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Biomedical subjects

A Kojima

Publications and source records attributed to A Kojima.

At least 127 records · Page 7Linked to original sources
PubMed1997

[Experimental study on the location of energy windows for scatter correction by the TEW method in 201Tl imaging].

To investigate validity of scatter correction by the TEW method in 201Tl imaging, we performed an experimental study using the gamma camera with the capability to perform the TEW method and a plate source with a defect. Images were acquired with the triple energy window which is recommended by the gamma camera manufacturer. The result of the energy spectrum showed that backscattered photons were included within the lower sub-energy window and main energy window, and the spectral shapes in the upper half region of the photopeak (70 keV) were not changed greatly by the source shape and the thickness of scattering materials. The scatter fraction calculated using energy spectra and, visual observation and the contrast values measured at the defect using planar images also showed that substantial primary photons were included in the upper sub-energy window. In TEW method (for scatter correction), two sub-energy windows are expected to be defined on the part of energy region in which total counts mainly consist of scattered photons. Therefore, it is necessary to investigate the use of the upper sub-energy window on scatter correction by the TEW method in 201Tl imaging.

Phantoms, Imaging↗
PubMed1996

p53 gene alterations and p53 protein in oral epithelial dysplasia and squamous cell carcinoma.

To examine the expression of p53 protein and gene alterations in oral epithelial lesions including epithelial dysplasias and primary squamous cell carcinomas, immunohistochemical and temperature gradient gel electrophoresis (TGGE) methods were applied to formalin-fixed and paraffin-embedded tissues. Morphologically normal mucosal epithelium stained negatively for p53 protein. Three out of 11 (27.3 per cent) epithelial dysplasias and 19 out of 57 (33.3 per cent) primary squamous cell carcinomas stained positively for p53 protein. Although more than half of the cases were positive for p53 protein in stage I, the positive cancer cases were found at other stages with variable frequency. Immunoreactive products were localized in the nucleus, especially in the basal and suprabasal layers. The analysis by TGGE revealed gene alterations in exons 5-8 in 3 out of 3 epithelial dysplasias and 17 out of 19 (89.5 per cent) primary squamous cell carcinomas which were immunohistochemically positive for p53 protein. These results suggest that p53 gene mutation may be involved in carcinogenesis in the oral squamous epithelium even in the early stage of the dysplasia-carcinoma sequence.

Adult↗
PubMed1996

Quantitative renography with the organ volume method and interporative background subtraction technique.

When quantification of renal activity is performed by planar imaging, many correction factors must be considered. To obtain quantitative renal images and renogram, we have examined our proposed method by using the organ volume for scatter, attenuation, and background activity, and the interporative background subtraction (IBS) technique in phantom and clinical studies. A renal phantom study was performed by varying the renal depth from 3 to 11 cm and the kidney-to-background activity concentration ratio from 5 to 80. Planar images were properly corrected for scatter, attenuation and background activity by our method and the corrected images were compared with the images obtained by the conventional method for the estimation of true renal activity. Clinical Tc-99m DTPA dynamic data for both a good and a poor renal function were also corrected by our method and volume-corrected renograms were obtained. For the phantom study, depth-independent images were obtained and these images gave a good estimation of the true count rate. In the clinical study, the conventional renogram was especially modified to allow for oversubtraction of background counts in the early phase (0-4 min). In conclusion, our proposed correction method can assess renal function qualitatively and quantitatively in both static and dynamic planar renal imaging.

Evaluation Studies as Topic↗
PubMed1996

Role of adenosine in pathogenesis of syndrome X: assessment with coronary hemodynamic measurements and thallium-201 myocardial single-photon emission computed tomography.

OBJECTIVES: This study was performed 1) to examine the role of adenosine in the pathogenesis of syndrome X in patients with this syndrome and abnormal results on myocardial scintigrams during exercise, and 2) to determine the susceptibility to myocardial ischemia in this subset of patients with syndrome X. BACKGROUND: A role for adenosine in the pathogenesis of syndrome X has recently been postulated, but there are few clinical data supporting this hypothesis. METHODS: Exercise thallium-201 myocardial scintigraphy after intravenous administration of aminophylline, an adenosine receptor blocking agent, or saline solution and adenosine thallium-201 scintigraphy were performed in 26 patients with syndrome X. Hemodynamic variables during exercise and perfusion defect size after aminophylline and saline infusions were compared. At cardiac catheterization, coronary hemodynamic variables during separate infusions of adenosine and doubutamine were also examined and were compared among patients with abnormal or normal scintigrams and 10 control subjects. RESULTS: Perfusion abnormalities on exercise-thallium-201 scintigraphy occurred in 14 of 26 patients with syndrome X. Intravenous infusion of aminophylline suppressed the scintigraphic perfusion defect and prolonged the time to 1-mm ST segment depression in patients with syndrome X with abnormal exercise scintigrams. Intravenous infusion of adenosine induced a perfusion defect in the same myocardial area where the perfusion defect was observed at exercise in 7 of the 14 patients with syndrome X. At cardiac catheterization, patients with syndrome X with abnormal exercise scintigrams had lower coronary flow reserve and a greater frequency of myocardial lactate production and ST segment depression in response to the infusions of adenosine and doubtamine than did the other two groups. During adenosine infusion, great cardiac vein blood flow and oxygen content were significantly increased and myocardial oxygen consumption and lactate extraction were significantly reduced from baseline without a significant increase in rate-pressure product in this subset of patients with syndrome X. CONCLUSIONS: Patients with syndrome X with abnormal exercise scintigrams have high susceptibility to myocardial ischemia during exercise or pharmacologic stress tests, probably owing to reduced coronary flow reserve. A heterogeneous response to endogenous adenosine may contribute to scintigraphic perfusion abnormalities and myocardial ischemia during exercise in this subset of patients with syndrome X.

Adenosine↗
PubMed1996

[Prognosis of the surgical treatment for non-Hodgkin lymphoma originating from chronic tuberculous empyema--analysis of 11 cases with pleuropneumonectomy].

In total 19 cases of non-Hodgkin lymphoma originating from the wall of chronic tuberculous empyema, pleuropneumonectomeic were performed since 1979, with the aim of total cures for not only lymphoma but empyema in 11 cases. Of these cases extraresections (5 of thoracic cages, 4 of diaphragms, 2 of axillar lymph nodes, each of adventitia of descending aorta and esophagus, of the liver, of the left adrenal grand) were added to extirpate tumors completely. The mean operating time was 6 degrees 55', the mean blood loss during operations was 3090 ml, but in the 3 most recent cases it was less than under 1000 ml using electrocartesy-cutting technique under direct observation. Although preoperative radiations were done to 4 cases to decrease invasive area of tumors and postoperative radiation was done to 1 case, there were no adjuvant chemotherapies. The indicative limitation for resections from the point of ventilatory functions was the same as that of pleuropneumonectomy for ordinary chronic tuberculous empyema. There were 2 cases with serious postoperative complications. One suffered from ARDS and died on the 14th postoperative day, and another developed acute respiratory failure and MOF. But the other 9 cases kept good postoperative courses with a few recurrences of minor empyema. The prognoses for 10 remaining cases is excellent. Only one case died from local recurrence in of lymphoma 27 months later, but all other 9 cases have revealed no recurrence in any places, and the 5 year survival rate based on Kaplan-Meier method of 10 cases is 85.7%. By the way no cases could survive one year later in unresected group. So under the poor prognosis of treatment with radiation or chemotherapy for non-Hodgkin lymphoma originating from chronic tuberculous empyema, we conclude that the complete resection of tumor and empyema, so called pleuropneumonectomy, is the best way to cure this disease.

Aged↗
PubMed1996

Development of intralobular bile ductules after spontaneous hepatitis in Long-Evans mutant rats.

Oval cell proliferation occurs during spontaneous hepatitis in Long-Evans cinnamon (LEC) rats. It has been reported that oval cells undergo differentiation into mature hepatocytes via small hepatocytes during carcinogenesis. This study was designed to demonstrate in vivo differentiation of oval cells into typical bile ductular cells in the liver lobule and the characteristic feature of intralobular bile ductule formation in LEC rats. We have examined kinetics, intralobular distribution, and morphology of oval cells, small hepatocytes, and bile ductular cells in LEC rat livers at prehepatitic, acute hepatitic, chronic hepatitic, and precancerous stages by conventional light and electron microscopy, immunostaining for cytokeratin, and 3-dimensional reconstruction analysis. Our results indicate that oval cells proliferated and extended into the periportal zone of the liver lobule during acute hepatitis at 20 to 23 weeks after birth. They exhibited tubular structures with a poorly defined lumen and incomplete basement membrane. After remission of the jaundice, small hepatocytes proliferated in association with oval cells and predominated in the periportal zone at 26 weeks. In a chronic hepatitic stage at 28 to 30 weeks, tubular structures were transformed into typical bile ductules, which had a well defined lumen and complete basement membrane, and small hepatocytes became a normal size. Intralobular bile ductules originated from the interlobular bile ducts, ran in the space of Disse, giving rise to several branches in the course, and were terminated at the hepatocytes. The present results indicate that oval cells that proliferate in the liver lobule of LEC rats after spontaneous hepatitis not only differentiate into small hepatocytes but also into typical bile ductular cells. This study suggests that intralobular bile ductules may play roles in maintaining the bile excretion during and after the disorganized proliferation of oval cells and small hepatocytes.

Animals↗
PubMed1996

[A case of de novo aneurysm of the distal posterior inferior cerebellar artery with intraventricular hemorrhage].

A case is presented of a de novo aneurysm of the distal posterior inferior cerebellar artery with intraventricular hemorrhage. A 67-year-old woman was admitted to our hospital with sudden onset of severe headache and loss of consciousness. Computed tomography (CT) scans showed subarachnoid hemorrhage. Angiography demonstrated three aneurysms: an aneurysm of the right vertebral-posterior inferior cerebellar artery, an aneurysm of the bifurcation of the basilar artery, and an aneurysm of the left middle cerebral artery. Considering the distribution of the hemorrhage on CT scans, we concluded that the cause of the hemorrhage was rupture of the vertebral-posterior inferior cerebellar aneurysm. The vertebral-posterior inferior cerebellar aneurysm and the middle cerebral aneurysm were successfully clipped, postoperative angiograms showing the complete clippings. At that time, however, there were no abnormal findings in the left posterior inferior cerebellar artery. Six years later, she was readmitted to our hospital because of sudden onset of headache, nausea, and vertigo. CT scans showed an intraventricular hemorrhage, especially in the fourth ventricle, although subarachnoid hemorrhage was not clearly found. Angiography revealed an aneurysm of the left distal posterior inferior cerebellar artery. She underwent clipping of the aneurysm verified by postoperative angiograms. However she had bacterial meningitis and died from pneumonia and disseminated intravascular coagulopathy. De novo aneurysms of the anterior circulation have often been reported. Carotid, ligation, smoking, the use of oral contraceptives, congenital anomalies and hypertension are major risk factors in the formation of aneurysms. A de novo aneurysm of the distal posterior inferior cerebellar artery is, however, extremely rare. In this case, the right posterior inferior cerebellar artery disappeared when the de novo aneurysm was found. So it is supposed that hemodynamic changes caused by the clipping of the right vertebral-posterior inferior cerebellar aneurysm and the left middle cerebral aneurysm had contributed to the formation of the de novo aneurysm of the left distal posterior inferior cerebellar artery. In the present study, we review the literature on the aneurysm at the distal posterior inferior cerebellar artery and on the de novo aneurysm of the vertebrobasilar artery, and discuss the radiological findings and features.

Aged↗
PubMed1996

[Hepatocellular carcinoma following interferon therapy].

We experienced six patients with resected hepatocellular carcinoma (HCC) following interferon (IFN) therapy. Hepatitis virus C-RNA in polymerase chain reaction was positive in all patients prior to the IFN therapy. HCV-RNA became negative in two patients following IFN therapy, and was re-positive at the time of detection of HCC. In histological studies prior to the IFN therapy, pre-cirrhosis was diagnosed in four out of six patients and chronic active hepatitis 2B (CAH2B) in one according to the Europian classification. In non-cancerous portion of the liver, cirrhosis developed in five patients, and CAH2B in one. There was no significant correlation among the interval of HCC detection following IFN therapy, tumor size, tumor location, and histological findings. Patients should be carefully followed up by serum alpha fetoprotein levels or ultrasonography of the liver during and following IFN therapy.

Aged↗
PubMed1996

In situ detection of platelet-derived growth factor-A and -B chain mRNA in human coronary arteries after percutaneous transluminal coronary angioplasty.

Experimental studies have shown that platelet-derived growth factor (PDGF) plays a role in wound-healing processes after angioplasty. In humans, after percutaneous transluminal coronary angioplasty (PTCA), this has not yet been documented. Six coronary arteries of five patients who died after PTCA were studied. The angioplasty sites were sliced serially, and the slices were studied using immunocytochemistry and in situ hybridization. Monoclonal antibodies were directed against muscle actin, vimentin, macrophages, and endothelium. In situ hybridization was performed using a synthetic oligonucleotide probe complementary to the PDGF-A and -B chain mRNAs. The identification of cells was based on a comparison with immune-stained sections. Positive autoradiographic signals for PDGF-A and -B chain mRNAs were found at the site of the PTCA injury and related to areas that contained macrophages, spindle cells, smooth muscle cells, and endothelial cells of neovascularization. In humans, both PDGF-A and -B chain mRNAs are expressed at sites of PTCA injury. The expression relates to the reparative response, and it appears that the cells involved are macrophages, spindle cells, smooth muscle cells, and endothelial cells of neovascularization. This is the first study to document the expression of PDGF-A and -B mRNAs at sites of repair in human coronary arteries after PTCA. It suggests strongly that PDGF is involved in the repair process after PTCA.

Aged↗
PubMed1996

[Evaluation of simultaneous acquisition of transmission and emission data on thallium-201 myocardial SPECT].

This study evaluates the usefulness of attenuation correction on regional myocardial tracer distributions defined by Thallium-201 myocardial SPECT images obtained from cardiac phantoms and patients with or without coronary heart disease. A three-detector SPECT system equipped with a Technetium-99m line source and a fan-beam collimator was used for simultaneous transmission and emission data acquisition. All three detectors were equipped with fan-beam collimators. Thallium-201 myocardial scintigraphy was performed on phantom study and 19 patients. Transmission images, uncorrected and corrected emission images were iteratively reconstructed with a EM-ML algorithm. Attenuation map computed from the transmission data was utilized for the attenuation correction. For the phantom study, circumferential profile analysis was applied to both datasets of horizontal long-axis slices through the center of the phantom. The maximum profile value in the circumferential profile set to 100% in the normalized uncorrected and corrected profiles. The uncorrected circumferential profiles from cardiac insert model 7070 and RH-2 cardiophantom showed decrease in activity in basal regions which appeared improvement in the attenuation corrected profiles. In clinical study, the inferior-to-anterior activity ratio, changed from 0.78 +/- 0.10 to 0.97 +/- 0.11 on stress images in patients with inferior ischemia and from 0.96 +/- 0.12 to 1.15 +/- 0.13 on 4 hour delayed or rest images in normal cases. The anteroapical wall of the attenuation corrected images, however, showed a decrease in activity relative to the inferior wall in normal cases. The increase in activity in inferior wall on attenuation corrected images was observed frequently in clinical study but not in phantom study. A presence of scatter from the liver or bowels may cause the increase in activity in the inferior wall in clinical study. In conclusion, transmission scan is one of the useful methods for the attenuation correction. Scatter correction, however, is also necessary to make an accurate attenuation corrected images.

Heart↗
PubMed1995

Translation of synonymous codons in family boxes by Mycoplasma capricolum tRNAs with unmodified uridine or adenosine at the first anticodon position.

In Myocoplasma capricolum, codon family boxes except for arginine and threonine (CUN leucine, GUN valine, UCN serine, CCN proline, GCN alanine, and GGN glycine) have only a single tRNA species with the anticodon sequence UNN (N is U, C, A or G), the first nucleoside U being unmodified. Incorporation of the [3H]amino acid into the peptide fraction was examined with the M. capricolum cell-free translation system. Synthetic mRNA containing each of the respective amino acid codons in the coding frame was subjected to translation. The tRNAUNN translated all the family box codons with similar, if not equal, efficiencies. In M. capricolum, there are two species of threonine tRNA, tRNA(UGUThr) and tRNA(AGUThr), the first nucleoside U or A being unmodified. The tRNA(UGUThr) species translates codons ACA, ACG and ACU efficiently, and ACC only poorly. In contrast, the tRNA(AGUThr) species translates codons ACU, ACC and ACG efficiently and ACA poorly.

Adenosine↗
PubMed1995

Human immunodeficiency virus type 1 reverse transcriptase: enhancement of activity by interaction with cellular topoisomerase I.

A number of studies have suggested that topoisomerase I (topo I) activity may be important in human immunodeficiency virus type 1 (HIV-1) replication. Specifically it has been reported that purified virus particles have topo I activity and that inhibitors of this enzyme can inhibit virus replication in vitro. We have investigated a possible association of HIV-1 gag proteins with topo I activity. We found that whereas the gag-encoded proteins by themselves do not have activity, the nucleocapsid protein p15 can interact with and enhance the activity of cellular topo I. Furthermore it could be demonstrated that topo I markedly enhanced HIV-1 reverse transcriptase activity in vitro and that this could be inhibited by the topo I-specific inhibitor camptothecin. The findings suggest that cellular topo I plays an important role in the reverse transcription of HIV-1 RNA and that the recruitment of this enzyme may be an important step in virus replication.

Base Sequence↗
PubMed1995

Normal activation of p70 S6 kinase by insulin in cells overexpressing dominant negative 85kD subunit of phosphoinositide 3-kinase.

The role of heteromeric phosphoinositide (PI) 3-kinase activity in insulin signal transduction was studied by investigating the effects of (i) overexpression of a dominant negative mutant p85 (delta p85) that lacks the binding site for p110 (delta p85-overexpressing cells) and (ii) inhibition of PI 3-kinase activity by wortmannin (wortmannin-treated cells). The insulin-induced association of PI 3-kinase activity with insulin receptor sustrate-1 (IRS-1) was inhibited in both wortmannin-treated cells and delta p85-overexpressing cells. However, whereas insulin-induced activation of p70 S6 kinase was completely abolished in wortmannin-treated cells, it appeared normal in delta p85-overexpressing cells. These results raise the possibility that a wortmannin-sensitive pathway independent of heteromeric PI 3-kinase is involved in the activation of p70 S6 kinase by insulin.

Amino Acid Sequence↗
PubMed1995

The SMXA: a new set of recombinant inbred strain of mice consisting of 26 substrains and their genetic profile.

A new set of recombinant inbred (RI) strain SMXA consisting of 26 substrains was established between SM/J and A/J. The history of the SMXA RI strains and their genetic profile covering 158 genetic marker loci are reported. From the strain distribution pattern among SMXA RI strains, the chromosomal location of salivary and tear protein genes Spe1-r, Spe1-s, Spe2, and Tpe1 were newly determined.

Animals↗
PubMed1995

Appearance of free radicals in the guinea pig inner ear after noise-induced acoustic trauma.

The emergence of superoxide anion radicals (O2-) in the guinea pig inner ear following acoustic trauma was investigated by histochemical methods. Five minutes after exposure to sound at 120-125 dB SPL for 3 h, an O2- reaction product was detected in the cochlea along the luminal membrane of the marginal cells of the stria vascularis. This reaction product could not be found at 30 min, but reappeared at 2 h. The first appearance of O2- is not explainable by our studies, but the second appearance may be related to recirculation of strial blood flow after blood flow stasis. The present observations raise the possibility that free radicals are produced in the inner ear after acoustic trauma and lead to inner ear damage.

Animals↗
PubMed1995

Direct 99mTc labeling of human immunoglobulin with an insoluble macromolecular Sn(II) complex.

An insoluble macromolecular Sn(II)(R-Sn) complex which strongly binds Sn(II) by chelation was applied to the direct 99mTc labeling of human immunoglobulin(IgG) to minimize the influence of Sn(II). 99mTc labeling was achieved at greater than 90% yield simply by the short-term mixing of IgGa containing > 2-SH groups per IgG molecule, 99mTc pertechnetate, and the R-Sn complex in pH 7 solution. The 99mTc-IgGa obtained by this labeling method has high stability based on the thiol-specific binding of 99mTc without transchelation from another weakly bound 99mTc-complex.

Animals↗