Localization of heat shock protein 27 (hsp27) in the rat gingiva and its changes with tooth eruption.

Heat shock protein 27 kDa (Hsp27) functions as a molecular chaperon to prevent apoptosis as well as to contribute to the regulation of cell proliferation and differentiation during development. In the present study, the localization of Hsp27 in the oral epithelium of rats and its expression change during formation of the gingiva with the tooth eruption were examined immunohistochemically to elucidate the roles of Hsp27 in the oral mucosa.In adult rats, Hsp27-immunoreactivity was localized in the prickle and granular layers but absent in the basal and horny layers of the oral epithelium. On the other hand, in the outer and sulcular epithelia of the free gingival, Hsp27-immunoreactivity was detected in the whole layers, while it was not found in the proliferation zone of the junctional epithelium immunoreactive for Ki67. In immature rats on 10th postnatal day, Hsp27-immunoreactivity was intense in the prickle and granular layers of the oral epithelium, but was not detected in its basal layer. In rats at the eruptive phase on 15th postnatal day, Hsp27-immunoreactivity was detected in sites of the basal layer adjacent to where the dental cusps penetrated through the oral epithelium. Although the immunoreactivity for Ki67 was found in the basal layer of the oral epithelium, it was not localized in the Hsp27-immunopositive sites of tooth-penetration in the basal layer. Just after the tooth-eruption on 20th postnatal day, Hsp27-immunoreactivity was not found in the stratified squamous epithelium at the dentogingival junction, whereas it was intense in a single layer of cuboidal epithelial cells attached to the tooth neck. Ki67-positive cells were scattered in the stratified squamous epithelium at the dentogingival junction, whereas no positive cells were found in the portion of a single layer of cuboidal epithelial cells.These findings suggest that the outer and sulcular epithelia of the free gingiva have a relatively slower rate of proliferation than other gingival and oral epithelia, and that Hsp27 might inhibit the proliferation of the basal cells. Such specific phenomenon in the free gingiva occurred immediately after the dental cusps were exposed to the oral cavity.

Involvement of macrophage inflammatory protein 1alpha (MIP1alpha) in promotion of rat lung and mammary carcinogenic activity of nanoscale titanium dioxide particles administered by intra-pulmonary spraying.

Titanium dioxide (TiO(2)) is evaluated by World Health Organization/International Agency for Research on Cancer as a Group 2B carcinogen. The present study was conducted to detect carcinogenic activity of nanoscale TiO(2) administered by a novel intrapulmonary spraying (IPS)-initiation-promotion protocol in the rat lung. Female human c-Ha-ras proto-oncogene transgenic rat (Hras128) transgenic rats were treated first with N-nitrosobis(2-hydroxypropyl)amine (DHPN) in the drinking water and then with TiO(2) (rutile type, mean diameter 20 nm, without coating) by IPS. TiO(2) treatment significantly increased the multiplicity of DHPN-induced alveolar cell hyperplasias and adenomas in the lung, and the multiplicity of mammary adenocarcinomas, confirming the effectiveness of the IPS-initiation-promotion protocol. TiO(2) aggregates were localized exclusively in alveolar macrophages and had a mean diameter of 107.4 nm. To investigate the underlying mechanism of its carcinogenic effects, TiO(2) was administered to wild-type rats by IPS five times over 9 days. TiO(2) treatment significantly increased 8-hydroxydeoxy guanosine level, superoxide dismutase activity and macrophage inflammatory protein 1alpha (MIP1alpha) expression in the lung. MIP1alpha, detected in the cytoplasm of TiO(2)-laden alveolar macrophages in vivo and in the media of rat primary alveolar macrophages treated with TiO(2) in vitro, enhanced proliferation of human lung cancer cells. Furthermore, MIP1alpha, also detected in the sera and mammary adenocarcinomas of TiO(2)-treated Hras128 rats, enhanced proliferation of rat mammary carcinoma cells. These data indicate that secreted MIP1alpha from TiO(2)-laden alveolar macrophages can cause cell proliferation in the alveoli and mammary gland and suggest that TiO(2) tumor promotion is mediated by MIP1alpha acting locally in the alveoli and distantly in the mammary gland after transport via the circulation.

Role of the Met(287)Thr polymorphism in the AS3MT gene on the metabolic arsenic profile.

Chronic exposure to arsenic involves a biotransformation process leading to the excretion of methylated metabolites, such as monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA), as well as the parental inorganic species (As(III) and As(V)). Inter-individual variations in arsenic biotransformation have been reported and polymorphisms affecting the genes involved in arsenic biotransformation have been considered as one of the plausible explanations for this variation. Coding and flanking regions of the human arsenic methyltransferase (AS3MT) gene have been analysed in 50 Chilean men exposed to arsenic. Nine polymorphisms were found, including one non-synonymous SNP at exon 9 (Met(287)Thr) with an allele frequency of 0.14. Other four changes occurred at potentially regulatory regions: a variable number of tandem repeats (VNTR) at the 5'-untranslated region (UTR5'), a G/C substitution at the promoter region, a GC/AT substitution inside the VNTR, and a G/A substitution at the 3'-untranslated region (UTR3'). The rest of polymorphisms were located in non-coding regions: a T/G substitution in intron 1, a CTC deletion in intron 2 and a TTT and ATT insertions in intron 5. In addition, the individual urinary arsenic profiles were analysed. Our results indicate that genetic polymorphisms in AS3MT contribute to inter-individual variation in arsenic biotransformation and, therefore, may contribute to inter-individual variations in risk of arsenic toxicity and arsenic carcinogenesis. Individuals with the Met(287)Thr polymorphism displayed increased arsenic methylation and might be at increased risk for toxic and genotoxic effects of arsenic exposure if, as the classical arsenic metabolic pathway indicates, methylation enhances toxicity.

[Hazard identification of nanomaterials].

It is considered that the materials with new properties may lead to novel biological effects or unknown adverse health effects. To gather proper hazard information, it is important to develop both experimental protocols and detection/measurement methods for nanomaterials in the body, in parallel. Since 2005, we are running research projects to develop methods to monitor health risk effects for the assessment of manufactured nanomaterials funded by the Ministry of Health, Labour and Welfare. For the experimental protocols, these projects focus on the development of 1) in vitro experimental systems, 2) in vivo experimental systems (mainly focusing on long-term health implication, especially carcinogenesis), and 3) proper inhalation system. Firstly, fullerene (C60), titanium dioxide and multi-walled carbon nanotube were chosen to be tested because of their high production volume. Safety issues for new materials such as nanoparticles is a new paradigm. The key is that the full scale exposure to the public has not been started yet. Therefore, there is a good chance that information from hazard identification studies can be directly fed back to the product development plan. Manufacturers can produce safer products without risking themselves waiting for the toxicology studies to be finished after their products are widely marketed.

[Construction of three-dimensional human skin model involving dendritic cells and its application to skin sensitization test].

Recently, to study an in vitro evaluation method of skin irritation and acute toxicity, many three-dimensional human skin models consisting of normal human keratinocytes and fibroblasts have been used. However, these skin models did not have any dendritic cells so were difficult to apply to an in vitro skin sensitization test. On the other hand, a single cell-culture model using normal human dendritic cells was recently studied for an in vitro evaluation method of immune-sensitizing compounds. However, these models have various problems: 1) the life span of dendritic cells is short(within 1 week) and 2) it is difficult to apply water-insoluble samples to these models. To study an alternative to animal testing using immune-sensitizing compounds, we therefore constructed a three-dimensional human skin model consisting of three different cells, dendritic cells (keratinocytes, and fibroblasts) then exposed immune-sensitizing compounds and non-sensitizers to the new skin model for 1 h and investigated the effect of these compounds on cytokine release and expression of CD86. Due to immune-sensitizing compounds, the new skin model significantly released cytokine and significantly expressed CD86. On the other hand, non-sensitizers did not induce IL-1alpha, IL-2, and IL- 4 release and expression of CD86. These results suggest that the new skin model is suitable for study as an alternative to animal testing using immune-sensitizing compounds.

[Risk assessment of arsenic for people who live in the area of arsenic-contaminated undergroundwater in Bangladesh].

Arsenic is a very harmful environmental pollutant and arsenic contamination of groundwater has been reported in Bangladesh, West Bengal, India and Nepal. In order to examine the risk assessment of arsenic, we made the plan to deliver the safe water for purpose of drinking and cooking for one year to 16 arsenic-affected families in Chunakali village, Chapai Nawabganj district, Bangladesh. We supplied the safe water after treatment of Gravel Sand Filter facility. The arsenic in drinking water didn't exceed almost 50 ppb for one year. Before delivering the safe water both on June 2005 and on February 2006, we visited Chunakali village with Professor Rahman, Associated Professor Belgum and Zaman and diagnosed the arsenic symptom of the arsenic-affected families and collected their urines and hairs. Also we visited that village on August 2006 of a half year after delivering the safe water and on March 2008 of one year after delivering the safe water. Due to the supply of safe water for one year for purpose of drinking and cooking, the arsenic symptoms were recovering and the amounts of arsenic in hairs were decreasing. If Bangladesh government has the good water management in rural areas of arsenic-polluted underground and adopted the appropriate water supply system, the arsenic symptom caused by arsenic should be recovered.

[Studies for analyzing prohibited ingredients such as cadmium sulfide in cosmetics].

Cadmium sulfide is one kind of the prohibited ingredients in cosmetics by the Japanese Pharmaceutical Affairs Act. We established the analytical method for cadmium sulfide in cosmetics by ICP-MS. Analytical procedures were as follows: Cosmetics of 1 g contained inorganic pigment were put into a 100 ml flask glass. After adding 100 ml of 12% nitric acid into the 100 ml flask glass, the filtrate was sonicated for 30 min. After sonicating, the mixture was centrifuged at 3000 rpm for 5 min and then the supernatant was filtrated through a millipore membrane filter (0.45 microm). After filtration, the filtrate was made up to 200 ml with 12% nitric acid. The solution was diluted 100 times with 12% of nitric acid and used as the test solution. The test solution of 100 microl was analyzed by ICP-MS (HP-4500, monitoring mass 111). The working curve from 1 to 1000 microg/l showed a linear line between the concentrations of cadmium and the peak areas. Detection limit of cadmium is 0.02 microg/l. There was no effect of the ingredients in the cosmetics on cadmium sulfide determination.

[Studies for analyzing prohibited ingredients such as mercury in cosmetics].

Mercury is one kind of prohibited ingredients in cosmetics by the Japanese Pharmaceutical Affairs Act. We established the analytical method for mercury in cosmetics by ICP-MS. Analytical procedures were as followed: Ten microl of 1 g/l mercury solution and 1 g of whitening cream were put into a 50 ml plastic tube. After adding 20 ml of 12% nitric acid into the 50 ml plastic tube, the mixture was sonicated for 10 min. After sonicating, the mixture was centrifuged at 3000 rpm for 10 min and then the supernatant was filtrated through a milli-pore membrane with the pore size of 0.45 microm and 0.1 microm. After filtration, the mixture was made up to 25 ml with 7% nitric acid and used as the test solution. The test solution of 100 microl was analyzed by ICP-MS (HP-4500, monitoring mass 202). The calibration curve from 1 to 1000 microg/l showed a linear line between the concentrations of mercury and the peak areas. Detection limit of mercury was 0.1 microg/l. There was no effect of the ingredients in the whitening cream on mercury determination.

[Simultaneous determination of 9 ultraviolet absorbers in cosmetics by high-performance liquid chromatography].

Simultaneous determination for 9 ultraviolet absorbers those set a limit to the amount in cosmetics was performed. Ultraviolet absorbers were extracted from cosmetics with tetrahydrofuran (THF) by ultrasonication. After centrifugation, the supernatant was collected, and the sample solution was injected into the HPLC. Separation was archived using an ODS column with the mixture of THF and water as the mobile phase. Detection wavelength was set at 310 nm. The linearity was obtained between the peak areas and the concentrations of each ultraviolet absorber in the range of 5 - 100 microg/ml. In 70 commercial cosmetic products, such as sunscreen, face powder, foundation, massage cream, moisture lotion, lip balm and essence, 2-ethylhexyl-p-methoxycinnamate (EMC), 2-hydroxy-4-methoxybenzophenone (HMB), 4-tert-butyl-4'-methoxydibenzoylmethane (BMB) and 2-ethylhexyl salicylate (ES) were detected.

[Impact of air fresheners and deodorizers on the indoor total volatile organic compounds].

Indoor air quality is a growing health concern because of the increased incidence of the building-related illness, such as sick-building syndrome and multiple chemical sensitivity/idiopathic environmental intolerance. In order to effectively reduce the unnecessary chemical exposure in the indoor environment, it would be important to quantitatively compare the emissions from many types of sources. Besides the chemical emissions from the building materials, daily use of household products may contribute at significant levels to the indoor volatile organic compounds (VOCs). In this study, we investigated the emission rate of VOCs and carbonyl compounds for 30 air fresheners and deodorizers by the standard small chamber test method (JIS A 1901). The total VOC (TVOC) emission rates of these household products ranged from the undetectable level (< 20 microg/unit/h) to 6,900 microg/unit/h. The mean TVOC emission rate of the air fresheners for indoor use (16 products) was 1,400 microg/unit/ h and that of the deodorizers for indoor use (6 products) was 58 microg/unit/h, indicating that the fragrances in the products account for the major part of the TVOC emissions. Based on the emission rates, the impacts on the indoor TVOC were estimated by the simple model with a volume of 17.4 m3 and a ventilation frequency of 0.5 times/h. The mean of the TVOC increment for the indoor air fresheners was 170 microg/m3, accounting for 40% of the current provisional target value, 400 microg/m3. These results suggest that daily use of household products can significantly influence the indoor air quality.

[Evaluation of volatile organic compounds (VOCs) emitted from household products by small chamber test method].

Identification and removal/replacement of sources of indoor air pollutants, such as volatile organic compounds (VOCs) and aldehydes, are most effective measures to reduce indoor chemical exposures. For instance, formaldehyde emissions from building materials have been successfully decreased by the restrictions on interior finishing materials under the amended Building Standard Low in Japan. This study was performed to estimate quantitatively influence of household products on indoor air quality. VOC emissions were investigated for 51 products including interior materials, bedclothes, stationeries, toys and printed matters by the small chamber test method (JIS A 1901) under the standard conditions of 28 degrees C, 50% relative humidity and 0.5 times/h ventilation. Total VOC (TVOC) emissions from the tablecloth and gloves, both of which were made of polyvinyl chloride, showed the highest emission rates; over 2000 microg/(m2 x h) after 1 day, and then rapidly decreased to less than 500 microg/(m2 x h) in a week. Among stationeries/toys for schoolchildren and infants, jigsaw puzzle and play mat exhibited higher TVOC emission rates (38 and 24 microg/(m2 x h) after 1 day, respectively). As for VOCs emitted from printed matters, high boiling-point compounds (higher than that of n-tridecane) were typically identified along with toluene, xylenes and ethylbenzene. These results revealed that VOC emissions from household products may influence significantly indoor air quality.

Determination of orthophthalaldehyde in air using 2,4-dinitrophenylhydrazine-impregnated silica cartridge and high-performance liquid chromatography.

A new method is described for the determination of orthophthalaldehyde in air which is used for the disinfection of various instruments (e.g. endoscopes) in hospital. Orthophthalaldehyde in air was collected with a silica gel cartridge impregnated with acidified 2,4-dinitrophenylhydrazine (DNPH-cartridge) and derivatives were analyzed by high-performance liquid chromatography (HPLC). In this study, the derivatization was examined by comparing the process with three phthalaldehyde isomers (ortho-, iso- and tere-). In the case of iso- and tere-phthalaldehyde, derivatives synthesized with excess of aldehyde consisted mainly of mono-derivatives, and derivatives synthesized with excess of DNPH consisted mainly of bis-derivative. In the case of orthophthalaldehyde, derivative consisted of only bis-derivative and mono-derivative was never observed under any conditions. Orthophthalaldehyde was completely retained by the DNPH-cartridge during air sampling, however, the derivatization reaction was incomplete and unreacted orthophthalaldehyde was flushed from the cartridge during the subsequent solvent extraction process. Unreacted orthophthalaldehyde and DNPH reacted again in the extraction solvent solution. Immediately after the solvent extraction, both mono- and bis-DNPhydrazone derivatives of orthophthalaldehyde were present in the solution. However, over time, the mono-derivative decreased and bis-derivative increased until only the bis-derivative was left allowing accurate determination of the orthophthalaldehyde concentration. The transformation of mono-derivative to bis-derivative was faster in polar aprotic solvents such as acetonitrile, dimethyl sulfoxide and ethyl acetate. Transformation was found to occur most quickly in acetonitrile solvent and was completed in 4 h in this case. It was possible to measure orthophthalaldehyde in air as bis-derivative using a DNPH impregnated silica cartridge and HPLC analysis.

Metabolic profile in workers occupationally exposed to arsenic: role of GST polymorphisms.

Arsenic is a well-known human carcinogen with a ubiquitous distribution in the natural environment. Chronic exposure to inorganic arsenic involves a biotransformation process that leds to the main excretion of organic methylated metabolites, such as monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA), as well as the parental inorganic species. Interindividual variation in arsenic metabolism has been extensively reported, and polymorphisms in genes involved in such process could be related to changes in the arsenic excretion profile and the response to chronic exposures. Our analysis of the metabolic profiles in three groups of workers exposed to different arsenic exposure levels showed high amounts of inorganic arsenic and MMA in the most-exposed workers versus the least-exposed workers, in whom high amounts of DMA were observed. With respect to the role of different genetic polymorphisms in the glutathione S-transferase (GST) genes in the modulation of the urinary profiles, for the overall population only a tendency was just observed between GSTM1 null and MMA excretion as well as between GSTP1 val/val and DMA excretion.

[Studies for analyzing the prohibited ingredients such as selenium disulfide in cosmetics].

Selenium disulfide is one kind of prohibited ingredients in cosmetics by the Japanese Pharmaceutical Affairs Act. We established the analytical method for selenium disulfide in cosmetics by ICP-MS. Selenium disulfide of 20 mg was put into a teflon vessel. After adding 5 ml of concentrated nitric acid and 2 ml of the shampoo into the teflon vessel, the mixture was digested with microwave-oven. After digesting, the mixture was made up to 25 ml with milliQ water and then it was filtrated through a milli-pore membrane (0.45 micro). After filtration, the solution was diluted with 7% of nitric acid and used as the test solution. The test solution of 100 microl was analyzed by ICP-MS (HP-4500, monitoring mass 82). The working curve from 10 to 1000 microg/l showed a linear line between the concentrations of selenium and the peak areas. Detection limit of selenium disulfide is 22 microg/l. There was no effect of the ingredients in the shampoo on selenium disulfide determination.

[Studies for analyzing the prohibited ingredients such as disodium monofluorophosphate in cosmetics].

Disodium monofluorophosphate is one kind of the prohibited ingredients in cosmetics due to the Japanese Pharmaceutical Affairs Act. We established the analytical method for disodium monofluorophosphate in cosmetics by capillary electrophoresis (CE). The tooth paste of 1 g was put into a 50-ml plastic tube. After adding 7.0 mg of disodium monofluorophosphate and 50 ml of milliQ water into the plastic tube, the mixture was ultrasonicated for 10 min. After centrifuging, the supernatant was filtrated through a milli-pore membrane (0.45 microm). After filtration, the solutionwas put into a 100-ml volumetric flask, made up to 100 ml with milliQ water and used as the test solution. The mouthwash of 1 ml and 7.0 mg of disodium monofluorophosphate were put into a 100-ml volumetric flask, made up to 100 ml with milliQ water and used as the test solution. The testing solution was analyzed by CE. The working curve from 10 to 100 microg/ml showed a linear line between the concentrations of disodium monofluorophosphate and monofluorophosphate peak areas. Detection limit of disodium monofluorophosphate is 0.3 microg/ml. There was no interference of peak of monofluorophosphate with the ingredients in the tooth paste and mouthwash.

[Analysis of Helindone Pink CN and Permaton Red in cheek rouge].

Analytical methods for red tar colors, Helindone Pink CN (R226) and Permaton Red (R228), in cheek rouge were developed. R226 and R228 were extracted from cheek rouge with chloroform by ultrasonication. After centrifugation, the supernatant was collected for the determination of R226 and R228. Methanol was then added to the residue for the extraction of Pigment Red 57-1 (R201) and Pigment Red 57 (R202). Each R226 and R228 was separately detected by the silica-gel thin-layer chromatography using the mixture of hexane and chloroform (2:1) or (3:1), or hexane and tetrahydrofuran (THF) (2:1) as a developing solvent. For the determination of R226 and R228, the extract in chloroform was injected into the HPLC equipped with Amide colomn and UV-VIS detector (detection wavelength 535 nm and 487 nm) using the mixture of hexane and THF as mobile phase. The linearity was obtained between the peak areas and the concentrations of R226 and R228 in the range of 0.625-10 microg/ml. R201 and R202 were determined using ODS column and the mixture of acetonitrile and phosphate buffer as mobile phase. Seven cheek rouge samples were analyzed. The red tar colors listed in each cheek rouge were contained in the range of 247 to 6574 microg/g.

[Studies for analyzing restricted ingredients such as phenylbenzoimidazole sulfonic acid].

Phenylbenzoimidazol sulfonic acid (PBS) is a kind of sunscreens in cosmetics and is nominated as the restricted ingredients in cosmetics in Japanese Pharmaceutical Affairs Act. So the analytical method for PBS was investigated by HPLC. 1.0 g of the lotions with 1.0% PBS was exactly weighed, put into a 50-mL volumetric flask. Water was added to make exactly 50 mL and this mixture was used as the sample solution. On the other hand, 1.0 g of the creams with 1.0% PBS was exactly weighed, put into a beaker. After adding 1 mL of tetrahydrofuran and dissolving the cream, that mixture was transferred to a 50-mL volumetric flask. And then the beaker was rinsed with 1 mL of tetrahydrofuran and the rinsed solution was put together into the volumetric flask. After adding water to the volumetric flask to make exactly 50 mL, this mixture was used as the sample solution. If necessary, the mixture was filtrated with a membrane filter (0.45 microm). 5.0 mL of the sample solution was pipetted and put into a 200-mL volumetric flask. After adding water to make exactly 200 mL, 20 microL of this solution was analyzed by HPLC using the ODS column (CAPCELL PAK C18 column, 4.6 mm i.d. x 250 mm), the mixture of 40 mmol/L acetic buffer (pH 3.4) and acetonitrile (3:1) with 0.8 mmol/L dodecyltrimethyl ammonium bromide and the detection wavelength of 305 nm. The working curve from 0.5 to 20.0 microg/mL showed a linear line between the concentrations of PBS and the peak areas. There was no interference of peak of PBS from the lotion and cream.

Reactive oxygen species from mitochondria induce cyclooxygenase-2 gene expression in human mesangial cells: potential role in diabetic nephropathy.

Hyperglycemia increases the production of reactive oxygen species (ROS) from the mitochondrial electron transport chain in bovine endothelial cells. Because several studies have postulated a role for prostaglandins (PGs) in the glomerular hyperfiltration seen in early diabetes, we evaluated the effect of mitochondrial ROS on expression of the inducible isoform of cyclooxygenase (COX-2) in cultured human mesangial cells (HMCs). We first confirmed that incubation of HMC with 30 mmol/l glucose significantly increased COX-2 mRNA but not COX-1 mRNA, compared with 5.6 mmol/l glucose. Similarly, incubation of HMCs with 30 mmol/l glucose significantly increased mitochondrial membrane potential, intracellular ROS production, COX-2 protein expression, and PGE2 synthesis, and these events were completely suppressed by thenoyltrifluoroacetone or carbonyl cyanide m-chlorophenylhydrazone, inhibitors of mitochondrial metabolism, or by overexpression of uncoupling protein-1 or manganese superoxide dismutase. Furthermore, increased expression of COX-2 mRNA and protein was confirmed in glomeruli of streptozotocin-induced diabetic mice. In addition, hyperglycemia induced activation of the COX-2 gene promoter, which was completely abrogated by mutation of two nuclear factor kappaB (NF-kappaB) binding sites in the promoter region. Our results suggest that hyperglycemia increases mitochondrial ROS production, resulting in NF-kappaB activation, COX-2 mRNA induction, COX-2 protein production, and PGE2 synthesis. This chain of events might contribute to the pathogenesis of diabetic nephropathy.

Inorganic arsenic compounds and methylated metabolites induce morphological transformation in two-stage BALB/c 3T3 cell assay and inhibit metabolic cooperation in V79 cell assay.

We have performed two-stage transformation assay using BALB/c 3T3 cells to determine initiating and promoting activities of disodium arsenate, sodium arsenite, monomethylarsonic acid (MMAA) and dimethylarsinic acid (DMAA). Treatment with these arsenic compounds at the initiating stage induced significant numbers of transformed foci when cells were post-treated with 12-O-tetradecanoylphorbol-13-acetate (TPA). Disodium arsenate was active at the concentrations of 15-30 microM, sodium arsenite 5-20 microM, and DMAA 1-2 mM. MMAA required 10 mM to induce cell transformation. The concentrations of these compounds (except DMAA) that induced transformation were highly growth-inhibitory (more than 50%). DMAA induced transformation foci at growth inhibition levels of 66 to 84%. In experiments on promoting activity, cells pretreated with a sub-threshold dose of 20-methylcholanthrene (MCA, 0.2 microg/ml) or sodium arsenite (10 microM) were used. Transformation was enhanced by post-treatment with disodium arsenate (1-10 microM), sodium arsenite (0.5-2 microM), and MMAA (200-1000 microM), but not with DMAA. Studies of gap junctional intercellular communication using the V79 cell metabolic cooperation assay showed that the arsenic compounds (except DMAA) exhibited inhibitory activity. Thus, most arsenicals were shown to have not only initiating activity, but also promoting activity. In addition, inorganic arsenicals, especially trivalent sodium arsenite, were more active than organic ones and exhibited promoting activity at one-order of magnitude lower than initiating activity. These results suggest that from the viewpoint of human hazard, more attention should be paid to the tumor promoting activity of inorganic arsenic compounds.

Use of cholinesterase activity as an indicator for the effects of combinations of organophosphorus pesticides in water from environmental sources.

Organophosphorus pesticides (OPs) are commonly detected in agricultural products, animal-derived foodstuffs, and environmental samples. Until now, the focus of research has been to evaluate the adverse effect of a single OP. While each OP may be present at concentrations under recognized as "no observed adverse effect level (NOAEL)", the combined effects of multiple OPs present at these low concentrations have not been sufficiently studied. Therefore, we developed an in vitro testing method to evaluate the toxicity of multiple OPs based on the degree of inhibition of cholinesterase (ChE) activity. This method requires only 10 min to complete and no specialized technology. We examined 15 OPs by this method and categorized them into three groups according to the degree of ChE inhibition. A relationship between the OPs' chemical structures and the degree of ChE inhibition emerged with the moiety -P-O-CN- showing the strongest action. The degree of ChE inhibition increased with multiple OPs, and the degree of inhibition seemed to be additive. These results demonstrate that the combined toxicity of multiple OPs present in food or environmental samples is an easily determined and toxicologically relevant measure of overall toxicity of complex OPs mixtures. It is possible to apply this testing method as a monitoring technique in water quality management in order to control OPs. As a result, this method can play the role for the potential risk reduction to the ecosystem and may contribute to the preservation of the environment.