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Biomedical subjects

H Ohshima

Publications and source records attributed to H Ohshima.

At least 55 records · Page 3Linked to original sources
PubMed2000

The development of terminal Schwann cells associated with periodontal Ruffini endings in the rat incisor ligament.

The postnatal development of the terminal Schwann cell, an analogue of the lamellar cell in cutaneous sensory receptors, was examined by histochemistry for non-specific cholinesterase and immunohistochemistry for S-100 protein in the periodontal Ruffini endings of the rat incisor. Double immunohistochemistry for S-100 protein and protein gene product 9.5 (PGP 9.5) was also performed to examine the relationship between terminal Schwann cells and axons. Histochemistry for non-specific cholinesterase was able to demonstrate the age-related development of the terminal Schwann cells; the morphology and distribution of the developing terminal Schwann cells became almost identical to those in adults during postnatal days 15-18. Axons showing PGP 9.5-like immunoreactivity elongated and expanded after arrangement of terminal Schwann cells in the alveolus-related part. This suggests that the terminal Schwann cell is important in the development and maturation of the periodontal Ruffini endings.

Animals↗
PubMed2000

Nitric oxide nitrates tyrosine residues of tumor-suppressor p53 protein in MCF-7 cells.

It has been reported that mammalian cells incubated with excess nitric oxide (NO) accumulate p53 protein but concomitantly this p53 loses its capacity for binding to its DNA consensus sequence. As nitration of tyrosine residues in various proteins has been shown to inhibit their functions, we examined whether NO nitrates tyrosine residues in p53 protein. MCF-7 cells expressing wild-type p53 were incubated with S-nitrosoglutathione for 4 h and cellular extracts were immunoprecipitated with an anti-p53 antibody. Western blot analyses of immunoprecipitates for p53 or for nitrotyrosine revealed low levels of nitrotyrosine in p53 from untreated cells. Incubation with 2 mM S-nitrosoglutathione induced a significant increase in the nitrotyrosine level in p53 protein compared to nontreated cells. These results suggest that excess NO produced in inflamed tissues could nitrate p53 protein, playing a role in carcinogenesis by impairing functions of this tumor-suppressor protein.

Binding Sites↗
PubMed2000

Responses of immunocompetent cells in the dental pulp to replantation during the regeneration process in rat molars.

Responses of immunocompetent cells to tooth replantation during the regeneration process of the dental pulp in rat molars were investigated by immunocytochemistry using antibodies to class II major histocompatibility complex (MHC) molecules (OX6 antibody), monocyte/macrophage lineage cells (ED1 antibody) and protein gene product 9.5 (PGP 9.5), as well as by histochemical reaction for periodic acid-Schiff (PAS). Tooth replantation caused an increase in both the number of OX6- and ED1-positive cells and their immunointensity in the replanted pulp, but almost all PGP 9.5-immunoreactive nerves diminished in the initial stages. By postoperative day 3, many OX6- and ED -immunopositive cells had accumulated along the pulp-dentin border to extend their cytoplasmic processes into the dentinal tubules in successful cases. Once reparative dentin formation had begun after postoperative day 7, OX6- and ED1-immmunopositive cells became scattered in the odontoblast layer, while reinnervation was found in the coronal pulp. The temporal appearance of these immunocompetent cells at the pulp-dentin border suggests their participation in odontoblast differentiation as well as in initial defense reactions during the pulpal regeneration process. On postoperative day 14, the replanted pulp showed three regeneration patterns: (1) reparative dentin, (2) bone-like tissue formation, and (3) an intermediate form between these. In all cases, PAS-reactive cells such as polymorphonuclear leukocytes (PML) and mesenchymal cells occurred in the pulp space. However, the prolonged stagnation of inflammatory cells was also discernible in the latter two cases. Thus, the findings on PAS reaction suggest that the migration of the dental follicle-derived cells into the pulp space and the subsequent total death of the proper pulpal cells are decisive factors for eliciting bone-like tissue formation in the replanted pulp.

Animals↗
PubMed2000

Formation of N-nitrosamines and N-nitramines by the reaction of secondary amines with peroxynitrite and other reactive nitrogen species: comparison with nitrotyrosine formation.

Reactive nitrogen species, including nitrogen oxides (N(2)O(3) and N(2)O(4)), peroxynitrite (ONOO(-)), and nitryl chloride (NO(2)Cl), have been implicated as causes of inflammation and cancer. We studied reactions of secondary amines with peroxynitrite and found that both N-nitrosamines and N-nitramines were formed. Morpholine was more easily nitrosated by peroxynitrite at alkaline pH than at neutral pH, whereas its nitration by peroxynitrite was optimal at pH 8.5. The yield of nitrosomorpholine in this reaction was 3 times higher than that of nitromorpholine at alkaline pH, whereas 2 times more nitromorpholine than nitrosomorpholine was formed at pH <7.5. For the morpholine-peroxynitrite reaction, nitration was enhanced by low concentrations of bicarbonate, but was inhibited by excess bicarbonate. Nitrosation was inhibited by excess bicarbonate. On this basis, we propose a free radical mechanism, involving one-electron oxidation by peroxynitrite of secondary amines to form amino radicals (R(2)N(*)), which react with nitric oxide ((*)NO) or nitrogen dioxide ((*)NO(2)) to yield nitroso and nitro secondary amines, respectively. Reaction of morpholine with NO(*) and superoxide anion (O(2)(*)(-)), which were concomitantly produced from spermine NONOate and by the xanthine oxidase systems, respectively, also yielded nitromorpholine, but its yield was <1% of that of nitrosomorpholine. NO(*) alone increased the extent of nitrosomorpholine formation in a dose-dependent manner, and concomitant production of O(2)(*)(-) inhibited its formation. Reactions of morpholine with nitrite plus HOCl or nitrite plus H(2)O(2), with or without addition of myeloperoxidase or horseradish peroxidase, also yielded nitration and nitrosation products, in yields that depended on the reactants. Tyrosine was nitrated easily by synthetic peroxynitrite, by NaNO(2) plus H(2)O(2) with myeloperoxidase, and by NaNO(2) plus H(2)O(2) under acidic conditions. Nitrated secondary amines, e.g., N-nitroproline, could be identified as specific markers for endogenous nitration mediated by reactive nitrogen species.

Aniline Compounds↗
PubMed2000

Coexpression of interleukin-8 and inducible nitric oxide synthase in gastric mucosa infected with cagA+ Helicobacter pylori.

The cagA-positive Helicobacter pylori strains are thought to be able to induce interleukin-8 expression and to be associated with gastroduodenal diseases. Inducible nitric oxide synthase (iNOS) may be involved in inflammatory pathogenesis. Our aim was to investigate the interrelationships between cagA and the expression of interleukin-8 and iNOS messenger RNAs, and with the type and degree of inflammation in gastric mucosa. In biopsies from 108 Chinese patients, the cagA, 16S rRNA, interleukin-8, and iNOS mRNAs were analyzed using reverse-transcription polymerase chain reaction. Specimens infected with cagA-positive strains had significantly more severe infiltration by mononuclear and polymorphonuclear leukocytes and more frequently expressed interleukin-8 and iNOS mRNAs than those infected with cagA-negative strains. iNOS and interleukin-8 mRNAs were significantly more frequently expressed together in the specimens with moderate or severe inflammation than in those with normal mucosa or mild inflammation. Our data suggest that interleukin-8 and excess nitric oxide play important roles in the pathogenesis of H. pylori-associated gastroduodenal diseases.

Antigens, Bacterial↗
PubMed2000

Msx2 deficiency in mice causes pleiotropic defects in bone growth and ectodermal organ formation.

The composite structure of the mammalian skull, which forms predominantly via intramembranous ossification, requires precise pre- and post-natal growth regulation of individual calvarial elements. Disturbances of this process frequently cause severe clinical manifestations in humans. Enhanced DNA binding by a mutant MSX2 homeodomain results in a gain of function and produces craniosynostosis in humans. Here we show that Msx2-deficient mice have defects of skull ossification and persistent calvarial foramen. This phenotype results from defective proliferation of osteoprogenitors at the osteogenic front during calvarial morphogenesis, and closely resembles that associated with human MSX2 haploinsufficiency in parietal foramina (PFM). Msx2-/- mice also have defects in endochondral bone formation. In the axial and appendicular skeleton, post-natal deficits in Pth/Pthrp receptor (Pthr) signalling and in expression of marker genes for bone differentiation indicate that Msx2 is required for both chondrogenesis and osteogenesis. Consistent with phenotypes associated with PFM, Msx2-mutant mice also display defective tooth, hair follicle and mammary gland development, and seizures, the latter accompanied by abnormal development of the cerebellum. Most Msx2-mutant phenotypes, including calvarial defects, are enhanced by genetic combination with Msx1 loss of function, indicating that Msx gene dosage can modify expression of the PFM phenotype. Our results provide a developmental basis for PFM and demonstrate that Msx2 is essential at multiple sites during organogenesis.

Abnormalities, Multiple↗
PubMed2000

Oxidative DNA damage in human lymphocytes: correlations with plasma levels of alpha-tocopherol and carotenoids.

In order to investigate whether oxidative damage is associated with differences in antioxidant intake, we measured the levels of 8-oxo-7, 8-dihydro-2'-deoxyguanosine (8-oxodGuo) in lymphocytes and alpha-tocopherol and several carotenoids in plasma of women with different dietary habits. We found that women from Granada (Spain), a region with a typically Mediterranean diet, had significantly higher levels of 8-oxodGuo compared with Malmö (Sweden), a region with a Northern European dietary intake pattern (2.30 +/- 0.78 versus 1.59 +/- 1.01 8-oxodGuo/10(-6) deoxyguanosine). Levels of plasma alpha-tocopherol and carotenoids were higher in Granada and these values were significantly positively correlated with levels of 8-oxodGuo. Our results do not support the hypothesis that a Mediterranean diet rich in alpha-tocopherol and carotenoids protects cells against oxidative DNA damage. It is possible, however, that consumption of foods other than fruits and vegetables, including fats, are responsible for the higher levels of 8-oxodGuo in Granada. Further studies are warranted to better elucidate the role of antioxidants in the modulation of oxidative stress in vivo.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2000

Effect of short-duration spaceflight on thigh and leg muscle volume.

PURPOSE: Human skeletal muscle probably atrophies as a result of spaceflight, but few studies have examined this issue. Thus, little is known about the influence of microgravity upon human skeletal muscle, nor is it possible to assess the validity of ground based models of spaceflight. This study tested the hypothesis that the magnitude of spaceflight induced muscle atrophy would be a function of flight duration and greater than that of bed rest. METHODS: Three astronauts flew 9, 15, and 16 d in space. Volume of the knee extensor (quadriceps femoris), knee flexor (hamstrings, sartorius, and gracilis), and plantar flexor (triceps surae) muscle groups was measured using magnetic resonance imaging before and after spaceflight and during recovery. The volume of each muscle group in each image was determined by multiplying cross-sectional area by slice thickness. These values were subsequently summed to calculate muscle volume. RESULTS: Volume changes in the knee extensor, knee flexor, and plantar flexor muscle groups ranged from -15.4 to -5.5, -14.1 to -5.6, and -8.8 to -15.9%, respectively. Muscle volume decreases normalized by flight duration ranged from 0.62 to 1.04% x d(-1). These relative changes appeared to be greater than those that we have reported previously for bed rest (Akima et al., J. Gravitat. Physiol. 4:15-22, 1997). CONCLUSIONS: These results suggest that atrophy as a result of at least 2 wk of spaceflight varied among individuals and muscle groups and that the degree of atrophy appeared to be greater than that induced by 20 d of bed rest.

Astronauts↗
PubMed2000

Transient expression of heat shock protein (Hsp)25 in the dental pulp and enamel organ during odontogenesis in the rat incisor.

The expression of heat shock protein (Hsp) 25 during odontogenesis in the dental pulp and enamel organ of rat incisors was investigated by immunocytochemistry and confocal microscopy. In the process of dentin formation, immature odontoblasts first exhibited Hsp 25-immunoreactivity, and increased in immunointensity with the advance of their differentiation. In the dental pulp, in contrast, intense immunoreaction in the mesenchymal cells became weak or negative in parallel with the progress of cell differentiation. The immunoreaction for Hsp 25 in the enamel organ revealed a characteristic stage-related alteration during amelogenesis. In secretory ameloblasts, the immunoreaction for Hsp 25 was found throughout their cell bodies, intense reactivity being located near the proximal and distal terminal webs. At the maturation stage, ruffle-ended ameloblasts (RA) consistently showed Hsp 25-immunoreactivity throughout the cell bodies, whereas smooth-ended ameloblasts (SA) lacking a ruffled border were weak in immunoreaction at the distal cytoplasm. Other cellular elements of the enamel organ were negative. The subcellular localization of Hsp 25-immunoreactivity in this study appeared essentially identical to that of actin filaments as demonstrated by confocal microscopy using rhodamine-labeled phalloidin. These immunocytochemical data suggest that the Hsp 25 molecule is involved in reinforcement of the cell layer following cell movement during odontogenesis and in the formation and maintenance of the ruffled border of RA.

Actins↗
PubMed2000

Tissue response to titanium implants in the rat maxilla: ultrastructural and histochemical observations of the bone-titanium interface.

BACKGROUND: The detailed mechanism of osseointegration, the most appropriate implant-bone interface, remains unclear in jaw tissues at the ultrastructural level in contrast to the many reports using long bones. The present study reports on tissue response to titanium-implantation on an animal model using rat maxilla. METHODS: Animals were sacrificed at 1 to 28 days post-implantation and prepared tissue specimens, freed from implants by a cryofracture technique, were processed for transmission electron microscopy and histochemistry for tartrate resistant acid phosphatase activity (TRAPase). RESULTS: Different patterns in bone formation were recognized between lateral and base areas of implant cavities. In the lateral area with narrow gaps, bone deposition took place from the pre-existing bone towards the implant after active bone resorption by osteoclasts reactive to TRAPase. However, no distinct bone formation appeared in the lateral area where the implant had been installed close to the osteotomy margin. On the other hand, new bone formation was found at the base area without any apparent bone resorption. Interestingly, mononuclear cells reactive to TRAPase, presumably preosteoclasts, frequently occurred near preosteoblasts. Osseointegration around the implants was obtained in this model by 28 days post-implantation except for the lateral area with complete contact with implants, where the thin layer remained in contact with the implant surface. CONCLUSIONS: These findings indicate that ossification proceeds at different modes around the titanium implant in rat maxilla, depending on the nature of the recipient bones and the dimension of the gap between the implant and osteotomy margin.

Animals↗
PubMed2000

[Clinical study of selective intra-arterial infusion chemotherapy using trans-radial arterial approach in 4 cases of advanced breast cancer].

We administered neoadjuvant chemotherapy by a selective intra-arterial infusion method using a trans-radial approach in patients with advanced breast cancer (stage III and stage IV). The trans-radial approach uses the arterial flow, based on the Seldinger technique. In this method, the radial artery is cannulated, and epirubucin is infused into the artery that carries blood from the subclavical artery to the breast. We have used this method in 4 cases thus far. Two of the patients received a single intra-arterial infusion of epirubicin. The other 2 patients were catheterized before they received chemotherapy by intra-arterial infusion. This technique decreased the pain or discomfort caused by the catheterizations during chemotherapy in all 4 cases. However, the currently available catheters are not always able to approach the artery flowing into the breast, thus the protocol will need to be refined.

Adenocarcinoma, Scirrhous↗
PubMed1999

Electrokinetic Phenomena in a Concentrated Dispersion of Charged Mercury Drops.

Equations are derived which govern the electrokinetic phenomena in a concentrated dispersion of charged spherical mercury drops in an electrolyte solution on the basis of Kuwabara's cell model. Expressions for the electrophoretic mobility and the sedimentation velocity are obtained. For the case in which the overlapping of the electrical double layers of adjacent drops is negligible, expressions for the electrical conductivity and the sedimentation potential are derived. An Onsager relation between electrophoretic mobility and sedimentation potential is also obtained. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Two-Layer Structure of Microcapsule Membrane as Predicted from Electrophoretic Studies.

Four types of hydrophilic gel microcapsules containing water have been prepared by an interfacial polymerization method. Each type of microcapsules has membranes of different compositions. Using three kinds of monomers, N,N-dimethylacrylamide (DMAAm), 4-aminomethylstyrene (AmSt), and N,N-dimethylaminopropylacrylamide (DMAPAA), two types of water-soluble copolymers with different compositions having primary and tertiary amino groups were obtained. Two more types of copolymers were synthesized by copolymerization of alpha-acryloxy-omega-methoxy-poly(ethylene glycol) (a-PEG) with the above two kinds of monomer mixtures. These copolymers were polymerized with terephthaloyldichloride at the water/oil interface to prepare four types of microcapsules containing water. By electrophoretic mobility measurements of these microcapsules and the analyses of the data, it was found that the surface layer of the microcapsule membranes were composed of two sublayers, each of which has different charge density and softness. The outer sublayer was negatively charged and inner sublayer was positively charged. By PEGylation, the charge density in the outer sublayer decreased, while that in the inner sublayer was not affected. Also, the surface layer became softer by PEGylation. The effects of membrane composition upon the swellability of the microcapsule membrane were studied. It was found that the asymmetrical structure of the microcapsule membranes causes the nonuniform distribution of charges and then the swellability of the microcapsule membrane changes depending on the permittivity of the dispersing medium. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Cytotoxicity and site-specific DNA damage induced by nitroxyl anion (NO(-)) in the presence of hydrogen peroxide. Implications for various pathophysiological conditions.

Nitroxyl anion (NO(-)), the one-electron reduction product of nitric oxide (NO(.)), is formed under various physiological conditions. We have used four different assays (DNA strand breakage, 8-oxo-deoxyguanosine formation in calf thymus DNA, malondialdehyde generation from 2'-deoxyribose, and analysis of site-specific DNA damage using (32)P-5'-end-labeled DNA fragments of the human p53 tumor suppressor gene and the c-Ha-ras-1 protooncogene) to study the effects of NO(-) generated from Angeli's salt on DNA damage. It was found that strong oxidants are generated from NO(-), especially in the presence of H(2)O(2) plus Fe(III)-EDTA or Cu(II). NO(.) released from diethylamine-NONOate had no such effect. Distinct effects of hydroxyl radical (HO(.)) scavengers and patterns of site-specific DNA cleavage caused by Angeli's salt alone or by Angeli's salt, H(2)O(2) plus metal ion suggest that NO(-) acts as a reductant to catalyze the formation of the HO(.) from H(2)O(2) plus Fe(III) and formation of Cu(I)-peroxide complexes with a reactivity similar to HO(.) from H(2)O(2) and Cu(II). Angeli's salt and H(2)O(2) exerted synergistically cytotoxic effects to MCF-7 cells, determined by lactate dehydrogenase release assay. Thus NO(-) may play an important role in the etiology of various pathophysiological conditions such as inflammation and neurodegenerative diseases, especially when H(2)O(2) and transition metallic ions are present.

Antioxidants↗
PubMed1999

Electrical Conductivity of a Concentrated Suspension of Spherical Colloidal Particles.

A general expression for the electrical conductivity of a concentrated suspension of spherical colloidal particles is obtained for the case where the particle zeta potential is low and the overlapping of the electrical double layers of adjacent particles is negligible by using Kuwabara's cell model. It is shown how the conductivity of a concentrated suspension depends on the particle volume fraction, the zeta potential zeta, and the reduced particle radius kappaa (kappa = Debye-Hückel parameter and a = particle radius). It is also found that the obtained conductivity formula tends to Maxwell's formula for two different extreme cases: (i) when the particles are uncharged (zeta = 0) and (ii) when the electrical double layers around the particles are infinitesimally thin (kappaa --> infinity). That is, in the latter limiting case (kappaa --> infinity), the conductivity becomes independent of the zeta potential, just as in the case of dilute suspensions. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Colloid Vibration Potential in a Concentrated Suspension of Spherical Colloidal Particles.

A relation between the dynamic electrophoretic mobility of spherical colloidal particles in a concentrated suspension and the colloid vibration potential (CVP) generated in the suspension by a sound wave is obtained from the analogy with the corresponding Onsager relation between electrophoretic mobility and sedimentation potential in concentrated suspensions previously derived on the basis of Kuwabara's cell model. The obtained expression for CVP is applicable to the case where the particle zeta potential is low, the particle relative permittivity is very small, and the overlapping of the electrical double layers of adjacent particles is negligible. It is found that CVP shows much stronger dependence on the particle volume fraction &phi; than predicted from the &phi; dependence of the dynamic electrophoretic mobility. It is also suggested that the same relation holds between the electrokinetic sonic amplitude of a concentrated suspension of spherical colloidal particles and the dynamic electrophoretic mobility. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Approximate Expression for the Double-Layer Interaction Energy between Two Parallel Plates with Constant Surface Charge Density.

An approximate expression for the potential energy of the double-layer interaction between two parallel similar plates with constant surface charge density is derived via a novel linearization method, in which the Poisson-Boltzmann is linearized with respect to the deviation of the electric potential from the surface potential (which is a function of the interplate separation h). This approximation works quite well for small plate separations h for all values of the surface charge density (or the unperturbed surface potential) and gives a correct limiting form of the interaction energy (or the interaction force) as h --> 0. Copyright 1999 Academic Press.

Journal Article↗