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  • Crustacea  (5)
  • Model  (2)
  • 67.40.Yv  (1)
  • Springer  (8)
  • Macmillan Magazines Ltd.
  • Blackwell Science Ltd
Collection
Publisher
  • Springer  (8)
  • Macmillan Magazines Ltd.
  • Blackwell Science Ltd
Years
  • 1
    ISSN: 1432-136X
    Keywords: Crustacea ; Amphipoda ; Haemocyanin ; Temperature sensitivity ; l-Lactate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The effect of pH, temperature, and l-lactate on the O2 bindign properties of haemocyanin (Hc) from three talitroidean species i.e., the aquatic Apohyale pugettensis, the semi-terrestrial Megalorchestia californiana, and the semi-/euterrestrial Traskorchestia traskiana was studied. The Hc of A. pugettensis was characterized by a higher O2 affinity (and more pronounced Bohr shift) than the Hc of either M. californiana or T. traskiana. Apohyale was the only species that possessed He that was sensitive to temperature change. Resuspending Hc from each of the three species in a stock Ringer's solution (based on the ionic composition of the haemolymph of T. traskiana) showed that the persistence of the difference in Bohr shift between Apohyale and the other two species was due to differences in the haemocyanins themselves and not attributable to their respective ionic environments. An inverse relationship was found between the cooperativity (n 50) and pH of Hc from T. traskiana and A. pugettensis but not for M. californiana. In each case adding l-lactate increased Hc O2 affinity, but this was most pronounced for A. pugettensis.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-9686
    Keywords: Elastance ; Stroke volume ; Model ; Cardiomyoplasty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Dynamic cardiomyoplasty (DCM) is an emerging surgical procedure for heart failure in which the patient's latissimus dorsi (LD) muscle is wrapped around the heart and stimulated to contract in synchrony with the heartbeat as a cardiac assist measure. A 6 week training protocol of progressive electrical stimulation renders the normally fatigueable skeletal muscle fatigue-resistant and suitable for chronic stimulation. To date, over 500 procedures have been performed in worldwide clinical trials. Investigators typically report symptomatic improvement and modest hemodynamic improvement in patients. Controversy exists regarding the exact mechanism of DCM. To test the hypothesis that DCM augments cardiac stroke volume through improvement in systolic function, we formulated an engineering model of dynamic cardiomyoplasty to predict stroke volume. The heart and the LD were modeled as nested (series) elastance chambers, and the vasculature was represented by a two-element Windkessel model. Using five healthy goats, we verified model predictions of stroke volume for both stimulator ON beats (y=1.00x−0.08, r=0.87, p 〈 0.0001) and OFF beats (y=1.01x+1.06, r=0.91, p 〈 0.0001), where x and y are the measured and predicted stroke volumes, respectively. The model confirms that using untrained latissimus dorsi applied to the normal myocardium produces only moderate increases in stroke volume and suggests that future research should focus on increasing LD strength after training.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-9686
    Keywords: Clinical cardiomyoplasty ; Nomogram ; Muscle transformation ; Model ; Cardiomyoplasty ; Applications
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Previously, a modification to the Sunagawa engineering model for the isolated left ventricle and arterial system was proposed and validated for dynamic cardiomyoplasty in an acute goat preparation. To test the hypothesis that this model may be applied to the clinical scenario in cardiomyoplasty patients, we predicted human stroke volume using the model with human clinical data from the literature. Predicted stroke volume correlated well with published stroke volume in patients who have had the dynamic cardiomyoplasty procedure. These results suggest that the modest hemodynamic improvement commonly reported after the procedure is performed may be due to diminished latissimus dorsi strength after transformation. The validity of both the original Sunagawa model and the previously proposed modification for dynamic cardiomyoplasty is further supported with these results. A nomogram methodology for predicting stroke volume after dynamic cardiomyoplasty for any particular patient is presented.
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  • 4
    ISSN: 1432-136X
    Keywords: Crustacea ; Amphipoda ; Haemocyanin ; O2 transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Haemolymph PO2 and pH of two amphipod species, Apohyale pugettensis (aquatic) and Megalorchestia californiana (semi-terrestrial) in vivo were examined during immersion and emersion at 15 and 25°C, and also after activity in air at 15°C. For M. californiana arterial O2 tensions were higher in air than in water. This situation was reversed in A. pugettensis, although all O2 tensions measured for both species were comparatively high. No arterial-venous PO2 difference was apparent in the haemolymph of quiescent M. californiana. Haemocyanin (Hc) was 100% saturated in vivo only in the following; A. pugettensis in water (15 and 25°C) and air (15°C), and M. californiana in air (15°C). The Hc of both species becomes important in O2 transport during activity; under such circumstances the haemolymph of M. californiana delivered more O2 to the tissues than did that of A. pugettensis, despite the greater O2 content of the latter. The animals studied here may exhibit a stage (size class?) where cutaneous gas exchange is sufficient for resting aerobic metabolism while specialized respiratory carriers (and respiratory structures) are important in meeting the increased aerobic demands of activity or environmental stress.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1434-6036
    Keywords: 36.40.+d ; 33.70.Jg ; 67.40.Yv
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We examine the effects of impurities (“doping”) and rotational excitation on the structural and energetic properties of helium clusters. Quantum Monte Carlo (QMC) techniques are used to study ground and rotationally excited states of pure and doped clusters. We use exponentially correlated wave functions and treat the molecular impurities as rigid. Whereas pure HeN show essentially monotonic decay of density from a central maximum value, addition of impurities induces local ordering of He to an extent dependent on the impurity-He binding. Rotational excitation of HeN gives rise to extremely large centrifugal distortions. The location of impurities also appears to change upon rotational excitation. The implications of these distortions on impurity spectra are discussed for SF6HeN, and compared to recent experimental results.
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  • 6
    ISSN: 1432-136X
    Keywords: Amphipoda ; Crustacea ; Haemocyanin ; Freezing ; Inorganic effectors ; Urate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The effect of variations in [K], [Ca], [Mg], [NaCl], and [urate] on the in vitro O2 binding properties of haemocyanin (Hc) from three talitroidean species, viz. the aquatic Apohyale pugettensis, the semi-terrestrial Megalorchestia californiana, and the semi-/euterrestrial Traskorchestia traskiana were studied. Freezing altered the cooperativity of Hc from A. pugettensis and M. californiana but not T. traskiana. Variations in [NaCl], [K], and [Mg] had no effect on cither O2 affinity or cooperativity of the Hc except for A. pugettensis Hc where an increase in [Mg] resulted in an increase in both O2 affinity and cooperativity. Increasing [Ca] or [urate] increased O2 affinity of both A. pugettensis and M. californiana but not T. traskiana Hc. These effects were most marked in A. pugettensis. The results suggest a negative correlation between sensitivity to Hc effectors and the degree of terrestrial adaptation of a particular amphipod species.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-136X
    Keywords: Key words Cardiovascular ; Hypoxia ; Crustacea ; Respiratory ; Doppler
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The heart rate of crayfish (Procambarus clarkii) and lobsters (Homarus americanus) decreased (bradycardia) as partial pressure of O2 (P O 2) decreased, yet cardiac output (V b) was maintained via an increased stroke volume (S v) to P O 2s of 40 mmHg and 75 mmHg for crayfish and lobsters, respectively. V b was redistributed in both animals. Flow through the anterior aorta increased while flow dropped through the posterior aorta and sternal artery to a P O 2 of 30 mmHg; below this flow was no longer maintained in crayfish. In the lobster, flow increased to the lateral arteries and the ventral thoracic artery while flow through the anterior and posterior aortas, sternal artery and ventral abdominal artery decreased to a P O 2 of 75 mmHg. Anterior hemolymph flow was maintained or increased in both animals presumably to supply nervous tissue and cephalic sense organs better. Crayfish showed an increase in intracardiac and mean arterial hemolymph pressures as P O 2 declined. The increased pressures combined with the net increase in cardiac filling pressure and diastolic filling time could have accounted for the increased S V. The cardiovascular response exhibited by both the crayfish and lobster was P O 2 dependent; below a critical water P O 2 active compensation was no longer observed.
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  • 8
    ISSN: 1420-9071
    Keywords: Cardiac output ; cardio-regulatory nerves ; hemodynamics ; neurohormones ; pericardial organ ; Crustacea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract This report provides the first direct measurements of the stroke volume and total cardiac output of crustacean hearts, as recorded from a semi-isolated in vitro preparation. The responses to mechanical perturbations, changes in preload and afterload, show that these hearts do not possess automatic compensatory Frank-Starling-like mechanisms. Heart rate, reflecting the burst rate of the cardiac ganglion, is minimally affected by stretch. On the other hand, these hearts are exquisitely responsive to the neurohormones of the pericardial organs. Serotonin, CCAP and proctolin all produce positive chronotropic and inotropic effects, but the responses to each are unique. Two FMRFamide peptides were positively chronotropic, but negatively inotropic.
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