Andreas Artlich

Exhaled nitric oxide in childhood asthma

Endogenous synthesis of nitric oxide (NO) and its presence in exhaled air was observed in various species including humans. Particularly high levels were found in adults with bronchial asthma, possibly because of the underlying pulmonary inflammatory activity. We studied oral and nasal exhaled NO by chemiluminescence in 47 children aged between 6 and 10 years. Thirty children had bronchial asthma, 17 were healthy controls. In asthmatic children oral exhaled NO was 13.4±1.4 parts per billion (ppb) (mean±SEM), nasal exhaled NO was 21.7±1.5 ppb. In healthy controls oral exhaled NO was 7.2±1.0 ppb, nasal exhaled NO was 18.2±2.2 ppb. Oral exhaled NO was significantly higher in asthmatic children compared to healthy controls (P=0.0017). Nasal exhaled NO did not differ significantly in the two groups. There was a significant negative correlation between oral exhaled NO and forced expiratory volume in 1 s (FeV1). No significant correlation between oral or nasal exhaled NO and other markers of obstructive lung function impairment, oral minute ventilation, the body mass index and the presence of upper respiratory tract infection could be found.

Mechanisms of nitric oxide generation from nitroglycerin and endogenous sources during hypoxia in vivo

Nitroglycerin (GTN), often used in conditions of cardiovascular ischaemia, acts through the liberation of nitric oxide (NO) and the local concentration of NO in the tissue is responsible for any biological effect. However, little is known about the way in which the concentration of NO from GTN and other NO‐donors is influenced by low oxygen tension in the target tissues. To evaluate the impact of changes in oxygen tension in the metabolism of NO‐donors we measured exhaled NO in anaesthetized rabbits in vivo and expired NO and perfusate nitrite (NO2−) in buffer‐perfused lungs in situ. The impact of acute hypoxia on NO formation from GTN, isosorbide‐5‐mononitrate (ISMN), dissolved authentic NO, NO2− and NO generated from endogenous NO‐synthase (NOS) was studied in either model. Acute hypoxia drastically increased exhaled NO concentrations from all NO‐donors studied, both in vivo and in the perfused lung. During similar conditions endogenous NO generation from NOS was strongly inhibited. The effects were most pronounced at less than 3% inspired oxygen. The mechanisms for the increased NO‐formation during hypoxia seems to differ between GTN‐ and NO2−‐derived NO. The former phenomenon is likely due to diminished breakdown of NO. In conclusion, hypoxic conditions preserve very high local NO concentrations generated from organic nitrates in vivo and we suggest that this might benefit preferential vasodilation in ischaemic tissue regions. Our findings point out the necessity to consider the influence of oxygen tension when studying the action of NO‐donors.

Exhaled nitric oxide in preterm infants

Nitric oxide (NO) is detectable in the exhaled gas of adults during spontaneous respiration and, according to current knowledge, mainly originates from the paranasal sinuses. We studied total NO excretion rates by chemiluminescence in preterm infants whose paranasal sinuses are known to be only partially pneumatized. NO excretion was 7.15 +/- 1.13 nl/min (mean +/- SD, range 6.33-9.36 nl/min) measured from spontaneously exhaled nasal gas (n = 6) and 0.3 +/- 0.05 nl/min (range 0.26-0.36 nl/min) measured from the lower airways in intubated individuals (n = 3). These values are considerably lower than those reported for older children and adults. Body weight-related amounts of NO excretion, however, seem comparable between infants and adults.

Single Breath Analysis of Endogenous Nitric Oxide in the Newborn

Nitric oxide (NO) is found in the exhaled gas of humans immediately after birth. However, variations of endogenous NO concentration during the breathing cycle have not been studied in newborns. We examined 24 newborns without acute respiratory compromise during spontaneous nasal breathing. Gas was sampled from the tip of a thin nasal catheter placed in the hypopharynx. Endogenous NO concentrations measured by chemiluminescence were assigned to the breathing cycle using synchronized CO2 recording. Exhaled NO could reproducibly be measured at 1.9 ± 0.2 parts per billion (ppb, mean ± SEM). Autoinhaled nasal NO peaks during regular breathing were 12.0 ± 1.7 ppb and reached intermittent maxima of 52.2 ± 5.8 ppb. During regular breathing 6 infants exhibited sudden decreases of nasal NO peaks to periods with <50% amplitude suggesting transient shortage of autoinhaled nasal NO. We conclude that tidal NO analysis can be used to assess upper and lower airway NO production noninvasively during spontaneous breathing in the newborn.

Teratogenic effects in a case of maternal treatment for acute myelocytic leukaemia- neonatal and infantile course

Experience with the use of cytotoxic drugs in the first trimester of pregnancy is limited. We report on the clinical phenotype and infantile development of a girl born to a 36-year-old mother. Before recognition of pregnancy, the latter had been treated for acute myelocytic leukaemia receiving cytarabine, daunorubicin and doxorubicin at conception and cytarabine and thioguanine at about 35–37 days post conception. At delivery, there were severe brachycephaly, hypoplasia of the anterior cranial base and the midface as well as synostoses of both coronal and metopic sutures. Further findings included bilateral four-finger hands with hypoplastic thumbs and absent radii. This phenotype is reminiscent of the Baller-Gerold syndrome. The child, at present 15 months old, has had to undergo two operations for fronto-orbital advancement because of insufficient growth of the mid-face, nasal airway hypoplasia and increased intracranial pressure. Motor milestones are slightly retarded—neurodevelopment is otherwise normal. These findings are discussed in the context of the few previous reports and are particularly important for future genetic counselling.

EXHALED NITRIC OXIDE INCREASES DURING HIGH FREQUENCY OSCILLATORY VENTILATION IN RABBITS

This study compared the effects of high frequency oscillatory ventilation (HFOV) and intermittent mandatory ventilation (IMV) on the homeostasis of nitric oxide (NO) in the lower respiratory tract of healthy rabbits. The mechanisms underlying a putative stretch response of NO formation in the airways were further elucidated. Male New Zealand White rabbits were anaesthetized, tracheotomized and ventilated with IMV or HFOV in random order. Total NO excretion increased from 9·6 ± 0·8 nl min−1 (mean ±s.e.m.) during IMV to 22·6 ± 2·7 nl min−1 during HFOV (P < 0·001). This increase was not explained by changes of functional residual capacity (ΔFRC). A similar increase in NO excretion during HFOV was seen in isolated buffer‐perfused lungs under constant circulatory conditions (P < 0·05, n= 4). Intratracheal mean CO2 and NO concentrations, measured at 2·5, 5, 7·5 and 10 cm below tracheostomy, increased significantly with increasing distance into the lung during both IMV and HFOV (P < 0·001 for each comparison). At every intratracheal location of the sampling catheter, particularly low in the airways, both CO2 and NO concentrations were significantly higher during HFOV than during IMV (P < 0·01 for each comparison). We conclude that HFOV increases pulmonary NO production in healthy rabbits. Increased stretch activation of the respiratory system during HFOV is suggested as a possible underlying mechanism. The increase in mean airway NO concentrations may have biological effects in the respiratory tract. Whether it can account for some of the benefits of HFOV treatment needs to be considered.

Common CFTR mutations are not likely to predispose to chronic bronchitis in northern Germany.

The frequency of six common mutations in the cystic fibrosis transmembrane conductance regulator gene was studied in 100 patients hospitalized with chronic bronchitis. Only one patient with chronic bronchitis and diffuse bronchiectasis was heterozygous for the common ΔF508 mutation. R553X, G542X, G551D, N1303K and 621+1G→T were not detected. This result is not significantly different from the frequency of cystic fibrosis carriers in Northern Europe. Predisposition of heterozygotes for chronic bronchitis is therefore unlikely.

Beta-adrenoceptor agonist stimulation of pulmonary nitric oxide production in the rabbit

Nitric oxide (NO) is continuously produced in the lung and is present in exhaled air. We examined the effect of β‐adrenoceptor stimulation on the production of pulmonary NO in rabbits. Exhaled NO was measured by chemiluminescence in anaesthetized and mechanically ventilated rabbits and in buffer‐perfused rabbit lungs. Intravenous infusions of adrenaline (0.1–10 μg kg−1  min−1) elicited dose‐dependent increases in exhaled NO. The increases in exhaled NO comprised an initial peak followed by a lower plateau level. The increase in exhaled NO was inhibited by propranolol (1 mg kg−1) but not by phentolamine (1 mg kg−1). Prenalterol, a β1‐adrenoceptor agonist, and terbutaline, a β2‐adrenoceptor agonist, also caused dose‐dependent increases in exhaled NO. However, prenalterol was >100 times more potent than terbutaline. Infusions of forskolin (0.01–0.03 μmol kg−1  min−1), an adenylate cyclase stimulator, elicited dose‐dependent decreases in blood pressure and concomitant increases in heart rate but caused no alterations in exhaled NO. Nimodipine, a L‐type calcium channel blocker, antagonized the increases in exhaled NO in response to prenalterol infusions. The increases in exhaled NO in response to adrenaline and prenalterol were also present in blood‐free, buffer perfused lungs during constant‐flow conditions. These results demonstrate that pulmonary nitric oxide production can be enhanced by β‐adrenoceptor stimulation. Furthermore, the results indicate that the β‐adrenergic stimulation of pulmonary NO production is not critically dependent on cyclic AMP formation but may require intact calcium‐channels.

Activation of sympathoadrenomedullary system increases pulmonary nitric oxide production in the rabbit.

Nitric oxide (NO) is continuously produced in the lung and can be measured in exhaled gas of different species. To investigate a possible neuro-humoral regulation of pulmonary NO production in vivo we injected veratrine, an activator of Na(+) channels known to activate the sympathoadrenal system, in anaesthetized, mechanically ventilated and laparotomized rabbits. Exhaled NO concentration increased by 38+/-3% when plasma adrenaline rose from 12.3+/-3.1 to 49.5+/-10.7 pmol ml(-1) in response to veratrine (500 microg kg(-1), i.v.). Pretreatment with atenolol, a beta(1)-adrenoceptor antagonist (1 mg kg(-1)), or bilateral ligation of adrenal blood vessels inhibited the increase in exhaled NO in response to veratrine. Atenolol also decreased basal NO, suggesting an endogenous regulation of pulmonary NO by adrenaline. Neither phentolamine (1 mg kg(-1)), atropine (1 mg kg(-1)) nor vagotomy inhibited the veratrine-induced pulmonary NO production. These results suggest a role of the sympathoadrenal system in the regulation of pulmonary NO production.

TERATOGENIC EFFECTS IN A CASE OF MATERNAL TREATMENT FOR ACUTE LYMPHOBLASTIC LEUKEMIA (ALL)

Acute lymphoblastic leukaemia (ALL) was diagnosed in a 36-year-old and treated with cytarabin, daunorubicin, doxorubicin and cytarabin, thioguanin, respectively, in an unrecognized pregnancy at conception and at about 35-37 days p.c., Amniocentesis at 16 weeks of gestation revealed a normal female karyotype.At delivery, brachycephaly, hypoplasia of supraorbital bony structures and hypotelorism were seen. Hypoplastic nasal root, bilateral choanal atresia and micrognathia caused hypoplasia of naso- and oropharynx. There was also bilateral aplasia of the radius and hypoplasia of the first ray of the hands. Internally, an atrial septal defect II could be demonstrated. The malformations detected are in accord with the timing of teratogenesis. Neurodevelopment is normal at the age of 8 months. Experience with the use of cytotoxic drugs in pregnancy has so far been limited to folate antagonists.