RT received doxazosin 4 mg once daily for 4 weeks (W4) followed by a 4-week washout (W0) and 17/23 treated with doxazosin 8 mg for 4 more weeks (W8) due to persistent HT. All patients underwent 24-hour ambulatory blood pressure monitoring (ABPM) after W0, W4, and W8. Laboratory tests were performed, adverse events recorded, and prostatic symptomatology examined. Statistical analysis included Saphiro-Wilks, Student t, ANOVA, Wilcoxon, or Friedman tests. RESULTS: The systolic, diastolic, and mean BP were significantly lowered at W4 in awake (P<.001) and 24 hour period (P<.005) but not sleep recordings. Doxazosin 8 mg had no significant additional effect to lower BP at any period. Normotension was reached in 13% and 21.7% of patients at W4 and W8, respectively. Palpitations were the only reported adverse event after treatment (incidence similar to placebo). There was no significant change in the laboratory values. CONCLUSIONS: Doxazosin (-4 mg) effectively decreased BP in awake and 24-hour periods without a significant improvement during sleep. A double dose of the drug added little benefit. Optimal BP was reached by an insufficient number of patients. Doxazosin proved to have a good tolerance and safe profile. This results suggest that doxazosin should be considered a good add-on treatment to other antihypertensive drugs in RT.

Adrenergic alpha-Antagonists↗
PubMed2001

Variants of the Plasmodium vivax circumsporozoite protein (VK210 and VK247) in Colombian isolates.

Phenotypic diversity has been described in the central repeated region of the circumsporozoite protein (CSP) from Plasmodium vivax. Two sequences VK210 (common) and VK247 (variant) have been found widely distributed in P. vivax isolates from several malaria endemic areas around the world. A third protein variant called P. vivax-like showing a sequence similar to the simian parasite P. simioovale has also been described. Here, using an immunofluorescent test and specific monoclonal antibodies, we assessed the presence of two of these protein variants (VK210 and VK247) in laboratory produced sporozoite. Both sequences were found in parasite isolates coming from different geographic regions of Colombia. Interestingly, sporozoites carrying the VK247 sequence were more frequently produced in Anopheles albimanus than sporozoites with the VK210 sequence. This difference in sporozoites production was statistically significant (p <0.05, Kruskal-Wallis); not correlation was found with parameters as the total number of parasites or gametocytes in blood from human donors used to feed mosquitoes. Previous studies in the same region have shown a higher prevalence of anti-VK210 antibodies which in theory may suggest their role in blocking the development of sporozoites carrying the CSP VK210 sequence.

Amino Acid Sequence↗
PubMed1999

Effect of NMDA antagonists on the activity of glutaminase and aspartate aminotransferase in the developing rat cerebellum.

Chronic treatment of rats from postnatal day 6 to 25 with drugs that interact with the N-methyl-D-aspartate (NMDA) receptor induced a differential effect on the activity of some enzymes involved in neurotransmitter synthesis. Two of these drugs ((5R,10S)-(+)-5-methyl-10,11 -dihydro-5H-dibenzo(a,d)cyclohepten-5,10-imine hydrogen maleate (MK-801) and 3-(2-carboxypiperazin-4-yl)propyl-1phosphonic acid (CPP)) caused a marked reduction (20-40%) of glutaminase and aspartate aminotransferase activity in the cerebellum. These changes were observed only at a very precise time of development (i.e. 10 to 19 postnatal day). The competitive antagonist, amino phosphonovaleric acid (APV), did not affect any of the enzymes studied at all tested ages. When animals were treated with NMDA only a slight, but significant, increase in the activity of glutaminase was observed at 9-11 postnatal day only. Any of the agonists or antagonists tested significantly affected the activity of lactate dehydrogenase as compared to control animals. Histologic observations of cerebella treated with the indicated drugs showed that only MK-801, and CPP to a lesser extent, induced a small reduction in the width of the internal granule layer. The body weight of animals treated with MK-801 was clearly reduced, but only in more mature rats (> 16 postnatal day), when animals did not show any alteration in the enzymes tested. These results support the suggestion that presynaptic influences, particularly from glutamatergic neurons, are critical to promote cerebellar granule neurons differentiation during critical periods of the cerebellar development.

2-Amino-5-phosphonovalerate↗
PubMed1997

Regular production of infective sporozoites of Plasmodium falciparum and P. vivax in laboratory-bred Anopheles albimanus.

One of the major constraints for studies on the sporogonic cycle of the parasites causing human malaria, and on the protective efficacy of pre-erythrocytic vaccines, is the scarcity of laboratory-reared Anopheles mosquitoes as a source of infective sporozoites. The aim of the present study was to reproduce the life-cycles of Plasmodium falciparum and P. vivax in the laboratory and so develop the ability to produce infective sporozoites of these two species regularly under laboratory conditions. Colonized Anopheles albimanus, of Buenaventura and Tecojate strains, were infected by feeding either on Plasmodium-infected blood, from human patients or experimentally inoculated Aotus monkeys, or on gametocytes of the P. falciparum NF-54 isolate grown in vitro. The monkeys were infected with the blood stages of a Colombian P. vivax isolate and then, after recovery, with the Santa Lucia strain of P. falciparum from El Salvador. Although both of the mosquito strains used were successfully infected with both parasite species, the Buenaventura strain of mosquito was generally more susceptible to infection than the Tecojate strain, and particularly to infection with the parasites from the patients, who lived where this strain of mosquitoes was originally isolated. Monkeys injected intravenously with the P. vivax sporozoites produced in the mosquitoes developed patent sexual and asexual parasitaemias; the gametocytes that developed could then be used to infect mosquitoes, allowing the development of more sporozoites. However, experimental infections failed to establish after the P. falciparum sporozoites were used to inoculate monkeys. The ability to reproduce the complete life cycle of P. vivax in the laboratory, from human to mosquito and then to monkey, should greatly facilitate many studies on vivax malaria and on the efficacy of candidate malaria vaccines. The availability of the sporogonic cycles of P. falciparum from three different sources should also permit a variety of biological studies.

Animals↗
PubMed1995

Characterization of the regional distribution of selenium in Chile using selenium in hens' eggs as a monitor.

Regional distribution of selenium (Se) in Chile was investigated by using the concentration of Se in hens' eggs as a monitor. Forty-one locations along the entire length of the country were sampled. Average (+/- SD) egg-white Se content (mg/kg dry) was 0.79 +/- 0.41, range 0.22-2.23. Corresponding yolk Se values were, mean 0.81 +/- 0.43, (mg/kg dry) range 0.26-2.23. Locations grouped in five main areas, according to their geographic-climatic characteristics, showed significant differences regarding both egg-white Se and yolk Se. Analyzed dietary Se intake from two distinct areas reflected the trends observed in the Se content of egg fractions from such regions. These data support the utilization of the concentration of Se in hens' eggs as a useful monitor of dietary selenium consumed by selected populations.

Animals↗
PubMed1992

[Puerperal uterine involution: an echographic follow-up].

We have studied 87 puerperal women during the first month postpartum. They were liable to ultrasound on the first, second and third day of this period. Eighteen of them were examined on the 15th and 30th day. The measure of the uterine area (pi x 1/2 length x 1/2 width) is seen as the most sensible method for this evaluation. The uterus involutionated symmetrically and in thirty days complete this process. They were no significative differences appreciated in the uterine involution that depends on the lactation, parity and the use of uterine retractors.

Adolescent↗
PubMed1991

Similar properties of taurine release induced by potassium and hyposmolarity in the rat retina.

Increasing external K+ concentration to 56, 75 or 100 mM stimulated taurine release by 3-, 7- and 11-fold, respectively. The K(+)-evoked release of [3H]taurine was markedly delayed, sustained and Ca(2+)-independent, in clear contrast to the usual neurotransmitter release pattern. These high K+ concentrations caused a marked increase in retinal cell volume which was prevented by removal of Cl-, or in hyperosmotic solutions. In these conditions [3H]taurine release also was abolished, suggesting an association of taurine efflux and cell swelling. Taurine release was also markedly increased 10- and 20-fold upon reduction of external osmolarity by 25 and 50%, respectively. Both, K(+)- and hyposmolarity-induced release were markedly inhibited by DIDS and quinidine. Total inhibition of the K(+)-evoked release was observed at 200 microM DIDS or 1 mM quinidine, whereas the drugs inhibited the hyposmolarity-evoked release by 50 and 68% respectively, at these concentrations. It is suggested that swelling is the signal for the K(+)-induced taurine release from rat retina.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1988

Substance P: the relationship between receptor distribution in rat lung and the capacity of substance P to stimulate vascular permeability.

The interaction of substance P (SP) with specific receptors in intact lung tissue was autoradiographically visualized, using slide-mounted tissue sections of rat lung tissue. SP receptors are highly concentrated in the central airways and are not detectable in peripheral bronchi, vessels, and alveoli. Within central airways, receptor distribution is most concentrated in the epithelium and small vessels in the lamina propria. Smooth muscle in airway or blood vessel walls expressed no detectable SP receptors. Immunohistochemical staining for SP revealed SP-containing nerves in the same areas where the receptors are localized. Displacement curves of SP bound to rat lung indicated that the C-terminal fragment was much more effective than the N-terminal fragment at competing for SP binding. Injection of 0.3 to 30 nmol/kg SP dramatically increased vascular permeability in the trachea and to a lesser extent in the hilus. Peripheral lung failed to respond to SP with increased vascular permeability unless toxic concentrations of SP were employed. SP increased the transudation of protein into the trachea within 5 min of injection, and the extravasated protein persisted through at least 2 h. Both SP and SP(3-11) were capable of stimulating increased vascular permeability, but SP(1-4) was inactive. SP caused mast cell degranulation as reflected in increased plasma histamine levels after SP or SP(3-11) injection, but SP(1-4) had no effect. In order to determine if histamine release caused by SP contributed to the vascular permeability response, the effects of H1 and H2 antihistamine treatment were studied.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Monte Carlo simulation of the response of a germanium detector for low-level spectrometry measurements using GEANT4.

In this paper, we will expose the work performed for the adaptation and refinement of the GEANT4 simulation toolkit (originally designed for Monte Carlo simulations in High-Energy Physics) in order to simulate Ge detectors in low-level gamma spectrometry. Special emphasis will be given to show and validate our own algorithms implemented in GEANT4 code for variance reduction and data analysis, that have been used for a quicker and precise efficiency calibration at different source-detector configurations of one of the low-level germanium gamma systems available in our laboratory.

Journal Article↗