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Irit Rubinstein

Publications and source records attributed to Irit Rubinstein.

8 recordsLinked to original sources
PubMed2005

Involvement of Rho kinase pathway in the mechanism of renal vasoconstriction and cardiac hypertrophy in rats with experimental heart failure.

Rho-dependent kinases serve as downstream effectors of several vasoconstrictor systems, the activities of which are upregulated in congestive heart failure (CHF). We evaluated renal and cardiac effects of Y-27632, a highly selective Rho kinase inhibitor, in an experimental model of volume-overload CHF. Effects of acute administration of Y-27632 (0.3 mg/kg) on renal hemodynamic and clearance parameters and effects of chronic treatment (10.0 mg.kg(-1).day(-1) for 7 days via osmotic minipumps) on cardiac hypertrophy and cumulative Na+ excretion were studied in male Wistar rats with aortocaval fistula and control rats. The Y-27632-induced decrease in renal vascular resistance (from 40.4 +/- 4.6 to 26.0 +/- 3.1 resistance units, P < 0.01) in CHF rats was associated with a significant increase in total renal blood flow (+34%) and cortical and medullary blood flow (approx +37 and +27%, respectively). These values were significantly higher than those in control rats and occurred despite a decrease in mean arterial pressure (-15 mmHg). Despite the marked renal vasodilatory effect, Y-27632 did not alter glomerular filtration rate and renal Na+ excretion. Chronic administration of Y-27632 did not alter daily or cumulative renal Na+ excretion in CHF rats but was associated with a significant decrease in heart-to-body weight ratio, an index of cardiac hypertrophy: 0.32 +/- 0.007, 0.46 +/- 0.017, and 0.37 +/- 0.006% in control, CHF, and CHF + Y-27632 rats, respectively. The findings suggest that Rho kinase-dependent pathways are involved in the mechanisms of renal vasoconstriction and cardiac hypertrophy in rats with volume-overload heart failure. Selective blockade of these signaling pathways may be considered an additional tool to improve renal perfusion and attenuate cardiac hypertrophy in heart failure.

Animals↗
PubMed2005

[Oxygen effect on ocular lens].

BACKGROUND: Cataract is the leading cause of preventable blindness worldwide. Clinical observations and laboratory results have shown that oxygen has a possible toxic role in cataract formation. AIM: The aim of the present study was to demonstrate, measure and characterize the damage caused to bovine lenses in organ culture as a result of their exposure to hyperbaric oxygen pressure. MATERIALS AND METHODS: Twenty bovine lenses exposed to hyperbaric pressure were compared to 20 control lenses. Lenses were kept in an organ culture for 14 days. Each day the focusing ability of the exposed lenses was compared to controls. The comparison was based on the amount to which the focus point of each measured ray diverged from the focus point of the lens. Lenses were also examined under the microscope and morphologic changes in study lenses were compared to controls. RESULTS: A statistically significant difference in focusing ability between the study and control lenses was observed. The difference became larger during the incubation period indicating an accumulation of damage. The damage resulted from the peripheral but not the central part of the lenses. The morphologic changes observed under the microscope matched the damage profile of the focusing ability. CONCLUSIONS: Oxygen has a possible role in cataract formation. The effect of oxygen is cumulative. The route of damage formation follows the diffusion of oxygen into the lens.

Animals↗
PubMed2004

Effects of endothelin-1 on systemic and renal hemodynamics in hypertensive-diabetic rats (CRDH), diabetic rats (CDR), and hypertensive rats (SHR).

The Cohen-Rosenthal diabetic hypertensive rat is a unique animal model in which genetic hypertension and diabetes developed after crossbreeding of a sensitive substrain of Cohen diabetic rats and spontaneously hypertensive rats (SHR) and feeding them a copper-poor sucrose diet. This study examined the acute effects of endothelin-1 on the systemic and renal hemodynamics in Cohen-Rosenthal diabetic hypertensive rats, Cohen diabetic rats and spontaneously hypertensive rats. Intravenous injection of endothelin- 1 (1.0 nmol/kg) into anesthetized SHR resulted in a significant immediate depressor response in mean arterial pressure [from 165 +/- 3 mmHg to 124 +/- 12 mmHg (P < 0.0001)] followed by a minor hypertensive phase (mean arterial pressure increased to 170 +/- 2 mmHg). Simultaneously, the administration of endothelin-1 caused a significant decrease in renal blood flow from 5.8 +/- 0.9 mL/minute to 3.2 +/- 0.5 mL/minute (P = 0.026). These responses were blunted in Cohen-Rosenthal diabetic hypertensive rats and Cohen diabetic rats. Analysis of intrarenal blood flow by laser-Doppler in Cohen-Rosenthal diabetic hypertensive rats revealed that endothelin-1 injection caused a decrease in cortical blood flow (Delta = -12 +/- 2.9%). However, in contrast to its well known renal medullary vasodilatory effect, endothelin-1 produced a significant decline in the medulla blood flow (Delta = -17.5 +/- 3.4%) (P = 0.0125). These findings suggest that Cohen diabetic rats and Cohen-Rosenthal diabetic hypertensive rats have reduced sensitivity to the vascular and renal action of endothelin-1. Furthermore, in the Cohen-Rosenthal diabetic hypertensive rats the expected endothelin- 1-induced medullary vasodilation was abolished and even reversed into prolonged vasoconstrictor response.

Animals↗
PubMed2003

Vascular endothelial growth factor (VEGF) fails to improve blood flow and to promote collateralization in a diabetic mouse ischemic hindlimb model.

BACKGROUND: Angiogenic therapy with vascular endothelial growth factor (VEGF) has been proposed as a treatment paradigm for patients suffering from an insufficiency of collateral vessels. Diabetes is associated with increase in the production of VEGF and therefore additional VEGF may not be beneficial. Accordingly, we sought to determine the efficacy of VEGF therapy to augment collateral formation and tissue perfusion in a diabetic mouse ischemic hindlimb model. METHODS: Diabetic and non-diabetic mice were studied in parallel for the efficacy of VEGF administration. Diabetes was induced with streptozotocin. Hindlimb ischemia was produced by severing the left iliac artery. An outlet tube from an osmotic infusion pump with placebo/500 micrograms of plasmid-DNA encoding VEGF was fenestrated and tunneled into the left quadriceps muscle. RESULTS: VEGF induced more rapid and complete restoration of blood flow in normal mice. However, in the setting of diabetes there was no difference between VEGF vs. placebo in the rate or adequacy of flow restoration. There was a significant increase in smooth muscle actin and Factor-VIII antigen densities in diabetic animals and in animals which received VEGF. CONCLUSIONS: Angiogenic therapy with VEGF in the setting of diabetes does not appear to have the beneficial effects seen in the absence of diabetes.

Journal Article↗
PubMed2003

Restoration of blood flow by using continuous perimuscular infiltration of plasmid DNA encoding subterranean mole rat Spalax ehrenbergi VEGF.

The optimal vector, regulatory sequences, and method of delivery of angiogenic gene therapy are of considerable interest. The Spalax ehrenbergi superspecies live in subterranean burrows at low oxygen tensions and its tissues are highly vascularized. We tested whether continuous perimuscular administration of Spalax vascular endothelial growth factor (VEGF) DNA could increase tissue perfusion in a murine hindlimb ischemia model. Placebo or VEGF +/- internal ribosome entry site (IRES) was continuously administrated perimuscularly in the ischemic zone by using an infusion pump. None of the mice in the VEGF-treated group (>50 microg) developed visible necrosis vs. 33% of the placebo group. Microscopic necrosis was observed only in the placebo group. Spalax VEGF muscular infiltration resulted in a faster and more complete restoration of blood flow. The restoration of blood flow by VEGF was dose-dependent and more robust and rapid when using the VEGF-IRES elements. The flow restoration using continuous perimuscular infiltration was faster than single i.m. injections. Vessel density was higher in the VEGF and VEGF-IRES (-) groups compared with the placebo. Continuous perimuscular administration of angiogenic gene therapy offers a new approach to restore blood flow to an ischemic limb. Incorporation of an IRES element may assist in the expression of transgenes delivered to ischemic tissues. Further studies are needed to determine whether VEGF from the subterranean mole rat Spalax VEGF is superior to VEGF from other species. If so, 40 million years of Spalax evolution underground, including adaptive hypoxia tolerance, may prove important to human angiogenic gene therapy.

Animals↗
PubMed2003

Lenticular oxygen toxicity.

PURPOSE: To investigate the possible toxic effect of oxygen on lenses in an organ culture. METHODS: Bovine lenses were exposed to four different combinations of ambient pressure and oxygen concentration in an organ culture throughout a 7-day period. Lens transparency, histology, enzymatic activities, and photomicrographs were compared in study and control groups. RESULTS: No differences were observed between study and control lenses in all measured parameters in a group subjected to a single exposure of 100% oxygen under increased (i.e., hyperbaric) ambient conditions and a group exposed repeatedly to high ambient pressure and normal oxygen partial pressure. Decreased lenticular transparency and enzymatic activities along with structural changes were observed in lenses exposed repeatedly to 100% oxygen concentration under both normal and increased ambient pressures. The observed changes were oxygen-load-dependent: the higher the oxygen partial pressure and the longer the time of exposure, the more severe the changes observed. Optical and structural changes in the lens occurred in a centripetal orientation: the greater the oxygen load, the more central the damage. CONCLUSIONS: High oxygen load has a toxic effect on bovine lenses in organ culture. These effects appear to be cumulative: the higher the oxygen partial pressure and the greater the number of exposures, the more severe the changes observed in the lenses. Changes marking toxicity follow the route of oxygen diffusion into the lens, from the periphery to the center. Cautious interpretation of the results may indicate a role of oxygen (and/or its derivatives) in human cataract formation.

Animals↗
PubMed2002

Role of myocardial inducible nitric oxide synthase in contractile dysfunction and beta-adrenergic hyporesponsiveness in rats with experimental volume-overload heart failure.

BACKGROUND: Whereas nitric oxide (NO) has been implicated in the pathophysiology of heart failure (HF), the significance and functional role of different NO synthase (NOS) isoforms in this pathology are controversial. Our aim was to study in the myocardium of rats with volume-overload-induced HF the expression, activity, and localization of endothelial (eNOS) and inducible (iNOS) isoforms and the involvement of iNOS in depressed cardiac contractile properties, intracellular Ca(2+) ([Ca(2+)](i)) transients, and beta-adrenergic hyporesponsiveness. METHODS AND RESULTS: HF was induced by aortocaval fistula (ACF). Compensated and decompensated subgroups of HF were selected on the basis of daily sodium excretion. ACF induced cardiac hypertrophy in rats with compensated (36%) and decompensated (76%) HF. Whereas in HF rats, cardiac eNOS expression and activity were unchanged, iNOS expression and activity increased approximately 2-fold. iNOS immunostaining was observed in ventricular myocytes of compensated and decompensated HF rats but not in controls. Isoproterenol-positive inotropic and lusitropic effects were markedly attenuated in papillary muscle of HF rats, more pronouncedly in decompensated than in compensated rats. Isoproterenol-induced increases in the rates of [Ca(2+)](i) activation and relaxation were also depressed in ACF rats. Selective iNOS blockade by N-(3-(aminomethyl)benzylacetamidine improved the attenuated beta-adrenergic responsiveness in HF rats. CONCLUSIONS: Our findings indicate that myocardial iNOS is activated in rats with volume-overload HF and suggest that increased iNOS activity contributes to depressed myocardial contractility and beta-adrenergic hyporesponsiveness.

Adrenergic beta-Agonists↗