Makoto Shigeta

Ability of polymorphonuclear leukocytes to generate active oxygen species in children with bronchial asthma : use of chemiluminescence probes with a cypridina luciferin analog and luminol

Airway inflammation with polymorphonuclear leukocytes (PMN) may play an important role in bronchial hyperresponsiveness (BHR). PMN generate superoxide anion (O2-) and other oxygen radicals that can damage lung tissue. We investigated the ability of peripheral PMN of children with bronchial asthma and control subjects to generate O2- and other active oxygen species using a 2-methyl-6-(p-methoxyphenyl)-3,7-dihydroimidazo[1,2-a]pyrazin++ +-3-one, a highly sensitive and specific chemiluminescence (CL) probe for O2-, and luminol-dependent CL. The ability of PMN of subjects with asthma to generate O2- and other active oxygen species was significantly greater than that of PMN of control subjects when stimulated with opsonized zymosan (OZ), phorbol myristate acetate or N-formyl-methionyl-leucyl-phenylalanine. Furthermore, in the same asthmatic children, the generation of O2- and other active oxygen species was significantly higher with attacks than without attacks when PMN were stimulated with OZ. We also demonstrated that O2- generation correlated with the degree of BHR to inhaled histamine. These results suggest that PMN of asthmatic children, especially those with attacks, generate more active oxygen species than that of control subjects and that airway inflammation caused by O2- may be closely related to BHR in subjects with bronchial asthma.

Development of bronchial hyperresponsiveness during childhood

Bronchial hyperresponsiveness (BHR) produces the characteristic pathological abnormalities seen in asthma and clearly plays a central role in the pathophysiology of asthma. The presence of BHR has been demonstrated in infants with asthma, as has the possibility of BHR persisting through the childhood period. The level of BHR may not only reflect the state of the airways, as a marker of airway dysfunction, but may also predict the persistent prognosis of the disease. Thus, measurement of BHR may provide important information about the symptoms and lung function in children with asthma. In view of multiple pathophysiological mechanisms, BHR does not seem to have a single cause. Many potential confounding variables, such as age, gender, and genetic status, and some environmental factors, such as allergens, infections, and pollutants, could be responsible for the establishment of childhood BHR. There may be differences between the mechanisms that induce transient BHR and the mechanisms that induce persistent BHR. Also, there may be differences between the causes that induce BHR in the infantile period and the causes that maintain persistent BHR during childhood asthma. There is also disagreement as to the most suitable method to measure BHR in children, especially in infants. The assessment of BHR in young children has not been uniformly successful, and measurements of BHR changes over the childhood period are associated with a number of problems. To resolve these problems, there may be two ways to study childhood BHR. One is to use age-matched specific techniques to clarify the precise BHR in each age group; the other is to use simple techniques that can be performed over the childhood period on a large number of subjects. In studies of infantile respiratory dysfunction the ultimate goal is to establish a simple, noninvasive method by which measurements of respiratory function may be obtained in infants. Further investigations and acceptable methods will be needed to clarify the mechanisms involved in the establishment of asthma throughout the childhood period.

Effect of age, height, and prechallenge respiratory resistance on bronchial hyperresponsiveness in childhood asthma using the forced oscillation technique

To evaluate the effects of age, height and prechallenge respiratory system resistance (Rrs) on bronchial responsiveness to methacholine inhalation (BRm) as measured by the oscillation technique in children with mild asthma, we studied BRm in 92 atopic children aged from 8 to 13 years (mean ± SD, 10.5 ± 1.7 years). Inhalation challenge was performed by administering progressively doubling doses of methacholine, until a twofold increase in Rrs from baseline had been reached. The minimum cumulative dose of methacholine (Dmin) at which Rrs deviated from baseline was identified by the point of deflection of the continuously recorded Rrs tracing. The Dmin represented the amount of methacholine which elicited BRm. By using single‐regression analysis, height was negatively correlated with Rrs (p < 0.001). Height was positively and Rrs was negatively correlated with age (p < 0.001 and p < 0.001, respectively). Furthermore, height and age were correlated with Dmin (p < 0.001 and p < 0.001, respectively), but prechallenge Rrs was not correlated with Dmin (p > 0.1). To minimize the effect of height and prechallenge Rrs on BRm, the relationships between Dmin and age was studied in a subgroup with a narrow range of heights (135–155 cm, n = 32), and a narrow range of prechallenge Rrs (5.0–6.9 cmH2 O/L/s, n = 42); there remained a statistically significant correlation between Dmin and age in the groups with comparable heights (p = 0.026) and Rrs (p = 0.003). These data suggest that the BHR in childhood asthma may be affected by height and age when measured by the oscillation technique. Considering the many advantages of the oscillation method, this technique may be very suitable for measuring BHR in childhood asthma. Pediatr Pulmonol. 1996;22:1–6.

Diurnal variation of peak expiratory flow in children with cough variant asthma.

Cough variant asthma (CVA) is thought to be a variant form of asthma in which cough is the sole clinical manifestation of airways hyperresponsiveness, a characteristic feature of asthma. Another characteristic feature of asthma includes an increased diurnal variation of peak expiratory flow (PEF) compared to normal subjects. To examine whether diurnal variation of PEF might also increase in children with CVA, we have examined the degree of diurnal variation of PEF in these children (n = 7) by measuring peak flow serially for a week, and compared it with those in mild to moderate asthma (n = 17) and in control children without cough (n = 8). In control children without cough, the average value of the mean diurnal variation of PEF was 10.4 +/- 0.8%. In both groups of children with asthma and with CVA, there was a significant increase in the value (20.5 +/- 1.3% and 23.6 +/- 3.6%, respectively) compared to that in control children (p < 0.01 in both groups), although there was no significant difference between these 2 groups. These results show that mild, but significant airway obstruction is occurring in children with CVA, although clinical wheezing is not recognized. Serial measurements of diurnal variation of PEF may be helpful for the diagnosis of CVA in children.

Age-Related Changes in Bronchial Hyperreactivity During the Adolescent Period

To evaluate the influence of bronchial hyperreactivity on the improvement of asthma seen during adolescence, age-related changes of bronchial reactivity to methacholine (BRm) in adolescence were evaluated in two studies. Study 1 included 261 asthmatic children and 89 controls, aged 6-26 years, and in Study 2, yearly BRm variations from age 11 to 16 years of 23 asthmatic children of study 1 were studied. Methacholine inhalation challenge was performed by using an oscillation method; that is, respiratory resistance (Rrs) was directly measured by an oscillation technique, and subsequent doses were then doubled, until a twofold increase in Rrs from the baseline was reached. The cumulative dose of methacholine at the inflection point of the Rrs was considered to represent the BRm. From ages 6 to 9, Dmin in the asthmatic children were low (from 2.07 units to 1.38 units), but after age 12, the value gradually increased, and finally became sustained after age 16 (from 2.27 units to 4.80 units). These same age-related changes were seen in the age-matched controls. From ages 6 to 11, Dmin in the control children were also low (from 8.07 units to 12.9 units), but after age 12, Dmin gradually increased, and finally became sustained after age 16 (from 18.5 units to 43.2 units). However, for each year, the Dmin of the asthmatic children were significantly lower than those of the controls. Further, the mean of yearly Dmin variation from age 13 was less than that of younger subjects (from 0.65 unit/year to 0.92 unit/year, from 1.16 units/year younger subjects (from 0.65 unit/year to 0.92 unit/year, from 1.16 units/year to 4.16 units/year, respectively). We, therefore, concluded that the natural age-related BRm changes and the increased stability of yearly BRm variation that occur in adolescence may play a role in the improvement of childhood asthma seen during this period.

Plasma theophylline concentrations and airway function in asthmatic children receiving standard and modified RTC therapy

The effects of three different dosage schedules for sustained-release theophylline (Theolong) were investigated in children with asthma. With regimen II (unequal doses at 0800 h and 2000 h), the maximum plasma theophylline concentration following the evening dose was significantly higher than that following the morning dose, and also was larger than that following the evening dose with regimen I (equal doses at 0800 and 2000 h). With regimen III (equal doses at 0600 h and 2100 h), the mean theophylline concentration-time curve showed a single large peak at 1100 h, whereas with regimen I, there were two peaks at 2300 and at 1400 h. Knowledge that a change of the dosage schedule can affect the pharmacokinetics of theophylline in this way should aid physicians in its safe and effective use.

Studies of Dialyzates from Dermatophagoides farinae: Partial Purification and Haptenic Properties of Dialyzates from Dermatophagoides farinae

Dialyzates from Dermatophagoides farinae were partially purified. Fractionation on HPLC and anion exchange chromatography revealed that the dialyzates consisted of 5 major fractions of glycoprotein whose apparent molecular sizes were 5.1, 4.1, 3.2, and less than 1.35 kD on HPLC. The apparent molecular size of two fractions was 5.3 and 2.9 kD on SDS-PAGE. They were basic glycoproteins which had a pi ranging from 7.46 to 8.71 on PAG-IEF. These fractions were allergenic in the RAST and ELISA inhibition tests but not in the skin prick test (SPT). Our results suggest that the dialyzates from D. farinae have haptenic properties. The dialyzates from D. faunae (low molecular weight) and its 5 fractions bound noncovalently to human serum albumin (HSA) at the free tyrosine residues of HSA. They proved to bind noncovalently to serum proteins and collagens. Once they bound to proteins, the conjugates became allergenic not only in the RAST and ELISA inhibition test but also in the SPT. Our results provide evidence that the dialyzates from D. farinae have haptenic properties.

Effect of theophylline on insulin-like growth factor I in children with asthma

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