Kinetic analysis of the swimming behaviour of bluegill sunfish, Lepomis macrochirus Rafinesque, exposed to copper: hypoactivity induced by sublethal concentrations

The concentration of copper which caused 50% mortality of bluegill in 96 h (96-h LC50) was between 4 and 16 ppm of the metal, copper. During the 6–8 day treatment period, sublethal concentrations of copper elicited a hypoactive locomotor response which was dependent on both concentration and time of exposure. Fish treated in 0.04, 0.08 and 0.4 ppm of copper were only 67, 61 and 44% as active, respectively, as they were prior to treatment. Locomotor activity decreased dramatically during the first 4 days of exposure to copper and remained low during further exposure.     

Respiration and osmoregulation of the estuarine crab, Rhithropanopeus harrisii (Gould): effects of the herbicide, alachlor

1. The effects of a sudden decrease in salinity and exposure to sublethal concentrations of the herbicide, alachlor, on osmoregulation and respiration of the crab, Rithropanopeus harrisii, were studied. 2. Crabs were hyperosmotic regulators at salinities below 24 ppt and became hypoosmotic at higher salinities. Upon a salinity decrease from 20 to 1 ppt, crabs adjusted their haemolymph osmolality to a stable hyperosmotic level in 8 hr. Alachlor concentrations to 50 ppm did not affect this adjustment. 3. A salinity decrease from 10 to 0 ppt elevated VO2 and the critical oxygen tension. This response was unaffected by alachlor concentrations as high as 25 ppm.     

Ocular Injury by Transient Formaldehyde Exposure in a Rabbit Eye Model

Formaldehyde (FA) is frequently used in sterilizing surgical instruments and materials. Exposure to FA is highly concerned for eye tissues. Rabbit corneal epithelial cells were examined for changes after FA exposure. Our results showed that cell survival decreased 7 days after transient 3 min exposure to more than 100 ppm FA by trypan blue staining while MTT assay detected significant decrease at 20 ppm at 24 hours observation. The decrease of cell survival rate was concentration (up to 600 ppm)- and observation time (1–7 day)- dependent. The cell number decreased after 100 ppm FA exposure for more than 10 min at 7-day observation. The FA treated cells showed increased apoptosis/necrosis and cell cycle accumulation at sub G1 phase as well as mitochondria clustering around nucleus. The in vivo rabbit eye exposure for tear production by Schirmer’s test revealed that the FA-induced overproduction of tear also exhibited observation time (1–10 day)- and FA concentration (20–300 ppm for 5 min exposure)-dependent. Activated extracellular signal-regulated kinase (pERK2) in cornea explants by western blotting was reduced and increased c-Jun amino - terminal kinase (JNK) activation (pJNK) in cornea and conjunctiva was evident at 2 month after exposure to 50–200 ppm FA for 5 min. In conclusion, injury to the eye with transient exposure of up to 100 ppm FA for 3 min decreased corneal cell survival while a more sensitive MTT test detected the cell decrease at 20 ppm FA exposure. Morphology changes can be observed even at 5 ppm FA exposure for 3 min at 7 days after. The FA exposure also increased apoptotic/necrotic cells and sub-G1 phase in cell cycle. Long term effect (2 months after exposure) on the eye tissues even after the removal of FA can be observed with persistent JNK activation in cornea and conjunctiva.     

Protective<Emphasis Type="Italic">in vivo</Emphasis> effect of curcumin on copper genotoxicity evaluated by comet and micronucleus assays

Curcumin is a phytochemical with antiinflammatory, antioxidant and anticarcinogenic activities. Apparently, curcumin is not genotoxic in vivo, but in vitro copper and curcumin interactions induce genetic damage. The aim of this study was to test if in vivo copper excess induces DNA damage measured by comet and micronucleus assays in the presence of curcumin. We tested 0.2% curcumin in Balb-C mice at normal (13 ppm) and high (65, 130 and 390 ppm) copper ion concentrations. The comet and micronucleus assays were performed 48 hr after chemical application. Comet tail length in animals treated with 0.2% curcumin was not significantly different from the control. Animals exposed to copper cations (up to 390 ppm) exhibited higher oxidative DNA damage. Curcumin reduced the DNA damage induced by 390 ppm copper. We observed statistically significant increase in damage in individuals exposed to 390 ppm copper versus the control or curcumin groups, which was lowered by the presence of curcumin. Qualitative data on comets evidenced that cells from individuals exposed to 390 ppm copper had longer tails (categories 3 and 4) than in 390 ppm copper + curcumin. A statistically significant increase in frequency of micronucleated erythrocytes (MNE/10000TE) was observed only in 390 ppm copper versus the control and curcumin alone. Also cytotoxicity measured as the frequency of polychromatic erythrocytes (PE/1000TE) was attributable to 390 ppm copper. The lowest cytotoxic effect observed was attributed to curcumin. In vivo exposure to 0.2% curcumin for 48 hr did not cause genomic damage, while 390 ppm copper was genotoxic, but DNA damage induced by 390 ppm copper was diminished by curcumin. Curcumin seems to exert a genoprotective effect against DNA damage induced by high concentrations of copper cations. The comet and micronucleus assays prove to be suitable tools to detect DNA damage by copper in the presence of curcumin.     

Reversal of Cadmium-Induced Thyroid Dysfunction by Selenium, Zinc, or Their Combination in Rat

The aim of this study was to evaluate the potential benefit of combined treatment with zinc (Zn) and selenium (Se) in reversing cadmium (Cd)-induced thyroid dysfunction compared to Se or Zn treatment alone in rats exposed to Cd. For this purpose, 30 adult male Wistar albino rats were equally divided into control and four treated groups receiving either 200 ppm Cd (as CdCl2), 200 ppm Cd + 500 ppm Zn (as ZnCl2), 200 ppm Cd + 0.1 ppm Se (as Na2SeO3), or 200 ppm Cd + 500 ppm Zn + 0.1 ppm Se in their drinking water for 35 days. The results showed that Cd exposure increased significantly the relative thyroid weight (RTW), the thyroid Cd concentration, and the serum thyroid stimulating hormone (TSH) level, whereas the serum thyroxine (T4) level was decreased compared to control rats. The treatment of Cd-exposed rats with Se alone only partially protected from the Cd-induced decrease in serum T4 level. The treatment of Cd-exposed animals with Zn alone partially protected against Cd-induced thyroid dysfunction by maintaining normal RTW and by decreasing Cd concentration in the thyroid. It also partially prevents Cd-induced decrease in serum T4 level. The combined treatment of Cd-exposed animals with Se and Zn induced a more significant decrease in the thyroid Cd concentration than the Zn supplement and a total correction of the RTW. This treatment was also more effective than that with Se or Zn alone in reversing Cd-induced decrease in serum T4 level and Cd-induced increase in serum TSH level. Se and Zn can have a synergistic role against Cd-induced thyroid dysfunction.     

Response of hepatic function to hepatic copper deposition in rats fed a diet containing copper

Fischer rats were a fed diet supplied with copper chloride (150–600 ppm) for 60 d from weaning. Serum (glutamic-oxaloacetic transaminase (GOT) and glutamic-pyruvic transaminase (GPT) activities were increased with the increase of Cu concentration in the diet. Biliary excretion of Cu was related to the dietary Cu level. Depositions of hepatic and renal Cu were also related to the dietary Cu level in a dose-dependent manner. In particular, hepatic (155.2±13.3 μg/g) and renal (44.9±4.4 μg/g) Cu concentrations increased abruptly in the Cu-600 ppm group. In the liver, about 60% of Cu was distributed in the soluble fraction (100,000 g supernatant). In the Cu-600 ppm group, 25% of cystosolic Cu was bound to metallothionein (MT). Our results suggest that chronic exposure to Cu appears to have a deleterious effect on the hepatic function, and further, that even in rats with normal biliary Cu excretion, clearance of Cu from the liver may be marginal when dietary Cu is near the 600-ppm level. Although Cu is an essential nutrient, an overload of Cu should be avoided.     

Effect on soil and plant mineral levels following application of manures of different copper contents

Summary Manure from finishing pigs fed diets with and without a growth stimulating level of added copper (250 ppm in 1972, 370 ppm in 1973 and 300 ppm in 1974) was incorporated into a Groseclose silt loam at the rate of 15.5, 12.9 and 15.7 metric tons of dry matter per hectare, respectively, for 1972, 1973 and 1974. A third treatment was no manure. The manure was applied between rows when corn was about 10 cm tall and worked into the surface 10 cm of the soil with a rotary tiller. The average composition of the manure for the three years on a dry basis was 3.6 per cent nitrogen, 2.87 per cent calcium, 0.93 per cent magnesium, 2.22 per cent phosphorus, 1.30 per cent potassium, 648 ppm zinc, 2191 ppm iron. The copper content was 73 ppm for control manure and 1719 ppm for high copper manure. The copper content in the upper 10 cm of the soil was significantly increased each year when high copper manure was applied. During one growing season, copper did not appear to move down, however, plowing after the first year increased the copper level in the 10–20 cm depth with a small increase in the 20–30 cm depth. Potassium, zinc, phosphorus, calcium and magnesium levels of the soil were increased when manure was applied. There was a small increase in the copper content of the maize ear leaf (average of one ppm per year) when manure from pigs fed diets containing high copper was applied. Copper in the washed roots of the mature maize plants was doubled (5.6 vs 11.2 ppm) when the high copper manure was added. The copper content of grain from plants grown on soil receiving high copper manure was not different from that of grain from soil receiving no manure. The zinc, potassium and phosphorus contents of the maize ear leaf were increased a small amount when both control and high copper manure were applied with the effect of potassium and phosphorus carrying over to the grain. The iron and calcium contents of the ear leaf were not affected by application of manure, but there was a decrease in calcium content of the grain from the application of control and high copper manure. re]19750305Department of Animal ScienceDepartment of AgronomyDepartment of Statistics     

Genotoxicity assessment of amino zinc nanoparticles in wheat (Triticum aestivum L.) as cytogenetical perspective

Nanoparticles have a positive impact in several subjects especially in agriculture, while their safety is still being debated. Numerous commercial nano pesticide, insecticides, and fertilizers products are found in the local markets without any intensely studies on the side effect of these products on plant, human as well as environmental effects. The present study aimed to evaluate the genotoxicity of commercial amino zinc nanoparticles (AZ NPs) on Triticum aestivum L. during seeds germination and root elongation using concentration ranges (50, 100, and 150 ppm) at different exposure times (8, 16 and 24 hrs). Long term exposure to AZ NPs, exhibited only slight variation in germination rates and the elongation of roots was affected by AZ NPs treatment ranged from 97.66 to 100%. Significant reduction in the mitotic index was 35.33% after 24 hrs and 150 ppm of AZ NPs, was also observed comparing with control which was 88.0%. Genotoxicity was evaluated at a cytological level in root meristems that revealed sever variations in mitotic activity, chromosomal aberrations, and micronuclei release. Results exhibited that nano amino zinc could enter effortlessly into the cells and inhibit the normal cellular function. The decrease in the emergence of chromosomal aberrations resulting from AZ NPs exposure in a dose-dependent manner was clearly indicated that AZ NPs has induced genotoxic effect on wheat root tips.     

Ozone inhibits prostacyclin synthesis in pulmonary endothelium

The effects of ozone on lung arachidonate metabolism in-vitro were studied in cultured bovine pulmonary endothelial cells exposed for 2 hours to ozone in concentrations up to 1.0 ppm. A concentration-dependent decrease in prostacyclin synthesis was found (90% decrease at the highest ozone level of 1.0 ppm). The inhibition of prostacyclin synthesis was not due to a decreased release of arachidonic acid from membrane lipids. We also examined the hypoxic pulmonary vasoconstrictive response to 10% oxygen inhalation in anesthetized dogs in-vivo after exposure to 1.0 ppm ozone for 1 hour. Pulmonary vascular resistance was significantly increased after ozone exposure, similar to the findings in dogs given indomethacin (15 mg/kg). The percentage change in the hypoxic pulmonary pressor response was similar between the ozone exposure and indomethacin-treated groups, although due to the variance of the pulmonary vascular resistance values during hypoxia the results did not reach statistical significance. These results suggest that ozone inhalation affects pulmonary endothelial arachidonate metabolism in-vivo as well as in-vitro.     

Specific-locus mutation rates in the mouse following inhalation of ethylene oxide, and application of the results to estimation of human genetic risk

Male (101 × C3H)F₁ mice were exposed in an inhalation chamber to ethylene oxide (EtO) in air at a concentration of (generally) 255 ppm. After accumulating total exposures of 101 000 or 150 000 ppm.h in 16–23 weeks, the males were mated to T-stock females for a standard specific-locus mutation-rate study in which 71 387 offspring were observed. The spermatogonial stem-cell mutation rate at each exposure level, as well as the combined result, does not differ significantly from the historical control frequency. At the lower and higher exposure levels, the results rule out (at the 5% significance level) an induced frequency that is, respectively, 0.97 and 6.33 times the spontaneous rate; the combined results rule out a multiple of 1.64.

The relationship between mouse spermatogonial stem-cell mutation rates and EtO-induced testis ethylations was compared with the relationship between Drosophila post-stem-cell mutation rates and sperm ethylations (Lee, 1980). The comparison does not rule out equal mutability per ethylation; but it cannot prove parallelism. An assessment of the mouse-Drosophila relationship will require a more efficient alkylator than EtO and the use of comparable germ-cell stages.

More meaningful conclusions may be drawn by utilizing the data for direct estimation of human risk by expressing the induced mutation frequency that is ruled out (at the 5% significance level) as a multiple of control rate and extrapolating to human exposure levels. The probable absence of major stem-cell killing (and thus, possibly, cell selection) by EtO indicates that such extrapolation probably does not produce an underestimate. For a human exposure concentration of 0.1 ppm on working days during the reproductive lifespan, the mouse experimental results rule out (at the 5% significance level) an induced spermatogonial stem-cell gene mutation rate greater than 8% of the spontaneous rate; for 1.0 ppm, they rule out an induced rate roughly equal to the spontaneous rate. The induced rate for any one poststem-cell stage would have to be about 3 orders of magnitude higher than that for stem cells to constitute an equivalent risk.     

The effect of copper and nitrogen on the amino acid composition of oat straw

Summary The effect of fertilization with nitrogen and copper on the amino acid composition of oat straw has been studied.The plants (Avena sativa cv Yielder) were grown in peat with a very low copper content and supplied with two levels of nitrogen (NH₄ or NO₃) and three levels of copper sulphate.The higher level of nitrogen stimulated growth only when copper was added, whereas, without copper, it had an adverse effect on growth and prevented grain formation altogether. The higher level of nitrogen increased the nitrogen content of the straw at all levels of copper, but particularly in plants receiving no copper.Total amino acids in the straw hydrolysate of copper sufficient oats accounted for about 50% of the total N and was about 20% higher in copper-deficient tissues. The addition of copper caused a decrease in the amounts of all amino acids. The relative proportions of most of the amino acids to glycine remained fairly constant. Threonine, serine, alanine, iso-leucine, histidine and arginine showed small significant differences with copper treatment, whereas valine, tyrosine, phenylalanine, proline, lysine and cysteic acid (derived from cysteine and cystine) showed no differences. The proportion of aspartic acid relative to glycine in the straw hydrolysate was greatly increased in copper deficient plants supplied with the higher level of nitrogen, particularly as ammonium. The proportion of glutamic acid was also increased by the higher level of nitrogen, but showed no effect of added copper. Most of the difference in aspartic acid could be accounted for as free asparagine. The possible reasons for higher proportions of asparagine are discussed in relation to the metabolism of the oat plant.     

Interaction of maternal protein and carbon monoxide on pup mortality in mice: implications for global infant mortality

BACKGROUND: The United States Surgeon General declared 2005 as the "Year of Healthy Child." To improve the health of all children, we need to start before pregnancy, with their mothers. Unfortunately, protein deficiency in the diets of poor pregnant mothers in developing countries is widespread. Carbon monoxide (CO) pollution is serious public health problem in developed and developing countries. METHODS: A two-way factorial experimental design was used. Mice were maintained on 27%, 16%, 8%, or 4% protein diets. Dams were exposed to 0 ppm (control), 65 ppm, or 125 ppm CO in air, in environmental chambers for 6 hr/day during the first 2 weeks of pregnancy. Controls were also subjected to environmental chamber conditions. Food and water were available at all times. Animals were allowed to deliver, and data on pup mortality was recorded. RESULTS: Litter size was not affected by CO exposure, but was directly related to the dietary protein levels. Pup weight was inversely related to the CO exposure level, and directly related to the dietary protein levels. Pup mortality on date of birth was increased by CO exposure and was inversely related to the dietary protein levels. Pup mortality at 1 week of age was increased by CO exposure and 55% of all pups died in 125 ppm CO exposed group. Pup mortality at 1 week of age was inversely related to dietary protein levels. All pups in the 4% dietary protein and in all concentrations of CO died. All pups in the 8% protein group and in all CO concentrations died except in 125 ppm CO group. Pup mortality in the 16% dietary protein group ranged from 14.8% in 0 ppm to 36.8% in 65 ppm CO groups. Pup mortality in the 27% dietary protein group ranged from 14.3% in the 0 ppm to 41.1% in the 125 ppm CO groups. CONCLUSIONS: DATA suggest that protein deficiency and CO exposure enhance pup mortality. The protein and CO also interact to increase pup mortality in 16% and 27% protein groups. Carbon monoxide exposure, along with protein deficiency during gestation, may be contributing factors for high rates of infant mortality in developing countries. The results of the study also suggest that un-vented combustion for heating and cooking, ambient pollution, and biomass smoke may have a major impact on the health of children worldwide; and may explain the causes of high infant mortality in poor countries and some sections of the United States population.     

Ozone inhibits endothelial cell cyclooxygenase activity through formation of hydrogen peroxide

We have previously demonstrated that a 2H exposure of cultured pulmonary endothelial cells to ozone (0.0-1.0 ppm) in-vitro resulted in a concentration-dependent reduction of endothelial prostacyclin production (90% decrease at the 1.0 ppm level). Ozone-exposed endothelial cells, incubated with 20 uM arachidonate, also demonstrated a significant inhibition of prostacyclin synthesis. To further examine the mechanisms of the inhibition of prostacyclin synthesis, bovine pulmonary endothelial cells were exposed to 1.0 ppm ozone for 2H. A significant decrease in prostacyclin synthesis was found within 5 min of exposure (77 +/- 36% of air-exposed control values, p less than 0.05). Endothelial prostacyclin synthesis returned to baseline levels by 12H after ozone exposure, a time point which was similar to the recovery time of unexposed endothelium treated with 0.5 uM acetylsalicylic acid. Incubation of endothelial cells, previously exposed to 1.0 ppm ozone for 2 hours, with 4 uM PGH2 resulted in restoration of essentially normal prostacyclin synthesis. When endothelial cells were co-incubated with catalase (5 U/ml) during ozone exposure, no inhibition of prostacyclin synthesis was observed. Co-incubation with either heat-inactivated catalase or superoxide dismutase (10 U/ml) did not affect the ozone-induced inhibition of prostacyclin synthesis. These data suggest that H2O2 is a major toxic species produced in endothelial cells during ozone exposure and responsible for the inhibition of endothelial cyclooxygenase activity.     

Effects of nitrogen dioxide exposure on the contents of prostaglandins and thromboxane B2 in broncho alveolar lavage

Effects of 10 ppm nitrogen dioxide (NO2) exposure on the contents of prostaglandins (PGs) and thromboxane (TX) B2 in bronchoalveolar lavage (BAL) of rats were studied. In the BAL of normal rats, the amounts of PGs and TXB2 in the whole lavage were 6-keto-PGF1 alpha (38.0 +/- 6.4 ng) greater than TXB2 (11.8 +/- 4.0 ng) greater than PGF2 alpha (5.7 +/- 1.6 ng) much greater than PGE (0.5 +/- 0.3 ng). Rats were exposed to NO2 for 1,3,5,7 and 14 days. The NO2 exposure decreased in the level of 6-keto-PGF1 alpha by about 35% throughout the exposure. The level of TXB2 was higher in the day 5 exposure group (155%). The contents of PGF2 alpha and PGE first, decreased and then transiently increased on days 3 and 5. PG 15-hydroxy-dehydrogenase activity of lung homogenate decreased correspondingly on day 3 and 5. Then the contents PGF2 alpha and PGE decreased on day 7 and 14. 6-keto-PGF1 alpha and TXB2 are stable metabolites of PGI2, a strong bronchorelaxant and TXA2, a strong bronchoconstrictor respectively. Therefore the results suggested that the decrease in 6-keto-PGF1 alpha, a major prostanoid in the BAL and the increase in TXB2 may correlate with broncho constriction by NO2 exposure.     

Characteristics of Plant Communities and Copper Content in Dominant Plants in Hongtou Shan Copper Ore Region of Liaoning Province

Copper content in the soil of Hongtou Shan copper ore is 40–2000 ppm, with mean value at 471 ppm. Standard deviation is 667.5. There are many principal types of plant communities: Coppice of Quercus liaotungensis and Corylus sp. and Lespedeza bicolor scrub. In the soli with copper content more than 500 ppm, Gypsophila pacffica usually grows together. It significantly indicates the abnormal soil with respect to copper content. Analysis of copper content for 347 samples of 48 species shows: Limiting value of copper content is 8.45–44.40 ppm in dry plants, with difference of the values being 35.95. The plants contained copper at 5–10 ppm account for 12.8% of the total plants, at 10–30 ppm for 76.9% and at 30–45 ppm for 10.6%. Direct correlation is found between copper content in the Plants and in the soil, for example, Gypsophila pacifiea r=0.844 (N=8) It is important in biogeoehemical prospecting. There are no striking correlation between copper content of the plants and pH and organic matter content of soil.     

Copper nanoparticles: Green synthesis and managing fruit rot disease of chilli caused by Colletotrichum capsici

The present study was focused on synthesis and characterization of copper nanoparticles to evaluate their efficacy against fruit rot pathogen of chilli crop. The green synthesis of nanoparticles was carried out by using extracts of Eucalyptus and Mint leaves. The synthesis of copper nanoparticles was confirmed by XRD, PSA, SEM and TEM. The average size of these particles synthesized by Eucalyptus leaf extract (CuNP-E) ranged from 10 to 130 nm, while as size of Mint leaf extract synthesized particles (CuNP-M) ranged from 23 to 39 nm, thus confirming their nano size. These green synthesized copper nanoparticles were evaluated against Colletotrichum capsici where Carbendazim 50 WP @ 500 ppm and copper oxychloride 50 WP @ 2500 ppm served as standard checks. The mycelia inhibition of Colletotrichum capsici caused by copper nanoparticles was studied on PDA medium. CuNP-M @ 1000 ppm showed highest mycelial inhibition of 99.78% followed by 93.75% at 500 ppm and CuNP-E @ 1000 ppm compared to standard fungicides, carbendazim 50 WP @ 500 ppm (72.82%), and copper oxychloride 50 WP @ 2500 ppm (85.85%). The CuNP-M @ 500 ppm were significantly superior to carbendazim 50 WP @ 500 ppm and copper oxychloride 50 WP @ 2500 ppm, but was statistically at par with CuNP-E @ 1000 ppm. This shows effectiveness of much lower concentration of copper nanoparticles compared to conventional fungicides. In detached fruit method, nanoparticles applied before inoculation of pathogen showed better results with regard to incubation period, lesion number and lesion size than after inoculation of pathogen. The present study reveals a simple, convenient, non-toxic and cost-efficient technique for the synthesis of nanoparticles and their effectiveness against Colletotrichum capsici. CuNP-M first time synthesized and evaluated against Colletotrichum capsici performed better than CuNP-E.     

急性臭氧暴露对大鼠肺部细胞遗传毒性的影响*

目的: 探讨不同浓度臭氧急性暴露对大鼠肺部细胞的遗传毒性的影响。方法: 36只wistar大鼠随机分为对照组(过滤空气暴露)、臭氧暴露组(0.12 ppm、0.5 ppm、1.0 ppm、2.0 ppm、4.0 ppm)共6组,每组6只。以不同浓度的臭氧对大鼠进行动态染毒4 h后,取肺组织并分离单细胞,采用酶联免疫吸附法检测8-羟基脱氧鸟苷(8-OHdG),利用彗星实验、微核试验和DNA-蛋白质交联实验进行DNA和染色体损伤分析。结果: 与对照组相比,肺组织中8-OHdG含量从臭氧暴露浓度为0.12 ppm起即显著增加,在0.5 ppm时达到最高值。随着臭氧暴露浓度升高,彗星拖尾率逐渐上升,且存在明显的剂量-效应关系;DNA-蛋白质交联率有先升高后下降的趋势,且在2.0 ppm时达到最大值;而肺部细胞微核率尽管呈现出上升趋势,但与对照组相比无显著性差异。结论: 急性臭氧暴露在较低浓度(0.12 ppm)时即可导致大鼠肺部细胞的DNA损伤;而在较高浓度(4 ppm)时却未见显著的染色体损伤。     

Environmental contaminants influencing immunefunction in marine bivalve molluscs

The increased observation of pollution induced disease conditions in marine organisms has led to a growing interest on the effects of environmental contaminants on the immune system. Most studies on modulation of the immune system in bivalves by pollutants have concentrated on the effects of heavy metals and polycyclic aromatic hydrocarbons (PAHs). The current literature on contaminant effects on specific components of the bivalve immune system is reviewed together with the effects on susceptibility to infection. Data are presented showing the effects on immune parameters of exposure to Vibrio tubiashi following pre-exposure to copper or cadmium. Mussels exposed to cadmium for 7 days followed by 7 days exposure to V. tubiashi demonstrated significantly higher numbers of circulating haemocytes compared with non-Vibrio-exposed groups. Similar experiments conducted with copper exposure for both 7 days and 7 weeks followed by V. tubiashi for 7 days demonstrated a significant decrease in the percentage of circulating eosinophils compared with basophilic cells for both short and long term exposures. The intracellular release of superoxide (NBT reduction) by haemocytes was stimulated in Vibrio-challenged mussels with no copper pre-exposure but was significantly reduced in mussels pre-exposed to 0·2 ppm of copper for 7 weeks. The mortalities for the copper experiments showed increased levels with increasing copper concentration and were consistently higher in the V. tubiashi challenged mussels which had also been exposed to copper.     

Neurochemical effects of extended exposure to white spirit vapour at three concentration levels

Male Wistar rats were exposed to 575 (100 ppm), 2875 (500 ppm) or 5750 mg/m³ (1000 ppm) white spirit vapour for 4–17 weeks 5 days a week, 6 h daily. Perirenal fat solvent concentration corresponded in composition and concentration to those of the vapour at all times. The neurochemical effects included a dose-dependent decrease in the cerebellar succinate dehydrogenase activity for 8 weeks while creatine kinase activity increased after 12 weeks. The specific creatine kinase activity in the glial cell fraction, a marker for astroglia, did not increase suggesting proliferation of astroglial cells in the homogenate. The serum creatine kinase activity originating mainly from striated muscle was below the control range at the two higher concentrations after 12 weeks. Simultaneous analyses for isolated muscle membrane sialic acid and uronic acid residues showed decreased concentrations in proportion to lipid phosphorus or total membrane protein. Thus, the white spirit mixture has neurochemical effects possibly caused by paraffins and the same components may have caused the muscle cell membrane effects. The lowest exposure concentration represents a virtual ‘no effect’ level for rats in the 17-week exposure.     

The effect of the particle size of alumina sand on the combustion and emission behavior of cedar pellets in a fluidized bed combustor

A combustion experiment with cedar pellet fuel was carried out in a semi-pilot scale bubbling fluidized bed combustor. The effects of temperature, fluidized velocity, and bed material particle size on the emission of NOx, CO, and CO2 were investigated. The variations in the temperature profile and gas concentration in the vertical and horizontal directions of the combustor were also studied. The results showed that high temperature can improve the combustion efficiency and decrease CO emission. Moreover, increasing the fluidized velocity suppressed CO formation. In addition to temperature and fluidized velocity, the bed material also played an important role during cedar pellet combustion. Coarse bed materials were better than fine materials. In these test runs, the CO emission varied from 20 to 189 ppm, CO2 emission ranged from 5.7% to 19.5%, while NOx emission was quite stable at about 220 ppm.