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Biomedical subjects

A Castro

Publications and source records attributed to A Castro.

At least 253 records · Page 14Linked to original sources
PubMed1996

Evaluation of autosensing as an automatic means of maintaining a 2:1 sensing safety margin in an implanted pacemaker. Autosensing Investigation Team.

As intracardiac signal amplitudes fluctuate due to patient activity, drug intake, and other factors, it is imperative that an adequate sensing safety margin in an implanted pacemaker be used to compensate. We studied an investigational autosensing feature that automatically adjusts the device's sensitivity. Data were collected from 55 patients, with Intermedics model 292-03 or 294-03 pacemakers, upon inclusion of the study (Visit 1); 1 month postinclusion (Visit 2); 1 month, 1 day postinclusion (Visit 3); then 1 month, 2 days postinclusion (Visit 4). Atrial (N = 45) and/or ventricular (N = 54) thresholds were assessed at each visit; during Visit 2, myopotential tests were performed at two sensitivity settings. Autosensing was activated following Visit 1, then programmed on randomly at Visit 2 or Visit 3. From Visit 2-Visit 4, patients were monitored during daily activities (D), exercise (E), and sleep (S) with 24-hour Holter. With Autosensing on, atrial undersensing episodes were D = 33 (P > 0.2), and S = 28 (p < 0.05); ventricular undersensing episodes were D = 6 (p > 0.5). Ventricular oversensing episodes were S = 2; atrial oversensing episodes were S = 34 (p > 0.5), D = 2, and E = 3. Comparing Autosensing adjusted sensitivity with the recommended 2:1 safety margin, 4 patients (p = 0.15) experienced atrial myopotential oversensing, and 2 patients (p = 0.15) ventricular. No unanticipated clinical events occurred. Compared with the recommended 2:1 sensing safety margin, the Autosensing feature performed equal to manual programming in preventing episodes of under/oversensing, and was better for atrial undersensing during sleep. Autosensing obviates the need for periodic reprogramming of a fixed sensitivity value.

Action Potentials↗
PubMed1996

Detection of immunoglobulin G to a Sindbis-related virus by a membrane antigen enzyme immunoassay.

We determined the seroprevalence of a Sindbis-related virus isolated for the first time in 1975 from ticks in south-east Sicily and typed by Gresikova et al. in 1978. An indirect enzyme immunoassay based on viral membrane antigen for coating microtiter strips was used for the detection of immunoglobulin G to the Sindbis-related virus. The method appeared more sensitive than a similar enzyme immunoassay based on crude lysate antigen. Comparison of the results obtained from sera tested both by membrane antigen enzyme immunoassay and microneutralization test showed 92% agreement, while the agreement between microneutralization test and crude antigen enzyme immunoassay was 76%. An overall elevated seroprevalence (63.66%) was found in a population group living in and around the area of first isolation and seroprevalence in different age groups was also studied.

Adolescent↗
PubMed1996

[Pseudotumor cerebri secondary to cerebral venous defects not identified by magnetic resonance].

Pseudotumour cerebri is the name of a syndrome characterized by headache and papilloedema, with normal cerebral CT/MR studies and CSF with a high pressure and normal laboratory findings. We describe four patients who fulfilled the diagnostic criteria of this condition (including normal 0.5T MR studies). They all had cerebral angiograms showing minor abnormalities localized to the level of the superior longitudinal sinus. All improved on treatment with anticoagulants and steroids. In view of these findings we consider that in cases of pseudotumour cerebri without a clear aetiological factor, an angio MR study should be done, or if this technique is not available, a cerebral angiogram should be done, to exclude cerebral venous drainage defects.

Adult↗
PubMed1996

Lymphocyte adhesion to endothelium derived from human lymphoid tissue.

The development of an efficient immune response depends on the capacity of antigen-specific lymphocytes to migrate into secondary lymphoid organs. The first step in the process of lymphocyte extravasation involves lymphocyte binding to the vascular endothelium. Although several adhesion receptors have been implicated in the migration of lymphocytes to inflamed tissue, their role in the extravasation of these cells to normal lymphoid organs is not yet clearly established. The involvement of adhesion molecules in lymphocyte entrance to secondary lymphoid organs can be better assessed in an in vitro system using endothelial cells in culture. Here we report on the isolation and culture of a homogeneous population of adherent cells of endothelial origin derived from human tonsils (TEC) and on adhesion studies performed with these cells. Beginning from primary cultures of human tonsils, we isolated a population of cells that we show by FACScan analysis to present the intracellular endothelial cell marker Von Willebrand factor and LVAP-2, a surface molecule present in venules from lymphoid organs. The cells are negative for FDC, IDC and macrophage markers. They express ICAM-1, VCAM-1 and CD40 both constitutively and in inducible forms and are induced by IFN-gamma to express major histocompatibility complex class II antigens. As opposed to endothelial cells from human umbilical cord (HUVEC), they do not need to be activated by cytokines to bind lymphoid cells via VLA-4. The mAb HP2/1 directed to the integrin VLA-4 blocks adhesion of Ramos and Daudi cells to tumor necrosis factor alpha (TNF-alpha)-treated HUVEC and to untreated TEC but not of tonsil-derived MNC. On the other hand, an anti-VCAM-1 antibody that blocks adhesion of Ramos and Daudi cells to TNF-alpha-treated HUVEC, does not block adhesion of these cells to TEC, suggesting the presence on the tonsillar endothelial cells of a ligand for VLA-4 different from VCAM-1. We show here that this ligand is not fibronectin.

Antibodies↗
PubMed1996

[Ventricular nodal reentry tachycardia without ventricular dilatation: diagnosis and treatment by radiofrequency catheter ablation].

Bundle branch reentry tachycardia has been reported in patients with left ventricular dilatation, especially in those with dilated cardiomyopathy and aortic regurgitation. These patients show aspecific intraventricular conduction delay on the ECG and a prolonged H-V interval at the electrophysiologic study. We report 2 cases of bundle branch reentry tachycardia in patients without left ventricular enlargement to help the correct diagnosis of the arrhythmia. A correct diagnosis is very important because bundle branch reentry tachycardia is easily and safely treated by right bundle transcatheter radiofrequency ablation. We also report electrophysiologic characteristics we found during the study and the ablation: -contrary to the data reported in literature, at ventricular tachycardia starting, modifications of the V-V interval are not always preceded by similar variations in the H-H interval. -during right bundle radiofrequency ablation, a QRS narrowing may precede right bundle branch block appearance. This QRS normalisation should induce to continue and not to stop energy delivering.

Aged↗
PubMed1996

[Prevalence of the genotypes of the hepatitis C virus in Spanish drug addicts with chronic hepatitis C. Spanish Group for the Study of Viral Hepatitis in HIV Positive Patients].

The hepatitis C virus (HCV) shows a wide genetic variability. The different variants of HCV have been classified into 9 types and different subtypes. Some genotypes have a characteristic geographic distribution and seem to be associated with precise ways of contagion. Serum samples from 107 spanish patients with chronic hepatitis C were studied, which were distributed as follows: 88 parenteral drug addicts (PDA) and a control group of 19 subjects made up by 4 transfused, 5 probably sexually infected and 10 with unknown contagion source (sporadic cases). HCV typing was made by means of the PCR method and later hybridization analysis with complementary probes of different types and subtypes of HCV exposed on a smooth surface (Inno-LiPA). A total to 105 (98.4%) patients had their viruses genotypes. There was more than one genotype in the same subject (co-infection) in 43.8% of cases and co-infection 1a + 1b was the most common (82.7%). While not reaching a statistic significance, co-infections were more frequent in PDA (47.1%) than in the remaining patients (27.8%). In the infected patients with only one genotype, the most common genotype was 1a, both in PDA (22.9%) and in subjects with transfusional HCV, sexual or sporadic (38.9%). In decreasing frequency came genotypes 1b (13.3%) and 3a (11.4%). Other genotypes were very uncommon (2a and 4) or were absent (2b and 5) as unique infections. In conclusion, genotypes non-1b of HCV, mainly 1a and to a lesser extent 3a, are the most common in a spanish population made up mainly by young persons with risk antecedents for HIV infection, particularly PDA. Furthermore, co-infection with HCV genotypes is frequent in this population.

Adult↗