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The reservoir competence of the meadow vole, Microtus pennsylvanicus Ord, for the Lyme disease spirochete Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner was established on Patience Island, RI. Meadow voles were collected from 5 locations throughout Rhode Island. At 4 of the field sites, M. pennsylvanicus represented only 4.0% (n = 141) of the animals captured. However, on Patience Island, M. pennsylvanicus was the sole small mammal collected (n = 48). Of the larval Ixodes scapularis Say obtained from the meadow voles on Patience Island, 62% (n = 78) was infected with B. burgdorferi. Meadow voles from all 5 locations were successfully infected with B. burgdorferi in the laboratory and were capable of passing the infection to xenodiagnostic I. scapularis larvae for 9 wk. We concluded that M. pennsylvanicus was physiologically capable of maintaining B. burgdorferi infection. However, in locations where Peromyscus leucopus (Rafinesque) is abundant, the role of M. pennsylvanicus as a primary reservoir for B. burgdorferi was reduced. 相似文献
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During exercise, dynamic hyperinflation-induced intrinsic positive end-expiratory pressure (PEEPi) and decreased dynamic lung compliance (CL,dyn) of patients with chronic obstructive pulmonary disease (COPD) increase the elastic work of inspiration (Wi) more than would be predicted from the increase in tidal volume (VT). This contributes significantly to their exertional breathlessness. In 10 stable patients with COPD, the dynamic Wi was measured during incremental bicycle exercise to exhaustion. The total Wi was then partitioned into the portion required to overcome PEEPi (Wi,PEEPi) and nonPEEPi elastic load (Wi,nonPEEPi). The latter is used to overcome the increase in the total respiratory system elastance during inflation. From resting breathing to peak exercise, Wi more than doubled (p<0.001). This increase was largely due to Wi,PEEPi, which significantly rose from 1.7+/-0.3 to 5.3+/-0.8 L x cm H2O(-1) (p<0.001). In comparison, Wi,nonPEEPi increased from only 3.0+/-0.4 to 5.1+/-0.5 L x cm H2O(-1) (p<0.01). Consequently, Wi,PEEPi as a fraction of total Wi increased from 35.5+/-5.6 to 51.0+/-3.3% (p<0.02). In addition, the measured Wi,nonPEEPi at peak exercise, when expressed as a percentage of its value during resting breathing, was 25% more than that predicted from the increase in VT alone. Assuming a constant chest wall compliance, this can be attributed to the exercise-induced decrease in CL,dyn, which was 0.27+/-0.04 and 0.17+/-0.02 L x cm H2O(-1) (p<0.01), respectively, during resting breathing and peak exercise. In conclusion, the dynamic hyperinflation-induced intrinsic positive end-expiratory pressure is more important than the increase in tidal volume in raising the work of inspiration during exercise in patients with chronic obstructive pulmonary disease; the decrease in dynamic lung compliance plays a definite but less important role. 相似文献
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JJ Chu KD Chen YL Lin CY Fei AS Chiang CD Chiang YK Lai 《Canadian Metallurgical Quarterly》1998,68(4):472-483
Taxol, a microtubule stabilizing agent, has been extensively investigated for its antitumor activity. The cytotoxic effect of taxol is generally attributed to its antimicrotubule activity and is believed to be cell cycle dependent. Herein, we report that taxol induces hyperphosphorylation and reorganization of the vimentin intermediate filament in 9L rat brain tumor cells, in concentration- and time-dependent manner. Phosphorylation of vimentin was maximum at 10(-6) M of taxol treatment for 8 h and diminished at higher (10(-5) M) concentration. Enhanced phosphorylation of vimentin was detectable at 2 h treatment with 10(-6) M taxol and was maximum after 12 h of treatment. Taxol-induced phosphorylation of vimentin was largely abolished in cells pretreated with staurosporine and bisindolymaleimide but was unaffected by H-89, KT-5926, SB203580, genistein, and olomoucine. Thus, protein kinase C may be involved in this process. Hyperphosphorylation of vimentin was accompanied by rounding up of cells as revealed by scanning electron microscopy. Moreover, there was a concomitant reorganization of the vimentin intermediate filament in the taxol-treated cells, whereas the microtubules and the actin microfilaments were less affected. Taken together, our data demonstrate that taxol induces hyperphosphorylation of vimentin with concomitant reorganization of the vimentin intermediate filament and that this process may be mediated via a protein kinase C signaling pathway. 相似文献