In vivo sister chromatid exchange in cells of various organs of the mouse

The relationship between dioxin congeners in the breast milk of Vietnamese women and sister chromatid exchange

The aim of this study was to clarify the relationship between dioxin concentrations in breast milk and the sister chromatid exchange (SCE) frequency in women from herbicide-sprayed and non sprayed areas. Blood samples were taken from 21 women with high TCDD (tetrachlorodibenzo-p-dioxin) levels from sprayed areas, 23 women with moderate TCDD levels from sprayed areas, and 19 women from non sprayed areas to determine their SCE frequency. The SCE frequencies for the high and moderate TCDD groups from the sprayed area and for the non sprayed area group were 2.40, 2.19, and 1.48 per cell, respectively. Multiple regression analysis showed that the standardized β values for 1,2,3,6,7,8-hexaCDD (β = 0.60), 1,2,3,4,6,7,8-heptaCDD (β = 0.64), and octaCDD (β = 0.65) were higher than those for TCDD (β = 0.34) and 1,2,3,7,8-pentaCDD (β = 0.42). The adjusted R² value for polyCDDs (R² = 0.38) was higher than that for polyCDD toxic equivalents (TEQ (toxic equivalents); R² = 0.23). This study therefore shows that levels of hexa-, hepta-, and octaCDD, which were previously regarded as being less toxic than TCDD, are closely related to SCE frequency and that the level of dioxin (pg/g lipid) is potentially more useful as an indicator than TEQ value for explaining SCE frequency.

Preclinical studies on NSC290205 aza-steroid alkylator activity in combination with adriamycin against lymphoid leukaemia

Summary NSC290205 (A) is an hybrid synthetic antineoplastic ester that is a combination of a d-lactam derivative of androsterone and an alkylating derivative of N,N-bis(2-chloroethyl)aniline. We tested NSC290205 for synergistic antileukaemic activity with adriamycin (ADR), (i) in vitro against the human lymphoid leukaemia cell lines: CCRF-CEM, MOLT-4, and RPMI-8226, (ii) in vivo against P388 lymphocytic and L1210 lymphoid murine leukaemias (at incipient and advanced phase). Our results indicated significant cytostatic and cytotoxic synergy of NSC290205 and ADR in vitro. We further examined these results in vivo by replacing cyclophosphamide in the standard CHOP (cyclophosphamide, hydroxydaunomycin, Oncovin, prednisone) regimen with NSC290205 (AHOP) and comparing the efficiency of these two regimens in vivo. Although treatment of P388 and L1210 with cyclophosphamide or NSC290205 alone yielded equivalent results, AHOP produced a clear benefit for survival compared with CHOP against advanced leukaemias, confirming the in vitro observations [higher percentage increase in median lifespan of treated animals over the untreated (control): 188% and 239% in L1210, 308% and 353% in P388, P < 0.01, for CHOP and AHOP respectively]. AHOP also proved to be more genotoxic and cytostatic than CHOP, inducing higher sister chromatid exchange levels and cell division delays on P388 cells in vivo. NSC290205 showed superior antineoplastic potential against lymphoid leukaemia and significant synergy with ADR, producing an excellent therapeutic outcome.

Sister chromatid exchange in vivo, chromosomal characterization and NORs activity of leukemia cells during 5FU-treatments

A transplantable mouse leukemia model, the leukemia cell of which has a marker chromosome and the XX genome type which differ obviously from their male host cells provides a possibility to precisely identify the leukemia cells among their male host cells cytogenetically. A sister chromatid exchange (SCE) plus chromosomal C-banding technique that we report here is very useful. The SCE frequencies in vivo of both leukemia cells and host cells were twice as high as the normal mouse cells. The higher SCE frequencies of the host cells in the leukemia mice may be due to some toxicities from the leukemia cells or some biological large molecule exchanges between the leukemia cells and the host cells. There was no significant difference in SCE frequencies between cells from the spleen and from the bone marrow of the leukemia mice. The percentages of leukemia cells in both spleen and bone marrow were more than 90% when the mice had been injected with the leukemia cells for five days. The host cells in the leukemia mice did not become leukemia cells. The 5FU-treated leukemia mice survived very well for more than twenty-three days. After the 5FU-treatments, most of the leukemia cells died, subsequently, SCE frequencies decreased to a normal level. Both the number of Ag-NORs per cell and the number of chromosomes bearing Ag-NORs per cell in the leukemia mice decreased to 60% and 40%, respectively, of the level found in normal mouse cells.

The lens and cataract: clastogenic responses in epithelial cells of the organ-cultured rat lens

The epithelial cells of the vertebrate lens have an unique character and a probable involvement in cataract formation, which could be initiated by exogenous stimuli. Individual rat lenses were organ-cultured, and the effects of mitomycin C and gamma rays on sister chromatid exchanges (SCE), chromosomal aberrations, and cellular kinetics assessed in cells from the epithelial monolayer. SCE showed about a 5.5-fold increase over the mitomycin C dose range (0, 17, 83, 170 nM), while chromosomal aberrations increased 38-fold. In cells from untreated lenses, SCE were 1,600 times more frequent than aberrations and at a level consistent with in vivo assessments in other cell types. Gamma rays (up to 4 Gy) had a greater inhibiting effect on cellular progression, while 17 nM mitomycin C and 1 Gy induced similar clastogenic responses. This first demonstration of such changes in lens epithelial cells expands on the cell types available for monitoring potential mutagen-carcinogens. Additionally chromosomal changes resulting from lens cellular challenge could be the basis of later cytopathological changes in the lens, of which cataract is the primary concern to humans. Potential cataractogens warrant monitoring, and the study outlined may aid in this endeavor, as well as contributing to an understanding of cataract etiology.

Assessment of sister chromatid exchange in spermatogonia and intestinal epithelium in Chinese hamsters

The induction of sister chromatid exchange (SCE) has been proposed as a predictive test for the identification of mutagens/carcinogens. The in vivo application of this test was investigated by examining the chemical induction of SCE in spermatogonia, intestinal epithelium and bone marrow cells from Chinese hamsters. Sister chromatid differentiation (SCD) was achieved in differentiating spermatogonial cells of male Chinese hamsters by the abdominal subcutaneous (sc) implantation of an agar-coated bromodeoxyuridine (BrdUrd) tablet. A number of genotoxins were administered intraperitoneally (ip) and the induction of SCE in spermatogonia and bone marrow was compared. A significant increase in SCE frequency in spermatogonia occurred following treatment with mitomycin C (MMC), cyclophosphamide (CP), or N,N',N"-triethylenethiophosphoramide (ThioTEPA). Treatment with busulfan, hycanthone (HC), or triethylenemelamine (TEM) failed to induce SCE in vivo in spermatogonia, but these compounds did induce SCE in bone marrow. Differences in cell cycle kinetics were considered to be the major factor involved in the differential induction of SCE in spermatogonia and bone marrow. The induction of SCE in intestinal epithelium was investigated as a system for the identification of genotoxins that may result from the metabolism of xenobiotics by the gastrointestinal flora. Nitro-aromatic compounds were administered orally to Chinese hamsters. Nitro-aromatic compounds were chosen for this study since the mutagenic activity of these compounds is thought to result from their metabolism by bacterial nitroreductase. Metronidazole (MN) and 2-nitro-p-phenylenediamine (2NPPD) induced a dose-related increase in SCE formation in intestinal epithelium but not in bone marrow. Treatment with 3-nitro-o-phenylenediamine (3NOPD) or 4-nitro-o-phenylenediamine (4NOPD) did not induce the formation of SCE in either intestinal epithelium or bone marrow. These findings indicate that studies in axenic animals will be required to elucidate the contribution of the enteric flora to the metabolic activation of some genotoxins.

Sister chromatid exchange levels and cell cycle time in human bone marrow cells and lymphocytes

The frequency of sister chromatid exchange (SCE) and the cell-cycle-specific pattern of mitoses were analyzed at the same time in normal bone marrow cells and lymphocytes of six healthy donors. The SCE frequency was found to be significantly higher in lymphocytes. The cell-cycle-specific pattern revealed significantly shorter cell cycle times for normal bone marrow cells as compared with those of phytohemagglutinin (PHA) stimulated lymphocytes. Chromosomes of bone marrow metaphases displayed a more contracted morphology.

Analysis of baseline and BrdU-dependent SCEs at different BrdU concentrations

In the present paper we have used a rationale based on the development of theoretical equations that define sister-chromatid exchange (SCE) frequencies as a function of two variables, namely the baseline (BrdU-independent) and the BrdU-dependent SCE frequencies. The experimental design includes the estimation of SCE frequencies in second division chromosomes when both cycles occurred in the presence of BrdU and when BrdU incubation took place only during the first cycle in a wide range of BrdU concentrations. The final SCE yields in second division chromosomes could be separated into three different components: (1) The BrdU-independent, 'spontaneous' or baseline SCEs, whose low but biologically significant frequency was calculated to be about 0.06 SCEs per pg of DNA; this figure could be similar for most of the cell types; (2) the BrdU-dependent SCEs whose frequency increases with BrdU dose, probably as a result of BrdU substitution for thymidine; (3) the BrdU-dependent SCEs as a consequence of other cellular factors such as disturbance of nucleotide pool sizes. At high BrdU concentrations (300 microM upward) the three components appear to have a significant value in the final SCE yield, whereas at lower BrdU doses the third component seems to be negligible.

In vivo sister chromatid exchange analysis of a mouse plasmacytoma cell line NP-38

In vivo sister chromatid exchange (SCE) frequencies have been compared between the mouse plasmacytoma NP-38 and normal bone marrow cells of the host BALB/c mouse. NP-38 cells, transplanted subcutaneously showed a two-fold increase in SCEs (4.35-5.76/cell) compared with the bone marrow cells of the host (1.65-2.14/cell). Such an increase in SCE rates was also observed in NP-38 cells metastasized in spleen, bone marrow, liver, or mesentery, upon inoculation of NP-38 cells by intravenous injection. Even in such tumor-bearing mice, the SCE rates of the bone marrow cells were equivalent to the SCE level found in uninfected mice. These results indicate that the high SCE incidence in NP-38 cells is an inherent characteristic of this tumor cell line.

Selective differential staining of sister chromatids of the facultative heterochromatic X chromosome in the female mouse

Selective differential staining of sister chromatids for the facultative heterochromatic X chromosome in the female mouse has been achieved by the combination of two differential staining techniques; one for the heterochromatic X chromosome and the other for sister chromatids. Thermal hypotonic treatment moderately destroyed the chromosome structure except for the heterochromatic X in BrdU labelled metaphase cells, resulting in the selective sister chromatid differentiation of this X with Giemsa stain. This technique enables us to know the exact frequency of th spontaneous sister chromatid exchanges in the heterochromatic X without using 3H-TdR labelling for detecting the late DNA replication. The results indicate that the sister chromatid exchange frequency of the heterochromatic X chromosome is not affected by its late DNA replication during S phase, or by the genetic inactivation and the resulting heterochromatinization.

Sister-chromatid exchange analyses in rodent maternal, embryonic and extra-embryonic tissues: transplacental and direct mutagen exposures

Sister-chromatid exchange (SCE) analyses were conducted in maternal, embryonic and extraembryonic tissues of pregnant rats and mice. The various tissues were substituted in vivo with 5-bromodeoxyuridine (BrdU) by implantation of a BrdU tablet in pregnant animals at mid-gestation. Following maternal exposure to 5-20 mg/kg cyclophosphamide, embryonic liver cells demonstrated dose-dependent SCE increases up to 10-fold that of control. Rat embryos revealed little intralitter variability for this transplacental effect. Maternal marrow and yolk sac cells examined in the rat also underwent significant increases in SCE, although to different extents. While marrow SCE frequencies were similar to those of embryo liver, yolk sac SCE frequencies were generally much lower. SCE analyses were also conducted in rat yolk sac cells substituted in vivo with BrdU and subsequently explanted to whole-embryo culture. In vitro exposure to cyclophosphamide at concentrations up to 100 microgram/ml had no SCE-inducing effect. However, similar exposures to phosphoramide mustard, a presumed metabolite of cyclophosphamide, caused dose-dependent increases in SCE up to 8-fold higher than control at 2 microgram/ml. Thus, cyclophosphamide appears to require maternal metabolic activation in order to cause an increased SCE frequency in yolk sac cells. The system described permits versatile SCE analyses which can help to define relative maternal and embryo tissue-specific sensitivities to chemical-induced genetic damage.

Methods for analysis of the mutagenicity of indirect mutagens/carcinogens in eukaryotic cells

The review discusses the variety of methods for activation of indirect mutagens/carcinogens and testing them in cell cultures, especially in mammalian cell cultures. After the necessity for including metabolizing components in mutagenicity tests has been pointed out, the enzymes that transform foreign compounds metabolically, and the factors influencing them, are described. In the main section the various methods of activating indirect mutagens/carcinogens are presented. The methods of including in vivo metabolism in mutagenicity tests are: Analysis of cells from organisms contaminated with a chemical (III.l.a); body fluid-mediated mutagenesis (III.l.b); host-mediated assay (III.l.c). The following activation systems are suitable for including in vitro metabolism of test compounds in mutagenicity tests: Liver and lung perfusion (III.2.a.alpha); organ slices and homogenates (III.2.a.beta); subcellular fractions (III.2.a.gamma); cultivated cells (cell-mediated mutagenesis) (III.2.b); nonenzymatic activation systems (III.2.c). Finally the main factors that influence the metabolism of test substances are summarized. Two factors illustrate the mutagenicity tests with regard to the metabolism of mammalian livers and the methods of performing mutagenicity tests in man.

Analysis of crossing over in mouse meiotic cells by BrdU labelling technique

Differential staining of sister chromatids in male mouse meiotic cells was achieved by continuous infusion with BrdU from the tail vein followed by Giemsa staining (the FPG technique of Perry and Wolff, 1974). Analysis of 341 bivalents including XY, and 21 univalents reveals that: (1) visible crossing over coincided exactly with the site of chiasmata; (2) no evidence was obtained in support of chiasma terminalisation; (3) an anomalous type of crossing over was found in the monochiasmatic bivalents, which could not be explained by the conventional hypothesis for crossing over; (4) some of the terminally associated bivalents might be achiasmatic, and univalents might have originated from such bivalents; (5) in XY bivalents, sister chromatid association was between lightly and darkly stained chromatids, suggesting a lack of crossing over and the existence of other genetic controls for this association; (6) during meiosis sister chromatid exchanges (SCEs) might be less frequent than crossovers.