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131.
The susceptibility of uninfected or Staphylococcus chromogenes-infected quarters to challenge with Staphylococcus aureus was measured. Seventeen S. chromogenes-infected quarters were challenged by infusion of S. aureus into the teat sinus; 47% (8 of 17) became infected and all 18 uninfected quarters challenged similarly with S. aureus became infected. No differences in daily milk yield were seen between uninfected quarters and S. chromogenes-infected quarters prior to S. aureus infusion. Postinfusion, milk yield for S. aureus-infected, S. chromogenes-infected, and S. chromogenes- and S. aureus-infected quarters differed. Somatic cell counts were elevated in S. chromogenes-infected quarters compared with uninfected quarters prior to S. aureus infusion. Somatic cell counts were not different between S. aureus- and S. chromogenes- and S. aureus-infected quarters postinfusion, but were different for S. chromogenes-infected quarters. Chloride concentrations in S. chromogenes- and S. aureus-infected quarters were different from either S. aureus-infected or S. chromogenes-infected quarters. Staphylococcus aureus colony forming units in quarters with preexisting S. chromogenes infections were lower than S. aureus colony-forming units in previously uninfected quarters. Possible protective mechanisms induced by S. chromogenes against superinfection by S. aureus are discussed. 相似文献
132.
Early surgery in patients with mitral regurgitation due to flail leaflets: a long-term outcome study
LH Ling M Enriquez-Sarano JB Seward TA Orszulak HV Schaff KR Bailey AJ Tajik RL Frye 《Canadian Metallurgical Quarterly》1997,96(6):1819-1825
BACKGROUND: The optimal timing for surgery in patients with mitral regurgitation is disputed. Because of the frequency of left ventricular dysfunction, which is difficult to predict, early surgery has been recommended, but its potential benefits have not been demonstrated. METHODS AND RESULTS: The outcomes of 221 patients (mean age, 65 +/- 13 years; 71% males) with flail leaflets diagnosed with two-dimensional echocardiography between 1980 and 1989 who were eligible for operation were analyzed. Group I comprised 63 patients who had early mitral valve surgery (within 1 month after diagnosis). Group II comprised 158 patients initially treated conservatively (80 of whom were operated on later). Group I patients were younger (P=.009), had more symptoms (P<.0001), and were more frequently in atrial fibrillation (P=.023) than group II patients. There was no difference in ejection fraction between the groups. The early surgery strategy was followed by an improved overall survival rate (P=.028) and a lower incidence of cardiovascular deaths (P=.025), congestive heart failure (P=.046), and new chronic atrial fibrillation (P=.032), as confirmed by multivariate analysis (adjusted risk ratios of 0.31, 0.18, 0.38, and 0.05, respectively; all P<.02). CONCLUSIONS: In patients with mitral regurgitation due to flail leaflets, the strategy of early surgery versus conservative management is associated with an improved long-term survival rate, decreased cardiac mortality, and decreased morbidity after diagnosis. This outcome advantage suggests that early surgery is a reasonable treatment option to be considered in low-risk candidates with repairable valves and severe mitral regurgitation. 相似文献
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The influence of visual workload history on visual performance 总被引:3,自引:0,他引:3
M L Matthews 《Human factors》1986,28(6):623-632
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This study was conducted to determine whether submaximal cardiovascular responses at a given rate of work are different in children and adults, and, if different, what mechanisms are involved and whether the differences are exercise-modality dependent. A total of 24 children, 7 to 9 yr old, and 24 adults, 18 to 26 yr old (12 males and 12 females in each group), participated in both submaximal and maximal exercise tests on both the treadmill and cycle ergometer. With the use of regression analysis, it was determined that cardiac output (Q) was significantly lower (P = 0.05) at a given O2 consumption level (VO2, l/min) in boys vs. men and in girls vs. women on both the treadmill and cycle ergometer. The lower Q in the children was compensated for by a significantly higher (P = 0.05) arterial-mixed venous O2 difference to achieve the same or similar VO2. Furthermore, heart rate and total peripheral resistance were higher and stroke volume was lower in the children vs. in the adult groups on both exercise modalities. Stroke volume at a given rate of work was closely related to left ventricular mass, with correlation coefficients ranging from r = 0.89-0.92 and r = 0.88-0.93 in the males and females, respectively. It was concluded that submaximal cardiovascular responses are different in children and adults and that these differences are related to smaller hearts and a smaller absolute amount of muscle doing a given rate of work in the children. The differences were not exercise-modality dependent. 相似文献
138.
Wray Jonathan W.; Baase Walter A.; Ostheimer Gerard J.; Zhang Xue-jun; Matthews Brian W. 《Protein engineering, design & selection : PEDS》2000,13(5):313-321
It is not easy to find candidate sites within a given proteinwhere the geometry of the polypeptide chain matches that ofmetal-binding sites in known protein structures. By choosinga location in T4 lysozyme that is inherently flexible, it waspossible to engineer a two-histidine site that binds differentdivalent cations. Crystallographic analysis shows that the geometryof binding of zinc is distorted tetrahedral while that of cobaltand nickel is octahedral. Insofar as spectroscopic data canbe measured, they indicate that similar modes of coordinationare retained in solution. The two substitutions, Thr21 相似文献
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