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  • 1
    ISSN: 1523-536X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background: Patterned breathing is one way that women cope with labor. Fatigue is a frequently reported symptom over which women and caregivers have little control. The purpose of this study was to examine the relationship between the use of patterned breathing, a traditional intervention, and the level of fatigue reported during the first stage of labor. Method: A secondary analysis was conducted on a subset (n= 56) of a prospective longitudinal study of fatigue during the intrapartum period. The sample comprised primiparous women in labor whose fatigue was measured every two hours for six hours after admission. At each data point the investigator evaluated the method of breathing that participants used.Results:During the latent phase of labor, women using patterned breathing exhibited significantly more fatigue. In the active phase, differences between groups were not significant. Controlling for age, education, and marital status of participants did not change the results.Conclusions:It is appropriate for nurses, midwives, physicians, and doulas to encourage the use of patterned breathing as an intervention in active labor; however, patterned breathing may increase the mother's fatigue level if begun too early. (BIRTH 25:4 December 1998)
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  • 2
    ISSN: 1745-4549
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: This study was undertaken to determine the pressure and time required to inactivate Saccharomyces cerevisiae and Listeria innocua on apples and blueberries while maintaining a “fresh-like” fruit texture and color.d-values for inactivation of S. cerevisiae and L. innocua inoculated on diced apples and blueberries following ultra high pressure treatment at 300 and 375 MPa at room temperature were determined.d-values for inactivation of S. cerevisiae at 300 MPa ranged from 19.7 s on diced apples to 22.4 s on blueberries.d-values for inactivation of L. innocua at 375 MPa ranged from 67.1 s on diced apples to 46.7 s on blueberries. Ultra high pressure is an efficient and effective option for inactivating S. cerevisiae and L. innocua on apples, blueberries or other fruit while preserving a fresh appearance and texture.
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  • 3
    ISSN: 1526-100X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: For an estuarine restoration project to be successful it must reverse anthropogenic effects and restore lost ecosystem functions. Restoration projects that aim to rehabilitate endangered species populations make project success even more important, because if misjudged damage to already weakened populations may result. Determining project success depends on our ability to assess the functional state or “performance” and the trajectory of ecosystem development. Mature system structure is often the desired “end point” of restoration and is assumed to provide maximum benefit for target species; however, few studies have measured linkages between structure and function and possible benefits available from early recovery stages. The Salmon River estuary, Oregon, U.S.A., offers a unique opportunity to simultaneously evaluate several estuarine restoration projects and the response of the marsh community while making comparisons with a concurring undiked portion of the estuary. Dikes installed in three locations in the estuary during the early 1960s were removed in 1978, 1987, and 1996, creating a “space-for-time substitution” chronosequence. Analysis of the marsh community responses enables us to use the development state of the three recovering marshes to determine a trajectory of estuarine recovery over 23 years and to make comparisons with a reference marsh. We assessed the rate and pattern of juvenile salmon habitat development in terms of fish density, available prey resources, and diet composition of wild juvenile Oncorhynchus tshawytscha (chinook salmon). Results from the outmigration of 1998 and 1999 show differences in fish densities, prey resources, and diet composition among the four sites. Peaks in chinook salmon densities were greatest in the reference site in 1998 and in the youngest (1996) site in 1999. The 1996 marsh had higher densities of chironomids (insects; average 864/m2) and lower densities of amphipods (crustaceans; average 8/m3) when compared with the other sites. Fauna differences were reflected in the diets of juvenile chinook with those occupying the 1978 and 1996 marshes based on insects (especially chironomids), whereas those from the 1987 and reference marshes were based on crustaceans (especially amphipods). Tracking the development of recovering emergent marsh ecosystems in the Salmon River estuary reveals significant fish and invertebrate response in the first 2 to 3 years after marsh restoration. This pulse of productivity in newly restored systems is part of the trajectory of development and indicates some level of early functionality and the efficacy of restoring estuarine marshes for juvenile salmon habitat. However, to truly know the benefits consumers experience in recovering systems requires further analysis that we will present in forthcoming publications.
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  • 4
    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
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  • 5
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Restitution and Spatial Heterogeneities vs Arrhythmias. Introduction: The slope of the action potential duration (APD) restitution curve has been used to explain wavebreaks during arrhythmia initiation and maintenance. This hypothesis remains incomplete to fully describe the experimental data. Other factors contributing to wavebreaks must be studied to further understand arrhythmia dynamics. Methods and Results: Control APDs were measured from isolated rabbit hearts using a monophasic action potential probe. APD and conduction velocity (CV) restitution were quantified over the heart surface for two drugs, diacetyl monoxime (DAM) and cytochalasin D (CytoD), using a dual camera video imaging system. For all pacing intervals: (1) control APDs were shorter than for CytoD but longer than for DAM; and (2) CV was greater for CytoD compared with DAM. APD dispersion increased as pacing interval decreased for both drugs. For DAM, increased dispersion was due to a difference in APD restitution between the right and left ventricle. For CytoD, increased dispersion was due to discordant alternans, with no significant spatial variation in restitution. Fibrillation was sustained only in the control hearts; with DAM, stable reentry was sustained with shorter APD and cycle length compared with CytoD for which only nonsustained unstable reentry occurred. Conclusion: Alternans and arrhythmia dynamics are affected by the spatial dispersion of APD restitution as well as CV restitution, not simply the slope of APD restitution. Therefore, a direct link of the APD restitution slope to alternans and arrhythmia dynamics in rabbit heart does not exist. Designing antiarrhythmic drugs to alter only the restitution slope may not be appropriate.
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  • 6
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Shock Effects on Reentry. Introduction: Although numerous theories exist for the mechanisms of defibrillation, experimental data directly relating these mechanisms to the termination of reentry in whole hearts are lacking. Methods and Results: Using video imaging technology, we recorded ~5,000 optical action potentials simultaneously from the anterior and posterior ventricular epicardium of rabbit hearts during cardioversion of stable reentrant arrhythmias. Monophasic shocks at three strengths for each polarity were delivered between electrodes inside the right ventricle (RV) and above the left atrium. Cardioversion efficacy at the three strengths was 21%, 42%, and 92% for RV+ shocks, which primarily depolarized the epicardium, and 10%, 15%, and 33% for RV– shocks, which primarily hyperpolarized the epicardium. The mechanism of cardioversion for RV+ shocks was elimination of excitable gaps and reentry via excitation ahead of wavefronts and action potential prolongation at wavetails, both of which increased with shock strength. Partial elimination of these gaps resulted in resetting of preshock reentry and/or induction of new reentry. RV– shocks cardioverted primarily via deexcitation, which terminated reentry by creating new postshock wavefronts via break excitation that rapidly activated excitable gaps. Outcome was dependent on the preshock state for both polarities at strengths near the 50% success level. Before successful shocks, more epicardium was recovered, resulting in more excitation and longer postshock depolarization (RV+ shocks) and faster postshock elimination of excitable gaps (RV– shocks). Conclusion: These findings provide a direct mechanistic link between shock-induced changes in Vm and the effect of polarity, strength, and timing on cardioversion efficacy.
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Inc
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
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  • 8
    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: The dependence of action potential duration (APD) on the preceding diastolic interval (DI), i.e., restitution, has been purported to predict the development of alternans and reentrant arrhythmias. However, restitution depends on the history of activation (i.e., memory), and its relevance to arrhythmia induction and maintenance is unknown. Methods and Results: Using a dual-camera video imaging system, we recorded action potentials from thousands of sites on the surface of the isolated pig heart. A steady-state pacing (SSP) protocol was performed to generate the SSP APD restitution curve. During SSP, the minimum DI and APD were 57 ± 6 ms and 107 ± 6 ms, respectively. The restitution slope was 〉1 for DIs 〈85 ± 5 ms; however, alternans were not observed. Abrupt decreases in cycle length (CL) resulted in a rapid (〈5 beats) decrease in APD followed by a slower decrease to “steady state.” DI, APD pairs for the initial beats following these rate changes were significantly above the SSP restitution curve. DI, APD pairs measured during sustained ventricular fibrillation clustered significantly below the SSP restitution curve, at significantly shorter APDs (57 ± 4 ms) and DIs (49 ± 6 ms) than could be achieved during SSP. In addition, abrupt increases in CL following SSP resulted in APDs significantly shorter than those predicted from the SSP restitution curve. Conclusion: Our results indicate that the responses of APD and DI to sudden rate changes and during arrhythmias are not predicted by the SSP restitution relationship. Acute dynamics act to damp out the proarrhythmic oscillations predicted from the SSP restitution curve. (J Cardiovasc Electrophysiol, Vol. 15, pp. 455-463, April 2004)
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  • 9
    Electronic Resource
    Electronic Resource
    350 Main Street , Malden , MA 02148 , USA , and 9600 Garsington Road , Oxford OX4 2DQ , UK . : Blackwell Science Inc
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
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  • 10
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Cellular Response to Premature Stimuli. Introduction: Little is known about how the amplitude and timing of transmembrane current pulses affect transmembrane potential (Vm) and action potential duration (APD) in isolated myocytes. Methods and Results: Ten ventricular myocytes were isolated from five rabbit hearts. Each cell was paced at an S1 cycle length of 250 msec, and S2 pulses of 10-msec duration were delivered at various strengths and time intervals. For all S2 strengths (0.2 to 1.5 nA), the magnitude of changes in Vm did not depend on polarity during the plateau, but were larger for depolarizing pulses during phase 3 repolarization. However, the magnitude of changes in APD varied with polarity during the entire action potential for strengths ranging from 0.5 to 1.5 nA. Greater changes in APD occurred for hyperpolarizing pulses during the plateau and depolarizing pulses during phase 3. In addition, we used a cardiac phase variable to quantify the current threshold for regenerative depolarization and repolarization as a function of prestimulus Vm. Regenerative depolarization occurred during phase 3 repolarization, and its current threshold was less than that required for regenerative repolarization that occurred during the plateau. These data were compared to computer simulations in a patch of membrane represented by Luo-Rudy dynamic kinetics, and the results were qualitatively similar, including the higher threshold for regenerative repolarization compared to regenerative depolarization. Conclusion: This characterization of the nonlinear response of isolated cells to transmembrane current, including phase resetting, should aid in understanding the mechanisms of defibrillation because shockinduced changes in Vm and APD have been implicated as important factors in determining defibrillation success.
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