Mechanisms of formation of background activity of cerebral neurons in ontogenesis

Background activity of brain cortex neurons in ontogenesis appears very early, soon after completion of their migration. At the moment of its appearance, the background activity has several peculiarities, the most characteristic of which are its episodic character and synchronous bursts of adjacent neurons forming domains. This paper considers mechanisms determining the appearance and the most characteristic peculiarities of the background activity of cerebral cortex neurons in ontogenesis.     

Prenatal ontogenesis of the human brain cortex temporal area

Prenatal ontogenesis of temporal areas of the human cortex was studied. In the fetal cortex at the gestational age of 16-18 weeks three zones can be distinguished: marginal zone (eI layer), cortex plate and subplate. At 20-26 weeks cortex plate is divided into following layers: eII, eIII, eIV, eV and eVI, with "efferent" complex of layers being wider than "associative" one. The subplate neurons are eliminated in the fetus at 27-33 weeks, when "associative" complex composes over 50 per cent of the cortex thickness. The subplate has been identified by positive correlation between layer eII and the upper subplate layer spu cell density.     

Comparative study of formation of the frontal cortex of the brain of monkeys and man in ontogenesis]

The development of the fields of the frontal zone (8, 3, 10, 11, 12) were compared in the pre- and postnatal periods oflife in the nacaque-rhesus and man. The cyto-mielcarchitectonical and guantitative methods wereused. The square surfaces of the above fields were measured, their per cent ratios to thesquare surface of all the cortex, new cortex and frontal zone were calculated. The work hasrevealed the following: 1. General regularities in the development of frontal zones in monkeysand man: a) shorter terms for the formation of philogenetically old fields-11, 12, 8 andlonger terms for the new ones-9 and 10:b) predominant development of the frontal zone at theexpense of progressive young fields 9 and 10: c) predominat formation of the frontal zone bothkinds of primates in the postnatal period. 2. The specific features for each field (the termsfor isolation of the fields, the rate and direction of their development). 3.Substantial difference: more rapid maturation of the frontal zone in macaques (by the 6th -12th months of life)and more prolonged one in humans-by 12 years. A considerable growth of philogenetically newstructures (fields 9 and 10) in the system of all the cortex and the frontal zone wasshown in man as compared with monkey. The experimental ontogentical material is interpreted.     

The background and evoked neuronal impulse activity of embryonic neurotransplant of somatosensory brain cortex in rats

The investigation was intended for studying the character of the background and evoked impulse activity of embryonic neurotransplant neurons 4 months after homotopical allotransplantation into the barrel field of somatosensory recipient's brain cortex of the rat. It is established, that the current average frequency of background impulse activity of transplant neurons is reduced in comparison with one of the control rats. It is shown that the evoked impulse activity of neurotransplant develops with the long latency than in somatosensory cortex of the control animals. Thus in patterns of the evoked activity of neurotransplant cells reactions, characteristic for the neurons of barrel field somatosensory recipient's cortex of control rats are registered: an increase of frequency of pulses' generating, or alternating of the activation and reduction periods of impulse frequency with its subsequent regeneration up to a pristine level.     

Distribution and activity of pyridoxal kinase in human brain during ontogenesis]

The activity of pyridoxal kinase was sharply increased in whole brain tissue of human, embryos and fetuses within 6-11 weeks of development. In brain stem the maximal values of the enzyme activity was observed at early stages of prenatal development of fetuses. The activity of pyridoxal kinase was increased in cerebral cortex and in the limbic system up to complete maturation of fetuses. It correlated with the fetus age within 14-40 weeks of development as calculated per 1 g of tissue wight or 1 mg of protein. The enzyme is distributed evenly in brain of newborns, babies and adult people. Its activity in grey cortex substance is higher, than in white one. There are 2-10-fold individual fluctuations of pyridoxal kinase activity in brain of people without CNS pathology. In newborns, having prolonged hypoxy at prenatal period, the enzyme activity was on the average by 70-80% lower at different brain parts than in newborns which had no primary asphyxia. A low pyridoxal kinase activity (not more than 1-5% as compared with its normal level) was observed in different brain parts of a child affected by focal gliosis and epilepsy.     

The formation of heart-proportion in fetal ontogenesis.

In the paper, the formation of basic heart proportions in the period from the 19th to 43rd week of intrauterine development was investigated. The material consisted of 1505 fetuses (930 male and 575 female). Length, width and thickness of the heart were measured to 0.1 mm on unpreserved fetus material within 24 hours after stillbirth or death, in the natural position of the organ. The material was divided into groups representing seven developmental periods, from the 5th to the 10th lunar month. Individuals from the 41st-43rd week were recognized as carried beyond term and included in the age category above the 10th month (< 10). Formation of heart proportions was investigated on the basis of a statistical analysis of the results, with both sexes considered separately. Evaluation of the research results confirmed previous results indicating a slightly different shape of the heart in the fetal period. In addition, the results show the changes that occur in heart proportions during the period of intrauterine development. A comparison of these proportions with analogous indices in adult individuals makes it possible to predict further developmental changes in the postnatal period. In comparison to the conical heart found in a grown-up individual, the fetal heart is more spherical. At the beginning of the fetal period, the length dimension of the heart is greater than its width. Beginning with the 9th month of development, a relatively slower elongation of the heart occurs in favour of a more rapid increase in its width dimension.(ABSTRACT TRUNCATED AT 250 WORDS)