scholarly journals ELECTRON MICROSCOPY OF SYNAPTIC STRUCTURE OF OCTOPUS BRAIN

1964 ◽  
Vol 21 (1) ◽  
pp. 87-103 ◽  
Author(s):  
E. G. Gray ◽  
J. Z. Young
Keyword(s):  
Electron Microscopy ◽  
Frontal Lobe ◽  
Synaptic Vesicles ◽  
Membrane Conductance ◽  
Amacrine Cells ◽  
Synaptic Membranes ◽  
Inhibitory Mechanism ◽  
Synaptic Structure ◽  
Spinous Processes ◽  
The Brain

The well known type of synapse between a presynaptic process containing vesicles and a "clear" postsynaptic process can be commonly observed in the various lobes of the brain of Octopus. The presynaptic vesicles are aggregated near regions of the synaptic membranes which show specialisation and asymmetric "thickening" indicating functional polarisation, and here chemical transmission is presumed to take place. In addition, in the vertical lobe a very interesting serial arrangement of synaptic contacts occurs. Presynaptic bags, formed from varicosities of fibres from the superior frontal lobe, contact the trunks of amacrine cells in the manner just described. The trunks, however, although apparently postsynaptic are themselves packed with synaptic vesicles. The trunks, in turn, make "presynaptic" contacts with clear spinous processes of other neurons of yet undetermined origin. Typical polarised membrane specialisations occur at the contact regions. The trunk vesicles aggregated closest to the contact regions have a shell of particles round their walls. At present, there is no way of telling whether the membrane conductance to the various ions is differently affected at either of the transmission sites, and, if an inhibitory mechanism is involved, whether it is of the presynaptic or postsynaptic variety.

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 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.

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.

Application of Scanning Electron Microscopy to Medical Research

1969 ◽  
Vol 27 ◽  
pp. 12-13
Author(s):  
J. D. Hutchison
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Medical Research ◽  
Prosthetic Heart Valve ◽  
School Of Medicine ◽  
Transmission Electron ◽  
Definition Of ◽  
Mechanism Of Failure ◽  
The Brain ◽  
Scanning Electron

When the transmission electron microscope was commercially introduced a few years ago, it was heralded as one of the most significant aids to medical research of the century. It continues to occupy that niche; however, the scanning electron microscope is gaining rapidly in relative importance as it fills the gap between conventional optical microscopy and transmission electron microscopy.IBM Boulder is conducting three major programs in cooperation with the Colorado School of Medicine. These are the study of the mechanism of failure of the prosthetic heart valve, the study of the ultrastructure of lung tissue, and the definition of the function of the cilia of the ventricular ependyma of the brain.

Analytical Electron Microscopy (AEM) of Meningeal Cells Exposed to Particulate Cobalt During Studies of Experimental Epilepsy

1982 ◽  
Vol 40 ◽  
pp. 186-187
Author(s):  
R.G. Frederickson ◽  
R.G. Ulrich ◽  
J.L. Culberson
Keyword(s):  
Electron Microscopy ◽  
Analytical Electron Microscopy ◽  
Experimental Epilepsy ◽  
Metallic Cobalt ◽  
Experimental Animals ◽  
X Ray ◽  
Brain Surface ◽  
Meningeal Cells ◽  
Analytical Electron ◽  
The Brain

Metallic cobalt acts as an epileptogenic agent when placed on the brain surface of some experimental animals. The mechanism by which this substance produces abnormal neuronal discharge is unknown. One potentially useful approach to this problem is to study the cellular and extracellular distribution of elemental cobalt in the meninges and adjacent cerebral cortex. Since it is possible to demonstrate the morphological localization and distribution of heavy metals, such as cobalt, by correlative x-ray analysis and electron microscopy (i.e., by AEM), we are using AEM to locate and identify elemental cobalt in phagocytic meningeal cells of young 80-day postnatal opossums following a subdural injection of cobalt particles.

The Role of Mitochondria in the Genesis of Neuroaxonal Dystrophy in the Brains of Aging Mice

1975 ◽  
Vol 33 ◽  
pp. 372-373
Author(s):  
J.E. Johnson
Keyword(s):  
Electron Microscopy ◽  
Present Report ◽  
Light And Electron Microscopy ◽  
Dorsal Column ◽  
Neuroaxonal Dystrophy ◽  
Nucleus Gracilis ◽  
Dystrophic Axons ◽  
The Brain ◽  
Nucleus Cuneatus

Although neuroaxonal dystrophy (NAD) has been examined by light and electron microscopy for years, the nature of the components in the dystrophic axons is not well understood. The present report examines nucleus gracilis and cuneatus (the dorsal column nuclei) in the brain stem of aging mice.Mice (C57BL/6J) were sacrificed by aldehyde perfusion at ages ranging from 3 months to 23 months. Several brain areas and parts of other organs were processed for electron microscopy.At 3 months of age, very little evidence of NAD can be discerned by light microscopy. At the EM level, a few axons are found to contain dystrophic material. By 23 months of age, the entire nucleus gracilis is filled with dystrophic axons. Much less NAD is seen in nucleus cuneatus by comparison. The most recurrent pattern of NAD is an enlarged profile, in the center of which is a mass of reticulated material (reticulated portion; or RP).

scholarly journals Topological Data Analysis reveals robust alterations in the whole-brain and frontal lobe functional connectomes in Attention-Deficit/Hyperactivity Disorder

2019 ◽  
Author(s):  
Zeus Gracia-Tabuenca ◽  
Juan Carlos Díaz-Patiño ◽  
Isaac Arelio ◽  
Sarael Alcauter
Keyword(s):  
Attention Deficit Hyperactivity Disorder ◽  
Data Analysis ◽  
Frontal Lobe ◽  
Attention Deficit ◽  
Brain Network ◽  
Topological Data Analysis ◽  
Hyperactivity Disorder ◽  
The Brain ◽  
Connectivity Threshold ◽  
Topological Data

AbstractThe functional organization of the brain network (connectome) has been widely studied as a graph; however, methodological issues may affect the results, such as the brain parcellation scheme or the selection of a proper threshold value. Instead of exploring the brain in terms of a static connectivity threshold, this work explores its algebraic topology as a function of the filtration value (i.e., the connectivity threshold), a process termed the Rips filtration in Topological Data Analysis. Specifically, we characterized the transition from all nodes being isolated to being connected into a single component as a function of the filtration value, in a public dataset of children with attention-deficit/hyperactivity disorder (ADHD) and typically developing children. Results were highly congruent when using four different brain segmentations (atlases), and exhibited significant differences for the brain topology of children with ADHD, both at the whole brain network and at the functional sub-network levels, particularly involving the frontal lobe and the default mode network. Therefore, this approach may contribute to identify the neurophysio-pathology of ADHD, reducing the bias of connectomics-related methods.HighlightsTopological Data Analysis was implemented in functional connectomes.Betti curves were assessed based on the area under the curve, slope and kurtosis.The explored variables were robust along four different brain atlases.ADHD showed lower areas, suggesting decreased functional segregation.Frontal and default mode networks showed the greatest differences between groups.Graphical Abstract

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