We studied lung development in children with or without bronchopulmonary dysplasia (BPD) using light microscopic morphometry and thick lung sections stained for elastic fibers. One lung was obtained at autopsy from each of eight patients with BPD (ages, 2 to 28 months) and six children (ages, 5 days to 51 months) who died without lung disease. Patients with BPD demonstrated severe somatic growth retardation and had reduced lung volumes with abnormal lobar volume proportions. In the central bronchi mean volume proportion of glands and smooth muscle was increased in BPD. Bronchiolar density was also increased, but it tended to normalize with advancing age. Mean bronchiolar diameter was slightly smaller in BPD, and bronchiolar smooth muscle hypertrophy was a constant histologic feature. The most striking change, however, was noted in alveolar structure and development. Total alveolar number was severely decreased in patients with BPD compared with that in control subjects, and there was little evidence of compensatory alveolar development with increasing age. Lung internal surface area was correspondingly reduced, and mean linear intercept was increased. Sections stained for elastic tissue demonstrated in the patients with BPD a simplified acinar structure with thickened, tortuous, and irregularly distributed alveolar elastic fibers. We conclude that in severe, fatal BPD there is marked impairment of lung development with alveolar hypoplasia and reduced internal surface area. In addition, bronchial and bronchiolar smooth muscle hypertrophy and bronchial gland hyperplasia may be important contributing factors to airflow limitation.

In the rat lung, primary saccules are transformed into alveoli from postnatal Days 4 to 13, after which time there is a 20% reduction in the number of lung fibroblasts as the interstitial volume of the alveolar walls decreases. Our objective was to determine whether apoptosis is a factor in the observed decrease in the number of interstitial lung fibroblasts beyond Day 13. We used both histologic and flow cytometric assays to detect in lung fibroblasts the DNA fragmentation and condensation that are characteristic of apoptosis. In addition, we evaluated levels of bcl-2 and BAX messenger RNAs (mRNAs) using a reverse transcriptase-polymerase chain reaction (RT-PCR) assay. Apoptotic cells were quantitated in glycol methacrylate-embedded sections of neonatal rat lungs using the terminal transferase dUTP-digoxygenin nick end-labeling (TUNEL) method. Although TUNEL-positive interstitial cells were observed in the lungs of rats ranging in age from 10 to 16 d, a dramatic increase in apoptotic cells was seen on Day 17. Although diminished in number, TUNEL-positive cells were still present on Day 28. Hoechst-stained apoptotic bodies were observed in isolated lung cells that were vimentin-positive and factor VIII-negative, which identified the apoptotic cells as fibroblasts as opposed to endothelial cells. Flow cytometric analysis of freshly isolated lung fibroblasts stained with Hoechst 33342 indicated a 24% increase in chromatin condensation in cells from 17-d versus 16-d rats. DNA fragmentation was also quantitated by flow cytometry in freshly isolated fibroblasts labeled with BODIPY-conjugated dUTP in the presence of terminal deoxynucleotidyl transferase. The percentage of lung fibroblasts containing fragmented DNA was 51.4 +/- 13.4 in 17-d, 36.9 +/- 8.6 in 18-d, and 13.8 +/- 5.4 in 19-d rat pups. Finally, evaluation by RT-PCR indicated that on postnatal Day 17, mRNA for bcl-2, which inhibits apoptosis, was decreased to 73.5 +/- 11.4% (P < 0.001) of Day 5 controls; whereas mRNA for BAX, which enhances apoptosis, was increased to 243.0 +/- 102.0% (P < 0.001) of Day 5 values. These results demonstrate that rat lung fibroblasts undergo apoptosis after the completion of alveolarization, and suggest that this decrease in fibroblast number plays an important role in the thinning and remodeling of the alveolar walls of the lung.

We have developed a model that predicts the distribution of carbon monoxide (CO) in the body resulting from acute inhalation exposures to CO. The model includes a lung compartment, arterial and venous blood compartments, and muscle and nonmuscle soft tissues with both vascular and nonvascular subcompartments. In the model, CO is allowed to diffuse between the vascular and nonvascular subcompartments of the tissues and to combine with myoglobin in the nonvascular subcompartment of muscle tissue. The oxyhemoglobin dissociation curve is represented by a modified Hill equation whose parameters are functions of the carboxyhemoglobin (HbCO) level. Values for skeletal muscle mass and cardiac output are calculated from prediction formulas based on age, weight, and height of individual subjects. We demonstrate that the model fits data from CO rebreathing studies when diffusion of CO into the muscle compartment is considered. The model also fits responses of HbCO to single or multiple exposures to CO lasting for a few minutes each. In addition, the model reproduces reported differences between arterial and venous HbCO levels and replicates predictions from the Coburn-Forster-Kane equation for CO exposures of a 1- to 83-h duration. In contrast to approaches based on the Coburn-Forster-Kane equation, the present model predicts uptake and distribution of CO in both vascular and tissue compartments during inhalation of either constant or variable levels of CO.

The regularity of EEG signals was compared between middle-aged (47.2 ± 2.0 yrs) and elderly (78.4 ± 3.8 yrs) female subjects in Wake (W), NREM stages 2 and 3 (S2, S3), and REM. Signals from C3A2 leads of healthy normal subjects, acquired from polysomnograms obtained from the Sleep Heart Health Study, were analyzed using both Sample Entropy (SaEn) and power spectral analysis (delta, theta, alpha, and beta frequency band powers). SaEn changed systematically and significantly (p<0.001) with sleep state in both age groups, following the relationships W > REM > S2 > S3. SaEn was found to be negatively correlated with delta power and positively correlated with beta power. Small changes in SaEn appear to reflect changes in spectral content rather than changes in regularity of the signal. A better predictor of SaEn than the frequency band powers was the logarithm of the power ratio (alpha+beta)/(delta+theta). Thus, SaEn appears to reflect the balance between sleeppromoting and alertness-promoting mechanisms. SaEn of the elderly was larger than that of middleaged subjects in S2 (p=0.029) and REM (p=0.001), suggesting that cortical state is shifted towards alertness in elderly subjects in these sleep states compared to middle-aged. Keywords elderly; polysomnography A. IntroductionAging is associated with major changes in the quality and structure of sleep. Sleep efficiency is reduced in older subjects and the percent of time spent in restorative slow wave sleep (SWS) decreases markedly [Dijk, et al., 2001]. The incidence of sleep fragmentation and the frequency of arousals and awakenings also increase significantly with age [Boselli, et al., 1998;Klerman, et al., 2004;Bonnet and Arand, 2007]. Analyses of EEG signals document these changes but have provided limited insight regarding the neurophysiological mechanisms underlying them. Although there are shifts in the power spectrum of the EEG with increasing age in both wakefulness and sleep, the mechanisms responsible for these changes and their relationship to changes in the quality and structure of sleep are poorly understood [Dustman et al., 1985;Giaquinto and Nolfe, 1986;Dijk et al., 1989;Veldhuizen et al., 1993; Larson et al., 1995;Mourtazaev et al., 1995;Shigeta et al., 1995;Carrier et al., 2001;Feinberg and Campbell, 2003;Mann and Roschke, 2004]. On the one hand, such changes may reflect age-related alterations in functional connections among cortical and subcortical neuronal networks that determine sleep state or in the functional and physical properties of these neural circuits. On the other hand, such differences may represent alterations in modulating inputs to brainstem or thalamocortical circuits related to extrinsic factors such as the greater incidence of sleepdisordered breathing and of joint pain in elderly subjects.To further probe the EEG for aging-related differences that might not be apparent from the power spectrum, various measures which reflect the temporal "regularity" of a signal have been investigated [Roschke et al. 1993;Roschke et al. 19...

Airway smooth muscle (ASM) cell hyperplasia is a common finding in lung diseases in which increased transpulmonary pressure is necessary for adequate ventilation. The extent to which mechanical deformation of ASM cells contributes to the observed hyperplastic changes has not been addressed. To determine if cyclic stretch alters ASM cell proliferation and protein content in vitro, canine ASM cells were cultured on collagen-coated silastic membranes, subjected to a stretch-relaxation regimen, and compared with cultured cells on a rocking platform or with control (unmanipulated) cells. During the log phase of cell growth, cyclic stretch resulted in increased cell numbers (P < 0.001). Incorporation of [3H]thymidine ([3H]TdR) was assessed after 5 or 14 days in culture during 12-h pulse in stretched, rocked, and control cells. Incorporation of [3H]TdR per cell was elevated in stretched cells when compared with either rocked or control cells at 5 days but not 14 days. Total cellular protein content per well determined after cells had reached confluence was greater in stretched cells than in the controls (74.2 +/- 7.9 stretched versus 49.1 +/- 5.6 control versus 51.1 +/- 6.5 rocker; microgram/10(5) cells; P < 0.05). Transmission electron microscopic observations of stretched cells suggested increased concentrations of myofilaments compared with control cells. These observations suggest that stretch may contribute to increased ASM hyperplasia and airway resistance.

Prolonged hyperoxic exposure is associated with impaired alveolarization of the lung in both the rat and the human neonate. Elastin is currently thought to play a pivotal role in the alveolarization of the lung by providing the structural framework around which new alveoli will develop. Previous studies in both the rat and the human neonate have demonstrated a risk for proteolytic destruction of lung elastin associated with prolonged hyperoxic exposure. The present study was undertaken to determine whether continuous exposure to 100% oxygen during the period of alveolar development in the rat (Days 4 to 13) would alter lung elastin. Parenchymal lung elastic fiber length, volume density of parenchyma, mean linear intercept, and internal surface area were quantitated using morphometric techniques, and the values were compared in control, oxygen-exposed, and malnourished rat pups. Stereologic measurements indicated that total elastic fiber length was significantly greater in lungs of control pups than in lungs of either the oxygen-exposed or the malnourished pups. Examination of sections of lung tissue 20 to 30 microns thick indicated altered elastic fiber structure and numerous alveolar fenestrae only in the hyperoxic pups. The results of these studies demonstrated that hyperoxic exposure during alveolarization alters both total length and structure of lung elastic fibers and suggest that impaired lung development might be due in part to these observed changes.

ABSTRACT. Because increased complement receptor expression is necessary for optimal function of adult neutrophils, we tested the hypothesis that the increased susceptibility of neonates to infection might be due to an impaired ability of neonatal neutrophils to increase expression of complement receptors in response to chemotactic stimuli. We used monoclonal antibodies and flow cytometry to compare surface expression of the receptors for the complement components C3b (CR1) and C3bi (CR3) on adult and neonatal cord blood neutrophils (PMNs). We also compared receptor expression on PMNs from infants delivered by cesarean section without labor versus infants delivered vaginally. Expression of both CR1 and CR3 was minimal on resting adult and neonatal PMNs maintained at 0" G. There was a modest increase in expression of both receptors when PMNs were warmed to 37" C. This increase was similar on adult and neonatal cells, both unfractionated in whole blood and after isolation with Percoll density centrifugation, with one exception. Expression of CR1 was greater on isolated PMNs from vaginally delivered infants versus adults when the cells were warmed to 37" C. This difference was not observed with cells from infants delivered by cesarean section without labor, suggesting this modest increase in receptor expression may be due to factors associated with labor. When isolated cells were stimulated with either N-formyl-methionyl-leucyl-phenylalanine or zymosan-activated serum, expression of CR1 increased to the same extent in both neonatal and adult PMNs. In contrast, maximal CR3 expression on cord PMNs stimulated with N-formyl-methionyl-leucyl-phenylalanine or zymosan-activated serum was only 75% of the adult values. This was significantly less than CR3 expression in adult PMNs across a broad range of N-formylmethionyl-leucyl-phenylalanine concentrations. Maximal stimulated expression of both receptors was the same in PMNs from infants delivered by cesarean section without labor and from infants delivered vaginally. The diminished CR3 expression on cord PMNs was not due to decreased responsiveness to N-formyl-methionyl-leucyl-phenylalanine per se since deficient CR3 expression was observed at all concentrations tested and also when zymosan-activated serum was the stimulus. Our observations of impaired expression of CR3, which is necessary for adherence and directed migration, may explain some of the impairment of these functions in neonatal neutrophils. (Pediatr Res 21: 306-311,1987)

All trans-retinoic acid (RA) enhances alveolarization in neonates and reinitiates alveolarization in emphysematous adult rat lungs, suggesting that RA may stimulate cell proliferation by upregulating growth factor ligand and/or receptor expression either indirectly or directly by acting on RA-responsive genes encoding growth factors. We report that RA and 1,25-dihydroxyvitamin D(3) (Vit D), alone and in combination, significantly increase [(3)H]thymidine incorporation in cultured fetal and postnatal rat lung fibroblasts (P < 0.05). The greatest increase (11-fold) was seen in 4-day cells treated with the two agents in combination (P < 0.0001). [(3)H]thymidine incorporation was age dependent. The greatest response to RA occurred in 4-day fibroblasts (P < 0.01), whereas the response to Vit D was greatest in embryonic day 20 fibroblasts (P < 0.001). Neutralizing antibody to platelet-derived growth factor (PDGF)-AB decreased [(3)H]thymidine incorporation in response to RA alone or in combination with Vit D, indicating a role for PDGF. Expression of mRNAs for PDGF-A and PDGF receptor (PDGFR)-alpha and -beta was upregulated at the transcriptional level in an age- and treatment-dependent manner. Thus exogenous RA may influence alveolarization by stimulating fibroblast proliferation through a PDGF-mediated autocrine mechanism, which is enhanced when RA and Vit D are administered in combination.