O. Douglas Wangensteen

Gas exchange by a bird's embryo

Abstract Current knowledge about the mechanism of chick embryo gas exchange is outlined. The overall gas exchange pathway between ambient air and chorioallantoic capillary blood is divided into two components and each are discussed separately. The first component, comprised of the shell and outer shell membrane, separates ambient air and air cell gas. Equations are given for transport of O 2 , CO 2 and water vapor across this barrier. Evidence is presented which shows that transport of these gases is by diffusion. This means that the relationship between the embryos metabolic rate and the permeability of the shell is important in determining the P O 2 and P CO 2 the air cell. The second component, comprised of the inner shell membrane and a thin tissue layer, separates air cell gas and allantoic capillary blood. Little is known about transport across this barrier. Separate measurements of air cell and allantoic venous blood P O O2 and P CO 2 , for the same age embryo, are compared. These data indicate that O 2 transport by this barrier is inefficient but CO 2 is transported readily. Possible explanations for these observations are briefly discussed.

Psychological and physiological predictors of response to carbon dioxide challenge in individuals with panic disorder

Past studies in nonclinical samples have found that suffocation fear, but not a behavioral index of carbon dioxide (CO2) sensitivity (i.e., breath-holding duration), predicts anxious response to CO2 challenge. These associations were examined in individuals with panic disorder while adding more sensitive indices of CO2 sensitivity. Consistent with the earlier studies, the authors found that suffocation fear predicted anxious responding to CO2 challenge but breath-holding duration did not. However, highly precise measures of CO2 sensitivity, not included in earlier studies, did predict anxious challenge responding. These findings support the predictive value and possible etiological relevance of both specific psychological variables and physiological CO2 sensitivity in panic vulnerability. Further work is still needed to determine whether the findings are specific to panic disorder.

Hyperoxic effects on alveolar sodium resorption and lung Na-K-ATPase

Active Na+ transport by the alveolar epithelium keeps alveoli relatively dry. Hyperoxia increases epithelial permeability, resulting in pulmonary edema. We sought to determine whether active Na+ resorption from the air spaces and Na-K-ATPase activity increased in rats exposed to > 95% O2 for 60 h. The permeability x surface area products for unidirectional resorption of alveolar [14C]sucrose (PSsucrose) and 22Na+ (PSNa+) were measured in isolated, perfused rat lungs immediately after hyperoxia and after 3 and 7 days of recovery in room air. At 60 h of hyperoxia, the mean PSsucrose and PSNa+ increased from 6.71 +/- 0.8 x 10(-5) to 12.6 +/- 1.6 x 10(-5) cm3/s (P = 0.029) and from 23.6 +/- 1.1 x 10(-5) to 31.0 +/- 1.6 x 10(-5) cm3/s (P < 0.008), respectively. However, the values in individual rats ranged widely from no change to nearly a fourfold increase. Subgroup analysis revealed that benzamil- or amiloride-sensitive (transcellular) PSNa+ was significantly reduced in the exposed lungs with normal PSsucrose but was maintained in the lungs with high PSsucrose. By day 3 of recovery, mean Na+ and sucrose fluxes returned to values similar to control. Na-K-ATPase membrane hydrolytic maximal velocity (Vmax) activity fell significantly immediately after hyperoxic exposure but recovered to normal values by day 3 of recovery. The Na-K-ATPase beta 1-subunit antigenic signal did not significantly change, whereas the alpha 1-subunit levels increased during recovery. In summary, there was a heterogeneous response of different rats to acute hyperoxia. Hyperoxia led to complex, nonparallel changes in Na+ pump antigenic protein, hydrolytic activity, and unidirectional active Na+ resorption. Active Na+ transport was differentially affected, depending on degree of injury, but permeability and transport normalized by day 3 of recovery.Active Na+ transport by the alveolar epithelium keeps alveoli relatively dry. Hyperoxia increases epithelial permeability, resulting in pulmonary edema. We sought to determine whether active Na+ resorption from the air spaces and Na-K-ATPase activity increased in rats exposed to >95% O2 for 60 h. The permeability × surface area products for unidirectional resorption of alveolar [14C]sucrose ( PS sucrose) and22Na+([Formula: see text]) were measured in isolated, perfused rat lungs immediately after hyperoxia and after 3 and 7 days of recovery in room air. At 60 h of hyperoxia, the mean PS sucrose and[Formula: see text]increased from 6.71 ± 0.8 × 10-5 to 12.6 ± 1.6 × 10-5cm3/s ( P = 0.029) and from 23.6 ± 1.1 × 10-5 to 31.0 ± 1.6 × 10-5cm3/s ( P < 0.008), respectively. However, the values in individual rats ranged widely from no change to nearly a fourfold increase. Subgroup analysis revealed that benzamil- or amiloride-sensitive (transcellular)[Formula: see text]was significantly reduced in the exposed lungs with normal PS sucrose but was maintained in the lungs with high PS sucrose. By day 3of recovery, mean Na+ and sucrose fluxes returned to values similar to control. Na-K-ATPase membrane hydrolytic maximal velocity ( V max) activity fell significantly immediately after hyperoxic exposure but recovered to normal values by day 3 of recovery. The Na-K-ATPase β1-subunit antigenic signal did not significantly change, whereas the α1-subunit levels increased during recovery. In summary, there was a heterogeneous response of different rats to acute hyperoxia. Hyperoxia led to complex, nonparallel changes in Na+ pump antigenic protein, hydrolytic activity, and unidirectional active Na+ resorption. Active Na+ transport was differentially affected, depending on degree of injury, but permeability and transport normalized by day 3 of recovery.

Riboflavin-enhanced transport of serum albumin across the distal pulmonary epithelium

AbstractPurpose. Conjugation of bovine serum albumin (BSA) with riboflavin (BSA-riboflavin) increases its uptake into cultured epithelial cells. Our purpose was to determine whether transport of BSA-riboflavin across the intact distal pulmonary epithelium is also increased, and whether transcytosis plays a role. Methods. In anesthetized rats, we instilled 3H-BSA-riboflavin or 3H-BSA into the trachea and measured their appearance in blood. In isolated, perfused rat lungs we measured the distal pulmonary epithelium permeability-surface area product (PS) for FITC-BSA or FITC-BSA-riboflavin. Results. In intact rats we found 2.1 times more 3H-BSA-riboflavin than 3H-BSA appeared in blood 60 min after intratracheal instillation of the protein. In isolated, perfused rat lungs we found that BSA-riboflavin had double the PS of BSA (2.63 vs. 1.46 × 10−5 cm3/sec). The addition of transcytosis inhibitors monensin or nocodazole (both 3 × 10−5 M) reduced the BSA-riboflavin PS to that of BSA and had no effect on the PS of unconjugated BSA. Simultaneous measurements of 3H-sucrose PS showed no differences in paracellular transport among any of the experimental groups. Conclusions. Conjugation with riboflavin increases the flux of BSA across the distal pulmonary epithelium. The increased transport appears to be due to transcytosis, which apparently does not play a significant role in the movement of unconjugated BSA across the distal pulmonary epithelium.

Effect of eosinophil peroxidase on airway epithelial permeability in the guinea pig

Increased numbers of eosinophils and increased concentrations of plasma proteins have been found in the airways of patients with mild asthma. We used an intact guinea pig trachea model to investigate the role of eosinophil peroxidase (EPO) in altering the function of the airway epithelial barrier, EPO in the presence of hydrogen peroxide (H2O2) and bromide (Br−) catalyzes the production of hypobromous acid (HOBr), which is felt to have a toxic effect on airway epithelial cells. An intact guinea pig trachea was mounted on an apparatus in a way that would allow the tracheal epithelium to be exposed to different solutions. Following these exposures, a test solution containing 14C‐sucrose (S), 3H‐inulin (I), and FITC‐dextran‐20 (D) was placed in the tracheal lumen and positioned in the center of the segment for 90 minutes. Flux of these molecules across the epithelial barrier into a bath was measured, and the permeability (P) was calculated for each molecule to quantify epithelial barrier function. Light and electron micrographic studies were performed to assess cellular damage. We found that there was a dose response to EPO (in the presence of fixed amounts of H2O2 and Br−). EPO at 7.3 × 10−7 M caused no increase in P over controls (Ringers solution alone) for S, I, or D (P > 0.05), whereas EPO at 2.7 × 10−6 M caused a significant increase in P over controls (P = 0.008) for all test molecules. Light and electron micrographs of the latter tracheas showed no evidence of microscopic changes despite the increased P. Further testing verified that the increase in permeability was caused by the EPO catalyzed reaction and not the individual substrates themselves, and that the reaction was inhibited by a peroxidase inhibitor. We conclude that EPO can alter the barrier function of the airway epithelium before gross cellular damage becomes visible. We hypothesize that changes in the tight junctions are responsible for the alteration in the barrier function of the airway epithelium and that this may play an important role in the pathophysiology of mild asthma. Pediatr Pulmonol. 1996; 21:159–166.

Mass spectrometer evaluation of ventilation-perfusion abnormalities in respiratory distress syndrome.

Extract: Mass spectrometers should have unique advantages in the evaluation of VA/Q, [20] inequalities in neonatal respiratory distress syndrome (RDS), especially, in neonates requiring assisted ventilation. The purposes of this report are to (1) describe a method for continuous measurement of respired gas composition utilizing a mass spectrometer system, and (2) describe the results of serial aADCO2 and AaDO2 (expressed as Qs/Q) measurements in 63 neonates with RDS.The mass spectrometer system utilized is a mobile unit which includes the following components: quadrupole mass spectrometer for gas analysis, flow meter, and an analogue computer for measurement of respiratory flows and volumes.In 17 patients not requiring assisted ventilation, initial aADCO2 levels ranged from normal (<5) to 26 mm Hg; there was considerable variation in initial Qs/Q In 46 patients requiring assisted ventilation, Qs/Q measurements did not distinguish pulmonary from nonpulmonary deaths or survivors from nonsurvivors. Serial aADCO2 measurements, however, indicated a correlation between ability to achieve an aADCO2 < 10 mm Hg by age 7–10 days and potential for pulmonary survival.Speculation: Full utilization of a mass spectrometer system will allow for breath-by-breath measurement of AaDO2, CO2, and N2, as well as a variety of respiratory flows and volumes. Such measurements should provide further understanding of VA/Q, inequalities in RDS. Serial aADCO2 levels may provide a more objective measurement of acute severity as well as a better definition of potential for pulmonary survival.

Proteinase-free myeloperoxidase increases airway epithelial permeability in a whole trachea model.

In cystic fibrosis the bronchiectatic conducting airways have large numbers of neutrophils in their walls and in their luminal contents. The neutrophils primary granule enzyme activities of elastase and peroxidase are increased in the sputum of these patients. It has been postulated that these enzymes—together or individually—act to damage the airway epithelium. However, only peroxidase activity has consistently correlated with the degree of structural and functional airway disease in these patients with leakage of plasma protein into the airway lumen (Regelmann et al., Pediatr Pulmonol. 1995; 19: 1–9). The present study was designed to test whether human neutrophil‐derived myeloperoxidase can independently produce bronchial epithelial damage without the presence of proteases, as measured by increased permeability of the airway epithelium. Human peripheral blood neutrophils were purified, their primary granules isolated, and their peroxidase purified using affinity and ion exchange column chromatography. Activity of the proteinase‐free peroxidase was measured using a chromogenic substrate. The effect of this peroxidase on the permeability of excised rat tracheas was measured using radioactive and fluorescent‐labeled non‐ionic molecules of varying molecular weight.

Pulmonary microvascular filtration and reflection coefficients in two- and four-week-old rabbits.

Abstract Several researchers have determined that pulmonary capillaries in young mammals are significantly more permeable to water and lipid-insoluble solutes than are the pulmonary capillaries in the adult counterparts. Our purpose was to quantify the microvascular fluid flux parameters in 2- and 4-week-old rabbit lungs and to compare our results with adult and newborn data previously reported. Using an isolated, Ringer-perfused lung preparation, we measured the values for the microvascular filtration coefficient and the reflection coefficients for NaCl and albumin. We found a filtration coefficient value of 2.57 × 10 −4 ml/sec-cm H 2 O-m 2 for the 2-week-old population. For the 4-week-old rabbit we evaluated the filtration coefficient to be 3.18 × 10 −4 ml/sec-cm H 2 O-m 2 . These values are normalized for the estimated exchange area, and neither is significantly different from the adult value. The reflection coefficients for NaCl and albumin were measured using an osmotic transient technique. Correcting the albumin data for flow across the endothelial cell membrane, we arrived at the following values for the pulmonary microvascular reflection coefficient of 2- and 4-week-old rabbits, respectively: σ cap alb = 0.17, and σ cap alb = 0.23. Based on these values we estimated the equivalent pore radii of large pores in the pulmonary microvascular wall to be approximately 175 A in the 2-week-old, and 145 A in the 4-week-old rabbits. These results indicate that in the rabbit K f /m 2 has reached the adult value by 2 weeks of age; however, the number of pores increases, and the pore radius decreases, continuously even beyond 4 weeks of age.

Regulation of the Sodium Pump in Hyperoxic Lung Injury

A major component of the early lesion in the adult respiratory distress syndrome (ARDS) is alveolar edema. Considerable data suggests that decreasing alveolar flooding improves the outcome from acute lung injury (ALI). Studies in humans with ARDS demonstrate that prognosis correlates with the capacity to resorb fluid (Matthay 1990). Retrospective studies indicate that patients with fluid balance out>in, lesser weight gain, lower pulmonary capillary wedge pressures or diuretic treatment have greater survival rates. It is not surprising that decreasing the degree of early alveolar flood could decrease the subsequent need for high pressure ventilation or high levels of oxygen — thus avoiding amplification of the injury.