Dorsal Bodies Research Articles

Neurosecretion of the mediodorsal cells of the central nervous system of the snail Helisoma duryi

The neurosecretory mediodorsal cells that produce a putative growth hormone of the snail Helisoma duryi were studied in fast-growing virgin snails and in slow-growing reproducing snails. There are about 60 mediodorsal cells in clusters on each side of the cerebral commissure of the central nervous system, and they contain dense-cored granules which are 100–200 nm in diameter. The cells of virgin snails have dense Golgi bodies, scattered ER cisternae, and few granules, while those of reproducing snails have pale Golgi bodies, stacked ER cisternae, and numerous granules. Thus the mediodorsal cells of the virgin snails appear to be more active synthetically than those of the reproducing snails. The cells near the endocrine dorsal bodies contain many dorsal body precesses in their membrane interdigitations. There are junction-like interactions between some of the interdigitations. Gap junction-like contacts are seen between mediodorsal cells and glial cells. The axon endings of the mediodorsal cells at the neurohemal area in the labial nerve show more release profiles in virgin snails than in reproducing snails. A daily pattern of release has been observed in reproducing snails, and rates of release are higher in the evening than in the morning.

Acetylcholine receptors of thoracic dorsal midline neurones in the cockroach, Periplaneta americana

The actions of acetylcholine and cholinergic ligands have been studied using dorsal midline neurones from the rnetathoracic ganglion of the cockroach Periplaneta americana.Both nicotine and oxotremorine depolarized dorsal midline neuronal cell bodies.Dose-response curves for nicotine and oxotremorine saturated at different levels. Nicotine-induced depolarizations were completely or partially blocked by mecamylamine, d-tubocurarine, strychnine, and bicuculline, but were insensitive to alpha-bungarotoxin(100 nM), atropine (100 micronM),Scopolamine (10 micronM), and pirenzepine (50 micronM). Following pretreatment with collagenase, the dorsal midline neurones were sensitive to high doses of alpha-bungarotoxin (3 micronM). Oxotremorine-induced depolarizations were blocked by scopolamine (10 micronM) atropine (100 micronM), and pirenzepine (50 micronM) and were insensitive to mecamylamine (10 micronM) and d-tubocurarine (100 micronM). The results indicate the coexistence of at least two distinct acetylcholine receptors on dorsal midline neuronal cell bodies in the cockroach metathoracic ganglion.

Étude de l'action des ganglions cérébroïdes et des corps dorsaux sur la synthèse d'ADN induite par la chaleur dans l'ovotestis d'Helix aspersa en hibernation

Brain extirpation of snails at the start of their natural hibernation increased the synthesis of DNA in spermatogonia when the animals were transferred from 5 to 25 degrees C for a 4-week period. This effect did not occur if animals were maintained at 5 degrees C. The reimplantation of brain (cerebral ganglia: CG + associated dorsal bodies: DB) in brain-ablated snails failed to correct the effects of brain extirpation. The implantation of either DB or CG in cerebrotomized hosts showed that, compared to shams, DB restored the level of DNA synthesis and spermatogonial proliferations whereas CG stimulated it. The CG and associated DB were therefore found to exert antagonistic effects which are responsible for the control of spermatogonial DNA synthesis in hibernating Helix aspersa.

An ultrastructural study of the activation of the endocrine dorsal bodies in the snail Helix aspersa by mating

The ultrastructural organization of the dorsal bodies of Helix aspersa was studied using serial sections. The dorsal body cells, which were found in groups of two to six in the connective tissue surrounding the brain, contacted each other and formed a network. They were innervated by two types of axons. Type I axons conformed with those described in earlier studies as inhibitory and originating from the cerebral green cells. Type II axons contained secretory granules that were morphologically distinct from and smaller than type I granules. Between the dorsal body cells and both axon types, localized modifications of the membrane were evident. Virgin snails, which grew faster (wet weight) than mated snails, did not lay viable eggs. A comparative morphometric analysis of the dorsal bodies of virgin and mated snails showed that in the latter there was an increase in the numbers of mitochondria, secretory granules, and Golgi bodies, with a concomitant decrease in the numbers of lipid droplets. However, no difference was found in the numbers of profiles of exocytotic release of secretory granules with the use of tannic acid methods. Mating, obligatory for oviposition of viable eggs, appeared to cause ultrastructural changes consistent with increased synthesis and release of the dorsal body hormone essential for vitellogenesis, ovulation, and, consequently, egg laying.

The presence of peptides related to the adipokinetic hormone/red pigment-concentrating hormone family in the nematode, Panagrellus redivivus

Immunocytochemistry using polyclonal antisera raised to fragments or derivatives of locust adipokinetic hormone (AKH) I and IIs (Schooneveld et al., 1983, 1985, 1986) selectively stained cells in the nervous system of the free-living nematode, Panagrellus redivivus. Antiserum 528 (raised to the C-terminus of AKH IIs) stained the dorsal cephalic papillary cell bodies and the anterior nerve ring. Fibres in the lateral cords were stained with antiserum 241 that recognises the C-terminus of AKH I. Substances reacting to antisera 433 (raised to the N-terminal sequence of AKH I and IIs) 528 and 241 were present in the preanal ganglion and associated ventral nerve fibres. In males, all three antisera stained fibres leading to the base of the spicules. A peptide fraction from whole P. redivivus evoked an adipokinetic response in the locust, Schistocera gregaria which was dose dependent and was abolished by treatment with endopeptidase 24:11 but not by boiling or by incubation with leucine aminopeptidase. The adipokinetic activity was reduced by over 70% on incubation of the peptide fraction with pyroglutamyl aminopeptidase. The same fraction induced hyperglycaemia when injected into the cockroach, Periplaneta americana. These results are consistent with the existence in P. redivivus of peptides that are structurally related to the arthropod adipokinetic hormone/red pigment-concentrating hormone (AKH/RPCH) family.

Parallel motor pathways from thoracic interneurons of the ventral giant interneurons system of the cockroach, Periplaneta americana

The data described here complete the principal components of the cockroach wind-mediated escape circuit from cercal afferents to leg motor neurons. It was previously known that the cercal afferents excite ventral giant interneurons which then conduct information on wind stimuli to thoracic ganglia. The ventral giant interneurons connect to a large population of interneurons in the thoracic ganglia which, in turn, are capable of exciting motor neurons that control leg movements. Thoracic interneurons that receive constant short latency inputs from ventral giant interneurons have been referred to as type A thoracic interneurons (TIAs). In this paper, we demonstrate that the motor response of TIAs occurs in adjacent ganglia as well as in the ganglion of origin for the TIA. We then describe the pathway from TIAs to motor neurons in both ganglia. Our observations reveal complex interactions between thoracic interneurons and leg motor neurons. Two parallel pathways exist. TIAs excite leg motor neurons directly and via local interneurons. Latency and amplitude of post-synaptic potentials (PSPs) in motor neurons and local interneurons either in the ganglion of origin or in adjacent ganglia are all similar. However, the sign of the responses recorded in local interneurons (LI) and motor neurons varies according to the TIA subpopulation based on the location of their cell bodies. One group, the dorsal posterior group, (DPGs) has dorsal cell bodies, whereas the other group, the ventral median cells, (VMC) has ventral cell bodies. All DPG interneurons either excited postsynaptic cells or failed to show any connection at all. In contrast, all VMC interneurons either inhibited postsynaptic cells or failed to show any connection. It appears that the TIAs utilize directional wind information from the ventral giant interneurons to make a decision on the optimal direction of escape. The output connections, which project not only to cells within the ganglion of origin but also to adjacent ganglia and perhaps beyond, could allow this decision to be made throughout the thoracic ganglia as a single unit. However, nothing in these connections indicates a mechanism for making appropriate coordinated leg movements. Because each pair of legs plays a unique role in the turn, this coordination should be controlled by circuits dedicated to each leg. We suggest that this is accomplished by local interneurons between TIAs and leg motor neurons.

Evidence for decreased transport of tryptophan hydroxylase in Alzheimer's disease

Tryptophan hydroxylase (TPH) is the rate-limiting enzyme in the synthesis of serotonin and a specific marker for serotonergic neurons. These neurons are affected in Alzheimer's disease (AD) in several ways: serotonin is decreased in axon terminals, serotonin neurons accumulate neurofibrillary protein, and these neurons are lost in AD brains. One subcellular mechanism which may underlie degeneration of neurons in AD is decreased axonal transport with accumulation of enzymes and their potentially toxic metabolites in the cell body. To determine whether there is a defect in axonal transport in serotonin neurons in AD we measured TPH activity, serotonin and its oxidative metabolite 5-hydroxyindoleacetic acid (5-HIAA) in dorsal raphe cell bodies from Alzheimer and control cases. TPH activity is increased 4.7-fold in raphe neuron cell bodies in Alzheimer brains. Serotonin and 5-HIAA are increased by 4.0- and 2.0-fold, respectively in Alzheimer compared to control raphe cell bodies. In contrast, in synaptic terminals of the amygdala 5-HT and 5-HIAA were decreased by 41% and 50%, respectively in the same AD cases. We propose that the accumulation of TPH and its products in the raphe perikarya in AD results from a diminished transport of TPH to axon terminals. The accumulation of oxidative metabolites of serotonin may contribute to the degeneration of serotonergic neurons in AD.

In vitro synthetic activity of the juvenile ovotestis ofHelix aspersa: Influence of the brain and the dorsal bodies

A bioassay was developed inHelix aspersa to study the effect of known endocrine centers on the twomonth-old gonad, using organ culture. The incorporation of14C leucine and3H fucose in the juvenile gonad almost doubled over control levels, in the presence of the brain and the dorsal bodies.

Extirpation and transplantation of the brain of the snail Helix aspersa: a study of the survival of the animal and the implant

Dormant, hibernating snails whose brains (supraoesophageal cerebral ganglia and associated dorsal bodies) were removed by surgery continued to live retracted in their shells. The remaining ganglia of the circumoesophageal ring did not regenerate in the 12 months following the removal of the brain. The transplanted brains in the haemocoel (auto- or allo-graft) were not rejected and many of their cerebral neurosecretory cells and the endocrine dorsal bodies appeared normal structurally and functionally, as evidenced by ultrastructural and immunocytochemical studies. The data from these experiments demonstrate the possibility of studying by in vivo culture methods the roles of cerebral ganglia and endocrine dorsal bodies on the control of reproduction under different temperature regimes.

Neuropeptide Y-immunoreactive spinal neurons make close appositions on axons of primary sensory afferents

The dorsal cells in the lamprey are primary sensory neurons located in a parasagittal region of the spinal cord. In the same plane neuropeptide Y (NPY) immunoreactivity has been described. To investigate if the dorsal cells were in contact with NPY-immunoreactive (ir) fibers and cell bodies, intracellular injections of Lucifer yellow into identified dorsal cells were combined with NPY immunohistochemistry. NPY-ir varicosities were found to be in close apposition to both the descending and the ascending axon of dorsal cells. No NPY-ir boutons were seen in close contact with the dorsal cell bodies.

Regulation of the intracellular free calcium concentration in single rat dorsal root ganglion neurones in vitro.

1. Simultaneous whole-cell patch-clamp and Fura-2 microfluorimetric recordings of calcium currents (ICa) and the intracellular free Ca2+ concentration ([Ca2+]i) were made from neurones grown in primary culture from the dorsal root ganglion of the rat. 2. Cells held at -80 mV and depolarized to 0 mV elicited a ICa that resulted in an [Ca2+]i transient which was not significantly buffered during the voltage step and lasted long after the cell had repolarized and the current ceased. The process by which the cell buffered [Ca2+]i back to basal levels could best be described with a single-exponential equation. 3. The membrane potential versus ICa and [Ca2+]i relationship revealed that the peak of the [Ca2+]i transient evoked at a given test potential closely paralleled the magnitude of the ICa suggesting that neither voltage-dependent nor Ca2(+)-induced Ca2+ release from intracellular stores made a significant contribution to the [Ca2+]i transient. 4. When the cell was challenged with Ca2+ loads of different magnitude by varying the duration or potential of the test pulse, [Ca2+]i buffering was more effective for larger Ca2+ loads. The relationship between the integrated ICa and the peak of the [Ca2+]i transient reached an asymptote at large Ca2+ loads indicating that Ca2(+)-dependent processes became more efficient or that low-affinity processes had been recruited. 5. Inhibition of Ca2+ influx with neuropeptide Y demonstrated that inhibition of a large ICa produced minor alterations in the peak of the [Ca2+]i transient, while inhibition of smaller currents produced corresponding decreases in the [Ca2+]i transient. Thus, inhibition of the ICa was reflected by a change in the peak [Ca2+]i only when submaximal Ca2+ loads were applied to the cell, implying that modulation of [Ca2+]i is dependent on the activation state of the cells. 6. Intracellular dialysis with the mitochondrial Ca2+ uptake blocker Ruthenium Red in whole-cell patch-clamp experiments removed the buffering component which was responsible for the more efficient removal of [Ca2+]i observed when large Ca2+ loads were applied to the cell. 7. When cells were superfused with 50 mM-K+, [Ca2+]i transients recorded from the cell soma returned to control levels very slowly. Pharmacological studies indicated that mitochondria were cycling Ca2+ during this sustained elevation in [Ca2+]i. In contrast, [Ca2+]i transients recorded from cell processes returned to basal levels relatively rapidly. 8. Extracellular Na(+)-dependent Ca2+ efflux did not significantly contribute to buffering [Ca2+]i transients in dorsal root ganglion neurone cell bodies.(ABSTRACT TRUNCATED AT 400 WORDS)

Retrograde axonal transport in chronic ethanol-fed and thiamine-deficient rats

Retrograde axonal transport may play an important role in the feedback regulation of protein synthesis in neuronal perikarya, and the anterograde axonal transport of protein. The “dying-back” neuropathies associated with thiamine deficiency and chronic alcoholism may arise as a consequence of altered axonal transport. We have reported alterations in fast anterograde axonal transport in rats as a result of ethanol exposure or thiamine deficiency. The present studies were undertaken to determine whether retrograde transport was also affected by these experimental treatments. One group of rats was fed a liquid diet containing 6.7% ethanol for 16 weeks. Another group of rats was made thiamine deficient with a thiamine-free diet for 4 weeks. Retrograde axonal transport was labeled by injecting the left sciatic nerve unilaterally with 3H-N-succinimidyl propionate. This compound covalently labels proteins in the nerve at the site of injection and is accumulated by retrograde axonal transport to sensory nerve cell bodies in the dorsal root ganglia and motor nerve cell bodies in the spinal cord. After 7 days, dorsal root ganglia of chronic ethanol-fed rats showed a significant 45% decrease in the amount of accumulated retrograde label compared to controls. No significant differences in accumulation were found in the spinal cords. These results suggest that the peripheral neuropathies caused by chronic alcoholism and thiamine deficiency follow different etiologies, and that motor and sensory fibers are affected differently by ethanol.

On the central nervous system of Smeagolidae and Rhodopidae, two families questionably allied with the Gymnomorpha (Gastropoda: Euthyneura)

The central nervous systems (CNS) of Smeagol manneringi Climo, 1980 (Smeagolidae), of Rhodope veranü Kölliker, 1847, and of Rhodope transtrosa Salvini‐Plawén, 1989 are redescribed in detail. The smeagolid CNS exhibits diagnostic pulmonate characters (procerebrum, cerebral gland, dorsal bodies). Sharing a distinctly structured abdominal ganglion and other peculiarities, the Smeagolidae are closely related to the Onchidüdae, and both families are united as Onchidioidea. The consequences of this close relationship for the origin and evolution of the Gymnomorpha are discussed and the value of the pulmonate CNS for phylogenetics is reconsidered. On the basis of neural characters, which are correlated with the mode of breathing organs, the Pulmonata are divided into Basommatophora, Systellommatophora (Otinidae and Gymnomorpha) and Eupulmonata (ord. nov.: Trimusculidae, Ellobüdae, Stylommatophora).In contrast, the CNSs of the rhodopid species lack the pulmonate attributes, but show diagnostic opisthobranch characters such as a rhinophoral nerve. Accordingly, the Rhodopidae are excluded from the Pulmonata and are classified as a separate order Rhodopemorpha among the Opisthobranchia.

Changes in the fine structure of the endocrine dorsal body cells of Helisoma duryi (mollusca) induced by mating.

The morphology and the organization of the endocrine dorsal bodies (DB) of non-reproducing virgin and castrated, and reproducing mated Helisoma duryi have been examined using serial sectioning. The DB cells occur in two masses on the mid-dorsal side of the cerebral commissure, each of which has a cortical zone containing the cell bodies and a medulla where cell processes terminate. The cell bodies measure 10-15 μm in diameter, and are arranged in lobules of 6-12 cells. The complex cell processes are winding and terminate at various distances from their cell bodies in both reproducing and non-reproducing snails. Few 70-90-nm membrane-bound granules are found in the cell bodies and many are seen in the cell processes, which seem to penetrate the perineurium of the cerebral ganglia and make close contacts with neurosecretory cells. In reproducing snails the DB cells display a significantly larger amount of plasma membrane sproutings in the form of loops and circles compared to that in reproductively inactive virgin or castrated snails. Images of thin-sections and freeze-fracture replicas of these membranes suggest that they are gap junctions, which join the DB cells with each other. It is likely that gap junction-mediated cell to cell communication is involved in the activation of the DB cells for their role(s) in reproduction.

L'escargot ou les difficultés de l'hermaphrodisme

Summary The article summarizes the research carried out in Besancon on the stylommatophoran snail Helix aspersa, a pulmonate gastropod mollusc. The influence that external factors like photoperiod and temperature have on growth and reproduction was studied in this animal. The obtained results made possible a great development of snail breeding. The potentialities of the hermaphroditism emerge from the observations made on the ovotestis: differentiation and development of the different cell types, presence of fibronectin, richness in neuropeptides, existence of male and female steroids, vitellogenesis processes. In vivo experiments as well as in vitro cultures demonstrated the involvement of the cerebral complex in the control of reproduction. The dorsal bodies (DB)—(it consists of scattered cells)—stimulate the growth of the oocytes. The DB are under an inhibitory nervous control of the cerebral green cells (CGC); the FMRF-amide might be involved in this process. A map of the neurons of the cerebral compl...

Mating‐induced release of granules by the endocrine dorsal body cells of the snail Helisoma duryi (Mollusca)

AbstractThe hermaphrodite snail Helisoma duryi reproduces preferentially by cross‐fertilization. Virgin and castrated snails lay an insignificant number of egg masses. The fine structure of its endocrine dorsal bodies (DB), which regulate reproduction, has been studied in reproductively inactive virgin and castrated snails and in reproductively active mated snails, using tannic acid staining and autoradiography after injection of [3H]leucine. The DB cells of the mated snails appear synthetically active, containing scattered rough endoplasmic reticulum (RER) and probably smooth endoplasmic reticulum (SER), many Golgi complexes, and putative DB hormone‐containing granules. On the other hand, the DB cells of the virgin and castrated snails appear synthetically inactive, containing RER in circular stacks, few Golgi complexes, many lipid droplets, and scattered glycogen. Mitochondria appear slender in mated snails, whereas those in virgin and castrated snails appear large and spherical. With tannic acid treatment, the processes of the DB cells of mated snails exhibited more released granules than those of virgin and castrated snails. Many silver grains were seen on RER, Golgi complexes, and mitochondria in the autoradiographs of the DB cells of mated snails. It is suggested that the DB cells of the reproductively active snails are synthetically more active than those in virgin and castrated snails and that the DB cells may produce peptide hormone as well as a steroid hormone.

In vitro inhibition of methionine incorporation in the dorsal bodies of Helix aspersa by synthetic FMRFamide

1. In in vitro conditions, synthetic FMRFamide was shown to inhibit the uptake of labelled methionine by the dorsal bodies (DB)-containing connective tissue of Helix aspersa. 2. This effect occurred at physiological concentrations and in a dose-dependent manner. 3. Among the different cell types of the explants, the DB cells preferentially incorporated the radioactive precursor. 4. These results suggest that FMRFamide plays a biological role in controlling the DB activity (protein synthesis) of Helix aspersa.

Investigations of the Diurnal Activity of the Endocrine Dorsal bodies inHelix aspersa

Summary The activity of the endocrine dorsal bodies (DB) of the adult land snail Helix aspersa living in the field shows striking fluctuations during a 24 hr cycle. Quantitative electron microscopical data revealed that the number of secretory granules, the volume of the Golgi apparatus and the number of Golgi saccules containing electron-dense material were maximal at 1 am and minimal at 1 pm. The use of tannic acid indicated the exocytosis of secretory material was intense around 1 pm and only moderate at 1 am. The results suggest that, under natural conditions, the DB have a diurnal rhythm of activity, packaging secretory material into secretory granules mainly during the night and releasing it during the afternoon.

Neuropharmacologic Effects of Vibration on the Dorsal Root Ganglion

The neuropharmacologic effects of low frequency vibration on the dorsal root ganglion, a reported epidemiological cause of low-back pain, have only recently been described. This investigation was undertaken to validate the hypothesis that substance P and VIP, known to be produced in the dorsal root ganglion cell bodies, will be affected by low frequency vibration. Three New Zealand white rabbits were vibrated at discrete frequencies (2-10 Hz) to determine the resonant frequency of the rabbit spine. The resonating frequency was in the (3.5-5.0 Hz) range. The peak amplitude was at 4.5 Hz. Ten female New Zealand white rabbits were then paired into two groups of five. One group served as a control and had exactly the same procedures performed as the experimental group except for the vibration. The L4-5 and L5-6 dorsal root ganglia were removed bilaterally and prepared for substance P and VIP extraction by radioimmunoassay technique. The control rabbits mean immunoreactive substance P was 14.06 pg/ml tissue, whereas the experimental or vibrated rabbits had a mean of 8.40 pg/ml (P less than 0.003). The control rabbits mean immunoreactive vasoactive intestinal peptide was 9.58 pg/ml whereas the experimental or vibrated rabbits had a mean of 20.9 pg/ml, P less than 0.07. Substance P is only one of several dorsal root ganglion neuropeptides that may play a role in nociceptor transmission. VIP is a neuropeptide that plays a role in reorganization of the nervous system following injury. The effects of low frequency vibration on dorsal root ganglion transmitters are essential to the understanding of vibration as a cause of back pain.(ABSTRACT TRUNCATED AT 250 WORDS)

Postembryonic Development of Endocrine Dorsal Bodies and Neuroendocrine Egg Laying and Growth Hormone Producing Neurons ofLymnaea stagnalis

Summary The postembryonic development of three (neuro) endocrine centres in the snail Lymnaea stagnalis has been studied: (l) the endocrine Dorsal Bodies (DB), which are involved in the stimulation of vitellogenesis, and of growth, differentiation and secretory activity of the female accessory sex glands, (2) the Caudodorsal Cells (CDC), which control egg laying and egg-laying behaviour, and (3) the Light Green Cells (LGC), which stimulate body growth. Light microscopy, including immunocytochemistry with monoclonal antibodies, and electron microscopy show that the DB and LGC are already present in snails of 1 mm shell height, whereas CDC first appear in snails of 3 mm shell height. In such juvenile snails all cell types have a small size and occur in low numbers, but they show clear, morphological signs of formation of secretory granules. During development the cells strongly increase in size and, especially the DB cells, in number. The diameter of the secretory granules also increases, particularly in CD...