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41.
BJÖRN SÖDER BÄCK 《Freshwater Biology》1995,33(2):291-304
1. The introduced North American crayfish Pacifastacits leniusculus is currently replacing the native crayfish Astacus astacus in a Swedish lake. Using field data from co-occurring populations on life-history traits and population size structure of the two species, this study evaluated possible mechanisms behind the replacement. 2. Pacifastacus showed a higher capacity for population increase; the species had a higher individual growth rate, reached sexual maturity at a smaller size and lower age, and had a higher per capita egg production than Astacus. 3. A higher frequency of non-lethal injuries in Astacus suggested the predominance of Pacifastacus in interference interactions. These results support a competitive exclusion hypothesis. 4. A dramatic change in relative abundance of the two species in recent years was the result of an almost complete cessation in recruitment of young-of-the-year (YOY) in Astacus. Poor recruitment in Astacus was probably caused by the combined effects of interspecific competition and predation, resulting in increased mortality among YOY Astacus, and by reproductive interference, suppressing the less common species. 5. The results support the hypothesis that the observed replacement of Astacus by Pacifastacus is governed by a combination of several interacting mechanisms, of which 相似文献
42.
The ciliated epidermis of Xenoturbella bocki (Platyhelminthes, Xenoturbellida) with some phylogenetic considerations 总被引:1,自引:0,他引:1
The epidermis of Xenoturbella bocki Westblad was studied by scanning and transmission electron microscopy. Two cell types predominate in the epidermis: multiciliated epidermal cells and non-ciliated or monociliated gland cells. A conspicuous feature is the dense ciliary coverage and the numerous gland cell openings. Xenoturbella has a characteristic pattern of axonemal filament termination in the distal tips of their cilia. Each epidermal cilium has the typical 9 + 2 patten through the major part of its shaft. Near the tip there is a shelf at which doublets 4–7 terminate. Doublets 1, 2, 3, 8 and 9 continue into the thinner distal part of the cilium. A similar shelf in cilia is known only from the turbellarian orders Nemertodermatida and Acoela, and hence may be an apomorphic feature which indicates a close relationship between Xenoturbellida, Nemertoder-matida and Acoela. The basal body is provided with a so-called basal foot which has a cross-striated appearance and an expanded distal plate that seems to act as a microtubule organizing center. Approximately 15–25 microtubuli radiate from the endplate of the basal foot to the basal bodies caudally. The arrangement of basal foot and ciliary rootlets in Xenoturbella differs from that of Acoela and related orders in that there are two striated rootlets only (an anterior and a posterior one), rather than one main rootlet and two lateral rootlets. 相似文献
43.
Molecular evolution of rodent insulins 总被引:1,自引:0,他引:1
Several trees of amino acid sequences of rodent insulins were derived with
the maximum-parsimony procedure. Possible orthologous and paralogous
relationships were investigated. Except for a recent gene duplication in
the ancestor of rat and mouse, there are no strong arguments for other
paralogous relationships. Therefore, a tree in agreement with other
biological data is the most reasonable one. According to this tree, the
capacity to form zinc-binding hexamers was lost once in the ancestor of the
hystricomorph rodents, followed by moderately increased evolutionary rates
in the lineages to African porcupine and chinchilla but highly increased
rates in at least three independent lines to other taxa of this suborder:
guinea pig, cuis, and Octodontoidea (coypu and casiragua).
相似文献
44.
JAN HANNEMANN HENDRIK POORTER BJÖRN USADEL OLIVER E. BLÄSING ALEX FINCK FRANCOIS TARDIEU OWEN K. ATKIN THIJS PONS MARK STITT & YVES GIBON 《Plant, cell & environment》2009,32(9):1185-1200
Data mining depends on the ability to access machine-readable metadata that describe genotypes, environmental conditions, and sampling times and strategy. This article presents Xeml Lab. The Xeml Interactive Designer provides an interactive graphical interface at which complex experiments can be designed, and concomitantly generates machine-readable metadata files. It uses a new eXtensible Mark-up Language (XML)-derived dialect termed XEML. Xeml Lab includes a new ontology for environmental conditions, called Xeml Environment Ontology. However, to provide versatility, it is designed to be generic and also accepts other commonly used ontology formats, including OBO and OWL. A review summarizing important environmental conditions that need to be controlled, monitored and captured as metadata is posted in a Wiki ( http://www.codeplex.com/XeO ) to promote community discussion. The usefulness of Xeml Lab is illustrated by two meta-analyses of a large set of experiments that were performed with Arabidopsis thaliana during 5 years. The first reveals sources of noise that affect measurements of metabolite levels and enzyme activities. The second shows that Arabidopsis maintains remarkably stable levels of sugars and amino acids across a wide range of photoperiod treatments, and that adjustment of starch turnover and the leaf protein content contribute to this metabolic homeostasis. 相似文献
45.
E. V. Vorobeva I. N. Krasikova A. S. Dmitrenok P. S. Dmitrenok V. V. Isakov O. I. Nedashkovskaya T. F. Solov’eva 《Russian Journal of Bioorganic Chemistry》2006,32(5):485-491
The hydrolysis of defatted cells of the marine bacterium Chryseobacterium scophtalmum CIP 104199T with 10% acetic acid (3 h, 100°C) led to an unusual lipid A (LA) (yield 0.6%), obtained for the first time. Using chemical analysis, FAB MS, and NMR spectroscopy, it was shown to be D-glucosamine 1-phosphate acylated with (R)-3-hydroxy-15-methylhexadecanoic and (R)-3-hydroxy-13-methyltetroadecanoic acids at the C2 and C3 atoms, respectively. It is similar to the monosaccharide biosynthetic precursor of lipopolysaccharide (LPS), so-called lipid X (LX). Unlike LX, LA can be isolated by the treatment of bacteria with organic solvents only after the preliminary acidic hydrolysis of the cells, which suggests that LA might be strongly, probably chemically, linked to other components of the outer membrane. However, LPS cannot be such a component, because extraction with phenol-water or phenol-chloroform-petroleum ether mixtures in high yields (5.34% and 0.5%, respectively) leads to preparations that do not contain 3-deoxy-D-manno-oct-2-ulopyranosonic acid, 3-hydroxyalkanoic acids, or LA. 相似文献
46.
Kulikova Tatiana Maslova Antonina Starshova Polina Rodriguez Ramos Juan Sebastian Krasikova Alla 《Chromosoma》2022,131(4):207-223
Chromosoma - In diplotene oocyte nuclei of all vertebrate species, except mammals, chromosomes lack interchromosomal contacts and chromatin is linearly compartmentalized into distinct... 相似文献
47.
Molecular Biology - The base and nucleotide excision DNA repair (BER and NER) systems are aimed at removing specific types of damaged DNA, i.e., oxidized, alkylated, or deaminated bases in the case... 相似文献
48.
Co-expression tools for plant biology: opportunities for hypothesis generation and caveats 总被引:1,自引:0,他引:1
BJÖRN USADEL TAKESHI OBAYASHI MAREK MUTWIL FEDERICO M. GIORGI GEORGE W. BASSEL MIMI TANIMOTO AMANDA CHOW DIRK STEINHAUSER STAFFAN PERSSON & NICHOLAS J. PROVART 《Plant, cell & environment》2009,32(12):1633-1651
Gene co‐expression analysis has emerged in the past 5 years as a powerful tool for gene function prediction. In essence, co‐expression analysis asks the question ‘what are the genes that are co‐expressed, that is, those that show similar expression profiles across many experiments, with my gene of interest?’. Genes that are highly co‐expressed may be involved in the biological process or processes of the query gene. This review describes the tools that are available for performing such analyses, how each of these perform, and also discusses statistical issues including how normalization of gene expression data can influence co‐expression results, calculation of co‐expression scores and P values, and the influence of data sets used for co‐expression analysis. Finally, examples from the literature will be presented, wherein co‐expression has been used to corroborate and discover various aspects of plant biology. 相似文献
49.
Simple Methods for the Calibration of Light Measuring Equipment 总被引:1,自引:0,他引:1
L. O. BJöRN 《Physiologia plantarum》1971,25(2):300-307
Simple methods are described for
- a) absolute calibration of thermal radiation detectors (thermopiles, bolometers);
- b) absolute calibration at various wavelengths of photoelectric devices;
- c) obtaining the relative spectral sensitivity of the detector systems of spectrofluorimeters.
50.
Kapustina NV Krasikova IN Isakov VV Gorshkova NM Solov'eva TF 《Biochemistry. Biokhimii?a》2004,69(4):407-412
The chemical structure of a novel lipid A obtained as a major component on hydrolysis of LPS from the marine gamma-proteobacterium Marinomonas vaga ATCC 27119T with 1% AcOH was determined. Using chemical analysis and NMR data, it was shown to be beta-1,6-glucosaminobiose 1-phosphate acylated with R-3-hydroxydecanoic acid (at position 3), and R-3-dodecanoyloxydecanoic (or R-3-decanoyloxydecanoic) acid and R-3-(R-3-hydroxydecanoyl)oxydecanoic acids (at the 2- or 2;-positions). The absence of a fatty acid at the 3;-position and a phosphoryl group at the 4;-position, and also the presence of R-3-acyloxyalkanoic acid with R-3-hydroxyalkanoic acid as the secondary acid are unique features distinguishing the M. vaga lipid A from other ones. 相似文献