Chromosomal abnormalities and sister-chromatid exchange in bone marrow cells of mice and Chinese hamsters after inhalation and intraperitoneal administration: I. Diepoxybutane

Diepoxybutane (DEB), a direct-acting animal carcinogen, was found to increase the frequency of structural chromosomal abnormalities (CA) and sister-chromatid exchange (SCE) in bone marrow cells of mice and Chinese hamsters, when inhaled from an aerosol during a 2-h head-only exposure or administered as a single intraperitoneal injection. For the purpose of comparing the genotoxicity in the 2 species, both after inhalation and intraperitoneal administration, the systemic DEB dose obtained by inhalation was determined on the basis of blood concentrations and inhalation duration after the investigation of the blood kinetics. The bone marrow cells of male and female NMRI mice were found to be more sensitive than those of Chinese hamsters to the genotoxic activity of DEB.     

Chemically-induced sister-chromatid exchange in vivo in bone marrow of Chinese hamsters. An evaluation of 24 compounds

Chemically-induced sister-chromatid exchange (SCE) was measured in vivo in bone marrow of Chinese hamsters. Chemicals were administered either intraperitoneally or orally and increased SCE frequencies were noted with 6 of 6 direct-acting genotoxins and with 9 of 14 activation-dependent genotoxins. Metronidazole, o-toluidine, 4-nitro-o-phenylenediamine and 2-nitro-p-phenylenediamine, compounds which have shown either mutagenic or carcinogenic activity, did not induce SCE in vivo, 4 non-genotoxins and 4 different control treatments did not induce SCE. The results show that the in vivo SCE method may be useful for the identification of genotoxins and that the outcome of the test is, for certain chemicals, dependent upon the route of exposure.     

Chemically-induced sister-chromatid exchange in vivo in bone marrow of Chinese hamsters An evaluation of 24 compounds

Chemically-induced sister-chromatid exchange (SCE) was measured in vivo in bone marrow of Chinese hamsters. Chemicals were administered either intraperitoneally or orally and increased SCE frequencies were noted with 6 of 6 direct-acting genotoxins and with 9 of 14 activation-dependent genotoxins. Metronidazole, O-toluidine, 4-nitro-O-phenylenediamine and 2-nitro-p-phenylenediamine, compounds which have shown either mutagenic or carcinogenic activity, did not induce SCE in vivo. 4 non-genotoxins and 4 different control treatments did not induce SCE. The results show that the in vivo SCE method may be useful for the identification of genotoxins and that the outcome of the test is, for certain chemicals, dependent upon the route of exposure.     

小鼠腹腔注射甲醛后骨髓细胞微核变化检测

本实验目的是检测不同剂量甲醛经腹腔注射染毒小鼠后,小鼠骨髓嗜多染红细胞数量和微核的数量与注射剂量之间的关系。结果甲醛剂量和嗜多染红细胞数、微核数、微核率(‰)均呈正相关。     

Chromosomal changes induced in mouse bone marrow cells following six weeks inhalation of cyclohexanol

The effects of low doses of cyclohexanol exposure were studied in mouse bone marrow cells including chromosome aberrations (CA), micronucleus (MN) and sister chromatid exchanges (SCE) as biomarkers. Capillaries with a tested agent that was evaporated continuously were placed in an experimental chamber for six weeks. No clastogenic and/or aneugenic effect of CA and MN induction was observed. A significant elevation of induced damage was achieved in the SCE study (p < 0.001) that has confirmed the early exposure of cyclohexanol to mice.     

The effect of inflammation on splenic colony formation after the intraperitoneal administration of bone marrow cells

The number of spleen colonies formed after intraperitoneal injection of bone marrow cells increases approximately 100-fold in mice with inflammation induced by nitrocellulose filters implanted into the intraperitoneal cavity. By transplanting these filters together with cells grown on them into intact animals and replacing them with clean filters we have demonstrated that this effect is associated with inflammation focus in the peritoneal cavity rather than with CFU-S proliferation of the filter surface.     

Radiomodifying influence of camphor on sister-chromatid exchange induction in mouse bone marrow

The frequency of sister-chromatid exchanges (SCE) in mouse bone marrow exposed to gamma-irradiation was used to assess the radiomodifying effect of camphor. Hoechst 33258 plus Giemsa was used for SCE analysis. The radiation-induced SCE frequency was significantly low after a single dose of camphor (0.5 microM/g b.w.) administered 30, 45 or 60 min before irradiation; the effect was enhanced with increasing time intervals.     

Chronotoxicity of methotrexate in mice after intraperitoneal administration

Methotrexate (MTX), an effective agent in treatment of cancer, is one of the most versatile antineoplastic agents in spite of severe toxicity problems. The purpose of this study was to determine the circadian variation of this toxicity in order to decrease the side effects. The experiments were done in mice given a single i.p. dose. The toxicity of MTX, estimated from the relative weight loss, varied according to the time of administration, with a maximum after administration at 0900 (02 HALO). The dose-effect relationship can be described by a linear function: delta P/P versus log (dose). The slope of this line varies with the time of administration. These variations are correlated with the variations in biochemical [dihydrofolate reductase (DHFR) activity] and pharmacokinetic parameters (AUC) studied in previous works.     

Chromosomal aberrations and sister-chromatid exchanges in Chinese hamster cells treated in vitro with hexavalent chromium compounds.

Chinese hamster cells (CHO line) were treated in vitro for 30--39 h with hexavalent chromium compounds (K2Cr2O7 and Na2CrO7), at concentrations ranging from 0.1 to 1.0 microgram of Cr6+ per ml, in medium containing BUdr. Chromosomal aberrations and sister-chromatid exchanges were scored on BUdr-labelled 2nd division metaphases, collected at the end of treatment and stained with Giemsa. Treatment with mitomycin C 0.009--0.030 microgram/ml) was carried out as a control for the responsiveness of the cell system to chromosomal damage. Both chromium compounds induced marked mitotic delays. Chromosomal aberrations were increased about 10-fold by exposure to Cr6+ (1.0 microgram/ml). The principal aberrations observed were single chromatid gaps, breaks and interchanges, whose frequencies increased proportionally to the concentration of chromium. Dicentric chromosomes, isochromatid breaks, chromosome and chromatid rings were also induced. The frequenyc of sister-chromatid exchanges was hardly doubled 30 h after exposure to Cr6+ at 0.3 microgram/ml, whereas it was trebled 39 h after treatment, in the cells whose division cycle had been slowed down by chromium.     

Length of cell cycle in vitro and sister-chromatid exchange (SCE) frequency in bone marrow cells from severely malnourished rats

Cell proliferation and SCE frequency were evaluated through differential staining of sister chromatids in cultured bone marrow cells from rats malnourished during the lactation period. Cell proliferation was studied in vitro in sequential analysis every 5 h in cultures from 20 to 40 h of incubation. Results show a longer generation cycle in malnourished rat cells, revealing a delay in cell proliferation. Cells of this group of animals showed a higher percentage of first-cycle metaphases and lacked third-cycle metaphases even after 40 h of culture. This shows that the damage caused to cells of undernourished organisms used in this experiment persists even when they are placed in a nutrient-rich medium. The SCE frequency did not show differences between malnourished rats and their controls.     

Investigations on the frequency of chromosome aberrations in bone marrow cells of Chinese hamsters after simultaneous application of caffeine and cyclophosphamide

Summary The potentiating effect of caffeine (1,3,7-trimethylxanthine) on chemically induced chromosome aberrations was studied in bone marrow cells of chinese hamsters, exposed to the alkylating agent cyclophosphamide.Four experimental series were performed: In the first two tests caffeine (200 mg/kg) or cyclophosphamide (40 mg/kg), respectively, were administered. A third and fourth test was performed with caffeine plus cyclophosphamide (200+40 mg/kg and 35+40 mg/kg, respectively) simultaneously.Aberrations induced by cyclophosphamide (40 mg/kg) were strongly potentiated by simultaneous application of caffeine (200 mg/kg) not only additively but even synergistically. This increase of aberrations cannot be found after injection of the lower dose of caffeine (35 mg/kg).     

Spontaneous and busulphan-induced sister-chromatid exchange (SCE) frequencies in haematologically normal human bone marrow and lymphocytes

In a study of 14 patients who were not treated with either chemotherapy or irradiation, 13 patients had lower siste-chromatid exchange (SCE) frequencies in their bone-marrow cells than in their lymphocytes. For both bone marrow and lymphocytes, there was significant inter-patient variability in SCE frequencies, but there was no correlation between the bone-marrow and lymphocyte values.

The effect of exposing bone-marrow cells to busulphan (BUS) in vitro was investigated using doses up to 5.0 μg/ml. The dose-response relationships between BUS and SCEs in vitro were found to be similar for bone marrow and lymphocytes.     

Increased sister-chromatid exchange in bone-marrow cells of mice exposed to whole cigarette smoke

Male Wistar rats were fed diets of varying selenium content in order to obtain selenium-deficient and selenium-supplemented rats. After 5-6 weeks on the respective diet, the rats were used to investigate how selenium influences the effect of dimethylnitrosamine (DMN) on some liver enzymes and related reactions. The selenium-dependent glutathione peroxidase activity in postmicrosomal supernatant from liver was about 1% in selenium-deficient rats as compared to selenium-supplemented rats or rats fed a standard diet. The highest DMN-demethylase activity was observed in postmitochondrial supernatant from selenium-deficient rat liver, and the lowest in selenium-supplemented rats. No dietary effect was observed on hepatic microsomal cytochrome P450 levels. C-Oxygenation of N,N-dimethylaniline (DMA) was not affected by the selenium level. On the other hand, selenium deficiency seemed to reduce N-oxygenation of DMA. The mutagenicity of DMN in Chinese hamster V79 cells after metabolic activation by the isolated perfused rat liver, was approximately doubled when selenium-deficient livers were used as compared to selenium-supplemented livers and livers from rats fed a standard diet. A negative correlation between DMA-N-oxygenation and mutagenicity from DMN was observed, whereas no correlation between DMA-C-oxygenation and mutagenicity from DMN was found.     

Fluorodeoxyuridine-induced sex differences in baseline sister-chromatid exchanges in C57BL/6 mice and Chinese hamsters

The baseline sister-chromatid exchanges (SCEs) and the percentage of first (M1), second (M2) and third or higher metaphase (M3+) chromosomes were analysed in bone-marrow cells of male and female C57BL/6 mice and Chinese hamsters following serial intraperitoneal injections of 40 micrograms/g body weight (b.w.) of 5-bromo-2'-deoxyuridine (BrdUrd) and 2 micrograms/g b.w. of 5-fluorodeoxyuridine (FdUrd) or 40 micrograms/g b.w. of BrdUrd and 10 micrograms/g b.w. of deoxycytidine (dC). Female animals receiving BrdUrd/FdUrd showed significantly higher (P less than 0.01) baseline SCEs compared to the other groups. No sex difference in the baseline SCEs was found in animals treated with BrdUrd/dC. The distribution patterns of M1, M2 and M3+ metaphases in BrdUrd/FdUrd-treated animals differ significantly from those in BrdUrd/dC-treated animals.     

Sparing of bone marrow stem cells by long-term administration of Na-alginate to 226Ra contaminated mice.

226Ra toxicity studies form the experimental basis for the estimation of radiation risk from internal emitters in man. We investigated whether treatment with Na-alginate is able to protect haemopoietic bone marrow cells against alpha-irradiation from 226Ra contamination. Doses from 4 to 14 micronCi/kg were injected intraperitoneally in mice 12 days before the start of the treatment. Damage to marrow stem cells was assessed by the exogene clonal spleen technique. Collection of marrow cells by two methods was compared. In the lower dose groups no influence on stem cell survival is noticed. but from 9.0 micronCi/kg a decrease in the number of surviving stem cells is observable in non treated animals. while in animals treated with Na-alginate fewer stem cells are damaged. These preliminary data agree with the hypothesis that Na-alginate stimulates removal of 226Ra mainly from the endosteal bone surfaces, reducing the local 226 Ra dose which accounts for damage to marrow stem cells within the range of alpha-rays at the endosteal surfaces.     

Benzene and the genotoxicity of its metabolites. II. The effect of the route of administration on the micronuclei and bone marrow depression in mouse bone marrow cells

Benzene (880 mg/kg) and 4 of its metabolites, i.e., phenol (265 mg/kg), hydroquinone (80 mg/kg), catechol (40 mg/kg), and p-benzoquinone (5-20 mg/kg) have been tested for their capability to induce micronuclei in bone marrow cells of male mice after oral administration or intraperitoneal injection. Oral administration of benzene shows more activity than intraperitoneal injection, whereas the metabolites show more activity if administered by the latter method. The respective genotoxic strengths of the benzene metabolites are the following: hydroquinone much greater than phenol greater than catechol = p-benzoquinone. This last is active when administered orally.