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  • 1
    Electronic Resource
    Electronic Resource
    Central control of cardiac and scaphognathite pacemakers in the crab,Cancer magister (1974)
    Springer
    Journal of comparative physiology 90 (1974), S. 89-104 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Command fibers located in the circumesophageal connectives which modify scaphognathite and heart rhythms have been mapped and characterized in the crab,Cancer magister. Behavior: Crabs show a variety of responses to external stimuli often including simultaneous cessation of cardiac and scaphognathite “pumping”. Habituation and a return to prestimulus rhythms results from continued stimulation. The response to short stimulus durations, on the other hand, generally outlasts the stimulus indicating the playing-out of a motor program. Neurophysiology: Small bundles of fibers have been isolated from desheathed connectives. Activity in these fibers resulting from stimulation of various anterior sensory receptors was recordeden passant with suction electrodes. When sensory stimulation produced both electrical activity in the nerves under examination and a cardiac and/or scaphognathite response it was assumed such units were involved in inducing this response. This was tested by electrical stimulation delivered through the same electrode. Those units which produced similar responses to natural and artificial stimulation were deemed “command fibers”. It was invariably found that the minimum stimulating frequency needed to mimic naturally induced responses was much greater than the frequency at which the units discharged in response to those stimuli. During mapping experiments, command fibers were characterized with respect to their positions in the connectives and by the responses they produced at different frequencies of stimulation. 68% of the fibers identified affected both cardiac and scaphognathite systems, 29% the scaphognathites alone and 3% the heart alone. The frequency-response profiles of single bivalent command fibers were often different from the heart and scaphognathites. These findings help explain the responses of both systems to natural stimuli and also indicate that the circulatory and respiratory systems not only perform in concert, but are often under common control.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00698370
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  • 2
    Electronic Resource
    Electronic Resource
    Neuronal activity in neurosecretory cells of the fleshfly,Sarcophaga bullata (1976)
    Springer
    Journal of comparative physiology 112 (1976), S. 109-122 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Microelectrode recording and computer-based analytical techniques were used to investigate the activity patterns of neurosecretory cells (NSC) in the insect protocerebral neurosecretory system. 1. Although the spike activity of NSC could change with time, three basic type of activity patterns were found, designated silent, regular and irregular. These patterns were detected both centrally and at the release site, the corpus cardiacum. 2. Combining extracellular recording with manipulation of Mg2+ in the neurons' environment, it was established that the NSC activity patterns represent the summed effects of: endogenously-generated activity, synaptic inputs from the central nervous system, and connections between the NSC themselves. 3. Computer-based analytical techniques were used to determine the sources of synaptic input to the NSC. Optic, ocellar, antennal and thoracicoabdominal pathways were found to contribute inputs to NSC.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00612679
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  • 3
    Electronic Resource
    Electronic Resource
    Pharmacological dissection of a neural pattern generator (1980)
    Springer
    Journal of comparative physiology 139 (1980), S. 1-10 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Injection of picrotoxin solutions into the pericardium of lobsters,Homarus americanus, to produce final, estimated blood concentrations of between 8×10−8M and 4.5×10−6M led to disruption of the normal motor output to the scaphognathite. The phase separation of the starts of the bursts in the D1 and D2 muscles (Young, 1975) was reduced on the average by 49%; that of L1 and L2 muscles by 16%. The durations of the D1 and L1 bursts increased by 94% and 48% respectively. The phase separation between the starts of the levator and depressor portions of the cycle was not altered. Whilst rhythmic activity persisted ventilatory rates were depressed, and reversals and ventilatory pauses continued to occur. The rate of reversals and their pattern were not greatly altered. Inexplicably, tonic, synchronous spikes occurred in all four groups of muscles, levator and depressor, during periods of severe disruption. It was concluded that in spite of this, the observations supported the proposals of Young (1975) that (a) recruitment of the D2 and L2 bursts normally is delayed partly by inhibition from D1 and L1 units respectively, and (b) termination of D1 and L1 bursts results normally from inhibition due to activity in D2 and L2 units respectively. The findings also indicated that the synaptic mechanism determining timing within the depressor and levator sessions differs fundamentally from that operating between sessions. One mechanism may be based on picrotoxin-sensitive, and the other on picrotoxin-insensitive inhibition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00666189
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of scaphognathite nerve stimulation on the acutely deafferented crab ventilatory central pattern generator (1994)
    Springer
    Journal of comparative physiology 174 (1994), S. 195-209 
    Details
    ISSN: 1432-1351
    Keywords: Central pattern generator ; Afferent feedback ; Crustacea ; Acute deafferentation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract 1. Sensory axons from crab (Carcinus maenas) scaphognathites enter the thoracic ganglion primarily via the LNb branch of the levator nerve. The LNa branch of the levator nerve and the depressor nerve each contain relatively few sensory axons. 2. Acutely deafferented ventilatory central pattern generators show a free running burst rate which is lower than that observed in intact crabs. Electrical stimulation of the levator nerve, or of its LNb branch, increases the burst rate in a frequency dependent manner. Stimulation at high enough intensity to recruit afferents will restart a paused motor rhythm. Stimulation of the levator nerve with short pulse trains phase resets and can entrain the rhythm. 3. In addition to increasing the burst rate, LNb stimulation also causes a progressive elimination of motor neurons from the bursts as the stimulating frequency increases, probably due to depolarization of the 3 oval organ ‘giant’ afferent axons in this branch. Intracellular depolarization of single oval organ afferents will also inhibit some motor neurons as well as slow or stop the rhythm. 4. Continuous stimulation of the depressor nerve does not affect the ganglionic burst rate and this nerve contains only a few small diameter afferent axons; however, brief trains of stimuli can reset the rhythm in a phase-dependent manner.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00193786
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  • 5
    Electronic Resource
    Electronic Resource
    Degeneration of afferent neurons and long-term stability of the ventilatory central pattern generator in chronically deafferented crabs (1994)
    Springer
    Journal of comparative physiology 174 (1994), S. 211-220 
    Details
    ISSN: 1432-1351
    Keywords: Central pattern generator ; Chronic deafferentation ; Crustacean ; Ventilation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract 1. The effects of chronic deafferentation, 3–180 days, are tested on the function and morphology of the crab (Carcinus maenas) ventilatory central pattern generator (CPGv). Almost all afferent axons are carried in the mixed sensory/motor levator nerve. The ability to speed the CPGv cycle rate by stimulating this nerve (Wilkens and DiCaprio 1994) decreases as the afferent neurons degenerate. Stimulation of the levator nerve eliminates motor units from the output even after 60 days of deafferentation, similar to the effects seen in acute preparations. 2. The 3 oval organ afferent axons of the levator nerve have central somata and survive scaphognathectomy. Impulses carried by these axons are known to inhibit the CPGv in acutely deafferented preparations and they are believed to be responsible for the persistent inhibition following small afferent degeneration seen here. 3. After 6 months of deafferentation the motor neuron collateral arborization densities within the thoracic ganglia are reduced, but all motor neurons appear to survive. These long-term deafferented CPGvs generate accurate motor patterns at similar rates to the control CPGv, but at reduced intraburst spike frequency. The crab CPGv is quite stable following chronic deafferentation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00193787
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  • 6
    Electronic Resource
    Electronic Resource
    Cardiac and circulatory control in decapod Crustacea with comparisons to molluscs (1987)
    Springer
    Cellular and molecular life sciences 43 (1987), S. 990-994 
    Details
    ISSN: 1420-9071
    Keywords: Decapod Crustacea ; cardiac control ; cardiac output
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In this review I will attempt to identify the circulatory requirements a decapod is likely to encounter and how the heart is controlled to meet these demands. The decapod heart has been designed as an autonomous system endowed with an intrinsic autorhythmic pacemaker ganglion. Muscle fibers are multiply-innervated and capable of producing regenerative action potentials. This vitally important organ has been designed to be nearly fail-safe. Stroke volume is more important than heart rate in determining cardiac output. Stretch sensitivity of the cardiac ganglion and of the myocardium as well as extrinsic nervous and hormonal modulation of the heart can all contribute to changes in stroke volume. It may be advantageous to an animal to switch the circulation between various vascular beds to meet changing perfusion demands. Neuronal and hormonal mechanisms have been identified which exert differential control of the cardioarterial valves, but it is not known whether switching does occur and if so whether these valves participate in the process. Changes in peripheral resistance can also redirect circulatory flow. The circulatory and ventilatory systems demonstrate coordinated rate changes which suggest that the heart is responding to meet changing ventilatory performance requirements. This coupling is controlled both by the hydrostatic pressure pulses generated within the branchial chambers and by common higher level nervous inputs. Comparisons of the cardiovascular systems of crustaceans and molluscs, based on the papers presented at this symposium, are high-lighted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01952215
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  • 7
    Electronic Resource
    Electronic Resource
    Intrinsic properties and extrinsic neurohormonal control of crab cardiac hemodynamics (1992)
    Springer
    Cellular and molecular life sciences 48 (1992), S. 827-834 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02118415
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  • 8
    Electronic Resource
    Electronic Resource
    The principal toxin ofDelphinium brownii Rydb., and its mode of action (1979)
    Springer
    Cellular and molecular life sciences 35 (1979), S. 1367-1368 
    Details
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Examination ofD. brownii, a stock-poison of Western Canada, revealed that the principal toxin was methyllycaconitine: a potent neuromuscular blocking agent which appears to act competitively at nicotinic receptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01964013
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  • 9
    Electronic Resource
    Electronic Resource
    Neuronal properties of the neurosecretory cells in the flySarcophaga bullata (1970)
    Springer
    Cellular and molecular life sciences 26 (1970), S. 275-276 
    Details
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Zusammenfassung Endogene Erregungspotentiale wurden von den Perikarya der protozerebralen, neurosekretorischen Zellen der FleischfliegeSarcophaga bullata abgeleitet. Diese Potentiale scheinen nur teilweise in die Perikarya einzudringen. Erregungshemmende postsynaptische Potentiale wurden ebenfalls festgestellt. Sie scheinen ihren Ursprung nahe der Somata zu haben. Potentiale wurden selten von den geschwollenen Endungen der neurosekretorischen Neuriten des Corpus Cardiacum abgeleitet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01900092
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  • 10
    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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