Immune responses in piglets infected with highly pathogenic porcine reproductive and respiratory syndrome virus

Porcine reproductive and respiratory syndrome virus (PRRSV) infection compromises the host's innate and adaptive immunity. The aim of this study was to investigate the immune responses of piglets infected with highly pathogenic (HP) PRRSV (HuN4 strain) with or without the immunization with CH-1R attenuated PRRSV vaccine. The response was evaluated for the clinical signs, pathological changes and virus load in immune organs, antibody responses and levels of serum IFN-γ, IL-4 and IL-10. The result showed that in comparison with the piglets received the immunization, the piglets infected with HP-PRRSV alone had the thymus atrophy, decreased serum levels of IL-4 and increased serum levels of IL-10 and INF-γ. These results suggest that elevated IL-10 levels at the early stage of the infection may enhance virus survival and delay the induction of protective immunity, while increased levels of IL-4 induce the effective immune responses and increase the animals' health status.     

Comparison of larval thermal maxima between <Emphasis Type="Italic">Fundulus heteroclitus</Emphasis> and <Emphasis Type="Italic">F. grandis</Emphasis>

Fundulus heteroclitus and F. grandis are resident salt marsh fishes that overlap in distribution over a narrow range in northeastern Florida. The objective of the present study was to examine whether the limits of the species’ ranges could be explained by differences in thermal tolerance. Two populations of each species were collected and then spawned in the laboratory, and 9-day-old larvae were used for critical thermal maxima trials. Mean LOE temperatures of larvae ranged from 43.04 to 43.65°C and showed little difference between species. Therefore, differences in high temperatures experienced cannot account for the differences of the distributions of the two species. Condition-specific competition may play a greater role in determining the observed range of the two species.     

常年性变应性鼻炎手术疗法探讨

探索常年性变应性鼻炎的治疗新方法,方法选择各种非手术疗法不佳的常年性变应性鼻炎患者３６例为手术组（６例伴有支气管哮喘）,病程１．５－２０ａ局麻下行双侧蝶腭,筛前神经电灼加下鼻甲部切除切;另选３１例未行手术首作为对照组。结论蝶腭,筛前神经电灼加下鼻部分切除的新方法为治疗常年性变性鼻炎之有效的方法之一。     

Effects of nitrogen and water stress on the rehydration,endogenous hormonal regulation and yield of maize

Water scarcity is known to be a strong limiting factor affecting maize grown and yield in cold semi-arid regions. Numerous studies have shown that rehydration improves maize growth. Our study aimed to explore the effects of rehydration treatments on maize growth and yield under water and nitrogen stress during different growth stages. We selected the drought-tolerant maize variety Nendan 19 (ND19) and subjected it to water stress during the V6 (sixth-leaf), R2 (filling) and R6 (maturity) growth stages and a rehydration treatment after each stress stage. Our results indicated that N1 (N100 kg N ha⁻¹) and N3 (N300 kg N ha⁻¹) treatments significantly increased the leaf moisture status relative to water content (RWC), bound water content (BWC), free water content (FWC) and water potential (WP)) at different growth stages. Similar trends were observed in the accumulation of plant leaf and root hormones (zeatin+zeatin riboside, indole-3-acetic acid, abscisic acid and gibberellic acid), photosynthetic pigments and chlorophyll fluorescence. However, under the same water stress conditions, they decreased as the N rate increased and reached a minimum value in the S3 (water stress for N3) treatments. In addition, with growth stage advancement and extension of the rehydration time, both showed a gradual upward trend. The results showed that to save water resources in the cold semi-arid region, rehydration treatments (R2S1 and R2S3) significantly increased the photosynthetic pigments and chlorophyll fluorescence parameters, leaf moisture status, biomass, 100-grain weight, hormone content, ear characteristics and grain yield of maize.     

Magnesium influence on plant uptake of phosphorus in a calcareous soil

A pot experiment was conducted to investigate the role of magnesium (Mg) in plant utilization of ³²phoshorus (P)‐labelled P in a calcareous soil (Typic Hapluquent). Results with two successive harvests of ryegrass shoots indicated that Mg had no obvious influence on plant uptake of the P applied. In a separate incubation study with the same soil, labelled P along with different levels of Mg was introduced to the soil at two time intervals and soil inorganic P was fractionated. The isotope data of P in various fractions indicated that Mg at the test levels had no obvious influence on P transformation either. It is suggested from the experiments that Mg is unlikely to be able to promote plant utilization of fertilizer P in calcareous soils.     

Factors affecting the adoption of agroforestry practices by farmers in Cameroon

This paper presents empirical evidence on the impact of socio-economic factors on the adoption of agroforestry practices in Cameroon. The analysis uses primary farm-level data collected from June to December 1996. Three major provinces of the country were covered, namely Centre, Southwest and Northwest Several agroforestry technologies have been promoted among farmers in the zone, including alley farming, improved fallow, live fencing, cut-and-carry fodder and apiculture. The status of adoption of each agroforestry practice is described and factors that affect adoption identified. These are gender of farmer, household family size, level of education, farmer’s experience, membership within farmers’ associations, contact with research and extension, security of land tenure, agroecological zone, distance of the village from nearest town, village accessibility and income from livestock. Research findings indicate that since factors affecting farmers’ adoption of agroforestry practices differ across techniques, generalisation is to be avoided.     

良种桉中大径材复层林经营试验研究

对复层林中3种大径材保留密度及对照的纯纸浆材萌芽林进行试验研究,结果表明：大径材3种不同密度处理对其平均树高生长影响不大,而对平均胸径和蓄积生长量的影响较大.大径材低密度有利于胸径的生长,3种处理之间的相互差异都比较大.复层林所保留的大径材对林下萌芽的生长有明显的抑制作用,蓄积所受的影响比高和胸径所受的影响大.随着林龄的增大,复层林的经济效益比纯纸浆材林大,约为2倍.复层林经营是一个值得借鉴的新的营林方式.     

马尾松,大头茶针阔混交林森林结构的研究

典型选样调查测定,分析马尾松、大头茶常绿针阔混交林的森林特征、种群结构、林分结构、生物量结构及生态功能。结果表明:1.该混交林是亚热带常绿阔叶林前一阶段的过渡性森林类型,在干扰状态下保持其相对的稳定性。2.复层、异龄现象是该混交林的主要特征。建群种充分利用了林地空间营养面积,发挥了林地的生产潜力。叶面积指数达6.86～8.83,林分木材蓄积量达160～222m~3/ha,林分总生物量达114～163t/ha。其中,乔木层生物量达105～154t/ha。光照充足的林下,草本层生物量可达2.5t/ha,对庇护地表起到了最直接、最明显的作用,而调节林冠密度,可控制或促进草本层生物量的增长。3.此种混交林改善了森林立地的蓄水功能和贮水方式。林地土壤最大贮水量达2645～4100t/ha,降水贮存量达565～1256t/ha,林地枯枝落叶层饱和持水量达4589～8702kg/ha。该类型达到了生态与经济效益兼顾,可在我国南方亚热带山地各类工程造林中推广应用。     

雏鹅氨气中毒的诊治

一发病情况 本镇李某购进太湖雏鹅1000只,在一面积60余平方米的塑料薄膜棚内育雏。该棚没有门窗,四面塑料薄膜下垂到地面,用砖头和木板压紧,内装有6只250W红外线灯作取暖用。雏鹅在11日龄前一切正常,12日龄时有4只死亡,以后每天都有死亡,至3月5日现场检查发现,棚内共死亡56只。     

杂交狼尾草亲本的开花特性

杂交父本象草Ｎ５１是对光照最为敏感的短日照作物,每日９ｈ,光照处理２～３周,能有效地诱导抽穗开花。象草的穗由分蘖穗和分枝穗组成,由于单株分蘖穗和分枝穗发育程度的差异和群体中个体间的差异致使Ｎ５１群体散粉期可达３０ｄ,散粉高峰期２周。母本Ｔｉｆｔ２３Ａ在南京能完成生育过程,开花期与播期有关,相关系数为０．８８６,群体散粉期与Ｎ５１同样有３０ｄ。由于亲本花期长,因此花期能很好地相遇、杂交、结实