Vagal cooling experiments suggest that the deep slow breathing observed after vagotomy results not only from loss of pulmonary stretch receptor feedback, but also from loss of some unidentified vagal input. To investigate this possibility we cooled the vagus nerves in anesthetized dogs. In dogs breathing spontaneously, the Hering-Breuer reflex was abolished at 7 degrees C, but average expiratory time was unchanged and lengthened only on cooling below 3 degrees C. In artificially ventilated dogs the pulmonary vagus nerves were cooled in the chest and phrenic activity was recorded. Entrainment of phrenic bursts to the ventilator cycle ceased at 7 degrees C, and expiratory pauses shortened; they lengthened again on cooling below 3 degrees C. Cervical vagotomy did not change breathing pattern after the pulmonary vagus nerves were cut. Recording of afferent impulses during cooling showed that at 5 degrees C or less pulmonary vagal input was confined largely to nonmyelinated fibers; at 3 degrees C, background activity in pulmonary C-fibers was still 78% of control whereas myelinated afferents were virtually silent. We suggest that in eupnea low frequency, background activity in pulmonary afferent C-fibers shortens expiratory time. 相似文献
本文用热变性温度法研究一定浓度 H_2O_2对 C.albicans DNA 破坏作用。结果表明,经6%和10%H_2O_2处理后,C.albicans DNA G c Mol%(分别为28.1±0.82和14.4±1.51)显著低于对照 DNA G C Mol%(85.9±0.62),并推断 H_2O_2可能作用于 C.albicans DNA 碱基以及其间的氢键上;DNA 电泳图谱发现,经3%和6%H_2O_2处理的 C.albicans DNA 电泳带明显不同于对照,提示 H_2O_2更易造成 C.albicans DNA 核苷酸链的降解或断裂.H_2O_2对 C.albicans DNA 的破坏,增强了其杀菌作用。 相似文献
Background. A membrane oxygenator consisting of a microporous polypropylene hollow fiber with a 0.2-μm ultrathin silicone layer (cyclosiloxane) was developed. Animal experimental and preliminary clinical studies evaluated its reliability in bypass procedures.
Methods. Five 24-hour venoarterial bypass periods were conducted on dogs using the oxygenator (group A). In 5 controls, bypass periods were conducted using the same oxygenator without silicone coating (group B). As a preliminary clinical study, 14 patients underwent cardiopulmonary bypass with the silicone-coated oxygenator.
Results. Eight to 16 hours (mean, 12.2 hours) after initiation of bypass, plasma leakage occurred in all group B animals, but none in group A. The O2 and CO2 transfer rates after 24 hours in group A were significantly higher than at termination of bypass in group B (p < 0.005 and p < 0.03, respectively). Scanning electron microscopy of silicone-coated fibers after 24 hours of bypass revealed no damage to the silicone coating of the polypropylene hollow fibers. In the clinical study, the oxygenator showed good gas transfer, acceptable pressure loss, low hemolysis, and good durability.
Conclusions. This oxygenator is more durable and offers greater gas transfer capabilities than the previous generation of oxygenators. 相似文献