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.

Allelotype and replication error phenotype of small cell lung carcinoma

Allelotype and replication error (RER) phenotype analyses were performed to clarify the pathogenetic significance of inactivation of tumor suppressor genes and genomic instability in the genesis and progression of small cell lung carcinoma (SCLC). We examined 37 cases of SCLC for loss of heterozygosity (LOH) and microsatellite instability at 49 loci on all 39 nonacrocentric chromosomal arms. LOH was frequently (>70%) detected on chromosomes 3p (29/32, 90.6%), 5q (15/21, 71.4%), 13q (25/26, 96.2%), 17p (22/25, 88.0%), and 22q (24/33, 72.7%). Frequent LOH (>70%) on these loci was observed even among seven cases of stage I tumors. The incidence of LOH on all 39 nonacrocentric chromosomal arms was not significantly different between primary tumors and metastases. These results suggest that inactivation of multiple tumor suppressor genes accumulates relatively early during progression of SCLC and it may be responsible for clinically and biologically aggressive phenotype of SCLC. RER was observed in 6/37 (16.2%) of SCLC, however, RER at multiple loci was observed only in two cases. Therefore, it was indicated that genomic instability is uncommon, but might play a role in the genesis of a small subset of SCLC.

[Salivary gland masses: dynamic MR imaging and pathologic correlation]

PURPOSE

To evaluate the efficiency of dynamic contrast-enhanced magnetic resonance imaging (MRI) for the diagnosis of salivary gland masses.

MATERIALS AND METHODS

We retrospectively examined 19 salivary gland masses that were pathologically diagnosed by surgical operation or biopsy. We obtained T1- and T2-weighted images on MRI, performed dynamic studies on each mass and examined the correlation between enhancement patterns and pathological findings.

RESULTS

Four enhancement patterns were recognized on contrast-enhanced MRI: type 1 showed marked, homogeneous enhancement; type 2 slight, homogeneous enhancement; type 3 marginal enhancement; and type 4 poor enhancement of the mass. Most pleomorphic adenomas had a type 1 enhancement pattern, but two had a type 2 pattern. Pathologically, each mass enhancement pattern had different tumor cell and matrix components. Warthin's tumor generally showed the type 4 pattern. Primary malignant tumors of the salivary gland all showed the type 3 pattern, and pathological specimens showed many tumor cells along the marginal portion of the tumor. One inflammatory cyst and one Warthin's tumor also showed the type 3 pattern. Except for metastatic renal cell carcinoma, the enhancement patterns of late phase images and dynamic study images were the same.

CONCLUSIONS

Dynamic MRI added little diagnostic information about salivary gland masses, but the contrast-enhanced MR features correlated well with the pathological findings.

Inhibition of the binding of SNAP-23 to syntaxin 4 by Munc18c

SNARE proteins have been implicated in the insulin-induced translocation of vesicles containing the GLUT4 glucose transporter to the plasma membrane of adipocytes. The role of the target SNARE SNAP-25 or its homologs in this process was investigated by screening a mouse adipocyte cDNA library with rat SNAP-25 and human SNAP-23 cDNA probes. Both positive clones isolated encoded a protein with 87% sequence identity to human SNAP-23, and which was therefore designated mouse SNAP-23. Immunoblot and immunofluorescence analyses revealed that SNAP-23 is located predominantly in the plasma membrane of 3T3-L1 adipocytes incubated in the absence or presence of insulin. Of syntaxins 1 to 5, SNAP-23 bound with the highest affinity to syntaxins 1 and 4 in the yeast two-hybrid system. Expression of SNAP-23, syntaxin 4, and the syntaxin-binding protein Munc 18c in COS cells revealed that Munc18c reduced the amount of SNAP-23 bound to syntaxin 4 in a concentration-dependent manner. These results suggest that the binding of SNAP-23 to syntaxin 4 is inhibited by Munc18c in adipocytes.

Topographic anatomy of paraclinoid carotid artery aneurysms: usefulness of MR angiographic source images

We evaluated the usefulness of magnetic resonance angiography (MRA) for showing the topography of paraclinoid carotid artery aneurysms in 27 patients with 30 paraclinoid aneurysms undergoing conventional angiography, three-dimensional time-of-flight MRA and surgery. The anatomy shown on the axial MRA source images was consistent with that found at surgery. The neck of the aneurysm could always be identified on the source images, while it could not be analysed exactly on conventional angiography in 3 cases (10%). The optic nerves, including those displaced by the aneurysm, were recognised in all patients. The anterior clinoid process was shown as a low-intensity rim or area contiguous with the cortical bone. The source images were of great value in understanding the topography of paraclinoid carotid artery aneurysms.

Quantitative analysis of NM23 protein immunoreactivity in renal cell carcinoma using an image analyzer

PURPOSE

nm23 is a candidate tumor suppressor gene. Whether or not tumor metastasis suppressive activity is present in renal cell carcinoma (RCC) was studied.

MATERIALS AND METHODS

Immunohistochemical analysis of nm23 protein using an anti-human nm23 H1/H2 polyclonal antibody was performed in 67 RCCs and in the corresponding 67 normal proximal renal tubules (NTs). The quantity and intensity of nm23 protein immunoreactivity were evaluated using a computer-interfaced image analyzer, and the obtained results were compared with pathological findings and clinical outcome.

RESULTS

The quantity and intensity of nm23 protein immunoreactivity were significantly higher in RCCs than those observed in NTs (p <0.0001, respectively). Both quantity and intensity of nm23 protein immunoreactivity held a tendency to increase along with histological grade (p = 0.094 and p = 0.089, respectively) and T category (p = 0.063 and p = 0.063, respectively). Similarly, the immunoreactivity had a tendency to be higher in RCCs with lymph node involvement than those tumors without involvement (p = 0.060 and p = 0.067, respectively). However, no significant difference in nm23 protein immunoreactivity was found between tumors with and without distant metastasis. Using a univariate analysis, a high nm23 protein immunoreactivity (quantity > or = 51.0% or intensity > or = 72.5%) significantly correlated with a poor clinical outcome (p = 0.0051 and p = 0.0013, respectively). Furthermore, a multivariate analysis adjusted to age, T, N and M categories, showed that a high intensity of nm23 protein immunoreactivity was significantly associated with a poor clinical outcome in patients with RCCs (p = 0.0192).

CONCLUSIONS

Immunohistochemical analysis of nm23 protein intensity is an additional tool for analyzing the difference of biological features in RCCs. The potential role of the tumor metastasis suppressive activity of nm23 remains unclear in RCCs.