Transplacental genotoxicity of triethylenemelamine, benzene, and vinblastine in mice.

Transplacental cytogenetic effects of triethylenemelamine (TEM), benzene, and vinblastine on maternal mice and their fetuses have been investigated using micronucleus and sister chromatid exchange (SCE) as genetic endpoints. CD-1 mice were treated on day 14 and 15 of gestation with TEM (0.125, 0.25, and 0.5 mg/kg), benzene (439,878, and 1,318 mg/kg), and vinblastine (0.5, 1, and 2 mg/kg) by intraperitoneal injection at 24 hr intervals, and sacrificed 40 hr after the first injection. Erythrocytic precursor cells in maternal bone marrow and fetal livers (2-4) from each pregnant mouse were used for the micronucleus and/or the SCE analyses. Significant dose-related increases in both micronuclei and SCE were found in maternal bone marrow and fetal liver following TEM treatment. Benzene at the highest dose (1,318 mg/kg) also caused a significant increase in micronuclei and SCE in both maternal bone marrow and fetal liver cells. The embryonic genotoxic effect of TEM was much higher than that of benzene for both genetic endpoints, and the frequency of micronuclei induced by benzene was higher in fetal liver than in maternal bone marrow cells. Vinblastine, a spindle poison, induced micronuclei but not SCE. Micronuclei induction by vinblastine was 7 fold greater in maternal bone marrow than in fetal liver cells. All three chemicals were cytotoxic in maternal bone marrow cells, but not in fetal liver cells except for TEM, which showed a weak cytotoxicity in fetal liver cells in the micronucleus assay. These results indicate that TEM, benzene, and vinblastine are transplacental genotoxicants in mice.

Comparison of single/multiple-dose protocols using triethylenemelamine and procarbazine hydrochloride for the mouse bone marrow micronucleus test.

Treatment of mice with a single dose of either 4.8 mg/kg of triethylenemelamine (TEM) or 348 mg/kg of procarbazine hydrochloride (PC) induced higher frequencies of micronucleated polychromatic erythrocytes (MPE) after 48 h than after 24 h. The same observation was made when animals were treated with 1.6 or 8 mg/kg of TEM or 116 or 580 mg/kg of PC for 2 consecutive days (double-dose protocol). Surprisingly, the third dose of either 1.6 or 8 mg/kg of TEM caused lower MPE frequencies at the 72-h than at the 48-h sampling time. The observation that lower MPE frequencies after 72 h were also accompanied by reduced bone marrow toxicity might have reflected a drug-related adaptive reaction of the animals, for example the induction of detoxifying enzymes. Mean MPE frequencies as well as bone marrow toxicity were also slightly decreased after the third dose of either 116 or 580 mg/kg of PC, but statistical analysis showed no differences between the 48-h and the 72-h sampling times as regards the MPE frequencies and bone marrow toxicity. In addition to the high mean MPE frequency observed after 2 doses of 116 mg/kg of PC at the 48-h sampling time, a late increase in micronucleus induction was also seen after triple dosing at the 96-h sampling time. The present experiments with TEM and PC showed similar sensitivity for the multiple-dose assays when compared with the single-dose micronucleus test. In the case of the triple-dose assay, bone marrow toxicity proved to be a critical factor for appropriate dose selection. The computerized image analysis system was a convenient and time-saving tool for the automatic scoring of large quantities of cells for micronuclei as well as for the evaluation of bone marrow depression from the entire cell population analyzed for micronuclei.

Effect of mode of administration of methyl methanesulfonate and triethylenemelamine on induction of unscheduled DNA synthesis in mouse germ cells.

The effect of route of administration on induction of unscheduled DNA synthesis (UDS) in mouse germ cells in vivo was studied using two germ cell mutagens, methyl methanesulfonate (MMS) and triethylenemelamine (TEM). The chemicals were administered to male mice (C3Hf X 101)F1 by IP injection or gavage using acute or 5-day subacute regimens. After completion of dosing, methyl-[3H]thymidine [( 3H]TdR) was injected into the testes, and spermatozoa were collected 16 days later. The sperm heads were isolated, and UDS was determined by the amount of [3H]TdR incorporated. Acute administration of MMS (2-100 mg/kg) induced a strong, dose-related UDS response. The response was slightly higher with IP injection than with gavage. The UDS response after five daily doses of 50 mg MMS/kg was 20-30% higher than that induced by a single IP or gavage dose. Acute administration of TEM (0.05-4.0 mg/kg) by IP injection or gavage induced weak and variable responses. Retesting TEM using inbred C3Hf mice produced weak but exposure-related responses with both acute IP and gavage treatments. There was a slight increase in UDS response with subacute IP injection but not with subacute gavage. Acute testicular injection of TEM produced a higher but more variable UDS response. The study showed that gavage, as well as IP injection, can be used for the administration of test chemicals and that the subacute 5-day regimen induced a higher UDS response than the acute regimen. Furthermore, the testicular route may enhance the detection of weak UDS inducers.

Medical therapy of retinoblastoma in children.

Retinoblastoma is the most common ocular tumour which occurs in infancy. Unfortunately, it is diagnosed only when the disease is in an advanced phase and the prognosis is decidedly unfavorable. Patients treated early, in the first stage of the disease can be cured with surgical and radiation treatment. For patients who are already in an advanced stage, the risk of metastatic dissemination is very high and therefore the introduction of chemotherapy, particularly vincristine and cyclophosphamide is believed to be useful. The authors report on their results obtained in patients with retinoblastoma who have been treated with combined surgical, radio- and chemotherapic treatment.

An analysis of meiotic chromosomes of inbred male mice and their F1 sons after long-term treatment of sires with triethylenemelamine.

The dose-dependent effects of triethylenemelamine (TEM) on fertility and the induction of chromosomal translocation in treated mice and their F1 sons were examined C3H mice were treated with TEM for 8 successive weeks at doses of 0.02 and 0.04 mg/kg of body weight. All males treated with TEM were fertile,and cytological analysis of meiotic cells showed no chromosomal rearrangements. Semi-sterility and sterility were noted in F1 sons of TEM-treated animals. This semi-sterility and sterility were associated with reciprocal translocations. The percentage of animals heterozygous for translocations was higher for F1 males originating from sires treated with TEM at 0.04 mg/kg than from sires treated with 0.02 mg/kg.

Triethylenemelamine induced dominant lethals in mice--comparisons of oral versus intraperitoneal injection.

We have compared the relative effectiveness of oral and i.p. injections of triethylenemelamine (TEM) in inducing dominant lethality in male mice. The standard dominant lethal protocol was used in these experiments. TEM, when injected i.p. resulted in significant increased in fetal mortality during the first three weeks post-treatment. Decreases in the number of implants per pregnant female were noted during this same period, with only minor decreases in fertility. In contrast, oral injections of TEM resulted in only fluctuations in the percent of fetal mortality. In addition, oral injections of TEM did not result in significant differences in either total implants or percent fertility. Possible causes of the observed differences between these two routes of administration are discussed.

An evaluation of the micronuclei test using triethylenemelamine, trimethylphosphate, hycanthone and niridazole.

To determine the feasibility of the micronuclei procedure for cytogenetic studies, a comparatively weak chromosome breaking agent, trimethylphosphate (TMP) and the potent alkylating agent, triethylenemelamine (TEM) were evaluated. The procedure followed was that of Matter and Schmid with the following modifications: (a) direct flushing of bone marrow with 0.2 ml calf fetal serum. (b) air drying slides for a period of only I h, and (c) the use of pH 6.0 phosphate buffer to dilute both Wright and Giemsa stains. With this technique a dose response curve was generated for both TMP and TEM, using mice as the experimental animal. With TMP, a doubling over background was found when a concentration of 0.5 g/kg per day for five days was administered. To establish a statistically significant doubling dose over the control, a minimum of five animals must be used with 2000 polychromatic cells being analyzed per animal. Of the two antischistosomal agents tested, hycanthone yielded an increase of 20-fold in the number of micronuclei over control at 40 mg/kg administered i.p. for five days, while with niridazole no increase in micronuclei at several concentrations tested both by single and multiple injection was found. The results obtained with these compounds compare favorably with what has been reported for the standard in vivo metaphase analysis.

Effects of dose on the induction of dominant-lethal mutations with triethylenemelamine in male mice.

Dose effects of triethylenemelamine (TEM) in the induction of dominant-lethal mutations were studied at the early spermatozoon, midspermatid and spermatocyte stages. The pattern of effects on spermatocytes, unlike midspermatids and early spermatozoa, indicated possible cytotoxic damage, so for the determination of TEM dose-response curves in the induction of genetic damage only the data for midspermatids and early spermatozoa were used. The TEM dose-effect curves for those two stages differ markedly from ethyl methanesulfonate (EMS) dose-effect curves. Beginning with the lowest doses at which significant effects are observed, there is a considerably more rapid increase in dominant-lethal effects with dose of EMS than TEM. Another marked difference between the two compounds is in the ratio of the genetically effective dose (as measured by dominant-lethal mutations) to the lethal dose. The ratio is 1:100 for TEM and only 1:3.5 for EMS; thus, TEM is mutagenic far below its toxic level. Obviously, these results have important implications not only for our understanding of the nature of chemical induction and recovery of chromosomal aberrations but also for the practical problems of evaluating the mutagenic effects of chemicals.