Brain acetylcholinesterase (AChE) activity was evaluated after two different swimming tests in coho salmon (Oncorhynchus kisutch; 238 +/- 5 g) given 96-h exposures to 0, 5, 10, 20, or 40 microg/L of chlorpyrifos. Brain AChE activity decreased in a concentration-dependent manner (AChE activities were 81.8, 52.2, 37.3, and 21.3% of control for the 5, 10, 20, and 40 microg/L exposures, respectively), whereas swimming performance was impaired after a threshold of AChE impairment was reached. Specifically, for swimming performance (U(crit)) measured using the established ramp-U(crit) test (duration, 152 +/- 8 min), this threshold occurred with AChE activity of 68.5% +/- 18.1% of control. For a rapid acceleration test (U(deltav), where V represents velocity; 27.6 +/- 0.8 min), this value was 52.6% +/- 15.4% of control. Both swim protocols resulted in similar maximum swim speeds (control ramp-U(crit) and U(deltav) values of 3.44 +/- 0.09 and 3.71 +/- 0.13 body lengths/s, respectively), and performance was significantly reduced after 20 and 40 microg/L exposures in both groups (ramp-U(crit) values: 86.4 and 83.6 %, respectively, of control; U(deltav) values: 85.2 and 77.8%, rsepectively, of control). Although both tests yielded similar swim speeds, postexercise plasma lactate concentrations were greater for the U(deltav) test (11.3 +/- 0.6 vs 8.6 +/- 0.5 mmol/L), indicating a greater anaerobic effort. This increase was exaggerated after 10 microg/L of chlorpyrifos (14.6 +/- 1.3 mmol/L), indicating that anaerobic muscle was used to attain the same speed. Given the threshold relationship between AChE inhibition and swimming performance, coho salmon appear able to maintain integrated swimming activity despite significant impairment of an underlying neurological control mechanism.

Objectives-To examine long axis excursion in patients with all grades of aortic stenosis and preserved transverse systolic function, and to compare long axis excursion in symptomatic with that in asymptomatic severe aortic stenosis. Design-Prospective comparative study. Setting-Regional cardiothoracic centre. Patients-78 patients with all grades of aortic stenosis and normal fractional shortening and ejection fraction were studied. There were two comparison groups, 10 age matched normal subjects and 14 patients with aortic stenosis and fractional shortening < 26%. Methods-Aortic valve function and left ventricular mass were assessed echocardiographically. M mode measurements of long axis excursion at the septal and lateral sides of the mitral annulus were taken. Results-There were significant diVerences between the groups in long axis excursion at both the septal (p < 0.0001) and lateral sides of the mitral annulus (p = 0.002 by analysis of variance). Long axis excursion was independently related to both left ventricular mass index (p = 0.001) and the grade of aortic stenosis (p = 0.002). Comparing patients with severe aortic stenosis with and without symptoms, there were significant diVerences in eVective orifice area (p = 0.02 ) and long axis excursion at the lateral side of the mitral annulus (p = 0.04), but not in fractional shortening, ejection fraction, or peak or mean pressure diVerence. Conclusion-In patients with aortic stenosis, long axis excursion is reduced even in the presence of normal fractional shortening or ejection fraction. It is lower in patients with symptomatic compared with asymptomatic severe aortic stenosis and may be of use in predicting the onset of symptoms. (Heart 2001;86:52-56)

Objective-To investigate the relation between transaortic pressure diVerence and flow in patients with aortic stenosis. Methods-50 asymptomatic patients with all grades of aortic stenosis were studied using dobutamine stress echocardiography. Individual plots of mean pressure drop against flow were drawn. Comparisons were made between grades of aortic stenosis as defined by the continuity equation. Results-A significant linear relation between pressure diVerence and flow was found in 34 patients (68%). There was a significant curvilinear relation in four (8%), while no significant regression line could be fitted in 12 (24%). In the 34 patients with linear fits, the slopes (mean

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OBJECTIVESTo examine long axis excursion in patients with all grades of aortic stenosis and preserved transverse systolic function, and to compare long axis excursion in symptomatic with that in asymptomatic severe aortic stenosis.DESIGNProspective comparative study.SETTINGRegional cardiothoracic centre.PATIENTS78 patients with all grades of aortic stenosis and normal fractional shortening and ejection fraction were studied. There were two comparison groups, 10 age matched normal subjects and 14 patients with aortic stenosis and fractional shortening < 26%.METHODSAortic valve function and left ventricular mass were assessed echocardiographically. M mode measurements of long axis excursion at the septal and lateral sides of the mitral annulus were taken.RESULTSThere were significant differences between the groups in long axis excursion at both the septal (p < 0.0001) and lateral sides of the mitral annulus (p = 0.002 by analysis of variance). Long axis excursion was independently related to both left ventricular mass index (p = 0.001) and the grade of aortic stenosis (p = 0.002). Comparing patients with severe aortic stenosis with and without symptoms, there were significant differences in effective orifice area (p = 0.02 ) and long axis excursion at the lateral side of the mitral annulus (p = 0.04), but not in fractional shortening, ejection fraction, or peak or mean pressure difference.CONCLUSIONIn patients with aortic stenosis, long axis excursion is reduced even in the presence of normal fractional shortening or ejection fraction. It is lower in patients with symptomatic compared with asymptomatic severe aortic stenosis and may be of use in predicting the onset of symptoms.