An exact method to obtain effective electrostatic interactions from computer simulations: the case of effective charge amplification.

We discuss here an exact method to determine the parameters regulating the screened Coulomb interactions among spherical macroions immersed in a simple electrolyte. This approach provides rigorous definitions for the corresponding screening length, effective permittivity, and renormalized charges, and can be employed for precise and reliable calculations of these parameters within any scheme. In particular, we introduce a simple procedure for extracting this information from computer simulations. The viability of this approach is demonstrated by applying it to a three-component model system which includes anionic nanoparticles and monovalent cations and anions. The mean forces between nanoparticles are determined directly from simulations with two macroions, plus small ions, inside a single cell with periodic boundary conditions. The values of the parameters of interest, on the other hand, are gathered from two separate sets of computer simulations: one set provides information about the short-range correlations among the small ions, which in turn determine the screening length and effective permittivity; the second set supplies the short-range components of the ionic distribution around one isolated macroion, which also determine its renormalized charge. The method presented here thus avoids the uncertain fitting of these parameters from the asymptotic tail of the mean force and allows us to investigate in detail this connection between the renormalized charge of the macroion and the short-range (virtual) part of the ionic cloud surrounding it. Using the standard prescription to extract an effective charge from the corresponding renormalized value, we then proceed to clarify the mechanisms behind the possibility of effective charge amplification (i.e., an effective charge larger than the bare macroion charge). Complementarily, we report results for the corresponding bridge functions too.

El cuestionario tridimensional para la depresión (CTD): un nuevo instrumento para medir la tristeza/depresión / The Three-dimensional Questionnaire of Depression (CTD); A new instrument for the measurement of sadness and depression

En este trabajo se presenta el proceso de elaboración y desarrollo de un nuevo autoinforme para evaluar la tristeza y la depresión, el Cuestionario Tridimensional para la Depresión CTD. Este instrumento está basado en la consideración multidimensional de la tristeza como una emoción básica y universal, así como de la depresión como la patología de la tristeza. En la elaboración del CTD se aplicó el modelo tridimensional de las emociones, empleado con éxito en la investigación de la ansiedad. El conocimiento derivado de las investigaciones clínicas se empleó para diseñar un instrumento capaz de valorar individualmente los componentes : cognitivos subjetivos, fisiológicos-somáticos y motórico-expresivos de la tristeza y la depresión. Además, el CTD incluye una escala de riesgo de suicidio, útil en el contexto clínico. Los análisis psicométricos muestran una alta fiabilidad, tanto testretest como en su consistencia interna, alta capacidad para distinguir entre poblaciones clínicas y de control, así como una adecuada validez convergente y una sólida estructura factorial. (AU)

[Biliary stenosis in patients treated with liver transplantation. Diagnostic approach]. / Stenosi biliare nei pazienti trattati con trapianto epatico (OLT). Approccio diagnostico.

Between April 1986 and August 1994, 393 orthotopic liver transplantation (OLT) have been performed at "12 de Octubre" Hospital. Among these ones we consider 274 OLT made in 223 adults and in 47 children (4 intraoperative deaths). The reconstruction of the biliary tract was performed with a choledocho-choledochostomy with T tube (CD-CD T) in 131 patients, a choledocho-choledochostomy without T tube or stent (CD-CD) in 75, a Roux-en-y-hepatico-jejunostomy (H-J) in 248, a hepatico-jejunostomy with stent (H-J St) in 13 and a choledocho-cholecisto-jejunostomy (CD-CC-J) in 3 patients. Thirthy six (13.3%) patients developed biliary complications (30 adults and 6 childrens). Fourteen (18.6%) occurred in CD-CD reconstruction and 13 (11.4%) in CD-CD T. The most common complications were leakage and stricture. Thirteen ERCP were performed in 12 patients (1 failed), all adults (CD-CD T: 3; CD-CD: 10). The main indication for ERCP was cholestasis and inability of non invasive methods ultrasound, scintigraphy and computerized tomography in determining the underlying etiology. ERCP was successful in all 12 patients: detecting strictures in 8, strictures + lithiasis in 1, stricture+lekage in 1 and leakage in 2. No complications were encountered after ERCP in our patients. ERCP is the method of choice in diagnosis of biliary complications in CD-CD biliary reconstruction.

Prenatal detection of anterior abdominal wall defects with US.

The size and position of an anterior abdominal wall defect, its contents, and its association with other anomalies are features that can be diagnosed in utero with ultrasound and that allow a differential diagnosis to be made. The correct prenatal diagnosis is extremely important for patient management. The key feature for sonographically distinguishing these conditions is the position of the defect in relation to the umbilical cord insertion. Omphaloceles and pentalogy of Cantrell usually involve a midline defect at the umbilical cord insertion. Gastroschisis most frequently consists of a small, right-sided paraumbilical defect. Eccentric, large lateral defects are typically present in limb-body wall complex or amniotic band syndrome. Bladder and cloacal exstrophy involve the infraumbilical region. In addition, the size of the defect, the organs eviscerated, the presence of membranes or bands, and any associated abnormalities help determine the correct diagnosis. Increased knowledge of these uncommon fetal conditions should result in better detection, more accurate diagnosis, and improved management of anterior abdominal wall defects.

Liver transplantation in patients with fulminant hepatic failure.

Fulminant hepatic failure without liver transplantation is associated with a high mortality rate (80-100 per cent). Some 254 liver transplantations were performed on 202 patients between April 1986 and February 1992. Of these, 26 patients had fulminant hepatic failure. The median age was 31.5 (range 3-60) years. Reduced-size grafts were used in seven patients. The preoperative mortality rate was six of 26 patients, and five patients died during follow-up. Ten patients underwent retransplantation and two a second retransplant. The overall mortality rate was 16 of 26 and actuarial survival rate was 62.7 per cent at 12 months and 48.7 per cent at 36 months. The preoperative mortality rate is relatively high but liver transplantation is currently recommended as a last-resort treatment for patients with fulminant hepatic failure in the absence of response to medical treatment.

[Results of hepatic transplantation from donors older than 50 years of age. Comparison with other age groups]. / Resultados del trasplante hepático utilizando donantes de más de 50 años. Comparación con otros grupos de edad.

We have performed 284 OLT and from 1990 we accept donors older than 50 years. We analyzed 100 consecutive OLT from 1990 in relation to donor age and we divided them in three groups: A) 10 liver transplants with donors < 16 years old; B) 76 liver transplants with donors between 16 and 49 years old, and C) 14 liver transplants with donors > 49 years old. The follow-up was more than 6 months. The liver preservation was carried out with Belzer solution and the immunosuppression was performed with cyclosporine A, corticoids and azathioprine. The C group donors were more stable haemodynamically (less dopamine dosage-p < 0.001- and less hours with arterial hypotension-p < 0.05-) and they died less of craneoencephalic traumatism than A group donors (p < 0.01). The C group donors didn't have more frequence of liver esteatosis or greater graft harvest lesions (p = n.s.). The cold ischaemia time was greater in C group vs A (p < 0.05) and its pretransplant clinical status was more serious than in A and B groups (p < 0.05). There were no significant differences between groups in relation to recipient status, frequence of hepatic artery or portal vein thrombosis, frequence of acute rejection, chronic rejection or biochemical graft evolution at first month. There were more primary graft non functions in B vs A (p < 0.05) and retransplants in B vs A and C (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Utilization of split liver grafts in orthotopic liver transplantation.

Among a total of 220 liver transplants, reduced-size liver was used in 21 cases due to discrepancies in size between recipient and donors in 19 patients. In the case of two adult patients suffering from fulminant hepatic failure and in a critical condition, only one donor organ became available, so that the graft was divided to give the two recipients an equal opportunity. The two patients with fulminant hepatic failure were admitted to the ICU requiring mechanical respiration almost at the same time. Hepatitis serologies were HBcAb+, HBsAb+, and VCA+ in one and negative in the second. They had different blood groups (A.Rh+, O.Rh-), and the only donor available was located in Milan, Italy. The graft perfused with UW. was divided into two (right side, segments IV, V, VI, VII, and VIII, and left side, segments I, II and III). The recipients were transplanted 50 and 48 hours after admission. The cold ischemia time was 7.10 and 16.50 hours. The first patient, who received the right lobe, was extubated at 48 hours and discharged on the 40th postransplant day. The second patient remained unconscious with progressive deterioration; an EEG on the 4th day revealed absence of higher cortical function.

Results of orthotopic liver transplantation: a personal experience.

The authors report on their experience of 158 liver transplants performed on 135 patients. Nineteen underwent re-transplantation and four of these required a second re-transplantation; total number of re-transplantations: 23 (14.6%). Hepatic cirrhosis was the most common indication (50.6%), of which alcoholic cirrhosis was the most common type (32.5%). The authors briefly report on their operative techniques and the results of their procedures. The operative mortality (30 days) was 13.3% (18 out of 135 patients). Complications included nine cases of hepatic artery thrombosis (5.7%), four of arterial stenosis (2.5%), one case of portal venous stenosis (0.63%), four cases of post-operative portal venous thrombosis (2.5%), seven of biliary fistula (4.4%; five following choledochocholedochostomy and two following choledochojejunostomy), and two cases of common bile duct stenosis (1.3%). The actuarial survival rate at 48 months is 80%.

Results of transhiatal esophagectomy in cancer of the esophagus and other diseases.

We present the results we obtained during the last 12 years with transhiatal esophagectomy. Two hundred and eighty-three patients were operated on using this procedure; 171 of them underwent the operation for cancer of the esophagus, 73 for cancer of the cardia, and 11 for cancer of the hypopharynx. The tumor stage, the operative technique, and the type of esophageal replacement (stomach: 62.9%; colon: 37.1%) are described. Overall operative mortality was 5.6%, mainly as a result of respiratory insufficiency. Long-term survival was 11.9% at five years for cancer of the esophagus, much lower than the 48.3% for cancer of the cardia.

Effects of prestorage white cell-reduction of apheresis platelets on platelet glycoprotein Ib and von Willebrand factor.

Twenty plateletpheresis components were harvested from 11 healthy donors and stored in polyolefin bags on a horizontal flatbed agitator at 22 degrees C. After 24 hours, white cells were reduced in one aliquot by centrifugation while the other aliquot was stored unaltered. Samples were obtained aseptically from each of these platelets at intervals for up to 10 days, and measurements were made of platelet glycoprotein Ib (GPIb) by both flow cytometry and polyacrylamide gel electrophoresis, of ristocetin-induced platelet aggregation by impedance aggregometry, and of plasma and platelet von Willebrand factor (vWF) by enzyme-linked immunosorbent assay. Storage of platelets under these conditions was associated with only minor decreases in surface GPIb, intraplatelet vWF, and ristocetin-induced platelet aggregation, and no differences were observed between the white cell-reduced and nonreduced aliquots. No benefit of white cell reduction in such components before prolonged storage is evident in the vWF-platelet interaction.