Cytochrome P-450-dependent metabolism in isolated liver cells from fed and starved rainbow trout,Salmo gairdneri

The cytochrome P-450 content in liver cells from rainbow trout was not affected by starvation for 12 weeks whereas the rate of cytochrome P-450-dependent deethylation of 7-ethoxycoumarin in liver cells from 6 or 12 weeks starved fish was 60% of the rate in fed fish. Treatment of fish with -naphthoflavone increased the 7-ethoxycoumarin metabolism several-fold in both starved and fed fish.Optimal cytochrome P-450 monooxygenation in liver cells from fed or starved fish was not affected by addition of glucose or 2-bromooctanoate, an inhibitor of fatty acid -oxidation which is the main source of metabolic fuel in trout liver. The cellular content of NADPH, an obligatory cofactor for cytochrome P-450 monooxygenation, was not affected by addition of substrate to cytochrome P-450, inhibition of fatty acid -oxidation or inhibition of the oxidative phosphorylation. This indicates a great capacity of rainbow trout liver cells to retain high NADPH/NADP⁺ ratios. These results suggest that the cytochrome P-450 mediated metabolism of xenobiotics in liver cells from fed or starved trout is not limited by the availability of reducing equivalents.     

磷化铝熏杀柠条豆象的试验研究

通过采用不同药量、不同温度、不同时间磷化铝熏杀柠条豆象的试验,结果认为磷化铝熏杀柠条豆象,以1 m3种子用12 g~16 g磷化铝片,温度20℃,熏蒸12 d~16 d,杀虫率可达85.6%;处理方法,以室外黑塑料袋密封法最好。     

Cytochrome P-450 mediated O-dealkylation of 7-alkoxycoumarins in liver microsomes from rainbow trout (Salmo gairdneri)

Evidence has recently been presented for variation in the inducibility of various 7-alkoxycoumarin-O-dealkylase activities in liver microsomes from a number of mammalian species by -naphthoflavone (NF). In the present study we have investigated the inducibility of hepatic microsomal 7-methoxycoumarin-O-demethylase, 7-ethoxycoumarin-O-deethylase, 7-propoxycoumarin-O-depropylase and 7-butoxycoumarin-O-debutylase activities in rainbow trout by NF. O-demethylase activity was increased approximately 17-fold, O-deethylase and O-depropylase activities approximately 9-fold and O-debutylase activity approximately 25-fold. The kinetics of the various hepatic microsomal 7-alkoxycoumarin-O-dealkylase activities were investigated in control and NF-treated rainbow trout. The O-demethylase-, O-depropylase- and O-debutylase activities exhibited monophasic Michaelis-Menten kinetics in liver microsomes from both control and NF-treated rainbow trout, whereas the O-deethylase activity exhibited biphasic Michaelis-Menten kinetics in control liver microsomes and monophasic Michaelis-Menten kinetics in liver microsomes from NF-treated rainbow trout.     

应用压力-容积技术测定3个防火树种的水分特征

此研究旨在研究防火树种的水分特性,为南方地区防火树种选择提供理论依据。应用压力-容积（P-V）分析技术测定了木荷Schima superba,秃瓣杜英Elaeocarpus galbripetalus和青冈Cyclobalanopsis glauca等3个防火树种春季、夏季和秋季的水分特征参数,即初始质壁分离点渗透势πp,饱和含水量时的最大渗透势π₀,细胞弹性模数ξ,细胞质壁分离时的共质体水体积量与饱和时共质体水体积量之比V_p /V₀。结果表明：①在不同季节中,木荷与青冈的4项水分特征参数变化趋势与范围相似,而与秃瓣杜英的相差较大;②通过比较3个树种的4项水分参数在3个生长季节的平均数,得出抗旱性排列顺序是青冈＞木荷＞秃瓣杜英。图2表1参11     

Regional distribution of microsomal xenobiotic and steroid metabolism in kidney microsomes from rainbow trout

The regional distribution of microsomal cytochrome P-450-mediated reactions with exogenous and endogenous substrates in the kidney of rainbow trout was studied. The cytochrome P-450-dependent 7-ethoxyresorufin- and 7-ethoxycoumarin-0-deethylase activities were significantly higher (3–4 and 10–14 fold, respectively) in the trunk kidney than in the head kidney, whereas ethylmorphine-N-demethylase activity was evenly distributed along the kidney. The microsomal cytochrome P-450-dependent steroid hydroxylases and steroid reducing enzymes when using androstenedione as substrate also exhibited a regional distribution in trout kidney. The 6β- and 16-hydroxylase activities as well as the 5α-reductase and 17 hydroxysteroid oxidoreductase activities were higher in the anterior part of the trunk kidney than in the head kidney and posterior trunk kidney.     

Effects of phosphorus and potassium deficiency treatment on roots secretion of wheat and rice seedlings

Abstract

Firstly, the secretion of sugars, protein and acid phosphatase from wheat and rice roots into surrounding medium under conditions of P and K deficiency stresses were studied. Secondly, Sephadex elution patterns of wheat root exudates labeled with ¹⁴C under N, P and K deficiency treatments were compared.

P deficiency treatment induced acid phosphatase activity in medium, in spite of the decrease in the secretion of total sugars and pro tein from roots into medium, whereas no such increase was observed in K deficiency stress.

Secretion of high molecular fraction of ¹⁴C compounds from roots was accelerated by P deficiency stress, probably being associated with the presence of phosphatase activity in the medium.

Activity of acid phosphatase secreted from P-deficient roots corresponded to nearly one half of the rate of P absorption by normal plant.     

自然降雨条件下紫色土区磷素的非点源输出规律

2003年8月8日在中国科学院盐亭紫色土研究站采集动态降雨径流样并进行分析,研究了紫色土区典型土地利用方式下磷素的非点源输出规律。结果表明,在该区各形态的磷随地表径流的输出不一定随时间递减。旱地径流输出主要以颗粒吸附态磷素为主。水田在该区中因降雨引起的磷素迁移而造成的非点源污染不可忽视,其磷酸盐随径流的排放浓度在0.06mg·L-1左右波动,远超过富营养化的警戒线浓度0.02mg·L-1,溶解性磷与磷酸盐随径流迁移的浓度均达水体富营养化的警戒线。     

Resistance in Maconellicoccus hirsutus (Green) in India to selected insecticides and quantification of detoxifying enzymes imparting resistance

Pink mealybug Maconellicoccus hirsutus (Green) (Hemiptera: Pseudococcidae) is a destructive pest of agricultural and horticultural crops. Insecticides are the major tool used to control M. hirsutus. The present study was conducted to evaluate resistance to the commonly used insecticides acephate, dichlorvos, imidacloprid and buprofezin in M. hirsutus collected from seven different geographical locations of mulberry and vineyards in India. Detoxifying enzymes, namely esterase, glutathione S transferase (GST) and cytochrome P-450 (cyt-P450), were quantified in populations. One population from Erode showed a low level of resistance to acephate (resistance ratio [RR] 10.3-fold), one from Salem showed a low level of resistance to dichlorvos (resistance ratio [RR] 13.7-fold), one from Sangli showed a very low level of resistance to imidacloprid (RR 10.2-fold), and one from Chikkaballapur showed a low level of resistance to buprofezin (RR 14.8-fold). Activity ratios for detoxifying enzymes ranged from 1.8- to 4.9-fold for GST, 1.8- to 3.7-fold for esterase and 1.9- to 2.4-fold for cyt-P450. Furthermore, organophosphate resistance and activity of enzymes (esterase, GST and cyt-P450) were positively correlated. To contain the evolution of resistance to M. hirsutus infestation, buprofezin and imidacloprid could be used, supplemented with biointensive integrated management strategies and regular resistance monitoring programs.