MEK modulates force-fluctuation-induced relengthening of canine tracheal smooth muscle.

Tidal breathing, and especially deep breathing, is known to antagonise bronchoconstriction caused by airway smooth muscle (ASM) contraction; however, this bronchoprotective effect of breathing is impaired in asthma. Force fluctuations applied to contracted ASM in vitro cause it to relengthen, force-fluctuation-induced relengthening (FFIR). Given that breathing generates similar force fluctuations in ASM, FFIR represents a likely mechanism by which breathing antagonises bronchoconstriction. Thus it is of considerable interest to understand what modulates FFIR, and how ASM might be manipulated to exploit this phenomenon. It was demonstrated previously that p38 mitogen-activated protein kinase (MAPK) signalling regulates FFIR in ASM strips. Here, it was hypothesised that the MAPK kinase (MEK) signalling pathway also modulates FFIR. In order to test this hypothesis, changes in FFIR were measured in ASM treated with the MEK inhibitor, U0126 (1,4-diamino-2,3-dicyano-1,4-bis[2-aminophenylthio]butadiene). Increasing concentrations of U0126 caused greater FFIR. U0126 reduced extracellular signal-regulated kinase 1/2 phosphorylation without affecting isotonic shortening or 20-kDa myosin light chain and p38 MAPK phosphorylation. However, increasing concentrations of U0126 progressively blunted phosphorylation of high-molecular-weight caldesmon (h-caldesmon), a downstream target of MEK. Thus changes in FFIR exhibited significant negative correlation with h-caldesmon phosphorylation. The present data demonstrate that FFIR is regulated through MEK signalling, and suggest that the role of MEK is mediated, in part, through caldesmon.

Steroids augment relengthening of contracted airway smooth muscle: potential additional mechanism of benefit in asthma.

Breathing (especially deep breathing) antagonises development and persistence of airflow obstruction during bronchoconstrictor stimulation. Force fluctuations imposed on contracted airway smooth muscle (ASM) in vitro result in its relengthening, a phenomenon called force fluctuation-induced relengthening (FFIR). Because breathing imposes similar force fluctuations on contracted ASM within intact lungs, FFIR represents a likely mechanism by which breathing antagonises bronchoconstriction. While this bronchoprotective effect appears to be impaired in asthma, corticosteroid treatment can restore the ability of deep breaths to reverse artificially induced bronchoconstriction in asthmatic subjects. It has previously been demonstrated that FFIR is physiologically regulated through the p38 mitogen-activated protein kinase (MAPK) signalling pathway. While the beneficial effects of corticosteroids have been attributed to suppression of airway inflammation, the current authors hypothesised that alternatively they might exert their action directly on ASM by augmenting FFIR as a result of inhibiting p38 MAPK signalling. This possibility was tested in the present study by measuring relengthening in contracted canine tracheal smooth muscle (TSM) strips. The results indicate that dexamethasone treatment significantly augmented FFIR of contracted canine TSM. Canine tracheal ASM cells treated with dexamethasone demonstrated increased MAPK phosphatase-1 expression and decreased p38 MAPK activity, as reflected in reduced phosphorylation of the p38 MAPK downstream target, heat shock protein 27. These results suggest that corticosteroids may exert part of their therapeutic effect through direct action on airway smooth muscle, by decreasing p38 mitogen-activated protein kinase activity and thus increasing force fluctuation-induced relengthening.

Airway smooth muscle dynamics: a common pathway of airway obstruction in asthma.

Excessive airway obstruction is the cause of symptoms and abnormal lung function in asthma. As airway smooth muscle (ASM) is the effecter controlling airway calibre, it is suspected that dysfunction of ASM contributes to the pathophysiology of asthma. However, the precise role of ASM in the series of events leading to asthmatic symptoms is not clear. It is not certain whether, in asthma, there is a change in the intrinsic properties of ASM, a change in the structure and mechanical properties of the noncontractile components of the airway wall, or a change in the interdependence of the airway wall with the surrounding lung parenchyma. All these potential changes could result from acute or chronic airway inflammation and associated tissue repair and remodelling. Anti-inflammatory therapy, however, does not "cure" asthma, and airway hyperresponsiveness can persist in asthmatics, even in the absence of airway inflammation. This is perhaps because the therapy does not directly address a fundamental abnormality of asthma, that of exaggerated airway narrowing due to excessive shortening of ASM. In the present study, a central role for airway smooth muscle in the pathogenesis of airway hyperresponsiveness in asthma is explored.

Effects of dietary flaxseed on vascular contractile function and atherosclerosis during prolonged hypercholesterolemia in rabbits.

Dietary flaxseed has significant anti-atherogenic effects. However, the limits of this action and its effects on vascular contractile function are not known. We evaluated the effects of flaxseed supplementation on atherosclerosis and vascular function under prolonged hypercholesterolemic conditions in New Zealand White rabbits assigned to one of four groups for 6, 8, or 16 wk of feeding: regular diet (RG), 10% flaxseed-supplemented diet (FX), 0.5% cholesterol-supplemented diet (CH), and 0.5% cholesterol- and 10% flaxseed-supplemented diet (CF). Cholesterol feeding resulted in elevated plasma cholesterol levels and the development of atherosclerosis. The CF group had significantly less atherosclerotic lesions in the aorta and carotid arteries after 6 and 8 wk than the CH animals. However, the anti-atherogenic effect of flaxseed supplementation was completely attenuated by 16 wk. Maximal tension induced in aortic rings either by KCl or norepinephrine was not impaired by dietary cholesterol until 16 wk. This functional impairment was not prevented by including flaxseed in the high-cholesterol diet. Aortic rings from the cholesterol-fed rabbits exhibited an impaired relaxation response to acetylcholine at all time points examined. Including flaxseed in the high-cholesterol diet completely normalized the relaxation response at 6 and 8 wk and partially restored it at 16 wk. No significant changes in the relaxation response induced by sodium nitroprusside were observed in any of the groups. In summary, dietary flaxseed is a valuable strategy to limit cholesterol-induced atherogenesis as well as abnormalities in endothelial-dependent vasorelaxation. However, these beneficial effects were attenuated during prolonged hypercholesterolemic conditions.

Latrunculin B increases force fluctuation-induced relengthening of ACh-contracted, isotonically shortened canine tracheal smooth muscle.

We hypothesized that differences in actin filament length could influence force fluctuation-induced relengthening (FFIR) of contracted airway smooth muscle and tested this hypothesis as follows. One-hundred micromolar ACh-stimulated canine tracheal smooth muscle (TSM) strips set at optimal reference length (Lref) were allowed to shorten against 32% maximal isometric force (Fmax) steady preload, after which force oscillations of +/-16% Fmax were superimposed. Strips relengthened during force oscillations. We measured hysteresivity and calculated FFIR as the difference between muscle length before and after 20-min imposed force oscillations. Strips were relaxed by ACh removal and treated for 1 h with 30 nM latrunculin B (sequesters G-actin and promotes depolymerization) or 500 nM jasplakinolide (stabilizes actin filaments and opposes depolymerization). A second isotonic contraction protocol was then performed; FFIR and hysteresivity were again measured. Latrunculin B increased FFIR by 92.2 +/- 27.6% Lref and hysteresivity by 31.8 +/- 13.5% vs. pretreatment values. In contrast, jasplakinolide had little influence on relengthening by itself; neither FFIR nor hysteresivity was significantly affected. However, when jasplakinolide-treated tissues were then incubated with latrunculin B in the continued presence of jasplakinolide for 1 more h and a third contraction protocol performed, latrunculin B no longer substantially enhanced TSM relengthening. In TSM treated with latrunculin B + jasplakinolide, FFIR increased by only 3.03 +/- 5.2% Lref and hysteresivity by 4.14 +/- 4.9% compared with its first (pre-jasplakinolide or latrunculin B) value. These results suggest that actin filament length, in part, determines the relengthening of contracted airway smooth muscle.

Myosin light chain phosphorylation facilitates in vivo myosin filament reassembly after mechanical perturbation.

Phosphorylation of the 20-kDa regulatory myosin light chain (MLC) of smooth muscle is known to cause monomeric myosins in solution to self-assemble into thick filaments. The role of MLC phosphorylation in thick filament formation in intact muscle, however, is not clear. It is not known whether the phosphorylation is necessary to initiate thick filament assembly in vivo. Here we show, by using a potent inhibitor of MLC kinase (wortmannin), that the MLC phosphorylation and isometric force in trachealis muscle could be abolished without affecting calcium transients. By measuring cross-sectional densities of the thick filaments electron microscopically, we also show that inhibition of MLC phosphorylation alone did not cause disassembly of the filaments. The unphosphorylated thick filaments, however, partially dissolved when the muscle was subjected to oscillatory strains (which caused a 25% decrease in the thick filament density). The postoscillation filament density recovered to the preoscillation level only when wortmannin was removed and the muscle was stimulated. The data suggest that in vivo thick filament reassembly after mechanical perturbation is facilitated by the cyclic MLC phosphorylation associated with repeated stimulation.

Simple freezing apparatus for resolving rapid metabolic events associated with smooth muscle activation.

A method is described for freezing thin strips of smooth muscle by replacing physiological saline in the muscle chamber with cold organic solvent in <100 ms. Calculations suggest that, with a perfectly stirred boundary at the tissue surface, freezing could occur within approximately 15 ms at the center of a 200-microm-thick piece of tissue by use of acetone coolant at -78.5 degrees C and in approximately half the time with either isopentane at its freezing point (-160 degrees C) or aluminum chilled with liquid nitrogen. Myosin light chain phosphorylation in muscles frozen with cold acetone began to rise approximately 200 ms earlier than force and increased at a much more rapid rate. The difference in onsets of the two processes reflects the delay in arresting phosphorylation plus two lags associated with force generation, attachment of phosphorylated bridges followed by force generating movements of the attached bridges. The much more rapid rise of phosphorylation, once it began, suggests that most of this delay is due to physiological lags and not to slow arrest of metabolism.

Relationship between myosin phosphorylation and contractile capability of canine airway smooth muscle.

To better understand excitation-contraction coupling in smooth muscle, myosin phosphorylation and force-velocity properties of canine tracheal muscle were compared during the rise and early plateau of force in electrically stimulated tetani. Velocity reached a peak of approximately 1.5 times plateau value when force had risen to approximately 45% of its maximum value and then declined progressively. Except early in the tetanus, when phosphorylation rose rapidly, maximum power and phosphorylation had nearly parallel time courses, reaching peaks of 1.2-1.3 times reference at 6-8 s before declining to the plateau level at approximately 12 s. Force, velocity, maximum power, and phosphorylation fell somewhat during the plateau, with the closest correlation between phosphorylation and power. These results suggest that 1) early velocity slowing is not associated with light chain dephosphorylation and 2) maximum power, which we use to signal changes in activation, is closely correlated with the degree of light chain phosphorylation, at least when phosphorylation level is not changing rapidly. Dissociation of these two properties would be expected early in the tetanus if phosphorylation precedes mechanical activity.

Selective restoration of calcium coupling to muscarinic M(3) receptors in contractile cultured airway myocytes.

We previously demonstrated that after several days of serum deprivation about one-sixth of confluent cultured canine tracheal myocytes acquire an elongated, structurally and functionally contractile phenotype. These myocytes demonstrated significant shortening on ACh exposure. To evaluate the mechanism by which these myocytes acquire responsiveness to ACh, we assessed receptor-Ca(2+) coupling using fura 2-AM fluorescence imaging and muscarinic receptor expression using Western analysis. Cells were grown to confluence in 10% fetal bovine serum and then maintained for 7-13 days in serum-free medium. A fraction of serum-deprived cells exhibited reproducible intracellular Ca(2+) mobilization in response to ACh that was uniformly absent from airway myocytes before serum deprivation. The Ca(2+) response to 10(-4) M ACh was ablated by inositol 1,4,5-trisphosphate (IP(3)) receptor blockade using 10(-6) M xestospongin C but not by removal of extracellular Ca(2+). Also, 10(-7) M atropine or 10(-7) M 4-diphenylacetoxy-N-methylpiperidine completely blocked the response to ACh, but intracellular Ca(2+) mobilization was not ablated by 10(-6) M pirenzepine or 10(-6) M methoctramine. In contrast, 10(-5) M bradykinin (BK) was without effect in these ACh-responsive myocytes. Interestingly, myocytes that did not respond to ACh demonstrated robust increases in intracellular Ca(2+) on exposure to 10(-5) M BK that were blocked by removal of extracellular Ca(2+) and were only modestly affected by IP(3) receptor blockade. Serum deprivation increased the abundance of M(3) receptor protein and of BK(2) receptor protein by two- to threefold in whole cell lysates within 2 days of serum deprivation, whereas M(2) receptor protein fell by >75%. An increase in M(3) receptor abundance and restoration of M(3) receptor-mediated Ca(2+) mobilization occur concomitant with reacquisition of a contractile phenotype during prolonged serum deprivation. These data demonstrate plasticity in muscarinic surface receptor expression and function in a subpopulation of airway myocytes that show mutually exclusive physiological and pharmacological diversity with other cells in the same culture.

Macaques but not lemurs co-orient visually with humans.

The ability to engage in visual co-orientation (VCO) is suggested by naturalistic observations of primates, but experimental comparisons of different species are lacking. This study compared the propensity of lemurs (Eulemur macaco) and macaques (Macaca arctoides) to engage in VCO, defined as turning to look in the same direction as another individual whose focus of attention changes. The macaques consistently showed VCO whereas the lemurs showed no such response. This species difference has implications for understanding the evolutionary origins of more advanced abilities that build upon VCO, such as shared visual attention and theory of mind.

Divergent differentiation paths in airway smooth muscle culture: induction of functionally contractile myocytes.

We tested the hypothesis that prolonged serum deprivation would allow a subset of cultured airway myocytes to reacquire the abundant contractile protein content, marked shortening capacity, and elongated morphology characteristic of contractile cells within intact tissue. Passage 1 or 2 canine tracheal smooth muscle (SM) cells were grown to confluence, then serum deprived for up to 19 days. During serum deprivation, two differentiation pathways emerged. One-sixth of the cells developed an elongated morphology and aligned into bundles. Elongated myocytes contained cables of contractile myofilaments, dense bodies, gap junctions, and membrane caveoli, ultrastructural features of contractile SM in tissue. These cells immunostained intensely for SM alpha-actin, SM myosin heavy chain (MHC), and SM22 (an SM-specific actin-binding protein), and Western analysis of culture lysates disclosed 1.8 (SM alpha-actin)-, 7.7 (SM MHC)-, and 5.8 (SM22)-fold protein increases during serum deprivation. Immunoreactive M3 muscarinic receptors were present in dense foci distributed throughout elongated, SM MHC-positive myocytes. ACh (10(-3) M) induced a marked shortening (59.7 +/- 14.4% of original length) in 62% of elongated myocytes made semiadherent by gentle proteolytic digestion, and membrane bleb formation (a consequence of contraction) occurred in all stimulated cells that remained adherent and so did not shorten. Cultured airway myocytes that did not elongate during serum deprivation instead became short and flattened, lost immunoreactivity for contractile proteins, lacked the M3 muscarinic-receptor expression pattern seen in elongated cells, and exhibited no contractile response to ACh. Thus we demonstrate that prolonged serum deprivation induces distinct differentiation pathways in confluent cultured tracheal myocytes and that one subpopulation acquires an unequivocally functional contractile phenotype in which structure and function resemble contractile myocytes from intact tissue.

Eosinophils, major basic protein, and polycationic peptides augment bovine airway myocyte Ca2+ mobilization.

Previous studies in vivo or in isolated airway preparations have suggested that eosinophil-derived polycationic proteins enhance airway smooth muscle tone in an epithelium-dependent manner. We assessed the direct effects of activated human eosinophil supernatant, major basic protein (MBP), and polycationic polypeptides on basal and agonist-stimulated intracellular Ca2+ concentrations ([Ca2+]i) in cultured bovine tracheal smooth muscle (TSM) cells. A 1-h incubation of myocytes with activated eosinophil buffer resulted in a doubling of basal [Ca2+]i and increased responsivity to histamine compared with myocytes that were exposed to sham-activated eosinophil buffer. In addition, concentration-dependent acute transient increases and subsequent 1-h sustained elevations of basal [Ca2+]i were observed immediately after addition of MBP and model polycationic proteins. Finally, both peak and plateau [Ca2+]i responses to bradykinin addition were augmented significantly in cultured myocytes that had been exposed to low concentrations of MBP or model polycationic proteins but were inhibited at greater concentrations. This elevated [Ca2+]i to polycationic proteins was manifest in epithelium-denuded bovine TSM strips as concentration-dependent increased basal tone. We conclude that activated eosinophil supernatant, MBP, and other polycationic proteins have a direct effect on both basal and subsequent agonist-elicited Ca2+ mobilization in cultured TSM cells; TSM strips in vitro demonstrated, respectively, augmented and diminished responses to the contractile agonist acetylcholine. It is possible that alteration in myocyte Ca2+ mobilization induced by these substances may influence clinical states of altered airway tone, such as asthma.

Differential effects of cyclosporine A after acute antigen challenge in sensitized cats in vivo and ex vivo.

1. We determined the effect of cyclosporine A (CsA) treatment on mast cell degranulation and lung resistance (R(L)) in vivo, and tracheal smooth muscle (TSM) contraction ex vivo after antigen challenge in sensitized cats. We also determined the direct effects of addition of CsA to the tissue bath on antigen-induced responses of TSM in vitro. 2. Cats (n=10) were sensitized by i.m. injection of Ascaris suum antigen (AA); 5 cats (CsA+) received CsA twice daily for 2 weeks before acute antigen challenge in doses sufficient to suppress interleukin-2 secretion from feline peripheral blood mononuclear cells ex vivo. 3. Lung resistance increased comparably within 10 min of exposure to AA (P<0.03). Histamine content in bronchoalveolar lavage fluid from both groups increased comparably within 30 min of antigen challenge, from undetectable levels to 542+/-74 pg ml(-1) post AA for CsA+ and from 74+/-19 pg ml(-1) at baseline, to 970+/-180 pg ml(-1) post AA CsA- (P<0.05; P=NS vs CsA+). 4. In excised TSM, active tension elicited by exposure to AA in vitro was 107+/-38% KCl in the CsA+ group vs 144+/-56% KCl in the CsA- group (P=NS). However, contraction of TSM (n=4) harvested from both groups was abolished or greatly diminished after AA challenge when tissues were pre-incubated with 1 microM CsA in vitro (8+/-8% KCl, P<0.05 vs CsA+ and CsA-). This was associated with inhibited release of 5-hydroxytryptamine into the organ bath fluid of tissues treated with CsA in vitro only. 5. We demonstrated that CsA treatment in vivo does not inhibit the early phase asthmatic response or mast cell degranulation following antigen challenge in sensitized cats. Additionally, the effects of CsA on mast cell function ex vivo do not reflect lack of effects of CsA on mast cell function in vivo in this animal model of atopic asthma.

EP1 receptor blockade attenuates both spontaneous tone and PGE2-elicited contraction in guinea pig trachealis.

We assessed the effect of prostaglandin (PG) E2 on tone of guinea pig tracheal smooth muscle (TSM) strips in vitro. In the presence of spontaneous tone [ST; i.e., no indomethacin (-Indo)], exogenous PGE2 caused a significant relaxation of ST at concentrations > 10(-6) M [to -127 +/- 40.8% electric field stimulation (EFS); P = 0.001 vs. baseline ST] and at concentrations < 10(-6) M caused a variable change in contractile force (51.6 +/- 29.6% EFS; P = NS vs. baseline ST). In the absence of ST (i.e., +Indo) 10(-10) to 10(-7) M PGE2 elicited contraction of TSM to 126.3 +/- 10.5% EFS (P = 0.001 vs. baseline) and no relaxation. Addition of prostanoid EP1 receptor antagonist (either AH-6809 or SC-19220) to Indo-treated TSM caused a substantial rightward shift and attenuation of contraction in response to PGE2 (55.9 +/- 16.8% EFS for 10(-5) MAH-6809; P = 0.007 vs. +Indo alone, and 80.5 +/- 12.7% EFS for 10(-5) M SC-19220, P = 0.03 vs. +Indo alone). We further assessed the effect of EP1 and EP4 receptor antagonism on the ST of guinea pig TSM strips. Concentration-response curves to the EP1 receptor-specific antagonists AH-6809 or SC-19220 and the EP4 receptor-specific antagonist AH-23848B were generated (10(-7) to 10(-5) M); AH-6809 caused relaxation of ST to 11.4 +/- 2.9% ST (P = 0.001 vs. initial ST) and SC-19220 caused relaxation to 31.0 +/- 12.7% ST (P = 0.02 vs. initial ST). However, AH-23848B did not significantly affect ST (to 60.9 +/- 7.7% ST; P = 0.07 vs. initial ST). Furthermore, AH-6809 specifically inhibited contraction elicited by the EP1 receptor agonist Iloprost but had no effect on contraction elicited by the EP3 receptor agonist Enprostil. We demonstrate that in the presence of ST (-Indo), exogenous PGE2 elicits a biphasic response in guinea pig TSM in which relaxation predominates. In the absence of ST (+Indo), exogenous PGE2 elicits contraction of guinea pig TSM strips that is inhibited by EP1 receptor-specific antagonism. Spontaneous tone of guinea pig TSM strips also is inhibited by EP1 receptor antagonism. Our data suggest that both PGE2-elicited contraction and ST of guinea pig TSM are mediated through activation of EP1 prostanoid receptors.

Passive sensitization of human airways induces myogenic contractile responses in vitro.

We assessed effects of passive sensitization on human bronchial smooth muscle (BSM) response to mechanical stretching in vitro. Bronchial rings were sham (control) or passively sensitized overnight by using sera from donors demonstrating sensitivity to Dermatophagoides farinae and having immunoglobulin E (IgE) concentrations of 2,600 +/- 200 U/ml. Tissues were fixed isometrically to force transducers to measure responses to electrical field stimulation (EFS) and quick stretch (QS). The myogenic response to QS was normalized to the maximal response to EFS (%EFS). The myogenic response of sensitized BSM was 47.9 +/- 10.9 %EFS to a QS of approximately 6.5% optimal length (Lo); sham-sensitized tissues had a myogenic response of 13.5 +/- 6.4 %EFS (P = 0.012 vs. passively sensitized). A QS of approximately 13% Lo in sensitized BSM caused a response of 82.8 +/- 20.9 %EFS; sham-sensitized tissues developed a response of 38.2 +/- 17.3 %EFS (P = 0.004). BSM incubated with serum from nonallergic donors did not demonstrate increased QS response (4.6 +/- 1.4 %EFS, P = not significant vs. tissue exposed to atopic sera). However, tissues incubated in sera from nonatopic donors supplemented with hapten-specific chimeric IgE (JW8) demonstrated augmented myogenic response to QS of approximately 6.5% Lo (21.9 +/- 6.2 %EFS, P = 0. 027 vs. nonatopic sera alone). We demonstrate that passive sensitization of human BSM preparations causes induction and augmentation of myogenic contractions to QS; this hyperresponsiveness corresponds to the IgE concentration in sensitizing sera.

Muscarinic hyperresponsiveness of antigen-sensitized feline airway smooth muscle in vitro.

OBJECTIVE: To determine the effect of in vivo antigen sensitization (Ascaris suum) of cats on tracheal smooth muscle (TSM) and bronchial smooth muscle (BSM) muscarinic reactivity in vitro. ANIMALS: Healthy domestic shorthair cats of either sex. PROCEDURE: Cats were sensitized and were long-term antigen (or sham) challenge exposed for 6 weeks by aerosolization with soluble Ascaris suum. Tracheal and BSM preparations were obtained and stimulated in vitro by electrical field stimulation (EFS), acetylcholine (ACh, a muscarinic agonist), and physostigmine (an AChase inhibitor). Responses were compared with responses of comparable tissues from sham antigen challenge-exposed cats. RESULTS: Tracheal and BSM from sensitized, compared with sham-sensitized (control), cats had greater isometric contraction (expressed as percentage of the response observed for isotonic, 63 mM KCl-elicited contraction [% KCl]) in response to endogenous (EFS) and exogenous muscarinic receptor activation (ACh). Contractions in response to EFS by TSM from control cats were 74% KCl vs 97% KCl for antigen-sensitized TSM (P < 0.04). Muscarinic responses were augmented comparably by in vivo sensitization; TSM from control cats contracted to 190% KCl vs 230% KCl (P < 0.03) for TSM from immune-sensitized cats. Physostigmine augmented responses of all tissues to ACh so that TSM from control (290% KCl) and antigen-sensitized (257% KCl) cats were similar. Responses of BSM from antigen-sensitized cats had similar augmentation of contractile response to EFS and ACh. CONCLUSIONS: Long-term in vivo antigen sensitization increases numbers of muscarinic receptors on airway smooth muscle or decreases the availability or activity of AChase in cats. CLINICAL RELEVANCE: Modulation of muscarinic receptors may be useful for treatment of asthmatic cats with in vivo airway hyperreactivity.

Conservation of bronchiolar wall area during constriction and dilation of human airways.

We assessed the effect of smooth muscle contraction and relaxation on airway lumen subtended by the internal perimeter (Ai) and total cross-sectional area (Ao) of human bronchial explants in the absence of the potential lung tethering forces of alveolar tissue to test the hypothesis that bronchoconstriction results in a comparable change of Ai and Ao. Luminal area (i.e., Ai) and Ao were measured by using computerized videomicrometry, and bronchial wall area was calculated accordingly. Images on videotape were captured; areas were outlined, and data were expressed as internal pixel number by using imaging software. Bronchial rings were dissected in 1.0- to 1.5-mm sections from macroscopically unaffected areas of lungs from patients undergoing resection for carcinoma, placed in microplate wells containing buffered saline, and allowed to equilibrate for 1 h. Baseline, Ao [5.21 +/- 0.354 (SE) mm2], and Ai (0.604 +/- 0.057 mm2) were measured before contraction of the airway smooth muscle (ASM) with carbachol. Mean Ai narrowed by 0.257 +/- 0.052 mm2 in response to 10 microM carbachol (P = 0.001 vs. baseline). Similarly, Ao narrowed by 0.272 +/- 0.110 mm2 in response to carbachol (P = 0.038 vs. baseline; P = 0.849 vs. change in Ai). Similar parallel changes in cross-sectional area for Ai and Ao were observed for relaxation of ASM from inherent tone of other bronchial rings in response to 10 microM isoproterenol. We demonstrate a unique characteristic of human ASM; i.e., both luminal and total cross-sectional area of human airways change similarly on contraction and relaxation in vitro, resulting in a conservation of bronchiolar wall area with bronchoconstriction and dilation.

Pointing, withholding information, and deception in capuchin monkeys (Cebus apella).

Brown capuchin monkeys, like 4-year-old children and human-socialized chimpanzees, showed communicative and deceptive pointing in experiments in which they benefited by indicating, accurately or falsely, the location of hidden food. All 3 capuchin monkeys tested (13, 19, and 26 years old) pointed communicatively in the presence of a cooperative trainer. One human-reared monkey pointed without any training and frequently gazed at her human respondent; as with apes, extensive exposure to humans may promote some human-like responses in monkeys. Another capuchin withheld pointing when beneficial, whereas the 3rd learned to obtain the hidden food by pointing deceptively in the presence of a competitive trainer. Such deceptive pointing by one monkey and withholding of information by another suggest that primates' deceptive pointing in an experimental situation is explainable in terms of response inhibition and conditional discrimination learning.

Differential tachykinin receptor subtype activation in capsaicin and KCl contractions of guinea pig trachealis.

We assessed the role of endogenously secreted tachykinins in mediating contraction caused by potassium chloride (KCl) in guinea pig tracheal smooth muscle (TSM) strips in vitro. Maximal isometric contraction was elicited with approximately 45 mM KCl and was 196 +/- 8% of the response to electrical field stimulation (% EFS) in the same tissues. Muscarinic receptor blockade with atropine modestly attenuated this contraction caused by KCl to 175 +/- 9 %EFS (P < 0.05), and treatment with a selective neurokinin subtype 1 (NK1) receptor antagonist, LY-297911, caused even greater inhibition of KCl-elicited contraction to 124 +/- 8 %EFS (P < 0.001). By contrast, SR-48968, a selective NK2 antagonist, had no effect on contraction caused by KCl (183 +/- 9 %EFS; P = NS vs. KCl alone). However, given together at the same concentration, SR-48968 augmented the inhibition of contraction caused by LY-297911 to 93 +/- 15 %EFS (P < 0.05 vs. LY-297911 alone). In contrast to the effect on KCl-induced contraction, LY-297911 caused only moderate inhibition of the contraction caused by capsaicin to 81 +/- 13 %EFS (P < 0.05 vs. control, 114 +/- 15 %EFS), whereas SR-48968 caused substantial attenuation of contraction caused by capsaicin to 23 +/- 5 %EFS (P < 0.005 vs. LY-297911). We demonstrate that a significant portion of the contraction caused by KCl, in addition to capsaicin, is elicited in guinea pig TSM through neurokinin secretion. However, NK1 receptors predominantly mediate contraction caused by KCl, and NK2 receptors predominantly mediate contraction elicited by capsaicin in guinea pig airway smooth muscle.