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1.
Quantitative electron probe analysis was employed to analyse refractile granules of T. pyriformis individually and in situ. The mean ratios of , , and in granules were similar in cells grown in three different nutrient media. Supplementing the calcium content of proteose-peptone medium with 0.3 and 3 mM calcium depressed the mean ratio and increased the ratio of the granules. The mean ratio and ratio were not significantly altered. When medium M was supplemented with 0.3 mM calcium, there was no significant change in the , , nor ratios. When supplemented with 3 mM Ca, the ratio increased slightly, and the ratio decreased slightly. There was no significant change in the and ratio. When each medium was supplemented with strontium, all granules incorporated this element, probably at the expense of calcium. The ratios in granules in each strontium-containing medium were comparable to the ratio in the granules in strontium-free media, indicating that the mix of divalent ions in granules may vary, but the proportion of divalent ions to phosphorus tends to be uniform. 相似文献
2.
H T Tien 《Biochemical and biophysical research communications》1979,89(1):226-232
It is generally accepted that purple membrane of functions as a light-driven hydrogen ion pump translocating hydrogen ions from inside the cell to the external medium. However, experimental data from this laboratory together with those obtained by others have always shown an initial alkalinization of the external medium in the light. Additionally, we have found that oxygen can also induce an alkalinization of the bathing solution in the dark. These results can be readily explained if the direction of hydrogen-ion translocation is reversed, that is that both light and oxygen generate an electrochemical gradient of hydrogen ions, which is outwardly directed for ATP synthesis. 相似文献
3.
A manganese-stimulated endonuclease from Bacillus subtilis 总被引:6,自引:0,他引:6
An endonuclease activity has been identified in extracts of . This activity is stimulated by Mn++ or Ca++ ions but not by Mg++ ions. The enzyme catalyzes the breakdown of native DNA of high molecular weight to fragments of molecular weights ranging from 3 × 106 to 20 × 106. A variety of DNA's from sources such as and T7 phage are attacked. About 61% of the activity of the cells is released into the medium during protoplast formation under conditions where 98% of the glucose 6-P dehydrogenase activity is retained by the cells. 相似文献
4.
The transmembrane electropotential of microsomal vesicles from pea internode segments, monitored by equilibrium distribution of the permeant anion SCN?, is strongly hyperpolarized when ATP is present in the incubation medium.The stimulation of SCN? uptake by ATP is rather specific with respect to the other nucleoside di- and triphosphates tested: ADP, GTP, CTP and UTP. ATP-stimulated SCN? uptake is strongly inhibited by ATPase inhibitors such as and and by 2.5% toluene/ethanol (1 : 4, v/v), the latter being a treatment which makes the vesicles permeable. On the contrary, oligomycin is almost ineffective in influencing ATP-induced SCN? uptake. The proton conductor carbonyl cyanide strongly inhibits ATP-stimulated SCN? uptake. The effect of ATP on SCN? uptake depends on the pH of the medium, the maximum being reached at about pH 7.0.These data support the view that microsomal fractions from pea internodes contain membrane vesicles endowed with a membrane-bound ATPase coupling ATP hydrolysis to electrogenic transport of ions, probably H+. 相似文献
5.
K D Garlid 《Biochemical and biophysical research communications》1979,87(3):842-847
Mitochondria respiring in media containing 80 mM tetraethylammonium ions lose all of their endogenous K+ within 7 minutes. K+-loss is associated with uptake of tetraethylammonium ions. K+ efflux under these conditions is energy-dependent and electroneutral. It is concluded that tetraethylammonium uptake unmasks the endogenous exchanger. Considered in relation to the chemiosmotic theory, these results support the existence of a “carrier-brake” mechanism which modulates exchange to maintain volume homeostasis . 相似文献
6.
Induction by ouabain of hemoglobin synthesis in cultured friend erythroleukemic cells 总被引:1,自引:0,他引:1
Induction of erythroid differentiation in ouabain-resistant murine erythroleukemia cells by ouabain is reported. Ouabain induction results in the appearance of hemoglobin-containing cells 12–24 hr earlier than induction of the same clone by dimethyl sulfoxide. The levels of globin mRNA after ouabain induction are similar in amount to the globin mRNA levels observed after induction by dimethyl sulfoxide. The concentration of ouabain required to induce hemoglobin synthesis depends upon the K+ ion levels in the culture medium. Lowering the extracellular K+ ion concentration 2–4 fold reduced by 10–40 fold the ouabain concentration necessary for the induction of hemoglobin synthesis. In low K+ medium (1.8 mM), ouabain is an effective inducer of hemoglobin synthesis at a concentration of 0.02 mM. This K+ effect is specific for ouabain induction, since induction by other inducers, such as dimethyl sulfoxide and dimethyl acetamide, does not exhibit this marked sensitivity to the levels of K+ ions in the culture medium. These results suggest that the binding of ouabain to the plasma membrane enzyme, ATPase, is required for the induction of erythroid differentiation by ouabain. A small but significant proportion of wild-type, ouabain-sensitive cells also can be induced by ouabain, below ouabain concentrations that are toxic to these cells. The observation that the binding of ouabain to the ATPase induces hemoglobin synthesis suggests that changes in the intracellular concentration of K+ ions may be involved in the control of erythroid differentiation in Friend erythroleukemic cells. 相似文献
7.
R Simantov 《Life sciences》1978,23(25):2503-2508
Mouse pituitary tumor cells grown in tissue culture release endorphins spontaneously to the culture medium. Depolarization of these cells by incubation with high K+ concentration (56 mM) increased 2–3 folds the release of endorphins. The K+ evoked release was Ca++ dependent by that: , removal of Ca++ ions inhibited 90% of K+ stimulated release. , ethyleneglycol-bis (β-aminoethyl ether) N,N′-tetraacetic acid (EGTA) inhibited release of endorphins in the presence of high K+ and Ca++. It is suggested that dual regulatory system inhibit and/or stimulate release of endorphins from the pituitary glands. 相似文献
8.
P Robertson K A Koehler R G Hiskey 《Biochemical and biophysical research communications》1979,86(2):265-270
The binding of magnesium ions to two tripeptides, -Arg--Gla--Gla-OMe and Z--Arg(NO2)--Gla--Gla-OMe, and to bovine prothrombin fragment 1 as a function of pH has been monitored by 25Mg NMR spectroscopy. Binding to the tripeptide was dependent on peptide ionizations occurring at pH 4.6 – 4.8. The pH dependence of magnesium ion binding to fragment 1 reveals two inflection points 4.2 may be attributed to the deprotonation of the third side chain carboxylic acid group of the double γ-carboxyglutamic acid sequence. The origin of the increased binding of magnesium ions to fragment 1 at pH values above 7 is unknown. 相似文献
9.
Robert D. Koos Martin R. Clark Per O. Janson Kurt E.B. Ahrén William J. LeMaire 《Prostaglandins & other lipid mediators》1983,25(5):715-724
Prostaglandin (PG) levels in follicular fluid from preovulatory follicles of rabbit ovaries perfused were measured in order to compare PG changes in this model system with those that occur and in isolated, LH-treated follicles . One ovary from each rabbit was perfused without further treatment (control). The other ovary was exposed to LH (0.1 or 1 ug/ml) beginning 1 hour (h) after initiation of perfusion. Samples of perfusion medium were taken at frequent intervals for measurement of PGE, PGF, progesterone and estradiol 17β. The perfusions were terminated when the first ovulation occurred or appeared imminent as judged by changes in the size and shape of the follicles. Follicular fluid was then rapidly aspirated from all large follicles on both ovaries for PGE and PGF measurement.Ovulations occurred only in the LH-treated ovaries. Progesterone and estradiol levels were significantly elevated in the perfusion medium within 1 h of LH treatment in comparison to controls. PG levels in perfusion medium from the control and LH-treated ovaries were not different throughout perfusion and increased in both groups. In contrast, PG levels measured in follicular fluid from LH-treated ovaries were 4- to 5-fold greater than in fluid from control ovaries. It is concluded that ovulation induced by LH in this experimental model is accompanied by an increase in follicular PG levels similar to that seen in other and models. This difference in follicular PG levels between the LH-treated and control ovaries is, however, not reflected in the perfusion medium. 相似文献
10.
María M. Elías Elbio J. Comín Marta E. Grosman Susana A. Galeazzi Emilio A. Rodriguez Garay 《生物化学与生物物理学报:生物膜》1982,693(2):265-272
(1) The effects of unconjugated bilirubin on the accumulation of , kinetics of uptake, the efflux of pre-accumulated and water and electrolyte distribution were investigated in the rat kidney cortical slice. (2) The addition of unconjugated bilirubin to the incubation medium decreased the 60 min slice-to-medium concentration ratio of . (3) The decrease in accumulation by unconjugated bilirubin was found to be more pronounced by increasing the concentration of pigment in the medium. (4) The rate of uptake of as a function of concentration differed in aerobiosis and anaerobiosis, and unconjugated bilirubin decreased only the uptake of in aerobic conditions. (5) The efflux of pre-accumulated decreased when unconjugated bilirubin concentration in the medium was low (10–20 μM) but the efflux increased when the concentration of pigment was much higher (100 μM). (6) The addition of unconjugated bilirubin to the medium (40–100 μM) increased intracellular sodium and total tissue water content, and decreased intracellular potassium and oxygen consumption of tissue. However the slices incubated with low concentration of pigment (20 μM) did not exhibit significative changes in cellular functional parameters. (7) These findings suggest that unconjugated bilirubin impairs transport by a complex mechanism that might involve binding of pigment to sites necessary for anion transport, although effects related to pigment toxicity or to its oxidative decomposition are not excluded. 相似文献
11.
With the aid of direct microfluorimetric determination of marker organic anions (fluorescein and uranin) accumulated in the proximal tubules the influence of Na+ in the bath medium on the active transport of these anions was studied. Kinetic analysis of the rate dependence of organic acid active transport into tubules on their concentration in the bath medium with a constant Na+ concentration permitted to define values of apparent and for uranin and fluorescein transport in the medium with different Na+ content. It was shown that a decrease of Na+ concentration in the medium increases and lowers the ratio with uncharged . By varying the Na+ concentration in the medium with a constant concentration of the marker anion the and values for fluorescein and uranin transport were determined. A value for fluorescein in twice as much that for uranin. The value for uranin transport is a linear function of Na+ concentration, while for fluorescein transport it is a quadratic one. Therefore it is concluded that two Na+ from the medium participate in active transfer of one fluorescein anion whereas only one Na+ from the medium is required for active transfer of one uranin anion. The run out of fluorescein from tubules preloaded with this acid is sharply reinforced by the Na+ omission from the medium. Thus, active transport of organic acids in proximal tubules of frog kidney is Na+-dependent, and Na+ from the medium is likely to participate directly in formation of a transport complex. When Na+ is absent in the medium a carrier fulfils a facilitated diffusion only. 相似文献
12.
We have studied the kinetics of ionophore X-537A-mediated transport of manganese ions into small unilamellar vesicles formed from dipalmitoylphosphatidylcholine. To follow the transport we used the paramagnetic effect of manganese on the 1H-NMR signal from choline trimethylammonium groups on the inner phospholipid monolayer. The transport of only one manganese ion produces an intravesicular concentration which is high enough (approx. 1 mM) to substantially broaden this signal. The observed signal thus arises predominantly from those vesicles which contain no manganese. Therefore, as manganese is transported into the vesicles the observed signal decreases in intensity, but does not broaden. The initial time-dependence of the intensity of the signal, , can be approximated by the simple first-order rate law: , where is the probability per unit time for the transport of a manganese ion from the external medium to the intravesicular space. From the dependence of on the ionophore X-537A concentration we conclude that manganese is transported into the vesicles via both 1 : 1 and 2 : 1 complexes with ionophore X-537A. At low ratios of ionophore X-537A to vesicles transport via the 1 : 1 complex predominates; at high ratios transport via the 2 : 1 complex predominates. From the dependence of on manganese concentration we determined that under our conditions the equilibration of ionophore X-537A between vesicles is much faster than the transport of manganese through the vesicles. Lastly, from the dependence of on temperature, we conclude that the ionophore X-537A-mediated transport of manganese into the dipalmitoylphosphatidylcholine vesicles is very sensitive to the gel-liquid crystalline phase transition. 相似文献
13.
Lucio Annunziato Gianfranco Di Renzo Salvatore Amoroso Aldo Quattrone 《Life sciences》1984,35(4):399-407
Release of endogenous dopamine (DA) from arcuate-periventricular nucleus-median eminence fragments has been analyzed in an static incubation system.Exposure of these hypothalamic fragments to increasing concentrations of K+ ions produced a dose-dependent release of endogenous DA. The highest rate of K+-stimulated DA efflux occurred in the first 10 minutes, thereafter it progressively decline reaching prestimulated levels at 30 minutes. If two consecutive depolarizing stimuli of 40 mM KCl were applied to the same hypothalamic fragment, after a 40 minutes rest period, an equivalent release of endogenous DA occurred. Removal of Ca++ ions from the incubation medium containing the Ca++ chelator EGTA caused a decrease of basal DA efflux and completely prevented the K+-induced release of DA.Furthermore when verapamil, a blocker of Ca++ entrance, was added to the incubation medium in a concentration of 50 μM, the K+-induced DA efflux was completely counteracted, whereas spontaneous release was unmodified.Finally nomifensine, a potent blocker of DA uptake, added in a final concentration of 10 μM, significantly reinforced K+-induced release of endogenous DA. Since nomifensine did not modify basal DA release, this study confirmed its prevalent uptake blocking property rather than its releasing action on DA. 相似文献
14.
Juvenile hormones radiobiosynthesised by corpora allata of adult female locusts in vitro 总被引:4,自引:0,他引:4
When corpora allata from adult female are incubated with either 3H-, farnesenic acid or 3H-, , bishomo-farnesenic acid and [-14C] methionine, they fabricate large quantities of the corresponding double labelled methyl 10, 11-epoxy esters. Radio GLC of these products indicates retention of geometric configuration at the C-2 and C-6 double bonds. Separate analyses of the contents of the glands and medium after incubation show that the epoxy esters are rapidly released from the glands into the medium and that only the glands contain the corresponding unepoxidized esters. We suggest that unepoxidized esters are the intracellular intermediates in the formation of juvenile hormones from the unsaturated acids. Gel filtration shows that the epoxy esters are not released as stable protein complexes but as simple solutes into the medium. Using this method of promoting the synthesis of juvenile-hormone-active compounds, rates of biosynthesis of epoxy esters of up to 33 ng. per pair of glands per hour have been achieved. 相似文献
15.
Robert E. Lynch Barry C. Cole 《Biochemical and biophysical research communications》1980,96(1):98-105
Superoxide dismutase and catalase were not detected in . and several other species of some of which consume oxygen and secrete H2O2. . in suspension formed O2? in the presence of NADH and flavins and extracts of . formed O2? in the presence of either NADH or NADPH. The lack of superoxide dismutase in . could not be attributed to superoxide dismutase in the complex medium in which the organisms were grown because organisms grown in medium in which the superoxide dismutase had been inactivated by heat still contained undetectable amounts. Mycoplasmas appear to be an exception to the rule that organisms which consume O2 synthesize superoxide dismutase. 相似文献
16.
Two media supporting the growth of several established lepidopteran cell lines in monolayer and suspension culture are described. The medium designated was developed specifically as an inexpensive medium for production of cells of Spodoptera frugiperda and the homologous nuclear polyhedrosis virus (NPV) of this species. Simultaneously, a second medium was formulated in which the amino acid requirements were provided by enzymatic protein hydrolysates, one of which was termed . Several cell lines could be adapted easily to this medium. supported growth of S. frugiperda cells and production of the NPV's of S. frugiperda and Autographa californica. supported the growth of cells of S. frugiperda. Carpocapsa pomonella, Heliothis zea, and Trichoplusia ni. Cells of the latter produced the polyhedra of T. ni and A. californica NPV's in this medium. 相似文献
17.
Wolfgang Feller Hartmut Follmann 《Biochemical and biophysical research communications》1976,70(3):752-758
A ribonucleoside diphosphate reductase is demonstrated in the algae, and . In synchronized cultures an activity maximum at the 12th hour of the cell cycle coincides with maximum DNA production. Induction of reductase activity is prevented by cycloheximide. The enzyme requires dithiols for reduction of CDP ; it is not significantly stimulated by iron or magnesium ions nor dependent upon deoxyadenosylcobalamin. ATP stimulates the reaction but dATP or dTTP act as inhibitors. The ribonucleotide reductase of green algae differs from the B12-requiring enzyme characterized in . 相似文献
18.
Even though injected radioactive carnitine is found to accumulate in brown adipose tissue of suckling rats, no consistent specific binding to a protein in the high speed supernatant of this tissue could be demonstrated, either or . On incubation of prelabelled brown fat, 80% of the label was released into the medium within 20 minutes. 相似文献
19.
The interaction of the oligonucleotides ApA, ApApA, ApApC and ApApU with poly(U) and (Ip)5I and (Ip)6 with poly(C) has been studied by means of equilibrium gelfiltration through Sephadex.From sorption isotherms the free energies, energies and entropies of complexing have been computed for different concentrations of magnesium ions in the medium.The stoichiometric ratio of polymers to oligomers has been measured and found equal to 2 in the case of ApApA and ApApC. This shows that the cytidylic acid residue is included in the ternary complex. But in the case of ApApU the noncomplementary base is partly squeezed out of the complex.The stacking free energy of neighbouring oligomers has been found to be in the range 1000–3000 depending on the conditions.The stoichimetric ratio has been found to be 1 in the case of poly(C): oligo(I), the stacking energy is equal to 1.2 . The effect of magnesium is somewhat different in the case of double and triple helices and probably reflects the formation of coordination compounds with the nitrogen bases of nucleotides. 相似文献
20.
A method for extracting intact chloroplast and cytoplasmic ribosomal RNA from leaves 总被引:1,自引:0,他引:1
D P Bourque A Hagiladi A W Naylor 《Biochemical and biophysical research communications》1973,51(4):993-999
A method is described for extracting intact chloroplast and cytoplasmic ribosomal RNA from leaves of two higher plant species. Sodium dodecyl sulfate (1%) and 25 mM magnesium ions are required to inhibit ribonuclease action during RNA purification by phenol deproteinization. The ethanol-precipitated RNA product, including 23s chloroplast ribosomal RNA, is completely stable during electrophoresis in the absence of magnesium ions, even in the presence of EDTA. The mole fraction of chloroplast ribosomes relative to cytoplasmic ribosomes is estimated. Bentonite is shown to cause preferential losses of chloroplast RNA during extraction. 相似文献