Microspectrophotometry of cell nuclei stained with the Feulgen reaction. IV. Formation of tetraploid nuclei in rat liver cells during postnatal growth

Density gradient isolation of rat liver nuclei with high DNA content

Rat liver nuclei, after preliminary isolation in 2.2 molar sucrose solution, were separated into density classes by centrifugation at 95,000 g for 45 to 85 minutes in a sucrose density gradient (density range, 1.28 to 1.33). Nuclei from normal liver separated into three bands with average DNA phosphorus content per nucleus of 0.67, 0.84, and 0.93 picogram for top, middle, and bottom bands, respectively. Nuclei from regenerating liver (26 hours after one-third hepatectomy) yielded three bands and a pellet fraction with average DNA phosphorus content per nucleus of 0.76, 1.02, 1.38, and 1.51 picograms (top to bottom of tube). This method appears capable of yielding nuclei which have increased their DNA content prior to mitosis, and this procedure should be valuable in studies of biochemical changes which occur in nuclei preparing for mitosis.

Effect of dietary restriction and aging on polyploidy in rat liver

Liver polyploidy levels were compared as a function of age and diet in male Fischer 344 rats between 1 and 24 months of age. Dietary restriction was imposed on one group by reducing their food intake to 60% of ad libitum food intake. Histological sections of the livers of animals at each age and diet were examined. Diploid, tetraploid and octaploid nuclei were observed, and their size and frequency established. There were no differences in the diameter or volume of these size classes as a function of age or diet. An age-related decline in the percentage of diploid nuclei, coupled with an increase in the percentage of tetraploid and octaploid nuclei was observed in both groups. The major difference between the two groups was that the adult level of liver polyploidy was attained more slowly in the animals on dietary restriction as compared to the ad libitum fed controls. Polyploid cell formation in the liver is under the control of growth hormone, thyroid hormone and thymus, all of which might be influenced by dietary restriction.

Accumulation of abnormally high ploid nuclei in the liver of LEC rats developing spontaneous hepatitis

Enlarged hepatocytes with huge nuclei were found in LEC rats with hereditary hepatitis. Flow cytometric analysis of the DNA content of nuclei from jaundiced LEC rats revealed the presence of very high polyploids, such as 32n and 64n. At the age of 12 weeks, before the onset of hepatitis, 8n polyploid nuclei were more frequent in LEC rats than in LEA rats, a sibling line of LEC rats. Binucleated hepatocytes were also more frequent in LEC rats than in LEA rats at week 4. Bi-, tri- and tetra-nucleated cells whose nuclei were sometimes different in size were observed when jaundice became manifest. The number of proliferating liver cells, determined by pulse labeling with 5-bromo-2'-deoxyuridine (BrdU), was higher in LEC rats than in LEA rats at 2, 4, 8, 12 and 14 weeks, with a maximum at week 4. A remarkable increase of BrdU uptake was observed at week 16, when jaundice developed. The possible involvement of abnormal cytokinesis and kariokinesis in the manifestation of hepatitis was suggested.

Sequential changes of nuclear DNA content caused by chemotherapy in experimental canine gastric cancer

It is well known that the nuclear DNA content closely correlates with the histologic grade of malignancy. In this study, eight beagle dogs with gastric cancer induced by N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG) received weekly administration of 7-N-(p-hydroxyphenyl)-mitomycin C (M-83), a variant of mitomycin C. Endoscopic observations were carried out biweekly, and a biopsy specimen was taken from the same tumor site on each occasion. The nuclear DNA content of these biopsy specimens was measured by Feulgen-DNA-cytofluorometry and was sequentially observed in comparison with histologic findings. In conclusion, 1) the appearance rate of cells over 4C decreased from 25.6% to 14.7% on an average (p less than 0.02); 2) the maximum value of distribution decreased from 9.55C to 7.64C on an average (p less than 0.001); 3) the stem line reduced from 2.63C to 2.20C on an average (p less than 0.05) at the early stage of administration of the oncostatic agent prior to the appearance of histologic changes; 4) in the chemotherapy-effective group, the histogram approached a normal pattern; 5) this procedure will be useful for objective evaluation of oncostatic effects at the cytomorphologic level.

Growth and aging in the rat: changes in total protein, cellularity, and polyploidy in various organs

The objectives of this study were to determine the influence of growth and aging on ploidy, cell number, and protein content of various organs. Tissue homogenates were prepared at 3, 8, 25, 50, and 100 weeks of age. Samples were analyzed for DNA per nucleus (by flow cytofluorometry), nuclei number, and protein content. Livers of 8- and 100-week-old animals were also perfused with collagenase and the released cells separated into parenchymal and nonparenchymal populations by unit gravity sedimentation. Nuclei of these cells were also analyzed for DNA. In all four zones of the kidney and in thyroid, 4n nuclei diminished in percentage between 3 and 50 weeks and increased at 100 weeks. In the growth phase these probably are cycling cells and after 50 weeks represent an increasing population of nuclei arrested after synthesis of DNA. Constant levels of ploidy were found in brain, heart, rectus abdominis, and adrenal throughout the 3-100 weeks. A dramatic increase in 4n nuclei occurred between 3 and 8 weeks in liver with little change occurring thereafter. Ploidy is a property of only parenchymal cells in liver and this probably is also true in other organs. The 4n nuclei that remain in constant proportion to the total population are established early in life and are not related to aging. They are probably tetraploid and replicate into 4n daughter cells during growth. Cerebrum shows no changes in nuclei number but exhibits a 70% increase in protein between 3 and 100 weeks. Although kidney, liver and adrenal show large increases in number of nuclei (approximately equal to fourfold) with growth, these are not as great as increases in body weight (approximately equal to 11-fold). With regard to organ protein, only liver shows increases approximating those in body weight. Increases in organ nuclei appear to occur in concert for adrenal, kidney, and liver whereas increases in organ protein bear no relationship to each other. Protein content remains at stable levels in organs of 100-week-old animals and little (adrenal, liver) or no (brain, kidney) diminution occurs in nuclei numbers.

Flow cytometric analysis of mouse hepatocyte ploidy. II. The development of polyploidy pattern in four mice strains with different life spans

The development of liver ploidy in mice aged up to 24 months was investigated by flow cytometry in four mouse strains. A mathematical procedure was applied for correction of flow cytometry histograms. In two of the mouse strains, C3H and DBA, both cellular and nuclear ploidy proceed in the same way. The octoploid cell with two tetraploid nuclei is the most numerous cell type in adulthood. On the other hand, strain NZB and the out-bred strain NMRI show at the corresponding age a higher proportion of diploid cells with strikingly low proportions of 4c cells. In addition, high values of 16c cells and nuclei are present in NMRI. In all strains the proportion of binucleate hepatocytes is in the same range (60%). However, the strains differ in ploidy classes of binucleate cells. Development of liver polyploidization does not depend on life span of the specific strain.

Occurrence of polyploidy and multinuclearity in the differentiating liver of chick embryo

Increase in nuclear size in liver has been used as an index of polyploidy. It has long been considered that the occurrence of polyploidy and multinuclearity are characteristics of mammalian liver. The present study shows the occurrence of these phenomena in the liver of birds, so these features are not confined to mammals. 3 classes of nuclear size groups have been identified. The simultaneous occurrence of polyploidy and binuclearity indicates some sort of interrelationship between them.

Liver polyploidy: influence of age and of dietary restriction

Polyploidy increases with age in mammalian liver. Since dietary restriction increases lifespan, the question posed in this study was whether liver polyploidy would be influenced by dietary protein restriction. Restricted mice were fed a 4% protein diet, while control mice received a 26% protein diet. Polyploidy was determined from measurements of nuclear diameter on liver of 3 week, 1 1/2, 3, 10, 20 and 24-1/2 month old Swiss albino mice. The percentage of polyploid cells increased steadily with age. The rate of increase, expressed as the polyploidization index, was greater in the fully fed control animals as compared to the animals on protein restriction. Protein restriction thus retards the age associated process of polyploidization of liver nuclei. Nuclear diameter increased slightly with age, but was not influenced by protein restriction.

Some flow cytofluorimetric studies of the nuclear ploidy of mouse hepatocytes. II. Early changes in nuclear ploidy of mouse hepatocytes following carbon tetrachloride administration: evidence for polyploid nuclei arrested in telophase

Mature mice have a large proportion of their hepatocyte nuclei in polyploid states (tetraploid and octaploid), and this is more prominent in females. We measured nuclear ploidy distribution cytometrically using ethidium bromide-stained hepatocyte nuclei liberated by in situ collagenase perfusion of the liver via the portal vein. After s.c. administration of 0.2 ml carbon tetrachloride the ploidy distributions of 8-month-old female mice changed from a control of 35% 2N, 45% 4N, and 20% 8N to 54% 2N, 45% 4N and 1% 8N at 6 h, and 65% 2N, 35% 4N and 0% 8N at 24 h. By 72 h 92% of the nuclei were diploid. These changes preceded any changes in mitotic index and S-phase index (3H-TdR autoradiographs). Histology confirmed the loss of higher-ploid nuclei but without mitotic figures or selective cell necrosis to account for the observations. Cleaved nuclei were prominent in sections of liver examined 3 h after CCl4 administration and suggested division of polypoid nuclei that had undergone prior segregation of chromatids and had presumably been arrested in telophase.

Effects of the type of dietary fat at two levels of vitamin E in Wistar male rats during development and aging. III. Biochemical and morphometric parameters of the liver

The purpose of this study was to explore in rats the possible influence of the type of dietary fat at two extreme levels of vitamin E on several biochemically determined hepatic changes and on a number of quantitatively analyzed structural and ultrastructural variations with age in hepatic cells. Six groups of weanling Wistar male rats were fed ad libitum isoenergetic diets containing similar amounts (15 g per 100 g diet) of saturated fat (coconut oil), unsaturated fat (safflower oil) or a combination of both at two levels of dl-alpha-tocopherol (2 or 200 mg per 100 g of diet). Determinations were performed in rats killed at 3, 6, 12, 18 and 24 months. Although in relation to age and irrespective of the type of diet, several of the biochemical parameters fluctuated with time, comparisons of the results between the youngest and oldest rats showed no changes in the levels of hepatic RNA, phospholipids, cholesterol, total tocopherols and total collagens, significant increases in DNA and triglycerides and a significant decrease in total protein. While the type of diet did not have in general significant influences on the levels of DNA, RNA, total protein and collagens, either the type of dietary fat and/or the levels of vitamin E had some definite effects on the levels of triglycerides, cholesterol, phospholipids and total tocopherols, as well as on the in vitro formation of malonaldehyde and on the eventual occurrence of in vivo lipoperoxidation (diene conjugation). These effects, however, varied in relation to the duration of the diverse dietary treatments. The morphologic studies indicated that all the livers had variable but generally moderate degrees of fatty changes (mainly due to triglyceride accumulation) which were attributed to the moderate obesity found in the rats. The mean nuclear and cell dimensions of hepatocytes, the number of binucleated hepatocytes, surface density of rough endoplasmic reticulum, numerical density of mitochondria and the fractional cytoplasmic volume occupied by lipofuscin pigment in hepatocytes were not significantly affected by the type of diet, by age or by the eventual occurrence of in vivo hepatic lipoperoxidation, whereas the numerical density of hepatocytes (mono- and binucleated) and "litoral cells" (endothelial, Kupffer and Ito cells), although unaffected by diet, significantly increased with age. On the other hand, the fractional volume of mitochondria and peroxisomes, as well as the numerical density of peroxisomes, were significantly influenced by the type of dietary fat and to lesser extent by the dietary levels of vitamin E.

The development of polyploidy in two classes of rat liver nuclei

Two classes of nuclei from livers of Sprague-Dawley rats were isolated, one pelleting in 2.3 M sucrose (H nuclei) and the second class sedimenting through 1.6 and 1.8 M sucrose and banding at the 1.8/2.3 M sucrose interface (L nuclei) of a three-step discontinuous gradient. In younger animals, the L nuclear fraction was the major fraction, but the percentage of nuclei found in the L fraction decreased as the animals grew. Nuclear ploidy was determined by flow microfluorometry using propidium iodide as a DNA stain. Both the H and L nuclear fractions contained diploid, tetraploid and octaploid nuclei; but the degree of polyploidy was greater in the H fraction. Concomitant with the change in distribution of nuclei between the H and L fractions with increasing age was a progressive increase in the degree of polyploidy in the H fraction. Polyploidy did not increase linearly with age in the H nuclear fraction but increased in cycles marked by large changes in the numbers of nuclei found in H and L nuclear fractions. By 12 weeks of age, 4n-H nuclei were the largest single population of nuclei in rat liver. These observations suggested that the shift of liver nuclei from the L fraction to the H fraction was associated with the development of polyploidy and with the differentiation of hepatocytes.

Analysis of cell cycle compartments of hepatocytes after partial hepatecomy

An analysis of cell kinetic parameters as a function of intralobular localization of hepatocytes was performed using autoradiographic methods to obtain a basis for a quantitative description of cell cycle compartments after partial hepatectomy. The influx into the S compartment revealed a maximum in a lobular zone not immediately adjacent to the portal tract, with a decrease towards the perivenous and periportal area of the lobule. The maximum influx was found in the intermediate zone at 34 hr and a lower one in the perivenous parts of the lobule at 40 hr. The influx pattern at 56 hr was similar to the situation at 18 hr. The fraction of labelled mitoses in the whole liver and in subunits of the lobule disclosed a constant duration of S whereas the duration of G2 + M was prolonged from the periportal to the perivenous zone. A graphical model of kinetic events after partial hepatectomy is proposed, which describes the sizes of the various cell cycle compartments; the model successfully predicted the results of a continuous labelling experiment.

Nucleotidase activity in regenerating liver and in clonal strains of hepatoma and pituitary cells in culture

A nucleotidase of the combined 3'- and 5'-type (nucleotide phosphohydrolase, E.C.3.1.3.31) was present in the cytosol of regenerating rat liver cells, and of rat hepatoma and pituitary cells in culture. The enzyme activity per milligram of cell protein was very similar in regenerating liver and in three of the different cell types. The hepatoma cell strain which showed the slowest growth rate had a three-fold higher basal enzyme activity. After the first days of regenerative growth in rat liver and during early plateau phase of cell growth, there was a 50-120% increase in specific enzyme activity. In the hepatoma cells, the enzyme activities were also compared to the cellular content and synthesis of RNA and DNA. The increase in enzyme activity occurred concomitantly with a reduced incorporation of 3H-thymidine into DNA. The possible physiological role of this nucleotidase in nucleic acid and nucleotide metabolism is discussed.

DNA synthesis and cell proliferation in the simple liver acinus of 10 to 20-day-old rats: evidence for cell fusion

Radioautography after 3H-thymidine injection, mitotic arrest by colchicine and camera lucida drawings were used to study DNA synthesis, mitosis, formation of binucleated cells and morphogenesis in the simple liver acinus of Rappaport in 10-20-day old rats. By ten days the arrangement of hepatic cell plates had already attained the adult configuration - irregular and thick in acinar zone 1 (periportal), straight and thin in acinar zone 3 (pericentral). The DNA synthetic index of parenchymal and bile duct cells slowly decreased during the observation period. Zonal labeling remained steady in the relationship: zone 1 greater than zone 2 greater than zone 3. Mitosis of parenchymal and bile duct cells reached a peak at 12 days, decreasing slowly thereafter. Mitosis also exhibited the relationship zone 1 greater than zone 2 greater than zone 3. The number of binucleated cells remained constant until after day 14 when it increased rapidly. Zonal distribution of binucleated cells was just the reverse of that for DNA synthesis and mitosis, that is zone 3 greater than zone 2 greater than zone 1. Radioautographic studies of binucleated cells labeled with 3H-thymidine indicated that a small percentage of them were formed by fusion of mononucleated cells. Conclusions are: (1) the 10-20-day old rat liver is expanding its cell population primarily in acinar zones 1 and 2 while overt differentiation is occurring in acinar zone 3, (2) ingestion of solid food around day 16 may be related to binucleated cell production due in part to altered portal venous blood changing the cellular microenvironments, (3) binucleated cells arise by suppression of cytokinesis, cell fusion and/or other non-mitotic routes.

[The karyogram of normal and of fatty livers in man (author's transl)]

The karyomgrams of normal human livers (50 biopsides from patients of varied age) and of fatty livers (350 biopsies from patients with diabetes, alcoholism, and fatty cirrhosis) were investigated. The nuclear diameters were measured with an analyzer of particle size--the "TGZ-3 Zeiss"--, the cut surface of the nuclei was determined and the nuclei categorized accordingly. 1. The normal liver in each age group is characterized by a well-defined nuclear pattern that is specific for this organ. In the 3rd decade nuclei of the main class predominate. In later decades 2 classes of large nuclei gradually appear and reach their mximum after the 50th year. In the 7th decade a reduction of the cut nuclear surface takes place in all the categoreis, presumably determined by a reduction of function. 2. The increase in the number of large nuclei is explained by abortive karyokineses which in the course of the normal turnover of cells ("Zellmauserung"), increasingly replace normal mitoses. This is This is attributed to disturbances of the achromatic apparatus that occur with increasing age. 3. Alcoholic, and even more so diabetic, fatty change leads to the formation of particularly large nuclei. This appears to depend on the volume of the individual fat droplet within the individual cell rather than on the degree of fatty change of the whole liver. 4...

The synthesis of homocystine, cystathionine, and cystine by cultured diploid and heteroploid human cells

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