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Biomedical subjects

Y Miyata

Publications and source records attributed to Y Miyata.

At least 217 records · Page 12Linked to original sources
PubMed1990

[Stereoscopic MR angiography of the abdomen].

We have developed a new method of stereoscopic MR angiography of the abdomen using gradient echo images. Consecutive coronal scanning of the abdomen was performed by fast scan during breath hold. These images were overlapped by means of MR angiography. Then two slightly different views that can give a true stereoscopic effect were constructed. The more precise spatial relationship of the abdominal vessels can be visualized with our new method.

Abdomen↗
PubMed1990

Unique precursor structure of an extracellular protease, aqualysin I, with NH2- and COOH-terminal pro-sequences and its processing in Escherichia coli.

Aqualysin I is a subtilisin-type serine protease which is secreted into the culture medium by Thermus aquaticus YT-1, an extremely thermophilic Gram-negative bacterium. The nucleotide sequence of the entire gene for aqualysin I was determined, and the deduced amino acid sequence suggests that aqualysin I is produced as a large precursor, consisting of at least three portions, an NH2-terminal pre-pro-sequence (127 amino acid residues), the protease (281 residues), and a COOH-terminal pro-sequence (105 residues). When the cloned gene was expressed in Escherichia coli cells, aqualysin I was not secreted. However, a precursor of aqualysin I lacking the NH2-terminal pre-pro-sequence (38-kDa protein) accumulated in the membrane fraction. On treatment of the membrane fraction at 65 degrees C, enzymatically active aqualysin I (28-kDa protein) was produced in the soluble fraction. When the active site Ser residue was replaced with Ala, cells expressing the mutant gene accumulated a 48-kDa protein in the outer membrane fraction. The 48-kDa protein lacked the NH2-terminal 14 amino acid residues of the precursor, and heat treatment did not cause any subsequent processing of this precursor. These results indicate that the NH2-terminal signal sequence is cleaved off by a signal peptidase of E. coli, and that the NH2- and COOH-terminal pro-sequences are removed through the proteolytic activity of aqualysin I itself, in that order. These findings indicate a unique four-domain structure for the aqualysin I precursor; the signal sequence, the NH2-terminal pro-sequence, mature aqualysin I, and the COOH-terminal pro-sequence, from the NH2 to the COOH terminus.

Amino Acid Sequence↗
PubMed1990

Pepsin, an aspartic protease, converts porcine big endothelin to 21-residue endothelin.

Porcine big endothelin (big ET-39) at 1 nM, a concentration with no influence on contractile activity in isolated rat aorta, induced a slow-onset and sustained contraction by the pre-incubation with pepsin. When the incubation mixture of big ET-39 with pepsin was analyzed by high-performance liquid chromatography on an octadecyl silica column, two major products of pepsin hydrolysis were obtained; their amino acid sequences were identical with those of 21-residue endothelin (ET-21) and a C-terminal peptide of big ET-39, big ET (22-39), respectively. On the other hand, no degradation of ET-21 was observed by pepsin treatment. These results indicate that pepsin specifically cleaves a Trp21-Val22 bond in the big ET-39 molecule, producing ET-21 and big ET (22-39). Thus, the possibility that pepsin-like aspartic protease may participate in the conversion of big ET-39 to ET-21 in vivo warrants further attention.

Animals↗
PubMed1990

[Slow eye movements and transitional periods of EEG sleep stages during daytime sleep].

Slow eye movements (SEMs) were analyzed in 28 young adult females during daytime sleep. Data from transitional periods of each EEG stage were obtained by accumulating its epoch series synchronized to the onset or termination of the other stages. Sleepiness was reported by the subject by pressing a button switch. SEMs were prominent at the transitional period of stage W approaching the onset of stage 1 (sleep tendency). They declined with deepening of sleep at the transitional periods of EEG stages 22 and 2, and disappeared completely during slow wave sleep (SWS) periods. The recovery of SEMs occurred towards awakening at every EEG transitional period except for SWS. The individual difference in the appearance of SEMs was partly explained by a positive correlation with stage 3 latency: the longer the latency was, the larger the mean SEMs. Perceived sleepiness increased in proportion to SEMs during the entry and re-entry periods to sleep. These results suggest that SEMs are strongly associated with a wake-sleep transition.

Adult↗
PubMed1990

[Hepatic functional reserve and tumor size as prognostic factors in patients with primary liver cancer undergoing non-surgical therapy].

A prognostic study on 119 patients with primary liver cancer undergoing nonsurgical therapy was carried out to evaluate the relevance of hepatic functional reserve and tumor size to their cumulative survival rates. All patients were classified into the three groups of Child's classification (A, B and C) according to their hepatic functional reserve and were also divided into the five groups according to their tumor size. The cumulative survival rates of all patients at 1, 2, 3, 4 and 5 years after the diagnosis were 50.9, 28.3, 18.8, 13.5 and 6.7%, respectively. The cumulative survival rates of group V whose tumor occupied more than 40% of the liver area were significantly lower than those of the other tumor-size-groups. The survival rates of Child's group A were significantly higher than those of group B and C. But in those patients who were classified into group V according to their tumor size, there was no significant difference in their survival rates among the three groups of Child's classification. These results suggest that hepatic functional reserve as well as tumor size is an important prognostic factor in patients with primary liver cancer. But if the cancer once develops greater than 40% of the liver area, hepatic functional reserve diminishes in value as a prognostic factor.

Antineoplastic Agents↗
PubMed1990

[Effects of controlled hypotension induced by prostaglandin E1 on the cerebral blood flow].

The effect of controlled hypotension induced by prostaglandin E1 (PGE1) on the cerebral blood flow (CBF) was studied in 14 patients undergoing neurosurgery. CBF was measured by thermal diffusion using a flow probe with a Peltier stack. PGE1 was injected i.v. continuously, at a dose of 0.05, 0.1 and 0.2 micrograms.kg-1.min-1. CBF tended to increase dose-dependently but not significantly by PGE1 administration. Cerebral vascular resistance was reduced significantly by every dose of PGE1 administered. Therefore, the results indicate that the cerebral vascular beds are dilated directly by PGE1. In conclusion, this study suggests that PGE1 can be used safely to control hypotension without reducing CBF during neurosurgery.

Adult↗
PubMed1990

[A case of bilateral atrial myxoma].

A case of 47-year-old female who underwent the surgery for the bilateral atrial myxoma two times was reported. At the first operation both tumors were attached to the same level of the atrial septum and were removed simultaneously followed by the resection of the left atrial wall. Six months later, she complained of dyspnea and easy fatigability for the recurrence of the tumor. She was operated again for the removal of the tumor. But she died of the re-recurrence of the tumor 4 months after the second operation.

Female↗
PubMed1989

[N-isopropyl I-123 p-iodoamphetamine single photon emission computed tomography of herpes simplex encephalitis].

Two patients with herpes simplex encephalitis were studied with N-Isopropyl I-123 p-Iodoamphetamine (IMP) single photon emission computed tomography (IMP-SPECT) and X-ray computed tomography (CT). In both cases the affected temporal lobes showed an increased IMP uptake. In case 1, the initial increased IMP uptake decreased as symptoms and CT findings improved. In case 2, the increased IMP uptake was shown at the time of symptoms progressed, while CT had no abnormal findings. IMP uptake is sensitive for its demonstration of inflammatory processes of herpes simplex encephalitis.

Aged↗
PubMed1989

Protein kinase C-dependent and -independent pathways in the growth factor-induced cytoskeletal reorganization.

Human epidermoid carcinoma KB cells exhibit rapid induction of membrane ruffling in response to epidermal growth factor (EGF), insulin, and insulin-like growth factor-I (IGF-I) (Kadowaki, T., Koyasu, S., Nishida, E., Sakai, H., Takaku, F., Yahara, I., and Kasuga, M. (1986) J. Biol. Chem. 261, 16141-16147). We have analyzed the role of protein kinase C (PKC) in this response. Treatment of KB cells with 4 beta-phorbol 12,13-dibutyrate (PDBu) (100 ng/ml) for 30 min caused translocation of PKC to the membrane. This treatment completely inhibited the induction of membrane ruffling by EGF, insulin, and IGF-I. Prolonged treatment with PDBu (200 ng/ml for 15 h) induced complete depletion of the PKC activity in the cells. Under these conditions, EGF binding to cells and autophosphorylation of the EGF receptor occurred normally, while EGF could not induce membrane ruffling. In contrast, insulin- or IGF-I-induced membrane ruffling occurred normally in the PKC-depleted cells. Moreover, H-7 (PKC inhibitor) inhibited only EGF-induced membrane ruffling in a dose-dependent manner. We further found that EGF, but not insulin/IGF-I, caused transient translocation of PKC to the membrane. All these results suggest that PKC is required for the membrane ruffling induced by EGF but not for that induced by insulin/IGF-I. Therefore, there are PKC-dependent and independent pathways in the growth factor-induced membrane ruffling. Furthermore, we propose dual roles of PKC in the EGF signaling, a signal transmitting role and a negative feedback role.

Cell Membrane↗
PubMed1989

HSP100, a 100-kDa heat shock protein, is a Ca2+-calmodulin-regulated actin-binding protein.

The 100-kDa heat shock protein, HSP100, was purified from mouse lymphoma cells. Amino acid sequences of three peptide fragments which were obtained from the purified protein by lysylendopeptidase digestion were completely or nearly identical with those of a mouse endoplasmic reticulum protein, ERp99, of a hamster glucose-regulated protein, GRP94, and of a chicken heat shock protein, HSP108, all of which have been known to have strong homology with the 90-kDa heat shock protein, HSP90. HSP100 bound to actin filaments and an apparent Kd for the binding was determined to be 8 x 10(-7) M in 2 mM MgCl2 + 100 mM KCl. Calmodulin inhibited the binding in a Ca2+-dependent manner. Equilibrium gel filtration demonstrated that HSP100 has an ability to bind to calmodulin only in the presence of Ca2+. Moreover, HSP100 competed with HSP90 for binding to actin filaments. These results together with our previous findings that HSP90 and HSP100 have similar physicochemical properties (Koyasu, S., Nishida, E., Kadowaki, T., Matsuzaki, F., Iida, K., Harada, F., Kasuga, M., Sakai, H., and Yahara, I. (1986) Proc. Natl. Acad. Sci. U.S.A. 83, 8054-8058) and HSP90 is a calmodulin-regulated actin-binding protein (Nishida, E., Koyasu, S., Sakai, H., and Yahara, I. (1986) J. Biol. Chem. 261, 16033-16036), strongly suggest that HSP100 is structurally and functionally related to HSP90.

Actin Cytoskeleton↗
PubMed1989

Regulation by intracellular Ca2+ and cyclic AMP of the growth factor-induced ruffling membrane formation and stimulation of fluid-phase endocytosis and exocytosis.

Insulin, insulin-like growth factor-I (IGF-I), and epidermal growth factor (EGF) induce formation of ruffling membranes [T. Kadowaki et al. (1986) J. Biol. Chem. 261, 16,141-16,147] and stimulate the fluid-phase endocytosis and exocytosis [Y. Miyata et al. (1988) Exp. Cell Res. 178, 73-83] in human epidermoid carcinoma KB cells. An increase in intracellular Ca2+ concentration by treatment with A23187, a calcium ionophore, or an increase in intracellular cAMP level by treatment with dibutyryl cAMP or forskolin almost completely inhibited the insulin-, IGF-I-, or EGF-induced formation of ruffling membranes. Increases in Ca2+ or cAMP concentration also inhibited almost completely the stimulation of fluid-phase endocytosis and exocytosis elicited by these growth factors. These results suggest that the growth factor-induced ruffling membrane formation and the stimulation of fluid-phase endocytosis and exocytosis have a common regulatory mechanism involving intracellular concentrations of Ca2+ and cAMP. 125I-EGF binding assays and immunoprecipitation experiments with anti-phosphotyrosine antibody revealed that treatment of KB cells with A23187, dibutyryl cAMP, or forskolin did not inhibit the EGF binding to the cells nor subsequent tyrosine autophosphorylation of its receptors. These results indicate that Ca2+- and/or cAMP-sensitive intracellular reactions exist downstream from the receptor kinase activation in the process of these early cellular responses.

Bucladesine↗
PubMed1989

Radiosensitization by a new nucleoside analogue: 1-[2-hydroxy-1-(hydroxymethyl)ethoxy]methyl-2-nitroimidazole (RP-170).

A new potent hypoxic cell sensitizer, a 2-nitroimidazole nucleoside analogue having methoxyglycerol as a sugar moiety at the N-1 position of the imidazole ring (RP-170), has been synthesized. Its radiosensitizing activities in vitro and in vivo were investigated and compared with those of misonidazole (MISO) and etanidazole (SR-2508). As might be expected from the almost identical electron affinities of the three compounds, they were equally effective against hypoxic EMT6 cells in vitro. The in vivo-in vitro excision analysis showed that RP-170 was also as effective as MISO and etanidazole to radiosensitize solid tumor cells in vivo. An intraperitoneal administration of 200 mg/kg of RP-170 and an intravenous administration of the same dose of etanidazole showed an equal sensitizer-enhancement ratio of 1.51 to solid EMT6/KU tumors. Its effectiveness was also demonstrated by growth delay assay using solid SCCVII tumors. As predicted from the low partition coefficient, RP-170 and etanidazole showed apparently lower toxicity in vivo than MISO; their LD50/14 were 4.3, 4.8, and 1.8 g/kg in our experiment, respectively. Moreover, RP-170 showed fast clearance from serum in mice (t1/2 = 10.24 min) and poor penetration into neural tissues. Although RP-170 does not show any advantages over etanidazole in terms of sensitization or toxicity, RP-170 might be preferable under certain circumstances because it can be given orally.

Animals↗
PubMed1989

Delayed-type hypersensitivity skin reaction to HBsAg and immunohistopathologic study of liver in patients with acute type B viral hepatitis.

In an attempt to clarify the role of cellular immunity in the pathogenesis of acute type B viral hepatitis (AHB, we studied delayed-type hypersensitivity (DTH) skin reaction to hepatitis B surface antigen (HBsAg) and immunohistopathology of livers in patients with AHB. DTH skin reaction to HBsAg developed early in the convalescent phase in all 14 patients with AHB. In contrast, the production of anti-HBs was significantly delayed in these patients, compared with healthy controls immunized with HB vaccine intradermally (P less than 0.001). These observations suggest that DTH to HBsAg but not anti-HBs may be associated with recovery from AHB. In the biopsied livers obtained from patients with AHB, the proliferation of Kupffer cells was extensive and immunohistopathologic studies revealed an accumulation of CD-4 positive lymphocytes in the portal area, a finding which suggested a DTH reaction in the liver with AHB. CD-8 positive cells had infiltrated the lobule and made contact with affected hepatocytes, thereby indicating that a cytotoxic T cell response is involved in damaging of the infected cells. All these observations taken together, we propose that not only a cytotoxic T cell response but also a DTH reaction may be involved in the pathogenesis of AHB.

Acute Disease↗
PubMed1989

Thalamic projections to the cortical gustatory area in the cat studied by retrograde axonal transport of horseradish peroxidase.

The thalamic projections to the cortical gustatory area in the cat were studied using the horseradish peroxidase (HRP) method. The gustatory area extends from the lateral lip of the presylvian sulcus (posterior two-thirds) to the posterior part of the orbital gyrus. It is bounded anteriorly by area 6a beta, laterally by the first somatosensory area, medially by the fundus and medial bank of the presylvian sulcus (prefrontal area), and posteriorly by the insular area. The cortical gustatory area receives fibers mainly from the medial smaller-celled part of the posteromedial ventral nucleus (VPMM). Cortical projections of the VPMM are organized topically; the anterior part of the gustatory cortex receives fibers from the anterodorsal and posteroventral portions of the anterior two-thirds of the VPMM, whereas the posterior gustatory cortex receives fibers from the anteroventral, posterodorsal and posterior portions of the posterior two-thirds of the VPMM. In addition, there appears to be a mediolateral organization of the cortical projections of the VPMM to the gustatory area. The cortical gustatory area receives a few projections from the ventral lateral, ventral medial, submedial, paracentral, lateral central, parafascicular and medial central nuclei.

Animals↗