Biomedical subjects

S Koyama

Publications and source records attributed to S Koyama.

At least 91 records · Page 5Linked to original sources

PubMed2000

Development of a hybrid artificial liver using a polyurethane foam/hepatocyte-spheroid packed-bed module.

Primary dog hepatocytes spontaneously formed spheroids in the pores of polyurethane foam (PUF) within 1-2 days of stationary culture. The spheroids, about 100-150 microm in diameter, partly attached to the surface and immobilized inside these pores. The lidocaine disappearance rate decreased to about 4 microg/10(5) viable cells/day for 10 days, while in the PUF/spheroid culture the rate was maintained at almost the initial level of 8 microg/10(5) viable cells/day for 10 days. Then, two scales of PUF packed-bed modules were designed. A small module (PUF volume; 14.5 cm3) was used for in vitro culture to investigate optimum culture conditions, and a large module (PUF volume; 300 cm3) was designed for dog experiments. Hepatocytes inoculated in these modules also formed spheroids and maintained almost the same activity of albumin secretion rate (111 microg/cm3 PUF/day in the small module and 87.7 microg/cm3 PUF/day in the large module). These results indicate that the PUF packed-bed module containing hepatocyte-spheroids is promising as a hybrid artificial liver.

Albumins↗

PubMed2000

Conditions required for a hybrid artificial liver support system using a PUF/hepatocyte-spheroid packed-bed module and it's use in dogs with liver failure.

We studied the effects of a hybrid artificial liver support system we developed on dogs with hepatic failure. The system consisted of a multi-channel polyurethane foam packed-bed culture module, including primary dog hepatocyte spheroids. Blood ammonia was well metabolized by 20 g hepatocytes, but the other functions such as glucose concentration, total bile acid concentration, and survival time required 30 g hepatocytes to improve conditions. We found that we should use a culture substratum that easily forms spheroids, and that an artificial liver module should be used as soon as possible after spheroid formation by hepatocytes in the module.

Animals↗

PubMed2000

[Gastric acid secretion in gastroesophageal reflex disease].

The gastric acid secretion was evaluated by serum pepsinogen I/II ratio and serum Helicobacter pylori IgG antibody titer in gastroesophageal reflux disease(GERD) patient. GERD patients was 81 patients. Los-Angeles classification (LA)O, so called endoscopy negative reflux disease, was 6 patients, and LA-O-B patients was 68 patients. Helicobacter pylori infection ratio in GERD patients was 50.6%(41/81 patients). Pepsinogen I/II ratio in Helicobacter pylori positive GERD patients was no significant different from Helicobacter pylori negative GERD patients. We concluded that the gastric acid secretion in GERD patients was normal secretion.

Gastric Acid↗

PubMed2000

Bleomycin stimulates lung fibroblast and epithelial cell lines to release eosinophil chemotactic activity.

The presence of eosinophils in the lungs of patients with pulmonary fibrosis correlates with poor prognosis or resistance to therapy. Furthermore, eosinophils localize to areas undergoing active fibrosis. It was hypothesized that a human lung fibroblast (HFL-1) and a human lung epithelial cell line (BEAS-2B) might release eosinophil chemotactic activity (ECA) in response to bleomycin, a chemotherapeutic agent associated with pulmonary fibrosis. HFL-1 and BEAS-2B cells were cultured in the presence of bleomycin and their supernatant fluids evaluated for ECA by means of a Boyden chamber method. HFL-1 and BEAS-2B cells released ECA in a dose- and time-dependent manner in response to bleomycin, and partial characterization revealed that the ECA was heterogeneous. ECA release from HFL-1 and BEAS-2B cells was significantly reduced by a leukotriene B4 (LTB4) receptor antagonist and an antibody directed against granulocyte-macrophage colony-stimulating factor. HFL-1 cells released LTB4, eotaxin, and GM-CSF constitutively, and BEAS-2B cells released LTB4, eotaxin, regulated on activation, normal T-cell expressed and presumably secreted, and GM-CSF constitutively. In both cases, the release of GM-CSF was significantly increased in response to bleomycin. These data suggest that lung fibroblasts and epithelial cells may modulate eosinophil recruitment into the lung in bleomycin-induced pulmonary fibrosis.

Antibodies↗

PubMed2000

[Radiation exposure to patient and radiologist during transcatheter arterial embolization for hepatocellular carcinoma].

PURPOSE: To evaluate radiation exposure to patients and radiologists during transcatheter arterial embolization(TAE) for hepatocellular carcinoma. MATERIALS AND METHODS: In 39 TAE procedures performed at eight institutes, skin doses were evaluated with thermoluminescence dosimeters at the patient's back(entrance surface) and lower abdomen, and at the radiologist's forehead and abdomen. Real-time dosimeters were also used to evaluate patient skin dose. RESULTS: The patients' mean entrance surface dose was 973 +/- 681 mGy(range, 185 to 3543 mGy) with the mean fluoroscopic time of 21 minutes and 6 digital subtraction angiography(DSA) acquisitions. The dose at the patients' lower abdomen was 0.98 +/- 0.77 mGy. Doses for the radiologists were 0.04 +/- 0.04 mGy at the forehead and 0.15 +/- 0.19 mGy and 0.005 +/- 0.01 mGy at the abdomen over and under the apron, respectively. Fifty-six percent of the patients' skin dose was from DSA and 44% from fluoroscopy. CONCLUSIONS: Patient skin dose may occasionally exceed the dose for transient erythema. Because a patient may have repeated TAEs, skin doses or X-ray conditions should be recorded. The exposed doses of radiologists were considered to be acceptable with proper techniques. Further efforts to reduce radiation should be directed toward both DSA and fluoroscopy.

Aged↗

PubMed1999

Individual differences in working memory and the peak alpha frequency shift on magnetoencephalography.

The effect of the working memory demands on the peak alpha frequency of the power spectrum of magnetoencephalography (MEG) was investigated. There were one control condition and four listening span test (LST) conditions demanding the use of working memory. The results showed that the peak alpha frequency of the averaged MEG power shifted to the higher frequency region in the LST condition dominantly in the fronto-temporal region. Individual differences in working memory capacities were observed in the shift of peak alpha frequency of MEG.

Adult↗

PubMed1999

Epsin binds to the EH domain of POB1 and regulates receptor-mediated endocytosis.

POB1 has been identified as a RalBP1-binding protein and has the Eps15 homology (EH) domain. The EH domain-containing proteins have been suggested to be involved in clathrin-dependent endocytosis. To clarify the function of POB1, we purified a protein which binds to the EH domain of POB1 from bovine brain cytosol and identified it as Epsin, which is known to bind to the EH domain of Eps15. Epsin has three Asn-Pro-Phe (NPF) motifs in the C-terminal region, which are known to form the core sequence for the binding to the EH domain. The EH domain of POB1 interacted directly with the region containing the NPF motifs of Epsin. Expression of Epsin in CHO-IR cells inhibited internalization of insulin although it affected neither insulin-binding nor autophosphorylation activities of the insulin receptor. Taken together with the observations that Epsin is involved in internalization of the receptors for epidermal growth factor and transferrin, these results suggest that Epsin is a binding partner of POB1 and their binding regulates receptor-mediated endocytosis.

Adaptor Proteins, Vesicular Transport↗

PubMed1999

The Drosophila Ral GTPase regulates developmental cell shape changes through the Jun NH(2)-terminal kinase pathway.

The Ral GTPase is activated by RalGDS, which is one of the effector proteins for Ras. Previous studies have suggested that Ral might function to regulate the cytoskeleton; however, its in vivo function is unknown. We have identified a Drosophila homologue of Ral that is widely expressed during embryogenesis and imaginal disc development. Two mutant Drosophila Ral (DRal) proteins, DRal(G20V) and DRal(S25N), were generated and analyzed for nucleotide binding and GTPase activity. The biochemical analyses demonstrated that DRal(G20V) and DRal(S25N) act as constitutively active and dominant negative mutants, respectively. Overexpression of the wild-type DRal did not cause any visible phenotype, whereas DRal(G20V) and DRal(S25N) mutants caused defects in the development of various tissues including the cuticular surface, which is covered by parallel arrays of polarized structures such as hairs and sensory bristles. The dominant negative DRal protein caused defects in the development of hairs and bristles. These phenotypes were genetically suppressed by loss of function mutations of hemipterous and basket, encoding Drosophila Jun NH(2)-terminal kinase kinase (JNKK) and Jun NH(2)-terminal kinase (JNK), respectively. Expression of the constitutively active DRal protein caused defects in the process of dorsal closure during embryogenesis and inhibited the phosphorylation of JNK in cultured S2 cells. These results indicate that DRal regulates developmental cell shape changes through the JNK pathway.

Amino Acid Sequence↗

PubMed1999

Human face perception traced by magneto- and electro-encephalography.

The temporal and spatial processing of face perception in normal subjects was traced by magnetoencephalography (MEG) and electroencephalography (EEG). We used 5 different visual stimuli: (1) face with opened eyes, (2) face with closed eyes, (3) eyes, (4) scrambled face, and (5) hand, and they were shown in random order. Subjects were asked to count the number of hand stimuli. To analyze the complicated brain responses to visual stimuli, we used brain electric source analysis (BESA) as the spatio-temporal multiple source model. In MEG recording, the 1M and 2M components were identified in all subjects. The 1M component was recorded to all kinds of stimuli. The 2M component was clearly identified only to face stimulation in all subjects, but to eyes stimulation in only 3 subjects with a small amplitude. The 2M component was not identified to scrambled face nor hand stimulation. The 2M component was recorded from the right hemisphere in all subjects, but in only 5 of 10 subjects from the left hemisphere. The mean peak latencies of the 1M and 2M components were approximately 132 and 179 ms, respectively. The interpeak latency between 1M and 2M was approximately 47 ms on average but the interindividual difference was large. There was no significant difference of the 2M latency between face with opened eyes and face with closed eyes. The 1M component was generated in the primary visual cortex in the bilateral hemispheres, and the 2M component was generated in the inferior temporal cortex, around the fusiform gyrus. In the EEG recording, face-specific components, positive at the vertex, P200 (Cz), and the negative at the temporal areas, N190 (T5') and N190 (T6'), were clearly recorded. The EEG results were fundamentally compatible with the MEG results. The amplitude of the component recorded from the right hemisphere was significantly larger than that from the left hemisphere. These findings suggest that the fusiform gyrus is considered to play an important role in face perception in humans, and that the right hemisphere is more dominant. Face perception takes place approximately 47 ms after the primary response to visual stimulation in the primary visual cortex, but the period of information transfer to the fusiform gyrus is variable among subjects. Detailed temporal and spatial analyses of the processing of face perception can be achieved with MEG.

Adult↗

PubMed1999

Presynaptic serotonergic inhibition of GABAergic synaptic transmission in mechanically dissociated rat basolateral amygdala neurons.

1. The basolateral amygdala (ABL) nuclei contribute to the process of anxiety. GABAergic transmission is critical in these nuclei and serotonergic inputs from dorsal raphe nuclei also significantly regulate GABA release. In mechanically dissociated rat ABL neurons, spontaneous miniature inhibitory postsynaptic currents (mIPSCs) arising from attached GABAergic presynaptic nerve terminals were recorded with the nystatin-perforated patch method and pharmacological isolation. 2. 5-HT reversibly reduced the GABAergic mIPSC frequency without affecting the mean amplitude. The serotonergic effect was mimicked by the 5-HT1A specific agonist 8-OH DPAT (8-hydroxy-2-(di-n-propylamino)tetralin) and blocked by the 5-HT1A antagonist spiperone. 3. The GTP-binding protein inhibitor N-ethylmaleimide removed the serotonergic inhibition of mIPSC frequency. In either K+-free or Ca2+-free external solution, 5-HT could inhibit mIPSC frequency. 4. High K+ stimulation increased mIPSC frequency and 8-OH DPAT inhibited this increase even in the presence of Cd2+. 5. Forskolin, an activator of adenylyl cyclase (AC), significantly increased synaptic GABA release frequency. Pretreatment with forskolin prevented the serotonergic inhibition of mIPSC frequency in both the standard and high K+ external solution. 6. Ruthenium Red (RR), an agent facilitating the secretory process in a Ca2+-independent manner, increased synaptic GABA release. 5-HT also suppressed RR-facilitated mIPSC frequency. 7. We conclude that 5-HT inhibits GABAergic mIPSCs by inactivating the AC-cAMP signal transduction pathway via a G-protein-coupled 5-HT1A receptor and this intracellular pathway directly acts on the GABA-releasing process independent of K+ and Ca2+ channels in the presynaptic nerve terminals.

Adenylyl Cyclases↗

PubMed1999

It takes longer to recognize the eyes than the whole face in humans.

Brain responses to eyes and whole face were studied by magnetoencephalography (MEG). We used five different visual stimuli, face with opened eyes, face with closed eyes, eyes, scrambled face, and hand. 1M was evoked in response to all kinds of stimuli but 2M peaking at approximately 180 ms was recorded only for face and eyes. The peak latencies of 1M and 2M and the interpeak latency 1M-2M to eyes were significantly longer than those to face, and there was no significant difference of latency between face with opened eyes and face with closed eyes. The 2M both for face and eyes was generated in the same area, the inferior temporal cortex, around the fusiform gyrus.

Adult↗

PubMed1999

Small G protein Ral and its downstream molecules regulate endocytosis of EGF and insulin receptors.

The involvement of Ral and its downstream molecules in receptor-mediated endocytosis was examined. Expression of either RalG23V or RalS28N, which are known to be constitutively active and dominantnegative forms, respectively, in A431 cells blocked internalization of epidermal growth factor (EGF). Stable expression of RalG23V or RalS28N in CHO-IR cells also inhibited internalization of insulin. Internalization of EGF and insulin was not affected by full-length RalBP1 which is an effector protein of Ral, but was inhibited by its C-terminal region which binds directly to Ral and POB1. POB1 is a binding protein of RalBP1 and has the Eps15 homology (EH) domain. Deletion mutants of POB1 inhibited internalization of EGF and insulin. However, internalization of transferrin was unaffected by Ral, RalBP1, POB1 and their mutants. Epsin and Eps15 have been reported to be involved in the regulation of endocytosis of the receptors for EGF and transferrin. The EH domain of POB1 bound directly to Epsin and Eps15. Taken together with the observation that EGF and insulin activate Ral, these results suggest that Ral, RalBP1 and POB1 transmit the signal from the receptors to Epsin and Eps15, thereby regulating ligand-dependent receptor-mediated endocytosis.

Adaptor Proteins, Signal Transducing↗

PubMed1999

ATP-sensitive and Ca2+-activated K+ channel activities in the rat locus coeruleus neurons during metabolic inhibition.

Locus coeruleus (LC) is the significant nucleus for consciousness and it is sensitive to metabolic inhibition. We investigated the effects of a metabolic inhibitor sodium cyanide (NaCN) on the rat dissociated LC neurons using nystatin-perforated patch recordings. Under voltage-clamp (VH=-40 mV), application of NaCN evoked outward currents composed of ATP-sensitive and Ca2+-dependent K+ channel currents (IKATP and IKCa2+). Onset of IKATP was faster than that of IKCa2+. Prolonged application of NaCN brought IKATP rundown but not IKCa2+ rundown. Okadaic acid prevented IKATP rundown, indicating that KATP channels are deactivated by dephosphorylation with protein phosphatase.

Adenosine Triphosphate↗

PubMed1999

Bleomycin stimulates lung fibroblasts to release neutrophil and monocyte chemotactic activity.

We determined whether human lung fibroblasts might release chemotactic activity for neutrophils (NCA) and monocytes (MCA) in response to bleomycin. The human lung fibroblasts supernatant fluids were evaluated for chemotactic activity by a blind well chamber technique. Human lung fibroblasts released NCA and MCA in a dose- and time-dependent manner in response to bleomycin. Checkerboard analysis of supernatant fluids revealed that both NCA and MCA were chemotactic. Partial characterization revealed that NCA was partly heat labile, trypsin sensitive, and predominantly ethyl acetate extractable. In contrast, MCA was partly trypsin sensitive and ethyl acetate extractable. The release of chemotactic activity was inhibited by lipoxygenase inhibitors and cycloheximide. Molecular sieve column chromatography revealed that both NCA and MCA had multiple chemotactic peaks. NCA was inhibited by leukotriene B4 receptor antagonist and anti-IL-8 and G-CSF Abs. MCA was attenuated by leukotriene B4 receptor antagonist, and monocyte chemoattractant protein-1, GM-CSF, and TGF-beta Abs. Leukotriene B4 receptor antagonist and these Abs inhibited the corresponding m.w. chemotactic activity separated by column chromatography. The concentrations of IL-8, G-CSF, monocyte chemoattractant protein-1, GM-CSF, and TGF-beta in the supernatant fluids significantly increased in response to bleomycin. These data suggest that lung fibroblasts may modulate inflammatory cell recruitment into the lung by releasing NCA and MCA in response to bleomycin.

Bleomycin↗

PubMed1999

Novel proteoglycan linkage tetrasaccharides of human urinary soluble thrombomodulin, SO4-3GlcAbeta1-3Galbeta1-3(+/-Siaalpha2-6)Galbeta1-4Xyl.

O-linked sugar chains with xylose as a reducing end linked to human urinary soluble thrombomodulin were studied. Sugar chains were liberated by hydrazinolysis followed by N-acetylation and tagged with 2-aminopyridine. Two fractions containing pyridylaminated Xyl as a reducing end were collected. Their structures were determined by partial acid hydrolysis, two-dimensional sugar mapping combined with exoglycosidase digestions, methylation analysis, mass spectrometry, and NMR as SO4-3GlcAbeta1-3Galbeta1-3(+/-Siaalpha2-6)Galbeta1+ ++-4Xyl. These sugar chains could bind to an HNK-1 monoclonal antibody. This is believed to be the first example of a proteoglycan linkage tetrasaccharide with glucuronic acid 3-sulfate and sialic acid.

Binding Sites, Antibody↗

PubMed1999

A kuroko-type polymetallic sulfide deposit in a submarine silicic caldera

Manned submersible studies have delineated a large and actively growing Kuroko-type volcanogenic massive sulfide deposit 400 kilometers south of Tokyo in Myojin Knoll submarine caldera. The sulfide body is located on the caldera floor at a depth of 1210 to 1360 meters, has an area of 400 by 400 by 30 meters, and is notably rich in gold and silver. The discovery of a large Kuroko-type polymetallic sulfide deposit in this arc-front caldera raises the possibility that the numerous unexplored submarine silicic calderas elsewhere might have similar deposits.

Journal Article↗

PubMed1999

Topography of the secondary somatosensory cortex in humans: a magnetoencephalo-graphic study.

The topography of the secondary somatosensory cortex (SII) responses to somatosensory stimulation applied to various parts of the body of normal volunteers was analyzed using magnetoencephalography (MEG). Although there were large inter-individual differences, the following orders of a location of equivalent current dipoles (ECDs) were found; (1) Anterior-posterior direction: lower lip-upper lip-thumb-middle finger-foot, (2) Medial-lateral direction: foot-middle finger-thumb-upper lip-lower lip, and (3) Lower-upper direction: lower lip-upper-lip-thumb-middle finger-foot. In general, these findings are similar to those obtained in studies of monkeys. However, the differentiation was not as clear as that seen in the homunculus in the primary somatosensory cortex (SI). The auditory cortex is located at a site more posterior, lateral and lower than the SII.

Adult↗

PubMed1999

Axin prevents Wnt-3a-induced accumulation of beta-catenin.

When Axin, a negative regulator of the Wnt signaling pathway, was expressed in COS cells, it coeluted with glycogen synthase kinase-3beta (GSK-3beta), beta-catenin, and adenomatous polyposis coli protein (APC) in a high molecular weight fraction on gel filtration column chromatography. In this fraction, GSK-3beta, beta-catenin, and APC were co-precipitated with Axin. Although beta-catenin was detected in the high molecular weight fraction in L cells on gel filtration column chromatography, addition of conditioned medium expressing Wnt-3a to the cells increased beta-catenin in the low molecular weight fraction. However, Wnt-3a-dependent accumulation of beta-catenin was greatly inhibited in L cells stably expressing Axin. Axin also suppressed Wnt-3a-dependent activation of Tcf-4 which binds to beta-catenin and acts as a transcription factor. These results suggest that Axin forms a complex with GSK-3beta, beta-catenin, and APC, resulting in the stimulation of the degradation of beta-catenin and that Wnt-3a induces the dissociation of beta-catenin from the Axin complex and accumulates beta-catenin.

Adenomatous Polyposis Coli Protein↗