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Biomedical subjects

T Ikeuchi

Publications and source records attributed to T Ikeuchi.

At least 55 records · Page 3Linked to original sources
PubMed1999

Studies of the candidate genes in X-linked congenital cerebellar hypoplasia.

A gene for X-linked congenital cerebellar hypoplasia was recently localized to chromosome Xp11.21-q24. This region comprises several brain-specific genes responsible for various neurological disorders, including the proteolipid protein (PLP), doublecortin, and PAK3 genes. We screened these genes for mutations in patients with X-linked congenital cerebellar hypoplasia and found no pathogenic nucleotide changes or gene dose alterations. These findings allow the ruling out of PLP, doublecortin, and PAK3 as the disease-causing genes in this hereditary neurological syndrome.

Cerebellum↗
PubMed1999

Evaluation of the accuracy of preoperative staging in thoracic esophageal cancer.

BACKGROUND: Exact clinical staging before treatment of esophageal cancer has become increasingly important in the evaluation and comparison of the results of different treatment modalities, including surgery, chemotherapy, and radiotherapy. METHODS: The accuracy of preoperative tumor staging by using an esophagography, esophagoscopy, percutaneous and endoscopic ultrasonography, and computed tomography was assessed in 224 patients with resectable esophageal cancer. The results of tumor staging by these tests were compared prospectively with the pathologic stage of the esophagectomy specimens with respect to the T and N categories defined by the International Union Against Cancer TNM classification. RESULTS: For the T category, the overall accuracy was 80%. For the N category, overall accuracy was 72%, with a sensitivity of 78%, a specificity of 60%, and a positive predictive value of 78%. Overall, the accuracy of stage grouping was 56%. CONCLUSIONS: Either the T or N categories can be predicted reliably by clinical staging techniques. However, the preoperative stage grouping might not be valid in resectable, localized esophageal cancer.

Adult↗
PubMed1999

Brain-derived neurotropic factor prevents superoxide anion-induced death of PC12h cells stably expressing TrkB receptor via modulation of reactive oxygen species.

In our previous report (Satoh et al., 1999. Regulation of reactive oxygen species by nerve growth factor but not by Bcl-2 as a novel mechanism of protection of PC12 cells from superoxide anion-induced death. J. Biochem. 125, 952-959), we reported that nerve growth factor (NGF) protected PC12 cells from superoxide anion (O2-)-induced cell death through a novel regulation of reactive oxygen species (ROS) which increased O2- and decreased hydrogen peroxide (H2O2), indicating that decreasing conversion from O2- to H2O2 is a critical process for the protection by NGF. In the present study, we performed a comparative study on protective mechanisms between NGF and brain-derived neurotrophic factor (BDNF) using TrkB-expressing PC12h cells. When compared with NGF, BDNF induced a weaker but significant protective effect on the cells from O2- induced death. BDNF did not seem to change the total amount of ROS in the cells treated with xanthine and xanthine oxidase. On the other hand, BDNF increased O2- and decreased H2O2- levels in the same cells, although not so strongly as NGF. These results suggest that decreasing conversion from O2- to H2O2 is also critical for the protection by BDNF, which is considered to play a central role in survival and differentiation of CNS neurons.

Animals↗
PubMed1999

Novel chloride channel gene mutations in two unrelated Japanese families with Becker's autosomal recessive generalized myotonia.

We investigated the skeletal muscle voltage-gated chloride channel gene (CLCN1) in two unrelated Japanese patients with Becker's myotonia congenita. The non-myotonic parents of each patient were consanguineous. The proband of each family shares generalized myotonia, transient weakness after rest, and leg muscle hypertrophy. However, the disease severity related to the degree of myotonia differed, even in view of the response to long train nerve stimulation tests. CLCN1 gene analysis revealed a novel Ala659Val missense mutation identified to be homozygous in the more severe patient, while a novel Gln445Stop nonsense mutation was present in the other patient. Both mutations were absent in 90 Japanese normal controls. This is the first report of Japanese cases of Becker's myotonia congenita with CLCN1 gene mutations.

Adult↗
PubMed1999

Inactivation patterns of the p16 (INK4a) gene in oral squamous cell carcinoma cell lines.

To determine whether inactivation of the p16 gene mapped to the chromosome 9p21 region is associated with the development of oral squamous cell carcinoma (SCC), we investigated the mutational states of two forms of alternative transcripts (alpha and beta) from the p16 gene in 14 oral SCC cell lines by means of RT-PCR, PCR, direct sequencing and methylation analyses. Alterations of the alpha transcript were detected in all of the cell lines examined: homozygous deletions in three lines; subtle mutations in exons 1 alpha or 2 in four lines; skipping of exon 2 in two lines; hypermethylation of the 5' CpG island of the p16 gene in four lines; and an unknown mechanism in one line. On the other hand, abnormalities of the beta transcript were observed in seven of the 14 cell lines. Nonetheless, the mutations that essentially affect the function of the encoded protein were found only in five cell lines, including three lines with homozygous deletion. There was no cell line having only beta transcript alterations. Thus, alteration of the alpha transcript of the p16 gene was a highly frequent event in oral SCC. Since this type of alteration resulted in gene inactivation through multiple pathways, it may play a major role in the process of oral SCC development.

Carcinoma, Squamous Cell↗
PubMed1999

Superinfection of TT virus and hepatitis C virus among chronic haemodialysis patients.

BACKGROUND: The TT virus (TTV), a new DNA virus found in Japan from a patient with post-transfusion hepatitis non-A-non-G, is frequently positive in the sera of patients with liver disease. It is not established whether this virus causes liver damage. We studied the frequency of superinfection of this virus and hepatitis C virus (HCV) known to be endemic among haemodialysis patients, and the possible deleterious effect of TTV on HCV-induced chronic liver disease. METHODS: We used primers from a conservative region in the TTV genome (Okamoto, 1998) to detect TTV. Sera from 163 dialysis patients positive for anti-HCV and 77 dialysis patients negative for anti-HCV (control) were tested. RESULTS: TT Virus positivity was 35% among HCV antibody (anti-HCV)-positive patients and 45.4% among anti-HCV-negative patients. TT Virus positivity was unrelated to the length of haemodialysis or amounts of blood the patients had received in the past. More anti-HCV-positive patients had a history of transfusion, but TTV positivity was not as closely associated with transfusion as anti-HCV positivity. The severity of chronic liver disease was estimated from peak serum alanine aminotransferase levels in the preceding 6 months. Among anti-HCV positives, TTV-positive patients tended to have less active disease; at least there was no indication that TTV superinfection aggravated chronic hepatitic C in long-term dialysis patients. Four of 35 anti-HCV-negative, TTV-positive patients had chronic active liver disease, while none of the anti-HCV-negative and TTV-negative patients did. CONCLUSIONS: TT Virus infection is prevalent among haemodialysis patients. Its transmission occurs not only by blood transfusion, but also by non-parenteral infection. Superinfection of TTV does not exert deleterious effects on the liver disease induced by HCV. However, it may cause chronic hepatitis in a limited number of patients, but remains dormant most of the time. Triple infection, HCV and TTV plus HBV or HGV (one case each), did not cause severe liver disease.

Antibodies, Viral↗
PubMed1999

Brain-derived neurotrophic factor stimulates interactions of Shp2 with phosphatidylinositol 3-kinase and Grb2 in cultured cerebral cortical neurons.

Shp2, a protein tyrosine phosphatase possessing SH2 domains, is utilized in the intracellular signaling of various growth factors. Shp2 is highly expressed in the CNS. Brain-derived neurotrophic factor (BDNF), a member of the neurotrophin family, which also shows high levels of expression in the CNS, exerts neurotrophic and neuromodulatory effects in CNS neurons. We examined how BDNF utilizes Shp2 in its signaling pathway in cultured cerebral cortical neurons. We found that BDNF stimulated coprecipitation of several tyrosine-phosphorylated proteins with anti-Shp2 antibody and that Grb2 and phosphatidylinositol 3-kinase (PI3-K) were coprecipitated with anti-Shp2 antibody in response to BDNF. In addition, both anti-Grb2 and anti-PI3-K antibodies coprecipitated Shp2 in response to BDNF. The BDNF-stimulated coprecipitation of the tyrosine-phosphorylated proteins, Grb2, and PI3-K with anti-Shp2 antibody was completely inhibited by K252a, an inhibitor of TrkB receptor tyrosine kinase. This BDNF-stimulated Shp2 signaling was markedly sustained as well as BDNF-induced phosphorylation of TrkB and mitogen-activated protein kinases. In PC12 cells stably expressing TrkB, both BDNF and nerve growth factor stimulated Shp2 signaling similarly to that by BDNF in cultured cortical neurons. These results indicated that Shp2 shows cross-talk with various signaling molecules including Grb2 and PI3-K in BDNF-induced signaling and that Shp2 may be involved in the regulation of various actions of BDNF in CNS neurons.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Transgenic mice harboring a full-length human mutant DRPLA gene exhibit age-dependent intergenerational and somatic instabilities of CAG repeats comparable with those in DRPLA patients.

Dentatorubral-pallidoluysian atrophy (DRPLA) is one among an increasing number of hereditary neurodegenerative diseases determined as being caused by unstable expansion of CAG repeats coding for polyglutamine stretches. To investigate the molecular mechanisms underlying CAG repeat instability, we established three transgenic lines each harboring a single copy of a full-length human mutant DRPLA gene carrying a CAG repeat expansion. These transgenic mice exhibited an age-dependent increase (+0.31 per year) in male transmission and an age-dependent contraction (-1.21 per year) in female transmission. Similar tendencies in intergenerational instabilities were also observed in human DRPLA parent-offspring pairs. The intergenerational instabilities of the CAG repeats may be interpreted as being derived from the instability occurring during continuous cell division of spermatogonia in the male, and that occurring during the period of meiotic arrest in the female. The transgenic mice also exhibited an age-dependent increase in the degree of somatic mosaicism which occurred in a cell lineage-dependent manner, with the size range of CAG repeats being smaller in the cerebellum than in other tissues including the cerebrum, consistent with observations in autopsied tissues of DRPLA patients. Thus, the transgenic mice described in this study exhibited age-dependent intergenerational as well as somatic instabilities of expanded CAG repeats comparable with those observed in human DRPLA patients, and are therefore expected to serve as good models for investigating the molecular mechanisms of instabilities of CAG repeats.

Adult↗
PubMed1999

A neurological disease caused by an expanded CAG trinucleotide repeat in the TATA-binding protein gene: a new polyglutamine disease?

To investigate whether the expansion of CAG repeats of the TATA-binding protein (TBP) gene is involved in the pathogenesis of neurodegenerative diseases, we have screened 118 patients with various forms of neurological disease and identified a sporadic-onset patient with unique neurologic symptoms consisting of ataxia and intellectual deterioration associated with de novo expansion of the CAG repeat of the TBP gene. The mutant TBP with an expanded polyglutamine stretch (63 glutamines) was demonstrated to be expressed in lymphoblastoid cell lines at a level comparable with that of wild-type TBP. The CAG repeat of the TBP gene consists of impure CAG repeat and the de novo expansion involves partial duplication of the CAG repeat. The present study provides new insights into sporadic-onset trinucleotide repeat diseases that involve de novo CAG repeat expansion.

Adolescent↗
PubMed1999

The effect of the lipid A analog, E5531 on fever induced by endotoxin from Escherichia coli.

E5531 is a specific lipid A antagonist and is expected to be a drug for the treatment of septic shock. The LAL (limulus amebocyte lysate) activity and pyrogenicity of E5531 were determined. The LAL activity of E5531 is large and confirmed that E5531 had a high affinity to the lipopolysaccharide receptor. The pyrogenic activity of E5531 is weak and the pyrogenic profile of E5531 is different from that of USP (United States Pharmacopoeia) reference standard endotoxin (ETX). E5531 suppressed the pyrogenicity of ETX in rabbits, indicating that E5531 is expected to be useful for the treatment of fever induced by ETX.

Analgesics, Non-Narcotic↗
PubMed1999

Characterization of kintoki bean (Phaseolus vulgaris) alpha-amylase inhibitor: inhibitory activities against human salivary and porcine pancreatic alpha-amylases and activity changes by proteolytic digestion.

The effects of some experimental parameters on alpha-amylase inhibition by an alpha-amylase inhibitor from kintoki bean were examined. The rate of inhibition against pancreatic alpha-amylase increased with a rise in temperature to 50 degrees C, but the inhibition of salivary alpha-amylase reached a maximum above 35 degrees C. Although an increase in NaCl concentration to 1.5 M caused an increase in the inhibitory activities against both amylases, these inhibitory activities tended to decrease above 1.5 M NaCl. The effects of proteolytic digestion on the amylase inhibitory activity were also studied. The inhibitor was slightly inactivated by pepsin digestion for 2 h. Although the inhibitor rapidly lost the inhibitory activity by chymotrypsin digestion within 2 h, it was quite resistant to proteolytic digestion by trypsin.

Animals↗
PubMed1999

EXTL3/EXTR1 alterations in colorectal cancer cell lines.

We previously demonstrated that metastasis-related tumor suppressor gene(s) may exist on chromosome 8p21-22 on allelotype analysis of early colorectal carcinomas (CRC) with lymph node metastasis. Here, we searched for target gene(s) in this chromosomal region in the UniGene database. The EXTL3 (also called EXTR1) gene was selected as a candidate because of its homology to EXT1 and EXT2, putative tumor suppressor genes. We screened 12 CRC cell lines for mutations by means of polymerase chain reaction (PCR)-single strand conformation polymorphism. Three cell lines showed EXTL3 mutations, all of which were located within exon 3 and caused amino acid substitutions. Reverse transcription-PCR analysis showed that the EXTL3 expression was lacking in 1 of the 12 colorectal cancer cell lines. Although there is still no definitive evidence that EXTL3 is a tumor suppressor gene for CRC, these data suggest that inactivation of the EXTL3 gene may at least offer a selective growth advantage for some CRC cell lines.

Adenomatous Polyposis Coli↗
PubMed1999

[Molecular and clinical features in spinocerebellar ataxia type 6 (SCA6) in Japanese].

Spinocerebellar ataxia type 6 (SCA6, MIM 183086) is an autosomal dominant spinocerebellar degeneration. Mild expansion of a CAG repeat in voltage-dependent Ca2+ channel alpha 1A subunit (CACNL1A) gene, which was predicted to encode a polyglutamine tract, has been identified as a causative mutation for SCA6. SCA6 is one of the common subtypes of spinocerebellar degeneration, accounting for approximately 12% in the dominantly inherited ataxias in Japan. Mean age at onset in the SCA6 patients is 52 years, which is much later than those reported for other autosomal dominant ataxias including SCA1, SCA2, Machado-Joseph disease, and dentatorubral-pallidoluysian atrophy. Anticipation in SCA6 is quite mild. The size of expanded CAG repeats ranged 21 to 26 repeats and was found to be correlated inversely with age at onset in patients with SCA6. Ataxia is most common and cardinal clinical features in SCA6. Patients with a prolonged clinical course, however, show other accompanying clinical features including dystonic postures, involuntary movements, and abnormalities in tendon reflexes. Investigations of the mechanisms of neuronal death in the cerebellum, in particular relation to the impaired function of the voltage-dependent Ca2+ channel and the toxic effects of expanded polyglutamine tracts, will be indispensable for the development of therapeutic measures for SCA6.

Adult↗
PubMed1999

Severe phenotype of neurofibromatosis type 2 in a patient with a 7.4-MB constitutional deletion on chromosome 22: possible localization of a neurofibromatosis type 2 modifier gene?

Neurofibromatosis type 2 (NF2) is an autosomal dominant disorder predisposing to multiple neoplastic lesions with the hallmark of schwannoma arising at the eighth cranial nerve. NF2 shows a distinct clinical variability, with a mild and a severe form of the disease. The NF2 gene is mutated in constitutional DNA of affected patients from NF2 families and in sporadic cases. Comprehensive mutation analyses in patients with severe and mild phenotypes revealed mutations in only 34%-66%. In the remaining fraction, the genetic mechanism behind the development of NF2 is unknown. Analyses of germline mutations do not provide a conclusive explanation for the observed clinical heterogeneity of NF2. It can therefore be hypothesized that other factors, e.g., modifier gene(s), contribute to the development of a more severe NF2 phenotype. We report a mentally retarded patient with the severe form of NF2 who displays a 7.4 million base pair deletion on chromosome 22. We performed a full genetic characterization of this case using heterozygozity analysis of 41 markers from chromosome 22, detailed FISH mapping of deletion breakpoints, allelotyping of all other chromosomes, and sequencing of the NF2 gene in tumor DNA. Two genomically large deletions similar in size (700-800 kb), which encompass the entire NF2 gene, have been reported previously in mildly affected NF2 patients. The centromeric breakpoints of these deletions were similar to the centromeric breakpoint in the present case. However, the deletion in our patient extends over a much larger distance toward the telomere of 22q. Our results support the existence of NF2 modifier gene(s) and suggest that such a putative locus maps to a 6.5-MB interval on 22q, between D22S32 and the MB gene.

Adult↗
PubMed1998

Synthetic lipid products of PI3-kinase which are added to culture medium prevent low K+-induced apoptosis of cerebellar granule neurons via Akt kinase activation.

To examine which lipid product of phosphatidylinositol 3-kinase (PI3-K) is essential for the survival-promoting pathway in cultured cerebellar granule neurons, three synthetic derivatives of lipid products of PI3-K were added to culture medium containing a low concentration (5 mM) of potassium (LK+) which induces apoptotic cell death. We found that dipalmitoylphosphatidylinositol 3,4-bisphosphate and dipalmitoylphosphatidylinositol 3,4,5-trisphosphate, but not dipalmitoylphosphatidylinositol 3-monophosphate, effectively blocked the LK+-induced apoptosis. These two synthetic phospholipids increased Akt activity but not that of PI3-K. These findings demonstrated that specific lipid products of PI3-K which are added to culture medium activate Akt/PKB without modulating PI3-K itself, and as a result prevent neuronal cell death in cerebellar granule neurons.

Animals↗