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Biomedical subjects

K Takaya

Publications and source records attributed to K Takaya.

At least 37 records · Page 2Linked to original sources
PubMed1998

Vascular endothelial growth factor (VEGF) expression in human coronary atherosclerotic lesions: possible pathophysiological significance of VEGF in progression of atherosclerosis.

BACKGROUND: Vascular endothelial growth factor (VEGF) is an important angiogenic factor reported to induce migration and proliferation of endothelial cells, enhance vascular permeability, and modulate thrombogenicity. VEGF expression in cultured cells (smooth muscle cells, macrophages, endothelial cells) is controlled by growth factors and cytokines. Hence, the question arises of whether VEGF could play a role in atherogenesis. METHODS AND RESULTS: Frozen sections from 38 coronary artery segments were studied. The specimens were characterized as normal with diffuse intimal thickening, early atherosclerosis with hypercellularity, and advanced atherosclerosis (atheromatous plaques, fibrous plaques, and totally occlusive lesions). VEGF expression as well as the expression of 2 VEGF receptors, flt-1 and Flk-1, were studied with immunohistochemical techniques in these samples at the different stages of human coronary atherosclerosis progression. The expression of VEGF mRNA was also studied with reverse transcription-polymerase chain reaction. Normal arterial segments showed no substantial VEGF expression. Hypercellular and atheromatous lesions showed distinct VEGF positivity of activated endothelial cells, macrophages, and partially differentiated smooth muscle cells. VEGF positivity was also detected in endothelial cells of intraplaque microvessels within advanced lesions. In totally occlusive lesions with extensive neovascularization, intense immunostaining for VEGF was observed in accumulated macrophages and endothelial cells of the microvessels. Furthermore, VEGF mRNA expression was detected in atherosclerotic coronary segments but not in normal coronary segments. The immunostainings for flt-1 and Flk-1 were detected in aggregating macrophages in atherosclerotic lesions and also in endothelial cells of the microvessels in totally occlusive lesions. CONCLUSIONS: These results demonstrate distinct expression of VEGF and its receptors (flt-1 and Flk-1) in atherosclerotic lesions in human coronary arteries. Considering the multipotent actions of VEGF documented experimentally in vivo and in vitro, our findings suggest that VEGF may have some role in the progression of human coronary atherosclerosis, as well as in recanalization processes in obstructive coronary diseases.

Adult↗
PubMed1998

Identification of cis-elements of the human endothelin-A receptor gene and inhibition of the gene expression by the decoy strategy.

Previously, we succeeded in molecular cloning of the cDNA and the gene for human endothelin-A receptor (ET-AR). In the present study, we define cis-elements in the 5'-flanking region of the ET-AR gene. Deletion analyses were performed in A7r5 cells, rat vascular smooth muscle cell line, and Chinese hamster ovary cells using ET-AR promoter-luciferase gene constructs including 5 kilobases of the 5'-flanking region. These analyses demonstrated the existence of one negative regulatory element (-2.0 kilobases to -857 bases) and two positive regulatory elements (-137 to -53 and -53 to +251). Gel mobility shift assay revealed a nuclear protein binding to the region (-104 to -78) (R1). DNase I footprinting analysis showed a footprint spanning from -91 to -83 whose sequence is CCCCACCTT (ETA-P1). When a plasmid including R1 fragments (R1 decoy) was co-transfected into A7r5 cells with ET-AR (-137 to +251)-luciferase gene construct, it significantly reduced the luciferase activity in a dose-dependent manner. Moreover, R1 decoy down-regulated the endogenous ET-AR mRNA in A7r5 cells by a maximum of 75%. Thus, we identified cis-elements that regulate basal transcriptional activity of the ET-AR gene and proved the feasibility to suppress the expression of the ET-AR gene by the DNA decoy strategy using the positive regulatory element we identified.

Animals↗
PubMed1998

Clinical study on localization-related epilepsy in infancy without underlying disorders.

A clinical study of 15 patients without underlying disorders whose first seizures occurred before 1 year of age was performed to determine the characteristics of localization-related epilepsies in infancy. The patients were retrospectively divided into two groups: the seizure-controlled group (10 patients) and the refractory group (five patients). The seizure-controlled group included patients whose seizures were controlled completely within 1 year after onset; the refractory group included all other patients. The characteristics of the refractory group were as follows: (1) interictal electroencephalography showed focal abnormalities, particularly on the left side, and (2) all of the patients exhibited developmental retardation. Even in the seizure-controlled group, 40% of the patients exhibited developmental retardation, and all of them were indistinguishable from patients with benign complex partial epilepsies in infancy at the onset of the seizures. Aggressive treatment should be re-evaluated for early-onset localization-related epilepsies.

Anticonvulsants↗
PubMed1998

Association of oxygen tension in human periodontal pockets with gingival inflammation.

The objective of this study was to investigate the association of the oxygen tension in the periodontal pockets with clinical parameters of gingival inflammation of the maxillary anterior teeth of 32 patients. The pocket oxygen tension (pO2) was measured by a polarographic method with electronic compensation for temperature change. The oxygen saturation of hemoglobin (SO2) in the gingiva was determined with tissue reflectance spectrophotometry. Gingival crevicular fluid flow (GCF) was measured with electronic impedance. No significant association was found between pocket pO2 and the modified gingival index, the plaque index, and GCE Pocket pO2 showed significant correlation with probing depth (r = -0.57, P = 0.0005). Significant correlation was observed between pocket pO2 and gingival SO2 (r = 0.69, P < 0.0001). When all variables were entered into a multiple regression model, only gingival SO2 had a significant independent effect on the pocket pO2 (P = 0.0005). These results indicate that the oxygen sufficiency in the gingiva has a significant independent influence on the pocket oxygen tension. These studies provide the basis for understanding the oxygen tension in the periodontal pocket, which likely is a major determinant of the subgingival microflora. The studies may also lead to the development of methods for diagnosing and monitoring periodontal diseases.

Adult↗
PubMed1998

[Leptin Receptor].

Leptin is a fat cell-derived satiety factor that regulates food intake and energy expenditure. Its effects are mediated by interactions with the leptin receptor (Ob-R) that is alternatively spliced to encode at least five isoforms(a-e), which are distributed in a wide range of tissues including the hypothalamus. Ob-R is a member of cytokine receptors and involves the JAK-STAT signal transduction system. We found Ob-R mutations in Zucker fatty rats and obese Koletsky rats and demonstrated that Ob-R dysfunction brings around hyperphagia and obesity. However we and others have not found any Ob-R mutation in human obese subjects.

Animals↗
PubMed1997

Augmentation of obese (ob) gene expression and leptin secretion in obese spontaneously hypertensive rats (obese SHR or Koletsky rats).

To explore the pathophysiologic roles of the obese (ob) gene product, leptin, in the development of obesity and hypertension, we examined ob gene expression and leptin secretion in obese spontaneously hypertensive rats (obese SHR or Koletsky rats) at the stage of established obesity and hypertension. Expression of the ob gene was augmented in the epididymal, mesenteric, subcutaneous, and retroperitoneal white adipose tissue (WAT) from 20-week-old male obese SHR compared to their lean littermates (lean SHR). Using a radioimmunoassay for rat leptin, we also measured plasma leptin levels in 20-week-old lean and obese SHR. Plasma leptin levels in obese SHR (292.5 +/- 37.1 ng/ml) were more than 100-fold higher than those in lean SHR (2.8 +/- 1.0 ng/ml). The present study demonstrates that ob gene expression and leptin secretion are markedly augmented in obese SHR.

Animals↗
PubMed1997

An investigation into the prevalence of thyroid disease on Kwajalein Atoll, Marshall Islands.

The prevalence of thyroid nodules and thyroid cancer was studied in the indigenous population residing on Ebeye Island, Kwajalein Atoll, in the Republic of the Marshall Islands. This island, centrally located in the nation, is home to about 25% of the nation's population, many who have migrated there from other atolls. The objective of the study was to obtain thyroid disease rate statistics on as much of the population as possible that was alive during the years of nuclear testing and to test the hypothesis that described a linearly decreasing prevalence of palpable nodules with increasing distance from the Bikini test site. 1,322 Marshallese born before 1965 were given a thyroid examination using neck palpation, fine needle aspiration biopsy, and high resolution ultrasound imaging. Approximately 40% of the total population living on this island who are at risk from exposure to radioactive fallout during the years 1946-1958 were screened. Of that group, 815 were alive at the time of the BRAVO test on 1 March 1954. Two hundred sixty-six people with thyroid nodules were found (32.6%): 132 were palpable nodules (16.2%), and 134 were nodules that could be diagnosed with ultrasound only (15.7%). Prevalence of palpable nodules was particularly high in men and women older than 60 y, in men who were 6 to 15 y of age at the time of the BRAVO test, and in women 1 to 10 y of age at the time of the BRAVO test. In 22 people, the clinical diagnosis was most likely cancer though histopathological evidence was only available from 11 operated cases. Of the 11 operated cases, 10 were cancer. Cancer prevalence was particularly high in those women born between 1944 and 1953 (7/220 = 3.2%), i.e., who were children during the early years of nuclear testing. The Ebeye data showed a marginally significant correlation between palpable nodule prevalence among women and distance to Bikini (r = -0.44, p = 0.06). This report summarizes the clinical findings of the thyroid examinations, the age distributions for nodular disease and cancer, and examines the relationship between prevalence of nodules and present day levels of 137Cs in the environment of each atoll.

Adult↗
PubMed1997

Opposite regulation of Gax homeobox expression by angiotensin II and C-type natriuretic peptide.

Growth arrest-specific homeobox (Gax) gene was isolated from rat aorta cDNA library and its expression was largely confined to the cardiovascular tissues. Gax gene was rapidly downregulated by platelet-derived growth factor in vascular smooth muscle cells (VSMCs) and overexpressed Gax was reported to reduce the neointimal thickening after balloon injury in vivo. We have demonstrated that angiotensin II (Ang II) stimulates vascular growth. In contrast, we also reported that C-type natriuretic peptide (CNP) is secreted from vascular endothelial cells to act as a novel endothelium-derived relaxing peptide and inhibits vascular growth via cGMP cascade. In the present study, we examined the effects of Ang II and CNP on Gax gene expression in VSMCs. In quiescent rat aortic VSMCs. Gax mRNA (2 3 kb) level became negligible 6 hours after the addition of Ang II (10(-6) mol/L). The inhibitory action of Ang II on Gax mRNA expression (ED50: 10(-11) mol/L) was almost completely blocked by an AT1R antagonist, CV11974. In contrast, CNP 10(-6) mol/L augmented Gax mRNA expression to exhibit 1.8-fold increase of the control 12 hours after the stimulation. This effect of CNP was mimicked by the addition of 8-bromoadenosine 3'-5'-cyclic monophosphate. The addition of C-ANF[4-23], an atrial natriuretic peptide-C receptor-specific agonist and devoid of stimulating cGMP production, exhibited no effect on Gax mRNA expression. Simultaneous administration of Ang II and CNP revealed that CNP (10(-6) mol/L) significantly attenuated the inhibitory action of Ang II (10(-10) mol/L) on Gax mRNA expression. These results suggest that Gax is a common transcription factor involved in the signaling pathway of vascular growth for Ang II and CNP and regulates the cell cycle and/or phenotype of VSMCs for vascular remodeling in hypertension and atherosclerosis.

Angiotensin II↗
PubMed1997

Shear stress augments expression of C-type natriuretic peptide and adrenomedullin.

Shear stress is known to dilate blood vessels and exert antiproliferative effects on vascular walls: these effects have been ascribed to shear stress-induced upregulation of endothelium-derived vasoactive substances, mainly nitric oxide and prostacyclin. We have demonstrated the significance of C-type natriuretic peptide (CNP) as a novel endothelium-derived relaxing peptide (EDRP) that shares a cGMP pathway with nitric oxide. Adrenomedullin is a recently isolated EDRP that elevates intracellular cAMP as prostacyclin does. To elucidate the possible role of these EDRPs under shear stress, we examined the effect of physiological shear stress on CNP mRNA expression in endothelial cells derived from the human umbilical vein (HUVECs), bovine aorta (BAECs), and murine lymph nodes (MLECs) as well as adrenomedullin mRNA expression in HUVECs. CNP mRNA was stimulated prominently in HUVECs under shear stress of 15 dyne/cm2 in a time-dependent manner (4 hours, sixfold increase compared with that in the static condition; 24 hours, 30-fold increase). Similar results were obtained in BAECs (4 hours, twofold increase; 24 hours, threefold increase) and MLECs (4 hours, threefold increase; 24 hours, 10-fold increase). Augmentation of CNP mRNA expression that was dependent on shear stress intensity was also observed (5 dyne/cm2, 2.5-fold increase of static; 15 dyne/cm2, 4.5-fold increase). Increased CNP secretion was also confirmed by the specific radioimmunoassay for CNP. Adrenomedullin mRNA expression in HUVECs increased under shear stress of 15 dyne/cm2 in a time-dependent manner (4 hours, 1.2-fold increase of static: 24 hours, threefold increase) and shear stress intensity-dependent manner (15 dyne/cm2, threefold increase compared with that at 5 dyne/cm2). These results suggest that the coordinated augmentation of mRNA expression of these novel EDRPs may constitute shear stress-dependent vasodilator and antiproliferative effects.

Adrenomedullin↗
PubMed1997

[Transient inhibitors developed in two cases of hemophilia A].

This report describes the transient development of inhibitors in two cases of hemophilia A. Case 1 was an 8-month-old boy who suffered from subcutaneous hematoma with extremely low level (1.5%) of plasma factor VIII activity (F VIII:C). He showed an inhibitor titer of 2.5 Bethesda units (BU)/ml when he suffered from measles at age 24 months with poor clinical response to factor VIII. This inhibitor elevated to 11.6 BU/ml at 29 months, but completely disappeared at 32 months. Case 2 was a 5-month-old boy who suffered from subcutaneous hematoma with extremely low level (< 1%) of plasma F VIII:C. At 8 months his inhibitor titer peaked at 19 BU/ml but subsequently declined to 11.5 BU/ml at 12 months and completely disappeared at 14 months. A review of the literature revealed that the median (range) titer of transient inhibitor initially developed at 2 (0.5-19) BU/ml on 225 (79-448) days, immediately peaked at 3.6 (0.5-60) BU/ml and disappeared by 665 (282-1140) days, suggesting that careful monitoring of F VIII inhibitors is required in the treatment of hemophilia A.

Autoantibodies↗
PubMed1996

Molecular cloning of rat leptin receptor isoform complementary DNAs--identification of a missense mutation in Zucker fatty (fa/fa) rats.

We cloned the full-length rat leptin receptor (Ob-R) isoform complementary DNAs (cDNAs) and examined the gene expression in rats. We also identified a mutation in Ob-R in Zucker fatty (fa/fa) rats. Three alternatively spliced isoforms (Ob-Ra, Ob-Rb, and Ob-Re) have been identified, which are closely related to the gp130 signal-transduction component of class I cytokine receptors. Rat Ob-Ra and Ob-Rb were single transmembrane proteins, which differ in the C-terminal amino acid sequences. On the other hand, Ob-Re had no transmembrane domain and was a soluble form of the receptor. Reverse transcription-polymerase chain reaction analysis revealed that Ob-R isoform messenger RNAs (mRNAs) are expressed in a wide variety of rat tissues in tissue-specific manners. A missense mutation (an A to C conversion at nucleotide position 806) was found in the extracellular domain of all the isoforms in Zucker fatty (fa/fa) rats, which resulted in an amino acid change from Gln to Pro at + 269 (the Gln269Pro mutation). These Ob-R isoform mRNAs were present in the brain from Zucker fatty (fa/fa) rats at comparable amounts to those in their lean littermates. The present study provides new insight into the molecular mechanisms for Ob-R.

Alternative Splicing↗
PubMed1996

Alternative RNA splicing of the human endothelin-A receptor generates multiple transcripts.

In order to elucidate the regulatory mechanisms of expression of the human endothelin-A receptor (hET-AR) gene, we characterized hET-AR transcripts using reverse transcriptase (RT)-PCR analysis in a variety of human tissues. RT-PCR of lung mRNA using a set of primers from exons 2 and 5 showed two lower-molecular-mass transcripts in addition to the expected fragment. When RT-PCR with primers from exons 4 and 8 was performed, no transcripts other than the expected one were detected. PCR cloning utilizing a set of primers from exons 2 and 8 which covered the entire coding sequence revealed that the cDNA clones corresponding to the two novel transcripts contained deletions of 199 bp and 327 bp respectively compared with the previously described hET-AR cDNA. Comparison of their sequences with that of the hET-AR gene showed that the deleted sequences correspond exactly to exon 4 and exons 3 and 4 respectively, indicating that these lower-molecular-mass ET-AR transcripts results from alternative RNA splicing (designated ET-AR delta 4 and ET-AR delta 3,4 respectively). Alternative splicing of exon 4 results in a transcript which would be translated into a C-terminal truncated protein containing the first, second and third transmembrane domains, while the splicing out of exons 3 and 4 would produce a protein with five membrane-spanning domains but lacking the third and fourth domains present in the ET-AR protein. An RNase protection assay revealed that ET-AR delta 4 and ET-AR delta 3,4 as well as ET-AR, transcripts were observed in various human tissues, including the lung, aorta, atrium, kidney and placenta, which are known to express ET-AR abundantly. Thus we have isolated the cDNAs of novel transcripts of hET-AR which are generated by alternative RNA splicing, and these results suggest that this alternative RNA splicing might contribute to the regulation of ET-AR gene expression.

Alternative Splicing↗
PubMed1996

Expression of the RET proto-oncogene in normal human tissues, pheochromocytomas, and other tumors of neural crest origin.

In order to evaluate the roles of the RET proto-oncogene in normal human tissues and tumors derived from the neural crest cells, we examined the expression of RET in a variety of adult human tissues, pheochromocytomas, medullary thyroid carcinomas (MTCs), ganglioneuromas, and a neurinoma. Northern blot analysis demonstrated that RET is normally expressed in the adrenal medulla and cerebellum among adult human tissues. RET transcripts were detected in all of 11 sporadic and one familial pheochromocytomas. The levels of RET mRNA were higher in 8 of 12 pheochromocytomas than in the normal adrenal medulla, indicating that RET is overexpressed in the majority of sporadic pheochromocytomas. There was a considerable difference in the level of RET expression in each pheochromocytoma ranging from 0.2 to 10 times the transcripts found in the normal adrenal medulla. The sizes of the transcripts of 7.0, 6.0, 4.5, and 3.9 kb were the same as those found in the adrenal medulla, suggesting no rearrangements of the RET gene in pheochromocytomas. Southern blot analysis revealed neither amplification nor gross structural changes in the RET gene. RET was also expressed at high levels in four MTCs examined, whereas its transcripts were detected at low abundance in only one of three ganglioneuromas. RET was not expressed in a neurinoma. These results suggest that RET may play some roles in a limited range of adult human tissues, and that its high levels of expression may have relevance to development or growth of pheochromocytomas and MTCs.

Adult↗
PubMed1996

Vascular endothelial growth factor suppresses C-type natriuretic peptide secretion.

Angiogenesis plays a pivotal role not only in wound healing and tumor progression but also in diabetic angiopathy, arteriosclerosis, and collateral formation of obstructive vascular diseases. Vascular endothelial growth factor (VEGF) is now thought to be an endothelium-specific and potent angiogenic factor. We previously demonstrated that C-type natriuretic peptide (CNP), originally isolated from porcine brain, is produced by endothelial cells and proposed that CNP can exert control over vascular tone and growth as a local vascular regulator. In the present study, we examined the effect of VEGF on CNP secretion from endothelial cells using the specific radioimmunoassay for CNP we developed. VEGF (1 to 100 ng/mL) dose-dependently suppressed CNP secretion from cultured bovine endothelial cells, and 100 ng/mL VEGF suppressed endothelial CNP secretion to 28% of control levels (31.7 +/- 5.5 versus 8.9 +/- 0.8 fmol/mL, vehicle versus VEGF). VEGF also suppressed CNP mRNA expression in endothelial cells 9 hours after administration. In contrast, basic fibroblast growth factor (20 ng/mL), an endothelium-nonspecific angiogenic factor, significantly stimulated CNP secretion by 290%. These results indicate that VEGF can regulate vascular tone and growth in the process of angiogenesis through suppression of endothelial secretion of CNP, which is an endothelium-derived vasorelaxing and growth-inhibitory peptide.

Animals↗
PubMed1996

The RET proto-oncogene in sporadic pheochromocytomas.

In order to evaluate the role of RET proto-oncogene in the development and growth of pheochromocytomas, we examined mutations in RET and expression of RET in 7 cases of sporadic pheochromocytomas. Tumors were screened for mutations in exons 10 and 11 and codon 918 which are identified in multiple endocrine neoplasia types 2A and 2B. No mutations were found in these regions in all of the sporadic pheochromocytomas examined. On the other hand, RET mRNA was detected in all pheochromocytomas and the levels of RET expression were higher in 5 of 7 pheochromocytomas than in normal adrenal medulla, indicating that RET is overexpressed in a sizable portion of sporadic pheochromocytomas. These results suggest that high levels of expression of RET may have relevance to the development or growth of sporadic pheochromocytomas.

Adrenal Gland Neoplasms↗
PubMed1996

[Quality of life of patients with chronic neurological diseases living in institutions].

The hospitals or residential institutions for patients with chronic neurological diseases have to provide the function of medical treatment and well living support. The living space should be made at home and familiar. It means 1. providing a small group life, 2. giving warm atmosphere, 3. providing living functions. Medical and living functions are necessary both in housing (hard phase) and in care given by staff (soft phase). For the QOL of children who are treated for their chronic disease in institutions, the next three conditions are important. 1. comfortable physical conditions, 2. human relations, 3. hope.

Child↗