摘要:

The effects of brain irradiation on the enzyme activity of monoamine oxidase (MAO) and catecholamine O‐methyltransferase (COMT), as well as on the rate of incorporation of [14C]tyrosine into catecholamines (CAs), were examined in brain regions of the squirrel monkey (Saimiri sciureus). Results indicated that proton irradiation of the striate visual cortex at either 10,000 or 20,000 rad drastically affected the MAO activity, moderately affected the COMT activity, and significantly altered the incorporation of [14C]tyrosine into CAs in several brain regions.

ISSN:0098-4108    

DOI:10.1080/15287398409530623

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

This study determines the in vivo percutaneous absorption of paraquat in humans. Three skin sites of application were used in a crossover manner for six subjects. The percents of applied dose (9 μg/cm2) absorbed were 0.29 ± 0.2 (SD) for the leg, 0.23 ± 0.1 for the hand, and 0.29 ± 0.1 for the forearm. This gives an in vivo absorption rate of 0.03 μg/cm2for the 24‐h exposure. Paraquat can be absorbed in vivo through the skin of humans; however, it is considered a minimally absorbed chemical.

ISSN:0098-4108    

DOI:10.1080/15287398409530624

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The herbicide paraquat and the antibiotic nitrofurantoin (redox‐active compounds that can transfer electrons singly to oxygen) induced intracellular accumulation of the regulatory inhibitor guanosine tetraphosphate (stringency) in Escherichia coli. This mechanism is sufficient to account for the rapid bacteristasis produced in minimal medium by these agents. The growth inhibition and stringency induction were prevented by inclusion of specific amino acids in the medium. Stringency was first reported to result from amino acid starvation, with unloaded transfer ribonucleic acids (tRNAs) acting as the trigger. Previously, inhibition of growth of E. coli by paraquat and hyperbaric oxygen were shown to be prevented by inclusion in the medium of a nearly identical profile of specific amino acids, including branched‐chain amino acids, which were required because of poisoning of their biosynthesis at the dihydroxyacid dehydratase site, and stringency has been induced by hyperbaric oxygen poisoning. Thus, stringency induction via a common poisoned site in branched‐chain amino acid biosynthesis appears to be a shared mechanism of toxicity for these agents and hyperbaric oxygen, which also share the propensity for one‐electron‐transfer, free‐radical reactions in cells.

ISSN:0098-4108    

DOI:10.1080/15287398409530625

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The potential of isopropyl triphenyl phosphate (ITP) to produce delayed neurotoxicity in hens was examined using several techniques. ITP contained O,O,O‐triphenyl phosphate (24%), O‐o‐isopropylphenyl O,O‐diphenyl phosphate (25%), O,O‐diisopropyl‐phenyl O‐phenyl phosphate (20%), O‐o, p‐diisopropylphenyl O,O‐diphenyl phosphate (18%) and O‐p‐isopropylphenyl O,O‐diphenyl phosphate (6%). Hens treated twice, 3 wk apart, with doses of ITP as high as 11.7 g/kg showed no clinical signs of delayed neurotoxicity and only mild signs of general toxicity. Furthermore, none showed even subtle neurohistologic changes suggestive of delayed neurotoxicity. ITP produced dose‐dependent inhibition of hen plasma cholinesterase and brain neurotoxic esterase (NTE). The study was continued because NTE inhibition has been shown to be a reliable predictor of organophosphates that produce delayed neurotoxicity. ITP was administered prior to tri‐o‐tolyl phosphate (TOCP) challenge in order to determine if it altered development of TOCP delayed neurotoxicity. ITP neither enhanced nor reduced the onset or severity of neurotoxicity produced by TOCP. The time‐course for brain and spinal cord NTE inhibition by ITP and TOCP were compared and found to be different. The maximum brain NTE inhibition produced by ITP (doses up to 11.7 g/kg) was never complete (always less than 90%), and spinal cord NTE inhibition was significantly less than that produced in the brain. In contrast, brain and spinal cord inhibition produced by 500 mg TOCP/kg were equal and greater than 90%.

ISSN:0098-4108    

DOI:10.1080/15287398409530626

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Trio‐o‐cresyl phosphate (TOCP), leptophos [O‐methyl O‐(4‐bromo‐2,5,‐dichlorophenyl) phenylphosphonothioate] and cyanofenphos [O‐ethyl O‐(4‐cyanophenylj phenyl‐phosphonothioate] were used to determine whether adult peking ducks would exhibit neurotoxicity after exposure to such chemicals. Clinical, histopathological, and specific biochemical tests were used to detect the neurologic dysfunctions that were induced by these neurotoxic agents. Ducks were orally treated with TOCP or leptophos at 100 or 10 mg/kg· d for 30 d, respectively. Another group of ducks received cyanofenphos at 4 mg/kg·d for 10 d. All the TOCP‐ and leptophos‐treated ducks developed clinical signs of delayed neuropathy, as manifested by ataxia and paralysis. Two of the cyanofenphos‐treated ducks died from cholinergic effect during the course of dosing. Surviving ducks of this group completely recovered from the cholinergic effect 2 or 3 d after finishing the dosing regimen. However, they developed signs of delayed neurotoxicity 10–17 d later. Surviving ducks of all groups were sacrificed for biochemical and for histopathologic tests 1 d after the last treatment or when they became paralyzed. Histopathologic examinations indicated that degenerative lesions of axons consistent with the type occurring in delayed neurotoxicity were seen in all TOCP‐, leptophos‐, or cyanofenphos‐treated ducks and were specially evident in sections of spinal cord. Biochemically, it was found that duck brain neurotoxic esterase (NTE) activity was inhibited in vivo to less than 15% of control levels as measured 24 h after the last treatment with TOCP, leptophos, or cyanofenphos. These results indicate that adult peking ducks could be used to screen organophosphorus compounds for delayed toxic neuropathy.

ISSN:0098-4108    

DOI:10.1080/15287398409530627

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Tolerance to Cd‐induced toxicity following pretreatment with Cd is well documented, yet the exact mechanism of tolerance and role of metailothionein (MT) remains equivocal. In this study it was determined if the rapid induction of MT following injection of a challenge dose of Cd or the concentration of presynthesized MT induced by Cd pretreatment is more important for development of tolerance by ascertaining (1) whether the rates of synthesis of MT differ following injection of the challenge dose of Cd in control and Cd‐pretreated rats and (2) if a relationship exists between presynthesized hepatic or renal MT and tolerance to Cd‐induced lethality. Rates of hepatic and renal MT synthesis did not differ following injection of a challenge dose of Cd (2.0 mg Cd/kg, iv) in control and Cd‐pretreated (2.0 mg Cd/kg, sc) rats. However, the progressive increase in concentration of MT in liver after Cd pretreatment correlated with the increase in tolerance to a lethal dose of Cd (4.0 mg Cd/kg, iv), as evidenced by a decrease in mortality in pretreated rats. A similar correlation was not observed between kidney MT levels and tolerance. Therefore, it appears that presynthesized MT in liver rather than increased synthesis of MT following injection of a second dose of Cd is responsible for Cd‐induced tolerance.

ISSN:0098-4108    

DOI:10.1080/15287398409530628

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Residue levels of the chlorinated hydrocarbons hexachlorobenzene (HCB), polychlori‐nated biphenyls (PCBs), α‐, β‐, and γ‐hexachlorocyclohexane (HCH), oxychlordane, trans‐nonachlor, aldrin, and dieldrin in adult puffins (Fratercula arctica) from two colonies in Norway (Røst 67°30'N and Hornøy 70° 20'N) showing differences in breeding performance were compared in 1982. Furthermore, residue levels in puffin chicks from Røst in 1982, when breeding failed totally, were compared with the corresponding levels in 1983, when breeding was successful. Residue levels of chlorinated hydrocarbons were also measured in eggs from Røst 1982. An autoradiographic study of the distribution of [14C] HCB in adult puffins and chicks from Røst 1982 was included.

ISSN:0098-4108    

DOI:10.1080/15287398409530629

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

AIR MONITORING METHODS FOR INDUSTRIAL CONTAMINANTS. Edited byDavid A. Halliday, Biomedical, Davis, California, 428 pp., $35.00.

ISSN:0098-4108    

DOI:10.1080/15287398409530630

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

ISSN:0098-4108    

DOI:10.1080/15287398409530612

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor