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Biomedical subjects

J Chiba

Publications and source records attributed to J Chiba.

At least 73 records · Page 4Linked to original sources
PubMed1997

Visualisation of exercise-induced ischaemia of the right ventricle by thallium-201 single photon emission computed tomography.

OBJECTIVE: Exercise thallium-201 (201T1) single photon emission computed tomography (SPECT) has been used to detect potential ischaemia in the left ventricular myocardium but not in the right ventricle. The purpose of this study was to establish the clinical usefulness of a right ventricular polar map of 201T1 SPECT for visualisation of exercise-induced right ventricular ischaemia. METHODS: Myocardial 201T1 SPECT was obtained immediately after treadmill exercise in 97 patients with suspected coronary artery disease. A region of interest was placed over the right ventricle (RV) on post-stress transaxial images. Short axis images of this region were generated and reconstructed as a bull's eye polar map. Normal ranges of RV 201T1 uptake were determined in 12 patients with normal coronary arteries. Scintigraphic criteria for identifying RV perfusion abnormality were derived from 25 patients with right coronary artery (RCA) stenosis greater than 75%. These criteria were applied to 60 consecutive patients with suspected coronary artery disease. RESULTS: Perfusion defects in the RV were larger in patients with proximal RCA stenosis than in those with distal RCA stenosis (mean (SD) 28 (16)% v 6 (5)%, P < 0.001). The sensitivity and specificity of the RV polar map for the detection of proximal RCA stenosis were 67% (8/12) and 98% (47/48), respectively. RV perfusion defects became undetectable in 9 patients who had successful percutaneous transluminal coronary angioplasty to a proximal RCA lesion. CONCLUSIONS: A right ventricular polar map display was useful for visualising exercise-induced right ventricular ischaemia.

Adult↗
PubMed1996

A novel neutralization epitope on the 'thumb' subdomain of human immunodeficiency virus type 1 reverse transcriptase revealed by a monoclonal antibody.

We have prepared a MAb, 7C4, which inhibits the RNA-dependent DNA polymerase activity of human immunodeficiency virus type 1 (HIV- 1) reverse transcriptase (RT); this MAb has allowed identification of a previously unknown neutralizing epitope of RT. Analysis of the epitope and of the mechanism of polymerase inhibition revealed that 7C4 acts by interfering with the interaction between RT and the template-primer. 7C4 recognizes a discontinuous epitope on the two alpha-helices, alphaH and alpha(I), that make up the 'thumb' subdomain of RT. The existing crystallographic model of HIV-1 RT suggests that the 'thumb' subdomain, together with the 'fingers' and 'palm', form a nucleic-acid-binding cleft in the 66 kDa subunit of RT and that alphaH is in contact with the primer strand of the template-primer. The extent of inhibition of enzyme activity produced by 7C4 correlates with the reported primer-length-dependency of template-primer binding to RT. Inhibition by 7C4 was competitive with respect to the template-primer and mixed with respect to the substrate. Binding of 7C4 to RT was prevented by preincubation of the enzyme with high concentrations of template-primer but not with substrate. Thus, the 7C4 epitope apparently exists on part of the template-primer binding site of the alphaH and alpha(I) regions of the 'thumb' subdomain. This neutralization epitope is a logical target for the development of new types of HIV-1 RT inhibitors.

Animals↗
PubMed1995

A new strategy of gene trapping in ES cells using 3'RACE.

"Gene trapping" in embryonic stem (ES) cells is a novel approach to identify a series of genes in mammals concomitant with the production of the corresponding mutant mice. However, this approach is currently unable to identify genes that are not expressed in ES cells. Here we describe a strategy to identify gene trapping clones which is not based on expression of a reporter gene. It uses the neor gene which lacks a polyadenylation signal and has a splice donor signal. Expression of the neor gene as fusion transcripts with the 3' end containing the polyadenylation signal of tagged genes allows the identification of these clones by 3' rapid amplification of the cDNA end in undifferentiated ES cells, even if the genes are not expressed in ES cells. Amplification was observed in about 25% of G418-resistant clones. Sequence analyses suggested the amplifications represent gene trapping events. The feasibility of this approach was further assessed by analysing one clone, PAT-12, in detail.

Amino Acid Sequence↗
PubMed1995

Citrate synthase purified from Tetrahymena mitochondria is identical with Tetrahymena 14-nm filament protein.

A 14-nm filament protein (designated as 49K protein) was purified from a ciliated protozoan, Tetrahymena, using the polymerization and depolymerization procedure. Previous studies in our laboratory showed that its primary structure shared a high sequence identity with citrate synthases known so far and that the 49K protein possessed citrate synthase activity. To ascertain whether or not Tetrahymena's mitochondrial citrate synthase is identical to the 49K protein, citrate synthase was purified from Tetrahymena mitochondria using ammonium sulfate fractionation, Butyl-Toyopearl and SP-Toyopearl column chromatographies, based on monitoring of the enzymatic activity. The molecular weight of the purified citrate synthase was estimated to be 49 kDa, as was that of the 49K protein and the enzyme cross-reacted with an anti-49K protein antiserum. The purified citrate synthase showed much the same optimum pH, optimum KCl concentration, effects of substrate concentrations (acetyl-CoA and oxaloacetate), and inhibitory effect by ATP as those of purified 49K protein. Furthermore, an anti-49K protein monoclonal antibody strongly suppressed the enzymatic activity of the purified citrate synthase. Thus, we suggest that mitochondrial citrate synthase and the 49K protein are identical and that the 49K protein has dual functions in the cytoskeleton in cytoplasm and as a TCA cycle enzyme, citrate synthase, in mitochondria.

Animals↗
PubMed1995

Nuclear localization of the truncated hepatitis C virus core protein with its hydrophobic C terminus deleted.

The core protein of hepatitis C virus (HCV) is considered to be cleaved from the N terminus of the large precursor polyprotein by cellular signalase. The HCV cDNA encoding the core protein was expressed (i) in monkey COS cells by a plasmid expression vector driven by the SR alpha promoter, and (ii) in insect cells by a recombinant baculovirus. The expressed product had an M(r) of 22,000 and was located in the cytoplasm. When the C-terminal hydrophobic domains were deleted, however, the truncated core proteins were translocated into the nucleus. The truncated core proteins were located in the nucleus even when they were expressed as a fusion protein with E. coli beta-galactosidase, which is essentially localized in the cytoplasm. Plasmids containing HCV cDNAs with a deletion in one of the regions encoding clusters of basic amino acids were expressed in COS cells and the localization of the core protein was examined. The residues PRRGPR were suggested to play an important role in nuclear localization. HCV is an RNA virus and its life cycle was originally considered to be confined to the cytoplasm; the present study, however, suggests that the HCV core protein can translocate into the nucleus under certain circumstances.

Amino Acid Sequence↗
PubMed1995

Isolation and characterization of wear particles generated in patients who have had failure of a hip arthroplasty without cement.

Wear particles from thirty-five membranes obtained during revision hip-replacement operations were studied after digestion of the soft tissue with papain. The particles were isolated and were characterized with use of light and scanning electron microscopic techniques, x-ray microanalysis, and an automated particle analyzer. The mean size of the polyethylene particles was 0.5 micrometer, and the metal particles were a mean of 0.7 micrometer, as determined with scanning electron microscopy. The automated particle analyzer revealed a mean particle diameter of 0.63 micrometer (more than 90 per cent of all particles were less than 0.95 micrometer) and a mean of 1.7 billion particles per gram of tissue, compared with only 143 million per gram of tissue for the control samples. X-ray microanalysis revealed metal debris in sixteen (46 per cent) of the thirty-five membranes after digestion. Thirteen (50 per cent) of the twenty-six membranes surrounding a titanium-alloy stem contained metal particles, compared with three of the nine membranes surrounding a chromium-cobalt stem. Metal debris was present in only one of the twelve membranes surrounding a titanium-alloy stem without a porous coating, compared with twelve of the fourteen membranes surrounding a titanium-alloy stem with a porous coating. This tenfold difference in prevalence was significant (p < 0.005). On the average, the total number of particles (expressed in millions per gram of tissue) associated with the bipolar acetabular components was twice that associated with the fixed acetabular components. In addition, there was a trend toward a larger mean size of the polyethylene particles in association with the bipolar cups. Our data indicate that particulate prosthetic debris in the tissues around failed femoral components that have been inserted without cement constitutes a class of particles that are predominantly less than one micrometer in size and are present in amounts of more than one billion particles per gram of tissue. Routine histological methods did not detect this class of wear debris and led to a gross underestimation of the amount of debris in these membranes.

Adult↗
PubMed1995

[A case of p-ANCA positive necrotizing vasculitis associated with Graves' disease].

A 22-year-old female who had been suffering from Graves' disease developed p-ANCA positive necrotizing vasculitis. Her Graves' disease has been treated with propylthiouracil (PTI) for 6 years, which failed to improve serum TSH. She developed transient and recurrent polyarthralgia 4 years before. Because of microscopic hematuria and polyarthralgia, She visited our hospital last year. She had hypergammaglobulinemia and microhematuria at that time. But no autoantibody was noted except anti-microsomal antibody at that time. Skin biopsy from her finger subdermal nodule revealed necrotizing vasculitis of small vessels. Serum p-ANCA was positive. She was admitted under the diagnosis of p-ANCA positive necrotizing vasculitis. Renal biopsy revealed mesangium proliferative glomerulonephritis. Since she developed telescoped sediments after admission, predonisolone (PSL) 50 mg daily was started. Clinical and laboratory findings improved quite well. PSL was gradually tapered after 6 weeks. She is being maintained in good condition on tapering doses of both PSL and PTI. The coincidence of Graves' disease and vasculitis is rare. This case may provide some important immunological insights into the study of pathogenesis of necrotizing vasculitis and Graves' disease.

Adult↗
PubMed1994

Noninvasive identification of left main and three-vessel coronary artery disease by thallium-201 single photon emission computed tomography during adenosine infusion.

Advanced coronary artery disease, defined as left main or three-vessel coronary disease, was identifiable noninvasively by means of adenosine Tl-201 single photon emission tomography. Among 75 consecutive patients with angiographically documented coronary artery disease, there were 11 patients with the presence (group 1) and 64 patients with the absence (group 2) of advanced coronary artery disease. The lung-to-heart ratio (L/H ratio) of Tl-201 uptake was calculated as the fraction of average Tl-201 counts per pixel in the lung divided by those in the myocardium. The left ventricular dilation ratio (LVDR) was determined as a ratio of left ventricular cavity size in the early image to that in the delayed image. The patients in group 1 had more defects (2.3 +/- 0.6 seg. vs. 0.9 +/- 0.7 seg., p < 0.001), a higher L/H ratio (35 +/- 4% vs. 28 +/- 5%, p < 0.001) and a higher LVDR (1.13 +/- 0.04 vs. 1.06 +/- 0.04, p < 0.001) than those in group 2. The diagnostic accuracy of the identification of advanced coronary artery disease was 89% by perfusion defects, 68% by L/H ratio and 81% by LVDR. Stepwise discriminant analysis revealed that LVDR (F = 36.2, p < 0.0001) and perfusion defects (F = 8.9, p < 0.004) were the significant and independent discriminators of advanced coronary disease. Identification of patients with left main or three-vessel coronary disease was enhanced by additional analysis of cavity dilation of the left ventricle and increased Tl-201 activity in the lung.

Adenosine↗
PubMed1994

Adenosine-induced heterogeneous perfusion accompanies myocardial ischemia in the presence of advanced coronary artery disease.

The aim of the present study was to elucidate the characteristics of patients in whom transient myocardial ischemia was evoked during adenosine infusion. Thallium-201 (Tl-201) myocardial imaging and two-dimensional echocardiography during adenosine infusion were performed simultaneously in 61 consecutive patients enrolled for the diagnosis of coronary artery disease. Transient reduction of systolic wall motion after adenosine infusion was considered evidence of myocardial ischemia. Tl-201 redistribution was noted in 38 patients, and 23 of them showed a wall motion abnormality during adenosine infusion. Stepwise discriminant analysis was applied to eight variables that showed significant differences by the univariate analysis between patients with the presence and the absence of adenosine-induced wall motion abnormality: myocardial infarction, anginal pain, ST depression, collateral vessels, Tl-201 redistribution, number of diseased vessels of > or = 75% or 90% stenosis and number of segments with Tl-201 redistribution. The number of diseased vessels with > or = 75% stenosis (F = 43.5, p < 0.0001), ST depression (F = 16.0, p < 0.0002), collateral vessels (F = 11.7, p < 0.001) and Tl-201 redistribution (F = 5.6, p < 0.02) were the statistically significant discriminators relating to adenosine-induced wall motion abnormality. Adenosine-induced myocardial ischemia was related to the number of coronary stenoses, reflecting the presence of severe coronary artery disease, and well-developed collaterals that might be integral factors in a coronary steal phenomenon.

Adenosine↗
PubMed1994

Organ distribution of thallium-201 during intravenous adenosine infusion: comparison with exercise.

Thallium-201 (Tl-201) distribution during adenosine infusion was assessed quantitatively and compared with that of exercise imaging. Adenosine and exercise Tl-201 single-photon emission computed tomography (SPECT) were performed in 40 patients with suspected coronary artery disease. In the whole-body images (n = 5) and the unprocessed anterior projection images acquired as part of the initial imaging (n = 35), Tl-201 counts in the myocardium were normalized for the injected dose. Total heart counts were higher during adenosine infusion than during exercise (190 +/- 43 counts/MBq vs 145 +/- 31 counts/MBq, p < 0.01). A heart-to-lung count ratio between adenosine infusion and exercise was not different. A heart-to-liver count ratio was lower during adenosine infusion than during exercise (1.3 +/- 0.3 vs 2.3 +/- 0.5, p < 0.01). Regional Tl-201 uptakes at the inferior wall of the left ventricle during adenosine infusion were closely correlated with those uptakes during exercise (r = 0.94, p < 0.01, slope = 0.96). The sensitivity, specificity, and accuracy of adenosine Tl-201 SPECT for the detection of right coronary artery stenosis were comparable with those of exercise imaging. These results indicated that higher Tl-201 uptake in the liver during adenosine than during exercise did not interfere with the interpretation of myocardial images. Tl-201 counts in the myocardium that were larger during adenosine infusion than during exercise reflected a larger increase in coronary blood flow and thus resulted in better image quality.

Adenosine↗
PubMed1994

A novel nonreceptor tyrosine kinase, Srm: cloning and targeted disruption.

We have isolated a novel nonreceptor tyrosine kinase, Srm, that maps to the distal end of chromosome 2. It has SH2, SH2', and SH3 domains and a tyrosine residue for autophosphorylation in the kinase domain but lacks an N-terminal glycine for myristylation and a C-terminal tyrosine which, when phosphorylated, suppresses kinase activity. These are structural features of the recently identified Tec family of nonreceptor tyrosine kinases. The Srm N-terminal unique domain, however, lacks the structural characteristics of the Tec family kinases, and the sequence similarity is highest to Src in the SH region. The expression of two transcripts is rather ubiquitous and changes according to tissue and developmental stage. Mutant mice were generated by gene targeting in embryonic stem cells but displayed no apparent phenotype as in mutant mice expressing Src family kinases. These results suggest that Srm constitutes a new family of nonreceptor tyrosine kinases that may be redundant in function.

Amino Acid Sequence↗
PubMed1994

Alterations in vascular pattern of the developing palate in normal and spontaneous cleft palate mouse embryos.

The alterations in the vascularization of the developing palate were studied through the use of resin cast images of vascular networks in normal and spontaneous cleft lip and palate (CL/Fr) mouse embryos (crown rump [CR] Length 9-18 mm, body wt. 0.11-0.65 g). A more dense vascular plexus was observed in the oral side than in the nasal side before the reorientation of the palatal shelves. Prominent terminal dilatations of the vascular plexus were observed in the extreme medial edge of the elevating palatal shelves which may exert significant force for palatal shelf elevation. The vascular plexus showed a lateral extension. Many small spherical masses of resin were observed in the medial edge of the palatal shelves at the time of medial extension and during fusion, indicating some changes occurring in the capillary wall leading to the resin leakage. In the spontaneous cleft group, a similar vascular pattern was observed, but the greater palatine artery showed discontinuity in the premaxillary region at an early stage. At the same time, terminal dilatations were delayed and frequently absent in the contralateral shelf. After the reorientation of the palatal shelves, the vascular plexus formed an irregular lattice pattern. Dilated vasculature was apparent in the anterior nasopalatine region, indicating the persistence of a more primitive vascular structure in the spontaneous cleft embryos. However, the area where capillary dilatation occurred was different between unilateral and bilateral cleft embryos. In conclusion, blood vessels in the palatal shelves are underdeveloped and remained immature in cleft lip and palate embryos and showed different patterns in the anterior nasopalatine region between unilateral and bilateral cleft embryos. These variant vascular patterns may be due to the inadequate blood supply to the nasopalatine region from the early embryonic stages possibly resulting from the discontinuity of the greater palatine artery.

Animals↗
PubMed1994

In vivo and in vitro analysis of membranes from hip prostheses inserted without cement.

Biochemical, histological, and immunohistochemical studies of interface membranes surrounding failed hip prostheses that had been inserted without cement were done to examine specific factors involved in the development of aseptic loosening. Membranes from sixty-four femoral components were obtained from sixty-three patients during revision arthroplasty. Fifty-seven membranes were from implants that articulated with polyethylene (thirty-two were made of cobalt-chromium alloy and twenty-five, titanium alloy), and seven were from unipolar endoprostheses made of cobalt-chromium alloy that did not articulate with polyethylene. The membranes from implants with a polyethylene articulation produced significantly higher levels of collagenase and interleukin-1 (p < 0.05). However, there was no significant difference in the levels of prostaglandin E2 between the three groups. Furthermore, membranes from implants with roentgenographic evidence of focal osteolysis (endosteal erosion) released significantly higher levels of interleukin-1 (p < 0.05) than did membranes from implants without focal osteolysis. Although the membranes from the titanium-alloy implants tended to contain more metal debris than those from the cobalt-chromium-alloy implants, the biochemical findings were not significantly different between these two groups. Many macrophages that were filled with polyethylene and metal debris were present in the membranes from both groups with a polyethylene articulation. Few T lymphocytes or B lymphocytes were identified in the three groups.

Adult↗
PubMed1994

The characterization of cytokines in the interface tissue obtained from failed cementless total hip arthroplasty with and without femoral osteolysis.

The histologic, biochemical, and immunohistologic characteristics of the interface membranes surrounding the femoral component of failed cementless total hip arthroplasty (THA) in patients with (Group I) and without (Group II) radiographic evidence of focal endosteal erosion (osteolysis) were studied. Group I membranes had more macrophages and small particles of polyethylene debris in the membrane, but both groups had similar amounts of metal particles. A greater activity level of interleukin-1 (IL-1), tumor necrosis factor (TNF), and interleukin-6 (IL-6) was seen in the culture supernatant of the membranes from Group I than in that of Group II. Group I membranes also had more cells (macrophages, fibroblasts, and endothelial cells) that stained positively with anti-IL-6 antibody. These results suggest that IL-6, IL-1, and TNF play a role in the focal femoral osteolysis observed in patients with failed cementless hip prostheses.

Aged↗