Preliminary Analysis of the Results of Selective Therapy Against Strongyles in Pasturing Horses

Control of horse parasites often omits application of measures to eradicate the free-living stages in pastures and frequently relies on chemotherapy only. Selective therapy was used for Spanish Sport horses grazing either in the same pasture (continuous) or in rotated meadows. In each group, equines exceeding a cutoff value of 300 strongyle eggs per gram of feces received ivermectin or moxidectin. Efficacy of the treatment was assessed by estimating reduction of fecal egg counts and the number of horses shedding parasite eggs (PHR). Coprocultures revealed presence of the cyathostomins Cyathostomum and Gyalocephalus spp. In all treated groups, a 100% value for both reduction of fecal egg counts and PHR against cyathostomins was obtained, and PHR values ranged from 100% to 12%. The longest strongyle egg reappearance period was observed in horses undergoing rotation grazing and receiving ivermectin (9 weeks), compared with a 6-week period recorded for the other treated equines. Our results seem to point that the efficacy of selective therapy in equine herds could be reduced if the horses with fecal egg counts below the threshold value (thus not receiving chemotherapy) remain grazing in the same pastures with the treated ones. It is strongly suggested that interested parties consider performing periodic fecal analyses to monitor fecal egg counts, together with the percentage of horses passing eggs in feces, to improve the effect of this procedure.     

Natural diterpene β-lactone derivative as photosystem II inhibitor on spinach chloroplasts

α,7β-Dihydroxyvouacapan-17β-oic acid (1) was isolated from Pterodon polygalaeflorus Benth. Then, (1) was modified to obtain 6α-hydroxyvouacapan-7β,17β-lactone (2). Inhibition properties of both (1) and (2) were evaluated in spinach chloroplasts. Only compound (2) inhibited non-cyclic electron transport and ATP synthesis, i.e., (2) behaved as a Hill reaction inhibitor. Compound (2) did not affect photosystem I (PSI) activity but it did inhibit electron flow through PSII. Analysis of the partial PSII reactions from water to DCPIP_ox, water to silicomolybdate, and diphenylcarbazide to DCPIP_ox allowed locating inhibition sites at (i) the oxygen-evolving complex (OEC) and (ii) the redox enzymes of the electron transport chain, in the span of P₆₈₀ to Q_A. Chlorophyll a fluorescence measurements confirmed the action site for (2).     

银杏杂交子代药用质量指标的变异研究

[目的]为了准确地选择黄酮、内酯含量高的银杏叶用家系。[方法]以一年生控制授粉的银杏杂交子代苗为试材,采用高效液相色谱法测定杂交子代的黄酮、内酯含量,通过方差分析研究银杏杂交子代药用质量指标的变异情况。[结果]家系间叶片总黄酮含量差异极显著(F=82.99,Pr<0.0001),平均值是13.63 mg/g,变异系数是20.09%;家系间叶片银杏总内酯含量差异极显著(F=33.48,Pr<0.0001),平均值是6.86 mg/g,变异系数是25.82%;家系间单株生物量差异极显著(F=11.63,Pr<0.0001),平均值是4.81 g,变异系数是19.45%;家系间叶片单株有效经济产量有极显著差异(F=14.46,Pr<0.0001),平均值是20.25 mg,变异系数是34.14%。通过聚类分析初步筛选出优良的叶用家系8个。[结论]生态因子和不同种源、品种、采叶时间、树龄、采叶部位、加工方法影响银杏叶黄酮和内酯含量。