[Effect of prostaglandin (PGE2) in biliary atresia]

We studied the choleretic effect of Prostaglandin E2 (PGE2) in patients with biliary atresia. In the last four years PGE2 was used in ten cases with extrahepatic biliary atresia. All of them were treated by Kasai technique and temporary exteriorization of the bilioenteric conduit, permitting analyses of the postoperative bile flow. Mean age al operation was 50 days (range 30-70 days). The histology studies of liver and porta hepatis showed severe hepatic fibrosis in three patients, moderate in seven, bile ducts less than 100 mu in five and more than 100 mu in another five. The mean postoperative bile flow was 15 c.c./day (range 0-30 c.c.). We used PGE2 during postoperative period because the bile excretion was partial or total stopped (PGE2 0.125 mgr./kgr./day). In six cases the bile flow increase until 90 c.c./day (range 40-160 c.c./day) and four patients no response. Eight patients are alive, four without jaundice with normal hepatic function (serum bilirubin 1.04 mgr./dl) and four are waiting for liver transplantation. Two have died 7 and 30 months after Kasai procedure. The long-term follow-up was between 6 to 53 months. In conclusion the PGE2 has choleretic action in biliary atresia and could be a coadjuvant treatment to improve the bile flow.

Functional reconstitution of the glycine receptor

The functional reconstitution of the chloride channel coupled glycine receptor is described. Glycine receptors were purified from the cholate extract of rat spinal cord membranes by affinity chromatography and incorporated into phospholipid vesicles by the addition of phosphatidylcholine and removal of detergent by gel filtration. The reconstituted vesicles showed the same polypeptide composition as the purified receptor (proteins of Mr 48,000 and 58,000). The pharmacological characteristics of the glycine receptor were also preserved in the proteoliposomes, as demonstrated by the displacement of [3H]strychnine binding by several glycinergic ligands and by photoaffinity labeling experiments. In order to observe functional responses (i.e., specific agonist-induced anion translocation), we have developed an assay based on the fluorescence quenching of an anion-sensitive entrapped probe, SPQ [6-methoxy-N-(3-sulfopropyl)quinolinium]. Reconstituted vesicles were loaded with the fluorescent probe during a freeze-thaw-sonication cycle in the presence of added liposomes containing cholesterol. In such a reconstituted system, glycine receptor agonists are able to increase the rate of anion influx into the vesicles. The action of agonists is blocked by the simultaneous presence of strychnine or other glycine antagonists. Our results show that the purified 48,000- and 58,000-dalton polypeptides reconstituted into phospholipid vesicles can bind ligands and promote specific ion translocation in a way similar to the glycine receptor in its native environment.

[Reoperation in biliary atresia]

From July 1976 to February 1988 52 cases of extrahepatic biliary atresia were treated at our institution and 16 patients underwent reoperation. The original procedure were portojejunostomy in 11 cases (68 for 100), portocholecystostomy in four (25 for 100) and omento-duodenopexy in one (6 for 100). Age average at operation was 61 days; twelve had bile excretion. The reoperation was performed due to absence of bile drainage in three cases, cholangitis in 9 and bile peritonitis in four. Surgical procedures used at reoperation were: excision of scar tissue at the porta hepatis (12 patients) and portojejunostomy (five patients). Age average at reoperation was 105 days. Seven cases excreted bile. Liver pathology studies showed fibrosis in 12 cases and precirrhosis in four. The porta hepatis showed biliary ducts less than 100 mu in 10 cases, between 100mu-200mu in two, and absence of bile ducts in four. Currently four children are doing well with a mean long-term follow-up of 48 months, five are awaiting liver transplantation and one patient is doing well sixteen months post-transplant. Six patients (38 for 100) died. The best results were observed in those cases with early bile flow excretion after the first operation.

Interaction of bilirubin with gangliosides

Gangliosides seem to play an important role in the interaction of the neurotoxic pigment bilirubin with the synaptosomal plasma membrane (Vázquez et al. [1988] J. Biol. Chem. 263, 1255-1265). In this report, a further characterization of the bilirubin-ganglioside interaction is presented. The interaction is fast, and it is observed at any pH in the range 7.0-9.0. The characteristics of the interaction are different from those observed with other membrane lipids, including sphingomyelin. A model of binding to a single population of sites is able to adequately fit the experimental data. This model predicts a decrease in the tendency of bilirubin to interact with gangliosides and an increase in the binding capacity as the pH is decreased from 8.0 to 7.0. Our data would suggest a role for gangliosides in explaining the preferential accumulation of bilirubin in some areas of the brain and the toxic effect of this pigment in neuronal membrane-related functions.

Thermodynamics of agonist and antagonist interaction with the strychnine-sensitive glycine receptor

The thermodynamic parameters associated with the interactions of agonists and antagonists with glycine receptors in rat spinal cord membranes were determined. The binding of the antagonist [3H]strychnine and the inhibition of strychnine binding by 11 different glycinergic ligands were examined at temperatures between 0.5 and 37 degrees C. The density of receptors was not affected by the temperature at which the incubation was performed, but the ability of glycine receptor agonists and antagonists to compete with [3H]strychnine binding varied markedly. The affinity of the receptor for the antagonists strychnine, 2-aminostrychnine, RU-5135, 5,6,7,8-tetrahydro-4H-isoxazolo[5,4-c]azepin-3-ol, and the ligands bicuculline, norharmane, and PK-8165 decreased at higher temperatures. The binding of these ligands was enthalpy-driven. In contrast, the affinity of the agonists glycine, beta-alanine, and taurine and of the antihelmintic ivermectin increased at higher temperatures, and their binding was characterized by substantial increases in entropy. In addition, temperature affected the allosteric interaction between the glycine and strychnine sites of the receptor, as indicated by changes in the Hill number of the competition curves for glycine. Our results clearly indicate that the binding of agonists and antagonists to the glycine receptor is differentially affected by temperature, probably as a consequence of the different changes induced in the receptor conformation.

[Vasculo-renal arterial hypertension. Apropos of 2 very representative cases]

Authors's presents two clinical cases representatives of vasculo-renal hypertension, as much by its etiology and physiopathological mechanisms, as the therapeutics solutions successfully applied.

[Neurologic manifestations of dissecting aneurysms of the aorta]

Dissecting aneurysm of the aorta keeps on being nowadays a diagnostic problem, although it is a well known entity. Dissecting aneurysms may be classified into type A, dissection involving the ascending aorta, and type B, dissection involving descending aorta. The frequency of neurologic manifestations oscillates from 18 to 30%. From the 133 cases of dissecting aneurysm attended at our hospital, 30 (22.5%) presented neurologic manifestations. Nine patients (30%) had symptoms of ischemic neuropathy; 13 (43.3%) presented symptoms compatible with spinal ischemia and 14 (46.7%) presented manifestations of brain ischemia, with involvement of supraaortic trunks proven at autopsy in eight cases. The neurologic complications of type A and B dissecting aneurysms were similar (28 and 26%); in up to 30% of patients, it was the initial symptom. In type A dissecting aneurysm, the most frequent neurologic manifestation was brain ischemia (57.1%) whereas ischemic neuropathy and spinal ischemia predominated in type B dissecting aneurysm. The overall mortality rate reached 76.7% (85.7% for type A and 55.5% for type B). The modality of treatment had no clear influence on the survival. In the presence of brain complications, the mortality was 100%.

[Aspects related to extraction and preservation in 60 cases of liver transplant]

Extraction and preservation are of special interest in any liver transplant program. The viability and correct early function of the graft are determinant factors of the success or failure of the transplant. Application of a restrictive criterion in the acceptance of donor livers has allowed us to achieve an optimal viability (96.7%) in our first 60 cases of liver transplant.

Interaction of bilirubin with the synaptosomal plasma membrane

The interaction of the neurotoxic pigment bilirubin with synaptosomal plasma membrane vesicles (SPMV) isolated from rat brain was investigated. The interaction seems to involve three steps: (a) a rapid formation of an electrostatic complex between bilirubin and polar lipid head groups; (b) a slow inclusion of the pigment into the hydrophobic core of the membrane; and (c) a SPMV-induced bilirubin aggregation, observed when membrane capacity for bilirubin is exceeded. The association constant of the initial complex increased markedly when pH was lowered below 7.4, particularly in SPMV isolated from newborn rats. A preferential binding of bilirubin to pure gangliosides and sphingomyelin was observed, thus suggesting a role for these lipids as first targets of the pigment in the synaptic membrane. The inclusion of bilirubin into the membranes was gradually enhanced when decreasing the pH or the age of the rats from which SPMV were isolated. In addition, membranes from 2-day-old rats have a higher capacity for bilirubin incorporation compared to those from adult rats. Experiments with reconstituted liposomes of varying protein and cholesterol contents suggest that the effect of age may be related to changes in synaptosomal membrane fluidity during development. Our results support the hypothesis that the interaction of bilirubin with the synaptic membrane plays an important role in the molecular mechanisms of bilirubin neurotoxicity.

[Anomalies of the urinary tract associated with congenital heart diseases]

Due to the frequent association of congenital heart disease and urinary tract malformations we studied 434 patients undergoing angiocardiograms for diagnosis of their congenital heart disease. In every patient a plain abdominal X-ray film was made in order to observe urinary elimination of the contrast material. We found 70 patients with urinary tract malformations, the most frequent of which was pyelo-chaliceal dilatation, accounting for 47.1% of all the malformations found. A double pyelo-chaliceal system was found in 25.7%, kidney hypoplasia in 10% and in lower frequencies double urethers, kidney agenesia, pelvic kidneys, horseshoe-shaped kidney and others. Patients were usually urologically asymptomatic. In view of the frequent association of congenital heart disease and urinary tract malformations a plain abdominal X-ray film should always be performed postangiographically. In some cases a contrast urography is recommended.

The glycine receptor: pharmacological studies and mathematical modeling of the allosteric interaction between the glycine- and strychnine-binding sites

The displacement by glycine of 3H-strychnine binding to rat spinal cord membranes cannot be explained by a simple competitive interaction. Indeed, protein-modifying reagents can completely abolish the inhibition of 3H-strychnine binding by glycine and other agonists, whereas the interaction of strychnine itself and other related compounds with the binding site is unimpaired. Moreover, glycine cannot inhibit completely saturable 3H-strychnine binding, the extent of its maximum inhibitory effect depending on the ionic composition of the medium. Hill coefficients less than 1 (whose magnitude also depends on the assay medium) were obtained from glycine displacement curves. These properties are consistent with a mathematical model of two different, but mutually interacting, binding sites for strychnine and glycine on the glycine receptor. The effect of ions and protein-modifying reagents might be explained in this model as modifications of the mechanisms that mediate the allosteric interaction, and/or the affinity of glycine for the receptor. The agonists beta-alanine and taurine and the new antagonists, THAZ, iso-THAZ, and 4,5-TAZA, also seem to interact with a site different from the strychnine-binding site, probably the glycine-binding site.

Activation and inhibition of 3H-strychnine binding to the glycine receptor by Eccles' anions: modulatory effects of cations

The ammonium salts of Eccles' anions are inhibitors of 3H-strychnine binding. By contrast, the binding is activated by the sodium salts of these anions. This activation is due to an increase in the affinity for 3H-strychnine. Pretreatment of the membranes with acetic anhydride abolishes the effect of sodium salt, whereas ammonium salts remain unaffected. In the presence of chloride the inhibitory effect of ammonium predominates over the effect of sodium. These results suggest that the effect of Eccles' anions is profoundly modified by their counter-ions and that Na+ and ammonium are acting through distinct sites on the glycine receptor.