scholarly journals ULTRASTRUCTURE OF THE SPOON TYPE SYNAPTIC ENDINGS IN THE NUCLEUS VESTIBULARIS TANGENTIALIS OF THE CHICK

1967 ◽  
Vol 34 (2) ◽  
pp. 421-430 ◽  
Author(s):  
Raúl Hinojosa ◽  
J. David Robertson
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Synaptic Vesicles ◽  
Synaptic Cleft ◽  
Synaptic Membrane ◽  
Electrical Transmission ◽  
Membrane Complex ◽  
Pattern Characteristic ◽  
Oriented Parallel ◽  
Nucleus Vestibularis

The fine structure of the "spoon" type synaptic endings of the chick tangential nucleus was studied with the electron microscope. These endings often measure ∼18 µ in length by ∼3–4 µ in width. The axoplasm of the endings contains very few synaptic vesicles, a large number of neurofilaments oriented parallel to the long axis of the nerve fiber, and microtubules and numerous mitochondria. The synaptic membrane complex shows areas of localized occlusion of the synaptic cleft with the formation of an external compound membrane. It has not been decided whether these areas have a disc shape; their length measures between 0.04 and 0.47 µ. The five-layer pattern characteristic of an external compound membrane is shown in specimens fixed with formalin—OsO4, glutaraldehyde—acrolein—OsO4, and acrolein KMnO4 but it does not appear in the glutaraldehyde-OsO4-fixed specimens. The over-all thickness of the external compound membrane varies depending upon the fixative used. The synaptic clefts in the regions between the external compound membrane discs are widened and measure ∼300 A. A condensation of dense material occurs in pre- and postsynaptic cytoplasms all along the synaptic membrane complex. The morphological relationships described in the spoon endings are suggestive of electrical transmission.

scholarly journals THE ULTRASTRUCTURE OF MAUTHNER CELL SYNAPSES AND NODES IN GOLDFISH BRAINS

1963 ◽  
Vol 19 (1) ◽  
pp. 159-199 ◽  
Author(s):  
J. David Robertson ◽  
Thomas S. Bodenheimer ◽  
David E. Stage
Keyword(s):  
Extracellular Matrix ◽  
Synaptic Vesicles ◽  
Matrix Material ◽  
Synaptic Cleft ◽  
Dense Material ◽  
Synaptic Membrane ◽  
Electrical Transmission ◽  
Mauthner Cell ◽  
Membrane Complex ◽  
Cell Processes

An electron microscope study of goldfish Mauthner cells is reported.1 The cell is covered by a synaptic bed ∼ 5 µ thick containing unusual amounts of extracellular matrix material in which synapses and clear glia processes are implanted. The preterminal synaptic neurites are closely invested by an interwoven layer of filament-containing satellite cell processes. The axoplasm of the club endings contains oriented mitochondria, neurofilaments, neurotubules, and relatively few synaptic vesicles. That of the boutons terminaux contains many unoriented mitochondria and is packed with synaptic vesicles and some glycogen but no neurofilaments or neurotubules. The bare axons of club endings are surrounded by a moderately abundant layer of matrix material. The synaptic membrane complex (SMC) in cross-section shows segments of closure of the synaptic cleft ∼ 0.2 to 0.5 µ long. These alternate with desmosome-like regions of about the same length in which the gap widens to ∼ 150 A and contains a condensed central stratum of dense material. Here, there are also accumulations of dense material in pre- and postsynaptic neuroplasm. The boutons show no such differentiation and the extracellular matrix is largely excluded around them. The axon cap is a dense neuropil of interwoven neural and glial elements free of myelin. It is covered by a closely packed layer of glia cells. The findings are interpreted as suggestive of electrical transmission in the club endings.

scholarly journals ELECTRON MICROSCOPE OBSERVATIONS ON SYNAPTIC VESICLES IN SYNAPSES OF THE RETINAL RODS AND CONES

1956 ◽  
Vol 2 (3) ◽  
pp. 307-318 ◽  
Author(s):  
Eduardo De Robertis ◽  
Carlos M. Franchi
Keyword(s):  
Electron Microscope ◽  
Synaptic Vesicles ◽  
Sharp Decrease ◽  
Albino Rabbit ◽  
Synaptic Membrane ◽  
Complete Darkness ◽  
Rods And Cones ◽  
Retinal Rods ◽  
Filamentous Material ◽  
Rod Cell

The submicroscopic organization of the rod and cone synapses of the albino rabbit has been investigated with the use of the electron microscope. The most common rod synapse consists of an enlarged expansion of the rod fiber (the so called spherule) into which the dendritic postsynaptic fiber of the bipolar cell penetrates and digitates. The membrane surrounding the terminal consists of a double layer, the external of which is interpreted as belonging to the intervening glial cells. The synaptic membrane has a pre- and a postsynaptic layer with a total thickness of 180 to 300 A. The presynaptic layer is frequently denser and is intimately associated with the adjacent synaptic vesicles. The synaptic membrane shows processes constituted by foldings of the presynaptic layer. The entire spherule is filled with synaptic vesicles varying in diameter between 200 and 650 A with a mean of 386 A. In addition, the spherule contains a few large vacuoles near the rod fiber, interpreted as endoplasmic reticulum, and a matrix in which with high resolution a fine filamentous material can be observed. The postsynaptic fiber is homogeneous and usually does not show synaptic vesicles. In animals maintained in complete darkness for 24 hours vesicles appear to accumulate near the synaptic membrane and its processes. After 9 days there is a sharp decrease in size of the synaptic vesicles. A special rod synapse in which the dendritic postsynaptic expansion penetrates directly into the rod cell body has been identified. In line with Cajal's classification this type of synapse could be considered as a somatodendritic one. The cone synapse has a much larger terminal with a more complex relationship with the postsynaptic fiber. However, the same components recognized in the rod synapse can be observed. In animals maintained for 9 days in complete darkness there is also a considerable diminution in size of the synaptic vesicles.

scholarly journals The Fine Structure of Synapses in the Ciliary Ganglion of the Chick

1960 ◽  
Vol 7 (1) ◽  
pp. 31-36 ◽  
Author(s):  
A. J. de Lorenzo
Keyword(s):  
Fine Structure ◽  
Synaptic Vesicles ◽  
Ganglion Cells ◽  
Single Cells ◽  
Synaptic Cleft ◽  
Structural Features ◽  
Ciliary Ganglion ◽  
Single Axon ◽  
Electron Microscopes ◽  
Electron Microscope Image

Ciliary ganglia of chick embryos and newly hatched chicks were examined in the light and electron microscopes. Particular attention was given to the fine structure of calyciform synapses, which are characteristically found in ciliary ganglia of birds. The calyciform endings are characterized by large expansions of the presynaptic axons upon ganglion cells, and the terminal processes extend over a considerable area of the cell surface. Often, indeed they appear to envelop the cell. In the electron microscope image, the appositional membranes are separated by a space about 300 to 400 A wide; i.e., the synaptic cleft. At irregularly spaced regions, the appositional membranes show areas of increased density. The presynaptic processes contain clusters of synaptic vesicles, localized at these dense regions. Thus the fine structure complex typical of other synapses is evident. The unique structural features of this synapse are as follows: (a) The calyx or presynaptic terminal derives from a single axon, does not arborize, and terminates upon a single ganglion cell. Thus, unlike the classical bouton terminal, this represents an anatomical device for firing single cells by single axons. (b) The surface area in contiguity, i.e., the area of appositional membranes, is far more extensive than the bouton terminal. The fine structure of this synapse is compared with others, for example, the classical boutons terminaux and purely electrical synapses, in an attempt to correlate fine structure with function.

Neurotransmitter Release

2017 ◽  
Author(s):  
Peggy Mason
Keyword(s):  
Plasma Membrane ◽  
Synaptic Vesicle ◽  
Active Zone ◽  
Neurotransmitter Release ◽  
Synaptic Vesicles ◽  
Synaptic Cleft ◽  
Fusion Pore ◽  
Synaptic Membrane ◽  
Specialized Region ◽  
Synaptic Vesicle Fusion

The biochemical and physiological processes of neurotransmitter release from an active zone, a specialized region of synaptic membrane, are examined. Synaptic vesicles containing neurotransmitters are docked at the active zone and then primed for release by SNARE complexes that bring them into extreme proximity to the plasma membrane. Entry of calcium ions through voltage-gated calcium channels triggers synaptic vesicle fusion with the synaptic terminal membrane and the consequent diffusion of neurotransmitter into the synaptic cleft. Release results when the fusion pore bridging the synaptic vesicle and plasma membrane widens and neurotransmitter from the inside of the synaptic vesicle diffuses into the synaptic cleft. Membrane from the active zone membrane is endocytosed, and synaptic vesicle proteins are then reassembled into recycled synaptic vesicles, allowing for more rounds of neurotransmitter release.

The fine structure of the vertical lobe of Octopus brain

1970 ◽  
Vol 258 (827) ◽  
pp. 379-394 ◽  
Keyword(s):  
Electron Microscopy ◽  
Fine Structure ◽  
Electron Microscope ◽  
Light Microscopy ◽  
Synaptic Vesicles ◽  
Structural Organization ◽  
Amacrine Cells ◽  
Large Cell ◽  
Inhibitory Effect ◽  
Tactile System

Although much is known about the structural organization and connexions of the various lobes of the octopus brain from light microscopy, this is the first attempt at a detailed analysis of one of the lobes— the vertical lobe, with the electron microscope. The vertical lobe consists of five lobules. The median superior frontal (MSF) axons enter each lobule from the MSF lobe. The MSF axons contain both microtubules and neurofilaments. The varicosities of the MSF axons contain both agranular and dense-cored vesicles and synapse with trunks of the amacrine cells. These trunks run together in bundles termed amacrine tracts into the centres of the lobules. The amacrine trunks contain microtubules but no neurofilaments. The trunks contain large and small agranular synaptic vesicles and synapse with what are in all probability branches of the trunks of the large cells. These trunks contain microtubules but no neurofilaments. They run out through the bases of the lobules probably without forming synaptic contacts within the lobule. Fibres signalling ‘pain’ (nocifensor) enter the lobules from below. They can be recognized by their content of neurofilaments. Their terminals contain numerous very small synaptic vesicles and a few larger and dense-cored ones. These ‘pain’ fibres appear to synapse mostly with processes of the large cells. J. Z. Young has shown that the vertical lobe is especially concerned with the integrative action of the visual system, linked with the chemo-tactile system. Electron microscopy supports Young’s suggestion that the superior frontal and interconnected vertical lobe systems constitute a loop which could sustain a positive feed-back mechanism (MSF —> amacrine -> large cell -> lateral superior frontal -> MSF) while the ‘pain’ (nocifensor) input could exert a suppressor (inhibitory) effect on the loop by its action on the large cells.

scholarly journals Naked Axons and Symmetrical Synapses in Coelenterates

1962 ◽  
Vol s3-103 (64) ◽  
pp. 531-541
Author(s):  
G. A. HORRIDGE ◽  
BRUCE MACKAY
Keyword(s):  
Electron Microscope ◽  
Synaptic Vesicles ◽  
Nervous Tissue ◽  
Synaptic Cleft ◽  
Nerve Cells ◽  
Bipolar Cells ◽  
Intercellular Spaces ◽  
Golgi Region ◽  
Sensory Cilia ◽  
Nissl Substance

Examination of sections of the marginal ganglion of the jellyfish Cyanea and the hydromedusan Phialidium by the electron microscope, in a region where nervous tissue is readily identified on account of its abundance, reveals the following features. Nerve-cell bodies and axons are crowded together without special glial cells. The axons form a layer between the cell-bodies and the mesogloea and the spaces between them are continuous with other intercellular spaces and with the mesogloea. Features typical of nerve-cells in other animals are mitochondria, Golgi region (= γ-cytomembranes), neurotubules (= canaliculi) about 16 mµ wide, and several types of vesicle ranging in size from 50 to 200 mµ, including synaptic vesicles of 50 to 100 mµ. Features not typical of nerve-cells are the modified (possibly sensory) cilia on the dendrites of bipolar cells and the absence of clumps of Nissl substance and neurofilaments. Synapses between axons (or with a perikaryon) have a synaptic cleft of 18 to 22 mµ and a crowded row of synaptic vesicles within the neurones on each side of the synapse.

scholarly journals LE COMPLEXE MEMBRANAIRE SUPERFICIEL ET SON EVOLUTION LORS DE L'ELABORATION DES INDIVIDUS-FILS CHEZ TOXOPLASMA GONDII

1969 ◽  
Vol 43 (2) ◽  
pp. 329-342 ◽  
Author(s):  
Emile Vivier ◽  
André Petitprez
Keyword(s):  
Plasma Membrane ◽  
Fine Structure ◽  
Electron Microscope ◽  
Toxoplasma Gondii ◽  
Outer Membrane ◽  
Molecular Architecture ◽  
Daughter Cells ◽  
Membrane Complex ◽  
Local Differentiation

The parasitic protozoan Toxoplasma gondii has been examined with the electron microscope in order to study the fine structure and the formation of the membranes surrounding the cell. The study of the ultrastructure of the membranes covering the parasite shows the existence of a three-membraned complex. Only the outer membrane is considered to be the plasma membrane; the two membranes below it form an inseparable whole of changeable molecular architecture (modifications in appearance depending on the methods of fixation, local differentiation). During reproduction, which takes place by fission or more often by endogeny, the membranes of the daughter individuals are formed from the membranes of the parent. At first the middle and inner membranes of the parent extend, separating the cytoplasm of the daughter cells from that of the parent. The three-membrane complex of the endozoites is completed at the time of their liberation; the external membrane of the parent covers the leaving endozoites; thus, the plasma membrane of the daughter cells derives also from that of the parent. These findings on the origin and role of limiting membranes during reproduction differ entirely from those described so far for other cells.

A Study on the Fine Structure of the Lateral Line Organ of the Sea Eel

1973 ◽  
Vol 31 ◽  
pp. 648-649
Author(s):  
K. Hama
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Lateral Line ◽  
Low Frequency ◽  
Sensory Cells ◽  
Apical Surface ◽  
Voltage Electron ◽  
Sensory Epithelia ◽  
Low Frequency Vibration ◽  
Transmission Electron

The lateral line organs of the sea eel consist of canal and pit organs which are different in function. The former is a low frequency vibration detector whereas the latter functions as an ion receptor as well as a mechano receptor.The fine structure of the sensory epithelia of both organs were studied by means of ordinary transmission electron microscope, high voltage electron microscope and of surface scanning electron microscope.The sensory cells of the canal organ are polarized in front-caudal direction and those of the pit organ are polarized in dorso-ventral direction. The sensory epithelia of both organs have thinner surface coats compared to the surrounding ordinary epithelial cells, which have very thick fuzzy coatings on the apical surface.

Fine Structure of Interdental Cells in the Mouse Cochlea

1970 ◽  
Vol 28 ◽  
pp. 140-141
Author(s):  
Roberta M. Bruck
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Young Adult ◽  
Uranyl Acetate ◽  
Ground Substance ◽  
Tectorial Membrane ◽  
Lead Citrate ◽  
Unusual Structure ◽  
Thin Sections ◽  
Collagenous Fibers

An unusual structure in the cochlea is the spiral limbus; this periosteal tissue consists of stellate fibroblasts and collagenous fibers embedded in a translucent ground substance. The collagenous fibers are arranged in vertical columns (the auditory teeth of Haschke). Between the auditory teeth are interdental furrows in which the interdental cells are situated. These epithelial cells supposedly secrete the tectorial membrane.The fine structure of interdental cells in the rat was reported by Iurato (1962). Since the mouse appears to be different, a description of the fine structure of mouse interdental cells' is presented. Young adult C57BL/6J mice were perfused intervascularly with 1% paraformaldehyde/ 1.25% glutaraldehyde in .1M phosphate buffer (pH7.2-7.4). Intact cochlea were decalcified in .1M EDTA by the method of Baird (1967), postosmicated, dehydrated, and embedded in Araldite. Thin sections stained with uranyl acetate and lead citrate were examined in a Phillips EM-200 electron microscope.

Fine structure of the retina of the giant scallop, Placopecten magellanicus

1984 ◽  
Vol 42 ◽  
pp. 312-313
Author(s):  
C.V.L. Powell
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Light Intensity ◽  
Scanning Electron Microscope ◽  
Eye Development ◽  
Preliminary Observation ◽  
Columnar Epithelium ◽  
Placopecten Magellanicus ◽  
Environmental Light ◽  
Scanning Electron

The overall fine structure of the eye in Placopecten is similar to that of other scallops. The optic tentacle consists of an outer columnar epithelium which is modified into a pigmented iris and a cornea (Fig. 1). This capsule encloses the cellular lens, retina, reflecting argentea and the pigmented tapetum. The retina is divided into two parts (Fig. 2). The distal retina functions in the detection of movement and the proximal retina monitors environmental light intensity. The purpose of the present study is to describe the ultrastructure of the retina as a preliminary observation on eye development. This is also the first known presentation of scanning electron microscope studies of the eye of the scallop.

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