低丘红壤地区几种农林复合系统的生态经济效益

低丘红壤地区几种农林复合系统的生态经济效益傅庆林,罗永进（浙江省农科院土壤肥料研究所,杭州３１００２１）柴锡周（浙江省林业科学研究所,杭州３１００２３）ＥｃｏｌｏｇｉｃａｌＥｆｆｅｃｔｓａｎｄＥｃｏｎｏｍｉｃＢｅｎｃｆｉｔｏｆｔｈｅＣｏｍｐｌｅｘＡｇ...     

Modified nucleoside-dependent transition metal binding to DNA analogs of the tRNA anticodon stem/loop domain

Biologically active DNA analogs of tRNA^Phe (tDNA^Phe) were used to investigate metal ion interaction with tRNA-like structures lacking the 2OH. Binding of Mg²⁺ to the 76 oligonucleotide tDNA^Phe, monitored by circular dichroism spectroscopy, increased base stacking and thus the conformational stability of the molecule. Mg²⁺ binding was dependent on a d(m⁵C) in the anticodon region. In contrast to Mg²⁺, Cd²⁺ decreased base stacking interactions, thereby destabilizing the molecule. Since alterations in the anticodon region contributed to most of the spectral changes observed, detailed studies were conducted with anticodon hairpin heptadecamers (tDNA_AC ^Phe). The conformation of tDNA_AC ^Phe-d(m⁵C) in the presence of 1 mm Cd²⁺, Co²⁺, Cr²⁺, Cu²⁺, Ni²⁺, Pb²⁺, VO²⁺ or Zn²⁺ differed significantly from that of the biologically active structure resulting from interaction with Mg²⁺, Mn²⁺ or Ca²⁺. Nanomolar concentrations of the transition metals were sufficient to denature the tDNA_AC ^Phe-d(m⁵C) structure without catalyzing cleavage of the oligonucleotide. In the absence of Mg²⁺ and at [Cd²⁺] to [tDNA_Ac ^Phe-d(m⁵C)] ratios of approximately 0.2–1.0, tDNA_AC ^Phe-d(m⁵C₄₀) formed a stable conformation with one Cd²⁺ bound with a K _d = 3.7 × 10^-7. In contrast to Mg²⁺, Cd²⁺ altered the DNA analogs without discriminating between modified and unmodified tDNA_AC ^Phe. This ability of transition metals to disrupt higher order DNA structures, and possibly RNA, at M concentrations, in vitro, demonstrates that these structures are potential targets in chronic metal exposure, in vivo.     

Transition metal-saccharide chemistry: d-glucose complexes of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II)

Metal complexes of d-glucose (d-Glc) from large cation containing dibromo-dichloro salts of dipositive metals [NEt₄]₂[MBr₂Cl₂] (M = Mn, Co, Ni, Cu and Zn) and the disodium salt of glucose were synthesized from a MeOH:MeCN mixture. The complexes were characterized by UV-vis absorption, circular dichroism, IR and proton magnetic resonance spectroscopies, and by elemental analysis, and were found to be Na[M(d-Glc)(OMe)Cl]. Cyclic voltammetric studies of these complexes, in the acidic to neutral pH range, indicated no dissociation, even in highly acidic conditions.This paper is dedicated to Professor Richard H. Holm (Harvard University) on the occasion of his 60th birthday.     

Women's changing economic roles with pastoral sedentarization: Varying strategies in alternate Rendille communities

The trend of pastoral sedentarization in Africa presents new economic opportunities to women through the sale of dairy products, agricultural produce, and labor. This study of Rendille of northern Kenya shows a variety of economic strategies pursued by women in nomadic pastoral, settled agro-pastoral, and town communities. Results of household budgets and interviews with married women indicate that urban centers attract both wealthier Rendille women selling milk and poorer women engaged in wage-labor and petty commodity trade; time allocation data shows that women living in towns work as strenuously as those in pastoral communities, while men in towns work less than in pastoral communities and less than women in both communities; and anthropometric data of women and children suggest that increases in women's income may have a beneficial effect on the nutrition and well-being of their children.     

Effect of β-carotene,lutein and violaxanthin on structural properties of dipalmitoyl-phosphatidylcholine liposomes as studied by ultrasound absorption technique

The effect of three carotenoid pigments, -carotene, lutein, and violaxanthin, on structural properties of dipalmitoylphosphatidylcholine liposomes was studied by means of ultrasound absorption technique. It was found that the polar carotenoid-lutein enhances drastically ultrasound absorption related to energy consumption during phase transition of a lipid component. The effect of apolar -carotene was not so much evident. No differences between the sample and control were found in the case of violaxanthin presence in liposomes. The effect of a polar carotenoid is discussed in terms of the reinforcement of the lipid matrix. Physiological aspects of carotenoid action in membranes are also briefly discussed.     

Characterization of a Synechococcus sp. strain PCC 7002 mutant lacking Photosystem I. Protein assembly and energy distribution in the absence of the Photosystem I reaction center core complex

A Synechococcus sp. strain PCC 7002 psaAB::cat mutant has been constructed by deletional interposon mutagenesis of the psaA and psaB genes through selection and segregation under low-light conditions. This strain can grow photoheterotrophically with glycerol as carbon source with a doubling time of 25 h at low light intensity (10 E m^–2 s^–1). No Photosystem I (PS I)-associated chlorophyll fluorescence emission peak was detected in the psaAB::cat mutant. The chlorophyll content of the psaAB::cat mutant was approximately 20% that of the wild-type strain on a per cell basis. In the absence of the PsaA and PsaB proteins, several other PS I proteins do not accumulate to normal levels. Assembly of the peripheral PS I proteins PsaC,PsaD, PsaE, and PsaL is dependent on the presence of the PsaA and PsaB heterodimer core. The precursor form of PsaF may be inserted into the thylakoid membrane but is not processed to its mature form in the absence of PsaA and PsaB. The absence of PS I reaction centers has no apparent effect on Photosystem II (PS II) assembly and activity. Although the mutant exhibited somewhat greater fluorescence emission from phycocyanin, most of the light energy absorbed by phycobilisomes was efficiently transferred to the PS II reaction centers in the absence of the PS I. No light state transition could be detected in the psaAB::cat strain; in the absence of PS I, cells remain in state 1. Development of this relatively light-tolerant strain lacking PS I provides an important new tool for the genetic manipulation of PS I and further demonstrates the utility of Synechococcus sp. PCC 7002 for structural and functional analyses of the PS I reaction center.Abbreviations ATCC American type culture collection - Chl chlorophyll - DCMU 3-(3,4-dichlorophyl)-1,1-dimethylurea - DBMIB 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone - HEPES N-[2-hydroxyethyl]piperazine-N-[2-ethanesulfonic acid] - PCC Pasteur culture collection - PS I Photosystem I - PS II Photosystem II - SDS sodium dodecyl sulfate     

PCR-generated cDNA library of transition-stage maize embryos: cloning and expression of calmodulin genes during early embryogenesis

One hundred maize zygotic embryos microdissected at the transition stage were used to construct a cDNA library after non-selective PCR (NS-PCR) amplification of whole cDNA populations. The library contains 2.3 × 10⁵ recombinants and two different calmodulin cDNAs were cloned using a heterologous probe from petunia. Calmodulin expression was confirmed throughout maize embryogenesis at the mRNA, amplified cDNA and protein levels. Sequence analysis suggests a maize origin for both clones and negligible nucleotide changes linked to PCR. This library is the first described for early plant embryos and represents a breakthrough to isolate genes involved in embryo differentiation.     

Mitochondrial Permeability Transition in the Central Nervous System: Induction by Calcium Cycling-Dependent and -Independent Pathways

Abstract: Isolated rat CNS mitochondria and cultured cortical astrocytes were examined for behavior indicative of a mitochondrial permeability transition (mPT). Exposure of isolated CNS mitochondria to elevated calcium or phosphate or both produced loss of absorbance indicative of mitochondrial swelling. The absorbance decreases were prevented by ADP and Mg²⁺ and reduced by cyclosporin A, dithiothreitol, and N -ethylmaleimide. Ruthenium red prevented calcium cycling-induced, but only attenuated phosphate-induced losses of absorbance. In cultured astrocytes permeabilized with digitonin or treated with the calcium ionophore, 4-bromo-A23187, elevations of external calcium altered mitochondrial morphology visualized with the dye, JC-1, from rod-like to rounded, swollen structures. Similar changes were observed in digitonin-permeabilized astrocytes exposed to phosphate. The incidence of calcium-induced changes in astrocyte mitochondria was prevented by Mg²⁺ and pretreatment with dithiothreitol and N -ethylmaleimide, and was reduced by cyclosporin A, ADP, and butacaine alone or in combinations. Ruthenium red and the Na⁺/Ca²⁺ exchange inhibitor CGP 37157 blocked calcium cycling and prevented mitochondrial shape changes in digitonin-treated, but not ionophore-treated astrocytes. Thus, the demonstrated induction conditions and pharmacological profile indicated the existence of an mPT in brain mitochondria. The mPT occurred consequent to activation of calcium cycling-dependent and -independent pathways. Induction of an mPT could contribute to neuronal injury following ischemia and reperfusion.     

甘肃河西野生经济植物资源及其利用的研究

甘肃河西地区约有野生经济植物50科200余种（不包括药用植物）。本文列出了该区具有代表性和较高利用价值的野生经济植物38科85种;评价了部分植物的利用价值;对资源的进一步开发利用提出探讨。