The Frank -Starling mechanism is a fundamental property of the vertebrate heart, which allows the myocardium to respond to increased filling pressure with a more vigorous contraction of its lengthened fibres. In mammals, myocardial stretch increases cardiac nitric oxide (NO) release from both vascular endothelium and cardiomyocytes. This facilitates myocardial relaxation and ventricular diastolic distensibility, thus influencing the Frank -Starling mechanism.In the in vitro working heart of the eel Anguilla anguilla, we previously showed that an endogenous NO release affects the Frank -Starling response making the heart more sensitive to preload. Using the same bioassay, we now demonstrate that this effect is confirmed in the presence of the exogenous NO donor S-nitroso-N-acetyl penicillamine, is independent from endocardial endothelium and guanylate cyclase/ cGMP/protein kinase G and cAMP/protein kinase A pathways, involves a PI(3)kinase-mediated activation of endothelial NO synthase and a modulation of the SR-CA 2þ ATPase (SERCA2a) pumps. Furthermore, we show that NO influences cardiac response to preload through S-nitrosylation of phospholamban and consequent activation of SERCA2a. This suggests that in the fish heart NO modulates the Frank -Starling response through a beat-to-beat regulation of calcium reuptake and thus of myocardial relaxation.We propose that this mechanism represents an important evolutionary step for the stretch-induced intrinsic regulation of the vertebrate heart, providing, at the same time, a stimulus for mammalian-oriented studies.
ISO-and endothelin-1-induced positive inotropism and coronary constriction . Thus, besides its antihypertensive properties, CST is now emerging as a novel cardiac modulator, which would protect the heart against excessive systemic and/or intra-cardiac excitatory stimuli (e.g. catecholamines and endothelin-1). Accepted 4 August 2010 SUMMARY Catestatin (CST), the 21-amino acid, cationic and hydrophobic peptide proteolytically derived from the ubiquitous chromogranin A (CgA), is an endogenous inhibitor of catecholamine release, a potent vasodilator in vivo and an anti-hypertensive agent in mammals, including humans. Recently, we discovered that CST also functions as an important negative modulator of heart performance in frog and rat. To gain an evolutionary perspective on CST cardiotropism in fish, we analysed the influence of bovine CST (CgA 344-364 ) on the eel heart, as well as the eventual species-specific mechanisms of its myocardial action. Experiments were carried out on fresh-water eels (Anguilla anguilla L.) using an electrically paced isolated working heart preparation.
Cytogenetic studies showed that a number of New World primate taxa, particularly the genera Alouatta, Aotus, and Callicebus, have highly derived karyotypes. Cytogenetics in these primates, at every level of analysis, has contributed to the recognition of species and revealed that their number was certainly underestimated by researchers relying solely on traditional morphological data. Further attention was drawn to Alouatta and Aotus because they are characterized by translocations of the Y chromosome to autosomes, generating multiple sex chromosome systems. Here we present a report on the hybridization of human chromosome-specific paints on metaphases from 4 individuals originally assigned to Alouatta caraya and 1 individual of Aotuslemurinus. This is only the third karyotype studied with chromosome painting out of more than 10 known karyomorphs in Aotus. The banded chromosomes matched those of karyotype II as defined by Ma et al. [1976a], and we were able to more precisely assign the origin of the sample to A. l. griseimembra. Our results on the Argentinean Alouatta caraya samples were generally comparable to the banding and hybridization pattern of previous studies of A. caraya including the presence of an X1X1X2X2/X1X2Y1Y2 sex chromosome system. The karyotype of the Brazilian Alouatta sample labeled as A. caraya differs from the 3 Argentinean samples by at least 10 chromosome rearrangements. The diploid number, G banding, and hybridization pattern of this female cell line was almost identical to previous painting results on Alouatta guariba guariba. Therefore we must conclude that this cell line is actually from an A. guariba guariba individual. The contribution of cytogenetic tools in identifying species or in this case assigning individuals or cell lines to their precise taxonomic allocation is stressed. Gathering further molecular cytogenetic data on New World primates should be conservation and management priorities.
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