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1.
Previous studies, both in intact lungs and epithelial lining fluid (ELF) (J. Appl. Physiol. 68: 594-603, 1990 and J. Appl: Physiol. 69: 523-531, 1990), have suggested that the steady-state absorption of inhaled NO2 is mediated by chemical reaction(s) between NO2 and ELF solute reactants. To characterize the kinetics of NO2 absorption into aqueous biological substrates across a gas-liquid interface, we utilized a closed system of known geometry and initial gas phase [NO2] [([NO2]g)0] to expose ELF (as bronchoalveolar lavage; BAL) and a biochemical model system (glutathione, GSH). Assessments of NO2 reactive uptake, into both GSH and ELF, indicated first-order NO2 kinetics [([NO2]g)0 less than or equal to 10.5 ppm] with effective rate constants of (kNO2)GSH = 4.8 and (kNO2)BAL = 2.9 ml.min-1.cm-2 (stirred). Above 10.5 ppm (1 mM GSH), zero-order kinetics were observed. Both (kNO2)GSH and (kNO2)BAL showed aqueous reactant dependence. The reaction order with respect to GSH and BAL was 0.47 and 0.64, respectively. We found no effect of interfacial surface area or bulk phase volume on kNO2. In unstirred systems, significant interfacial resistance was observed and was related to reactant concentration. These results indicate that NO2 reactive uptake follows first-order kinetics with respect to NO2 ([NO2]g less than or equal to 10.5 ppm) and displays aqueous substrate dependence. Furthermore the site of reactive absorption appears to be limited to near the aqueous surface interface. Unstirred conditions confine interfacial mass transfer kinetics in a dose-dependent manner. These phenomenological coefficients may provide the basis for direct extrapolation to environmentally relevant exposure concentrations. 相似文献
2.
3.
Hardies SC; Martin SL; Voliva CF; Hutchison CA d; Edgell MH 《Molecular biology and evolution》1986,3(2):109-125
4.
Outer membrane proteins of gentamicin induced small colony variants of Pseudomonas aeruginosa 总被引:1,自引:0,他引:1
Small colony variants (SCVs) of Pseudomonas aeruginosa NCTC 6750 (WT) were repeatedly isolated in an in vitro kinetic model after exposure to gentamicin (GM). There were minor differences biochemically and in phage and serotyping between the wild type (WT) strain and SCVs. Changes in outer membrane protein profiles were found. SCVs were more resistant to polymixin and to a range of aminoglycosides (except kanamycin), but were more susceptible to a range of other antibiotics (hydrophilic and hydrophobic) with differing modes of action. 相似文献
5.
The dilution rate affects the outer membrane protein and lipopolysaccharide composition of Haemophilus influenzae type b grown under iron limitation.
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When Haemophilus influenzae type b was grown under iron limitation in continuous culture, the dilution rate affected the outer membrane protein and lipopolysaccharide composition. Investigations of the effect of the reduced availability of iron or other environmental parameters on these surface components should be controlled for growth rate. 相似文献
6.
Steven D. Clouse Allen F. Hall Mark Langford Trevor C. McMorris Michael E. Baker 《Journal of Plant Growth Regulation》1993,12(2):61-66
We examined the effects of brassinosteroids on Arabidopsis thaliana (L.) Henyh. ecotype Columbia in order to develop a model system for studying gene regulation by plant steroids. Submicromolar concentrations of two brassinosteroids, brassinolide and 24-epibrassinolide, stimulated elongation of Arabidopsis peduncles and inhibited root elongation, respectively. Furthermore, brassinolide altered the abundance of specific in vitro translatable mRNAs from peduncles and whole plants of Arabidopsis. Root elongation in the auxin-insensitive Arabidopsis mutant axr1 was inhibited by 24-epibrassinolide but not by 2,4-D, indicating an independent mode of action for these growth regulators in this physiological response.Abbreviations BR
brassinolide
- EBR
24-epibrassinolide; 2.4-D,2,4-dichlorophenoxyacetic acid
- KPSC
10 mM potassium phosphate, pH 6.0, 2% sucrose, 50 g/ml chloramphenicol
- PAGE
polyacrylamide gel electrophoresis 相似文献
7.
A major difference between the divergence patterns within the lines-1 families in mice and voles 总被引:3,自引:0,他引:3
Vanlerberghe F; Bonhomme F; Hutchison CA d; Edgell MH 《Molecular biology and evolution》1993,10(4):719-731
L1 retroposons are represented in mice by subfamilies of interspersed
sequences of varied abundance. Previous analyses have indicated that
subfamilies are generated by duplicative transposition of a small number of
members of the L1 family, the progeny of which then become a major
component of the murine L1 population, and are not due to any active
processes generating homology within preexisting groups of elements in a
particular species. In mice, more than a third of the L1 elements belong to
a clade that became active approximately 5 Mya and whose elements are >
or = 95% identical. We have collected sequence information from 13 L1
elements isolated from two species of voles (Rodentia: Microtinae: Microtus
and Arvicola) and have found that divergence within the vole L1 population
is quite different from that in mice, in that there is no abundant
subfamily of homologous elements. Individual L1 elements from voles are
very divergent from one another and belong to a clade that began a period
of elevated duplicative transposition approximately 13 Mya. Sequence
analyses of portions of these divergent L1 elements (approximately 250 bp
each) gave no evidence for concerted evolution having acted on the vole L1
elements since the split of the two vole lineages approximately 3.5 Mya;
that is, the observed interspecific divergence (6.7%-24.7%) is not larger
than the intraspecific divergence (7.9%-27.2%), and phylogenetic analyses
showed no clustering into Arvicola and Microtus clades.
相似文献
8.
M E Drew C K Langford E M Klamo D G Russell M P Kavanaugh S M Landfear 《Molecular and cellular biology》1995,15(10):5508-5515
The vast majority of surface molecules in such kinetoplastid protozoa as members of the genus Leishmania contain inositol and are either glycosyl inositol phospholipids or glycoproteins that are tethered to the external surface of the plasma membrane by glycosylphosphatidylinositol anchors. We have shown that the biosynthetic precursor for these abundant glycolipids, myo-inositol, is translocated across the parasite plasma membrane by a specific transporter that is structurally related to mammalian facilitative glucose transporters. This myo-inositol transporter has been expressed and characterized in Xenopus laevis oocytes. Two-electrode voltage clamp experiments demonstrate that this protein is a sodium-independent electrogenic symporter that appears to utilize a proton gradient to concentrate myo-inositol within the cell. Immunolocalization experiments with a transporter-specific polyclonal antibody reveal the presence of this protein in the parasite plasma membrane. 相似文献
9.
Molecular phylogeny and divergence times of drosophilid species 总被引:32,自引:15,他引:17
The phylogenetic relationships and divergence times of 39 drosophilid
species were studied by using the coding region of the Adh gene. Four
genera--Scaptodrosophila, Zaprionus, Drosophila, and Scaptomyza (from
Hawaii)--and three Drosophila subgenera--Drosophila, Engiscaptomyza, and
Sophophora--were included. After conducting statistical analyses of the
nucleotide sequences of the Adh, Adhr (Adh-related gene), and nuclear rRNA
genes and a 905-bp segment of mitochondrial DNA, we used Scaptodrosophila
as the outgroup. The phylogenetic tree obtained showed that the first major
division of drosophilid species occurs between subgenus Sophophora (genus
Drosophila) and the group including subgenera Drosophila and Engiscaptomyza
plus the genera Zaprionus and Scaptomyza. Subgenus Sophophora is then
divided into D. willistoni and the clade of D. obscura and D. melanogaster
species groups. In the other major drosophilid group, Zaprionus first
separates from the other species, and then D. immigrans leaves the
remaining group of species. This remaining group then splits into the D.
repleta group and the Hawaiian drosophilid cluster (Hawaiian Drosophila,
Engiscaptomyza, and Scaptomyza). Engiscaptomyza and Scaptomyza are tightly
clustered. Each of the D. repleta, D. obscura, and D. melanogaster groups
is monophyletic. The splitting of subgenera Drosophila and Sophophora
apparently occurred about 40 Mya, whereas the D. repleta group and the
Hawaiian drosophilid cluster separated about 32 Mya. By contrast, the
splitting of Engiscaptomyza and Scaptomyza occurred only about 11 Mya,
suggesting that Scaptomyza experienced a rapid morphological evolution. The
D. obscura and D. melanogaster groups apparently diverged about 25 Mya.
Many of the D. repleta group species studied here have two functional Adh
genes (Adh-1 and Adh-2), and these duplicated genes can be explained by two
duplication events.
相似文献
10.
P. W. Gunning S. B. Por C. J. Langford J. Scheffer L. Austin P. L. Jeffrey 《Journal of neurochemistry》1979,32(6):1737-1743
Analysis of chick retinal and tectal RNA revealed that in addition to the major cytoplasmic RNAs (rRNA and tRNA), a number of the small mol wt nuclear RNAs (snRNAs) can also be detected. Subfractionation data indicated that one of these molecules, DD′, is of at least 95% nuclear location within the retina. Thus, very little, if any, of the retinal DD′ is available for axoplasmic transport from the retina into the optic nerve and tectum. Following intraocular injection of [3H]uridine, considerable incorporation of isotope into DD′ was observed within the optic tectum after 4, 8 and 16 days. This result indicates the presence of considerable local (i.e. tectal) synthesis. The specific activities of 29S, 18S and 5S rRNA and 4s tRNA relative to that of DD′ were measured in the optic tectum 8 and 16 days after the intraocular introduction of [3H]uridine. The same measurements were also made in intracranially injected animals. While the 29S/DD′, 18S/DD′ and 5S/DD′ specific activity ratios obtained were independent of the injection route, the 4S/DD′ ratio obtained from intraocularly injected animals was significantly greater (at least 2-fold) than that obtained from intracranially injected animals. Similar analysis was also performed with the optic nerve complex at 16 days post-injection with identical results. These results demonstrate that tRNA, but not rRNA, is transported from the retina into the optic nerve and tectum in the 2-day-old chicken. 相似文献