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Biomedical subjects

I Rubinstein

Publications and source records attributed to I Rubinstein.

At least 109 records · Page 6Linked to original sources
PubMed1994

Effects of endothelin receptor antagonists on bradykinin-induced increases in macromolecular efflux.

The goal of this study was to determine the effects of endothelin receptor antagonists on agonist-induced increases in macromolecular extravasation in the hamster cheek pouch in vivo. We used intravital fluorescent microscopy and fluorescein isothiocyanate dextran (FITC-dextran; mol wt = 70 K) to examine extravasation from postcapillary venules in response to bradykinin and endothelin before and following application of inhibitors of endothelin receptors (ETAB and ETA). Increases in extravasation of macromolecules were quantitated by counting the number of venular leaky sites. Bradykinin (0.5 and 1.0 microM) and endothelin-1 (0.01 and 0.1 nM) produced a dose-related increase in the number of venular leaky sites and superfusion of PD 142893 (ETAB antagonist), and PD 147953 and BQ-123 (ETA antagonists) significantly decreased bradykinin- and endothelin-induced responses. Addition of calcium to the superfusate restored bradykinin-induced increases in venular leaky sites in the presence of endothelin receptor antagonism. Thus, the findings of the present study suggest that endothelin receptor antagonists abrogate bradykinin- and endothelin-induced increases in macromolecular efflux from postcapillary venules. The mechanism for the effects of endothelin receptor antagonists appears to be related to inhibition of the ETA receptor which, in turn, alters the mobilization of calcium across venular endothelium.

Animals↗
PubMed1994

Vasoactive intestinal peptide encapsulated in liposomes: effects on systemic arterial blood pressure.

The purpose of this study was to determine whether encapsulation of vasoactive intestinal peptide (VIP) in liposomes enhances its vasoactive effects. Liposomes were formed from a solution of VIP in phospholipids and cholesterol, resulting in incorporation of 0.008 mole peptide/mole phospholipid. Leakage of VIP from the liposomes was undetectable over several days of incubation at 4 degrees C in 0.15 M sodium chloride. Under conditions permitting rapid hydrolysis of VIP by trypsin, there was no breakdown of the encapsulated peptide. Increasing concentrations of the liposome-encapsulated VIP administered intravenously to anesthetized hamsters produced a concentration-dependent decrease in the mean arterial blood pressure. The duration and magnitude of the hypotensive effect of the encapsulated VIP was significantly greater (p < 0.05) compared to equivalent concentrations of the unencapsulated peptide. Infusion of empty liposomes was without significant effect on the mean arterial blood pressure. We conclude that encapsulation of VIP in liposomes potentiates the blood pressure-lowering effect of the peptide.

Animals↗
PubMed1994

Effects of smokeless tobacco on chemically transformed hamster oral keratinocytes: role of angiotensin I-converting enzyme.

The purpose of this study was to determine whether exposure of chemically transformed golden Syrian hamster oral epidermoid carcinoma cell (HCPC-1) cultures to smokeless tobacco extract (STE) is associated with a decrease in specific angiotensin I-converting enzyme (ACE) activity and whether this decrease potentiates bradykinin-induced cell growth. We found that STE induced a significant concentration- and time-dependent decrease in ACE activity in cultured HCPC-1 cells (P < 0.05). STE alone had no significant effect on cell number. Bradykinin alone induced a slight, but significant, increase in cell number (P < 0.05). These effects were significantly potentiated by STE (P < 0.01). We conclude that STE potentiates bradykinin-induced HCPC-1 cell growth, in part by attenuating specific ACE activity in these cells.

Animals↗
PubMed1994

Peptidases modulate bradykinin-induced arteriolar dilation in the hamster cheek pouch.

The purpose of this study was to investigate whether angiotensin-converting enzyme (ACE; EC 3.4.15.1) and neutral endopeptidase (NEP; EC 3.4.24.11), two membrane-bound metalloenzymes that are widely distributed in the peripheral microcirculation and degrade kinins very effectively, modulate bradykinin-induced arteriolar dilation in vivo. Using intravital microscopy, we measured diameter of second-order arterioles in the hamster cheek pouch during suffusion of bradykinin (0.1-10.0 microM) before and after topical application of captopril (10.0 microM) and phosphoramidon (10.0 nM). We found that each inhibitor significantly potentiated bradykinin-induced increase in arteriolar diameter (P < 0.05). Suffusion of other proteinase inhibitors (excluding ACE and NEP inhibitors) had no significant effect on bradykinin-induced responses. Captopril and phosphoramidon did not potentiate isoproterenol (0.1 microM)-induced arteriolar dilation in the cheek pouch. Collectively, these data indicate that ACE and NEP each plays an important role in regulating bradykinin-induced vasorelaxation in the peripheral microcirculation in vivo.

Animals↗
PubMed1993

Modulation of airway epithelial cell ciliary beat frequency by nitric oxide.

NOS activity has been recently described in airway epithelial cells. Because these cells are often ciliated we hypothesized that NO modulates airway ciliary beating. CBF was measured in cultured BBECs using video microscopy. L-NMMA, a NOS inhibitor, caused a 40% decrease in CBF following pre-stimulation with isoproterenol (8.5 +/- 0.3 Hz vs 14.6 +/- 0.2 Hz; p < 0.0001) which lasted approximately 60 minutes. Similar attenuation in CBF after isoproterenol pre-treatment was observed with another NOS inhibitor, L-NAME. NOS inhibitor-induced CBF slowing was also observed when cells were pre-stimulated with either bradykinin or substance P and was completely reversed by L-arginine or SNP but not by D-arginine. These observations demonstrate a novel NO-dependent mechanism that upregulates ciliary motility in response to stimulation.

Amino Acid Oxidoreductases↗
PubMed1993

Regulation of angiotensin I-converting enzyme in cultured bovine bronchial epithelial cells.

The purpose of this study was to determine whether angiotensin I-converting enzyme (ACE) is present in cultured bovine bronchial epithelial cells (BBECs) and whether its activity can be modulated. We found that extracts of confluent monolayers of cultured BBECs degraded [glycine-1-14C]hippuryl-L-histidyl-L-leucine at a rate of 843 +/- 66 pmol/hr/mg protein (mean +/- SEM, n = 5). In addition, we found that the enzyme was shed into the culture medium. ACE activity in BBECs was inhibited by three selective, but structurally different, ACE inhibitors (captopril, quinapril, and cisalaprilat) with an IC50 of approximately 2 nM. Increasing chloride concentration in the assay buffer resulted in an increase in BBECs ACE activity of 63%. Enzyme activity was also modulated by the presence of zinc cation in the assay buffer. Addition of dexamethasone to the culture medium was associated with a significant increase in BBECs ACE activity (P < 0.05), which was inhibited by the steroid receptor antagonist RU 38486. Western blot analysis of BBECs, tracheal and bronchial mucosal strips utilizing a cross-reacting rabbit anti-mouse ACE antibody, showed a faint 175 kDa band and additional strong 52 kDa and 47 kDa band. The mechanism of generation of the low M.W. bands is unknown. Our data indicate the presence of ACE in cultured BBECs and that enzyme activity can be modulated.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1993

Nitric oxide synthase inhibitors attenuate human monocyte chemotaxis in vitro.

Nitric oxide synthase (NOS) inhibitors have been shown to modulate neutrophil migration. We hypothesized that the NOS inhibitors NG-monomethyl-L-arginine (L-NMMA), NG-nitro-L-arginine methyl ester (L-NAME), and L-canavanine (L-CAN) also modulate human peripheral blood monocyte chemotaxis. To test this hypothesis, monocyte chemotaxis toward formylmethionylleucyl-phenylalanine (fMLP) was assessed using a modified blindwell chemotaxis chamber technique. L-NMMA and L-NAME, but not D-NMMA or L-CAN, significantly attenuated fMLP-induced monocyte chemotaxis (P < .05). L-Arginine and sodium nitroprusside, but not D-arginine, reversed NOS inhibitor-induced responses. Dibutryl cyclic guanyl monophosphate (cGMP) attenuated the inhibitory effects of L-NMMA on monocyte chemotaxis (P < .05). Finally, fMLP increased cGMP generation by monocytes, which was significantly attenuated by L-NMMA (P < .05). These data indicate that the L-arginine/NO biosynthetic pathway regulates human monocyte chemotaxis in vitro.

Amino Acid Oxidoreductases↗
PubMed1993

Bovine bronchial epithelial cells metabolize L-arginine to L-citrulline: possible role of nitric oxide synthase.

The conversion of L-arginine to L-citrulline is catalyzed by nitric oxide synthase (NOS), and results in the release of nitric oxide (NO). We hypothesized that bronchial epithelial cells metabolize L-arginine to L-citrulline. We found that cell lysates obtained from unstimulated, cultured bovine bronchial epithelial cells (BBECs) converted L-[3H]arginine to L-[3H]citrulline. This conversion was attenuated by three competitive NOS inhibitors and modulated by lipopolysaccharide and cigarette smoke extract (p < 0.01, all comparisons). These data demonstrate that BBECs metabolize L-arginine to L-citrulline and implicate a role for the L-arginine:NOS biosynthetic pathway in modulating airway responses.

Amino Acid Oxidoreductases↗
PubMed1993

NK1 receptors mediate tachykinin-induced increase in microvascular clearance in hamster cheek pouch.

The purpose of this study was to determine the receptor subtype(s) that mediates tachykinin-induced neurogenic plasma extravasation in the hamster cheek pouch. Changes in microvascular clearance were quantified by counting the number of leaky sites and calculating the clearance of fluorescein isothiocyanate-dextran [mol wt 70,000 (Dextran 70)] during suffusion of the cheek pouch with substance P, neurokinin A, neurokinin B, and capsaicin. Suffusion of substance P, capsaicin, and neurokinin A, but not neurokinin B, was associated with a significant concentration-dependent increase in leaky site formation and clearance of fluorescein isothiocyanate-Dextran 70 (P < 0.05). However, the responses to substance P and capsaicin were significantly greater than those to neurokinin A. Pretreatment with the selective, nonpeptide NK1 receptor antagonist, CP-96,345, significantly attenuated substance P- and capsaicin-induced but not neurokinin A-induced responses (P < 0.05). These effects were specific, since the 2R,3R enantiomer, CP-96,344, was inactive, and CP-96,345 had no significant effect on adenosine-induced responses. We conclude that, in the hamster cheek pouch, NK1 receptors are the predominant receptors that mediate neurogenic plasma extravasation.

Animals↗
PubMed1993

Mechanisms of T-kinin-induced increases in macromolecule extravasation in vivo.

The purpose of this study was to investigate the mechanisms that mediate T-kinin- (Ile-Ser-bradykinin) induced increases in macromolecule extravasation in the hamster cheek pouch. Changes in plasma extravasation were quantified by counting the number of leaky sites and calculating the clearance of fluorescein isothiocyanate- (FITC) dextran (mol mass = 70 kDa) during suffusion of the cheek pouch with T-kinin (0.1-1.0 microM) by using intravital microscopy. T-kinin induced a significant time- and concentration-dependent increase in leaky site formation and clearance of FITC-dextran (P < 0.05). The increase in plasma extravasation in response to T-kinin was mediated by two mechanisms: a COOH-terminal-mediated stimulation of B2 bradykinin receptors in postcapillary venules and an NH2-terminal-mediated degranulation of mast cells leading to histamine release. Indomethacin and CP 96345, a selective nonpeptide neurokinin-1 receptor antagonist, had no significant effects on T-kinin-induced responses. We conclude that T-kinin increases macromolecule extravasation in the peripheral microcirculation by stimulating B2 bradykinin receptors in post-capillary venules and by degranulating mast cells.

Amino Acid Sequence↗
PubMed1993

Cigarette smoke extract potentiates bradykinin-induced increases in microvascular permeability.

The first goal of this study was to determine whether cigarette smoke extract (CSE) increases microvascular permeability of the hamster cheek pouch in vivo. The second goal was to determine whether CSE potentiates bradykinin-induced increases in vascular permeability in the hamster cheek pouch. Using intravital microscopy, we examined the permeability of the hamster cheek pouch to fluorescein isothiocyanate-dextran (mol wt 70,000). Increases in permeability were quantitated by counting the number of postcapillary venular leaky sites per 0.11 cm2. Superfusion of CSE (1, 5, and 10%) did not produce venular leaky sites and, thus, did not alter macromolecular permeability. Superfusion of bradykinin (0.1, 0.5, and 1.0 microM) produced a dose-related increase in the number of venular leaky sites. Formation of leaky sites in response to bradykinin was potentiated by CSE. To determine whether potentiation of bradykinin-induced leaky site formation by CSE was related to products released via the cyclooxygenase pathway, we examined the effects of pretreatment with indomethacin (10 mg/kg i.v.). Indomethacin did not alter the potentiating effect of CSE on bradykinin-induced leaky site formation. These findings suggest that CSE does not alter basal permeability of the hamster cheek pouch microcirculation in vivo. However, CSE potentiates bradykinin-induced increases in microvascular permeability. The mechanism of CSE-induced potentiation of microvascular permeability does not appear to be related to substances produced via the cyclooxygenase pathway.

Animals↗
PubMed1993

The bronchitis index. A semiquantitative visual scale for the assessment of airways inflammation.

Flexible fiberoptic bronchoscopy has been proven to be an effective tool for the assessment and characterization of airway inflammation. Visual inspection of airways affected by chronic bronchitis discloses an abnormal appearance characterized by erythema, edema, secretions, and friability. It was hypothesized that the visual appearance of airway inflammation could be assessed in a semiquantitative manner. A bronchitis index (BI) was developed that scores the visual appearance of airways according to the presence or absence of abnormal edema, erythema, secretions, and friability (0 = normal, 3 = remarkably abnormal). The BI was determined in three study groups: 86 subjects with chronic bronchitis, 15 subjects who smoked cigarettes, but did not have chronic bronchitis, and 25 normal, nonsmoking control subjects. The reproducibility of the BI was determined by comparing the results from pairs of two independent observers assessing 249 subjects undergoing fiberoptic bronchoscopy under various investigative protocols. In total, nine investigators scored the airways. For the three observer pairs with more than six observations, there were no differences noted in the BI (p = 0.43, 0.67, 0.82). To control for the effect of cough upon the BI, lidocaine usage was recorded. No correlation was found between lidocaine usage and BI. As previously noted for a smaller group of subjects, the BI was found to be elevated in those with chronic bronchitis (13.2 +/- 0.53) compared with both asymptomatic smokers (8.5 +/- 0.89, p < 0.0005) and normal volunteers (2.3 +/- 0.55, p < 0.0001); the latter two groups also differed significantly (p < 0.0001). The BI was also found to correlate significantly with bronchial sample lavage fluid neutrophil content in lavage fluid obtained after determination of the BI and with cigarette smoking as quantitated by pack years. Conversely, the BI correlated negatively with the spirometric measures of airway obstruction, FEV1, FEV1/FVC, FEV25-75, and FEFmax. Thus, the BI appears to be a reproducible, semiquantitative assessment of the visual appearance of airway inflammation. It may be a useful bronchoscopic adjunct for the assessment of airway inflammation in clinical investigations.

Adult↗
PubMed1993

General vs local anesthesia. Effect on bronchoalveolar lavage findings.

Bronchoalveolar lavage (BAL) can be performed with the patient undergoing either local or general anesthesia (GA). This study investigates whether the type of anesthesia affects BAL fluid and cell recovery. Eighty patients, were selected for study. Fluid recoveries were significantly less in the GA group for both the bronchial and alveolar lavages. The differences were confirmed for BAL fluid recovery in a subsequent group of 120 unselected patients. Bronchoscope size did not appear to affect recovery, nor did anesthesia time; BAL fluid recovery from patients with respiratory failure who were intubated and mechanically ventilated was similar to that in the GA group, suggesting that lower recovery rates may be due to mechanical ventilation. The BAL fluid cell counts were related to fluid recovery, but airway neutrophils represented a higher percentage of BAL lavage fluid cells in the GA lavages, independent of differences in the volume of lavage fluid recovered.

Adult↗
PubMed1993

Inhibitors of nitric oxide synthase attenuate human neutrophil chemotaxis in vitro.

Products released through the L-arginine/nitric oxide biosynthetic pathway regulate soluble guanyl cyclase activity, which in turn modulates polymorphonuclear leukocyte chemotaxis. We hypothesized that inhibitors of nitric oxide synthase attenuate polymorphonuclear leukocyte chemotaxis in vitro. To test this hypothesis, unstimulated polymorphonuclear leukocytes were pretreated with buffer or the nitric oxide synthase inhibitors NG-monomethyl-L-arginine (L-NMMA), NG-nitro-L-arginine methyl ester, and L-canavanine before being exposed to three structurally unrelated chemoattractants, N-formyl-methionyl-leucyl-phenylalanine, C5a des arginine, and leukotriene B4. Polymorphonuclear leukocyte chemotaxis was quantified with a modified blind-well chamber technique. We found that L-NMMA and L-canavanine but not NG-nitro-L-arginine significantly attenuated polymorphonuclear leukocyte chemotaxis (p < 0.05). L-Arginine but not D-arginine, the nitric oxide donor sodium nitroprusside, and 8-bromo-cyclic guanosine monophosphate restored polymorphonuclear leukocyte chemotaxis attenuated by L-NMMA. Chemotaxis of polymorphonuclear leukocytes primed with lipopolysaccharide (Escherichia coli 0127:B8) or phorbol-13-butyrate was also significantly attenuated by pretreatment with L-NMMA and L-canavanine. Consistent with these observations, intracellular concentrations of cyclic guanosine monophosphate in polymorphonuclear leukocytes was decreased by L-NMMA during exposure to N-formyl-methionyl-leucyl-phenylalanine. These data indicate that nitric oxide synthase inhibitors attenuate chemotaxis of unstimulated and primed polymorphonuclear leukocytes in vitro. We suggest that the L-arginine/nitric oxide biosynthetic pathway plays an important role in regulating polymorphonuclear leukocyte emigration in vivo.

Amino Acid Oxidoreductases↗
PubMed1992

Acetylcholine induces vasoconstriction in the microcirculation of cardiomyopathic hamsters: reversal by L-arginine.

The goal of this study was to determine whether endothelium-dependent responses of the microcirculation are altered during cardiomyopathy. We examined in vivo responses of cheek pouch arterioles to an endothelium-dependent agonist (acetylcholine) and an endothelium-independent agonist (nitroglycerin) in normal and in cardiomyopathic hamsters. In normal hamsters, acetylcholine produced dose-related dilatation of arterioles. In contrast, acetylcholine produced constriction of arterioles in cardiomyopathic hamsters. Nitroglycerin produced similar dose-related dilatation in normal and cardiomyopathic hamsters. We also examined whether impaired responses to acetylcholine in cardiomyopathic hamsters were related to an alteration in the L-arginine/nitric oxide pathway. We found that L-arginine (100 microM) restored endothelium-dependent vasodilatation to acetylcholine in cardiomyopathic hamsters. Thus, cardiomyopathy impairs endothelium-dependent responses of the microcirculation which is reversed by L-arginine.

Acetylcholine↗
PubMed1992

Tissue angiotensin I-converting enzyme activity in spontaneously hypertensive hamsters.

The purpose of this study was to measure angiotensin I-converting activity in heart, kidney, lung and cheek pouch tissue homogenates of spontaneously hypertensive and normotensive hamsters. We also determined inhibitor sensitivity and the effects of chloride anion concentration on kidney angiotensin I-converting activity in these animals. We found no significant differences in angiotensin I-converting activity between hypertensive and normotensive hamsters in all tissues tested. Inhibitor sensitivity of kidney angiotensin I-converting activity with captopril and lisonopril was similar in both groups. Finally, kidney angiotensin I-converting activity increased significantly in both groups as chloride anion concentration in the assay buffer increased. Substituting chloride anion for citrate abrogated the increase in angiotensin I-converting enzyme activity.

Angiotensin I↗
PubMed1992

Immunological rejection of heart transplant: how lytic granules from cytotoxic T lymphocytes damage guinea pig ventricular myocytes.

We investigated the mechanism by which lytic granules extracted from cytotoxic T lymphocytes (CTL) damage guinea pig ventricular myocytes in order to determine whether their actions can be related to the overall immunological rejection of the transplanted heart. Granule-induced myocyte morphological changes and final destruction were preceded by shortening of action potential duration (APD) and reductions of the resting potential and the action potential amplitude. APD shortening was probably caused by a granule-induced increase in outward current (most likely non-specific). Ryanodine, which blocks Ca2+ release from the sarcoplasmic reticulum, did not interfere with the morphological and electrophysiological effects of lytic granules. Fura-2 imaging indicated that [Ca2+]i initially increased about 2-fold from 90.0 +/- 11.5 nM, while cell length decreased less than 5% from a mean value of 99.0 +/- 9.0 microns. A further increase in [Ca2+]i (greater than 10 fold) was associated with progressive contracture and destruction, suggesting that the structural damage inflicted by lytic granules is caused by [Ca2+]i overload. The results indicate that the cytocidal action of CTL-derived lytic granules may be involved in immunologically induced damage, even to the extent of rejection of the transplanted heart.

Action Potentials↗