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1.
This study examined the toxicological and physiological responses of a commercially important coral-reef grouper, Plectropomus leopardus (Serranidae), to injection of enriched stable-isotope barium chloride (BaCl2) solution. Thirty adult P. leopardus were subject to one of two 138BaCl2 injection treatment groups (corresponding to dosage rates of 2 and 4 mg 138Ba kg−1 body mass), and a control group in which fish were injected with 0·9% sodium chloride (NaCl) solution. Fish from each group were sampled at post-injection intervals of 48 h and 1, 3, 5 and 8 weeks, at which time blood and tissue samples were removed from each fish. Residual concentrations of Ba and 138Ba:137Ba ratios were measured in muscle, gonad, liver and bone tissues of each experimental fish. Elevated Ba concentrations were detected in all treatment fish tissue samples within 48 h post injection. Residual Ba concentrations decreased throughout the remainder of the 8 week experimental period in all tissues except bone. The BaCl2 injection had no significant effects on measured whole blood variables or on the plasma concentrations of steroid hormones. Enriched Ba stable isotopes can therefore be used at low dosages to mark larvae of commercially important marine fishes, without adverse effects on the health of the fishes or on humans who may consume them.  相似文献   

2.
Synthetic chlorochromate derivatives of pyridine and quinoline were active in vitro against type cultures of Escherichia coli (ATCC 128), Staphylococcus aureus (ATCC 14775), Pseudomonas aeruginosa (ATCC 10145) and Bacillus subtilis (NCTC 8236). The minimum inhibitory concentrations (MIC) were 125–250 μg ml−1 and 250–500 μg ml−1 for pyridinium chlorochromate and quinolinium chlorochromate, respectively. An established derivative of quinoline (Perfloxacin) had an MIC of 125–250 μg ml−1. The extinction time for 105 cfu in broth was 90 min for pyridinium chlorochromate and 120 min for quinolinium chlorochromate, except for B. subtilis which survived up to about 180 min and 360 min. A combination of the two compounds produced an antagonistic effect. The 50% lethal dose (LD50 toxicity) in mice was estimated at 76 μg g−1 and 33 μg g−1 body weight for the quinolinium and pyridinium chlorochromates. The compounds also exhibited some potential for suppressing a simulated staphylococcal infection in mice at the dosage levels of ca 22 μg g−1 for pyridinium chlorochromate and 45 μg g−1 for quinolinium chlorochromate.  相似文献   

3.
Ascorbate concentration in fish ontogeny   总被引:2,自引:0,他引:2  
The ontogenetic trend of ascorbate has been quantified in three freshwater fishes: roach ( Rutilus rutilus ), whitefish ( Coregonus lavaretus ) and Arctic charr ( Salvelinus alpinus ). Total ascorbate (reduced and oxidized) declined from 150 to μg g−1 as newly hatched larvae grew to become several-months-old juveniles. Declining total ascorbate with increasing size of metamorphosing fish could not be reversed by feeding on brine shrimp, Artemia salina nauplii, zooplanktonic food containing > 74μg g−1 total ascorbate. The proportion of reduced ascorbate in total ascorbate increases with fish size/age. The physiological mechanism of the changes in transferable ascorbate forms remains unknown, but high dehydroascorbate concentrations suggest high vulnerability of larval fish to oxidation stress. This is the first report on quantity of vitamin C retained in actively-feeding larval and juvenile fish. The efficiency of ascorbate transfer from zooplankters to larval fish amounted to 5–20%. The ecological significance of larval fish feeding on various zooplankters and/or phytoplankton may reflect a trend toward maximum transfer of this vitamin in freshwater food webs.  相似文献   

4.
The effects of water hardness (9 and 220 mgl−1 as CaCO3) upon zinc exchange in brown trout exposed to 0.77 μmol Zn 1−1 have been investigated using artificial soft water (<49.9 μmol Ca l-1, <40.1 μmol Mg 1−1) and mains hard water (1671.7 μmol Ca 1−1, 493.6 μmol Mg 1−1) of known composition. Both hard and soft water-adapted fish exhibited a bimodal pattern of net zinc influx. Net zinc influxes during both fast and slow uptake phases were significantly greater ( P <0.001) in soft (82.9 and 6.2 μmol Zn 100 g−1 h−1) than in hard water (46.3 and 2.4 μmol Zn 100 g h−1). Zinc efflux (- 0.2 μmol Zn 100 g−1 h−1) was enhanced only in hard water during the slow net influx phase.
Brown trout exposed to zinc in hard water and placed in metal-free media exhibited a greater net efflux (- 25.6 μmol Zn 100 g−1 h−1) of the metal than did fish in soft water (-4.2 μmol Zn 100 g−1 h−1) treated in the same manner. Tissue 65Zn activities reflected both the differences in uptake and excretion rates of the metal between hard and soft water fish. During zinc exposure (0.77 μmol Zn 1−1) high water hardness reduced tissue burdens of the metal by reducing net branchial influx, and enhancing efflux of the metal in hard water fish.  相似文献   

5.
Iron inefficiency in the maize ( Zea mays L.) mutant ysl is caused by a defect in the uptake system for Fe-phytosiderophores. To characterize this defect further, the uptake kinetics of Fe-phytosiderophores in ysl was compared to the Fe-efficient maize cultivar Alice. Short-term uptake of 59Fe-labeled Fe-deoxymugineic acid (Fe-DMA) was measured over a concentration range of 0.03 to 300 μM. Iron uptake in Fe-deficient plants followed Michaelis-Menten kinetics up to about 30 μM and was linear at higher concentrations, indicating two kinetically distinct components in the uptake of Fe-phytosiderophores. The saturable component had similar Km (∼ 10 μM) in both genotypes. In contrast. Vmax was 5.5 μmol Fe-DMA g−1 dry weight [30 min]−1 in Alice, but only 0.6 μmol Fe-DMA g−1 dry weight [30 min]−1 in ysl. Uptake experiments with double-labeled 59Fe-[14C]DMA suggest that in both cultivars Fe-DMA was taken up by the roots as the intact chelate. The results indicate the existence of a high-affinity and a low-affinity uptake system mediating Fe-phytosiderophore transport across the root plasma membrane in maize. Apparently, the mutation responsible for Fe inefficiency in ysl affected high-affected uptake and led to a decrease in activity and/or number of Fe-phytosiderophore transporters.  相似文献   

6.
The protective effects of dietary Ca2+ supplementation against Cd accumulation in rainbow trout Oncorhynchus mykiss fed with Cd-contaminated food were evaluated in relation to chronic changes in intestinal absorption rates. The changes were measured ' in vitro '. The control diet contained c. 20 mg Ca2+ g−1 food and 0·25 μg Cd g−1 food; the experimental diets were supplemented with CaCO3 and Cd(NO3)2·4H2O to levels of 50 mg Ca2+ g−1 food and 300 μg Cd g−1 food, alone and in combination. The Ca2+ and Cd absorption rates were measured using radiotracers (45Ca, 109Cd) at total Ca2+ and Cd concentrations of 3·0 and 0·12 mmol l−1, respectively in the intestinal saline. Chronically elevated dietary Cd caused a significant increase in Cd absorption rate by up to 10-fold at 30 days in the mid-intestine. The high Ca2+ diet prevented this up-regulation of Cd transport rate. Conversely, intestinal Ca2+ absorption was significantly increased by two- to five-fold by the Ca2+-supplemented diet at 30 days in both the mid- and posterior intestine, and this effect was eliminated when Cd was simultaneously elevated in the diet. Ca2+ and Cd probably interact at common pathways and transport mechanisms in the intestine, though independent pathways may also exist.  相似文献   

7.
Abstract A method was developed for direct extraction, purification and amplification of DNA from forest soil. Eighty-two % of the DNA in Pseudomonas aeruginosa UG2Lr introduced into soil was recovered. The detection limit for the strain was approximately 800 cfu g−1 of dry soil based on the polymerase chain reaction (PCR). Survival of κ-carrageenan-encapsulated and unencapsulated UG2Lr was monitored by antibiotic selective and bioluminescence-based nonselective plating and PCR-amplification of a tnsA fragment. After freeze-thaw treatment of soil samples, the unencapsulated UG2Lr declined from an initial population density of 1 × 109 cfu g−1 of dry soil to below the detection threshold of both selective (14 cfu g−1 of dry soil) and nonselective (1 × 103 cfu g−1 of dry soil) plating. However, presence of nonculturable UG2Lr cells in the soil was revealed by PCR and resuscitation of the bacteria. Population density of the encapsulated UG2Lr increased from 2.7 × 106 to 2.9 × 108 cfu g−1 of dry soil after a 3-week incubation at 22°C and declined to 6.3 × 106 cfu g−1 of dry soil after the freeze-thaw treatment.  相似文献   

8.
Abstract An optimized polyethylene glycol (PEG) method of transformation was developed for Methanococcus maripaludis using the pKAS102 integration vector. The frequency of transformation with 0.8 μg of plasmid and 3×109 cells was 4.8×10−5 transformants cfu−1, or 1.8×105 transformants μg−1, which was four orders of magnitude greater than with the natural transformation method. A Pst I restriction activity in M. maripaludis was also identified. Methylation of the plasmid with Pst I methylase increased the methanococcal transformation frequency at least four-fold. Also, chromosomal DNA from M. maripaludis was resistant to digestion by the Pst I endonuclease.  相似文献   

9.
The distribution of microbial populations that decomposed sugar, cellulose and lignin-related substrates was examined in a beech Fagus grandifolia Ehrh. and maple Acer saccharum Marsh. dominated woodlot developed on glacial till. The topography of the woodlot, characterized by rises, depressions and more extensive level areas about 1 m in diameter with a 0.5 m vertical maximum, produced a mosaic of decomposer habitats designated as high, level and low sites.
In general, populations of sugar, cellulose and lignin decomposing organisms (based on ten estimates made from April to October) were two to four times higher in litter and soil samples from low sites than those from high sites. Sugar decomposing bacteria in litter were most abundant at all topographic sites. 135 × 106 g−1 dry litter at high sites, 396 × 106 g−1 at level sites and 456 × 106 g−1 at low sites; lignolytic fungi were least abundant, 391 × 102 g−1 dry litter at high sites. 700 × 106 g−1 at level sites and 954 × 102 g−1 at low sites. Numbers of microbial decomposers in the topographic sites were correlated with organic matter content. Distribution of fungal genera did not appear to be related to topographic site. Most populations examined showed two numerical peaks, one in late May or June and one in late September or October. It is suspected that these peaks were influenced by the coincident timing of favourable physical conditions and priming by soluble nutrients leached from litter.  相似文献   

10.
Five strains of filamentous fungi belonging to the genera Mortierella and Cunninghamella were examined for the content of dihomo-γ-linolenic, arachidonic, eicosapentaenoic acids and prostaglandins (type E2 and F ). Prostaglandins were detected using an ELISA method in mycelia of all tested strains (range 50–4800 ng g−1 of PGE2 and 6–30 ng g−1 of PG F ). Several micro-organisms also produced prostaglandins in the culture medium (2·2–137·6 μg l−1 for PGE2 and 0·4–7·8 μg l−1 for PG F ).  相似文献   

11.
In the present study, profiles of stable isotope composition were characterized for two species with partially migratory populations in rivers along the latitudinal gradient of Patagonia, brown trout Salmo trutta and rainbow trout Oncorhynchus mykiss . The effects of factors ( e.g. ontogeny of fishes, location, species and fasting) that may influence the stable isotope analysis (SIA) were evaluated, as was SIA evaluated as a tool to assign individual fish to their corresponding ecotype. Anadromous fishes exhibited enriched δ15N (15·2 ± 1·0‰; mean ± s . d .) and δ13C (−19·2 ± 1·3‰) relative to resident fishes'δ15N (8·8 ± 1·1‰) and δ13C (−23·2 ± 2·5‰). For both species, the difference in δ15N was larger between resident (range 6·8–10·7‰) and anadromous (range 14·3–17·8‰) fishes than that in δ13C. Values of δ13C, while not as dramatically contrasting in rainbow trout, provided a powerful anadromy marker for brown trout in the region. Increases were found in both δ15N and δ13C during the spawning migration of anadromous rainbow trout, most likely due to fasting. Differences in stable isotopes between location, size and species were found, suggesting different stable isotopes base levels in freshwater environments and different trophic levels and feeding location of anadromous populations. The SIA was demonstrated as a powerful tool for ecotype discrimination in Patagonian Rivers, overriding any effect of sampling location, size or species.  相似文献   

12.
Abstract The fate of a Bacillus amyloliquefaciens with the recombinant plasmid pSB20 sprayed on the phyllosphere of grass, and of a Tn 5 marked Pseudomonas syringae sprayed on the phyllosphere of bush beans was studied in planted soil microcosms. B. amyloliquefaciens showed a decline from 1.5×108 to 3.1×102 cfu g−1 on the phylloplane of grass in the course of the experiment. B. amyloliquefaciens was easy to follow by selective cultivation due to the complete absence of bacterial background growth. Southern blot hybridization of Hin dIII digested genomic DNA showed plasmid restriction patterns identical with pSB20 indicating high plasmid stability. In total DNA extracts from phyllosphere bacteria the recombinant plasmid was detectable by Southern blot hybridization up to 6×104 cfu g−1 (wet weight). Counts of hybridizing colonies showed that P. syringae established on the phyllosphere of bush beans at between 5×103 and 4×106 cfu g−1 fresh weight. During senescence of the bean plants the strain was no longer detectable by selective cultivation and subsequent colony hybridization. In contrast, Tn5 marked DNA was detected after PCR amplification over the whole period of the experiment.  相似文献   

13.
The sludge from hospital waste treatment facilities is a potential source of infectious organisms. The average numbers of micro-organisms in the sludge of hospital wastewater in Taiwan were as follows: total count 8·1 × 107 cfu g−1 (dry weight of sludge), and 1·4 × 106, 3·6 × 105, 1·6 × 105, 2·2 × 105 and 5·5 × 104 cfu g−1 (dry weight of sludge) for total coliforms, faecal coliforms, faecal streptococci, Pseudomonas aeruginosa and Salmonella spp., respectively . Salmonella spp. were detected in 37% (10 of 27) of the sludges from hospital wastewaters. Therefore, the treatment of such sludge to reduce pathogenic micro-organisms should be considered.  相似文献   

14.
The relationship between fungal growth and the production of fumonisin on maize grain by 25 strains of Fusarium moniliforme of different origins has been investigated. Although sporulation was essentially the same for all the strains (about 108 propagules g−1 dry matter), ergosterol assays revealed marked variations in fungal biomass. All strains studied produced highly variable amounts of fumonisin B1, the highest levels being observed in strains of ergosterol content above 400 μg g−1. However, no correlation could be established between the synthesized biomass and the quantity of fumonisins produced. We verified that ergosterol is an indicator of mycelial growth, and therefore of the potential toxicity of the analysed grain.  相似文献   

15.
The respiration of coho salmon, Oncorhynchus kisutch , weighing between 15 and 50 g was measured at gradually declining oxygen levels and at temperatures ranging between 14 and 17°C. The maximum and minimum oxygen concentrations tested were 250 and 40 μmol L−1, respectively. Respiration rates were measured for 1 h periods before oxygen concentration was lowered by 12.5 or 25.0 μmol oxygen L−1. At the end of these endurance tests the oxygen level was returned to normoxic conditions and respiration rates were determined for the recovery period. Under normoxic conditions (> 200 μmol L−1) the respiration of coho levelled around 5.1 μmol g−1 wet weight h−1. At intermediate levels between 150 and 200 μmol oxygen L−1, the average rate increased to 5.8 μmol g−1 h−1, which could be attributed to higher spontaneous activity of the test animals. At low oxygen levels (< 150 μmol−1) average respiration rates dropped to values between 5.5 and 5.7 μmol g−1 h−1, reaching a minimum of 3.8 μmol g−1 h−1 at oxygen levels below 50 μmol Lμ. First mortality was observed in this range. After exposure to reduced oxygen levels the fish maintained a higher respiration rate when again exposed to normoxic oxygen levels above 200 μmol L−1. Increased respiration rates were observed for a recovery period of 6 h.  相似文献   

16.
Preference responses of zebrafish to 10−3, 10−4 and 10−5M alanine (Ala) were concentration- dependent. Behavioural responses to copper (Cu) and Cu + Ala mixtures were also assessed. Zebrafish avoided 100 and 10 μg Cu l−1, but not 1 μg l−1. Mixtures of 10−3 m Ala+ 100 μg Cu l−1 and 10 4 M Ala + 10 μg Cu 1−1 were avoided as intensely as was Cu alone. Responses to 10−3 M Ala + 10 or 1 μg Cu l−1 and 10 4 M Ala +1 μg Cu l−1 did not differ statistically from controls (no detectable preference or avoidance). These results demonstrate, firstly, that a concentration of a pollutant avoided by itself (10 μg Cu l−1) may not be avoided when encountered with an attractant chemical stimulus (Ala) and may suppress the preference for an attractant stimulus, and secondly, that a concentration of a pollutant not avoided by itself and not considered deleterious (1 μg Cu l−1) suppresses attraction to Ala (an important constituent of prey odours for many fishes).  相似文献   

17.
The levels of polyamines (PA) and abscisic acid (ABA) in the pericarp of California variety pepper fruit ( Capsicum annuum L.) were analyzed during development and ripening. Putrescine level was 2.75 μmol g−1 fresh weight 7 days after fruit set and fell during the exponential stage of growth to 1.05 μmol g−1 fresh weight. During the second growth stage. PA and ABA levels remained stable and fell sharply at the beginning of maturation. The levels of spermidine and spermine decreased throughout fruit development and maturation from 0.61 to 0.05 and 0.31 to 0.02 μmol g−1 fresh weight, respectively, but no changes were associated with the onset of maturation. ABA levels remained high (0.70-0.80 μg g−1 fresh weight) during the stages of fruit growth and fell at the beginning of maturation to 0.12 μg g−1 fresh weight, before rising again during the last stages of maturation and senescence. The decrease in putrescine and ABA levels and the subsequent increase in the latter may be responsible for controlling the processes of ripening in pepper fruit.  相似文献   

18.
Mercury concentrations in the axial muscle tissue of most (243) of the 254 Anguilla australis and most (20) of the 27 A. reinhardtii collected from 30 sites in coastal rivers and lakes in Victoria, Australia, during 1975–78 were well below the Australian statutory health limit (0.5 μg g−1 wet weight). For A. australis the mean mercury concentration was 0.17 μg g−1 (±0.16 s.d. , range 0.01–1.60 μg g−1); for A. reinhardtii the values were 0.37 ± 0.23 μg g−1 (range 0.12–1.10 μg g−1). Statistical analyses showed that variation in mercury concentration due to total length accounted for only 13% of the total variation in A. australis and 2% in A. reinhardtii whereas locality accounted for 54 and 68%, respectively. Both species are thus considered suitable as indicators of mercury pollution.  相似文献   

19.
Oxygen consumption rates during embryonic and the first 38 days of larval development of the striped mullet were measured at 24° C by differential respirometry. Measurements were obtained at the blastula, gastrula and four embryonic stages, and at the yolk-sac, preflexion, flexion and post-flexion larval stages.
Oxygen uptake rates of eggs increased linearly from 0.024 μl O2 per egg h-1 (0·323 μl O2 mg-1 dry wt h-1) by blastulae to 0·177 μlO2 per egg h-1 (2·516 μlO2mg 1dry wth-1) by embryos prior to hatching. Respiration rates did not vary significantly among four salinities (20,25, 30, 35%0).
Larval oxygen consumption increased in a curvilinear manner from 0·243 μl O2 per larva h-1 shortly after hatching to 18·880 μl O2 per larva h-1 on day 38. Oxygen consumption varied in direct proportion to dry weight. Mass-specific oxygen consumption rates of preflexion, flexion, and postflexion larvae did not change with age (10·838 μl O2 mg 1dry wt h-1).
Larval oxygen consumption rates did not vary significantly among salinities 10–35%. Acute temperature increases elicited significant increases in oxygen consumption, these being relatively greater in yolk-sac larvae ( Q10 = 2·75) than in postflexion larvae ( Q10 = 1·40).  相似文献   

20.
Ethylene production from an embryogenic culture of Norway spruce ( Picea abies L.) was generally low. ca 2.5 nl g−1 h−1, whereas 1-aminocyclopropane-1 -carboxylic acid (ACC) concentration was high, fluctuating between 50 and 500 nmol g−1 during the 11-day incubation period. Hypoxia (2.5 and 5 kPa O2) rapidly inhibited ethylene production without subsequent accumulation of ACC. Exogenous ACC (1, 10 and 100 μ M ) did not increase ethylene production, but the highest concentrations inhibited tissue growth. Ethylene (7 μl I−1) did not inhibit growth either when supplied as ethephon in the medium or in a continuous flow system. Benzyladenine (BA) had little effect on ethylene production, although it was necessary for sustaining the ACC level. Omission of 2.4-dichloro-phenoxyacetic acid (2.4-D) from the medium caused ethylene production to increase from about 2.5 to 7 nl g−1 h−1 within the 11-day incubation period. Although 2.4-D did not specifically alter the endogenous level of ACC, the lowest ACC level, 33 nmol g−1, was observed in tissue treated with 2.4-D (22.5 μ M ) and no BA for 11 days. Data from this treatment were used to estimate the kinetic constants for ACC oxidase, the apparent Km was 50 μ M and Vmax 2.7 nl g−1 h−1. Growth of the tissue was strongly inhibited by 2.4-D in the absence of BA, but weakly in the presence of BA (4.4 μ M ). The results suggest that ethylene or ACC may be involved in the induction of embryogenic tissue and in the early stages of embryo maturation.  相似文献   

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