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1.
Abstract: The pentameric subunit composition of a large population (36%) of the cerebellar granule cell GABAA receptors that show diazepam (or clonazepam)-insensitive [3 H]Ro 15-4513 binding has been determined by immunoprecipitation with subunit-specific antibodies. These receptors have α6 , α1 , γ2S , γ2L , and β2 or β3 subunits colocalizing in the same receptor complex. 相似文献
2.
Photosynthetic CO2 -fixation, chlorophyll content, growth rate and nitrate reductase activity were used to examine the influence of NH+ 4 -N and NO− 3 -N on Sphagnum magellanicum cultivated under defined conditions in phytotrons. NO− 3 -concentrations up to 322 μ M were found to be favourable. Increased NH+ 4 concentrations, however, resulted in growth inhibition and decreased chlorophyll content at concentrations ≧ 255 μ M ; e.g. 600 μ M NH+ 4 caused a 20% reduction of nitrate reductase activity and net photosynthesis. For raised bog Sphagna an improved standard nutrient solution is proposed with the following ion concentrations (μ M ): 55 Na+ ; 17 K+ ; 95 NH+ 4 ; 22 Ca2+ ; 22 Mg2+ ; 2 Fe3+ ; 20 Cl− ; 100 NO− 3 ; 57 SO2- 4 ; 7.4 H2 PO− 4 ; trace elements: A-Z solution (Hoagland) 50 μl 1000 ml−1 ; pH 5.8. 相似文献
3.
Nancy C. Lan Jie-Sheng Chen Deborah Johnson † Kelvin W. Gee 《Journal of neurochemistry》1995,64(2):684-688
Abstract: The interactions of the atypical benzodiazepine 4'-chlorodiazepam (Ro 5-4864) with functionally expressed human GABAA receptor cDNAs were determined. Cotransfection of human α2 , β1 , and γ2 subunits was capable of reconstituting a 4'-chlorodiazepam recognition site as revealed by a dose-dependent potentiation of t -[35 S]butylbicyclophosphorothionate ([35 S]TBPS) binding to the GABA-activated chloride channel. This site is found on GABAA receptor complexes containing sites for GABA agonist-like benzodiazepines and neuroactive steroids. The importance of the α subunit was further demonstrated as substitution of either α1 or α3 for the α2 subunit did not reconstitute a 4'-chlorodiazepam recognition site that was capable of modulating [35 S]TBPS binding under the same experimental conditions. The 4'-chlorodiazepam modulatory site was shown to be distinct from the benzodiazepine site, but the phenylquinolines PK 8165 and PK 9084 produced effects similar to 4'-chlorodiazepam, consistent with the previous analysis of the 4'-chlorodiazepam site in brain homogenates. Further analysis of the subunit requirements revealed that coexpression of α2 and β1 alone reconstituted a 4'-chlorodiazepam recognition site. It is interesting, however, that the 4'-chlorodiazepam site was found to inhibit [35 S]TBPS binding to the GABA-activated chloride channel. Thus, the 4'-chlorodiazepam site may be reconstituted with only the α and β polypeptides. 相似文献
4.
The psychoactive ingredient of marijuana, Δ9 -tetrahydrocannabinol (Δ9 -THC), can evoke apoptosis in cultured cortical neurones. Whilst the intracellular mechanisms responsible for this apoptotic pathway remain to be fully elucidated, we have recently identified a role for the CB1 type of cannabinoid (CB) receptor and the tumour suppressor protein, p53. In the current study, we demonstrate the Δ9 -THC promotes a significant increase in lysosomal permeability in a dose- and time-dependent manner. The increase in lysosomal permeability was blocked by the CB1 receptor antagonist, AM251. Δ9 -THC increased the localization of phospho-p53Ser15 at the lysosome and stimulated the release of the lysosomal cathepsin enzyme, cathepsin-D, into the cytosol. The p53 inhibitor, pifithrin-α and small interfering RNA-mediated knockdown of p53 prevented the Δ9 -THC-mediated increase in lysosomal permeability. Furthermore, the Δ9 -THC -mediated induction of apoptosis was abrogated by a cell-permeable cathepsin-D inhibitor (10 μM). Thus, the study demonstrates that Δ9 -THC impacts on the lysosomal system, via p53, to evoke lysosomal instability as an early event in the apoptotic cascade. This provides evidence for a novel link between the CB1 receptor and the lysosomal branch of the apoptotic pathway which is crucial in regulating neuronal viability following exposure to Δ9 -THC. 相似文献
5.
S. Abarzua R. Altenburger R. Callies L.-H. Grimme A. Mayer D. Leibfritz U. Schiewer 《Physiologia plantarum》1993,89(3):659-663
Over a period of several days, rhythmic changes in extracellular NH+ 4 concentration take place in cultures of the cyanobacterium Microcystis firma (Bré et Lenorm.) Schmidle, strain Gromov/St. Petersb. 398, under conditions of restricted CO2 supply and light/dark alternation. The changes are enhanced by nitrate supply. Among the various processes generating intracellular NH+ 4 (NH4 4 uptake, NO− 3 reduction, protein and amino acid degradation, photorespiration), NO− 3 reduction appears as the one most important. This can be concluded from experiments with and without nitrate and/or ammonium in the medium. In the presence of saturating CO2 , continuous light, or continuous darkness, rhythmic NH+4 4 oscillations are not induced. Studies of the incorporation of NH+ 4 nitrogen by in vivo 15 N-NMR show that if CO2 is supplied, 15 N is accumulated in several components with the following time course: in the first hour in Gln (δ), in the second hour in the α-amino groups of most nonbranched amino acids, in the third hour in γ-aminobutyric acid (GABA), Orn (δ) and Lys (ε), and in the sixth hour in Ala. Carbon limitation, however, results in accumulation of label in the amide nitrogen of glutamine only. 相似文献
6.
LUCAS A. CERNUSAK KLAUS WINTER & BENJAMIN L. TURNER 《Plant, cell & environment》2009,32(10):1441-1455
Water-use efficiency and stable isotope composition were studied in three tropical tree species. Seedlings of Tectona grandis , Swietenia macrophylla and Platymiscium pinnatum were grown at either high or low water supply, and with or without added fertilizer. These three species previously exhibited low, intermediate and high whole-plant water-use efficiency ( TE ) when grown at high water supply in unfertilized soil. Responses of TE to water and nutrient availability varied among species. The TE was calculated as experiment-long dry matter production divided by cumulative water use. Species-specific offsets were observed in relationships between TE and whole-plant 13 C discrimination (Δ13 Cp ). These offsets could be attributed to a breakdown in the relationship between Δ13 Cp and the ratio of intercellular to ambient CO2 partial pressures ( c i / c a ) in P. pinnatum , and to variation among species in the leaf-to-air vapour pressure difference ( v ). Thus, a plot of v · TE against c i / c a showed a general relationship among species. Relationships between δ 18 O of stem dry matter and stomatal conductance ranged from strongly negative for S. macrophylla to no relationship for T. grandis . Results suggest inter-specific variation among tropical tree species in relationships between stable isotope ratios ( δ 13 C and δ 18 O) and the gas exchange processes thought to affect them. 相似文献
7.
F. Nicoletti M. L. Barbaccia M. J. Iadarola O. Pozzi H. E. Laird II 《Journal of neurochemistry》1986,46(1):270-273
Abstract: We found that the binding of [3 H]prazosin, a selective ligand for α1 -adrenergic recognition sites, is significantly lower in the frontal cortex of the genetically epilepsy-prone rats (GEPRs), as compared with normal Sprague-Dawley rats. Scatchard analysis reveals a decrease in the B max of [3 H]prazosin binding with no change in the apparent K D , suggesting that there are fewer α1 -adrenergic recognition sites in the frontal cortex of the GEPR. This abnormality is associated with a reduced capacity of norepinephrine (NE) to stimulate [3 H]inositol monophosphate ([3 H]IP1 ) formation in frontal cortex slices prelabeled with [3 H]inositol. No significant differences in [3 H]prazosin binding as well as NE-stimulated [3 H]IP1 formation have been observed in other brain regions including hippocampus, corpus striatum, and inferior colliculus. These results indicate that a deficit in the α1 -adrenergic receptor system in the frontal cortex may play a role in the seizure process in the GEPR. 相似文献
8.
Irreversible blockade of sigma-1 receptors by haloperidol and its metabolites in guinea pig brain and SH-SY5Y human neuroblastoma cells 总被引:3,自引:0,他引:3
We evaluated the effect of haloperidol (HP) and its metabolites on [3 H](+)-pentazocine binding to σ1 receptors in SH-SY5Y human neuroblastoma cells and guinea pig brain P1 , P2 and P3 subcellular fractions. Three days after a single i.p. injection in guinea pigs of HP (but not of other σ1 antagonists or (−)-sulpiride), [3 H](+)-pentazocine binding to brain membranes was markedly decreased. Recovery of σ1 receptor density to steady state after HP-induced inactivation required more than 30 days. HP-metabolite II (reduced HP, 4-(4-chlorophenyl)-α-(4-fluorophenyl)-4-hydroxy-1-piperidinebutanol), but not HP-metabolite I (4-(4-chlorophenyl)-4-hydroxypiperidine), irreversibly blocked σ1 receptors in guinea pig brain homogenate and P2 fraction in vitro . We found similar results in SH-SY5Y cells, which suggests that this process may also take place in humans. HP irreversibly inactivated σ1 receptors when it was incubated with brain homogenate and SH-SY5Y cells, but not when incubated with P2 fraction membranes, which suggests that HP is metabolized to inactivate σ1 receptors. Menadione, an inhibitor of the ketone reductase activity that leads to the production of HP-metabolite II, completely prevented HP-induced inactivation of σ1 receptors in brain homogenates. These results suggest that HP may irreversibly inactivate σ1 receptors in guinea pig and human cells, probably after metabolism to reduced HP. 相似文献
9.
LUCAS C. R. SILVA MADHUR ANAND JULIANO M. OLIVEIRA† VALÉRIO D. PILLAR† 《Global Change Biology》2009,15(10):2387-2396
Araucaria angustifolia (Bertol.) Kuntze is an indigenous conifer tree restricted to the southern region of South America that plays a key role in the dynamics of regional ecosystems where forest expansion over grasslands has been observed. Here, we evaluate the changes in intrinsic water use efficiency (iWUE) and basal area increment (BAI) of this species in response to atmospheric CO2 , temperature and precipitation over the last century. Our investigation is based on tree-rings taken from trees located in forest and grassland sites in southern Brazil. Differences in carbon isotopic composition ( δ 13 C), 13 CO2 discrimination (Δ13 C) and intracellular carbon concentration ( C i ) are also reported. Our results indicate an age effect on Δ13 C in forest trees during the first decades of growth. This age effect is not linked to an initial BAI suppression, suggesting the previous existence of nonforested vegetation in the forest sites. After maturity all trees show similar temporal trends in carbon isotope-derived variables and increasing iWUE, however, absolute values are significantly different between forest and grassland sites. The iWUE is higher in forest trees, indicating greater water competition or nutritional availability, relative to grassland, or both. BAI is also higher in forest trees, but it is not linked with iWUE or atmospheric CO2 . Nevertheless, in both forest and grassland sites A. angustifolia has had growth limitations corresponding to low precipitation and high temperatures observed in the 1940s. 相似文献
10.
Jasmina B. Mackic Martin H. Weiss Wesley Miao Erlinda Kirkman †Jorge Ghiso †Miguel Calero ‡James Bading †Blas Frangione § Berislav V. Zlokovic 《Journal of neurochemistry》1998,70(1):210-215
Abstract: Senescent squirrel monkey is a valuable model to study pathogenesis of cerebrovascular amyloid angiopathy (CAA). Cerebrovascular sequestration and blood-brain barrier (BBB) permeability to 125 I-amyloid β(1-40) synthetic peptide (sAβ1-40 ) were studied in adult versus aged squirrel monkey 1 h after a single intravenous injection. In aged monkey, the half-time of elimination of sAβ1-40 , t e 1/2 , was prolonged by 0.6 h, the systemic clearance, Cl SS , was reduced from 1.8 to 1.1 ml/min/kg, and the mean residence time of intact peptide in the circulation was increased by 1 h (45%). In adult monkey, cerebrovascular sequestration of intact sAβ1-40 was significant, and the BBB permeability was 18.6-fold higher than for inulin. In aged monkey, the sequestration of intact sAβ1-40 by cortical and leptomeningeal microvessels and the BBB permeability were increased by 5.9, 1.8-, and 2.1-fold, respectively, in the presence of an unchanged barrier to inulin. In brain parenchyma of aged animals, 76.1% of circulating sAβ1-40 remained intact versus 45.7% in adult. We conclude that multiple age-related systemic effects, i.e., reduced body elimination and systemic clearance of sAβ1-40 , and reduced peripheral metabolism, may act in concert with BBB mechanisms, i.e., increased transendothelial transport and microvascular accumulation of blood-borne sAβ1-40 , and reduced brain metabolism to enhance the development of CAA. 相似文献
11.
Cloning and Characterization of a Mouse σ1 Receptor 总被引:1,自引:1,他引:0
Ying-Xian Pan Jianfeng Mei Jin Xu Ban-Lin Wan Amy Zuckerman Gavril W. Pasternak 《Journal of neurochemistry》1998,70(6):2279-2285
Abstract: A cDNA clone (S2-1a) isolated from a mouse brain cDNA library, using a guinea pig σ1 cDNA as probe, has high homology to the predicted protein sequence of the guinea pig (88%) and human (90%) σ1 receptors. Northern analysis revealed a major mRNA of ∼1.8 kb in a wide range of mouse tissues, with highest levels in brain, liver, kidney, and thymus. Southern analysis and chromosomal mapping in the mouse suggested a single-copy gene in region A5-B2 of chromosome 4. Expression of the clone in MCF-7 and CHO cells led to a pronounced increase in (+)-[3 H]pentazocine binding with a selectivity profile consistent with σ1 receptors. In vitro translation yielded a protein of ∼28 kDa, as did transfection of a probe containing the hemagglutinin (HA) epitope (S2-1a.HA) into CHO cells, as determined by western analysis using an antibody directed against HA. (+)-[3 H]-Pentazocine binding to immunopurified HA-tagged receptor demonstrated conclusively that S2-1a.HA encodes a high-affinity (+)-[3 H]pentazocine binding site with characteristics of a murine σ1 receptor. An antisense oligodeoxynucleotide designed from S2-1a potentiated opioid analgesia in vivo. 相似文献
12.
K. S. METCALF J. SUTTON M. D. MOLONEY L. A. BROWN K. R. PEEL A. BAINES 《Cytopathology》1994,5(4):219-225
Four cytology sampling methods were compared in 1063 patients referred for colposcopy with a recent abnormal smear. A dyskaryotic smear of any grade was considered a positive result, though comparisons were limited to cases with a subsequent biopsy confirming CINII or III. There were no differences between the abilities of any of the four methods to detect higher grades of CIN (χ2 3 =4.603, P >0.20). the presence or absence of endocervical cells in a smear was not significantly associated with any variation in success rate (χ2 1 =0.959, P >0.30). the joint analysis of the four methods and the presence/absence of endocervical cells also showed no significant effects (χ2 7 =12.768, 0.1 > P >0.05). In the latter analysis the trend towards a conventional level of significance was accounted for by the Aylesbury spatula giving a relatively high success rate when endocervical cells were present. the suggestion of advantage for the Aylesbury spatula merits further investigation. 相似文献
13.
Abstract: Tolerance to and withdrawal from pentobarbital were induced in rats by continuous intracerebroventricular infusion via subcutaneously implanted osmotic minipumps. In situ hybridization of GABAA receptor α1 - and β3 -subunit mRNA was conducted using synthetic 3'- end 35 S-dATP-labeled oligodeoxynucleotide probes. Results were quantified by film densitometry. In animals that were tolerant to pentobarbital, levels of α1 -subunit mRNA were decreased in hippocampus, superior colliculus, and inferior colliculus, but levels of β3 -subunit mRNA were not affected. Dramatically increased levels of GABAA receptor subunit mRNA were observed in animals 24 h after withdrawal from chronic pentobarbital treatment. These increases occurred in cerebral cortex and cerebellum for the α1 subunit and in cerebral cortex only for the β3 -subunit. These data provide further support to the structural and pharmacological GABAA receptor heterogeneity in discrete brain areas. The observed changes of subunit expression may underlie, at least in part, the receptor up- and down-regulation observed in receptor ligand binding studies. 相似文献
14.
Abstract: The excitatory amino acid glutamate was previously shown to stimulate aerobic glycolysis in astrocytes by a mechanism involving its uptake through an Na+ -dependent transporter. Evidence had been provided that Na+ ,K+ -ATPase might be involved in this process. We have now measured the activity of Na+ ,K+ -ATPase in cultured astrocytes, using ouabain-sensitive 86 Rb uptake as an index. l -Glutamate increases glial Na+ ,K+ -ATPase activity in a concentration-dependent manner with an EC50 = 67 µ M . Both l - and d -aspartate, but not d -glutamate, produce a similar response, an observation that is consistent with an uptake-related effect rather than a receptor-mediated one. Under basal conditions, concentration-dependent inhibition of Na+ ,K+ -ATPase activity in astrocytes by ouabain indicates the presence of a single catalytic site with a low affinity for ouabain ( K 0.5 = 113 µ M ), compatible with the presence of an α1 isozyme. On stimulation with glutamate, however, most of the increased activity is inhibited by low concentrations of ouabain ( K 0.5 = 20 n M ), thus revealing a high-affinity site akin to the α2 isozyme. These results suggest that astrocytes possess a glutamate-sensitive isoform of Na+ ,K+ -ATPase that can be mobilized in response to increased neuronal activity. 相似文献
15.
The effect of N-source on the interaction between carbon and nitrogen metabolism was evaluated by measuring phosphoenolpyruvate carboxylase (PEPcase; EC 4.1.1.31) activity in callus tissue of maize ( Zea mays L. cv. Prisma) sub-cultured under different N-nutrition conditions: nitrate, ammonium or combinations of both. By comparison with the condition where both salts were supplied (control), nitrate as the sole N-source led to an increase in PEPcase activity. Ammonium alone gave a drastic decrease of tissue growth. Extracts from calli grown on equivalent media supplied with 15 N-nitrate or 15 N-ammonium were analysed by 15 N-NMR. The labelling of amino acids in the NMR spectra showed that when 15 NO− 3 was the unique N-source, 15 N mainly accumulated in NδGln, Glu and Ala. With 15 NH+ 4 only the NδGln and γ-aminobutyric acid were labelled. The addition of both gave rise to labelled Gln, Asn, Glu, Asp, Ala, Val and γ-aminobutyric acid independently of the origin of the label. In vivo 31 P-NMR allowed the cytoplasmic and vacuolar pH to be measured. The cytoplasmic pH showed an increase of approximately 0.3 units when nitrate was the sole source of nitrogen and a corresponding decrease when ammonium was added alone. Vacuolar pH decreased in both treatments. These results are discussed on the basis of the effect of the N-source on carbon metabolism. A hypothesis of PEPcase activation as due to the increase of cytoplasmic pH upon nitrate uptake is proposed. 相似文献
16.
Although it is widely recognised that spatial subdivision of populations is common in nature, there is no consensus as to how metapopulation dynamics affect genetic diversity. We investigated the genetic differentiation of natterjack toads, Bufo calamita , in three regions of Britain where habitat continuity indicated the likely occurrence of extensive metapopulations. Our intention was to determine whether genetic analysis supported the existence of metapopulation structures, if so of what type, and to identify barriers to migration between subpopulations. Allele frequencies were determined across eight polymorphic microsatellite loci for a total of 24 toad subpopulations at three separate sites. Genetic differentiation was assessed using five measures of genetic distance, notably F ST , R ST , Nei's standard distance D s , Δμ2 and the Cavalli-Sforza chord distance D c . B. calamita exhibited small but significant levels of genetic differentiation between subpopulations in all three study areas, and genetic and geographic distance correlations indicated isolation-by-distance effects in all three cases. The effects on correlation strengths of compensation for positive (sea, rivers, urban development) and negative (pond clusters) barriers to toad migration between the subpopulations in each area were also determined. D c , a measure which assumes that differentiation is caused by drift with negligible mutation effect, yielded the most plausible interpretation of metapopulation structures. Overall the patterns of genetic variation suggested the existence of a mixed metapopulation model for this species, with high levels of gene flow compatible with one version of the classical model but often supported by particularly stable subpopulations as in the mainland-island model. 相似文献
17.
C.E. DEANE-DRUMMOND 《Plant, cell & environment》1985,8(2):105-110
Abstract. Net NO3 uptake by NO− 3 deficient Chara cells was used to calculate [NO− 3 ]c assuming that the cytoplasm occupies 10% total volume and that nitrate reduction and storage are negligible (i.e. maximum [NO− 3 ]c was calculated). A linear relationship was found between NO− 3 efflux and [NO− 3 ]c . There was an initial burst of NO− 3 efflux when NH+ 4 was added, followed by a slower efflux rate which matched influx rate such that net NO− 3 uptake was zero. Over 50% of NO− 3 that had been taken up in 2 h was lost within the first 5 min of NH+ 4 addition. The Nernst equation was used to predict the direction of the electrochemical driving force for NO− 3 entry. Under the experimental conditions used NO− 3 efflux is actively transported. The differential involvement of both NO− 3 influx and NO− 3 efflux in the regulation of NO− 3 uptake is discussed and a model is proposed to account for these results which envisages discrete NO− 3 influx and NO− 3 efflux carriers. 相似文献
18.
Alteration of N nutrition in Myrica gale induces changes in nodule growth, nodule activity and amino acid composition 总被引:1,自引:0,他引:1
Changes in nodule growth and activity and in the concentrations of soluble N compounds in nodules, leaves and xylem sap under conditions of altered N nutrition in the actinorhizal plant Myrica gale L. are reported. Altering the N nutrition of symbiotic plants may alter the internal regulation of combined N which in turn may regulate nodule growth and activity. Flushing nodules daily with 100% O2 caused a decline in amide concentration and an increase in nodule growth although plants had recovered some nitrogenase activity within 4 h of exposure to O2 . Samples of nodules, leaves and xylem sap were derivatized and amino acids identified and quantified using either reverse phase high performance liquid chromatography or gas chromatography-mass spectrometry in single ion monitoring mode. The ratio of asparagine in the nodules to that in the xylem was much higher in plants fed N (6.7 for NH+ 4 -fed and 8.3 for NO− 3 -fed plants) than for N2 -fixing plants (2.5). Significant amounts of 15 N added as 15 NH+ 4 or 15 NO− 3 accumulated in nodules following accumulation in the shoot which is consistent with the translocation of N to the nodules via the phloem. The uptake of 15 NH+ 4 led to the synthesis and subsequent translocation of glutamine in the xylem sap. These results are discussed in terms of the feedback mechanisms that may regulate nitrogen fixation in Myrica root nodules. 相似文献
19.
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
20.
Abstract: Ischemia-induced changes in 31 P NMR relaxation were examined in 16 piglets. NMR spectra were acquired under control conditions and during complete cerebral ischemia induced via cardiac arrest. Changes in T 1 were assessed directly in six animals during control conditions and after 30–45 min of complete ischemia when changes in brain P1 levels had reached a plateau. The T 1 for P1 did not change, i.e., 2.3 ± 0.5 s during control conditions versus 2.4 ± 1.0 s during ischemia. To evaluate phosphocreatine and ATP, two types of spectra, with a long (25-s) or short (1-s) interpulse delay time, were collected during the first 10 min of ischemia (n = 10). Both types of spectra showed the same time course of changes in phosphocreatine and ATP levels, implying that the T 1 relaxation times do not change during ischemia. There were no changes in the linewidths of phosphocreatine, ATP, or P1 during ischemia, implying that the T *2 values remain constant. Our results suggest that the 31 P T 1 and T *2 for phosphocreatine, Pi , and ATP do not change during ischemia, and therefore changes in 31 P NMR peak intensity accurately reflect changes in metabolite concentrations. 相似文献