The structure and function of the labrum in the lobster Homarus gammarus (L.).

The labrum of decapod crustaceans is a soft lobe overhanging the mouth. The labral skeleton, musculature and innervation of Homarus gammarus are described. There are three bilateral groups of sensory neurons innervating the floor, lobe and lateral walls of the labrum. These are probably responsible for the phasic afferent activity that can be recorded from the inner labral nerve on mechanical deformation of the labrum. The labrum undergoes rhythmical retraction-protraction movements during ingestion and is shown to be active during both mandibular activity and oesophageal peristalsis. Studies were made on the duration and frequency of labral "swallowing" activity. The role of the labrum in feeding is discussed.     

The anatomy and physiology of the stomatogastric nervous system ofSquilla

Summary The stomatogastric nervous system of a mantis shrimp,Squilla oratoria, is described. The motor nerves of the stomatogastric ganglion (STG) and their innervation of muscles of the posterior cardiac plate (pcp) and pyloric systems are detailed.The STG contains more than 25 neurons. It sends out one pair of major output nerves. The pcp-pyloric cycle recorded from the motor axons in this nerve consists of rhythmic bursts of several units which fire with a characteristic phase relationship to each other. The rhythm is intrinsic to the STG itself, but it is modifiable.Recordings from the peripheral nerves reveal that identifiable cardiac plate, pyloric dilator and pyloric neurons control sequential contractions of the pcp and pyloric muscles to constrict or dilate a number of their attached ossicles.Several modulatory input fibres in the stomatogastric nerve, activated via stimulation of the superior or inferior oesophageal nerve (son, ion), prime or trigger the cyclic motor outputs. The son inputs induce distinct effects on the cardiac and pcp-pyloric pattern generators, while the ion inputs, via the oesophageal ganglion, excite only the pcp-pyloric generator.On the basis of anatomical and physiological observations, the possible functions of motor neurons involved in the pcp-pyloric cycle are described with reference to opening of the pcp and pyloric channels.This stomatogastric nervous system inSquilla is compared to that in decapods which has been well analyzed.Abbreviations CG commissural ganglion - ion inferior oesophageal nerve - lvn lateral ventricular nerve - OG oesophageal ganglion - pep posterior cardiac plate - son superior oesophageal nerve - STG stomatogastric ganglion - stn stomatogastric nerve - ivn inferior ventricular nerve     

MUSCLE TENSION AND REFLEXES IN THE EARTHWORM

1. By the use of preparations of earthworm in which the cutaneous receptors have been anesthetized with a solution of M/8 MgCl₂, it is shown that peristalsis can be initiated by tension alone. 2. The receptors of the tension reflex are the intermyal sensory cells of the ventral region of the body wall. 3. It is concluded that Straub obtained the tension reflex because his preparations contained the intermyal receptors; Budington was unable to observe the tension reflex in any preparation from which the intermyal receptors had been removed. 4. Intermyal receptors are the receptors of the following reaction: Passive unilateral tension of the posterior part of an earthworm induces active homolateral tension of the musculature of the anterior segments, and results in the course of progress being brought into line with the enforced orientation of the tail. This reaction is termed the homostrophic reflex. 5. The receptors for the reaction are distributed throughout the entire length of the worm, the effectors are limited to the anterior 15 to 20 segments. The impulse is conducted by the ventral nerve cord. 6. The interaction of the homostrophic reflex and tropisms is considered.     

Immunocytochemistry of the nervous system and the musculature of the chordoid larva of Symbion pandora (Cycliophora)

To date, the phylum Cycliophora comprises only one described extant species of acoelomate marine invertebrates, Symbion pandora. Adult specimens live commensally on the mouthparts of the Norwegian lobster, Nephrops norvegicus. Its complicated life cycle includes an asexually produced Pandora larva and a sexually produced chordoid larva. Despite detailed TEM investigations and its inclusion in recent molecular phylogenetic analyses, cycliophoran relationships still remain enigmatic. In order to increase the morphological database, I investigated the anatomy of the nervous system and the musculature of the chordoid larva by applying fluorescence-coupled antibodies against the neurotransmitters serotonin and FMRFamide, as well as FITC-coupled phalloidin to label filamentous F-actin, in combination with confocal laser scanning microscopy. The FMRFamidergic nervous system shows a bilobed anterior ganglion and one pair of ventral nerve cords, while serotonin is distributed in a scattered pattern in the anterior ganglion. In addition, there are two pairs of ventral serotonergic nerves, of which the inner pair fuses with the outer nerve cords in the posterior third of the larva. The musculature comprises an outer layer of six units of circular body wall muscles, several helicoid muscle fibers, a set of paired longitudinal muscles that span the entire anterior-posterior axis of the larva, and a few oblique muscle strands. Furthermore, an anterior muscle complex and one pair of posterior muscles are present. The chordoid organ consists of a number of distinct subunits that are each formed by a dense layer of circular muscle fibers.The overall arrangement of the oblique and longitudinal muscles as well as the body wall musculature in the chordoid larva of Symbion pandora exhibits similarities with the condition found in certain rotifers. This is congruent with some recent phylogenies based on 18S rRNA sequences but additional morphological, developmental, and molecular data are needed to clarify the phylogenetic relationships of Cycliophora.     

大鼠脊髓诱发电位与脊髓损伤的关系——Ⅲ.脊髓局部损毁后电位的变化及电位来源分析

本文描述了大鼠脊髓L_1节段后柱、后索、侧索和前角的诱发电位及其损伤后的变化,并观察了切断L_4、L_5脊神经背、腹根与横断高位颈髓对电位的影响,以进行行电位来源分析。结果可见,上述四个区域的诱发电位基本由早反应三相波和晚反应组成。分别电解损毁这些部位后,电位波幅均普遍降低,晚期反应较早反应降低明显。后柱或后索受损对电位影响最大。局部损毁后可见L_1及T_(13)水平的硬膜上电位改变明显,尤其晚反应减弱、波峰平坦。反应时值与潜伏时未见明显改变。切断L_4脊神经背、腹根后、电位基本消失。去大脑对电位未见明显影响。结果表明,刺激坐骨神经诱发的脊髓电位起源于低位腰段传入神经和脊髓内多通路的兴奋传导,在一定程度上受腹根逆行活动的影响,与大脑及脊髓下行传导束活动无直接联系。脊髓诱发电位的幅度与波形改变可作为脊髓损伤的判断指标之一。     

Electrical stimulation of glossopharyngeal nerve and oesophageal EMG response in the pigeon

The effects of the efferent glossopharyngeal nerve stimulation, on EMG activity of the pigeon cervical oesophagus, were studied. In control animals, stimulation caused a biphasic response characterized by an intra-stimulus excitatory component followed by a post-stimulus inhibitory one. The EMG response to glossopharyngeal stimulation appeared simultaneously throughout the cervical oesophagus. A bell-shaped mechanical wave was detected relating to the electrical excitatory component. Atropine administration antagonized the excitatory component, while the inhibitory one persisted. It occurs intra-stimulus, and its duration is increased, compared to control ones. A reduction in the oesophageal resting pressure was observed relating to the electrical inhibitory component. Hexamethonium caused complete disappearance of any EMG response to glossopharyngeal stimulation, as well as suppression of mechanical responses. The comparison between the EMG responses to swallow and to efferent glossopharyngeal stimulation suggests that in pigeon cervical oesophagus: primary peristalsis is central in origin; a dual system of glossopharyngeal fibres, excitatory and inhibitory, carries the central control for oesophageal motility; these excitatory and inhibitory fibres supply the oesophageal muscle via intramural neurons; the synaptic arrangement of the inhibitory pathway is more complex than the excitatory one.     

Characteristics of esophageal antiperistaltic activity in sheep

Oesophageal motility was investigated in standing conscious sheep. A manometric method was used in four animals; two sheep, fitted with permanent electrodes at four levels, were used for oesophageal electromyography. The occurrence of retrograde peristalsis (mean speed 71,5 cm.s-1) at the beginning of every rumination cycle is reasserted. The characteristics of this activity are pointed out, with reference to normal peristalsis during the deglutition of saliva. Different types of stimulation have been compared. Retrograde peristalsis (mean speed 66 cm.s-1) can be triggered readily in non-ruminating animals by the association of two stimulations. One being oesophageal distension and the other injection of a solution prepared with some physical or chemical components of the rumen liquid. No specialized sensitive area could be demonstrated. However, facilitation is evident during reticular contractions. Retrograde waves of contraction always start from the terminal part of the thoracic oesophagus, whatever the level of stimulation.     

Behavioral and synaptic defects in C. elegans lacking the NK-2 homeobox gene ceh-28

C. elegans pharyngeal behavior consists of two distinct types of muscle contractions, termed pumping and peristalsis. Pumping ingests and concentrates bacteria in the anterior pharyngeal lumen, and it is occasionally followed by a transient peristaltic contraction that carries ingested bacteria through the posterior pharyngeal isthmus. These behaviors are controlled by a small pharyngeal nervous system consisting of 20 neurons that is almost completely independent of the extra-pharyngeal nervous system. The cholinergic motor neuron M4 controls peristalsis via synapses with the posterior isthmus muscles. Here we show that the NK-2 family homeobox gene ceh-28 is expressed in M4, where it regulates synapse assembly and peristalsis. ceh-28 mutants exhibit frequent and prolonged peristalses, and treatment with agonists or antagonists of muscarinic acetylcholine receptors can phenocopy or suppress ceh-28 mutant defects, respectively. Synapses in ceh-28 mutant M4 cells are irregularly spaced and sized, and they are abnormally located along the full length of the isthmus. We suggest that CEH-28 inhibits synaptogenesis, and that ceh-28 mutant behavioral defects result from excessive or ectopic stimulation of muscarinic acetylcholine receptors in the isthmus muscles.     

THE REACTION OF NEREIS VIRENS TO UNILATERAL TENSION OF ITS MUSCULATURE

1. The anterior segments of Nereis are oriented reflexly by passive unilateral tension of the posterior musculature. 2. The afferent impulses of the homostrophic reflex rise from any part of the worm and are conducted forward by way of the ventral nerve cord. 3. The efferent impulses flow out from the brain and anterior two or three ventral ganglia. 4. The homostrophic reflex may be partially or wholly masked by stereotropism.     

Glossopharyngeal evoked potentials in normal subjects following mechanical stimulation of the anterior faucial pillar

The anterior faucial pillar, which is innervated by the glossopharyngeal nerve, is thought to be important in eliciting the pharyngeal swallow in awake humans. Glossopharyngeal evoked potentials (GPEP), elicited by mechanically stimulating this structure, were recorded from 30 normal adults using standard averaging techniques and a recording montage of 16 scalp electrodes. Ten of the subjects experienced a desire to swallow in response to stimulation. Repeatable responses were recorded from all 30 subjects. The GPEPs recorded from the posterior scalp were W-shaped and consisted of P1, N1, P2, N2 and P3 peaks. Mean latencies of P1, N1 and P2 were 11, 16 and 22 msec, respectively, for both left and right pillar stimulation. In contrast, latencies of N2 and P3 varied significantly between left and right pillar stimulation. Mean latencies of N2 and P3 were 27 and 34 msec for left, and 29 and 35 msec for right pillar stimulation. Topographical maps acquired at peak latencies for P1, N1 and P2 revealed consistent asymmetrical voltage distributions between the two hemispheres; the largest responses were recorded from the hemisphere ipsilateral to the side of stimulation. The scalp topography of N2 and P3 varied between male and female subjects as well as between left and right pillar stimulation. These findings support the hypothesis that mechanical stimulation to the anterior faucial pillar alone can elicit repeatable responses from the central nervous system. The integration of this subcortical/cortical activity with that of the medullary swallowing center may play an important role in eliciting the pharyngeal swallow.     

Use of a triaxial magnetometer for respiratory measurements

We describe a triaxial magnetometer (Tri-mag) system, which consists of a transmitter, four sensors, a processing unit, and a personal computer (PC). The Tri-mag processing unit outputs the position of each sensor relative to the transmitter in three orthogonal coordinates, and this information is communicated to the PC. First, we demonstrated that within a defined octant of a sphere in which the center is the transmitter, we can measure radial distances with an accuracy of +/- 1 mm over a range extending from 10 to 70 cm from the transmitter. Second, we recorded the three-dimensional movement of sensors on the anterior and posterior surfaces of the chest wall during maximum voluntary ventilation in four normal men; all sensors were placed in the midsagittal plane of the body. Anterior sensors were located on the sternum at the level of the third intercostal space and at 2 cm above the umbilicus, whereas posterior sensors were located on the posterior spine at the same vertical levels as the anterior sensors. In all subjects the following was found. 1) Both anterior sensors moved anterior and cephalad during inspiration. The anterior thoracic sensor showed greater vertical than anteroposterior (A-P) movement, whereas the anterior abdominal sensor showed greater A-P than vertical movement. 2) Inspiration was associated with spinal extension, whereas expiration was associated with spinal flexion. Third, we used Tri-mag information to 1) measure tidal volume (VT) over a range extending from 500 ml to inspiratory capacity and 2) measure the change in end-expiratory lung volume (EELV) over a range extending from FRC to FRC plus a minimum of 1.5 liters. Our results indicate that greater than 96% of the changes in VT and greater than 82% of the changes in EELV can be accounted for by changes in A-P, vertical, and lateral dimensions of the chest wall.     

The stomatogastric nervous system of the house cricket Acheta domesticus L. I. The anatomy of the system and the innervation of the gut

The distribution of the ganglia and nerves of the stomatogastric nervous system and the innervation of the extrinsic and intrinsic muscles are described. Median unpaired frontal and hypocerebral ganglia and paired ingluvial ganglia are present. The anterior pharynx is innervated by branches of the frontal nerve and by the anterior and posterior pharyngeal nerves, originating from the frontal ganglion. The posterior pharyngeal nerves are linked to nerves innervating the posterior part of the pharynx which have their origin in the hypocerebral ganglion, the anterior portion of which has previously been regarded as part of the recurrent nerve. Paired esophageal nerves run the length of the esophagus and crop between the hypocerebral and and ingluvial ganglia, innervating the muscularis by serial side branches. From each ingluvial ganglion runs an ingluvial nerve which innervates the gizzard and a cecal nerve which innervates the midgut and its ceca. At the posterior end of the midgut there is a poorly developed nerve ring. Nerves running posteriorly from this nerve ring link the stomatogastric nervous system with the proctodeal innervation from the terminal abdominal ganglion. Multipolar peripheral neurons are present on the muscularis of the whole of the foregut, rather randomly distributed on the crop and gizzard but forming fairly definite groupings at some points on the pharynx. Though of varied appearance, these cells could not be divided into discrete morphological categories. Peripheral neurons on the midgut are of different and characteristic morphology, though a few cells of the same appearance as those of the foregut occur at the midgut-hindgut boundary. Nerve fibers on the gut almost invariably terminate on the fibers of the muscularis.     

Epidural recordings of electrical events produced in the spinal cord by segmental, ascending and descending volleys

Epidural electrodes implanted for a percutaneous trial of therapeutic spinal cord stimulation were used to record electrical events evoked by the stimulation of peripheral nerves or of the spinal cord itself. The data collected in patients with no neurological deficit were analyzed in order (1) to check the consistency between epidural and surface recordings, (2) to get information on the genesis of such potentials, and (3) to demonstrate the feasibility of complex neurophysiological studies by means of epidural electrodes. Spinal cord potentials evoked by segmental volleys were recorded at cervical levels with the recording electrodes anterior, lateral and posterior to the spinal cord. The refractory period of the evoked potentials has been studied as well. Responses to stimulation of the tibial nerve were obtained at T11-12 vertebral level with posterior epidural electrodes. Segmental cervical potentials were characterized by a P10, N11, N13/P13 followed by a slow positivity/negativity. A response of similar waveform, but with different peak latencies, was recorded at segmental levels following tibial nerve stimulation. Such a response showed an increasing number of spikes while ascending along the spinal cord. Maximum conduction velocities in the cord were between 65 and 85 m/s. Our epidural recordings are similar to those obtained from the skin, but with a greater amplitude and waveform resolution. Furthermore, the use of epidural electrodes made it feasible to perform complex examinations of sensory function (i.e., the study of orthodromic and antidromic conduction along the dorsal cord and of the influence of a single dorsal cord volley on the segmental cervical potential). Finally, the genesis of the potentials recorded is discussed.     

Ciliary and nervous structures in juvenile females of the annelid Dinophilus gyrociliatus (O. Schmidt, 1848) (Annelida: Polychaeta)

Ciliary and nerve structures were described in juvenile female Dinophilus gyrociliatus (O. Schmidt, 1848) after immunochemical staining with tubulin, serotonin, and FMRFamide antibodies. Anti-tubulin antibodies revealed the following external structures: two head and seven body ciliary bands, a ventral ciliary band, and head ciliary fields. Gut cilia and five pairs of protonephridia were detected inside the body. The nervous system consists of an oval headed neuropile with anterior and posterior nerves extending from it, seven longitudinal nerve cords, commissures, and circular nerves. Anti-serotonin antibodies revealed the head neuropile, neurons at the base of the ventral ciliary band, an oesophageal ring, and seven longitudinal ventral cords. Anti-FMRFamide antibodies revealed approximately ten neurons in the cerebral ganglion, five longitudinal cords, and the oesophageal and caudal-nerve rings. The presented data suggest the simplification of the nervous system structure in D. gyrociliatus, which probably reflects pedomorphosis.     

Mandibular movements and their control inHomarus gammarus

Summary The skeletal morphology, musculature and innervation of the mandible of the common lobster,Homarus gammarus, are described as a basis for the functional study included in the two subsequent papers.Although the mandible articulation takes the form of a hinge with movement in a single plane, the musculature of the mandible is complex. The main muscles are similar to those ofAstacus (Schmidt, 1915) but some smaller, previously undescribed muscles were found.As forAstacus (Keim, 1915) andCambarus (Chaudonneret, 1956) the mandibular muscles are innervated by two nerve trunks, the inner and outer mandibular nerves. However, differences occur in the branching of these nerves and the muscles which they innervate.A group of sensory cells associated with the posterior stomach nerve (omn 4) are described. It is suggested that these form a proprioceptive organ associated with the hypodermis overlying the lateral mandible articulation.An interesting group of neurones lying at the confluence of nerve branches from omn 2, omn 3, and omn 4 is described.     

Studies on the mid-gut of the desert locust, Schistocerca gregaria.

ABSTRACT. The gross morphology of the mid-gut musculature of the desert locust, Schistocerca gregaria is described. Some of the electrophysiological characteristics of the external longitudinal muscle fibres were examined. The membrane potentials have mean values of -24.7mV (SE ± 7.3). Spontaneous post-synaptic potentials were recorded, and the responses of the muscle fibres to electrical stimulation of their nerve supply studied.     

Functionally heterogeneous segmental oscillators generate swimming in the medicinal leech

Swimming behavior in the leech Hirudo medicinalis arises from neuronal circuits within the ventral nerve cord. Although the ventral nerve cord comprises a series of homologous segmental ganglia, it remains unresolved whether the swim oscillator circuits within individual ganglia are functionally equivalent. We have extended previous studies on pairs of ganglia to test whether individual ganglia throughout the nerve cord are capable of generating swim oscillations and to measure the cycle periods of local oscillations. We found that the swim-generating function of individual ganglia is broadly distributed, but not uniform. The swim-like oscillations in isolated ganglia from the anterior ganglia nerve cord were less robust than those from mid-cord. Swimming activity in posterior cord ganglia is even weaker we were unable to obtain swim-like oscillations from individual ganglia of the nerve cord posterior to segment 12. Swim-cycle periods exhibited a U-shaped function: those recorded in the most anterior individual ganglia (2.3 s for ganglion M2) and short chains of posterior ganglia (up to 4.0 s) were two to four times longer than those obtained from mid-cord ganglia (near 1.0 s). We conclude that the leech swim system comprises a functionally heterogeneous set of local oscillator units.     

Localization of functional regions of human mesial cortex by somatosensory evoked potential recording and by cortical stimulation

We describe methods of localizing functional regions of the mesial wall, based on 47 patients studied intraoperatively or following chronic implantation of subdural electrodes. Somatosensory evoked potentials were recorded to stimulation of posterior tibial, dorsal pudendal, median, and trigeminal nerves. Bipolar cortical stimulation was performed, and in 4 cases movement-related potentials were recorded.The cingulate and marginal sulci formed the inferior and posterior borders of the sensorimotor areas and the supplementary motor area (SMA). The foot sensory area occupied the posterior paracentral lobule, while the genitalia were represented anterior to the foot sensory area, near the cingulate sulcus. The foot motor area was anterior and superior to the sensory areas, but there was overlap in these representations. There was a rough somatotopic organization within the SMA, with the face represented anterior to the hand. However, there was little evidence of the “pre-SMA” region described in monkeys. Complex movements involving more than one extremity were elicited by stimulation of much of the SMA. The region comprising the supplementary sensory area was not clearly identified, but may involve much of the precuneus. Movement-related potentials did not provide additional localizing information, although in some recordings readiness potentials were recorded from the SMA that appeared to be locally generated.     

Relating divergence in polychaete musculature to different burrowing behaviors: A study using opheliidae (Annelida)

Divergent morphologies among related species are often correlated with distinct behaviors and habitat uses. Considerable morphological and behavioral differences are found between two major clades within the polychaete family Opheliidae. For instance, Thoracophelia mucronata burrows by peristalsis, whereas Armandia brevis exhibits undulatory burrowing. We investigate the anatomical differences that allow for these distinct burrowing behaviors, then interpret these differences in an evolutionary context using broader phylogenetic (DNA‐based) and morphological analyses of Opheliidae and taxa, such as Scalibregmatidae and Polygordiidae. Histological three‐dimensional‐reconstruction of A. brevis reveals bilateral longitudinal muscle bands as the prominent musculature of the body. Circular muscles are absent; instead oblique muscles act with unilateral contraction of longitudinal muscles to bend the body during undulation. The angle of helical fibers in the cuticle is consistent with the fibers supporting turgidity of the body rather than resisting radial expansion from longitudinal muscle contraction. Circular muscles are present in the anterior of T. mucronata, and they branch away from the body wall to form oblique muscles. Helical fibers in the cuticle are more axially oriented than those in undulatory burrowers, facilitating radial expansion during peristalsis. A transition in musculature accompanies the change in external morphology from the thorax to the abdomen, which has oblique muscles similar to A. brevis. Muscles in the muscular septum, which extends posteriorly to form the injector organ, act in synchrony with the body wall musculature during peristalsis: they contract to push fluid anteriorly and expand the head region following a direct peristaltic wave of the body wall muscles. The septum of A. brevis is much thinner and is presumably used for eversion of a nonmuscular pharynx. Mapping of morphological characters onto the molecular‐based phylogeny shows close links between musculature and behavior, but less correlation with habitat. J. Morphol. 275:548–571, 2014. © 2014 Wiley Periodicals, Inc.