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41.
Enhanced biodegradation of aromatic pollutants in cocultures of anaerobic and aerobic bacterial consortia 总被引:10,自引:0,他引:10
Toxic aromatic pollutants, concentrated in industrial wastes and contaminated sites, can potentially be eliminated by low cost bioremediation systems. Most commonly, the goal of these treatment systems is directed at providing optimum environmental conditions for the mineralization of the pollutants by naturally occurring microflora. Electrophilic aromatic pollutants with multiple chloro, nitro and azo groups have proven to be persistent to biodegradation by aerobic bacteria. These compounds are readily reduced by anaerobic consortia to lower chlorinated aromatics or aromatic amines but are not mineralized further. The reduction increases the susceptibility of the aromatic molecule for oxygenolytic attack. Sequencing anaerobic and aerobic biotreatment steps provide enhanced mineralization of many electrophilic aromatic pollutants. The combined activity of anaerobic and aerobic bacteria can also be obtained in a single treatment step if the bacteria are immobilized in particulate matrices (e.g. biofilm, soil aggregate, etc.). Due to the rapid uptake of oxygen by aerobes and facultative bacteria compared to the slow diffusion of oxygen, oxygen penetration into active biofilms seldom exceeds several hundred micrometers. The anaerobic microniches established inside the biofilms can be applied to the reduction of electron withdrawing functional groups in order to prepare recalcitrant aromatic compounds for further mineralization in the aerobic outer layer of the biofilm.Aside from mineralization, polyhydroxylated and chlorinated phenols as well as nitroaromatics and aromatic amines are susceptible to polymerization in aerobic environments. Consequently, an alternative approach for bioremediation systems can be directed towards incorporating these aromatic pollutants into detoxified humic-like substances. The activation of aromatic pollutants for polymerization can potentially be encouraged by an anaerobic pretreatment step prior to oxidation. Anaerobic bacteria can modify aromatic pollutants by demethylating methoxy groups and reducing nitro groups. The resulting phenols and aromatic amines are readily polymerized in a subsequent aerobic step. 相似文献
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43.
M A Spence L L Field M L Marazita J Joseph M Sparkes M Crist B F Crandall C E Anderson J B Bateman J I Rotter 《Human heredity》1984,34(6):343-347
Linkage analysis of 146 informative families for MN and Ss resulted in an estimate of the recombination frequency greater than previously reported. Our total is 7 recombinant children out of 467 individuals, including 1 confirmed recombinant (retested and HLA-compatible) and 6 not verified. The 95% confidence interval of our estimate of recombination is 0.0033-0.0167. Our results are compared with two earlier studies. 相似文献
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45.
Basolateral plasma membrane localization of ouabain-sensitive sodium transport sites in the secretory epithelium of the avian salt gland 下载免费PDF全文
The distribution of Na+ pump sites (Na+-K+-ATPase) in the secretory epithelium of the avian salt gland was demonstrated by freeze-dry autoradiographic analysis of [(3)H] ouabain binding sites. Kinetic studies indicated that near saturation of tissue binding sites occurred when slices of salt glands from salt-stressed ducks were exposed to 2.2 μM ouabain (containing 5 μCi/ml [(3)H]ouabain) for 90 min. Washing with label-free Ringer's solution for 90 min extracted only 10% of the inhibitor, an amount which corresponded to ouabain present in the tissue spaces labeled by [(14)C]insulin. Increasing the KCl concentration of the incubation medium reduced the rate of ouabain binding but not the maximal amount bound. In contrast to the low level of ouabain binding to salt glands of ducks maintained on a freshwater regimen, exposure to a salt water diet led to a more than threefold increase in binding within 9-11 days. This increase paralleled the similar increment in Na+-K+-ATPase activity described previously. [(3)H]ouabain binding sites were localized autoradiographically to the folded basolateral plasma membrane of the principal secretory cells. The luminal surfaces of these cells were unlabeled. Mitotically active peripheral cells were also unlabeled. The cell-specific pattern of [(3)H]ouabain binding to principal secretory cells and the membrane-specific localization of binding sites to the nonluminal surfaces of these cells were identical to the distribution of Na+-K+-ATPase as reflected by the cytochemical localization of ouabain-sensitive and K+-dependent nitrophenyl phosphatase activity. The relationship between the nonluminal localization of Na+-K+-ATPase and the possible role of the enzyme n NaCl secretion is considered in the light of physiological data on electrolyte transport in salt glands and other secretory epithelia. 相似文献
46.
Ion transport across the isolated intestinal mucosa of the winter flounder,Pseudopleuronectes americanus 总被引:3,自引:0,他引:3
Michael Field Karl J. Karnaky Jr. Philip L. Smith Jennifer E. Bolton William B. Kinter 《The Journal of membrane biology》1978,41(3):265-293
The isolated intestinal mucosa of the flounder, Pseudopleuronectes americanus, when bathed in a 20 mM HCO3-Ringer's solution bubbled with 1% CO2 in O2, generated a serosa-negative PD and, when short-circuited, absorbed Cl at almost 3 times the rate of Na. Reducing HCO3 to 5 mM decreased the net Cl flux by more than 60%. The following results suggest that, despite the PD, Na and Cl transport processes are nonelectrically coupled: replacing all Na with choline abolished both the PD and net Cl flux; replacing all Cl with SO4 and mannitol abolished the PD and the net Na flux; and adding ouabain (to 0.5 mM) abolished the PD and the net Cl flux. Nearly all of the unidirectional serosa-to-mucosa Cl flux (JClsm) seemed to be paracellular since it varied with PD and Cl concentration in a manner consistent with simple diffusion. JClsm was only about one-fourth of JNasm, suggesting that the paracellular pathway is highly cation-selective. The data can be explained by the following model: (i) Na and Cl uptake across the brush border are coupled 1 : 1; Na is pumped into the lateral space and Cl follows passively, elevating the salt concentration there; (ii) the tight junction is permeable to Na but relatively impermeable to Cl; and (iii) resistance to Na diffusion is greater in the lateral space (considered in its entirety) than in the tight junction. If these assumptions are correct, the serosa-negative transmural PD is due mainly to a salt diffusion potential across the tight junction and, under short-circuit condition, most of the Na pumped into the lateral space diffuses back into the luminal solution, whereas most of the Cl enters the serosal solution. Morphological features of the epithelium support this interpretation: the cells are unusually long (60 micrometer); there is little distension of the apical 12 micrometer of the lateral space during active fluid absorption; and distension distal to this region is intermittently constricted by desmosomes. 相似文献
47.
Abstract The respiratory activity of cysts of Azotobacter vinelandii has been compared with that of vegetative cells. Whole cysts had a much reduced respiratory activity which was less sensitive to KCN. Substrate oxidation rates by membrane preparations from cysts were reduced approximately 10-fold and sensitivity to KCN was decreased by a similar factor. Difference spectra of cyst membranes revealed changes in cytochrome content. Cytochrome oxidase d was apparently absent, cytochrome a 1 levels were approximately halved whilst those of cytochrome oxidase o were almost doubled. Cytochromes of the b and c -type were present in similar amounts to those in vegetative cells. 相似文献
48.
Bovine thyroid tissue exhibited cAMP-dependent and Ca2+-dependent protein kinase activities as well as a basal (cAMP- and Ca2+-independent) one, and phosphoprotein phosphatase activity. Although the former two protein kinase activities were not clearly demonstrated using endogenous protein as substrate, they were clearly shown in soluble, particulate and plasma membrane fractions using exogenous histones as substrate. The highest specific activities were in the plasma membrane. The apparent Km values of cAMP and Ca2+ for the membrane-bound protein kinase were 5 . 10(-8) M and 8.3 . 10(-4) M in the presence of 1 Mm EGTA), respectively. The apparent Km values of Mg2+ were 7.10-4M (without (in the cAMP and Ca2+), 5 . 10(-4) M (with cAMP) and 1.3 . 10(-3) M (with Ca2+), and those of ATP were 3.5 . 10(-5)M (with or without cAMP) and 8.5 . 10(-5) M (with Ca2+). The Ca2+-dependent protein kinase could be dissociated from the membrane by EGTA-washing. The enzyme activity so released was further activated by added phospholipid (phosphatidylserine/1,3-diolein), but not by calmodulin. Phosphoprotein phosphatase activity was also clearly demonstrated in all of the fractions using 32P-labeled mixed histones as substrate. The activity was not modified by either cAMP or Ca2+, but was stimulated by a rather broad range (5-25 mM) of Mg2+ and Mn2+. NaCl and substrate concentrations also influenced the activity. Pyrophosphate, ATP, inorganic phosphate and NaF inhibited the activity in a dose-dependent manner. Trifluoperazine, chlorpromazine, dibucaine and Triton X-100 (above 0.05%, w/v) specifically inhibited the Ca2+-dependent protein kinase in plasma membranes. Repetitive phosphorylation of intrinsic and extrinsic proteins by the membrane-bound enzyme activities clearly showed an important co-ordination of them at the step of protein phosphorylation. These findings suggest that these enzyme activities in plasma membranes may contribute to regulation of thyroid function in response to external stimuli. 相似文献
49.
C J Field R Chayoth M Montambault E B Marliss 《The Journal of biological chemistry》1991,266(6):3675-3681
Glucose metabolism in splenocytes from the BB rat was studied for the presence of abnormalities in [14C] 2-deoxy-D-glucose (2-dGlc) uptake, [U-14C]glucose conversion to 14CO2, and the production of lactate and pyruvate. Cells were studied freshly isolated ("resting"), and following culture both unstimulated (control) and stimulated with concanavalin A (ConA) or phorbol myristate acetate (PMA) + ionomycin. Both resting and control cells from diabetic (BBd) and diabetes-prone (BBdp) rats transported more (p less than 0.05) 2-dGlc than did cells from nondiabetes-prone (BBn) rats. Consistent with prior in vivo activation, sustained in vitro, lactate production was higher (p less than 0.05) under control conditions in BBd and BBdp than in BBn cells. Lactate production increased less with ConA and PMA + ionomycin in both BBd and BBdp than in BBn cells. PMA + ionomycin increased 2-dGlc uptake as much in BBd and BBdp cells as in BBn cells. Elevated rates of pyruvate production were observed in BBd cells under resting, control, and (especially) ConA conditions, suggesting an abnormality in pyruvate conversion to lactate. Few changes were observed in 14CO2 production. The presence of similar abnormalities in BBdp cells to those of the BBd cells suggests that the diabetic state is not causal, and the absence of an in vitro effect of 15 mmol/liter glucose in BBn cells further tends to exclude hyperglycemia as a cause of these alterations. 相似文献
50.
The major surface antigen of the mammalian bloodstream form of Trypanosoma brucei, the variant surface glycoprotein (VSG), is attached to the cell membrane by a glycosylphosphatidylinositol (GPI) anchor. The VSG anchor is susceptible to phosphatidylinositol-specific phospholipase C (PI-PLC). Candidate precursor glycolipids, P2 and P3, which are PI-PLC-sensitive and -resistant respectively, have been characterized in the bloodstream stage. In the insect midgut stage, the major surface glycoprotein, procyclic acidic repetitive glycoprotein, is also GPI-anchored but is resistant to PI-PLC. To determine how the structure of the GPI anchor is altered at different life stages, we characterized candidate GPI molecules in procyclic T. brucei. The structure of a major procyclic GPI, PP1, is ethanolamine-PO4-Man alpha 1-2Man alpha 1-6 Man alpha 1-GlcN-acylinositol, linked to lysophosphatidic acid. The inositol can be labeled with [3H]palmitic acid, and the glyceride with [3H]stearic acid. We have also found that all detectable ethanolamine-containing GPIs from procyclic cells contain acylinositol and are resistant to cleavage by PI-PLC. This suggests that the procyclic acidic repetitive glycoprotein GPI anchor structure differs from that of the VSG by virtue of the structures of the GPIs available for transfer. 相似文献