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N Iwai

Publications and source records attributed to N Iwai.

At least 19 recordsLinked to original sources
PubMed2001

Alteration of cell adhesion and cell cycle properties of ES cells by an inducible dominant interfering Myb mutant.

The Myb transcription factors, c-Myb, A-Myb, and B-Myb, regulate cell differentiation and/or proliferation. To investigate the role of B-Myb in embryogenesis, we introduced an inducible dominant interfering Myb protein (MERT) into embryonic stem (ES) cells, which express B-Myb as an exclusive member of Myb family. Disruption of normal B-Myb function by the conditional activation of MERT caused a drastic morphological alteration of ES cells and G(1)-S cell cycle arrest. The inhibition of B-Myb function by MERT dissociated tightly packed ES cell colonies into dispersed single cells that subsequently detached from the culture dish. Cell adhesion analyses revealed that suppression of B-Myb function reduced the adhesion with extracellular matrix proteins, such as laminin, collagen, and fibronectin. This reduction was presumably due to decreased cell surface expression of beta1 integrin. Embryoid body formation was also severely retarded by the activation of MERT. This impairment was attributed to reduced expression of E-cadherin, which functions as a homophilic intercellular adhesion molecule. Simultaneously, blocking B-Myb function did not alter the expression of differentiation markers. Our data indicate that B-Myb plays important roles in regulating cell adhesion and cell cycle progression. These results are well consistent with the recent report on the phenotype of B-Myb null mice and show that the regulation of cell adhesion is an important B-Myb function that has not yet been assumed.

Animals↗
PubMed2001

Impaired distribution of retinoic acid receptors in the hindgut-tailgut region of murine embryos with anorectal malformations.

BACKGROUND/PURPOSE: Retinoid-mediated signal transduction plays a crucial role in the organogenesis of various organs. To investigate the pathogenesis of anorectal malformations (ARM), the authors studied the distribution pattern of retinoic acid receptors (RARs) in ARM murine embryos induced by overdose of all-trans retinoic acid (ATRA). METHODS: Pregnant mice were gavage-fed 100 mg/kg of ATRA on the ninth gestational day (E9.0). Embryos were obtained between E11.0 and E14.0 and were fixed immediately in a 4% paraformaldehyde solution. Frozen sections were prepared for immunohistochemistry using antibodies specifically raised against RAR-alpha, RAR-beta, and RAR-gamma. RESULTS: Over 98% of the embryos administered ATRA had ARM; rectoprostatic urethral and rectocloacal fistulas were the most frequent anomalies. The immunoreactivity of RAR-alpha was found equally in the epithelium of hindgut-tailgut in normal embryos on E11.5. However, it was absent in the hindgut in the treated embryos. The immunoreactivities of RAR-beta and RAR-gamma showed no difference in the distal hindgut. CONCLUSIONS: Impaired distribution of RAR-alpha in the hindgut-tailgut on E11.5 resulted in the incomplete partitioning of the cloaca and the rectourethral or rectocloacal fistula on E14.0. These results suggest that overdose of ATRA affects the distal hindgut development by directly disrupting the retinoid-mediated signalling pathway.

Anal Canal↗
PubMed2001

Relationship between the type of RET/GDNF/NTN or SOX10 gene mutations and long-term results after surgery for total colonic aganglionosis with small bowel involvement.

BACKGROUND/PURPOSE: Germline mutations of the RET-mediated or SOX10-mediated signaling pathway genes have been reported in total colonic aganglionosis (TCA). The authors investigated the possible relationship between the type of such genomic abnormalities and surgical outcomes. METHODS: Sixteen patients with TCA with extensive small bowel involvement were studied. DNA sequences of all the RET/GDNF/NTN and SOX10 coding regions were determined by the direct DyeDeoxy Terminator Cycle method. Data on the patients' clinical courses were obtained retrospectively from their medical charts and surgical records. RESULTS: RET or SOX10 germline mutations were identified in 11 of the 16 patients (68.8%). In children with aganglionosis up to the jejunum or ileum, most grew up within normal ranges, and the frequency of bowel movements decreased to 2 to 4 times per day within 5 years. However, in 5 infants with total intestinal aganglionosis, only 2 survived beyond 2 years of age, both of whom underwent Ziegler's myectomy-myotomy. A SOX10 mutation was identified in an infant with Shah-Waardenburg's syndrome, and he showed persistent bowel malfunction. CONCLUSION: The existence or type of RET mutation usually did not affect surgical results in this series of TCA patients, whereas the mutational analysis suggested 2 disease categories of TCA showing different postoperative courses, which may reflect the disparate pathogenesis in the enteric nervous system development induced by impaired RET or SOX10 signaling pathway.

Body Height↗
PubMed2001

Factors of biliary carcinogenesis in choledochal cysts.

The long-term complications of choledochal cysts include malignant degeneration of the epithelial lining of the biliary tract. Possible factors leading to malignant degeneration were examined by measuring amylase levels in the biliary tract, intraoperative biliary manometry and a histopathological study. 27 patients, 1 to 13 years of age, with choledochal cysts, were studied over a 13-year period. Amylase levels in the bile of choledochal cysts and the gallbladder were measured. The pressure profile of the biliary tract was recorded as the probe was withdrawn from the sphincter of Oddi (SO) to the distal end of the common bile duct. Hyperplasia of the gallbladder mucosa and malignancy of the biliary tract were investigated. Patients with high levels of biliary amylase had higher pressure differences between the SO and the duodenum than those with low levels of biliary amylase. The incidence of mucosal hyperplasia of the gallbladder mucosa was significantly higher in the fusiform type than in the cystic type. Adenocarcinoma in a cystic choledochal dilatation was found in a 12-year-old girl with high amylase levels. The cause of regurgitation of pancreatic juice into the biliary system might be due to a high pressure difference between the SO and the duodenum in addition to the lack of sphincter function at the abnormal junction of the pancreaticobiliary ductal system. Early diagnosis and surgical treatment to prevent the regurgitation leading to hyperplasia and malignancy of the biliary tract are important for children with choledochal cysts.

Adolescent↗
PubMed2001

Mutational analysis of the RET and GDNF gene in children with hypoganglionosis.

Germline mutations of the RET (10q11.2) have been reported in Hirschsprung's disease (HSCR) at a rate of 15-45%. Recently, the glial cell line-derived neurotrophic factor (GDNF) was identified as one of the ligands of the RET, and GDNF (5p12-p13.1) mutations were also found in association with RET mutations in HSCR patients. We analysed the DNA sequence of RET and the GDNF of patients with hypoganglionosis. We investigated the germline mutation in 5 patients histologically diagnosed with hypoganglionosis. DNAs were extracted from peripheral blood lymphocytes of these patients. The PCR primers were designed for RET tyrosine kinase domain (exon 13-17) and GDNF (exon 1-2). The DNA sequence was determined using a direct DyeDeoxy Terminator Cycle method. The analysis of RET showed silent mutation at the codon 769 (CTT-->CTG) by DNA polymorphism in all patients. No other mutation of the RET or GDNF was evident. These results suggest that the RET or GDNF may not contribute to the pathogenesis of hypoganglionosis, which is suspected to be genetically different from HSCR.

Child↗
PubMed2001

Association analyses between genetic polymorphisms of endothelial nitric oxide synthase gene and hypertension in Japanese: The Suita Study.

OBJECTIVES: Endothelium-derived nitric oxide plays a key role in the regulation of vascular tone. Recently, endothelial nitric oxide synthase (eNOS) gene polymorphisms were reported to be associated with hypertension or coronary spasm. We investigated the association between the eNOS gene polymorphisms and hypertension in a large population-based sample of 4055 Japanese. DESIGN AND METHODS: We investigated two polymorphisms of the eNOS gene, Glu298Asp polymorphism of exon 7 and T(-786)C polymorphism of the promoter region. The genotype distribution in hypertensive subjects was compared to that in the other subjects. The influence of the genotype on blood pressure values was analyzed in the subjects not taking hypertensive medication. The promoter activities of the eNOS gene with the (-786)T or (-786)C allele were measured by a luciferase reporter gene assay. RESULTS: There was significant linkage disequilibrium between the two polymorphisms (P < 0.0001). The genotype distribution of the Glu298Asp or T(-786)C polymorphism did not differ between the hypertensive and the other subjects. No significant differences in the blood pressure of subjects not taking hypertensive medication were observed among the three genotypes of Glu298Asp or T(-786)C polymorphisms. No significant differences in the promoter activity were observed between bovine endothelial cells transfected with the (-786)T and (-786)C alleles. CONCLUSIONS: Our data suggested that these polymorphisms of the eNOS gene are unlikely to be major factors in the susceptibility to hypertension in the Japanese population studied.

Adult↗
PubMed2001

A homozygous missense mutation in the tyrosine E kinase domain of the RET proto-oncogene in an infant with total intestinal aganglionosis.

Germline mutations of the RET proto-oncogene (RET), its ligand glial cell-derived neurotrophic factor (GDNF), and neurturin (NTN) gene have been reported in patients with Hirschsprung's disease. A targeted mutation in the tyrosine kinase domain of RET produced total intestinal aganglionosis and renal agenesis in homozygous transgenic mice. Here we describe a homozygous mutation of the human gene for the RET tyrosine kinase domain that was present in a male neonate with total intestinal aganglionosis. Gut wall biopsy specimens from the stomach to the anorectum showed no ganglion cells. No urinary tract abnormalities were detected. Genomic DNAs were isolated from peripheral blood lymphocytes of the infant and his parents. DNA sequences of all the RET/GDNF/NTN coding regions were determined using a direct DyeDeoxy Terminator Cycle method. A homozygous missense mutation (CGG-to-TGG) at RET codon 969 was identified in this patient, which resulted in an amino acid change from arginine to tryptophan. No germline RET/GDNF/NTN mutations were found in his parents. In this case, the homozygous RET mutation seemed to cause a critical alteration of the Ret tyrosine kinase activity, which resulted in total intestinal aganglionosis but not renal agenesis. Discrepancies in phenotypic expression between humans and mice suggest differing threshold values for RET signal transduction in species or organs.

Drosophila Proteins↗
PubMed2001

T+31C polymorphism of angiotensinogen gene and essential hypertension.

A common variant at codon 235 of the angiotensinogen gene with methionine to threonine amino acid substitution (AGT M235T) has been reported as a genetic risk for essential hypertension. However, the frequency of AGT T235 was heterogeneous among races, and a positive association between AGT M235T and hypertension was not settled. To examine the association in a general population of Japanese (n=4013), we introduced the TaqMan polymerase chain reaction method and examined the relation between hypertension and T+31C polymorphism, which was in absolute linkage disequilibrium with AGT M235T. The C+31 allele of AGT was significantly associated with the positive family history of hypertension (FH) but not with the presence of hypertension or blood pressure. The subjects with CC tended to have hypertensive relatives, especially a hypertensive father or siblings, and its statistical significance was stronger in men. Adjustment of confounding factor did not alter the results of simple association study, suggesting that this positive association with FH is independent and significant. Our findings revealed that the TaqMan polymerase chain reaction method is a powerful tool for genetic association study with a large number of subjects and that AGT T+31C is significantly associated with paternal FH.

Aged↗
PubMed2001

Association of sodium channel gamma-subunit promoter variant with blood pressure.

The SCNN1G gene, located on human chromosome 16p12, encodes the gamma subunit of the amiloride-sensitive epithelial sodium channel, and mutations in SCNN1G can result in Liddle's syndrome or pseudohypoaldosteronism type I. We identified sequence variations in the promoter region of SCNN1G and examined the association between this polymorphism and blood pressure in a large cohort (n=4075) representing the general population in Japan. We found T(-1290)C, T(-501)G, G(-173)A, and G(-104)T polymorphisms in the promoter region of SCNN1G and confirmed the existence of T387C and T474C polymorphisms in exon 3 and the C1947G polymorphism in exon 13. Because the genotypes of the T(-1290)C, T(-501)G, G(-104)T, and T474C polymorphisms were in tight linkage disequilibrium, we selected the T474C and G(-173)A polymorphisms for an association study. The G(-173)A polymorphism of SCNN1G had a significant effect on systolic pressure (P=0.0050) and pulse pressure (P=0.0050). The AA genotype was associated with an 11 mm Hg drop in systolic pressure and an 8 mm Hg drop in pulse pressure and with a higher prevalence of hypotension (P=0.0195). A transient transfection assay using MDCK cells and human renal epithelial cells indicated that the promoter activity of the G(-173) allele was higher than that of the A(-173) allele. Although the effects of the A(-173) allele were recessive and although the AA genotype was found in just 0.7% of our study population, we observed that this variation of human SCNN1G had significant effects on blood pressure.

Adult↗
PubMed2001

Lack of association between genetic polymorphism of CYP11B2 and hypertension in Japanese: the Suita Study.

Aldosterone synthase (CYP11B2) is a key enzyme in the biosynthesis of aldosterone. Recently, a polymorphism in the 5'-flanking region of the CYP11B2 gene [T(-344)C] has been reported to be associated with blood pressure and plasma aldosterone levels. We investigated the association between this polymorphism and hypertension in a large population-based sample of 4,000 Japanese. The genotype distribution in hypertensive subjects (n=1,535) was compared to that in normotensive subjects (n=2,514). In subjects not receiving antihypertensive medication, the influence of the genotype on blood pressure values adjusted for clinical covariates was analyzed. All analyses were performed separately for men and women. The genotype distribution did not differ between hypertensive and normotensive subjects in either men (frequency of C allele: 30.3% vs. 31.4%, p=0.48) or women (31.5% vs. 31.7%, p=0.93). There were no significant differences in systolic blood pressure, diastolic blood pressure, or pulse pressure among the three genotypes in either men or women who had not received hypertensive medication. Our data suggest that the T(-344)C polymorphism of CYP11B2 is unlikely to influence blood pressure status in the Japanese population.

Aged↗
PubMed2001

The aldehyde dehydrogenase 2 gene is a risk factor for hypertension in Japanese but does not alter the sensitivity to pressor effects of alcohol: the Suita study.

Excessive alcohol consumption is a potent risk factor for high blood pressure. About half of Japanese show an extremely high sensitivity to alcohol, which is due to a genetic deficiency in an isoenzyme of aldehydede-hydrogenase with a low Km (ALDH2). It is possible that the effects of alcohol consumption on blood pressure differ according to the ALDH2 genotype. The purpose of the present study was to assess the influence of the ALDH2 genotype on the pressor effects of alcohol. The influence of the ALDH2 genotype on blood pressure was investigated in a large cohort (4,000 subjects) representing the general population in Japan. The genotype was determined by the TaqMan method. The genotype was significantly associated with alcohol consumption, gamma-GTP level, and HDL cholesterol level in both males and females. The odds ratio for the presence of hypertension for the Glu/Glu genotype in comparison to other genotypes was 1.67 (p< 0.0001, odds ratio=1.37-2.08, 95% confidence interval) among males. In contrast, the ALDH2 genotype had no significant effects on blood pressure among females. To investigate whether the ALDH2 genotype affected the sensitivity to the pressor effects of alcohol, we analyzed the effects of the ALDH2 genotype (Lys/Lys+Lys/Glu=0, Glu/Glu=1) and the level of alcohol consumption on blood pressure values after adjusting for age and BMI (residuals after adjusting for age and BMI). Among males, while the level of alcohol consumption significantly affected systolic, diastolic and pulse pressure, no significant interaction was observed between the ALDH2 genotype and the level of alcohol consumption in determining blood pressure levels. These results suggest that the Glu/Glu genotype is a potent risk factor for hypertension among males mainly through its association with the level of alcohol consumption, and that the ALDH2 genotype does not affect the sensitivity to the pressor effects of alcohol.

Adult↗
PubMed2001

Validity and reliability of single-item questions about physical activity.

The Japan Collaborative Cohort Study for Evaluation of Cancer Risk Sponsored by Monbusho (JACC Study) included in its self-administered questionnaires some single-item questions concerning physical activity. We examined the validity of the questions among 1,730 Japanese adults and the reliability of the questions among 1,075 Japanese adults. The validity of the sports and physical exercise questions was estimated by comparing the self-administered questionnaire responses with the time spent on the activity and the energy expenditure index for the previous 12-month period, elicited by the interviewing method used in the Japan Lifestyle Monitoring Study with a minor modification. The Spearman's rank correlation coefficients ranged from 0.43 to 0.60, showing moderate correlations. On the other hand, test-retest reliability was estimated by comparing the responses from two separate surveys conducted roughly one year apart. Weighted kappa coefficients of sports and physical exercise questions, classified according to sex and age, ranged from 0.39 to 0.56, showing moderate reliability; and those of a question about walking ranged from 0.25 to 0.39, showing fair reliability. We suggest that measuring physical activity level with these single-item questions may be appropriate for establishing baseline data that reflects long-term physical activity in a large-scale cohort study targeting lifestyle-related diseases.

Adult↗
PubMed2000

Diminution of the AML1 transcription factor function causes differential effects on the fates of CD4 and CD8 single-positive T cells.

In the thymic cortex, T lymphocytes are positively selected to survive and committed either to the CD4 single-positive (SP) or the CD8 SP lineage. The SP cells then pass through a step of maturation in the medulla and are delivered to peripheral lymphoid tissues. We examined the role of AML1, the gene encoding a transcription factor, in the above processes by using the transgenic mice expressing a dominant interfering form of AML1 as well as mice targeted heterozygously for AML1. One phenotypic change seen in the AML1-diminished mice was the reduction in the numbers of both CD4 SP and CD8 SP thymocytes, reflecting the partial impairment of the transition from the double-positive to SP stage. In addition, distinct from the above abnormality, perturbed were several aspects of SP cells, including the maturation of SP thymocytes, the recent thymic emigration, and the proliferative responsiveness of peripheral T cells to TCR stimulation. Interestingly, the AML1 diminution caused inhibitory and enhancing effects on the CD4 SP and CD8 SP cells, respectively. These differential effects are most likely related to the reduction in the peripheral CD4 SP/CD8 SP ratio observed in the AML1-diminished mice. The AML1 transcription factor thus maintains the homeostasis of each SP subset by functioning at the later stages of T lymphocyte differentiation.

Animals↗
PubMed2000

Mutational analysis of RET/GDNF/NTN genes in children with total colonic aganglionosis with small bowel involvement.

Hirschsprung disease (HSCR) is characterized by the absence of intramural ganglion cells in the distal gut, resulting in bowel obstruction shortly after birth. Aganglionosis usually affects the distal colon, but may also extensively involve the entire colon and, rarely, the more proximal bowel. Recently, germline mutations of RET, GDNF, and NTN genes have been reported in HSCR. Here we describe the results of mutational analysis of these genes in 15 Japanese child patients with total colonic aganglionosis with small bowel involvement. DNA sequences of all the RET/GDNF/NTN coding regions were determined by the direct dyedeoxy terminator cycle method. Eight different RET mutations were identified in exons 1, 7, 10, 12, 15, and 17 in 10 of the 15 patients. Of these eight mutations, five were found in the tyrosine kinase domain. No GDNF or NTN mutation was found. Compared with typical HSCR, this patient group appeared to exhibit a higher percentage of RET mutations and accumulation of mutations in the tyrosine kinase domain. A homozygous (or hemizygous) RET mutation was found in a male baby with total intestinal aganglionosis, while the heterozygosity of the same mutation resulted in a less severe type of aganglionosis. In familial cases, all heterozygous for the same mutation, aganglionosis was more severe in male than in female siblings. These results also urge us to examine if the RET germline mutation may cause critical alteration of the GDNF/NTN-Ret signal transduction more severely in homo(hemi)zygosity and in male fetuses during organogenesis.

Child↗
PubMed2000

Ultrasonographic detection of intrauterine intussusception resulting in ileal atresia complicated by meconium peritonitis.

A neonate with ileal atresia (IA) complicated by meconium peritonitis (MP) whose prenatal ultrasonography (US) detected an intrauterine intussusception (IUI) is reported. Fetal ascites, dilated bowel loops, and abdominal calcifications were identified on serial US from 25 weeks of gestation. Intestinal loops with high echogenecity and a "target-like" appearance suggestive of IUI were detected in the right lower quadrant. The 2,680-g male was delivered vaginally at term and underwent a laparotomy. Fibrous adhesions and small calcifications were scattered throughout the peritoneal cavity. IA (interrupted type) was confirmed 17.0 cm cranial to the ileocecal valve (ICV). An ileo-ileal intussusception was also found between 16.5 cm and 9.0 cm cranial to the ICV. Partial resection of the ileum and an ileo-ileal anastomosis was performed. The postoperative course was uneventful. In this case, the pathological process of IUI resulting in IA and MP was demonstrated sonographically by identifying the "target-like" appearance in the fetus.

Adult↗
PubMed2000

A bleeding tendency as the first symptom of a choledochal cyst.

We report an 8-month-old male presenting with gingival hemorrhages and nasal bleeding as the first symptom of a choledochal cyst (CC). On physical examination, there was a large cystic mass in the right upper abdominal quadrant. Laboratory studies on admission revealed moderate liver dysfunction and a bleeding tendency due to vitamin K deficiency. After administration of 5 mg vitamin K the bleeding tendency disappeared. At laparotomy, a large CC 5 cm in diameter was found and the liver showed moderate cholestasis. The sudden onset of a bleeding tendency in infants with congenital liver or biliary-tract disease may suggest not only biliary atresia, but also CC.

Choledochal Cyst↗