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J Egberts

Publications and source records attributed to J Egberts.

At least 55 records · Page 3Linked to original sources
PubMed1990

Fetal mouse alveolar type II cells in culture express several type II cell characteristics found in vivo, together with major histocompatibility antigens.

Alveolar type II cells were isolated from fetal mouse lung by differential adherence and obtained in monolayer culture. Cultures display a high degree of purity as shown by histochemical and immunocytochemical staining procedures. Seventy-five percent of cells stained positive with specific anti-lavage serum mouse (SALS-M), an antiserum specific for (pre)alveolar type II cells of the mouse, and osmiophilic bodies were present in 82% of cells. These and other characteristics of type II cells in culture correspond to those of alveolar type II cells in fetal mouse lung. The pattern of reactivity of these cells with various anti-cytokeratin antibodies is described, and we show that, in contrast to rat type II cells, they do not exhibit alkaline phosphatase activity. Identity of the type II cell cultures was shown by their specific phospholipid composition and surfactant protein A (SP-A) content. The fetal alveolar type II cells in culture were found to synthesize and express class I but not class II major histocompatibility complex (MHC) antigens. The possibility to culture fetal alveolar type II cells of the mouse and the availability of genetically well-defined inbred and transgenic mouse strains opens ways to study the genetics of type II cell differentiation and function. Also, the in vitro availability of alveolar type II cells, the progenitor cells of mouse lung tumors, will enable us to study in vitro several of the processes involved in lung tumorigenesis in the mouse.

Alkaline Phosphatase↗
PubMed1989

Minimal surface tension, squeeze-out and transition temperatures of binary mixtures of dipalmitoylphosphatidylcholine and unsaturated phospholipids.

Fluorescence polarization (FP) measurements and surface tension (ST) experiments were performed to determine the gel-to-liquid-crystal transition or melting temperature of phospholipid mixtures. The FP-temperature diagrams showed main transition temperatures of 41 degrees C for dipalmitoylphosphatidylcholine (DPPC). The 7:3 and 9:1 binary mixtures of DPPC and phosphatidylinositol (PI), phosphatidylglycerol (PG) and phosphatidylcholine (PC) had main transition temperatures of, respectively, 32-36 degrees C and 37-39 degrees C. The minimal surface tension of DPPC monolayers increased rapidly at 40 degrees C, suggesting that this was the transition temperature for the melting of these monolayers. This value was in close accordance with the main transition temperature of DPPC, observed with the fluorescence polarization measurements. Melting temperatures of monolayers were higher for almost all mixtures than the temperatures at which the transition started, indicating preferential squeeze out of the unsaturated component and enrichment of the monolayer with DPPC. However, neither the 7:3 DPPC/PC nor the DPPC/PG mixtures could withstand high surface pressures at temperatures above 30 degrees C, whereas monolayers of DPPC/PG (9:1) became fluid at temperatures above 35 degrees C. Preferential squeeze-out of the unsaturated phospholipid was especially effective in both the 7:3 and 9:1 DPPC/PI mixtures. These monolayers started to melt at 39-40 degrees C, which is above their main transition temperatures of, respectively, 32 and 37 degrees C, and which approximate the melting temperature of DPPC. Preferential squeeze-out is essential for an artificial lung surfactant. The estimation of this phenomenon by determining the monolayer melting temperatures is therefore useful for distinguishing between mixtures which are effective surfactants at body temperature and those which are less effective.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1988

Isolation of the acidic phospholipid phosphatidylglycerol from pulmonary surfactant by sorbent extraction chromatography.

Aminopropyl solid-phase columns can be used for phospholipid fractionation. A method has been developed to elute the acidic phospholipid phosphatidylglycerol (PG) separately, and it is applicable to both standard (phospho)lipid mixtures and pulmonary surfactants. The simplicity, rapidity, and high recovery make this method of isolating PG superior to other chromatographic procedures.

Animals↗
PubMed1987

Phosphatidylinositol and not phosphatidylglycerol is the important minor phospholipid in rhesus-monkey surfactant.

Pulmonary surfactant was isolated from lung tissue and alveolar washes of lungs of adult rhesus monkeys (Macaca mulatta). The phospholipid composition was determined and compared to the composition of human surfactant fractions. Contrary to human surfactant, phosphatidylinositol is the major acidic phospholipid, whereas phosphatidylglycerol is only a minor component in rhesus-monkey surfactant. These differences are not caused by a difference in plasma myo-inositol concentrations between the two species.

Animals↗
PubMed1986

Lack of change in the composition of fetal lamb lung surfactant during gestation.

Fetal surfactant from lamb lung fluids collected daily from day 114 to day 146 of gestation, was isolated by centrifugation (pellet material) and further purified by sucrose density gradient centrifugation. The concentration of the pellet material from lung fluid (crude surfactant) increased from day 125 till day 135 and fluctuated strongly from that period onwards, whereas lung fluid secretion increased linearly until a few days before parturition. The pellet phospholipid composition changed with gestational age, suggesting biochemical maturation of the surfactant-producing system. The purified surfactant fraction, of which approximately 85% was phosphatidylcholine, did not change however from day 122 onwards except for a small increase in the percentage of phosphatidylglycerol. Alveolar wash surfactant or the lamellar body material, isolated from fetal lungs at different gestational ages had the same composition as surfactant from lung fluids. Only the composition of lamellar bodies of '125 day' lungs differed slightly from that of the lung fluid surfactant. The similar characteristics of all purified surfactant fractions throughout gestation indicate that, in the fetal lamb, lung maturation is associated with an increase in surfactant production no significant changes in phospholipid composition.

Animals↗
PubMed1986

Determination of lamellar body phospholipids in amniotic fluid: a method to predict when the fetal lung becomes mature.

Lamellar body material was isolated by highspeed centrifugation from the amniotic fluids of 10 mildly diseased patients followed longitudinally and of 60 other women. Three stages of development were defined: (1) immature stage: the phospholipid concentration is less than 20 mumol/l and phosphatidylcholine (PC) is approximately 50%; (2) transitional stage: the phospholipid concentration is between 18 and 40 mumol/l, of which PC is approximately 75% and phosphatidylinositol (PI) 10%. Phosphatidylglycerol (PG) is absent or present at very low concentrations; (3) mature stage: the phospholipid concentration is above 40 mumol/l; its PC percentage is 75% or more. PG is present and the percentage of PI decreases. An increase in phospholipid concentration of 3.27 +/- (SD) 0.75 mumol/l/day was found during the transitional stage. The rate of increase enables us therefore to approximate the number of days that it will take before the fetal lung is mature.

Amniotic Fluid↗
PubMed1986

Gestational age-dependent changes in plasma inositol levels and surfactant composition in the fetal rat.

To study the possibility that changes in fetal surfactant composition depend on the availability of inositol, we isolated surfactant material from lungs of fetal and neonatal rats and estimated their plasma inositol concentration. During the 18- to 22-day gestational period the amount of surfactant increases from 0.17 to 3.10 mumol phospholipids/g wet lung. From day 20 onward, 70% or more of the phospholipids is phosphatidylcholine. In this period the relatively high percentage of phosphatidylinositol (8%) in the lung surfactant decreases to 4% whereas the percentage of phosphatidylglycerol increases from 2 to 8% at parturition. During gestation the phospholipid/protein ratio of the surfactant material increase from 3 to 11 and the highest ratio is found immediately after birth. It decreases again 24 h after birth to values characteristic for surfactant from adult rats. The plasma inositol concentration drops during the 18- to 22-day period from 0.81 to 0.26 mmol/liter and a similar decrease in inositol concentration occurs in amniotic fluids. The phosphatidylglycerol/phosphatidylinositol ratio of surfactant correlated negatively with the fetal plasma inositol concentration. It is most likely that the reduction in the level of fetal plasma inositol resulting from a declining production and an increasing metabolism, causes the decrease in phosphatidylinositol and increase in PG content of the surfactant of the fetal rat.

Amniotic Fluid↗
PubMed1985

A semi-automated and standardized method of determining the lamellar body content of amniotic fluid.

We have simplified and standardized the method of determining the lamellar bodies (LB) in amniotic fluid as a measure of fetal lung maturity. For this purpose we have first diluted the amniotic fluid and then concentrated its LB by low-speed centrifugation at the interface of a 10% Nycodenz solution. As a standard we use liposomes which consist of phospholipids enclosing a Nycodenz solution with a density similar to that of the LB. The phosphorus content of the LB and liposome standard is then determined by an automated fluorimetric method. There is an excellent correlation between the newly described procedure and the lecithin/sphingomyelin ratio. One technician can easily analyse 40 samples in a working day.

Amniotic Fluid↗
PubMed1985

Inositol affects the intracellular turnover of pulmonary surfactant phospholipids in the rat.

Rats, given a diet supplemented with 20% inositol, had threefold increased plasma inositol concentrations. The pool size of their alveolar surfactant fraction and their lamellar body fraction were the same as in the control rats and differences in phospholipid composition of the surfactant fractions were mainly restricted to changes in the percentages phosphatidylinositol (PI) and phosphatidylglycerol (PG). The change in phospholipid composition did not affect the pressure-volume relationship of the lungs. The labeling of phosphatidylcholine (PC), saturated phosphatidylcholine (SPC) or PI in the alveolar lavage fraction was the same for both groups, whereas labeling of alveolar PG was delayed in the inositol-fed rats. The specific activity-time relationships of the lamellar body phospholipids differed significantly between the control and inositol-fed rats and the differences in disappearance rate of the label from these fractions suggest that approximately 25-30% of the lamellar body material in inositol-fed rats is directed to a third, intracellular pool. We conclude that an increase in PI and a concomitant decrease in PG content of surfactant do not affect the clearance of alveolar surfactant, but enlarge the turnover of the lamellar body fraction because of intracellular degradation.

Animals↗
PubMed1984

Effects of artificial ventilation on surfactant phospholipid metabolism in rabbits.

Surfactant phospholipid metabolism and lung stability were studied in mechanically ventilated and in spontaneously breathing rabbits (control group). During ventilation the dynamic lung-thorax compliance decreased to 79% after 6 h. Static compliance and amount and composition of surfactant phospholipids remained unaltered. These data indicate inactivation of alveolar surfactant during ventilation, which is reversible by a single large inflation. Incorporation of injected radioactively labeled palmitate into saturated phosphatidylcholine (SPC) of the lamellar body fraction increased significantly in the ventilated group; maximal specific activity increased from 20 dpm/nmol SPC at 6 h in the control group to 30 dpm/nmol SPC at 2 h in the ventilated group. The clearance of radioactivity from the lamellar bodies into the alveolar lumen was greatly enhanced in the ventilated group. The results are explained by assuming that as a result of the inactivation of alveolar surfactant, endocytosed surfactant is degraded in the type II cells instead of being recycled and that the degradation products are subsequently reutilized in surfactant synthesis. This interpretation is supported by computer simulations.

Animals↗
PubMed1984

High-frequency oscillation affects surfactant phospholipid metabolism in rabbits.

Surfactant phospholipid metabolism was studied in anesthetized rabbits ventilated with high-frequency oscillation at a frequency of 5 Hz and a mean airway pressure of 5 cm H2O. Blood gases were normal although some atelectasis was evident after 1 h. The static compliance of the lungs and amount and composition of surfactant phospholipids of the lamellar body and alveolar lavage fraction were comparable to values found for spontaneously breathing rabbits. The data obtained for the incorporation of radioactively labeled palmitate into phospholipids are compatible with intracellular degradation of newly synthesized surfactant phospholipids. This hypothesis is supported by two observations. First, the rapid initial increase in specific activity of SPC and PC of the lamellar body fraction is not accompanied by a similar rapid increase in specific activity of SPC and PC of the lamellar body fraction is not accompanied by a similar rapid increase in specific activity of the alveolar lavage fraction. Second, a dissociation occurs between the metabolism of PC and SPC for the lamellar body fraction but not for the alveolar lavage fraction. The change in metabolism might be caused by the absence of large pressure swings during this pattern of ventilation.

Animals↗