Morphology and Ploidy of Smooth Muscle Cells in Chorionic Arteries under Different Hemodynamic Conditions.

Smooth muscle cells from the arterial wall of placental chorion were studied at 39-40-week gestation. The content of mono- and binuclear tetraploid myocytes was higher in sites of arterial branching and turns (27.3% vs. 4.4% straight parts of the arteries; DNA cytophotometry data). Mitoses were found only in these arterial regions (0.18%). Regional changes in the sizes of diploid and polyploid myocytes were detected, associated with the blood flow pattern in the chorion; myocyte hypertrophy was 17-fold more incident in sites of arterial turns and branching than in straight arteries. Possible causes of changes in the proliferative characteristics and subsequent growth of the chorionic arterial wall myocytes are discussed.

Structural Organization of Arterial Vessels in Placental Hypoplasia.

Structure of the placental arterial bed was studied using histological and morphometric methods. The formation of smooth muscle regulatory complexes in blood vessels of the chorionic plate and chorionic villi was demonstrated. These complexes are genetically determined and represent a variant of compensatory and adaptive reorganization of the placental arteries for adequate fetoplacental blood supply under normal conditions and placental underdevelopment.

The use of micronucleus test for detection of genotoxic damage to the thyroid gland.

We studied the possibility of using the micronucleus test in in vivo experiments on the model of rat follicular thyrocytes prestimulated to cell division (hemithyroidectomy). Single administration of N-nitroso-N-methylurea produced a significant dose-dependent effect on micronucleus formation in thyrocytes and polychromatophilic erythrocytes of the bone marrow. The test system allowed us to reveal a cumulative effect of 2-fold and 4-fold treatment with the mitogen in low or subthreshold doses on the thyroid gland. Our results indicate that the micronucleus test is an informative method for the analysis of the effect of genotoxic agents on the thyroid parenchyma.

[Smooth myocytes of cerebral arteries at the emergency stage of hypertension].

The objective of this study was to analyze the structural modifications of smooth myocytes (SM) in the tunica media of cerebral arteries at the emergency stage of hypertension. SM were isolated by the method of targeted alkaline dissociation from the tunica media of medial cerebral artery in 22 pups (10 animals comprising the control group). Emergency stage of hypertension was induced by an experimental aortal coarctation. Mathematical analysis of parameters of arterial pressure, inner diameter and tunica media thickness is indicative of a reduction of permissible tensile strength of cerebral arteries. The transformation of vascular SM was demonstrated that included the increase in their dimensions and the decrease of their nuclear/cytoplasmic ratio. Destructive and compensatory-adaptive SM changes (increase of nuclear DNA content and of the proportion of binuclear forms) were detected. These changes in the structure of arterial SM population in combination with the decrease of permissible tensile strength, may contribute to an increased risk of vascular wall rupture and the development of an acute dysfunction of cerebral circulation.

Ploidy of micronucleated thyrocytes induced by methylnitrosourea injection.

Ploidy of thyroid parenchyma was studied in adult rats in the control and on day 9 after hemithyroidectomy; operated animals received 3 injections of N-nitroso-N-methylurea. The population of follicular thyrocytes is mainly diploid; total count of polyploid cells increased from 4.4% in the control to 8.5% in experimental rats. All thyrocytes containing micronuclei were tetraploid. No diploid micronucleated elements were detected. This suggests that genetically damaged thyrocytes divide by the mechanism of acytokinetic (polyploidizing) mitosis.

Polyploidy of smooth myocytes in coronary arteries.

Study of smooth myocytes in coronary arteries of dogs with experimental coarctation of the aorta revealed increased DNA content in myocyte nuclei and increased percentage of binucleated cells. Polyploidy of vascular myocytes did not disappear after correction of the aortal defect.

[Proliferative properties of cell differons in the vascular wall]. / Proliferativnye svoistva kletochnykh differonov sosudistoi stenki.

Using quantitative methods (radioautography using thymidine label, DNA cytophotometry and mitotic index definition) proliferative properties of the vascular wall main cell differons (endothelium, smooth myocytes and fibroblasts) were investigated in 60 rats during postnatal and reparative morphogenesis. Most pronounced DNA synthesis was noted to occur in aortal endothelium in newborn animals and in fibroblasts of adventitia in 1 and 6 months and old aged (2.5 years) rats. In various vessel types of adult animals significant differences of label incorporation in fibroblasts of adventitia were not revealed whereas endothelial daily proliferation pool varies significantly showing minimal value (0.5%) in inferior caval vein and maximal (6%)-in capillaries. During the regenerative morphogenesis of aorta, caused by adventita cryodestruction proliferative activity elevation was noted in all the cell types, most reactive of them being smooth myocyte differon of the media.

[The cytological mechanisms of the postnatal growth of aortic endothelium]. / Tsitologicheskie mekhanizmy postnatal'nogo rosta éndoteliia aorty.

Contribution of proliferation and hypertrophy of endotheliocytes to the postnatal growth of the internal aortic lining in rats was estimated using organo- and cytometry, cytophotometry of nuclear DNA, radioautographic analysis of 3H-thymidine incorporation, determination of the mitotic index and the number of binucleated cells. Mitotic divisions of diploid endotheliocytes (in adult rats, their proportion attains 97-98%) is the principal cytological mechanism that, throughout the life of an animal, provides for an increase in the area of endothelial layer. Cell hypertrophy, which is unrelated to polyploidization, develops only during the first month of postnatal life. In old rats (2.5 years of age), an increased proportion of binucleate cells (2c x 2) and cells with pycnotic nuclei is observed.

[The mitotic origin of binucleated cells in regenerating endothelium]. / Mitoticheskoe proiskhozdenia dvukhiadernykh kletok v regeneriruiushchem éndotelii.

Regeneration of endothelium after the local cryodestruction of the aortic wall in rats was studied using quantitative methods (determination of the pool of proliferating cells after multiple injections of 3H-thymidine, of the mitotic index and proportion of binucleated cells, and cytophotometry of DNA content in cell nuclei). It is demonstrated that binucleate endotheliocytes are formed as the result of acytokinetic mitosis. According to our calculations, this mechanism completely provides for the increase in the proportion of binucleated cells observed in the regenerating endothelium on days from 2 to 6 after the operation.

[State of the rabbit aorta after orthostatic tests]. / Sostoianie aorty krolikov posle ortostaticheskogo vozdeistviia.

Morphometric examinations of endothelium film preparations and histological investigations of aortic sections were performed 1 to 50 days after exposure of rabbits to orthostatic tests. Immediately and 1.5 months after exposure the intima showed a significant increase of endotheliocytes, vacuolization of the cytoplasm and nuclei, development of karyopyknosis and karyolysis as well as increase of monocytes and lymphocytes. Beginning with day 4 the inner surface of the intima displayed microthrombi and beginning with day 7 the media showed necrotic changes, which may cause wall deformation due to the destruction of the collagen and elastic layers. At the same time the endothelium exhibited adaptive-compensatory processes, which included increased mitotic activity of endotheliocytes and their intracellular regeneration. The identification of the coefficient of variation of centered ordinates helped to distinguish an early phase of orthostatic responses (days 1-2), phase of adaptive and compensatory changes (3-15), and phase of remote effects and stabilization of the aortic endothelium. These observations should be taken into consideration when determining optimal time periods of recovery after lesions caused by acute fluid shifts.

[Aortic endothelium and serum lipoproteins in rats during the restorative period after 30-day hypokinesia]. / Endotelii aorty i lipoproteidy syvorotki krovi krys v vosstanovitel'nom periode posle 30-sutochnoi gipokinezii.

Experiments in 49 albino rats indicated that serum beta-lipoprotein levels were increased on days 1 to 8 and 24 to 29 of readaptation following 30-day restriction of motor activity of the animals kept in the individual cramped cages. The alpha-lipoprotein concentrations were decreased in initial periods and elevated on days 18 to 23 of restoration. In the course of readaptation, the aortic endothelial layer showed greater lymphocyte and monocyte counts and larger number of endotheliocytes with karyopyknosis, karyolysis, and larger number of mitotically divided and binuclear cells. The extent of endotheliocytes and their cytoplasm and nucleus was persistently lower on day 3 to 55 of readaptation.

[Body weight dynamics of laboratory white rats in the postnatal development period]. / Dinamika massy tela laboratornykh belykh krys v postnatal'nom periode razvitiia.

Dynamics of body mass has been followed in 663 noninbred animals from birth up to 3.5 years of age. The rats are kept in vivarium, taking into account necessary demands upon their diet, breeding, amount of the brood and sex dimorphism. The offspring is obtained with a strictly dated time of birth. During the first month of life they are weighed daily (up to a complete maturation, specimens of both sex are measured, till intensity of males and females growth is similar), and then with the interval, increasing as a geometrical progression, with a coefficient 1.1 up to the 1231st day after birth (males only). At every period of observations no less than 7 animals are examined, average mass and standard deviation are calculated. Dynamics of the parameters are determined by means of sliding average. Using the curves on the body mass changes in the laboratory rats during nearly their whole life, it is possible with a desired precise to determined their age at carrying out investigations of wide range on ontogenesis of organs and tissues, when the animals are bred in nurseries.

[Morphometric analysis of aortic endothelium and serum lipoproteins in rats during readaptation after 15-day hypokinesia]. / Morfometricheskii analiz éndoteliia aorty i lipoproteidy krovi u krys v period readaptatsii posle 15 sut gipokinezii.

On hypokinesia day 15, the serum concentration of beta-lipoproteins increased and that of alpha-lipoproteins decreased, and the aortic endothelium was damaged. During the recovery period, the amount of pre-beta-lipoproteins was normal. After hypokinesia the concentration of alpha-lipoproteins increased and returned to normal by the 10th day while that of beta-lipoproteins remained lower for a long time. During the recovery period the number of endothelial cells showing karyopyknosis and karyolysis was increased. At later recovery-periods, the surface area of endothelial cells and their cytoplasm increased and the nucleus/plasma ratio decreased. However, lesions in the structure of the endothelial layer were less expressed than during hypokinesia. In the recovery period, the number of binuclear cells and the number of mitoses grew suggesting greater activity of regeneratory processes.

[Blood supply of the main vessels in laboratory rats and rabbits]. / Krovosnabzhenie magistral'nykh sosudov laboratornykh krys i krolikov.

The vascular bed in 25 rabbits and 25 white rats has been revealed by means of vital injection of Indian ink into the intraorganic vessels, staining of erythrocytes (benzidine reaction) and silver impregnation. In preparations of the aorta, inferior and superior vena cava diameter of the vessels, the wall and middle membrane thickness, amount of elastic membranes have been measured. Ramification of small vessels and capillaries are revealed only in the paravasal tissues, surrounding the aorta and veins. In serial sections it has been stated that at their greatest extent vasa vasorum has no walls and only in places, where the intercostal (or others) vessels get out of the aorta in its middle or external tunics, a limited, as to its spread, network of intramural vessels exists. The morphometrical analysis does not show any regular connection between the vascular diameter, wall thickness, or middle membrane thickness, amount of elastic membranes in it with presence or peculiarities in distribution of the intramural vessels.

[Morphometric analysis of the aortic endothelium of rats exposed to prolonged hypokinesia]. / Morfometricheskii analiz éndoteliia aorty krys v usloviiakh dlitel'noi gipokinezii.

Twenty-four white rats were exposed to 30-, 60- and 100-day hypokinesia. Using the stereological technique, film preparations of their aortic endothelium were examined for the mean area of endothelial cells, nuclei and cytoplasm. Also, the content of endothelial cells showing karyopyknosis, karyolysis or binuclear structures was measured morphometrically. As compared to the matched controls, the number of cells with karyopyknosis, karyolysis and two nuclei increased significantly at every time interval studied. On hypokinesia day 30, the area of endothelial cells, nuclei and cytoplasm was greater than that in the controls. On hypokinesia days 60 and 100, the cell size was within the normal limits and the nuclear size was smaller. This lead to a decrease of the nucleus-plasma ratios. Together with other factors responsible for hypercholesterinemia, the above changes in the endothelial layer may facilitate atherosclerotic lesions of the vascular wall during prolonged hypokinesia.