Stimulation of acetylcholinesterase activity by triiodothyronine in the brain of Singi fish,Heteropneustes fossilis (Bloch)

Three consecutive days of injections of triiodothyronine (T₃)(0.038, 0.075, 0.15 and 1.54 nmoles/g) significantly elevated the acetylcholinesterase (AchE) activity in the brain of Singi fish, Heteropneustes fossilis (Bloch). The higher doses of 0.075, 0.15 and 1.54 nmoles of T₃/g induced a greater increase in enzyme activity than 0.038 nmoles/g. A T₃ dose of 0.019 nmoles/g was found to be ineffective. The T₃ action on AchE activity was blocked by cycloheximide. Thiourea treatment for 30 days decreased the AchE activity below the control level. This reduced level of the enzyme activity was brought back even above the control level by T₃ injections. It is, therefore, suggested that thyroid hormone is involved in the sustenance of AchE activity in fish brain.     

In vitro effect of recombinant human tumor necrosis factor-alpha on canine neutrophil apoptosis

Neutrophils (polymorphonuclear leukocytes: PMNs) are essential for the host defense against various infections and are often injurious to the host, causing inflammatory diseases where tumor necrosis factor-alpha (TNF-alpha) is suggested to play an important role. Since an effect of TNF-alpha on canine PMN apoptosis has not been studied, canine PMNs were stimulated with recombinant human (rh)TNF-alpha in the present study to investigate the effect of TNF-alpha on canine PMN apoptosis. PMN apoptosis and function to produce ROS were assessed by flow cytometry. Delayed apoptosis was observed in the PMNs treated with rhTNF-alpha at 100 ng/ml, accompanied by retention of capability to produce ROS. However, PMN apoptosis was accelerated by rhTNF-alpha combined with cycloheximide. Therefore, it is indicated that TNF-alpha is able to activate anti- and pro-apoptotic pathways in PMNs and that the inhibition of PMN apoptosis by TNF-alpha requires protein synthesis in the PMNs.     

暗黑链霉菌PY-1抑菌活性产物的结构鉴定及其对葡萄霜霉病菌的抑制作用

 从暗黑链霉菌(Streptomyces atratus)PY-1菌株发酵液中分离鉴定抑菌活性产物,评价其对葡萄霜霉病菌(Plasmopara viticola)的抑制作用,为该菌株及其产生的抑菌活性物质的应用提供依据。PY-1菌株发酵液经二氯甲烷萃取,减压浓缩获得抑菌粗提物,稳定性测定结果显示,避光条件下,15℃~65℃、pH 6~10、4℃或常温保存6个月,抑菌活性稳定。采用硅胶柱层析、Sephadex LH-2柱层析、薄层层析和HPLC等技术,对抑菌粗提物进一步分离纯化,得到2种抑菌活性组分;采用ESI-MS、¹H NMR、¹³C NMR等波谱分析技术,对活性组分进行结构鉴定,2种活性组分分别鉴定为5-乙酸环已基酰亚胺(5-acetoxycycloheximide)和环己酰亚胺(cycloheximide)。采用离体叶片法测定2种组分的抑菌活性,不同浓度(10⁴ ng·mL^-1、10² ng·mL^-1、1 ng·mL^-1)的5-乙酸环已基酰亚胺和环己酰亚胺对葡萄霜霉病菌的抑制作用分别为92.59%、86.30%、64.81%和97.04%、91.85%、84.07%。     

Conversion of forest to agricultural land affects the relative contribution of bacteria and fungi to nitrification in humid subtropical soils

Land-use and management practices can affect soil nitrification. However, nitrifying microorganisms responsible for specific nitrification process under different land-use soils remains unknown. Thus, we investigated the relative contribution of bacteria and fungi to specific soil nitrification in different land-use soils (coniferous forest, upland fields planted with corn and rice paddy) in humid subtropical region in China. ¹⁵N dilution technique in combination with selective biomass inhibitors and C₂H₂ inhibition method were used to estimate the relative contribution of bacteria and fungi to heterotrophic nitrification and autotrophic nitrification in the different land-use soils in humid subtropical region. The results showed that autotrophic nitrification was the predominant nitrification process in the two agricultural soils (upland and paddy), while the nitrate production was mainly from heterotrophic nitrification in the acid forest soil. In the upland soils, streptomycin reduced autotrophic nitrification by 94%, whereas cycloheximide had no effect on autotrophic nitrification, indicating that autotrophic nitrification was mainly driven by bacteria. However, the opposite was true in another agricultural soil (paddy), indicating that fungi contributed to the oxidation of NH₄⁺ to NO₃^?. In the acid forest soil, cycloheximide, but not streptomycin, inhibited heterotrophic nitrification, demonstrating that fungi controlled the heterotrophic nitrification. The conversion of forest to agricultural soils resulted in a shift from fungi-dominated heterotrophic nitrification to bacteria- or fungi-dominated autotrophic nitrification. Our results suggest that land-use and management practices, such as the application of N fertilizer and lime, the long-term waterflooding during rice growth, straw return after harvest, and cultivation could markedly influence the relative contribution of bacteria and fungi to specific soil nitrification processes.     

Role of prostaglandin in the control of ovulation in the Japaneseeel Anguilla japonica

ABSTRACT:   The in vitro effects of 17,20β-dihydroxy-4-pregnen-3-one(DHP) and prostaglandins (PGE₁, PGE₂, PGF_1α,PGF_2α) on ovulation in the Japanese eel Anguillajaponica were examined. Oocytes with follicle layers at themigratory nucleus stage (approximately 850–900 µmdiameter) were removed using a polyethylene cannula from artificiallymatured fish. At concentrations of 10 and 100 ng/mL,DHP was found to induce both germinal vesicle breakdown and ovulation.The prostaglandins, except for PGE₁, effectively inducedovulation of previously matured oocytes by DHP treatment in vitro .Prostaglandin F_2α was the most effective. Asignificant increase in ovulation rate was observed even at a concentrationof 0.01 µg/mL PGF_2α.Indomethacin blocked the in vitro ovulation induced by DHPand addition of PGF_2α reversed indomethacin-blockedovulation. Actinomycin D and cycloheximide blocked DHP-induced ovulationand PGF_2α reversed the effects of both inhibitors. Theseresults indicate that DHP induces ovulation through endogenous prostaglandinsynthesis in the follicle layers of the Japanese eel.     

蛋白核酸合成抑制剂对甜菜谷氨酰胺合成酶活性调控分析

在氮素诱导下,进行甜菜谷氨酰胺合成酶(GS)活性的测定,筛选出最佳的氮素诱导处理,研究核酸合成抑制剂放线菌素D和蛋白合成抑制剂放线菌酮对GS在酶活水平上的表达调控。结果表明,NO3-:NH4+=80:20处理时,GS活性最高,并且在此处理下放线菌素D和放线菌酮均能抑制GS活性。说明甜菜GS的表达可能在转录水平和翻译水平上均受到调控。     

3种真菌抗生素对绿僵菌和6种非目标真菌的生长影响分析

文章比较了两性霉素、伊曲康唑和放线菌酮对土壤内金龟子绿僵菌（Metarhizium anisopliae）、黄绿绿僵菌（M．flavoviride）和6种非目标真菌生长的影响。结果表明,伊曲康唑对毛霉（Mucor racemosus）和黑曲霉（Aspergillus niger）的抑菌效果较差,浓度达200μg／mL时对毛霉的抑制率仅达54．84％,且对绿僵菌生长的抑制作用显著大于两性霉素和放线菌酮（P＜0．01）,不适宜用于土壤绿僵菌的分离。两性霉素和放线菌酮在浓度为100μg／mL时,对6种非目标真菌抑制率达69％以上,可作为绿僵菌分离的真菌抗生素。     

玉米青贮饲料乳酸菌检测培养基中放线菌酮添加量的优选

通过在MRS培养基、马丁培养基中添加放线菌酮0、5、10、20、40、80、160、320mg/L和640mg/L的5个试验,研究了玉米青贮饲料乳酸菌检测中放线菌酮在培养基中的适宜添加量。结果表明:添加放线菌酮40mg/L以上时能够极显著(P<0.01)抑制青贮玉米霉菌的生长。因此,确定40mg/L为检测或纯化培养青贮玉米乳酸菌时的适宜添加量;鉴于青贮玉米中乳酸菌是真菌的100倍以上,在乳酸菌培养时通过加大接种液的稀释倍数可达到避免样品真菌污染的目的。     

环己酰亚胺对烟草疫霉菌的抑制作用

利用生物测定法研究了环己酰亚胺对烟草疫霉的菌丝生长、孢子萌发的抑制作用,并进行了环己酰亚胺对烟草黑胫病的盆栽药效试验.结果表明:环己酰亚胺浓度为5μg/mL时对烟草疫霉菌的孢子萌发已起到明显的抑制作用,浓度为20μg/mL时抑制率达100%;环己酰亚胺能够抑制烟草疫霉菌丝的生长,在燕麦片培养基平板上,4μg/mL和8μg/mL的环己酰亚胺抑制效果达到84.0%和98.5%;在盆栽试验中15μg/mL的环己酰亚胺对烟草黑胫病的防治效果为75%.     

渗透胁迫下群众杨根细胞中的K+累积效应

群众杨插条苗经PEG渗透胁迫处理后,取根部样品,经过快速冷冻、冷冻干燥、乙醚真空渗透及塑料包埋后,用透射电镜X-射线能谱微区分析技术,对根表皮层、皮层及中柱薄壁组织细胞的细胞壁、细胞质和液泡中的K+含量与分布进行了测定.结果表明,在渗透胁迫下,在根各部位组织细胞的细胞壁、细胞质和液泡中,K+含量都有不同程度的增加,增加的K+主要积累在液泡中.渗透胁迫所促进的K+吸收可被蛋白质合成抑制剂环己酰亚胺所抑制.