ISSN:0268-2605    

DOI:10.1002/aoc.590080302

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractTen Japanese gallium arsenide wafer manufacturers voluntarily formed The Japan Manufacturers' Society of Compound Semiconductor Materials (JAMS‐CS) in 1983. This report summarizes the theories, the systems, and the operations of gallium arsenide production: the gradient freeze (GF) method, the liquidencapsulated Czochralski (LEC) method, the wafer processing, the vapor‐phase epitaxial (VPE) growth method, the liquid‐phase epitaxial (LPE) growth method, the metalorganic chemical vapor deposition (MO‐CVD) method and the molecular beam epitaxial (MBE)

ISSN:0268-2605    

DOI:10.1002/aoc.590080303

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractHumans are exposed via air, water and food to a number of different arsenic compounds, the physical, chemical, and toxicological properties of which may vary considerably. In people eating much fish and shellfish the intake of organic arsenic compounds, mainly arsenobetaine, may exceed 1000 μg As per day, while the average daily intake of inorganic arsenic is in the order of 10–20 μg in most countries. Arsenobetaine, and most other arsenic compounds in food of marine origin, e.g. arsenocholine, trimethylarsine oxide and methylarsenic acids, are rapidly excreted in the urine and there seem to be only minor differences in metabolism between animal species. Trivalent inorganic arsenic (AsIII) is the main form of arsenic interacting with tissue constituents, due to its strong affinity for sulfhydryl groups. However, a substantial part of the absorbed AsIII is methylated in the body to less reactive metabolities, methylarsonic acid (MMA) and dimethylarsinic acid (DMA), which are rapidly excreted in the urine. All the different steps in the arsenic biotransformation in mammals have not yet been elucidated, but it seems likely that the methylation takes place mainly in the liver by transfer of methyl groups fromS‐adenosylmethionine to arsenic in its trivalent oxidation state. A substantial part of absorbed arsenate (AsV) is reduced to AsIII before being methylated in the liver. There are marked species differences in the methylation of inorganic arsenic. In most animal species DMA is the main metabolite. Compared with human subjects, very little MMA is produced. The marmoset monkey is the only species which has been shown unable to methylate inorganic arsenic. In contrast to other species, the rat shows a marked binding of DMA to the hemoglobin, which results in a low rate of urinary excretion of ar

ISSN:0268-2605    

DOI:10.1002/aoc.590080304

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe solubilization of arsenic in solid gallium arsenide by aqueous solutions/suspensions of organic halides is described. Although arsenic is removed from gallium arsenide surfaces, excess quantities of gallium are not found in the solution. The abilities of the organic halide to solubilize arsenic decreases as follows: C2H5Br>CH3I>2‐C3H7I>1‐C3H7I>2‐C4H9Br>CH2CHCH2I>2‐C3H7Br≃ 1‐C4H9Br.The results correlate with a combination of organic halide solubility, bond enthalpy and carbonium ion stability factors. Other parameters investigated using gallium arsenide and iodomethane include concentration, physical state of the arsenide, pH, role of oxygen and

ISSN:0268-2605    

DOI:10.1002/aoc.590080305

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe toxicity of inorganic trivalent arsenic for living organisms is reduced byin vivomethylation of the element. In man, this biotransformation leads to the synthesis of monomethylarsonic (MMA) and dimethylarsinic (DMA) acids, which are efficiently eliminated in urine along with the unchanged form (Asi). In order to document the methylation process in humans, the kinetics of Asi, MMA and DMA elimination were studied in volunteers given a single dose of one of these three arsenicals or repeated doses of Asi. The arsenic methylation efficiency was also assessed in subjects acutely intoxicated with arsenic trioxide (As2O3) and in patients with liver diseases. Several observations in humans can be explained by the properties of the enzymic systems involved in the methylation process which we have characterizedin vitroandin vivoin rats as follows: (1) production of Asimetabolites is catalyzed by an enzymic system whose activity is highest in liver cytosol; (2) different enzymic activities, using the same methyl group donor (S‐adenosylmethionine), lead to the production of mono‐ and di‐methylated derivatives which are excreted in urine as MMA and DMA; (3) dimethylating activity is highly sensitive to inhibition by excess of inorganic arsenic; (4) reduced glutathione concentration in liver moderates the arsenic methylation process through several mechanisms, e.g. stimulation of the first methylation reaction leading to MMA, facilitation of Asiuptake by hepatocytes, stimulation of the biliary excretion of the element, reduction of pentavalent forms before methylation, and protection of a reducing environment in the cells necessary to maintain the activity of the enzymic sy

ISSN:0268-2605    

DOI:10.1002/aoc.590080306

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe modifying effects of dimethylarsinic acid (DMA) on tumor induction in various organs were examined using a multi‐organ rat carcinogenesis bioassay. A total of 124 six‐week‐old male F344/DuCrj rats were divided randomly into seven groups. For establishment of wide‐spectrum initiation, animals in Groups 1–5 were treated with five carcinogens, namelyN‐nitrosodiethylamine (DEN),N‐methyl‐N‐nitrosourea (MNU), 1,2‐dimethylhydrazine (DMH),N‐butyl‐N‐(4‐hydroxybutyl)nitrosamine (BBN) andN‐bis(2‐hydroxypropyl)nitrosamine (DHPN) in the first four weeks. After a two‐week interval, Groups 1–5 were then given 0, 50, 100, 200 and 400 ppm DMA, respectively, in drinking water. Groups 6 and 7 received 100 and 400 ppm DMA without any carcinogen pretreatment. All rats were sacrificed at the end of week 30. In the initiated groups (Groups 1–5), DMA enhanced tumor development in the urinary bladder, kidney, liver and thyroid gland. The main arsenic species in urine samples was DMA itself. In conclusion, the observed enhancement of carcinogenesis in the urinary tract as well as in the liver and thyroid gland may be

ISSN:0268-2605    

DOI:10.1002/aoc.590080307

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractMicrobial degradation of a tetramethylarsonium salt during incubation at 25°C was investigated under both aerobic and anaerobic conditions. Two media (1/5 ZoBell 2216E and inorganic salt medium), added with the sediments or suspended substances as the sources of the microorganisms, were used. Degradation of the tetramethylarsonium salt occurred only in the ZoBell medium: under anaerobic conditions, trimethylarsine oxide and dimethylarsinic acid were derived with the sediments, and dimethylarsinic acid with the suspended substances, the salt degrading more rapidly with the former than with the latter. Small amounts of two metabolites, trimethylarsine oxide and inorganic arsenic(V), was also derived in the aerobically incubated ZoBell medium added with the suspended substances. This result means that the tetramethylarsonium salt is degraded to inorganic arsenic, which is the starting material for arsenic circulation in marine ecosystems, via trimethylarsine oxide and dimethylarsinic acid

ISSN:0268-2605    

DOI:10.1002/aoc.590080308

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractIntratracheal instillation of a GaAs suspension has been histopathologically shown to induce a diffuse pulmonary response. In the present study, magnetometry was used to evaluate the effects of intratracheally instilled GaAs and Ga2O3on the behavior of externally magnetized iron oxide (Fe3O4) particles instilled in rabbit lung. Magnetometric evaluation of the effects of GaAs in rabbits dosed with 30 mg or 300 mg per animal showed a significantly decreased relaxation of iron oxide particles at 1, 3, 7, 14, 21 and 28 days following instillation compared with the controls. On the other hand, in the rabbits exposed to Ga2O3, significantly reduced decay constants were observed only on the first and third days following instillation.Relaxation indicates a rapid decrease of remanent magnetic field following magnetization of the lungs due to random rotation of phagocytosed iron oxide particles in macrophages.Clearance of the iron oxide particles was measured by serial determinations of the remanent magnetic field at the end of magnetization estimated from relaxation curves. Clearance was significantly impaired at 14, 21 and 28 days after instillation in rabbits exposed to both doses of GaAs. Slightly delayed clearance was also observed in rabbits exposed to Ga2O3.Histological examination of lungs instilled with GaAs indicated active phagocytosis of GaAs and iron oxide particles by pulmonary macrophages, as well as pneumonocytes hyperplasia with marked thickening of the alveolar walls. Minimal histological changes with retention of iron oxide particles were found in the lungs exposed to Ga2O3.

ISSN:0268-2605    

DOI:10.1002/aoc.590080309

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe acute influences of arsenic compounds on the metabolism of porphyrins and heme in various organs of rats after oral or intratracheal administration of disodium arsenate (Na2HAsO4) and gallium arsenide (GaAs) were examined and compared.For the oral administration experiments, 21 or 84 mg of Na2HAsO4, or 2 or 4 g of GaAs, per cm3saline per kg body weight of each animal was administered to Jcl: Wistar male rats and the organs were removed after exsanguination from the vein of the right axilla under anesthesia with ether, 16 h after administration. In the case of intratracheal administration, rats given 8.2 or 16.4 mg of Na2HAsO4, or 0.2 or 0.4 g GaAs per cm3saline per kg body weight were examined under the same experimental conditions as for the administration route.Increase in the body weight of rats was suppressed after intratracheal administration of the two arsenic compounds. In these rats the hematocrit value increased significantly. These changes were not shown by the orally administered rats. Elevation in δ‐aminolevulinate synthase (ALA‐S, EC 2.3.1.37) activity in erythroblasts by Na2HAsO4was much higher after intratracheal administration than after oral administration. Suppression in the activities of δ‐aminolevulinate dehydratase (ALA‐D, EC 4.2.1.24) and porphobilinogen deaminase (PBG‐D, EC 4.3.1.8) in peripheral erythrocytes by Na2HAsO4and GaAs were stronger by intratracheal administration than by the oral route. Influences of GaAs on the activity of PBG‐D in rat liver were shown to be more effective by oral administration than by the intratracheal route. Oral administration of Na2HAsO4and GaAs had a stronger suppression effect on the activities of ALA‐D and PBG‐D in rat kidney.It seems from these results that the different extents of the influence of arsenic compounds might depend on the

ISSN:0268-2605    

DOI:10.1002/aoc.590080310

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractAdult male Wistar rats averaging 380 g in weight were injected with single doses (100 mg kg−1body weight) of humic acids intraperitoneally. ‘Black tails’ were noticed 12 days later. In severely affected regions, thrombosis with mild to moderate acute necrotizing vasculitis was seen in most of the blood vessels located in the dermis, subcutaneous fat and muscle. These blood vessels were markedly dilated. Frequently, colonies of a shortrod bacterium of varying sizes were observed in necrotic tissues. There was mild to moderate edema and minimal accumulation of mast cells and macrophages in the dermis. Acute fat necrosis with fibrin deposition was also seen in the subcutaneous fat. Based on the pathological findings, we diagnosed that the tails of Wistar rats which had been injected with humic acids had severe multifocal thrombosis and mild to moderate, multifocal, acute necrotizing vasculitis with bacterial colonization, mild dermatitis, and fat necrosis. The relevance of these observations to the discussions on arsenic as an etiological factor of human Blackfoot disease is exa

ISSN:0268-2605    

DOI:10.1002/aoc.590080311

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY