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F Pi

Publications and source records attributed to F Pi.

At least 19 recordsLinked to original sources
PubMed2003

Nucleotides modulate renal ischaemia-reperfusion injury by different effects on nitric oxide and superoxide.

1. The present study investigated the effects of kidney ischaemia duration on nitric oxide (NO) and superoxide (O2-) generation at reperfusion and the role of xanthine and adenosine as mediators of NO/O2- generation. 2. The effect of the duration of ischaemia on renal nucleotide levels was studied in two ischaemic groups (10 and 30 min). The role of adenosine and xanthine was studied in ischaemic-reperfused groups (subjected to 10 and 30 min ischaemia and 60 min reperfusion). 3. Tissue levels of adenosine decreased significantly after 30 min ischaemia, whereas xanthine/hypoxanthine levels increased concomitantly with renal dysfunction and histological damage. 4. Nitric oxide production increased significantly after 10 min ischaemia and 60 min reperfusion, whereas lipoperoxidation increased significantly after 30 min ischaemia and 60 min reperfusion. The administration of theophylline (40 mg/kg, i.p.) reversed the early increase in NO production. 5. Xanthine supplementation decreased renal function and increased lipoperoxidation. 6. In conclusion, NO/O2- production and the subsequent renal injury/dysfunction may be modified by changes in the adenosine and xanthine levels of the injured kidney, although the present data show a significant in vivo role only for xanthine.

Adenosine↗
PubMed2002

Phase synchronization in bidirectionally coupled optothermal devices.

We present the experimental observation of phase synchronization transitions in the bidirectional coupling of chaotic and nonchaotic oscillators. A variety of transitions are characterized and compared to numerical simulations of a time delayed model. The characteristic 2pi phase jumps usually appear during the transitions, specially in those clearly associated with a saddle-node bifurcation. The study is done with pairs of optothermal oscillators linearly coupled by heat transfer.

Journal Article↗
PubMed2001

Effects of adenosine on ischaemia-reperfusion injury associated with rat pancreas transplantation.

BACKGROUND: During cold preservation, cellular consumption of adenosine triphosphate leads to the accumulation of nucleotides and nucleosides. The precise role of adenosine in modulating the inflammatory response of cold-preserved pancreas after reperfusion remains to be elucidated. The aim of this study was to assess the influence of adenosine on the inflammatory response associated with the process of ischaemia-reperfusion in rat pancreas transplantation. METHODS: The effect of adenosine from preservation solution on the levels of high-energy nucleotides and their breakdown products after cold ischaemic preservation was determined. In addition, the inflammatory response associated with the process of ischaemia-reperfusion in pancreas transplantation was quantified with and without pretreatment with the adenosine antagonist theophylline, and during preservation of the organ in University of Wisconsin solution with and without adenosine. RESULTS: Adenosine from preservation solution is able to modify the nucleotide and nucleoside content of preserved pancreas, indicating that adenosine is incorporated and metabolized in tissue. Administration of the adenosine antagonist to transplanted rats moderated the increases in nitrite and nitrate, myeloperoxidase activity and lipoperoxidation levels in the pancreas. CONCLUSION: Adenosine in the preservation solution may enhance the inflammatory response in rat pancreas transplantation.

Adenosine↗
PubMed2001

CO2 in static mesenteric venous blood during intestinal ischemia and ischemic preconditioning in rats.

During intestinal ischemia, CO2 accumulates in tissue as a result of bicarbonate buffering of anaerobic acid generation. Previous studies have shown that nitric oxide (NO) generated during ischemic preconditioning acts as a glycolytic modulator, thus decreasing tissue lactate production. We studied if ischemic preconditioning induces NO-dependent changes in static mesenteric venous blood Pco2 values and CO2 accumulation during intestinal ischemia. Superior mesenteric venous (smv) acid base variables were studied in 4 groups of rats: a control group (C), an ischemic (90-min period of flow arrest) group (I), an ischemic group subjected to previous ischemic preconditioning (P), and an ischemic group subjected to previous ischemic preconditioning in which nitric oxide synthase (NOS) was inhibited by N-nitro-L-arginine methyl ester (L-NAME) administration (P+N). Preconditioning induced acidosis in smv blood during reperfusion before ischemia, but this effect was counteracted by L-NAME. Group P showed the lowest values of end-ischemic tissue lactate, smv blood CO2 accumulation, and LDH in perfusate, whereas group P+N showed the highest level of LDH in perfusate but the lowest end-ischemic smv blood Pco2 and acidity. We conclude that lower ischemic CO2 accumulation in static smv blood, but not lower end-ischemic Pco2, was related with the protective effect of ischemic preconditioning in our rat model. Thus, the use of stagnant smv blood Pco2 as an indicative of intestinal dysoxia can lead to misinterpretations if a broader acid-base picture is not considered.

Anaerobiosis↗
PubMed2000

Full instability behavior of N-dimensional dynamical systems with a one-directional nonlinear vector field

We show how certain N-dimensional dynamical systems are able to exploit the full instability capabilities of their fixed points to do Hopf bifurcations and how such a behavior produces complex time evolutions based on the nonlinear combination of the oscillation modes that emerged from these bifurcations. For really different oscillation frequencies, the evolutions describe robust wave form structures, usually periodic, in which self-similarity with respect to both the time scale and system dimension is clearly appreciated. For closer frequencies, the evolution signals usually appear irregular but are still based on the repetition of complex wave form structures. The study is developed by considering vector fields with a scalar-valued nonlinear function of a single variable that is a linear combination of the N dynamical variables. In this case, the linear stability analysis can be used to design N-dimensional systems in which the fixed points of a saddle-node pair experience up to N-1 Hopf bifurcations with preselected oscillation frequencies. The secondary processes occurring in the phase region where the variety of limit cycles appear may be rather complex and difficult to characterize, but they produce the nonlinear mixing of oscillation modes with relatively generic features.

Journal Article↗
PubMed1998

Endothelin mediated nitric oxide effects in ischemia--reperfusion associated with pancreas transplantation.

Formation of nitric oxide (NO) in ischemia-reperfusion (I-R) associated with pancreas transplantation could modulate the inflammatory response. In this sense, previous studies have demonstrated the action of NO on vasoactive substances like prostacyclin or endothelin. The present study was designed to evaluate the contribution of endothelin to the inflammatory events induced by NO in the I-R process associated with pancreas transplantation. For this purpose, pancreatic levels of endothelin, neutrophil infiltration, and prostacyclin were evaluated in an experimental model of pancreas transplantation after inhibition of NO synthesis or after NO inhibition plus addition of endothelin. Results show significant posttransplantation increases in endothelin, neutrophil infiltration, and prostacyclin production. These increases were prevented by NO inhibition. Endothelin administration plus nitric oxide inhibition reversed this effect, resulting in an increase in myeloperoxidase and 6-keto-prostaglandin F1alpha. These results suggest that the proinflammatory effects of NO in I-R associated with pancreas transplantation are mediated by the induction of endothelin generation.

Animals↗
PubMed1997

[Central venous catheter location by endocavitary ECG: an alternative to chest radiography].

BACKGROUND: The location of a central venous catheter is checked with a chest radiograph. Right endocavitary electrocardiography (ECG), a technique in which the catheter is connected to the ECG recorder wire to record ECG in DII, might be an alternate method to check the position of the catheter. When the catheter enters the right atrium, there is a large increase in the amplitude of P wave. The aim of this study was to compare the efficacy of endocavitary ECG against the chest radiography as a method to check the position of a central catheter, and to determine whether the ECG method can replace the radiological method. MATERIAL AND METHODS: One-hundred central catheters which location was checked by ECG and by chest X-ray entered the study. Efficacy of endocavitary ECG, delay between catheter insertion and radiological check, and the cost of the two methods were studied. RESULTS: Endocavitary ECG determined that de catheter was in a correct position in 80 cases and malpositioned in 20 cases. ECG check agreed with radiological check in 93 catheters. There were 4 false-positive and 3 false-negative cases. The efficacy of endocavitary ECG was 93% (sensitivity: 82%; specificity: 81%; positive predictive rate: 95%; negative predictive rate: 85%). Catheter location was checked immediately on insertion by ECG in all cases, while radiological check was delayed 32 +/- 25 min in the emergency department and 68 +/- 206 min in the admitted patients. The cost of the ECG method was less than that of the radiological method. CONCLUSIONS: The check of the position of a central venous catheter by endocavitary ECG is taster, cheaper, and of similar efficacy to the radiological method. Endocavitary ECG can replace chest X-rays to check the position of the catheter in more than 90% of cases.

Catheterization, Central Venous↗
PubMed1997

Free radical enhancement promotes leucocyte recruitment through a PAF and LTB4 dependent mechanism.

In the present investigation we studied the concerted role of superoxide anion, platelet activating factor (PAF) and leukotriene B4 (LTB4) in the mechanism that results in polymorphonuclear leucocyte accumulation induced by oxygen free radicals in rat pancreas. This was done by comparing the effects of a PAF antagonist (BN-52021), a LTB4 inhibitor (MK-886) and superoxide dismutase (SOD) in a experimental rat model of inflammation elicited by the oxygen free radicals induced via infusion of xanthine/xanthine oxidase. Also, the effect of independent LTB4 infusion has been studied. The results show that increases in polymorphonuclear cell infiltration (evaluated by tissue histology), myeloperoxidase and LTB4 levels induced in pancreas by infusion of xanthine/xanthine oxidase were abolished by the administration of either the PAF antagonist, the LTB4 inhibitor, or SOD. The fact that BN-52021 could prevent neutrophil recruitment and LTB4 synthesis suggests that PAF is a necessary step for subsequent LTB4 synthesis and polymorphonuclear leucocyte accumulation.

Animals↗
PubMed1997

Differential effect of nitric oxide inhibition as a function of preservation period in pancreas transplantation.

The role of nitric oxide, produced during reperfusion as a function of preservation time, in the development of the inflammatory process in pancreas transplantation has been explored. For this purpose, the effect of nitric oxide synthase inhibition, as well as 6-keto-prostaglandin F1alpha, leukotriene B4, and lipoperoxidation levels were evaluated in an experimental model of rat pancreas transplantation after different periods of cold preservation. The results show posttransplantation increases in 6-keto-prostaglandin F1alpha, leukotriene B4, and lipoperoxidation levels in pancreatic tissue and in plasma lipase. When ischemia was induced for 30 min, nitric oxide synthase inhibition prevented these increases, and L-arginine was able to reverse this effect. By contrast, nitric oxide synthase inhibition has no effect when ischemia was prolonged for 12 hr. In summary, this study suggests that, during reperfusion, nitric oxide modulates 6-keto-prostaglandin F1alpha synthesis, lipoperoxidation levels, and the development of pancreatic injury but only when the ischemic period is quite short.

6-Ketoprostaglandin F1 alpha↗
PubMed1997

Nitric oxide enhances endothelin production in pancreas transplantation.

The role of endothelin and its relationship with nitric oxide (NO) production in ischemia-reperfusion associated with pancreas transplantation has been explored. For this purpose, pancreatic levels of endothelin were evaluated in an experimental model of pancreas transplantation after different periods of cold preservation. The effects of NO synthase inhibition were also evaluated. Results show posttransplantation increases in lipase and endothelin production. The release of lipase and endothelin was only prevented by NG-nitro-L-arginine methyl ester after a short ischemic period. Thus, endothelin synthesis could be a consequence of stimulation with NO in the ischemia-reperfusion associated with pancreas transplantation.

Animals↗
PubMed1997

Clinical skills assessment with standardized patients.

Previous projects (Combell I & II) to assess clinical skills were conducted in medical schools in Catalonia, in order to introduce a model of such an assessment using standardized patients (SP). The aim of this study (Combell III) was to measure selected characteristics of our model. Seventy-three medical students in the final year at the Bellvitge teaching unit of the University of Barcelona participated in a clinical skills assessment (CSA) project that used 10 SP cases. The mean group scores for the four components of clinical skills for each day of testing were studied, and ratings for each student in the 10 sequential encounters were checked. The study also compared the clinical skills scores with their academic grades. The total case mean score (mean score of history-taking, physical examination and patient notes scores) was 51.9%, and the mean score for communication skills was 63.6%. The clinical skills scores over the 8 testing days showed no day-to-day differences. The study did not find differences among the sequential encounters for each student (training effect). There was a lack of correlation between clinical skills scores and academic grades. The project demonstrated the feasibility of the method for assessing clinical skills, confirmed its reliability, and showed that there is no correlation between scores with this method and academic examinations that mainly reflect knowledge.

Clinical Competence↗
PubMed1997

[An analysis of the impact of the COMBELL project on clinical medical competence. Competencia clínica Bellvitge].

OBJECTIVE: The most frequent tests for evaluate medical education in our country, do not analyze clinical competence. The aims of this project was to introduce a method for the assessment of clinical skills in two different groups of students using the simulation methodology with standardized patients and to compare with classical methods of assessment. METHODS: Seventy three last year medical students were evaluated using 10 standardized patients encounters in April 1995 (COMBELL III project) and the other group of last year medical students was assessed in March 1996 using the same group of standardized patients (COMBELL IV project). RESULTS: The global score for the COMBELL III, was 50.6% +/- 4.8 lower to COMBELL IV, 55.6% +/- 6 (p = 0.0001), remarking the improving of the item of physical examination (39.6% +/- 7.7 versus 48.1 +/- 9.6 p < 0.0001). Personal intercommunication also improved, 63.1% +/- 11.4 versus 70.4% +/- 12.2 (p = 0.0008). We did not find differences between academic grades and did not find correlations between clinical competence assessment and academic grades in COMBELL III but we found correlations in COMBELL IV. CONCLUSIONS: Our results show that when this new assessment method was introduces in our medical school the clinical competence levels improved.

Clinical Competence↗
PubMed1996

Gallbladder dyskinesia in acalculous biliary colic.

AIMS: To test the hypotheses that: 1) postprandial gallbladder emptying might be abnormal in patients with acalculous biliary colic; and 2) that hymecromone, a drug that increases bile flow and relaxes biliary muscle might improve symptoms. METHODS: Twenty-four women were studied. Twelve patients presented recurrent biliary type of pain in the absence of gallstones, and persistence of contrast in the gallbladder, 24 hours after an oral cholecystogram, suggesting cholesterolosis. Twelve healthy volunteers used as controls had no symptoms and the gallbladder was not visible the day after an oral cholecystogram. Gallbladder emptying induced by an oral meal was studied with ultrasound in both groups before and after the administration of hymecromone. RESULTS: Gallbladder volumes were similar in both groups (23 +/- 10 ml vs. 31 +/- 11 ml; NS). Gallbladder emptying in the control group was simple exponential (R2 = 0.948 +/- 0.059) with a rate of 32 +/- 16 minutes. Gallbladder emptying was bimodal in patients. Gallbladder volume increased to 120% in the first 10 minutes, to empty exponentially thereafter (R2 = 0.964 +/- 0.040. Rate: 29 +/- 22 minutes). This resulted in a marked reduction in gallbladder volume emptied at 40 minutes when compared to controls (30% +/- 27% vs. 54% +/- 14%; p = 0.012). Pretreatment of controls with hymecromone induced an emptying pattern similar to that of patients. In patients, emptying after hymecromone did not change but symptoms were improved. CONCLUSIONS: An abnormal emptying pattern of the gallbladder was identified in patients with acalculous biliary colic, and hymecromone was partly effective to reduce pain, despite a minor effect on gallbladder emptying pattern.

Biliary Tract Diseases↗
PubMed1995

Nitric oxide and arachidonate metabolism in ischemia-reperfusion associated with pancreas transplantation.

The role of eicosanoid metabolism and its relationship with nitric oxide production in the ischemia-reperfusion associated with pancreas transplantation in the rat is explored in this study. Twenty-six male Sprague-Dawley rats were randomized into 3 groups, as follows: group 1, control animals not surgically manipulated; group 2, pancreas transplantation, after 12 hr of organ preservation in University of Wisconsin solution; group 3, same as group 2 but with administration of NG-nitro-L-arginine methyl ester (a nitric oxide synthase inhibitor) (10 mg/kg) before organ revascularization. The results show posttransplantation increases in edema and in 6-keto-prostaglandin F1 alpha (x1.9), thromboxane B2 (x4), and prostaglandin E2 (x5) levels in pancreatic tissue. Nitric oxide synthase inhibition reversed the increases in edema and eicosanoid production, which suggests that eicosanoid generation in the recipient rat would be mediated, in part, through a nitric oxide-dependent mechanism.

Adenosine↗
PubMed1994

Effect of a platelet-activating factor antagonist and desferrioxamine administration on eicosanoid production in rat pancreas transplantation.

Eicosanoid metabolism and its relationship with platelet-activating factor and oxygen free radical production in rat pancreas transplantation has been studied herein. Male Sprague-Dawley rats were classified in 4 experimental groups (n = 8 each) as follows: group 1, control; group 2, pancreas transplantation, after 12 hr of organ preservation in University of Wisconsin solution; group 3, same as group 2 with desferrioxamine administration before revascularization of the organ in the recipient rat; and group 4, same as group 3 with administration of a platelet-activating factor antagonist (BN-52021). The results show post-transplantation increases in eicosanoid production in pancreatic tissue. The fact that desferrioxamine and BN-52021 administration could reverse increases in thromboxane B2, leukotriene B4, and 12-hydroxyeicosatetraenoic acid but only BN-52021 affected 6-keto-PGF1 alpha levels suggests the existence of a close relationship between platelet-activating factor and oxygen free radical in eicosanoid production in pancreas transplantation and it points to a differential role of metabolites produced by circulatory cells and endothelial cells.

Animals↗