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H Watada

Publications and source records attributed to H Watada.

33 records · Page 2Linked to original sources
PubMed1997

The Arg192 isoform of paraoxonase with low sarin-hydrolyzing activity is dominant in the Japanese.

The high-density-lipoprotein-associated enzyme paraoxonase, which has a role in the detoxification of organophosphorus compounds, is known to be polymorphic in humans. The Arg192 isoform of paraoxonase hydrolyzes paraoxon more rapidly than the Gln192 isoform. However, with respect to the hydrolysis of toxic nerve agents, such as diazoxon, soman, and sarin, the Arg192 isoform displays a lower activity than the other isoform. To evaluate the possibility that the genetic polymorphism was involved in the aggravated extent of human injury in the sarin gas poisoning incident in the Tokyo subway in March 1995, we investigated the prevalance of this polymorphism in the Japanese population. We found that the Arg192 allele is more common in the Japanese (allele frequency: 0.66) than in people of other races (ranging 0.24-0.31). In the Japanese, 135 out of the 326 subjects (41.4%) investigated were homozygous for the Arg192 allele, which shows a very low hydrolysis activity for sarin. Thus, there seems to be a racial difference in vulnerability to toxic nerve agents, such as sarin. The dominance of the Arg192 allele in the Japanese population probably worsened the tragedy of March 1995 in the Tokyo subway.

Alleles↗
PubMed1997

Demonstration of two different processes of beta-cell regeneration in a new diabetic mouse model induced by selective perfusion of alloxan.

To clarify the regeneration process of pancreatic beta-cells, we established a new mouse model of diabetes induced by selective perfusion of alloxan after clamping the superior mesenteric artery. In this model, diabetes could be induced by the destruction of beta-cells in alloxan-perfused segments, while beta-cells in nonperfused segments were spared. Intraperitoneal glucose tolerance tests showed glucose intolerance, which gradually ameliorated and was completely normalized in 1 year with a concomitant increase of insulin content in the pancreas. Histological examination showed neo-islet formation in the alloxan-perfused segment and the proliferation of spared beta-cells in the nonperfused segment. In the alloxan-perfused segment, despite a marked reduction of islets in size and number at an early stage, both the number of islets, including islet-like cell clusters (ICCs), and the relative islet area significantly increased at a later stage. Increased single beta-cells and ICCs were located in close contact with duct cell lining, suggesting that they differentiated from duct cells and that such extra-islet precursor cells may be important for beta-cell regeneration in beta-cell-depleted segment. In addition to beta-cells, some nonhormone cells in ICCs were positive for nuclear insulin promoter factor 1, which indicated that most, if not all, nonhormone cells positive for this factor were beta-cell precursors. In the nonperfused segment, the islet area increased significantly, and the highest 5-bromo-2-deoxyuridine-labeling index in beta-cells was observed at day 5, while the number of islets did not increase significantly. This indicated that the regeneration of islet endocrine cells occurs mostly through the proliferation of preexisting intra-islet beta-cells in the nonperfused segment. In conclusion, the regeneration process of beta-cells varied by circumstance. Our mouse model is useful for studying the mechanism of regeneration, since differentiation and proliferation could be analyzed separately in one pancreas.

Alloxan↗
PubMed1996

Involvement of the homeodomain-containing transcription factor PDX-1 in islet amyloid polypeptide gene transcription.

The AT-rich cis-motif A elements of the insulin gene promoter contribute to directing the gene's expression to pancreatic beta-cells, bound by a homeodomain-containing transcription factor, PDX-1/IPF1/STF-1/IDX-1. The islet amyloid polypeptide (IAPP; amylin) gene, which is also expressed in limited tissues such as pancreatic beta- and delta-cells, contained similar AT-rich sequences in its regulatory sequences. To understand the molecular basis of IAPP gene regulation, we evaluated the possible physiological significance of the motif in human IAPP gene regulation. All of the three typical A element-like sequences that matched the CT-box consensus (AT-1, -207/-202; AT-2, -154/-142; and AT-3, -88/-83) were shown to bind specifically to a nuclear factor in the beta-cell-derived MIN6 cells, which was subsequently identified immunologically as the insulin gene transcription factor PDX-1. When the promoter activity was examined in MIN6 cells, the disruption of AT-1 or AT-3 but not of AT-2 caused a marked reduction in the IAPP gene promoter. Thus, despite the observation that all the three A element-like regions could bind to PDX-1, the AT-2 site may not be involved in mediating the PDX-1 action in vivo. These observations suggest the involvement of PDX-1 in human IAPP gene regulation, which seems to be mediated through at least two A element-like cis-motifs in the gene promoter.

Amyloid↗
PubMed1996

Pancreatic islet cells express BST-1, a CD38-like surface molecule having ADP-ribosyl cyclase activity.

Cyclic ADP-ribose (cADPR), a well-known stimulator of ca(2+) release from the intracellular Ca(2+) pool, has recently emerged as a potential regulator of insulin secretion in pancreatic beta cells. As recently described, BST-1 is a glycosyl-phosphatidylinositol (GPI)-anchored surface molecule that exhibits homology with CD38 and Aplysia ADP-ribosyl cyclase. Like CD38, BST-1 has both ADP-ribosyl cyclase and cADPR hydrolase activities. As a step toward elucidating the physiological role of cADPR in insulin secretion we examined whether BST-1 is expressed in pancreatic islet cells. Sensitive reverse transcription-polymerase chain reaction detected almost as abundant expression of BST-1 mRNA in pancreatic islets as CD38 mRNA. Immunohistochemical analyses utilizing mirror image sections revealed that BST-1 protein is expressed in a majority of the cells in pancreatic islets and that at least beta cells and, to an even greater extent, alpha cells express BST-1. These observations suggest the involvement of multiple enzymes in the regulation of cADPR concentrations in pancreatic islet cells.

ADP-ribosyl Cyclase↗
PubMed1996

The human glucokinase gene beta-cell-type promoter: an essential role of insulin promoter factor 1/PDX-1 in its activation in HIT-T15 cells.

The glycolytic enzyme glucokinase plays a primary role in the glucose-responsive secretion of insulin, and defects of this enzyme can cause NIDDM. As a step toward understanding the molecular basis of glucokinase (GK) gene regulation, we assessed the structure and regulation of the human GK gene beta-cell-type promoter. The results of reporter gene analyses using HIT-T15 cells revealed that the gene promoter was comprised of multiple cis-acting elements, including two primarily important cis-motifs: a palindrome structure, hPal-1, and the insulin gene cis-motif A element-like hUPE3. While both elements were bound specifically by nuclear proteins, it was the homeodomain-containing transcription factor insulin promoter factor 1 (IPF1)/STF-1/PDX-1 that bound to the hUPE3 site: IPF1, when expressed in CHO-K1 cells, became bound to the hUPE3 site and activated transcription. An anti-IPF1 antiserum used in gel-mobility shift analysis supershifted the DNA protein complex formed with the hUPE3 probe and nuclear extracts from HIT-T15 cells, thus supporting the involvement of IPF1 in GK gene activation in HIT-T15 cells. In contrast to the insulin gene, however, neither the synergistic effect of the Pan1 expression on the IPF1-induced promoter activation nor the glucose responsiveness of the activity was observed for the GK gene promoter. These results revealed some conservative but unique features for the transcriptional regulation of the beta-cell-specific genes in humans. Being implicated in insulin and GK gene regulations as a common transcription factor, IPF1/STF-1/PDX-1 is likely to play an essential role in maintaining normal beta-cell functions.

Amino Acid Sequence↗
PubMed1996

PDX-1 induces insulin and glucokinase gene expressions in alphaTC1 clone 6 cells in the presence of betacellulin.

The pancreatic beta- and alpha-cells are developmentally related to each other but reveal diverse gene expression patterns. Among the two important transcription factors for insulin gene expression, IEF1 is present both in alpha- and beta-cells, but PDX-1/IPF1/STF-1/IDX-1, a homeodomain-containing transcription factor, is present in beta-cells but not in alpha-cells. To elucidate the function of PDX-1 in the expression of beta-cell-specific genes, we established stable alphaTC1 clone 6 (alphaTC1.6)-derived transfectants expressing PDX-1 and examined the changes in the gene expression patterns in them. The exogenous expression of PDX-1 in alphaTC1.6 cells alone could induce islet amyloid polypeptide (IAPP) mRNA expression in the cells but not the expression of insulin, glucokinase, or GLUT2 gene. However, when betacellulin was added to the medium, the PDX-1-expressing alphaTC1.6 cells, but not the control alphaTC1.6 cells, came to express insulin and glucokinase mRNAs. This did not occur with other growth factors such as epidermal growth factor, transforming growth factor alpha, and insulin-like growth factor I. GLUT2 mRNA remained undetectable in the PDX-1--expressing alphaTC1.6 cells. These observations demonstrate the potency of PDX-1 for the expression of the insulin, glucokinase, and IAPP genes and suggest that certain regulatory factors, which can partially be modified by betacellulin, also contribute to the beta-cell specificity of gene expression.

Amyloid↗
PubMed1995

Expression of CD38 gene, but not of mitochondrial glycerol-3-phosphate dehydrogenase gene, is impaired in pancreatic islets of GK rats.

Goto-Kakizaki (GK) rat, a rodent model of spontaneously occurring non-insulin dependent diabetes mellitus (NIDDM), exhibits impaired glucose-stimulated insulin secretion. To explore the background of the beta-cell dysfunction in NIDDM, we investigated whether and how the expression pattern of factors that would potentially be involved in the glucose-stimulated insulin secretion machinery is changed in GK rats. Using quantitative reverse transcription-PCR (RT-PCR) method, we found that the gene expression of CD38, a type 2 membrane protein which has ADP-ribosyl cyclase activity, is reduced by approximately 50% in islets of GK rats. Despite previous studies showing reduction in the FAD-linked mitochondrial glycerol-3-phosphate dehydrogenase (mGPDH) activity in GK rats, the mGPDH mRNA amounts were equal to those in the control Wistar rats, suggesting a difference that arose post-transcriptionally. These observations support the idea that multiple defects of the glucose-responsive insulin secreting machinery are involved in the development of diabetes in GK rats.

ADP-ribosyl Cyclase↗
PubMed1995

Ubiquitous, but variable, expression of two alternatively spliced mRNAs encoding mouse homologues of transcription factors E47 and E12.

Two basic helix-loop-helix (bHLH) transcription factors, E47 and E12, are involved in cell-specific gene expression as part of dimeric complexes which interact with the cis-acting motif E-box. Although both generated from a single gene (E2A) by means of alternative splicing, the structural difference in these bHLH regions between the two suggests that the two bHLH proteins may differ in some of their functions. As a step toward elucidating the individual implications of E47 and E12, we investigated the mRNA expression ratios of their homologues (A1 and kA1, respectively) in mouse tissues and cell lines. Both the A1 and kA1 mRNAs were ubiquitously expressed in all tissues examined. However, their ratios varied: e.g., skeletal muscle, 2.2 +/- 0.3 (mean +/- SE); spleen, 2.0 +/- 0.2; pancreatic islet cells, 1.2 +/- 0.2. The A1/kA1 ratios in the cell lines investigated were similar to those of their original tissues. In conclusion, the ubiquity in mRNA expression observed for both the E47 and E12 homologues in mouse provides support for their involvement in a broad range of transcriptional regulation. The variation in the A1/kA1 expression ratios, on the other hand, supports the idea that A1 (E47) and kA1 (E12) each have some unique roles in the functions of these E2A gene-encoded bHLH proteins.

Alternative Splicing↗
PubMed1995

Alterations in the mitral flow velocity pattern induced by acute myocardial infarction. Doppler findings before and after infarction.

Several studies have demonstrated that myocardial infarction (MI) is likely to alter left ventricular diastolic function. However, it is unclear whether MI per se alters Doppler transmitral flow velocity patterns (TMF) clinically. To investigate how myocardial infarction alters TMF clinically, we assessed serial changes in TMF in 13 patients whose TMF patterns were recorded at a mean of 7 months before and after MI in relation to the size of MI. From TMF, early and atrial filling flow velocities (E and A (m/s), respectively), and the E/A ratio, were measured. From simultaneously recorded two-dimensional echocardiograms, left ventricular dimensions and wall motion score (WMS: sum of 17 segmental scores (dys/akinesis = 3 to normal = 0)) were determined. The patients were divided into two subsets based on the values for WMS in the convalescent stage; 8 patients had small MI (WMS < or = 10) and 5 patients had large MI (WMS > 10). In patients with small MI, although E and the E/A ratio decreased at day-1 compared with pre-MI values (pre-MI vs day-1, E; 0.54 +/- 0.12 vs 0.39 +/- 0.15, p < 0.05, E/A ratio 0.91 +/- 0.23 vs 0.68 +/- 0.14, p < 0.05), these values increased to levels similar to those observed at pre-MI in the convalescent stage. There were no changes in left ventricular dimensions between pre-MI and in the convalescent period. In patients with large MI, the changes in the TMF patterns varied among patients after MI. In 3 patients with WMS < or = 25, E and E/A ratio were decreased in the convalescent stage, compared with pre-MI values. In 2 patients with WMS > 25, TMF patterns showed 'pseudonormalization' (E/A ratio > 1.0) throughout the follow-up period, with a progressive increase in left ventricular dimension. Thus, MI per se does not always produce clear changes in the Doppler TMF pattern in clinical settings, and the size of the MI seems to be a determinant of the TMF pattern after MI.

Adult↗
PubMed1994

Estrogen regulation of the insulin-like growth factor I gene transcription involves an AP-1 enhancer.

As a step toward elucidating the physiological role of insulin-like growth factor-I (IGF-I) in mediating estrogen action, we sought to determine the molecular basis of the phenomenon. In HepG2 cells expressing exogenous estrogen receptors (ER), a reporter gene plasmid containing 600 base pairs of the chicken IGF-I promoter enhanced expression of luciferase 8.6-fold in response to 10(-6) M 17 beta-estradiol, indicating that the IGF-I promoter is a target of estrogen regulation. Although no conventional estrogen-responsive element was identified within the promoter fragment, the AP-1 motif located therein was shown to be essential; the estrogen-responsive enhancement of the Fos-Jun binding to the AP-1 motif, which takes place by means of post-translational modification, mediates the estrogen action. A direct or indirect interaction between the estrogen-ER complex and the Fos-Jun complex seems to facilitate the Fos-Jun binding to the target DNA. Although ER binding to the target DNA was not considered to be involved in the signaling pathway, the DNA binding domain-deficient ER did not mediate the phenomenon, providing support for the existence of a unique function of the DNA binding domain of ER in facilitating some protein-protein interaction. In conclusion, our present observations demonstrate that the chicken IGF-I gene promoter is controlled by estrogen through a unique pathway involving Fos, Jun, and the DNA binding domain of ER.

Animals↗
PubMed1994

Incidence and time course of left ventricular dilation in the early convalescent stage of reperfused anterior wall acute myocardial infarction.

The incidence and early process of left ventricular (LV) dilation in 52 patients with reperfused anterior wall acute myocardial infarction (AMI) were assessed. All patients achieved coronary reflow within 24 hours of the onset and had a patent infarct-related artery in the convalescent stage. Left ventriculography was performed at pre-reflow and 25 days (mean) later to determine LV end-diastolic volume (ml) with the area/length method. Short-axis echo images at the midpapillary muscle level were recorded at days 1, 7, 14, and 28 of the AMI. With use of the papillary muscles as the internal landmarkers, the LV wall was divided into the anterior and posterior segments, and length and thickness of each segment were determined. Among 52 patients, 10 (19%) had a > or = 20% increase in end-diastolic volume in the convalescent stage. Echocardiographic studies demonstrated that there were no significant changes in lengths and thicknesses of the anterior and posterior segments during follow-up study relative to his or her baseline value in 42 patients without LV dilation. In the patients with LV dilation, however, the anterior segment exhibited a mean increase of 25% in its length with a mean decrease of 21% in its thickness at day 7 relative to their baseline values, but no progressive expansion was observed after day 7. A mean increase of 7% in the posterior segment length without reduction in its thickness first became evident at day 28.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Angiography↗
PubMed1994

Identification of amino-acid polymorphism within the leucine zipper motif of mouse transcription factor A1.

Mouse transcription factor A1 (A1) is a mouse homologue of human E47, a ubiquitously expressed DNA-binding protein which contains a basic region, helix-loop-helix (HLH) and leucine zipper (LZ) motifs [Walker et al., Nucleic Acids Res. 18 (1990) 1159-1166]. Analyses of the nucleotide (nt) sequences of A1 cDNAs isolated from various mouse strains revealed amino acid (aa) polymorphism in the highly conserved region within the LZ motif. Interestingly, the location and pattern of aa deletions are identical to those previously described for the aa polymorphism within the human counterpart, E47 (E12) [Kamps et al., Cell 60 (1990) 547-555].

Amino Acid Sequence↗
PubMed1994

Dobutamine stress echocardiography predicts reversible dysfunction and quantitates the extent of irreversibly damaged myocardium after reperfusion of anterior myocardial infarction.

OBJECTIVES: This study was designed to evaluate dobutamine stress echocardiography in identifying reversible dysfunction and assessing the extent of irreversibly damaged myocardium early in acute myocardial infarction. BACKGROUND: Several experimental and clinical studies have suggested that dobutamine enhances contractile function of stunned or hibernating, or both, myocardium. It is important for clinical strategy to predict the magnitude of improvement in myocardial function early in acute myocardial infarction. METHODS: We studied 21 patients with a reperfused first anterior myocardial infarction. Two-dimensional echocardiography was performed before and during dobutamine infusion (10 micrograms/kg body weight per min) at a mean of 3 days after the infarction. Follow-up echocardiography was performed at a mean of 25 days later. To assess segmental wall motion, we divided the left ventricle into 17 segments and assigned a wall motion abnormality score: 3 = dyskinesia or akinesia; 0 = normal. Improvement in wall motion was indicated by a decrease of at least one grade in segmental score. For quantitative assessment, the ratio of endocardial length showing dyskinesia or akinesia to a left ventricular endocardial length (akinetic length ratio) was determined in the apical long-axis view at each stage. RESULTS: Sensitivity and specificity of dobutamine infusion in detecting improvement in wall motion at follow-up echocardiography were 83% (55 of 66 segments) and 86% (43 of 50 segments), respectively. Excellent correlation was found (r = 0.93, p < 0.001; absolute difference [mean +/- SD] 0.03 +/- 0.05) between the akinetic length ratios measured during dobutamine infusion and in the late convalescent stage. CONCLUSIONS: In the early stage of acute myocardial infarction, low dose dobutamine stress echocardiography provides a useful method for predicting reversible dysfunction with excellent sensitivity and specificity and can also be used to quantitate the extent of irreversibly damaged myocardium.

Adult↗
PubMed1994

[Transcription factors for the insulin gene].

Production of insulin is stringently restricted to the beta cells of the endocrine pancreas. The major mechanism directing this specificity operates at the level of transcription. Previous studies have demonstrated that the tissue specificity in the insulin gene expression results from the cell-specific activity of its 5'-flanking enhancer/promoter, which limits the expression of a linked gene to the beta cell in tissue culture and transgenic mouse. Deletion, mutation, DNase I foot-printing, and gel-shift analyses revealed the presence of multiple cis-acting motifs. A set of positive and, possibly, negative trans-acting factors that are found in insulin-producing and noninsulin producing cells bind to these cis-acting elements and thus regulate transcription. Included among those are IEB (E-box)-binding IEF-1, a nuclear protein complex which consists of two basic helix-loop-helix proteins, and CT-box (TAAT box)-binding IPF1/STF-1, a homeodomain-containing transcription factor.

Animals↗