Search PubMed⌕ Search

Biomedical subjects

Y Oka

Publications and source records attributed to Y Oka.

At least 325 records · Page 18Linked to original sources
PubMed1993

Mitochondrial gene mutation in islet-cell-antibody-positive patients who were initially non-insulin-dependent diabetics.

Autoimmunity is thought to lead to islet-cell-antibody (ICA) formation in diabetes mellitus. However, we found a mitochondrial gene mutation at nucleotide pair 3243 in 3 of 27 Japanese ICA-positive, initially non-insulin-dependent diabetic patients. All 3 progressed to insulin-dependency within 13-31 months, whereas 5 of the other 24 are non-insulin-dependent after 54-90 months. ICA, at least in these 3 patients, may follow gradual beta-cell destruction due to mitochondrial gene mutation, although the possibility of beta-cells with the mutation being susceptible to autoimmune destruction cannot be excluded.

Adolescent↗
PubMed1993

The role of N-glycosylation in the targeting and stability of GLUT1 glucose transporter.

The cDNAs encoding the GLUT1 glucose transporter protein were altered by site-directed mutagenesis at consensus sites for the addition of N-linked glycosylation. These cDNAs were transfected into CHO cells with an expression vector and the subcellular distribution and stability of the expressed glycosylation-defective GLUT1 protein were analyzed. Immunohistochemical analysis with a specific antibody demonstrated that a significant portion of glycosylation-defective GLUT1 protein remained in the intracellular compartment. By contrast, most of the wild-type GLUT1 protein expressed with the same procedures resided in the plasma membranes. Metabolic labeling studies revealed that the half-life of the glycosylation-defective GLUT1 protein was significantly shorter than that of wild-type GLUT1 protein. These results indicate that N-glycosylation of the glucose transporter affects its intracellular targeting and protein stability.

Animals↗
PubMed1993

Role of tryptophan-388 of GLUT1 glucose transporter in glucose-transport activity and photoaffinity-labelling with forskolin.

GLUT1 glucose-transporter cDNA was modified to substitute leucine for Trp-388 and transfected into Chinese hamster ovary cells using the expression vector termed pMTHneo. This tryptophan residue is conserved among most of the facilitative glucose-transporter isoforms and has been proposed to be the photolabelling site of forskolin, a competitive inhibitor of glucose transport. In addition, this residue is located on membrane-spanning helix 10 which is suggested to contain the dynamic segment of the transporter. The mutated glucose transporter was expressed and inserted into the plasma membrane in a fashion similar to the wild-type. Unexpectedly, this mutation did not abolish photolabelling with forskolin. However, the mutation induced a marked decrease in 2-deoxyglucose uptake with a 4-fold decrease in turnover number and a 1.25-fold increase in Km compared with the wild-type GLUT1. A similar decrease in zero-trans influx activity was also observed for 3-O-methylglucose. In contrast, no apparent decrease was observed in zero trans efflux activity for 3-O-methylglucose. The mutation decreased the turnover number of the glucose transporter in equilibrium exchange influx for 3-O-methylglucose by 33% without any change in Km. These results indicate that (1) Trp-388 is not the photolabelling site for forskolin, if we assume that the labelling occurs at a single site and (2) Trp-388 is more likely to be involved in interconversion between the inward-facing and outward-facing conformers of GLUT1 than binding of glucose, and thus, substitution of leucine for Trp-388 in this dynamic segment would decrease the rate of alternating conformation, which would preferentially affect the influx activity.

3-O-Methylglucose↗
PubMed1993

[Comparison of the casual serum triglyceride levels at health check-up with the values during fasting].

Since higher levels of serum triglycerides were frequently found during the UOEH physical check-up for employees and students in 1989, we analysed subjects with higher triglyceride levels and discussed ways of handling them. Blood sampling to determine serum lipids was done between 13:00-15:00. Of the total (males 1257, females 1267), 272 had higher serum triglyceride levels (over 200 mg/dl) (males 246, females 26) (1st TG). One hundred and twenty-one of the group with higher TG levels in the 1st examination were reevaluated by blood sampling the morning after overnight fasting (2nd TG). There was a significant positive correlationship between the TG levels from the 1st examination and those from the 2nd examination (r = 0.62, n = 121, P < 0.0001). The predictive value calculated from the equation between the TG in the first and second measurements was 341.7 mg/dl. There was a 14.9% rate of false negatives in subjects under 341.7 mg/dl on the first TG measurement. However, there were only 6.3% false negatives in the subjects under 250 mg/dl on the first TG measurement. Age, body mass index and serum cholesterol level were significantly higher in the group with the higher TG level on reevaluation (more than 160 mg/dl) than those in the group with the lower TG level on reevaluation (less than 160 mg/dl). We concluded from these results that the casual serum TG levels above 250 mg/dl might be a suitable cut off level in physical check-ups.

Adolescent↗
PubMed1993

Desensitization of canine histamine H2 receptor expressed in Chinese hamster ovary cells.

Canine histamine H2 receptor DNA was transfected into Chinese hamster ovary cells using an expression vector. Expression of H2 receptors was demonstrated by immunoblotting with specific antibodies and the binding of tiotidine, an H2 receptor antagonist. H2 receptor-specific cAMP production was observed only in the cells expressing canine H2 receptor with 10(-9)-10(-4) M histamine in a dose-dependent manner. Preincubation of transfected cells with 10 microM histamine for 10 min or 60 min at 37 degrees C decreased both the maximal response and the sensitivity of the subsequent histamine-stimulated cAMP production, showing desensitization. Under these circumstances, tiotidine binding was decreased by 25% in intact cells. A similar decrease in the tiotidine binding was observed also in the membrane without changes in the affinity, whereas no decrease in total H2 receptor number was observed. Thus, desensitization of histamine H2 receptor was associated with the sequestration of receptors.

Adenylyl Cyclases↗
PubMed1993

Therapeutic efficacy of granulocyte colony stimulating factor against rat cecal ligation and puncture model.

To identify the therapeutic efficacy of granulocyte colony stimulating factor (G-CSF) in severe sepsis, we examined its effect on the mortality and pathological changes in vital organs using the rat lethal sepsis model. Rats were given 15 micrograms of recombinant human (rh)G-CSF after the onset of peritonitis brought about by cecal ligation and puncture. The mortality rate after 72 h was significantly decreased by administration of 15 micrograms of rhG-CSF (p < 0.001). In addition, the administration of rhG-CSF induced an improvement in liver and renal functions. It also produced marked pathological improvement in the lungs. These results strongly indicated that administration of rhG-CSF, even after the onset of sepsis, was effective in decreasing the mortality from peritonitis-induced multiple organ failure, and this finding was clearly useful in the clinical treatment of such sepsis-induced critical illness.

Animals↗
PubMed1993

The mechanism of hepatic cellular injury in sepsis: an in vitro study of the implications of cytokines and neutrophils in its pathogenesis.

Neutrophil-mediated injury to hepatocytes was evaluated in vitro. A new in vitro coculture system of neutrophils and a human hepatoblastoma cell line (HuH-6), instead of normal hepatocytes, was established. Recombinant human tumor necrosis factor (TNF) activated neutrophils to release neutrophil elastase and showed the significant cytotoxicity for HuH-6 cells, which was determined by measuring the release of the cytoplasmic enzyme, lactate dehydrogenase (LDH), from HuH-6 cells. The concentration of neutrophil elastase from zymosan-primed/TNF (1.0 ng/ml)-stimulated neutrophils cocultured with HuH-6 cells reached to the level of 1.59 +/- 0.18 micrograms/10(6) cells in 24 hr. The release of LDH from HuH-6 cells in this coculture system was 84.8 +/- 17.8 units/liter after 24 hr incubation. Purified human neutrophil elastase also increased LDH release from HuH-6 cells. When HuH-6 cells were cocultured with zymosan-primed/TNF (1.0 ng/ml)-stimulated neutrophils, the secretion of the negative acute phase reactant (APR), alpha-fetoprotein, from HuH-6 cells was significantly decreased, and the production of the positive APR, pancreatic secretory trypsin inhibitor, was decreased in response to the stimulation of interleukin 6. Urinary trypsin inhibitor, the inhibitor of neutrophil elastase, decreased the release of LDH from HuH-6 cells cocultured with stimulated neutrophils, while superoxide scavenger did not. These results show that human neutrophils activated by TNF injure hepatocytes, thus causing hepatic dysfunction, through the release of neutrophil elastase.

Culture Media, Conditioned↗
PubMed1993

A novel mutation within the kinase domain of v-abl gene responsible for temperature-sensitive colony-forming ability in soft agar.

Mutation sites of unique temperature-sensitive (ts) mutants of Abelson murine leukemia virus(A-MuLV) that exhibited the ts phenotype in colony-forming ability in soft agar, but not in morphological transformation, were determined. Cloning and sequencing analysis of the full viral genomes of five independent ts mutants revealed a total of 10 mutation sites: 3 mutations (bp714, 742, and 817) located in the 5' untranslated region between LTR and gag gene; 4 mutations (bp1227, 1229, 1512, and 1634) in the gag gene; 3 mutations (point mutations at bp2764 and 3265, and 2-base deletion of bp3448 and 3449) in the abl gene. To determine the mutation sites critical for the ts phenotype in colony-forming ability in soft agar, hybrid viruses were constructed by exchanging the corresponding restriction fragments between wild-type and ts A-MuLV. The hybrid virus containing only the point mutation (T-->G) at bp2764 that exchanged leucine with arginine exhibited the ts phenotype in colony-forming ability in soft agar. Thus, a novel mutation within the kinase domain of the abl gene critical for the ts phenotype in colony-forming ability in soft agar was determined here.

3T3 Cells↗
PubMed1993

Pancreatic beta cell line MIN6 exhibits characteristics of glucose metabolism and glucose-stimulated insulin secretion similar to those of normal islets.

Glucose-stimulated insulin secretion, glucose transport, glucose phosphorylation and glucose utilization have been characterized in the insulinoma cell line MIN6, which is derived from a transgenic mouse expressing the large T-antigen of SV40 in pancreatic beta cells. Glucose-stimulated insulin secretion occurred progressively from 5 mmol/l glucose, reached the maximal level approximately seven-fold above the basal level at 25 mmol/l, and remained at this level up to 50 mmol/l. Glucose transport was very rapid with the half-maximal uptake of 3-O-methyl-D-glucose being reached within 15 s at 22 degrees C. Glucose phosphorylating activity in the cell homogenate was due mainly to glucokinase; the Vmax value of glucokinase activity was estimated to be 255 +/- 37 nmol.h-1.mg protein-1, constituting approximately 80% of total phosphorylating activity, whereas hexokinase activity constituted less than 20%. MIN6 cells exhibited mainly the high Km component of glucose utilization with a Vmax of 289 +/- 18 nmol.h-1.mg protein-1. Thus, glucose utilization quantitatively and qualitatively reflected glucose phosphorylation in MIN6 cells. In contrast, MIN7 cells, which exhibited only a small increase in insulin secretion in response to glucose, had 4.7-fold greater hexokinase activity than MIN6 cells with a comparable activity of glucokinase. These characteristics of MIN6 cells are very similar to those of isolated islets, indicating that this cell line is an appropriate model for studying the mechanism of glucose-stimulated insulin secretion in pancreatic beta cells.

3-O-Methylglucose↗
PubMed1993

Establishment of a human anaplastic thyroid cancer cell line secreting granulocyte colony-stimulating factor in response to cytokines.

A human anaplastic thyroid cancer cell line K-119, derived from a 77-yr-old woman who had developed marked neutrophilia and underwent surgery for anaplastic thyroid cancer, has been established. The spindlelike and polygonal cells in shape are stably proliferating since the beginning of its culture 2 yr ago. The cells grow rapidly and the population doubling time is 26 h. The chromosomes show many abnormalities and many marker chromosomes have been observed. Heterotransplantation of the cells into nude mice has resulted in the formation of tumors that are histologically interpreted as anaplastic cancer. The most noteworthy characteristics of the cell line are the many Ki-67-positive cells (86.3%) and that the cell line spontaneously secretes granulocyte colony-stimulating factor (G-CSF) and releases increased amounts of G-CSF in response to the stimulation of tumor necrosis factor, interleukin 1 alpha, and interleukin 1 beta. The conditioned medium obtained from K-119 cells contains an autocrine factor stimulating the proliferation of themselves.

Aged↗
PubMed1993

The scid mutation in mice causes defects in the repair system for both double-strand DNA breaks and DNA cross-links.

The sensitivity of scid fibroblasts established from C.B17-scid/scid fetuses to the DNA-damaging agents bleomycin, neocarzinostatin, mechlorethamine, mitomycin C, methyl methanesulfonate, and ultraviolet light, all of which induce different types of DNA damage, was examined. Scid fibroblasts were 2.8-, 3.7-, and 3.0-fold more sensitive to bleomycin, neocarzinostatin, and mechlorethamine, respectively, than wild-type fibroblasts derived from C.B17-+/+ fetuses. These findings indicate that the scid mutation in mice causes defects in repairing both double-strand DNA breaks and DNA cross-links.

Animals↗
PubMed1993

Does transesophageal echocardiography improve postoperative outcome in patients undergoing coronary artery bypass surgery?

The incidence and characteristics of ischemic episodes as detected by transesophageal echocardiography (TEE) and their relationship to postoperative myocardial infarction (MI) and adverse clinical outcome were studied in patients undergoing coronary artery bypass grafting (CABG). Seventeen of 50 patients had 21 TEE-defined ischemic episodes: 4 patients (8%) had 4 ischemic episodes in the pre-cardiopulmonary bypass (CPB) period, and 15 patients (30%) had 17 ischemic episodes in the post-CPB period, whereas 19 patients had 20 ECG ischemic episodes: 3 patients (6%) had 3 ischemic episodes in the pre-CPB period and 17 (34%) had 17 ischemic episodes in the post-CPB period. In 14 patients, ischemic episodes were detected by both TEE and ECG. Clinicians were made aware of the TEE data and appropriate treatments were undertaken during ischemic episodes: of the 15 patients with TEE-defined post-CPB ischemia, 4 had an additional saphenous vein graft placed, 8 had an intra-aortic balloon pump (IABP) inserted, 3 were given sublingual nifedipine, and 13 received nitroglycerin. These treatments resulted in improvement in regional wall motion abnormalities (RWMA) by the end of surgery in 11 of the 15 patients (73%), including the 4 with postoperative MI and 2 who died with cardiogenic shock. The authors conclude that: (1) significantly more patients had TEE-defined ischemic episodes in the post-CPB period (30%) than in the pre-CPB period (8%); (2) a poor graft and/or inadequate myocardial protection were strongly suggestive of post-CPB ischemia, which was significantly related to adverse outcome; and (3) TEE was a useful tool enabling detection of problem areas at an early stage and timely and appropriate treatment to support and sustain patients.

Adult↗
PubMed1993

Expression of GLUT-4 glucose transporter in unweighted soleus muscle of normal and STZ-induced diabetic rats.

Effects of 6 days of hindlimb suspension on expression of glucose transporters were studied in the skeletal muscle of nondiabetic and streptozotocin-induced diabetic rats. Although total membrane protein recovered from soleus muscles tended to decrease with suspension, GLUT-4 protein concentration (amount per gram membrane protein) was increased by 66 and 91% compared with weight-bearing control in nondiabetic and diabetic rats, respectively. Therefore, the amount of GLUT-4 protein in whole soleus muscle did not decrease with the hindlimb suspension in normal and diabetic rats. In contrast, hindlimb suspension decreased GLUT-4 mRNA amount in whole soleus muscle by 47 and 27% in nondiabetic and diabetic rats, respectively. Thus the GLUT-4 protein-to-GLUT-4 mRNA ratio was increased 2.1-fold in nondiabetic and 1.4-fold in diabetic rats. The extensor digitorum longus muscle, which generally shows little response to unweighting, exhibited no such changes. These results suggest that the amount of GLUT-4 glucose transporter in the unweighted soleus muscle was maintained via a translational and/or posttranslational mechanism in nondiabetic rats as well as in streptozotocin-induced diabetic rats under the condition of reduced weight-bearing activity.

Animals↗
PubMed1993

Differential activation of polymorphonuclear leukocytes from peripheral blood and exudate in surgical patients.

We examined the effects of surgical trauma on polymorphonuclear leukocyte (PMN) chemotaxis, production of phagocytosis-dependent intracellular chemiluminescence (CL) and production of phagocytosis-independent total CL in two groups: group A with esophageal cancer, and group B with gastric cancer. The scale of surgical trauma was quantified by measuring interleukin-6 in plasma and exudate from drainage tubes. We found a significant augmentation of chemotaxis, total CL and intracellular CL in both groups during the post-operative week. In group A, the increments in both chemotaxis and total CL of circulating cells were smaller than those in group B, but there was no significant difference in intracellular CL between the two groups. Exudate PMNs were more chemotactic, but produced smaller amounts of total CL than circulating cells. No significant difference in intracellular CL between exudate and circulating PMNs was detected, indicating that phagocytic activity was not affected. We conclude that severe surgical trauma causes circulating PMNs with high chemotactic activity to migrate to sites of injury, but that preactivated PMNs in exudate examined in vitro produce lower amounts of reactive oxygen metabolites in response to soluble chemoattractants in vitro than cells circulating in plasma.

Adult↗
PubMed1993

Cloning and increased expression with fructose feeding of rat jejunal GLUT5.

We have isolated a clone from the rat jejunum cDNA library using a fragment of human GLUT5 cDNA as a probe. The coding region of this clone shares 80% nucleotide and 81% amino acid identity with human GLUT5 and is thus termed rat GLUT5 cDNA. Rat GLUT5 mRNA exhibited a tissue distribution very similar to that of human GLUT5, with the highest levels in the jejunum, but was not detected in fat, muscle, or testis on Northern blot analysis. The antipeptide antibody raised against the C-terminal domain of rat GLUT5 protein specifically recognized a rat jejunal protein with an apparent mol wt of 60,000 on immunoblots. The amount of GLUT5 mRNA and protein in the jejuni of rats fed a fructose-enriched diet (50%, wt/wt) for 3 days were increased 2.5- and 6-fold, respectively, compared to those of rats fed standard rat chow, whereas those of rats fed a starch-enriched diet (50%, wt/wt) were not altered. Similarly, GLUT5 mRNA and protein in the jejunum were increased 5- and 8-fold, respectively, after 15 days of fructose feeding. Thus, an increase in fructose absorption up-regulates GLUT5 expression in the jejunum. These results are consistent with the notion that GLUT5 plays a major role in fructose absorption in the small intestine.

Amino Acid Sequence↗
PubMed1993

The short- and long-term prognosis for acute myocardial infarction after emergency coronary angioplasty.

The short- and long-term prognosis for acute myocardial infarction after reperfusion was examined in 175 patients with successful emergency angioplasty and in 29 failed cases. During hospitalization, more cardiac events occurred in the failed group than in the successful group (58.6% versus 12.6%; p < 0.001), especially cardiac death and coronary bypass surgery (27.6% versus 4.0%, and 41.4% versus 4.6%; p < 0.001, respectively). The only difference found in the incidence of post-discharge cardiac events was a higher frequency of cardiac death in the failed group (9.5% versus 1.2%; p < 0.02). The failed group also had a lower cumulative survival rate at 5 years (69.0% versus 95.3%; p < 0.01). Cox proportional hazard analysis showed that the results of angioplasty, cardiac index, peak creatine kinase level, and the number of diseased vessels were significant independent variables for the prediction of subsequent cardiac death at long-term follow-up. Thus, successful reperfusion by emergency angioplasty improved the prognosis of acute myocardial infarction, even when other important variables were considered.

Adult↗