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T Kadowaki

Publications and source records attributed to T Kadowaki.

At least 217 records · Page 12Linked to original sources
PubMed1994

Substitution at Pro385 of GLUT1 perturbs the glucose transport function by reducing conformational flexibility.

The mammalian glucose transporter, GLUT1, is capable of alternating between two conformations which expose either an outward- or inward-facing ligand binding site. The possibility that these conformational changes are related to the presence of prolines and glycines in transmembrane region 10 was investigated by site-directed mutagenesis. Chinese hamster ovary clones which were transfected with Pro385-->Ile and Pro385-->glycine mutations of GLUT1 were shown, by Western blotting and cell surface carbohydrate labelling, to have expression levels which were comparable with the wild type. The transport activity was markedly reduced as a result of the Pro385-->isoleucine but not in the Pro385-->glycine mutation. The loss of transport activity in the Pro385-->isoleucine clone was associated with loss of labeling by the exofacial photoaffinity ligand, 2-N-4-(1-azi-2,2,2-trifluoroethyl)benzoyl-1,3-bis(D-mannos-4 -yloxy)-2- propylamine (ATB-BMPA), but there was no loss in labeling by the inside site-directed ligand cytochalasin B. These results suggest that the transporter cannot adopt the outward-directed conformation in the Pro385-->isoleucine clone. By contrast, the glycine substitution for proline at this position resulted in a retention of the ligand binding properties at both inside and outside sites. We suggest a putative mode of operation of the transporter which involves conformational flexibility about the prolines in transmembrane segment 10 such that helices 11 and 12 can alternately either pack against the outside (ATB-BMPA binding) site in helices 7, 8, and 9 or against the inner (cytochalasin B binding) site at the base of transmembrane segment 10.

Amino Acid Sequence↗
PubMed1994

E-cadherin and alpha-catenin expression in human esophageal cancer.

Intercellular adhesion of the epithelial tissue is mainly regulated by the E-cadherin (E-cad) molecule. alpha-Catenin (alpha-cat) is one of the E-cad-associated cytoplasmic proteins that forms a linkage to the cytoskeleton and regulates E-cad function. To investigate the mechanism of dysfunction in cell-cell adhesion in cancerous tissues, we examined E-cad and alpha-cat expression by immunohistochemical staining on 46 human esophageal cancers using our specific monoclonal antibodies. By grading of E-cad and alpha-cat expression as uniformly positive (+), heterogeneous (+/-), or uniformly negative (-), the 46 tumors could be classified into 9 (20%) E-cad(+)/alpha-cat(+), 15 (33%) E-cad(+/-)/alpha-cat(+/-), 21 (46%) E-cad(+/-)/alpha-cat(-), and 1 (2%) E-cad(-)/alpha-cat(-). Twenty-five (54%) of the 46 tumors showed a similar expression of both molecules, while the other 21 tumors (46%) showed E-cad(+/-)/alpha-cat(-). Thus, although the expression of alpha-cat was significantly correlated with that of E-cad, in some tumors the reduction of alpha-cat was greater. Regarding the clinicopathological features, the reduction of alpha-cat expression, as well as that of E-cad, was significantly associated with tumor dedifferentiation, infiltrative growth, and lymph node metastasis (P < 0.01). Furthermore, the frequency of lymph node metastasis in E-cad(+/-)/alpha-cat(-) tumors was significantly higher (90%) than in E-cad(+)/alpha-cat(+) tumors (22%) (P < 0.01) or in E-cad(+/-)/alpha-cat(+/-) tumors (47%) (P < 0.05). These results suggest that not only E-cad but also alpha-cat are important regulators of intercellular adhesion and that alpha-cat is also involved in invasion and metastasis. In particular, reduction of alpha-cat expression is more correlated with invasive phenotype and lymph node metastasis than E-cad expression in human esophageal cancer.

Adult↗
PubMed1994

Immunohistochemical evaluation of alpha-catenin expression in human gastric cancer.

E-cadherin (E-cad) plays a major role in the maintenance of cell-cell adhesion in epithelial tissues, and impaired E-cad expression correlates with tumour invasion and metastasis. Alpha-catenin (alpha-cat), an undercoat protein of adherens junctions, binds to the cytoplasmic domain of E-cad and is essential for linking E-cad to actin-based cytoskeleton. We investigated E-cad and alpha-cat expression in 60 human gastric cancers immunohistochemically. The 60 gastric cancers were classified into 18 (30%) in which alpha-cat expression was preserved, and 42 (70%) reduced cases. The reduction of alpha-cat expression was significantly related to dedifferentiation, depth of invasion, infiltrative growth and lymph node metastasis. We also examined the co-expression of alpha-cat and E-cad. Seventeen (28%) tumours preserved both molecules [alpha-cat(+)/E-cad(+)] and 33 (55%) tumours reduced both [alpha-cat(-)/E-cad(-)], whereas 9 (15%) tumours exhibited alpha-cat(-)/E-cad(+). The frequency of lymph node metastasis in alpha-cat(-)/E-cad(+) tumour (67%) was significantly higher than that in alpha-cat(+)/E-cad(+) tumours (24%) and was close to that in alpha-cat(-)/E-cad(-) tumours (82%). The frequency of haematogenous liver metastasis in alpha-cat(-)/E-cad(+) tumours (44%) was significantly higher than that in alpha-cat(+)/E-cad(+) tumours (6%) or alpha-cat(-)/E-cad(-) tumours (9%). Thus, in all E-cad(+) tumours, the frequency of lymph node and liver metastasis was higher in alpha-cat(-) tumours than in alpha-cat(+) tumours. alpha-Cat expression is apparently better at predicting tumour invasion and metastasis than E-cad expression.

Adult↗
PubMed1994

Risk factors for the development of non-insulin-dependent diabetes mellitus (NIDDM) in Japan.

Follow-up studies of subjects with impaired glucose tolerance in Japan have shown that a higher level of blood glucose is a major predictor of the subsequent development of non-insulin-dependent diabetes mellitus (NIDDM). In addition, subjects with a lower insulin response to glucose show a higher risk for the development of NIDDM. In fact, most of the subjects who later develop diabetes show a lower insulin response to glucose at the initial examination. Moreover, obesity is generally associated with a higher risk of developing NIDDM. We conclude that low insulin secretion forms an important basis and obesity plays a precipitating role among low-insulin responders in the pathogenesis of the majority of NIDDM patients in Japan.

Blood Glucose↗
PubMed1994

Insulin receptor disorders in Japan.

The clinical features of insulin receptor disorders found in Japan are summarized. About 20 cases of primary receptor mutations (type A syndrome of insulin resistance, leprechaunism and Rabson-Mendenhall syndrome) and 16 cases of autoantibodies against insulin receptor (type B syndrome of insulin resistance) are described in Japan. There was a trial of IGF-1 for some of the patients, revealing its usefulness.

Acanthosis Nigricans↗
PubMed1994

Morbidity rates of complications in persons with spinal cord injury according to the site of injury and with special reference to hypertension.

It has been reported that since 1982 the incidence in persons with spinal cord injury (SCI) of hypertension is commoner than it is in the general population of the same age groups in Japan. In the current study, we examined outpatient morbidity rates and standardised outpatient morbidity ratios (SOMR) according to the site of injury, as well as blood pressure levels and history of disease, and compared the incidences with those for the general population. The subjects consisted of 195 men with SCI. All were engaged in light work at special centres while living with other persons at the centres. The mean age was 49.5 years old, and the average post-injury period was 17.9 years. With respect to the site of injury, 19 patients had had injuries at the level of C-T5, 24 at T6-T10, 139 at T11-L1, and 13 at L2 or lower. The SOMR (general population = 100) for hypertension was closely related to the site of injury, i.e. 0 at C-T5, 250 at T6-T10, 221 at T11-L1 and 308 at L2 or below. Among the patients treated with antihypertensive agents (41 persons), 17.1% were under treatment for renal diseases, 4.9% for diabetes, and 4.9% for hepatic disorders. In 68% of the SCI persons examined, however no disease (such as renal disease, diabetes mellitus, hepatic disease or endocrine abnormality) could be regarded as a cause of secondary hypertension. In addition, the survey revealed that the body weight of SCI persons was lower than that of the general populations.

Age Factors↗
PubMed1994

Isolation and characterization of Saccharomyces cerevisiae mRNA transport-defective (mtr) mutants.

To understand the mechanisms of mRNA transport in eukaryotes, we have isolated Saccharomyces cerevisiae temperature-sensitive (ts) mutants which accumulate poly(A)+ RNA in the nucleus at the restrictive temperature. A total of 21 recessive mutants were isolated and classified into 16 complementation groups. Backcrossed mRNA transport-defective strains from each complementation group have been analyzed. A strain which is ts for heat shock transcription factor was also analyzed since it also shows nuclear accumulation of poly(A)+ RNA at 37 degrees C. At 37 degrees C the mRNA of each mutant is characterized by atypically long polyA tails. Unlike ts pre-mRNA splicing mutants, these strains do not interrupt splicing of pre-mRNA at 37 degrees C; however four strains accumulate oversized RNA polymerase II transcripts. Some show inhibition of rRNA processing and a further subset of these strains is also characterized by inhibition of tRNA maturation. Several strains accumulate nuclear proteins in the cytoplasm when incubated at semipermissive temperature. Remarkably, many strains exhibit nucleolar fragmentation or enlargement at the restrictive temperature. Most strains show dramatic ultrastructural alterations of the nucleoplasm or nuclear membrane. Distinct mutants accumulate poly(A)+ RNA in characteristic patterns in the nucleus.

Biological Transport↗
PubMed1994

Nuclear mRNA accumulation causes nucleolar fragmentation in yeast mtr2 mutant.

We have identified a set of genes that affect mRNA transport (mtr) from the nucleus to the cytoplasm of Saccharomyces cerevisiae. One of these genes, MTR2, has been cloned and shown to encode a novel 21-kDa nuclear protein that is essential for vegetative growth. MTR2 shows limited homology to a protein implicated in plasmid DNA transfer in Escherichia coli. PolyA+RNA accumulates within the nucleus of mtr2-1 in two to three foci at 37 degrees C. mRNA, tRNA, and rRNA synthesis continue as do pre-mRNA splicing, tRNA processing, and rRNA export at 37 degrees C. Under these conditions the polyA tail length increases, and protein synthesis is progressively inhibited. Nucleolar antigens also redistribute to two to three nuclear foci at 37 degrees C, and this redistribution depends on ongoing transcription by RNA polymerase II. Surprisingly, these foci coincide with the sites of polyA+RNA accumulation. Comparable colocalization and dependance on RNA polymerase II transcription is seen for the mtr1-1 mutant. The disorganization of the nucleolus thus depends on mRNA accumulation in these mutants. We discuss the possible functions of MTR2 and the yeast nucleolus in mRNA export.

Amino Acid Sequence↗
PubMed1994

Angiotensin II receptor antagonist TCV-116 induces regression of hypertensive left ventricular hypertrophy in vivo and inhibits the intracellular signaling pathway of stretch-mediated cardiomyocyte hypertrophy in vitro.

BACKGROUND: Previous studies have demonstrated that angiotensin II (Ang II) acts as a growth-promoting factor directly on cardiac myocytes and that angiotensin-converting enzyme inhibitor induces regression of hypertrophied hearts both in experimental animals and in humans. These results suggest that the renin-angiotensin system (RAS) is involved in the formation of left ventricular hypertrophy (LVH). To elucidate the role of RAS in the progression of cardiac hypertrophy, we evaluated the effect of an Ang II receptor antagonist on LVH in spontaneously hypertensive rats (SHRs) and investigated the molecular mechanisms by which antagonizing Ang II receptors reduces cell hypertrophy of myocytes using the in vitro model of mechanical stretch. METHODS AND RESULTS: In the in vivo study, we treated SHRs with the nonpeptide Ang II receptor antagonist TCV-116 (0.1, 1, or 10 mg/kg per day) or hydralazine (10 mg/kg per day). Blood pressure was measured by the tail-cuff method, and wall thickness of left ventricle was serially monitored using M-mode echocardiography. Rats were killed at the age of 13, 17, 21, or 25 weeks, and left ventricular (LV) weight, transverse diameter of cardiomyocytes, relative amount of V3 myosin heavy chain (MHC), and degree of interstitial collagen accumulation were examined. Untreated SHRs progressively developed severe hypertension, but treatment with TCV-116 or hydralazine inhibited the increase in blood pressure. Treatment with TCV-116 reduced LV weight, LV wall thickness, transverse diameter of myocytes, relative amount of V3 MHC, and interstitial fibrosis, whereas treatment with hydralazine slightly prevented an increase in LV wall thickness but did not exert significant reduction in other parameters. In the in vitro study, neonatal rat cardiomyocytes were cultured on deformable silicone dishes and mechanically stretched with or without pretreatment of CV-11974 (an active metabolite of TCV-116), and [3H]phenylalanine incorporation, activity of mitogen-activated protein (MAP) kinase, and c-fos mRNA expression were analyzed. Pretreatment of cultured cardiomyocytes with 10(-7) mol/L CV-11974 inhibited an increase in [3H]phenylalanine incorporation, MAP kinase activity, and c-fos gene expression induced by stretch of cardiomyocytes. CONCLUSIONS: The Ang II receptor antagonist TCV-116 induced regression of cardiac hypertrophy and had cardioprotective effects on hypertrophied myocardium in vivo, and antagonizing Ang II receptors inhibited intracellular signaling of stretch-mediated cardiomyocyte hypertrophy in vitro. These results suggest a crucial role of the cardiac RAS in the development of LVH produced by pressure overload.

Angiotensin II↗
PubMed1994

Analysis of the glucokinase gene promoter in Japanese subjects with noninsulin-dependent diabetes mellitus.

Glucokinase plays an important role in glucose metabolism in pancreatic beta-cells and liver. Recently, several mutations responsible for noninsulin-dependent diabetes mellitus (NIDDM) have been identified within the coding regions of the glucokinase gene. We screened the promoter regions using polymerase chain reaction followed by single strand conformation polymorphisms in 240 Japanese NIDDM and 111 control subjects. In the beta-cell promoter, two kinds of sequence variations were detected. One variation, in which 2 nucleotides at position -282 (C-->T) plus -194 (A-->G) were changed simultaneously, was found in 23 NIDDM (9.6%) and 12 control (10.8%) subjects. The other variation [e.g. -30 (G-->A)] was identified in 87 NIDDM (36.3%) and 40 control (36.0%) subjects. In the liver promoter, in addition to the -603 (G-->T) substitution in 1 NIDDM (0.4%) and 2 control (1.8%) subjects, the -120 (G-->T) substitution in 1 control (0.9%) subject was found. However, there were no differences in these allele frequencies between NIDDM and control subjects. We conclude that the prevalence of mutations in the promoter of the glucokinase gene responsible for NIDDM is rare among Japanese patients.

Adolescent↗
PubMed1994

A 3-basepair in-frame deletion (delta Leu999) in exon 17 of the insulin receptor gene in a family with insulin resistance.

We studied a woman with acanthosis nigricans and insulin resistance. The patient's Epstein-Barr virus-transformed lymphocytes revealed slightly decreased insulin binding and markedly decreased insulin-stimulated autophosphorylation of the insulin receptor. The nucleotide sequence analysis of the patient's genomic DNA revealed a 3-basepair in-frame deletion in one allele, resulting in the loss of leucine at position 999 of the insulin receptor (delta Leu999). The messenger ribonucleic acid transcripts from the mutant allele in the patient's lymphocytes were not decreased. Insulin-stimulated autophosphorylation of the insulin receptor from cells expressing delta Leu999 mutant insulin receptor complementary DNA was markedly decreased. The proband, her mother, elder brother, and younger brother, who were heterozygous for this mutation, showed moderate or marked hyperinsulinemia during oral glucose tolerance tests. Although fasting glucose levels were normal and fasting insulin values were preserved in all subjects with the mutation for the 8-yr period of observation, a tendency of progressive increase in postload glucose levels was observed. These results suggest that the delta Leu999 mutation, which reduces tyrosine kinase activity, was responsible for insulin resistance and contributed to postload hyperglycemia.

Acanthosis Nigricans↗
PubMed1994

[HAIR-AN syndrome].

Many clinical observations have suggested that there is a strong relationship between hyperinsulinemia and hyperandrogenism. HAIR-AN syndrome is defined as a constellation of hyperandrogenism (HA), insulin resistance (IR), and acanthosis nigricans (AN). Two major mechanisms could account for this syndrome: (i) hyperinsulinemia induced by insulin resistance causes hyperandrogenism, and (ii) hyperandrogenism causes insulin resistance and hyperinsulinemia. Acanthosis nigricans is considered to be an epiphenomenon caused by hyperinsulinemia. The causes of HAIR-AN syndrome include syndromes of extreme insulin resistance due to mutations in the insulin receptor gene, lipoatrophic diabetes, obesity, some endocrinopathies, and genetic and acquired ovarian hyperandrogenism.

Acanthosis Nigricans↗
PubMed1994

[Classification of mutations in the insulin receptor gene].

Mutations in the insulin receptor gene can cause insulin resistance by interfering with a step (s) in the life cycle of the insulin receptor. These steps include biosynthesis, posttranslational modifications and transport to plasma membrane, ligand binding, trans membrane signaling, and endocytosis, recycling and degradation. Mutations are functionally classified into five classes: mutations that decrease the rate of receptor biosynthesis (class I), mutations that impair intracellular transport and post-translational processing (class II), mutations that cause defects in insulin binding (class III), mutations that impair receptor tyrosine kinase activity (class IV), and mutations that accelerate receptor degradation (class V). Examples of insulin receptor gene mutations for each of these five classes are shown.

Biological Transport↗
PubMed1994

[The role of phosphorylation cascade in insulin action].

Insulin induces a wide variety of growth and metabolic response in many cell types. Insulin initiates its biological effects by activation of tyrosine kinase in the beta-subunit and phosphorylates several proteins, such as insulin receptor substrate-1 (IRS-1), Shc. thereby activating phosphatidyl inositol 3-kinase activity, and ras activity. MAP kinase cascade activated by ras, 70kDaS6 kinase lying downstream of PI3-kinase, and the regulation of glycogen synthase have been discussed.

Animals↗
PubMed1994

[Mutations in the mitochondrial gene in patients with NIDDM].

Since the identification of an A to G mutation at position 3243 of mitochondrial leucine tRNA (3243 bp mutation) in families with diabetes and deafness, the prevalence, clinical characteristics, pathophysiology of diabetes associated with 3243 bp mutation have been studied in Japan. Our study has shown that diabetes cosegregates with 3243 bp mutation in more than 30 Japanese families and that the prevalence of 3243 bp mutation in randomly selected diabetic patients (0.9%, 5 out of 550) is significantly higher than that in non-diabetic controls without family history (0.0%, 0 out of 250). Diabetes mellitus with 3243 bp mutation is often accompanied by distinct clinical features such as maternal inheritance, hearing disturbance, insulin deficiency and tendency to progression and can be regarded as a new subtype of diabetes mellitus.

Asian People↗
PubMed1994

Immunohistochemical detection of alpha-catenin expression in human cancers.

The function of E-cadherin is thought to be regulated by its associated cytoplasmic proteins including alpha-catenin. To determine whether possible downregulation of alpha-catenin expression may play a role in tumor invasion and metastasis through the dysfunction of E-cadherin, we investigated the expression of alpha-catenin in human carcinoma samples (esophagus, stomach, and colon) by immunohistochemistry using our monoclonal antibody against alpha-catenin (alpha-18). Normal epithelium expressed alpha-catenin strongly without exception. However, alpha-catenin expression was frequently reduced in primary tumors of esophagus (12 of 15:80%), stomach (14 of 20: 70%), and colon (8 of 10: 80%). Of the tumors with reduced alpha-catenin expression, alpha-catenin expression was completely negative in 70.6% of them (9 of 12 in esophagus, 9 of 14 in stomach, and 6 of 8 in colon). These results also suggested that some human cancer cells may have impaired E-cadherin-mediated cell adhesiveness through the downregulation of alpha-catenin expression.

Adenocarcinoma↗