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Biomedical subjects

M Itakura

Publications and source records attributed to M Itakura.

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

Infrequent detectable somatic mutations of the RET and glial cell line-derived neurotrophic factor (GDNF) genes in human pituitary adenomas.

RET is a receptor tyrosine kinase expressed in neuroendocrine cells and tumors. RET is activated by a ligand complex comprising glial cell line-derived neurotrophic factor (GDNF) and GDNF receptor-alpha (GDNFR-alpha). Activating mutations of the RET proto-oncogene were found in multiple endocrine neoplasia (MEN) 2 and in sporadic medullary thyroid carcinoma and pheochromocytoma of neuroendocrine origin. Mutations of the RET proto-oncogene and the glial cell line-derived neurotrophic factor (GDNF) gene were examined in human pituitary tumors. No mutations of the RET proto-oncogene including the cysteine-rich region or codon 768 and 918 in the tyrosine kinase domain were detected in 172 human pituitary adenomas either by polymerase chain reaction (PCR)-single strand conformation polymorphism (SSCP) or by PCR-restriction fragment length polymorphism (RFLP). Further, somatic mutations of the GDNF gene in 33 human pituitary adenomas were not detected by PCR-SSCP. One polymorphism of the GDNF gene at codon 145 of TGC or TGT was observed in a prolactinoma. The RET proto-oncogene message was detected in a normal human pituitary gland or 4 of 4 human pituitary adenomas with reverse transcription (RT)-PCR, and in rodent pituitary tumor cell lines with Western blotting. The expression of GDNF gene was detected in 1 of 4 human somatotroph adenomas, 1 of 2 corticotroph adenomas, and 2 of 6 rodent pituitary tumor cell lines with RT-PCR. Based on these, it is concluded that somatic mutations of the RET proto-oncogene or the GDNF gene do not appear to play a major role in the pituitary tumorigenesis in examined tumors.

Adenoma↗
PubMed1999

Development of pancreatic islets (review).

Recent studies have revealed that islet cells differentiate from the epithelial cells of primitive pancreatic ducts during embryogenesis, and can regenerate in response to the loss of islet cells even in adult pancreas. The ability of islet cells to regenerate raises the possibility that impaired and decreased islets of diabetic patients can be restored. In this review, factors regulating islet development including differentiation factors (Shh, activin, follistatin, and TGF alpha), transcriptional factors (PDX1, Isl1, Pax4, Pax6, Nkx2.2, Nkx6.1, BETA2, and HNF), growth factors (the EGF family, HGF, IGF-I, IGF-II, Reg, INGAP, PDGF, FGF, VEGF, and NGF), hormones (insulin, the GH family, PTHrP, TRH, and gastrin), and cell adhesion molecules (N-CAM and cadherins) are described after a short introduction and an outline of pancreatic development.

Animals↗
PubMed1998

Abrogation of autoimmune diabetes in nonobese diabetic mice and protection against effector lymphocytes by transgenic paracrine TGF-beta1.

Paracrine effect of transforming growth factor-beta1 (TGF-beta1) on autoimmune insulitis and diabetes was studied by transgenic production of the active form of porcine TGF-beta1 (pTGF-beta1) in pancreatic islet (islet) alpha cells in nonobese diabetic (NOD) mice under the control of rat glucagon promoter (RGP) (NOD-RGP-TGF-beta1). None of 27 NOD-RGP-TGF- beta1 mice developed diabetes by 45 wk of age, in contrast to 40 and 71% in male and female nontransgenic mice, respectively. None of the NOD-RGP-TGF-beta1 mice developed diabetes after cyclophosphamide (CY) administration. Adoptive transfer of splenocytes of NOD-RGP-TGF-beta1 mice to neonatal NOD mice did not transfer diabetes after CY administration. Adoptive transfer of three types of diabetogenic lymphocytes to NOD-RGP-TGF-beta1 and nontransgenic mice after CY administration led to the lower incidence of diabetes in NOD-RGP-TGF-beta1 mice versus that in nontransgenic mice: 29 vs. 77% for diabetogenic splenocytes, 25 vs. 75% for islet beta cell-specific Th1 clone cells, and 0 vs. 50% for islet beta cell-specific CD8(+) clone cells, respectively. Based on these, it is concluded that autoimmune diabetes in NOD mice is not a systemic disease and it can be completely prevented by the paracrine TGF-beta1 in the islet compartment through protection against CD4(+) and CD8(+) effector lymphocytes.

Adoptive Transfer↗
PubMed1998

Hypoplasia of pancreatic islets in transgenic mice expressing activin receptor mutants.

Activin, a member of the TGF-beta superfamily, regulates the growth and differentiation of a variety of cell types. Based on the expression of activin in pancreatic rudiments of rat embryos and stimulation of insulin secretion from adult rat pancreatic islets by activin, activin is implicated in the development and function of islets. To examine the significance of activin signaling in the fetal and postnatal development of islets, transgenic mice expressing a dominant negative form of activin receptor (dn-ActR) or a constitutively active form of activin receptor (ActR-T206D) in islets were generated together with the transgenic mice expressing intact activin receptor (intact ActR) as a negative control. Transgenic mice with both dn-ActR and ActR-T206D showed lower survival rates, smaller islet area, and lower insulin content in the whole pancreas with impaired glucose tolerance when compared with transgenic mice with intact ActR or littermates, but they showed the same alpha cell/beta cell ratios as their littermates. In addition to islet hypoplasia, the insulin response to glucose was severely impaired in dn-ActR transgenic mice. It is suggested that a precisely regulated intensity of activin signaling is necessary for the normal development of islets at the stage before differentiation into alpha and beta cells, and that activin plays a role in the postnatal functional maturation of islet beta cells.

Activin Receptors↗
PubMed1998

Molecular cloning of a human cDNA for the 41-kDa phosphoribosylpyrophosphate synthetase-associated protein.

A human cDNA encoding 41-kDa phosphoribosylpyrophosphate (PRPP) synthetase (PRS)-associated protein (PAP41) was cloned from two expressed sequence tag (EST) clones having the nucleotide similarity of 61.5 and 70.0% to human PAP39 cDNA. The predicted open reading frame of 1107 base pairs (bp) has the nucleotide identity of 91.8% to rat PAP41 and encodes a protein of 369 amino acids with a calculated molecular weight (MW) of 40,925. The deduced amino acid sequence exhibits the 98.9% identity to rat PAP41 and 72.2, 50.6, and 50.0% identity with human PAP39, PRS I, and PRS II, respectively, but lacks the PRPP binding site. Southern blot analysis suggested that the PAP41 gene exists as a single copy in the human genome. The single PAP41 mRNA of about 2.1 kb was shown to be present in five human cell lines by Northern blot analysis.

Adenocarcinoma↗
PubMed1998

Molecular cloning of mouse paired-box-containing gene (Pax)-4 from an islet beta cell line and deduced sequence of human Pax-4.

A mouse cDNA encoding paired-box-containing gene (Pax-4) was cloned from a cDNA library of a mouse pancreatic islet beta cell line of MIN6. The predicted open reading frame encodes a protein of 349 amino acids with a calculated molecular weight (MW) of 38-kD. A human Pax-4 cDNA sequence encoding 350 amino acids was deduced from a human cosmid clone. The mouse nucleotide and deduced amino acid sequences exhibit 83.4 and 80.0% identity with those of deduced human Pax-4, respectively. Southern blot analysis suggested that the mouse Pax-4 gene exists as a single copy in the genome. Reverse transcription (RT)-PCR analysis suggested that the mouse Pax-4 gene is expressed in pancreatic islets, cultured islet beta cell lines of MIN6, beta TC, and NIT-1 cells, but not detectable in any of 13 adult mouse organs examined.

Amino Acid Sequence↗
PubMed1998

Polymorphisms of thymidine kinase gene in herpes simplex virus type 1: analysis of clinical isolates from herpetic keratitis patients and laboratory strains.

Drug-resistance of herpes simplex virus (HSV) is caused most frequently by mutation of the viral thymidine kinase (TK) gene. To elucidate the significance of detecting nucleotide changes of the TK gene for screening drug-resistant viruses, the frequency and variation of the genetic polymorphisms in the whole coding region of the TK gene were studied in 14 acyclovir-susceptible HSV type 1 (HSV-1) clinical isolates from 14 patients with epithelial herpetic keratitis. Two reference HSV-1 laboratory strains, McKrae and PH, and two acyclovir-resistant variants of the PH strain were also studied as controls. Polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) and direct sequencing detected nucleotide differences at 24 positions, and amino acid substitutions at 12 codons in the TK gene of the examined viruses. Nucleotide diversity of 0.0029 per base (the average number of nucleotide substitutions of 3.3 per 1,131 base pairs) in the TK gene in the clinical isolates was comparable to 0.0037 per base of the whole HSV-1 genome in Japanese isolates reported previously. PCR-SSCP analysis of the acyclovir-resistant strains easily detected aberrantly shifted bands by comparing them with those of the parental strain, followed by the quick determination of mutated sequences. These results suggest that detection of nucleotide changes of the TK gene is useful for serial observation of persistent or recurrent HSV infection as observed in immunocompromised hosts, but that it is not useful for screening drug-resistant viruses from nonepidemic clinical isolates because of the comparable genetic polymorphisms in the TK gene as in the whole HSV-1 genome.

Acyclovir↗
PubMed1998

Familial isolated primary hyperparathyroidism with parathyroid carcinomas: clinical and molecular features.

OBJECTIVE: Familial isolated primary hyperparathyroidism (FIHP) is a rare hereditary disorder. We present four patients from a single family with FIHP, and genetic analysis of their parathyroid adenomas and parathyroid carcinoma. DESIGN: DNA was extracted from tumours resected at surgery. Tumours were examined for loss of heterozygosity (LOH) with microsatellite polymorphic markers. PATIENTS: The 27-year-old proband (Patient 1) died of parathyroid carcinoma with metastases to the lungs and chest wall. Sixteen years later, his 34-year-old sister (Patient 2) presented with a neck tumour and primary hyperparathyroidism. Family screening revealed parathyroid tumours in his 36-year-old sister (Patient 3) and 29-year-old cousin (Patient 4). Histological examination of resected tumours showed parathyroid carcinoma and adenoma in Patient 2, a parathyroid adenoma in Patient 3, and an atypical parathyroid adenoma in Patient 4. Autopsy of the proband ruled out multiple endocrine neoplasia (MEN) type 1, and the three patients who underwent parathyroidectomy did not exhibit any abnormalities in the pancreas or the pituitary gland. RESULTS: Analysis of tumour DNA from one parathyroid carcinoma (Patient 2), the atypical parathyroid adenoma (Patient 4), and two parathyroid adenomas (Patients 2 and 3) showed limited LOH on chromosomes 13q12.3-q32 in an adenoma of Patient 2 and 9p21-p22 and 13q12.3-q32 in an adenoma of Patient 3. CONCLUSION: These results suggest the possible contribution of tumour suppressor genes including the retinoblastoma gene and the hereditary breast cancer susceptibility gene (BRCA2) on 13q to parathyroid tumours in this family.

Adenoma↗
PubMed1998

Relationship between platelet membrane lipid compositions and platelet aggregability in alcoholic liver disease.

We studied the relationship between changes in platelet aggregability and platelet membrane lipid in alcoholic liver disease. The maximal rate of ADP-induced platelet aggregation was significantly increased in the alcoholic liver disease group than in the control group. No significant difference was observed in the maximal rate of collagen-induced platelet aggregation. However, a lag time required for the start of platelet aggregation was significantly shortened in the alcoholic liver disease group, indicating increased platelet aggregability. Results of the platelet aggregation test suggested that alcoholic liver disease patients have their platelet aggregation affected by the abnormality of prostaglandin metabolism. The alcoholic liver disease group was further divided into two subgroups: the hyperaggregation group and the unchanged aggregation group. Both free cholesterol and phospholipid in the platelet membrane were significantly increased in the alcoholic liver disease group. In phospholipid compositions, phosphatidylserine plus phosphatidylinositol were significantly decreased in the alcoholic liver disease group, whereas a significant decrease in phosphatidylserine plus phosphatidylinositol was observed in the hyperaggregation group of alcoholic liver disease. Analysis of fatty acid compositions of platelet membrane showed significantly decreased palmitic acid in the alcoholic group. There was no significant change of arachidonic acid, which directly affects platelet aggregation. Eicosapentaenoic acid significantly decreased in the alcoholic liver disease group, but there was no difference in docosahexaenoic acid. Meanwhile, the thrombogenic index, calculated from the fatty acids of platelet membrane, showed no difference between the alcoholic liver disease group and the control group. However, the thrombogenic index was significantly increased in the hyperaggregation group than in the unchanged aggregation group. These data suggested that platelet aggregation is affected by not only a change in arachidonic acid, but also changes in fatty acid compositions of the platelet membrane.

Adult↗
PubMed1998

Absence of germ-line mutations of the multiple endocrine neoplasia type 1 (MEN1) gene in familial pituitary adenoma in contrast to MEN1 in Japanese.

Germ-line mutations of the MEN1 gene were analyzed in five cases of familial and four cases of sporadic multiple endocrine neoplasia type 1 (MEN-1), six cases in three independent pedigrees of familial pituitary adenoma without MEN-1, and three cases of familial isolated primary hyperparathyroidism (FIHP) in Japanese. Eight different types of germ-line mutations in all nine cases of MEN-1 were distributed in exons 2, 3, 7, and 10 and intron 7 of the MEN1 gene. Loss of heterozygosity (LOH) on 11q13 was detected in all nine tumors of these cases with microsatellite analysis. No germ-line mutation of the MEN1 gene was detected in three pedigrees of familial pituitary adenoma and three cases of FIHP. LOH on 11q13 was detected in two cases in one pedigree of familial pituitary adenoma, and one of them showed a heterozygous somatic mutation of the MEN1 gene. No LOH on 11q13 was detected in three cases of FIHP. Based on these, we conclude that the loss of function of menin is etiological for familial or sporadic MEN-1, but not for FIHP or most familial pituitary adenoma without MEN-1.

Adenoma↗
PubMed1998

Analysis of loss of heterozygosity on chromosome 11 and infrequent inactivation of the MEN1 gene in sporadic pituitary adenomas.

To investigate the role of tumor suppressor genes in sporadic pituitary adenomas, we first analyzed loss of heterozygosity on 11q13 with microsatellite analysis in 31 tumors. Loss of heterozygosity on 11q13 was detected in 1 mixed GH/PRL adenoma, and the somatic 22-bp deletion of the multiple endocrine neoplasia type 1 (MEN1) gene encoding menin was detected in this tumor. Trisomy 11 suggested by the decreased mean allelic ratios of 66% or 65% for 16 or 13 microsatellite markers, respectively, in 2 of 31 pituitary adenomas was confirmed by interphase fluorescence in situ hybridization. Screening for mutations of the MEN1 gene did not find mutations with PCR-single strand conformation polymorphism analysis in other pituitary adenomas retaining heterozygosity on 11q13. Based on these, it is concluded that inactivation of the MEN1 gene comprises a rare etiology for tumorigenesis of the pituitary gland, and that trisomy 11 or another gene(s) may contribute to the pathogenesis of sporadic pituitary adenomas.

Adenoma↗
PubMed1997

Proximal 5'-flanking sequence of the human gamma-glutamylcysteine synthetase heavy subunit gene is involved in cisplatin-induced transcriptional up-regulation in a lung cancer cell line SBC-3.

The contribution of the 5'-flanking sequence of the human gamma-glutamylcysteine synthetase heavy subunit (gamma-GCSh) gene to cisplatin-induced transcriptional up-regulation was studied using various human growth hormone reporter constructs which were transfected to a human lung cancer cell line SBC-3. Cisplatin at the concentration of 3 microM increased the transcriptional activity of the longest sequence from -1,413 to +91 bp of the gamma-GCSh gene to 246% of that in non-exposed cells. The distal sequence from -1,413 to -193 bp was shown to negatively regulate transcriptional activity in both cisplatin-exposed and non-exposed cells using deletion and thymidine kinase (TK) promoter-linked constructs. Cisplatin increased the transcriptional activity of the proximal GC-rich sequence from -192 to +91 bp to 340%, of which magnitude was the maximum among deletion constructs. A deletion from -108 to -28 bp, or +34 to +91 bp significantly decreased cisplatin-induced increases in transcriptional activity from 258 to 105%, or 340 to 160%, respectively. When the sequence from -108 to -22 bp, or +26 to +91 bp was linked to the heterologous TK promoter, cisplatin increased the transcriptional activity to 171 or 181%, respectively, from that of 128 or 137%, respectively, in non-exposed cells. These findings indicate that the proximal sequence from -192 to +91 bp of the gamma-GCSh gene, especially from -108 to -28 bp, and +34 to +91 bp, is involved in cisplatin-induced transcriptional up-regulation in SBC-3 cells.

Antineoplastic Agents↗
PubMed1997

p53 gene mutation in N-butyl-N-(4-hydroxybutyl)nitrosamine-induced urinary bladder tumors and N-methyl-N-nitrosourea-induced colon tumors of rats.

We analyzed p53 mutations in 17 N-butyl-N-(4-hydroxybutyl) nitrosamine-induced bladder transitional cell carcinomas (TCCs) with or without areas of squamous cell carcinoma (SCC) of Long-Evans Cinnamon (LEC) and F344 rats, and in 7 N-methyl-N-nitrosourea-induced colon adenocarcinomas of LEC rats by polymerase chain reaction-single strand conformation polymorphism analysis and DNA sequencing. Of these bladder tumors, one TCC with moderately differentiated SCC had a T to G transversion mutation at codon 141, leading to a Val to Gly amino acid change. No p53 mutation was found in colon adenocarcinomas. Thus a p53 gene mutation seems infrequent in these rat bladder and colon carcinogenesis models even in the late stage.

Animals↗
PubMed1997

Amidophosphoribosyltransferase limits the rate of cell growth-linked de novo purine biosynthesis in the presence of constant capacity of salvage purine biosynthesis.

Factors controlling relative flux rates of the de novo and salvage pathways of purine nucleotide biosynthesis during animal cell growth are not fully understood. To examine the relative role of each pathway for cell growth, three cell lines including CHO K1 (a wild-type Chinese hamster ovary fibroblast cell line), CHO ade -A (an auxotrophic cell line deficient of amidophosphoribosyltransferase (ATase), a presumed rate-limiting enzyme of the de novo pathway), and CHO ade -A transfected with human ATase cDNA (-A+hATase) resulting in 30-350% of the ATase activity of CHO K1, were cultured in purine-rich or purine-free media. Based on the enzyme activities of ATase and hypoxanthine phosphoribosyltransferase, the metabolic rate of the de novo and salvage pathways, the rate of cell growth (growth rate) in three cell lines under various culture conditions, and the effect of hypoxanthine infusion on the metabolic rate of the de novo pathway in rat liver, we concluded the following. 1) In -A+hATase transfectants, ATase activity limits the rate of the de novo pathway, which is closely linked with the growth rate. 2) Purine nucleotides are synthesized preferentially by the salvage pathway as long as hypoxanthine, the most essential source of purine salvage, can be utilized, which was confirmed in rat liver in vivo by hypoxanthine infusion. The preferential usage of the salvage pathway results in sparing the energy expenditure required for de novo synthesis. 3) The regulatory capacity of the de novo pathway (about 200%) was larger than that of the salvage pathway (about 20%) with constant hypoxanthine phosphoribosyltransferase activity.

Amidophosphoribosyltransferase↗