稀土La~(3 )跨PC12细胞膜行为研究

使用AR-CM-M1C阳离子测定系统,发展Fura-2荧光测定技术,将其应用于测定细胞内游离稀土离子La3+,并以此研究了La3+跨PC12细胞(大鼠嗜铬细胞瘤细胞)膜的行为.结果表明:在模拟细胞内离子组分,pH=7.05的溶液中,测得La3+-Fura-2的表观解离常数为3.27×10-11mol@L-1.对于PC12细胞,静息条件下La3+不能跨越细胞膜进入胞内.与钙离子通道相关的KCI和去甲肾上腺素均不能刺激稀土La3+过膜.用哇巴因(ouabain)使胞内Na+超载后,La3+可过膜进入细胞内,且过膜量与胞外La3+浓度和胞内Na+超载程度有一定的浓度依赖关系,提示La3+可以经由Na+/La3+交换机制过膜而进入细胞内.     

Resistance to dieldrin + fipronil assorts with chromosome inversion 2La in the malaria vector Anopheles gambiae

Cyclodiene insecticide resistance in malaria vector mosquitoes of the Anopheles gambiae species complex (Diptera: Culicidae) has been reported previously from several parts of Africa. We report resistance to dieldrin, a cyclodiene, in two laboratory strains of An. gambiae Giles sensu stricto code-named Ian P20 from Nigeria (1979) and CIG from Cote d'Ivoire (1997). Dieldrin resistance levels were high in adult female mosquitoes (40-75% survived exposure to 4% dieldrin for 1 h) and was closely linked with chromosomal paracentric inversion 2La. This inversion did not occur in Hardy-Weinberg proportions, but showed an excess of heterozygotes in both strains, which may account for the high levels of resistance. This linkage also suggests that dieldrin resistance in Ian P20 is dominant. After subsamples of strain Ian P20 were exposed for 1 h to dieldrin 4% or fipronil 2% (discriminating concentrations), the resultant mortality-rates (61% and 65%) were not significantly different. Most survivors after fipronil treatment also survived subsequent exposure to dieldrin (46/50=92%). This apparent cross-resistance between insecticides of two classes (cyclodiene and phenyl pyrazole) has implications for the management of insecticide resistance in wild populations of the An. gambiae complex.     

Meteorological influences on algal bloom potential in a nutrient-rich blackwater river

1. The effect of variability in rainfall on the potential for algal blooms was examined for the St Johns River in northeast Florida. Water chemistry and phytoplankton data were collected at selected sites monthly from 1993 through 2003. Information on rainfall and estimates of water turnover rates were used in the analyses of trends in phytoplankton biomass.
2. Major trends in rainfall and runoff within the lower St Johns River catchment over the 10-year study period were marked by both significant drought and flood periods. Autumn and winter rainfall patterns were strongly correlated with the range of Pacific sea surface temperature anomalies associated with El Niño events and La Niña periods. The effect of these major shifts in rainfall was evident in the strong relationship to replacement rates for water within the lower St Johns River.
3. The eutrophic status of the river was reflected in the high concentrations of nitrogen and phosphorus observed at all sampling sites, with total nitrogen concentrations up to 3100  μ g L⁻¹ and total phosphorus concentrations up to 180  μ g L⁻¹.
4. While it is clear that the high phytoplankton biomass and frequent blooms that characterize the freshwater portions of the lower St Johns River are fundamentally based on nutrient status, the expression of that potential was strongly correlated to water replacement rates, as revealed by the inverse relationship between phytoplankton biovolume increase and water turnover rate, with an R ² of 0.80 for the major bloom season. The sensitivity of algal blooms to rainfall patterns over the 10-year study period suggest that longer-term temporal and spatial shifts in rainfall, such as multi-decadal cycles and the global-warming phenomenon, will also influence the frequency and intensity of algal blooms.     

Seed arrival under different genera of trees in a neotropical pasture

Trees in pastures attract seed dispersers, leading to increased seed arrival under their canopies and more rapid regrowth around them. The characteristics that make some trees better `recruitment foci' than others, however, are poorly understood. In a neotropical pasture, we examined the arrival of seeds to open areas and underneath four genera of trees that varied in canopy architecture and type of fruit produced: Ficus trees had dense canopies and fleshy fruits, Pentaclethra trees had dense canopies and dry fruits, Cecropia trees had sparse canopies and fleshy fruits, and Cordia trees had sparse canopies and dry fruits. We found that all trees received more seeds than open pasture, probably because trees provided seed dispersers with better perches, protection from predators, nesting sites, etc. Among the tree genera, more seeds arrived under trees that produced fleshy fruits than trees that did not. This occured even during periods when trees were not fruiting (i.e., non-fruiting Ficus and Cecropia trees received more seeds than Cordia or Pentaclethra trees). Seed dispersers may periodically check Ficus and Cecropia trees for fruits, or they may become familiar with these trees while feeding and thereafter use them for other reasons. Height of trees had a slight positive effect on seed arrival, possibly because taller trees offered more protection from predators. Canopy architecture and distance to forest edge did not significantly affect seed arrival. This study demonstrates that trees in general are potentially important recruitment foci, but that different types of trees vary in the kind of recruitment that they foster in pastures.     

Effect of La(NO3)3 on Root Growth and IAA Content of Masson Pine Seedlings

Treated with 0.1 to 1.0 mg/L La(NO3)3 in Hoagland solution, root-pruning masson pine ( Pinus massoniana Lamb. ) seedlings developed the lateral roots 1.75 to 3.75 times more in number than the control. The fresh and dry weight of roots were increased by 33.7 % and 46.4 %. The root length was only in the range of 0.05 to 0.5 mg/L La(NO3)3, had slightly pmmotive effect but when the concentration of La(NO3)3 exceeded more than 1.0 mg/L, the root length of root-pruning masson pine seedling was decreased to 53.3% of the control. The free-lAA content of the lateral root was raised with the increase of La(NO3)3 concentration in cultural solution, while the activity of IAA oxidase was decreased. On the other hand, La (NO3)3 was exerted less pmmotive effect on shoots than on roots.     

RT-PCR测定组织纤溶酶原激活剂突变体(La-tPA)在转基因鼠乳腺表达的研究

利用所构建的乳腺表达组织纤溶酶原激活剂突变体（Ｌａ－ｔＰＡ）载体．对５４０枚小鼠受精卵进行显微注射,经ＰＣＰ和Ｓｏｕｔｈｅｒｎｂｌｏｔ检测,获得６只整合有人Ｌａ－ｔＰＡ转基因小鼠．为了精确研究转基因在小鼠体内的表达,采用ＲＴ－ＰＣＰ方法测定转基因鼠在泌乳期１～２０ｄＬａ－ｔＰＡ基因的转录,结果表明,在转基因鼠乳腺的Ｌａ－ｔＰＡｍＲＮＡ水平在１０～１５ｄ最高,在２０ｄ时降为最低．外源基因在转基因小鼠乳腺的表达规律研究为未来利用转基因动物生产Ｌａ－ｔＰＡ提供依据     

Logs and Fern Patches as Recruitment Sites in a Tropical Pasture

Forest recovery in degraded pastures is often highly variable, possibly due to variation in the availability of adequate recruitment sites. In an actively grazed pasture in northeastern Costa Rica, this study examines how recruitment of woody species in patches of the fern Nephrolepsis sp. and near logs compares with recruitment in grassy areas. Fern patches and logs had five and eight times higher densities of woody recruits, respectively, as grassy areas. They also had more than twice the species richness and growth as grassy areas. Grass apparently presents a competitive barrier against invading woody recruits, and also attracts cattle that may trample and/or consume recruits. Both logs and patches of fern appeared to provide superior conditions for establishment and growth of woody species, and they did not attract cattle. This study suggests that fern patches and logs can be managed to accelerate forest succession.     

Quantifying mortality of tropical rain forest trees using high-spatial-resolution satellite data

Assessment of forest responses to climate change is severely hampered by the limited information on tree death on short temporal and broad spatial scales, particularly in tropical forests. We used 1‐m resolution panchromatic IKONOS and 0.7‐m resolution QuickBird satellite data, acquired in 2000 and 2002, respectively, to evaluate tree death rates at the La Selva Biological Station in old‐growth Tropical Wet Forest in Costa Rica, Central America. Using a calibration factor derived from ground inspection of tree deaths predicted from the images, we calculated a landscape‐scale annual exponential death rate of 2.8%. This corresponds closely to data for all canopy‐level trees in 18 forest inventory plots, each of 0.5 ha, for a mostly‐overlapping 2‐year period (2.8% per year). This study shows that high‐spatial‐resolution satellite data can now be used to measure old‐growth tropical rain forest tree death rates, suggesting many new avenues for tropical forest ecology and global change research.     

La(NO3)3浸种对镉胁迫下油菜种子萌发及幼苗生长的影响

通过水培实验研究了La(NO3)3浸种对镉胁迫下油菜(Brassicanapus)种子萌发及幼苗生长的影响。结果表明,当镉浓度≤10mg·L-1时,La(NO3)3浸种(0～50mg·L-1)能提高油菜种子的活力,促进油菜幼苗的生长,并提高脂肪酶的活性和幼苗根细胞有丝分裂指数。其中以10mg·L-1La(NO3)3浸种处理效果最佳,与对照相比,种子活力指数及油菜幼苗各生长指标显著提高,脂肪酶活性增加40.41%～65.09%,幼苗根细胞有丝分裂指数增加62.76%～77.02%。当镉浓度>10mg·L-1时,La(NO3)3浸种对镉胁迫的缓解效用明显减弱,与对照相比,仅脂肪酶活性显著提高,其它指标无明显变化。