Effect of copper on growth, yield and concentration of Fe, Mn, Zn and Cu in wheat plants (Triticum aestivum L.).

A pot experiment was conducted at six graded levels of copper (Cu) viz., 0, 0.5, 1.0, 1.5, 2.0 and 2.5 mg kg(-1) to test the response of wheat plants grown in a copper-responsive alluvial soil (entisol) under glass house conditions. The growth attributes like plant height, fresh and dry matter yield, percent dry matter enhanced with increasing Cu levels and was maximum at 1.5 mg kg(-1) Cu while the number of tillers was minimum at this level. The grain yield at 1.5 mg kg(-1) Cu was enhanced by 62.9% from the control. The increase in weight of 1000 grains ranged from 33.93 to 41.35 g in comparison to control (32.58 g). Harvest index (%) also increased and ranged from 39.42 to 47.73 in different treatments in comparison to control (35.92). Both 1000 grain weight and harvest index were maximum in the plants at 1.5 mg kg(-1) copper. Cu concentrations in leaves, grain and straw enhanced with increasing levels of Cu application. The Fe concentration in leaves was significantly reduced by Cu application and the reduction was 10.3% at 2.5 mg kg(-1) Cu and was not influenced in by Cu application in grain and straw. The Mn concentration was not affected by Cu application in any of the plant part studied. However, Zn concentration decreased significantly at higher levels of Cu (2.0 and 2.5 mg kg(-1)) in leaves and remained unaffected in the grain and straw.

Evaluation of carcinogenic and co-carcinogenic potential Quinalphos in mouse skin.

Quinalphos [O,O-diethyl-O-quinoxalinyl-phosphorothidate] is an organophosphorus pesticide with tremendous utility in mixed pest control due to its insecticidal and acaricidal properties. Apart from its pesticidal property, Quinalphos is known to induce various toxic effects in nontarget species and experimental animals. No studies have been conducted to evaluate the carcinogenic/co-carcinogenic hazards associated with Quinalphos exposure. In the present set of investigations, the tumorigenic potential of Quinalphos has been evaluated following topical exposure in Swiss albino mice. Long-term animal bioassays conducted for the evaluation of complete carcinogenic, tumour-initiating and tumour-promoting potential of Quinalphos revealed that it has only tumour-initiating potential at a dose of 10 mg/kg body weight (b.wt.), in the two-stage mouse skin model of carcinogenesis. Quinalphos exposure failed to produce neoplasia when tested for complete carcinogenic activity at all three tested dose levels or tumour promoting activity.

Carcinogenicity and co-carcinogenicity studies on propoxur in mouse skin.

Propoxur (2-isopropoxyphenyl methylcarbamate) is a widely used broad spectrum carbamate insecticide mainly used to control household pests. Propoxur exposure is reported to inhibit cholinesterase activity in rodents. Apart from other toxic effects, propoxur was found to possess tumorigenic activity in rats after oral administration. Propoxur does not produce tumours in mice or hamsters, or bladder hyperplasia in dogs and monkeys following oral feeding. In this set of investigations the complete carcinogenic, tumour initiating and promoting potential of propoxur was evaluated in male and female Swiss albino mice, since no information was available following dermal exposure of propoxur. The animals were exposed to propoxur through topical painting on the interscapular region at a dose of 100 mg/kg body weight. The results revealed that propoxur has tumour promoting potential on mouse skin following a two-stage initiation-promotion protocol, but it failed to induce the tumour(s) at a significant level, when tested for tumour initiating and complete carcinogenic property.

Chemopreventive effects of black tea polyphenols in mouse skin model of carcinogenesis.

In the present investigations, the antitumorigenic effect of black tea polyphenols (BTP) in two-stage mouse skin model of carcinogenesis was studied. The animals were initiated with a single "subcarcinogenic" topical dose (52 micrograms/200 microliters acetone) of 7, 12-dimethylbenzanthracene (DMBA). To evaluate the anti-tumour initiating activity, BTP was topically applied twice a week for three weeks prior to DMBA application, followed by topical treatment with 12-o-tetradecanoyl phorbol-13-acetate (TPA) (5 micrograms/200 microliters acetone, 2x/wk.) as promoter. For evaluation of antitumor promoting activity, BTP was applied prior to each treatment of TPA. BTP application showed marked inhibitory effect as antitumour initiator as well as antitumour promoter in mouse skin model of two-stage carcinogenesis. Since initiation involves genetic pathway and tumour promotion involves epigenetic pathway, it seems that BTP exerts its antitumorigenic effect by altering both genetic and epigenetic pathways.

Assessment of mutagenic potential of thiram.

Thiram is a widely used dithiocarbamate fungicide. In this study, the mutagenicity of thiram was investigated using the micronucleus and dominant lethal tests in Swiss albino mice. A single ip injection of 100 mg thiram/kg body weight, which is the maximum tolerated dose (MTD), significantly induced micronucleus formation in bone marrow cells after 30 and 48 hr of exposure; 50% and 25% of the MTD also induced micronucleus formation after the above time periods. A significant number of dead implants were induced when thiram was given to male mice in the diet at 10% of the oral LD50 during the whole spermatogenesis cycle (8 wk); this post-implantation loss indicates a dominant lethal mutation.

Assessment of mutagenic potential of propoxur and its modulation by indole-3-carbinol.

Propoxur is a widely used dithiocarbamate pesticide. In the present set of investigations, mutagenicity of propoxur (in formulation) was studied using the micronucleus assay in bone marrow of Swiss mice. Single intraperitoneal (i.p.) administration of 25 mg/kg body weight dose of propoxur, which is a maximum tolerated dose (MTD), significantly induced the micronucleus formation in bone marrow cells after a 24- and 48-hr exposure. A half and a quarter of the MTD (12.5 and 6.25 mg/kg) were found ineffective to induce the micronuclei formation after 24- and 48-hr time periods by the i.p. route. However, the PCE:NCE ratio was inhibited significantly with all the dose levels at both time periods. Oral administration of propoxur at different dose levels also induced micronuclei formation. A single application of 50 and 25 mg/kg dose levels of propoxur, which are MTD and 50% of MTD, also significantly induced micronuclei formation after 24- and 48-hr time periods in bone marrow cells of Swiss mice as compared with solvent control group, whereas a 12.5 mg/kg dose of propoxur was ineffective in inducing micronuclei formation. Single application of indole-3-carbinol (I3C), a glucobrassicin derivative present in cruciferous vegetables, significantly inhibited the propoxur-induced micronuclei formation when it was given at the dose level of 500 mg/kg body weight 48 hr before the single application of propoxur. Therefore, it seems that propoxur is mutagenic in the above test systems and I3C inhibited the mutagenicity of propoxur significantly.

Differential effects of butyric acid on mouse skin tumorigenesis.

We studied the effects of butyric acid (BA) on mouse skin tumorigenesis using chronic animal bioassays. Topical application of BA immediately after each treatment with 12-0-tetradecanoylphorbol-13-acetate (TPA) promoter-inhibited skin tumors. The effect was dependent on the dose of BA applied. BA showed no marked inhibitory effect on either skin tumor initiation or complete tumorigenesis induced by dimethylbenzanthracene (DMBA). Since tumor promotion reportedly involves epigenetic events whereas tumor initiation or complete tumorigenesis takes place through genetic pathways, it is possible that BA exerts its antitumorigenic effects mainly by altering the epigenetic events responsible for tumor promotion. The results of the study could further be used to study the mechanism of action and modification of antitumorigenic effects of BA in combination with other substances.

Micronucleus induction by diuron in mouse bone marrow.

Diuron, a widely used substituted urea herbicide, induced the formation of micronuclei in bone marrow cells of Swiss mice. A single i.p. dose of 340 mg/kg b.w. diuron which is maximum tolerated dose (MTD) increased significantly the number of micronuclei at 30 h and 48 h time period. The dose of 170 mg/kg b.w. also induced the micronuclei formation in the above time period. However, a dose of 85 mg/kg b.w. was ineffective at the time periods studied. No induction of micronuclei was observed at 72 h time period after all the doses of diuron studied as compared to the solvent control. The diuron-induced frequency of micronucleated erythrocytes was independent of the sex of the test animals.

Antitumour activity of protein A in a mouse skin model of two-stage carcinogenesis.

Protein A (PA) is an immunostimulating glycoprotein (mol. wt. 43,000 kDa) obtained from Staphylococcus aureus cowan I. The antitumour property of PA is well documented in the literature in various transplantable tumours of rats and mice. In the present set of investigations, the antitumour property of PA was tested in Swiss albino mice in a two-stage initiation-promotion mouse skin carcinogenesis model. The animals were initiated topically with a single subcarcinogenic dose (52 microgram) of 7,12-dimethylbenzanthracene (DMBA). PA was administered intraperitoneally (1 microgram/animal), twice weekly for 2 weeks. Promotion was performed by twice weekly applications of 12-O- tetradecanoyl phorbol-13-acetate (TPA) at a dose of 5 microgram/animal for 32 weeks. The result showed that the treatment schedule can effectively check the onset of tumorigenesis, the cumulative number of tumours and the average number of tumours per mouse. In the PA administered group, 30% of the animals remained tumour free until the termination of the experiments (i.e. 32 weeks of promotion). Thus the present study proves that protein A can effectively inhibit DMBA initiated and TPA promoted mouse skin carcinogenesis.

Carcinogenic and co-carcinogenic studies of thiram on mouse skin.

Thiram (tetramethyl thiuram disulfide), a carbamate fungicide, is used in the rubber processing industry as an accelerator and vulcanizing agent. Previous studies evaluated the tumorigenic potential of thiram in rodents, but failed to provide conclusive results. In the present study the tumorigenic potential of thiram was evaluated in Swiss albino mice by a two-stage initiation-promotion protocol and a long-term in vivo bioassay for carcinogenicity. Results revealed that following tumour initiation with thiram and promotion with 12-O-tetradecanoyl phorbol 13-acetate, skin tumours developed, mostly at the site of treatment (dorsal skin) in single and multiple dose-initiated animals. Similarly, papillomatous growths were observed on the dorsal skin of the mice initiated with a single subcarcinogenic dose of dimethylbenzanthracene and promoted with thiram. Thiram failed to provoke tumorigenesis when tested as a complete carcinogen for up to 52 wk and thereafter the study was terminated due to increased mortality. It is concluded that thiram has both tumour initiating and tumour-promoting potential in both sexes of Swiss albino mice following topical exposure at the tested dose level.

Tumour-promoting activity of ninhydrin on mouse skin.

Ninhydrin (2,2-dihydroxy-1,3-indanedione; CAS No. 485-47-2) is widely used as a reagent for the detection of free amino and carboxyl groups in proteins and peptides. It is an irritant to mammalian skin. Various toxic effects of ninhydrin have been reported in laboratory animals; however, so far there has been no evaluation of its carcinogenic and co-carcinogenic potential in laboratory animals by long-term in vivo bioassay. Ninhydrin was found to induce the activity of gamma-glutamyl transpeptidase (GGT) in mouse skin but it failed to alter the activity of the enzyme ornithine decarboxylase when compared with animals treated with standard tumour promoter 12-O-tetradecanoyl phorbol-13-acetate (TPA). In the present investigations, the tumour-promoting activity of ninhydrin (including both stage I and stage II of tumour promotion) was tested on Swiss albino mice in a multistage mouse skin model of carcinogenesis. The animals were initiated with a single topical application of 7,12-dimethylbenz-anthracene followed by four topical applications of ninhydrin biweekly as stage I promoter for 2 wk. Stage II promotion was twice weekly through topical application of mezerein. The results revealed that ninhydrin is a strong stage I tumour promoter and its efficacy was comparable with that of TPA at the dose level used in the experiment. However, ninhydrin failed to produce tumours when tested as a stage II or complete tumour promoter on mouse skin.

Ornithine decarboxylase inactivation by putrescine: involvement of lipid peroxidation.

Effect of polyamines on 12-O-tetradecanoyl phorbol-13-acetate (TPA)-induced reduction of lipid peroxidation was studied. Putrescine protected this lowering of lipid peroxidation in a concentration-dependent manner, but spermidine or spermine could not do so. Putrescine also inhibited the TPA-induced ornithine decarboxylase (ODC) activity and lowered the free sulfhydryl content of TPA exposed mouse skin. These observations indicate that putrescine inactivates ODC probably by lowering SH groups through lipid peroxidation.

Carcinogenic and cocarcinogenic studies with carbaryl following topical exposure in mice.

Carbaryl (1-naphthyl methyl carbamate: C12H11NO2) CAS Reg. No. 63-25-2) is a widely used broad spectrum carbamate insecticide known to exert various toxic effects on experimental animals. Along with various other toxicological effects carbaryl is reported to increase the incidence of neoplasm in various tissues in rats after oral or intraperitoneal administration. No study has so far been reported in rodents to assess its carcinogenic/cocarcinogenic potential after topical exposure. In this set of investigations, the complete carcinogenic, tumour initiating and tumour promoting property of carbaryl was tested on the skin of female Swiss albino mice. The animals were exposed to carbaryl through topical painting on the interscapular region at a dose of 100 mg/kg body wt. The results revealed that carbaryl has tumour initiating potential, at the test dose, on mouse skin following two stage, initiation-promotion protocol, but, it failed to induce the tumour(s) when tested for complete carcinogenic and tumour promoting properties.

Protection against 7,12-dimethylbenzanthracene-induced tumour initiation by protein A in mouse skin.

Protein A is an immunostimulating glycoprotein obtained from Staphylococcus aureus Cowan I. Its antitumour activity is proven in various tumour models. Its ability to provide protection against tumour initiation by the chemical carcinogen 7,12-dimethylbenzanthracene (DMBA) has been investigated in the present study using a mouse skin model of two-stage carcinogenesis. Protein A was administered intraperitoneally (1 microgram/animal 20 g body wt.) twice a week for 2 weeks, prior to initiation by DMBA. The promotion was performed by twice weekly applications of 12-O-tetradecanoyl phorbol-13-acetate (TPA) (3 or 5 micrograms/animal in 100 microliters acetone). Protein A provided significant protection to animals from DMBA-induced tumour initiation as was observed by the decrease in cumulative number of tumours, percent of animals developing tumours, number of tumours per animal and rate of tumour growth. Our data indicate that protein A has anticarcinogenic properties.

Status of ornithine decarboxylase activity and DNA synthesis in mancozeb-exposed mouse skin.

The effect of mancozeb, a fungicide, on mouse skin ornithine decarboxylase (ODC) activity and DNA synthesis was studied. ODC activity was induced after topical application of mancozeb and exhibited a peak level at 5 h. This ODC induction was dependent on the dose of mancozeb applied. Cycloheximide, an inhibitor of protein synthesis, inhibited the mancozeb-caused ODC induction, indicating the effect on enzyme protein synthesis. The rate of DNA synthesis was also increased by mancozeb, as indicated by increased [3H]thymidine incorporation into skin DNA. Induction of ODC activity and DNA synthesis are among the events probably involved in the tumorigenic action of mancozeb on mouse skin.

Inhibition of mouse skin tumor promotion by tenuazonic acid.

Tenuazonic acid (TA) was topically applied to the interscapular region of Swiss albino mice at different doses before the application of 12-O-tetradecanoyl phorbol-13-acetate (TPA). Skin from the painted area was examined for ornithine decarboxylase (ODC) enzyme estimation. It was observed that TA inhibited TPA induced ODC activity. The inhibitory effect of TA was also found in mouse skin tumor promotion in the two stage initiation promotion protocol. There was a remarkable delay in the latency period and decrease in the number of tumors developed and the percentage of tumor bearing animals after TA treatment.

Carcinogenic activity of a carbamate fungicide, mancozeb on mouse skin.

Mancozeb, a polymeric complex of ethylene bis (dithiocarbamate) manganese with zinc salt is a protective fungicide. In the present study complete carcinogenic activity of mancozeb, has been observed following topical application on dorsal mouse skin. Female Swiss albino mice were exposed to mancozeb at a dose of 100 mg/kg body weight dissolved in 100 microliters dimethyl sulfoxide 3 times per week. Development of tumours was observed after 31 weeks (217 days) of mancozeb application. A high rate of mortality was observed after 54 weeks (378 days) of mancozeb application due to its toxicity and the study was terminated after 60 weeks. On histological examination, these tumours were found mostly to be benign in nature, e.g., squamous cell papillomas and keratoacanthomas.

Mouse skin ornithine decarboxylase induction and tumor promotion by cyclohexane.

Cyclohexane, a frequently used solvent in industry, was assessed for its tumorigenic potential on mouse skin following multistage initiation-promotion protocols. The activity of ornithine decarboxylase (ODC), a marker of tumor promotion was found to be induced by the topical application of cyclohexane. This ODC induction was dependent on the dose of cyclohexane used and the duration of application. Effect of protein synthesis inhibitors and the modifiers of tumor promotion on the cyclohexane induced ODC activity was also studied. ODC induction was inhibited by cycloheximide and also, up to some extent, by actinomycin D. Inhibitors of stage II tumor promotion showed more effect on the ODC induction by cyclohexane as compared to the inhibitors of stage I tumor promotion. In chronic animal bioassay experiments topical application of cyclohexane to DMBA initiated mouse skin resulted in just 10% of tumor bearing animals while prior application of TPA for two weeks resulted in 45% of tumor bearing animals. Collectively, the present study demonstrates that cyclohexane is more effective as a stage II tumor promoter over mouse skin and possibly affects the biochemical events at the molecular level.