PubMed Health⌕ Search

Biomedical subjects

J Ribas

Publications and source records attributed to J Ribas.

At least 55 records · Page 3Linked to original sources
PubMed1995

Kinetics of plasma potassium concentrations during exhausting exercise in trained and untrained men.

The purpose of this study was to examine the time course of changes in plasma potassium concentration during high intensity exercise and recovery in trained and untrained men. The subjects performed two exercise protocols, an incremental test and a sprint, on a cycle ergometer. A polyethylene catheter was inserted into the antecubital vein to obtain blood samples for the analysis of plasma electrolyte concentrations and acid-base parameters, during and after exercise. During both tests, venous plasma sodium, potassium and chloride concentrations increased in all the subjects, although the largest relative increase was detected in potassium concentration--35% and 31% over rest in the progressive test and 61% and 37.7% in the sprint test, for cyclists and controls, respectively. After exercise plasma potassium concentration decreased exponentially to below resting values. There was a linear correlation between the amount of potassium accumulated in plasma during exercise and the amount eliminated from plasma when the exercise ceased. We found that, although plasma potassium accumulation occurred in both forms of exercise in the trained and nontrained subjects, the time constant of potassium decrease following exercise was shorter in the trained subjects. Thus, the trained subjects exhibited a better capacity to recover to resting concentrations of plasma potassium. We propose that the extracellular potassium accumulation acts as a negative feedback signal for sarcolemma excitability depending on the muscle metabolic rate.

Acid-Base Equilibrium↗
PubMed1995

Efficiency of the anorectal manometry for the diagnosis of Hirschsprung's disease in the newborn period.

We have used a continuous perfusion probe for manometry in newborns. We carried out 95 pressure recordings in 56 patients labeled as delayed passage of meconium longer than 24 h. When the relaxation reflex of the anal canal was not present after rectal stimulation with a distensible balloon, the tests were repeated weekly up to the first month of life. Thereafter, suction biopsies were carried out to confirm the final Hirschsprung's disease (HD) diagnosis. The amplitudes of the fluctuating waves in HD subjects were higher than those in non-HD patients. Although the procedure could provide false positive results, no possibilities exist for false negative results as proved in our study. All the five cases with HD were diagnosed by our manometric procedure as well as by histochemistry. The method is advantageous and profitable for the diagnosis of HD in case of delayed passage of meconium or distal functional obstruction of the anal canal.

Biopsy↗
PubMed1995

A cluster of fever and hypotension on a surgical intensive care unit related to the contamination of plasma expanders by cell wall products of Bacillus stearothermophilus.

OBJECTIVE: To evaluate an outbreak of fever and hypotension after cardiac surgical procedures and the role of polygeline, a plasma expander. DESIGN: Unmatched case-control study. SETTING: A six-bed cardiac surgery intensive care unit (SICU) of the Hospital Clinic of Barcelona (Spain), a 940-bed public teaching hospital. PATIENTS: Eight cases and 25 control patients admitted to the SICU over a 4-week epidemic period. MAIN OUTCOME MEASURES: Development of hypotension (systolic blood pressure < or = 90 mm Hg or a drop of 40 mm Hg from baseline systolic blood pressure) and fever (axillary temperature > 38.5 degrees C) within 24 hours of a cardiac surgical procedure. RESULTS: The single risk factor significantly different between cases and controls was the total volume of polygeline used throughout the surgical procedure for extracorporeal circulation: a median of 1,250 mL (mean, 1,312.5 +/- 842.5 mL) in cases versus 500 mL (mean, 566.0 +/- 159.9 mL) in controls (P = .0029). By multiple logistic regression analysis, polygeline use was the single risk factor significantly related to the outcome (odds ratio, 8.75; CI95, 1.36 to 56.2; P = .01). Neither blood cultures from patients nor cultures of the polygeline used yielded growth of any microorganism. Stopping use of the implicated polygeline lot controlled the outbreak. CONCLUSIONS: Use of polygeline was associated with an outbreak of fever and hypotension in a SICU. Information from the manufacturer indicated the likelihood of contamination of the product with Bacillus stearothermophilus components. The manufacturer has since changed the production and control processes, and no further adverse events have been seen.

Bacterial Proteins↗
PubMed1995

[Age is the independent prognostic factor in acute myocardial infarct. The clinical course of infarct in the elderly patient].

We analyze the influence of age in the evolution of patients with acute myocardial infarction admitted to our Coronary Care Unit throughout two years (1990 and 1991). All 542 patients admitted during this period were classified in three groups: 299 less than 65 year old (group A), 170 between 65 and 74 year old (group B), and 73 with 75 year old or more (group C). Aged patients had a worse clinical condition, with significantly more previous heart failure, diabetes or hypertension, and the Killip's class was worse in group C than in group B, and worse in this than in group A (p = 0.00000). The mortality rate was 6.7% in group A, 12.9% in group B, and 31.5% group C (p = 0.00000). After a multivariate analysis, only three factors were significantly associated to prognosis: previous stroke, Killip's class, and group of age. Fibrinolytic therapy and coronary arteriography were less frequent with old people (p = 0.00000 and p = 0.00000 respectively). We conclude that age is an independent factor of prognosis during myocardial infarction. Old people have a worse clinical condition and the treatment is less aggressive than in young people.

Age Factors↗
PubMed1995

[The prognosis for elderly patients admitted to a coronary unit for myocardial infarct: the changes over a decade].

INTRODUCTION AND AIM: New therapies have been added that improve prognosis of patients with myocardial infarction. Our purpose was to know if elderly patients reach benefit from these therapeutic changes. METHODS: We have analyzed the clinical data of 227 patients older than 70 who were admitted in our coronary care unit: 78 admitted in 1980-81 and 14 admitted in 1990-91. RESULTS: Although differences were not significant, in 1990-91 there were more women (36% versus 28%), less smoking (24% versus 33%), more patients with previous infarction (19% versus 12%), more hypertension (53% versus 43%), less anterior infarcts (38% versus 45%) more non Q infarcts (11% versus 1%), and less bundle branch block (21% versus 31%). In 1990-91, pacemakers were used less often (13% versus 27%, p = 0.03), thrombolytic therapy was given to 16 patients (10.7%), and the mortality rate was a little inferior (22% versus 30%, not significant). Female sex, not being a smoker, Killip class and bundle branch block were significantly related to mortality. After a multivariate analysis in which these factors we included, the date of admission resulted an independent predictor of mortality, with an odds ratio of 1990-91 to 1980-81 of 0.43 (p = 0.039). CONCLUSIONS: The management of patients older than 70 with myocardial infarction has improved, with a significantly lesser risk of dead after multivariate analysis, despite that thrombolysis has been scarcely applied.

Aged↗
PubMed1994

Stability of an oral midazolam solution for premedication in paediatric patients.

The objectives of this study were to assess the stability of a 1 mg/ml oral midazolam solution elaborated by our Hospital Pharmacy Service, and to confirm its clinical effect in presurgical paediatric patients. The solution's stability was tested by determining its pH and its UV-visible absorption spectrum at room temperature for up to 60 days. A high performance liquid chromatography method was used to confirm it. There was no significant change in pH value of either the test or a control solution. No loss of midazolam could be detected during the test. The Anaesthesiology Service assessed the sedation quality (very good, good, bad) and the venous puncture response, 20 minutes after the administration of 0.3 mg/kg of an oral midazolam solution. Twenty children were examined (age: 4-7 years). In addition, the haemodynamic and ventilatory functions were evaluated.

Administration, Oral↗
PubMed1992

Hydrocortisone anaphylaxis: a new case report.

In this report we describe a case of a nonatopic patient who developed an anaphylactoid reaction immediately after receiving intravenous hydrocortisone. The patient recovered after reanimation techniques and intravenous administration of atropine, epinephrine and plasma expanders. Although allergic reactions to corticosteroids appear to be rare there are a few case reports in the literature. This case is presented to draw the attention of clinicians to the occasional hazard of intravenous corticosteroid preparations, specially hydrocortisone.

Anaphylaxis↗
PubMed1991

Technical improvement for anorectal manometry in newborns.

A modification of the anorectal manometric technique has been devised to improve its accuracy in 31 low-weight newborn and premature infants. The characteristics of the probes used allowed long recording sessions without any sedation of patients. The pressure records fit well the classically accepted requisites. All recordings showed spontaneous fluctuating waves and increased mean pressure in the aboral direction. The anorectal reflex was observed in all cases. Clear reflex waves were recorded in the most caudal third of the anal canal. In this zone the recording showed more distinct features with respect to fluctuation and relaxation waves than those located in more proximal parts. The validity of this technique is unquestionable from the view of the reliability of the recordings independent of the weight, gestational age, and birth age of the infants.

Anal Canal↗
PubMed1991

Properties and ionic basis of the action potentials in the periaqueductal grey neurones of the guinea-pig.

1. Action potentials of neurones of the ventral part of the guinea-pig periaqueductal grey (PAG) were studied by intracellular recording in a mesencephalic slice preparation maintained in vitro. 2. Fast spikes spontaneously fired last 2.8 +/- 0.6 ms (mean +/- S.D.) and have an amplitude of 72.3 +/- 5.3 mV (n = 28). The neurones could be antidromically activated from the neighbouring white matter and these spikes show an initial segment component that triggers the soma-dendritic spike. These two components were dissociated by hyperpolarization. Action potentials are Na+ dependent and a Ca2+ conductance is responsible for the hump on the falling phase. Hyperpolarization makes the hump disappear and a faster rate of rise and fall are seen. Accommodation of the firing threshold is observed in response to depolarizing ramps, which is eliminated with hyperpolarization. 3. High-threshold Ca2+ spikes are evoked in either Na(+)-free solution or in the presence of tetrodotoxin (TTX). These presumed dendritic action potentials display a fast repolarization and a large after-hyperpolarization (AHP) that prevent repetitive firing. This AHP is mainly generated by Ca(2+)-dependent K+ conductances. 4. The repolarization of fast action potentials depends on the activation of K+ conductances as well as a Na+ inactivation process. A fast-activated tetraethyl-ammonium (TEA)-sensitive K+ conductance, that could be Ca2+ dependent, and a K+ conductance blocked by apamin seem to be involved in the repolarization. 5. Each fast action potential is followed by a pronounced AHP with two components, an initial fast and a slow decaying phase. Membrane hyperpolarization around -60 mV eliminated the first component and the AHP acquired a plateau-like shape. At -90 mV the AHP was nullified. The slow phase was Ca2+ dependent and an apamin-sensitive K+ conductance is involved in its generation. This conductance may be active during the early part of the AHP, but a fast-activated TEA-sensitive K+ conductance and other voltage-dependent K+ conductances might also be present. A Ca2+ conductance is hypothesized to account for the fast depolarizing change after the AHP peak. 6. A delayed return to the baseline is observed after hyperpolarizing pulses. It is generated by the activation of a transient voltage-dependent K+ conductance that is inactive at resting membrane potential (RMP, around -50 mV). This transient hyperpolarization is abolished by Ca2+ channel blockers and insensitive to high external concentrations of 4-aminopyridine, TEA and Cs+.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1991

The inability of human immunodeficiency virus to infect chimpanzee monocytes can be overcome by serial viral passage in vivo.

Studies of lentivirus infection in ruminants, nonhuman primates, and humans suggest that virus infection of macrophages plays a central role in the disease process. To investigate whether human immunodeficiency virus type 1 (HIV-1) can infect chimpanzee macrophages, we recovered monocytes from peripheral blood mononuclear cells of HIV-1-negative animals and inoculated these and control human monocytes with a panel of four human-passaged monocytotropic virus strains and one chimpanzee-passaged isolate. HIV-1 infected human monocytes synthesized proviral DNA, viral mRNA, p24 antigen, and progeny virions. In contrast, except for the chimpanzee-passaged HIV-1 isolate, chimpanzee monocytes failed to support HIV-1 replication when cultured under both identical and a variety of other conditions. Proviral DNA was demonstrated only at background levels in these cell cultures by polymerase chain reaction for gag- and env-related sequences. Interestingly, the chimpanzee-passaged HIV-1 isolate did not replicate in human monocytes; viral p24 antigens and progeny virions were not detected. The same monocytotropic panel of HIV-1 strains replicated in both human and chimpanzee CD4+ T lymphoblasts treated with phytohemagglutinin and interleukin-2. The failure of HIV-1 to infect chimpanzee monocytes, which can be overcome by serial in vivo viral passage, occurs through a block early in the viral life cycle.

Animals↗
PubMed1988

Periaqueductal gray neurons' activity in a mesencephalic slice preparation.

The electrophysiological characteristics of periaqueductal gray (PAG) neurons were studied using intracellular techniques in guinea pig brainstem slices maintained 'in vitro'. Input resistance and time constant ranged between 60-110 M omega and 11-20 ms respectively. Direct activation elicited action potentials generated by a Na+-conductance and characterized by a remarkable Ca2+-dependent plateau in the falling phase and a long-lasting afterhyperpolarization which is probably due to a Ca2+-dependent K+-conductance. These cells also showed a slow return to the resting membrane potential after hyperpolarizing pulses which was Ca2+-dependent. All PAG neurons had a low resting membrane potential and displayed a tonic spontaneous firing at a frequency around 7 impulses/s.

Action Potentials↗