Ultrastructural changes in the lateral reticular nucleus of the medulla oblongata in prepubertal rats under the effect of long-term stress exposure.

Ultrastructural changes in the lateral reticular nuclei of the medulla oblongata of rat pups developing under the effect of chronic mental and pain stress indicate impaired histogenesis of structures of the medulla oblongata reticular formation and appearance of pronounced morphofunctional differences between the neurons.

Ultrastructural changes in neurons of medullary giant-cell nucleus in growing rat exposed to acute stress.

Ultrastructural transformations in neurons of the medullary giant-cell reticular nucleus of young rats during exposure to acute emotional and painful stress attest to activation of the protein synthesis system (nucleolar hypertrophy, well-developed elements of the granular endoplasmic reticulum, increased content of free ribosomes and polysomes) in the majority of cells and the appearance of organelle injuries in some these cells.

[Cardiomyogenesis in the embryonic period of human development]. / Protsessy kardiomiogeneza v zarodyshevom periode razvitiia cheloveka.

The morphological analysis of major processes involved in cardiac myogenesis (including cytodifferentiation, proliferation, integration and apoptosis) was carried out by studying the myocardium of 52 human embryos at weeks 4 to 8 of development. The data provided by this study, permit to draw a conclusion on the coupling of high proliferative activity of cardiomyocytes, their active divergent differentiation, formation of the integrative intercellular communications and manifestations of programmed cell death relations during this period of ontogenesis. Starting with week 6 of intrauterine life, the developing atrial and ventricular cardiac muscular tissue demonstrates the heteromorphy of constituting cardiomyocytes, which differentiate into three types: contractile, contractile-secretory and conducting ("light").

Ultrastructural analysis of reorganization of the periodontium in simulated torsion abnormality and its correction with succinic acid.

Morphological study confirmed the positive effect of succinic acid on tissue ultrastructure, energy metabolism in cells of fibroblastic differon, reorganization and neogenesis of intercellular substance of the periodontal connective tissue during the retention period after correction of simulated dental torsion abnormality in dogs.

[Reparative processes during embryonal and postembryonal myocardiogenesis in Gallus domesticus L]. / O reparativnykh protsessakh v émbrional'nom i postémbrional'nom miokardiogeneze Gallus domesticus L.

By means of light and electron microscopy methods during embryonal and postembryonal periods in birds (Gallus domesticus L.) myocardial reparative processes have been studied after its lesions produced with electrothermocoagulation. Primary closing of the wound in the cardiac wall of 3- and 5-day-old chick embryos is connected with certain reactive changes in epicardium and endocardium. In 7-10 days the cardiac wall completely restores its integrity by an intensive growth and development of intact cardiac areas. A weak development of the myocardial connective tissue stroma contributes to it. Reparative processes in the cardiac wall of 18-day-old chick embryos and in newly hatched chickens proceed with an active participation of the connective tissue, which subsequently forms a scar at the place of the lesion. Isolated redifferentiating cardiomyocytes surrounded with the connective tissue are subjected to atrophy on the 45th-60th day.

[Morphologic aspects of cardiac myocyte differentiation in Black Sea--Sea of Azov sturgeon (Acipenser güldenstädti colchicus V. Marti)]. / Morfolgicheskie aspekty differentsiatsii serdechnykh miotsitov chernomorsko-azovskogo osetra (Acipenser güldenstädti colchicus V. Marti).

Processes of ultrastructural organization of cardiac myocytes have been studied in the Russian sturgeon (Acipenser güldenstädti colchicus V. Marti) during germinal, prelarval, larval periods of development and in mature specimens. One of the main peculiarities of early cardiogenesis in this representative of Chondrostei fishes is a prolonged, observed during germinal and early prelarval periods, repression in multiplication of myocardial cells. Decreasing amount and size of yolk platelets in cytoplasm of these cells at the end of the germinal period could be connected with their intensive specific differentiation and increasing functional activity. Accumulation of free lipids during this period and their decreasing contents in early prelarval period demonstrate a certain transition to another way of metabolism. The data obtained on ultrastructure in mature specimens corresponds mainly to modern ideas on organization of the cardiac muscular tissue in other species of lower vertebrates.

[Fluorescence and electron-microscopic analysis of differentiation of the myocytes of the ventricles and atria of the avaian heart in ontogenesis]. / Svetoopticheskii i elektronnomikroskopicheskii analiz differentsirovki miotsitov zheludochkov in predserdii serdtsa v ontogeneze ptits

The histogenesis of the ventricle and atria myocardium was studied in 240 chick embryos of from 30--34 hours up to 20 days of incubation and in 66 chickens at the age of 1--90 days. Fixators were the Bouin's Carnoy's and Newkomer's fluids and the 100% solution of neutral formalin. The paraffin sections were stained by histological and histochemical methods. RNA, DNA, glycogen and lipids were detected. The ultrafine sections of the material fixed in 1% buffer solution of osmium tetroxide (pH 7,2) and embedded in araldite were prepared for electron microscopy. The contrasting was made in solutions of acetic uranium and lead citrate. Electron microscope--UEMB-100K, accelarating voltage--75 kV. The prefunctional period of cardiogenesis is characterized by most intensive processes of specific differentiation of cardiac myocytes and by accumulation of energetic material. With the growing functional activity of the tubular heart the amount and size of lipid drops in the cytoplasm of differentiating cardiomyocytes diminished suggesting the use of lipids as the main source of energy. In the period of formation of the heart the trabecular myocardium of ventricles and the atria myocardium, seeming to perform the main functional load, are characterized by a better developed contracting apparatus and a considerable content of glycogen granules. A sharp decrease of the glycogen content at the end of the embryonic period is likely to be due to growing hypoxia, the appearance of lung respiration and transition to the other type of energy metabolism.