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  • 11
    Electronic Resource
    Electronic Resource
    Responses of the isolated crab ventilatory central pattern generators to variations in oxygen tension (1989)
    Springer
    Journal of comparative physiology 159 (1989), S. 29-36 
    Details
    ISSN: 1432-136X
    Keywords: Ventilation ; Central pattern generator ; $$P_{O_2 }$$ ; Apnea ; Hypoxia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. The response of the isolated crab ventilatory central pattern generator (CPG) to changes in oxygen tension was examined. The ventilatory rate increased and motor neuron burst durations decreased as oxygen tension ( $$P_{O_2 }$$ ) was increased from hypoxic to hyperoxic levels. The number of spikes per motor neuron burst, and intraburst phase relationships, were relatively insensitive to $$P_{O_2 }$$ . 2. Pauses in ventilation (apnea) were a common occurence at elevated $$P_{O_2 }$$ , but were rarely seen under hypoxic conditions. During prolonged periolds of apnea, hypoxia was an effective stimulus for eliciting the ventilatory rhythm, although hypoxia depresses the ventilatory rate. 3. Transient (〈3 min) increases in ventilatory rate follow steps from higher to lower levels of $$P_{O_2 }$$ ; longer compensatory increases (〉5 min) occur upon return to normoxia or hyperoxia following prolonged exposure to hypoxia. 4. The latencies for changes in the rate of ventilation in the isolated thoracic ganglion are much longer (3–5 min) than those observed in intact crustaceans following similar changes in $$P_{O_2 }$$ , supporting the view that peripheral oxygen receptors may help to mediate in vivo responses to changes in oxygen tension.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00692680
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  • 12
    Electronic Resource
    Electronic Resource
    Comparison of the roles of neurohormones in the regulation of blood distribution from the hearts of American and Japanese lobsters (1998)
    Springer
    Journal of comparative physiology 168 (1998), S. 483-490 
    Details
    ISSN: 1432-136X
    Keywords: Key words Cardioarterial valves ; Blood distribution ; American lobster ; Japanese lobster ; Hormone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The decapod cardiovascular system consists of a single ventricle that pumps blood into seven arteries; previous work has shown that the outflow distribution patterns of intact animals are variable. In the present study, flow recordings were made from pairs of arteries in semi-isolated hearts whilst different cardioactive hormones were infused into the heart. Each hormone (5-hydroxytryptamine, octopamine, dopamine, proctolin and F1) changed the outflow pattern, heart rate and ventricular pressure in a unique way. The probable sites of hormone action are the cardioarterial valves located at the origin of each artery except one, the dorsal abdominal. Outflow from the dorsal abdominal is controlled downstream by valves located at the origin of the segmental lateral arteries. The responses to a particular hormone were sometimes different between the hearts of American and Japanese lobsters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003600050168
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    Paper (German National Licenses)
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  • 13
    Electronic Resource
    Electronic Resource
    Structure and contractile properties of the ostial muscle (musculus orbicularis ostii) in the heart of the American lobster (1999)
    Springer
    Journal of comparative physiology 169 (1999), S. 529-537 
    Details
    ISSN: 1432-136X
    Keywords: Key words Contraction ; Heart ; Ostium ; Homarus americanus (Crustacea) ; AbbreviationEPSP excitatory postsynaptic potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract “Venous” blood enters the crustacean heart through bivalved ostia. Each ostium is a discrete anatomical unit that remains functional even when isolated from the heart. Muscle fibers produce overshooting action potentials that have a plateau of variable duration in response to nervous drive from the cardiac ganglion or during trains of electrical stimuli. Contractions show summation and facilitation when stimulated by trains of stimuli delivered at rates greater than 0.5 s−1 and 0.2 s−1, respectively. Contraction amplitude increases with stimulating impulse frequency and train duration. Maximum force occurs at 1.2 times the slack length. The morphology of ostial fibers resembles that of myocardial fibers. Interconnected bundles of myofilaments occur in both the ostial fibers and the myocardial fibers. In ostial and myocardial fibers, the myofilament bundles are invested by perforated sheets of sarcoplasmic reticulum, and these sheets interface with a network of sarcolemmal tubules to form dyadic interior couplings at the level of the sarcomeric H-bands. The contractile apparatus originates and terminates at intermediate junctions on the transverse cellular boundaries, and the lateral surfaces of the muscle fibers are linked by a modest number of communicating (gap) junctions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003600050252
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    Paper (German National Licenses)
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