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  • 1
    ISSN: 1526-100X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The laborious process of manual seagrass transplanting has often limited the size of seagrass restoration efforts. This study tested the efficiency of a mechanized planting boat, previously used for transplanting Halodule wrightii, relative to manual transplanting methods for establishing Zostera marina in Chesapeake Bay. Eelgrass planting was conducted at two sites, one each in the Rappahannock and James rivers, in October 2001. The methods were evaluated by three criteria: (1) initial planting success = proportion of attempted planting units (PUs) initially established (number confirmed in sediment by divers/number attempted); (2) survival = proportion of the initially established PUs persisting over 1, 4, and 24 weeks; and (3) efficiency = labor (in person·seconds) invested in each surviving PU. Initial planting success was significantly lower for the planting boat (24 and 56% at the Rappahannock and James sites, respectively) than for manual transplanting (100% at both sites). At the Rappahannock site, survival of initially established PUs declined over time for both methods, but while mean survival was always higher for manually planted rows, differences in survival between methods were not statistically significant. At the James site, survival to 1 and 4 weeks was significantly lower for the machine than for the manual method, but survival to 24 weeks was not significantly different. While the machine was able to attempt PUs faster than the manual method (2.2 s/PU vs. 5.8 s/PU, respectively), this speed was offset by poorer planting success rates, resulting in a much greater total labor investment for each machine-planted PU that persisted to 24 weeks than for each similarly persisting manually planted PU (40.6 person·seconds/PU and 22.4 person·seconds/PU, respectively, averaged across sites). In summary, those PUs successfully planted by the machine survived similarly to PUs planted by hand, but as a result of poorer initial planting success, the machine required a greater investment of labor and plant donor stock for each PU surviving to 24 weeks. Therefore, in its tested configuration this planting boat is not a significant improvement over the manual method for transplanting eelgrass.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    350 Main Street , Malden , MA 02148-5018 , USA , and 9600 Garsington Road , Oxford OX4 2DQ , UK . : Blackwell Science Inc
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Introduction: RSD1235 is a novel drug recently shown to convert AF rapidly and safely in patients.1 Its mechanism of action has been investigated in a rat model of ischemic arrhythmia, along with changes in action potential (AP) morphology in isolated rat ventricular myocytes and effects on cloned channels. Methods and Results: Ischemic arrhythmias were inhibited with an ED50 of 1.5 μmol/kg/min, and repolarization times increased with non-significant effects on PR and QRS durations. AP prolongation was observed in rat myocytes at low doses, with plateau elevation and a reduction in the AP overshoot at higher doses. RSD1235 showed selectivity for voltage-gated K+ channels with IC50 values of 13 μM on hKv1.5 (1 Hz) versus 38 and 30 μM on Kv4.2 and Kv4.3, respectively, and 21 μM on hERG channels. RSD1235 did not block IK1 (IC50 〉 1 mM) nor ICa,L (IC50= 220 μM) at 1 Hz in guinea pig ventricular myocytes (n = 4–5). The drug displayed mild (IC50= 43 μM at 1 Hz) open-channel blockade of Nav1.5 with rapid recovery kinetics after rate reduction (10→1 Hz, 75% recovery with τ= 320 msec). Nav1.5 blocking potency increased with stimulus frequency from an IC50= 40 μM at 0.25 Hz, to an IC50= 9 μM at 20 Hz, and with depolarization increasing from 107 μM at −120 mV to 31 μM at −60 mV (1 Hz). Conclusions: These data suggest that RSD1235's clinical selectivity and AF conversion efficacy result from block of potassium channels combined with frequency- and voltage-dependent block of INa.
    Type of Medium: Electronic Resource
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