Chemically induced rhabdomyosarcomas in rats. Ultrastructural, immunohistochemical, biochemical features and expression of alpha-actin isoforms

A series of 14 primary and two metastatic rat rhabdomyosarcomas (RMS) induced with nickel sulfide was studied by light microscopy, transmission electron microscopy, indirect immunofluorescence, avidin-biotin-peroxidase immunohistochemistry and two-dimensional gel electrophoresis. Monoclonal or affinity-purified polyclonal antibodies were used for the immunohistochemical demonstration of vimentin, desmin, alpha-smooth muscle (alpha-sm) actin and alpha-sarcomeric (alpha-sr) actin. By histological and ultrastructural studies, four categories of RMS were diagnosed on the basis of the neoplastic cell types. These were: (1) well-differentiated RMS (n = 2), (2) pleomorphic RMS (n = 8), (3) embryonal RMS (n = 4), and (4) embryonal myosarcomas (n = 2). Immunohistochemically, all these neoplasms expressed desmin and alpha-sr actin, reflecting their rhabdomyoblastic origin. Two dimensional gel electrophoresis performed on five neoplasms demonstrated alpha, beta and gamma actins spots in all cases. This study demonstrates that the alpha-sr actin antibody represents a good marker for rhabdomyoblastic differentiation is useful in the diagnosis of RMS since it was present in all morphologically confirmed RMS and in two ultrastructurally undifferentiated sarcomas positive for desmin. Neoplastic cells positive for alpha-sm actin were noted in 11 confirmed RMS. Double indirect immunofluorescence showed that all alpha-sm and alpha-sr positive cells also contained desmin. Co-expression of alpha-sr and alpha-sm actins was studied in serial sections of formalin-fixed, paraffin-embedded tumor tissue. Both alpha-sm and alpha-sr actins were localized in some rhabdomyoblasts. This study confirms our previous observations in human tumors and shows, for the first time, that alpha-sr and alpha-sm actins can be present in the same neoplastic cell in vivo.     

Chemically induced aneuploidy in mammalian cells in culture

Our objectives were to assess whether there exist useful aneuploidy tests in vitro, to identify chemicals that showed potential for mitotic aneuploidy induction, and to recommend some features of suitable protocols for such testing. From over 100 papers we selected 24 for review. The acceptable studies examined hyperdiploidy at metaphase, had concurrent negative controls with low background rates of hyperdiploidy, used a fixation time sufficient for cells to complete more than one cell cycle after treatment and had multiple dose levels with at least 100 cells scored per point. We judged that 12 compounds were positive, 7 inconclusive, and 4 negative with the reservation that 2 of the 4 compounds had not been tested up to toxic doses. Many of the positive compounds are also known to cause structural chromosome aberrations. We separately reviewed qualitative reports of 'C-mitotic' effects, anaphase lagging, multipolar mitoses, or altered DNA content, since these effects may sometimes by associated with aneuploidy induction. No well-validated in vitro aneuploidy assay exists, and much research is required to develop tests, perhaps using chromosome counts, DNA content, or effects on cell organelles necessary for mitosis. In test protocol development we should carefully consider choice of cell sample size, use of in vitro metabolic activation systems, and selection of doses, especially with regard to the problem of whether cytotoxic concentrations should be used.     

Chemically induced mouse models of intestinal inflammation

Animal models of intestinal inflammation are indispensable for our understanding of the pathogenesis of Crohn disease and ulcerative colitis, the two major forms of inflammatory bowel disease in humans. Here, we provide protocols for establishing murine 2,4,6-trinitro benzene sulfonic acid (TNBS)-, oxazolone- and both acute and chronic dextran sodium sulfate (DSS) colitis, the most widely used chemically induced models of intestinal inflammation. In the former two models, colitis is induced by intrarectal administration of the covalently reactive reagents TNBS/oxazolone, which are believed to induce a T-cell-mediated response against hapten-modified autologous proteins/luminal antigens. In the DSS model, mice are subjected several days to drinking water supplemented with DSS, which seems to be directly toxic to colonic epithelial cells of the basal crypts. The procedures for the hapten models of colitis and acute DSS colitis can be accomplished in about 2 weeks but the protocol for chronic DSS colitis takes about 2 months.     

Chemically induced K+ conduction noise in squid axon

Internal perfusion of tetraethylammonium ions (TEA) in squid axons produces a significant high frequency noise component. Although internal TEA suppresses the potassium conductance (G _K) noise at relatively low frequencies, it induces high frequency noise which exceeds the intensity of the normal potassium and sodium noise. In addition, the induced noise is dependent on the presence of internal potassium ions (K⁺) suggesting that this source of noise arises from a modulation of the K⁺ conductance due to the blocking and unblocking of the K⁺ channel. The simplest model describing the TEA data is a two-step sequential pseudo-unimolecular reaction where TEA binds during an open conductance state. A unit channel conductance of 2 pS is estimated from the TEA data as well as noise induced by triethyldecylammonium (TEDA) ions. Thus, these data are consistent with the hypothesis that the channel is blocked whenever the quaternary ammonium ion binding site, located near or within the K⁺ channel, is occupied.     

Chemically induced abnormal chromosome behavior at meiosis in maize

Experimental induction of a variety of meiotic abnormalities in maize microsporocytes is described. One class of abnormal chromosome behavior observed is characterized by aberrant centromere-spindle interactions such that the first meiotic division may be equational, the second disjunctional. This abnormality was found following treatment with ethylene oxide-treated cornstarch extracts, ethylene glycol, polyethylene glycols and glyoxal, at synapsed chromosome stages. These is no evidence that crossover frequency was affected in abnormal cells although premature loss of chiasmata may follow such treatment. The results suggest novel approaches to studies of the mechanism of co- and auto-orientation, chiasma maintenence and chromosome functions during synapsis.     

Chromosomal alterations in cell lines derived from mouse rhabdomyosarcomas induced by crystalline nickel sulfide

Summary Prior studies have shown a preferential decondensation (or fragmentation) of the heterochromatic long arm of the X chromosome of Chinese hamster ovary cells when treated with carcinogenic crystalline NiS particles (crNiS). In this report, we show that the heterochromatic regions of mouse chromosomes are also more frequently involved in aberrations than euchromatic regions, although the heterochromatin in mouse cells is restricted to centromeric regions. We also present the karyotypic analyses of four cell lines derived from tumors induced by leg muscle injections of crystalline nickel sulfide which have been analyzed to determine whether heterochromatic chromosomal regions are preferentially altered in the transformed genotypes. Common to all cell lines was the presence of minichromosomes, which are acrocentric chromosomes smaller than chromosome 19, normally the smallest chromosome of the mouse karyotype. The minichromosomes were present in a majority of cells of each line although the morphology of this extra chromosome varied significantly among the cell lines. C-banding revealed the presence of centromeric DNA and thus these minichromosomes may be the result of chromosome breaks at or near the centromere. In three of the four lines a marker chromosome could be identified as a rearrangement between two chromosomes. In the fourth cell line a rearranged chromosome was present in only 15% of the cells and was not studied in detail. One of the three major marker chromosomes resulted from a centromeric fusion of chromosome 4 while another appeared to be an interchange involving the centromere of chromosome 2 and possibly the telomeric region of chromosome 17. The third marker chromosome involves a rearrangement between chromosome 4 near the telomeric region and what appears to be the centromeric region of chromosome 19. Thus, in these three major marker chromosomes centromeric heterochromatic DNA is clearly implicated in two of the rearrangements and less clearly in the third. The involvement of centromeric DNA in the formation of even two of four markers is consistent with the previously observed preference in the site of action of crNiS for heterochromatic DNA during the early stages of carcinogenesis.     

Chemically induced fusion of fresh human erythrocytes.

The fusion of fresh human erythrocytes was shown to be induced by calcium and phosphate ions. Prior treatment of erythrocytes with phosphate ion was a pre-requisite for the calcium-induced fusion. ATP levels in cells incubated with phosphate and calcium decreased 46 fold while cell-associated calcium increased 70 fold during 1 hour of incubation at 37°C as compared to cells which were incubated with calcium in saline. Our results suggest that a phosphate complex formed bridges between adjacent erythrocytes causing agglutination followed by aggregation of membrane proteins leading to protein-free areas of lipids. Where these protein-free areas are in close contact fusion may occur.     

Chemically induced carcinogenesis affecting chromatin structure in rat hepatocarcinoma cells

A new, chemically induced animal tumor cell line (HeDe) was established and characterized by its property of causing aggressively growing tumors in specific strain of rats and changes in the chromatin structure. Results show that (1) the nuclear material in nuclei of normal resting (G0) hepatocytes consists mainly of decondensed veil-like chromatin, chromosomes being clustered in six lobular domains; (2) nuclei of HeDe cells contain primarily supercoiled chromatin; or (3) the nuclear material of tumor cells undergoes apoptosis seen as apoptotic bodies. Heterogeneity of chromatin structures was expressed as contour/area ratio and was nine times higher in apoptotic cells and two times higher in tumor cells compared to resting cells.