Synaptic Actions of Oesophageal Proprioceptors in the Mollusc, Philine

1981 ◽  
Vol 94 (1) ◽  
pp. 95-104
Author(s):  
J. N. SIGGER ◽  
D. A. DORSETT
Keyword(s):  
Receptive Fields ◽  
Large Cell ◽  
The Other ◽  
Small Cells ◽  
Sensory Cells ◽  
Periodic Activity ◽  
Buccal Ganglia ◽  
Excitatory Synaptic Input ◽  
Feeding Cycle ◽  
Protraction Phase

The buccal ganglia of Philine each contain a group of mechanoreceptors, consisting of 1 large and 3 small cells, with receptive fields in the oesophagus. Synaptic contacts occur between the receptors; the large cell providing an EIPSP input to its contralateral partner and to the two groups of smaller receptors. The small receptors make weak excitatory contacts with both the large receptors. The sensory cells synapse with other buccal motoneurones and interneurones, some of which show periodic activity associated with the feeding movements. Protraction phase neurones are divisible into two groups, one of which receives EPSPs from the receptors, while the other group receives IPSPs. Retraction phase neurones receive a biphasic EIPSP. The receptors provide excitatory synaptic input to a pair of interneurones which ‘gate’ the feeding cycle. A third class of neurones which are not rhythmically active during feeding receive a predominantly inhibitory EIPSP.

The Morphology and Physiological Properties of the Small White Neurones in the Buccal Ganglia of Tritonia Hombergi

1986 ◽  
Vol 122 (1) ◽  
pp. 237-256
Author(s):  
D. A. DORSETT
Keyword(s):  
Phase I ◽  
Feeding Activity ◽  
The Other ◽  
Inhibitory Input ◽  
Cyclic Activity ◽  
Buccal Ganglia ◽  
Physiological Properties ◽  
Feeding Cycle ◽  
F Cells ◽  
P Cells

The two small white (W) cells in the buccal ganglia of Tritonia hombergi can initiate and modulate cyclic activity in the pattern generating neurones which drive feeding activity in the buccal mass. They also make extensive monosynaptic connections with the buccal motoneurones, generating EPSPs on protractor (P) cells, IPSPs on retractor (R) cells, and EIPSPs on the small radula flattener (F) cells. Two F motoneurones receive a chemically mediated, facilitating EPSP from the W cells. Inactive W cells receive weak excitatory feedback from the pattern generating network interneurones (FPG) in phase I of the feeding cycle and also from some F cells. Prolonged depolarization of one W cell recruits the other. When both are active they adopt a patterned burst mode with a common inhibitory input in phase I.

Micromere lineages in the glossiphoniid leechHelobdella

Development ◽  
2002 ◽  
Vol 129 (3) ◽  
pp. 719-732 ◽  
Author(s):  
Françoise Z. Huang ◽  
Dongmin Kang ◽  
Felipe-Andres Ramirez-Weber ◽  
Shirley T. Bissen ◽  
David A. Weisblat
Keyword(s):  
Early Development ◽  
Normal Development ◽  
The Other ◽  
Small Cells ◽  
Spiral Cleavage ◽  
Helobdella Robusta

In leech embryos, segmental mesoderm and ectoderm arise from teloblasts by lineages that are already relatively well characterized. Here, we present data concerning the early divisions and the definitive fate maps of the micromeres, a group of 25 small cells that arise during the modified spiral cleavage in leech (Helobdella robusta) and contribute to most of the nonsegmental tissues of the adult. Three noteworthy results of this work are as follows. (1) The c′′′ and dm′ clones (3d and 3c in traditional nomenclature) give rise to a hitherto undescribed network of fibers that run from one end of the embryo to the other. (2) The clones of micromeres b′′ and b′′′ (2b and 3b in traditional nomenclature) die in normal development; the b′′ clone can be rescued to assume the normal c′′ fate if micromere c′′ or its clone are ablated in early development. (3) Two qualitative differences in micromere fates are seen between H. robusta (Sacramento) and another Helobdella sp. (Galt). First, in Helobdella sp. (Galt), the clone of micromere b′′ does not normally die, and contributes a subset of the cells arising exclusively from c′′ in H. robusta (Sacramento). Second, in Helobdella sp. (Galt), micromere c′′′ makes no definitive contribution, whereas micromere dm′ gives rise to cells equivalent to those arising from c′′′ and dm′ in H. robusta (Sacramento).

A System of Electrically Coupled Small Cells in the Buccal Ganglia of the Pond Snail Planorbis Corneus

1972 ◽  
Vol 56 (3) ◽  
pp. 621-637
Author(s):  
MICHAEL S. BERRY
Keyword(s):  
Synaptic Input ◽  
Action Potentials ◽  
Burst Activity ◽  
Small Cells ◽  
Pond Snail ◽  
Trigger System ◽  
Buccal Ganglia ◽  
Large Numbers ◽  
Planorbis Corneus

1. The buccal ganglia of Planorbis contain a population of electrically coupled small cells. This has been studied, in preparations of isolated ganglia, by recording intracellularly from the cells two at a time. 2. The population is usually silent but activity initiated in any one of its members tends to spread to the rest of the population in both ganglia. Failure of spread, or fatigue, gradually occurs on repetition. 3. The group has the properties of a trigger system, initiating prolonged patterned activity in large numbers of neurones in the buccal ganglia. This may normally initiate feeding. 4. In addition to central processes, both in the buccal ganglia and to the rest of the CNS, the system has peripheral axons in most of the buccal nerves. No synaptic input could be demonstrated. 5. Action potentials in some of the cells increase greatly in duration with repetition. The resulting electrotonic EPSP's, recorded in closely coupled trigger cells, correspondingly increase in size. The possible integrative significance of this is discussed, especially its effect in offsetting fatigue. 6. In some preparations spontaneous bursting occurred in trigger cells and this elicited burst activity in large neurones, including motoneurones. The system may have an intrinsic pacemaker.

Fine Structure of the Eye of a Nudibranch Mollusc, Hermissenda Crassicornis

1967 ◽  
Vol 2 (3) ◽  
pp. 349-358
Author(s):  
R. M. EAKIN ◽  
JANE A. WESTFALL ◽  
M. J. DENNIS
Keyword(s):  
Electron Microscopy ◽  
Fine Structure ◽  
Optic Nerve ◽  
Light And Electron Microscopy ◽  
The Other ◽  
Sensory Cells ◽  
Nerve Fibres ◽  
Supporting Cells ◽  
Small Bodies ◽  
Receptor Cells

The eye of a nudibranch, Hermissenda crassicornis, was studied by light and electron microscopy. Three kinds of cells were observed: large sensory cells, each bearing at one end an array of microvilli (rhabdomere) and at the other end an axon which leaves the eye by the optic nerve; large pigmented supporting cells; and small epithelial cells, mostly corneal. There are five sensory cells, and the same number of nerve fibres in the optic nerve. The receptor cells contain an abundance of small vesicles, 600-800 Å in diameter. The lens is a spheroidal mass of osmiophilic, finely granular material. A basal lamina and a capsule of connective tissue enclose the eye. In some animals the eye is ‘infected’ with very small bodies, 4-5 µ in diameter, thought to be symbionts.

The Integration of the Patterned Output of Buccal Motoneurones During Feeding in Tritonia Hombergi

1979 ◽  
Vol 79 (1) ◽  
pp. 23-40
Author(s):  
A.G. M. BULLOCH ◽  
D. A. DORSETT
Keyword(s):  
Feeding Activity ◽  
Electrical Coupling ◽  
Cell Activity ◽  
Giant Cells ◽  
Posterior Border ◽  
Buccal Ganglion ◽  
Synaptic Inputs ◽  
Proprioceptive Input ◽  
Buccal Ganglia ◽  
Feeding Cycle

Three phases of activity may be recognized in the buccal mass of Tritonia hombergi during the feeding cycle. These have been termed Protraction, Retraction and Flattening. Each phase is driven by a group of motoneurones along the posterior border of the buccal ganglia. The patterned bursting observed in the motoneurone groups during feeding activity is phased by synaptic inputs which are common to two or more groups. Evidence is presented which indicates these inputs are derived from three unidentified multi-action interneurone sources within each buccal ganglion, and whose action primarily determines the patterned output of the motoneurones. Electrical coupling between between synergistic motoneurones and, in one case, post-inhibitory rebound, contribute to the synchronization of group activity. Proprioceptive input to the motoneurones was not identified, but may project to the interneurones. Some small neurones having synaptic inputs on the motoneurones appropriate to two of the interneurones were found, but require confirmation in this role. The cerebral giant cells synapse on representatives of three motoneurone groups, and also activate the buccal interneurones driving the feeding cycle. The patterned activity of the motoneurones can occur in the absence of cerebral cell activity.

Giant Primary Neuroendocrine Neoplasms of the Liver: Report of 2 Cases With Molecular Characterization

2019 ◽  
Vol 27 (8) ◽  
pp. 893-899
Author(s):  
Laura G. Pastrián ◽  
Ignacio Ruz-Caracuel ◽  
Raul S. Gonzalez
Keyword(s):  
World Health Organization ◽  
Neuroendocrine Tumor ◽  
Large Cell ◽  
The Other ◽  
World Health ◽  
Neuroendocrine Neoplasms ◽  
Molecular Testing ◽  
Well Differentiated ◽  
Grade 3 ◽  
Health Organization

Primary neuroendocrine neoplasms of the liver have occasionally been reported in the liver, though many reports do not convincingly exclude metastases. In this article, we report 2 “giant” hepatic neuroendocrine lesions without evidence of a primary elsewhere after clinical workup. One occurred in a 21-year-old male; the lesion was a large cell neuroendocrine carcinoma measuring 24 cm. The patient died of disease in 10 months. The other occurred in a 25-year-old patient, was 18 cm wide, and was diagnosed as a well-differentiated neuroendocrine tumor, World Health Organization grade 3. The patient died of disease after 30 months. Molecular testing demonstrated only the presence of TP53 mutations in common. These cases expand our knowledge of seemingly primary neuroendocrine neoplasms of the liver, in particular, giant cases measuring more than 8 cm. Guidelines for clinical workup and therapy for these lesions remain unclear, but future thorough workup of such cases is necessary for specific characterization.

Synaptic Modulation Contributes to Firing Pattern Generation in Jaw Motor Neurons During Rejection of Seaweed in Aplysia kurodai

1999 ◽  
Vol 82 (5) ◽  
pp. 2579-2589 ◽  
Author(s):  
Tatsumi Nagahama ◽  
Kenji Narusuye ◽  
Hidekazu Arai
Keyword(s):  
Motor Neurons ◽  
Firing Frequency ◽  
Pattern Generation ◽  
Jaw Movements ◽  
Japanese Species ◽  
Initial Portion ◽  
Synaptic Modulation ◽  
Buccal Ganglia ◽  
Cerebral Neurons ◽  
Protraction Phase

Japanese species, Aplysia kurodai, feeds well on Ulva but rejects Gelidium ( Geli.) or Pachydictyon ( Pach.) with different rhythmic patterned movements of the jaws and radula. During ingestion the jaws open at the radula-protraction phase and remain half open at the initial phase of the radula-retraction, whereas during rejection the jaws open similarly but start to close immediately after the onset of the radula-retraction. These can be induced not only by the natural seaweed but by the extract solutions. We previously showed that the change of the patterned jaw movements from the ingestion to the rejection may result from the decrease in the delay of the firing onset of the jaw-closing (JC) motor neurons during their depolarization. This diminished delay produces a phase advance relative to the radula-retraction phase. In that study, we showed that during ingestion the buccal multiaction (MA) neurons may generate the delay of firing onset of the JC motor neurons by producing monosynaptic inhibitory postsynaptic potentials (IPSPs) during the initial portion of their depolarization. In the present experiments, the firing patterns in the MA neurons induced by application of the Geli. or Pach. extract to the lips were explored in the semi-intact preparations. During the Pach. response the duration and the firing frequency of the MA firing at each depolarizing phase were decreased in comparison with the Ulvaresponse. No decreases in the MA firing were observed during the Geli. response, suggesting that the similar patterned jaw movements during rejection of Geli. and Pach. may be generated by different neural mechanisms. Moreover, the size of the MA-induced IPSP in the JC motor neurons was largely decreased by application of the Geli. or Pach. extract to the lips in the reduced preparations consisting of the tentacle-lips and the cerebral-buccal ganglia. Voltage-clamp experiments on the JC motor neurons showed that the size of synaptic current induced by the MA spikes was decreased by application of these solutions to the lips. The decrease was induced when the buccal ganglia were bathed in a solution to block polysynaptic pathways. These results suggest that the advance of the onset of the JC firing at each depolarizing phase during the Geli. or Pach. response may be mainly or partly caused by the decrease in the size of the MA-induced IPSP in the motor neurons. Modulatory action of cerebral neurons or peripheral afferent neurons in the lip region may contribute to this synaptic plasticity.

scholarly journals Neutral glycosphingolipids and gangliosides of human lung and lung tumours

1979 ◽  
Vol 179 (1) ◽  
pp. 199-211 ◽  
Author(s):  
R Narasimhan ◽  
R K Murray
Keyword(s):  
Cancer Cells ◽  
Squamous Cell ◽  
Human Lung ◽  
Large Cell ◽  
The Other ◽  
Polymorphonuclear Leucocytes ◽  
Lung Tumours ◽  
Neutral Glycosphingolipids ◽  
Human Tumours

In order to help determine whether alterations of the profiles of glycosphingolipids occur consistently in human tumours, the neutral glycosphingolipids and gangliosides of nine lung tumours (one adenocarcinoma, four squamous cell, two mixed adeno-squamous cell, one large cell and one oat-cell carcinomata) were analysed. The control tissue consisted of adjacent lung; it contained neutral glycosphingolipids corresponding in properties to glucosyl-, lactosyl-, globotriaosyl- and globotetraosyl-ceramides. All of the tumours also contained these four neutral glycosphingolipids. However, in addition, five of the tumours (two of the squamous, the large cell and the two mixed adeno-squamous cell carcinomata) contained neutral glycosphingolipids corresponding in properties to lactotriaosyl- and neolactotetraosyl-ceramides; these same tumours also exhibited higher amounts of lactosylceramide than the other tumours analysed. Both of the two former neutral glycosphingolipids and very substantial amounts of the latter neutral glycosphingolipid were detected in pneumonic lung and in polymorphonuclear leucocytes; it thus appears possible that these particular compounds were derived from these latter cells rather than from the tumour cells. The ganglioside patterns of the tumours were almost equivalent in complexity to that exhibited by the control lung tissue. This study shows that the profiles of two major classes of glycosphingolipids (neutral glycosphingolipids and gangliosides) occurring in lung tumours are almost as complex as those of the parent tissue, a finding in contrast with the notably simplified patterns of these lipids found in many cancer cells grown in vitro. It also suggests that when lactotriaosyl- and neolactotetraosyl-ceramides and high amounts of lactosylceramide are detected in human tumours, the possibility must be considered that these compounds are derived from polymorphonuclear leucocytes.

Spatial representations of self and other in the hippocampus

Science ◽  
2018 ◽  
Vol 359 (6372) ◽  
pp. 213-218 ◽  
Author(s):  
Teruko Danjo ◽  
Taro Toyoizumi ◽  
Shigeyoshi Fujisawa
Keyword(s):  
Receptive Fields ◽  
Pyramidal Cells ◽  
Spatial Location ◽  
The Self ◽  
The Other ◽  
Spatial Representations ◽  
Self And Other ◽  
Ca1 Pyramidal Cells ◽  
Ca1 Region ◽  
Reward Information

An animal’s awareness of its location in space depends on the activity of place cells in the hippocampus. How the brain encodes the spatial position of others has not yet been identified. We investigated neuronal representations of other animals’ locations in the dorsal CA1 region of the hippocampus with an observational T-maze task in which one rat was required to observe another rat’s trajectory to successfully retrieve a reward. Information reflecting the spatial location of both the self and the other was jointly and discretely encoded by CA1 pyramidal cells in the observer rat. A subset of CA1 pyramidal cells exhibited spatial receptive fields that were identical for the self and the other. These findings demonstrate that hippocampal spatial representations include dimensions for both self and nonself.

Leech Mechanosensation

2017 ◽  
Author(s):  
Brian D. Burrell
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Sensory Neurons ◽  
Receptive Fields ◽  
Model Systems ◽  
Sensory Cells ◽  
Mechanical Stimuli ◽  
Nociceptive Neurons ◽  
Mechanosensory Neurons ◽  
The Central Nervous System

The medicinal leech (Hirudo verbana) is an annelid (segmented worm) and one of the classic model systems in neuroscience. It has been used in research for over 50 years and was one of the first animals in which intracellular recordings of mechanosensory neurons were carried out. Remarkably, the leech has three main classes of mechanosensory neurons that exhibit many of the same properties found in vertebrates. The most sensitive of these neurons are the touch cells, which are rapidly adapting neurons that detect low-intensity mechanical stimuli. Next are the pressure cells, which are slow-adapting sensory neurons that respond to higher intensity, sustained mechanostimulation. Finally, there are nociceptive neurons, which have the highest threshold and respond to potentially damaging mechanostimuli, such as a pinch. As observed in mammals, the leech has separate mechanosensitive and polymodal nociceptors, the latter responding to mechanical, thermal, and chemical stimuli. The cell bodies for all three types of mechanosensitive neurons are found in the central nervous system where they are arranged as bilateral pairs. Each neuron extends processes to the skin where they form discrete receptive fields. In the touch and pressure cells, these receptive fields are arranged along the dorsal-ventral axis. For the mechano-only and polymodal nociceptive neurons, the peripheral receptive fields overlap with the mechano-only nociceptor, which also innervates the gut. The leech also has a type of mechanosensitive cell located in the periphery that responds to vibrations in the water and is used, in part, to detect potential prey nearby. In the central nervous system, the touch, pressure, and nociceptive cells all form synaptic connections with a variety of motor neurons, interneurons, and even each other, using glutamate as the neurotransmitter. Synaptic transmission by these cells can be modulated by a variety of activity-dependent processes as well as the influence of neuromodulatory transmitters, such as serotonin. The output of these sensory neurons can also be modulated by conduction block, a process in which action potentials fail to propagate to all the synaptic release sites, decreasing synaptic output. Activity in these sensory neurons leads to the initiation of a number of different motor behaviors involved in locomotion, such as swimming and crawling, as well as behaviors designed to recoil from aversive/noxious stimuli, such as local bending and shortening. In the case of local bending, the leech is able to bend in the appropriate direction away from the offending stimuli. It does so through a combination of which mechanosensory cell receptive fields have been activated and the relative activation of multiple sensory cells decoded by a layer of downstream interneurons.

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