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131.
Macroinvertebrate density, biomass and drift were studied from moss-covered and moss-free channels in the South Fork Salmon River, Idaho. Insect densities were compared for 10 different substrate types and locations involving moss (Fontinalis neo-mexicana), sand, pebbles and cobbles. An ANOVA test demonstrated that insect densities varied significantly with substrate type (P < 0.05), and that total insect density in moss clumps differed significantly from densities in mineral substrates. Insect densities were 4–18 times greater in moss clumps than in mineral substrates under and adjacent to moss; sands under moss supported the lowest densities. During most tests, densities in pebble and cobble substrates adjacent to moss clumps were not significantly different from those found in similar substrates in the moss-free channel. The 20% moss-covered channel had 1.6 to 7.2 greater insect density and 1.4 to 6.1 greater biomass than did the moss-free channel for the tests conducted. Generally, midges (Chironomidae) made up over 50% of the insect community; annelids were the principal non-insect invertebrates.In spite of greater insect density and biomass in a moss-covered than in the moss-free channel, we did not demonstrate universally increased drift of the immature stages from the moss-covered channel, at least during daylight hours. As a consequence, we infer that salmonid fishes, feeding primarily on drifting insects during the daytime, may not derive increased caloric benefit from moss habitats until the insects emerge as adults. 相似文献
132.
The degradation of phenol by Rhodococcus sp. P1 was studied in continuous culture systems. The organism could be adapted by slowly increasing concentration, step by step, up to 30.0 g · 1-1 phenol in the influent. The degradation rate reached values of about 0.3 g · g dry mass-1 ·h-1. Large step increases in phenol concentration and addition of further substrates (e.g., catechol) were tolerated up to a certain concentration. With increasing dilution rate and increasing inlet phenol concentration the stability of the system decreased. 相似文献
133.
Horse liver contains previously unrecognized isozymes of alcohol dehydrogenase. In contrast to the molecular forms identified up to now, under the conditions employed these variants migrate toward the anode on starch gel electrophoresis and were separated from the cathodic isozymes by DEAE-cellulose chromatography. They were then purified on agarose-hexane-AMP. Their physicochemical and compositional characteristics are similar to those x alcohol dehydrogenases from human liver. Like these and similar ones from simian liver, they retain most of their activity in the presence of10
mm 4-methylpyrazole, oxidize short-chain primary alcohols very poorly, and appear to prefer longer chain primary alcohols and -hydroxy fatty acids as substrates. 相似文献
134.
The growth of Hansenula polymorpha and Kloeckera sp. 2201 with a mixture of glucose and methanol (38.8%/61.2%, w/w) and the regulation of the methanol dissimilating enzymes alcohol oxidase, catalase, formaldehyde dehydrogenase and formate dehydrogenase were studied in chemostat culture, as a function of the dilution rate. Both organisms utilized and assimilated glucose and methanol simultaneously up to dilution rates of 0.30 h-1 (H. polymorpha) and 0.26h-1, respectively (Kloeckera sp. 2201) which significantly exceeded max found for the two yeasts with methanol as the only source of carbon. At higher dilution rates methanol utilisation ceased and only glucose was assimilated. Over the whole range of mixed-substrate growth both carbon sources were assimilated with the same efficiency as during growth with glucose or methanol alone.In cultures of H. polymorpha, however, the growth yield for glucose was lowered by the unmetabolized methanol at high dilution rates. During growth on both carbon sources the repression of the synthesis of all catabolic methanol enzymes which is normally caused by glucose was overcome by the inductive effect of the simultaneously fed methanol. In both organisms the synthesis of alcohol oxidase was found to be regulated differently as compared to catalase, formaldehyde and formate dehydrogenase. Whereas increasing repression of the synthesis of alcohol oxidase was found with increasing dilution rates as indicated by gradually decreasing specific activities of this enzyme in cell-free extracts, the specific activities of this enzyme in cell-free extracts, the specific activities of catalase and the dehydrogenases increased with increasing growth rates until repression started. The results indicate similar patterns of the regulation of the synthesis of methanol dissimilating enzymes in different methylotrophic yeasts.Abbreviations and Terms C1
Methanol
- C6
glucose; D dilution rate (h-1)
-
D
c
critical dilution rate (h-1)
-
q
s
specific, rate of substrate consumption (g substrate [g cell dry weight]-1 h-1)
-
q
CO2 and q
O2
are the specific rates of carbon dioxide release and oxygen consumption (mmol [g cell dry weight]-1 h-1)
- RQ
respiration quotient (q
CO2
q
O2
1
)
-
s
0(C1) and s
0(C6)
are the concentrations of methanol and glucose in the inflowing medium (g l-1)
-
s
residual substrate concentration in the culture liquid (g l-1)
- Sp. A.
enzyme specific activity
- x
cell dry weight concentration (gl-1)
-
Y
X/C6
growth yield on glucose (g cell dry weight [g substrate]-1 相似文献
135.
Dissolved and suspended mercury. species in the Wabigoon River (Ontario,Canada): seasonal and regional variations 总被引:1,自引:1,他引:0
Jackson T. A. Parks J. W. Jones P. D. Woychuk R. N. Sutton J. A. Hollinger J. D. 《Hydrobiologia》1982,91(1):473-487
Seasonal and regional variations in the speciation, sediment-water partitioning, and dynamics of mercury (Hg) were studied
at selected sites along the Hg-polluted Wabigoon River, and at unpolluted headwater and tributary sites, during April–September,
1979. ‘Dissolved’ and ‘particulate’ forms of Hg in the water were separated by continuous-flow centrifugation in the field.
The Hg and other pollutants such as wood chips and salt had been discharged from a chlor-alkali plant and paper mill at Dryden,
Ontario.
Concentrations and loadings of particulate methyl mercury (CH3Hg+) and total particulate Hg (and loadings of total ‘dissolved’ Hg) were greatest during the spring flood (April-May) owing
to accelerated resuspension and transport of sediments. Concentrations of ‘dissolved’ CH3Hg+, however, were highest in the summer (July–September), probably reflecting stimulation of microbial methylating activity
by elevated temperatures, together with factors such as reduced levels of metal-scavenging particulates and minimal dilution
by runoff. Total dissolved Hg concentrations were relatively high in September at polluted sites only, possibly because of
desorption from sediments due to elevated concentrations of Cl− ions. Loadings of dissolved CH3Hg+ tended to be high in the summer but were generally depressed (suggesting sorption by suspended particles) during the major
spring-flood episode in May.
During July–August dissolved CH3Hg+ was a function of total dissolved Hg, suggesting rapid biomethylation of desorbed inorganic Hg; but in general dissolved
and suspended CH3Hg+ levels depended on environmental variables and were unrelated to total Hg concentrations. In the summer only, total dissolved
Hg was a function of dissolved Cl−. Hg species in particulates were associated with sulfides, hydrated Fe and Mn oxides, organic matter (notably high molecular
weight humic and humic-Fe components), and selenium (Se); but CH3Hg+ and total Hg differed in their specific preferences for binding agents, implying that binding sites discriminate between
CH3Hg+ and Hg2+ ions. CH3Hg+ was associated with sulfide and (in the spring only) with Fe oxides, whereas total Hg was associated with organic matter
and Se and with DTPA- and NaOH-extractable Fe in the spring but with Mn oxide and NaOH-extractable organics in the summer.
Sulfides were most abundant in May, indicating that they were eroded from bottom sediments, but Fe and Mn oxides were most
abundant in the summer, probably owing to activities of filamentous iron bacteria and other micro-organisms.
Particulate Hg was 98–100% nonextractable by mild solvents such as Ca acetate, CaCl2, dilute acetic acid, and (at polluted sites only) DTPA solutions, suggesting that the particulate Hg mobilized in the spring
may not be readily available to organisms; association with Se and high molecular weight humic matter also supports this hypothesis.
Hg probably becomes more bio-available in the summer, as suggested by the upsurge in dissolved CH3Hg+ and total dissolved Hg levels, and by increases in the solubility of particulate Hg in acetic acid, DTPA, H2O2, and NaOH solutions, as well as an increase in the relative importance of lower molecular weight fractions of NaOH-extractable
Hg (in September).
Regional variations in Hg speciation and partitioning reflected a gradient in sediment composition from wood chips near Dryden
to silt-clay mud further downstream. Hg in silt-clay mud relatively far (> 35 km) downstream from the source of pollution
or in unpolluted areas appeared to be more readily solubilized by Cl− ions or chelators such as DTPA, more readily methylated (as indicated by downstream increases in dissolved CH3Hg+ levels and CH3Hg+/total Hg ratios), and was to a greater degree organically bound (H2O2-extractable), and thus was probably more bio-available, than Hg in wood-chip deposits. Possible explanations include weaker
binding of Hg by the mud, the more finely divided state of the mud, and improved microbial growth at lower concentrations
of toxic pollutants. Owing to enrichment in sulfides and Fe oxides, resuspended wood-chip sediments were especially efficient
scavengers of CH3Hg+.
The results indicate that in any pollution abatement plan aimed at lowering the Hg levels in the biota of lakes fed by the
Wabigoon River, immobilization, removal, or detoxification of dissolved as well as particulate forms of Hg in the river would
probably have to be considered. Possibly, Hg species could be ‘scrubbed’ from the river water by increasing the suspended
load and by sedimentation and treatment with Hg-binding agents in special receiving basins. 相似文献
136.
Koichi Hirata Tadashi Oku Aaron E. Freeman 《In vitro cellular & developmental biology. Plant》1982,18(9):789-799
Summary Twenty to twenty-two days postcoitum mouse fetal pancreas organ bits were cultured on the dermal surface of irradiated pigskin
as a substrate. The medium used for long term culture consisted of Eagle’s Minimum Essential Medium with the addition of 10%
bovine serum, 0.02 U/ml insulin, 0.025 μg/ml glucagon, 3.63 μg/ml hydrocortisone, 100 μg/ml soybean trypsin inhibitor or 10−8
M atropine. When the medium lacked trypsin inhibitor or atropine but contained the three hormones, the pigskin support began
to be destroyed after 2 to 4 wk in culture. Thereafter, the cultured cells could not grow and survive on the digested pigskin.
When 10−6
M atropine was added to the medium, amylase secretion from cultured cells and destruction of pigskin were inhibited completely
but pancreas cells could not grow or survive. In contrast, 100 μg/ml soybean trypsin inhibitor or 10−8
M atropine permitted cell growth, permitted amylase secretion from the cultured acinar cells, and prevented the destruction
of pigskin. Under these conditions pancreas cells migrated or grew or both from the organ bits onto the surface of the pigskin
dermis and organoid aggregations formed. Hydrocortisone was needed to permit growth for more than 2 wk. Glucagon and insulin
had additive effects. Light and electron microscopic observations indicated the culture of at least five kinds of cells, i.e.,
duct, acinar, centroacinar, endocrine, and mesenchymal. The majority of cultured cells were duct cells and acinar cells. There
were few mesenchymal cells. Mouse pancreas cells were cultured for at least 12 wk by this method.
This investigation was supported by PHS Grant CA 30220 awarded by the National Cancer Institute, DHHS, Grant 1203M awarded
by the Council for Tobacco Research, Inc., and Grant RD-65 (for equipment) awarded by the American Cancer Society. Nude mice
were provided by Dr. Wendall M. Farrow of Life Sciences, Inc., Resource Laboratory N01, CP6-1005 of the National Cancer Institute. 相似文献
137.
D. Dudley Williams 《Hydrobiologia》1981,83(2):257-260
The relative efficiencies of two sizes of a standpipe corer were evaluated. The size composition of the gravel sampled by the corer was very similar to that (below the opening size of the core chamber) of the streambed. The small corer (25 cm3 sample size) produced a mean overestimate of total numbers of only 19% even in highly heterogeneous gravels. Most of the taxa commonly in the substrates sampled did not escape from the corer. A few rare taxa were consistently over- or under-estimated and possible reasons for this are discussed. 相似文献
138.
N. Collins 《Hydrobiologia》1980,68(2):99-112
The population of Ephydra cinerea was studied during three summers when dissolved solids levels were about 130 g/l. All life stages are present year-round, but there is apparently some coordination of the initial pulse of adult emergence in June. There are probably 1–2 generations per year.Eggs are deposited on the water surface; inputs to three locations were similar. Larvae successfully avoid the large benthic area covered by an anaerobic monimolimnion. They tend to immigrate from substrates where they grow relatively poorly, and to remain on substrates where they grow better. Consequently, larval densities are more than ten times higher on reef and shallow water mud substrates than on sand. This marked spatial specialization in the absence of substrate-specific predators or competitors illustrates the power of habitat quality by itself in determining spatial patterns of abundance in a lake.Experiments showed larval growth on the reef was inversely related to density, and the lake as a whole produced relatively larger flies in a year when larval and pupal densities were relatively low. Yearly production by E. cinerea is roughly 50 g/m2, about 88% of which comes from reefs and shallow water mud areas covering only 18% of the bottom area.Past studies indicate that blue-green algae dominate the lake's benthic flora when salt concentrations are high (due to low lake levels), and diatoms take over when salt concentrations are low. Fly abundance appears to be inversely related to salinity.The lake's present high planktonic primary production is equal to that of eutrophic freshwater lakes, yet it has water clarity more characteristic of an oligotrophic lake. The high water clarity (which makes possible the high benthic production) probably depends on the absence of phytoplankters that can both tolerate the high salinity and avoid being eaten by Artemia salina. Continued dilution of the lake will probably upset this situation and result in reorganization of the lake's energy flow pattern. 相似文献
139.
Partially purified preparations of Phe- and Tyr-tRNA synthetases were obtained from seed or seedlings of Phaseolus aureus, Delonix regia and Caesalpinia tinctoria, and the ability of a variety of structural analogues of Phe or Tyr to act as alternative substrates or inhibitors was tested. 3-Hydroxymethylphenylalanine, a natural product of C. tinctoria, formed a particularly effective substrate for the Tyr-tRNA synthetase from P. aureus. The structural features commensurate with substrate activity in an analogue molecule are discussed. 相似文献
140.