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排序方式: 共有404条查询结果,搜索用时 15 毫秒
51.
Andrew J Ellis Stephen G Hales Naheed G A Ur-Rehman Graham F White 《Applied and environmental microbiology》2002,68(1):31-36
Recent reports show that contrary to common perception, branched alkyl sulfate surfactants are readily biodegradable in standard biodegradability tests. We report here the isolation of bacteria capable of biodegrading 2-butyloctyl sulfate and the identification of novel enzymes that initiate the process. Enrichment culturing from activated sewage sludge yielded several strains capable of growth on 2-butyloctyl sulfate. Of these, two were selected for further study and identified as members of the genus PSEUDOMONAS: Strain AE-A was able to utilize either sodium dodecyl sulfate (SDS) or 2-butyloctyl sulfate as a carbon and energy source for growth, but strain AE-D utilized only the latter. Depending on growth conditions, strain AE-A produced up to three alkylsulfatases, as shown by polyacrylamide gel electrophoresis zymography. Growth on either SDS or 2-butyloctyl sulfate or in nutrient broth produced an apparently constitutive, nonspecific primary alkylsulfatase, AP1, weakly active on SDS and on 2-butyloctyl sulfate. Growth on 2-butyloctyl sulfate produced a second enzyme, AP2, active on 2-butyloctyl sulfate but not on SDS, and growth on SDS produced a third enzyme, AP3, active on SDS but not on 2-butyloctyl sulfate. In contrast, strain AE-D, when grown on 2-butyloctyl sulfate (no growth on SDS), produced a single enzyme, DP1, active on 2-butyloctyl sulfate but not on SDS. DP1 was not produced in broth cultures. DP1 was induced when residual 2-butyloctyl sulfate was present in the growth medium, but the enzyme disappeared when the substrate was exhausted. Gas chromatographic analysis of products of incubating 2-butyloctyl sulfate with DP1 in gels revealed the formation of 2-butyloctanol, showing the enzyme to be a true sulfatase. In contrast, Pseudomonas sp. strain C12B, well known for its ability to degrade linear SDS, was unable to grow on 2-butyloctyl sulfate, and its alkylsulfatases responsible for initiating the degradation of SDS by releasing the parent alcohol exhibited no hydrolytic activity on 2-butyloctyl sulfate. DP1 and the analogous AP2 are thus new alkylsulfatase enzymes with novel specificity toward 2-butyloctyl sulfate. 相似文献
52.
N M Braslow C A Hales B Hoop D J Kanarek H Kazemi 《Journal of applied physiology (Bethesda, Md. : 1985)》1982,53(5):1125-1132
Inhaled oxygen-15-labeled carbon dioxide (CO2*) is hydrated in the alveolar capillary blood to produce oxygen-15-labeled water (H2O*). This allows noninvasive delivery of a traceable indicator into the pulmonary circulation. Removal of oxygen-15 marker from the lung is a function of pulmonary perfusion. Two techniques were evaluated for computing cardiac output (CO) following single bolus inhalation of CO2*: 1) continuous monitoring of arterial blood activity through an external detector and 2) noninvasive positron imaging of oxygen-15-label washout from the chest and simultaneous emergence of activity in arterial blood. In seven mongrel dogs studied using technique 1, 46 determinations of CO were made from 1.2 to 8.0 l/min and compared with simultaneous indocyanine green dye-dilution determination. Correlation coefficient was 0.90 with slope of linear regression of 1.05. In 12 mongrel dogs studied using technique 2, 23 determinations of CO were made from 0.9 to 9.2 l/min and compared with simultaneous indocyanine green dye determination. Correlation coefficient was 0.985 (P less than 0.001) with slope of linear regression of 0.898. This noninvasive technique (2) for determination of CO is independent of assumptions regarding regional ventilation or perfusion of the lung and appears valid in animal studies. 相似文献
53.
54.
Hari G. Garg Hicham Mrabat Craig Freeman Fuming Zhang Charles A. Hales 《Carbohydrate research》2010,345(9):1084-1087
Heparin (HP) inhibits the proliferation of bovine pulmonary artery smooth muscle cells (BPASMC’s), among other cell types in vitro. In order to develop a potential therapeutic agent to reverse vascular remodeling, we are involved in deciphering the relationship between the native HP structure and its antiproliferative potency. We have previously reported the influence of the molecular size and the effects of various O-sulfo and N-acetyl groups of HP on growth-inhibitory activity. In this study, to understand the influence of carboxyl groups in the HP structure required for endogenous activity, a chemically modified derivative of native HP was prepared by converting the carboxyl groups of hexuronic acid residues in HP to primary hydroxyl groups. This modification procedure involves the treatment of HP with N-(3-dimethylaminopropyl)-N-ethylcarbodiimide followed by reduction with NaBH4 to yield carboxyl-reduced heparin (CR-HP). When compared to the antiproliferative potency of native HP on cultured BPASMC’s at three dose levels (1, 10, and 100 μg/mL), the CR-HP showed significantly less potency at all the doses. These results suggest that hexuronic acid residues in both major and variable sequences in HP are essential for the antiproliferative properties of native HP. 相似文献
55.
56.
57.
Chronic low dose cyclophosphamide treatment of adult male rats: effect on fertility, pregnancy outcome and progeny 总被引:5,自引:0,他引:5
Cyclophosphamide is an anticancer and immunosuppressive agent commonly used in men of reproductive age. The relationship between the effects of paternal cyclophosphamide treatment on the male reproductive system and the pregnancy outcome is unknown. To study this relationship, adult male Sprague-Dawley rats were administered saline or cyclophosphamide (1.4, 3.4, and 5.1 mg/kg) daily for 11 wk by gavage. Each male was mated weekly with two females in proestrous; 20 days later, the females were caesarean-sectioned and the number of corpora lutea, resorptions, and normal and abnormal fetuses were noted. After 11 wk of treatment, none of the drug-treated males showed any significant difference compared to controls with respect to male reproductive organ weights, serum testosterone, luteinizing hormone or follicle-stimulating hormone, epididymal sperm counts or fertility. Despite the apparent minimal effects of the treatment regimen on the male reproductive system, there were a number of effects on pregnancy outcome. There was a dose-dependent increase in preimplantation loss at 5-6 wk that was not evident at other times, a progressive dose-dependent increase in postimplantation loss starting at 2 wk, and an increase in malformed and growth-retarded fetuses at 3-4 and 7-9 wk. These results indicate that low dose chronic cyclophosphamide treatment of the male rat can affect the outcome of his progeny; such effects are seen in the absence of any apparent alteration of a number of measures of male reproductive function. 相似文献
58.
Numerous transposed sequences of mitochondrial cytochrome oxidase I-II in aphids of the genus Sitobion (Hemiptera: Aphididae) 总被引:4,自引:1,他引:3
Polymerase chain reaction (PCR) products corresponding to 803 bp of the
cytochrome oxidase subunits I and II region of mitochondrial DNA (mtDNA
COI-II) were deduced to consist of multiple haplotypes in three Sitobion
species. We investigated the molecular basis of these observations. PCR
products were cloned, and six clones from one individual per species were
sequenced. In each individual, one sequence was found commonly, but also
two or three divergent sequences were seen. The divergent sequences were
shown to be nonmitochondrial by sequencing from purified mtDNA and Southern
blotting experiments. All seven nonmitochondrial clones sequenced to
completion were unique. Nonmitochondrial sequences have a high proportion
of unique sites, and very few characters are shared between
nonmitochondrial clones to the exclusion of mtDNA. From these data, we
infer that fragments of mtDNA have been transposed separately (probably
into aphid chromosomes), at a frequency only known to be equalled in
humans. The transposition phenomenon appears to occur infrequently or not
at all in closely related genera and other aphids investigated. Patterns of
nucleotide substitution in mtDNA inferred over a parsimony tree are very
different from those in transposed sequences. Compared with mtDNA,
nonmitochondrial sequences have less codon position bias, more even
exchanges between A, G, C and T, and a higher proportion of nonsynonymous
replacements. Although these data are consistent with the transposed
sequences being under less constraint than mtDNA, changes in the
nonmitochondrial sequences are not random: there remains significant
position bias, and probable excesses of synonymous replacements and of
conservative inferred amino acid replacements. We conclude that a
proportion of the inferred change in the nonmitochondrial sequences
occurred before transposition. We believe that Sitobion aphids (and other
species exhibiting mtDNA transposition) may be important for studying the
molecular evolution of mtDNA and pseudogenes. However, our data highlight
the need to establish the true evolutionary relationships between sequences
in comparative investigations.
相似文献
59.
H. J. Carlisle T. G. Hales B. A. Schlinger 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1998,182(4):531-538
Songbirds are widely studied to investigate the hormonal control of behavior. However, little is known about the effects
of steroids on neurotransmission in these birds. We used electrophysiological and pharmacological techniques to characterize
γ-aminobutyric acid (GABA) type A receptors (GABAA) of primary cultured telencephalic and hippocampal neurons from developing zebra finches. Additionally, their modulation
by 17β-estradiol(E2), 5α- and 5β-dihydrotestosterone (DHT), 5α- and 5β-pregnan-3α-ol-20-one, and corticosterone was examined. Whole-cell GABA-evoked
currents were inhibited by picrotoxin (10 μmol l−1) and bicuculline methiodide (10 μmol l−1) and potentiated by pentobarbital (100 μmol l−1) and propofol (3 μmol l−1). Loreclezole (10 μmol l−1) potentiated GABA-evoked currents, suggesting the presence of β2, β3 and/or β4 subunits. Diazepam (1 μmol l−1) potentiated currents, while Zn2+ (1 μmol l−1) caused no inhibition, indicating the presence of γ subunits. 5α- and 5β-Pregnan-3α-ol-20-one (100 nmol l−1) potentiated currents, whereas E2 (1 μmol l−1), 5α- and 5β-DHT (1 μmol l−1), and corticosterone (10 μmol l−1) had no detectable effect. We conclude that zebra finch telencephalic and hippocampal GABAA receptors include α, β, and γ subunits and are similar to their mammalian counterparts in both their biophysical and pharmacological
properties. Additionally, GABA-evoked currents are greatly potentiated by 5α- and 5β-pregnan-3α-ol-20-one but show little
or no acute modulation by sex steroids or corticosterone.
Accepted: 12 November 1997 相似文献
60.