Electron microscopy of optic nerves and optic lobes of Octopus and Eledone

1963 ◽  
Vol 158 (973) ◽  
pp. 446-456 ◽  
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Optic Nerve ◽  
Schwann Cells ◽  
Synaptic Vesicles ◽  
Optic Lobe ◽  
Granule Cells ◽  
Proximal Region ◽  
Optic Lobes ◽  
Optic Axons

Each optic nerve contains several bundles of axons. The axons have their surface membranes directly apposed and the bundles lie in troughs of the elongated Schwann cells. The axons have pronounced varicosities along their length. The axons enter the optic lobe and run between the granule cells to synapse in the plexiform zone. The granule cells are small neurons. Their cytoplasmic organelles include endoplasmic reticulum, ribosomes, agranular reticulum and of special interest, oval or spherical bodies with a lamellated cortex and granular medulla. The elongated varicose presynaptic bags of the optic axons contain mitochondria in the proximal region, numerous synaptic vesicles and, sometimes, neurofilaments. Below the mitochondrial zone, synaptic contacts are made with small spines invaginated into the bags. The spines probably originate from the trunks of the granule cells. Tunnel fibres that are probably trunks of the outer granule cells, run through channels in the synaptic bags.

The Question of Relationship Between Golgi Vesicles and Synaptic Vesicles in Octopus Neurons

1970 ◽  
Vol 7 (1) ◽  
pp. 189-201
Author(s):  
E. G. GRAY
Keyword(s):  
Electron Microscopy ◽  
Golgi Apparatus ◽  
Frontal Lobe ◽  
Synaptic Vesicles ◽  
Optic Lobe ◽  
Visual Cell ◽  
Visual Cells ◽  
Golgi Vesicles

Electron microscopy of the vertical lobe of octopus brain shows that the synaptic knobs of axons with perikarya in the median superior frontal lobe have synaptic vesicles, approximately 28% of which are dense-cored (or granulated). In contrast, the endings of the amacrine neurons in the vertical lobe and the endings in the retina and optic lobe, both of which are derived from the retinal visual cells, have only agranular synaptic vesicles. The Golgi apparatuses of the median superior frontal perikarya have vesicles, approximately 4.3% of which are granulated. The amacrine Golgi apparatuses have 1.5% granulated vesicles. The visual cell Golgi apparatuses have virtually no dense-cored vesicles, only agranular ones. The question of the formation of dense-cored and agranular synaptic vesicles at the Golgi apparatus and their subsequent transport to the terminals are related to these observations.

The optic lobes of Octopus vulgaris

1962 ◽  
Vol 245 (718) ◽  
pp. 19-58 ◽  
Keyword(s):  
Optic Nerve ◽  
Optic Lobe ◽  
Optic Tract ◽  
Amacrine Cells ◽  
Visual Input ◽  
Octopus Vulgaris ◽  
Coding System ◽  
Nerve Fibres ◽  
Dendritic Trees ◽  
Optic Lobes

The optic lobes provide a system for coding the visual input, for storing a record of it and for decoding to produce particular motor responses. There are at least three types of optic nerve fibre, ending at different depths in the layered dendritic systems of the plexiform zone. Here the optic nerve fibres meet the branches of at least four types of cell. (1) Centripetal cells passing excitation inwards. The dendrites of these are very long, with fields orientated more often in horizontal and vertical than in other directions. (2) Numerous amacrine cells, with cone-shaped dendritic fields but no determinable axon. (3) Centrifugal cells conducting back to the retina. (4) Commissural fibres from the opposite optic lobe, and other afferents. After section of the optic nerves the plexiform layer of the corresponding part of the optic lobe becomes reduced, but the tangential layers of dendrites remain. There is a reduction in the thickness of the layers of amacrine and other cells and a shrinkage of the whole lobe. Conversely the tangential layers can be degenerated, leaving the optic nerve fibres, by severing the arteries to the optic lobe. The centre of the optic lobe contains cells with spreading dendritic trees of many forms. Some run mainly tangentially, others are radial cones. Those towards the centre send axons to the optic tract. Small multipolar cells accompany the large neurons of the cell islands. About 2 x 10 7 optic nerve fibres visible with the light microscope enter the lobes but only 0-5 x 106, or less, leave in the optic tract, these being distributed to some ten centres in the supraoesophageal lobes. It is suggested that the variety of shapes of the dendritic trees within the optic lobes provides the elements of the coding system by which visual input is classified.

Nerve Cells and Fibers in the Optic Lobe Cortex of Octopus

1971 ◽  
Vol 29 ◽  
pp. 238-239 ◽  
Author(s):  
Norman M. Case ◽  
E. G. Gray
Keyword(s):  
Optic Nerve ◽  
Synaptic Vesicles ◽  
Granular Layer ◽  
Optic Lobe ◽  
Synaptic Contact ◽  
Plexiform Layer ◽  
Amacrine Cells ◽  
Nerve Fibers ◽  
Fiber Types ◽  
Basement Layer

Montages of electron micrographs from the outer portion of the cortex of the optic lobe of Octopus are shown. Sheets of dark cytoplasm which originate from glial cells in the outer granular layer form a basement layer separating the outer granular layer from the deeper plexiform layer.Optic nerve fibers from the retina entering the optic lobe around its periphery must pass between the amacrine cells composing the bulk of the outer granular layer. Here they are the darker of the two fiber types that can be identified. Passing through the basement layer they expand into large “carrot” shaped terminal endings easily identified by their dark appearance caused by the extremely high content of synaptic vesicles they contain.Fibers in the neuropil press tightly against and indent the “carrots” and occasionally make synaptic contact with them. Some fibers penetrate deeply into the “carrots” where they branch and terminate in grape-like clusters that show many synaptic contacts with the enveloping bag.

Pre-existing neuronal pathways in the developing optic lobes of Drosophila

Development ◽  
1989 ◽  
Vol 105 (4) ◽  
pp. 739-746 ◽  
Author(s):  
S. Tix ◽  
J.S. Minden ◽  
G.M. Technau
Keyword(s):  
Optic Nerve ◽  
Visual System ◽  
Optic Lobe ◽  
Adult Stage ◽  
Insertion Site ◽  
Optic Tract ◽  
Optic Stalk ◽  
Optic Lobes ◽  
First Order ◽  
Form Part

We have identified a set of larval neurones in the developing adult optic lobes of Drosophila by selectively labelling cells that have undergone only a few mitoses. A cluster of three cells is located in each of the optic lobes near the insertion site of the optic stalk. Their axons fasciculate with fibres of the larval optic nerve, the Bolwig's nerve, and then form part of the posterior optic tract. These cells are likely to be first order interneurones of the larval visual system. Unlike the Bolwig's nerve, they persist into the adult stage. The possibility of a pioneering function of the larval visual system during formation of the adult optic lobe neuropil is discussed.

A Note on Synaptic Structure of the Retina of Octopus Vulgaris

1970 ◽  
Vol 7 (1) ◽  
pp. 203-215
Author(s):  
E. G. GRAY
Keyword(s):  
Electron Microscopy ◽  
Synaptic Vesicles ◽  
Synaptic Contact ◽  
Octopus Vulgaris ◽  
Synaptic Membrane ◽  
Visual Cell ◽  
Regular Pattern ◽  
Synaptic Structure ◽  
Optic Axons

Electron microscopy of the octopus retina shows that both types of synapse (formed by the visual cell collaterals and the efferents respectively) have synaptic membrane specializations with associated aggregations of synaptic vesicles--features usually regarded as indicative of synaptic contact. These have hitherto been considered as absent from the octopus retina. Other details of the retinal synapses are described and in addition the grouped microtubules in the initial portions of the optic axons are seen to have in association a regular pattern of micro-filaments.

scholarly journals MORPHOLOGICAL AND BIOCHEMICAL CORRELATES OF CEREBRAL MICROSOMES

1965 ◽  
Vol 25 (2) ◽  
pp. 69-80 ◽  
Author(s):  
F. de Balbian Verster ◽  
O. Z. Sellinger ◽  
J. C. Harkin
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Cerebral Cortex ◽  
Glutamine Synthetase ◽  
Nerve Ending ◽  
Synaptic Vesicles ◽  
Lactic Dehydrogenase ◽  
The Other ◽  
Rat Cerebral Cortex ◽  
Microsomal Pellet

Microsomal fractions, both homogeneous in appearance and functionally operative, were isolated from a homogenate of rat cerebral cortex by fractionation in water. The preparations thus obtained contain the membranous elements of the endoplasmic reticulum, synaptic vesicles, and ribosomes. Esterase, ATPase, and glutamine synthetase were found to be present and fully functional in the microsomal fractions isolated in water. The contamination of the water-isolated microsomal fractions by mitochondria and lysosomes was found to be considerably lower than in microsomal pellets isolated in sucrose. The contamination by nerve ending particles, as judged by electron microscopy and by the levels of soluble lactic dehydrogenase entrapped in the cytoplasm of the particles, was also low. Most of the contamination by mitochondria and nerve ending particles could be removed by treatment of the microsomal pellet with 150 mM NaCl. Resistant to elution by this treatment is the lysosomal contamination as well as microsomal esterase and ATPase. Glutamine synthetase, on the other hand, was almost totally solubilized. Microsomal preparations isolated in water are also shown to contain amounts of protein, RNA, phospholipid, and ganglioside comparable to those found in microsomal preparations isolated in sucrose.

Cytochemistry and Electron Microscopy: ACYL Hydrolase and Transferase Reactions

1968 ◽  
Vol 26 ◽  
pp. 2-3
Author(s):  
Russell J. Barrnett ◽  
Joan A. Higgins
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Carboxylic Acid ◽  
Synaptic Vesicles ◽  
Serum Cholinesterase ◽  
Compromise Solution ◽  
Thioacetic Acid ◽  
Myoneural Junction ◽  
Enzyme Cytochemistry ◽  
Esterase Activities

The use of enzyme cytochemistry with electron microscopy depends on the compromise solution of combining the rigid requirements of both fields. The ability to make the combination has limiting as well as definitive conditions.In illustration of some of the above problems, thiol substituted carboxylic acids should be satisfactory substrates for the demonstration of carboxylic acid esterase activities with Pb++ as the capture reagent. However, utilizing thioacetic acid which is hydrolized by acetylcholinesterase, sites of hydrolysis other than those of carboxylic acid esterases (not affected by the usual inhibitors of esterase activity) are revealed. Among these sites are synaptic vesicles of the myoneural junction, and endoplasmic reticulum and mitochondria of a variety of cells. Contrary to expectations, thiobutyric acid was not split by serum cholinesterase but it, as well as longer chain substrates (thiohexanoic and thio-octonoic acids), was also hydrolysed by enzymes in mitochondria and in the endoplasmic reticulum.

The retina of cephalopods and its degeneration after optic nerve section

1962 ◽  
Vol 245 (718) ◽  
pp. 1-18 ◽  
Keyword(s):  
Optic Nerve ◽  
Horizontal Plane ◽  
Optic Lobe ◽  
Retinal Cell ◽  
Cell Nuclei ◽  
Supporting Cells ◽  
Nerve Section ◽  
Retinal Cells ◽  
Optic Lobes ◽  
Retrograde Degeneration

Each retinal cell of Octopus carries a rhabdomere on two opposite faces. Rhabdomeres from four cells combine to make a square rhabdome. The cells are mainly arranged with their axes in approximately either the vertical or horizontal plane as the eye is usually held in the head. Counts show that there are about twice as many retinal cell nuclei as there are rhabdomes. There are altogether about 2 x 10 7 retinal cells in each eye, with a density of about 50 000/mm 2 . The retinal cells at the centre of the retina are longer and thinner than those at the periphery. There is a strip of longer, thinner cells running horizontally along the equator. These often have less pigment in their distal ends than do the cells dorsally and ventrally, but other distributions of the pigment are seen, depending on the previous illumination. There are several types and sizes of retinal cell and not all are associated in fours to make rhabdomes. The proximal segments carry fine collateral twigs, these interdigitate and may allow mutual interaction between neighbours. The main meshes of the retinal plexus are not formed by fibres of the retinal cells but by the axons of cells in the optic lobes, presumably efferents. After severing the optic nerves to any region of the retina all the retinal cells undergo retrograde degeneration, leaving only the supporting cells intact. The retinal nerve plexus disappears almost completely, but a few fibres remain. At the boundary between a region with severed and intact nerves the plexus continues for some distance into the denervated region. After removal of all the optic lobe except a portion of its outermost (plexiform) zone the retinal receptors do not degenerate completely but are reduced in length. Their axons have not been interrupted by the operation and this is therefore a partial transneuronal retrograde degeneration.

Modification of Pineal Ultrastructure by Exogenous Hormones

1967 ◽  
Vol 25 ◽  
pp. 170-171
Author(s):  
R. A. Turner ◽  
A. E. Rodin ◽  
D. K. Roberts
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Rough Endoplasmic Reticulum ◽  
Estradiol Benzoate ◽  
Female Rats ◽  
List Type ◽  
Type Number ◽  
Pregnant Rats ◽  
Gonadal Atrophy ◽  
Pineal Ultrastructure

There have been many reports which establish a relationship between the pineal and sexual structures, including gonadal hypertrophy after pinealectomy, and gonadal atrophy after injection of pineal homogenates or of melatonin. In order to further delineate this relationship the pineals from 5 groups of female rats were studied by electron microscopy:ControlsPregnant ratsAfter 4 weekly injections of 0.1 mg. estradiol benzoate.After 8 daily injections of 150 mcgm. melatonin (pineal hormone).After 8 daily injections of 3 mg. serotonin (melatonin precursor).No ultrastructural differences were evident between the control, and the pregnancy and melatonin groups. However, the estradiol injected animals exhibited a marked increase in the amount and size of rough endoplasmic reticulum within the pineal cells.

Copper Localization in Cirrhotic Rat Liver by Scanning Electron Microscopy

1969 ◽  
Vol 27 ◽  
pp. 38-39 ◽  
Author(s):  
J. C. Russ ◽  
E. McNatt
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Electron Microscope ◽  
Copper Acetate ◽  
Lead Citrate ◽  
Dense Bodies ◽  
Transmission Electron ◽  
Electron Mode ◽  
Scanning Electron

In order to study the retention of copper in cirrhotic liver, rats were made cirrhotic by carbon tetrachloride inhalation twice weekly for three months and fed 0.2% copper acetate ad libidum in drinking water for one month. The liver tissue was fixed in osmium, sectioned approximately 2000 Å thick, and stained with lead citrate. The section was examined in a scanning electron microscope (JEOLCO JSM-2) in the transmission electron mode.Figure 1 shows a typical area that includes a red blood cell in a sinusoid, a disse, and a portion of the cytoplasm of a hepatocyte which contains several mitochondria, peribiliary dense bodies, glycogen granules, and endoplasmic reticulum.

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