Pulmonary neuroepithelial bodies are polymodal airway sensors: evidence for CO2/H+ sensing.

Pulmonary neuroepithelial bodies (NEB) in mammalian lungs are thought to function as airway O2 sensors that release serotonin (5-HT) in response to hypoxia. Direct evidence that NEB cells also respond to airway hypercapnia/acidosis (CO2/H(+)) is presently lacking. We tested the effects of CO2/H(+) alone or in combination with hypoxia on 5-HT release from intact NEB cells in a neonatal hamster lung slice model. For the detection of 5-HT release we used carbon fiber amperometry. Fluorescence Ca(2+) imaging method was used to assess CO2/H(+)-evoked changes in intracellular Ca(2+). Exposure to 10 and 20% CO2 or pH 6.8-7.2 evoked significant release of 5-HT with a distinct rise in intracellular Ca(2+) in hamster NEBs. This secretory response was dependent on the voltage-gated entry of extracellular Ca(2+). Moreover, the combined effects of hypercapnia and hypoxia were additive. Critically, an inhibitor of carbonic anhydrase (CA), acetazolamide, suppressed CO2/H(+)-mediated 5-HT release. The expression of mRNAs for various CA isotypes, including CAII, was identified in NEB cells from human lung, and protein expression was confirmed by immunohistochemistry using a specific anti-CAII antibody on sections of human and hamster lung. Taken together our findings provide strong evidence for CO2/H(+) sensing by NEB cells and support their role as polymodal airway sensors with as yet to be defined functions under normal and disease conditions.

alpha1-Antitrypsin: the presence of excess mannose in the Z variant isolated from liver.

The Z variant of alpha1-antitrypsin was isolated by a new technique from the liver of a patient homozygous for the Z allele of the protease inhibitor locus. The material was homogenous and antigenically competent but had no protease inhibiting capacity. An interesting correlation was found between the subcellular localization and the carbohydrate composition of the Z variant from liver. Carbohydate analysis of this glycoprotein showed an absence of galactose and sialic acid, an appreciable decrease in N-acetylglucosamine, and an almost twofold increase in mannose residues. These data indicate a considerable slowdown in the processing of the oligosaccharides of liver Z variant. In spite of the absence of sialyl residues, the liver Z varant was microheterogeneous by analytical isoelectric focusing. The isoproteins of liver Z variant coincided with those of asialo M variant in the focusing field.

Massive hemoptysis in an 11-year-old girl with isolated pulmonary arteritis.

A 10-year-old girl developed recurrent bouts of massive hemoptysis over a 9-month period. No obvious bleeding source was detected. Her pulmonary angiogram showed a pulmonary aneurysm of the second branch of the left main pulmonary artery as well as widespread irregularities of the pulmonary arteries including areas of stenosis and pruning. Elective embolization of the aneurysm did not control hemoptysis and emergency left upper lobectomy had to be performed. Histology showed large artery wall injury with acute leucocytoclastic inflammation, fibrinoid necrosis, granulomatous inflammation, and ectasia of vessel wall. This combination of abnormalities has not been described to date and represents the first case of isolated pulmonary arteritis in children prior to puberty.

Oxygen sensing in neuroepithelial and adrenal chromaffin cells.

Oxygen sensing and initiation of appropriate physiological responses to hypoxia are crucial for survival. The molecular identity of the sensor has generally sparked considerable interest and controversy in O2-sensitive cells. In mammals, pulmonary neuroepithelial bodies (NEBs) and adrenal chromaffin cells (AMCs) are O2 sensitive, particularly during the transition from intrauterine to air-breathing life. In NEBs, there is good evidence that the O2 sensor is a plasma membrane-bound NADPH oxidase which during hypoxia, signals K+ channel inhibition, membrane depolarization and neurosecretion via changes in reactive oxygen species (ROS) (e.g. H2O2). Accordingly, hypoxic sensitivity is lost in NEBs from transgenic mice deficient in the gp91(phox) subunit of NADPH oxidase; it is, however, retained in neonatal AMCs from these transgenic mice. A search for the O2 sensor in neonatal rat AMCs suggests a role for the mitochondrial electron transport chain. For example, the complex I blocker, rotenone (1 microM), mimics hypoxia in causing K+ channel inhibition and ATP secretion, and occludes hypoxic sensitivity. The evidence is consistent with hypoxia and rotenone acting via a decrease in ROS. In contrast, the complex IV blocker cyanide (2 mM) did not mimic the effects of hypoxia. We propose thatchanges in ROS serve as a common link between the O2 sensor and secretion in perinatal NEBs and chromaffin cells. However, the subcellular localization of the O2 sensor appears to be different between these two cell types.

Assessment of the efficacy of in vivo CFTR protein replacement therapy in CF mice.

Cystic Fibrosis (CF) is caused by mutations in the CF gene that lead, for the most part, to mislocalization of the protein product, the cystic fibrosis transmembrane conductance regulatory (CFTR). CFTR is a chloride channel normally situated in the apical membrane of epithelial cells where it contributes to transepithelial ion transport. In this study we demonstrated the feasibility of in vivo transfer of purified CFTR protein via phospholipid liposomes into the apical membrane of nasal epithelia of CFTR knockout mice. Membrane incorporation of immunogold-labeled CFTR could be visualized by electron microscopy and correction of CF-related defects in ion transport measured by nasal potential difference (PD) measurements in about one-third of the animals treated. Although these initial results are promising, effectiveness of this therapeutic approach appears to be limited by the inefficient incorporation of CFTR into the apical epithelial cell membrane.

Localization of MOC-1 cell surface antigen in small-cell lung carcinoma cell lines: an immunohistochemical and immunoelectron microscopic study.

Expression of cell surface antigens of the neural cell adhesion molecule (N-CAM) class was recently shown to be shared by both fetal and neoplastic neuroendocrine cells, including those of the lung. We investigated the expression and localization of MOC-1 antigen on small-cell (neuroendocrine) lung carcinoma cell lines with immunohistochemical methods at the light (LM) and electron microscopy (EM) level and by Western blot. At LM level, using monoclonal antibody (MAb) MOC-1 with the ABC method and immunofluorescence, positive staining was observed on surfaces of cells from all tumor lines examined. Strongest immunostaining was found on cell surfaces of pulmonary small-cell carcinoma-derived cell line NCI-H69 with the majority of cells showing positive staining. An adherent variant of NCI-H69 cell line, H69V, exhibited positive staining in about 60% of cells, whereas only occasional cells of NCI-H727 cell line derived from pulmonary carcinoid tumor were positive for MOC-1 antigen. Western blot analysis confirmed these findings, showing a strong MOC-1-specific band in cell extracts of NCI-H69, with weaker band densities for H69V and NCI-H727. Immunoelectron microscopy (IEM) revealed that MOC-1 was not uniformly distributed on the outer surface of plasma membrane; immunogold particles appeared concentrated in areas of thick cell surface "fuzz" coating, surface microvilli, and in areas of cell-cell contact. In some cells, areas of plasma membrane invaginations and a few intracytoplasmic vesicles were also labeled, suggesting endocytosis. Surface labeling for SEM confirmed the finding of more dense labeling over the microvilli, cell membrane folds, and in areas of cell-cell contact. The cell lines derived from pulmonary neuroendocrine cell tumors can provide a useful model to study the role and function of neural adhesion molecules in pulmonary neoplasia and during lung development.

Membranoproliferative glomerulonephritis in childhood cirrhosis associated with alpha1-antitrypsin deficiency.

Three alpha1-antitrypsin (alpha1AT) deficient, protease inhibitor type ZZ children who died from cirrhosis and its complications had membranoproliferative glomerulonephritis at postmortem examination. During life, all three had clinical and laboratory evidence of renal disease which became apparent when hepatic decompensation developed. Immunofluorescence studies and electron microscopy performed in one patient revealed subendothelial deposits of alpha1AT, complement, and immune globulins along the glomerular basement membrane. The pathogenesis of these renal lesions is speculative. Glomerular lesions were not observed in kidney sections of 16 children who died from cirrhosis but who were not alpha1AT-deficient. The present study suggests that renal involvement may be yet another manifestation of disease associated with alpha1AT deficiency.

Ultrastructure of carotid bodies in sudden infant death syndrome.

Recent studies have implicated an abnormality in carotid body structure and function in the pathogenesis of sudden infant death syndrome (SIDS). In the present investigation, the light and electron microscopic findings in carotid bodies from ten victims of SIDS were compared with those in six control infants and five infants dying of congenital heart disease. The cross-sectional area of carotid body chemoreceptor cells and the frequency, distribution, and size of neurosecretory granules were assessed morphometrically. The area of carotid body occupied by chemoreceptor cells (the functional area) was comparable in SIDS victims, control infants, and infants with congenital heart disease. By electron microscopy, the carotid body chief cells from all groups contained numerous electron-dense neurosecretory granules. Distribution, frequency, and size of neurosecretory granules in SIDS victims and control infants did not differ significantly. Morphology of carotid bodies from SIDS victims was found to be normal. The presence of neurosecretory granules in chemoreceptor cells of SIDS victims suggests that the cellular mechanism of neurotransmitter synthesis and storage is not altered.

Campylobacter pyloridis-associated primary gastritis in children.

Campylobacter pyloridis are spiral-shaped Gram-negative bacteria that have recently been associated with gastritis and peptic ulcer diseases in adults. The organisms have been identified in biopsy specimens of the gastric antrum by staining sections with silver stain. To determine the frequency of colonization of the antral mucosa with C pyloridis in association with gastritis in childhood, we retrospectively reviewed 53 cases in patients (mean age 11.9 years) in whom upper endoscopy with antral biopsy was performed for the evaluation of symptoms referable to the upper gastrointestinal tract. A silver impregnation method was used to detect the presence of C pyloridis. Nineteen of 53 antral biopsy specimens showed evidence of mucosal inflammation. Ten of these 19 patients had no apparent predisposing etiology for gastritis, and six of these ten had C pyloridis identified on antral biopsies. Nine of the 19 patients had secondary causes of gastric inflammation (two gastroduodenal Crohn disease, two eosinophilic gastroenteritis, four drug related, and one dys-gamma-globulinemia and lymphonodular hyperplasia). In contrast, none of these nine patients had C pyloridis demonstrated on antral biopsies. Silver stain for C pyloridis was negative in all 34 of the 53 children who had normal antral histologic findings. C pyloridis was not demonstrated by silver stain on any of the duodenal sections, although eight of the 19 children with gastritis and nine of the 34 children with normal antral histologic findings had histologic evidence of duodenal inflammation. We conclude that C pyloridis is associated with primary antral gastritis but not with secondary gastritis in the pediatric population.

Maternal smoking and pulmonary neuroendocrine cells in sudden infant death syndrome.

BACKGROUND: Maternal smoking is a well-recognized risk factor for sudden infant death syndrome (SIDS), but the precise mechanism is unknown. We tested a hypothesis that maternal smoking affects pulmonary neuroendocrine cells (PNECs) and neuroepithelial bodies (NEBs), which are innervated PNEC clusters and presumed airway chemoreceptors. METHODS: Lung sections from infants who died of SIDS and whose mothers smoked during pregnancy (n = 22), infants who died of SIDS and whose mothers were nonsmokers (n = 17), and age-matched control infants (n = 15) who died of other causes were immunostained for bombesin (a PNEC and NEB marker) and assessed morphometrically. RESULTS: The frequency of PNEC (the percentage of airway epithelium immunoreactive for bombesin) was increased up to twofold in the lungs of infants who died of SIDS (7.7 +/- 0.4%) compared with controls (4.9 +/- 0.4%), as was the frequency (40 +/- 3.5 vs 23 +/- 3.7/cm2) and size (748 +/- 46.5 vs 491 +/- 25.8 microns2) of NEBs. In infants who died of SIDS and who were born to smoking mothers, PNEC frequency was increased significantly compared with that in those born to nonsmoking mothers, but the frequency and size of NEBs were not significantly different between the two groups. CONCLUSION: Our findings suggest that maternal smoking potentiates hyperplasia of the PNEC system in the lungs of infants who die of SIDS and that a dysfunction of these cells may contribute to the pathophysiology of SIDS.

Hyperplasia of pulmonary neuroendocrine cells in a case of childhood pulmonary emphysema.

Pulmonary emphysema is very uncommon in children in the first decade of life. The few cases documented in the literature were all due to alpha1-antitrypsin deficiency. We present the case of a 6-year-old white boy with chronic cough and dyspnea on exertion. Lung biopsy showed panacinar type emphysema with patent airways and diffuse hyperplasia of pulmonary neuroendocrine cells revealed after immunostaining for bombesin, a peptide produced by these cells. We speculate that idiopathic diffuse hyperplasia of bombesin-producing pulmonary neuroendocrine cells may contribute to the pathogenesis of unusual COPD in childhood.

Occult pulmonary abnormalities in asymptomatic asthmatic children.

The pulmonary status of 178 asymptomatic asthmatic children with normal time-volume spirograms was further evaluated using flow-volume loops, body plethysmographic studies, and blood gas tensions in arterialized capillary blood. Residual volume (RV) was abnormal in 26%, total lung capacity (TLC) in 33%, RV/TLC% in 41%, and arterial oxygen pressure in 23% of them. All values for expiratory flow measured relative to observed vital capacity (VC), (ie, the forced expiratory volume in one second [FEV1], the mean forced expiratory flow during the middle half of the forced vital capacity [FEF25-75%; FVC], FEV1/VC, and the instantaneous forced expiratory flow after 75% and after 50% of the FVC has been exhaled) were normal, and VC was subnormal in only five instances, but flow rates measured relative to TLC were abnormal in 26% of the patients. Some abnormality of pulmonary function was present in all but 13% of these asymptomatic children. Reliance upon conventional evaluation of pulmonary function by forced expiratory spirograms and freedom from wheezing may frequently give the clinician a false impression of the true conditon of the lungs of the asthmatic child.

Metered-dose inhaler salbutamol-induced tracheal epithelial lesions in intubated rabbits. Effects of the site of administration and time.

STUDY OBJECTIVES: To determine (1) whether metered-dose inhaler (MDI) salbutamol administered at the elbow connector of the anesthetic circuit produced tracheal epithelial lesions in intubated rabbits, and (2) the time course for resolution of tracheal lesions produced by MDI salbutamol through an intratracheal catheter. DESIGN: Prospective, randomized, controlled trial. SETTING: University-affiliated animal research laboratory. PARTICIPANTS: Thirty-nine adult New Zealand white rabbits. INTERVENTIONS: (1) Twenty-one intubated rabbits received 0,5, or 20 puffs of MDI salbutamol delivered at the elbow connector of the anesthetic circuit. (2) Eighteen intubated rabbits received five puffs of MDI salbutamol through an intratracheal catheter and were killed 1 h, 24 h, or 1 week later. MEASUREMENTS: Samples of trachea, bronchi, and lungs were examined by light microscopy, and the degree of epithelial injury was assessed semiquantitatively. RESULTS: MDI salbutamol (5 or 20 puffs) administered at the elbow did not induce tracheal epithelial injury. When administered through an intratracheal catheter, MDI salbutamol (five puffs) produced moderate or severe tracheal epithelial injury in those killed 1 h after the study. Evidence of epithelial regeneration was observed 24 h after the injury and recovery was virtually complete by 1 week. CONCLUSION: Epithelial lesions do not occur when the MDI salbutamol (5 or 20 puffs) is administered at the elbow connector of the ventilation circuit. Tracheal epithelial lesions produced by MDI salbutamol (five puffs) administered through an intratracheal catheter resolve within 1 week of the injury.

Rapid reperfusion causes stress failure in ischemic rat lungs.

OBJECTIVE: Rapid reperfusion may be injurious to the ischemic lung. Our aim was to confirm that slow reperfusion improves postischemic pulmonary function and to elucidate the ultrastructural changes associated with slow versus rapid reperfusion. METHODS. We used an ex vivo perfused rat lung transplant model to study the effect of slow versus rapid reperfusion on subsequent lung function and morphologic conditional. Functional assessment was performed in (1) fresh lung, slowly reperfused; (2) fresh lung, rapidly reperfused; (3) ischemic lung (4 hours at 22 degrees C), slowly reperfused; and (4) ischemic lung, rapidly reperfused. RESULTS: In group 4, the shunt fraction (P=.001), airway pressure (P=.001), and wet/dry ratio (P=.01) were significantly higher than in groups 1 through 3. Light and electron microscopy of slowly reperfused ischemic lungs (n=4) appeared normal. Rapidly reperfused ischemic lungs (n=4) demonstrated massive alveolar edema hemorrhage, and epithelial "blebbing" by light microscopy. Electron microscopy identified the blebbing as separation of the epithelial layer from an intact basement membrane by edema fluid. The epithelial layer was disrupted in numerous locations. Complete disruption of all layers of the blood-gas barrier was occasionally present. CONCLUSION: Rapid reperfusion of the ischemic lung is an important contributing factor to reperfusion lung injury resulting in mechanical stress failure of the alveolar/capillary barrier. Gradual reintroduction of blood flow to the ischemic lung improves oxygenation.

Esophagatis and perinatal cytomegalovirus infection.

A 6-week-old male infant presented to hospital with a large upper gastrointestinal hemorrhage. Endoscopic biopsies of his esophagus and duodenum showed cytomegalovirus (CMV) inclusions and CMV early antigen was detected by immunohistochemistry. There were no other signs of congenital CMV infection. This case adds to the clinical spectrum of perinatal CMV infection and may be more common than is currently recognized.

Histological improvement with lamivudine therapy for de novo hepatitis B occurring in an anti-HBs-positive child after bone marrow transplantation.

We describe a 14-year-old bone marrow transplant recipient who was anti-HBs-positive before the procedure and afterwards developed acute infection with hepatitis B virus (HBV). Liver biopsies taken while symptomatic showed portal fibrosis progressing to cirrhosis. The patient responded to lamivudine treatment with HBeAg seroconversion and significant regression of fibrosis. Although the source and timing of HBV exposure remain unclear, the potential for severe hepatitis B infection following bone marrow transplant warrants caution. This case demonstrates that a symptomatic HBV infection can occur in an immunocompromised patient who had originally been anti-HBs-positive.

Association of gastric metaplasia and duodenitis with Helicobacter pylori infection in children.

Helicobacter pylori infection causes chronic-active gastritis and is associated with peptic ulceration. However, the link between gastric H pylori colonization and duodenal ulcers is not well understood. Therefore, a retrospective, case-controlled study was conducted to determine whether H pylori infection is associated with gastric metaplasia and mucosal inflammation in the duodenum. Biopsy specimens from the duodenal bulb were obtained from 31 of 47 children with H pylori-induced gastritis. Two control groups, matched for age and sex, consisted of 33 children with normal antral histologic evaluation and 33 with H pylori-negative gastritis. Coded duodenal sections were stained with periodic acid-Schiff, hematoxylin-eosin, and silver to examine for gastric metaplasia, mucosal inflammation, and Helicobacter-like organisms, respectively. Thirteen of 31 (42%) H pylori-infected children had gastric metaplasia, in contrast to 1 of 33 with normal histologic characteristics (P < .0001) and 2 of 33 with H pylori-negative gastritis (P < .001). H pylori was detected overlying ectopic gastric mucosa in only 2 of 13 cases. Duodenal ulcers were identified endoscopically in 10 of 13 children with gastric metaplasia and 9 of 18 H pylori-infected subjects without metaplasia (P = NS). Twenty-four of 31 (77%) children with H pylori gastritis had duodenitis compared with 4 of 33 (12%) with H pylori-negative gastritis (P < .001) and 2 of 33 (6%) with a normal antrum (P < .001). Duodenitis was present in 14 of 19 children with H pylori infection and duodenal ulcers and 10 of 12 infected patients without mucosal ulceration (P not significant). These findings demonstrate a higher frequency of both gastric metaplasia and mucosal inflammation in the proximal small intestine of H pylori-infected children. However, there was a lack of correlation between the presence of duodenal ulceration and both gastric metaplasia and duodenitis.

Immunocytochemical localization on O2-sensing protein (NADPH oxidase) in chemoreceptor cells.

A potential candidate for an oxygen-sensing protein in chemoreceptor cells is a heme-linked multicomponent NADPH oxidase, originally described in neutrophils. The postulated function for the oxidase in chemoreceptor cells is to signal changes in oxygen levels (either in the blood or in the airway lumen) via changes in oxygen metabolite production. An alteration in either superoxide (or dismuted hydrogen peroxide) production may affect the gating properties of the O2-sensitive K+ channels. We have previously reported immunohistochemical localization of gp91 glycoprotein component of the oxidase to the plasma membrane of pulmonary neuroepithelial body (NEB) cells. In this study we have investigated the immunocytochemical localization of the other polypeptide components of the oxidase in NEB cells and in the glomus cells of the carotid body. Cultures of dissociated fetal rabbit NEB cells and newborn rat glomus cells were immunostained with specific antibodies recognizing the various polypeptide subunits of the oxidase using indirect immunofluorescence methods. Immunostaining with the anti-oxidase antibodies reveal strong positive reaction in both NEB and glomus cell clusters while other cells were unstained. The positive reaction product was localized to the plasma membrane and/or cytoplasm and no nuclear staining was observed. Live cell labelling studies with anti-p22 antibody showed positive immunofluorescence on the surface of NEB cells, suggesting that this component of the oxidase is also associated with the plasma membrane. In glomus cells, similar strongly positive immunofluorescence signal was observed for p22 and gp91 in paraformaldehyde-fixed cultures, regardless whether they were permeabilized or not. Taken together, our findings of cell surface localization of gp91 and p22 components of the oxidase in chemoreceptive cells suggests that the heme-linked cytochrome b558 component is associated with the plasma membrane. This association allows for direct interaction with the O2-sensitive K+ channel thus forming the molecular complex of membrane bound O2 sensor.

Effect of granulocyte depletion in a ventilated surfactant-depleted lung.

In a previous paper Cutz, Bryan et al. showed that in rabbits after repetitive lung lavage high-frequency oscillatory ventilation maintained excellent gas exchange and did not cause hyaline membrane formation (J. Appl. Physiol. 55: 131-138, 1983). In contrast, conventional mechanical ventilation had poor gas exchange and extensive hyaline membrane formation and we attributed these differences to mechanical barotrauma. However, we completely overlooked the large number of granulocytes in the damaged lung. To investigate this using the same model we have used mechanical ventilation on two groups of rabbits, one with normal granulocytes, the other depleted of granulocytes by pretreatment with nitrogen mustard. The nondepleted rabbits had poor gas exchange, a substantial protein leak into the lung and extensive hyaline membranes. The depleted animals had good gas exchange, a very small protein leak and no hyaline membranes. Repletion of granulocytes from donor rabbits lead to poor gas exchange and hyaline membrane formation. It is concluded that lung lavage causes prompt margination of granulocytes which become activated by the ongoing epithelial barotrauma of conventional ventilation.

Raffinose improves 24-hour lung preservation in low potassium dextran glucose solution: a histologic and ultrastructural analysis.

BACKGROUND: We have previously shown that the addition of raffinose to low potassium dextran (LPD) preservation solution improves transplanted rat lung function after 24 hours of storage. The mechanisms by which raffinose acts are unclear. The aim of this study was to examine the histologic and ultrastructural correlates of this enhanced pulmonary function after preservation with raffinose. METHODS: In a randomized, blinded study, rat lungs were flushed with LPD, or LPD containing 30 mmol/L of raffinose, and stored for 24 hours at 4 degrees C. Control lungs were flushed with LPD but not stored (n = 5 each group). Changes in postpreservation edema were determined. In addition, lungs were flushed with a trypan blue solution to quantify cell death, and examined using both light and electron microscopy. RESULTS: The LPD lungs gained significantly more weight (25.5%+/-5.5%) compared with raffinose-LPD lungs (5.2%+/-5.3%; p < 0.0001). There were higher percentages of dead cells in the LPD lungs (29%+/-0.3% of total cells) compared with raffinose-LPD lungs (14%+/-1.4%; p < 0.001) and control lungs (0.2%+/-5%; p < 0.001). Control lungs maintained normal ultrastructure, whereas LPD lungs showed a decreased number of intact type II pneumocytes and significant cellular necrosis. Interstitial and alveolar edema with interstitial macrophage infiltration was also observed. Alveolar capillaries were collapsed. In contrast, raffinose-LPD lungs showed only mild alterations such as minimal interstitial edematous expansion, fewer damaged cells, and minimal capillary injury. CONCLUSIONS: Raffinose exerts a cytoprotective effect on pulmonary grafts during preservation, which explains the previously documented improved function. This simple modification of LPD with raffinose may provide clinical benefit in extended pulmonary preservation.