PubMed Health⌕ Search

Biomedical subjects

T A Leontovich

Publications and source records attributed to T A Leontovich.

At least 19 recordsLinked to original sources
PubMed2006

A common system of sparsely-branched projection (reticular) NADPH-diaphorase neurons in formations of densely-branched cells in the human forebrain.

Morphometric studies of human forebrain formations composed of densely branched cells - the entorhinal cortex, the basolateral amygdala, the nucleus accumbens, the striatum, and the dorsal thalamus - were performed using nine parameters, with statistical analysis of the resulting data; measurements addressed the major projection-type densely branched and sparsely branched reticular neurons (scattered reticular and marginal reticular cells of the dorsal thalamus) stained by the Golgi method and with NADPH-diaphorase. Scattered reticular cells in the various formations showed no differences in any of the nine measures, while there were significant differences (in 5-7 measures, apart from one comparison, where there were differences in two measures) in their major projection-type densely branched cells. Scattered reticular and main projection-type densely branched neurons in each formation differed in terms of 7-9 measures. In endbrain formations, scattered reticular neurons contained NADPH-diaphorase; in the dorsal thalamus, only intermediate marginal reticular neurons were NADPH-diaphorase-positive. Thus, these human formations contained a common system of ancient integrative NADPH-diaphorase-containing reticular cells. Our results, along with published data, show these to be projection-type cells with projections to layers V and VI of the neocortex, which suggests that they have modulatory influences on its descending systems.

Adult↗
PubMed2004

Neurons of the basal ganglia of the human brain (striatum and basolateral amygdala) expressing the enzyme NADPH-d.

Types of NADPH-d+ neurons (Vincent et al., 1983) were identified in the striatum and basolateral nuclei of the amygdala; striocortical neurons were detected in the striatum using the DiI marker (Belichenko and Dahlström, 1995). NADPH-d+ cells were numerous. Staining of these cells and all their processes, along with our previous studies of the neurons in these formations in the human brain using the Golgi method, allowed us to identify their shapes and identify them as sparsely or extensively branched cells. The main efferent neurons of the striatum and basolateral amygdala (extensively branched medium spiny cells and bushy spiny cells respectively) and their extensively branched interneurons did not contain NADPH-d. Efferent NADPH-d+ neurons included reticular, sparsely branched cells with long dendrites, which were the most numerous cells in both formations, as well as occasional large multipolar branched neurons; the striatum also contained numerous sparsely branched short-dendrite cells (a neuron type most represented in the brainstem and especially the reticular formation). Projections of reticular cells from the striatum to the cortex were demonstrated. NADPH-d+ interneurons were sparsely branched: in the striatum, these were slender, long-dendrite, bipolar cells (numerous), ordinary bipolar cells, twisted and large dendrite-poor cells; the amygdala contained the same bipolar cells along with radial neurons. Thus, NADPH-d+ neurons in these formations were more ancient, i.e., structurally less complex, cell types.

Adult↗
PubMed2002

[Neurons of the human basal ganglia (striatum and basolateral amygdala) expressing the enzyme NADPH-d].

In human striatum and basolateral amygdala NADPH-d+ neurons were revealed (after Vincent et al., 1983); and in striatum strio-cortical neurons were also revealed using DiI marker (after Dahtstrom and Belichenko, 1995). The NADPH-d+ neurons were numerous in both formations. Staining of NADPH-d+ neurons with their processes, and our previous study of striatal and amygdalar human neurons by Golgi method made it possible to identify the species of neurons with their assessment as sparsely or densely branched. The main efferent neurons of striatum and basolateral amygdala (densely branched medium spiny and bushy spiny, respectively) and their densely branched interneurons were not marked. Efferent NADPH-d+ neurons included the most numerous ones in both formations. A projection of reticular striatal neurons to cortex was also shown. The NADPH-d+ interneurons belonged to sparsely branched forms. In striatum they included slender-dendritic and long-dendritic bipolars (numerous), ordinary bipolars, twisted and large poor-dendritic cells; in amygdala--the same bipolars and radial cells. Thus, the NADPH-d positive cells in the formations under study were represented by more "ancient" or less structurally complex cell forms.

Adult↗
PubMed1999

Morphological study of the entorhinal cortex, hippocampal formation, and basal ganglia in Rett syndrome patients.

Entorhinal cortex (EC), fascia dentata (FD), hippocampus (HP), and basal ganglia (BG) were studied in Rett syndrome (RS) cases and compared with control brains and an autism case. Kluver-Barrera and Golgi methods were used. In RS most of the areas of EC, HP, and FD showed severe cell hypochromia. In the EC all cells of layer II and most in layer III were in a state of total chromatolysis or were "ghost" cells, but the cells of layers V and VI were preserved and moderately hyperchromic. In FD and HP the majority of the granular cells and cells of CA3 and CA4 fields were severely hypochromic, whereas in the CA1 field most cells were normal or slightly hypercaryochromic. In BG mostly mild or moderate aberration from normal cell structure was observed: in striatum, mild hypercaryochromia of small neurons and more expressive hyperchromia of large neurons were found; and in pallidum, mild or moderate hypercaryochromia to severe hyperchromia in pallidum internum was found. Degeneration of thick myelinated fibers was evident in pallidum. Large striatal and pallidal neurons showed signs of constructive changes in Golgi slices. These data allow the determination of the cause of the main symptoms of RS. The motor disorders, including specific stereotyped movements, could be related to the enhanced activity of BG cells due to their deafferentation from the side of the neocortex and to supposed hyperactivity of the EC-striatal pathway; the mental retardation and epileptic seizures could be due to FD-HP involvement.

Adolescent↗
PubMed1998

[The cellular structure of the islands of Calleja Magna in the brain of carnivores].

Complex study of the structure of islands of Calleja in carnivore brain (cat and dog) was conducted. Using Nissl and Golgi methods, HRP axonal transport and electron microscopy the islands were found to be composed of cells of 3 types varying in size, shape, dendrite spatial distribution and ultrastructure. The majority of cell population in the islands is formed by small granular cells with scarce medium-sized, mitral-like and larger cells among them. The administration of retrograde marker into posterolateral hypothalamus provided the evidence for the presence of cells in the islands of Calleja projecting to this area. These were found to be mitral-like cells. Other cells did not exhibit staining. The resemblance between mitral-like and granular cells of the large islands of Calleja with mitral-like and granular cells of olfactory bulb, respectively, supports our assumption that these islands compose the central sensory nucleus (presumably of the sensory terminal nerve).

Animals↗
PubMed1990

Peculiarities of the polypeptide composition of the morphofunctionally different neurons of the rat brain.

The present study was aimed to identify peculiarities of the polypeptide composition in three morphofunctionally different classes of neurons of the rat brainstem: giant multipolar neurons of n. reticularis gigantocellularis, relay sensory neurons of lateral geniculate body and pyramidal neurons of the pyramidal layer of the CA3 - CA4 fields of hippocampus. The method of free hand dissection of neurons and sodium dodecyl sulfate (SDS) slab gel microelectrophoresis in our modifications were used. Polypeptide peculiarities for each class of investigated neurons have been found. Most of these polypeptides belong to the low molecular weight range (8.8-24.3 KD) of the polypeptide spectra and only some of them to the high one (64.6-75.3 KD).

Animals↗
PubMed1990

[The effects of the electrical microstimulation of the areas of the location of different cell types in the caudate nucleus].

Effects of electrostimulation of the caudate nucleus in cats were studied in chronic experiments. Position of electrolytic lesions resulting from stimulation was examined histologically with respect to the surrounding cell type. Stimulation of the caudate nucleus zones with cells responding to sensory stimuli induced cat's movement and corresponding lesions were situated around striosomes among large cells with long axons. Stimulation of "silent" zones (where we failed to record any neuronal activity) did not modify cat's behaviour, corresponding lesions were found inside striosomes in clusters of small and medium-size cells. Results obtained from this study confirm the previous conclusion that neurons which activity was recorded extracellularly in the caudate nucleus belong to large long-axon cells.

Animals↗
PubMed1989

[Morphometry of giant multipolar neurons of the brain stem reticular formation in rats on board the Kosmos-1667 biosatellite].

Giant multipolar neurons of nucleus reticularis gigantocellularis of rats which had been kept on board the biosatellite "Kosmos-1667" were morphometrically studied. There was a trend towards the increase in the cellular surface, the maximum diameter of dendritic field, the volume of the whole dendritic territory in the test group ad in the control experimental group kept on the earth. A reliable decrease in dendritic mass oriented to nucleus vestibularis and an increase in dendritic mass oriented to the midline were also found in test group, as compared to 3 control groups. Our data were discussed in the light of nervous tissue plasticity in adult mammals.

Animals↗
PubMed1989

[Various principles of the organization of preterminal and terminal branches of afferent conductors in neuropil of the snail dorsal ganglia].

Character of ramifications in the preterminal and terminal axonal parts in the neuropil of the dorsal ganglia have been studied in 16 edible snails (Halix pomatia). The nervous tissue is impregnated with silver nitrate after Golgifast method. Serial sections are made in two projections: horizontal and vertical. The analysis of peculiarities of the spatial distribution of the afferent fibers (AF) demonstrates their several forms that are united into the following types: dominant, probable and transitional. Comparison of the edible snail AF with those in the higher vertebrata makes it possible to conclude that the character of ramification of their preterminal and terminal parts and principle of organizational connections of the AF with the postsynaptical structures are principally similar.

Afferent Pathways↗
PubMed1986

Dendritic changes in the basal nucleus of Meynert and in the diagonal band nucleus in Alzheimer's disease--a quantitative Golgi investigation.

Golgi-impregnated reticular neurons and multipolar giant neurons, the two main classes of neurons in the basal nucleus of Meynert and in the diagonal band nucleus, were investigated morphometrically in five cases of Alzheimer's disease, and compared to controls. Both degenerative as well as regenerative neuronal changes were observed in cases of Alzheimer's disease. Degenerative changes such as irregular swellings and the fragmentation of dendrites are most pronounced on reticular neurons but can also be detected to a lesser extent on multipolar giant neurons. Regenerative changes are restricted to reticular neurons. They are characterized by the appearance of perisomatic filopodia, by an increase in the size of cell soma, by an increase in the degree of dendritic arborization and spatial extension of the dendritic tree. These regenerative changes are probably signs of a compensatory mechanism which might be induced by degeneration in this area.

Alzheimer Disease↗
PubMed1986

[Efferent connections of the striatum with the Ep field of the temporal cortex in the cat].

When horseradish peroxidase was injected into the Ep area of the temporal cortex of 5 cats, the distribution of the labelled neurons in the strio-pallidum and in the nucleus of Meynert was similar in all the cases. In the striatum predominantly large cells (in the nucleus caudatus and in the putamen), as well as middle and small (in the putamen) cells were labelled. Comparing the form and size of the labelled cells in the striatum, revealed in Golgi preparations, it is possible to conclude that large labelled neurons correspond to long-axonal sparsely-branching reticular neurons, and middle and small--to long-axonal densely-branching dendroid "spinular" neurons. The large cells of the striatum can be considered as a part of a vast macrocellular ascending system of the forebrain, its preservation maintains the higher integrative functions of the brain.

Animals↗
PubMed1985

[Quantitative analysis of the structure of neuronal dendritic spines in the striatum using the Leitz-ASM system].

Two principal classes of striatum long axonal neurons (sparsely ramified reticular cells and densely ramified dendritic cells) were analyzed quantitatively in four animal species: hedgehog, rabbit, dog and monkey. The cross section area, total dendritic length and the area of dendritic field were measured using "LEITZ-ASM" system. Classes of neurons studied were significantly different in dogs and monkeys, while no differences were noted between hedgehog and rabbit. Reticular neurons of different species varied much more than dendritic ones. Quantitative analysis has revealed the progressive increase in the complexity of dendritic tree in mammals from rabbit to monkey.

Animals↗
PubMed1985

[Quantitative morphologic characteristics of neurons of the sensory nuclei of the trigeminal nerve developing after partial deafferentation].

Five types of neurons were studied in the sensory nuclei of the trigeminal nerve stained by the Golgi method in kittens aged 30 days with bilateral transection of the lingual branches of trigeminal nerve made on the fifth postnatal day. Partial deafferentation resulted in changes of dendrite apparatus of reticular, arborescent and bushy neurons (68.61 and 48% of neurons changed). Short-dendritic cells changed slightly. The multipolar giant neurons underwent practically no changes. All the changes could be divided into two groups: destructive changes and constructive changes. The destructive changes consisted in the decrease of cell body sizes, number, length and ramification of dendrites and constructive changes--in the increase of these parameters. Various types of trigeminal neurons responded to deafferentiation in different ways. Bushy neurons displayed mainly destructive changes and reticular and arborescent neurons--both destructive and constructive ones.

Animals↗
PubMed1983

[Spatial organization of tissue elements of the caudate nucleus in the dog].

Simple methods for quantitative analysis of nerve cells and their processes in n. caudatus of dog are suggested. Some principal features of the internal arrangement of n. caudatus are established and correlated with other brain system. Graphic reconstruction of small cells ensembles and their distribution within the nucleus is given. Physiological role of small cell ensembles and large caudate cells (long axoned and short axoned) for caudatocortical transmission of excitation is considered.

Animals↗
PubMed1982

[Quantitative morphologic characteristics of developing neurons of the sensory nuclei of the trigeminal nerve in the kitten].

The paper presents a quantitative Golgi study of the kitten sensory trigeminal complex. Kittens of 1-5 and 30 days were used. Trigeminal neurons were divided into five groups. Neurons of two groups ramified sparsely and were defined as "reticular" and "short dendritic" neurons. Neurons of three other groups ramified densely and were defined as "bushy" neurons, "arbory dendritic" and "multipolar giant" neurons. The quantitative morphological data were obtained by measuring cell sizes, number, length, relative length, degree of branching of dendrites and total cell branching. The neurons of different groups had different parameters and a special mode of their maturation. "Bushy" neurons showed regressive changes during ontogenesis. All their parameters were reduced during the first month. Foci of maximal dendritic branching were displaced towards the distal portions of dendrites during the processes of cell maturation. All trigeminal neurons reached the high degree of maturity at birth.

Animals↗