Characterization of secondary ultrasonic waves radiated by two oscillating bubbles.

Purpose: A bubble oscillating under an ultrasonic wave produces an interference sound field with the incident ultrasonic wave, forming fringe patterns of trapped microbubbles. We discuss secondary ultrasonic waves radiated by two oscillating bubbles in the incident ultrasonic wave in terms of both theory and experimental conditions.

Methods: Two oscillating bubbles produce an inherent secondary wave field that varies with the distance between the two bubbles and the phases of these waves.

Role of keratinocyte growth factor in the control of surfactant synthesis by fetal lung mesenchyme.

Fetal lung maturation is regulated by mesenchymal-epithelial cell communication, which plays a major role in the control of surfactant synthesis by alveolar type II cells. We have recently shown that keratinocyte growth factor (KGF), also called fibroblast growth factor-7, enhances the maturation of fetal alveolar epithelial type II cells. Here, we investigated, among the factors produced by lung mesenchyme, the part attributable to KGF in the control of surfactant synthesis.

Mild vitamin A deficiency delays fetal lung maturation in the rat.

During late pregnancy, the fetal lung stores surfactant in preparation for extrauterine life. Surfactant deficiency, most often due to prematurity, precipitates respiratory distress syndrome (RDS) of the neonate. Although vitamin A (retinol) and retinoic acid have been shown to enhance the synthesis of phospholipid surfactant components, their effect on surfactant-specific proteins is unclear.

Keratinocyte growth factor enhances maturation of fetal rat lung type II cells.

Keratinocyte growth factor (KGF) or fibroblast growth factor (FGF)-7, a peptide produced by stromal cells and in particular by lung mesenchyme, has recently been shown to influence early lung morphogenesis and to be a mitogen for fetal and adult alveolar type II cells. Although contradictory findings have been reported regarding its effects on surfactant protein expression, its effects on surfactant phospholipids have not been studied. We investigated the effects of KGF on the synthesis of surfactant components by cultured fetal rat type II cells isolated during the late gestational period, when surfactant accumulates in preparation for extrauterine life.