Biomedical subjects

Shinji Takai

Publications and source records attributed to Shinji Takai.

At least 91 records · Page 5Linked to original sources

PubMed2004

Significant target organs for hypertension and cardiac hypertrophy by angiotensin-converting enzyme inhibitors.

To clarify the mechanisms by which angiotensin-converting enzyme (ACE) inhibitors lower blood pressure or inhibit cardiac hypertrophy, we analyzed the correlations among tissue ACE activities, blood pressure and cardiac hypertrophy. In spontaneously hypertensive rats (SHR), blood pressure, heart weight and ACE activities in plasma and various tissues were measured 3, 24 and 48 h after repeated daily treatment for 2 weeks with the ACE inhibitors trandolapril, perindopril, temocapril and enalapril. For all four ACE inhibitors, blood pressure and ACE activities in the plasma, aorta and kidney were significantly reduced 3 h after the last treatment. Although hypotensive effects were maintained at 24 h, ACE activities in plasma were not suppressed by temocapril and enalapril. Even at 3 h, enalapril could not suppress ACE activity in the brain, and temocapril and enalapril could not inhibit ACE activities in the heart. Significant correlations between ACE activity in the aorta and blood pressure were observed for all four ACE inhibitors, while the ACE activities in the heart and brain were not correlated with changes in blood pressure. Significant decreases in the ratio of heart weight to body weight were observed in SHR treated with trandolapril and perindopril, whereas they were not observed with temocapril and enalapril. The ratio of heart weight to body weight was significantly correlated with ACE activity in the heart. ACE activities in vascular tissues and the heart may be important targets in terms of the ability of ACE inhibitors to lower blood pressure or inhibit cardiac hypertrophy, respectively.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed2004

Comparative effects of candesartan and amlodipine in a monkey atherosclerotic model.

Angiotensin II receptor blockers could prevent the development of atherosclerosis beyond reducing blood pressure in monkeys fed a high-cholesterol diet. However, it has been unclear whether hypotensive effects improve atherosclerosis in primates. We investigated whether antihypertensive agents, an angiotensin II receptor antagonist, candesartan, and a calcium channel blocker, amlodipine, prevent areas of atherosclerotic lesions in the aorta of monkeys fed a high-cholesterol diet. Seventeen male monkeys fed a high-cholesterol diet for 6 months were grouped as follows: a high-cholesterol diet group (n=5), a candesartan-treated group (1 mg/kg per day, n=6) and an amlodipine-treated group (5 mg/kg per day, n=6). Candesartan and amlodipine showed a similar hypotensive effect by decreasing the systolic blood pressure approximately 20 mmHg, while these agents did not affect serum cholesterol levels. The ratio of atherosclerotic area to total area in thoracic aorta was significantly decreased by treatment with candesartan, but the ratio tended to be decreased by treatment with amlodipine. Although the angiotensin-converting enzyme activity in plasma was not changed by treatment with candesartan or amlodipine, the angiotensin-converting enzyme activity in the thoracic aorta was obviously reduced by treatment with candesartan, but not with amlodipine. Therefore, a blockade of angiotensin II action rather than a hypotensive effect may play an important role in preventing the development of atherosclerosis in primates.

Amlodipine↗

PubMed2004

Isolation of Rhodococcus equi from the feces of indigenous animals and soil from the Lower Zambezi National Park and Lochinvar National Park, Zambia.

Rhodococcus equi is an important pathogen in foals; however, its incidence in African indigenous animals is poorly understood. Fecal samples (92 from nine indigenous species) and 43 soil samples were collected from two Zambian National Parks. The presence of R. equi was investigated and 533 isolates were tested for the presence of 15- to 17-kDa antigens (VapA) and a 20-kDa antigen (VapB) by immunoblotting and PCR. R. equi was isolated (10(2)-10(4) colony forming units/g) from 75% of fecal and 74% of soil samples. Neither antigen was detected; however, about 20% of the isolates contained cryptic plasmids of various sizes. There was no evidence of virulent R. equi, but the avirulent form was widespread in the animals and the soil.

Animals↗

PubMed2003

Molecular epidemiology of Rhodococcus equi of intermediate virulence isolated from patients with and without acquired immune deficiency syndrome in Chiang Mai, Thailand.

We investigated the prevalence of virulent Rhodococcus equi in clinical isolates from 69 sporadic cases (60 men, 8 women, and 1 patient of unknown sex) in Chiang Mai, Thailand, between 1993 and 2001. Fifty were human immunodeficiency virus (HIV) positive, 3 were HIV negative, and HIV status was unknown for 16. Fifty-two (75%) of 69 isolates were strains of intermediate virulence that contained the virulence-associated 20-kDa antigen, and 17 isolates (25%) were avirulent. No virulent strains with the virulence-associated 15-17-kDa antigens were identified. R. equi was isolated from HIV-positive patients' houses and those of their neighbors: avirulent strains were widespread, but only 1 strain of intermediate virulence was isolated. R. equi strains of intermediate virulence were isolated from 4 (0.8%) of 500 submaxillary lymph nodes from apparently healthy pigs in Chiang Mai. The routes of R. equi acquisition should be investigated from the viewpoint of zoonosis and public health.

Acquired Immunodeficiency Syndrome↗

PubMed2003

Impact of chymase inhibitor on cardiac function and survival after myocardial infarction.

OBJECTIVES: Recent studies have demonstrated that hamsters, like humans, possess both angiotensin converting enzyme (ACE)- and chymase-dependent angiotensin (Ang) II-forming pathways in cardiovascular tissues. We recently found that, after myocardial infarction (MI) in hamsters, cardiac chymase was significantly activated. In order to determine whether suppression of cardiac chymase activity could provide prognostic benefit after MI, we examined the effects of NK3201, a novel, orally active and specific chymase inhibitor, on cardiac function and survival during the acute phase of MI in hamsters. METHODS: Two hundred and ten male Syrian hamsters were used in the present study. The left coronary artery of each hamster was ligated to induce MI. NK3201 at a dose of 30 mg/kg per day was administered orally by gastric gavage, starting either 3 days before or 1 day after MI. RESULTS: ACE and chymase activities were significantly increased in the infarcted left ventricle 3 days after MI. NK3201 treatment starting 3 days before MI significantly inhibited the increase in cardiac chymase activity, while it did not affect ACE activity either in plasma or in heart 3 days after MI. A significant improvement in cardiac function was observed 3 and 14 days after MI in the group receiving NK3201. Compared with vehicle treatment, NK3201 treatment initiated either 3 days before or 1 day after MI significantly reduced the mortality rate during the 14 days of observation following MI. CONCLUSIONS: These findings indicate that cardiac chymase plays an important role after MI and this finding may provide a novel therapeutic target in post-MI treatment.

Acetamides↗

PubMed2003

Bone marrow monocyte lineage cells adhere on injured endothelium in a monocyte chemoattractant protein-1-dependent manner and accelerate reendothelialization as endothelial progenitor cells.

Peripheral blood (PB)-derived CD14+ monocytes were shown to transdifferentiate into endothelial cell (EC) lineage cells and contribute to neovascularization. We investigated whether bone marrow (BM)- or PB-derived CD34-/CD14+ cells are involved in reendothelialization after carotid balloon injury. Although neither hematopoietic nor mesenchymal stem cells were included in human BM-derived CD34-/CD14+ monocyte lineage cells (BM-MLCs), they expressed EC-specific markers (Tie2, CD31, VE-cadherin, and endoglin) to an extent identical to mature ECs. When BM-MLCs were cultured with vascular endothelial growth factors, hematopoietic markers were drastically decreased and new EC-specific markers (Flk and CD34) were induced. BM-MLCs were intra-arterially transplanted into balloon-injured arteries of athymic nude rats. When BM-MLCs were activated by monocyte chemoattractant protein-1 (MCP-1) in vivo or in vitro, they adhered onto injured endothelium, differentiated into EC-like cells by losing hematopoietic markers, and inhibited neointimal hyperplasia. Ability to prevent neointimal hyperplasia was more efficient than that of BM-derived CD34+ cells. MCP-dependent adhesion was not observed in PB-derived CD34-/CD14+ monocytes. Regenerated endothelium exhibited a cobblestone appearance, blocked extravasation of dye, and induced NO-dependent vasorelaxation. Basal adhesive activities on HUVECs under laminar flow and beta1-integrin expression (basal and active forms) were significantly increased in BM-MLCs compared with PB-derived monocytes. MCP-1 markedly enhanced adhesive activity of BM-MLCs (2.8-fold) on HUVECs by activating beta1-integrin conformation. Thus, BM-MLCs can function as EC progenitors that are more potent than CD34+ cells and acquire the ability to adhere on injured endothelium in a MCP-1-dependent manner, leading to reendothelialization associated with inhibition of intimal hyperplasia. This will open a novel window to MCP-1-mediated biological actions and vascular regeneration strategies by cell therapy.

Angioplasty, Balloon↗

PubMed2003

Molecular cloning and characterization of a 79-kDa iron-repressible outer-membrane protein of Moraxella bovis.

Moraxella bovis expresses an iron-repressible 79-kDa outer-membrane protein, IrpA. DNA and N-terminal amino acid sequence analysis indicate that IrpA is closely related to FrpB of Neisseria meningitidis, FetA of Neisseria gonorrhoeae and CopB of Moraxella catarrhalis. The results of manganese mutagenesis and a gel-shift assay suggested that the transcription of irpA is negatively regulated by the ferric uptake regulator. The insertion of an antibiotic resistance cassette into the irpA gene affected the strain's ability to utilize bovine transferrin and lactoferrin. IrpA was detected in geographically diverse clinical isolates, and the antigenicity of IrpA was conserved in all the isolates tested. Therefore, IrpA may have potential as a candidate vaccine.

Amino Acid Sequence↗

PubMed2003

Mechanisms of angiotensin II type 1 receptor blocker for anti-atherosclerotic effect in monkeys fed a high-cholesterol diet.

OBJECTIVE To clarify the mechanism of the anti-atherosclerotic effect of angiotensin II type 1 receptor blocker (ARB) in primates, we investigated whether an ARB (CS-866) affects the serum markers of inflammation and growth factors, and the endothelial function in monkeys fed a high-cholesterol diet. DESIGN Monkeys fed a high-cholesterol diet for 6 months were divided into two groups: one group was given an ARB, CS-866 (10 mg/kg per day), and the other group was not. The control group was fed a normal diet. RESULTS Blood pressure and the plasma cholesterol level were not affected by CS-866. Plasma levels of angiotensin II, renin, angiotensin converting enzyme and chymase were not changed by the high-cholesterol diet, whereas vascular angiotensin converting enzyme, but not chymase, was significantly increased. Serum levels of macrophage-colony stimulating factor, transforming growth factor-beta1 and intracellular adhesion molecule-1 were significantly increased in monkeys fed a high-cholesterol diet but they were suppressed by CS-866. The relaxation response of isolated carotid arteries to acetylcholine was suppressed in the high-cholesterol group, whereas it was improved by CS-866. CONCLUSIONS CS-866 reduced lipid deposition along with the suppression of serum macrophage-colony stimulating factor, transforming growth factor-beta 1 and intracellular adhesion molecule-1, and the improvement of vascular functions, suggesting that ARB has multiple mechanisms for reducing lipid deposition in primates.

Acetylcholine↗

PubMed2003

Cloning and characterization of the fur gene from Moraxella bovis.

A homologue of the ferric uptake regulator gene (fur) was isolated from Moraxella bovis by degenerate polymerase chain reaction and cloning. Fur protein of M. bovis exhibited 72.1% amino acid identity with Acinetobacter calcoaceticus Fur. Western blot analysis showed a decrease of Fur expression in response to sufficient-iron conditions compared with deficient-iron conditions. An electrophoretic mobility-shift assay indicated that Fur protein binds to DNA fragments containing a putative Fur-box derived from the upstream region of the M. bovis fur gene. Fur of M. bovis may regulate the expression of iron transport systems in response to iron limitation in the environment.

Amino Acid Sequence↗

PubMed2003

Application of a chymase inhibitor, NK3201, for prevention of vascular proliferation.

NK3201 is an orally active chymase inhibitor. Its inhibitory activity leads to formation of acyl-intermediate between active serine residue of the enzyme and di-ketone structure of NK3201. NK3201 inhibits human, dog and hamster chymases with IC(50) of 2.5, 1.2, and 28 nM, respectively. On the other hand, NK3201 does not inhibit other types of serine proteases, tryptase, thrombin, elastase, plasmin, and plasminogen activator. In dogs, at 8 h after oral administration of NK3201, 1 mg/kg, the drug levels in plasma, heart, and aorta reached 470, 195, and 78 nM, respectively. In a dog model NK3201, 5 mg/kg/day, increased chymase activity in grafted veins, and suppressed vascular proliferation. After balloon injury in dog vessels, chymase activity was increased locally, in the injured artery, and NK3201, 1 mg/kg/day was effective in preventing vascular proliferation. On the other hand, NK3201, unlike angiotensin converting enzyme inhibitors or angiotensin II receptor blockers, did not affect blood pressure. These findings indicate that local angiotensin II production by chymase is involved only in vascular proliferation, as seen in the injured vessels. Therefore, NK3201 may be useful for preventing vascular proliferation without affecting blood pressure.

Acetamides↗

PubMed2003

A novel chymase inhibitor, 2-(5-formylamino-6-oxo-2-phenyl-1,6-dihydropyrimidine-1-yl)-N-[[,4-dioxo-1-phenyl-7-(2-pyridyloxy)]2-heptyl]acetamide (NK3201), suppressed intimal hyperplasia after balloon injury.

In this study, we investigated whether an orally active chymase inhibitor, 2-(5-formylamino-6-oxo-2-phenyl-1,6-dihydropyrimidine-1-yl)-N-[[3,4-dioxo-1-phenyl-7-(2-pyridyloxy)]-2-heptyl]acetamide (NK3201), prevents intimal hyperplasia in carotid arteries injured by a balloon catheter in dog. Each dog was administered NK3201 (1 mg/kg per day, p.o.) or placebo beginning 5 days before balloon injury and continuing through the experiments. Four weeks after balloon injury, NK3201 did not affect the plasma renin and angiotensin-converting enzyme activities. The chymase activity was significantly increased in the injured arteries, whereas the angiotensin-converting enzyme activity was not. NK3201 significantly reduced the chymase activity in the injured arteries. The intimal area in the placebo- and NK3201-treated group and was 0.46 +/- 0.06 and 0.24 +/- 0.04 mm2, respectively, and this difference was significant. In this study, we demonstrated for the first time that a chymase inhibitor prevented the development of intimal hyperplasia in the balloon-injured arteries.

Acetamides↗

PubMed2003

A novel chymase inhibitor, 4-[1-([bis-(4-methyl-phenyl)-methyl]-carbamoyl)3-(2-ethoxy-benzyl)-4-oxo-azetidine-2-yloxy]-benzoic acid (BCEAB), suppressed cardiac fibrosis in cardiomyopathic hamsters.

Previously, we reported that levels of chymase activity and its mRNA in cardiac tissues were significantly increased along with progression of cardiac fibrosis in cardiomyopathic hamsters, but the involvement of chymase in the progression of fibrosis has been unclear. In cultured human fibroblasts, the concentration of transforming growth factor-beta in the supernatant of medium was significantly increased after injection of human chymase. Furthermore, human chymase dose dependently increased cell proliferation, and this chymase-dependent proliferation was completely suppressed by a chymase inhibitor, Suc-Val-Pro-Phe(p)(OPh)(2) (10 micro M) or an anti-transforming growth factor-beta antibody (100 micro g/ml). In this study, we used Bio14.6 and F1B hamsters as cardiomyopathic and control hamsters, respectively. Cardiomyopathic hamsters were orally administered a novel chymase inhibitor, 4-[1-([bis-(4-methylphenyl)-methyl]-carbamoyl)-3-(2-ethoxy-benzyl)-4-oxo-azetidine-2-yloxy]-benzoic acid (BCEAB; 100 mg/kg per day), or placebo from 5- to 45-week-old. In the placebo-treated group, the cardiac chymase activity in cardiomyopathic hamsters 45 weeks old was significantly increased compared with that in control hamsters. BCEAB significantly reduced the cardiac chymase activity. The indexes (+dP/dt and -dP/dt) of cardiac function were significantly improved by treatment with BCEAB. The mRNA levels of collagen I and collagen III in the placebo-treated hamsters were significantly reduced to 69.6 and 76.5% by treatment with BCEAB, respectively. The fibrotic area in cardiac tissues in the BCEAB-treated hamsters was significantly suppressed to 50.7% compared with that in the placebo-treated treated hamsters. Therefore, the activation of transforming growth factor-beta by chymase may play an important role in the progression of cardiac fibrosis and cardiac dysfunction in cardiomyopathy.

Animals↗

PubMed2003

Performance of five serological assays for diagnosis of Rhodococcus equi pneumonia in foals.

The performance of four enzyme-linked immunosorbent assays (ELISAs) (ELISA-6939, ELISA-33701, ELISA-VapA, and ELISA-California) and an agar gel immunodiffusion test for diagnosis of Rhodococcus equi pneumonia in foals was evaluated. Antibody concentrations of foals with culture-confirmed R. equi pneumonia (n = 41) were compared to those of age-matched pasturemates that remained clinically healthy during the entire breeding season (n = 24). For each serological assay evaluated, selection of a low cutoff resulted in high sensitivity but low specificity. Increasing the cutoff value resulted in better specificity but to the detriment of sensitivity. The best diagnostic performance was achieved with ELISA-California at a cutoff of 40%, resulting in a sensitivity of 59% and a specificity of 88%. We conclude that current serological assays do not differentiate between diseased and clinically healthy foals.

Actinomycetales Infections↗

PubMed2003

Virulence of Rhodococcus equi isolated from cats and dogs.

Nine cat isolates and nine dog isolates of Rhodococcus equi from clinical material were investigated for the presence of the virulence-associated antigens (VapA and VapB) and virulence plasmids. Five of the cat isolates and one dog isolate were VapA positive and contained an 85-kb type I or an 87-kb type I plasmid. The remaining 12 isolates were avirulent R. equi strains and contained no virulence plasmids.

Animals↗

PubMed2003

[Detections of matrix metalloproteinases activities and localization by film in situ zymography (FIZ)].

Extracellular proteolysis is an essential process for cell migration in several diseases such as tumor invasion, metastasis, and angiogenesis. In an invasive process, matrix metalloproteinases (MMPs) play a central role as degradation enzymes of extracellular matrix. Immunohistochemical staining (IHC) or ELISA methods have been carried out for the detection of tissue MMP proteins, and MMP activities have been mainly measured by gelatin zymography. Recently, film in situ zymography (FIZ) was developed for the regional detection of tissue MMP activities. FIZ uses a polyester film coated with gelatin uniformly and thinly. Frozen sections are incubated on the film at 37 degrees for optimal time. After gelatin staining with Biebrich Scarlet, the unstained area corresponds to MMP activities. The regional detection of tissue MMP activities by FIZ is simple and quantitative, and it is a useful tool for the studies of many diseases involving MMP. The detection of precise localization of MMP activity in tissues by FIZ may contribute the new classification of diseases involving MMP.

Animals↗

PubMed2003

[Role of chymase in vascular diseases and the efficacy of chymase inhibitor].

In vascular tissues, angiotensin II is cleaved from angiotensin I by chymase and angiotensin converting enzyme (ACE). In the normal state, chymase is stored in mast cells and has no angiotensin II-forming activity, while chymase is activated immediately where mast cells have been activated by local stimuli. A clinical trial of an angiotensin receptor blocker (ARB) for preventing restenosis after percutaneous transluminal coronary angioplasty was successful, but that of an ACE inhibitor was not. After balloon injury in dog vessels, chymase activity was significantly increased in the injured artery, and a chymase inhibitor and an ARB were effective in preventing the vascular proliferation, but an ACE inhibitor was ineffective. In dog grafted veins, intimal area, chymase activity, and angiotensin II concentration were significantly increased after the operation, while they were significantly suppressed by a chymase inhibitor. However, the chymase inhibitor, unlike ACE inhibitor and ARB, did not affect blood pressure. These reports indicate that local angiotensin II production by chymase is involved only in the injured vessels. Therefore, a chymase inhibitor may be useful for preventing vascular disorders without affecting blood pressure.

Angioplasty, Balloon, Coronary↗

PubMed2003

Rhodococcus equi virulence plasmids recovered from horses and their environment in Jeju, Korea: 90-kb type II and a new variant, 90-kb type V.

Rhodococcus equi was isolated from fecal and soil samples from four native Jeju horse farms and six Thoroughbred farms in Jeju, Korea. The isolates were examined for the presence of virulence-associated 15-17-kDa antigens (VapA) by colony blotting, using the monoclonal antibody 10G5, and for the gene encoding VapA by PCR. R. equi was isolated from all 36 soil samples collected from the 10 farms with between 5.0 x 10(2) and 7.5 x 10(4) colony-forming units (cfu) per gram of soil, and from 37 of 40 fecal samples with between 5.0 x 10(1) and 1.1 x 10 (5) cfu per gram of feces. Virulent R. equi was isolated from seven farms and appeared in 2.0% of isolates (10 of 508). Of the 10 virulent isolates, four contained a 90-kb type II plasmid, which has been found in isolates from the Kiso native horses of Japan, and the other six contained a new variant, which did not display the EcoRI and EcoT22I digestion patterns of the 10 representative plasmids already reported (85-kb types I, II, III, and IV; 87-kb types I and II; 90-kb types I, II, III, and IV). We designated the new variant as the "90-kb type V" plasmid, because its EcoRI digestion pattern is similar to that of the 90-kb type II plasmid. This is the first report of the prevalence of virulent R. equi in Jeju, Korea. The same virulence plasmid type is found in both Korean and Japanese isolates, providing insight into the origin, ancestry, and dispersal of native horses in Korea and Japan.

Actinomycetales Infections↗

PubMed2003

A novel therapeutic strategy against vascular disorders with chymase inhibitor.

In vascular tissues, angiotensin II is potentially cleaved from angiotensin I by chymase and angiotensin converting enzyme (ACE). In the normal state, ACE regulates angiotensin II formation and plays a crucial role in the regulation of blood pressure, whereas chymase is stored in mast cells and has no angiotensin II-forming activity. Chymase is activated immediately upon its release into the extracellular matrix in vascular tissues after mast cells have been activated by local stimuli such as vessel injury by grafting or a balloon catheter. In dog grafted veins, vascular proliferation, chymase activity, angiotensin II concentration and mRNA levels of fibronectin, collagen I and collagen III were significantly increased after the operation, while they were significantly suppressed by a chymase inhibitor. A clinical trial of an angiotensin II receptor blocker (ARB) for preventing restenosis after percutaneous transluminal coronary angioplasty was successful, but that of an ACE inhibitor was not. After balloon injury in dog vessels, chymase activity was signifcantly increased in the injured artery, and a chymase inhibitor and an ARB were effective in preventing the vascular proliferation, but an ACE inhibitor was ineffective. On the other hand, a chymase inhibitor, unlike an ACE inhibitor and an ARB, did not affect blood pressure. These reports indicate that local angiotensin II production by chymase is involved only in the intimal hyperplasia seen in the injured vessels. Therefore, chymase inhibitors may be useful for preventing vascular disoders without affecting blood pressure.

Angioplasty, Balloon↗