Cavitation fatigue - the weakening of cavitation resistance of xylem and its reversibility

Journal ArticleXylem function is essential for the growth and survival of higher land plants. Xylem must not only be efficient under favorable conditions to facilitate high rates of stomatal conductance and carbon uptake, but it should also remain functional under drought conditions, when water potential (Ψ) drops to low values. Since water in the xylem is lifted up to the leaves by negative pressure (Steudle, 2001; Zimmermann, 1983), it is intrinsically vulnerable to cavitation

Hydraulic consequences of vessel evolution in angiosperms

Journal ArticleWe tested two hypotheses for how vessel evolution in angiosperms influenced xylem function. First, the transition to vessels decreased resistance to flow--often considered the driving force for their evolution. Second, the transition to vessels compromised safety from cavitation--a constraint emerging from the "pit area hypothesis" for vulnerability to cavitation. Data were obtained from branch wood of 17 basal taxa with vessels and two eudicots possessing "primitive" perforation plates. Results were compared with previous data from vesselless angiosperms and eudicots with simple perforation plates. Contrary to the first hypothesis, basal taxa did not have significantly lower sapwood-specific resistivity than vesselless angiosperms, despite vessels being wider than tracheids

Analysis of circular bordered pit function II. Gymnosperm tracheids with torus-margo pit membranes

Journal ArticleA model of xylem conduit function was applied to gymnosperm tracheids with torus-margo pit membranes for comparison with angiosperm vessels. Tracheids from 17 gymnosperm tree species with circular bordered pits and air-seed pressures from 0.8 to 11.8 MPa were analyzed. Tracheids were more reinforced against implosion than vessels, consistent with their double function in transport and support

Water transport in vesselless angiosperms: conducting efficiency and cavitation safety

Journal ArticleTwo structure-function hypotheses were tested for vesselless angiosperm wood. First, vesselless angiosperm wood should have much higher flow resistance than conifer wood because angiosperm tracheids lack low-resistance torus-margo pits. Second, vesselless wood ought to be exceptionally safe from cavitation if the small cumulative area of pits between tracheids confers safety (the pit area hypothesis). Data were obtained from branch wood of 19 vesselless angiosperms: Amborella trichopoda, Trochodendron aralioides, Tetracentron sinense, and 16 Winteraceae from Tasmannia, Zygogynum, Bubbia, Pseudowintera, and Drimys

Stroke outcome in clinical trial patients deriving from different countries

<p><b>Background and Purpose:</b> Stroke incidence and outcome vary widely within and across geographical locations. We examined whether differences in index stroke severity, stroke risk factors, mortality, and stroke outcome across geographical locations remain after adjusting for case mix.</p> <p><b>Methods:</b> We analyzed 3284 patients from the Virtual International Stroke Trials Archive (VISTA). We used logistic regression to examine the incidence of mild index stroke, functional, and neurological outcomes after accounting for age, medical history, year of trial recruitment, and initial stroke severity in the functional and neurological outcome analyses. We examined mortality between geographical regions using a Cox proportional hazards model, accounting for age, initial stroke severity, medical history, and year of trial recruitment.</p> <p><b>Results</b> Patients enrolled in the USA and Canada had the most severe index strokes. Those recruited in Austria and Switzerland had the best functional and neurological outcomes at 90 days (P<0.05), whereas those enrolled in Germany had the worst functional outcome at 90 days (P=0.013). Patients enrolled in Austria, Switzerland, Belgium, Netherlands, Finland, Germany, Greece, Israel, Spain, and Portugal had a significantly better survival rate when compared with those enrolled in USA and Canada. Patients enrolled in trials after 1998 had more severe index strokes, with no significant difference in outcome compared with those enrolled before 1998.</p> <p><b>Conclusion:</b> We identified regional variations in index stroke severity, outcome, and mortality for patients enrolled in ischemic stroke clinical trials over the past 13 years that were not fully explained by case mix. Index stroke severity was greater in patients enrolled after 1998, with no significant improvement in outcomes compared to those enrolled before 1998.</p&gt

Dose escalation of desmoteplase for acute ischemic stroke (DEDAS): evidence of safety and efficacy 3 to 9 hours after stroke onset

<p><b>Background and Purpose:</b> Desmoteplase is a novel plasminogen activator with favorable features in vitro compared with available agents. This study evaluated safety and efficacy of intravenous (IV) desmoteplase in patients with perfusion/diffusion mismatch on MRI 3 to 9 hours after onset of acute ischemic stroke.</p> <p><b>Methods:</b> DEDAS was a placebo-controlled, double-blind, randomized, dose-escalation study investigating doses of 90 μg/kg and 125 μg/kg desmoteplase. Eligibility criteria included baseline National Institute of Health Stroke Scale (NIHSS) scores of 4 to 20 and MRI evidence of perfusion/diffusion mismatch. The safety end point was the rate of symptomatic intracranial hemorrhage. Primary efficacy co-end points were MRI reperfusion 4 to 8 hours after treatment and good clinical outcome at 90 days. The primary analyses were intent-to-treat. Before unblinding, a target population, excluding patients violating specific MRI criteria, was defined.</p> <p><b>Results:</b> Thirty-seven patients were randomized and received treatment (intent-to-treat; placebo: n=8; 90 μg/kg: n=14; 125 μg/kg: n=15). No symptomatic intracranial hemorrhage occurred. Reperfusion was achieved in 37.5% (95% CI [8.5; 75.5]) of placebo patients, 18.2% (2.3; 51.8) of patients treated with 90 μg/kg desmoteplase, and 53.3% (26.6; 78.7) of patients treated with 125 μg/kg desmoteplase. Good clinical outcome at 90 days occurred in 25.0% (3.2; 65.1) treated with placebo, 28.6% (8.4; 58.1) treated with 90 μg/kg desmoteplase and 60.0% (32.3; 83.7) treated with 125 μg/kg desmoteplase. In the target population (n=25), the difference compared with placebo increased and was statistically significant for good clinical outcome with 125 μg/kg desmoteplase (P=0.022).</p> <p><b>Conclusions:</b> Treatment with IV desmoteplase 3 to 9 hours after ischemic stroke onset appears safe. At a dose of 125 μg/kg desmoteplase appeared to improve clinical outcome, especially in patients fulfilling all MRI criteria. The results of DEDAS generally support the results of its predecessor study, Desmoteplase in Acute Ischemic Stroke (DIAS).</p&gt

Analysis of circular bordered pit function I. Angiosperm vessels with homogenous pit membranes

Journal ArticleA model predicted pit and vessel conductivity, the air-seed pressure for cavitation, and the implosion pressure causing vessel collapse. Predictions were based on measurements from 27 angiosperm species with circular bordered pits and air-seed pressures of 0.2-11.3 MPa. Vessel implosion pressure exceeded air-seed pressure by a safety factor of 1.8 achieved by the increase in vessel wall thickness per vessel diameter with air-seed pressure

Comparison of Outcomes Following Thrombolytic Therapy Among Patients With Prior Stroke and Diabetes in the Virtual International Stroke Trials Archive (VISTA)

OBJECTIVE - The use of alteplase in patients who have had a prior stroke and concomitant diabetes is not approved in Europe To examine the influence of diabetes and prior stroke on outcomes we compared data on thrombolysed patients with nonthrombolysed comparators RESEARCH DESIGN AND METHODS - We selected patients with ischemic stroke on whom we had data on age pretreatment baseline National Institutes of Health Stroke Scale (b-NIHSS) and 90-day outcome measures (functional modified Rankin score [mRS]) and neurological measures [NIHSS]) in the Virtual International Stroke Trials Archive We compared outcomes between thrombolysed patients and nonthrombolysed comparators in those with and without diabetes those who have had a prior stroke or both and report findings using the Cochran Mantel-Haenszel (CMH) test and proportional odds logistic regression analyses We report an age adjusted and b NIHSS adjusted CMH P value and odds ratio (OR) RESULTS - Rankin data were available for 5 817 patients 1 585 thrombolysed patients and 4 232 nonthrombolysed comparators A total 1 334 (24 1%) patients had diabetes 1 898 (33 7%) patients have had a prior stroke and 491 (8%) patients had both Diabetes and non-diabetes had equal b-NIHSS (median 13 P = 0 3) but patients who have had a prior stroke had higher b-NIHSS than patients who have not had a prior stroke (median 13 vs 12 P < 0 0001) Functional outcomes were better for thrombolysed patients versus nonthrombolysed comparators among both nondiabetic (P < 0 0001 OR 1 4 vertical bar 95% CI 1 3-1 6]) and diabetic (P = 0 1 1 3 [1 05-1 6 ]) subjects Similarly outcomes were better for thrombolysed patients versus nonthrombolysed comparators among who have not had a prior stroke (P < 0 0001 1 4 [1 2-1 6]) and those who have (P = 002 1 3 [1 04-1 6]) There was no interaction of diabetes and prior stroke with treatment (P = 0 8) Neurological outcomes were consistent with the mRS CONCLUSIONS - Outcomes from thrombolysis are better among patients with diabetes and/or those who have had a prior stroke than in control subjects Withholding thrombolytic treatment from otherwise eligible patients may not be justifie