Coordination of movements of the tube feet and arms of ophiurans during locomotion

The role of the tube feet in locomotion of the ophiuranAmphipholis kochii Lütken is examined. During stepping movements the anterior tube feet attach themselves to the supporting surface and at the end of the step they detach themselves from it. The signal for detachment is deviation of the foot into the posterior (relative to the direction of motion) position. Because of this arrangement of the "stepping" mechanism of the tube feet the task of coordinating their activity with arm movements is greatly simplified. The feet "automatically" attach themselves to the support when the arm which carries them plays the role of motor; conversely, they detach themselves from the support when this arm moves forward. The CNS thus evidently does not participate in foot and arm movement coordination. It simply assigns the general direction of motion to all the feet and coordination takes place "automatically" as a result of the special properties of the "stepping" mechanism of individual feet.Institute of Oceanology, Academy of Sciences of the USSR, Moscow. Institute of Problems of Information Transmission, Academy of Sciences of the USSR, Moscow. Moscow State University. Translated from Neirofiziologiya, Vol. 8, No. 6, pp. 633–639, November–December, 1976.     

Coordination of arm movement during locomotion in ophiurans

During movement of the ophiuranAmphipholis kochii Lutken, any one of its arms can point forward and, consequently, any arm can perform different functions. The arm, when separated from the ophiuran together with the adjacent part of the nerve ring, is capable of complex motor acts, including locomotion. Division of the nerve ring in the ophiuran disturbs coordination of the arms. The results of experiments in which one or more arms were amputated showed that the choice of leading arm and of method of locomotion depends mainly on afferent impulses received from the arms. The results indicate that the neural centers of individual arms possess relative autonomy. Coordinated working of the centers is achieved through their interaction. This interaction ensures the distribution of functions between the arms in accordance with the motor task to be undertaken and coordinates the activity of the arms in time. The dominant role in the distribution of functions between the arms is played by the center of the leading arm, which controls the activity of at least the adjacent centers.Institute of Oceanology, Academy of Sciences of the USSR, Moscow. Institute of Problems in Information Transmission, Academy of Sciences of the USSR, Moscow. Moscow State University. Translated from Neriofiziologiya, Vol. 8, No. 5, pp. 529–537, September–October, 1976.     

Activity of propriospinal neurons in segments C3 and C4 during fictitious locomotion in cats

Activity of propriospinal neurons in segments C3 and C4 was recorded in immobilized decerebrate cats, whose spinal cord was divided at the lower thoracic level, during locomotor activity of neuronal mechanisms controlling the forelimbs (fictitious locomotion of the forelimbs). Neurons were identified according to antidromic responses to stimulation of the lateral column of the spinal cord at level C6. Antidromic responses also appeared in 70% of these neurons to stimulation of the medullary lateral reticular nucleus. During fictitious locomotion, i.e., in the absence of afferent signals from the limb receptors, rhythmic modulation of the discharge of most neurons was observed, correlating with activity of motoneurons. If the rostral region of the cervical enlargement of the spinal cord was cooled, causing generation of the locomotor rhythm to cease, rhythmic activity of propriospinal neurons in segments C3 and C4 also ceased. The main source of modulation of activity of propriospinal neurons in segments C3 and C4 is thus the central spinal mechanisms controlling activity of the forelimbs.Institute for Problems in Information Transmission, Academy of Sciences of the USSR, Moscow. M. V. Lomonosov Moscow University. Translated from Neirofiziologiya, Vol. 17, No. 3, pp. 320–326, May–June, 1985.     

Regeneration of pedal ganglion neurons in the sea butterfly Clione limacina

In the pedal ganglia ofClione limacina the growth of neurites is traced in motoneurons after transection of the wing nerve and in interneurons after transection of the pedal commissure. Neurons were stained intracellularly with Lucifer yellow. In the motoneurons the neurites growing from the transected end of the axon and from the neuron soma spread to all nerve trunks departing from the ipsi- and contralateral ganglia. For nerve transection in the intact mollusk, wing movements were restored 10 days after the operation. In the interneurons the growing neurites branched within the pedal ganglion or spread to the cerebral ganglia, but they never reached the periphery.Institute of Problems of Information Transmission, Academy of Sciences of the USSR, Moscow. M. V. Lomonosov State University, Moscow. Translated from Neirofiziologiya, Vol. 17, No. 4, pp. 449–455, July–August, 1985.     

Electrophysiological study of serotoninergic neuron Cl in the pteropod mollusk Clione

Functional characteristics of cerebral serotoninergic neuron Cl, axons of which terminate at the buccal ganglia [7], were investigated in the pteropod molluskClione. Stimulating neuron Cl induced activation of the feeding rhythm generator located in the buccal ganglia — an effect arising after a long latency and persisting for some tens of seconds once stimulation had ended. Neuron Cl receives feedback from buccal ganglion cells and this brings about periodic modulation in ganglia activity during the generation of feeding rhythm. Activity of neuron Cl is correlated with operation of the locomotor rhythm generator located in the pedal ganglia. The firing rate of Cl neurons increased upon activation of the locomotor generator (whether spontaneous or induced by stimulating certain command neurons). The correlation found between workings of the locomotor generator and activity of Cl neurons is thought to be one of the manifestations of feeding synergy involving simultaneous activation of the locomotor and buccal apparatus.Institute for Research on Information Transmission, Academy of Sciences of the USSR, Moscow. M. V. Lomonosov State University, Moscow. Translated from Neirofiziologiya, Vol. 23, No. 1, pp. 18–25, January–February, 1991.     

Activity of propriospinal neurons during the scratch reflex in cats

Fictitious scratching, i.e., rhythmic activity of hind-limb motoneurons at the characteristic scratching frequency, was evoked by tactile stimulation of the ear in thalamic cats immobilized with flaxedil. Activity of propriospinal neurons in segments C₁, C₂, and T₄–T₇ was recorded extracellularly. The neurons were identified by their antidromic response to stimulation of their axons in segment L₁. Most neurons did not respond to stimulation of the ear. Some neurons, however, were activated during fictitious scratching. Neurons of the cervical segments responded not only to stimulation of the ear, but also to tactile stimulation of the forelimbs and also to passive movements of those limbs. Neurons of the thoracic segments were activated only by stimulation of the ipsilateral ear; these neurons were inhibited by stimulation of the contralateral ear. The role of the propriospinal neurons in the activation of the spinal mechanisms of scratching is discussed.Institute for Problems of Information Transmission, Academy of Sciences of the USSR, Moscow. M. V. Lomonosov Moscow State University. Translated from Neirofiziologiya, Vol. 9, No. 5, pp. 504–511, September–October, 1977.     

Vestibular responses of neurons of the descending tracts during locomotion

Responses of vestibulo-, reticulo-, and rubro-spinal neurons to tilting decerebrate cats in the frontal plane were investigated. Tilting was carried out both at rest and during induced locomotion (walking and running on a treadmill). During locomotion the vestibular responses were greatly reduced or they disappeared completely.M. V. Lomonosov Moscow State University. Translated from Neirofiziologiya, Vol. 4, No. 3, pp. 311–316, May–June, 1972.     

State of the NPY-ergic System of the Hypothalamic Arcuate Nucleus in Rats with Experimentally Induced Diabetes Mellitus

We have carried out a quantitative study of the state of a neuropeptide Y (NPY)-ergic system of the hypothalamic arcuate nucleus (AN) in rats in the norm and in streptozotocin (STZ)-induced diabetes mellitus. The NPY-containing objects were identified using an indirect immunofluorescent technique; a system of digital analysis of images and a special software were used. Analysis of the morphometric parameters of the NPY-immunopositive objects within the AN sections allowed us to classify in an automatic mode such objects as neurons of various sizes, fibers, and terminals, as well as to count the number of objects of each class. In addition, the fluorescent intensity of the objects under study (directly proportional to the concentration and amounts of NPY in these objects) was determined. On the basis of these parameters, criteria of the state of synthesis and secretion of NPY and NPY-ergic innervation in the AN subnuclei were proposed. In control animals, the greatest number of NPY-immunopositive neurons and total content of NPY in the neurons and terminals were observed in the ventrolateral and dorsomedial subnuclei of the AN (vl- and dmAN, respectively); this fact points to the high intensities of NPY synthesis and secretion in these structures. The greatest content of NPY in the nerve terminals within the vlAN zone is indicative of the highest intensity of NPY-ergic afferent influences on this subnucleus. It is concluded that the approach we proposed is adequate enough for integral quantitative estimation of the state of peptidergic systems. The development of STZ-induced diabetes mellitus caused changes in the NPY-ergic system in different AN subnuclei; such changes demonstrated certain specificity. In particular, an increase in the number of immunopositive neurons and the total content of NPY in the neurons of vlAN and the ventromedial AN subnucleus (vmAN), which is evidence in favor of intensification of synthesis of the neuropeptide, was not accompanied by an adequate rise in the NPY content in the terminals located in the subnucleus under study. The content of NPY in the eminentia medianus also decreased. The above data allow us to hypothesize that the NPY-ergic system of the AN under conditions of diabetes mellitus is functionally insufficient.     

Neural control of heartbeat in the pteropod mollusk Clione limacina

The heart of the pteropod molluskClione limacina is innervated by the median nerve arising from the left abdominal ganglion. Five neurons sending axons to the heart have been identified in theClione central nervous system with retrograde cobalt or Lucifer yellow staining. Neuron H1 located in the left pedal ganglion produced an excitatory effect on heart beat. Stimulation of three neurons, H2–H4, situated in a compact group in the medial region of the left abdominal ganglion, led to inhibition of cardiac contraction, while H5, located in the caudal region of the left abdominal ganglion, did not affect heart beat. The activity of efferent cardiac neurons (ECN) was found to be related to the operation of the locomotor rhythm generator. Spontaneous or reflex depression of the latter was found to inhibit neuron H1 and activate units H2–H4. The behavior of these ECN accounts for the positive correlation between heart operation and locomotor activity inClione limacina.Institute of Research on Information Transmission, Academy of Sciences of the USSR, Moscow, M. V. Lomonosov State University, Moscow. Translated from Neirofiziologiya, Vol. 21, No. 2, pp. 185–192, March–April, 1989.