[Oxygen-enhanced functional MR lung imaging]

Current diagnostic tools for the assessment of lung function are limited by global measurements or the need for radioactive tracers. Ideally, these tools should allow quantitative, regional distinct analyses without exposure to radiation. The current paper presents oxygen-enhanced functional MRI for assessment of lung ventilation. First applied in humans in 1996, a considerable amount of experience is now available on 1.5T scanners. The generation of quantitative T1-maps shows a high clinical potential. Low-field MR scanners, which are mostly open-designed, are especially interesting for functional lung imaging. The open design has advantages in respect to patient comfort by lower noise production and easy access to the patients and the costs are lower (no need for helium cooling). Lower signal-to-noise ratios can be overcome by changing the relaxation times. New navigator techniques allow further compensations. This article focuses on the presentation of low-field scanners and the application of T1 and T2(*) maps is described for healthy volunteers and first patients.

Physical activity is independently related to aerobic capacity in cystic fibrosis

It is unclear whether a relationship between physical activity (PA) and maximal oxygen uptake (V'(O2,max)) exists in cystic fibrosis (CF) and, if so, whether the relationship reflects a direct effect or is mediated by the effects of confounding variables, such as pulmonary or muscle function. The objective of the present study was to determine the relationship between PA and V'(O2,max) in CF while adjusting for possible influences of confounding factors. In total, 36 female and 35 male patients with CF from Germany and Switzerland (aged 12-40 yrs, forced expiratory volume in one second (FEV1) 25-107% predicted) were studied. A Wingate test was employed to measure muscle power. PA was monitored for 7 days and expressed in two ways: 1) average daily accelerometer count (ADAC) and 2) time spent in moderate-to-vigorous PA (MVPA). V'(O2,max) was determined during an incremental cycle exercise test to volitional fatigue. PA was positively related to V'(O2,max). In a multiple linear regression analysis, height, sex, FEV1, muscle power and ADAC (additionally explained variance 2.5%) or time spent in MVPA (additionally explained variance 3.7%) were identified as independent predictors of V'(O2,max). In conclusion, high levels of physical activity in addition to good muscular and pulmonary functions are associated with a high aerobic capacity in cystic fibrosis.

Applicability of an allometric power equation to children, adolescents and young adults of extreme body size

AIM

The aim of this study was to assess the applicability of a regression model for peak power (PP) and total mechanical work (TMW) for healthy children, adolescents and young adults especially in the extreme ranges of stature, mass, and body mass index (BMI).

METHODS

A total of 454 children, adolescents and young adults aged 6-20 years volunteered for the study. Subjects, whose stature, mass and BMI were between the 10(th) and the 90(th) centile, were selected to calculate the prediction equation: 267 subjects fulfilled these criteria. Each subject performed two unilateral Wingate tests (ULWAnT), one with each leg. PP (Watts) and TMW (Joules) of the left and right leg were averaged for each individual. Ln(mass), in(stature), age, age(2), gender, and age x gender were used as predictors for in(PP) and ln(TMW). The applicability of the prediction equation was tested on individuals who were less than the 10(th) centile or greater than the 90(th) centile for stature, body mass and BMI.

RESULTS

All independent variables were statistically significant (P<0.05) predictors of in(PP), adjusted R(2)=0.93 and all but gender were significant predictors for in(TMW), adjusted R(2)=0.95. However, measured in(PP) and in(TMW) were significantly lower than predicted in(PP) and in(TMW) for subjects >90th centile for stature, body mass, or BMI.

CONCLUSIONS

the prediction equations overestimated PP and TMW in children, adolescents and young adults who were heavier than the reference subjects, as indicated by a relatively high body mass or high BMI for age or were taller than the reference subjects. The findings might reflect a deficit in anaerobic capacity in children, adolescents and young adults with relatively large body size for their age.

Follow-up of acute pulmonary complications in cystic fibrosis by magnetic resonance imaging: a pilot study

The aim of this pilot study was to obtain information on the value of MRI in the follow-up of atelectasis and pneumonic infiltrates in cystic fibrosis (CF). Six patients aged 5-15 y were initially examined using chest X-ray and magnetic resonance imaging (MRI). Both methods provided identical information. During follow-up, MRI proved suitable to monitor pulmonary complications.

CONCLUSION

MRI of the lung is feasible and valuable in the follow-up of atelectasis and pulmonary infiltrates in CF.

Necrotizing sarcoid granulomatosis: a rarity in childhood

Necrotizing sarcoid granulomatosis (NSG) is characterized by pulmonary nodular infiltrates, a typical histology, and a benign clinical course. The etiology and pathogenesis of the disease are still unknown. In childhood, it is extremely rare, with only three reported cases so far. Here we report on an 8-year-old girl, who to our knowledge is the youngest reported patient with NSG. The girl presented with shortness of breath and a sore throat. Chest X-ray and computed tomography (CT) scan revealed multiple nodular opacities of the lung. The symptoms and radiological findings disappeared within 6 months without any treatment. The diagnosis was based on the typical signs and symptoms of NSG and on the exclusion of other diseases. As abnormal immunological findings such as the lack of specific diphtheria antibodies in spite of vaccination against diphtheria were present, we suggest that immunologic mechanisms could play an etiologic role in the pathogenesis of NSG. In addition, the ratio of CD4+/CD8+ T-cells in the peripheral blood was significantly reduced, whereas the CD4+/CD8+ T-cell ratio in the immunohistochemical staining of the lung tissue was elevated. Since this compartmentalization is a typical finding in sarcoidosis, it supports the theory that NSG may represent a variant of sarcoidosis. However, because some characteristics of NSG are uncommon in typical sarcoidosis, NSG may also be an entity in its own right.

Exercise and the child born prematurely

With the increase in survival rates of children born prematurely, issues related to their active pursuits and responses to exercise have been gaining increasing attention. In some preterm children with an extremely low birthweight, bronchopulmonary dysplasia or cerebral palsy exercise capacity may be limited, especially in tasks requiring good neuromotor coordination. Deficiencies in aerobic and anaerobic performance, strength and coordination may even occur in children without overt manifestations of a neuromuscular or pulmonary disease. However, as a rule, children born prematurely may engage in physical activities and competitive sports without limitations. Exercise is safe in almost all such children as long as precautions are taken to avoid exercise-induced bronchoconstriction. However, to date there are no studies that have determined the efficacy of training. A wide variety of activities should be encouraged in all children born prematurely at an early age, to support the development of skills and to compensate for the possible effects of their premature birth on coordination.

Exercise inhibits epithelial sodium channels in patients with cystic fibrosis

The aim of this study was to determine the effects of a single exercise bout on luminal Cl(-) and Na(+) conductance in the respiratory epithelium of patients with cystic fibrosis (CF). In nine patients with CF and nine healthy control subjects, the transepithelial electrical potential difference (PD) of the nasal respiratory epithelium was recorded, first at rest and then during moderate-intensity exercise. Under both conditions, PD was first measured while superfusing the epithelium with isotonic saline. Then, the effects of amiloride and amiloride plus low chloride plus isoproterenol were determined. Exercise resulted in a significant lower PD compared with rest in patients with CF (-6.6 +/- 16.6 mV versus -33.6 +/- 10.0 mV, p < 0.0001) and control subjects (0.1 +/- 8.7 mV versus -7.1 +/- 5.1 mV, p < 0.01). The effects of amiloride on PD were reduced during exercise compared with rest in patients with CF (+15.8 +/- 9.5 mV versus +26.1 +/- 11.0 mV, p < 0.01) and control subjects (+5.8 +/- 4.8 mV versus +10.0 +/- 3.1 mV, p < 0.01). There was no effect of exercise on chloride conductance in patients with CF and control subjects. We conclude that moderate-intensity exercise partially blocks the amiloride-sensitive sodium conductance in the respiratory epithelium. The inhibition of luminal sodium conductance could increase water content of the mucus in the CF lung during exercise and may, in part, explain the beneficial effects of exercise in patients with CF.

Bilateral deficit during short-term, high-intensity cycle ergometry in girls and boys

Peak torque during an isokinetic bilateral knee extension or flexion is usually lower than the summed peak torque of two unilateral contractions, and this phenomenon is designated as bilateral deficit (BD). The objectives of this study were to determine whether a BD also exists for more complex, alternating movements (e.g., short-term, high-intensity cycling), and to assess the possible effects of gender and maturity. Forty children and adolescents performed two unilateral (ULWAnT) and one bilateral Wingate anaerobic test (BLWAnT). The highest power reached in any 3-s interval (peak power; PP), and the total mechanical work (TMW) performed during the test was determined. Individual BD for PP (BDpp, %) was calculated by dividing the PP in the BLWAnT by the sum of the PP values of both ULWAnTs. The BD for TMW (BDTMw) was calculated in the same way. The sum of PP generated during the two ULWAnTs was larger than the PP measured in the BLWAnT (P<0.000001). The same difference was observed for TMW (P<0.0001). Maturity did not affect the BDpp or BDTMW (P=0.34). However, the BD was more pronounced in females compared to males (P= 0.03). In conclusion, a BD is evident during cycling exercise.

Ventilatory threshold: a useful method to determine aerobic fitness in children?

PURPOSE

The objective of this study was to assess intra- and inter-evaluator reliability and validity of ventilatory threshold (VT) determination in children.

METHODS

At the age of 6-12 yr, 35 children born prematurely and 20 controls born at term performed an incremental continuous cycling task until volitional fatigue. Fifteen-second averages of VE/VO2, VE/VCO2, and respiratory exchange ratio were plotted 1) over time (X-time) and 2) over VO2 (X-VO2). VCO2 was plotted over VO2 only (X-VO2). Two experienced evaluators, blind to the identity of plots, independently assessed VT from X-time and X-VO2 plots on two occasions, 6 wk apart. Thus, for each of the 55 subjects, four VT values were expected from X-time plots and four from X-VO2 plots (2 evaluators, 2 occasions).

RESULTS

VT expressed as VO2 in mL x min(-1) could be determined by both evaluators on both occasions in 40/55 children from X-time and in 45/55 children from X-VO2. VT was significantly different between evaluators for X-time plots. Using X-time plots, intraevaluator ICC were 0.88 and 0.98 and interevaluator ICC were 0.82 and 0.79. The respective values for X-VO2 plots were 0.94 and 0.95, and 0.96 and 0.92. Intra- and inter-evaluator reliability of VT determinations tended to be slightly lower in children born prematurely compared with those born at term. There was a close association between VT and VO2peak (r = 0.92).

CONCLUSION

Plotting gas exchange data over VO2 is likely to be the method of choice for determining VT. Although a minority of children have uninterpretable X-VO, plots, VT can be reliably interpreted in the remainder. Furthermore, VT is a valid marker of aerobic capacity. Thus, VT is a useful measure of aerobic fitness in children.

Kinetics of oxygen uptake at the onset of exercise near or above peak oxygen uptake

We tested the hypothesis that kinetics of O(2) uptake (VO(2)) measured in the transition to exercise near or above peak VO(2) (VO(2 peak)) would be slower than those for subventilatory threshold exercise. Eight healthy young men exercised at approximately 57, approximately 96, and approximately 125% VO(2 peak). Data were fit by a two- or three-component exponential model and with a semilogarithmic transformation that tested the difference between required VO(2) and measured VO(2). With the exponential model, phase 2 kinetics appeared to be faster at 125% VO(2 peak) [time constant (tau(2)) = 16.3 +/- 8.8 (SE) s] than at 57% VO(2 peak) (tau(2) = 29. 4 +/- 4.0 s) but were not different from that at 96% VO(2 peak) exercise (tau(2) = 22.1 +/- 2.1 s). VO(2) at the completion of phase 2 was 77 and 80% VO(2 peak) in tests predicted to require 96 and 125% VO(2 peak). When VO(2) kinetics were calculated with the semilogarithmic model, the estimated tau(2) at 96% VO(2 peak) (49.7 +/- 5.1 s) and 125% VO(2 peak) (40.2 +/- 5.1 s) were slower than with the exponential model. These results are consistent with our hypothesis and with a model in which the cardiovascular system is compromised during very heavy exercise.

Single-leg Wingate Test in children: reliability and optimal braking force

PURPOSE

Single-leg cycle ergometry employing the protocol of the Wingate Test (WAnT) has been used to assess unilateral muscle power and leg-dominance. The objectives of this study were to determine the reliability of the single-leg WAnT (SLWAnT) and to establish optimal braking force for the SLWAnT.

METHODS

Twenty female and 19 male subjects (prepubertals: 6.0-9.9 yr, 7 female and 6 male; midpubertals: 11.0-14.9 yr, 7 female and 7 male; and postpubertals: 17.0-20.9 yr, 6 female and 6 male) came to the laboratory on three occasions. On each visit, they first performed two SLWAnT after a standardized warm-up, one with each leg. Braking force for these tests was kept constant throughout all visits. On each of the following visits, subjects performed four additional SLWAnT, two with each leg, with braking force varying from test to test to determine the braking force associated with the highest performance over 30 s.

RESULTS

Although a significant increase in performance was observed from visit to visit in some groups, intraclass correlation coefficients (which included trial-to-trial differences) of peak power and total work generated during the first two SLWAnT of each visit ranged from 0.89 to 0.98. Optimal braking force (J x rev(-1)) could be estimated from 0.4052 x body mass(1.4662) for all subjects irrespective of gender or maturity. The standard error of estimate was lowest in the prepubertals and highest in postpubertals (8.3-31.4 J x rev(-1)).

CONCLUSIONS

SLWAnT is a highly reliable method to measure single-leg power. The above equation provides good estimates of optimal braking force. The SLWAnT can, therefore, be used to monitor changes in single-leg power and to assess leg-dominance.

Impact of a single exercise bout on energy expenditure and spontaneous physical activity of obese boys

The main objective of the present study was to determine whether a structured, laboratory-based exercise task would modify the energy expenditure (EE) and the pattern of spontaneous physical activity (PA) of obese boys on the day of an exercise laboratory visit and on the following day. Fourteen 10- to 15-y-old moderately obese (36.6+/-3.3% fat) boys volunteered. They each had three laboratory visits, I wk apart. In one visit, they performed a strenuous 50-min cycling task; in another, a 30-min medium-intensity cycling task; and in another (which served as placebo), they did not exercise. PA was monitored the day before (d 1), during (d 2), and after (d 3) each laboratory visit by use of a heart rate monitor and a 12-h recall interview. EE was calculated from minute-by-minute heart rate and each child's predetermined relationship between oxygen uptake and heart rate. EE and PA were analyzed from 1300 to 1900 h each day using 15-min intervals. EE tended to decrease (p < 0.087) in the afternoon of all d 2 compared with d 1, and it increased on d 3 after the medium-intensity exercise (p < 0.0005). EE during d 2 and 3 combined, compared with d 1, decreased after the high-intensity exercise (534.2 versus 564.3 kJ/h, p < 0.05). It increased after the medium-intensity exercise (561.8 versus 526.7 kJ/h, p = 0.052) and was not affected after the placebo visit (589.4 versus 574.3 kJ/h). Time spent outdoors was consistently reduced on the day of laboratory visit compared with the day before and after the visit, regardless of the contents of intervention. In conclusion, a single laboratory visit is followed by a reduction in EE and PA on the day of intervention. However, its effect on EE the following day may be dose dependent: medium-intensity exercise induces an increase in EE, but high-intensity exercise causes a decrease in EE. One implication is that intervention by physical training should employ medium-intensity exercise to enhance the EE of obese boys.

Kinetics of oxygen uptake at the onset of exercise in boys and men

The objective of this study was to compare the O2 uptake (VO2) kinetics at the onset of heavy exercise in boys and men. Nine boys, aged 9-12 yr, and 8 men, aged 19-27 yr, performed a continuous incremental cycling task to determine peak VO2 (VO2 peak). On 2 other days, subjects performed each day four cycling tasks at 80 rpm, each consisting of 2 min of unloaded cycling followed twice by cycling at 50% VO2 peak for 3.5 min, once by cycling at 100% VO2 peak for 2 min, and once by cycling at 130% VO2 peak for 75 s. O2 deficit was not significantly different between boys and men (respectively, 50% VO2 peak task: 6.6 +/- 11.1 vs. 5.5 +/- 7.3 ml . min-1 . kg-1; 100% VO2 peak task: 28.5 +/- 8.1 vs. 31.8 +/- 6.3 ml . min-1 . kg-1; and 130% VO2 peak task: 30.1 +/- 5.7 vs. 35.8 +/- 5.3 ml . min-1 . kg-1). To assess the kinetics, phase I was excluded from analysis. Phase II VO2 kinetics could be described in all cases by a monoexponential function. ANOVA revealed no differences in time constants between boys and men (respectively, 50% VO2 peak task: 22. 8 +/- 5.1 vs. 26.4 +/- 4.1 s; 100% VO2 peak task: 28.0 +/- 6.0 vs. 28.1 +/- 4.4 s; and 130% VO2 peak task: 19.8 +/- 4.1 vs. 20.7 +/- 5. 7 s). In conclusion, O2 deficit and fast-component VO2 on-transients are similar in boys and men, even at high exercise intensities, which is in contrast to the findings of other studies employing simpler methods of analysis. The previous interpretation that children rely less on nonoxidative energy pathways at the onset of heavy exercise is not supported by our findings.

Aerobic fitness and physical activity in patients with HLA-B27 positive juvenile spondyloarthropathy that is inactive or in remission

OBJECTIVE

To assess aerobic fitness (AF) and physical activity (PA) in patients with HLA-B27 positive juvenile spondyloarthropathy (JSpA) in remission at the time of testing.

METHODS

Twenty-one previous patients (12 male, 9 female), age 6-26 years (median age 17.8), and 21 healthy controls matched for age, sex, height, and weight participated. AF was determined by measuring maximal power and peak oxygen uptake (VO2 peak) during a continuous incremental cycling task. PA was assessed by Seven-Day Recall and Lipid Research Clinic questionnaire.

RESULTS

There was only a tendency for a lower maximal power and O2 peak in the 21 patients compared to controls for the total group (median/range: 191/49-306 W vs 219/41-337 W; 2385/998-3962 ml x min(-1) vs 2761/10434221 ml x min(-1); both p < 0.10). However, patients who were older than 18 years had a significantly lower maximal power and VO2 peak than their controls (median/range: 199/126-306 W vs 255/194-337 W; 2785/1570-3962 ml x min(-1) vs 3308/2049-4221 ml x min(-1); both p < 0.05). Many of the older patients had also had arthritis for longer than 2 years and felt limited in their AF or PA. PA was not significantly different between patients and controls.

CONCLUSION

These data suggest that some patients have an impairment of their AF long after arthritis has ceased, which is likely attributable to psychological factors. Changes in the heart and skeletal muscle might also contribute to the lower AF. Participation in physical exercise is encouraged especially in older or "anxious" patients with inactive JSpA.

Role for tyrosine phosphorylation and Lyn tyrosine kinase in fas receptor-mediated apoptosis in eosinophils

Fas ligand/Fas receptor molecular interactions have been implicated as having an important function for the regulation of eosinophil apoptosis. The purpose of the present study was to investigate biochemical events triggered by the engagement of the Fas receptor in freshly isolated human and mouse eosinophils. Activation of the Fas receptor on eosinophils with the agonistic anti-Fas monoclonal antibody (MoAb) resulted in increased tyrosine phosphorylation of several intracellular proteins. The tyrosine kinase inhibitors lavendustin A and genistein inhibited Fas receptor-induced cell death in both human and mouse eosinophils in vitro and prevented, at least partially, Fas receptor-mediated resolution of eosinophilic inflammation in a mouse in vivo model of lung eosinophilia. In addition, in freshly purified human eosinophils, lavendustin A prevented anti-Fas MoAb-induced proteolytic cleavage of lamin B, suggesting that tyrosine kinases may amplify the proteolytic signaling cascade within interleukin-1beta converting enzyme (ICE) family proteases. Moreover, the tyrosine kinase Lyn was identified as being involved in Fas receptor-mediated cell death. Collectively, these results demonstrate that tyrosine phosphorylation is an important step in the generation of the Fas receptor-linked transmembrane death signal in eosinophils and that Lyn participates in this pathway.

Influence of climate on heart rate in children: comparison between intermittent and continuous exercise

Heart rate (HR) monitoring is commonly used to assess 24-h energy expenditure (EE) in children but it has been found to overestimate the true values. One reason for this may be the effect of climatic heat stress on HR. An equation has been previously developed to adjust HR measured during continuous exercise for the influence of climate. Since play in children is rarely of a continuous pattern, one objective of this study was to compare the effects of climatic heat stress on the HR response to intermittent and to continuous exercise. A second objective was to determine whether the previously developed equation is suitable for intermittent exercise. A group of 12 boys and 8 girls (aged 8-11 years) cycled in a climatic chamber. The exercise consisted of continuous cycling for 5 min at 35%, 55%, and 75% of peak oxygen up take (random order) followed by alternating cycling at the same resistance and cadence (30 s) and rest (30 s) for 3 additional min. The oxygen uptake (VO2) and HR were determined for 2 min at the end of continuous cycling and for 2 min during intermittent cycling. Climatic conditions (randomly assigned) were dry bulb temperature T(db) 22 degrees C, 50% relative humidity (rh); T(db) 28 degrees C, 55% rh; T(db) 32 degrees C, 52% rh; or T(db) 35 degrees C, 58% rh. The difference between HR measured at a given T(db) (HR(meas)) and HR at 22 degrees C and at the same VO2 was then calculated (deltaHR). The deltaHR increased linearly with increasing temperature but was not related to VO2 or to exercise type. However, a small but significant difference was found if the published equation was used with data from intermittent exercise. The accuracy of the existing equation adjusting HR(meas) for the influence of T(db) (HR(corr)) could be improved to HR(corr) = HR(meas) x (1.18308-(0.0083218 x T(db))). In conclusion, the effects of climatic heat stress on HR were similar in continuous and intermittent exercise, and HR can be adjusted for the influence of climate in groups of pre- and early pubertal children during rest, intermittent and continuous exercise at ambient temperatures between 22 degrees C and 35 degrees C, thereby reducing the error in predicting EE from HR.

Disruption of fas receptor signaling by nitric oxide in eosinophils

It has been suggested that Fas ligand-Fas receptor interactions are involved in the regulation of eosinophil apoptosis and that dysfunctions in this system could contribute to the accumulation of these cells in allergic and asthmatic diseases. Here, we demonstrate that nitric oxide (NO) specifically prevents Fas receptor-mediated apoptosis in freshly isolated human eosinophils. In contrast, rapid acceleration of eosinophil apoptosis by activation of the Fas receptor occurs in the presence of eosinophil hematopoietins. Analysis of the intracellular mechanisms revealed that NO disrupts Fas receptor-mediated signaling events at the level of, or proximal to, Jun kinase (JNK), but distal to sphingomyelinase (SMase) activation and ceramide generation. In addition, activation of SMase occurs downstream of an interleukin 1 converting enzyme-like (ICE-like) protease(s) that is not blocked by NO. However, NO prevents activation of a protease that targets lamin B1. These findings suggest a role for an additional NO-sensitive apoptotic signaling pathway that amplifies the proteolytic cascade initialized by activation of the Fas receptor. Therefore, NO concentrations within allergic inflammatory sites may be important in determining whether an eosinophil survives or undergoes apoptosis upon Fas ligand stimulation.