The effects of DDT and dieldrin on rat peritoneal macrophages

The effects of DDT and dieldrin on cell population, viability, and phagocytic activity on the rat peritoneal macrophages were studied. It was observed that both pesticides, at low levels of concentration, exhibited a marked effect on this cell type. At the lowest concentrations tested both pesticides produced an increase in the macrophage population which appeared to be the result of a foreign-body response. At higher concentrations of pesticide this foreign-body response appears to be inhibited. The phagocytic activity of the cells steadily decreased as the concentration of the pesticide administered increased, and a decrease in cell viability with increased pesticide exposure was also noted.     

Protective effects of Nigella sativa oil on propoxur-induced toxicity and oxidative stress in rat brain regions

Propoxur (PPr) is a widely used broad spectrum carbamate insecticide mainly used to control household pests. Because of the widespread use of pesticides for domestic and industrial applications, evaluation of their neurotoxic effects is of major concern to public health. The aim of the present study was to evaluate the possible protective effects of Nigella sativa oil (NSO), an antioxidant agent, against PPr-induced toxicity and oxidative stress in different brain regions of rats including cerebellum, cortex and hippocampus. In the present study, 32 male Sprague-Dawley rats were used and divided into four equal groups. Group 1 was allocated as the control group. Groups 2-4 were orally administered 1 ml/kg/bw/day NSO, 8.51 mg/kg/bw/day PPr or NSO plus PPr, respectively, for 30 days. Lipid peroxidation (LPO), protein carbonyl content (PCC) and acetylcholine esterase activity (AChE) were determined. Enzymatic antioxidant activities [superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione-S-transferase (GST)] and non-enzymatic antioxidants [reduced glutathione (GSH)] were determined. PPr treatment significantly increased the levels of LPO, PCC and oxidized glutathione (GSSG) in brain regions. On the contrary, levels of GSH and the activities of SOD, CAT, GSH-Px, GST and AChE were significantly decreased. NSO treatment to PPr intoxicated rats restored such biochemical parameters to within control levels except GST activity, emphasizing its antioxidant role. We conclude that NSO significantly reduces PPr-induced toxicity and oxidative stress in rat brain regions via a free radicals scavenging mechanism.     

The control of Plasmopara viticola with the 1:1 complex of zineb with 2-(2-aminoethylamino)ethanol and the potential effect of the use of this complex on ethylenethiourea residues

Zineb 1:1 complex with 2-(2-aminoethylamino)ethanol was shown to be more active than zineb in glasshouse and field trials against Plasmopara viticola. The effects of this increase in efficacy on the potential reduction of ethylenethiourea residues are discussed.     

Comparative effects of organophosphorus insecticides on the activities of acetylcholinesterase,diacylglycerol kinase,and phosphatidylinositol phosphodiesterase in rat brain microsomes

The activities of acetylcholinesterase, diacylglycerol kinase, and phosphatidylinositol phosphodiesterase in rat brain microsomes were measured in the presence and absence of the organophosphorus insecticides, parathion and diazinon, and their respective oxon analogs, paraoxon and diazoxon. Marked inhibition of acetylcholinesterase (by 45–99%) was observed in the presence of paraoxon (10^?2–10^?6M) and diazoxon (10^?2–10^?4M). Reduction of acetylcholinesterase activity (by 22–33%) was achieved with the parent insecticides at high concentrations only (10^?2M). In most cases, diacylglycerol kinase was insensitive to the pesticides. Marked stimulation of phosphatidylinositol phosphodiesterase (by 10–57%) was observed in the presence of all pesticides (10^?2–10^?3M). The phosphodiesterase exhibited slightly greater sensitivity to the parent compounds compared to the oxon derivatives. Stimulation of the phosphodiesterase by the insecticides was not correlated with acetylcholinesterase inhibition. Accordingly, the increase in phosphodiesterase activity was judged not to be acetylcholine mediated, but rather represented a direct effect of the pesticides on the enzyme or its microenvironment. Based on the present in vitro observations, it is proposed that certain organophosphorus pesticides may interfere with the normal process of synaptic transmission through both the inhibition of acetylcholinesterase and the stimulation of phosphatidylinositol phosphodiesterase. In view of the high concentrations of pesticides required to elicit the latter effect, interpretation of its physiological significance must await results from further studies performed in vivo.     

Binary mixtures of pyrethroids produce differential effects on Ca influx and glutamate release at isolated presynaptic nerve terminals from rat brain

Isolated rat brain synaptosomes were used to evaluate the action of pyrethroid mixtures on Ca²⁺ influx and subsequent glutamate release under depolarizing conditions. In equipotent binary mixtures at their respective and/or estimated EC₅₀s with deltamethrin always as one of the two components, cismethrin, λ-cyhalothrin, cypermethrin, esfenvalerate and permethrin were additive and S-bioallethrin, fenpropathrin and tefluthrin were less-than-additive on Ca²⁺ influx. In binary mixtures with deltamethrin always as one of the two components, esfenvalerate, permethrin and tefluthrin were additive and λ-cyhalothrin was less-than-additive on glutamate release. Binary mixture of S-bioallethrin and cismethrin was additive for both Ca²⁺ influx and glutamate release. Only a subset of pyrethroids (S-bioallethrin, cismethrin, cypermethrin, and fenpropathrin) in binary mixtures with deltamethrin caused a more-than-additive effect on glutamate release. These binary mixtures were, however, only additive (cismethrin and cypermethrin) or less-than-additive (S-bioallethrin and fenpropathrin) on Ca²⁺ influx. Therefore, increased glutamate release evoked by this subset of pyrethroids in binary mixture with deltamethrin is not entirely occurring by Ca²⁺-dependent mechanisms via their action at voltage-sensitive calcium channels. These results suggest that pyrethroids do not share a common mode of toxicity at presynaptic nerve terminals from rat brain and appear to affect multiple target sites, including voltage-sensitive calcium, chloride and sodium channels.     

Biochemical evidence on positive effects of rolipram a phosphodiesterase-4 inhibitor in malathion-induced toxic stress in rat blood and brain mitochondria

Malathion is an organophosphate (OP) pesticide that has been shown to induce oxidative stress in brain through the generation of free radicals and alteration of the cellular antioxidant defense system independent of its anticholinesterase effects. The aim of this study was to investigate the possible protective role of rolipram as a selective phosphodiesterase (PDE) type 4 inhibitor, on toxicity of malathion, by measuring the activities of brain mitochondrial and plasma peroxynitrite (ONOO⁻), glutathione peroxidase (GPx), superoxide dismutase (SOD), Mn-SOD, catalase (CAT), and lipid peroxidation (LPO) in rats. Effective doses of malathion (200 mg/kg/day) and rolipram (200 μg/kg/day) were administered alone or in combination for 7 days by intraperitoneal injection. At the end of the experiment, the brain mitochondria and plasma of the animals were separated. In the brain cells mitochondria and blood plasma, the LPO, ONOO⁻, and GPx were higher in the malathion group as compared with controls. Rolipram ameliorated all of malathion-induced changes. Plasma CAT decreased in malathion-treated animals while it increased in brain mitochondria comparing with controls. Co-administration of rolipram with malathion improved CAT in both brain mitochondria and plasma. Malathion and rolipram did not alter total SOD or Mn-SOD in the plasma while both caused a significant elevation in brain mitochondria. In conclusion, this model of study that we employed, in a large extent, characterized the relationships among malathion-induced neurotoxicity, mitochondrial dysfunction, and significant increase in systemic and local oxidative/nitrosative stress in plasma and brain, respectively. Intracellular cAMP-elevating agents like rolipram, may be considered beneficial for the protection or recovery of malathion-induced toxic damage in brain mitochondria and blood.     

Divergent effects of PVY-infected potato plant on aphids

Host plant selection by aphids can be positively or negatively affected when plants are infected by phytoviruses. Potato plants infected by Potato virus Y (PVY), a non-persistent virus, are reported to affect settling behaviour and growth parameters of Myzus persicae Sulzer and Macrosiphum euphorbiae Thomas. Using the Electrical penetration graph system (EPG), we demonstrated that PVY-infection of potato plants influences the feeding behaviour of these two aphid species. Myzus persicae exhibited increased phloem sap ingestion and reduced non-probing duration. Macrosiphum euphorbiae showed delayed stylet insertion, reduced activity in the phloem vessels and an enhanced non-probing duration. In addition, we showed that these two species exhibited different transmission rates. The opposite effects of PVY-infected potato plant on these two aphids are discussed in terms of PVY spreading in the field.     

节水灌溉对两个冬小麦品种影响效应的初步研究

在全生育期防止天然降水情况下,研究了节水灌溉对2个冬小麦品种（系）若干重要性状和土壤含水量的影响。结果表明,不同处理2个品种生育期缩短幅度为3d-24d,水分利用率较高。豫麦34抽穗－成熟阶段耗水量约占全生育期耗水量的2／5,且灌浆开始早,速度快,千粒重显著提高,产量和水分利用率均高,洛阳8716由于前中期生育时期长,开花迟,节水灌溉又使开花－成熟期大幅度缩短,导致粒重变小,产量降低。     

Modelling the effects of weeds on crop production

In most quantitative studies on interplant competition, static regression models are used to describe experimental data. However, the generality of these models is limited. More mechanistic models for interplant competition, which simulate growth and production of species in mixtures on the basis of the underlying physiological processes, have been developed in the past decade. Recently, simulation models for competition between species for light and water were improved and a detailed version was developed for sugarbeet and fat hen (Chenopodium album L.). The model was validated with data sets of five field experiments, in which the effect of fat hen on sugarbeet production was analysed. About 98% of the variation in yield loss between the experiments (which ranged from –6 to 96%) could be explained with the model. Further analysis with the model showed that the period between crop and weed emergence was the main factor causing differences in yield loss between the experiments. Sensitivity analysis showed a strong interaction between the effect of the variables weed density and the period between crop and weed emergence on yield reduction. Different quantitative approaches to crop-weed competition are discussed in view of their practical applicability. Simulations of experiments, where both the weed density and the period between crop and weed emergence were varied over a wide range, showed a close relation between relative leaf cover of the weeds shortly after crop emergence and yield loss. This relation indicates that relative leaf cover of the weeds accounts for both the effect of weed density and the period between crop and weed emergence. This relation has the potential to be developed into a powerful tool for weed-control advisory systems.     

Pesticide effects on secondary metabolism of higher plants

Secondary compounds serve both endogenous and exogenous functions in higher plants because they are involved in plant growth and development as well as intraspecies and interspecies interactions. Documentation of the effects of pesticides on secondary compound biosynthesis in higher plants is increasing. While several herbicides have been reported to reduce levels of secondary compounds by non-specific mechanisms, a few herbicides, such as alachlor and glyphosate, directly affect specific biosynthetic steps. Alachlor reduces flavonoid synthesis at a step late in the biosynthetic pathway, and glyphosate blocks synthesis of all cinnamate derivatives by inhibiting 5-enolpyruvyl shikimate-3-phosphate (EPSP) synthase. Inhibition of EPSP synthase also leads to the accumulation of high levels of shikimate, benzoic acids and benzoic acid derivatives. The sulfonylureas and p-nitro-substituted diphenylether (DPE) herbicides can cause increases in the level of cinnamatederived phenolic compounds and the DPEs can cause dramatic increases in terpenoid stress metabolites. Certain fungicides are thought to act through enhancing the capacity of plants to produce phytoalexins. These and other data suggest that sublethal effects of pesticides on target and non-target plants can significantly affect agricultural ecosystems by altering the synthesis of compounds important in inter- and intraspecies interactions.     

遮阴对作物生长影响的研究进展

光照环境对植物光能利用效率和生产力起着决定性作用。从植物的生长、光合作用（光合速率、蒸腾速率、气孔开度、水分利用效率）、植物矿质营养等方面就国内外有关遮阴对作物影响的许多研究成果进行了分析和评述,讨论了遮阴条件下作物的生态、生理和生化因子之间的相互关系以及对遮阴的适应机制,指出了该领域研究中存在的问题和今后应加强研究的方向。     

Studies on the effects of herbicides on soil nitrification,II

The effects of selected herbicides have been studied on the following parameters of soil nitrification processes: the rates of nitrate and nitrite formation from ammonia in freshly perfused soils and in soils previously saturated with nitrifying organisms in an improved perfusion apparatus; the rates of oxygen consumption and of oxidation of ammonia and nitrite in washed cell suspensions of Nitrosomonas europaea and Nitrobacter winogradskii, respectively; the rates of growth of those two organisms in newly established cultures; the rates of oxygen uptake by soil enriched in nitrifying organisms; the rates of proliferation of nitrifying populations in freshly perfused soil. ID50 values were computed for all parameters and herbicides studied. On average, the most sensitive parameters were the metabolism and growth of the two organisms in pure culture, while the least sensitive were the corresponding measures in the soil environment. Similarly, herbicides fell into four distinct groups. The most toxic were the formulated octanoates of bromoxynil and ioxynil (NPH1320 and Totril, respectively); next in order of toxicity were chlorbufam, phenmedipham, formulated oxadiazon, formulated legurame, ioxynil, formulated trifluralin, and bromoxynil; low toxicity was shown by terbacil, dicamba, and tricamba, whereas asulam and the related experimental herbicide MB9555 showed activity on some parameters at the very highest concentrations only. Comparisons of soil with pure-culture parameters showed that the relative toxicities of herbicides to Nitrosomonas in culture bore little relationship to those in soil. The inhibitions of Nitrobacter proliferations in soil on the other hand were correlated with the inhibitions of growth and metabolism in pure culture. Within these overall effects, individual herbicides showed marked differential actions on various parameters. Thus, the formulated octanoates of bromoxynil and ioxynil were extremely toxic to the growth of nitrifying organisms in culture, an action probably due to an unknown formulation component. Relative to other herbicides, bromoxynil and ioxynil were more effective on nitrification processes in the soil environment. Both in culture and in the soil, Nitrobacter is more sensitive than Nitrosomonas to these four herbicides. Legurame and oxadiazon are relatively more toxic to Nitrosomonas in culture, but this differential action is not demonstrable in the soil. Dicamba, tricamba, trifluralin, and chlorbufam are more toxic to Nitrobacter than to Nitrosomonas in the soil environment. Formulated trifluralin seems to exert a stimulating action on the growth of nitrifying organisms, but only in the soil; suppression of antagonistic organisms is suggested as a possible cause. Extrapolation of these results to the field situation suggests that the only herbicide which might cause small inhibitions of nitrification at field rates is terbacil, which is disproportionately toxic at low concentrations. At rates somewhat in excess of normal, the formulated octanoates of bromoxynil and ioxynil and possibly dicamba and oxadiazon could also cause small inhibitions.     

生态调控对东亚飞蝗的控制作用研究

东亚飞蝗的成活率,在野生植物中以取食荻和稗者最高,在栽培作物中以取食小麦、玉米最高。生殖力,在野生植物中以取食食狗芽牙根最强,在栽培作物中以取食高粱最强。据此,应用以植被改造为主的生态调控技术,可以形成不利东亚飞蝗的发生、繁衍,而有利天敌繁衍和觅食的生态环境,从而抑制东亚飞蝗的发生。生态控制区在战略上还对飞蝗的迁移起到了隔离作用,但种植棉花、苜蓿、冬枣等不同作物的生态控制区的控蝗效果有一定差异。     

Modeling environmental effects on enhanced carbofuran degradation

Prediction of the fate of pesticides in soil is of interest from an environmental (pollution) as well as an agricultural (efficacy, carryover) viewpoint. Two environmental parameters that control microbial degradation of pesticides in soil are moisture and temperature. This study was designed to quantify the impact of soil water content and temperature on microbial degradation rates of the insecticide carbofuran (2, 3-dihydro-2, 2-dimethylbenzofuran-7-yl methyl-carbamate). Carbofuran degradation was determined by monitoring the [ 14 C] carbondioxide production from soils amended with [carbonyl- 14 C]carbofuran. Soils were incubated at seven soil-water tensions over the range of 0–03 to 1–5 MPa, and at five temperatures (10°C to 30°C). The sigmoidal degradation kinetics observed from these incubations were modeled using a general saturation model. For the moisture experiments, maximum rate of hydrolysis and half-life (DT₅₀) were accurately modeled by an exponential relationship. The response of carbofuran degradation to temperature was also well described by an exponential relationship, from which it was estimated that the Q₁₀ associated with the maximum rate was 1.68, and the Q₁₀ for DT₅₀ was 1–89.     

Inhibitory effects of validamycin compounds on the termites trehalase

Trehalase, with the target to control insects, nematodes and fungi, is of increasing interest and has been investigated extensively in recent years. Validamycin compounds, as competitive trehalase inhibitors and lead compounds with broad applications have attracted substantial attention as well. In this study, the characterizations of termites trehalase were investigated and the inhibitory effects of validamycin compounds on the termites trehalase were studied as well. Results showed that the termites trehalase is presumably belonging to the acid trehalase with optimal pH of 3.3 and optimal temperature of 37 °C. It was investigated that the concentrations of validoxylamine A (VAA), validoxylamine B (VBB), validamycin A (VA) and validamycin B (VB) required for 50% inhibition IC₅₀ of termites trehalase were calculated to be 14.73 mg l⁻¹, 20.80 mg l⁻¹, 3.17 × 10³ mg l⁻¹and 2.24 × 10³ mg l⁻¹, respectively. The inhibition kinetic constant K_i values for the above validamycin compounds were 3.2 × 10⁻⁶ mol l⁻¹, 1.03 × 10⁻⁵ mol l⁻¹_, 4.02 × 10⁻⁴ mol l⁻¹and 2.69 × 10⁻⁴ mol l⁻¹, respectively. Validoxylamine A appeared to be the most potential termites trehalase inhibitor among the four compounds.     

栽培技术措施对水稻条纹叶枯病发生的控制作用

通过实践探索,分析了靖江市近年来水稻条纹叶枯病发生情况变化与栽培措施演变的关系,阐明了生产上利用水稻抗性品种、采用合理的栽培方式、适期播种等栽培技术措施对水稻条纹叶枯病有明显的控制作用.     

烟嘧磺隆OF防除玉米田杂草的效果及安全性

8％烟嘧磺隆0F48—72g/hm^2能有效防除玉米田一年生杂草,药后30d对马唐、狗尾草、藜、铁苋菜、异型莎草的株防效为94．7％-98．5％,鲜重防效为93．7—98.4％。在推荐剂量下,对玉米生长安全。     

Genetic effects of phthalimide fungicides on diploid Aspergillus nidulans

A few specimens of ‘Ridomil 25 WP’, a commercial formulation of metalaxyl, showed high genetic activity on a heterozygous diploid strain of Aspergillus nidulans. This activity was due to an impurity which was identified by mass and n.m.r. spectroscopy as captafol. This and the related fungicides captan, dichlofluanid, and tolyfluanid greatly increased the yield of euploid colour segregants from the diploid strain. At low captafol concentrations, most of the induced segregants resulted from mitotic crossing over but chromosome non-disjunction or loss was also caused at high concentrations. Mitotic crossing over could be induced also by vapour-phase action of captafol and captan. The mechanism by which these phthalimides may exert their genetic effects is discussed.     

Studies on the therapeutic effects of pectolytic enzyme inhibitors

A few polyphenols (tannic acid and digallic acid), anthraquinone derivatives (rufianic acid and quinalizarin), and detergents (an alkylaryl sulfonate) proved to be especially effective inhibitors of pectolytic and cellulolytic enzymes of four phytopathogenic fungi. Some of these substances prevented the infection of tomato leaves withAlternaria solani. It appears, however, that inhibition of the germination of conidia was the crucial effect rather than inhibition of the enzymes. Alkylaryl sulfonate and rufianic acid were able to reduce the maceration of bean hypocotyls byRhizoctonia solani. Rufianic acid also counteracted tomato wilt, caused byFusarium oxysporum f.lycopersici, especially in the case of postinfectional application. On the other hand preinfectional rather than postinfectional application of rufianic acid had effect onVerticillium wilt of tomato.In one case, viz.Fusarium wilt, the mode of action of rufianic acid was investigated in greater detail. The presence of this substance could be demonstrated in the exudates of healthy and infected plants after application to the roots. The pectolytic and cellulolytic activity of the exudates and the pectinmethylesterase activity of stem extracts of infected, rufianic acid treated plants were reduced, as well as the quantity of mycelium in the stems. Possibly other mechanisms are also involved in the mode of action of rufianic acid.The prospects of using pectolytic enzyme inhibitors for the therapy of plant diseases are discussed.