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1.
Eight pilot-scale in-line filtration trials were performed to evaluate the passage of cyanobacterial cells through drinking water filters after sudden increases in hydraulic loading rates. Trials were performed at 30 °C using two coagulant combinations (aluminum sulfate and cationic polymer or ferric chloride and cationic polymer), two initial filter loading rates (7 or 10 m/h) and two species of morphologically different cyanobacteria (Microcystis aeruginosa or Anabaena flos aquae). The filter was perturbed by instantaneously increasing the hydraulic loading rate by 50%. Filter influent and effluent water qualities were characterized by measuring turbidity, particles and chlorophyll a. The observed post-perturbation filter effluent chlorophyll a peaks were 1.6–48 times greater than the pre-perturbation averages. Chlorophyll a peaks were larger for M. aeruginosa than for A. flos aquae. Chlorophyll a peaks were also larger for the higher (10 m/h) than for the lower (7 m/h) initial filter loading rate. The post-perturbation effluent turbidity peaks were 1.4–7.2 times greater than the pre-perturbation averages. The post-perturbation effluent particle peaks were 6.5–25 times greater than the pre-perturbation averages. These results indicate that particles were a more sensitive indicator of cyanobacterial passage than turbidity. 相似文献
2.
Interaction between the Effects of Inside and Outside Na and K on Bullfrog Skin Potential 总被引:2,自引:1,他引:1
Daniel E. Leb Charles Edwards Barry D. Lindley T. Hoshiko with the technical assistance of James A. Dugan 《The Journal of general physiology》1965,49(2):309-320
The composition of the solution bathing one border of the isolated frog skin affects the response of the potential across the skin to changes in the composition of the solution bathing the opposite border. Increasing the K concentration of the inside (corium) bathing solution decreased the sensitivity of the potential to a change in outside Na concentration. Decreasing the outside Na concentration decreased the sensitivity of the potential to a change in inside K concentration. Increasing the total ionic strength of the outside bathing solution or of both bathing solutions decreased the sensitivity of the potential to a change in outside Na concentration. 相似文献
3.
S-(4-Bromo-2,3-dioxobutyl)-coenzyme A inactivates both yeast and rat liver beta-hydroxy-beta-methylglutaryl-coenzyme A reductase. The inactivation is irreversible, complete in 15 s, and proportional to the concentration of the reagent. beta-Hydroxy-beta-methylglutaryl-CoA provides protection against inactivation, whereas NADPH does not. Inactivation is attributed to reaction with an essential cysteine at the beta-hydroxy-beta-methylglutaryl-CoA binding site. Experiments with other active site-directed reagents confirm the involvement of a cysteine and support the presence of an active-site histidine, but rule out the participation of arginine or serine. 相似文献
4.
Activity of Microorganisms in Acid Mine Water I. Influence of Acid Water on Aerobic Heterotrophs of a Normal Stream 总被引:13,自引:4,他引:9
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Comparison of microbial content of acid-contaminated and nonacid-contaminated streams from the same geographical area indicated that nonacid streams contained relatively low numbers of acid-tolerant heterotrophic microorganisms. The acid-tolerant aerobes survived when acid entered the stream and actually increased in number to about 2 × 103 per ml until the pH approached 3.0. The organisms then represented the heterotrophic aerobic microflora of the streams comprised of a mixture of mine drainage and nonacid water. A stream which was entirely acid drainage did not have a similar microflora. Most gram-positive aerobic and anaerobic bacteria died out very rapidly in acidic water, and they comprised a very small percentage of the microbial population of the streams examined. Iron- and sulfur-oxidizing autotrophic bacteria were present wherever mine water entered a stream system. The sulfur-oxidizing bacteria predominated over iron oxidizers. Ecological data from the field were verified by laboratory experiments designed to simulate stream conditions. 相似文献
5.
6.
We have broadly defined the DNA regions regulating esterase6 activity in
several life stages and tissue types of D. melanogaster using P-
element-mediated transformation of constructs that contain the esterase6
coding region and deletions or substitutions in 5' or 3' flanking DNA.
Hemolymph is a conserved ancestral site of EST6 activity in Drosophila and
the primary sequences regulating its activity lie between -171 and -25 bp
relative to the translation initiation site: deletion of these sequences
decrease activity approximately 20-fold. Hemolymph activity is also
modulated by four other DNA regions, three of which lie 5' and one of which
lies 3' of the coding region. Of these, two have positive and two have
negative effects, each of approximately twofold. Esterase6 activity is
present also in two male reproductive tract tissues; the ejaculatory bulb,
which is another ancestral activity site, and the ejaculatory duct, which
is a recently acquired site within the melanogaster species subgroup.
Activities in these tissues are at least in part independently regulated:
activity in the ejaculatory bulb is conferred by sequences between -273 and
-172 bp (threefold decrease when deleted), while activity in the
ejaculatory duct is conferred by more distal sequences between -844 and
-614 bp (fourfold decrease when deleted). The reproductive tract activity
is further modulated by two additional DNA regions, one in 5' DNA (-613 to
-284 bp; threefold decrease when deleted) and the other in 3' DNA (+1860 to
+2731 bp; threefold decrease when deleted) that probably overlaps the
adjacent esteraseP gene. Collating these data with previous studies
suggests that expression of EST6 in the ancestral sites is mainly regulated
by conserved proximal sequences while more variable distal sequences
regulate expression in the acquired ejaculatory duct site.
相似文献
7.
Litman GW; Rast JP; Shamblott MJ; Haire RN; Hulst M; Roess W; Litman RT; Hinds- Frey KR; Zilch A; Amemiya CT 《Molecular biology and evolution》1993,10(1):60-72
Immunoglobulins are encoded by a large multigene system that undergoes
somatic rearrangement and additional genetic change during the development
of immunoglobulin-producing cells. Inducible antibody and antibody-like
responses are found in all vertebrates. However, immunoglobulin possessing
disulfide-bonded heavy and light chains and domain-type organization has
been described only in representatives of the jawed vertebrates. High
degrees of nucleotide and predicted amino acid sequence identity are
evident when the segmental elements that constitute the immunoglobulin gene
loci in phylogenetically divergent vertebrates are compared. However, the
organization of gene loci and the manner in which the independent elements
recombine (and diversify) vary markedly among different taxa. One striking
pattern of gene organization is the "cluster type" that appears to be
restricted to the chondrichthyes (cartilaginous fishes) and limits
segmental rearrangement to closely linked elements. This type of gene
organization is associated with both heavy- and light-chain gene loci. In
some cases, the clusters are "joined" or "partially joined" in the germ
line, in effect predetermining or partially predetermining, respectively,
the encoded specificities (the assumption being that these are expressed)
of the individual loci. By relating the sequences of transcribed gene
products to their respective germ-line genes, it is evident that, in some
cases, joined-type genes are expressed. This raises a question about the
existence and/or nature of allelic exclusion in these species. The
extensive variation in gene organization found throughout the vertebrate
species may relate directly to the role of intersegmental
(V<==>D<==>J) distances in the commitment of the individual
antibody-producing cell to a particular genetic specificity. Thus, the
evolution of this locus, perhaps more so than that of others, may reflect
the interrelationships between genetic organization and function.
相似文献
8.
Leakage of cellular material from Thiobacillus ferrooxidans in the presence of organic acids. 总被引:6,自引:4,他引:2
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Thiobacillus ferroodixans cells released varying amounts of iron, phosphate, sugar, ribonucleic acid, deoxyribonucleic acid, and substances that absorbed light at both 260 and 280 nm, when exposed to 10(-2) to 10(-1) M concentrations of these organic acids: propionic, butyric, valeric, hexanoic, and oxalacetic. These acids also retarded iron oxidation by the cells. Electron microscope observation of cells after exposure to the organic acids showed varying degrees of cell envelope disruption, suggesting that the mode of inhibition of autotrophic iron oxidation in the cell involves interference with the function of the cell envelope, possibly the cell membrane. 相似文献
9.
Formation of exospores in Methylosinus trichosporium was examined by electron microscopy; serial sectioning was used to visualize the shape and location of the developing exospore in relation to the vegetative cell. The initial stage was the formation of a budlike enlargement on one end of the vegetative cell. The enlargement was surrounded by the exospore capsule, and the cell wall was continuous around both the cell and the developing exospore. A constriction occurred in the area where the budlike structure was attached to the vegetative cell, and the constriction continued to form until the immature exospore was detached from the vegetative cell. The cup-shaped immature exospore was surrounded by the exospore capsule, which appeared to hold the exospore close to the vegetative cell. After separation from the vegetative cell, the immature exospore developed further by forming the exospore wall and by becoming spherical. 相似文献
10.
B K Tamarappoo M E Handlogten R O Laine M A Serrano J Dugan M S Kilberg 《The Journal of biological chemistry》1992,267(4):2370-2374
In the liver, glutamine utilization may be limited by the rate of transport across the plasma membrane by the System N carrier. System N-mediated transport activity has been solubilized from rat liver plasma membrane, partially purified, and then reconstituted into proteoliposomes. To identify the System N carrier protein, monoclonal antibodies were generated against the protein fraction enriched for System N activity. Two antibodies , 3E1-2 and 1E7-3, inhibited System N activity in hepatocytes. These antibodies also immunoprecipitated System N activity from a mixture of solubilized proteins and were specific for antigen recognition in that neither immunoprecipitated System A activity. The antibody recognized a single protein of molecular size 100 kDa by immunoblot analysis. Recognition of this protein by the antibody increased in parallel with the enrichment of System N activity in solubilized membrane fractions. These data suggest that a 100-kDa plasma membrane protein mediates System N transport activity in rat hepatocytes. 相似文献