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Biomedical subjects

F Possmayer

Publications and source records attributed to F Possmayer.

At least 127 records · Page 7Linked to original sources
PubMed1983

Alveolar pre-type II cells from the fetal rabbit lung. Isolation and characterization.

A method for preparing a homogeneous population of undifferentiated cells from the fetal rabbit lung is described. This method utilizes enzymatic digestion, differential adhesion to remove fibroblasts and centrifugation on a discontinuous metrizamide gradient. Cells isolated by this procedure replicate in vitro in medium supplemented with carbon-stripped fetal bovine serum. Mitosis can also be stimulated by heat-inactivated medium conditioned by fetal lung fibroblasts. After confluence, exposure of these cells to 0.55 or 55 nM dexamethasone significantly increased the incorporation of [14C]choline into phosphatidylcholine. Lower concentrations of the drug also increased incorporation, but not significantly so. Addition of heat-inactivated fibroblast-conditioned medium produced a 25% increase in choline incorporation, but this was not significant. Furthermore, the presence of conditioned medium tended to reduced the response of the cells to dexamethasone. After confluence, lamellar inclusion bodies were present in more than 90% of those cells exposed to dexamethasone. These organelles were not observed in cell monolayers not exposed to the steroid. These cells did contain a few small electron-dense bodies. The latter may be immature multivesicular bodies.

Animals↗
PubMed1983

A synthetic emulsion reproduces the functional properties of pulmonary surfactant.

An effective substitute for pulmonary surfactant must be able to reduce water-vapour surface tensions to under 1 mN/m and it must spread rapidly and spontaneously at the air interface from the aqueous phase. Pure dipalmitoylphosphatidylcholine meets the former requirement, but not the latter. A synthetic surfactant is described which meets both of these criteria. The surfactant is prepared as a DPPC monolayer stabilizing an aqueous emulsion of an inert fluorocarbon oil; it spreads rapidly at the air/liquid interface, lowers the surface tension to under 1 mN/m during compression at the air/liquid interface and restores normal pressure-volume characteristics to surfactant-depleted lungs.

Animals↗
PubMed1983

Bovine pulmonary surfactant: chemical composition and physical properties.

Bovine pulmonary surfactant was obtained by endotracheal lavage of lungs from newly slaughtered cows followed by differential centrifugation. Lipid extracts of bovine surfactant contained 3% neutral lipid, mainly as cholesterol and diacylglycerol and 97% phospholipid. Phosphatidylcholine (79%) and phosphatidylglycerol (11%) accounted for most of the phospholipids with smaller amounts of phosphatidylethanolamine, phosphatidylinositol, lyso-bis-phosphatidic acid and sphingomyelin. Fatty acid analysis revealed high levels of palmitate in phosphatidylcholine and to a lesser extent phosphatidylglycerol, but not in the other diacylphospholipids. Phosphatidylcholine was 53% disaturated and phosphatidylglycerol was 23% disaturated. Monoenoic species accounted for the major proportion of the remaining lipid. The protein content was 10% as estimated by the Lowry procedure and 5% when determined by amino acid analysis. Extraction with chloroform/methanol removed ca. 90% of the protein but had no effect on the surfactant properties as evaluated by a pulsating bubble technique.

Animals↗
PubMed1983

Accelerated prepartum maturation of the fetal sheep lung with physiological doses of andrenocorticotrophin.

The role of Adrenocorticotrophin (ACTH), administered in physiological doses (12 micrograms/d), on lung maturation was investigated in the intact ovine fetus at 127-130 days of gestation. ACTH1-24 was administered in a pulsatile or continuous dose for 72 hours. Compared to untreated twins (n = 4) and saline infused fetuses (n = 4), the lungs of the pulsatile-ACTH (n = 10) and continuous-ACTH (n = 4) treated fetuses showed accelerated prepartum maturation by all indices used. Lung distensibility (V40-ml of air per g of wet lung at 40 cm H2O pressure), as determined by pressure-volume curves with air was 1.62 +/- 0.18 vs 0.72 +/- 0.23 and 0.66 +/- 0.12 while the stability (Vo-ml of air per g of wet lung at atmospheric pressure) was 0.33 +/- 0.07 vs 0.10 +/- 0.01 and 0.21 +/- 0.09 for the P-ACTH group vs the control groups (P less than 0.005). In the continuous-ACTH group vs their untreated twins the distensibility was 1.58 +/- 0.10 vs 0.56 +/- 0.11 while the stability was 0.83 +/- 0.20 vs 0.09 +/- 0.01 respectively (less than 0.005). Phosphotidylcholine concentration in lavage fluid increased from 0.05 +/- 0.02 mg/g of lung to 0.24 +/- 0.07 in the pulsed-ACTH group compared to untreated twin fetuses (P less than 0.05). Morphologically the lungs of the treated groups were well aerated with thin walled airsacs. In both treated groups, there was a doubling of the adrenal weight (P less than 0.005). Fetal plasma cortisol basal level increased from less than 5 ng/ml to 143.5 +/- 66.5 ng/ml in the continuous-ACTH group while it only rose to 36.6 +/- 7.5 ng/ml in the pulsed-ACTH group by 72 hours. Superimposed on the rise in basal fetal cortisol, there was an acute increase in cortisol temporally related to each ACTH pulse; the peaks reaching levels indistinguishable from the levels of the continuous-ACTH infusion. It is concluded that the administration of low doses of ACTH markedly accelerate prepartum maturation of the intact ovine lung over 72 hours. The mechanism by which ACTH exerts this powerful maturation effect on the fetal lung remains to be elucidated.

Adrenocorticotropic Hormone↗
PubMed1983

Hyaline membrane disease treated with bovine surfactant.

Six preterm infants with severe hyaline membrane disease requiring ventilation were treated, at a median age of 15.5 hours, with a single intratracheal bolus of a bovine surfactant suspension. Arterial oxygenation increased dramatically, and chest radiograms showed improvement after two to four hours. However, a variable degree of deterioration occurred within 24 hours. All of the infants required oxygen therapy for several weeks, and one developed severe bronchopulmonary dysplasia.

Animals↗
PubMed1982

Concerning the coidentity of phosphatidic acid phosphohydrolase and phosphatidylglycerophosphate phosphohydrolase in rat lung lamellar bodies.

The properties of the phosphatidylglycerophosphate phosphohydrolase activity in lamellar bodies from rat lung have been compared with the properties of the activities responsible for the degradation of aqueously-dispersed phosphatidic acid (PAaq) and membrane-bound phosphatidic acid (PAmb). Subcellular fractionation studies revealed that the phosphatidylglycerophosphate phosphohydrolase activity and the PAaq-dependent phosphatidic acid phosphohydrolase activity were predominantly associated with the mitochondrial and microsomal fractions, while the PAmb-dependent phosphohydrolase activity was associated with the cytosol. Although the lamellar body fraction contained less than 1% of the total activity, the phosphatidic acid phosphohydrolase activities associated with this fraction could not be explained by contamination with microsomes or cytosol. The three activities exhibited similar heat inactivation profiles at 55 degree C. However, differences in the responses of these activities to the presence of iodoacetate, p-chloromercuriphenyl sulphonate, mercaptoethanol, mercaptoethanol plus MgCl2, and Triton X-100 indicated that the enzymes responsible for these activities may be distinct. Furthermore, addition of up to a ten-fold greater amount of PAaq did not seriously affect the hydrolysis of phosphatidylglycerophosphate. These results indicate that the phosphatidic acid phosphohydrolase and phosphatidylglycerophosphate phosphohydrolase activities in rat lung lamellar bodies are not necessarily catalyzed by the same protein.

Animals↗
PubMed1981

Pool sizes of the precursors for phosphatidylcholine synthesis in developing rat lung.

1. Pulmonary maturation in the rat is accompanied by a 30% postnatal increase in the pool size of choline, a 4-fold overall prenatal and postnatal decrease in the level of cholinephosphate, a 3-fold decrease in CDPcholine levels and a 2-fold increase in the content of phosphatidylcholine. 2. The level of 1,2-diacyl-sn-glycerol in rat lung increases 5-fold during the fetal and neonatal periods. Only minor alterations were noted in the fatty acid composition. 3. These results are consistent with an increase in the relative rates of the cholinephosphate cytidylyl-transferase and cholinephosphotransferase steps of phosphatidylcholine production during pulmonary maturation. The relative rate of the step catalyzed by phosphatidate phosphohydrolase may also be increased.

Animals↗
PubMed1981

Pulmonary phosphatidic acid phosphohydrolase. Developmental patterns in rabbit lung.

1. The developmental patterns of the phosphatidic acid phosphohydrolase activities in developing rabbit lung were determined using both aqueously dispersed phosphatidic acid (PAaq) and membrane-bound phosphatidic acid (PAmb) as the substrates. 2. The specific activities and the total activities of the PAmb-dependent phosphohydrolase activities in the microsomes and to a lesser extent in the homogenates increased between 26 and 30 days gestation (term 31), but decreased in the adult. The PAaq-dependent activities demonstrated a smaller increase during late gestation and a decrease in the adult. 3. There was little change in either the Paaq- or the Pamb-dependent activities in the cytosol between 25 and 30 days gestation. The total activities per g lung were increased in the adult. 4. Fractionation of adult cytosol on Bio-Gel A5m revealed PAaq-dependent activities in the void volume (Vo) (50% total), a peak with an apparent molecular mass (Mr) = 150 kdaltons (25% total) and a peak with Mr = 110 kdaltons (25% total). The PAaq-dependent peak with Mr = 150 kdaltons was not detected in the fetal cytosols. 5. Gel filtration revealed PAmb-dependent activity in the Vo (15% total), a major peak with an apparent Mr = 390 kdaltons (44% total) and minor peaks with Mr = 240 kdaltons (16% total) and Mr = 110 kdaltons (24% total). Little change was observed during development. 6. Thermal denaturation studies on he PAmb-dependent activities in the cytosols produced biphasic curves with a rapidly inactivated component and a relatively heat-stable component. The thermal denaturation profiles for the PAmb-dependent activities remained relatively unaltered throughout fetal development. The thermal denaturation profiles of the PAaq-dependent activities in the fetal cytosols were also biphasic. In contrast, the inactivation profiles of the PAaq-dependent activities in adult cytosol were monophasic.

Aging↗
PubMed1981

Hormonal induction of pulmonary maturation in the rabbit fetus: effects of maternal treatment with estradiol-17 beta on th endogenous levels of cholinephosphate, CDP-choline and phosphatidylcholine.

1. Administration of estradiol-17 beta to pregnant rabbits at 25 days gestation (term, 31 days) resulted n a significant increase in the incorporation of [14C]-choline, but not [14C]ethanolamine, into the lipids of fetal lung slices. The incorporation of [35S]methionine was not affected. 2. Enzymatic assays conducted in vitro revealed no significant effect on either the activities of several enzyme markers for subcellular organelles, the activities of the enzymes responsible for the production of phosphatidylglycerol and phosphatidylinositol, membrane-bound or aqueously dispersed phosphatidate-dependent phosphatidic acid phosphohydrolase activities or the activities of the auxiliary enzymes responsible for the synthesis of dipalmitoylphosphatidylcholine. 3. The activity of the enzymes involved in the choline pathway for the de novo biosynthesis of phosphatidylcholine were not significantly altered except for a 66% increase in the CTP:cholinephosphate cytidylyltransferase activity assayed in the cytosol. The addition of phosphatidylglycerol stimulated cholinephosphate cytidylyltransferase activity approx. 3-fold. However, in the presence of this lipid, the activities in cytosol from control and treated fetuses were similar, indicating that the increased activity noted in the absence of phosphatidylglycerol was due to an activation of existing cytidylyltransferase activity rather than an increase in total enzyme units. 4. Estrogen treatment of the does was also associated with a marked decrease in the levels of cholinephosphate in fetal lung and significant increases in the levels of CDPcholine and phosphatidylcholine. These alterations in pool size are consistent with an increase in the activity of cholinephosphate cytidyltransferase in vivo. The results suggest that cholinephosphate cytidylyltransferase may catalyse an important rate-determining reaction in the synthesis of phosphatidylcholine in fetal lung. The data also support the view that the reaction catalysed by CDPcholine:diacylglycerol cholinephosphotransferase also has a regulatory role during development.

Animals↗
PubMed1981

Pulmonary phosphatidylcholine biosynthesis. Alterations in the pool sizes of choline and choline derivatives in rabbit fetal lung during development.

1. Progressive changes were noted in the pool sizes of choline in fetal rabbit lung between 25 and 30 days gestation (term, 31 days) and between 30 days gestation and adult lung. The level of choline in adult lung was double the level in the fetal lung at 25 days gestation. The pool size of choline phosphate decreased 10-fold during this period while the level of CDPcholine decreased by 30%. The phosphatidylcholine content increased 3-fold during development. The major change in the relative pool sizes was a marked decrease in the ratio of choline phosphate to CDPcholine from 26:1 at 25 days gestation to 3.4:1 in adult lung. 2. No differences were detected between the uptake of [14C]choline into slices from fetal lungs at 25 days gestation or slices from adult lung. However, the ability of the adult slices to convert [14C]choline into its derivatives was 30% lower than slices from fetal lung. In addition, whereas fetal slices contained significantly more radioactivity in choline phosphate and CDPcholine, adult slices incorporated significantly more [14C]choline into phosphatidylcholine. Experiments with [3H]choline and 32Pi revealed that the 3H/32P ratio of choline phosphate in fetal or adult slices was identical to the isotopic ratio in phosphatidylcholine, indicating that under the experimental conditions, negligible radioactivity was incorporated by base-exchange. Because of the marked decrease in the pool size of choline phosphate during development, it cannot be concluded that the increase in the incorporation of radioactive choline into phosphatidylcholine is indicative of increased production of phosphatidylcholine by the de novo pathway. The results suggest that if the de novo pathway is responsible for the increase in phosphatidylcholine content, this increase is due to a change in the parameter controlling the flux through the choline phosphate cytidylyltransferase step. The results also indicate that the metabolic flux through choline phosphotransferase is also enhanced during pulmonary development.

Animals↗
PubMed1981

Pulmonary phosphatidic acid phosphohydrolase: further studies on the activities in rat lung responsible for the hydrolysis of membrane-bound and aqueously dispersed phosphatidate.

Rat lung cytosol and microsomal fractions both contain phosphohydrolase activity towards membrane-bound phosphatidic acid (PAmb) and aqueously dispersed phosphatidic acid (PAaq) which cannot be explained through contamination with the other fraction. The phosphohydrolase activities with PAaq demonstrated Km and Vmax values which were more than an order of magnitude greater than those observed with PAmb and with vesicles prepared from the lipids extracted from [32P]PA-labelled microsomes. The PAaq-dependent activities in both fractions were stimulated by preparing mixed liposomes with phosphatidylcholine. The PAmb-dependent activities in rat lung microsomes and cytosol were markedly stimulated by high concentrations of Triton X-100 and Nonidet P-40. The PAmb- and PAaq-dependent activities in the microsomes were stimulated by deoxycholate. Although no difference was observed in the inhibition profiles of the PAmb- and PAaq-dependent activities of the cytosol in the presence of various mercurials, the PAmb-dependent activity in the microsomes was somewhat more susceptible than the PAaq-dependent activity. The PAmb-dependent activities in both fractions were more susceptible to inhibition by iodoacetamide. These results support the view that separate rat lung enzymes were involved in the hydrolysis of PAmb and PAaq. The relative abilities of rat lung cytosol and microsomes to hydrolyse PA endogenously generated on the microsomes were compared using relative concentrations of cytosol corresponding to the levels in intact rat lung. During the initial period (5-10 min) the cytosol phosphohydrolase activity was more effective than the microsomal activity. At later stages (10-20 min), the rates were comparable.

Animals↗
PubMed1980

Relative suitability of 1-palmitoyl and 1-stearoyl homologues of 1-acyl-sn-glycerylphosphorylcholine and different acyl donors for phosphatidylcholine synthesis via acyl-CoA:1-acyl-sn-glycero-3-phosphorylcholine acyltransferase in rat lung microsomes.

The relative suitability of the 1-palmitoyl and 1-stearoyl homologues of 1-acyl-sn-glyceryl-phosphorylcholine and different acyl donors were tested as substrates for phosphatidylcholine synthesis via the acyl-CoA:1-acyl-sn-glycero-3-phosphorylcholine acyltransferase in rat lung microsomes. The acyl acceptor was an almost equi-molar mixture of the [3H]palmitoyl plus [14C]stearoyl species of 1-acyl-sn-glycero-3-phosphorylcholine with palmitoyl-, stearoyl-, oleoyl-, linoleoyl-, or arachidonoyl-CoA serving as the acyl donor. At all concentrations of acyl acceptor, reaction velocities with 20:4-CoA greater than or equal to 18:2-CoA > 18:1-CoA > 16:0-CoA >18:0-CoA. Furthermore, the acyltransferase selectively utilized the 1-palmitoyl over the 1-stearoyl species of 1-acylglycerylphosphorylcholine by 4.2- to 5.7-fold under optimal assay conditions with the various acyl-CoA thiolesters. However, the degree of preference exhibited for the 1-palmitoyl-sn-glycero-3-phosphorylcholine, as acyl acceptor, versus the 1-stearoyl homologue with palmitoyl-CoA as the acyl donor was not significantly different from that obtained with the other acyl-CoA derivatives. Thus, the specificity of the acyl-CoA:1-acyl-sn-glycero-3-phosphorylcholine acyltransferase indicates an ability of this enzyme to produce dipalmitoyl phosphatidylcholine but it cannot independently explain the predominance of dipalmitoyl phosphatidylcholine in lung or the tendency of stearate at the 1-position to associate with fatty acids of increasing unsaturation at the 2-position.

1-Acylglycerophosphocholine O-Acyltransferase↗
PubMed1980

Effect of birth and surfactant treatment on phospholipid synthesis in the premature rabbit.

The incorporation of intraperitoneally injected 3H-glycerol and 14C-palmitate into the lipids of lung, liver and brain was examined in premature rabbits (27 days gestation, term 31) both in utero and in control or surfactant-treated neonates. With the lung, there was an increased incorporation after delivery, especially with the surfactant-treated pups. The incorporation of 3H-glycerol into liver lipids was markedly reduced after birth, particularly with the nontreated controls. The liver:lung ratios of the incorporations were decreased after delivery. In all three tissues, the relative incorporations into the individual lipids were not affected to any great extent by birth or surfactnat treatment. In lung, the disaturated and monoenoic species, respectively, of phosphatidylcholine accounted for the major proportion of the radioactivity. After birth there was a small increase in the labelling of the monoenoic species at the expense of the disaturated species with both control and surfactant-treated neonates. These observations support the proposal that surfactant treatment of the prematurely delivered neonate could be used prophylactically for the prevention of the respiratory distress syndrome.

Animals↗