The L1 cell adhesion molecule is a potential biomarker of human distal nephron injury in acute tubular necrosis.

The L1 cell adhesion molecule (CD171) is a multidomain membrane glycoprotein of the immunoglobulin superfamily. We evaluated its expression in human acute kidney injury and assessed its use as a tissue and urinary marker of acute tubular injury. Using immunohistochemical studies with antibodies to the extracellular or cytoplasmic domains, we compared L1 expression in normal kidneys in 24 biopsies taken from patients with acute tubular necrosis. L1 was found at the basolateral and the lateral membrane in all epithelial cells of the collecting duct in the normal kidney except for intercalated cells. In acute tubular necrosis, L1 lost its polarized distribution being found in both the basolateral and apical domains of the collecting duct. Further, it was induced in thick ascending limb and distal tubule cells. Apically expressed L1 found only when the cytoplasmic domain antibody was used in biopsy specimens of patients with acute tubular necrosis. The levels of urinary L1, normalized for creatinine, were significantly higher in all 24 patients with acute tubular necrosis compared to five patients with prerenal azotemia or to six patients with other causes of acute kidney injury. Our study shows that a soluble form of human L1 can be detected in the urine of patients with acute tubular necrosis and that this may be a marker of distal nephron injury.

TCF-4 isoforms absent in TCF-4 mutated MSI-H colorectal cancer cells colocalize with nuclear CtBP and repress TCF-4-mediated transcription.

TCF-4 is the main effector of the Wnt/Wingless signalling pathway. As with other TCF/LEF factors, numerous alternative splicings at its 3' end affect its expression. Such a mechanism leads to the synthesis of numerous TCF-4 isoforms among which some contain binding domains for CtBP, an ubiquitous transcriptional corepressor. Of interest, we described a frequent TCF-4 frameshift mutation in mismatch-repair deficient colorectal cancers (MSI-H cancers) that leads to the selective loss of TCF-4 isoforms with CtBP binding abilities. We provide here data that argue for a partial colocalization of CtBP with TCF-4 isoforms containing CtBP binding domains in cellulo, and for a functional role of CtBP in repressing TCF-4 mediated transcription. We also demonstrate that such a colocalization is not observed in MSI-H colorectal cancer cells that harbour the TCF-4 frameshift mutation, and that CtBP is not able to repress TCF-4-mediated transcription in this context. Taken together, our results strongly suggest that CtBP would play a role in regulating TCF-4 mediated transcription upon its binding with some TCF-4 isoforms encoded by alternatively spliced mRNA. They also suggest a role for TCF-4 frameshift mutation during MSI-H colorectal tumour progression, by regulating the relative proportion of the different TCF-4 isoforms.

The nuclear pore complex is involved in nuclear transfer of plasmid DNA condensed with an oligolysine-RGD peptide containing nuclear localisation properties.

One of the major barriers to efficient gene transfer and expression of nonviral vectors for gene therapy is passage across the nuclear envelope. We have previously shown that an oligolysine-RGD peptide that condenses plasmid DNA and binds to cell surface integrins can mediate increased internalisation of plasmid DNA into cells and synergistic enhancement of gene expression when complexed to a cationic lipid. In this report, we show that this enhancement is due to increased nuclear transfer of the plasmid DNA. We have applied the digitonin-permeabilised cell system that has been well established for the study of the nuclear transport of proteins to examine the nuclear transfer of plasmid DNA. Nuclear transfer of plasmid DNA complexed to an oligolysine-RGD peptide and lipofectamine appears to be an energy-dependent process involving the nuclear pore complex, since it is inhibited at 4 degrees C and by treatment with wheat germ agglutinin or with an antibody to the nuclear pore complex which all block nuclear protein import. In accordance with active nuclear transport, we have shown that all these treatments inhibit expression of a luciferase reporter plasmid in permeabilised cells. Nuclear transfer of pDNA is enhanced in mitotic cells, but cell division is not a prerequisite for transfer. We propose that the oligolysine-RGD peptide acts as a nuclear localisation signal and that the cationic lipid is more important for cell entry and endosome destabilisation than nuclear transfer.

[Direct electric stimulation of the denervated posterior cricoarytenoid muscle triggered by subglottic temperature in the cat. Preliminary to a laryngeal pacemaker]. / Stimulation électrique directe du muscle crico-aryténoïdien postérieur dénervé, déclenchée par la température sous-glottique chez le chat. Préliminaires au pacemaker laryngé.

Using a temperature sensor to detect inspiratory fresh air flow in the subglottis, we triggered direct electrical stimulation of unilaterally denervated posterior cricoarytenoid muscle (PCA) in cats. Respiratory air flow temperature variations were recorded in awake animals and stimulation of the PCA resulting in vocal cord abduction was obtained several weeks after surgery. Difficulties related to chronic implantation and stimulation are discussed. Their solutions are required before laryngeal pacemaker is used.

Portable stimulator for direct electrical stimulation of denervated muscles in laboratory animals.

A portable lightweight stimulator for small animals is described. It delivers pulse trains of high intensity and is convenient for denervated muscle studies. It does not cause discomfort and does not restrict activity.