Toxicity of Jatropha curcas phorbol esters in mice

Phorbol esters are the main toxins in Jatropha curcas seed and oil. The aim of this study was to assess the acute toxicity of phorbol esters given by intragastric administration and to determine the LD₅₀ for Swiss Hauschka mice. The LD₅₀ and 95% confidence limits for male mice were 27.34 mg/kg body mass and 24.90–29.89 mg/kg body mass; and the LD₅ and LD₉₅ were 18.87 and 39.62 mg/kg body mass, respectively. The regression equations between the probits of mortalities (Y) and the log of doses (D) was Y = −9.67 + 10.21 log (D). Histopathological studies on the organs from the dead mice showed: (1) no significant abnormal changes in the organs at the lowest dose (21.26 mg/kg body mass) studied, (2) prominent lesions mainly found in lung and kidney, with diffused haemorrhages in lung, and glomerular sclerosis and atrophy in kidney at doses ?32.40 mg/kg body mass, and (3) multiple abruption of cardiac muscle fibres and anachromasis of cortical neurons at the highest dose of 36.00 mg/kg body mass. The results obtained would aid in developing safety measures for the Jatropha based biofuel industry and in exploiting the pharmaceutical and agricultural applications of phorbol esters.     

Modulatory role of Emblica officinalis against alcohol induced biochemical and biophysical changes in rat erythrocyte membranes

This study investigated the protective effect of Emblica officinalis against alcohol-induced biochemical and biophysical changes in rat erythrocyte membranes. Thirty-two male rats were divided into four groups (n = 8 in each group): control (C), alcohol (A), alcohol plus Emblica fruit extract (A + EFE) and Emblica fruit extract (EFE) alone. Administration of twenty percent alcohol (5 g/kg body weight) to rats significantly increased cholesterol/phospholipid (C/P) ratio, lipid peroxidation and the activities of Na⁺/K⁺ and Mg²⁺ ATPases in erythrocyte membranes as well as augmented nitric oxide (NO) levels. However, membrane fluidity studies using the fluorescent probe DPH (1,6 diphenyl 1,3 hexatriene) reveals that alcohol administration significantly (p < 0.05) increased membrane anisotropic values and altered membrane individual phospholipid content. Administration of EFE (250 mg/kg body weight) to alcoholic rats resulted in significant (p < 0.05) reduction of NO levels, erythrocyte membrane lipid peroxidation, C/P ratio, activities of Na⁺/K⁺ and Mg²⁺ ATPases and fluorescent anisotropic values. Further, EFE administration to alcoholic rats beneficially modulated membrane properties as evidenced from the contents of total phospholipids as well individual phospholipid classes. The tannoid principles present in Emblica offers protection against alcohol induced adverse effects in rats.     

Influence of GSTs, CYP2E1 and mEH polymorphisms on 1, 3-butadiene-induced micronucleus frequency in Chinese workers

1,3-butadiene (BD) has been classified as a human carcinogen, however, the relationship between chromosomal damage and its metabolic polymorphisms is not clear. The present study used the CBMN assay to detect chromosomal damage in the peripheral lymphocytes of 166 exposed workers and 41 non-exposed healthy individuals. PCR and PCR-RFLP were applied to detect GSTT1, GSTM1, CYP2E1 c1c2 and mEH Tyr113His, His139Arg polymorphisms. The results demonstrated that the micronucleus (MN) frequency of the exposed workers was significantly higher than controls (P < 0.01). Among the exposed workers, the individuals with high BD exposures are more susceptible to chromosomal damage than those with low exposures (FR = 1.30, 95% CI 1.14-1.53; P < 0.05). Gender-difference was also found in our study: males got lower micronucleus frequency than females. Workers who carried the genotypes of GSTM1 (+), CYP2E1 (c1c2/c2c2) and mEH intermediate (I) group had significantly higher MN frequency than those carrying the genotypes of GSTM1 (−) (FR = 1.29, 95% CI 1.05-1.59; P < 0.05), CYP2E1 (c1c1) (FR = 1.55, 95% CI 1.24-1.93; P < 0.01) or mEH high (H) group (FR = 1.57, 95% CI 1.08-2.34; P < 0.05), respectively. Our data indicated that the current BD exposure level could cause significantly higher MN frequency in workers than controls. Polymorphisms of GSTM1, CYP2E1 and mEH are susceptible to altered chromosome damage.     

In vitro antioxidant and in vivo anti-inflammatory potential of crude polysaccharide from Turbinaria ornata (Marine Brown Alga)

Water-soluble crude polysaccharide from a brown alga Turbinaria ornata (TCP) was screened for its antioxidant and anti-inflammatory potential. The major functional groups of polysaccharide were analyzed by Fourier Transmission-Infra Red (FT-IR). In vitro free radical quenching and total antioxidant activity of TCP was investigated by 1, 1-diphenyl-2-picryl hydrazyl (DPPH), nitric oxide (NO) scavenging, lipid peroxidation (LPO) inhibition and ABTS radical assay. Evaluation of anti-inflammatory activity of TCP was performed using carrageenan-induced paw edema in rats and vascular permeability test in mice. Phytochemical analysis of TCP showed the presence of carbohydrates, proteins and polyphenols further, the FT-IR analysis of TCP showed the presence of functional groups of sugar moiety, uronic acids and sulfate groups. TCP showed maximum LPO, NO and DPPH inhibition of 78.04%, 38.82% and 80.21% at a concentration of 1000, 125 and 500 μg/ml respectively. Oral administration of TCP (2.5, 5, 10, 20 mg/kg) reduced the paw edema considerably (p < 0.05) in a dose dependent manner compared to carrageenan induced rats. Similarly, oral administration of TCP (3, 10, 30 mg/kg) evoked a significant (p < 0.05) dose dependent inhibitory effect on vascular permeability in mice. Altogether, these results suggest that the crude polysaccharide of T.ornata could be considered as a potential antioxidant and anti-inflammatory agent.     

The Fusarium mycotoxins enniatins and beauvericin cause mitochondrial dysfunction by affecting the mitochondrial volume regulation,oxidative phosphorylation and ion homeostasis

The mechanisms of cell toxicity of mycotoxins of the enniatin family produced by Fusarium sp. enniatin B, a mixture of enniatin homologues (3% A, 20% A₁, 19% B, 54% B1) and beauvericin, were investigated. In isolated rat liver mitochondria, exposure to submicromolar concentrations of the enniatin mycotoxins depleted the mitochondrial transmembrane potential, uncoupled oxidative phosphorylation, induced mitochondrial swelling and decreased calcium retention capacity of the mitochondria. The mitochondrial effects were strongly connected with the potassium (K⁺) ionophoric activity of the enniatins. The observed enniatins induced K⁺ uptake by mitochondria. This shows that the enniatins acted as ionophores highly selective for potassium ions. The effects were observed in potassium containing media whereas less or no effect remained to be observed when K⁺ was partially or totally replaced by isomolar concentrations of Na⁺. The rank order of enniatin induced mitochondrial impairment was beauvericin > enniatin mixture > enniatin B. Exposure to the enniatins depleted the mitochondrial membrane potential also in intact human neural (Paju), murine insulinoma (Min-6) cells as well as boar spermatozoa. Exposure to enniatin B in media with physiological (4 mM) or low (<1 mM) but not in high (60 mM) external concentration of K⁺ induced hyperpolarization of the spermatozoal plasma membrane indicating enniatin that catalysed efflux of the cytosolic K⁺ ions. These results indicate that the cellular toxicity targets of the enniatin mycotoxins are the mitochondrion and the homeostasis of potassium ions.     

Induction of hsp70, hsp60, hsp83 and hsp26 and oxidative stress markers in benzene, toluene and xylene exposed Drosophila melanogaster: Role of ROS generation

Exposure to benzene, toluene and xylene in the human population may pose a health risk. We tested a working hypothesis that these test chemicals cause cellular toxicity to a non-target organism, Drosophila melanogaster. Third instar larvae of D. melanogaster transgenic for hsp70, hsp83 and hsp26 and Oregon R⁺ strain were exposed to 1.0-100.0 mM benzene, toluene and xylene for 2-48 h to examine the heat shock proteins (hsps), ROS generation, anti-oxidant stress markers and developmental end points. The test chemicals elicited a concentration- and time-dependent significant (p < 0.01) induction of the hsps in the exposed organism in the order of hsp70 > hsp83 ≥ hsp26 as evident by β-galactosidase activity after 24 h. RT-PCR amplification studies in Oregon R⁺ larvae revealed a similar induction pattern of these genes along with hsp60 in the order of hsp70 > hsp60 > hsp26 ≥ hsp83. Under similar experimental conditions, a significant induction of ROS generation and oxidative stress markers viz. superoxide dismutase, catalase, glutathione S-transferase, thioredoxin reductase, glutathione, malondialdehyde and protein carbonyl content was observed. Sub-organismal response was propagated towards organismal response i.e., a delay in the emergence of flies and their reproductive performance. While hsp70 was predominantly induced in the organism till 24 h of treatment with the test chemicals, a significant or insignificant regression of Hsp70 after 48 h was concurrent with a significant induction (p < 0.01) of hsp60 > hsp83 ≥ hsp26 in comparison to the former. A significant positive correlation was observed between ROS generation and these hsps in the exposed organism till 24 h and a negative correlation between ROS generation and hsp70 in them after 48 h indicating a modulatory role of ROS in the induction of hsps. The study suggests that among the tested hsps, hsp70 may be used as an early bioindicator of cellular toxicity against benzene, toluene and xylene and D. melanogaster as an alternative animal model for screening the risk posed by environmental chemicals.     

In vitro pharmacokinetic/pharmacodynamic activity of NXL103 versus clindamycin and linezolid against clinical Staphylococcus aureus and Streptococcus pyogenes isolates

NXL103 (linopristin/flopristin, 30/70) is a novel oral streptogramin combination with activity against a large variety of multidrug-resistant Gram-positive pathogens. The objective of this study was to evaluate the in vitro activity of NXL103 in comparison with oral comparators (clindamycin and linezolid). Six clinical isolates [four meticillin-resistant Staphylococcus aureus (MRSA) and two Streptococcus pyogenes] were exposed for 48 h in an in vitro pharmacokinetic/pharmacodynamic (PK/PD) model at a starting inoculum of ca. 10⁶ colony-forming units (CFU)/mL. Antimicrobial simulations included NXL103 500 mg every 12 h, linezolid 600 mg every 12 h and clindamycin 450 mg every 6 h. Bactericidal and static effects were defined as ≥3 log₁₀ and <3 log₁₀ CFU/mL kill from the starting inoculum, respectively. Experiments were performed in duplicate to ensure reproducibility, and differences between regimens were evaluated by analysis of variance (ANOVA) with Tukey's post-hoc test. NXL103 exhibited lower minimum inhibitory concentrations than comparators, with values ≤0.06 mg/L for S. pyogenes and 0.125-0.25 mg/L for MRSA isolates. In the PK/PD model, NXL103 demonstrated significantly better activity than linezolid and clindamycin (P < 0.05), achieving sustained bactericidal activity within <2 h against S. pyogenes strains and between 7.3-32 h against MRSA isolates. In contrast, linezolid only exhibited a static effect, whereas clindamycin achieved 3 log₁₀ kill at 6 h against the unique clindamycin-susceptible S. pyogenes strain evaluated. In conclusion, at therapeutic concentrations NXL103 exhibits promising activity against both MRSA and S. pyogenes strains, including clindamycin-resistant organisms. Further in vitro and in vivo experiments are warranted to explore the therapeutic benefit of NXL103 for the treatment of Gram-positive skin and soft-tissue infections.     

Potential analgesic,anti-inflammatory and antioxidant activities of hydroalcoholic extract of Areca catechu L. nut

The hydroalcoholic extract of Areca catechu L. (ANE) nut was screened for its analgesic, anti-inflammatory and in vitro antioxidant potential. Three doses of ANE (250, 500 and 1000 mg/kg orally) were tested for analgesic and anti-inflammatory activities. Evaluation of analgesic activity of ANE was performed using hot plate and formalin test in mice. ANE showed maximum increase in hot plate reaction time (56.27%, p < 0.01), while reduced the duration of licking/biting behaviors in first (39.45%, p < 0.05) and second (92.71%, p < 0.01) phases of the formalin test indicating significant analgesic activity. ANE reduced the paw edema considerably (86.79% inhibition after 24 h, p < 0.01) in dose-dependent manner compared to carrageenan-induced rat. In addition, in vitro antioxidant activity of ANE was investigated by total phenolic content (TPC) and hydrogen peroxide assay. The IC₅₀ observed in hydrogen peroxide assay was 83.14 μg/ml and TPC 120.56 ± 21.09 mg QE/g. Altogether, these results suggest that the hydroalcoholic extract of Areca catechu could be considered as a potential analgesic, anti-inflammatory and antioxidant agent.     

Effect of heparin treatment on the expression and activity of different ion-motive P-type ATPase isoforms from mouse extensor digitorum longus muscle during degeneration and regeneration after Bothrops jararacussu venom injection

Ca²⁺ ions are essential to myonecrosis, a serious complication of snake envenomation, and heparin seems to counteract this effect. We investigated the effect of local injection of Bothrops jararacussu venom in mouse fast-twitch extensor digitorum longus (EDL) muscle, without or with heparin, on functional/molecular alterations of two central proteins involved in intracellular Ca²⁺ homeostasis, sarco(endo)plasmic reticulum Ca²⁺-ATPase (SERCA) and Na⁺/K⁺-ATPase. EDL-specific SERCA1 isoform expression dropped significantly just after venom administration (up to 60% compared to control EDL values at days 1 and 3; p < 0.05) while SERCA2 and Na⁺/K⁺-ATPase α₁ isoform expression increased at the same time (3-6- and 2-3-fold, respectively; p < 0.05). Although not significant, Na⁺/K⁺-ATPase α₂ isoform followed the same trend. Except for SERCA2, all proteins reached basal levels at the 7th day. Intravenous heparin treatment did not affect these profiles. Ca²⁺-ATPase activity was also decreased during the first days after venom injection, but here heparin was effective to reinstate activity to control levels within 3 days. We also showed that B. jararacussu venom directly inhibited Ca²⁺-ATPase activity in a concentration-dependent manner. Our results indicate that EDL SERCA and Na⁺/K⁺-ATPase are importantly affected by B. jararacussu venom and heparin has protective effect on activity but not on protein expression.     

Genetic variations of CYP2B6 gene were associated with plasma BPDE-Alb adducts and DNA damage levels in coke oven workers

Polycyclic aromatic hydrocarbons (PAHs), the main components of coke oven emissions, can induce activation of cytochrome P450 (CYP) enzymes, which metabolize PAHs and result in DNA damage by forming adducts. This study was designed to know whether genetic variants of CYP genes are associated with plasma benzo[a]pyrene-7,8-diol-9,10-epoxide-albumin (BPDE-Alb) adducts and DNA damage in coke oven workers. In this study, 298 workers were divided into four groups according to the environmental PAHs exposure levels. The concentrations of plasma BPDE-Alb adducts were detected by reverse-phase high-performance liquid chromatography and the DNA damage levels were measured using comet assay. Twelve tag single nucleotide polymorphisms (tagSNPs) of 4 CYP genes were selected and genotyped by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. In the top group, workers with CYP2B6 rs3760657GA genotype have lower BPDE-Alb adducts and DNA damage levels than those with rs3760657GG genotype (P < 0.05). In the control group, the DNA damage levels of subjects with CYP1A1 rs4646421AA or GA + AA genotypes were lower than those with GG genotype (P < 0.05). However, no such effects were shown for the other tagSNPs. These results suggested that genetic variations of CYP2B6 might be associated with low BPDE-Alb adducts and DNA damage levels in worker with high exposure to PAHs.     

Anti-inflammatory, antinociceptive and antioxidant activities of the endemic Soqotraen Boswellia elongata Balf. f. and Jatropha unicostata Balf. f. in different experimental models

In the present study, the two endemic Soqotraen plants Boswellia elongata and Jatropha unicostata were investigated for their anti-inflammatory, antinociceptive and antioxidant potential. To assess the anti-inflammatory and antinociceptive activities, two concentrations of each extract (200 and 400 mg/kg, p.o.) were tested in carrageenan-induced rat paw edema, cotton pellet granuloma in rats, acetic acid-induced abdominal writhing and hot-plate test model in mice. Moreover, the antioxidant activity was determined in vitro, using scavenging activity of DPPH radical and β-carotene-linoleic acid assays. Both plants produced significant (P < 0.05-0.01) anti-inflammatory and antinociceptive effects; however the results suggest that B. elongata possesses the highest activities. B. elongata and J. unicostata at (400 mg/kg) reduced the paw edema considerably (82% and 53%) and the weight of cotton pellet granuloma (51% and 32%), respectively. Furthermore, they diminished the abdominal constriction induced by acetic acid with a 67% and 41% inhibition respectively, and prolonged significantly the reaction time of animal with relatively extended duration of stimulation. In addition, both plants showed considerable antioxidant activity in both assays. These results clearly confirmed the traditional anti-inflammatory indication of B. elongata and suggest that B. elongata could be a potential source for anti-inflammatory, antinociceptive and antioxidant agents.     

Effects of Thai Musa species on prevention of UVB-induced skin damage in mice

The effects of oral administration of Musa sapientum and Musa suerier on prevention of UVB induced skin damages were investigated in male ICR mice. Animals were orally administered 50 mg/day ascorbic acid, or M. sapientum or M. suerier’s fruit pulps at dose of 0.5, 1 or 1.5 mg/g body weight/day for 12 weeks. Concurrently, the shaved backs of animals were irradiated with UVB for 12 weeks. The intensity of irradiation was progressively increased, from 54 mJ/cm² per exposure at week 1–126 mJ/cm² at week 11. A significant decrease (p < 0.05) in skin elasticity (from 0.82 ± 0.02 to 0.42 ± 0.09) and total glutathione (from (193.6 ± 18.7 to 152.7 ± 7.8 ng/mg protein) as compared with the control group (water-administered UVB-irradiated mice) was observed after 12 weeks of UVB exposure. When l-ascorbic acid (0.72 ± 0.01) or 1 mg/g body weight/day M. suerier (0.84 ± 0.06) were administered to UVB-irradiated mice, the reduction in skin elasticity was significantly inhibited (p < 0.05). Moreover, the significant increase (p < 0.05) in level of total glutathione was found in these groups (220.8 ± 13.3 ng/mg protein for l-ascorbic acid and 224.9 ± 20.1 ng/mg protein for M. suerier). These findings suggest the potential effect of daily consumption of M. suerier on prevention of skin damage from repeated UVB exposure.     

Toxicities of destruxins against Bemisia tabaci and its natural enemy, Serangium japonicum

The bioactivities of destruxins against whitefly, Bemisia tabaci and its natural enemy, ladybird beetle Serangium japonicum were evaluated. Destruxins A and B (DA and DB) showed insignificant ovicidal, oviposition deterrent and systemic insecticidal activities to B. tabaci; however, DA and DB had certain contact virulence to its nymphs. The LC₅₀ values of DA at 120 h to 2nd, 3rd and 4th instars were 89.8 (95% confidence interval as 85.4-94.4), 199.3 (187.7-211.5) and 270.7 (251.5-291.5) mg/L, while the LC₅₀s of DB at 120 h were 96.5 (92.0-101.2), 216.7 (203.0-231.2), 359.4 (326.6-395.4) mg/L, respectively. In addition, DA exhibited moderate acute contact toxicities towards S. japonicum, the LC₅₀s at 48 h were 165.4 (132.3-229.4) and 192.5 (148.1-289.2) mg/L for 4th instar larvae and adults. Furthermore, the results from experiments of residual toxicities of DA towards mortalities of 4th instar larvae and adults, pupation rate, emergence rate, average number of egg/female and hatching rate suggested that DA had minimal effects to the ladybird beetle. Generally, the toxicity decreased about 50% from 1st to 3rd-5th day of post-treatment. Specially, the residual toxicity at 50 mg/L and the 7th day post-treatment was down to a value not differing significantly from the control.     

Caffeine-induced inhibition of the activity of glutamate transporter type 3 expressed in Xenopus oocytes

Caffeine has been known to trigger seizures, however, the precise mechanism about the proconvulsive effect of caffeine remains unclear. Glutamate transporters play an important role to maintain the homeostasis of glutamate concentration in the brain tissue. Especially, dysfunction of excitatory amino acid transporter type 3 (EAAT3) can lead to seizures. We investigated the effects of caffeine on the activity of EAAT3 and the involvement of protein kinase C (PKC) and phosphatidylinositol 3-kinase (PI3K). Rat EAAT3 was expressed in Xenopus oocytes by injecting EAAT3 mRNA. l-Glutamate (30 μM)-induced inward currents were recorded via the two-electrode voltage clamp method. Caffeine decreased EAAT3 activity in a dose-dependent manner. Caffeine (30 μM for 3 min) significantly reduced V_max, but did not alter K_m value of EAAT3 for glutamate. When preincubated oocytes with phorbol-12-myristate-13-acetate (PMA, a PKC activator) were exposed to caffeine, PMA-induced increase in EAAT3 activity was abolished. Two PKC inhibitors (chelerythrine and staurosporine) significantly reduced basal EAAT3 activity. Whereas, there were no significant differences among the PKC inhibitors, caffeine, and PKC inhibitors + caffeine groups. In similarly fashion, wortmannin (a PI3K inhibitor) significantly decreased EAAT3 activity, however no statistical differences were observed among the wortmannin, caffeine, and wortmannin + caffeine groups. Our results demonstrate that caffeine attenuates EAAT3 activity and this reducing effect of caffeine seems to be mediated by PKC and PI3K.     

Protective effects of a polysaccharide from Hizikia fusiformis against ethanol toxicity in rats

Hizikia fusiformis is an edible brown alga that is widely consumed in Korea, Japan, and China and possesses a number of potentially beneficial compounds, including antioxidants and anticoagulants. No reports have investigated potential H. fusiformis protectants against ethanol-induced peptic injury. We extracted a polysaccharide from H. fusiformis (Hf–PS-1) that exhibited protective effects against ethanol-induced peptic injury and related mechanisms in rats. Experimental animals were divided into three groups: control, ethanol-only, and ethanol + Hf–PS-1. The ethanol-only group exhibited decreased levels of total glutathione (GSH) and increased levels of jun N-terminal kinase (JNK) phosphorylation relative to the control group, whereas levels were significantly increased and decreased, respectively, in the ethanol + Hf–PS-1 group. The ethanol-only group also exhibited increased levels of extracellular signal-regulated kinase 1/2 (ERK 1/2) phosphorylation relative to the control group; these levels were not significantly different in the ethanol + Hf–PS-1 group. Hf–PS-1 appeared to reduce ethanol-induced gastric injury. Therefore, we suggest that Hf–PS-1 could protect against ethanol-induced peptic ulcers primarily through a mechanism associated with the inhibition of JNK activation.     

Assessment of a dry extract from milk thistle (Silybum marianum) for interference with human liver cytochrome-P450 activities

The effect of a standardised dry extract from Silybum marianum (HEPAR-PASC®) on the enzyme kinetics of cytochrome-P450 isoenzymes (CYP) was investigated with primary human hepatocytes and human liver microsomes in order to assess the potential for drug-drug interactions. A cytotoxic effect on hepatocytes was observed at concentrations at and above 50 μg/ml. The EC₅₀ value was calculated to be 72.0 μg/ml. Therefore, the chosen test concentrations for CYP induction on human hepatocytes were 50, 10, and 1.5 μg/ml, which allowed for interpretation of the clinical significance of the data with a range of 50-1-fold c_max at maximal recommended doses. No induction was observed at the lowest concentration of 1.5 μg/ml, which is close to c_max. The extract did not induce CYP 3A4 at any of the tested concentrations. A low or marginal induction of 1A2, 2B6, and 2E1 at the maximum concentration of 50 μg/ml was observed. CYP inhibition on human microsomes was tested at concentrations of 150, 15, and 1.5 μg/ml. No or minor CYP inhibition was observed for all CYPs tested at the lowest concentration of 1.5 μg/ml, i.e. CYPs 1A2, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, 2E1, and 3A4. At concentrations of 15 and 150 μg/ml the extract significantly inhibited CYP 2B6, 2C8, 2C9, 2C19, 2E1, and 3A4. In these cases, K_i values were determined. All K_i values exceeded c_max by at least a factor of 10-fold. According to FDA regulations 1 > c_max/K_i > 0.1 indicates, that drug-drug interactions are possible for CYPs 2C8, and 2C9, but not likely, and are remote for CYPs 2C19, 2D6, and 3A4.     

Genetic polymorphisms in hMTH1, hOGG1 and hMYH and risk of chronic benzene poisoning in a Chinese occupational population

Oxidative damage to DNA induced by benzene is an important mechanism of its genotoxicity, which leads to chronic benzene poisoning (CBP). Therefore, genetic variation in DNA repair genes may contribute to susceptibility to CBP in the exposed population. We hypothesized that single nucleotide polymorphisms (SNPs) in hMTH1, hOGG1 and hMYH genes are associated with risk of CBP. We genotyped SNPs at codon 83 of hMTH1, codon 326 of hOGG1, and codon 324 of hMYH in 152 CBP patients and 152 healthy workers occupationally exposed to benzene without poisoning manifestations. The genotypes were determined by polymerase chain reaction-restrained fragment length polymorphism (PCR-RFLP) technique. There were 2.51-fold [adjusted odds ratio (OR_adj), 2.51; 95% CI, 1.14-5.49; P = 0.02] and 2.49-fold (OR_adj, 2.49; 95% CI: 1.52-4.07; P < 0.01) increased risk of CBP for individuals carrying genotypes of hMTH1 83Val/Met + Met/Met and hOGG1 326Cys/Cys, respectively. Compared with individuals carrying genotypes of hOGG1 326Cys/Cys and hMYH 324His/His at the same time, there was a 0.33-fold (OR_adj, 0.33; 95% CI: 0.15-0.72; P < 0.05) decreased risk of CBP for those with genotypes of hOGG1 326Ser/Cys + Ser/Ser and hMYH 324His/Gln + Gln/Gln. In the smoking group, there was a 0.15-fold (OR_adj, 0.15; 95% CI, 0.03-0.68; P = 0.01) decreased risk of CBP for subjects carrying genotypes of hMYH 324His/Gln + Gln/Gln compared with those of genotype of hMYH 324His/His. Therefore, our results suggested that polymorphisms at codons 83 of hMTH1 and codon 326 of hOGG1 might contribute to CBP in a Chinese occupational population.     

Presynaptic action of Bothriopsis bilineata smargadina (forest viper) venom in vitro

In this work, we examined the neuromuscular activity of Bothriopsis bilineata smargadina (forest viper) venom in vertebrate isolated nerve-muscle preparations. In chick biventer cervicis preparations the venom caused concentration-dependent (0.1-30 μg/ml) neuromuscular blockade that was not reversed by washing, with 50% blockade occurring in 15-90 min. Muscle contractures to exogenous acetylcholine and KCl were unaffected by venom, but there was a slight increase in creatine kinase release after 120 min (from 80 ± 15 to 206 ± 25 U/ml, n = 6, p < 0.05). In mouse phrenic nerve-diaphragm preparations, the venom (1, 10 and 30 μg/ml) produced marked facilitation (∼120% increase above basal) at the highest concentration followed by neuromuscular blockade; the effects at lower concentrations were considerably less marked. Venom increased the quantal content values after 15 and 30 min followed by significant inhibition at ≥90 min. However, venom did not alter the muscle membrane resting potential or the response to exogenous carbachol. In both preparations, incubation at 22 °C instead of 37 °C delayed the onset of blockade, as did inhibition of venom PLA₂ activity. In curarized mouse preparations, the venom produced only muscle facilitation. These results indicate that B. b. smargadina venom causes neuromuscular blockade in vitro by a presynaptic mechanism involving PLA₂.     

In vitro and in vivo antioxidant activity of Symplocos cochinchinensis S. Moore leaves containing phenolic compounds

Methanol extract of Symplocos cochinchinensis S. Moore leaves was evaluated for its in vitro and in vivo antioxidant activity. The total phenolic content of the extract was 230 mg of gallic acid equivalents/g extract. The extract showed very good scavenging activity on 2,2-diphenyl-picrylhydrazyl (DPPH) (IC₅₀ 620.30 ± 0.14 μg/ml), hydroxyl (IC₅₀ 730.21 ± 1.05 μg/ml), nitric oxide (IC₅₀ 870.31 ± 0.19 μg/ml) radicals, as well as high reducing power. The extract also showed strong suppressive effect on lipid peroxidation. In in vivo study CCl₄ induced oxidative stress produced significant increase in SGOT, SGPT and LDH levels along with reduction in liver SOD, CAT, GSH and GPx levels. Pre-treatment of rats with the extract (250 and 500 mg/kg) for 7 days showed significant reduction in the levels of SGOT, SGPT and LDH compared to CCl₄ treated rats. SOD, CAT, GSH and GPx levels were increased significantly due to treatment with the extract. The activity of the extract was comparable to the standard drug, silymarin (25 mg/kg). The results suggest that the leaves of S. cochinchinensis are a source of natural antioxidants.