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H Takagi

Publications and source records attributed to H Takagi.

At least 235 records · Page 13Linked to original sources
PubMed1998

Identification of a novel adenylate kinase system in the brain: cloning of the fourth adenylate kinase.

We identify a novel subtype of adenylate kinase, which is the 4th adenylate kinase (AK4), in the vertebrate. AK4 mRNA is expressed in the mammalian central nervous system in a region-specific manner from the middle stage of embryogenesis to the adulthood in the rodent. The presence of three isozymes of adenylate kinase (AK1, AK2 and AK3) that maintains the homeostasis of adenine and guanine nucleotide composition has been reported in the vertebrate. Obtained mouse AK4 cDNA is 3667 bp in size. The predicted open reading frame consists of 223 amino acid residues. Rat AK4 cDNA is also obtained, and the predicted open reading frame is the same length as that of the mouse. The predicted rat AK4 molecule shows 97.8% homology with mouse AK4. Rat AK4 protein is distinct from rat AK3, 53.8% homologous with rat AK3, although the adenylate kinase signature and the mitochondrial energy transfer protein signature are found in both sequences. Interestingly, rat AK4 is 89.2% homologous with the human AK3 over 223 amino acid residues and rat AK3 is 53.7% homologous with the human AK3 indicating that the reported human AK3 actually belongs to the AK4 group (therefore, it should be referred to as human AK4). Although the sequence of AK4 is most similar to that of AK3 among the AK isozymes, its in vivo expression is completely different from AK3; AK4 mRNA is expressed in the pyramidal cells in the hippocampus (mainly in the subfield CA3), the granular cells in the cerebellum, nasal neuroepithelium and the liver while AK3 mRNA is expressed ubiquitously in the body. It is probable that AK4 acts on the specific mechanism of energy metabolism rather than control of the homeostasis of the ADP pool ubiquitously.

Adenylate Kinase↗
PubMed1998

Roles of A- and D-type K channels in EPSP integration at a model dendrite.

We examined the roles of A- and D-type K channels in the integration of EPSPs, particularly EPSP reduction, in a model dendrite using a computer simulation program (NEURON), instead of conventional electrophysiological methods which present technical difficulties. We obtained two important results: (1) KD channels play a crucial role in every synaptic input event, and (2) KA channels affect reduction of the second EPSP only when the second synaptic input is applied with a short interval (<100 ms). These results suggest that KD channels, which have not yet been analyzed experimentally, play a major role in synaptic integration in dendrites by altering their cable properties.

Animals↗
PubMed1998

Molecular cloning of the dnaK locus, and purification and characterization of a DnaK protein from Bacillus brevis HPD31.

Using part of the dnaK gene from Bacillus subtilis as a probe, a 4. 4-kbp SacI-BglII fragment of chromosomal DNA of Bacillus brevis, a protein-hypersecreting bacterium, was cloned. Nucleotide sequencing revealed 3 open reading frames in the order of grpE-dnaK-dnaJ homologues. We purified DnaK protein to homogeneity from B. brevis HPD31 harboring a multi-copy dnaK expression plasmid. Purified DnaK showed ATPase activity which was synergistically stimulated 14-fold by the addition of glutathione S-transferase-DnaJ and glutathione S-transferase-GrpE fusion proteins. DnaK hydrolyzed not only ATP but also CTP, UTP, and GTP at about 40% of the efficiency of ATP. The specific activity of DnaK-ATPase was 7.25x10-3 unit/mg protein (the turnover number against ATP was 0.47 min-1) under our assay conditions. The DnaK dimers dissociated into monomers on addition of ATP, GTP, CTP, UTP and ATPgammaS, but not ADP or AMP. DnaK formed a stable complex with permanently unfolded carboxymethylated alpha-lactalbumin but not with native alpha-lactalbumin, and this complex was dissociated by addition of ATP/Mg. Formation of this complex was inhibited in the presence of inorganic phosphate.

Adenosine Triphosphatases↗
PubMed1998

Cloning and heterogeneous in vivo expression of Tat binding protein-1 (TBP-1) in the mouse.

Tat binding protein-1 (TBP-1) is one of the molecules that interact with HIV Tat protein and have influence on Tat-mediated transactivation of HIV. In addition, TBP-1 has been recognized as a component of the 19S regulatory subunit of the multiprotein complex, the 26S proteasome, that is essential for many basic events in cells, e.g. cell cycle regulation, by degrading the ubiquitinized proteins. Here we have cloned a mouse TBP-1, confirmed its inhibitory action on Tat activity and revealed its in vivo heterogeneous expression pattern in the mouse. The cloned mouse TBP-1 cDNA is 1569 bp in size, longer than reported human TBP-1 cDNA, and another possible initiation site has been identified. Robust expression of TBP-1 mRNA can be observed in the testis, especially in the spermatogonia and spermatocytes. Our immunohistochemical study has revealed that TBP-1 is mainly localized in the nuclei of these testicular cells. Expression of TBP-1 mRNA in CD4+ lymphocytes is confirmed by RT-PCR. Localization of TBP-1 transcripts in vivo is similar to the reported distribution of constitutive components of the 20S proteasome. The heterogeneous and restricted expression of TBP-1 in vivo suggests that there may be a diverse reaction of tissues against the HIV proliferation and a diverse capability of tissues in degrading ubiquitinized proteins in vivo.

ATPases Associated with Diverse Cellular Activitie↗
PubMed1998

Localized unfolding at the junction of three ferritin subunits. A mechanism for iron release?

How and where iron exits from ferritin for cellular use is unknown. Twenty-four protein subunits create a cavity in ferritin where iron is concentrated >10(11)-fold as a mineral. Proline substitution for conserved leucine 134 (L134P) allowed normal assembly but increased iron exit rates. X-ray crystallography of H-L134P ferritin revealed localized unfolding at the 3-fold axis, also iron entry sites, consistent with shared use sites for iron exit and entry. The junction of three ferritin subunits appears to be a dynamic aperture with a "shutter" that cytoplasmic factors might open or close to regulate iron release in vivo.

Amino Acid Substitution↗
PubMed1998

Feasibility of double-expression retroviral vector using complement regulatory factor gene.

The donor source of vascular endothelial cells for hybrid blood vessels seeded with genetically engineered endothelial cells is generally considered to be autologous. The purpose of this study was to determine whether porcine endothelial cells transduced with double-expression retroviral vector using complement-resistant gene could be substituted for autologous endothelial cells. Decay-accelerating factor (DAF) and tissue plasminogen activator (tPA) cDNA were inserted into retroviral vector with homologous restriction factor 20 cDNA as a complement regulatory factor gene. Porcine aortic endothelial cells were transduced with these double-expression retroviral vectors, followed by the complement-dependent selection. Porcine endothelial cells transduced withdouble-expression retroviral vectors showed a high gene expression of both DAF and tPA. Complement-dependent cytotoxicity and adherence of U937 were significantly inhibited by the transduction of double-expression vectors with complement regulatory factor gene. Double-expression retroviral vector using complement regulatory factor gene was efficacious in substituting porcine endothelial cells for the autologous endothelial cells.

3T3 Cells↗
PubMed1998

Differential roles of two types of voltage-gated Ca2+ channels in the dendrites of rat cerebellar Purkinje neurons.

The distribution and function of voltage-gated Ca2+ channels in Purkinje neurons in rat cerebellar slices were studied using simultaneous Ca2+ imaging and whole-cell patch clamp recording techniques. Voltage-gated Ca2+ channels were activated by applying depolarizing voltage steps through the pipette attached at the soma in a voltage-clamp mode in the presence of tetrodotoxin. Poor space clamp due to extensive arborization of the dendrites allowed the dendrites to fire Ca2+ spikes. Ca2+ imaging with Fura-2 injected through the pipette, showed a steady [Ca2+]i increase at the soma and transient, spike-linked [Ca2+]i jumps in the dendrites. omega-Agatoxin-IVA (200 nM) abolished the depolarization-induced Ca2+ spikes, the spike-linked [Ca2+]i increase in the dendrites, and the steady [Ca2+]i increase at the soma. omega-Conotoxin-GVIA (5 microM) and nifedipine (3 microM) had no significant effect on the depolarization-induced responses. In the presence of 4-aminopyridine(2 mM) and omega-Agatoxin-IVA, transient [Ca2+]i increases remained in the dendrites. Low concentrations of Ni2+(100 microM) reversibly suppressed this [Ca2+]i increase. The voltage for half-maximal activation and inactivation of this component were lower than -50 mV and -31 mV, respectively. In normal conditions, low concentration of Ni2+ slowed the onset of the Ca2+ spike without changing the time course of the spikes or the amplitude of the accompanying [Ca2+]i increase. These results show that omega-Agatoxin-IVA-sensitive Ca2+ channels are distributed both in the soma and the dendrites, and are responsible for dendritic Ca2+ spikes, whereas low-voltage activated, Ni2+-sensitive Ca2+ channels are distributed in the whole dendrites including both thick and fine branches, and provide boosting current for spike generation.

Animals↗
PubMed1998

Angiotensin II potentiates vascular endothelial growth factor-induced angiogenic activity in retinal microcapillary endothelial cells.

Angiotensin II (Ang II) plays a role in the development of many vascular diseases. In the present study, we have investigated the effect of Ang II on vascular endothelial growth factor (VEGF) receptor expression and VEGF-induced angiogenic activity in bovine retinal microcapillary endothelial cells (BRECs). Ang II induced a significant increase of kinase domain-containing receptor/total liver kinase (KDR/Flk-1) mRNA in a time- and dose-dependent manner, with a maximal 4.3+/-0.8-fold increase after a 4-hour stimulation. Ang II increased the rate of KDR gene transcription by 5.4-fold, whereas the half-life of KDR mRNA was not increased significantly. The increase depended partially on new protein synthesis. The Ang II-induced KDR mRNA increase was inhibited by either [Sar1,Ile8]angiotensin or angiotensin type 1 receptor antagonists but was not significantly altered by angiotensin type 2 receptor antagonists. The PKC inhibitor reduced Ang II-induced KDR mRNA expression by 70+/-15%. The tyrosine kinase inhibitor reduced the Ang II- and phorbol 12-myristate 13-acetate-induced KDR mRNA increases by 35+/-8% and 44+/-26%, respectively. Ang II increased by 3.1-fold the 35S-labeled KDR/Flk-1 immunoprecipitated by a specific antibody to KDR/Flk-1. Scatchard analysis demonstrated that Ang II induced a significant increase of binding sites without changing binding affinity. Ang II enhanced VEGF-induced cell growth and tube formation. Ang II itself had no effect on cell growth, tube formation, or mRNA levels of VEGF and tms-like tyrosine kinase (Flt-1) in BRECs. These findings suggest that Ang II might potentiate VEGF-induced angiogenic activity through an increase of the VEGF receptor KDR/Flk-1.

Angiotensin II↗
PubMed1998

Deficiency in protein L-isoaspartyl methyltransferase results in a fatal progressive epilepsy.

Protein L-isoaspartyl methyltransferase (PIMT) is suggested to play a role in the repair of aged protein spontaneously incorporated with isoaspartyl residues. We generated PIMT-deficient mice by targeted disruption of the PIMT gene to elucidate the biological role of the gene in vivo. PIMT-deficient mice died from progressive epileptic seizures with grand mal and myoclonus between 4 and 12 weeks of age. An anticonvulsive drug, dipropylacetic acid (DPA), improved their survival but failed to cure the fatal outcome. L-Isoaspartatate, the putative substrate for PIMT, was increased ninefold in the brains of PIMT-deficient mice. The brains of PIMT-deficient mice started to enlarge after 4 weeks of age when the apical dendrites of pyramidal neurons in cerebral cortices showed aberrant arborizations with disorganized microtubules. We conclude that methylation of modified proteins with isoaspartyl residues is essential for the maintenance of a mature CNS and that a deficiency in PIMT results in fatal progressive epilepsy in mice.

Animals↗
PubMed1998

Increases in the mitochondrial DNA replication and transcription in the remnant liver of rats.

We studied mitochondrial DNA (mtDNA) replication and transcription in association with major hepatectomy. Changes in nuclear respiratory factor 1 (NRF-1) mRNA and RNA moiety of mitochondrial RNA-processing endoribonuclease (MRP-RNase RNA) were followed at 0, 3, 6, 12, and 24 h after hepatectomy. Contents of mtDNA, cytochrome b mRNA, and beta-actin mRNA were also measured. Contents of NRF-1 mRNA and MRP-RNase RNA increased to maximum or sub-maximum level 1 h after hepatectomy. mtDNA and cytochrome b mRNA increased to maximum level 3 h after. On the contrary, content of beta-actin mRNA increased to maximum level 12 h after. From these results, mtDNA replication and transcription occurred in the initial phase of liver regeneration, which might lead to an increase in mitochondrial respiratory function in the remnant liver, and cytoskeleton proteins such as beta-actin were followed thereafter.

Actins↗
PubMed1998

Single stranded DNA as an immunocytochemical marker for apoptotic change of ischemia in the gerbil hippocampus.

The light and electron microscopic localizations of single stranded DNA (SSD) protein, a marker of apoptosis and programmed cell death, in the gerbil hippocampus were examined by immunocytochemistry after transient brain ischemia. SSD-immunoreactive (IR) cells appeared from post-operative day 1 (PO 1) to PO 7 after 5- or 10-min ischemia. Immunoreaction was recognized in the nucleus of the CA1 pyramidal neurons without remarkable morphological changes on PO 1. These findings suggest that SSD degradation can occur during delayed neuronal death in the CA1, preceding the appearance of double strand breaks, one of the characteristic features of apoptosis.

Animals↗
PubMed1998

Involvement of adhesion molecules in metastasis of SW1990, human pancreatic cancer cells.

BACKGROUND AND OBJECTIVE: Peritoneal dissemination and hepatic metastasis commonly occur after patients with pancreatic cancer have undergone surgery. It is thought that specific adhesion molecules play corresponding roles in cancer metastasis. STUDY DESIGN/MATERIALS AND METHODS: We conducted in vitro and in vivo studies to assess the role of adhesion molecules in these processes, using SW1990 cells derived from human pancreatic cancer. RESULTS: SW1990 cells pronouncedly expressed sialyl Lewis(a) (s-Le[a]) and sialyl Lewis(x) antigens (s-Le[x]), CD44H, and beta1 integrin. Also, SW1990 cells showed a strong binding activity to IL-1beta activated human umbilical vein endothelial cells, cultured murine endothelial cells (F-2 cells), and human peritoneal mesothelial cells. Invasive ability of SW1990 cells to F-2 cells was also observed. The adhesion leading to implantation of cancer cells to endothelial cells were inhibited by treatment with the antibodies against s-Le(a) and against beta1 integrin, respectively. Treatments with the antibodies against s-Le(a) and beta1 integrin each inhibited the development of liver metastasis in nude mice with SW1990 cells. The adhesion of SW1990 cells to peritoneal mesothelial cells was markedly inhibited by antibodies each against CD44 or beta1 integrin, but was completely blocked by using a combination of these two antibodies. These antibodies inhibited the dissemination of SW1990 cells in the peritoneal cavity of nude mice and prolonged their survival. CONCLUSION: These findings suggest that s-Le(a) and integrin mediate the process from adhesion to implantation of SW1990 cells to endothelial cells, and CD44 and integrin play important roles in the initial attachment of SW1990 cells to mesothelial cells. It is thus speculated that compounds that interfere with the function of cell adhesion molecules may decrease the incidence of pancreatic cancer metastasis.

Animals↗
PubMed1998

Preoperative embolization therapy for esophageal operation.

BACKGROUND AND OBJECTIVES: Since 1993, we have performed preoperative embolization therapy (PET) in an attempt to augment the blood flow of the gastric tube and prevent anastomotic leakage after esophageal resection. The clinical effects and complications associated with PET are reported. METHODS: The femoral artery was punctured and the left gastric artery, right gastric artery, and splenic artery underwent embolization, leaving the right gastroepiploic artery as the only patent feeding artery for the stomach. PET was performed in 54 patients, and data concerning blood flow of the stomach before and after the construction of the gastric tube were available in 51 patients. Of the 25 patients who were operated in the same period without undergoing PET, similar data were available in 20 patients. RESULTS: In the group of patients who underwent PET, the blood flow of the gastric tube after its construction was 67% of the value measured at the upper part of the stomach just after opening the abdominal cavity. For those who were not pretreated by PET, it declined to 33%. CONCLUSIONS: PET for esophageal cancer is a safe procedure that contributes to the decrease in the frequency of anastomotic dehiscence after esophageal operation, owing to the augmented tissue blood flow of the upper portion of the stomach following the construction of gastric tubes.

Anastomosis, Surgical↗
PubMed1998

Increased expression of KDR/Flk-1 (VEGFR-2) in murine model of ischemia-induced retinal neovascularization.

Although the vascular endothelial growth factor (VEGF)/VEGF receptor system plays a critical role in the pathogenesis of ischemic retinal neovascular diseases such as diabetic retinopathy, regulation of VEGF receptor expression in ischemic retina has not been fully investigated in vivo. Accordingly, we studied the regulation of Flt-1 (VEGFR-1) and KDR/Flk-1 (VEGFR-2) expression in a mouse model of ischemia-induced retinal neovascularization. Immunohistochemistry for Flt-1 and KDR/Flk-1 revealed that, in hypoxic retina, the immunoreactivity of KDR/Flk-1 was increased in both intensity and extent of involvement in the vessels near the avascular area, particularly at the neovascular tufts, but that the pattern of Flt-1 expression in hypoxic retina was almost the same as that of control animals. The number of KDR/Flk-1-positive vessels was significantly increased in hypoxic retina (P < 0.01). In addition, expression of both Flt-1 and KDR/Flk-1 was observed in nonvascular cells of the neural retina. Northern blot analysis demonstrated that the mRNA levels of KDR/Flk-1 were greater in the neovascular retina of hypoxic animals than in control animals. We suggest that the increased expression of KDR/Flk-1 in vascular cells might potentiate the VEGF-mediated angiogenesis that accompanies many ischemic retinal diseases.

Animals↗
PubMed1998

Pharmacokinetics of serum glycerol and changes of ICP: comparison of gastric and duodenal administration.

To investigate the more effective route of oral administration of glycerol to decrease the raised ICP, two different routes were employed in the clinical practice. The one was through a Naso-Gastric tube, and the other was through an Entero-Duodenal tube. Pharmacokinetics of glycerol in relation to the decrease of ICP, and the changes of other parameters which could influence the serum osmotic pressure were sequentially monitored for initial 30 minutes. In the group of Entero-Duodenal route, the time to reach to the maximum glycerol concentration (Tmax) was faster, the maximum concentration of glycerol (Cmas) was higher, and ICP reduction rate was greater than these in the group of Naso-Gastric route. Other parameters (Na, K, BUN and Glucose) showed no significant difference between the two routes. It can be concluded that the Entero-Duodenal administration of glycerol is the more effective route to decrease the raised ICP, when it is administered orally.

Brain Injuries↗
PubMed1998

Parathyroid hormone suppression by 22-oxacalcitriol in the severe parathyroid hyperplasia.

The suppression of parathyroid hormone (PTH) secretion by the administration of 1,25-dihydroxyvitamin D [1,25(OH)2D3] and 22-oxacalcitriol (OCT) was evaluated in nude mice transplanted with human hyperplastic parathyroid tissue. The parathyroid tissue was obtained for transplantation from a patient with severe secondary hyperparathyroidism who had undergone a parathyroidectomy. Tissue specimens were transplanted into the gluteus muscle of female nude mice. Animals were divided into two groups; one group was fed a normal diet, and the other group was fed a low calcium diet during the administration of OCT and 1,25(OH)2D3. OCT and 1,25(OH)2D3 were intraperitoneally administered two times every week, for a total of eight times. Serum calcium and phosphate levels were significantly higher in the mouse administered 1,25(OH)2D3 than in the mouse administered OCT. Serum alkaline phosphatase activity was elevated similarly in the mouse administered either OCT or 1,25(OH)2D3. OCT strongly suppressed human PTH secretion from the graft in mice with normal serum calcium levels as did 1,25(OH)2D3. However, human PTH secretion from the graft was stimulated by the administration of a low-calcium diet, despite OCT and 1,25(OH)2D3 administration. In summary, OCT and 1,25(OH)2D3 suppress PTH secretion even from severe secondary hyperplastic parathyroid tissue only in mice with normal or high calcium serum levels.

Alkaline Phosphatase↗
PubMed1998

Combination splitting using both in situ and ex situ techniques in triple split liver transplantation in pigs.

In situ splitting of cadaver livers has been reported to reduce cold ischemic damage, to avoid biliary complications, and to result in improved graft survival. In this study, which involved a wider application of split liver transplantation (SLT), we examined the effects of a technique combining both ex situ and in situ splittings in triple SLT in pigs and compared it to ex situ splitting alone. In the combination splitting group, the splitting between the right and left lobes was done in situ with perfusion of the left lobe with cold, lactated Ringer's solution; that between the lateral and medical right lobes was done ex situ in backtable surgery. The time required for in situ splitting was 28 +/- 5 min. The time for backtable surgery and the total ischemia time were significantly shorter in the combination splitting group than that in the ex situ splitting group (P < 0.05). One day after triple SLT, the elevations in both serum AST and LDH in the ex situ splitting group were significantly greater than those in the combination splitting group (P < 0.05). We conclude that combination splitting may provide a technical improvement and have a beneficial effect on the clinical application of triple SLT.

Animals↗