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71.
Anthers of different species of the genera Anemone, Clematis, Papaver and Nicotiana were cultured by floating on a liquid medium which overlay an agarified charcoal medium . This technique proved to be superior to conventional methods i.e. culture on either solid or liquid media. Cold treatment of Anemone anthers for 7 days after inoculation on the double layer medium gave about the same frequency of embryos per anther as corresponding cultures cold treated before inoculation. An elevation of the CO2 concentration to 2% stimulated embryogenesis in anther cultures of Anemone canadensis, Anemone vitifolia, Papaver setigerum and Papaver radicatum . Cold treatment of cultures of Anemone canadensis inhibited embryogenesis if the ensuing culture was performed in 2% CO2. On the other hand, cold treatment was stimulating, with an optimum of about 20 days, if the cultures were maintained in normal air. Chemical analysis of untreated anthers of Anemone canadensis showed the presence of abscisic acid (2.2 × 10−6 g/g anthers). Cold treatment reduced the concentration of abscisic acid to 0.6 × 10−6 g/g anthers. By use of assays with Lemna gibba as test organism, activated charcoal was shown to adsorb abscisic acid that was added to the medium. Medium treated with charcoal before inoculation of anthers of Anemone canadensis provided to inhibit embryo production. 相似文献
72.
Nitrogenase activity of ‘membrane-free’ extracts, produced from nitrogenstarved Rhodospirillum rubrum to which 4 mM NH+4 had been added is only about 10% of the activity in the control. The activity could be restored to 80% by including the membrane component, earlier found to activate R. rubrum nitrogenase, in the reaction mixture. The relation between this ‘switch-off/switch-on’ effect and the function of the membrane component is discussed.Hydrogen production catalyzed by R. rubrum nitrogenase is also dependent on activation by the membrane component. Hydrogen production is inhibited by acetylene but the degree of inhibition is dependent on the nitrogenase component ratio. The strongest inhibition is achieved at low MoFe protein/Fe protein ratios. The values are 4–5 at the component ratios giving the highest activity and increase at high MoFe protein/Fe protein ratios. CO inhibits acetylene reduction but has no effect on the hydrogen production. 相似文献
73.
Ove Eriksson 《Nordic Journal of Botany》1981,1(6):800-800
The morphology and nomenclature of ca. 195 families of bitunicate or alleged bitunicate ascomycetes are discussed. Available representatives of these families were studied especially with respect to the morphology of the asci and ascospores. The morphology of the ascomata, etc. was studied in the SEM in 73 species. The following morphological terms are introduced: hamathecium, pseudoprototunicate, pseudofis–situnicate, semifissitunicate, and umbilicus. The following taxa are described as new: Coccodiniaceae O. Erikss. fam. nov., Microtheliopsidaceae O. Erikss. fam. nov., Amarenomyces O. Erikss. gen. nov., and Euantennaria abietina O. Erikss. sp. nov. The name Lecanidiaceae is proposed to replace Patellariaceae Corda, and Cyanoder–mella to replace Cyanoderma Höhn. The Massariaceae are treated as Trypetheliaceae subfam. Massarioideae (Nits.) O. Erikss. The following new combinations are proposed: Amarenomyces ammophilae (Lasch) O. Erikss., Cyanodermella viridula (Berk. & Curt.) O. Erikss., C. Candida (Setch.) O. Erikss., Dictyotrichiella delicatula (Ves–tergr.) O. Erikss., Laurera sepulta (Mont.) O. Erikss., Splanchnonema superans (Mull. Arg.) O. Erikss. and Thelenella antarctica (M. Lamb) O. Erikss. The origin and evolution of the Ascomycetes are discussed, and the importance of paedomor–phosis in the transspeciation of the group is emphasized. The stratigraphic classification of the Ascomycetes is discussed. In a transitional classification of the Ascomycetes, 109 monophyletic entities (clades) are recognized. La morphologie et la nomenclature ?environ 195 families ?ascomycétes bituniques ou soit–disant bituniques sont étudiées, spécialement en respectant la morphologie des asques et des ascospores. La morphologie des ascocarpes, etc. de 73 espèces fut étudiée dans le SEM. Les termes morphologiques suivants sont introduits: hamathecium, pseudoprototunique, pseudofissitunique, semifissitunique et umbilicus. Ces nouveaux taxa sont decrits: Coccodiniaceae O. Erikss. fam. nov., Microtheliopsidaceae O. Erikss. fam. nov., Amarenomyces O. Erikss. gen. nov. et Euantennaria abietina O. Erikss. sp. nov. Le nom Lecanidiaceae est proposéà la place de Patellariaceae Corda, Cyanodermella à la place de Cyanoderma Höhn. Les Massariaceae sont traitées comme Trypetheliaceae subfam. Massarioideae (Nits.) O. Erikss. Les nouvelles combinations suivantes sont proposées: Amarenomyces ammophilae (Lasch) O. Erikss., Cyanodermella viridula (Berk. & Curt.) O. Erikss., C. Candida (Setch.) O. Erikss., Dictyotrichiella delicatula (Vestergr.) O. Erikss., Laurera sepulta (Mont.) O. Erikss., Splanchnonema superans (Müll. Arg.) O. Erikss. et Thelenella antarctica (M. Lamb) O. Erikss. ?origine et ?évolution des ascomycètes sont discutées, et I'importance de la paedomorphose dans la transspeciation du groupe est mise en évidence. La classification stratigraphique des ascomycètes est discutée. Dans une classification de transition des ascomycètes, 109 entités monophyletiques sont reconnues. 相似文献
74.
Summary Rough microsomes were subfractionated on the basis of different properties in order to investigate the nature and extent of the enzyme heterogeneity of these vesicles. A discontinuous gradient, containing monovalent cations allowed the separation of a ribosome-poor membrane fraction which was enriched in electron transport enzymes and relatively poor in phosphatases. Zonal centrifugation on a stabilizing gradient separated 3 fractions characterized by enrichment of electron transport enzymes, glucose-6-phosphatase and adenosinetriphosphatase, respectively. An essentially similar pattern was seen when ribosomes were removed with EDTA and the denuded vesicles subfractionated on a sucrose gradient. Rough microsomes from phenobarbitaltreated rats exhibited the same pattern both qualitatively and quantitatively. It appears that electron transport enzymes and two types of phosphatases are heterogeneously distributed among rough microsomal vesicles.This work has been supported by grants from the Swedish Medical Research Council. The authors wish to thank Mrs. Ulla-Britta Torndal for her valuable technical assistance 相似文献
75.
Copper toxicosis of Bedlington Terriers (Chronic progressive hepatitis) is a genetically transmitted disease. The typical feature of this disease is accumulation of copper in the liver tissue. The changes vary from mild hepatitis to chronic progressive hepatitis and cirrhosis. The material of this study consists of 2 cases of copper toxicosis examined at the Department of Pathology in Helsinki in the years 1980–82. Moreover a re-examination of tissue samples was made of all Bedlington Terriers examined during the years 1969–1982 at the same department. Six of the 14 examined dogs showed a positive reaction for copper in their liver tissues. The possible relationship of the examined dogs is not yet known. 相似文献
76.
Differential expression of platelet-derived growth factor receptors in human malignant glioma cell lines. 总被引:5,自引:0,他引:5
M Nistér L Claesson-Welsh A Eriksson C H Heldin B Westermark 《The Journal of biological chemistry》1991,266(25):16755-16763
Glioma cells in culture express platelet-derived growth factor (PDGF) A- and B-chains and secrete PDGF-like activity that is mainly PDGF-AA. In this work, we show that the PDGF alpha- and beta-receptors are independently expressed in human malignant glioma cells. We also define three different receptor phenotypes that are related to the morphology of glioma cells: cells with only alpha-receptors, only beta-receptors, or with both types of receptors. By the help of Northern blot analyses, 125I-PDGF-binding experiments, and immunoprecipitations the receptors are shown to be structurally normal PDGF receptors, except for minor variations in size that probably are due to differences in glycosylation. PDGF-BB induces DNA synthesis in cells of all three receptor phenotypes, whereas PDGF-AA or PDGF-AB has this effect only on cells with alpha- or with alpha- and beta-receptors. 125I-PDGF-AB binds with high affinity and down-regulates beta-receptors only in cells where alpha-receptors are present in addition to beta-receptors. Thus, the different functional capacities of PDGF isoforms on glioma cells fit with their known receptor-binding specificities and are compatible with the hypothesis that the isoforms act by inducing dimeric receptor complexes. When data on PDGF A- and B-chains, as well as alpha- and beta-receptor expression are compiled and the pattern of receptor binding specificity is taken into account, the majority of glioma cell lines are found to have a phenotype that makes autocrine stimulation possible. 相似文献
77.
Stream pretreatment of wheat straw solubilized most of the xylan present. Xylose and other sugars were recovered by washing the substrate with water but only a minor part (34%) was monomeric. Treatment of this solutions with celulases and hemicellulases improved the yield of monomeric sugars to 69%, the main product being xylose. Some xylose was also obtained during enzymatic hydrolysis of the solid substrate although the pretreatment step contributed 64% (mean value) of total xylose formed. A reference model, No. 1, and two other models, Nos. 2 and 4, described in the first part of this article series (this issue) have been studied experimentally and results confirm the theoretical conclusions. An uninterrupted hydrolysis over a given time period leads to a lower degree of saccharification than when hydrolysate is withdrawn several times. Saccharification is also favored if the residue is removed at a late stage, i.e., at the end of the 24 h hydrolysis cycle. Extended recirculation of the enzymes during a 4 x 24-h experimental period gave the following average yields of saccharification on a 24-h basis: 65% (Reference), 73% (Model 2), and 79% (Model 4). It is concluded that enzyme recovery with model 4 is 70% or more, while the Reference and Model 2 attain a lower level of recovery. The design of an improved hydrolysis model is also discussed. 相似文献
78.
Seed and microsite limitation of recruitment in plant populations 总被引:40,自引:0,他引:40
Summary Availability of seed and microsites, respectively, are two factors that potentially may limit recruitment in plant populations. Microsites are small-scale sites suitable for germination and survival of seedlings. We discuss this dichotomy of recruitment limitation both from a theoretical and empirical point of view. Investigations of recruitment in 14 woodland species showed that 3 species were seed limited, 6 species were limited by a combination of seed and microsite availability, and 5 species were found not to be seed limited, but the limiting factor was not identified. A combination of seed and microsite limitation implies that recruitment is promoted by increasing both seed and microsite availability. We suggest that the importance of seed limitation in plant populations has been underestimated, and that the operating limiting factors may be dependent on spatial and temporal scale. We expect that many species, if adequately studied, will turn out to be both seed and microsite limited. Experimental field studies that incorporate a range of seed and microsite densities in various spatial and temporal scales are needed to examine the extent to which plant populations are seed and microsite limited. 相似文献
79.
Johanna Puonti-Kaerlas Agneta Ottosson Tage Eriksson 《Plant Cell, Tissue and Organ Culture》1992,30(2):141-148
Protoplasts from two different pea cultivars, Belman and Filby, were stably transformed by direct gene transfer using electroporation. Transgenic calli could be obtained after selection, when hygromycin resistance was used as the selective trait introduced into the protoplasts, while no transformants were obtained when kanamycin resistance was used as selective marker in either of the two pea cultivars tested. The effect of the field strength on survival and division rates of the protoplasts was studied. Two different culture systems and osmotica were compared for induction of sustained divisions in and regeneration of transgenic callus from the protoplasts. The choice of the culture system had a considerable effect on the initial division frequency of the treated protoplasts, as well as on the later growth of the colonies. Transformation efficiency was monitored by histochemical GUS assay, and the transgenic nature of the calli selected for resistance against antibiotics was confirmed by DNA analysis. 相似文献
80.
Fiber type composition of the human female trapezius muscle: enzyme-histochemical characteristics 总被引:3,自引:0,他引:3
Tne anatomy of the human trapezius muscle is complex, with an extensive origin and fibers running in different directions. The muscle is commonly divided into three different muscle portions according to the fiber direction: the descending, transverse, and ascending portions. In a previous study in males, the structure of the muscle differed between different portions with respect to the enzyme-histochemical fiber-type profile. The lower regions of the descending portion and the transverse and the ascending portions had a predominance of type I fibers. The type II fibers were more frequent in the upper regions of the descending portion, and the cross-sectional fiber area in this region of the muscle was smaller. In this study, we have investigated the trapezius muscle in females and compared the results with those from males. The different portions of the female muscle had a relatively even fiber-type composition. However, there tended to be fewer type I fibers and more type IIB fibers in the descending portion of the muscle, and the fibers of the lower regions of the descending portion were somewhat larger. The fiber-type distribution pattern was similar to that of the male trapezius muscle, but the mean cross-sectional area of the fibers in the female muscle was considerably smaller. Thus, our conclusion is that the trapezius muscle of females has a similar activity pattern as that of males. The significantly smaller cross-sectional fiber area, however, may indicate a lower functional capacity which may be of importance in the development of neck and shoulder dysfunction in females. 相似文献