On the nervous system of Saccoglossus cambrensis (Enteropneusta)

1952 ◽  
Vol 236 (634) ◽  
pp. 315-354 ◽  
Keyword(s):  
Fine Particles ◽  
Basal Layer ◽  
Superficial Layer ◽  
Nerve Ring ◽  
Cell Nuclei ◽  
Nerve Fibres ◽  
Giant Axons ◽  
Almost Everywhere ◽  
Peristaltic Contractions ◽  
Nerve Cords

A layer of nerve fibres is present almost everywhere at the base of the epidermis. It consists of a very thin basal layer of irregularly arranged fibres, and generally a thicker, more superficial layer of orientated fibres, which forms the main nerve cords and subsidiary systems of smaller through-conducting bundles. In the proboscis there are numerous longitudinal bundles, an anterior nerve ring round the basal periphery and a nerve loop under the pre-oral ciliary organ. The neurocord appears to be a simple conducting tract. In the collar epidermis numerous bundles are formed posteriorly, connecting with the prebranchial nerve ring. In the trunk the size of the longitudinal cords and the distribution of the general plexus is related to the degree of development of the muscles and cilia. The gut is well equipped with nerve fibres anteriorly, where it is particularly muscular. Practically all the nerve-cell nuclei lie outside the plexus of nerve fibres. They are very numerous and widely distributed. A concentration of bipolar neurones (Hess’s cells) occurs at the proboscis tip. Cells regarded as sensory on histological grounds are abundant round the base of the proboscis and in the groove of the ciliary organ. Large unipolar neurones are concentrated in the neurocord, some possessing ‘giant’ axons, which run posteriorly or anteriorly. The cilia of the epidermis are the chief agents of locomotion, those of the trunk being capable of synchronized reversal. They are aided by peristaltic contractions of the longitudinal muscles, which are controlled by the main longitudinal nerve cords. Burrowing peristalsis is controlled by the dorsal nerve cord of the proboscis. Some reactions to light, to the presence of fine particles and to adrenaline are described. The proboscis is necessary for spontaneous and varied activity, but the considerable degree of co-ordination shown is not due to any localized centre but to a longitudinal reflex path involving the main nerve cords. Rapid contractions of the anterior end are probably due to the giant axons. The peculiarities of the neurocord are difficult to interpret, except as a result of degeneration and paedomorphosis. The greater part of the richly nervous epidermis may be compared with the vertebrate neural plate.

Immunocytochemical and radioimmunometrical demonstration of serotonin- and neuropeptide-immunoreactivities in the adult rat tapeworm,Hymenolepis diminuta(Cestoda, Cyclophyllidea)

Parasitology ◽  
1991 ◽  
Vol 103 (2) ◽  
pp. 275-289 ◽  
Author(s):  
D. M. McKay ◽  
I. Fairweather ◽  
C. F. Johnston ◽  
C. Shaw ◽  
D. W. Halton
Keyword(s):  
Nerve Cell ◽  
Peptide Yy ◽  
Hymenolepis Diminuta ◽  
Epifluorescence Microscopy ◽  
Confocal Scanning Laser Microscopy ◽  
Nerve Fibres ◽  
Cerebral Ganglia ◽  
Longitudinal Nerve ◽  
Small Nerve ◽  
Nerve Cords

Standard indirect immunocytochemical techniques have been interfaced with confocal scanning laser microscopy (for whole-mount preparations) and epifluorescence microscopy (for cryosections) to investigate the occurrence and distribution of serotoninergic and peptidergic nerve elements in adultH. diminuta. Serotonin (5-HT)-immunoreactivity (IR) was widespread throughout the worm, occurring in the paired cerebral ganglia, transverse commissure, the 10 longitudinal nerve cords and in a plethora of small nerve fibres of the peripheral nervous system. An abundance of serotoninergic nerve cell bodies was found in association with the lateral nerve cords. The genital atrium and accessory reproductive ducts were richly innervated with serotoninergic nerve fibres. Thirty-five antisera to 20 vertebrate regulatory peptides and 1 invertebrate peptide (FMRFamide) were used to screen the worm for neuropeptide IR. Immunostaining was obtained with antisera raised to pancreatic polypeptide (PP), peptide YY (PYY), neuropeptide Y (NPY), substance P (SP), peptide histidine isoleucine (PHI), xenopsin (XP) and FMRFamide. The most extensive pattern of IR occurred with antisera to PP and PYY, IR being evident in the cerebral ganglia, transverse commissure, longitudinal nerve cords and in small nerve fibres that ramified throughout the parenchyma. A series of bipolar nerve cell bodies between the median nerve cords displayed PP/PYY-IR. The distribution of FMRFamide-IR was reminiscent of the PP/PYY pattern but was less extensive. Comparison of the serotoninergic and peptidergic nervous systems has revealed general similarities and some distinct differences, especially with regard to the distribution of immunoreactive nerve cell bodies. Quantitative data are presented on the levels of PP-, SP-, PH1-, and gastrin-releasing peptide (GRP)-immunoreactivities demonstrable in acid-alcohol extracts of whole worms. The highest level of peptide IR determined was recorded for PP.

Coordinated Excitation of Flexor Inhibitors in the Crayfish

1980 ◽  
Vol 86 (1) ◽  
pp. 187-195
Author(s):  
CHIKAO UYAMA ◽  
TAKASHI MATSUYAMA
Keyword(s):  
Giant Axon ◽  
Experimental Results ◽  
Abdominal Ganglion ◽  
Giant Axons ◽  
The Third ◽  
Nerve Cords

In isolated abdominal nerve cords of crayfish, the medial or lateral giant axons were stimulated at a position just rostral to the first abdominal ganglion. Recordings of the impulse sequences of the flexor inhibitor (FI) were made from the anterior five ganglia, three ganglia at a time. In 20% of our preparations, one giant axon impulse caused one to four FI impulses in every abdominal third root. An equal number of FI impulses were usually produced by each abdominal ganglion for any given stimulation. The earliest FI impulse was observed at the third root of the fourth ganglion. FI impulses occurred with increasing latencies rostrally and caudally from the fourth ganglion. The FI responses to medial and lateral giant axons stimulation were essentially equivalent. FI impulses were recorded from the rostral three abdominal ganglia, while the caudal ganglia were cut off one after another from the sixth to the third ganglion. Little change was noted until after the removal of the fourth ganglion, which usually caused all FI impulses to disappear. From these experimental results, we propose a model of central mechanisms for FI excitation.

scholarly journals STUDIES ON AMPHIBIAN YOLK

1963 ◽  
Vol 18 (1) ◽  
pp. 135-151 ◽  
Author(s):  
Shuichi Karasaki
Keyword(s):  
Fine Particles ◽  
Lattice Structure ◽  
Hexagonal Lattice ◽  
Superficial Layer ◽  
Crystalline Lattice ◽  
Main Body ◽  
Embryonic Cells ◽  
Amphibian Species ◽  
Ca 50 ◽  
Band Spacing

The yolk platelets of mature eggs and young embryonic cells of all amphibian species studied (Rana pipiens, Triturus pyrrhogaster, Diemictylus viridescens, Rana nigromaculata, and Bufo vulgaris) have a superficial layer of fine particles or fibrils (ca. 50 A in diameter), a central main body with a crystalline lattice structure, and an enclosing membrane approximately 70 A in thickness. Electron micrographs of the main body reveal hexagonal net (spacing ca. 70 A), square net (spacing ca. 80 A), and parallel band (spacing from 35 to 100 A but most frequent at ca. 70 A) patterns. The crystalline structure is believed to be a simple hexagonal lattice made of closely packed cylindrical rods. Each rod is estimated to be about 80 A in diameter and 160 A in length.

Echinoderm Nervous System

2018 ◽  
Author(s):  
Carlos A. Díaz-Balzac ◽  
José E. García-Arrarás
Keyword(s):  
Nervous System ◽  
Radial Nerve ◽  
Regulatory Networks ◽  
Nerve Ring ◽  
Neural Net ◽  
System P ◽  
Embryonic Nervous System ◽  
Body Wall Muscles ◽  
Areas Of Interest ◽  
Nerve Cords

The nervous system of echinoderms has been studied for well over a century. Nonetheless, the information available is disparate, with in-depth descriptions for the nervous component of some groups or of particular organs while scant data is available for others. The best studied representatives to date are the nervous system of echinoid embryos and larva, and the adult holothurian nervous system. Although described sometimes inaccurately as a neural net, the echinoderm nervous system consists of well-defined neural structures. This is observed since early embryogenesis when activation of the anterior neuroectoderm gene regulatory networks initiate the formation of the embryonic nervous system. This system then undergoes expansion and differentiation to form the larval nervous system, which is centered on the ciliary bands. This “simpler” nervous system is then metamorphosed into the adult echinoderm nervous system. The adult echinoderm nervous system is composed of a central nervous system made up of a nerve ring connected to a series of radial nerve cords. Peripheral nerves extending from the radial nerve cords or nerve ring connect with the peripheral nervous system, located in other organs or effectors including the viscera, podia, body wall muscles, and connective tissue. Both the central and peripheral nervous systems are composed of complex and diverse subdivisions. These are mainly characterized by the expression of neurotransmitters, namely acetylcholine, catecholamines, histamine, amino acids, GABA, and neuropeptides. Other areas of interest include the amazing regenerative capabilities of echinoderms that have been shown to be able to regenerate their nervous system components; and the analysis of the echinoderm genome that has provided essential insights into the molecular basis of how echinoderms develop an adult pentaradial symmetry from bilaterally symmetric larvae and the role of the nervous system in this process.

Cellular events during wound periderm formation in Dioscorea bulbifera bulbils

1989 ◽  
Vol 67 (10) ◽  
pp. 3090-3102 ◽  
Author(s):  
Ina Knobloch ◽  
Günter Kahl ◽  
Pierre Landré ◽  
Arlette Nougarède
Keyword(s):  
Cell Walls ◽  
Superficial Layer ◽  
Cell Nuclei ◽  
Meristematic Cells ◽  
Cellular Events ◽  
Fluorescence And Electron Microscopy ◽  
Deep Wound ◽  
Dioscorea Bulbifera ◽  
Cytoplasmic Ribosomes ◽  
Periderm Formation

The cytological events induced by a deep wound applied to Dioscorea bulbifera bulbils were studied using specific cytochemical methods and fluorescence and electron microscopy. Following wounding, a superficial layer with lignified (3rd h) and weakly suberized (6th h) cell walls formed in the original starchy parenchyma in contact with the wounded cells. Before the first mitoses (72nd h), an extensive dedifferentiation occurred in the underlying layers and involved reactivation of cell nuclei, nucleoli, and plastids. A concomitant aggregation of cytoplasmic ribosomes into polysomes occurred. Starch hydrolysis in the amyloplasts was evident before the first periclinal divisions. Periclinal divisions occurred in the reactivated cells from the second to the fourth layers beneath the wound. These newly meristematic cells could be divided into two to four new cells, leading to a periderm without a true phellogen. These covering layers degenerated during the period of lignification and weak suberization of cell walls. The thickness of the wound periderm depended on the age of the wounded bulbil.

Methyl green-pyronin stain distinguishes proliferating from differentiated nonproliferating cell nuclei after acid denaturation of DNA.

1986 ◽  
Vol 34 (5) ◽  
pp. 683-687 ◽  
Author(s):  
S Iseki ◽  
T Mori
Keyword(s):  
Basal Layer ◽  
Methyl Green ◽  
Esophageal Mucosa ◽  
Cell Renewal ◽  
Cell Nuclei ◽  
Proliferating Cells ◽  
Selective Staining ◽  
Acid Denaturation ◽  
Dna And Rna ◽  
Granular Layers

We applied methyl green-pyronin (MG-P) stain, which is usually used for the selective staining of DNA and RNA, to frozen sections of rat jejunal and esophageal mucosa, following digestion with RNase and treatment with various concentrations of HCl. The pyroninophilia of the nuclei increased with increasing strength of the acid, but the susceptibility of the nuclei to acid differed among cell populations. In the jejunal epithelium, at an appropriate acid strength the nuclei in the crypts of Lieberkuhn were less acid-sensitive and remained blue-green, whereas those in the villi were more pyroninophilic and stained lavender. Under the same conditions, the nuclei in the basal layer of the esophageal epithelium were blue-green and those in the spinous and granular layers were increasingly lavender. These results suggest that in cell-renewal systems the differentiated, nonproliferating cells are more sensitive to acid denaturation of DNA than the undifferentiated, actively proliferating cells. MG-P stain, which is able to distinguish double-stranded from single-stranded DNA, may be used as a tool to stain proliferating and nonproliferating cell nuclei differentially in tissue sections.

scholarly journals Variation of Human Hairiness: A Possible Adaptation to Solar Radiation and Melanin

2014 ◽  
Vol 77 (2) ◽  
pp. 219-232
Author(s):  
Amrita Dhugga ◽  
Maciej Henneberg ◽  
Jaliya Kumaratilake
Keyword(s):  
Solar Radiation ◽  
Hair Loss ◽  
Hair Growth ◽  
Full Range ◽  
Basal Layer ◽  
Superficial Layer ◽  
Melanin Production ◽  
Melanin Pigmentation ◽  
Skin Reflectance ◽  
High Concentrations

Abstract Many theories have been advanced to explain human hairlessness, however, there is no consensus. This study of 76 males observed that skin reflectance measuring skin colouration and melanin pigmentation correlated with hair size and follicle density. Individuals with a greater concentration of melanin within the superficial layer of the skin had a lower follicle density and smaller sizes of hairs. In contrast, individuals with a lower melanin concentration and lighter skin colour had a full range of hairiness. This leads to the suggestion that over the course of human evolution, high concentrations of melanin in consistently exposed to ultraviolet radiation areas developed first and that hair loss was a consequence of competition in the skin between melanin production and hair growth. Darker pigmented skin and lower follicle density are significantly correlated (R2=0.283; p<0.05). Individuals with darker skin had a mean of 4.91 follicles per cm2 whereas those with lighter skin reflectance had 11.20 follicles per cm2. This suggests that increased concentrations of melanin in the basal layer of the epidermis may limit hairiness by negatively influencing the skin's ability to produce hair.

Immunocytochemical demonstration of a neuropeptide in Ascaris suum (Nematoda) using an antiserum to FMR Famide

Parasitology ◽  
1988 ◽  
Vol 97 (1) ◽  
pp. 81-88 ◽  
Author(s):  
T. R. B. Davenport ◽  
D. L. Lee ◽  
R. E. Isaac
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Peripheral Nervous System ◽  
Ascaris Suum ◽  
Nerve Ring ◽  
Immunocytochemical Technique ◽  
The Central Nervous System ◽  
Nerve Cords

SUMMARYA FMRFamide-like peptide has been detected in the nematode Ascaris suum, using the peroxidase-anti-peroxidase (PAP) immunocytochemical technique. Positive reactions were obtained in both the central nervous system and the peripheral nervous system of the worm, the strongest reactions being in the anterior nerve ring, the cephalic papillary ganglia, the lateral ganglia and the dorso-rectal ganglion. Immunoreactivity was observed along the length of the main nerve cords of the worm and, to a lesser extent, in the pharyngeal nerve cords. The possible role of this neuropeptide in the physiology of the nematode is discussed.

scholarly journals Biological Assessment of Zn–Based Absorbable Metals for Ureteral Stent Applications

Materials ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3325 ◽  
Author(s):  
Devi Paramitha ◽  
Stéphane Chabaud ◽  
Stéphane Bolduc ◽  
Hendra Hermawan
Keyword(s):  
Urinary Tract Obstruction ◽  
Basal Layer ◽  
Superficial Layer ◽  
Biological Assessment ◽  
Basal Cells ◽  
Ureteral Stents ◽  
Urothelial Cells ◽  
Cytoskeletal Networks ◽  
2D And 3D ◽  
Tissue Construct

The use of ureteral stents to relieve urinary tract obstruction is still challenged by the problems of infection, encrustation, and compression, leading to the need for early removal procedures. Biodegradable ureteral stents, commonly made of polymers, have been proposed to overcome these problems. Recently, absorbable metals have been considered as potential materials offering both biodegradation and strength. This work proposed zinc-based absorbable metals by firstly evaluating their cytocompatibility toward normal primary human urothelial cells using 2D and 3D assays. In the 2D assay, the cells were exposed to different concentrations of metal extracts (i.e., 10 mg/mL of Zn–1Mg and 8.75 mg/mL of Zn–0.5Al) for up to 3 days and found that their cytoskeletal networks were affected but were recovered at day 3, as observed by immunofluorescence. In the 3D ureteral wall tissue construct, the cells formed a multilayered urothelium, as found in native tissue, with the presence of tight junctions at the superficial layer and laminin at the basal layer, indicating a healthy tissue condition even with the presence of the metal samples for up to 7 days of exposure. The basal cells attached to the metal surface as seen in a natural spreading state with pseudopodia and fusiform morphologies, indicating that the metals were non-toxic.

Ionic Composition of Haemolymph and Nervous Function in the Cockroach, Periplaneta Americana L

1968 ◽  
Vol 49 (1) ◽  
pp. 31-38
Author(s):  
Y. PICHON ◽  
J. BOISTEL
Keyword(s):  
Action Potentials ◽  
Periplaneta Americana ◽  
Extracellular Fluid ◽  
Sodium Concentration ◽  
Resting Potential ◽  
Equilibrium Potential ◽  
Unequal Distribution ◽  
High Sodium ◽  
Giant Axons ◽  
Nerve Cords

1. Resting and action potentials have been recorded in giant axons of the cockroach when the intact nerve cord was bathed in the insect's own haemolymph. 2. Low resting potentials (43.0±4.8 mV.) and large action potentials (105.1±6.8 mV.) were obtained in these preparations as compared with those recorded in de-sheathed nerve cords. 3. Recordings of the maximum rates of rise and fall have shown that the shape of the action potential was essentially similar in de-sheathed preparations and in intact nerve cords. 4. These results have been discussed in terms of the unequal distribution of ions between the haemolymph, the extracellular fluid and the axoplasm of the giant axons. 5. The low measured resting potential agrees with a K+ concentration in the haemolymph of about 20 mM./l., a value which is only slightly lower than the measured one (Pichon, 1963). 6.The occurrence of large action potentials in these apparently depolarized axons may be related to the stabilizing action of divalent cations such as Ca2+ which are contained in the extracellular fluid in relatively large amounts. 7. The very large recorded overshoots (62.1±7.0 mV.) may be linked with a low sodium concentration in the axoplasm and a high sodium concentration in the extracellular fluid of the giant axons of intact nerve cords, thus resulting in a high sodium equilibrium potential, ENa.

Sign in / Sign up

Export Citation Format

Share Document