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Biomedical subjects

T A Bragina

Publications and source records attributed to T A Bragina.

At least 19 recordsLinked to original sources
PubMed2006

[Ultrastructure of optic nerve fibers in rabbits after intravitreal infusion of perfluoroorganic compounds].

Ultrastructure of optic nerve myelinated fibers after intravitreal infusion of perfluorooctylbromide (PFOB) and perfluorodecaline (PFD) for 30 days was studied in rabbits (n = 14). After inraocular administration of PFOB, the ultrastructural changes of optic nerve fibers were mainly reactive in nature. Mitochondrial swelling and partial destruction of cristae were detected in the axons. After PFD infusion, the changes were observed that were not only reactive, but highly degenerative, including destruction of organelles and myelin sheath and axon cytoskeleton disintegration. Thus, the changes associated with PFOB were less pronounced than those found after PFD application. Therefore, PFOB is more promising for the use as an ophthalmologic implant.

Animals↗
PubMed1998

[Structural basis for the regulation of the neuronal sensitivity].

Using light and electron microscopy structural bases for intracellular, extracellular and integrative regulation of synaptic efficiency and neuron sensitivity were established in rat sensomotor cortex. Intracellular regulation is realized basically through modulation of postsynaptic components of the synapse, while extracellular one is provided by synaptic endings of "recurrent" axons on GABA-ergic relay and interneurons. Integrative regulation is realized by means of concentration of similar axonal terminals in restricted cortical area and arrangement of "neuromediatory" pool.

Animals↗
PubMed1996

[The identification of synapses in the cerebral cortex].

The correlation between structure and function of synapses is discussed. Identification of 4 types of synapses has been made based on the authors' own evidence provided for the rat sensomotor cortex with the light and electron microscopy: 1--asymmetrical (excitatory, glutamate- or aspartatergic); 2--symmetrical (inhibitory, GABAergic); 3--symmetrical (disinhibitory, GABAergic); 4--symmetrical or asymmetrical (modulatory, monoaminergic). The ultrastructure of some synaptic categories may be equalized with their function. It makes possible to identify not only excitatory and inhibitory synapses, as considered before, but also disinhibitory and modulatory ones.

Animals↗
PubMed1988

[Structural bases of the plasticity of the nervous system].

The present state of morphological study of variability in the nervous elements under conditions of adaptive change under the influence of afferent effects, age changes during different periods of ontogenesis, under conditions of de- and regeneration of synapses have been considered. A question on correlation between structure and the function of synapses during the change has been analysed. The tasks of subsequent study of this problem have been outlined.

Adaptation, Physiological↗
PubMed1984

[Structural organization of preganglionic sympathetic neurons].

Distribution of marked preganglionic neurons over spinal nuclei and segments was studied in cats with the aid of microinjections of the horse-radish peroxidase into the cranial cervical ganglion. The major part of these neurons were revealed in the main part of the intermediolateral nucleus. A somewhat lesser number of the cells were found in the funicular part of the nucleus. In the T1 segment they constituted about 90% of cells containing the peroxidase. Other neurons were localized in the paraependymal and intercalative nuclei. In longitudinal sections of the spinal cord, the preganglionic sympathetic neurons projecting their axons into the cranial cervical ganglion, form a rostro-caudal chain made of small ensembles of cells.

Animals↗
PubMed1983

[Ultrastructure of the synapses of the initial axonal segment of the pyramidal neuron].

Ultrastructure of the proximal part of the axon in the neurons, identified according to a number of morphological signs as pyramidal, has been studied in the layer III of the cat cerebral hemisphere sensomotor cortex. In sections, tangential to the cortical surface, in the initial axonal segment, a submembranous osmophilic layer and fasciculi of microtubules are revealed. On the initial segment spines are found, they contain cysterns resembling by their structure the spine system of the dendritic spines. Axonal terminals revealed along the axonal distribution are in contact both with the axonal trunk and with the spines. Regarding the initial segment, they are presynaptic, contain oval synaptic vesicles and form symmetric axo-axonal synapses only. In transversal sections axonal terminals are detected, arranging on the surface of the initial segment mostly as single ones, in longitudinal sections they are seen as clusters. Analysing the author's data and those from the literature, a conclusion is made that in intact animals the synaptic contacts at the initial segment of the axon are the only form of axo-axonal synapses in the neocortex.

Animals↗
PubMed1977

[Structural characteristics of the mediodorsal nucleus of the cat thalamus].

By means of the light and electron microscopy, construction and architectonics of neurons in the cat thalamus medio-dorsal nucleus are described. Differences in the neuronal body dimentions, their form, number of deferent dendrites and character of axonal branching made it possible to define 3 types of neurons. Applying the method based on retrograde axonal transport of exogenous horse-radish peroxidase, it was demonstrated that neurons of type II, contrary to the existing opinion, send their axons into the prefrontal cortex and, hence, are associative-projective. Ultrastructural difference of axonal terminals, differences in the form and size of synaptic vesicles made it possible to reveal 5 types of presynapses.

Animals↗
PubMed1976

[Experience with the use of horseradish peroxidase for light and electron microscope studies of interneuronal connections].

By the method based on a retrograde axonal transport of exogenous horseradish peroxidase (HRP), the origins of afferentation of the motor cortex of adult cats, kittens and albino rats were studied. HRP-positive neurons were found by light and electron microscopy in the somatosensory cortex (C1) of the ipsilateral hemisphere and in the portions of the cortex of the contralateral hemisphere which were symmetrical to the site of injection of HRP. The disposition of neurons, marked by HRP, in the Vth layer of the motor cortex suggest that these neurons may send their axons into the bundles of comissural fibres going to the motor cortex of the opposite hemisphere. This method considerably expands possibilities of revealing the origins of afferentation of the investigated portion of the nervous system and allows more complete and reliable investigation of interneuronal connections.

Animals↗
PubMed1975

[Ultrastructural characteristics of axon terminals of the posterior lateral nucleus of the thalamus in the cat].

Two kinds of axon terminals: fine M-terminals with the diameter up to 2 mkm and large K-terminals with the diameter up to 6 mkm were found in electron microscopic study of the posterior lateral nucleus of the cat's thalamus. M-terminals comprising 88% of the total amount of the axon terminations under analysis are characterized by a great amount of densely packed light round synaptic vesicles and solitary mitochondria. These terminals form asymmetrical type of contacts in which the post-synaptic network is distinguished with a high degree of osmiophilia. The K-terminals contain a few rarely distributed round light synaptic vesicles and many mitochondria which are disposed in the central part of the termination. These terminals form a symmetrical type of synaptic contacts with poorly pronounced active zones in these formations. In axo-axonal contacts between the described kinds of terminals the K-terminals always serve as a presynapse. After extirpation of the sincipital cortex M-terminals underwent degeneration.

Animals↗
PubMed1975

[Changes in the synaptic vesicles of cat motor cortex axon terminals upon stimulation].

The relation of the synaptic vesicle size to the distance between the vesicle and the synapse active zone was studied in the axon terminals at the motor cortex neuron spines and dendrites of resting cats (under moderate barbiturate anesthesia) and after prolonged repetitive stimulation of the somatosensory SII area. Thes sizes of the vesicles belonging to any of the three strata observed in the terminal section profile under the electron microscope were registered as a decrementing variation sequence. The predominance of small vesicles in stratum I adjoining to the synapse active zone was found by means of the statistical analysis (symbol criterion and criterion chi2), both in the control and experimental material. A significant gradient of the vesicle size diminution from peripheral stratum III to stratum I as well as vesicle size decrease both in stratum I and intermediate stratum II in comparison with the control developed after the cortico-cortical projection stimulation. The functional role of this phenomenon is discussed.

Animals↗