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1.
Peter Buchwald 《Theoretical biology & medical modelling》2009,6(1):5-13
Background
The function and viability of cultured, transplanted, or encapsulated pancreatic islets is often limited by hypoxia because these islets have lost their vasculature during the isolation process and have to rely on gradient-driven passive diffusion, which cannot provide adequate oxygen transport. Pancreatic islets (islets of Langerhans) are particularly susceptible due to their relatively large size, large metabolic demand, and increased sensitivity to hypoxia. Here, finite element method (FEM) based multiphysics models are explored to describe oxygen transport and cell viability in avascular islets both in static and in moving culture media. 相似文献2.
3.
The effect of 253.7 nm ultraviolet radiation on elongation growth, medium acidification and changes in electric potential difference between vacuole and external medium in cells of maize ( Zea mays L.) coleoptile segments was investigated. It was found that irradiation with 390, 1170, 3900 and 5 850 J m−2 UV-C (ultraviolet radiation 253.7 nm) inhibited elongation growth, whereas at 195 J m−2 stimulation of growth was observed. The administration of IAA (10−5 M ) to the incubation medium of coleoptile segments partially abolished the inhibitory effect of UV-C. The pH of the incubation medium, measured simultaneously with growth, showed that the exposure of the segments to UV-C caused inhibition of H+ -extrusion (or stimulation of H+ uptake). The presence of IAA (10−5 M ) in the incubation medium promoted (except after 5850 J m−2 irradiation) H+ -extrusion to a level comparable with that produced by IAA in non-irradiated segments. In UV-C irradiated segments the potential difference underwent significant alterations. Irradiation of coleoptile segments with 390 J m−2 caused a transient depolarization, which was fully reversible within 30 min, while at higher doses depolarization was irreversible. The hyperpolarization of the membrane potential (MP) in cells of maize coleoptile induced by IAA was completely nullified by subsequent irradiation with UV-C. It is suggested that UV-C inhibited IAA-induced growth by a mechanism independent of cell wall acidification. 相似文献
4.
Immunological identification of yeast SCO1 protein as a component of the inner mitochondrial membrane 总被引:4,自引:0,他引:4
Summary The SCO1 gene of Saccharomyces cerevisiae encodes a 30 kDa protein which is specifically required for a post-translational step in the accumulation of subunits 1 and 2 of cytochrome c oxidase (COXI and COXII). Antibodies directed against a -Gal::SCO1 fusion protein detect SCO1 in the mitochondrial fraction of yeast cells. The SCO1 protein is an integral membrane protein as shown by its resistance to alkaline extraction and by its solubilization properties upon treatment with detergents. Based on the results obtained by isopycnic sucrose gradient centrifugation and by digitonin treatment of mitochondria, SCO1 is a component of the inner mitochondrial membrane. Membrane localization is mediated by a stretch of 17 hydrophobic amino acids in the amino-terminal region of the protein. A truncated SCO1 derivative lacking this segment, is no longer bound to the membrane and simultaneously loses its biological function. The observation that membrane localization of SCO1 is affected in mitochondria of a rho
0 strain, hints at the possible involvement of mitochondrially coded components in ensuring proper membrane insertion. 相似文献
5.
Determination was made of the proportion of selected by-products (acetaldehyde, ethyl acetate, methanol, propanol, isobutanol, 2-methyl-butanol, 3-methyl-butanol) of batch and continuous ethanol fermentation carried out with the use of yeastSaccharomyces cerevisiae, strain 0–11, cells immobilized by adsorption on selected carriers (foamed polystyrene, bone shot, beech wood chips, porous glass) as well as by entrapping in calcium alginate and calcium pectinate gel. 相似文献
6.
7.
High Performance Liquid Chromatography of Molecular Species from Free Sterols and Sterylglycosides Isolated from Oat Leaves and Seeds 总被引:1,自引:0,他引:1
Free sterols and sterylglycosides (SG) from oat leaves and seedswere isolated by conventional thin layer chromatography (TLC)and subjected to high performance liquid chromatography (HPLC)for resolution of molecular species. Acylsterylglycosides, isolatedby TLC, were converted to SG by mild alkaline hydrolysis anddetermined as SG. Sterols and SG were injected onto the columnwithout any chemical treatment and the separated species weredetected at 200 nm. The separation of SG-species follows exactlythe separation of free sterols. Though gas liquid chromatography still is the method of choice,advantages of HPLC is to analyse directly the SG-species withouthydrolysis and derivatization as compared to GLC. After TLCthe sterol- and the SG-fraction are injected directly onto thecolumn. This is extremely important for labile sterylglycosidesor sterols, as demonstrated for the avenasterols.
1 Preliminary reports have been presented on the "4. Arbeitstagung,Pflanzliche Lipide", October 78, 1983 in M?nster (FRG)and on the "6th International Symposium on the Structure, Functionand Metabolism of Plant Lipids", Neuchatel, Switzerland, July1620, 1984. (Received November 12, 1984; Accepted January 14, 1985) 相似文献
8.
Zusammenfassung Regionale und artliche Unterschiede der Rückstände von Quecksilber in Eiern von sieben Brutvogelarten der deutschen Nordseeküste wurden untersucht. Bei vier Arten stellten wir deutliche geographische Unterschiede in der Kontamination fest (Abb. 1). Höchstgehalte fanden wir in Eiern von der Elbmündung (Region V). Austernfischer- und Flußseeschwalbeneier von der inneren Deutschen Bucht (Region VI) enthielten größere Mengen als solche von Nordfriesland (Region VII). Der gesetzliche Richtwert für Eier (0,03 mg/kg) wurde von 353 der 355 untersuchten Eier überschritten. Fluß- und Brandseeschwalbe waren am stärksten, Brandgans, Austernfischer und Lachmöwe am wenigsten mit Quecksilber kontaminiert (Abb. 2, 4.2.). Mit Ausnahme von Brandgans und Silbermöwe erreichten die Rückstände in vielen Eiern der anderen Arten, an der Elbe sogar in allen Eiern, eine den Bruterfolg gefährdende Größenordnung, insbesondere bei der Flußseeschwalbe.
Pollutants in eggs of birds breeding at the German North Sea Coast. II. Mercury
Summary Regional and interspecific differences of mercury residues were investigated in the eggs of seven species breeding at the German North Sea Coast (Tadorna tadorna, Haematopus ostralegus, Charadrius hiaticula, Larus argentatus, L. ridibundus, Sterna hirundo, S. sandvicensis). We found distinct geographical differences in contamination (Fig. 1): In eggs from the Elbe Eastuary (region V) maximum residues of mercury were ascertained. Eggs of Oystercatcher and Common Tern from the Bay of Helgoland (region VI) contained larger quantities than eggs from Northern Frisia (region VII). 353 from 355 eggs examined showed a value exceeding the legal standard value for eggs which is 0,03 mg/kg in Germany. Common Tern and Sandwich Tern eggs had the highest, Shelduck, Oystercatcher and Blackheaded Gull eggs the lowest mercury contamination (Fig. 2, 4.2.). With the exception of Shelduck and Herring Gull, residues in many eggs of the other species — at the river Elbe in all eggs — came up to a range endangering breeding success, especially in Common Terns.相似文献
9.
Christina Scharnhorst Hartmut Heinze Gabriele Meyer Waldemar Kolanus Klaus Bartsch Susanne Heinrichs Thomas Gudschun Margret Möller Frank Herzfeld 《Plant molecular biology》1985,4(4):241-245
Summary cDNA clones were isolated for a chloroplast protein, the mRNA of which is induced to maximum levels within 2–4 h after onset
of illumination in five day old, etiolated pea seedlings.
The cDNA library was constructed from poly(A)+-mRNA which was isolated from 4 h illuminated seedlings. The extremely short induction period of the early light induced protein(ELIP)-mRNA
established the basis of our screening procedure. Colony hybridization experiments were performed with32P-labelled cDNA probes, synthesized from RNA of seedlings which had been exposed to different programs of illumination. Plasmid
DNAs were isolated from colonies showing strong hybridization signals exclusively with cDNA corresponding to the 4 h-mRNA.
Hybrid released translation of preselected plasmids p 17/C2 and p17/C4 revealed a peptide of Mr 24 000. After posttranslational importin vitro, the processed product of Mr 17 000 appears in the chloroplast. Using these clones, the expression of the ELIP-mRNA was investigated by DOT-hybridization.
The ELIP-mRNA reaches maximum levels within 2–4 hours after onset of illumination. Our results correspond precisely to thein vivo characteristics and indicate positive identification of the sought clones. 相似文献
10.