Masatoshi Kuroki

A New Spontaneously Diabetic Non-obese Torii Rat Strain With Severe Ocular Complications

A new spontaneously diabetic strain of the Sprague-Dawley rat was established in 1997 and named the SDT (Spontaneously Diabetic Torii) rat. In this research, we investigated the characteristics of the disease condition in the SDT rats. The time of onset of glucosuria was different between male and female SDT rats; glucosuria appeared at approximately 20 weeks of age in male rats and at approximately 45 weeks of age in female rats. A cumulative incidence of diabetes of 100% was noted by 40 weeks of age in male rats, while it was only 33.3% even by 65 weeks of age in female rats. The survival rate up to 65 weeks of age was 92.9% in male rats and 97.4% in female rats. Glucose intolerance was observed in male rats from 16 weeks of age. The clinical characteristics of the male SDT rats were (1) hyperglycemia and hypoinsulinemia (from 25 weeks of age); (2) long-term survival without insulin treatment; (3) hypertriglyceridemia (by 35 weeks of age); however, no obesity was noted in any of the male rats. The histopathological characteristics of the male rats with diabetes mellitus (DM) were (1) fibrosis of the pancreatic islets (by 25 weeks of age); (2) cataract (by 40 weeks of age); (3) tractional retinal detachment with fibrous proliferation (by 70 weeks of age) and (4) massive hemorrhaging in the anterior chamber (by 77 weeks of age). These clinical and histopathological characteristics of the disease in SDT rats resemble those of human Type 2 diabetes with insulin hyposecretion. In conclusion, SDT rat is considered to be a potentially useful model for studies of diabetic retinopathy encountered in humans.

ENDOTHELIAL CELL INJURY IN VENULE AND CAPILLARY INDUCED BY CONTRAST ULTRASONOGRAPHY

The aim of the present study was to test the hypothesis that microvascular endothelial cells (EC) are subject to the bioeffects induced by contrast ultrasound (US) because of their proximity to the circulating microbubbles. We examined EC injury in each microvessel section (arteriole, capillary or venule) in rat mesenteries among the following five groups: three controls (sham operation, microbubble injection alone, US exposure with saline injection), and two contrast-US groups (US exposure at a 1-Hz or 30-Hz frame rate with microbubble injection). Propidium iodide (PI), a fluorescent indicator of cell injury, was employed to visualize impaired EC. PI-positive nuclei were equally few among the three controls. Contrast-US increased PI-positive cells in capillaries (1-Hz frame rate, 2.4 +/- 2.2 cells per 0.1-mm vessel length, p = 0.09; 30-Hz frame rate, 4.3 +/- 1.8 cells, p < 0.01) and in venules (1-Hz frame rate, 4.1 +/- 2.5 cells, p < 0.05; 30-Hz frame rate, 13.8 +/- 3.6 cells, p < 0.01) compared with sham operation (0.10 +/- 0.22 cells). The finding indicates that diagnostic contrast US potentially causes EC injury, particularly in venules and capillaries.

Transient rise in serum interleukin-8 concentration during acute myocardial infarction.

OBJECTIVE--To determine whether interleukin-8 (IL-8, a potent activator of neutrophils) is involved in tissue injury during ischaemia and reperfusion in patients with acute myocardial infarction. SETTING--Teaching hospital. SUBJECTS--Five consecutive patients with acute Q-wave myocardial infarction, two patients with stable angina who underwent elective percutaneous transluminal coronary angioplasty, and 10 normal controls. MAIN OUTCOME MEASURE--Serum IL-8 concentration measured by enzyme linked immunosorbent assay (ELISA) over time (every four, eight or 12 hours for 36-72 hours). RESULTS--All five patients with acute myocardial infarction had a transient but significant rise in serum IL-8 concentration (13-1100 ng/l) within 22 hours after the onset of symptoms, whereas IL-8 was not detected in any of the samples from patients with angina pectoris or normal controls. One patient who died of pump failure and two patients who had mild congestive heart failure showed the highest values (1100, 920, and 190 ng/l respectively). CONCLUSIONS--Serum IL-8 concentration showed a transient rise during the very early phase of acute myocardial infarction. In combination with several recent lines of evidence indicating the importance of injurious activities of neutrophils as a cause of tissue damage in acute myocardial infarction and the potent stimulation of neutrophils by IL-8, these results strongly suggest that IL-8 is important in the development of myocardial injury in acute myocardial infarction.

Nicorandil and leukocyte activation.

Nicorandil, a hybrid compound of an ATP-sensitive potassium (KATP) channel opener and a nitric oxide donor, has been reported to preserve microvascular integrity in patients with reperfused myocardial infarction. The aim of the current study was to test the hypothesis that nicorandil suppresses activation of polymorphonuclear leukocytes (PMNLs), resulting in reduction of PMNL migration into tissue upon ischemia/reperfusion. Nicorandil, along with the mitochondrial KATP channel opener diazoxide and the nitric oxide donors nitroglycerin and isosorbide dinitrate, suppressed pseudopod projection in human PMNLs treated with 10−9M N-formyl-methionyl-leucyl-phenylalanine (FMLP) and subjected to shear stress (5 dyn/cm2) with a cone-and-plate shear device. Suppression by nicorandil and diazoxide was reversed by KATP channel blockers, 5 hydroxydecanoate and glibenclamide. FMLP-induced increase of [Ca2+]in in PMNLs was suppressed by nicorandil and diazoxide, and 5 hydroxy-decanoate and glibenclamide reversed this suppression. Results of reverse transcription polymerase chain reaction with rat PMNL mRNA indicated the presence of mRNAs of Kir6.2 and Kir6.1 but not mRNAs of sulfonylurea receptor 1 or 2. Isosorbide dinitrate, diazoxide, and nicorandil reduced leukocyte migration and microvascular obstruction in reperfused ischemic tissue of rat mesenteric microcirculation. In conclusion, nicorandil attenuates ischemia/reperfusion-induced PMNL activation via donation of nitric oxide and K channel–related cascade.

Src family kinases and nitric oxide production are required for hepatocyte growth factor-stimulated endothelial cell growth

Hepatocyte growth factor (HGF) is a potent mitogen for vascular endothelial cells (EC); however, signal transduction pathways for HGF-stimulated EC growth remain unclear. In the present study we investigated the role of Src family kinases and nitric oxide (NO) in HGF-stimulated EC growth. Human umbilical vein endothelial cells (HUVEC) were stimulated with HGF and NO was measured by an NOx analyzing HPLC system. Activation of ERK1/2 and p38 MAPK was assessed by Western blot. NO production in HUVEC increased 1.8-fold by HGF. A Src family kinases inhibitor PP1 inhibited HGF-stimulated NO production by 71%. HUVEC growth increased 1.9-fold in cell number by HGF. PP1 and Nitro-L-arginine methylester (L-NAME) inhibited HGF-stimulated HUVEC growth by 51 and by 71%. ERK1/2 and p38 MAPK were phosphorylated by HGF and a MEK inhibitor PD98059 and a p38 MAPK inhibitor SB203580 inhibited HGF-stimulated HUVEC growth by 66% and by 58%; however, HGF-induced phosphorylation of ERK1/2 and p38 MAPK was not inhibited by L-NAME, indicating that NO is not an upstream activator of ERK1/2 and p38 MAPK. These findings demonstrated that Src family kinases regulate HGF-stimulated NO production in HUVEC and that HGF stimulates HUVEC growth through NO-dependent and NO-independent pathways.

Effect of the Cholesteryl Ester Transfer Protein Genotypes on Plasma Lipid and Lipoprotein Levels in Vietnamese Children

Cholesteryl ester transfer protein (CETP) is understood to play a regulatory role in HDL cholesterol (HDLC) metabolism. In this study, the effect of CETP genotypes on plasma lipid and lipoprotein levels in 348 Vietnamese girls (aged 7–9) with different nutritional conditions was analyzed. The two mutations, intron 14 G(+1)-to-A (I14A) and Asp 442 to Gly within exon 15 (D442G), and the TaqIB polymorphism in the CETP gene were identified by an Invader assay. The D442G mutation was present with a frequency of 0.034, while the I14A mutation was absent. HDLC levels were significantly higher in carriers of the D442G mutation than in noncarriers, regardless of the nutritional status. Low-density lipoprotein (LDL) cholesterol and triglyceride levels were not significantly lower in carriers of D442G mutation. The frequency of the TaqIB2 allele was 0.34, which was lower than that observed in other Asian populations. TaqIB2B2 carriers also had significantly higher HDLC levels, but this association was weaker than that of the D442G mutation. Overall, genetic variations at the CETP gene locus may account for a significant proportion of HDLC variation in Vietnamese children.

A new form of retinopathy associated with myocardial infarction treated with percutaneous coronary intervention

Aim: To report a new form of retinopathy that was observed in patients who had undergone percutaneous coronary intervention (PCI) following acute myocardial infarction (AMI). Methods: Serial ophthalmological examinations were conducted in 40 patients who underwent PCI. Thirty patients were diagnosed with AMI, and another 10 had stable angina pectoris. Results: Cotton wool spots developed in 17 (57%) patients from the group with AMI undergoing PCI (n = 30) within 2 months. Of these, 41% (seven patients) also developed superficial haemorrhages. Retinopathy was most prominent 1–2 months after AMI and then tended to become quiescent afterwards, without treatment. Conclusion: We have identified a new form of retinopathy in patients with AMI that spontaneously subsides without treatment.