For an arbitrary ring $R$, the zero-divisor graph of $R$, denoted by $Gamma (R)$, is an undirected simple graph that its vertices are all nonzero zero-divisors of $R$ in which any two vertices $x$ and $y$ are adjacent if and only if either $xy=0$ or $yx=0$. It is well-known that for any commutative ring $R$, $Gamma (R) cong Gamma (T(R))$ where $T(R)$ is the (total) quotient ring of $R$. In this...

 Letbe a ring with an endomorphism and an -derivationAntoine studied the structure of the set of nilpotent elements in Armendariz rings and introduced nil-Armendariz rings. In this paper we introduce and investigate the notion of nil--compatible rings. The class of nil--compatible rings are extended through various ring extensions and many classes of nil--compatible rings are constructed. We al...

Site selectivity, regioselectivity and stereoselectivity of [2 + 3] cycloaddition of 4-trifluoromethylbenzonitrile oxide to polyunsaturated medium size rings including 1,5,9-cyclododecatriene, 11-membered sesquiterpenes, 1,3-cyclooctadiene and 5-vinyl-2norbornene were examined. Site selectivity was correlated with electron charges of alkenyl carbon atoms. Structure of the products has been esta...

A large set of lowest and medium energy conformers of aliphatic tetramine trien was used to uncover structural-topological preferences of poliamines. Numerous common structural features among HL and H 2 L tautomers were identified, e.g., H-atoms of protonated functional groups are always involved in intramolecular NH•••N interactions and they result in as large and as many as possible rings in ...

Independent of its lipid-lowering properties, simvastatin (Sim) induces vasorelaxation; however, the underlying mechanisms have remained elusive. The aim of the present study was to investigate the vasorelaxant effects of Sim on rat superior mesenteric arteries and the mechanisms involved. The isometric tension of rat superior mesenteric arterial rings was recorded in vitro on a myograph. The r...

OBJECTIVE Since the role of Ca2+ in angiogenesis is not fully understood, we investigated the effect of thapsigargin (TG: depletes intracellular Ca2+ pools) and other Ca2+ modulators [ionomycin, calcium ionophore A23187 and dibutyrylhydroquinone (DBHQ)] on in vitro angiogenesis by rat aortic rings. METHODS Aortae from Sprague-Dawley rats were cut into 2-mm rings, embedded in a fibrin clot and...

The study tested the hypothesis that human chorionic gonadotrophin (hCG) attenuates isolated vascular smooth muscle contractility and investigated the role of the vascular endothelium in hCG-induced altered responses of vascular smooth muscle. The contractile responses of isolated aortic rings from normal, hCG-treated, and estrogen-treated female virgin Wistar rats to phenylephrine, angiotensin...