Metabolism of Exogenous Malonate by Coffee Leaf Tissue

When [l-¹⁴C]-malonate was supplied to discs cut from matureleaves of Coffea arabica, ¹⁴CO₂ was released (approximately12% of the total CO₂ respired) and organic acids of the Krebscycle, uronic acids, sugars and amino acids became radioactive.There was no incorporation of MC into either lipids or phenoliccompounds. The formation of glucose from malonate has not beenobserved in other studies with plant tissues. The synthesisof labelled glucose together with an active pentose phosphatepathway that is stimulated by malonate explains the accumulationof radioactive phosphogluconate in the leaf discs. Tentativeproposals are made for pathways to account for the results obtained. Key words: Coffee leaves, Malonate metabolism, Pentose phosphate pathway     

The etiology of hop chlorotic disease

Hop chlorotic disease was first described in England in 1930, but it has since been seldom seen and its etiology has remained unknown. In 1983 a patch of plants with the disease occurred in a large area of hops (Humulus lupulus) cv. Bramling Cross planted at Yalding, Kent in 1967. All plants in a rectangular area enclosing the disease outbreak were infected with hop mosaic, hop latent and prunus necrotic ringspot viruses; the diseased plants were additionally infected with arabis mosaic virus (AMV). The disease was also associated with seed-transmitted AMV, and was induced in hop seedlings inoculated with partially purified preparations of AMV originating from chlorotic disease-affected hops prepared from Chenopodium quinoa. The disease appears to be caused by AMV, but AMV isolates from hops with chlorotic disease were serologically indistinguishable from AMV isolates from hops with symptoms of bare-bine and/or nettlehead and showed similar pathogenicity in diagnostic hosts. The basis of the difference between isolates in their pathogenicity in hop remains unknown.     

Complete nucleotide sequence of insertion element IS4351 from Bacteroides fragilis.

The nucleotide sequence and genetic analyses of one of the directly repeated sequences flanking the macrolide-lincosamide-streptogramin B drug resistance determinant, ermF, from the Bacteroides fragilis R plasmid, pBF4, suggested that this region is an insertion sequence (IS) element. This 1,155-base-pair element contained partially matched (20 of 25 base pairs) terminal-inverted repeats, overlapping, anti-parallel open reading frames, and nine promoterlike sequences, including three that were oriented outward. Analysis of this sequence revealed no significant nucleotide homology to 13 other known IS elements. Inasmuch as Southern blot hybridization analysis detected homologous sequences in chromosomal DNA and its G+C content (42 mol%) was similar to that of B. fragilis, the data suggested that this element is of Bacteroides origin. Transposition promoted by this element was demonstrated in recA E. coli. Recombinants were recovered by selecting for the activation of a promoterless chloramphenicol resistance gene on the plasmid pDH5110 and were characterized by restriction endonuclease mapping and Southern blot hybridization. We propose that this IS element be designated IS4351.     

浙江天童国家森林公园微地形与植被结构的关系

植物群落的本质特征之一是群落中的植物和环境之间存在一定的相互关系。丘陵地区的地形由各种微地形单元构成,这些微地形单元在空间上的分化提供的异质化的生境导致了区域丰富的物种和群落多样性的形成。选择浙江东部低山丘陵地区具有典型代表意义的天童国家森林公园,在地形识别的基础上,结合详细的植被调查,分析了不同微地形单元物种组成及其林分结构的变化。结果表明,基于物种组成相似性,7个微地形单元可以归为2组,与通过侵蚀前线划分结果一致。依据物种在这2个小尺度地形单元的分布格局,可以划分出3个特征种组,即上部坡面分布型、下部坡面分布型和无统计偏差型。壳斗科、山茶科、冬青科和山矾科常绿物种是构成上部坡面植被的主要成分,而榆科、槭树科、胡桃科和漆树科等的落叶种及樟科常绿种则是构成下部坡面植被的主要成分。下部坡面各微地形单元的林分垂直构造比上部坡面复杂,由榆科、槭树科、胡桃科和漆树科生境先锋种形成的明显超高层以及超大个体的存在是其显著特征。但其密度低于上部坡面微地形单元。上部坡面的顶坡和谷头凹地明显缺乏乔木层的存在。侵蚀前线是丘陵地区不同生境最重要的划分界限,由其切分的上部坡面和下部坡面是评价物种组成和林分结构的两大基本功能区域。     

Acanthamoeba Interaction with Extracellular Matrix Glycoproteins: Biological and Biochemical Characterization and Role in Cytotoxicity and Invasiveness

ABSTRACT. Acanthamoeba are free-living amoebae that are dispersed in most environments. Occasionally, Acanthamoeba cause serious human infections, such as keratitis and encephalitis. During the infection process, amoebic adhesion to, and degradation of, host cells and their extracellular matrix (ECM) appear to be important requirements. We examined the interaction of Acanthamoeba with the ECM, and related this event to host cell destruction and tissue invasion. Pathogenic Acanthamoeba culbertsoni differentially attached on the ECM glycoproteins laminin-1, collagen-I, and fibronectin, as compared with non-pathogenic Acanthamoeba astronyxis . Binding to collagen-I and laminin-1 induced A. culbertsoni to become flattened and elongated. Because attachment on laminin-1 was higher in A. culbertsoni , laminin-1 was chosen for further analysis. A 55-kDa laminin-binding protein was identified in pathogenic amoebae, but it was not found in non-pathogenic amoebae. No differential cytotoxicity against distinct cell types was observed between A. culbertsoni incubated with or without ECM. On the other hand, binding on collagen-I or matrigel scaffolds induced a differential effect where A. culbertsoni invaded collagen-I matrices more rapidly. These results indicate that ECM recognition, as an antecedent to tissue invasion, may be a trait characteristic of pathogenic Acanthamoeba .     

Comparison of the Protein Kinase and Acid Phosphatase Activities of Five Species of Leishmania1

Promastigotes from log phase and stationary phase cultures of Leishmania donovani, L. braziliensis panamensis, L. tropica, L. major, and L. mexicana amazonensis were analyzed for their content of protein kinase and acid phosphatase activities. Cell surface, historic-specific protein kinase activity was 1.3- to 2.8-fold higher in stationary phase cells of all species except for L. tropica in which the activities of stationary and log phase cells were equal; L. mexicana amazonensis had the highest histone-specific protein kinase activity and L. donovani the lowest. When viable, motile promastigotes of all five species were incubated for 10 min with [γ-³²P]ATP and Mg²⁺ (10 mM) in the absence of exogenous histone acceptor; about one dozen proteins were phosphorylated in each case. Both log phase and stationary phase promastigotes of all five species extensively phosphorylated a 50-kDa protein that had the mobility of tubulin. Incubation of pure calf brain tubulin with [γ-³²P]ATP and purified L. donovani protein kinase resulted in extensive phosphorylation of the former. Highly infective metacyclic forms (PNA^-) of L. major, isolated from a stationary culture using the peanut agglutinin (PNA), contained eight times more histone-specific protein kinase activity than noninfective log phase cells (PNA⁺). The PNA^- and PNA⁺ forms of L. major both phosphorylated a 50-kDa protein when incubated with [γ-³²P]ATP and magnesium or manganese ions (10 mM); the 50-kDa protein was precipitated by anti-tubulin rabbit antibodies. Extracts of all five species contained large amounts of acid phosphatase activity. With the exception of L. braziliensis panamensis for which late log phase organisms contained 12-fold more tartrate-resistant acid phosphatase activity than did early log phase cells, stationary and log phase parasites contained approximately the same amount of acid phosphatase activity.     

祁连山青海云杉林地土壤水分特征研究

通过对祁连山青海云杉林地土壤水分含量及主要影响因子的测定,结果表明,青海云杉林地土壤具有容重低、入渗率高、土壤水分含量垂向分布受降水影响明显等特征,灌木-青海云杉林、苔藓-青海云杉林和草地(对照)平均容重分别为0．522、0．641、0．874g·cm^-3．土壤初渗率分别为6．0、21．0、2．5mm·min^-1,稳渗率分别为3．98、11．2、0．5mm·min^-1．苔藓-青海云杉林地土壤可划分为4层：水分活跃层(0～30cm)、水分调节层(30～60cm)、水分传输层(60～80cm)和蓄水层(80ClTI以下),各层土壤贮水量分别为3．30、3．17、2．80和2．83mm·cm^-1．灌木-青海云杉林可分为3层：水分稳定层(0～30cm)、水分活跃层(30～60cm)和水分传输层(60cm以下),各层土壤贮水量分别为3．98、3．65、3．48mm·cm^-1．两种林地土壤水分含量的季节变化受降水影响较大,相比而言,苔藓．青海云杉林地入渗率更高,有较明显的蓄水层,水分传输能力更强,而灌木-青海云杉林地贮水能力更强．     

A Comparison of the Use of In Vitro-Transcribed and Native rRNA for the Quantification of Microorganisms in the Environment

Abstract Nearly full-length, small subunit (SSU) rRNA was transcribed in vitro from clones of SSU rDNA genes. Comparing the use of in vitro-transcribed and native rRNA indicated that, when in vitro-transcribed rRNA was used as a standard for quantitative hybridizations with oligonucleotide probes, the population was consistently underestimated. The population abundance was expressed as a percentage of specific target SSU rRNA (determined with a specific oligonucleotide probe), relative to the total SSU rRNA (measured with a universal probe). Differences in hybridization signals could be related to specific probe target locations and rRNA denaturation conditions, suggesting that higher order structure is important in quantitative membrane hybridizations. Therefore, in vitro-transcribed rRNA cannot always be used for the absolute quantification of microbial populations, but can be employed as a standard to quantify shifts in population abundance over time, and to compare community structure in various environments.     

Influence de la carence hydrique sur la repartition cellulaire de l'acide ribonucleique foliaire chez le cotonnier

Water stress, induced by addition of polyethyleneglycol 600 to the nutrient solution, reduces the ribonucleic acid content of cotton leaves. The chloroplastic compartment, especially its ribosomal fraction, was most affected, even losing ribonucleic acid to the cytoplasmic compartment. Decrease of ribonucleic acid content on dehydration of leaf tissue is linked with an increase of ribonuclease.     

Cellulase and Other Polymer-Hydrolyzing Activities of Trichomitopsis termopsidis, a Symbiotic Protozoan from Termites

Crude extracts of the anaerobic, cellulolytic protozoan Trichomitopsis termopsidis possessed endo-β-1,4-glucanase and cellobiase activities, as evidenced by hydrolytic action on carboxymethyl cellulose and cellobiose, respectively. Cell extracts also hydrolyzed microcrystalline cellulose. Hydrolysis of microcrystalline cellulose displayed optima at pH 5 and at 30°C, and glucose was the sole product liberated. Cellulolytic activities of T. termopsidis appeared to be entirely cell associated. Hydrolytic activity was also detected against Douglas fir wood powder, xylan, starch, and protein, but not chitin. The importance of these enzymes in the nutrition of T. termopsidis is discussed in terms of the natural habitat of this protozoan (the hindgut of wood-eating termites).