Refractory ascites: definition, pathogenesis and treatment

Refractory ascites, that is ascites which cannot be mobilized by low sodium diet and maximal doses of diuretics (up to 400 mg spironolactone or potassium canrenoate and 160 mg furosemide per day), occurs in 5% of cirrhotic patients with ascites. The development of refractory ascites is mainly related to the progression of arterial vasodilation-mediated vascular underfilling and to the imbalance between reduced synthesis of renal vasodilating factors (especially renal prostaglandins) and extreme activation of vasoconstricting systems. Further features include increased sodium reabsorption in the proximal tubule and altered pharmacokinetics and pharmacodynamics of diuretics. In patients with impaired renal function (as is the case for most patients with refractory ascites), the marked reduction of renal perfusion and glomerular filtration rate, with the consequent decrease of filtered sodium load, becomes the main pathogenetic factor. The principal therapeutic options for refractory ascites include repeated paracentesis and implantation of the LeVeen shunt. Paracentesis is a rapid and safe procedure to remove ascites, but it does not correct sodium retention. Ascites recurrence, therefore, may occur after a brief interval. The LeVeen shunt allows for better long-term control of ascites, but severe complications may supervene, and shunt occlusion is common. Neither therapeutic procedure improves survival. Different experimental therapeutic procedures have been proposed. Administration of ornipressin corrects hyperdynamic circulation and improves renal function. Thromboxane synthase inhibitors, by reducing renal synthesis of thromboxane A2, potentiate the diuretic and natriuretic response to furosemide. More invasive procedures, including portosystemic shunt and transjugular intrahepatic stent, are rarely used in the treatment of refractory ascites.(ABSTRACT TRUNCATED AT 250 WORDS)     

A distributed control strategy for wireless ATM networks

Cellular networks are expected to be upgraded to offer Personal Communication Services (PCS). The mobility management and wireless call control approach used in cellular networks are currently being proposed for use in PCS networks. Recent work indicates that both the signaling load and database update rates caused by these mobility management and call control procedures will increase significantly in next generation PCS networks. In this paper, we propose and analyze a new cluster-based architecture and define algorithms to effectively handle mobility management and call control functions for PCS. We assume an ATM network infrastructure. Some of the key aspects of our proposal include simplifying the mobile location and tracking function, performing connection setup in segments, eliminating the need for user service profile downloads between networks, and more efficient routing of connections by removing the need for an anchor switch. Advantages of this approach include a reduction in signaling traffic load, improved call/connection setup delays, and more efficient routing of connections. We carry out an analysis of our solution for high-tier PCS applications.     

Malignant vascular tumors in young patients

BACKGROUND: To the authors' knowledge there are few published series of malignant vascular tumors in patients age < or = 21 years. METHODS: The authors retrospectively documented the clinical presentation, pathology, treatment, and outcome of patients age < or = 21 years with malignant vascular tumors treated between 1970-1995 at Memorial Sloan-Kettering Cancer Center. The histologic sections were rereviewed to confirm the diagnosis. RESULTS: Four patients were identified with angiosarcoma and two with malignant hemangioendothelioma. Five patients were female and one was male; the median age at diagnosis was 11.8 years (range, 8 months-21 years). The tumor involved the skin in one patient, soft tissue in one patient, bone in two patients, and internal organs in two patients. One patient had associated diffuse angiomatosis and another had the Klippel-Trenaunay-Weber syndrome. This patient received prior radiation therapy to the primary site with the subsequent development of a vascular sarcoma. None of the patients had distant metastases at diagnosis. Resection was attempted in five patients and completed in four. Chemotherapy alone was given to three patients whereas radiation therapy alone and radiation plus chemotherapy were administered to one patient each. The median follow-up was 4.9 years (range, 1 month-12 years). There were three deaths from progressive disease and two deaths from locoregional recurrences. Reexcision and radiotherapy controlled one local recurrence. Another patient developed recurrence to regional lymph nodes and further dissemination. The primary tumor in all three survivors was excised completely whereas two of the three patients who died of progressive disease underwent an incomplete excision or biopsy alone. CONCLUSIONS: Malignant vascular tumors are rare in the first two decades of life and when they do occur are very aggressive. Complete resection is curative for patients with localized lesions.     

Cytogenetics of myelodysplastic syndromes

The authors review the main cytogenetic abnormalities encountered in MDS particularly del 5q, -7, +8, and complex abnormalities. Their presence may be useful to the diagnosis of MDS in difficult cases. Their prognostic value is important, and cytogenetics have recently been included in prognostic scores in MDS. Knowledge of recurrent chromosomal rearrangements is finally a first step in the discovery of genes implicated in the pathogenesis of MDS.     

浅谈沥青路面的质量控制

介绍了沥青路面的现状，指出了影响行车速度和行车安全的常见病害，如开裂、下沉、剥落、泛油、油包、车辙等现象。分析了病害产生的原因，并提出了加强沥青路面质量控制的观点和方法，使其达到设计所要求的寿命，以创造更大的经济效益和社会效益。     

Rheological behavior of a semirigid liquid crystal polymer

The rheological behavior of liquid crystal polymers is still far from completely clarified from both experimental and theoretical points of view. In this paper, the shear flow and the non-isothermal elongation flow behavior of a semirigid liquid crystal copolyester is discussed. The viscosity strongly decreases when the test temperature is increased above the crystal-nematic transition temperature; below this temperature the viscosity is very high. The thermal history strongly affects the shear viscosity. The elongational flow behavior depends also on temperature. Above the crystal-nematic transition temperature and the mesophase is easily spinnable, whereas below this temperature, the spinnability is very poor.     

Effects of dietary fish oil on biliary phospholipids and prostaglandin synthesis in the cholesterol-fed pairie dog

Cholesterol gallstone formation in the prairie dog is accompanied by an increase in the percentage of biliaryphospholipids containing arachidonic acid, and an increase in gallbladder prostaglandin (PG) synthesis, but the pathogenetic significance of these changes is unclear. Dietary supplementation with eicosapentaenoic acid (EPA), an omega-3 fatty acid which is commonly found in fish oil, decreases prostaglandin synthesis in some tissues by replacing arachidonic acid, and by competitively inhibiting prostaglandin synthesis. We studied the effect of dietary fish oil on gallbladder PG synthesis, and the relative abundance of various molecular species of phosphatidylcholines and phosphatidylethanolamines in bile and gallbladder epithelium in the cholesterol-fed prairie dog. Prairie dogs were maintained for 4 weeks on one of four diets: i) control, ii) cholesterol-supplemented (0.34%), iii) menhaden oil (50 g/kg chow), or iv) cholesterol plus menhaden oil. Supplementation with menhaden oil resulted in a replacement of arachidonic and linoleic acids with EPA and docosahexaenoic acids in the phospholipids of bile and gallbladder mucosa. In cholesterol-fed animals, supplementation with menhaden oil prevented increased gallbladder PG synthesis. Menhaden oil also reduced the incidence of cholesterol monohydrate crystals among cholesterol-fed animals (9/20 with cholesterol plus menhaden oil vs 21/22 with cholesterol alone), but the improvement could not clearly be attributed to decreased PG synthesis since supplementation with menhaden oil also increased the total phospholipid concentration in bile, and decreased the degree of cholesterol saturation. These results demonstrate that dietary supplementation with omega-3 fatty acids significantly influences biliary phospholipids, and decreases the incidence of cholesterol monohydrate crystal formation in this animal model.     

Synthesis and local anaesthetic activity of some 7-amino-2-dialkylaminoalkylpyrrolo[3,4-c]pyridine derivatives

A number of 7-amino-2-dialkylaminoalkylpyrrolo[3,4-c] pyridin-1,3(2H)-dione derivatives were synthesized and their local anaesthetic activity was evaluated in vivo by corneal anaesthesia in rabbits. Only compounds 3,9 and 14 showed any activity, albeit lower than that of the reference drug lidocaine.     

Shear and nonisothermal elongational characterization of a liquid crystalline polymer

A commercial liquid crystalline polymer (LCP) sample was characterized both in shear and in nonisothermal elongational flow over a wide range of temperatures (240–350°C). The LCP sample employed was a copolyesteramide of 2,6 hydroxynaphthoic acid, terephthalic acid, and aminophenol manufactured by Celanese and commercially known as Vectra B950. The viscosity decreases dramatically at temperatures above the crystal-nematic transition of the polymer. At lower temperatures, the extrusion of the sample is mainly due to plastic flow. Die-swell values are very small and contraction of the extrudate is also revealed, but the sample shows high elasticity. The polymer is not spinnable at very low temperatures, and the melt strength rapidly decreases with increasing temperature.