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R W Wiseman

Publications and source records attributed to R W Wiseman.

79 records · Page 5Linked to original sources
PubMed1986

Activating mutations of the c-Ha-ras protooncogene in chemically induced hepatomas of the male B6C3 F1 mouse.

Activated c-Ha-ras protooncogenes have recently been identified in the DNA of some spontaneous hepatic tumors found in 2-year-old B6C3 F1 mice. Activation of c-Ha-ras has now been demonstrated in DNA from well-differentiated hepatomas initiated by a single dose of carcinogen given to male B6C3 F1 mice at 12 days of age. DNA from each of 25 hepatomas, induced by N-hydroxy-2-acetylaminofluorene, vinyl carbamate, or 1'-hydroxy-2',3'-dehydroestragole, containing transforming activity in the NIH 3T3 transfection assay. Southern analysis of NIH 3T3 cells transformed by DNA from 24 of these hepatomas revealed amplified and/or rear-ranged restriction fragments homologous to a Ha-ras probe. The other tumor contained an activated Ki-ras gene. Immunoprecipitation and NaDodSO4/PAGE analysis of p21 ras proteins in NIH 3T3 transformants derived from a majority of the hepatomas suggested that the activating mutations were localized in the 61st codon of the c-Ha-ras gene. Creation of a new Xba I restriction site by an AT----TA transversion at the second position of codon 61 was detected in DNA from primary tumors and NIH 3T3 cells transformed by DNA from 6 of 7 vinyl carbamate- and 5 of 10 1'-hydroxy-2',3'-dehydroestragole-induced hepatomas. Selective oligonucleotide hybridization demonstrated a CG----AT transversion at the first position of the 61st codon in NIH 3T3 transformants derived from 7 of 7 N-hydroxy-2-acetylaminofluorene-induced hepatomas. By the same criterion, an AT----GC transition at the second position of codon 61 was the activating mutation in 1 of 7 vinyl carbamate- and 5 of 10 1'-hydroxy-2',3'-dehydroestragole-induced tumors. Thus, c-Ha-ras activation is apparently an early event in B6C3 F1 mouse hepatocarcinogenesis that results directly from reaction of ultimate chemical carcinogens with this gene in vivo.

Animals↗
PubMed1986

Apurinic/apyrimidinic site induction in supercoiled DNA and mutagenesis in Salmonella typhimurium TA100 by 1'-acetoxysafrole and related electrophilic alkenylbenzene derivatives.

The abilities of seven electrophilic alkenylbenzene derivatives related to 1'-acetoxysafrole to induce apurinic/apyrimidinic (AP) sites in supercoiled SV40 DNA were quantitated by gel electrophoresis after neutral thermal hydrolysis of DNA adducts with unstable N-glycosidic bonds and putrescine/Mg2+ ion-enhanced cleavage of the adjacent phosphodiester linkages. A 20-fold range in AP site production was observed for this series of closely related electrophiles. Analysis of SV40 DNA modified with [2',3'-3H]-1'-acetoxysafrole indicated that approximately 14% of the total safrole-DNA adducts generated AP sites under the conditions used. Neutral thermal hydrolysis of the modified DNA released a product with the same h.p.l.c. retention time as N7-(isosafrol-3'-yl)guanine. The mutagenic potencies in Salmonella typhimurium strain TA100 of these seven electrophilic alkenylbenzene derivatives covered a 75-fold range (from 0.1 to 7.7 revertants/nmol). Although the mutagenic activities of these electrophiles generally correlated well with the hepatocarcinogenic activities of the parent 1'- or 3'-hydroxy derivatives on administration to preweanling male mice, the mutagenic and carcinogenic activities did not correlate with the abilities to induce AP sites.

Alkylation↗
PubMed1985

Major role of hepatic sulfotransferase activity in the metabolic activation, DNA adduct formation, and carcinogenicity of 1'-hydroxy-2',3'-dehydroestragole in infant male C57BL/6J x C3H/HeJ F1 mice.

1'-Hydroxy-2',3'-dehydroestragole is a synthetic acetylenic analogue of 1'-hydroxyestragole, the proximate carcinogenic metabolite of the naturally occurring hepatocarcinogen estragole (1-allyl-4-methoxybenzene). This analogue is considerably more potent than 1'-hydroxyestragole as an hepatocarcinogen in mice. 1'-Acetoxy-2',3'-dehydroestragole reacted readily with deoxyguanosine or deoxyguanosine 5'-monophosphate at neutrality to form two adducts. Adduct I, isolated and characterized after dephosphorylation of the deoxyguanosine 5'-monophosphate product, was a 1:1 mixture of two diastereomers of N2-(2',3'-dehydroestragol-1'-yl)deoxyguanosine. Adduct II was shown to be N-7-(2',3'-dehydroestragol-1'-yl)guanine. The reaction of deoxyadenosine with 1'-acetoxy-2',3'-dehydroestragole at neutrality produced Adducts III and IV. Adduct IV was characterized as N6-(2',3'-dehydroestragol-1'-yl)deoxyadenosine. Administration of [1'-3H]-1'-hydroxy-2',3'-dehydroestragole to male preweanling C57BL/6J x C3H/HeJ F1 (hereafter called B6C3F1) mice resulted in extensive covalent binding to hepatic DNA, RNA, and protein. On hydrolysis of the DNA to nucleosides, a single major adduct accounted for greater than 85% of the DNA-bound 3H. This adduct comigrated with Adduct I in two high performance liquid chromatography systems, had a pH partition profile identical to that of Adduct I, and was present as a mixture of diastereomers in a ratio of 2:1. The identity of the DNA adduct formed in vivo with Adduct I from the reaction of 1'-acetoxydehydroestragole indicated that a reactive ester was a major metabolic precursor in vivo. There was no significant loss of Adduct I from the hepatic DNA by 21 days after a single injection of a carcinogenic dose of 1'-hydroxy-2',3'-dehydroestragole. Adducts II, III, and IV were not detected in significant amounts in the hepatic DNA isolated by a phenol extraction method or by a more rapid hydroxylapatite method. Cytosolic sulfotransferase activity was demonstrated for 1-hydroxy-2',3'-dehydroestragole in mouse liver, and inhibition of this activity by greater than 95% was found on addition of 10 microM pentachlorophenol. The administration of pentachlorophenol (0.04 mumol/g body weight) 45 min prior to a single dose of 1'-hydroxy-2',3'-dehydroestragole (0.04 mumol/g body weight) in 12-day-old male B6C3F1 mice greatly inhibited (87-97%) the covalent binding of 1'-hydroxy-2',3'-dehydroestragole to hepatic macromolecules and the formation of hepatomas at 10 months.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

Further characterization of the DNA adducts formed by electrophilic esters of the hepatocarcinogens 1'-hydroxysafrole and 1'-hydroxyestragole in vitro and in mouse liver in vivo, including new adducts at C-8 and N-7 of guanine residues.

The identities of the adducts formed on reaction of the model electrophilic and carcinogenic esters 1'-acetoxysafrole or 1'-acetoxyestragole with deoxyguanosine in vitro and those formed in vivo in the hepatic DNA of 12-day-old male C57BL/6 X C3H/He F1 (hereafter called B6C3F1) mice treated with 1'-hydroxysafrole or 1'-acetoxysafrole were investigated further with more discriminating high-performance liquid chromatography systems than previously used. The adducts formed from the reactions of 1'-acetoxysafrole or 1'-acetoxyestragole are strictly analogous and are distinguished by the prefixes S and E, respectively. Five adducts, including S(E)-II identified by Phillips et al. (Cancer Res., 41: 176-186, 2664-2671, 1981) as N2-(trans-isosafrol-3'-yl)deoxyguanosine and the analogous isoestragole derivative, have been characterized from the reactions with each ester. Adducts S-I and E-I, tentatively identified by Phillips et al. as N2-(safrol-1'-yl)- or N2-(estragol-1'-yl)deoxyguanosine, were each resolved into a pair of diastereomers. The proposed structures for each diastereomer were confirmed by nuclear magnetic resonance and circular dichroism spectroscopy. Two new adducts, i.e., S(E)-V and S(E)-VI, were isolated from each reaction mixture. On the basis of their pKas, their loss of 3H from [8-3H]deoxyguanosine, their retention of 3H from [1',2'-3H]deoxyguanosine, and their nuclear magnetic resonance spectra, Adducts S-V and E-V were characterized as 8-(trans-isosafrol-3'-yl)- and 8-(trans-isoestragol-3'-yl)deoxyguanosine, respectively. Adducts S-VI and E-VI were characterized in a similar manner as 7-(trans-isosafrol-3'-yl)- and 7-(trans-isoestragol-3'-yl)guanine, respectively. Adducts S-III and E-III, minor components described in the earlier studies, were not observed in the present work. High-performance liquid chromatography of hydrolysates of the hepatic DNA of male 12-day-old B6C3F1 mice killed 9 h after a single dose (0.1 mumol/g body weight) of [2',3'-3H]-1'-hydroxysafrole showed that Adducts S-Ia, S-Ib, S-II, S-IV (identified by Phillips et al. as N6-(trans-isosafrol-3'-yl)deoxyadenosine), S-V, and S-VI were present at average levels of 3.5, 7.0, 24.4, 2.9, 1.2, and 3.6 pmol/mg DNA, respectively. Similar levels of these adducts were found in the hepatic DNA after administration of the same dose of [2',3'-3H]-1'-acetoxysafrole under identical conditions.

Animals↗
PubMedDate not supplied

Biological applications for small solenoids: NMR spectroscopy of microliter volumes at high fields.

In this paper we describe features of an NMR probe designed for the study of small, superfused muscles. We also present the results of an empirical study of the performance characteristics of several configurations of small solenoid coils, ca 2 mm diameter. Our data show that optimal use of the available volume of sample becomes the prime consideration in coil design at this scale. In contrast to large biological samples, for such small coils the equivalent resistance associated with the sample is minor relative to the resistance of the RF coil itself. Thus, substantial improvements in the S/N ratio can be obtained by adopting coil configurations that are inferior electrically, but which can sample a greater volume of tissue.

Animals↗
PubMedDate not supplied

Mammary tumor induction and premature ovarian failure in ApcMin mice are not enhanced by Brca2 deficiency.

Inherited BRCA2 mutations predispose individuals to breast cancer and increase risk at other sites. Recent studies have suggested a role for the APC I1307K allele as a low-penetrance breast cancer susceptibility gene that enhances the phenotypic effects of BRCA1 and BRCA2 mutations. To model the consequences of inheriting mutant alleles of the BRCA2 and APC tumor suppressor genes, we examined tumor outcome in C57BL/6 mice with mutations in the Brca2 and Apc genes. We hypothesized that if the Brca2 and Apc genes were interacting to influence mammary tumor susceptibility, then mammary tumor incidence and/or multiplicity would be altered in mice that had inherited mutations in both genes. Female and male offspring treated with a single IP injection of 50 mg/kg N-ethyl-N-nitrosourea (ENU) at 35 days of age developed mammary adenoacanthomas by 100 days of age. The female Apc-mutant and Brca2/Apc double-mutant progeny had mean mammary tumor multiplicities of 6.7+/-2.8 and 7.2+/-2.7, respectively, compared to wild-type and Brca2-mutant females, which had mean mammary tumor multiplicities of 0.1+/-0.4 and 0.3+/-0.5, respectively. Female ENU-treated Apc-mutant and Brca2/Apc double heterozygotes were also susceptible to premature ovarian failure. Thus, the inheritance of an Apc mutation predisposes ENU-treated female and male mice to mammary tumors and, in the case of female mice, to ovarian failure. These results indicate that mammary tumor development in Apc-mutant mice can progress independently of ovarian hormones. The Apc mutation-driven phenotypes were not modified by mutation of Brca2, perhaps because Brca2 acts in a hormonally dependent pathway of mammary carcinogenesis.

Adenocarcinoma↗