Search PubMed⌕ Search

Biomedical subjects

T Shibata

Publications and source records attributed to T Shibata.

At least 235 records · Page 13Linked to original sources
PubMed1999

Cytoplasmic delayed neuronal death in the myenteric plexus of the rat small intestine after ischemia.

The present study demonstrates light and electron microscopic changes in neurons in the myenteric plexus of the rat ileum following four-hour ischemia. Macroscopically, an intestinal constriction occurred at the damaged portion at three weeks after ischemia; the segment oral to the constriction markedly swelled at four weeks. In light microscopy, at three weeks after ischemia, the myenteric neurons appeared spongy or foamy, containing many vacuoles in their somatic cytoplasm. At four weeks, the neuronal cytoplasm and nerve fiber bundles had disintegrated to form vacant spaces in the myenteric plexus. The neuronal nucleus of the damaged plexus did not show positive nick-end labeling. In electron microscopy, neuronal cytoplasm revealed degenerative signs already at one week after ischemia: a distended endoplasmic reticulum and swollen mitochondria with fragmentary cristae. The nerve fibers also showed destruction of the mitochondria, and degenerative changes in the postsynaptic sites appeared earlier than the presynaptic terminals. The results suggest that intestinal ischemia causes delayed neuronal death, which differs from the apoptotic process previously demonstrated in the ischemia-damaged brain.

Animals↗
PubMed1999

Severe hyponatremia caused by hypothalamic adrenal insufficiency.

A 60-year-old woman was admitted with severe hyponatremia. Basal values of adrenocorticotropic hormone (ACTH), thyroid hormone and cortisol were normal on admission. Impairment of water diuresis was observed by water loading test. Initially, we diagnosed her condition as the syndrome of inappropriate secretion of antidiuretic hormone (SIADH). By provocation test, we finally confirmed that the hyponatremia was caused by hypothalamic adrenal insufficiency. The basal values of ACTH and cortisol might not be sufficient to exclude the possibility of adrenal insufficiency. Therefore, it is necessary to evaluate adrenal function by provocation test or to re-evaluate it after recovery from hyponatremia.

Adrenal Insufficiency↗
PubMed1999

Percutaneous microwave hepatic tumor coagulation with segmental hepatic blood flow occlusion in seven patients.

OBJECTIVE: We assess the usefulness of microwave hepatic tumor coagulation therapy with balloon occlusion of segmental hepatic blood flow for eight recurrent metastatic hepatic tumors in seven patients. CONCLUSION: Limited early experience with microwave hepatic tumor coagulation therapy and segmental hepatic blood flow occlusion has been positive, suggesting that further clinical evaluation is warranted.

Catheterization↗
PubMed1999

Tumor staging of pancreatic adenocarcinoma using early- and late-phase helical CT.

OBJECTIVE: We compared early-phase CT with late-phase CT in the evaluation of pancreatic adenocarcinoma. MATERIALS AND METHODS: Both early- and late-phase CT images of 25 pancreatic adenocarcinomas were compared with surgical-pathologic findings. We evaluated tumor detectability, tumor size, and local tumor invasion. RESULTS: Tumor detectability was 96% on early-phase CT imaging and 64% on late-phase CT imaging (p < .01). Sensitivity for anterior serosal invasion, retroperitoneal invasion, and arterial invasion on early-phase CT exceeded sensitivity on late-phase CT (p < .05). However, specificity for all factors on early-phase CT was less than or equal to specificity on late-phase CT. The grade of local tumor invasion on early-phase CT achieved better agreement with the surgical-pathologic results than did late-phase CT, especially for tumor size and retroperitoneal invasion. CONCLUSION: Early-phase CT was better than late-phase CT in revealing tumors, tumor size, and retroperitoneal invasion.

Adenocarcinoma↗
PubMed1999

Bone augmentation by recombinant human BMP-2 and collagen on adult rat parietal bone.

A composite of recombinant human bone morphogenetic protein-2 (rhBMP-2) and collagen was implanted beneath the cranial periosteum of 10-month-old rats to observe bone development and absorbent change of carrier collagen. The rhBMP-2/collagen onlay implant resulted in active bone formation and the augmented bone was connected directly with the original bone, whereas the collagen alone resulted in neither bone nor cartilage. The ossification process in the rhBMP-2/collagen occurred directly through bone formation, similar to intramembranous ossification. The carrier collagen fibers were found in the woven bone and were completely absorbed at 8 weeks in the presence of rhBMP-2, while the collagen alone implant remained encapsulated by a thin, fibrous connective tissue. Our results indicate that rhBMP-2/collagen is an effective material as a biological onlay implant, showing osteoinductive properties and being completely replaced by new bone. Carrier collagen not only plays a role in rhBMP-2 delivery, but also provides a cell anchorage for cell differentiation and remains as an artificial matrix in woven bone.

Absorbable Implants↗
PubMed1999

Use of heparin-coated cardiopulmonary bypass circuit with low-dose heparin reduces postoperative bleeding.

Postoperative bleeding was examined in patients undergoing cardiopulmonary bypass with a heparin-coated circuit and low-dose heparin. Out of 150 patients who underwent cardiopulmonary bypass for longer than 90 minutes, 74 received a standard dose (300 IU/kg) of heparin with an uncoated circuit (group C) and 76 received a low-dose (150 IU/kg) of heparin with a heparin-coated circuit (group H). The coagulation and fibrinolytic systems were investigated in 24 patients. Re-opening of the chest due to bleeding was performed in 5 patients in group C (7%), but none of the patients in group H (p=0. 03). The median of blood loss in the first 12 hours after surgery was 292 ml in group C, and 216 ml in group H (p=0.006). There were no significant differences in the peak thrombin-antithrombin complex concentration between the two groups. The plasmin-alpha 2 plasmin inhibitor complex concentrations after protamine administration were 1.9 ng/ml (median) in group C and 1.1 ng/ml in group H (p=0.002). The use of heparin-coated cardiopulmonary bypass circuits with low-dose heparin suppressed the activation of fibrinolysis. This may explain the reduction in postoperative bleeding.

Adult↗
PubMed1999

Correction of knee deformity in patients with Ellis-van Creveld syndrome.

Six knees in three patients with Ellis-van Creveld syndrome were treated with lateral soft tissue release and corrective osteotomy of the tibia at 10 years of age on average. The main feature was valgus deformity with lateral dislocation of the patella. All patellae were reduced. The valgus deformity improved from 35 degrees (range, 48 degrees-20 degrees) to 17 degrees (range, 35 degrees-5 degrees) of the femorotibial angle (FTA) on average, although the FTA in five of six knees was < 5 degrees after surgery. There was one recurrent case and one transient peroneal nerve palsy. The reason for undercorrection was a depression of the lateral tibial plateau. The deformity of the articular surface is the most important problem in correcting the valgus deformity of the knee in this syndrome.

Adolescent↗
PubMed1999

Use of a retractor designed to harvest an internal thoracic artery graft during cardiac surgery for patients with a unilateral lung.

Adequate exposure of the heart is required for safe cardiac surgery. We performed open heart surgery for 2 patients with a unilateral lung. In one patient, coronary artery bypass grafting was performed 13 years after left pneumonectomy for lung cancer. Mitral valve replacement was performed in the other patient whose left lung was entirely collapsed due to tuberculosis. The heart was markedly deviated to the left in both patients. A retractor designed to harvest the internal thoracic artery was very useful to obtain a good operative view of the heart. The operations were uncomplicated, and postoperative recovery was uneventful in both patients.

Aged↗
PubMed1999

[Microwave coagulation therapy under laparotomic ischemia for multiple liver metastases of colorectal cancer].

Microwave coagulation therapy (MCT) under laparotomic ischemia induced by partial obstruction of the hepatic artery and portal vein was conducted on patients with multiple liver metastases of colorectal cancer. The patients were then compared with those who underwent non-ischemic MCT. Among the patients with liver metastasis of colorectal cancer we encountered between August 1990 and October 1998, 14 patients who developed multiple cancer (five or more) in the bilateral liver lobes were enrolled in the study. No clear differences were observed in the sex, age, frequency of simultaneousness, therapy other than MCT, number of foci, and number of MCT between the ischemic MCT and non-ischemic MCT group. Postoperative CT revealed residual foci in one of the seven patients in the ischemic MCT group. A comparison of the cumulative survival rate revealed that the ischemic MCT group had a higher one-year survival rate (50%) than the non-ischemic MCT group (14%). A comparison of patients with a residual lesion and those with no residual lesion showed that all six patients with a residual lesion died less than one year after surgery. Eight patients with no residual lesion had a significantly better prognosis (p < 0.05). It is important to eliminate any residual metastatic lesion during surgery in multiple liver metastases of colorectal cancer If the residual lesion is non-resectable, its elimination by ischemic MCT would contribute to the long-term survival of the patients.

Adult↗
PubMed1999

Tomograms of the arterial system of the human fetal auditory apparatus obtained by very-high-resolution microfocus X-ray CT and 3D reconstruction.

A series of 500 tomograms and 3D reconstructions of the small arterial vessels of the human fetal auditory apparatus were obtained for the first time by employing very-high-resolution microfocus X-ray computed tomography (MFXCT, mu-CT) with injection of contrast medium into the fetal aorta. Contrast images were obtained with barium sulfate (BaSO4) but not with iopamidol (C17H12I3N3O8). The anterior, posterior, superior, and inferior tympanic arteries, internal carotid artery, internal auditory artery, deep auricular artery, and stylomastoid artery were identified on tomograms of a crown-rump length (CRL) 224-mm fetus. MFXCT tomograms of some arteries about 30 microns in diameter were successfully obtained by the present method despite the difficulty associated with injection of contrast medium into 40-year-old specimens that had been perfused with formalin. This procedure is very useful for making anatomical observations without subjecting the specimens to any mechanical stress.

Angiography↗
PubMed1999

Cardiac surgery in patients with dialysis-dependent renal disease.

This study was designed to evaluate the operative outcome of dialysis patients undergoing cardiac surgery. A retrospective review was performed of 28 consecutive patients with end-stage renal disease dependent on maintenance hemodialysis (n = 26) or peritoneal dialysis (n = 2) who underwent cardiopulmonary bypass (CPB). The operations included isolated coronary artery bypass grafting (CABG) (n = 21), aortic valve replacement (n = 4) and CABG plus aortic valve replacement (n = 3). Seven operations were emergent or urgent. In 23 patients, a heparin-coated (HC) circuit with reduced systemic heparinization was used for CPB. The hospital mortality was 7.1%. Complications occurred in 13 patients (46%). Although thoracotomy for bleeding was required in 3 patients, only 1 had undergone CPB with an HC circuit. There were 7 late deaths. All survivors showed improvement in symptoms and overall functional status. The actuarial survival rates were 78% and 58% at 1 and 4 years, respectively. In the 10 patients with diabetes mellitus, the 4-year survival rate was 50%. In the patients who underwent non-elective surgery, the survival rate was 29%. Cardiac surgery can be performed with increased but acceptable mortality in dialysis patients. Good symptomatic relief can be expected. Surgery should be performed before the general condition deteriorates.

Actuarial Analysis↗
PubMed1999

Heparin-coated circuits prevent renal dysfunction after open heart surgery.

UNLABELLED: We examined whether heparin-coated (HC) circuits can improve the operative results in patients with chronic renal insufficiency. SUBJECTS AND METHODS: Elective cardiac surgery was performed in 24 patients with a serum creatinine (Cr) level of at least 1.5 mg/dl. Uncoated circuits were used in 12 patients, and HC circuits were used in 12 patients. The results of surgery were compared between the two groups. RESULTS: The mean preoperative Cr concentration was significantly higher in the HC group (2.3 vs 1.8 mg/dl). The heparin doses, protamine dose, and activated clotting times were significantly lower in the HC group. The mean blood loss was also less, although this difference was not significant. The postoperative increase in the Cr level was small in the HC group (2.3-->2.5 mg/dl) compared to that in the noncoated group (1.8-->2.3 mg/dl). Postoperative dialysis was not required in the 5 patients in the HC group with a preoperative Cr clearance less than 20 ml/min. CONCLUSION: HC circuits and low-dose heparin can be used to maintain renal function after cardiopulmonary bypass, even in patients with severe kidney disease.

Aged↗
PubMed1998

Dipole source localization of ictal epileptiform activity.

Dipole source localization of ictal epileptiform activity recorded by scalp EEG was performed in patients prior to surgical treatment. The dipole tracing method combined with the scalp-skull-brain head model was used to locate epileptogenic foci. A digital EEG system was used for data collection. The accuracy of dipole source localization was evaluated by comparing the focus location with that obtained by chronic subdural electrocorticography. In a case of frontal lobe epilepsy with epileptogenic focus in the frontoparietal convexity, the results of dipole source localization agreed well with those obtained with chronic subdural electrocorticography. In a case of lateral temporal lobe epilepsy, the results of dipole source localization were consistent with those obtained with chronic subdural electrocorticography, but a small localization error was observed. The clinical usefulness of and suggestions for improving this method are discussed.

Adult↗
PubMed1998

Identification of a defined epitope on the surface of the active RecA-DNA filament using a monoclonal antibody and three-dimensional reconstruction.

Studies of the Escherichia coli RecA protein are expected to illuminate mechanisms of DNA recombination and repair in bacteria, and in all higher organisms as well, due to the functional and structural homology with the eukaryotic Rad51 protein. The active form of the RecA protein is a helical filament formed on DNA in the presence of ATP or ATP analogs, and this has been studied at low-resolution by electron microscopy. An atomic model of the protein comes from an X-ray crystallographic study of a filament formed in the absence of DNA and ATP. This filament is believed to be an inactive, storage form of the protein. A key step in generating an atomic model of the active filament, and a detailed model for function, is to understand the large conformational changes that occur between these two states. Towards this end, we have decorated active RecA-DNA filaments with monoclonal antibodies (ARM191) against a known epitope (residues 285 to 320) to determine the position of this epitope in the low-resolution structure. Electron microscopy and three-dimensional reconstruction of the RecA-antibody complex reveal that the lobe containing the epitope is very disordered on the surface of the filament, but in a position similar to that in the inactive crystal filament. The antibody binding also induces a significant conformational change in the RecA filament. This study shows that the basic orientation of the subunit is likely to be similar within the inactive and active filaments, and that the large movement of mass that occurs between these two states must involve other residues than the 285-320 region.

Animals↗
PubMed1998

Distinct roles of two separable in vitro activities of yeast Mre11 in mitotic and meiotic recombination.

UNLABELLED: In Saccharomyces cerevisiae, Mre11 protein is involved in both double-strand DNA break (DSB) repair and meiotic DSB formation. Here, we report the correlation of nuclease and DNA-binding activities of Mre11 with its functions in DNA repair and meiotic DSB formation. Purified Mre11 bound to DNA efficiently and was shown to have Mn2+-dependent nuclease activities. A point mutation in the N-terminal phosphoesterase motif (Mre11D16A) resulted in the abolition of nuclease activities but had no significant effect on DNA binding. The wild-type level of nuclease activity was detected in a C-terminal truncated protein (Mre11DeltaC49), although it had reduced DNA-binding activity. Phenotypes of the corresponding mutations were also analyzed. The mre11D16A mutation conferred methyl methanesulfonate-sensitivity to mitotic cells and caused the accumulation of unprocessed meiotic DSBs. The mre11DeltaC49 mutant exhibited almost wild-type phenotypes in mitosis. However, in meiosis, no DSB formation could be detected and an aberrant chromatin configuration was observed at DSB sites in the mre11DeltaC49 mutant. These results indicate that Mre11 has two separable functional domains: the N-terminal nuclease domain required for DSB repair, and the C-terminal dsDNA-binding domain essential to its meiotic functions such as chromatin modification and DSB formation. KEYWORDS: DNA binding/double-strand break repair/DSB formation/Mre11/nuclease

Bacteriophage M13↗
PubMed1998

Enhancement of gene expression under hypoxic conditions using fragments of the human vascular endothelial growth factor and the erythropoietin genes.

PURPOSE: Selective gene expression in response to tumor hypoxia may provide new avenues, not only for radiotherapy and chemotherapy, but also for gene therapy. In this study, we have assessed the extent of hypoxia responsiveness of various DNA constructs by the luciferase assay to help design vectors suitable for cancer therapy. MATERIALS AND METHODS: Reporter plasmids were constructed with fragments of the human vascular endothelial growth factor (VEGF) and the erythropoietin (Epo) genes encompassing the putative hypoxia-responsive elements (HRE) and the pGL3 promoter vector. Test plasmids and the control pRL-CMV plasmid were cotransfected into tumor cells by the calcium phosphate method. After 6 h hypoxic treatment, the reporter assay was performed. RESULTS: The construct pGL3/VEGF containing the 385 bp fragment of the 5' flanking region in human VEGF gene showed significant increases in luciferase activity in response to hypoxia. The hypoxic/aerobic ratios were about 3-4, and 8-12 for murine and human tumor cells, respectively. Despite the very high degree of conservation among the HREs of mammalian VEGF genes, murine cells showed lower responsiveness than human cells. We next tested the construct pGL3/Epo containing the 150 bp fragment of the 3' flanking region in the Epo gene. Luciferase activity of pGL3/Epo was increased with hypoxia only in human cell lines. The insertion of 5 copies of the 35-bp fragments derived from the VEGF HREs and 32 bp of the E1b minimal promoter resulted in maximal enhancement of hypoxia responsiveness. CONCLUSIONS: The constructs with VEGF or Epo fragments containing HRE may be useful for inducing specific gene expression in hypoxic cells. Especially, the application of multiple copies of the HREs and an E1b minimal promoter appears to have the advantage of great improvement in hypoxia responsiveness.

Animals↗
PubMed1998

Effects of SN-38 (an active metabolite of CPT-11) on responses of human and rodent cells to irradiation.

PURPOSE: Modulators of the DNA-unwinding enzyme, topoisomerase I (Topo I), inhibit DNA repair and have been reported to increase the lethal effects of X rays, which create breaks in DNA. CPT-11 is a derivative of camptothecin, a Topo I inhibitor, and is clinically available. In this study, we tested the in vitro combination effects of SN-38, an active form of CPT-11, and irradiation on several cell lines. MATERIALS AND METHODS: Exponentially growing or confluent cultures of CHO cells were treated with SN-38 for 30 min. Cells were then irradiated. Thereafter, the cells were further incubated with the drug for 0 to 3 h. Exponentially growing other cell lines were exposed to 200 nM SN-38 for 30 min before, during, and 3 h after irradiation. The cell survival rate was determined using a conventional clonogenic assay. RESULTS: SN-38 (200 nM to 4 microM) alone showed slight toxicity to CHO cells in the confluent culture after a 3.5-h incubation. When the cells were treated with the lower doses of SN-38 (50 to 800 nM) during the exponentially growing phase, the cell survival rates were much lower. In combination with irradiation, SN-38 showed only additive effects to irradiation when cells were treated in confluent cultures. However, higher combination effects of SN-38 and irradiation were observed in the cells treated in the exponentially growing phase. When cells were irradiated during the exponentially growing phase, a significant combination effect of 200 nM SN-38 and irradiation was also observed in some cell lines, but not in others. CONCLUSION: SN-38 and irradiation showed supraadditive effects in some cell lines, when treated in the exponentially growing phase, but not in other cell lines or when cells were treated in the confluent phase.

Animals↗