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Biomedical subjects

J Goerke

Publications and source records attributed to J Goerke.

At least 37 records · Page 2Linked to original sources
PubMed1989

A captive bubble method reproduces the in situ behavior of lung surfactant monolayers.

We tested a new captive bubble surface tensiometer with films adsorbed from aqueous suspensions of rabbit lung surfactant and a bovine lung surfactant lipid extract and with films of dipalmitoyl-sn-3-glycerophosphorylcholine (DPPC) spread from solvents. The lack of tubes penetrating the bubble surface eliminated potential leakage pathways for the surface film, which was compressed by increasing external pressure. Surface tensions and areas were calculated directly from bubble shapes without the need of pressure measurements. After only one to two compressions, the rabbit surfactant films exhibited the low surface tension, collapse rates, and compressibilities characteristic of the alveolar surface in situ and approached the behavior of spread DPPC films. The bubble "clicking" phenomenon described earlier by Pattle (Proc. R. Soc. Lond. B Biol. Sci. 148: 217-240, 1958) was also reproduced, but only with the bovine extract, which did not perform as well as the rabbit surfactant in surface tests. These findings suggest that surfactant apoprotein SP-A, which was probably present in the rabbit but not the bovine preparations, enhances both adsorption and stability of pulmonary surfactant monolayers.

Animals↗
PubMed1988

Interactions of the low molecular weight group of surfactant-associated proteins (SP 5-18) with pulmonary surfactant lipids.

The interaction of the low molecular weight group of surfactant-associated proteins, SP 5-18, with the major phospholipids of pulmonary surfactant was studied by fluorescence measurements of liposomal permeability and fusion, morphological studies, and surface activity measurements. The ability of SP 5-18 to increase the permeability of large unilamellar lipid vesicles was enhanced by the presence of negatively charged phospholipid. The permeability of these vesicles increased as the protein concentration was raised and the pH was lowered. SP 5-18 also induced leakage from liposomes made both from a synthetic surfactant lipid mixture and from lipids separated from SP 5-18 during its purification from canine sources. When SP 5-18 was added to egg phosphatidylglycerol liposomes, the population of liposomes which became permeable leaked all encapsulated contents, while the remaining liposomes did not leak at all. The extent of leakage was higher in the presence of 3 mM calcium. SP 5-18 also induced lipid mixing between two populations of egg phosphatidylglycerol liposomes in the presence of 3 mM calcium, as monitored by resonance energy transfer between two different fluorescent lipid probes, N-(7-nitro-2,1,3-benzoxadiazol-4-yl)phosphatidylethanolamine and N-(lissamine rhodamine B sulfonyl)phosphatidylethanolamine. Negative-staining electron microscopy showed that the addition of SP 5-18 and 3 mM calcium produced vesicles twice the size of control egg phosphatidylglycerol liposomes. In addition, surface balance measurements revealed that the adsorption of liposomal lipids to an air/water interface was enhanced by the presence of SP 5-18, negatively charged phospholipids, and 3 mM calcium. These observations suggest a similar lipid dependence for the interactions observed in the fluorescence and adsorption experiments.

Animals↗
PubMed1988

Interaction of erythrocyte protein 4.1 with phospholipids. A monolayer and liposome study.

We have studied the interaction of purified human erythrocyte protein 4.1 with phospholipid membranes by monitoring both the increase in surface pressure of monolayers at the air/water interface and the change in permeability in liposomes to fluorescent molecules, in the presence of protein 4.1. Protein 4.1 penetrated into monolayers of brain phosphatidylserine (PS) and egg phosphatidylcholine (PC), even above surface pressures of 30 mN/m. Protein 4.1 increased the permeability of negatively charged PS, but not PC, liposomes, measured as the increase in fluorescence when encapsulated 1-aminonaphthalene-3,6,8-trisulfonic acid (ANTS) and p-xylenebispyridinium bromide (DPX) or carboxyfluorescein were released into the medium. The interaction of protein 4.1 with PS large unilamellar vesicles (LUV) was increased as the pH and the ionic strength were lowered, and decreased as the Ca2+ or Mg2+ concentrations and ionic strength were raised. In order to study the relevance of these measurements to the erythrocyte, we prepared LUV of synthetic lipid mixtures characteristic of both the inner and the outer membrane leaflets. Protein 4.1 increased the permeability of inner, but not outer, leaflet LUV at both pH 6.0 and 7.4. These observations suggest that negatively charged phospholipid domains around the protein 4.1 high-affinity protein-binding site(s) may contribute to the anchoring of protein 4.1 to the cytoplasmic surface of the red cell membrane.

Blood Proteins↗
PubMed1984

Protein composition of rabbit alveolar surfactant subfractions.

The goal of this investigation was to characterize the proteins in subfractions of alveolar surfactant obtained by lung lavage and separated by differential centrifugation. It was previously demonstrated that the material in the more sedimentable fraction, which was enriched in tubular-myelin and was surface-active may be a precursor to the less sedimentable, vesicular, inactive material [1]. Separation of the proteins by polyacrylamide gel electrophoresis showed that the more sedimentable subfractions and rabbit surfactant isolated by conventional methods contained proteins with molecular weights comparable to those previously reported for alveolar surface active material (approximately 36 000 and 10 000). The less sedimentable subfractions contained less of these proteins. Immunoblots with anti-dog surfactant apoprotein antibodies, which cross-react with rabbit proteins, supported these observations. Immunoblots also showed that all of the subfractions contained serum proteins and secretory IgA, with the less sedimentable subfractions containing more secretory IgA. These results suggested that changes in protein composition may accompany functional changes in surfactant in the alveoli.

Animals↗
PubMed1984

Role of calcium ions the structure and function of pulmonary surfactant.

Pulmonary surfactant isolated by centrifugation in buffers containing ions contains at least three different morphologic structures. The presence of one of these, tubular myelin, is dependent on calcium ions, since chelation of the calcium ions causes disruption of this structure. Addition of EDTA also decreases the ability of the surfactant to absorb rapidly to air-water interfaces and lower surface tension. Titration with calcium ions (2.5 or 5 mM) restores rapid surface adsorption and restores the tubular myelin structural forms. Magnesium ions cannot substitute for calcium ions in these processes. The reversibility of structure and function induced by calcium ions and EDTA is also accompanied by reversible isopycnic density shifts probably related to aggregation and disaggregation of the lipid-protein complex with calcium ions and EDTA, respectively.

Animals↗
PubMed1983

Subfractionation of lung surfactant. Implications for metabolism and surface activity.

Because previous studies have suggested that lung surfactant is not a simple compartment of homogeneous material, we subfractionated lamellar bodies and components of alveolar lavage from male New Zealand white rabbits, according to differences in sedimentability. We recovered two lamellar body populations at different densities in discontinuous sucrose density gradients; we separated six subfractions of alveolar lavage by differential centrifugation. To determine whether or not precursor-product relationships existed among the subfractions, we injected radioactive palmitate intravenously, killed the rabbits 1-72 h later, and measured phospholipid specific activities. The two populations of lamellar bodies had similar phospholipid composition, fatty acyl composition of phosphatidylcholine and phosphatidylglycerol, and surface activity. Light lamellar bodies had a higher ratio of phospholipid to protein, and labelled with tracer later in time than dense ones. For alveolar lavage subfractions, later labelling with tracer, lower adsorption rate and lower total protein and phosphatidylglycerol content seemed to correlate with decreasing average density and particle size as well as with the disappearance of tubular myelin structure and appearance of predominantly vesicular structure. The subfractions appear to be in a metabolic sequence in which heavier, more dense material is a precursor to lighter, less dense material. The results suggest that subfractions of surfactant are extensively recycled.

Animals↗
PubMed1983

Phosphatidylglycerol-deficient lung surfactant has normal properties.

We have investigated the effects of substituting phosphatidylinositol (PI) for phosphatidylglycerol (PG) on the functional properties of rabbit lung surfactant. We gave oral 10% glucose solution for 3 days to 11 rabbits and 10% inositol to 12 others. Lung lavage surfactant phospholipids were normal in both groups, except that PG was low and PI was high in the inositol group. Fatty acyl group distributions did not differ, except for a slight decrease of oleic acid in the inositol group. Electron microscopic examination showed normal surfactant structure in both. The time course of surfactant adsorption to an air-water interface was similar in both groups. Minimum surface tension after film compression was 4.0 +/- 0.8 mN . m-1 in the glucose group and 2.9 +/- 1.3 mN . m-1 in the inositol group (mean +/- SE). Surface potential-surface pressure isotherms were identical to within 12 mV. Arterial blood gases breathing air and 100% O2 were the same in both groups, as were pressure-volume curves of excised lungs, with both air and saline filling. The results suggest that, if acidic phospholipids are necessary for maintaining normal surfactant structure and surface properties, normal pressure-volume relationships, and normal gas exchange, then PI may substitute for PG.

Animals↗
PubMed1981

Precursor-product relationship between rabbit type II cell lamellar bodies and alveolar surface-active material. Surfactant turnover time.

To estimate the turnover time of alveolar surfactant in New Zealand white rabbits, we injected [9,10-(3)H] palmitic acid and [2-(14)C] glycerol intravenously. From 1-48 h after injection, wer killed the animals, lavaged the lungs for alveolar surfactant with saline, and isolated the lamellar bodies by homogenization and sucrose density gradient centrifugation. Lamellar bodies and alveola surfactant had comparable phospholipid composition and surface activity. Lamellar bodies contained little DNA, no mitochondrial enzyme activity and less than 5% contaminating phospholipids from microsomal and Golgi-enriched fractions. We measured radioactivity of phosphatidylcholine, saturated phosphatidylcholine and phosphatidylglycerol for each isotope in lamellar bodies and surfactant at each time point. The plot of the integral with respect to time of the difference between lamellar body and surfactant specific activity against surfactant specific activity has a slope determined by the turnover time, and a shape which tests the precision of the precursor-product relationship. This analysis does not assume a pulse label and allows for possible recycling of tracer from surfactant to lamellar bodies. We obtained turnover times of 4-11 h. We detected an imprecise precursor-product relationship between lamellar bodies and alveolar surfactant, which is not due to experimental variability or to contamination of lamellar bodies by other subcellular fractions but may reflect imperfect mixing within surfactant compartments.

Animals↗
PubMed1981

Alveolar subphase pH in the lungs of anesthetized rabbits.

We measured the pH of the alveolar subphase fluid by puncturing the most superficial alveoli of the exposed lungs of anesthetized rabbits with H+-selective and nonselective KCl microelectrodes. In these experiments, we bathed the lung surface with paraffin oil or buffered Ringer's solutions that had a CO2 tension of 40 Torr (1 Torr = 133.3 Pa) and found an alveolar pH of 6.92 +/- 0.01 (mean +/- sEM). When the pH of the surface buffer was below 6.7 or above 7.5, alveolar pH varied with surface buffer pH. With the nonselective electrode, we did not find a significant electrical potential difference between the alveolar fluid and the pleural surface. These results are consistent with active transport of H+ (or HCO3(-) across alveolar epithelium.

Anesthesia, General↗
PubMed1981

Surfactant release in excised rat lung is stimulated by air inflation.

Because increased ventilation has been associated with an acceleration of lung surfactant turnover, we investigated the effect of fluid and air inflations on the release of surfactant into the air spaces. We found that excised rat lungs, initially lavaged three times at 23 degrees C, release approximately 40-90 micrograms of phospholipid/g wet lung wt into the air spaces in response to a further infusion of fluid into the airway equal to total lung capacity. A single air inflation to the same volume, followed by degassing and lavage, contributes approximately 230 micrograms to the yield of phospholipid. We estimated basal release of phospholipid as 112 micrograms wet lung wt-1 . h-1, which is far less than the 2,050 micrograms -1 . h-1 retrieved during a series of air and fluid inflations. The above findings are consistent with the hypothesis that air inflation to total lung capacity is a major physiological stimulus to release of lung surfactant into the alveolar space. The lung lavage process itself also causes the release of surfactant.

Air↗
PubMed1981

Temperature dependence of dipalmitoyl phosphatidylcholine monolayer stability.

Dipalmitoyl phosphatidylcholine is the principal component of lung surfactant, and knowledge of its behavior as a film spread at the air-water interface is essential for understanding how lung surfactant itself works. We therefore studied the collapse rates of very low surface tension air-water monolayers of dipalmitoyl, dimyristoyl, and palmitoyl-myristoyl phosphatidylcholines at different temperatures. In each case we found that the monolayers abruptly became unstable at temperature 3-4 degree C above their bulk lipid-water phase transition temperatures (Tc). This accords with a comparable increase in Tc occurring in bulk systems subjected to high pressure. These findings are also consistent with the behavior of isolated rat lungs, which have been found to require higher transmural pressures to maintain a given volume on deflation when kept at temperature above the Tc of dipalmitoyl phosphatidylcholine.

Air↗
PubMed1980

Interaction of unilamellar liposomes with serum lipoproteins and apolipoproteins.

The effect of rat whole blood plasma, serum, serum lipoproteins, and apolipoproteins on the stability of unilamellar liposomes prepared with French pressure cell was evaluated by measuring the release of entrapped carboxyfluorescein and by electron microscopy. In the absence of serum components, dye escaped very slowly (hours) from egg phosphatidylcholine and phosphatidylcholine-cholesterol (43 mol % cholesterol) vesicles without apparent change in liposomal structure. This slow release was both temperature- and size-dependent. serum and some of its constituents induced a far more rapid (seconds) loss of entrapped dye from phosphatidylcholine liposomes, associated with structural changes. For equal masses of protein the order of potency of this induced activity was: free apolipoproteins (apo A-I, apo E) > isolated lipoproteins (HDL and VLDL) > whole serum or whole plasma. Substantial activity was found in three preparations of bovine serum albumin. This activity could be attributed to small and variable amounts of contaminating lipoprotein-like particles and apolipoprotein A-I. Induced release of dye from liposomes by apolipoproteins was usually associated with rapid formation of discs although other structures were sometimes formed. Purified rat apolipoproteins A-I and E appeared to interact identically with liposomes to induce dye release. This effect was progressively impaired for both apoproteins by increasing amounts of cholesterol and was completely inhibited when liposomes contained 37 mol % cholesterol.

Adult↗
PubMed1980

Unilamellar liposomes made with the French pressure cell: a simple preparative and semiquantitative technique.

A simple, rapid, and almost quantitative technique is described for the preparation of 1-40 ml of homogeneous unilamellar liposomes from dilute or concentrated aqueous suspensions of egg phosphatidylcholine. Aqueous suspensions of lipid are placed with the chamber of a French pressure cell at room temperature and rapidly extruded at 20,000 psi through the small orifice. A single pass transforms more than 70% of the extruded lipid into a homogeneous population of single-wall bilayer vesicles; more than 90% is transformed by recycling the lipid through the French pressure cell. About 95% of these liposomes range between 150-300 A in diameter (mean 200 A). The liposomes are stable for days to months when stored under nitrogen at 0.4 degrees C and can be prepared at 0 degrees, 25 degrees, or 37 degrees C. The liposomes appeared unaltered by repeated passages through the French pressure cell and no degradation of the phospholipid was detected after ten consecutive cycles at 20,000 psi in the absence of a nitrogen atmosphere. The method is especially useful for trapping small molecular weight substances because the concentration of both lipid and solute can be made quite high. Cholesterol up to 45 mole % can be incorporated into larger liposomes of egg phosphatidylcholine (mean diameter 315 A). Other phospholipids and different lipid mixtures can also be transformed into unilamellar vesicles with this method which has the advantage that additional steps of ultracentrifugation, column chromatography, dialysis, and concentrating procedures are usually unnecessary. Multilayered liposomes of small size (980 A mean diameter; > 95% between 500-1,500 A) are produced at lower pressure (3,000 psi). The latter are separated by gel permeation chromatography from a second population of homogeneous vesicles of even smaller size (580 A mean diameter; > 95% between 300-900 A) that contain two bilayer shells.

Biochemistry↗
PubMed1979

Pulmonary surface film stability and composition.

Stability of pulmonary alveoli at end expiration requires a very low air-water surface tension (e.g., less than 10 mN.m-1). Another important requirement is that the surface film maintain this low surface tension for a sufficiently long time at fixed lung volume. We measured monolayer collapse rates at 37 degrees C of lung surface-active material (SAM) and certain lipids found in this material and compared them with alveolar monolayer collapse rates calculated from published lung compliance changes. We found collapse rates for purified SAM or a mixture of dipalmitoyl lecithin (DPPC):monoenoic lecithin (PC):cholesterol (CHOL) (3.03:1.65:1 molar ratios) to be much greater than collapse rates of alveolar films estimated from indirect measurements. Monolayers of pure DPPC or DPPC with 10 mol% monoenoic PC and/or CHOL had collapse rates equal to or less than those estimated from lungs. We conclude that the alveolar monolayer is enriched in DPPC to the extent of 90 mol% or greater. Enrichment may exclude more mobile components from the monolayer during expiration when surface tension reaches verry low values.

Animals↗
PubMed1979

Left ventricular volume from paired biplane two-dimensional echocardiography.

To evaluate the applicability of two-dimensional echocardiography to left ventricular volume determination, 30 consecutive patients undergoing biplane left ventricular cineangiography were studied with a wide-angle (84 degrees), phased-array, two-dimensional echocardiographic system. Two echographic projections were used to obtain paired, biplane, tomographic images of the left ventricle. We used the short-axis view (from the precordial window) as an anolog of the left anterior oblique angiogram, and the long-axis, two-chamber view (from the apex impulse window) as a right anterior oblique angiographic equivalent. A modified Simpson's rule formula was used to calculate systolic and diastolic left ventricular volumes from the biplane echogram and the biplane angiogram. These methods correlated well for ejection fraction (r = 0.87) and systolic volume (r = 0.90), but only modestly for diastolic volume (r = 0.80). These correlations are noteworthy because 65% of the patients had significant segmental wall motion abnormalities. The volumes determined from the minor-axis dimensions of M-mode echograms in 23 of the same patients correlated poorly with angiography.

Adult↗
PubMed1978

Direct determination of volume- and time-dependence of alveolar surface tension in excised lungs.

We measured alveolar surface tension directly by observing the spreading properties of fluid droplets placed by micropipette within individual alveoli. Alveolar surface tension in excised rat lungs at total lung capacity and 37 degrees was 29.7 +/- 1.4 mN-m-1. In lungs held at functional residual capacity, surface tension changed slowly, rising to 9 mN-m-1 at 30 min with a subsequent approximately linear rise to 16 mN-m-1 at 115 min. Thereafter it rose more rapidly (20 mN-m-1 at 140 min), suggesting that it was not asymptotically approaching an equilibrium value.

Animals↗