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Biomedical subjects

T Sakaguchi

Publications and source records attributed to T Sakaguchi.

At least 109 records · Page 6Linked to original sources
PubMed1997

The active oligomeric state of the minimalistic influenza virus M2 ion channel is a tetramer.

The influenza A virus M2 integral membrane protein is an ion channel that permits protons to enter virus particles during uncoating of virions in endosomes and also modulates the pH of the trans-Golgi network in virus-infected cells. The M2 protein is a homo-oligomer of 97 residues, and analysis by chemical cross-linking and SDS/PAGE indicates M2 forms a tetramer. However, a higher order molecular form is sometimes observed and, thus, it is necessary to determine the active form of the molecule. This was done by studying the currents of oocytes that expressed mixtures of the wild-type M2 protein (epitope tagged) and the mutant protein M2-V27S, which is resistant to the inhibitor amantadine. The composition of mixed oligomers of the two proteins expressed at the plasma membrane of individual oocytes was quantified after antibody capture of the cell surface expressed molecules and it was found that the subunits mixed freely. When the ratio of wild-type to mutant protein subunits was 0. 85:0.15, the amantadine sensitivity was reduced to 50% and for a ratio of 0.71:0.29 to 20%. These results are consistent with the amantadine-resistant mutant being dominant and the oligomeric state being a tetramer.

Amantadine↗
PubMed1997

Simultaneous detection of near-field topographic and fluorescence images of human chromosomes via scanning near-field optical/atomic-force microscopy (SNOAM).

Scanning near-field optical/atomic-force microscopy (SNOAM) provided us with simultaneous topographical and optical images of human chromosomes using a sharp and bent optical fiber as a near-field optical probe. Native chromosomes were spread out onto a coverslip using the surface-spreading whole-mount method. The SNOAM system does not need pretreatment of samples such as metal coating or chemical immobilization. Near-field topographic and fluorescence images provided useful information on native chromosome structure.

B-Lymphocytes↗
PubMed1997

Effect of beryllium chloride on porphyrin metabolism in pregnant mice administered by subcutaneous injection.

The effect of beryllium (Be) compounds on porphyrins was investigated in pregnant mice. The blood protoporphyrin (Proto) and zinc protoporphyrin (Zn Proto) concentrations were increased in pregnancy. Regardless of pregnancy or nonpregnancy, the Proto concentration was decreased after Be injection. Delta-aminolevulinic acid dehydratase (ALA-D) and porphobilinogen deaminase (PBG-D) activities in blood were significantly elevated in the pregnant untreated (Con-pregnant) group, compared to the nonpregnant mice untreated (Con-nonpregnant) and nonpregnant mice treated with Be (Be-nonpregnant) groups. The blood ALA-D activity of the pregnant mice treated with Be (Be-pregnant group) tended to decrease, compared to Con-pregnant group. The blood PBG-D activity in the Be-pregnant group was significantly lower compared with that of the Con-pregnant group. The ALA-D and PBG-D activities in the spleen were also significantly elevated in the Con-pregnant group, compared to nonpregnant groups. However, it was noted that these values in the Be-pregnant group were almost the same as that of the Con-nonpregnant group and were significantly lower than that in the Con-pregnant group. The elevation of ALA-D and PBG-D activities in the blood and spleen, which play a role in the hematopoietic function of mice, was observed in the Con-pregnant mice compared to the nonpregnant mice. However, the phenomenon was not observed in the Be-pregnant mice, it suggesting that Be suppressed the pregnancy-induced increase in hematopoietic function.

Animals↗
PubMed1997

Expression of tPA mRNA in the facial nucleus following facial nerve transection in the rat.

Plasminogen activators (PAs) have been suggested to play a role in neuronal migration and glial cell proliferation in the developing CNS. Less is known, however, about the role of PAs in the mature nervous system. To elucidate the role of tissue type plasminogen activator (tPA) in the nervous system we used in situ hybridization to study the expression of tPA mRNA within the rat facial nucleus after facial nerve transection. We also studied the effect of MK-801 on tPA mRNA expression in order to investigate whether the previously reported N-methyl-D-aspartate (NMDA) receptor activation is involved in this model. tPA mRNA was expressed in the ipsilateral facial motoneurones from 6 h after injury. This expression continued for at least 2 weeks after facial nerve transection. Administration of MK-801 before axonal injury did not affect the expression of tPA mRNA in the facial nucleus. These data suggest that tPA might be involved in the regenerative process without NMDA receptor activation in mature facial neurones.

Animals↗
PubMed1997

Immunohistochemical studies on endothelial cell phenotype in hepatocellular carcinoma.

To examine the phenotype of the sinusoidal endothelial cells (SECs) surrounding tumor cells and the process of capillarization in hepatocellular carcinoma (HCC), 51 primary HCCs, 4 adrenal metastases, and 3 portal tumor thrombi were immunohistochemically stained with monoclonal antibodies (MAbs) for CD4, CD14 (lipopolysaccharide-binding protein complex receptors), and CD32 (Fc gamma receptor II), which are specifically found on the SECs in normal liver, but not on ordinary vascular endothelial cells (ECs). Immunostaining was also performed for CD36 (thrombospondin receptors), EN4 antigen (Ag) (a pan-vascular endothelial cell Ag), PAL-E Ag (a venous and capillary EC Ag), factor VIII-related Ag (FVIIIRAg), and laminin. MAb 25F9, which identifies macrophages, was simultaneously used with the other MAbs to distinguish macrophages from SECs in HCCs (HCC SECs). CD4, CD14, and/or CD32 were found on HCC SECs only in 12 well-differentiated primary HCCs showing a thin trabecular or pseudoglandular tumor cell arrangement. These 12 tumors were smaller than those without CD4-, CD14-, and/or CD32-positive SECs (P < .05). Among them, 7, 5, and 11 tumors were negative or only partially positive for laminin, PAL-E Ag, and FVIIIRAg, respectively. Staining for laminin and PAL-E Ag showed an inverse relationship to the expression of CD4, CD14, and CD32 on HCC SECs and the tumor differentiation. In conclusion, the phenotypes of the SECs in early and well-differentiated HCC are thought to be similar to those of the SECs in normal liver. With progressing tumor dedifferentiation the HCC SECs lose the phenotypes peculiar to liver SECs and acquire the characteristics of capillary ECs, though both types of phenotypical change occur independently of each other.

Antigens, CD↗
PubMed1997

Omental delivery of prostaglandin E1 effectively increases portal venous blood flow in 66%-hepatectomized rats.

Changes in portal venous blood flow (PVF) and systemic arterial blood pressure (SAP) were examined following prostaglandin E1 (PGE) application to the greater omentum and femoral vein in 66%-hepatectomized rats. PVF increased when PGE was administered to the omentum and femoral vein at 7.5 micrograms/kg per min for 2 min. The magnitude of PVF response due to both administrations was dose-dependent, but the duration of the PVF response in the omental application was longer than that in the femoral administration. SAP was unchanged after omental application, while femoral administration reduced SAP concomitant with an increase in PVF. These results suggest that, in this hepatectomized model, the omentum is a better site for PGE administration than the vein, and that omental PGE delivery is also effective for enhancing PVF without inducing any changes in SAP.

Alprostadil↗
PubMed1997

The appearance of a normal appendix on barium enema examination does not rule out a diagnosis of chronic appendicitis: report of a case and review of the literature.

We report herein the rare case of a 15-year-old girl with chronic appendicitis in whom the appendix was clearly depicted by a barium enema (BE) examination. The patient presented with a 4-month history of diffuse abdominal pain and tenderness in the lower abdomen. Neither computed tomography nor ultrasonography showed any abnormal findings in the lower abdomen or pelvic cavity. Furthermore, BE examination depicted an appendix filled with the contrast medium. However, at elective surgery, she was found to have chronic appendicitis which was later confirmed histologically. Following this case report, a discussion on the value and limitations of BE examination for the diagnosis of acute and chronic appendicitis is presented.

Abdominal Pain↗
PubMed1997

Binding of 8-mer to 11-mer peptides carrying the anchor residues to slow assembling HLA class I molecules (HLA-B*5101).

The binding of 303 8-mer to 11-mer peptides carrying the anchor residues at P2 and the C-terminus to HLA-B*5101 molecules was examined by a stabilization assay in which peptides were incubated with RMA-S-B*5101 cells at 26 degrees C for 3 h. Analysis of the binding of these peptides to HLA-B*5101 molecules showed that Pro and Ala at P2, and Ile, Val, and Leu at the C-terminus functioned as anchor residues, while Gly at P2 and Met at the C-terminus were weak anchors. Pro was a stronger anchor residue than Ala at P2, while Ile was the strongest anchor at the C-terminus. Among 8-mer to 11-mer peptides, the 9-mer peptides showed the strongest binding to HLA-B*5101 molecules. This is in contrast to our recent findings that 10-mer and 11-mer peptides bind to HLA-B*3501 molecules as effectively as 9-mer peptides. Since both HLA class I molecules have the same B-pocket and the binding peptides carry the same anchor residues, it is assumed that the structure of the F-pocket may restrict the length of binding peptides. The ability of HLA-B*5101 binding peptides to stabilize the HLA-B*5101 molecules was markedly lower than that of HLA-B*3501 binding peptides to stabilize the HLA-B*3501 molecules. It is known that HLA-B*5101 is a slow assembling molecule, while HLA-B*3501 assembles rapidly. The results imply that the slow assembling of HLA-B*5101 molecules results from the low affinity of peptides to HLA-B*5101 molecules.

Cell Line↗
PubMed1997

Dual mode of N-methyl-D-aspartate-induced neuronal death in hippocampal slice cultures in relation to N-methyl-D-aspartate receptor properties.

Hippocampal slices prepared from neonatal rats were cultured for several weeks, and excitotoxicity induced in CA1 pyramidal neurons by N-methyl-D-aspartate was evaluated at different culture stages. CA1 neurons cultured for one week exhibited cell death predominantly within 1-3 h after a 15-min N-methyl-D-aspartate insult (early death), whereas those cultured for three weeks showed cell death mainly a few hours to 24 h after the insult (delayed death). CA1 neurons cultured for two weeks were in a transitional state, expressing only weak early and delayed forms of cell death in response to N-methyl-D-aspartate. The N-methyl-D-aspartate-induced early cell death observed in the one-week group depended on external Cl- but did not require external Ca2+; rather, early cell death was enhanced in Ca2+-free solution. This early cell death was accompanied by cell swelling, but cell swelling alone produced by osmotic changes failed to induce cell death. There was no evidence that CA1 neurons in the one-week group were more responsive to N-methyl-D-aspartate than those in the two other groups. Delayed cell death examined in the three-week group depended on external Ca2+ but was independent of Cl-. The density of N-methyl-D-aspartate-induced whole-cell currents recorded from CA1 neurons in Mg2+-free solution remained unchanged during three weeks of culture. However, the N-methyl-D-aspartate receptor channel in the three-week group was more resistant to Mg2+ block than that in the one- or two-week group. The incidence of N-methyl-D-aspartate-induced delayed cell death was higher in the three-week group than in the two-week group in normal solution but not in Mg2+-free solution. Thus, Mg2+ block-resistant properties of the N-methyl-D-aspartate receptor channel acquired during prolonged culture may account for the high incidence of N-methyl-D-aspartate-induced delayed cell death in the three-week group. However, the N-methyl-D-aspartate receptor subunits expressed in the CA1 subfield did not show any feature specific to the three-week group. These results show that two mechanistically distinct modes of N-methyl-D-aspartate-induced neuronal death are manifested differentially at different culture stages, depending on the intrinsic neuron properties (i.e. early cell death) and on the properties or the responsiveness of the N-methyl-D-aspartate receptor (i.e. delayed cell death).

Animals↗
PubMed1997

Expression of growth inhibitory factor mRNA after focal ischemia in rat brain.

Growth inhibitory factor (GIF) is a small protein belonging to the metallothionein family that has the capacity to inhibit neuronal survival and neurite formation in vitro. This study was conducted to investigate the role of GIF in the brain afflicted with ischemic injury. We used the in situ hybridization technique and Northern blot analysis to study the changes in GIF messenger RNA (mRNA) expression in a rat focal ischemia model. On the first day, the expression tended to decrease in the hemisphere ipsilateral to the injury. It returned to normal levels on the second day except for the central area of the middle cerebral artery (MCA) territory. On the third and fourth day, the expression increased diffusely in the hemisphere of the affected side, including the subcortical area. Two weeks after ischemia, the GIF mRNA expression increased again but only in the peri-infarcted area. Down-regulation of GIF on the first day in the cortex ipsilateral to the infarction might promote neurite sprouting. The subsequent increase in GIF mRNA expression on the third and fourth day might be a symptom of neurons attempting to inhibit excessive neurite outgrowth, or to protect themselves against toxicity caused by oxygen radicals. The later increase in the limited area around the infarction may be related to astroglial reaction. Growth inhibitory factor may play an important role in regulating the central nervous system after ischemic insults.

Animals↗
PubMed1997

Potent and selective inhibition of human immunodeficiency virus type 1 transcription by piperazinyloxoquinoline derivatives.

We have found novel piperazinyloxoquinoline derivatives to be potent and selective inhibitors of human immunodeficiency virus type 1 (HIV-1) replication in both acutely and chronically infected cells. 8-Difluoromethoxy-1-ethyl-6-fluoro-1,4-didehydro-7-[4-(2-met hoxyphenyl)-1-piperazinyl]-4-oxoquinoline-3-carboxylic acid (K-12), the most potent congener of the series, completely inhibited HIV-1 replication in acutely infected MOLT-4 cells at a concentration of 0.16 to 0.8 microM without showing any cytotoxicity. The compound completely suppressed tumor necrosis factor alpha (TNF-alpha)-induced HIV-1 expression in latently infected cells (OM-10.1) and constitutive viral production in chronically infected cells (MOLT-4/III(B)) at a concentration of 0.8 microM. K-12 could also inhibit HIV-1 antigen expression in OM-10.1 and MOLT-4/III(B) cells at this concentration. Northern blot analysis revealed that K-12 selectively prevented the accumulation of HIV-1 mRNA in MOLT-4/III(B) and TNF-alpha-treated OM-10.1 cells in a dose-dependent fashion. It was not inhibitory to HIV-1 Tat or the cellular transcription factors NF-kappaB and Sp1, suggesting that the piperazinyloxoquinoline derivatives are a group of HIV-1 transcription inhibitors with a unique mechanism of action.

Anti-HIV Agents↗
PubMed1997

Protection of mice from respiratory Sendai virus infections by recombinant vaccinia viruses.

Mechanisms of protection of mice from Sendai virus, which is exclusively pneumotropic and causes a typical respiratory disease, by immunization with recombinant vaccinia viruses (RVVs) were investigated. Although the RVV carrying a hemagglutinin-neuraminidase gene of Sendai virus (Vac-HN) propagated in the noses and lungs of mice by either intranasal (i.n.) or intraperitoneal (i.p.) inoculation, no vaccinia virus antigens were detected in the mucosal layer of upper and lower airways of the i.p.-inoculated mice. The mice immunized i.n. with Vac-HN or Vac-F (the RVV carrying a fusion protein gene of Sendai virus) demonstrated the strong resistance to Sendai virus challenge both in the lung and in the nose, whereas the i.p.-immunized mice showed almost no resistance in the nose but showed a partial resistance in the lung. Titration of Sendai virus-specific antibodies in the nasal wash (NW), bronchoalveolar lavage (BAL), and serum collected from the Vac-F-immunized mice showed that the NW from the i.n.-immunized mice contained immunoglobulin A (IgA) antibodies but no IgG and the BAL from the mice contained both IgA and IgG antibodies. On the other hand, neither IgA nor IgG antibodies were detected in the NW from the i.p.-immunized mice and only IgG antibodies were detected in the BAL, although both i.n.- and i.p.-immunized mice exhibited similar levels of serum IgG, IgA, and neutralizing antibodies. The resistance to Sendai virus in the noses of i.n.-immunized mice could be abrogated by the intranasal instillation of anti-mouse IgA but not of anti-IgG antiserum, while the resistance in the lung was not significantly abrogated by such treatments. These results demonstrate that IgA is a major mediator for the immunity against Sendai virus induced by the RVVs and IgG is a supplementary one, especially in the lung, and that the RVV should be intranasally inoculated to induce an efficient mucosal immunity even if it has a pantropic nature.

Administration, Intranasal↗
PubMed1997

Radiation dosimetry measurements with real time radiation monitoring device (RRMD)-II in Space Shuttle STS-79.

The real-time measurement of radiation environment was made with an improved real-time radiation monitoring device (RRMD)-II onboard Space Shuttle STS-79 (S/MM#4: 4th Shuttle MIR Mission, at an inclination angle of 51.6 degrees and an altitude of 250-400km) for 199 h during 17-25 September, 1996. The observation of the detector covered the linear energy transfer (LET) range of 3.5-6000 keV/micrometer. The Shuttle orbital profile in this mission was equivalent to that of the currently planned Space Station, and provided an opportunity to investigate variations in count rate and dose equivalent rate depending on altitude, longitude, and latitude in detail. Particle count rate and dose equivalent rate were mapped geographically during the mission. Based on the map of count rate, an analysis was made by dividing whole region into three regions: South Atlantic Anomaly (SAA) region, high latitude region and other regions. The averaged absorbed dose rate during the mission was 39.3 microGy/day for a LET range of 3.5-6000 keV/micrometer. The corresponding average dose equivalent rates during the mission are estimated to be 293 microSv/day with quality factors from International Commission on Radiological Protection (ICRP)-Pub. 60 and 270 microSv/day with quality factors from ICRP-Pub. 26. The effective quality factors for ICRP-Pub. 60 and 26 are 7.45 and 6.88, respectively. From the present data for particles of LET > 3.5keV/micrometer, we conclude that the average dose equivalent rate is dominated by the contribution of galactic cosmic ray (GCR) particles. The dose-detector depth dependence was also investigated.

Aerospace Medicine↗
PubMed1997

Measurements of LET distribution and dose equivalent onboard the Space Shuttle IML-2 (STS-65) and S/MM#4 (STS-79).

Space radiation dosimetry measurements have been made onboard the Space Shuttle STS-65 in the Second International Microgravity Laboratory (IML-2: 28.5 degrees x 300 km: 14.68 days) and the STS-79 in the 4th Shuttle MIR mission (S/MM#4: 51.6 degrees x 300-400km: 10.2 days). In these measurements, three kinds of detectors were used; one is a newly developed active detector telescope called "Real-time Radiation Monitoring Device (RRMD-I for IML-2 and RRMD-II with improved triggering system for S/MM#4)" utilizing silicon semi-conductor detectors and the other detectors are conventional passive detectors of thermoluminescence dosimeters (TLDs) and CR-39 plastic track detectors. The main contribution to dose equivalent for particles with LET > 5.0 keV/micrometer (IML-2) and LET > 3.5 keV/micrometer (S/MM#4) is seen to be due to galactic cosmic rays (GCRs) and the contribution of the South Atlantic Anomaly (SAA) is less than 5% (IML-2: 28.5 degrees x 300 km) and 15% (S/MM#4: 51.6 degrees x 400 km) in the above RRMD LET detection conditions. For the whole LET range (> 0.2 kev/micrometer) obtained by TLDs and CR-39 in these two typical orbits (a small inclination x low altitude and a large inclination x high altitude), absorbed dose rates range from 94 to 114 microGy/day, dose equivalent rates from 186 to 207 microSv/day and average quality factors from 1.82 to 2.00 depending on the locations and directions of detectors inside the Spacelab at the highly protected IML-2 orbit (28.5 degrees x 300 km), and also, absorbed dose rates range from 290 to 367 microGy/day, dose equivalent rates from 582 to 651 microSv/day and average quality factors from 1.78 to 2.01 depending on the dosimeter packages around the RRMD-II "Detector Unit" at the S/MM#4 orbit (5l.6 degrees x 400km). In general, it is seen that absorbed doses depend on the orbit altitude (SAA trapped particles contribution dominant) and dose equivalents on the orbit inclination (GCR contribution dominant). The LET distributions obtained by two different types of active and passive detectors, RRMDs and CR-39, are in good agreement for LET of 15 - 200 kev/micrometer and difference of these distributions in the regions of LET < 15 kev/micrometer and LET > 200 kev/micrometer can be explained by considering characteristics of CR-39 etched track formation especially for the low LET tracks and chemical etching conditions.

Atlantic Ocean↗
PubMed1997

[Peptide binding motif for HLA class I and autoimmune disease].

Some HLA class I alleles are strongly associated with autoimmune diseases, such as HLA-B27 for ankylosing spondylitis (AS), and HLA-B51 for Behçet's disease. But it is not clear how the class I molecules play a role in induction of the diseases. Recent studies have shown that HLA class I associates with beta 2-microglobulin and one of a range of naturally processed short peptides. The peptides bind into a groove formed by two alpha helices and a beta-pleated sheet of HLA class I molecules. HLA class I molecules present peptides with allele-specific motifs to T cells, and CTL recognize the peptides on HLA class I molecules. Further studies of peptides bound to HLA class I molecules are expected to identify peptides associated with autoimmune disease.

Amino Acid Sequence↗
PubMed1997

[Changes in porphyrin metabolism of mice given beryllium and/or zinc].

Beryllium chloride and/or zinc chloride were intraperitoneally injected into mice. The amount of beryllium (Be) injected corresponded to 1/10th of the LD50 dose intravenously administered. The amount of zinc (Zn) injected was the same as Be. The changes in porphyrin metabolism of the mice were studied. Delta-aminolevulinic acid dehydratase (ALA-D) activities in the blood were found to increase significantly in Zn and BeZn groups when compared to the control level. The blood porphobilinogen deaminase (PBG-D) activity in the Zn group was slightly less than that in the controls. The ALA-D and PBG-D activities in liver were higher in the Be and BeZn groups than in the controls. The splenic ALA-D activities were significantly higher in the Zn and BeZn groups than in the control and Be groups. The splenic PBG-D activities were markedly higher in the Be and/or Zn groups than in the controls. An increase in ALA-D activities in the blood and spleen was observed in the BeZn group, together with an increase in ALA-D activities caused by Zn administration. Furthermore, the increase in PBG-D activities in liver and spleen was observed in the Be and/or Zn groups. The results suggested that chemical similarity between Be and Zn brought about these phenomena.

Animals↗