Extrahepatic metabolism of 4-methylumbelliferone and lidocaine in the anhepatic rabbit

OBJECTIVE: The initially well-fixed implants of total hip replacement (THR) are in the long-term subject to aseptic loosening. Many cytokines can contribute to osteolysis due to osteoclast recruitment and/or activation. However, in this respect tumor necrosis factor-alpha (TNF-alpha) plays a pivotal role, because it upregulates interleukin-1 and 6 and granulocyte-macrophage colony stimulating factor. The aim of this study was to assess the eventual presence, cellular localization and extent of expression of TNF-alpha in the synovial-like membrane at the implant or at the cement to bone interface compared to control synovial membrane. METHODS: Twenty samples from the synovial-like membrane of the periprosthetic tissues were compared to control samples. TNF-alpha containing cells were visualized using an avidin-biotin-peroxidase complex (ABC) method and analyzed by light microscopy, double labelling and image analysis. RESULTS: TNF-alpha was found in the periprosthetic tissues in fibroblasts and vascular endothelial cells, but mainly in the macrophages was it found to coincide with areas containing implant-derived debris. TNF-alpha containing cells were more numerous in the synovial-like membrane in the interface tissue from the proximal stem area (2816 +/- 318 cells) than in the control synovial membrane (565 +/- 93 cells, p < 0.01). Interestingly, similarly high TNF-alpha expression (3452 +/- 582 cells) was also seen in the synovial-like membrane of the pseudocapsule. CONCLUSION: These findings suggest that the foreign body-type host reaction caused by THR is characterized by the high expression of TNF-alpha. Because such expression occurred in the interface tissue between the implant and surrounding bone, TNF-alpha, due to its pivotal direct and indirect role in the activation and recruitment of osteoclasts, may contribute to periprosthetic osteolysis and to the loosening of THR.     

Evidence for McKusick''s hypothesis of deficient collagen cross-linking in patients with homocystinuria

Fractionation of the venom of the spider Phoneutria nigriventer revealed that it was a mixture of several neurotoxic peptides. The peptides so far characterized either inhibited or induced neurotransmitter release. These effects were mediated by Ca2+ channels or increasing Na+ permeability through voltage sensitive Na(+)-channels, respectively. The pooled toxic components (fraction P4) showed stimulatory effects on acetylcholine release from brain cortical slices. In addition, a component of the observed effects resembling that of alpha-latrotoxin was identified, which was characterized by the ability to provoke release of acetylcholine (ACh) at low temperature and in a manner independent of extracellular Ca2+ and of voltage sensitive Na(+)-channels.     

Construction and characterization of a set of E. coli strains deficient in all known loci affecting the proteolytic stability of secreted recombinant proteins

Even though secretion offers numerous advantages for the production of proteins in Escherichia coli, the expression of many heterologous proteins is severely limited by degradation in the periplasmic space. We found that mutations in rpoH, the RNA polymerase sigma factor responsible for heat shock protein synthesis, affect the stability of heterologous secreted proteins. A particularly dramatic increase in expression was further observed in rpoH degP double mutants. To minimize proteolytic degradation, we constructed a family of 25 isogenic strains deficient in all known cell envelope proteases (DegP, Protease III, Tsp(Prc), and OmpT), as well as the rpoH15 mutant allele, and characterized their growth in both shake flasks and fermentors. The availability of this set of strains permits the selection of a suitable host based on the optimal combination between the optimum reduction in protease activity and acceptable growth properties.     

Symmetry breaking and training from incomplete data with Radial Basis Boltzmann Machines

A Radial Basis Boltzmann Machine (RBBM) is a specialized Boltzmann Machine architecture that combines feed-forward mapping with probability estimation in the input space, and for which very efficient learning rules exist. The hidden representation of the network displays symmetry breaking as a function of the noise in the dynamics. Thus, generalization can be studied as a function of the noise in the neuron dynamics instead of as a function of the number of hidden units. We show that the RBBM can be seen as an elegant alternative of k-nearest neighbor, leading to comparable performance without the need to store all data. We show that the RBBM has good classification performance compared to the MLP. The main advantage of the RBBM is that simultaneously with the input-output mapping, a model of the input space is obtained which can be used for learning with missing values. We derive learning rules for the case of incomplete data, and show that they perform better on incomplete data than the traditional learning rules on a 'repaired' data set.     

FDG PET of the retroperitoneum: normal anatomy, variants, pathologic conditions, and strategies to avoid diagnostic pitfalls

Evaluation of the retroperitoneum is important to assess the extent of retroperitoneal malignancies and because the retroperitoneum is a route of nodal spread for other malignancies. Positron emission tomography (PET) with 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) allows detection of small malignant nodes not identified or not meeting size criteria for malignancy with computed tomography (CT) and tumor recurrences in surgical beds that are otherwise difficult to assess. However, evaluation of retroperitoneal malignancies or adenopathy with FDG PET can be complicated by urinary and colonic activity or anatomic variants. Urinary artifacts are avoided with intravenous hydration, administration of furosemide, and catheterization and retrograde filling of the bladder with saline solution. Colonic artifacts are avoided by cleansing the bowel with an isosmotic solution. FDG PET is useful in assessing the retroperitoneum for adenopathy in malignancies such as testicular cancer; lymphoma; and rectal ovarian, or cervical cancer that spread along retroperitoneal lymphatics. FDG PET is especially useful for detection of malignant nodes that do not meet size criteria at CT or when lack of retroperitoneal fat makes it difficult to identify retroperitoneal nodes with CT. FDG PET has an important role in evaluation of postoperative beds, where CT has limited useful because of altered anatomy, surgical clip artifacts, and scar issue.