摘要:

The uptake and elimination of Cr VI in a male volunteer who ingested 2 L d of water containing 2 mg L for 17 consecutive days was measured Total chromium was measured in urine plasma and red blood cells RBCs for 4 d prior to and 2 wk after dosing 34 d total The estimated bioavailability 2 and the plasma elimination half life 36 h were consistent with our previous studies of Cr VI ingestion in humans Steady state chromium concentrations in urine and blood were achieved after 7 d of Cr VI ingestion Both plasma and red blood cell RBC chromium concentrations returned rapidly to background levels within a few days after cessation of dosing Since the concentration of chromium in the RBC should not decrease quickly if the chromium had entered the RBC as Cr VI these data support our prior work suggesting that concentrations of 10 mg Cr VI L or less in drinking water of exposed humans appears to be completely reduced to Cr III prior to systemic distribution Clinicalchemistry data indicate that no toxicity occurred

ISSN:0098-4108    

DOI:10.1080/009841096160682

出版商:Informa UK Ltd    

年代:1996

数据来源: Taylor

摘要:

Nonoxidative metabolism of ethylene glycol monobutyl ether 2 butoxyethanol or BE via fatty acid conjugation was studied in the liver of Fischer 344 male rats following a single 14 oral administration of 500 mg kg body weight ethyl1 2 C BE 70 Ci kg Animals were killed 2 h after the treatment hepatic lipids extracted and the neutrallipids were separated using solid phase extraction The neutral lipid fraction was subjected to preparative thin layer chromatography and the esters corresponding to the relative flow of authentic fatty acid 2 butoxyethylesters were recovered and analyzed by reversed phase high performance liquid chromatography HPLC using methanol water 37 3 v v as solvent Approxi 14 mately 85 of the C label present in the ester fraction was coeluted at retention times corresponding to the different fatty acid 2 butoxyethyl ester standards The radioactive fractions were analyzed by electron impact mass spectrometry Molecular ion peaks and fragmentation patterns similar to that of 16 0 18 0 18 1 18 2 and 20 4 fatty acid 2 butoxyethyl ester standards were detected in the corresponding radioactive HPLC frac tions Fatty acid ethyl ester synthase FAEES purified from the rat liver microsomal frac tion was also found to catalyze the formation of 18 1 fatty acid 2 butoxyethyl ester These studies demonstrate that BE is metabolized nonoxidatively via conjugation with long chain fatty acids and the formation of these esters appears to be catalyzed by the enzyme s involved in fatty acid conjugation of xenobiotic alcohols However the biolog ical significance of BE conjugation with fatty acids remains to be investigated

ISSN:0098-4108    

DOI:10.1080/009841096160691

出版商:Informa UK Ltd    

年代:1996

数据来源: Taylor

摘要:

Effects of continuous feeding flavonoids flavone flavanone and tangeretin on drug metabolizing enzymes in rat liver were investigated to ascertain how long feeding is required to reach maximal induction and to determine whether maximal induction is maintained for a long period of feeding In the first experiment rats received a diet con taining 10 mmol flavonoid kg dry matter for 4 8 16 or 32 d The second experiment was designed to examine the time course for induction during the first 4 d The kinetics of induction depended on the chemical structure of the flavonoid and was different from one enzyme to another Flavone increased P450 1A and P450 2B apoproteins and stimu lated many enzyme activities A significant increase of P450 1A1 2 proteins ethoxyre sorufin O deethylase EROD and methoxyresorufin O demethylase MROD activities occurred as early as 6 h after the first administration and a gradual increase was observed up to 4 d of feeding P450 2B1 2 proteins and pentoxyresorufin O depentylase PROD activity were also increased but after a lag period when compared with P450 1A1 2 proteins EROD and MROD activities declined after 4 d whereas PROD activity remained steady during 32 d of flavone feeding Glutathione transferase GST and p nitrophenol UDP glucuronosyl transferase UGT activities were also increased The maxi mal induction was reached by 4 d of feeding for UGT and after a longer duration of feed ing 16 d for GST Flavanone treatment induced mostly P450 2B1 2 proteins and PROD GST and UGT activities After 4 d of feeding P450 2B1 2 proteins and PROD activity declined whereas GST and UGT activities remained steady Tangeretin treatment pro duced changes similar to flavone but of lesser magnitude and after a longer delay

ISSN:0098-4108    

DOI:10.1080/009841096160709

出版商:Informa UK Ltd    

年代:1996

数据来源: Taylor

摘要:

The distribution of 2 4 dichlorophenoxyacetic acid 2 4 D was examined in maternal and fetal rabbits Pregnant New Zealand rabbits 28 30 d gestational age were anesthetized with ketamine xylazine and the femoral vein and artery were catheterized for compound 14 administration and sampling Dams received iv C 2 4 D 12 5 Ci kg with unlabeled sodium 2 4 D 1 10 or 40 mg kg in saline Blood and tissue were collected up to 2 h after dosing Fetal to maternal plasma AUC ratios were 0 09 0 07 and 0 16 after the 1 10 or 40 mg kg dose respectively Extraplasma AUCs were greatest in maternal kidney and uterus and lowest in maternal and fetal brain A greater than fourfold elevation in fetalAUC was found when the dose was increased from 10 to 40 mg kg suggesting satu ration of maternalplasma binding of 2 4 D Although the in vitro fetal brain tissue to incu bation media ratio was unity 1 03 0 1 mean SD fetal brain AUCs were 10 or less of the fetalplasma AUCs indicating the brain barrier system to 2 4 D is functioning in the late gestation fetal rabbit However its development may not be complete due to the higher brain tissue to plasma ratios in the fetus compared to the dam

ISSN:0098-4108    

DOI:10.1080/009841096160718

出版商:Informa UK Ltd    

年代:1996

数据来源: Taylor

摘要:

Previous studies have shown that vitamin E may be an integral part of lung surfactant and may function to protect this materialfrom oxidant damage Therefore we measured the vita min E levels in alveolar lavage materials from rats exposed to crystalline silica or treated with chlorphentermine CP two treatments that are known to increase surfactant phospholipids PL by different mechanisms Silica exposure leads to increased PL synthesis and CP treat ment causes a reduction in PL degradation Two different silica preparations HClwashed and unwashed silica were used because exposure to each of them leads to different degrees of phospholipidosis Exposure to HClwashed silica results in a more than 17 fold increase in lavage PL and protein levels and a 12 2 fold increase in the amount of vitamin E Exposure to unwashed silica leads to an approximately 7 fold increase in PL and proteins and a 5 8 fold increase in lavage vitamin E Following treatment of rats with CP there is a 15 to 19 fold increase in lavage PL and proteins and a 13 6 fold increase in vitamin E When the results are expressed as micrograms vitamin E per milligram of lavage PL or protein there is not much difference between controls and each treatment group Because surfactant synthe sis occurs in the endoplasmic reticulum we also measured vitamin E in lung microsomes Both silica exposure and CP treatment also lead to 1 8 to 2 5 fold increases respectively in the lung microsomal levels of vitamin E These results demonstrate that alveolar lavage vita min E levels are elevated along with lavage PL and proteins and lung microsomal vitamin E levels are increased following exposure of ratsto silica ortreatment ofthe animals with CP

ISSN:0098-4108    

DOI:10.1080/009841096160727

出版商:Informa UK Ltd    

年代:1996

数据来源: Taylor

摘要:

In the present study the effects of preweaning cement vapor inhalation on exploratory behavior and cerebellar Purkinje cell differentiation were assessed Sprague Dawley albino rats were daily exposed to glue vapors between postnatal d 2 and 21 At postnatal d 22 all animals were submitted to the open field test in order to evaluate their exploratory behavior Then they were sacrificed their brains dissected out and cerebella stained according to the Golgi Cox Sholl procedure Purkinje cells sampled from parasagittal sec tions of the cerebellar vermis were drawn under camera lucida and their dendritic domain was determined The collected data indicate that glue solvent inhalation impairs both Purkinje celldifferentiation and locomotor exploratory behavior

ISSN:0098-4108    

DOI:10.1080/009841096160736

出版商:Informa UK Ltd    

年代:1996

数据来源: Taylor

摘要:

A life cycle experiment with fathead minnows and Ceriodaphnia survival reproduction tests were used to evaluate the quality of the effluent from a bleached kraft mill after the implementation of various process modifications and effluent treatment changes In the life cycle experiment the fish were exposed in the laboratory to well water control and five concentrations 1 25 2 5 5 10 or 20 of effluent from the egg stage to sexual maturity and reproduction 190 d None of the effluent concentrations signifi cantly affected the hatching of the eggs the mortality weight length gender balance reproduction and prevalence of visible morphologicalor histopathologicalabnormalities of the hatched fish and the hatchability of the first generation eggs In Ceriodaphnia tests the IC25 of the effluent affecting reproduction was approximately 80 This threshold concentration is well above the 0 7 average yearly concentration of the effluent that exists in the recipient near the point of discharge The results of these biotests were com pared to the results of the same biotests conducted earlier with the effluent from the mill prior to process and treatment modifications The comparison indicated that since the ear lier work the quality of the mills effluent improved substantially Threshold concentrations affecting fathead minnows in the life cycle experiment and the Ceriodaphnia tests increased by more than eightfold and approximately twofold respectively While the most important change in the mill operating conditions responsible for the improvement could not be identified these results indicate that mills can undertake process and treatment modifications that result in the discharge of effluents seemingly compatible with the aquatic environment

ISSN:0098-4108    

DOI:10.1080/009841096160745

出版商:Informa UK Ltd    

年代:1996

数据来源: Taylor