Conduction and coordination in deganglionated ascidians

2000 ◽  
Vol 78 (9) ◽  
pp. 1626-1639 ◽  
Author(s):  
G O Mackie ◽  
R C Wyeth
Keyword(s):  
Body Wall ◽  
Motor Nerve ◽  
Histological Study ◽  
The Body ◽  
Nerve Terminals ◽  
Sea Anemones ◽  
Nerve Net ◽  
Electrophysiological Recordings ◽  
Motor Neurones ◽  
Conduction Of Excitation

The behaviour of Chelyosoma productum and Corella inflata (Ascidiacea) was studied in normal and deganglionated animals. Chelyosoma productum lived for over a year after deganglionation and the ganglion did not regenerate. Electrophysiological recordings were made from semi-intact preparations. Responses to stimulation and spontaneous activity continued to be transmitted through the body wall and branchial sac after deganglionation. Spread was slow, decremental, and facilitative. Treatment with >10 µg·mL-1 d-tubocurarine abolished all responses, indicating that nerves mediate conduction of excitation after deganglionation. Histological study using cholinesterase histochemistry and immunolabelling with antisera against tubulin and gonadotropin-releasing hormone showed no evidence of a peri pheral nerve net in regions showing conduction, contrary to previous claims. The cell bodies of the motor neurones were found to lie entirely within the ganglion or its major roots. Their terminal branches intermingled to form netlike arrays. Sensory neurons were identified with cell bodies in the periphery, in both the body wall and the branchial sac. Their processes also intermingled in netlike arrays before entering nerves going to the ganglion. It is concluded that the "residual" innervation that survives deganglionation is composed of either interconnected motor nerve terminals, interconnected sensory neurites, or some combination of the two. In re-inventing the nerve net, ascidians show convergent evolution with sea anemones, possibly as an adaptation to a sessile existence.

scholarly journals A method for recording electrical activity from the body wall nerve nets in sea anemones

1995 ◽  
Vol 198 (3) ◽  
pp. 817-820
Author(s):  
K Cho ◽  
I D McFarlane
Keyword(s):  
Electrical Activity ◽  
Body Wall ◽  
Myoepithelial Cells ◽  
The Body ◽  
Sea Anemones ◽  
Nerve Net ◽  
Slow Conduction ◽  
Calliactis Parasitica ◽  
Type C ◽  
First Time

Glass microelectrodes were used to record electrical activity from thin rings cut from the column of the sea anemone Calliactis parasitica. This is the first time that pulses have been recorded from the nervous system in the column. Three pulse types were detected, types A, B and C. Type A pulses are probably associated with neurones of the through-conducting nerve net. Type B pulses may be from the endodermal slow conduction system (SS2). Type C pulses have not previously been recorded and are thought to represent activity in a local nerve net. At this stage we cannot positively state whether the recordings are intracellular from endodermal myoepithelial cells or are extracellular from the sub-epithelial region.

Viso-Elastic Properties of the Body-Wall of Sea Anemones

1962 ◽  
Vol 39 (3) ◽  
pp. 373-386
Author(s):  
R. MCN. ALEXANDER
Keyword(s):  
Tensile Stress ◽  
Elastic Properties ◽  
Body Wall ◽  
The Body ◽  
Polymeric System ◽  
Retardation Time ◽  
Sea Anemones

1. Creep of narcotized Metridium and Calliactis body-wall at constant tensile stress has been studied quantitatively. 2. It was found to be reversible, and seemed to be controlled by the mesogloea. Its course could be represented by equations of the formε(t)= εo+ευ(I-e-t/τ),where the retardation time τ was about 1 hr. for Metridium and many hours for Calliactis. 3. The results can most simply be explained in terms of a cross-linked and a noncross-linked polymeric system, acting in parallel. An explanation in terms of a lattice of inextensible fibres is not satisfactory. 4. The results are discussed in relation to the behaviour of the animals.

The effect of the anthelmintic emodepside at the neuromuscular junction of the parasitic nematode Ascaris suum

Parasitology ◽  
2003 ◽  
Vol 126 (1) ◽  
pp. 79-86 ◽  
Author(s):  
J. WILLSON ◽  
K. AMLIWALA ◽  
A. HARDER ◽  
L. HOLDEN-DYE ◽  
R. J. WALKER
Keyword(s):  
Neuromuscular Junction ◽  
Body Wall ◽  
Parasitic Nematode ◽  
Ascaris Suum ◽  
Muscle Relaxation ◽  
The Body ◽  
The Novel ◽  
Similar Action ◽  
Inhibitory Neurotransmitter ◽  
Electrophysiological Recordings

Here we report on the action of the novel cyclo-depsipeptide anthelmintic, emodepside, on the body wall muscle of the parasitic nematode, Ascaris suum. Emodepside caused (i) muscle relaxation, (ii) inhibition of muscle contraction elicited by either acetylcholine (ACh), or the neuropeptide, AF2 (KHEYLRFamide) and (iii) a rapid relaxation of muscle tonically contracted by ACh. The inhibitory action of emodepside on the response to ACh was not observed in a denervated muscle strip, indicating that it may exert this action through the nerve cord, and not directly on the muscle. Electrophysiological recordings showed emodepside elicited a Ca++-dependent hyperpolarization of muscle cells. Furthermore, the response to emodepside was dependent on extracellular K+, similar to the action of the inhibitory neuropeptides PF1 and PF2 (SDPNFLRFamide and SADPNFLRFamide). Thus emodepside may act at the neuromuscular junction to stimulate release of an inhibitory neurotransmitter or neuromodulator, with a similar action to the PF1/PF2 neuropeptides.

scholarly journals Histology and Mucous Histochemistry of the Integument and Body Wall of a Marine Polychaete Worm,Ophryotrochan. sp. (Annelida: Dorvilleidae) Associated with Steelhead Trout Cage Sites on the South Coast of Newfoundland

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
H. M. Murray ◽  
D. Gallardi ◽  
Y. S. Gidge ◽  
G. L. Sheppard
Keyword(s):  
Alcian Blue ◽  
Body Wall ◽  
Histological Study ◽  
Periodic Acid ◽  
The Body ◽  
South Coast ◽  
Steelhead Trout ◽  
The South ◽  
Periodic Acid Schiff ◽  
Marine Polychaete

Histology and mucous histochemistry of the integument and body wall of a marine polychaete worm,Ophryotrochan. sp. (Annelida: Dorvilleidae) associated with Steelhead trout cage sites on the south coast of Newfoundland. A new species of polychaete (Ophryotrochan. sp. (Annelida: Dorvilleidae)) was identified from sediment below Steelhead trout cages on the south coast of Newfoundland, Canada. The organisms were observed to produce a network of mucus in which groups of individuals would reside. Questions regarding the nature and cellular source of the mucus were addressed in this study. Samples of worms were taken from below cages and transported to the laboratory where individuals were fixed for histological study of the cuticle and associated mucus histochemistry. The body wall was organized into segments with an outer cuticle that stained strongly for acid mucopolysaccharides. The epidermis was thin and supported by loose fibrous connective tissue layers. Channels separating individual segments were lined with cells staining positive for Alcian blue. Mucoid cellular secretions appeared thick and viscous, strongly staining with Alcian blue and Periodic Acid Schiff Reagent. It was noted that lateral channels were connected via a second channel running through the anterior/posterior axis. The role of mucus secretion is discussed.

Pigments of Chaetopterus variopedatus (polychaeta)

1959 ◽  
Vol 150 (941) ◽  
pp. 509-538 ◽  
Keyword(s):  
Body Wall ◽  
Histological Study ◽  
The Body ◽  
Bile Pigment ◽  
Green Pigment ◽  
Chaetopterus Variopedatus ◽  
Pigment Type ◽  
Constant Feature ◽  
Chlorophyll Derivatives

A chemical and histological study has been made of the pigments of the polychaete worm Chaetopterus variopedatus . The conspicuous green colour of the gut in the middle and posterior regions is due to a green pigment hitherto known as ‘chaetopterin’, which is localized in small green spherules in the gut epithelial cells. ‘Chaetopterin’ is a mixture of phaeophorbides a and b , the former predominating. Other pigments found in the gut-wall of the middle region of the worm include the chlorophyll derivatives iso -phaeophorbide d , dioxymesophyllochlorin, copper phaeophorbide chelation compounds, and possibly rhodoporphyrin g 7 carboxylic acid; coproporphyrin III; bile pigment-type compounds turbo-glaucobilin and helioporobilin, and the carotenoids β -carotene and traces of a xanthophyll. The body wall contains β -carotene. A black melanin is present in the black chaetae of setigerous segment IV, and a reddish melanoid pigment in a red stripe at the anterior margin of the head. Pigments present in the faeces include phaeophorbides and β -carotene. The phaeophorbides a and b are derived from chlorophylls a and b in the animal’s food (detritus). The green spherules in vivo are not fluorescent, suggesting that fluorescent, suggesting that the pigment is adsorbed on to some large molecule, possibly a mucopolysaccharide. No evidence was found that the green spherules are symbionts. Since they are such a constant feature of the animals, even during prolonged starvation, they would appear to play some essential biochemical role.

scholarly journals Okadaic acid disrupts clusters of synaptic vesicles in frog motor nerve terminals

1994 ◽  
Vol 124 (5) ◽  
pp. 843-854 ◽  
Author(s):  
WJ Betz ◽  
AW Henkel
Keyword(s):  
Okadaic Acid ◽  
Synaptic Vesicles ◽  
Motor Nerve ◽  
Time Lapse ◽  
Nerve Terminals ◽  
Cell Nuclei ◽  
Motor Nerve Terminals ◽  
Electrophysiological Recordings ◽  
Translocation Mechanism ◽  
Active Zones

The fluorophore FM1-43 appears to stain membranes of recycled synaptic vesicles. We used FM1-43 to study mechanisms of synaptic vesicle clustering and mobilization in living frog motor nerve terminals. FM1-43 staining of these terminals produces a linear series of fluorescent spots, each spot marking the cluster of several hundred synaptic vesicles at an active zone. Most agents we tested did not affect staining, but the phosphatase inhibitor okadaic acid (OA) disrupted the fluorescent spots, causing dye to spread throughout the terminal. Consistent with this, electron microscopy showed that vesicle clusters were disrupted by OA treatment. However, dye did not spread passively to a uniform spatial distribution. Instead, time lapse movies showed clear evidence of active dye movements, as if synaptic vesicles were being swept along by an active translocation mechanism. Large dye accumulations sometimes occurred at sites of Schwann cell nuclei. These effects of OA were not significantly affected by pretreatment with colchicine or cytochalasin D. Electrophysiological recordings showed that OA treatment reduced the amount of acetylcholine released in response to nerve stimulation. The results suggest that an increased level of protein phosphorylation induced by OA treatment mobilizes synaptic vesicles and unmasks a powerful vesicle translocation mechanism, which may function normally to distribute synaptic vesicles between active zones.

Limb regeneration in Amphiuma tridactylum (Amphibia, Urodela)

1978 ◽  
Vol 56 (11) ◽  
pp. 2327-2332 ◽  
Author(s):  
Steven R. Scadding
Keyword(s):  
Wound Healing ◽  
Body Wall ◽  
Histological Study ◽  
Limb Regeneration ◽  
Complete Loss ◽  
The Body ◽  
Limb Amputation ◽  
Slow Process

This paper reports a histological study of the response of Amphiuma to simple limb amputation. The results of simple limb amputation in this species are variable. Some limbs undergo wound healing only, others regress, resulting in complete loss of the limb except for a residual rudiment embedded in the body wall, and still others produce heteromorphic limb regenerates of size comparable with the amputated limb. Heteromorphic limb regeneration when it occurs in Amphiuma is a very slow process compared with other urodeles. After 7.5 months (longest observed specimens in this study), the process was still not complete.

Rhythmic swimming activity in neurones of the isolated nerve cord of the leech

1976 ◽  
Vol 65 (3) ◽  
pp. 643-668
Author(s):  
W. B. Kristan ◽  
R. L. Calabrese
Keyword(s):  
Nerve Cord ◽  
Body Shape ◽  
Sensory Input ◽  
Body Wall ◽  
Motor Neurone ◽  
The Body ◽  
Burst Duration ◽  
Cycle Period ◽  
Motor Neurones ◽  
Central Oscillator

1. Repeating bursts of motor neurone impulses have been recorded from the nerves of completely isolated nerve cords of the medicinal leech. The salient features of this burst rhythm are similar to those obtained in the semi-intact preparation during swimming. Hence the basic swimming rhythm is generated by a central oscillator. 2. Quantitative comparisons between the impulse patterns obtained from the isolated nerve cord and those obtained from a semi-intact preparation show that the variation in both dorsal to ventral motor neurone phasing and burst duration with swim cycle period differ in these two preparations. 3. The increase of intersegmental delay with period, which is a prominent feature of swimming behaviour of the intact animal, is not seen in either the semi-intact or isolated cord preparations. 4. In the semi-intact preparation, stretching the body wall or depolarizing an inhibitory motor neurone changes the burst duration of excitatory motor neurones in the same segment. In the isolated nerve cord, these manipulations also change the period of the swim cycle in the entire cord. 5. These comparisons suggest that sensory input stabilizes the centrally generated swimming rhythm, determines the phasing of the bursts of impulses from dorsal and ventral motor neurones, and matches the intersegmental delay to the cycle period so as to maintain a constant body shape at all rates of swimming.

Reproductive biology of two epizoic anemones from the deep north-eastern Atlantic Ocean

1993 ◽  
Vol 73 (3) ◽  
pp. 531-542 ◽  
Author(s):  
S. K. Bronsdon ◽  
P. A. Tyler ◽  
A. L. Rice ◽  
J. D. Gage
Keyword(s):  
Body Weight ◽  
Reproductive Biology ◽  
Body Wall ◽  
Early Spring ◽  
The Body ◽  
Sea Anemones ◽  
Eastern Atlantic Ocean ◽  
North Eastern ◽  
Seasonal Basis ◽  
Wet Weight

The reproductive biology of two epizoic deep-sea anemones reveals contrasting reproductive strategies. Amphianthus inornata (Cnidaria: Anthozoa) lives attached to the bathyal gorgonian Acanella arbuscula (Cnidaria: Anthozoa). Females of A. inornata increase in wet body weight as a result of increased oocyte production until 40% of the body weight is reproductive tissue. The anemone reproduces on a seasonal basis, releasing eggs in the early spring of each year. By contrast, Kadosactis commensalis (Cnidaria: Anthozoa) lives attached to the body wall of the abyssal holothurian Paroriza prouhoi (Echinodermata: Holothurioidea). This anemone is a protandric hermaphrodite, females being found only at the anterior end of the holothurian, whilst males are found at any point on the host. Females have a significantly higher wet weight than males and neither sex shows any reproductive seasonality.

Neurones in the leech that facilitate an avoidance behaviour following nearfield water disturbances

1978 ◽  
Vol 75 (1) ◽  
pp. 1-23
Author(s):  
D. C. Mistick
Keyword(s):  
T Cells ◽  
T Cell ◽  
Temporal Summation ◽  
Body Wall ◽  
Cell Activity ◽  
The Body ◽  
Repetitive Firing ◽  
Impulse Frequency ◽  
Longitudinal Contraction ◽  
Motor Neurones

1. A multimodel, multisegmental interneurone (Rohde's fibre, RF) and previously identified mechanoreceptors (T-cells) are shown to respond to nearfield disturbances. Both the T-cells and RF can fire for hundreds of milliseconds following a brief stimulus, and both have subthreshold excitatory synapses onto motor neurones that cause longitudinal contraction of the body wall, an avoidance response. 2. Natural stimulation or electrical stimulation of T-cells in one hemiganglion causes synaptic excitation of T-cells in adjacent ipsilateral hemiganglia and re-excitation of T-cells in the hemiganglion stimulated. A model of repetitive T-cell activity that incorporates previously described synapses among T-cells is presented: the T-cells in adjacent ipsilateral hemiganglia form a reverberatory circuit, re-exciting one another via electrical synapses; repetitive firing is terminated by synaptic inhibition onto T-cells provided by an interneurone excited by the T-cells. With repeated stimulation (0.1--0.2 Hz, 0.2 ms pulses) of a segmental root (directly exciting all the T-cells of a hemiganglion), the number of T-cell impulses per stimulus decreases. Facilitation of inhibition may contribute to the response decrement. 3. The T-cell-RF pathway is investigated. T-cell stimulation can elicit RF impulses in the same and in adjacent ganglia. The long delay between mechanoreceptor stimulation and a response in the interneurone suggests that spatial and temporal summation of T-cell inputs may be required to reach firing threshold in the interneurone. 4. The impulse frequency of the RF response was compared for a travelling surface wave that is approaching a segment v. one that is moving away from the segment. It was found that the frequency was greater as the stimulus approaches; this should allow more effective temporal summation of the subthreshold synaptic potentials which RF evokes in motor neurones that cause longitudinal contraction of the body wall. Therefore, the probability of contraction is greater in segments toward which a stimulus is moving.

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