Insecticide resistance in cotton aphid Aphis gossypii (Glov.) in the Sudan Gezira

The resistance to insecticides of three Sudanese strains of A. gossypii (Glov.) collected from cotton fields in the Sudan Gezira Scheme over three seasons (1988, 1989, 1990) and that of two French strains was studied in the laboratory. When compared with a known susceptible strain, the aphids were found to be resistant-to the eight insecticides tested. Evolution of resistance in Sudanese strains during the three crop seasons was observed. Assay of aphid homogcnate for carboxytesterase activity towards the substrates α-naphthyl acetate and β-naphthyl acetate showed that there was no enhancement of this class of enzyme and thus it was not a cause of resistance in this species. A study of interaction between the acetylcholinesterase (AchE) and pirimicarb established the kinetics of the inhibition process. I₅₀ values were found to be much higher for the Sudanese strains than for the susceptible strain. First-order inhibition kinetics revealed that resistance towards pirimicarb in Sudanese-strains was caused by a modified AchE which had a reduced affinity (higher K_a value) and poor carbamylation ability (lower K₂ value) for pirimicarb. The resistance mechanisms for the other insecticides remain to be studied.     

Do VA mycorrhizae enhance transpiration by affecting host phosphorus content?

The prevailing indication in the literature is that enhancement of transpiration by vesicular‐arbuscular (VA) mycorrhizae is usually mediated by improved host phosphorus nutrition. The present experiments were conducted to investigate this in mycorrhizal Rosa hybrida L. ‘Samantha’ plants. In growth room and greenhouse studies, roses colonized by either a native or an exotic VA mycorrhizal fungus had greater transpiration rates than nonmycorrhizal rose plants of similar size and phosphorus content, under similar conditions. This mycorrhizal effect on transpiration was observed throughout a range of soil water potential. Whether or not plants were mycorrhizal, phosphorus content was not correlated with transpiration rate on an individual leaf basis.     

食用菌代谢产物研究及其在农业上的应用

本文综述了食用菌核酸类物质、多糖、生理活性物质等代谢产物的研究现状。这些代谢产物作为植物生长调节物质、抗病物质及营养物质调控植物的生长发育,尤其是为植物病害的防治提供了一条新途径。     

Truncating neurotrypsin mutation in autosomal recessive nonsyndromic mental retardation

A 4-base pair deletion in the neuronal serine protease neurotrypsin gene was associated with autosomal recessive nonsyndromic mental retardation (MR). In situ hybridization experiments on human fetal brains showed that neurotrypsin was highly expressed in brain structures involved in learning and memory. Immuno-electron microscopy on adult human brain sections revealed that neurotrypsin is located in presynaptic nerve endings, particularly over the presynaptic membrane lining the synaptic cleft. These findings suggest that neurotrypsin-mediated proteolysis is required for normal synaptic function and suggest potential insights into the pathophysiological bases of mental retardation.     

球虫疫苗对种用雏鸡免疫效果的观测

通过两批（２．８万羽）艾维茵父母代种雏,１０日龄饮水接种７０％剂量的美国ｃｏｃｃｉｖａｃ球虫疫苗。观测结果表明,在舍温２０￣２８℃,垫料湿度２５￣３０％时免疫效果良好。６周龄球虫病死亡率０．０１￣０．３４％,总死亡率低于２．５％;６周后不使用抗球虫病,未见发生球虫病,２４周龄成活率均达９３％以上,与药物防治相比,在种,蛋鸡场使用该疫苗更为方便且经济。     

Predicting interactions between recolonising marine mammals and fisheries: defining precautionary management

Interactions between fisheries and marine mammals have created costly and unresolved issues throughout the world. This study examines the spatial and resource overlaps between recolonising New Zealand sea lions, Phocarctos hookeri (Grey) (using satellite tracking) and local fisheries (using spatio‐temporal catch database) on the Otago coast, New Zealand. Around Otago, spatial and resource overlaps existed year‐round and it is predicted that incidental deaths in fishing gear and resource competition may arise as the sea lion population increases. Preventive management methods (e.g. marine protected areas) and monitoring studies (e.g. fish stock assessments) are proposed. The use of precautionary management could ensure sustainable profitable fisheries and successful recolonisation by sea lions around Otago, and it could be used as a case study for other areas with recovering marine mammal populations that interact with fisheries.