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Biomedical subjects

I Rubinstein

Publications and source records attributed to I Rubinstein.

At least 37 records · Page 2Linked to original sources
PubMed1999

Cardiac dysfunction in murine autoimmune myocarditis.

We have investigated the pathophysiological basis of cardiac dysfunction in autoimmune myocarditis and in the resulting dilated cardiomyopathy. To this end we utilized the myosin-induced autoimmune myocarditis model in BALB/c mice. Myocarditis has been found to be associated with massive ventricular lymphocyte infiltration and a 50% reduction in tail artery blood flow, reflecting the depressed cardiac function in myocarditis. Action potential characteristics of control and diseased isolated ventricular myocytes were (mean+/-SEM): resting potential: -68.1+/-1. 1,-68.3+/-0.7 mV; action potential amplitude: 96.5+/-10.4, 92.3+/-4. 4 mV; action potential duration at 80% repolarization (APD80) 38+/-5, 116+/-24* ms; * P<0.05. We utilized the whole cell voltage clamp technique to explore ion currents involved in APD prolongation and arrhythmogenic activity, and found that in diseased myocytes the transient outward current (Ito) was markedly attenuated. At a membrane potential of +40 mV, in control and in diseased myocytes, I(to) current density was 14.7+/-1.5 and 6.5+/-1.4 pA/pF, respectively, P<0.005. In contrast, the L-type Ca2+current (ICa,L) remained unchanged. To further explore the basis for cardiac impairment, we simultaneously measured [Ca2+]i transient and contraction in isolated normal and diseased myocytes. The major findings indicated that both the relaxation kinetics of [Ca2+]i transients and myocyte contraction were significantly faster in the diseased myocytes. In conclusion, substantial, potentially reversible, electrophysiological and mechanical perturbations in ventricular myocytes from mice with myosin-induced autoimmune myocarditis appear to contribute to disease-related cardiac dysfunction.

Action Potentials↗
PubMed1999

Conformation and vasoreactivity of VIP in phospholipids: effects of calmodulin.

The purpose of this study was to determine the conformation and vasorelaxant effects of vasoactive intestinal peptide (VIP) self-associated with sterically stabilized phospholipid micelles (SSM) and whether calmodulin modulates both of these processes. Circular dichroism spectroscopy revealed that VIP is unordered in aqueous solution at room temperature but assumes appreciable a helix conformation in SSM. This conformational transition was amplified at 37 degrees C and by a low concentration of calmodulin (0.1 nM). Suffusion of VIP in SSM elicited significant time- and concentration-dependent potentiation of vasodilation relative to that elicited by aqueous VIP in the in situ hamster cheek pouch (P < 0.05). This response was significantly potentiated by calmodulin (0.1 nM). Collectively, these data indicate that exogenous calmodulin interacts with VIP in SSM to elicit conformational transition of VIP molecule from a predominantly random coil in aqueous environment to alpha helix in SSM. This process is associated with potentiation and prolongation of VIP-induced vasodilation in the in situ peripheral microcirculation.

Animals↗
PubMed1999

A novel formulation of VIP in sterically stabilized micelles amplifies vasodilation in vivo.

PURPOSE: To determine whether human vasoactive intestinal peptide (VIP)-poly(ethylene glycol) (PEG)-grafted distearoyl-phosphatidylethanolamine (DSPE) micelles elicit potent and stable vasodilation in vivo. METHODS: PEG-DSPE micelles were prepared by co-precipitation. VIP was loaded into micelles by incubation at room temperature. Vasoactivity of VIP in SSM was determined by monitoring changes in diameter of resistance arterioles in the in situ hamster cheek pouch using intravital microscopy. RESULTS: VIP easily undergoes self-assembly into small PEG-DSPE micelles (mean [+/-SEM] size, 18+/-1 nm) in a time-dependent fashion. This generates a potent vasoactive matrix at nanomole concentrations of VIP as manifested by approximately 3-fold potentiation and prolongation of vasodilation relative to that evoked by aqueous VIP alone (p < 0.05). This response is specific and mediated by the L-arginine/nitric oxide (NO) biosynthetic pathway. Micellar VIP dispersion remains vasoactive for at least 14 days after preparation and storage at 4 degrees C. CONCLUSIONS: A novel, self-associated, small and stable PEG-DSPE micellar formulation of VIP amplifies vasodilation in the in situ peripheral microcirculation in a specific fashion by elaborating NO. An optimized formulation could be considered for certain cardiovascular disorders associated with L-arginine/NO biosynthetic pathway dysfunction.

Animals↗
PubMed1999

Exogenous calmodulin potentiates vasodilation elicited by phospholipid-associated VIP in vivo.

The purpose of this study was to determine whether exogenous calmodulin potentiates vasoactive intestinal peptide (VIP)-induced vasodilation in vivo and, if so, whether this response is amplified by association of VIP with sterically stabilized liposomes. Using intravital microscopy, we found that calmodulin suffused together with aqueous and liposomal VIP did not potentiate vasodilation elicited by VIP in the in situ hamster cheek pouch. However, preincubation of calmodulin with liposomal, but not aqueous, VIP for 1 and 2 h and overnight at 4 degrees C before suffusion significantly potentiated vasodilation (P < 0.05). Calmodulin-induced responses were significantly attenuated by calmidazolium, trifluoperazine, and NG-nitro-L-arginine methyl ester (L-NAME) but not D-NAME. The effects of L-NAME were reversed by L- but not D-arginine. Indomethacin had no significant effects on calmodulin-induced responses. Calmodulin had no significant effects on adenosine-, isoproterenol-, acetylcholine-, and calcium ionophore A-23187-induced vasodilation. Collectively, these data indicate that exogenous calmodulin amplifies vasodilation elicited by phospholipid-associated, but not aqueous, VIP in the in situ peripheral microcirculation in a specific, calmodulin active sites-, and nitric oxide-dependent fashion. We suggest that extracellular calmodulin, phospholipids, and VIP form a novel functionally coordinated class of endogenous vasodilators.

Acetylcholine↗
PubMed1999

Dexamethasone attenuates grain sorghum dust extract-induced increase in macromolecular efflux in vivo.

The purpose of this study was to determine whether dexamethasone attenuates grain sorghum dust extract-induced increase in macromolecular efflux from the in situ hamster cheek pouch and, if so, whether this response is specific. By using intravital microscopy, we found that an aqueous extract of grain sorghum dust elicited significant, concentration-dependent leaky site formation and increase in clearance of FITC-labeled dextran (FITC-dextran; mol mass, 70 kDa) from the in situ hamster cheek pouch (P < 0.05). This response was significantly attenuated by dexamethasone (10 mg/kg iv). Dexamethasone also attenuated substance P-induced leaky site formation and increase in clearance of FITC-dextran from the cheek pouch but had no significant effects on adenosine-induced responses. Dexamethasone had no significant effects on arteriolar diameter in the cheek pouch. On balance, these data indicate that dexamethasone attenuates grain sorghum dust extract- and substance P-induced increases in macromolecular efflux from the in situ hamster cheek pouch in a specific fashion.

Adenosine↗
PubMed1999

Dexamethasone attenuates acute macromolecular efflux increase evoked by smokeless tobacco extract.

The purpose of this study was to determine whether dexamethasone attenuates the acute increase in macromolecular efflux from the oral mucosa elicited by an aqueous extract of smokeless tobacco (STE) in vivo, and, if so, whether this response is specific. Using intravital microscopy, we found that 20-min suffusion of STE elicited significant, concentration-related leaky site formation and an increase in clearance of fluorescein isothiocyanate-labeled dextran (FITC-dextran; mol mass 70 kDa) from the in situ hamster cheek pouch (P < 0.05). This response was significantly attenuated by dexamethasone (10 mg/kg iv). Dexamethasone also attenuated the bradykinin-induced leaky site formation and the increase in clearance of FITC-dextran from the cheek pouch. However, it had no significant effects on adenosine-induced responses. Dexamethasone had no significant effects on baseline arteriolar diameter and on bradykinin-induced vasodilation in the cheek pouch. Collectively, these data indicate that dexamethasone attenuates, in a specific fashion, the acute increase in macromolecular efflux from the in situ oral mucosa evoked by short-term suffusion of STE. We suggest that corticosteroids mitigate acute oral mucosa inflammation elicited by smokeless tobacco.

Adenosine↗
PubMed1998

Involvement of nitric oxide system in experimental muscle crush injury.

Muscle crush injury is often complicated by hemodynamic shock, electrolyte disorders, and myoglobinuric renal failure. In this study, we examined the involvement of the nitric oxide (NO) system in the development of muscle damage in an experimental model of crush injury induced by exertion of standardized mechanical pressure on tibialis muscle of rat. The intact limb served as a control. Four days after injury, the crushed muscle was characterized by extreme capillary vasodilatation as demonstrated by histological morphometric analysis. These changes were accompanied by muscle hyperperfusion as evaluated by measurements of femoral blood flow (ultrasonic flowmetry) and capillary blood flow (laser-doppler flowmetry). Treatment with Nomega-nitro-L-arginine methyl ester, a NO synthase (NOS) inhibitor, largely decreased the hyperperfusion. Furthermore, the expression of the different NOS isoforms, assessed by reverse transcription-PCR and immunoreactive levels, determined by Western blot, revealed a remarkable induction of the inducible NOS in the crushed limb. Similarly, endothelial NOS mRNA increased gradually after the induction of muscle damage. In contrast, the major muscular NOS, i.e., neuronal isoform remained unchanged. In line with the alterations in the mRNA levels, Western blot analysis revealed parallel changes in the immunoreactive levels of the various NOS. These findings indicate that muscle crush is associated with activation of the NO system mainly due to enhancement of iNOS. This may contribute to NO-dependent extreme vasodilatation in the injured muscle and aggravate the hypovolemic shock after crush injury.

Animals↗
PubMed1998

Sterically stabilized phospholipids attenuate human neutrophils chemotaxis in vitro.

The purpose of this study was to determine whether sterically stabilized liposomes (SSL) and poly(ethylene glycol)-distearoylphosphatidylethanolamine (PEG-DSPE) attenuate polymorphonuclear neutrophils (PMNs) chemotaxis in vitro and, if so, whether incorporation of vasoactive intestinal peptide (VIP), a pleiotropic neuropeptide, on the surface of SSL amplifies SSL-induced responses. Using a modified blind-well chamber chemotaxis assay, we found that N-formyl-methionyl-leucyl-phenylalanine (FMLP; 0.1 microM) and zymosan opsonized with purified human complement (2 x 10(9) yeast wall particles/ml) elicit significant human PMNs chemotaxis (95+/-9 and 103+/-3 cells/high power field; p<0.05). These effects are significantly attenuated by SSL and PEG-DSPE (p<0.05). By contrast, aqueous VIP and VIP on SSL have no significant effects on FMLP- and zymosan-induced responses. We conclude that certain sterically stabilized liposomes and phospholipids attenuate human PMNs chemotaxis in vitro and that VIP does not modulate this response.

Chemotaxis, Leukocyte↗
PubMed1998

Increased tissue neutral endopeptidase 24.11 activity in spontaneously hypertensive hamsters.

The purpose of this study was to determine whether tissue neutral endopeptidase (NEP) 24.11 activity, a membrane-bound metalloenzyme widely distributed in the peripheral circulation that cleaves and inactivates vasodilator peptides, is increased in spontaneously hypertensive hamsters relative to genetically/age-matched normotensive hamsters. Mean arterial pressure and heart rate were 163 +/- 11 mm Hg and 312 +/- 7 beats/min in spontaneously hypertensive hamsters and 99 +/- 3 mm Hg and 302 +/- 10 beats/min in normotensive hamsters, respectively (mean +/- SEM). NEP 24.11 activity is significantly increased in the kidney, cheek pouch, and spinotrapezius muscle, and significantly decreased in the heart and aorta of spontaneously hypertensive hamsters relative to controls (P < .05). Lung and brain NEP 24.11 activity is similar in both groups. Renal NEP 24.11 activity increases and to a similar extent in spontaneously hypertensive and normotensive hamsters as chloride anion concentration in the assay buffer is increased. Substituting citrate for chloride anion significantly attenuates renal NEP 24.11 activity. Taken together, these data indicate that NEP 24.11 activity in spontaneously hypertensive hamsters is increased in two organs that contribute appreciably to peripheral vascular resistance, skeletal muscle, and kidney. We suggest that the spontaneously hypertensive hamster is a suitable model to study the role of skeletal muscle and renal NEP 24.11 in regulating vasomotor tone in essential hypertension.

Animals↗
PubMed1998

Endothelin-1-like immunoreactivity in a new rodent model of spontaneous hypertension.

The purpose of this study was to determine plasma and tissue endothelin-1 (ET-1)-like immunoreactivity in a new rodent model of spontaneous hypertension. Plasma and tissues were procured from pentobarbital-anesthetized 16- to 18-week-old male hamsters with spontaneous hypertension and genetically/age-matched normotensive hamsters. We found that ET-1-like immunoreactivity in the plasma was similar in both groups. However, renal and cardiac ET-1-like immunoreactivity was 11- and 1.7-fold higher in spontaneously hypertensive hamsters relative to normotensive hamsters, respectively (P < .05). ET-1-like immunoreactivity was slightly, but significantly, lower in the lung and spleen of spontaneously hypertensive hamsters relative to normotensive hamsters (P < .05). ET-1-like immunoreactivity in the liver and brain was similar in both groups. We conclude that ET-1-like immunoreactivity is significantly higher in two target organs for hypertension, kidney and heart, but not in plasma or brain of adult male hamsters with spontaneous hypertension, relative to genetically/age-matched normotensive hamsters. We suggest that renal and cardiac ET-1 could play a role in the natural history of spontaneous hypertension in hamsters.

Animals↗
PubMed1998

Renal endothelin-converting enzyme in rats with congestive heart failure.

The expression and immunoreactivity of endothelin-converting enzyme (ECE) were examined in the renal tissue of rats with experimental congestive heart failure (CHF). Reverse transcriptase polymerase chain reaction (RT-PCR) revealed that ECE mRNA was more abundant (about twofold) in the renal medulla than in the cortex. Induction of heart failure caused a significant enhancement in the expression of this key enzyme in the renal cortex of rats with compensated CHF (delta + 28%) and in animals with decompensated heart failure (delta + 58%). An identical trend was also observed in the renal medulla, although these increases were moderate compared to those in the cortex. Similar findings were observed with Western blot techniques applying two monoclonal antibodies to rat ECE (AEC32-236 and AEC27-121). Taken together, these data suggest that upregulation of ECE is an important component in the activated renal ET system in CHF.

Animals↗
PubMed1998

The nose and obstructive sleep apnea.

The role of the nasal passage in the pathophysiology of obstructive sleep apnea (OSA) is still controversial. To this end, induction of acute nasal obstruction in healthy volunteers is associated with sleep fragmentation and an increase in the number of obstructive and central apneas. Moreover, nasal topical anesthesia, which alters nasal reflexes, is associated with an increase in the number of obstructive and central apneas during sleep. Although nasal resistance is increased in patients with OSA, chronic nasal obstruction appears to play no significant role in the genesis, maintenance, or severity of OSA. Moreover, surgical correction of nasal obstruction does not alleviate OSA appreciably. The purpose of this review is to outline the current body of knowledge on the pathophysiology, diagnosis, and treatment of nasal obstruction in patients with OSA.

Female↗
PubMed1998

Smokeless tobacco-exposed oral keratinocytes increase macromolecular efflux from the in situ oral mucosa.

The purpose of this study was to determine whether supernatants of cultured human oral keratinocytes (HOK) exposed to an aqueous extract of smokeless tobacco (STE) increase macromolecular efflux from the oral mucosa in vivo and, if so, whether bradykinin mediates in part this response. Subconfluent monolayers of HOK were incubated with STE or media, and supernatants were collected 24, 48, and 72 h thereafter. Using intravital microscopy, we found that suffusion of supernatants of STE- but not media-exposed HOK elicited significant concentration- and time-dependent increases in efflux of fluorescein isothiocyanate-labeled dextran (mol mass 70 kDa) from the in situ hamster cheek pouch (P < 0.05). These effects were significantly attenuated by HOE-140 and NPC-17647 but not by des-Arg9, [Leu8]-bradykinin. Proteolytic activity was increased in supernatants of STE- but not media-exposed HOK. However, a mixture of leupeptin, Bestatin, and DL-2-mercaptomethyl-3-guanidinoethylthiopropanoic acid had no significant effects on HOK supernatant-induced responses. Collectively, these data suggest that oral keratinocytes modulate smokeless tobacco-induced increase in macromolecular efflux from the in situ oral mucosa in part by elaborating proteases that may account for local bradykinin production.

Animals↗
PubMed1998

Vasodilation elicited by liposomal VIP is unimpeded by anti-VIP antibody in hamster cheek pouch.

The purpose of this study was to determine whether a monoclonal anti-vasoactive intestinal peptide (VIP) antibody, which binds VIP with high affinity and specificity and catalyzes cleavage of the peptide in vitro, attenuates VIP vasorelaxation in vivo and, if so, whether insertion of VIP on the surface of sterically stabilized liposomes (SSL), which protects the peptide from trypsin- and plasma-catalyzed cleavage in vitro, curtails this response. Using intravital microscopy, we found that suffusion of monoclonal anti-VIP antibody (clone c23.5, IgG2ak), but not of nonimmune antibody (myeloma cell line UPC10, IgG2ak) or empty SSL, significantly attenuates VIP-induced vasodilation in the in situ hamster cheek pouch (P < 0.05). By contrast, anti-VIP antibody has no significant effects on vasodilation elicited by isoproterenol, nitroglycerin, and calcium ionophore A-23187, agonists that activate intracellular effector systems in blood vessels that mediate, in part, VIP vasoreactivity. Suffusion of VIP on SSL, but not of empty SSL, restores the vasorelaxant effects of VIP in the presence of anti-VIP antibody. Collectively, these data suggest that VIP catalysis by high affinity and specific VIP autoantibodies displaying protease-like activity constitutes a novel mechanism whereby VIP vasoreactivity is regulated in vivo.

Animals↗
PubMed1998

Liposomal VIP attenuates phenylephrine- and ANG II-induced vasoconstriction in vivo.

The purpose of this study was to determine whether vasoactive intestinal peptide (VIP) modulates vasoconstriction elicited by phenylephrine and ANG II in vivo and, if so, to begin to elucidate the mechanisms underlying this phenomenon. Using intravital microscopy, we found that suffusion of phenylephrine and ANG II elicits significant vasoconstriction in the in situ hamster cheek pouch that is potentiated by VIP-(10-28), a VIP receptor antagonist, but not by VIP-(1-12) (P < 0.05). Aqueous VIP has no significant effects on phenylephrine- and ANG II-induced vasoconstriction. However, VIP on sterically stabilized liposomes (SSL), a formulation where VIP assumes a predominantly alpha-helix conformation, significantly attenuates this response. Maximal effect is observed within 30 min and is no longer seen after 60 min. Empty SSL are inactive. Indomethacin has no significant effects on responses induced by VIP on SSL. The vasodilators ACh, nitroglycerin, calcium ionophore A-23187, 8-bromo-cAMP, and isoproterenol have no significant effects on phenylephrine- and ANG II-induced vasoconstriction. Collectively, these data suggest that vasoconstriction modulates VIP release in the in situ hamster cheek pouch and that alpha-helix VIP opposes alpha-adrenergic- and ANG II-induced vasoconstriction in this organ in a reversible, prostaglandin-, NO-, cGMP-, and cAMP-independent fashion.

Acetylcholine↗
PubMed1998

Regulation of intrarenal blood flow in experimental heart failure: role of endothelin and nitric oxide.

Congestive heart failure(CHF) is associated with a marked decrease in cortical blood flow and preservation of medullary blood flow. In the present study we tested the hypothesis that changes in the endothelin (ET) and nitric oxide (NO) systems in the kidney may contribute to the altered intrarenal hemodynamics in rats with aortocaval fistula, an experimental model of CHF. Cortical and medullary blood flow were measured simultaneously by laser-Doppler flowmetry in controls and rats with compensated and decompensated CHF. As previously reported [K. Gurbanov, I. Rubinstein, A. Hoffman, Z. Abassi, O. S. Better, and J. Winaver. Am. J Physiol. 271 (Renal Fluid Electrolyte Physiol. 40): F1166-F1172, 1996], administration of ET-1 in control rats produced a sustained cortical vasoconstriction and a transient medullary vasodilatory response. In rats with decompensated CHF, cortical vasoconstriction was severely blunted, whereas ET-1-induced medullary vasodilation was significantly prolonged. This prolonged response was mimicked by IRL-1620, a specific ETB agonist, and partially abolished by NO synthase (NOS) blockade. In line with these findings, expression of ET-1, ETA and ETB receptors, and endothelial NOS (eNOS), assessed by RT-PCR, and eNOS immunoreactivity, assessed by Western blotting, was significantly higher in the medulla than in the cortex. Moreover, expression of ET-1 mRNA in the cortex and eNOS mRNA in the cortex and the medulla increased in proportion to the severity of heart failure. These findings indicate that CHF is associated with altered regulation of intrarenal blood flow, which reflects alterations in expression and activity of the ET and NO systems. It is further suggested that exaggerated NO activity in the medulla contributes to preservation of medullary blood flow in the face of cortical vasoconstriction in CHF.

Animals↗