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1.
Zinc is essential for normal growth, development and brain function although little is known about brain zinc homeostasis. Therefore, in this investigation we have studied65Zn uptake from blood into brain and other tissues and have measured the blood-brain barrier permeability to65Zn in the anaesthetized rat in vivo. Adult male Wistar within the weight range 500–600 g were used.65ZnCl2 and [125I]albumin, the latter serving as a vascular marker, were injected in a bolus of normal saline I.V. Sequential arterial blood samples were taken during experiments that lasted between 5 min and 5 hr. At termination, samples from the liver, spleen, pancreas, lung, heart, muscle, kidney, bone, testis, ileum, blood cells, csf, and whole brain were taken and analysed for radio-isotope activity. Data have been analysed by Graphical Analysis which suggests65Zn uptake from blood by all tissues sampled was unidirectional during this experimental period except brain, where at circulation times<30 min,65Zn fluxes were bidirectional. In addition to the blood space, the brain appears to contain a rapidly exchanging compartment(s) for65Zn of about 4 ml/100g which is not csf. 相似文献
2.
Summary The effects of short- and long-term exposure to a range in concentration of sea salts on the kinetics of NH
inf4
sup+
uptake by Spartina alterniflora were examined in a laboratory culture experiment. Long-term exposure to increasing salinity up to 50 g/L resulted in a progressive increase in the apparent Km but did not significantly affect Vmax (mean Vmax=4.23±1.97 mole·g–1·h–1). The apparent Km increased in a nonlinear fashion from a mean of 2.66±1.10 mole/L at a salinity of 5 g/L to a mean of 17.56±4.10 mole/L at a salinity of 50 g/L. These results suggest that the long-term effect of exposure to total salt concentrations within the range 5–50 g/L was a competitive inhibition of NH
inf4
sup+
uptake in S. alterniflora. No significant NH
inf4
sup+
uptake was observed in S. alterniflora exposed to 65 g/L sea salts. Short-term exposure to rapid changes in salinity significantly affected both Vmax and Km. Reduction of solution salinity from 35 to 5 g/L did not change Vmax but reduced Km by 71%. However, exposing plants grown at 5 g/L salinity to 35 resulted in an decrease in Vmax of approximately 50%. Exposure of plants grown at 35 g/L to a total sea salt concentration of 50 g/L for 48h completely inhibited uptake of NH
inf4
sup+
. For both experiments, increasing salinity led to an increase in the apparent Km similar to that found in response to long-term exposure. Our data are consistent with a conceptual model of changes in the productivity of S. alterniflora in the salt marsh as a function of environmental modification of NH
inf4
sup+
uptake kinetics. 相似文献
3.
In isolated synaptosomes from rat brain, 100 M antimycin A and 10 M oxamic acid inhibit the32Pi-labeling of phosphatidylinositol-4,5-bisphosphate (PIP2) and phosphatidylinositol-4-phosphate (PIP) by 90% and 95–99% respectively. 10 mM sodium fluoride inhibits the labeling by 50–60% and 10 mM A23187 inhibits the labeling by 63–70%. Phospholipase A2 inhibits the labeling of PIP2 and PIP by 93–94% and stimulates their degradation by 84–92%. Depolarization of synaptosomes with 75 mM K+ or 100 M veratrine decreases the labeling of PIP2 and PIP by 66–74%. The decreased labeling results in large part from the Ca2+-dependent degradation of32P-labeled PIP2 and PIP as shown by pulse-chase experiments in which PIP2 and PIP were prelabeled with32Pi. Depolarization of synaptosomes results in the stimulation of45Ca2+ uptake with the concomitant hydrolysis of PIP and PIP2. Addition of 1 mM Ca2+ accounts for 25% of the enhanced degradation whereas depolarization with 75 mM K+ accounts for 75% of the enhanced degradation of PIP2 and PIP. Depolarization with 100 mM veratrine results in a 223% increase in inositol trisphosphate as evidenced by stimulation of45Ca2+ uptake. EGTA (10mM) and Mg2+ (5–10 mM) inhibit the degradation of PIP and PIP2 and counteract the action of 1 mM Ca2+. Our data demonstrate that45Ca2+, Mg2+, and membrane depolarization play an important role in the turnover of membrane phosphatidylinositols.Abbreviations ATP
adenosine triphosphate
- Pi
inorganic orthophosphate
- PIP
phosphatidylinositol-4-phosphate
- PIP2
phosphatidylinositol-4,5,-bisphosphate
- IP3
inositol-1,4,5-trisphosphate 相似文献
4.
Phosphate uptake capacity of summer phytoplankton of the Loosdrecht Lakes in relation to phosphorus loading and irradiance 总被引:1,自引:0,他引:1
Summer populations of the phytoplankton of the Loosdrecht Lakes were enclosed in laboratory scale enclosures (LSE), supplied with 7.5 g P.l–1.d–1 and 105 g P.l–1.d–1, respectively. The maximum initial phosphate uptake rate (Vm) was related to irradiance and primary production. At phosphate uptake saturating light-irradiance Vm values up to 4 times the Vm values in the dark were measured.The phosphate uptake capacity per unit dry weight remained more or less constant throughout the experiments in the LSE receiving the lower amount of phosphorus, and declined in the LSE receiving the higher amount of phosphorus. Within the range of Vm values measured (<10 g P.mg DW–1.h–1 or 1,3 g P. g chla
–1.h–1), the growth rate of the phytoplankton was not influenced by alterations in phosphorus availability. 相似文献
5.
H. McLean S. Caveney 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1993,163(4):297-306
It is proposed that the activity of an epidermal cotransport system for Na+ and dicarboxylic amino acids accounts for the small amounts of L-glutamate and L-aspartate in the otherwise amino-acid-rich blood plasma of insects. This Na+-dependent transport system is responsible for more than 95% of the uptake of these amino acids into the larval epidermis of the beetle Tenebrio molitor. Kinetic analysis of uptake showed that the Na+-dependent co-transporter has medium affinity for L-glutamate and L-aspartate. The K
m for L-glutamate uptake was 146 mol·l-1, and the maximum velocity of uptake (V
max) was 12.1 pmol·mm-2 of epidermal sheet per minute. The corresponding values for L-aspartate were 191 mol·l-1 and 8.4 pmol·mm-2·min-1. The Na+/L-glutamate co-transporter has a stoichiometry of at least two Na+ ions for each L-glutamate-ion transported (n=217). The co-transporter has an affinity for Na+ equivalent to a K
m of 21 mmol · l-1 Na+. Na+ is the only external ion apparently required to drive L-glutamate uptake. Li+ substitutes weakly for Na+. Removal of external K+ or addition of ouabain decreases uptake slowly over 1 h, suggesting that these treatments dissipate the Na+/K+ gradient by inhibiting epidermal Na+/K+ ATPase. Several structural analogues of L-glutamate inhibit the medium-affinity uptake of L-glutamate. The order of potency with which these competitive inhibitors block glutamate uptake is L-cysteatethreo-3-hydroxy-Dl-aspartate >
D-aspartateL-aspartate>
L-cysteine sulphinate >
L-homocysteateD-glutamate. L-trans-Pyrrolidine-2,4-dicarboxylate, a potent inhibitor of L-glutamate uptake in mammalian synaptosomes, is a relatively weak blocker of epidermal uptake. The epidermis takes up substantially more L-glutamate by this Na+-dependent system than tissues such as skeletal muscle and ventral nerve cord. The epidermis may be a main site regulating blood L-glutamate levels in insects with high blood [Na+]. Because L-glutamate and L-aspartate stimulate skeletal muscle in insects, a likely role for epidermal L-glutamate/L-aspartate transporter is to keep the level of these excitatory amino acids in the blood below the postsynaptic activation thresholds.Abbreviation ac
acetate
- Ch
choline
- CNS
central nervous system
- cpm
counts per minute
- CDTA
trans-1,2-diaminocyclohexane-N,N,N,N-tetraacetic acids
- HPLC
high performance liquid chromatography
-
K
m
Michaelis constant
-
n
app
apparent number
- NMG
N-methyl-D-glucamine
- Pipes
Piperazine-N,N-bis-[2-ethanesulfonic acid]
- SD
standard deviation
- TEA
tetraethyl-ammonium
-
V
velocity of uptake
-
V
max
maximum velocity of uptake 相似文献
6.
Summary Sodium, potassium and veratridine were tested for their effects on the uptake of gamma-aminobutyric acid (GABA) by pinched-off presynaptic nerve terminals (synaptosomes). As noted by previous investigators, the uptake from media containing 1 m GABA (high-affinity uptake) is markedly Na-dependent; the uptake averaged 65 pmoles/mg synaptosome protein × min, with [Na]0=145mm and [K]0=5mm, and declined by about 90% when the external Na concentration ([Na]0) was reduced to 13mm (Na replaced by Li). The relationship between [Na]0 and GABA uptake was sigmoid, suggesting that two or more Na+ ions may be required to activate the uptake of one GABA molecule. Thermodynamic considerations indicate that with a Na+/GABA stoichiometry of 21, the Na electrochemical gradient, alone, could provide sufficient energy to maintain a maximum steady-state GABA gradient ([GABA]
i
/[GABA]0) of about 104 across the plasma membrane of GABA-nergic terminals.In Ca-free media with constant [Na]0, GABA uptake was inhibited, without delay, by increasing [K]0 or by introducing 75 m veratridine; the effect of veratridine was blocked by 200nm tetrodotoxin. The rapid onset (within 10 sec) of the veratridine and elevated-K effects implies that alterations in intra-terminal ion concentrations are not responsible for the inhibition. The uptake of GABA was inversely proportional to log [K]0. These observations are consistent with the idea that the inhibitory effects of both veratridine and elevated [K]0 may be a consequence of their depolarizing action. The data are discussed in terms of a barrier model (Hall, J. E., Mead, C.A., Szabo, G. 1973.J. Membrane Biol.
11:75) which relates carrier-mediated ionic flux to membrane potential. 相似文献
7.
Influx, efflux and net uptake of NO
3
–
was studied in Pisum sativum L. cv. Marma in short-term experiments where 13NO
3
–
was used to trace influx. The influx rate in N-limited plants was similar both during net uptake at external concentrations of around 50 M, and at low external NO
3
–
concentrations (4–6 M) when net uptake was practically zero. Efflux could be inferred from discrepancies between influx and net uptake but was never very high in the N-limited plants during net uptake. Close to the threshold concentration for not NO
3
–
uptake, efflux was high and equalled influx. Thus, the threshold concentration can be regarded as a NO
3
–
compensation point. The inclusion of NH
4
+
in the outer medium decreased influx by about 40% but did not significantly affect efflux. The roles of NO
3
–
fluxes and nitrate-reductase activity in regulating/limiting NO
3
–
utilization are discussed.Abbreviations DW
dry weight
- FW
fresh weight
- RN
relative nitrogen addition rate 相似文献
8.
Requirement, uptake, and subcellular distribution of Na2 75SeO3 in the larvae of the insectC. cephalonica was investigated. That Se is well tolerated byC. cephalonica upto an added level of 2 ppm in the diet is suggested by the observed increase in body weight, total protein, and succinate dehydrogenase levels. Significant increases in the State 3 respiration ensued with Se supplementation up to 2 ppm in the mitochondrial oxidation of D-glycerol 1-phosphate, succinate and NADH, along with concomitant unaltered State 4 respiration, leading to enhanced RCR values. Maximal uptake of75Se was registered in the larvae maintained on basal diet when subjected to short-term exposure to 0.5 ppm75Se level. When exposure level was further increased up to 20 ppm, the observed decrease in the uptake of75Se suggested that Se status of larvae itself controlled the tissue uptake. Subcellular distribution pattern revealed maximal incorporation of75Se (cpm/g tissue) in the supernatant fraction, whereas, maximal specific75Se activity (cpm/mg protein) was associated with the mitochondrial fraction. Autoradiography of the soluble fractions indicated the presence of single selenoprotein in the larval group with short term 2 ppm75Se exposure. Inherent Se controls both the extent and the nature of distribution of mitochondrial75Se incorporation. Uptake of45Ca by the insect mitochondria was enhanced by dietary Se up to 2 ppm but was unaffected by addition ofin vitro 75Se in the medium. A more fundamental role for Se in the mitochondrial energy metabolism emerges from these studies. 相似文献
9.
Summary A method for the determination of exchangeable lithium using 0.5M NH4Cl is described. The range of exchangeable Li in the fifty Papua New Guinea (PNG) soils analyzed was 0.002 to 0.409 gg–1 in contrast to five Australian soils which ranged from 0.032 to 0.830 gg–1. The PNG soils were divided into hill and alluvial soils with average exchangeable Li contents of 0.062 and 0.263 gg–1 respectively. No significant correlation between total and exchangeable Li was found in either group of soils althoughr=0.67 for the comined data and was significant at the 5% level. From the analysis of three profiles exchangeable Li was found to be at least twice as high (0.27 gg–1) in surface soils as in subsurface samples (0.10 gg–1). The average value of the deeper subsoil samples was 0.18 ppm.R mode cluster analysis of the data for village garden soils collected on a sampling grid showed that exchangeable Li was more strongly assoicated with Ca and Mg than with pH, 0.05M EDTA soluble Zn, 0.5M NaHCO3 soluble P or exchangeable Na and K. Computer constructed isographs using the analyses of grid samples from a garden illustrated the association between Li, Ca and Mg and the inverse association with Na.The correlation coefficient between Ca and Li in the ash of three food plants (Gnetum gnemon, Hibiscus abelmoschus andStenochlaena plustris) while not significant on an individual basis, was significant when the data was combined suggesting that the association between these elements in the soil may reflect an association in the ash returned to the soil when the garden was cleared. The correlation coefficient between soil exchangeable Li and Li in plant ash was positive, but not significant.Adsorption experiments over a five-day period demonstrated that Li was strongly adsorbed from solution. On average 63–75% of the adsorbed Li was fixed in a form which was not exchangeable with 0.5M NH4Cl or soluble in 0.05M EDTA. 相似文献
10.
Nickel localization and response to increasing Ni soil levels in leaves of the Ni hyperaccumulator Alyssum murale 总被引:1,自引:1,他引:0
C. Leigh Broadhurst Rufus L. Chaney J. Scott Angle Eric F. Erbe Timothy K. Maugel 《Plant and Soil》2004,265(1-2):225-242
We have previously developed phytoremediation and phytomining technologies employing Alyssum Ni hyperaccumulators to quantitatively extract Ni from soils. Implementation of these technologies requires knowledge of Ni localization patterns for the Alyssum species/ecotypes of interest under realistic growth conditions. We investigated Ni uptake and localization in mature Alyssum murale Kotodesh and AJ9ç leaves. Seedlings were grown in potting mix with an increasing series of NiSO4 addition (0, 5, 10, 20, 40, 80 mmol Ni kg–1), NiC4H6O4 addition (0, 5, 10, 30, 60, 90 mmol Ni kg–1), in Ni-contaminated soil from metal refining operations, and serpentine soil. Plants at Ni levels 0, 5, 10, 20 mmolkg–1 and in native soils grew normally. Plants at 40 mmolkg–1 exhibited the onset of phytotoxicity, and 60, 80, and 90 mmolkg–1 were demonstrably phytotoxic, but symptoms of phytotoxicity abated within 6 months. Cryogenic complement fractures were made from frozen hydrated samples. High-resolution scanning electron microscope (SEM) images were taken of one half. The other half was freeze-dried and examined with SEM and semi-quantitative energy dispersive x-ray analysis. Ni was highly concentrated in epidermal cell vacuoles and Ni and S counts showed a positive correlation. Trichome pedicles and the epidermal tissue from which the trichome grows were primary Ni compartments, but Ni was not distributed throughout trichomes. Palisade and spongy mesophyll and guard/substomatal cells contained lesser Ni concentrations but palisade mesophyll was an increasingly important compartment as Ni soil levels increased. Ni was virtually excluded from vascular tissue and trichome rays. 相似文献
11.
Somatic embryogenesis and regeneration of plants in the bamboo Dendrocalamus strictus 总被引:1,自引:0,他引:1
Somatic embryogenesis leading to plant regeneration has been achieved in the bamboo, Dendrocalamus strictus, by culturing seeds (caryopses) on B5 basal medium supplemented with 2,4-dichlorophenoxyacetic acid. Callus cultures obtained from the embryonal end of the seeds differentiated chlorophyllous embryoids. On transfer to a germination medium (B5 liquid, sucrose, indolebutyric acid, and -naphthaleneacetic acid) 40% of the embryoids developed into plantlets. Further development of the plantlets occured on B5 liquid medium (half strength) + sucrose (1%) + IBA (5 × 10–7M) + NAA (10–7M).Abbreviations 2,4-D
2,4-dichlorophenoxyacetic acid
- IBA
Indolebutyric acid
- NAA
-naphthaleneacetic acid 相似文献
12.
Pond cultivation of the subtropical, euryhaline macroscopic red algaGracilaria tenuisipitata var.liui Zhanget Xia was carried out in brackish seawater (6–7) in the Gryt archipelago on the east coast of Sweden, using four outdoor tanks of 30–40 m3. Growth rate and nutrient uptake in batch culture were measured with the aim of estimating the water purification capacity ofG. tenuisipitata in outdoor conditions. Its ability to withstand epiphytic infections was also studied. An average growth rate of 4 biomass increase per day was recorded during two seasons with a maximum growth rate of 9 d–1. The initial biomass was usually 1 kgFW m–3 (FW, fresh weight). The nutrient uptake capacity was on average ca. 1 g Ni kgFW–1 d–1 and 0.08 g Pi kgFW–1 d–1 and the uptake rates for NH4
+-N were higher than those for NO3
–-N. Both the growth rate and the nutrient uptake rate were highest at the highest water temperature. Co-cultivation with rainbow trout (Oncorhynchus mykiss) was tested: with trout fodder as the only nutrient inputG. tenuistipitata could grow and maintain low levels of Ni and Pi with optimum efficiency at a trout: alga ratio of 1:1 (w:w). Epiphytic growth of filamentous green and brown algae was limited, probably as a result of the high pH values caused by inorganic carbon uptake byG. tenuistipitata. The growth ofEnteromorpha intestinalis, the only significant epiphyte, was completely inhibited and the majority of plants died by a few days treatment with 100 µg 1–1 Cu2+, a concentration that did not severely affectG. tenuistipitata. We conclude thatG. tenuistipitata can be cultivated in outdoor ponds in southern Sweden during 5–6 months of the year using aerated or unaerated batch cultures and that wastewater from trout cultivation may be used as a nutrient source, resulting in purification with respect to N and P. 相似文献
13.
Uptake of phosphate in the light by Amphidinium carterae, Amphidinium klebsii, cultured and symbiotic Gymnodinium microadriaticum conformed to Michaelis-Menten type saturation kinetics with all organisms showing similar K
m values, namely 0.005 to 0.016 M phosphorus. V
max values were 0.009–0.32 nmol phosphorus · 105 cells-1 · 10 min-1. Phosphate uptake by all the dinoflagellates was greater in the dark than in the light. The metabolic inhibitor 3-(3,4-dichlorophenyl) 1,1-dimethylurea stimulated phosphate uptake in the light by A. carterae and A. klebsii, but inhibited uptake by cultured and symbiotic G. microadriaticum. Carbonylcyanide 3-chlorophenylhydrazone (CCCP) inhibited phosphate uptake by A. carterae and A. klebsii under both light and dark conditions. Uptake of phosphate by cultured and symbiotic G. microadriaticum in the light, but not in the dark, was inhibited by CCCP. Low concentrations of arsenate (5 g As · l-1) stimulated phosphate by A. carterae and A. klebsii, but inhibited uptake by cultured and symbiotic G. microadriaticum. High concentrations of arsenate (100 g As · l-1) did not affect uptake of phosphate by A. carterae and A. klebsii. 相似文献
14.
Magnesium uptake kinetics in loblolly pine seedlings 总被引:1,自引:0,他引:1
Recent studies have suggested that the growth of loblolly pine (Pinus taeda L.) has declined in the southern United States and it has been hypothesized that foliar Mg deficiency may play an important role in the perceived decline. Quantitative nutrient uptake models such as the Barber-Cushman model have been used successfully to investigate nutrient uptake by crop species under a variety of field and experimental conditions and may provide one approach to evaluating this question. However, in order to use this approach it is necessary to develop, for the plant species and nutrient of interest, values for maximal nutrient influx rate at high solution concentrations (Imax), the solution concentration where net influx is 0.5 Imax (Km), and the nutrient concentration below which influx ceases (Cmin). As a first step in evaluating the potential of such an approach, two sets of experiments using established solution nutrient depletion techniques were used to define these values for loblolly pine seedlings 180, 240, 365, and 425 days in age. Observed Imax values for Mg range from 7.90E-8 to 1.29E-7 mol cm–2 s–1 with younger seedlings having higher values. Values of Km for all seedling ages were quite similar ranging from 8.69 to 8.58E-3 mol cm–3. Most importantly, the results of both experiments indicate that during a growth flush, seedlings will withdraw Mg from solution until the concentration is essentially zero (Cmin=0). During non-flush periods uptake rates appear to be greatly reduced. Therefore, efforts to model Mg uptake will need to take these differences as well as seedling age influences into consideration. 相似文献
15.
The kinetic parameters of lipase, bacterial secondaryproduction (BSP) and bacterial numbers (BN) were determined fortnightlyduringthe development of the summer phytoplankton bloom at twostationsof Alte Donau, a hypertrophic stagnant dead arm of the riverDanubein Vienna. Until the middle of August we observed a gradualincrease in lipase activity as well as BN and BSP rates tothe maximum of 19.9 nmol l–1 h–1,4.5×109cells l–1 and 8.1 g C l–1 h–1,respectively. Atthe end of August and during September we found a markeddecreasein all bacterial parameters, coinciding with a progressingincreaseof chlorophyll a concentrations at both sampling sites. Themaximalvalues of lipase Vmax were determined in the bottom waterlayer (avg. 13.7±6.5 nmol l–1 h–1) probablyowingto the predominating importance of polymeric matter in thesubstrate pool for microheterotrophs in this water zone.Differential filtration experiments showed that 20.1% to56.3% ofthe total lipase activity and 4.2% to 9.0% of the totalbacterialnumbers in Alte Donau water samples occurred in 0.2-mfiltrate. Further experiments indicated that the highcontributionto lipase activity in the 0.2-m filtrate was rather dueto thepresence of 0.2 m filterable bacteria than to solubleenzymemolecules. Moreover, we observed higher bacterial lipaseactivityin 0.2 m filtrate than in unfiltered samples. Thepossibleinfluence of limiting factors on the metabolism of insitubacteria is discussed. 相似文献
16.
William Breuer 《The Journal of membrane biology》1989,107(1):35-42
Summary The basolateral membrane of the thick ascending loop of Henle (TALH) of the mammalian kidney is highly enriched in Na+/K+ ATPase and has been shown by electrophysiological methods to be highly conductive to Cl–. In order to study the Cl– conductive pathways, membrane vesicles were isolated from the TALH-containing region of the porcine kidney, the red outer medulla, and Cl– channel activity was determined by a36Cl uptake assay where the uptake of the radioactive tracer is driven by the membrane potential (positive inside) generated by an outward Cl– gradient. The accumulation of36Cl– inside the vesicles was found to be dependent on the intravesicular Cl– concentration and was abolished by clamping the membrane potential with valinomycin. The latter finding indicated the involvement of conductive pathways. Cl– channel activity was also observed using a fluorescent potential-sensitive carbocyanine dye, which detected a diffusion potential induced by an imposed inward Cl– gradient. The anion selectivity of the channels was Cl–>NO
3
–
=I– gluconate. Among the Cl– transport inhibitors tested, 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPAB), 4,4-diisothiocyano-stilbene-2,2-disulfonate (DIDS), and diphenylamine-2-carboxylate (DPC) showed IC50 of 110, 200 and 550 m, respectively. Inhibition of36Cl uptake by NPPAB and two other structural analogues was fully reversible, whereas that by DIDS was not. The nonreactive analogue of DIDS, 4,4-dinitrostilbene-2,2-disulfonate (DNDS), was considerably less inhibitory than DIDS (25% inhibition at 200 m). The irreversible inhibition by DIDS was prevented by NPPAB, whereas DPC was ineffective, consistent with its low inhibitory potency. It is proposed that NPPAB and DIDS bind to the same or functionally related site on the Cl– channel protein. 相似文献
17.
Mandal A Chakraborti T Choudhury R Ghosh B Ghosh AN Das S Chakraborti S 《Molecular and cellular biochemistry》2005,270(1-2):79-87
Treatment of microsomes (preferentially enriched with endoplasmic reticulum) isolated from bovine pulmonary artery smooth muscle tissue with H2O2 (1 mM) markedly stimulated matrix metalloproteinase activity and also inhibited Na+ dependent Ca2+ uptake. Electron micrograph revealed that H2O2 (1 mM) does not cause any damage to the microsomes. MMP-2 and TIMP-2 were determined to be the ambient protease and corresponding antiprotease of the microsomes. Pretreatment with vitamin E (1 mM) and TIMP-2 (50 g/ml) reversed the effect produced by H2O2 (1 mM) on Na+ dependent Ca2+ uptake in the microsomes. However, H2O2 (1 mM) caused changes in MMP-2 activity and Na+ dependent Ca2+ uptake were not reversed upon pretreatment of the microsomes with a low concentration of 5 g/ml of TIMP-2 which otherwise reversed MMP-2 (1 g/ml) mediated increase in 14C-gelatin degradation and inhibition of Na+ dependent Ca2+ uptake. Combined treatment of the microsomes with a low dose of MMP-2 (0.5 g/ml) and H2O2 (0.5 mM) inhibited Na+ dependent Ca2+ uptake in the microsomes compared to the respective low dose of either of them. Direct treatment of TIMP-2 (5 g/ml) with H2O2 (1 mM) abolished the inhibitory effect of the inhibitor on 14C-gelatinolytic activity elicited by 1 g/ml of MMP-2. Thus, one of the mechanisms by which H2O2 activates MMP-2 could be due to inactivation of TIMP-2 by the oxidant. The resulting activation of MMP-2 subsequently inhibits Na+ dependent Ca2+ uptake in the microsomes. (Mol Cell Biochem 270: 79–87, 2005) 相似文献
18.
Dissolved oxygen tension and oxygen uptake rate are critical parameters in animal cell culture. However, only scarce information of such variables is available for insect cell culture. In this work, the effect of dissolved oxygen tension (DOT) and the utility of on-line oxygen uptake rate (OUR) measurements in monitoring Spodoptera frugiperda (Sf9) cultures were determined. Sf9 cells were grown at constant dissolved oxygen tensions in the range of 0 to 30%. Sf9 metabolism was affected only at DOT below 10%, as no significant differences on specific growth rate, cell concentration, amino acid consumption/production nor carbohydrates consumption rates were found at DOT between 10 and 30%. The specific growth rate and specific oxygen uptake rate followed typical Monod kinetics with respect to DOT. The calculated max and
max were 0.033 h-1 and 3.82×10-10 mole cell-1h-1, respectively, and the corresponding saturation constants were 1.91 and 1.57%, respectively. In all aerated cultures, lactate was consumed only after glucose and fructose had been exhausted. The yield of lactate increased with decreasing DOT. It is proposed, that an apparent DOT in non-instrumented cultures can be inferred from the lactate yield of bioreactors as a function of DOT. Such a concept, can be a useful and important tool for determining the average dissolved oxygen tension in non-instrumented cultures. It was shown that the dynamic behavior of OUR can be correlated with monosaccharide (fructose and glucose) depletion and viable cell concentration. Accordingly, OUR can have two important applications in insect cell culture: for on-line estimation of viable cells, and as a possible feed-back control variable in automatic strategies of nutrient addition.Abbreviations DOT
Dissolved oxygen tension
- OUR
Oxygen uptake rate
-
specific oxygen uptake rate
-
specific growth rate
- Xv
viable cell concentration
- CL, C*, and
oxygen concentrations in liquid phase, in equilibrium with gas phase, and medium molar concentration, respectively
- H
Henry's constant
- KLa
volumetric oxygen transfer coefficient
- PT
total pressure
-
oxygen partial pressure
-
oxygen molar fraction
- i
discrete element 相似文献
19.
Popykina N. A. Gladysheva I. P. Zamolodchikova T. S. Larionova N. I. 《Russian Journal of Bioorganic Chemistry》2003,29(6):550-555
The interaction of duodenase, a new serine protease from a small group of Janus-faced proteases, with serpins, 1-protease inhibitor (1-PI) and antichymotrypsin (ACT) from human blood serum, was studied. The stoichiometry of the inhibition process was found to be 1.2 and 1.3 mol/mol for 1-PI and ACT, respectively. The presence of a stable enzyme–inhibitory complex duodenase–1-PI was confirmed by SDS-PAGE. The formation of the duodenase–ACT complex was not demonstrated; instead, the band of the cleaved inhibitor indicated the ACT hydrolysis. The suicide mechanism of the duodenase interaction with the human blood serpins was proved. The association rate constants (k
× 105, –1 s–1) were 2.4 ± 0.3 × 105 for 1-PI and 3.0 ± 0.4 × 105 for ACT. These results indicate the possibility of the regulation of duodenase activity by endogenous serpins. 相似文献
20.
B. Bengtsson 《Plant Ecology》1992,101(1):35-41
Beech seedlings (Fagus sylvatica L. provenance Västra Torup) were grown in nutrient solution at low pH (4.2) and exposed to AlCl3 and different concentrations of nitrogen. The effects of AlCl3 and nitrogen on uptake of Ca2+ (45Ca) and H2PO4
- (32P) in roots of intact beech were studied. Crossections of roots were analyzed with respect to element concentrations, by use of Mikro-PIXE (particle induced X-ray emission). The distribution of Al, Ca, P, Mg, K, and S was analysed. The experiments were designed to evaluate the effects of aluminium on localization of elements in plant root tissue.Aluminium reduced the concentration of Ca in plants and increased that of K. High nitrogen levels in the solution further decreased the concentration of Ca in the roots. Aluminium (1.0 mM) effectively reduced the Ca2+ (45Ca) uptake in short time experiments. Aluminium accumulated in high concentration (up to 500 mol/g dry weight in areas of 30×30 m2) on the root surface, epidermis and outer layers of cortex. Corresponding areas had an extremely low Ca concentration (ca 5 mol/g dry weight) which could be harmful for regulation of mineral uptake and development of roots.It is concluded that the calcium concentration in roots was reduced by aluminium. The combination with high nitrogen levels further reduced calcium changing the mineral balance which could result in deficiency conditions of calcium in the root. 相似文献