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81.
Schenk U.; Manderscheid R.; Hugen J.; Weigel H.J. 《Journal of experimental botany》1995,46(8):987-993
Seedlings of perennial ryegrass (Lolium perenne L. cv. Parcour)and white clover (Trifolium repens L. cv. Karina) grown at fivedifferent plant densities were exposed to ambient (390 ppm)and elevated (690 ppm) CO2 concentrations. After 43 d the effectsof CO2 enrichment and plant density on growth of shoot and root,nitrogen concentration of tissue, and microbial biomass carbon(Cmic) in soil were determined. CO2 enrichment of Lolium perenneincreased shoot growth on average by 17% independent of plantdensity, while effects on root biomass ranged between -4% and+ 107% due to an interaction with plant density. Since tilernumber per plant was unaffected by elevated CO2, the small responseof shoot growth to CO2 enrichment was atributed to low sinkstrength. A significant correlation between nitrogen concentrationof total plant biomass and root fraction of total plant drymatter, which was not changed by CO2 enrichment, indicates thatnitrogen status of the plant controls biomass partitioning andthe effect of CO2 enrichment on root growth. Effects of elevatedCO2 and plant density on shoot and root growth of Trifoliumrepens were not significantly interacting and mean CO2-relatedincrease amounted to 29% and 66%, respectively. However, growthenhancement due to elevated CO2 was strongest when leaf areaindex was lowest. Total amounts of nitrogen in shoots and rootswere bigger at 690 ppm than at 390 ppm CO2. There was a significantincrease in Cmic in experiments with both species whereas plantdensity had no substantial effect. Key words: CO2 enrichment, intraspecific competition, biomass partitioning, Lolium perenne, Trifolium repens, grassland 相似文献
82.
Small intensely fluorescent (SIF) cells are paraganglionic cells derived from sympathicoblasts which may serve as interneurons,
endo-/paracrine cells or arterial chemoreceptors within sympathetic ganglia. Like paraganglionic cells of other locations,
e.g., carotid body glomus cells, they are responsive to hypoxia. Recent studies on glomus cells and other hypoxia-sensing
cells suggested the involvement of a b
558
-type cytochrome and intracellular generation of H2O2 in the process of oxygen sensing. In the present study, we demonstrate the occurrence of the small subunit of cytochrome b
558
, p22phox, in SIF cells of guinea-pig sympathetic ganglia by immunohistochemistry using two different antisera. H2O2 production was monitored in explanted intact superior cervical ganglia of 2-day-old rats by confocal laser scanning analysis
of rhodamine 123 fluorescence generated due to oxidation of dihydrorhodamine 123 by H2O2. Using this technique, SIF cell clusters appeared as sites of highest H2O2 production within the ganglia. Thus, SIF cells exhibit two key features of an oxidase system generating reactive oxygen species.
This may be involved in the proposed chain of events in oxygen sensing, but alternative cellular functions of this system
have also to be considered.
Accepted: 19 September 1996 相似文献
83.
Antoni Rozalski Lore Brade Paul Kosma Richard Moxon Shoichi Kusumoto & Helmut Brade 《Molecular microbiology》1997,23(3):569-577
Monoclonal antibodies against the lipopolysaccharide (LPS) of the deep rough mutant I-69 Rd− /b+ of Haemophilus influenzae were obtained after immunization of mice with sheep erythrocytes which had been coated with de- O -acylated LPS. Characterization of antibodies was performed by enzyme immuno assay (EIA) using LPS or neoglycoconjugates containing partial structures of LPS as solid-phase antigens and by haemagglutination with sheep erythrocytes coated with de- O -acylated LPS. Binding data were confirmed by EIA inhibition experiments using deacylated LPS or synthetic partial structures thereof. Three antibodies were specific for 3-deoxy- d - manno -octulopyranosonic acid- (Kdo) 5-phosphate, one for Kdo-4-phosphate, and one required, in addition to a Kdo-phosphate, parts of the phosphorylated glucosamine backbone of lipid A. All antibodies also bound in (i) Western blots to bacterial whole-cell lysates or isolated LPS separated by SDS–PAGE, (ii) bacterial colony blots, and (iii) immunofluorescence with live bacteria. The latter result indicated that Kdo-4- and Kdo-5-phosphate are synthesized by the bacteria and are not the result of phosphate migration. 相似文献
84.
Identification of a 175 kDa protein as the ligand-binding subunit of the rat liver sinusoidal endothelial cell hyaluronan receptor 总被引:2,自引:1,他引:1
The rat liver sinusoidal endothelial cell (LEC) hyaluronan (HA)receptor was previously identified using a photoaffinity HAderivative (J. BioL Chem., 267, 2045120456, 1992). Twopolypeptides with Mr = 175,000 and 166,000, were consistentlycrosslinked, suggesting that the LEC HA receptor is an oligomer.Whether one or both subunits participate in HA binding, wasnot determined. Here we investigate the HA-subunit interactionsand the potential oligomeric nature of the LEC HA receptor.When Sephacryl-400 gel filtration chromatography was used toenrich the HA receptor, the 175 kDa polypeptide was the majorband seen by SDS-PAGE analysis. Little staining was seen at166 kDa, suggesting that the 175 kDa protein could be separatedfrom the 166 kDa protein and still retain HA-binding activity.A ligand blot assay was used to determine if each individualsubunit could bind HA. LEC proteins were separated by nonreducingSDS-PAGE, and then immobilized onto nitrocellulose. 125I-HAbound to a 175 kDa polypeptide but not to the 166 kDa protein.A high molecular weight band of 相似文献
85.
Larvae of the two southern hemisphere lamprey genera, Mordacia and Geotria, possess one and two intestinal diverticula, respectively, each originating at the oesophageal-intestinal junction. These diverticula comprise an inner layer of simple columnar epithelium composed solely of zymogen and mucous cells, a middle layer consisting mainly of a blood sinus, and an outer serosa layer covered by a simple squamous epithelium (mesothelium). The inner surface is highly folded only in Mordacia. The secretion of mucus probably protects the epithelium from the effects of digestive enzymes secreted by the zymogen cells and/or bile, which enters the diverticulum at its tip. Unlike the situation in southern hemisphere lampreys, the zymogen cells of the larvae of holarctic lampreys are located in the anterior intestine, a condition considered to be primitive. It is thus proposed that intestinal diverticula were developed during the evolution of southern hemisphere lampreys. The relocation of zymogen cells in the diverticula increases the area for these cells, and thus the capacity for the synthesis and secretion of digestive enzymes, particularly in Mordacia where the inner surface is folded. 相似文献
86.
An immunohistological study of L3T4(CD4)+ and LYT-2(CD8)+ lymphocytes, Mac-1(CD11b)+ monocytes and granulocytes in experimental murine cryptococcal meningoencephalitis was conducted. To assess the concomitant inflammatory reaction in an extracerebral site, livers were examined in parallel. Mice were infected i.v. withCryptococcus neoformans, group A/D, and organs were examined immunohistologically for CD4-, CD8- and monocyteand granulocyte-specific CD11b-phenotypic leukocytes over a period of 60 days. Intracerebrally, agglomerations of cryptococci formed pseudocysts that were surrounded by CD4+ and CD8+ lymphocytes at the end of the second week post-infection, followed by the invasion of monocytes and granulocytes into the lesions. After the fourth week post-infection, most of the invaded lesions were transformed into glious scars. Meningitis was usually marked and showed a homogenous distribution of CD4-, CD8- and CD11b-phenotypic cells, with a predominance of monocytes and CD4+ lymphocytes. Inflammatory infiltrates in the liver were found already 4 days post-infection. CD4+ lymphocytes and monocytes were distributed homogenously in the infiltrates, with a lower number of CD8+ lymphocytes being located rather in the periphery of the infiltrates. Comparing leukocyte kinetics in brain and liver, an important observation was the delayed immigration of immune cells at the intracerebral cryptococcal lesions as compared with the liver, and the different migration patterns of T-lymphocyte subgroups and macrophages. These results suggest that there are differential leukocyte migration patterns in the liver and brain following disseminated cryptococcosis. The immunological aspects of the observed leukocyte kinetics are discussed. 相似文献
87.
Attempts to induce enantioselectivity in the catalytic hydrogenation of unsymmetrically substituted aromatics using covalently bound, well known chiral auxiliaries are described. Marked differences in stereoselectivity and rate of hydrogenolysis are noted as a function of the auxiliary used. Enantioselectivities obtained in the resulting cyclohexyl derivatives are rather poor. © 1995 Wiley-Liss, Inc. 相似文献
88.
Frieder Schauer Kirsten Henning Helmut Pscheidl Rolf M. Wittich Peter Fortnagel Heinz Wilkes Volker Sinnwell Wittko Francke 《Biodegradation》1995,6(2):173-180
Trichosporon beigelii SBUG 752 was able to transform diphenyl ether. By TLC, HPLC, GC, GC-MS, NMR- and UV-spectroscopy, several oxidation products were identified. The primary attack was initiated by a monooxygenation step, resulting in the formation of 4-hydroxydiphenyl ether, 2-hydroxydiphenyl ether and 3-hydroxydiphenyl ether (48:47:5). Further oxidation led to 3,4-dihydroxydiphenyl ether. As a characteristic product resulting from the cleavage of an aromatic ring, the lactone of 2-hydroxy-4-phenoxymuconic acid was identified. The possible mechanism of ring cleavage to yield this metabolite is discussed. 相似文献
89.
Helmut Kroll 《Vegetation History and Archaeobotany》1995,4(1):51-66
Publications on archaeological remains of cultivated plants have been collected, mainly from 1992 and 1993, with some earlier and later ones. A list is given of the finds according to taxon, country, site and age. 相似文献
90.
Comparison of ccd of F, parDE of RP4, and parD of R1 using a novel conditional replication control system of plasmid R1 总被引:5,自引:2,他引:3
Rasmus Bugge Jensen Elisabeth Grohmann Helmut Schwab Ramón Díaz-Orejas Kenn Gerdes 《Molecular microbiology》1995,17(2):211-220
A number of plasmid-encoded gene systems are thought to stabilize plasmids by killing plasmid-free cells (also termed post-segregational killing or plasmid addiction). Here we analyse the mechanisms of plasmid stabilization by ccd of F, parDE of RP4 and parD of R1, and compare them to hok/sok of R1. To induce synchronous plasmid loss we constructed a novel plasmid replication-arrest system, which possesses the advantage that plasmid replication can be completely arrested by the addition of IPTG, a non-metabolizable inducer. Using isogenic plasmid constructions we have found, for the first time, consistent correlation between the effect on steady-state loss rates and the effect on cell proliferation in the plasmid replication-arrest assay for all three systems. The parDE system had the most pronounced effect both on plasmid stabilization and on plasmid retention after replication arrest. In contrast, ccd and parD both exhibited weaker effects than anticipated from previously published results. Thus, our results indicate that the function and efficiencies of some of the systems should be reconsidered. Our results are consistent with the previously postulated hypothesis that ccd and parDE act by killing plasmid-free segregants, whereas parD seems to act by inhibiting cell division of plasmid-free segregants. 相似文献