Biomedical subjects

S Naylor

Publications and source records attributed to S Naylor.

At least 127 records · Page 7Linked to original sources

PubMed1991

Mutation in the TP53 gene in colorectal carcinoma detected by polymerase chain reaction.

The human TP53 gene is a possible tumor suppressor since TP53 gene mutations are observed in greater than 70% of sporadic colorectal carcinoma DNAs. In genomic DNAs from seven colon cancer cell samples, a 405 base pair DNA fragment containing exon 5, intron 5, and exon 6 of the TP53 gene was amplified by polymerase chain reaction and analyzed for mutations. One sample [human colon cancer (HCC) 278] was found to have a TP53 mutation altering the amino acid glutamine 167 in exon 5. A deletion of 2 bases changed glutamine 167 (CAG) to alanine (GCA) and the resulting frame-shift produced an in-frame stop codon at amino acid 179. While the normal TP53 gene gives rise to a 53 kD protein, the estimated size of this mutant TP53 protein if expressed would be approximately 20 kD.

Adenocarcinoma↗

PubMed1991

Takayasu's arteritis in a pregnant woman. A case report.

Takayasu's arteritis in a pregnant white patient is described. This case highlights the fact that, irrespective of race, any patient who presents for the first time in pregnancy with pulseless hypertensive disease or other features suggestive of Takayasu's arteritis, should have their management in labour determined by the number of complications that are present. These are retinopathy, arterial aneurysms, hypertension and aortic regurgitation. These prognostic criteria will result in a classification of patients that will lead to appropriate management.

Adult↗

PubMed1990

Molecular dosimetry of polycyclic aromatic hydrocarbon epoxides and diol epoxides via hemoglobin adducts.

Ten reactive metabolites of five polycyclic aromatic hydrocarbons and styrene were investigated to determine the generality of ester adduct formation with human hemoglobin in the form of RBC and hydrolysis to the corresponding tetrahydrotetrols or dihydrodiols. No exceptions were noted among the compounds tested, which included the anti-diol epoxides of benzo[a]pyrene (BaP), chrysene, and benz[a]anthracene; the syn-diol epoxide of BaP; a mixture of syn- and anti-diol epoxides of benzo[e]pyrene; and epoxides of styrene, benzo[e]pyrene, BaP, and cyclopenta[c,d]pyrene. A test of the propensity of the simplest benzylic epoxide, styrene oxide, to form esters that hydrolyze via a BAL1 mechanism was performed. Hydrolysis of styrene oxide-adducted hemoglobin in H2(18)O at neutral pH yielded 18O incorporation results that suggest this mechanism of hydrolysis is operant to a minor degree in styrene oxide-hemoglobin ester adducts. A method was developed for the isolation and quantification of the polycyclic aromatic alcohols, which consists of enzymatic proteolysis, immunoaffinity chromatography, and gas chromatography-mass spectrometry or fluorimetry. The method allows for routine analysis of hemoglobin from individual samples as small as 1 ml of whole blood. Analysis of blood from different human populations revealed that hemoglobin adducts of the anti-diol epoxide of BaP dominated the spectrum of adducts formed by the selected metabolites.

Chromatography, Affinity↗

PubMed1990

Effect of different target gases on low-energy collision-activated dissociation of peptides.

Experimental variables affecting the daughter-ion spectra of a series of protonated peptides [MH]+, produced by fast-atom bombardment ionization, using a low energy (0-450 eV) quadrupole collision cell are investigated. The parameters studied include target gas pressure, collision energy, cross-sectional area and acidity of the target gas. The results show that low-mass immonium ions are preferentially formed both at high collision energies (greater than 200 eV) and at target gas pressures greater than 10(-6) mBar (where multiple collisions occur in the gas cell). Positive fragment ion abundance is maximized when acidic gases are used as the target gases, and this is rationalized on the basis of a proton-transfer reaction from the target gas to the amide nitrogen of the peptide bond promoting fragmentation.

Enkephalin, Leucine↗

PubMed1990

Collision-activated dissociation studies of alkylamines formed from copper-induced dealkylation of N-alkylporphyrins.

A low-energy (5-450 eV) collision-activated dissociation (CAD) study of a series of aliphatic amines revealed that at collision energies above 200 eV, charge-site-initiated fragmentation occurs. The resulting fragment ions can be utilized in the characterization of alkyl substituents of di- and trisubstituted aliphatic amines. In the presence of Cu2+ and a suitable nucleophile, such as n-dodecylamine, N-alkyl protoporphyrins dealkylate to afford copper protoporphyrin and an alkyl-dodecylamine adduct. A CAD study of a number of alkyl-dodecylamine adducts derived from the copper-induced dealkylation of synthetic N-alkyl protoporphyrins, using charge-site-initiated fragment ions, showed that the alkyl group was trapped by the nucleophilic amine present. Subsequently this method was used to identify the alkyl group of a biologically derived N-alkyl protoporphyrin.

Amines↗

PubMed1990

Identification of phosphoramide mustard/DNA adducts using tandem mass spectrometry.

The reaction pathway of alkylating agents is often exploited in the design of bifunctional anti-cancer drugs. These drugs form mono-DNA adducts as well as inter- and intra-strand cross-linked adducts, notably by reaction at DNA bases, including the N-7-position of guanine (G). A positive-ion fast-atom bombardment (FAB) mass spectrum of an in vitro preparation of DNA alkylated with phosphoramide mustard (the active metabolite of the anti-cancer drug cyclophosphamide) indicated the presence of the two mono-DNA adducts N-(2-chloroethyl)-N-[2-(7-guaninyl)ethyl] amine, designated NOR-G, and N-(2-hydroxyethyl)-N-[2-(7-guaninyl)ethyl] amine, designated NOR-G-OH, (MH+ 257/259 and 239, respectively) but not the presence of the cross-linked adduct N,N-bis-[2-(7-guaninyl)ethyl] amine, designated G-NOR-G (MH+ 372). Using synthetic standards, daughter-ion spectra of NOR-G, NOR-G-OH and G-NOR-G were obtained (matrix 0.2 M p-toluene sulphonic acid in glycerol) by positive-ion FAB tandem mass spectrometry (FAB-MS/MS). The daughter-ion spectra of both mono-DNA adducts NOR-G and NOR-G-OH contained a fragment ion at m/z 152 [G + H]+, whereas the cross-linked adduct, G-NOR-G, showed an ion at m/z 221, [MH-G]+. Evidence for the presence of NOR-G, NOR-G-OH and G-NOR-G in the in vitro preparation was obtained by performing a double parent-ion scan on m/z 152 and 221. The presence of G-NOR-G was further supported by performing a single parent-ion scan on m/z 221.(ABSTRACT TRUNCATED AT 250 WORDS)

DNA↗

PubMed1990

Deuterium exchange studies in the identification of alkylated DNA bases found in urine, by tandem mass spectrometry.

Humans are exposed to a large number of carcinogens which may react at various sites throughout the body, including the N-7-, N2-, and O6-positions of guanine. The effects of this are various but may result in depurination and eventual excretion of the modified base in the urine. Various alkylguanine derivatives with substituents at the N-7-, N2- and O6-positions were synthesized and daughter-ion spectra obtained. Apart from the methyl and dialkylguanines all other spectra exhibited an ion at m/z 151 using electron ionization (EI) and m/z 152 using fast-atom bombardment (FAB). The daughter-ion spectra of dialkylguanines contained an ion at m/z 150 (EI). Hence, scans of m/z 150 and 151 using EI, to detect all parent-ions from which they are formed (parent-ion scans) should indicate the presence of alkyl and dialkylguanine bases in a complex biological matrix such as human urine. Parent-ion scans of m/z 150 and 151 (EI) of a partially purified human urine sample exhibited numerous ions, including a prominent ion at m/z 179. A daughter-ion spectrum of m/z 179 revealed fragment ions that suggested the presence of N2-dimethylguanine and an ethylated guanine. Any confusion due to the presence of daughter ions from different alkylguanines in the same spectrum can be resolved by the fact that an ethylated guanine has four exchangeable protons, whereas N2-dimethylguanine has only three. By performing hydrogen/deuterium exchange it is possible to distinguish the N2-dimethylguanine from ethylated guanine isomers.(ABSTRACT TRUNCATED AT 250 WORDS)

Guanine↗

PubMed1989

A rapid method for isolation of human hemoglobin benzo[a]pyrene diol epoxide derived adducts using high performance liquid chromatography.

A method is described to isolate rapidly human hemoglobin-benzo[a]pyrene diol epoxide adducts. A combination of 300 A pore size C4 reversed phase HPLC to effect separation of adducted protein from native protein, and mu-bore C18 reversed phase HPLC to isolate and partially characterize proteolytic peptide adducts (by UV), was used.

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

PubMed1989

Factors affecting the fragmentation of peptides in fast atom bombardment mass spectrometry.

Positive ion fast atom bombardment mass spectra of a series of biologically active peptides were obtained in order to ascertain conditions that contribute to an increase in fragment ion abundance of such peptides. The effect of derivatization, hydrophobic character and the presence of acid in the matrix on fragmentation of peptides were all investigated. It is shown that a substantial increase in fragment signal ion abundance is observed when mineral acid is present in the matrix, and is in accord with the gas-phase collision model proposed by Kebarle.

Acetylation↗

PubMed1989

Rapid determination of sequence variations in actinidin isolated from Actinidia chinensis (var. Hayward) using fast atom bombardment mapping mass spectrometry and gas phase microsequencing.

A current limitation in the use of fast atom bombardment (FAB) mass spectrometric mapping of peptide mixtures, derived from enzymic digestion of proteins, is that most of the hydrophilic peptides are not observed. However, it has been demonstrated from previous work that esterification of the peptide mixture results in the detection of almost all peptides in FAB mass spectrometry. This strategy of FAB mapping was applied to the protein actinidin, isolated from an Italian variety of Actinidia chinensis. Two of the 12 tryptic peptides in FAB mass spectrometry did not exhibit molecular ions predicted from the known sequence of actinidin isolated from the New Zealand variety of A. chinensis. The two peptides were isolated by high-performance liquid chromatography, subjected to Staphylococcus aureus V8 protease digestion and sequenced by gas-phase microsequencing. Nine changes in amino acid composition were detected using the rapid and powerful combination of FAB mass spectrometric mapping and gas-phase microsequencing.

Amino Acid Sequence↗

PubMed1988

Isolation and characterization of the major fluoranthene-hemoglobin adducts formed in vivo in the rat.

The binding of fluoranthene (FA) to hemoglobin was studied both in vitro and in vivo in the rat. The in vitro binding of microsomally activated FA to rat hemoglobin appeared to involve the fluoranthene 2,3-dihydrodiol-1,10b-epoxides. Three classes of hemoglobin adducts were observed in rats chronically administered FA in the diet. Based on high pressure liquid chromatography retention times, UV and mass spectral evidence, and behavior upon cis-diol affinity chromatography, the major class of globin adducts formed in vivo was demonstrated to result from binding of syn and anti isomers of FA 2,3-dihydrodiol-1,10b-epoxides to beta-cysteine-125 of rat hemoglobin. These adducts represented at least 41% of the total binding to globin. A minor class of adducts (12% of the total binding) appeared to involve the binding of an unidentified FA metabolite to the same cysteine residue of the protein. A substantial portion of FA binding to rat hemoglobin in vivo (29%) involved metabolic pathways which were not duplicated by simple in vitro systems. That portion of the binding to globin has not been characterized.

Amino Acid Sequence↗

PubMed1988

Formaldehyde adducts of glutathione. Structure elucidation by two-dimensional n.m.r. spectroscopy and fast-atom-bombardment tandem mass spectrometry.

Aqueous mixtures of formaldehyde and glutathione react to form a variety of cyclized adducts in addition to S-hydroxymethylglutathione. The adducts are in labile equilibrium with each other and are not readily separated. The structures of two of the other major adducts were determined by concerted application of 13C-1H two-dimensional chemical-shift correlation, fast-atom-bombardment mass spectrometry and tandem mass spectrometry to the adduct mixtures in aqueous solution.

Chemical Phenomena↗

PubMed1987

Evidence for tumour necrosis factor/cachectin production in cancer.

Labile tumour-necrosis-factor-like (TNF) activity was detected by means of an enzyme-linked immunosorbent assay in 50% of 226 freshly obtained serum samples from cancer patients with active disease. In contrast, only 3% of 32 samples from normal subjects and 18% of 39 samples from cancer patients with no clinically evident disease were positive for this factor, with low levels of activity. Greater proportions of serum samples from patients with ovarian or oat-cell carcinoma were positive (69% and 63%) than those from patients with lymphoma (26%). RNA preparations from peripheral-blood mononuclear cells and solid tumours were probed with TNF complementary DNA; evidence of TNF messenger RNA was found in 8 of 11 samples of peripheral-blood mononuclear cells from cancer patients, but only 1 of 8 normal subjects, and in 2 of 6 colorectal tumours. As yet the inducing stimulus and the clinical significance of TNF production in cancer are not understood.

Adult↗

PubMed1986

Linkage of cystic fibrosis to two tightly linked DNA markers: joint report from a collaborative study.

A collaborative study involving seven research groups provided an opportunity to investigate the linkage relationships between cystic fibrosis and two DNA marker loci, MET and pJ3.11 (D7S8), on an extended sample of 211 tested families. The maximum lod scores, recombination estimates, and confidence upper bounds (in parentheses) were 91.0 at theta = .004 (.012) for CF and MET, 71.3 at theta = .003 (.011) for CF and D7S8, and 69.3 at theta = .018 (.036) for MET and D7S8. Three-locus analyses yielded best support for the order MET-CF-D7S8, with odds against the alternate orders CF-MET-D7S8 and CF-D7S8-MET of 9:1 and 161:1, respectively. However, the number of observed recombinants was small and only one of the recombinants was jointly informative for all three markers. Significant allelic association was found between CF and both MET and D7S8. Weaker association between the latter two loci is consistent with the order MET-CF-D7S8.

Alleles↗

PubMed1985