Arrhythmias in the developing heart.

Prevalence of cardiac arrhythmias increases gradually with age; however, specific rhythm disturbances can appear even prior to birth and markedly affect foetal development. Relatively little is known about these disorders, chiefly because of their relative rarity and difficulty in diagnosis. In this review, we cover the most common forms found in human pathology, specifically congenital heart block, pre-excitation, extrasystoles and long QT syndrome. In addition, we cover pertinent literature data from prenatal animal models, providing a glimpse into pathogenesis of arrhythmias and possible strategies for treatment.

Neumomediastino espontáneo (síndrome de Hamman), una entidad poco frecuente no siempre reconocida / Spontaneous pneumomediastinum

Introduction: pneumomediastinum or Hamman syndrome usually appears in young males; any condition provoking Valsalva maneuvers can be a predisposing factor. Clinical case: we report an 18 years old male admitted to the emergency room for polydipsia, polyphagia, malaise, profuse vomiting and chest pain. A diabetic ketoacidosis was diagnosed and a chest X ray film showed a pneumomediastinum. The patient was compensated metabolically and an esophageal X ray examination discarded esophageal perforation. He was discharged in good conditions seven days after admission.

Introducción: el neumomediastino espontáneo corresponde a la presencia de aire en el mediastino sin relación con patología traumática o iatrogénica. Fue descrito por primera vez por Hamman en 1939. Se presenta con baja frecuencia y se caracteriza principalmente por dolor torácico y disnea. La manifestación más importante al examen físico es el enfisema subcutáneo. Material y Método: se presenta un caso clínico de un paciente de 18 años de edad que consulta por un cuadro de cuatro semanas de evolución caracterizado por compromiso del estado general y polidipsia, polifagia y baja de peso acompañados de vómitos profusos. Se diagnostica una cetoacidosis diabética como debut de una Diabetes Mellitus tipo I. El paciente evoluciona con dolor torácico y en el TC de tórax se evidencia la presencia de un neumomediastino. Discusión: el neu-momediastino espontáneo se produce habitualmente en pacientes jóvenes de sexo masculino sin morbilidad crónica pero se reconocen numerosas condiciones predisponentes y factores desencadenantes. Dentro de las condiciones que más se asocian a este cuadro se encuentra el asma, consumo de tabaco y drogas. Como factores desencadenantes se reconoce cualquier situación que genere una maniobra de Valsalva. El diagnóstico se hace en base al cuadro clínico y radiografía o TC de tórax. Se deben descartar otras causas más graves de neumomediastino. Conclusión: ésta es una enfermedad de baja frecuencia. El diagnóstico se realiza en base a un cuadro clínico compatible y estudios de imagen. El tratamiento es conservador y el curso clínico es habitualmente benigno. Las recurrencias son inhabituales.

Intususcepción intestinal posterior a bypass gástrico en Y de Roux / Intussusception after Roux-en-Y gastric bypass causing bowel obstruction: report of one case

We report a 41 years old female who underwent a gastric bypass 10 years ago. She presented an excess weight loss of 114 percent. She required a cholecystectomy and another surgical procedure due to an internal hernia. The patient complained of recurrent abdominal pain and an abdominal computed tomography showed an intestinal intussusception located at the jejuno-jejuno anastomosis. She was operated and the diagnosis was confirmed. An enlargement of the biliopancreatic loop and a bezoar were also found. A 15 cm intestinal resec-tion of the enlarged portion of the biliopancreatic loop and a new jejuno-jejuno anastomosis were performed. The patient recovered uneventfuUy and was discharged on the fourth postoperative day. The occurrence of intestinal intussusception as a cause of intestinal obstruction after gastric bypass is rare. It has been reported after open and laparoscopic surgery. There are several theories about the cause of intussusceotion, like changes in intestinal motility, a high excess weight loss, but a conclusive cause has not been identified. Generally the location of the intussusceptions is at the jejuno-jejuno anastomosis and it appears to be in a retrograde fashion in the majority of cases. The treatment is controversial, with several options; simple reduction, reduction and intestinal fixation, but apparently intestinal resection has better results.

Reportamos el caso de una paciente con antecedente de un bypass gástrico hace 10 años, que presentó una pérdida del exceso de peso de 114 por ciento. Posteriormente se realizó una colecistectomía y cirugía por hernia interna. Debido a cuadros de dolor abdominal a repetición fue estudiada con una tomografía computada de abdomen que demostró una intususcepción intestinal a nivel de la entero-entero anastomosis. La paciente fue intervenida, se confirmó el diagnóstico y se encontró también una dilatación del asa biliopancreática y un bezoar. Se realizó una resección intestinal del asa biliopancreática de 15 cms y anastomosis yeyuno-yeyunal, con buena evolución postoperatoria y alta a los 4 días de la cirugía. La intususcepción intestinal posterior a un bypass gástrico es poco frecuente como causa de obstrucción intestinal y ha sido descrita luego de cirugía abierta y laparoscópica. No existe una explicación definitiva para su patogenia. Presenta algunas características particulares como producirse en la mayoría de los casos en relación a la entero-entero anastomosis y ser una intususcepción retrograda. Su tratamiento es controversial, existiendo varias alternativas; reducción simple, reducción y fijación del asa comprometida, pero aparentemente la resección intestinal tendría mejores resultados, con menor frecuencia de recurrencia.

Physiopathology of the embryonic heart (with special emphasis on hypoxia and reoxygenation).

The adaptative response of the developing heart to adverse intrauterine environment such as reduced O2 delivery can result in alteration of gene expression with short- and long-term consequences including adult cardiovascular diseases. The tolerance of the developing heart of acute or chronic oxygen deprivation, its capacity to recover during reperfusion and the mechanisms involved in reoxygenation injury are still under debate. Indeed, the pattern of response of the immature myocardium to hypoxia-reoxygenation differs from that of the adult. This review deals with the structural and metabolic characteristics of the embryonic heart and the functional consequences of hypoxia and reoxygenation. The relative contribution of calcium and sodium overload, pH disturbances and oxidant stress to the hypoxia-induced cardiac dysfunction is examined, as well as various cellular signaling pathways (e.g. MAP kinases) involved in cell survival or death. In the context of the recent advances in developmental cardiology and fetal cardiac surgery, a better understanding of the physiopathology of the stressed developing heart is required.

Postanoxic functional recovery of the developing heart is slightly altered by endogenous or exogenous nitric oxide.

Nitric oxide synthase (NOS) is strongly and transiently expressed in the developing heart but its function is not well documented. This work examined the role, either protective or detrimental, that endogenous and exogenous NO could play in the functioning of the embryonic heart submitted to hypoxia and reoxygenation. Spontaneously beating hearts isolated from 4-day-old chick embryos were either homogenized to determine basal inducible NOS (iNOS) expression and activity or submitted to 30 min anoxia followed by 100 min reoxygenation. The chrono-, dromo- and inotropic responses to anoxia/reoxygenation were determined in the presence of NOS substrate (L-arginine 10 mM), NOS inhibitor L-NIO (1-5 mM), or NO donor (DETA NONOate 10-100 microM). Myocardial iNOS was detectable by immunoblotting and its activity was specifically decreased by 53% in the presence of 5 mM L-NIO. L-Arginine, L-NIO and DETA NONOate at 10 microM had no significant effect on the investigated functional parameters during anoxia/reoxygenation. However, irrespective of anoxia/reoxygenation, DETA NONOate at 100 microM decreased ventricular shortening velocity by about 70%, and reduced atrio-ventricular propagation by 23%. None of the used drugs affected atrial activity and hearts of all experimental groups fully recovered at the end of reoxygenation. These findings indicate that (1) by contrast with adult heart, endogenously released NO plays a minor role in the early response of the embryonic heart to reoxygenation, (2) exogenous NO has to be provided at high concentration to delay postanoxic functional recovery, and (3) sinoatrial pacemaker cells are the less responsive to NO.

Ectopic pacing at physiological rate improves postanoxic recovery of the developing heart.

Recently, rapid and transient cardiac pacing was shown to induce preconditioning in animal models. Whether the electrical stimulation per se or the concomitant myocardial ischemia affords such a protection remains unknown. We tested the hypothesis that chronic pacing of a cardiac preparation maintained in a normoxic condition can induce protection. Hearts of 4-day-old chick embryos were electrically paced in ovo over a 12-h period using asynchronous and intermittent ventricular stimulation (5 min on-10 min off) at 110% of the intrinsic rate. Sham (n = 6) and paced hearts (n = 6) were then excised, mounted in vitro, and subjected successively to 30 min of normoxia (20% O(2)), 30 min of anoxia (0% O(2)), and 60 min of reoxygenation (20% O(2)). Electrocardiogram and atrial and ventricular contractions were simultaneously recorded throughout the experiment. Reoxygenation-induced chrono-, dromo-, and inotropic disturbances, incidence of arrhythmias, and changes in electromechanical delay (EMD) in atria and ventricle were systematically investigated in sham and paced hearts. Under normoxia, the isolated heart beat spontaneously and regularly, and all baseline functional parameters were similar in sham and paced groups (means +/- SD): heart rate (190 +/- 36 beats/min), P-R interval (104 +/- 25 ms), mechanical atrioventricular propagation (20 +/- 4 mm/s), ventricular shortening velocity (1.7 +/- 1 mm/s), atrial EMD (17 +/- 4 ms), and ventricular EMD (16 +/- 2 ms). Under anoxia, cardiac function progressively collapsed, and sinoatrial activity finally stopped after approximately 9 min in both groups. During reoxygenation, paced hearts showed 1) a lower incidence of arrhythmias than sham hearts, 2) an increased rate of recovery of ventricular contractility compared with sham hearts, and 3) a faster return of ventricular EMD to basal value than sham hearts. However, recovery of heart rate, atrioventricular conduction, and atrial EMD was not improved by pacing. Activity of all hearts was fully restored at the end of reoxygenation. These findings suggest that chronic electrical stimulation of the ventricle at a near-physiological rate selectively alters some cellular functions within the heart and constitutes a nonischemic means to increase myocardial tolerance to a subsequent hypoxia-reoxygenation.

Mdx myotubes have normal excitability but show reduced contraction-relaxation dynamics.

The pathogenesis of Duchenne muscular dystrophy (DMD), characterised by lack of the cytoskeletal protein dystrophin, is not completely understood. An early event in the degenerative process of DMD muscle could be a rise in cytosolic calcium concentration. In order to investigate whether this leads to alterations of contractile behaviour, we studied the excitability and contractile properties of cultured myotubes from control (C57BL/10) and mdx mice, an animal model for DMD. The myotubes were stimulated electrically and their motion was recorded photometrically. No significant differences were found between control and mdx myotubes with respect to the following parameters: chronaxy and rheobase (0.33 +/- 0.03 ms and 23 +/- 4 V vs. 0.39 +/- 0.07 ms and 22 +/- 2 V for C57 and mdx myotubes, respectively), tetanisation frequency (a similar distribution pattern was found between 5 and 30 Hz), fatigue during tetanus (found in 35% of both types of myotubes) and post-tetanic contracture. In contrast, contraction and relaxation times were longer (P < 0.005) in mdx (36 +/- 2 and 142 +/- 13 ms, respectively) than in control myotubes (26 +/- 1 and 85 +/- 9 ms, respectively). Together with our earlier findings, these results suggest a decreased capacity for calcium removal in mdx cells leading, in particular, to alterations of muscle relaxation.

Oxidative and glycogenolytic cCapacities within the developing chick heart.

Cardiac morphogenesis and function are known to depend on both aerobic and anaerobic energy-producing pathways. However, the relative contribution of mitochondrial oxidation and glycogenolysis, as well as the determining factors of oxygen demand in the distinct chambers of the embryonic heart, remains to be investigated. Spontaneously beating hearts isolated from stage 11, 20, and 24HH chick embryos were maintained in vitro under controlled metabolic conditions. O(2) uptake and glycogenolytic rate were determined in atrium, ventricle, and conotruncus in the absence or presence of glucose. Oxidative capacity ranged from 0.2 to 0.5 nmol O(2)/(h.microg protein), did not depend on exogenous glucose, and was the highest in atria at stage 20HH. However, the highest reserves of oxidative capacity, assessed by mitochondrial uncoupling, were found at the youngest stage and in conotruncus, representing 75 to 130% of the control values. At stage 24HH, glycogenolysis in glucose-free medium was 0.22, 0.17, and 0.04 nmol glucose U(h.microg protein) in atrium, ventricle, and conotruncus, respectively. Mechanical loading of the ventricle increased its oxidative capacity by 62% without altering glycogenolysis or lactate production. Blockade of glycolysis by iodoacetate suppressed lactate production but modified neither O(2) nor glycogen consumption in substrate-free medium. These findings indicate that atrium is the cardiac chamber that best utilizes its oxidative and glycogenolytic capacities and that ventricular wall stretch represents an early and major determinant of the O(2) uptake. Moreover, the fact that O(2) and glycogen consumptions were not affected by inhibition of glyceraldehyde-3-phosphate dehydrogenase provides indirect evidence for an active glycerol-phosphate shuttle in the embryonic cardiomyocytes.

Pacing redistributes glycogen within the developing myocardium.

Electrical pacing at physiological rate induces myocardial remodeling associated with regional changes in workload, blood flow and oxygen consumption. However, to what extent energy-producing pathways are also modified within the paced heart remains to be investigated. Pacing could particularly affect glycogen metabolism since hypertrophy stimulates glycolysis and increased workload favors glucose over fat oxidation. In order to test this hypothesis, we used the embryonic chick heart model in which ventricular pacing rapidly resulted in thinning of the ventricle wall and thickening of the atrial wall. Hearts of stage 22HH chick embryos were submitted in ovo to asynchronous and intermittent ventricular pacing delivered at physiological rate during 24 h. The resulting alterations of glycogen content were determined in atrium, ventricle and conotruncus of paced and sham-operated hearts. Hemodynamic parameters of the paced and spontaneously beating hearts were derived from computerized image analysis of video recordings. With respect to sham, paced hearts showed a significant decrease in glycogen content (nmoles glucose units/microg protein; mean+/-S.D.) only in atrium (1.48+/-0.40 v 0.84+/-0.34, n=8) and conotruncus (0.75+/-0.28 v 0.42+/-0.23, n=8). Pacing decreased the end diastolic and stroke volumes by 34 and 44%, respectively. Thus, the rapid glycogen depletion in regions remote from the stimulation site appears to be associated with regional changes in workload and remodeling. These findings underscore the importance of the coupling mechanisms between metabolic pathways and myocardial remodeling in the ectopically paced heart.

TFIIA-TAF regulatory interplay: NMR evidence for overlapping binding sites on TBP.

TATA box binding protein (TBP)-promoter interaction nucleates assembly of the RNA polymerase II transcription initiation complex. Transcription factor IIA (TFIIA) stabilizes the TBP-promoter complex whereas the N-terminal domain of the largest TAF(II) inhibits TBP-promoter interaction. We have mapped the interaction sites on TBP of Drosophila TAF(II)230 and yeast TFIIA (comprising two subunits, TOA1 and TOA2), using nuclear magnetic resonance (NMR), and also report structural evidence that subdomain II of the TAF(II)230 N-terminal inhibitory domain and TFIIA have overlapping binding sites on the convex surface of TBP. Together with previous mutational and biochemical data, our NMR results indicate that subdomain II augments subdomain I-mediated inhibition of TBP function by blocking TBP-TFIIA interaction.

Inhibition of bicarbonate transport protects embryonic heart against reoxygenation-induced dysfunction.

It has not been well established whether the mechanisms participating in pH regulation in the anoxic-reoxygenated developing myocardium resemble those operating in the adult. We have specially examined the importance of Na+/H+ exchange (NHE) and HCO3-dependent transports in cardiac activity after changes in extracellular pH (pHo). Spontaneously contracting hearts isolated from 4-day-old chick embryos were submitted to single or repeated anoxia (1 min) followed by reoxygenation (10 min). The chronotropic, dromotropic and inotropic responses of the hearts were determined in standard HCO3- buffer at pHo 7.4 and at pHo 6.5 (hypercapnic acidosis). In distinct experiments, acidotic anoxia preceded reoxygenation at pHo 7.4. NHE was blocked with amiloride derivative HMA (1 micro mol/l) and HCO3-dependent transports were inactivated by replacement of HCO3 or blockade with stilbene derivative DIDS (100 micro mol/l). Anoxia caused transient tachycardia, depressed mechanical function and induced contracture. Reoxygenation temporarily provoked cardiac arrest, atrio-ventricular (AV) block, arrhythmias and depression of contractility. Addition of DIDS or substitution of HCO3 at pHo 7.4 had the same effects as acidosis per se, i.e. shortened contractile activity and increased incidence of arrhythmias during anoxia, prolonged cardioplegia and provoked arrhythmias at reoxygenation. Under anoxia at pHo 6.5/reoxygenation at pHo 7.4, cardioplegia, AV block and arrhythmias were all markedly prolonged. Interestingly, in the latter protocol, DIDS suppressed AV block and arrhythmias during reoxygenation, whereas HMA had no effect. Thus, intracellular pH regulation in the anoxic-reoxygenated embryonic heart appears to depend predominantly on HCO3 availability and transport. Furthermore, pharmacological inhibition of anion transport can protect against reoxygenation-induced dysfunction.

Effects of verapamil and ryanodine on activity of the embryonic chick heart during anoxia and reoxygenation.

Perturbations of the trans-sarcolemmal and sarcoplasmic Ca2+ transport contribute to the abnormal myocardial activity provoked by anoxia and reoxygenation. Whether Ca2+ pools of the extracellular compartment and sarcoplasmic reticulum (SR) are involved to the same extent in the dysfunction of the anoxic-reoxygenated immature heart has not been investigated. Spontaneously contracting hearts isolated from 4-day-old chick embryos were submitted to repeated anoxia (1 min) followed by reoxygenation (5 min). Heart rate, atrioventricular propagation velocity, ventricular shortening, velocities of contraction and relaxation, and incidence of arrhythmias were studied, recorded continuously. Addition of verapamil (10 nM), which blocks selectively sarcolemmal L-type Ca2+ channels, was expected to protect against excessive entry of extracellular Ca2+, whereas addition of ryanodine (10 nM), which opens the SR Ca2+ release channel, was expected to increase cytosolic Ca2+ concentration. Verapamil (a) had no dromotropic effect by contrast to adult heart, (b) attenuated ventricular contracture induced by repeated anoxia, (c) shortened cardioplegia induced by reoxygenation, and (d) had remarkable antiarrhythmic properties during reoxygenation specially. On the other hand, ryanodine potentiated markedly arrhythmias both during anoxia and at reoxygenation. Thus despite its immaturity, the SR seems to be functional early in the developing chick heart and involved in the reversible dysfunction induced by anoxia-reoxygenation. Moreover, Ca2+ entry through L-type channels appears to worsen arrhythmias especially during reoxygenation. These findings show that the Ca2+-handling systems involved in irregular activity in immature heart, such as the embryonic chick heart, may differ from those in the adult.

Glucose is arrhythmogenic in the anoxic-reoxygenated embryonic chick heart.

Unlike in adult heart, embryonic myocardium works at low PO2 and depends preferentially on glucose. Therefore, activity of the embryonic heart during anoxia and reoxygenation should be particularly affected by changes in glucose availability. Hearts excised from 4-d-old chick embryos were submitted in vitro to strictly controlled anoxia-reoxygenation transitions at glucose concentrations varying from 0 to 20 mmol/L. Spontaneous and regular heart contractions were detected optically as movements of the ventricle wall and instantaneous heart rate, amplitude of contraction, and velocities of contraction and relaxation were determined. Anoxia induced transient tachycardia and rapidly depressed contractile activity, whereas reoxygenation provoked a temporary and complete cardioplegia (oxygen paradox). In the presence of glucose, atrial rhythm became irregular during anoxia and chaotic-periodic during reoxygenation. The incidence of these arrhythmias depended on duration of anoxia, and no ventricular ectopic beats were observed. Removal of glucose or blockade of glycolysis suppressed arrhythmias. These results show similarities but also differences with respect to the adult heart. Indeed, glucose 1) delayed and anoxic contractile failure, shortened the reoxygenation-induced cardiac arrest, and improved the recovery of contractile activity; 2) attenuated stunning at 20 mmol/L but worsened it at 8 mmol/L; and 3) paradoxically, was arrhythmogenic during anoxia and reoxygenation, especially when present at the physiologic concentration of 8 mmol/L. The last named phenomenon seems to be characteristic of the young embryonic heart, and our findings underscore that fluctuations of glycolytic activity may play a role in the reactivity of the embryonic myocardium to anoxiareoxygenation transitions.

Melanoma anorrectal / Anorectal melanoma

Una de las neoplasias más excepcionales a nivel anorrectal es el melanoma maligno. Han sido atendidas cinco pacientes en el período 1987-1994. El diagnóstico se sospechó durante el examen proctológico y corroborando en todos los casos mediante la biopsia endoscópica. El estudio de diseminación preoperatorio fue negativo en todos los casos y se planteó la cirugía resectiva con intención curativa en todos ellos. El grado de compromiso tumoral es variable, pudiendo comprometer sólo mucosa y submucosa, planos musculares, todo el espesor de la pared y ganglios linfáticos. No se hizo tratamiento complementario de radioterapia o quimioterapia

Pancreatoduodenectomía en el cáncer de la cabeza del páncreas / Pancreatoduodenectomy in pancreas head cancer

Entre 1977 y 1993, 40 pacientes han sido sometidos a una resección pancreatoduodenal por cáncer de la cabeza del páncreas. La indicación más frecuente fue el carcinoma ductal en 36 enfermos (90 por ciento). En 33 pacientes (83,5 por ciento) se practicó pancreatoduodenectomía con preservación pilórica y en los otros 17 (17,5 por ciento) se asoció a gastrectomía. En 8 pacientes (20 por ciento) se realizó pancreatectomía total y, en 5 (12,5 por ciento) se resecaron porciones de la vena porta o mesentérica superior. Complicaciones postoperatorias se presentaron en 21 pacientes (52,5 por ciento) siendo la más frecuente la fístula pancreática en 8 (20 por ciento) y la atelectasia pulmonar infectada en 6 (15 por ciento). Fallecen 3 enfermos (7,5 por ciento). Se realizó seguimiento y etapificación TNM a 31 pacientes portadores de carcinoma ductal, correspondiendo 3 a etapa I, 13 a etapa II, 13 a etapa III y 2 a etapa IV. La sobrevida global a 1 año fue del 61,3 por ciento, a 2 años del 35,5 por ciento, a 3 años del 19,4 por ciento y a 4 años del 6,5 por ciento. La mediana de sobrevida fue de 19 meses. Los resultados obtenidos parecen justificar la pancreatoduodenectomía cada vez que sea factible como el tratamiento de elección en el cáncer de la cabeza del páncreas

Hallazgos quirúrgicos en pacientes con shock por heridas penetrantes abdominales por arma blanca / Surgical findings in patients with shock due to penetrating abdominal wounds by knife

Se estudian pacientes operados por heridas penetrantes abdominales por arma blanca en un período de 8 años. Al ingreso, 72 casos presentan schock y sus resultados se comparan con los de 119 pacientes con signos peritoneales como única manifestación clínica. Hubo baja frecuencia de ausencia de hallazgos patológicos en la laparotomía, 3 casos con shock y 7 casos con signos peritoneales. En los pacientes con shock se observa mayor frecuencia, p< 0,001 de lesiones vasculares, 32 por ciento, en relación a los pacientes con signos peritoneales, 5 por ciento. El PATI fue 14 en pacientes con shock y 8,9 en pacientes con signos peritoneales. Hubo 19 casos con shock y herida sobre el área hepática, entre los cuales, 3 casos presentan lesión de grandes vasos. La mortalidad de la serie corresponde a 2 pacientes que ingresan en shock, uno de los cuales fallece por lesión transfixiante de aorta. El shock es una indicación absoluta de cirugía en pacientes con herida penetrante abdominal por arma blanca

Heridas penetrantes abdominales por arma blanca: análisis de 500 pacientes operados / Abdominal penetrating wounds by steelarm: analysis of 500 operated patients

Se desea determinar las indicaciones absolutas de cirugía en pacientes con heridas penetrantes abdominales (HPA) por arma blanca. Para ello se estudiaron retrospectivamente todos los pacientes con HPA por arma blanca operados en nuestro centro en un período de 8 años. Se excluyeron pacientes con lesiones de cuello o tórax o con heridas por arma de fuego. Para identificar las condiciones más frecuentemente asociadas a laparotomías en blanco (LB) se analizaron los hallazgos quirúrgicos en pacientes con indicación única de cirugía. Se estimó el PATI en todos los pacientes y se hizo análisis estadístico con testx*. La serie está formada por 500 pacientes, 492 son hombres y la edad promedio es 28 años. Hubo 53 LB, con 20% de complicaciones y 5,6% de reoperaciones. Entre las indicaciones frecuentes de laparotomía, el shock y los signos peritoneales presentaron la más baja frecuencia de LB (<6%) y el más elevado PATI (x-14 y 8,9 respectivamente). Las indicaciones de cirugía con mayor frecuencia de LB (>10%) fueron la exteriorización de vísceras o epiplón, el dolor abdominal y las HPA múltiples. Considerando que no toda lesión de órgano intraabdominal requiere reparación, que la cirugía de urgencia se asocia a una importante morbilidad y que las LB están condicionadas principalmente por las indicaciones de laparotomía, concluimos que el manejo de los pacientes con HPA por arma blanca debe destinarse a disminuir las LB y evitar la reparación de lesiones asintomáticas, siendo el schock y los signos peritoneales las únicas indicaciones absolutas de cirugía en pacientes con HPA por arma blanca

Oxygen uptake during early cardiogenesis of the chick.

Oxidative metabolism of the isolated embryonic heart of the chick has been determined using a spectrophotometric technique allowing global as well as localized micromeasurements of the O2 uptake. Entire hearts, excised from embryos of 10 somites (primordia fused, stage 10 HH) and 40 somites (S shaped, stage 20 HH) were placed in a special chamber under controlled metabolic conditions where they continued to beat spontaneously and regularly. During the 32 h of development, the O2 consumption of the whole heart increased from 0.9 +/- 0.1 to 5.3 +/- 0.8 nmol O2/h. These values corrected for protein content were, however, comparable (0.45 nmol O2.h-1.micrograms-1). At stage 10-12, the O2 uptake varied along the cardiac tube (from 0.74 to 1.0 nmol O2.h-1.mm-2). From stage 10 to 20, the O2 uptake per unit area of ventricle wall increased from 0.7 +/- 0.2 to 1.8 +/- 0.2 nmol O2.h-1.mm-2, and the O2 uptake per myocardial volume during one cardiac cycle varied from 7 to 2.5 nmol O2/cm3. These results indicate that, despite an intense morphogenesis, the cardiac tissue has a rather low and stable oxidative metabolism, although the O2 requirement of the whole heart increases significantly. Moreover, the normalized suprabasal aerobic energy expenditure decreases throughout early cardiogenesis. The functional integrity of the isolated embryonic heart combined with the experimental possibilities of the microtechnique make the preparation appropriate for studying the changes in cardiac metabolism during development.

Oxygen uptake of isolated toad skin epithelium: micromeasurement and effect of ionic acclimation.

Oxidative metabolism of isolated toad skin epithelium (Bufo viridis) was investigated in vitro under open-circuit conditions using the spectrophotometric oxyhemoglobin micromethod. This highly sensitive technique has been adapted for studying several epithelia in parallel and for detecting possible regional variations of oxygen uptake in individual epithelium. Changes in the proportion of mitochondria-rich cells (MRC) by ionic acclimation affected oxidative metabolism under nontransporting condition. After acclimation of animals to either NaNO3 or NaCl solutions (100 mmol/l, for greater than 2 wk), the number of MRC per square millimeter in epithelia from nonacclimated and NaNO3- and NaCl-acclimated animals was 350 +/- 113, 460 +/- 196, and 107 +/- 52, respectively. O2 uptake of nonacclimated and NaNO3-acclimated epithelia was significantly higher than that of NaCl-acclimated epithelia (i.e., 0.89 and 0.90 vs. 0.57 nmol O2.h-1.mm-2, respectively). The correlation established between O2 uptake and number of MRC allowed evaluation of the respiration rate of one single MRC, i.e., approximately 1 pmol O2/h. The lowest mitochondrial oxidative activity was found in the epithelia from NaCl-acclimated toads where the uncoupler 2,4-dinitrophenol (50 mumols/l) had the highest relative stimulatory effect (+114%). Acetazolamide (50 mumols/l), a potent inhibitor of carbonic anhydrase mainly present in the MRC, reduced selectively by 31% O2 uptake of the MRC-rich epithelia (NaNO3 acclimated). O2 uptake increased significantly by approximately 80% when basolateral pH increased from 5.8 to 7.8, but did not depend on apical pH. These findings indicate that under nontransporting (open-circuit) conditions, aerobic metabolism of the isolated toad skin epithelium is related to the density and/or characteristics of the MRC.(ABSTRACT TRUNCATED AT 250 WORDS)