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R Marthan

Publications and source records attributed to R Marthan.

At least 73 records · Page 4Linked to original sources
PubMed1995

IgE-induced passive sensitization of human isolated bronchi and lung mast cells.

Passive sensitization of human isolated lung with serum from atopic asthmatic patients provides an opportunity to study the link between airway hyper-responsiveness and the allergic process. To directly demonstrate the role of immunoglobulin E (IgE) in the effect of the atopic serum, we have compared the effect of passively sensitizing both human bronchi and isolated lung mast cells with either serum from atopic asthmatic patients or human monoclonal IgE. Peripheral bronchi ( < 5 mm in internal diameter) were dissected out from human lung obtained at thoractomy and isometric contraction was studied in response to a variety of immunological stimuli according to the sensitization protocol. Mast cells were also isolated from human lung and histamine release was measured under similar experimental conditions. A contractile response was elicited by either the specific antigen or anti-IgE (0.6-600 ng.mL-1) but not anti-immunoglobulin G (IgG) 0.2-20 micrograms.mL-1) in airways sensitized with atopic serum (total IgE concentration of approximately 1,000 international units (IU).mL-1). The maximal contractile response to anti-IgE was 75 +/- 22% of the response to 1 mM acetylcholine. Similarly, anti-IgE released histamine from isolated lung mast cells sensitized with atopic serum up to 22.4 +/- 2% of total histamine measured within mast cells. When isolated airways or mast cells were sensitized with human monoclonal IgE (1,000 IU.mL-1), response to anti-IgE in terms of contractile response or histamine release, respectively, were not significantly different from those obtained following passive sensitization with atopic serum. Finally, the bronchial contractile response to anti-IgE depended not only on the concentration of anti-IgE but also on that of IgE (300-2,000 IU.mL-1) used to sensitize the airways. These results indicate that the effect of antigen or anti-IgE in peripheral bronchi passively sensitized with atopic serum is mimicked when sensitization is carried out directly with human monoclonal IgE.

Adult↗
PubMed1994

Activation properties of chemically skinned fibres from human isolated bronchial smooth muscle.

1. The contractile activation properties of human isolated bronchial smooth muscle were investigated using chemically (beta-escin) skinned strips. 2. Concentration-dependent contractions were induced by free ion concentrations of Ca2+ (0.5-3 microM), Sr2+ (2-200 microM) and Ba2+ (50-1000 microM). The resulting -log[cation]-tension relationships were fitted by sigmoidal curves with EC50 values (cation concentration required to produce half-maximal tension) and co-operativity factors (Hill coefficient, nH) of, respectively, 0.25 microM and 3.4 for Ca2+, 12 microM and 2.64 for Sr2+ and 100 microM and 1.73 for Ba2+. Maximal responses to Sr2+ and Ba2+ were 125.5 +/- 15.4 and 96 +/- 8.1% (n = 5) respectively of the maximum tension induced by Ca2+. 3. Trifluoperazine (5-100 microM), cyclic AMP (50-300 microM) and cyclic GMP (50-100 microM) each antagonized Ca2+ in a concentration-dependent manner. On the other hand, okadaic acid (OA, 0.2-1 microM) potentiated Ca2+ and increased the maximum response to Ca2+ (+25 +/- 5.4%, n = 5, for 1 microM OA). 4. This study has demonstrated the high Ca2+ sensitivity of the activation mechanism of human isolated bronchial smooth muscle. It also suggests that control of the contractile machinery in the human bronchus involves processes of phosphorylation and dephosphorylation. The beta-escin-treated human bronchus may be a useful model for investigating the cellular basis of some pathophysiological processes such as bronchial hyper-responsiveness.

Adult↗
PubMed1994

Diosmin-induced increase in sensitivity to Ca2+ of the smooth muscle contractile apparatus in the rat isolated femoral vein.

The effect of diosmin, a flavone derivative, on the Ca2+ sensitivity of the venous contractile apparatus was investigated in chemically (beta-escin) skinned strips from the rat isolated femoral vein. Diosmin (0.5-10 microM) shifted to the left the concentration-response curve to Ca2+ (0.05-5 microM). The maximal effect was observed in the presence of 1 microM diosmin which increased the contractile response evoked by 0.15 microM Ca2+ from 26.3% to 78.9% of the maximal Ca(2+)-induced response. This work demonstrates that the venotonic action of diosmin involves an increase in the Ca2+ sensitivity of the contractile apparatus. Such a mechanism of action could represent a new and important means of therapeutic control of vasomotor activity.

Animals↗
PubMed1994

Human airway smooth muscle responsiveness in neonatal lung specimens.

The mechanical activity of proximal airways isolated from human lung specimens obtained at autopsy from 11 neonates was studied in response to the following compounds: carbachol, histamine, potassium chloride (KCl), neurokinin A (NKA) (both in the presence and in the absence of the neutral endopeptidase inhibitor phosphoramidon) and isoproterenol. Isometric responses to the various concentrations of each of the compounds were expressed as both raw values of force normalized to smooth muscle cross-sectional area (SMCSA), i.e., muscle stress and percentages of the maximal response to acetylcholine. Maximal active muscle stress of human neonatal bronchi was induced by carbachol and averaged 95 +/- 25 mN/mm2 SMCSA (n = 8). The rank of maximal force induced by the contractile agonists was carbachol > histamine > KCl > NKA, and the rank of the concentration of drug producing one-half of the maximum effect (EC50) was NKA < carbachol < histamine < KCl. The EC50 value for isoproterenol was the lowest, although it generated the smallest mechanical response. When compared with results obtained under identical experimental conditions in the human adult lung, except for carbachol and isoproterenol, general trends were an increase in force generation with age and little changes in EC50 values. There was a decrease in carbachol-induced force with age, whereas the opposite was observed with isoproterenol. We conclude that most of the mechanisms that control airway tone in humans are already present in the neonate. Alterations in the response to agonists with the maturational process may have implications in the pharmacologic modulation of bronchial obstruction in neonates.

Carbachol↗
PubMed1994

Human bronchial smooth muscle responsiveness after in vitro exposure to acrolein.

Human isolated bronchi obtained at thoracotomy from 42 patients were exposed to aqueous solutions of acrolein, and the resulting change in contractile responses was evaluated by measuring agonist cumulative concentration-response curves (CCRC). Contractile responses to carbachol were measured after a variety of exposure concentrations, from 0.01 to 3.0 microM, and at times from 5 to 60 min. The optimal condition to induce airway smooth muscle hyperresponsiveness was an exposure duration of 20 min at a concentration of 0.3 microM. The effect of acrolein exposure on human bronchial smooth muscle was also assessed by examining the contractile responses to potassium chloride (KCl), histamine, and neurokinin A (NKA) in both the absence and the presence of phosphoramidon. Although in vitro exposure of the human bronchus to 0.3 microM acrolein did not alter responses to KCl, it did increase the efficacy of carbachol and NKA without altering their potency. This concentration of acrolein also increased the contractile response to low concentrations of histamine and shifted the CCRC to the left. Pretreatment with phosphoramidon abolished the differential effect of acrolein on airway response to NKA. These results suggest that the mechanism of action of acrolein includes inactivation of airway neutral endopeptidase as well as alterations in the pharmacomechanical, but not the electromechanical, coupling of human bronchial smooth muscle.

Acrolein↗
PubMed1994

[Mechanisms of bronchial hyperreactivity. Role of smooth muscle].

The understanding of the cellular and molecular mechanisms involved in the contraction of airway smooth muscle has tremendously advanced in the recent years. Extracellular messengers that control the muscle contraction as well as both the membrane transduction processes and the activation of the contractile proteins are known in some details. Sensitization alters the contractility of airway smooth muscle. It increases shortening in the early phase of the contraction when rapidly cycling cross bridges are operative. At the molecular level, the responsible mechanism is an increment in the activity of the processes leading to phosphorylation of the myosin light chain. Such an alteration in the airway smooth muscle contractility may be observed in the early phase of the development of bronchial hyperresponsiveness.

Animals↗
PubMed1993

Effect of vascular smooth muscle relaxants on the protein kinase C-mediated contraction in the rat pulmonary artery.

In the rat pulmonary artery, phorbol 12,13-dibutyrate induces a contraction due to the activation of the protein kinase C. We investigated the sensitivity of this protein kinase C-mediated contraction to a variety of vascular smooth muscle relaxants. Pretreatment of rat pulmonary artery with relaxant compounds altered the subsequent concentration-response curve to phorbol 12,13-dibutyrate (0.05-2 microM) in a variable manner. Isoprenaline (0.1-10 microM), nifedipine (0.01-1 microM) and cromakalim (0.1-10 microM) had no effect, whereas vasoactive intestinal peptide (VIP, 1-10 nM), forskolin (0.1-2 microM), theophylline (0.1-2.5 mM), 4-(3-butoxy-4-methoxybenzyl)-2-imidazolidinone (RO 20-1724, 2-20 microM), dipyridamole (10-100 microM), 8 bromo-cyclic GMP (8-br-cGMP, 5-500 microM) and dibutyryl cyclic AMP (db-cAMP, 100-500 microM) shifted the concentration-response curve to phorbol 12,13-dibutyrate to the right and decreased the maximal response. When cumulative concentrations of relaxants were applied on the plateau of the contraction induced by 0.2 or 2 microM phorbol 12,13-dibutyrate, again, isoprenaline, nifedipine and cromakalim failed to decrease the protein kinase C-mediated contraction, whereas the other agents produced concentration-dependent relaxation. From their inhibitory effect on the 0.2 microM phorbol 12,13-dibutyrate-induced contraction, the rank order of potency of these relaxants was: VIP >> forskolin > RO 20-1724 > 8-br-cGMP > theophylline > dipyridamole > db-cAMP. In chemically (beta escin) skinned preparations, cGMP (5-500 microM) and cAMP (50-1000 microM) antagonized in a concentration dependent manner the contraction induced by phorbol 12,13-dibutyrate at constant Ca2+ concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Effect of cromakalim on KCl-, noradrenaline- and angiotensin II-induced contractions in the rat pulmonary artery.

The effect of cromakalim on vascular reactivity was studied in rat isolated pulmonary arterial strips. Cromakalim (0.1-1 microM) inhibited contractions induced by low (20-30 mM) KCl concentrations in a concentration-dependent manner. It had no effect on those elicited by 60-100 mM KCl. However, a higher concentration of cromakalim (10 microM) slightly decreased (-5 to -10%) KCl efficacy. Contractions induced by noradrenaline (NA, 0.01-1 microM) and angiotensin II (AII, 0.5-50 nM) were reduced by cromakalim (0.1-10 microM). The maximal response to NA and AII was decreased by 54 +/- 6.4% and 70 +/- 5.8% (n = 5), respectively, in the presence of 10 microM cromakalim. The inhibitory effect of cromakalim was not dependent on the presence of vascular endothelium. After blockade of calcium influx by verapamil (10 microM), cromakalim had no further effect on NA- and AII-induced contractions. Cromakalim (0.1-1 microM) had no effect on the amplitude of the transient contraction evoked by NA and AII in Ca(2+)-free solution. The inhibitory effect of cromakalim (1 microM) was reversed by glibenclamide (1-10 microM) and phentolamine (5-100 microM) which, however, did not alter the relaxant effect of verapamil (1 microM), papaverine (1 microM) or theophylline (1 mM). Contractions induced by NA and AII in the presence of tetraethylammonium (TEA, 10 mM) were also depressed by cromakalim. These results show that cromakalim is a potent anticonstrictor agent in the pulmonary circulation. As in other smooth muscles, its mechanism of action involves an interaction with potassium channels at the vascular smooth muscle cell membrane level.

Angiotensin II↗
PubMed1993

Effect of in vitro exposure to acrolein on carbachol responses in rat trachealis muscle.

Isolated tracheal rings obtained from male Wistar rats 10 to 15 weeks old and weighing 300 to 400 g were exposed to aqueous solutions of acrolein, and the resulting change of smooth muscle contractility was evaluated by measuring the cumulative carbachol concentration-response curve. Using the product of acrolein concentration and time as a surrogate for the acrolein dose delivered to the smooth muscle cells, contractility measured after a variety of exposure concentrations from 0.01 to 3.0 microM and times from 5 to 60 min could be correlated in a dose-dependent manner. In the range of doses from 0.1 to 6 microM-min, relative contractility continuously increased from 0 to 50% above unexposed control values. At doses greater than 6 microM-min, the enhancement in contractility declined. This decline may have been due to cell damage or cell death which was so severe at a dose of 60 microM-min that contractility fell below control values. Below a threshold dose of 0.1 microM-min, acrolein had no effect on contractility. The role arachidonic acid metabolism in the enhancement of smooth muscle reactivity to carbachol was studied using indometacin to block the cyclo-oxygenase pathway and NDGA to block the lipoxygenase pathway. At a concentration of 10 microM of either indometacin or NDGA, the acrolein-induced enhancement in airway reactivity was completely inhibited. At lower concentrations, inhibition by these two chemicals was partially additive, suggesting that both the lipoxygenase and cyclo-oxygenase pathways play a role in the hyperreactive response.

Acrolein↗
PubMed1993

Effect of passive sensitization on the mechanical activity of human isolated bronchial smooth muscle induced by substance P, neurokinin A and VIP.

1. The effect of passive sensitization on the mechanical activity of human isolated bronchial smooth muscle induced by the following neuropeptides substance P (SP), neurokinin A (NKA) and vasoactive intestinal peptide (VIP) was studied both in the absence and in the presence of the neutral endopeptidase (NEP) inhibitor, phosphoramidon. 2. Cumulative concentration-response curves (CCRC) to these neuropeptides were constructed in human passively sensitized isolated bronchial rings and compared to those in paired controls. Passively sensitized human isolated bronchial rings were tissues incubated overnight in serum from asthmatic patients atopic to Dermatophagoides pteronyssinus and paired controls were tissues originating from the same lung specimens but incubated overnight in serum from healthy donors. 3. In the absence of phosphoramidon, passive sensitization significantly increased the amplitude of the contractile responses to SP and NKA including that to the maximal concentration given from 50 +/- 5% to 76 +/- 6% (n = 5, P < 0.05) and from 70 +/- 7% to 101 +/- 6% (n = 5, P < 0.05) of the maximal response to acetylcholine, respectively. Passive sensitization significantly shifted to the left the CCRC for both tachykinins as measured by the geometric means dose-ratios which were 8.5 (95% confidence limits (CL): 3.1-13.9) and 7.3 (95% CL: 4.2-10.3) for SP and NKA, respectively. 4. In the presence of phosphoramidon (10 microM), passive sensitization still increased significantly the amplitude of the contractile responses to SP and NKA including that to the maximal concentration given from 74 +/- 4% to 115 +/- 7% (n = 5, P<0.05) and from 104 +/- 9% to 146 +/- 16% (n = 5, P<0.05)of the maximal response to acetylcholine, respectively. Passive sensitization still significantly shifted to the left the CCRC for both tachykinins as measured by the dose-ratios which were 9.0 (95% CL:4.3-13.6) and 5.4 (95% CL: 2.9-7.9) for SP and NKA, respectively.5. The relaxant response to the maximal concentration of VIP given in tissues precontracted with histamine (0.5 mM) was significantly reduced by passive sensitization from 41 +/- 4% to 25 +/- 3% (n = 5,P <0.05) of the amplitude of the precontraction in the absence of phosphoramidon and from 72 +/- 1%to 49 +/- 4% (n = 5, P<0.05) in the presence of phosphoramidon (10 microM). Passive sensitization significantly shifted to the right the CCRC for VIP as measured by the dose-ratios which were 10.4(95% CL: 6.6-14.1) and 6.4 (95% CL: 3.0-9.8) in the absence and in the presence of phosphoramidon,respectively.6. We conclude that passive sensitization enhances the mechanical response to neuropeptides which contract human isolated bronchial smooth muscle and reduces that to a neuropeptide which relaxes it.The mechanism of passive sensitization-induced changes in the mechanical activity appears to be independent of a decrease in NEP activity since these changes persist in the presence of the NEP inhibitor, phosphoramidon.

Acetylcholine↗
PubMed1993

Sensitization decreases relaxation in human isolated airways.

Passively sensitized human isolated airways provide an opportunity to study some aspects of bronchial hyperresponsiveness in vitro. Since it has been suggested that excessive airway narrowing could be due to impaired relaxation, we examined the effect of a variety of agents producing relaxation via different mechanisms, i.e., verapamil and lemakalim (a calcium channel antagonist and a potassium channel opener, respectively) and isoproterenol, forskolin, and dibutyryl cAMP (modulators of the beta-adrenoceptor signal transduction pathway). Human bronchial rings, obtained at thoracotomy, were passively sensitized by incubation in serum from atopic asthmatic patients, and control rings were incubated in serum from nonatopic subjects. We also studied bronchial rings from five spontaneously sensitized human lung specimens. Responses to the relaxant compounds were measured isometrically. Passive sensitization significantly decreased the efficacy of verapamil in maximally contracted tissues from 60 +/- 10 to 45 +/- 7% of the maximal carbachol response (n = 6, p < 0.05) and that of lemakalim from 51 +/- 16 to 38 +/- 14% (n = 7, p < 0.05) in tissues at baseline tone. Similarly, spontaneously sensitized tissues relaxed less to lemakalim (64 +/- 6% of the maximal response to isoproterenol, n = 5, p < 0.05) than did nonsensitized tissues (80 +/- 4%). Sensitization did not alter responses to isoproterenol, forskolin, and dibutyryl cAMP. We conclude that sensitization of human isolated airways reduces relaxation responses that depend upon activation of ion channels but not those that depend upon activation of beta-adrenoceptors and transduction processes directly coupled to these receptors.

Asthma↗
PubMed1992

Responsiveness to histamine in human sensitized airway smooth muscle.

Passive sensitization of human isolated airway smooth muscle increases contractile responses to histamine. We looked to see whether this increase was due to an alteration in the relative role of histamine H1 and H2 receptors. Human bronchial spiral strips obtained at thoracotomy were passively sensitized by incubation in serum from atopic asthmatic patients to Dermatophagoïdes pteronyssinus and control strips were incubated in serum from healthy non-allergic non-atopic subjects. We also studied spiral strips dissected from two spontaneously sensitized human lung specimens. Cumulative concentration-response curves (CCRC) to Ca2+ (10(-5) -3 x 10(-2) M) were constructed either in the presence of 10(-5) M histamine alone or in that of the combination histamine and the H2 antagonist cimetidine (10(-5) M). Unlike in the absence of histamine, Ca2+ CCRC in the presence of histamine alone were significantly shifted to the left in the passively sensitized tissues (mean EC50: 5.7 x 10(-4) M) compared to control ones (mean EC50: 9.3 x 10(-4) M, n = 6, P < 0.05). Addition of cimetidine to histamine did not alter the Ca2+ CCRC either in the control or in passively or spontaneously sensitized airway smooth muscle. These results suggest that (i) passive sensitization increases contractile response to Ca2+ of human bronchial smooth muscle in the presence of histamine; (ii) this increase is not due to a difference in the H1- vs H2-mediated response; and (iii) H2-mediated effects do not play a significant role in spontaneously sensitized human lung as both in the non-sensitized and passively sensitized lung.

Aged↗
PubMed1992

The effect of sodium cromoglycate on platelets: an in vivo and in vitro approach.

Platelet functions are altered in patients suffering from atopic diseases, including asthma. Such alterations might be related to IgE since platelets bear a specific IgE receptor termed Fc epsilon receptor II, and there is some evidence that IgE alone, that is, in the absence of antigen, could modify platelet functions, such as monoamine uptake. Although disodium cromoglycate (DSCG) has been demonstrated to interfere with IgE-mediated activation of human platelets, its effect in the absence of antigen remains unknown. We examined the DSCG effect on IgE-induced alterations both in vivo and in vitro. The effect, in vivo, of a daily intake of 40 mg of DSCG for 4 weeks was assessed on platelet kinetics, studied by a labeling technique on four patients with stable asthma. The effect, in vitro, of DSCG was assessed on IgE-induced alteration in monoamine uptake in platelets from 12 healthy subjects. DSCG significantly increased, in vivo, the mean time constant of platelet-survival curves from 234 +/- 40 to 463 +/- 150 hours (p less than 0.01). The amplitude of this effect increased with the patient's serum IgE concentration. DSCG, in vitro, reduced the inhibitory effect of IgE on monoamine uptake by 82%. This effect was concentration dependent and not related to IgE binding. It is concluded that DSCG alters both the survival time of platelets from allergic patients in vivo and the IgE-dependent monoamine uptake in platelets from normal subjects in vitro. These effects are likely to be related to the direct action of DSCG on cells bearing the Fc epsilon receptor II and might be independent of the specific trigger.

Adult↗
PubMed1992

IgE binding inhibits arachidonic acid-induced chemiluminescence of human platelets.

Arachidonic acid (AA)-induced chemiluminescence (CHL) was studied in vitro by means of a luminometer in platelets from nine healthy volunteers and six allergic patients. The amplitude of the CHL signal increased with AA concentration from 250 microM to 7 mM. At a low AA concentration (250 microM), the CHL signal consisted of two peaks. The first one occurred at 6 +/- 3 sec and the second one at 90 +/- 15 sec (n = 9). The mean amplitude of these peaks was 1.95 +/- 0.61 mV/sec and 0.82 +/- 0.22 mV/sec for normal subjects, and 2.35 +/- 0.62 mV/sec and 0.78 +/- 0.26 mV/sec for allergic patients, respectively. Aspirin (a cyclooxygenase inhibitor) and baicalein (a lipoxygenase inhibitor) reduced in a concentration-dependent manner, the first and second peak, respectively. The binding of immunoglobulin E (IgE) alone to platelets from both normal and allergic subjects inhibited both the first and second peak of AA-induced CHL. This inhibitory effect was specifically due to the action of IgE as it was (i) concentration-dependent and (ii) not observed when immunoglobulin G (IgG) was substituted for IgE. It is concluded that in normal subjects, as well as in allergic patients, the binding of IgE alone to its specific receptor on human platelets could alter arachidonate metabolism that probably involves cyclooxygenase and lipoxygenase pathways.

Adult↗
PubMed1992

Unilateral diaphragmatic paralysis: an electrophysiological study.

An electrophysiological study was carried out on four patients with unilateral diaphragmatic paralysis. Whereas neurogenic involvement of the paralysed hemidiaphragm was roughly similar in all cases, neurogenic patterns could be detected in the normally moving contralateral hemidiaphragm in three cases, and the degree of involvement could be correlated with the respiratory state of the patients. EMG also showed that the neuropathic process affected the limb muscles. Thus unilateral diaphragmatic paralysis may be, at least in some cases, the localised expression of a more diffuse neuropathy, perhaps a peculiar form of neuralgic amyotrophy.

Adult↗
PubMed1992

Effect of in vitro nitrogen dioxide exposure on human bronchial smooth muscle response.

The aim of this study was to develop an in vitro system in which an isolated bronchus from human lung was exposed, during 30 min, to a constant flow of either air or nitrogen dioxide (NO2), and to examine subsequently the contractile response of airway smooth muscle rings to carbachol, histamine, and substance P. Two proximal bronchi were mounted in an organ bath, perfused externally with Krebs-Henseleit solution and ventilated with clean air, 1.0 or 2.0 ppm NO2. The exposed bronchi were then cut into rings and mounted in a computerized organ bath system. Contractile responses to agonists were measured isometrically. In each ring, a cumulative concentration response curve was obtained to the desired agonist. We found that in vitro exposure of human lumen bronchus to a constant flow of air did not alter the contractility of the smooth muscle. Whereas in vitro exposure of the bronchus to 1.0 ppm NO2 did not significantly increase the efficacy or the potency of carbachol, exposure to 2.0 ppm NO2 increased airway smooth muscle contractions in response to carbachol, histamine, and substance P. These results indicate that our experimental preparation is well suited to study the respiratory toxicity of inhaled pollutants in order to understand further the mechanisms underlying toxicant-induced airway hyperresponsiveness.

Acetylcholine↗