Effects of granulocyte colony-stimulating factor on hyperoxia-induced lung injury in newborn piglets.

Granulocyte colony-stimulating factor (G-CSF) increases the concentration and activation of neutrophils in the peripheral blood and has been used to prevent late-onset infection in premature infants. However, if G-CSF also augmented the inflammatory response in the lung, the incidence and severity of acute and chronic lung injury might be expected to increase. Using a newborn piglet model of acute lung injury, we examined the effects of rhG-CSF (recombinant-metHuG-CSF) on lung injury. Thirty-three newborn piglets were studied as follows: 1). Unventilated controls; 2). normally ventilated (PaCO2 = 35-45 torr) with room air(RA) for 48 h; 3). normally ventilated with RA for 48 h and received rhG-CSF (10 mg/kg/dose IV) at 0, 12, 24, and 36 h; 4). hyperventilated (PaCO2 = 15-25 torr) with 100% O2 for 48 h; 5) hyperventilated with 100% O2 for 48 h and received rhG-CSF (10 mg/kg/dose IV) at 0, 12, 24 and 36 h. Complete blood counts and and differentials were performed at 0, 24, and 48 h. Animals were sacrificed at 48 h, lungs were removed en bloc, and bronchoalveolar lavage (BAL) was performed. Total blood white blood cells and neutrophil counts increased significantly over 48 h in animals who received rhG-CSF either with normoventilation (p <0.0001) or hyperventilation with 100% O2 (p <0.003), and did not change significantly in the other experimental groups. However, there were no significant differences in BAL total cell counts, neutrophil chemotaxis activity, total protein, or albumin concentrations among the groups. Despite significantly increasing peripheral neutrophil counts, rhG-CSF did not potentiate acute lung injury or inflammation. This suggests that prophylactic administration strategies using rhG-CSF to prevent sepsis in premature infants should not increase the risk for developing acute and chronic lung disease.

Issues in neonatal and pediatric oxygen therapy.

This article reviews the complex physiology of oxygen transport in the fetus and neonate, and how it differs from the older pediatric patient and adult. The common causes of respiratory distress unique to the neonatal and pediatric populations are reviewed in detail, including a brief discussion regarding the different modes of mechanical ventilation used in neonates. The increased susceptibility of infants to the toxic effects of oxygen is reviewed.

Delivery room resuscitation of the newborn.

Expertise in neonatal resuscitation is essential for all hospital personnel involved in the care of newborn infants. The guidelines to resuscitation reviewed here have been established by the American Academy of Pediatrics and the American Heart Association and have resulted in significantly improved training and expertise of delivery room personnel. Although widely accepted, many of these guidelines are only now being rigorously studied in controlled trials. This lack of rigorous testing has raised some questions regarding routine resuscitative practices and indicates that present-day standard therapies must always be under constant review.

Purinoceptor P2U identification and function in human intrahepatic biliary epithelial cell lines.

The mechanisms that regulate ion and fluid transport by the human intrahepatic bile duct have not been well defined. Human intrahepatic biliary cell lines that we have developed were used to identify and characterize purinoceptors based on increases in intracellular calcium in response to ATP and other nucleotides. Intracellular free calcium was measured in cell suspensions using the fluorescent probe Fura-2 and a fluorescence spectrophotometer. Halide efflux was measured in single cells using fluorescence microscopy and the fluorescent probe SPQ. Intracellular calcium increases equivalently in response to ATP and UTP, peaking, then diminishing to a new, elevated baseline. The peak elevation of calcium is the result of both the release of intracellular stores of calcium and the influx of extracellular calcium. The purinoceptor P2U-subtype was identified based on the potency rank order of ATP-analogues. Halide efflux increases with P2U-purinoceptor stimulation which is consistent with the opening of a Ca(2+)-sensitive Cl- channel. The physiological significance of P2U-purinoceptor activation and its effect on the ionic content and flow rate of bile remains to be determined.

Regulation of intracellular pH by immortalized human intrahepatic biliary epithelial cell lines.

We have produced continuous cell lines using retroviral transduction of SV40 large T antigen into human intrahepatic biliary epithelial (IBE) cells from three different normal individuals. These IBE cell lines grow in a hormone-supplemented medium in the presence of NIH/3T3 fibroblast coculture. These cells maintain their epithelial appearance and are positive for the biliary-specific markers cytokeratins 7 and 19 and gamma-glutamyl transpeptidase while being negative for the hepatocyte markers albumin and asialoglycoprotein receptor. To evaluate ion transport pathways in IBE cell lines, we utilized intracellular pH (pHi) measurements obtained using the intracellular fluorescent indicator 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein. In the absence of HCO3(-)-CO2, an amiloride-sensitive Na(+)-H+ exchanger participated in the regulation of basal pHi. In the presence of HCO3(-)-CO2, a 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS)-sensitive, Na-, Cl-, and HCO3(-)-dependent acid extrusion mechanism accounted for approximately 60% of pHi recovery from acidic pHi; this mechanism is most consistent with the presence of a Na-dependent Cl-HCO3- exchanger (Na+HCO3(-)-Cl-H+). Under basal conditions, Cl- depletion revealed a DIDS-sensitive alkalinization consistent with a Na-independent Cl(-)-HCO3- exchanger. These model systems will allow the opportunity to study the normal mechanisms of IBE function and to study the pathobiology of IBE processes in disease states.