黄花蒿生物学特性研究

本文报道在广西桂北地区人工裁培的黄花蒿的生物学特性包括物候期、生长特性、开花结果习性、抗逆性等的观察结果     

Actions and interactions of growth hormone and insulin-like growth factor-II: body and organ growth of transgenic mice

To characterize long-term actions and interactions of growth hormone (GH) and insulin-like growth factor-II (IGF-II) on postnatal body and organ growth, hemizygous phosphoenolpyruvate carboxykinase (PEPCK)-human IGF-II transgenic mice were crossed with hemizygous PEPCK-bovine GH transgenic mice. The latter are characterized by two-fold increased serum levels of IGF-I and exhibit markedly increased body, skeletal and organ growth. Four different genetic groups were obtained: mice harbouring the IGF-II transgene (I), the bGH transgene (B), or both transgenes (IB), and non- transgenic controls (C). These groups of mice have previously been studied for circulating IGF-I levels (Wolf et al., 1995a), whereas the present study deals with body and organ growth. Growth curves (week 3 to 12) were estimated by regression with linear and quadratic components of age on body weight and exhibited significantly (p < 0.001) greater linear coefficients in B and IB than in I and C mice. The linear coefficients of male I and C mice were significantly (p < 0.001) greater than those of their female counterparts, whereas this sex-related difference was absent in the bGH transgenic groups. The weights of internal organs as well as the weights of abdominal fat, skin and carcass were recorded from 3.5- to 8- month-old mice. In addition, organ weight-to-body weight-ratios (relative organ weights) were calculated. Except for the weight of abdominal fat, absolute organ weights were as a rule significantly greater in B and IB than in I and C mice. IGF-II overproduction as a tendency increased the weights of kidneys, adrenal glands, pancreas and uterus both in the absence and presence of the bGH transgene. Analysis of relative organ weights demonstrated significant (p < 0.05) effects of elevated IGF- II on the relative growth of kidneys (males and females) and adrenal glands (females), confirming our previous report on organ growth of PEPCK-IGF-II transgenic mice. In females, IGF-II and GH overproduction were additive in stimulating the growth of spleen and uterus, providing evidence for tissue-specific postnatal growth promoting effects by IGF-II in the presence of elevated IGF-I     

神经生长因子结构与功能研究进展

神经生长因子(NGF)是神经营养因子家族的典型代表, 它控制着脊椎动物周围和中枢神经系统中部分神经元的发育和存活.NGF的三维结构是以“胱氨酸结”和β折叠为基础,它以二聚体的形式结合细胞表面的受体从而发生生物学效应.参与这些反应的氨基酸残基已通过化学修饰和定点突变法加以确定,这有助于更进一步理解其结构与功能的关系.     

蛋白质晶体的优化生长

蛋白质晶体的优化生长是获得高质量蛋白质晶体, 进而得到高精度晶体结构的有效途径.针对不同的晶体生长方法,已尝试了不同的优化手段,这对改善某些蛋白质晶体的质量显示了明显的成效.然而,鉴于蛋白质晶体生长的多样性与复杂性,这些方面均未发展成为实用的技术.文章综述了这类研究进展,分析了各手段的利弊,并指出了应着重解决的问题.     

The effect of temperature,and food quantity and quality on the growth and development rates in laboratory-cultured copepods and cladocerans from a Sri Lankan reservoir

Length growth, instar durations, fecundity and mortality rates of fivespecies of microcrustacean zooplankton from a tropical reservoir weremeasured in relation to food quantity and temperature in laboratorycultures. Three cladocerans (Ceriodaphnia cornuta, Moina micrura,Diaphanosoma excisum), one calanoid copepod (Heliodiaptomus viduus), and onecyclopoid copepod (Mesocyclops thermocyclopoides) were studied. Filteredseston (45 µm mesh) from a local pond was used for food. Two foodconcentrations were employed: (1) 10 µg chlorophyll l^–1(ca 0.25 mg Cl^–1), and (2) 50 µg chlorophylll^–1 (ca 1.25 mg C l^–1). Food levels and watertemperature (22.5, 27.5, and 32.5 °C) used, roughly covered the rangesfound in the reservoir. Although all the three growth parameters were oftenaffected to some degree by temperature and food, the quantitative responseof the species differed. Also, the species reacted differently to the threepossible interactions (i.e. food×temperature,food×instar, andtemperature×instar). This contributed to the overalldifferences in the species responses. For the cladocerans, instar durationswere always affected by temperature. The food did not affect the durationtime of the adults and that of the combined juvenile instars, the latterexcept in one case significantly. For the two copepods food level affectedthe duration times of naupliar and copepodite instars, but the effect oftemperature was only significant for H. viduus. The development timesobserved for H. viduus were extraordinary long compared with values reportedin the literature for other tropical calanoids. This suggests that foodconditions in our culture were adversely affecting its growth rates.     

Mapping and characterization of mangrove plant communities in Hong Kong

Ecological surveys were carried out to investigate the distribution and characterization of remaining mangrove stands in Hong Kong. The field studies indicate that 43 mangrove stands, excluding Mai Po Nature Reserve, still remained along the coastline of Hong Kong despite tremendous reclamation and development which occurred in the past 40 years. Most mangrove stands were found in Deep Bay (western part)and Sai Kung District (eastern coasts). The total areas occupied by these mangrove stands were 178 ha,varying from a very small stand (with 1–2 mangrove shrubs) to fairly extensive mangroves in Deep Bay (> 10 ha). It appeared that mangrove stands located in Deep Bay area were larger than those in the eastern coasts. Twenty plant species were identified from these stands, with 13 being exclusive or associate mangrove species. The major constituent species were Kandelia candel, Aegiceras corniculatum, Excoecaria agallocha and Avicennia marina. Rare species such as Heritiera littoralis were only found in a few mangrove stands. Out of the 43remaining mangrove stands, 23 were more worthwhile for conservation and their plant community structures were further investigated by transect and quadrat analyses. The importance values (sum of relative abundance,frequency and dominance) show that K. candel was the most dominant species. Species richness and Simpson's indices together with tree height, tree density and canopy area fluctuated significantly between mangrove stands. These values were used to prioritize the conservation potential of the remaining mangrove stands in Hong Kong. This revised version was published online in August 2006 with corrections to the Cover Date.     

Molecular Phylogeny and Evolution of the Neurotrophins from Monotremes and Marsupials

We have investigated the phylogenetic relationships of monotremes and marsupials using nucleotide sequence data from the neurotrophins; nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3). The study included species representing monotremes, Australasian marsupials and placentals, as well as species representing birds, reptiles, and fish. PCR was used to amplify fragments encoding parts of the neurotrophin genes from echidna, platypus, and eight marsupials from four different orders. Phylogenetic trees were generated using parsimony analysis, and support for the different tree structures was evaluated by bootstrapping. The analysis was performed with NGF, BDNF, or NT-3 sequence data used individually as well as with the three neurotrophins in a combined matrix, thereby simultaneously considering phylogenetic information from three separate genes. The results showed that the monotreme neurotrophin sequences associate to either therian or bird neurotrophin sequences and suggests that the monotremes are not necessarily related closer to therians than to birds. Furthermore, the results confirmed the present classification of four Australasian marsupial orders based on morphological characters, and suggested a phylogenetic relationship where Dasyuromorphia is related closest to Peramelemorphia followed by Notoryctemorphia and Diprotodontia. These studies show that sequence data from neurotrophins are well suited for phylogenetic analysis of mammals and that neurotrophins can resolve basal relationships in the evolutionary tree. Received: 27 January 1997 / Accepted: 20 March 1997     

Differential Effects of Pratylenchus neglectus Populations on Single and Interplantings of Alfalfa Grasses

The invasion by three different Utah populations of Pratylenchus neglectus (UTI, UT2, UT3) was similar in single and interplantings of ''Lahontan'' alfalfa and ''Fairway'' crested wheatgrass at 24 ñ 3 °C. Population UT3 was more pathogenic than UT1 and UT2 on both alfalfa and crested wheatgrass. Inoculum density was positively correlated with an invasion by P. neglectus. Invasions by UT3 at all initial populations (Pi) exceeded that of UT1 and UT2 for both single and interplanted treatments. The greatest reductions in shoot and root weights of alfalfa and crested wheatgrass were at a Pi of 8 P. neglectus/cm³ soil. Pi was negatively correlated with alfalfa and crested wheatgrass shoot and root growth and nematode reproduction. The reproductive factor (Rf) for UT3 exceeded that of UT1 and UT2 in single and interplantings at all inoculum levels. There were no differences in Rfin the Utah populations in single or interplantings. A nematode invasion increased with temperature and was greatest at 30 °C. Population UT3 was more pathogenic than UT1 and UT2 and reduced shoot and root growth at all soil temperatures. Populations UT1 and UT2 reduced shoot and root growth at 20-30 °C. Soil temperature was negatively correlated with shoot and root growth and positively correlated with nematode reproduction. Reproduction of UT3 exceeded that of UT1 and UT2 at all soil temperatures.     

Effect of Temperature on Pratylenchus penetrans Development

Reproduction and development of Pratylenchus penetrans were studied on genetically transformed ladino clover roots. Solitary females developing on transformed roots in nutrient gellan gum medium (pH 5.5) deposited 1.2, 1.5, 1.6, 1.8, and 2.0 eggs per day at the respective temperatures of 17, 20, 25, 27, and 30 °C. The number of eggs deposited was highly correlated with temperature. A reduction in egg-laying rates at the start of hatching was observed at all temperatures. Juvenile mortality was higher at 17 °C (50.4%), 20 °C (50.3%), and 30 °C (58.4%) than at 25 °C (34.6%) and 27 °C (37.6%). Life-cycle (egg deposition to egg deposition) duration was 46, 38, 28, 26, and 22 days at the respective temperatures. The developmental zero degrees (°C) and the effective accumulative temperatures (degree-days) required for hatching, female emergence, and onset of oviposition (completion of one generation) of P. penetrans were estimated to be 2.7 and 200, 4.2 and 548, and 5.1 and 564, respectively. Pratylenchus penetrans reproduces over a wide range of temperatures.