Antenatal Terbutaline Administration Decreases the Lung Hyaluronan Concentration in Preterm Rabbit Pups

Abstract

Objectiv: To determine whether antenatal exposure to terbutaline alters the lung hyaluronan concentration or lung water content at birth in preterm rabbit pups. Study Design: Rabbit dams (n = 18) with timed pregnancies were injected with 30 µg terbutaline or saline (controls) one day before delivery at 27–29 days of gestation. Pups were killed immediately after delivery. Lung water content and hyaluronan concentrations were determined. Results: Pups exposed antenatally to terbutaline had lower mean lung hyaluronan concentrations than control pups. Lung hyaluronan/dry lung weight was significantly lower in pups delivered at 28 (p = 0.034) or 29 days (p < 0.001), while lung hyaluronan/wet lung weight was significantly lower at all three gestational ages. Conclusion: Antenatal exposure to terbutaline lowers the lung hyaluronan concentration at birth in preterm (27–29 days) rabbit pups without altering the lung water content.

Hyaluronan in the Human Neonatal Lung: Association with Gestational Age and Other Perinatal Factors

“…This is in contrast to our previous finding in preterm rabbits that antenatal exposure to betamethasone or terbutaline administered to the dams before preterm delivery decreased the lung hyaluronan concentration significantly [5,8] compared to that in nonexposed control pups. The perinatal conditions differed considerably between the infants and the rabbit pups exposed to antenatal steroids or terbutaline.…”

“…Increased hyaluronan staining in alveolar walls and around small and mid-sized vessels was found in hyperoxia-exposed lungs in both these studies. The lung hyaluronan concentration at birth in preterm rabbit pups is also affected by antenatal administration of betamethasone [5] or terbutaline [8] to the rabbit dam, but antenatal exposure to these drugs does not significantly alter the lung water content at birth.…”

An Epitaxial Model for Heterogeneous Nucleation on Potent Substrates

“…[44] In order to increase the potency of TiB 2 particles in the grain refiner alloy, excess Ti is added to form a thin layer of Al 3 Ti on the TiB 2 surface. [45] This effectively replaces the original TiB 2 substrate with Al 3 Ti which has an extremely small lattice misfit with a-Al (0.09 pct), resulting in enhanced grain refinement. [46] In contrast, Zr addition to TiB 2 inoculated Al-alloys will cause the conversion of TiB 2 to (Ti 1Àx Zr x )B 2 through the substitution of Ti by Zr because ZrB 2 is more stable than TiB 2 .…”

“…During solidification processing, the exogenous particles from the grain refiner are in direct competition with the endogenous particles. If the endogenous particles have higher nucleation potency Al/TiB 2 S: fcc, a = 0.42112 [45] (111)[110]// 0.30372 0.29141 À4.22 N: hcp, a = 0.30372, c = 0.32368 [45] (0001)[11À20] Al/Al 3 Ti S: fcc a = 0.42112 (111)[110]//(112)[20À1] 0.29116 0.29141 0.09 N: tetragonal, a = 0.3883, c = 0.8679 [51] Al/ZrB 2 S: fcc a = 0.41212 (111)[110]//(0001)[11À20] 0.31690 0.29141 À8.75 N: hcp, a = 0.3883, c = 0.8679 [52] Mg/Zr S: hcp, a = 0.3265, c = 0.5308 [31] (0001)[11À20]//(0001)[11À20] 0.32431 0.32650 0.67 N: hcp, a = 0.32431, c = 0.5180 [53] Mg/Al 3 Zr S: hcp, a = 0.3265, c = 0.5308 (0001)[11À20]//(114)[110] 0.28553 0.32650 12.55 N: tetragonal, a = 0.4038, c = 1.7428 [54]c a The lattice parameters were calculated from room temperature data from JCPDS files and the coefficients of thermal expansion given in the relevant references. b The orientation relationship (OR) is obtained by assuming that the close packed direction on the close packed plane of the solid is parallel to its counterpart of the substrate.…”