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Biomedical subjects

T Maeda

Publications and source records attributed to T Maeda.

At least 379 records · Page 21Linked to original sources
PubMed1998

Amelioration of liver injury by ischaemic preconditioning.

BACKGROUND: Ischaemic preconditioning, i.e. preparatory brief ischaemia before subsequent long ischaemia, can effectively protect the heart from ischaemia-reperfusion injury in animals. The purpose of this study was to demonstrate the same phenomenon in the liver. METHODS: Using warm ischaemia-reperfusion of 70 per cent of the liver followed by resection of the non-ischaemic portion in rats, livers with 10 min of ischaemic preconditioning, i.e. 10 min of warm ischaemia and reperfusion, were compared with those that had not been subjected to such a manoeuvre. RESULTS: At 120 min after reperfusion following 40 min of warm ischaemia, the livers with 10 min of ischaemic preconditioning had a significantly lower mean(s.d.) serum alanine aminotransferase level (492(217) versus 1236(695) units/l; P < 0005) and lactic dehydrogenase level (7905(4002) versus 15066(9201) units/l; P< 0.05), as well as a higher bile output (0.12(0.03) versus 0.09(0.04) ml per g liver; P < 0.05) and liver tissue adenosine 5'-triphosphate level (78(13) versus 61(11) per cent; P< 0.05) than the control livers. The necrosis rate, histologically defined as the percentage of necrotic area in given liver sections, was reduced significantly by this manoeuvre (mean(s.d.) 1.3(1.3) versus 5.3(1.7) per cent; P< 0.05). CONCLUSION: Ischaemic preconditioning exerts a protective effect on hepatic warm ischaemia-reperfusion injury. Such a manoeuvre may be useful for hepatic resection in the clinical setting.

Adenosine Triphosphate↗
PubMed1998

Mechanisms of excitatory amino acid release in contused brain tissue: effects of hypothermia and in situ administration of Co2+ on extracellular levels of glutamate.

In order to elucidate the mechanisms of release of EAAs and their excitotoxicity in cerebral contusion, cortical contusion was produced in the rat parietal cortex, and the changes in extracellular levels of EAAs in the central and peripheral areas of contusion were investigated using microdialysis. The cortical contusion induced a rapid increase in dialysate concentration of glutamate ([Glu]d) from a baseline level of 4.6+/-2.8 microM to a maximum level of 36.3+/-12.8 microM. This elevation of glutamate was significantly attenuated by mild hypothermia (32 degrees C for 90 min, comprising 20 min before and 70 min after the injury induction) in the peripheral area of contusion (p < 0.01) but not in the central area. Histological evaluations revealed that the hypothermia reduced the necrosis volume of contusion to 38.3% of that in the normothermic control (p < 0.01). In situ administration of Co2+, an inhibitor of Co2+-dependent exocytotic release of EAAs from the nerve terminals, via the microdialysis system, also attenuated the [Glu]d elevation following cortical contusion, in the peripheral area of contusion (p < 0.01) but not in the central area. These findings indicate that cerebral contusion involves heterogeneous and complex mechanisms of EAA release into the extracellular space. The release of EAAs in the contusion core was nonsensitive to hypothermia and Co2+ administration, suggesting that such EAA release was related to primary disruption of the cell membrane or vascular wall by the physical force of the head trauma, resulting in leakage of EAAs from the metabolic pool in the cytosole or blood stream. In contrast, in the peripheral area, the effectiveness of hypothermia and Co2+ administration implied a presynaptic mechanism of EAA release, which consisted, at least in part, of Ca2+-dependent exocytotic EAA release from depolarized nerve terminals. The EAAs released in the contusion core may diffuse towards a peripheral direction and act on the postsynaptic receptors, causing neuronal depolarization. Such a diffusion-reaction process appears to induce additional release of EAAs from the depolarized nerve terminals. Hypothermia may block this diffusion-reaction process and eventually reduce the contusion volume.

Animals↗
PubMed1998

Deletion of signaling molecule genes resembling the cytoplasmic domain of Igbeta in autoimmune-prone mice.

The P8.6 gene is encoded upstream of the mouse TCR Valpha1 gene in the anti-sense strand and its gene product contains the proline-rich region and tyrosine-isoleucine (Y-I) motif, which are consensus sequences for the SH2 and SH3 binding motifs respectively. It was found that this protein is highly homologous to Igbeta. We also found that the P8.6 protein associates with a 170 kDa phosphorylated protein in vivo. To examine the polymorphism of the P8.6 gene, we carried out a single-strand conformation polymorphism analysis and found that the P8.6 gene comprises a family of at least 13 independent genes arising from single or multiple mutations. The mutated P8.6 gene with the Y-L motif was deleted, especially in NZW and BXSB mice, whereas normal BALB/c mice have a P8.6 gene bearing both the Y-I and Y-L motifs, suggesting a dysregulation in signaling through the B cell receptor or TCR in these two autoimmune mice. Functional analysis using transfectant cells carrying P8.6-1 (Y-I motif) and P8.6-3 (Y-L motif) clearly demonstrated that P8.6-3 gene inhibited the signal transduction upon the stimulation of ionomycin and cell growth. The TANYSNI sequence has been proposed as the immunoreceptor tyrosine-based inhibitory motif, this motif is replaced by AANYSNI in the NZW mice. In conclusion, some P8.6 are deleted in particular autoimmune-prone mice.

Amino Acid Sequence↗
PubMed1998

Distribution of calcium ions at the interface between resin bonding materials and tooth dentin. Use of commercially available adhesive systems.

It has been proposed that calcium ions play a key role in chemical (chelate) binding between the adhesive resin and dentin surface. However, no data is available concerning how calcium ions are distributed at the binding sites. The aim of this study is to demonstrate calcium ions at the resin-dentin interface by means of X-ray microanalysis and calcium ion-sensitive histochemical staining. The dentin surface in human teeth was ground by use of 240 grit silicon carbide abrasive paper under running water and treated with the dentin-primer and adhesive resin in Clearfil Liner Bond System or IMPERVA Bond System according to the manufacturer's instructions. After removing dentin matrix and isolating adhesive resin by the KOH-digestion method, one half of the samples were processed for scanning electron microscopy. The rest were embedded in Epon 812 and processed either for glyoxal bis (2-hydroxyanil) (GBHA) staining or transmission electron microscopy combined with X-ray microanalysis. Transmission electron microscopy revealed Ca-phosphate deposits at the bottom of the resin-impregnated layer. The adhesive resin above the resin-impregnated layer was amorphous and showed no precipitates of Ca-phosphate. GBHA displayed intense calcium reactions throughout the resin-impregnated layer and also moderate ones in the 10 microns (Clearfil Liner Bond System) or 30 microns (IMPERVA Bonding System) thick boundary zone of the adhesive resin as well as in the resin tags. These data are the first to offer a distinct localization of calcium ions within the adhesive resin at the dentin-resin interface.

Calcium↗
PubMed1998

Mortality, size of the gonads, and ultrastructure of primordial germ cell in chick embryos treated with gamma-irradiation or injected with donor cells.

The effects of injection and/or gamma-irradiation prior to injection on mortality, size of the gonads, and ultrastructure of primordial germ cell (PGC) were examined after 5 d of incubation. The mortality of embryos injected with donor cells was significantly higher than that of control and irradiated embryos. All irradiated embryos were alive, although their development was delayed compared to those not exposed to irradiation. The size of the gonads of embryos injected with donor cells were similar to those of control embryos, however, the size of the gonads in irradiated embryos was significantly smaller than those of control embryos. The number of PGC in the gonads was significantly decreased by irradiation. There was no notable effect of irradiation or injection on the nuclei and cytoplasmic organelles in PGC.

Animals↗
PubMed1998

Prognostic factors after repeat hepatectomy for recurrent hepatocellular carcinoma.

OBJECTIVE: The aims of this study were to identify prognostic factors in patients who developed recurrent hepatocellular carcinoma (HCC) after repeat hepatectomy and to elucidate the role of multicentric occurrence in the second tumor after a first hepatectomy. SUMMARY BACKGROUND DATA: A repeat hepatectomy for recurrent HCC has been established as the most effective treatment modality, whenever it is possible. However, the prognostic factors for recurrent HCC after repeat hepatectomy have yet to be clarified. METHODS: Forty-one patients who underwent a curative repeat hepatectomy were retrospectively studied. Patient survival and disease-free survival after recurrence were univariately and multivariately analyzed using 38 clinicopathologic variables. The histologic grade of HCC at repeat hepatectomy was also compared with that at first hepatectomy. RESULTS: Patient survival after repeat hepatectomy did not differ substantially from that in 312 patients undergoing primary hepatectomy. However, the disease-free survival after repeat hepatectomy was significantly lower than that in patients with only a primary hepatectomy (p < 0.05). Multivariate analysis revealed only portal vein invasion in the first hepatectomy to be an independent and significantly poor prognostic factor. Regarding multicentric occurrence at repeat hepatectomy, only 6 of 40 patients (15%) whose specimens could be evaluated histologically were determined to be Edmondson and Steiner's Grade 1. CONCLUSIONS: The only prognostic factor identified in patients with recurrent HCC after repeat hepatectomy was portal vein invasion in the first hepatectomy. Most second tumors after the first hepatectomy are considered to be caused by metastatic recurrence, not by multicentric occurrence.

Algorithms↗
PubMed1998

Tc-99m MIBI localization in bone marrow: a marker of bone marrow malignancy.

To determine the potential of Tc-99m MIBI for detecting bone marrow malignancy, MIBI imaging of the femur was evaluated. There was no detectable MIBI activity in 125 of 141 (89%) control patients. Clearly demonstrated focal or tubular MIBI activity indicating intramedullary accumulation was demonstrated in 44 of 45 (98%) patients with proven marrow malignancy: 9 patients with multiple myeloma, 10 patients with malignant lymphoma, 11 patients with acute leukemia, 1 patient with chronic leukemia, and 14 patients with skeletal metastases. No abnormal MIBI activity was observed in the femur in 19 of 22 (86%) patients who had no evidence of malignant involvement in the femoral marrow, in 3 patients with solitary plasmacytomas of the spine, sternum or iliac bone, or in 16 patients with malignant lymphoma. In 12 of 24 patients with acute leukemia in complete remission, no abnormal MIBI accumulation was shown in the femur, but in 12 patients, abnormal accumulation indicating residual leukemic activity was demonstrated. MIBI imaging correlated extremely well with MRI studies; 26 of 28 patients with focal or tubular increased MIBI activity in the femur showed decreased signal on T1-weighted images and a high signal on short inversion recovery images, and 11 patients with no abnormal activity showed a high signal on T1 images. MIBI imaging of the femoral bone marrow may be a new modality for detecting marrow malignancy.

Adult↗
PubMed1998

Magnetic resonance imaging of fetal autosomal recessive polycystic kidney disease.

We present a case of fetal autosomal recessive polycystic kidney disease (ARPKD) at 34 weeks of gestation, diagnosed by magnetic resonance imaging (MRI). MRI demonstrated enlarged fetal kidneys that were low signal intensity on T1-weighted images and high signal intensity on T2-weighted images. These MRI findings suggested a high water content in the renal parenchyma, consistent with the innumerable, tiny renal cysts present in ARPKD.

Adult↗
PubMed1998

Innervation of the periodontal ligament in the alligatorid Caiman crocodilius.

The mode of development and structure of crocodilian teeth and periodontium parallels that of mammals, but the teeth are continuously replaced throughout the lifetime of those animals. In this report, the innervation and fibres of the crocodilian periodontal ligament were examined using histology, immunohistochemistry for S-100 protein and transmission electron microscopy. Crocodilian periodontal ligaments had the following characteristics: (1) horizontal fibres, which connect the alveolar bone to the root cementum and (2) longitudinal fibres, which ran parallel to the tooth axis, with nerves and blood vessels in the middle layer of the ligament. The apex of root and tooth germs were both embedded in thick circular fibres. S-100 protein was detected in neural elements including terminal portions which were densely distributed in the periodontal ligament and dental follicle. The S-100 positive neural elements formed a periodontal plexus. We found two types of nerve endings; free endings and simple encapsulated corpuscles as described in mammals. The presence of such nerve endings in caiman suggests that these teeth, in addition to having a biting function, may also act as highly sensitive sensory organs.

Alligators and Crocodiles↗
PubMed1998

[Background and prognostic factors of fungemia in patients with hematological disease].

Sixty-two episodes of fungemia which occurred in patients with hematological disorders between 1976 and 1996 in our hospital were analyzed with respect to background and prognostic factors. Forty-four of the patients were male and 18 were female. The underlying diseases were acute leukemia in 36 cases, chronic myelogenous leukemia in 9, malignant lymphoma in 9 and others in 8 cases. Trichosporon beigelii and Candida tropicalis were the most frequently isolated fungal pathogens. The prevalence of C. crusei increased while that of C. albicans decreased after 1988. Fuungemia frequently occurred in patients with following factors: 1) advanced disease, such as relapse of acute leukemia or malignant lymphoma or blast crisis of chronic myelogenous leukemia; 2) neutrophil count less than 100/microliter; 3) administration of antibiotics; 4) focal infection, gastrointestinal hemorrhage or urinary catheterization; and 5) isolation of causative organisms from surveillance cultures obtained just before the onset of fungemia. The mortality rate of patients with fungemia was 74%. Absence of hypotension, increased neutrophil count for a week after the onset of fungemia, and the intravenous administration of Amphotericin B (AMPH) were good prognostic factors. Fungemia frequently occurred in patients with advanced disease and had a very poor prognosis. These results emphasized the importance of isolation of fungus from surveillance cultures, early initiation of AMPH administration, and attempts to increase neutrophil counts with G-CSF and other measures for improving the prognosis of fungemia in patients with hematological disorders.

Adolescent↗
PubMed1998

Requirement for activation of the serine-threonine kinase Akt (protein kinase B) in insulin stimulation of protein synthesis but not of glucose transport.

A wide variety of biological activities including the major metabolic actions of insulin is regulated by phosphatidylinositol (PI) 3-kinase. However, the downstream effectors of the various signaling pathways that emanate from PI 3-kinase remain unclear. Akt (protein kinase B), a serine-threonine kinase with a pleckstrin homology domain, is thought to be one such downstream effector. A mutant Akt (Akt-AA) in which the phosphorylation sites (Thr308 and Ser473) targeted by growth factors are replaced by alanine has now been shown to lack protein kinase activity and, when overexpressed in CHO cells or 3T3-L1 adipocytes with the use of an adenovirus vector, to inhibit insulin-induced activation of endogenous Akt. Akt-AA thus acts in a dominant negative manner in intact cells. Insulin-stimulated protein synthesis, which is sensitive to wortmannin, a pharmacological inhibitor of PI 3-kinase, was abolished by overexpression of Akt-AA without an effect on amino acid transport into the cells, suggesting that Akt is required for insulin-stimulated protein synthesis. Insulin activation of p70 S6 kinase was inhibited by approximately 75% in CHO cells and approximately 30% in 3T3-L1 adipocytes, whereas insulin-induced activation of endogenous Akt was inhibited by 80 to 95%, by expression of Akt-AA. Thus, Akt activity appears to be required, at least in part, for insulin stimulation of p70 S6 kinase. However, insulin-stimulated glucose uptake in both CHO cells and 3T3-L1 adipocytes was not affected by overexpression of Akt-AA, suggesting that Akt is not required for this effect of insulin. These data indicate that Akt acts as a downstream effector in some, but not all, of the signaling pathways downstream of PI 3-kinase.

3T3 Cells↗
PubMed1998

Expression of vascular endothelial growth factor in human oral squamous cell carcinoma: its association with tumour progression and p53 gene status.

AIMS: To correlate vascular endothelial growth factor (VEGF) expression in oral squamous cell carcinoma with the clinicopathological characteristics and prognosis; and to assess whether p53 gene status is associated with VEGF expression in human cancers. METHODS: Tumour specimens from 45 patients with oral squamous cell carcinomas were examined. Expression of VEGF was determined using an immunohistochemical method, and a tumour was considered positive when more than 5% of the neoplastic cells showed VEGF immunoreactivity. The p53 gene status was screened using a polymerase chain reaction--single strand conformation polymorphism analysis. RESULTS: VEGF positive staining was detected in 19 (42.2%) of the 45 cases. VEGF immunoreactivity did not correlate with the histological degree of tumour differentiation, clinical stages, or lymph node metastasis. The patients with VEGF positive tumours had a significantly worse prognosis than those with VEGF negative tumours. The five year overall survival rate of the VEGF negative patients was 76.5%, as compared with 48.8% for the VEGF positive patients. No significant association between VEGF expression and the p53 gene status of the tumours was found. CONCLUSIONS: VEGF is a good prognostic indicator of the survival of patients with oral squamous cell carcinoma. The p53 gene status does not seem to be associated with VEGF expression in these cancers.

Adult↗
PubMed1998

Extrahepatic arterial supply to the liver: observation with a unified CT and angiography system during temporary balloon occlusion of the proper hepatic artery.

PURPOSE: To evaluate routes of potential extrahepatic arterial supply to the liver. MATERIALS AND METHODS: Twenty-three patients with liver tumors underwent computed tomographic (CT) arteriography of extrahepatic arteries before and after temporary balloon occlusion of the proper hepatic artery. The right inferior phrenic artery (RIPA), left inferior phrenic artery (LIPA), superior mesenteric artery (SMA), celiac axis, and left gastric artery (LGA) were evaluated. RESULTS: During temporary balloon occlusion of the proper hepatic artery, extrahepatic arterial supply was immediately evident in 22 of 23 patients (96%). The liver was supplied by the RIPA in 17 of 20 patients (85%), by the LIPA in five of six (83%), by the SMA in eight of 16 (50%), by the celiac axis in two of 10 (20%), and by the LGA in one of six (17%). There was no apparent relationship between the enhanced zones supplied by extrahepatic arteries and the presence or absence of nearby tumors. CONCLUSION: Extrahepatic arterial supply to the liver was readily evident in a large proportion of patients during temporary balloon occlusion of the proper hepatic artery. This finding suggests a need for consideration of extrahepatic arterial supply when angiographic intervention for liver tumors is contemplated.

Aged↗
PubMed1998

Pulmonary embolism in patients with isolated soleal vein thrombosis.

This study investigated the features of calf deep vein thrombosis (DVT) as a pulmonary embolic source. Fifty-eight lower limbs in 29 patients who were suspected of having DVT distal to the popliteal vein were screened by ultrasonography. Then, ascending venography was performed to confirm the diagnosis. Pulmonary embolism (PE) was diagnosed in suspected patients by use of pulmonary perfusion scanning or pulmonary angiography. Venography revealed calf DVT in 33 limbs in 28 patients. Of 28 patients, six had symptomatic PE. Thrombosis was found in the muscle veins in 18 limbs, the trunk veins in 11, and both veins in four. Isolated single vein thrombosis was found in the soleal vein in 14 limbs (42%), the posterior tibial vein in eight, the peroneal vein in two, and the gastrocnemius vein in two. The overall percentage of soleal vein thrombi was 61%. All six patients with symptomatic PE had isolated soleal vein thromboses. Calf DVT was a pulmonary embolic source when isolated thrombosis of the large soleal vein was more than 7 mm in diameter. Soleal veins were the most frequent and important location of calf DVT, suggesting that these were an occasional embolic source of critical PE.

Aged↗
PubMed1998

Alterations in ultrastructural localization of growth-associated protein-43 (GAP-43) in periodontal Ruffini endings of rat molars during experimental tooth movement.

It is known that orthodontic forces induce discomfort and/or abnormal sensation after application of an orthodontic appliance in patients, suggesting the adaptation of periodontal neural elements to environmental changes. However, no morphological data have been provided. The present study investigated, by immunoelectron microscopy, the localization of growth-associated protein-43 (GAP-43) in periodontal Ruffini endings in rat molars during experimental tooth movement. In the untreated control group, immunoelectron microscopy demonstrated that GAP-43-like immunoreactivity in the Ruffini endings was confined to the Schwann sheaths around the axon terminals, and was in neither the cell bodies of terminal Schwann cells nor the axon terminals themselves. Immunoelectron microscopic observation revealed alterations in the localization of GAP-43-like immunoreactivity in the periodontal Ruffini endings during experimental tooth movement. After 1 day of treatment, the cell bodies of the terminal Schwann cells associated with Ruffini endings appeared to contain immunoreaction products for GAP-43, and retained GAP-43-like immunoreactivity during tooth movement. From 5 to 7 days, a major population of the axoplasm of the periodontal Ruffini endings, which was immunonegative in control, filled the GAP-43 immunoreactions, showing a tendency to decrease in number later, and disappeared completely at 14 days. These findings suggest that orthodontic forces easily induce the remodeling of the mechanoreceptive Ruffini endings as well as the active tissue remodeling in a close relationship. Since the ultrastructural localization of GAP-43-like immunoreactivity was drastically changed in the Ruffini endings during tooth movement, GAP-43 functions as one of the key molecules in the remodeling of mechanoreceptive Ruffini endings during tooth movement.

Acid Phosphatase↗