Kinetics of the Action of Na2SeO3 on Bacillus subtilis Growth as Studied by Microcalorimetry

Microcalorimetric bioassay for acute cellular toxicity is based on metabolic heat production from cultured cells.The biological response to toxicants is the inhibition of the heat production rate in cells,and toxicity is expressed as the concentration of toxicant that is 50% effective in this inhibition(IC50).In this paper,the effect of Na2SeO3 on Bacillus subtilis growth was investigated at 37℃ by microcalorimetry.The relationship between growth rate constants(k) and concentration of Na2SeO3(c) shows a logarithmic normal distribution,and IC50 is 20.3μg/mL.All these thermokinetic information is readily obtained by an LKB 2277-204 heat conduction microcalorimeter.Microcalorimetry is a quantitative,inexpensive,and versatile method for toxicology research.     

Microcalorimetric Study of the Biological Effects of Zn^＋ on Bacillus thuringiensis Growth

A microcalorimetric technique was used to investigate the influence of Zn^2 on the growth metabolism of Bacillus thuringiensis .LKB-2277 Bioactivity Monitor was employed to obtain the power-time curves,from which the maximum peak-heat output power(Pmax) in the log phase,the growth rate constants(k), the inhibitory ratios(I) ,the generational time(tG) and the total heat effect (Qtotal) in 23 h for the growth metabolism of Bacillus thuringiensis at 28℃ can be evaluated,The results indicate that the concentration of Zn^2 affects its growth obviously,Low concentration (0-50μg/mL) of Zn^2 promotes the growth of Bacillus thuringiensis while high concentration (50-500μg/mL) of Zn^2 inhibits its growth .When the concentration reached up to 600μg/mL,it can not grow at all.     

A microcalorimetric study of the biologic effect of Mn(II) on Bacillus thuringiensis growth

A microcalorimetric technique based on the bacterial heat-output was explored to evaluate the effect of Mn(II) on Bacillus thuringiensis. The power-time curves of the growth metabolism of B. thuringiensis and the effect of Mn(II) on it were studied using an LKB-2277 BioActivity Monitor, ampoules method, at 28°C. For evaluation of the results, the maximum peak-heat output power (P _max) in the growth phase, the growth rate constants (k), the log phase heat effects (Q _log ), and the total heat effect in 23 h (Q _T) for B. thuringiensis were determined. Manganese has been regarded as the essential biological trace element. Mn(II) of different concentration have different effects on B. thuringiensis growth metabolism. High concentration (800-1600 μg mL^-1) of Mn(II) can promote the growth of B. thuringiensis; low concentration (500-800 μg mL^-1) can inhabit its growth. This revised version was published online in August 2006 with corrections to the Cover Date.     

The effect of zinc(II) on the growth of <Emphasis Type="Italic">E . coli</Emphasis> studied by microcalorimetry

By using an LKB2277 Bioactivity Monitor, stop-flow mode, the power-time curves of E . coli at 37°C effected by zinc(II) were determined. Some parameters, such as growth rate constants k, inhibitory ratio I, the maximum heat production rate P _max heat output Q and the time in the maximum heat production t _max were obtained. According these parameters, we found that a low concentration of zinc(II) had a promoting action on the growth of E. coli, but a high concentration of zinc(II) had an inhibitory action. The toxicity of zinc(II) can also be expressed as half inhibitory concentration IC ₅₀ of zinc(II), i.e., 50% effective in this inhibition. The value of IC ₅₀ of zinc(II) on E. coliis 28.09 µg mL^-1. The assay is quantitative, inexpensive and versatile.     

微量热法比较黄连中四种生物碱的抗菌作用

采用微量热法研究和比较中药黄连中四种生物碱(BAs)的抗菌(大肠杆菌)作用。这四种生物碱分别为小檗碱、黄连碱、巴马汀和药根碱。用LKB-2277生物活性检测系统,以停留法测定了37 ℃时大肠杆菌在BAs作用下的热流功率-时间曲线,并记录生长速率常数k, 指数生长期和稳定期的最大热功率Pm, log、Pm, stat, 生长抑制率I, 传代时间tg,指数生长期的总产热量Qt, log,半数抑菌浓度IC50等热动力学参数。结果显示这四种生物碱具有相异的抗大肠杆菌生长代谢的作用,k, Pm, log和Qt, log值随BAs浓度的增加而相应的减少。综合分析k, Pm, log, Qt, log, I 和IC50值可以看出,BAs抑制大肠杆菌生长代谢强度按小檗碱、黄连碱、巴马汀、药根碱的顺序依次减弱。构效关系研究表明,母环C-2和C-3上连接的亚甲二氧基比甲氧基更能显著增强相应化合物的抗菌作用,而C-9和C-10上连接的亚甲二氧基或甲氧基对这种抗菌作用影响不大。     

Microcalorimetric Study on Effect of Chromium(III) and Chromium(VI) Species on the Growth of Escherichia coli

The effects of Cr(III) and Cr(VI) species (Cr₂O₇^2?, CrO₄^2? and Cr³⁺) on the growth of Escherichia coli (E. coli) have been investigated in detail by microcalorimetry at 37 °C. Parameters including the growth rate constant (k), inhibitory ratio (I), half‐inhibitory concentration (IC₅₀), total heat output (Q_total), time of the maximum heat production (t_log) in the log phase have been obtained. The results showed that Cr(VI) and Cr(III) had the inhibition effect on the growth of E. coli in aquatic environment; however, the inhibitory ratio of Cr(III) to E. coli was smaller than that of Cr(VI). The k values of E. coli in the presence of Cr(VI) and at high concentrations of Cr(III) were decreased with increasing the concentrations of these chromium species. Among the three chromium species investigated, Cr₂O₇^2? was found to be the most poisonous species against E. coli with an IC₅₀ value of 35.52 µg·mL^?1. CrO₄^2? exhibited moderate toxicity on E. coli with an IC₅₀ of 50.24 µg·mL^?1, and Cr³⁺ had the lowest toxicity with an IC₅₀ of 84.30 µg·mL^?1. Microcalorimetry can provide a convenient, sensitive and reliable method to study the effect of various metal species on the growth of bacteria or other microorganisms.     

Microcalorimetric Studies on Influence of Sm^3＋, Dy^3＋ on Growth and Sporulation of Bacillus thuringiensis

By using an LKB-2277 Bioactivity Monitor and cycle-flow method, the thermogenic curves of aerobic growth for Bacillus thuringiensis cry Ⅱ strain at 28 ℃ have been obtained. The metabolic thermogenic curves of Bt cry Ⅱ contain two distinct parts: the first part reflects the changes of bacterial growth phase and the second part corresponds to sporulation phase. From these thermogenic curves in the absence or presence of Sm^3 , Dy^3 ions, the thermokinetic parameters such as the growth rate constants k. the interval time τ1, the maximum power PMAX1 and heat-output QLOG for log phase, the maximum power PMAX2 and heat-output QSTAT for stationary phase, the heat-output QSPOR for sporulation phase and total heat effects QT were calculated. Sm^3 and Dy^3 ions have promoting action on the growth of Bt cryⅡ in their lower concentration range, on the other hand, they have inhibitory action on the sporulation of Bt in their higher concentration range, It has also been found that the effects of Sm^3 and Dy^3 ions on Bt during the sporulation phase were far greater than those during the bacterial growth phase. It was concluded that the application of Bt for controlling insecticide could not be affected by the presence of the rare-earth elements in the environmental ecosystem.     

Microcalorimetric investigation on antibacterial activity of the peptide from Plutella xylostella

The antibacterial activities of a kind of novel peptide from Plutella xylostella (pxCECA1) on methicillin-resistant staphylococcus aureus (MRSA) and Escherichia coli (E. coli) growth were investigated by microcalorimetry. The heat flow power–time curves of MRSA and E. coli growth in the presence of pxCECA1 were recorded using the 3114/3115 Thermal Activity Monitor Air Isothermal Calorimeter based on ampoule mode at 37 °C. Some parameters including growth rate constant k, maximum power output P _max, total heat output Q_t, generation time t _g, growth inhibitory ratio I, and half-inhibitory concentration of the drugs IC₅₀ were obtained to elucidate the antibacterial activity of pxCECA1. The results showed that k, P _max, and Q _t decreased, but I and t _g increased or delayed with the increase in pxCECA1 concentration. The IC₅₀ of pxCECA1 on E. coli was 6.122 μg mL^?1 and MRSA was 7.809 μg mL^?1. It could be concluded that pxCECA1 had stronger inhibitory effect on E. coli than MRSA. In vivo test was simultaneously performed using an E. coli and MRSA infection model to validate the antibacterial activity of pxCECA1. The results revealed that pxCECA1 with broad spectrum antimicrobial activities hopefully represented a class of promising substitute of antimicrobial agents.     

A microcalorimetric method to determine antimicrobial effects of two bile acid derivatives on Staphylococcus aureus

Using microcalorimetry, the characteristic metabolic heat flow power-time curves of S. aureus growth affected by Ursodesoxycholic acid and Hyodeoxycholic acid were measured at 37?°C. The thermal-kinetic parameters such as, growth rate constant k, the maximum power output (P _m), the time corresponding to the maximum power output (t _p), total heat-production Q _t , half inhibitory concentration of the drugs (IC ₅₀) were calculated from the growth curves. For both HDCA and UDCA, with the increasing of concentration, k, P _m, and Q _t decreased, meanwhile, k?Cc fit a linear equation, t _p was prolonged correspondingly. Principle component analysis, the results indicated t _p might be the main parameter in evaluating the antibacterial activity of HDCA and UDCA in microcalorimetric method. Combining with t _p and IC ₅₀, the results revealed that the differences and trends of antibacterial activity of these bile acid derivatives were: HDCA?>?UDCA. Structure-activity relationship (SAR) analysis showed that the ??-OH at C-3 and C-6 position at equal pace on the steroid nucleus enhanced the hydrophilicity of HDCA, which led to a stronger antibacterial effect than UDCA. In this study, a useful tool was provided to accurately evaluate the antibacterial effects of bile acid derivatives. The thermolysis curve recorded by microcalorimetry could provide a lot of kinetic and thermodynamic information for the study of growth process of living microbial, which could be helpful in the screening of high efficacy antibacterial agents.     

Investigation of the Effect of Four Organic Acids in Radix Isatidis on E. coli Growth by Microcalorimetry

The inhibitory effects of four organic acids (OAs) in Radix Isatidis, a traditional Chinese medicinal herb, on Escherichia coli (E. coli) growth were investigated by microcalorimetry. The power‐time curves of E. coli growth with and without OAs were acquired, meanwhile the extent and duration of inhibitory effects on the metabolism were evaluated by growth rate constants (k₁, k₂), half inhibitory ratio (IC₅₀), maximum heat output (P_max) and peak time (t_p). The values of k₁ and k₂ of E. coli growth in the presence of the four OAs decreased with the increasing concentrations of OAs. Moreover, P_max was reduced and the value of t_p increased with increasing concentrations of the four drugs. The sequence of anti‐microbial activity of the four OAs was: syringic acid>2‐amino‐benzoic acid>salicylic acid>benzoic acid. IC₅₀ of the four OAs was respectively 56 µg/mL for syringic acid, 75 µg/mL for 2‐amino‐benzoic acid, 86 µg/mL for salicylic acid and 224 µg/mL for benzoic acid. The existence of the functional groups on phenyl ring improves the anti‐microbial activity compared to benzoic acid. The functional groups methoxyl at C(3) and C(5) improve anti‐microbial activity more strongly than the other functional groups, and the functional group amino at C(2) improve anti‐microbial activity more strongly than hydroxyl at C(2) on phenyl ring.     

Microcalorimetry coupled with principal component analysis for comparing the effects of two Panax species on mice splenic lymphocytes

A powerful microcalorimetric method based on the cell heat production was applied to evaluate the effects of two Panax species on mice splenic lymphocytes growth. Some qualitative and quantitative information, such as the metabolic power-time curves, growth rate constant k, maximum heat-output power P _max, appearance time for the highest peak t _max, total heat production Q _t for all the metabolic progress of mice splenic lymphocytes were obtained to present the effects of Panax ginseng and American Ginseng on these cells. Coupled with principal component analysis (PCA) on these quantitative thermokinetic parameters, the effects of the two Panax species on mice splenic lymphocytes could be quickly evaluated by analyzing the change of the main parameter k. From the values of k, it could be concluded quickly and accurately that Panax ginseng and American Ginseng both showed strong inhibitory effects on mice splenic lymphocytes, and the inhibitory effects was strengthened with increasing concentration of the two Panax species in the concentration range of 0–3.2 mg mL^?1. Panax ginseng with IC ₅₀ of 1.38 mg mL^?1 showed stronger inhibitory effect on mice splenic lymphocytes growth than American Ginseng with IC ₅₀ of 2.08 mg mL^?1. This study indicates that microcalorimetry is a powerful tool for evaluating the drugs’ efficiency on living system, providing some useful references for the application of Panax ginseng and American Ginseng in practice.     

Cloning, characterization, and expression of a new cry2Ab gene from Bacillus thuringiensis strain 14-1

Bacillus thuringiensis is the major source for transfer of genes to impart insect resistance in transgenic plants. Cry2A proteins of B. thuringiensis are promising candidates for management of resistance development in insects owing to their difference from the currently used Cry1A proteins, in structure and insecticidal mechanism. The cry2Ab gene was found to lack a functional promoter and, hence, is cryptic in nature. The cry2Ab7 gene was cloned from a new indigenous B. thuringiensis strain, 14-1. Nucleotide sequencing of the cry2Ab gene cloned from B. thuringiensis strain 14-1 revealed an open reading frame of 1902 bp. The deduced amino acid sequence of Cry2Ab of B. thuringiensis strain 14-1 showed a variation in three amino acid residues in comparison to the holotype sequence, Cry2Ab1. Expression of the newly cloned cry2Ab gene was studied in an acrystalliferous strain of B. thuringiensis (4Q7) by fusing the cry2Ab gene downstream of cry2Aa promoter and orf1+orf2 sequences. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of a spore-crystal mixture obtained from transformants of B. thuringiensis strain 4Q7 showed production of Cry2Ab protein of about 65 kDa. Alkali solubilized Cry2Ab7 protein showed toxicity against Helicoverpa armigera neonates.     

Investigation of the effect of berberines alkaloids in <Emphasis Type="Italic">Coptis chinensis</Emphasis> Franch on <Emphasis Type="Italic">Bacillus shigae</Emphasis> growthby microcalorimetry

The inhibitory effects of five berberines alkaloids (BAs) from rhizoma of Coptis chinensis Franch, a traditional Chinese medicinal (TCM) herb, on Bacillus shigae (B. shigae) growth were investigated by microcalorimetry. The power-time curves of B. shigae with and without BAs were acquired; meanwhile, the extent and duration of inhibitory effects on the metabolism were evaluated by growth rate constants (k1, k2), half inhibitory ratio (IC50), maximum heat output (Pmax), and peak time (tp). The values of k1 and k2 of B. shigae in the presence of the five BAs decreased with the increasing concentrations of BAs. Moreover, Pmax was reduced, and the value of tp increased with increasing concentrations of the five drugs. The inhibitory activity varied with different drugs. IC50 of the five BAs was respectively 75 μg/mL for berberine, 90 μg/mL for coptisine, 115 μg/mL for palmatine, 220 μg/mL for epiberberine, and 400 μg/mL for jatrorrhizine. The sequence of antimicrobial activity of the five BAs berberine ＞ coptisine ＞ palmatine ＞ epiberberine ＞ jatrorrhizine. The functional groups methylenedioxy at C2 and C3 on phenyl ring improve antimicrobial activity more strongly than methoxyl at C2 and C3 on phenyl ring. However, the effect of bacteriostasis is not significant with methylenedioxy or methoxyl at C9 and C10 on phenyl ring.     

Microcalorimetric investigation of the effect of berberine alkaloids from <Emphasis Type="Italic">Coptis chinensis</Emphasis> Franch on <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> growth

The inhibitory effects of three berberine alkaloids (BAs) from rhizome of Coptis chinensis Franch, a traditional Chinese medicinal (TCM) herb, on Staphylococcus aureus growth were investigated by microcalorimetry. The power-time curves of S. aureus with and without BAs were acquired; meanwhile the extent and duration of inhibitory effects on the metabolism were evaluated by studying the growth rate constant (k), half inhibitory ratio (IC₅₀), maximum heat-output power (P _max), peak time of maximum heat-output power (t _p) and total heat production (Q _t). The value of k of S. aureus in the presence of the three BAs decreased with the increasing concentrations of BAs. Moreover, P _max was reduced and the value of t _p increased with increasing concentrations of the three drugs. The inhibitory activity varied with different drugs. The values of IC₅₀ of the three BAs are respectively, 101.4 μg/mL for berberine, 241.0 μg/mL for palmatine and 792.3 μg/mL for jateorrhizine. The sequence of antimicrobial activity of the three BAs is: berberine > palmatine > jateorrhizine. It is suggested that the functional group methylenedioxy or methoxyl at C2 on the phenyl ring could possibly improve antimicrobial activity more strongly than hydroxyl at C2 on the phenyl ring. Supported by the National Natural Science Foundation of China (Grant No. 30625042)     

Über die Löslichkeit von Na2SeO4 und das Verhalten von Na2SeO4·10H2O in organischen Lösungsmitteln

Zusammenfassung Untersucht wurde die Löslichkeit von Na₂SeO₄ in den organischen Lösungsmitteln CH₃OH, C₂H₅OH,n-C₃H₇OH und Aceton bei 20°, 30°, 40°, 50°C und die Dichte der so erhaltenen gesätt. Lösungen bestimmt. Das Verhalten von Na₂SeO₄·10 H₂O zu diesen organischen Lösungsmitteln zeigte Entwässerung zu Na₂SeO₄ in CH₃OH und C₂H₅OH, während bein-C₃H₇OH und Aceton der Entwässerungsprozeß nicht zu Ende geht. Es wurde auch die Löslichkeit von Na₂SeO₄·10 H₂O in obigen Lösungsmitteln sowie die Dichte der Lösungen bestimmt.

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The solubility of Na₂SeO₄ and the behaviour of Na₂SeO₄·10H₂O in organic solvents

The solubility of Na₂SeO₄ in the organic solvents CH₃OH, C₂H₅OH,n-C₃H₇OH and acetone at 20°, 30°, 40° and 50°C has been determined, and the specific gravity of the solutions measured. The behaviour of Na₂SeO₄·10 H₂O in the same solvents was also studied. Dehydration to Na₂SeO₄ occurs in CH₃CH and C₂H₅OH, whereas inn-C₃H₇OH and acetone, dehydration is incomplete. The solubility of Na₂SeO₄·10 H₂O in these solvents and the specific gravity of the solutions have also been determined.

     

The First Boroselenates as new Silicate Analogues

The first boroselenates were obtained as single crystals by the reaction of selenic acid with boron acid and the corresponding alkali carbonates. The structure determinations showed a far‐reaching analogy to very recently described borosulfates and the borophosphates, that is, tetrahedral BO₄ and SeO₄ units linked by common corners. In each case, the BO₄ tetrahedra are surrounded by SeO₄ tetrahedra. As a function of the B/Se ratio, this results in chains (1:3; Cs₃[B(SeO₄)₃], Rb₃[B(SeO₄)₃]), isolated pentamers (1:4; HK₄[(B(SeO₄)₄]), or pentamers with additional isolated SeO₄ tetrahedra (1:5; (H₃O)Na₆[B(SeO₄)₄](SeO₄). Compound Rb₃[B(SeO₄)₃] (orthorhombic, Ibca, Z=8, a=7.508(2), b=15.249(3), c=23.454(5) Å) is isotypic to Rb₃[B(SO₄)₃]) and Ba₃[B(PO₄)₃]. Compound Cs₃[B(SeO₄)₃] (monoclinic, P2₁/c, Z=4, a=11.3552(4), b=7.9893(3), c=15.7692(6) Å, β=101.013(1)°) represents a distorted variant of Rb₃[B(SeO₄)₃]. The isolated pentamers in HK₄[(B(SeO₄)₄]) (triclinic, P$\bar 1$ , Z=6, a=7.5303(1), b=7.5380(1), c=42.3659(4) Å, α=88.740(1), β=89.971(1), γ=89.971(1)°) were also found in K₅[(B(SO₄)₄] and Na₅[(B(SO₄)₄]. Compound (H₃O)Na₆[B(SeO₄)₄](SeO₄) (tetragonal, I$\bar 4$ , a=9.9796(1), c=18.2614(2) Å) is a super structure of the borophosphates Sr₆[B(PO₄)₄](PO₄) and Pb₆[B(PO₄)₄](PO₄). Because the tetrahedra are only connected through apices, there are topological analogies to silicates. Therefore, boroselenates may have a similar variability of crystal structures, such as borosulfates and borophosphates.     

Microcalorimetric study of the opposing effects of ginsenosides Rg<Subscript>1</Subscript> and Rb<Subscript>1</Subscript> on the growth of mice splenic lymphocytes

Splenic lymphocytes play an important role in host acute or chronic diseases. The abnormality of these cells in the spleens of humans might lead to some riskful diseases for human. Hence, in this study, the effects of two ginsenosides Rg₁ and Rb₁ on splenic lymphocytes growth were studied by microcalorimetry. Some qualitative and quantitative information, such as the metabolic power-time curves, growth rate constant k, maximum heat-output power of the exponential phase P _max, total heat output Q _t of splenic lymphocytes were obtained to present the effects of Rg₁ and Rb₁ on these cells. The values of k, P _max, and Q _t from the thermogenic growth curves of splenic lymphocytes were found to increase in the presence of Rg₁, while the change was adverse for Rb₁, illustrating that Rg₁ had promotion effect and Rb₁ had inhibitory effect on splenic lymphocytes growth and these promotion or inhibitory effects were enhanced with increasing the concentration of the two compounds, respectively. The microcalorimetric results were confirmed by MTT assay for determining the MTT optical density (OD) value and [³H] Thymidine incorporation assay ([³H]-TdR) for determining the count per minute (cpm) value: Rg₁ could increase the MTT OD value and the cpm value of [³H]-TdR incorporation into splenic lymphocytes, and these values were increased with increasing the concentration of this compound, while Rb₁ had the adverse results. The structure–activity relationships showed that the glucopyranoside and hydroxyl groups at the dammarane-type mother nucleus skeleton might play a crucial role for the opposing effects of the two ginsenosides on splenic lymphocytes. Compared with the other two assay methods, the microcalorimetric method provided more useful and reliable information for quickly and objectively evaluating the effects of drugs or compounds on the living cells, which would be a highly promising analytical tool for the characterization of the biological process and the estimation of the drugs’ efficiency.     

Hydrothermal Synthesis and Crystal Structures of Na2Be3(SeO3)4·H2O and Cs2[Mg(H2O)6]3(SeO3)4

The selenites, Na₂Be₃(SeO₃)₄ · H₂O and Cs₂[Mg(H₂O)₆]₃(SeO₃)₄, were synthesized under hydrothermal conditions. The crystal structures of Na₂Be₃(SeO₃)₄ · H₂O and Cs₂[Mg(H₂O)₆]₃(SeO₃)₄ were determined by single‐crystal X‐ray diffractions. Na₂Be₃(SeO₃)₄ · H₂O crystallizes in the triclinic space group P1 (no. 2) with unit cell parameters a = 4.8493(9), b = 12.013(2), c = 12.077(2) Å, and Z = 2, whereas Cs₂[Mg(H₂O)₆]₃(SeO₃)₄ crystallizes in the monoclinic space group C2/m (no. 12) with lattice cell parameters a = 12.596(6), b = 7.297(4), c = 16.914(8) Å, and Z = 2. Na₂Be₃(SeO₃)₄ · H₂O features a three‐dimensional open framework structure formed by BeO₄ tetrahedra and SeO₃ trigonal pyramids. Na cations and H₂O molecules are located in different tunnels. Cs₂[Mg(H₂O)₆]₃(SeO₃)₄ has a structure composed of isolated [Mg(H₂O)₆] octahedra and SeO₃ trigonal pyramids interacted by hydrogen bonds, and Cs cations are resided in‐between. Both compounds were characterized by thermogravimetric analysis and FT‐IR spectroscopy.     

Antimicrobial substances from the rare actinomycete Nonomuraea rhodomycinica NR4-ASC07T

Nonomuraea rhodomycinica NR4-ASC07^T is a rare actinomycete isolated from soil in Sirindhorn peat swamp forest. The crude extract of its culture broth exhibited antimicrobial and anticancer against diverse human pathogens and cancer cells. The chemical investigation of the crude extract led to the isolation of two new metabolites named nonomuric acid (1) and 3-hydroxy deoxydaunorubicinol aglycone (2), along with two known bioactive compounds [ε-rhodomycinone (3) and 7-deoxy-13-dihydrocarminomycinone (4)]. Compounds 1 and 3 showed antimalarial activity with the half maximal inhibitory concentration (IC₅₀) of 8.00 and 8.88 μg mL^?1, respectively. Compound 4 inhibited growth of Mycobacterium tuberculosis and Bacillus cereus at the minimum inhibitory concentrations of 50.0 and 12.50 μg mL^?1, respectively. Every compound exhibited cytotoxicity against cancer cells tested at IC₅₀ ≥ 6.34 μg mL^?1. These finding are the first report of bioactive metabolites produced by strain NR4-ASC07^T, suggesting that rare actinomycetes are yet promising sources for novel drug discovery.     

微量热法研究亚砷酸钠对鲫鱼肝脏线粒体的影响

Metabolic thermogenic curves of mitochondria isolated from liver tissue of Carassius auratus and the effect of different concentration of NaAsO2 on it were investigated by TAM air isothermal microcalorimeter, ampoule method, at 28.00 ℃. From the thermogenic curves, activity recovery rate constants k, the maximum heat production rate （Pmax） and the total heat produced （Q） were obtained. The values of k and Pmax decline gradually with the increase of the concentration of NaAsO2, and both of the values of Pmax and k are highly correlated to the concentration of NaAsO2. When concentration of NaAsO2 reached 16.0 μg/mL, the maximum heat production rate dropped to 70.8% of the control group, and the corresponding percentage of k was 71.4% of the control group. This experimental result indicates that the addition of NaAsO2 has restrained the metabolic activities of mitochondria in vitro.