Transplacental genotoxicity of a tobacco-specific N-nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, in Syrian golden hamster

NNK is abundant in cigarette smoke and is a potent respiratory carcinogen in adult Syrian golden hamsters. Micronucleus (MN) induction in fetal liver and maternal bone marrow polychromatic erythrocytes (PCEs) were assayed after i.p. injection of NNK to 14-day pregnant hamsters. The frequency of MN induction observed in fetal PCEs reached a maximum 18 h after treatment. The relationship dose NNK (0-200 mg/kg) to MN frequency was significant (P less than 0.005). In contrast no significant MN induction was observed in adult bone-marrow PCEs (P greater than 0.1). Extraction of fetal liver and amniotic fluid and HPLC separation of NNK metabolites revealed that NNK and its metabolite NNA1 could cross the placental barrier and be activated to protein-binding intermediates. These results suggest that NNK could be a transplancental carcinogen in Syrian golden hamsters.     

In vivo cytogenetic activity of diphenylhydantoin in mice.

Diphenylhydantoin was tested in vivo in mice using a variety of cytogenetic endpoints to evaluate its genotoxicity. Injected doses of 125, 250 and 500 mg/kg failed to increase the number of chromosome aberrations in marrow cells at 17 h post-treatment, and 37.5, 75 and 150 mg/kg doses were likewise ineffective at 36 h. SCEs were significantly increased by doses of 125 mg/kg (but not 250 mg) after 23 h and modestly, in relation to dose, at 42 h. No increase in the number of micronuclei among marrow PCEs was seen following single i.v. injections ranging from 0.1 to 20 mg/kg. Three daily i.p. injections of doses up to 70 mg/kg also failed to increase the number of micronuclei in either marrow or peripheral blood PCEs. Some cytotoxic effect was evident following relatively high doses.     

In vivo cytogenetic activity of diphenylhydantoin in mice

Diphenylhydantoin was tested in vivo in mice using a variety of cytogenetic endpoints to evaluate its genotoxicity. Injected doses of 125, 250 and 500 mg/kg failed to increase the number of chromosome aberrations in marrow cells at 17 h post-treatment, and 37.5, 75 and 150 mg/kg doses were likewise ineffective at 36 h. SCEs were significantly increased by doses of 125 mg/kg (but not 250 mg) after 23 h and modestly, in relation to dose, at 42 h. No increase in the number of micronuclei among marrow PCEs was seen following single i.v injections ranging from 0.1 to 20 mg/kg. Three daily i.p. injections of doses up to 70 mg/kg also failed to increase the number of micronuclei in either marrow or peripheral blood PCEs. Some cytotoxic effect was evident following relatively high doses.     

Cytogenetic effects of extremely low frequency magnetic field on Wistar rat bone marrow

In this study, the genotoxic and cytotoxic potential of extremely low frequency magnetic fields (ELF-MF) was investigated in Wistar rat tibial bone marrow cells, using the chromosomal aberration (CA) and micronucleus (MN) test systems. In addition to these test systems, we also investigated the mitotic index (MI), and the ratio of polychromatic erythrocytes (PCEs) to normochromatic erythrocytes (NCEs). Wistar rats were exposed to acute (1 day for 4h) and long-term (4h/day for 45 days) to a horizontal 50Hz, 1mT uniform magnetic field generated by a Helmholtz coil system. Mitomycin C (MMC, 2mg/kg BW) was used as positive control. Results obtained by chromosome analysis do not show any statistically significant differences between the negative control and both acute and long-term ELF-MF exposed samples. When comparing the group mean CA of long-term exposure with the negative control and acute exposure, the group mean of the long-term exposed group was higher, but this was not statistically significant. However, the mean micronucleus frequency of the longer-term exposed group was considerably higher than the negative control and acutely exposed groups. This difference was statistically significant (p<0.01). The results of the MI in bone marrow showed that the averages of both A-MF and L-MF groups significantly decreased when compared to those in the negative control (p<0.001 and p<0.01, respectively). No significant differences were found between the group mean MI of A-MF exposure with L-MF. We found that the average of PCEs/NCEs ratios of A-MF exposed group was significantly lower than the negative control and L-MF exposed groups (p<0.001 and p<0.01, respectively). In addition, the group mean of the PCEs/NCEs ratios of L-MF was significantly lower than negative control (p<0.01). We also found that the MMC treated group showed higher the number of CA and the frequency of MN formation when compared to those in all other each groups (p-values of all each groups <0.01) and also MMC treated group showed lower MI and the PCEs/NCEs ratios when compared to those in all other each groups (p-values of all groups <0.01). These observations indicate the in vivo suspectibility of mammals to the genotoxicity potential of ELF-MF.     

Induction of micronuclei in mouse polychromatic erythrocytes by the administration of non-radioactive CsCl by the oral and intraperitoneal route

In the present study, we describe the effects of the concentration and route of administration of non-radioactive cesium chloride (CsCl) in inducing micronuclei in mouse bone marrow polychromatic erythrocytes (PCEs). When the dose of 500mg/kg body weight was administered perorally (p.o.), no significant incidence of micronuclei was detected. However, when the same dose was administered intraperitoneally (i.p.), a significant induction of micronuclei in PCEs was observed compared to control. At the dose of 1000mg/kg, both routes were efficient, with no significant difference in micronucleus frequencies. We conclude that both the p.o. and i.p. routes are efficient in inducing micronuclei, with the i.p. route being more efficient when lower CsCl doses are used.     

Evaluation of genotoxic effects of fumagillin by cytogenetic tests in vivo

Fumagillin is a naturally secreted antibiotic of the fungus Aspergillus fumigatus. It is used in veterinary medicine against microsporidiosis of bees and fish. In this study, the genotoxicity of fumagillin (in the form of fumagillin dicyclohexylamine) was evaluated in mouse bone-marrow cells using the mitotic index (MI), the chromosome aberration (CA) assay, and the micronucleus (MN) test. Fumagillin was administered to BALB/c mice by gavage, at doses of 25, 50, 75 mg/kg body weight (bw), repeated for 7 days at 24-h intervals, with water-sugar syrup as a negative control and cyclophosphamide (40 mg/kg bw) as a positive control. All experimental doses of fumagillin induced a significant decrease (p<0.001) in MI (3.47+/-0.04%, 3.17+/-0.01%, and 2.27+/-0.02%, respectively) in comparison with the negative control (6.00+/-0.01%). Fumagillin significantly (p<0.001) increased the frequency of MN (4.98+/-0.35, 8.45+/-0.57, and 12.02+/-0.37, respectively) over negative control (1.04+/-0.28). Significantly increased frequencies (p<0.01 or p<0.001) of numerical chromosomal aberrations (aneuploidies and polyploidies) and structural chromosomal aberrations such as gaps, breaks, and centric rings were observed at the highest experimental dose of fumagillin (75 mg/kg bw) compared with the negative control. However, with respect to the induction of Robertsonian translocations, both the intermediate (50 mg/kg bw) and highest (75 mg/kg bw) experimental dose caused a significant (p<0.001) increase (7.12+/-0.26 and 9.00+/-0.10, respectively) in comparison with the negative control (0.00+/-0.00). Chromosomes 4 and 19 participated in these Robertsonian translocations. Regarding total cytogenetic changes, a significant increase (p<0.001) was observed in both the intermediate dose group (17.36+/-1.83) and the highest dose group (59.49+/-1.92) compared with the negative control (7.00+/-1.35). These results suggest that fumagillin has genotoxic (clastogenic) potential in mammals in vivo.     

The modifying effect of beta-carotene on gamma radiation-induced elevation of oxidative reactions and genotoxicity in male rats

The aim of the present work was to evaluate the modulatory role of beta-carotene on the radiation-induced changes in certain biochemical and cytogenetic parameters. beta-Carotene was given by gavage at a dose of 5 mg/kg body weight for 7 consecutive days before whole body gamma irradiation with 7 Gy (single dose). The levels of beta-carotene in plasma, thiobarbituric acid-reactive substances (TBARS) in plasma and liver, the activities of superoxide dismutase (SOD) and catalase in blood and liver were the selected parameters. Furthermore, the frequency of micronuclei (MN) of polychromatic erythrocytes (PCEs), normochromatic erythrocytes (NCEs), the ratio of PCEs/NCEs and the mitotic index (MI) of bone marrow cells were also evaluated. The biochemical and cytogenetic determinations were carried out 1, 24, and 72 h after radiation exposure.The results obtained revealed that administration of beta-carotene pre-irradiation significantly inhibited the decrease in plasma beta-carotene, significantly reduced the levels of TBARS in plasma and liver. Significant protection of the radiation-induced changes in the activities of SOD and catalase was also recorded in the blood and liver of beta-carotene-treated and -irradiated rats. beta-Carotene resulted in significant inhibition in the frequency of radiation-induced MN, as well as in the ratio of PCEs/NCEs and the MI of bone marrow cells. These results suggest that beta-carotene as a natural product with its antioxidant capacity and capability of quenching singlet oxygen, could play a modulatory role against the cellular damage affected by free radicals induced by whole body irradiation.     

Effect of aqueous fruit extract of xylopia aethiopica on intestinal fluid and glucose transfer in rats

Intestinal fluid and glucose absorption was studied in jejunal and ileal segments in Xylopia aethiopica fed rats using inverted sac technique. Thirty male Wistar rats were assigned into three groups of 10 rats each; control, 100mg/kg and 200mg/kg Xylopia aethiopica treated groups. The control group received normal rat chow and water while the low dose and high dose groups received oral administration of Xylopia aethiopica extract at doses of 100mg/kg and 200mg/kg body weight respectively in addition to daily rat chow and water intake for 28 days. The results showed significant reduction and increase in fluid transfer in the jejunum and ileum respectively compared with control. 100mg/kg increased gut fluid uptake in the ileum while 200mg/kg treatment reduced uptake in jejunum compared with control. Both doses had significantly increased jejunal and ileal glucose transfer. Gut glucose uptake was increased in jejunum and ileum of Xylopia aethiopica treated groups. Both doses increased the crypt depth but significantly decreased the villus height in the ileum. In conclusion, increased ileal gut fluid uptake may be beneficial in diarrheal state while an enhanced glucose uptake implies that glucose substrate may be made available to cells for synthesize of ATP for cellular activities. Keywords: Xylopia aethiopica, Glucose, Absorption, Jejunum, Ileum, Rat.     

Assessment of the genotoxicity of imidacloprid and metalaxyl in cultured human lymphocytes and rat bone-marrow

Imidacloprid and metalaxyl are two pesticides that are widely used in agriculture, either separately, or in combination. These agents were studied for their possible genotoxic effects with respect to the following cytogenetic end-points: (1) in vitro micronucleus (MN) formation and sister-chromatid exchange (SCE) induction in human lymphocytes and (2) in vivo micronucleus induction in polychromatic erythrocytes (PCEs) of the rat bone-marrow. The results of the MN analysis indicate that MN frequencies after treatment with both pesticides, separately or as a mixture, do not significantly differ from those in the controls except after treatment with metalaxyl alone at 50 microg/ml (p<0.05). The results of the SCE analysis show that SCE frequencies after treatment with imidacloprid do not differ significantly from those in the controls. A statistically significant increase (p<0.05) in SCE frequency resulted from treatments with metalaxyl at 5, 10 and 100 microg/ml and with the combination of imidacloprid and metalaxyl at 100 and 200 microg/ml. Finally, the in vivo micronucleus assay with rat bone-marrow polychromatic erythrocytes showed a statistically significant effect upon separate treatments with imidacloprid and metalaxyl at doses of 300 mg/kg body weight (b.w.) (p<0.01) or upon combined treatment with 200 mg/Kg b.w. (p<0.001) and 400 mg/kg b.w. (p<0.05).     

Activity of the human carcinogens benzidine and 2-naphthylamine in triple- and single-dose mouse bone marrow micronucleus assays: results for a combined test protocol

The activities of the human bladder carcinogens benzidine and 2-naphthylamine in the mouse bone marrow micronucleus assays using a limited test protocol (oral dosing to male mice, sampling 24 h later) have recently been established. As a contribution to the International Collaborative Study on the evaluation of the sensitivity of the triple-dose micronucleus test protocol it was decided to re-evaluate benzidine and 2-naphthylamine using a combined triple- and single-dose test protocol. Benzidine gave a clear positive response in male mice 24 h after 3 daily doses of 150 and 300 mg/kg. A single dose of 900 mg/kg of benzidine gave a weaker response 24 h after dosing. In the case of 2-naphthylamine a stronger positive response was observed 24 h after a single dose of 600 mg/kg as compared to 3 daily doses of 200 or 400 mg/kg. There was no significant difference in the increased positive response observed for a single dose of 30 mg/kg of cyclophosphamide compared with 3 successive daily doses of 10 mg/kg. Based on the present data the combined triple/single-dose micronucleus test protocol is strongly supported.     

Effect of antiepileptic drugs valproic acid, carbamazepine and ethosuccimide on exploratory behaviour in mice

Valproic acid in 100, 200 and 400 mg/kg doses produced a significant dose dependent decrease in exploratory behaviour, tested as number of head dips on the hole board. In the open field test, control mice entered less number of peripheral squares and more number of central squares on day 4 as compared to day 1 of the test. In the lower doses (100 and 200 mg/kg) valproic acid increased central square entries on day 1 with significant decrease by all doses on subsequent days indicating inhibition of exploratory behaviour. However, in peripheral square entry they followed the same pattern as control mice. Neither carbamazepine (10 and 20 mg/kg) nor ethosuccimide (100 and 200 mg/kg) affected exploratory behaviour in either the hole board or open field test.     

Micronucleus studies in the peripheral blood and bone marrow of mice treated with jet fuels, JP-8 and Jet-A

The potential adverse effects of dermal and inhalation exposure of jet fuels are important for health hazard evaluation in humans. The genotoxic potential of jet fuels, JP-8 and Jet-A, was investigated in an animal model. Mice were treated dermally with either a single or multiple applications of these jet fuels. Peripheral blood and bone marrow smears were prepared to examine the incidence of micronuclei (MN) in polychromatic erythrocytes (PCEs). In all experiments, using several different exposure regimens, no statistically significant increase in the incidence of MN was observed in the bone marrow and/or peripheral blood of mice treated with JP-8 or Jet-A when compared with those of untreated control animals. The data in mice treated with a single dose of JP-8 or Jet-A did not confirm the small but statistically significant increase in micronuclei reported in our previous study.     

Hypotensive response of ethanol in rats pretreated with disulfiram or nitrefazole

The effect of disulfiram or nitrefazole pretreatment on ethanol induced hypotension was examined in urethane anesthetized rats. A relatively low dose of ethanol (150 mg/kg; i.p.) produced a characteristic hypotensive response in rats pretreated for various periods with disulfiram or nitrefazole. This hypotensive episode started 5-10 minutes following ethanol administration and lasted 40-60 minutes. The hypotensive response was not seen unless disulfiram or nitrefazole treatment preceded ethanol administration by a least 6-8 hours. The low dose of ethanol produced a plasma ethanol concentration of 10mg/100ml or less. One treatment with nitrefazole (200 mg/kg) rendered rats vulnerable to ethanol-induced hypotension for 6 but not 8 days. One treatment with disulfiram (200 mg/kg) lasted 4 but not 6 days. In addition, the hypotensive response was greater in rats treated with nitrefazole than in rats treated with an equal dose (200 mg/kg) of disulfiram.     

Central effects of citral, myrcene and limonene, constituents of essential oil chemotypes from Lippia alba (Mill.) n.e. Brown.

Citral, myrcene and limonene (100 and 200 mg/kg body wt., i.p.), constituents of essential oils from Lippia alba chemotypes, decreased not only the number of crossings but also numbers for rearing and grooming, as measured by the open-field test in mice. Although muscle relaxation detected by the rota rod test was seen only at the highest doses of citral (200 mg/kg body wt.) and myrcene (100 and 200 mg/kg body wt.), this effect was observed even at the lowest dose of limonene (50 mg/kg body wt.). Also, citral and myrcene (100 and 200 mg/kg body wt.) increased barbiturate sleeping time as compared to control. Limonene was also effective at the highest dose, and although citral did not increase the onset of sleep, it increased the duration of sleep, which is indicative of a potentiation of sleeping time. Citral (100 and 200 mg/kg body wt.) increased 2.3 and 3.5 times, respectively, the barbiturate sleeping time in mice. Similar effects were observed for myrcene and limonene at the highest dose (200 mg/kg body wt.) which increased the sleeping time around 2.6 times. In the elevated-plus maze, no effect was detected with citral up to 25 mg/kg body wt., while at a high dose it decreased by 46% the number of entries in the open arms. A smaller but significant effect was detected with limonene (5 mg/kg body wt.). While myrcene (10 mg/kg body wt.) decreased only by 22% the number of entries in the open arms, this parameter was decreased by 48% at the highest dose. Our study showed that citral, limonene and myrcene presented sedative as well as motor relaxant effects. Although only at the highest dose, they also produced a potentiation of the pentobarbital-induced sleeping time in mice, which was more intense in the presence of citral. In addition, neither of them showed an anxiolytic effect, but rather a slight anxiogenic type of effect at the higher doses.     

Acute cytogenetic effects of tyramine and MTCAs on mouse bone marrow cells in vivo by the micronucleus test

We studied the acute cytogenetic effects of tyramine and MTCAs--precursors of the mutagen present in soy sauce--on mouse bone marrow cells in vivo by the micronucleus test. The incidence of MNPCE in bone marrow cells gradually increased and reached a maximum level 24 h after intraperitoneal injection of tyramine or MTCAs and decreased within 36 h. A dose-dependent increase in MNPCE was clearly observed for both compounds. Compared to the values for the untreated control, significant positive results were obtained with 0.5 mmole tyramine/kg (68.5 mg/kg) and with 0.1 mmole MTCAs/kg (23 mg/kg) 24 h after intraperitoneal administrations. Micronuclei were significantly induced but no severe reduction in the ratio of PCEs/NCEs was observed.     

Cytogenetic studies in mice treated with the jet fuels, Jet-A and JP-8

The genotoxic potential of the jet fuels, Jet-A and JP-8, were examined in mice treated on the skin with a single dose of 240 mg/mouse. Peripheral blood smears were prepared at the start of the experiment (t = 0), and at 24, 48 and 72 h following treatment with jet fuels. Femoral bone marrow smears were made when all animals were sacrificed at 72 h. In both tissues, the extent of genotoxicity was determined from the incidence of micronuclei (MN) in polychromatic erythrocytes. The frequency of MN in the peripheral blood of mice treated with Jet-A and JP-8 increased over time and reached statistical significance at 72 h, as compared with concurrent control animals. The incidence of MN was also higher in bone marrow cells of mice exposed to Jet-A and JP-8 as compared with controls. Thus, at the dose tested, a small but significant genotoxic effect of jet fuels was observed in the blood and bone marrow cells of mice treated on the skin.     

Mutagenic effects of carbosulfan,a carbamate pesticide

The genotoxic effects of carbosulfan were evaluated using chromosome aberration (CA), bone marrow micronucleus (MN) and sperm abnormality assays in mice. All the three acute doses (1.25, 2.5 and 5mg/kg) of carbosulfan induced significant dose-dependent increase in the frequency of CA (P<0.02), micronucleated polychromatic erythrocytes (PCEs) (P<0.05) and sperm head abnormalities (P<0.05) but did not affect the total sperm count. The highest acute dose of carbosulfan induced >7-fold increase in the frequency of CA, >3.5-fold increase in the frequency of micronucleated PCEs and >4.6-fold increase in the frequency of sperms with abnormal head morphology following intraperitoneal exposure as compared to the untreated controls. The present findings suggest that carbosulfan is a potent genotoxic agent and may be regarded as a potential germ cell mutagen also.     

Enhancement of benzene clastogenicity by praziquantel in mice

Praziquantel (PQ) is a commonly used drug to treat patients with schistosomiasis. Previous studies using cells in vitro have shown that PQ can enhance the mutagenic activities of known mutagens. We have conducted a cytogenetic - urine metabolite study to determine the in vivo clastogenic and co-clastogenic potential of PQ with a ubiquitous environmental contaminant, benzene (BZ). 16 groups of adult male ICR mice (5 animals per group) were used. They were negative control, solvent controls (cremophore E1 3%, olive oil and combined), positive control (BZ 440 mg/kg b.w.) and 11 exposed groups. To test for clastogenicity of PQ, mice were treated orally with 100, 400, 800 and 1200 mg/kg b.w. PQ and sacrificed 30 h later for determination of micronuclei (MN) frequency in bone-marrow polychromatic erythrocytes (PCE). None of these PQ does induced an increase of MN frequency. On the other hand, BZ induced, as expected, a high frequency of MN (46.4 +/- 6.34/1000 PCE). The enhancement effect of PQ was tested in 7 groups of mice using 3 different protocols. Mice were treated with 440 mg/kg b.w. BZ and 1 h later with 0, 100, 200, 400, 800 and 1200 mg/kg b.w. PZ. In another group, 800 mg/kg PQ was administered at 3 h after BZ exposure. In the last group, PQ (800 mg/kg) was administered at 1 h prior to BZ exposure. Results from the first combined exposure group showed a significant PQ dose-dependent increase in the frequency of MN in PCE (p less than 0.05). The increase with the two high doses of praziquantel is significantly higher (p less than 0.05) than the MN frequencies in the benzene control and the expected value based on the additive effects of the two agents. Studies with other combined treatment groups showed that the induction of MN was highest when PQ was administered at 1 h before BZ exposure. Moreover, the presence of BZ metabolites (muconic acid, phenol, catechol and hydroquinone) in urine was studied in 6 of the combined treatment groups. This metabolite study revealed that PQ enhanced the metabolism of BZ towards the pathway to form muconaldehyde which is converted to muconic acid in urine. In conclusion, our study showed that PQ is not a clastogen but can enhance the clastogenic activity of BZ in vivo by shifting the metabolic pathways of BZ towards formation of muconaldehyde which may be responsible for the enhancement effect.     

Long-term gentamicin ototoxicity in the rat: research on retro-cochlear involvement by study of evoked auditory potentials of the brain stem

Four groups of rats treated with single (50 mg/kg and 200 mg/kg) or multiple (3 X 200 mg/kg and 5 X 200 mg/kg) doses of gentamycin were studied over a 6-month period and compared with a control group. At 50 mg/kg no significant changes were observed. Significant signs of intoxication were observed at 200 mg/kg doses and at multiple doses. A significant lengthening of the latencies with changes in amplitude and a transitional increase in the auditory threshold were observed as early as the end of treatment. This was followed by a phase of amplitude decrease, a rise in auditory threshold and a decrease in latencies which remains unexplained.     

不同剂量炔雌醚对小鼠器官鲜重、繁殖生理和肝肠CYP3A4酶含量的影响

为探究不同剂量炔雌醚对小鼠器官、激素和肝肠药解酶的影响,分别以0.008 mg/kg、0.04 mg/kg、0.2 mg/kg、1.0 mg/kg和5.0 mg/kg的炔雌醚油溶液连续3d灌胃小鼠,首次给药7d后解剖取材,检测其器官鲜重、雄鼠精子数量、血清中激素浓度、小肠和肝脏中CYP3 A4酶含量的变化.结果 发现:...