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871.
Georg Heinrich 《Protoplasma》1966,61(1-2):157-163
Zusammenfassung Die Proteinoplasten vonHelleborus corsicus erweisen sich als arm an Thylakoiden, diese kommen nur selten gehäuft vor, sind aber nie zu Granen aggregiert. Sie enthalten immer eine Vakuole, deren Wandung wahrscheinlich einer Thylakoidmembran entspricht. Stärkebildung läßt sich in den Leukoplasten durch Zusatz von Glucose-1-phosphat nicht erzwingen. Frostwirkung verändert sie weniger als die Chloroplasten des Schwammparenchyms. Die einzig sichtbare Reaktion der Leukoplasten auf den Frost ist eine Entmischung des Vakuoleninhaltes.Herrn Doz. Dr. Eberhard Schnepf, Fräulein Dr. Marianne Mix und Fräulein Ingeborg Zillmann danke ich für die Einführung in die Elektronenmikroskopie, Fräulein Thummer für das Anfertigen der Positive. 相似文献
872.
Georg F. Weiller Helmut Bruckner Sang Ho Kim Elke Pratje Rudolf J. Schweyen 《Molecular & general genetics : MGG》1991,226(1-2):233-240
Summary In a random collection of mit– mutations of the yeast strain 777-3A we find that deletions are exceptionally frequent in the OXI3 gene, a large mosaic gene coding for subunit I of cytochrome oxidase. About 10% of all oxi3
– mutants carry the same macro-deletion, del-A, extending from the 5 non-translated leader of OXI3 to intron 5b of this gene. Determination of the respective wild-type sequences and of the del-A junction sequence revealed that the end-points of the deletion are in two GC clusters with 31 by sequence identity which are located at a distance of 11.3 kb. We speculate that not only the sequence identity of the two GC clusters but also the palindromic structure of these putatively mobile elements of yeast mitochondrial DNA (mtDNA) plays a role in deletion formation. 相似文献
873.
Werner Dangel Ruth Brackmann Achim Lack Magdy Mohamed Jürgen Koch Brigitte Oswald Birgit Seyfried Andreas Tschech Georg Fuchs 《Archives of microbiology》1991,155(3):256-262
The regulation of the expression of enzyme activities catalyzing initial reactions in the anoxic metabolism of various aromatic compounds was studied at the whole cell level in the denitrifying Pseudomonas strain K 172. The specific enzyme activities were determined after growth on six different aromatic substrates (phenol, 4-hydroxybenzoate, benzoate, p-cresol, phenylacetate, 4-hydroxyphenylacetate) all being proposed to be metabolized anaerobically via benzoyl-CoA. As a control cells were grown on acetate, or aerobically on benzoate. The expression of the following enzyme activities was determined.Phenol carboxylase, as studied by the isotope exchange between 14CO2 and the carboxyl group of 4-hydroxybenzoate; 4-hydroxybenzoyl-CoA reductase (dehydroxylating); p-cresol methylhydroxylase; 4-hydroxybenzyl alcohol dehydrogenase; 4-hydroxybenzaldehyde dehydrogenase; coenzymeA ligases for the aromatic acids benzoate, 4-hydroxybenzoate, phenylacetate, and 4-hydroxyphenylacetate; phenylglyoxylate: acceptor oxidoreductase and 4-hydroxyphenylglyoxylate: acceptor oxidoreductase; aromatic alcohol and aldehyde dehydrogenases.The formation of most active enzymes is strictly regulated; they were only induced when required, the basic activities being almost zero. The observed whole cell regulation pattern supports the postulate that the enzyme activities play a role in anoxic aromatic metabolism and that the compounds are degraded via the following intermediates: Phenol 4-hydroxybenzoate 4-hydroxybenzoyl-CoA benzoyl-CoA; 4-hydroxybenzoate 4-hydroxybenzoyl-CoA benzoyl-CoA; benzoate benzoyl-CoA; p-cresol 4-hydroxybenzaldehyde 4-hydroxybenzoate 4-hydroxybenzoyl-CoA benzoyl-CoA; phenylacetate phenylacetyl-CoA phenylglyoxylate benzoyl-CoA plus CO2; 4-hydroxyphenylacetate 4-hydroxyphenylacetyl-CoA 4-hydroxyphenylglyoxylate 4-hydroxybenzoyl-CoA plus CO2 benzoyl-CoA. 相似文献
874.
Anaerobic degradation of cresols by denitrifying bacteria 总被引:15,自引:0,他引:15
The initial reactions in anaerobic metablism of methylphenols (cresols) and dimethylphenols were studied with denitrifying bacteria. A newly isolated strain, possibly a Paracoccus sp., was able to grow on o-or p-cresol as sole organic substrate with a generation time of 11 h; o-or p-cresol was completely oxidized to CO2 with nitrate being reduced to N2. A denitrifying Pseudomonas-like strain oxidized m-or p-cresol as the sole organic growth substrate completely to CO2 with a generation time of 14 h. Demonstration of intermediates and/or in vitro measurement of enzyme activities suggest the following enzymatic steps:(1) p-Cresol was metabolized by both strains via benzoyl-CoA as central intermediate as follows: p-cresol 4-OH-benzaldehyde 4-OH-benzoate 4-OH-benzoly-CoA benzoyl-CoA. Oxidation of the methyl group to 4-OH-benzaldehyde was catalyzed by p-cresol methylhydroxylase. After oxidation of the aldehyde to 4-OH-benzoate, 4-OH-benzoyl-CoA is formed by 4-OH-benzoyl-CoA synthetase; subsequent reductive dehydroxylation of 4-OH-benzoyl-CoA to benzoyl-CoA is catalyzed by 4-OH-benzoyl-CoA reductase (dehydroxylating).(2) o-Cresol was metabolized in the Paracoccus-like strain via 3-CH3-benzoyl-CoA as central intermediate as follows: o-cresol 4-OH-3-CH3-benzoate 4-OH-3-CH3-benzoyl-CoA 3-CH3-benzoyl-CoA. The following enzymes were demonstrated: (a) An enzyme catalyzing an isototope exchange reaction between 14CO2 and the carboxyl of 4-OH-3-CH3-benzoate; this activity is thought to be a partial reaction catalyzed by an o-cresol carboxylase. (b) 4-OH-3-CH3-benzoyl-CoA synthetase (AMP-forming) activating the carboxylation product 4-OH-3-CH3-benzoate to its coenzyme A thioester. (c) 4-OH-3-CH3-benzoyl-CoA reductase (dehydroxylating) catalyzing the reductive dehydroxylation of the 4-hydroxyl group with reduced benzyl viologen as electron donor to yield 3-CH3-benzoyl-CoA. This thioester may also be formed by action of a coenzyme A ligase when 3-CH3-benzoate is metabolized. 2,4-Dimethylphenol was metabolized via 4-OH-3-CH3-benzoate and further to 3-CH3-benzoyl-CoA.(3) The initial reactions of anaerobic metabolism of m-cresol in the Pseudomonas-like strain were not resolved. No indication for the oxidation of the methyl group nor for the carboxylation of m-cresol was found. In contrast, 2,4-and 3,4-dimethylphenol were oxidized to 4-OH-3-CH3-and 4-OH-2-CH3-benzoate, respectively, probably initiated by p-cresol methylhydroxylase; however, these compounds were not metabolized further.The hydroxyl and methyl groups are abbreviated as OH-and CH3-, respectively 相似文献
875.
876.
Carl R. Middlehurst Georg R. Beilharz Glenn E. Hunt Philip W. Kuchel Gordon F. S. Johnson 《Journal of neurochemistry》1984,42(3):878-879
Abstract: Proton nuclear magnetic resonance (1 H NMR) spectroscopy in conjunction with the inversion-recovery spin-echo pulse sequence was used to obtain spectra from rabbit brain homogenate. The instrumental parameters required for the acquisition of spectra together with the assignment of major peaks are given. The rationale and prospectus for the use of this technique for the study of neurochemistry is outlined. 相似文献
877.
Prof. Dr. Karl Georg Götz 《Biological cybernetics》1987,56(2-3):107-109
The orientation selective neurons in the monkey striate cortex seem to be organized in pairs of mirror symmetrical hypercolumnar patches, each of which centered by a cytochrome oxidase blob. A simple scheme derived from recent data of Blasdel and Salama reconciles earlier models assuming either linear or circular representation of the preferred direction of edges in the visual field. 相似文献
878.
Stefan Hockertz Jürgen Plönzig Georg Auling 《Applied microbiology and biotechnology》1987,25(6):590-593
Summary The effect of managanese on Aspergillus niger ATCC 11414 was studied during the trophophase in a citric acid-accumulating sucrosemineral medium. The absence of manganese ions restricted growth and caused characteristic morphological aberrations. Labelling with (814-C) adenine in-vivo revealed a reversible inhibition of DNA synthesis, but not of RNA synthesis in mycelia starved of manganese. A strong inhibition of DNA synthesis in the presence of 0.2 M Mn2+ was observed upon addition of 200 mM hydroxyurea (HU) which is known as specific inhibitor of the ribonucleotide reductase.The hypothesis is proposed that inhibition of DNA formation in A. niger may be traced back to an impairment of manganese dependent ribonucleotide reduction which provides the monomeric precursors for DNA replication. 相似文献
879.
Widespread occurrence of calicin, a basic cytoskeletal protein of sperm cells, in diverse mammalian species 总被引:1,自引:0,他引:1
Jorma Paranko Frank Longo Jay Potts Georg Krohne Werner W. Franke 《Differentiation; research in biological diversity》1988,38(1):21-27
A novel cytoskeletal element consisting of dense webs of thin (3-14 nm) filaments surrounding the nucleus of the sperm head has recently been isolated and shown to be associated with certain major basic proteins. Using antibodies specific for calicin, a prominent Mr-60,000 cytoskeletal protein of the posterior calyx of bull sperm heads detected in immunoblotting on gel electrophoretically separated polypeptides as well as in immunofluorescence and immunoelectron microscopy, we show that the same--or an immunologically related--polypeptide occurs in sperm heads of other species with greatly different morphology, including human, boar, guinea pig, hamster, rat and mouse. The calicin localization in the various species is described and discussed in relation to the specific sperm morphology. 相似文献
880.
H. Carl Gerhardt Georg M. Klump 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1988,163(6):795-802
1. | We tested the long-standing hypothesis that female frogs are attracted to the sound of a chorus of conspecific males from a distance. We studied the barking treefrog (Hyla gratiosa) because the location of choruses is unpredictable; thus, chorus sound indicates the presence of conspecific males as well as the location of a suitable breeding site. |
2. | We measured the sound pressure level (SPL in dB re 20 Pa) in the 500 Hz octave band at various distances from choruses. The primary spectral peak in the advertisement call of this species is 400–500 Hz. |
3. | The pattern of chorus sound attenuation in the 500 Hz band at two different sites was very similar and generally followed the pattern expected from geometrical spreading from a point source (Fig. 3). At one of the sites the SPL measured near ground level was always higher than that at a point 1 m above the ground (Fig. 3). |
4. | Spectral analyses of the chorus sound at different distances showed that the low-frequency spectral peak in the range of 400–500 Hz was a prominent component, especially at 80–160 m (Figs. 1, 4). Amplitude peaks that corresponded to individual calls ofH. gratiosa and other species were also evident in oscillograms of recordings made at 160 m (Fig. 1). |
5. | Gravid females oriented and moved toward a source of conspecific chorus sounds (originally recorded at 160 m from the pond) played back at 38–40 dB SPL in the 500 Hz octave band (Fig. 1, Table 1). Background noise levels were 43–47 dB SPL (C-weighted) and 24–25 dB SPL in the 500 Hz octave band. |
6. | In a two-stimulus, choice experiment, females ofH. gratiosa always chose the source of a mixed chorus (H. gratiosa andH. cinerea) sound with conspecific males to a source of a pure chorus sound ofH. cinerea (Fig. 2, Table 2). |