[Light modes and ovulation function in rats in ontogenesis].

Enhancement of illumination was shown to lead to occurrence of early and more obvious age-dependent changes of ovulation cycle in rats as compared with the same changes in animals staying in conditions of light deprivation or standard illumination. The effect of 24-hour illumination during a year induced more obvious and still earlier changes of the estrus cycle that the effect of natural illumination in the North-West of Russia with its peculiar yearly photo-periodicity (short light day in the autumn-winter period and "white nights" in the spring-summer period).

[Effect of light regimens on the age dynamics of estrous function and serum prolactin level in rats].

The effect of different light regimens (standard 12 h. light : 12 h. darkness LD; 24-hour constant light LL, light deprivation DD, natural light regimen of the North-West of Russia NL) on the age dynamics of estrous function and on the serum prolactin in female LIO rats has been studied for two years. The rats were maintained at the one of above-mentioned regimes from the age of 25 days. The cytological monitoring of the estrous cycle was conducted every three months. The level of prolactin was studied at the age of 6, 12, 18 and 24 months. It has been found out that the regimen of constant light (LL) and the spring-summer period lead to earlier maturation, premature age-related changes of the rats' estrous cycle and to the increase of the level of serum prolactin in comparison with those in rats kept at the LD regimen. Light deprivation (DD) leads to the opposite changes. It has been noted that the exposure to constant light during the whole year is accompanied by more expressed and earlier developed age-related changes of estrous cycle in comparison with the natural light of the North-West of Russia with its peculiar year photoperiodicity (short day in autumn-winter period and white nights in spring-summer period).

[Synaptogenesis in the anterior horns of the spinal cord of human embryos]. / Sinaptogenez v perednikh rogakh spinnogo mozga u émbrionov cheloveka.

Synaptogenesis in the anterior horns of the brachial spinal cord in 6-week-old human embryos (CR : 13) was studied by electron microscopy. Asymmetrical and symmetrical contacts on the soma of differentiating neurons and on the leading processes were found in the ventrolateral area of the anterior horns of the test embryos. A hypothesis is suggested about the role of these early synapses in neuronal differentiation in the embryonal nervous system.

[Structural organization of the synaptic connections of developing neurons in the anterior horns of the spinal cord in early human fetuses]. / Strukturnaia organizatsiia sinapticheskikh sviazei razvivaiushchikhsia neironov v perednikh rogakh spinnogo mozga u rannikh plodov cheloveka.

Synaptogenesis in the presumptive anterior horns of the spinal cord in early human fetuses (weeks 11 -- 12 of intrauterine development) was studied by electron microscopy. In this period of human nervous system development, various stages of the synaptic contact forming process were elucidated in the region under study: from the growth cone attachment to the neuroblastic surfaces up to mature synapses. The appearance of the first synaptic complexes provides evidence of the presence of the high-functional specialization of the synaptic apparatus in the course of differentiation of motoneurons of the spinal cord in the early stages of human antenatal ontogenesis.

[Neuroblast differentiation and migration in the developing human spinal cord in the 1st half of prenatal ontogenesis]. / Differentsirovanie i migratsiia neiroblastov v razvivaiushchemsia spinnom mozge cheloveka v pervoi polovine prenatal'nogo ontogeneza.

The processes of neuroblasts differentiation and migration in the developing human spinal cord in the first half of antenatal ontogenesis were studied by the Golgi method. The neuron development was traced from the neuroepithelial matrix cells to the maturing neurons. A possible role of a special neuroblast outgrowth as a channel for its nucleus migration to the definite typological position of the mature neuron is suggested.

[Microtubules and their relationship with the subsynaptic structures and the nuclear membrane in human neuroblasts]. / Mikrotrubochki i ikh vzaimootnosheniia s subsinapticheskimi strukturami i iadernoi obolochkoi v neiroblastakh cheloveka.

The appearance of microtubules and the development of their interrelations with the synaptic area and the nuclear envelope in differentiating neuroblasts from the anterior horn of the spinal cord in the first half of human antenatal ontogenesis was traced by methods of electron microscopy. A hypothesis was put forward on the functional purpose of the above interrelations between the microtubules with the subsynaptic area of the neuroblast and its nucleus.

[Development of interneuronal synaptic junctions in neuroblasts of the anterior horn of the spinal cord during early prenatal human ontogenesis (7--9 wks. of pregnancy)]. / Razvitie mezhneironal'nykh sinapticheskikh sviazei u neiroblastov perednikh rogov spinnogo mozga v rannem prenatal'nom ontogeneze cheloveka (7--9 ned beremennosti)

A method of electron microscopy was applied to the study of the synaptogenesis in the presumptive ventral horns of the spinal cord (C4--Th3) at the early prenatal human ontogeny. The morphological stages of synaptogenesis were traced, and the minimum of the structrual organization of the synapse, correspoding to the beginning of its functional activity, was determined. A hypothesis is put forward on possible mechanisms of synaptogenesis.