Constricted Type Research Articles

Simulation Studies of Domain Wall Width Changes in Various Nanoconstriction Shapes

In magnetic nanoconstriction systems, the magnetic calculations on the domain wall width (DWW) were carried out using the micromagnetics simulation based on Landau-Lifschitz-Gilbert equation. The results for the normal constriction type and the newly designed round constriction type were compared. DWW changes in various nanoconstriction sizes and shapes were studied while domain walls were constricted at the nanoconstriction. Calculations showed that the domain wall (DW) configurations in the normal constriction type were unstable depending on the initial state, whereas the domain wall configurations were stable in the round constriction type independent of the initial state. The stable DW configuration in the round constriction type seems to be due to the same spatial gradient across the structure

A boundary-integral study of a drop squeezing through interparticle constrictions

A three-dimensional boundary-integral algorithm is developed to study the squeezing of a deformable drop through a tight constriction formed by several solid particles rigidly held in space. The drop is freely suspended and driven by a flow that is uniform away from the solid obstacles. Particular emphasis is on the trapping mechanism and flow conditions close to critical, when the drop squeezes with high resistance. The problem is a close prototype of drop–solid interactions for emulsion flow through a granular material; such interactions are much more lubrication-sensitive than drop–drop interactions and require advanced numerical tools to succeed. The algorithm is based on the Hebeker representation for the solid–particle contribution, leading to a well-behaved system of second-kind integral equations, combined with novel regularization techniques for singular and near-singular boundary integrals; high-order near-singularity subtraction for the solid-to-drop double-layer contribution is the most crucial element. Simulations are performed for drop squeezing between (i) two close spheres, (ii) two parallel spheroidal disks, and (iii) three close spheres forming an equilateral triangle (including the case of close solid–solid contact). The drop non-deformed diameter is from two to several times larger than the inner constriction diameter and, in some simulations, the drop decelerates $10^3$ – $10^4$ times in the throat before being able to pass through. The effects of the constriction type, capillary number, and viscosity ratio on the drop velocity in the throat, exit time, and drop–solid spacing (of the order of 1% of the particle size) are explored in detail; critical capillary numbers (below which trapping occurs) are accurately determined. Even for a substantially supercritical capillary number, the drop has to nearly coat solid particles to be able to pass through a tight constriction. The ability of the algorithm to simulate both supercritical and subcritical conditions (when the drop is trapped, with a small but non-zero drop–solid spacing) is vital for future applications to large-scale simulations of emulsion flow through granular media.

Vigabatrin and Visual Field Defects in Pediatric Epilepsy Patients

We studied the prevalence, type and severity of vigabatrin (VGB)-attributed visual field defects (VFDs), and used these data to assess the associated risk factors in pediatric patients. Medical records were retrospectively reviewed for 67 pediatric patients who received VGB alone or in combination with other antiepileptic drugs, and who had undergone visual field examinations using a Humphrey visual field analyzer. Of the 67 patients, 15 had VGB-attributed VFDs: 13 had nasal arcuate type, 1 had nasal and temporal constricted type and 1 had nasal constricted type. In terms of severity, 7 patients had Grade I VGB-attributed VFDs, 5 had Grade II, 2 had Grade III, and 1 had Grade IV. Although there were no significant differences between the VFD and non-VFD groups with regards to all tested parameters, there were no cases of VGB-attributed VFDs in patients with total treatment durations <2 yr and cumulative doses <10 g/kg. In conclusion, the prevalence of VGB-attributed VFDs in VGB-treated pediatric epilepsy patients was 22%. The high frequency of VGB-attributed VFDs indicates that physicians should inform all patients of this risk prior to VGB treatment and perform periodic visual field examinations.

Mast cell mediators in citric acid-induced airway constriction of guinea pigs

We demonstrated previously that mast cells play an important role in citric acid (CA)-induced airway constriction. In this study, we further investigated the underlying mediator(s) for this type of airway constriction. At first, to examine effects caused by blocking agents, 67 young Hartley guinea pigs were divided into 7 groups: saline + CA; methysergide (serotonin receptor antagonist) + CA; MK-886 (leukotriene synthesis inhibitor) + CA; mepyramine (histamine H 1 receptor antagonist) + CA; indomethacin (cyclooxygenase inhibitor) + CA; cromolyn sodium (mast cell stabilizer) + CA; and compound 48/80 (mast cell degranulating agent) + CA. Then, we tested whether leukotriene C 4 (LTC 4) or histamine enhances CA-induced airway constriction in compound 48/80-pretreated guinea pigs. We measured dynamic respiratory compliance (Crs) and forced expiratory volume in 0.1 s (FEV 0.1) during either baseline or recovery period. In addition, we detected histamine level, an index of pulmonary mast cell degranulation, in bronchoalveolar lavage (BAL) samples. Citric acid aerosol inhalation caused decreases in Crs and FEV 0.1, indicating airway constriction in the control group. This airway constriction was significantly attenuated by MK-886, mepyramine, cromolyn sodium, and compound 48/80, but not by either methysergide or indomethacin. Both LTC 4 and histamine infusion significantly increased the magnitude of CA-induced airway constriction in compound 48/80-pretreated guinea pigs. Citric acid inhalation caused significant increase in histamine level in the BAL sample, which was significantly suppressed by compound 48/80. These results suggest that leukotrienes and histamine originating from mast cells play an important role in CA inhalation-induced noncholinergic airway constriction.

Underplating-related finite-strain patterns in the Gran Paradiso massif, Western Alps, Italy: heterogeneous ductile strain superimposed on a nappe stack

A finite-strain study in the central and northern Gran Paradiso massif of the Italian Western Alps has been carried out to elucidate whether ductile strain shows a relationship to nappe contacts and to shed light on the nature of the subhorizontal foliation typical of the gneiss nappes in the Alps. The R f /φ and Fry methods were used on feldspar porphyroclasts from 98 samples of the Gran Paradiso unit (upper tectonic unit of the Gran Paradiso massif) and 12 samples from the underlying Erfaulet unit (lower unit of the Gran Paradiso massif). Microstructures and thermobarometric data show that feldspar ductility at temperatures higher than c . 450 °C occurred only during high-pressure metamorphism, when the rocks were underplated beneath the overriding Adriatic plate. Therefore, the finite-strain data can be related to high-pressure metamorphism in the Alpine subduction zone. The augen gneiss was heterogeneously deformed and axial ratios of the strain ellipse in xz sections range from 2.1 to 69.8. The long axes of the finite-strain ellipsoids trend west–WNW and the short axes are subvertical, associated with a subhorizontal foliation. The strain magnitudes do not increase towards the nappe contacts. The data indicate flattening strain type in the Gran Paradiso unit and constrictional strain type in the Erfaulet unit and prove deviations from simple shear. We conclude that nappe stacking occurred early during subduction probably by brittle imbrication and that ductile strain was superimposed on and modified the nappe structure during high-pressure underplating in the Alpine subduction zone. The accumulation of ductile strain during underplating was not by simple shear and involved a component of vertical shortening, which caused the subhorizontal foliation in the Gran Paradiso massif.

Lymphocytic inflammation in childhood bronchiolitis obliterans.

Childhood bronchiolitis obliterans (CBO) is an infrequent, severe disorder characterized by persistent obstructive respiratory symptoms after an acute episode of bronchiolitis. The viral etiology is most common, and adenovirus is the most frequently identified causative agent. Pathologically, the disease is characterized as constrictive type BO, with variable degrees of chronic inflammation and fibrosis in the bronchioles. The nature of the cellular infiltrate is largely unknown, and its characterization may provide better understanding of the disease and offer clues for therapy. Therefore, the aim of the present study was to characterize the inflammatory infiltrate in the bronchioles of 23 open lung biopsies of children with CBO and to compare this to the infiltrate in histologically normal airways. Our results show that CD3+ T cells were the most frequent cell type observed in CBO, with a predominance of the CD8+ T-cell subtype. When compared to the control group, there was a larger number of CD8+, CD4+, CD20+, granzyme B+, and perforin+ lymphocytes in the CBO group. Further studies are needed to address the role of different cell types in the development of CBO.

Performance characteristics of forced constricted type plasma jet generator with divergent nozzle anode for processing

In order to increase a jet power and an operating duration time of the forced constricted type plasma jet generator developed by authors, newly designed divergent nozzle anodes were developed. The diameter of nozzle anode changed in two steps, i.e. the inner diameter increased stepwise from the inlet towards the exit. The effects of the nozzle configuration on the characteristics of the arc and plasma jet were studied experimentally. The anode spot always attached at the taper section between the inlet region and the exit region. The arc voltage decreased by 3.2–9.1 V compared with that of a cylindrical nozzle anode, but a stable operating arc current expand up to 200 A. A stable and high power plasma jet was maintained over a long time at 200 A in arc current. The most suitable length of the inlet region was 2 mm, when the diameter of the inlet and exit regions was 6 and 8 mm, respectively.

Low friction coatings prepared by high performance type spray gun

To produce low friction coatings to be used as overlays for automobile journal bearings and to perform depositions with high rate, we prepared composite coatings of Ag and graphite by using the new-type spray gun based on the forced constricted type plasma jet generator (i.e. the high performance type spray gun). Characterization of the films showed the graphite phase dispersed into the Ag matrix, analyzed by optical microscopy, electron probe microanalysis and X-ray diffraction. The coefficient of friction of the Ag/graphite overlay measured using ball-on-disc tribometer was reduced by a factor of five compared with that of bronze substrate and by factor of two compared with that of the Ag/graphite overlay prepared by ECR sputtering.

Histology of childhood bronchiolitis obliterans.

Childhood bronchiolitis obliterans (CBO) is an uncommon disease characterized by persistent signs and symptoms of obstructive respiratory disease after an acute bronchiolar injury. It is considered to be a complication of viral infection, most often of adenovirus, and is usually classified as a constrictive-type bronchiolitis obliterans (BO). Few reports have described its histology. We present the histopathological features of 34 pediatric patients with a diagnosis of BO, comprising 30 open lung biopsies (OLB), 2 lobectomies, and 2 autopsies. Quantitative analysis was performed on the OLB to better characterize the morphological changes observed in these lungs. Of 37 patients, 25 were male and 9 were female, ranging from 7 months to 15 years of age. Airway diameter in terminal bronchioles varied from 50-600 microm. Ninety-seven percent of the CBO were of constrictive type, with variable degrees of airway obstruction. Chronic inflammation in the bronchioles was mild in 63% of the patients. Aggregates of foamy macrophages, mucostasis, and bronchiectasis appeared in, respectively, 93%, 40%, and 30% of the biopsies. There was more hyperinflation than atelectasis (40.1% and 24.3%, respectively). Lobectomies and autopsies showed more severe bronchiolar obliteration, associated with bronchiectasis. The results show that CBO is characterized histologically mainly by a constrictive pattern, with variable degrees of inflammation and airway obliteration. Secondary signs of airway obstruction are invariably present. Mild histological changes may predominate and should be carefully evaluated by the pathologist.

Obstruction Identification in a Compliant Tube with Application to Airway Passages

Using the acoustic input impedance, an appropriate theoretical technique for identifying constrictions in a tube with wall inertance and elastance being considered is developed. Although the technique could work for various types of tubes, it is applied to identifying occlusion in an upper airway passage. The frequency spectrum of the input impedance is examined for three types of constrictions, namely localized, uniform and gradual models. The result demonstrates that the input impedance resonant frequencies can map the location, severity and degree of the constriction.

Domain walls in ferromagnetic nanoconstriction

180° domain walls in ferromagnetic nanoconstrictions are investigated by classical atomic Monte Carlo simulations. Two types of constrictions are considered; one is a uniform circular cylinder (isthmus), the other is a double-truncated cone (hour glass). The wall width is determined by the effective length of the constriction, which may be as little as a nanometer. The wall can have a Néel-like configuration for constrictions much narrower than the normal wall width, but there is a crossover region with vortex-type walls before reaching a Bloch-type wall at larger diameters. In very narrow constrictions, effects of the atomic-scale structure become evident as the domain-wall structure depends on the number of atoms in the cross section. The simulations confirm the prospect of creating very narrow domain walls in a nanoconstricted soft magnetic material, and they indicate the possibility of spontaneous thermal fluctuations between different magnetic modes in walls smaller than about 10 nm.

Integrated synthesis of AMTEC electrode by using controlled thermal plasma processing

Thermoelectric materials (β″-alumina) for the alkali metal thermoelectric converter (AMTEC) have been synthesized with the use of a thermal plasma reactor based on the forced constricted type plasma jet generator. It is reconfirmed that the powder mixing ratio (i.e. the ratio between α-Al 2O 3, Na 2CO 3 and MgO), jet power and substrate position, strongly affect the synthesis of β″-alumina. Besides these, the synthesis of β″-alumina is also enhanced in the high-temperature region by oxygen injection. Those dependences are correlated with jet temperature and particle heating. The metal electrode of molybdenum is also prepared by spraying Mo powders. Porosity of the prepared films could be well controlled by varying the pressure.

Hyperpnea-induced production of TBHP-initiated chemiluminescence in guinea pigs

Antioxidants attenuate hyperpnea-induced airway constriction. It was hypothesized that this type of airway constriction is closely related to reactive oxygen species (ROS). However, there is no direct evidence of an increase in ROS during or right after the course of hyperpnea. To detect ROS production induced by hyperpnea, forty one guinea pigs were divided into four groups: control; control with 95% O 2–5% CO 2; hyperpnea with 95% air–5% CO 2; and hyperpnea with 95% O 2–5% CO 2. Three minutes following hyperpnea or at the equivalent time, we obtained bronchoalveolar lavage (BAL) and measured its chemiluminescence (CL) counts. In addition, hyperpnea with 95% O 2–5% CO 2 gas mixture was carried out and BAL was collected 3 minutes after the hyperpnea in an additional forty animals. We measured CL counts in BAL samples before and after the treatments of the following ROS scavenger(s) or saline in vitro: control (saline); superoxide dismutase (SOD); catalase; dimethylthiourea (DMTU); and SOD+catalase+DMTU. Hyperpnea with 95% O 2–5% CO 2, but not with 95% air–5% CO 2, gas mixture induced significant increase in t-butyl hydroperoxide-initiated CL counts, which were inhibited by DMTU, catalase, or SOD in vitro. Our data suggest that hyperpnea with a 95% O 2–5% CO 2, but not with 95% air–5% CO 2, gas mixture induced an increase in ROS production.

Cretaceous structural evolution of the Pelagonian crystalline in western Voras Mt (Macedonia, Northern Greece)

The kinematic of the Cretaceous deformation and the relationship between deformation and metamorphism of the Pelagonian crystalline was studied in Voras Mt (northern Greece). The Pelagonian crystalline in this area has been subdivided into a lower, core part, consisting mainly of gneissic rocks and schists and an upper, cover part, consistine of schists and quartzites with marble intercalations. Intensely deformed granitic rocks of Upper Paleozoic age intrude the Pelagonian crystalline basement. An S j foliation is the oldest fabric recognized in the Pelagonian crystalline. Sj is mainly defined by syn-Sjgarnet(Gr1), biotite(Btj), white mica (Wnij), chloritoid, kyanite and plagioclase in the metapelitic rocks and green amphibole, epidote, plagioclase, and biotiteiBtj) in the amphibolite. Garnet grows also in some cases post-kinematically. Ilmenite and tourmaline are often found in the pelitic rocks as well. S is overprinted by an S2 foliation that developed as a crenulation cleavage. In most places, however, S2 has destroyed all earlier fabrics and a single S2 fabric is present related to, isoclinal or sheath folds intrafolial in places. S2 in the metapelitic rocks is characterized by the syn-S2 development of chlorite, white mica(Wm2) and plagioclase. In the amphibolite S2 is mainly defined by the syn-kinematic development of actinolite, plagioclase, biotite(Bt2), white mica(Wm2) and chlorite. During D2 garnet(Gr1) and biotiteiBtj) are partially replaced by chlorite, while green amphibole is replaced by actinolite and chlorite. Chloritoid remains generally stable along the S2-planes but in some places transforms to chlorite and sericite. Furthermore, D2 was locally followed by a static post-kinematic annealing indicated by polygonal quartz microfabrics with equilibrated grain boundaries and triple points. The overall orientation of S2 is dome shaped with a gentle SW-ward and NE-ward dip in the southwestern and northeastern flanks of the dome respectively. Syn-S2 minerals defined a very well exposed NW-SE trending stretching lineation. Kinematic indicators show a main top to the SE sense of movement. An S3 crenulation cleavage associated with asymmetric NW-SE trending folds is also present in most parts of the core and cover rocks, possibly, related to a constrictional type of deformation. A well developed, S4 shear band cleavage is mainly present in the upper parts of the metamorphic dome and formed under cooler conditions. S4 shear bands are associated with a NW-SE developed stretching lineation defined by elongated and dynamically recrystallized quartz grains and a preferred orientation of white mica and chlorite. Along the S4 shear bands a transformation of garnet, biotite, chloritoid and amphibole into chlorite is always observed. S4 shear bands indicate a main top to the SE sense of movement. The P-T metamorphic conditions were derived from textural equilibria and mineral assemblages, as well as from the spatial distribution of the metamorphic minerals. Syn-Dj metamorphism reached the conditions of the boundaries between greenschist and amphibolite facies. Syn-D2 retrogression took place under greenschist facie conditions. K/Ar radiometric datings on coarse-grained syn-St and younger fine-grained syn-S2 micas define an Early Cretaceous cooling age ('135Ma) for the older event and a Mid- to Late Cretaceous age ('90-80Ma) for the second event. A white mica age of ca. 65Ma correlates with S4 shear band clevage. Furthermore, the intrusion age of a granitic body into the Pelagonian crystalline is dated using the Pb/Pb single zircon evaporation method. The estimated intrusion age of 300±3Ma suggests that the Pelagonian crystalline was affected by a pre-kinematic magmatic activity relative to its Cretaceous deformation.

Thermal plasma processing — syntheses of diamond and β″-alumina

Thermal plasma processing using a plasma jet with high speed and high heat capacity under reduced pressure (≦100 torr) is one of the most promising methods for synthesizing new materials. We have newly developed a thermal plasma reactor composed of a forced constricted type plasma jet generator with a feed ring, and confirmed that this reactor generates stable plasma jets with a high heat capacity under various operating conditions. In this paper, to realize the large area deposition at a high rate, synthesis of diamond films from gas mixtures of CH 4 and H 2 is studied. Synthesis of β″-alumina, thermoelectric materials for the alkali metal thermoelectric converter (AMTEC), from powder mixtures is also discussed.

The significance of late developmental crowding to early treatment planning for incisor crowding

Incisor crowding has traditionally been attributed to discrepancies in either tooth-jaw size or interarch tooth-size ratios. Such concepts have led orthodontists to develop mixed and permanent dentition space and interarch tooth-size analyses to assist in the diagnosis of crowded dentitions. Treatment plans have emphasized the removal of 4 premolars in an attempt to stabilize the dentition. Although individuals with large teeth may tend to have more incisor crowding, several factors other than tooth size may contribute to incisor crowding, for example, altered resting or functional activity in the facial and masticatory muscles. Thus, changes in occlusion, incisor crowding-spacing, lower anterior face height, and mandibular and maxillary retrognathism or prognathism have all been induced in primates through the application of a single chronically acting, environmental impact, such as either altered tongue posture or oral respiration.1-4 In addition, similar changes have been shown in human beings that were partially reversible after removal of the environmental impact.5,6 Thus, adverse neuromuscular changes, such as chronic mouth open breathing, have been associated with narrowing of both arches and lingual inclination of the incisor teeth and crowded dentitions.1,7-10 These dentoalveolar and skeletal changes were partially or fully reversible without orthodontic therapy after removal of the chronic input8,10 It follows that judicious orthodontic expansion procedures might be warranted to assist recovery in such cases after removal of the neuromuscular insult. We are indebted to the University of Washington for their documentation of late developmental crowding up to age 40 in orthodontically untreated as well as treated individuals. Study of untreated individuals at the University of Toronto shows that this phenomenon continues to at least age 70. Such crowding seen during the teen and adult years cannot be called tooth-jaw size discrepancy and must be neuromuscular in nature. Strong evidence supports the view that many of the crowdings we see during the mixed dentition are also neuromuscular or developmental. In a previous study9 of the relationship between mandibular incisor crowding and nasal mucosal swelling, cephalometric and dental cast variables from 30 male and 20 female children (8 to 13 years old) with chronic nasal mucosal swelling were compared with matched controls. These controls were orthodontically untreated and had no history of airway obstruction. The nasal mucosal swelling was confirmed with active posterior rhinomanometry and a headout volume-displacement plethysmograph. The subjects with nasal mucosal swelling had significantly (P < .001) more mandibular incisor crowding aDepartment of Orthodontics, University of Toronto. Reprint requests to: Donald G. Woodside, CM, DDS, MSc(D), PhD(hc), Department of Orthodontics, University of Orthodontics, 124 Edward Street, Toronto, Ontario, Canada M5G 1G6. Copyright © 2000 by the American Association of Orthodontists. 0889-5406/2000/$12.00 + 0 8/1/106117 doi.10.1067/mod.2000.106117 The significance of late developmental crowding to early treatment planning for incisor crowding

Pressure Transients Across Constrictions

The modeling of pressure transient across constrictions is achieved by using a one-dimensional, isothermal, noncompositional, single-phase representation of the Eulerian model. A TVD scheme was used to solve the ensuing nonhomogeneous hyperbolic set of first-order quasi-linear partial differential equations. Three types of constrictions were modeled and in each case the behavior of the transient was analyzed. This analysis was used to interpret the pressure response at the inlet resulting from the reflection of the transient at the constrictions. The comparisons between the predicted and inputted data are very good, suggesting that the technique has much promise. [S0195-0738(00)00301-0]

Fgf8 and Gbx2 induction concomitant with Otx2 repression is correlated with midbrain-hindbrain fate of caudal prosencephalon.

Chick/quail transplantation experiments were performed to analyse possible factors involved in the regionalisation of the midbrain-hindbrain domain. The caudal prosomeres, expressing Otx2, were transplanted at stage HH10 into rostrocaudal levels of the midbrain-hindbrain domain, either straddling the intra-metencephalic constriction (type 1 grafts), or at rostral and medial levels of pro-rhombomere A1 (type 2 and 3 grafts, respectively); thus, in all situations, one border of the graft was in contact with the host Gbx2- and Fgf8-expressing domains. The area containing the graft, recognised by QCPN immunohistochemistry, was first analysed 48 hours after transplantation for Otx2, Gbx2, En2 and Fgf8. Although in all three situations, a large part of the graft maintained Otx2 expression, another part became Otx2 negative and was induced to express Gbx2 and Fgf8. These inductive events occurred exclusively at the interface between the Otx2-positive transplanted domain and the ipsilateral host Gbx2-positive rhombomere 1, creating a new Otx2-Gbx2 boundary within the grafted territory. In type 1 and 2 grafts, the induced Fgf8 domain is in continuity with the host Fgf8 isthmic domain, whereas for type 3 grafts, these two domains are separate. High levels of En2 expression were also induced in the area expressing Gbx2 and Fgf8, and Wnt1 and Pax2 expressions, analysed in type 3 grafts, were induced at the intragraft Otx2-Gbx2 new boundary. Moreover, at later embryonic stages, the graft developed meso-isthmo-cerebellar structures. Thus, gene expressions induced in the grafted prosencephalon not only mimicked the pattern observed in the normal midbrain-hindbrain domain, but is followed by midbrain-hindbrain cytodifferentiation, indicating that not only Fgf8 but also confrontation of Otx2 and Gbx2 may play an essential role during midbrian-hindbrain regionalisation.

Synthesis of β′′-Alumina from Powder Mixture Using Thermal Plasma Processing

With the use of a thermal plasma reactor based on the forced constricted type plasma jet generator, the synthesis of thermoelectric materials (β′′-alumina) for the alkali metal thermoelectric converter (AMTEC) has been studied. Under not only atmospheric pressure but also low pressure, thin films of β′′-alumina are successfully synthesized for the first time from powder mixtures of α-Al2O3, Na2CO3 and MgO. The powder mixing ratio, jet power and substrate position strongly affect the synthesis of β′′-alumina, which is found to be correlated with jet temperature.

Roles of oxygen radicals and elastase in citric acid-induced airway constriction of guinea-pigs.

Antioxidants attenuate noncholinergic airway constriction. To further investigate the relationship between tachykinin-mediated airway constriction and oxygen radicals, we explored citric acid-induced bronchial constriction in 48 young Hartley strain guinea-pigs, divided into six groups: control; citric acid; hexa(sulphobutyl)fullerenes + citric acid; hexa(sulphobutyl)fullerenes + phosphoramidon + citric acid; dimethylthiourea (DMTU) + citric acid; and DMTU + phosphoramidon + citric acid. Hexa(sulphobutyl)fullerenes and DMTU are scavengers of oxygen radicals while phosphoramidon is an inhibitor of the major degradation enzyme for tachykinins. Animals were anaesthetized, paralyzed, and artificially ventilated. Each animal was given 50 breaths of 4 ml saline or citric acid aerosol. We measured dynamic respiratory compliance (Crs), forced expiratory volume in 0.1 (FEV0.1), and maximal expiratory flow at 30% total lung capacity (Vmax30) to evaluate the degree of airway constriction. Citric acid, but not saline, aerosol inhalation caused marked decreases in Crs, FEV0.1 and Vmax30, indicating marked airway constriction. This constriction was significantly attenuated by either hexa(sulphobutyl)fullerenes or by DMTU. In addition, phosphoramidon significantly reversed the attenuating action of hexa(sulphobutyl)fullerenes, but not that of DMTU. Citric acid aerosol inhalation caused increases in both lucigenin- and t-butyl hydroperoxide-initiated chemiluminescence counts, indicating citric acid-induced increase in oxygen radicals and decrease in antioxidants in bronchoalveolar lavage fluid. These alterations were significantly suppressed by either hexa(sulphobutyl)fullerenes or DMTU. An elastase inhibitor eglin-c also significantly attenuated citric acid-induced airway constriction, indicating the contributing role of elastase in this type of constriction. We conclude that both oxygen radicals and elastase play an important role in tachykinin-mediated, citric acid-induced airway constriction.