Influence of cis-dichlorodiamineplatinum on glioma cell morphology and cell cycle kinetics in tissue culture

Fluorochromes for DNA Staining and Quantitation

In these last few decades the great explosion of the molecular approaches has casted a little shadow on the DNA quantitative analysis. Nevertheless DNA cytochemistry represented a long piece of history in cell biology since the advent of the Feulgen reaction. This discovery was really the milestone of the emerging quantitative cytochemistry, and scientists from all over the world produced a very large literature on this subject. This first era of quantitation (histochemistry followed by cytochemistry) started by means of absorption measurements (histophotometry and cytophotometry). The successive introduction of fluorescence microscopy gave a great boost to quantitation, making easier and faster the determination of cell components by means of cytofluorometry. The development of flow cytometry further contributed to the importance of quantitative cytochemistry. At its beginning, the mission of flow cytometry was still DNA quantitation. For a decade the Feulgen reaction had been the reference methodology for both conventional and flow cytofluorometry; the advent of Shiff-type reagents contributed to expand the variety of possible fluorochromes excitable in the entire visible spectrum as well as in the ultraviolet region. The fluorescence scenario was progressively enriched by new probes among which are the intercalating dyes which made DNA quantitation simple and fast, thus spreading it worldwide. The final explosion of cytofluorometry was made possible by the availability of a large variety of probes directly binding DNA structure. In addition, immunofluorescence allowed to correlate the cell cycle-related DNA content to other cell markers. In the clinical application of flow cytometry, this promoted the introduction of multiparametric analyses aimed at describing the cytokinetic characteristics of a given cell subpopulation defined by a specific immunophenotype setting.

Intranuclear microtubules are hallmarks of an unusual form of cell death in cisplatin-treated C6 glioma cells

We describe an unusual form of non-accidental cell death marked by ectopic microtubules in the nucleus of a subpopulation of cisplatin-treated C6 glioma astrocytes in culture. At electron microscopy, the perinuclear condensed chromatin did not completely adhere to the nuclear envelope of these cells being separated by single or loosely bundled 20-nm-thick microtubules located in an electron-lucid slit-like zone; the presence of alpha-tubulin lining the inner membrane of the nuclear envelope was confirmed by immunolabeling at confocal microscopy. Since tufts of microfilaments-like fibers also occurred in their central nuclear areas, these cells are referred to as CIMMs (Cells with Intranuclear Microtubules and Microfilaments). The nuclear reorganization of CIMMs also involved nucleolar segregation and formation of heterogeneous ectopic ribonucleoprotein (RNP)-derived structures, indicating disruption of the RNP-based transcription machinery. The cytoplasmic organelles of CIMMs were structurally intact, and propidium iodide did not accumulate intracellularly under vital conditions while the plasma membrane was often Annexin V-positive. All these findings suggest that CIMMs were lethally damaged and committed to an atypical programmed cell death resembling early apoptosis (this is also supported by the presence of a limited number of TUNEL-positive CIMMs). CIMMs appeared well before the main cisplatin-induced cycling arrest of the cell population (G2/M block at 72 h) and had mostly G1 DNA content: this suggests that they may represent the cohort of cells which passed cisplatin-altered mitoses with intranuclear retention of microtubules from an incompletely disassembled mitotic spindle.

Ultrastructure of nuclei of cisplatin-treated C6 glioma cells undergoing apoptosis

C6 glioma cells, treated with a cytostatic dose of cisplatin (1.66 x 10(-5) M) ceased dividing by 24 h and, most of them had undergone apoptosis by 72-96 h. The reactive cells were classified into 5 types (T-I to V), according to the ultrastructure of nuclei. At 4 h, 20.4% of cells (T-I) showed minute condensation and margination of chromatin. The nuclear envelope (NE) formed slim and deep invaginations consisting of the inner or both membranes. The later kind of NE invaginations often extended to the enlarged nucleoli and contained nucleolus-like material at its cytoplasmic side. Some nuclear pores were covered with a dome-shaped "cap" formed by fine filamentous material. The number of T-I cells increased to 53.3% by 72 h. In T-II cells, which appeared at 24 h, the chromatin was condensed into dense irregular masses separated from the NE by a lucent space with filamentous structures preventing complete margination of chromatin. Nucleoli of T-II cells were small and showed partial segregation of their components. The "capped" pores were absent in these apparently more damaged cells. From 24 h, cells with large and lobulated nuclei (T-III) started to increase in number and peaked at 72 h (6.6%). Except for some small lobules, the chromatin of T-III cells was moderately aggregated and the NE was well preserved. Typical apoptotic cells with highly condensed and marginated chromatin (T-IV) peaked at 48-72 h (2.4-4.8%). They appeared in 2 varieties, including cells with wrinkled nuclei with less condensed and incompletely marginated chromatin or more lobulated forms with highly condensed marginated chromatin suggesting their origin from T-II or T-III cells. T-IV cells, as well as their fragments, underwent phagocytosis and secondary necrosis (T-V cells, 48.6% at 96 h). Two alternative routes of nuclear changes leading to cisplatin-triggered apoptosis, as represented by the sequence T-I --> T-III --> T-IV/V or T-I --> T-II --> T-IV/V, may explain the initially less or more damaged cells. These alternatives, together with progressive recruitment of reactive cells, suggest intrapopulation differences in the sensitivity of cells or in the cell cycle perturbations induced by cisplatin. Except for the T-IV and T-V cells, observed alterations of cytoplasmic organelles, including mitochondria, were fewer than reported in previous studies on cisplatin.

Glial cell reaction to cis-dichlorodiammine platinum treatment in the immature rat cerebellum

In this study we have investigated changes in glial cells of the cerebellum of cis-dichlorodiammine platinum (cisDDP)-treated rats. The expression of S-100 protein and glial fibrillary acidic protein (GFAP), taken as markers of glial cell function, was evaluated using immunocytochemical methods. In parallel, immunoreactivity for calbindin, parvalbumin, and phosphorylated 200-kDa neurofilament protein was observed in Purkinje cells as markers for neuronal integrity and activity. Results showed that, although no difference in the immunostaining of S-100 protein between control and treated animals could be observed, an increase in the frequency of GFAP immunoreactive cells was present in cisDDP-treated rats. In Purkinje cells, immunocytochemical expression of calbindin and parvalbumin was decreased after drug treatment. In addition, following immunoreaction for phosphorylated 200-kDa neurofilament protein, the somata of Purkinje cells, which were negative in control animals, were stained in treated rats. These findings suggest that cisDDP does not significantly interfere with pathways of glial cell activity and that the increased number of GFAP positive astrocytes may be due to an activation of glial cells consequent upon neuronal death.

Growth related changes in sugar determinants on the surface of C6 glioma cells in culture: a cytochemical lectin-binding study

The cell surface sugar determinants (CSSD) were examined in C6 glioma cells in cultures at different conditions of growth by peroxidase conjugates of the lectins: peanut agglutinin (PNA), Ricinus communis agglutinin (RCA), Helix pomatia agglutinin (HPA), wheat germ agglutinin (WGA), lentil agglutinin (LCA), laburnum bork agglutinin (LABA), and lotus agglutinin (TPA). It was found that the cells bound more intensively WGA, LCA, and RCA compared to PNA, HPA; the weakest staining was provided by LABA and TPA. Binding intensity for PNA significantly increased after pretreatment of the cells with neuraminidase. This indicates that a part of the beta-D-galactose residues on the surface membrane of C6 glioma cells is covered by sialic acid. The process of sialization was increased during the culturing of C6 glioma cells. Addition of cis-DDP or dBcAMP to cultures growing in medium with 10% of CS increased the number of Gal residues which are not covered by sialic acid. The expression of beta-D-galactose (Gal), N-acetyl-D-galactosamine (NAcDGal), and fucose (Fuc) residues appeared to be most responsive to changes in growth conditions and degree of cell differentiation. The expressions of N-acetyl-D-glucosamine (NAcDGlc) and mannose (Man) residues were high and seems did not depend on changing of the conditions of culturing. In C6 glioma cells cultures in which the rate of cell division, formation of the cell processes, and adhesiveness of the cells to the substratum were reduced by growing cells in MEM+, expression of beta-Gal, NAcDGal, and Fuc was considerably reduced. The decrease of expression of beta-Gal, NAcDGal, and Fuc on the surface of cell membrane was more pronounced in MEM+ with 1% of CS than in MEM+ with 10% of CS. In DbcAMP and cis-DDP treated cultures, grown in medium with 1% serum, in which cell division was inhibited without obvious changes in cell adhesiveness to the substratum, binding of PNA and HPA was increased due to higher expression of beta-Gal and NAcDGal. From these observations it was concluded that the pattern of expression of sugar residues on the cell surface varies according to the biological state of the cells and are easily affected by tissue culture conditions.

Comparative studies on the effects of doxorubicin and differentiation inducing agents on B16 melanoma cells

The differentiation-inducing activity of doxorubicin on B16 melanoma cells grown in vitro was compared with that of other known differentiation inducers, such as theophylline, retinoic acid, and melanocyte-stimulating hormone (MSH). At drug concentrations resulting in cytostatic effects, doxorubicin and theophylline induced morphological changes (dendritic-like structures with a terminal melanin granule) with an enhancement of total melanin content and tyrosinase activity. Retinoic acid did not alter melanin content and cell morphology, although it affected cell growth. MSH enhanced total melanin content and tyrosinase activity, with no significant morphological changes. Flow cytometric analysis showed that MSH led to an accumulation of cells in G1 phase whereas doxorubicin induced an accumulation of cells in G2 + M. Studies on DNA content in doxorubicin-treated cells, selected on the basis of a morphologically differentiated pattern, showed a clustering of these cells in G2 + M, probably due to a cytokinesis block. Thus doxorubicin can induce cell differentiation comparable with other differentiation inducers.

Changes in cell cycle and chromatin distribution in C6 glioma cells treated by dibutyryl cyclic AMP

C6 glioma cells in culture were treated with 1 mM dibutyryl cyclic AMP (Db-cAMP) for 5, 8, 24 and 72 h. The cells were labelled with [3H]-thymidine before either the end, or the beginning, of the Db-cAMP treatment. The cell cycle passage was monitored by the simultaneous determination of DNA content and DNA synthesis in propidium iodide stained autoradiograms. The data revealed an early (t less than or equal to 3-8 h) and moderate inhibitory effect of Db-cAMP on all phases of the cell cycle except mitosis; some cells (2%) were completely blocked in the S phase. Later (8 less than t less than 24-72 h), the cycling of a substantial part of the population became inhibited in G1 phase. Microdensitometric texture analysis of Feulgen-stained nuclei, performed 24 h after administration of Db-cAMP, showed a higher inhomogeneity of the DNA distribution in cell nuclei, caused by the condensation of a part of the chromatin. This may reflect either changes in genome expression taking part in the process of cAMP induced differentiation or transit of some cells into quiescent G0 or S0 phases.