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Biomedical subjects

W Alvarez

Publications and source records attributed to W Alvarez.

14 recordsLinked to original sources
PubMed2006

[Control of hypertension in nursing homes].

In a cross sectional study we determined prevalence of hypertension among institutionalized old subjects. Prevalence of hypertension was 69%. Among detected hypertensive patients, 76% received an antihypertensive drug treatment. 61% of the declared hypertensive patients and 80% of the treated hypertensive patients had their blood pressure controlled. The general practitioners should better detect and treat this common geriatric problem associated with a high comorbidity.

Aged, 80 and over↗
PubMed2000

Iron overload in cirrhosis-HFE genotypes and outcome after liver transplantation.

Previously, we found appreciable hepatic iron deposition in one third of our patients undergoing liver transplantation (LTx) with approximately 10% of cases having quantifiable iron in the range of that seen in hereditary hemochromatosis (HHC). The aim of this study was to compare clinical outcome in liver transplant patients with and without iron overload. We also sought to determine the prevalence of HFE mutations in liver transplant patients with iron overload. Of 456 consecutive liver transplants, 41 explants had an hepatic iron index (HII) greater than 1.9, and these cases were compared to 41 matched liver transplant recipients without increased hepatic iron. Posttransplantation complications, along with patient and graft survival were monitored. HFE gene testing was performed using DNA-based techniques. Kaplan-Meier 5-year patient survival after LTx was significantly lower in cases with hepatic iron overload compared to matched controls without iron excess (48% vs. 77%; P =.045). Fatal infections (especially fungal) were more common in patients with iron overload (24% vs. 7%; P =.03). Of the 41 patients with a liver explant HII greater than 1.9, only 4 were C282Y homozygotes. Patients with severe hepatic explant iron overload undergoing LTx have a reduced survival compared to liver transplant recipients without explant iron excess. The reduced survival was attributable mainly to fatal bacterial and fungal infections. Despite the iron overload, HFE gene mutations were uncommon in patients with hepatic explant hemosiderosis.

Female↗
PubMed1996

[The applicability and diagnostic effectiveness of transjugular liver biopsy].

BACKGROUND: The aim of this study was to evaluate the applicability, the diagnostic profitability and the incidence of complications associated with tranjugular liver biopsy associated with the measurement of the hepatic venous pressure gradient (HVPG). PATIENTS AND METHODS: The clinical histories of 829 consecutive patients in whom transjugular liver biopsy was performed from 1982 to 1993 were reviewed. The diagnostic value of the sample obtained was evaluated in all the patients and the HVPG determined. Moreover, the size of the greatest fragment obtained during biopsy was also determined. RESULTS: Material for histologic study was obtained in 95% of the cases. In 70% the biopsy was diagnostic, in 11% it provided data contributing to diagnosis and in 19% it was not useful. Potentially severe complications were presented in 0.8% of cases being fatal in one (0.1%). The obtention of a fragment of small size was significantly associated with the presence of disease with marked fibrosis and high HVPG. A HVPG > 10 mmHg in patients with a suspicion of liver disease had a sensibility of 92% and a specificity of 63% for the diagnosis of hepatic cirrhosis. In 83% of patients with a GPVH > 10 mmHg in whom the biopsy was not useful, the diagnosis of hepatic cirrhosis was performed by other methods. CONCLUSIONS: Transjugular biopsy in a safe, effective diagnostic method in patients with severe coagulation disorders. The appearance of the material obtained and the HVPG provide useful information for diagnosis although the biopsy is not diagnostic.

Biopsy, Needle↗
PubMed1995

Short- and long-term effect of oral salbutamol on growth hormone secretion in prepubertal asthmatic children.

Salbutamol, a beta 2-adrenergic agonist, is being extensively used in Venezuela as a brochodilator in the treatment of asthma in children. Previous reports have shown oral salbutamol either to inhibit or not to affect growth hormone (GH) secretion. We evaluated the effect of oral salbutamol (0.1 mg/kg every 6 hours for 3 months) on GH secretion in eight prepubertal short children with mild asthma. Levels of GH during sleep (samples taken every 30 minutes from 9 PM to 6 AM) and after GH-releasing hormone ([GHRH] 1 microgram/kg intravenously [IV]) were measured before, at 24 hours, and at 3 months of salbutamol treatment. Overnight integrated concentrations of GH and peak GH levels following GHRH diminished significantly after 24 hours of salbutamol therapy (from 4.5 +/- 1.3 to 3.4 +/- 0.8 micrograms/L and from 46.6 +/- 47.3 to 16.2 +/- 7.9 micrograms/L, respectively, P < .05). However, GH levels after 3 months of salbutamol were not different from basal levels (4.5 +/- 1.3 v 5.1 +/- 5.1 +/- 2.9 micrograms/L during the overnight studies and 46.6 +/- 47.3 v 37.8 +/- 30.4 micrograms/L after GHRH). Our data suggest an inhibition of both spontaneous and stimulated GH secretion following short-term oral salbutamol ingestion, but this suppressive effect is not maintained with its long-term use.

Administration, Oral↗
PubMed1992

Tektite-bearing, deep-water clastic unit at the Cretaceous-Tertiary boundary in northeastern Mexico.

The hypothesis of Cretaceous-Tertiary (K-T) boundary impact on Yucatán, Mexico, predicts that nearby sites should show evidence of proximal impact ejecta and disturbance by giant waves. An outcrop along the Arroyo el Mimbral in northeastern Mexico contains a layered clastic unit up to 3 m thick that interrupts a biostratigraphically complete pelagic-marl sequence deposited at more than 400 m water depth. The marls were found to be unsuitable for determining magnetostratigraphy, but foraminiferal biostratigraphy places the clastic unit precisely at the K-T boundary. We interpret this clastic unit as the deposit of a megawave or tsunami produced by an extraterrestrial impact. The clastic unit comprises three main subunits. (1) The basal "spherule bed" contains glass in the form of tektites and microtektites, glass spherules replaced by chlorite-smectite and calcite, and quartz grains showing probable shock features. This bed is interpreted as a channelized deposit of proximal ejecta. (2) A set of lenticular, massive, graded "laminated beds" contains intraclasts and abundant plant debris, and may be the result of megawave backwash that carried coarse debris from shallow parts of the continental margin into deeper water. (3) At the top, several thin "ripple beds" composed of fine sand are separated by clay drapes; they are interpreted as deposits of oscillating currents, perhaps a seiche. An iridium anomaly (921 +/- 23 pg/g) is observed at the top of the ripple beds. Our observations at the Mimbral locality support the hypothesis of a K-T impact on nearby Yucatán.

Animals↗
PubMed1992

Proximal impact deposits at the Cretaceous-Tertiary boundary in the Gulf of Mexico: a restudy of DSDP Leg 77 Sites 536 and 540.

Restudy of Deep Sea Drilling Project Sites 536 and 540 in the southeast Gulf of Mexico gives evidence for a giant wave at Cretaceous-Tertiary boundary time. Five units are recognized: (1) Cenomanian limestone underlies a hiatus in which the five highest Cretaceous stages are missing, possibly because of catastrophic K-T erosion. (2) Pebbly mudstone, 45 m thick, represents a submarine landslide possibly of K-T age. (3) Current-bedded sandstone, more than 2.5 m thick, contains anomalous iridium, tektite glass, and shocked quartz; it is interpreted as ejecta from a nearby impact crater, reworked on the deep-sea floor by the resulting tsunami. (4) A 50-cm interval of calcareous mudstone containing small Cretaceous planktic foraminifera and the Ir peak is interpreted as the silt-size fraction of the Cretaceous material suspended by the impact-generated wave. (5) Calcareous mudstone with basal Tertiary forams and the uppermost tail of the Ir anomaly overlies the disturbed interval, dating the impact and wave event as K-T boundary age. Like Beloc in Haiti and Mimbral in Mexico, Sites 536 and 540 are consistent with a large K-T age impact at the nearby Chicxulub crater.

Animals↗
PubMed1990

Iridium profile for 10 million years across the Cretaceous-Tertiary boundary at Gubbio (Italy).

The iridium anomaly at the Cretaceous-Tertiary (KT) boundary was discovered in the pelagic limestone sequence at Gubbio on the basis of 12 samples analyzed by neutron activation analysis (NAA) and was interpreted as indicating impact of a large extraterrestrial object at exactly the time of the KT mass extinction. Continuing controversy over the shape of the Ir profile at the Gubbio KT boundary and its interpretation called for a more detailed follow-up study. Analysis of a 57-meter-thick, 10-million-year-old part of the Gubbio sequence using improved NAA techniques revealed that there is only one Ir anomaly at the KT boundary, but this anomaly shows an intricate fine structure, the origin of which cannot yet be entirely explained. The KT Ir anomaly peaks in a 1-centimeter-thick clay layer, where average Ir concentration is 3000 parts per trillion (ppt); this peak is flanked by tails with Ir concentrations of 20 to 80 ppt that rise above a background of 12 to 13 ppt. The fine structure of the tails is probably due in part to lateral reworking, diffusion, burrowing, and perhaps Milankovitch cyclicity.

Biological Evolution↗
PubMed1989

Topographic mapping and habituation of event related EEG alpha band desynchronization.

Habituation of alpha wave suppression to an external auditory signal was studied using computer assisted EEG quantification procedures. Topographic maps of alpha amplitude were constructed from multiple electrode placements for seven healthy adults. The EEG preceding and following 10 standard or habituating stimuli, and 1 novel or sensitizing stimulus, was spectrally analyzed and stored as color amplitude maps. Individual and group composite maps were read-out and comparisons in alpha amplitude were made across stimulus conditions. The initial standard stimulus produced a sharp reduction in alpha amplitude whereas the 10th trial had no appreciable effect on spontaneous EEG activity. The novel stimulus immediately restored alpha desynchronization. The colormaps permitted easy visualization and quantification of the process of habituation and sensitization of the alpha rhythm.

Adult↗
PubMed1980

Signs and symptoms of posttraumatic stress disorder.

The new diagnostic nomenclature of the American Psychiatric Association (DSM-III) provides well-described categories of stress response syndromes that were not included in the previous nosology. The signs and symptoms of these syndromes used in the descriptive statements have been understood largely in terms of field studies of nonpatient populations and clinical descriptive and impressionistic studies of patient populations. We report quantitative data from the study of a population with post-traumatic stress disorder. The results confirm clinical impressions of the importance and wide prevalence of episodes of intrusive ideas and feelings in states of distress precipitated by serious life events.

Adult↗
PubMed1980

News of risk for early heart disease as a stressful event.

Modern prevention includes efforts to reduce the frequency of coronary heart disease by screening populations for certain risk factors, and then advising persons high in risk on how to alter their vulnerability. But what is the effect of telling persons they are at increased risk for such threatening events as heart attacks? Without such information they may not be motivated to change such behavior as cigarette smoking or to comply with blood pressure reducing regimens. With it, worry about their health status may increase. The present study examined such variables in 575 men with no previous symptoms of heart disease who were informed of increased risk and followed for three years. The men were divided at random into two groups of equal size. A Special Intervention group received repeated reminders of risk and procedures for cessation of smoking, reduction of blood pressure, and dietary alteration to lower serum cholesterol. A contrast group received usual medical care, as they saw fit, in response to the news of risk. At yearly intervals, scores on level of subjective distress, avoidance, and coping were obtained. One-third of the men reported intrusive or avoidance experiences one year after receipt of the news of increased risk. The Special Intervention group, with its more frequent reminders, had significantly higher levels of intrusive ideas and feelings about the news of risk than the Usual Care group, and significantly higher levels of coping experiences.

Adult↗
PubMed1979

Impact of Event Scale: a measure of subjective stress.

Clinical, field, and experimental studies of response to potentially stressful life events give concordant findings: there is a general human tendency to undergo episodes of intrusive thinking and periods of avoidance. A scale of current subjective distress, related to a specific event, was based on a list of items composed of commonly reported experiences of intrusion and avoidance. Responses of 66 persons admitted to an outpatient clinic for the treatment of stress response syndromes indicated that the scale had a useful degree of significance and homogeneity. Empirical clusters supported the concept of subscores for intrusions and avoidance responses.

Adaptation, Psychological↗