[Workshop: "modern confocal microscopes "Leica" and their application in biology"].
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Animals↗
Biomedical subjects
G I Shteĭn
Publications and source records attributed to G I Shteĭn.
[A study of DNA depolyploidization and depolytenization of the heterochromatized gonosomal chromatin bodies in the secondary giant trophoblast cells of the field vole Microtus rossiaemeridionalis using cytophotometry].
A study was made of the distribution of the heterochromatized gonosomal chromatin bodies (GCB) material in the course of nuclear fragmentation of secondary giant trophoblast cells resulting in polykaryocyte formation at the late stage of their differentiation. A simultaneous DNA cytophotometry in GCBs and nuclear fragments showed a progressive GCB DNA content decrease proportional to that of DNA content in nuclear fragments. DNA contents in the nuclear fragments corresponded to 2c, 4c and 8c. In most cases 1-2 GCBs were found in the nuclear fragments of different ploidy levels. Both the total DNA content in GCBs and the DNA content in separate GCBs well correlated with the ploidy levels of fragments. The data obtained demonstrate a regular, whole-genome distribution of chromosomal materials into the nuclear fragments exemplified by sex chromosome distribution in compliance with the ploidy of nuclear fragments. We discuss a possible mechanism of nuclear fragmentation that may ensure substantially a balanced genome of nuclear fragments without leading to mitotic cycle renewal in the giant trophoblast cell population.
Animals↗
[The effect of image analyser noises in studies of cell structure].
Using image analysers, the influence of noises on the quality of images obtained from three types of digital CCD videocameras was studied. Algorithms for calculating the heterogeneity coefficient of cell structures have been proposed, which take into account the noises on the images. Application of procedures of image smoothing or averaging from a few shots, calculation of differences in heterogeneity coefficients of the object and a free field, and a combination of these methods have significantly reduced the influence of noises and increased the informativeness of texture features.
Algorithms↗
[Gene hACR-1 suppresses apoptosis of striated muscle fibres of m. quadriceps femoris after ballistic transfection of mdx mice].
Human minidystrophin gene (pSG5dys plasmid) and hACR-1 gene (pRc-CMV-10.1 plasmid) were cotransfected by means of "gene-gun" to M. quadriceps femoris of mdx mice. Effects of transfection on dystrophin expression and survival of striated muscle fibres (SMF) were studied on the 21st day after shots. In the control mdx dystrophin-positive muscular fibers [D(+)] SMF and destroyed SMF made 2.1 +/- 0.1 and 2.1 +/- 0.3%, respectively. In mice transfected with pSG5dys plasmid (20 mkg of DNA per mouse), the shares of D(+) SMF and dead SMF raised, respectively, up to 5.6 +/- 1.4 and 4.5 +/- 0.9%. Transfection of mice with pRc-CMV-10.1 (DNA dose is 20 mkg per mouse) reduced the levels of apoptosis in SMF and D(+) SMF level to 1.6 +/- 0.6 and 1.1 +/- 0.4%, respectively. Cotransfection by pSG5dys and pRc-CMV-10.1 plasmids (10 and 10 mkg of each plasmids DNA per mouse) reduced the share of D(+) SMF to 1.1 +/- 0.5% and SMF destruction to 0.9 +/- 0.3%. pSG5dys transfection considerably reduced the share of SMF having peripherally located nuclei, thus indicating a decrease in SMF differentiation level after transfection. Cotransfection of ACR-1 gene and a dystrophin minigene did not suppress further cytodifferentiation of mdx muscle fibers. A conclusion is made that ballistic transfection by hACR-1 gene reduces the level of apoptosis in mdx mice SMF without changing the level of SMF differentiation. The cotransfection of mdx mice muscle by hACR-1 and human minidystrophin gene reduces SMF destruction and supports SMF differentiation, too.
Animals↗
[The BCL-xL and ACR-1 genes promote differentiation and reduce apoptosis in muscle fibers of mdx mice].
The effects of the human BCL-xL and ACR-1 genes on dystrophin expression in cross-striated muscle fibers (CSMF) and on CSMF viability were studied in mdx mice after ballistic cotransfection with the human dystrophin minigene. In control mice, the proportion of dystrophin-positive (D(+)) and dying CSMF were 2.1 +/- 0.1 and 2.1 +/- 0.3%, respectively. Introduction of the dystrophin minigene (20 micrograms of the pSG5dys plasmid) increased the proportions of D(+) and dying CSMF to 5.6 +/- 1.4% and 4.5 +/- 0.9%, respectively. When pSG5dys was introduced along with the pSFFV-Neo plasmid carrying the BCL-xL gene (10 micrograms of each plasmid per shot), the death of CSMF decreased to 3.7 +/- 1% and the proportion of D(+) CSMF significantly (P < 0.05) increased to 12.2 +/- 2.2%. Contransfection with the dystrophin minigene and the BCL-xL gene at 20 micrograms of each plasmid per shot did not stimulate generation of D(+) CSMF, but did reduce the CSMF death to 1.5 +/- 0.3%. Introduction of pSG5dys along with the pRc-CMV-10.1 plasmid containing the ACR-1 gene (10 micrograms of each plasmid per shot) reduced the proportion of D(+) CSMF to 1.1 +/- 0.5% and significantly reduced the proportion of dying CSMF to 0.9 +/- 0.3% as compared with the proportions observed in intact mice or in mice subjected to transfection with pSG5dys. Introduction of the pSG5dys plasmid substantially reduced the proportion of CSMF with peripheral nuclei, suggesting disturbed CSMF differentiation. After cotransfection with the human-dystrophin minigene, the BCL-xL and ACR-1 genes did not affect the extent of CSMF differentiation as compared with that observed in the case of the dystrophin minigene alone. Thus, ballistic transfection of mdx mice with the human dystrophin gene used along with the BCL-xL or ACR-1 gene was shown to suppress the death of muscle fibers and to expedite dystrophin synthesis and cell differentiation.
Animals↗
[Quantitative investigation of reproduction of condensed chromatin of sex chromosomes during trophoblast cell polyploidization and endoreduplication in the East European field vole Microtus rossiaemeridionalis].
Simultaneous measurement of DNA content in cell nuclei and condensed chromatin bodies formed by heterochromatized regions of sex chromosomes (gonosomal chromatin bodies, GCB) has been performed in two trophoblast cell populations of the East-european field vole Microtus rossiaemeridionalis, namely in the proliferative population of trophoblast cells of the junctional zone of placenta and in the secondary giant trophoblast cells. One or two gonosomal chromatin bodies have been observed in trophoblast cell nuclei of all embryos studied (perhaps both male and female), In the proliferative trophoblast cell population, characterized by low ploidy levels (2c-16c), and in the highly polyploid population of secondary giant trophoblast cells (16c-256c), the total DNA content in GCB increased proportionally to the ploidy level. In separate bodies, the DNA content rose also in direct proportion with the ploidy level seen in the nuclei with both one and two GCBs in the two trophoblast cell populations. A certain increase in percentage of the nuclei with 2-3 GCBs was shown in the nuclei of the junctional zone of placenta; this may be accounted for by genome multiplication via uncompleted mitoses. In the secondary giant trophoblast cell nuclei (16c-256c), the number of GCBs did not exceed 2, and the share of nuclei with two GCBs did not increase, thus suggesting the polytene nature of sex chromosome in these cells. At different poloidy levels, the ratio of DNA content in the nucleus to the total DNA content in GCB did not change significantly giving evidence of a regular replication of sex chromosomes in each cycle of genome reproduction. In all classes of ploidy, the mean total DNA content in trophoblast cell nuclei with single heterochromatic body was less than in the nuclei with two and more GCBs. This may indicate that a single GCB in many cases does not derive from the fusion of two GCBs. To put it another way, in the nuclei with one GCB and in those with two or more GCBs, different chromosome regions may undergo heterochromatization. The regularities observed here are, most probably, associated with the peculiarities in the structure of X- and Y-chromosomes in a range of species of Microtus (M. agrestis, M. rossiaemeridionalis, M. transcaspicus). As a result, gonosomal chromatin bodies may include large blocks of both constitutive heterochromatin of X- and Y-chromosomes (in male and female embryos) and inactivated euchromatin of "lyonized" X-chromosome in female embryos. Therefore the presence of two or more GCBs in trophoblast cells of M. rossiaemeridionalis may be accounted for by both polyploidy and functional state of the nucleus, in which gonosomal constitutive heterochromatin and inactivated euchromatin form two large chromocenters rather than one. The differences in DNA content in GCBs in the nuclei with one and two GCBs seem to be an indirect indication that the two chromocenters may be formed by two different gonosomes, with the extent of their heterochromatization being higher than that in the nuclei with one GCB. GCBs in the trophoblast cells of M. rossiaemeridionalis are observed not only at the early developmental stages, as it was observed in rat at the first half of pregnancy (Zybina and Mosjan, 1967), but also at the later stages, up to the 17th day of gestation. At these stages, the nuclei with non-classical polytene chromosomes rearrange to those with a great number of endochromosomes, probably because of disintegration of chromosomes into oligotene fibrils. However, it does not seem unlikely that this process may involve heterochromatized gonosomal bodies, since only one or two large GCBs can be seen in the nuclei as before. The presence of prominent blocks of constitutive heterochromatin seems to favor a closer association of sister chromatids in polytene chromosomes, which prevents their dissociation into endochromosomes with the result that polyteny of sex chromosomes in the field vole trophoblast is probably retained during a longer period of embryonic development.
Animals↗
[Ultrastructural and morphometrical analysis of apoptosis stages in cardiomyocytes of MDX mice].
Our previous study of apoptosis in mdx mouse myocardium cells demonstrated the presence of middle-sized DNA fragments (60-65 kbp) in extracts of myocardium DNA, and irregular shape of membrane enveloped nuclei in cardiomyocytes. The DNA fragmentation (DNA laddering) was observed after biomechanical stress (5 min sweeming) only. Based on these results we concluded that the majority of cardiomyocytes were at the first stage of apoptosis. The purpose of this work was to provide some morphometrical quantitive characteristics of ultrastructural properties of the nuclei and mitochondria, and to determine morphological patterns of apoptosis in cardiomyocytes of mdx and C57B1 mice. To resolve the task, we made a morphometrical analysis of the electron microscope images of nuclei and mitochondria. First of all, we divided all nuclear images into three categories: normal, semi-pathological, and pathological forms according to the extent of nuclear membrane invaginations and that of condensed chromatin spreading. The most part of C57B1 cardiomyocyte nuclei belonged to the normal form (88.9 +/- 4.3%), while the smaller part (11.1 +/- 4.3%) was regarded as semi-pathological forms. Just a reverse was observed in mdx mice: the largest part of cardiomyocytes fell into category of semi-pathological (54.6 +/- 4.4%) and pathological (31.5 +/- 4.1%) forms while, the smallest part belonged to the normal form (13.8 +/- 3.0%). 24 h after biodynamic stress, the quantity of normal nuclei of C57B1 cardiomyocytes decreased to 61 +/- 5%, the number of semi-pathological nuclei increased to 39.0 +/- 4.4% (P < 0.05). The number of pathological nuclei of mdx, cardiomyocytes fell to 15.4 +/- 3.0% (P < 0.05). It means that mdx cardiomyocytes with pathological form of their nuclei disappear because of emerging the second, destructive stage of apoptosis. To estimate the degree of ultrastructural changes in the nuclei of all three forms of cardiomyocytes we counted the square/perimeter ratio in each nucleus (circle shape factor; CSF). The value of CSF for normal nuclei of all the forms of cardiomyocytes varied between 0.65 +/- 0.02 and 0.71 +/- 0.04. In semi-pathological and pathological nuclei a significant decrease in CSF to 0.56 +/- 0.02 and 0.56 +/- 0.03 was observed, respectively (P < 0.05). The biodynamical stress did not reduce the CSF value below this level. We also counted the ratio of the square to the product of a long and a short axes (ellipse shape factor; ESF). The ESF value for normal nuclei of all forms of cardiomyocytes varied between 0.97 +/- 0.01 and 0.99 +/- 0.01. In the case of mdx mice the biodynamical stress reduced ESF to 0.95 +/- 0.01 (P < 0.05) for pathological form of nuclei. The specific density of mitochondria in mdx cardiomyocytes (0.274 +/- 0.016) was less than that in C57B1 cardiomyocytes (0.329 +/- 0.018). At the destructive stage of apoptosis, the nuclei of cardiomyocytes were round in shape, the nuclear chromatin being hypercondensed, and mitochondria swollen. The cardiomyocyte morphology was in agreement with the definition of the final stage of apoptosis as secondary necrosis. Morphometrical results show that as many as 86-90% of nuclei of mdx cardiomyocytes have abnormal structure that confirms our conclusion that mdx cardiomyocytes were at the first stage of apoptosis. The final stage of apoptosis is rarely observed by biochemical or morphological methods. It suggests the presence of some inner mechanisms regulating the initiation of the final (destructive) stage of mdx cardiomyocyte apoptosis.
Animals↗
[Change in morphometric parameters in silver-stained nucleoli from hepatocytes of rats with liver cirrhosis and during rehabilitation from it].
Silver-stained nucleoli of rat hepatocytes were studied in norm, in liver cirrhosis produced by CCl4 poisoning and after cessation of the poisoning. Morphometric parameters of nucleoli were measured using a Videotest computer image analyser. Under cirrhosis the mean number of nucleoli per nucleus was determined to exceed their normal number by 1.27 times. The total volume of nucleoli in the nucleus also exceeded the normal level (by 1.15 times). 3 months after the end of CCl4-poisoning, these parameters decreased almost to normal values. A statistically significant correlation was revealed between the number of nucleoli and their total volume (0.881). Changes of the parameters also correlated with the total protein content in the hepatocytes. Possible reasons for this correlation are discussed. The ratio of the number of chromosomal NORs to the mean number of nucleoli in the nucleus is proposed to be used as a feature for comparative analysis of functional status of nucleoli in the nuclei of different ploidy and in cells of different animal species.
Animals↗
[Differentiation of muscle fibers in mdx mice after ballistic transfection of cDNA of the human dystrophin gene].
Changes in morphological dimensions of MDX mouse myofibres in M. rectus femoris were recorded after ballistic transfection (BT) with pHSADys and pVMMDys plasmids containing cDNA of the full-length human dystrophin gene. The dystrophin expression was observed by an immunomorphological procedure with P6 antibody and PAP method. Dystrophin positive (dyst+) myofibres were divided into two types, with a typical dystrophin expression under sarcoplasma membrane and an atypical expression through the whole sarcoplasm, respectively. The share of atypical dyst+ myofibres was seen to rise during the experiment from 27%, at 2-3 weeks after BT, up 84% by 2 months after BT. The atypical dyst+ myofibres usually underwent destruction. At the same time, the share of entire dyst+ myofibres decreased from 17 to 2-5% by 2 months. Morphological dimensions of the myofibres (square in mkm2, perimeter, smallest and largest diameters) were calculated with the help of computer analyser. The middle square of both types of dyst+ myofibres was larger than that of dyst- myofibres, both in BT target M. rectus femoris and in the same contralateral muscle, but never exceeded the value of middle square of C57B1 mouse myofibres in the same muscle. The form of dyst+ myofibres was not modified by the dystrophin expression. The nuclei of dyst+ myofibres remained in the central region of sarcoplasm. A conclusion is made that BT of human dystrophin gene inside MDX mouse myofibres allows dystrophin gene expression and enlargement of the dyst+ myofibres. Dystrophin expression is not able to induce a complete and stable differentiation of striated muscle of adult MDX mice.
Animals↗
[Apoptosis and DNA degradation of cardiomyocytes of mdc and C57Bl mice].
DNA destruction and apoptosis of ventricular cardiomyocytes were studied using DMX and C57Bl10/J mice. According to our electron microscope observations the cardiomyocyte nuclei undergo chromatin condensation with the nuclear membrane folding. In cardiomyocytes with significant nuclear destruction, structural disturbances in the cytoplasm are also seen. The 0.5% agarose gel electrophoresis reveals DNA fragments, sized 64 kb and more, inside the total DNA of MDX mice myocardium. No kinds of DNA fragments are available inside samples of the total DNA of C57Bl mice myocardium. Swimming during 5 min induces formation of the same type of DNA fragments inside the total of DNA of C57Bl mice myocardium, which was registered after 2 and 22 hours of the experiment. The DNA fragments disappear from the total C57Bl mice myocardium DNA within 48 h after the stress. Trypan blue evokes formation of the same 64 kb fragments inside DNA of myocardium within 24 h after injection to C57Bl mice. Electrophoresis of the total DNA with 2% agarose gel or 5% PAAG revealed no DNA samples analysed during this study. The authors conclude that DNA destruction and apoptosis characteristic features of MDX mice cardiomyocytes of mice, have a common mechanism of DNA degradation that works both after the stress of trypan blue action in case of C57Bl mice, and as a consequence of dystrophin absence in cardiomyocytes in the case of MDX mice.
Animals↗
[Cellular mechanisms of postnatal growth of rat liver in during chronic exposure of cadmium sulfate and strontium chloride].
A cytophotometric investigation was performed to study the ploidy level and total protein content in hepatocytes of rats of different ages (1, 7, 14, 21, 30, 90, 180, 365 days), both intact and chronically treated with cadmium sulfate or strontium chloride. It was established that during the first month of postnatal ontogenesis, compositions of liver parenchyma cell population of intact and treated rats did not differ. Compared to control animals, the process of cell polyploidization in the liver of rats treated with heavy metal salts of 30-90 days proceeded slower, especially in Cd(2+)-treated rats. Within 180-365 days the cell polyploidization in the treated animals increased. The proportion of (4c x 2)-hepatocytes in 1 year old Cd(2+)- or Sr(2+)-treated rats increased, resp., by 2.7 and 1.5 times, and that of 8c hepatocytes was higher by 3.9 and 1.5 times than in the control, the average ploidy level rising by 20 and 5%. respectively. It was established that until 90 days the rate of protein accumulation in liver cells of intoxicated rats was slower than in intact animals. Thus, the average protein content per diploid hepatocyte in Cd(2+)- or Sr(2+)-treated 30 day old rats was lower by 20 and 16%, respectively, compared to control animals. The protein content increased in liver cells of Cd(2+)- or Sr(2+)-intoxicated rats following 90 and 180 days, respectively, and this process was exclusively associated with cell polyploidization. During the first 3 weeks after birth, no significant difference was observed in the extent of involvement of cell proliferation, polyploidization and hypertrophy in the growth of liver in intact and intoxicated animals. At this period the liver was growing due completely to cell proliferation and hypertrophy. During 21-30 days the contribution of cell proliferation to the liver growth of intact rats was not significant (29%), whereas it remained at higher level (50%) in the treated animals. In 30-90 days after birth, the involvement of proliferation process to the liver growth of intoxicated rats decreased to 25-28%, while in intact animals it increased up to 37%. At this period the cell polyploidization plays an essential role in the growth of liver in both intact and intoxicated animals to reach in average 37-46%. The contribution of polyploidization and hypertrophy to the liver growth of Cd(2+)-treated rats within 30-90 days was obviously higher than in Sr(2+)-treated animals. Both at the late (3-12 months) and at the early (1-21 days) stages of experiments, the pattern of correlation of different cell components in the growing liver of intact and intoxicated rats differed only a little.
Administration, Oral↗
[A morphometric study of the silver-stained nucleoli in mononuclear and binuclear rat hepatocytes].
Investigation of silver-stained nucleoli has been made in mono- and binuclear rat hepatocytes of different ploidy. Morphometric parameters of nucleoli and cell ploidy (after silver removing and Feulgen staining) were measured by image analyzer "Videotest". It has been shown that the total area and total volume of nucleoli correlate with cell ploidy, but the found dependence deviates from the proportional one. Possible reasons of such a deviation have been discussed. Marked correlation of total area or total volume of nucleoli was detected between pairs of nuclei of binuclear hepatocytes, whereas between accidental pairs of mononuclear hepatocytes such correlation is practically lacking.
Animals↗
[A quantitative evaluation of the glycogen content of the hepatocytes from different lobular ares of the normal human liver and in chronic hepatitides of different etiologies].
Investigation of glycogen function in hepatocytes of different liver lobule zones is particularly important in understanding glycogen metabolism in humans and animals in norm and pathology. The present study was done to investigate glycogen contents in hepatocytes of different lobule zones of human liver in norm, and in patients with chronic hepatitis of viral or alcohol etiology. Quantitative analysis of glycogen content in hepatocytes of portal and central lobule zones was conducted on slices of human liver (the material of series live punctional biopsies) stained using a quantitative variant of PAS-reaction (Kudryavtseva et al., 1970, 1974). The measurements were done by image analyzer < >, which allows to make jointly cytophotometric analysis of substance in cells and definition of cell localization in tissue. The results showed clear differences of glycogen contents in different lobule zones in normal liver and in liver during chronic viral and alcohol hepatitis. Glycogen contents in hepatocytes of portal lobule zone were significantly higher than in the central lobule zone in patients with chronic viral hepatitis. Opposite data were obtained in patients with chronic alcohol hepatitis. Significantly higher glycogen contents were found in hepatocytes of the central liver lobule zone. Possible mechanisms of such a phenomenon are discussed . Thus, if glycogen contents in hepatocytes may be taken as an indicator of liver chronic damage degree (as has been shown elsewhere: Kudryavtseva, 1987; Kudryavtseva et al., 1988) the pattern of distribution of hepatocytes with different glycogen content in the liver lobule can be used as an indicator of etiology of chronic hepatitis. The obtained data seem to be important and actual, particularly for diagnostic of subclinical and symptomless forms of these diseases. Further investigation is required to find out reasons and mechanisms of this phenomenon.
Adolescent↗
[The quantitative study of the areas of active rDNA location and of the other parameters of the interphase nucleolus detectable by silver staining during the cell differentiation of the rat trophoblast].
Different quantitative parameters of nucleolar silver staining have been studied in the cambial rat trophoblast cells on the 12th, 13th and 14th days of gestation. It has been shown that the number of Ag-positive granules in the nucleoli varied from 10 to 120. The number and the total area of silver stained granules in the nuclei increased progressively in the course of polyploidization, but was not doubled passing to the next ploidy level. Nevertheless, nucleolar area increased proportionally to the ploidy degree. The mean number and the total area of Ag-stained granules as well as the nucleolar area estimated for each ploidy level did not change significantly in the course of placenta development, suggesting an unchanged level of NOR activity at the studied stages of trophoblast cell differentiation. The data obtained on the interphase nucleoli differ from the data of the analysis of the metaphase Ag-NOR at the same period of placenta development, suggesting a diversity in the interphase and metaphase NOR organization. A proportion of cells with different number of nucleoli in the cambial rat trophoblast cells was maintained unchanged in the studied period of the placenta development, the majority (80-90%) of cells contained from 1 to 3 nucleoli. Such a proportion was similar in the cells of different levels of ploidy up to 16c. In this connection the association of NORs is suggested to be in relation with switching from the polyploid mitotic cycle to the endoreduplication leading to polyteny.
Animals↗
[Hepatocyte polyploidization in chronic liver diseases in man].
Levels of hepatocyte ploidy were investigated in patients with chronic viral hepatitis, alcohol hepatitis, and liver cirrhosis. It was shown that in spite of some decrease in the share of mononucleate diploid hepatocytes these cells equally make the main part of hepatocyte population (about 80% on the average) both during chronic liver diseases and in the norm. In chronic hepatitis and cirrhosis processes of polyploidization in the human liver, unlike those in livers of laboratory animals (rats and mice), are accomplished with much lower rates and characterized by accumulation of binucleate diploid cells. These processes differ from those occurring under ageing. Reparative regeneration of human liver under chronic hepatitis and cirrhosis is accomplished on the whole by proliferation of mononucleate diploid hepatocytes but processes of polyploidization in the liver of some patients can play a significant role in reparative liver growth.
Adolescent↗
[A cytophotometric study of the RNA and glycogen content of human hepatocytes at different stages in the development of traumatic disease].
Absorption and fluorescent cytophotometry techniques were applied to studies of RNA, glycogen and its fractions in hepatocytes of patients with hard mechanic trauma, both with and without endointoxication. For measuring RNA and glycogen contents, slides were stained by gallocyanin-chromalum or underwent fluorescent PAS-reaction, respectively. The repeated aspiration biopsy material was used for investigation of RNA and glycogen contents in dynamics. A quick increase in RNA content took place at the first stage (within the first 3 days) of traumatic illness of both the groups of patients. At the second stage of illness the hepatocyte RNA content in patients without endointoxication was seen to decrease to the initial level, whereas that in patients with endointoxication increased from the initial level by 36%. At different stages of illness the total glycogen content is changed insignificantly in the course of illness, but its labile fraction decreases to 70% of the total glycogen in patients with endointoxication. The increase of hepatocyte synthetic activity and the maintenance of the normal glycogen level may suggest a sufficient compensatory possibility of the liver, in spite of a high functional load under endointoxication.
Biopsy, Needle↗
[Polyploidy and polyteny in the trophoblast cells of the mink].
According to cytophotometry, trophoblast cells in the mink placenta are both diploid and polyploid, the ploidy level ranging from 2c to 64c. A great number of mink trophoblast cells were seen to divide mitotically. In addition to the ordinary mitotic figures, polyploid mitoses as well as abnormal mitotic figures were observed. Non-classic polytene chromosomes, peculiar to the mammalian trophoblast, appeared in the mink trophoblast cells to have the highest ploidy. A relatively low ploidy degree is due, probably, to a lesser invasive activity of the mink trophoblast cells as compared to the rodent giant trophoblast cells.
Animals↗
[Changes in the amount of 3H-thymidine label in hepatocytes of different ploidies in rat ontogeny after a single administration of the isotope].
Change of 3H-thymidine quantity in mono- and binuclear rat hepatocytes of different ploidy was investigated during the first 6 weeks after a single injection of isotope to newborn rats. Rates of cell transitions (arbitrary number of cells in the time unit) from one ploidy class to another, and coefficients of the reducing of hepatocyte proliferative activity with increasing the hepatocyte ploidy were calculated on the basis of ideas about the process of autoradiographic label "diluting" in the course of the postnatal development as a result of polyploidization and ordinary mitotic divisions of hepatocytes. The calculated values are close to values of parameters, which were calculated with assistance of the model, which describes the process of polyploidization in the liver, on the basis of data on the change in the arbitrary number of different ploidy hepatocytes.
Animals↗