Callosal connections in the cat parietal cortex during postnatal ontogenesis

By means of the method based on the retrograde axonal transport of horseradish peroxidase topography, quantitative and qualitative composition of homotopic neurons in the cat cerebral parietal associative cortex performing callosal connections have been studied. When comparing the data of the experiment with those previously obtained on distribution of the axonal terminals in the comissural neurons, certain places are revealed where concentration of the homotopic callosal connections of the parietal cortex field 7 take place. A morphological characteristic of the longaxonal pyramidal and stellate neurons forming these connections is presented.     

Compensatory hypertrophy of golden hamster ovaries during early postnatal ontogenesis]

The right-side ovariectomy in the golden hamster females during the prepubertate period resulted in the compensatory hypertrophy of the rest paired organ. The morphological rearrangement of the hypertrophied ovary represented the shift in the quantitative distribution of follicles by the maturation stages towards the predominance of mature forms. The accelerated growth and differentiation along the path of normal postnatal ontogenesis led to the earlier ovulations in the hypertrophied ovary.     

Functional and morphologic characteristics of limbic cortex maturation during early ontogenesis

Development of the limbic cortical area in postnatal ontogenesis of the rabbit comprises three periods judging by the parameters of impulse activity of neurones and cytoarchitectonic differentiation. The period of stratification and beginning of cellular differentiation functionally corresponds to the manifestation of simple forms of spike activity (single, group) with long inactivation periods (the first week of life). The period of intensive cytoarchitectonic differentiation with separation of the agranular type of the anterior limbic area structure correlates with a more complex neuronal impulse activity (burst discharges), augmenting spectrum of dominating spike frequencies, predominance of phasic activation and specific responses together with a high total neuronal responsiveness to sensory (acoustic) stimuli (the second to third week of life). The period of complete cytoarchitectonic maturation corresponds to the stabilization of functional properties of neurones (the fourth to sixth week of life). The revealed ontogenetic dynamics of morpho-functional reorganizations in the limbic cortex point to its involvement at an early stage of postnatal life in the mechanisms of sensory analysis and of the formation of adequate adaptive reactions.     

Hypoxia-induced lipid peroxidation in the brain during postnatal ontogenesis

Reactive oxygen species (ROS) are common products of the physiological metabolic reactions, which are associated with cell signaling and with the pathogenesis of various nervous disorders. The brain tissue has the high rate of oxidative metabolic activity, high concentration of polyunsaturated fatty acids in membrane lipids, presence of iron ions and low capacity of antioxidant enzymes, which makes the brain very susceptible to ROS action and lipid peroxidation formation. Membranes of brain cortex show a higher production of thiobarbituric acid-reactive substances (TBARS) in prooxidant system (ADP.Fe(3+)/NADPH) than membranes from the heart or kidney. Lipid peroxidation influences numerous cellular functions through membrane-bound receptors or enzymes. The rate of brain cortex Na(+),K(+)-ATPase inhibition correlates well with the increase of TBARS or conjugated dienes and with changes of membrane fluidity. The experimental model of short-term hypoxia (simulating an altitude of 9000 m for 30 min) shows remarkable increase in TBARS in four different parts of the rat brain (cortex, subcortical structures, cerebellum and medulla oblongata) during the postnatal development of Wistar rat of both sexes. Young rats and males are more sensitive to oxygen changes than adult rats and females, respectively. Under normoxia or hypobaric hypoxia both ontogenetic aspects and sex differences play a major role in establishing the activity of erythrocyte catalase, which is an important part of the antioxidant defense of the organism. Rats pretreated with L-carnitine (and its derivatives) have lower TBARS levels after the exposure to hypobaric hypoxia. The protective effect of L-carnitine is comparable with the effect of tocopherol, well-known reactive species scavenger. Moreover, the plasma lactate increases after a short-term hypobaric hypoxia and decreases in L-carnitine pretreated rats. Acute hypobaric hypoxia and/or L-carnitine-pretreatment modify serum but not brain lactate dehydrogenase activity. The obtained data seem to be important because the variations in oxygen tension represent specific signals of regulating the activity of many specific systems in the organism.     

Local proliferation of cells of the granular layer of the dentate gyrus of the mouse hippocampus during postnatal ontogenesis and following brain injury]

The local cellular proliferation takes place in the inner part of the dentate gyrus granular layer, the subgranular zone, of mice. The proliferating cells of the subgranular zone are one of two sources of postnatal neurogenesis of the granular layer (another source-cells of the subependymal zone). The subgranular zone becomes markedly thinner with the age but even in adult mice the cellular proliferation occurs in it. Under the brain trauma, the proliferation of the subgranular zone cells is activated. Besides cell division in the subgranular zone, there is insignificant proliferation in the differentiated part of the granular layer. Special studies are, however, necessary to identify dividing cells in the differentiated part of the granular layer.     

Incorporation of 3H-thymidine into glial cells of the parietal region and cells of the subependymal zone of two-week and adult mice under normal conditions and following brain injury]

Potencies of brain cells to DNA synthesis and proliferation were studied in two weeks old and adult mice in the norm and after the brain mechanical injury. No labeled large and middle neurons were found in the brain of intact and operated animals both under the pulse 3H-thymidine incorporation and saturation of mice with 3H-thymidine during 36 hrs. The same types of brains cells were labeled both in intact and operated two weeks old and adult mice: glial cells, cells of the subependymal zone, cells of the dentate gyrus inner margin, and sometimes, cells having characteristics of microneurons. The number of glial cells in the temporal cortex of intact mice diminished with the age. Under the brain trauma, the proliferative reaction of glia was expressed in a similiar way both in two weeks old and adult mice. The index of labeled cells in the subependymal zone is the same in these two age groups. With the age the cellular mass of subependymal zone decreases, rather than proliferative tendencies of supependymal zone. The brain traumatization resulted in the increase of labeled subependymal cell only under the direct injury of subependymal zone.     

Quantitative changes of the C-cell population in the rat thyroid during postnatal ontogenesis

Summary The number and distribution of C-cells in the rat thyroid gland, have been investigated during postnatal ontogenesis from birth to 120 days of age. The argyrophilic and metachromatic properties of these cells were used to identify them. In the thyroid of newborn rats the C-cells do not exhibit argyrophilia and metachromasia. These reactions appear at 10 days and can be seen at all subsequent ages. The number of C-cells shows a parallel increase with age as demonstrated by the change in the proportion of C-cellsF-cellscolloidstroma during development. A marked increase in C-cells was found at 50 days of age when the proportion of C-cells rose to 27.67% from the value of 16.78% at 30 days. At 70 days a decrease was noted (20.50%) which hardly changed until 120 days of age (22.20%). The numerical increase in C-cells occurs at the expense of the follicular epithelium and stroma.The C-cells occupy elongated islet-like region in the central part of the lobe, decreasing in number towards the periphery where no C-cells are present. The long axis of the C-cells area is parallel with the longitudinal axis of the lobe. The area of C-cells is largest at the centre of the lobe, corresponding to the territory of the peak of the Gaussian curve for the numerical distribution of C-cells.     

Quantitative microscopic characteristics of cardial glands in in the human esophagus in postnatal ontogenesis

Microscopical investigation of oesophagus, obtained from corpses of 33 men and 33 women has been carried out (staining with hematoxylin and eosin, van Gieson). The cardial glands have been revealed in 92.4% of cases in the inferior and in 4.6% of cases in the superior third of the oesophageal wall. They have not been revealed in the superior third of the oesophageal wall. They have not been revealed in its medial third. Amount of acini in the section is essentially changeable. In elderly and old persons the ducts of the glands often form ampullar dilatations. The acinar areas on the section remain stable during the greatest++ period of the postnatal ontogenesis and only during old age they decrease slightly. The proper plate of the mucous membrane in the inferior part of the oesophagus in the zone, where the cardial glands are situated, is always thicker than in the area free from the acini. Close interrelations have been revealed between the cardial glands and lymphoid tissue of the oesophageal wall. The intensity of the glandular-lymphoid interrelations is insignificant in newborns and in children of suckling age. It is maximal in persons of mature and elderly age. Remaining at a sufficiently high level, the glandular-lymphoid associations in old persons are manifested in a less degree than in the previous age groups. No difference in organization of the cardial glands has been revealed in the superior and inferior parts of the oesophageal wall, as well as any sex peculiarities.     

Functional maturation of the cat visual cortex during prenatal ontogenesis]

Development of the perceiving function of the visual cortex was studied on the foeti of cats in the second stage of antenatal development with intact placental blood circulation. It has been found that functional maturing of the cortical end of the visual analyser starts at the beginning of the second half of antenatal life. At this period EPs to stimulation of the optic nerve are recorded throughout the dorsal cortex of the contralateral hemisphere. At first they appear as slow three-phase (positive-negative-positive) oscillations of a small amplitude. As the foetus develops, the EP amplitude increases, and the EP configuration in the striate zone of the cortex becomes complex. Two weaks before birth, a short-latency negative wave appears against the background of the primary positive oscillation. In the last week of antenatal development of the foeti and in the first few days of the kittens life, EPs are represented in the specific zone of the visual cortex (g. lateralis) as two negative oscillations, and in the so-called associative zone (the middle part of the suprasylvian gyrus) by one long-latency high-amplitude negative oscillation which corresponds by latency to the second negative EP component in the striate cortex.     

Various characteristics of the activity of skeletal muscles in humans and dogs during postnatal ontogenesis

At normal ambient temperatures, in absence of stress, in babies during first months of life (in contrast to less maturely born mammals), the respiratory activity of skeletal muscles is not realized, being observed only under stress conditions. In 1-1 1/2 months old puppies, after deafferentation of the hindlimb, the frequency of movements of a jerk type increases approximating the level observed in newborn animals. At normal ambient temperatures, these puppies exhibit respiratory activity of skeletal muscles which is not observed at this age in control animals.     

Differentiation of oxyntic cells during early ontogenesis in the bovine

The origin and the differentiation of oxyntic cells in fetal bovine abomasum were investigated using transmission electron and light microscopic methods. In the oxyntic gland region oxyntic cell precursors and immature oxyntic cells appear as early as at the end of the first trimester of gestation--much earlier than described in any other mammalian animal species. Immature oxyntic cells are characterized by long apical microvilli, by their triangular-shaped light cytoplasm rich in large and numerous mitochondria, by the existence of vesicular profiles and by the incipient invagination of the apical plasma membrane forming a primitive intracellular canaliculus expanding into central areas of the cell. The oxyntic cell represents the first exocrine cell type developing from secretory granule-containing cells in the base of the primitive gastric glands.     

Quantitative and qualitative characteristics of synapses in different layers of the auditory cortex

An electron-microscopic study was made of 4520 synapses in different layers of the cat auditory cortex. Of the total number of synapses 53% were located on dendritic spines, 37% on dendrites, and 10% on neuron bodies; 91% of the synapses belonged to Gray's type I, 9% to type II. Most of the type I synapses were located on dendrites and dendritic spines, whereas the type II synapses were distributed on neuron bodies, axon hillocks, and large dendrites. Signs of degeneration were discovered 60 h after complete neuronal isolation of an area of the auditory cortex in 22.8% of synapses. No degenerating type II synapses were found. This indicates that they are formed by axons of intracortical neurons. The quantitative and qualitative composition of the synapses were shown to differ in different layers of the auditory cortex.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 12, No. 2, pp. 131–137, March–April, 1980.     

Ultrastructure of the hypophysiotropic region of the hypothalamus in early ontogenesis in rats]

The results of electron microscopic studies have shown that the 16--18 days old rat embryos already have in the hypophysiotropic area some structures necessary for the realization of neuroendocrine regulations. In the arcuate nuclei, the neurosecretory cells differentiate which are capable to synthesize specific neurosecretory granules of 800--1,000 A in diameter. In the median eminence, the primary portal capillaries develop with which tanicytes and a few axon terminals make contact. One can see in the tanicytes the signs of active transport and accumulation of electron dense polymorphic material. All these phenomena are strengthen during the subsequent development. Hence, several days are before birth the neurosecretory and glial elements of the embryos show the signs of functional activity which strengthen during ontogenesis and are expressed most distinctly in the adult animals.