Ventral Cell Bodies Research Articles

Dual Cellular Supporters: Multi-Layer Glial Wrapping and the Penetrative Matrix Specialized in Deep-Sea Hydrothermal Vent Endemic Scale-Worms

Hydrothermal vent organisms undergo extreme environments that may require unique innovations. The present study reports a distinct case of cellular supportive systems in the nervous systems of a scale-worm, Branchinotogluma japonica, endemic to deep-sea hydrothermal vents. We found two organizations in the tissues of these animals. First, multi-layers of glia ensheath the ventral cell bodies of the brain and ventral nerve cord, in a manner similar to that of myelin or lamellar ensheathments. Second, matrices of numerous penetrative fibers, or tonofilaments, composed of bundles of ca. 20-nm fibers, are directly connected with the basal parts of epidermal cuticles and run into the diffuse intercellular spaces of the brain neuropils and peripheral nerves. Both types of tissue might be mechanical supportive structures for the neuronal cell bodies. In addition, as a glial function, the multi-layer membranes and the epithelial support cells may be required for physicochemical homeostatic regulation to filter toxic heavy metals and for inhibiting breakdown of glial membrane integrity under strong oxidative stress imposed by hypoxia in the hydrothermal vent environment. Similar functions are known in the well-studied cases of the blood-brain barrier in mammalian brains, including in human stroke.

UNC-6 and UNC-40 promote dendritic growth through PAR-4 in Caenorhabditis elegans neurons

Axons navigating through the developing nervous system are instructed by external attractive and repulsive cues. Emerging evidence suggests the same cues control dendrite development, but it is not understood how they differentially instruct axons and dendrites. We studied a C. elegans motor neuron whose axon and dendrite adopt different trajectories and lengths. We found that the guidance cue UNC-6 (Netrin) is required for both axon and dendrite development. Its repulsive receptor UNC-5 repelled the axon from the ventral cell body, whereas the attractive receptor UNC-40 (DCC) was dendritically enriched and promotes antero-posterior dendritic growth. Although the endogenous ventrally secreted UNC-6 instructs axon guidance, dorsal or even membrane-tethered UNC-6 could support dendrite development. Unexpectedly, the serine-threonine kinase PAR-4 (LKB1) was selectively required for the activity of the UNC-40 pathway in dendrite outgrowth. These data suggest that axon and dendrite of one neuron interpret common environmental cues with different receptors and downstream signaling pathways.

Octopamine-like immunoreactivity in the brain and suboesophageal ganglion of two parasitic wasps, Cotesia glomerata and Cotesia rubecula

Abstract Two closely related parasitoid wasp species, Cotesia glomerata L. and C. rubecula Marshall (Hymenoptera: Braconidae), differ in their display of associative learning and memory during host searching. As octopamine is involved in learning and memory in insects we investigated octopaminergic pathways in the brain and suboesophageal ganglion (SOG) of the two wasps. We used an anti-octopamine antibody and subsequent whole mount analysis using a confocal laserscanning microscope and pertinent software. Three groups of octopaminergic cells were located in the brain and suboesophageal ganglion. One group was located near the antennal lobes and consisted of six to eight cell bodies. A second group was located ventrally in the SOG and was most likely formed by ventral unpaired median (VUM) and VCBN (ventral cell body neurite) neurons. A third group was located in the pars intercerebralis and consisted of four to six cells. Octopamine-like immunoreactivity was furthermore present in the central body, protocerebral bridge, the SOG, antennal lobe, near the alpha and beta lobes of the mushroom bodies and in the mushroom body calyces. Due to the used methods and a high variability in staining intensity it was not possible to detect if there were any differences in the number of neurons, in arborisation patterns or in labelling intensity between the two wasp species.

Evidence for the association of FMRFamide-related peptides with the spermatheca of Locusta migratoria

The association of FMRFamide-related peptides (FaRPs) with the spermatheca of Locusta migratoria was demonstrated using radioimmunoassay and immunohistochemical techniques. The physiological effects of various FaRPs on the neurally evoked contractions of the spermatheca were also examined. FMRFamide-like immunoreactivity (FLI) was demonstrated in processes and cell bodies situated in the VIIIth (terminal) abdominal ganglion. These included an anterior, central and posterior pair of ventral cell bodies positioned near the midline of the ganglion, in addition to two bilaterally paired dorsal cell bodies in the posterior region of the VIIIth abdominal ganglion. Two axons displaying FLI proceed down the ventral ovipositor nerve (VON) and into the receptaculum seminis nerve which innervates the anterior regions of the spermatheca. FLI was also noted in processes on the spermathecal muscle with the highest density occurring on the spermathecal sac and coil duct. FaRPs applied to the spermathecal muscle included GQERNFLRFamide, NFIRFamide, ADDRNFIRFamide, YGGFMRFamide, FMRFamide, ADVGHVFLRFamide and SchistoFLRFamide (PDVDHVFLRFamide). Dose-dependent physiological effects were only noted for FMRFamide, ADVGHVFLRFamide and SchistoFLRFamide. FMRFamide led to a dose-dependent increase in the amplitude of neurally evoked contractions with a threshold of approximately 5 × 10 −7 M. SchistoFLRFamide, and ADVGHVFLRFamide, had an inhibitory effect, decreasing the amplitude of neurally evoked spermathecal contractions.

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.

Activity of myotomal motoneurons during fictive swimming in frog embryos.

1. Dye-filled microelectrodes have been used to identify and to examine the electrical activity of spinal cord motoneurons during fictive swimming in amphibian embryos. 2. Impaled neurons all had ventral cell bodies, dorsal, lateral, or ventral dendrites, and most showed either damaged or complete peripheral axons projecting out to the myotomes. It was rarely possible to identify cells by recording 1:1 motor root spikes evoked by intracellular current pulses. 3. During fictive swimming, motoneurons are tonically depolarized, fire 1 spike per swimming cycle, and are inhibited in phase with motor root activity on the opposite side. Motoneurons can also fire synchronously on the two sides, at double the normal swimming frequency. They occasionally also show a pattern of lower frequency alternating activity in which there is a prolonged burst of discharge on each cycle.

Sound production and hearing in the cicada,Cicadetta sinuatipennis osh. (Homoptera, Cicadidae)

1. The spontaneous song ofCicadetta sinuatipennis males consists of alternating tymbal sound production and wing-clicking (Fig. 1). The temporal and spectral characteristics of tymbal and wing sounds are unalike (Table 1, Fig. 7). 2. Wing-clicking is the result of sudden lateral movements of the forewings. A click is generated by the outward buckling of a specialized caudal margin of a forewing which is locked in a narrow groove on the scutellum before sound production (Fig. 2). 3. Central projections of auditory and motor fibres with axons in the tympanal and tensor nerves were shown with the help of axonal cobalt iontophoresis (Figs. 3–5). The anatomy of the large tymbal motor neuron and three tensor motor neurons with ventral cell bodies is described. 4. Stimulus thresholds for the summed response of primary auditory fibres were measured for different sound frequencies. The resulting hearing curves show that the auditory organs have a sharp peak of sensitivity near 6–6.5 kHz. When stimulated by the natural spontaneous song of a male, the ear gives clear “on”-responses to each click of a wing sound with thresholds of about 21–31 dB SPL and very weak asynchronous reaction to tymbal sounds with thresholds of about 70 dB SPL. This is a result of the different spectral content of these sounds (Fig. 6, 7). It is suggested that wing sounds are used for long-range communication between males and females. Tymbal sounds can be used only for short-range communication or have another, possibly repellent function.

The morphology of the fourth abdominal ganglion of the hermit crab: A light microscope study.

The hermit crab, Pagurus pollicarus, has the same organization in its fourth abdominal ganglion as its macruran relatives in spite of the reduction in abdominal muscles, sensory receptors, and appendages. Connective axons are grouped into discrete bundles between which five groups of commissural fibers run to connect left and right sides. The neurites of ventral cell bodies run dorsally in characteristic groups between the connective bundles. The hermit crab fourth ganglion has two thirds as many cells as the crayfish and is laterally compressed. This reduction appears related to the reduction in the sizes of the ganglionic roots. The ventral fine fibered neuropil is larger on the left than the right side reflecting the loss of pleopods on the right side. The basic organization of decapod abdominal ganglia appears to permit considerable integrative flexibility within a relatively conservative morphological framework.