Mechanism of antagonistic effects of Andrographis paniculata methanolic extract against Staphylococcus aureus

Objective: To investigate the effects of Andrographis paniculata(Burm.f.) Wall. Ex Nees(A. paniculata) on expressions and activities of catalase, superoxide dismutase and alkylhydroperoxide reductase C in Staphylococcus aureus(S. aureus) with respect to its survival in vitro. Methods: Antioxidative property of methanolic leaves extract of A. paniculata(0.06 mg/m L). Minimum inhibitory concentration(MIC) was determined by its ability to reduce hydrogen peroxide(H_2O_2) toxicity against S. aureus ATCC 25923(3.8×10~8 cfu/m L). Effects of the extract on expressions of kat A(encoding catalase), sod A and sod M [encoding superoxide dismutases(SODs)], and ahp C [encoding alkylhydroperoxide reductase C(AhpC)] in S. aureuswere determined by RT-q PCR and corresponding enzyme activity assays were performed. Nitroblue tetrazolium reduction(NBT) assay was performed to determine effects of the extract on intracellular and extracellular levels of O_2-in S. aureus. Results: Cells challenged with 7.5 mmol/L H_2O_2 showed 0% survival in 30 min whereas 25% survived after treatment with the extract and H_2O_2. Cells that were treated with the extract alone had 43% survival in the same exposure period. Expressions of sod A and sod M genes in extract-treated cells were lowered 0.8-fold and 0.7-fold, respectively with decrease in total SOD activity of 26.8 U compared to untreated cells, 32.4 U(P<0.05). In contrast, extract-treated S. aureus cells showed 3.3-fold increase in kat A expression with corresponding increase in catalase activity of 1.828 U compared to untreated cells which was 1.248 U,(P<0.05). More profoundly, ahp C expression was increased 61-fold in extract-treated cells,(P<0.05) with corresponding increase in Ahp C activity of 0.018 U compared to untreated cells, 0.012U,(P<0.05). Extract-treated cells had significantly lower intra-and extracellular O_2-levels with absorbance readings(A_(575nm)) of 0.340 and 0.524 compared to untreated cells which were 0.516 and 0.928(P<0.05), respectively. Conclusions: Taken together these results suggest that the low MIC of A. paniculatamethanolic leaves extract(0.06 mg/m L) reduce H_2O_2 toxicity and more importantly, was in itself effectively inhibitory against S. aureus. Further, our observations suggest that a probable mode of its inhibitory mechanism against S. aureus is by reducing total SOD activity through downregulation of sod A and sod M expressions.

Antagonistic Effect of Russula virescens(Schaeff.) Fr.against Bortrytis cinerea

[Objective] The paper was to study the antagonistic effect of Russula virescens （Schaeff.） Ft. against Bortrytis cinerea. [Method] Using the confrontation culture method, the antagonistic effect of mycelium, fermentation broth and mycelial extract of R. virescens against B. cinerea was studied. [Result] The antagonistic ef- fect of R. vivesscens against B. cinerea was mainly manifested as hyperparasitism of mycelium and inhibition effect of metabolites. The inhibition rate of confrontation growth was between 46.9% and 52.3%, and hyperparasitism phenomenon was obvi- ous. The fermentation broth of R. virescens cultured by PDB medium had the strongest growth inhibition effect, and the growth inhibition rate against B. cinerea was the highest of 61.59%. The thermal stability of fermentation broth was good, the mycelial extract of R. virescens had no inhibition effect against the growth of B. cinerea. [Conclusion] The study provided theoretical basis for subsequent differentiation and drug sensitivity of B. cinerea.

Screening,identification and antagonistic effect of antagonistic bacteria JTFM1001 against aflatoxin contamination in corn

Aflatoxin is a strong carcinogenic and toxic fungal toxin produced by Aspergillus flavus and other Aspergillus species,and can seriously threaten the health of consumers,thus becoming a global concern.Corn,as an important oil and economic crop,is highly susceptible contaminated by aflatoxin.In this study,antagonistic bacteria with strong inhibitory effect on aflatoxin were screened to provide support for the treatment aflatoxin contamination control in corn.Ten strains which have strong antagonistic effects against A.flavus were isolated from healthy corn from different corn producing areas in China.Among them,the antagonistic bacteria JTFM1001 through corn kernels in vivo and field experiment,the inhibition effect of aflatoxin contamination reached above 70%and 55%,respectively.And the strain was identified as Bacillus subtilis based on its morphological,physiological and biochemical characteristics and phylogenetic analysis of 16S rDNA.In addition,our data showed that it can colonize in the rhizosphere and survive for a long time,forming the dominant flora,with broad application prospect.Finally,we were surprised to find that the antibacterial metabolites secreted by the antagonistic bacteria was one of the mechanisms of its inhibition of A.flavus and aflatoxin.This will provide us with new ideas and perspectives on the effective prevention and control of aflatoxin contamination in corn and corn oil.

Joint effects of microwave and chromium trioxide on root tip cells of Vicia faba

The mutagemc effects of microwave and chromium trioxide （CrO3） on Vicia faba root tip were studied. Micronucleus assay and chromosomal aberration assay were used to determine the mitotic index, the micronucleus frequency and chromosomal aberration frequency of Vicia faba root tip cells induced by microwave and CrO3. The results showed that the micronucleus frequency decreased, and that the mitotic index and chromosomal aberration frequency showed linear dose responses to CrO3, in treatment of microwave for 5 s. In microwave of 25 s, the mitotic index decreased, the micronucleus frequency and chromosomal aberration frequency increased with increase of CrO3 concentration. We concluded that microwave and CrO3 had antagonistic effect on the mitotic index of Vicia faba root tip cells, but had synergetic effect on micronucleus frequency and chromosomal aberration frequency of Viciafaba root tip cells.

Protective Effects of Calcium Antagonists on Cadmium-induced Toxicity in Rats

Protective effects of calcium antagonists, chlorpromazine (CPZ) and nimodepine (NI-MO), on cadmium-induced toxicity were investigated. After giving CdCl2 (0. 44mg Cd/kg,ip), CPZ (5mg/kg, ip) or NIMO (8mg/kg, po) were administered every day to Sprague-Dawley (S. D. ) rats for a week. Then, urinary N- acetyl-β-D- glucosaminidase (NAG ), uri -nary cadmium and bloocl cadmium were measured. The accumulation of cadmium in the kid-ney cortex, content of renal calmodulin, hemoglobin and the ultrastructural damage of proxi-mal convoluted tubules of rats were examined three weeks after the last administration. Re-sults indicated that the calcium antagonists partly protected against toxic effects induced bycadmium in different manners. These data provide further evidence for the new hypothesisthat the cross effect of cadmium and calcium in calmodulin regulated systems may be responsi-ble for the mechanism of cadmium intoxication. 'The results suggested that the calcium antag-onists could be a new and promising approach in the therapy of heavy metaLinduced diseases

Isolation,Screening and Identification of Antagonistic Actinomycetes against Ustilago scitaminea Syd

[Objectives] This study was conducted to obtain actinomycetes strains having antagonistic effect on Ustilago scitaminea Syd.[Methods] At first, actinomycetes strains were isolated from 22 soil samples in Hainan sugarcane regions. Then, antagonistic actinomycetes against U. scitaminea were screened by confrontation culture. Finally, the taxonomic status of antagonistic actinomycetes was determined using 16S rDNA.[Results] From the 22 samples, 984 actinomycetes strains were isolated. From all the isolated strains, 23 antagonistic actinomycetes strains were obtained through primary screening, and one strains with better antagonistic effect was then obtained through secondary screening, and designated FAS. 16S rDNA identification showed that strain FAS shared 99% sequence similarity with Streptomyces cealestis US24. A phylogenetic tree was built with MAGE 7.0 software, and the results showed that strain FAS had the shortest genetic distance with S. caelestis US24. Therefore, the actinomycetes FAS was determined as S. caelestis .[Conclusions] This study provides a new biocontrol method for the biological control of sugarcane smut, thereby ensuring sustainable development of sugarcane industry and sugar industry.

Antagonistic interaction between caffeine and ketamine in zebrafish: Implications for aquatic toxicity

The coexistence of caffeine(CF)and ketamine(KET)in surface waters across Asia has been widely reported.Previous studies have implied that CF and KET may share a mechanism of action.However,the combined toxicity of these two chemicals on aquatic organisms remains unclear at environmental levels,and the underlying mechanisms are not well understood.Here we demonstrate that KET antagonizes the adverse effects of CF on zebrafish larvae by modulating the gamma-aminobutyric acid(GABA)ergic synapse pathway.Specifically,KET(10e250 ng L^(-1))ameliorates the locomotor hyperactivity and impaired circadian rhythms in zebrafish larvae induced by 2 mg L^(-1) of CF,showing a dose-dependent relationship.Additionally,the developmental abnormalities in zebrafish larvae exposed to CF are mitigated by KET,with an incidence rate reduced from 26.7%to 6.7%.The competition between CF and KET for binding sites on the GABA-A receptor(in situ and in silico)elucidates the antagonistic interactions between the two chemicals.Following a seven-day recovery period,the adverse outcomes of CF exposure persist in the fish,whereas the changes observed in the CFþKET groups are significantly alleviated,especially with KET at 10 ng L^(-1).Based on these results,it is imperative to further assess the environmental risks associated with CF and KET co-pollution.This pilot study underscores the utility of systems toxicology approaches in estimating the combined toxicity of environmental chemicals on aquatic organisms.Moreover,the nighttime behavioral functions of fish could serve as a sensitive biomarker for evaluating the toxicity of psychoactive substances.

Control Efficacy and Antifungal Mechanism of Bacillus Cereus Strain JK14 against Wheat Take-all Disease

[Objective] Study on control efficacy and inhibitory effect of Bacillus cereus strain JK14^·against wheat take-all disease, investigating its antifungal mechanism. [Method] B. cereus JK14^· was isolated from soil in the rhizosphere of wheat, inhibitory effects of whose nutrient solution form against Gaeumannomyces graminis var tritici strains 9862 and 9812 were measured in laboratory and then for its antifungal mechanism. The strain JK14^· with rifampicin and wheat take-all disease resistance was screened by increasing concentration of the two substrates, and colonization of JK14^·was studied. [Result] In pot experiment, the control effects of JK14^·, against 9862 and 9812 are 63% and 59%, respectively, which are higher than that of chemical fungicides, with 55% and 51% , respectively. JK14^· could deform mycelium and causes degradation of cell wall. And there are also dynamic change of JK14^· in root system. JK14^· on seed could extend to root along with seed germination and rooting, but per unit tissue mycelium number decreased gradually. [Conclusion] The results indicate some control efficacy of B. cereus strain JK14^· against wheat take-all disease.

Separation and Screening of Biocontrol Actinomyces against Alfalfa Root Rot

[Objective] Actinomycetes with high antagonistic effects on alfalfa root rot pathogen was isolated from 10 soil samples in Chifeng Inner Mongolia. [Method] 91 actinomyces were separated from 10 soil samples in Chifeng Inner Mongolia by gradient dilution separation method. In duel culture tests, all isolates were tested for their antagonism by using 3 strains including Fusarium solani, F. oxysoporum, F. avenaceum of alfalfa root rot pathogenic bacteria as indicator strains. [Result] 5 strains with strong antagonistic effect on tested alfalfa root rot pathogen were obtained from No.1, No.4, No.6 and No.7 soil samples which were numbered 1-3-6, 4-4-2, 6-2-27 and 7-2-13 respectively, accounted for 5.50% in separated strains. [Conclusion] This study laid certain foundation for biological control of alfalfa root rot disease.

Impact of tree litter identity, litter diversity and habitat quality on litter decomposition rates in tropical moist evergreen forest

Background:Attempts to restore degraded highlands by tree planting are common in East Africa.However,up till now,little attention has been given to effects of tree species choice on litter decomposition and nutrient recycling.Method:In this study,three indigenous and two exotic tree species were selected for a litter decomposition study.The objective was to identify optimal tree species combinations and tree diversity levels for the restoration of degraded land via enhanced litter turnover.Litterbags were installed in June 2019 into potential restoration sites(disturbed natural forest and forest plantation)and compared to intact natural forest.The tested tree leaf litters included five monospecific litters,ten mixtures of three species and one mixture of five species.Standard green and rooibos tea were used for comparison.A total of 1,033 litters were retrieved for weight loss analysis after one,three,six,and twelve months of incubation.Results:The finding indicates a significant effect of both litter quality and litter diversity on litter decomposition.The nitrogen-fixing native tree Millettia ferruginea showed a comparable decomposition rate as the fast decom-posing green tea.The exotic conifer Cupressus lusitanica and the native recalcitrant Syzygium guineense have even a lower decomposition rate than the slowly decomposing rooibos tea.A significant correlation was observed be-tween litter mass loss and initial leaf litter chemical composition.Moreover,we found positive non-additive ef-fects for litter mixtures including nutrient-rich and negative non-additive effects for litter mixtures including poor leaf litters respectively.Conclusion:These findings suggest that both litter quality and litter diversity play an important role in decom-position processes and therefore in the restoration of degraded tropical moist evergreen forest.

UV-Vis Spectroscopy Study on Interaction between Microperoxidase-11 and Pr Ion Under Acid Rain Stress

Interaction between rare earth ion praseodymium (Pr(Ⅲ)) and MP11 with/without hydrogen ion (H +) in different media( aqueous, phosphate buffer, physiological condition) were studied by UV Vis spectroscopy. All the results indicate that Pr(Ⅲ) interacts with MP11, increasing the non planarity of porphyrin periphery, leading MP11 to form two conformations when titrated by Pr(Ⅲ). Excessive Pr(Ⅲ) acts as a contaminant in living organism. H + and Pr(Ⅲ) have antagonistic effect on MP11, suggesting that at suitable concentration under physiological conditions, Pr(Ⅲ) can be used as biomodulator in protecting plants from acid rain stress or in rehabilitating the harm.

Effect of inorganic arsenic in paddy soil on the migration and transformation of selenium species in rice plants

Selenium(Se)in paddy rice is one of the significant sources of human Se nutrition.However,the effect of arsenic(As)pollution in soil on the translocation of Se species in rice plants is unclear.In this research,a pot experiment was designed to examine the effect of the addition of 50 mg As/kg soil as arsenite or arsenate on the migration of Se species from soil to indica Minghui 63 and Luyoumingzhan.The results showed that the antagonism between inorganic As and Se was closely related to the rice cultivar and Se oxidation state in soil.Relative to the standalone selenate treatment,arsenite significantly(p<0.05)decreased the accumulation of selenocystine,selenomethionine and selenate in the roots,stems,sheaths,leaves,brans and kernels of both cultivars by 21.4%-100.0%,40.0%-100.0%,41.0%-100%,5.4%-96.3%,11.3%-100.0% and 26.2%-39.7% respectively,except for selenocystine in the kernels of indica Minghui 63 and selenomethionine in the leaves of indica Minghui 63 and the stems of indica Luyoumingzhan.Arsenate also decreased(p<0.05)the accumulation of selenocystine,selenomethionine and selenate in the roots,stems,brans and kernels of both cultivars by 34.9%-100.0%,30.2%-100.0%,11.3%-100.0% and 5.6%-39.6%respectively,except for selenate in the stems of indica Minghui 63.However,relative to the standalone selenite treatment,arsenite and arsenate decreased(p<0.05)the accumulation of selenocystine,selenomethionine and selenite only in the roots of indica Minghui 63 by 45.5%-100.0%.Our results suggested that arsenite and arsenate had better antagonism toward Se species in selenate-added soil than that in selenite-added soil;moreover,arsenite had a higher inhibiting effect on the accumulation of Se species than arsenate.

5-Aminolevulinic acid against strawberry Fusarium wilt:Bidirectional regulation of biocontrol agents and pathogens

Strawberry Fusarium wilt (SFW) is a systematic soil-borne disease caused by Fusarium oxysporum f.sp.fragaria (Fof),which infects the vascular bundles,blocking water and nutrient transport from roots to the aboveground.It is a severe pathogen which spreads rapidly and destroys strawberry production.Finding a way to control this disease is of great scientific value and practical importance.In this study,three fungi were isolated from the vascular tissues of sick strawberries in the field.After DNA sequencing,they were identified as Fof,Aspergillus fumigatus and Trichoderma harzianum,respectively,among which the first two are pathogens and the third is a probiotic.All fungi were controlled by thiophanate-methyl (TM),a commercial fungicide.On PDA medium,20 mg·L^(-1)5-aminolevulinic acid (ALA),a natural non-protein amino acid,promoted T.harzianum proliferation,but inhibited Fof and A.fumigatus.In confrontation test,the growth of Fof or A.fumigatus was inhibited by T.harzianum and exogenous ALA promoted T.harzianum growth but significantly inhibited the pathogen growth.When three species of fungi were separately or combinedly inoculated on healthy strawberry plants,T.harzianum promoted plant growth and development while Fof or A.fumigatus caused growth retardation,where Fof directly caused leaf yellowing and plant wilting.When the plants inoculated with different fungus were treated with ALA,the results turned out that ALA alleviated SFW symptoms by bidirectionally promoting T.harzianum proliferation and inhibiting Fof and A.fumigatus.Thus,ALA might be used in comprehensively controlling SFW in strawberry industry.

EFFECTS OF ENDOTHELIN-1 RECEPTOR ANTAGONISTS BO123 AND BQ610

Using endothelin-1 (ET-1) antagonists BQ123 and BQ610. we tested whether endogenous ET-1 contributes to ischemia / re-perfusion injury in isolated. Langendorff rat hearts. BQ123 (7μg/min) and BQ610 (1.75μg/ min) did not affect mechanical function or coronary flow and shifted the dose-response curves for ET-1 (boluses of 4-400 pmol) significantly to the right. Isovolumic rat hearts were

EFFECTS OF LEUKOTRIENE D4 AND ITS SPECIFIC ANTAGONIST L-660, 711 ON ISOLATED RAT HEART WITH CHRONIC MYOCAROIAL INFARCTION

Coronary reserve is reduced in residual myocardium after myocardial infarction and endogenous vasoconstrictors

Potential probiotic and health fostering effect of host gut-derived Enterococcus faecalis on freshwater prawn,Macrobrachium rosenbergii

The present study investigated the potential probiotic effect of Enterococcus faecalis against a pathogenic microorganism,Vibrio harveyi occurring in the giant freshwater prawn(Macrobrachium rosenbergii).V.harveyi was isolated from the intestine of M.rosenbergii through biochemical tests and PCR-based molecular assays.An in-vitro challenge was conducted by mixing isolated probiotic(5.12 log CFU/g)and V.harveyi(3.09 log CFU/g).Feeds incorporated with E.faecalis(9.02 log CFU/g)were applied to the treatment group during in vivo test in the aquarium and earthen pond(70 m^(2),1 m depth).Pathogenic bacteria were found to be reduced after 8 h(from 5.02 to 3.62 log CFU/g)and 60 days(from 5.44 to 2.15 log CFU/g)of probiotic administration in the in vitro and in vivo test,respectively.The E.faecalis mixed feed also showed higher weight gain(WG%,481.22%±17.71%;SGR%,2.93%±0.18%)and digestive enzymes activities(amylase,1.26±0.08 unit/mg;protease,2.78±0.02 unit/mg)compared to control group(WG%,371.31%±13.35%;SGR%,2.30%±0.32%;amylase,0.7±0.03 unit/mg;protease,1.82±0.02 unit/mg).Furthermore,the probiotic also improved the immune response by augmenting NGH(from 73.33%±0.23%to 74.63%±0.11%)and SGH(from 22.24%±0.06%to 23.13%±0.08%)in the treatment group.Therefore,E.faecalis could be recommended to use against bacterial infections of the M.rosenbergii.