Identification of Hb C [beta 6(A3)Glu-->Lys] in a Thai male

The propositus was a 29-year-old Thai male, whose electrophoretic pattern showed Hb A (58%) plus an abnormal hemoglobin (42%) with mobility identical to Hb A2 and Hb E. Protein sequencer analysis and tryptic peptide mapping of the beta chain indicated that the abnormal hemoglobin was Hb C [beta 6(A3)Glu-->Lys], rather than Hb E which is more commonly found in South East Asia. This conclusion was confirmed by direct sequence analysis of the propositus' DNA, which showed AAG as well as GAG at codon 6 of the beta gene, in agreement with heterozygosity for Hb C and Hb A. Furthermore, the beta gene framework (Ava II-, Bam HI+) of the propositus suggested that the beta C gene may have arisen from an independent mutation. Since Hb C and Hb E have the same mutation (Glu-->Lys) in the beta chain, although at different positions, and behave similarly in electrophoresis, cases of Hb C and Hb E may sometimes have been mistakenly identified for each other, based on whichever variant is most prevalent in the particular population.     

A new hemoglobin variant found during Hb A1c measurement: Hb Hokusetsu [beta52(D3)Asp-->Gly]

A new beta chain variant was accidentally found through the assay of Hb A1c in a diabetic patient. The variant was detected by polyacrylamide gel isoelectrofocusing and electrospray ionization mass spectrometry. For sequence determination, globin was cleaved with combination of trypsin and lysyl endopeptidase and analyzed by high performance liquid chromatography connected to electrospray ionization mass spectrometry. An abnormal betaT-5 peptide was found by reconstructed selected ion monitoring. The collision-induced dissociation spectrum of an ion derived from the abnormal betaT-5 peptide revealed a new substitution, [beta52(D3)Asp-->Gly], named Hb Hokusetsu. The sequence was confirmed with an automatic sequencer using peptides isolated by reversed phase high performance liquid chromatography. Amplification of the beta-globin exon 2 and nucleotide sequencing revealed a GAT-->GGT mutation in codon 52 corresponding to an Asp-->Gly replacement. Electrospray ionization mass spectrometry analysis of the hemolysate showed a reasonable value of 10.4% for glycated globin. The variant migrated as Hb S on isoelectrofocusing. Hematological analysis revealed normal parameters. The patient's hemolysate showed normal stability in the isopropanol test. Oxygen equilibrium studies on the patient's red blood cells and hemolysate showed no significant change in oxygen affinity or cooperativity.     

Hb Valletta [beta 87(F3)Thr-->Pro] due to an A-->C substitution at codon 87 in a Calabrian family with alpha-thalassemia

Genetic effects were studied in house mice caught from 1986 to 1994 in regions polluted by radionuclides as a result of the Chernobyl disaster. The dose rates of gamma-radiation on the soil surface ranged from 0.0002 to 2 mGy/h. The frequency of reciprocal translocations in mouse spermatocytes was relatively low, but increased with the dose rate. Embryo mortality was increased only in the progeny of male mice in males caught in 1987 in the area with maximal contamination. The frequency of mice heterozygous for recessive lethal mutations decreased with time after the accident.     

Hb Sinai-Baltimore or alpha 2 beta (2)18(A15)Val->Gly, a silent, mildly unstable beta chain variant detected by isoelectrofocusing and high performance liquid chromatography

Isoelectrofocusing and high performance liquid chromatographic methods were used to study an abnormal hemoglobin present in a Black male infant and his mother. The variant, named Hb Sinai-Baltimore, focused slightly behind Hb A and separated incompletely from Hb A by cation exchange high performance liquid chromatography, while the separation of the beta A and beta X chains by reversed phase high performance liquid chromatography was complete. The variant was identified through an analysis of peptides in a tryptic digest of the isolated beta X chain and by sequencing of amplified DNA which included the beta-globin gene. The Val->Gly replacement at position beta 18 (codon 18; GTG->GGG) or at the last position of the A helix decreases the stability of the variant without affecting the hematological parameters of its carrier. The propositus was a compound heterozygote for Hb Sinai-Baltimore and Hb S; the relative quantities of the two variant chains were somewhat different from those of the beta X and beta A chains in the mother with the simple Hb Sinai-Baltimore heterozygosity. An uncertainty about the alpha-globin gene status in the child prevented a further evaluation of these differences.     

Hemoglobin St. Louis [beta 28 (B10) Leu replaced by Gln]: crystal structure of the fully reduced (deoxy) form

The three-dimensional structure of fully reduced Hb St. Louis has been determined to 3.5 A resolution. The difference electron density map clearly shows the site of the mutation and the effects it produces. Glutamine B10 and histidine E7 (the distal histidine) swing towards each other and, between them, stabilize a water molecule in the normally hydrophobic heme pocket. This creation of an aqueous microenvironment near the heme accounts for the thermal instability, high rate of methemoglobin formation, and increased oxygen affinity observed in solution studies of the mutant as described in the preceeding paper. Other than a small increase in tilt of the heme, virtually no further stereochemical disturbances result.     

Spillover-mediated transmission at inhibitory synapses promoted by high affinity alpha6 subunit GABA(A) receptors and glomerular geometry

Divergence and convergence of synaptic connections make a crucial contribution to the information processing capacity of the brain. Until recently, it was thought that transmitter released at a synapse affected only a specific postsynaptic cell. We show here that spillover of inhibitory transmitter at the Golgi to granule cell synapse produces significant cross-talk to non-postsynaptic cells, which is promoted both by the anatomical specialization of this glomerular synapse and by the presence of the high affinity alpha6 subunit-containing GABA(A) receptor in granule cells. Cross-talk is manifested as a novel slow rising and decaying small amplitude inhibitory postsynaptic current (IPSC) that can also contribute a long-lasting component to more typical IPSCs, which is prolonged by inhibition of the neuronal GABA transporter GAT-1. Because of the long duration of IPSCs generated by spillover, the total charge carried is three times that of IPSCs generated by directly connected terminals. GABA spillover within the mossy fiber glomerulus may play an important role in regulating the number of granule cells active in the cerebellar cortex, a regulation that is suggested by theoretical models to optimize cerebellar information processing.     

Dibasic benzo[b]thiophene derivatives as a novel class of active site directed thrombin inhibitors. 2. Exploring interactions at the proximal (S2) binding site

In an effort to increase the thrombin inhibitory activity of a novel series of inhibitors (i.e., 1a), substituents were incorporated at the C-3" position of the C-3 aryl ring (2). Consistent with the X-ray crystallography studies, small hydrophobic groups at the C-3" site (Br and Me) enhanced thrombin inhibitory activity by 8-fold. However, a few more hydrophilic substituents (NO2 and OMe) also enhanced the potency of the series. The biological results are discussed in terms of molecular modeling studies.     

Identification of His141 in the active site of Bacillus subtilis adenylosuccinate lyase by affinity labeling with 6-(4-bromo-2,3-dioxobutyl)thioadenosine 5'-monophosphate

Adenylosuccinate lyase of Bacillus subtilis is inactivated by 25-400 microM 6-(4-bromo-2,3-dioxobutyl)thioadenosine 5'-monophosphate (6-BDB-TAMP) at pH 7.0 and 25 degrees C. The initial inactivation rate constant exhibits nonlinear dependence on the concentration of 6-BDB-TAMP, implying there is reversible formation of enzyme-reagent complex (K(I) = 30 +/- 4 microM) prior to irreversible modification (kmax = 0.139 +/- 0.005 min(-1)). The tetrameric enzyme incorporates about 1 mol of 6-BDB-[32P]TAMP per mol of enzyme subunit concomitant with complete inactivation. Protection against inactivation and incorporation of [32P]reagent is provided by adenylosuccinate or a combination of AMP and fumarate, whereas either AMP or fumarate alone is much less effective. These observations suggest that 6-BDB-TAMP targets the adenylosuccinate-binding site. Hydrolyzed 6-BDB-TAMP is a competitive inhibitor with respect to adenylosuccinate in the catalytic reaction and also decreases the rate of inactivation by 6-BDB-TAMP. These results account for the decrease in the inactivation rate as the reaction of 6-BDB-TAMP with the enzyme proceeds. Purification by chromatography on dihydroxyboryl-agarose and high performance liquid chromatography of the tryptic digest of inactivated enzyme yields a single radioactive peptide, Thr140-Phe150, as determined by gas-phase sequencing. Modified His141 is the reaction product of 6-BDB-TAMP and adenylosuccinate lyase. We conclude that 6-BDB-TAMP functions as a reactive adenylosuccinate analog in modifying His141 in the substrate-binding site of adenylosuccinate lyase, where it may serve as a general base accepting a proton from the succinyl group during catalysis.     

Almost complete protection from [Met5]-enkephalin-Arg6-Gly7-Leu8 (Met-enk-RGL) hydrolysis in membrane preparations by the combination of amastatin, captopril and phosphoramidon

The contents of [Met5]-enkephalin-Arg6-Gly7-Leu8 (met-enk-RGL) and its seven hydrolysis products-Y, YG, YGG, YGGF, YGGFM, YGGFMR, and YGGFMRG-were estimated after incubating met-enk-RGL with a membrane fraction from either guinea pig ileum or striatum for various times at 37 degrees C. After 15 min of incubation, met-enk-RGL was completely hydrolyzed in both the ileal and the striatal membrane preparations. The major hydrolysis products were YGGFMR, YGGF and Y, which indicates that dipeptidyl carboxypeptidase and aminopeptidase activities were mainly involved in the hydrolysis. Additionally, even when the ileal and the striatal preparations were incubated for 60 min in the presence of both captopril, a dipeptidyl carboxypeptidase inhibitor, and amastatin, an aminopeptidase inhibitor, 24% and 44% of enkephalin octapeptide, respectively, were hydrolyzed. The YGG fragment was the major hydrolysis product in both preparations. When the ileal and the striatal membrane fractions were incubated with met-enk-RGL in the presence of three peptidase inhibitors-captopril, amastatin, and phosphoramidon (an inhibitor of endopeptidase-24.11)-approximately 95% of the enkephalin octapeptide, remained intact in both cases. This shows that met-enk-RGL was almost exclusively hydrolyzed by three enzymes, amastatin-sensitive aminopeptidase, captopril-sensitive dipeptidyl carboxypeptidase I and phosphoramidon-sensitive endopeptidase-24.11, in both ileal and striatal membranes. We also reported the potencies of several opioids relative to that of met-enk-RGL in guinea pig ileum pretreated with the three peptidase inhibitors.     

Cellular determinants of resistance to indolocarbazole analogue 6-N-formylamino-12,13-dihydro-1,11-dihydroxy-13(beta-D-glucopyranosyl)- 5H-indolo[2,3-alpha]pyrrolo[3,4-c]carbazole-5,7(6H)-dione (NB-506), a novel potent topoisomerase I inhibitor, in multidrug-resistant human tumor cells

1. In this study we hypothesized that in individuals with certain genetic makeup, MTBE, benzene or their metabolites act as adducts and may induce programmed cell death. 2. Our study involved a group of 60 male and female subjects who were exposed to MTBE and benzene-contaminated water concentrations up to 76 PPB for MTBE and 14 PPB for benzene, for a period of 5 to 8 years. For comparison, we recruited a control group consisting of 32 healthy males and females with similar age distribution and without a history of exposure to MTBE or benzene. 3. Peripheral blood lymphocytes (PBL) of both groups were tested for the percentage of apoptotic cells and cell cycle progression using flow cytometry. 4. When apoptotic lymphocytes from exposed individuals were compared to apoptotic lymphocytes from the control group, statistically-significant differences between each mean group were detected (26.4 +/- 1.8 and 12.1 +/- 1.3, respectively), indicating an increased rate of apoptosis in 80.5% of exposed individuals (P < 0.0001, Mann-Whitney U-Test). MTBE and benzene-induced apoptosis is attributed to a discrete block within the cell cycle progression. Because cell cycle analysis showed that in PBL from chemically-exposed individuals, between 20-50% of cells were accumulated at the S-G2/M boundaries. 5. One of the signaling molecules which mediates programmed cell death is nuclear factor Kappa-B (NF-kappa B). NF-kappa B was examined as one of the many molecular mechanisms for mediating cell death by MTBE and benzene. Indeed, addition of inhibitors of NF-kappa B activation pyrrolidine dithiocarbamate (PDTC), to the lymphocytes of the chemically-exposed group was capable of inhibiting programmed cell death by 40%. This reversal of apoptosis almost to the control level by inhibitor of NF-kappa B activation may indicate involvement of this signaling molecule in MTBE and benzene induction of programmed cell death.     

In vivo metabolism of a new anticancer agent, 6-N-formylamino-12, 13-dihydro-1,11-dihydroxy-13-(beta-D-glucopyranosil)5H-indolo [2,3-a]pyrrolo [3,4-c]carbazole-5,7(6H)-dione (NB-506) in rats and dogs: pharmacokinetics, isolation, identification, and quantification of metabolites

BACKGROUND: Epidemiologic studies have shown alcohol consumption to be inversely as well as positively related to body weight and body fat. Metabolic studies have shown an increase in energy intake as well as compensation after alcohol consumption. OBJECTIVE: Our objective was to assess the effects on energy intake of an apéritif compared with those of a water appetizer and 3 fruit juice appetizers. DESIGN: Fifty-two men and women aged 20-45 y with a body mass index (in kg/m2) between 20 and 32 were randomly given 1 MJ (340 mL) alcohol (wine or beer), fat (cream fruit juice), protein (protein fruit juice), carbohydrate (grape juice), or water, or no preload 30 min before an ad libitum lunch consumed from the universal eating monitor. RESULTS: Energy intake (3.5+/-0.3 MJ compared with 2.7+/-0.2 MJ, P < 0.001) and eating rate were higher (44+/-3 g/min compared with 38+/-3 g/min, P < 0.01), meal duration was longer (14 min compared with 12.0 min, P < 0.01), satiation started to increase later (3.5 min compared with 1.5 min, P < 0.01), and eating was prolonged after maximum satiation (2.5 min compared with 0.6 min, P < 0.01) after an apéritif than after a fat, protein, or carbohydrate appetizer,. Twenty-four-hour energy intake was higher on a day that an apéritif was consumed than after water or no preload. CONCLUSION: Twenty-four-hour energy intake was elevated with a 1-MJ apéritif but not with a 1-MJ liquid carbohydrate, fat, or protein appetizer.     

(S)-(-)-[11C]nicotine binding assessed by PET: a dual tracer model evaluated in the rhesus monkey brain

PURPOSE: Determine the tissue distribution patterns for tissue inhibitors of metalloproteinases (TIMP-1, TIMP-2, TIMP-3), gelatinase A and gelatinase B in normal and pathologic corneas. METHODS: Corneas were examined by immunohistochemistry, using antibodies to TIMP-1, TIMP-2, TIMP-3, gelatinase A or gelatinase B. RESULTS: In normal corneas, TIMP-1 antibody stained the epithelium and endothelium. TIMP-2 and TIMP-3 stained the epithelium, keratocytes and endothelium. Gelatinase A staining was weak and restricted to the epithelial cells. Radial keratotomy scars showed increased staining for TIMP-1 and TIMP-2 around the epithelial cell plug and along the incision. Bullous keratopathy corneas showed TIMP staining patterns similar to normal corneas and increased gelatinase A staining in regions of subepithelial fibrosis. Stromal scars of keratoconus corneas also had increased staining with TIMP-1 and TIMP-2 antibodies. In many keratoconus corneas, the TIMP-3 staining pattern was similar to normal corneas. However, in some keratoconus corneas, when Bowman's layer was missing, the stroma beneath was completely devoid of TIMP-3 antibody staining. No gelatinase B was seen in either the normal or diseased corneas. CONCLUSION: These data suggest that TIMP-1 and TIMP-2 are important for scar formation and corneal remodeling, since they were found in increased amounts at radial keratotomy incision sites and keratoconus scars. The significance of the focal stromal defects in TIMP-3 staining, associated with absence of Bowman's layer on keratoconus corneas, needs to be elucidated. At the stages of disease examined in this study, gelatinase B may not play a significant role in these pathological processes, since it was not seen in any of the corneas examined.     

S 18126 ([2-[4-(2,3-dihydrobenzo[1,4]dioxin-6-yl)piperazin-1-yl methyl]indan-2-yl]), a potent, selective and competitive antagonist at dopamine D4 receptors: an in vitro and in vivo comparison with L 745,870 (3-(4-[4-chlorophenyl]piperazin-1-yl)methyl-1H-pyrrolo[2, 3b]pyridine) and raclopride

The novel benzoindane S 18126 possessed > 100-fold higher affinity at cloned, human (h) D4 (Ki = 2.4 nM) vs. hD2 (738 nM), hD3 (2840 nM), hD1 (> 3000 nM) and hD5 (> 3000 nM) receptors and about 50 other sites, except sigma1 receptors (1.6 nM). L 745,870 similarly showed selectivity for hD4 (2.5 nM) vs. hD2 (905 nM) and hD3 (> 3000 nM) receptors. In contrast, raclopride displayed low affinity at hD4 (> 3000 nM) vs. hD2 (1.1 nM) and hD3 receptors (1.4 nM). Stimulation of [35S]-GTPgammaS binding at hD4 receptors by dopamine (DA) was blocked by S 18126 and L 745,870 with Kb values of 2.2 and 1.0 nM, respectively, whereas raclopride (> 1000 nM) was inactive. In contrast, raclopride inhibited stimulation of [35S]-GTPgammaS binding at hD2 sites by DA with a Kb of 1.4 nM, whereas S 18126 (> 1000 nM) and L 745,870 (> 1000 nM) were inactive. As concerns presynaptic dopaminergic receptors, raclopride (0.01-0.05 mg/kg s.c. ) markedly enhanced DA synthesis in mesocortical, mesolimbic and nigrostriatal dopaminergic pathways. In contrast, even high doses (2. 5-40.0 mg/kg s.c.) of S 18126 and L 745,870 were only weakly active. Similarly, raclopride (0.016 mg/kg i.v.) abolished inhibition of the firing rate of ventrotegmental dopaminergic neurons by apomorphine, whereas even high doses (0.5 mg/kg i.v.) of S 18126 and L 745,870 were only weakly active. As regards postsynaptic dopaminergic receptors, raclopride potently (0.01-0.3 mg/kg s.c.) reduced rotation elicited by quinpirole in rats with unilateral lesions of the substantia nigra, antagonized induction of hypothermia by PD 128, 907, blocked amphetamine-induced hyperlocomotion and was effective in six further models of potential antipsychotic activity. In contrast, S 18126 and L 745,870 were only weakly active in these models (5.0-> 40.0 mg/kg s.c.). In six models of extrapyramidal and motor symptoms, such as induction of catalepsy, raclopride was likewise potently active (0.01-2.0 mg/kg s.c.) whereas S 18126 and L 745,870 were only weakly active (10.0-80.0 mg/kg s.c.). In freely moving rats, raclopride (0.16 mg/kg s.c.) increased levels of DA by + 55% in dialysates of the frontal cortex. However, it also increased levels of DA in the accumbens and striatum by 70% and 75%, respectively. In contrast to raclopride, at a dose of 0.16 mg/kg s.c. , neither S 18126 nor L 745,870 modified frontal cortex levels of DA. However, at a high dose (40.0 mg/kg s.c.), S 18126 increased dialysate levels of DA (+ 85%) and noradrenaline (+ 100%), but not serotonin (+ 10%), in frontal cortex without affecting DA levels in accumbens (+ 10%) and striatum (+ 10%). In conclusion, S 18126 and L 745,870 behave as potent and selective antagonists of cloned, hD4 vs. other dopaminergic receptor types in vitro. However, their in vivo effects at high doses probably reflect residual antagonist actions at D2 (or D3) receptors. Selective blockade of D4 receptors was thus associated neither with a modification of dopaminergic transmission nor with antipsychotic (antiproductive) or extrapyramidal properties. The functional effects of selective D4 receptor blockade remain to be established.     

Regional decreases in alpha-[3H]amino-3-hydroxy-5-methylisoxazole-4-propionic acid ([3H]AMPA) and 6-[3H]cyano-7-nitroquinoxaline-2,3-dione ([3H]CNQX) binding in response to chronic low-level lead exposure: reversal versus potentiation by chronic dopamine agonist treatment

This study evaluated the hypotheses that in vivo lead (Pb) exposure would alter alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor binding and, based on known glutamate-dopamine interactions and Pb-induced changes in dopamine (DA) systems, that AMPA binding might be differentially influenced by DA agonist treatment under conditions of Pb exposure. Alterations in high-affinity ([3H]AMPA) versus total AMPA [6-[3H]cyano-7-nitroquinoxaline-2,3-dione ([3H]CNQX)] receptor binding were determined in medial frontal cortex, dorsal striatum, and nucleus accumbens of rats exposed to 0, 50, or 150 ppm of Pb acetate for 2 weeks or 8 months. Additional 8-month groups received chronic intermittent treatment with saline, the D1 agonist SKF82958, or the general DA agonist apomorphine. Two-week exposures increased AMPA receptor densities, whereas robust decreases occurred after 8 months of Pb; at the latter time point changes were more pronounced for high-affinity than total AMPA receptor binding, with high-affinity effects expressed preferentially in dorsal striatum and nucleus accumbens. DA agonist treatments almost fully reversed Pb-related declines in [3H]AMPA binding but either had no effect (apomorphine) or even further potentiated (SKF82958) the decreases in [3H]CNQX binding. One possible basis for the long-term (8-month) decrease in AMPA binding is a postsynaptic glutamatergic stimulation of non-NMDA receptors.     

In vitro cytotoxicity and DNA damage production in Chinese hamster ovary cells and topoisomerase II inhibition by 2-[2''-(dimethylamino)ethyl]-1, 2-dihydro-3H-dibenz[de,h]isoquinoline-1,3-diones with substitutions at the 6 and 7 positions (azonafides)

The p53 tumor suppressor gene encodes a phosphoprotein which when overexpressed can induce growth arrest at the G1 and G2/M phases of the cell cycle, promote differentiation and apoptosis. This paper demonstrates that p53 can associate with trk tyrosine kinase. Expression of a murine temperature-sensitive (ts) p53 mutant in PC12 cells overexpressing trk (a model system to analyse cellular differentiation and signal transduction induced by NGF) induces morphological changes in the absence of NGF stimulation at 32 degrees C but not at 37 degrees C. In cells differentiated by p53, trk, but not EGFr, was hyperphosphorylated on tyrosine. Furthermore trk was not phosphorylated when expressed in Saos-2 cells (human osteosarcoma cells that lack expression of both endogenous trk and p53) at either temperature. However, transfection of ts p53 into these cells induces trk phosphorylation at 32 degrees C in the absence of NGF stimulation. Association of trk and p53 can be detected in NIH3T3 and PC12 cells co-expressing trk and the ts p53 mutant, in NIH3T3 and PC12 cells transfected with trk alone, and in untransfected PC12 cells, showing that overexpressed and/or endogenous trk associates with endogenous, low levels of p53. These data suggest a novel function for p53 which involves the stimulation of signal transduction pathways (mediating morphological properties of cells), possibly through association with and hyperphosphorylation of trk.     

DNA adducts of 2,3-epoxy-4-hydroxynonanal: detection of 7-(1', 2'-dihydroxyheptyl)-3H-imidazo[2,1-i]purine and 1,N6-ethenoadenine by gas chromatography/negative ion chemical ionization/mass spectrometry

2,3-Epoxy-4-hydroxynonanal (EH) is a bifunctional aldehyde formed by epoxidation of trans-4-hydroxy-2-nonenal, a peroxidation product of omega-6 polyunsaturated fatty acids. EH is mutagenic and tumorigenic and capable of modifying DNA bases forming etheno adducts in vitro. Recent studies showed that etheno adducts are present in tissue DNA of humans and untreated rodents, suggesting a potential endogenous role of EH in their formation. A sensitive assay is needed so we can determine whether EH is involved in etheno adduct formation in vivo and study the biological significance of the etheno adducts in DNA. In this study, we developed a gas chromatography/negative ion chemical ionization/mass spectrometry assay for the analysis of 1, N6-ethenoadenine (epsilonAde) and 7-(1', 2'-dihydroxyheptyl)-3H-imidazo[2,1-i]purine (DHH-epsilonAde) in DNA; both are products from the reaction of adenine with EH. The assay entails the following sequence of steps: (1) addition of [15N5]epsilonAde and [15N5]DHH-epsilonAde to DNA as internal standards, (2) acid hydrolysis of DNA, (3) adduct enrichment by C18 solid phase extraction (SPE), (4) derivatization by pentafluorobenzylation (PFB), (5) separation of PFB-epsilonAde and PFB-DHH-epsilonAde on a Si SPE column, (6) acetonide (ACT) formation of PFB-DHH-epsilonAde, and (7) GC/MS analysis with selective ion monitoring (SIM). The limit of detection by on-column injection for PFB-epsilonAde monitoring of the (M - PFB)- ion at m/z 158 was 30 amol and for ACT-PFB-DHH-epsilonAde monitoring of the (M - PFB)- ion at m/z 328 was 0.4 fmol; the detection limits for the entire assay were 6.3 fmol for epsilonAde and 36 fmol for DHH-epsilonAde. In calf thymus DNA modified with EH at 37 degreesC for 50 h, both epsilonAde and DHH-epsilonAde were detected at high levels by this method, 4.5 +/- 0.7 and 90.8 +/- 8.7 adducts/10(3) adenine, respectively. These levels were also verified by HPLC fluorescence analysis, indicating that EH extensively reacts with adenine in DNA, forming etheno adducts. The high sensitivity of the assay suggests that it may be used in the analysis of ethenoadenine adducts in vivo.