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201.
The ability of human fibroblasts to repair bleomycin-damaged DNA was examined in vivo. Repair of the specific lesions caused by bleomycin (BLM) was investigated in normal cell strains as well as those isolated from patients with apparent DNA repair defects. The diseases ataxia telangiectasia (AT), Bloom syndrome (BS), Cockayne syndrome (CS), Fanconi anemia (FA), and xeroderma pigmentosum (XP) were those selected for study. The method used for studying the repair of DNA after BLM exposure was alkaline sucrose gradient centrifugation. After exposure to BLM, a fall in the molecular weight of DNA was observed, and after drug removal the DNA reformed rapidly to high molecular weight. The fall in molecular weight upon exposure to BLM was observed in all cells examined with the exception of some XP strains. Prelabeled cells from some XP complementation groups were found to have a higher percentage of low molecular weight DNA on alkaline gradients than did normal cells. This prelabeled low molecular weight DNA disappeared upon exposure to BLM. 相似文献
202.
Promoter-Like Mutant with Increased Expression of the Glycerol Kinase Operon of Escherichia coli 总被引:13,自引:9,他引:4
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A glycerol-specific phenotypic revertant isolated from a mutant of Escherichia coli missing enzyme I of the phosphoenolpyruvate phosphotransferase system was studied. This revertant is capable of producing higher levels of glycerol kinase and the protein mediating the facilitated diffusion of glycerol (facilitator) than wild-type cells. The kinase of the revertant is indistinguishable from the wild-type enzyme with respect to its sensitivity to feedback inhibition by fructose-1,6-diphosphate, its pH optimum, and its turnover number. The synthesis of glycerol kinase in strains bearing the suppressor locus is resistant to catabolite repression. The suppressor mutation mapped at the known glpK locus. Thus, it is suggested that the mutation occurred in the promoter of the operon specifying the kinase and the facilitator. 相似文献
203.
R Nath K McGinnis S Dutta B Shivers K K Wang 《Cellular & molecular biology letters》2001,6(2):173-184
The mitogen-activated protein kinase (MAPK) cascades are thought to be important mediators in the transduction of extracellular signals into cellular responses. The p38 kinase, a member of the MAPK superfamily, is activated by a wide variety of extracellular stimuli and has been implicated in neuronal apoptosis induced by glutamate. In this study we have examined the role of p38 kinase in the potassium deprivation model of apoptosis in rat cerebellar granule neurons (CGN). An increase in p38 kinase activity was observed with a 15-minute potassium deprivation when compared to the basal level. We also found that SB203580 and PD169316, specific p38 kinase inhibitors, significantly attenuated apoptosis in potassium-deprived cells in a dose dependent manner. A decrease in caspase-3 mediated DEVD-MCA, substrate hydrolysis and the appearance of the 120 kDa-spectrin breakdown product in cells treated with SB203580 further suggests that the p38 kinase acts upstream of caspase-3 in the apoptosis cascade. The data provides evidence for an essential role of p38 kinase in mediating apoptotic cell death in CGN and the inhibition of p38 kinase mimics the suppression of apoptosis provided by natural survival signals. 相似文献
204.
Angeles M. Cabello Gonzalo Platas Javier Collado Teresa M. Díez Isabel Martín Francisca Vicente María Meinz Janet C. Onishi Cameron Douglas John Thompson Myra B. Kurtz Robert E. Schwartz Gerald F. Bills Robert A. Giacobbe George K. Abruzzo Amy M. Flattery Li Kong Fernando Peláez 《International microbiology》2001,4(2):93-102
Echinocandins, the lipopeptide class of glucan synthase inhibitors, are an alternative to ergosterol-synthesis inhibitors to treat candidiasis and aspergillosis. Their oral absorption, however, is low and they can only be used parenterally. During a natural product screening program for novel types of glucan synthesis inhibitors with improved bioavailability, a fungal extract was found that inhibited the growth of both a wild-type Saccharomyces cerevisiae strain and the null mutant of the FKS1 gene (fks1::HIS). The mutant strain was more sensitive to growth inhibition, suggesting that the fungal extract could contain an inhibitor of glucan synthesis. A novel acidic steroid, named arundifungin, was purified from a fungal extract obtained from a liquid culture of Arthrinium arundinis collected in Costa Rica. Arundifungin caused the same pattern of hallmark morphological alterations in Aspergillus fumigatus hyphae as echinocandins, further supporting the idea that arundifungin belongs to a new class of glucan synthesis inhibitors. Moreover, its antifungal spectrum was comparable to those of echinocandins and papulacandins, preferentially inhibiting the growth of Candida and Aspergillus strains, with very poor activity against Cryptococcus. Arundifungin was also detected in nine other fungal isolates which were ecologically and taxonomically unrelated, as assessed by sequencing of the ITS1 region. Further, it was also found in two more Arthrinium spp from tropical and temperate regions, in five psychrotolerant conspecific isolates collected on Macquarie Island (South Pacific) and belonging to the Leotiales, and in two endophytes collected in central Spain (a sterile fungus belonging to the Leotiales and an undetermined coelomycete). 相似文献
205.
Drexler AL Harris CC dela Pena MG Asuncion-Uchi M Chung S Webster S Fuse M 《Cell and tissue research》2007,329(2):391-408
The crustacean hyperglycemic hormone (CHH) peptides regulate diverse physiological processes from reproduction to metabolism
and molting in arthropods. In insects, the ion transport peptides (ITP), also members of the CHH family, have only been implicated
in ion transport. In this study, we sequenced a nucleotide fragment spanning the conserved A1/A2 region of the putative CHH/ITP
gene. This fragment was amplified from larval cDNA of the tobacco hornworm, Manduca sexta and showed a high degree of sequence conservation with the same region from other insects and, to a lesser degree, with that
of crustacean species, suggesting the presence of a Manduca-specific CHH/ITP mRNA (MasITP mRNA). CHH-like immunocytochemical analyses with two crustacean antisera (from Carcinus maenas and Cancer pagurus) identified the presence of CHH-like immunoreactivity in nervous tissue of all developmental stages, but not in the gut of
M. sexta. Specifically, CHH-like peptides localized to paired type IA2 neurosecretory cells of the pars lateralis of the brain (projecting ipsilaterallly to the corpora cardiaca-allata complex)
and to neurosecretory cells and transverse nerves of the ventral nerve cord in larvae, pupae, and adults. The distribution
of the putative MasITP peptide shifted during development in a manner consistent with metamorphic reorganization. A comparison of hemolymph equivalents
of CHH detected by enzyme-linked immunosorbent assay with CHH-like immunoreactivity in transverse nerves provided evidence
for the release of MasITP from the transverse nerves into the hemolymph at insect ecdysis. These data suggest the presence of an insect ITP in M. sexta and a role for this hormone during ecdysis.
This research was funded by the National Institutes of Health (MBRS SCORE Program-NIGMS) to M.F. (grant no. 2S06 GM52588-09),
by the National Center on Minority Health and Health Disparities (grant no. 5P20-MD000262), an NIH RISE graduate fellowship
to A.L.D. (5 R25 GM59298), an NIH PREP fellowship to C.C.H. and M.A.U. (5 R25 GM64078), an NSF CSU LS-AMP fellowship to C.C.H.
(HRD-9802113), and by NIH MBRS-MARC to M.D.P. (T34 GM08574) and NIH MA/MS-PhD Bridge Scholarship to A.L.D. and C.C.H. (5R25
GM48972). 相似文献
206.
Verdoes M Hillaert U Florea BI Sae-Heng M Risseeuw MD Filippov DV van der Marel GA Overkleeft HS 《Bioorganic & medicinal chemistry letters》2007,17(22):6169-6171
The synthesis of three acetylene functionalized BODIPY dyes is described. These dyes are used to fluorescently modify an azido functionalized epoxomicin analogue employing the Huisgen 1,3-dipolar cycloaddition, resulting in a panel of fluorescent epoxomicin derived proteasome probes. 相似文献
207.
Victoria J. Bakker Donald R. Smith Holly Copeland Joseph Brandt Rachel Wolstenholme Joe Burnett Steve Kirkland Myra E. Finkelstein 《EcoHealth》2017,14(1):92-105
Translocation is an increasingly important tool for managing endangered species, but factors influencing the survival of translocated individuals are not well understood. Here we examine intrinsic and extrinsic drivers of survival for critically endangered California condors (Gymnogyps californianus) whose wild population recovery is reliant upon releases of captively bred stock. We used known fate models and information-theoretic methods to compare the ability of hypothesized covariates, most of which serve as proxies for lead exposure risk, to predict survival rates of condors in California. Our best supported model included the following predictors of survival: age of the recovery program, precipitation, proportion of days observed feeding on proffered carcasses, maximum blood lead concentration over the preceding 18 months, and time since release. We found that as flocks have increased in size and age, condors are increasingly likely to range more widely and less likely to be observed feeding on proffered food, and these “wilder” behaviors were associated with lower survival. After accounting for these behaviors, we found a positive survival trend, which we attribute to ongoing improvements in management. Our findings illustrate that the survival of translocated animals, such as highly social California condors, is influenced by behaviors that change through time. 相似文献
208.
Comparative Experiments To Examine the Effects of Heating on Vegetative Cells and Spores of Clostridium perfringens Isolates Carrying Plasmid Genes versus Chromosomal Enterotoxin Genes 总被引:1,自引:0,他引:1
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Mahfuzur R. Sarker Robert P. Shivers Shauna G. Sparks Vijay K. Juneja Bruce A. McClane 《Applied microbiology》2000,66(8):3234-3240
Clostridium perfringens enterotoxin (CPE) is an important virulence factor for both C. perfringens type A food poisoning and several non-food-borne human gastrointestinal diseases. Recent studies have indicated that C. perfringens isolates associated with food poisoning carry a chromosomal cpe gene, while non-food-borne human gastrointestinal disease isolates carry a plasmid cpe gene. However, no explanation has been provided for the strong associations between certain cpe genotypes and particular CPE-associated diseases. Since C. perfringens food poisoning usually involves cooked meat products, we hypothesized that chromosomal cpe isolates are so strongly associated with food poisoning because (i) they are more heat resistant than plasmid cpe isolates, (ii) heating induces loss of the cpe plasmid, or (iii) heating induces migration of the plasmid cpe gene to the chromosome. When we tested these hypotheses, vegetative cells of chromosomal cpe isolates were found to exhibit, on average approximately twofold-higher decimal reduction values (D values) at 55°C than vegetative cells of plasmid cpe isolates exhibited. Furthermore, the spores of chromosomal cpe isolates had, on average, approximately 60-fold-higher D values at 100°C than the spores of plasmid cpe isolates had. Southern hybridization and CPE Western blot analyses demonstrated that all survivors of heating retained their cpe gene in its original plasmid or chromosomal location and could still express CPE. These results suggest that chromosomal cpe isolates are strongly associated with food poisoning, at least in part, because their cells and spores possess a high degree of heat resistance, which should enhance their survival in incompletely cooked or inadequately warmed foods. 相似文献
209.
210.
Maroun J. Beyrouthy Karen E. Alexander Amy Baldwin Michael L. Whitfield Hank W. Bass Dan McGee Myra M. Hurt 《PloS one》2008,3(12)