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51.
J F Rice R F Fowler A A Arrage D C White Dr G S Sayler 《Journal of industrial microbiology & biotechnology》1995,15(4):318-328
An alginic acid biosynthesis bioluminescent reporter plasmid, pUTK50, was transconjugated into environmental strains ofPseudomonas putida, Pseudomonas fluorescens, andStenotrophomonas maltophilia. Bioluminescent transconjugates were selected from each strain for investigation of environmental stress factors that promote alginic acid exopolymer biosynthesis in developing biofilms. Environmental stimuli associated with increased levels of alginate synthesis, in a previously developed organism,P. aeruginosa FRD1, were applied to the environmental strains. Increased salt concentrations and higher ratios of nitrate vs ammonium ions as the limiting nitrogen source induced bioluminescence in FRD1 and the environmental strains. However, for environmental strains ofP. putida, P. fluorescens andS. maltophilia, polysaccharides were detected with low uronic acids content and different structural components. When tested within a biofilm,S. maltophilia O46 demonstrated exceptional adhesive and corrosive properties while alginic acid synthesis was not high. In most of the environmental strains, periods of increased bioluminescence were induced by external stimuli, but exopolysaccharides other than alginic acid were expressed. It is hypothesized that the environmental strains have homologous but nonidentical promoter sequences which are responsive to certain environmental stimuli and may control genes necessary for the production of alternative exopolysaccharides. 相似文献
52.
53.
Multivariate morphometrics and allometry in a polymorphic ant 总被引:1,自引:0,他引:1
54.
S. John Gatley Ding-Wei Yu Joanna S. Fowler Robert R. MacGregor David J. Schlyer Stephen L. Dewey Alfred P. Wolf Thomas Martin Colleen E. Shea Nora D. Volkow 《Journal of neurochemistry》1994,62(3):1154-1162
Abstract: The psychostimulant drug of abuse, cocaine (benzoylecgonine methyl ester), is rapidly metabolized by cleavage of its two ester groups, to give benzoylecgonine (BE) and ecgonine methyl ester, and by N-demethylation, to give N-norcocaine (NC). The recent use of [N-methyl-11CH3]cocaine to image brain cocaine binding sites with positron emission tomography (PET) raises the question of whether PET images partially reflect the distribution and kinetics of labeled cocaine metabolites. We prepared [O-metty/-11CH3]cocaine by methylation of the sodium salt of BE with [11C]CH3l, and showed that PET baboon brain scans, as well as regional brain kinetics and plasma time-activity curves corrected for the presence of labeled metabolites, are nearly identical to those seen with [N-methyl-11CH3]cocaine. This strongly suggests that 11C metabolites do not significantly affect PET images, because the metabolite pattern is different for the two labeled forms of cocaine. In particular, nearly half the 11C in blood plasma at 30 min was [11C]CO2 when [N-methy/-11CH3]cocaine was administered, whereas [11C]CO2 was not formed from [O-methy/-11CH3]cocaine. Only a trace of [11C]NC was detected in plasma after [O-methyl-11CH3]cocaine administration. Nearly identical brain PET data were also obtained when 4′-[N-methy/-11CH3]fluorococaine and 4′-[18F]fluoro-cocaine (prepared by nucleophilic aromatic substitution from [18F]fluoride-and 4′-nitrococaine) were compared with [N-methy/-11CH3]cocaine. In vitro assays with rat brain membranes showed that cocaine and 4′-fluoroco-caine were equipotent at the dopamine reuptake site, but that 4′-fluorococaine was about 100 times more potent at the 5-hydroxytryptamine reuptake site. The studies with positron-emitting 4′-fluorococaines thus support the lack of significance of labeled metabolites or of binding to 5-hydroxytryptamine reuptake sites to PET images taken with [N-methy/-11CH3]cocaine. [11C]NC prepared by O-methylation of norbenzoylecgonine gave PET images with preferential uptake in striatum, but slower clearance from all brain regions than [O-methy/-11CH3]cocaine. [11C]BE prepared by N-methylation of norbenzoylecgonine did not show brain uptake. 相似文献
55.
Graham J. Moore Renee C. Ganter John M. Matsoukas John Hondrelis George Agelis Klemoenis Barlos Scott Wilkinson John Sandall Patrick Fowler 《Journal of molecular recognition : JMR》1994,7(4):251-256
A triad of interacting group (TyrOH? His$ \underline\ominus$O2C) in angiotensin II (ANG II) has been postulated to create the tyrosinate anion pharmacophore (tyanophore) responsible for receptor activation/triggering (Biochim. Biophys. Acta 1991, 1065, 21). In the present study we investigated the effects on bioactivity of substituting the Tyr4 residue in [Sar1]ANG II with other anionic or electronegative amino acids, and with a number of aromatic amino acids lacking a hydroxyl group. [Sar1 Nva(δ-OH)4]ANG II, [Sar1 Nva(δ-OCH3)4]ANG II, [Sar1 Met4]ANG II, [Sar1 Gln4]ANG II, [Sar1 Glu4]ANG II and [Sar1 DL -Alg4]ANG II had agonist activities in the rat isolated uterus assay of 4, 3, 19, 10, > 0.1 and > 0.1%, respectively, of that of ANG II. [Sar1 Nal4]ANG II, [Sar1 Pal4]ANG II, [Sar1 DL -Phg(4′-F)4]ANG II, [Sar1 Phe(4′-F)4]ANG II, [Sar1 Phe(F5)4]ANG II and [Sar1 His4]ANG II had agonist activities of 4.5, 7, < 0.1, 0.2, 1 and 0.6%, respectively. All peptides investigated were devoid of measurable antagonist activity except [Sar1] Phe(4′-F)4 ANG II (pA2 = 7.7). These findings illustrate that anionic or electronegative aliphatic side chains replacing tyrosinate at position 4 can partially activate the angiotension receptor. For ANG II analogues containing an aromatic amino acid other than Tyr at position 4, ligand binding and agonist activity are not dependent on the electronegativity or dipole moment of the aromatic ring, or on the ability of the 4′ ring substituent to accept a proton. Modelling based on ab initio calculations of aromatic ring multipoles illustrate that the apparent binding affinity (PA2) of ANG II analogues is associated with a perpendicular electrostatic interaction of the position 4 aromatic ring with a receptor-based group. In addition, intramolecular interactions providing for the conformation of the ligand as it approaches its receptor appear to have a role in determining agonist vs antagonist activity. 相似文献
56.
Smoking is the single most important cause of cancer. The risk of developing cancer is reduced by stopping smoking and decreases substantially after five years. Reduction in smoking must be central to any programme aimed seriously at the prevention of cancer. An individual approach, based in primary care, has the potential to bring about modest but important reductions in risk. Many randomised trials have shown the effectiveness of various smoking cessation interventions in primary care. Given resource limitations in primary care, individual effort should be focused on those at highest risk who are motivated to stop smoking. A population strategy has considerable advantages over the high risk approach as the potential for reducing morbidity and mortality in the whole population is much greater. The government must acknowledge its major responsibility; the outstanding example of its failure to do this is its persistent refusal to ban outright all forms of advertising and promotion of tobacco. There is clear evidence that a ban would contribute to a reduction in smoking prevalence and especially in the uptake of smoking by children. 相似文献
57.
Linda Partridge Kevin Fowler 《Evolution; international journal of organic evolution》1993,47(1):213-226
Two sets of four replicate lines of Drosophila melanogaster were selected for large and small thorax with controls. F, progeny of crosses between the selected lines within each size category showed (a) a reduction in preadult viability in large lines relative to control and small lines when they were cultured at medium or high density in competition with a standard mutant marked competitor stock, and (b) an increase in larval development time in large lines relative to control and small lines. Natural selection for increased body size in adults may therefore be opposed by adverse effects on larval viability. The results are discussed in terms of the developmental mechanisms probably responsible for the change in body size. The preadult survival of the large and control lines was measured at three different temperatures, and there was no evidence for a significant interaction between size and temperature. The observed evolutionary increase in body size in response to reduced temperature in Drosophila must therefore involve either different genes from those subject to selection for size at a single temperature, or a fitness component other than preadult survival. There was no significant asymmetry in response to selection, and thorax length showed heterosis in crosses between the selected lines. 相似文献
58.
E Mougneau D von Seggern T Fowler J Rosenblatt T Jongens B Rogers D Gietzen S K Beckendorf 《Molecular and cellular biology》1993,13(1):184-195
Pig-1 and Sgs-4 are a pair of closely linked and divergently transcribed Drosophila melanogaster genes, which are both expressed in larval salivary glands but at different times during development. While Sgs-4 is expressed at high levels only at the end of the third instar, Pig-1 exhibits a major peak of expression during late second and early third instar. Thus, Pig-1 expression declines as Sgs-4 expression is induced. In this paper, we show that three adjacent elements located within the short region between these genes can account for the switch from Pig-1 to Sgs-4 expression. A 170-bp segment acts as an enhancer to direct Sgs-4 expression in late-third-instar salivary glands. A 64-bp sequence located just upstream from the enhancer can modify its temporal specificity so that it works throughout the third instar. Expression induced at mid-third instar by a combination of these two elements can be repressed by a negative regulatory sequence located still further upstream. We present evidence suggesting that the changing interactions between these regulatory elements and the Sgs-4 and Pig-1 promoters lead to the correct pattern of expression of the two genes. 相似文献
59.
Variation in the ribosomal internal transcribed spacers (ITS1 and ITS2) among eight taxa of the Mimulus guttatus species complex 总被引:1,自引:0,他引:1
The internal transcribed spacer region (ITS1 and ITS2) of the 18S-25S
nuclear ribosomal DNA sequence and the intervening 5.8S region were
sequenced from three individuals in each of eight taxa of the Mimulus
guttatus species complex. Three discrete variants, or "types," of ITS
sequences were found, among which 30%-40% of sites differed, compared with
1%-2% within types. Dot plots indicate that these types were not related by
conspicuous rearrangements or inversions. More than one ITS type was often
found in the same taxon, and two of three ITS types span species
boundaries, indicating their presence prior to speciation. These ITS
sequences showed essentially no positional homology with the nearest
sequenced relative, tomato. In contrast, the 5.8S region was relatively
unvaried, with 8 of 162 sites varied in the sample among all eight taxa.
The phylogeny inferred by the most common ITS sequence type, rooted by the
two other ITS types, agreed with isozymes in showing the distinctness of M.
nudatus, M. laciniatus, and M. tilingii from the other five taxa.
相似文献
60.
TGFα is a mitogenic polypeptide found in the conditioned media of transformed cell lines as well as in various solid tumors. Although its physiological role in normal tissues is uncertain, the autocrine action of TGFα on the EGF receptor is postulated to play a role in tumorigenesis. To explore the possibility that pre-existing mouse mutants might have concordance with the mouse TGFα locus (Tgfa) we sought to establish the chromosomal localization of the murine TGFα gene. Using Southern analysis we have detected NcoI and PvuII RFLP in the TGFα gene of progenitor RI mouse strains. These RFLPs have been used to analyze four different RI sets of DNA and to assign Tgfa to the 35-cM region of chromosome 6. Linkage has been established and the data suggest that the distance between Igk and wa-1 anchor loci may be less than 8 cM and that the gene order for the proximal to mid region of mouse chromosome 6 may be: Ggc-Xmmv27-[Brp-1, Lvp-1, Ms6-4]-[Igk, Ly2, Ly3 Odc-rs5, Rn7s-6, Fabp1]-[Tgfa/wa-1]-IL5-R. Homology of synteny has been further defined between the proximal region of mouse chromosome 6 and with the 2p 13-p11 region of human chromosome 2 encompassing TGFA, IGK, CD8A, and FABP1 . 相似文献