Creation and characterization of a mitochondrial DNA-depleted pancreatic beta-cell line: impaired insulin secretion induced by glucose, leucine, and sulfonylureas.

It has been proposed that mitochondrial oxidative phosphorylation in pancreatic beta-cells plays an important role in insulin secretion. To examine the impact of mitochondrial dysfunction on insulin secretion, we created a MIN6 cell line that depleted mitochondrial DNA (mtDNA) by treatment with ethidium bromide (EtBr), and studied the response of the cell line to various secretagogues. MIN6 cells cultured with 0.5 microg/ml EtBr for over 2 months (termed MIN6 deltamt cells) revealed a marked (>90%) decrease in mtDNA content and a lack of mRNAs encoded by mtDNA. MIN6 deltamt cells showed the defects of cytochrome c oxidase activity, glucose- and leucine-induced increase in cellular ATP content, and respiratory chain-driven ATP synthesis, suggesting that MIN6 deltamt cells lost oxidative phosphorylation activity due to the selective disruption of the subunits of respiratory chain enzymes encoded by mtDNA. MIN6 deltamt cells also showed a decrease in glucose utilization, suggesting the impairment of the glycolytic pathway as well. After stimulation with glucose and leucine, MIN6 deltamt cells showed no response in insulin secretion or intracellular free Ca2+ concentration ([Ca2+]i). On the other hand, arginine stimulated insulin secretion and an increase in [Ca2+]i in MIN6 deltamt cells as in MIN6 cells. Glibenclamide also stimulated insulin secretion and an increase in [Ca2+]i in both types of cells, but the responses of MIN6 deltamt cells were significantly lower than those of MIN6 cells. These results suggest the importance of ATP production in insulin secretion and an increase in [Ca2+]i, both induced by glucose and leucine. Moreover, mitochondrial function turns out to be not essential but important for the activation of sulfonylurea-induced insulin secretion.

HTLV-I-associated myelopathy with adult T-cell leukemia.

We report a 42-year-old Japanese woman with HTLV-I-associated myelopathy (HAM) combined with adult T-cell leukemia (ATL). Combination of the 2 diseases has been extremely rare. The infrequency is explained by HLA types unique to each disease. Our patient suggests that the HAM-associated HLA haplotype does not prevent the development of ATL.

Heterozygous knockout of the IRS-1 gene in mice enhances obesity-linked insulin resistance: a possible model for the development of type 2 diabetes.

Insulin receptor substrate 1 (IRS-1) gene polymorphisms have been identified in type 2 diabetic patients; however, it is unclear how such polymorphisms contribute to the development of diabetes. Here we introduced obesity in heterozygous IRS-1 knockout (IRS-1(+/-)) mice by gold-thioglucose (GTG) injection and studied the impact of reduced IRS-1 expression on obesity-linked insulin resistance. GTG injection resulted in approximately 30% weight gain in IRS-1(+/-) and wild type (WT) mice, compared with saline-injected controls. There was no difference in insulin sensitivity between lean IRS-1(+/-) and lean WT. Elevated fasting insulin levels but no change in fasting glucose were noted in obese IRS-1(+/-) and WT compared with the respective lean controls. Importantly, fasting insulin in obese IRS-1(+/-) was 1.5-fold higher (P<0.05) than in obese WT, and an insulin tolerance test showed a profound insulin resistance in obese IRS-1(+/-) compared with obese WT. The islets of obese IRS-1(+/-) were 1.4-fold larger than those of obese WT. The expression of insulin receptor and IRS-1 and IRS-2 was decreased in obese IRS-1(+/-), which could in part explain the profound insulin resistance in these mice. Our results suggest that IRS-1 is the suspected gene for type 2 diabetes and its polymorphisms could worsen insulin resistance in the presence of other additional factors, such as obesity.

Metabolism of plasma fibronectin in rabbits with experimental hyperthyroidism and hypothyroidism.

We previously reported that the concentration of plasma fibronectin (pFN) is increased in patients with hyperthyroidism and decreased in those with hypothyroidism. In this work, labeled pFN was given intravenously to euthyroid, hyperthyroid, and hypothyroid rabbits to examine its metabolism in states of thyroid dysfunction. In euthyroid rabbits, the serum concentration of thyroxine (T4) was 2.94 +/- 0.59 micrograms/dL, and that of pFN was 24.2 +/- 1.2 mg/dL. With 125I-FN as tracer, the half life was estimated as 72.8 +/- 2.6 hours, the fractional catabolic rate (FCR) as 2.08 +/- 0.07%/h, the rate of synthesis (SR) as 3.84 +/- 0.20 mg/kg/day and j1/j2 (the ratio of the exchange coefficients between intravascular and extravascular compartments) of pFN as 0.295 +/- 0.051. With 3H-FN as tracer, these values were not significantly different. In hyperthyroid rabbits, obtained by treatment with I-thyroxine, the serum T4 concentration was increased to 5.73 +/- 1.58 micrograms/dL and the pFN concentration to 29.6 +/- 2.2 mg/dL. In these animals, the half life of pFN was shortened to 59.8 +/- 1.0 hour, the FCR was slightly increased to 3.07 +/- 0.52%/h and the SR was greatly increased to 7.13 +/- 1.17 mg/kg/d. In hypothyroid rabbits, obtained by treatment with methylthiouracil, the serum T4 and pFN levels were reduced to 1.50 +/- 0.36 micrograms/dL and to 20.7 +/- 1.7 mg/dL, respectively, the FCR and SR were also decreased to 1.39 +/- 0.04%/h and 2.26 +/- 0.14 mg/kg/d, respectively. The values of j1/j2 did not significantly change during this work.(ABSTRACT TRUNCATED AT 250 WORDS)

Involvement of bradykinin in acute exercise-induced increase of glucose uptake and GLUT-4 translocation in skeletal muscle: studies in normal and diabetic humans and rats.

Acute exercise induces glucose uptake in skeletal muscle in vivo, but the molecular mechanism of this phenomenon remains to be identified. In this study, we evaluated the involvement of bradykinin in exercise-induced glucose uptake in humans and rats. In human studies, plasma bradykinin concentrations increased significantly during an ergometer exercise (20 minutes) in 8 healthy normoglycemic subjects and 6 well-controlled type 2 diabetic patients (mean hemoglobin A1c [HbA1c], 6.4% +/- 0.6%), but not in 6 poorly controlled type 2 diabetics (mean HbA1c, 11.6% +/- 2.6%). In rat studies, plasma bradykinin concentrations also significantly increased after 1 hour of swimming in nondiabetic and mildly diabetic (streptozotocin [STZ] 45 mg/kg intravenously [IV]) rats, but not in rats with severe diabetes (STZ 65 mg/kg IV). Glucose influx (maximum velocity [Vmax]) and GLUT-4 translocation in skeletal muscle of nondiabetic rats significantly increased after 1 hour of swimming, but these increases were abrogated by subcutaneous infusion of bradykinin B2 receptor antagonist HOE-140 (400 microg x kg(-1) x d(-1)). Insulin-stimulated tyrosine phosphorylation and phosphatidylinositol (PI) 3-kinase activity in response to insulin injection (20 U/kg IV) in the portal vein were significantly attenuated in exercised rats pretreated with HOE-140 compared with saline-treated exercised rats. Our results suggest that plasma bradykinin concentrations increase in response to acute exercise and this increase is affected by blood glucose status in diabetic patients. Moreover, the exercise-induced increase in bradykinin may be involved in modulating exercise-induced glucose transport through an increase of GLUT-4 translocation, as well as enhancement of the insulin signal pathway, during the postexercise period in skeletal muscle, resulting in a decrease of blood glucose.

Detection of a single base substitution of the gene for prothrombin Tokushima. The application of PCR-SSCP for the genetic and molecular analysis of dysprothrombinemia.

The genetic and molecular basis of a mutant prothrombin of 'prothrombin Tokushima' was studied by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) and PCR-restriction fragment length polymorphism (PCR-RFLP) analyses. The abnormal gene was detected by altered migration by PCR-SSCP and by the loss of an MspI site by PCR-RFLP. The gene for prothrombin Tokushima was shown to be inherited from the mother of the proband. Sequencing analysis using PCR-amplified genomic DNA clarified a substitution of thymine (T) for cytosine (C) at position 9,490, changing arginine (Arg) to tryptophan (Trp) at position 418 of the polypeptide chain. This point mutation is assumed to be the molecular basis of prothrombin Tokushima, firstly, because of the absence of distinct changes in Southern blot analysis of the proband's DNA (using a full-length human prothrombin cDNA as a probe), secondly, because it has the same molecular weight as the abnormal gene product, and, thirdly, because of the absence of other amino acid abnormalities in the proteolytic peptide-fragments. It is concluded that PCR-SSCP and PCR-RFLP were useful for detecting the abnormal gene and for directly diagnosing the carrier status of dysprothrombinemia. This is the first report of gene analysis of dysprothrombinemia.

Bradykinin enhances insulin receptor tyrosine kinase in 32D cells reconstituted with bradykinin and insulin signaling pathways.

We have previously shown that bradykinin potentiated insulin-induced glucose uptake through GLUT4 translocation in canine adipocytes and skeletal muscles. The aim of this study was to determine the molecular mechanism of bradykinin enhancement of the insulin signal. For this purpose, 32D cells, which express a limited number of insulin receptors and lack endogenous bradykinin B2 receptor (BK2R) or insulin receptor substrate (IRS)-1 were transfected with BK2R cDNA and/or insulin receptor cDNA and/or IRS-1 cDNA, and analyzed. In 32D cells that expressed BK2R and insulin receptor (32D-BKR/IR), bradykinin alone had no effect on the phosphorylation of the insulin receptor, but it enhanced insulin-stimulated tyrosine phosphorylation of the insulin receptor. In 32D cells that expressed BK2R, insulin receptor and IRS-1 (32D-BKR/IR/IRS1), bradykinin also enhanced insulin-stimulated tyrosine phosphorylation of the insulin receptor and IRS-1. An increase in insulin-stimulated phosphorylation of IRS-1 by treatment with bradykinin in 32D-BKR/IR/IRS1 cell was associated with increased binding of 85 kD subunit of phosphatidylinositol 3 (PI 3)-kinase and increased IRS-1 associated PI 3-kinase activity. These effects of bradykinin were not observed in 32D cells which lack the expression of BK2R (32D-IR/IRS1) or insulin receptor (32D-BKR/IRS1). Furthermore, tyrosine phosphatase activity against insulin receptor beta-subunit in plasma membrane fraction of 32D-BKR/IR cells was significantly reduced by bradykinin, suggesting that the effect of bradykinin was in part mediated by inhibition of protein tyrosine phosphatase(s). Our results clearly demonstrated that bradykinin enhanced insulin-stimulated tyrosine kinase activity of the insulin receptor and downstream insulin signal cascade through the BK2R mediated signal pathway.

Second national external quality assessment scheme in hematology: the Philippine experience.

The Philippine Council for Quality Assurance In Clinical Laboratories has conducted two National External Quality Assessment Schemes (NEQAS) in Hematology. The first survey was conducted in December 1999 and the second in August 2000, with 95 and 187 laboratories, using mostly automated analyzers, participating respectively. Control materials were distributed during a two-week period by human network, and analyzed over a six to eight week period. For the first survey, only 36 laboratories (38.0%) submitted results. Data was divided into 4 peer groups based on the manufacturer. Since most of the samples were hemolysed upon analysis, only WBC and HGB parameters were evaluated. No outliers were detected in each peer group after analysis by the 'Peer Group Mean and SDI' method. Using the clinical laboratory improvement act of 1988 proficiency testing criteria (CLIA'88), only 5 results (13.9%) were unsatisfactory for WBC, and all results were satisfactory for HGB. For the second survey, 87 laboratories (47%) responded. Data was divided into 5 peer groups. There were few incidents of sample deterioration. Although majority of the coefficient of variations were acceptable, about 23 (12.6%) participants showed abnormality in at least one parameter after analysis by the 'Peer Group Mean and SDI'. Using CLIA'88, 5 WBC (6.5%), 6 RBC (7.6%), 8 HGB (9.7%), 15 HCT (19.0%), and 7 PLT (8.0%) results were unsatisfactory. In summary, the first NEQAS study served as a pilot study. Valuable lessons were learned for the improvement of the second NEQAS. The second NEQAS study was marked by a much larger sample size and better results.

[Clinical study on effects of cefmetazole on severe infections accompanied by hematologic diseases].

Severe infections accompanied by hematopathy under granulocytopenic conditions were treated with cefmetazole (CMZ). Subject diseases mainly consisted of acute leukemia, agranulocytosis and aplastic anemia; combined infections were septicemia, pneumonia, fever of an undetermined origin, etc. As for causative organisms found in cases that could be examined, Gram-negative bacilli such as Klebsiella pneumoniae, Klebsiella oxytoca, Pseudomonas aeruginosa and Enterobacter cloacae were isolated, as was Staphylococcus aureus. In general, 4 g of CMZ divided into 2 administrations was given per day through intravenous injection or intravenous drip infusion. On the basis of the judgement criteria for effectiveness established by Takaku et al., the efficacy rate in this study was found to be 68%, including 2 cases that showed excellent responses to treatment of infections caused by S. aureus. Cases that showed pyretolysis within 4 days had over 1,000/microliter of neutrophils, while cases with less than 1,000/microliter showed no pyretolysis. No hepatorenal dysfunctions related to the treatment with CMZ were seen as side effects except increases of transaminase in 1 case. These results indicate that CMZ is a useful drug for the treatment of infections accompanied by hematopathy under granulocytopenic condition.

[IBL-type lymphadenopathy after infection of rubella virus].

A 52-year-old woman presented slight fever, diffuse papular skin rash and painful cervical lymph node swelling. Her lymph node swelling generally up to 3 cm in diameter, with petechiae on the lower legs and hepato-splenomegaly within a few weeks. ESR was 45 mm/h, Hb 10.0 g/dl, RBC 345 x 10(4)/microliter, WBC 22,600/microliter (atypical lymphocyte 47%), PLT 1.0 x 10(4)/microliter, GPT 91 U/L, gamma-globulin 34.3%, EBV-VCA x 2,560, EBNA x 20, and anti-rubella antibody x 512. The biopsied cervical lymph node showed histologic features of effacement of nodal architecture by an exuberant vascular proliferation accompanied with infiltration of the immunoblasts, and was diagnosed as immunoblastic lymphadenopathy (IBL)-type lymphadenopathy. The pulse therapy of methylprednisolone and high dose of gamma-globulin improved lymphadenopathy, thrombocytopenia and anemia. IBL-type lymphadenopathy after infection of rubella virus may be different from true IBL, but is important to discuss the pathogenesis of IBL.