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1.
Sieglinde Ott 《Nordic Journal of Botany》1987,7(2):219-228
Thalli of Xanthoria parietina have been grown in cultures in the natural environment. In early phases of development the fungus associates with foreign algae and only later forms a symbiosis with Pseudotrebouxia . The lichen is shown to have a very effective mechanism for distribution by sexual spores followed by relichenization. 相似文献
2.
Heterogenous staining of D-amino acid oxidase in peroxisomes of rat liver and kidney. A light and electron microscopic study 总被引:1,自引:0,他引:1
The localization of D-amino acid oxidase (D-AAOX) in rat liver and kidney has been investigated using the cerium technique for electron microscopy and a recent modification of it for light microscopy. In the liver a mosaic pattern with strongly and weakly stained cells together with some completely negative hepatocytes is observed. The staining is stronger and more uniform in periportal than in perivenous regions of the liver lobule. In the kidney the reaction is confined to the proximal tubules of the renal cortex with the rest of the nephron being negative. At the ultrastructural level in both liver and kidney a marked heterogeneity is observed in the intensity of reaction in peroxisomes of some neighbouring cells. Moreover, in some cells heavily and weakly stained peroxisomes are seen side by side. When Pipes buffer is used in the incubation medium the D-AAOX reaction in kidney peroxiosomes is aggregated in the central region of the matrix with weaker staining of the periphery. A similar result is obtained when the enzyme is localized by immunocytochemistry confirming a recent report by Usuda et al. (1986). The heterogeneous staining of peroxisomes for D-AAOX suggests that subpopulations of this organelle with specialized functions may exist not only in different tissues and cells but even within the same cell. 相似文献
3.
Summary The localization ofd-amino acid oxidase (d-AAOX) in rat liver and kidney has been investigated using the cerium technique for electron microscopy and a recent modification of it for light microscopy. In the liver a mosaic pattern with strongly and weakly stained cells together with some completely negative hepatocytes is observed. The staining is stronger and more uniform in periportal than in perivenous regions of the liver lobule. In the kidney the reaction is confined to the proximal tubules of the renal cortex with the rest of the nephron being negative. At the ultrastructural level in both liver and kidney a marked heterogencity is obseved in the intensity of reaction in peroxisomes of some neighbouring cells. Moreover, in some cells heavily and weakly stained peroxisomes are seen side by side. When Pipes buffer is used in the incubation medium thed-AAOX reaction in kidney peroxiosomes is aggregated in the central region of the matrix with weaker staining of the periphery. A similar result is obtained when the enzyme is localized by immunocytochemistry confirming a recent report by Usuda et al. (1986). The heterogeneous staining of peroxisomes ford-AAOX suggests that subpopulation of this organelle with specialized functions may exist not only in different tissues and cells but even within the same cell.Dedicated to Professor Dr. T.H. Schiebler on the occasion of his 65th birthday 相似文献
4.
Summary The substrate specificity and the intraperoxisomal localization of -hydroxyacid oxidase in rat liver has been investigated cytochemically by the cerium technique and biochemically with a luminometric assay. Rat liver is fixed by perfusion with a low concentration (0.25%) of glutaraldehyde and vibratome sections are incubated for 60 min at 37°C in a medium containing 3 mM CeCl3, 100 mM NaN3 and 5 mM of an -hydroxyacid in 0.1M of one of the following buffers: Pipes, Mops, Na-cacodylate,Tris-maleate, all adjusted to pH 7.8. Ten different -hydroxyacids with a chain length between 2 and 8 carbon atoms were tested. The best results were obtained with glycolic, argininic andl--isocaproic acids. These cytochemical findings were confirmed also biochemically using purified peroxisomal fractions isolated by gradient centrifugation in metrizamide. The pattern of the intraperoxisomal localization of the enzyme was influenced markedly by the type of buffer used for the cytochemical incubation. Whereas in theTris-maleate medium both the cores and the matrix stained with the same intensity, with all other buffers the reaction in cores was more prominent. The staining of cores was abolished by pretreating sections inTris-maleate (pH 7.8) or alkaline pyrophosphate buffers. These observations establish the substrate specificity of -hydroxyacid oxidase in rat liver and demonstrate the delicate association of this enzyme with the crystalline cores and the matrix of peroxisomes in rat liver.Abbreviations -HAOX
l-hydroxyacid oxidase
- Argininic acid
l--hydroxy--guanidinovaleric acid
- Pipes
piperazine-N,N-bis(2ethane sulfonic acid)
- Mops
3(N-morpholino) propane sulfonic acid
-
Tris
tris-(hydroxymethyl)-aminomethane
- Luminol
5-amino-2,3 dihydrophthalazine-1,4-dione
- GA
glutaraldehyde 相似文献
5.
6.
Various aspects of excitation energy conversion in anoxygenic photosynthetic bacteria are surveyed. This minireview discusses
different models that have been proposed during the past 60 years to describe excitation energy transfer from an antenna molecule
to the reaction center. First, a simple one-dimensional model was suggested, but over time the models became more detailed
when structural and dynamic information was included. This review focuses mainly on the picture of purple bacteria and green
sulfur bacteria developed during the past decades.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
7.
de Boer AL Neerken S de Wijn R Permentier HP Gast P Vijgenboom E Hoff AJ 《Photosynthesis research》2002,71(3):221-239
Mutants of Rhodobacter (Rba.) sphaeroides are described which were designed to study electron transfer along the so-called B-branch of reaction center (RC) cofactors.
Combining the mutation L(M214)H, which results in the incorporation of a bacteriochlorophyll, β, for HA [Kirmaier et al. (1991) Science 251: 922–927] with two mutations, G(M203)D and Y(M210)W, near BA, we have created a double and a triple mutant with long lifetimes of the excited state P* of the primary donor P, viz. 80 and 160 ps at room temperature, respectively. The yield of P+QA
− formation in these mutants is reduced to 50 and 30%, respectively, of that in wildtype RCs. For both mutants, the quantum
yield of P+HB
− formation was less than 10%, in contrast to the 15% B-branch electron transfer demonstrated in RCs of a similar mutant of
Rba. capsulatus with a P* lifetime of 15 ps [Heller et al. (1995) Science 269: 940–945]. We conclude that the lifetime of P* is not a governing factor in switching to B-branch electron transfer. The direct photoreduction of the secondary quinone,
QB, was studied with a triple mutant combining the G(M203)D, L(M214)H and A(M260)W mutations. In this triple mutant QA does not bind to the reaction center [Ridge et al. (1999) Photosynth Res 59: 9–26]. It is shown that B-branch electron transfer
leading to P+QB
− formation occurs to a minor extent at both room temperature and at cryogenic temperatures (about 3% following a saturating
laser flash at 20 K). In contrast, in wildtype RCs P+QB
− formation involves the A-branch and does not occur at all at cryogenic temperatures. Attempts to accumulate the P+QB
− state under continuous illumination were not successful. Charge recombination of P+QB
− formed by B-branch electron transfer in the new mutant is much faster (seconds) than has been previously reported for charge
recombination of P+QB
− trapped in wildtype RCs (105 s) [Kleinfeld et al. (1984b) Biochemistry 23: 5780–5786]. This difference is discussed in light of the different binding
sites for QB and QB
− that recently have been found by X-ray crystallography at cryogenic temperatures [Stowell et al. (1997) Science 276: 812–816].
We present the first low-temperature absorption difference spectrum due to P+QB
−.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
8.
Neerken S Ma YZ Aschenbrücker J Schmidt KA Nowak FR Permentier HP Aartsma TJ Gillbro T Amesz J 《Photosynthesis research》2000,65(3):261-268
Properties of the excited states in reaction center core (RCC) complexes of the green sulfur bacterium Prosthecochloris aestuarii were studied by means of femtosecond time-resolved isotropic and anisotropic absorption difference spectroscopy at 275 K.
Selective excitation of the different transitions of the complex resulted in the rapid establishment of a thermal equilibrium.
At about 1 ps after excitation, the energy was located at the lowest energy transition, BChl a 835. Time constants varying between 0.26 and 0.46 ps were observed for the energy transfer steps leading to this equilibrium.
These transfer steps were also reflected in changes in polarization. Our measurements indicate that downhill energy transfer
towards excited BChl a 835 occurs via the energetically higher spectral forms BChl a 809 and BChl a 820. Low values of the anisotropy of about 0.07 were found in the ‘two-color’ measurements at 820 and 835 nm upon excitation
at 800 nm, whereas the ‘one-color’ kinetics showed much higher anisotropies. Charge separation occurred with a time constant
varying between 20 and 30 ps.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
9.
Sieglinde S. Snapp Kanchan U. Date William Kirk Katherine O’Neil Amy Kremen George Bird 《Plant and Soil》2007,294(1-2):55-72
Brassica species are increasingly being used as cover crops to suppress soil-borne diseases in potato cropping systems. Experiments
were conducted in controlled environments and in the field to evaluate the effects of cover crop root or shoot or a combination
of root and shoot tissues on potato root and tuber health. In a lab assay we examined the extent to which volatile compounds
released from tissues of two cover crop species, rye (Cereale secale L.) and oriental mustard (Brassica juncea L.), could inhibit mycelium growth of two important potato diseases, Rhizoctonia solani and Pythium ultimum. Twenty-four hours into the lab assay, volatile compounds from all residues suppressed fungal growth. After 48 h, marked suppression
of hyphal growth continued in the presence of mustard residues but not in the presence of rye tissues or the control without
tissues. A 75 L volume container experiment evaluated the effect of incorporating different quantities of mustard shoot and
root tissues (none, comparable to field level and fourfold field level) into R. solani and P. ultimum infested soil on potato growth, root health and tuber disease. In the container study, incorporating mustard shoots at the
highest dose increased potato yield by 54% and reduced disease rating to 2.3 compared to a severe rating of 4.4 in the control.
In the field trial, potato growth, root health and tuber disease levels were evaluated in plots where disease management involved
either incorporation of mustard or rye cover crop roots, shoots and whole plants (roots plus shoots) or standard farmer practice
of a fumigated fallow as a control. White root tissue was used as a health indicator, and averaged 58 and 78% in the fumigated
control and mustard cover crop treatments, respectively. The highest healthy root tissue status (91%) was recorded where whole
plants of mustard were incorporated. In contrast to the visual assessment of root and tuber health, tuber yield in the field
was not influenced by cover crop treatment. Across experiments, the incorporation of or exposure to whole mustard plants was
consistently effective at suppressing soil-borne fungi and promoting healthy roots and tubers, especially at higher rates
of biomass. Mustard should be managed so as to maximize incorporated biomass for effective biofumigation. Multipurpose management
requiring removal of mustard shoots is incompatible with promoting potato rhizosphere health. 相似文献
10.
Jürgen?MierschEmail author Dieter?Neumann Sieglinde?Menge Felix?B?rlocher Renate?Baumbach Olaf?Lichtenberger 《Mycological Progress》2005,4(3):185-194
Growth of three strains of Tetracladium marchalianum was inhibited by Cd-, and, to a lesser extent, by Cu-and Zn-chloride. In the presence of 50 μM Cd(II), all strains increased
total thiol and glutathione production to 6, 11, and 21 μmoles · mg−1 dry mass, respectively. Cd(II) also induced the synthesis of one to several compounds reacting with 5,5′-dithio-bis-(2-nitrobenzoic
acid). In order to identify buffer-soluble thiolic compounds other than cysteine, γ-EC and γ-ECG (glutathione) were analyzed
and confirmed by mass spectrometry. No water soluble sulfides were detectable in any of the culture filtrates, but Cd(II)
exposure at a concentration of 50 μM raised sulfide levels in the mycelia of two of the strains between 3 and 7-fold, Cu(II)
and Zn(II) had no effect. Energy Dispersive X-ray-analysis (EDX) and Electron Spectrometry-Images (ES-I) of one strain revealed
increased levels of Cu and Zn in the cytoplasm and even higher levels in vacuolar precipitates. Zn and Cu are accumulated
in the vacuoles as polyphosphates, identified by Electron Energy Loss-Spectrometry (EELS). Cd was found only in the vacuoles. 相似文献