Apoptosis corrected proliferation fraction in childhood ALL is related to karyotype

BACKGROUND

Tumour doubling time, a parameter in drug sensitivity testing, reflects both cell proliferation and apoptosis. Variable apoptosis fractions may explain the poor correlation of S-fraction and drug response. DNA aneuploidy (reflecting intrinsic DNA instability) may, by increasing apoptosis, affect drug response.

AIM

To assess the relationship between apoptosis corrected proliferation fraction and DNA ploidy in childhood acute lymphoblastic leukemia (ALL).

METHODS

1.3.1. Study Groups. Thirty two consecutive, unselected diagnostic cases of childhood ALL were included in the study. 1.3.2. Karyotype. A normal karyotype was found in 15 cases (7M, 8F, age 8 m-12 yrs); high hyperdiploid aneuploidy (DNA index > 1.5) was found in 7 patients (1M, 7F, age 3-12 yrs) whereas complex karyotypic anomalies, but with 2n or near 2n DNA were present in 10 patients (7M, 3F, age 1 y 7 m -16 yrs). 1.3.3. Proliferation Fraction Assessment. Immunocytochemical demonstration of S-phase associated nuclear expression of the Ki-67 antigen (MM1, NovaCastra, UK). 1.3.4. Apoptosis Fraction Assessment. Binding of a horse radish peroxidase labelled DNA probe for the 3'-OH ends of apoptosis derived Klenow fragments (Frag-EL, CalBiochem, USA). 1.3.5. Quantitation. Computer assisted image analysis (Quantimet 570C), of 10 systematically random fields of a minimum of 20 nuclei each. A nuclear size bias correcting counting frame and rule were used to correct for cell proliferation associated nuclear volume increase and for the expected nuclear volume reduction resulting from apoptosis.

RESULTS

Corrected for apoptosis, proliferation fraction was highest (mean 57.5%, range 1-100) in poor prognosis, complex karyotype anomalies. Good prognosis, high hyper diploidy showed significantly lower proliferation rates (mean 24.7%, range 12-40) (p < 0.01, t-test).

CONCLUSION

Apoptosis corrected cell proliferation rate in childhood ALL is not independent of karyotype abnormality which may partly explain a relation to therapy response and prognosis.

Proliferation and apoptosis does not affect presenting white cell count in childhood ALL

BACKGROUND

Treatment response/drug resistance in childhood acute lymphoblastic leukaemia (ALL) is related to presenting white cell count. This relationship might be explained by high proliferation fraction or by absence of significant apoptosis, but is presently unknown.

AIMS

To study the relationship between proliferation and apoptosis in childhood ALL.

METHODS

1.3.1. Study Groups. Thirty consecutive, unselected cases of childhood ALL (15M,15F). White cell count varied from 1-200 at presentation. 1.3.2. Proliferation/Apoptosis Fraction. Immunocytochemical detection of Ki-67 (MM1, NovaCastra, UK) on 5 microns paraffin slides, Immunocytochemical detection of apoptosis specific DNA (Klenow) fragments by labelling of 3'-OH ends in 10 microns paraffin sections (Frag-EL, CalBiochem, USA). 1.3.3. Quantitation. Image analysis (Quantimet 570C) using nuclear size bias correcting counting frame and rule. Calculation of proliferation (%Ki-67) fraction and of apoptosis corrected proliferation fraction (%Ki-67/100-%apoptosis).

RESULTS

Using both linear, logarithmic regression as well as power analysis, no relationship between variables was detected.

CONCLUSION

Presenting white cell count is not related to apoptotic or cell proliferative activity or to net tumour growth defined by the balance between these two processes. The relationship to treatment resistance still requires explanation.

Demonstration of differences in drug resistance by direct testing of DNA excision repair activity following standard and liposomal daunorubicin exposure in normal paediatric marrow using high resolution CLSM

BACKGROUND

High resolution Confocal Laser Scanning Microscopy (CLSM) may be applied to testing of drug resistance in vitro in clinical setting. Rapid analysis of DNA damage by precise quantitation of excised DNA in bone marrow samples exposed to potential treatment moieties directly after isolation but the relative sensitivity of the integrated method is as yet untested.

AIMS

To test the clinical applicability of SCGE/high resolution CLSM for differences in drug resistance in marrow cells.

METHODS

Cells from normal bone marrow samples were exposed for identical periods and at 4 concentrations to either 1 hour of standard Daunorubicin (.5, 1, 1.5, 2 micrograms/ml) or 8 hours DaunoXome (courtesy of NeXstar Inc, USA) (.05, .1, .15, .2 microgram/ml). After 2 and 6 hours recovery, cells were harvested for SCGE, randomization, analysis of tail length, total excised DNA and fragment size distribution using high resolution CLSM.

RESULTS

Tail length and fragment size distribution was not, but total excised DNA was significantly increased after 0.1 microgram/ml Liposomal Daunorubicin (DaunoXome) compared to 1.0 microgram/ml Daunorubicin.

CONCLUSION

SCGE/high resolution CLSM effectively demonstrated differences in Daunorubicin resistance of human marrow cells to alternative formulations. The method has potential for use in clinical testing of neoplastic cell drug resistance.

Differential kinetics of drug resistance in human leukaemic cells measured by SCGE/CLSM

BACKGROUND

New analogues of DNA directed chemotherapy moieties are available for comparative efficacy testing in human neoplastic disease. In addition to MTT testing direct assessment of DNA excision repair activity after direct exposure of marrow cells may provide information on relative DNA effects in vitro.

AIMS

To assess the ability of SCGE/high resolution CLSM to detect differences in drug resistance between human neoplastic cell lines in the DNA excision repair response to chemotherapy.

METHODS

Eight human leukaemia samples (4 childhood, 4 adult) were exposed to 1 hour of single concentrations of daunorubicin, DaunoXome (courtesy NeXstar Pharmaceuticals Inc, USA), cyclophosphamide and 4-hydroperoxycyclophosphamide (4-HC, courtesy Dr. M. Colvin, Duke University, USA), followed by SCGE/high resolution CLSM with quantitation of total excised DNA. Differences between cases/drug moieties/exposures were analysed.

RESULTS

Although generally equal effect dose levels for DaunoXome were lower than for standard daunorubicin, patients/individual neoplastic cells differed considerably in optimal dose levels. Conventional cyclophosphamide in comparison to 4-HC showed inconsistent results indicating considerable differences in the level of drug resistance to the conventional product.

CONCLUSIONS

Direct testing for drug resistance patterns in DNA directed drug moieties by SCGE/CLSM reveals individual variability of human malignant cell lines warranting comparison with results of MTT testing and in-vivo patient response.

Apoptotic fraction in childhood ALL assessed by DNA in situ labelling is ploidy independent

BACKGROUND

Apoptotic cell fraction and presence or degree of aneuploidy may both affect treatment outcome in childhood acute lymphoblastic leukaemia (ALL), which is largely defined by drug resistance. Independence of the variables is at present not established. Until the development of in situ labelling of cells committed to the apoptotic pathway, the fraction of cells in apoptosis could not be determined objectively.

AIM

To determine the relationship between apoptotic cell fraction and karyotype in childhood ALL using in situ labelling.

METHODS

1.3.1. Study Groups and Samples. Diagnostic, pretreatment bone marrow trephine and aspirate samples of 24 consecutive, unselected cases of childhood ALL were included in the study: Normal karyotype (n = 11, 5M,6F), high hyperdiploid aneuploidy (DNA index > 1.5, n = 7, 1M,6F), complex karyotypic anomalies (n = 6, 5M,1F). 1.3.2. Apoptotic Cell Labelling. In situ labelling of the 3'-OH ends of the apoptosis specific DNA (Klenow) fragment (Frag-EL, CalBiochem, USA). 1.3.3. Quantitation. Apoptotic cell fraction was established using 10 systematically random fields of > 20 nuclei. Results were tabled per group. After calculations of means, differences between groups were assessed using t-test.

RESULTS

Apoptotic cell fraction, ranging from < 1 to 95%, did not differ statistically significant between the three study groups.

CONCLUSION

Apoptotic cell fraction in childhood leukaemia is independent of ploidy status and euploid karyotypic anomalies.

PCNA bearing structures are retained in apoptotic phase of childhood ALL cell cycle

BACKGROUND

Drug resistance to DNA directed therapy may depend on proliferative as well as apoptotic cell fraction. PCNA/Ki67 ratio excess, possibly reflecting DNA excision repair, is of additional interest to drug resistance in MTT testing. The cell cycle phase/antigen expression pattern in childhood acute lymphoblastic leukemia (ALL) is not known.

AIMS

To study the relationship between nuclear expression of PCNA, Ki-67 and Frag-EL positivity in childhood ALL.

METHODS

1.3.1. Study Groups. Diagnostic bone marrow trephine biopsies of 32 consecutive unselected cases of childhood ALL were included in the study. 1.3.2. Immunohistochemistry. Commercially available Moab PCNA (PC10, DAKO, USA), Ki-67 (MM1, NovaCastra, UK) were used to label cycling cells in routinely processed 5 microns paraffin sections. 1.3.3. In-Situ Labelling of Apoptotic Cells. The 3'-OH ends of apoptosis specific DNA fragments were labelled in-situ on subsequent 10 microns sections (Frag-EL, CalBiochem, USA). 1.3.4. Quantitation. After blinding and randomisation, 10 systematic random fields of > 20 nuclei and nuclear size bias correction was used to determine positive nuclei fraction.

RESULTS

While the sum of apoptotic and proliferative cell fraction (Ki-67 + Frag-EL%) equalled 100% in 5/32 cases, PCNA expression into at least the early phases of apoptosis ([%PCNA-%K-67] > [100-%Frag-EL] was found in 17/32 cases.

CONCLUSIONS

PCNA/Ki67 ratio excess may not reflect DNA excision repair activity but rather slow degradation of antigen bearing structures limiting relevance to drug resistance study.

High resolution confocal laser scanning microscopy analysis of DNA excision repair capability in small volume marrow samples exposed to DNA directed treatment moieties

BACKGROUND

Assessment of resistance to drug moieties in tissue culture is complicated by limited sample, clonal selection and alteration of cycling fraction and cycle duration in clonally mixed lesions. DNA damage assessment by single cell gel electrophoresis (SCGE) of excised DNA is limited by non-linear analysis in fluorescent light microscopy. Confocal Laser Scanning Microscopy (CLSM) with high N.A. magnification allows for quantitation of total excised DNA fragment size distribution but is still limited by the large volume required for labour intensive SCGE, precluding multi-exposure clinical testing.

AIMS

To optimise sample requirement for SCGE and CLS.

METHODS

Standard slide mounted bed gels were punched with multiple coded 6 mm wells and filled with suspensions of cells subjected to drug/concentration variations. After SCGE, 30 microns frozen sections were prepared of each well and mounted in ethidium bromide solution on multi-well hydrophilic slides to allow for short working distance of high resolution CLSM in a Zeiss Axiovert L410 SM. Testing for feasibility, reproducibility and consistency used both cultured standard leukaemic cell lines, normal human control marrow and clinical samples.

RESULTS AND CONCLUSION

Multiple well SCGE followed by frozen section, high resolution CLSM allows for rapid analysis of high numbers of multiple drug exposure permutations clinically required.

Microsatellite instability assessment in prediction of drug resistance in childhood Burkitt's and large cell diffuse malignant non-Hodgkin lymphoma (MNHL)

BACKGROUND

Genomic instability may, especially with DNA directed treatment, be associated with increased therapeutic response; absence may be associated with drug resistance. In childhood MNHL, drug response is variable. At present the degree of presence of microsatellite variation, i.e., intrinsic DNA instability is not known.

AIMS

To determine presence and range of microsatellite variability in common childhood MNHL.

METHODS

1.3.1. Study Populations. Consecutive, unselected (1976-96) cases of childhood Large Cell diffuse, N = 16; (9T,7B), age range 1y5m-16y8m; Burkitt's Lymphoma, n = 13, age range 4y2m-14y. Non-malignant/pre-treatment tissue of 20 cases, 13 LC, 7 Burkitt's MNHL. 1.3.2. Molecular Pathology. Routine DNA extraction, amplifications at loci D3S 1304 and D3S1537 (both closely distal to VHL, tumour suppressor gene); ELN gene D7S1870; IFNA D1S243 (1p36) which show microsatellite variation. Isotopic labelling in amplification, non-denaturing gel electrophoresis, autoradiography.

RESULTS

Microsatellite variability was found 3/16 LC and 2/13 Burkitt's MNHL. LC MNHL, 4 abnormal areas: n = 1, 3 abnormal areas: n = 1, 2 abnormal areas n = 1; Burkitt's MNHL, 3 abnormal areas: n = 1, 1 abnormal area n = 1. No variability was found in the normal (constitutional) DNA of any of the 20 patients studied.

CONCLUSIONS

Microsatellite variability occurred in 5/29 patients with common types of childhood MNHL, indicating a limited contribution to reduced drug resistance through this mechanism.

Compound I and Compound II Analogues from Porpholactones

The tetraaza macrocycles 2-oxa-3-oxotetramesitylporphine (|H(2) 1|) and 2-oxa-3-oxotetrakis(2,6-dichlorophenyl)porphine (|H(2) 2|) and the corresponding iron complexes (|Fe(III)(X) 1| and |Fe(III)(X) 2|; X= Cl(-), OH(-), or SO(3)CF(3)(-)) have been synthesized. These macrocycles are derived from porphyrins by transformation of one pyrrole ring to an oxazolone ring. The resulting lactone functionality serves to restrict but not completely block pi-conjugation around the periphery. These complexes thus share properties with both porphyrins and chlorins. The ferric and high-valent iron complexes have been characterized by a variety of spectroscopic techniques. The molecular structure of |Fe(III)(Cl) 2| has been obtained by X-ray crystallography and shows that the structural changes at the macrocycle periphery do not perturb the coordination sphere of iron relative to the corresponding porphyrin complexes. This is illustrated by the observation that Fe-O frequencies in the resonance Raman spectra of the porpholactone analogues of compounds I and II are not substantially different from those of porphyrins and by the axial appearance of the EPR signals of the high-spin ferric complexes. This is consistent with reports that the Fe=O unit of oxidized porphyrins and chlorins is relatively insensitive to alteration of macrocycle symmetry. Nevertheless, probes of properties of the porpholactone macrocycle ((1)H NMR, resonance Raman skeletal modes) show effects of the asymmetry induced by the oxazolone ring. On the basis of (1)H NMR, EPR, Mössbauer, and resonance Raman data, the singly occupied molecular orbital of oxoferryl porpholactone pi-cation radicals correlates with the a(1u) molecular orbital of porphyrins under D(4)(h)() symmetry. Moreover, the paramagnetic properties and the intramolecular exchange interaction of ferryl iron and the porpholactone pi-radical have been characterized by EPR and magnetic Mössbauer measurements and spin-Hamiltonian analyses. The values J(0) = 17 cm(-)(1) and J(0) = 11 cm(-)(1) obtained for the exchange coupling constants of the oxoferryl porpholactone pi-cation radical complexes |Fe(IV)=O 1|(+) and |Fe(IV)=O 2|(+), respectively, are among the lowest found for synthetic compound I analogues.

Role of O-acetyltransferase in activation of oxidised metabolites of the genotoxic environmental pollutant 1-nitropyrene

The genotoxic environmental contaminant 1-nitropyrene is metabolised in mammalian systems by pathways more complex than the straightforward nitroreduction which accounts for most of its biological activity in bacteria. In order to evaluate the role of O-acetyltransferase (OAT) activity in generation of genotoxic intermediates from 1-nitropyrene, the mutagenicity of the major primary oxidised metabolites of 1-nitropyrene was characterised in the Ames Salmonella typhimurium plate incorporation assay with strain TA98, and with variants of TA98 deficient (TA98/1,8-DNP6) or enhanced (YG1024) in O-acetyltransferase. 1-Nitropyren-3-ol was more mutagenic in the absence than in the presence of S9, while 1-nitropyren-4-ol, 1-nitropyren-6-ol and 1-nitropyren-8-ol required S9 for maximum expression of mutagenicity. 1-Nitropyren-4-ol (176 rev/nmol without S9, 467 rev/nmol with S9 in TA98) and 1-nitropyren-6-ol (13 rev/nmol without S9, 266 rev/nmol with S9 in TA98) were overall the most potent nitropyrenol isomers assayed. 1-Acetamidopyren-8-ol and 1-acetamidopyrene 4,5-quinone were only minimally active. 1-Acetamidopyren-3-ol exhibited direct-acting mutagenicity. 1-Acetamidopyren-6-ol, previously shown to be a major contributor to mutagenicity in the urines of rats dosed with 1-nitropyrene (Ball et al., 1984b), was confirmed as a potent (359 rev/nmol) S9-dependent mutagen. Both the direct-acting and the S9-dependent mutagenicity of all the compounds studied was enhanced in the OAT-overproducing strain and much diminished (though not always entirely lost) in the OAT-deficient strain, showing that OAT amplifies expression of the genotoxicity of these compounds. 1-Acetamidopyren-6-ol required both S9 and OAT activity in order to exhibit any mutagenicity; this finding strongly implicates N-hydroxylation followed by O-esterification, as opposed to further S9-catalyzed ring oxidation, as a major route of activation for urinary metabolites of 1-nitropyrene.

Comparative and experimental pathology of fibrosing colonopathy

Although the occurrence of fibrosing colonopathy is temporally associated with the introduction of high-strength pancreatic enzyme supplements, its pathogenesis remains uncertain. The UK case-control study showed fibrosing colonopathy to be associated with high doses of high-strength pancreatic enzyme supplements and with a group of brands which occupy only 30% of the market. Two alternative hypotheses were proposed to explain the aetiology of fibrosing colonopathy: exposure to high levels of enzymes or to as yet unidentified components of the formulation. Comparison of the anatomical pathology of fibrosing colonopathy with that of previously encountered forms of obstructive gastrointestinal pathology, such as stricturing lesions due to potassium chloride preparations and nonsteroidal anti-inflammatory drugs, confirmed it to be a previously unencountered, long-segment lesion of the colon. Thus the use of the descriptive term 'stricture' is a misnomer leading to much clinical confusion when discussing obstructive bowel pathology in cystic fibrosis patients. Gavage studies in the rat with one of the two monomers (ethyl acrylate) forming the methacrylic acid copolymer (Eudragit L30D55) used for the enteric coating of the high-strength pancreatic enzyme supplements, have shown pathology comparable to fibrosing colonopathy. These findings prompted a series of exploratory studies in adolescent pigs. After seven days caecal gavage of Eudragit L30D55 at doses of 10, 50 or 500 mg/kg/day (comparable to human intake), extensive fibrosing colonopathy-like changes, inclusive of dense submucosal fibrosis, were noted at all dose levels in seven out of nine animals. Similar studies of the monomer components of the Eudragit L30D55 copolymer, at dose levels of 0.015 to 50 mg/kg/day, representing possible residues in Eudragit L30D55, did not produce comparable changes. The conclusion is that, although the precise mechanisms have not been elucidated, the role of enteric coatings containing Eudragit L30D55 in the pathogenesis of fibrosing colonopathy requires urgent further study.

Metabolic activation of the genotoxic environmental contaminants 2- and 3-nitrofluoranthene in variants of Salmonella typhimurium TA98

The mutagenic environmental pollutants 2-nitrofluoranthene (2-NFA) and 3-nitrofluoranthene (3-NFA), labelled with 3H and 14C respectively, were incubated with Salmonella typhimurium strain TA98, its nitroreductase-deficient variant TA98NR and its O-acetytransferase-deficient variant TA98/1,8-DNP6, to investigate the activity of these metabolic pathways under conditions approximating those of the Ames assay, hence their contribution to mutagenic potency. 2-Aminofluoranthene (2-AFA) was the major metabolite of 2-NFA (4 microM) in all three TA98 variants, isolated by reverse-phase HPLC and identified by UV-vis and NMR spectroscopy and mass spectrometry. 2-AFA was formed more slowly in TA98NR (65 pmol/h/ml resting phase bacterial broth, 1 to 2 x 10(9) bacteria/ml) than in TA98 (295 pmol/h/ml) or TA98/1,8-DNP6 (82 pmol/h/ml). 2-Acetamidofluoranthene (2-AAFA) was also identified in incubations with TA98 (80 pmol/h/ml), TA98NR (21 pmol/h/ml), and TA98/1,8-DNP6 (8 pmol/h/ml). 3-Aminofluoranthene (3-AFA, confirmed by UV-vis and NMR spectroscopy and mass spectrometry) was formed by all three variants from 3-NFA (4 microM): TA98, 1.76 nmol/h/ml; TA98NR, 0.55 nmol/h/ml; TA98/1,8-DNP6, 2.93 nmol/h/ml. 3-Acetamidofluoranthene (3-AAFA) was not detected in any of the variants. 3-AFA and 3-AAFA were less mutagenic than 3-NFA, and required S9 for activation. Mutagenicity of 3-NFA relative to initial nitroreduction rate was similar in TA98 and in TA98NR, but almost 10-fold lower in TA98/1,8-DNP6; hence O-acetylation considerably enhances the mutagenicity of reduction products of 3-NFA. Mutagenicity of 2-NFA relative to initial nitroreduction rate was similar in TA98 and in TA98/1,8-DNP6; the bacterial genotoxicity of 2-NFA is therefore largely independent of O-acetyltransferase activity. Ratios of mutagenicity to nitroreduction rate were similar in TA98 for 2-NFA and 3-NFA; differences in the potency of these isomers arise primarily from their respective suitabilities as substrates for nitroreductase enzymes.

PCNA Ki-67 dissociation in childhood acute lymphoblastic leukaemia. An immunofluorescent laser confocal scanning microscopical study

Cell proliferation rates of diagnostic marrow aspirate cells of 21 children with Acute Lymphoblastic Leukaemia and 16 controls were compared using immunocytochemical labelling of PCNA and Ki-67 antigen as assessed by Confocal Laser Scanning Microscopy. The results showed an unexpected, highly significant degree of dissociation between PCNA and Ki-67 expression in ALL blasts. The PCNA labelling indices of ALL patients were significantly increased (mean 44, range 24-77) compared with normal reactive marrow cells (mean 13.8, range 4-26) (p < 0.000001, Mann Whitney U two tailed test), suggesting an abnormal commitment to proliferation. Ki-67 expression was raised to a lesser extent in ALL cells (mean 14.8, range 1.2-35) when compared to non-malignant proliferations (mean 6.6, range 1.7-25) (p < 0.02). PCNA/Ki-67 LI ratios in ALL (mean 7, range 1.1-35) were higher than in controls (mean 2.7, range 1.04-6.5, p < 0.09). As cell proliferation rates actually achieved in the bone marrow do not differ as strongly as suggested by the extreme difference in PCNA labelling, a pathological dissociation of PCNA/Ki-67 expression exists, suggesting immortalisation.

PCR-mediated genotyping of Candida albicans strains from bone marrow transplant patients

DNA amplification using polymerase chain reaction (PCR) primers aiming at eukaryotic or prokaryotic repetitive DNA motifs enables discrimination between individual Candida albicans isolates. This PCR-mediated DNA fingerprinting procedure was used to monitor yeast colonisation in immune-compromised leukaemia patients (n = 11) who were undergoing bone marrow transplantation (BMT). The leukaemia patients remained colonised by the same strain throughout a 5 month study period, irrespective of intermediate treatment with fungostatics or application of BMT-related therapies. All 11 strains could be identified separately by PCR fingerprinting. This implies that spreading of C. albicans from patient to patient does not seem to occur in this study group, despite the fact that medical employees frequently travel between wards which are in close proximity to other departments harbouring neutropenic patients. Several of the patients (n = 35) were also monitored for C. albicans colonisation and strain typing corroborated the lack of extensive cross-contamination during the study period. The application of PCR-mediated genotyping of fungi in epidemiological analyses and evaluation of hospital hygiene is discussed.

Morphological transformation of C3H10T1/2CL8 cells by cyclopenta-fused derivatives of benzo[a]pyrene and benzo[e]pyrene

Cyclopenta-fused homologs of polycyclic aromatic hydrocarbons (PAH) have proven to be more genotoxic and tumorigenic than their parent PAHs. In an effort to uncover their mechanisms of metabolic activation, the morphological transforming activities of dibenzo[k,mno]acephenanthrylene (CP(3,4)B[a]P), dibenzo[j,mno]acephenanthrylene (CP(1,12)B[a]P) and naphtho[1,2,3,4-mno]acephenanthrylene (CPB[e]P) were studied in C3H10T1/2CL8 mouse embryo fibroblasts. CP(3,4)B[a]P, a PAH with a blocked K region and unblocked bay region, was highly active inducing an average of 1.1 Type II and III foci/dish at 5 micrograms/ml with an average of 67% of the dishes containing foci. This activity was similar to that of benzo[a]pyrene. CP(1,12)B[a]P and CPB[e]P were inactive. The relative positions of the cyclopenta-ring and bay region may play an essential role in the metabolic activation of these PAHs and their biological activities.

Synthesis and mutagenicity of a series of nitrated carbazoles and hydroxycarbazoles

Nitrated derivatives of the aza-arenes carbazole and 2-hydroxycarbazole were synthesized and tested for mutagenicity in the Ames plate-incorporation assay. 3,6-Dinitrocarbazole was the most mutagenic towards Salmonella typhimurium strain TA98 (> 100 revertants/micrograms, 25 revertants/nmol, with or without S9) followed by 2-hydroxy-1,3,6-trinitrocarbazole (24 revertants/micrograms, 7 revertants/nmol without S9) and 2-hydroxy-3-nitrocarbazole (27 revertants/micrograms, 6 revertants/nmol without S9). 2-Hydroxy-1,3-dinitrocarbazole, 1,6-dinitrocarbazole, 3-nitrocarbazole and 1-nitrocarbazole ranged from moderately to weakly active (7-1 revertants/micrograms, 2-0.3 revertants/nmol without S9). Carbazole and 2-hydroxycarbazole, and 2-hydroxy-1-nitrocarbazole, were quite inactive. Activity was generally decreased by the presence of S9, except for the dinitrocarbazoles, and was also lower in the variant TA98NR, indicating that mutagenicity was largely dependent on the presence of the 'classical' bacterial nitroreductase. The relative activities of these compounds are consistent with the hypothesis that structural features (orientation of the nitro group relative to the plane and to the long axis of the molecule, and ability to resonance-stabilize the positive charge on the arylnitrenium active electrophile intermediate) are major influences determining mutagenic potency of nitrated compounds.

Activation and metabolism of benz[j]aceanthrylene-9,10-dihydrodiol, the precursor to bay-region metabolism of the genotoxic cyclopenta-PAH benz[j]aceanthrylene

Benz[j]aceanthrylene, a cyclopentafused polycylic aromatic hydrocarbon produced in combustion emissions, possesses a bay region and an etheno bridge which may both contribute to the overall genotoxicity of the compound. In order to assess the role of activation at the bay region, the precursor epoxide benz[j]aceanthrylene 9,10-oxide, its dehydration product 10-hydroxybenz[j]aceanthrylene, the key dihydrodiol 9,10-dihydroxy-9,10-dihydrobenz[j]aceanthrylene and the bay-region diol-epoxide 7,8-epoxy-9,10-dihydroxy-7,8,9,10- tetrahydrobenz[j]aceanthrylene were evaluated in the bacterial histidine-reversion plate incorporation assay (Ames assay) with Salmonella typhimurium strain TA98. The diol-epoxide alone showed direct-acting mutagenicity (10 revertants per nmole), which was decreased by addition of exogenous metabolic activation (Aroclor 1254-treated rat-liver S9), whereas all the other compounds tested were activated by increasing concentrations of S9. The potency of the diol-epoxide was not sufficient to account for the activity of the parent compound. Identification by proton nuclear magnetic resonance and mass spectrometry of the major products of further metabolism by Aroclor 1254-treated rat-liver S9 of the bay region precursor dihydrodiol 9,10-dihydroxy-9,10-dihydrobenz[j]aceanthrylene indicated that oxidation occurred predominantly at the etheno bridge, to give 9,10-dihydroxy-9,10-dihydrobenz[j]aceanthrylene-2(1H)-one, arising by (non-enzymic) rearrangement of the etheno bridge epoxide and the tetrol 1,2,9,10-tetrahydroxy-1,2,9,10- tetrahydrobenz[j]aceanthrylene. The bay region tetrol 7,8,9,10-tetrahydroxy-7,8,9,10-tetrahydrobenz[j] aceanthrylene was observed, implying further bay-region metabolism; re-aromatization of the benzo ring to benz[j]aceanthrylene-9,10-diol also occurred. Thus oxidation at the etheno bridge accounts for the majority of the activity of benz[j]aceanthrylene and its derivatives when Aroclor 1254-treated rat-liver S9 is used for exogenous metabolic activation.

Microbial carriage, sepsis, infection and acute GVHD in the first 25 BMT at the Royal Liverpool Children's Hospital

The first 25 BMTs at the Royal Liverpool Children's Hospital (Alder Hey) were performed between April 1987 and July 1991. The aim of this report is to evaluate selective decontamination of the digestive tract (SDD) during the first post-BMT month in this series of 14 allografts and 11 autografts. SDD is a method used to abolish carriage of potentially pathogenic microorganisms including yeasts, Staphylococcus aureus and Gram-negative bacilli (GNB). Chlorhexidine mouth wash was used to decontaminate the oropharynx, and neomycin, colistin (polymyxin E) and nystatin (NEOCON) were given to eradicate gut carriage. Oropharyngeal decontamination was successful in 48% of patients, gut carriage was abolished in 60%, and eradication of the carrier state at both sites was achieved in 33%. A septic response was seen in 76% of children and 36% developed septicaemia (indigenous Gram-positive cocci only). A low carriage index for the target microorganisms during the study manoeuvre of SDD was associated with negative blood cultures (p < 0.01). Acute GVHD occurred in 28% of allografts, but was seen in none of the successfully decontaminated children (p < 0.05). It is concluded that septicaemia from yeasts and GNB, but not the septic response, were successfully prevented by SDD.