Fatty acid composition of adipose tissue at term indicates deficiency of arachidonic and docosahexaenoic acid and excessive linoleic acid supply in preterm infants

BACKGROUND

Arachidonic (ARA) and docosahexaenoic acid (DHA) are constitutive to membrane phospholipids, and essential for brain and overall development. ARA/DHA pools in term infants (TI) are built during the third trimester, stored as adipose tissue triglycerides and predominantly distributed via plasma phosphatidylcholine (PC). In preterm infants (PTI), placental ARA/DHA supply is replaced by linoleic-acid (LA)-enriched nutrition. This study aimed to investigate the impact of PTI nutrition, compared to placental supply, on fatty acid composition in adipose tissue and blood.

METHODS

Prospective observational study (4/2017-3/2019) in 12 PTI and 3 PTI with enterostomy (PTI/E) (gestational age (GA) < 32 weeks) with surgical intervention at term (± 6 weeks) and 14 TI (GA ≥ 34 weeks, surgical intervention < 2 weeks postnatally). PTI/E were analyzed descriptively only. PC and triglyceride fatty acids were analyzed with tandem mass spectrometry and gas chromatography, respectively. Results were compared between TI and PTI with Wilcoxon Test and shown as median [25th percentile-75th percentile] mol%.

RESULTS

PTI had less ARA in adipose tissue TG (0.77[0.67-0.87]% vs. 1.04[0.95-1.14]%, p = 0.0003) and plasma PC (20.7[18.7-22.8]% vs. 28.3[22.7-33.5]%, p = 0.011) than TI. PTI also had less DHA in adipose tissue TG (0.6[0.4-0.8]% vs. 1.1[0.8-1.4]%, p = 0.006) and plasma PC (6.4[5.6-7.1]% vs. 8.4[7.8-13.1]%, p = 0.002). LA was increased in PTI's adipose tissue TG (10.0[8.8-12.3]% vs. 3.0[2.5-3.6]%, p < 0.0001) and plasma PC (48.4[44.6-49.6]% vs. 30.6[24.9-35.6]%, p = 0.0002). Similar differences were observed in erythrocyte PC.

CONCLUSION

In PTI, LA is increased and ARA/DHA decreased in adipose tissue, plasma and erythrocyte lipids as proxies for other tissues, likely caused by PTI nutrition. This may contribute to impaired PTI development.

Oxidative stress markers and micronutrients in maternal and cord blood in relation to neonatal outcome

BACKGROUND/OBJECTIVES

Oxidative stress and micronutrient deficiencies have been related to lower birth weight (BW), small for gestational age (SGA) offspring and preterm delivery.

SUBJECTS/METHODS

The relation between neonatal outcome (BW, head circumference, SGA, preterm delivery) with markers of oxidative stress and micronutrients in maternal and cord blood was to be examined. Oxidative stress markers (protein carbonyls (PrCarb), 3-nitrotyrosine (3NT), malondialdehyde (MDA)), total protein concentration and lipid-soluble micronutrients (carotenoids, retinol, tocopherols) were measured in 200 newborns (11% preterms, 13% SGA) and 151 mothers. Associations between target parameters in cord plasma and maternal serum with BW, head circumference and risk of being SGA or preterm were explored.

RESULTS

Maternal protein concentration, PrCarb, MDA and all lipid-soluble micronutrients were significantly higher compared with newborns, except for 3NT, which was significantly elevated in newborns. Newborn parameters correlated positively with those of mothers. Preterms had lower proteins and retinol but higher PrCarb than terms. Maternal PrCarb and retinol were inversely associated with BW and head circumference. Mothers with PrCarb, MDA and retinol in the highest quintile had a 3.3-fold (0.9; 12.1), 2.1-fold (0.7; 6.4) and 3.3-fold (1.2; 9.4) risk, respectively, for delivering an SGA newborn, whereas the lowest quintile of retinol in cord blood was associated with an increased risk for preterm delivery.

CONCLUSIONS

Oxidative stress (elevated PrCarb) was associated with lower BW/head circumference and SGA. Inadequate hemodilution may explain the inverse relation of maternal retinol with BW and head circumference, and the association between highest maternal retinol and risk for SGA.

5-Methyltetrahydrofolate and thiamine diphosphate in cord-blood erythrocytes of preterm versus term newborns

BACKGROUND/OBJECTIVES

A low folate or low thiamine status may be associated with the risk of preterm delivery, small for gestational age (SGA) offspring and adverse pregnancy outcomes.

SUBJECTS/METHODS

5-Methyltetrahydrofolate (5MTHF) and thiamine diphosphate (TDP) were measured directly in cord-blood erythrocytes (CBEs) of early preterm (n=26; <32 weeks gestational age; including 50% multiple births), late preterm (n=38; 32 to <37 weeks; including 24% multiple births) and term newborns (n=60, 37-42 weeks) via high-performance liquid chromatography and fluorescence detection. Associations between 5MTHF and TDP with gestational age, newborn anthropometrics (birth weight, newborn's length and head circumference) and risk of being SGA were explored.

RESULTS

Group comparison as well as multivariate linear regression analysis of cord-blood vitamins revealed that 5MTHF was significantly lower in late preterms compared with terms but did not differ between singletons and multiples. TDP tended to be higher in preterms than in terms and lower in multiples than in singletons in both early and late preterms. Multivariate analysis on birth outcomes showed that 5MTHF was significantly positively associated with gestational age, birth weight and newborn's length. 5MTHF, increasing gestational age and parity were associated with a significantly reduced risk for being SGA, while TDP, multiple births and gender were not associated with the risk for being SGA.

CONCLUSIONS

Higher CBE concentrations of 5MTHF were associated with improved birth outcomes. Lower TDP concentrations were observed in multiple births. Future studies evaluating cord-blood vitamin concentrations and their associations with birth outcomes should additionally include dietary intakes and maternal blood concentrations at different stages of pregnancy.

A historic cohort study on accelerated advancement of enteral feeding volumes in very premature infants

BACKGROUND

The optimal rate of enteral feeding (EF) advancement in very low birth weight infants is under debate.

OBJECTIVES

To evaluate the effects of accelerated EF advancement on the time to full enteral feeds, on early postnatal growth as well as on the frequency of necrotizing enterocolitis (NEC) and focal intestinal perforation (FIP) in very premature infants.

METHODS

In a retrospective single-center historic cohort study, infants with a gestational age <32 weeks at birth and birth weight <1,500 g, born between January 1, 2006, and December 31, 2007 (n = 136), were compared with infants born between January 1, 2010, and December 31, 2010 (n = 88). In 2006/2007, enteral feeds were initiated on day 1 with 10-15 ml/kg/day and advanced by 15-20 ml/kg/day. In 2010, enteral feeds were initiated with 20 ml/kg/day on day 1 and advanced by 25-30 ml/kg/day. Full enteral feeds were defined as ≥ 140 ml/kg/day. Data are presented as median (P25-P75).

RESULTS

The time to establish full enteral feeds was shorter in 2010: 8 (7-11) days in 2006/2007 versus 6 (5-9) days in 2010. The incidences of NEC and FIP were 2.7 and 4.1% in 2006/2007 and 3.3 and 2.2% in 2010, respectively. Weight gain was not affected by the rate of EF advancement. Higher parenteral protein intake during week 1 in 2006/2007 was associated with better head circumference growth.

CONCLUSIONS

The new approach was associated with a significantly shorter period to establish full enteral feeds. No difference in the incidence of FIP or NEC was observed; however, the study was underpowered to detect small but possibly important differences.

Altered regulation of beta-amylase activity in mutants of Arabidopsis with lesions in starch metabolism

Three classes of mutants of Arabidopsis thaliana (L.) Heynhold with alterations in starch metabolism were found to have higher levels of leaf amylase activity than the wild type when grown in a 12-hr photoperiod. This effect was dependent upon the developmental stage of the plants and was largely suppressed during growth in continuous light. The various amylolytic activities in crude extracts were separated by electrophoresis in nondenaturing polyacrylamide gels and visualized by activity staining. The increased amylase activity in the mutants was due to an up to 40-fold increase in the activity of an extrachloroplast beta-amylase (EC 3.2.1.2). These observations indicate the existence of a regulatory mechanism that controls the amount of beta-amylase activity in response to fluctuations in photosynthetic carbohydrate metabolism. It is paradoxical that beta-amylase appears to be a highly regulated enzyme, but as yet no physiologically relevant function can be assigned to this enzyme due to the absence of starch in the cytoplasmic compartment of leaf cells.

Residual cftr expression varies with age in cftr(tm1Hgu) cystic fibrosis mice: impact on morphology and physiology

Mouse models for cystic fibrosis (CF) mimic intestinal manifestations of the human disease, but the lung disease phenotypes are lacking in most strains. In this work, the issue was addressed whether aging of the respiratory tract leads to lung pathophysiology in the exon 10 insertional mutant cftr(tm1Hgu) mouse. Weight gain, body weight and life-span of cftr(tm1Hgu) mice were significantly reduced compared with control mice. cftr(tm1Hgu) mice expressed 20, 21 or 37% (median) of wild-type cystic fibrosis conductance transmembrane regulator (cftr) mRNA transcript in lungs, intestine and kidney. Wild-type cftr mRNA in renal and respiratory epithelia varied with age from levels similar to Ztm:MF1 controls at the age of 2 and 4 months to levels seen in patients with CFTR splice mutations beyond the age of 6 months. The morphology of the bronchi and more distal airways was apparently normal in cftr(tm1Hgu) mice during their first year of life. The alveolar surfactant phospholipid pool was increased in cftr(tm1Hgu) mice by 1.5- to 2-fold compared with Ztm:MF1 controls. Alveolar clearance of gamma-labelled scandium oxide - the first report of lung clearance measurement in living mice - was reduced in cftr(tm1Hgu) mice compared with littermate controls. Although no progressive lung pathology was seen in the cftr expression of cftr(tm1Hgu) mice, surfactant phospholipid homeostasis, and alveolar and mucociliary clearance were abnormal. Therefore, the described model is useful for studying the initial CF lung pathophysiology.

Quantitation using GC-TOF-MS: example of bromazepam

Time-of-flight mass spectrometry (TOF-MS) offers new perspectives for forensic toxicology. Qualitative and quantitative analyses of a mixture of three selected benzodiazepines (diazepam, nordazepam and bromazepam) were used to compare gas chromatography (GC-TOF-MS, quadrupole GC-MS, GC-ECD) and liquid chromatography (HPLC-DAD) data. Method validation parameters like LOD, LOQ, S/N-ratios reflect the capabilities of GC-TOF-MS. Five-point calibrations for bromazepam in human peripheral blood (50, 100, 160, 200, 300 ng/ml) using medazepam as internal standard (1000 ng/ml) were performed. The calibrations using GC-TOF-MS (using the fragments of m/z 236 and 288), GC-ECD (dual system) and HPLC-DAD (at 235 nm) all showed correlation coefficients close or superior to 0.99. Quadrupole GC-MS data was not used in the comparison of extracted samples due to the low sensitivity in the full scan mode. Two analyses of real cases concerning bromazepam are presented. In the first case, the presence or absence of bromazepam could not be established with both HPLC-DAD and GC-ECD due to background signals. The extracted ion chromatograms and spectrum traces after the analysis with the GC-TOF-MS could clearly excluded the presence of bromazepam. The second case illustrates the quantitation of bromazepam, where both HPLC-DAD and GC-ECD were unable to give satisfactory results, again due to interfering background signals. The analyses performed on the GC-TOF-MS-system demonstrated high sensitivity and also high selectivity due to the high quality of mass spectra obtained. The advantages of GC-TOF-MS make it a promising analytical technique for forensic toxicology.

Phosphatidylcholine molecular species in lung surfactant: composition in relation to respiratory rate and lung development

Surfactant reduces surface tension at the air-liquid interface of lung alveoli. While dipalmitoylphosphatidylcholine (PC16:0/ 16:0) is its main component, proteins and other phospholipids contribute to the dynamic properties and homeostasis of alveolar surfactant. Among these components are significant amounts of palmitoylmyristoylphosphatidylcholine (PC16:0/ 14:0) and palmitoylpalmitoleoylphosphatidylcholine (PC16:0/ 16:1), whereas in surfactant from the rigid tubular bird lung, PC16:0/14:0 is absent and PC16:0/16:1 strongly diminished. We therefore hypothesized that the concentrations of PC16:0/14:0 and PC16:0/16:1 in surfactants correlate with differences in the respiratory physiology of mammalian species. In surfactants from newborn and adult mice, rats, and pigs, molar fractions of PC16:0/14:0 and PC16:0/16:1 correlated with respiratory rate. Labeling experiments with [methyl-(3)H]choline in mice and perfused rat lungs demonstrated identical alveolar proportions of total and newly synthesized PC16:0/14:0, PC16:0/16:1, and PC16:0/16:0, which were much higher than those of other phosphatidylcholine species. In surfactant from human term and preterm neonates, fractional concentrations not only of PC16:0/16:0 but also of PC16:0/14:0 and PC16:0/ 16:1 increased with maturation. Our data emphasize that PC16:0/14:0 and PC16:0/16:1 may be important surfactant components in alveolar lungs, and that their concentrations are adapted to respiratory physiology.

Pulmonary surfactant in birds: coping with surface tension in a tubular lung

As birds have tubular lungs that do not contain alveoli, avian surfactant predominantly functions to maintain airflow in tubes rather than to prevent alveolar collapse. Consequently, we have evaluated structural, biochemical, and functional parameters of avian surfactant as a model for airway surfactant in the mammalian lung. Surfactant was isolated from duck, chicken, and pig lung lavage fluid by differential centrifugation. Electron microscopy revealed a uniform surfactant layer within the air capillaries of the bird lungs, and there was no tubular myelin in purified avian surfactants. Phosphatidylcholine molecular species of the various surfactants were measured by HPLC. Compared with pig surfactant, both bird surfactants were enriched in dipalmitoylphosphatidylcholine, the principle surface tension-lowering agent in surfactant, and depleted in palmitoylmyristoylphosphatidylcholine, the other disaturated phosphatidylcholine of mammalian surfactant. Surfactant protein (SP)-A was determined by immunoblot analysis, and SP-B and SP-C were determined by gel-filtration HPLC. Neither SP-A nor SP-C was detectable in either bird surfactant, but both preparations of surfactant contained SP-B. Surface tension function was determined using both the pulsating bubble surfactometer (PBS) and capillary surfactometer (CS). Under dynamic cycling conditions, where pig surfactant readily reached minimal surface tension values below 5 mN/m, neither avian surfactant reached values below 15 mN/m within 10 pulsations. However, maximal surface tension of avian surfactant was lower than that of porcine surfactant, and all surfactants were equally efficient in the CS. We conclude that a surfactant composed primarily of dipalmitoylphosphatidylcholine and SP-B is adequate to maintain patency of the air capillaries of the bird lung.

Metabolism of surfactant phosphatidylcholine molecular species in cftr(tm1HGU/tm1HGU) mice compared to MF-1 mice

In cftr(tmIHGU/m1HGU) mice, an animal model designed to study pathophysiologic alterations due to the CFTR defect found in cysticfibrosis, surfactant phospholipids of bronchoalveolar lavage fluid (BALF) are increased. To study the metabolical basis of such increases, we intraperitoneally injected cft(tm1HGU/tm1HGU) mice [methyl-3H]choline and measured [methyl-3H]choline incorporation into phosphatidylcholine (PC) molecular species of lung tissue and BALF after 1.5 to 24 hours. MF1 and MF1 x cftr(tm1HGU/tm1HGU) hybrid mice served as controls. In tissue [methyl-3H]choline incorporation into total PC was constant for 24 hours and identical in control and cftr(tmIHGU/m1HGU) mice. However, from 7.5 to 24 hours there was a shift of [methyl-3H]choline incorporation from palmitoyloleoyl-PC and palmitoyllinoleoyl-PC towards PC species enriched in surfactant, dipalmitoyl-PC, palmitoylmyristoyl-PC, and palmitoylpalmitoleoyl-PC. The relative and absolute 3H-labels of PC species were identical for cftr(tmIHGU/m1HGU) compared to control mice. In BALF [methyl-3H]choline of total PC increased from 1.5 to 24 hours (R2 > .98), mainly due to [methyl-3H]choline-labelled dipalmitoyl-PC, in all experimental groups. In BALF from cftr(tmIHGU/m1HGU) mice, the [methyl-3H]choline label of total PC and individual PC species was significantly increased over control values after 24 hours, but not after 1.5 to 6 hours. Numbers and composition of BALF cells were not different between controls and cftr(tmIHGU/m1HGU) mice. We, conclude that increased alveolar phospholipid in cftr(tmIHGU/m1HGU) mice is likely due to decreased reuptake of surfactant.

Pulmonary and gastric surfactants. A comparison of the effect of surface requirements on function and phospholipid composition

Surfactant is present in the alveoli and conductive airways of mammalian lungs. The presence of surface active agents was, moreover, demonstrated for avian tubular lungs and for the stomach and intestine. As the surface characteristics of these organs differ from each other, their surfactants possess distinct biochemical and functional characteristics. In the stomach so-called 'gastric surfactant' forms a hydrophobic barrier to protect the mucosa against acid back-diffusion. For this purpose gastric mucosal cells secrete unsaturated phosphatidylcholines (PC), but no dipalmitoyl-PC (PC16:0/16:0). By contrast, surfactant from conductive airways, lung alveoli and tubular avian lungs contain PC16:0/16:0 as their main component in similar concentrations. Hence, there is no biochemical relation between gastric and pulmonary surfactant. Alveolar surfactant, being designed for preventing alveolar collapse under the highly dynamic conditions of an oscillating alveolus, easily reaches values of <5 mN/m upon cyclic compression. Surfactants from tubular air-exposed structures, however, like the conductive airways of mammalian lungs and the exclusively tubular avian lung, display inferior compressibility as they only reach minimal surface tension values of approximately 20 mN/m. Hence, the highly dynamic properties of alveolar surfactant do not apply for surfactants designed for air-liquid interfaces of tubular lung structures.

Commercial versus native surfactants. Surface activity, molecular components, and the effect of calcium

Despite their broad clinical use, there is no standardized comparative study on the functional, biochemical, and morphologic differences of the various commercial surfactants in relation to native surfactant. We investigated these parameters in Alveofact, Curosurf, Exosurf, and Survanta, and compared them with native bovine (NBS) and porcine (NPS) surfactant. For Curosurf and Alveofact the concentrations necessary for minimal surface tensions < 5 mN/m were six to 12 times higher (1.5 and 3 mg/ml, respectively) than with NPS and NBS. Exosurf and Survanta only reached 22 and 8 mN/m, respectively. Increasing calcium to nonphysiologic concentrations artificially improved the function of Alveofact and Curosurf, but it had little effect on Exosurf and Survanta. Impaired surface activity of commercial versus native surfactants corresponded with their lack in surfactant protein SP-A and decreased SP-B/C. The higher surface activity of Curosurf compared with Alveofact corresponded with its higher concentration of dipalmitoylphosphatidylcholine (DPPC). Despite their enrichment in DPPC Survanta and Exosurf exhibited poor surface activity because of low or absent SP-B/C. Ultrastructurally, Curosurf and Alveofact consisted mainly of lamellar and vesicular structures, which were also present in NPS and NBS. Exosurf contained crystalline structures only, whereas the DPPC-enriched Survanta contained separate lamellar/vesicular and crystalline structures. We conclude that in vitro surface activity of commercial surfactants is impaired compared with native surfactants at physiologic calcium concentrations. In the presence of SP-B/C, surface activity corresponds to the concentration of DPPC. Our data underscore the importance of a standardized protocol at physiologic calcium concentrations for the in vitro assessment of commercial surfactants.

[Brief history of recent hemp cultivation in Switzerland and subsequent medico-legal problems resulting from hemp cultivation]

In March 1995, a decision about cultivation of cannabis was issued by the Swiss Federal Offices of Public Health, Police and Agriculture in order to satisfy the growing interest of farmers and other people in hemp farming. It pointed out that 1)... each hemp plant contains THC and must be therefore considered a drug, 2)... no permission is required for those who grow hemp without the intention to produce drugs ... meaning that the choice of the plant variety was not restricted to those which are characterized by a low THC concentration and grown in a few countries belonging to the European Union. Claiming that natural hemp must contain significant amounts of THC and thanks to the Swiss legislation, areas dedicated to hemp cultivation develop considerably. Most hemp plants which are submitted to our laboratories by the police for THC quantification belong to the drug-type. Nowadays, a great deal of goods (food and beverages, cosmetics, drugs) made of hemp are marketed in Switzerland. Strong suspicions exist however that several of these products could be used as a screen for the illegal market of cannabis. For instance, despite financial support from the state, fiber hemp cultivation remains unsuccessful. No advantage with regard to seed productivity, edible seed and essential oils qualities and yields have been found for drug hemp over fiber hemp by agricultural research stations up to now. Several clues about the possible illicit use of hemp goods rich in THC, especially hemp tea made of flower tops and "therapeutic" pillows filled with cannabis exist. Recently, two Federal edits were issued in order to restrict the selling of hemp seedlings and of hemp foods and beverages to those containing only low amounts of THC. However, the marketing of hemp plants used for decorating remains free partly explaining the recent success of these "beautiful" plants. Broadly speaking, the Swiss and European legislations about hemp have approached mutually during the last years.

Intrabronchial surfactant application in cases of inhalation injury: first results from patients with severe burns and ARDS

Damage to the respiratory tract caused by inhalation of toxic products of combustion with subsequent development of an acute respiratory distress syndrome (ARDS) is one of the main causes of death in burn patients. Treatment with an exogenous surfactant is a therapeutic option for which there has previously been no empirical data. We report on four severely burned patients with deep partial thickness and full thickness burns of between 40 and 70 per cent body surface area (BSA), and with inhalation injury complicated by ARDS. These patients were treated once or more than once with bovine surfactant replacement (Alveofact). In addition to biophysical and biochemical analysis, the influence of this substance on oxygenation and lung function were evaluated. After the limits of mechanical ventilation had been reached, bronchoscopic intrabronchial administration of surfactant was followed by temporarily improved gas exchange with an increase in arterial O2 partial pressure (PaO2), accompanied by a reduction in inspiratory O2 concentration (FiO2), and also improved lung compliance. All the patients survived in spite of an initially unfavourable prognosis. Replacement of exogenous surfactant in the treatment of inhalation traumatized severe burn patients with ARDS appears to show considerable promise as an approach to improving the survival chances of these high-risk patients.

Lung surfactant in a cystic fibrosis animal model: increased alveolar phospholipid pool size without altered composition and surface tension function in cftrm1HGU/m1HGU mice

BACKGROUND

Progressive pulmonary dysfunction is a characteristic symptom of cystic fibrosis (CF) and is associated with functional impairment and biochemical alterations of surfactant phospholipids in the airways. However, the fundamental question of whether surfactant alterations in the CF lung are secondary to the pulmonary damage or are present before initiation of chronic infection and inflammation has yet to be resolved in patients with cystic fibrosis but can now be addressed in CF mice that exhibit the basic defect in the airways. A study was therefore undertaken to investigate the pool sizes, composition, and function of lung surfactant in the non-infected cftrm1HGU/m1HGU mouse.

METHODS

The amount and composition of phospholipid classes and phosphatidylcholine molecular species were determined in bronchoalveolar lavage (BAL) fluid and lavaged lungs by high performance liquid chromatography (HPLC). Surfactant protein A (SP-A) levels in BAL fluid were determined by ELISA and surfactant for functional measurements was isolated from BAL fluid by differential ultracentrifugation. Equilibrium and minimal surface tension of surfactant was assessed by the pulsating bubble surfactometer technique. MF1, BALB/c, C57/BL6, and C3H/He mice served as controls.

RESULTS

BAL fluid of cftrm1HGU/m1HGU mice contained 1.02 (95% confidence interval (CI) 0.89 to 1.16) mumol phospholipid and 259 (239 to 279) ng SP-A. BAL fluid of MF1, BALB/c, C57BL/6, and C3H/He mice contained 0.69 (0.63 to 0.75), 0.50 (0.42 to 0.57), 0.52 (0.40 to 0.64), and 0.45 (0.27 to 0.63) mumol phospholipid, respectively. After correction for the different body weights of mouse strains, phospholipid levels in BAL fluid of cftrm1HGU/m1HGU mice were increased by 64 (52 to 76)%, 60 (39 to 89)%, 72 (45 to 113)%, and 92 (49 to 163)%, respectively, compared with controls. The amount of SP-A in BAL fluid and the composition of phospholipid as well as phosphatidylcholine molecular species in BAL fluid and lung tissue was unchanged in cftrm1HGU/m1HGU mice compared with controls. The increase in phospholipids in BAL fluid of cftrm1HGU/m1HGU mice resulted from an increased fraction of large aggregates which exhibited normal surface tension function.

CONCLUSION

In cftrm1HGU/m1HGU mice surfactant homeostasis is perturbed by an increased phospholipid pool in the alveolar compartment.

Conductive airway surfactant: surface-tension function, biochemical composition, and possible alveolar origin

Alveolar surfactant is well known for its ability to reduce minimal surface tension at the alveolar air-liquid interface to values below 5 mN/m. In addition, it has been suggested that an analogous conductive airway surfactant is also present in the airways. To elucidate the composition, possible origin, and surface activity of conductive airway phospholipids (PL), we compared in adult porcine lungs the PL classes and phosphatidylcholine (PC) molecular species of nonpurified tracheal aspirate samples with those of bronchoalveolar lavage fluid (BAL), tracheobronchial epithelium, and lung parenchyma. We also analyzed PL and PC composition, protein content, and surface activity of surfactant isolated from tracheal aspirates (SurfTrachAsp), BAL (SurfBAL), and the 27,000 x g pellet of BAL (SurfP27000) by density-gradient centrifugation. Although PL composition revealed contributions of the airways to tracheal aspirates, the composition of PC molecular species of tracheal aspirates was similar to that of BAL and lung parenchyma, but differed considerably from that of airway epithelium. SurfTrachAsp had the same PL and PC composition as SurfBAL and SurfP27000, indicating that this fraction of tracheal aspirates may have originated from the alveoli. Nevertheless, minimal and maximal surface tensions were higher in SurfTrachAsp than in SurfBAL and SurfP27000. Analysis of surfactant proteins A, B, and C (SP-A, SP-B, and SP-C) revealed that SP-A was decreased and SP-B and SP-C were absent, whereas total protein was increased in SurfTrachAsp. We conclude that as compared with alveolar surfactant, PL of SurfTrachAsp show the same composition, but that surface-tension function is impaired and the concentration of surfactant proteins is decreased in SurfTrachAsp.

Active surfactant in pharyngeal aspirates of term neonates: lipid biochemistry and surface tension function

Alveolar surfactant is well known for its ability to reduce minimal surface tension at the alveolar air-liquid interface to values below 5 mN m-1. In addition, it has been suggested that surfactant is also present in the airways, particularly in the perinatal period. We isolated surfactant from pharyngeal aspirates obtained from 33 neonates immediately after delivery and analysed it for both phospholipid (PL) composition and surface tension function. PL classes and phosphatidylcholine (PC) molecular species were determined by normal and reversed-phase high-performance liquid chromatography (HPLC), respectively. Static and dynamic surface properties of the surfactant were studied in a pulsating bubble surfactometer. Sample volume was 1.3 +/- 0.5 mL (mean +/- SD) with a total amount of 2.5 +/- 1.3 mumol of PL and a concentration of 2.1 +/- 1.0 mumol mL-1 PL. HPLC analyses of PL classes revealed a composition identical with surfactant prepared from alveolar washes, i.e. PC 83.6 +/- 2.1%, sphingomyelin 1.4 +/- 0.5%, phosphatidylglycerol 8.1 +/- 1.6%, phosphatidylethanolamine 2.1 +/- 0.5% and phosphatidylinositol 2.6 +/- 1.1%. Thin-layer chromatography showed almost identical results but was more time-consuming and needed more material for analysis. Analysis of PC molecular species revealed a composition typical of human alveolar surfactant with 54.7 +/- 3.9% dipalmitoyl PC, 10.3 +/- 1.9% palmitoyloleoyl PC and 9.1 +/- 1.5% palmitoylmyristoyl PC. Minimal surface tension fell to values below 5 mNm-1 within 5 min of cycling in all subjects. The methods used in this study allowed for complete PL and surface tension analyses of surfactant obtained during routine pharyngeal suctioning after delivery at term. Whether they are also applicable to preterm neonates with respiratory distress remains to be determined.

A method for the isolation and preparation of surfactant from tracheobronchial aspirates in infants and children for quantitative and pulsating bubble analysis

A method is presented for the investigation of surfactant function after isolation and preparation of pulmonary surfactant from tracheobronchial aspirates of mechanically ventilated infants and children. This method involved purification of surfactant from contaminating non-surfactant phospholipids and mucus by sodium bromide density gradient centrifugation. The surfactant concentration in undiluted fluids (3.5 +/- 0.8 mg mL-1; mean +/- SD) was calculated by extrapolating from the urea concentration in aspirates and serum. Phospholipid concentration was adjusted to approximately 3 mg mL-1 and the surface activity was determined by means of a pulsating bubble surfactometer. Mean minimal and maximal tension values of all cycles were calculated after reaching steady state. Measurements obtained from surfactant isolated with this method showed a high reproducibility: the coefficient of variation for minimal surface tension was 6.1%. Therefore this method enables functional surfactant analysis in tracheobronchial aspirates.

Synthesis and release of phosphatidylcholine by isolated porcine gastric mucous cells in primary culture

Phosphatidylcholine (PC) is the major phospholipid of the hydrophobic gastric mucosal barrier and is chiefly released from mucous cells into the gastric mucus. Whereas the mucosa contains highly unsaturated PC, gastric mucus predominantly contains palmitoyl-oleoyl-PC and palmitoyl-linoleoyl-PC, indicating a selective release of these PC species into the gastric lumen. In order to understand gastric PC metabolism, we investigated synthesis and release of PC in cultivated porcine gastric mucous cells, using dual labelling with [methyl-3H]-choline and [1-14C]-palmitate, in the presence of 12-O-tetradecanoylphorbol-13-acetate (TPA), indomethacin and prostaglandin E2 (PGE2). Linear incorporation of [methyl-3H]-choline and [1-14C]-palmitate into PC was achieved for at least 8h. In contrast to type II pneumocytes TPA increased PC synthesis in gastric mucous cells but not its release. Indomethacin did not influence PC synthesis, but it decreased the release of newly synthesized PC. PGE2 antagonized the effect of indomethacin on PC release. We conclude that PC release by isolated porcine gastric mucous cells is regulated in a manner different from type II pneumocytes. PC release is impaired by indomethacin and this impairment is restored by PGE2.

Rat gastric hydrophobic barrier: modulation of phosphatidylcholine molecular species by dietary lipids

Phospholipids protect the gastric mucosa by forming a proton-repellent hydrophobic layer on its luminal surface. We have recently shown that two molecular species of phosphatidylcholine (PC), PC16:0/18:1, and PC16:0/18:2, but not PC16:0/16:0, are predominantly released into gastric mucus. We investigated whether these molecular species in mucus are modified by dietary fat. Rats were fed (for three weeks) a diet supplemented with either 10% cod liver, palm, or sunflower oil, or 10% corn starch as a control. In tissue, cod liver oil decreased PC16:0/20:4 and PC18:0/20:4. Cod liver oil and palm oil increased PC16:0/18:1, whereas sunflower oil decreased PC16:0/18:1. Palm oil additionally decreased PC16:0/18:2, whereas the other diets had no effect on PC16:0/18:2. In mucus, however, PC16:0/18:1 and PC16:0/18:2 were not significantly altered by any diet. They were increased over tissue values and comprised 37.6 +/- 3.3 and 33.1 +/- 1.4 mol% in controls. PC16:0/16:0 was lower in mucus than in mucosa and even decreased by cod liver oil (1.2 +/- 0.2 vs. 2.7 +/- 0.3 mol%; P < 0.01). We conclude that PC16:0/18:1 and PC16:0/18:2 are modified by dietary fat in tissue. In gastric secretions, however, PC16:0/18:1 and PC16:0/18:2 are kept constant and together comprise 70 mol% of the released PC species, whereas PC16:0/16:0 does not play a role for the gastric hydrophobic barrier under any dietary treatment. Additionally, cod liver oil decreases the content of PC16:0/20:4 and PC18:0/20:4 in gastric mucosa, thereby possibly decreasing the formation of eicosanoids.

[New investigations on the question of secular acceleration of permanent dentition]

A sample of 1,310 girls, 5 to 13 years of age, drawn from Mainz, Wiesbaden and vicinity was studied to establish the eruption time of the permanent dentition. The data of the median date of eruption of different teeth was determined employing a nonparametric test for the estimation of a survivorship function with doubly censored data (TURNBULL 1974). The method presented shows a marked superiority over other techniques used to verify the median date of eruption. The diachronic comparison of several samples--mainly from the Rhine-Main-Area-encompassing the years 1909 till today, showed no uniform trend towards an earlier eruption date. In some cases, temporal differences were ascertained which can be readily attributed to varied definitions of dental status. Furthermore, a recalculation--using this innovative mathematical approach--of a sample from the Frankfurt area, originally studied by FRANZ (1938) did not show any unambiguous acceleration tendencies-at least not within the past 50 years. These results suggest that the human dentition is predominantly genetically determined and therefore environmental factors play a by far lesser role than in general physical development.

Composition of phospholipid classes and phosphatidylcholine molecular species of gastric mucosa and mucus

Phospholipids have been proposed to protect the gastric mucosa by forming a proton-repellant hydrophobic layer on the gastric luminal surface, acting as a so-called gastric surfactant. The composition of this hydrophobic phospholipid layer has not previously been analysed in detail. Therefore, we measured the composition of phospholipid classes and phosphatidylcholine (PC) molecular species in gastric mucosa and mucus of rats and pigs using high resolution HPLC techniques. The predominant phospholipids of both mucosa and mucus were PC and phosphatidylethanolamine (PE). Little phosphatidylglycerol was present. The most abundant PC species of rat mucosa were PC16:0/18:1, PC16:0/18:2, PC16:0/20:4 and PC18:0/20:4. Pig mucosa also contained PC16:0/18:1, PC16:0/18:2, and PC18:0/20:4, but was poor in PC16:0/20:4. Dipalmitoyl-PC (PC16:0/16:0), the surface-active component of pulmonary surfactant, comprised only 6.42 +/- 0.33% of total PC in rat mucosa and only 5.50 +/- 1.46% of total PC in pig mucosa. Gastric mucus, isolated from both rat and pig, contained largely PC16:0/18:1 and PC16:0/18:2. The content of PC16:0/16:0 was even lower in mucus than in mucosal PC (rat 2.86 +/- 0.40%, P < 0.01; pig 1.92 +/- 0.55%, P < 0.05). We conclude that, in contrast to pulmonary surfactant, any surfactant function of the hydrophobic barrier of the stomach is unlikely to be mediated by PC16:0/16:0.

High-performance liquid chromatographic analysis of phospholipids from different sources with combined fluorescence and ultraviolet detection

An isocratic high-performance liquid chromatographic (HPLC) system was developed for the separation of major phospholipid classes, i.e., phosphatidylcholine, sphingomyelin, lysophosphatidylcholine, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, and phosphatidylserine. Phospholipids were detected with ultraviolet absorption at 205 nm and subsequent fluorescence detection. Fluorescence of the phospholipids (excitation, 340 nm; emission, 460 nm) was achieved by postcolumn formation of mixed micelles with 1,6-diphenyl-1,3,5-hexatriene. For ultraviolet absorption there were great differences depending on the saturation of phospholipid fatty acids but for fluorescence the sensitivity was almost identical for all phospholipids except phosphatidylinositol and lysophosphatidylcholine. Dipalmitoylphosphatidylcholine showed nearly no ultraviolet but good fluorescence response. Ultraviolet to fluorescence ratio was characteristic for different phospholipids and for identical phospholipids from different sources. Quantification of phosphatidylcholine and phosphatidylethanolamine with HPLC using N-monomethylphosphatidylethanolamine (dioleoyl) as an internal standard gave the same results as phospholipid phosphorus quantification after thin-layer chromatography.

beta-Adrenergic priming of rats in vivo modulates the effect of beta-agonist in vitro on surfactant phospholipid metabolism of isolated lungs

To evaluate the effects of multiple beta-adrenergic stimulations on pulmonary surfactant phospholipids, perfused lungs from beta-adrenergic primed and non-primed rats were challenged with the beta-agonist terbutaline in vitro. Cell-free lung lavage, lavagable alveolar cells and lung tissue were analysed for phospholipid content and incorporation of precursors. In lung lavage, terbutaline in vitro doubled the incorporation of 14C-choline and 3H-palmitate into total phosphatidylcholine (PC) and of 3H-palmitate into phosphatidylglycerol (PG). beta-adrenergic priming in vivo prior to terbutaline in vitro lowered the increase of precursor incorporation. For lavagable cells, terbutaline in vitro increased the incorporation of 3H-palmitate into PC. Priming in vivo reduced this effect and diminished the specific 3H-choline incorporation into lavagable cell PC below control level. For lung tissue, priming increased the amounts of PC and disaturated PC (DSPC) whereas terbutaline in vitro decreased DSPC in both primed and non-primed lungs. Terbutaline in vitro slightly increased the incorporation of 14C-choline and 3H-palmitate into PC and DSPC in non-primed but not in primed lungs. beta-adrenergic blockade by ICI 118.551 prevented all effects but generally increased 3H-palmitate incorporation into the phospholipids and, in lavagable cells, the amount of PC. We conclude that long-term beta-adrenergic treatment may alter the metabolism of pulmonary surfactant phospholipids by increasing tissue PC and DSPC and by decreasing the secretion of newly-synthesized PC.

Phospholipid synthesis in isolated porcine gastric mucous cells

Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) are the major phospholipids of the gastric mucosal surface barrier and chiefly originate from mucous cells. Among these phospholipids PC with palmitic acid as its hydrophobic moieties is believed to protect the gastric mucosa by its hydrophobic properties. We investigated the phospholipid synthesis of isolated porcine gastric mucous cells in vitro and incubated them in the presence of radiolabelled precursors. Incorporation of 3H-choline into PC and of 14C-ethanolamine into PE was linear at 1, 10, and 100 mumol/l substrate concentration for at least 6 h. Half-maximal rate of precursor incorporation was achieved at 21 and 15 mumol/l of choline and ethanolamine, respectively. Ethanolamine inhibited PC synthesis and choline inhibited PE synthesis. A small amount of radioactivity originating from 14C-ethanolamine and from the methyl groups of 3H-methionine were incorporated into PC. Palmitic acid was incorporated into PC more than PE. Indomethacin did not influence the de novo synthesis of PC and PE via the Kennedy pathway, but inhibited the incorporation of 3H-methionine into PC. These results indicate that in gastric mucous cells PC and PE synthesis de novo depends on the concentrations of choline and ethanolamine. The palmitic acid content of PC depends on the availability of palmitic acid as a substrate: indomethacin-induced mucosal damage is not explained by modulation of phospholipid synthesis de novo.

Impaired regulation of surfactant phospholipid metabolism in the isolated rat lung after nitrogen dioxide inhalation

Various drugs have been shown to stimulate surfactant phospholipid metabolism. Particularly beta-adrenergic agonists play an important role under physiologic conditions. For the first time we have studied whether nitrogen dioxide (NO2) inhalation alters beta-adrenergic regulation of surfactant phospholipid metabolism in the model of the isolated lung. Rats were continuously exposed in vivo to a 5 ppm NO2-containing atmosphere for 48 hr. The lungs were isolated and perfused in presence of the beta-adrenergic agonist dopexamine and surfactant metabolism was studied in three lung compartments: (1) lung lavage, (2) lung tissue, and (3) lavagable free alveolar cells. We found that (1) in normal rat lungs dopexamine increased the incorporation of palmitate and choline from the perfusate into lung lavage phospholipids. In nitrogen dioxide exposed rat lungs beta-adrenergic stimulation did not cause an increase in precursor incorporation. No significant difference in unstimulated precursor incorporation was found for normal and NO2-exposed rat lungs. (2) Lung tissue from rats exposed to NO2 showed a decreased precursor incorporation into disaturated phosphatidylcholine due to an augmented cellular pool size. (3) Lavagable alveolar cells showed an increased palmitate uptake after nitrogen dioxide inhalation and by beta-adrenergic stimulation. From these data we conclude that nitrogen dioxide inhalation impairs the beta-adrenergic regulation of surfactant phospholipid metabolism. Moreover these data underline the importance of beta-adrenergic agonists in surfactant metabolism.