Mercuric chloride mediates a protein sulfhydryl modification-based pathway of signal transduction for activating Src kinase which is independent of the phosphorylation/dephosphorylation of a carboxyl terminal tyrosine

Little is known about the regulatory mechanism of c-Src kinase in cells except the suggested regulation through phosphorylation and dephosphorylation of its carboxyl terminal tyrosine residue (Y527). We here demonstrated that exposure of NIH3T3 cells to mercuric chloride (HgCl2) induces both aggregation and activation of Src kinase protein through a redox-linked mechanism. The aggregation of Src proteins was suggested to be induced by the sulfhydryl groups-to-Hg2+ reaction-mediated polymerization of cell membrane proteins to which the Src proteins associate noncovalently. The possibility was ruled out that the aggregation occurred secondarily to the promotion of protein tyrosine phosphorylation. Further study revealed that the Src kinase was activated by HgCl2 at least in part independent of the known Csk kinase-linked or Y527-phosphorylation/dephosphorylation-mediated control. Correspondingly, CNBr cleavage mapping of phosphopeptides for autophosphorylated c-Src protein demonstrated selective promotion of phosphorylation at Y416 in HgCl2-treated cells without obvious change in the phosphorylation level at Y527. These results suggest a unique protein sulfhydryl modification-based pathway of signal transduction for activating Src kinase in NIH3T3 cells.

Low expression of erythrocyte complement receptor type 1 in chronic hepatitis C patients

Primate erythrocyte complement receptor type 1 (CR1) plays an essential role in complement-associated immune complex clearance by transporting complexes to macrophages in the liver and/or spleen. Antibody-bound hepatitis C virus, which consists of immune complexes, is observed in patients with chronic hepatitis C. The aim of this study was to clarify the pathophysiological roles of erythrocyte CR1 in hepatitis C virus-infected individuals. We quantified the expression of erythrocyte CR1 with a fluorescence-activated cell sorter system in 57 chronic hepatitis C and 37 chronic hepatitis B cases and 20 normal volunteers. Complement-bound immune complexes were quantified by means of an enzyme-linked immunosorbent assay using anti-C1q and anti-C3d antibodies. Hepatitis C virus-infected patients showed lower erythrocyte CR1 and higher C3d immune complex levels than volunteers (P < 0.01 and P < 0.05, respectively). An inverse correlation was observed between the erythrocyte CR1 and C3d immune complex levels in hepatitis C virus infection (r = -0.300, P = 0.032). The erythrocyte CR1 levels in hepatitis C virus infection were lower in patients with severe liver inflammation, cirrhosis, or hepatocellular carcinoma than in those with mild inflammation, whereas the levels did not differ regardless of the disease stage in hepatitis B virus infection. These findings demonstrate that the expression of erythrocyte CR1 is related to immune complex quantity and the severity of liver disease in hepatitis C virus infection.

Truncation at the C-terminus of the DAX-1 protein impairs its biological actions in patients with X-linked adrenal hypoplasia congenita

The DAX-1 [DSS (dosage-sensitive sex)-AHC critical region in the X, gene 1] gene has been reported to be responsible for X-linked adrenal hypoplasia congenita (AHC) and hypogonadotropic hypogonadism. However, the function and structure of the DAX-1 protein have not been characterized. In this study, molecular analysis of the DAX-1 gene from 6 patients with AHC, including 2 siblings, identified 5 novel mutations with 3 nonsense mutations and 2 frameshift mutations. Case 1 had a nonsense mutation at position 395 (Q395X). Cases 2 and 3, who were siblings, had a nonsense mutation at position 91 (Y91X). Case 4 had a 2-base deletion (AT) at nucleotides 1610 and 1611 and a 1-base insertion (G) resulting in a premature stop codon at position 462 (1610-1611 del AT ins G). Case 5 had a nonsense mutation at position 271 (Y271X). Case 6 had a 1-base deletion (C) at nucleotide 1169, which induced a frame shift and a premature stop codon at position 371 (1169 del C). All mutated DAX-1 proteins had truncated C-terminal domains. In addition, reverse transcription-PCR and direct sequencing characterized the mutant messenger ribonucleic acid in testis from case 1. Our results suggest that these 5 novel mutations are responsible for X-linked AHC and that the C-terminus of the DAX-1 protein, especially the terminal 11 amino acids, is necessary for normal adrenal cortical embryogenesis.

Cardiac angiosarcoma

Angiosarcoma is one of the most common cardiac tumors, but early detection of this tumor is often difficult, as exemplified by our patient, a 55-year-old woman whose cardiac tumor was first detected by echocardiography. Surgical removal of the tumor was impossible due to its extensive pericardial invasion. Pathological diagnosis was not complete before autopsy because of the wide occupied necrotized area of the tumor. There is no diagnostic imaging technique available to detect such a necrotized area. An imaging technique more powerful than echocardiography and able to diagnose angiosarcoma earlier is needed.

Treatment with recombinant interferon-alpha 2a for patients with chronic hepatitis C: predictive factors for biochemical and virologic response. Osaka Liver Disease Study Group

BACKGROUND

The heterogeneity of the hepatitis C virus (HCV) genome has been reported to be associated with the effectiveness of interferon therapy. We investigated the correlation of the viral and host factors, including the degree of sequence complexity of the HCV genome for responses to interferon-alpha in patients with chronic hepatitis C.

METHODS

Ninety-seven patients received a 26-week course of recombinant interferon-alpha 2a therapy. The sequence complexity of the envelope 1-2 region was evaluated by polymerase chain reaction-mediated single-strand conformation polymorphism (PCR-SSCP) analysis.

RESULTS

Of the 85 patients who completed the treatment, 31 (36%) achieved a sustained response, and 28 (33%) showed a sustained loss of HCV RNA. A low HCV RNA level, determined by the branched DNA probe assay, and serotype group 2 HCV correlated with a sustained response. In patients with serotype group 1 HCV of more than the threshold of the branched DNA probe assay, a band number on PCR-SSCP analysis of more than 2 could be associated with inefficacy of interferon therapy. Multivariate analysis in the 50 patients whose sera were available for all the virologic tests showed that only the HCV RNA level is independently predictive of a sustained response.

CONCLUSIONS

Determination of the HCV RNA level is most important for predicting the response before interferon therapy. PCR-SSCP analysis may be useful as an additional test for patients with a high HCV RNA level of serotype group 1 HCV.

Raw-starch-digesting and thermostable alpha-amylase from the yeast Cryptococcus sp. S-2: purification, characterization, cloning and sequencing

A starch-degrading enzyme produced by the yeast Cryptococcus sp. S-2 was purified in only one step by using an alpha-cyclodextrin-Sepharose 6B column, and was characterized as an alpha-amylase (EC 3.2.1.1). The molecular mass and isoelectric point of purified alpha-amylase (AMY-CS2) were estimated to be 66 kDa and 4.2 respectively. AMY-CS2 has raw-starch-digesting and raw-starch-absorbing activities. Furthermore it was shown to be thermostable. An open reading frame of the cDNA specified 611 amino acids, including a putative signal peptide of 20 amino acids. The N-terminal region of AMY-CS2 (from the N-terminus to position 496) had 49.7% similarity with the whole region of alpha-amylase from Aspergillus oryzae (Taka-amylase), whereas the C-terminal region had a sequence that was similar to the C-terminal region of glucoamylase G1 from A. niger. In addition, putative raw-starch-binding motifs exist in some amylolytic enzymes. A mutant AMY-CS2 that lacks the C-terminal domain lost not only its ability to bind or digest raw starch, but also its thermostability. Consequently it is possible that the putative raw-starch-binding domain of AMY-CS2 plays a role not only in the molecule's raw-starch-digesting ability but also in its thermostability.

[Locoregional therapy for liver metastases of colorectal cancer]

The role of biological response modifiers (BRM) in locoregional therapy for liver metastases of colorectal cancer was studied clinically and experimentally. Seven patients with numerous metastases to both lobes of liver were given intraarterial administration of BRM in combination with anticancer drugs. A partial response was observed in 1 patient. The response rate was 14.3%. Alternatively, intraarterial administration of both OK-432 and IL-2 into the rabbit with liver metastases of VX-2 tumors could bring about the infiltration of cytotoxic T lymphocytes around the tumors, followed by a significant decrease of the metastatic nodules. In addition, the same anti-tumor effect was observed when PSK was administered intraperitoneally into the BALB/c mouse with liver metastases of colon 26 tumors. Moreover, the therapeutic effect of water in oil type emulsion encapsulating both OK-432 and IL-2 was greater than that of the solution of BRM in BALB/c mouse with liver metastases of colon 26 tumors. These results indicated that BRM could be one of the promising agents in locoregional therapy against liver metastases of colorectal cancer.

Application of a novel B cell line MIN6 to a mesh-reinforced polyvinyl alcohol hydrogel tube and three-layer agarose microcapsules: an in vitro study

This study examines the function of a novel B cell line (MIN6) enclosed in hybrid bioartificial pancreas with mesh-reinforced polyvinyl alcohol hydrogel tube (MRPT) or with improved, three-layer agarose microcapsules. MIN6 was established from insulinomas obtained by targeted expression of the simian virus 40 T-antigen gene in transgenic mice. MIN6 retains the ability to secrete insulin in response to physiological glucose concentrations. The MRPT and the three-layer agarose microcapsules, which were developed to act as an artificial pancreas, were readily permeated by insulin, glucose, and other nutrients. Both can immunoisolate enclosed MIN6 cells from the recipient's humoral and cellular immunosystems, which causes a xenogeneic rejection response. MIN6 cells (5.0 x 10(6) or 1.5 x 10(6)) were enclosed in MRPT or in a hundred three-layer microcapsules and subjected to an in vitro perifusion study or a static incubation study to observe the insulin release from each bioartificial pancreas in response to glucose stimulation. In vitro study revealed that the insulin secretion in response to 16.7 mM glucose stimulation was twice that with 3.3 mM glucose stimulation with both MRPT and the three-layer agarose microcapsules. The present study demonstrates that MIN6 effectively functions as a bioreactor for the hybrid bioartificial pancreas. The application of MIN6 cells to the hybrid bioartificial pancreas may offer a solution to the current serious dearth of organs.

Changes in liver blood flow after hepatectomy in conscious dogs

Hepatic circulation after hepatectomy was investigated in conscious dogs under fasting and feeding conditions. After a 40% hepatectomy, both the hepatic arterial and portal blood flow were measured simultaneously using ultrasonic transit time flowmeters. During fasting, the total hepatic blood flow (i.e., the sum of arterial and portal blood flow) changed in a biphasic pattern after hepatectomy. The first peak (517.9 +/- 42.7 ml/min; 130.1% of preoperative flow) was seen on the 1st postoperative day (POD) and the second peak (444.8 +/- 25.6 ml/min; 112.7% of preoperative flow) occurred on the 7th POD. The portal flow demonstrated the same biphasic changes as the total hepatic flow, although the hepatic arterial flow showed only the first peak. A heart rate analysis suggested that the first peak was probably due to hyperdynamic circulatory conditions, as has been previously reported. In addition, the existence of the second peak was established by the present study. The postprandial hepatic blood flow decreased during the first 2 weeks postoperatively, but exceeded the presurgical levels on PODs 21 and 28.

Successful coronary artery bypass grafting for a patient with myelodysplastic syndrome: report of a case

We report herein the case of a 61-year-old man with myelodysplastic syndrome causing pancytopenia who underwent successful coronary artery bypass grafting (CABG). Preoperatively, his hemoglobin (Hb) value was 10.4 g/dl while receiving transfusions of 1 or 2 units of red blood cells (RBC) every 2 weeks, his white blood cell (WBC) count was 8200/microliter with injections of 100 micrograms granulocyte colony-stimulating factor (G-SCF) every 5 days, and his platelet count was 4.5 x 10(4)/ microliter without platelet transfusion. From the time the pancytopenia was diagnosed in his peripheral blood, he had received a total of 104 units of RBC and 472 units of platelets, following which he developed an antiplatelet antibody, not for a platelet-specific antigen, but for an HLA antigen. Thus, HLA-matched platelets were prepared to prevent bleeding caused by thrombocytopenia, and the WBC count was elevated preoperatively by G-CSF injections. Thereafter, CABG was performed on three vessels. The HLA-matched platelets were transfused as the patient was weaned from the extracorporeal circulation. As a result of these preparations, we were able to protect the patient against bleeding and infection.

Examination of lesions in the urinary bladder and kidney of dogs induced by nefiracetam, a new nootropic agent

Toxic lesions induced by nefiracetam, a nootropic drug, in the urinary bladder and kidney were examined by repeated oral administration of 300 mg/kg/day for 1, 2, 3, 4, or 11 wk to male and female beagle dogs. Each dog was sacrificed after each treatment period, and urinalysis and serum biochemistry were performed for surviving dogs at several time points. One male and 2 females died during week 10 or 11. Degeneration and desquamation of epithelial cells and edema and hemorrhage in the lamina propria were observed in the urinary bladder after 1 wk of treatment. These changes became severe as time progressed and were reflected in the clinical abnormalities of hematuria and increased protein excretion in urine. However, epithelial regeneration and hyperplasia were seen thereafter, and almost no change was seen in the urinary bladder after treatment for 11 wk. Instead of recovery as in the urinary bladder, the kidney showed epithelial degeneration and hyperplasia in the papilla and collecting duct and interstitial congestion and hemorrhage after treatment for 11 wk. Extensive hemorrhage and papillary necrosis were seen in animals that died during week 10 or 11 of dosing. These kidney changes were associated with increased urinary volume and decreased osmotic pressure. The lesions are thought to have a common etiopathogenesis and to be initiated by the epithelial damage with a time lag between expression of injury in the urinary bladder and the kidney.

Somatic embryogenesis from immature leaves of in vitro grown tea shoots

Immature leaves of in vitro grown shoots of tea were cultured on various levels of 2,4-D. Somatic embryos were induced directly on leaves or via embryogenic callus produced at the basal regions of the leaves. Induction of embryogenesis appeared to be correlated with the maturity of the leaf explants, with younger leaves responding better. The embryogenic response of leaf explants also was correlated with the period of culture in 2,4-D containing liquid medium. Embryogenic calli or repetitive somatic embryos maintained their regeneration capacity for more than 3 years. Histological observation revealed somatic embryos were formed on various regions of the leaf midrib. Somatic embryos germinated and developed into plantlets on agar medium containing BA and IBA.

Exercise-induced U-wave changes in patients with coronary artery disease--correlation with tomographic thallium-201 myocardial imaging

We studied the relation between exercise-induced U-wave changes and the site of a reversible defect in tomographic 201Tl myocardial imaging. Coronary artery disease and control groups consisted of 116 and 42 patients, respectively. In the anteroapical-ischemia group (n = 37), the sensitivity of U-wave inversion in the anterior precordial leads for ischemia was 62% (23/37) and that of prominent U-waves without an increase in the height of the T-wave in the inferior limb leads was 57% (21/37). In this group, 18 patients (49%) met both criteria (18 [78%] of 23 patients with the former; 18 [86%] of 21 patients with the latter). In the posterior-ischemia group (n = 59), the sensitivity of prominent U-waves with a decrease in the height of the T-wave in the anterior precordial leads for ischemia was 63% (37/59) and that of U-wave inversion in the inferior limb leads was 20% (12/59). In this group, 12 patients (20%) met both criteria (12 [32%] of 37 patients with the former; all 12 patients with the latter). The specificity of U-wave criteria was 100%. In the anteroapical and posterior ischemia group (n = 20), the sensitivity of U-wave criteria for anteroapical and posterior ischemia was 85% (17/20) and 40% (8/20), respectively. In conclusion, U-wave criteria are not only specific but also sensitive for myocardial ischemia determined by 201Tl imaging.

Chemotherapeutic agent CPT-11 induces the new expression of the apoptosis initiator to the cytoplasm

CPT-11, a derivative of camptothecin, induced apoptotic cell death characterized by chromosomal DNA fragmentation in human hepatoma PLC cells in vitro. Cell viability of PLC cells was significantly decreased by CPT-11 in a dose-dependent manner, and CPT-11-induced cytotoxic activity was completely prevented by an interleukin-1 beta converting enzyme-like protease inhibitor YVAD and a protein synthesis inhibitor cycloheximide. To examine the roles of the cytoplasm and the nucleus in CPT-11-induced apoptosis, we prepared cytoplasts from PLC cells and nuclei from rat hepatocytes (RHN). Apoptotic cell death as characterized by cell fragmentation was observed in whole PLC cells but not in PLC cytoplasts after incubation with CPT-11. In addition, CPT-11 could not induce chromosomal DNA fragmentation in RHN. In contrast, the extracts of CPT-11-treated PLC cells, which mainly contained cytosol proteins, induced chromosomal DNA fragmentation of RHN in a dose-dependent manner. These results indicate that CPT-11-induced apoptosis required the presence of both the cytoplasm and the nucleus and suggest that the apoptosis required the de novo synthesis of an apoptosis initiator.

Reduced messenger RNA expression level of p21 CIP1 in human colorectal carcinoma tissues and its association with p53 gene mutation

p21 Cip1 was first isolated as one of the cyclin-dependent kinase (Cdk) interacting proteins induced by wild-type p53 gene product, and it appears to play an essential regulatory role in the control of cell proliferation as a potent, tight-binding inhibitor of cyclin-Cdk complex that blocks the G1/S transition of the cell cycle. We have now examined the p21 Cip1 mRNA expression levels in 16 surgically excised human colorectal tumor and non-tumor tissues by Northern-blot analysis with reference to the identification of p53 gene mutations. p53 gene mutations were detected in 6 tumor tissues but not in the other 10 tissues by the polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) method and following direct sequencing. The mean p21 Cip1 mRNA expression level in tumor tissues was significantly suppressed compared to that of non-tumor tissues, irrespective of p53 gene mutations. In p53 gene mutation-detected cases, the mean expression level of p21 Cip1 mRNAs of tumor tissues was about 60% of that of cases without p53 gene mutation. Moreover, the relative mRNA expression levels of p21 Cip1 significantly decreased as the pathohistological stages progressed by Dukes' staging system, while in patients with liver metastasis these levels were significantly suppressed compared to those of patients without organ metastasis. These results indicate that reduced expression of p21 Cip1 mRNA is critical for growth activity and malignant potential of human colorectal carcinoma, and that the decrease in p21 Cip1 mRNA level is due to p53 gene mutation as well as other mechanisms during human colorectal carcinogenesis.

Involvement of beta-glucuronidase in intestinal microflora in the intestinal toxicity of the antitumor camptothecin derivative irinotecan hydrochloride (CPT-11) in rats

Irinotecan hydrochloride (CPT-11), an antitumor camptothecin derivative, causes severe forms of diarrhea clinically. We characterized CPT-11-induced diarrhea histologically and enzymologically and assessed the relationships between intestinal toxicity and the activity of the enzymes that play a key role in the major metabolic pathway of CPT-11 in rats. CPT-11 (60 mg/kg i.v. for 4 days) induced intestinal toxicity characterized by severe chronic diarrhea, loss of body weight, and anorexia. Histological damage was most severe in the cecum. The segmental difference in the degree of the damage showed good correlation with the beta-glucuronidase activity in the contents of the lumen in each case, but not with the intestinal tissue carboxylesterase activity, which converts CPT-11 to its active form (7-ethyl-10-hydroxycamptothecin). Inhibition of the beta-glucuronidase activity in the intestinal microflora by antibiotics (1 mg penicillin and 2 mg streptomycin per ml of drinking water) markedly ameliorated the diarrhea and reduced cecal damage. Analysis of CPT-11 and its metabolites in the feces indicated that antibiotics completely inhibited the deconjugation of the glucuronic conjugate of 7-ethyl-10-hydroxycamptothecin by beta-glucuronidase. It is suggested that CPT-11-induced diarrhea would be attributable to the damage to the cecum, and that the inhibition of the beta-glucuronidase activity in the intestinal microflora is a major protective effect of antibiotics.

No significant changes in the expression of the fas,fasl,bcl-2 and bax genes in apoptosis of an erythroleukemic cell line by p53

A murine erythroleukemic cell line (1-2-3) which expresses only the temperature-sensitive mutant p53 gene (Ala-to-Val substitution at codon 135) was established. When these cells were cultured at 32 degrees C, the growth rate was reduced significantly and DNA fragmentation, a typical character of apoptosis, was observed. In this process, p53 migrated from cytoplasm to nucleus and protein complexes binding to the p53-responsive element were detected in nuclear extracts of the cells cultured at 32 degrees C by gel-shift assay and transactivation from the p53-responsive element was detected. The expression of the p21 (waf1/cip1/sdi1), cyclin G and gadd45 genes was increased (about 3- to 4-fold that at 37 degrees C), when the cells were cultured at 32 degrees C. However, no significant change was detected in expression of the mdm2, bax and fas genes. No change in the amount of Fas antigen was observed by flow cytometric analysis. Transcripts of the bcl-2 and fas1 gene were not detected in the cells either at 37 degrees C or 32 degrees C. These results suggest that other gene(s) than bax, fas, fas1 and bcl-2 may be important for induction of apoptosis of this erythroleukemic cell line by p53.

Acid xylanase from yeast Cryptococcus sp. S-2: purification, characterization, cloning, and sequencing

A xylan-degrading enzyme produced by yeast Cryptococcus sp. S-2 was isolated and purified, and characterized as an endoxylanase (1,4-beta-D-xylan xylanohydrolase [EC 3.2.1.8]). We estimated the molecular weight and isoelectric point of purified xylanase (xyn-CS2) to be 22,000 and 7.4, respectively. This low-molecular-weight xylanase had an unusual pH optimum of 2.0, and showed 75% of maximal activity even at pH 1.0. An open reading frame of the cDNA specified 209 amino acids, including a putative signal peptide of 25 amino acids. The deduced amino acid sequence of xyn-CS2 shared significant similarities with the family-G xylanases of B. pumilus, C. acetobutylicum, T. reesei, and A. kawachii. Xyn-CS2 included two unique cysteine residues in a putative catalytic region, raising the possibility that these residues are at least partially responsible for its acidophilic nature.

Loss of expression of transforming growth factor beta type I and type II receptors correlates with tumor grade in human prostate cancer tissues

Transforming growth factor beta1 (TGF-beta1) is a potential regulator of prostate cancer cell growth that signals through a heteromeric complex composed of type I and type II receptors. In the present study, an attempt was made to establish a correlation between expression of TGF-beta receptors and tumor grade in archival human prostate cancer tissues. To this end, immunohistochemical studies for TGF-beta receptors were carried out on 32 cases of human prostate cancer and 8 samples of benign human prostate. In both benign and malignant human prostate tissues, immunoreactivity for both type I and type II receptors was detected predominantly in epithelial cells. In addition, there was an inverse correlation between the loss of expression of TGF-beta1 type I and type II receptors and the tumor grade. Of the 32 prostate cancer cases screened, staining was completely absent in four samples for type II receptor (P < 0.05) and eight samples for type I receptor (P < 0.025). In contrast, all eight samples of benign prostate tissues investigated in this study showed strong staining for both type I and type II receptors. These results, taken together, indicate that human prostate cancer cells frequently have loss of expression of TGF-beta type I and/or type II receptors. Furthermore, these observations provide a potential mechanism for prostate cancer cells to escape the growth-inhibitory effect of TGF-beta.

Zopiclone pharmacodynamics: by monitoring event-related potentials and psychometric scores

To investigate the pharmacological effects of zopiclone in the central nervous system, we monitored event-related potentials (ERPs, N100 and P300), the reaction time and the scores for subjective mental and emotional state (by using the Polarity Profile Questionnaire, PPQ) on 10 healthy right-handed male volunteers between 21 and 32 years old. Subjects were randomly allocated to receive a single oral administration of zopiclone 7.5 mg or placebo at the first-session, and the drug was crossed over at the second session 1 week later. ERPs, the reaction time and the psychometric scores were monitored at pre-drug, and 1, 3 and 5 hours after drug administration. In the zopiclone group, the reaction time was prolonged significantly at 1 hour after drug administration, the amplitudes of the ERPs significantly decreased at 1 and 3 hours after, and the PPQ scores showed significant changes. Maximum effects on the psychometric scores appeared later than those on ERPs and reaction time. Zopiclone decreased the arousal level and sensory sensitivity, and induced sedation through changes in subjective mental and emotional states.

Prognostic value of monolayer culture patterning in primary cell culture of oesophageal cancer

The growth of primary cell cultures of oesophageal cancer was compared with the clinical outcome of patients from whom the cancers were taken. Ninety-three patients underwent curative resection, with no operative deaths, and were divided into three groups according to the monolayer culture pattern of the primary cell culture: culture from 43 patients (46 per cent) grew no malignant cells (group 1), 21 (23 per cent) produced monolayer epithelial growth (group 2) and the rest (from 29 patients) established cell lines (group 3). The 5-year survival rate of patients in group 2 (29 per cent) and group 3 (23 per cent) was significantly lower (P < 0.005) than that of those in group 1 (51 per cent). Monolayer epithelial growth potential is a significant prognostic factor in patients with oesophageal cancer.

Three-dimensional structure of a DNA repair enzyme, 3-methyladenine DNA glycosylase II, from Escherichia coli

The three-dimensional structure of Escherichia coli 3-methyladenine DNA glycosylase II, which removes numerous alkylated bases from DNA, was solved at 2.3 A resolution. The enzyme consists of three domains: one alpha + beta fold domain with a similarity to one-half of the eukaryotic TATA box-binding protein, and two all alpha-helical domains similar to those of Escherichia coli endonuclease III with combined N-glycosylase/abasic lyase activity. Mutagenesis and model-building studies suggest that the active site is located in a cleft between the two helical domains and that the enzyme flips the target base out of the DNA duplex into the active-site cleft. The structure of the active site implies broad substrate specificity and simple N-glycosylase activity.