High-frequency oscillation (HFO) prevents activation of NF-kappaB found with conventional mechanical ventilation (CMV) in surfactant-depleted rabbit lung.

High-frequency oscillation (HFO) has been recognized as an effective ventilatory strategy to minimize lung injury during respiratory support. Conventional mechanical ventilation (CMV) compared with HFO was shown to result in an increased number of PMNs and inflammatory cytokines in the lung lavage fluid. However how mechanical forces can be sensed by cells and converted into biochemical signals for intracellular signal transduction is still unknown. In this current study, we sought to determine whether the activation of Nuclear factor-kappa B (NF-kappaB) might be involved in the lung injury caused by CMV. Surfactant-depleted Japanese white rabbits received 1- or 4-hr CMV or 1- or 4-hr HFO. Then, activation of NF-kappaB in the lungs was assessed by conducting electrophoretic mobility shift assays (EMSA). In the experiment with whole lungs, NF-kappaB activity was much higher in the 4-hr CMV lungs than in the 4-hr HFO lungs. To clarify the origin of the cells in which NF-kappaB was activated, we did a second lung lavage at the end of ventilation and washed out the cells that had infiltrated the alveoli. The levels of NF-kappaB activity were the similar in the lungs of 4-hr HFO rabbits and in those of 4-hr CMV ones. On the other hand, NF-kappaB activity was much higher in the 4-hr CMV lungs than in the 4-hr HFO lungs in the experiment with the lung lavage fluid cells. These results show that the increase in NF-kappaB activity in the lungs of 4-hr CMV rabbits was due mainly to the cells that had infiltrated the alveoli.

Production of TNF-alpha by polymorphonuclear leukocytes during mechanical ventilation in the surfactant-depleted rabbit lung.

Previous studies showed that the production of tumor necrosis factor-alpha (TNF-alpha) and the number of recovered cells were much higher in the conventional mechanical ventilation (CMV) group than in the high-frequency oscillation (HFO) group at the end of mechanical ventilation in this model. But the type of cells that generated TNF-alpha in the lungs remained unclear. It was shown that the alveolar macrophage was the source of TNF-alpha in the early stage, but that in the later stage, the cells in the lung lavage fluid contained almost no macrophages. Thus we hypothesized that in the surfactant-depleted lung model, one of the sources of TNF-alpha after 4 hr of CMV is polymorphonuclear leukocyte (PMN), a type of cell which was numerous at that time. We performed the experiment in the same lung lavage model. The results were as follows. All PaO2 values for the HFO group were significantly greater than the corresponding values for the CMV group throughout the experiment (P < 0.05). More than 96% of the recovered cells of the lung lavage fluid at the end of ventilation were PMN. Cell counts after ventilation of HFO and CMV groups were 183.0 +/- 40.8 (mean +/- SD, n = 6)/microl and 1,106.0 +/- 310.0/microl, respectively (P < 0.05). Levels of rabbit TNF-alpha in the lavage fluid before and after 4 hr ventilation were 43.3 +/- 103.7 pg/ml and 2,406.0 +/- 1,525.1 pg/ml, respectively, in the CMV group. In the HFO group, these levels were 26.6 +/- 52.0 pg/ml and 613.3 +/- 362.2 pg/ml, respectively. The level of TNF-alpha was significantly greater in the CMV group after ventilation (P < 0.05). We performed RT-PCR analysis, in which we showed the presence of TNF-alpha mRNA in the intraalveolar cells (PMN) after 4 hr of CMV, and then demonstrated a positive immunofluorescence reaction to anti-TNF-alpha antibody in PMN separated from the lavage fluid. Our conclusion is that in this surfactant-depleted lung model, PMN is one of the sources of TNF-alpha in the lavage fluid after 4 hr of CMV.

Chimerism of buccal membrane cells in a monochorionic dizygotic twin.

No monochorionic dizygotic twins (MCDZTs) with cellular chimerism involving cells other than blood cells have been reported in the literature to date. Here we report a probable first case of MCDZTs with buccal cell chimerism. A 32-year-old woman conceived twins by in vitro fertilization by using 2 cryopreserved blastocysts that were transferred into her uterus. An ultrasound scan at 8 weeks' gestation showed signs indicative of monochorionic twins. A healthy boy and a healthy girl were born, showing no sexual ambiguity. Cytogenetic analyses and microsatellite studies demonstrated chimerism in blood cells of both twins. Notably, repeated fluorescence in situ hybridization and microsatellite studies revealed chimerism in buccal cells obtained from 1 of the twins. Although the mechanism through which buccal cell chimerism was generated remains to be elucidated, ectopic differentiation of chimeric hematopoietic cells that migrated to the buccal membrane or the cellular transfer between the 2 embryos at the early stage of development might be responsible for the phenomenon. This hypothesis raises an interesting issue regarding embryonic development and cellular differentiation into organs during fetal development. Given the possibility of cryptic chimerism in various organs including gonadal tissues in MCDZTs, close observation will be required to determine whether complications develop in the course of the patients' growth.