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1.
Properties of the Sodium Extrusion Mechanism Controlled by Nerve Growth Factor in Chick Embryo Dorsal Root Ganglionic Cells 总被引:3,自引:3,他引:0
Abstract: Cell dissociates from embryonic chick dorsal root ganglia, incubated for 6 h with 22 Na+ , accumulated four to six times more radioactivity in the absence than in the presence of Nerve Growth Factor (NGF). The accumulation of radioactivity paralleled the external Na+ concentration, indicating that the cells may have been reaching equilibrium with the medium. Delayed presentation of NGF to 22 Na+ -loaded cells caused a rapid loss of radioactivity, even with extracellular 22 Na+ still present, demonstrating that NGF caused an overall efflux of Na+ rather than an accelerated equilibration. The Na+ exclusion from 22 Na+ -loaded cells was dependent upon NGF concentration. Use of nutrient-rich medium, serum, and certain hormones and other proteins did not prevent the Na+ accumulation in the absence of NGF or its reversion by delayed NGF administration. Incubation of the ganglionic cells with ouabain or dinitrophenol during the 22 Na+ loading period (no NGF) increased the rate, but not the magnitude, of loading. The same incubation carried out in a Na+-free medium and followed by 22 Na+ presentation resulted in fast radioactive loading that was identical to that occurring in drug-free, NGF-deprived cells and was not prevented by presentation of NGF together with the 22 Na+ . These data are consistent with a model in which NGF acts through a Na+ pump rather than by restricting Na+ influxes. 相似文献
2.
Abstract. Mass spectrometry has been used to measure the rates of CO2 uptake of acid- and alkali-grown cells of the green algae Chlorella ellipsoidea (UTEX 20) and C. saccharophila (UTEX 27). The time course of CO2 formation on addition of 100mmol m−3 K2 CO3 to cells in the dark was used as an assay for external carbonic anhydrase (CA). No external CA was detected in acid-grown cells of either species or in alkali-grown cells of C. ellipsoidea but was present in alkali-grown C. saccharophila . In the absence of external CA, or when it was inhibited by 5mmol m−3 acetazolamide, cells of both species, on illumination, rapidly depleted the free CO2 in the medium at pH 7.5 to near zero concentrations before maximum photosynthetic O2 evolution rates were established. Addition of bovine CA rapidly restored the equilibrium CO2 concentration in the medium, indicating that the cells were selectively taking up CO2 . Transfer of cells to the dark caused a rapid increase in the CO2 concentration in the medium largely due to the efflux of inorganic carbon from the cells as CO2 . This rapid light-dependent CO2 uptake takes place against pH and concentration gradients and, thus, has the characteristics of active transport. 相似文献
3.
MASAHISA NAKAMURA IKUO YASUMASU SHOICHI OKINAGA KIYOSHI ARAI 《Development, growth & differentiation》1982,24(3):265-272
Rotenone-sensitive 14 CO2 formation from [14 C]lactate and oxygen consumption by round spermatids were found to be greater at elevated temperatures than at 34°C. More than 96% of the total radioactivity of the metabolized [14 C]lactate was recovered in the released CO2 and the acid soluble fraction of the cells. There was practically no incorporation of [14 C]latctate into the lipid, nucleic acid, and protein fractions. Intracellular level of ATP in spermatids was enhanced in the presence of lactate (20 mM) at 34°C (scrotal temperature), whereas it was decrease at 37°C (body temperature). However, this was reversible when the cells were transferred from the elevated temperature to 34°C. It was also found that oxygen consumption and CO2 production were increased at 34°C by 2, 4-dinitrophenol (DNP), but decreased by oligomycin. On the other hand, oligomycin and DNP had no effect on oxygen consumption and 14 CO2 formation at the elevated temperature.
These findings provide evidence that lactate utilization by spermatids is coupled with oxidative phosphorylation at scrotal temperature, but becomes uncoupled at elevated temperature, although more lactate is consumed. 相似文献
These findings provide evidence that lactate utilization by spermatids is coupled with oxidative phosphorylation at scrotal temperature, but becomes uncoupled at elevated temperature, although more lactate is consumed. 相似文献
4.
Abstract The kinetic parameters of NH+ 4 -uptake in yeast cells were determined by a method that is based on the following changes in the external NH+ 4 concentration in cell suspensions by using NADH-dependent glutamate formation from NH+ 4 and 2-oxoglutarate. The kinetics of the observed NADH oxidation were analyzed by computer and enabled an estimation of V max and K m of the NH+ 4 -uptake system of the cells. 相似文献
5.
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
6.
Newly extruded cod eggs have a similar osmoconcentration ( c. 400 mosmol kg-1 ) to maternal blood, maternal ovarian fluid and paternal semen. After extrusion, average egg osmolarities rise rapidly to about 520 mosmol kg-1 but this is entirely due to the cortical reaction resulting in the formation of a perivitelline space filled with fluid isosmotic with the external medium. The ovoplasm remains at around 400 mosmol throughout development; free swimming cod larvae also possess body fluids of this concentration. Over the salinity range 10.2-37.4%0 , salinity had no effect on egg dimensions and average egg osmolarities were consistent with a model assuming changes in perivitellic fluid concentration only. 相似文献
7.
After stimulation in a hypotonic solution (9.4 mOsm kg−1 ), inseminated eggs of the chum salmon Oncorhynchus keta initiate cleavages in isotonic salmon Ringer's solution (267.3 mOsm kg−1 ) containing 3.2 mM Ca2+ ions. Blastomeres of these eggs, however, separate from each other and the enveloping layer is not observed at the blastula stage. An increase in external divalent cations rescues the separation; the concentration of CaCl2 in the external medium should be 25 mM or more to induce close contact of blastomeres and the formation of an enveloping layer in isotonic salt solutions. The effectiveness of Ca2+ ions can be substituted by Mg2+ , Sr2+ and Zn2+ ions; the same results are obtained in isotonic MgCl2 and SrCl2 solutions (100 mM) or in isotonic salmon Ringer's solution containing Zn ions (6.2 mM). The close contact of blastomeres and the formation of an enveloping layer are also observed in a low Ca2+ concentration (< 0.1 mM) in a hypotonic salt solution (9.4 mOsm kg−1 ). The Ca2+ level in the external medium to induce the enveloping layer formation seems to be correlated with the salinity of the incubation medium. It is suggested that adhesion molecules on the surface of blastomeres in the chum salmon eggs are different in properties from those found in sea urchin and other fish species. 相似文献
8.
Ion accumulation in the cell walls of rice plants growing under saline conditions: evidence for the Oertli hypothesis 总被引:10,自引:3,他引:7
Abstract. When plants of rice ( Oryza saliva L.) are subjected to mildly saline (50mol m−3 NaCl) conditions, the leaves show symptoms of water deficit, even though ion accumulation has been more than sufficient to adjust to the decrease in external water potential. After a few days of exposure to salt, there is a negative correlation, in a population of leaves, between the leaf water concentration (g water per g dry weight) and their sodium concentration (mmol Na per g dry weight). Ion concentrations in the cell walls and the cytoplasm of cells of plants grown in low salinity were measured by X-ray microanalysis. The NaCl concentration in solution in the apoplast was calculated to be around 600mol m−3 in leaves of plants whose roots were exposed to only 50 mol m−3 NaCl. This constitutes strong evidence that an important factor in salt damage in rice is dehydration due to the extracellular accumulation of salt as suggested in the Oertli hypothesis. The implication, that changes in tissue ion concentration and solute potentials equivalent to the external medium is not evidence of plant osmotic adjustment to salinity, is discussed. 相似文献
9.
Abstract— The influx and efflux of 45 Ca has been studied in cultured human glioma and mouse neuroblastoma cells and in isolated fractions enriched in synaptosomes, neuronal and astrocytic perikarya from rabbit brain.
The uptake of45 Ca was somewhat more efficient in glioma compared to neuroblastoma cells, whereas there was little difference in the rate of 45 Ca uptake by isolated glial cells and neuronal perikarya. Isolated synaptosomes showed the highest rate of 45 Ca accumulation. An increase of K concentration to 50 m m in the medium, with a corresponding lowering of Na, stimulated both glioma and glial as well as synaptosomal 45 Ca uptake more markedly than the uptake by neuroblastoma cells and neuronal perikarya. Lowering the Na concentration and replacing it by choline had no effect on the cultured cells and astrocytes. Na-free media caused massive stimulation of 45 Ca influx in all fractions and cells tested.
The efflux of45 Ca was studied after preloading of cells. Three phases could be resolved from the desaturation curves. All cells had nearly similar half-lives for 45 Ca efflux under standard conditions. Pulses of media containing 50 m m -K stimulated 45 Ca efflux from glioma cells and astrocytes more efficiently than from neuroblastoma cells, neuronal perikarya and synaptosomes. The stimulated release was exclusively seen in Ca-containing media in experiments with the cultured cells and in Ca-free media in experiments with cell perikarya. The effect of transmitter pulses on the release of 45 Ca was examined in a limited series. Acetylcholine and isoproterenol were found to stimulate 45 Ca release more actively from glia than from neurons. 相似文献
The uptake of
The efflux of
10.
Abstract The endogenous ATPase activity of rat brain mitochondria was stimulated 30-50 per cent by 15-50 m m concentrations of NaCl or Na acetate. The Na stimulation was completely abolished by small amounts of oligomycin but unaffected by ouabain. The differential effects of these inhibitors indicated that the Na-induced ATPase activity did not result from microsomal or synaptosomal contamination of mitochrondria. Sodium salts decreased the stimulatory effects of DNP, gramicidin, or Ca, but not that of Mg on the endogenous ATPase activity. These interactions were specific for Na+ as the corresponding salts of K+ did not affect the endogenous ATPase or inhibit the DNP-stimulated ATPase activity except at high concentrations. The Na-induced increases in ATPase activity and respiration were more sensitive to aging of the mitochondria than were ADP/O and respiratory control ratios, or the DNP-induced ATPase activity. These results suggest that Na+ may interact in brain mitochondria with the same high-energy intermediate of oxidative phosphorylation proposed for DNP and Ca. 相似文献
11.
Nickel and rubidium uptake by oat plants ( Avena sativa L. cv. Victory) were examined in relation to solution temperature, solution concentrations, metabolic inhibitors, anaerobic root conditions, transpiration and time. Over a 4-h period, uptake rates for both Ni2+ and Rb+ remained constant at 23°C. Decreasing temperatures to 2°C, 20 μ M concentrations of 2,4-dinitrophenol (DNP), or anaerobic root conditions decreased Ni2+ and Rb+ uptake rates by 97 to 86% in whole plants. Treatment of excised roots with 20 μ M DNP decreased Ni2+ uptake by 93%. Nickel and Rb+ uptake rates measured as a function of the external solution concentration followed a typical parabolic curve. Km (0.012 m M ) and Vmax [2.72 μmol (g dry weight)-1 h-1 ] values for Ni2+ were nearly 7 times lower than those for Rb+ [0.09 m M and 19.2 μmol (g dry weight)-1 h-1 ]. In all experiments, Ni2+ and Rb+ showed qualitatively similar uptake patterns, but Rb+ uptake was quantitatively more sensitive than Ni2+ to experimental manipulations. 相似文献
12.
Effect of high external NaCl concentrations on ion transport within the shoot of Lupinus albus. I. Ions in xylem sap 总被引:1,自引:1,他引:0
RANA MUNNS 《Plant, cell & environment》1988,11(4):283-289
Abstract. Xylem sap was collected from individual leaves of intact transpiring lupin plants exposed to increasing concentrations of NaCl by applying pneumatic pressure to the roots. Concentrations of Na+ and Cl− in the xylem sap increased linearly with increases in the external NaCl concentration, averaging about 10% of the external concentration. Concentrations of K+ and NO3 − , the other major inorganic ions in the sap, were constant at about 2.5 and 1.5 mol m−3 , respectively. There was no preferential direction of Na + or Cl− to either young or old leaves: leaves of all ages received xylem sap having similar concentrations of Na+ and Cl− , and transpiration rates (per unit leaf area) were also similar for all leaves. Plants exposed to 120–160 mol m−3 NaCl rapidly developed injury of oldest leaves; when this occurred, the Na+ concentration in the leaflet midrib sap had increased to about 40 mol m−3 and the total solute concentration to 130 osmol m−3 . This suggests that uptake of salts from the transpiration stream had fallen behind the rate of delivery to the leaf and that salts were building up in the apoplast. 相似文献
13.
Abstract The heterobasidiomycetous yeast Rhodosporidium sphaerocarpum isolated from the Antarctic Ocean and a saltpan, showed marked tolerance to high concentrations of NaCl in the growth medium. This yeast accumulated glycerol as a major osmoregulator, as well as Na+ and Cl− , in response to changes in the concentration of NaCl in the external medium. The low levels of another cellular polyol, xylitol, did not respond to changes in the external medium. 相似文献
14.
Relation of source and sink during grain filling period in wheat and some aspects of its regulation 总被引:1,自引:0,他引:1
H. Herzog 《Physiologia plantarum》1982,56(2):155-160
The effect of Mg2+ , Na+ , K+ , ouabain and pH on ATPase activity of purified membrane fractions enriched in plasmalemma fragments from Hordeum vulgare L. (glycophyte) and Halocnemum strobilaceum L. (halophyte) was studied. Membrane ATPases from both plants were synergistically activated by K+ and Na+ in the presence of Mg2+ . The maximum activity of the enzymes were observed at the ratio Na/K = 2–3. Ouabain (10-4 M) almost completely eliminated the (Na+ + K+ )-stimulated component of the ATPase activity. The Na, K, Mg-ATPase of Hordeum had a single pH optimum (pH 8), but that of the Halocnemum had two optima(pH 6 and 8). It appears that similar enzymes operate in the cells of both plants studied. The higher Na, K, Mg-ATPase activity of the halophyte compared to that of the glycophyte suggests the involvement of the enzyme in the extrusion of Na+ from the cytoplasm of cells of both plants. 相似文献
15.
Indispensability of Iron for the Growth of Cultured Chick Cells 总被引:1,自引:0,他引:1
KOJI SAITO YASUKO HAGIWARA TAKAYUKI HASEGAWA EIJIRO OZAWA 《Development, growth & differentiation》1982,24(6):571-580
In order to clarify the role of iron in the growth promoting effect of transferrin (Tf), the effects of the following substances were examined in cultured chick skeletal myogenic cells: transition metal ions (Fe2+ , Fe3+ , Cr3+ , Cu2+ , Mn2+ , Co2+ , Cd2+ , Zn2+ and Ni2+ ), Tf complexes with these metals and metal-free apoTf.
The cells did not grow well when incubated in a culture medium composed of Eagle's minimum essential medium and horse serum. But they grew well in the presence of Fe2+ or Fe3+ (10–100 μM) or iron-bound Tf (10–500 nM) in the medium. None of the transition metal ions other than iron was effective. Neither apoTf nor Tf complexes with these metals showed the growth promoting effect. The generality of the requirement of iron for cell growth was ascertained in the primary culture of other types of chick embryonic cells: fibroblasts, cardiac myocytes, retinal pigment cells and spinal nerve cells.
The results show that iron is one of the indispensable substances for cell growth and suggest that Tf protein plays a role in facilitating the transport of iron into the cells. 相似文献
The cells did not grow well when incubated in a culture medium composed of Eagle's minimum essential medium and horse serum. But they grew well in the presence of Fe
The results show that iron is one of the indispensable substances for cell growth and suggest that Tf protein plays a role in facilitating the transport of iron into the cells. 相似文献
16.
Abstract Transport of Mn2+ was repressed in Candida utilis cells grown in continuous culture in high-Mn2+ (100 μM Mn2+ ) medium as compared to cells grown in basic (0.45 μM Mn2+ ) and low-Mn2+ (< 0.05 μM Mn2+ ) media. In contrast, no repression of Cu2+ uptake occurred in high-Cu2+ -grown (25 μM Cu2+ ) cells as compared to cells grown in basic medium (0.54 μM Cu2+ ). Cu2+ -limited cells did not hyperaccumulate Cu2+ and there was not significant difference in initial uptake rates for all 3 Cu2+ conditions. Mn2+ uptake appears to be regulated by a mechanism sensitive to the external Mn2+ concentration, whereas Cu2+ transport is not governed in this way by the external Cu2+ . 相似文献
17.
KIYOTA GOSHIMA HACHIRO YAMANAKA GORO EGUCHI SHIGEO YOSHINO 《Development, growth & differentiation》1978,20(2):191-204
Increase in the extracellular Ca2+ concentration from low (≤ 10−7 M) to normal (10−3 M) caused morphological changes of cultured myocardial cells obtained from fetal mouse heart. The extracellular Na+ and K+ concentrations of the normal medium (10−3 M Ca2+ ) did not significantly affect the genesis of these morphological changes. Like Ca2+ , Ba2+ and Sr2+ , but not Mg2+ , Co2+ or Ni2+ , could induce morphological changes. Increase in the extracellular Ca2+ concentration from 10−8 M to 10−3 M also caused excess uptake of 45 Ca2+ by cultured myocardial cells. B–16CW 1 cells, which did not show these morphological changes, did not take up excess 45 Ca2+ on this treatment. Treatments, such as addition of verapamil or incubation at pH 6.3, which reduced the genesis of morphological changes, reduced the rate of 45 Ca2+ uptake by myocardial cells. These facts show that the morphological changes of myocardial cells induced by increasing the extracellular Ca2+ concentration from low to normal are due to excess uptake of Ca2+ by the myocardial cells.
The morphological changes of cultured myocardial cells induced by increasing the extracellular Ca2+ concentration from low to normal were reversed on further incubation of the cells in medium with or without Ca2+ . 相似文献
The morphological changes of cultured myocardial cells induced by increasing the extracellular Ca
18.
Jeffrey A. Jankowski Jennifer M. Finnegan R. Mark Wightman 《Journal of neurochemistry》1994,63(5):1739-1747
Abstract: The temporal resolution of carbon-fiber microelectrodes has been exploited to examine the plasticity of quantal secretory events at individual adrenal medullary cells. The size of individual quantal events, monitored by amperometric oxidation of released catecholamines, was found to be dependent on the extracellular ionic composition, the secretagogue, and the order of depolarization delivery. Release was observed with either exposure to 60 m M K+ in the presence of Ca2+ or exposure to 3 m M Ba2+ in solutions of different pH, with and without external Ca2+ . Ba2+ was demonstrated to induce Ca2+ -independent exocytotic release for an extended period of time (>4 min) relative to release induced by K+ (∼30 s), which is Ca2+ dependent. In all cases, simultaneous changes of intracellular divalent cations, monitored by fura-2 fluorescence, accompanied quantal release and had a similar time course. Exocytosis caused by Ba2+ in Ca2+ -free medium had a larger mean spike area at pH 8.2 than at pH 7.4. When Ba2+ -induced spikes measured at pH 7.4 were compared, the spikes in Ca2+ -free medium were found to be broader and shorter but had the same area. Release induced by K+ after exposure to Ba2+ was comprised of larger quantal events when compared with preceding K+ stimulations. Finally, spikes obtained with Ba2+ exposure at an extracellular pH of 5.5 had a different shape than those obtained in more basic solutions. These changes in spike size and shape are consistent with the interactions between catecholamines and other intravesicular components. 相似文献
19.
Ionic Composition of Cisternal CSF in Acute Respiratory Acidosis: Lack of Effect of Large Dose Bumetanide 总被引:1,自引:0,他引:1
Abstract: Sodium/chloride cotransport carrier is known to be involved in transepithelial fluid absorption and secretion in various tissues. Recent studies indicate that Na,K,2CI cotransport carrier also exists in the choroid plexus cells and inhibition of the carrier alters ionic composition of the choroidal tissue. In this study, we report the effects of large dose intravenous bumetanide, a potent inhibitor of Na,K,2CI carrier, on cisternal CSF ionic composition in acute respiratory acidosis in pentobarbital-anesthetized mechanically ventilated dogs. Renal pedicles were ligated to prevent bumetanide-induced diuresis. The experirnental group (Group II, n = 7) received 50 mg/kg of bumetanide intravenously and Group I (the control group, n = 7) received the vehicle. Analysis of serum and choroidal plexus tissue revealed bumetanide concentration of ∼10− -5 mol/L in Group II. During 5 h of acute respiratory acidosis in both groups, the mean Paco2 increased ∼25 mm Hg, with comparable changes in CSF Pco2 . In both groups, CSF [HCO3 − ] and [H+ ] increased ∼3 mEq/L and 20 nEq/L, respectively. Furthermore, changes in CSF [Na+ ], [K+ ], [Ca2+ ], [Mg2+ ], [CI− ], and [Na+ -CI− ] were also similar and were not significantly different from each other. These data show that bumetanide, at the dose that inhibits NaCl cotransport carrier, does not significantly affect ionic composition of cisternal CSF. 相似文献
20.
Metabolism of hydrogen peroxide by the scavenging system in Chlamydomonas reinhardtii 总被引:1,自引:0,他引:1
The metabolism of hydrogen peroxide by the scavenging system was studied in Chlamydomonas grown in a selenium-lacking and a selenium-containing medium. In cells of the former, 40% of external hydrogen peroxide (H2 O2 ) was scavenged by ascorbate peroxidase (AsAP; EC 1.11.1.11) and the residual H2 O2 by catalase (EC 1.11.1.6). The enzymes involved in the ascorbate-glutathione cycle including AsAP. were localized in the chloroplast. In cells of the latter, glutathione peroxidase (GSHP; EC 1.11.1.9) functioned primarily in the removal of external H2 O2 . GSHP was located solely in the cytosol. The Chlamydomonas AsAP was relatively stable in ascorbate-depleted medium as compared with chloroplast AsAP of higher plants. No inactivation of the enzyme was found upon its incubation with hydroxyurea, an inhibitor of the chloroplast enzyme of higher plants. The enzyme showed higher specificity with pyrogallol than with ascorbate. The amino acid sequences in the N-terminal region of Chlamvdomonas AsAP showed no significant similarity to any other AsAP from higher plants and Euglena . The enzyme had a molecular mass of 34 kDa. The Km values of the enzyme for ascorbate and H2 O2 were 5.2±0.3 and 25±3.4 μ M , respectively. Hydrogen peroxide was generated at a rate of 6.1±0.8 μmol mg-1 chlorophyll h-1 in intact chloroplasts isolated from Chlamydomonas cells grown in the presence of Na-selenite, and it diffused from the organelles into the medium. 相似文献