土壤微量节肢动物组织中镉测定方法的改进

Highly precise and reliable determination of heavy metals in soil micro-arthropod tissues remains a challenge because of the small size of the animals and their typical low abundance in metal-contaminated agricultural soils. The present study sought to develop a method for cadmium(Cd) determination in soil micro-arthropods by optimizing the sample digestion procedure, reducing sample weight, modifying sample pre-treatment and validating the methodology with field samples. The optimized digestion conditions comprised a sample mass of 50–150 μg, digestion reagent of nitric acid:hydrogen peroxide(3:1), digestion temperature of 105℃,digestion period of 3 h and digestion volume of 30 μL. Defecation of the standard Collembola Folsomia candida(92 h) and the indigenous Collembola Onychiurus yodai(42 h) and ultrasonic cleaning of F. candida increased the accuracy of Cd determination.The recovery of Cd using the refined procedure was 98.9% and the limits of detection and quantification were 0.002 and 0.008 μg L~(-1), respectively. The within-batch precision values were 3%. The Cd concentrations in the tissues of the Collembola Isotoma sp.collected from a range of metal-contaminated fields determined by the improved method were consistent with the Cd concentrations in the field soils. The results indicate that the optimized method can be used for more accurate or reliable determination of Cd concentrations in soil micro-arthropod tissues.     

Endozoochory of frugivorous birds as potential dispersal of seed parasites from Pistacia chinesis: experimental evidence

The plant–disperser–fruit pest triads involve 3 interacting animals or groups (plants, vertebrates and seed parasites), and the dispersal of both seeds and seed parasites, which can both benefit from endozoochory via defecation or regurgitation by frugivorous vertebrates. However, we have very limited knowledge about the ecological and evolutionary consequences of these plant–disperser–fruit pest triads. Across central Northern China, several seed wasps (mainly Eurytoma plotnikov attack Pistacia chinensis fruits, and seed wasp larvae can develop, diapause and finally emerge as adults inside a seed during the following 1–3 years. In this study, we experimentally investigated whether frugivorous birds discriminated P. chinesis fruits with or without seed parasites, and whether bird endozoochory (by defecation or regurgitation) affected larval survival of seed parasites. The infestation rate by seed parasites was 37% of the P. chinesis fruit crop but with up to 48% of aborted fruits. We found that all 5 bird species can discriminate and then reject all unhealthy fruits (including aborted and insect‐infested). However, 4 of the 5 bird species, in particular bulbul species, consumed 15–41% of aborted and insect‐infested fruits as complementary food only when these unhealthy fruits were provided. Moreover, all larva of seed parasites remained alive after bird defecation or regurgitation. In conclusion, our study demonstrates that endozoochory by frugivorous birds could lead to potential dispersal of seed parasites of P. chinensis but with a very low probability.     

谈利小便实大便

“利小便实大便”是中医重要的治疗方法之一。下焦主分清浊,下利者,水谷不分也;三焦湿郁,升降失司,脘连腹胀,大便不爽。临床上利小便实大便,一方面不仅治疗大便泄泻,同时也治疗大便黏腻不爽,使二便分消,水湿从小便而去。五苓散渗湿利水,温阳化气,治疗便溏;一加减正气散化湿和中,理气健脾,治疗大便不爽。本文结合治疗慢性腹泻和糖尿病的病例,论述利小便实大便理论在临床上的应用。但久泻不可纯利小便,温病利小便宜甘苦合化阴利小便。