阿特拉津和林丹对紫贻贝生长与繁殖净能的影响

本研究评估了亚致死浓度的林丹(1/2的60dLC50,0.935mg/L)和阿特拉津(1/2的60dLC50,3.585mg/L)对海洋性贝类影响的生理学反应。林丹和阿特拉津是已被公认的环境污染物质。56d的实验表明,这两种农药在贝类体内具有积累作用,而且在体内各器官的积累程度与其作用的靶器官相一致。林丹在体内的积累浓度(每克干重372μg)比阿特拉津(每克干重137μg)更高。该贝类在林丹中暴露56d,其氧的消耗比对照组降低10%,而在阿特拉津中则比对照组提高了29%。经林丹和阿特拉津暴露后,增加了氨排泄物。但是,两种农药均使贝类的取食率和吸收率下降。林丹会降低贝类的取食率、氧消耗、氨排泄、食物吸收率以及生长范围。在形式上,阿特拉津对贝类的影响与林丹的影响有不同之处,它会降低贝类的取食率和食物吸收率,但与林丹不同的是,它会提高贝类的氧消耗和氨排泄。总之,阿特拉津会明显地减小贝类繁殖净能。因此,阿特拉津暴露与林丹暴露的毒性症状是一致的。结合组织化学分析,贝类的生理学反应可作为一种理想的环境监测工具。研究结果表明,在二分之一的半致死浓度下暴露两个月,不仅能有效地证明林丹和阿特拉津在贝类组织内具有积累作用,而且对这些积累能产生生理反应。     

Larval development of hermit crab Clibanarius longitarsus: Synergistic effect of heavy metals

The levels of heavy metals copper and zinc were found to be high in the Vellar estuary. Therefore their effects on the larval development of the abundant hermit crab Clibanarius longitarsus were studied individually and in combination from hatching till moulting to glaucothoe stage in the laboratory using freshly hatched Artemia nauplii as food. The 96 h LC50 values found with 100 larvae each kept in 10 different concentrations of copper and zinc (350, 300, 250, 200, 150, 100, 50, 25, 10 and 5 ppb) were 50 ppb for copper and 90 ppb for zinc. Based on these 96 h LC50 values, three sublethal concentrations were chosen for the metals copper and zinc at 50%, 25% and 10% levels of the LC50 values. With increase in concentration of the test medium, the survival rate decreased and the time required for the completion of each zoeal stage increased. Copper was found to be more toxic than zinc as the survival rate in copper concentrations was lower than those in zinc concentrations. The survival rate in the mixed concentrations of metals was lower than in individual concentrations.     

The energy metabolism of common carp (Cyprinus carpio) when exposed to salt stress: an increase in energy expenditure or effects of starvation?

Stenohaline common carp (Cyprinus carpio) were chronically exposed to the two main osmoregulatory ions, Na+ and Cl-, at levels close to their isoosmotic value for 28 d (171 mM NaCl; 324 mosm kg-1; 10 per thousand). The aim of this study was to assess whether or not the disturbed ion and osmoregulation affected the energy demand and the energy stores of the exposed fish. Salt exposure reduced food intake by 70% and had adverse effects on growth and survival. Although food consumption decreased and growth was seriously affected, routine oxygen consumption of the exposed fish did not drop, indicating a reallocation of energy expenditure from growth toward other processes. A stress-induced increase in plasma glucose was observed. As a result of low food intake, lower levels of protein were used for fuel. Protein use itself was probably replaced by the use of carbohydrates. These effects were confirmed by the depletion of both muscle and liver glycogen stores during the experimental period. We conclude that, besides the effects of reduced feeding, stress induced extra energy requirements leading to the depletion of energy stores.     

Toxic effects of zinc and iron on the routine oxygen consumption of Tilapia sparrmanii (Cichlidae)

1. The routine oxygen consumption of Tilapia sparrmanii without the addition of any toxicants over a 72 hr period showed a decrease for the first 48 hr, but stabilised thereafter.2. Addition of zinc (98 mg l⁻¹) resulted in a drastic decrease of oxygen consumption for 3 hr. The routine oxygen consumption showed a significant decrease for the first 24 hr, while the second and third 24 hr revealed significant differences with great individual variance.3. The decrease in oxygen consumption observed after exposure to zinc, could be caused by gill damage as well as the internal action of zinc.4. An increase in oxygen consumption was noted for almost 3 hr after addition of iron (88mg l⁻¹). During the first-, second- and third 24 hr the oxygen consumption increased significantly, compared to the control values.5. The increase in routine oxygen consumption of T. sparrmanii when compared to control values after exposure to iron, could be attributed to stress and possible gill changes.6. The study revealed that after acute (72 hr) exposure to sublethal concentrations of zinc and iron, the routine oxygen consumption of T. sparrmanii was altered.     

Influence of food ration, copper exposure and exercise on the energy metabolism of common carp (Cyprinus carpio)

The present study was conducted to extend the understanding of the combined physiological effects of different food rations in combination with sublethal levels of copper in common carp (Cyprinus carpio). Fish acclimated to low (0.5% body weight) and high (5% body weight) food rations were exposed to 1 microM copper for a period of 28 days and kept for a further 14 days in copper free water to examine their recovery. Measurements of oxygen consumption, ammonia excretion and ammonia accumulation in plasma and muscle were done at various time intervals during the experimental period. Overall, oxygen consumption and ammonia excretion rates were significantly affected by food ration in both copper free and copper exposed fish. Additional challenges, such as copper exposure and/or exercise, significantly increased plasma and muscle ammonia in the fish fed a high food ration. Muscle ammonia levels in general responded slower (first increase after 72 h) and recovered within 2 weeks of exposure. There was a significant correlation between plasma ammonia levels, muscle ammonia levels and ammonia excretion rates. Influence of copper in terms of ammonia excretion and plasma ammonia accumulation was observed in high ration fish but low ration fish remained unaffected. This clearly indicates that ammonia metabolism was significantly influenced by copper in this group of fish showing that during unfavourable environmental conditions a high amount of food supply may turn deleterious to fish.     

Quantification of toxic and inhibitory impact of copper and zinc on mixed cultures of sulfate-reducing bacteria

The adverse effects of copper and zinc on an acetate-utilizing mixed cultures of sulfate-reducing bacteria (SRB) at concentrations below the toxic concentration (minimum metal concentration at which no sulfate reduction is observed) are reported in this paper. Mathematical models were developed to incorporate the toxic and inhibitory effects (defined as the reduction in bacterial population upon exposure to the metal and the decrease in the metabolic rate of sulfate reduction by the SRB, respectively) into the sulfate-reduction biokinetics. The characteristic toxicity and inhibition constants were obtained from the measurements of bacterial populations and dissolved metal concentrations in serum bottle studies conducted at 35 degrees C and pH 6.6. Both copper and zinc had toxic and inhibitory effects on SRB. The toxicity constants for copper and zinc were 10.6 and 2.9 mM(-1), respectively, indicating that exposure to copper resulted in a higher mortality of SRB than did exposure to zinc. The values of the inhibition constants were found to be 17.9 +/- 2.5 and 25.2 +/- 1.0 mM(-1) for copper and zinc, respectively. This implies that dissolved zinc was slightly more inhibitory to SRB than copper. The models presented in the paper can be used to predict the response of a sulfate-reduction bioreactor to heavy metals during acid mine drainage treatment.     

Iron and zinc status in rats with diet-induced marginal deficiency of vitamin A and/or copper

The hypothesis was tested that there are interactions of marginal copper and vitamin A deficiency regarding iron and zinc status. Copper restriction (1 vs 5 mg Cu/kg diet) significantly lowered copper concentrations in plasma and tissues of rats and reduced blood hemoglobin, hematocrit, and iron concentrations in tibia and femur, but raised iron concentrations in liver. Vitamin A restriction (0 vs 4000 IU vitamin A/kg diet) reduced plasma retinol concentrations and induced a fall of blood hemoglobin and hematocrit. Neither copper nor vitamin A restriction for up to 42 d affected feed intake and body wt gain. There were no interrelated effects of vitamin A and copper deficiency on iron status. Copper deficiency slightly depressed liver, spleen, and kidney zinc concentrations. Vitamin A deficiency lowered zinc concentrations in heart, but only when the diets were deficient in copper.     

Effects of cadmium,copper, and zinc on growth and thiol content of aquatic hyphomycetes

The effects of cadmium, copper, and zinc on the growth of ten strains ofaquatic hyphomycetes were investigated. On a solid medium, Cd and Cu reducedradial growth of most strains by 50% at concentrations between150–400 µM; in a liquid medium, the strains were more sensitive.The inhibitory effects of zinc were much less severe. Two isolates(Articulospora tetracladia and Tetracladium marchalianum) from a copper-minestream were more resistant against copper than conspecific strains from anon-polluted stream. Heliscus lugdunensis and Varicosporium elodeaeresponded to Cd exposure, but not to Cu or Zn exposure, by increasedsynthesis of SH-containing compounds. Glutathione levels showed a unimodalresponse to increasing Cd and Zn exposure. With copper, glutathionedecreased at intermediate levels of contamination. In the presence of Cd, H. lugdunensis synthesized several unknown sulfur-rich substances that wereabsent or produced at reduced rates in control cultures.     

Effects of reduced salinities on growth, food conversion efficiency and osmoregulatory status in the spotted wolffish

No significant differences in mean mass between groups were found at any time in spotted wolffish Anarhichas minor , mean (±S.D.) initial mass 76 (±21) g, reared at salinities of 12, 17, 25 and 34‰ for 12 weeks at 8° C. Salinity did not have a significant effect on daily feeding rates, total food consumption, food conversion efficiency and protein efficiency ratio. Growth trajectories varied between groups, but no overall difference in growth was found. Plasma osmolality and plasma chloride levels decreased with salinity in a 48 h abrupt exposure trial, and in the growth experiment the low salinity groups (12 and 17‰) exhibited significantly lower values compared with 25 and 34‰. The decrease was moderate and concentrations were well within the range described for other marine species. The results indicate that the spotted wolffish is a strong osmoregulator which could be reared at various salinity levels.     

Effect of dietary tin deficiency on growth and mineral status in rats

To clarify the influence of dietary tin deficiency on growth and mineral status, the following two different synthetic diets were fed to male Wistar rats: group 1—a diet containing 1.99 μg tin/g; group 2—a diet containing 17 ng tin/g. The rats in group 2 showed poor growth, lowered response to sound, and alopecia, with decreased food efficiency compared with rats in group 1. The changes of mineral concentrations in tissues observed in group 2, compared with group 1, are summarized as follows: calcium concentration in lung increased; magnesium concentration in lung decreased; iron concentrations in spleen and kidney increased; iron concentration in femoral muscle decreased; zinc concentration in heart decreased; copper concentrations in heart and tibia decreased; manganese concentrations in femoral muscle and tibia decreased. These results suggest that tin may be essential for rat growth.     

Effect of dietary tin deficiency on growth and mineral status in rats.

To clarify the influence of dietary tin deficiency on growth and mineral status, the following two different synthetic diets were fed to male Wistar rats: group 1--a diet containing 1.99 micrograms tin/g; group 2--a diet containing 17 ng tin/g. The rats in group 2 showed poor growth, lowered response to sound, and alopecia, with decreased food efficiency compared with rats in group 1. The changes of mineral concentrations in tissues observed in group 2, compared with group 1, are summarized as follows: calcium concentration in lung increased; magnesium concentration in lung decreased; iron concentrations in spleen and kidney increased; iron concentration in femoral muscle decreased; zinc concentration in heart decreased; copper concentrations in heart and tibia decreased; manganese concentrations in femoral muscle and tibia decreased. These results suggest that tin may be essential for rat growth.     

The role of coprophagy in the feeding strategies of terrestrial isopods

Summary The hypothesis that faeces recycling in isopods evolved as an adaption to facilitate maintenance of an adequate copper balance in terrestrial environments is examined. Experimental observations on the consumption, absorption and growth rates of Porcellio scaber fed Betula pendula leaf litter varying in copper content and extent of microbial decay are reported. Preventing the isopods from reingesting their faeces caused a reduction in the growth rates of experimental animals fed their natural low copper diet but also of those fed copper enriched diets. When the availability of copper in the primary food was increased consumption of the litter decreased and growth rates were significantly reduced. These results suggest that copper is not normally a critically limiting nutrient for terrestrial isopods.When the primary diet was supplemented with shredded carrot, faeces deprivation did not cause a decrease in growth rates. These experimental animals gained weight significantly faster than controls fed decaying leaf litter alone.Faeces formed a significantly greater proportion of the diet when the animals were fed freshly fallen rather than decayed litter.We conclude a) that enhanced microbial activity in the faeces increases their nutrient status in such a way that some coprophagy is necessary in order to optimize overall nutrient uptake, and b) that theability to vary the extent to which faeces are recycled in response to differences in food quality is important in that it introduces greater flexibility into the feeding strategies of these generalist macro-decomposers.     

Effect of copper,zinc and cadmium on the promoter of selenoprotein W in glial and myoblast cells

Rat selenoprotein W (SeW) promoter activity was investigated using different concentrations of cadmium, copper, and zinc. Two fragments (404 and 1265 bp) of the SeW promoter, containing a single metal response element (MRE), were ligated into the multiple cloning site of a pGL3-Basic reporter plasmid. The constructs were transfected into cultured C6 (rat glial) and L8 (myoblast) cells and promoter activity measured by means of luciferase reporter gene fused to the SeW promoter fragments in the reporter plasmid. With post-transfection exposure of these cell lines to these metals, copper and zinc, but not cadmium, significantly increased promoter activity of the unmutated 1265 bp (not 404 bp) construct (p<0.05) only in the C6 cells. Mutation of the MRE sequence abolished promoter response to metal exposure but did not eliminate promoter activity. The results suggest that SeW expression in glial cells can be increased on exposure to copper and zinc and that this response is dependent on the MRE sequence present in the SeW promoter.     

Mechanism of a plastic phenotypic response: predator-induced shell thickening in the intertidal gastropod Littorina obtusata

Phenotypic plasticity has been the object of considerable interest over the past several decades, but in few cases are mechanisms underlying plastic responses well understood. For example, it is unclear whether predator-induced changes in gastropod shell morphology represent an active physiological response or a by-product of reduced feeding. We address this question by manipulating feeding and growth of intertidal snails, Littorina obtusata, using two approaches: (i) exposure to predation cues from green crabs Carcinus maenas and (ii) reduced food availability, and quantifying growth in shell length, shell mass, and body mass, as well as production of faecal material and shell micro-structural characteristics (mineralogy and organic fraction) after 96 days. We demonstrate that L. obtusata actively increases calcification rate in response to predation threat, and that this response entails energetic and developmental costs. That this induced response is not strictly tied to the animal's behaviour should enhance its evolutionary potential.     

Facultative monophagy as a consequence of prior feeding experience: behavioral and physiological specialization in Colias philodice larvae

Summary Although newly-emerged Colias philodice readily accept Medicago sativa, Melilotus alba, and Coronilla varia, fifth instar larvae reared on any single plant species display a highly significant induced feeding preference for their rearing host. Forced host-switching reveals that fifth instar relative growth rate (RGR) on M. sativa and M. alba is significantly reduced by prior feeding on either alternative host. Moreover, regardless of rearing diet, switching to a novel host during the fifth instar results in reduced RGR, relative consumption rate (RCR), efficiency of conversion of digested food (ECD), and pupal weight. These results support the hypothesis that induction of feeding preference is an adaptive response that predisposes larvae to feed on the plant species they are most capable of utilizing for growth.     

Effect of transition metals on stress, lipid peroxidation and antioxidant enzyme activities in tobacco cell cultures

to-baccoBright Yellow 2 (BY-2) suspension culture to understand the mechanisms of metal resistance in plant cells.We have analysed superoxide dismutase, catalase, and ascorbate peroxidase enzyme activities and superoxidedismutase-isoforms by isoelectric focusing gels in tobacco cells grown at two different toxic concentrations ofeach of the transition metals: copper, iron, manganese and zinc. Exposure of tobacco cells to these metals causedchanges in total superoxide dismutase activity in a different manner, depending on the metal assayed: after cop-perand manganese treatments, total superoxide dismutase activity was enhanced, while it was reduced after ironand zinc exposure. Superoxide dismutase-isoforms were affected by the metal used, and a Fe-SOD band with thesame isoelectric point as a Cu, Zn-SOD from non-treated cells, was induced after iron and zinc treatments. Cu,Zn-SODs were present in all metal-treatments whereas Mn-SOD was not detected in any case. Concerning otherantioxidant enzymes tested, such as catalase and ascorbate peroxidase, the latter showed a remarkable increase inactivity in response to copper treatments and catalase activity was enhanced after iron and with the lowest man-ganeseconcentration. Lipid peroxidation was increased after each metal treatment, as an indication of the oxi-dativedamage caused by metal concentration assayed in tobacco cells. These results suggest that an activation ofsome antioxidant enzymes in response to oxidative stress induced by transition metals is not enough to confertolerance to metal accumulation.     

Induction of metallothionein by exposure to normobaric 100% oxygen atmosphere in rats with different zinc supply

The objective of this study was to determine the effects of an oxygen enriched environment on the induction of the metalloprotein metallothionein (MT) and its relation to zinc metabolism in rats supplied with different levels of dietary zinc. Male albino rats were fed purified diets based on maize starch, egg white, saccharose and soybean oil differing in the concentration of zinc (1; 20; 100; 500 mg Zn/kg diet). At a dietary zinc supply of 1 mg/kg, the rats developed a zinc deficiency indicated by visual and biochemical parameters. At the end of the 37-day feeding period, half of the rats were exposed to 100% oxygen for 12 h.

The oxygen treatment significantly reduced plasma zinc in the zinc supplemented rats and reduced it in tendency in the zinc deficient rats. The MT concentration was increased in the zinc supplemented groups in the liver, kidney and lung. The oxygen treatment elevated the metallothionein concentration in the two high zinc supplemented groups (100 and 500 mg Zn/kg diet) in the liver. The response of the zinc concentration in plasma and of hepatic metallothionein levels to oxygen exposure indicates a role of metallothionein in zinc distribution or interactions with other trace elements to support antioxidant capacity, rather than an impact on direct scavenging activity of free radicals.     

Serum calcium, zinc, and copper in relation to biomarkers of lead and cadmium in men

The influence of exposure to lead and cadmium on serum concentrations of calcium, zinc, and copper was examined in 299 healthy Croatian men 20-55 years of age, including 143 workers in a lead battery factory and 156 control subjects. The interrelationship of blood lead, activity of delta-aminolevulinic acid dehydratase, erythrocyte protoporphyrin, blood cadmium, age, smoking habits, and alcohol consumption with respect to serum calcium, zinc, and copper levels was calculated by forward stepwise multiple regression. The results showed that chronic moderate exposure to lead decreased serum zinc, calcium and, to a lesser extent, copper levels. Exposure to cadmium occurred mostly through smoking and seemed to contribute to a decrease of serum zinc. All changes in serum concentrations of these essential elements were significant but remained within the normal range. The results suggest possible mechanisms of lead- and/or cadmium-induced adverse health effects in humans.     

Effects of temperature and ration level on the growth and food conversion efficiency of Salmo gairdneri, Richardson

The effects of temperature and ration size on the growth rate and gross efficiency of food conversion of juvenile rainbow trout Salmo gairdneri were evaluated during 25-day seasonal experiments. Rations ranged from near-starvation to repletion levels. Test temperatures were 3 and 6°C higher than the controls which fluctuated dielly and seasonally. At rations near maintenance, elevated temperatures decreased trout growth. As the feeding rate increased the detrimental effect of temperature on growth was ameliorated. At repletion feeding levels, elevated temperature up to 17°C improved trout growth by increasing the maximum food consumption rate. With a temperature increase from 6.9 to 22.5°C maintenance rations increased from 2.2 to 7.5 % body weight per day. Gross efficiency was dependent upon ration level and temperature. As the food consumption rate increased, efficiency increased to a maximum, then generally declined at repletion levels. Elevated temperatures resulted in reduced efficiencies at low consumption rates but temperatures had little effect at high ration levels. A field study provided estimates of the food consumption relationships established in the laboratory, suggested any substantial increase of stream temperature without a concomitant increase of food abundance would result in decreased trout production.     

The Effect of Peripheral Administration of Zinc on Food Intake in Rats Fed Zn-adequate or Zn-deficient Diets

Zinc deficiency induces a striking reduction of food intake in animals. To elucidate the mechanisms for this effect, two studies were connectedly conducted to determine the effects of peripheral administration of zinc on food intake in rats fed the zinc-adequate or zinc-deficient diets for a 3-week period. In study 1, two groups of male Sprague-Dawley rats were provided diets made either adequate (ZA; 38.89 mg/kg) or deficient (ZD; 3.30 mg/kg) in zinc. In study 2, after feeding for 3 weeks, both ZA and ZD groups received intraperitoneal (IP) injection of zinc solution with three levels (0.5, 1.0, and 2.0 mug zinc/g body weight, respectively) and cumulative food intake at 0.5, 1, 2, 4, and 24 h, and plasma hormones concentrations were measured. The results in study 1 showed rats fed the ZD diets revealed symptoms of zinc deficiency, such as sparse and coarse hair, poor appetite, susceptibility to surroundings, lethargy, and small movements. Zinc concentrations in serum, femur, and skeletal muscle of rats fed the ZD diets declined by 26.58% (P < 0.01), 27.32% (P < 0.01), and 24.22% (P < 0.05), respectively, as compared with ZA control group. These findings demonstrated that rat models with zinc deficiency and zinc adequacy had been fully established. The results in study 2 showed that IP administration of zinc in both ZA and ZD rats did not influence food intake at each time points (P > 0.05), although zinc deficiency suppressed food intake. Plasma neuropeptide Y (NPY) was higher, but insulin and glucagon were lower in response to zinc deficiency or zinc administration by contrast with their respective controls (P < 0.05). Leptin, T3, and T4 concentrations were uniformly decreased (P < 0.05) in rats fed the ZD diets in contrast to ZA diets; however, no differences (P > 0.05) were observed during zinc injection. Calcitonin gene-related peptide was unaffected (P > 0.05) by either zinc deficiency or zinc administration. The present studies suggested that zinc administration did not affect short-term food intake in rats even in the zinc-deficient ones; the reduced food intake induced by zinc deficiency was fprobably associated with the depression in thyroid hormones. The results also indicated that NPY and insulin varied conversely during the control of food intake.