Sulfotransferase-mediated chlorination of 1-hydroxymethylpyrene to a mutagen capable of penetrating indicator cells.

Methylated polycyclic aromatic hydrocarbons are common in the human environment. Many of them are stronger carcinogens than their purely aromatic congeners. They may be metabolized to benzylic alcohols. We report here on biochemical and toxicological characteristics of 1-hydroxymethylpyrene (HMP), a typical representative of this class of compounds. Rat liver cytosol, fortified with 3'-phosphoadenosine-5'-phosphosulfate, converted HMP into its sulfate ester (HMPS), HMPS bound covalently to isolated DNA. In physiological buffer at 37 degrees C, HMPS had a half-life of 2 min, the major decomposition product being HMP. Thus, cyclic activation is possible. When Cl- anions were present at physiological concentrations, an additional reaction product of HMPS, 1-chloromethylpyrene (ClMP), could be identified on the basis of its chromatographic properties and its mass spectrum, using the authentic standard for comparison. ClMP was shorter-lived in buffer than HMPS. ClMP reacted with DNA, the adduct pattern in the 32P-postlabeling analysis being similar, or identical, to that of HMPS. ClMP proved to be a very potent mutagen in Salmonella typhimurium, whereas HMPS, and HMP in the presence of a sulfate-conjugating system, showed strong mutagenicity only when Cl- or Br- ions were present in the exposure buffer. It is concluded that HMPS is capable of reacting with DNA, but is hampered in its distribution by membrane barriers.(ABSTRACT TRUNCATED AT 250 WORDS

Program user's manual for optimizing the design of a liquid or gaseous propellant rocket engine with the automated combustor design code AUTOCOM

This computer program manual describes in two parts the automated combustor design optimization code AUTOCOM. The program code is written in the FORTRAN 4 language. The input data setup and the program outputs are described, and a sample engine case is discussed. The program structure and programming techniques are also described, along with AUTOCOM program analysis

Hybridisierungskinetiken von Oligo- und Polynukleotiden an Glas-Oberflächen

Cytosolische Sulfotransferasen katalysieren den Transfer der Sulfonatgruppe auf endogene Verbindungen wie z.B. Steroide oder Katecholamine sowie auf Xenobiotika. Die Sulfonierung bestimmter Substanzen führt abhängig von deren Struktur jedoch zur Bildung reaktiver, mutagener and carcinogener Metaboliten. Im SULT1A1-Gen wurden Punktmutationen ('Single-Nucleotide-Polymorphisms', SNPs) identifiziert, die zu Aminosäureaustausch führen. Der am häufigsten vorkommende Austausch G638A führt zu den beiden Alloenzymen SULT1A1*Arg213 und *His213. Um mögliche Assoziationen zwischen Krankheitsbildern und bestimmten SULT1A1 Genotypen feststellen zu können, ist eine Untersuchungsmethode notwendig, bei der in kurzer Zeit der Genotyp möglichst vieler Probanden ermittelt werden kann. Daher soll anhand des Modells der humanen Sulfotransferase SULT1A1 der Einfluß von Punktmutationen auf das Hybridisierungsverhalten von Oligo- und Polynukleotiden untersucht werden. Diese Untersuchungen dienen als Vorversuche für die Etablierung und Automatisierung der SNP-Analyse auf DNA-Chips, die den gewünschten Probendurchsatz ermöglichen soll. Die SNP-Analyse erfolgt mittels Glasfaser-Optik. Auf einer streptavidinbeschichteten Glasfaser-Oberfläche ist ein 13 Bp langes Oligonukleotid - der SNP und 12 flankierende Nukleotide - über Biotin immobilisiert. Nach Zugabe eines mit Fluorescein gelabelten Proben-Amplifikats findet die Hybridisierung am 13mer statt. Anschließend wird durch Spülen mit Puffer die Dissoziation des Polynukleotids ausgelöst. Anhand des emittierten Fluoreszenz-Signals kann die Reaktionsgeschwindigkeitskonstante der Dissoziation bestimmt werden. Es konnte gezeigt werden, daß sich die Dissoziationsgeschwindigkeit eines mis-match (Bsp. Mutante - Wildtyp) wesentlich von der eines full-match (Bsp. Mutante - Mutante) unterscheidet. Es ist somit möglich, anhand der Dissoziationskinetik Mutante und Wildtyp eines SNP-haltigen DNA-Abschnitts zu identifizieren

Genotoxicity characteristics of reverse diol-epoxides of chrysene

Trans-3,4-dihydroxy-3,4-dihydrochrysene (chrysene-3,4-diol), a major metabolite of chrysene, is further metabolized by rat liver enzymes to products which effectively revert the his− Salmonella typhimurium strain TA98 to histidine prototrophy, but are only weakly mutagenic in strain TA100 and in Chinese hamster V79 cells (acquisition of resistance to 6-thioguanine). The liver enzyme mediated mutagenicity of chrysene-3,4-diol is substantially enhanced in the presence of 1,1,1-trichloropropene 2,3-oxide, an inhibitor of microsomal epoxide hydrolase. The predominant metabolites of chrysene-3,4-diol, namely the anti- and syn-isomers of its 1,2-oxide (termed reverse diol-epoxides), proved to be extraordinarily effective mutagens in S.typhimurium strain TA98, but were only moderately active in strains TA100 and TA104, and in the SOS induction in Escherichia coli PQ37. These genotoxicity spectra in bacteria are completely different from those observed with the bay-region diol-epoxides of chrysene and 3-hydroxychrysene. In V79 cells, the reverse diol-epoxides formed low levels of DNA adducts and were very weak inducers of gene mutations. In M2 mouse prostate cells, however, high numbers of transformed foci were induced by chrysene-3,4-diol and its diastereomeric 1,2-oxides. Chrysene-3,4-diol was somewhat more potent than chrysene-1,2-diol. The potency of both reverse diol-epoxides was similar to that of the syn-diastereomers of the bay-region diol-epoxides of chrysene and 3-hydroxychrysene, but lower than that of their anti-diastereomers. The reverse diol-epoxides of chrysene, unlike the bay-region diol-epoxides, were inactivated by purified microsomal epoxide hydrolase. Noteworthy findings were also made with regard to the chemical stability of the diol-epoxides in buffer, determined from the decline in mutagenicity after preincubation in the absence of the target cells. Despite its lower ΔEdeloc/β value for the formation of the benzylic carbocation, anti-chrysene-3,4-diol 1,2-oxide was shorter-lived (t½ = 46 min) than anti-chrysene-l,2-diol 3,4-oxide (t½ = 74 min). Unlike other investigated diastereomeric pairs of diol-epoxides, it was also shorter-lived than its syn-diastereomer (t½12 = 340 min

Population Parameters of Intermediate-Age Star Clusters in the Large Magellanic Cloud. III. Dynamical Evidence for a Range of Ages Being Responsible for Extended Main Sequence Turnoffs

We present new analysis of 11 intermediate-age (1-2 Gyr) star clusters in the Large Magellanic Cloud based on Hubble Space Telescope imaging data. Seven of the clusters feature main sequence turnoff (MSTO) regions that are wider than can be accounted for by a simple stellar population, whereas their red giant branches indicate a single value of [Fe/H]. The star clusters cover a range in present-day mass from about 1E4 to 2E5 solar masses. We compare radial distributions of stars in the upper and lower parts of the MSTO region, and calculate cluster masses and escape velocities from the present time back to a cluster age of 10 Myr. Our main result is that for all clusters in our sample with estimated escape velocities > 15 km/s at an age of 10 Myr, the stars in the brightest half of the MSTO region are significantly more centrally concentrated than the stars in the faintest half AND more massive red giant branch and asymptotic giant branch stars. This is not the case for clusters with escape velocities < 10 km/s at an age of 10 Myr. We argue that the wide MSTO region of such clusters is mainly caused by to a 200 - 500 Myr range in the ages of cluster stars due to extended star formation within the cluster from material shed by first-generation stars featuring slow stellar winds. Dilution of this enriched material by accretion of ambient interstellar matter is deemed plausible if the spread of [Fe/H] in this ambient gas was very small when the second-generation stars were formed in the cluster.Comment: 11 pages (in emulateapj format), 6 figures, accepted for publication in Ap