1,721,315 research outputs found
Effect of long-term isradipine treatment on the hypertension-dependent changes in coronary arteries in spontaneously hypertensive rats.
No full textThe present study was designed to assess the effect of long-term isradipine treatment on the morphology of different-sized coronary artery branches in spontaneously hypertensive rats (SHR). Male SHR (12-week-old) received 1 mg/kg/day isradipine or vehicle (control group) orally for 12 weeks. Age-matched normotensive Wistar-Kyoto (WKY) rats were used as a reference group and did not receive any treatment. The animals were perfused with a fixative solution through the left ventricle and left ventricle blocks were embedded in resin. Sections including different-sized coronary artery branches were examined under a light microscope connected with an image analyser. The area occupied by the medial layer and the wall-to-lumen ratio were assessed in coronary artery branches of small (diameter less than 100 microns), medium (diameter 100-250 microns) and large (diameter greater than 250 microns) size. In control SHR, the blood pressure values and morphometric parameters examined significantly increased (p less than 0.001) in comparison with normotensive WKY rats. Isradipine treatment normalized blood pressure values in SHR and significantly reduced the area occupied by the medial layer and the wall-to-lumen ratio in small and medium-sized, but not in large-sized, coronary artery branches. These results indicate that isradipine treatment is able not only to reduce blood pressure elevation in SHR, but also to counteract the hypertension-dependent changes in the morphology of arterial branches controlling coronary resistances
Computational study of water adsorption on halloysite nanotube in different pH environments
Full text linkThe comprehension of structural and energetic features of halloysite nanotube (HNT) in different chemical environments plays a crucial role in developing new HNT based materials. So far these aspects were investigated by means of laboratory techniques that hardly are able to provide hints at atomistic level of detail. Our investigation aims to obtain such accurate informations through density functional theory calculations on HNT models, in order to figure out the most stable forms of HNT under different pH conditions. It turns out that, at low pH, the preferred protonation sites are located in the inner aluminic surface while in alkaline medium the silicic layer can show delocalized negative charges due to the formation of silanol groups. The adsorption of water molecules (WMs) on the HNT inner and outer surfaces in acidic and alkaline environments was investigated as well, so characterizing the hydrogen bonds which determine the adsorption geometry. Further, calculations allowed to verify how the modification of one layer affects the energetics of water adsorption on the other one
Observer Design for Linear Aperiodic Sampled-Data Systems: A Hybrid Systems Approach
No full textObserver design for linear systems with aperiodic sampled-data measurements is addressed. To solve this problem, a novel hybrid observer is designed. The main peculiarity of the proposed observer consists of the use of two output injection terms, one acting at the sampling instants and one providing an intersample injection. The error dynamics are augmented with a timer variable triggering the arrival of a new measurement and analyzed via hybrid system tools. Using Lyapunov theory, sufficient conditions for the convergence of the observer are provided. Relying on those conditions, an optimal LMI-based design is proposed for the observer gains. The effectiveness of the approach is illustrated in an example
Influence of isradipine treatment on left ventricular and coronary vascular hypertrophy in spontaneously hypertensive rats.
No full textThe purpose of this study was to ascertain if Isradipine treatment in spontaneously hypertensive rats (SHR) decreased hypertension-dependent left ventricular and coronary vascular hypertrophy. Twelve week male SHR were used in this study; one group of SHR was treated with Isradipine while the control group of SHR was left untreated. Age-matched normotensive Wistar-Kyoto rats (WKY) were utilized as a reference group. After 12 weeks of treatment rats were sacrificed. The hearts were removed and morphometric analysis was performed on the left ventricles. Isradipine treatment reduced systolic blood pressure in SHR. The heart/body weight ratio significantly increased in SHR and in Isradipine-treated SHR in comparison with WKY rats. Isradipine treatment decreased the left ventricular muscle fibre diameter and decreased the amount of focal necrosis in SHR. Different sized coronary arteries were also examined using a light microscope and an image analyzer. We found that the area occupied by the medial layer and the media-to-lumen ratio were significantly increased in comparison with WKY rats. In Isradipine-treated SHR the area of the medial layer and the media-to-lumen ratio in small and medium sized but not in large sized coronary arteries were significantly reduced in comparison with untreated SHR. The above results suggest that long term Isradipine treatment is not only able to reduce high blood pressure in SHR but is also able to counter the development of certain morphological changes often seen in the hypertensive heart and coronary arteries
Autoradiographic localization of [3H]nicardipine binding sites in the human renal artery.
No full textIn the present study the pharmacological profile and the anatomical distribution of dihydropyridine-type Ca2+ channels were analyzed in sections of the human renal artery by the use of combined radioligand binding and autoradiographic techniques with [3H]nicardipine as a ligand. The binding of [3H]nicardipine to sections of renal artery was time-, temperature- and concentration-dependent belonging, at least in the range of radioligand concentrations used, to a single class of high-affinity binding sites. The dissociation constant (KD) value was 0.3 nM and the maximum density of binding sites (Bmax) was 248 +/- 16 fmol/mg tissue. The pharmacological profile of [3H]nicardipine binding to sections of human renal artery was consistent with the labeling of dihydropyridine-type Ca2+ channels. In fact, dihydropyridine derivatives were the most powerful competitors of [3H]nicardipine binding, whereas phenylalkilamine, benzothiazepine or non-selective channel modulators were weak or ineffective competitors. Light microscope autoradiography revealed the highest density of [3H]nicardipine binding sites in the tunica media of the renal artery, probably within smooth muscle cells. A smaller accumulation of the radioligand occurred in the tunica adventitia, whereas the tunica intima did not show specific binding. These results indicate that light microscope autoradiography techniques associated with radioligand binding may represent a useful tool for analyzing the localization of receptors or targets of drug action within the arterial wall
Endothelin-1 displaces [3H]nicardipine binding in sections of human renal artery.
No full textEndothelin-1 (ET-1) is a potent vasoconstrictor peptide, the actions of which are mediated through interaction with specific ET receptors. Functional evidence has shown that the constrictor effect of ET may require extracellular Ca2+. Ca2+ antagonists of the dihydropyridine family attenuate the vasoconstriction caused by ET. However, the basis of the interactions between ET and dihydropyridine agents are not well understood. Our study was designed to assess whether different concentrations of ET-1 or ET-3 have any effect on [3H]nicardipine binding to sections of human renal artery. [3H]Nicardipine was specifically bound to sections of the human renal artery. Binding sites, which were located primarily over smooth muscle of the tunica media, showed the pharmacologic profile typical of a dihydropyridine Ca2+ channel. Increasing concentrations of ET-1, but not of ET-3, competed dose-dependently with [3H]nicardipine binding. A 1-nM concentration of ET-1 lessened specific [3H]nicardipine binding by approximately 80%. These results suggest the occurrence of an interaction in the human renal artery between dihydropyridine Ca2+ channels and ET-1. This interaction probably accounts for the inhibition of the ET-1-mediated vasoconstriction elicited by nicardipine
Boundary control design for conservation laws in the presence of measurement disturbances
No full textBoundary feedback control design for systems of linear hyperbolic conservation laws in the presence of boundary measurements affected by disturbances is studied. The design of the controller is performed to achieve input-to-state stability (ISS) with respect to measurement disturbances with a minimal gain. The closed-loop system is analyzed as an abstract dynamical system with inputs. Sufficient conditions in the form of dissipation functional inequalities are given to establish an ISS bound for the closed-loop system. The control design problem is turned into an optimization problem over matrix inequality constraints. Semidefinite programming techniques are adopted to devise systematic control design algorithms reducing the effect of measurement disturbances. The effectiveness of the approach is extensively shown in several numerical examples
Cholinergic nerves in dog cerebral vessels
No full textThe presence of a cholinergic innervation of the main cerebral blood vessels has been studied in the dog. Cholinergic nerve fibers are found in all examined arteries and veins, organized in two or in a single nerve plexus. The cerebral veins appear to be less innervated than arteries. The meaning of a cholinergic innervation in the cerebral circulation is discussed
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