Endogenous opioids modulate fetal rabbit lung maturation

To test the hypothesis that endogenous opioids modulate fetal lung development, separate groups of pregnant rabbits received daily injections of saline, morphine (1 mg/kg body wt), or the opioid antagonist naloxone (0.4 and 5.0 mg) for 10 days during their last trimester of pregnancy. The corresponding groups of fetuses were then delivered prematurely on day 28 of gestation (term approximately 31 days) and evaluated with respect to differences in body weight, lung weight, and the ratios of wet to dry lung weight and lung dry weight to body weight, the static inflation and deflation air and saline pressure-volume (P-V) characteristics of the lungs, and lung morphology. Mean values for body weight, lung weight, and the ratios of lung wet to dry weight and lung dry weight to body weight were not significantly different among the saline control (C), morphine (M)-, and naloxone (NLX)-treated fetuses. On the other hand, the fetal air P-V curves varied significantly (P less than 0.001), wherein the M-treated group depicted increased lung distensibility and alveolar stability on lung deflation, whereas the opposite was obtained in the NLX-treated fetuses. Moreover, morphometric analyses demonstrated that the mean alveolar air space-to-tissue ratio in lungs from M-treated fetuses were significantly greater than that observed either in C or in NLX-treated fetuses (P less than 0.05); however, the air space-to-tissue ratio did not significantly vary between the C and NLX-treated animals. These observations provide new evidence that endogenous opioids enhance fetal lung maturation.     

Influence of D-penicillamine on the formation of elastin and its cross-links.

The amount of insoluble elastin and its content of desmosine cross-links were investigated in aortas of chick embryos, to which D-penicillamine was administered on the 6th or 14th--16th day of incubation. D-Penicillamine was shown to alter the formation and maturation of elastin. Using lower doses (less than 50 mg) the weight of pooled aortic elastin is higher as compared with controls (related to 1 mg of elastin or to total weight of elastin). Increased isodesmosine:desmosine ratio in these samples indicates that this elastin is very young. On the other hand, a high dose of D-penicillamine (100 mg) decreased the content of elastin and also of its desmosine cross-links. The authors explain their findings by counteraction of two factors due to administration of penicillamine: the increased solubility of "insoluble elastin", and the decreased cross-link formation.     

Higher urine desmosine levels are associated with mortality in patients with acute lung injury

Desmosine is a stable breakdown product of elastin that can be reliably measured in urine samples. We tested the hypothesis that higher baseline urine desmosine would be associated with higher mortality in 579 of 861 patients included in the recent Acute Respiratory Distress Syndrome Network trial of lower tidal volume ventilation (1). We also correlated urine desmosine levels with indexes of disease severity. Finally, we assessed whether urine desmosine was lower in patients who received lower tidal volumes. Desmosine was measured by radioimmunoassay in urine samples from days 0, 1, and 3 of the study. The data were expressed as a ratio of urine desmosine to urine creatinine to control for renal dilution. The results show that higher baseline (day 0) urine desmosine-to-creatinine concentration was associated with a higher risk of death on adjusted analysis (odds ratio 1.36, 95% confidence interval 1.02-1.82, P=0.03). Urine desmosine increased in both ventilator groups from day 0 to day 3, but the average rise was higher in the 12-ml/kg predicted body weight group compared with the 6-ml/kg predicted body weight group (P=0.053, repeated-measures model). In conclusion, patients with acute lung injury ventilated with lower tidal volumes have lower urine desmosine levels, a finding that may reflect reduced extracellular matrix breakdown. These results illustrate the value of evaluating urinary biological markers that may have prognostic and pathogenetic significance in acute lung injury.     

Regulation of rabbit fetal glycogen: effect of in utero fetal decapitation on the metabolism of glycogen in fetal heart, lung, and liver

To understand the control mechanisms involved in the regulation of fetal glycogen, we have studied the effect of in utero fetal decapitations on glycogen metabolism in rabbit fetal heart, lung, and liver. In utero fetal decapitations were performed between days 18 and 21 of gestation. Two to four fetuses on one side of the horn were decapitated. Fetuses were delivered between days 23 and 26 or between days 28 and 30 of gestation. Fetal heart, lungs, and liver were analyzed for DNA, protein, glycogen, glycogen synthase (I and D forms), glycogen phosphorylase (a and b forms), phosphofructokinase, pyruvate kinase, and lactic dehydrogenase. In fetal heart and lung, no difference was observed in any of the above measurements in the intact and decapitated fetuses. In contrast, fetal liver does not appear to develop the glycogen system as indicated by the very low levels of glycogen (0.02 mg/mg DNA) in decapitated fetuses as compared with intact fetuses (0.4 mg/mg DNA). Similarly the levels of glycogen synthase and phosphorylase were two to three times lower in livers from decapitated fetuses as compared with the livers from intact fetuses. The three enzymes phosphofructokinase, pyruvate kinase, and lactic dehydrogenase were not affected by fetal decapitation in all three tissues. These results indicate that the fetal hypothalamic-pituitary-adrenal (thyroid) axis is not required at least after day 18 of gestation for the normal accumulation and subsequent utilization of glycogen in fetal heart and lungs, while it is an absolute requirement for the development of the fetal liver glycogen system.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of human urogastrone on lung phospholipids in fetal rabbits

Previous in vivo studies have demonstrated that mouse epidermal growth factor (EGF) can enhance fetal lung maturation. We have examined the effect of urogastrone, the human equivalent of mouse EGF and a related growth factor, on the phospholipid profile of fetal rabbit lung lavage and its action on fetal rabbit Type II pneumocytes in culture. Urogastrone (1 or 8 micrograms) given i.p. to fetal rabbits on day 25 of gestation resulted in increased total phospholipid, phosphatidylcholine, phosphatidylinositol and phosphatidylethanolamine contents, increased phosphatidylinositol and phosphatidylethanolamine as a proportion of phospholipid and decreased sphingomyelin as a proportion of phospholipid in lung lavages on day 28. These changes were unaccompanied by alterations in body weight or lung weight, DNA or protein concentrations. Urogastrone (16 micrograms) resulted in increased fetal deaths. Phospholipid profiles on day 27 were unchanged after fetal administration of urogastrone (1 microgram) on day 25. Urogastrone (0.01 and 0.1 ng/ml) added to fetal rabbit Type II pneumocytes in culture for 24 h enhanced the incorporation of radiolabelled choline and thymidine into phosphatidylcholine and DNA respectively. These findings indicate that human urogastrone can alter the phospholipid composition of the rabbit lung in a similar manner to that which occurs during maturation of the lung surfactant system in late pregnancy. This effect can be achieved, at least in part, by a direct action on Type II pneumocytes.     

The influence of experimentally produced oligohydramnios on lung growth and pulmonary surfactant content in fetal rabbits.

To study the effect of oligohydramnios on lung growth and biochemical lung development in fetal rabbits, amniotic fluid was drained through a tube inserted into the maternal peritoneal cavity on the 23 day of gestation. Littermate fetuses without an amniotic shunt were used as controls. The fetuses were delivered abdominally on the 28 day of gestation. In a total of 8 pregnant does, 17 fetuses underwent amniotic shunting and 22 fetuses were used as controls. The amniotic shunt produced a significant reduction in the amniotic fluid volume. There were no differences in the wet weights of the fetal body, liver or brain between the two groups. However, the amniotic shunt significantly decreased the wet weight of the fetal lung, fetal lung wet weight/body weight ratio, and protein concentration per lung as compared to the control fetuses. In the fetal liver and brain tissues, no changes were found in the concentrations of total phospholipids, phosphatidylcholine (PC) or disaturated phosphatidylcholine (DSPC, the main component of lung surfactant) per g of wet tissue and per mg of protein. However, the lungs of the fetuses with amniotic shunts contained significantly more PC and DSPC, and the L/S ratio was higher than in the control fetuses. These results suggest that the oligohydramnios produced by an amniotic shunt causes pulmonary hypoplasia, but raises the pulmonary surfactant content of fetal rabbit lung.     

Effect of D-penicillamine on rat lung elastin cross-linking during the perinatal period

This study was designed to clarify the effects of D-penicillamine (DPA), a drug used for treatment of various pathological events, on lung elastin formation and maturation of the newborn in the perinatal period. The investigation was conducted on 20 newborn rats bred from 40 female and six male rats. DPA doses 400 mg kg(-1) day(-1) and physiological saline were given intraperitoneally (i.p) to experimental and control groups. To assess newborn maturation, their body and lung weights were determined. Serum Cu levels were measured by atomic absorption spectroscopy and ceruloplasmin (Cp) activities were measured spectrophotometrically. Newborn lung tissue elastin, desmosine (DES) and isodesmosine (IDES) levels were measured by HPLC. The results showed that DPA treatment caused loss of skin elasticity and reduction in body and lung weight in newborns of the experimental group. The serum Cu levels and Cp activity were found to be significantly lower in both maternal and newborn of the experimental groups compared with the control group. The lung DES, IDES and elastin values of newborns in the experimental group were decreased compared with the control group. In conclusion, our results indicate that 400 mg kg(-1) day(-1) DPA, a dose that is used in the treatment of Wilson's disease, rheumatoid arthritis and cystinuria, caused the retardation of newborn maturation, a decrease in DES-IDES cross-links and levels of lung elastin of offspring in the perinatal period. Another conclusion to be drawn from this study is that even low levels of Cu depletion due to DPA administration induces a change in cross-linking in lung elastin during the perinatal period.     

Urinary desmosine excretion is inversely correlated with the extent of emphysema in patients with chronic obstructive pulmonary disease

An enhanced proteolysis of lung interstitium is key event in the pathogenesis of emphysema, a major constituent of chronic obstructive pulmonary disease. To assess whether urinary desmosine and/or hydroxyproline may be used as a marker of lung destruction we studied urinary excretions of these products in 20 patients with chronic obstructive pulmonary disease and in 19 appropriate controls in 24h urine collection samples. For desmosine measurements, we developed a new indirect competitive enzyme-linked immunosorbent assay. The extent of emphysema was measured in high resolution computed tomography (CT) scans, by considering lung area with CT numbers <-950 Hounsfield units (HU).Urinary desmosine excretion was significantly higher in patients with chronic obstructive pulmonary disease than in controls (294+/-121 microg versus 183+/-93 microg, P=0.003), and was unrelated with both age and smoking habits. In patients with no evidence or only mild emphysema, desmosine excretion values were significantly higher (P=0.006) than those of patients with moderate to severe emphysema. In patients with chronic obstructive pulmonary disease, urinary hydroxyproline excretion was positively correlated with urinary desmosine excretion but on the average, it was not different from that of controls.These data indicate that urinary desmosine is a sensitive biological marker of lung elastin catabolism. The relatively low levels of urinary desmosine observed in patients with severe emphysema may be accounted for a decrease in elastin catabolism due to reduced lung elastin mass. Urinary desmosine may be used to identify subjects at risk of developing emphysema and to assess the efficacy of therapeutic interventions.     

Postnatal glucocorticoids induce alpha-ENaC formation and regulate glucocorticoid receptors in the preterm rabbit lung

At birth, lung fluid clearance is coupled to Na+ transport through epithelial Na+ channels (ENaC) in the distal lung epithelium. We evaluated the effect of postnatal glucocorticoids (GC) on lung alpha-ENaC expression in preterm 29-day gestational age (GA) fetal rabbits. Postnatal treatment of 29-day GA fetuses with 0.5 mg/kg of dexamethasone (Dex) iv resulted in a 2- and 22-fold increase in lung alpha-ENaC mRNA expression compared with saline-treated fetuses after 8 and 16 h, respectively. Lung alpha-ENaC protein levels in Dex-treated fetuses were also elevated compared with saline-treated counterparts. The extravascular lung water (EVLW)/dry lung tissue weight ratios of 29-day GA fetuses treated with either saline or Dex decreased over 24 h compared with that observed at birth; however, at 24 h, the EVLW/dry lung tissue weight ratios of saline- and Dex-treated fetuses were similar. Dex-induced alpha-ENaC mRNA and protein levels were attenuated by glucocorticoid receptor (GCR) antagonist RU-486 in fetal distal lung epithelial cells isolated from 29-day GA fetuses, indicating that GC-dependent augmentation of lung alpha-ENaC requires the presence of functional GCR. Lung GCR mRNA expression and protein levels were elevated in 29-day GA fetuses compared with fetuses at earlier GA. Exposure of 29-day GA fetuses to Dex for 16 h caused a 2.1-fold increase in lung GCR mRNA expression, but GCR protein levels were decreased in Dex-treated fetuses after 24 h. We conclude that postnatal treatment of preterm 29-day GA fetal rabbits with GC results in an elevation of lung alpha-ENaC accompanied by an autoregulation of pulmonary GCR.     

Regulation of alveolar epithelial cell phenotypes in fetal sheep: roles of cortisol and lung expansion

Our aim was to determine whether cortisol's effect on alveolar epithelial cell (AEC) phenotypes in the fetus is mediated via a sustained alteration in lung expansion. Chronically catheterized fetal sheep were exposed to 1) saline infusion, 2) cortisol infusion (122-131 days' gestation, 1.5-4.0 mg/day), 3) saline infusion plus reduced lung expansion, or 4) cortisol infusion plus reduced lung expansion. The proportions of type I and II AECs were determined by electron microscopy, and surfactant protein (SP)-A, -B, and -C mRNA levels were determined by Northern blot analysis. Cortisol infusions significantly increased type II AEC proportions (to 38.2 +/- 2.2%), compared with saline-infused fetuses (23.8 +/- 2.4%), and reduced type I AEC proportions (to 59.0 +/- 2.2%), compared with saline-infused fetuses (70.4 +/- 2.4%). Reduced lung expansion also increased type II AEC proportions (to 52.9 +/- 3.5%) and decreased type I AEC proportions (to 34.2 +/- 3.7%), compared with control, saline-infused fetuses. The infusion of cortisol into fetuses exposed to reduced lung expansion tended to further increase type II (to 60.3 +/- 2.1%, P = 0.066) and reduce type I AEC (to 26.6 +/- 2.3%, P = 0.07) proportions. SP-A, -B, and -C mRNA levels changed in parallel with the changes in type II AEC proportions. These results indicate that cortisol alters the proportion of type I and type II AECs via a mechanism unrelated to the degree of fetal lung expansion. However, reductions in fetal lung expansion appear to have a greater impact on the proportion of AECs than cortisol.     

Decline in lung liquid volume and secretion rate during oligohydramnios in fetal sheep

Reduced amniotic fluid volume often results in fetal lung hypoplasia. Our aim was to examine the effects of prolonged drainage of amniotic and allantoic fluids on lung liquid volume (Vl), secretion rate (Vs), and tracheal flow rate (Vtr) in fetal sheep. In five experimental animals, amniotic and allantoic fluids were drained from 107 to 135 days of gestation. The volume of fluid drained from the experimental animals was 411.8 +/- 24.4 ml/day (n = 140). In six control animals, amniotic fluid volume was 747.7 +/- 89.7 ml (n = 15). Wet and dry lung weights were 20-25% lower in experimental fetuses than in control fetuses. Fetal hemoglobin, O2 saturation, arterial PO2, pH, and hematocrit were unchanged by drainage. During the drainage period, Vl was up to 65% lower, Vs was up to 35% lower, and Vtr was up to 40% lower in experimental fetuses than in control fetuses. We conclude that prolonged drainage of amniotic and allantoic fluids decreases Vl, Vs, and Vtr in fetal sheep. These findings indicate that fetal lung hypoplasia associated with oligohydramnios may be the result of a prolonged reduction in Vl.     

Influence of dexamethasone on growth and development of rat fetuses: changes in nucleic acids and protein content

Pregnant rats were treated with dexamethasone in drinking water (10 micrograms/ml) from the 15th to the 22nd day of pregnancy. Dexamethasone significantly reduced the weight of rat fetuses and concentration of DNA, RNA and proteins in fetal adrenal glands, liver, placenta, brain, kidneys, heart, lung, testes and pituitary from the 17th to the 22nd day of pregnancy. These data show that dexamethasone given to pregnant rat may lead to potentially deleterious effects on fetal rat development.     

Occurrence and inducibility of cytochrome P450IIIA in maternal and fetal rats during prenatal development

The purpose of this study was to quantify cytochrome P450IIIA1 in fetal and maternal livers of uninduced and pregnenolone-16 alpha-carbonitrile (PCN) induced rats during the course of prenatal development. The activities and levels of P450IIIA in hepatic microsomes from maternal rats and fetuses at 15-21 days of gestation were measured by triacetyloleandomycin (TAO) inhibited debenzylation of (benzyloxy)phenoxazone and by immunoassay with defined antiserum specific for P450IIIA. P450IIIA was not detectable (less than 10 pmol/mg for maternal microsomes and less than 2 pmol/mg for fetal microsomes) by immunoassay in uninduced maternal or fetal livers. In hepatic microsomes from PCN-induced dams, values ranged from 59.3 to 116 micrograms P450IIIA1/mg of protein during the same gestational period. Changes in debenzylase activity of 15.9-46.5 pmol of resorufin (mg of protein)-1 min-1 were consistent with these findings as were the changes in TAO-inhibitable debenzylase activity. In the transplancentally induced fetal liver, debenzylase activity increased steadily from 0.19 pmol of resorufin mg-1 min-1 at day 15 to 9.34 pmol of resorufin mg-1 min-1 at day 21 and was paralleled by the TAO-inhibitable activity that ranged from 0.09 pmol of resorufin mg-1 min-1 at day 15 to 3.33 pmol of resorufin mg-1 min-1 at day 21. The amount of immunoreactive P450IIIA1 also increased from 0.5 to 28.7 micrograms/mg of microsomal protein.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of the Ay gene on susceptibility to hydrocortisone fetotoxicity and teratogenicity in mice

Effects of the Ay gene, a coat color gene, on susceptibility to hydrocortisone fetotoxicity and teratogenicity were investigated by using the congenic strain of C57BL/6-Ay (Ay/a) which had been maintained by repeated back-crosses of the Ay gene to the C57BL/6 (a/a) background. Matings were conducted as follows (female x male): group I, a/a; group II, a/a x Ay/a; and group III, Ay/a x a/a. Pregnant females were subcutaneously given daily doses of 0, 12.5, 25, or 50 mg/kg of hydrocortisone on days 10-13 of pregnancy. On day 18 of pregnancy, fetuses were sexed, weighed, and examined for external abnormalities. In group I, the mean fetal weight was significantly decreased at a dose of 25 mg/kg or more. The incidences of cleft palate were 3.2 and 22.7% at 25 and 50 mg/kg, respectively. In group II, in which half of the fetuses were expected to carry the Ay gene, the mean fetal weight was decreased significantly at 12.5 mg/kg or more. The incidence of cleft palate in group II at 50 mg/kg was 44.2%, which was significantly higher than that in group I. In group III, in which maternal mice as well as half of their fetuses carried the Ay gene, a decrease in the mean fetal weight was greater than in group II. In addition, the mean percentage of fetal resorptions was significantly increased at 50 mg/kg. The incidence of cleft palate in group III was significantly increased at 25 mg/kg (10.5%) when compared with those in groups I and II. These results indicate that the Ay gene may be associated with susceptibility to hydrocortisone fetotoxicity and teratogenicity in mice.     

Quantification of surfactant pool sizes in rabbit lung during perinatal development

Methods are presented for the quantitative isolation of surfactants from fetal and newborn rabbit alveolar lavage returns and post-lavaged lung tissue homogenates. The phospholipid content of both fractions progressively increased between 27 days gestation and term (31 days). The tissue-stored fraction increased approximately 16-fold (from 0.48 +/- 0.13 to 7.83 +/- 0.86 mg/g dry lung) and the alveolar fraction more than 30-fold (from 0.08 +/- 0.02 to 2.69 +/- 0.52 mg/g dry lung). Developmental changes in phospholipid composition were also observed. Tissue-stored surfactant was prepared using differential and density gradient centrifugation. Alveolar surfactant was isolated during fetal development as a high-speed pellet following a one-step differential centrifugation. There was little change in the phospholipid content of fetal alveolar lavage supernatant (range 0.12 +/- 0.04 to 0.28 +/- 0.09 mg/g dry lung). By the first postnatal day the phospholipid content of both lavage fractions significantly increased (pellet, 7.51 +/- 1.79; supernatant, 4.01 +/- 1.36 mg/g dry lung) and both were identified as surfactant. This increase in alveolar surfactant was accompanied by an approximately twofold decrease (to 3.81 +/- 1.1 mg/g dry lung) in the tissue-stored fraction. These data provide a quantitative profile of surfactant accumulation and secretion in developing rabbit lung.     

Evaluation of the developmental toxicity of lenalidomide in rabbits

BACKGROUND: Lenalidomide, a thalidomide analog, is indicated for treatment of patients with deletion-5q myelodysplastic syndromes or multiple myeloma. NZW rabbits were used because of sensitivity to thalidomide's teratogenicity. METHODS: Range-finding and pulse-dosing studies preceded a full developmental toxicity study in New Zealand white (NZW) rabbits (25/group) given lenalidomide (0, 3, 10, or 20 mg/kg/day) or thalidomide (180 mg/kg/day) by stomach tube on gestation days (GD) 7-19. Clinical signs, body weights, and feed consumption were recorded daily from GD 7. On GD 29, standard maternal necropsy, uterine content, and fetal evaluations were carried out. RESULTS: In all studies, thalidomide was selectively toxic to development. In the pulse-dosing study, lenalidomide did not affect development at 100 mg/kg/day. Increases in C(max) and AUC(0-24 hr) values for lenalidomide were slightly less than dose-proportional; lenalidomide occurred in the fetuses. At 10 and 20 mg/kg/day, lenalidomide was maternally toxic (reduced body weight gain and feed consumption; at 20 mg/kg/day, weight loss and one abortion). Developmental toxicity at 10 and 20 mg/kg/day included reduced fetal body weights and increased postimplantation losses and fetal variations (morbidity/purple-discolored skin, undeveloped intermediate lung lobe, irregular nasal-frontal suture, and delayed metacarpal ossification). Thalidomide selectively reduced fetal body weight, increased postimplantation loss and caused characteristic limb and other dysmorphology. CONCLUSIONS: The maternal and developmental NOAELs for lenalidomide are 3 mg/kg/day. Unlike thalidomide, lenalidomide affected embryo-fetal development only at maternally toxic dosages, confirming that structure-activity relationships may not predict maternal or developmental effects. No fetal malformations were attributable to lenalidomide.     

Glucocorticoid induction of pulmonary maturation in the rabbit fetus. The effect of maternal injection of betamethasone on the activity of enzymes in fetal lung.

1. Maternal administration of betamethasone (0.2 mg/kg) on day 25 or 26 of gestation produced a significant decrease in the lung/body weight ratio of the rabbit fetuses within 24 h. 2. The incorporation of [14C]choline but not [14C]ethanolamine into the lipids of fetal lung slices was significantly increased, indicating that there was a specific effect on phosphatidylcholine synthesis. 3. The activities of a number of marker enzymes for subcellular organelles were elevated, especially in the lungs of fetuses delivered on day 26. The increases in monoamine oxidase (mitochondrial outer membrane), beta-glycerophosphatase and aqueously dispersed phosphatidic acid-dependent phosphatidic acid phosphohydrolase (lysosomal) activities were significant. 4. Although the activity of cholinephosphotransferase was not affected by glucocorticoid treatment, the activities of glycerol-3-phosphate phosphatidyltransferase and the activities of two enzymes in the auxiliary pathways for the production of disaturated phosphatidylcholine (lysophosphatidylcholine:lysophosphatidylcholine transacylase and lysophosphatidylcholine:acyl-CoA acyl-transferase) were significantly increased. 5. Membrane-bound phosphatidic acid-dependent phosphatidic acid phosphohydrolase activity was elevated to a lesser extent than the aqueously dispersed phosphatidate-dependent activity and this increase was not significant. 6. The incorporation of E135S]methionine into protein by slices of fetal lung was significantly reduced after maternal treatment with betamethosone. 7. These results are consistent with the general view that glucocorticoids can induce pulmonary maturation and surfactant production in the rabbit fetus but indicate that some of the former hypotheses regarding the mechanism by which lipid synthesis is accelerated must be reevaluated.     

Elastin synthesis by ligamentum nuchae fibroblasts: effects of culture conditions and extracellular matrix on elastin production

Fetal bovine ligamentum nuchae fibroblasts maintained in culture synthesized soluble elastin but were unable to form the insoluble elastic fiber. Secreted elastin precursors accumulated in culture medium and were measured using a radioimmunoassay for elastin. When elastin production was examined in ligament tissue from fetal calves of various gestational ages, cells from tissue taken during the last trimester of development produced significantly more elastin than did cells from younger fetal tissue, with maximal elastin synthesis occurring shortly before birth. Soluble elastin was detected in ligament cells plated at low density until proliferation began to be density inhibited and the cells became quiescent. Also, soluble elastin production per cell declined with increasing population doubling or with age in culture. Cells grown in the presence of 5% fetal calf serum produced approximately four times as much soluble elastin as cells grown in serum-free medium. The addition of dexamethasone (0.1 microM) and bleomycin (1 microgram/ml) increased soluble elastin production by cultured cells 180% and 50%, respectively, whereas theophylline (5 micrograms/ml) depressed production 50% and antagonized stimulation by dexamethasone. Ascorbate (50 micrograms/ml), soybean trypsin inhibitor (1 mg/ml), insulin (100 microunits/ml), and aminoacetonitrile (50 micrograms/ml) had no effect, but cycloheximide at 10(-4) M completely inhibited soluble elastin production. In contrast to cells in culture, ligament tissue minces (ligament cells surrounded by in vivo extracellular matrix) efficiently incorporated soluble elastin precursors into insoluble, cross-linked elastin. In addition, soluble elastin production per cell (per microgram of DNA) was higher in tissue minces than elastin production by cells maintained on plastic. These results suggest a role for extracellular matrix in formation of the elastic fiber and in stabilizing elastin phenotypic expression by ligament fibroblasts. Fibroblasts from the bovine ligamentum nuchae present an excellent model for in vitro studies of elastin biosynthesis.     

The effects of arginine vasopressin and epinephrine on lung liquid production in fetal goats

The effects of arginine vasopressin (AVP) and epinephrine on lung liquid secretion were investigated in 67 acute fetal goats (116 days of gestation to term) with intact umbilical cords after caesarean section. Secretion was measured by an impermeant tracer technique. AVP was infused intravenously (1.6-39.2 mU/(kg.min); 2 h) into 26 fetuses. All fetuses below 130 days of gestation, except one, showed no response. All above 133 days reduced secretion, or turned to reabsorption, except at the lowest infusion rate. The effect persisted, and usually increased postinfusion. Expansion of the lungs with saline did not change the response. The percentage reductions were linearly related to the logarithm of the infusion rate (threshold, 1.42 mU/(kg.min]. The absolute reductions were linearly related to fetal weight. Epinephrine was infused intravenously (0.30-6.72 micrograms/(kg.min); 1-2 h) into 12 fetuses. All fetuses (118 days to term) reduced secretion or reabsorbed by the second hour. At the highest infusion rate, reabsorption was immediate; at the lowest, secretion increased slightly, then fell significantly in the second hour. Epinephrine acted at levels considered physiological at delivery in the sheep. AVP appears to act at plasma levels found in most vaginal deliveries; it may augment epinephrine-induced reabsorption during stress, and help long-term removal of lung fluid.     

Effects of Anoectochilus formosanus Hayata extract and glucocorticoid on lung maturation in preterm rats.

We investigated the effects of maternal administration of Anoectochilus formosanus extract and dexamethasone on lung maturation in preterm rats. A. formosanus group mothers were tube-fed A. formosanus extract (300 mg/kg body wt./day) for 7 days from days 12-18 of gestation. Dexamethasone group mothers were injected intraperitoneally with dexamethasone (0.2 mg/kg body wt.) in saline on day 18 of gestation. Control group mothers were similarly injected with saline alone. On day 19 of gestation, fetuses were delivered by cesarean section. A. formosanus treatment significantly increased the fetal lung/body weight ratio, as compared to dexamethasone treatment. Saturated phosphatidylcholine levels in fetal lung tissue and growth hormone levels in maternal serum were significantly increased in the A. formosanus- and dexamethasone-treated groups as compared to controls. The histological appearance of preterm rat lungs revealed extensive branching of intermediate airways, denser mesenchyme, and more epithelial tubules in the dexamethasone and A. formosanus groups as compared with the control group. These results suggest that antenatal A. formosanus treatment may play a role in accelerating fetal rat lung maturation.