Paraclinoid aneurysms of the internal carotid artery: hydraulic simulation study on their locations and shape of the carotid siphon

Hemodynamics of paraclinoid aneurysms were investigated focusing on the effects of their locations and shape of the carotid siphon. A transparent silicon model of the carotid siphon was constructed and a model aneurysm was attached to the outside of the curvature at three different sites. Glycerol solution was perfused into the model, and the half-life of the dye injected into the aneurysm was calculated as an index of the stagnant flow. Values of half-life changed significantly depending on the aneurysmal location and the siphon angle. When the siphon angle was 0 degree where C2 and C4 segments were parallel to each other, the half-life value was the lowest in the C2-C3 junction aneurysm, highest in the C3 segment aneurysm and intermediate in the C2 segment aneurysm. While the C2-C3 junction aneurysm maintained low values regardless of the angle, the C3 segment aneurysm values decreased and C2 segment aneurysm values increased with increases in the angle. These changes of half-life occur because the point at which the faster moving fluid component strikes the curved wall changes according to the siphon angle. These results are considered useful to determine the surgical indications, treatment modalities and post-surgical management of the aneurysms.

Effects of ebselen on cerebral ischemia and reperfusion evaluated by microdialysis

Since ebselen is known to have glutathione peroxidase-like activity and inhibitory effects on lipoxygenase and cyclo-oxygenase, we investigated its protective effects against cerebral ischemia in the rat using microdialysis. Ebselen was given through a gastric tube 30 min before occlusion in the experimental groups. Ischemia was induced using 4-vessel occlusion either transiently (20-min occlusion of the arteries followed by reperfusion), or over a prolonged period (120-min occlusion). Extracellular lactate, pyruvate and purine catabolites were sampled using microdialysis and measured by high performance liquid chromatography. During ischemia, the level of lactate, adenosine, inosine and hypoxanthine in the control group increased markedly. The lactate: pyruvate ratio increased during ischemia and decreased after reperfusion. Although the level of lactate and adenosine decreased immediately after reperfusion, those of inosine and hypoxanthine showed delayed decrease. Ebselen reduced the maximum values of lactate and purine catabolites significantly and markedly in transient ischemia. Although it reduced the values significantly in prolonged ischemia, the decrements were less marked than those in transient ischemia. Based on these results we consider ebselen to protect against ischemic metabolic changes and to accelerate the recovery during reperfusion.

[Simulation study on parent artery occlusion therapy for basilar head giant aneurysms: hemodynamic efficacy of additional bypass on enhancing aneurysmal thrombosis]

Parent artery occlusion therapy has been used as an alternative for directly untreatable basilar head giant aneurysms. However, some aneurysms still require additional technique to further induce intraaneurysmal stagnation and thrombosis. Using a hydraulic model, half-life of the dye in the model aneurysm was measured as an index of the intraaneurysmal stagnation. The ratio of diameters (D1, D2) of the two posterior communicating arteries (PCom) is defined as diameter ratio (DR) (D1/D2, D1 < D2). Occlusion therapy was simulated in 4 different sites. The most distal site was at the distal BA (Type A) and the most proximal site at the bilateral VA (Type D). The additional technique investigated was bypass placement to the P2 segment of the posterior cerebral artery (PCA) on the smaller PCom side. The half-life was 2.5 +/- 0.2 (mean +/- 2SD) sec before occlusion. Occlusion therapy significantly increased the half-life depending on the occlusion site and DR values with the maximum values of infinite in Type A and 25 sec in Type D. Placement of the bypass decreased the tangential flow volume to the aneurysmal neck, and increased the time markedly in Types A and B, considerably in Type C and slightly in Type D. Parent artery occlusion therapy has been considered less beneficial for patients with a diameter ratio of less than 0.70 since aneurysmal stagnation depends on the diameter ratio. Bypass placement additional to the occlusion therapy is very useful in enhancing the aneurysmal stagnation, which would make those patients indicated for the therapy.

Molecular analysis of mutations induced by a benzene metabolite, p-benzoquinone, in mouse cells using a novel shuttle vector plasmid

Human population has been continually exposed to benzene which is present in our environment as an essential component of petroleum. p-Benzoquinone (p-BQ) is one of the benzene metabolites and is thought to be an ultimate toxic or carcinogenic substance. For molecular analysis of carcinogen-induced mutations in mouse cells, we constructed a new shuttle vector plasmid pNY200 that has supF gene as a target of the mutations and replicates in mouse and in Escherichia coli cells. In p-BQ-treated pNY200 propagated in mouse cells, base substitutions were induced predominantly at G:C sites, and the major mutation was G:C-->A:T transition. Many tandem base substitutions were also induced at CC:GG sequences. By a postlabeling analysis and a polymerase stop assay, we confirmed that p-BQ adducts formed in DNA and mutation sites roughly correspond to the sites where the adducts were formed. Comparing data of pNY200 in mouse cells with those of the similar shuttle vector plasmid pMY189 in human cells should be important for extrapolation of data from mouse to human, because carcinogenicity of chemicals is tested in mice.

Neural mechanisms of soleus H-reflex depression accompanying voluntary arm movement in standing humans

This study have investigated the changes in soleus (Sol) H-reflexes by arm movement during freely standing (FS) and back-supported standing (BS) in healthy subjects. Before the arm movement, there is an anticipatory phase, which includes increased electromyographic (EMG) activity in the biceps femoris (BF) and decreased EMG activity of the Sol muscle. The Sol H-reflex appeared to be inhibited during the anticipatory phase as well as during the time of arm movement. However, the inhibition appeared to be larger in FS than in BS conditions. Vibration applied to the tendon of the BF muscle depressed the Sol H-reflex. This inhibition was attributed to presynaptic inhibition and was reduced during the anticipatory phase, and was not very much changed during arm movements. It is suggested that the depression of the Sol H-reflex induced by voluntary arm movement has two inhibitory components of different origins. Descending motor commands generate the early inhibitory component, while the late component is produced by the presynaptic inhibition that results from peripheral inputs. The inhibition related to anticipatory postural adjustment (APA) indicates that a new-setting of the spinal mechanisms is required and responsible in order to stabilize body equilibrium which is dependent upon different postural conditions.

Dependence of deltoid muscle activity upon initial angles of shoulder abduction prior to flexion

The present study was undertaken to investigate the hypothesis that the direction and selectivity of an appropriately modified version of shoulder flexion is dependent upon initial angles of shoulder abduction. Analysis indicated that initial small angles of shoulder abduction were associated with longer electromyographic (EMG) durations of the agonist (anterior deltoid) muscle. Moreover, as initial angles became smaller, EMG onsets of the antagonist (posterior deltoid muscle) occurred nearer to those of the agonist. Modulations of duration of the agonist EMG activity can be explained by changes in amplitude of movement. Two possible interpretations of the changes of EMG onset of the antagonist in accordance with different initial angles of shoulder abduction are considered. One concerns the effect of the change on the load of the upper limb, dependent on different angles of shoulder abduction. The second concerns the changing role of the antagonist to a synergist, dependent upon decreased initial angles of shoulder abduction prior to the shoulder flexion. Based on the present findings, it is suggested that angles of shoulder abduction are an important determinant of agonist-antagonist muscle activity of the deltoid during flexion of the shoulder.

Effect of interferon therapy on hepatocellular carcinogenesis in patients with chronic hepatitis type C: A long-term observation study of 1,643 patients using statistical bias correction with proportional hazard analysis

The activity of interferon (IFN) is not elucidated from the viewpoint of cancer prevention in chronic hepatitis C patients en masse. The hepatocellular carcinogenesis rate was analyzed statistically in 1,643 patients with chronic hepatitis C: 1,191 patients with IFN therapy and 452 without IFN therapy. Hepatocellular carcinogenesis rates in the treated and untreated groups were 2.1% and 4.8% at the end of the 5th year, and 7.6% and 12.4% at the 10th year, respectively (P =.0036). Multivariate analysis showed that IFN slightly decreased the risk of carcinogenesis by 33%, compared with that of untreated patients (P =. 14), adjusting for the confounding effects of age, fibrotic stage, gender, and gamma-glutamyl transpeptidase (GGTP) value. Among 1,191 patients with IFN, 461 patients attained persistent loss of hepatitis C virus (HCV) RNA, and the other 145 patients retained normal alanine transaminase (ALT) values without loss of HCV RNA. The hazard of carcinogenesis in these 606 patients with persistent normal ALT with or without HCV-RNA clearance was significantly lower than that of untreated patients (hazard ratio: 0.32; P =.012) and that of the abnormal aminotransferase group. Among patients with chronic hepatitis C, IFN significantly decreased the hepatocellular carcinogenesis rate in those patients with normal or persistent low ALT values.

Simulation of therapeutic parent artery occlusion for basilar head aneurysms. Hemodynamic effect of occlusion sites and diameters of collateral arteries

We simulated parent artery occlusion therapy for basilar head aneurysms to elucidate the hemodynamic changes induced by different occlusion sites and diameters of the posterior communicating arteries (PCom) as collateral pathways. A vascular model of the vertebrobasilar system with a basilar head aneurysm was constructed. Four types of occlusion were simulated: Basilar artery occlusion distal to (Type A), between (Type B) and proximal to (Type C) the superior cerebellar arteries, and bilateral vertebral artery occlusion (Type D). Glycerol solution was perfused into the model, and the half-life of the dye injected into the aneurysm was calculated and regarded as an index of stagnant flow in the aneurysm. The half-life was increased significantly and nonlinearly after parent artery occlusion, depending on the occlusion site and the ratio of two PCom diameters (diameter ratio). Intra-aneurysmal stagnation developed markedly in Type A and Type B in the diameter ratio higher than 0.70 and considerably in Type C in the ratio higher than 0.80. Additional P1 occlusion of the posterior cerebral artery enhanced the stagnation in Type A and B. Since the results are consistent with the published clinical data, the simulation study will be useful for speculating the efficacy of the therapeutic occlusion.

Generation of hydrogen peroxide precedes loss of mitochondrial membrane potential during DNA alkylation-induced apoptosis

Pulsed field gel electrophoresis showed that the initiation time of DNA breakage induced by the DNA alkylating agent duocarmycin A, which is not a redox-cycling agent, was almost the same in the human leukemia cell line HL-60 and its H2O2-resistant clone HP100. Catalase activity of HP100 cells was much higher than that of HL-60 cells. Duocarmycin A-mediated DNA ladder formation in HP100 cells was delayed compared with that in HL-60 cells, suggesting the involvement of H2O2 in duocarmycin A-induced apoptosis. Flow cytometry demonstrated that peroxide formation preceded loss of mitochondrial membrane potential (delta psi m) in cells treated with duocarmycin A. Then, caspase-3 was activated, followed by DNA ladder formation. These findings suggest that DNA damage by duocarmycin A induces H2O2 generation, which causes delta psi m loss and subsequently caspase-3 activation, resulting in apoptosis.

Mutagenic specificity of a derivative of 3-nitrobenzanthrone in the supF shuttle vector plasmids

3-Nitrobenzanthrone (NBA) is a powerful bacterial mutagen and a suspected human carcinogen present in diesel exhaust and airborne particulates [Enya, T., et al. (1997) Environ. Sci. Technol. 31, 2772-2776]. In the accompanying paper [Enya, T., et al. (1998) Chem. Res. Toxcol. 11, 1460-1467], N-acetoxy-N-acetyl-3-aminobenzanthrone (N-Aco-N-Ac-ABA) was synthesized to yield the DNA adducts of NBA. In this work, to investigate the mutagenic specificity of NBA in human cells, we analyzed mutations induced by N-Aco-N-Ac-ABA using the supF shuttle vector plasmids. Base sequence analysis of 110 and 100 plasmids with mutations in the supF gene propagated in normal cells [WI38-VA13] and nucleotide excision repair deficient cells [XP2OS(SV)], respectively, revealed that the majority of the mutations were base substitutions (85 and 90%) and the rest were deletions and insertions (10 and 15%) in both cell lines. About half of the mutant plasmids had a single base substitution. Of the base substitutions, the most frequent mutation was G.C to T.A transversion (41 and 51%), followed by G.C to A.T transitions (18 and 24%) in either cell. The mutations were distributed not randomly but located at several hot spots, and almost all (nine of ten) hot spots were at the sites of G.C base pairs. The polymerase stop assay in the supF gene revealed that N-Aco-N-Ac-ABA preferentially bound to guanine residues, and mutation sites were generally consistent with the sites where the guanine adducts were formed.

An unusual DNA adduct derived from the powerfully mutagenic environmental contaminant 3-nitrobenzanthrone

The covalent binding of an N-hydroxy metabolite of the powerfully mutagenic 3-nitrobenzanthrone (NBA) to 2'-deoxyguanosine (dG) and calf thymus DNA has been investigated in vitro. The major adduct obtained from the reaction of the N-acetoxy-N-acetyl derivative (N-Aco-N-Ac-ABA) of 3-aminobenzanthrone (ABA) and dG was identified as N-acetyl-3-amino-2-(2'-deoxyguanosin-8-yl)benzanthrone (dG-N-Ac-ABA) by 1H NMR and mass spectroscopies as well as by the reaction of N-Aco-N-Ac-ABA with the double-stranded calf thymus DNA. The coupling with the dG moiety occurred exclusively at C-2 of benzanthrone (BA), suggesting a significant contribution of a resonance-stabilized arenium ion intermediate derived from BA to the production of this new type of adduct. The preferred conformation of the adduct has been shown to be syn by 1H and 13C NMR.

Abnormal branching of facial nerve with ossicular anomalies: report of two cases

Two cases with almost identical anomalies of the facial nerve and ossicles were reported. The two girls, ages 9 and 14 years, with unilateral hearing loss underwent exploratory tympanotomy. A huge suprameatal spine and tumor-like swelling of the facial nerve at the tympanic portion as well as its abnormal branching at the pyramidal bend were noted; one of the branches of the facial nerve appeared on the surface of the temporal bone running through the tympanomastoid suture. The distal parts of the long process and lenticular process of incus were missing as if they were eroded by the swollen facial nerve, and the superstructure of the stapes also was absent. No anomaly was seen in any other part of their ears or bodies. This specific type of anomaly is considered rare and important in that surgeons may misdiagnose the swollen facial nerve as a tumor, resulting in facial nerve paralysis due to injury or unnecessary biopsy.

[Rare intra-abdominal complications of a ventriculoperitoneal shunt: report of three cases]

Three cases of rare intra-abdominal complications of ventriculoperitoneal shunt (VPS) surgery are reported. Case 1 was a 32-year-old male who had undergone VPS surgery for hydrocephalus following meningitis on July 10, 1980. Two weeks later he developed fever and a cystic mass about 10 cm in diameter in the right hypochondrium. Shuntography and a barium enema study demonstrated a pseudocyst at the distal end of the shunt. The cyst wall was excised, the peritoneal tube removed, and VPS converted to a ventriculoatrial route following which the pseudocyst resolved. Case 2 was a 49-year-old female who developed hydrocephalus following subarachnoid hemorrhage, and VPS surgery was performed on March 10, 1989. Two weeks later, she developed fever and right upper abdominal pain. Abdominal x-ray and CT scan revealed a right subdiaphragmatic abscess. The abscess was drained and the shunt system was removed on April 4. VPS was placed again on April 21 without further complications. She was symptom free for the next 7 years. Case 3 was a 57-year-old female who presented in a semicomatose state after falling from bed on May 5, 1995. CT scan showed left-sided acute subdural hematoma (ASDH) for which surgery was performed. Her neurological status improved postoperatively. She eventually developed hydrocephalus and left-sided subdural effusion for which right VPS and left subduroperitoneal shunt (SPS) surgery was performed on January 25, 1996. The peritoneal end of the tube of the SPS protruded out of the anus one and a half year after shunt placement. The entire SPS system was removed as there was no more collection in the subdural space. We reviewed the literature and discussed the pathophysiology involved in the development of intraabdominal complications following VPS.

Molecular analysis of mutations induced by acrolein in human fibroblast cells using supF shuttle vector plasmids

Types of mutations induced by acrolein in the supF gene on the shuttle vector plasmid pMY189 replicated in normal human fibroblast cells were examined. Base sequence analysis of 92 plasmids with mutations in the supF gene revealed that the majority of the mutations were base substitutions (76%) and the others were deletions and insertions (24%). Single base substitutions were most frequently found (46%), while multiple base substitutions were 18% and tandem (two adjacent) base substitutions were 12% of the mutations. Of the base substitution mutations, G:C to T:A transversions were 44% and G:C to A:T transitions were 24%. The mutations were distributed not randomly but located at several hotspots. Acrolein produced DNA intra-strand cross-links between guanine residues, which might be responsible for rather high induction of the tandem base substitution mutations.

Inhibition of insulin-induced GLUT4 translocation by Munc18c through interaction with syntaxin4 in 3T3-L1 adipocytes

Insulin induces the translocation of vesicles containing the glucose transporter GLUT4 from an intracellular compartment to the plasma membrane in adipocytes. SNARE proteins have been implicated in the docking and fusion of these vesicles with the cell membrane. The role of Munc18c, previously identified as an n-Sec1/Munc18 homolog in 3T3-L1 adipocytes, in insulin-regulated GLUT4 trafficking has now been investigated in 3T3-L1 adipocytes. In these cells, Munc18c was predominantly associated with syntaxin4, although it bound both syntaxin2 and syntaxin4 to similar extents in vitro. In addition, SNAP-23, an adipocyte homolog of SNAP-25, associated with both syntaxins 2 and 4 in 3T3-L1 adipocytes. Overexpression of Munc18c in 3T3-L1 adipocytes by adenovirus-mediated gene transfer resulted in inhibition of insulin-stimulated glucose transport in a virus dose-dependent manner (maximal effect, approximately 50%) as well as in inhibition of sorbitol-induced glucose transport (by approximately 35%), which is mediated by a pathway different from that used by insulin. In contrast, Munc18b, which is also expressed in adipocytes but which did not bind to syntaxin4, had no effect on glucose transport. Furthermore, overexpression of Munc18c resulted in inhibition of insulin-induced translocation of GLUT4, but not of that of GLUT1, to the plasma membrane. These results suggest that Munc18c is involved in the insulin-dependent trafficking of GLUT4 from the intracellular storage compartment to the plasma membrane in 3T3-L1 adipocytes by modulating the formation of a SNARE complex that includes syntaxin4.

Surgical treatment of distal cervical internal carotid artery aneurysm

We report on a 55-year-old male with an internal carotid artery aneurysm at the level of the second cervical vertebra. Since ant-coagulation therapy failed to prevent the ischemic attack, aneurysmectomy with arterial reconstruction was performed. Vertical mandibular osteotomy allowed a wide working space in deep operative field. This technique is considered to be useful in surgery for aneurysms of the extracranial distal internal carotid artery.

Association of CDKN2A(p16)/CDKN2B(p15) alterations and homozygous chromosome arm 9p deletions in human lung carcinoma

To elucidate the possibility of the existence of multiple tumor suppressor genes on chromosome arm 9p, we performed genetic and epigenetic analyses of the CDKN2A/p16/MTS1 and CDKN2B/p15/MTS2 genes as well as homozygous deletion mapping of 9p in human lung carcinoma. To avoid overlooking genetic alterations due to contamination of noncancerous cells, we examined 32 non-small cell lung carcinoma (NSCLC) and 16 cell small cell lung carcinoma (SCLC) cell lines. (CDKN2A was mutated or homozygously deleted in 20 (63%) of 32 NSCLC cell lines, and methylation of the CpG island in the CDKN2A gene was detected in six of the 12 cell lines carrying the wild-type CDKN2A gene. Although homozygous deletions of the CDKN2B gene were also detected in NSCLC cell lines with CDKN2A deletions, mutation and methylation in the CDKN2B gene were infrequent. Thus, it was indicated that the CDKN2A gene rather than the CDKN2B gene plays a critical role as a tumor suppressor gene in NSCLC. Homozygous deletions on 9p were detected in 14 (44%) NSCLC cell lines. It is of note that two common regions of homozygous deletions were mapped proximal to the CDKN2A and CDKN2B loci, suggesting that tumor suppressor genes other than CDKN2A are present on 9p. In contrast to NSCLC, homozygous deletions on 9p as well as CDKN2A and CDKN2B alterations were infrequent in SCLC. Therefore, the pathogenetic significance of 9p alterations is likely to differ between SCLC and NSCLC.

[A case of choroidal malignant melanoma in which 123I-IMP scintigraphy was useful for diagnosis]

A case of choroidal malignant melanoma in which N-isopropyl-p-[123I]-iodoamphetamine (123I-IMP) scintigraphy was useful for diagnosis is reported. A 62-year-old man first visited our hospital 3 years ago complaining of decreases in left eyesight. CT showed a tumor with an arcuate high attenuation area on the aural side of the optic disk in the left eye. A crescent high attenuation area, evidence of retinal detachment, was also observed on the nasal side of the optic disk. T1-weighted MR images showed low signal intensity in most of the tumor and a high signal intensity area was seen in the center, T2-weighted MR images showed homogeneous and marked low signal intensity area. Differentiation from a hematoma or a vascular tumor associated with bleeding was impossible based on CT and MRI. However, because late-phase images obtained on 123I-IMP scintigraphy showed marked high accumulation in an area corresponding to almost the entire left eye, left eye enucleation was undertaken under a diagnosis of malignant melanoma. Histopathologic examinations showed tumor growth mainly in the subretinal area. The melanin content of the tumor was high in the periphery and relatively low in the center. Infiltration was observed into the sclera and around the vortex vein outside the eyeball, but this change could not be detected by CT or MRI. 123I-IMP scintigraphy was useful not only for qualitative diagnosis of choroidal malignant melanoma, but for the determination of the extent of the lesion as well.

Posture-dependent modulation of reciprocal inhibition upon initiation of ankle dorsiflexion in man

The present study tested whether soleus H-reflex depression recorded from normal subjects during isotonic ankle dorsiflexion is due to reciprocal inhibition and this might be modulated by varying postures. The soleus H-reflex amplitude of eight healthy adults was investigated at various times prior to and during tibialis anterior discharge while subjects were seated and when standing. Results showed that the amount of soleus H-reflex depression was significantly larger in the standing than that in the sitting posture in spite of the same dorsiflexion movement. Furthermore, the depression upon initiation of dorsiflexion movement appeared earlier in the standing than in the sitting. The results suggest that increasing amounts of reciprocal inhibition are correlated with and dependent upon the preceding postural conditions for voluntary movement, i.e., modulation of reciprocal inhibition seems to be dictated by the difference in functional demand between sitting and standing posture.

Specific tandem GG to TT base substitutions induced by acetaldehyde are due to intra-strand crosslinks between adjacent guanine bases

Acetaldehyde is present in tobacco smoke and automotive exhaust gases, is produced by the oxidation of ethanol, and causes respiratory organ cancers in animals. We show both the types and spectra of acetaldehyde-induced mutations in supF genes in double- and single-stranded shuttle vector plasmids replicated in human cells. Of the 101 mutants obtained from the double-stranded plasmids, 63% had tandem base substitutions, of which the predominant type is GG to TT transversions. Of the 44 mutants obtained from the single-stranded plasmids, 39% had tandem mutations that are of a different type than the double-stranded ones. The GG to TT tandem substitutions could arise from intra-strand crosslinks. Our data indicate that acetaldehyde forms intra- as well as inter-strand crosslinks between adjacent two-guanine bases. Based upon the following observations: XP-A protein binds to acetaldehyde-treated DNA, DNA excision repair-deficient xeroderma pigmentosum (XP) cells were more sensitive to acetaldehyde than the repair-proficient normal cells, and a higher frequency of acetaldehyde-induced mutations of the shuttle vectors was found in XP cells than in normal cells, we propose that the DNA damage caused by acetaldehyde is removed by the nucleotide excision repair pathway. Since treatment with acetaldehyde yields very specific GG to TT tandem base substitutions in DNA, such changes can be used as a probe to identify acetaldehyde as the causal agent in human tumors.

Homozygous deletion and frequent allelic loss of the 21q11.1-q21.1 region including the ANA gene in human lung carcinoma

The frequent occurrence of 21q deletions in human non-small cell lung carcinoma (NSCLC) indicates the presence of a tumor suppressor gene on this chromosome arm. Since the ANA (Abundant in Neuroepithelium Area) gene, a member of an antiproliferative gene family, was mapped to 21q11.2-q21.1, we searched for genetic alterations of the ANA gene in human lung cancers. The gene was homozygously deleted in a human NSCLC cell line, Ma17. The gene was mapped in the 0.33 Mb Not1 fragment at 21q21.1 of the Not1 restriction map for 21q. Loss of heterozygosity (LOH) at this locus was detected in 24/47 (51.1%) of NSCLC, and the frequency of LOH in brain metastases was significantly higher than that in stage I-II primary tumors (P = 0.018). These results suggested that the homozygously deleted region harbors a novel tumor suppressor gene involved in NSCLC progression. Since mutation of the ANA gene was not detected in other lung cancer cell lines and fresh lung tumors with LOH at this locus, it is unlikely that the ANA gene is a target gene inactivated by two mutational events in this chromosomal region. Physical mapping of the homozygously deleted region showed that the deletion had occurred interstitially at 21q11.1-q21.1 and the size of the deletion was estimated as being more than 3 Mb. Our mapping results will facilitate further efforts to identify a tumor suppressor gene on 21q.

Identification of CpG islands hypermethylated in human lung cancer by the arbitrarily primed-PCR method

DNA hypermethylation is believed to be involved in human carcinogenesis, since it suppresses the transcription of defined genes and is associated with chromosomal instability. In this study, we identified CpG islands that are hypermethylated in human lung cancer by a modified arbitrarily primed-polymerase chain reaction method using genomic DNAs digested with a methylation-sensitive restriction enzyme, HpaII, as templates. When we analyzed genomic DNAs from normal lung tissues and non-small cell lung carcinoma cell lines using three arbitrary primers, three DNA fragments were amplified from lung cancer DNAs but not from normal lung DNAs. Restriction mapping and Southern blot analysis revealed that all of these bands were amplified from CpG islands that were hypermethylated in the lung cancer cell lines. These islands were mapped to chromosomes 4q34, 10q26 and 17p13.1-p13.2, respectively, and these chromosomal regions were also hypermethylated in a subset of primary lung tumors in vivo. Thus, diverse chromosomal regions are hypermethylated in lung cancer cells. The results also indicate that this method is simple and effective for screening of CpG islands that are hypermethylated in cancer cells.

A spectrum of mutations induced by crotonaldehyde in shuttle vector plasmids propagated in human cells

A spectrum of crotonaldehyde-induced mutations in the supF gene of the shuttle vector plasmid pMY189 replicated in human fibroblast cells was examined. Base sequence analysis of 104 plasmids with mutations in the supF gene revealed that the majority of the mutations were base substitutions (85%) and the rest were frameshifts (15%). A single base substitution was most frequently found (47%), while 25% had multiple base substitutions and interestingly 13% had tandem (adjacent two) base substitutions. Of the base substitution mutations, 50% were G:C-->T:A transversions and 23% were G:C-->A:T transitions. The mutations were not distributed randomly but were located at several hotspots, most of which were G:C base pairs in 5'-AAGG-3' (or 5'-CCTT-3') sequences. Production of propanodeoxyguanosine adducts may be related to such specificity in the mutation spectrum.