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Biomedical subjects

T Mitsui

Publications and source records attributed to T Mitsui.

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

Glutelin basic subunits have a mammalian mucin-type O-linked disaccharide side chain.

Characterization was done on the sugar chains of glutelin, a major storage protein in rice seeds. The basic subunits of glutelin were shown to be glycoproteins by staining with PAS and the lectins concanavalin A (Con A) and peanut agglutinin (PNA). The binding of PNA to the basic subunits was substantially reduced by treatment of the glutelin with NaIO4, NaOH, or O-glycanase. The sugar chains of the subunits, obtained by hydrazinolysis and O-glycanase, were pyridylaminated and subjected to 2-dimensional HPLC analysis using C(18) and acrylamide-derivatized columns. It was found that the Galbeta-1,3GalNAc disaccharide, which was previously identified as a core 1 structure of mucin-type sugar chains, is conjugated to the glutelin subunits. Furthermore, amino acid sequencing of an 11-kDa peptide of the subunits, recognized by both PNA and Con A, suggested that both N-linked and O-linked glycosylation occurs in the carboxy-terminal region of these subunits.

Amino Acid Sequence↗
PubMed1999

Role of the N-terminal region of the regulatory light chain in the dephosphorylation of myosin by myosin light chain phosphatase.

Myosin regulatory light chain (RLC) is phosphorylated at various sites at its N-terminal region, and heterotrimeric myosin light chain phosphatase (MLCP) has been assigned as a physiological phosphatase that dephosphorylates myosin in vivo. Specificity of MLCP toward the various phosphorylation sites of RLC was studied, as well as the role of the N-terminal region of RLC in the dephosphorylation of myosin by MLCP. MLCP dephosphorylated phosphoserine 19, phosphothreonine 18, and phosphothreonine 9 efficiently with almost identical rates, whereas it failed to dephosphorylate phosphorylated serine 1/serine 2. Deletion of the N-terminal seven amino acid residues of RLC markedly decreased the dephosphorylation rate of phosphoserine 19 of RLC incorporated in the myosin molecule, whereas this deletion did not significantly affect the dephosphorylation rate of isolated RLC. On the other hand, deletion of only four N-terminal amino acid residues showed no effect on dephosphorylation of phosphoserine 19 of incorporated RLC. The inhibition of dephosphorylation by deletion of the seven N-terminal residues was also found with the catalytic subunit of MLCP. Phosphorylation at serine 1/serine 2 and threonine 9 did not influence the dephosphorylation rate of serine 19 and threonine 18 by MLCP. These results suggest that the N-terminal region of RLC plays an important role in substrate recognition of MLCP.

Amino Acid Sequence↗
PubMed1999

Differential effects of human granulocyte colony-stimulating factor (hG-CSF) and thrombopoietin on megakaryopoiesis and platelet function in hG-CSF receptor-transgenic mice.

Granulocyte-colony stimulating factor (G-CSF) has been found to act on the neutrophilic lineage. We recently showed that human G-CSF (hG-CSF) has effects similar to early-acting cytokines such as interleukin-3 (IL-3) in the development of multipotential hematopoietic progenitors in transgenic (Tg) mice expressing receptors (R) for hG-CSF. In the present study, we examined the effects of hG-CSF on more mature hematopoietic cells committed to megakaryocytic lineage in these Tg mice. The administration of hG-CSF to the Tg mice increased the numbers of both platelets in peripheral blood and megakaryocytes in the spleen, indicating that hG-CSF stimulates megakaryopoiesis in the Tg mice in vivo. The stimulatory effect of hG-CSF was also supported by the results of studies in vitro. hG-CSF supported megakaryocyte colony formation in a dose-dependent fashion in clonal cultures of bone marrow cells derived from the Tg mice. Direct effects of hG-CSF on megakaryocytic progenitors in the Tg mice were confirmed by culture of single-cell sorted from bone marrow cells. hG-CSF showed a stronger effect on maturation of megakaryocytes in the Tg mice than that of IL-3 alone, but weaker than that of TPO alone. In addition, hG-CSF induced phosphorylation of STAT3 but not Jak2 or STAT5, while TPO induced phosphorylation of both. In contrast to TPO, hG-CSF did not enhance ADP-induced aggregation. Thus, hG-CSF has a wide variety of functions in megakaryopoiesis of hG-CSFR-Tg mice, as compared with other megakaryopoietic cytokines, but the activity of hG-CSF in megakaryocytes and platelets does not stand up to a comparison with that of TPO. Specific signals may be required for the full maturation and activation of platelets.

Animals↗
PubMed1999

QT prolongation and torsades de pointes induced by an antifungal agent, D0870, in conscious dogs.

D0870 ((R)-2-(2,4-difluoro-phenyl)-1-[3-[(E)-4-(2,2,3,3-tetrafluoropropoxy+ ++)-styryl]-1H-1,2,4-triazol-1-yl]-3-(1H-1,2,4-triazole-1-yl) propan-2-ol), a novel bis-triazole antifungal agent, induced sudden deaths at a high dose of 5 mg/kg/day in a 6-month toxicity study in dogs. In the present study, we intended to elucidate the cause of the sudden death in dogs. When used in a single dose, D0870 induced prolongation of QTc intervals in proportion to its plasma concentration, and the threshold plasma concentration of the drug causing 10% QTc prolongation was estimated to be 3.8 microg/ml. Then, we conducted a study to induce sudden death in dogs using loading (50 mg/kg) and maintenance (5 mg/kg/day) doses with long-term ambulatory electrocardiographic monitoring. Marked QTc prolongation (52-96%), ventricular premature contractions, and T-wave alternans were observed in all 10 animals treated with the drug, and seven out 10 animals died of ventricular fibrillation (VF) associated with torsades de pointes (TdP) when the dogs were treated with D0870 for 14 or 16 days. The TdPs were elicited in both tachycardia and bradycardia, and some of them in the former proceeded to VF. Consequently, we clarified that D0870-induced sudden death is primarily attributable to the development of TdP preceding VF and may be enhanced by sympathetic nervous tone produced by emotional or physical stress.

Animals↗
PubMed1999

Prenatal diagnosis of long QT syndrome using fetal magnetocardiography.

We describe the detection of congenital long QT syndrome in a fetus at 37 weeks' gestation using magnetocardiography (MCG). The prenatal diagnosis was confirmed by standard electrocardiography (ECG) performed after birth. This is the first case report of fetal long QT syndrome detected by MCG. Fetal MCG may be useful in the prenatal diagnosis of congenital cardiac disease with abnormal ECG findings.

Adult↗
PubMed1999

Vesicourethral function in diabetic patients: association of abnormal nerve conduction velocity with vesicourethral dysfunction.

This study was undertaken to examine diabetic vesicourethral dysfunction in association with nerve conduction velocity. Uroflowmetry, water cystometry, International Prostate Symptom Score (IPSS), and nerve conduction velocity were analyzed in 29 diabetic patients (21 men and eight women; a mean age, 58.0 years). Nerve conduction velocity was measured for sensory nerve conduction velocity (SCV) of the sural nerve and motor nerve conduction velocity (MCV) of the peroneal nerve. Normal voiding was defined as continuous flow at the normal flow rate and residual urine <50 mL. Results of uroflowmetry and cystometry were compared with those of nerve conduction velocity. Eleven of 29 patients (38%) had voiding dysfunction. A vesical denervation supersensitivity test was negative in all patients. The mean IPSS was not significant different between patients with or without voiding dysfunction. Incidence of bladder volume at first desire to void >300 mL and maximum bladder capacity >500 mL were significantly higher in patients with abnormal SCV than those with normal SCV (P < 0.03 and 0.001, respectively). Eleven of 16 patients with abnormal MCV showed voiding dysfunction, whereas all patients with normal MCV showed normal voiding (P < 0.001). These results suggest that lower urinary tract symptoms alone cannot predict diabetic vesicourethral dysfunction and that diabetic vesicourethral dysfunction is highly correlated with abnormal nerve conduction velocity. Neurourol. Urodynam. 18:639-645, 1999.

Adolescent↗
PubMed1999

Sensitivity of foetal magnetocardiograms versus gestation week.

Foetal magnetocardiograms (FMCGs) were measured using a nine-channel SQUID system equipped with first-order gradiometers (60 mm baseline, 20 mm diameter). The system was installed in a magnetically shielded room in a hospital. The white noise level was less than 10 fT/square root of Hz, and FMCGs above 1 pT were detected. These results and the depth to the foetal heart were used to estimate the current dipole. The relationship between the current dipole (Q) and the gestation week (G) was calculated and the average performance was determined as Q = 18G - 295. By using the estimated foetal current dipole, the measurement limit (average value) between depth and gestation weeks was determined. When the depth from the pickup coil to the foetal heart is 50, 60, 70 and 80 mm, the first detectable gestation weeks of FMCGs above 1 pT measured by a first-order gradiometer with 60 mm baseline were determined at 21, 23, 26, and 30 weeks respectively, and the detectable gestation weeks in the case of a 30 mm baseline were determined at 22, 26, 30 and 36 weeks respectively.

Electrocardiography↗
PubMed1999

Atrial fibrillation after coronary artery bypass grafting. An increase in high-frequency atrial activity in patients with right coronary artery revascularization.

The increase in atrial high-frequency activity has been reported as a marker of the risk of paroxysmal atrial fibrillation. The presence of proximal right coronary artery disease is a predictor of atrial fibrillation after bypass surgery, however, the potential mechanism remains controversial. In this study, high-frequency atrial activity to clarify the electrophysiologic background for the predisposition to have proximal right coronary artery disease leading to atrial fibrillation after coronary revascularization was investigated. Before and soon after coronary revascularization, frequency analyses were performed on the 100 ms segment at the end of signal-averaged P waves in 22 patients with right coronary artery disease as opposed to the 23 patients without disease. Under the spectrum curve, area ratio (AR50) and magnitude ratios (MR) were calculated as follows; AR50 = (area 20-50 Hz/0-20 Hz) x 100, and MR = (magnitude at 20, 30, 40 and 50 Hz, respectively/maximal magnitude) x 100. In patients with proximal right coronary artery disease, high-frequency atrial components increased significantly in the 20 to 50 Hz range after coronary revascularization, and the incidence of postoperative atrial fibrillation was higher than in those without disease. In patients without right coronary artery disease, the frequency distribution of P waves was unchanged. Postoperatively, the two groups showed the same atrial frequency distribution. This data suggests that the increase in high-frequency atrial activity after right coronary artery revascularization might be associated with the pathogenesis of postoperative atrial fibrillation.

Adult↗
PubMed1999

Mitral regurgitation after pericardiectomy for constrictive pericarditis.

We report a case of constrictive pericarditis in which trace mitral valve regurgitation was detected preoperatively and temporarily worsened after a pericardiectomy was performed. The early postoperative data suggested that the increased mobility of the lateral wall, in conjunction with an increase in the left ventricular volume, might be one of the causes of the perioperative mitral valve dysfunction. The mitral valve function returned to the preoperative baseline thirteen months after the pericardiectomy.

Adult↗
PubMed1999

Aortic dissection in an elderly patient with atrial septal defect.

We report a case of acute aortic dissection that occurred in the late course of surgically untreated atrial septal defect. A 60-year-old man with acute aortic dissection and atrial septal defect was operated on successfully, and we discuss the causal relationship between these two unusual conditions.

Aortic Dissection↗
PubMed1999

Venous function and delayed leg swelling following saphenectomy in coronary artery bypass grafting.

Some patients are troubled by leg swelling following saphenectomy long after CABG. Postsaphenectomy venous function in the leg has not, however, been well clarified. To determine whether venous dysfunction caused postsaphenectomy swelling, we measured the maximum venous outflow and time constant (tau) in the leg by venous occlusion strain-gauge plethysmography in 45 patients; a venous Doppler test was also conducted in 33 of the 45 at a mean 57.6 +/- 21.3 months after CABG. The saphenous vein was harvested unilaterally from the lower leg or from both the thigh and lower leg in all patients. Edema was seen in 4 patients (8.9%) and 8 reported leg swelling after saphenous vein harvest (17.8%). Legs were classified into three groups: group 1 consisted of 12 with edema or reports of swelling ipsilateral to the saphenous vein harvest site, group 2 consisted of 33 ipsilateral to the saphenous vein harvest without edema, and group 3 consisted of the 45 nonoperated-on, contralateral legs of the same patients as controls. No significant differences were seen in maximum venous outflow, tau, or the incidence of deep vein reflux among groups. No significant relationship was found between venous function and leg swelling occurring delayed after saphenectomy.

Aged↗
PubMed1999

Aortic dissection complicating cardiac surgery in a patient with calcified ascending aorta.

Aortic dissection is a rare but devastating complication of cardiac surgery. Adequate and early diagnosis of intraoperative aortic dissection and quick therapeutic decision making are the keys for saving patients in such cases. We describe the case of a 68-year-old man referred for CABG and mitral valve replacement with severe calcification of the ascending aorta. Intra-operative transesophageal echocardiography was useful for diagnosis of intra-operative aortic dissection and malperfusion of the true lumen. Immediate switching of the arterial perfusion site established flow in the true lumen with prompt subsidence of the expanded false lumen. CABG, mitral valve replacement and graft replacement of the ascending aorta could be simultaneously performed in this patient.

Aged↗
PubMed1999

Implantation of a mechanical valve within a flexible mitral annular ring.

The implantation of a mechanical valve within the orifice of a mitral Duran flexible annular ring is presented. Exact orifice matches of the former ring and the new mechanical valve prosthesis (Advancing The Standard [ATS]; ATS Medical Inc, Minneapolis, MN) can be obtained using a standard mitral type ATS valve, when the size of the former Duran ring is larger than 31 mm. If ring dehiscence is not noted at reoperation after mitral valve repair, this procedure can be simply performed in patients with late mitral valve dysfunction requiring valve replacement.

Heart Valve Prosthesis Implantation↗
PubMed1999

Noninvasive visualization of multiple simultaneously activated regions on torso magnetocardiographic maps during ventricular depolarization.

The time course and instantaneous distribution of the electrophysiologic processes of the human heart were analyzed by using a multichannel superconducting quantum interference device (SQUID) system, enabling the tangential components of the cardiac magnetic fields to be measured. By visualizing the changing magnetic field pattern in a two-dimensional presentation of the anterior and posterior torso during depolarization, the existence of more than one simultaneously activated region and the effective intracardiac current distribution were estimated without using a mathematical algorithm. The mid-to-late QRS complex when the myocardium has widespread depolarizing regions was analyzed using this technique. Even in an early stage of the QRS, two discrete active regions were observed in the magnetic field maps, in all nine subjects (adults with normal hearts). Furthermore, differences in the current distribution between the front and back active region were observed.

Adult↗
PubMed1999

Low-dose protamine based on heparin-protamine titration method reduces platelet dysfunction after cardiopulmonary bypass.

OBJECTIVE: The heparin-protamine titration method that uses the Hepcon hemostasis management system (Medtronic HemoTec Inc, Englewood, Colo) reduced blood loss in cardiac surgery in previous reports, but the mechanism is not fully understood. This study tests the hypothesis that reduced protamine administration preserves platelet function in human cardiac surgery. METHODS: Platelet count, alpha-granule secretion, and aggregation to thrombin before and after cardiopulmonary bypass in human beings were evaluated. In the control group (n = 14), a fixed dose of protamine (3 mg/kg) was administered. In the titration group (n = 20), protamine doses were based on the heparin concentration measured by the Hepcon system. RESULTS: Heparin concentrations before protamine administration were higher in the titration group (P =.0012), but protamine doses of patients in the titration group were markedly lower than those of the control group (P <.0001). During protamine infusion at a rate of 0.3 mg. kg(-1). min(-1), the percentage of granule membrane protein-140-positive platelets significantly increased in the control group compared with the titration group (18.8% +/- 8.6% vs 13.0% +/- 5.3%, P =.0188). After protamine administration, aggregation of washed platelets to thrombin recovered almost to the preoperative level in the titration group; however, it remained lower in the control group (20% +/- 20% vs 55% +/- 18%, P =.0009). CONCLUSION: Low-dose administration of protamine, based on a heparin-protamine titration method, restores not only the blood coagulation but also the platelet responses to thrombin and attenuates platelet alpha-granule secretion during heparin neutralization. Overdose of protamine activates platelets and may predispose patients to excessive bleeding after cardiac surgery.

Blood Loss, Surgical↗