The action of histamine on pulmonary vessels of cats and rats

1. The actions of histamine on pulmonary vascular smooth muscle have been studied in isolated cat and rat lungs perfused with blood, lobes of cat lung perfused in vivo and isolated strips of rat, cat and rabbit pulmonary artery. 2. In all the lung preparations histamine caused both dilatation and constriction. In the rat strips it caused both contraction and relaxation. Dilatation was only well shown when the vessels were in a prior constricted state. In any one lung dilatation occurred with smaller doses than constriction. 3. Histamine caused both increases and decreases in pulmonary artery pressure in collapsed lungs. In this condition these effects are unlikely to have been a consequence of changes in airway pressure. 4. From forward and reverse perfusions of lungs in the waterfall state, where changes in postalveolar vessels do not affect pulmonary artery pressure, it appeared that histamine caused both dilatation and constriction on both sides of the point of collapse caused by alveolar pressure. 5. Plots of the relationship between left atrial and pulmonary artery pressure (at constant alveolar pressure and blood flow) showed that histamine caused both increases and decreases in pulmonary vascular resistance and sometimes also increased the "Starling resistor" properties of lung vessels. 6. In plethysmograph experiments histamine caused moderate dilatation and constriction without affecting lung volume but strong vasoconstriction was accompanied by increases in lung volume.     

Independent modulation of horse airway smooth muscle by epithelium and prostanoids

The effects of epithelial removal and cyclooxygenase inhibition on contractions induced by exogenous acetylcholine (ACh) and electrical field stimulation (EFS) were evaluated in horse tracheal strips and bronchial rings. Epithelial removal potentiated the response to ACh but had no influence on the response to EFS. The effect of epithelial removal was not altered by pretreating the tissues with meclofenamate, a cyclooxygenase inhibitor. In trachealis strips, meclofenamate augmented contractions induced by EFS but not by ACh. In bronchial rings, meclofenamate augmented EFS-induced contraction to a greater extent than ACh-induced contraction. These effects of meclofenamate were epithelium-independent. We conclude that horse airway epithelium produces a relaxant factor that is not a prostanoid. Endogenous prostanoids originating from non-epithelial sites inhibit only cholinergic nerves in the trachea but both parasympathetic nerves and smooth muscle in the bronchi.     

Preservation of vascular function in rat mesenteric resistance arteries following cold storage, studied by small vessel myography

1. The use of isolated blood vessels to investigate the physiological and pharmacological control of the vasculature is limited by the requirement to use freshly isolated vessels. Hence, the aim of this study was to determine whether vascular smooth muscle and endothelial cell function could be preserved in resistance arteries by storing them in physiological salt solution (PSS) at 4 degrees C. 2. Third order mesenteric resistance arteries (mean internal diameter 237+/-6 microm) were dissected from the mesenteric bed of male Cob-Wistar rats. The vessel segments were mounted in a small vessel myograph for measurement of isometric tension, and equilibrated at their optimum resting force. Contractile responses to noradrenaline (NA; 1 x 10(-9) - 3 x 10(-5) M), phenylephrine (PE, 1 x 10(-9)-3 x 10(-5) M), potassium chloride (KCI; 2.5-140 mM) and endothelin (ET-1, 1 x 10(-11)-3 x 10(-7) M) and relaxant responses to acetylcholine (ACh; 1 x 10(-9) - 3 x 10(-5) M) and 3-morpholinosydnonimine (SIN-1; 1 x 10(-9) - 1 x 10(-4) M) were obtained in arteries, immediately after dissection (day 0) and following one to four days storage (day 1-day 4). 3. All arteries produced concentration-dependent contractions in response to each of the vasoconstrictors. There were no significant differences in the magnitude or sensitivity (pD2) of the vasoconstrictor responses between fresh and stored vessels. 4. Arteries precontracted with NA to approximately 80% of the maximum response, relaxed in a concentration-dependent manner in response to ACh and SIN-1. Vessel storage for up to three days resulted in no change in response to ACh or SIN-1. 5. Vessels analysed after four days of storage demonstrated a significant increase in sensitivity to ACh and SIN-1 (-logIC50 (M) values; ACh; day 0, 7.46+/-0.13 vs day 4, 7.97+/-0.11, P<0.01 and SIN-1; day 0, 4.87+/-0.10 vs day 4, 5.52+/-0.08, P<0.01). There was also a significant increase in the maximum relaxant response to ACh after four days of storage (% relaxation; day 0, 92.65+/-2.84 vs day 4, 100.36+/-0.36, P<0.05). 6. These results demonstrate that small resistance arteries remain viable if stored in PSS at 4 degrees C for up to four days, with no loss in endothelial cell function. The altered sensitivity to the vasodilators on day 4 suggests that vessels should only be stored for up to three days following dissection for analysis of functional responses.     

A comparison of the antigen-presenting capabilities of class II MHC-expressing human lung epithelial and endothelial cells

Human lung alveolar epithelial cells constitutively express class II major histocompatibility complex (MHC). Human lung microvascular endothelial and small airway epithelial cells can be induced to express class II MHC by stimulation with the pro-inflammatory cytokine interferon-gamma. The levels of class II MHC on lung epithelial and endothelial cells were comparable to those seen on an Epstein-Barr virus (EBV)-transformed B-cell line. However, the costimulatory molecules B7-1 and B7-2 were not expressed. The ability of the class II MHC expressing human lung parenchymal cells to present alloantigen to CD4+ T lymphocytes was investigated. Freshly isolated human alveolar epithelial cells (type II pneumocytes) and monolayers of interferon-gamma-stimulated small airway epithelial and lung microvascular endothelial cells were co-cultured with allogeneic CD4+ T lymphocytes and proliferation determined by [3H]thymidine incorporation. A clear difference was observed between effects of the epithelial and endothelial cells on CD4+ T-lymphocyte activation. Alveolar and small airway epithelial cells failed to stimulate the proliferation of allogeneic CD4+ T lymphocytes whereas lung microvascular endothelial cells did stimulate proliferation. This difference could not be explained by the levels of class II MHC or the lack of B7-1 and B7-2 solely. Microvascular endothelial cells, and not alveolar or small airway epithelial cells, possess B7-independent costimulatory pathways.     

Chronic alcohol intake reduces retinoic acid concentration and enhances AP-1 (c-Jun and c-Fos) expression in rat liver

OBJECTIVES: In vivo studies of the human coronary resistance circulation cannot control for indirect effects of myocardial metabolism, compression, and neurohumoral influences. This study directly examined the vasodilator responses of the human coronary microcirculation to both receptor-dependent and -independent agonists. METHODS: Atrial arterioles were dissected from human right atrial appendage (103 +/- 2 microns diameter, n = 185 vessels from 145 patients) obtained at the time of cardiopulmonary bypass and left ventricular vessels from explanted human hearts (148 +/- 10 microns diameter, n = 57 vessels from 18 patients). After dissection, vessels were mounted onto pipettes in Kreb's buffer under conditions of zero flow and at a constant distending pressure of 60 mmHg. Drugs were applied extraluminally and steady state changes in diameter measured with videomicroscopy. RESULTS: After contraction by endothelin or spontaneous tone, increasing concentrations of adenosine diphosphate (ADP) produced a similar dose-dependent dilation in vessels from atria (maximum 89 +/- 4%, n = 76) and ventricles (maximum 74 +/- 9%, n = 10). The dilation to ADP was abolished by mechanical removal of the endothelium. Similar dilator responses were found to bradykinin, substance P, arachidonic acid, and the calcium ionophore A23187 in both atria and ventricle. In contrast, acetylcholine (ACh) constricted all atrial vessels (-58 +/- 3%, n = 63) regardless of patient age or underlying disease. This constriction was attenuated by denudation, but not affected by inhibition of nitric oxide synthase or cyclo-oxygenase. Microvessels isolated from human ventricle exhibited a heterogeneous response to ACh with dilation being the predominant response. CONCLUSIONS: We conclude that isolated human coronary arterioles demonstrate endothelium-dependent dilation. However, the response to acetylcholine is unique with vasoconstriction in atrial vessels and dilation in ventricular arterioles.     

Recovery of airway structure and function after hyperoxic exposure in immature rats

We have previously demonstrated that hyperoxic exposure (> 95% O2 for 8 d) induces airway cholinergic hyperresponsiveness and remodeling in 21-d-old rats. To examine the potential relationship between airway hyperresponsiveness and remodeling in these animals, we exposed rats to air or hyperoxia for 8 d, returned them to air-breathing, and measured airway responsiveness to inhaled acetylcholine (ACh) and layer thicknesses immediately after or 16 or 48 d after cessation of air or O2 exposure. The ACh concentration required to increase resistance by 100% (EC200ACh) was calculated by linear interpolation. Small airway (circumference < 1,000 microns) and medium-sized, conducting airway (1,000 to 3,000 microns) epithelial and smooth muscle layer mean thicknesses and fractional areas (layer area/luminal cross-sectional area) were determined from lung sections by contour tracing using a digitizing pad and computer. As we reported previously, after 8 d of O2 exposure, group mean log EC200ACh was significantly reduced relative to that in control animals (p < 0.001). Similarly, hyperoxic exposure was associated with significant increases in all parameters of airway layer thickness assessed (p < 0.05). However, by 16 d after cessation of O2 exposure, there were no longer statistically significant differences in log EC200ACh, airway layer thickness, or fractional area between control and O2-exposed animals. Further studies, in a second cohort of animals killed 0, 3, 6, 8, or 13 d after cessation of O2 exposure, demonstrated progressive reductions in small airway epithelial and smooth muscle layer thicknesses, confirming that hyperoxia-induced airway remodeling resolves by approximately 2 wk after termination of O2 exposure.(ABSTRACT TRUNCATED AT 250 WORDS)     

Nitric oxide-mediated changes in vascular reactivity in pregnancy in spontaneously hypertensive rats

1. To examine the mechanisms which may account for pregnancy-induced vasodilatation in spontaneously hypertensive rats (SHR), we have investigated the changes in vascular reactivity and the effects of endothelial nitric oxide (NO) inhibition in the in situ blood-perfused, mesenteric resistance vessels of 18-20 day pregnant SHR. The effects of NG-nitro-L-arginine (L-NOARG) were compared in pregnant and nonpregnant SHR and gestation matched normotensive Wistar-Kyoto (WKY) rats. 2. Intra-arterial mean blood pressures (MBP) were similar in pregnant and nonpregnant SHR. Basal perfusion pressures (BPP) were decreased in pregnant compared with nonpregnant SHR. Pregnant WKY had lower MBP and BPP than either pregnant or nonpregnant SHR. 3. Vasoconstrictor responses to electrical stimulation (ES) and intra-arterial noradrenaline (NA) were decreased in pregnant compared with nonpregnant SHR. These responses were still greater in pregnant SHR when compared with pregnant WKY. Vascular reactivity to angiotensin II (AII) in pregnant SHR was reduced to a similar level to that in pregnant WKY. 4. L-NOARG (5 mg kg-1, i.v.), an inhibitor of nitric oxide synthase, increased MBP and BPP in all groups. After L-NOARG, BPP were equalized between pregnant and nonpregnant SHR. Pregnant WKY still showed lower MBP and BPP than SHR groups. 5. L-NOARG potentiated vascular responses to ES, NA and AII in all groups. The blunted vascular responses to NA and ES were normalized and the reactivity to AII was only partially reversed in pregnant SHR compared with nonpregnant SHR. Pregnant WKY still had much lower vascular responses to ES and NA than either pregnant or nonpregnant SHR. L-NOARG enhanced vascular responses to All to a greater extent in pregnant SHR than in pregnant WKY.6. These results demonstrate that blunted responses to NA and ES were NO-dependent, while diminished reactivity to AII was only partially dependent on NO in the in situ blood perfused mesenteric resistance vessels of pregnant SHR.7. The present results in pregnant SHR differ from our previous finding with pregnant normotensive WKY, in which blunted responses to NA, but not to ES, were equalized by L-NOARG. Pregnancy induced vasodilatation in hypertensive rats appears to be more dependent on endothelial NO than in normotensive WKY. A defect of the endothelial NO generating pathway which promotes vasodilatation in pregnancy may contribute to the predisposition of women with essential hypertension to develop pre-eclampsia.     

Loss of nitric oxide release in passively sensitized guinea-pig aorta with purified immunoglobulin G1

BACKGROUND: Vascular hyperresponsiveness can be reproduced by in vitro passive sensitization of isolated aorta with immunoglobulin G1 (IgG1) taken from ovalbumen-sensitized BFA guinea-pig. OBJECTIVE: The aim of the present work was to investigate the role of nitric oxide in the sensitization-induced alteration of the contractile and relaxant responses of guinea-pig aorta to noradrenaline (NA) and acetylcholine (ACh), respectively. METHODS: Cumulative concentration-response curves to NA or ACh were established before and after IgG1 sensitization and then after successive treatments. RESULTS: IgG1 in vitro passive sensitization of aorta caused a significant hyperreactivity to NA and completely inhibited the relaxation to ACh. After sensitization, the addition of an intact aortic ring (with endothelium) in the organ chamber restored the maximal response to NA and ACh close to control but was ineffective in the presence of hemoglobin. The restoration of the control reactivity to NA was also inhibited in the presence of L-NAME or when the added aortic ring was endothelium-denuded. Moreover, L-arginine, a nitric oxide (NO) precursor, was able to restore the control reactivity to NA. CONCLUSION: The present results show that IgG1 in vitro sensitization induced a loss of NO release from the vascular endothelium. This loss of NO probably plays a great role in vascular hyperreactivity by increasing the contractile response and decreasing the relaxant response to mediators and would be a component of allergic diseases pathogenesis.     

Measurement of acetylcholine released from rabbit detrusor smooth muscle using HPLC with electro-chemical detection coupled with microdialysis procedure

We measured the amount of acetylcholine (ACh) released from rabbit detrusor smooth muscles induced by electrical field stimulation (EFS) using microdialysis procedure. The dialysis probe was inserted through the detrusor muscle strip and was continuously perfused with a Ringer solution containing physostigmine sulfate, at a rate of 2 microl/min. The strip was suspended in an organ bath filled with the modified Krebs-Henseleit solution and then EFS was delivered. The isometric force was recorded and monitored in each muscle preparation. The dialysates were collected every 10 min. ACh was determined by a high performance liquid chromatography with electro-chemical detection. The contraction of the muscle strip and ACh release induced by EFS were increased in a frequency and duration dependent manner. There were some differences between frequency response curves of contraction and frequency dependent ACh release. In the contractile response, the maximum contractions were observed at lower frequencies, while ACh releases reached the maximum at higher frequencies. There was a significant, but not simple correlation between EFS-induced contraction and ACh release. The results suggest that this new method is useful to investigate the ACh release from rabbit detrusor smooth muscles, and that other neurotransmitters than ACh possibly contribute to EFS-induced contraction.     

Distribution of CD4+ T-lymphocytes levels in patients with clinical symptoms of AIDS in three west African countries

The characteristics of airway responsiveness to acetylcholine (ACh) in congenitally bronchial-hypersensitive (BHS) and bronchial-hyposensitive (BHR) guinea pigs were clarified in vivo and in vitro. We measured the change in ventilatory mechanics in response to ACh inhalation by means of the bodyplethysmograph and the contractile responses of isolated trachea to ACh and carbachol (CCh). Further, muscarinic receptor subtypes involved these responses were identified. The basal values for ventilatory mechanics in BHS were not significantly different from those in BHR. Respiratory resistance to ACh was progressively increased in a time- and dose-dependent manner in BHS. The contractile responses of tracheal smooth muscle to ACh in BHS were significantly greater than those in BHR, but CCh-induced responses in BHS and BHR were similar. ACh- and CCh-induced contractions were mediated via M3 receptors. These results suggested that the falling-down of BHS in response to ACh inhalation was caused by the strong constriction of the airway and the reduction in ventilation. Moreover, the airway hyperresponsiveness to ACh in BHS might be partly dependent on the change in acetylcholinesterase activity.     

Nervous regulation of the tone of the retractor penis muscle in the goat

The nervous control of the retractor penis muscle (rp) was investigated in the anaesthetized goat. Also, isolated field stimulated strips of the muscle were studied. The noradrenaline (NA) and acetylcholine (ACh) content of the rp was determined, and histochemistry for adrenergic and acetylcholinesterase (AChE) positive nerves was performed. The muscle exhibited spontaneous activity that persisted after section of all nerves. There was, however, also a tendency of the activity to follow the general vasomotor tone, which disappeared after section of the sympathetic chains. The excitatory adrenergic nerves which innervate the muscle come from the sympathetic chains and run along the pudendal, the hypogastric and the pelvic nerves. The rp has a dense network of adrenergic fibres and is very sensitive to excitatory adrenergic stimulation. It has a fairly large NA content, which is higher in old goats (5.95 +/- 0.42 micrograms g-1) than in young goats (2.87 +/- 0.78 micrograms g-1). Inhibitory non-adrenergic non-cholinergic (NANC) innervation reaches it via the pelvic and the hypogastric nerves. The maximum inhibitory response is reached at low frequencies (2-4 Hz). Cholinergic prejunctional inhibition of the excitatory response to sympathetic chain stimulation was effected by simultaneous stimulation of the hypogastric nerves. In vitro experiments confirmed the presence of endogenous cholinergic muscarinic suppression of the excitatory adrenergic neurotransmission. Significant amounts of ACh (0.81 +/- 0.18 micrograms g-1) are present in the muscle, and it contains strongly AChE positive nerve fibres and nerve cell bodies. It is concluded that the goat rp is innervated by sympathetic adrenergic excitatory nerves and parasympathetic NANC inhibitory nerves. It further has a direct sympathetic inhibitory NANC innervation, and an indirect inhibitory cholinergic innervation which at least in part is sympathetic.     

Impaired endothelium-dependent relaxation in isolated resistance arteries of spontaneously diabetic rats

1. Previous studies have shown that endothelium-dependent relaxation in the aorta of spontaneously diabetic bio bred rats (BB) is impaired. 2. We have investigated noradrenaline (NA) contractility, endothelium-dependent acetylcholine (ACh) and bradykinin (BK) relaxation, and endothelium-independent sodium nitroprusside (SNP) relaxation in mesenteric resistance arteries of recent onset BB rats and established insulin treated BB rats, compared to their age-matched non diabetic controls. 3. There was no significant difference in the maximum contractile response or sensitivity to noradrenaline in either of the diabetic groups compared to their age-matched controls. 4. Incubation with the nitric oxide synthetase inhibitor NG-nitro-L-arginine (L-NOARG) resulted in a significant increase in maximum contractile response to noradrenaline in the recent onset age-matched control group (P < 0.05). Analysis of the whole dose-response curve (using ANOVA for repeated measures with paired t test) showed a significant left-ward shift following the addition of L-NOARG (P < 0.001). A similar but less marked shift (P < 0.01) was evident in vessels from recent onset diabetics. An overall shift in both sensitivity and maximum response was also evident in the age-matched non diabetic controls of the insulin-treated group (P < 0.05). However, by contrast, there was no significant change in sensitivity in the insulin-treated diabetic rats. 5. ACh-induced endothelium-dependent relaxation was significantly impaired in the recent onset diabetic rats compared to their age-matched controls (47 +/- 11% versus 92 +/- 2%, P < 0.05, n = 6), and in the insulin treated diabetic rats (34 +/- 5% versus 75 +/- 6%, P < 0.05, n = 6). The relaxation responses to BK also were significantly impaired in the diabetic rats compared to their age-matched controls (recent onset: 20 +/- 3% versus 72 +/- 7%, P < 0.05, n = 6; insulin treated: 12 +/- 9% versus 68 +/- 7%, P < 0.05, n = 7). 6. Incubation with either the nitric oxide synthetase substrate, U-arginine, or the free radical scavenging enzyme superoxide dismutase (150 mu ml-1) failed to improve the attenuated response of acetylcholine-induced relaxation in the diabetic vessels. 7. Endothelium-dependent relaxation mediated by ACh and BK was significantly attenuated in both the diabetic and control vessels after incubation with L-NOARG. 8. Pretreatment with a cyclo-oxygenase inhibitor, indomethacin, significantly enhanced the relaxation to ACh in both the recent onset and insulin treated diabetic rats (42 +/- 10%, n = 7 versus 64 +/- 7%, n = 7, P < 0.05, and 40 +/- 5%, n = 7 versus 65 +/- 9%, n = 6, P < 0.05). 9. Following endothelium removal, there was a marked impairment in endothelium-dependent relaxation responses to ACh and BK in both the diabetic and control vessels. 10. Incubation with the thromboxane A2 receptor antagonist SQ29548, did not significantly improve the ACh endothelium-dependent relaxation response in the diabetic vessels. 11. Endothelium-independent relaxation to sodium nitroprusside was significantly impaired in the first group of diabetic vessels studied; however, subsequent studies showed no impairment of the sodium nitroprusside response in the diabetic vessels. 12. In conclusion, the ability of the endothelium to regulate vascular contractility is reduced in recent onset diabetic vessels, and significantly impaired in established insulin treated diabetics. Relaxation to the endothelium-dependent vasodilators ACh and BK was impaired in both the recent onset and the established insulin treated diabetics, and the ACh response was significantly improved following pretreatment with indomethacin, suggesting a role for a cyclo-oxygenase-derived vasoconstrictor. Preliminary studies with a thromboxane A2, receptor antagonist, SQ29548 did not significantly improve the impaired relaxation to ACh, indicating that the vasoconstrictor prostanoid is not thromboxane A2.     

Evidence for a histaminergic mechanism on the effects of angiotensin II in the rabbit aorta and rat lung

The influence of a histidine decarboxylase (HD) inhibitor, GYKI 11.121, on the action of angiotension II (AII) was investigated in the isolated continuously superfused rabbit aortic strip and perfused rat lung. An A II analog, Sar1-Ile5-A II, was also used only in aortic strip experiments. The myotropic effects of both peptides on the rabbit aorta were found to be inhibited when GYKI 11.121 was added to the superfusion medium. However, the vasoconstrictor effect of A II was found to be enhanced in the isolated rat lung following the addition of GYKI 11.121 to the perfusion medium. These findings are explained by the presence of a histaminergic component in the myotropic action of A II peptides.     

Effects of parturition and maternal experience on noradrenaline and acetylcholine release in the olfactory bulb of sheep.

Acetylcholine (ACh) and noradrenaline (NA) release in the olfactory bulb (OB) of ewes was monitored using microdialysis. Both ACh and NA release increased at parturition in multiparous but not in primiparous ewes. However, vaginocervical stimulation performed 6 hrs postpartum induced an increase of ACh and NA release in both primiparous and multiparous ewes, indicating that a maturation process had occurred. Finally, pharmacological challenges to the ACh and NA inputs revealed differential responsiveness between nulliparous and multiparous nongestant ewes. These results suggest that the 1st parturition induces changes in neural circuitry involving ACh and NA inputs to the OB. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Endothelium-dependent modulation of resistance vessel contraction: studies with NG-nitro-L-arginine methyl ester and NG-nitro-L-arginine

1. The effect of NG-nitro-L-arginine methyl ester (L-NAME) and NG-nitro-L-arginine (L-NOARG) on noradrenaline (NA)-induced contractility and acetylcholine (ACh)-induced endothelium-dependent relaxation was studied in rat mesenteric resistance arteries. 2. Third order branches of mesenteric arteries were dissected and mounted on two forty micron wires in a Mulvany myograph. 3. Incubation with L-NAME and L-NOARG (10 microM) caused a time-dependent shift in the 50% response to NA (ED50) (0.01 microM-10 microM) but was not associated with an increase in the maximum contractile response. 4. L-NAME and L-NOARG (10 microM) caused a time-dependent inhibition of ACh (1 microM)-induced relaxation with a maximum effect after 120 min. 5. Following endothelium removal, incubation with either L-NAME or L-NOARG caused no significant shift in the ED50, although the residual relaxation response to ACh (1 microM) was further attenuated. 6. Incubation with the cyclo-oxygenase inhibitor, indomethacin, enhanced the relaxation to ACh and reduced the inhibitory effects of L-NAME and L-NOARG. 7. In conclusion, L-NAME and L-NOARG are potent inhibitors of acetylcholine-induced endothelium-dependent relaxation in mesenteric resistance arteries. The shift in ED50 associated with these inhibitors suggests a probable role for the endothelium in modulating the contractility of the resistance vasculature.     

Nisin resistance in Listeria monocytogenes ATCC 700302 is a complex phenotype

The constriction of pulmonary airways is limited by the tethering effect exerted by parenchymal attachments. To characterize this tethering effect at the scale of intraparenchymal airways, we studied the pattern of parenchymal distortion due to bronchoconstriction in a rat lung explant system. First, we measured the elastic modulus under tension for 2% (wt/vol) agarose alone (37.6 +/- 1.5 kPa) and for agarose-filled lung (5.7 +/- 1.3 kPa). The latter is similar to the elastic modulus of air-filled lung at total lung capacity (4.5-6 kPa) (S. J. Lai-Fook, T. A. Wilson, R. E. Hyatt, and J. R. Rodarte. J. Appl. Physiol. 40: 508-513, 1976), suggesting that explants can be used as a model of lung tissue distortion. Subsequently, confocal microscopic images of fluorescently labeled 0.5-mm-thick explants prepared from agarose-filled rat lungs inflated to total lung capacity (48 ml/kg) were acquired. Images were taken before and after airway constriction was induced by direct application of 10 mM methacholine, and the pattern of parenchymal distortion was measured from the displacement of tissue landmarks identified in each image for 14 explants. The magnitude of the radial component of tissue displacement was calculated as a function of distance from the airway wall and characterized by a parameter, b, describing the rate at which tissue movement decreased with radial distance. The parameter b was 0.994 +/- 0.19 (SE), which is close to the prediction of b = 1 of micromechanical modeling (T. A. Wilson. J. Appl. Physiol. 33: 472-478, 1972). There was significant variability in b, however, which was correlated with the fractional reduction in airway diameter (r = 0.496). Additionally, parenchymal distortion showed significant torsion with respect to the radial direction. This torsion was similar in concentric zones around the airway, suggesting that it originates from inhomogeneity in the parenchyma rather than inhomogeneous airway constriction. Our results demonstrate the significance of the nonlinear mechanical properties of alveolar walls and the anisotropy of the parenchyma in determining the nature of airway-parenchymal interdependence.     

The role of the N-methyl-D-aspartic acid receptor in the relaxant effect of ketamine on tracheal smooth muscle

Ketamine and magnesium (Mg2+), well known bronchodilators, have been used to treat patients with status asthmaticus. Both can block the N-methyl-D-aspartic acid (NMDA) receptor. NMDA receptors exist in the airway, and their activation seems to be linked to the release actions of sensory neuropeptides resulting in increased airway tone. We sought to determine whether ketamine relaxes the guinea pig trachea contracted by histamine by blocking the NMDA receptor. Female guinea pigs (250-400 g) were killed with an overdose of pentobarbital. The trachea was removed and cut spirally into strips 3 mm wide and 15 mm long. The strips were mounted in a 10-mL organ bath filled with Tyrode's solution bubbled through with 95% O2/5% CO2 at 37 degrees C. Strip contractions were measured isometrically with a force displacement transducer. We then studied the effect of NMDA receptor antagonists on histamine-induced tracheal contraction. In this protocol, we examined the effect of ketamine, Mg2+, zinc (Zn2+), or MK-801 (a noncompetitive NMDA receptor blocker) on strips contracted by 10(-5) M histamine. After full contraction was attained, ketamine (0.5-1.5 mM), MgSO4 (2-8 mM), ZnCl2(0.2-0.8 mM), or MK-801 (1.5-6 x 10(-5) M) was added, and the strip tension was measured again. We also studied the effect of NMDA on the relaxation by ketamine. After full contraction by 10(-5) M histamine, 0.5-1.5 mM KET was added alone or in combination with 0.1 mM NMDA, and the strip tension was measured again. Finally, we measured the effect of MK-801 on the relaxant effect of ketamine. After full contraction by 10(-5) M histamine, 0.5-2 mM ketamine was added alone or in combination with 0.75 or 1.5 x 10(-5) M MK-801, and the strip tension was measured again. All NMDA receptor antagonists tested reversed the tracheal contraction induced by histamine in a dose-dependent manner. However, neither the agonist NMDA nor the noncompetitive receptor blocker MK-801 affected tracheal relaxation induced by ketamine. We conclude that ketamine relaxes the tracheal smooth muscle contracted by histamine through a mechanism independent of NMDA receptors. The decreased bronchomotor tone induced by ketamine is probably due to interference with a Ca2+-requiring step necessary to maintain the contraction caused by histamine. IMPLICATIONS: Stimulation of the N-methyl-D-aspartic acid (NMDA) receptor in the airway results in airway constriction. The bronchodilator ketamine blocks the NMDA receptor. However, ketamine relaxes the guinea pig trachea contracted by histamine through a mechanism independent of the NMDA receptor.     

Caspase 1-independent IL-1beta release and inflammation induced by the apoptosis inducer Fas ligand

Anchietia salutaris tea is traditionally used in Brazil to treat allergies, suggesting it contains compounds with antagonistic activity on the allergic mediators. We have evaluated extracts and semi-purified fractions of Anchietia salutaris as a source of compounds having this type of antagonism on the contraction induced in guinea-pig lung parenchymal strips and on platelet aggregation and shape change. After 10 min pre-incubation dichloromethane extracts containing 30 or 100 microg mL(-1) inhibited the contraction induced by prostaglandin D2 (PGD2) in guinea-pig lung parenchymal strips with dose ratios (DR) of 0.76+/-0.14 and 0.93+/-0.19, respectively; the amount of inhibition depended both on the concentration and on the time of pre-incubation (DR after 30 min pre-incubation was 1.21+/-0.51). The dichloromethane extract and its semi-purified fractions also inhibited the contractions induced by U46619, a more potent, stable, synthetic agonist of thromboxane A2 (TxA2) prostanoid (TP) receptors, the receptors acted upon by PGD2 to produce lung contractions. The dichloromethane extract did not inhibit the lung parenchymal contractions induced by histamine, leukotriene D4 (LTD4) or platelet-activating factor (PAF). Platelet aggregation induced by U46619, adenosine 5'-diphosphate (ADP) or PAF was not inhibited by the dichloromethane extract. Indeed, the extract potentiated platelet aggregation induced by low concentrations of these agonists and also potentiated the shape change induced by U46619. These results imply that the dichloromethane extract of Anchietia salutaris and its semi-purified fractions contain an active principle that competitively inhibits TxA2 TP receptors, the stimulation of which causes lung parenchymal contraction. The inhibition seems to be selective for this receptor subtype, because the extract fails to inhibit platelet aggregation or shape change. This provides additional support of earlier reports suggesting the occurrence of TP receptor subtypes.     

Responses to electrical stimulation, noradrenaline, serotonin, and vasopressin in the isolated ear artery of the developing lamb and ewe

Responses of isolated helical strips of ovine ear artery to electrical stimulation of postganglionic adrenergic neurons and exogenous agonists were studied at various stages of development from 110 days of gestation through to adulthood. Only rudimentary responses were observed at 110-115 days of gestation. A parallel development of responses to noradrenaline (NA), serotonin, and lysine vasopressin began sometime after 110-115 days of gestation and continued until 133-137 days of gestation but there was little development of the latter responses until more than 3-5 days post partum. Development of responses to exogenous agonists was incomplete 2-3 weeks post partum. The development of postganglionic adrenergic responses lagged behind those to exogenous NA. Two to three weeks post partum the NA maximal response was one-third that of adult tissue whereas the response to 16 Hz (highest frequency used) was one-sixth that of adult tissue. The NA threshold concentration was lower in arterial strips of adult animals than it was in those of younger animals. The data suggest that development of functional post-ganglionic adrenergic innervation of vascular smooth muscle begins late in gestation and continues well after birth; this development is preceded by development of vascular mechanisms involved in the response to several agonists.