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Biomedical subjects

J Tejada

Publications and source records attributed to J Tejada.

At least 19 recordsLinked to original sources
PubMed2005

Quantum magnetic deflagration in acetate.

We report controlled ignition of magnetization reversal avalanches by surface acoustic waves in a single crystal of acetate. Our data show that the speed of the avalanche exhibits maxima on the magnetic field at the tunneling resonances of Mn(12). Combined with the evidence of magnetic deflagration in Mn(12) acetate, this suggests a novel physical phenomenon: deflagration assisted by quantum tunneling.

Journal Article↗
PubMed2005

Predictors of good outcome in medium to large spontaneous supratentorial intracerebral haemorrhages.

OBJECTIVE: To determine potential predictors of good outcome in primary medium to large intracerebral haemorrhages (ICH) which could be useful for selecting patients for surgical procedures. METHODS: Subjects were 138 patients with spontaneous hemispheric ICH >20 ml. They were non-surgically treated and were admitted consecutively to 15 hospitals within the first 12 hours of symptom onset (mean (SD), 5.8 (3.1) hours). Haematoma volume was measured on computed tomography (CT) at admission. Stroke severity was assessed by the Canadian stroke scale (CSS). Good outcome was defined as modified Rankin score < or =2 at three months. RESULTS: At the end of the follow up period, 45 patients (32.6%) had good outcome. Baseline stroke severity, systolic and diastolic blood pressure, body temperature, and acute phase reaction biochemical markers (ESR, C-reactive protein, fibrinogen, neutrophil count) were significantly associated with good outcome in bivariate analyses. Of the initial CT scan variables, intraventricular contamination, deep location, mass effect, and greater ICH volume were related to poor outcome. On multiple logistic regression analysis, cortical location of bleeding (odds ratio 3.79 (95% confidence interval 1.2 to 12.01); p = 0.023), high CSS score (OR 2.3 (1.6 to 3.1); p<0.0001), and low fibrinogen concentrations (OR 0.92 (0.87 to 0.97); p = 0.001) were independent predictors of good outcome. These three factors correctly classified 85% of patients. CONCLUSIONS: Good outcome in medium to large ICH can be predicted on admission by three readily assessable factors (CSS score, ICH location, and fibrinogen levels). These predictors may be helpful in selecting patients for surgical treatment.

Aged↗
PubMed2004

Early neurologic deterioration in intracerebral hemorrhage: predictors and associated factors.

OBJECTIVE: To identify potential predictors of and factors associated with early neurologic deterioration (END) in primary intracerebral hemorrhage (ICH). METHODS: Two hundred sixty-six patients with spontaneous supratentorial ICH admitted within 12 hours of stroke onset were investigated in a multicenter, prospective study. Sixty-one clinical, biochemical, and neuroimaging variables were registered on admission, and 37 clinical and neuroimaging variables were registered at 48 hours. The volumes of the ICH and peripheral edema on admission and at 48 hours were measured on CT scan. Stroke severity and functional outcome were evaluated with the Canadian Stroke Scale (CSS) and modified Rankin Scale. END was diagnosed when the CSS score decreased > or =1 points between admission and 48 hours. With use of logistic regression analyses, baseline variables that predicted END and factors measured after the early acute phase and associated with END were investigated. RESULTS: END occurred in 61 (22.9%) patients. Body temperature of >37.5 degrees C (odds ratio [OR] 24.5; 95% CI 4.8 to 125), neutrophil count (by 1,000-unit increase; OR 2.1; 95% CI 1.6 to 2.6), and serum fibrinogen levels of >523 mg/dL (OR 5.6; 95% CI 1.9 to 16.2) on admission were independent predictors of END. Among the factors recorded at 48 hours, early ICH growth (OR 4.3; 95% CI 1.3 to 14.5), intraventricular bleeding (OR 2.6; 95% CI 1.4 to 5.0), and highest systolic blood pressure (by 10-unit increase; OR 1.17; 95% CI 1.02 to 1.32) were associated with END in multivariate analyses. CONCLUSIONS: Clinical and biologic markers of the inflammatory reaction on admission are predictors of subsequent END, whereas early ICH growth, intraventricular bleeding, and high systolic blood pressure within 48 hours are factors associated with END in patients with spontaneous ICH.

Aged↗
PubMed2003

Does a relationship exist between carotid stenosis and lacunar infarction?

BACKGROUND AND PURPOSE: The presence of carotid stenosis (CS) in a patient with lacunar stroke is usually considered an indication of atherosclerosis and not directly related to the development of this infarction subtype. This study was designed to determine the relationship between CS and lacunar infarction (LI) and to assess the differences between single and multiple LIs. METHODS: We classified 330 patients with a first-ever cerebral infarction in the carotid territory into LI and non-LI (NLI) groups. In the LI group, patients with a single LI and those with multiple LIs were identified. In this last subgroup, 2 patterns were identified: 1 subtype with lacunar lesions distributed in both cerebral hemispheres, and another with lesions predominantly in 1 hemisphere. RESULTS: In the LI group, isolated CS was significantly more frequent on the homolateral side than on the contralateral side (odds ratio [OR], 5.5; 95% CI, 1.2 to 23; P=0.03). A significant relationship between the pattern of distribution of the infarctions in only 1 hemisphere and homolateral CS >70% was observed (OR, 4.4; 95% CI, 0.9 to 19; P=0.03). In a multivariate analysis, the following variables were found to predict unilateral multiple LI: left ventricular hypertrophy (OR, 9.1; 95% CI, 2.5 to 33.6) and homolateral CS >75% (OR, 14.4; 95% CI, 2.0 to 99.6). CONCLUSIONS: The significant incidence of isolated ipsilateral CS in patients with LI located in the carotid territory and the relationship of CS to ipsilateral multiple LI suggest that CS has a very important role in the development of LI.

Adult↗
PubMed2002

Trisetum paniceum (wild oats) pollen counts and aeroallergens in the ambient air of Madrid, Spain.

BACKGROUND: Madrid has a short but intensive grass pollen season, in which 79% of the total grass pollen load is released from the middle of May to the middle of June. The main objectives of this study were to quantify Trisetum paniceum (wild oats) aeroallergen in the atmosphere in Madrid from February to December 1996 and to correlate the aeroallergen concentrations with grass pollen counts. METHODS: Two different samplers were used to assess allergen exposure; a Burkard spore trap was used to collect pollen grains and a high-volume air sampler to collect airborne particles. A total of 182 air filters were collected and extracted in 1 ml of PBS and analysed by ELISA inhibition, using pooled sera from highly allergic individuals. RESULTS: T. paniceum aeroallergens were detected not only during the grass pollen season, but also before and after. Wild oat allergens had two main peaks of 1 and 1.9 microg/m(3), occurring in late May and July, respectively. The time series analysis established the existence of lags between the two main variables pollen counts and aeroallergen activity. Analysis of the data by the Spearman rank test and linear regression showed a weak correlation between grass allergenic activity and grass pollen counts (Spearman's rho = 0.29). Data obtained from time series analysis demonstrated that grass allergenic activity correlated strongly with current and 5-week-old grass pollen grain counts (r(2) = 0.73). CONCLUSIONS: Wild oats allergenic activity was detected during the entire year and not only during the pollen season. This fact is an important aspect to be considered in the clinical follow-up and treatment of grass pollen-sensitised patients in Madrid.

Air Pollutants↗
PubMed2001

Electrochemical synthesis of nanoparticles of magnetic mixed oxides of Sr-Fe and Sr-Co-Fe.

The electrochemical synthesis of magnetic nanoparticles of new Sr-Fe and Sr-Co-Fe oxides using an undivided cell with two Fe electrodes is reported in this work. These materials are collected as precipitates by electrolyzing acidic solutions containing mixtures of chlorides and nitrates of Sr2+, Fe3+ and, optionally, Co2+ at temperatures between 40 degrees C and 80 degrees C. Sr-Fe oxides are produced with energy costs lower than 2.7 kWh kg-1 in the pH range 2.0-6.0 at 50 mA cm-2, whereas Sr-Co-Fe oxides are obtained with a cost of 3.0 kWh kg-1 at pH 1.5 and at 35 mA cm-2. Inductively coupled plasma analysis of materials and energy dispersive X-ray microanalysis of single particles confirm that they are composed of pure mixed oxides, without metallic Fe impurities. All synthesized compounds crystallize as inverse cubic spinels, with structures similar to those of maghemite and magnetite. They are formed by round-shape nanoparticles with sizes lower than 50 nm, as observed by transmission electron microscopy. Thermal desorption spectrometry allows us to detect the presence of hydrogen and volatiles proceeding from water decomposition in their lattices. After heating the electrogenerated materials at 300 degrees C during 1 h to eliminate such species, Sr-Co-Fe oxides with similar magnetic properties to those of hard ferrites are obtained, but magnetic Sr-Fe oxides only behave as soft ferrites.

Cobalt↗
PubMed2000

Observation of quantum coherence in mesoscopic molecular magnets

By applying a transverse magnetic field B( perpendicular) of sufficient strength to the uniaxial molecular magnets Fe8 and Mn12, the tunneling splitting Delta(t) of their S = +/-10 magnetic ground states can be made large compared to perturbations such as hyperfine and dipolar interactions. We present evidence for such a Delta(t) from magnetic specific heat data below 1 K that is consistent with coherent quantum mechanical tunneling in a "mesoscopic" system under such conditions.

Journal Article↗
PubMed1999

Central motor conduction in hereditary motor and sensory neuropathy and hereditary spastic paraplegia.

Conduction of the central motor pathways (CMCT) by magnetic stimulation of the motor cortex (TMS) was performed in 17 patients with hereditary motor sensory neuropathy (HMSN) and 2 siblings with hereditary spastic paraplegia (HSP). CMCT was prolonged in two patients with HMSN I with associated pyramidal features and in two subjects with HMSN II without clinical pyramidal signs. CMCT may be abnormal in HMSN due to central motor pathways involvement or altered spinal excitability with increased synaptic delay. CMCT was normal in the upper limbs in patients with HSP but increased in the legs. Diagnostic yield of TMS increased in less disabled cases with HSP when selective conduction at the spinal level (C7-S1) was calculated. Abnormal spinal conduction in HSP is consistent with degeneration of the crossed corticospinal tracts at the thoracic level found in neuropathologic observations.

Adolescent↗
PubMed1998

Experimental and theoretical characterization of the high-affinity cation-binding site of the purple membrane.

Binding of Mn2+ or Mg2+ to the high-affinity site of the purple membrane from Halobacterium salinarium has been studied by superconducting quantum interference device magnetometry or by ab initio quantum mechanical calculations, respectively. The binding of Mn2+ cation, in a low-spin state, to the high-affinity site occurs through a major octahedral local symmetry character with a minor rhombic distortion and a coordination number of six. A molecular model of this binding site in the Schiff base vicinity is proposed. In this model, a Mg2+ cation interacts with one oxygen atom of the side chain of Asp85, with both oxygen atoms of Asp212 and with three water molecules. One of these water molecules is hydrogen bonded to both the nitrogen of the protonated Schiff base and the Asp85 oxygen. It could serve as a shuttle for the Schiff base proton to move to Asp85 in the L-M transition.

Aspartic Acid↗
PubMed1998

Multivariate time series analysis in nosocomial infection surveillance: a case study.

BACKGROUND: The present study describes the use of time series analysis in the evaluation of the incidence of nosocomial infection. The main hypothesis analysed was that monthly occurrence of nosocomial infection in a hospital may be related to work-related factors such as the control and training of personnel imposed by a surveillance system, strikes supported by medical personnel and movement of personnel. Time series analysis was used to quantify, model and statistically evaluate these interventions. METHODS: The data employed (March 1982-December 1990) were supplied by the nosocomial infection surveillance system of a primary-care general hospital. The monthly time series incidence of nosocomial infections (measured as percentage cumulative incidence) was analysed by curve fitting, autoregressive, integrated and moving average (ARIMA) modelling (Box-Jenkins) and intervention and dynamic regression analysis. RESULTS: The imposed control and training of personnel by the surveillance system was associated with a 3.63% decrease in the accumulated monthly incidence of nosocomial infection from 7.82% to a baseline level of 4.19%. There was a strong indication that an increase of infection incidence of 4.34% corresponded to a medical strike. This increase was maintained over the following months raising the baseline level to 4.84%. An increase of 0.18% was associated with each new nursing contract. Evidence was obtained for the possible relationship between incidence of nosocomial infection and vacation periods. CONCLUSIONS: The results suggest the need for strict control of the activities of hospital personnel and for the adoption of certain preventative measures during vacation periods to avoid an undesirable increase in the incidence of nosocomial infections.

Case-Control Studies↗
PubMed1997

[Association of plasmapheresis and high doses of intravenous immunoglobulins in the treatment of myasthenia gravis].

INTRODUCTION: In the past decade good therapeutic results have been reported with high dosage of intravenous immunoglobulins (Ig i.v.) in various autoimmune disorders, including myasthenia gravis (MG). Plasmapheresis has been used successfully in this disorder on indications similar to those described for the use of Ig i.v.. We have used sequential treatment of plasmapheresis followed by high doses of intravenous gammaglobulin in MG, seeking complementary benefits from the two kinds of treatment. MATERIAL AND METHODS: The sample included 10 patients with MG (7 of Osserman's grade II-B, 1 of II-A and 2 of III). We began treatment with plasmapheresis, and then continued with an i.v. infusion of Ig at a dose of 400 mg/Kg/day for 5 days. To evaluate the response to treatment, we used the classification system for muscle weakness based on the Virginia University modification of Osserman's grades, on the clinical involvement grade scales and on functional activity. RESULTS: All patients showed statistically significant improvement of the parameters studied. Improvement started between the first and sixth day, following administration of Ig i.v. and persisted for the following 16 weeks. CONCLUSIONS: We consider that combined treatment with plasmapheresis and Ig i.v. may synergically potentiate the immunological effects since they have different mechanisms of action. The indication for this is limited to serious clinical conditions resistant to other treatment, to speed recovery.

Adult↗