Search PubMed⌕ Search

Biomedical subjects

H Hatanaka

Publications and source records attributed to H Hatanaka.

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

The neurotrophic action and signalling of epidermal growth factor.

Epidermal growth factor (EGF) is a conventional mitogenic factor that stimulates the proliferation of various types of cells including epithelial cells and fibroblasts. EGF binds to and activates the EGF receptor (EGFR), which initiates intracellular signalling and subsequent effects. The EGFR is expressed in neurons of the cerebral cortex, cerebellum, and hippocampus in addition to other regions of the central nervous system (CNS). In addition, EGF is also expressed in various regions of the CNS. Therefore, EGF acts not only on mitotic cells, but also on postmitotic neurons. In fact, many studies have indicated that EGF has neurotrophic or neuromodulatory effects on various types of neurons in the CNS. For example, EGF acts directly on cultured cerebral cortical and cerebellar neurons, enhancing neurite outgrowth and survival. On the other hand, EGF also acts on other cell types, including septal cholinergic and mesencephalic dopaminergic neurons, indirectly through glial cells. Evidence of the effects of EGF on neurons in the CNS is accumulating, but the mechanisms of action remain essentially unknown. EGF-induced signalling in mitotic cells is better understood than that in postmitotic neurons. Studies of cloned pheochromocytoma PC12 cells and cultured cerebral cortical neurons have suggested that the EGF-induced neurotrophic actions are mediated by sustained activation of the EGFR and mitogen-activated protein kinase (MAPK) in response to EGF. The sustained intracellular signalling correlates with the decreased rate of EGFR down-regulation, which might determine the response of neuronal cells to EGF. It is likely that EGF is a multi-potent growth factor that acts upon various types of cells including mitotic cells and postmitotic neurons.

Animals↗
PubMed1997

Boron neutron capture therapy. Clinical brain tumor studies.

Since 1968, we have treated 149 patients and performed boron-neutron capture therapy (BNCT) on 164 occasions using 5 reactors in Japan. There were 64 patients with glioblastoma, 39 patients with anaplastic astrocytoma and 17 patients with low grade astrocytoma (grade 1 or 2). There were 30 patients with other types of tumor. The overall response rate in the glioma patients was 64%. Seven patients (12%) of glioblastoma, 22 patients (56%) of anaplastic astrocytoma and 8 patients (62%) of low grade astrocytoma lived more than 2 years. Median survival time of glioblastoma was 640 days. Median survival times of patients with anaplastic astrocytoma was 1811 days, and 1669 days in low grade astrocytoma. Six patients (5 glioblastoma and one anaplastic astrocytoma) died within 90 days after BNCT. Six patients (two glioblastoma and four anaplastic astrocytomas) lived more than 10 years. Histological grading, age of the patients, neutron fluence at the target point and target depth or size of the tumor were proved to be important factors. BNCT is an effective treatment for malignant brain tumors. We are now able to radiate the tumor more correctly with a high enough dose of neutron beam, even if we use thermal neutron beam.

Adult↗
PubMed1997

Pharmacokinetics and boron uptake of BSH (Na2B12H11SH) in patients with intracranial tumors.

We evaluated retrospectively the pharmacokinetics and boron uptake of BSH (mercaptoundecahydrododecarborate) for Boron Neutron Capture Therapy (BNCT) in 123 patients undergoing craniotomy for intracranial tumors. The pharmacokinetics revealed that BSH could move easily from blood to the peripheral organs; it was retained there and elimination was very slow. BSH after intra-arterial infusion (i.a.) was found to move into the peripheral organs more easily than after intra-venous (i.v.) infusion. In patients with malignant glioma, the average values of boron concentration in tumor and the tumor to blood ratio (T/B ratio) after i.a. infusion were 26.8 +/- 19.5 micrograms/g (range, 6.1-104.7 micrograms/g) and 1.77 +/- 1.30 (range, 0.47-6.65) respectively. On the other hand, after i.v. infusion the values were 20.9 +/- 12.2 micrograms/g (range, 7.0-39.7 micrograms/g) and 1.30 +/- 0.65 (range, 0.61-2.94) respectively. The differences are not statistically significant. Boron uptake in malignant glioma was about three times higher than low grade glioma. We found a good correlation between boron uptake and time interval from BSH infusion, and 15-20 hours after BSH infusion the boron concentration in tumor was above 20 micrograms/g 10B in 69% of the malignant glioma patients; T/B ratio was above one in 75%, and above two in 44% of them. We recommend intra-venous infusion of BSH clinically since it is safer, and results in sufficient boron concentration in tumor, and the planned irradiation might be optimal around 15-20 hours after the BSH infusion for treating malignant glioma.

Adolescent↗
PubMed1997

Conformation of an Shc-derived phosphotyrosine-containing peptide complexed with the Grb2 SH2 domain.

We have determined the structure of an Shc-derived phosphotyrosine-containing peptide complexed with Grb2 SH2 based on intra- and intermolecular NOE correlations observed by a series of isotope-filtered NMR experiments using a PFG z-filter. In contrast to an extended conformation of phosphotyrosine-containing peptides bound to Src, Syp and PLC gamma SH2s, the Shc-derived peptide formed a turn at the +1 and +2 positions next to the phosphotyrosine residue. Trp121, located at the EF1 site of Grb2 SH2, blocked the peptide binding in an extended conformation. The present study confirms that each phosphotyrosine-containing peptide binds to the cognate SH2 with a specific conformation, which gives the structural basis for the binding specificity between SH2s and target proteins.

Adaptor Proteins, Signal Transducing↗
PubMed1997

Brain-derived neurotrophic factor increases the stimulation-evoked release of glutamate and the levels of exocytosis-associated proteins in cultured cortical neurons from embryonic rats.

Differentiation and survival of neurons induced by neurotrophins have been widely investigated, but little has been reported about the long-term effect of brain-derived neurotrophic factor (BDNF) on synaptic transmission. Among many steps of neurotransmission, one important step is regulated release of transmitters. Therefore, the release of glutamate and GABA from cortical neurons cultured for several days with or without BDNF was measured by an HPLC-fluorescence method. Although BDNF had little effect on the basal release of glutamate, high K(+)-evoked release was greatly increased by BDNF. BDNF also tended to increase evoked release of GABA. Recently, several proteins involved in the step of "regulated release" have been identified. Thus, the effect of BDNF on the levels of these proteins was then investigated. Neurons were cultivated with or without BDNF, collected, and electrophoresed for western blotting. BDNF increased levels of synaptotagmin, synaptobrevin, synaptophysin, and rab3A, which were known as vesicle protein. Levels of syntaxin, SNAP-25, and beta-SNAP were also increased by BDNF. In addition, the numbers of cored and clear vesicles in nerve terminals or varicosities were also increased by BDNF. These results raise the possibility that BDNF increases regulated release of neurotransmitters through the up-regulation of secretory mechanisms.

Animals↗
PubMed1997

Loss of the xeroderma pigmentosum group A gene (XPA) enhances apoptosis of cultured cerebellar neurons induced by UV but not by low-K+ medium.

To study the involvement of the xeroderma pigmentosum group A gene (XPA) in neuronal apoptosis, we cultured cerebellar neurons from mice lacking XPA gene (XPA-/-) and induced apoptosis by exposure to UV irradiation or medium containing a low concentration of potassium (low-K+ medium). When cerebellar neurons from postnatal days 15-16 wild-type mice were treated with UV irradiation, apoptotic neuronal death was observed after 24-48 h. About 60% of neurons survived 48 h after UV irradiation at a dose of 5 J/m2. On the other hand, neurons from XPA-/- mice showed a significantly increased vulnerability to UV irradiation, and >90% of neurons died 48 h after UV irradiation at a dose of 5 J/m2. In contrast, low-K+ medium induced apoptosis of neurons from mice of each genotype with the same kinetics. These results suggest that the XPA gene is involved in neuronal DNA repair and that it thereby influences apoptosis induced by DNA damage in cultured cerebellar neurons.

Animals↗
PubMed1997

[Discovery and development of a novel immunosuppressant, tacrolimus hydrate].

Tacrolimus hydrate (FK506), a novel 23-membered macrolide, is an immunosuppressant isolated from Streptomyces tsukubaensis using extensive screening of fermentation products to identify a compound inhibiting the mixed lymphocyte reaction (MLR). The in vitro and in vivo immunosuppressive activities of FK506 were found to be more potent than those of cyclosporine (CyA). The superior immunosuppression with FK506 treatment was also confirmed in the skin allograft model in rats and liver transplantation in dogs. Clinical studies were initiated by Prof. Starzl at the University of Pittsburgh in 1989, and he demonstrated that FK506 surpassed CyA in the incidence of graft survival and the frequency of graft rejection. Multicenter randomized clinical studies, comparing FK506 to CyA corroborated the efficacy of FK506 on the survival of patients and of grafts, and especially on the appearance of severe refractory graft rejection. FK506 was marketed in 1993 in Japan, and was followed in 1994 in the U.S.A., U.K. and Germany. The mechanism of action of this compound was clarified by the endeavors of Prof. Schreiber, who demonstrated the existence of a binding protein for FK506 called FKBP, similar to cyclophilin for CyA. The FK506/FKBP complex binds with calcineurin, a serine/threonine phosphatase to inhibit the translocation of NFAT into the nucleus, resulting in inhibition of transcription of IL-2 mRNA. FK506 displays potent immunosuppressant activity, and contributes not only to the progress of transplantation therapy for clinical studies, but also to the clarification of signal transduction in T cell activation for basic science.

Animals↗
PubMed1997

[Immunosuppressive activity of a microbial product].

Microbial products have amazing diversity and complexity in their chemical structures as well as in their biological activities. The successful discovery and development of FK506 (Tacrolimus) adds a new example showing that microbial products are agents with potential therapeutic benefits. In 1984, we found a novel immunosuppressant FK506 during the course of our research program for discovery of specific inhibitors on IL-2 production in the microbial products. FK506, a new class of 23-membered macrolide lactone, was isolated the fermentation broth of Streptomyces tsukubaensis No.9993. This agent strongly inhibited the proliferative response of lymphocytes to alloantigen stimulation, and a variety of T cell associated immune reaction. FK506 also suppressed immune responses in vivo as well as in vitro and this immunosuppressive effect was more highly potent than cyclosporin, a well-known fungal metabolite. The profound immunosuppressive properties of FK506 were subsequently explored in organ transplantation in animal models. Clinical trials of FK506 were begun in 1989 by Professor Stazl and his colleagues at the University of Pittsburgh. Since then wider evaluation of FK506 in a variety of transplantation fields has been performed globally; in North America, Europe and Japan. In 1993, FK506 was commercialized in Japan for prevention of liver transplant rejection. FK506 is also undergoing extensive evaluation as an agent for the treatment of various autoimmune diseases.

Animals↗
PubMed1996

Signaling pathways and survival effects of BDNF and NT-3 on cultured cerebellar granule cells.

We investigated the signaling pathways exerted by brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) in relation to their survival-promoting effects on dissociated cultures of cerebellar granule cells prepared from postnatal 9-day-old rats. Granule neuron survival in culture was supported by BDNF, but not significantly by either nerve growth factor (NGF) or NT-3. BDNF and NT-3 resulted in not only the respective autophosphorylation of the Trk receptors, TrkB or TrkC, but also tyrosine phosphorylation of SHC, a protein involved in controlling p21ras activity, and phosphatidylinositol-3' (PI-3') kinase. NGF does not result in TrkA phosphorylation. In parallel, c-fos was induced within 30 min, in response to BDNF and NT-3. NT-3 induced the phosphorylation of these proteins to a lesser extent than BDNF. BDNF also induced the tyrosine phosphorylation of phospholipase C gamma (PLC gamma), but the NT-3-induced one was not detected. We postulate that no survival promotion by NT-3 is due to lesser level of trkC expression and of the NT-3-induced signaling in the cultured cerebellar granule neurons. Wortmannin, a specific inhibitor of PI-3' inhibited the BDNF effect on neuronal survival. PI-3' kinase-dependent pathways might be involved in the promotion of cerebellar granule cell survival by BDNF.

Adaptor Proteins, Signal Transducing↗
PubMed1996

Expression of cyclin A decreases during neuronal apoptosis in cultured rat cerebellar granule neurons.

Cultured cerebellar granule neurons died in an apoptotic manner when the K+ concentration in culture medium was lowered to the normal level (5 mM) after maturation of cells with a high concentration of K+ (26 mM). The changes in expression of 14 cell cycle-related genes in this CNS apoptosis model were analyzed by quantitative RT-PCR. Most of the genes analyzed were stable during apoptosis. The expression of cyclin A mRNA, however, transiently decreased 1 h after the induction of apoptosis, and recovered within 3 h to above the basal level. In this system, the level of cyclin D1, which has been reported to be up-regulated in apoptosis of NGF-deprived cultured sympathetic neurons, did not change. These results suggest that the molecular mechanisms in these two apoptosis models are different. To determine cyclin A protein level, we used an immunostaining method. The number of cyclin A-positive neurons decreased during apoptosis. Moreover, the numbers of MAP2- and cdk2-positive neurons also decreased in a similar manner. Taken together, these results suggest that there is a relationship between apoptosis and cell cycle, and that morphological changes during apoptosis result from cytoskeletal structure degradation.

Age Factors↗
PubMed1996

Oxygen-induced apoptosis in PC12 cells with special reference to the role of Bcl-2.

We previously reported that PC12h cells are killed by a high oxygen atmosphere. In this study, we further characterized this oxygen-induced cell death and found apoptotic features, as follows. Firstly, chromatin condensation was observed in cells cultured in a 50% O2 atmosphere. Secondly, cycloheximide and cordycepin, protein and RNA synthesis inhibitors, respectively, prevented the oxygen-induced cell death in PC12h cells, suggesting that it is mediated by an intracellular death program. Thirdly, NGF, CPT-cAMP and depolarization by high potassium medium also effectively inhibited this apoptotic cell death in PC12h cells. The effect of high K+ is thought to be mediated by the influx of Ca2+ into cells through voltage-dependent Ca2+ channels, because nifedipine, an L-type Ca2+ channel blocker, inhibited the effect of high K+. In addition, since the oxygen-induced apoptosis was blocked by the antioxidant vitamin E, this oxygen toxicity is suggested to be mediated by reactive oxygen species. To further characterize this oxygen-induced apoptosis at the molecular level, we used PC12 cells overexpressing the proto-oncogene bcl-2. Although a large number of PC12 cells transfected with the control vector died in a 50% O2 atmosphere within 6 days, bcl-2-transfected PC12 cells survived and proliferated. These findings suggested that our system using PC12 cells will be a useful model with which to analyze the molecular mechanisms of apoptosis induced by oxidative stress in neuronal cells.

Animals↗
PubMed1996

Survival factor-insensitive generation of reactive oxygen species induced by serum deprivation in neuronal cells.

To investigate the involvement of reactive oxygen species (ROS) in neuronal apoptosis, we performed confocal and flow cytometric analysis with a ROS-specific fluorogen, 6-carboxy-2', 7'-dichorodihydrofluorescein diacetate, di(acetoxymethyl ester) (C-DCDHF-DA). Serum deprivation significantly increased the level of ROS in PC12 cells and rat cortical neurons. N,N'-diphenyl-p-phenylenediamine (DPPD), an antioxidant, reduced ROS production induced by serum deprivation and recovered cell survival. However, some survival factors such as nerve growth factor and Bcl-2, which prevented the apoptosis of PC12 cells, did not affect the up-regulation of ROS induced by serum deprivation. Epidermal growth factor which prevented the apoptosis of cortical neurons, did not affect the increase of ROS. These data suggest that survival factors rescue the serum deprivation induced apoptosis independently of ROS production.

Animals↗
PubMed1996

Solution structure of the link module: a hyaluronan-binding domain involved in extracellular matrix stability and cell migration.

Link modules are hyaluronan-binding domains found in proteins involved in the assembly of extracellular matrix, cell adhesion, and migration. The solution structure of the Link module from human TSG-6 was determined and found to consist of two alpha helices and two antiparallel beta sheets arranged around a large hydrophobic core. This defines the consensus fold for the Link module superfamily, which includes CD44, cartilage link protein, and aggrecan. The TSG-6 Link module was shown to interact with hyaluronan, and a putative binding surface was identified on the structure. A structural database search revealed close similarity between the Link module and the C-type lectin domain, with the predicted hyaluronan-binding site at an analogous position to the carbohydrate-binding pocket in E-selectin.

Amino Acid Sequence↗
PubMed1996

Tertiary structure of destrin and structural similarity between two actin-regulating protein families.

Destrin is an isoprotein of cofilin that regulates actin cytoskeleton in various eukaryotes. We determined the tertiary structure of destrin by triple-resonance multidimensional nuclear magnetic resonance. In spite of there being no significant amino acid sequence homology, we found that the folding of destrin was strikingly similar to that of repeated segments in the gelsolin family, which resulted in a new protein fold group. Sequential dissimilarity of the actin-binding helix of destrin to that of gelsolin explains the Ca2+-independent actin-binding of destrin. Possible mechanisms of phosphorylation-sensitive phosphoinositide-competitive actin binding, of pH-dependent filament severing, and of nuclear translocation with actin in response to stresses, are discussed on the basis of the tertiary structure.

Actin Depolymerizing Factors↗