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Biomedical subjects

T Yoshimoto

Publications and source records attributed to T Yoshimoto.

At least 307 records · Page 17Linked to original sources
PubMed1997

T2*-weighted magnetic resonance imaging of cerebrovascular reactivity in rat reversible focal cerebral ischemia.

Cerebrovascular carbon dioxide (CO2) reactivity is an important hemodynamic index in cerebrovascular disease. In the present study T2*-weighted magnetic resonance image (T2* WI) was evaluated as a non-invasive method to investigate changes in CO2 reactivity. Fourteen rats were subjected to permanent or, 30 and 90 min of temporary middle cerebral artery occlusion. A series of T2* WIs and diffusion-weighted magnetic resonance images (DWI) was performed hourly under normo- and hypercapnic conditions. Triphenyltetrazolium chloride (TTC) staining of brain sections was obtained at the end of experiment to evaluate ischemic damage. During ischemia, a 4-6% signal increase upon hypercapnia was observed on T2* WI in the non-ischemic hemisphere, while no such reactivity was seen in the putamen and cortex ipsilateral to the MCA occlusion. After reperfusion, CO2 reactivity recovered in the putamen and cortex in the 30 min ischemia group and in the cortex alone of the 90 min ischemia groups. The areas with irreversible CO2 reactivity dysfunction coincidentally revealed no recovery on DWI and lack of TTC staining. The results indicate that T2* WI can be used to monitor changes in CO2 reactivity after various ischemic insults that may indicate tissue viability.

Animals↗
PubMed1997

Epidermal growth factor enhances transcription of human arachidonate 12-lipoxygenase in A431 cells.

Epidermal growth factor (EGF), determined by immunoprecipitation and Western blot analysis, increased both enzyme activity and protein level of 12-lipoxygenase in the solubilized microsomes of human epidermoid carcinoma A431 cells, respectively. The EGF-induced expression of 12-lipoxygenase mRNA was inhibited by transcription inhibitors such as actinomycin D and 5,6-dichlorobenzimidazole riboside. Promoters of different lengths for human 12-lipoxygenase gene were used to prepare the luciferase fusion vectors. These construct plasmids were transiently transfected into A431 cells, and the induction of luciferase expression by EGF was examined. A 4- to 6-fold increase in luciferase reporter activity stimulated by EGF for 18 h treatment was observed in plasmids with the 5'-flanking region length of -951 bp and that of -224 bp upstream from translation starting site. The time-dependent induction of luciferase activity by EGF paralleled the EGF-induced enzyme activity and expression of 12-lipoxygenase protein. Taken together, the results of this study indicate that EGF enhanced the transcription of the human 12-lipoxygenase gene, resulting in an increase in the amount and activity of 12-lipoxygenase.

Arachidonate 12-Lipoxygenase↗
PubMed1997

Genetic defect in T lymphocyte-specific homing into peripheral lymph nodes.

Lymphocytes circulating in the bloodstream home into lymph nodes (LN). T cells predominate in peripheral LN (PLN) and B cells in spleen or mucosal tissue, e.g. Peyer's patches (PP). DDD/1 mice are unique in marked paucity of LN cells, especially T cells. T cell frequency in PLN was 20-40% in this strain, compared to 60-80% in others. Immunohistochemistry confirmed the low density of T cells in the subcortical area but normal colonization of B cells in cortical area in PLN of DDD/1. In contrast, the T cell content of peripheral blood and spleen was higher in DDD/1 but that in PP was not significantly different compared to other strains. It was thus concluded that this abnormality in DDD/1 results from a homing defect of T cells into PLN but not from lymphopenia. Genetical analysis showed that the defect in T cell-specific homing was regulated by a single autosomal recessive gene, tentatively designated plt (paucity of lymph node T cells). Reciprocal bone marrow transplantation indicated that the plt phenotype may arise from some defect in PLN stroma but not in lymphocytes. An in vivo homing assay using fluorescence-labeled lymphocytes demonstrated that the homing defect was specific for T cells but not for B cells. A Stamper-Woodruff assay revealed that the binding between lymphocytes and PLN high endothelial venules was normal and that L-selectin and its ligand, peripheral node vascular addressin (PNAd), were expressed and functioned normally in DDD/1. These results taken together indicate that the T cell-specific homing into PLN is disturbed at a post-adhesion stage in DDD/1. The product of the plt locus may play a pivotal role at this stage.

Animals↗
PubMed1997

Induction of interleukin-12 p40 transcript by CD40 ligation via activation of nuclear factor-kappaB.

Interleukin-12 is produced in response to infection with bacteria or parasites or to bacterial constituents such as LPS in monocytes/macrophages and dendritic cells, and also generated by the interaction between activated T cells and antigen-presenting cells via CD40-CD40 ligand (CD40L). So far, transcriptional analyses of p40 have been carried out only using bacterial constituents such as LPS as stimuli. In the present study, we have characterized the transcriptional induction of p40 by CD40 ligation in a human B lymphoblastoid cell line, Daudi, and a human acute monocytic leukemia cell line, THP-1. These cells, stimulated by an agonistic monoclonal antibody against CD40 or by transfection with a CD40L expression vector, secreted p40 and showed enhanced p40 mRNA expression. Sequence analysis of the p40 promoter region identified two potential nuclear factor (NF)-kappaB binding sites conserved between mouse and human. Electrophoretic mobility shift assay revealed that the potential NF-kappaB binding sequence which is located around 120 bp upstream of the transcription initiation site in murine and human p40 genes formed an NF-kappaB complex with nuclear extract from Daudi cells stimulated by CD40 ligation. Moreover, transfection of Daudi cells with the polymerized NF-kappaB binding sequence ligated to a thymidine kinase/chloramphenicol acetyltransferase (CAT) reporter plasmid greatly induced CAT activity, but transfection with the polymerized mutated NF-kappaB binding sequence did not. These results suggest that the NF-kappaB binding site located around 120 bp upstream of the transcription initiation site in murine and human p40 promoter regions could be important for the p40 induction by CD40 ligation via activation of NF-kappaB.

Animals↗
PubMed1997

Expression of mRNA for Akt, serine-threonine protein kinase, in the brain during development and its transient enhancement following axotomy of hypoglossal nerve.

By in situ hybridization histochemistry, expression of mRNAs for the two species of serine/ threonine protein kinase Akt, Akt1 and Akt2, were examined in the mouse brain during normal development and in the hypoglossal nucleus following axotomy. On the embryonic days, the gene expression for Akt1 and Akt2 was detected at high levels throughout the entire neuroaxis, then decreased gradually to adult levels during postnatal development. In the adult brain, the gene expression for Akt1 and Akt2 was weak in almost all neurons with no difference of expression levels. The expression level of Akt1 mRNA in the affected hypoglossal nucleus increased dramatically after 48 h to 7 d following axotomy of the hypoglossal nerve, whereas no change was seen in the level of Akt2 mRNA. The present findings suggest that Akt may contribute some important roles not only in neurogenesis, but also in regeneration of injured neuron.

Animals↗
PubMed1997

Dural arteriovenous shunt involving the superior petrosal sinus: presentation and treatment by transvenous embolisation via the occipital and transverse sinuses.

We report a dural arteriovenous shunt on the superior petrosal sinus at the origin of the petrosal vein, and its treatment. This is the first report of transvenous embolisation of such a shunt through the contralateral occipital and transverse sinuses. It was possible to achieve complete obliteration of the superior petrosal sinus shunt by coils and polyvinyl acetate liquid embolisation, in a combined venous and arterial approach.

Aged↗
PubMed1997

Perioperative factors related to the development of ischemic complications in patients with moyamoya disease.

In purpose of clarifying the risk factors of perioperative ischemic complications in cases with moyamoya disease, a retrospective study was conducted on the perioperative care of 36 patients who underwent vascular reconstruction for moyamoya disease. Following surgery, 8 patients developed ischemic complications (5 with minor completed strokes and 3 with transient ischemic attacks). Three factors including the presence of a preoperative low density area (LDA), intra-operative urinary output, and a reduction in the hematocrit significantly differed with complications and those without. In an evaluation of individual cases, intra-operative hypercapnia, hypotension, and a reduction in the circulating blood volume also were identified as potential factors associated with complications. On the basis of these findings, it was concluded that it is necessary to infuse an adequate amount of fluids, maintain normocapnic and normothermic states, and actively correct anemia in patients undergoing vascular reconstruction for moyamoya disease. It is also necessary to pay particular attention to perioperative care in patients in whom a LDA is detected by preoperative CT.

Adolescent↗
PubMed1997

Multiple intracranial mixed germ cell tumors.

A case of sequential occurrence of multiple intracranial mixed germ cell tumors is presented. An 8-year-old boy with a cystic calcified tumor in the basal ganglia and an increased serum alpha-fetoprotein concentration was initially treated with radiotherapy. Six years later, a tumor composed of embryonal carcinoma and immature teratoma arose from the right temporo-parietal lobe. This tumor was treated successfully with surgery and radiochemotherapy. The possibility of multicentricity or intra-axial metastasis distant from the original site during the long-term course should be considered in treatment for intracranial germ cell tumors.

Brain↗
PubMed1997

Induction of cytokines, chemokines and adhesion molecule mRNA in a rat forebrain reperfusion model.

Cellular damage secondary to reperfusion following ischemic insult has been hypothetically attributed to an inflammatory cascade concerted by cell-to-cell interactions. While the role of several cytokines and adhesion molecules in reperfusion injury of the brain has been explored to a certain extent, their regulatory and temporary profiles remain unclear. We have addressed the temporal features of the induction of mRNA for proinflammatory cytokines, adhesion molecules and chemokines at an acute phase subsequent to reperfusion in rat forebrain. Semiquantitatively calibrated reverse transcription-polymerase chain reaction analysis was employed to assess the relative expression of mRNA for intercellular adhesion molecule (ICAM)-1, interleukin (IL)-1 alpha, IL-1 beta, 1L-2, 1L-6, tumor necrosis factor (TNF)-alpha, interferon (IFN)-gamma, monocyte-chemoattractant protein (MCP)-1, and macrophage migration inhibitory factor (MIF). The increase in mRNA from the basal levels after reperfusion followed one of two different patterns; an increase occurring as early as 1 h, or a slight increase continuing up to 24 h after reperfusion. The former pattern was seen for ICAM-1, IL-1 alpha, IL-1 beta, TNF-alpha, and MCP-1, and the latter for IL-6 and MIF. These results were consistent with the proinflammatory properties of the immediately induced cytokines, which may be involved in the initiation step of the inflammatory cascade, causing the secondary cellular responses and finally leading to further brain damage.

Animals↗
PubMed1997

Intra-aneurysmal GDC embolization followed by intrathecal tPA administration for poor-grade basilar tip aneurysm.

BACKGROUND: This 42-year-old male presented with subarachnoid hemorrhage of Hunt and Kosnik Grade IV, complicated by neurogenic pulmonary edema, prolongation of the electrocardiographic Q-Q interval, and acute renal failure. METHODS: Surgical clipping was not indicated, so intra-aneurysmal embolization using Guglielmi detachable coils (GDCs) was performed followed by intrathecal infusion of tissue-type plasminogen activator (tPA) via spinal drainage. RESULTS: The patient made a complete recovery 2 1/2 months later except for partial third cranial nerve palsy. CONCLUSIONS: Intra-aneurysmal GDC embolization followed by intrathecal tPA via spinal drainage is an excellent method for treating aneurysms that are difficult to treat surgically.

Adult↗
PubMed1997

Importance of management of unruptured cerebral aneurysms.

BACKGROUND: Since excellent recovery is hardly expected in patients with severe subarachnoid hemorrhage, management of unruptured aneurysms is essential in reducing the overall mortality and morbidity rates. The widespread use of less invasive imaging tools such as magnetic resonance angiography (MRA) has made "Brain Check-up Systems" very popular in Japan. Therefore, unruptured aneurysms have been found much more often than before. METHODS: During the 1-year period of 1994, 80 patients underwent radical surgery for aneurysms in our institute. Thirty-two patients (40%) underwent surgery for unruptured aneurysms, while 48 patients (60%) underwent surgery for ruptured aneurysms. In patients with unruptured aneurysms, we have operated when the aneurysm is larger than approximately 5 mm in diameter, arising from the common sites in the circle of Willis, and when the patient's age is under 70 years. To prevent surgical complications in unruptured aneurysms, we often use a wrapping technique with Bemsheets (cotton) and adhesives. RESULTS: The outcomes were good in all 32 cases of unruptured aneurysms. CONCLUSIONS: We believe that early detection and prophylactic surgery for unruptured aneurysms will improve the overall outcome of aneurysm treatment in the future.

Aged↗
PubMed1997

Combined intravascular parent artery and ophthalmic artery occlusion for giant aneurysms of the supraclinoid internal carotid artery.

BACKGROUND: Parent artery occlusion is an effective method to treat internal carotid giant aneurysms. However, incomplete parent artery occlusion may cause revascularization. Here, a modification of the parent artery occlusion procedure for giant aneurysms of the internal carotid artery is described. METHODS: Three patients with giant aneurysms of the internal carotid artery at the supraclinoid portion between the origin of the ophthalmic artery and the posterior communicating artery were treated by a combination of parent artery occlusion and occlusion of the origin of the ophthalmic artery. All patients had a giant aneurysm that manifested as cranial nerve palsy due to mass effect. RESULTS: A balloon occlusion test of the ipsilateral internal carotid artery together with the ophthalmic artery showed that permanent occlusion was tolerable. It was confirmed that the ipsilateral eye was supplied by maxilloophthalmic anastomosis instead of the ophthalmic artery. Cranial nerve palsy and visual acuity were markedly improved in two cases after the therapy. Follow-up selective internal and external carotid angiography did not demonstrate the aneurysm. CONCLUSIONS: Combined parent artery and ophthalmic artery occlusion is an effective treatment for a giant aneurysm located between the ophthalmic artery and the posterior communicating artery.

Adult↗
PubMed1997

Vasoreconstructive surgery for radiation-induced vasculopathy in childhood.

BACKGROUND: Cerebral vasculopathy associated with the appearance of netlike vessels can develop following irradiation therapy for parasellar brain tumors, especially in children. However, little is known regarding the clinical course of this disease or the appropriate therapy for it. CASE REPORTS: We experienced two surgically-treated patients with radiation-induced vasculopathy and reviewed the previously reported cases. Both of our patients were treated with encephalo-duro-arterio-myo-synangiosis combined with superficial temporal artery to middle cerebral artery (STA-MCA) bypass. Their ischemic symptoms improved following the surgery, associated with a good angiographic neovascularization from the STA-MCA bypass, as well as dural and muscular arteries. CONCLUSION: Our findings and the review of the previous reports suggested that surgical therapy may be beneficial for the patients with radiation-induced vasculopathy with the appearance of netlike vessels.

Brain Ischemia↗
PubMed1997

Low cerebral blood flow and perfusion reserve induce hyperperfusion after surgical revascularization: case reports and analysis of cerebral hemodynamics.

BACKGROUND: Hyperperfusion syndrome after surgical revascularization is a rare complication and there has not been any systematic study on factors that induce hyperperfusion after surgery. In this paper, we retrospectively analyzed the factors related to this syndrome. PATIENTS AND METHODS: We performed 46 cases of surgical revascularization including 33 cases of carotid endarterectomy (CEA) and 13 cases of superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis during the past 5 years. Among these, we encountered three cases of hyperperfusion syndrome despite well-controlled blood pressure postoperatively. To evaluate factors related to the occurrence of hyperperfusion syndrome, we examined four parameters: (1) regional cerebral blood flow (rCBF), (2) the increase in the ratio of the postoperative rCBF compared to the preoperative rCBF (increase ratio), (3) cerebral perfusion reserve presented by the increase of rCBF after acetazolamide administration (delta rCBF), and (4) the difference in mean blood pressure between the preoperative and postoperative state (delta BP). RESULTS: Preoperative rCBF was significantly lower in cases of hyperperfusion syndrome than the control cases (p < 0.01 Mann-Whitney U-test). Moreover delta rCBF was evidently lower in the hyperperfusion cases than the control (p < 0.05 Fisher's exact method). However, there was no significant difference in the delta BP between the hyperperfusion cases and the control cases. CONCLUSION: In cases of marked low perfusion (low rCBF) with poor perfusion reserve (low delta rCBF), hyperperfusion after surgical revascularization can occur even if blood pressure is adequately controlled.

Aged↗
PubMed1997

Localization of mRNA for fatty acid transport protein in developing and mature brain of rats.

Gene expression for rat fatty acid transport protein (FATP) and fatty acid translocase (FAT) were examined by Northern and in situ hybridization analysis. In Northern blot analysis of developing brain, FATP mRNA was detected weakly throughout all developing stages without any changes in the expression level, while no gene expression for FAT mRNA was detected at any stages. By in situ hybridization histochemistry, intense expression was seen in the ventricular germinal zone on pre- and perinatal stages, whereas distinct expression was observed in the cerebellar Purkinje and granule cell during postpostnatal development. No expression was detected in the cerebellar external granule cell layer. Because of the high expression of FATP mRNA in the embryonic ventricular zone and the postnatal cerebellar cortical neurons in parallel to the gene expression for fatty acid binding protein (FABP) which we have recently reported, co-operated involvement of FATP and FABP in the active uptake of long-chain fatty acids is plausible in these cells.

Amino Acid Sequence↗