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1.
The study of water relaxation rates of solutions of melanins with paramagnetic metal ions provides a powerful tool for investigating the binding sites and for obtaining useful structural and dynamic information. The measure of 1H- and 2H-longitudinal and transverse relaxation rates at a single, high-magnetic field for H2O/D2O (80:20) solutions allows the determination of tau c, tau R, tau e, tau M, r, q, and Z (the outer sphere contribution to the overall relaxation rate) for Mn(II)-L-Dopa melanin system. 相似文献
2.
Determination of urinary delta-amino levulinic acid (ALA) is now systematically used in occupational health to detect an excessive exposure to lead in professionally exposed workers. However, to determine whether circadian changes of the urinary excretion of ALA alter the significance of the test, we quantified the ALA levels in the urine of 19 healthy young adults. Urine samples were taken every 3 hr between 0700 and 2300 hr and ALA levels were determined by a spectrocolorimetric method. The data indicated that the 24-hr mean ALA level was: 1.81 mg/g creatinine. The peak values (2.24 +/- 0.24) were obtained between 1400 and 1700 hr whereas the lowest ALA levels were found between 2200 and 0300 hr. Cosinor analysis revealed a significant circadian rhythm while no significant difference could be found according to sex. Possible explanations of our findings are discussed. 相似文献
3.
G. Steiblen T. Orsire C. Pallen A. Botta D. Marzin 《Mutation Research - Genetic Toxicology and Environmental Mutagenesis》2005,588(2):143-151
Aneugenic compounds act on non-DNA targets to exert genotoxicity via an indirect mechanism. In contrast to DNA-binding agents, these compounds are expected to possess threshold levels of activity. Therefore, the risk for adverse effects following human exposure to an aneugen could be minimal, if the threshold of activity has been clearly determined in vivo and in vitro and providing the human exposure level is below this threshold. Thus, the development of a single-cell model to allow comparisons between in vitro and in vivo threshold values for aneugenic compounds is of importance.The in vivo micronucleus test is one of the main assays used in genetic toxicology, and is often performed in the mouse. Thus, an extensive database is available in the literature. However, there are only few data concerning the in vitro micronucleus assay using mouse cells, as the majority of in vitro micronucleus assays have been performed using human lymphocytes. In addition, there is a lack of data concerning thresholds for any compound using this model.First, we evaluated whether the use of mouse splenocytes would be an acceptable alternative to that of human lymphocytes to identify aneugens. To allow valid comparisons, the two protocols were first harmonized. Thus, phytohemagglutinin (PHA) and concanavalin A were used as specific mitogens for human lymphocytes and mouse splenocytes, respectively, in order to achieve similar cell-proliferation rates. To achieve similar and sufficient numbers of binucleated cells, cytochalasin B was added 44 and 56 h after culture initiation of the human and mouse cells, respectively.Second, we compared the sensitivity of the mouse protocol with that of the human protocol by exposing the cells to the aneugens nocodazole and paclitaxel.There was good reproducibility of the cytotoxic/genotoxic responses of the two cell models following exposure to the aneugens. The sensitivity of the mouse splenocytes to paclitaxel was higher than that of the human lymphocytes. The two cell types were equally sensitive to nocodazole. 相似文献
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Ester Cecere Orestina D. Saracino Margherita Fanelli Antonella Petrocelli 《Journal of applied phycology》1992,4(4):323-327
A survey is reported of the drifting algal community in Mar Piccolo, a polluted basin subject to sewage outlets. The key role was played by a few key species, mainly floridean red algae. 相似文献
7.
A thyroid binding peripheral membrane protein(s) has been characterized in human red cell. Two classes of affinity sites for triiodothyronine have been demonstrated. The high affinity, low capacity site showed values for dissociation constant of 2 X 10(-10)M. The binding activity depended on the presence of free -SH group and showed a high stereospecificity for L-triiodothyronine, L-thyroxine was less potent (about 1,000-fold) than L-triiodothyronine in competing for this site. The results are discussed with respect to their cellular significance. 相似文献
8.
B. Botta F. Delle Monache G. Delle Monache G.B. Marini Bettolo J.D. Msonthi 《Phytochemistry》1985,24(4):827-830
The roots of Psorospermum febrifugum collected in Malawi contained together with the known vismione D and geranyloxyemodin four new compounds: vismione F and the three bianthrones A1, A3a and A3b. All the isolated compounds contained C- or O-geranyl substituents and showed a close biogenetic relationship. 相似文献
9.
Inhibition of lateral wall elongation by mecillinam stimulates cell division in certain cell division conditional mutants of Escherichia coli. 总被引:5,自引:4,他引:1
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The effect of mecillinam, a beta-lactam antibiotic that specifically binds penicillin-binding protein 2 of Escherichia coli, causes transition from rod to coccal shape, and inhibits cell division in sensitive cells, has been tested on three different E. coli temperature-sensitive cell division mutants. At the nonpermissive temperature, the antibiotic allows an increase in cell number for strains BUG6 and AX655 but not for AX621. In strain AX655, the cell division stimulation was observed only if the antibiotic was added immediately after shifting to the nonpermissive temperature, whereas in BUG6, the rise in cell number was observed also when mecillinam was added after 90 min of incubation at the nonpermissive temperature. In all cases, cell division began occurring 30 min after addition of the antibiotic. Mecillinam had no effect on division of dnaA, dnaB temperature-sensitive mutants or on division of BUG6 derivatives made resistant to this antibiotic. Other beta-lactam antibiotics such as penicillin, ampicillin, cephalexin, and piperacillin and non beta-lactam antibiotics such as fosfomycin, teichomycin, and vancomycin that inhibit cell wall synthesis did not show any effect on cell division for any of the mutants. The response of the three cell division mutants to mecillinam is interpreted in terms of a recently proposed model for shape regulation in bacteria. 相似文献
10.
Hung Cao Danh Margherita Strolin Benedetti Philippe Dostert 《Journal of neurochemistry》1983,41(3):618-622
Abstract: Aldehyde dehydrogenase (ALDH) activity was measured in brains, livers, and hearts of 23–26-month-old and 3-month-old rats. A significant increase of ALDH activity was found in whole brain of old rats with both acetaldehyde (39%) and propionylaldehyde (15%) used as substrates. In different brain areas of old rats, with acetaldehyde used as substrate, a significant increase of ALDH activity was found in striatum (30–50%) and cerebral cortex (37%). However, no significant difference in ALDH activity was found in livers and hearts of young and old rats. Preliminary experiments showed a significant increase of aldehyde reductase activity (52%) with p -nitrobenzaldehyde used as substrate in whole brain of old rats compared with young rats. The present work indicates that an increase of ALDH activity in brain of old rats may be an adaptive phenomenon. 相似文献