Potentiometric and ion-selective electrode titrations together with batch sorption/desorption experiments, were performed to explain the aqueous and surface complexation reactions between kaolinite, Pb, Cd and three organic acids. Variables included pH, ionic strength, metal concentration, kaolinite concentration and time. The organic acids used were p-hydroxybenzoic acid, o-toluic acid, and 2,4-dinitrophenol. Titrations were used to derive previously unavailable aqueous conditional stability constants for the organometallic complexes. Batch results showed that aqueous lead-organic complexation reduced sorption of Pb by kaolinite. Cadmium behavior was similar, except for 2,4-dinitrophenol, where Cd sorption was increased. Metal sorption increased with increasing pH and decreasing ionic strength. Distribution ratios (Kd's) decreased with increasing solid/solution ratio. The subsurface transport of lead and cadmium may be enhanced via complex interactions with organic wastes or their degradation products and sorbent mineral surfaces.
Genetic diversity in 90 Indian soybean cultivars was assessed using 45 SSR markers distributed on 20 soybean chromosomes. Forty-five SSR markers generated 232 alleles with an average of five alleles/locus. The observed frequencies of the 232 alleles ranged from 0.01 to 0.94 with an average of 0.19. The polymorphic information content (PIC) value of the SSR markers varied from 0.10 to 0.83 with an average of 0.61 and about 71% markers have a PIC value of >0.5. In this study, 54 rare alleles including 19 genotype specific alleles were also identified. The observed hetrozygosity for SSR markers ranged from 0 to 0.11 with a mean of 0.10. Cluster analysis grouped the 90 soybean cultivars into three major clusters and principal coordinates analysis (PCoA) results were similar to those of the cluster analysis. A combination of eight SSR markers successfully differentiated all 90 soybean cultivars. The population structure analysis distributed the 90 soybean genotypes into two populations with mean alpha (α) value of 0.1873. In AMOVA analysis, proportion of variation within population was high (88%), whereas only 12% occurred among populations. In cluster and structure analyses, most of the genotypes with similar pedigree were grouped together. Soybean cultivars DS228, MACS-13, LSb-1, Hardee, Improved Pelican, and Pusa-24 were the six most genetically distinct cultivars identified. The study reported a moderate genetic diversity in Indian soybean cultivars and findings would be useful to the soybean breeders in selecting genetically distinct parents for a soybean improvement program. 相似文献
Anaemia is a common pathology associated with many infectious and non-infectious diseases. The effects of haemolytic anaemia
induced by i.p. injection of phenylhydrazine (PHZ) were studied in Atlantic cod. Phenylhydrazine injection (0.3 mg kg−1) in a DMSO and saline vehicle induced a reproducible and stable anaemia reducing haematocrit, (Hct) by 62% over 3 weeks.
Controls consisted of fish injected with saline and DMSO/saline vehicle with minimal effects on Hct or whole blood haemoglobin
(Hb). Although anaemia resulted in reduced blood lactate and glucose in PHZ injected fish, there were no effects of anaemia
on blood, sodium, chloride or potassium. Similarly, there were no changes in the relative proportions of leucocytes in the
blood although an increase in the number of immature erythrocytes was observed in the anaemic fish. Anaemic fish showed a
29 and 22% increase in cardiac somatic index (CSI) relative to saline and vehicle controls, respectively, although there were
no significant differences in the linear dimensions of the ventricle. Changes in cardiac somatic and ventricular somatic index
correlated positively and significantly with Hct but not with whole blood Hb concentration. Anaemic fish had significantly
reduced resting routine oxygen consumption compared with vehicle controls but were not able to increase oxygen consumption
following a bout of exhaustive exercise. Plasma lactate concentrations increased significantly after exercise to a greater
extent in anaemic fish compared with vehicle control fish. Phenylhydrazine is a useful model for studying haemolytic anaemia
in Atlantic cod with minimal effects on blood biochemistry and haematology and clearly reduces the aerobic capacity in Atlantic
cod. 相似文献
Elucidation of the role of infectious agents putatively involved in gill disease is commonly hampered by the lack of culture systems for these organisms. In this study, a farmed population of Atlantic salmon pre‐smolts, displaying proliferative gill disease with associated Candidatus Branchiomonas cysticola, Ca. Piscichlamydia salmonis and Atlantic salmon gill pox virus (SGPV) infections, was identified. A subpopulation of the diseased fish was used as a source of waterborne infection towards a population of naïve Atlantic salmon pre‐smolts. Ca. B. cysticola infection became established in exposed naïve fish at high prevalence within the first month of exposure and the bacterial load increased over the study period. Ca. P. salmonis and SGPV infections were identified only at low prevalence in exposed fish during the trial. Although clinically healthy, at termination of the trial the exposed, naïve fish displayed histologically visible pathological changes typified by epithelial hyperplasia and subepithelial inflammation with associated bacterial inclusions, confirmed by fluorescent in situ hybridization to contain Ca. B. cysticola. The results strongly suggest that Ca. B. cysticola infections transmit directly from fish to fish and that the bacterium is directly associated with the pathological changes observed in the exposed, previously naïve fish. 相似文献
Pseudomonas fluorescens F113, which produces the antimicrobial compound 2,4-diacetylphloroglucinol, is a prospective biocontrol agent. Soil enzyme
activities were used to investigate the ecological impact of strain F113 in the rhizosphere of field-grown sugar beet. There
were distinct trends in rhizosphere enzyme activities in relation to soil chemistry [determined by electro-ultrafiltration
(EUF)]. The activities of enzymes from the P cycle (acid phosphatase, alkaline phosphatase and phosphodiesterase) and of arylsulphatase
were negatively correlated with the amount of readily available P, whereas urease activity was positively correlated with
the latter. Significant correlations between nutrient levels determined by EUF and enzyme activities in the rhizosphere were
obtained, highlighting the usefulness of enzyme assays to document variations in soil nutrient cycling. Contrary to previous
microcosm studies, which did not investigate plants grown to maturity, the biocontrol inoculant had no effect on enzyme activities
or on soil chemistry in the rhizosphere. The results showed the importance of using homogenous soil microcosm systems, also
employed in previous work, for risk assessment studies, whereby the effects of inherent soil variability were minimised, and
effects of the pseudomonad on soil enzymology could be detected.
Received: 3 February 1997 相似文献
We recently reported that corn fiber oil contains high levels of three potential cholesterol-lowering phytosterol components: ferulate-phytosterol esters (FPE) (3–6 wt%), free phytosterols (1–2 wt%), and phytosterol-fatty acyl esters (7–9 wt%). A previous study also indicated that corn bran oil contained less phytosterol components than corn fiber oil. The current study was undertaken to attempt to confirm this preliminary observation using more defined conditions. Accordingly, oil was extracted from corn fiber and corn bran prepared under controlled laboratory conditions, using the same sample of corn hybrid kernels for each, and using recognized bench-scale wet-milling, and dry-milling procedures, respectively. After extraction, the chemical composition of the phytosterol components in the oil were measured. This study confirmed our previous observation—that FPE levels were higher in corn fiber oil than in corn bran oil. During industrial wet-milling, almost all of the FPE are recovered in the fiber fraction (which contains both fine and coarse fiber). During laboratory-scale wet-milling, ≈60–70% of the FPE are recovered in the coarse fiber (pericarp) and 30–40% are recovered in the fine fiber. During laboratory-scale dry-milling, <20% of the FPE are recovered in the bran (pericarp), and the rest in the grits. The recoveries of the other two phytosterol components (free phytosterols and phytosterol-fatty acyl esters) revealed a more complex distribution, with significant levels found in several of the dry- and wet-milled products. 相似文献