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Biomedical subjects

M Usui

Publications and source records attributed to M Usui.

At least 91 records · Page 5Linked to original sources
PubMed1999

Conserved T cell receptor complementarity-determining region 3 of ocular T cells in mice with experimental autoimmune uveoretinitis.

PURPOSE: To characterize T cells infiltrating into the ocular tissues of mice with experimental autoimmune uveoretinitis (EAU) immunized with interphotoreceptor retinoid-binding protein (IRBP). METHODS: The T cell receptor (TCR) repertoire on T cells obtained from ocular lesions of EAU mice was analyzed by reverse transcriptase-polymerase chain reaction. The clonotype of the T cells was examined by the single-strand conformation polymorphism (SSCP) method, followed by sequence analysis of the TCR beta-chain complementarity-determining region 3 (CDR3). RESULTS: The repertoire of the TCR BV gene in T cells from inflamed lesions was heterogeneous. SSCP analysis showed accumulation of multiple T cells specifically in ocular tissues of EAU mice, suggesting that these cells were expanded by an antigen-driven stimulation. Junctional sequence analysis demonstrated the presence of highly conserved amino acid sequence motifs (AGTGG, AGD) in CDR3 of BV2-positive T cells. CONCLUSIONS: Our findings suggest that T cells infiltrating into ocular lesions of EAU mice recognize restricted T cell epitopes of IRBP, resulting in autoimmune uveoretinitis.

Amino Acid Sequence↗
PubMed1999

Pathogenic role of oxidative stress in vascular angiotensin-converting enzyme activation in long-term blockade of nitric oxide synthesis in rats.

Inhibition of nitric oxide (NO) synthesis with N(omega)-nitro-L-arginine methyl ester (L-NAME) activates vascular angiotensin-converting enzyme (ACE) and causes oxidative stress. We investigated the role of oxidative stress in the pathogenesis of ACE activation in rats. Studies involved aortas of rats receiving no treatment, L-NAME, L-NAME plus L-arginine, or L-NAME plus an antioxidant drug (N-acetylcysteine, allopurinol, or ebselen) for 7 days. L-NAME significantly increased oxidative stress (O(2)(-)) and ACE activity. The increased O(2)(-) production was normalized by removal of endothelium. Immunohistochemistry showed the increased ACE activity in the endothelial layer. Treatment with antioxidant drugs did not affect the L-NAME-induced increase in systolic arterial pressure but did prevent increases in vascular O(2)(-) production and ACE activity. These results implicate oxidative stress in the pathogenesis of vascular ACE activation in rats with long-term inhibition of NO synthesis. The observed effects of antioxidant drugs on ACE activation do not appear to involve the hypertension induced by L-NAME.

Animals↗
PubMed1999

Risk of subarachnoid hemorrhage after surgical treatment of unruptured cerebral aneurysms.

BACKGROUND AND PURPOSE: Recent progress in noninvasive imaging techniques has resulted in increased detection of unruptured aneurysms. Although many neurosurgeons advocate surgical intervention for such unruptured aneurysms, the long-term results of surgery for unruptured aneurysms have not been carefully investigated. METHODS: We analyzed 173 consecutive patients who had unruptured intracranial saccular aneurysm(s) detected by angiography that was performed for reasons other than subarachnoid hemorrhage (SAH). Of those, 115 cases were surgically treated and studied. All patients were followed up for either SAH, repeat treatment of aneurysms, or death. The median follow-up period was 8.8 years. RESULTS: Four of the 115 patients suffered SAH either from a de novo aneurysm (2) or from regrowth of clipped aneurysm (1), or from regrowth after wrapping (1). Additionally, 1 patient also suffered SAH from an unstudied basilar aneurysm. One patient was incidentally found to have de novo aneurysm and underwent reoperation 14 years after the first operation. The cumulative risk for SAH for the 114 cases excluding the basilar aneurysm case was 1.4% in 10 years and 12.4% in 20 years. CONCLUSIONS: Although this study confirmed the long-term efficacy of clipping unruptured aneurysms, the risk of SAH was high compared with that in the general population, even after treatment. Considering the high mortality rate of SAH, long-term follow-up by angiography may be warranted for patients with surgically treated unruptured aneurysms.

Adult↗
PubMed1999

Fluorescence spectrum analysis of atherosclerotic plaque using doxycycline.

Using doxycycline (DOXY), fluorescence spectrum analysis was performed on arteriosclerotic lesions, and the efficacy of this method was examined in basic and clinical studies. In the basic study, DOXY 50 mg was administered intravenously to arteriosclerotic rabbits, and the thoracoabdominal aorta removed. Fluorescence spectral analysis was performed on each specimen, and the fluorescence spectral pattern, peak intensity and degree of intimal hypertrophy were studied. In the clinical study, DOXY 200 mg was administered intravenously to 6 human subjects with stable angina and coronary arterial stenosis of greater than 90%, and coronary angiography, coronary angioscopy and fluorescence spectral analysis were performed. DOXY accumulation in the arteriosclerotic intima of rabbit aortae was confirmed. The fluorescence spectrum was monomodal, peaking at around 532 nm. In the noncalcification group, significant correlation was observed between peak intensity and arteriosclerotic intimal thickness. Using DOXY as a fluorescent marker, it was possible to assess the level of arteriosclerotic intimal hypertrophy. Clinically, it was possible to obtain the DOXY spectrum of the coronary arteries.

Animals↗
PubMed1999

Photodynamic therapy for the prevention of intimal hyperplasia in balloon-injured rabbit arteries.

This study was performed to demonstrate accumulation of the photosensitizer hematoporphyrin derivative (HPD) in atherosclerosis and to determine whether intimal hyperplasia, the main cause of restenosis after angioplasty, can be inhibited by photodynamic therapy (PDT). Forty Japanese White rabbits were subjected to balloon endothelial injury in the common iliac artery. Five groups of rabbits, ie, immediately after, or 3, 7, 14 or 28 days after the balloon injury, were injected with HPD. These rabbits were sacrificed 24h after HPD administration, and HPD fluorescence was investigated in the injured arteries by fluorescence microscopy. Other groups of rabbits were injected with HPD 24h before PDT, and they were then subjected to intravascular Hg-Xe flash-lamp irradiation immediately after (0D-PDT), or 3 days (3D-PDT), 7 days (7D-PDT), or 14 days (14D-PDT) after the balloon injury. All rabbits were sacrificed 28 days after the balloon injury, and histological sections of PDT-treated arteries were examined by light microscopy. Slight, uniform HPD accumulation was observed in the injured media immediately after the balloon injury, and throughout the entire media and the neointima on day 7. On day 14, HPD accumulation had diminished in the media and increased in the intima, and on day 28 no HPD remained in the media. In the 0D- or 3D-PDT groups, no inhibition of intimal hyperplasia was observed. In contrast, there was significant inhibition of intimal hyperplasia in the 7D- and 14D-PDT groups, and the most effective inhibition was in the 7D-PDT group. This study demonstrated that PDT with HPD inhibits smooth muscle cell growth and decreases the intimal hyperplasia response in rabbits.

Animals↗
PubMed1999

Changes in autonomic nervous activity after catheter ablation of right ventricular outflow tract tachycardia.

Idiopathic right ventricular outflow tract (RVOT) tachycardia is prone to occur when sympathetic nervous activity increases. The effects of catheter ablation on the arrhythmia may be modified by changes in the sympathovagal balance induced by the ablation. In 8 patients with RVOT tachycardia, analyses of heart rate variability (HRV) were performed before, early (1-3 days, POST1) and late (7-14 days, POST2) after the ablation. From 24-h ambulatory Holter monitoring, RR intervals of a 2-h period during sleep (00.00-06.00 h) were analyzed. MSSD and pNN50 were increased along with a decrease in the frequency of ventricular arrhythmias at both POST1 and POST2 after successful ablation. In contrast, high frequency power (HF) was increased, and low frequency power (LF) and LF/HF were decreased only at POST2 in the 8 patients. In 4 patients in whom the initial ablation had been unsuccessful, the indices of HRV did not change significantly after the unsuccessful ablation, but after successful ablation they changed as in the other 4 patients. After successful catheter ablation of the RVOT tachycardia, sympathetic nervous activity was decreased and parasympathetic nervous activity was increased along with decrease in the frequency of ventricular arrhythmias. The presence of ventricular tachyarrhythmia could, therefore, elicit sympathetic predominance and consequently modify arrhythmogenesis.

Adult↗
PubMed1999

Electrophysiological mechanisms of conversion of typical to atypical atrioventricular nodal reentrant tachycardia occurring after radiofrequency catheter ablation of the slow pathway.

This report presents an adult patient with conversion of typical to atypical atrioventricular nodal reentrant tachycardia (AVNRT) after slow pathway ablation. Application of radiofrequency energy (3 times) in the posteroseptal region changed the pattern of the atrioventricular (AV) node conduction curve from discontinuous to continuous, but did not change the continuous retrograde conduction curve. After ablation of the slow pathway, atrial extrastimulation induced atypical AVNRT. During tachycardia, the earliest atrial activation site changed from the His bundle region to the coronary sinus ostium. One additional radiofrequency current applied 5 mm upward from the initial ablation site made atypical AVNRT noninducible. These findings suggest that the mechanism of atypical AVNRT after slow pathway ablation is antegrade fast pathway conduction along with retrograde conduction through another slow pathway connected with the ablated antegrade slow pathway at a distal site. The loss of concealed conduction over the antegrade slow pathway may play an important role in the initiation of atypical AVNRT after slow pathway ablation.

Catheter Ablation↗
PubMed1999

Reconstruction and limb salvage after resection for malignant bone tumour of the proximal humerus. A sling procedure using a free vascularised fibular graft.

We assessed the intermediate functional results of eight patients after wide resection of the proximal humerus for malignant bone tumour. We used a free vascularised fibular graft as a functional spacer and a sling procedure to preserve passive scapulohumeral movement. Scapulohumeral arthrodesis was not carried out. Five patients had osteosarcoma, two achondrosarcoma and one a malignant fibrous histiocytoma of the bone. The mean duration of follow-up was 70 months (median, 76) for the seven patients who were still alive at the time of the latest follow-up. One patient died from the disease 12 months after surgery. There were no local recurrences. The functional results were described and graded quantitatively according to the rating system of the Musculoskeletal Tumour Society. Our results were satisfactory with regard to pain, emotional acceptance and manual dexterity. Function and lifting ability were unsatisfactory in two patients. One patient had delayed union between host and graft, but this united after six months without further surgery. Radiographs of the shoulder showed absorption or collapse of the head of the fibula in four of the eight patients and a fracture in another. No functional problems related to absorption or fracture of the head of the fibula were noted. There was no infection or subluxation of the head. We conclude that this is a reasonably effective technique of limb salvage after resection of the proximal humerus.

Adolescent↗
PubMed1999

A study to determine if basic fibroblast growth factor (bFGF) reduces myocardial infarct size in acute coronary arterial occlusion.

We investigated the angiogenic and myocardial salvage effects of bFGF. Twelve beagles with ligated left anterior descending coronary arteries were divided into two groups: a FGF group administered bFGF intravenously, and a Control group, after CAG immediately post-ligation. One week post-ligation, CAG was repeated. The heart was sliced along the short axis. For each section, the fluorescein Na staining deficit area (DA) and ratio of DA to total area (DAR), TTC staining of the infarct area (IA) and ratio of IA to total area (IAR), and Masson trichrome staining of the fibrosed area (MA) and ratio of MA to total area (MAR), were calculated. The increase in the number of collateral vessels, seen on CAG from post-ligation to 1 week later, was significantly greater in the FGF group. No significant differences in IAR or MAR were seen between the groups. However, DAR and DA/IA were significantly less in the FGF group. In conclusion, bFGF had no effect on infarct size, but stimulated the growth of collateral vessels and improved coronary blood flow in IA.

Animals↗
PubMed1999

Successful radiofrequency catheter ablation of incessant ventricular tachycardia with a delta wave-like beginning of the QRS complex.

Ventricular tachycardia with a delta wave-like beginning of the QRS complex is considered to be refractory to endocardial catheter ablation because it originates from the epicardial region. A 45-year-old woman had incessant ventricular tachycardia with a delta wave-like beginning of the QRS complex which was resistant to several antiarrhythmic drugs. The origin of the arrhythmia was at the mitral annulus on the antero-lateral left ventricular wall. The earliest endocardial activation preceded the QRS complex by 18 msec. After 7 sec of endocardial radiofrequency application ventricular tachycardia was terminated. During a 2 year follow-up ventricular tachycardia did not recur and only small numbers of premature ventricular contractions (< 100/day) were noted. VT with delta wave-like QRS morphology which originates from the basal region of the ventricle may be treated successfully with radiofrequency catheter ablation using an endocardial approach.

Catheter Ablation↗
PubMed1999

Endothelial dysfunction by acute hyperhomocyst(e)inaemia: restoration by folic acid.

Recent evidence demonstrates that hyperhomocyst(e)inaemia is a novel risk factor for cardiovascular diseases. In patients with chronic hyperhomocyst(e)inaemia, endothelial function is impaired. However, whether hyperhomocyst(e)inaemia per se is a cause or an epiphenomenon of endothelial dysfunction remains unknown. In this study, we examined the effects of methionine-induced acute hyperhomocyst(e)inaemia on human endothelial function. In healthy volunteers we administered methionine (0.1 g/kg body weight, per os), a substrate of homocyst(e)ine, with or without folic acid (20 mg, per os) and examined flow-mediated vasodilatation of the brachial artery by high-resolution ultrasonography as a non-invasive measure of endothelial function. We also measured plasma levels of homocyst(e)ine before and 3, 8 and 24 h after methionine loading. Methionine administration increased plasma levels of homocyst(e)ine by four times the basal level at 8 h (P<0.0001, ANOVA). The plasma levels returned to baseline at 24 h. Flow-mediated vasodilatation was significantly decreased to half of the baseline value at 8 h and returned to baseline at 24 h (P<0.0001, ANOVA), whereas endothelium-independent vasodilatation by glyceryl trinitrate was not affected by the methionine loading. Co-administration of folic acid did not attenuate methionine-induced hyperhomocyst(e)inaemia but completely prevented endothelial dysfunction. Our results suggest that in humans a methionine-rich diet may acutely impair endothelial function, which can be prevented by folic acid supplementation.

Acute Disease↗
PubMed1999

[Suppression of experimental autoimmune uveoretinitis with a combination of cyclosporin and allopurinol].

PURPOSE: We assessed the suppressive effect of a combination of cyclosporin (an immunosuppressive agent) and allopurinol (a xanthine oxidase inhibitor and radical scavenger) on experimental autoimmune uveoretinitis (EAU) in Lewis rats, induced by interphotoreceptor retinoid-binding protein (IRBP). METHODS: After the immunization of Lewis rats with 30 micrograms of IRBP. We administrated cyclosporin and/or allopurinol to the IRBP-immunized Lewis rats. We observed the incidence and the severity of EAU. Histological, immunological, and biochemical examinations were performal 13 days after the immunization. The suppressive effect of these drugs in vitro on the production of free radicals derived from polymorphonuclear leukocytes. RESULTS: The incidence of EAU was suppressed by 50% at 13 days after immunization, and in terms of clinical and histological findings, inflammatory reaction was more inhibited by the combination of these drugs than by either cyclosporin or allopurinol alone. Lymphocyte proliferation assay against IRBP was significantly inhibited by the combination of drugs. No adverse systemic effects were identified. Cyclosporin and allopurinol inhibited radical production both separately and in combination. CONCLUSION: This suggests that suppression of EAU is based not only on inhibited cell-mediated immunity but also on inhibited production of free radicals derived from polymorphonuclear leukocytes.

Allopurinol↗
PubMed1999

[Clinical results and complications of refractive surgery].

PURPOSE: To evaluate the efficacy of photorefractive keratectomy (PRK) with a scanning type excimer laser MEL-60 (AESCLUP-MEDITEC, Co). SUBJECTS AND METHOD: We performed PRK on 102 eyes of 62 myopic patients whose refraction ranged from-3.00 to -12.50 D (mean, -6.47 D) and examined the clinical results of postoperative refraction and complications. RESULTS: At 12, 18, and 24 months after the operation, the mean refraction was -1.57 +/- 1.25D, -1.63 +/- 1.51 D and -1.73 +/- 1.47 D. At 12 months after the operation, 36 eyes (46.2%) were within +/- 0.5 D of intended correction, 61 eyes (78.3%) within +/- 1.0 D, and 76 eyes (97.4%) within +/- 2.0 D. Twenty-four months after the operation, 12 eyes (37.5%) were within +/- 0.5 D, 18 eyes (56.3%) within +/- 1.0 D and 29 eyes (90.6%) within +/- 2.0 D. The complications were as follows: keratitis filamentosa was observed in 10 eyes (10.5%), decrease of contrast sensitivity in 7 eyes (7.4%), subepithelial corneal haze in 4 eyes (1.2%), steroid-induced glaucoma was 2 eyes (2.1%), increase of astigmatism in 2 eyes (2.1%), decrease of best corrected visual acuity in 2 eyes (2.1%), and corneal ulcer in 1 eyes (1.1%). CONCLUSION: PRK with a scanning type excimer laser MEL-60 was effective to reduce refractive error in low and mild myopia, but there were some complications, so that a long, careful follow-up seems necessary.

Adult↗
PubMed1999

[A case of successful reoperation for aortic root pseudoaneurysm ruptured into right ventricle after modified Bentall operation].

The patient was a 51-year-old man with Marfan syndrome who had simultaneously undergone modified Bentall operation (Carrel patch method) and coronary artery bypass grafting. Prosthetic valve endocarditis (PVE) occurred 19 months after the operation. PVE had thereafter been treated by antibiotic therapy for 3 months, but echocardiography revealed prosthetic valve detachment and aortic root pseudoaneurysm ruptured into the right ventricle which appeared to have been caused by PVE. At reoperation there were no laboratory or intraoperative findings indicative of ongoing inflammation or infection. The composite graft, therefore, didn't require replacing, and it was possible to simply re-suture the composite graft and directly close the tear. The postoperative course has been uneventful with no further evidence of endocarditis.

Aneurysm, False↗
PubMed1999

[High inducibility of Epstein-Barr virus replication in B lymphocytes in Vogt-Koyanagi-Harada disease].

PURPOSE: The role of Epstein-Barr virus (EBV) reactivation in the pathogenesis of Vogt-Koyanagi-Harada (VKH) disease was examined. MATERIAL AND METHODS: Using B lymphocytes obtained from 8 patients with VKH disease and 10 patients with other types of uveitis, immortarized lymphoblast lines were established and infected with EBV. The degree of EBV activation in each lymphoblast line, in the presence and absence of various stimuli, was assessed by measuring the expression of 3 different antigens involved in replication by immunofluorescent staining and western blot analysis. Quantification of EBV DNA in cell culture supernatants was done by polymerase chain reaction. RESULT: Cell lines established from VKH patients expressed more viral antigens that those established from patients with other types of uveitis. There were greater amounts of EBV DNA in the VKH cell lines. CONCLUSION: B lymphocytes from VKH patients may be more susceptible to EBV activation, and the reactivation of EBV may be involved in the pathogenesis of VKH.

Adult↗
PubMed1999

A single cell analysis of TCR AV24AJ18+ DN T cells.

The T-cell receptor (TCR) BV gene of human TCR AV24+ double-negative (DN) T cells, a novel subset of natural killer (NK) T cells, was investigated by single-cell sorting and single-cell polymerase chain reaction (PCR) methods. Seven of eleven TCR AV24+ DN T-cell clones utilized TCR BV8, three BV9, and one BV6. Six of seven TCR AV24/BV8+ DN T-cell clones had identical TCR beta and alpha chains, indicating that they were the same clone. All three TCR AV24/BV9+ DN T-cell clones also demonstrated the same amino acids in the CDR3 region. These findings strongly suggest that the usage of TCR beta and alpha chains on TCR AV24+ DN T cells is extremely restricted, supporting the notion that these cells recognize highly limited T-cell epitopes on antigens. All TCR AV24+ clones expressed the NKR-P1A mRNA, and so were true NK T cells. IL-2 and IL-4 mRNAs were detected in all clones, suggesting that the majority of these cells were Th0-type T cells. Six clones overexpressed Fas-ligand (Fas-L) mRNA and Fas antigen was detected on all clones at the mRNA level. In conclusion, TCR AV24+ DN T cells might recognize restricted T-cell epitopes on antigens and function as Th0-type T cells, inducer cells to Th1- or Th2-type T cells (regulatory T cells), and as Fas-L-positive cytolytic T cells.

Amino Acid Sequence↗
PubMed1998

Cellular interaction of integrin alpha3beta1 with laminin 5 promotes gap junctional communication.

Wounding of skin activates epidermal cell migration over exposed dermal collagen and fibronectin and over laminin 5 secreted into the provisional basement membrane. Gap junctional intercellular communication (GJIC) has been proposed to integrate the individual motile cells into a synchronized colony. We found that outgrowths of human keratinocytes in wounds or epibole cultures display parallel changes in the expression of laminin 5, integrin alpha3beta1, E-cadherin, and the gap junctional protein connexin 43. Adhesion of keratinocytes on laminin 5, collagen, and fibronectin was found to differentially regulate GJIC. When keratinocytes were adhered on laminin 5, both structural (assembly of connexin 43 in gap junctions) and functional (dye transfer) assays showed a two- to threefold increase compared with collagen and five- to eightfold over fibronectin. Based on studies with immobilized integrin antibody and integrin-transfected Chinese hamster ovary cells, the interaction of integrin alpha3beta1 with laminin 5 was sufficient to promote GJIC. Mapping of intermediate steps in the pathway linking alpha3beta1-laminin 5 interactions to GJIC indicated that protein trafficking and Rho signaling were both required. We suggest that adhesion of epithelial cells to laminin 5 in the basement membrane via alpha3beta1 promotes GJIC that integrates individual cells into synchronized epiboles.

Animals↗