Leaf ultrastructure of C4 species possessing different Kranz anatomical types in the cyperaceae

The leaf ultrastructure of NADP-malic enzyme type C₄ species possessing different anatomical features in the Cyperaceae was examined: types were the Rhynchosporoid type, a normal Kranz type in which mesophyll cells are adjacent to Kranz cells, and Fimbristyloid and Chlorocyperoid types, unusual Kranz types in which nonchlorophyllous mestome sheath intervenes between the two types of green cells. They show structural characteristics basically similar to the NADP-malic enzyme group of C₄ grasses, that is, centrifugally located chloroplasts with reduced grana and no increase of mitochondrial frequency in the Kranz cells. However, the Kranz cell chloroplasts of the Fimbristyloid and Chlorocyperoid types exhibit convoluted thylakoid systems and a trend of extensive development of peripheral reticulum, although those of the Rhynchosporoid type do not possess such particular membrane systems. The suberized lamella, probably a barrier for CO₂ diffusion, is present in the Kranz cell walls of the Rhynchosporoid type and in the mestome sheath cell walls of the other two types, and tightly surrounds the Kranz cells (sheaths) that are the sites of the decarboxylation of C₄ acids. These ultrastructural features are discussed in relation to C₄ photosynthetic function.     

The ecology of a beech forest on Mt. Sanpoiwadake,Hakusan National Park,Japan II. The correlation of the subassociation within the Lindero membranaceae-fagetum crenatae association and environmental parameters

Detailed examination of a sample plot covered by the Lindero membranaceae-Fagetum crenatae association on Mt. Sanpoiwadake, Hakusan National Park, revealed a number of correlations between the distribution of subassociations and environmental factors. The subassociations on the south-facing slopes receive deep snow cover in winter with rapid melting in the spring. They occur on porous, freely draining soils, typical of the general range of brown forest soils. Conversely, on the north-eastern slopes there are widespread late-snow patches which delay leaf development and expansion and which provide an abundant water supply well into early summer. Under these conditions, bleached soil horizons have developed with iron pan formation, resulting in poor soil drainage, strongly correlated with quite different plant communities.     

The relationship between species richness and standing crop in wetlands: the importance of scale

One of the few important empirical generalizations regarding herbaceous plant systems has been the demonstration that species richness is related to standing crop with maximum richness occurring at moderate levels of standing crop. This relationship is normally demonstrated by comparing among vegetation types (i.e., vegetation with different dominants). We undertook this study to test whether the species richness-standing crop relationship was evident at a finer-grained level of organization, the within vegetation type level. Fifteen wetland sites were sampled in eastern Canada and species richness and standing crop determined in each of 224 0.25 m² quadrats. Each site was relatively homogeneous in terms of the dominant species present and were therefore categorized as single vegetation types. However, as a group, the sites comprised a wide range of vegetation types.A second order polynomial regression indicated a significant bitonic relationship between species richness and standing crop at the among-vegetation types scale, that is, when all 15 sites were combined. At the within-vegetation type level, however, no significant relationships were observed (p>0.05). The results indicate that the model of species richness proposed by Grime has predictive power at a coarse-grained level of organization, among vegetation types, but does not survive the transition to a finer-grained level of organization, the within vegetation type level. Therefore, the higher level processes which structure species richness patterns among vegetation types are not the same processes which determine richness patterns within a vegetation type.     

Segregation of viral double-stranded and single-stranded DNA molecules in nuclei of adenovirus infected cells as revealed by electron microscope in situ hybridization.

Formation of progeny viruses in the nuclei of HeLa cells infected with adenovirus type 5 was studied at the ultrastructural level by in situ hybridization techniques allowing specific detection of either viral double-stranded DNA (dsDNA) or single-stranded DNA (ssDNA). Prior to the initiation of replication of viral genomes, infective DNA molecules which entered the nucleus of the target cell were randomly distributed among host chromatin fibers including nucleolus-associated chromatin. They were double-stranded, that is, without single-strand breaks. Such association of viral DNA with host condensed chromatin also occurred in mitosis. The initiation of viral genome replication occurred simultaneously with the appearance in the nucleoplasm of small fibrillar regions containing intermingled viral dsDNA and ssDNA. Later, at the intermediate stage of nuclear transformation, viral dsDNA and ssDNA molecules were almost entirely separated into two contiguous substructures. At this stage, viruses were observed occasionally in the vicinity of viral ssDNA accumulation sites. Still later, an additional substructure developed in the centre of the nucleus which consisted of large quantities of viral dsDNA, traces of viral ssDNA and abundant viruses. Portions of viral ssDNA were attached to some viruses even at late stage of nuclear transformation, an association which strongly suggests the occurrence of encapsidation of at least some of the viral genomes while they are still engaged in replication.     

Purification and partial characterization of two azoreductases from Shigella dysenteriae Type 1

Two azoreductases (I and II) were purified to homogeneity from extracts of Shigella dysenteriae (type 1). Azoreductase I was a dimer of identical subunits of M(r) 28,000, whereas azoreductase II was a monomer of 11,000 M(r). Both were flavoproteins, each containing 1 mol of FMN per mol enzyme. Both NADH and NADPH functioned as electron donors for the azoreductases. Azoreductase I used Ponceau SX, Tartrazine, Amaranth and Orange II as substrates. Azoreductase II utilized all the dyes except Amaranth.     

桑树叶肉原生质体培养再生植株

近年来,木本植物原生质作诱导再生植株的研究越来越受到国内外学者关注。但在林木树种中,迄今成功的种类仍然不多,在文     

Pericellular substrates of human mast cell tryptase: 72,000 dalton gelatinase and fibronectin.

Migrating cells degrade pericellular matrices and basement membranes. For these purposes cells produce a number of proteolytic enzymes. Mast cells produce two major proteinases, chymase and tryptase, whose physiological functions are poorly known. In the present study we have analyzed the ability of purified human mast cell tryptase to digest pericellular matrices of human fibroblasts. Isolated matrices of human fibroblasts and fibroblast conditioned medium were treated with tryptase, and alterations in the radiolabeled polypeptides were observed in autoradiograms of sodium dodecyl sulphate polyacrylamide gels. It was found that an M(r) 72,000 protein was digested to an M(r) 62,000 form by human mast cell tryptase while the plasminogen activator inhibitor, PAI-1, was not affected. Cleavage of the M(r) 72,000 protein could be partially inhibited by known inhibitors of tryptase but not by aprotinin, soybean trypsin inhibitor, or EDTA. Fibroblastic cells secreted the M(r) 72,000 protein into their medium and it bound to gelatin as shown by analysis of the medium by affinity chromatography over gelatin-Sepharose. The soluble form of the M(r) 72,000 protein was also susceptible to cleavage by tryptase. Analysis using gelatin containing polyacrylamide gels showed that both the intact M(r) 72,000 and the M(r) 62,000 degraded form of the protein possess gelatinolytic activity after activation by sodium dodecyl sulphate. Immunoblotting analysis of the matrices revealed the cleavage of an immunoreactive protein of M(r) 72,000 indicating that the protein is related to type IV collagenase. Further analysis of the pericellular matrices indicated that the protease sensitive extracellular matrix protein fibronectin was removed from the matrix by tryptase in a dose-dependent manner. Fibronectin was also susceptible to proteolytic degradation by tryptase. The data suggest a role for mast cell tryptase in the degradation of pericellular matrices.     

The Linnaean fish collection in the Zoological Museum of the University of Uppsala

Specimens of fishes preserved in the Zoological Museum, University of Uppsala, which are believed to have been examined by Linnaeus, are listed. Most of these were originally given to the University in several donations by benefactors of the Academy and were described by Linnaeus in dissertations defended by students. Some specimens, however, are believed to have originated from Linnaeus's own collection. Many of the specimens have type status and this is discussed together with notes on other surviving Linnaean fish specimens.     

Nutrient transfer between the root zones of soybean and maize plants connected by a common mycorrhizal mycelium

The objective of the study was to determine whether nutrient fluxes mediated by hyphae of vesicular-arbuscular mycorrhizal (VAM) fungi between the root zones of grass and legume plants differ with the legume's mode of N nutrition. The plants, nodulating or nonnodulating isolines of soybean [ Glycine max (L.) Merr.], were grown in association with a dwarf maize ( Zea mays L.) cultivar in containers which interposed a 6-cm-wide root-free soil bridge between legume and grass container compartments. The bridge was delimited by screens (44 μm) which permitted the passage of hyphae, but not of roots and minimized non VAM interactions between the plants. All plants were colonized by the VAM fungus Glomus mosseae (Nicol. & Gerd.) Gerd. and Trappe. The effects of N input to N-sufficient soybean plants through N₂-fixation or N-fertilization on associated maize-plant growth and nutrition were compared to those of an N-deficient (nonnodulating, unfertilized) soybean control. Maize, when associated with the N-fertilized soybean, increased 19% in biomass, 67% in N content and 77% in leaf N concentration relative to the maize plants of the N-deficient association. When maize was grown with nodulated soybean, maize N content increased by 22%, biomass did not change, but P content declined by 16%. Spore production by the VAM fungus was greatest in the soils of both plants of the N-fertilized treatment. The patterns of N and P distribution, as well as those of the other essential elements, indicated that association with the N-fertilized soybean plants was more advantageous to maize than was association with the N₂-fixing ones.