Sequence and properties of the message encoding Tetrahymena hv1, a highly evolutionarily conserved histone H2A variant that is associated with active genes

hv1 is a histone H2A variant found in the transcriptionally active Tetrahymena macronucleus, but not in the transcriptionally inert micronucleus. hv1 also contains antigenic determinants conserved in the histone complements of representatives of all four eukaryotic kingdoms. A cDNA clone encoding hv1 has been isolated and sequenced. Comparison of the derived protein sequence of hv1 with that of the chicken variant H2A.F and the sea urchin variant H2A.F/Z reveals remarkable homology in all but the extreme amino- and carboxy-termini and a small region in the conserved core. Putative regions of conserved antigenicity are discussed. Evidence is presented that suggests that hv1 is a single-copy, intron-containing gene that encodes a polyadenylated message. Unusual features in the 3' flanking sequence and in codon usage are also described. Evidence is also presented showing that hv1 message amounts are ten-fold greater in growing cells than in starved cells.

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.

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.

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.

A quantitative study of the development of type II pneumocytes in fetal lung

Cell populations dissociated from fetal rabbit lungs were analyzed by laser flow cytometry for the presence of type II pneumocytes. These cells are distinguishable by the staining of their lamellar bodies with the fluorescent lipophilic dye, phosphine-3R and by their intensity of low-angle light scatter. Lung cells were obtained by enzymatic dissociation from fetal rabbits at gestational ages of 24 d, 27 d, and from 2-d newborn rabbits. Flow cytometric analysis was sufficiently sensitive to discriminate between fetuses. Quantitative analysis of type II pneumocytes showed that newborn rabbits had a distinct cell subpopulation in a region of low-angle light scatter and phosphine-3R fluorescence intensity similar to that previously reported on type II cells from adult rabbits. By contrast, 24-d gestation rabbits had a negligible type II cell subpopulation. Fetuses of 27 and 30 d gestation showed a slow but progressive increase in the numbers of cells in the type II region. Mathematical analyses of light scatter and fluorescence intensity distributions were used to define statistically significant (P less than .05) boundaries that characterize the development of the type II cell subpopulation in fetal rabbit lung. The methods employed offer new possibilities for quantification of developing lung cell subpopulations of particular interest to the problem of respiratory distress syndrome in human neonates.

Hydrophobic surfactant-associated protein in whole lung surfactant and its importance for biophysical activity in lung surfactant extracts used for replacement therapy

Hydrophobic protein of 6,000 and 14,000 daltons was isolated from mammalian pulmonary surfactant obtained from canine, human, and bovine alveolar lavage material. Low molecular weight, hydrophobic, surfactant-associated protein (SAP), herein referred to as SAP 6-14, was distinguished from SAP-35, the major glycoprotein in mammalian surfactants (the 35,000 dalton glycoprotein A or apolipoprotein A) by amino acid composition, peptide mapping, and by resistance of SAP 6-14 to digestion by endoglycosidase F, collagenase, trypsin, and other proteases. The amino acid composition of SAP 6-14 was found to be highly enriched in leucine and other hydrophobic amino acids. The characteristics of protein isolated from bovine replacement surfactant extracts utilized for the treatment of hyaline membrane disease in humans were also studied. SAP 6-14 isolated from calf lung surfactant replacement extracts (CLSE) and surfactant-TA were found to be identical to SAP 6-14 isolated from ether/ethanol extracts of various mammalian surfactants. By contrast, SAP-35, the major surfactant-associated glycoprotein of molecular weight = 35,000, and other higher molecular weight proteins were not detected in significant quantities in the CLSE or surfactant-TA replacement surfactants, either by highly sensitive silver stain analysis or by immunoblot using monospecific antisera generated against bovine SAP-35. Biophysical studies of the CLSE replacement surfactant containing only SAP 6-14 and native phospholipids demonstrated full surface activity compared to natural lung surfactant. Dynamic surface tension lowering and adsorption properties of CLSE were essentially identical to those of freshly isolated bovine whole surfactant. Thus, hydrophobic SAP 6-14 is the only protein detected in bovine lung extract surfactants with full biophysical activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Predictive biochemical assays for late radiation effects

Surfactant precursors or other products of Type II pneumocytes have the potential to be the first biochemical marker for late radiation effects. This is particularly clinically important in the combined modality era because of the frequent occurrence of pneumonitis and pulmonary fibrosis secondary to radiation or chemotherapy. Accordingly, correlative studies have been pursued with the Type II pneumocyte as a beginning point to understand the complex pathophysiology of radiation pneumonitis and fibrosis. From our ultrastructural and biochemical studies, it is evident that Type II pneumocytes are an early target of radiation and the release of surfactant into the alveolus shortly after exposure persists for days and weeks. Through the use of lavaging techniques, alveolar surfactant has been elevated after pulmonary irradiation. In three murine strains and in the rabbit, there is a strong correlation with surfactant release at 7 and/or 28 days in vivo with later lethality in months. In vitro studies using cultures of type II pneumocytes also demonstrate dose response and tolerance factors that are comparable to the in vivo small and large animal diagnostic models. New markers are being developed to serve as a predictive index for later lethal pneumonopathies. With the development of these techniques, the search for early biochemical markers in man have been undertaken. Through the use of biochemical, histological, and ultrastructural techniques, a causal relationship between radiation effects on type II pneumocytes, pulmonary cells, endothelial cells of blood vessels, and their roles in the production of pneumonitis and fibrosis will evolve.

Insulin receptors and insulin effects on type II alveolar epithelial cells

Type II alveolar epithelial cells (pneumocytes) were isolated to purity from adult rabbits and analyzed for the presence of cell surface insulin receptors and for effects of insulin on cells. Assays were performed on cells cultured for 24 h in Eagle's minimum essential medium. Insulin binding to cells in culture approached a steady-state level by 180 min at 15 degrees C and remained constant for at least 1 h. Competition experiments using native insulin, proinsulin and desoctapeptide supported specificity of binding. Scatchard analysis of binding revealed a class of high-affinity receptors with Kd = 1.5 X 10(-10) M and a low-affinity component with Kd = 4 X 10(-9) M. The number of receptors was estimated at 2000-4000/cell. Insulin added to cell cultures of type II pneumocytes in concentrations from 5 X 10(-11) to 5 X 10(-8) M resulted in a dose-related increase in uptake of 2-deoxyglucose by cells. Insulin also stimulated the incorporation of choline and glucose into phosphatidylcholine and disaturated phosphatidylcholine.

Adsorption of natural lung surfactant and phospholipid extracts related to tubular myelin formation

The microstructure of aqueous dispersions of pulmonary surfactant lipids extracted from bovine lung lavage was investigated by electron microscopic analysis. Following organic solvent extraction (chloroform/methanol) from natural lung surfactant, the mixed lipids (CLL), with 1% residual protein, were dispersed in water by two techniques, probe sonication at 4 degrees C and mechanical vortexing. Surface pressure-time adsorption isotherms were defined for the CLL dispersions, followed by staining with tannic acid, uranyl acetate, and lead citrate for electron microscopy of microstructure. CLL extract dispersions adsorbed in seconds to surface pressures near 45 dynes/cm (surface tension 25 dynes/cm) at low concentrations less than or equal to 0.25 mg/ml after dispersion by sonication of 4 degrees C and by mechanical vortexing. Ultrastructurally, the CLL dispersions were somewhat heterogeneous, but large thin-walled phospholipid vesicles, both intact and fragmented, predominated. No tubular myelin was formed. By contrast, natural lung surfactant (LS) from bronchoalveolar lavage had characteristic regions of tubular myelin when it adsorbed well at low concentrations (less than or equal to 0.25 mg phospholipid/ml). When divalent cations were removed from solution with 5 mM EDTA, this distinctive microstructure was not present and natural LS adsorbed less rapidly; higher concentrations of 0.63 mg phospholipid/ml were necessary for maximal adsorption of natural LS without tubular myelin. These results suggest that while tubular myelin is associated with optimal adsorption for natural LS, it is not a required configuration for rapid adsorption facility at low phospholipid concentrations in general. Specifically, for dispersions of surfactant extracts, other microstructures allow adsorption facility equivalent to that of natural LS with tubular myelin.

Double-blind clinical trial of calf lung surfactant extract for the prevention of hyaline membrane disease in extremely premature infants

A prospective, double-blind, controlled trial was conducted to determine whether instillation of an exogenous surfactant into the lungs before the first breath could prevent hyaline membrane disease. The surfactant is calf lung lipid extracted from saline lung lavage. Entry was limited to infants who were 24 to 28 weeks' gestation, who were born at Children's Hospital of Buffalo, and whose mothers had not received betamethasone for more than 24 hours before birth. Treated infants received 3 mL (90 mg) of calf lung surfactant extract instilled into their trachea before the first breath; control infants received 3 mL of normal saline. A prospective scoring system and respiratory support variables were used to compare the groups. At 48 hours of age, only two of 14 calf lung surfactant extract-treated infants (14%) had hyaline membrane disease compared with seven of 13 control infants (54%) (P = .033). Inspired oxygen, mean airway pressure, ventilator rate and ventilator efficiency index were also lower in the treated group during the first 48 hours of life (P less than .01 to P less than .001). Calf lung surfactant extract instillation at birth appears to be an effective material and method of preventing hyaline membrane disease in extremely premature infants.

Double-blind, randomized trial of a calf lung surfactant extract administered at birth to very premature infants for prevention of respiratory distress syndrome

Organic solvent extraction of surfactant obtained by lavage of calf lungs yields a highly surface-active material. A double blind, randomized clinical trial to determine the effect of this material on respiratory distress syndrome in premature infants was initiated in the Neonatal Intensive Care Unit at the University of Rochester in December 1983. Infants 25 to 29 weeks gestational age were eligible for entry into the trial. At the time of this interim analysis 32 patients had been randomly selected and entered into the trial, 16 surfactant-treated patients and 16 in a control group who received only saline. At birth, intrapulmonary instillation of the calf lung surfactant extract dispersed in saline or saline alone occurred in the delivery room immediately after intubation and prior to ventilation; infants were then ventilated and treated as usual. At 6, 12, 24, 48, and 72 hours after birth, the severity of respiratory distress was categorized as either minimal, intermediate, or severe based on oxygen and mean airway pressure requirements. Differences observed at six hours after birth were of marginal significance, but at 12 and 24 hours the surfactant-treated group had significantly (P less than .01) less severe respiratory distress compared with the control group. Differences between treated and control infants were not statistically significant at 48 and 72 hours after birth. In four surfactant-treated infants the severity of respiratory distress worsened between 24 and 48 hours after birth, suggesting that one dose of surfactant at birth may not be sufficient for some infants.

Lung surfactant replacement in premature lambs with extracted lipids from bovine lung lavage: effects of dose, dispersion technique, and gestational age

Extracted bovine calf lung lipids (CLL) with minimal protein (approximately 1%) were instilled prior to ventilation in groups of premature lambs of average gestational ages of 127 and 133 days. Aqueous dispersions of CLL were prepared by two techniques prior to instillation: sonication in an ice bath (S) and mechanical vortexing at room temperature (V). A low surfactant dose (15 mg CLL/kg animal weight) and a high dose (100 mg/kg) were investigated for each dispersion technique. Following tracheal instillation of surfactant, lambs were ventilated with 100% oxygen for 2 h with umbilical circulation intact, and for up to an additional 10 h after separation. A clear improvement in blood oxygenation and lung compliance was found over controls for lambs given 15 mg/kg and 100 mg/kg CLL(V), and 100 mg/kg CLL(S). Lambs treated with 15 mg/kg CLL(S) failed to improve over controls. Experimental groups treated with equal doses of CLL(V) and CLL(S) had similar amounts of lung lavage phospholipid, with values progressively declining during ventilation. Analyses of in vitro surface properties showed that both vortexed and sonicated CLL dispersions adsorbed to equilibrium surface pressures of 45-47 dynes/cm in seconds at concentrations greater than or equal to 0.25 mg CLL/ml. Both dispersions also lowered surface tension to less than 1 dyne/cm under dynamic compression at 37 degrees C in 100% humidity, although CLL(V) showed some enhancement over CLL(S) in dynamic surface activity at low subphase concentration (0.5 mg/ml). Moreover, CLL(V) and CLL(S) differed markedly in their effects on pressure-volume mechanics in a surfactant-deficient excised rat lung model. Instilled CLL(V) dispersions improved excised lung pressure-volume mechanics at significantly lower concentrations than CLL(S) dispersions.

Monoclonal antibodies to surface antigens of rabbit type II pneumocytes

Techniques for the production of monoclonal antibodies to cell surface antigens of type II pneumocytes are reported. Using these techniques, over 200 hybridomas were produced from spleen cell fusions of 8 mice. Of these, 25 expressed activity toward the type II pneumocyte cell surface. Many antibodies cross-reacted with a variety of cells and membranes from other organs and species, suggesting that these antibodies were ubiquitous to membrane antigens. Most of the antibodies cross-reacted strongly with dog lung membranes, suggesting the existence of common mammalian lung determinants. Five hybridomas produced supernatant antibody with considerable specificity for type II pneumocytes. Ascites fluid antibody was produced to these 5 hybridomas. Immunofluorescent staining of type II pneumocyte cell surfaces could be demonstrated with all 5 of these antibodies. This initial study demonstrates the feasibility of producing monoclonal antibodies to cell surface antigens of the type II pneumocyte.

Job satisfaction and stress among neonatologists

Neonatology is reputed to be a stressful pediatric subspecialty. To quantify objectively this stress and to assess the factors involved, a questionnaire was mailed to neonatologists in the northeastern United States. Ninety-six (70%) replied. A five-point scale was used to determine the level of satisfaction with neonatology as a career and the level and type of stress experienced at work. Almost all neonatologists experienced stress at work: 34% moderately severe and 16% very severe stress. Open-ended questions indicated that the major causes of stress were excessive work load, eg, on call too often or calls at night; problems in patient care, especially dealing with infant death; and staff disagreements, especially nurse or housestaff conflicts. Twenty percent of those surveyed suffered a stress-related illness in the previous 5 years. One sixth of the neonatologists were either moderately or very dissatisfied with their career. Major dissatisfactions were: too much work, especially managing many sick patients; lack of resources, including inadequate salary; too much stress at work; and administrative demands. Job satisfaction was derived from patient care, teaching, intellectual stimulation, and research. Altering subspecialty had been considered at some time by 58% (15% very seriously). This study confirms that neonatology, in the eyes of those who practice it, is a highly stressful career. It also suggests that job stress is a greater problem than job dissatisfaction.

Radiation induced secretion of surfactant from cell cultures of type II pneumocytes: An in vitro model of radiation toxicity

The pathogenesis of pneumonitis and fibrosis secondary to lung irradiation is incompletely understood. The role of the type II alveolar epithelial pneumocyte in these processes has been under investigation. The type II pneumocyte has been shown in vivo to respond to radiation induced injury with release of pulmonary surfactant. The effect of irradiation on cell cultures of type II pneumocytes was studied to determine if this could be reproduced in vitro. Type II pneumocytes were found to release surfactant material with a threshold of radiation dose between 1000 and 1500 rad. This is similar to the dosage range over which the same effect has been demonstrated in vivo. Experimental results support the concept that the release of surfactant is not due to either cell disruption or non-specific release of phospholipid from cell membranes. Irradiation appears to trigger membrane receptor mediated surfactant release. In addition, irradiation abolishes the ability of cells to subsequently respond to a physiologic agonist, suggesting radiation induced damage to the secretory mechanism. These studies establish that surfactant release in response to irradiation in vivo is a direct effect on type II pneumocytes. Cell cultures of type II pneumocytes can serve as a laboratory model of lung cell radiation toxicity.

Surfactant release as an early measure of radiation pneumonitis

The immediate release of surfactant into lung alveoli following irradiation has been studied as a potential indicator for the later development of radiation pneumonitis. Utilizing single dose radiation exposure to the whole thorax in male LAF1/J mice, steep dose response curves for lavaged alveolar surfactant were identified at 7 and 28 days after exposure. Seven days after irradiation there was no elevation with doses up to and including 12 Gy; above this dose a detectable increase occurred. At 28 days the surfactant recovered by lavage was elevated compared to the levels seen at day 7 for all doses; doses greater than 12 Gy produced surfactant values significantly greater than those found in mice treated with 12 Gy or less. The radiation pulmonary lethality dose response curve assessed four months later indicated an LD50 value of approximately 13 Gy. The early biochemical effect and the later radiation pneumonitis lethalities therefore closely coincided. The evidence strongly indicates that alveolar surfactant release uncovered hours to days after radiation exposure may be an early biochemical marker that predicts for subsequent pneumonitis radiation injury.

Natural and artificial lung surfactant replacement therapy in premature lambs

The effect of tracheal instillation of surface-active mixtures in premature lambs was studied as an animal model of exogenous surfactant replacement therapy for the respiratory distress syndrome (RDS). Specific mixtures studied were 7:3 (molar ratio) dipalmitoyl phosphatidylcholine (DPPC):egg phosphatidylglycerol (PG) and extracted mixed lipids (with 1% protein) from cow lung lavage (CLL). Preventilatory tracheal instillation of greater than 15 mg/kg of CLL in 10 ml 0.15 M NaCl to premature lambs gave improved alveolar-arterial O2 gradient and blood gases and increased lung compliance, compared with control lambs over a 15-h period. Lambs receiving 7:3 DPPC:PG dispersions were not improved over controls with regard to pressure-volume characteristics and were worse than controls in arterial oxygenation. In terms of in vitro surface properties, both extracted natural CLL and 7:3 DPPC:egg PG were able to lower aqueous surface tension to 1 dyn/cm under dynamic compression. However, the dynamic respreading of CLL films on successive surface cycles was superior to that of 7:3 DPPC:PG. Moreover, after dispersal in 0.15 M NaCl by vortexing (5 mg/80 ml), CLL adsorbed to surface pressure (tau values of 45 dyn/cm within 10 min. 7:3 DPPC:PG adsorbed to significantly lower tau values after subphase dispersal by a variety of methods.

Properties of freshly isolated type II alveolar epithelial cells

The biochemical characteristics of type II alveolar epithelial cells dissociated from adult rabbit lung by instillation of low concentrations of an elastase trypsin mixture are reported. Cells studied immediately (within 4 h) after isolation were found to incorporate the radioactively labelled precursors [U-14C]glucose, [methyl-3H]choline and [3H]palmitate into cellular phosphatidylcholine at rates 2-10-fold higher than previously reported for cells not subject to short-term cell culture. Secretion of phosphatidylcholine was stimulated by beta-adrenergic agonists. Measurement of specific activities of enzymes of phospholipid biosynthesis in subcellular fractions of isolated lung cells showed a significant enrichment of acyl coenzyme A-lysophosphatidylcholine acyltransferase, an enzyme believed to be involved in pulmonary surfactant phosphatidylcholine remodeling, in the endoplasmic reticulum of type II cells. These observations support the utility of freshly isolated type II cells as a model system for the study of the functions of the alveolar epithelium.

Effects of dexamethasone on beta-adrenergic receptors in fetal lung explants

The action of beta-adrenergic agonists on pulmonary surfactant secretion requires lung cell membrane beta-adrenergic receptors. In the fetus, the density of beta-adrenergic receptors in lung increases in the latter stages of gestation. The increase in density can also be induced by maternal glucocorticoid treatment. In this study, we measured beta-adrenergic receptors in developing rat lung by (-) [3H]-dehydroalprenalol (DHA) binding and confirmed the increase in beta-adrenergic receptors late in gestation. To determine if glucocorticoids have a direct effect on fetal lung to regulate beta-adrenergic receptors, we cultured fetal lung explants with dexamethasone. Treated explants had increased DHA binding compared with controls (138.0 +/- 8.8 versus 63.2 +/- 5.0 fmole/mg membrane protein). Scatchard analysis revealed that the increased DHA binding was due to an increase in maximum receptor number. There was also a significant difference in the dissociation constant of the treated and control explants (0.85 +/- 0.07 nM versus 0.43 +/- 0.08 nM, respectively; P less than 0.05), suggesting that the receptors induced by dexamethasone were of lower binding affinity. Cyclohexamide, an inhibitor of protein synthesis, completely eliminated the dexamethasone induced increase in DHA binding. These data indicate that glucocorticoids have a direct effect on fetal lung to increase beta-adrenergic receptor density and that new protein synthesis is required for this effect.

Sequential effects of irradiation on the pulmonary surfactant system

This study examines the effect of irradiation on lung surfactant synthesis and secretion in mice. Animals were irradiated with 650, 1300, or 1950 rad and morphological and biochemical indices of surfactant system function were followed for 18 weeks. No changes were seen at 650 rad; the results at 1300 and 1950 rad were virtually identical. Increased amounts of alveolar surfactant phospholipid were measureable by 24-hours. This persisted for four weeks and returned to normal by 18 weeks. Tissue surfactant phospholipid was initially reduced, returned to normal by four weeks and was increased at 18 weeks. At 18 weeks there was increased incorporation of surfactant precursor and increased production of alveolar surfactant. These biochemical changes were reflected in morphologic alterations showing release of lamellar body contents into alveoli in the first week and an increase in lamellar bodies in type II pneumocytes by 18 weeks. Elevated tissue protein levels and morphologic evidence of increased collagen formation were also found at 18 weeks. These findings indicate effects of irradiation on the pulmonary surfactant system and have important implications for the pathogenesis and potential therapy of radiation pneumonitis.

Concurrent outbreaks of rhinovirus and respiratory syncytial virus in an intensive care nursery: epidemiology and associated risk factors

An outbreak of viral respiratory disease occurred in eight infants in a neonatal intensive care unit during the 1980 winter respiratory season. Four infections with respiratory syncytial virus and four infections with rhinovirus were identified. Epidemiologic investigation revealed that viral respiratory infection was significantly associated with intubation with orotracheal tubes (P = 0.001), with the presence of both a nasal feeding tube plus an orotracheal tube together (P = 0.007), and with assisted ventilation (P = 0.009) when compared to uninfected controls. Twenty-seven of 85 (30.6%) personnel working in the unit at the time of the outbreak reported a history of upper respiratory illness during the week prior to the outbreak, and 46 (54.1%) of them had had contact with patients in areas of the hospital where patients infected with RSV and rhinovirus were housed. The data suggest that both viruses were transmitted to the babies by hospital personnel. Rhinoviruses can be nosocomial pathogen in neonates with compromised pulmonary function, and the clinical presentation of rhinovirus infection in neonates may be difficult to distinguish from that produced by RSV.

Isolation of type II pneumocytes by laser flow cytometry

The isolation of a pure population of type II pneumocytes from adult rabbit lung by the technique of multiparameter laser flow cytometry is reported here. Lipophilic phosphine-3R was used to stain cell dissociated from lungs by elastase and trypsin. Type II cells were then sorted by simultaneous measurement of high phosphine-3R fluorescent staining of lamellar bodies and intermediate intensity of low-angle light scatter. We were able to obtain an essentially pure population (98%) at sorting rates of 5 X 10(5) lamellar-body-containing cells per hour. The cell sorter technique offers an attractive alternative to the density gradient isolation of type II cells, particularly in terms of detailed population analysis. In addition, refinements in cell sorter methods offer the potential to discriminate differentiating type II cells with few lamellar bodies that do not segregate on the basis of buoyant density.