Biomedical subjects

R Takayanagi

Publications and source records attributed to R Takayanagi.

At least 37 records · Page 2Linked to original sources

PubMed2000

Inhibin-like immunoreactivity produced by the adrenal gland is circulating in vivo.

To clarify the contribution of the inhibin-like immunoreactivity (inhibin-LI) produced by adrenal glands to the total circulating levels of inhibin-LI, we measured serum inhibin-LI in normal and hypogonadal subjects under ACTH-loading or dexamethasone-loading condition. The mean basal concentration of inhibin-LI in the peripheral serum of the hypogonadal cases was 3.6 +/- 1.3 IU/ml (mean +/- SD, n = 5), which corresponded to 19.5 +/- 5.8% of that of normal controls matched for age and sex. The low levels of inhibin-LI in hypogonadal subjects (n = 7) rose significantly (3.6 +/- 1.1 vs 8.1 +/- 1.7 IU/ml, p < 0.001) after the administration of synthetic 1-24ACTH (40 units/day intramuscular injection) for 2 days, while the levels of serum inhibin-LI were not increased in two cases of Addison's disease with hypogonadism after the administration of ACTH. After the oral administration of a low dose of dexamethasone (1 mg) the serum inhibin-LI level in normal subjects (eight males and eight females) decreased significantly (male, 16.2 +/- 3.3 vs 14.5 +/- 4.1 IU/ml; female, 12.9 +/- 6.3 vs 10.8 +/- 5.6 IU/ml; p < 0.01 each) without significant change in the levels of serum gonadotropin (LH and FSH) and those of gonadal steroid (testosterone or estradiol). These results indicate that a small; but significant amount of inhibin-LI is secreted from the adrenal gland and circulating in vivo, and that the proportion of adrenal-derived inhibin-LI is much higher in patients with hypogonadism.

Adrenal Glands↗

PubMed1999

Nicotinamide potentiates TSHR and MHC class II promoter activity in FRTL-5 cells.

Here we show that nicotinamide modulates the promoter activity of rat thyrotropin (TSHR) and major histocompatibility complex (MHC) class II genes in rat FRTL-5 thyroid cells, and have identified a novel mechanism for its action. TSHR and MHC class II, are potentiated through reduced expression of a common repressor of these two genes, TSEP-1 (TSHR suppressor element binding protein-1)/YB-1. Thus we show that TSHR mRNA is increased and TSHR promoter activity was concentration-dependently activated from 0 to 40 mM nicotinamide. The promoter lengths of TSHR and MHC class II containing TSEP/YB-1 binding sites were enhanced by 40 mM nicotinamide, but not the ones deleted of these binding sites. TSEP-1/YB-1 binding to the recognition sites in both TSHR and MHC class II promoters was reduced in nicotinamide-treated FRTL-5 nuclear extracts. Nicotinamide reduced the expression of TSEP-1/YB-1 mRNA and TSEP-1/YB-1 protein in the nucleus.

Animals↗

PubMed1999

Novel germline mutations of the MEN1 gene in Japanese patients with multiple endocrine neoplasia type 1.

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant disorder characterized by tumors of the parathyroid glands, the pancreatic islet cells, and the anterior pituitary. Germline mutations of the MEN1 gene in three independent Japanese cases with MEN1 were analyzed. Case 1 has revealed a 2-bp (TA) insertion at nucleotide position 341 (341insTA) in exon 2, which shifts the reading frame such that the mutant protein has a completely different amino acid sequence from codon 78 to the premature stop codon at 119. In case 2, a nucleotide substitution, i.e., TAG in place of TGG, which encodes tryptophan at codon 198 was identified (nonsense mutation). These mutations were heterozygously present and have not been reported previously. Case 3 showed no mutations in the protein-coding exons and exon-intron junctions of the MEN1 gene by single-strand conformation polymorphism or direct sequencing of the polymerase chain reaction (PCR) fragments. We confirmed the finding that patients with MEN1 carry heterozygous germline mutations in the MEN1 gene, which is compatible with the idea that the MEN1 gene is a tumor suppressor gene. The reason why mutations in the coding region of the MEN1 gene could not be detected by PCR-based analysis in some of the MEN1 patients, e.g. case 3, needs to be clarified further.

Adult↗

PubMed1999

Thiazolidinedione induces apoptosis and monocytic differentiation in the promyelocytic leukemia cell line HL60.

Thiazolidinedione (TZD) is known to be a potent activator of peroxisome proliferator-activated receptor gamma (PPARgamma), a nuclear receptor that constitutes a heterodimer with retinoid X receptor (RXR). Since a considerable amount of PPARgamma is expressed in various hematopoietic cells, the present study was undertaken to examine the effect of TZD in the absence or presence of LG100268, an RXR-selective ligand, on a cultured promyelocytic leukemia cell line, HL60. Treatment with TZD (25-50 microM troglitazone or pioglitazone) markedly suppressed cell proliferation of HL60. A cell cycle analysis revealed that the suppressive effect of troglitazone on HL60 cell proliferations was caused by G0/G1 cell cycle arrest as well as by an apoptotic effect. Treatment with the same concentration of troglitazone also induced the monocytic differentiation of HL60 cells. The apoptotic or the differentiating effect of TZD on HL60 cells was synergistically enhanced by the combined treatment with 1 microM LG100268, while LG100268 alone neither had an apoptotic nor a differentiating effect on HL60 cells. These results suggest that these actions are mediated through the nuclear receptor system constituted by the PPARgamma: RXR heterodimer.

Antineoplastic Agents↗

PubMed1999

[Kinetic analysis of therapeutic doses of beta-blockers for angina pectoris based on receptor occupancy theory--relationship between beta 1-receptor occupancy or vasodilative action and dose].

Beta-adrenoceptor blocking agents (beta-blockers) have been widely used for the treatment of angina pectoris. The average/standard therapeutic doses vary widely among beta-blockers with the maximum of about a 120-fold difference. In order to clarify the mechanism of this difference, we analyzed retrospectively the pharmacological effects of beta-blockers in consideration of the beta 1-receptor binding affinity and the vasodilative activity on the basis of pharmacokinetics and the receptor occupancy theory. The analysis was performed on eight beta-blockers without a vasodilative effect and on four beta-blockers with a vasodilative effect. The beta 1-receptor occupancies at the steady-state condition after oral administration of standard doses were calculated by the use of the data on the concentration of unbound agents in plasma and on the dissociation constant of receptors. The estimated receptor occupancies were 87 +/- 6% or 88 +/- 10% for the beta-blockers with or without a vasodilative effect, respectively, and a significant difference was not observed between these groups. These results suggest that the beta 1-receptor occupancies may be a principal indicator for the therapeutic effects for angina pectoris regardless of their vasodilative effects.

Administration, Oral↗

PubMed1999

[Melatonin].

Explore the source record for details and available documents.

Humans↗

PubMed1998

Chromogranin B (secretogranin I), a neuroendocrine-regulated secretory protein, is sorted to exocrine secretory granules in transgenic mice.

Chromogranin B (CgB, secretogranin I) is a secretory granule matrix protein expressed in a wide variety of endocrine cells and neurons. Here we generated transgenic mice expressing CgB under the control of the human cytomegalovirus promoter. Northern and immunoblot analyses, in situ hybridization and immunocytochemistry revealed that the exocrine pancreas was the tissue with the highest level of ectopic CgB expression. Upon subcellular fractionation of the exocrine pancreas, the distribution of CgB in the various fractions was indistinguishable from that of amylase, an endogenous constituent of zymogen granules. Immunogold electron microscopy of pancreatic acinar cells showed co-localization of CgB with zymogens in Golgi cisternae, condensing vacuoles/immature granules and mature zymogen granules; the ratio of immunoreactivity of CgB to zymogens being highest in condensing vacuoles/immature granules. CgB isolated from zymogen granules of the pancreas of the transgenic mice aggregated in a mildly acidic (pH 5.5) milieu in vitro, suggesting that low pH-induced aggregation contributed to the observed concentration of CgB in condensing vacuoles. Our results show that a neuroendocrine-regulated secretory protein can be sorted to exocrine secretory granules in vivo, and imply that a key feature of CgB sorting in the trans-Golgi network of neuroendocrine cells, i.e. its aggregation-mediated concentration in the course of immature secretory granule formation, also occurs in exocrine cells although secretory protein sorting in these cells is thought to occur largely in the course of secretory granule maturation.

Animals↗

PubMed1998

Subcutaneous or visceral adipose tissue expression of the PPARgamma gene is not altered in the fatty (fa/fa) Zucker rat.

We cloned 537 basepairs (bp) of rat partial peroxisome proliferator-activated receptor gamma2 (PPARgamma2) cDNA and examined the effect of fasting or obesity on the expression of two isoforms of rat PPARgamma, gamma1 and gamma2, in either subcutaneous or mesenteric adipose tissue specimens using an RNase A protection assay. In Wistar rats, expression of both isoforms was dramatically reduced after 48 hours of fasting in the two fat tissue specimens. In comparing genetically obese (fa/fa) Zucker rats and lean control rats, no significant difference was observed in expression of the two isoforms in either type of adipose tissue. From these findings, we conclude that the adipose tissue level of rat PPARgamma depends on nutritional deprivation but is not closely associated with either obesity or insulin resistance in obese Zucker rats.

Adipose Tissue↗

PubMed1998

Expression of an orphan nuclear receptor DAX-1 in human pituitary adenomas.

OBJECTIVES: An orphan nuclear receptor, DAX-1, is known to be involved in the development and differentiation of anterior pituitary cells. The present study aimed to examine 1) whether DAX-1 is expressed in human pituitary adenomas, and 2) if it is expressed, what types of adenoma express the factor. MATERIALS AND METHODS: Adenoma tissues examined included 18 clinically non-functioning adenomas, 14 GH-secreting adenomas and 7 PRL-secreting adenomas. The expression of the following genes were tested by reverse transcription-polymerase chain reaction (RT-PCR): DAX-1, Adrenal-4-binding protein/steroidogenic factor-1 (Ad4BP/SF-1), Pit-1, LH beta, FSH beta, gonadotrophin-releasing hormone receptor (GnRH-R), GH, PRL, and TSH beta, as well as beta-actin as a control. RESULTS: Eleven clinically non-functioning adenomas expressed DAX-1, 10 of which also expressed Ad4BP/SF-1. Nine out of the 11 DAX-1 expressing adenomas also expressed LH beta, FSH beta and GnRH-R as well, indicating that these adenomas possessed gonadotrophic properties. Nine clinically non-functioning adenomas expressed Pit-1 as well as GH, PRL and/or TSH beta, thus having somatomammotrophic or thyrotrophic properties, 3 of which overlapped with the above DAX-1-expressing adenomas. One non-functioning adenoma expressed Ad4BP/SF1 and FSH beta but not DAX-1, and another one expressed DAX-1 and Ad4BP/SF-1 with PRL. On the other hand, all GH-secreting and PRL-secreting adenomas expressed Pit-1 and GH and/or PRL, but neither DAX-1 nor Ad4BP/SF-1. CONCLUSIONS: The results shown here indicate that DAX-1 is expressed in the majority of human pituitary adenomas of gonadotrophic origin in parallel with Adrenal-4-binding protein/steroidogenic factor-1.

Adenoma↗

PubMed1998

Low level of glucocorticoid receptor messenger ribonucleic acid in pituitary adenomas manifesting Cushing's disease with resistance to a high dose-dexamethasone suppression test.

OBJECTIVES: The overnight 8-mg dexamethasone suppression test is often used to differentiate Cushing's disease, due to an oversecretion of ACTH from the pituitary gland, from other kinds of Cushing's syndrome. However, a few patients with ACTH-producing pituitary adenoma show no suppression of plasma cortisol after the administration of 8 mg of dexamethasone. To clarify the relationship between the level of glucocorticoid receptor (GR) in the pituitary adenoma and the sensitivity to dexamethasone in Cushing's disease, we thus examined the levels of GR alpha and GR beta mRNAs in the pituitary adenomas in six patients who were proven at surgery to have pituitary ACTH-producing adenomas. MATERIALS: Total RNA was extracted from six pituitary adenomas and pituitary tissue adjacent to one of the adenomas, and the mRNA levels of GR alpha, GR beta, pro-opiomelanocortin (POMC) and beta-actin in these samples were sampled by quantitative RT-PCR. RESULTS: The GR alpha mRNA levels in the adenomas from the two patients who showed no response to the 8-mg dexamethasone suppression test were significantly lower than those in the adenomas of four patients who showed suppression. The GR beta mRNA level was much lower than that of GR alpha mRNA but not significantly different among the six adenomas. CONCLUSIONS: These results suggest strongly that decreased expression of GR alpha in pituitary adenomas may be the major reason for the marked insensitivity to the 8-mg dexamethasone suppression test observed in two patients with Cushing's disease.

Actins↗

PubMed1998

Big endothelin analogues with inhibitory activity on endothelin-converting enzyme-1.

Big endothelin-1 (big ET-1) is converted into an active form, ET-1, by endothelin-converting enzyme-1 (ECE-1). To assess the mechanism of substrate recognition by ECE-1, we examined the effects of variously substituted analogues of big ET-1 on ECE-1 activity, using solubilized membranes prepared from human ECE-1-expressed CHO-K1 cells. Among the big ET-1 analogues tested, [21Phe]big ET-1[18-34] and [31Ala]big ET-1[18-34] exhibited significant inhibition of ECE-1. A kinetic analysis revealed [21Phe]big ET-1[18-34] to be a competitive inhibitor (Ki = 21 microM) and [31Ala]big ET-1[18-34] to be a noncompetitive inhibitor (Ki = 36 microM). These results suggested that ECE-1 recognizes big ET-1 at the P1 position and the C-terminal region in a different manner and that modification of these regions can produce ECE-1 inhibitors.

Animals↗

PubMed1998

Immunohistochemical study of cytochrome b5 in human adrenal gland and in adrenocortical adenomas from patients with Cushing's syndrome.

Cytochrome b5, a component of the electron transfer system increases the relative activity of 17,20-lyase to 17alpha-hydroxylase of P450c17 in vitro. In the present study, immunohistochemical analysis of cytochrome b5 was performed in the human adrenal gland and in adrenocortical adenomas from patients with Cushing's syndrome. In the human adrenal gland, cytochrome b5 was stained in all three adrenocortical layers but the staining was most remarkable in the zona reticularis. All of the adenomas were composed mainly of compact cells, which exhibited immunoreactive staining for cytochrome b5 as well as for P450c17 and 3beta-hydroxysteroid dehydrogenase (3beta-HSD). The distribution of b5 in the adenomas was correlated with that of P450c17 rather than with that of 3beta-HSD. The immunoreactive staining for cytochrome b5 appeared to be more prominent in the two adenomas that produced relatively high concentrations of adrenal androgens than in adenomas that produced low concentrations of adrenal androgens. These results immunohistochemically support the functional association of b5 with androgen production through interaction with P450c17 and the previous finding that higher concentrations of cytochrome b5 are associated with greater production of adrenal androgens in adrenocortical adenomas from patients with Cushing's syndrome.

3-Hydroxysteroid Dehydrogenases↗

PubMed1998

Nur77, a member of the steroid receptor superfamily, antagonizes negative feedback of ACTH synthesis and secretion by glucocorticoid in pituitary corticotrope cells.

Nur77 is a member of the steroid receptor superfamily and is known to be expressed in animals under stress. We studied the role of nur77 in the regulation of the hypothalamic-pituitary-adrenal (HPA) axis during the stress response using a murine pituitary corticotrope cell line, AtT-20. Corticotropin-releasing hormone (CRH), a stress mediator in the HPA axis, induced the expression of nur77 transiently in AtT-20 cells. Gel shift assay showed that nur77 bound to negative glucocorticoid responsive element (nGRE) in the promoter of the human proopiomelanocortin (POMC) gene and the formation of the nur77-nGRE complex increased after treatment of the cells with CRH. Negative GRE is known to be necessary for the negative regulation by glucocorticoid of the POMC gene expression. In stable transformants of AtT-20 cells expressing a human homolog of nur77, NAK-1, at a high level, glucocorticoid-mediated inhibition of both POMC mRNA induction and ACTH secretion was significantly lower than that in the NAK-1-non-expressing cells (P < 0.001). These results strongly suggest that nur77 antagonizes the negative feedback effect of glucocorticoid on the synthesis and secretion of ACTH in pituitary corticotropes. This suggests that nur77 plays an important role in the pituitary gland in the biological adaptation to overcome stress.

Adaptation, Physiological↗

PubMed1998

A rare case of 46,XX true hermaphroditism with hidden mosaicism with sex-determining region Y chromosome-bearing cells in the gonads.

The sex-determining region Y chromosome (SRY) triggers testis determination. We report a 46,XX true hermaphrodite who had ambiguous genitalia at birth. A laparotomy at one year of age revealed this patient to have a testis on the right side and an ovotestis on the left side. By polymerase chain reaction analysis no SRY was detected in the DNA from the leukocytes but it was found in the DNA from the ovotestis. The hidden mosaicism with the Y-bearing cells in the gonads is likely the cause of the dual gonads in this patient.

Adult↗

PubMed1997

[Phe21]big endothelin-1(18-34) and [Ala31]big endothelin-1(18-34) inhibit the human endothelin-converting enzyme-1 (ECE-1) expressed in CHO-K1 cells in a different fashion.

Endothelin-converting enzyme-1 (ECE-1) is one of the most important enzymes to convert big endothelin-1 (big ET-1) to ET-1. To identify the inhibitors of ECE-1, we examined the effects of variously substituted analogues of big ET-1 on ECE-1 activity using solubilized membranes prepared from human ECE-1-expressed CHO-K1 cells. Among the big ET-1 analogues tested, [Phe21]big ET-1(18-34) and [Ala31]big ET-1(18-34) exhibited a significant inhibition of ECE-1. A kinetic analysis revealed [Phe21]big ET-1(18-34) to be a competitive inhibitor (Ki=20.6 microM) and [Ala31]big ET-1(18-34) to be a noncompetitive inhibitor (Ki=35.6 microM). These results not only support the concept that ECE-1 recognizes big ET-1 both at the P1 position and at the C-terminal region but also revealed that these two regions are recognized by this enzyme in a different manner.

Animals↗

PubMed1997

Differential expression of PPAR gamma1 and gamma2 isoforms in human adipose tissue.

One of the essential factors for adipogenesis, peroxisome proliferator activated receptor gamma (PPAR gamma), is classified into two isoforms, gamma1 and gamma2 encoded by a single PPAR gamma gene. To examine the mode of expressions of both the PPAR gamma1 and gamma2 isoforms in human adipose tissue, we cloned a partial cDNA of the human PPAR gamma2 (hPPAR gamma2) from a human adipose tissue cDNA library. The sequence encoded an additional 28 amino acids amino-terminal to the first ATG codon of hPPAR gamma1. The simultaneous quantitation of hPPAR gamma1 and gamma2 mRNA in subcutaneous or visceral (mesenteric) fat tissue from 10 different individuals was performed by an RNase protection assay and revealed a relatively higher expression of gamma1 than gamma2 in all specimens examined.

Adipose Tissue↗

PubMed1997

Cloning and characterization of the 4.2 kb region of the rat thyrotropin receptor promoter.

We previously identified an approximately 200 bp "minimal promoter" of the rat TSH receptor (TSHR) gene which is essential for the promoter activity. In the present study, we have cloned and characterized an upstream region of the TSHR promoter to disclose additional functional element(s). We screened a rat genomic library and obtained a DNA fragment which contained a 4.2 kb 5'-flanking region. This fragment was 2.5 kb longer than that we previously studied (1.7 kb). To assess the promoter activity, chimeric plasmids containing the 4.2 kb promoter and its 5'-deletions ligated to a chloramphenicol acetyltransferase gene were transfected into thyroid and non-thyroid cells. These plasmids expressed significant promoter activity in FRTL-5 and FRT thyroid cells, but not in BRL liver cells. The strongest promoter activity was expressed by the -199 bp promoter, and the longer promoter expressed rather decreased activity. Co-expression of thyroid transcription factor-1 (TTF-1) increased the activity of the promoter region from -3187 to -199 bp, which encompassed one or two TTF-1 binding sites we previously identified, but not the -4206 bp promoter. In addition, FRTL-5 stable transfectants each having a chimeric construct were cultured in the presence or absence of TSH. All transfectants expressed higher promoter activity in the absence of TSH than in the presence of TSH, in particular, the -3187 bp plasmid expressed significantly higher activity by comparison to the -2617 and -4206 bp constructs. This result indicates that the region between -3187 and -2617 bp may contribute to TSH/cAMP-induced suppression and also suggests that the region between -4206 and -3187 bp involves the element(s) for constitutive suppression of the promoter activity. These results not only suggest that the 4.2 kb upstream region of the TSHR gene possibly contains some elements for the regulation of the gene expression, but also emphasize the importance of the minimal promoter region which we previously identified for the efficient expression of the gene.

Animals↗

PubMed1997

A case of mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes associated with diabetes mellitus and hypothalamo-pituitary dysfunction.

A 45-year-old woman with mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS) had muscular atrophy, severe cerebral and cerebellar atrophy, and cardiac hypertrophy. She also had diabetes mellitus treated with insulin, and sensorineural hearing loss. Ragged-red fibers were observed on muscle biopsy and an adenine to guanine transition mutation at position 3243 of her mitochondrial DNA was confirmed. Further investigations revealed that she also had hypothalamo-pituitary dysfunction. It appears that diabetes mellitus, hypothalamo-pituitary dysfunction, and the other abnormalities are all associated with mitochondrial dysfunction in this patient.

Atrophy↗