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1.
Inge N. Bojesen 《Prostaglandins & other lipid mediators》1985,30(3):479-489
The glycerolipid production by rat renal papillary slices varied inversely with the urea concentration (0a–1660 mM) whether the production was measured as labelling of the glycerol backbone from glucose or as incorporation of labelled arachidonic acid and palmitic acid. The rate of phospholipid formation was most dependent on medium urea concentrations in the range between 0 and 1100 mM. The production of prostaglandins PGE2 and PGF2α, measured radioimmunologically or by an isotope derivative method was in the same range inversely related to the production of glycerolipids and chain elongations. The effect of urea on prostaglandin formation is probably indirectly caused by the inhibition of the phospholipid formation and chain elongation, since the effect was abolished by 1% defatted albumin in the medium. The data suggest that the level of free arachidonic acid within the cells is controlled to an important extent by glycerolipid formation and chain elongation. 相似文献
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Bicarbonate/chloride antiport in Vero cells: I. Evidence for both sodium-linked and sodium-independent exchange 总被引:2,自引:0,他引:2
Tor Inge Tnnessen Jannikke Ludt Kirsten Sandvig Sjur Olsnes 《Journal of cellular physiology》1987,132(2):183-191
The effect of bicarbonate on the ability of cells to regulate the internal pH after acid and alkali loads was studied. In the presence of Na+, the normalization of the internal pH after acid loads occurred more rapidly in the presence than in the absence of bicarbonate. DIDS (4,4'-diisothiocyano-2,2'-stilbene-disulfonic acid) strongly inhibited the pH increase, whereas amiloride inhibited it to a lesser extent. The Na+-linked, bicarbonate-dependent pHi increase after an acid load was strongly reduced in cells depleted of Cl-. When cells were transferred to gluconate or mannitol balanced buffers containing bicarbonate, there was a rapid alkalinization of the cytosol, apparently due to influx of bicarbonate induced by chloride efflux. When the internal pH was below 7.0, the pH increase was much more rapid in the presence than in the absence of Na+, whereas at higher internal pH, there was no measurable effect of Na+. The ability of the cells to reduce the internal pH after an alkali load was increased in the presence of bicarbonate. The data indicate that both Na+-linked and Na+-independent bicarbonate/chloride exchange occur in Vero cells. 相似文献
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Light and electron microscopical immunocytochemistry of 5'-nucleotidase in rat cerebellum 总被引:3,自引:0,他引:3
5'-Nucleotidase in nervous tissue has so far not been localised at the ultrastructural level using immunocytochemical techniques. We have now applied monoclonal antibodies and a polyclonal antiserum raised against this ecto-enzyme and describe the distribution of 5'-nucleotidase antigenicity in rat cerebellum both at the light and electron microscopic levels. Within all cerebellar layers, 5'-nucleotidase immunoreactivity was found on plasma membranes of glial elements, i.e. Bergmann glial cell processes crossing the molecular layer, astrocytic end-feet around blood vessels and glial cell extensions surrounding single Purkinje cells. In the granular layer, 5'-nucleotidase immunoreactivity was present on glial membranes interposed between granule cells. Neuronal cells or processes were devoid of immunoreactivity. The immunocytochemical results were compared with conventional 5'-nucleotidase histochemistry. Both techniques showed the same ecto-localisation of the enzyme and favour the view of 5'-nucleotidase being predominantly situated at glial plasma membranes. 相似文献
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Summary Palmitate binding to human erythrocyte ghost membranes has been investigated with ghost preparations suspended in 0.2% albumin solutions. Free unbound palmitate in the extracellular water phase was measured in equilibrium studies using albumin-filled acid loaded ghosts as small semipermeable bags. The apparent dissociation constant of binding to the membrane is 13.5 nM and the binding capacity 19 nmoles per 7.2 × 109 cells.The 0°C exchange efflux kinetics of palmitate from albumin-filled ghosts is described by a model, which provides estimates of the rate constant of membrane transfer, k3 = 0.024 s–1, independent of the molar ratio of palmitate to albumin () and of a mean dissociation rate constant of the palmitate-albumin complex, k1 = 0.0015 s–1 at 0.2, allowing for a heterogeneity of the palmitate binding to albumin.The values of a third kinetically determined dependent model constant, Q, the ratio of palmitate bound to the membrane inner surface to palmitate on intracellular albumin, are not different from the Q values obtained by equilibrium experiments.The temperature dependences of k1 and k3 in the interval 0°C to 15°C give activation energies of 96 and 103 kJ/mole, respectively. The 0°C exchange efflux increases about 2 fold in response to a rise of pH from 6 to 9. The results suggest a carrier mediated palmitate flux at low with a Vmax about 2 pmoles min–1 cm–2 at 0°C pH 7.3. 相似文献
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Zusammenfassung Bei Erstbelichtung des Senfkeimlings mit Dauer-Dunkelrot tritt der P730-abhängige Anstieg der Phenylalanindesaminase-Aktivität erst mit einer lag-Phase von 1,5 Std ein (Abb. 3, 4 unten). Bei einer Zweitbelichtung (Programm: Erstbelichtung — längere Dunkelperiode — Zweitbelichtung) fehlt die lag-Phase (Abb. 4, oben). Die Enzymaktivität steigt sofort linear an. Da der Anstieg der Enzymaktivität wahrscheinlich auf eine de novo Synthese von RNS und Enzymprotein zurückzuführen ist (Tabelle), so erscheint der Schluß berechtigt, daß P730 sehr rasch eine differentielle Genaktivierung mit anschließender Enzymsynthese bewirken kann, falls die Gene der Aktivierung durch P730 zugänglich sind. Die relativ lange lag-Phase nach Einsetzen der Erstbelichtung benötigt das P730 offenbar dazu, die potentiell aktiven Gene (P730) für das P730 zugänglich zu machen. Das Problem der primären lag-Phase ist in einer vorangegangenen Arbeit zur P730-abhängigen Anthocyansynthese ausführlich diskutiert worden (vgl. Lange, Bienger und Mohr, 1967).
Phytochrome-mediated enzyme formation (Phenylalanine deaminase) as a rapid process
Summary In previous papers we have reported (Mohr and Durst, 1966a, b) that synthesis of phenylalanine deaminase (EC 4.3.1.5), an important enzyme of phenolic metabolism, can be stimulated by the physiologically active phytochrome (=P730) in the mustard seedling. The data of the present paper suggest that induction of this enzyme is a rapid process if the gene in question is easily accessible for the activating action of P730.The seedlings were irradiated with continuous standard far-red light. Longtime irradiation with far-red will maintain a low but virtually constant level of P730 in the seedling over an extended period of time. At the moment when the far-red light is turned off the action of P730 will virtually cease. — Fig. 3 and Fig. 4, lower part, show the kinetics of enzyme induction by P730 in an etiolated seedling. The initial (or primary) lag-phase after the onset of far-red is 1.5 hours. If, however, a seedling which has been pre-irradiated with 12 hours of far-red is kept in darkness for 6 hours and is then re-irradiated with far-red no lag-phase for the action of the second irradiation can be found. Enzyme activity increases immediately after the onset of far-red. Since the action of the second irradiation as measured by increase of enzyme activity can be inhibited by relatively low doses of Puromycin and Cycloheximide (table) we conclude that the re-appearance of P730 leads to de novo synthesis of enzyme protein. — Application of Actinomycin D (10 g/ml) only partially inhibits the action of the second irradiation as measured by increase of enzyme activity. This finding was to be expected. In preceding papers (e.g. Mohr and Bienger, 1967) it has been concluded that genes which have once been activated by P730 remain less sensitive towards Actinomycin D even when P730 has disappeared. Taking into account all available data the conclusion seems to be justified that the induction of enzyme synthesis by P730 (i.e. differential gene activation followed by enzyme synthesis) is a rapid process if the genes are accessible for the action of P730. The relatively long initial lag-phase (1.5 hours) is needed to make the potentially active genes (P730) accessible for the action of P730. The problem of how the initial lag-phase can be understood has been dealt with more in detail in a previous paper on phytochrome-mediated anthocyanin synthesis (Lange, Bienger and Mohr, 1967).相似文献
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Zusammenfassung
Pinguicula lusitanica wurde in vitro auf stickstoff- und phorphorfreiem Mineralsalzagar kultiviert; jede Pflanze stand für sich in einem Erlenmeyerkolben.Als die Pflanzen 8 Wochen alt waren, wurden 20 Exemplare innerhalb von 5 Wochen viermal mit Pinuspollen gefüttet. 20 gleichgroße und gleichalte dienten als Kontrollen.Durch die Fütterung steigerte sich die Blattzahl und der Durchmesser der Blattrosette, die Blätter wurden intensiver grün und alterten langsamer.Vor allem wurde durch die Pollenfütterung die Blütenbildung ausgelöst. Schon nach der 2. Fütterung traten die ersten Knospen auf, eine Woche darauf blühten bereits 70% und noch vor der letzten Fütterung alle gefütterten Pflanzen, von den ungefütterten dagegen keine einzige. In dem anschließenden halben Jahr entwickelten die 20 gefütterten Pflanzen im ganzen 127 Blüten; die größte Blütenzahl einer Einzelpflanze was 14. Die nichtgefütterten Pflanzen waren auch jetzt noch rein vegetativ.
Mit Unterstützung durch die Deutsche Forschungsgemeinschaft 相似文献
Flowering of in vitro cultures of Pinguicula lusitanica after feeding with pinus pollen
Summary Plants of Pinguicula lusitanica were grown in individual Erlenmeyer flasks on an inorganic agar medium containing no nitrogen or phosphorus. After 8 weeks of culture, twenty of the plants were fed Pinus pollen 4 times over a period of 5 weeks.As a result of the feeding, the number of leaves as well as the diameters of the rosettes were increased. The leaves became turned a deeper green and aged more slowly.The most spectacular effect of the pollen feeding was an initiation of flowering. The first buds were already visible after the second feeding. All of the treated plants flowered before the last feeding, whereas none of the untreated plants flowered. During the following 6 months, the treated plants developed 127 flowers, the largest number on a single specimen being 14. Even after this period of time the untreated plants remained vegetative.
Mit Unterstützung durch die Deutsche Forschungsgemeinschaft 相似文献