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Biomedical subjects

M Iwamoto

Publications and source records attributed to M Iwamoto.

At least 91 records · Page 5Linked to original sources
PubMed2000

Local and chronic application of PTH accelerates tooth movement in rats.

We previously reported that whereas systemic continuous infusion of parathyroid hormone (PTH) accelerated orthodontic tooth movement, systemic but intermittent injection of PTH did not increase the rate of tooth movement. Analysis of these data suggested that continuous administration of PTH could be applicable for orthodontic therapy. In the present study, we investigated whether local and chronic application of PTH(1-34) would accelerate orthodontic tooth movement. To increase the residence time of PTH in the injected area, we used methylcellulose (MC) gel (2% W/V) for a slow-release formulation of PTH. MC gel containing PTH (PTH-MC) continuously released biologically active PTH into the acceptor medium for more than 72 hrs in vitro. When male rats received a local injection of PTH-MC into the subperiosteum in the mesio-palatal region of the maxillary first molar (M1) every other day, M1 movement, which was mesially drawn by an orthodontic coil spring attached to the maxillary incisors, was accelerated in a dose-dependent manner. PTH-MC injection at 1 microg/400 g body weight caused a 1.6-fold increase in the rate of tooth movement. The acceleration of tooth movement by PTH-MC injection was marked on days 6, 9, and 12. Local injection of PTH dissolved in saline without MC did not significantly accelerate tooth movement on day 6 or later. Histological examination revealed active osteoclastic bone resorption and a widened periodontal space on the compression side of the periodontal tissue in the PTH-MC-injected rats. These results suggest that local injection of PTH in a slow-release formulation is applicable to orthodontic therapy.

Animals↗
PubMed2000

Hedgehog proteins stimulate chondrogenic cell differentiation and cartilage formation.

Sonic hedgehog (Shh) and Indian hedgehog (Ihh) are important regulators of skeletogenesis, but their roles in this complex multistep process are not fully understood. Recent studies have suggested that the proteins participate in the differentiation of chondrogenic precursor cells into chondrocytes. In the present study, we have tested this possibility more directly. We found that implantation of dermal fibroblasts expressing hedgehog proteins into nude mice induces ectopic cartilage and bone formation. Immunohistological and reverse-transcription polymerase chain reaction (RT-PCR) analyses revealed that the ectopic tissues derived largely if not exclusively from host cells. We found also that treatment of clonal prechondrogenic RMD-1 and ATDC5 cells in culture with Ihh or recombinant amino half of Shh (recombinant N-terminal portion of Shh [rShh-N]) induced their differentiation into chondrocytes, as revealed by cytoarchitectural changes, Alcian blue staining and proteoglycan synthesis. Induction of RMD-1 cell differentiation by Ihh or rShh-N was synergistically enhanced by cotreatment with bone morphogenetic protein 2 (BMP-2) but was blocked by cotreatment with fibroblast growth factor 2 (FGF-2). Our findings indicate that hedgehog proteins have the ability to promote differentiation of chondrogenic precursor cells and that their action in this process can be influenced and modified by synergistic or antagonist cofactors.

Animals↗
PubMed2000

Effects of three characteristic amino acid residues of pharaonis phoborhodopsin on the absorption maximum.

Phoborhodopsin (pR or sensory rhodopsin II, sRII) or pharaonis phoborhodopsin (ppR or pharaonis sensory rhodopsin II, psRII) has a unique absorption maximum (lambda max) compared with three other archaeal rhodopsins: lambda max of pR or ppR at ca 500 nm and others at 560-590 nm. Alignment of amino acid sequences revealed three sites characteristic of the shorter wavelength-absorbing pigments. The amino acids of these three sites are conserved completely among archaeal rhodopsins having longer lambda max, and are different from those of pR or ppR. We replaced these amino acids of ppR with amino acids corresponding to those of bacteriorhodopsin, Val-108 to Met, Gly-130 to Ser and Thr-204 to Ala. The lambda max of V108M mutant was 502 nm with a slight redshift. G130S and T204A mutants had lambda max of 503 and 508 nm, respectively. Thus, each site contributes only a small effect to the color tuning. We then constructed three double mutants and one triple mutant. The opsin-shifts of these mutants suggest that Val-108 and Thr-204 or Gly-130 are synergistic, and that Gly-130 and Thr-204 work additively. Even in the triple mutant, the lambda max was 515 nm, an opsin-shift only ca 30% of the shift value from 500 to 560 nm. This means that there is another yet unidentified factor responsible for the color tuning.

Amino Acid Sequence↗
PubMed2000

Development of articular cartilage: what do we know about it and how may it occur?

Articular cartilage has a fundamental role in joint function. While much is known about its structure, organization and biomechanical properties, there is a very poor understanding of how articular chondrocytes develop during embryogenesis and acquire the unique ability to organize and maintain the articular tissue. Given that articular cartilage forms in close juxtaposition with the joint, here we review past studies on limb joint determination and morphogenesis and more recent studies on a number of factors thought to have roles in joint and epiphysis development. These factors include: the homeobox gene Barx-1; the bone morphogenetic protein (BMP) family member GDF-5; the growth factors HGF and PTHrP; and the transcription factor ERG. We summarize current thinking on how these factors participate in joint development and how some of these factors may influence development and behavior of epiphyseal chondrocytes. We also describe pertinent recent studies from our laboratories on ERG and the newly-identified alternatively spliced variant C-1-1, and finally propose a sequela of events that may subtend the process of determination and emergence of articular chondrocytes during limb synovial joint development.

Animals↗
PubMed2000

Lessons from BXSB and related mouse models.

The BXSB murine strain spontaneously develops an autoimmune syndrome with features of systemic lupus erythematosus (SLE) that affects males much earlier than females, due to the presence of an as yet unidentified mutant gene located on its Y chromosome, designated Yaa (Y-linked autoimmune acceleration). The Yaa gene by itself is unable to induce significant autoimmune responses in mice without an apparent SLE background, while it can induce and accelerate the development of an SLE in combination with autosomal susceptibility alleles present in lupus-prone mice. Although the genes encoded within or closely linked to the MHC locus play an important role in the development or protection of SLE, the MHC effect can be completely masked by the presence of the Yaa gene in mice highly predisposed to SLE. The role of the Yaa gene for the acceleration of SLE is apparently two-fold; it enhances overall autoimmune responses against autoantigens to which mice respond relatively weakly, and promotes Th 1 responses against autoantigens to which mice respond relatively well, leading to the production of more pathogenic autoantibodies, i.e., FcgammaR-fixing IgG2a and cryoglobulin IgG3 autoantibodies. Yaa+ - Yaa- double bone marrow chimera experiments revealed that the Yaa defect is expressed in B cells, but not in T cells, and that T cells from non-autoimmune mice are capable of providing help for autoimmune responses by collaborating Yaa+ B cells. We speculate that the Yaa defect may decrease the threshold for antigen receptor-dependent stimulation, leading to the triggering and excessive stimulation of autoreactive T and B cells.

Animals↗
PubMed2000

Cloning and molecular characterization of hrpX from Xanthomonas axonopodis pv. citri.

The hrpX gene of plant pathogenic Xanthomonas species is essential for pathogenicity on host plants and to cause hypersensitive reaction on non-host plants. We cloned and analyzed a hrpX homologue, designated hrpXct, of X. axonopodis pv. citri, a pathogen of citrus canker. The open reading frame of hrpXct has 1431 bp in nucleotides which has a coding capacity of 476 amino acid residues with a molecular mass of 52.4 kDa. The predicted amino acid sequence of HrpXct has 90% identity to the AraC family type transcriptional activator protein HrpXc of X. campestris pv. campestris, 95% to HrpXo of X. oryzae pv. oryzae and 97% to X. vesicatoria. These findings clearly indicate and confirm that the structure of the hrpX genes in plant pathogenic Xanthomonas species is highly conserved.

Amino Acid Sequence↗
PubMed2000

Expression of survivin and its relationship to loss of apoptosis in breast carcinomas.

Aberrant inhibition of programmed cell death (apoptosis) prevents normal homeostasis and promotes tissue tumorigenesis, but whether it also influences the outcome of common cancers has remained arguable. The expression of a novel IAP apoptosis inhibitor, survivin, in breast cancer and its association with tumor cell apoptosis and overall prognosis were examined in this study. Immunohistochemical analysis showed that survivin expression was positive in 118 of 167 cases (70.7%) of breast carcinomas of histological stages I to IH. In contrast, no expression of survivin in adjacent normal tissue was detected. Although survivin expression was not correlated with p53 mutations, survivin-positive cases were strongly associated with bcl-2 expression (78.0% versus 47.5%; P = 0.0005) and reduced apoptotic index (0.62% +/- 0.51% versus 1.27% +/- 1.37%; P < 0.0001). In addition, patients with low apoptotic index (<0.52%) had worse survival rates than the group with high apoptotic index (> or =0.52%; P = 0.028), and multivariate Cox proportional hazard model analysis identified apoptotic index as an independent prognostic factor (P = 0.024). The results suggest that apoptosis inhibition by survivin, alone or in cooperation with bcl-2, is a significant prognostic parameter of worse outcome in breast carcinoma.

Aged↗
PubMed2000

In vitro and in vivo inhibition of activation induced T cell apoptosis by bucillamine.

OBJECTIVE: To investigate the mechanism of autoimmune phenomena, occasionally seen in patients with rheumatoid arthritis treated with bucillamine (BUC) and D-penicillamine (D-Pen), by evaluating their effects on apoptosis of T cells induced by T cell receptor activation or dexamethasone. METHODS: In vitro apoptosis was induced in a T cell hybridoma (SSP3.7) and a B cell line (WEHI 231) by activation of respective receptors or dexamethasone, in the presence or absence of BUC or D-Pen. In vivo apoptosis was induced in BALB/c mice by staphylococcal enterotoxin B (SEB), with or without BUC or D-Pen, and thymocytes were examined for it by FACS. RESULTS: Stimulation with anti-CD3 and dexamethasone induced apoptosis in 72% and 71% of SSP3.7 cells, respectively. However, only 16% of SSP3.7 cells became apoptotic by anti-CD3 when BUC was added to the culture media. By contrast, 80% of SSP3.7 cells became apoptotic when stimulated by dexamethasone, even in the presence of BUC. BUC did not affect apoptosis of WEHI 231 cells induced by anti-IgM. Although SA981 (a metabolite of BUC) inhibited apoptosis of SSP3.7 cells induced by anti-CD3, D-Pen did not. BUC, SA981, or D-Pen did not significantly influence the level of interleukin 2 secretion stimulated by anti-CD3. In contrast, both BUC and D-Pen inhibited apoptosis of Vbeta8+ thymocytes induced in vivo by SEB superantigen. Neither BUC nor D-Pen significantly changed the number of CD4+CD8+ thymocytes in BALB/c mice injected with dexamethasone. CONCLUSION: BUC decreased, while D-Pen did not, the apoptosis of T cells stimulated by anti-CD3 in vitro, although they both inhibited the deletion of immature thymocytes reactive with SEB in vivo. This may explain autoimmune phenomena sometimes seen during the treatment of rheumatic patients with these drugs.

Animals↗
PubMed2000

[A case of pulmonary metastases of breast cancer responding remarkably to combined chemotherapy with 5-fluorouracil and low-dose cisplatin].

A 46-year-old-woman underwent breast preserving mastectomy for advanced breast cancer. Seven months after operation, pulmonary metastases were found. The patient was admitted and treated with combined chemotherapy of 5-fluorouracil and low-dose cisplatin for 4 weeks. After discharge, UFT 300 mg orally every day and cisplatin 5 mg div once week were administered for 2 years on an outpatient basis. The result was disappearance of the pulmonary metastases. Five years after operation, the patient is alive without any sign of the pulmonary metastasis.

Adenocarcinoma↗
PubMed1999

Matrix GLA protein is a developmental regulator of chondrocyte mineralization and, when constitutively expressed, blocks endochondral and intramembranous ossification in the limb.

Matrix GLA protein (MGP), a gamma-carboxyglutamic acid (GLA)-rich, vitamin K-dependent and apatite-binding protein, is a regulator of hypertrophic cartilage mineralization during development. However, MGP is produced by both hypertrophic and immature chondrocytes, suggesting that MGP's role in mineralization is cell stage-dependent, and that MGP may have other roles in immature cells. It is also unclear whether MGP regulates the quantity of mineral or mineral nature and quality as well. To address these issues, we determined the effects of manipulations of MGP synthesis and expression in (a) immature and hypertrophic chondrocyte cultures and (b) the chick limb bud in vivo. The two chondrocyte cultures displayed comparable levels of MGP gene expression. Yet, treatment with warfarin, a gamma-carboxylase inhibitor and vitamin K antagonist, triggered mineralization in hypertrophic but not immature cultures. Warfarin effects on mineralization were highly selective, were accompanied by no appreciable changes in MGP expression, alkaline phosphatase activity, or cell number, and were counteracted by vitamin K cotreatment. Scanning electron microscopy, x-ray microanalysis, and Fourier-transform infrared spectroscopy revealed that mineral forming in control and warfarin-treated hypertrophic cell cultures was similar and represented stoichiometric apatite. Virally driven MGP overexpression in cultured chondrocytes greatly decreased mineralization. Surprisingly, MGP overexpression in the developing limb not only inhibited cartilage mineralization, but also delayed chondrocyte maturation and blocked endochondral ossification and formation of a diaphyseal intramembranous bone collar. The results show that MGP is a powerful but developmentally regulated inhibitor of cartilage mineralization, controls mineral quantity but not type, and appears to have a previously unsuspected role in regulating chondrocyte maturation and ossification processes.

1-Carboxyglutamic Acid↗
PubMed1999

Analysis of the Dielectric Relaxation Property of Phospholipid Monolayers by Maxwell Displacement Current Measurement.

Using the Maxwell displacement current (MDC) measurement with alternating monolayer compression and expansion process, the dielectric property of monolayers has been investigated. The monolayer expansion and compression processes were analyzed on the basis of the Debye theory, and the relaxation time of dl-alpha-dilaurylphosphatidylcholine (DLPC) was determined using a whole curve of MDCs. It was suggested that the interaction among molecules makes a contribution to the dielectric relaxation phenomena, although the change in the orientational order of polar molecules is a main contribution of MDC. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Positioning proton-donating residues to the Schiff-base accelerates the M-decay of pharaonis phoborhodopsin expressed in Escherichia coli.

Phoborhodopsin (also called sensory rhodopsin II, sR-II) is a receptor for the negative phototaxis of Halobacterium salinarum (pR), and pharaonis phoborhodopsin (ppR) is the corresponding receptor of Natronobacterium pharaonis. pR and ppR are retinoid proteins and have a photocycle similar to that of bacteriorhodopsin (bR). A major difference between the photocycle of the ion pump bR and the sensor pR or ppR is found in their turnover rates which are much faster for bR. A reason for this difference might be found in the lack of a proton-donating residue to the Schiff base which is formed between the lysine of the opsin and retinal. To reconstruct a bR-like photochemical behavior, we expressed ppR mutants in Escherichia coli in which proton-donating groups have been reintroduced into the cytoplasmic proton channel. In measurement of the photocycle it could be shown that the F86D mutant of ppR (Phe86 was substituted by Asp) showed a faster decay of M-intermediate than the wild-type, which was even accelerated in the F86D/L40T double mutant.

Archaeal Proteins↗
PubMed1999

Characterization of the 4C8 antigen involved in transendothelial migration of CD26(hi) T cells after tight adhesion to human umbilical vein endothelial cell monolayers.

In extravasation of T cells, little is known about the mechanisms of transendothelial migration subsequent to the T cells' tight adhesion to endothelium. To investigate these mechanisms, we developed a monoclonal antibody (mAb), termed anti-4C8, that blocks transmigration but not adhesion in a culture system in which high CD26-expressing (CD26(hi)) T cells preferentially migrate through human umbilical vein endothelial cell (HUVEC) monolayers cultured on collagen gels. Anti-4C8 reacted with all CD3(+) T cells and monocytes but not neutrophils or HUVECs. The structure defined by this antibody was an 80-kD molecule. The mAb at 1 mug/ml inhibited 80-90% of migration of CD3(+) T cells through unstimulated and interferon gamma-stimulated HUVEC monolayers without interfering with adhesion and cell motility. When added to the cultures after the adhesion, anti-4C8 completely blocked subsequent transmigration of adherent T cells. Phase-contrast and electron microscopy revealed that T cells are arrested at the intercellular junctions of HUVECs in the presence of anti-4C8. Anti-4C8 exhibited agonistic effects on resting T cells without other stimuli under culture conditions in which anti-4C8 can stimulate T cells. First, in the checkerboard assay using collagen gels, the antibody promoted chemokinetic migration of the cells in a dose-dependent manner from 0.1 to 10 mug/ml. The predominant population of T cells that migrated into collagen gels with impregnated anti-4C8 were CD26(hi). Second, solid-phase-immobilized anti-4C8 induced adhesion of T cells to the substrate, often with polarizations in cell shape and large pseudopods rich in filamentous (F-) actin. Third, soluble anti-4C8 augmented F-actin content preferentially in CD26(hi) T cells when added to T cells at a high dose of 10 mug/ml. Finally, both anti-4C8-induced chemokinetic migration and transendothelial migration were inhibited by pretreatment of T cells with pertussis toxin. These findings suggest that stimulation via the 4C8 antigen increases cell motility of CD26(hi) cells with profound cytoskeletal changes through signaling pathways including G proteins. The 4C8 antigen may be involved in preferential transmigration of CD26(hi) cells adherent to HUVECs.

Actins↗
PubMed1999

Plant cis-acting regulatory DNA elements (PLACE) database: 1999.

PLACE (http://www.dna.affrc.go.jp/htdocs/PLACE/) is a database of nucleotide sequence motifs found in plant cis-acting regulatory DNA elements. Motifs were extracted from previously published reports on genes in vascular plants. In addition to the motifs originally reported, their variations in other genes or in other plant species in later reports are also compiled. Documents for each motif in the PLACE database contains, in addition to a motif sequence, a brief definition and description of each motif, and relevant literature with PubMed ID numbers and GenBank accession numbers where available. Users can search their query sequences for cis-elements using the Signal Scan program at our web site. The results will be reported in one of the three forms. Clicking the PLACE accession numbers in the result report will open the pertinent motif document. Clicking the PubMed or GenBank accession number in the document will allow users to access to these databases, and to read the of the literature or the annotation in the DNA database. This report summarizes the present status of this database and available tools.

Arabidopsis↗
PubMed1999

The role of the labyrinth, proprioception and plantar mechanosensors in the maintenance of an upright posture.

The maintenance of an upright posture in man requires information from vision, the labyrinth, proprioception and plantar mechanosensors. In order to evaluate the role of the labyrinth, proprioception and plantar mechanosensors, stabilometry was performed in subjects with closed eyes. Ten patients with bilateral severe or complete labyrinthine paresis were studied, as well as 9 patients with severe proprioceptive disorders and 10 normal healthy persons whose plantar mechanosensors were anesthetized by hypothermia. Both the area of sway and the total locus length (accumulated shift distance length) were evaluated. On closing eyes, in patients with labyrinthine disorders demonstrated that the area of sway increased more than length. On the other hand, in patients with proprioceptive disorders, length increased more than the area. In plantar anesthetized subjects, similar to the labyrinthine disorder cases, the area of sway increased more than length. These findings suggest that the labyrinth is a main monitor of the area of body sway, while proprioception is a principle monitor of the velocity of body movement of sway (or locus length). The plantar mechanosensor monitors the area of body sway similar to the labyrinth, but works less than the labyrinth. The locus length is the distance per minute and reflects the velocity of body sway. Thus, the length per area is a parameter for the velocity of body sway per area. Since proprioceptive disorders increase both the locus length and the length per area, present findings suggest that if proprioception is damaged, the body begins to move faster. Compensated labyrinthine disorders have a tendency to increase the length per area, indicating that if a labyrinthine disorder is compensated, the body adapts and moves faster to maintain an upright posture.

Achilles Tendon↗
PubMed1999

A tourist element in the 5'-flanking region of the catalase gene CatA reveals evolutionary relationships among Oryza species with various genome types.

Tourist-OsaCatA, a transposable element, was found in the 5'-flanking region of the rice gene CatA. The characteristics of this element are similar to those of the other Tourist elements so far found in Oryza sativa. PCR and sequence analyses of 37 accessions of 18 species revealed that all the Oryza species examined, except for one accession, have either a full-length or a partial Tourist element at this locus. Unlike the Tourist elements previously reported, this Tourist element is found in all four Oryza species complexes in the Oryzeae tribe. All AA genome Oryza species, except O. longistaminata, contain the full-length Tourist element. O. longistaminata and the species of the O. officinalis, O. meyeriana and O. ridleyi complexes contain the partial element. A phylogenetic tree of Oryza species based on the nucleotide sequences of these Tourist elements was constructed. The O. longistaminata accessions were placed near the neighboring cluster of the officinalis complex. We propose that the ancestor of O. longistaminata and that of other species with the AA genome diverged, and the ancestor(s) of the O. officinalis, O. ridleyi and O. meyeriana complexes then diverged from the ancestor of O. longistaminata in the course of the evolution of the Oryza species. The Tourist elements associated with CatA and its orthologs thus provide useful tools for examining evolutionary relationships among Oryza species.

Base Sequence↗