Seasonal population dynamics of Paraquimpevia tenevvima (Linstow) (Nematoda) in the European eel Anguilla anguilla (Linnaeus) in three localities of southwest England

Seasonal population dynamics of Puraquzmperia tenerrima (Linstow) in the European eel Anguillu anguillu (Linnaeus) have been investigated in three localities in Devon, southwest England. The nematode is common and exhibits very similar seasonal patterns in changes of prevalence and abundance in the three localities. The population increases over winter through to late spring or early summer as the recruitment of the new generation occurs throughout this period. Reproduction of the nematode starts in spring. A sharp decrease of prevalence and abundance accompanies or follows reproduction, and infection levels are very low in autumn and early winter. The dispersion pattern of the nematode varies with the infection levels from over-dispersion in spring and early summer to almost random dispersion in autumn and winter. It is suggested that P. tenerrimu is a common specific parasite of eels, especially in small streams or rivers and that insect larvae or species of crustaceans might serve as intermediate hosts for the nematode.     

Exploiting the complete yeast genome sequence

The completion of the genome sequence of the budding yeast Saccharomyces cerevisiae marks the dawn of an exciting new era in eukaryotic biology that will bring with it a new understanding of yeast, other model organisms, and human beings. This body of sequence data benefits yeast researchers by obviating the need for piecemeal sequencing of genes, and allows researchers working with other organisms to tap into experimental advantages inherent in the yeast system and learn from functionally characterized yeast gene products which are their proteins of interest. In addition, the yeast post-genome sequence era is serving as a testing ground for powerful new technologies, and proven experimental approaches are being applied for the first time in a comprehensive fashion on a complete eukaryotic gene repertoire.     

Tachykinin NK-1 receptor probed with constrained analogues of substance P

The action of rotameric probes introduced either in position 7 or 8 in the sequence of substance P (SP) was investigated, i.e. -tetrahydroisoquinoleic acid (Tic), -fluorenylglycine (Flg), -diphenylalanine (Dip), the diastereoisomers of -1-indanylglycine (Ing) and -benz[ƒ]indanylglycine (Bfi), the Z- and E-isomers of dehydrophenylalanine and dehydronaphthylalanine (Δ^ZPhe, Δ^EPhe, Δ^ZNal, Δ^ENal) and (Dmp). The aim of this study was the topographical characterization of the binding subsites of human NK-1 receptor expressed in CHO cells, especially the S₇ and S₈ subsites, corresponding to residues Phe⁷ and Phe⁸ of substance P. According to the binding potencies of these substituted-SP analogues, the S₇ binding subsite is smaller than the S₈ subsite: the S₇ subsite accepts only one aromatic nucleus, while the S₈ can accommodate three coplanar nuclei altogether. These findings are compatible with the idea that the S₈ binding subsite may reside in the extracellular loops of the hNK-1 receptor. NK-1 agonists bind to human NK-1 receptor and activate the production of both inositol phosphates and cyclic AMP. As already quoted for septide, [pGlu⁶, Pro⁹]SP(6–11), discrepancies are observed between affinity (K_i) and activity (EC₅₀) values for IPs production. While a weak correlation between K_i and EC₅₀ values for IPs production could be found (r = 0.70), an excellent correlation could be demonstrated between their affinities (K_i) and their potencies (EC₅₀) for cAMP production (r = 0.97). The high potency (EC₅₀) observed for ‘septide-like’ molecules on PI hydrolysis, compared to their affinity is not an artefact related to the high level of NK-1 receptors expressed on CHO cells since a good correlation was found between EC₅₀ values obtained for PI hydrolysis and those measured for spasmogenic activity in guinea pig ileum bioassay (r = 0.94).

According to the binding potencies of constrained analogues of phenylalanine, the S₇ binding subsite of human NK-1 receptor is small, whereas the S₈, which can accommodate three coplanar nuclei, might probably reside in the extracellular loop. The discrepancies observed between affinity (K_i) and activity (EC₅₀) values for IPs production are not an artefact of CHO cells since a good correlation was found between EC₅₀ for PI hydrolysis and those measured in guinea pig ileum bioassay.     

多组多滞后区间系数定常非线性关联控制大系统的结构与关联鲁棒镇定(I)

建立了多组多滞后区间系数定常非线性控制系统的结构概念,采用鲁棒镇定的等价法,给出了具有扰动结构参数的多组多滞后区问系数定常非线性关联控制大系统的结构与关联鲁棒镇定,同时给出了扰动参数与滞后非线性项界线的估价公式。     

Dendroecological reconstruction and interpretation of larch budmoth (Zeiraphera diniana) outbreaks in two central alpine valleys of Switzerland from 1470 – 1990

 Outbreaks of the larch budmoth (LBM) (Zeiraphera diniana) recur cyclically approximately every 7 to 10 years in subalpine larch-cembran pine and montane to subalpine larch-Norway spruce forests of the relatively dry valleys of the European Alps. By dendroecologically analyzing increment cores from 570 host (European larch –Larix decidua) and non-host trees (cembran pine –Pinus cembra, Norway spruce –Picea abies) through the use of skeleton plots, at least 57 (59) outbreaks could be reconstructed in the optimum Upper Engadine Valley (suboptimum Goms Valley), Switzerland, during the time period 1503 (1472) to 1990. The average interval between initial years of successive outbreaks was 8.58 (8.95) years, SD 1.66 (2.13) years. Over the centuries spatial shifts of LBM activity between the two study areas occurred, probably due to climatic changes. Clear, site-specific differences in LBM attack could only be found in the suboptimum area where high-lying (>1800 m) and/or south-facing stands were infested most. LBM-afflicted trees proved to be unsuitable for climate reconstructions because the impact of the persistently recurring outbreaks on tree growth is dominant. In order to provide sufficient information for a detailed ecological interpretation of the course of an outbreak, latewood widths and/or densities have to be analyzed in addition to the ring-widths. Received: 11 February 1995 / Accepted: 19 July 1996     

广西九万山藓类植物区系分析及其对划分热带,亚热带分界线的意义

九万山位于广西北部的中央(25°10’～25°25’N,108°27’E),界于泛北极植物区和古热带植物区的交汇处。其主要植被为亚热带常绿阔叶林。最高海拔为1693m,最低处仅170m。经对1850号标本的鉴定,共计有藓类植物35科、101属和189种。本文分析了九万山的藓类植物区系成分,将其划分为 10种类型。其中东亚成分最为丰富(39.33％),热带、亚热带成分次之(38.20％),而温带成分居第三位(18.54％)。本文选择了九万山临近的五个地区加以比较。其中,金佛山与九万山藓类植物的属和种的相似性系数分别为60.68％和36.87％,神农架为57.29％和33.13％。尖峰岭为48.83％和22.29％,西双版纳为57.29％和29.63％。而我国东部的武夷山则为69.86％和39.57％,其相似性系数在相比较的五个山区中为最高。九万山区有4个特有属并明显受喜马拉雅的影响。特别值得注意的是,在九万山区藓类区系中约有7％的种类是典型的热带成分。根据定量和定性的分析,笔者认为九万山的藓类区系表现出由热带向亚热带过渡的特性,其分界线可能位于九万山的南侧。     

The interactions of cis- and trans-diammineplatinum compounds with 5′-guanosine monophosphate and 5′-deoxyguanosine monophosphate. A proton nmr investigation

The interactions of cis- and trans-diammineplatinum compounds with 5′-GMP and 5′-dGMP in dilute aqueous solution at neutral pH were investigated by ¹H nmr. In addition to the 1:2 Pt nucleotide complexes cis- and trans-Pt(NH₃)₂(GMP)₂, it was possible to study the formation of the 1:1 Pt-nucleotide complexes with either one coordinated water or chloride ion. At 5°C GMP reacts with a stoichiometric amount of cis-diaquodiammine-platinum to yield cis-Pt(NH₃)₂(GMP) (H₂O) as a sole reaction product. From the present results it is concluded that such a complex may play an important role as the initial reaction product between antitumor compounds like cis-Pt(NH₃)₂Cl₂ and guanine in DNA in living organisms. The coupling constant ³J(H(1′)-H(2′)) of the H(1′) sugar proton in cis-Pt(NH₃)₂(GMP)₂ is temperature dependent, indicating a conformational change in the sugar moiety.     

Kinetic studies on the cupric ion oxidation of sheep hemoglobin

The oxidation of sheep hemoglobin, in both the oxygenated and deoxygenated forms, by cuprous ions have been studied by spectrophotometric and stopped-flow techniques. Mixing of both the oxy and deoxy forms with excess Cu²⁺ leads to the rapid oxidation of the iron atoms of all four of the hem groups of the tetrameric protein, followed by the slow formation of hemichromes (low spin Fe^III forms of hemoglobin). Stopped-flow studies show that the oxidations follow simple monophasic kinetics with second-order rate constants of 65 and 310 M^?1 sec^?1 for the oxy and deoxy forms, respectively. Variable temperature studies yield Arrhenius activation energies of 43 for the oxy form and 113 kJ mole^?1 for the deoxy form. For each form of the protein the activation energy is very similar to the activation enthalpy. While the deoxy form is characterized by an activation energy and enthalpy that is more than twice the corresponding value in the oxy form. The activation entropies show highly significant differences being ?128 e.u. and 136 e.u. at 25°C for the oxy and deoxy forms, respectively.