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T Izumi

Publications and source records attributed to T Izumi.

At least 19 recordsLinked to original sources
PubMed1992

Three types of Gi alpha protein of the guinea-pig lung: cDNA cloning and analysis of their tissue distribution.

cDNA clones encoding three types of Gi alpha, the alpha subunit of GTP-binding protein (Gi1 alpha, Gi2 alpha, and Gi3 alpha), were isolated from a cDNA library of the guinea-pig lung. Nucleotide sequence analysis revealed a high degree of homology with other mammalian Gi alpha cDNAs. By RNA blot analysis, the expression pattern of Gi1 alpha was more tissue-specific than those of other types of Gi alphas in the guinea-pig tissues examined. While Gi2 alpha and Gi3 alpha mRNAs were ubiquitously expressed in all tissues examined, Gi1 alpha mRNA was mainly expressed in the brain, lung and kidney. These results suggest that each Gi alpha protein may have a different role.

Amino Acid Sequence↗
PubMed1992

Biphasic activation of two mitogen-activated protein kinases during the cell cycle in mammalian cells.

We studied mitogen-activated protein kinase (MAPK) activities during the cell cycle of Chinese hamster ovary (CHO) cells using site-specific antibodies against extracellular signal-regulated kinase-1, a 44-kDa MAPK (Boulton, T.G., Yancopoulos, G.D., Gregory, J.S., Slauer, C., Moomaw, C., Hsu, J., and Cobb, M.H. (1990) Science 249, 64-67). These antibodies detected two distinct MAPKs (44- and 42-kDa MAPKs) in CHO cells. CHO cells were arrested at metaphase in the M phase by treatment with nocodazole, and activities of MAPKs were analyzed at specific time points after release from arrest. Immune complex kinase assay and renaturation and phosphorylation assay in substrate-containing gel revealed that both 44- and 42-kDa MAPKs had activities in the G1 through S and G2/M phases and were activated biphasically, in the G1 phase and around the M phase. MAPKs were inactivated in metaphase-arrested cells. The amount of MAPKs did not change significantly in the cell cycle. In the G1, S, and G2/M phases, MAPKs were phosphorylated on both tyrosine and threonine residues and dephosphorylated in metaphase-arrested cells. Our data suggest that MAPKs may play some role in the cell cycle other than G0/G1 transition.

Amino Acid Sequence↗
PubMed1992

Leukotriene A4 hydrolase, a bifunctional enzyme. Distinction of leukotriene A4 hydrolase and aminopeptidase activities by site-directed mutagenesis at Glu-297.

We previously obtained evidence for intrinsic aminopeptidase activity for leukotriene (LT)A4 hydrolase, an enzyme characterized to specifically catalyse the hydrolysis of LTA4 to LTB4, a chemotactic compound. From a sequence homology search between LTA4 hydrolase and several aminopeptidases, it became clear that they share a putative active site for known aminopeptidases and a zinc binding domain. Thus, Glu-297 of LTA4 hydrolase is a candidate for the active site of its aminopeptidase activity, while His-296, His-300 and Glu-319 appear to constitute a zinc binding site. To determine whether or not this putative active site is also essential to LTA4 hydrolase activity, site-directed mutagenesis experiments were carried out. Glu-297 was mutated into 4 different amino acids. The mutant E297Q (Glu changed to Gln) conserved LTA4 hydrolase activity but showed little aminopeptidase activity. Other mutants at Glu-297 (E297A, E297D and E297K) showed markedly reduced amounts of both activities. It is thus proposed that either a glutamic or glutamine moiety at 297 is required for full LTA4 hydrolase activity, while the free carboxylic acid of glutamic acid is essential for aminopeptidase.

Amino Acid Sequence↗
PubMed1992

Transforming growth factor beta 1 stimulates type II collagen expression in cultured periosteum-derived cells.

Chondrogenesis can occur during a bone repair process, which is related to several growth factors. Transforming growth factor beta 1 (TGF-beta 1) downregulates the expression of type II collagen by chondrocytes in vitro, but injection of TGF-beta 1 into the periosteum in vivo increases type II collagen mRNA levels and initiates chondrogenesis. We examined the effect of TGF-beta 1 on collagen gene expression in a bovine periosteum-derived cell culture system to evaluate its direct effect on the periosteum. Cultured cells expressed alkaline phosphatase and collagen pro alpha 1(I) and pro alpha 1(II) mRNAs. A low level of type II collagen synthesis was demonstrated by immunoprecipitation. TGF-beta 1 had no effect on periosteal cell proliferation. Expression of collagen pro alpha 1(I) mRNA did not change with TGF-beta 1 treatment, but alkaline phosphatase mRNA showed a dose-dependent decrease. Expression of collagen pro alpha 1(II) mRNA was stimulated 2.7-fold by TGF-beta 1. TGF-beta 1 also caused a 2.6-fold increase in type II collagen synthesis by immunoprecipitation. These findings indicate that TGF-beta 1 is an enhancer of the expression of the chondrocyte phenotype of the periosteal cells and suggest that TGF-beta 1 is important in initiating and promoting cartilage formation in vivo.

Alkaline Phosphatase↗
PubMed1992

Balloon catheter with check valves for experimental relief of acute aortic regurgitation.

To evaluate the ability of a newly designed balloon catheter with check valves to temporarily relieve hemodynamic deterioration in acute aortic regurgitation, we produced an experimental model of acute aortic regurgitation in closed-chest dogs using endomyocardial biopsy forceps. Aortic regurgitation was produced until an increase in aortic pulse pressure of over 50% was achieved. Left ventricular end-diastolic pressure rapidly increased after the production of aortic regurgitation. Immediately after the catheter began functioning, pulse pressure decreased from 133 +/- 1 to 78 +/- 5 mm Hg (mean +/- SEM) and left ventricular end-diastolic pressure also decreased from 26 +/- 1 to 13 +/- 1 mm Hg. These effects lasted as long as the catheter functioned. Although a mild (21 +/- 8 mm Hg) pressure gradient between the left ventricular peak systolic pressure and the aortic peak systolic pressure was observed when this catheter was used, forward stroke volume was no less than in the group in which the catheter had not been used. These findings suggest that the balloon catheter with check valves may effectively reduce aortic regurgitation.

Animals↗
PubMed1992

An immunosuppressant compound, FK-506, prevents the progression of autoimmune myocarditis in rats.

A new immunosuppressive compound, FK-506, is a macrolide produced by Streptomyces tsukubaensis. It is reported that FK-506 prolongs the viability of allogenic grafts of the heart and kidney in vivo and inhibits the development of autoimmune diseases. Furthermore, immunosuppressive therapy of myocarditis in humans has been given special attention by various observers; however, it is controversial. This study investigates the effects of FK-506 on experimental autoimmune myocarditis in rats. We performed two experiments. In Experiment 1, FK-506 was given intramuscularly on Days 11-20 after the first immunization. The rats were immunized twice (on Day 0 and Day 7). They were injected subcutaneously in the footpads with 1.0 mg of human cardiac myosin in equal volumes of complete Freund's adjuvant supplemented with Mycobacterium tuberculosis. They were divided into four groups: Control (six rats, saline), group 1 (six rats, FK-506: 0.1 mg/kg/day), group 2 (seven rats, FK-506: 0.32 mg/kg/day), and group 3 (six rats, FK-506: 1.0 mg/kg/day). To investigate the histologic extent of myocarditis, we formulated a histologic score (0-3). Histologic scores were: Control, 1.90 +/- 0.14; group 1, 0.97 +/- 0.46; group 2, 0.03 +/- 0.05; and group 3, 0 +/- 0. The indices of heart weight/body weight were: Control, 0.74 +/- 0.10%; group 1, 0.45 +/- 0.05%; group 2, 0.35 +/- 0.03%; and group 3, 0.35 +/- 0.03%. In Experiment 2, FK-506 was given on Days 1-10 after the first immunization, earlier than in Experiment 1. The rats were similarly divided into four groups. Each group was given the same dose of FK-506 as in Experiment 1. Histologic scores were: Control 1.49 +/- 0.24; group 1, 1.60 +/- 0.22; group 2, 0.29 +/- 0.41; and group 3, 0.03 +/- 0.03. The indices of heart weight/body weight were: Control, 0.69 +/- 0.15%; group 1, 0.76 +/- 0.09%; group 2, 0.42 +/- 0.08%; and group 3, 0.37 +/- 0.03%. Accordingly, in Experiments 1 and 2, the effects of FK-506 on autoimmune myocarditis were dose-dependent. On the other hand, in Experiments 1 and 2, not only in the control group but also in all treated groups, the titers of anti-myosin IgG were high. In conclusion, even if it is administered just before the onset of myocarditis, FK-506 is extremely effective at suppressing autoimmune myocarditis, despite a high titer of anti-myosin IgG.

Animals↗
PubMed1992

Platelet-activating factor (PAF) receptor in rat brain: PAF mobilizes intracellular Ca2+ in hippocampal neurons.

Platelet-activating factor (PAF), an alkylether phospholipid, is produced in the brain when it is subjected to various stimuli. Using a Xenopus oocyte expression system, we obtained evidence for functional PAF receptor mRNA expression in rat brain. The presence of the PAF receptor was confirmed and shown to be quite ubiquitous in the CNS by RNA blot and radioligand binding studies. To investigate the neuronal functions of PAF, intracellular Ca2+ increase elicited by nanomolar PAF application was analyzed in cultured rat hippocampal cells. Fractions of NMDA-responsive cells and non-NMDA-responsive cells were shown to respond to PAF, suggesting a potential role for PAF in the Ca2+ signaling pathway in the hippocampus.

Animals↗
PubMed1992

A comparative clinical and pharmacokinetic study of a new slow-release versus conventional preparations of valproic acid in children with intractable epilepsy.

Thirteen children with intractable epilepsy were treated by means of three-times-daily administration of a conventional preparation of valproic acid (C-VPA) and twice-daily administration of a new slow-release preparation of VPA (SR-VPA) with the cross-over technique. The frequency of seizures, side effect and steady-state pharmacokinetics of VPA were evaluated. With the change from C-VPA tid to SR-VPA bid, four patients exhibited a significant reduction in seizure frequency. The steady-state minimum concentration (Cmin) was higher, the maximum concentration (Cmax) lower and there were less diurnal fluctuations with SR-VPA, than with the respective values obtained in the C-VPA group, all the differences being statistically significant. Furthermore, a significant difference was unexpectedly found in the area under the curve (AUC) from 0 to 24 hours, the mean AUC in the period of SR-VPA being 9% higher than that with C-VPA. Five of the nine patients under 6 years of age showed more than 10% increase, and all four patients over 6 years of age less than 10% increase or a decrease in AUC. It was concluded that with SR-VPA bid, the pharmacokinetic features were more stable, the age-related AUC value was larger and the clinical effect was better than in comparison to C-VPA tid in children with intractable epilepsy.

Adolescent↗
PubMed1992

Periodic changes in phosphorylation of the Xenopus cdc25 phosphatase regulate its activity.

The cdc25 tyrosine phosphatase is known to activate cdc2 kinase in the G2/M transition by dephosphorylation of tyrosine 15. To determine how entry into M-phase in eukaryotic cells is controlled, we have investigated the regulation of the cdc25 protein in Xenopus eggs and oocytes. Two closely related Xenopus cdc25 genes have been cloned and sequenced and specific antibodies generated. The cdc25 phosphatase activity oscillates in both meiotic and mitotic cell cycles, being low in interphase and high in M-phase. Increased activity of cdc25 at M-phase is accompanied by increased phosphorylation that retards electrophoretic mobility in gels from 76 to 92 kDa. Treatment of cdc25 with either phosphatase 1 or phosphatase 2A removes phosphate from cdc25, reverses the mobility shift, and decreases its ability to activate cdc2 kinase. Furthermore, the addition of okadaic acid to egg extracts arrested in S-phase by aphidicolin causes phosphorylation and activation of the cdc25 protein before cyclin B/cdc2 kinase activation. These results demonstrate that the activity of the cdc25 phosphatase at the G2/M transition is directly regulated through changes in its phosphorylation state.

Amino Acid Sequence↗
PubMed1992

Intraoperative monitoring for thoracolumbar or lumbar surgery with somatosensory evoked potentials after double stimuli.

Somatosensory evoked potentials were after double stimuli on the posterior tibial nerve for the intraoperative monitoring in 58 thoracolumbar or lumbar surgeries. The first cortical positive potential P38 and P'38 after the second stimulus was recorded after double stimuli. Transient decreased amplitude more than 50% or missing potential of P'38 was found in 11 cases. These P'38 changes occurred in five procedures of retracting the nerve roots or dural sacs, three cases of reducing of thoracolumbar fractures, and two procedures of transpedicular screwing. No causative procedure was found in one case. In those 11 cases, 5 showed no abnormality in P38 potentials and 6 cases showed less decreased amplitude in P38 than in P'38. Consequently, P'38, which was evoked by the second stimulus, can be used for the intraoperative monitoring in the thoracolumbar and lower lumbar surgery.

Adolescent↗
PubMed1992

Characterization of IL-1 inhibitory factor released from human alveolar macrophages as IL-1 receptor antagonist.

IL-1 possesses pleiotropic properties on various cells and its activity may be stringently regulated in several ways. We have previously reported that both IL-1 and its inhibitory factor are concomitantly released from alveolar macrophages in both healthy subjects and patients with chronic inflammatory lung diseases. An increase in IL-1 activities and a decrease in inhibitory activities are characteristics found in both healthy smokers and patients with interstitial lung diseases. In this study, we further examined the biological properties of IL-1 inhibitory factor. The inhibitor exhibited a dose-dependent specific inhibition of an augmentation by IL-1 of PHA-induced murine thymocyte proliferation, while no inhibition of the augmentation by IL-2, IL-4, IL-6, or tumour necrosis factor (TNF) was found. 125I-labelled IL-1 alpha binding on PHA-stimulated murine thymocytes revealed two types of IL-1 binding sites, 44 sites/cell with a Kd of 2.7 x 10(-10) M and 230 sites/cell with a Kd of 2.5 x 10(-9) M. Alveolar macrophage culture supernatants blocked the binding of labelled IL-1 to the IL-1 receptor in a dose-dependent fashion. Scatchard plot analysis revealed that the inhibitory factor in the supernatants blocked the binding competitively. These results indicate that alveolar macrophages produce a specific IL-1 inhibitory factor, functioning as an IL-1 receptor antagonist.

Cells, Cultured↗
PubMed1992

A mutant endonuclease IV of Escherichia coli loses the ability to repair lethal DNA damage induced by hydrogen peroxide but not that induced by methyl methanesulfonate.

A mutant allele of the Escherichia coli nfo gene encoding endonuclease IV, nfo-186, was cloned into plasmid pUC18. When introduced into an E. coli xthA nfo mutant, the gene product of nfo-186 complemented the hypersensitivity of the mutant to methyl methanesulfonate (MMS) but not to hydrogen peroxide (H2O2) and bleomycin. These results suggest that the mutant endonuclease IV has normal activity for repairing DNA damages induced by MMS but not those induced by H2O2 and bleomycin. A missense mutation in the cloned nfo-186 gene, in which the wild-type glycine 149 was replaced by aspartic acid, was detected by DNA sequencing. The wild-type and mutant endonuclease IV were purified to near homogeneity, and their apurinic (AP) endonuclease and 3'-phosphatase activities were determined. No difference was observed in the AP endonuclease activities of the wild-type and mutant proteins. However, 3'-phosphatase activity was dramatically reduced in the mutant protein. From these results, it is concluded that the endonuclease IV186 protein is specifically deficient in the ability to remove 3'-terminus-blocking damage, which is required for DNA repair synthesis, and it is possible that the lethal DNA damage by H2O2 is 3'-blocking damage and not AP-site damage.

Amino Acid Sequence↗
PubMed1992

Usual interstitial pneumonia: histologic correlation with high-resolution CT.

The authors reviewed 46 cases of idiopathic pulmonary fibrosis with usual interstitial pneumonia (UIP), correlating findings on high-resolution computed tomographic (HRCT) scans with findings in specimens obtained at open lung biopsy and autopsy. The following HRCT findings were observed: (a) an accumulation of small cystic spaces with thick walls, (b) air bronchiolograms within areas of intense lung attenuation, (c) rugged pleural surfaces, (d) irregularly thickened pulmonary vessels, (e) bronchial wall thickening, and (f) slightly increased lung attenuation. Macroscopic honeycombing correlating with small cystic spaces was demonstrated at HRCT and pathologic examination. Air bronchiolograms in the areas of intense lung attenuation (ie, microscopic honeycombing) corresponded to dilated bronchioles (greater than 1 mm in diameter) with fibrosis. Irregularly thickened vessels and bronchial walls and irregular pleural surfaces were the result of fibrosis in the periphery of the secondary pulmonary lobules. Areas of slightly increased lung attenuation seen on the HRCT scans correlated with patchy alveolar septal fibrosis or inflammation. The authors conclude that microscopic honeycombing and a perilobular distribution in UIP may be clearly identified with HRCT.

Adult↗
PubMed1992

Diffuse panbronchiolitis: correlation of high-resolution CT and pathologic findings.

Diffuse panbronchiolitis (DPB) is characterized by chronic airflow limitation and airway inflammation with bronchiolar lesions. Chest radiographs of patients with DPB usually show small nodular shadows throughout both lungs. The authors investigated the nature and pathogenesis of the radiologic features of DPB by correlating high-resolution computed tomographic (HRCT) findings with histopathologic features. The HRCT images of nine patients with DPB were compared with the observations made with inflated lung specimens. The HRCT findings of DPB included centrilobularly distributed, small rounded areas of attenuation; branched linear areas of attenuation, contiguous with the small rounded areas; dilated airways with thick walls, also common outside secondary pulmonary lobules; and decreased lung attenuation in peripheral areas due to air trapping caused by bronchiolar narrowing in the subpleural zones. The authors believe that HRCT best demonstrates this characteristic location of small rounded areas of attenuation associated with dilated airways.

Adult↗