共查询到20条相似文献,搜索用时 613 毫秒
1.
Joyce Nikolakopoulos Cherian Zachariah Duarte Mota de Freitas †Evan B. Stubbs Jr. ‡Ravichandran Ramasamy §M. Margarida C. A. Castro §Carlos F. G. C. Geraldes 《Journal of neurochemistry》1998,71(4):1676-1684
Abstract: Lithium has been used clinically in the treatment of manic depression. However, its pharmacologic mode of action remains unclear. Characteristics of Li+ interactions in red blood cells (RBCs) have been identified. We investigated Li+ interactions on human neuroblastoma SH-SY5Y cells by developing a novel 7 Li NMR method that provided a clear estimation of the intra- and extracellular amounts of Li+ in the presence of the shift reagent thulium-1,4,7,10-tetrazacyclododecane- N,N ', N ", N ‴-tetramethylene phosphonate (HTmDOTP4− ). The first-order rate constants of Li+ influx and efflux for perfused, agarose-embedded SH-SY5Y cells in the presence of 3 m M HTmDOTP4− were 0.055 ± 0.006 (n = 4) and −0.025 ± 0.006 min−1 (n = 3), respectively. Significant increases in the rate constants of Li+ influx and efflux in the presence of 0.05 m M veratridine indicated the presence of Na+ channel-mediated Li+ transport in SH-SY5Y cells. 7 Li NMR relaxation measurements showed that Li+ is immobilized more in human neuroblastoma SH-SY5Y cells than in human RBCs. 相似文献
2.
The natural 15 N abundance of amide-exporting nodules was compared to that of shoots in 12 plant species. Nodules were statistically less abundant in 15 N than shoots in one of three cultivars of Pisum sativum L., in Vicia faba L. and in Medicago sativa L., but the 15 N depletion of nodules was very samall. Nodules were statistically more abundant in 15 N than shoots in Trifolium pratense L., depending on time during the growing season, Cyamopsis tetragonaloba L. Taub. and 7 Lupinus species, but the enrichment was small except for C. tetragonalova and 6 Lupinus species. Nodules of 3 Lupinus species infected with Rhizobium lupini isolated from Lupinus subcarnosa Hook, were only slightly enriched in 15 N, but nodules of two of these species were substantially enriched in 15 N when infected with a mix of other Rhizobium lupini strains. The third species, L. texensis Hook., was not infected by this mix of strains. Differences in 15 N abundance between nodules and other tissues of amide-exporting and ureide-exporting nodules from several studies are tabulated. All ureide-exporting nodules in this tabulation are enriched in 15 N. Amide-exporting nodules are considerably more variable in this regard. These results confirm that events associated with ureide synthesis or transport cannot be the sole cause of the substantial 15 N enrichment seen in nodules. 相似文献
3.
Abstract: Effects of barbiturates, diphenylhydantoin, and ethanol on 45 Ca2+ binding to acidic lipids have been examined in an organic solvent-aqueous partition system. Hexobarbital, pentobarbital, and phenobarbital, at concentrations of 0.3 and/or 0.6 mM, enhanced the binding of 45 Ca2+ to phosphatidic acid, phosphatidylserine, and sulfatide but not to phosphatidylinositol or cardiolipin. Diphenylhydantoin, 0.3 mM, enhanced 45 Ca2+ binding to phosphatidic acid and phosphatidylserine but not to sulfatide. Ethanol at 80 mM did not enhance 45 Ca2+ binding to phosphatidic acid, but ethanol decreased the binding to cardiolipin and increased it to sulfatide. 相似文献
4.
Abstract: [3 H]Nemonapride and [3 H]spiperone are very widely used to study dopaminergic systems in vitro and in vivo, but it has been reported that [3 H]nemonapride and [3 H]spiperone give markedly different B max values for preparations of D2 dopamine receptors from recombinant cell lines or animal tissues. We have used the two radioligands in parallel to study a range of dopamine receptors [D2(short) , D2(long) , and D3 ] in different buffers. B max values derived using either radioligand differ by an average of <20%, independent of receptor type or buffer conditions. All competition experiments show that the two ligands compete at a single site. It seems that [3 H]spiperone and [3 H]nemonapride do not differentiate between different forms or populations of D2 -like receptors. 相似文献
5.
Abstract: Cl and Na transport by the lateral ventricle (LVCP) and fourth ventricle (4VCP) choroid plexuses were examined by kinetic analysis of 36 Cl and 22 Na uptake into the choroid plexus-CSF system of the adult rat. Both radioisotopes required more than 5 h to reach steady-state distribution in the in vivo choroid plexuses and CSF after intraperitoneal injection. Whereas the LVCP and 4VCP 36 Cl steady-state spaces were comparable (55–56%), the 4VCP 22 Na space (39%) tended to be greater than the LVCP 22 Na space (36%). No evidence for inexchangeable Cl or Na was found for the choroid plexuses; the radioisotopic and chemical spaces were not significantly different. Choroid plexus 36 Cl and 22 Na uptake curves were resolved into two components, a fast component ( t 1/2 0.02–0.05 h) and a slow component ( t 1/2 0.85–1.93 h). By analysis of the distribution of [3 H]inulin, [3 H]mannitol, and 51 Cr-tagged erythrocytes within the choroid plexuses, the fast component of 36 Cl and 22 Na uptake was found to represent extracellular and erythrocyte contributions to the tissue radioactivity, whereas the slow component represented isotope movement into the epithelial cell compartment. The calculated cell [Cl] of LVCP and 4VCP, 67 mmol/kg cell water, was 3.9 times greater than that predicted by the membrane potential for passive distribution. It is postulated that Cl is actively transported into the choroid epithelial cell across the basolateral membrane; the energy source for active Cl transport may be the Na electrochemical potential gradient (˜90 mV), which is twice that of the Cl electrochemical potential gradient (˜45 mV). 相似文献
6.
The dynamics of a subtoxic pulse of non-dietary 109 Cd was followed for up to 304 days after the exposure period in female zebrafish. The retention of dietary 109 Cd was also estimated.
The distribution of109 Cd was studied by autoradiography, whole-body analysis and tissue sampling. After exposure to non-dietary 109 Cd for 10 days there was a rapid loss of 109 Cd from the gills. The 109 Cd content of the alimentary canal exceeded that which could have been expected from normal drinking. Based on the distribution pattern of non-dietary 109 Cd in tissues, two groups of tissues were distinguished:
Small amounts of109 Cd were noted in fry and fertilized eggs originating from zebrafish exposed to non-dietary 109 Cd. After exposure to dietary 109 Cd, less than 5% was retained in the zebrafish body, mainly in the alimentary canal. 相似文献
The distribution of
- (i)
the gills, alimentary canal and heart which showed maximum
109 Cd values directly after exposure, followed by a pronounced decrease up to day 21; - (ii)
the liver, kidney, ovary and muscle, in which there was a delay in maximum
109 Cd activity to days 21–42, with subsequent loss.
Small amounts of
7.
J.P. Ferrio M.A. Mateo J. Bort O. Abdalla J. Voltas & J.L. Araus 《The Annals of applied biology》2007,150(2):207-215
Stable carbon isotope composition (δ13 C) of dry matter has been widely investigated as a selection tool in cereal breeding programmes. However, reports on the possibilities of using stable oxygen isotope composition (δ18 O) as a yield predictor are very scarce and only in the absence of water stress. Indeed, it remains to be tested whether changes in phenology and stomatal conductance in response to water stress overrule the use of either δ13 C or δ18 O when water is limited. To answer this question, a set of 24 genotypes of bread wheat ( Triticum aestivum ) were assayed in two trials with different levels of deficit irrigation and a third trial under rainfed conditions in a Mediterranean climate (northwest Syria). Grain yield (GY) and phenology (duration from planting to anthesis and from anthesis to maturity) were recorded, and the δ13 C and δ18 O of grains were analysed to assess their suitability as GY predictors. Both δ13 C and δ18 O showed higher broad-sense heritabilities ( H 2 ) than GY. Genotype means of GY across trials were negatively correlated with δ13 C, as previously reported, but not with δ18 O. Both isotopes were correlated with grain filling duration, whereas δ18 O was also strongly affected by crop duration from planting to anthesis. We concluded that δ18 O of grains is not a proper physiological trait to breed for suboptimal water conditions, as its variability is almost entirely determined by crop phenology. In contrast, δ13 C of grains, despite being also affected by phenology, still provides complementary information associated with GY. 相似文献
8.
Cytokinin N6 -(δ2 -isopentenyl) adenosine (i6 A) was applied five times to runoff on the first leaf of Xanthium pennsylvanicum Wallr. After a 24 h application period the second leaf was treated with the herbicide methyl-14 C-glyphosate, [N-(phosphonomethyl)glycine]. The distribution of radioactivity was determined after 12 and 24 h. At no time after treatment did 14 C-glyphosate move preferentially into the i6 A treated leaf. Radioactivity accumulated in all plant parts, but in i6 A-treated plants, there were more counts in the actively growing areas after 12 h. The primary effect of i6 A after 24 h was enhanced uptake of 14 C-glyphosate into the plant. To determine if the increased uptake and altered movement of 14 C-glyphosate was due to a cytokinin-induced transpiration increase, leaf diffusive resistance was measured. Leaf diffusive resistances were unaffected by i6 A during the 48 h after application. By 12 h after the application of glyphosate, the herbicide was found not to affect the cytokinin content in the Xanthium root tips. 相似文献
9.
Abstract— Glycine sensitive [3 H]strychnine binding has been demonstrated in the pigeon CNS. The kinetic parameters in spinal cord, tectum, telencephalon and cerebellum in this order were: K n , (nM) 5 , 5, 2.3, 6 and B max (fmol/mg protein) 1000, 275, 92, 20. The effect of various amino acids and strychnine analogs on the binding was measured. Retinal ablation caused a 22% decrease in the glycine sensitive [3 H]strychnine binding in the tectum while lesions destroying up to 80% of the nucleus Ipc had no effect. 相似文献
10.
Abstract. We have studied carcinoma NT, a transplantable mouse adenocarcinoma of spontaneous origin. Cells labelled with [3 H]thymidine ([3 H]TdR) were restricted to a narrow zone around the periphery of this tumour and were also found in rings up to 50 μ m wide, around isolated blood vessels in the central necrotic area. Labelling with [3 H]deoxyuridine ([3 H]UdR), another DNA synthesis precursor, produced a very different pattern. The labelled zone around the periphery was much wider than with [3 H]TdR, and [3 H]UdR labelled cells were found up to 110 μ m from isolated vessels. [3 H]iododeoxyuridine ([3 H]IUdR) gave the same pattern of labelling as [3 H]UdR. In the heavily labelled zone, within 1 mm of the tumour periphery, the labelling index (LI) was 51% after [3 H]UdR or [3 H]IUdR injection, and only 36% with [3 H]TdR.
The data show that at least half of the DNA-synthesizing cells in this tumour did not incorporate [3 H]TdR. Previous workers reported cell loss factors for carcinoma NT of 60% calculated from [3 H]TdR labelling data and 30% from the rate of loss of [125 I]UdR. The present work suggests that calculations based on [125 I]UdR data are more likely to be accurate for carcinoma NT than those using [3 H]TdR data. 相似文献
The data show that at least half of the DNA-synthesizing cells in this tumour did not incorporate [
11.
A. Rotman 《Journal of neurochemistry》1977,28(6):1369-1372
Abstract— The uptake of [3 H]norepinephrine ([3 H]NE) and [3 H]serotonin ([3 H]5-HT) by rat brain synaptosomes is reduced as a result of pretreatment of the synaptosomes with phospholipase C (EC 3.1.4.3) or phospholipase A2 (EC 3.1.1.4). This effect is not due to inhibition of the Na+ -K+ -ATPase but rather is caused by hydrolysis of neuronal membrane phospholipids, mainly phosphatidylcholine, which seem to be important to the uptake. 相似文献
12.
To develop further the methods for estimation of NOx absorption by plants supplied with 15 N-labelled fertilizer, we proposed a new calculation method, total N fixed method (TNF), and compared with the 15 N dilution method and the classical mass balance method (MB).
Hydroponically grown soybean plants were supplied with15 N-labelled nitrate and exposed to 200–250 nl l−1 NO2 for 7 d. The proportions of the N derived from NO2 to total N in exposed plants were estimated by the three methods.
The reported rates of NO2 absorption by several plant species, estimated by the 15 N dilution method, were recalculated using the TNF method. The results of the two methods were compared and showed that: (1) The 15 N dilution method overestimated the content of NO2 -N in exposed plants compared with the MB method whilst the TNF method produced estimations of NO2 -N closer to those by the MB method when the plants were supplied with 5 m M nitrate. (2) The differences in estimations between the MB method and either the 15 N dilution method or the TNF method increased with decreasing supply of 15 N-labelled nitrate to roots. 相似文献
Hydroponically grown soybean plants were supplied with
The reported rates of NO
13.
Carme Solà Emili Martínez Lluïsa Camón Angel Pazos† Eduard Rodríguez-Farré 《Journal of neurochemistry》1993,60(5):1821-1834
Abstract: The effect of lindane administration on the specific binding of ligands to different sites on the GABAA receptor-ionophore complex was studied in the rat brain by receptor mapping autoradiography. [3 H]Muscimol (Mus), [3 H]flunitrazepam (Flu), and t -[35 S]butylbicyclophosphorothionate (TBPS) were used as specific ligands of GABA, benzodiazepine, and picrotoxinin binding sites, respectively. Rats received a single oral dose of 30 mg/kg lindane and they were classified into two groups according to the absence or presence of convulsions. Vehicle-treated groups acted as controls. The effect of the xenobiotic on ligand binding was measured in different brain areas and nuclei 12 min or 5 h after its administration. Lindane induced a generalized decrease in [35 S]TBPS binding, which was present shortly after dosing. In addition, [3 H]Flu binding was increased in lindane-treated animals, this modification also appearing shortly after administration but diminishing during the studied time. Finally, lindane induced a decrease in [3 H]Mus binding, which became more evident over time. These modifications were observed both in the presence and in the absence of convulsions. However, an increase in [3 H]-Mus binding was detected shortly after lindane-induced convulsions. The observed decrease in [35 S]TBPS binding is in agreement with the postulated action of lindane at the picrotoxinin binding site of the GABAA receptor chloride channel. The effects observed on the binding of [3 H]Flu and [3 H]Mus may be secondary to the action of lindane as an allosteric antagonist of the GABAA receptor. 相似文献
14.
The role of methionine as a precursor in mugineic acid (MA) biosynthesis was studied by feeding 15 N-ammonium sulfate, 14 C-amino acids, and [1-14 C, 15 N]-methionine to iron-deficient barley roots ( Hordeum vulgare L. cv. Minorimugi), grown hydroponically. The incorporation of isotopes into amino acids was also examined. Methionine appears to be the most efficient precursor of the mugineic acid family (MAs) of phytosiderophores; homoserine was also incorporated into the MAs, but other amino acids such as glutamate, alanine, and γ-amino butyric acid did not act as precursors of MAs. Carbon-14 and 15 N of methionine were incorporated into MAs. This specific incorporation of 14 C and 15 N indicated that the nitrogen atoms of MAs were derived from two molecules of methionine. It is suggested that deoxymugineic acid (DMA) is probably the first phytosiderophore to be synthesized on the biosynthetic pathway of MAs. 相似文献
15.
Abstract: The ability of adenosine agonists to modulate K+ -evoked 4D†-[3 H]aminobutyric acid ([3 H]GABA) and acetylcholine (ACh) release from rat striatal synaptosomes was investigated. The A2a receptor-selective agonist CGS 21680 inhibited Ca2+ -dependent [3 H]GABA release evoked by 15 m M KCI with a maximal inhibition of 29 ± 4% (IC50 of ∼4 ± 10 −12 M ). The relative order of potency of three agonists was CGS 21680 ± 5'- N -ethylcarboxamidoadenosine > R-phenylisopropyladenosine (R-PIA), with the inhibition being blocked by A2a receptor-selective antagonists (CP 66,713 and CGS 15943A) but not by the A1 -selective antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX). When release of [3 H]GABA was evoked by 30 mM KCI, no significant inhibition was observed. In contrast, CGS 21680 stimulated the release of [3 H]ACh evoked by 30 m M KCI, with a maximal stimulation of 26 ± 5% (IC50 of ∼10−11 M ). This effect was blocked by CP 66,713 but not by DPCPX. The A1 agonist R -PIA inhibited [3 H]ACh release, an effect blocked by DPCPX. It is concluded that adenosine A2a receptors are present on both GABAergic and cholinergic striatal nerve terminals where they inhibit and stimulate transmitter release, respectively. Key Words : GABA—Acetylcholine—Adenosine receptors—Striatum. 相似文献
16.
A. KOHZU T. YOSHIOKA T. ANDO M. TAKAHASHI K. KOBA & E. WADA 《The New phytologist》1999,144(2):323-330
The natural abundance of 13 C and 15 N was measured in basidiocarps of at least 115 species in 88 genera of ectomycorrhizal, wood-decomposing and litter-decomposing fungi from Japan and Malaysia. The natural abundance of 13 C and 15 N was also measured in leaves, litter, soil and wood from three different sites. 15 N and 13 C were enriched in ectomycorrhizal and wood-decomposing fungi, respectively, relative to their substrates. Ectomycorrhizal and wood-decomposing fungi could be distinguished on the basis of their δ13 C and δ15 N signatures. Although there was high variability in the isotopic composition of fungi, the following isotope- enrichment factors (ε, mean±SD) of the fungi relative to substrates were observed:
εectomycorrhizal fungi/litter = 6.1±0.4‰15 N
εectomycorrhizal fungi/wood = 1.4±0.8‰13 C
εwood-decomposing fungi/wood = −0.6±0.7‰15 N
εwood-decomposing fungi/wood = 3.5±0.9‰13 C
The basis of isotope fractionation in C metabolism from wood to wood-decomposing fungus is discussed. 相似文献
ε
ε
ε
ε
The basis of isotope fractionation in C metabolism from wood to wood-decomposing fungus is discussed. 相似文献
17.
Abstract— The specific binding of [3 H]spiperone and [3 H]domperidone, as defined by 1 μ m -(+)butaclamol, was compared in homogenates of bovine retina and caudate nucleus. Scatchard analyses of saturation data for [3 H]spiperone binding yielded dissociation constants ( K d ) of 0.35 n m in the retina and 0.64 n m in the caudate nucleus. Comparison of the maximum number of binding sites (Bmax ) present in each tissue indicated that the density of sites in bovine caudate nucleus (270 fmol/mg protein) was approximately three times higher than in bovine retina (92 fmol/mg protein). This difference was even more marked in guinea pig tissues, with a ratio of 7:1 between corpus striatum and retina. The pharmacological analysis of [3 H]spiperone binding in both the bovine retina and caudate nucleus indicated an interaction with dopaminergic rather than serotonergic sites. However, inhibition curves obtained to dopaminergic agonists in the bovine retina were significantly steeper than those observed in the bovine caudate nucleus, as reflected in the greater Hill coefficients obtained for these agents in the retina. Furthermore, only a small amount of specific [3 H]domperidone binding was observed in either the bovine caudate nucleus or the guinea pig striatum, whilst no specific [3 H]domperidone binding was detectable in homogenates of either bovine or guinea pig retina. These data suggest that the retina possesses only a small population of dopaminergic D2 sites and that these binding sites may differ from those present in the caudate nucleus. 相似文献
18.
We investigated the extent to which plant water and nutrient status are affected by intraspecific competition intensity and microsite quality in a monodominant tussock grassland. Leaf gas exchange and stable isotope measurements were used to assess the water relations of Stipa tenacissima tussocks growing along a gradient of plant cover and soil depth in a semi-arid catchment of Southeast Spain. Stomatal conductance and photosynthetic rate decreased with increasing intensity of competition during the wet growing season, leading to foliar δ 18 O and δ 13 C enrichment. A high potential for runoff interception by upslope neighbours exerted strong detrimental effects on the water and phosphorus status of downslope S. tenacissima tussocks. Foliar δ 15 N values became more enriched with increasing soil depth. Multiple stepwise regression showed that competition potential and/or rhizosphere soil depth accounted for large proportions of variance in foliar δ 13 C, δ 18 O and δ 15 N among target tussocks (57, 37 and 64%, respectively). The results presented here highlight the key role that spatial redistribution of resources (water and nutrients) by runoff plays in semi-arid ecosystems. It is concluded that combined measurement of δ 13 C, δ 18 O and nutrient concentrations in bulk leaf tissue can provide insight into the intensity of competitive interactions occurring in natural plant communities. 相似文献
19.
Martin Krüger Heike Wolters Matthias Gehre Samantha B. Joye & Hans-Hermann Richnow 《FEMS microbiology ecology》2008,63(3):401-411
The anaerobic oxidation of methane (AOM) is an important methane sink in marine ecosystems mediated by still uncultured Archaea . We established an experimental system to grow AOM communities in different sediment samples. Approaches to show growth of the slow-growing anaerobic methanotrophs have been either via nucleic acids (quantitative PCR) or required long-term incubations. Previous long-term experiments with 13 C-labelled methane led to an unspecific distribution of the 13 C-label. Although quantitative PCR is a sensitive technique to detect small changes in community composition, it does not determine growth yield. Therefore, we tested an alternative method to detect a biomass increase of AOM microorganisms with 15 N-labelled ammonium as N-source. After only 3 weeks, significant 15 N-labelling became apparent in amino acids as major structural units of microbial proteins. This was especially evident in methane-containing incubations, showing the methane-dependent uptake of the 15 N-labelled ammonium by microorganisms. Cell counts demonstrated a two- and fourfold increase at ambient or elevated methane concentrations. With denaturing gradient gel electrophoresis, over 6 months incubation no changes in community composition of sulphate-reducing bacteria and archaea were detected. These data indicate doubling times for AOM microorganisms between 2 and 3.4 months. In conclusion, the 15 N-labelling approach proved to be a sensitive and fast way to show growth of extremely slow-growing microorganisms. 相似文献
20.
The effects of drought stress and season on both allocation of photosynthates to stems and leaves and potential for stem rubber synthesis were studied in guayule ( Parthenium argentatum Gray USDA line 11604). Two-year-old plants grown under field conditions in the Negev desert of Israel were subjected to different irrigation regimes, and water status was assessed by measuring the relative water content (RWC). Undetached plant tips were exposed to a 1 h pulse of 14 CO2 , followed by a 24 h chase. 14 C fixed and translocated to different plants parts and notably 14 C incorporation into rubber and resin fractions was determined. The potential of detached branch slices to incorporate [14 C]-acetate into rubber was also studied. A higher percentage of fixed 14 C was translocated from shoot tips in winter (28–30%) than in summer (15–18%). The percentage of [14 C]-acctate incorporated into the rubber fraction by stem slices was maximal in winter (20%) and minimal in summer (3–5%) in both cases in the absence of drought stress. In summer the translocation of photosynthates into stems was inversely related to plant RWC, dropping from 18% three days after irrigation to 3% 14 days later, and the potential of stems to synthesise rubber was high under drought conditions and low in well irrigated plants. 相似文献