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1.
Complete dechlorination of tetrachloroethene to ethene in presence of methanogenesis and acetogenesis by an anaerobic sediment microcosm 总被引:5,自引:0,他引:5
An anaerobic consortium taken from brackish sediments, enriched byPCE/CH3OH sequential feeding, was capable of completely dechlorinating tetrachloroethene(PCE) to ethene (ETH). In batch experiments, PCE (0.5 mM) was dechlorinated to ethene (ETH) in approximately 75 h with either CH3OH or H2 as the electron donor. When VC (0.5 mM) was added instead of PCE it was dechlorinated without any initial lag by the PCE/CH3OHenriched consortium, although at a lower dechlorination rate. In batch tests H2 could readilyreplace CH3OH for supporting PCE dechlorination, with a similar PCE dechlorination rate andproduct distribution with respect to those observed with methanol. This indicates that H2 productionduring CH3OH fermentation was not the rate-limiting step of PCE or VC dechlorination.Acetogenesis was the predominant activity when methanol was present. A remarkable homoacetogenicactivity was also observed when hydrogen was supplied instead of methanol. 相似文献
2.
Aulenta F Gossett JM Papini MP Rossetti S Majone M 《Biotechnology and bioengineering》2005,91(6):743-753
This study examined the ability of different electron donors (i.e., hydrogen, methanol, butyrate, and yeast extract) to sustain long-term (500 days) reductive dechlorination of tetrachloroethene (PCE) in anerobic fill-and-draw bioreactors operated at 3:1 donor:PCE ratio (defined on a total-oxidation basis for the donor). Initially (i.e., until approximately day 80), the H(2)-fed bioreactor showed the best ability to completely dechlorinate the dosed PCE (0.5 mmol/L) to ethene whereas, in the presence of methanol, butyric acid or no electron donor added (but low-level yeast extract), dechlorination was limited by the fermentation of the organic substrates and in turn by H(2) availability. As the study progressed, the H(2)-fed reactor experienced a diminishing ability to dechlorinate, while more stable dechlorinating activity was maintained in the reactors that were fed organic donors. The initial diminished ability of the H(2)-fed reactor to dechlorinate (after about 100 days), could be partially explained in terms of increased competition for H(2) between dechlorinators and methanogens, whereas other factors such as growth-factor limitation and/or accumulation of toxic and/or inhibitory metabolites were shown to play a role for longer incubation periods (over 500 days). In spite of decreasing activity with time, the H(2)-fed reactor proved to be the most effective in PCE dechlorination: after about 500 days, more than 65% of the added PCE was dechlorinated to ethene in the H(2)-fed reactor, versus 36%, 22%, and <1% in the methanol-fed, butyrate-fed, and control reactors, respectively. 相似文献
3.
Heidrun Scholz-Muramatsu Anke Neumann Michael Meßmer Edward Moore Gabriele Diekert 《Archives of microbiology》1995,163(1):48-56
A strictly anaerobic bacterium dechlorinating tetrachloroethene (perchloroethylene, PCE) via trichloroethene (TCE) to cis-1,2-dichloroethene (DCE) was isolated from activated sludge with pyruvate plus PCE as energy substrates. The organism, called Dehalospirillum multivorans, is a gram-negative spirillum that does not form spores. The G+C content of the DNA was 41.5 mol%. According to 16S rRNA gene sequence analysis, D. multivorans represents a new genus and a new species belonging to the epsilon subdivision of Proteobacteria. Quinones, cytochromes b and c, and corrinoids were extracted from the cells. D. multivorans grew in defined medium with PCE and H2 as sole energy sources and acetate as carbon source; the growth yield under these conditions was 1.4g of cell protein per mol chloride released. Alternatively to PCE, fumarate and nitrate could serve as electron acceptors; sulfate could not replace fumarate, nitrate, or PCE in this respect. In addition to H2, the organism utilized a variety of electron donors for dechlorination (pyruvate, lactate, ethanol, formate, glycerol). Upon growth on pyruvate plus PCE, the main fermentation products formed were acetatc, lactate, DCE, and H2. At optimal pH (7.3–7.6) and temperature (30°C), and in the presence of pyruvate (20mM) and PCE (160M), a dechlorination rate of about 50 nmol min-1 (mg cell protein)-1 and a doubling time of about 2.5h were obtained with growing cultures. The ability to reduce PCE to DCE appears to be constitutive under the experimental conditions applied since cultures growing in the absence of PCE for several generations immediately started dechlorination when transferred to a medium containing PCE. The organism may be useful for bioremediation of environments polluted with tetrachloroethene.Abbreviations
PCE
Perchloroethylene, tetrachloroethene
-
TCE
Trichloroethene
-
DCE
cis-1,2-Dichloroethene
-
CHC
Chlorinated hydrocarbon 相似文献
4.
Oxidant Injury in PC12 Cells—A Possible Model of Calcium "Dysregulation" in Aging: I. Selectivity of Protection Against Oxidative Stress 总被引:1,自引:1,他引:0
Abstract: Previous research has suggested that the initial effects of cellular free radical neurotoxic insult involve large increases in intracellular Ca2+. However, the exact role of oxidative stress on the various parameters involved in these increases has not been specified. The present experiments were performed to examine these parameters in PC12 cells exposed to 5, 25, or 300 µM H2O2 for 30 min in growth medium alone or containing either nifedipine (L-type Ca2+ antagonist), conotoxin (N-type antagonist), Trolox (vitamin E analogue), or α-phenyl-n-tert-butylnitrone (nitrone trapping agent; PBN). The concentrations of H2O2 were chosen by examining the degree of cell killing induced by exposure to graded concentrations of H2O2. The 5 and 25 µM concentrations of H2O2 produced no significant cell killing at either 30 min or 24 h after treatment, whereas the 300 µM concentration produced a moderate degree of cell killing that did not increase between the two times. Fluorescent imaging was used to visualize intracellular Ca2+ changes in fura-2-loaded cells. Baseline (pre-30 mM KCI) Ca2+ levels were increased significantly by H2O2 treatment (e.g., 300 µM, 200%), but the rise in the level of free intracellular Ca2+ after KCI stimulation (i.e., peak) was decreased (e.g., 300 µM, 50%) and the cell's ability to sequester or extrude the excess Ca2+ (i.e., Ca2+ recovery time) after depolarization was decreased significantly. All compounds prevented baseline Ca2+ increases and, with the exception of conotoxin, antagonized the peak decreases in Ca2+. It is interesting that after 300 µM H2O2 exposure, only Trolox was partially effective in preventing these deficits in recovery. Conotoxin increased the decrement recovery in the absence of H2O2. However, in cells exposed to 5 or 25 µM H2O2, conotoxin as well as the other agents were effective in preventing the deficits in recovery. 相似文献
5.
Enhanced Depolarization-Evoked Calcium Signal and Reduced [ATP]/[ADP] Ratio Are Unrelated Events Induced by Oxidative Stress in Synaptosomes 总被引:1,自引:1,他引:0
Abstract: Oxidative insult elicited by hydrogen peroxide (H2O2) was previously shown to increase the basal intracellular Ca2+ concentration in synaptosomes. In the present study, the effect of H2O2 on the depolarization-evoked [Ca2+] signal was investigated. Pretreatment of synaptosomes with H2O2 (0.1–1 mM) augmented the [Ca2+] rise elicited by high K+ depolarization with essentially two alterations, the sudden sharp rise of [Ca2+]i due to K+ depolarization is enhanced and, instead of a decrease to a stable plateau, a slow, steady rise of [Ca2+]i follows the peak [Ca2+]i. H2O2 in the same concentration range lowered the ATP level and the [ATP]/[ADP] ratio. When carbonyl cyanide p-(trifluoromethoxy)phenylhydrazone (FCCP) (1 µM) or rotenone (2 µM)/oligomycin (10 µM) was applied initially to block mitochondrial ATP production, the lowered [ATP]/[ADP] ratio was further reduced by subsequent addition of 0.5 mM H2O2. The decline of the [ATP]/[ADP] ratio was parallel with but could not explain the enhanced K+-evoked [Ca2+]i signal, indicated by experiments in which the [ATP]/[ADP] ratio was decreased by FCCP (0.1 µM) or rotenone (2 µM) to a similar value as by H2O2 without causing any alteration in the [Ca2+]i signal. These results indicate that H2O2-evoked oxidative stress, in its early phase, gives rise to a complex dysfunction in the Ca2+ homeostasis and, parallel with it, to an impaired energy status. 相似文献
6.
Reductive dechlorination of tetrachloroethene by a stepwise catalysis of different organohalide respiring bacteria and reductive dehalogenases 总被引:1,自引:0,他引:1
Maillard J Charnay MP Regeard C Rohrbach-Brandt E Rouzeau-Szynalski K Rossi P Holliger C 《Biodegradation》2011,22(5):949-960
The enrichment culture SL2 dechlorinating tetrachloroethene (PCE) to ethene with strong trichloroethene (TCE) accumulation
prior to cis-1,2-dichloroethene (cis-DCE) formation was analyzed for the presence of organohalide respiring bacteria and reductive dehalogenase genes (rdhA). Sulfurospirillum-affiliated bacteria were identified to be involved in PCE dechlorination to cis-DCE whereas “Dehalococcoides”-affiliated bacteria mainly dechlorinated cis-DCE to ethene. Two rdhA genes highly similar to tetrachloroethene reductive dehalogenase genes (pceA) of S. multivorans and S. halorespirans were present as well as an rdhA gene very similar to the trichloroethene reductive dehalogenase gene (tceA) of “Dehalococcoides ethenogenes” strain 195. A single strand conformation polymorphism (SSCP) method was developed allowing the simultaneous detection of
the three rdhA genes and the estimation of their abundance. SSCP analysis of different SL2 cultures showed that one pceA gene was expressed during PCE dechlorination whereas the second was expressed during TCE dechlorination. The tceA gene was involved in cis-DCE dechlorination to ethene. Analysis of the internal transcribed spacer region between the 16S and 23S rRNA genes revealed
two distinct sequences originating from Sulfurospirillum suggesting that two Sulfurospirillum populations were present in SL2. Whether each Sulfurospirillum population was catalyzing a different dechlorination step could however not be elucidated. 相似文献
7.
Abstract: Methylmercury (MeHg) increases the concentration of intracellular Ca2+ ([Ca2+]i) and another endogenous polyvalent cation in both synaptosomes and NG108-15 cells. In synaptosomes, the elevation in [Ca2+]i was strictly dependent on extracellular Ca2+ (Ca2+e); similarly, in NG108-15 cells, a component of the elevations in [Ca2+]i was Ca2+e dependent. The MeHg-induced elevations in endogenous polyvalent cation concentration were independent of Ca2+e in synaptosomes and NG108-15 cells. The pattern of alterations in fura-2 fluorescence suggested the endogenous polyvalent cation may be Zn2+. Using 19F-NMR spectroscopy of rat cortical synaptosomes loaded with the fluorinated chelator 1,2-bis(2-amino-5-fluorophenoxy)ethane-N,N,N′,N′-tetraacetic acid (5F-BAPTA), we have determined unambiguously that MeHg increases the free intrasynaptosomal Zn2+ concentration ([Zn2+]i). In buffer containing 200 µM EGTA to prevent the Ca2+e-dependent elevations in [Ca2+]i, the [Zn2+]i was 1.37 ± 0.20 nM; following a 40-min exposure to MeHg-free buffer [Zn2+]i was 1.88 ± 0.53 nM. Treatment of synaptosomes for 40 min with 125 µM MeHg yielded [Zn2+]i of 2.69 ± 0.55 nM, whereas 250 µM MeHg significantly elevated [Zn2+]i to 3.99 ± 0.68 nM. No Zn2+ peak was observed in synaptosomes treated with the cell-permeant heavy metal chelator N,N,N′,N′-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN, 100 µM) following 250 µM MeHg exposure. [Ca2+]i in buffer containing 200 µM EGTA was 338 ± 26 nM and was 370 ± 64 nM following an additional 40-min exposure to MeHg-free buffer. [Ca2+]i was 498 ± 28 or 492 ± 53 nM during a 40-min exposure to 125 or 250 µM MeHg, respectively. None of the values of [Ca2+]i differed significantly from either pretreatment levels or buffer-treated controls. 相似文献
8.
Sayali S. Patil Eric M. Adetutu Arturo Aburto-Medina Ian R. Menz Andrew S. Ball 《Biotechnology letters》2014,36(1):75-83
Chlorinated ethenes are of environmental concern with most reports of successful microbial-mediated remediation being associated with major dechlorinating groups such as Dehalococcoides (Dhc) species. However, limited information is available on the community dynamics and dechlorinating activities of indigenous non-Dhc groups. Here, we present evidence of dechlorination of tetrachloroethene (perchloroethylene, PCE) in groundwater samples by indigenous microbial communities. 100 % PCE conversion to ethene was observed in acetate-stimulated 24 week-microcosms (controls; 15 %). Microbial community profiles showed dominance by groups such as Proteobacteria, Spirochaetes, Firmicutes, Methanomicrobiaceae and Methanosarcinaceae. Pareto-Lorenz (PL) analyses suggested an adapted (45 % PL value) but variable bacterial community (55.5 % Δ t(week)) compared to Archaea (25 % PL value; 46.9 % Δ t(week)). Our findings provide evidence of dechlorinating potential of indigenous microorganisms and useful information on their dynamics which may be exploited for in situ groundwater bioremediation. 相似文献
9.
The unique capacity of Dehalococcoides ethenogenes of completely dechlorinating the common groundwater pollutant tetrachloroethene (PCE) to the harmless ethene makes this microorganism very attractive for application in natural or engineered bioremediation systems. In this study, the qualitative and quantitative determination of Dehalococcoides spp. in a lab-scale bioreactor was performed based on the combination of fluorescent in situ hybridisation (FISH) for specific detection, and kinetic batch tests at non-limiting hydrogen and PCE concentration for quantitative determination. The dechlorinating bioreactor was operated at a high and constant PCE loading rate of 255 mol PCE [g volatile suspended solids (VSS)]–1 day–1. Pale coccoid cells resembling the distinctive morphotype of D. ethenogenes were present in the microbial culture. These cocci hybridised with both eubacterial probes and the Dhe1259t probe recently designed for detecting Dehalococcoides spp. Positive hybridisation was also observed when the DHC1377 reverse primer was used as a specific probe and applied to the dechlorinating microbial consortium. The maximum dechlorination rate obtained under non-limiting hydrogen and PCE concentrations was 3.22 ± 0.08 mmol Cl– l–1 day–1. From the specific activity of D. ethenogenes [i.e. 0.055 ± 0.008 mmol Cl– (mg VSS)–1 day–1], as reported from pure culture study, this observed maximum rate corresponded to a concentration of this bacterium in the mixed liquor of the bioreactor of 59.0±10.4 mg VSS·l–1 (41.5±11.2% of overall VSS). This calculated relative abundance of D. ethenogenes was in agreement with the percentage of methanol (in terms of reducing equivalents) channeled to reductive dechlorination (approximately 30%) supporting the assumption that most reductive dechlorination was actually due to this microorganism. 相似文献
10.
Tetrachloroethene (PCE) and trichloroethene (TCE) are common groundwater contaminants that also impact tidal flats, especially
near urban and industrial areas. However, very little is known about dechlorinating microbial communities in tidal flats.
Titanium pyrosequencing, 16S rRNA gene clone libraries, and dechlorinator-targeted quantitative real-time PCR (qPCR) characterized
reductive dechlorinating activities and populations in tidal flat sediments collected from South Korea’s central west coast
near Kangwha. In microcosms established with surface sediments, PCE dechlorination to TCE began within 10 days and 100% of
the initial amount of PCE was converted to TCE after 37 days. cis-1,2-Dichloroethene (cis-DCE) was observed as dechlorination end product in microcosms containing sediments collected from deeper zones (i.e., 35–40 cm
below ground surface). Pyrosequencing of bacterial 16S rRNA genes and 16S rRNA gene-targeted qPCR results revealed Desulfuromonas michiganensis-like populations predominanted in both TCE and cis-DCE producing microcosms. Other abundant groups included Desulfuromonas thiophila and Pelobacter acidigallici-like populations in the surface sediment microcosms, and Desulfovibrio dechloracetivorans and Fusibacter paucivorans-like populations in the deeper sediment microcosms. Dehalococcoides spp. populations were not detected in these sediments before and after incubation with PCE. The results suggest that tidal
flats harbor novel, salt-tolerant dechlorinating populations and that titanium pyrosequencing provides more detailed insight
into community structure dynamics of the dechlorinating microcosms than conventional 16S rRNA gene sequencing or fingerprinting
methods. 相似文献
11.
Abstract: Noradrenergic neuronal networks originating in the locus coeruleus have been implicated in the stress response. In order to study this system in vitro, we have employed a locus coeruleus-like cell line, CATH.a, and have determined the effect of dexamethasone on receptor-mediated second messenger responses. The CATH.a cell line produced increases in intracellular cyclic AMP conversion in response to corticotrophin-releasing factor (EC50 = 6.93 ± 1.26 nM, maximum conversion = 4.11 ± 0.20%) and vasoactive intestinal polypeptide (EC50 = 240 ± 40 nM, maximum conversion = 8.92 ± 1.24%). Forskolin (10 µM) increased conversion from 0.48 ± 0.05 to 6.39 ± 0.38%. The α2-adrenoceptor agonist 5-bromo-N-(4,5-dihydro-1H-imidazol-2-yl)-6-quinoxalinamine (UK14304) inhibited the forskolin response with an IC50 of 6.76 ± 0.11 nM. Carbachol increased total 3H-labelled inositol phosphate accumulation to a maximum of 3.01 ± 0.79 fold basal (EC50 = 7.94 ± 0.14 µM). Bradykinin produced a maximum 1.81 ± 0.05 fold basal stimulation of phosphoinositide hydrolysis (EC50 = 9.12 ± 0.16 nM). Both carbachol and bradykinin increased intracellular Ca2+ concentration probably via a combination of mobilisation of intracellular stores and gating of extracellular Ca2+. Incubation for 24 h with the glucocorticoid receptor agonist, dexamethasone (1 µM), significantly potentiated the receptor-mediated phosphoinositide responses to all the agents tested; however, of the receptor-mediated increases in cyclic AMP conversion, only the vasoactive intestinal polypeptide response was potentiated. These results show that the CATH.a cell line displays some of the properties expected of locus coeruleus neurons and that glucocorticoid receptor stimulation selectively modulates receptor-mediated increases in second messenger formation. 相似文献
12.
Osmotic Swelling-Induced Changes in Cytosolic Calcium Do Not Affect Regulatory Volume Decrease in Rat Cultured Suspended Cerebellar Astrocytes 总被引:2,自引:1,他引:1
Sandra Morales-Mulia Luis Vaca Arturo Hernandez-Cruz Herminia Pasantes-Morales 《Journal of neurochemistry》1998,71(6):2330-2338
Abstract: Hyposmotic swelling-induced changes in intracellular Ca2+ concentration ([Ca2+]i) and their influence on regulatory volume decrease (RVD) were examined in rat cultured suspended cerebellar astrocytes. Hyposmotic media (50 or 30%) evoked an immediate rise in [Ca2+]i from 117 nM to a mean peak increase of 386 (50%) and 220 nM (30%), followed by a maintained plateau phase. Ca2+ influx through the plasmalemma as well as release from internal stores contributed to this osmosensitive [Ca2+]i elevation. Omission of external Ca2+ or addition of Cd2+, Mn2+, or Gd3+ did not reduce RVD, although it was decreased by La3+ (0.1–1 mM). Verapamil did not affect either the swelling-evoked [Ca2+]i or RVD. Maneuvers that deplete endoplasmic reticulum (ER) Ca2+ stores, such as treatment (in Ca2+-free medium) with 0.2 µM thapsigargin (Tg), 10 µM 2,5-di-tert-butylhydroquinone, 1 µM ionomycin, or 100 µM ATP abolished the increase in [Ca2+]i but did not affect RVD. However, prolonged exposure to 1 µM Tg blocked RVD regardless of ER Ca2+ content or cytosolic Ca2+ levels. Ryanodine (up to 100 µM) and caffeine (10 mM) did not modify [Ca2+]i or RVD. BAPTA-acetoxymethyl ester (20 µM) abolished [Ca2+]i elevation without affecting RVD, but at higher concentrations BAPTA prevented cell swelling and blocked RVD. We conclude that the osmosensitive [Ca2+]i rise occurs as a consequence of increased Ca2+ permeability of plasma and organelle membranes, but it appears not relevant as a transduction signal for RVD in rat cultured cerebellar astrocytes. 相似文献
13.
Abstract: This study investigated possible D1/D2 interactions in rat and bovine striatal tissue by examining the effects of D2 antagonists on the action of dopamine at D1 dopamine receptors. In addition, the extent to which D2 antagonists may induce an agonist low-affinity state of the D1 receptor was evaluated in comparison with the effects of the guanine nucleotide analogue 5′-guanylylimidodiphosphate [Gpp(NH)p]. In saturation experiments dopamine caused a dose-dependent decrease in rat striatal and bovine caudate D1 receptor density. This effect of dopamine, which has been shown to be sensitive to Gpp(NH)p, was not altered by pretreatment with either of the selective D2 antagonists eticlopride (200 nM) or domperidone (200 nM). Results from displacement experiments show that the affinity of dopamine for D1 receptors and the proportion of receptors in an agonist high-affinity state, are reduced by Gpp(NH)p (100 µM) but not by eticlopride. A molar excess of dopamine (100 µM) promotes the dissociation of (±)-8-chloro-2,3,4,5-tetrahydro-3-methyl-5-phenyl-1H-3-benzazepine-7-ol ([3H]SCH 23390) from rat striatal D1 receptors at a rate that is significantly slower than when dissociation is initiated using 1 µM piflutixol. After pretreatment with Gpp(NH)p, [3H]SCH 23390 dissociation induced by dopamine occurred at an even slower rate. Pretreatment with eticlopride had no effect on the dopamine-induced rate of [3H]SCH 23390 dissociation. These results indicate that all experimental approaches detected dopamine effects at D1 receptors that are Gpp(NH)p sensitive and D2 antagonist insensitive and provide no evidence to support a D1/D2 link operating at the receptor level. 相似文献
14.
Abstract: δ-Opioids mobilize Ca2+ from intracellular stores in undifferentiated NG108-15 cells, but the mechanism involved remains unclear. Therefore, we examined the effect of [d -Pen2,5]enkephalin on inositol 1,4,5-trisphosphate formation in these cells. [d -Pen2,5]enkephalin caused a dose-dependent (EC50 = 3.1 nM) increase in inositol 1,4,5-trisphosphate formation (measured using a specific radioreceptor mass assay), which peaked (25.7 ± 1.2 pmol/mg of protein with 1 µM, n = 9) at 30 s and returned to basal levels (10.6 ± 0.9 pmol/mg of protein, n = 9) within 4–5 min. This response was fully naloxone (1 µM) reversible and pertussis toxin (100 ng/ml for 24 h) sensitive. Preincubation with Ni2+ (2.5 mM) or nifedipine (1 µM) had no effect on the [d -Pen2,5]enkephalin (1 µM)-induced inositol 1,4,5-trisphosphate response, and K+ (80 mM) was unable to stimulate inositol 1,4,5-trisphosphate formation, indicating Ca2+ influx-induced activation of phospholipase C is not involved. Preincubation with the protein kinase C inhibitor Ro 31-8220 (1 µM) enhanced, whereas acute exposure to phorbol 12,13-dibutyrate (1 µM) abolished, the [d -Pen2,5]enkephalin (0.1 µM)-induced inositol 1,4,5-trisphosphate response, suggesting protein kinase C exerts an autoinhibitory feedback action. [d -Pen2,5]Enkephalin also dose-dependently (EC50 = 2.8 nM) increased the intracellular [Ca2+], which was maximal (24 nM increase with 1 µM, n = 5) at 30 s. This close temporal and dose-response relationship strongly suggests that δ-opioid receptor-mediated increases in intracellular [Ca2+] results from inositol 1,4,5-trisphosphate-induced Ca2+ release from intracellular stores, in undifferentiated NG108-15 cells. 相似文献
15.
James R. Bunzow Ge Zhang Claudia Bouvier Carmen Saez Oline K. Ronnekleiv Martin J. Kelly David K. Grandy 《Journal of neurochemistry》1995,64(1):14-24
Abstract: We have cloned and expressed a rat brain cDNA, TS11, that encodes a μ-opioid receptor based on pharmacological, physiological, and anatomical criteria. Membranes were prepared from COS-7 cells transiently expressing TS11 bound [3H]diprenorphine with high affinity (KD = 0.23 ± 0.04 nM). The rank order potency of drugs competing with [3H]diprenorphine was as follows: levorphanol (Ki = 0.6 ± 0.2 nM) ≈β-endorphin (Ki = 0.7 ± 0.5 nM) ≈ morphine (Ki = 0.8 ± 0.5 nM) ≈ [d -Ala2, N-Me-Phe4,Gly-ol5]-enkephalin (DAMGO; Ki = 1.6 ± 0.5 nM) ? U50,488 (Ki = 910 ± 0.78 nM) > [d -Pen2,5]-enkephalin (Ki = 3,170 ± 98 nM) > dextrorphan (Ki = 4,100 ± 68 nM). The rank order potencies of these ligands, the stereospecificity of levorphanol, and morphine's subnanomolar Ki are consistent with a μ-opioid binding site. Two additional experiments provided evidence that this opioid-binding site is functionally coupled to G proteins: (a) In COS-7 cells 50 µM 5′-guanylylimidodiphosphate shifted a fraction of receptors with high affinity for DAMGO (IC50 = 3.4 ± 0.5 nM) to a lower-affinity state (IC50 = 89.0 ± 19.0 nM), and (b) exposure of Chinese hamster ovary cells stably expressing the cloned μ-opioid receptor to DAMGO resulted in a dose-dependent, naloxone-sensitive inhibition of forskolin-stimulated cyclic AMP production. The distribution of mRNA corresponding to the μ-opioid receptor encoded by TS11 was determined by in situ hybridization to brain sections prepared from adult female rats. The highest levels of μ-receptor mRNA were detected in the thalamus, medial habenula, and the caudate putamen; however, significant hybridization was also observed in many other brain regions, including the hypothalamus. 相似文献
16.
Abstract: The direct effect of melatonin and related agonists on Li+-amplified phosphoinositide breakdown was studied in chick brain slices prelabeled with myo-[2-3H]-inositol. The melatonin receptor agonist 6-chloromelatonin (10–100 µM) increased, in a concentration-dependent manner, the accumulation of inositol phosphates (IP) in chick brain slices. This effect of 6-chloromelatonin (10 µM) was rapid as transient increases in IP3/IP4 (maximal increase, 29% at 20 s) and IP2 levels (maximal increase, 36% at 1 min) were observed, followed by a slower but sustained increase in IP1 level (30% at 5 min), when the amount of IP3/IP4 and IP2 had already been decreased to the control level. The phosphoinositide response elicited by 6-chloromelatonin (10 µM) was dependent on the presence of extracellular calcium. Direct stimulation of membrane phospholipase C by 6-chloromelatonin (10 µM) in isolated myo-[2-3H]inositol-prelabeled optic tectum membranes was dependent on the presence of guanosine-5′-O-(3-thio)triphosphate (1 µM), thus suggesting that G protein(s) link melatonin receptor activation to phospholipase C stimulation. The competitive melatonin receptor antagonist luzindole (10–100 µM) inhibited in a concentration-dependent manner the IP1 accumulation stimulated by 6-chloromelatonin (10–100 µM); however, it did not affect the accumulation stimulated by 5-hydroxytryptamine (10 µM). By contrast, methysergide (10 µM) completely inhibited 5-hydroxytryptamine (10 µM)-, but not 6-chloromelatonin (10 µM)-, induced IP1 accumulation. Melatonin receptor agonists increased IP1 accumulation in a concentration-dependent manner reaching different maximal responses. N-Acetyl-5-hydroxytryptamine was more potent than melatonin in increasing IP1 accumulation, suggesting activation of a melatonin receptor site other than the ML-1 melatonin receptor (i.e., N-acetyl-5-hydroxytryptamine ≥ melatonin). In conclusion, these results demonstrate that activation of a melatonin receptor with pharmacological characteristics different from those of the ML-1 subtype leads to activation of the phospholipase C-mediated signal transduction pathway. 相似文献
17.
The extent of tetrachloroethene (PCE) dechlorination in two chemostats was evaluated as a function of hydraulic retention time (HRT). The inoculum of these chemostats was from an upflow anaerobic sludge blanket (UASB) reactor that rapidly converts PCE to vinyl chloride (VC) and ethene. When the HRT was 2.9 days, PCE was converted only to cis-dichloroethene (cDCE). When the HRT was 11 days, the end products were VC and ethene. Further studies showed that the dechlorinating microbial community in the UASB reactor contained two distinct populations, one of which converted PCE to cDCE and the other cDCE to VC and ethene. Methanogenic activity was very low in these cultures. The cDCE dechlorinating culture apparently has a lower growth rate than the PCE dechlorinating culture, and as a result, at a shorter HRT, the cDCE dechlorinating culture was washed out from the system leading to incomplete dechlorination of PCE. Both enrichment cultures used pyruvate or hydrogen as electron donors for dechlorination. Acetate was the carbon source (but not energy source) when hydrogen was used. Both cultures had undefined nutrient requirements and needed supplements of cell extract obtained from the mixed culture in the UASB reactor. However, the two cultures were different in their response to the addition of an inhibitor of methanogenesis (2-bromoethanesulfonate [BES]). BES inhibited the dechlorinating activity of the enriched cDCE dechlorinating culture, but had no influence on the PCE dechlorinating culture. Preliminary studies on BES inhibition are presented. 相似文献
18.
《Bioscience, biotechnology, and biochemistry》2013,77(7):1404-1406
A new lipoxygenase inhibitor, 6'-hydroxyoxosorbicillinol (1, C14H16O6), was identified from a culture of Penicillium sp. A known compound, oxosorbicillinol (2, C14H16O5), was also isolated. Compound 1 showed an approximately 10 times greater inhibitory effect on soybean lipoxygenase (IC50, 16 µM) than 2 (IC50, 150 µM), and also showed prostaglandin D2 (PGD2) and leucotriene B4 (LTB4) release suppression activity (IC50, 10 µM for PGD2 and 100 µM for LTB4). 相似文献
19.
Desulfomonile tiedjei, a strict anaerobe capable of reductively dechlorinating 3-chlorobenzoate, also dechlorinates tetrachloroethene and trichloroethene. It is not known, however, if the aryl and aliphatic dechlorination activities are catalyzed by the same enzymatic system. Cultures induced for 3-chlorobenzoate activity dechlorinated tetrachloroethene and trichloroethene to lower chlorinated products while uninduced parallel cultures did not dechlorinate either substrate. The observed rate of PCE dechlorination in induced cultures was 22 µmol h–1 g protein–1, which is considerably faster than previous rates obtained with defined cultures of this organism. These results show that both dechlorination activities are co-induced and therefore, that the dechlorination mechanisms may share at least some components.Abbreviations PCE
tetrachloroethene
- TCE
trichloroethene
-
cis-DCE
cis-dichloroethene
-
trans-DCE
trans-dichloroethene
- 3FBz
3-fluorobenzoate
- 3ClBz
3-chlorobenzoate 相似文献
20.
Leslie A. Carter §John K. Belknap ‡§John C. Crabbe †‡ Aaron Janowsky 《Journal of neurochemistry》1995,64(1):213-219
Abstract: The effects of ethanol, glycine, and spermidine on the specific binding of [3H]MK-801 were characterized in Triton-treated membranes prepared from the hippocampus and cortex of ethanol-withdrawal seizure-prone (WSP) and -resistant (WSR) mice. Glycine, an allosteric agonist at the NMDA receptor-linked ion channel complex, caused an increase in specific [3H]MK-801 binding to hippocampal membrane preparations. There were no significant differences in EC50 values between the selected lines for the effect of glycine (WSP, 391.7 ± 48.4 nM; WSR, 313.4 ± 77 nM) in the presence of 10 µM NMDA or in the maximal response to the agonist (WSP, 1.75 ± 0.26 pmol/mg of protein; WSR, 1.67 ± 0.22 pmol/mg of protein). The EC50 values for the spermidine-induced increase in [3H]MK-801 binding in membranes from hippocampus in the absence (WSP, 11.7 ± 0.83 µM; WSR, 9.98 ± 1.29 µM) or in the presence of 10 µM glycine and 10 µM NMDA (WSP, 2.1 ± 0.35 µM; WSR, 2.37 ± 0.42 µM) also did not differ. Similar results were obtained in cortical membranes. Saturation isotherms indicated that there was no difference in the density of [3H]MK-801 binding sites, or in their affinity for the radioligand, between the mouse lines. In addition, administration of ethanol by inhalation (24 h) to WSP and WSR mice did not cause an increase in the density of [3H]MK-801 binding sites, and there was no difference in the density or affinity of binding sites between the mouse lines. Withdrawal from ethanol (6 h), which causes an increase in the severity of handling-induced convulsions in WSP mice, also did not alter the binding site density or affinity for radioligand. The results suggest that the characteristics of the NMDA receptor-linked ion channel complex in the tissue preparations described here do not differ in WSP and WSR mice. Thus, genetic differences in seizure susceptibility during ethanol withdrawal can be dissociated from the total density of hippocampal or cortex NMDA receptors under activating conditions. 相似文献