Influence of magnesium and cysteine on vasopressin-induced contractions in various canine blood vessels

Zusammenfassung In-vitro-Versuche erwiesen, dass Magnesium-freie oder Cystein-enthaltende Krebs-Ringerlösung unterschiedlich auf vasopressininduzierte Kontraktionen an verschiedenen Blutgefässen des Hundes wirken. Zwei verschiedene Phänomene wurden beobachtet: entweder eine parallele Verschiebung der Dosis-Wirkungskurven nach rechts ohne Verminderung der maximalen VerkÜrzung oder eine Neigung der Dosis-Wirkungskurven mit einer auffallenden Verminderung der maximalen VerkÜrzung. Es wird auf Grund der Befunde angenommen, dass die Vasopressin-Rezeptoren verschiedener Blutgefässe nicht identisch sind.     

Radiation effects on embryonic chick tibiae

Zusammenfassung Hühnerschienbeine zeigen 2 strahlensensitive Perioden während der embryonalen Entwicklungszeit. Wachstumshemmung durch ionisierende Strahlen wirkt sich am stärksten während der ersten 3 Tage sowie am 10. Tag der Inkubation aus. Strahlendosiseffektkurven zeigen eine vergleichbare Strahlenempfindlichkeit am 3. und 10. Tag, wenn Schienbeinlänge und-gewicht als Dosiseffekt gemessen werden.     

Demethylcephaeline,a new alkaloid fromAlangium lamarckii. Characterization of AL 60, the hypotensive principle from the stem-bark

Résumé A partir de l'écorce de la tige d'Alangiumlamarckii Thw., une base, C₂₇H₃₆N₂O₄ (p.f. 147–149°, []_d-53,5°) ainsi que de la céphaeline, psychotrine, desméthylpsychotrine et tubulosine ont été isolées. Cette nouvelle base est identifiée comme déméthylcéphaeline, montrant que le principe hypotendu AL 60, précédemment obtenu de la même provenance est un mélange de psychotrine, de céphaeline et de déméthylcéphaeline.     

Dual effect of cannabinoid CB<Subscript>1</Subscript> receptor stimulation on a vanilloid VR1 receptor-mediated response

Cannabinoid CB1 receptors and vanilloid VR1 receptors are co-localized to some extent in sensory neurons of the spinal cord and dorsal root ganglia. In this study, we over-expressed both receptor types in human embryonic kidney (HEK)-293 cells and investigated the effect of the CB1 agonist HU-210 on the VR1-mediated increase in intracellular Ca2+ ([Ca2+]i), a well-known response of the prototypical VR1 agonist capsaicin. After a 5-min pre-treatment, HU-210 (0.1 microM) significantly enhanced the effect of several concentrations of capsaicin on [Ca2+]i in HEK-293 cells over-expressing both rat CB1 and human VR1 (CB1-VR1-HEK cells), but not in cells over-expressing only human VR1 (VR1-HEK cells). This effect was blocked by the CB1 receptor antagonist SR141716A (0.5 microM), and by phosphoinositide-3-kinase and phospholipase C inhibitors. The endogenous agonist of CB1 and VR1 receptors, anandamide, was more efficacious in inducing a VR1-mediated stimulation of [Ca2+]i in CB1-VR1-HEK cells than in VR1-HEK cells, and part of its effect on the former cells was blocked by SR141716A (0.5 microM). Pre-treatment of CB1-VR1-HEK cells with forskolin, an adenylate cyclase activator, enhanced the capsaicin effect on [Ca2+]i. HU-210, which in the same cells inhibits forskolin-induced enhancement of cAMP levels, blocked the stimulatory effect of forskolin on capsaicin. Our data suggest that in cells co-expressing both CB1 and VR1 receptors, pre-treatment with CB1 agonists inhibits or stimulates VR1 gating by capsaicin depending on whether or not cAMP-mediated signalling has been concomitantly activated.     

Role of Cys221 and Asn116 in the zinc-binding sites of the Aeromonas hydrophila metallo-β-lactamase

The CphA metallo--lactamase produced by Aeromonas hydrophila exhibits two zinc-binding sites. Maximum activity is obtained upon binding of one zinc ion, whereas binding of the second zinc ion results in a drastic decrease in the hydrolytic activity. In this study, we analyzed the role of Asn116 and Cys221, two residues of the active site. These residues were replaced by site-directed mutagenesis and the different mutants were characterized. The C221S and C221A mutants were seriously impaired in their ability to bind the first, catalytic zinc ion and were nearly completely inactive, indicating a major role for Cys221 in the binding of the catalytic metal ion. By contrast, the binding of the second zinc ion was only slightly affected, at least for the C221S mutant. Mutation of Asn116 did not lead to a drastic decrease in the hydrolytic activity, indicating that this residue does not play a key role in the catalytic mechanism. However, the substitution of Asn116 by a Cys or His residue resulted in an approximately fivefold increase in the affinity for the second, inhibitory zinc ion. Together, these data suggested that the first zinc ion is located in the binding site involving the Cys221 and that the second zinc ion binds in the binding site involving Asn116 and, presumably, His118 and His196.Received 3 March 2003; received after revision 4 August 2003; accepted 25 August 2003     

Programmed cell clearance

Apoptosis, a physiological process of self-annihilation, is essential during development and for the maintenance of tissue homeostasis. Considerable efforts have been made in recent years to elucidate the molecular mechanisms that govern this mode of cellular demise; however, the subsequent recognition and removal of apoptotic corpses by neighboring phagocytes has received less attention. Nevertheless, macrophage engulfment of apoptotic cells is known to be important in the remodeling of tissues, and contributes to the resolution of inflammation through the removal of effete cells prior to the release of noxious cellular constituents. Moreover, apoptotic cells are a potential source of self-antigens, and clearance of cell corpses is thought to preclude the induction of autoimmune responses. The view is thus emerging that tissue homeostasis is dependent not only on the balance between mitosis and apoptosis, but also on the rate of apoptosis versus that of cell clearance. This review aims to discuss the mechanisms and consequences of macrophage recognition and disposal of apoptotic cells, a process which will be referred to as programmed cell clearance.Received 16 April 2003; received after revision 22 May 2003; accepted 26 May 2003     

Phosphorylation by aurora kinase A induces Mdm2-mediated destabilization and inhibition of p53

Aurora kinase A (also called STK15 and BTAK) is overexpressed in many human cancers. Ectopic overexpression of aurora kinase A in mammalian cells induces centrosome amplification, chromosome instability and oncogenic transformation, a phenotype characteristic of loss-of-function mutations of p53. Here we show that aurora kinase A phosphorylates p53 at Ser315, leading to its ubiquitination by Mdm2 and proteolysis. p53 is not degraded in the presence of inactive aurora kinase A or ubiquitination-defective Mdm2. Destabilization of p53 by aurora kinase A is abrogated in the presence of mutant Mdm2 that is unable to bind p53 and after repression of Mdm2 by RNA interference. Silencing of aurora kinase A results in less phosphorylation of p53 at Ser315, greater stability of p53 and cell-cycle arrest at G2-M. Cells depleted of aurora kinase A are more sensitive to cisplatin-induced apoptosis, and elevated expression of aurora kinase A abolishes this response. In a sample of bladder tumors with wild-type p53, elevated expression of aurora kinase A was correlated with low p53 concentration. We conclude that aurora kinase A is a key regulatory component of the p53 pathway and that overexpression of aurora kinase A leads to increased degradation of p53, causing downregulation of checkpoint-response pathways and facilitating oncogenic transformation of cells.     

Assessing the impact of population stratification on genetic association studies

Population stratification refers to differences in allele frequencies between cases and controls due to systematic differences in ancestry rather than association of genes with disease. It has been proposed that false positive associations due to stratification can be controlled by genotyping a few dozen unlinked genetic markers. To assess stratification empirically, we analyzed data from 11 case-control and case-cohort association studies. We did not detect statistically significant evidence for stratification but did observe that assessments based on a few dozen markers lack power to rule out moderate levels of stratification that could cause false positive associations in studies designed to detect modest genetic risk factors. After increasing the number of markers and samples in a case-cohort study (the design most immune to stratification), we found that stratification was in fact present. Our results suggest that modest amounts of stratification can exist even in well designed studies.     

Mutations in a new member of the chromodomain gene family cause CHARGE syndrome

CHARGE syndrome is a common cause of congenital anomalies affecting several tissues in a nonrandom fashion. We report a 2.3-Mb de novo overlapping microdeletion on chromosome 8q12 identified by array comparative genomic hybridization in two individuals with CHARGE syndrome. Sequence analysis of genes located in this region detected mutations in the gene CHD7 in 10 of 17 individuals with CHARGE syndrome without microdeletions, accounting for the disease in most affected individuals.