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Biomedical subjects

C S Cooper

Publications and source records attributed to C S Cooper.

At least 145 records · Page 8Linked to original sources
PubMed1981

The metabolic activation of benz[alpha]anthracene in three biological systems.

The 3,4- and 8,9-dihydrodiols of benz[alpha]anthracene (BA) are formed as metabolites of the parent hydrocarbon by rat-liver microsomes, by mouse skin and by hamster embryo cells. In incubations with rat-liver microsomal fractions, only small amounts of the 3,4-dihydrodiol of BA were detected relative to other dihydrodiol metabolites and only small amounts of BA-deoxyribonucleoside adducts derived from the related diol-epoxide, t-3, r-4-dihydroxy-t-1,2-oxy-1,2,3,4-tetrahydrobenz[alpha]anthracene (anti-BA-3,4-diol 1,2-oxide), were detected relative to adducts derived from r-8,t-9-dihydroxy-t-10,11-oxy-8,9,10,11-tetrahydrobenz[alpha]anthracene (anti-BA-8,9-diol 10,11-oxide). However, in studies with mouse skin and hamster embryo cells, larger amounts of free 3,4-dihydrodiol were detected and a larger proportion of the hydrocarbon-deoxyribonucleoside adducts resulted from the reaction of anti-BA-3,4-diol 1,2-oxide with DNA.

Animals↗
PubMed1981

The metabolic and activation of dibenz[a,c]anthracene.

In rat liver microsomal preparations, the 10,11-dihydrodiol of dibenz[a,c]anthracene (DBA) is metabolized to r-10,t-11-dihydroxy-t-12,13-oxy-10,11,12,13-tetrahydrodibenz[a,c]anthracene (anti-DBA 10,11-diol 12,13-oxide), the anti isomer of a non-bay-region diol-epoxide of DBA. When 3H-labelled DBA or trans-10,11-dihydro-10,11-dihydroxydibenz[a,c]anthracene were metabolized in this system in the presence of DNA or when 3H-labelled DBA was added to primary cultures of hamster embryo cells, covalent reactions of hydrocarbon metabolites with DNA occurred. The chromatographic characteristics of the radioactive hydrocarbon-deoxyribonucleoside adducts formed in these reactions were examined using Sephadex LH20 column chromatography and high pressure liquid chromatography. The results showed that whilst some of the radioactive hydrocarbon-deoxyribonucleoside adducts formed were indistinguishable from adducts that were formed when anti-DBA 10,11-diol 12,13-oxide reacted with DNA, other, unidentified adducts, which did not apparently arise from reactions of this diol-epoxide with DNA, were also present. Hydrocarbon-nucleoside adducts were not detected in hydrolysates of nucleic acids that were isolated from mouse skin that had been treated in vivo with DBA.

Animals↗
PubMed1981

Fluorescence spectra of nucleoside-hydrocarbon adducts formed in mouse skin treated with 7,12-dimethylbenz[a]anthracene.

Hydrolysates of DNA that had been isolated from mouse skin treated with 3H-labelled 7,12-dimethylbenz[a]anthracene (DMBA) were subjected to chromatography on Sephadex LH20 columns and 3H-labelled products that eluted in the region expected for nucleoside-hydrocarbon adducts were purified further by high pressure liquid chromatography (h.p.l.c.). The fluorescence spectra of three major products that were resolved by this method were determined using photoncounting spectrophotofluorimetry. The fluorescence spectra of all three products were anthracene-like and similar to the spectra of nucleoside-hydrocarbon adducts obtained from DNA that was incubated with 3,4-dihydro-3,4-dihydroxy-7,12-dimethylbenz[a]anthracene 1,2-oxide (DMBA-3,4-diol 1,2-oxide). This is consistent with the idea that the metabolic activation of DMBA in mouse skin occurs through the formation of 'bayregion' diol-epoxides in the 1,2,3,4-ring.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1980

The metabolic activation of benz[a]anthracene in hamster embryo cells: evidence that diol-epoxides react with guanosine, deoxyguanosine and adenosine in nucleic acids.

The principal nucleoside-hydrocarbon adducts present in hydrolysates of RNA and DNA isolated from hamster embryo cells treated with benz[a]anthracene (BA) were examined by chromatography on Sephadex LH 20 and by high pressure liquid chromatography (HPLC) on Spherisorb 5 ODS. The results extend the previous finding that a non-'bay-region' diol-epoxide, anti-BA-8,9-diol 10,11-oxide (r-8,t-9-dihydroxy-t-10,11-oxy-8,9,10,11-tetrahydrobenz[a] anthracene) is involved in the binding of BA to cellular nucleic acids and show that this diol-epoxide most probably reacts with guanosine and adenosine in RNA and with deoxyguanosine in DNA. The results also show that a 'bay-region' diol-epoxide anti-BA-3,4-diol 1,2-oxide (t-3,-4-dihydroxy-t-1,2-oxy-1,2,3,4-tetrahydrobenz[a]anthracene, which is thought to be involved in the binding of benz[a]anthracene, which is thought to be involved in the binding of benz[a]anthracene to DNA in some situations, reacts mainly with deoxyguanosine.

Adenosine↗
PubMed1980

Additional evidence for the involvement of the 3,4-diol 1,2-oxides in the metabolic activation of 7,12-dimethylbenz[a]anthracene in mouse skin.

The role of vicinal diol-epoxides in the metabolic activation of 7,12-dimethylbenz[a]anthracene to intermediates that react with nucleic acids was investigated using Sephadex LH-20 column chromatography and high pressure liquid chromatography. The results show that some of the hydrocarbon-DNA products formed in mouse skin treated in vivo with 7,12-dimethylbenz[a]anthracene arise from the reaction of DNA with 3,4-dihydro-3,4-dihydroxy-7,12-dimethylbenz[a]anthracene 1,2-oxides which, on the basis of this and other evidence, appears to be a biologically-active metabolite of 7,12-dimethylbenz[a]anthracene. However, since other nucleic acid-hydrocarbon adducts were also present that have not been identified as resulting from the reaction of the 3,4-diol 1,2-oxides with DNA, other mechanisms may also be involved in the metabolic activation of 7,12-dimethylbenz[a]anthracene in mouse skin.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1980

The involvement of a non-'bay-region' diol-epoxide in the metabolic activation of benza[a]anthracene in hamster embryo cells.

The major hydrocarbon-nucleoside adduct present in hydrolysates of DNA from hamster embryo cells that had been treated with 3H-labelled benz[a]anthracene in culture has been examined by chromatography on Sephadex LH-20 columns and by high-pressure liquid chromatography. The results show that this adduct most probably arises from r-8,t-9-hydroxy-t-10,11-oxy-8,9,10,11-tetrahydrobenz[a]anthracene (anti-BA-8,9.-diol 10,11-oxide). On the basis of this and other evidence, this non-bay-region diol-epoxide appears to be a reactive intermediate involved in the metabolic activation of benz[a]anthracene.

Animals↗
PubMed1980

Metabolic activation of 3-methylcholanthrene in mouse skin: fluorescence spectral evidence indicates the involvement of diol-epoxides formed in the 7,8,9,10-ring.

Hydrolysates of DNA that had been isolated from mouse skin treated with 3H-labelled 3-methylcholanthrene were subjected to chromatography on Sephadex LH20 columns and 3H-labelled products that eluted in the region expected for nucleoside-hydrocarbon adducts were purified further by high pressure liquid chromatography; eight major and one minor products were resolved and their fluorescence spectra were determined using photon-counting spectrophotofluorimetry. The fluorescence spectra of six of the major products are anthracene-like and are similar to the previously-reported spectrum of 7,8,9,10-tetrahydro-3-methylcholanthrene, a result that is consistent with metabolic activation involving diol-epoxide formation in the 7,8,9,10-ring of 3-methylcholanthrene. The fluorescence spectra of the other two major products are also anthracene-like, but their maxima are shifted to longer wavelengths relative to the maxima in the spectrum of 7,8,9,10-tetrahydro-3-methylcholanthrene. The minor product possesses a fluorescence spectrum that is not anthracene-like and that is dissimilar from the spectra of products formed from 3-methylcholanthrene 11,12-oxide.

Animals↗
PubMed1980

The metabolism of the 10,11-dihydrodiol of benz[a]-anthracene to a vicinal diol-epoxide that is not involved in metabolic activation.

Benz[a]anthracene-10,11-diol, a major metabolite of benz[a]anthracene, is metabolized by a rat-liver microsomal system to form anti-BA-10,11-diol 8, 9-oxide (t-10,r-11-dihydroxy-t-8,9-oxy-8,9,10,11 -tetrahydrobenz[a]anthracene) and, to a lesser extent, syn-BA-10,11-diol 8,9-oxide (t-10,r-11-dihydroxy-c-8,9-oxy-8,9,10,11-tetrahydrobenz[a] anthracene). However, when benz[a]anthracene is incubated with DNA in a rat-liver microsomal system, anti-BA-10,11-diol 8,9-oxide does not contribute to the covalent binding of this hydrocarbon to DNA.

Animals↗
PubMed1980

Fluorescence spectral evidence that benzo[a]pyrene is activated by metabolism in mouse skin to a diol-epoxide and a phenol-epoxide.

Hydrolysates of DNA that had been isolated from mouse skin treated with 3H-labelled benzo[a]pyrene were subjected to chromatography on Sephadex LH20. Two major products were eluted in the region expected for deoxyribonucleoside-hydrocarbon adducts and these were purified further by h.p.l.c. The fluorescence emission and excitation spectra of one of the adducts were identical to that of the adduct obtained from DNA that was treated with BP-7,8-diol 9,10-oxide (r-7,t-8-dihydroxy-t-9,10-oxy-7,8,9,10-tetrahydrobenzo[a] pyrene). The fluorescence emission and excitation spectra of the other adducts were identical to the published spectra of 9-OHBP-4,5-diol (4,5-dihydro-4,5,9-trihydroxy-benzo[a]pyrene) and of the deoxyribonucleoside-hydrocarbon adduct obtained from DNA that had been incubated with 9-OHBP (9-hydroxybenzo[a] pyrene) in the presence of a rat-liver microsomal system. The metabolic activation of benzo[a]pyrene in mouse skin, a target tissue for carcinogenesis by this hydrocarbon, thus appears to involve the formation of adducts derived from both BP-7,8-diol 9,10-oxide and 9-OHBP 4,5-oxide (9-hydroxybenzo-[a]pyrene 4,5-oxide), although quantitatively, the adduct derived from 9-OHBP 4,5-oxide is a minor product.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1980

The enzyme-catalysed conversion of anti-benzo[a]pyrene-7,8-diol 9,10-oxide into a glutathione conjugate.

Anti-BP-7,8-diol 9,10-oxide (r-7,t-8-dihydroxy-t-9, 10-oxy-7,8,9,10-tetrahydrobenzo[a]pyrene) was converted in the presence of a rat-liver supernatant fraction and glutathione into a water-soluble metabolite that was identified as a glutathione conjugate. The formation of the glutathione conjugate appears to be catalysed by glutathione S-transferases, present in the rat-liver supernatant, because the amount of conjugate formed was reduced considerably when anti-BP-7,8-diol 9,10-oxide was incubated with glutathione either in the absence of the supernatant fraction or in the presence of heat-denatured supernatant fraction.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1980

Metabolic activation of benz[a]anthracene in hamster embryo cells: the structure of a guanosine-anti-BA-8,9-diol 10,11-oxide adduct.

The structures of two guanosine-hydrocarbon adducts prepared from polyG that had been incubated with anti-BA-8,9-diol 10,11-oxide (r-8,t-9-dihydroxy-t-10,11-oxy-8,9,10,11-tetrahydrobenz[a]anthracene) were investigated by examining their H-n.m.r. spectra, their pK values before and after treatment with nitrous acid and their stabilities in 1M KOH. The data show that both of the adducts were formed by reaction between the exocyclic amino group of guanine and the 11-position of the diolepoxide. One of these adducts is indistinguishable from an adduct isolated from hamster embryo cells that had been treated with benz[a]anthracene and that may contribute to the biological activity of this weak carcinogen.

Animals↗
PubMed1979

The role of subunits in yeast DNA-dependent ribonucleic acid polymerase A.

The properties of RNA polymerase A, which lacked the subunits of 48 000, 37 000 and 16 000 mol. wt., were compared with those of RNA polymerase A by using native calf thymus DNA as the template. The results showed that: (1) the specific activity of RNA polymerase A was about one-third that of RNA polymerase A; (2) more than 80% of RNA polymerase A, but only about 25% of RNA polymerase A, made RNA; (3) initiation by RNA polymerase A, but not by RNA polymerase A, began after a lag of 2 min; (4) the temperature-dependence for productive binding to DNA was greater for RNA polymerase A; (5) the apparent Km for UTP was greater for RNA polymerase A. These results support the supposition that the subunits missing from RNA polymerase A are involved in DNA binding [Huet, Dezélée, Iborra, Buhler, Sentenac & Fromageot (1976) Biochimie 58, 71-80] and show also that the loss of these subunits affects the elongation reaction.

Ammonium Sulfate↗
PubMed1979

Convolution analysis of transcription by yeast DNA-dependent ribonucleic acid polymerase A. A mathematical method for studying ribonucleic acid chain elongation.

The rate of initiation of RNA synthesis catalysed by yeast RNA polymerase A on native calf thymus DNA decayed exponentially with a half-life of about 4.3 min. The rate constant for initiation was unaffected by preincubating the enzyme with DNA, or by decreasing the concentration of GTP 4-fold. The rate of RNA synthesis was constant for 15--20 min and then decreased. Each enzyme molecule made no more than one RNA molecule. In this situation, initiation, elongation and total RNA synthesis are related by a convolution integral. Solution of the convolution integral revealed that the rate of elongation was apparently biphasic. Analysis of the size of the RNA product showed that this biphasic profile arose because most but not all of the enzyme stopped RNA synthesis soon after initiation.

DNA↗