Ganglia Of Ventral Nerve Cord Research Articles

Investigation of the development of a ventral nerve cord ganglion in Eisenia fetida: a histological and histochemical study.

Investigation of the development of a ventral nerve cord ganglion in Eisenia fetida: a histological and histochemical study.

Baratin, a nonamidated neurostimulating neuropeptide, isolated from cockroach brain: Distribution and actions in the cockroach and locust nervous systems

During the purification of tachykinin-related peptides from the brain of the cockroach Leucophaea maderae, a few other peptides were collected in adjacent high-performance liquid chromatography fractions. Edman degradation, mass spectrometry, and chemical synthesis revealed that one of these peptides had the sequence DNSQWGGFA. This nonamidated nonapeptide was designated baratin and appears not to be related to any known insect peptide. Baratin was not found to be bioactive in the L. maderae hindgut or oviduct muscle contraction assay. (Both synthetic nonamidated and amidated baratin were tested.) To screen for possible sites of action, we raised a rabbit antiserum to baratin. We found baratin-immunoreactive (BAR-IR) interneurons throughout the cockroach central nervous system. Some prominent brain neuropils were supplied by BAR-IR neuron processes: the central body, the calyx, and lobes of the mushroom bodies, parts of the optic lobe, and the tritocerebral neuropil. Additionally we found BAR-IR neurosecretory cells in the median neurosecretory cell group with processes supplying the storage lobe of the corpora cardiaca. In each of the thoracic and abdominal ganglia processes of BAR-IR projection neurons and local neurons were seen. The baratin antiserum also labeled neurons in the brain of the locust Locusta migratoria, some of which are similar to those of the cockroach. A prominent system of interganglionic BAR-IR processes was found in the locust subesophageal, thoracic, and abdominal ganglia. This was formed by four large projection neurons with cell bodies in the abdominal ganglia A1-2. The processes of these BAR-IR neurons are distributed dorsally and laterally in each of the ventral nerve cord ganglia. When baratin (10(-6)-10(-4) M) was applied to desheathed abdominal ganglia of locusts and cockroaches, we could monitor bursts of action potentials in neurons with axons in the anterior abdominal nerve (nerve 1), but not in the posterior nerve (nerve 2). In ganglia displaying spontaneous rhythmic firing in units of nerve 1, baratin strengthened the rhythmic pattern. Thus baratin appears to have a role in modulation of motor patterns in abdominal ganglia. The immunocytochemical findings suggest further modulatory actions of baratin in different circuits of the brain and ventral nerve cord.

Dopaminergic Control of Serotonergic Neuron Development in the Grasshopper Central Nervous System

The central nervous system (CNS) of the grasshopper consists of a brain and a set of segmental ganglia that together make up the ventral nerve cord. Each ventral nerve cord ganglion develops very similarly during early embryogenesis. The availability of cells that make stereotypical decisions in the developing CNS and that can be identified in the living embryo makes the grasshopper an attractive system for researching specific questions about neural development. Serotonin is a very important neuromodulator in invertebrates. Application of this compound to small neuronal circuits or whole nervous systems profoundly affects their physiological behavior. Invertebrates have small numbers of dopaminergic and serotonergic neurons that send extensive processes that innervate most of the central neuropil. Dopamine and serotonin receptors have been characterized in insects and mollusks, both pharmacologically and molecularly. These are remarkably conserved between vertebrates and invertebrates. Thus, these experimental observations made in insects may also be applicable to vertebrates. The experimental access afforded by insects makes such studies an attractive approach to understanding the much more complex vertebrate system. Serotonergic innervation of the neuropil of each ventral nerve cord hemiganglion derives from one local serotonergic interneuron, s1. It expresses serotonin uptake activity before making serotonin. Serotonin synthesis begins when the early branches reach the target neuropil. Dopamine seems to be required both for the serotonin synthesis and for controlling the rate of neurite extension. The receptors controlling these processes have been pharmacologically characterized.

The Drosophila fish-hook gene encodes a HMG domain protein essential for segmentation and CNS development.

We describe the isolation and analysis of the Drosophila fish-hook (fish) gene, which encodes a novel member of the SOX subgroup of High Mobility Group (HMG) domain proteins that exhibit similarity to the mammalian testis determining factor, SRY. The fish gene is initially expressed in a pair-rule-like pattern which is rapidly replaced by strong neuroectoderm expression. fish null mutants exhibit severe segmentation defects, including loss and/or fusion of abdominal denticle belts and stripe-specific defects in pair-rule and segment polarity gene expression.fish mutant embryos also exhibit loss of specific neurons, fusion of adjacent ventral nerve cord ganglia and aberrant axon scaffold organization. These results indicate an essential role for fish in anterior/posterior pattern formation and nervous system development, and suggest a potential function in modulating the activities of gap and pair-rule proteins.

The distribution and relative potency of diuretic peptides in the house cricket, Acheta domesticus

ABSTRACT Dose‐response curves are presented for the diuretic activity in aqueous extracts of brain, retrocerebral complex, and ventral nerve cord ganglia from Acheta domesticus. Diuretic activity is highest in extracts of brain and corpora cardiaca. In comparison with such extracts, those of the suboesophageal ganglia and thoracic ganglia I‐III produce truncated responses, whilst abdominal ganglia 1–4 show evidence of an inhibition of the diuretic response at high doses. ED50 values, obtained from Hill plots, are similar for extracts of brain, corpora cardiaca, corpora allata, and abdominal ganglia, but are 3–4 times higher for extracts of suboesophageal and thoracic ganglia.Separation of aqueous extracts of corpora cardiaca by reversed‐phase HPLC yields a number of fractions which stimulate fluid secretion in isolated tubules. Diuretic activity in these fractions is destroyed by treatment with Pronase E, and on this basis is identified as peptidic. In general, diuretic activity is found in the same RP‐HPLC fractions prepared from aqueous extracts of brain, suboesophageal ganglia, thoracic ganglia I‐III, and abdominal ganglia 1–4.

Extension and retraction of axonal projections by some developing neurons in the leech depends upon the existence of neighboring homologues. II. The AP and AE neurons.

To assess the generality of our previous finding (Gao and Macagno, 1987) that segmental homologues play a role in the establishment of the pattern of axonal projections of the heart accessory HA neurons, we have extended our studies to two other identified leech neurons: the anterior pagoda (AP) neurons and the annulus erector (AE) motor neurons. Bilateral pairs of AP neurons are found in the first through the twentieth segmental ganglia (SG1 through SG20) of the leech ventral nerve cord. All AP neurons initially extend axonal projections to the contralateral periphery as well as longitudinal projections along the contralateral interganglionic connective nerves toward anterior and posterior neighboring ganglia. Although the peripheral projections are maintained by all AP neurons throughout the life of the animal, the longitudinal projections disappear in all but two segments: the AP neurons in SG1 maintain their anterior projections and extend them into the head ganglion, and those in SG20 maintain their posterior projections and extend them into SG21 and the tail ganglion. When single AP neurons are deleted anywhere along the nerve cord before processes begin to atrophy, however, the longitudinal projections are retained by their ipsilateral homologues in adjacent ganglia. The rescued processes appear to take over the projections of the deleted neurons. In cases where two or more AP neurons on the same side of the nerve cord are deleted from adjacent ganglia, a contralateral homologue sometimes extends projections to the periphery ipsilaterally or on both sides. We obtained similar results when we deleted single AE neurons from midbody ganglia. Thus, our experiments with three different identified neurons consistently show that the initial pattern of projections is the same in all ganglia, but that the existence of homologues in adjacent ganglia leads to the pruning of some of the initial projections. A consequence of this homologue-dependent process retraction is that neurons normally lacking neighboring homologues will have patterns of projections different from those neurons that do have such neighbors. Process loss by the HA, AP, and AE neurons may be the result either of competition for targets, inputs, or growth factors or of direct interactions among homologous cells.

Extension and retraction of axonal projections by some developing neurons in the leech depends upon the existence of neighboring homologues. I. The HA cells.

The role of homologues in the establishment of the pattern of axonal projections of identified segmentally homologous neurons was investigated by means of selective cell ablation and dye injection. The cells studied were the bilateral pairs of heart accessory (HA) neurons found in the fifth and sixth segmental ganglia of the leech ventral nerve cord. Homologues start their morphological differentiation with identical axonal projections, and segmental differences are manifested later, when specific branches stop growing and disappear. The deletion of single HA cells at early stages, however, permits these branches to survive in their ipsilateral homologues and to grow and take over the projections of the deleted neurons. In addition, if both HA homologues on the same side of the nerve cord, or three of the four HA cells, are deleted in an animal, the remaining HA cells often extend novel projections. These observations suggest that either competition for targets, inputs or growth factors, or direct interactions among homologous cells may play a role in the differentiation of segment specific patterns of axonal projections.

Differential localization of vasopressin- and oxytocin-immunoreactive cells and conventional neurosecretory cells in the ganglia of the earthworm Pheretima hilgendorfi.

Cells containing arginine vasopressin (AVP)- and oxytocin (OXT)-like substances were immunohistochemically visualized in the cerebral, subesophageal, and ventral nerve cord ganglia of the earthworm Pheretima hilgendorfi. Whether these anti-AVP- and anti-OXT-reactive cells are identical with classical aldehyde fuchsin (AF)-positive neurosecretory cells was tested in serial sections. In all ganglia, groups of scattered neuronal cell bodies and axons strongly reactive to AVP and OXT antisera were observed, but AF-positive cells consisting of type a (dark blue) and type b (purple) cells were predominantly present in the cerebral and subesophageal ganglia. In the cerebral and subesophageal ganglia anti-AVP- and anti-OXT-reactive cells were generally larger than AF-positive cells. Some AF-positive cells were reactive either to anti-AVP or anti-OXT serum, but some failed to react to either serum. Anti-AVP- and anti-OXT-reactive cells were not immunoreactive to OXT and AVP antisera, respectively. Electron microscopic observations showed that the granules of type a cells were larger and less electron dense than those of type b cells and anti-AVP-reactive cells. The present cytological observations clearly showed that AVP- and OXT-like substances were widely present in the ganglionic cells of the earthworm.

Habituation of swimming activity in the medicinal leech.

Tactile stimulation (light stroking) of a body wall flap attached to the ventral nerve cord of the medicinal leech evokes episodes of swimming activity. This swimming response undergoes habituation, involving changes in swim initiation and swim maintenance. Repeated stimulation of the body wall flap evoked swimming activity between three and 39 times before this response failed. During repetitive stimulation, the length of swim episodes decreased by about 50%. The number of swim episodes which could be elicited was not correlated with swim episode length. Following habituation, swim initiation showed significant spontaneous recovery, but swim episode length returned only to 60% of control values. In preparations where spontaneous recovery was followed by rehabituation, the number of swim episodes elicited declined with each habituation-recovery sequence. Additional stimulation immediately following habituation trials had a dual effect: recovery of the swimming response was delayed, but the lengths of swim episodes following spontaneous recovery were increased. Pinching the body wall flap immediately restored the swimming response in an habituated preparation. Swim initiation habituated more rapidly during stimulation of anterior body wall flaps than during stimulation of mid-body or posterior flaps. However, swim length was independent of this regional variation in swim responsiveness. The number of swim episodes elicited by stimulation of body wall flaps attached to posterior or anterior segments depended upon whether this segment was stimulated before or after other flaps. In contrast, in mid-body segments there was no evidence for such stimulus generalization. The lengths of swim episodes elicited during sequential stimulation of several body wall flaps were independent of the stimulation sequence. We propose that separate processes control swim initiation and swim maintenance. These processes must be repeated in most, if not all, of the segmental ganglia of the leech ventral nerve cord.

3H-GABA uptake selectively labels identifiable neurons in the leech central nervous system.

Segmental ganglia of the leech ventral nerve cord synthesize the neurotransmitter gamma-aminobutyric acid (GABA) when incubated in the presence of the precursor glutamate, suggesting that there may be GABA-ergic neurons in the leech nerve cord. GABA-accumulating neurons of the two taxonomically distant leech species, Haementeria ghilianii and Hirudo medicinalis, have been labeled by taking advantage of their high-affinity uptake system for the neurotransmitter. Autoradiography of sectioned segmental ganglia previously exposed to 3H-GABA reveals a reproducible pattern of about thirty 3H-GABA-labeled neuronal cell bodies per ganglion. The majority of 3H-GABA-labeled neuronal cell bodies are bilaterally paired, although some apparently unpaired cell bodies also accumulate label. Neuronal processes were reproducibly labeled by GABA uptake and could be traced in the neuropil through commissures and fiber tracts into the segmental nerve roots and interganglionic connectives, respectively.

Morphology and number of neurons in two species of polychaetes.

Neurons of the ventral nerve cord (VNC) in the polychaete species Clymenella torquata and Nereis virens were ultrastructurally distinguished from glial cells by the smaller diameter and elongated shape of glial nuclei in adult organisms. In contrast to neurons, beta-glycogen-like particles and densely packed microfilaments were found in glial cytoplasm. Using these and other criteria, glial cells were distinguished from nerve cells in histologic preparations. All neuronal nuclei were counted in specified regions of the CNS of both polychaetes. In both species, the number of neuronal nuclei in various CNS regions remained constant in animals of very different body size. Since Clymenella has a set number of ganglia in the VNC and a set number of body segments, the total number of CNS neurons remains constant in adult members of this species. Since adult Nereis adds VNC ganglia in newly forming body segments, the total number of CNS neurons continuously increases, but the total number of CNS neurons in a ganglion does not change after it is formed.

Alcoholic Bouin fixation of insect nervous systems for Bodian silver staining. II. Modified solutions.

A previously devised synthetic equivalent of 'aged alcoholic Bouin (Duboscq-Brasil) fixative was modified in various ways to discover which of the chemical changes brought about by aging were important in improving fixation and staining. Effects were tested with ventral nerve cord ganglia of the cockroach Periplaneta americana, locust Schistocerca gregaria, and honey bee Apis mellifera. Formation of reaction products, chiefly ethyl acetate and diethoxymethane, seemed to play only a subsidiary role: neither individually appeared essential as long as a sufficient quantity of one or the other was present. In place of diethoxymethane, ethyl acetate concentration could be increased to 25% with little effect on results. Reduction in concentration of two of the original constituents, formaldehyde and ethanol, appeared to be the principal factor in improving fixation. Varying the concentration of each original constituent individually revealed that formaldehyde mainly increased glial staining, ethanol increased tissue shrinkage and reduced overall staining intensity, acetic acid improved preservation, and picric acid decreased glial staining but produced few other effects within a wide range of concentrations, though its omission seriously impaired overall preservation and staining. Varying the ethanol and acetic acid concentrations simultaneously confirmed that they acted in opposite ways. A decrease in ethanol and an increase in acetic acid both improved results. The optimum mixture, 'improved synthetic alcoholic Bouin' (40% formaldehyde 0-15: ethanol 25: acetic acid 5: ethyl acetate 5: diethoxymethane 15: picric acid 0.5: water to 100), gives better preservation and more intense staining, and formaldehyde content can be varied to give the degree of glial staining and more intense staining, and formaldehyde content can be varied to give the degree of glial staining required. Without formaldehyde glial staining is virtually eliminated, while preservation and staining of the neurons appears unaffected. This modification seems to offer a valuable advance in technique.

Alcoholic Bouin fixation of insect nervous systems for Bodian silver staining. I. composition of 'aged' fixative.

Alcoholic Bouin (Duboscq-Brasil) fixative being 'aged' at 60 C to improve tissue preservation and subsequent staining was sampled at various stages to determine its histological effectiveness and chemical composition. Histological performance was tested using ventral nerve cord ganglia of the cockroach Periplaneta americana and the locust Schistocerca gregaria. Chemical analysis was by ultraviolet spectroscopy, thin layer and gas-liquid chromatography, and mass spectrometry. Histological performance improved rapidly during the first 7-10 days and composition changed correspondingly. The rate of change then slowed as a more stable condition was approached. Fully aged solutions, after about 40 days, giving optimum fixation and staining, contained little more than half the amounts of the volatile components (formaldehyde, ethanol, and acetic acid) in the original mixture, together with ethyl acetate and a formal, diethoxymethane, as the principal reaction products, but picric acid content showed little change. Older ('overaged') solutions, fully aged and then kept at room temperature for 1-2 yr, gave poorer fixation and staining and contained still less of the original volatile constituents and correspondingly more of the reaction products. A 'simplified synthetic aged alcoholic Bouin' (15 ml 40% formaldehyde, 35 ml ethanol, 3.5 ml acetic acid, 5 ml ethyl acetate, 15 ml diethoxymethane, 0.46 g picric acid, and water to 100 ml) closely stimulated the performance of the fully aged orthodox fixative without the need for aging.

The distribution of putative neurosecretory cells in the central nervous system of the North American medicinal leech Macrobdella decora

Nerve cells that displayed a distinct Tyndall blue–white effect were observed in the supra- and sub-oesophageal ganglia, the ventral nerve cord ganglia, and the posterior ganglion of the Gnathobdellid leech Macrobdella decora. These cells formed four anatomically distinct groups in the supraoesophageal ganglion and occupied characteristic and analogous positions in the other ganglia. Light microscopy of these blue–white cells revealed histochemical properties not seen in other nerve cells. The perikarya of the four groups of blue–white cells in the supraoesophageal ganglion were examined with the electron microscope and found to contain large membrane-bounded electron-dense granules similar to those observed in proven neurosecretory cells. Tracts from two of these cell groups possibly form primitive neurohemal organs. A neurosecretory role for the blue–white cells is suggested.

On the neurosecretory system of Dendrobaena atheca Cernosvitov.

AbstractFour kinds of neurosecretory cells A, B, U and C are distinguished in the central nervous system of Dendrobaena atheca Cernosvitov. A cells, which show different morphological characteristics under different physiological states and during their cyclic changes, are the most active neurosecretory cells. They form the outer layer of the cortical cell zone in the cerebral ganglion. B cells are large and medium sized and are distributed in all parts of the central nervous system. U cells are found only in the sub‐pharyngeal ganglion while C cells are distributed in the sub‐pharyngeal as well as in the ventral nerve cord ganglion. The number and secretory activity of C cells decrease in caudal direction. Further, Gomori‐positive cells are also observed in the ganglia of the vegetative nervous system.A rudimentary neurohaemal organ, the storage zone, has been observed in the cerebral ganglion and there appears to be another neurohaemal area in the ventral nerve cord ganglion. The storage zone is formed by the terminal ends of the axons of A cells. The chrome alum haematoxylin phloxin (CHP) and aldehyde fuchsin (AF) positive substances in the form of granules are found in this area. The cerebral ganglion is richly supplied by blood capillaries. The distal end of the axons of B cells are swollen like a bulb while in some cases the axons are united to form an axonal tract. Extra‐cellular material is abundant in different parts of the nervous system. In all cell types, the perinuclear zone is the first to show activity in the secretory cycle. It appears that the nucleus may be involved in the elaboration of the neurosecretory material in the cells.

Transfer of radioactive material between electrically coupled neurons of the leech central nervous system

Intracellular application of tritiated precursors by means of microiontophoresis was performed on nerve cells in isolated segmental ganglia of the leech ventral nerve cord. Incorporation as well as intra- and interneuronal transport were studied by autoradiography after injection of fucose, glucosamine, glycine, leucine, orotic acid and uridine. Within several minutes of intraneuronal injection the precursors were incorporated into macromolecules. Depending upon the tracer used, the radioactive material was distributed in a specific pattern over the cell somata and then released into the nerve processes. After application of orotic acid and uridine a transport of radioactive material, presumably RNA, could be observed in the processes of the injected neurons at a distance of about 200–500 μm. Fucose and glucosamine injection resulted in the most extended labeling of the nerve cell processes, indicating a transport rate of about 11 mm/day. When the radiochemicals were injected into one of the two electrically coupled giant nerve cells — the so-called Retzius cells (Rc) — a specific labeling not only of the injected Rc but also of the coupled but not injected Rc was found. Injection of protein or glycoprotein precursors into one Rc produced heavy labeling of both Rcs including their processes; a slight labeling of other ganglion compartments was only found after increasing the dosage of the amino acids glycine and leucine. With orotic acid and uridine this interneuronal transfer was confined to the electrically coupled Rc twin. Intracellular injection of one Rc with puromycin followed by injection of amino acids or fucose into the same Rc or into the coupled Rc resulted in an inhibition of precursor incorporation within the puromycin-injected Rc and an exclusive labeling of the coupled Rc, thus indicating that the precursors themselves were transferred. It is suggested that after microiontophoretic application an interneuronal transfer of relatively low molecular weight material takes place, probably across the low-resistance junction through which the Rcs are electrically coupled.