ber das Karyogramm der menschlichen Leber unter normalen und pathologischen Bedingungen

Polyploidization: a Janus-faced mechanism

Normal human somatic cells are diploid. But sometimes certain tissues of the human body contain elevated numbers of tetraploid cells. This tetraploid cell population seems to represent the first step of an ongoing process of polyploidization. All tissues containing tetraploid cells have in common the fact that they are subjected to stress, which is caused by a variety of circumstances like inflammation, elevated metabolism, ageing, repair processes or selection pressure. Tetraploid cells are supposed to play a beneficial role in these stress situations, because they are known to be more resistant in general and because they are characterized by an elevated biosynthetic activity. In contrast to their beneficial character, they have a big potential concerning the malignant development of a tissue: they play a crucial role in early morphological stages of the pathway hyperplasia-metaplasia-dysplasia-carcinoma. This report links several intracellular mechanisms with each other, which potentially determine the real fate of tetraploid cells.

Centrosome multiplication accompanies a transient clustering of polyploid cells during tissue repair

Cells from different human wounds were analyzed concerning their degree of ploidy. The experiments showed an increased tetraploidization rate in well-healing wounds especially during inflammation and proliferation. Recent data described a polyploidization in different tissues, which is accompanied and maybe caused by the multiplication of the centrosome. We show here for the first time that cells from nonmalignant tissue, namely human wound cells, are characterized by an extensive centrosome multiplication. In an effort to identify a certain mechanism, by which the centrosome may act as a modulator of the cells' ploidy, we focused our interest on p53, whose interaction with the centrosome was recently described. Applying a wound model onto p53-wildtype (wt) and p53-knockout (ko) mice, we could show that polyploidization was not reversible in p53-ko mice during wound healing. The lack of p53, the centrosome multiplication, and the polyploidization therefore may contribute to the physiological process of tissue repair in physiologically "normal" tissue.

Human hepatocyte polyploidization kinetics in the course of life cycle

The processes of polyploidization in normal human liver parenchyma from 155 individuals aged between 1 day and 92 years were investigated by Feulgen-DNA cytophotometry. It was shown that polyploid hepatocytes appear in individuals from 1 to 5 years old. Up to the age of 50 years the accumulation rate of binucleate and polyploid cells is very slow, but subsequently hepatocyte polyploidization is intensified, and in patients aged 86-92 years the relative number of cells with polyploid nuclei is about 27%. Only a few hepatocytes in the normal human liver reach 16C and 8C x 2 ploidy levels for mononucleate and binucleate cells respectively. Using a mathematical modeling method, it was shown that during postnatal liver growth the polyploidization process in human liver is similar to that in the rat, and that polyploid cells are formed mainly from binucleate cells. As in rats, prior to an increase in ploidy level, diploid human hepatocytes can pass several times through the usual mitotic cycles maintaining their initial ploidy level. After birth, only one in ten hepatocytes starting DNA synthesis enters the polyploidization process. At maturity about 60% of 2C-hepatocytes starting DNA synthesis divide by conventional mitosis, the rest dividing by acytokinetic mitosis leading to the formation of binucleate cells. During ageing the probability of hepatocyte polyploidization increases and in this period there are two polyploid or binucleate cells for every diploid dividing by conventional mitosis.

Significance of polyploidy in megakaryocytes and other cells in health and tumor disease

Polyploidy--the doubling of chromosome sets of cells caused by a stop of mitosis at different levels of the mitotic cycle--is a phenomenon widely observed in plants, protozoa, metazoa, and animals. In man obligate polyploid tissues are found in liver parenchyma, heart muscle cells, and bone marrow megakaryocytes. Polyploidy occurs mostly in stable and highly differentiated cells and tissues. Besides age, stimulation of proliferation and increased metabolic function lead to polyploidization in these organs. Aneuploidy, however, is exclusively found in tumor cells. Megakaryocyte differentiation and polyploidy are controlled by thrombopoietin-like activities, of which the loci of production are still unknown. Megakaryocytes are unique among polyploid mammal cells. On the precursor level they maintain their proliferative activity independently of the mammal's age. Once having entered the incomplete mitotic cycle they stop cytokinesis and develop into highly polyploid cells. Polyploidization of megakaryocytes is the basic requirement for establishing highly effective hemostasis in mammals, which exhibit blood circulation based on high blood pressures. Every polyploidization results in increased production of membrane materials with which the platelet becomes endowed. By shedding cytoplasmic fragments approximately 3000 platelets are set free from a 32c megakaryocyte, compared with only 16 nucleated thrombocytes by mitotic division. There is further evidence that the heterogeneity of platelets mostly depends on the different polyploidy classes of the megakaryocytes from which they are derived. Changes in the polyploidy pattern of megakaryocytes could therefore have consequences for hemostatic disorders in several human diseases, particularly in malignancy.

A flow cytofluorometric study on age-dependent ploidy class changes in mouse hepatocyte nuclei

To quantitate the age-dependent hyperploidization of mouse hepatic cell nuclei, a cytophotometric study using FACS III was performed. The isolated nuclei from the liver of C57BL/6CrSlc mice at various ages were stained with chromomycin A3. The fraction of polyploid nuclei was increased with age and invariably greater in male than in female animals of corresponding ages. The highest ploidy class observed was 16C, but from the analysis of polyploidization ratio, increase in 4C and 8C nuclei was considered to be the characteristic of the age-related change.

Karyometry of pseudostratified, metaplastic and dysplastic nasal epithelium by morphometry and stereology. 1. A general model for automated image analysis of epithelia

Nuclear enlargement, usually due to the existence of abnormally high DNA (ploidy) values, is one of the alterations most often encountered in pathological epithelia, especially in cancerous and precancerous states. Direct DNA measurements on microscopic sections are impossible, and karyometric studies must take the difficult stereologic problem of spheroid sectioning into account. A mathematical model is proposed to describe an aggregate of separate parallel anisotropic prolate spheroids of variable size and eccentricity. This model appears suitable for the study of epithelial nuclei. After a tentative estimation of the biopsy angle, the application of the model to nuclear profile measurements produces the stereologic data of the mean spheroid nucleus: major and minor axes (and their ratio), volume, surface area (and the V/S ratio), and numerical density. Considerable time may be saved by the use of an image analyser with a specific algorithm. Most of the steps are entirely automated, but the user retains the interactive choice of the nuclei to be studied, for instance by separating the different epithelial layers. The profile data are computer-filed and several programs can yield the stereologic estimations and plots of nuclear profile areas. Poolings of cases of similar histologic staging and nearly the same sectioning angle can be used for the profile area plots. The model has been applied to pseudostratified and altered nasal mucosa of nickel workers. The stereologic estimates, mainly the nuclear volume, correlate well with histologic gradings. The nuclear profile area plots are considered useful for an assessment of the nuclear polyploidism. The complete model should be applicable to many other types of functionally or pathologically altered epithelia, particularly for cancer and precancer screenings, when the use of sectioned material is a prerequisite.

Relationship of ploidy and chromatin condensation in the rat liver, moreover a comparison of the nuclear texture in sections and touch preparations

In touch preparations and tissue sections from normal rat hepatocytes and alpha-amanitine- and actinomycin D-poisoned liver cells the extent of chromatin condensation relatively to the degree of ploidy and the chromatin distribution were studied by means of computer aided cytophotometry. It could be found, that the relationship of the condensed and decondensed chromatin is independent of the degree of ploidy and first of all dependent upon the intoxicant. Therefore, the extent of chromatin condensation can be utilized also in sections as additional parameter for automated cell screening.

Human hepatocytes and aging: a cytophotometrical analysis in 35 sudden-death cases

Alterations in the nuclear and cellular size of human hepatocytes occurring with age, and particularly in senescence, were studied by microphotometry. The material studied was obtained in 35 cases of sudden death, involving 17 males and 18 females ranging in age from 16 to 100 years. Cells of the peripheral zones of hepatic lobules were analyzed. The following results were obtained: 1. The mean nuclear area of hepatocytes remained relatively constant in subjects under 60 years of age but showed an increase in those over 60, this increase being associated with a greater standard deviation. 2. Volumetric analysis showed that the modal value included between 61 and 100% (mean 86%) of the cell nuclei examined and did not increase with age. This cell population was presumed to consist of diploid cells, the size of which remained constant. 3. An increase in mean nuclear area was due to the appearance of cells with larger nuclei which probably were the result of polyploidization. 4. Hepatocyte size increased with age. Analysis of the nucleus-to-cell sizes showed that the increase in cell size with age was more significant than the increase in nuclear size. 5. Cellular enlargement was more closely correlated with decrease in gross liver weight than with nuclear enlargement.

Image processing in pathology

The present study is an effort to ally biopsies to well defined groups of diseases by means of automatic analysis of liver cell nuclei. The results obtained should support the morphologic differential diagnosis of liver diseases. A total of 78 liver biopsies from patients with obstructive jaundice, chronic hepatitis, acute viral hepatitis or with alcoholic liver injury were investigated. Performing automatic analysis of the microscopic pictures 95% of the equatorial sectioned liver cell nuclei are correctly recognized.

Karyometric and cytophotometric studies on nucleic acids in the culture of human lymphocytes with phytohemagglutinin

Lymphocyte transformation with phytohemagglutinin (PHA) was analyzed by karyometry and cytophotometry of single cells. The former showed the distribution of various-sized transforming cells, and the latter the increase of DNA and RNA. Two different types of karyograms were obtained; one with three peaks corresponding to 2c, 4c, and 8c, and the other with only a 2c peak. Although small in number (8%), karyometry showed that DNA synthesis took place in the extremely early stage of transformation, 1 h after stimulation with PHA, which was proved by cytophotometry and ultrastructural findings. An increasing curve of DNA and RNA revealed that a lymphocyte continued to enlarge from 2c to 4c and divide again through the normal cell cycle in a suitable condition. The largest blast cell, a polyploid cell, may be induced by the lack of a sufficient amount of RNA and protein in need of cell division, and may be a degenerative cell in the strict sense. Among the large cells with blastlike appearance, there were a considerable number of so-called degenerative cells with a low amount of DNA. The ratio of RNA to DNA increased steeply in the actively DNA synthesizing S phase, which supports the morphologic findings of blast cell, the appearance of basophilic cytoplasm, and active-looking nucleoli.

Nuclear size classes in the follicular epithelium of lymphoid thyroiditis

Nuclear size classes of the type originally described by Jacobj were studied in the follicular epithelium of biopsy smears from lymphoid thyroiditis. Thus, a great number of large nuclei in size classes distinct from the bulk of fairly identically sized nuclei could be clearly distinguished. By cytophotometric measurement of Feulgen-DNA, these large nuclei were found to correspond closely to nuclei in separate DNA-content-classes and they were therefore called HDC-nuclei (High DNA-quantity Class nuclei). Such nuclei proved to be more common in lymphoid thyroiditis than in normal thyroids and non-toxic goitres without lymphoid thyroiditis. Among lymphoid goitres, the percentage of HDC-nuclei was positively correlated with the age of the patients. In the present paper, the relationship between Askanazy cells and HDC-nuclei is also discussed.

Disturbances of karyokinesis and its relation to the nuclear pattern

The main causes of mitotic disturbances of spindle formation and inadaequate development of the mitotic apparatus. Quantitatively of the greatest importance in both groups are collapse of the prophase and failure of cytokinesis, respectively. The division of polyploid nuclei is, in addition, complicated by alterations of multicentric spindles. Results of mitotic disturbances are changes in the degree of ploidy of cells or nuclei. In irreversible post-mitotic tissues these occur already in the growth phase, as is shown in the example of the heart. In reversible post-mitotic tissues these changes in the degree of ploidy modify the nuclelar pattern predominantly during the processes of ageing, reparation and regeneration, as is well documented in the liver.

[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...