饥饿和再投喂对青蛤(Cyclina sinensis)幼虫生长、存活及变态的影响

在温度18.2～20.6℃,盐度23～25,pH 7.96～8.14 的条件下,研究了饥饿和再投喂对青蛤幼虫生长、存活及变态的影响.结果表明:在饥饿状态下,幼虫具有生长现象,且随着饥饿时间的延长,壳长逐渐接近一个常值而不再生长;幼虫可以由面盘幼虫发育到足面盘幼虫.随饥饿时间延长存活率下降;且足面盘幼虫及其变态规格、单水管稚贝规格随着饥饿时间延长而减小;幼虫的不可逆点(PNR)为12.48d;延迟变态时间长达12.7d.饥饿后再投喂相同的时间,幼虫能够恢复生长,存活的幼虫能够变态;稚贝表现出补偿生长现象,以壳长作为衡量标准,完全补偿生长能力依次为:S10＞S11＞S12＞S1＞S2＞S3;超补偿生长能力依次为:S9＞S8＞S7＞S6＞S5＞S4.     

Epidermal growth factor (EGF) induces apoptosis in a transfected cell line expressing EGF receptor on its membrane

Interaction between epidermal growth factor (EGF) and EGF receptor (EGFR) promotes cell growth in most cell lines, but in a number of cell lines, EGF paradoxically inhibits proliferation. In the present study, we established a cell line expressing full-length human EGFR on membrane with a GFP fluorescence reporter at the C-terminal and studied the effects of EGF on cell proliferation in the transfected cell line. Our results suggested that low concentrations of EGF promoted proliferation, while high concentrations of EGF induced loss of adhesion, cell cycle arrest, apoptosis, and inhibition of proliferation. The effects of EGF on cell proliferation correlated well with the expression levels of EGFR. High concentrations of EGF induced both EGFR expression and apoptosis in a dose-dependent manner. Our study reported, for the first time, a relationship between the effects of EGF on cell proliferation and levels of EGFR expression in one cell line expressing different levels of EGFR caused by different concentrations of EGF treatment. The study should provide considerable insight into the effects of EGF on cell proliferation and tumor cell metastasis.     

南方菟丝子对加拿大一枝黄花的寄生控制效应

以安全性较高的本土植物南方菟丝子和重要的外来入侵植物加拿大一枝黄花为材料,于温室中采用盆栽试验在湿润和半湿润条件下用南方菟丝子寄生不同生长阶段(幼苗阶段、过渡阶段和成株阶段)的加拿大一枝黄花植株,考察加拿大一枝黄花植株被寄生后的营养生长、光合生理、逆境生理等指标,探索适宜南方菟丝子寄生加拿大一枝黄花的最佳条件阈值。结果显示:(1)寄生处理与对照之间,加拿大一枝黄花株高、基径、生物量、叶绿素含量、光合速率、可溶性糖、丙二醛、脯氨酸等指标差异均显著;(2)幼苗组、过渡组被寄生加拿大一枝黄花的株高增量、基径增量、生物量、叶绿素含量、净光合速率均显著低于相应对照组,而其可溶性糖、丙二醛、脯氨酸含量均显著高于相应对照组;(3)在半湿润条件下,加拿大一枝黄花的株高、基径增量均小于湿润条件下植株,其净光合速率、叶绿素含量在幼苗组和过渡组均小于湿润条件下植株,而可溶性糖、丙二醛、脯氨酸含量在在幼苗组和过渡组均大于湿润条件下相应指标;(4)幼苗组、过渡组加拿大一枝黄花被寄生后无法正常开花结实,寄生幼苗组加拿大一枝黄花的南方菟丝子亦无法正常开花结实。研究表明,在湿润与半湿润地区,南方菟丝子可以寄生各生长阶段的加拿大一枝黄花,并对株高1.2 m以下的植株产生较强的寄生胁迫;寄生的最佳时间段为每年的4月到8月。     

Infection with the fungal endophyte Epichloë festucae may alter the allelopathic potential of red fescue

Red fescue (Festuca rubra) is a perennial grass used as both forage and turfgrass. Asymptomatic plants of this species are systemically infected by the fungal endophyte Epichloë festucae, which has a beneficial effect on the infected plants. The aim of this study was to determine the effect of the endophyte Epichloë festucae on the allelopathic potential of F. rubra against four associated pasture species that are also considered as weeds in lawns, Trifolium pratense, Trifolium repens, Lotus corniculatus and Plantago lanceolata. Two experiments were designed to evaluate the allelopathic effect of extracts from the roots and leaves of endophyte‐infected (E+) and non‐infected (E?) plants on the germination and seedling growth of the four target species. Regardless of the endophyte status of the host plant, leaf extracts elicited a stronger reduction in germination and seedling growth than root extracts. Extracts from E+ plants reduced the speed of germination index of Trifolium spp. to a greater extent than those from E? plants. Radicle length of the target species was the parameter most affected by the presence of the endophyte in F. rubra. Root extracts from E+ plants had a greater inhibitory effect on the radicle growth of the target species than did root extracts from E? plants. A greater concentration in total phenolic compounds was found in the roots of E+ plants than of E?; however, this difference was not observed in the leaves. Thus, the allelopathic potential of F. rubra is altered in infected plants.     

柑橘体细胞杂种砧木对脐橙幼树生长及根和叶中抗氧化酶系活性的影响

以体细胞杂种红橘 枳、红橘 粗柠檬和有性杂种Troyer枳橙、Swingle枳柚作砧木的脐橙二年生嫁接苗为试材,于盆栽条件下研究砧木对苗木生长及根和叶中抗氧化酶系活性影响的结果表明,红橘 枳的生长势和花量明显强于和大于其它砧木,红橘 粗柠檬的生长和花量表现介于两种有性杂种之间;砧木不影响叶片中可溶性蛋白含量和超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性年动态变化特征.4、6、8月,叶中POD活性高低分别与各次新梢生长量和树冠体积(8月)大小呈负相关;12月,根系与叶片的SOD和POD活性分别呈正相关,根系可溶性蛋白含量和根系CAT活性呈正相关.     

Spatial structure of a subtidal macrobenthic community in the Bay of Veys (western Bay of Seine, English Channel)

The spatial distribution of the muddy fine sand community from the Bay of Veys (western English Channel) were investigated during spring and autumn 1997. A grid of 55 and 54 sites was sampled in March and October, respectively, using two replicates per site of a Hamon grab (0.25 m²) for macrofauna collection and an additional one for sediment analysis. A total of 172 species were sampled with a dominance of polychaetes, followed by crustaceans and bivalves. The species richness and abundance show low temporal changes despite higher values in October than in March. In March, the mean abundance was 165 ind. 0.5 m⁻²; in October, the mean abundance was 212 ind. 0.5 m⁻². Four assemblages from the Abra alba-Pectinaria koreni community were identified corresponding to a bathymetric and sedimentary gradient from muddy fine sands with high levels of fine particles in shallow water to fine sands in deeper water. The discussion focuses on factors prevailing on the spatial structure of sandy communities in the English Channel.     

极低频磁场对人肝癌细胞生长、代谢及细胞周期的影响

目的研究一定参数的极低频磁场对人肝癌细胞(SK-HEP-1)在诸多方面的影响。方法在整个SK-HEP-1细胞的培养周期中用50Hz,20mT的极低频磁场对其进行作用,并检测作用后细胞的增殖活性、生长动力学、代谢以及细胞周期的变化。结果50Hz,20mT的极低频磁场对SK-HEP-1细胞的生长与代谢有抑制作用,并能阻碍其有丝分裂的进行。结论50Hz,20mT的极低频磁场为治疗人类恶性肿瘤提供了一种可能的手段。     

甲羟戊酸通路对细胞生长调控作用的研究进展

甲羟戊酸(MVA)通路对细胞生长具有重要的调节作用,MVA及其衍生物通过对蛋白质异戊烯化和N糖基化修饰而影响Ras蛋白、生长因子及受体的功能、细胞内信号转导和细胞的生长。MVA通路参与血管活性物质生成的调节是其调节细胞生长的另一机制。MVA生成的限速酶羟甲基戊二酸单酰辅酶A(HMGCoA)则受MVA通路衍生物的反馈抑制。HMGCoA还原酶抑制剂通过抑制MVA及其衍生物的生成而抑制细胞的生长和增殖。