Percentage Of Aberrant Metaphases Research Articles

Isolate Loss of Y Chromosome Decreases the Risk of Leukemic Transformation in the Myelodysplastic Syndromes. a Study By the Spanish Group of Myelodysplastic Syndromes

▪BackgroundLoss of chromosome Y (-Y) is observed in 4-10% of male MDS patients as a single cytogenetic abnormality, and is associated to a better outcome. -Y is also known to be an age related phenomenon occurring in 8-10% of elderly men. The clinical significance of -Y in MDS has been a matter of discussion. However, there is increasing evidence that -Y involves the clonal population in MDS cases, and is more likely to be associated with a hematological malignancy when it involves a greater number of metaphases.AimsIn this study we aimed to 1) analyze the prognostic impact of -Y in the context of the IPSS-R cytogenetic classification, 2) evaluate the clinical significance of the percentage of metaphases with isolated -Y, 3) test whether finding -Y may predispose to over diagnose MDS in patients with borderline morphological features.MethodsWe evaluated 3581 male patients from the Spanish Registry of MDS with a diagnosis of MDS or CMML (WHO 2001). Patients with isolated -Y and normal karyotype by conventional cytogenetic analysis were selected. The main study outcomes were survival from diagnosis and transformation into acute myeloid leukemia (AML). Survival curves were drawn using the Kaplan-Meyer method and compared by log-rank test. The cumulative incidence of AML was estimated by taking non AML-related death as a competing risk. Statistical comparisons were done by the Mann-Whitney U-test for continuous data, and the chi-square test for categorical factors. Stata, version 11, software (www.stata.org) was used for the statistical analysis.ResultsIsolated -Y was identified in 177 patients (-Y group) and compared with the 2246 male patients with normal karyotype (46,XY group). The median age for the whole series was 74 years old (IQR 67-80). -Y patients were found to be older than patients in the 46,XY group with a median (IQR) of 78 (74-83) versus 74 (66-79) years old, respectively (n=0.0001). There was no difference between both groups in terms of hemoglobin concentration, neutrophil and platelet counts at diagnosis. Percentage of bone marrow (BM) blasts was significantly lower in the -Y group (median (IQR): 2(0-3) vs. 2(1-5), respectively; p=0.003). Differences in distribution by WHO 2001 classification of MDS were not found between the two groups. After a follow-up of 2,190 patient-years, 1684 (69.5%) patients had died and the median actuarial survival was 3.6 years (95% C.I, 3.3-3.9). A trend towards a larger median survival in the -Y group versus 46,XY group was observed, since it not reached statistical significance (5.2 years [95% CI, 3.89 to 6.40] versus 4.26 years [95% CI, 3.89 to 4.59], respectively) (P=0. 17; Fig. 1A). After a median follow-up of 1.6 years (IQR: 0.8 - 3.7) from MDS diagnosis, 296 patients had progressed to AML, 901 had died without AML, and 1224 were censored alive without transformation. -Y was associated with a decreased incidence of AML at univariate analysis (figure 1B), and after adjustment for the percentage of BM blasts (SHR: 0.46; 95%CI: 0.24-0.88; p=0.02). Within the -Y group, neither survival nor the risk of leukemic transformation were influenced by the percentage of aberrant metaphases (>75% vs, ≤ 75%). From the whole series, only 6.4% of the cases were classified as not having a "MDS strong phenotype", defined by the presence of megakaryocytic dysplasia, more than 5% blasts in the bone marrow, or more than 15% ring sideroblasts. These cases were uniformly distributed between the two groups, suggesting that the better outcome in the -Y group cannot be explained by enrichment in cases misdiagnosed as MDS.ConclusionsOur results derived from the largest series of patients with loss of chromosome Y support the current recommendation of classifying patients with -Y within the very good risk category of the IPSS-R for MDS and rule out a selection bias as a possible explanation of this better outcome. An analysis of the molecular basis of MDS with isolated -Y would be of interest as it may provide a biological basis of protection against AML progression. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Investigation of antigenotoxic potential of Syzygium cumini extract (SCE) on cyclophosphamide-induced genotoxicity and oxidative stress in mice

The present study investigated the protective effects of Syzygium cumini extract (SCE; 100 and 200 mg/kg) against genotoxicity and oxidative stress (OS) induced by cyclophosphamide (CP) in mice. Animals were received 14 days pretreatment (oral) of SCE, followed by induction of genotoxicity by CP (40 mg/kg), 24 hours before sacrifice. Mice bone marrow chromosomal aberration assay, micronucleus assay, and sperm abnormality assay were employed for the study. Activities of hepatic antioxidant enzymes were also investigated. Phytochemical investigation was done to determine total phenolic and flavonoid content in SCE. Results showed that CP produced a significant increase in average percentage of aberrant metaphases and chromosomal aberrations (CAs) excluding gap, and micronuclei (MN) formation in polychromatic erythrocytes produced cytotoxicity in mouse bone marrow cells and induced abnormal sperms in a male germ line. CP also markedly inhibited the activities of superoxide dismutase (SOD), catalase (CAT), and reduced glutahione (GSH) and increased malondialdehyde (MDA) content. Pretreatments with SCE significantly inhibited the frequencies of aberrant metaphases, CAs, MN formation, and cytotoxicity in mouse bone marrow cells induced by CP. SCE also produced a significant reduction of abnormal sperm and antagonized the reduction of CP-induced SOD, CAT, and GSH activities and inhibited increased MDA content in the liver. Total phenolic content present in SCE was 24.68%, whereas total flavonoids were calculated as 3.80%. SCE has a protective effect against genotoxicity and OS induced by CP.

Investigation of antimutagenic potential of Foeniculum vulgare essential oil on cyclophosphamide induced genotoxicity and oxidative stress in mice

The present study investigated the protective effects of Foeniculum vulgare (fennel) essential oil (FEO) against genotoxicity induced by cyclophosphamide (CP). Mice bone marrow chromosomal aberration (CA), micronucleus, and sperm abnormality assays were employed to measure genotoxicity and cytotoxicity, respectively. The activities of superoxide dismutase (SOD), glutathione (GSH), catalase (CAT), and malondialdehyde (MDA) content in the liver were also investigated spectrophotometrically. Animals were administered two different doses of FEO (1 and 2 mL/kg) continuously for 3 days at intervals of 24 hours by the oral route before tissue sampling. The results showed that CP produced a significant increase in the average percentage of aberrant metaphases and CAs, excluding gap and micronuclei formation in polychromatic erythrocytes (PCEs), produced cytotoxicity in mouse bone marrow cells, and induced abnormal sperms in the male germ line. CP also markedly inhibited the activities of SOD, CAT, and GSH and increased MDA content. Pretreatments with FEO significantly inhibited the frequencies of aberrant metaphases, CAs, micronuclei formation, and cytotoxicity in mouse bone marrow cells induced by CP and also produced a significant reduction of abnormal sperm and antagonized the reduction of CP-induced SOD, CAT, and GSH activities and inhibited increased MDA content in the liver. FEO inhibits genotoxicity and oxidative stress induced by CP.

Mechanisms of Susceptibility to 11q23 MLL Gene Locus Rearrangements in CD34+ Cells Exposed to Etoposide.

Abstract 185Exposure to the topoisomerase II inhibitor etoposide (VP16) is a significant risk factor in the development of t-MDS/AML. VP16 induces a variety of chromosomal lesions, with the most prominent ones involving the Mixed Lineage Leukemia (MLL) gene on chromosome 11q23. The MLL gene is essential for the maintenance of adult hematopoietic stem cells (HSCs) and progenitors. It is not clear whether the high frequency of MLL gene rearrangements in VP16-treated patients represents increased susceptibility of this locus to VP16-induced damage or a growth advantage of MLL-rearranged hematopoietic progenitors. In the present study we investigated the following: i) the sequence of acquisition of chromosomal lesions in normal CD34+ cells following in vitro exposure to VP16; ii) the specific propensity for development of lesions in 11q23 MLL locus; iii) and the fate of these lesions over time. CD34+ cells were selected from peripheral blood stem cell samples obtained from normal donors (n=5); they were exposed to increasing doses of VP16 (0-40 μM) for 4 hours; washed and cultured in serum-free medium containing growth factors; and assessed for apoptosis, colony forming cell (CFC) assay and chromosomal damage. Chromosome painting was performed using whole chromosome probes for chromosomes 1, 5, 7, 11 and 21, covering 25.2% of total genomic DNA with >100 metaphases scored per dose per time point. Evaluations were performed after 72 hours of culture, representing the 1st cell division after VP16 exposure, and after 144 hours representing 3-4 cell divisions. A dose-dependant decrease in colony formation (71.52 ± 0.99% of controls with 5 mM VP16, and 33.62 ± 4.4%%, with 20 mM VP16 at 72h, p<0.001), and increase in apoptosis (9.12 ± 1.67% with 5 mM VP16, and 39.3 ± 5.06 with 20 mM VP16 at 72h, p<0.001) was observed. The percentage of aberrant metaphases at 1st division was 2.4% with 5 μM and 14.9% with 20 μM of VP16. Both stable aberrations (translocations) and unstable (dicentrics, fragments) aberrations were observed. The percentage of aberrant metaphases was reduced after 3-4 cell divisions (1.4% with 5 μM and 8.7% with 20 μM VP16), and only stable aberrations were present whereas unstable aberrations were eliminated. A higher frequency of aberrations was observed in chromosome 11 compared to the other chromosomes. A 1.5- to 4-fold increase in stable lesions of chromosome 11 relative to other chromosomes was seen at the 1st division and a 2- to 3-fold increase relative to other chromosomes was seen after 3-4 divisions. To assess whether the 11q23 MLL locus was specifically affected by VP16 treatment, we performed interphase FISH with a break-apart probe for the MLL gene (11q23). A break-apart probe for the MYC gene (8q24) was studied as a control. Cells were cultured for three weeks. In preliminary experiments we observed that a higher percentage of cells showed 11q23 abnormalities (9.3%) compared with 8q24 abnormalities (5.4%) at the 1st division. 11q23 abnormalities persisted at high levels in cells (9.9%) cultured for 3 weeks. In contrast, 8q24 abnormalities were markedly reduced (0.4%) after 3 weeks of culture, suggesting selective maintenance of MLL-rearranged cells in culture. In conclusion we show that in vitro exposure to VP16 results in a dose-dependent induction of both stable and unstable chromosomal aberrations in CD34+ hematopoietic progenitors. We observe persistence of stable chromosomal aberrations with particular predisposition to aberrations in chromosome 11. Our results suggest a selective predisposition to 11q23 MLL locus rearrangements that appears to be related to enhanced susceptibility to damage to this locus following VP16 exposure as well as selective maintenance of MLL rearranged cells over subsequent cell divisions. These findings are now being applied to understand the relationship between individual susceptibility to acquisition of VP16-induced 11q23 abnormalities in CD34+ cells and risk of development of t-MDS/AML. Disclosures:No relevant conflicts of interest to declare.

Protective effect of Bixa orellana L. against radiation induced chromosomal aberration in Swiss Albino Mice.

Radioprotective effect of hydroalcoholic extract of seeds of Bixa orellana have been studied by examining chromosome aberration in cells of bone marrow in irradiated mice. Healthy adult Swiss mice were injected intraperitoneally (ip) with 500 mg kg–1 body weight, 1000 mg kg–1 of or double distilled water (DDW). They were exposed to whole body irradiation of 2.0 Gy gamma radiation 30 min later. After 24 h, chromosomal aberrations were studied in the bone marrow of the femur by routine metaphase preparation after colchicine treatment. Radiation (4.0 Gy) increased the number of aberrant cells from less than 1% in controls to almost 20%. Pre-treatment with the extract compounds resulted in a significant reduction in the percentage of aberrant metaphases as well as in the different types of aberration scored. The extract was not toxic at 1500 mg kg–1 body weight. Being non toxic and easily available natural source Bixa orellana extract may be use for as radioprotective for human beings. Keywords: – radioprotective, Bixa orellana

Improved Detection of Chromosomal Abnormalities in CLL by Conventional Cytogenetics Using CpG Oligonucleotide and Interleukin-2 Stimulation. A Belgian Multicentric Study

Numerous studies have shown that the presence, number and type of chromosomal aberrations represent an independent predictor of prognosis in B-cell chronic lymphocytic leukemia (CLL). Consequently, cytogenetic analysis is routinely performed in this disease. However, CLL lymphocytes have a poor mitotic index, generating only 40–50% of abnormal karyotypes. The rate of detection can be increased to 80% by interphase FISH analysis. Since some aberrations, i.e. those not involving the classical regions (13q, 12, 11q, 17p, and 6q), can escape FISH detection, there has been great interest in improved culturing methods with an immunostimulatory CpG oligonucleotide (CpG). We performed a multicentric cytogenetic study to assess the impact of 2 different culturing procedures on the detection of clonal abnormalities in 159 consecutive unselected cases with CLL referred to our centers for routine analysis from October 2007 to July 2008. Dual 72 hours cultures of bone marrow or peripheral blood were set up with the addition of either a conventional B cell mitogen (TPA) or CpG and interleukin-2 (IL2). Cytogenetic analysis was performed on both cultures. FISH analysis using a CLL probe panel analyzing 1–6 regions (13q, centromere 12, 11q, 17p, 6q and 14q32) was also applied on uncultured material, on CpG and/or on TPA culture in 146 cases. Quality of banding and proliferation capacity were assessed in 38 cases. The quality was good in 17 (CpG) and 8 (TPA), intermediate in 12 (CpG) and 18 (TPA), and poor in 9 (CpG) and 12 (TPA) cases. The mitotic index was slightly higher in CpG cultures: <15 mitoses/slide were seen in 12 (CpG) and 15 (TPA) cases, 15–20 mitoses/slide in 13 (CpG) and 14 (TPA) cases, and >20 mitoses/slide in 13 (CpG) and 9 (TPA) cases, respectively. Clonal abnormalities were identified in 89 cases (56%). In 56 cases, the aberrant clone was detected in both cultures. Of these, the percentage of aberrant metaphases was similar in both cultures in 13, higher in CpG culture in 32 and higher in TPA culture in 11 cases. In 29 and 4 additional cases, a clonal abnormality was detected only in CpG or TPA culture, respectively. Thus, the percentage of abnormal karyotypes with CpG and TPA was 53 and 38%, respectively (p=0,005). “Typical” aberrations, including del(13q), +12, del(11q), del(17p) and del(6q), were detected in 16, 26, 15, 9, and 7 (CpG) cases, and in 10, 20, 16, 8, and 3 (TPA) cases, respectively. Translocations (balanced and unbalanced) were observed in 46 (CpG) and 27 (TPA) cases, whereas aberrations involving 14q32 were seen in 5 (CpG) and 4 (TPA) cases, respectively. Interphase FISH detected del(13q), +12, del(11q), del(17p), del(6q) and del(14q) in 53, 1, 5, 0, 0 and 1 cases, respectively, in which cytogenetic analysis was either normal or abnormal but did not show the specific change. Conversely, FISH did not detect del(13q), +12, del(11q), del(17p), del(6q) and del(14q) in 1, 1, 4, 1, 2 and 0 cases in which the specific change was visible at karyotypic level. FISH was performed on both CpG and TPA cultures in 9 selected cases harbouring an aberration for which a specific commercial probe was available (+12, n=3; del(13q), n=4; del(11q), n=1; and del(17p), n=1) and showing different percentages of aberrant cells in both cultures. In 3 of these cases, fresh uncultured material was also analyzed. The highest percentage of abnormal nuclei was observed in TPA culture in all cases. In the 3 uncultured samples the percentage of aberrant nuclei was similar to the CpG culture. In conclusion, our results confirm an increased detection rate of abnormalities in CLL by using CpG/IL2 stimulation. Interphase FISH can further increase the detection rate of recurrent abnormalities. However, neither cytogenetics nor FISH detected all aberrations, demonstrating the complementary nature of these techniques and the necessity of performing both.

Sensitivity to cisplatin-induced mutations and elevated chromosomal aberrations in lymphocytes from sickle cell disease patients

Sickle cell disease (SCD) is an inherited disorder caused by a single nucleotide substitution in the beta-globin gene. The clinical heterogeneity observed in SCD patients has been attributed to environmental and genetic factors. The patients are subjected to increased oxidative stress, particularly during vaso-occlusive crises and acute chest pain. Another possible cause of oxidative stress in SCD is the high concentration of iron in the patients' plasma. The increase in oxidative stress could be a relevant risk factor for mutagenesis and carcinogenesis. Studies on the frequency of basal chromosomal aberrations in cultured lymphocytes from SCD patients have not been reported so far. In order to contribute to the understanding of the role of the different biomarkers and their relationship with the extremely variable clinical manifestation of SCD, we investigated the frequency of chromosome damage in peripheral lymphocytes from sickle cells patients and healthy controls. We found an increased frequency of chromosome damage and percentage of aberrant metaphases in these patients when compared with control subjects, even at basal values (p<0.05). In the cytogenetic sensitivity assay, the results showed that these patients presented a marked decrease in the mitotic index values compared with healthy controls. Cisplatin-induced chromosomal damage in lymphocytes from these patients was significantly higher than the frequency measured in healthy controls. The results obtained in the present study showed that more investigations are needed in order to elucidate the susceptibility to genomic instability of SCD patients.

Acetylsalicylic acid exhibits anticlastogenic effects on cultured human lymphocytes exposed to doxorubicin

Acetylsalicylic acid (ASA) is a non-steroidal anti-inflammatory drug (NSAID) with many pharmacological properties, such as anti-inflammatory, antipyretic and analgesic. Many studies have suggested the possible efficiency of ASA and other NSAIDs in preventing cancer. ASA could also have antimutagenic and antioxidant properties. The aim of this study was to investigate the possible clastogenic and anticlastogenic effects of different concentrations of ASA on doxorubicin-induced chromosomal aberrations in human lymphocytes. Human blood samples were obtained from six healthy, non-smoking volunteers; and the chromosomal aberration assay was carried out using conventional techniques. The parameters analyzed were mitotic index, total number of chromosomal aberrations and percentage of aberrant metaphases. The concentrations of ASA (25, 50 or 100 μg/mL) tested in combination with DXR (0.2 μg/mL) were established on the basis of the results of the mitotic index. The treatment with ASA alone was neither cytotoxic nor clastogenic ( p > 0.01). In lymphocyte cultures treated with different combinations of ASA and DXR, a significant decrease in the total number of chromosome aberrations was observed compared with DXR alone ( p < 0.01). This protective effect of ASA on DXR-induced chromosomal damage was obtained for all combinations, and it was most evident when ASA was at 25.0 μg/mL. In our experiments, ASA may have acted as an antioxidant and inhibited the chromosomal damage induced by the free radicals generated by DXR. The identification of compounds that could counteract the free radicals produced by doxorubicin could be of possible benefits against the potential harmful effects of anthracyclines. The results of this study show that there is a relevant need for more investigations in order to elucidate the mechanisms underlying the anticlastogenic effect of ASA.

Final Report on the Safety Assessment of Aluminum Silicate, Calcium Silicate, Magnesium Aluminum Silicate, Magnesium Silicate, Magnesium Trisilicate, Sodium Magnesium Silicate, Zirconium Silicate, Attapulgite, Bentonite, Fuller's Earth, Hectorite, Kaolin, Lithium Magnesium Silicate, Lithium Magnesium Sodium Silicate, Montmorillonite, Pyrophyllite, and Zeolite

This report reviews the safety of Aluminum, Calcium, Lithium Magnesium, Lithium Magnesium Sodium, Magnesium Aluminum, Magnesium, Sodium Magnesium, and Zirconium Silicates, Magnesium Trisilicate, Attapulgite, Bentonite, Fuller's Earth, Hectorite, Kaolin, Montmorillonite, Pyrophyllite, and Zeolite as used in cosmetic formulations. The common aspect of all these claylike ingredients is that they contain silicon, oxygen, and one or more metals. Many silicates occur naturally and are mined; yet others are produced synthetically. Typical cosmetic uses of silicates include abrasive, opacifying agent, viscosity-increasing agent, anticaking agent, emulsion stabilizer, binder, and suspending agent. Clay silicates (silicates containing water in their structure) primarily function as adsorbents, opacifiers, and viscosity-increasing agents. Pyrophyllite is also used as a colorant. The International Agency for Research on Cancer has ruled Attapulgite fibers &gt;5 μm as possibly carcinogenic to humans, but fibers &lt;5 μm were not classified as to their carcino-genicity to humans. Likewise, Clinoptilolite, Phillipsite, Mordenite, Nonfibrous Japanese Zeolite, and synthetic Zeolites were not classified as to their carcinogenicity to humans. These ingredients are not significantly toxic in oral acute or short-term oral or parenteral toxicity studies in animals. Inhalation toxicity, however, is readily demonstrated in animals. Particle size, fibrogenicity, concentration, and mineral composition had the greatest effect on toxicity. Larger particle size and longer and wider fibers cause more adverse effects. Magnesium Aluminum Silicate was a weak primary skin irritant in rabbits and had no cumulative skin irritation in guinea pigs. No gross effects were reported in any of these studies. Sodium Magnesium Silicate had no primary skin irritation in rabbits and had no cumulative skin irritation in guinea pigs. Hectorite was nonirritating to the skin of rabbits in a Draize primary skin irritation study. Magnesium Aluminum Silicate and Sodium Magnesium Silicate caused minimal eye irritation in a Draize eye irritation test. Bentonite caused severe iritis after injection into the anterior chamber of the eyes of rabbits and when injected intralamellarly, widespread corneal infiltrates and retrocorneal membranes were recorded. In a primary eye irritation study in rabbits, Hectorite was moderately irritating without washing and practically nonirritating to the eye with a washout. Rats tolerated a single dose of Zeolite A without any adverse reaction in the eye. Calcium Silicate had no discernible effect on nidation or on maternal or fetal survival in rabbits. Magnesium Aluminum Silicate had neither a teratogenic nor adverse effects on the mouse fetus. Female rats receiving a 20% Kaolin diet exhibited maternal anemia but no significant reduction in birth weight of the pups was recorded. Type A Zeolite produced no adverse effects on the dam, embryo, or fetus in either rats or rabbits at any dose level. Clinoptilolite had no effect on female rat reproductive performance. These ingredients were not genotoxic in the Ames bacterial test system. In primary hepatocyte cultures, the addition of Attapulgite had no significant unscheduled DNA synthesis. Attapulgite did cause significant increases in unscheduled DNA synthesis in rat pleural mesothelial cells, but no significant increase in sister chromosome exchanges were seen. Zeolite particles (&lt;10 μm) produced statistically significant increase in the percentage of aberrant metaphases in human peripheral blood lymphocytes and cells collected by peritoneal lavage from exposed mice. Topical application of Magnesium Aluminum Silicate to human skin daily for 1 week produced no adverse effects. Occupational exposure to mineral dusts has been studied extensively. Fibrosis and pneumoconiosis have been documented in workers involved in the mining and processing of Aluminum Silicate, Calcium Silicate, Zirconium Silicate, Fuller's Earth, Kaolin, Montmorillonite, Pyrophyllite, and Zeolite. The Cosmetic Ingredient Review (CIR) Expert Panel concluded that the extensive pulmonary damage in humans was the result of direct occupational inhalation of the dusts and noted that lesions seen in animals were affected by particle size, fiber length, and concentration. The Panel considers that most of the formulations are not respirable and of the preparations that are respirable, the concentration of the ingredient is very low. Even so, the Panel considered that any spray containing these solids should be formulated to minimize their inhalation. With this admonition to the cosmetics industry, the CIR Expert Panel concluded that these ingredients are safe as currently used in cosmetic formulations. The Panel did note that the cosmetic ingredient, Talc, is a hydrated magnesium silicate. Because it has a unique crystalline structure that differs from ingredients addressed in this safety assessment, Talc is not included in this report.

Final Report on the Safety Assessment of Aluminum Silicate, Calcium Silicate, Magnesium Aluminum Silicate, Magnesium Silicate, Magnesium Trisilicate, Sodium Magnesium Silicate, Zirconium Silicate, Attapulgite, Bentonite, Fuller's Earth, Hectorite, Kaolin, Lithium Magnesium Silicate, Lithium Magnesium Sodium Silicate, Montmorillonite, Pyrophyllite, and Zeolite

This report reviews the safety of Aluminum, Calcium, Lithium Magnesium, Lithium Magnesium Sodium, Magnesium Aluminum, Magnesium, Sodium Magnesium, and Zirconium Silicates, Magnesium Trisilicate, Attapulgite, Bentonite, Fuller's Earth, Hectorite, Kaolin, Montmorillonite, Pyrophyllite, and Zeolite as used in cosmetic formulations. The common aspect of all these claylike ingredients is that they contain silicon, oxygen, and one or more metals. Many silicates occur naturally and are mined; yet others are produced synthetically. Typical cosmetic uses of silicates include abrasive, opacifying agent, viscosity-increasing agent, anticaking agent, emulsion stabilizer, binder, and suspending agent. Clay silicates (silicates containing water in their structure) primarily function as adsorbents, opacifiers, and viscosity-increasing agents. Pyrophyllite is also used as a colorant. The International Agency for Research on Cancer has ruled Attapulgite fibers &gt;5 μm as possibly carcinogenic to humans, but fibers &lt;5 μm were not classified as to their carcino-genicity to humans. Likewise, Clinoptilolite, Phillipsite, Mordenite, Nonfibrous Japanese Zeolite, and synthetic Zeolites were not classified as to their carcinogenicity to humans. These ingredients are not significantly toxic in oral acute or short-term oral or parenteral toxicity studies in animals. Inhalation toxicity, however, is readily demonstrated in animals. Particle size, fibrogenicity, concentration, and mineral composition had the greatest effect on toxicity. Larger particle size and longer and wider fibers cause more adverse effects. Magnesium Aluminum Silicate was a weak primary skin irritant in rabbits and had no cumulative skin irritation in guinea pigs. No gross effects were reported in any of these studies. Sodium Magnesium Silicate had no primary skin irritation in rabbits and had no cumulative skin irritation in guinea pigs. Hectorite was nonirritating to the skin of rabbits in a Draize primary skin irritation study. Magnesium Aluminum Silicate and Sodium Magnesium Silicate caused minimal eye irritation in a Draize eye irritation test. Bentonite caused severe iritis after injection into the anterior chamber of the eyes of rabbits and when injected intralamellarly, widespread corneal infiltrates and retrocorneal membranes were recorded. In a primary eye irritation study in rabbits, Hectorite was moderately irritating without washing and practically nonirritating to the eye with a washout. Rats tolerated a single dose of Zeolite A without any adverse reaction in the eye. Calcium Silicate had no discernible effect on nidation or on maternal or fetal survival in rabbits. Magnesium Aluminum Silicate had neither a teratogenic nor adverse effects on the mouse fetus. Female rats receiving a 20% Kaolin diet exhibited maternal anemia but no significant reduction in birth weight of the pups was recorded. Type A Zeolite produced no adverse effects on the dam, embryo, or fetus in either rats or rabbits at any dose level. Clinoptilolite had no effect on female rat reproductive performance. These ingredients were not genotoxic in the Ames bacterial test system. In primary hepatocyte cultures, the addition of Attapulgite had no significant unscheduled DNA synthesis. Attapulgite did cause significant increases in unscheduled DNA synthesis in rat pleural mesothelial cells, but no significant increase in sister chromosome exchanges were seen. Zeolite particles (&lt;10 μm) produced statistically significant increase in the percentage of aberrant metaphases in human peripheral blood lymphocytes and cells collected by peritoneal lavage from exposed mice. Topical application of Magnesium Aluminum Silicate to human skin daily for 1 week produced no adverse effects. Occupational exposure to mineral dusts has been studied extensively. Fibrosis and pneumoconiosis have been documented in workers involved in the mining and processing of Aluminum Silicate, Calcium Silicate, Zirconium Silicate, Fuller's Earth, Kaolin, Montmorillonite, Pyrophyllite, and Zeolite. The Cosmetic Ingredient Review (CIR) Expert Panel concluded that the extensive pulmonary damage in humans was the result of direct occupational inhalation of the dusts and noted that lesions seen in animals were affected by particle size, fiber length, and concentration. The Panel considers that most of the formulations are not respirable and of the preparations that are respirable, the concentration of the ingredient is very low. Even so, the Panel considered that any spray containing these solids should be formulated to minimize their inhalation. With this admonition to the cosmetics industry, the CIR Expert Panel concluded that these ingredients are safe as currently used in cosmetic formulations. The Panel did note that the cosmetic ingredient, Talc, is a hydrated magnesium silicate. Because it has a unique crystalline structure that differs from ingredients addressed in this safety assessment, Talc is not included in this report.

Cytogenetic toxicity of methotrexate in mouse bone marrow

Methotrexate (MTX), a widely used anticancer drug, was tested for its cytogenetic toxicity in mouse bone marrow after a single intraperitoneal treatment with three different doses i.e. at the rate of 2, 10 and 20 mg/kg b.w. of mice. The end points selected were chromosomal aberrations and mitotic index study at 24-h post-treatment and micronucleus (MN) test at 30-h post-treatment. The induction of statistically significant number of chromosomal aberrations, percentage of aberrant metaphases and highly significant number of MN per thousand polychromatic erythrocytes by all the doses of MTX indicated it as highly clastogenic. MTX was found more clastogenic in male mice than the females and the intermediate dose tested (10 mg/kg) was found more effective than the other doses. In mitotic index study, none of the doses of MTX inhibited cell proliferation during the first post-treated cell cycle. The results were compared with the earlier reports on the clastogenicity and cell proliferation inhibition of MTX only after multiple treatments. The possible mechanism of the cytogenetic effects of MTX has been discussed.

The synergistic effects of SV40 and BUdR on induction of gene mutations and chromosomal aberrations in Chinese hamster cells.

The induction of chromosomal aberrations and gene mutations was studied in Chinese hamster cells after separate and combined treatment with BUdR and SV40. Separate treatment of cells with BUdR or virus infection increased the yield of chromosomal aberrations and reversions from glutamine requirement, expressed at 40 degrees C (a ts mutant), to prototrophy. The combined effect of the incorporation of BUdR into one DNA strand, and a subsequent infection by SV40 was additive as regards the percentage of aberrant metaphases. The integration of the analogue into both DNA strands followed by SV40 treatment resulted in a statistically significant increase in the frequency of aberration carrying metaphases, as compared with the frequency expected if the two agents had acted additively. The same phenomenon was detected when the frequency of reversions to glutamine independence was studied. Hence, the effect of the joint treatment by BUdR incorporated into both DNA strands and SV40 was synergistic. This is known to characterize the effect of BUdR on virus-induced transformation. Therefore, obviously the agent that enhances the malignant transformation of cells by the virus similarly modifies its mutagenic activity. The results obtained are presumed to confirm the previously advanced hypothesis that the same events following infection might control both the integration of viral DNA into the host-cell chromosome (and hence cell transformation) and virus-induced mutagenesis. The role of repair processes in the synergistic effect of BUdR and SV40 in the yield of reversions to glutamine independence is discussed.

Cytogenetic action of the antitumor photrin in cultures of human lymphocytes

Concentration curves of the cytogenetic action of the Soviet antitumor preparation photrin were studiedin 24-h cultures of human lymphocytes with an exposure of 1 h (concentrations from 10 to 70 μg/ml, interval 10 μg/ml). The percentage of aberrant metaphases at the minimal concentration was 19.0 and at the maximal 69.5. The relationship between the concentration of photrin and the number of damaged chromosomes per 100 cells within the range of concentrations studied was described by the equation $$Y = 3,126 + 1.33 c - 0.01156 c^2 .$$ where Y is the number of damaged chromosomes per 100 cells and c the concentration of photrin. The main types of chromosomal aberrations were single and paired fragments and chromatid exchanges. With respect to the type and frequency of the cytogenetic lesions induced b it, photrin resembles the known preparation thioTEPA and its is a typical alkylating mutagen.