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L López

Publications and source records attributed to L López.

At least 19 recordsLinked to original sources
PubMed2002

Vibrational resonance in a noise-induced structure.

We report on the effect of vibrational resonance in a spatially extended system of coupled noisy oscillators under the action of two periodic forces, a low-frequency one (signal) and a high-frequency one (carrier). Vibrational resonance manifests itself in the fact that for optimally selected values of high-frequency force amplitude, the response of the system to a low-frequency signal is optimal. This phenomenon is a synthesis of two effects, a noise-induced phase transition leading to bistability, and a conventional vibrational resonance, resulting in the optimization of signal processing. Numerical simulations, which demonstrate this effect for an extended system, can be understood by means of a zero-dimensional "effective" model. The behavior of this "effective" model is also confirmed by an experimental realization of an electronic circuit.

Journal Article↗
PubMed2002

Hydrogen peroxide-induced DNA damage and DNA repair in lymphocytes from malnourished children.

The aim of this study was to assess DNA repair capacity in lymphocytes of children with protein calorie malnutrition using the single-cell gel electrophoresis (comet) assay. Repair capacity was assessed by estimating the relative decrease of DNA migration length 5, 15, 30, and 60 min after hydrogen peroxide treatment, in three groups of children: well-nourished (WN), well-nourished infected (WN-I), and malnourished infected (MN-I). In addition, the DNA migration length was evaluated in all groups before and after peroxide treatment. Comparison of mean migration lengths observed in WN and WN-I children showed significant differences at all times tested; between WN-I and MN-I differences were also observed, except after hydrogen peroxide exposure. This implies that lymphocytes of WN-I and MN-I children were equally sensitive to hydrogen peroxide. Nevertheless, the MN-I group clearly shows the greatest overall percentage of damaged cells at all times tested. In relation to repair capacity, at 5 min it was approximately 30% in both groups of well-nourished children, but only 20% in MN-I; 15 min after exposure, repair capacity increased to 51% in well-nourished children but only to 31% in MN-I; and at 60 min this capacity increased to 82% in well-nourished but only to 55% in MN-I. These data indicate that lymphocytes of malnourished children show a decreased capacity to repair hydrogen peroxide-induced DNA damage compared to that of well-nourished controls. This reflects that only malnutrition is associated with decreased DNA repair capacity. Additionally, the data confirm that severe infection and malnutrition are two factors clearly associated with increased DNA damage.

Case-Control Studies↗
PubMed2002

Comparison between two static autoregulation evaluation methods.

Cerebral static autoregulation (AR) was evaluated at bedside in 14 severely head injured patients. 16 investigations were performed. Cerebral perfusion pressure (CPP) was increased by infusing vasopressors during one hour, and registered every 2-5 minutes. CBF was simultaneously estimated by: 1) middle cerebral artery mean flow velocity (FV) monitoring with Transcranial Doppler (TDC), and 2) the reciprocal of arteriovenous oxygen content difference, calculated from basal and hypertensive arterial and jugular bulb blood samples. AR assessment: For TCD results, linear regression method was used, studying two pairs of variables: a) %FV-CPP (the regression slope was the main AR value adopted) and b) % cerebrovascular resistance (CVR)-%CPP. For the AVDO2 method, autoregulation was considered preserved if estimated % delta CBF/delta PPE < 1%/mm Hg. TCD method clearly defined three groups. Group 1 and 2 (8 and 5 investigations) were considered as two grades of preserved AR, and the third one (3 cases) as impaired AR. AVDO2 method: 12 studies were evaluated. 10 showed preserved AR, and 2 impaired AR. There was coincidence of results from both methods in 10 out of 12 studies. (0.83).

Adolescent↗
PubMed2002

Susceptibility patterns of bacteria causing community-acquired respiratory infections in Spain: the SAUCE project.

Multicentre surveillance is essential in order to monitor the prevalence of certain resistance phenotypes and to identify rapidly the emergence of new ones. However, many surveillance studies are based either on a relatively small number of isolates from a single country, or on a large number of isolates from many different countries and so are not equally meaningful. Extensive national multicentre surveillance would provide a more reliable strategy for assessing the extent of antimicrobial resistance in individual countries. This article describes Spanish experience with the surveillance network SAUCE, and summarizes the main results on antimicrobial resistance in the three key bacterial pathogens involved in community-acquired respiratory tract infections in Spain: Streptococcus pneumoniae, Haemophilus influenzae and Streptococcus pyogenes.

Anti-Bacterial Agents↗
PubMed2002

Susceptibility to DNA damage induced by antibiotics in lymphocytes from malnourished children.

Infectious disease and malnutrition in children are public health problems in developing countries. Malnutrition is associated with higher levels of DNA damage, and this increased damage could be due to different factors, including the possibility that cells from malnourished children could be more susceptible to environmental damage. The aim of the present study was to evaluate the susceptibility of lymphocytes from malnourished children to DNA damage induced by antibiotics by using the comet assay. The same group of malnourished infected children were studied before and after a treatment period, and compared to a group of well-nourished infected children. Results showed that before and after drug treatment, tail length migration was two times greater in malnourished than in well-nourished children. The proportion of cells with high damage was also increased in malnourished children. Additionally in well-nourished and malnourished children, a cell subpopulation (non-damaged cells) more resistant to DNA damage induced by antibiotics was observed; this was more prevalent in the well-nourished children. Meanwhile, in malnourished children, a cell population seems to be more susceptible and reaches higher levels of DNA damage. This might help explain the impaired immune response observed in malnourished children. The increased DNA migration and the increased proportion of cells with higher levels of damage seem to indicate that malnourished children are more susceptible to DNA damage induced by drugs.

Anti-Bacterial Agents↗
PubMed2002

[Anterior sacral meningocele with Currarino's syndrome: report of two cases].

The anterior sacral meningocele is the congenital hernia of the thecal sac into the pelvis through a bone defect of the anterior wall of the sacrum. The association of anorectal anomaly, anterior sacral defect and presacral mass, known as Currarino's triad, can be diagnosed during the first decade of life in the eighty per cent of the cases However, in the incomplete syndrome, the symptoms appear in adults. In order to avoid late complications and due to the clear genetic origin of this uncommon pathology, the investigation of the family is of paramount importance for the early diagnosis and treatment. We review the literature and add two cases of anterior sacral meningocele with rectal fistula and incomplete Currarino's syndrome. In one of the cases the pathology is also present in another member of the same family and is complicated with meningitis. The importance of early diagnosis and treatment of these malformations and the need for fammily genetic investigation are discussed.

Adult↗
PubMed2002

[Retreatment with interferon plus ribavirin in chronic hepatitis C patients with genotype 1 who had no response or a relapse with a previous interferon treatment. Long term follow-up].

The aims of this study were twofold: i) to evaluate the sustained response rate at 6 months, at 12 months and at the end of the follow-up [(46.39 +/- 9.74 months) (range: 6-60 months)] in patients with chronic hepatitis C retreated with interferon-a (IFN-a) plus ribavirin for 6 months (group A), 12 months (group B), in patients with relapse and those with no response to a previous course of monotherapy with IFN-a; and ii) to evaluate changes in the histological liver lesion. One hundred and four patients (100 with genotype 1 and four without), 44 with relapse and 60 non-responders, were included. A total of 20.2% of the patients were excluded because of side effects. Fifty percent of the relapsing patients with genotype 1 showed a sustained response. The sustained response rate was higher in group B than in group A, whereas the rate for the relapsing patients was lower in group B than in group A (13/20 vs. 5/16; 7.2% vs. 61.5%; p <0.09 and p <0.009, respectively). However, 9.3% of the non-responding patients showed a sustained response (A/B: 2/2). The relapsing patients who had a genotype other than 1 showed a sustained response. The sustained response rate was constant throughout the follow-up, except in relapsing patients from group A (the late relapse rate was 28.6%). The viral load was not related to the response. The grade and stage of the histological lesion improved in patients with sustained response (n=20) and in one-third of the non-responding patients (n=45) (p <0.0001 and p <0.0001). IFN in combination with ribavirin was more effective in relapsing patients with genotype 1 at 12 months than in those at 6 months of treatment, whereas the effectiveness in non-responding patients was low. The sustained response evaluation at 6 months was reliable, except in relapsing patients with 6 months of treatment. The histological lesion improved significantly with combination antiviral therapy.

Adult↗
PubMed2001

[Cushing's disease in the 90's: a review].

Since 1932 when Cushing's disease has been described, several important advances have been made in diagnosis and management. However several points remain obscure and there is no general agreement among authors. An accurate biological diagnosis is one of the difficulties found when we face a patient with hypercortisolism. In addition, corticotropin dependent syndrome should be distinguished from the independent one, as well as identifying the source of ACTH hypersecretion. The main problem in Cushing's disease is to localise the secreting adenoma and at the moment there is not any diagnostic method with absolute sensibility and specificity. Magnetic Resonance Imaging shows a sensibility of 77% and 87% especificity; inferior petrosal sinus sampling may help in localising the side, where the adenoma lies, although an appropriate technique is mandatory. New developing techniques, such as intraoperative doppler and assessment of ACTH levels in the peripituitary veins may help us in localising the source of ACTH hypersecretion. Sometimes the adenoma cannot be identified and a surgical exploration of the pituitary is required. If an adenoma is found, a 89% probility of curation has been reported; on the contrary, incomplete tumor removal, no tumor found at surgery, or the presence of the so-called corticotrop hyperplasia where followed of bad results and may explain the failed surgery. Then, hypofisectomy, hemi-hypofisectomy, radiotherapy, photon knife or gamma knife, may be of help in the control of this condition. We reviewed the recent literature and analysed the diagnostic strategies and teatments currently available for this illness. In addition we propose an algohritm for diagnosis and treatment and analyze our results in a consecutive series of 38 patients.

Adrenocorticotropic Hormone↗
PubMed2001

CD45RA and CD45RO isoforms in infected malnourished and infected well-nourished children.

The aim of this study was to determine if the distribution in vivo of CD4(+)CD45RA(+)/CD45RO(-) (naive), CD4(+)CD45RA(+)/CD45RO(+) (Ddull) and CD4(+)CD45RO(+) (memory) lymphocytes differs in malnourished infected and well-nourished infected children. The expression of CD45RA (naive) and CD45RO (memory) antigens on CD4(+) lymphocytes was analysed by flow cytometry in a prospectively followed cohort of 15 malnourished infected, 12 well-nourished infected and 10 well-nourished uninfected children. Malnourished infected children showed higher fractions of Ddull cells (11.4 +/- 0.7%) and lower fractions of memory cells (20.3 +/- 1.7%) than the well-nourished infected group (8.8 +/- 0.8 and 28.1 +/- 1.8%, respectively). Well-nourished infected children showed increased percentages of memory cells, an expected response to infection. Impairment of the transition switch to the CD45 isoforms in malnourished children may explain these findings, and may be one of the mechanisms involved in immunodeficiency in these children.

Bacterial Infections↗
PubMed2001

Comparative effects of amlodipine and nifedipine GITS during treatment and after missing two doses.

OBJECTIVE: To compare the antihypertensive efficacy of amlodipine and nifedipine gastrointestinal therapeutic system (GITS) measured by office and ambulatory blood pressure monitoring (ABPM) during treatment and, after patients have missed two doses. METHOD: After a single blind run-in 4-week placebo period, 58 patients were randomly allocated to amlodipine (5mg/daily, n=30) or nifedipine GITS (30mg/daily; n=28) in a double-blind, double dummy fashion. Patients received active medication for 4 weeks. Then, to simulate failure of compliance, patients received two single blinded doses of placebo. Ambulatory blood pressure monitoring was carried out at the end of run-in placebo phase, the first day, the last day of active treatment and up to 72h after the last active dose. RESULTS: Diastolic blood pressure was controlled in 61.9% patients on amlodipine and 52.9% on nifedipine GITS. Reductions in blood pressure were similar in both groups. ABPM showed significant reduction in blood pressure from the first day in the nifedipine GITS group, while amlodipine group had marginal effect. Peak reduction in systolic/diastolic blood pressure was 26/15mmHg at 5-6h after ingestion of amlodipine tablets. The trough reduction was 22/13mmHg; with a trough-to-peak ratio of 84.61% for systolic and 86.67% for diastolic blood pressure. Peak reduction in systolic/diastolic blood pressure with nifedipine GITS was 19/15mmHg and the trough reduction was 21/17mmHg, giving a trough-to-peak ratio of 100% for both systolic and diastolic blood pressure. When patients received placebo after 4 weeks of active treatment, simulating a compliance failure, amlodipine maintained reduction in systolic and diastolic blood pressure for at least up to 72h after the last active dose, maintaining 57.71% of the effect for systolic blood pressure and 60.00% for diastolic blood pressure. In contrast, nifedipine GITS effect was rapidly lost during this study phase, with a reduction in systolic and diastolic blood pressure of only 14-16%, 72h after the last active dose. CONCLUSION: This study showed that amlodipine and nifedipine GITS reduce blood pressure to about the same extent during chronic treatment. In the case of compliance failure, such as missing one or two doses, amlodipine maintained significant and important antihypertensive effect with the trough-to-peak ratio still over 50% 72h after the last active dose. On the other hand, the coverage of nifedipine GITS was limited to about 36h after the last active dose.

Amlodipine↗
PubMed2001

Stenting as first option for endovascular treatment of malignant superior vena cava syndrome.

OBJECTIVE: Endoprostheses were inserted in cancer patients with superior vena cava syndrome to assess their effectiveness as first-choice, initial treatment for relief of symptoms. SUBJECTS AND METHODS: Wallstent prostheses (n = 73) of various lengths (5-14 cm; median, 7 cm) and diameters (10-16 mm; median, 16 mm) were inserted in 52 cancer patients (51 men, 1 woman; age range, 44-78 years; mean, 63 years) who were diagnosed and confirmed by cavography or phlebography as having superior vena cava syndrome. A single stent was sufficient in 37 patients, two stents were required in 11, three stents in two, and four stents in another two patients. Contraindications for the procedure were severe cardiopathy or coagulopathy. RESULTS: Resolution of symptoms was achieved in all patients within 72 hr. At follow-up, six obstructions, one partial migration to the right atrium, two incorrect placements, and four stent "shortenings" were noted. All were successfully resolved by repeated stenting. Symptom-free survival ranged from 2 days to 17 months (mean, 6.4 months). At the time of this writing, eight patients are alive and have patent stents. The rest have died from their cancer. CONCLUSION: The Wallstent vascular endoprosthesis is an effective initial treatment in superior vena cava syndrome of neoplastic origin. Morbidity and complications are minimal. Clinical relief of symptoms is rapid; therefore, the Wallstent endoprosthesis is highly recommended as the first choice for palliative treatment of superior vena cava syndrome, especially because the clinical decision for subsequent chemotherapy or radiotherapy or surgery is not in any way prejudiced.

Adult↗
PubMed2001

Combined effect of context change and retention interval on interference in causality judgments.

Four experiments studied the effects of context change and retention interval on retroactive interference in human causal learning. Experiment 1 found evidence of retroactive interference. Experiment 2 found that either a 48-hr retention interval or a change in the context after the interference treatment decreased retroactive interference. An interaction between context change and retention interval effects was also found, eclipsing the context change effect after the 48-hr retention interval. Experiments 3 and 4 found additivity between context change and retention interval effects when participants were remained of the difference between physical contexts before the test, independently of whether the context change involved a return to the original acquisition context. These results add to the evidence suggesting that spontaneous forgetting is caused by a change in either the physical or the temporal contexts where information is acquired.

Adolescent↗
PubMed2001

[Acute bilateral sensorineural hearing loss caused by immuno-mediated inner ear disease].

The audiovestibular system can be affected by an immunologic etiology. The immune-mediated inner ear disease (IMIED) is a syndrome that includes rapidly progressive sensorineural hearing loss, vertigo and tinnitus, which occurs as a primary disorder or complicates certain autoimmune systemic conditions. However, if treated promptly with immunosuppression, the audiological sequel of IMIED may be avoided. We present a 28 year old female patient, who after rhinitis and mioarthralgias developed a vestibular syndrome. A week later she experienced bilateral hearing loss that progressed to deafness in 72 hours. The examination revealed horizontal and torsional nystagmus, a disrupted vestibulo-ocular reflex and vertigo with the positional changes. Laboratory data were normal except for eritrosedimentation rate (75 mm/1 hour). The autoantibodies usually present in rheumatologic autoimmune systemic diseases were negative. The antibodies to the 68-kD antigen found in the inner ear were positive. The chest x-ray and sinus x-ray were normal. The head magnetic resonance imaging with gadolinium and ear computed tomography were normal. Cerebrospinal fluid studies showed normal findings. With the possible diagnosis of IMIED we started early treatment with corticosteroids, with improvement in auditory and vestibular function thereafter. We highlight the early recognition of IMIED as a differential diagnosis in patients with acute bilateral hearing loss, because prompt treatment with immunosuppression might have a positive effect on auditory function recovery.

Acute Disease↗
PubMed2001

Cytochrome oxidase activity in splanchnic organs of portal hypertensive rats.

OBJECTIVE: Portal hypertension is characterized by hyperdynamic splanchnic circulation associated with the development of portosystemic portal collateral circulation. Since blood flow regulation mechanisms in the splanchnic organs can be metabolic, its metabolic capacity has been studied using the mitochondrial enzyme cytochrome C oxidase as histochemical marker. METHOD: Cytochrome oxidase was quantified with a histochemical technique in the liver, pancreas and small bowel of Wistar rats in the control group (n = 8) and in rats with portal hypertension by triple stenosing ligation of the portal vein (n = 9) at 28 days of evolution. RESULTS: All rats with portal hypertension develop portosystemic collateral circulation. In these animals, cytochrome oxidase activity increases (p < 0.01) in the liver (left lateral lobe, periportal zone: 91.81 +/- 5.18 vs. 86.03 +/- 2.82) exocrine pancreas (125.6 +/- 7.25 vs 117.57 +/- 6.43; p < 0.05) as well as in the mucosa (crypts) and duodenum serosa, jejunum and ileum while it decreases in the pericentral zone of the hepatic acinus and intestinal villi. CONCLUSION: Cytochrome oxidase is considered an endogenous marker of local tissular metabolic capacity, so that its increased activity in the small bowel mucosa, crypts, exocrine pancreas and visceral peritoneum may be a metabolic factor that induces splanchnic hyperdynamic circulation in short-term portal hypertensive rats.

Animals↗
PubMed2001

[Disinfection treatment for lettuces (Lactuca sativa) and strawberries (Fragatia Chiloensis)].

The disinfection of vegetables and fruits is a treatment applied in order to reduce their natural contamination or processes to the product along the different steps of the food chain until its consumption. In the present work the effect of two disinfectants products was studied: grapefruit seed extract (400 ppm) for 10 min and peracetic acid (2000 ppm) for 1 min (action times assayed according to the manufacturer recommendations) and other additional times. The germicidal action was carried out against the natural contaminants of lettuces and strawberries, through the determination of the germicidal efficiency (%). Treated and untreated strawberries were also evaluated for flavor changes through a sensorial difference test, triangular test. None of the assayed products reached the 99.999% destruction of the natural contaminants according to the Chambers test. Peracetic acid was the most effective disinfectant, reaching the highest destruction percentages at a time lower than that for grapefruit seed extract. Sensory analysis showed no significant differences (p = .05) between strawberries with and without disinfection treatments, at the conditions suggested by the manufacturer.

Bacteria↗
PubMed2000

The vanadium isotopic constitution of petroleum asphaltenes: La Luna Formation (Venezuela).

High-resolution mass spectrometry indicates that the isotopic abundance of 50V of the Late Cretaceous La Luna petroleum asphaltenes of marine origin (highly enriched with V > 2000 ppm) is higher by about 3.5% than that of the inorganic source (VOSO4 x 5H2O, Merck). We propose that the difference in the 50V/51V values between the La Luna petroleum asphaltenes and the inorganic source can be best ascribed to the biological processing of seawater vanadium. The fact that the V isotopic compositions of petroleum asphaltenes vary over a very narrow range (2.46-2.52) suggests essentially the same (or similar) and fixed biological source of vanadium.

Hydrocarbons↗