Crystal structure of the Xpo1p nuclear export complex bound to the SxFG/PxFG repeats of the nucleoporin Nup42p

Xpo1p (yeast CRM1) is the major nuclear export receptor that carries a plethora of proteins and ribonucleoproteins from the nucleus to cytoplasm. The passage of the Xpo1p nuclear export complex through nuclear pore complexes (NPCs) is facilitated by interactions with nucleoporins (Nups) containing extensive repeats of phenylalanine-glycine (so-called FG repeats), although the precise role of each Nup in the nuclear export reaction remains incompletely understood. Here we report structural and biochemical characterization of the interactions between the Xpo1p nuclear export complex and the FG repeats of Nup42p, a nucleoporin localized at the cytoplasmic face of yeast NPCs and has characteristic SxFG/PxFG sequence repeat motif. The crystal structure of Xpo1p-PKI-Nup42p-Gsp1p-GTP complex identified three binding sites for the SxFG/PxFG repeats on HEAT repeats 14-20 of Xpo1p. Mutational analyses of Nup42p showed that the conserved serines and prolines in the SxFG/PxFG repeats contribute to Xpo1p-Nup42p binding. Our structural and biochemical data suggest that SxFG/PxFG-Nups such as Nup42p and Nup159p at the cytoplasmic face of NPCs provide high-affinity docking sites for the Xpo1p nuclear export complex in the terminal stage of NPC passage and that subsequent disassembly of the nuclear export complex facilitates recycling of free Xpo1p back to the nucleus.

Chromatin tethering to the nuclear envelope by nuclear actin filaments: a novel role of the actin cytoskeleton in the Xenopus blastula

The Xenopus oocyte is known to accumulate filamentous or F-actin in the nucleus, but it is currently unknown whether F-actin also accumulates in embryo nuclei. Using fluorescence-labeled actin reporters, we examined the actin distribution in Xenopus embryonic cells and found that F-actin accumulates in nuclei during the blastula stage but not during the gastrula stage. To further investigate nuclear F-actin, we devised a Xenopus egg extract that reproduces the formation of nuclei in which F-actin accumulates. Using this extract, we found that F-actin accumulates primarily at the subnuclear membranous region and is essential to maintain chromatin binding to the nuclear envelope in well-developed nuclei. We also provide evidence that nuclear F-actin increases the structural stability of nuclei and contributes to chromosome alignment on the mitotic spindle at the following M phase. These results suggest the physiological importance of nuclear F-actin accumulation in rapidly dividing large Xenopus blastula cells.

Small structural changes of the imidazopyridine diacylglycerol acyltransferase 2 (DGAT2) inhibitors produce an improved safety profile

Small molecule DGAT2 inhibitors have shown promise for the treatment of metabolic diseases in preclinical models. Herein, we report the first toxicological evaluation of imidazopyridine-based DGAT2 inhibitors and show that the arteriopathy associated with imidazopyridine 1 can be mitigated with small structural modifications, and is thus not mechanism related.

Structural insights into how Yrb2p accelerates the assembly of the Xpo1p nuclear export complex

Proteins and ribonucleoproteins containing a nuclear export signal (NES) assemble with the exportin Xpo1p (yeast CRM1) and Gsp1p-GTP (yeast Ran-GTP) in the nucleus and exit through the nuclear pore complex. In the cytoplasm, Yrb1p (yeast RanBP1) displaces NES from Xpo1p. Efficient export of NES-cargoes requires Yrb2p (yeast RanBP3), a primarily nuclear protein containing nucleoporin-like phenylalanine-glycine (FG) repeats and a low-affinity Gsp1p-binding domain (RanBD). Here, we show that Yrb2p strikingly accelerates the association of Gsp1p-GTP and NES to Xpo1p. We have solved the crystal structure of the Xpo1p-Yrb2p-Gsp1p-GTP complex, a key assembly intermediate that can bind cargo rapidly. Although the NES-binding cleft of Xpo1p is closed in this intermediate, our data suggest that preloading of Gsp1p-GTP onto Xpo1p by Yrb2p, conformational flexibility of Xpo1p, and the low affinity of RanBD enable active displacement of Yrb2p RanBD by NES to occur effectively. The structure also reveals the major binding sites for FG repeats on Xpo1p.

Rabeprazole 10 mg q.d.s. decreases 24-h intragastric acidity significantly more than rabeprazole 20 mg b.d. or 40 mg o.m., overcoming CYP2C19 genotype

BACKGROUND

Standard dosing (i.e. once daily) of proton pump inhibitors (PPIs) cannot inhibit acid secretion for a full 24 h. Better therapeutic regimens using PPIs are required to sustain potent acid inhibition for the full 24 h in all patients with acid-related diseases.

AIM

To evaluate acid inhibitory effects by different dosing times of a PPI at the same daily dosage, in a study involving 70 rounds of pH monitoring.

METHODS

Using pH monitoring, we evaluated the efficacy of different divided treatment regimens with the same total daily dose of rabeprazole (40 mg o.m., 15 rounds; 20 mg b.d., 20 rounds; 10 mg q.d.s., 35 rounds) on day 7 or 8 of PPI dosing.

RESULTS

In the study of divided treatment, the median pH (when administered once, twice or four times to achieve a daily dose of 40 mg) was 4.8 (3.6-6.4), 5.7 (4.1-7.4), 6.6 (4.9-8.4), respectively. When comparing the median pHs at the same CYP2C19 genotype among different dosing times of rabeprazole, the median pH attained with 10 mg q.d.s. was significantly higher than that in 40 mg o.m. or 20 mg b.d. Increase in the frequency of dosing effectively increased pH [median percent time of pH > 4.0 with q.d.s. therapy: 95.5% (63.2-100.0%)], irrespective to CYP2C19 genotype.

CONCLUSION

Four times daily dosing with rabeprazole 10 mg achieved potent acid inhibition, including during the night-time, suggesting its potential usefulness as a regimen for patients who are refractory to standard once daily PPI treatment.

Eosinophilic airway inflammation in a cynomolgus monkey

The present article describes an occurrence of eosinophilic airway inflammation of a 4-year-old female cynomolgus monkey in a vehicle control group of a routine toxicology study. Histologically, the airway lesion was characterized by prominent eosinophilic infiltrates, accompanied by mast cells, lymphocytes, and plasmacytes. The eosinophilic infiltrates were distributed throughout the airway: from trachea through respiratory bronchioles in the lung. The morphological feature of the lesion was indicative of an allergic airway disorder that can occur in humans with asthma. The present case is remarkable in that there is a paucity of reports on naturally occurring allergic airway disorders in nonhuman primates.

Effect of MDR1 C3435T polymorphism on cure rates of Helicobacter pylori infection by triple therapy with lansoprazole, amoxicillin and clarithromycin in relation to CYP 2C19 genotypes and 23S rRNA genotypes of H. pylori

BACKGROUND

Polymorphism in MDR1 is associated with variation in the plasma level of a proton pump inhibitor.

AIM

To investigate whether MDR1 polymorphism is associated with eradication rates of Helicobacter pylori by a triple therapy with lansoprazole, amoxicillin and clarithromycin in relation to CYP2C19 genotype status and bacterial susceptibility to clarithromycin.

METHODS

A total of 313 patients infected with H. pylori completed the treatment with lansoprazole 30 mg b.d., clarithromycin 200 mg b.d. and amoxicillin 750 mg b.d. for 1 week. MDR1 C3435T polymorphism and CYP2C19 genotypes of patients and sensitivity of H. pylori to clarithromycin were determined.

RESULTS

Logistic regression analysis revealed that the MDR1 polymorphism as well as CYP2C19 genotypes of patients and clarithromycin-resistance of H. pylori were significantly associated with successful eradication. Eradication rates for H. pylori were 82% (83/101: 95% CI = 73-89), 81% (112/139: CI = 73-87), and 67% (44/73: CI = 48-72) in patients with the MDR1 3435 C/C, C/T and T/T genotype, respectively (P = 0.001).

CONCLUSIONS

Polymorphism of MDR1 is one of the determinants of successful eradication of H. pylori by the triple therapy with lansoprazole, amoxicillin and clarithromycin, together with CYP2C19 genotype and bacterial susceptibility to clarithromycin.

Effect of MDR1 C3435T polymorphism on cure rates of Helicobacter pylori infection by triple therapy with lansoprazole, amoxicillin and clarithromycin in relation to CYP 2C19 genotypes and 23S rRNA genotypes of H. pylori

BACKGROUND

Polymorphism in MDR1 is associated with variation in the plasma level of a proton pump inhibitor.

AIM

To investigate whether MDR1 polymorphism is associated with eradication rates of Helicobacter pylori by a triple therapy with lansoprazole, amoxicillin and clarithromycin in relation to CYP2C19 genotype status and bacterial susceptibility to clarithromycin.

METHODS

A total of 313 patients infected with H. pylori completed the treatment with lansoprazole 30 mg b.d., clarithromycin 200 mg b.d. and amoxicillin 750 mg b.d. for 1 week. MDR1 C3435T polymorphism and CYP2C19 genotypes of patients and sensitivity of H. pylori to clarithromycin were determined.

RESULTS

Logistic regression analysis revealed that the MDR1 polymorphism as well as CYP2C19 genotypes of patients and clarithromycin-resistance of H. pylori were significantly associated with successful eradication. Eradication rates for H. pylori were 82% (83/101: 95% CI = 73-89), 81% (112/139: CI = 73-87), and 67% (44/73: CI = 48-72) in patients with the MDR1 3435 C/C, C/T and T/T genotype, respectively (P = 0.001).

CONCLUSIONS

Polymorphism of MDR1 is one of the determinants of successful eradication of H. pylori by the triple therapy with lansoprazole, amoxicillin and clarithromycin, together with CYP2C19 genotype and bacterial susceptibility to clarithromycin.

Neopterin is associated with plaque inflammation and destabilisation in human coronary atherosclerotic lesions

BACKGROUND

Previous studies have shown that recent activation of the inflammatory response in coronary atherosclerotic lesions contributes to rapid progressive plaque destabilisation. Neopterin, a by-product of the guanosine triphosphate pathway, is produced by activated macrophages and serves as an activation marker for monocytes/macrophages.

OBJECTIVE

To elucidate the role of neopterin in coronary plaque destabilisation by immunohistochemical study of the presence of neopterin in coronary atherectomy specimens obtained from patients with stable angina pectoris (SAP) and unstable angina pectoris (UAP).

PATIENTS AND METHODS

All patients underwent atherectomy of the primary atherosclerotic lesions responsible for SAP (n = 25) and UAP (n = 25). Frozen samples were studied with antibodies against smooth muscle cells, macrophages, T cells, neutrophils and neopterin.

RESULTS

In 22/25 patients with UAP, abundant neopterin-positive macrophages were found at the sites of coronary culprit lesions. However, in 25 lesions from patients with SAP, only 11 lesions showed neopterin positivity. Quantitatively, the neopterin-positive macrophage score was significantly higher (p<0.001) in patients with UAP than in patients with SAP. Moreover, the neopterin-positive macrophage score showed a significant positive correlation with the number of neutrophils or T cells, respectively (neutrophils, r = 0.55, p<0.001; T cells, r = 0.70, p<0.001).

CONCLUSIONS

Neopterin can be considered as one of the significant factors in the process of plaque inflammation and destabilisation in human coronary atherosclerotic lesions. Its exact role in the process needs to be investigated further.

Pharmacogenomics-based tailored versus standard therapeutic regimen for eradication of H. pylori

Helicobacter pylori eradication rates by triple therapy with a proton pump inhibitor, amoxicillin, and clarithromycin at standard doses depend on bacterial susceptibility to clarithromycin and patient CYP2C19 genotypes. We examined the usefulness of a personalized therapy for H. pylori infection based on these factors as determined by genetic testing. First, optimal lansoprazole dosing schedules that would achieve sufficient acid inhibition to allow H. pylori eradication therapy in each of different CYP2C19 genotype groups were determined by a 24-h intragastric pH monitoring. Next, 300 H. pylori-positive patients were randomly assigned to the standard regimen group (lansoprazole 30 mg twice daily (b.i.d.)), clarithromycin 400 mg b.i.d., and amoxicillin 750 mg b.i.d. for 1 week) or the tailored regimen group based on CYP2C19 status and bacterial susceptibility to clarithromycin assessed by genetic testing. Patients with failure of eradication underwent the second-line regimen. The per-patient cost required for successful eradication was calculated for each of the groups. In the first-line therapy, the intention-to-treat eradication rate in the tailored regimen group was 96.0% (95% CI=91.5-98.2%, 144/150), significantly higher than that in the standard regimen group (70.0%: 95% CI=62.2-77.2%, 105/150) (P<0.001). Final costs per successful eradication in the tailored and standard regimen groups were $669 and $657, respectively. In conclusion, the pharmacogenomics-based tailored treatment for H. pylori infection allowed a higher eradication rate by the initial treatment without an increase of the final per-patient cost for successful eradication. However, the precise cost-effectiveness of this strategy remains to be determined.

Poor metabolizer genotype status of CYP2C19 is a risk factor for developing gastric cancer in Japanese patients with Helicobacter pylori infection

BACKGROUND

Cytochrome P450 2C19 (CYP2C19) polymorphism has been associated with the development of lung, liver or oesophageal cancer by detoxification of carcinogen(s) or activation of procarcinogen(s).

AIM

To clarify the association between CYP2C19 polymorphisms and gastric cancer development in Japanese. Methods : We determined CYP2C19 genotypes (CYP2C19*1, *2 and *3) in 111 Helicobacter pylori-positive patients with gastric cancer and 315 H. pylori-positive controls without gastric cancer consisting of patients with gastritis only or peptic ulcer. Frequencies of CYP2C19 genotypes and serum pepsinogen I and II levels, a biomarker of gastric atrophy, in the gastric cancers and controls were compared.

RESULTS

Frequencies of homozygous extensive metabolizers, heterozygous extensive metabolizers and poor metabolizers were 31.5%, 42.3% and 26.2% in the gastric cancers and 38.1%, 47.0% and 14.9% in the controls, respectively (P = 0.046). Poor metabolizers were associated with an increased risk for developing gastric cancer with the age- and sex-adjusted odds ratio (OR) of 1.975 [95% confidence interval (CI): 1.068-3.649], especially for diffuse type (OR: 3.385, CI: 1.187-9.648). There is no significant association between CYP2C19 genotypes and serum pepsinogen I level or pepsinogen I/II ratios, although serum pepsinogen I level in gastric cancers were significantly decreased.

CONCLUSIONS

In H. pylori-positive Japanese, poor metabolizers of CYP2C19 appear to be at an increased risk for developing gastric cancer, especially diffuse type, and may require an intensive follow-up for scrutinizing possible gastric cancer development.

Efficacy of gemtuzumab ozogamicin on ATRA- and arsenic-resistant acute promyelocytic leukemia (APL) cells

Acute promyelocytic leukemia (APL) cells express a considerable level of CD33, which is a target of gemtuzumab ozogamicin (GO), and a significantly lower level of P-glycoprotein (P-gp). In this study, we examined whether GO was effective on all-trans retinoic acid (ATRA)- or arsenic trioxide (ATO)-resistant APL cells. Cells used were an APL cell line in which P-gp was undetectable (NB4), ATRA-resistant NB4 (NB4/RA), NB4 and NB4/RA that had been transfected with MDR-1 cDNA (NB4/MDR and NB4/RA/MDR, respectively), ATO-resistant NB4 (NB4/As) and blast cells from eight patients with clinically ATRA-resistant APL including two patients with ATRA- and ATO-resistant APL. The efficacy of GO was analyzed by (3)H-thymidine incorporation, the dye exclusion test and cell cycle distribution. GO suppressed the growth of NB4, NB4/RA and NB4/As cells in a dose-dependent manner. GO increased the percentage of hypodiploid cells significantly in NB4, NB4/RA and NB4/As cells, and by a limited degree in NB4/MDR and NB4/RA/MDR cells. Similar results were obtained using blast cells from the patients with APL. GO is effective against ATRA- or ATO-resistant APL cells that do not express P-gp, and the mechanism of resistance to GO is not related to the mechanism of resistance to ATRA or ATO in APL cells. Leukemia (2005) 19, 1306-1311. doi:10.1038/sj.leu.2403807; published online 26 May 2005.

Effect of concomitant dosing of famotidine with lansoprazole on gastric acid secretion in relation to CYP2C19 genotype status

BACKGROUND

Famotidine increases Helicobacter pylori-eradication rates by a triple lansoprazole/amoxicillin/clarithromycin therapy in patients with the rapid extensive metabolizer genotype of CYP2C19.

AIM

To determine the effect of famotidine on the gastric acid inhibition by lansoprazole in relation to CYP2C19 genotypes.

METHODS

Twenty healthy volunteers with different CYP2C19 genotypes--consisting of six rapid extensive metabolizers, nine intermediate metabolizers and five poor metabolizers--underwent three 7-day courses with placebo, lansoprazole 30 mg twice daily, and lansoprazole 30 mg twice plus famotidine 20 mg twice daily. Lansoprazole was dosed after breakfast and dinner. Famotidine was dosed after lunch and at bedtime. Intragastric pH monitoring was performed for 24 h on day 7 of each course.

RESULTS

With placebo, no difference was observed in intragastric pH profiles among the three CYP2C19 genotype groups. With lansoprazole 30 mg twice daily, the median of 24-h intragastric pH in poor metabolizers (6.1) was significantly higher than those of rapid extensive metabolizers (4.5) and intermediate metabolizers (5.0), respectively (P = 0.0176 and 0.0388), whereas with lansoprazole 30 mg twice and famotidine 20 mg twice daily, the medians were 5.4, 5.7, and 6.1, respectively (not significant).

CONCLUSION

Acid inhibition by lansoprazole was influenced by CYP2C19 genotype status. This influence was offset by the concomitant use of famotidine.

Concomitant dosing of famotidine with a triple therapy increases the cure rates of Helicobacter pylori infections in patients with the homozygous extensive metabolizer genotype of CYP2C19

BACKGROUND

Proton-pump inhibitors, such as lansoprazole, are metabolized in the liver by CYP2C19 and cannot inhibit acid sufficiently in homozygous extensive metabolizers of CYP2C19.

AIM

To examine whether famotidine would increase the cure rates of Helicobacter pylori infection by a standard triple therapy.

METHODS

A total of 177 H. pylori-positive patients were randomly assigned to either lansoprazole 30 mg b.d., clarithromycin 200 mg b.d. and amoxicillin 750 mg b.d. for 1 week (LCA group; n = 89) or famotidine 20 mg b.d., lansoprazole 30 mg b.d., clarithromycin 200 mg b.d. and amoxicillin 750 mg b.d. for 1 week (FLCA group; n = 88). Famotidine was administered after lunch and before sleep, and the others were after breakfast and dinner. CYP2C19 genotypes were determined by a polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) method.

RESULTS

In the LCA group, the eradication rates for homozygous extensive metabolizers, heterozygous extensive metabolizers, and poor metabolizers were 63%, 87%, and 100%, respectively (P = 0.014). Those in the FLCA group were 85%, 85%, and 100%, respectively (N.S.). The cure rate for homozygous extensive metabolizers in the FLCA group was significantly higher than that in the LCA group (P = 0.035).

CONCLUSION

Famotidine improves the cure rate of H. pylori infection by a triple therapy in CYP2C19 homozygous extensive metabolizers patients.

Acute improvement of atrial mechanical stunning after electrical cardioversion of persistent atrial fibrillation: comparison between biatrial and single atrial pacing

OBJECTIVE

To evaluate the acute effects of atrial pacing at different pacing sites on mechanical stunning after cardioversion of atrial fibrillation (AF).

SETTING

Tertiary referral centre.

PATIENTS

20 patients with persistent AF were studied.

INTERVENTIONS

Spontaneous echo contrast (SEC), left atrial appendage emptying velocity (LAAEV), and left atrial appendage emptying fraction (LAAEF) were assessed by transoesophageal echocardiography (TOE) during AF, after conversion to sinus rhythm, and during atrial pacing from the right atrial appendage, left lateral atrium, and both atria simultaneously. Transmitral inflow velocity of the atrial wave (TMIF-A) by TOE and the maximum P wave duration in 12 lead ECG were also measured during sinus rhythm and atrial pacing.

MAIN OUTCOME MEASURES

Comparison of atrial mechanical function and P wave duration in 12 lead ECG during atrial pacing from different sites after cardioversion of AF.

RESULTS

Compared with sinus rhythm, atrial pacing at 80 beats/min increased LAAEV from mean (SD) 14.6 (10.1) to 33.4 (19.8) cm/s (p = 0.001), LAAEF from 13.8 (8.5) to 32.1 (11.2)% (p < 0.001), and TMIF-A from 24.6 (11.9) to 45.6 (21.0) cm/s (p < 0.001) and reduced SEC grade from 2.6 (1.0) to 1.6 (0.9) (p < 0.001). These effects had a positive force-frequency relation. Biatrial pacing produced the shortest P wave duration and resulted in the most significant improvement in atrial function (LAAEV, 33.2 (19.3) v 53.7 (23.9) cm/s, p = 0.0001; LAAEF, 31.9 (11.1) v 46.2 (12.6)%, p < 0.0001; TMIF-A, 37.7 (18.3) v 54.1 (21.2) cm/s, p < 0.001; SEC grade, 1.4 (1.1) v 0.8 (0.9), p = 0.001, right atrial appendage versus biatrial pacing).

CONCLUSIONS

Atrial pacing at increased rates can improve atrial mechanical function after cardioversion of persistent AF. Biatrial pacing may be the most effective technique to reverse atrial mechanical stunning.

Differential expression of cornified cell envelope precursors in normal skin, intraorally transplanted skin and normal oral mucosa

BACKGROUND

Skin flaps have routinely been used as substitutes for oral mucosa after extensive resection of oral tissues. However, it remains unknown how the transplanted skin flaps perform as a host defence in the new environment of the oral cavity.

OBJECTIVES

To evaluate the expression of cornified cell envelope (CCE) precursors in pretransplanted (normal) skin, intraorally transplanted skin and normal oral mucosa, because CCEs are highly responsible for a protective barrier in each type of epithelium.

METHODS

We used immunohistochemistry and immunoelectron microscopy to examine the expression of CCE precursors, small proline-rich protein (SPR) 2 and 3 and loricrin, in biopsy specimens of normal skin, transplanted skin and normal oral mucosa, including buccal and lingual (non-keratinized) mucosae, and palatal (keratinized) mucosa.

RESULTS

Transplanted skin flaps were classified into two groups. About two-thirds of the transplanted skin flaps displayed a reddish appearance and were devoid of the stratum corneum (SC) together with a psoriasiform inflammatory tissue reaction. Others showed a native appearance, retaining the SC. While SPR2 expression was limited to the stratum granulosum (SG) in both normal and transplanted skin retaining the SC, it extended to the stratum spinosum (SS) of the transplanted skin lacking the SC and that of the normal oral mucosa. Although SPR3 expression was not found in normal skin or in the transplanted skin retaining the SC, it was strongly expressed in the SS of the transplanted skin lacking the SC and the non-keratinized oral mucosa, and in the SS and SG of the keratinized oral mucosa. Loricrin, which was expressed in the SG of normal skin, the transplanted skin retaining the SC and the keratinized oral mucosa, was not detected in the transplanted skin lacking the SC or in the non-keratinized oral mucosa. Immunoelectron microscopy confirmed the ultrastructural localization of SPR3 directly under the cytoplasmic membrane of keratinocytes of the transplanted skin lacking the SC and that of the oral mucosa.

CONCLUSIONS

The altered expression of SPR2, SPR3 and loricrin reflects the possible adaptation of epidermal keratinocytes in the new environment of the oral cavity.

Therapeutic impact of CYP2C19 pharmacogenetics on proton pump inhibitor-based eradication therapy for Helicobacter pylori

Current regimens for the eradication of Helicobacter pylori consist of a proton pump inhibitor (PPI) plus one or two antibacterial agents, such as amoxicillin (AMPC), clarithromycin (CAM) or metronidazole (MNZ). PPIs are mainly metabolized by S-mephenytoin 4'-hydroxylase (CYP2C19) in the liver. The polymorphism of CYP2C19 is associated with the pharmacokinetics and pharmacodynamics of PPIs. Eradication rates by PPI-based therapies are also affected by this genotype, as well as bacterial resistance to antibiotics. An individualized treatment strategy based on CYP2C19-related pharmacogenetics or pharmacogenomics and bacterial resistance is expected to increase the cure rate of the initial treatment. It is also necessary to recognize that there is a possible drug-drug interaction between some of the drugs used in this treatment regimen.

Proliferative activity of canine mast cell tumours evaluated by bromodeoxyuridine incorporation and Ki-67 expression

The proliferative activity of 91 canine mast cell tumours was assessed on the basis of the Ki-67 positive index (Ki-67 PI) and mitotic index (MI) and, in 15 cases, also by the labelling index of bromodeoxyuridine (BrdU; an analogue of tritiated thymidine) incorporated in vivo into S-phase cells. BrdU and Ki-67 were detected immunohistochemically. The tumours were graded histologically (I, II or III). The BrdU labelling index (BrdU LI) tended to increase as the grade became higher. In terms of the mean values of Ki-67 PI, significant differences were found between histological tumour grades I and II (P < 0.01) and between grades II and III (P < 0.01). In terms of mean MI, grades I and II were found to differ significantly (P < 0.05). With Spearman rank correlation coefficient and linear regression analysis, the BrdU LI and Ki-67 PI showed a highly significant correlation. This strong correlation indicated that Ki-67 was, like BrdU, a useful marker for proliferative potential in canine mast cell tumours; moreover, its use did not require the prior administration of any reagent to the live animal.

Effect of Helicobacter pylori infection and its eradication on nutrition

AIMS

To investigate the effects of Helicobacter pylori infection and eradication on nutrition.

METHODS

The body weight, height, blood pressure, gastric juice pH and fasting serum levels of glucose, total protein, albumin, total cholesterol and triglyceride were measured in H. pylori-positive and H. pylori-negative subjects, and the effect of eradication of H. pylori on these parameters was determined. The development of gastro-oesophageal reflux disease after treatment was also examined. Eight patients underwent a pancreatic function test before and after H. pylori eradication therapy.

RESULTS

The incidence of hypoproteinaemia in H. pylori-positive subjects was significantly higher than that in H. pylori-negative subjects. After eradication of H. pylori, the gastric juice pH values were significantly decreased, and the body weight and serum levels of total cholesterol, total protein and albumin were significantly increased. The incidence of hyperlipidaemia significantly increased and that of hypoproteinaemia significantly decreased in the group with eradication. Pancreatic function improved significantly after eradication of H. pylori. No significant changes in these parameters were observed in the group without eradication. Obese patients had a higher risk of the development of gastro-oesophageal reflux disease after eradication of H. pylori infection.

CONCLUSIONS

The eradication of H. pylori appears to improve some nutritional parameters.

Comparison of lansoprazole and famotidine for gastric acid inhibition during the daytime and night-time in different CYP2C19 genotype groups

BACKGROUND

The acid inhibitory effect of lansoprazole depends on the S-mephenytoin 4'-hydroxylase (CYP2C19) genotype status. The effect of famotidine is independent of this genotype.

AIM

To investigate the acid inhibitory effects of lansoprazole vs. famotidine during the daytime and night-time with reference to different CYP2C19 genotypes.

METHODS

Fifteen healthy volunteers were given 20 mg famotidine twice a day or 30 mg lansoprazole once a day for 8 days. On post-dose day 8, 24-h intragastric pH monitoring was performed.

RESULTS

During the daytime, the intragastric pH with lansoprazole was significantly higher than that with famotidine in the heterozygous extensive metabolizer group, whereas no significant difference was observed in the homozygous extensive metabolizer group. During the night-time, the intragastric pH with famotidine was quite similar to that with lansoprazole in the heterozygous extensive metabolizer and poor metabolizer groups. However, during the night-time, the intragastric pH with famotidine was significantly higher than that with lansoprazole in the homozygous extensive metabolizer group.

CONCLUSIONS

An insufficient acid inhibition by lansoprazole during the night-time in the homozygous extensive metabolizer group could be compensated for by famotidine. CYP2C19 genotype testing appears to be useful for predicting the optimal acid inhibitory drug treatment collated with circadian intragastric pH change.

Effects of CYP2C19 genotypic differences in the metabolism of omeprazole and rabeprazole on intragastric pH

BACKGROUND

Omeprazole is mainly metabolized in the liver by CYP2C19, a genetically determined enzyme, whereas rabeprazole is mainly reduced non-enzymatically and partially metabolized by CYP2C19. The therapeutic effects of rabeprazole are therefore assumed to be less affected by an individual's CYP2C19 status.

AIM

To investigate the acid inhibitory effects and plasma levels of omeprazole and rabeprazole with reference to different CYP2C19 genotypes.

METHODS

Fifteen healthy volunteers took a daily dose of 20 mg of omeprazole or rabeprazole for 8 days. On post-dose days 1 and 8, 24-h profiles of intragastric pH were recorded and plasma concentrations of omeprazole, rabeprazole and their metabolites were determined.

RESULTS

After single and repeated doses of omeprazole, the intragastric pH values and plasma concentrations of omeprazole and its metabolites were significantly dependent on the CYP2C19 genotype. Significant differences in the same kinetic and dynamic parameters were also observed after single doses of rabeprazole. Although the plasma levels of rabeprazole differed among the different CYP2C19 genotype groups after repeated doses, no significant differences in intragastric pH values were observed.

CONCLUSIONS

The acid inhibitory effects of omeprazole and rabeprazole are significantly dependent on the CYP2C19 genotype status, as well as on their intrinsic pharmacokinetic and pharmacodynamic characteristics and dosing schemes.

Comparison of reliability between the modified groin flap and the forearm flap in oral reconstruction

OBJECTIVE

The groin flap has the advantage of minimum donor-site morbidity, while having the disadvantage of short vascular pedicle of small caliber. Modification of the groin flap has improved the former disadvantage, but the latter one remains. The purpose of this study was to compare the reliability of the modified groin flap with the forearm flap.

STUDY DESIGN

Eleven modified groin flaps and 40 forearm flaps consecutively performed by a single surgeon in a hospital for patients with oral cancer were retrospectively reviewed.

RESULTS

The rate of total flap loss in the modified groin flap group (8.3%) was higher than that in the forearm flap group (2.5%). The rates of partial flap loss in both flaps were similar to those of total flap loss. The failures of the modified groin flap and the forearm flap were due to arterial and venous complications, respectively.

CONCLUSION

The modified groin flap appears to be a little less reliable than is forearm flap; nevertheless, it could be a good option for patients who desire less conspicuous postoperative scars.

Production and chemiluminescent free radical reactions of glyoxal in lipid peroxidation of linoleic acid by the ligninolytic enzyme, manganese peroxidase

Glyoxal is a key compound involved in glyoxal oxidase (GLOX)-dependent production of glyoxylate, oxalate and H2O2 by lignin-degrading basidiomycetes. In this paper, we report that glyoxal was produced from a metabolite of ligninolytic fungi, linoleic acid, by manganese peroxidase (MnP)-dependent lipid peroxidation. In the absence of the parent substrate of linoleic acid, the dialdehyde was oxidized by MnP and Mn(III) chelate to start free radical reactions with emission of chemiluminescence at 700-710 nm. The spectroscopic profile of the light emission is distinguishable from (a) singlet oxygen, (b) triplet carbonyls from dioxetane and alpha-hydroxyperoxyl radicals, and (c) biacyl triplet formed by the coupling of two acyl radicals. The photon emission of glyoxal by MnP was activated by co-oxidation of tartrate. The MnP-dependent oxidation of glyoxal in tartrate buffers continued for 10 days without addition of exogenous H2O2. The importance of these results is discussed in relation to the free radical chemistry of lignin biodegradation by wood rot fungi.

Effect of high-dose lansoprazole on intragastic pH in subjects who are homozygous extensive metabolizers of cytochrome P4502C19

BACKGROUNDS AND AIM

Lansoprazole is mainly metabolized by cytochrome P4502C19 (CYP2C19) in the liver. The effect of lansoprazole is assumed to be insufficient in subjects who are homozygous extensive metabolizers of CYP2C19. This study aimed to examine whether the CYP2C19 genotype status affected the acid-inhibitory effects of lansoprazole and to develop a strategy to overcome this pharmacogenetic problem.

METHODS

Eighteen Helicobacter pylori-negative healthy volunteers, whose CYP2C19 genotypic status had been assessed, participated in the study. They consisted of 7 subjects who were homozygous extensive metabolizers, 7 subjects who were heterozygous extensive metabolizers, and 4 subjects who were poor metabolizers of CYP2C19, who took a placebo or lansoprazole 30 mg once daily in the morning for 8 days. On day 8 of dosing, 24-hour intragastric pH values were recorded. Five of the homozygous extensive metabolizer subjects underwent the 24-hour intragastric pH monitoring on day 8 of dosing of lansoprazole 30 mg 4 times daily.

RESULTS

When lansoprazole 30 mg was given once daily, the mean 24-hour intragastric pH values in the subjects who were homozygous extensive metabolizers, heterozygous extensive metabolizers, and poor metabolizers were 4.5, 4.9, and 5.5, respectively (P <.005). On day 8 of dosing of lansoprazole 30 mg 4 times daily in subjects who were homozygous extensive metabolizers, the mean 24-hour intragastric pH value was 7.4.

CONCLUSION

The effect of lansoprazole on intragastric pH depended significantly on CYP2C19 genotype status. Complete acid inhibition could be achieved by the frequent administration of lansoprazole (eg, 30 mg 4 times daily) in subjects who were homozygous extensive metabolizers. A genotyping test of CYP2C19 status appears useful for prescribing an optimal dosing scheme of lansoprazole.

Differential effects of partial hepatectomy and carbon tetrachloride administration on induction of liver cell foci in a model for detection of initiation activity

Differential effects of partial hepatectomy (PH) and carbon tetrachloride (CCl(4)) administration on induction of glutathione S-transferase placental form (GST-P)-positive foci were investigated in a model for detection of initiation activity. Firstly, we surveyed cell proliferation kinetics and fluctuation in cytochrome P450 (CYP) mRNA levels by means of relative-quantitative real-time reverse transcriptase-polymerase chain reaction (RT-PCR) and CYP 2E1 apoprotein amount by immunoblotting (experiment I) after PH or CCl(4) administration. Next, to assess the interrelationships among cell proliferation, fluctuation of CYPs after PH or CCl(4) administration and induction of liver cell foci, the non-hepatocarcinogen, 1,2-dimethylhydrazine (DMH) was administered to 7-week-old male F344 rats and initiated populations were selected using the resistant hepatocyte model (experiment II). In experiment I, the values of all CYP isozyme mRNAs after PH or CCl(4) administration were drastically decreased at the 12-h time point. From 72 h, mRNAs for all CYP isozymes began increasing, with complete recovery after 7 days. The CYP 2E1 apoprotein content in the PH group fluctuated weakly, whereas in the CCl(4) group it had decreased rapidly after 12 h and was still low at the 48 h point. In experiment II, induction of GST-P-positive foci was related to cell kinetics in the PH group, with about a 6-h time lag between time for carcinogen administration giving greatest induction of GST-P-positive foci and peaks in bromodeoxyuridine (BrdU) labeling, presumably due to the necessity for bioactivation of DMH. With CCl(4) administration, induction of foci appeared dependent on the recovery of CYP 2E1. In conclusion, PH was able to induce cell proliferation with maintenance of CYP 2E1, therefore being advantageous for induction of liver cell foci in models to detect initiation activity.

Effects of smoking on myocardial injury in patients with conservatively treated acute myocardial infarction: a study with resting 123I-15-iodophenyl 3-methyl pentadecanoic acid/201Tl myocardial single photon emission computed tomography

Many reports have demonstrated that smokers who have suffered an acute myocardial infarction (AMI) have a better prognosis than nonsmokers. The present study investigated the effects of current smoking on myocardial injury with resting 123I-15-iodophenyl 3-methyl pentadecanoic acid (BMIPP)/201Tl myocardial single photon emission computed tomography in 103 patients with conservatively treated AMI. The left ventricular myocardium was divided into 9 segments and BMIPP and 201Tl defects were scored using a 5-point grading system (0 = normal and 4 = no uptake). The sum of the defect scores was defined as the total defect score. There was no significant difference in either the baseline severity of the coronary artery disease or the total defect scores for BMIPP and 201Tl between the current smoker and nonsmoker groups. The difference between the total defect scores for BMIPP and 201Tl tended to be larger in the current smoker group than in the nonsmoker group (2.0 +/- 1.9 vs 1.3 +/- 1.6, p = 0.056). Forty-one (53%) of 77 patients in the current smoker group exhibited a BMIPP/201Tl mismatch, whereas only 8 (31%) of 26 patients in the nonsmoker group did (p = 0.047). In conclusion, current smokers had more likelihood of salvageable myocardium in areas at risk, as demonstrated by BMIPP/201Tl mismatch, in AMI than nonsmokers.

Expression of cyclin kinase inhibitor p27(Kip1) in skin tumours of dogs

Skin tumours (n=148) of epidermal or hair follicle origin were examined immunohistochemically to determine the expression of p27(Kip1)(p27), a cyclin-dependent kinase inhibitor (CDKI), and of Ki-67. In normal skin, a large number of basal cells of the epidermis and hair follicles were positive for Ki-67 and many suprabasal epithelial cells were positive for p27. Most of the hair matrix cells were positive for Ki-67 but negative for p27. Hair papillae were strongly positive for p27. Squamous cell carcinomas had a p27 positive index (PI) significantly lower than that of trichoepitheliomas (P<0.005), basal cell tumours (P<0.05) and intracutaneous cornifying epitheliomas (P<0.001). In contrast, Ki-67 PIs of squamous cell carcinomas and pilomatrixomas were significantly higher than those of trichoepitheliomas, basal cell tumours and intracutaneous cornifying epitheliomas (P<0.01 to P<0.001). No significant difference was observed between the Ki-67 PI values of squamous cell carcinomas and pilomatrixomas. The results suggested that p27 is capable of suppressing cell proliferation in the differentiation of normal canine skin. In spite of being a benign neoplasm, pilomatrixomas had a low p27 expression; this may be a reflection of the proliferative potential of the hair matrix. The expression of p27 may be a useful marker for the analysis of cell kinetics.

Effects of genotypic differences in CYP2C19 status on cure rates for Helicobacter pylori infection by dual therapy with rabeprazole plus amoxicillin

Rabeprazole is a potent proton pump inhibitor and is mainly reduced to thioether rabeprazole by a non-enzymatic pathway and partially metabolized to demethylated rabeprazole by CYP2C19 in the liver. We intended to determine a cure rate for Helicobacter pylori infection by dual rabeprazole/amoxicillin therapy in relation to CYP2C19 genotype status prospectively. Ninety-seven patients with gastritis and H. pylori infection completed the dual therapy with 10 mg of rabeprazole bid and 500 mg of amoxicillin tid for 2 weeks. At 1 month after treatment, cure of H. pylori infection was assessed on the basis of histology, a rapid urease test, culture, polymerase chain reaction (PCR), and 13C-urea breath test. CYP2C19 genotype status was determined by a PCR-restriction fragment length polymorphism method. Of the 97 patients, 33 were homozygous extensive metabolizers (homEM), 48 were heterozygous extensive metabolizers (hetEM), and 16 were poor metabolizers (PM). Cure of H. pylori infection was achieved in 79 of the 97 patients (81.4%, 95%CI = 71.9-88.7). Significant differences in cure rates among the homEM, hetEM, and PM groups were observed; 60.6% (95%CI = 42.1-77.3), 91.7% (95%CI = 80.0-97.7), and 93.8% (95%CI = 69.8-99.8), respectively (P = 0.0007). Twelve patients without cure after initial treatment (10 homEMs and 2 hetEMs) were successfully retreated with rabeprazole 10 mg q.i.d. and amoxicillin 500 mg q.i.d. for 2 weeks. The cure rates for H. pylori infection by dual rabeprazole/amoxicillin therapy depended on the CYP2C19 genotype status. This dual therapy appears to be effective for hetEM and PM patients. However, high dose dual rabeprazole/amoxicillin therapy was effective even for homEM patients. Therefore, the genotyping test of CYP2C19 appears to be a clinically useful tool for the optimal dual treatment with rabeprazole plus amoxicillin.

Effects of cyclooxygenase-2 inhibitor on gastric acid secretion in Helicobacter pylori-infected C57BL/6 mice

BACKGROUND

Helicobacter pylori-associated body gastritis inhibits gastric acid secretion. The aim of this study was to determine the effects of H. pylori infection on gastric acid secretion and further determine whether cyclooxygenase-2 was involved.

METHODS

C57BL/6 mice (n = 40) were inoculated with the Sydney strain of H. pylori. Control mice (n = 40) were treated with vehicle only. Half of the infected and control mice were fed an experimental diet containing etodolac (10 mg/kg/day) from 1 week after inoculation until the end of the experiment. Before, 12 and 24 weeks after inoculation, the gastric acid secretion, prostaglandin E2 (PGE2) levels in the gastric mucosa, and gastritis scores according to the updated Sydney system were determined. Immunohistochemical staining of COX-2 protein was also performed.

RESULTS

No significant changes in gastric acid secretion, gastritis scores or PGE2 levels in the gastric mucosa were observed in uninfected groups with or without etodolac treatment during the study period. In the H. pylori-infected group without etodolac treatment, gastric acid secretion was significantly decreased with increases in PGE2 levels in the gastric mucosa 24 weeks after inoculation compared with the controls. Gastritis score for activity was significantly higher, and strong staining for COX-2 protein was observed in the H. pylori-infected group. In the H. pylori-infected group with etodolac treatment, PGE2 in the gastric mucosa was decreased and acid secretion was restored to the same level as in the control group.

CONCLUSION

One of the mechanisms by which H. pylori infection inhibits gastric acid secretion is increased release of PGE2 produced by COX-2, which is induced by H. pylori infection.

Involvement of cyclooxygenase-2 in hyperplastic gastritis induced by Helicobacter pylori infection in C57BL/6 mice

BACKGROUND AND AIMS

The hyperplastic changes observed in Helicobacter pylori-associated gastritis have been considered to increase the risk of gastric cancer. The aim of this study was to determine whether cyclooxygenase-2 is involved in the hyperplastic changes in mice infected with H. pylori.

METHODS

Seven-week-old, male C57BL/6 mice (n=40) were inoculated with the Sydney strain of H. pylori. Control mice (n=40) were treated with vehicle only. Half of the infected and control mice were fed an experimental diet containing etodolac (10 mg/kg/day) from 1 week after inoculation until the end of the experiment. The thickness of gastric pits, COX-2 mRNA and protein levels, and prostaglandin E2 (PGE2) levels in the gastric mucosa were determined before and 12, and 24 weeks after inoculation.

RESULTS

The thickness of gastric pits, COX-2 mRNA and protein levels, and PGE2 levels were significantly increased at 24 weeks after inoculation of H. pylori compared with the control groups. Treatment with etodolac resulted in significant decreases in PGE2 production and in the thickness of gastric pits in the infected groups at 24 weeks after inoculation.

CONCLUSIONS

Our findings suggest that COX-2 is involved in the development of hyperplastic gastritis caused by H. pylori infection via the production of PGE2.

Spawning and season affect lipid content and fatty acid composition of ovary and liver in Japanese catfish (Silurus asotus)

The influences of spawning and season on lipid content, lipid classes, and fatty acid composition were assessed in ovary and liver of wild and cultured Japanese catfish (Silurus asotus). The lipid content (7.3+/-1.6 g/100 g wet wt.) of ovary from wild catfish at spawning was higher than that at post-spawn. However, no influence of spawning on the lipid content of liver was observed. Docosahexaenoic acid [DHA, C22:6(n-3)] in ovary lipids was 12.3+/-0.5% of total fatty acids. The percentage of n-7 monounsaturated fatty acids in triacylglycerol from the ovary and liver in the spawning season was high. Percentages of C22:6(n-3) in phosphatidylcholine and phosphatidylethanolamine from ovary were higher during spawning than after spawning. No significant differences were observed in the lipid content of ovary and liver from cultured catfish between seasons (summer vs. winter). Content of arachidonic acid (C20:4n-6) in ovary and liver from cultured catfish was higher in summer than in winter. There were differences in lipid classes of ovary and liver by spawning and season. These results suggest that the lipid metabolism in Japanese catfish is greatly influenced by spawning and season.

Wavelength-multiplexing diffractive phase elements: design, fabrication, and performance evaluation

We report on the wavelength-multiplexing diffractive phase element (WMDPE) capable of generating independent spot patterns for different wavelengths. The iterative method proposed by Bengtsson [Appl. Opt. 37, 1998] for designing a kinoform that produces different patterns for two wavelengths is extended to the WMDPE for multiple wavelengths (more than two wavelengths). Effectiveness of the design algorithm is verified by design and computer simulations on the WMDPE's for four and nine wavelengths. The WMDPE for three wavelengths (441.6, 543.5, and 633 nm) is designed with five phase levels and is fabricated by electron-beam lithography. We observed that the individual spot patterns are reconstructed for the design wavelengths correctly. Performance of the WMDPE is evaluated by computer simulations on the uniformity error, the light efficiency, and the contrast. On the basis of the results, the characteristics of the WMDPE's are discussed in terms of various conditions of fabrication and usage.

Effect of genotypic differences in CYP2C19 on cure rates for Helicobacter pylori infection by triple therapy with a proton pump inhibitor, amoxicillin, and clarithromycin

BACKGROUND

Proton pump inhibitors such as omeprazole and lansoprazole are mainly metabolized by CYP2C19 in the liver. The therapeutic effects of proton pump inhibitors are assumed to depend on CYP2C19 genotype status.

OBJECTIVE

We investigated whether CYP2C19 genotype status was related to eradication rates of H pylori by triple proton pump inhibitor-clarithromycin-amoxicillin (INN, amoxicilline) therapy and attempted to establish a strategy for treatment after failure to eradicate H pylori.

METHODS

A total of 261 patients infected with H pylori completed initial treatment with 20 mg of omeprazole or 30 mg of lansoprazole twice a day, 200 mg of clarithromycin three times a day, and 500 mg of amoxicillin three times a day for 1 week. CYP2C19 genotypes of patients were determined with polymerase chain reaction-restriction fragment length polymorphism analysis. Patients without eradication after initial treatment were retreated with 30 mg of lansoprazole four times daily and 500 mg of amoxicillin four times daily for 2 weeks.

RESULTS

Eradication rates for H pylori were 72.7% (95% confidence interval, 64.4%-81.8%), 92.1% (confidence interval, 86.4%-97.3%), and 97.8% (confidence interval, 88.5%-99.9%) in the homozygous extensive, heterozygous extensive, and poor metabolizer groups, respectively. Thirty-four of 35 patients without eradication had an extensive metabolizer genotype of CYP2C19. Nineteen of those patients were infected with clarithromycin-resistant strains of H pylori. However, there were no amoxicillin-resistant strains of H pylori. Re-treatment of H pylori infection with dual high-dose lansoprazole-amoxicillin therapy succeeded in 30 of 31 patients with extensive metabolizer genotype of CYP2C19.

CONCLUSION

The majority of patients without initial eradication of H pylori had an extensive metabolizer CYP2C19 genotype but were successfully re-treated with high doses of lansoprazole and an antibiotic to which H pylori was sensitive, such as amoxicillin, even when the patients were infected with clarithromycin-resistant strains of H pylori.

Tumorigenicity of four optically active bay-region 3,4-diol 1, 2-epoxides and other derivatives of the nitrogen heterocycle dibenz[c,h]acridine on mouse skin and in newborn mice

The nitrogen heterocycle dibenz[c,h]acridine (DB[c,h]ACR) and the enantiomers of the diastereomeric pair of bay-region 3,4-diol 1, 2-epoxides as well as other bay-region epoxides and dihydrodiol derivatives of this hydrocarbon have been evaluated for tumorigenicity on mouse skin and in the newborn mouse. On mouse skin, a single topical application of 50 or 200 nmol of compound was followed 10 days later by twice-weekly applications of the tumor promoter 12-O:-tetradecanoylphorbol-13-acetate for 20 weeks. DB[c, h]ACR and the four optically pure, bay-region 3,4-diol-1,2-epoxide isomers all had significant tumor- initiating activity. The isomer with (1R,2S,3S,4R) absolute configuration [(+)-DE-2] was the most active diol epoxide isomer. The (-)-(3R,4R)-dihydrodiol of DB[c, h]ACR, the expected metabolic precursor of the bay-region (+)-DE-2, was 4- to 6-fold more tumorigenic than its corresponding (+)-enantiomer. In tumorigenicity studies in newborn mice, a total dose of 70-175 nmol of DB[c,h]ACR or one of its derivatives was injected i.p. on days 1, 8 and 15 of life, and tumorigenic activity was determined when the mice were 36-39 weeks old. DB[c,h]ACR produced a significant number of pulmonary tumors and also produced hepatic tumors in male mice. Of the four optically active bay-region diol epoxides, only (+)-DE-2 and (+)-DE-1 with (1R,2S,3S,4R) and (1S, 2R,3S,4R) absolute configuration, respectively, produced a significant tumor incidence. At an equivalent dose, the (+)-DE-2 isomer produced several-fold more pulmonary tumors and hepatic tumors than the (+)-DE-1 isomer. The (-)-(3R,4R)-dihydrodiol, metabolic precursor of the bay-region (+)-DE-2, was strongly active and induced an equal number of pulmonary and hepatic tumors as did DB[c,h]ACR. The (+)-(3S,4S) dihydrodiol was less active. The bay-region (+)-(1R,2S)-epoxide of 1,2,3,4-tetrahydro DB[c,h]ACR was strongly tumorigenic in newborn mice whereas its (-)-(1S, 2R)-enantiomer was inactive. This contrasts with the data on mouse skin where both enantiomers had substantial tumorigenic activity. In summary, the bay-region (+)-(1R,2S,3S,4R)-3,4-diol 1,2-epoxide of DB[c,h]ACR was the most tumorigenic of the four optically active bay-region diol epoxides of DB[c,h]ACR on mouse skin and in the newborn mouse. These results with a nitrogen heterocycle are similar to earlier data indicating high tumorigenic activity for the R,S,S,R bay-region diol epoxides of several carbocyclic polycyclic aromatic hydrocarbons.

p53 knockout mice (-/-) are more susceptible than (+/-) or (+/+) mice to N-methyl-N-nitrosourea stomach carcinogenesis

Mutations of the p53 tumor suppressor gene constitute one of the most frequent molecular changes in a wide variety of human cancers. Mice deficient in p53 have recently attracted attention for their potential to identify chemical genotoxins. In this study we have investigated the susceptibility of p53 nullizygote (-/-), heterozygote (+/-) and wild-type (+/+) mice to N:-methyl-N:-nitrosourea (MNU) gastric carcinogenesis. p53 knockout mice were treated with 30 p.p.m. MNU in the drinking water 1 week on and 1 week off and killed after 5 weeks. The numbers of pepsinogen-altered pyloric glands (PAPG), putative preneoplastic lesions, were 1.8, 1.7 and 22.6 in p53 (+/+), (+/-) and (-/-) mice, respectively. In a 15 week experiment, adenomas were found in 0 of 19 (+/+) (0%), 2 of 21 (+/-) (9.5%) and 6 of 10 (-/-) (60.0%) animals. Also, one well-differentiated adenocarcinoma was observed in a p53 (-/-) mouse. After 40 weeks treatment with 120 or 30 p.p.m. MNU there was no significant difference in the incidence of gastric tumors between p53 (+/+) and (+/-) mice. However, mortality from carcinogen-induced lymphomas, leukemias and sarcomas was very much greater in the latter group. Homozygous knockout animals could not be maintained long term. PCR-single strand conformation polymorphism analysis of exons 5-8 of the p53 gene of DNA extracts from 68 gastric tumors consisting of 16 and 20 30 p.p.m. MNU-treated p53 (+/+) and (+/-) mice and 14 and 18 120 p.p.m. MNU-treated p53 (+/+) and (+/-) mice demonstrated no mutations. These results suggest that p53 may not be a direct target of MNU but rather play an important role as a gatekeeper in mouse stomach carcinogenesis induced by this direct acting agent.