Oxidative Inactivation of Surfactants

Reactive oxygen species (ROS) may play an important role in the chronic pulmonary morbidity of preterm infants. We therefore studied the magnitude and mechanisms of oxidative inactivation of a natural lung surfactant (NLS) and of two surfactants used for treatment of respiratory distress syndrome, beractant and KL₄ surfactant (KL₄). Incubation with Fenton reagents, 2-4 mM peroxynitrite (ONOO⁻) or 0.5 mM hypochlorous acid (OCl⁻), resulted in an increased minimum surface tension (MST) of all surfactants; the order of effect on MST was beractant > KL₄ > NLS. After incubation with Fenton reagents, NLS contained a higher concentration of conjugated dienes (p < 0.01) but lower concentration of malondialdehyde (p < 0.001) than beractant. Protein carbonyl concentrations after treatment with Fenton reagents were higher in NLS and KL₄ than in beractant (p < 0.05). Surface area cycling for 24 h with 2 mM ONOO⁻ or 0.5 mM OCl⁻ caused both beractant and KL₄ to increase the proportion of light subtypes from 8–10% to 26–29%; with Fenton reagents, there was disappearance of the light subtype and formation of ultraheavy subtype 74–91% with poor MST. Natural and therapeutic surfactants differ markedly in their sensitivity to ROS, which may be important for surfactants in therapeutic use because oxidative inactivation may limit their effect. Oxidation of natural surfactant may result in reduced function and contribute to chronic lung disease. Accepted for publication: 8 January 1999     

The influence of pH on surface properties of lung surfactants

Protein-lipid interactions at air-liquid interfaces are dependent on electrostatic charges, cations, anions, distribution of protons, and surface potential, which are influenced by pH changes. All of these factors may affect lung surfactant function. To verify the pH dependence of surface activity of pulmonary surfactant, we studied the in vitro effects of pH and Ca²⁺ on the surface tension-lowering abilities of various surfactants in an oscillating bubble surfactometer. Surface tension measurements were made of mixtures at known pHs or after the replacement of the subphase fluid of surfactant films with buffered saline at various pH values. At the pH range 4.0–7.0, the average equilibrium surface tension (EST)/minimum surface tension (MST) for natural surfactants human amniotic fluid and natural lung surfactant from rabbit lung lavage was 24/2 mN/m. At the same pH range, Exosurf and phospholipids alone had an EST/MST of 44/25 and 44/12 mN/m, respectively. Survanta (SUR) containing SP-B and SP-C and a phospholipid surfactant (KL₄) containing a leucine/lysine peptide had an EST/MST of 29/5 and 36/3, respectively. Alkalinization of the subphase (pH > 7.4) significantly decreased the surface tension-lowering ability of SUR (P < 0.01) and to a lesser extent that of KL₄ surfactant (P < 0.05), but natural lung surfactants were not significantly affected over a pH range of 3–7.5. These data demonstrate that natural surfactants maintain their optimal surface activities over a broader pH range than do the commercial products because of a lack of SP-A. Careful monitoring of the pH for optimal surface activity is recommended when evaluating surfactant function and the effects of specific inhibitors on this function. Offprint requests to: J. D. Antirkhanian, PhD     

Characterization of Surfactant Subtypes of Beractant and a Synthetic Peptide Containing Surfactant KL4 following Surface Area Cycling and Addition of Fibrinogen

Surfactant is not a homogeneous material and can be separated into subtypes. Subtype conversion is clinically important because it is thought to occur naturally and because surface activity varies depending on the subtype. Fibrinogen, a naturally occurring serum protein, is known to affect this conversion. In this study we studied two surfactants, beractant and KL₄, to examine their subtype characteristics. Surface area cycling, an in vitro method, was used in conjunction with sucrose gradient ultracentrifugation to separate subtypes in both surfactants. Activity, expressed as minimum surface tension of these subtypes, was measured using a pulsating bubble surfactometer. The effect of fibrinogen on subtype conversion and subsequent change in activity was elucidated. Our results indicate that following surface area cycling, beractant and KL₄ have different subtypes and different responses to fibrinogen. Cycling of beractant resulted in two bands, representing a heavy and a light subtype. In the presence of fibrinogen, cycling resulted in two separate heavy subtypes. Cycling of KL₄ surfactant also yielded light and heavy subtypes. However, in the presence of fibrinogen, cycling of KL₄ resulted in ultraheavy subtypes. These ultraheavy subtypes retained minimum surface tension comparable to that of native KL₄ surfactant. We conclude that these two surfactant preparations have different subtype conversions when subjected to surface area cycling and in the presence of fibrinogen. These conversions result in different activities toward lowering surface tension. We speculate that endogenous fibrinogen will also affect these two surfactants differently in vivo and thus affect their clinical effectiveness. Accepted for publication: 14 November 1996     

Byssinosis: Role of Polymer Length on the Effect of Tannin on the Airway β-Adrenergic Receptor

Tannin, isolated from cotton bracts and implicated in the pathogenesis of byssinosis, inhibits isoproterenol and forskolin-stimulated cAMP release from airway cells in part by decreasing cell surface β-adrenergic receptor number and uncoupling the β-adrenergic receptor from its stimulatory G-protein (G_s) and in part by inhibiting adenylyl cyclase activity. We have hypothesized that cotton tannin, because of its long polymer length, interacts with the hydrophobic binding pocket of the β-adrenergic receptor and alters β-adrenergic receptor binding and G_s coupling. In these studies, tannins of three different polymer lengths and molecular masses were isolated from cotton bracts using sequential Amicon ultrafiltration [molecular mass > 10,000 (YM10 retentate), 1,000–10,000 (YM10 filtrate), and 1,000–5,000 Da (YM2 retentate)]. The YM10 retentate (25 μg/ml) decreased chloride secretion (Jnet = 1.11 ± 0.28 (control) to 0.59 ± 0.18 μEq/cm²·h, p < 0.05, n= 6), decreased cell surface β-adrenergic receptor number (18.0 ± 1.8 (control) to 10.6 ± 0.9 fmol/mg protein, p < 0.02, n= 4), and inhibited forskolin-stimulated cAMP release (5,254 ± 1,290 (control) to 2,968 ± 620 pmol/mg protein, p < 0.01, n= 8). In contrast, neither the YM10 filtrate nor the YM2 retentate had any effect on net chloride secretion, β-adrenergic cell surface receptor number, or forskolin-stimulated cAMP release. We conclude that polymer length is essential for the effect of tannin on the β-adrenergic receptor and on adenylyl cyclase. Accepted for publication: 28 June 1998     

Involvement of Tachykinins in Endotoxin-Induced Airway Hyperresponsiveness

Inhaled endotoxin, lipopolysaccharide (LPS), has been shown to result in bronchial hyperresponsiveness (BHR) to endogenous bronchoconstrictive mediators such as histamine. To determine the role of sensory neuropeptides released from bronchopulmonary C-fibers in LPS-induced BHR, 24 guinea pigs were allocated randomly to the following four groups. Animals in Groups I and IV were challenged with intratracheal instillation of 100 μl of saline vehicle, and those in Groups II and III with 1 mg of LPS (Escherichia coli, 0111:B4) in 100 μl of saline. Groups III and IV also received a high dose capsaicin (HDC) treatment to deplete tachykinins from C-fibers 1–2 weeks prior to the experiment. Animals were anesthetized and paralyzed, and total lung resistance (R_L) and compliance (C_dyn) were measured continuously during the experiment. Dose responses of R_L and C_dyn to histamine (0–8 μg/kg, intravenously) and capsaicin (0–1.6 μg/kg, intravenously), a specific C-fiber stimulant, were obtained prior to and at 1, 2, and 3 h following LPS/saline vehicle challenge. At 2 h after LPS, ΔR_L caused by histamine (8 μg/kg) was significantly higher in Group II (1.145%) than that in Group I (280%; p < 0.05); similarly, ΔR_L caused by capsaicin (1.6 μg/kg) was also increased after LPS (Group I, 107%; Group II, 267%; p < 0.05). Although HDC treatment completely abolished the bronchomotor response to capsaicin in both Groups III and IV, it enhanced the LPS-induced BHR to histamine (8 μg/kg; Group III, 1.834%; p < 0.05). In conclusion, these results suggest that the role of tachykinins in LPS-induced BHR may be dependent upon the type and the route of administration of the bronchoactive substance studied. Accepted for publication: 13 December 1996     

Guinea Pig Pulmonary Mechanics: Altered Sensitivity to Carbachol by Cadmium and/or Selenium

Male Hartley guinea pigs (480–610 g) were treated intratracheally as follows: saline, cadmium (Cd, 0.3 mg), selenium (Se, 0.3 or 0.06 mg), or Se (0.06 mg) and Cd (0.3 mg) simultaneously. Selenium and Cd were administered as sodium selenite and cadmium chloride, respectively. Twenty-four h later, dynamic lung compliance (C_dyn) and pulmonary resistance (R_p) were measured before (baseline C_dyn and R_p) and after carbachol administration (0.0001, 0.001, 0.01, and 0.1 μmol/kg, intravenously). Results indicated a significant decrease in baseline C_dyn caused by 0.3 mg of Cd, 0.3 mg or 0.06 mg of Se, and 0.3 mg of Cd with 0.06 mg of Se (p < 0.05). A significant increase in baseline R_p due to 0.3 mg of Se was observed (p < 0.05). Carbachol decreased C_dyn significantly below baseline, evident after lower doses of carbachol, in guinea pigs pretreated with 0.3 mg of Se, whereas a significant improvement in C_dyn was seen after 0.0001 μmol/kg carbachol in the group pretreated with Se and Cd simultaneously (p < 0.05) compared with the respective baseline values of the saline-treated group. Similarly, a significant increase in R_p was observed after carbachol in groups pretreated with 0.3 mg of Cd or Se (p < 0.05). Results also indicated a significant increase in large airway constriction caused by Cd and/or Se (p < 0.05). A leftward shift in the carbachol dose-response curve indicated increased sensitivity to carbachol in Cd- and/or Se-pretreated guinea pigs. Accepted for publication: 14 March 1997     

Airway Eosinophilic Inflammation and Bronchial Hyperresponsiveness after Allergen Inhalation Challenge in Asthma

Allergen exposure in atopic asthmatic patients is associated with recruitment and activation of eosinophils in the airways. Once activated, eosinophils release toxic products, including the eosinophil cationic protein (ECP), able to damage bronchial structures and to increase bronchial hyperresponsiveness. With this background, the present study was designed to evaluate whether ECP levels in bronchoalveolar lavage (BAL) fluid could reflect, better than BAL eosinophil counts, the cellular activation that follows allergen exposure in atopic asthmatics. Twenty-two atopic patients attended the laboratory on two separate days. On the 1st day, they underwent methacholine (MCh) inhalation challenge to detect the degree of nonspecific bronchial hyperresponsiveness. On the 2nd day, they underwent fiberoptic bronchoscopy and BAL, at baseline or 4–6 h after allergen inhalation challenge. In this latter patient group, MCh challenge was repeated 3–5 h after allergen challenge, 1 h before fiberoptic bronchoscopy. The analysis of the mean baseline FEV₁ values and the degree of bronchial reactivity to MCh (MCh Pd₂₀) on the 1st study day did not demonstrate differences between the two patient groups (p > 0.1, each comparison). In addition, in the allergen-challenged group, MCh Pd₂₀ was decreased significantly after allergen challenge (151.4 μg/ml and 67.6 μg/ml, respectively, before and after challenge; p < 0.05). Evaluation of the different BAL cell types demonstrated that the proportions of eosinophils and epithelial cells were increased significantly in the allergen-challenged group compared with the group evaluated at baseline (p < 0.01 and p < 0.05, respectively). Moreover, ECP levels, corrected by the correspondent albumin levels (ECP/Alb), were higher in the allergen-challenged group compared with the group evaluated at baseline (p < 0.05). In addition, although a positive correlation was demonstrated between BAL eosinophil percentages and ECP/Alb values (r= 0.72, p < 0.05) in the group evaluated at baseline, no links were found between these parameters in the allergen-challenged group (p > 0.1). However, in this latter group, a weak positive correlation was demonstrated between eosinophil percentages and ΔMch, i.e., the increased nonspecific bronchial reactivity, which is observed after allergen challenge (r= 0.55; p < 0.05). Thus, in stable asthmatic patients an ongoing activation of eosinophils parallels their migration, but this eosinophilic inflammation is not strictly related to bronchial reactivity to Mch. By contrast, after allergen inhalation challenge, eosinophil recruitment and activation seem to follow different temporal kinetics, and eosinophilic inflammation may be partially associated with the degree of airway hyperresponsiveness. Accepted for publication: 15 September 1997     

Short Term Effects of Bracing on Exercise Performance in Mild Idiopathic Thoracic Scoliosis

In adolescent idiopathic thoracic scoliosis (ITS) working capacity may be reduced during exercise. Despite concern about its usefulness, bracing is still being used in ITS. Thus the effects of bracing on exercise performance need to be examined. We studied six females, ages 12–15 years who had mild ITS (Cobb angle range 20–35°). Pulmonary volumes, maximal voluntary ventilation (MVV), breathing pattern, the lowest (most negative in sign) pleural pressure during sniff maneuver (Ppl_sn), and pleural pressure swings (Ppl_sw) were measured first. Then, Ppl_sw, O₂ uptake (Vo ₂), CO₂ output (Vco ₂), heart rate (HR) at rest and during progressive incremental exercise on a cycling ergometer (10 watts/min) were recorded. The exercise test was performed under control conditions without bracing (C) and after 7 days of bracing with the brace on (B). Dyspnea was measured by a modified Borg scale. At rest, bracing mildly affected total lung capacity and forced vital capacity (p <0.03 for both) but not breathing pattern, Ppl_sn, or Ppl_sw(%Ppl_sn), a measure of respiratory effort. Furthermore, bracing did not consistently affect maximum work rate (WR_max). In both B and C VO₂ was below (<70%) the predicted value, Ve was below (<45%) MVV, and HR reserve was <15 beats/min, indicating some cardiovascular deconditioning. On the other hand, respiratory frequency (Rf) increased more in B than in C (p < 0.03). In addition, Ppl_sw, Ppl_sw(%Ppl_sn), and Ppl_sw(%Pplsn)/Vt, an index of neuroventilatory dissociation (NVD) of the respiratory pump, were greater in B (p < 0.03 for all). At a similar work rate, the Borg rating score was greater with bracing on than off, and the difference (ΔBorg) tended to relate to concurrent changes in Ppl_sw(%Ppl_sn)/Vt (r ²= 0.71; p < 0.07). We conclude that bracing affects respiratory effort, NVD, and dyspnea score during progressive exercise. These effects are consistent with increased lung elastance. Diminished exercise tolerance in patients with mild ITS probably reflects impaired physical fitness but is not affected by bracing. Training programs proposed for this subset of patients to increase peripheral muscle performance might also consider NVD of the respiratory pump. Accepted for publication: 27 January 1997     

Lipid Peroxidation of Lung Surfactant by Bacteria

The epithelium of the lung is lined with extracellular pulmonary surfactant. This is the surface that invading bacteria first come into contact with when they enter the alveoli. As bacteria become established and interact with this layer, various characteristics of surfactant may become altered. We studied free radical production by three bacterial species, group B streptococci, Escherichia coli, and Pseudomonas aeruginosa, as well as the effect of two concentrations of lung surfactant (Curosurf at 0.04 and 0.4 mg/ml) on this production estimated by the nitro blue tetrazolium reduction test. We also measured the lipid peroxidation of surfactant at various incubation times (0–20 h), using a LPO-586 test kit. In addition, the effect of vitamin E as an antioxidant in a concentration of 0.5 μM was determined by the lipid peroxidation test. We found that the nitro blue tetrazolium reduction by the three bacterial species and lipid peroxidation of lung surfactant increased with time. Vitamin E reduced the lipid peroxidation of this surfactant. By measuring bacterial growth at various incubation times we showed that lung surfactant was bactericidal to group B streptococcal and E. coli strains and that P. aeruginosa strains were resistant to surfactant. We conclude that bacteria, probably by their production of reactive oxygen species, cause lipid peroxidation of lung surfactant. Accepted for publication: 5 October 1998     

Bronchial Hyperresponsiveness in Farmers: Relation to Respiratory Symptoms, Lung Function, and Atopy

There is only limited information on the factors associated with nonspecific bronchial hyperresponsiveness (BHR) in farmers. Our purpose was to examine the relationship between BHR and respiratory symptoms, atopy, and abnormalities of lung function in a sample of French farmers. Farmers scheduled for a preventive medicine check-up in northeastern France were examined. Occupational exposure, respiratory symptoms, and work-related symptoms were assessed by questionnaire, sensitization to 34 common and agricultural allergens by skin prick tests, and BHR by the single-dose (1,200 μg) acetylcholine (ACh) challenge test. Data were obtained from 741 farmers (95% of those invited). Seventy-seven subjects (10.3%) had BHR defined as a fall in forced expiratory volume in 1 s (FEV₁) ≥ 10% after the inhalation of ACh or, for those with a poor lung function, an increase in FEV₁ > 10% and > 200 ml after the inhalation of 200 μg of salbutamol. The proportion of asthmalike symptoms, especially wheeze during work, positive skin tests to acarian (storage mites) and cereal dust allergens, and low levels of lung function was significantly greater among reactors than among nonreactors. Stepwise logistic regression analysis showed a significant and independent association between BHR and wheezing during work (OR = 4.99; 95% CI = 2.29–10.89; p= 0.0001) and baseline FEV₁ (OR = 1.49; 95% CI = 1.05–2.20; p= 0.026). In conclusion, hyperreactive farmers had significantly more asthmalike symptoms, positive skin tests, and abnormal lung function than normoreactive farmers. Work-related wheeze and low baseline FEV₁ were significantly and independently associated with BHR. Accepted for publication: 26 January 1999     

Effects of Age, Gender, Bolus Volume, and Trial on Swallowing Apnea Duration and Swallow/Respiratory Phase Relationships of Normal Adults

The effects of age, gender, bolus volume, and trial on swallowing apnea duration (SAD) and swallow/respiratory phase relationships were examined. Sixty adults, composed of ten males and ten females in each of three age groups (i.e., 20–39, 40–59, and 60–83 years), participated. SAD was assessed via nasal airflow during saliva swallows and 10-, 15-, 20-, 25-mL bolus volumes across three trials. Results revealed SAD is consistent across trial (p>0.05). Significant main effects of age, gender, and bolus volume were found (p<0.05), i.e., elderly adults had longer SAD than young and middle-aged adults; women had longer SAD than men; and SAD increased as bolus volume increased. With respect to saliva swallows, a significant interaction of age by gender was found (p<0.05), i.e., males exhibited a decrease in SAD with increasing age while females exhibited an increase in SAD with increasing age. Concerning swallow/respiratory phase relationships, the pattern of exhale–swallow–exhale was evident during 62% of participants' swallows. Furthermore, age, gender, or bolus volume did not predict the pattern of exhale–swallow–exhale (p>0.05). Submitted February 23, 2000; accepted October 2, 2000     

Changes in Pulmonary Mechanics after Lung Volume Reduction Surgery

Lung volume reduction surgery (LVRS) is a promising new treatment for emphysema and leads to increased flow rates. We investigated the mechanisms by which flow rates could increase and the correlates of lessened dyspnea in patients undergoing LVRS before and 3 months after LVRS in patients with severe emphysema. The following were done: routine pulmonary function testing, measurements of elastic recoil (Pel), tidal breathing patterns, inspiratory work of breathing (W_insp), construction of static recoil-maximum flow curves, and measurement of baseline and transitional dyspnea index (TDI). There were increases in forced vital capacity (FVC: 2.24 ± 0.71 to 2.92 ± 0.63 liters; p < 0.05), forced expired volume in 1 (FEV₁: 0.64 ± .16 to 1.03 ± 0.28 liters; p < 0.01), and decreases in all divisions of lung volume, e.g. total lung capacity (TLC: 6.86 ± 1.41 to 5.96 ± 1.49 liters; p < 0.01). Maximum Pel increased (11.7 ± 3.7 to 19.8 ± 7.8 cmH₂O; p < 0.02) as did the coefficient of retraction (C_R= Pel/TLC: 1.8 ± 0.7 to 3.6 ± 3.6 ± 2.2 cmH₂O/liter). However, the individual responses in other parameters were markedly different among patients. There was no consistent trend in changes in the slope or position of the static recoil-maximum flow curve or W_insp. The only positive correlate of improved dyspnea (TDI = 3.22 ± 2.22; p < 0.01) was improvement in C_R, FEV₁ being a weak negative correlate and change in lung volume not being a correlate at all. We conclude that there is a heterogeneous response of the airways to LVRS. Increased elastic recoil was the primary determinant of improved flow rates after LVRS and is the only positive correlate for improvement in dyspnea. Accepted for publication: 14 July 1997     

Budesonide Down-Regulates Eosinophil Locomotion But Has No Effects on ECP Release or on H2O2 Production

Treatment of allergic asthma with inhaled corticosteroids results in local down-regulation of proinflammatory cytokine synthesis and in marked decrease in tissue eosinophilia. Blood concentrations of inhaled corticosteroids, although significantly lower than those measured in the lung, may still have antiinflammatory effects on circulating eosinophils, reducing their ability to migrate. The aim of our study was to evaluate in vitro the activity of budesonide on blood eosinophils by measuring their chemotactic response, eosinophil cationic protein (ECP) release, and hydrogen peroxide (H₂O₂) production in the presence of different drug concentrations similar to those obtained at airway level (10⁻⁸ and 10⁻⁷ M) and at blood level (10⁻¹⁰ and 10⁻⁹ M). Partially purified blood eosinophils, isolated from 23 asthmatic subjects, were used to evaluate the activity of budesonide on: (1) chemotaxis toward the activated fifth component of complement (C5a, 0.1 μg/ml) or recombinant human (rh) interleukin (IL)-5 (200 pg/ml), (2) ECP release by cells stimulated with tetradecanoylphorbol acetate (TPA) and (3) H₂O₂ production by TPA-activated cells. The chemotactic response to C5a was down-regulated significantly by budesonide only by the highest concentrations tested (10⁻⁸ and 10⁻⁷ M); differently, budesonide was effective in inhibiting eosinophil migration toward rhIL-5, at all concentrations tested (p < 0.01, each comparison). By contrast, no drug-induced modifications were observed in ECP release or in H₂O₂ production (p > 0.05, each comparison). We conclude that concentrations of budesonide similar to those obtained in vivo are effective in inhibiting eosinophil locomotion but not in down-regulating the release of reactive oxygen species and granule-associated proteins. Accepted for publication: 11 February 1999     

Videomanometric Analysis of Supraglottic Swallow, Effortful Swallow, and Chin Tuck in Healthy Volunteers

Simultaneous videoradiography and solid-state manometry (videomanometry) was applied in eight healthy volunteers (four women, four men; age range 25–64 years, mean age 41 years) without swallowing problems. Three different swallowing techniques were tested; supraglottic swallow, effortful swallow, and chin tuck. Seven videoradiographic variables and six manometric variables were analyzed. The supraglottic swallowing technique did not differ significantly from that of the control swallows. The effortful swallow had a significantly (p= 0.0001) reduced hyoid–mandibular distance preswallow due to an elevation of the hyoid and the larynx, which caused a significantly (p= 0.007) reduced maximal hyoid movement and a significantly (p= 0.009) reduced laryngeal elevation during swallow. The chin tuck swallow had a significantly (p= 0.001) reduced laryngohyoid distance and also a significantly (p= 0.004) reduced hyoid–mandibular distance. The chin tuck swallow also displayed significantly (p= 0.003) weaker pharyngeal contractions. Videomanometry allows for analysis of bolus transport, movement of anatomical structures, and measurement of intraluminal pressures. These variables are important when evaluating swallowing techniques. In the present study, we made a few observations that never have been reported before. When healthy volunteers performed supraglottic swallow, they performed the technique somewhat differently. Therefore, we assume dysphagic patients would need a substantial period of training to perform a technique efficiently. Chin tuck could impair protection of the airways in dysphagic patients with weak pharyngeal constrictor muscles.     

The Relation of Fat-free Mass to Maximum Exercise Performance in Patients with Chronic Obstructive Pulmonary Disease

To assess the factors determining maximum exercise performance in patients with chronic obstructive pulmonary disease (COPD), we examined nutritional status with special reference to body composition and pulmonary function in 50 stable COPD patients. Nutritional status was evaluated by body weight and body composition, including fat mass (FM) and fat-free mass (FFM) assessed by bioelectrical impedance analysis (BIA). Exercise performance was evaluated by maximum oxygen uptake (Vo _2max) on a cycle ergometer. A total of 50 patients (FEV₁= 0.98 L) was divided randomly into either a study group (group A, n= 25) or validation group (group B, n= 25). Stepwise regression analysis was performed in group A to determine the best predictors of Vo _2max from measurements of pulmonary function and nutritional status. Stepwise regression analysis revealed that Vo _2max was predicted best by the following equation in group A: Vo _2max (mL/min) = 10.223 × FFM (kg) + 4.188 × MVV (L/min) + 9.952 × DL_co (mL/min/mmHg) − 127.9 (r= 0.84, p < 0.001). This equation was then cross-validated in group B: Measured Vo _2max (mL/min) = 1.554 × Predicted Vo _2max (mL/min) − 324.0 (r= 0.87, p < 0.001). We conclude that FFM is an important factor in determining maximum exercise performance, along with pulmonary function parameters, in patients with COPD. Accepted for publication 15 February 2000     

Atypical Adrenoceptor-mediated Relaxation of Canine Pulmonary Artery Through a Cyclic Adenosine Monophosphate–dependent Pathway

To determine whether functional atypical β-adrenoceptors (β₃-adrenoceptors) are present in pulmonary vascular smooth muscle, we studied isolated canine pulmonary arterial rings under isometric conditions in vitro. Addition of β-adrenoceptor agonists produced a concentration-dependent relaxation of noradrenaline-precontracted tissues, a rank order potency being isoproterenol (1) > salbutamol (0.95) > selective β₃-adrenoceptor agonists, CL 316243 (0.85), and BRL 37344 (0.83). A marked desensitization to salbutamol occurred by pretreatment with salbutamol but not with CL 316243. When β₁-adrenoceptors had been blocked, the relaxant responses to salbutamol were competitively antagonized by the β₂-adrenoceptor antagonist ICI 118551 with a pA₂ value of 7.67 ± 0.21 (mean ± S.E.), but the response to CL 316243 was weekly antagonized by ICI 118551 only at a high concentration of 10⁻⁵ M, where an apparent pA₂ value was 5.24. In contrast, cyanopindolol, a nonselective β-adrenoceptor antagonist, antagonized CL 316243–induced relaxation in a competitive manner with a pA₂ of 6.10 ± 0.11. This pA₂ value was lower than that when salbutamol was used as an agonist (6.69 ± 0.14, p < 0.01). Intracellular 3′,5′-cyclic adenosine monophosphate (cAMP) levels were increased by CL 316243 in a concentration-dependent fashion, an effect that was not altered by ICI 118551. These results suggest that β₃-adrenoceptors may exist in canine pulmonary artery smooth muscle and that stimulation of this atypical receptor causes vasodilation through a cAMP-dependent pathway. Accepted for publication: 17 June 1999     

Methacholine Dose-Response Slopes from Maximal Bronchial Challenge Tests in Asthmatic Children: Methodological Aspects

To determine whether the slope of a maximal bronchial challenge test (in which FEV₁ falls by over 50%) could be extrapolated from a standard bronchial challenge test (in which FEV₁ falls up to 20%), 14 asthmatic children performed a single maximal bronchial challenge test with methacholine (dose range: 0.097–30.08 μmol) by the dosimeter method. Maximal dose-response curves were included according to the following criteria: (1) at least one more dose beyond a ΔFEV₁≥ 20%; and (2) a MFEV₁≥ 50%. PD₂₀ FEV₁ was calculated, and the slopes of the early part of the dose-response curve (standard dose-response slopes) and of the entire curve (maximal dose-response slopes) were calculated by two methods: the two-point slope (DRR) and the least squares method (LSS) in % ΔFEV₁×μmol⁻¹. Maximal dose-response slopes were compared with the corresponding standard dose-response slopes by a paired Student's t test after logarithmic transformation of the data; the goodness of fit of the LSS was also determined. Maximal dose-response slopes were significantly different (p < 0.0001) from those calculated on the early part of the curve: DRR_20% (91.2 ± 2.7 ΔFEV₁% ·μmol⁻¹) was 2.88 times higher than DRR_50% (31.6 ± 3.4 ΔFEV₁% ·μmol⁻¹), and the LSS_20% (89.1 ± 2.8% ΔFEV₁·μmol⁻¹) was 3.10 times higher than LSS_50% (28.8 ± 1.5% ΔFEV₁·μmol⁻¹). The goodness of fit of LSS_50% was significant in all cases, whereas LSS_20% failed to be significant in one. These results suggest that maximal dose-response slopes cannot be predicted from the data of standard bronchial challenge tests. Accepted for publication: 12 December 1996     

Assessment of Ingestive and Oral Praxis Skills: Children with Cerebral Palsy vs. Controls

Eating impairments (dysphagia) in children with cerebral palsy (CP) have been well documented. However, individual components of ingestion, such as the feeding skills of eating and drinking and their relationship to oral-motor planning skills (praxis), remain largely undetermined. The purpose of the present study was to examine functional feeding and oral praxis skills in a group of children with CP and mild eating impairment and to compare their skills with a group of age-matched controls. As well, interobserver reliabilities and concurrent validity of these tests were examined to determine their reliability and to what extent they may be measuring similar constructs. Twenty-seven children with CP and 21 age-matched controls, aged 4.0–16 years, participated in this study. Two oral praxis tests (OFMF and OPT) and two standard ingestive skills tests (GVA and FFAm) were administered to each child. Children with CP scored consistently and significantly lower on the OFMF than controls (p < 0.001); similar results were achieved on the OPT (p < 0.001). Children with CP had difficulty with items where there was a high demand for repetition and smooth sequencing. On the ingestive skills tests children with CP took significantly longer for chewing a hard solid food texture than controls (p < 0.001), and functional feeding skills were also significantly poorer than in controls. Interrater reliability coefficients for the OPT and OFMF were excellent (all ICCs > 0.90). There was high concurrent validity between the OPT and OFMF (r= 0.90, p < 0.0001). The correlations for the FFAm and GVA tests were somewhat weaker (r=−0.54, p < 0.0001). Correlations were negative; as functional feeding scores increased (improved), chewing time decreased (improved). Excellent reliable and valid assessment instruments are available to the practicing clinician. They cover a wide range of oral-motor performance and, so, must be used judiciously and for the purpose that they have been developed.     

Health-Related Quality of Life in Long Term Oxygen-Treated Chronic Obstructive Pulmonary Disease Patients

Chronic obstructive pulmonary disease (COPD) induces changes in daily activities and mood. Health-related quality of life (HRQL) measures are of particular relevance in the management of such patients, but predictors of HRQL have rarely been investigated. The aim of this study was to seek factors predicting HRQL in severe COPD patients under long term oxygen therapy (LTOT). The pulmonary function parameters at the start of LTOT were studied as potential predictors of future HRQL. HRQL was assessed after an average of 40 months follow-up by the Duke Health Profile (Duke) and by the St. George Respiratory Questionnaire (SGRQ). Sixty-one patients (47 males and 14 females) with a mean age of 66 years were included in the study. Stepwise multiple regression analyses conducted in each HRQL dimension identified few significantly predictive factors. By the Duke, higher Self-esteem scores were associated with higher Pao ₂ (p < 0.01) and with older age (p < 0.05); higher Social Health scores were associated with older age (p < 0.005), and higher Pain scores were associated with a higher FEV₁/FVC ratio (p < 0.05). By the SGRQ, the Activity score correlated with FEV₁/FVC (p < 0.05). The proportion of the variance in each score accounted for by covariates in the model did not exceed 10%. No other significant regression models could be identified using the other HRQL dimensions. Our findings demonstrated weak relations between lung function at the start of LTOT and some dimensions of HRQL measured by the Duke and the SGRQ at the end of follow-up. Accepted for publication: 9 July 1996     

Antioxidant Function of Ambroxol in Mononuclear and Polymorphonuclear Cells in Vitro

This study quantifies the antioxidant function of ambroxol (2-amino-3,5-dibromo-N-[trans-4-hydroxycyclohexyl]benzylamine) in vitro. Polymorphonuclear cells (PMN) and mononuclear cells were isolated from the blood of healthy volunteers (n= 46) to determine reactive oxygen species (ROS) by luminol-enhanced chemiluminescence. Ambroxol or the controls N-acetylcysteine (NAC), nacystelyn (NAL), glutathione (GSH), superoxide dismutase (SOD), catalase, and the combination of SOD/catalase were incubated for 1 or 2 h with zymosan-activated cells in vitro using concentrations ranging from 10⁻⁶ to 10⁻³ mol/liter. Reduction of ROS-mediated luminescence was similar within the cell types. Ambroxol (10⁻⁴ mol/liter) reduced ROS about 75% (1-h incubation) and 98% (2-h incubation), respectively (p < 0.001). SOD and SOD/catalase, but not the H₂O₂-catalyzing substances (NAC, NAL, GSH, and catalase), reduced cellular ROS. This indicates that inflammatory cells predominantly generate O⁻ ₂, which can be scavenged by ambroxol. The antioxidant function of ambroxol with increasing incubation time suggests additional cellular antiinflammatory properties of this substance. Our results indicate that good antioxidant function of ambroxol is related mainly to direct scavenger function of reactive oxygen metabolites such as O⁻ ₂. However, an antioxidative effect of ambroxol may also be associated with the reduction of prooxidative metabolism in inflammatory cells. Concluding from this observation, and because of the well known high affinity of ambroxol for lung tissue, ambroxol may be an alternative in antioxidant augmentation therapy, particularly in pulmonary diseases characterized by an overburden of toxic oxygen metabolites. Accepted for publication: 5 December 1996