稀土元素镧在植物细胞中超微结构定位及与钙、铝关系研究

本文主要利用等离子体发射光谱元素含量分析( ICP)、亚细胞定位观察技术、以及电镜与能谱分析相结合技术，研究镧在绿豆(Phmeatus radiatus L.)幼苗不同部位组织细胞中的进入、运转、分配、含量和超微结构定位及与钙、铝关系。在全营养液加镧和缺钙营养液加镧处理的幼苗中，细胞超微结构受到不同程度影响，但其内未检测到镧。无离子水加镧处理幼苗，在低浓度、短时间条件下，镧进入、分布在质膜以外质外体系统中。高浓度镧处理时，镧沉淀能进入细胞内，并常看到堵塞胞间连丝，在质膜以外发现解体物质穿壁转移，并在壁中形成明暗相间的染色带。镧在植株中运输层层受阻，由根向叶其含量逐渐减少，而钙含量变化呈负相关，表明镧钙之间存在拮抗作用。 用焦锑酸钙的电镜细胞化学方法与能谱分析技术相结合，研究镧对细胞内Ca2+定位分布的影响，发现镧、钙沉淀颗粒的差异。在镧胁迫下，细胞质和核中Ca2+增多，液泡中Ca2+趋向于沿被膜分布，细胞结构受到破坏，说明镧胁迫下Ca2+水平增加与膜透性变化和Ca2+_CaM相关的许多生理生化过程有关。 初步探讨铝的毒害机理，发现铝也能进行超微结构定位观察，铝通过拮抗钙起作用，其作用机制与镧相似。

Age and growth of the estuarine dolphin (Sotalia guianensis) (Cetacea, Delphinidae) on the Paraná Coast, southern Brazil

Teeth of 71 estuarine dolphins (Sotalia guianensis) incidentally caught on the coast of Paraná State, southern Brazil, were used to estimate age. The oldest male and female dolphins were 29 and 30 years, respectively. The mean distance from the neonatal line to the end of the first growth layer group (GLG) was 622.4 ±19.1 μm (n=48). One or two accessory layers were observed between the neonatal line and the end of the first GLG. One of the accessory layers, which was not always present, was located at a mean of 248.9 ±32.6 μm (n=25) from the neonatal line, and its interpretation remains uncertain.The other layer, located at a mean of 419.6 ±44.6 μm (n=54) from the neonatal line, was always present and was first observed between 6.7 and 10.3 months of age. This accessory layer could be a record of weaning in this dolphin. Although no differences in age estimates were observed between teeth sectioned in the anterior-posterior and buccal-lingual planes, we recommend sectioning the teeth in the buccal-lingual plane in order to obtain on-center sections more easily. We also recommend not using teeth from the most anterior part of the mandibles for age estimation. The number of GLGs counted in those teeth was 50% less than the number of GLGs counted in the teeth from the median part of the mandible of the same animal. Although no significant difference (P>0.05) was found between the total lengths of adult male and female estuarine dolphins, we observed that males exhibited a second growth spurt around five years of age. This growth spurt would require that separate growth curves be calculated for the sexes. The asymptotic length (TL∞), k, and t0 obtained by the von Bertalanffy growth model were 177.3 cm, 0.66, and –1.23, respectively, for females and 159.6 cm, 2.02, and –0.38, respectively, for males up to five years, and 186.4 cm, 0.53 and –1.40, respectively, for males older than five years. The total weight (TW)/total length (TL) equations obtained for male and female estuarine dolphins were TW = 3.156 × 10−6 × TL 3.2836 (r=0.96), and TW = 8.974 × 10−5 × TL 2.6182 (r=0.95), respectively.