The role of vitamin D in corticosteroid-induced osteoporosis: a meta-analytic approach

OBJECTIVE

To determine if vitamin D is more effective than no therapy or calcium alone in the management of corticosteroid-induced osteoporosis, and to determine how vitamin D compares with other osteoporosis therapies, e.g., bisphosphonates, calcitonin, or fluoride, for this condition.

METHODS

We evaluated all formulations of vitamin D, including its active metabolites and analogs. A systematic search for published and unpublished studies was conducted using MEDLINE (1966-December 1997), bibliographic references, abstracts from proceedings of recent national meetings, and contact with pharmaceutical companies and content experts. We included all randomized controlled trials lasting at least 6 months (and reporting extractable results), of patients receiving oral corticosteroids, that compared vitamin D with either 1) no therapy or calcium alone, or 2) bisphosphonates, calcitonin, or fluoride. The primary outcome measure of interest was change in lumbar spine bone mineral density.

RESULTS

We found a moderate beneficial effect of vitamin D plus calcium versus no therapy or calcium alone (9 trials) (effect size 0.60; 95% confidence interval [95% CI] 0.34, 0.85; P < 0.0001). In comparisons of vitamin D with other osteoporosis therapies, bisphosphonates were more effective than vitamin D (6 trials) (effect size 0.57; 95% CI 0.09, 1.05). Calcitonin was similar in efficacy to vitamin D (4 trials) (effect size 0.03; 95% CI -0.39, 0.45). Fluoride was more effective than vitamin D, but there were only 2 trials.

CONCLUSION

Vitamin D plus calcium is superior to no therapy or calcium alone in the management of corticosteroid-induced osteoporosis. Vitamin D is less effective than some osteoporosis therapies. Therefore, treatment with vitamin D plus calcium, as a minimum, should be recommended to patients receiving long-term corticosteroids.

Outcome of psychosis in people of African-Caribbean family origin. Population-based first-episode study

BACKGROUND

An increased incidence of psychotic disorders has repeatedly been reported among African-Caribbeans in the UK.

AIMS

To test whether the increased incidence of psychotic disorders in first- and second-generation African-Caribbeans in the UK could be caused by a relative excess of affective-related psychoses with good prognosis.

METHOD

Thirty-three patients of African-Caribbean family origin identified in a population-based study of first-episode psychoses were compared with the remaining cases. Three-year outcomes and patterns of course were compared.

RESULTS

There was a trend for better outcomes in African-Caribbean patients for symptoms and social disability, but patterns of course were similar (odds ratio = 0.9 (0.50 to 2.00)) [corrected]. Pattern of course improved after adjustment for confounding by gender, social class, age, diagnosis and duration of untreated illness (odds ratio = 0.59 (0.21 to 1.66)) [corrected]. Diagnostic profiles were similar, with no evidence of greater diagnostic instability in the African-Caribbean group.

CONCLUSION

Pattern of course of psychosis did not differ significantly by ethnic family background. An excess of good-prognosis affective psychoses is an unlikely explanation for increased rates of psychosis in African-Caribbeans.

Cost-effectiveness of atypical antipsychotics in chronic schizophrenia

It is nearly a decade since the first atypical antipsychotic, clozapine, was launched in the UK. There are now several other similar drugs on the market. They are all more expensive than traditional antipsychotics and the question of whether they are a cost-effective use of scare NHS resources is an important one. This article reviews the evidence in the area of treatment-resistant schizophrenia.

Learning and memory in rats gestationally and lactationally exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)

Recently we reported that in utero and lactational exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) or coplanar polychlorinated biphenyls (PCBs) resulted in a reduction of errors on a radial arm maze (RAM) working memory task. The effect was more pronounced in males than in females. In this study, we further investigated the effects of in utero and lactational exposure to TCDD on learning and memory by testing male and female TCDD-exposed rats on three different spatial learning and memory tasks: the RAM, the Morris water maze (MWM), and spatial discrimination-reversal learning (RL), as well as on a nonspatial learning task, visual RL. Time-mated Sprague-Dawley rats were gavaged with either TCDD (0.1 microg/kg/day) or corn oil vehicle on gestation days 10-16. Litters were culled to eight on day 2 and weaned on day 21. Beginning on day 80, one male and one female from each litter were tested on the same RAM working memory task used in the previous study. Again, the TCDD-exposed male rats displayed a pronounced decrease in errors relative to control males. Following the RAM testing, the same animals were tested on the MWM, but no differences between the exposed and control rats were observed. Another male and female from each litter were tested on spatial RL on a T-maze. There were no differences between the exposed and control rats on this task. Following spatial RL, the same rats were tested on visual RL on the same maze. The exposed animals did not differ from controls on original learning, but took more trials to reach criterion on the first and second reversals. These results demonstrate a reliable, but task-specific, facilitation of spatial learning and memory in male rats exposed to TCDD during gestation and lactation. In contrast, both male and female TCDD-exposed rats showed a deficit in learning on the visual RL task. This pattern is consistent with that seen in earlier monkey studies. Perinatally TCDD-exposed monkeys were facilitated on certain spatial tasks, but impaired on visual RL tasks.

Evaluating the Health of the Nation Outcome Scales. Reliability and validity in a three-year follow-up of first-onset psychosis

BACKGROUND

The HoNOS has been developed as a routine measure of outcomes in mental health.

AIMS

To explore the validity and interrater reliability of HoNOS in a first-onset psychosis follow-up study.

METHOD

Between 1992 and 1994 we ascertained a cohort of all persons with first-onset psychosis. We re-assessed these people at 3 years (n = 166) with several outcome scales, including HoNOS. Patients' keyworkers also completed the HoNOS. We estimated concurrent validity by calculating correlations between HoNOS and other scales, and interrater reliability.

RESULTS

Researcher HoNOS correlated highly with other scales (0.46 < p < 0.86; P < 0.001). Keyworker HoNOS correlations were lower (0.41 < p < 0.51; P < 0.05), but still significant for all scores except the HoNOS-social subscale (0.12 < p < 0.28). Agreements between researcher and keyworker HoNOS were modest (0.47 < ICC < 0.85).

CONCLUSIONS

In this research cohort HoNOS correlates well with established outcome scales. Keyworker ratings show similar, but weaker, relationships; its use in routine settings may require further training for calibration of severity.

Increased expression of cyclooxygenase-2 in rat lung tumors induced by the tobacco-specific nitrosamine 4-(methylnitrosamino)-4-(3-pyridyl)-1-butanone: the impact of a high-fat diet

Aberrant or excessive expression of cyclooxygenase (COX)-2 has been implicated in the pathogenesis of many disease processes, including carcinogenesis. COX-2 expression was immunohistochemically examined in archival samples (D. Hoffmann et al., Cancer Res., 53: 2758-2761, 1993) of lung neoplasms (adenomas, adenocarcinomas, and adenosquamous carcinomas) induced by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in male F344 rats that had been fed either a semipurified AIN-76A diet with high-fat (HF; 23.5% corn oil) or low-fat (LF; 5% corn oil) content. The intensity and extent of COX-2 positivity was graded from 0 (undetectable or negligible expression) to grades 1 (<30% expression), 2 (30-60% expression), 3 (60-90% expression), and 4 (>90% expression). The scoring criteria were similar to those used with specimens from human lung cancers (T. Hida et al., Cancer Res., 58: 3761-3764, 1998). In group 1 (NNK plus HF diet), adenomas, adenocarcinomas, and adenosquamous carcinomas were of mean grades 2, 3, and 4, respectively; in group 2 (NNK plus LF diet), the corresponding mean grades were 1, 1, and 3. Although control rats, given HF (group 3) or LF (group 4) diets but no NNK, developed spontaneous lung tumors, the expression of COX-2 was either negligible (one adenoma of grade 0 in group 3) or of a very low grade (one adenocarcinoma of grade 1 in group 4). In addition, the latency of the tumors in the peripheral lung in assays with NNK is significantly shorter in rats maintained on the HF diet than in those on LF diet. COX-2 expression was not evident in normal lung tissues. We report here for the first time that NNK induces increasingly higher levels of COX-2 expression with progressive stages of lung tumorigenesis when rats are fed the HF diet. The increase in COX-2 expression may be associated with the development of lung tumors induced by NNK. This well-defined animal model is valuable for studying modulation of COX-2 expression in lung carcinogenesis by various factors, including dietary components.

Synthesis of anti-7,8-dihydroxy-9,10-epoxy-7,8,9, 10-tetrahydro-11-methylbenzo[a]pyrene and its reaction with DNA

Substitution of a methyl group in the bay region can enhance the tumorigenicity of polycyclic aromatic hydrocarbons such as chrysene, benz[a]anthracene, and others. This phenomenon has been related to facile DNA adduct formation of bay region diol epoxides with a methyl group and epoxide ring in the same bay. While anti-7, 8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene and its DNA adduct formation have been studied extensively, it is not known whether a methyl substituent in the bay region alters the reactivity of DNA in this system. This is of interest because 11-methylbenzo[a]pyrene, which has a bay region methyl group, is more tumorigenic than benzo[a]pyrene. To examine the question, we have devised and employed an efficient synthesis based on photochemical cyclization, and prepared anti-7,8-dihydroxy-9, 10-epoxy-7,8,9,10-tetrahydro-11-methylbenzo[a]pyrene, the likely ultimate carcinogen of 11-methylbenzo[a]pyrene. We have then reacted anti-7,8-dihydroxy-9,10-epoxy-7,8,9, 10-tetrahydro-11-methylbenzo[a]pyrene with calf thymus DNA and found that it gives three major adducts. These were identified as having resulted from cis- and trans-ring opening of the (S,R,R, S)-enantiomer and from trans-ring opening of the (R,S,S, R)-enantiomer. The standard deoxyguanosine adduct markers were prepared, and their structures were tentatively assigned on the basis of their CD and 1H NMR spectra. The adduct distribution of anti-7,8-dihydroxy-9,10-epoxy-7,8,9, 10-tetrahydro-11-methylbenzo[a]pyrene is quite different from that observed in the reaction of DNA with the corresponding diol epoxides of benzo[a]pyrene or with 5-methylchrysene. The heterogeneity of adducts obtained with anti-7,8-dihydroxy-9,10-epoxy-7,8,9, 10-tetrahydro-11-methylbenzo[a]pyrene thus may be related to the enhanced tumorigenicity of 11-methylbenzo[a]pyrene.

Reactions of dihydrodiol epoxides of 5-methylchrysene and 5, 6-dimethylchrysene with DNA and deoxyribonucleotides

Both syn and anti dihydrodiol epoxides from 5-methylchrysene (5-MCDE) and 5,6-dimethylchrysene (5,6-DMCDE) were reacted under the same conditions with native DNA, denatured DNA, and purine deoxyribonucleotides, and the products were quantified. The extents of reaction with the deoxyribonucleotides were consistently greater for 5,6-DMCDE than for 5-MCDE. The yield of adducts in the reaction with DNA ranged from being a few-fold to 50-fold greater than those found in the corresponding deoxyribonucleotide reactions for both 5-MCDE and 5,6-DMCDE. The DNA-dependent enhancement of product yield was greater for 5-MCDE than for 5,6-DMCDE with a few exceptions among cis and trans deoxyadenosine adducts. The most substantial differences in DNA-dependent enhancement were found for deoxyguanosine adducts; thus, steric hindrance between the 6-methyl group in the 5,6-DMCDE and the minor groove in the DNA double helix may account for the greater DNA-dependent enhancement found in the 5-MCDE reactions.

Prognosis in cutaneous T-cell lymphoma by skin stage: long-term survival in 489 patients

BACKGROUND

Although a number of studies have documented the long-term survival of patients with cutaneous T-cell lymphoma (CTCL), none have provided data as to the relative survival of all 4 skin stages.

OBJECTIVE

We document survival of CTCL patients by T stage relative to that of an age-, sex-, and race-matched population.

METHODS

The survival of 489 patients with CTCL registered since 1957 was compared with that of a California control population.

RESULTS

For stage T1 (< 10% skin involved) there was no significant difference between the observed and expected survivals. For the other 3 stages the observed survival was significantly inferior to that of the expected survival (P = .002). At 10 years the relative survivals were: T2 (10% or more skin involved) 67.4%, T3 (tumor stage) 39.2%, T4 (generalized erythroderma) 41.0%. T2 plaque stage patients had an inferior relative survival (P = .001), whereas T2 patch stage patients did not. Lymphadenopathy had an unfavorable impact on prognosis. There was a strong trend toward diagnosing CTCL at an earlier stage in more recent years. We estimate that from 15% to 20% of our patients died of CTCL or related complications.

CONCLUSION

The relative survival of CTCL patients worsens with increasing skin stage, although stages T3 and T4 had closely similar survivals. The great majority of patients with CTCL do not die of their disease.

Retinoic acid increases tyrosine phosphorylation of focal adhesion kinase and paxillin in MCF-7 human breast cancer cells

Treatment of estrogen receptor (ER)-positive MCF-7 human breast cancer cells with retinoic acid (RA) inhibited cell growth and increased cell adhesion to fibronectin. In contrast, ER- MDA-MB-231 cells failed to respond. Western blot analysis showed that tyrosine phosphorylation of two major bands at Mr 125,000 and Mr 68,000 was induced by RA in ER+ MCF-7 human breast carcinoma cells. However, this induction was a late phenomenon detectable at 12 and 24 h, but not within 3 h. A similar increase of tyrosine phosphorylation by RA was observed in ER+ human breast cancer cell lines T-47D and ZR-75-1, but not in the ER- cell lines MDA-MB-231, MDA-MB-453, and MDA-MB-468. Focal adhesion kinase and paxillin, which localize in focal adhesion plaques and may play important roles in the integrin signaling pathway, were identified as the major proteins showing RA-induced tyrosine phosphorylation. The retinoid X receptor-selective compound SR11237 failed to induce tyrosine phosphorylation, indicating that retinoid X receptor activation is not involved in this phenomenon. In contrast, stable overexpression of a truncated RA receptor (RAR) alpha cDNA, RARalpha403, with strong RAR dominant negative activity prevented the increase in tyrosine phosphate, suggesting that RAR signaling is involved in RA-induced tyrosine phosphorylation. Tyrosine phosphorylation was induced the most by the RAR-alpha (193836), followed by RAR-gamma (194433), but was not significantly induced by RAR-gamma (193174)-selective retinoids. This study demonstrates a coordinated albeit relatively late effect of RA on cell adhesion and tyrosine phosphorylation in ER+ human breast cancer cells and suggests RAR-alpha as the major responsible retinoid receptor.

Mass spectrometric sequencing of site-specific carcinogen-modified oligodeoxyribonucleotides containing bulky benzo[a]pyrene diol epoxide-deoxyguanosyl adducts

Site-specific carcinogen-modified oligonucleotides are often used in site-directed mutagenesis and other biological and biochemical studies of structure-function relationships. Postsynthetic analysis and confirmation of the sites of carcinogen binding in such oligonucleotides is an important step in the characterization of these site-specific carcinogen-DNA adducts. It is shown here that negative ion mode electrospray tandem mass spectrometry methods and collision-induced dissociation offer a rapid and convenient approach for the sequencing of products derived from the reaction of the carcinogenic and mutagenic metabolite of benzo[a]pyrene, the diol epoxide r7,t8-dihydroxy-t9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (anti-BPDE), with the 11-mer oligonucleotide d(CATGCGGCCTAC). The site of reaction of anti-BPDE with either one of the three dG residues in this oligonucleotide can be accurately established by comparing the mass/charge ratios of the observed collision-induced dissociation fragments with calculated values.

Specificities of human glutathione S-transferase isozymes toward anti-diol epoxides of methylchrysenes

The specificities of human glutathione (GSH) S-transferase (GST) isozymes of class alpha (hGSTA1-1), mu (hGSTM1-1) and pi (hGSTP1-1), including the three allelic forms of hGSTP1-1 [hGSTP1-1(I104,A113), hGSTP1-1(V104,A113) and hGSTP1-1(V104,V113)], in catalyzing the GSH conjugation of anti-diol epoxide stereoisomers of 5-methylchrysene (anti-5-MeCDE) have been examined. The specific activities of human GSTs were significantly higher toward (+)-anti-5-MeCDE than toward the (-)-enantiomer of anti-5-MeCDE. All three variants of hGSTP1-1 were significantly more efficient than either hGSTA1-1 or hGSTM1-1 in GSH conjugation of (+)-anti-5-MeCDE. The catalytic efficiencies of hGSTP1-1 variants toward (+)-anti-5-MeCDE were in the order hGSTP1-1(I104,A113) > hGSTP1-1(V104,V113) > hGSTP1-1(V104,A113). The present study suggests that the I104,A113 allele, which is most frequent in human populations, may play a major role in the detoxification of (+)-anti-5-MeCDE. This may point to specificity, because previous studies from our laboratory have shown that the hGSTP1-1(V104,V113) isoform is significantly more efficient than the other two variants of hGSTP1-1 in catalyzing GSH conjugation of (+)-anti-7R,8S-dihydroxy-9S,10R-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene [(+)-anti-BPDE], the ultimate carcinogen of benzo[a]pyrene. Even though the mechanism of the differences in the activities of hGSTP1-1 variants toward anti-5-MeCDE versus anti-BPDE remains to be elucidated, it seems that the molecular configuration of the diol epoxide is an important determinant of the activity of hGSTP1-1 isoforms toward polycyclic aromatic hydrocarbon diol epoxides.

Hydrophobic forces dominate the thermodynamic characteristics of UvrA-DNA damage interactions

The Escherichia coli DNA repair proteins UvrA, UvrB and UvrC work together to recognize and incise DNA damage during the process of nucleotide excision repair (NER). To gain an understanding of the damage recognition properties of UvrA, we have used fluorescence spectroscopy to study the thermodynamics of its interaction with a defined DNA substrate containing a benzo[a]pyrene diol epoxide (BPDE) adduct. Oligonucleotides containing a single site-specifically modified N2-guanine (+)-trans-, (-)-trans-, (+)-cis-, or (-)-cis-BPDE adducts were ligated into 50-base-pair DNA fragments. All four stereoisomers of DNA-BPDE adducts show an excitation maximum at 350 nm and an emission maximum around 380 to 385 nm. Binding of UvrA to the BPDE-DNA adducts results in a five to sevenfold fluorescence enhancement. Titration of the BPDE-adducted DNA with UvrA was used to generate binding isotherms. The equilibrium dissociation constants for UvrA binding to (+)-trans-, (-)-trans-, (+)-cis-, and (-)-cis- BPDE adduct were: 7.4+/-1.9, 15. 8+/-5.4, 11.3+/-2.7 and 22.4+/-2.0 nM, respectively. There was a large negative change in heat capacity DeltaCpo,obs, (-3.3 kcal mol-1 K-1) accompanied by a relatively unchanged DeltaGoobs with temperature. Furthermore, varying the concentration of KCl showed that the number of ions released upon formation of UvrA-DNA complex is about 3.4, a relatively small value compared to the contact size of UvrA with the substrate. These data suggest that hydrophobic interactions are an important driving force for UvrA binding to BPDE-damaged DNA.

Aortoesophageal fistula: case report and review of the literature

Aortoesophageal fistula is a rare but fatal cause of upper gastrointestinal bleeding. The classic clinical triad consists of midthoracic pain or dysphagia, a sentinel episode of hematemesis, followed by fatal exsanguination. In a patient with hemodynamically significant upper gastrointestinal bleeding of unknown etiology, who has evidence of a tortuous aorta or aneurysm by chest x-ray or who exhibits Chiari's triad, the presence of AEF should be entertained. A prompt and definitive diagnosis at the time of the initial hemorrhage is necessary for a successful surgical outcome. Cautious endoscopy to exclude other causes of bleeding followed by either thoracic CT scan or thoracic aortography are indicated based on circumstances. We report a case of a 76-year-old man who presented with two discrete episodes of hemodynamically significant upper gastrointestinal bleeding. Although there was no radiological evidence of an aneurysm on chest x-ray and no endoscopic evidence of an aortoesophageal fistula, a saccular descending thoracic aorta aneurysm was found by thoracic aortogram. The patient underwent immediate surgical repair of the aorta by graft and esophagectomy, followed by a staged gastric pull-up. Left thoracotomy with fistula repair is the only definitive treatment for AEF. Use of a Sengstaken-Blakemore tube or embolization of the fistula prior to surgery should be considered only if the patient is exsanguinating. Although surgical repairs have high morbidity and mortality, surgery should be undertaken, as untreated cases of AEF are uniformly fatal.

Topical corticosteroids for mycosis fungoides. Experience in 79 patients

OBJECTIVE

To determine the effectiveness of topical corticosteroids in the management of mycosis fungoides.

DESIGN

Prospective study.

SETTING

Academic referral center, Veterans Affairs Medical Center, and private practice.

PATIENTS

Seventy-nine patients with patch or plaque stage of mycosis fungoides. Fifty-one were stage T1 (less than 10% of skin involved) and 28 were stage T2 (10% or more of skin involved). Seventy-five had patch-stage and 4 had plaque-stage disease as determined by histological examination.

INTERVENTION

Patients were treated with topical class I to III corticosteroids. Of the stage T1 patients, all used class I corticosteroids, and 4 (8%) also used class II or III corticosteroids. Of the stage T2 patients, 19 (68%) used class I and 12 (43%) used class II or III compounds. Some patients used more than 1 class of corticosteroid. Applications were almost always twice daily. Three stage T1 and 2 stage T2 patients used plastic film occlusion. Baseline and monthly morning serum cortisol levels were obtained during treatment.

MAIN OUTCOME MEASURES

Response to treatment and side effects.

RESULTS

The median follow-up period was 9 months. Thirty-two (63%) of stage T1 patients achieved complete remission and 16 (31%) achieved partial remission, for a total response rate of 48 (94%). The comparable figures for stage T2 patients were 7 (25%), 16 (57%), and 23 (82%), respectively. Responses were determined by clinical examination. Thirty-nine patients achieved clinical clearing. In 7 of these, posttreatment biopsy specimens were obtained, and all showed histological clearing. Reversible depression of serum cortisol levels occurred in 10 (13%). Minor skin irritation occurred in 2 patients and localized, reversible skin atrophy in 1.

CONCLUSION

Topical corticosteroids, especially class I compounds, are an effective treatment for patch-stage mycosis fungoides.

Inhibition of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) metabolism in human hepatic microsomes by ipomeanol analogs--an exploratory study

The tobacco-specific 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is a potent lung carcinogen in mice, rats and Syrian golden hamsters and a suspected human lung carcinogen. We have reported earlier that structural analogs of the naturally occurring pulmonary toxin 4-ipomeanol (IPO) were non toxic up to 50 micromol/mouse. Because these analogs are in part structurally similar to NNK, they are expected to compete for the same enzymes and/or reactive sites within DNA. Both NNK and IPO are primarily metabolized by cytochrome P450 enzymes in the Clara cells of the lung but also in the liver. We describe here the optimal conditions for the study of NNK metabolism in human liver microsomes and our investigation of four non-toxic IPO analogs as potential inhibitors of NNK activation. The IPO analogs studied were 4-hydroxy-1-phenyl-1-octanone (4-HPO), 1,4-diphenyl-4-hydroxy-1-butanone (DPHB), 4-hydroxy-1-phenylpentane (HPPentane) and amyl benzene (AB). When added to microsomal incubations of human liver cells at a concentration of 100 microM, all of these compounds were strong inhibitors of NNK activation, decreasing the total alpha-hydroxylation of NNK, which is the main pathway of activation, by 60-70% and preventing N-oxidation by 78-86%.

Mutagenic potential of stereoisomeric bay region (+)- and (-)-cis-anti-benzo[a]pyrene diol epoxide-N2-2'-deoxyguanosine adducts in Escherichia coli and simian kidney cells

We have investigated the mutagenic potential of site-specifically positioned DNA adducts with (+)- and (-)-cis-anti stereochemistry derived from the binding of r7,t8-dihydroxy-t9,10-epoxy-7,8,9, 10-tetrahydrobenzo[a]pyrene (BPDE) to N2-2'-deoxyguanosine (G1 or G2) in the sequence context 5'TCCTCCTG1 G2CCTCTC. BPDE-modified oligodeoxynucleotides were ligated to a single-stranded DNA vector and replicated in Escherichia coli or simian kidney (COS7) cells. The presence of (+)- or (-)-cis adduct strongly reduced the yield of transformants in E. coli, and the yield was improved by the induction of SOS functions. Both adducts were mutagenic in E. coli and COS cells, generating primarily G --> T transversions. In E. coli, the (-)-cis adduct was more mutagenic than the (+)-cis adduct, while in COS cells, both adducts were equally mutagenic. These results were compared with those obtained with stereoisomeric (+)- and (-)-trans adducts [Moriya, M., et al. (1996) Biochemistry 35, 16646-16651). In E. coli, cis adducts, especially (-)-cis adducts, are consistently more mutagenic than the comparable trans adduct. In COS cells, trans adducts yield higher frequencies of mutations than the two cis adducts and, with the exception of the high-mutation frequency associated with the (+)-trans adduct at G2, relatively small differences in mutation frequencies are observed for the three other adducts. In E. coli, mutation frequency is a pronounced function of adduct stereochemistry and adduct position. These findings suggest that the fidelity of translesional synthesis across BPDE-dG adducts is strongly influenced by adduct stereochemistry, nucleotide sequence context, and the DNA replication complex.

Transition to adulthood of female garment-factory workers in Bangladesh

This article examines data from a study on garment-factory workers in Bangladesh to explore the implications of work for the early socialization of young women. For the first time, large numbers of young Bangladeshi women are being given an alternative to lives in which they move directly from childhood to adulthood through early marriage and childbearing. Employment creates a period of transition in contrast to the abrupt assumption of adult roles at very young ages that marriage and childbearing mandate. This longer transition creates a period of adolescence for young women working in the garment sector that is shown to have strong implications for the women's long-term reproductive health.

Sequence dependence and characteristics of bends induced by site-specific polynuclear aromatic carcinogen-deoxyguanosine lesions in oligonucleotides

The tumorigenic metabolite of benzo[a]pyrene, the (+)-7R,8S,9S,10R enantiomer, and the nontumorigenic mirror-image isomer, (-)-7S,8R,9R, 10S, of r7,t8-dihydroxy-t9,10-epoxy-7,8,9, 10-tetrahydrobenzo[a]pyrene (anti-BPDE) bind covalently to the exocyclic amino group of deoxyguanosine (N2-dG) in native DNA. These adducts can cause structural perturbations such as DNA bends, which in turn may influence the cellular processing of these lesions. The characteristics of bends in site-specifically modified oligodeoxyribonucleotide duplexes induced by single (+)- and (-)-anti-[BP]-N2-dG lesions were examined by self-ligation and gel electrophoresis techniques. The modified residues (dG*) were centrally positioned in the 11-mer oligonucleotide d(CACAXG*XACAC) complexed with the natural complementary strands, with X = T or C, or in oligonucleotides 16 or 22 base pairs long with the same centrally positioned 11-mer. Among the four stereochemically distinct lesions, the 10S(+)-trans-anti-[BP]-N2-dG adducts were significantly more bent than any of the other three stereoisomeric adducts and were selected for detailed studies. In the TG*T sequence context (X = T), the retardation factor RL (apparent length of multimer/sequence length) is approximately independent of the phasing (distance, in base pairs, between the lesions) of the adducts with respect to the helical repeat (10.5 base pairs/helix turn). In contrast, in the CG*C sequence context (X = C), RL is markedly lower in the case of ligated 16-mers than in the case of ligated 11-mer duplexes. The dependence of RL on the phasing of the bends as a function of the helical repeat, indicate that the bends associated with (+)-trans-anti-[BP]-N2-dG lesions are relatively rigid in the d(...CG*C...).d(...GCG...) sequences, and flexible in the d(...TG*T...).d(...ACA...) sequence context. These differences are attributed to the orientations of the pyrenyl residues on the 5'-side of the modified deoxyguanosine residues in the minor groove and to the intrinsic roll and tilt characteristics of DNA dinucleotide steps CG, GC, TG, and GT. The influence of flanking bases on the extent and character of DNA bending suggest that base sequence effects may be important in the cellular processing of (+)-trans-anti-[BP]-N2-dG lesions.

Role of hydrophobic effects in the reaction of a polynuclear aromatic diol epoxide with oligodeoxynucleotides in aqueous solutions

The need for large-scale direct synthesis of stereochemically defined and site-specific benzo[alpha]pyrenediol epoxide-oligodeoxyribonucleotide adducts for detailed NMR and other biochemical and physicochemical studies has necessitated a better understanding of variables that lead to an enhancement of the reaction yields. It is shown that, in aqueous solution, the formation of noncovalent hydrophobic complexes between 7r, 8t-dihydroxy-9t,10t-epoxy-7,8,9,10-tetrahydrobenzo[alpha] pyrene (BPDE) and the single-stranded oligonucleotide 5'-d(CCATCGCTACC) precedes the covalent binding reaction of BPDE with the single deoxyguanosine residue. The yield of covalent reaction products (involving reaction of BPDE at the C10 position with the exocyclic amino group of the dG residue) increases with increasing DNA concentration and tends toward saturation at oligonucleotide single-strand concentrations above approximately 3 mM. The addition of NaCl (0.3 M) also tends to enhance the adduct reaction yields. However, organic solvents such as tetrahydrofuran in the reaction mixtures (10-40%) decrease the stabilities of the noncovalent complexes, which in turn leads to reductions in the yields of covalent BPDE-dG oligonucleotide adducts. The efficiencies of formation of hydrophobic complexes were probed by fluorescence and UV absorption techniques using the BPDE tetrol hydrolysis product 7,8,9,10-tetrahydroxytetrahydrobenzo[alpha]pyrene as a model system.

Bending and circularization of site-specific and stereoisomeric carcinogen-DNA adducts

The potent tumorigen and mutagen (+)-7(R),8(S)-dihydroxy-9(S), 10(R)-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene ((+)-anti-BPDE) is a metabolite of benzo[a]pyrene that binds predominantly to the exocyclic amino group of guanine residues in DNA in vivo and in vitro. While the (-)-7S,8R,9R,10Senantiomer, (-)-anti-BPDE, also reacts with DNA to form similar covalent N2-deoxyguanosyl adducts, this diol epoxide is nontumorigenic and its mutagenic activities are different from those of (+)-anti-BPDE. In this work, T4 ligase-induced cyclization methods have been employed to demonstrate that the (+)-anti-[BP]-N2-dG lesions (G*) cause significantly greater amounts of bending and circularization of the one-base overhang undecamer duplex 5'-d(CACAT[G*]TACAC).d(TGTACATGTGG) than the stereoisomeric oligonucleotide duplex with G* = (-)-anti-[BP]-N2-dG. In the case of the (+)-anti-BPDE-modified oligonucleotides, the ratio of circular to linear DNA multimers reaches values of 8-9 for circle contour sizes of 99-121 base pairs, while for the (-)-anti-[BP]-N2-dG-modified DNA this ratio reaches a maximum value of only approximately 1 at 154-176 base pairs. Assuming a planar circle DNA model, the inferred bending angles for 90-92% of the observed circular ligation products range from 30 to 51 degrees per (+)-trans-anti-[BP]-N2-dG lesion and from 20 to 40 degrees per (-)-trans-anti-[BP]-N2-dG lesion. In the case of unmodified DNA, the probability of circular product formation is at least 1 order of magnitude less efficient than in the BPDE-modified sequences and about 90% of the circular products exhibit bending angles in the range of 14 -19 degrees . In the most abundant circular products observed experimentally, the bending angles are 40 degrees and 26 +/- 2 degrees per (+)-anti-[BP]- or (-)-anti-[BP]-modified 11-mer; these values correspond to a net contribution of 21-26 degrees and 5-19 degrees , respectively, to the observed overall bending per lesion. The coexistence of circular DNA molecules of different sizes and, therefore, different average bending angles per lesion, suggest that the lesions induce both torsional flexibility and flexible bends, which permit efficient cyclization, especially in the case of (+)-trans-[BP]-N2-dG adducts. The NMR characteristics of (+)-trans-[BP]-N2-dG lesion in the 11-mer duplex 5'-d(CACAT[G*]TACAC).d(GTGTACATGTG) indicate that all base pairs are intact, except at the underlined base pairs. This suggests a distortion in the normal conformation of the duplex on the 5'-side of the modified guanosine residue, which may be due to bending enhanced base pair opening and bending induced by the bulky carcinogen residue. The implications of base sequence-dependent flexibilities and conformational mobilities of anti-[BP]-N2-dG lesions on DNA replication and mutation are discussed.

Comparative mouse skin tumorigenicity and induction of Ha-ras mutations by bay region diol epoxides of 5-methylchrysene and 5,6-dimethylchrysene

We compared the tumor-initiating activities toward mouse skin of two structurally related polycyclic aromatic hydrocarbon diol epoxides: racemic anti-1,2,3,4-tetrahydro-5,6-dimethylchrysene-1,2-diol-3,4-epoxide (5,6-diMeCDE) and racemic anti-1,2,3,4-tetrahydro-5-methylchrysene-1,2-diol-3,4-epoxide (5-MeCDE). Tumors induced by these diol epoxides were analysed for mutations in the Ha-ras gene. 5,6-diMeCDE is derived from the non-planar parent compound 5,6-dimethylchrysene, and reacts to approximately equal extents with dA and dG in DNA, whereas 5-MeCDE is derived from a nearly planar parent compound, 5-methylchrysene, and reacts mainly with dG in DNA. 5,6-diMeCDE, at initiating doses of 33, 100 or 400 nmol per mouse, induced 1.2, 2.2 and 6.2 skin tumors per mouse, respectively. It was significantly less tumorigenic than 5-MeCDE which induced 3.1, 7.5 and 9.1 skin tumors per mouse at the same doses. Tumors induced by 5,6-diMeCDE had a large number of CAA-->CTA mutations in codon 61 of the Ha-ras gene: 50, 55 and 75% of the tumors analysed had this mutation at the 33, 100 and 400 nmol doses. No mutations were found in codons 12 and 13 in the tumors induced by 5,6-diMeCDE. In contrast, CAA-->CTA mutations in codon 61 were rarely seen in tumors induced by 5-MeCDE. At the highest dose of 5-MeCDE, 20% of the tumors analysed had mutations at G of codons 12 and 13. The results of this comparative study support the hypothesis that mutations in the Ha-ras gene in mouse skin tumors induced by PAH diol epoxides occur as a result of their direct reaction with the gene. However, pathways other than the commonly observed Ha-ras codon 61 mutations are clearly important in mouse skin tumorigenesis by these diol epoxides.

Chemopreventive activity of thiol conjugates of isothiocyanates for lung tumorigenesis

A series of L-cysteine (L-Cys), glutathione (GSH), and N-acetyl-L-cysteine (NAC) conjugates of phenethyl (PEITC), benzyl (BITC), and 6-phenylhexyl isothiocyanate (PHITC) were studied for their inhibitory activity toward metabolic activation of the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in mouse lung microsomes. Selected compounds, PEITC, PEITC-GSH, PEITC-NAC and PHITC-NAC, were also assayed for the potential chemopreventive activity toward NNK-induced lung tumorigenesis in A/J mice. Results showed that PEITC and its conjugates inhibited NNK metabolism with decreasing potency: PEITC < PEITC-GSH > PEITC-Cys > PEITC-NAC. PHITC and its GSH and NAC conjugates exhibited nearly 10 times higher inhibitory activity toward NNK metabolism than the PEITC counterparts. In the tumor bioassay, as expected, the conjugates exhibited inhibitory activity against lung tumorigenesis induced by NNK. PEITC-GSH was not inhibitory at 4 micromol/mouse, but it inhibited approximately 32% of lung tumor multiplicity at 8 micromol/mouse. PEITC-NAC at 5 and 20 micromol/mouse both inhibited approximately 30% tumor multiplicity. Among all the conjugates examined, PHITC-NAC was the most potent. At a 5-micromol dose, it completely inhibited tumor multiplicity and incidence to the background level observed in the control group. These results revealed that the structure-activity relationships of the conjugates are similar to those found with their parent isothiocyanates (ITCs), i.e., the potency increased with the increasing alkyl chain length from two to six carbons in arylalkyl ITCs, suggesting that a common active species is involved. The inhibitory activity of ITC conjugates and the expected low toxicity make thiol conjugates of ITC a promising new series of chemopreventive agents.

Effects of 1,4-phenylenebis(methylene)selenocyanate and selenomethionine on 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone-induced tumorigenesis in A/J mouse lung

We reported earlier that continuous feeding of 1,4-phenylenebis(methylene)selenocyanate (p-XSC) inhibited lung tumor induction by the tobacco-specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in the A/J mouse (El-Bayoumy et al., Carcinogenesis, 14, 1111-1113, 1993). The present investigation was designed to determine whether p-XSC inhibits pulmonary neoplasia induced by NNK in female A/J mice during the initiation phase of carcinogenesis or during the post-initiation phase. The naturally occurring selenomethionine was also included in this study. Doses higher than 4 p.p.m. of selenomethionine can induce toxic effects, therefore, dietary supplementation of this compound was selected at a dose level of 3.75 p.p.m. However, we were able to give p-XSC at selenium levels of 7.5 and 15 p.p.m., as mice can tolerate such doses in this form without any adverse effects. NNK was given by a single i.p. injection at dose of 10 micromol in 0.1 ml of saline. Selenomethionine did not show chemopreventive activity when administered in either phase of tumorigenesis. In contrast, p-XSC significantly reduced lung tumor multiplicity regardless of whether it was given during the initiation phase of tumorigenesis (P = 0.0009 at both levels of selenium) or post-initiation (P = 0.0009 at 15 p.p.m. and P = 0.036 for 7.5 p.p.m.). This is the first report describing that the synthetic organoselenium compound, p-XSC, can effectively block and suppress chemically (NNK)-induced lung tumor development in mice.