Fluctuations in active membranes

Active contributions to fluctuations are a direct consequence of metabolic energy consumption in living cells. Such metabolic processes continuously create active forces, which deform the membrane to control motility, proliferation as well as homeostasis. Membrane fluctuations contain therefore valuable information on the nature of active forces, but classical analysis of membrane fluctuations has been primarily centered on purely thermal driving. This chapter provides an overview of relevant experimental and theoretical approaches to measure, analyze and model active membrane fluctuations. In the focus of the discussion remains the intrinsic problem that the sole fluctuation analysis may not be sufficient to separate active from thermal contributions, since the presence of activity may modify membrane mechanical properties themselves. By combining independent measurements of spontaneous fluctuations and mechanical response, it is possible to directly quantify time and energy-scales of the active contributions, allowing for a refinement of current theoretical descriptions of active membranes.Comment: 38 pages, 9 figures, book chapte

The use of positron emission tomography in detecting hepatoblastoma recurrence - A cautionary tale

Purpose: The use of positron emission tomography (PET) with [18F] fluorodeoxyglucose (FDG) in the detection of recurrences has been well established in many tumor types. Here the authors present their experience using this modality in the evaluation of posttreatment hepatoblastoma patients. Methods: The authors conducted a retrospective review on patients with hepatoblastoma diagnosed from 1996 to 2003. FDG-PET imaging was performed together with measurement of alpha-fetal protein (AFP) during posttreatment follow-up. Results: Sixteen patients (8 boys and 8 girls) were identified in this series. The mean age was 23.5 months (range, 5 months to 4 years). Three posttreatment patients had PET results suggestive of tumor recurrence. One of these patients had normal AFP level and suspected recurrence in the caudate lobe. Radiologic-guided biopsy was performed 3 times, and there was no evidence of tumor. The other 2 patients underwent further liver resections because of mildly raised AFP levels. The histology of these showed regenerative liver tissue only with no hepatoblastoma recurrence. Conclusions: Although PET has been gaining popularity as a tool in the detection of tumor recurrences worldwide, it has been shown in this series that PET may not be useful in hepatoblastoma patients, and caution must be taken in the interpretation of positive results. © 2004 Elsevier Inc. All rights reserved.link_to_subscribed_fulltex

Small bowel herniation and gangrene from peritoneal dialysis catheter exit site

Peritoneal dialysis is one of the standard methods for blood purification. It is particularly well suited for treating children with acute renal failure. Here we report a rare case of small bowel herniation at the peritoneal catheter exit site following removal, leading to gangrenous infarction.link_to_subscribed_fulltex

Effective antibiotic regime for postoperative acute cholangitis in biliary atresia - An evolving scene

Purpose: The prompt use of empirical antibiotics is vital in managing post-Kasai cholangitis. The authors published findings of their clinical trial in 1991 and established the use of cefoperazone, with a response rate of 88.9%. Here its clinical use since its introduction is reviewed and the trend in its efficacy is assessed. Methods: A retrospective review was carried out between 1997 and 2003. All episodes of acute cholangitis in patients who underwent Kasai procedure were recorded. Cholangitis was defined as unexplained fever with derangement of liver enzymes. Cefoperazone was started empirically according to the established protocol, and the response to treatment was analyzed. Results: There were 19 patients with a total of 49 episodes of cholangitis. Cefoperazone was used as the first-line empirical antibiotic in 40 of these episodes. Only 30 showed successful response (75%). For the 10 unresponsive episodes, meropenem was used as second-line antibiotic with complete response in all. Conclusions: The efficacy of cefoperazone in the treatment of post-Kasai cholangitis has decreased over the last years. This suggests a need for a more effective first-line empirical antibiotic. From this review, meropenem seems to be a suitable candidate, and a future prospective clinical trial is warranted. © 2004 Elsevier Inc. All rights reserved.link_to_subscribed_fulltex