Intra-renal and subcellular distribution of the human chloride channel, CLC-5, reveals a pathophysiological basis for Dent's disease

Dent's disease, which is a renal tubular disorder characterized by low molecular weight proteinuria, hypercalciuria and nephrolithiasis, is associated with inactivating mutations of the X-linked chloride channel, CLC-5. However, the manner in which a functional loss of CLC-5 leads to such diverse renal abnormalities remains to be defined. In order to elucidate this, we performed studies to determine the segmental expression of CLC-5 in the human kidney and to define its intracellular distribution. We raised and characterized antisera against human CLC-5, and identified by immunoblotting an 83 kDa band corresponding to CLC-5 in human kidney cortex and medulla. Immunohistochemistry revealed CLC-5 expression in the epithelial cells lining the proximal tubules and the thick ascending limbs of Henle's loop, and in intercalated cells of the collecting ducts. Studies of subcellular human kidney fractions established that CLC-5 distribution was associated best with that of Rab4, which is a marker of recycling early endosomes. In addition, confocal microscopy studies using the proximal tubular cell model of opossum kidney cells, which endogenously expressed CLC-5, revealed that CLC-5 co-localized with the albumin-containing endocytic vesicles that form part of the receptor-mediated endocytic pathway. Thus, CLC-5 is expressed at multiple sites in the human nephron and is likely to have a role in the receptor-mediated endocytic pathway. Furthermore, the functional loss of CLC-5 in the proximal tubules and the thick ascending limbs provides an explanation for the occurrences of low molecular weight proteinuria and hypercalciuria, respectively. These results help to elucidate further the patho-physiological basis of the renal tubular defects of Dent's disease.     

KinMutBase, a database of human disease-causing protein kinase mutations

KinMutBase (http://www.uta.fi/laitokset/imt/KinMut Base.html) is a registry of mutations in human protein kinases related to disorders. Kinases are essential cellular signalling molecules, in which mutations can lead into diseases including, e.g., immunodeficiencies, cancers and endocrine disorders. The first release of KinMutBase contains information for nine protein tyrosine kinases. There are altogether 170 entries representing 273 families and 403 patients. Mutations appear both in conserved hallmark residues of the kinases as well as in non-homologous sites. The KinMutBase WWW pages provide plenty of information, namely mutation statistics and display, clickable sequences with mutations, restriction enzyme patterns and online submission.     

Stable association of PYK2 and p130(Cas) in osteoclasts and their co-localization in the sealing zone

Bone resorption is initiated by osteoclast attachment to the mineralized matrix, cytoskeletal reorganization, cellular polarization, and the formation of the sealing zone. The present study examines the interaction between PYK2 and p130(Cas) (Crk-associated substrate), suggested to be part of the signaling pathway initiated by osteoclast adhesion. Using murine osteoclast-like cells (OCLs) and their mononuclear precursors (pOCs), generated in a co-culture of bone marrow and osteoblastic MB1.8 cells, we show that: 1) p130(Cas) is tyrosine-phosphorylated upon adhesion of pOCs to vitronectin or ligation of beta3 integrins; 2) p130(Cas) colocalizes with PYK2 and the cytoskeletal proteins F-actin, vinculin, and paxillin in the podosomal-rich ring-like structures of OCLs plated on glass and in the sealing zone in actively resorbing OCLs on bone; 3) p130(Cas) and PYK2 form a stable complex in pOCs, independent of tyrosine phosphorylation of either molecule, and this complex is present in Src (-/-) OCLs, in which neither protein is phosphorylated or associated with the osteoclast adhesion structure; 4) the association of p130(Cas) and PYK2 is mediated by the SH3 domain of p130(Cas) and the C-terminal domain of PYK2. These findings suggest that p130(Cas) and its association with PYK2 may play an important role in the adhesion-dependent signaling that leads to cytoskeletal reorganization and formation of the sealing zone during osteoclast activation.     

Some implications of nanoscience in food dispersion formulations containing phospholipids as emulsifiers

This contribution is concerned with phospholipid films in relation to food dispersions such as emulsions and foams. Structural, morphological and surface rheological characteristics of dipalmitoyl phosphatidylcholine (DPPC) and dioleoyl phosphatidylcholine (DOPC) monolayers were determined at the air–water interface at 20 °C and at pH 5, 7, and 9, by means of surface pressure (π)–area (A) isotherms coupled with Brewster angle microscopy (BAM), atomic force microscopy (AFM) and surface dilatational and shear rheometry. From the π–A isotherms it was deduced that DPPC monolayers show structural polymorphism at the air–water interface. DOPC monolayers formed a liquid-expanded (LE) structure under all experimental conditions, a consequence of the weak molecular interactions due to the double bond in the hydrocarbon chain. Electrostatic interactions between film-forming components influence the monolayer structure. BAM and AFM images corroborate, at a microscopic and at nanoscopic level respectively, the structural polymorphism deduced from the π–A isotherm for DPPC monolayers as a function of surface pressure and the pH of the aqueous phase. However, the homogeneous morphology of DOPC monolayers at a microscopic level, as observed by BAM, shows structural heterogeneity at a nanoscopic level when observed by AFM. The relative monolayer thickness increases with surface pressure and is a maximum at the collapse point, especially for DPPC monolayers. The results confirm that the interfacial rheological characteristic measured under dilatation and shear conditions are very dependent on the structural characteristics and morphology of the phospholipids (DPPC and DOPC) monolayers.     

Sydenham Chorea: magnetic resonance imaging reveals permanent basal ganglia injury

We report the case of a 26-year-old man with diffuse esophageal leiomyomatosis involving the trachea. The tumor was resected by total esophagectomy and partial resection of the trachea and the left main bronchus. The tracheobronchial defect was repaired with a free forearm skin graft with satisfactory outcome. This approach offers good long-term prospects.     

The Kock pouch urinary reservoir

The use of detubularized ileum for the Kock pouch produced a low pressure, high capacity system superior to large bowel segments that provided excellent continence and protection of the upper urinary tracts. The early enthusiasm was tempered, however, by the technically demanding aspects of the construction of the nipple valves, the early and late complications, and occasional catheterization problems. With simple modifications in the fixation of the intussuscepted nipples, limiting use of staples and mesh collars, and tapering of the stoma, much of those problems have been resolved. The nipple valve is reliable and superior to the tunneled implant for the dilated ureter. With more widespread indications for continent neobladders, the hemi-Kock reservoir remains one of the most dependable and stable neobladders.