Increased pressor responsiveness to kidney extracts

Résumé La réponse hypertensive à des injections s.c. d'extrait de rein n'ayant initialement que peu ou pas d'effet sur la tension artérielle s'accroit progressivement avec la durée du traitement.

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Supported by NIH Grant No. HE-6835.     

Helical Molecular Orbitals Around Straight-Line Oligomers of H_2C_nH_2 as a Model for a Molecular Device

Allene-like and cumulene-like oligomers with two CH2 groups at both ends of the oligomers(H2CnH2) have been found to give helical molecular orbitals for HOMO and LUMO and around the MOs when two CH2 groups are tilted from their equilibrium position.This result can be explained due to the change of the symmetry for H2C2m+1H2 from D2d to D2,the former has degenerate molecular orbitals but latter has non-degenerate ones.This helical mo-     

Retinoic acid induces polarizing activity but is unlikely to be a morphogen in the chick limb bud.

Retinoic acid is a putative morphogen in limb formation in the chick and other vertebrates. In chick limb formation, it is thought that retinoic acid is released from the zone of polarizing activity (ZPA) and the concentration gradient of retinoic acid formed from the posterior to the anterior provides positional cues for digit formation. Implantation of a bead containing retinoic acid at the anterior margin of the limb bud induces a mirror-image symmetrical duplication of the digit pattern similar to that observed when the ZPA is grafted into the anterior margin of the host limb bud. Also, the level of endogenous retinoic acid (25 nM on average) is higher in the posterior one third of the limb bud. We found that when the bead containing either retinoic acid or an analogue but not the ZPA, was implanted in the anterior margin of the chick limb bud, expression of the retinoic acid receptor type-beta gene was induced around the bead within 4 h. These results indicate that exogenous retinoic acid is not identical with the ZPA morphogen. As the anterior tissue exposed to retinoic acid has polarizing activity, we conclude that the primary function of exogenous retinoic acid is to induce polarizing activity in the limb bud.     

Autotaxin (NPP-2) in the brain: cell type-specific expression and regulation during development and after neurotrauma

Autotaxin is a secreted cell motility-stimulating exo-phosphodiesterase with lysophospholipase D activity that generates bioactive lysophosphatidic acid. Lysophosphatidic acid has been implicated in various neural cell functions such as neurite remodeling, demyelination, survival and inhibition of axon growth. Here, we report on the in vivo expression of autotaxin in the brain during development and following neurotrauma. We found that autotaxin is expressed in the proliferating subventricular and choroid plexus epithelium during embryonic development. After birth, autotaxin is mainly found in white matter areas in the central nervous system. In the adult brain, autotaxin is solely expressed in leptomeningeal cells and oligodendrocyte precursor cells. Following neurotrauma, autotaxin is strongly up-regulated in reactive astrocytes adjacent to the lesion. The present study revealed the cellular distribution of autotaxin in the developing and lesioned brain and implies a function of autotaxin in oligodendrocyte precursor cells and brain injuries. Received 18 September 2006; received after revision 30 October 2006; accepted 4 December 2006     

Germline mutations in HRAS proto-oncogene cause Costello syndrome

Costello syndrome is a multiple congenital anomaly and mental retardation syndrome characterized by coarse face, loose skin, cardiomyopathy and predisposition to tumors. We identified four heterozygous de novo mutations of HRAS in 12 of 13 affected individuals, all of which were previously reported as somatic and oncogenic mutations in various tumors. Our observations suggest that germline mutations in HRAS perturb human development and increase susceptibility to tumors.