摘要:

AbstractEffects of treatment of mice with chlordecone (25 mg/kg/d) on striatal dopaminergic activities such as synthesis, turnover, uptake, and release were investigated in vivo and in vitro. In mice receiving chlordecone for five days, there were no significant changes in in vivo dopamine (DA) synthesis and turnover in striatum and in vitro [3‐H]‐dopamine uptake and K+‐stimulated [3‐H]‐dopamine release in striatal slices. In mice receiving chlordecone for eight days, the in vivo synthesis of [3‐H]‐dopamine from [3‐H]‐tyrosine in striatum was slightly inhibited and the in vitro [3‐H]‐dopamine synthesis in striatal slices was significantly decreased. Furthermore, both uptake and K+‐stimulated release of [3‐H]‐dopamine from striatal slices were significantly reduced. The turnover rate of newly synthesized [3‐H]‐dopamine from [3‐H]‐tyrosine in striatal slices was unchanged after eight consecutive days of chlordecone administration. These results suggest that chlordecone may cause impairments in pre‐ and/or postsynaptic membranes of dopaminergic

ISSN:0887-2082    

DOI:10.1002/jbt.2570010402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractCyclopiazonic acid (CPA), a fungal metabolite produced byAspergillusandPenicillium, potentiated the accumulation of the quaternary cation tetraphenylphosphonium (TPP+) in cultured pig renal epithelial cells. This is the first report of a natural product mediating the tight and apparently nonsaturable binding of a membrane potential probe to subcellular compartments. The potentiated TPP+accumulation was dose dependent, nonsaturable, and not a result of hyperpolarization across the plasma membrane. Cyclopiazonic acid–potentiated accumulation was completely inhibited by the protonophore carbonylcyanide‐m‐chlorophenylhydrazone (CCCP). Dinitrophenol (DNP), tetrahexylammonium (THA), andn‐ethylmaleimide (NEM) were also effective inhibitors of CPA‐appeared to be energy dependent, TPP+efflux (in the presence of CCCP) from CPA‐treated cells was incomplete and most of the TPP+accumulated in the presence of CPA was tightly bound. Dicyclohexylcarbodiimide (DCC), verapamil, and monensin also stimulated TPP+accumulation, but the TPP+which accumulated in the presence of these compounds was not tightly bound. As with controls, fractionation of cells which had accumulated TPP+in the presence of DCC, verapamil, or monensin always resulted in near complete recovery (>93%) of the TPP+in the cytosolic fraction, whereas with CPA, greater than 88% of the TPP+was recovered noncovalently bound in the plasma membrane and mitochondrial fractions. These results are consistent with the hypothesis that CPA‐potentiated TPP+accumulation is a result of potentiated partitioning of TPP+into the plasma membranes and mitochondria of

ISSN:0887-2082    

DOI:10.1002/jbt.2570010403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractAdministration of Prudhoe Bay crude oil (PBCO) to rats resulted in an abrupt drop in liver mitochondrial and microsomal ATP‐dependent calcium uptake activity. Also, in vitro incubations of either mitochondria or microsomes in the presence of a dimethyl sulfoxide (DMSO) extract of PBCO resulted in a dose‐dependent inhibition of calcium influx. The release of calcium from calciumloaded mitochondria and microsomes was also observed in the presence of the PBCO extract. At concentrations which effect calcium sequestration, the PBCO extract produced swelling of mitochondria. Microsomal ATPase activity in the presence or absence of calcium was unaffected by PBCO. The results indicate that increased permeability of the membranes to calcium is a contributory factor in the inhibition of calcium uptake by P

ISSN:0887-2082    

DOI:10.1002/jbt.2570010404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractThe effect of 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD) on epidermal growth factor (EGF)‐binding characteristics was studied in a cultured embryonic fibroblast cell line, C3H 10T1/2. At very low concentrations, TCDD was found to cause a persistent decline in EFG binding, the median effective concentration (EC‐50) being 10−12M. This particular effect was most conspicuous when TCDD was added at the time of medium change with fresh Dulbecco's modified Eagle's medium. Cells at an early stage of confluency were more responsive to TCDD than those at a later stage. Although most reported TCDD‐evoked biological changes are recognized to occur slowly during the course of a few days to weeks, the response of C3H 10T1/2 cells to TCDD was swift, showing a sign of decline of EGF binding as early as three hours after TCDD addition. C3H 10T1/2 cells appear to be an excellent in vitro model to study TCDD's biochemical acti

ISSN:0887-2082    

DOI:10.1002/jbt.2570010405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractPrevious studies from this laboratory have indicated that tricyclohexyltin hydroxide (Plictran) is a potent inhibitor of both basal‐ and isoproterenol‐stimulated cardiac sarcoplasmic reticulum (SR) Ca2+‐ATPase, with an estimated IC‐50 of 2.5 × 10−8M. The present studies were initiated to evaluate the mechanism of inhibition of Ca2+‐ATPase by Plictran. Data on substrate and cationic activation kinetics of Ca2+‐ATPase indicated alteration of Vmaxand Kmby Plictran (1 and 5×10−8M), suggesting a mixed type of inhibition. The beta‐adrenergic agonist isoproterenol increased Vmaxof both ATP‐ and Ca2+‐dependent enzyme activities. However, the Kmof enzyme was decreased only for Ca2+Plictran inhibited isoproterenol‐stimulated Ca2+‐ATPase activity by altering both and VmaxandKmof ATP as well as Ca2+‐dependent enzyme activities, suggesting that after binding to a single independent site, Plictran inhibits enzyme catalysis by decreasing the affinity of enzyme for ATP as well as for Ca2+Preincubation of enzyme with 15 μM cAMP or the addition of 2mM ATP to the reaction mixture resulted in slight activation of Plictran‐inhibited enzyme. Pretreatment of SR with 5 × 10−7M propranolol and 5 × 10−8M Plictran resulted in inhibition of basal activity in addition to the loss of stimulated activity. Preincubation of heart SR preparation with 5 × 10−5M coenzyme A in combination with 5 × 10−8M Plictran partly restored the beta‐adrenergic stimulation. These results suggest that some critical sites common to both basal‐ and beta‐adrenergic‐stimulated Ca2+‐ATPase are sensitive to binding by Plictran, and the resultant conformational change

ISSN:0887-2082    

DOI:10.1002/jbt.2570010406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractImmunochemical techniques were used to investigate the biochemical properties of human lung epoxide hydrolases. Two epoxide hydrolases with different immunoreactive properties were identified. These two epoxide hydrolases were found in both cytosolic and microsomal cell fractions. Immunotitration of enzyme activity showed that enzymes that catalyze the hydration of benzo(a)pyrene 4,5‐oxide react with antiserum to rat microsomal epoxide hydrolase; those that hydratetrans‐stilbene oxide do not. Immunotitration and Western blot experiments showed that microsomal and cytosolic benzo(a)pyrene 4,5‐oxide hydrolases have significant structural homology. Immunohistochemical staining of human lung benzo(a)pyrene 4, s‐oxide hydrolase showed that the enzyme is localized primarily in the bronchial epithelium. No cell type‐specific localization was observed. An enzyme‐linked immunosorbent assay was developed which allows direct quantitation of benzo(a)pyrene 4,5‐oxide hydrolase protein. Levels of enzyme protein detected by this assay correlated well with enzyme levels determined by substrate conv

ISSN:0887-2082    

DOI:10.1002/jbt.2570010407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractPeroxidase activity was partially purified from neonatal (3 to 6 days old) rat skin. The membrane‐bound peroxidase activity was extracted with 0.5 calcium chloride and was monitored spectrophotometrically at 470 nm with 2‐methoxyphenol (guaiacol) and hydrogen peroxide as substrates. Subcellular distribution studies indicated the activity to be highest and comparable in nuclei mitochondria, lowest in microsomes, and absent in cytosol. The peroxidase activity was partially purified by affinity chromatography on concanavalin A‐sepharose 4B and by gel filtration using Bio‐Gel P‐150. Purification factors from these two steps were about 25 and 4, respectively. Peroxidase extraction in the presence of 2mMN‐ethylmaleimide increased activity about twofold. The combination of 2 mMN‐ethylmaleimide and 10% (w/v) glycerol was found to be optimal for preservation of activity. Peroxidase activity increased linearly with increases in protein concentration, time, and guaiacol concentration. Activity was inhibited approximately 75% by 0.1 mM potassium cyanide or 0.05 mM sodium azide. Pyrogallol, hydroquinone,p‐cresol, catechol, benzidine, 3,3′‐dimethoxybenzidine, tetramethyl‐benzidine, andp‐phenylenediamine also acted as substrates for the r

ISSN:0887-2082    

DOI:10.1002/jbt.2570010408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

ISSN:0887-2082    

DOI:10.1002/jbt.2570010401

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY