Biomedical subjects

N Fujii

Publications and source records attributed to N Fujii.

At least 181 records · Page 10Linked to original sources

PubMed1998

Intracortical microstimulation of bilateral frontal eye field.

We trained two monkeys to perform a fixation task. Intracortical microstimulation (ICMS) was applied to the monkey frontal eye field (FEF) while monkeys were fixating on one of five fixation LEDs. The ICMS was applied in two different manners. Under the single stimulation condition, ICMS was delivered to either right or left FEF. Under the paired stimulation condition, bilateral FEF were successively stimulated with an interval of 30-250 ms. The single stimulation elicited contraversive saccades. As reported previously, these saccades were not much affected by initial eye positions, maintaining the same vector. In contrast, the paired stimulation elicited double-step saccades. The first of the paired stimulation elicited constant vector saccades, but the second of the paired stimulation evoked saccades whose vector varied greatly depending on the eye position at the start of individual saccades. The second saccades, starting from various initial positions, were directed to the endpoint of saccades that were elicited from the same FEF site under the single stimulation condition. Endpoints of second saccades varied little despite variations of intervals of the stimulation pairs, ranging from 60 to 150 ms. On the basis of these observations, we propose a novel view that the FEF is involved in directing saccades to an internally referenced visual target.

Animals↗

PubMed1998

A histological study on tissue responses to titanium implantation in rat maxilla: the process of epithelial regeneration and bone reaction.

The present study aimed to establish a titanium implantation model using rat maxillae as well as demonstrate the chronological tissue responses to implantation. Pure titanium implants were inserted in the upper first molar extraction sites of Wistar rats 1 month after tooth extraction. The animals were sacrificed at 1 to 30 days postimplantation, and prepared tissue specimens were processed for light microscopy. The removal of implants from tissue blocks was done using 2 methods: mechanical removal or a cryofracture technique. In the early stages, peri-implant tissues showed severe damage to the oral epithelium and collagen bundles with significant inflammatory cell infiltration. The peri-implant epithelium grew apically along the implant by 10 days postimplantation, and regenerated to show a similar feature of junctional epithelium seen in normal rats at 15 days postimplantation, at which time no signs of inflammation were observed. The regenerated collagen bundles in the connective tissue were arranged circumferentially to the implants in the horizontal sections. New bone formation first appeared around the implants at 5 days postimplantation, covering the entire perimeter of implants by 30 days postimplantation. Scanning electron microscopic observations of the surface texture of the removed implants suggest the probability of an adhesive mechanism between the implants and the peri-implant epithelium and/or the alveolar bone. These findings indicate that this experimental model is useful for detailed analysis of peri-implant tissue because of its easy implantation procedure.

Animals↗

PubMed1998

Hypotensive effects of an angiotensin II type 1 receptor antagonist differ between exercised and sedentary rats aged from 4 to 19 weeks.

The hypotensive effects of an angiotensin II type 1 receptor antagonist TCV-116 were accelerated by swimming training in the early period of chronic administration in young rats. In the latter period, however, a severe decrease in blood pressure that appeared during long-term administration of TCV-116 was prevented by swimming training. Therefore exercise may contribute to the stabilization of blood pressure in young rats treated with TCV-116.

Angiotensin Receptor Antagonists↗

PubMed1998

[Intracellular signaling pathways of angiotensin II receptor type 1 involved in the development of cardiovascular diseases].

Angiotensin II (AII) receptor type 1 (AT1), a G-protein-coupled receptor, is involved in the development of cardiovascular diseases such as hypertensin, cardiac hypertrophy, and atherosclerosis. Recent reports indicate that tyrosine phosphorylation of multiple intracellular molecules is responsible for most of these AII actions mediated by AT1, similar to receptor tyrosine kinase signaling pathways. AII activates MAPK by tyrosine phosphorylating the EGF receptor by the mechanism called transactivation with subsequent Ras activation in vascular smooth muscle and cardiac fibroblast cells. In contrast, AT1 leads to MAPK activation through PKC in cardiac myocytes. In addition to these signals, JAK/STAT pathways, which mediate cytokine actions, are also important for several AII functions through AT1.

Animals↗

PubMed1998

[An adult case of Reye syndrome induced by diclofenac sodium, and recovered by plasma exchange].

Reye syndrome (RS) is an acute encephalopathy in childhood, and is very rare in adulthood. Here we report a 21-year-old woman with RS. Because of her dysmenorrhea, she took 3 tablets of diclofenac sodium (25 mg) per day in 3 divided doses for two days. Two days after the last intake of the medicine, she developed high fever, nausea, vomiting, and disturbance of consciousness with delirium, i.e., acute encephalopathy. She did not have seizure, hemiplegia, or other focal neurological manifestations. The serum GOT level was normal at onset, but in 12 hours dramatically increased up to 8,632 IU/L. The serum bilirubin level was normal. The cerebrospinal fluid revealed normal cell count, and protein. Although the liver biopsy was not performed because of thrombocytopenia, we diagnosed her as an adult case of RS according to the clinical criteria of the Center for Disease Control. In addition to treatment for the brain edema, plasma exchange was performed once treat the encephalopathy at the onset. The next day, her consciousness level and serum GOT level markedly improved. She completely recovered from acute encephalopathy in a week after her admission. In conclusion, diclofenac sodium, as well as aspirin, should be considered as a possible causal agent for RS, and early plasma exchange may be beneficial.

Adult↗

PubMed1997

Osteopontin involvement in integrin-mediated cell signaling and regulation of expression of alkaline phosphatase during early differentiation of UMR cells.

To clarify the function of osteopontin in osteoblast differentiation, we have examined the signal transduction pathway in an osteoblastic cell line (UMR106-6) bound to osteopontin, fibronectin, vitronectin and collagen type I surfaces. This was done by investigating the production and autophosphorylation of focal adhesion kinase (FAK) and the expression of alkaline phosphatase (ALP) at the transcription level. Results suggest that osteopontin was not only responsible for the autophosphorylation of FAK but regulated the expression of ALP, which was strongly correlated with FAK activity. These results suggest that osteopontin might act as a trigger in the early differentiation of osteoblasts.

Alkaline Phosphatase↗

PubMed1997

Pattern of DNA binding of nuclear proteins to the proximal Agrobacterium rhizogenes rolC promoter is altered during somatic embryogenesis of carrot.

Carrot cells cultured in vitro in a medium supplemented with 2,4-D (2,4-dichlorophenoxyacetic acid) proliferate as unorganized cell clusters. Upon removal of 2,4-D from the culture medium, these cells undergo somatic embryo formation through globular, heart, and torpedo stages. Since the proximal -255 bp upstream region of the rolC gene of the Ri plasmid confers somatic embryogenesis-related activation on the uidA gene in transgenic carrot cell culture, we investigated the interaction of nuclear proteins with the proximal -255bp upstream sequences to characterize the mechanism of somatic embryogenesis-related activation. Gel retardation experiments revealed that there were several different profiles of the relative levels of DNA binding activities in nuclear protein extracts from calli, PEMs (proembryogenic masses), globular embryos, and heart/torpedo embryos. The binding activity associated with a fragment (-203 bp to -92 bp) of one protein (BI) was most abundant in globular embryos. Another DNA binding protein (AII) showed the highest DNA binding activity in calli, but had low binding activities in PEMs and globular embryos. Such an altered pattern of DNA binding activities of nuclear proteins may contribute to somatic embryogenesis-related activation of the rolC promoter. Competition experiments with oligonucleotides revealed that the BI protein interacts with AT-rich sequences.

Bacterial Proteins↗

PubMed1997

Thrombin reduces large heparan sulfate proteoglycan molecules in cultured vascular endothelial cell layers through inhibition of core protein synthesis.

We investigated the alteration of heparan sulfate proteoglycans induced by thrombin in cultured vascular endothelial cells. Heparan sulfate proteoglycans, which were metabolically labeled with [3H] glucosamine and [35S] sulfate, were isolated by DEAE-Sephacel ion-exchange chromatography and characterized by molecular sieve gel filtration. Core proteins were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of [35S] amino acids-labeled heparan sulfate proteoglycans after digestion with hepartinase. It was revealed that the high molecular weight subclass of heparan sulfate proteoglycans in the cell layer was markedly decreased by thrombin without changes of the hydrodynamic size of the molecules and the molecular weight of heparan sulfate chains. In addition, thrombin decreased the amount of large heparan sulfate proteoglycan core protein with a molecular weight of approximately 400 kDa, probably perlecan core, in the cell layer and the conditioned medium. The present data suggest that thrombin-induced decrease in the amount of heparan sulfate in vascular endothelial cell layer includes a reduction of the number of large heparan sulfate proteoglycan perlecan molecules through a suppression of the core protein synthesis.

Animals↗

PubMed1997

The conformation formed by the domain after alanine-155 induces inversion of aspartic acid-151 in alpha A-crystallin from aged human lenses.

A new cleavage site, which is a post-translational modification, was found between residues His-154 and Ala-155 in alpha A-crystallin from the aged human lens. After trypsin digestion of alpha A-crystallin two peptides that include Asp-151 were obtained and have remarkable differences. That is, the stereo-configuration of the Asp-151 in the normal length peptide was predominately inverted to the D-isomer of beta-aspartyl form (D/L of 5.7). However, the stereoconfiguration of the Asp-151 in the cleavage peptide, that lacks the sequence following Ala-155 to the C-terminus, remained predominately in the L-isomer form as indicated by a D/L value of 0.3. The results suggest that the secondary structure in the region of Ala-155 to the C-terminus may constitute a field that causes the inversion of the Asp-151 to the D-isomer form. Since this kind of cleavage was not found in alpha A-crystallin from young lens, the cleavage between His-154 and Ala-155 is probably the result of aging.

Aged↗

PubMed1997

A small molecule CXCR4 inhibitor that blocks T cell line-tropic HIV-1 infection.

Several members of the chemokine receptor family have been shown to function in association with CD4 to permit human immunodeficiency virus type 1 (HIV-1) entry and infection. The CXC chemokine receptor CXCR4/fusin is a receptor for pre-B cell growth stimulating factor (PBSF)/stromal cell-derived factor 1 (SDF-1) and serves as a coreceptor for the entry of T cell line-tropic HIV-1 strains. Thus, the development of CXCR4 antagonists or agonists may be useful in the treatment of HIV-1 infection. T22 ([Tyr5,12,Lys7]-polyphemusin II) is a synthesized peptide that consists of 18 amino acid residues and an analogue of polyphemusin II isolated from the hemocyte debris of American horseshoe crabs (Limulus polyphemus). T22 was found to specifically inhibit the ability of T cell line-tropic HIV-1 to induce cell fusion and infect the cell lines transfected with CXCR4 and CD4 or peripheral blood mononuclear cells. In addition, T22 inhibited Ca2+ mobilization induced by pre-B cell growth stimulating factor (PBSF)/SDF-1 stimulation through CXCR4. Thus, T22 is a small molecule CXCR4 inhibitor that blocks T cell line-tropic HIV-1 entry into target cells.

3T3 Cells↗

PubMed1997

Amino-terminus truncated apolipoprotein E is the major species in amyloid deposits in Alzheimer's disease-affected brains: a possible role for apolipoprotein E in Alzheimer's disease.

Amyloid deposits in Alzheimer's disease (AD) are composed of amyloid beta protein (A beta) and many other components called amyloid-associated proteins. Apolipoprotein E (apoE) is one of the most important amyloid-associated proteins. The role apoE plays in AD, however, is yet to be determined. In this study, we present the biochemical and histochemical nature of apoE in AD-affected brains using four monoclonal antibodies (mAbs) against apoE and newly established antibodies against the amino-terminal (anti-apoE-N), and carboxyl-terminal regions (anti-apoE-C) of apoE. Competitive ELISA and Western-blot analysis combined with thrombolytic digestion of apoE indicated that our four mAbs recognized at least two different epitopes within a 22-kDa amino-terminal domain of apoE. Using these mAbs and an anti-A beta mAb, double immunostaining showed that the majority of amyloid deposits were stained by both anti-apoE and anti-A beta mAbs, but the minority of them were detected only by either anti-apoE or anti-A beta mAbs. Differences in staining properties between anti-apoE-N and anti-apoE-C were that anti-apoE-C recognized both amyloid deposits and astrocytes similar to anti-apoE mAbs, but anti-apoE-N strongly stained only astrocytes. Preliminary semi-quantitative determinations of apoE in CSF and brain homogenate showed that the amount of apoE increased in AD and Creutzfeldt-Jakob disease brains compared to normal samples. Our immunological data, using antibodies specific for the amino and carboxyl termini of apoE, suggest that apoE may, in some circumstances, initiate plaque formation, and that apoE in amyloid deposits has at least part of its amino termini cleaved out.

Alzheimer Disease↗

PubMed1997

Membrane permeabilization mechanisms of a cyclic antimicrobial peptide, tachyplesin I, and its linear analog.

Tachyplesin I (T-SS), an antimicrobial peptide from Tachypleus tridentatus, has a cyclic antiparallel beta-sheet structure maintained by two disulfide bridges. The peptide effectively permeabilizes both bacterial and artificial lipid membranes. T-Acm, a linear analog peptide with the four SH groups protected by acetamidomethyl groups, exhibits a much weaker membrane-permeabilizing activity in spite of a greater disruption of the lipid organization [Matsuzaki, K., Nakayama, M., Fukui, M., Otaka, A., Funakoshi, S., Fujii, N., Bessho, K., & Miyajima, K. (1993) Biochemistry 32, 11704-11710]. To clarify the efficient permeabilization mechanism of T-SS, we studied the interactions of both peptides with liposomes and planar lipid bilayers. The cyclic peptide capable of spanning the bilayer (ca. 3 nm length) was found to form an anion-selective pore and translocate across the bilayer coupled with the pore formation. A cis-negative transmembrane potential facilitated the pore formation compared with the cis-positive potential. In contrast, the linear peptide failed to translocate. Instead, it impaired the membrane barrier by disrupting the lipid organization with morphological changes in the vesicles.

Amino Acid Sequence↗

PubMed1997

Amyloid precursor protein, A beta and amyloid-associated proteins involved in chloroquine retinopathy in rats--immunopathological studies.

To understand the retinal changes in Alzheimer disease (AD) patients, pathological and immunocytochemical studies were performed on retinal cells in the chloroquine-treated rats at 0, 4, 8, 12, 16, 20, and 24 weeks after the initial injection, using anti-amyloid precursor protein (APP), -amyloid beta protein (A beta), -apolipoprotein E (apoE), -ubiquitin, and -cathepsin D antibodies. Pathological alterations consistent with chloroquine retinopathy were recognized in the ganglion cells of the ganglion cell layer (GCL) and the inner plexiform layer (IPL) 4 weeks after initial chloroquine injection. Rat retinal changes appear to have a direct relationship to the duration of chloroquine administration. Intense immunoreactivities for anti-APP, A beta, apoE (an associated protein), and ubiquitin co-localized in the swollen ganglion cells and Muller cells by 20-24 weeks together with the lysosomal enzyme cathepsin D. The present data indicate that the endosomal/lysosomal pathway plays an important role in the processing of APP in rat retina. This experimental model is considered to be a suitable neural model to understand retinal pathology and the processing of APP in terms of the pathogenesis of AD, whereas chloroquine-induced myopathy is a useful extra neuronal model.

Amyloid↗

PubMed1997

Interactions of an antimicrobial peptide, magainin 2, with outer and inner membranes of Gram-negative bacteria.

Magainin peptides, isolated from Xenopus skin, have broad spectra of antimicrobial activity and low toxicities to normal eukaryotic cells, thus being good candidates for therapeutic agents. The mechanism of action is considered to be the permeabilization of bacterial membranes. A number of studies using lipid vesicles have elucidated its molecular detail. However, their interactions with bacteria are not yet well understood. In this paper, we synthesized several magainin analogs with different charges (0 to +6) and hydrophobicities, and systematically studied their interactions with the outer and inner membranes of three species of Gram-negative bacteria (Escherichia coli, Acinetobacter calcoaceticus, Proteus vulgaris). The treatment of the E. coli cells with native magainin 2 (+4) immediately induced the efflux of the intracellular K+ ions and the cell death. A number of blebs were formed on the bacterial surface and the outer membrane became leaky. An increase in the peptide's positive charge enhanced the outer membrane permeabilization and the bactericidal activity. The cationic peptides also effectively permeabilized the inner membranes rich in acidic phospholipids, indicating the importance of electrostatic interactions. Substitution of Trp for Phe simultaneously increased the bactericidal activity and the hemolytic activity. A strategy to develop potent antimicrobial peptides was discussed on the basis of these results.

Acinetobacter↗

PubMed1997

Involvement of cholinergic processes in cholecystokinin (CCK) release [corrected] by luminal oleic acid.

Cholecystokinin (CCK) is an important bioactive peptide that stimulates pancreatic enzyme secretion. Circulating CCK is secreted from endocrine cells in the upper small intestine in response to various luminal stimuli and to vascular administration of gastrin releasing peptides. However, the mechanism of its release has not been fully elucidated. In the present study, the vascularly perfused duodenojejunum was isolated from male Wistar rats. The effects of luminal infusion of sodium oleate (2 or 0.4%) or intra-arterial infusion of neuromedin C(10(-7) M) with or without atropine and with a recently synthesized specific bombesin antagonist (EABI) were examined. The CCK release produced by intra-arterial infusion of neuromedin C was inhibited by EABI in a dose-dependent manner. The CCK release produced by luminal sodium oleate was inhibited by atropine, but not affected by EABI. The CCK release stimulated by luminal sodium oleate is mediated, at least in part, by a cholinergic mechanism, but neuromedin C directly stimulates CCK release via its receptor on CCK-producing cells.

Animals↗

PubMed1997

Modulation of magainin 2-lipid bilayer interactions by peptide charge.

Magainin 2, an antimicrobial peptide from Xenopus skin, assumes an amphiphilic helix when bound to acidic phospholipids, forming a pore composed of a dynamic, peptide-lipid supramolecular complex [Matsuzaki et al. (1996) Biochemistry 35, 11361-11368]. Upon the disintegration of the pore, a fraction of the peptide molecules stochastically translocates across the bilayer (Matsuzaki, et al., 1995). In order to investigate the effects of peptide charge on the magainin 2-lipid bilayer interactions, we synthesized four magainin 2 analogs with different charges (0-6+). MG0: K10E, K11E, F12W-magainin 2. MG2+: K10E, F12W-magainin 2. MG4+: F12W-magainin 2. MG6+: F12W, E19Q-magainin 2 amide. An increase in charge resulted in a stronger binding of the peptide to the negatively charged membranes, suggesting that electrostatic attractions play a crucial role in the binding process. The helical stability in a trifluoroethanol/buffer mixture was decreased with increasing positive charge because of electrostatic repulsions between the closely spaced positive side chains, whereas the helicity in the lipid bilayer was much higher and appeared to be independent of the peptide charge. However, enhanced repulsions between the highly positively charged helices destabilized the pore. Therefore, the efficiency of the most basic peptide (MG6+) to translocate across the bilayer was the greatest by virtue of the short life span of its pore and the very tight membrane binding. The charge distribution of wild-type magainin 2 was found to be so designed as to exhibit the maximal lytic activity by simultaneously achieving a strong binding and a moderate pore stability.

Amino Acid Sequence↗

PubMed1997

Amyloid beta protein and transthyretin, sequestrating protein colocalize in normal human kidney.

The localization of amyloid beta protein (A beta), A beta 40, A beta 42, and transthyretin (TTR) was investigated immunohistochemically in the autopsied human kidney, using polyclonal antibodies against TTR, A beta and C-terminal end-specific antibodies against A beta 40 and 42. Immunoreactivities of A beta and A beta 40 were found both in the proximal and distal tubular epithelial cells. But the immunolocalization of A beta 40 was observed predominantly in the distal tubules whereas that of A beta 42 was predominantly recognized in the proximal tubules. TTR, sequestrating protein for A beta, was present in the proximal tubules. The mechanism by which A beta does not form amyloid in Alzheimer's disease outside the brain remains unknown. The tubular epithelial cells in the kidney may provide a useful system to shed light on this issue.

Amyloid beta-Peptides↗

PubMed1997

Specific racemization and isomerization of the aspartyl residue of alphaA-crystallin due to UV-B irradiation.

We have reported that the aspartyl (Asp)-151 residue in alphaA-crystallin in human eye lens was inverted to the D-isomer and isomerized to beta-Asp residue with age. We report here that ultraviolet (UV)-B irradiation induces the racemization and isomerization of the Asp-151 residue of alphaA-crystallin from lenses of 6-week-old rats to form D-isomer and beta-Asp residue. Simultaneous racemization and isomerization of the specific Asp residue indicate that the reaction proceeds via formation of a succinimide intermediate. This modification was not observed in UV-A irradiated and normal lenses. UV-B irradiation induced the racemization of only the Asp-151 residue and did not affect the other Asp residues in alphaA-crystallin. On the other hand, the high molecular weight fraction of the lens protein increased upon UV-B irradiation. Modification of the Asp residue would affect the three-dimensional packing array of the lens protein.

Amino Acid Sequence↗