Biomedical subjects

R H Notter

Publications and source records attributed to R H Notter.

At least 55 records · Page 3Linked to original sources

PubMed1990

Early pulmonary changes associated with high-frequency jet ventilation in newborn piglets.

To assess the short-term effects of high-frequency jet ventilation (HFJV) on the neonatal lung, 28 newborn piglets were studied. Nine piglets were unventilated except during brief pulmonary measurements, nine animals were conventionally ventilated (arterial CO2 tension 35-45 torr, arterial O2 tension 70-80 torr) for 4 h, and 10 piglets were ventilated with HFJV for the same period. Pulmonary function was analyzed using a computerized technique and tracheobronchial aspirates were examined for biochemical indicators of lung injury; after 4 h, bronchoalveolar lavage was obtained for surfactant composition and activity, and lung sections were examined by light and electron microscopy. Results showed that HFJV provided adequate ventilation at lower inspiratory pressure compared with conventional ventilation (8.6 +/- 0.3 versus 13.8 +/- 1.3 cm H2O; p less than 0.01), while pulmonary mechanics did not vary significantly among the three animal groups. Tracheobronchial aspirates from HFJV animals had higher elastase activity versus unventilated piglets (118.5 +/- 14.1 versus 57.7 +/- 8.4 micrograms/mL; p less than 0.01), as well as higher albumin concentration versus unventilated animals (94.2 +/- 18.7 versus 23.2 +/- 6.5 micrograms/mL; p less than 0.01). In addition, there were small but statistically significant differences between all three groups in the distribution of surfactant phospholipids in bronchoalveolar lavage, although biophysical activity was normal. Scanning electron microscopy revealed flattening of Clara cells in the terminal bronchioles of HFJV animals due to loss of glycogen and secretory granules. These data indicate that despite lower peak inspiratory pressures, HFJV can cause subtle biochemical changes in lungs. Further studies are indicated to determine if these changes precede significant lung injury.

Animals↗

PubMed1989

Hyperoxic exposure alters gene expression in the lung. Induction of the tissue inhibitor of metalloproteinases mRNA and other mRNAs.

Exposure to high concentrations of oxygen can result in tissue damage, particularly in the lung. Lung pathology induced by hyperoxia includes changes in lung cell populations and morphology. Presumably, alterations in gene expression underlie some of these cellular changes. In order to better understand the molecular basis of these events, a cDNA library was constructed from the mRNA of the lungs of a hyperoxia-exposed rabbit and differentially screened for clones corresponding to hyperoxia-induced messages. This approach has led to the isolation of four clones, three of which are presented in this communication. One clone corresponds to a message whose steady state levels were induced 6-fold and encodes the tissue inhibitor of metalloproteinases, a protein that plays a key role in the regulation of connective tissue turnover in some cells and potentiates erythroid development in others.

Amino Acid Sequence↗

PubMed1989

Alveolar hyperoxic injury in rabbits receiving exogenous surfactant.

We have previously demonstrated that instillation of a calf lung surfactant extract (CLSE) in rabbits after exposure to 100% O2 for 64 h mitigates the progression of lung pathology after return to room air (J. Appl. Physiol. 62: 756-761, 1987). In the present study, we investigated whether we could prevent or reduce the onset and development of hyperoxic lung injury by sequential instillations of CLSE during the hyperoxic exposure. Rabbits were exposed to 100% O2. CLSE (125 mg, approximately 170 mumol of phospholipid) was suspended in 10 ml of sterile saline and instilled intratracheally into their lungs, starting at 24 h in O2, a time at which no physiological or biochemical injury was detected, and at 24-h intervals thereafter. Control rabbits breathed 100% O2 and received either equal volumes of saline or no instillations at all. CLSE-instilled rabbits had higher arterial PO2 (Pao2) values throughout the exposure period and survived longer when compared with saline controls [120 +/- 4 vs. 102 +/- 4 (SE) h; n greater than or equal to 10; P less than 0.05]. At 72 h in O2, CLSE-instilled rabbits had significantly higher lavageable alveolar phospholipid levels (12.5 +/- 1.5 vs. 5 +/- 1 mumol/kg) and total lung capacities (41 +/- 2 vs. 25 +/- 3.5 ml/kg) and lower levels of alveolar protein (24 +/- 3 vs. 52 +/- 8 mg/kg), minimum surface tension (2 +/- 1 vs. 26.1 dyn/cm), and lung wet-to-dry weights (5.9 +/- 0.2 vs. 6.5 +/- 0.3). After 72 h in O2, lungs from both CLSE- and saline-instilled rabbits showed evidence of diffuse hyperoxic injury. However, atelectasis was less prominent in the former. We concluded that instillation of CLSE limits the onset and development of hyperoxic lung injury to the alveolar epithelium of rabbits.

Animals↗

PubMed1989

Lung injury in the neonatal piglet caused by hyperoxia and mechanical ventilation.

Neonatal lung injury from hyperoxia and mechanical hyperventilation was studied in newborn piglets hyperventilated (arterial PCO2 15-20 Torr) for 24-48 h with 100% O2 and compared with unventilated controls. Pulmonary function testing was performed, and biochemical indicators of lung injury were analyzed from tracheobronchial aspirates at 0, 24, and 48 h. Lung sections were obtained for light and electron microscopy, and bronchoalveolar lavage fluid was analyzed for surfactant composition and activity. At 24 h significant changes in tracheobronchial aspirate albumin concentrations (up 78%) and percent of polymorphonuclear cells (up 16%) were demonstrated. At 48 h a 35% decrease in dynamic lung compliance (P less than 0.05) and a 36% increase in pulmonary resistance (P less than 0.05) were noted. Further biochemical abnormalities occurred with total cell counts increased by 271% (P less than 0.02), albumin 163% (P less than 0.05), total protein 217% (P less than 0.01), and elastase 108% (P less than 0.02). Pathological analyses revealed mild lung injury at 24 h and marked inflammation, abnormal inflation patterns, flattening of Clara cells, fibrinous exudate and edema, early collagen formation, and cell necrosis observed at 48 h. Bronchoalveolar lavage surfactant had normal biophysical activity. Results demonstrate that exposure of neonatal piglets to O2 and mechanical hyperventilation for 48 h cause severe progressive lung injury.

Animals↗

PubMed1988

Changes in pulmonary mechanics after the administration of surfactant to infants with respiratory distress syndrome.

We assessed pulmonary mechanics in 35 premature infants with respiratory distress syndrome just before and one hour after the administration of 90 mg of surfactant to each infant. Transpulmonary pressure was measured between the airway opening and an esophageal balloon with use of a differential transducer, and flow rates were measured by a pneumotachometer. Values for pulmonary mechanics were then calculated by microcomputer processing. The administration of surfactant produced a large decrease (56 percent) in the mean (+/- SEM) ratio of alveolar to arterial oxygen, from 7.1 +/- 0.5 to 3.1 +/- 0.2 (P less than 0.0001)--a change that indicates improvement in gas exchange. Associated changes in pulmonary mechanics were not demonstrable when 10 of the infants were studied during continuous mechanical ventilation. However, in the 25 infants examined during spontaneous breathing with continuous positive airway pressures (identical airway pressures before and after treatment), large and consistent improvements in pulmonary mechanics were found after the administration of surfactant. Tidal volume increased by 32 percent (P less than 0.03), minute ventilation by 38 percent (P less than 0.02), dynamic compliance by 29 percent (P less than 0.004), and inspiratory flow rates by 54 percent (P less than 0.01). We conclude that significant improvement in pulmonary mechanics results from surfactant-replacement therapy for respiratory distress syndrome, but that these mechanical changes are apparent only during spontaneous respiration and can be masked if measurements are made during mechanical ventilation.

Humans↗

PubMed1988

A biophysical mechanism by which plasma proteins inhibit lung surfactant activity.

These in vitro experiments study a potential mechanism by which plasma proteins, found in the alveoli during pulmonary edema and hemorrhage, may act to inhibit the surface activity of pulmonary surfactant. The results indicate that the inhibition of the adsorption facility and surface tension lowering ability of a calf lung surfactant extract (CLSE) by albumin, hemoglobin, or fibrinogen may be completely abolished by centrifugation of the protein-surfactant mixture at 12,500 x g. Furthermore, albumin, hemoglobin and fibrinogen (1.25 mg/ml) were shown to inhibit the adsorption of high concentrations of CLSE (0.32 mg/ml), normally unaffected by the addition of exogenous proteins, when the CLSE was injected into the subphase under a preformed protein surface film. Similarly, injection of large amounts of these proteins (2.5 mg/ml) into the subphase beneath a preformed CLSE surface film was without effect, even though the CLSE concentration was only 0.06 mg/ml, a surfactant concentration which is normally inhibited by even small amounts of exogenous protein. Taken together, the data suggest that some proteins may inhibit surfactant function by preventing the surfactant phospholipids from adsorbing to the air-liquid interface, possibly by a competition between the proteins and CLSE phospholipids for space at the air-liquid interface rather than direct molecular interactions between proteins and surfactant.

Adsorption↗

PubMed1988

Fetal cerebral responses to ventilation and oxygenation in utero.

Previous studies have shown that cerebral oxygen consumption (CMRO2) increases by nearly 50% at birth. The perinatal factors responsible for this increase are unknown; however, one possibility is that fetal CMRO2 is constrained by the normal intrauterine arterial PO2 (PaO2) of approximately 20 mmHg. We investigated this possibility in seven near-term chronically instrumented fetal sheep (131-138 days gestation) in which we inserted vascular catheters and an endotracheal tube. After 1-3 days recovery, we measured cerebral blood flow (CBF) with radiolabeled microspheres and calculated CMRO2. Measurements were made in utero under three conditions for each fetus: 1) nonventilated control; 2) ventilation with 3% O2-5% CO2-92% N2; and 3) ventilation with an inspired oxygen concentration sufficient to raise fetal PaO2 to normal newborn levels (mean 73 mmHg). A calf lung surfactant extract (CLSE) was instilled into the endotracheal tube of the fetus before ventilation to ensure adequate levels of alveolar surfactant and to maintain stable pH and arterial PCO2. The results showed that increasing fetal arterial PO2 to postnatal levels did not consistently increase CMRO2. CBF decreased as arterial O2 content (CaO2) rose, with an inverse hyperbolic response similar to that previously found to relate CBF to CaO2 during fetal hypoxic hypoxia. This indicates that the normally low intrauterine PaO2 does not intrinsically limit CMRO2 and implies that the rapid increase in CMRO2 at birth reflects the activation of specific cellular and physiological processes at (or near) this unique developmental event.

Animals↗

PubMed1988

Type II pneumocyte changes during hyperoxic lung injury and recovery.

Adult rabbits exposed to 100% O2 for 64 h and then returned to room air for up to 200 h, develop a lung injury characterized by decreased levels of alveolar surfactant followed by a rebound recovery. In the present study we isolated alveolar type II cells from rabbits at various times during hyperoxic exposure and recovery and measured rates of phosphatidylcholine (PC) synthesis, cellular lipid content, and the specific activity of glycerol 3-phosphate (G-3-P) acyltransferase, an enzyme that catalyzes one of the early reactions in phosphoglyceride biosynthesis. These biochemical parameters were compared with measurements of cell size and cell cycle phase by laser flow cytometry. Results showed that alterations in alveolar phospholipid levels in vivo correlated consistently with cellular lipid metabolic changes measured in isolated type II pneumocytes. In particular, alveolar pneumocytes isolated from lungs of rabbits exposed to 100% O2 for 64 h exhibited a 60% decrease in PC synthesis, cell lipid content, and G-3-P acyltransferase activity. All variables then followed a pattern of recovery to normal and ultimately supranormal levels beginning at approximately 3 days postexposure, at which point there was also a measured increase in the number of type II cells in S phase. These findings suggest that O2-induced changes in type II cell surfactant biosynthesis may account, at least in part, for observed changes in lung phospholipid levels in vivo.

Animals↗

PubMed1988

Sublethal hyperoxic injury to the alveolar epithelium and the pulmonary surfactant system.

We quantified the effects of continuous exposure to 100% O2 on the development of sublethal injury to the pulmonary alveolar epithelium of rabbits. There was a progressive increase in alveolar permeability to solute after 48 h in O2, which coincided with the onset of damage to the pulmonary microvasculature. Rabbits that were exposed to 100% O2 for 64 h and returned to room air for 24 h had, in addition to increased permeability to solute, decreased phospholipid levels, decreased total lung capacity, pulmonary edema, high minimum surface tensions in their bronchoalveolar lavage, and moderate hypoxemia. Intratracheal instillation of calf lung surfactant (CLSE) significantly ameliorated the progression of hyperoxic injury by increasing alveolar phospholipid levels and thus preventing the inhibition of lung surfactant activity by plasma proteins and other high molecular weight components of alveolar edema. We concluded that the alveolar epithelium and the pulmonary microvasculature show similar sensitivity to hyperoxia and that clinical manifestations of hyperoxic lung injury may be due, at least in part, to surfactant dysfunction.

Animals↗

PubMed1988

Biophysical behavior of lung surfactant: implications for respiratory physiology and pathophysiology.

The major emphasis of this article has been the complex, multicomponent system of surfactants that are required for proper pulmonary mechanics and function in the mammalian lung. Although LS was discovered over 30 years ago, and soon after was linked directly with neonatal RDS, it has taken a significant time for researchers to develop a fundamental understanding of the pulmonary surfactant system, and its actions and roles in respiratory physiology. Nonetheless, knowledge about LS has increased greatly over the past decade, and it is now clear that exogenous surfactant replacement therapy for infants with RDS provides a substantial clinical advantage for these patients. Indeed, the therapy is life-saving in many very small premature infants, and as experience accrues, and therapy is optimized, this advance is clearly a major step forward in neonatology. Perhaps the most prominent theme that has been presented throughout the discussion here is that pulmonary surfactant research must take advantage of interdisciplinary descriptions and cross-correlations for accurate and rapid progress. One positive feature of prior work on lung surfactant replacement and RDS is that its difficulty has forced investigators toward a level of understanding that is sound enough to extend LS research into related fields, such as lung injury and ARDS. These areas have their own complications, including a much more diverse pathology and injury progressions than found with neonatal RDS. In fact, if defining the role of lung surfactant in ARDS (and developing replacement therapy for it) had been the goal of investigators before considering neonatal RDS, it is difficult to imagine a positive outcome. The situation now, however, is one where it is realistic to think of recognizing when and how LS effects will occur in different ARDS lung injuries, so that surfactant replacement will have the best opportunity to help mitigate their progressive pathology. In dealing with ARDS, it is well to remember that there are a variety of complicating factors, since lung injuries vary with animal age and species, and according to the level and duration of exposure. For example, in the hyperoxic injury described in the previous section there was clearly significant LS involvement. However, had animals been subjected to a lower level of oxygen (eg, 60%), even for a comparatively long time (eg, 21 days), the entire pathologic pattern would have been altered, as demonstrated, for example, by Holm et al.(ABSTRACT TRUNCATED AT 400 WORDS)

1,2-Dipalmitoylphosphatidylcholine↗

PubMed1988

Surfactant replacement therapy at birth: final analysis of a clinical trial and comparisons with similar trials.

A randomized trial of surfactant replacement therapy at birth was conducted at the University of Rochester between June 1983 and November 1985. Thirty-four premature infants, 25 to 29 weeks' gestational age, received a preventilatory dose of a calf lung surfactant extract in saline prepared at the University of Rochester. A control group of 31 infants received a preventilatory dose of saline alone. The major finding of this trial is that a single preventilatory dose of calf lung surfactant extract reduces the severity of the respiratory distress syndrome during the first 24 hours of life. The beneficial effects, however, are not sustained in many infants and diminish after 24 hours of life. The survival rate was 71% in both the control and surfactant-treated groups. There was a lower incidence of pneumothorax in the surfactant-treated group. There were no differences in the incidence of bronchopulmonary dysplasia, patent ductus arteriosus, and intraventricular hemorrhage. No adverse effects of surfactant replacement therapy were identified. Results of this study suggest that multiple postventilatory doses of surfactant will be required for optimal therapy.

Clinical Trials as Topic↗

PubMed1988

Controversies regarding surfactant replacement therapy.

Surfactant replacement therapy for the respiratory distress syndrome is being actively studied in clinical trials. The therapy has great potential for reducing morbidity and mortality in premature infants. Some issues about surfactant replacement therapy are not yet clear, and a number of these are discussed in this article.

Humans↗

PubMed1987

Biophysical activity of synthetic phospholipids combined with purified lung surfactant 6000 dalton apoprotein.

This research studies the biophysical surface activity of synthetic phospholipids combined in vitro with purified lung surfactant apoprotein, having an Mr of 6000. Hydrophobic surfactant-associated protein (SAP-6) was delipidated and purified from both bovine and canine lung lavage, and was combined in vitro with a synthetic phospholipid mixture (SM) of similar composition to natural lung surfactant phospholipids. SM phospholipids were also combined and studied biophysically with another purified surfactant-associated protein, SAP-35. The biophysical activity of synthetic phospholipid-apoprotein combinants was assessed by measurements of adsorption facility and dynamic surface tension lowering ability at 37 degrees C. The SM-SAP-6 combinants had adsorption facility equivalent to natural lung surfactant, and to the surfactant extract preparations CLSE and surfactant-TA used in exogenous surfactant replacement therapy for the neonatal Respiratory Distress Syndrome (RDS). The synthetic phospholipid-SAP-6 combinants also lowered surface tension to less than 1 dyne/cm under dynamic compression in an oscillating bubble apparatus at concentrations as low as 0.5 mg phospholipid/ml. A striking finding was that this excellent dynamic surface activity was preserved as SAP-6 composition was reduced to values as low as 5 micrograms/5 mg SM phospholipid (0.1% SAP-6 protein), an order of magnitude less than the 1% protein content of CLSE and surfactant-TA. Mixtures of SM phospholipids plus SAP-35, the major surfactant glycoprotein, had significantly lower biophysical activity, which did not approach that of a functional lung surfactant. These results suggest that synthetic exogenous surfactants of potential utility for replacement therapy in RDS can be formulated by combining synthetic phospholipids in vitro with specifically purified, hydrophobic surfactant-associated protein, SAP-6.

Animals↗

PubMed1987

Exogenous lung surfactant: effect on radiographic appearance in premature infants.

At birth, premature infants of 25-29 weeks gestation, at high risk for development of neonatal respiratory distress syndrome (RDS), were given a single dose (90 mg) of calf lung surfactant extract (CLSE) by intratracheal instillation. The frequency and severity of RDS were assessed with use of a simple radiographic scoring system in which pulmonary parenchymal densities and the prominence of the air-bronchogram effect were used as indicators of widespread atelectasis. Radiographs were obtained in surfactant-treated and control infants within the first 90 minutes of life as part of an initial evaluation of their pulmonary status. Subsequent examinations were performed at less than 24 hours and less than 48 hours of age. Radiographic assessment of lung disease compared consistently with coordinated data on oxygen and mean airway pressure requirements of the infants. Both indicated a significantly decreased frequency and severity of RDS in the infants treated with surfactant. The results provide supporting evidence of the effectiveness of exogenous lung surfactant replacement in mitigating RDS in very premature infants.

Animals↗

PubMed1987

Mitigation of pulmonary hyperoxic injury by administration of exogenous surfactant.

We studied the effects of surfactant supplementation on the progression of lung injury in rabbits exposed to 100% O2 for 64 h and returned to room air for 24 h. At this time, rabbits not treated with surfactant exhibit a severe lung injury with hypoxemia, increased alveolar premeability to solute, decreased total lung capacity (TLC) and lung edema. For surfactant treatment, 125 mg of calf lung surfactant extract (CLSE), suspended in 6-8 ml of normal saline, were instilled intratracheally at 0 and 12 h posthyperoxic exposure. At 24 h postexposure, these CLSE-treated rabbits compared with saline controls had significantly higher amounts of lung phospolipids (34 +/- 4 vs. 4.5 +/- 0.6 mumol/kg body wt) and increased TLC (42 +/- 2 vs. 27 +/- 1 ml/kg), with significantly lower amounts of alveolar protein (36 +/- 3 vs. 56 +/- 3 mg/kg) and decreased lung wet weight-to-dry weight ratios (5.6 +/- 0.1 vs. 6.3 +/- 0.3). Surfactant supplementation also decreased the degree of lung atelectasis as reflected by the increase in arterial O2 partial pressure (PaO2) after breathing 100% O2 for 20 min (PaO2 = 460 +/- 31 vs. 197 +/- 52 Torr). These findings indicate that instillation of exogenous surfactant mitigates the progression of hyperoxic lung injury in rabbits.

Animals↗

PubMed1987

Alveolar epithelial changes in rabbits after a 21-day exposure to 60% O2.

This study characterizes the biochemical and physiological effects of prolonged exposure of rabbits to sublethal (60%) O2 concentrations. After 3 wk in 60% O2, rabbits had arterial PO2 values of 69 +/- 2 vs. 79 +/- 3 Torr for control animals (means +/- SE; P less than 0.05) and a small but significant rise in pulmonary wet weight-to-dry weight ratios (5.6 +/- 0.3 vs. 4.1 +/- 0.3; P less than 0.05). Alveolar permeability to solute, lung compliance, total lung capacity, and alveolar protein levels were unchanged from control, but the amount of lavagable alveolar phospholipid was 90% higher in the O2-exposed rabbits. The lipid biosynthetic ability of isolated alveolar type II pneumocytes, measured by radiolabeled precursor [3H]choline incorporation, indicated that type II cells isolated from hyperoxic animals synthesized phosphatidylcholine at a rate 110% higher than those from control animals. Laser flow cytometric analyses of isolated type II cells showed a significant increase in type II cell diameter, based on time-of-flight measurements, and an average 60% increase in lipid content per cell, based on phosphine-3R fluorescence intensity. These findings indicate that exposure to 60% O2 for 21 days results in a decrease in arterial PO2 and induces several important biochemical and morphological changes in alveolar type II pneumocytes.

Animals↗

PubMed1987

Effects of hemoglobin and cell membrane lipids on pulmonary surfactant activity.

These experiments characterize the effects of hemoglobin and erythrocyte membrane lipids on the dynamic surface activity and adsorption facility of whole lung surfactant (LS) and a calf lung surfactant extract (CLSE) used clinically in surfactant replacement therapy for the neonatal respiratory distress syndrome (RDS). The results show that, at concentrations from 25 to 200 mg/ml, hemoglobin (Hb) increased the minimum dynamic surface tension of LS or CLSE mixtures (0.5 and 1.0 mumol/ml) from less than 1 to 25 dyn/cm on an oscillating bubble apparatus at 37 degrees C. Similarly, erythrocyte membrane lipids (0.5-3 mumol/ml) also prevented LS and CLSE suspensions (0.5-2.0 mumol/ml) from lowering surface tension below 19 dyn/cm under dynamic compression on the bubble. Surface pressure-time adsorption isotherms for LS suspensions (0.084 and 0.168 mumol phospholipid/ml) were also adversely affected by Hb (0.3-2.5 mg/ml), having a slower adsorption rate and magnitude. Significantly, these inhibitory effects of Hb and membrane lipids could be abolished if LS and CLSE concentrations were raised to high levels. In complementary physiological experiments, instillation of Hb, membrane lipids, or albumin into excised rat lungs was shown to cause a decrease in pressure-volume compliance. This decreased compliance was most prominent in lungs made partially surfactant deficient before inhibitor delivery and could be reversed by supplementation with active exogenous surfactant. Taken together, these data show that molecular components in hemorrhagic pulmonary edema can biophysically inactivate endogenous LS and adversely affect lung mechanics. Moreover, exogenous surfactant replacement can reverse this process even in the continued presence of inhibitor molecules and thus has potential utility in therapy for adult as well as neonatal RDS.

Adsorption↗

PubMed1987

Lung surfactants for replacement therapy: biochemical, biophysical, and clinical aspects.

This article characterizes and analyzes current concepts of the pulmonary surfactant system, and its actions and importance in respiration. Much of the discussion concerns the fundamental role of lung surfactant in the respiratory distress syndrome (RDS) of premature infants, and the success of exogenous surfactant replacement in clinical therapy for this disease. In addition, basic descriptions of the biophysical and physiological activity of lung surfactant are provided to define mechanisms behind surfactant replacement therapy, and how it might be optimized by the further development of appropriate synthetic lung surfactant substitutes.

Animals↗