Search PubMed⌕ Search

Biomedical subjects

R Segura

Publications and source records attributed to R Segura.

At least 19 recordsLinked to original sources
PubMed1999

Adrenomedullin, a vasodilator peptide implicated in hemodynamic alterations of liver cirrhosis: relationship to nitric oxide.

This prospective cohort study was aimed at investigating the role of adrenomedullin, a potent vasodilator peptide, in liver cirrhosis and its relationship with nitric oxide and cytokines. Overall, 66 consecutive patients with liver cirrhosis and 15 controls matched for age and sex distribution were included. Adrenomedullin levels in patients with cirrhosis were higher than in controls [28.1 (23.5-34.8) vs 21.9 (21.1-26.4) pmol/liter, P = 0.002]. Child class A patients had adrenomedullin levels similar to those of controls, but lower than patients in class B and C, respectively (P = 0.01). Patients with ascites showed more elevated adrenomedullin levels than patients without (P = 0.001). Adrenomedullin levels had significant correlations with aldosterone (r = 0.55; P < 0.001), plasma renin activity (r = 0.49; P < 0.001) and nitrates-nitrites levels (r = 0.52; P < 0.001). Weak correlations were found with tumor necrosis factor-alpha and interleukin-6. This study shows that high levels of adrenomedullin in liver cirrhosis correlate with features associated with plasma volume expansion, and suggests that, in late stages of cirrhosis, adrenomedullin might contribute to vasodilatation by increasing the generation of nitric oxide.

Adrenomedullin↗
PubMed1999

Interleukin-6, nitric oxide, and the clinical and hemodynamic alterations of patients with liver cirrhosis.

OBJECTIVE: Nitric oxide has been proposed as a mediator of hyperdynamic circulation in cirrhosis. Endotoxin and cytokines induce the synthesis of nitric oxide. The aim of this study was to investigate the relationship between endotoxemia, cytokines, and nitric oxide in patients with cirrhosis, and to correlate these findings with clinical, biochemical, and hemodynamic parameters. METHODS: Clinical, biochemical, and hemodynamic parameters were assessed in 66 patients with cirrhosis and 15 controls. Levels of antidiuretic hormone, plasma renin activity, aldosterone, interferon gamma, interleukin-1, interleukin-6, tumor necrosis factor alpha, endotoxin, and nitrates-nitrites were determined. RESULTS: Mean arterial pressure was lower and interleukin-6, tumor necrosis factor alpha, nitrites-nitrates levels, and endotoxin positivity rates were higher in cirrhotics than in controls (p < 0.005). Mean arterial pressure decreased and interleukin-6 levels increased with worsening of Child score (p < 0.005). Patients with ascites had higher levels of interleukin-6, tumor necrosis factor alpha, and nitrates-nitrites than patients without ascites (p < 0.01). Elevated levels of interleukin-6 were found in patients with encephalopathy grade I, compared with patients without (p < 0.001); this association was independent of the severity of liver disease. In patients with low mean arterial pressure, interleukin-6 levels were higher than in patients with high mean arterial pressure (p = 0.001), whereas tumor necrosis factor alpha and nitrates-nitrites levels were not different. By multivariate analysis, high interleukin-6 levels showed independent associations with the presence of ascites, encephalopathy, and low mean arterial pressure. Only interleukin-6 levels had significant correlations with Child score, plasma renin activity, serum and urinary sodium, and mean arterial pressure (r > or = 0.4, p < 0.005). CONCLUSIONS: Although the activity of the nitric oxide pathway is increased in patients with cirrhosis and might contribute to the hemodynamic alteration, other factors are involved. Interleukin-6, possibly through nitric oxide-independent mechanisms, also might play a role in the vasodilatation of cirrhosis and the pathogenesis of hepatic encephalopathy.

Aged↗
PubMed1998

Heritability of running economy: a study made on twin brothers.

Running economy (RE), defined as the steady-state of oxygen uptake (VO2) for a given running velocity, is a factor of sports performance the genetic component of which has seldom been reported to date. We studied this component using a heritability index (HI) in a group of 32 male twins, 8 monozygotic (MZ) and 8 dizygotic (DZ) pairs, all sportsmen with similar perinatal and environmental backgrounds. Zygocity was determined by the identity of erythrocytic antigenic, protein and enzymatic polymorphism, and human leucocyte antigen serologic types between co-twins. The subjects exercised twice on a treadmill, once until exhaustion and again at submaximal intensities. Pulmonary gas exchange was measured continuously using an automatic analyser system during both tests. Blood samples were obtained during the recovery period to determine lactate concentrations. No significant differences were observed between MZ and DZ, in respect of RE at any speed or in maximal VO2 relative to body mass. Nevertheless, significant HI (P < 0.05) was found in maximal lactate concentrations (HI=0.75) and in respiratory equivalent for oxygen at two speeds, 7 km x h(-1) HI=0.71) and 8 km x h(-1) (HI=0.79), differences which probably suggest that there are differences in RE. In conclusion, we did not detect a genetic component in RE or in maximal oxygen uptake, but a genetic component for markers of anaerobic metabolism was present.

Adult↗
PubMed1998

Normoxic ventilatory response in lowlander and Sherpa elite climbers.

The differences in ventilatory response to exercise of some highland ethnic communities is a controversial issue. We have evaluated the differences in ventilatory response to exercise at sea level between two groups of elite climbers, four Himalayan Sherpas (S) and four Caucasian lowlanders (C), after descent from extreme altitude. All of them performed a progressive-intensity exercise test on a treadmill under normoxic conditions. Pulmonary gas exchange was obtained until exhaustion by means of an automatic gas-analyzer system. Significant differences in expired ventilation and carbon dioxide production were found between the two groups, the VE x VO2(-1) being lower in the S at rest (41.9 +/- 5) in comparison with C (48.7 +/- 9) (P < 0.05), higher at medium loads of the test (S = 28.2 +/- 4 vs. C = 25.7 +/- 2; P < 0.05) and reaching similar values at higher loads (S = 34.5 + 2 vs. C = 35.6 +/- 4; NS). We conclude that the special ventilatory response observed in these highlanders could explain their adaptation to altitude, allowing higher oxygen blood saturation at medium working loads and reducing the risk of neurological injury caused by a high ventilatory response when exercising at high intensity effort under extreme altitude environment.

Acclimatization↗
PubMed1997

Could the A2A11 human leucocyte antigen locus correlate with maximal aerobic power?

1. The power of the aerobic metabolic pathway correlates well with successful physical performance in endurance sports events. The ability to alter the pathway through training presents well-known limitations, and consequently a good genetic endowment is essential to participate in elite sporting activities. 2. In 32 subjects (16 healthy pairs of male twin sportsmen, 8 monozygotic and 8 dizygotic) zygosity was determined by means of the genetic analysis of human leucocyte antigen (HLA) system specificities at class I and II loci and other genetic variants. The subjects performed a progressive exercise test on a treadmill to ascertain the maximal oxygen uptake (VO2max), measured by an automatic breath-by-breath analyser. We have considered the relationship between the A, B and C loci of the HLA system and VO2max. 3. We found a high correlation between the presence of both HLA A2 and A11 and VO2max. In the A2A11 group (n = 6) we found a VO2max (mean +/- SD) equal to 71 +/- 4 ml min-1 kg-1. The group without this pair of alleles (n = 26) showed a much lower aerobic power (58 +/- 5 ml min-1 kg-1). Differences between the two groups were found to be largely significant (P < 0.001). It is noteworthy that in two pairs of dizygotic twins, the higher VO2max value corresponded to the twin with the A2A11 allele. 4. The very marked concordance between the presence of the A2A11 locus of the HLA system and the VO2max could be of great interest for the identification of outstanding performers.

Energy Metabolism↗
PubMed1997

Cardiorespiratory response to exercise in elite Sherpa climbers transferred to sea level.

Himalayan Sherpas are well known for their extraordinary adaptation to high altitude and some of them for their outstanding physical performance during ascents to the highest summits. To cast light on this subject, we evaluated the cardiorespiratory response during exercise at sea level of six of the most acknowledged Sherpa climbers, mean age (+/- SD) 37 (+/- 7) yr old. Continuous electrocardiogram and breath-by-breath pulmonary gas exchange until exhaustion were obtained by following the Bruce protocol. We detected a maximal oxygen uptake (VO2max) of 66.7 (+/- 3.7) mL-min-1.kg-1, maximal cardiac frequency of 199 (+/- 7) beats.min-1, and ventilatory anaerobic threshold at 62 (+/- 4) % of VO2max. These factors could help to explain the greater performance level shown by several elite climbers of this ethnic group. The high functional reserve demonstrated by this very select group of highlanders could be associated with natural selection and with special physiological adaptations probably induced by long-training in a hostile environment.

Adult↗
PubMed1997

Infected abdominal aortic aneurysm: in situ replacement with cryopreserved arterial homograft.

Infected aortic aneurysms are a rare (1.3% of all abdominal aortic aneurysms) but life-threatening disease. At present controversy continues about the specific diagnosis and the best surgical management. We present one case of infected aortic aneurysm treated with in situ reconstruction with cryopreserved arterial homograft. He was a 50-year-old man with recent history of pneumococcal meningitis who is readmitted because he suffered a stroke and during physical examination a pulsatile abdominal mass was discovered. Blood cultures were done and the result was repeatedly negative. Radiological studies were performed: the abdominal CT scanning showed a non ruptured 5 cm infrarenal aortic aneurysm with irregular wall and in the aortography it appeared eccentric, multilobulated with a clear neck in an otherwise normal size aorta but with some arteriosclerotic lesions. The diagnosis of infected aneurysm was suspected and the patient received antibiotic therapy and was operated on: aneurysm resection with wide debridement of surrounding tissues and in situ aortic replacement with aortobifemoral cryopreserved arterial homograft. Cultures of the aneurysm wall and contents were negative but aneurysm wall biopsy suggested an infected aortic aneurysm. The postoperative course was uneventful and antibiotics were continued for 6 weeks. The patient is doing well 7 months after surgery without signs of recurrent infection and normal appearance of the cryopreserved arterial homograft. We conclude that specific diagnosis of infected aortic aneurysms is essential for correct treatment but may be difficult, in these cases a history of infection supported by radiologic findings and aneurysm wall biopsy are of great value. Cryopreserved arterial homografts constitute a good alternative to prosthetic grafts for in situ reconstructions in the treatment of infected aortic aneurysms, decreasing the risk of re-infection or septic complications.

Aneurysm, Infected↗
PubMed1997

Is physical training a good synchronizer of the performance?

Whether changes in the training schedule are capable of modifying the daily pattern of performance has been studies. Twelve swimmers were selected to determine their performance in 25 meter crawl races. Their body temperature was also measured. This group was subsequently divided into 3 subgroups: Sub-group 1, made up of 2 subjects who acted as the control subgroup, trained only in the afternoon; Sub-group 2, composed of 5 subjects, trained only in the morning; and Subgroup 3, also made up of 5 subjects, trained in the afternoon but with an additional session of 10 min of swimming in the morning. All subjects followed their corresponding training pattern for three weeks after which they were subjected to a second study or testing day. Thereafter, they all trained one more week according to the same habitual schedule in the evening; after that, they were tested again. A significant variance in the performance time was observed throughout the day (a maximum performance being observed at around 20:30 h), although the changes introduced in the training schedule did not modify the curve of performance.

Adolescent↗
PubMed1997

Creatine supplementation does not improve physical performance in a 150 m race.

Creatine supplementation has been shown by several authors to improve physical performance in very high intensity, intermittent, exercises. The effect on performance, as well as in plasma creatine and lactate concentrations has been studied in a group of twelve sprinters of national class when running a distance of 150 m on two occasions, before and after creatine (or placebo) supplementation for the previous three days. The most important differences in the biochemical parameters analyzed have been in plasma creatinine concentration, which increased substantially both before and after the race in the group that had received a daily supplement of 25 grams of creatine monohydrate for the previous three days. Creatine supplementation, therefore, did not improve physical performance, in the conditions, when running a 150 m distance.

Administration, Oral↗
PubMed1996

Repeated 15-minute coronary occlusions in pigs increase occlusion arrhythmias but decrease reperfusion arrhythmias that are associated with extracellular hypokalemia.

OBJECTIVES: We sought to evaluate the effects of repetitive 15-min coronary occlusions followed by 45-min reperfusions on the incidence of occlusion and reperfusion arrhythmias in pigs. BACKGROUND: Brief 2- to 5-min coronary occlusions seem to exert a protective effect on occlusion and reperfusion arrhythmias. However, because clinical ischemic episodes are often longer, it would be appropriate to assess whether such protection also occurs when longer cycles of occlusion-reperfusion are produced. METHODS: Three to four cycles of 15-min coronary occlusions with 45-min reperfusions were performed in 34 pigs, and changes in ST segment and incidence of ventricular arrhythmias were assessed. Plasma potassium ion concentrations in eight pigs and blood gas in six were measured from blood from the ischemic area during reperfusion. RESULTS: Repetitive occlusions were associated with a progressively higher ST segment elevation and a higher incidence of ST segment alternans (p < 0.001) and ventricular fibrillation (VF) (p < 0.01). However, during repetitive reperfusions, normalization of the ST segment was increasingly faster, the incidence of VF was progressively reduced (p < 0.03), and there was progressively less severe regional acidosis ([mean +/- SD] 7.06 +/- 0.12 vs. 7.26 +/- 0.06, p < 0.05) and hypokalemia (1.9 +/- 0.7 vs. 2.3 +/- 0.4 mEq/liter, p = NS). CONCLUSIONS: The progressive electrocardiographic deterioration and increasing incidence of ventricular arrhythmias during repetitive 15-min occlusions in pigs suggest increasing metabolic derangement. However, the progressively faster normalization of the ST segment and the reduced incidence of ventricular arrhythmias during reperfusion suggest an increasingly faster restoration of the metabolic and ionic balance.

Acid-Base Equilibrium↗
PubMed1996

Are Himalayan Sherpas better protected against brain damage associated with extreme altitude climbs?

1. The potential risk of brain damage when low-landers attempt to climb the highest summits is a well-known fact. However, very little is known about what occurs to Himalayan natives, perfectly adapted to high altitude, when performing the same type of activity. 2. Taking into account their long-life climbing experience at extreme altitudes, we examined seven of the most recognized Sherpas with the aim of performing a comprehensive neurological evaluation based on medical history, physical examination and magnetic resonance brain imaging. We compared them with one group of 21 lowland elite climbers who had ascended to altitudes of over 8000 m, and another control group of 21 healthy individuals who had never been exposed to high altitude. 3. While all of the lowland climbers presented psychoneurological symptoms during or after the expeditions, and 13 of them (61%) showed magnetic resonance abnormalities (signs of mild cortical atrophy and/or periventricular high-intensity signal areas in the white matter), only one Sherpa (14%) showed similar changes in the scans, presenting neurological symptoms at extreme altitude. The neurological examination was normal in all three groups, and no neuroimaging abnormalities were detected in the control group. 4. The significant differences, in both clinical and neuroimaging terms, suggest that Sherpa highlanders have better brain protection when exposed to extreme altitude. Although the key to protection against cerebral hypoxia cannot be established, it is possible that an increase in the usually short period of acclimatization could minimize brain damage in those low-landers who attempt the highest summits without supplementary oxygen.

Adult↗
PubMed1996

Influence of sleep and meal schedules on performance peaks in competitive sprinters.

The influence of sleep and meal schedules on performance in short distance running was assessed in a group of 8 national-class competition male sprinters. They were tested on Saturdays for five consecutive weeks. On each testing day, the performance time for an 80 m sprint was registered on eight different occasions during days 1 and 4, on 9 occasions on days 2 and 5, and on 7 occasions on day 3. On control days (days 1 and 4) performance gradually improved during the morning up to 13:00 h, decreased at 15:00 h, and again improved thereafter, with a maximum peak performance at 19:00 h. On day 2, in which sleep/wake cycles and meal-times were advanced for two hours, and on day 3, in which timetables were delayed for two hours, maximum peak performance was observed at 17:00 h and 21:00 h, respectively. At the time of maximum peak performance on both days a statistically significant improvement was observed as compared with the control day (day 2, p < 0.01; day 3, p = 0.001). On day 5, in which only the sleep/wake cycle was advanced for two hours, performance in the afternoon and evening was similar to that recorded on days 1 and 4. We observed that easy manipulation of sleep and meal schedules would allow competitive sprinters to synchronize peak power output with the time of the athletic event, increasing the chances for improvement in performance.

Adult↗
PubMed1996

A new approach to the assessment of anaerobic metabolism: measurement of lactate in saliva.

OBJECTIVE: To test the hypothesis that saliva lactate concentrations may reflect those present in blood and that saliva lactate can be used as a very convenient and useful variable in the study of anaerobic metabolism. METHODS: Parallel determinations were made of lactate in saliva and in capillary blood samples, obtained at 3 min intervals from nine individuals during the performance of a maximum graded exercise test on a cycle ergometer against increasing workloads (from 25 up to a maximum of 300 W). Lactate determinations were done by means of an electroenzymatic method using 25 microliters samples in both types of fluids. RESULTS: For each situation, the concentration of lactate in saliva was shown to be about 15% of that in plasma but it followed the same pattern of evolution during the exercise test. A good correlation (r = 0.81) between blood and saliva lactate concentrations was found. The precision of the method was very good, with a coefficient of variation ranging (n = 10) between 2.2% for samples with very low lactate concentrations and 0.7% for sample with moderate lactate concentrations. Lactate appeared to be very stable in saliva over a period of 40 days after collection, when kept at 4 degrees C. The values obtained after this period were virtually identical to those shown in fresh samples. CONCLUSIONS: Determination of lactate in saliva can be used as an alternative to determination in blood, overcoming most of the drawbacks of the procedures being used at present, since the collection of the samples required no special expertise.

Adult↗
PubMed1996

Is the post-lunch dip in sprinting performance associated with the timing of food ingestion?

To detect whether the drop in performance around lunch has any direct association with the time of food ingestion, a group of 8 sprinters were studied for 5 consecutive Saturdays. On each testing day, the times achieved during 80 meter sprints performed at eight different times of the day separated by 2 hour intervals were recorded. The 1st and 4th testing days, had identical sleep and mealtime schedules, and were therefore considered "control days", while on the 2nd and 3rd testing days the schedule was brought forward ("advanced") or backward ("delayed") by 2 hours respectively. On the 5th testing day the sleep-wake cycle was brought forward 2 hours without changing the mealtime schedule. A post-lunch dip (PLD) was detected on all testing days although at different times. No significant differences in performance were observed between days 1 and 4 while there were differences in performance during the other testing days. It is worth pointing out that PLD occurred at about 15:00 h on the control days, with significant differences between the 2nd (p < 0.05) and 3rd days (p < 0.05), and with the deterioration in performance starting at 15:00 h on the 3rd day despite the fact that lunch had been served at 16:00 h. In conclusion, PLD does not appear to be directly linked to the time of lunch, although lunch itself could potentiate its effects. It is also worth mentioning the fact that this deteriorating effect does not occur after any other meals of the day.

Adult↗
PubMed1995

New evidence from magnetic resonance imaging of brain changes after climbs at extreme altitude.

The aim of the present study was to look for anatomical changes in climbers' brains, using magnetic resonance imaging (MRI), after extremely high-altitude climbs and to relate them to possible associated risk factors. Clinical history, neurological examinations and MRI were carried out on a group of nine climbers before and after climbing to over 7500 m without the use of supplementary oxygen. None of the subjects showed any neurological dysfunctions. In five climbers MRI abnormalities (high signal areas, cortical atrophy) were observed before the expedition. After the descent, two of them showed new high intensity signal areas recorded by MRI. Both subjects suffered severe neurological symptoms during the climb. The present study suggested that the brain changes observed by MRI could be related to the severity of clinical events at high altitude. However, we do not know the exact meaning of such MRI findings or the reason for their location, predominantly in posterior regions of the brain. The new evidence that a high percentage of climbers show MRI brain abnormalities, and especially the appearance of changes after the ascent, reinforces the possibility of a potential neurological risk in high-altitude climbing.

Adult↗
PubMed1994

Effect of prior ingestion of glucose or fructose on the performance of exercise of intermediate duration.

The metabolic responses induced by the ingestion of a beverage containing glucose (G), fructose (F) or placebo (W) 30 min before exercise of high intensity and intermediate duration have been investigated; in these conditions the energy processes are mostly dependent on aerobic reactions. A group of 11 male recreational sportsmen ran on a treadmill, at an intensity corresponding to 82% of peak oxygen consumption, until exhaustion on three different occasions (after ingestion of a beverage containing 75 g of G, 75 g of F or W). Plasma glucose, insulin, and lactic acid concentrations were determined just prior to the ingestion of the beverages, 30 min afterwards and 10 and 30 min after completion of the exercise. The mean endurance time was 644 (SD 261) s after the ingestion of G, 611 (SD 227) s after the ingestion of F and 584 (SD 189) s after the ingestion of the W (P < 0.05 between G and W). No differences in the oxygen uptake, respiratory quotient or lactate concentrations between the three trials were observed. Both plasma glucose and insulin concentrations determined in samples obtained immediately before the onset of exercise were higher when G was ingested than when F (P < 0.05 and P < 0.05, respectively) or W (P < 0.001 and P < 0.005, respectively) were ingested. These findings would suggest that the ingestion of G prior to an effort of intermediate duration may improve physical performance.

Adult↗