The determination of absolute electron affinities of the purines and pyrimidines in DNA and RNA from reversible reduction potentials.

We report the reversible reduction potentials of the purines and pyrimidines of DNA and RNA. These were determined in dimethylsulfoxide using cyclic voltammetry. The absolute electron affinities have been determined from these reduction potentials by calibration with the absolute electron affinities for acridine and anthracene measured in the gas phase. These are the first experimentally determined values of the electron affinities of these purines and pyrimidines and are: Guanine = 1.51 eV, Adenine = 0.95 eV, Uracil = 0.80 eV, Thymine = 0.79 eV and Cytosine = 0.56 eV.     

Effect of combined exposure to cadmium and ethanol on regional brain biogenic amine levels in the rat

The effect of ethanol ingestion on regional brain biogenic amine levels in cadmium exposed animals was examined. The rats were given either ethanol (1 g/kg, first week, 5 g/kg, second week and 10 g/kg for rest of the weeks) or cadmium (40 ppm in drinking water) or a combination of both for 8 weeks. Simultaneous exposure to cadmium and ethanol produced a greater elevation of norepinephrine in hypothalamus and mid brain when compared with rats receiving only cadmium. A significant elevation of 5-hydroxy-tryptamine in medulla oblongata was also noticed in cadmium and ethanol treated rats compared to cadmium alone treatment animals. The present results suggest industrial workers consuming alcohol may be more susceptible to cadmium neurotoxicity.     

Repair of DNA containing Fapy.dG and its beta-C-nucleoside analogue by formamidopyrimidine DNA glycosylase and MutY

Fapy.dG is produced in DNA as a result of oxidative stress. Under some conditions Fapy.dG is formed in greater yields than 8-oxodG from a common chemical precursor. Recently, Fapy.dG and its C-nucleoside analogue were incorporated in chemically synthesized oligonucleotides at defined sites. Like 8-oxodG, Fapy.dG instructs DNA polymerase to misincorporate dA opposite it in vitro. The interactions of DNA containing Fapy.dG or the nonhydrolyzable analogue with Fpg and MutY are described. Fpg excises Fapy.dG (K(M) = 2.0 nM, k(cat) = 0.14 min(-1)) opposite dC approximately 17-fold more efficiently than when mispaired with dA, which is misinserted by DNA polymerase in vitro. Fpg also prefers to bind duplexes containing Fapy.dG.dC or beta-C-Fapy.dG.dC compared to those in which the lesion is opposite dA. MutY incises dA when it is opposite Fapy.dG and strongly binds duplexes containing the lesion or beta-C-Fapy.dG. Incision from Fapy.dG.dA is faster than from dG.dA mispairs but slower than from DNA containing 8-oxodG opposite dA. These data demonstrate that Fapy.dG closely resembles the interactions of 8-oxodG with two members of the GO repair pathway in vitro. The similar effects of Fapy.dG and 8-oxodG on DNA polymerase and repair enzymes in vitro raise the question as to whether Fapy.dG elicits similar effects in vivo.     

Cadmium-induced oxidative stress and DNA damage in kidney of pregnant female rats

In the present study, we have investigated the influence of sub-acute treatment with cadmium (Cd) on some parameters indicative of oxidative stress and DNA damage in tissues of pregnant female rats. Pregnant female rats (n=6) were injected subcutaneously, daily with a dose of cadmium chloride of 3 mg/kg body weight (b.w.) from day 6 to day 19 of pregnancy, and they were allowed to deliver normally. MDA level and GPx, CAT and SOD activities were used as markers of oxidative stress in liver and kidney. The 8-oxo-dG level was measured by the HPLC-EC system. Cd treatment increased MDA (+116%, p<0.01) in kidney. Moreover, Cd treatment also decreased CuZn-SOD (-11%, p<0.05) and GSH level (-52%, p<0.05) in kidney. Treated rats displayed an increase of the liver metallothionein (MT) level. Induction of MT in liver was probably implicated in the detoxification of Cd. The high level of Cd (3 mg/kg) used in the present study is partially neutralized by MT in liver, whereas the free fraction could be implicated in the oxidative stress and DNA oxidation observed in kidney. Cd treatment failed to alter 8-oxodGuo, indicating the absence of DNA oxidation in liver; by contrast, the same treatment increased the 8-oxodGuo level (+51%, p<0.05) in the kidney of pregnant female rats, indicating an oxidative stress associated with DNA damage only in kidney.     

Oxidative damage to proteins and DNA in rats exposed to cadmium and/or ethanol

The study was aimed to estimate whether rat's exposure to cadmium (Cd; 50 mg/l in drinking water for 12 weeks) and/or ethanol (EtOH; 5 g/kg b.wt./24 h p.o. for 12 weeks), noted by us to induce oxidative stress and stimulate lipid peroxidation, can cause oxidative damage to proteins and DNA, and whether and to what extent the effects of co-exposure differ from those observed under the treatment with each substance alone. Protein carbonyl groups (PC) and protein thiol groups (PSH) in the serum, liver and kidney, as markers of oxidative protein damage, and 8-hydroxy-2′-deoxyguanosine (8-OHdG) in the serum, as a marker of DNA oxidation, were determined. The exposure to Cd or/and EtOH led to oxidative protein damage (increased PC and decreased PSH concentrations in the serum and/or liver), and to DNA oxidation (increased 8-OHdG concentration in the serum). The effects were more advanced at the co-exposure than at the treatment with each substance alone. The more serious damage to proteins and DNA at the co-exposure to Cd and EtOH seems to be the effect of independent action of both xenobiotics. The results of the present paper together with our recent findings in the same rats seem to indicate that at co-exposure to Cd and EtOH proteins and DNA may be more vulnerable to oxidation than lipids. The paper is the first report suggesting that excessive EtOH consumption during exposure to Cd may increase the risk of health damage via enhancing protein and DNA oxidation.     

Genetic effects of oxidative DNA damages: comparative mutagenesis of the imidazole ring-opened formamidopyrimidines (Fapy lesions) and 8-oxo-purines in simian kidney cells

Fapy.dG and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dG) are formed in DNA by hydroxyl radical damage. In order to study replication past these lesions in cells, we constructed a single-stranded shuttle vector containing the lesion in 5'-TGT and 5'-TGA sequence contexts. Replication of the modified vector in simian kidney (COS-7) cells showed that Fapy.dG is mutagenic inducing primarily targeted Fapy.G-->T transversions. In the 5'-TGT sequence mutational frequency of Fapy.dG was approximately 30%, whereas in the 5'-TGA sequence it was approximately 8%. In parallel studies 8-oxo-dG was found to be slightly less mutagenic than Fapy.dG, though it also exhibited a similar context effect: 4-fold G-->T transversions (24% versus 6%) occurred in the 5'-TGT sequence relative to 5'-TGA. To investigate a possible structural basis for the higher G-->T mutations induced by both lesions when their 3' neighbor was T, we carried out a molecular modeling investigation in the active site of DNA polymerase beta, which is known to incorporate both dCTP (no mutation) and dATP (G-->T substitution) opposite 8-oxo-G. In pol beta, the syn-8-oxo-G:dATP pair showed greater stacking with the 3'-T:A base pair in the 5'-TGT sequence compared with the 3'-A:T in the 5'-TGA sequence, whereas stacking for the anti-8-oxo-G:dCTP pair was similar in both 5'-TGT and 5'-TGA sequences. Similarly, syn-Fapy.G:dATP pairing showed greater stacking in the 5'-TGT sequence compared with the 5'-TGA sequence, while stacking for anti-Fapy.G:dCTP pairs was similar in the two sequences. Thus, for both lesions less efficient base stacking between the lesion:dATP pair and the 3'-A:T base pair in the 5'-TGA sequence might cause lower G-->T mutational frequencies in the 5'-TGA sequence compared to 5'-TGT. The corresponding lesions derived from 2'-deoxyadenosine, Fapy.dA and 8-oxo-dA, were not detectably mutagenic in the 5'-TAT sequence, and were only weakly mutagenic (<1%) in the 5'-TAA sequence context, where both lesions induced targeted A-->C transversions. To our knowledge this is the first investigation using extrachromosomal probes containing a Fapy.dG or Fapy.dA site-specifically incorporated, which showed unequivocally that in simian kidney cells Fapy.G-->T substitutions occur at a higher frequency than 8-oxo-G-->T and that Fapy.dA is very weakly mutagenic, as is 8-oxo-dA.     

Antioxidant enzyme activity and lipid peroxidation in liver of female rats co-exposed to lead and cadmium: effects of vitamin E and Mn2+

The oxidative status of liver of female rats exposed to lead acetate and cadmium acetate either alone or in combination at a dose of 0.05 mg/kg body wt intraperitoneally for 15 days was studied. After the administration of lead alone, the activity of superoxide dismutase (SOD) decreased in liver, whereas no changes were observed in catalase (CAT) activity, and glutathione (GSH) and thiobarbituric acid (TBARS) levels. Cadmium exposure and combined exposure to lead and cadmium led to decrease in GSH content and increased TBARS levels. Moreover, animals exposed to either cadmium alone or in combination with lead showed a decrease in SOD activity and an increase in CAT activity. The in vitro experiments showed that vitamin E failed to restore the antioxidant enzyme activities in metal treated postmitochondrial supernatant fraction of liver. But Mn²⁺ ions protected the mitochondria from lipid peroxidation and could completely restore Mn-superoxide dismutase (Mn-SOD) activity following metal intoxication. The results of this study indicate that despite the ability of lead and cadmium to induce oxidative stress the effect in liver is not intensified by combined exposure to both lead and cadmium. The observed changes in various oxidative stress parameters in the liver of rats co-exposed to lead and cadmium may result from an independent effect of lead and /cadmium and also from their interaction such as changes in metal accumulation and content of essential elements like Cu, Zn and Fe. These results suggest that when lead and cadmium are present together in similar concentrations, cadmium mediates major effects due to its more reactive nature.     

Antioxidant enzyme activity and lipid peroxidation in liver of female rats co-exposed to lead and cadmium: Effects of vitamin E and Mn2+

The oxidative status of liver of female rats exposed to lead acetate and cadmium acetate either alone or in combination at a dose of 0.05?mg/kg body wt intraperitoneally for 15 days was studied. After the administration of lead alone, the activity of superoxide dismutase (SOD) decreased in liver, whereas no changes were observed in catalase (CAT) activity, and glutathione (GSH) and thiobarbituric acid (TBARS) levels. Cadmium exposure and combined exposure to lead and cadmium led to decrease in GSH content and increased TBARS levels. Moreover, animals exposed to either cadmium alone or in combination with lead showed a decrease in SOD activity and an increase in CAT activity. The in vitro experiments showed that vitamin E failed to restore the antioxidant enzyme activities in metal treated postmitochondrial supernatant fraction of liver. But Mn²⁺ ions protected the mitochondria from lipid peroxidation and could completely restore Mn-superoxide dismutase (Mn-SOD) activity following metal intoxication. The results of this study indicate that despite the ability of lead and cadmium to induce oxidative stress the effect in liver is not intensified by combined exposure to both lead and cadmium. The observed changes in various oxidative stress parameters in the liver of rats co-exposed to lead and cadmium may result from an independent effect of lead and /cadmium and also from their interaction such as changes in metal accumulation and content of essential elements like Cu, Zn and Fe. These results suggest that when lead and cadmium are present together in similar concentrations, cadmium mediates major effects due to its more reactive nature.     

Cytoarchitectural alterations in kidney of Wistar rat after oral exposure to cadmium chloride

Male Wistar rats were randomly divided into three groups - A, B and C. A dose of 5 mg and 10 mg of cadmium chloride/kg body weight/day was orally administered to groups B and C, respectively. Rats from group A served as control. Rats were sacrificed on 1st, 2nd, 4th, 6th, and 8th week after initiation of the experiment. Kidneys were removed immediately, fixed in Bouin's fixative, routinely processed and stained with hematoxylin and eosin. The present study showed that the histopathological changes were caused in kidney of rats by cadmium exposure. The changes noticed were mainly - the glomerular swelling (at initial stage), the shrinkage of glomerulus (at later stage), the tubular dilatation, hypertrophy of tubular epithelium, degeneration of glomerulus and renal tubules and deposition of eosin-positive substances in the glomerulus and renal tubules. However, lesions were depended upon the doses and duration of the treatment.     

Probing the configurations of formamidopyrimidine lesions Fapy.dA and Fapy.dG in DNA using endonuclease IV

The formamidopyrimidines Fapy.dA and Fapy.dG are produced in DNA as a result of oxidative stress. These lesions readily epimerize in water, an unusual property for nucleosides. The equilibrium mixture slightly favors the beta-anomer, but the configurational status in DNA is unknown. The ability of endonuclease IV (Endo IV) to efficiently incise alpha-deoxyadenosine was used as a tool to determine the configuration of Fapy.dA and Fapy.dG in DNA. Endo IV incision of the C-nucleoside analogues of Fapy.dA was used to establish selectivity for the alpha-anomer. Incision of alpha-C-Fapy.dA follows Michaelis-Menten kinetics (K(m) = 144.0 +/- 7.5 nM, k(cat) = 0.58 +/- 0.21 min(-1)), but the beta-isomer is a poor substrate. Fapy.dA incision is considerably slower than that of alpha-C-Fapy.dA, and does not proceed to completion. Endo IV incision of Fapy.dA proceeds further upon rehybridization, suggesting that the lesion reequilibrates and that the enzyme preferentially cleaves duplex DNA containing alpha-Fapy.dA. The extent of Fapy.dA incision suggests that the lesion exists predominantly ( approximately 90%) as the beta-anomer in DNA. Endo IV incises Fapy.dG to less than 5% under comparable reaction conditions, suggesting that the lesion exists almost exclusively as its beta-anomer in DNA.     

Tomato-oleoresin supplement prevents doxorubicin-induced cardiac myocyte oxidative DNA damage in rats

Doxorubicin (DOX) is an efficient chemotherapeutic agent used against several types of tumors; however, its use is limited due to severe cardiotoxicity. Since it is accepted that reactive oxygen species are involved in DOX-induced cardiotoxicity, antioxidant agents have been used to attenuate its side effects. To determine tomato-oleoresin protection against cardiac oxidative DNA damage induced by DOX, we distributed Wistar male rats in control (C), lycopene (L), DOX (D) and DOX+lycopene (DL) groups. They received corn oil (C, D) or tomato-oleoresin (5mg/kg body wt. day) (L, DL) by gavage for a 7-week period. They also received saline (C, L) or DOX (4mg/kg body wt.) (D, DL) intraperitoneally at the 3rd, 4th, 5th, and at 6th week. Lycopene absorption was checked by HPLC. Cardiac oxidative DNA damage was evaluated by the alkaline Comet assay using formamidopyrimidine-DNA glycosylase (FPG) and endonuclease III (endo III). Cardiomyocyte levels of SBs, SBs FPG and SBs Endo III were higher in rats from D when compared to other groups. DNA damage levels in cardiomyocytes from DL were not different when compared to C and L groups. The viability of cardiomyocytes from D or DL was lower than C or L groups (p<0.01). Lycopene levels (mean+/-S.D.nmol/kg) in saponified hearts were similar between L (47.43+/-11.78) and DL (49.85+/-16.24) groups. Our results showed: (1) lycopene absorption was confirmed by its cardiac levels; (2) DOX-induced oxidative DNA damage in cardiomyocyte; (3) tomato-oleoresin supplementation protected against cardiomyocyte oxidative DNA damage.     

Biochemical effects of gestational coexposure to lead and cadmium on reproductive performance, placenta, and ovary

Adult virgin 4-day cycling synchronized Charles foster females were treated subcutaneously (0.05 mg/kg body wt/day) with sodium acetate (control), lead acetate or cadmium acetate alone, or both during gestational period, with pretreatment of 5 days prior to mating. There were no alterations in reproductive performance in all metal-treated groups. Implantation enzymes, cathepsin-D and alkaline phosphatase, activity were altered, but no change in the reproductive performance was observed. The key steroidogenic enzymes of ovary and placenta (3beta-HSD and 17beta-HSD), along with gonadal steroids, were affected the most in cadmium and combined treated animals whereas lead-treated animals showed a minimum change compared to the control group. Maximum displacement of zinc bound to metallothionein was more in cadmium and combined treated rats when compared to other metal-treated groups. Biomolecules such as glycogen, protein, RNA, DNA, and protein content were affected in all metal-treated groups, whereas cadmium-treated animals showed greater effect. General parameters of toxicity such as alkaline phosphatase, serum glutamate pyruvate transaminase, and creatinine were altered but were within the normal range. Biochemical effects are correlated with metals accumulated in blood, reproductive tissue such as placenta and ovary.     

Dietary supplementation of vitamin A, C and E prevents p-dimethylaminoazobenzene induced hepatic DNA damage in rats

The preventive effect of antioxidant vitamins A, C, E and their analogues against DNA damage induced by a hepatocarcinogen p-dimethylaminoazobenzene (DAB) was assessed by comet assay. For genotoxicity (DNA damage) study, male albino rats were divided into 11 groups, consisting of four rats each. Group I served as control. Group II to VII received 1, 10, 100, 200, 300 and 400 mg per kg body wt of DAB respectively; group VIII to XI received 500 mg/kg body wt of DAB. They were sacrificed by cervical decapitation 3, 6, 12 and 24 h after treatment; livers were excised immediately and subjected to comet assay to measure DNA damage. To study the effect of vitamins, experiments were conducted on a group of 275 rats divided into 3 sets of 25 rats each. First set served as control; second set received 0.06% DAB and third set received 0.06% DAB, along with analogues of vitamins A, C and E. Rats fed with 0.06% DAB were provided water ad libitum for a period of 4 months, followed by a normal (basal) diet for further 2 months. Vitamins A (10,000-50,000 IU), C (75-1000 mg) and E (50-500 mg) and their analogues were given (per kg body wt) to the third set of rats by gavage route once in a week for a period of 6 months. The DAB induced DNA damage only at the highest tested dose of 500 mg/kg body wt. Administration of high doses of vitamin A acid, L-ascorbic acid and vit. E succinate individually prevented the DNA damage. However, administration of a mixture of these vitamins at low doses prevented the DAB-induced DNA damage, which may be due to their synergistic effect. The results indicate that there is a significant advantage in mixed vitamins therapy at low dose over the treatment with individual vitamins.     

Variable effect of ghrelin administration on pancreatic development in young rats. Role of insulin-like growth factor-1.

Ghrelin, an endogenous ligand of the growth hormone secretagogue receptor, has been primarily isolated from the human and rat stomach. Ghrelin has been shown to stimulate appetite and fat deposition in adult rats and humans. The aim of this study was to investigate the effect of ghrelin administration on pancreatic growth in suckling, weaned and peripubertal seven week old rats. Rats were treated with saline or ghrelin (4, 8 or 16 nmol/kg/dose) intraperitoneally twice a day: suckling rats were treated for 7 or 14 days starting from the first postnatal day, three week old weaned rats and seven weeks old rats were treated for 5 days. Treatment with ghrelin did not affect animal weight in suckling or weaned rats, whereas in young seven week old rats, ghrelin caused a significant increase in body weight. Ghrelin decreased food intake in weaned rats; whereas in seven week old rats, food intake was enhanced. In suckling rats, ghrelin decreased the pancreatic weight, pancreatic amylase content, DNA synthesis and DNA content. In contrast, ghrelin increased pancreatic weight, DNA synthesis, DNA content and amylase content in weaned or young seven week old rats. Pancreatic blood flow was not affected by ghrelin in any group of rats tested. Ghrelin increased serum level of growth hormone in all rats. This effect was weak in suckling rats, higher in weaned and the highest in seven week old animals. Ghrelin did not affect serum level of insulin-like growth factor-1 (IGF-1) in suckling rats. In weaned and in seven week old rats, treatment with ghrelin caused increase in serum level of IGF-1. We conclude that ghrelin reduces pancreatic growth in suckling rats; whereas in weaned and young seven week old animals, treatment with ghrelin increases pancreatic growth. This biphasic effect of ghrelin in young animals on pancreatic growth seems to be related to age-dependent changes of the release of anabolic IGF-1.     

Studies on the replication of the ring opened formamidopyrimidine, Fapy.dG in Escherichia coli

Fapy.dG is produced in DNA as a result of oxidative stress from a precursor that also forms OxodG. Bypass of Fapy.dG in a shuttle vector in COS-7 cells produces G --> T transversions slightly more frequently than does OxodG (Kalam, M. A., et al. (2006) Nucleic Acids Res. 34, 2305). The effect of Fapy.dG on replication in Escherichia coli was studied by transfecting M13mp7(L2) bacteriophage DNA containing the lesion within the lacZ gene in 4 local sequence contexts. For comparison, experiments were carried out side-by-side on OxodG. The efficiency of lesion bypass was determined relative to that of a genome containing native nucleotides. Fapy.dG was bypassed less efficiently than OxodG. Bypass efficiency of Fapy.dG and OxodG increased modestly in SOS-induced cells. Mutation frequencies at the site of the lesions in the originally transfected genomes were determined using the REAP assay (Delaney, J. C., Essigmann, J. M. (2006) Methods Enzymol. 408, 1). G --> T transversions were the only mutations observed above background when either Fapy.dG or OxodG was bypassed. OxodG mutation frequencies ranged from 3.1% to 9.8%, whereas the G --> T transversion frequencies observed upon Fapy.dG bypass were T transversions.     

Hepatoprotective effect of aqueous extract of Phyllanthus niruri on nimesulide-induced oxidative stress in vivo

Nimesulide (NIM), an atypical non-steroidal anti-inflammatory drug (NSAID) is also used as analgesic. In the present study, we evaluated its effect on the prooxidant-antioxidant system of liver and the hepatoprotective potential of aqueous extract of the herb Phyllanthus niruri (PN) on NIM-induced oxidative stress in vivo using a murine model, by determining the activities of hepatic anti-oxidant enzymes superoxide dismutase (SOD) and catalase (CAT), levels of reduced glutathione (GSH) and lipid peroxidation (expressed as malonaldialdehyde, MDA). Aqueous extract of PN at a dose of 50 or 100 mg/kg body wt was administered either intraperitoneally or orally for 7 days, before NIM administration at a dose of 8 mg/kg body wt twice daily for 7 days in mice. Animals were sacrificed 24 h after administration of final dose of NIM. In another set of experiments, both aqueous extract of PN (at a dose of 50 or 100 mg/kg body wt) and NIM (8 mg/kg body wt) were administered simultaneously for 7 days. Animals were sacrificed 24 h after administration of final dose of the extract and NIM, liver tissues were collected, and the activities of SOD and CAT and levels of GSH and lipid peroxidation end-product (as MDA), were determined from the livers of all the experimental animals. Appropriate NIM control was maintained for all sets of experiments. NIM administration (8 mg/kg body wt) for 7 days caused significant depletion of the levels of SOD, CAT and reduced GSH, along with the increased levels of lipid peroxidation. Intraperitoneal administration of the extract at a dose of 50 mg/kg body wt for 7 days,. prior to NIM treatment, significantly restored most of the NIM-induced changes and the effect was comparable to that obtained by administering 100 mg/kg body wt of the extract orally. Thus, results suggested that intraperitoneal administration of the extract could protect liver from NIM-induced hepatic damage more effectively than oral administration. Antioxidant property of the aqueous extract of PN was also compared with that of a known potent antioxidant, vitamin E. The PN extract at a dose of 100 mg/kg body wt along with NIM was more effective in suppressing the oxidative damage than the PN extract at a dose of 50 mg/kg body wt. Results suggested that beneficial effect of the aqueous extract of PN, probably through its antioxidant property, might control the NIM-induced oxidative stress in the liver.     

The protection role of heat shock protein 70 (HSP-70) in the testes of cadmium-exposed rats

Cadmium (Cd) is an environmental carcinogenic pollutant known to inactivate several proteins involved in DNA repair systems while at the same time creating an oxidative stress that can result in additional DNA lesions. The testis and the lung are the target organs for cadmium carcinogenesis. Increased production of oxidants in vivo can cause damage to intracellular macromolecules such as DNA, proteins and lipids, which in turn lead to oxidative injury. So, this investigation aimed to evaluate the protective role of L-Carnitine through up regulation of HSPs against DNA damage induced by cadmium chloride. The current study was carried out on forty adult male rats, each with average weight 220-250g., were divided into 4 equal groups. 1(st) group was received saline solution (0.5 ml/100 g body weight) and kept as control. 2(nd) group was received 500mg / kg body weight L-Carnitine intraperitoneally (IP). 3(rd) group was administered 1.2 mg cadmium chloride IP. 4(th) group was received both cadmium chloride and L-Carnitine simultaneously. The comet assay parameters showed significantly increased HSP70 and DNA damage in testis cells after 10 and 56 days in the third group. Meanwhile, HSP70 showed significantly decreased levels after 10 days and 56 days in the fourth group after L-Carnitine treatment simultaneously with cadmium chloride. The results of the present study demonstrate a damaging effect of cadmium chloride on DNA of the testis cells (with low stress response). This damaging effect increases the synthesis of HSP70 that upregulated by L-Carnitine treatment and showed ameliorative effect of the cells for recovery.     

The role of cernitins in cadmium effect on the absorption processes in rat small intestine

The effect of long-term intoxication of cadmium (administered subcutaneously in a dose of 1 mg Cd/kg of body weight once a week for one month) on the absorption of water, sodium, potassium, glucose, glycine and thiamine in the small intestine of rats was investigated. In addition, the influence of cernitins (special pollen extract) on the action of cadmium intoxication was tested. The cernitins were given by stomach pump in the form of an aqueous solution of Pollitabs Sport tablets in a dose of 1.5 mg of cernitin T-60 and 0.075 mg of cernitin GBX per individual twice a week for two weeks or four weeks according to the group of animals tested. The results indicated that long-term administration of cadmium increased the intestinal absorption of all tested substances. Meanwhile, the application of cernitins reduced the effects of cadmium intoxication upon intestinal absorption and the processes of absorption was close to normal.     

The modulatory influence of p-methoxycinnamic acid, an active rice bran phenolic acid, against 1,2-dimethylhydrazine-induced lipid peroxidation, antioxidant status and aberrant crypt foci in rat colon carcinogenesis

We investigated the chemopreventive effect of p-methoxycinnamic acid (p-MCA), an active phenolic acid of rice bran, turmeric, and Kaemperfia galanga against 1,2-dimethylhydrazine-induced rat colon carcinogenesis. Male albino Wistar rats were randomly divided into six groups. Group 1 consisted of control rats that received a modified pellet diet and 0.1% carboxymethyl cellulose. The rats in Group 2 received a modified pellet diet supplemented with p-MCA [80 mg/kg body weight (b.wt.) post-orally (p.o.)] everyday. The rats in Groups 3-6 received 1,2-dimethylhydrazine (DMH) (20 mg/kg b.wt.) via subcutaneous injections once a week for the first 4 weeks; additionally, the rats in Groups 4, 5 and 6 received p-MCA at doses of 20, 40 and 80 mg/kg b.wt./day p.o., respectively, everyday for 16 weeks. The rats were sacrificed at the end of the experimental period of 16 weeks. The DMH-treated rats exhibited an increased incidence of aberrant crypt foci (ACF) development; an increased crypt multiplicity; decreased concentrations of tissue lipid peroxidation markers such as thiobarbituric acid reactive substances (TBARS), conjugated dienes (CD) and lipid hydroperoxides (LOOH); decreased levels of tissue enzymic antioxidants such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR); and decreased levels of non-enzymic antioxidants such as reduced glutathione (GSH) and vitamins C, E and A in the colon. Supplementation with p-MCA significantly reversed these changes and significantly inhibited the formation of ACF and its multiplicity. Thus, our findings demonstrate that p-MCA exerts a strong chemopreventive activity against 1,2-dimethylhydrazine-induced colon carcinogenesis by virtue of its ability to prevent the alterations in DMH-induced circulatory and tissue oxidative stress and preneoplastic changes. p-MCA was more effective when administered at a dose of 40 mg/kg b.wt. than at the other two doses tested.     

Imidazole ring-opened DNA purines and their biological significance

Fragmentation of purine imidazole ring and production of formamidopyrimidines in deoxynucleosides (Fapy lesions) occurs upon DNA oxidation as well as upon spontaneous or alkali-triggered rearrangement of certain alkylated bases. Many chemotherapeutic agents such as cyclophosphamide or thiotepa produce such lesions in DNA. Unsubstituted FapyA and FapyG, formed upon DNA oxidation cause moderate inhibition of DNA synthesis, which is DNA polymerase and sequence dependent. Fapy-7MeG, a methylated counterpart of FapyG-, a efficiently inhibits DNA replication in vitro and in E.coli, however its mutagenic potency is low. This is probably due to preferential incorporation of cytosine opposite Fapy-7MeG and preferential extension of Fapy-7MeG:C pair. In contrast, FapyA and Fapy-7MeA possess miscoding potential. Both lesions in SOS induced E.coli preferentially mispair with cytosine giving rise to A-->G transitions. Fapy lesions substituted with longer chain alkyl groups also show simult aneous lethal and mutagenic properties. Fapy lesions are actively eliminated from DNA by repair glycosylases specific for oxidized purines and pyrimidines both in bacteria and eukaryotic cells. Bacterial enzymes include E.coli formamidopyrimidine-DNA-glycosylase (Fpg protein), endonuclease III (Nth protein) and endonuclease VIII (Nei protein).