[The phenomenon of nucleolar segregation: specificity of action of certain antimetabolites]

Myocardial Injury Induced by a Single Dose of Adriamycin: An Electron Microscopic Study

Adriamycin cardiomyopathy has been studied under the electron microscope using myocardial ventricular cells of CRF mice, previously treated with 10 mg/kg body weight of the drug given in a single intravenous injection. Within 10 min myocardial cell nucleoli show a nucleolonema fragmentation, and during the following 3 hours they acquire the nucleolar segregation pattern. Fourteen hours after drug injection, nucleolar morphology again becomes normal, while areas of focal degeneration, characterized by damaged mitochondria and enlarged smooth reticulum cisternae, appear in the sarcoplasm. One to 3 days later the degeneration process involves the myofibrillar component, and after 50 days the great majority of myocardial ventricular cells is damaged. The early appearance and the functional significance of nucleolar segregation support the hypothesis that adriamycin cardiotoxicity might be dependent on its ability to bind to myocardial cell DNA. The consequent failure of UNA and protein synthesis, impairing the continuous renewal of myofibrillar and mitochondrial components of the cell, might explain the progressive myocardial damage.

Synergistic antitumor cytotoxic actions of ascorbate and menadione on human prostate (DU145) cancer cells in vitro: nucleus and other injuries preceding cell death by autoschizis

Scanning (SEM) and transmission electron microscopy (TEM) were used to characterize the cytotoxic effects of ascorbate (VC), menadione (VK3), or a VC:VK3 combination on a human prostate carcinoma cell line (DU145) following a 1-h vitamin treatment and a subsequent 24-h incubation in culture medium. Cell alterations examined by light and electron microscopy were treatment-dependent with VC + VK3 >VK3 > VC > Sham. Oxidative stress-induced damage was found in most organelles. This report describes injuries in the tumor cell nucleus (chromatin and nucleolus), mitochondria, endomembranes, lysosomal bodies (autophagocytoses) and inclusions. Morphologic alterations suggest that cytoskeleton damage is likely responsible for the superficial cytoplasmic changes, including major changes in cell shape and size and the self-excising phenomena. Unlike apoptotic bodies, the excised pieces contain ribonucleoproteins, but not organelles. These deleterious events cause a progressive, significant reduction in the tumor cell size. During nuclear alterations, the nuclei maintain their envelope during chromatolysis and karyolysis until cell death, while nucleoli undergo a characteristic segregation of their components. In addition, changes in fat and glycogen storage are consistent the cytotoxic and metabolic alterations caused by the respective treatments. All cellular ultrastructural changes are consistent with cell death by autoschizis and not apoptosis or other kinds of cell death.

Nucleolar changes and fibrillarin redistribution following apatone treatment of human bladder carcinoma cells

Ascorbate and menadione (Apatone) in a ratio of 100:1 kills tumor cells by autoschizis. In this study, vitamin-induced changes in nucleolar structure were evaluated as markers of autoschizis. Human bladder carcinoma (T24) cells were overlain with vitamins or with culture medium. Supernatants were removed at 1-hr intervals from 1 to 4 hr, and the cells were washed with PBS and prepared for assay. Apatone produced marked alterations in nucleolar structure including redistribution of nucleolar components, formation of ring-shaped nucleoli, condensation and increase of the proportion of perinucleolar chromatin, and the enlargement of nucleolar fibrillar centers. Immunogold labeling of the nucleolar rRNA revealed a granular localization in treated and sham-treated cells, and immunogold labeling of the rDNA revealed a shift from the fibrillar centers to the condensed perinucleolar chromatin. Fibrillarin staining shifted from the fibrillar centers and adjacent regions to a more homogeneous staining of the entire nucleolus and was consistent with the percentage of autoschizic cells detected by flow cytometry. Because autoschizis entails sequential reactivation of DNase I and DNase II, and because the fibrillarin redistribution following DNase I and Apatone treatment is identical, it appears that the nucleolar and fibrillarin changes are markers of autoschizis.

The cytoplasmic zinc finger protein ZPR1 accumulates in the nucleolus of proliferating cells

The zinc finger protein ZPR1 translocates from the cytoplasm to the nucleus after treatment of cells with mitogens. The function of nuclear ZPR1 has not been defined. Here we demonstrate that ZPR1 accumulates in the nucleolus of proliferating cells. The role of ZPR1 was examined using a gene disruption strategy. Cells lacking ZPR1 are not viable. Biochemical analysis demonstrated that the loss of ZPR1 caused disruption of nucleolar function, including preribosomal RNA expression. These data establish ZPR1 as an essential protein that is required for normal nucleolar function in proliferating cells.

Neurotoxicity of adriamycin passed through the transiently disrupted blood-brain barrier by mannitol in the rat brain

Neurotoxicity of adriamycin (ADM) was investigated following the transient disruption of the blood-brain barrier (BBB) in rats. The BBB disruption by the hyperosmotic agent (1.4 M mannitol) was confirmed by the leakage of ADM and Evans blue administered intravenously. Neuropathological changes due to the toxicity of ADM were found as early as day 4. The neurons in the cerebral cortex and nucleus caudatus-putamen showed focal clearing of the nuclear chromatin, increased dense bodies in the cytoplasm and dilatation of the cisternae of the rough endoplasmic reticulum (r-ER) and Golgi apparatus. By day 7, nucleolar segregation and irregular membranous structures appeared in the nuclei with the progression of cytoplasmic changes. By day 10, the cytoplasm of many neurons was vacuolated. Electron-microscopically, the cisternae of the r-ER and Golgi apparatus were prominently dilated in these neurons. Neuronal microtubules were increased in number, in particular in the perinuclear region. Numerous whorl-like membranous structures and separation of nuclear membrane were also observed. Some astrocytic processes surrounding the blood vessels revealed loss of organelles and a few pericytes showed an increased number of lysosomes on days 7 and 10. This experiment clearly demonstrates that ADM has strong neurotoxic effects in the central nervous system when the BBB is disrupted, and provides the warning for the possibilities of neurotoxic side effects when ADM is administered, in combination with a hyperosmotic agent, for the treatment of human malignant tumors, including brain tumors.

Nuclear and nucleolar damage in adriamycin-induced toxicity to rat sensory ganglion cells

A single dose (10 mg/kg) of Adriamycin was given to 23 adult Wistar rats and the spinal ganglia were studied from 6 h to 15 days after. As previously described, this drug results in the appearance of 'clear' areas in the nuclei of rat spinal ganglion cells as seen by light and by electron microscopy. The 'clear' areas become less conspicuous during the week before the onset of cytoplasmic degeneration. In addition, nucleolar changes become increasingly evident with time after injection. Fibrillar centres enlarge and nucleolar segregation is present from 24 h onwards, although the latter is invariably partial and more readily seen with the electron microscope. Nucleolar fragmentation is seen more frequently from 3 days onwards and nucleolar enlargement is common from 6 days. Early cytoplasmic abnormalities are associated with pronounced loss of Nissl substance. Adriamycin must bind extensively to nuclear DNA in spinal ganglion cells, causing the 'cleared' nuclear areas and the changes in dense chromatin. In addition, the binding of Adriamycin to nucleolar DNA with disturbance to nucleolar functions must be important in producing later cytoplasmic changes that precede cell death. There are thus similarities between the action of Adriamycin on these cells and those of Cisplatin, although in the latter intoxication the nuclear effects are significantly less prominent.

The effects of cisplatin on rat spinal ganglia: a study by light and electron microscopy and by morphometry

Cisplatin given in doses of 0.5-2 mg to Wistar and to Sprague-Dawley rats produced nucleolar segregation of the dense fibrillar from the granular component in spinal root ganglion cells. The nucleolar segregation, found to the same extent in large and small neurons, was confirmed by specific silver staining and by electron microscopy. After repeated doses of 1 mg or 0.5 mg, up to 40% of affected nucleoli were observed by light microscopy. Focal clearing of the nucleoplasm of nuclei also occurred. Disorganisation of ribosomes was found in more severely intoxicated animals, especially in large light cells with shrinkage of the Nissl substance and apparent increase in neurofilaments, the latter occasionally distending the initial segment of the axon, but never extending further. Hypertrophy of the satellite cells with increase in the perineuronal intercellular spaces, often associated with irregular, scalloped nuclear and cell outlines, suggested that neuron shrinkage had occurred. This was confirmed by morphometry and marked alterations were found in nucleolar-to-nuclear and nucleolar-to-cell diameter ratios, nuclear and cell diameters were also somewhat reduced without change in the nucleus-to-cell ratios. Peripheral sensory nerve degeneration was not seen, and the animals died from non-neural causes. The probable role of these events in the production of sensory neuropathy is discussed.

Inhibition of protein synthesis and cell proliferation in cultured human breast cancer cells treated with mitoxantrone

Mitoxantrone suppresses cell proliferation, inhibits protein synthesis and induces ultrastructural alterations in the T-47D and MDA-MB-231 breast cancer cell lines. After 24 h treatment with 10(-9), 10(-7) and 10(-5) M drug and 8 h incubation with [35S]methionine, protein synthesis declined rapidly. While a 10-15% decrease in protein synthesis at 10(-9) M was observed, more than 95% inhibition of protein synthesis occurred at 10(-5) M mitoxantrone in both cell lines. Sodium dodecylsulfate (SDS) gel electrophoresis of labeled proteins revealed no qualitative changes in either cell line. However, only trace amounts of several proteins were present in T-47D cells treated with 10(-5) M drug. At 10(-9) M mitoxantrone had little effect on cell proliferation. At 10(-7) M, 25% and 35% growth inhibition in T-47D and MDA-MB-231 cells was observed, respectively. Cell growth at 10(-5) M was abolished. Cytotoxicity was evident at drug concentrations above 10(-5) M. Ultrastructural alterations in the nucleoli of both cell lines included disintegration and segregation of granular and fibrillar components and the disappearance of nucleolar organizers at 10(-7)-10(-5) M mitoxantrone.

Cytochemical study of the nucleolus of the slime mold Dictyostelium discoideum

The nucleus of the slime mold Dictyostelium discoideum is characterized by the presence of several large dense masses which are all in tight contact with the nuclear membrane. These dense masses, considered as nucleoli, present a rather homogeneous texture, in which dense chromatin, fibrillar, and granular material are not easily detected. The autoradiographic study of [3H]uridine pulse-labeled cells showed that the majority of the silver grains were located inside these masses. The use of EDTA regressive-staining, acetylation and enzymatic digestion indicated that they are mostly composed of RNP and are totally devoid of dense chromatin as the rest of the nucleus is. After treatment with actinomycin D, fibrillar and granular material segregated but no chromatin could be found. All these observations confirmed that the dense masses correspond to nucleoli despite their peculiar ultrastructure. It can also be concluded that this type of nucleoli cannot be considered as a taxonomic character of the slime molds because it does not exist in all slime molds and was observed in some dinoflagellates, and ascomycetes.

Cytochemical and autoradiographic study of the early nuclear lesions induced by an ellipticine derivative in isolated rat hepatocytes

Isolated rat liver cells maintained in primary culture were treated with 9-OH ellipticinium (9-OH E+). The effects of this drug on the nuclear ultrastructure and on the chromatin transcriptional activity were studied by the combination of cytochemistry with hgih resolution autoradiography. At a low concentration (1 microgram/ml) for periods ranging from 10 min to 3 hr, 9-OH E+ induced chromatin clumping, nucleolar microsegregation and a diminution in the number of perichromatin and interchromatin fibrils. Autoradiography revealed that this compound inhibited rapidly the incorporation of [5-3H]-uridine in the nucleus, preferentially but not exclusively in the nucleolar area. In addition, the distribution of the radioactivity in the nucleoli proved that the processing of the pre-ribosomal ribonucleic acids (pre-rRNA) synthesized in the presence of the drug was blocked while the processing during 9-OH E+ treatment of normally synthesized pre-rRNA was not altered. These findings suggest that the inhibition of pre-rRNA processing might result from an impairment of factors controlling this processing rather than from a direct action of 9-OH E+ on pre-rRNA molecules.

Early changes in regenerating hamster pancreas following a single dose of N-nitrosobis (2-oxopropyl)amine (NBOP) administered at the peak of DNA synthesis

A single dose of N-nitrosobis(2-oxopropyl)amine, a carcinogen for hamster pancreas, was administered to hamsters with regenerating pancreas 60 hours after initiation of regeneration when the maximum number of acinar cells are in S phase of the cell cycle. This led to nucleolar segregation and mitotic abnormalities from which the acinar cells quickly recovered. Two months later there was moderate pancreatic atrophy in which there were populations of acinar cells containing a variable complement of zymogen granules. In addition, there were nests of eosinophilic cells of unknown derivation which, though disposed in configurations resembling acinar cells, differed distinctly from them. They were devoid of the rich concentric lamellar arrays of ER and zymogen granules characteristic of acinar cells. In addition, differences existed in the chromatin pattern of their nuclei and the number and morphology of their mitochondria. These results suggest that NBOP induced the emergence of a new cell population with a phenotype distinctly different from any of the component cells of normal hamster pancreas.

Induction of nucleolar segregation in adrenal fasciculata cells by actinomycin D

Actinomycin D administration to young rats provokes segregation of the nucleoli of adrenal fasciculata cells into 5 distinct zones (granular, fibrillar and vacuolar zones, a fibrillar center, and a dense fibrillar or "contrasted" zone); in the cytoplasm, there were dilations of Golgi cisternae. In spite of the nucleolar segregation, the cytoplasmic alterations suggest the maintenance of protein synthesis.

Nucleolar reorganization in liver cells of the aging rat

The nucleoli of rat liver cells duplicate in great detail the life-long series of reorganizational changes encountered in kidney and intestinal epithelial cells. The ultrastructural components of the large, loosely organized polymorphous nucleoli, which are dominant in the rapidly multiplying stem cells of embryos, are readily accessible for chemical activities. Smaller, more compact amphinucleoli are dominant in more mature cells, which were characterized by Smetana ('70) as "idling" cells, showing slowly continuing ribosome formation and RNP synthesis. In older cells bipartite nucleoli become dominant and are reorganized in increasing numbers from the younger amphinucleoli. These, however, are not replaced in equal numbers from the shrinking pool of polymorphs of young cells which have greatly reduced mitotic potential. Paralleling the shifts in dominant nucleolar types, the high level of protein synthesis declines in older cells not only in the quantity of proteins synthesized but also in kinds of enzymes produced. These fail to meet the structural and functional requirements of aging cells leading ultimately to the onset of age-related degenerative changes. Again it is noted that separation of the karyosomal DNA from the plasmosomal RNA-protein complex of the nucleolus may lead to possible breakdown of the DNA-dependent RNA-protein transcription system ultimately bringing protein synthesis to a very low level in the senescent animal.

Effects of antimitotic agents either free or bound to DNA on mouse peritoneal macrophages cultivated in vitro

Mouse peritoneal macrophages were cultivated in vitro and treated with ethidium bromide (EB) or with cis-dichloro-diammine platinum (II) (cis-Pt). EB provokes strong cytological alterations and cell degeneration; cis-Pt was not toxic under our experimental contitions. EB-DNA complex penetrates into the macrophages, is liberated from DNA in vacuoles, then diffuses into the cell and is highly cytotoxic. Cis-Pt-DNA complex also penetrates into the cells, but cis-Pt cannot be released from DNA, cis-Pt-DNA complex accumulates inside cytoplasmic vacuoles but has no cytotoxic activity.

Nucleolar reorganization in cells of the kidney of the rat and its relation to aging

A process of nucleolar reorganization apparently identical to that encountered in intestinal epithelial cells (Adamstone and Taylor, '72) develops in kidney cells of aging rats. The polymorphic nucleoli of young tubule cells soon change to amphinucloeli and, while terminal nucleolar reorganization is delayed in cells of collecting tubules, in the nephrons nucleoli soon begin to undergo terminal reorganization becoming bipartite structures with separate plasmosomes and karyosomes. This suggests disruption of the DNA-dependent RNA protein transcription system and failure to maintain the flow of messenger RNA into the cytoplasm. Old cells are not discarded immediately from the kidney tubules and they retain much rough endoplasmic reticulum, numerous ribosomes and polysomes and large plasmosomes. Thus a high RNA concentration is known to develop in old kidney tissue while protein synthesis is also known to be low (Kanungo et al., '70; Buetow and Ghandi, '73). Nucleolar counts show gradual increase in bipartite nucleoli at the expense of amphinucleoli and in the senescent kidney bipartite nucleoli predominate. It is suggested that nucleolar reorganization, with final separation of plasmosomes and karyosomes, includes the process of nucleolar segregation and is triggered by some innate nucleolar mechanism in response to encoded genetic information stored in the nucleolus during nucleogenesis. At this time both DNA and RNA are incorporated into the developing nucleolus. It is also to be noted that two shifts in nucleolar dominance occur with advancing age. These may be fundamental to the process of aging and to the onset of senescence. Furthermore, the changes in dominant nucleolar types are the direct result of the process of nucleolar reorganization.

Adaptive changes of the rat liver cells induced by repeated intraperitoneal injections of d-galactosamine. II. Light and electron microscopic investigations of hepatocellular nucleolar alterations

The effects of repeated d-galactosamine (GalN) administration - i.e. subacute GalN intoxication - on rat liver cell nucleoli were examined. After an initial intraperitoneal injection of 375 mg GalN/kg body weight the rats were treated with 250 mg GalN/kg body weight daily at intervals between 24 h and 30 days. The rats were sacrificed six h after the last injection by decapitation. Specimens of liver were studied by light and electron microscopy. According to the nucleolar size three stages were to be distinguished. Stage I: decreased nucleolar size after one injection, stage II: increased and maximal nucleolar size after two to five injections, stage III: slightly increased relatively stable nucleolar size after six and more injections. Fine structural observations suggest a nucleolar hyperfunction in subacute GalN intoxication as well as a minor disturbance of the transcription and the transfer of the nucleolar RNA.

Nuclear translocation of the estradiol receptor: partial inhibition by ethidium bromide

Ethidium bromide (EB), an intercalating drug, has been shown to prevent the in vitro interaction of the estrogen receptor (R) with DNA (André et al., 1976). We have now studied the effect of this drug on the nuclear translocation of R in order to determine whether DNA integrity is needed for this translocation. In a cell-free reconstituted system made of purified nuclei and cytosol, the pretreatment of nuclei by EB prevented approximately half of the R nuclear translocation, but was unable to extract more than 17% of the E2-R previously translocated. A series of indirect evidences suggests that EB inhibits the nuclear translocation of R by interacting with nuclear DNA. The degree of the inhibition was related to the amount of drug bound to nuclei and was in agreement with the degree of ultrastructural modifications of chromatin. R was not irreversibly altered by the drug. The EB inhibition was only observed with DNA-containing particles and with estrogen receptor able to bind to DNA. In surviving uteri the drug also inhibited the R nuclear translocation. These resuts indicate two types of nuclear translocation of R, one sensitive and the other resistant to EB, and suggest that DNA is required for the EB-sensitive translocation.

[The structure of the nucleolus during the inhibition of RNA-and protein synthesis (author's transl)]

In cells treated with antimetabolites to inhibit RNA- and protein synthesis, electron microscopic studies reveal structural alterations of the nucleolus. The morphological appearance of the nucleolus differs depending of the inhibitor used. If transcription is prevented, segregation of nucleolar components is observed. Inhibition of processing of newly synthesized RNA results in a degranulation and an increase in the amount of nucleolar fibrils. A disturbance of the release of nucleolar ribonucleoproteins into the cytoplasm leads to an enlargement and a hypergranulation of the nucleolus. On the other hand interruption of translation of mRNAs has no immediate effect on the appearance of the nucleolar structure. Only after longer treatment of the cells with the translation inhibitor the nucleolus shrinks and becomes degranulated. The use of inhibitors with clearly defined mechanisms of action in a morphological study should make it possible to interpret similar nucleolar alterations seen in cancer cells and virus-infected cells on a molecular biological basis.

Comparison of the effects of ethidium bromide and of ethidium bromide-deoxyribonucleic acid complex in fibroblasts cultivated in vitro

Chick embryo fibroblasts cultivated in vitro were treated with ethidium bromide (E.B.) or with DNA-E.B. complex (DNA-E.B.). E.B. (5 mug/ml) provokes morphological alterations and cell death, inhibits DNA synthesis and mitotic activity. DNA-E.B. (E.B. 5 mug/ml) is less toxic to the fibroblasts as far as cell structure, DNA synthesis and mitotic activity are concerned. DNA alone has no apparent effect on the fibroblasts. As shown by fluorescence microscopy, the lower toxicity of DNA-E.B. seems to be related to its mode of penetration into the cells.

4-Hyroxyaminoquinoline-1-oxide-induced ultrastructural changes in the guinea-pig exocrine pancreas

4-hydroxyaminoquinoline, a carcinogen was injected into guinea-pigs intravenously in a single dose of 22-5 mg/kg. The sequential morphological changes in the exocrine cells of the pancreas were studied by electron microscopy at selected intervals between 18 and 60 hr. The earliest alterations in the acinar cells comprised nucleolar segregation into granular and fibrillar components and minimal dilatation of endoplasmic reticulum. At later intervals all the cytoplasmic organelles appeared altered. The endoplasmic reticular channels were markedly dilated with depletion of membrane bound and free ribosomes. The mitochondria were swollen and irregular with disruption of limiting membranes and cristae. The zymogen granules were markedly reduced or completely absent. The hyaloplasm contained morphologically variable cytoplasmic degenerative bodies. In addition to the acinar cells, centriacinar and ductal epithelial cells showed similar changes.

Drug effects on the fine structure of Trypanosoma rhodesiense: puromycin and its aminonucleoside, Cordycepin and Nucleocidin

The effects of four trypanocidal adenine nucleosides on the fine structure of a monomorphic strain of Trypanosoma rhodesiense have been examined. All four drugs, Puromycin and its aminonucleoside, Cordycepin and Nucleocidin, induced electron-lucent cytoplasmic clefts in the cytoplasm, which were generally acicular or spindle-shaped, with long axes lying in any direction. The clefts had an intimate relationship with the rough endoplasmic reticulum. The drugs also produced excessive lysosomal vacuolation, and two, Cordycepin and Nucleocidin, caused nucleolar fragmentation and probable segregation, indicative of interference with RNA synthesis. The significance of the lesions is discussed in relation to known properties of adenine nucleoside drugs.

Nucleolar RNA synthesis of meiotic prophase spermatocytes in the human testis

Human meiotic prophase spermatocyte nuclei were studied by electron microscope autoradiography after a 3 hours 3H-uridine labeling pulse, followed by postincubation in non-radioactive medium. In autosomes, 3H-uridine nucleolar labeling reaches a peak during early-middle zygotene prior to the peak labeling of chromosmal RNA species at middle pachytene. Transcription activities of sex chromosomes are inconspicuous when compared with that of autosomes. An increasing condensation of nucleolar-associated chromatin in acrocentric bivalents contributes to the formation of basal knobs in human pachytene spermatocytes. Upon completion of knob formation, nucleolar components segregate and the uptake of 3H-uridine decreases. These findings suggest that the template capability of ribosomal DNA cistrons, located next to the basal knob region, is largely associated with a dispersed state of chromatin whereas increased chromatin condensation is correlated with a restriction of ribosomal RNA transcription.

Effects of aflatoxin on seedling growth and ultrastructure in plants

Nineteen plants belonging to 11 species of the cruciferae were studied to determine the effects of aflatoxin B(1) on seed germination and seedling development. Germination was not inhibited in any test organism at a concentration of 100 mug of aflatoxin per ml of agar substrate. Inhibition of elongation of the hypocotyls and roots in the species studied varied from 29 to 93% and from 22 to 91% in the respective tissues. Lepidium sativum was the most susceptible plant studied and exhibited the maximal inhibitory response noted above at concentrations of 8 mug of aflatoxin per ml. The ultrastructure of Lepidium root cells treated with crystalline aflatoxin B(1) exhibited morphological changes characteristic of those found in aflatoxin-treated animal cells. In addition to changes in the cytoplasmic organelles, numerous ring-shaped nucleoli with prominent nucleolar caps were produced. The effect of aflatoxin on plant cells is compared with similar effects induced by actinomycin D. Seed germination and seedling development is discussed in relation to the effects of both compounds on deoxyribonucleic acid-dependent ribonucleic acid biosynthesis.