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  • 1
    Electronic Resource
    Electronic Resource
    Functional subdivision within a lobster motor unit (1982)
    Springer
    Cellular and molecular life sciences 38 (1982), S. 362-363 
    Details
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A discrete middle band of tonic fibers in the claw closer muscles of lobsters functions as a sub-unit of the slow motor unit in maintaining dactyl posture at a low frequency of firing due to its synaptic properties and strategic location.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01949394
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  • 2
    Electronic Resource
    Electronic Resource
    Innervation and neuromuscular physiology of intrinsic foregut muscles in the blue crab and spiny lobster (1975)
    Springer
    Journal of comparative physiology 96 (1975), S. 185-204 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. The innervation pattern of the intrinsic foregut musculature was determined using physiological methods in blue crabs (Callinectes) and spiny lobsters (Panulirus) (Tables 1, 2). The distributions of individual axons were observed in methylene blue stained preparations and their physiological effects were observed by recording excitatory postsynaptic potentials (EPSPs) in various muscles while stimulating the axons directly or while the stomatogastric ganglion was active (Figs. 4–8). 2. InCallinectes the gastric mill muscles were all singly motor innervated, while many of the pyloric muscles were multiply innervated with as many as 3 motor axons to a single muscle (Table 1). InPanulirus the pyloric muscles also showed multiple innervation with a maximum of 5 axons to a single muscle (Table 2). 3. EPSPs varied in shape and amplitude from one muscle to another in both species even when two or more muscles were innervated by the same axon (Fig. 4). InPanulirus variation of EPSPs along individual muscle fibers was observed, indicating non-uniform innervation. 4. InCallinectes the variation in size of the EPSP from one recording site to another was correlated with degree of facilitation and with sarcomere length. Fibers with small EPSPs generally showed more facilitation and relatively shorter sarcomere lengths than fibers with large EPSPs (Table 1). However, instances were found in which the usual correlation did not hold. 5. Also in the blue crab a correlation was found between resting sarcomere length and contractile properties with short sarcomered fibers giving faster contractions than longer sarcomered fibers, as in other crustacean muscles. 6. The complex variety of muscle fiber types and EPSP properties apparently serves to translate the bursts of impulses from the stomatogastric ganglion into the necessary stomach movements. 7. Comparison of the innervation patterns of the gastric mill and pyloric regions suggest that the innervation patterns may be related to the functional roles of these two regions. Multiple innervation of the pyloric region allows rapid depolarization of the muscles to be achieved with a comparatively low frequency of impulses in each axon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00612694
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  • 3
    Electronic Resource
    Electronic Resource
    Non-fibrillar muscles and the start and cessation of flight in the milkweed bug,Oncopeltus (1972)
    Springer
    Journal of comparative physiology 77 (1972), S. 398-417 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. The behavioural sequence at the start of flight inOncopeltus has been analysed by high speed photography (Fig. 1). The flight muscles (in particular the non-fibrillar ones) responsible for this behaviour have been identified by electrical recordings, ablation experiments and anatomical evidence. 2. The release of the wing base by the prothoracic lobe is assigned to the prothoracic dorsoventralis and mesosterni primus muscles on anatomical evidence. 3. The wing opening, consisting of unlocking and unfolding of the fore wings, is performed by a high frequency discharge of a motor neuron of the tergal promoter, remotor and tergotrochanteral muscles (Fig. 5). Non-flight wing opening is also similarly achieved (Fig. 6). 4. It is argued that the action of the leg muscles additionally triggers the oscillatory contractions of the myogenic motor by stretching the neurally activated dorsal longitudinal muscle. Thus the first half stroke in flight is a downstroke which serves to link the fore and hind wings. 5. At the start of flight the click mechanism in the wing articulation is put into operation by contraction of the tonic pleurofurcal muscle (Fig. 8) which adjusts the lateral stiffness of the thoracic box. 6. The take-off jump occurs after flight has started and is executed by a complex of trochanteral depressor muscles of the meso- and metathoracic legs (Fig. 9). 7. At the end of flight the wings are flexed and locked by the firing of a motor neuron in the episterno-alaris muscle (Fig. 10).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00694943
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  • 4
    Electronic Resource
    Electronic Resource
    Coordinated activation of muscle fibres by different conduction velocities in branches of a crustacean motor axon (1976)
    Springer
    Cellular and molecular life sciences 32 (1976), S. 1170-1171 
    Details
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Higher conduction velocities in branches of the fast excitor axon to distal muscle fibres ensure that these fibres are activated almost simultaneously with proximal fibres in the claw closer muscle of lobsters, producing a contraction of maximal force.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01927607
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  • 5
    Electronic Resource
    Electronic Resource
    Transformation of fast fibres to slow prevented by lack of activity in developing lobster muscle (1982)
    [s.l.] : Nature Publishing Group
    Nature 298 (1982), S. 755-757 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The adult lobster Homarus americanus has dimorphic claws consisting of a slender fast-acting cutter claw and a stout, slow-acting crusher claw13'14. The claw closer muscles are similarly differentiated, the cutter having a majority (60-80%) of fast fibres and the crusher having all slow ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/298755a0
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  • 6
    Electronic Resource
    Electronic Resource
    Transmitter output increases in an identifiable lobster motoneurone with growth of its muscle fibres (1978)
    [s.l.] : Nature Publishing Group
    Nature 273 (1978), S. 676-678 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The proximal accessory flexor muscle (PAFM) in the first walking leg of lobsters H. americanus was exposed together with its nerve and held at 13C. The preparation was continually superfused with lobster saline of the following composition: NaCl, 427 mM; KC1, 10 mM; CaCl2, 16 mM; MgCl2-6H2O, 7 mM; ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/273676a0
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  • 7
    Electronic Resource
    Electronic Resource
    Lengthening of lobster muscle fibres by two age-dependent mechanisms (1977)
    Springer
    Cellular and molecular life sciences 33 (1977), S. 35-36 
    Details
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Fibres of the lobster accessory flexor muscle elongate by 2 mechanisms: an increase in sarcomere length, which is restricted to their early development and by the addition of serial sarcomeres of a relatively constant size, which prevails throughout the life of the animal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01936738
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  • 8
    Electronic Resource
    Electronic Resource
    Differentiation of identifiable lobster neuromuscular synapses during development (1982)
    Springer
    Journal of neurocytology 11 (1982), S. 235-247 
    Details
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The ultrastructure of physiologically identified low and high release synapses arising from a single axon on fibres of the distal accessory flexor muscle (DAFM) in a mature lobster was examined by serial section electron microscopy. Low release neuromuscular terminals located only on the proximal fibre were characterized by large synapses (mean area 2.084 μm2), small presynaptic dense bars (mean area 0.021 μm2) and hence a low (2.3%) ratio of dense bar area to synaptic area. In contrast high output terminals located only on the distal fibre had smaller synapses (mean area 0.625 μm2), larger dense bars (mean area 0.066 μm2) and a high (23.9%) ratio of bar area to synaptic area. A similar ratio was consistently found for each synaptic type in several other examples of mature lobsters. Hence it was used as a criterion for determining the point at which differentiation occurs during development. In the first larval stage (24 h old) the innervation was localized and undifferentiated. In the fourth (2 week old) and twelfth (1 y old) stage lobsters, the innervation had proliferated to small bundles of proximal and distal fibres. During development synapses increase in their mean surface area in the proximal fibre while remaining constant in the distal fibre. The mean surface area of the dense bars is similar in all stages except for the proximal fibres of the twelfth stage where it is smaller by 50%. Similarly the ratio of dense bar area to synaptic area is not significantly different for all stages except for the twelfth stage proximal fibres where it is half the value. Consequently differentiation of low and high release neuromuscular terminals occurs by the twelfth stage with an increase in the mean surface area of synapses and a decrease in the mean surface area of dense bars. This morphological differentiation is enhanced in the mature lobster.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01258245
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  • 9
    Electronic Resource
    Electronic Resource
    Reorganization of synaptic ultrastructure at facilitated lobster neuromuscular terminals (1986)
    Springer
    Journal of neurocytology 15 (1986), S. 63-74 
    Details
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Prolonged stimulation of the single excitor axon to the lobster distal accessory flexor muscle in the presence of ouabain caused long-term facilitation at its neuromuscular synapses. Hence the extracellularly recorded synaptic potentials failed less frequently and increased their mean amplitude, compared to the non-facilitated (control) potentials from homologous sites in the contralateral muscle. The fine structure of synaptic terminals between matched pairs of facilitated and control preparations was compared with the aid of serial section electron microscopy. Differences between facilitated and control preparations were similar both when the latter were bathed in normal saline or ouabain-containing saline, suggesting that the changes were related to the electrical stimulation rather than to the presence of ouabain. First, the facilitated terminals were smaller in surface area than the control. Second, the number and size of synaptic contacts in the facilitated terminals resembled those in the control. Third, presynaptic dense bodies or active sites increased in number although their sizes remained unaltered in the facilitated terminal. This increase is attributed to the addition of dense bodies at existing synaptic contacts since synaptic contacts remained constant in number between facilitated and control preparations. Fourth, the number and size of synaptic vesicles were unaffected by prolonged stimulation although there was a redistribution of vesicles such that they appeared to be channelled in distinct streams to synaptic contacts. Fifth, mitochondria increased in number and were situated closer to the dense bodies at facilitated nerve terminals than at control terminals. Overall, these changes denote considerable reorganization of the synaptic terminals associated with elevated transmitter release.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02057905
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  • 10
    Electronic Resource
    Electronic Resource
    Structural-functional differences of a crab motoneuron to four stomach muscles (1997)
    Springer
    Journal of neurocytology 26 (1997), S. 389-398 
    Details
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A motor unit in the stomach of the blue crab, Callinectes sapidus, consists of four separate muscles involved in different aspects of the trituration and filtering of food. Motor nerve terminals to two of the muscles (CPV7a and GM5) release small amounts of transmitter (low-output) while those to the other two muscles (CV2 and CV3) release between three and five-fold greater amounts (high-output). Structural features underlying the disparity in synaptic strength were analysed with thin serial-section electron microscopy. Nerve terminals were similar in their volume percent of mitochondria, clear vesicles and dense core vesicles among the four muscles. This was also the case for the number and size of synaptic contacts. However, presynaptic dense bars representing active zones were longer and occurred more frequently at high-output synapses than at low-output ones. High-output synapses were also characterized by the close spacing of adjacent dense bars. The longer and more closely spaced dense bars at high-output synapses would be factors in the generation of larger synaptic potentials in these terminals compared to their low-output counterparts. Other factors, however, need to be considered to fully account for the physiological differences in synaptic strength among the four muscles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018517021008
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