Search PubMed⌕ Search

Biomedical subjects

M Yamaguchi

Publications and source records attributed to M Yamaguchi.

At least 433 records · Page 24Linked to original sources
PubMed1999

Perfusion MR imaging with a superparamagnetic iron oxide using T2-weighted and susceptibility-sensitive echoplanar sequences: evaluation of tumor vascularity in hepatocellular carcinoma.

OBJECTIVE: The study purpose was to examine the usefulness of perfusion echoplanar MR imaging with a superparamagnetic iron oxide (SHU-555A) for evaluating the vascularity of hepatocellular carcinomas. SUBJECTS AND METHODS: Twenty-two patients with 32 hepatocellular carcinomas underwent perfusion imaging with bolus injection (0.7-1.1 ml) of SHU-555A. Echoplanar sequences included multishot spin-echo (17 patients) and single-shot gradient-echo (five patients) imaging. Image acquisition was repeated every 30 sec for 3 min with the multishot spin-echo sequence and every 2 sec for 100 sec with the single-shot gradient-echo sequence. Lesion signal intensity versus time curves were created for quantitative analysis. RESULTS: Transient decreases in tumor signal intensity (28.8% with multishot spin-echo and 63.3% with the single-shot gradient-echo) were seen in the perfusion phase. These decreases in signal intensity were statistically significantly (p < .01) different for each histologic type of hepatocellular carcinoma (poorly differentiated, 43.3%; well differentiated, 18.4%; and moderately differentiated, 24.8%). After the perfusion phase, the tumor signal intensities rapidly recovered. The multishot spin-echo sequence could detect some signal changes even in lesions smaller than 1 cm. CONCLUSION: Hepatocellular carcinoma vascularity can be evaluated with perfusion echoplanar imaging with SHU-555A. Because of its excellent temporal resolution, the single-shot gradient-echo echoplanar sequence detects the transient signal decrease in most lesions. The high image quality of the multishot spin-echo echoplanar sequence allows evaluation of the vascularity of even very small lesions.

Aged↗
PubMed1999

New methods for solving the Rescorla-Wagner model.

Two new methods for generating predictions from the Rescorla-Wagner model are presented. One is to solve the simultaneous equations of the model as differential equations, and the other is to solve them as difference equations, by using recent computer software. The model has been described in terms of simultaneous difference equations, and its predictions have traditionally been derived by performing an iterative computer simulation. But the limit can be taken, and the model can be considered in terms of simultaneous differential equations. Computer software, such as Mathematica and Maple, can solve simultaneous differential or difference equations. The author shows how to use Mathematica for some experimental paradigms, from simple acquisition to more complex cue competition paradigms, and also explains the rule for constructing input. The relative merits of these methods and of simulation are discussed.

Computer Simulation↗
PubMed1999

Enhancement of protein kinase activity in the cytosol of regenerating rat liver: regulatory role of endogenous regucalcin.

The effect of regucalcin, a Ca2+-binding protein, on protein kinase activity in the cytosol of regenerating rat liver was investigated. Protein phosphorylation was significantly increased in the liver cytosol obtained at 6, 24, and 48 h after a partial hepatectomy (about 65%) in comparison with that of sham-operated rats. This increase was significantly inhibited by the addition of trifluoperazine (2x10(-5) M), staurosporine (10(-7) M) or genistein (10(-5) M), which is an inhibitor of protein kinases, in the reaction mixture. The presence of regucalcin (0.1-0.5 microM) caused a significant decrease in protein phosphorylation in the cytosol from normal and regenerating rat livers. The effect of regucalcin (0.5 microM) was completely abolished by the addition of anti-regucalcin monoclonal antibody (50 ng/ml). The elevation of protein phosphorylation in regenerating rat liver was significantly enhanced by the presence of anti-regucalcin monoclonal antibody (50 ng/ml). The effect of regucalcin in decreasing protein phosphorylation in the cytosol of regenerating rat liver was not seen in the presence of the antibody. The present study demonstrates that protein kinase activity, is enhanced in the cytosol of regenerating rat liver, and that endogenous regucalcin has an inhibitory role in the enhancement of protein phosphorylation by various protein kinases.

Animals↗
PubMed1999

Inhibitory effect of regucalcin on Ca2+/calmodulin-dependent protein phosphatase activity in rat brain cytosol.

The effect of Ca2+-binding protein regucalcin on neutral phosphatase activity in rat brain cytosol was investigated. Phosphatase activity was assayed in a reaction mixture containing the cytosolic protein in the presence of phosphotyrosine, phosphoserine, and phosphothreonine. The presence of calcium chloride (10(-5) and 10(-4) M) in the enzyme reaction mixture caused a significant increase in phosphatase activity toward three phosphoaminoacids. The enzyme activity toward phosphoserine and phosphothreonine was significantly enhanced by the addition of calmodulin (1 or 5 microg/ml) in the presence of calcium (10(-5) M). Such an effect was not seen in the presence of phosphotyrosine. Trifluoperazine (2x10(-5) M), an antagonist of calmodulin, completely inhibited calcium (10(-5) M)-increased phosphatase activity toward phosphoserine and phosphothreonine, whereas it had no effect on the enzyme activity toward phosphotyrosine. Regucalcin (10(-9) M) significantly inhibited phosphatase activity toward three phosphoaminoacids without or with Ca2+ addition. The inhibitory effect of regucalcin (10(-10) and 10(-9) M) was also seen in the presence of Ca2+ (10(-5) M) and calmodulin (5 microg/ml). The presence of anti-regucalcin monoclonal antibody (20 or 50 ng/ml) in the enzyme reaction mixture caused a significant elevation of phosphatase activity toward three phosphoaminoacids; this effect was completely abolished by addition of regucalcin (10(-9) M). The present study suggests that the endogenous regucalcin has an inhibitory effect on Ca2+/calmodulin-dependent protein phosphatase activity in rat brain cytosol.

Animals↗
PubMed1999

Increase in bone protein components with healing rat fractures: enhancement by zinc treatment.

The alteration in bone components in the femoral-diaphyseal tissues with fracture healing was investigated. Rats were sacrificed 7 and 14 days after the femoral fracture. Protein content in the femoral-diaphyseal tissues was markedly elevated by fracture healing. Analysis with sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that many protein molecules were induced in the diaphyseal tissues with fracture healing. Moreover, when the femoral-diaphyseal tissues with fracture healing were cultured for 24 and 48 h in a serum-free medium, many proteins in the bone tissues were released into the medium. Also, the culture of the diaphyseal tissues with fracture healing caused a significant increase in bone alkaline phosphatase activity and deoxyribonucleic acid (DNA) content. Meanwhile, the presence of zinc acexamate (10-5 and 10-4 M), a stimulator of bone formation, in a culture medium induced a significant elevation of protein content and alkaline phosphatase activity in the diaphyseal tissues with fracture healing. Such an effect was completely abolished by the presence of cycloheximide (10-6 M), an inhibitor of protein synthesis. The present study suggests that fracture healing induces a newly synthesized bone protein component including stimulatory factor(s) for bone formation. Zinc supplementation may stimulate the healing of femoral fracture.

Alkaline Phosphatase↗
PubMed1999

Brain microsomal calcium accumulation in rats with increasing age: involvement of thapsigargin-sensitive Ca2+-ATPase.

The alteration in calcium content and Ca2+-ATPase activity in the brain microsomes of rats with increasing age was investigated. Brain microsomal calcium content was significantly increased in aged rats (50 weeks old) as compared with that of young rats (5 weeks old). Such an increase was not seen in the brain mitochondria of aged rats. Increasing age caused a significant elevation of Ca2+-ATPase activity in the brain microsomes. The microsomal Ca2+-ATPase activity of young rats was significantly decreased by the addition of thapsigargin (10-7-10-5 M), a specific inhibitor of microsomal Ca2+ pump enzyme (Ca2+-ATPase), in the enzyme reaction mixture. The inhibitory effect of thapsigargin (10-5 M) was also seen in the brain microsomes of aged rats. Moreover, the effect of calcium (5 and 10 microM) addition in elevating Ca2+-ATPase activity was not revealed in the microsomes of aged rats, whereas the metal could increase the enzyme activity in young rats, suggesting an involvement of activatory factor on the enzyme with increasing age. The present study demonstrates that ageing induces an increase in thapsigargin-sensitive Ca2+-ATPase activity and a corresponding elevation of calcium content in the brain microsomes. This finding suggests a cellular mechanism by which ageing causes calcium accumulation in brain.

Aging↗
PubMed1999

HUB1 is an autoantigen frequently eliciting humoral immune response in patients with adult T cell leukemia.

The immunological screening of a cDNA phage expression library prepared from an adult T cell leukemia (ATL) cell line, ST1, was performed with IgG class antibodies in the serum of an ATL patient by the SEREX method to analyze the repertoire of antigen molecules in ATL. Ten different cDNAs, 7 previously reported and 3 newly identified, were isolated. One of the identified cDNAs was homologous to the recently reported gene, HTLV-I U5RE binding protein 1 (HUB1) encoding a protein binding to a possible repressor element of the long terminal repeat of the human T lymphotropic virus type I (HTLV-I). The obtained cDNA was expressed as a fusion protein with glutathione S-transferase. HUB1 protein was prepared by subsequent treatment of the fusion protein with thrombin. Reactivity of IgG serum samples from ATL patients, asymptomatic HTLV-I carriers and normal donors against the purified protein was examined by Western blot analysis. Twenty-one out of 30 samples (70.0%) from ATL patients, 10/24 samples (41.7%) from HTLV-I carriers and 9/24 samples (37.5%) from healthy donors showed positive reactivity, indicating the autoantigenicity of HUB1. The development of ATL may be related to higher production of antibodies against HUB1.

Adult↗
PubMed1999

[Concomitant mitral valvuloplasty and fenestrated total cavopulmonary connection: a case report].

A seven-year-old boy with tricuspid atresia successfully underwent a fenestrated total cavopulmonary connection and mitral valvuloplasty. Preoperative cardiac catheterization showed a mean pulmonary artery pressure of 16 mmHg. Pulmonary arteriography showed poor development of the branches (PA index: 180). Echocardiography revealed mild to moderate mitral valve incompetence due to prolapse of anterior leaflet. Mitral valve was exposed through the trans-septal approach. The excess chorda length was tucked into a longitudinal split in the top of the posterior papillary muscle. Then wedge resection of the redundant segment of the anterior leaflet and bilateral annuloplasty were performed. Finally, a total extracardiac cavopulmonary anastomosis with a 6 mm fenestration was completed. Postoperative clinical course was uneventful, and he is doing well with no recurrence of mitral incompetence 1 year after the operation.

Child↗
PubMed1999

[Posterior mediastinal diffuse pleomorphic lymphoma].

A 26-year-old man presented with a 38 degrees C fever of undetermined origin in November 1977. His fever subsided in 1 month, but recurred concomitantly with dysphagia on December 10. For this reason, the patient visited our out patient clinic on December 15, and was hospitalized because a mass was found radiographically in the left lower lung field. A contrast-enhanced computed tomographic scan of the chest revealed an irregularly-shaped mass encircling the esophagus. Based on open-lung biopsy findings, the mass was diagnosed as non-Hodgkin's lymphoma, diffuse pleomorphic type. Neither swelling of the superficial lymph nodes nor hepatosplenomegaly was detected, and a bone-marrow aspiration specimen disclosed no atypical cells. Ga scintigraphy found accumulation only in this region, suggesting the posterior mediastinum as the origin of the lymphoma. Reports of non-Hodgkin's primary lymphoma in the posterior mediastinum are rare. Further, to our knowledge, there have been no reports at all on the diffuse pleomorphic type to date. This case was accordingly considered to be of highly informative value.

Adult↗
PubMed1999

Classic Blalock-Taussig shunt in neonates.

BACKGROUND: The choice of palliative procedure for neonates with congenital cyanotic heart defects remains controversial. Several reports have questioned whether the classic Blalock-Taussig shunt is adequate in neonates, because it shows a high rate of mortality and early shunt failure. The purpose of this study is to evaluate the early and late results of classic Blalock-Taussig shunt in neonates. METHODS: From December 1981 to December 1996, 31 neonates underwent a classic Blalock-Taussig shunt. Mean age at operation was 15.9 days (range, 2 to 28 days), and mean body weight was 3214 g (range, 2229 to 4468 g). The major diagnoses were pulmonary atresia with intact ventricular septum (6 patients) and with ventricular septal defect (4), univentricular heart (6), tricuspid atresia (5), tetralogy of Fallot (4), transposition of the great arteries (3), and double outlet right ventricle (3). RESULTS: There were no early deaths. There was one early shunt failure. The patient underwent a replacement of Blalock-Taussig shunt by vascular graft on the 1st postoperative day. Two patients with non-confluent central pulmonary artery underwent a contralateral modified Blalock-Taussig shunt on the 22nd and 42nd postoperative day, respectively. There were two late deaths before the definitive repair was performed. Twelve patients required an additional shunt operation. The mean interval between the initial and the second shunt procedure was 27.7 months (range, 6 to 67 months). Ten patients underwent definitive operation and the mean interval to that procedure was 55.5 months (range, 14 to 121 months). Shunt patency was 94.7+/-5.1% at 3 years. The freedom from cardiac event (cardiac deaths or repeat shunting procedure) was 80.5+/-7.1% at 1 year and 54.9+/-9.4% at 3 years. CONCLUSIONS: The classic Blalock-Taussig shunt has a low operative mortality and has provided excellent long-term palliation in the neonate. We conclude that a classic Blalock-Taussig shunt should be considered a reasonable choice in neonates requiring a palliative procedure for congenital cyanotic heart defects.

Heart Defects, Congenital↗
PubMed1999

gamma delta T-cell lymphoma: a clinicopathologic study of 6 cases including extrahepatosplenic type.

We report 6 cases of gamma delta T-cell lymphoma (GDTL) among 115 peripheral T-cell lymphomas over a 12-year period. All patients exhibited extranodal lymphomas, comprising 3 hepatosplenic, 1 cutaneous, 1 intestinal, and 1 thyroidal lymphoma. Despite therapies, all but 1 patient died of disease within 16 months of diagnosis. The cytologic features of lymphoma cells in 4 of 5 cases examined were very similar: coarsely reticulated nuclear chromatin, multiple small nucleoli, abundant faintly eosinophilic granular cytoplasm, and focal angiocentric proliferation. All 6 lymphomas showed Cd3+CD4-CD8-/+ phenotype. CD56 was positive in 3 cases, 1 of which was also CD16 positive. Perforin and T-cell intracellular antigen-1 were positive in all 5 cases examined. Southern blot analysis revealed clonal gene rearrangements of the T-cell receptor delta-chain gene in all 5 cases examined. Based on these findings, together with a review of the literature, GDTLs seem to have several common lineage-specific features, although clinical presentation and course of GDTL are heterogeneous.

Adolescent↗
PubMed1999

[Midterm results of bilateral enlargement of the aortic valve ring for valve replacement].

From 1989, 4 patients underwent bilateral enlargement of the aortic valve ring for valve replacement. Age at the operation ranged from 2 to 8 (mean 6) years; body weight ranged from 14.9 to 25.4 (mean 19.0) kg. This procedure enabled us to implant a prosthesis 3 to 4 sizes larger (19 to 23 mm) than that measured with the native aortic annulus (13 to 17 mm). There was no late death and no cardiac event over a mean follow-up period of 6.2 years. Pressure gradient across the prosthesis measured by echocardiography was 40 mmHg in 1 patient who underwent aortic valve replacement with the use of 19 mm St. Jude Medical valve at 2 years of age. There was no significant pressure gradient in other 3 patients. All patients showed normal left ventricular function. We conclude that bilateral enlargement of the aortic valve ring for valve replacement has provided good midterm results with no mortality and no cardiac event.

Aortic Valve↗
PubMed1999

[A surgical case of right coronary artery-right atrial fistula complicated with postoperative myocardial infarction].

We report a 10-year-old girl with a right coronary artery-right atrial fistula and aneurysm formation. The proximal orifice was closed from the inside of the aneurysm, and the distal orifice through the right atrium under cardiopulmonary bypass. On the 9th postoperative day, myocardial infarction developed due to thrombosis in the fistula stump and the dilated coronary artery. Thrombosis may have been induced by postoperative dehydration and inadequate anticoagulant therapy. It is important to minimize a fistula stump and to strictly administer postoperative anticoagulant therapy.

Arterio-Arterial Fistula↗
PubMed1999

[Cell cycle-dependent change of the adhesive character of CD34+ progenitor cells and their VLA-4 expression].

We identified the cell cycle status of CD34+ cells of steady-state bone marrow (BM) and peripheral blood (PB) obtained from healthy volunteers, and those of BM and apheresis PB samples collected from donors who had been administered granulocyte colony-stimulating factor (G-CSF). Regardless of whether G-CSF treatment was undergone, more than 10% of CD34+ cells in the BM was in the S + G2/M phase. In contrast, less than 2% of CD34+ cells in the PB was cycling. After co-culturing BM CD34+ cells with a monolayer of the stromal cell line MS-5 for 1 hour, some cells adhered to the stroma. The percentage of cells in the S + G2/M phase among these adherent cells was higher than that among the non-adherent cells. Flow cytometric analysis revealed that CD34+ cells in mobilized PB expressed less VLA-4 than those in BM and that in in vitro-cultured non-adherent cells exhibited a lower level of VLA-4 expression than adherent cells. In addition, CD34+ cells in the G0/G1 phase expressed lower levels of VLA-4 than those in the S + G2/M phase. These findings suggested that the reduced expression of adhesion molecules such as VLA-4 by the progenitor cells in the G0/G1 phase of the cell cycle result in the release of progenitor cells from the hematopoietic microenvironment to peripheral blood.

Antigens, CD34↗
PubMed1999

[Epidural abscess associated with epidural block in a patient with immunosuppressive disease].

A patient with myeloproliferative disorders and diabetes mellitus received epidural block twice for treatment of the low back and leg pain. The drugs used were 1% mepivacaine 4 ml for the first and 1% mepivacaine 6 ml and dexamethazone 4 mg for the second on the next day. Epidural abscess was noticed 2 days later when pus was aspirated through a block needle. MRI revealed the abscess localized at L5/S1. Intensive treatment including epidural drainage and antibiotics succeeded in healing the abscess. Use of epidural block for immunocompromized patients should be decided carefully.

Abscess↗