Pairs Of Nerves Research Articles

Studies on the nervous system ofPolystoma integerrimum as revealed by acetylthiocholine activity

The nervous system ofPolystoma integerrimum was studied histochemically using acetylthiocholine iodide as a substrate. The nervous system consists of two cerebral ganglia which are connected by a transverse commissure. These ganglia give off five pairs of nerves anteriorly and four pairs posteriorly. The anterior nerves contribute to the formation of the circum-oral ring located near the anterior sucker. The posterior nerves, after their fusion anterior to the haptor, contribute to the innervation of suckers and hamuli. Histological techniques including haematoxylin-eosin and AF techniques were employed. At least two types of nerve cells, the small and the large ones, were observed. The large cells show secretory properties and were observed in different parts of the nervous system.

Nervous system in Olveria indica, a rumen paramphistome (Digenea) of bovines, as revealed by non-specific esterase staining

On the basis of esterase localization the complete nervous system has been visualized in Olveria indica Thapar & Simha, 1945, a paramphistome from the rumen of cattle, recorded for the first time from the north-east region of India. The basic number of posterior longitudinal nerves (i.e., 3 pairs) is the same as in other paramphistomes; four pairs of anterior longitudinal nerves are present, there being an extra pair of pharyngeal nerves. Conspicuous differences in the innervation patterns were observed, mainly in the innervation of the genital atrial region and acetabulum. The presence of prominent longitudinal connections, joining the anterior and posterior dorsal nerves and the anterior and posterior ventral nerves on either side, is a feature not hitherto found in other paramphistome species. The details of the course of all the nerves and their branches are discussed.

The distribution of monosynaptic connexions from inspiratory bulbospinal neurones to inspiratory motoneurones in the cat.

Monosynaptic connexions were sought between bulbospinal inspiratory neurones and inspiratory motoneurones of the C5 phrenic nerve or the intercostal nerves of up to six segments in the anaesthetized cat; they were identified by the presence of narrow peaks in cross-correlation histograms constructed from the spontaneous discharges of these neurones. About half of the bulbospinal neurones tested with the phrenic gave a monosynaptic connexion, as did just under half of those tested with the intercostal nerves. Some neurones gave connexions to both. For pairs of bulbospinal neurones and intercostal nerves, connexions were seen in 50 out of 295 instances (17%). No evidence was found of systematic patterns of connexions to different segments. Some neurones gave connexions to adjacent segments, others up to five segments apart. Bulbospinal neurones were not equipotent at giving connexions to the intercostal motoneurones. If a neurone gave a connexion to one segment, it was more likely to give connexion to another segment than chance would predict. The neurones with strong connexions were concentrated rostral to obex in the ventral respiratory group; neurones in both the caudal part of the ventral group and in the dorsal group gave weaker connexions. Regional variation within the medulla in the proportions of neurones giving connexions to the phrenic motoneurones was not seen, in particular neurones of the dorsal group (eight out of sixteen) and the ventral group (five out of eleven) were equipotent. When the strength of the connexions was assessed by k, the ratio of the peak count in the cross-correlation histogram to the base-line count, the mean strength was similar for the peaks seen for the phrenic (k = 1.113) and the intercostal (k = 1.114) motoneurones. However, because, on a segment-by-segment basis, fewer connexions were seen for the intercostals, the over-all mean value of k (absence of a narrow peak taken as k = 1.0) was stronger for the phrenic (k = 1.055) than for the intercostals (k = 1.019). For the phrenic, the apparent strength of connexion (assessed by k) was considerably stronger for the motoneurones giving large spikes than for those giving small ones. The same result was probably also true for the intercostals. With several assumptions, the total depolarization during inspiration derived monosynaptically in phrenic or intercostal motoneurones was calculated and found to be low, about 1 mV for the intercostals and 3-4 mV for the phrenic.(ABSTRACT TRUNCATED AT 400 WORDS)

The nervous system of a pilidium larva: evidence from electron microscope reconstructions

The principal ultrastructural features of a pilidium larva from Friday Harbor (pilidium A, unidentified as to species) are summarized and, based on electron microscope reconstructions, the larval nervous system is described for the first time. Ciliary effectors in the larva include the marginal ciliary band, which is drawn out to form a small accessory ridge at each of the junctions between lobes, and a pair of suboral (buccal) ridges, one on either side of the stomodeum, that run between the mouth and marginal band. The nervous system consists of a small intratrochal nerve supplying the marginal band, an oral nerve that encircles the mouth at the junction of stomodeum and stomach, and a pair of nerves connecting these that run beneath the suboral ridges. The nerve fibres appear to arise from uniciliate cells in the marginal band and the suboral region. The organization, innervation, and behavior of pilidium A are discussed briefly with reference to Müller's larva, a related larva with a similar type of trochal innervation.

Animal phylogeny in the light of the trochaea theory

Ultrastructural similarities unite Choanoflagellata and Metazoa as the Kingdom Animalia. Mctazoa (Porifera + Placozoa + Gastraeozoa) are characterized by the presence of collagen, septate/tight junctions and spermatozoa. Porifera and Placozoa lack basal lamina, nerve cells and synapses, which characterize Gastraeozoa (Cnidaria + Trochaeozoa). Gnidaria have cnidoblasts and lack the multiciliate cells found in almost all Trochaeozoa (Gastroneuralia + Protornaeozoa). Gastroneuralia (Spiralia + Aschelminthes) have an apical brain and a pair of ventral nerves, a blastopore which becomes mouth and anus, a mouth surrounded by a downstream collecting system of compound cilia, and a mesoderm formed from the blastopore lips. Spiralia (Articulata + Parenchymia + Bryozoa) have spiral cleavage and 4d-cell mesoderm, whereas these characters are lacking in Aschelminthes, which all lack primary larvae. Protornaeozoa (Ctenophora + Notoneuralia) have mesoderm from vegetal cells. Ctenophores have colloblasts. Notoneuralia have a dorsal nervous system behind the apical area and form a new mouth surrounded by an upstream collecting system of single cilia on monociliate cells; the blastopore becomes the anus surrounded by a ring of compound cilia. These features fit the trochaea theory, which proposes that Gastroneuralia and Notoneuralia evolved independently from the trochaea, a blastaea with the blastopore surrounded by a ring of compound cilia, which were both locomotory and particle collecting.

Serotonergic terminals in the neural sheath of the blowfly nervous system: Electron microscopical immunocytochemistry and 5,7-Dihydroxytryptamine labelling

With serotonin immunocytochemistry we have demonstrated an extensive plexus of immuno-reactive varicose fibres in the neural sheath of the nervous system of the blowfly, Calliphora. These fibres are located in the neural sheath of the following regions: the maxillary-labial and labrofrontal nerves of the cerebral ganglia, the cervical connective, the dorsal surface of the thoracicoabdominal ganglia, two pairs of prothoracic nerves and the median abdominal nerve. We identified the serotonin-immunoreactive neural processes in the electron microscope by means of the peroxidase-antiperoxidase method. Immunoreactivity was seen in large granular vesicles ( ca 100 nm), on membranes of smaller ( ca 60 nm) and larger ( ca100 nm) agranular vesicles, along the inner surface of the axolemma, along neurotubules and outer membranes of mitochondria. By conventional electron microscopy we found numerous varicose neural processes in the neural sheath of some of the above regions. These varicosities are of at least two types. One type corresponds to the serotonin-immunoreactive profiles. A second type contains large granular vesicles ( ca 200 nm) of variable electron density. 5,7-Dihydroxytryptamine injected into the head capsule labelled varicosities in the neural sheath, corresponding to the ones identified with serotonin immunocytochemistry. The electron-dense labelling was seen in flattened vesicles within these varicosities. We propose that the serotonin-immunoreactive fibers in the neural sheath constitute neurohemal regions for the release of serotonin into the circulation. The finding of another morphological type of varicose fibers in the neural sheath suggests the presence of further putative neurohormones in these regions.

The musculature of the prothoracic legs and its innervation inHierodula membranacea(Mantidea)

The musculature of the fore limbs and the innervation pattern of the muscles in the praying mantidHierodula membranacea(Burm.) are described. There are three antagonistic pairs of muscles (promotors-remotors, abductors-adductors, anterior rotator-posterior rotators) operating the prothoracic-coxal joint around three different axes. At the coxo-trochanteral, femoro-tibial and tibio-tarsal joints there are flexor and extensor muscles, but at the tarsal-pretarsal joint only flexors are present. The trochanteral extensor is a complex muscle, with both parallel-fibred and pennate parts. The trochanteral-femoral joint is operated by a single muscle, the femoral reductor. There are six pairs of prothoracic nerves, the first of which innervates the musculature of the neck and pro-mesothoracic joints. The other five nerves are all concerned with the innervation of the muscles and sense organs of the prothoracic legs. Some of the motor neuron somata in the prothorathic ganglion have been identified by using the cobalt chloride backstaining technique. The leg musculature, its innervation pattern and the location of the motor neuron somata are compared with those of other orthopteroid insects.

Topography of nervous system in two pouched paramphistomes

Using the indigogenic technique for localizing the non-specific esterases, the complete nerve arrangement inFischoederius elongatus andGastrothylax crumenifer, the paramphistome parasites in the rumen of cattle, has been visualized. InF. elongatus, of the three pairs of anterior nerves given off from the cerebral ganglia, two are ventral and one is dorsal in disposition. The nerves running posterior from the cerebral ganglia include two pairs of ventral nerves and one of dorsals. Throughout their course the two ventrals of either side are joined to each other by several loop-like connectives. InG. crumenifer, the overall nerve arrangement is somewhat similar to that inF. elongatus; the connectives joining the posterior ventrals of each side are not loop-like. The course of all the nerves and the innervation to the various parts of the body is traced in both the species.

Neural control of the cardio-arterial valves in an isopod crustacean,Bathynomus doederleini: Excitatory and inhibitory junctional potentials

1. InBathynomus doederleini, there are cardio-arterial valves at the junctions between the heart and the arteries. These comprise: one anterior median artery, a pair of anterior lateral arteries and five pairs of lateral arteries. 2. The valves at the cardiac junctions of the three anterior arteries receive innervation from a pair of anterior cardiac nerves. The anterior cardiac nerve on each side contains one excitatory and one inhibitory motor axon for the valves. 3. Excitatory junctional potentials (EJPs) were recorded from all three valves of the anterior arteries. Inhibitory junctional potentials (IJPs) were recorded from the valves of the pair of anterior lateral arteries, but not from the valve of the anterior median artery. 4. A whole-mount preparation treated with glyoxylic acid developed fluorophore processes on all three valves of the anterior median and lateral arteries, suggesting that the processes are due to a pair of aminergic excitatory valve nerves. 5. The lateral arterial valves receive innervation from the valve nerves running alongside the arteries. Each of the valves of the lateral arteries are innervated by inhibitory motor nerves producing IJPs in the valves, and probably only by these nerves. 6. It is suggested that the flow of haemolymph to individual arteries is regulated by three types of innervation of the cardio-arterial valves. These are: dual innervation by excitatory and inhibitory axons, and single innervation which may be either excitatory or inhibitory.

Intercostal-lumbar-spinal nerve anastomoses for cord transection. A preliminary investigation.

Since 1978, 10 intercostal nerve-cauda equina anastomoses and 11 intercostal nerve-lumbar anastomoses were performed for thoracolumbar spinal cord transection. Three to four pairs of intercostal nerves above the traumatic level of the cord were anastomosed with two to four pairs of cauda equina or lumbar nerve roots below the traumatic level, using microsurgical technique. The surgical techniques used for the latter 11 cases were performed through an extraperitoneal approach. The operative technique is described in detail. These 21 cases have been followed-up for six to 48 months. Electromyography (EMG) shows that action potentials are present in several previously paralyzed muscles in 11 cases. Muscle strength of some previously paralyzed muscles in three cases recovered to Grades 1 to 3. There is evidence that intercostal-lumbar-spinal nerve anastomoses provide a chance for neuronal regeneration, but unsatisfactory functional results are still questions for further study.

Neuroanatomy of the central nervous system of the wandering spider, Cupiennius salei (Arachnida, Araneida)

In Cupiennius salei (Ctenidae), as in other spiders, the central nervous system is divided into the supraoesophageal ganglion or brain and the suboesophageal ganglia (Fig. 1). The two masses are interconnected by oesophageal connectives. The brain gives off four pairs of optic and one pair of cheliceral nerves. From the suboesophageal ganglia arise a pair of pedipalpal, four pairs of leg, and several pairs of opisthosomal nerves (Fig. 2).

The tail flattening reflex in Lumbricus: reconstitution after tail amputation and modifications in segmental nerve roots.

On stimulation of the head, the caudal 20-30 segments of intact earthworms exhibit a marked dorso-ventral flattening reflex which is an element of the escape response. When the tail is removed this reflex is reconstituted gradually in segments anterior to the amputation level without regeneration of new tail segments. It takes longer to reestablish the flattening if larger parts of the body are cut off, but after 60 days p.o. all animals regained the full response independent of the number of segments amputated. Extirpation of three consecutive ganglia from the ventral nerve cord also suffices to develop flattening anterior to the operated segments, but the reaction is less pronounced and appears later than after tail amputation. Moreover, it vanishes at the same time the normal tail flattening is observed again, presumably after regeneration across the gap in the cord. In different regions of the body, area and perimeter distributions of transversely sectioned axons in the three pairs of segmental nerves (SN I-III) of the cord were measured. Characteristic changes along the length of the animal were found for SN I and SN III. In tail segments the axonal size distributions are more variable than "typical" segments. The flattening reflex is mediated by axons in SN III (Pallas and Drewes, 1981). In body segments having reconstituted behavioral characteristics of the lost tail segments, the area of the largest axons and the general size distribution in SN III approximate those found in normal tail segments.

On the organization of the thoracic spinal ganglion and nerve in the rat.

The location of spinal ganglion cells projecting into various thoracic spinal nerve branches in the rat has been investigated using retrograde transport of horseradish peroxidase (HRP). In addition, total numbers of myelinated and unmyelinated axons in three consecutive pairs of thoracic spinal nerves have been analyzed. The animals were perfused one to 2 days after application of HRP to thoracic spinal nerve branches and several ipsilateral spinal ganglia sectioned and processed for HRP histochemistry. Labeled cells were found in ganglia corresponding to the level of operation, as well as several adjacent rostrally and caudally located ganglia. No somatotopic organization was found within the ganglia, but occasionally a clustering of labeled cells belonging to the same peripheral nerve was observed. Pieces from three consecutive pairs of ventral and dorsal spinal nerve rami were removed from two normal rats and embedded in Vestopal. Semithin sections including the entire cross-sectional area of the rami were used to count the total number of myelinated axons. The number of unmyelinated axons was estimated by sample counting in the electron microscope. The ventral ramus of the spinal nerve contained about twice as many axons and a lower proportion of unmyelinated fibers in comparison with the dorsal ramus. Large differences in the number of axons between the two sides in pairs of spinal nerve rami and entire spinal nerves were found. These differences diminished when comparing the total number of axons from three consecutive rami or nerves on each side.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardioregulatory nerves in the spider Eurypelma marxi Simon

The objective of this study was to locate nerves arising from the CNS that have a cardioregulatory function in the tarantula, Eurypelma marxi Simon. Ramifications of the paired abdominal nerve VIIIb merge with the cardiac ganglion within the first heart segment. Electrical stimulation of the branches of nerve VIIIb that connect with the cardiac ganglion produce changes in heartbeat rate and amplitude. Nerve cutting experiments indicate that no other cardioregulatory nerves are present. Both increases and decreases in heart activity can be produced upon electrical stimulation of nerve VIIIb on each side of the heart. Only one action potential associated with the response of each type could be recorded in each member of the nerve pair. Therefore, we conclude that there are two inhibitory and two acceleratory neurons that arise in the central nervous system to modulate heartbeat activity. The inhibitory effect becomes maximal at a stimulation frequency of 20-30 Hz and the accelerator effect at 30-40 Hz. The aftereffect of acceleratory nerve activity exceeds that of inhibitory nerve activity. When the inhibitor and accelerator are activated simultaneously, the inhibitor dominates. The regulatory nerves interact with neurons in the cardiac ganglion. During inhibition, the number of externally recorded spikes in each ganglionic burst is decreased. The rate and magnitude of the heartbeat are decreased concomitantly. Stimulation of the accelerator enhances electrical activity in the cardiac ganglion at the same time that the heartbeat rate and amplitude are increased.

Shoot development in Betula papyrifera. IV. Comparisons between growth characteristics and expression of vegetative long and short shoots

Postflush observations on shoots of Betula papyrifera Marsh. indicated that long and short shoots differ in a range of morphological characteristics. Long shoots developed from distal axillary buds and short shoots developed from proximal axillary buds on the previous year's long shoots. Consequently, the potential of a bud to develop into a long shoot decreased basipetally. Potential long-shoot buds had higher bud-relative growth rates, stem-relative growth rates, leaf-relative growth rates, and stem dry weights during the course of postflush growth. Changes in leaf thickness, expressed in terms of specific leaf area and specific leaf weight, indicated that long shoots temporarily had thinner leaves than did short shoots a few weeks after flushing. Net assimilate requirements in long shoots for late leaf and internodal expansion may explain these observations. Nearing maturity, long-shoot early leaves became thicker, possibly owing to greater shoot vigour and (or) higher photosynthetic efficiency. Consequently, mature long-shoot early leaves possessed larger and thicker laminae, longer petioles, more side nerve pairs, and tended to grow more in length than width than short-shoot leaves on shoots of comparable age. Leaves of older short shoots, 2–10 years old, attained a greater size and had longer petioles than those of 1-year-old short shoots. Stem elongation and the development and expression of leaves in long shoots seemed to have a correlative influence on the overall vigour of long shoots.

A neuroanatomical and electrophysiological analysis of nervous regulation in the heart of an isopod crustacean,Bathynomus doederleini

1. We have used anatomical, histological, and electrophysiological techniques to study the innervation of the heart of an isopod,Bathynomus doederleini. 2. The heart beat was driven by a cardiac ganglion consisting of twelve morphologically identical neurones. 3. The paired anterior cardiac nerves each contained five axons: three cardio-regulator axons, and two motor axons to anterior cardio-arterial valves. 4. The functions of the cardio-regulator axons were elucidated by stimulating individually one inhibitor and two accelerator axons on either side. 5. The two cardio-accelerator axons (on each side) were functionally identical. They innervated the cardiac ganglion, producing discrete EPSPs. 6. The cardio-inhibitor axon induced discrete IPSPs in the cardiac ganglion. This axon may also directly innervate the myocardium. 7. The two pairs of valve motor nerves each contained one excitor axon and one inhibitor axon. The excitatory innervation produced valve contraction resulting in a decrease of arterial dilation during systole. The inhibitory innervation produced valve relaxation resulting in an increase of arterial dilation. 8. The valve axons may regulate the distribution of haemolymph among arteries. The cardiac output may be regulated by the nerves to the cardio-arterial valves and the cardio-regulator nerves to the heart.

Shoot development in Betula papyrifera. II. Comparison of vegetative and reproductive short-shoot growth

Short shoots of Betula papyrifera Marsh, may be vegetative or reproductive. The latter bear a female inflorescence. Early flushing and rapid growth of short-shoot buds depend on the age and position of the short shoot. Axillary short-shoot buds flush later than 2- to 4-year-old short-shoot terminal buds, which in turn flush later than 5- to 10-year-old shoots. Mean relative growth rate (RGR) of 5- to 10-year-old short-shoot buds is greater than that of younger short-shoot buds. It is suggested that older short-shoot buds are relatively autonomous and that the flushing long shoot exhibits an inhibitory influence on the proximal axillary buds and possibly on young short-shoot terminal buds. Reproductive short shoots differ from vegetative short shoots in that they have lower leaf area ratios and leaf RGR, higher specific leaf area, smaller leaf areas, and fewer side nerve pairs and they grow more in length than in width. These findings are related to reproductive cost. The developing inflorescences act as preferred "sinks" for resource allocation.

Spontaneous and neurally evoked contractions of visceral muscles in the oviduct of Locusta migratoria

AbstractThe oviducts of Locusta migratoria are innervated by a pair of nerves which arise from, the seventh abdominal ganglion. A distinctive network of striated muscle fibres occurs in the oviducts. The lateral oviducts and common oviduct consist of an inner circular layer of muscle and an outer longitudinal layer of muscle. At the junction of the lateral and common oviduct an additional thin longitudinal layer is found adjacent to the basement epithelium.The oviducts contracted spontaneously when isolated from the central nervous system. These myogenic contractions took the form of peristaltic contractions in the lateral oviduct, and intermittent phasic‐like contractions of the posterior regions of the lateral oviduct and the common oviduct. These phasic‐like contractions were associated with individual complex potentials recorded extracellularly from the muscle fibres.In locusts that had been interrupted in the process of egg laying, there were large‐amplitude action potentials, firing in a bursting pattern, in the oviducal nerves. These large action potentials were absent in locusts that had not been egg‐laying. These action potentials were associated with both bioelectric potentials and mechanical events in the posterior region of the lateral oviduct and the common oviduct.Electrical stimulation of the oviducal nerve mimicked the effects of spontaneous action potentials, resulting in the appearance of monophasic potentials and contractions. The contractions were graded and dependent upon both frequency and duration of stimulation.It is concluded that the oviducts of Locusta are both myogenic and neurogenic. The role of these contractions in oviposition is discussed.

Fibers in spinal nerves of tree frogs: Eleutherodactylus and Hyla.

This is a study on numbers and sizes of nerve fibers as determined by electron microscope mapping of the spinal nerves of two species (in different families) of free frogs. The study provides data for comparison of fiber populations in the grass frog, Rana pipiens. In both free frogs the greatest number of fibers in the ten pairs of spinal nerves are in the second and ninth rami. The combined counts of myelinated and unmyelinated fibers in the rami on one side of the cord in Eleutherodactylus and Hyla are respectively: to the forelimb, 3,147 and 4,460 fibers; to the trunk, 334 and 1,234 fibers; and to the hindlimb, 4,335 and 6,213 fibers. With a few notable differences this distribution of fibers to regional body parts correlates closely with that found in Rana. The arboreal frogs have a relatively smaller number of medium and especially large size fibers in comparison with the aquatic-terrestrial living grass frog. The importance is stressed of examining the spinal nerves of an entirely aquatic frog with different feeding habits, such as Xenopus, for further comparison.

Excitatory and inhibitory interactions of extraocular and dorsal neck muscle afferents in the cat frontal cortex

Excitatory and inhibitory responses of 318 neurons to extraocular and dorsal neck muscle afferent stimulation were recorded extracellularly in the frontal cortex of 34 chloralose-anesthetized cats. Electrical stimulation of the oculomotor nerve to the ipsilateral and contralateral superior rectus muscle of the eye elicited single-cell responses in 33 and 40% of more than 160 cells tested, respectively, and stimulation of the abducens nerve to the lateral rectus muscle elicited responses in 47% of 161 cells tested, at latencies of 7 to 50 ms. Responses to a branch of the ipsilateral and contralateral biventer cervicis/complexus nerve of the dorsal neck were observed in 42 and 64% of more than 150 cells tested, respectively, and 32% of 165 cells responded to the contralateral rectus capitis dorsalis major/obliquus capitis caudalis nerve, at latencies of 5 to 47 ms. Inhibitory effects were evaluated extracellularly by observing the effect of electrical nerve stimulation against a background of glutamate-induced excitation of cells in the frontal cortex. Stimulation of extraocular muscle nerves inhibited activity in 20 of 93 cells, and dorsal neck muscle afferent fibers had inhibitory effects on 20 of 64 cells tested. Excitatory and inhibitory convergence between afferent fibers from one extraocular and one or more dorsal neck muscles was observed in 60% of 234 cells tested, and was higher than the degree of convergence between some pairs of extraocular muscle nerves, or between pairs of dorsal neck muscle nerves. The highest degree of convergence was between extraocular muscle afferent fibers and those from longitudinally extended dorsal neck muscles, which cause large head deviations upon contraction. The interacting effects of dorsal neck and extraocular muscle afferent fibers at comparable latencies in the cat frontal cortex suggest an involvement of these regions in coordinated eye and head movement.