On the origins of esterases

Comparisons among the primary sequences of five cloned eukaryotic esterases reveal two distinct lineages, neither bearing any significant overall sequence similarity to the functionally related serine protease multigene family. We have not eliminated the possibility that the esterases may have residual conformational similarities to the serine proteases. However, our profile analysis and analyses of the predicted conformations of the esterases reveal little similarity to the serine proteases. Four of the esterase proteins share 27%-53% overall sequence similarity and evidence of a catalytic mechanism involving the same Arg- Asp-Ser or His-Asp-Ser charge relay. We propose that these four esterases, three of them cholinesterases, form part of a multigene family essentially separate from the serine proteases.      

Phentolamine and dibenamine action on the carotid reflexes induced by lobeline]

On the carotid reflexogenic zone lobeline provoques : 1) a increase of amplitude and rate of respiratory movements with bradycardia and hypotension ; 2) a secondary decrease of amplitude and rate of breathing with tachycardia. Acting on the reflexogenic zone, phentolamine and dibenamine provoque a transitory weakening or disappearance of these reflexes. These effects are induced by a local action, because they are not observed by intravenous injection of the drugs and the lobeline reflexes starting from the carotid sinus of the other side are not affected.     

Duplicate Gene Evolution Toward Multiple Fates at the <Emphasis Type="Italic">Drosophila melanogaster HIP</Emphasis>/<Emphasis Type="Italic">HIP-Replacement</Emphasis> Locus

Hsc/Hsp70-interacting protein (HIP) is a rapidly evolving Hsp70 cofactor. Analyses of multiple Drosophila species indicate that the HIP gene is duplicated only in D. melanogaster. The HIP region, in fact, contains seven distinctly evolving duplicated genes. The regional duplication occurred in two steps, fixed rapidly, and illustrates multiple modes of duplicate gene evolution. HIP and its duplicate HIP-R are adaptively evolving in a manner unique to the region: they exhibit elevated divergence from other drosophilids and low polymorphism within D. melanogaster. HIP and HIP-R are virtually identical, share polymorphisms, and are subject to gene conversion. In contrast, two other duplicate genes in the region, CG33221 and GP-CG32779, are pseudogenes, and the chimeric gene Crg1 is subject to balancing selection. HIP and HIP-R are evolving rapidly and adaptively; however, positive selection is not sufficient to explain the molecular evolution of the region as a whole. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Effect of phentolamine on carotid reflexes induced by acetylcholine

Acetylcholine was injected into the common carotid artery of 15 mongrel dogs. In the animals with tied internal carotid artery, hyperpnoea, bradycardia and hypotension was observed, and in the animals with free internal carotid artery the hyperphoea was followed by apnoea. The administration of phentolamine provokes a temporary decrease or abolition of the reflexes produced by acetylcholine. This action of the alpha-blocker is due to a local effect because when phentolamine is injected intravenously it does not happen and the reflexes produced by acetylcholine with starting place at the carotid sinus of the opposite side are not affected.     

Organotin in the Tagus estuary

The tri(n-butyl)tin (TBT) moiety has been shown to have complex ecotoxicological effects on estuarine populations. In the Tagus the massive die-off of the Portuguese oyster (Crassostrea angulata Lmk), has been attributed to the introduction and use of this contaminant by shipyards. This paper reviews previous work by others and reassesses our results obtained in water and sediments of the Tagus estuary, as a contribution to the understanding of tin geochemistry and organotin speciation in this estuary. Contrary to earlier results, the latest surveys show that in the open waters of the Tagus measurable concentrations of all the three butyltin species occur, exhibiting peak concentrations at two locations that indicate two previously undetected sources of TBT. TBT also presents a peak concentration in sediments near the Lisnave shipyards, as previously suggested. The latest surveys still detected methylated forms of tin, particularly monomethyltin (Me Sn³⁺), in Tagus sediments, with maximum concentrations in the vicinity of urban effluent discharges. The concentrations for TBT and its degradation products found in the Tagus are potentially harmful to the populations of gastropods and endemic bivalves.