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Biomedical subjects

C M Harris

Publications and source records attributed to C M Harris.

At least 91 records · Page 5Linked to original sources
PubMed1997

Smooth pursuit development in infants.

PURPOSE: We set out to assess the development of pursuit eye movements in normal infants in an objective, longitudinal fashion. We asked whether smooth pursuit (SP) was present under 2 months of age and how the saccade ratio changed with increasing infant age. METHODS: Smooth pursuit was recorded longitudinally from 25 infants aged 1-7 months, using DC electro-oculography, in a clinically practical manner. Four uninstructed adults acted as controls. RESULTS: Smooth pursuit was present under 2 months of age. The gain of SP increased with increasing infant age. However, it had still not reached adult levels by 6 months of age. Latency decreased with increasing infant age. Monocular SP asymmetry was present in the younger infants. CONCLUSIONS: Smooth pursuit is present under 2 months of age, but at 6 months SP has still not reached adult levels. The traditional model of SP development is questionable.

Child Development↗
PubMed1997

Eye movement abnormalities in a case of Tourette syndrome.

Tourette syndrome (TS) is a neuropsychiatric disorder that is characterised by the presence of multiple vocal, facial, and motor tics which change with time, and a number of other behavioural phenomena. Previous studies have not revealed any ocular-motor abnormalities. We report the eye movement studies of a patient with TS, using electrooculography and simultaneous video recording. Intrusive saccades occurred during smooth pursuit and optokinetic nystagmus. Reflexive and voluntary saccades were dysmetric and there was a complete failure of antisaccades. These abnormalities are characteristic of disease of the frontal lobes and basal ganglia. We review the literature with respect to the eye movement abnormalities associated with TS.

Adolescent↗
PubMed1997

Enhanced endothelium-dependent vasodilator responses in patients with systemic vasculitis.

The aim of the study was to investigate endothelium-dependent vasodilator responses in the forearm vasculature of patients with systemic vasculitis. We studied 10 patients with systemic vasculitis and 16 healthy control subjects using forearm venous occlusion plethysmography to assess changes in forearm blood flow in response to acetylcholine (ACh). NG-monomethyl-L-arginine (L-NMMA), was also used to assess the contribution of endothelium derived relaxing factor/nitric oxide (EDRF/NO) to the vasodilator responses to acetylcholine. A significantly greater vasodilator response to ACh was seen in the patient group at all doses infused (p < 0.01). After pre-infusion of L-NMMA, the differences in ACh dilator responses were no longer significant. There was a greater magnitude of inhibition of ACh responses by L-NMMA in the patient group. The enhanced vasodilator response to ACh observed was in part abolished by L-NMMA, suggesting that EDRF/NO is produced in excess in systemic vasculitis. The precise role played by EDRF/NO in the pathogenesis of systemic vasculitis requires further study.

Acetylcholine↗
PubMed1996

Fundholders' prescribing costs: the first five years.

OBJECTIVES: To determine whether the first five waves of English fundholding practices have reduced their prescribing costs relative to non-fundholding practices, and the duration of any reduction achieved. DESIGN: Analysis of item and cost data for all general practices in England in the six years from April 1990 to March 1996. The practices of each of the first five waves were identified at the Prescription Pricing Authority. SETTING: All general practices in England. MAIN OUTCOME MEASURES: Changes and rates of change in net ingredient cost per prescribing unit, and changes in number of items per prescribing unit in fundholding practices, before and after fundholding, relative to continuing non-fundholders. RESULTS: Absolute prescribing costs increased over the six years, by 66% in the continuing non-fundholders and by 56-59% for fundholders. Successive waves of fundholders showed a similar pattern of change: a small relative reduction in the pre-fundholding year, maximum relative reduction in the first year, and a declining relative reduction in the second and third years. After this, their increases in costs were largely similar to those of non-fundholders. The number of items dispensed remained stable over the six years in all groups. CONCLUSIONS: The real budgets operated by fundholders were associated with a reduction in costs of about 6% relative to continuing non-fundholders, and this saving seemed to be retained during the study. The relative reduction was small compared with the absolute increase seen in all groups and disappeared after the third year of fundholding. It was brought about by lowering the average cost per item rather than by giving fewer items.

Budgets↗
PubMed1996

Major groove (S)-alpha-(N6-adenyl)styrene oxide adducts in an oligodeoxynucleotide containing the human N-ras codon 61 sequence: conformations of the S(61,2) and S(61,3) sequence isomers from 1H NMR.

The (S)-alpha-(N6-adenyl)styrene oxide adducts at positions X6 in d(CGGACXAGAAG). d(CTTCTTGTCCG) and X7 in d(CGGACAXGAAG).d(CTTCTTGTCCG), incorporating codons 60, 61 (underlined), and 62 of the human n-ras protooncogene, were examined by 1H NMR. These were the S(61,2) and S(61,3) adducts. Chemical shift perturbations were in the 3'-direction from the sites of adduction; upfield changes associated with the styrene aromatic ring current were noted for S-SOA6 H2 and H1', T16 N3H, H6, and CH3 resonances in the S(61,2) oligomer. In the S(61,3) oligomer, S-SOA7 H1', T16 H1', C15 N4Ha, and H5 shifted upfield. The styrene aromatic rings flipped rapidly on the NMR time scale; under these conditions the ortho and meta aromatic protons were equivalent. A sequence effect, in which the S(61,2) adduct equilibrated between two conformers, while the S(61,3) adduct exhibited only a single conformation, was observed. Potential energy minimization of the S(61,2) adduct major conformation yielded a structure in which the styrene ring was oriented in the 3'-direction and interacted primarily with the complementary strand. For the S(61,3) adduct, 291 restraints were obtained from NOE data at three mixing times using relaxation matrix analysis. The emergent structures refined to an average rms difference of 1.3 A, determined by pairwise analysis. These were compared to NOE intensity data; the calculated sixth root residual index was 9.2 x 10-2 at 250 ms. In the refined structure, the styrene ring was also oriented in the 3'-direction and interacted with the complementary strand. The minor conformation of the S(61,2) adduct was not identified. These results contrasted with the diastereomeric R(61,2) and R(61,3) adducts, which underwent slow ring flips on the NMR time scale and for which small sequence effects involving the minimum energy conformation of the styrene ring were observed.

Adenine↗
PubMed1996

Adduction of the human N-ras codon 61 sequence with (-)-(7S,8R,9R,10S)-7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a] pyrene: structural refinement of the intercalated SRSR(61,2) (-)-(7S,8R,9S,10R)-N6-[10-(7,8,9,10- tetrahydrobenzo[a]pyrenyl)]-2'-deoxyadenosyl adduct from 1H NMR.

The structure of the (-)-(7S,8R,9S,10R)-N6-[10-(7,8,910-tetrahydrobenzo [a]pyrenyl)]-2'-deoxyadenosyl adduct at X6 of 5'-d(CGGACXAGAAG)-3'-5'-d(CTTCTTGTCCG)-3', derived from trans addition of the exocyclic N6-amino group of dA to (-)-(7S,8R,9R,10S)-7, 8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene [(-)-DE2], was determined using molecular dynamics simulations restrained by 369 NOEs from 1H NMR. This was named the SRSR(61,2) adduct, derived from the N-ras protooncogene at and adjacent to the nucleotides encoding amino acid 61 (underlined) of the p21 gene product. NOEs between C5, S.R.S.R A6, and A7 were disrupted, as were those between T17 and G18. NOEs between benzo[a]pyrene and DNA protons were localized on the two faces of the pyrenyl ring. The benzo[a]pyrene H3-H6 protons showed NOEs to T17 CH3, while H1, H2, and H3 showed NOEs to T17 deoxyribose; the latter protons and H4 showed NOEs to T17 H2', H2" and to T17 H6. Noes were observed between H11 and H12 and C5 H]',H2', H2". G18 N1H showed NOEs to both faces of benzo[a]pyrene. Upfield shifts of 2.6 ppm for T17 N3H and 1.8 ppm for G18 N1H. 1 ppm for T17 H6 and CH3, and 0.75 ppm for C5 H5, with a smaller shift for C5 H6, and a 1.5 ppm dispersion of the pyrenyl protons suggested that benzo[a]pyrene intercalated above the 5'-face of S.R.S.R A6. The precision of the refined structures was monitored by pairwise root mean square deviations. which were < 1.5 A; accuracy was measured by complete relaxation matrix calculations, which yielded a sixth root R factor of 8.1 x 10(-2). Interstrand stacking between the pyrenyl ring and the T17 pyrimidine and G18 purine rings was enhanced by the bay ring. Changes of +30 degrees and -25 degrees in buckle for C5.G18 and S.R.S.R A6.T17, respectively, were calculated, as was a -40 degrees change in propeller twist for C5.G18. The rise between C5.G18 and S.R.S.R A6.T17 was calculated to be 7 A. The work extended the pattern for adenine N6 benzo[a]pyrene adducts, in which the R stereochemistry at C10 predicted 5'-intercalation of the pyrenyl moiety.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1996

Styrene oxide adducts in an oligodeoxynucleotide containing the human N-ras codon 12 sequence: structural refinement of the minor groove R(12,2)- and S(12,2)-alpha-(N2-guanyl) stereoisomers from 1H NMR.

The structures of the (R)- and (S)-alpha-(N2-guanyl)styrene oxide adducts at X6 in d(GGCAGXTGGTG).d(CACCACCTGCC), encompassing codon 12 of the human n-ras protooncogene (underlined), were refined from 1H NMR data. These were the R(12,2) and S(12,2) adducts. For the R(12,2) adduct, upfield chemical shifts were observed for the T7 H6, H1', and N3H resonances. At 30 degrees C, R-SOG 6 N1H, T7 N3H, and T10 N3H disappeared due to exchange with solvent. For the S(12,2) adduct, S-SOG6 H1' shifted upfield 0.33 ppm, but all imino resonances were observed. The styrene methylene protons were nonequivalent for both adducts, suggesting hydrogen bonding between the hydroxyl and C18 O2 or O4' in the R(12,2) adduct and C17 O2 in the S(12,2) adduct. The styrene aromatic protons appeared as three signals in the R(12,2) adduct and as two signals in the S(12,2) adduct, suggesting rapid rotation of the styrene ring on the NMR time scale. NOE data revealed that the phenyl ring was oriented in the 3'-direction relative to R-SOG6 for the R(12,2) adduct and in the 5'-direction relative to S-SOG6 for the S(12,2) adduct. A total of 253 and 221 interproton distances were obtained from relaxation matrix analyses of the R(12,2) and S(12,2) adducts, respectively. NOE-restrained molecular dynamics calculations converged with root mean square deviations of 0.8-1.2 A for the R(12,2) adduct and 0.82-1.4 A for the S(12,2) adduct. Complete relaxation matrix analyses of the nine inner base pairs yielded sixth root residual indices between calculated and experimental NOE intensities of 8.8 x 10(-2) for the R(12,2) adduct and 7.9 x 10(-2) for the S(12,2) adduct. The refined structure for the R(12,2) adduct showed a 0.4 A increase in the stretch of R-SOG6.C17 and T7.A16, and a 1-2 A widening of the minor groove at and adjacent to the SO lesion, with the styrene ring oriented edgewise in the minor groove. Smaller minor groove disturbances were observed for the S(12,2) adduct, which had the styrene ring oriented flat in the minor groove. No DNA bending was predicted by the calculated structures.

Base Sequence↗
PubMed1996

Delayed visual maturation in infants: a disorder of figure-ground separation?

Delayed visual maturation (DVM) is characterised by visual unresponsiveness in early infancy, which subsequently improves spontaneously to normal levels. We studied the optokinetic response and recorded pattern reversal VEPs in six infants with DVM (aged 2-4 months) when they were at the stage of complete visual unresponsiveness. Although no saccades or visual tracking with the eyes or head could be elicited to visual objects, a normal full-field rapid buildup OKN response occurred when viewing biocularly or during monocular stimulation in the temporo-nasal direction of the viewing eye. Almost no monocular OKN could be elicited in the naso-temporal direction, which was significantly poorer than normal age-matched infants. No OKN quick phases were missed, and there were no other signs of "ocular motor apraxia." VEPs were normal in amplitude and latency for age. It appears, therefore, that infants with DVM are delayed in orienting to local regions of the visual field, but can respond to full-field motion. The presence of normal OKN quick-phases and slow-phases suggests normal brain stem function, and the presence of normal pattern VEPs suggests a normal retino-geniculo-striate pathway. These oculomotor and electrophysiological findings suggest delayed development of extra-striate cortical structures, possibly involving either an abnormality in figure-ground segregation or in attentional pathways.

Attention↗
PubMed1996

The role of ERG/VEP and eye movement recordings in children with ocular motor apraxia.

Ocular motor apraxia (OMA) is characterised by an intermittent inability to initiate voluntary saccades, and a failure to produce optokinetic and vestibular quick phases. Some patients have no other abnormalities (idiopathic OMA), whereas in others it appears associated with a variety of neurological conditions which may affect the sensory visual pathway. Electroretinograms (ERGs), flash and pattern visual evoked potentials (VEPs) and eye movements were assessed in 53 children with OMA (age range 17 days to 14 years) to determine their efficacy in helping to distinguish between idiopathic and non-idiopathic cases. Seven patients (13.2%) had idiopathic OMA and the remaining 46 (86.8%) had other associated clinical conditions. All patients had episodes of absent quick phases ('lock up') during optokinetic nystagmus (OKN) and/or vestibular testing. Flash ERGs were abnormal in only 7 patients (13.2%); 6 had syndromes involving a pigmentary retinopathy (Joubert's, Bardet-Biedl, infantile Refsum's, Kearns-Sayre's), and the seventh had a cone dystrophy with vermis hypoplasia. VEPs were normal in all 7 patients with idiopathic OMA. Thirty-three (72%) patients with OMA in association with neurological conditions had abnormal VEPs and 13 had normal VEPs (28%). There was a significant positive correlation between VEP abnormality and poor OKN gain. VEP/ERG testing and eye movement studies are useful when OMA is suspected as they help in distinguishing isolated idiopathic cases from those with more widespread neurological abnormalities.

Adolescent↗
PubMed1996

Intermittent horizontal saccade failure ('ocular motor apraxia') in children.

BACKGROUND: Ocular motor apraxia (OMA) in childhood is a poorly understood condition involving a failure of horizontal saccades. OMA is thought to be rare but the literature indicates wide clinical associations. OMA is often identified by abnormal head movements, but failure of reflexive quick phases has been reported in all but a few patients. The extent of this oculomotor disorder was examined in a large group of children with diverse clinical backgrounds. METHODS: The degree of quick phase failure during horizontal vestibular and optokinetic nystagmus was measured using DC electro-oculography and video in 74 affected children, aged 17 days to 14 years. RESULTS: All children showed an intermittent failure of nystagmic quick phases, except for total failure in one case. Other visuomotor abnormalities were common including saccadic hypometria (85%), low gain smooth pursuit (70%), neurological nystagmus (28%), strabismus (22%), and vertical abnormalities (11%). Non-ocular abnormalities were common including infantile hypotonia (61%), motor delay (77%), and speech delay (87%). There was a wide range of clinical associations including agenesis of the corpus callosum, Joubert syndrome, Dandy-Walker malformation, microcephaly, hydrocephalus, vermis hypoplasia, porencephalic cyst, megalocephaly, Krabbe leucodystrophy, Pelizaeus Merzbacher disease, infantile Gaucher disease, GM1 gangliosidosis, infantile Refsum's disease, propionic acidaemia, ataxia telangiectasia, Bardet-Biedl syndrome, vermis astrocytoma, vermis cyst, carotid fibromuscular hypoplasia, Cornelia de Lange syndrome, and microphthalmos. Perinatal and postnatal problems were found in 15% including perinatal hypoxia, meningitis, periventricular leucomalacia, athetoid cerebral palsy, perinatal septicaemia and anaemia, herpes encephalitis, and epilepsy. Only 27% were idiopathic. CONCLUSION: Quick phase failure is a constant feature of OMA, whereas abnormal head movements were detected in only about half, depending on the underlying diagnosis. This oculomotor sign is better described as an intermittent saccade failure rather than as a true apraxia. It indicates central nervous system involvement, has wide clinical associations, but it is not a diagnosis.

Adolescent↗
PubMed1996

Comparison of two warfarin regimens in the prevention of venous thrombosis following total knee replacement.

A prospective, randomized trial was conducted to compare the effectiveness and safety of warfarin given in two regimens in prevention of venous thrombosis after total knee replacement. Adult patients scheduled for primary or revision total knee replacement were randomly assigned to receive either a "two-step" warfarin regimen beginning 10-14 days pre-operatively or, alternatively, to begin warfarin the night before surgery. Post-operatively, the dose was adjusted in both groups to achieve a target International Normalized Ratio (INR) of 2.2 and prophylaxis was continued until venography on post-operative days five through nine. Bleeding was assessed by surgical blood loss, transfusion requirements, changes in hematocrit, and clinically identified bleeding complications. The occurrence of deep vein thrombosis was nearly the same in the two treatment groups, 39% in patients randomized to the two-step regimen as compared to 38% in those beginning the night before surgery. The occurrence of proximal vein thrombosis was also similar, 5% versus 7% (p = NS). Patients in the two-step group received 1.33 +/- 1.26 transfusions compared to 0.95 +/- 1.22 in the night before group (p < 0.05) and also had a lower nadir post-operative hematocrit of 26.7 +/- 3.1 as compared to 28.5 +/- 3.2 (p < 0.0001). Major bleeding complications were associated with excessively prolonged INRs and occurred in five patients in the two-step group and two in the night before group. Patients in both groups who developed thrombosis had a significantly lower INR on post-operative days two and three compared to those without thrombosis. We conclude that a prophylactic warfarin regimen for prevention of deep vein thrombosis after total knee replacement beginning the night before surgery is more convenient and may be associated with less bleeding than a regimen beginning warfarin 10-14 days pre-operatively. Careful control of anticoagulant intensity is needed to achieve maximum effectiveness and avoidance of bleeding complications.

Adult↗
PubMed1996

The scale of repeat prescribing.

BACKGROUND: Repeat prescribing has long been seen as a potential cause of poor clinical care, despite its obvious advantage to both doctors and patients. Previous studies have had no common definition of the term, and have been small in scale, but it is clear that repeat prescribing has increased over the past 25 years with a recent acceleration due to computerization. Managing the process has become more important as the scale has increased. A computer-related standard definition would provide linkage with other information held on the practice computer about the recipients. Using aggregated practice data the current national picture could be ascertained for comparison with that of individual practices. At practice level it will be less important simply to know the scale of repeat prescribing than to make analyses of repeat prescribing of particular drug groups, and of the age and sex groups of the recipients. This could provide a valuable basis for improving clinical care. AIM: To estimate the present scale of repeat prescribing-overall, for specific age-sex groups, and for some specific drug groups; to provide a much needed standard definition of repeat prescribing, now inevitably related to computer procedures; and to show how clinically valuable audits might be simply generated as reports by a practice computer. METHOD: Repeat prescriptions were defined as those printed by a practice computer from its repeat prescribing program over a period of one year. Prescribing data for a year, with demographic details of the patients involved, were obtained for 115 practices from the IMS MediPlus database. These practices had 750390 patients and issued 5.82 million prescriptions during the year. Analyses were made of the overall percentages of items and costs due to repeats; the percentage of patients receiving repeats, by age and sex; the percentage receiving repeats, by age and sex, in areas of particular concern; and percentage repeat prescribing in 46 drug groups. RESULTS: No differences were found between fundholding and non-fundholding practices, or between dispensing and non-dispensing practices. The ratio of acute to repeat prescriptions in the practices was stable over four years. Repeats accounted for 75% of all items and 81% of prescribing costs; 48.4% of all patients were receiving a repeat prescription. Many drugs, including hypnotics, were given almost entirely as repeats. The percentage of repeats increased with patients' age, from 36% in the 0-4 year age group to more than 90% for patients aged 85 and over. It was higher overall for males than for females, though this relationship did not hold for older patients. CONCLUSION: This study gives the best available national picture of the use of repeat prescribing. The definition employed does not allow any direct conclusions to be drawn about whether the patients involved were being given adequate clinical care, but it permits analyses at practice level that can indicate where special attention may be required. It could usefully be adopted as the much-needed standard definition.

Adolescent↗
PubMed1995

Major groove (R)-alpha-(N6-adenyl)styrene oxide adducts in an oligodeoxynucleotide containing the human N-ras codon 61 sequence: conformations of the R(61,2) and R(61,3) sequence isomers from 1H NMR.

Conformations of (R)-alpha-(N6-adenyl)styrene oxide adducts at positions X6 in d(CGGACXAGAAG).d(CTTCTTGTCCG) and X7 in d(CGGACAXGAAG).d(CTTCTTGTCCG), incorporating codons 60, 61 (underlined), and 62 of the human n-ras protooncogene, were refined from 1H NMR data. These were the R(61,2) and R(61,3) adducts. Chemical shift perturbations were in the 5'-direction from the sites of adduction; large changes were observed for C5 H5 and H6 in the R(61,2) adduct. The styrene moieties were only partially defined by NOE data. Spectral overlap, particularly for the R(61,2) adduct, prevented complete assignments of the aromatic resonances; likewise, there were insufficient data to orient the CH2OH moieties. Ring flips were slow on the NMR time scale. For the R(61,2) adduct 260 restraints were obtained from NOE data at three mixing times using relaxation matrix analysis; for the R(61,3) adduct 230 restraints were obtained. Structures emergent from molecular dynamics/simulated annealing for the R(61,2) adduct converged to average and maximum pairwise rms differences of 1.3 and 1.7 A, respectively, while those for the R(61,3) adduct converged to average and maximum pairwise rms differences of 1.2 and 1.6 A. Sixth root residual indices of 7.5 and 6.8 x 10(-2) were measured between the refined structures and NOE intensities using relaxation matrix calculations for the R(61,2) and R(61,3) adducts, respectively. The styrene rings were in the 5'-direction from the lesion sites in the major groove. The preferred orientation calculated for the R(61,2) adduct placed the styrene ring edgewise and approximately orthogonal to C5, while that calculated for the R(61,3) duplex had the styrene ring approximately orthogonal to the major groove edges of base pairs A6.T17 and R-SOA7.T16.

Adenine↗
PubMed1995

Specific therapeutic group age-sex related prescribing units (STAR-PUs): weightings for analysing general practices' prescribing in England.

OBJECTIVES: To derive cost comparators for prescribing by English general practitioners in eight specific therapeutic groups, based on age-sex related weightings, and to confirm, from a new dataset, earlier age-sex weightings for overall prescribing (ASTRO-PUs). DESIGN: Calculations based on one year's prescribing data from selected practices using AAH Meditel software, held on MediPlus by Intercontinental Medical Statistics (IMS, UK and Ireland), and research practices using VAMP software, held on the General Practice Research Database. SETTING: 112 English practices with 739,672 patients and 510 British practices with 3,126,570 patients. MAIN OUTCOME MEASURES: Cost based weightings for 18 age-sex groups and for temporary residents for eight leading specific therapeutic groups and for prescribing overall. RESULTS: The two datasets were similar in age distribution and in the way that prescription numbers were distributed by age-sex band in each therapeutic group. The cost based weightings for specific therapeutic groups showed great variation in the use of these groups for patients in different age-sex groups. When these weightings were applied to the prescribing of practices in two family health services authorities they differed in their power to predict prescribing costs: for cardiovascular and gastrointestinal drugs predictive power was particularly high; for drugs for infections it was particularly low, since these are widely used at all ages and for both sexes. Cost based weightings for overall prescribing derived from the IMS data were similar to those of the ASTRO-PU system even though they were derived by different methods from different datasets. CONCLUSIONS: The weightings (STAR-PUs) offer a sound basis for cost comparisons at the therapeutic group level. Cost-based weightings for overall prescribing derived from the IMS data were reassuringly similar to those of the existing ASTRO-PU system.

Adolescent↗
PubMed1995

In vivo and in vitro replication consequences of stereoisomeric benzo[a]pyrene-7,8-dihydrodiol 9,10-epoxide adducts on adenine N6 at the second position of N-ras codon 61.

Benzo[a]pyrene-7,8-dihydrodiol 9,10-epoxide (BPDE), a metabolite of the widespread environmental pollutant benzo[a]pyrene, is a mutagenic in both bacterial and mammalian systems. Toward understanding the mutagenic effects of different stereoisomers of BPDE at specific sites in DNA, six stereochemically defined BPDE adducts were constructed on adenine N6 at position 2 of the human N-ras 61 codon within an 11-base oligonucleotide fragment. Both the nonadducted and BPDE-adducted N-ras 61 11-mers were inserted into a unique EcoRI site in single-stranded M13mp7L2 DNA and utilized for in vivo studies. The ligation efficiencies of BPDE-adducted 11-mers into the single-stranded vector were determined by Southern hybridization and confirmed by electron microscopy. Repair-deficient AB2480 E. coli cells were transformed with adducted and non-adducted DNA samples. The resultant plaque-forming abilities were used to evaluate the replication competence of the various BPDE adducts with respect to the nonadducted 11-mer. Point mutations due to aberrant replication at the adducted site were identified by the technique of differential DNA hybridization. All of the six BPDE adducts examined were mutagenic in vivo, generating exclusively A-->G mutations at frequencies ranging from 0.26 to 1.20%. In vitro replication studies using these BPDE-adducted 11-mers involved primer extension assays with Klenow fragment. All of the BPDE-modified templates demonstrated distinct blockage at the adducted site and/or 1 base 3' to the adducted site, allowing essentially no translesion synthesis to form fully extended polymerization products in vitro.

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