Toxic effects of mercury, lead and gadolinium on vascular reactivity

Heavy metals have been used in a wide variety of human activities that have significantly increased both professional and environmental exposure. Unfortunately, disasters have highlighted the toxic effects of metals on different organs and systems. Over the last 50 years, the adverse effects of chronic lead, mercury and gadolinium exposure have been underscored. Mercury and lead induce hypertension in humans and animals, affecting endothelial function in addition to their other effects. Increased cardiovascular risk after exposure to metals has been reported, but the underlying mechanisms, mainly for short periods of time and at low concentrations, have not been well explored. The presence of other metals such as gadolinium has raised concerns about contrast-induced nephropathy and, interestingly, despite this negative action, gadolinium has not been defined as a toxic agent. The main actions of these metals, demonstrated in animal and human studies, are an increase of free radical production and oxidative stress and stimulation of angiotensin I-converting enzyme activity, among others. Increased vascular reactivity, highlighted in the present review, resulting from these actions might be an important mechanism underlying increased cardiovascular risk. Finally, the results described in this review suggest that mercury, lead and gadolinium, even at low doses or concentrations, affect vascular reactivity. Acting via the endothelium, by continuous exposure followed by their absorption, they can increase the production of free radicals and of angiotensin II, representing a hazard for cardiovascular function. In addition, the actual reference values, considered to pose no risk, need to be reduced.

Correlation between biochemical properties and adaptive diversity of skeletal muscle myofibrils and myosin of some air-breathing teleosts.

Functional properties of myofibrils and relative stability of myosin of five teleosts Channa punctata, Clarias batrachus, M astacembalus armatus, Labeo rohita and Catla catla adapted to different breathing modes were compared. Myofibrillar contractility and m-ATPase of air-breathing organ (ABO) possessing C.punctata and C. batrachus were low and least affected by pH in the range of 7.1-8.5. However, their myosin isoforms were relatively thermostable, more soluble at sub-neutral pH values, between 0.1 to 0.15 M KCl concentrations and less susceptible to a-chymotryptic digestion. In contrast, myofibrils and myosin of water-breather major carps L. rohita and C. catla were more contractile and susceptible to pH and salt concentrations. Thus, correlation between catalytic efficiency and relative stability of myofibrils and myosin of ABO-possessing teleosts was of reverse order and magnitude, as compared to water-breathers. Interestingly, myofibrils and myosin of the behavioral air-breather M. armnatus showed intermediate properties. The specific levels of m-ATPase of all the five teleosts were in conformity with the levels of metabolic marker, the lactate dehydrogenase. The effect of chymotryptic cleavage of 94 and 173 kDa domains on ATPase, individuality of peptide maps of MyHC isomers and perturbation of phenylalanine residues by urea implicated hydrophobic residues in stabilizing myosin structure in these fish. The present study suggests two apparent evolutionary modifications of myofibrils and myosin in ABO-possessing teleosts: (i), 'down-regulation' of ATPase that explains sluggishness of such species and, (ii), more stable molecular structure to support stress of air-breathing modes of life.

Effect of C-terminal 44 amino acids deletion on activity of Haemophilus influenzae UvrA protein.

UV-sensitive mutant strain of Haemophilus influenzae Rd MBH3, is 20 times more sensitive to UV irradiation than the wild type strain. The mutation responsible for increased UV sensitivity of the strain was identified as G --> A transition predicting synthesis of truncated UvrAdeltaC44 protein (Balsara & Joshi). Recombinant UvrAdeltaC44 protein was purified for the first time under denaturing conditions. The molecular weight of the recombinant protein was estimated as approximately100 kDa. Recombinant UvrAdeltaC44 protein was found to be less efficient in its ATPase and DNA binding activity as compared to the wild type protein. Recombinant plasmid carrying uvrAdeltaC44 gene could partially complement the UvrA deficiency in E. coli UvrA mutant.

La segunda bomba de sodio: de la proteína al gen / The second sodium pump: from protein to gene

En la membrana laterobasal del epitelio del intestino delgado y del túbulo renal proximal han sido descrito dos mecanismos diferentes de transporte activo primario de Na+: (1) uno dependiente de K+, sensible a la ouabaina e insensible a la furosemida, correspondiente a la bomba de Na+/K+; y (2) otro independiente de K+, insensible a la ouabaina pero inhibida por furosemida, el cual es referido como la segunda bomba de sodio. De igual modo, dos actividades ATPásicas, dependientes de Mg2+, estimuladas por Na+ e inhibidas por vanadato, han sido descritas en esta membrana: (1) una dependiente de K+, sensible a la ouabaina e insensible a la furosemida, correspondiente a la ATPasa de Na+/K+; y (2) otra independiente de K+, insensible a la iuabaina pero inhibida por furosemida, la cual ha sido denominada como la ATPasa de Na+. Dadas las similitudes bioquímicas, se considera que la bomba de Na+/K+ y la segunda bomba de sodio están asociadas con las ATPasas de Na+/K+ y de Na+, respectivamente, como una entidad bioquímica única. No obstante, no había sido posible la separación óptima de ambas enzimas. Recientemente, se logró solubilizar ambas ATPasas utilizando un detergente no-iónico (C12E9), preservando sus actividades, y purificar la ATPasa de Na+ por selección negativa a través de una cromatografía de afinidad con Concanavalina-A-sefarosa. La ATPasa de Na+ esta constituida por dos subunidades: una subunidad alfa de 98 KDa y una subunidad beta de 50 KDa. La subunidad alfa fue parcialmente secuenciada por espectrometría de masa en serie, identificándose tres péptidos que están presentes en la subunidad alfa1 de la ATPasa de Na+/K+. La formación de intermediarios fosforilados durante el ciclo de reacción de la ATPasa de Na+, así como su dependencia de Mg2+ y sensibilidad a vanadato, identifican a esta enzima como integrante de las ATPasas tipo P.

Basolateral plasma membranes of small intestine and proximal renal tubule present two active Na+-transportmechanisms: (1) The Na+/K+-pump, which depends on K+, is inhibited by ouabain but insensitive to furosemide and (2) The Second sodium pump, which is K+-independent, insensitive to ouabain but inhibited by furosemide. Thse two transport mechanisms have been associated with two different Mg2+-dependent Na+-ATPases, inhibited by vanadate: (1) The K+-dependent Na+/K+-ATPase, sensitive to ouabain and insensitive to furosemide, and (2) The K+ independent, Na+-ATPase, which is inhibitable by furosemide and insensitiveto ouabain. There exist multiple biochemical and functional evidences indicating that these two ATPases are different but only recently it has been possible to identify the Na+-ATPase as a unique biochemical entity. Both ATPases can be solubilized in an active form using C12E9 as detergent and separated by exclusion chromatography in sepharose 6-B and affinity chromatography in concanavalinA-sepharose. The Na+-ATPase is constituted by two sub-units: an alpha subunit of 98 KDa and a beta subunit of 50 KDa. The alpha subunit was partially sequenced by Tandem Mass Spectrometry, evidenced three peptides that are also present in the alpha1 subunit of the Na+/K+-ATPase. Na+-ATPase is Mg2+-dependent, inhibited by vanadate and forms phosphorylated intermediate during its reaction cycle ATP, indicating that it si a P-type ATPase. These facts induced us to design degenerated primers against the most preserves motifs present in these ATPases and to intent the cloning of the Na+-ATPase. Thus, we identified a cDNA for a new P-type ATPase probably related with this enzyme.