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J Egberts

Publications and source records attributed to J Egberts.

At least 19 recordsLinked to original sources
PubMed1992

[Prevention and treatment of respiratory distress syndrome in premature infants using intratracheally administered surfactants].

OBJECTIVE: To study the effects of administration of surfactant immediately after birth (prophylactic) or after 6 hr (therapeutic) to 81 Dutch preterm infants from a multicentre trial. SETTING: University Hospital Leiden and Sint Joseph Hospital, Veldhoven. DESIGN: A randomized controlled trial with stratification for biochemical lung (im)maturity. The aims of the study were (I): to improve the TcPO2/FiO2 ratio by 40% and (2) to prevent the respiratory distress syndrome by 50% at 6 hours after birth. The secondary goal was to compare effects of prophylactic versus therapeutic use of exogenous surfactant (from 6 hours onwards) in surfactant-deficient infants. PATIENTS: The entrance criteria of the study were: (I) inborn children with a gestational age between 26 and 30 weeks, (2) elective intubation and (3) sampling of bronchotracheal or gastric aspirate. After randomization the children received surfactant within 10 minutes after birth prophylactically (n = 42) or 6 hours after birth if they needed more than 60% oxygen (13 of 39 control infants). A second dose of surfactant was given if, at 6 hours after the first dose, the FiO2 was still high (> or = 0.6). TREATMENT: We used a natural porcine surfactant preparation (Curosurf) in a dose of 200 mg/kg given through the endotracheal tube. RESULTS: The mean gestational age of the 81 infants was 28.2 weeks. The TcPO2/FiO2 ratios increased in the prophylactic group compared with the controls (38 versus 30 kPa; p < 0.05). RDS occurred less often and less severely in the prophylactic group (p < 0.05). Neonatal mortality was lower in the prophylactically treated infants (3/42) than in the control group (10/39; p < 0.05). Compared with the control infants with immature lungs, the immature prophylactically treated infants had six hours after birth higher TcPO2/FiO2 ratios (35 vs 13 kPa; p < 0.001), a 35% reduction of the incidence of RDS with a significant reduction of its severity (p < 0.05), and significantly lower mean airway pressures (0.87 versus 1.24 kPa; p < 0.005). The surfactant given 6 hours after birth to the immature controls resulted in an immediate improvement of the oxygenation. Nevertheless, these infants spent more time on the respirator and needed extra oxygen for longer periods than the immature infants prophylactically treated (p < 0.05). CONCLUSION: Surfactant, given either prophylactically or therapeutically, results in clinical improvement of children with biochemically immature lungs. A prophylactic treatment, moreover, results in reduced incidence and severity of RDS, in a significant shortening of the time spent on the respirator and in reduced need of extra oxygen compared with therapeutic treatment. We recommend to give surfactant prophylactically or at the first signs of RDS.

Gestational Age↗
PubMed1992

Derivation of tumorigenic and non-tumorigenic mouse alveolar type-II cell lines from fetal type-II cells after a combined in vivo/in vitro carcinogen treatment.

Alveolar type-II cells were isolated from the lungs of fetuses (day 18 of gestation) of the A/WySnAf (A/Sn) mouse strain, which were treated in utero at day 15 with the directly-acting carcinogen N-ethyl-N-nitrosourea (ENU). The isolated type-II cells were again treated with ENU during their initial growth in vitro. After a prolonged culture period, 5 cell lines were obtained, which were identified as type-II cell lines. Differences between cell lines were found with respect to contact-inhibited growth, cell doubling time and ability to grow in a serum-free medium. Two out of the 5 cell lines produced highly invasive type-II cell carcinomas after s.c. injection of 5 x 10(6) cells into nude mice. Thus, both tumorigenic and non-tumorigenic mouse alveolar type-II cell lines were derived after this combined in vivo and in vitro carcinogen treatment of fetal mouse alveolar type-II cells. This offers the possibility of studying in vitro the factors thought to influence lung tumorigenesis in vivo. In addition, our findings strongly suggest that alveolar type-II cells are the progenitor cells of malignant mouse lung tumors.

Animals↗
PubMed1992

Estimated costs of different treatments of the respiratory distress syndrome in a large cohort of preterm infants of less than 30 weeks of gestation.

Within a model cohort of 1,000 preterm infants of less than 30 weeks of gestation, the incidence and mortality of RDS change if corticosteroids are used prenatally and surfactant prophylactically or therapeutically after birth. Combined pre- and postnatal therapies give the best results: approximately 125 extra survivors. Therapeutic surfactant administration even in combination with prenatal corticosteroids has cost implications because extra intensive care beds (7-11%) are needed. More special care places (12-24%) are required after each type of intervention. The estimated costs per extra survivor are the lowest for prenatal corticosteroid administration. The combination of corticosteroids prenatally and prophylactic surfactant postnatally seems to be most cost-effective because it produces the greatest number of survivors and the lowest number of intensive and high dependency care days in hospital.

Adrenal Cortex Hormones↗
PubMed1991

Development of a human lung surfactant, derived from extracted amniotic fluid.

Using a surfactant preparation of human origin for the treatment of the respiratory distress syndrome (RDS) instead of an animal-derived surfactant will minimize immunological problems. Therefore we isolated surfactant material from human amniotic fluid. Protein and phospholipid fractions of extracted human amniotic fluid (HAFS) were separated by Lipidex 5000 or acidulated LH20 liquid chromatography systems. Fractions of HAFS, the phospholipid or the recombined phospholipid-protein fractions, were tested in the 27-day fetal rabbit model. The results were compared with the results of the corresponding fractions of extracted ovine lung lavage (EOS) and of the already clinically tested surfactant Curosurf. The in situ surface activity of HAFS, EOS, and of their combined phospholipid + protein fractions (200 mg/kg body wt.) resulted in a lung compliance which was significantly higher than the control (saline) values. The compliances of HAFS, EOS, their combined fractions, and Curosurf were similar, but the lung stability values (V5) differed significantly among these surfactant extracts. The best V5 values (greater than or equal to 0.020 ml/g body wt.) were found after installing EOS or its LH20 phospholipid + protein fractions. HAFS had a poor stabilizing capacity which increased significantly after Lipidex chromatography and even more after enrichment of the Lipidex material with 10% palmitic acid. The Lipidex HAFS + 10% palmitic acid surfactant is at present the best obtainable human surfactant extract. Further development is in progress for the clinical application of this surfactant in preterm neonates.

Amniotic Fluid↗
PubMed1990

Postmortem effects on the yield and composition of alveolar surfactant from rat lungs.

Isolation of alveolar surfactant from human cadaver lungs might be ineffective because of postmortem effects. We studied therefore in the rat the effect of autolysis on the yield and composition of alveolar surfactant at different intervals after death. The total amount of phospholipids in the lavage fluids decreased at 4 h postmortem and increased thereafter again. Increased amounts of proteins, significant deviations from the normal phospholipid composition of surfactant and decreased surface activity were already present from 2 h onwards. However, a normal alveolar surfactant can be obtained up to 16 h after death by using a sucrose gradient centrifugation procedure. With this procedure it is possible to isolate a surfactant with adequate surface activity from mildly, but not from severely autolytic rat lungs.

Animals↗
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↗