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Biomedical subjects

M Takata

Publications and source records attributed to M Takata.

At least 109 records · Page 6Linked to original sources
PubMed1999

Angiotensin-converting enzyme gene polymorphism and geometric patterns of hypertensive left ventricular hypertrophy.

Polymorphism in the angiotensin-converting enzyme (ACE) gene has been found to be associated with left ventricular hypertrophy (LVH) in patients with essential hypertension (EHT) in certain populations. We sought to evaluate, in a Japanese population, whether ACE genotype is related to left ventricular mass, or to the geometry of LVH in EHT. Eighty-seven patients with EHT were examined. Their relative wall thickness (RWT) and left ventricular mass index (LVMI), determined by echocardiogram, were used to divide them into 4 groups: normal (normal RWT and LVMI, n = 35); concentric remodeling (increased RWT but normal LVMI, n= 10); eccentric hypertrophy (increased LVMI but normal RWT, n = 20); and concentric hypertrophy (increased LVMI and RWT, n = 22). Genetic analysis for ACE genotypes was performed on peripheral leukocytes using PCR techniques. Interventricular septal thickness and RWT were significantly greater in the patients with the DD genotype than in those with the II genotype, but LVMI did not differ among the three ACE genotypes. The frequency of the DD genotype was higher in the concentric hypertrophy group than in each of the other groups, and the frequency of the II genotype was lower in the concentric hypertrophy group than in either the normal or eccentric hypertrophy group. The geometric pattern of hypertensive LVH was associated with ACE genotype in a Japanese population. The DD genotype may contribute to concentric hypertrophy, but not to eccentric hypertrophy.

Adult↗
PubMed1998

Posttranscriptional control of adipocyte differentiation through activation of phosphoinositide 3-kinase.

Differentiation of adipocytes is an important aspect of energy homeostasis. Although the transcriptional regulation of adipocyte differentiation is relatively well characterized, the subsequent molecular events remain unclear. The activity of phosphoinositide (PI) 3-kinase precipitated with antibodies to phosphotyrosine has now been shown to increase transiently during adipocyte differentiation of 3T3-F442A and of 3T3-L1 cells. PI 3-kinase activity precipitated with antibodies to insulin receptor substrate 1 (IRS1) and association of subunits of PI 3-kinase with IRS1 were also increased at this stage of differentiation, suggesting that IRS1 contributes to PI 3-kinase activation. Inhibition of the activation of PI 3-kinase by expression of dominant negative mutant subunits of the enzyme prevented adipogenesis, as assessed by lipid accumulation and expression of key adipocyte proteins such as GLUT4, adipsin, and aP2, suggesting that PI 3-kinase activation is essential for adipocyte differentiation. However, these mutant proteins did not affect either the expression of the transcription factor PPARgamma at the mRNA or protein level or the increase in the abundance of mRNAs encoding the adipocyte marker proteins. These results demonstrate that adipocyte differentiation is regulated at the posttranscriptional level and that activation of PI 3-kinase is required for this regulation.

3T3 Cells↗
PubMed1998

Homologous recombination and non-homologous end-joining pathways of DNA double-strand break repair have overlapping roles in the maintenance of chromosomal integrity in vertebrate cells.

Eukaryotic cells repair DNA double-strand breaks (DSBs) by at least two pathways, homologous recombination (HR) and non-homologous end-joining (NHEJ). Rad54 participates in the first recombinational repair pathway while Ku proteins are involved in NHEJ. To investigate the distinctive as well as redundant roles of these two repair pathways, we analyzed the mutants RAD54(-/-), KU70(-/-) and RAD54(-/-)/KU70(-/-), generated from the chicken B-cell line DT40. We found that the NHEJ pathway plays a dominant role in repairing gamma-radiation-induced DSBs during G1-early S phase while recombinational repair is preferentially used in late S-G2 phase. RAD54(-/-)/KU70(-/-) cells were profoundly more sensitive to gamma-rays than either single mutant, indicating that the two repair pathways are complementary. Spontaneous chromosomal aberrations and cell death were observed in both RAD54(-/-) and RAD54(-/-)/KU70(-/-) cells, with RAD54(-/-)/KU70(-/-) cells exhibiting significantly higher levels of chromosomal aberrations than RAD54(-/-) cells. These observations provide the first genetic evidence that both repair pathways play a role in maintaining chromosomal DNA during the cell cycle.

Amino Acid Sequence↗
PubMed1998

Structural studies of endohedral metallofullerenes by synchrotron radiation powder diffraction.

The endohedral natures of the metallofullerenes Y@C(82) and Sc(2)@C(8)4 are described based on synchrotron radiation powder diffraction experiments. For structural analysis, a combination of the maximum-entropy method (MEM) and Rietveld refinement was employed to analyse the complicated powder pattern. The obtained MEM charge densities show a clear distinction of the endohedral natures of the mono- and dimetallofullerenes.

Journal Article↗
PubMed1998

Prognostic significance of allelic losses in primary melanoma.

Loss of genetic material, including loss of loci on chromosome arms 6q, 9p, and 10q, occurs frequently in cutaneous melanoma but infrequently in benign melanocytic nevi or other melanocytic lesions, suggesting that these genetic alterations are important in the development and progression of melanoma. To examine whether allelic loss is of prognostic importance in melanoma, disease-free survival was related to loss of heterozygosity on 6q, 9p and 10q in 83 individuals with sporadic primary cutaneous melanoma. Loss of chromosome arms 6q and 10q were each significantly associated with a poorer clinical outcome (P=0.013 and P=0.001 respectively). In a subgroup of 41 subjects whose primary tumours were allelotyped, the fractional allelic loss (FAL) at 39 autosomal arms also significantly correlated with disease-free survival (P=0.013), with an increase in FAL associated with a poorer outcome; this association remained significant when controlled for tumour thickness (P=0.035). In addition, a greater proportion of cells were immunopositive for Ki67 antigen, p53 and p21WAF1 protein in the primary melanomas than in the benign melanocytic nevi, however, only p53 over-expression was significantly associated with improved survival (P=0.041).

Alleles↗
PubMed1998

Requirement of Src kinase Lyn for induction of DNA synthesis by granulocyte colony-stimulating factor.

Treatment of cells with granulocyte colony-stimulating factor (G-CSF) leads to tyrosine phosphorylation of cellular proteins. G-CSF stimulates both the activation of protein tyrosine kinases Lyn, Jak1, and Jak2 and the association of these enzymes with the G-CSF receptor. Wild-type, lyn-deficient, and syk-deficient chicken B lymphocyte cell lines were transfected with the human G-CSF receptor, and stable transfectants were studied. G-CSF-dependent tyrosyl phosphorylation of Jak1 and Jak2 occurred in all three cell lines. Wild-type and syk-deficient transfectants responded to G-CSF in a dose-responsive fashion with increased thymidine incorporation, but none of the clones of lyn-deficient transfectants did. Ectopic expression of Lyn, but not that of c-Src, in the lyn-deficient cells restored their mitogenic responsiveness to G-CSF. Ectopic expression in wild-type cells of the kinase-inactive form of Lyn, but not of the kinase-inactive form of Jak2, inhibited thymidine incorporation in response to G-CSF. These studies show that the absence of Lyn results in the loss of mitogenic signaling in the G-CSF signaling pathway and that activation of Jak1 or Jak2 is not sufficient to cause mitogenesis.

Animals↗
PubMed1998

Rad51-deficient vertebrate cells accumulate chromosomal breaks prior to cell death.

Yeast rad51 mutants are viable, but extremely sensitive to gamma-rays due to defective repair of double-strand breaks. In contrast, disruption of the murine RAD51 homologue is lethal, indicating an essential role of Rad51 in vertebrate cells. We generated clones of the chicken B lymphocyte line DT40 carrying a human RAD51 transgene under the control of a repressible promoter and subsequently disrupted the endogenous RAD51 loci. Upon inhibition of the RAD51 transgene, Rad51- cells accumulated in the G2/M phase of the cell cycle before dying. Chromosome analysis revealed that most metaphase-arrested Rad51- cells carried isochromatid-type breaks. In conclusion, Rad51 fulfils an essential role in the repair of spontaneously occurring chromosome breaks in proliferating cells of higher eukaryotes.

Animals↗
PubMed1998

Idiopathic benign biliary stricture.

A rare case of idiopathic benign biliary stricture is reported. A 50-year-old man with liver dysfunction underwent ultrasonography, which revealed dilation of the intrahepatic bile ducts, and endoscopic retrograde cholangiopancreatography, which revealed a short, ring-like stenosis at the junction of the left and right hepatic ducts. Although a benign stricture was suspected, radiologic tests alone were insufficient to make a firm diagnosis. Therefore, a cholecystectomy and resection of the extrahepatic biliary tract were performed. Microscopic examination of the resected specimen demonstrated no evidence of malignancy. The final diagnosis was mild, localized, chronic cholangitis. The patient had not had previous biliary tract surgery, choledocholithiasis, nor did he have a congenital abnormality of the biliary tract, bile duct carcinoma, or pancreatic disease. Since there was no evidence of primary sclerosing cholangitis, the stricture was considered to be idiopathic.

Anastomosis, Surgical↗
PubMed1998

A trichilemmal carcinoma arising from a proliferating trichilemmal cyst: the loss of the wild-type p53 is a critical event in malignant transformation.

The genetic events responsible for tumor progression may be defined by careful analysis of genetic changes in well-chosen tumors which contain distinct cell populations representing each stage of progression. Here we report a case of a trichilemmal carcinoma arising in the wall of a proliferating trichilemmal cyst (PTC). DNA was isolated from microdissected areas of the PTC and the carcinoma respectively, and PCR-based microsatellite loss of heterozygosity (LOH) analysis as well as p53 gene sequencing performed. A CGA to TGA nonsense mutation at codon 306 in exon 8 of the p53 gene was found in both samples. LOH analysis showed that the PTC retained chromosome arm 17p (where the p53 gene resides), whereas the carcinoma was associated with the loss of this allele. All the other loci examined were retained including 3p, 9q, 13q and 17q in both tumor parts. The results confirm a common clonal origin of the PTC and the trichilemmal carcinoma, and strongly suggest that the complete loss of the wild-type p53 is a critical event responsible for malignant transformation in this particular case.

Aged↗
PubMed1998

Comparison of genetic profiles between primary melanomas and their metastases reveals genetic alterations and clonal evolution during progression.

To examine for the genetic basis of metastatic progression in cutaneous melanoma, we have compared loss of heterozygosity (LOH) of several selected chromosome regions that are implicated in the initiation and progression of melanoma, and alterations of the p16INK4a gene in 14 pairs of primary tumor and synchronous or asynchronous metastasis excised from the same patients. The most frequent genetic alteration during metastatic progression detected was the loss of p16INK4a protein expression (four of 14 cases), whereas no somatic p16INK4a gene mutations were found in any primary or metastatic tumors. LOH analyses showed that most of the chromosome losses including 6q, 8p, 9p, 9q, and 18q were shared between primary tumors and their metastases. Nevertheless, LOH of 6q and 11q and LOH of 7q not detected in primary tumors were, respectively, observed in two lymph node metastases. These results suggest that loss of p16INK4a protein expression (but not p16INK4a gene mutation) and the losses of chromosome arms 6q, 7q, and 11q play an important role in the acquisition of metastatic potential in sporadic melanoma. Furthermore, comparison of genetic profiles between the primary tumor and its metastasis revealed in several cases that heterogenous tumor cell populations might already exist at the early stage of tumorigenesis and evolve independently in the primary tumor and its metastasis, strongly suggesting that metastatic progression of sporadic melanoma is not accounted for by a linear progression model.

Adult↗
PubMed1998

Differential expression of activin subunits, activin receptors and follistatin genes in bovine oocytes and preimplantation embryos.

The presence of inhibin subunits (alpha, betaA and betaB), activin binding protein follistatin and activin receptors (ActR-I, ActR-IB, ActR-II and ActR-IIB) mRNA transcripts in bovine oocytes and preimplantation embryos was examined by reverse transcription-polymerase chain reaction. Immature and matured oocytes, zygotes, 2-cell, 3-4-cell, 5-8-cell, 9-16-cell embryos, morulae, blastocysts and hatched blastocysts were produced by in vitro maturation, fertilization and culture for this study. Activin betaA subunit and follistatin transcripts were detected in all of the stages tested. However, alpha subunit transcripts were detected only in oocytes (immature and matured), blastocysts and hatched blastocysts, and no betaB subunit transcripts were found in any of the stages. Whereas ActR-I transcripts were detectable in all stages, ActR-IB transcripts were not detectable in oocytes or embryos except in matured oocytes. Activin type II receptors (ActR-II and ActR-IIB) transcripts were detectable in oocytes and embryos except for ActR-IIB, which was not found in the 5-8-cell stage embryos. The results suggest that bovine embryos may produce activin A (homodimer of the betaA subunits) at least from zygotes to morulae. Furthermore, bovine oocytes and embryos express the activin receptors mainly by the combination of ActR-I and either ActR-II or ActR-IIB.

Activin Receptors↗
PubMed1998

Homologous recombination, but not DNA repair, is reduced in vertebrate cells deficient in RAD52.

Rad52 plays a pivotal role in double-strand break (DSB) repair and genetic recombination in Saccharomyces cerevisiae, where mutation of this gene leads to extreme X-ray sensitivity and defective recombination. Yeast Rad51 and Rad52 interact, as do their human homologues, which stimulates Rad51-mediated DNA strand exchange in vitro, suggesting that Rad51 and Rad52 act cooperatively. To define the role of Rad52 in vertebrates, we generated RAD52(-/-) mutants of the chicken B-cell line DT40. Surprisingly, RAD52(-/-) cells were not hypersensitive to DNA damages induced by gamma-irradiation, methyl methanesulfonate, or cis-platinum(II)diammine dichloride (cisplatin). Intrachromosomal recombination, measured by immunoglobulin gene conversion, and radiation-induced Rad51 nuclear focus formation, which is a putative intermediate step during recombinational repair, occurred as frequently in RAD52(-/-) cells as in wild-type cells. Targeted integration frequencies, however, were consistently reduced in RAD52(-/-) cells, showing a clear role for Rad52 in genetic recombination. These findings reveal striking differences between S. cerevisiae and vertebrates in the functions of RAD51 and RAD52.

Animals↗
PubMed1998

Requirement for activation of the serine-threonine kinase Akt (protein kinase B) in insulin stimulation of protein synthesis but not of glucose transport.

A wide variety of biological activities including the major metabolic actions of insulin is regulated by phosphatidylinositol (PI) 3-kinase. However, the downstream effectors of the various signaling pathways that emanate from PI 3-kinase remain unclear. Akt (protein kinase B), a serine-threonine kinase with a pleckstrin homology domain, is thought to be one such downstream effector. A mutant Akt (Akt-AA) in which the phosphorylation sites (Thr308 and Ser473) targeted by growth factors are replaced by alanine has now been shown to lack protein kinase activity and, when overexpressed in CHO cells or 3T3-L1 adipocytes with the use of an adenovirus vector, to inhibit insulin-induced activation of endogenous Akt. Akt-AA thus acts in a dominant negative manner in intact cells. Insulin-stimulated protein synthesis, which is sensitive to wortmannin, a pharmacological inhibitor of PI 3-kinase, was abolished by overexpression of Akt-AA without an effect on amino acid transport into the cells, suggesting that Akt is required for insulin-stimulated protein synthesis. Insulin activation of p70 S6 kinase was inhibited by approximately 75% in CHO cells and approximately 30% in 3T3-L1 adipocytes, whereas insulin-induced activation of endogenous Akt was inhibited by 80 to 95%, by expression of Akt-AA. Thus, Akt activity appears to be required, at least in part, for insulin stimulation of p70 S6 kinase. However, insulin-stimulated glucose uptake in both CHO cells and 3T3-L1 adipocytes was not affected by overexpression of Akt-AA, suggesting that Akt is not required for this effect of insulin. These data indicate that Akt acts as a downstream effector in some, but not all, of the signaling pathways downstream of PI 3-kinase.

3T3 Cells↗
PubMed1998

Polymerase chain reaction and immunohistochemistry frequently detect occult melanoma cells in regional lymph nodes of melanoma patients.

AIMS: To evaluate immunohistochemistry and reverse transcriptase polymerase chain reaction (RT-PCR) for melanoma associated antigens (MAA) in detecting occult melanoma cells in lymph nodes which were missed on routine pathology. METHODS: Occult melanoma cells were sought in 436 lymph nodes from 32 patients with cutaneous melanoma of the lower extremities by immunohistochemistry using the melanoma specific antibody HMB-45. The detection sensitivity of routine histology, immunohistochemistry, and RT-PCR was also compared in 23 lymph node samples from six patients. RESULTS: Immunohistochemistry showed that 15 of 24 patients (62.5%) who had no detectable metastasis by routine histology had at least one lymph node containing HMB-45 positive cells, mostly seen singly in the medullary sinus. No difference was found in known clinicopathological prognostic factors and recurrence rates between the two groups of patients with and without occult HMB-45 positive cells. RT-PCR analyses showed that the nested PCR for tyrosinase was more sensitive than a combination of single round PCR for five different MAA, including tyrosinase, MART-1/Melan A, Pmel-17, TRP-1, and TRP-2, detecting tyrosinase mRNA in six nodes which were negative by HMB-45 immunohistochemistry. CONCLUSIONS: Immunohistochemistry + RT-PCR is more sensitive than routine histology in detecting occult melanoma cells in lymph nodes. The nested PCR for tyrosinase should be used in future studies investigating the prognostic significance of such lymph node micrometastases.

Antigens, Neoplasm↗
PubMed1998

Relationship between electrocardiographic voltage and geometric patterns of left ventricular hypertrophy in patients with essential hypertension.

To assess whether we could predict left ventricular (LV) geometric patterns on echocardiography from voltages in standard electrocardiograms (ECG) in patients with essential hypertension, standard 12-lead ECG and echocardiograms were recorded in 106 consecutive, untreated patients (50+/-11 yr old) with essential hypertension. Subjects were assigned to the following four groups based on relative wall thickness (RWT) and LV mass index (LVMI) as determined by echocardiography: a normal geometry group (n = 44), a concentric remodeling group (increased RWT and normal LVMI, n = 10), an eccentric hypertrophy group (increased LVMI and normal RWT, n = 23), and a concentric hypertrophy group (increased RWT and LVMI, n = 29). The following ECG variables were determined: Sokolow-Lyon voltage (SV1 = RV5: SL), Cornell voltage (RaVL + SV3: CN), sum of 12-lead QRS voltage (12-lead sum), and RV6/RV5 ratio (RV6/V5). LVMI correlated with SL, CN, and 12-lead sum, but not with RV6/V5 in the study group as a whole. The concentric hypertrophy group showed increased voltages for all ECG variables except RV6/V5. The concentric remodeling group showed increased voltages for SL and 12-lead sum, but a decreased RV6/V5 ratio. In contrast, the eccentric hypertrophy group had increased voltage only for the 12-lead sum. The combination of SL, RV6/V5, and CN showed modest sensitivity and specificity in the diagnosis of concentric remodeling, concentric hypertrophy, and normal geometry, but not in the diagnosis of eccentric hypertrophy. Conventional ECG criteria can predict LVMI, but not LV geometry in the patients with essential hypertension. The combination of SL, CN, and RV6/V5 is useful in differentiating the four LV geometric patterns seen in essential hypertension.

Adult↗
PubMed1998

Molecular cloning of bovine thyrotropin-releasing hormone receptor gene.

The genomic DNA encoding bovine Thyrotropin-Releasing Hormone Receptor (TRHR) was isolated from a bovine (Holstein) genomic library. Using PCR fragments of bovine candidate TRHR Transmembrane domain (TMD-III-IV) and C-terminus domain of mouse TRHR cDNA as probes, 9 x 10(5) plaques were screened to obtain several clones each containing the N-terminus or C-terminus domain. The bovine TRHR gene encoded 398 amino acids and has a long intron. The identity of the deduced amino acid sequence of bovine TRHR exceeded 88% that of mouse, rat or human. RT-PCR analysis indicated TRHR mRNA to be expressed in the pituitary and brain.

Amino Acid Sequence↗
PubMed1998

Increased plasma granulocyte elastase levels in Behçet's disease.

OBJECTIVE: To assess the role of granulocyte elastase in the development of thromboembolic vasculopathy in patients with Behçet's disease. METHODS: Plasma granulocyte elastase-alpha1-proteinase inhibitor (E-PI) complex levels were measured by ELISA in 11 healthy subjects and 19 patients with Behçet's disease (BD). Eight of 19 patients showed deep vein thrombosis on (99m)technetium-macro-agglutinate albumin venography. Hemostatic variables were measured at the same time. RESULTS: The mean plasma E-PI complex level was significantly higher in the 8 patients with than in the 11 patients without deep vein thrombosis (242 +/- 73 vs 165 +/- 97 ng/ml; p = 0.033). The mean plasma E-PI complex level in the 11 patients without deep vein thrombosis was significantly higher than in controls (165 +/- 97 vs 96 +/- 40 ng/ml; p = 0.038). Plasma E-PI complex levels correlated with the serum plasmin-alpha2-plasmin inhibitor complex levels (r = 0.621, p = 0.0084). CONCLUSION: Plasma E-PI complex levels appear to be a useful marker of thromboembolic vasculopathy in BD.

Antifibrinolytic Agents↗