Nitrilotriacetic acid removal in septic tanks: A field study     

T. Stephenson  J. N. Lester  R. Perry 《Water, air, and soil pollution》1987,33(3-4):349-357

The removal of nitrilotriacetic acid (NTA) dosed to two full-scale septic tanks each connected to a single dwelling was monitored weekly over a period of 75 weeks. Nitrilotriacetic acid in the septic tank effluent was detected in samples diluted at least 25 times by a differential pulse polarographic technique. After an initial period of stabilization, concentrations of NTA in the effluent at both sites were always > 10 mg L^?1. Mean five-weekly estimated removals of NTA during the last 50 weeks of the study ranged from 33 to 52%. Removal of NTA was probably by solids adsorption only as no acclimatization period or overall increase in removal during the investigation was apparent.  相似文献   

Insecticide inhibition of herbicide metabolism in leaf tissues   总被引：1，自引：0，他引：1  

F Y Chang  L W Smith  G R Stephenson 《Journal of agricultural and food chemistry》1971,19(6):1183-1186

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Influence of herbicides on insecticide metabolism in leaf tissues     

F Y Chang  G R Stephenson  L W Smith 《Journal of agricultural and food chemistry》1971,19(6):1187-1190

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A field study of cadmium dynamics in periphyton and in Hyalella azteca (crustacea: amphipoda)     

Malcolm Stephenson  Michael A. Turner 《Water, air, and soil pollution》1993,68(3-4):341-361

We studied the dynamics of Cd uptake and depuration in epilithic periphyton and in the grazing amphipod Hyalella azteca. Both stable Cd, sufficient to achieve an aqueous concentration of 90 ng L^?1, and its radiotracer ¹⁰⁹Cd, were added during 1987 to the epilimnion of oligotrophic Lake 382 of the Experimental Lakes Area in northwestern Ontario. Cadmium dynamics within both periphyton and Hyalella were rapid, with equilibrium being approached within two weeks. For periphyton, the Cd uptake rate constant (K _uw ) was 3.8×10⁴ d^?1 with a depuration rate of 0.29 d^?1. For Hyalella the depuration rate was 0.36 d^?1, 10% due to growth dilution and 90% to excretion or desorption. The total Cd uptake rate (k _ut ) by Hyalella was 6.1×10⁴ d^?1, with more of the uptake (58%) derived from food (periphyton) than from water. Hyalella assimilated 80% of ingested Cd. Steady-state bioconcentration factors (BCF) were at least 10-fold higher than previously published values for Amphipoda. In periphyton and Hyalella the BCF were 1.2×10⁵ and 3.2×10⁵, respectively.  相似文献   

Total cadmium concentrations in the water and littoral sediments of Central Ontario Lakes     

M. Stephenson  G. L. Mackie 《Water, air, and soil pollution》1988,38(1-2):121-136

Lakes within 20 km of Sudbury, Ontario, have significantly higher Cd concentrations in surface waters (geometric mean 122 ng L^?1; n = 7) than lakes elsewhere in central Ontario (10.8 ng L^?1; n = 57). Cadmium concentrations in water from lakes beyond the Sudbury halo were negatively correlated (r = 0.797; p < 0.001) with pH. A weak correlation between fluoride and Cd concentrations leads to speculation that some Cd may be mobilized from watersheds with Al. Cadmium concentrations in littoral sediments are not elevated near Sudbury. The geometric mean Cd concentration of littoral sediments in central Ontario lakes is 0.08 mg Cd kg^?1 dry mass (n = 75). Cadmium concentrations in littoral sediments are strongly correlated with sediment loss on ignition (r = 0.860; p < 0.001). After correction for differences in organic content, littoral sediments are less enriched with Cd than profundal sediments, as reported in the literature. The difference between littoral and profundal sediments, and the sensitivity of Cd concentrations in water to pH, may be due to the importance of Cd binding by Fe/Mn hydrous oxides in the profundal zone, while organic matter binds Cd in the littoral zone. The lack of sensitivity of Cd concentrations in littoral sediments to acidification may be due to the incorporation of much of the Cd in those sediments into organic particulates.  相似文献   

Assessment of mechanical ventricular synchrony in Doberman Pinschers with dilated cardiomyopathy     

Jordi López-Alvarez LltVet  MRCVS  Sonja Fonfara Dr Med Vet  MRCVS  Brigite Pedro DVM  MRCVS  Hannah Stephenson BVMS  MRCVS  Peter J. Cripps BSc  BVSc  MSc  PhD  MRCVS  Joanna Dukes-McEwan BV  MS  MVM  PhD  MRCVS 《Journal of Veterinary Cardiology》2011,13(3):183-195

Objectives

Loss of temporal synchrony of myocardial contraction has been shown to reduce systolic function and be responsible for disease progression in people. The objective of this study is the assessment of inter- and intra ventricular synchrony in healthy Doberman Pinschers and those with dilated cardiomyopathy (DCM) by use of conventional Doppler and tissue velocity imaging.

Animals

A total of 60 scans from 35 client-owned Doberman Pinschers presented for cardiac evaluation were analysed.

Methods

Retrospective analysis of data. Using the European Society of Veterinary Cardiology DCM taskforce scoring system, Doberman Pinschers were classified into 4 groups: Control (Group 1; n = 12), depressed systolic function other than DCM (Group 2; n = 9), preclinical DCM (Group 3; n = 8) and symptomatic DCM (Group 4; n = 6). The time intervals between the beginning of the QRS complex and the peak velocity of pulmonic flow (Q-P) and the peak aortic flow (Q-Ao) were used to assess global synchrony between both ventricles. The time intervals between the beginning of the QRS complex and the peak myocardial systolic velocity (Q-peak S) and the onset of myocardial systolic velocity (Q-start S) were measured at the base of the right and left ventricular free wall (RVFW and LVFW) and interventricular septum (IVS), and used to determine segmental longitudinal inter- and intra ventricular synchrony.

Results

No significant loss of global or segmental longitudinal inter- or intra ventricular synchrony was identified between the groups.

Conclusion

Impairment of longitudinal fibre synchrony does not appear to be significantly associated with clinical status of DCM in Doberman Pinschers, although it was identified in certain individuals.  相似文献   

Myxomycetes in soil     

Steven L. Stephenson  Anna Maria Fiore-Donno 《Soil biology & biochemistry》2011,43(11):2237-2242

The myxomycetes are a group of protists that form a monophyletic taxon in the phylum Amoebozoa. Evidence of their evolutionary success is the fact that they account for more species (ca. 900 are currently recognized) than the combined total for the rest of the Amoebozoa. Moreover, myxomycetes are present in every terrestrial environment investigated to date and also, as amoebae or flagellated cells, in aquatic environments where they cannot form fruiting bodies. Even if culture-based methods tend to underestimate their occurrence in soil, myxomycetes probably account for ∼50% of soil amoebae. The emergence of molecular-based methods has revolutionized our concepts of biodiversity, but myxomycetes are conspicuously absent from all environmental surveys. Herein we show that this is due to their highly diverging SSU rRNA gene sequences, which contain numerous Group I introns.Further proof comes from a recent study that used a massive sequencing approach without primer bias to amplify RNAs. The results obtained show that the mycetozoans (myxomycetes along with dictyostelids and protostelids) are indeed a dominant group of soil protozoans.  相似文献   

Intracellular acidosis enhances the excitability of working muscle     

Pedersen TH  Nielsen OB  Lamb GD  Stephenson DG 《Science (New York, N.Y.)》2004,305(5687):1144-1147

Intracellular acidification of skeletal muscles is commonly thought to contribute to muscle fatigue. However, intracellular acidosis also acts to preserve muscle excitability when muscles become depolarized, which occurs with working muscles. Here, we show that this process may be mediated by decreased chloride permeability, which enables action potentials to still be propagated along the internal network of tubules in a muscle fiber (the T system) despite muscle depolarization. These results implicate chloride ion channels in muscle function and emphasize that intracellular acidosis of muscle has protective effects during muscle fatigue.  相似文献   

L-dihydroxyphenylalanine: effect on S-adenosylmethionine in brain   总被引：2，自引：0，他引：2  

R J Wurtman  S RoseMatthysse  J Stephenson  R Baldessarini 《Science (New York, N.Y.)》1970,169(943):395-397

Forty-five minutes after intraperitoneal injection of a single dose (100 milligrams per kilogram) of L-dihydroxyphenylalanine, the concentration of S-adenosylmethionine in rat brain was lowered by 76 percent. As little as 10 milligrams of L-dihydroxyphenylalanine per kilogram decreased content of S-adenosylmethionine in the adrenal medulla by 51 percent, whereas 100 milligrams per kilogram did not significantly depress concentration of S-adenosylmethionine in the liver in this time interval. Concentration of S-adenosylmethionine in the brain varied diurnally; L-dihydroxyphenylalanine lowered this concentration whether administered at the daily peak or at the nadir.  相似文献   

Role of the conserved AAUAAA sequence: four AAUAAA point mutants prevent messenger RNA 3' end formation   总被引：97，自引：0，他引：97  

M Wickens  P Stephenson 《Science (New York, N.Y.)》1984,226(4678):1045-1051

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