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Biomedical subjects

A V Akhmadeev

Publications and source records attributed to A V Akhmadeev.

At least 19 recordsLinked to original sources
PubMed2006

Characteristics of small neurons of the reticular thalamic nucleus in WAG/Rij rats.

The aim of the present work was to study the ultrastructure of small neurons in the reticular thalamic nucleus (RTN) in WAG/Rij rats, which are used as a model of absence epilepsy. A total of 24 rats were studied. The brains of 10 rats were used for studies of the cytoarchitectonics and cytological characteristics of neurons, for which paraffin sections were stained with cresyl violet by the Nissl method. Electron microscopic studies were performed by microscope-controlled harvesting of the RTN with fixation in 2.5% glutaraldehyde in phosphate buffer pH 7.4. Small neurons were found to account for 5-8% of all neurons in the RTN. These had oval bodies, sparse and pale-staining cytoplasm, and were frequently located in pairs. The ultrastructure of these neurons was characterized by poor development of cell membranes, branching of the axon close to the cell body, and multiple axon contacts with the body and dendrites. It is suggested that these neurons are short-axon neurons.

Animals↗
PubMed2006

Structural organization, neurochemical characteristics, and connections of the reticular nucleus of the thalamus.

This review analyzes current concepts of the structural organization and ultrastructure of the reticular nucleus of the thalamus (RNT) and the neurochemical characteristics of its neurons. The topography, cytoarchitectonics, and neuronal organization of this nucleus are considered in detail, as are questions of its neurogenesis. Neurochemical data clarifying the representation of neurotransmitter systems in the RNT and data on neuropeptides synthesized in its neurons are systematized. The complex ultrastructural organization of the RNT is characterized in terms of recent data from state-of-the-art immunocytochemical methods allowing localization of glutamatergic and GABAergic receptors on synaptic elements. Data on the afferent and efferent connections of the RNT demonstrate its influences on various parts of the brain and the specific features of its interactions with cortical formations.

Animals↗
PubMed2006

[Effect of gender and neonatal androgenization on dendroarchitectonics of neurons in the dorsomedial nucleus of amygdala].

The aim of this study was to establish gender-associated differences in dendroarchitectonics of neurons in dorsomedial nucleus of amygdala and the role of androgens in their formation during the period of sexual differentiation of the brain. Using Golgi method, it was demonstrated that the quantitative characteristics of long-axon sparsely branched neurons of all classes--neuroblastoform, short-dendrite and reticular--reflected the influence of gender. Specifically, it was detected that long-axon sparsely branched neurons had more branching primary dendrites and greater total dendrite length in adult males as compared to females. In adult females, androgenized neonatally by injection of 1250 mg of testosterone propionate on their postnatal day 5, the neuronal characteristics were different from those in normal females, and these differences were even more pronounced in comparison with males.

Age Factors↗
PubMed2005

Neurosecretory cells of the amygdaloid complex during estrous cycle.

Ultrastructure of neurosecretory cells of the dorsomedial nucleus of the cerebral amygdaloid complex (one of the main zones of sexual dimorphism) was studied in different phases of the estrous cycle. The characteristics of the "light" and "dark" cells change depending on the concentrations of sex steroids during estrus and metestrus.

Amygdala↗
PubMed2005

Dendroarchitectonics of neurons in the posterior cortical nucleus of the amygdaloid body of the rat brain as influenced by gender and neonatal androgenization.

The aim of the present work was to identify gender-related differences in the dendroarchitectonics of neurons in the posterior cortical nucleus of the amygdaloid body and the role of androgens in forming the dendroarchitectonics during the period of sexual differentiation of the rat brain. Golgi staining showed that long-axon, sparsely branched neurons in males had large numbers of primary dendrites, while long-axon densely branched neurons had a greater total dendrite length in females. Administration of testosterone propionate (1250 microg) to females on postnatal day 5 increased the number of primary dendrites in long-axon, sparsely branched neurons in adults as compared with the number in control females; treatment also produced a significant increase in dendrite length in long-axon, densely branched neurons, leading to an increase in the area of the dendritic field.

Amygdala↗
PubMed2005

The paleoamygdala: cytoarchitectonics, organization, and the cytological characteristics of its neurons.

The aim of the present work was to compare the cytoarchitectonics, neuronal organization, and cytological characteristics of the dorsomedial, posterior medial, and posterior cortical nuclei of the amygdaloid body (AB) of the rat brain. Series of frontal brain sections stained with cresyl violet and silver nitrate impregnation by the Golgi method were studied. The results showed that rearrangements of the nuclear principle of organization of the gray matter of the nervous system into the screened organization occur within the territory of this complex of nuclei; it consists of a sparsely branched neuron system and contains neuroendocrine cells. It is concluded that this complex of nuclei is unique in terms of its structural organization and the mechanism of development of this part of the AB, which forms in the earliest stages of AB development; it is termed the "paleoamygdala."

Amygdala↗
PubMed2005

[Characteristics of small neurons in the reticular thalamic nucleus of WAG/Rij rat].

The aim of this investigation was to study the ultrastructure of small neurons in the reticular thalamic nucleus (RTN) in rats of the WAG/Rij strain, which is a recognized model for human absence epilepsy. 24 rats were used in these studies. The paraffin sections of the brain taken from 10 rats were stained with Nissl's cresyl violet and were used for the study of neuronal cytoarchitecture and cytological characteristics. For electron microscopic study, RTN was dissected under microscopic control and fixed in cooled 2.5% glutaraldehyde solution in 0.1 M sodium phosphate buffer (pH 7.4). Small neurons were found to constitute 5-8% of the total number of RTN neurons. They had ovoid cell body, scanty pale-staining cytoplasm, often were seen in pairs. The ultrastructure of these neurons was characterized by poor development of membranes, axonal branching close to the cell body, multiple contacts of axon with cell body and dendrites. It is suggested that the neurons described are short-axonal.

Animals↗
PubMed2005

[Ultrastructural characteristics of the reticular thalamic nucleus neurons in WAG/Rij rats].

The aim of this study was to investigate the ultrastructure of the reticular thalamic nucleus (RTN) in rats of WAG/Rij strain, an established model for human absence epilepsy. Most RTN neurons are medium-to large-sized and have either dark or light appearance, depending on their functional state. Moreover, small-sized neurons with short axons are present, their characteristics being described for the first time.

Animals↗
PubMed2005

[Structural organization of the reticular thalamic nucleus].

This review presents an analysis of current data on the structural organization of the reticular thalamic nucleus (RTN). In contains a detailed discussion on topography, cytoarchitecture, neuronal organization and neurogenesis in this nucleus. The materials on RTN neurochemistry are systematized specifying the topographic representation of neurotransmitter systems and neuropeptides which are synthesized in RTN neurons. Complex ultrastructural organization of RTN is characterized on the basis of modern immunocytochemical methods, which allow to detect the localization of glutamatergic and GABAergic receptors on synaptic elements. Data on afferent and efferent connections of RTN demonstrate its influence on various brain regions and the specificity of RTN interrelations with some cortical formations.

Animals↗
PubMed2004

Structural organization of the amygdaloid complex of the rat brain.

The amygdaloid complex, traditionally regarded as part of the system of basal endbrain nuclei, has a unique structure in that it combines the two major principles of organization of the gray matter--the nuclear and the screening. Working from the studies of Zavarzin on the nuclear and screening centers, the authors suggest a classification of its structures into nuclei, paleocortex, and intermediate formations.

Amygdala↗
PubMed2004

Structural and quantitative characteristics of the dendrites of neurons in the posterior zone of the amygdaloid body in the rat brain.

The aim of the present work was to study the structure of the dendritic tree of the main groups of neurons in the posterior zone of the amygdaloid body and to analyze their quantitative characteristics. Frontal sections of rat brain impregnated with Golgi silver nitrate were used to study the characteristics of neuronal organization. Classification of neurons was based on criteria developed by Leontovich (1978) and Polyakov (1973). The main groups of neurons were long-axon, rarely branched cells, long-axon, densely branched subcortical cells, and long-axon, densely branched cortical cells. Quantitative studies of seven measures of the dendrite tree showed that the most informative parameters for differences between the main groups of neurons were the number of branching points and the number of free dendrite tips. The contents of rarely and densely branched neuron systems in the nuclei, paleocortex, and intermediate formations are described.

Amygdala↗
PubMed2004

[Rostro-caudal gradient in the amygdala structural and functional organisation].

New data supporting the assumptions of the hypothesis stating the rostro-caudal gradient in the amygdala structural and functional organization are presented. First formulated on the basis of particular location of amygdala zones possessing sexual dimorphism, the above hypothesis is corroborated by the works which characterize its structural organization, participation of amygdala rostral and caudal parts in ensuring various functions including behavior. The authors believe that the amygdala rostro-caudal gradient is predetermined by the phase character of its formation in phylogenesis.

Amygdala↗
PubMed2004

[Gender-associated and androgen dependent neonatal dendrite morphology in neurons of the posterior cortical nucleus of the amygdala].

The aim of this study was to establish gender-associated differences in dendroarchitectonics of neurons in posterior cortical nucleus of amygdala and the role of androgens in their formation during the period of sexual differentiation of rat brain. Using Golgi method, it was demonstrated that long-axon sparsely branched neurons had more primary dendrites in males, while long-axon densely branched neurons had greater total dendrite length in females. In mature female rats that received 1250 mg of testosterone propionate on their postnatal day 5, the number of primary dendrites in long-axon sparsely branched neurons was increased, while the dendrites in long-axon densely branched neurons were elongated as compared to those in control females.

Amygdala↗
PubMed2004

["Dark" and "pale" cells of the amygdala complex in dynamics of the estrous cycle].

Data on cytological peculiarities of dorsomedial nucleus neurones of the amygdala complex, one of the main zones of sexual dimorphism, in dynamics of estrous cycle are reported. We show that structural and functional characteristics of "dark" and "pale" cells may change depending on the concentrations of gonadal steroids in estrous and metaestrous stages. This specifies the previous hypothesis about mutual reorganization of these cells.

Amygdala↗
PubMed2004

[Cytochemical characteristics of neurons in the posterior amygdala].

This investigation was aimed at the comparative analysis of the intensity of RNA precursor 3H-uridine incorporation in the neurons of nuclear, transitional formations and paleocortical structures of amygdala posterior division. Significant differences were detected in the label incorporation intensity in the neurons of piriform cortex as compared to that one in neurons of the medial portion of posterior cortical nucleus.

Amygdala↗
PubMed2004

[Paleoamygdala: cytoarchitectonics, organization and cytological characteristics of neurons].

This investigation was aimed at the comparative analysis of cytoarchitectonics, neuronal organization and cytological peculiarities of dorsomedial, posterior medial and posterior cortical nuclei of rat amygdala. The series of brain frontal sections stained with cresyl violet and impregnated with silver nitrate using Golgi method were studied. It was shown that within the territory of the nuclear complex studied, the organization of the centers of the nervous system gray matter evolved from the nuclear-type into the screen-type. This formation belongs to a sparcely-dendritic neuronal system and it contains the neuroendocrine cells. As a result, it is suggested that on the basis of its structural organization and developmental mechanisms, the nuclear complex studied comprises a unified area of amygdala, which was formed at the earliest stages of its evolution, therefore it should be named a "paleoamygdala".

Amygdala↗