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Biomedical subjects

K Nemoto

Publications and source records attributed to K Nemoto.

At least 91 records · Page 5Linked to original sources
PubMed1998

Immunosuppressant deoxyspergualin induces apoptotic cell death in dividing cells.

Deoxyspergualin (DSG) has been found to have an antitumour and immunosuppressive activity. However, the precise mechanism of action of DSG has not been clarified. We have used its analogue, methyldeoxyspergualin (MeDSG) for in vitro culture studies of DSG since it shows good stability in aqueous solution and retains strong immunosuppressive activity. In the present study, we found that MeDSG inhibited proliferation of rapidly dividing murine T-cell hybridomas, resulting in cell death. The cell death was accompanied by chromatin condensation and DNA cleavage at the linker regions between nucleosomes. Furthermore, MeDSG induced a reduction in mitochondrial transmembrane potential. When murine thymocytes were treated with MeDSG for 48 hr, a slight increase of DNA fragmentation was constantly observed, and selective depletion of CD4- CD8- cells was noticed. In contrast, CD4+ CD8+ cells were hardly affected. Moreover, splenic T-cells are resistant to MeDSG-induced apoptosis, as evaluated by measuring DNA cleavage. Our findings may account for the immunosuppressive and antitumour properties of DSG which were described in a number of previous studies.

Animals↗
PubMed1998

Fatal hemorrhage in irradiated esophageal cancer patients.

Between 1980 and 1994, 423 patients with esophageal cancer were given curative radiation therapy. Of these patients, 31 died of massive hemorrhage and were used as the subjects of analysis in this study. The incidence of massive hemorrhage in all patients was 7% (31/423). In the 31 patients who died of massive hemorrhage, 27 had local tumors and two had no tumors at hemorrhage (two unknown cases). The mean time interval from the start of radiation to hemorrhage was 9.2 months. In 9 autopsy cases the origin of hemorrhage was a tear of the aorta in 5 cases, necrotic local tumor in 3 cases and esophageal ulcer in 1 case. The positive risk factors for this complication seemed to be excess total dose, infection, metallic stent, and tracheoesophageal fistula. Chest pain or sentinel hemorrhage proceeding to massive hemorrhage was observed in about half of the patients.

Aged↗
PubMed1998

Characterization of a protein kinase gene responsive to auxin and gibberellin in cucumber hypocotyls.

By means of the PCR, cDNA clones encoding putative protein kinases have been obtained from cucumber hypocotyls. The abundance of the transcript of one of these genes, which was named CsPK3, increased on treatment with gibberellin (GA4) and/or auxin (IAA). We screened a cucumber cDNA library to clone CsPK3 cDNA. The cDNA clone (cCsPK3) encodes an open reading frame of 1,413 bp (471 amino acids), and its predicted amino acid sequence showed homology with those of serine/threonine protein kinases. Northern blot analysis indicated that IAA was more active than GA4 in increasing the level of CsPK3 mRNA in cucumber hypocotyls and that the increase in the level of CsPK3 mRNA on treatment with IAA was not inhibited by pretreatment with a protein synthesis inhibitor. The level of CsPK3 mRNA was high in hypocotyls of dark-grown cucumber seedlings and decreased to less than 50% of the original level within 15 min of the start of irradiation with white light.

Amino Acid Sequence↗
PubMed1998

Fosfomycin reduces CD15s-related antigen expression of Streptococcus pyogenes.

We have previously shown the immunological mimicry of human sialyl-Lewis(x) (CD15s) by a surface antigen of Streptococcus pyogenes. This mimicking surface antigen may act as a ligand to the selectin family and may induce antibody production against CD15s on host cells, suggesting a possible role in the pathogenesis of S. pyogenes. In this study, the effects of antibiotics on the CD15s-related antigen expression of S. pyogenes were examined at a concentration below the MIC (sub-MIC). The amounts of CD15s on the surfaces of S. pyogenes cells and on the surfaces of S. pyogenes biofilms were determined by a whole-cell enzyme-linked immunosorbent assay and by laser scanning fluorescence microscopy, respectively, by using an anti-CD15s monoclonal antibody. At the sub-MICs, fosfomycin (1R,2S-1,2-epoxypropyl phosphonic acid), its enantiomer (1S,2R-1,2-epoxypropyl phosphonic acid), and benzylpenicillin significantly inhibited the CD15s expression of all strains studied. The effects of fosfomycin and its enantiomer on biofilms were also observed by scanning electron microscopy. Incubation of S. pyogenes with the sub-MIC of fosfomycin or its enantiomer, which has no antibacterial activity, reduced the amount of CD15s on the biofilm surface and made it smooth. These results suggest that fosfomycin or its enantiomer might be useful for preventing S. pyogenes adherence to human CD15s receptors and the resulting immunological pathogenicity.

Anti-Bacterial Agents↗
PubMed1998

Suppressive activity of the chloroform extract of Tripterygium wilfordii Hook f on effector T cell activation during Hymenolepis nana infection in mice.

The chloroform extract of Tripterygium wilfordii Hook f (TWH extract) administered into mice daily at doses of 80.0 to 200.0 micrograms/kg (but not 40.0 micrograms/kg) caused suppression of protective immunity to Hymenolepis nana when the extract was injected subcutaneously during the induction phase of protective immunity. Daily administration of 200.0 micrograms/kg TWH extract, during the course of larval development from challenge, also suppressed protective immunity. Inhibition of protective immunity was only observed in mice that received TWH extract for 6 days at a daily dose of 200.0 micrograms/kg and were challenged 24 h after the final injection. TWH extract did not inhibit formation of effector cells that mediate delayed type hypersensitivity (DTH) to H. nana egg antigen when the extract was administered subcutaneously at a dose of 200.0 micrograms/kg/day for 5 days before cell preparation. However, TWH extract did inhibit DTH effector cell activation when cells prepared from infected, PBS-injected mice were transferred into 200.0 micrograms/kg TWH extract-treated recipient mice. These results strongly indicate that TWH extract cannot inhibit the generation of effector cells but will suppress their function in vivo.

Animals↗
PubMed1998

Distortion behavior of heat-activated acrylic denture-base resin in conventional and long, low-temperature processing methods.

There have been many reports on fatal distortion of heat-activated acrylic denture-base resin which is still widely used in the field of removable prosthodontics. However, these reports have failed to report quantitatively on polymerization and thermal shrinkage factors. In the present study, we attempted to verify that the shrinkage of heat-activated acrylic denture-base resin was caused mainly by thermal contraction after processing. Furthermore, we examined the degree of distortion resulting from long, low-temperature processing, and compared the results with that of the conventional method. The strain gauge and thermo-couple were embedded in a specimen at the time of resin packing. The measurement started from the beginning of processing and continued until the specimen was bench-cooled and immediately before and after it was de-flasked, as well as during seven-day immersion in water at 37 degrees C. The resin expanded when processed by the conventional method. Meanwhile, mild shrinkage, possibly polymerization shrinkage, was observed when the resin was processed by the low-temperature method. This suggested that polymerization shrinkage was compensated for by thermal expansion during processing by the conventional method. Moreover, the shrinkage strains in the period from the completion of processing to immediately after de-flasking, in both the conventional and low-temperature methods, were identical to the theoretical value of thermal shrinkage which we obtained by multiplying the linear coefficients of thermal expansion by temperature differences. The shrinkage strain in the specimen processed by the low-temperature method, measured from the end of processing to immediately after de-flasking, averaged 64% of that in the specimen processed by the conventional method. The results revealed quantitatively that the shrinkage of heat-activated acrylic denture-base resin was mainly thermal shrinkage, and demonstrated the advantage of the low-temperature method in reducing thermal shrinkage.

Acrylic Resins↗
PubMed1998

Effects of N-methacryloyl amino acid applications on hybrid layer formation at the interface of intertubular dentin.

To understand the role of NMAA in the bonding of composite resin to a dentin surface, we investigated the effects of N-methacryloyl amino acid (NMAA) application on the expansion of aggregated collagen fibers, formation of a hybrid layer, and the tensile bond strength between composite resin and dentin. Four NMAA derivatives--N-methacryloyl-alpha-glycine (NMGly), N-methacryloyl-gamma-amino n-butyric acid (NMBu), N-methacryloyl-alpha-hydroxyproline (NMHPro), and N-methacryloyl-alpha-glutamic acid (NMGlu)--were prepared and applied to dentin surfaces which had been etched with 40% by mass H3PO4 and air-blown. The shrunken collagenous layer expanded by approximately 50% to 70% by volume of the original collagenous layer thickness after application of the NMAA primers. Application of the bonding agent and composite resin after NMAA treatment resulted in the formation of a hybrid layer. The thickness of the hybrid layer was somewhat smaller than the collagenous layer formed by the NMAA treatment only, regardless of the type of NMAA used. The thickness of the hybrid layer was approximately ten times larger than that formed without NMAA treatment. Although all NMAA primers formed hybrid layers of similar thickness, higher tensile bond strengths, from 13 to 15 MPa, were obtained when etched and air-blown dentin was treated with NMBu, NMGly, or NMGlu. NMHPro gave only 6.6 MPa, a value similar to that obtained when no NMAA was used. We concluded, therefore, that formation of the hybrid layer is a necessary but insufficient condition for high bond strength.

Analysis of Variance↗
PubMed1998

Parathyroid hormone induces expression of the inducible cAMP early repressor in osteoblastic MC3T3-E1 cells and mouse calvariae.

Parathyroid hormone (PTH) regulates gene expression in skeletal osteoblasts mainly through the cAMP-protein kinase A (PKA) pathway. In neuroendocrine cells, activation of the cAMP-PKA signaling pathway leads to induction of the inducible cAMP early repressor (ICER), which is transcribed from an intronic promoter of the CREM gene and acts as a transcriptional repressor. To investigate whether PTH induces ICER expression in osteoblastic cells, RNA from MC3T3-E1 cells was subjected to reverse transcriptase-polymerase chain reaction using primers spanning the ICER sequence. Amplified products were subcloned, sequenced, and used as a probe for Northern blot analysis. In MC3T3-E1 cells, PTH induced ICER mRNA levels, which peaked at 2 h and declined to baseline by 8 h. Cycloheximide caused superinduction of ICER mRNA in response to PTH. In cultured mouse calvariae, PTH also induced ICER mRNA accumulation, which peaked at 2 h and returned almost to baseline by 10 h. Overexpression of ICER IIgamma decreased both baseline and PTH-stimulated prostaglandin G/H synthase 2 promoter activity in MC3T3-E1 cells. The induction of ICER represents a novel mechanism by which PTH regulates gene expression in osteoblastic cells.

3T3 Cells↗
PubMed1998

Efficacy of self-etching primers containing carboxylic acid monomers on the adhesion between composite resin and dentin.

A study was conducted to examine the efficacy of carboxylic acid monomers as self-etching primers by measuring the tensile bond strengths between composite resin and dentin. Several kinds of carboxylic acid monomers, such as o-(N-methacryloyl amino)benzoic acid (o-MABA), m-(N-methacryloyl amino)benzoic acid (m-MABA), p-(N-methacryloyl amino)benzoic acid (p-MABA), 4-methacryloxy phthalic acid (4-MPA), 2-(N-methacryloyl amino) terephthalic acid (2-MATPA), and 5-(N-methacryloyl) amino)isophthalic acid (5-MAIPA), were prepared. 4-methacryloxyethyl trimellitic anhydride (4-META) was also used as a component of the self-etching primer. The DMSO solutions of these monomers were used as self-etching primers. The tensile bond strengths between composite resin and dentin were measured after 24 h immersion in water at 37 degrees C. When DMSO was used as a self-etching primer, the bond strengths were below 5 MPa. Among the monocarboxylic acid monomers, m-MABA gave the highest mean bond strength at 60 s application, and 5MAIPA gave the highest mean bond strength at 30 s application among the dicarboxylic acid monomers, although the differences among the values were not always significant. The smear layer was partially dissolved by treatment with the self-etching primer.

Acid Etching, Dental↗
PubMed1998

[Treatment outcome on 52 patients with 53 testicular germ cell tumors].

Between August 1983 and April 1996, 53 testicular germ cell tumors in 52 patients were treated at Toranomon Hospital. The average age of the patients was 36.1 years (range 21-89). The affected side was the right side in 24, left in 27 and bilateral in 1 case. Of the 53 tumors 34 (64.2%) were seminoma and 19 (35.8%) were non-seminomatous germ cell tumor (NSGCT). High ligation orchiectomy was performed in all cases. Of 29 stage I seminomas, post-operative adjuvant radiotherapy was performed in 6 cases prior to 1991. None of these tumors recurred. Two cases of relapses (8.7%) were found among the 23 stage I seminomas followed by surveillance. Of 8 stage I NSGCTs followed by surveillance, 4 (50.0%) tumors which contained embryonal carcinoma element and vascular invasion relapsed within 12 months after orchiectomy. A case of stage IIA seminoma was treated successfully by irradiation. Seven cases of stage II (3 seminomas and 4 NSGCTs) and 8 cases of stage III (1 seminoma and 7 NSGCTs) as well as cases of 6 stage I patients who developed relapse during surveillance were treated by VAB-6 chemotherapy. Of these 21 cases, 11 (52.4%) achieved complete response (CR) and 10 (47.6%) partial response (PR). Salvage surgery and/or additional chemotherapy was successful to bring the 10 PR cases into CR condition. One NSGCT patient, however, died of electrolyte imbalance during the maintenance chemotherapy for disease progression after achieving CR. All 34 patients with seminomas and 18 of the 19 with NSGCTs were alive without evidence of disease after a mean follow up period of 61.1 months (range 4-150 months).

Adult↗
PubMed1997

Degradation of the 74 kDa form of L-histidine decarboxylase via the ubiquitin-proteasome pathway in a rat basophilic/mast cell line (RBL-2H3).

L-Histidine decarboxylase (HDC) is a dimer consisting of two identical 53 kDa subunits. On the other hand, the size of HDC deduced from its cDNA sequence is around 74 kDa, indicating that the translated 74 kDa form of HDC is subjected to post-translational processing to generate the 53 kDa form. However, modification of the translated 74 kDa form of HDC in histamine-forming cells is unknown. Here we demonstrate that the 74 kDa form is translated in rat basophilic leukemia cells, followed by conversion to the 53 kDa form, and that the 74 kDa form is a short half-life protein because of the degradation mediated by the ubiquitin-proteasome pathway. Degradation of the 74 kDa form was stimulated in the presence of an ATP-generating system, accompanied by ubiquitination, and inhibited by specific proteasome inhibitors such as ZL3H and lactacystin. A significant amount of proteasome activity was detected in RBL-2H3 cells.

Adenosine Triphosphate↗
PubMed1997

Relationship between BDNF- and trk-expressing neurones in rat dorsal root ganglion: an analysis by in situ hybridization.

Brain-derived neurotrophic factor (BDNF) is synthesized in sensory neurones and suggested to operate on these same neurones by an autocrine mechanism, but it is unclear whether these neurones express the functional receptor (TrkB) for BDNF. We therefore examined the co-localization of BDNF and neurotrophin receptor mRNAs in adult rat dorsal root ganglion (DRG) neurones by in situ hybridization histochemistry. BDNF mRNA signals were detected in about 40-50% of DRG neurones (L4-5). Almost all the trkA mRNA-expressing neurones (95%) were positive for BDNF mRNA, while no trkB mRNA- and few trkC mRNA-expressing neurones displayed BDNF mRNA signals. These findings suggest that BDNF is mainly synthesized in the sensory neurones that are responsive to nerve growth factor but not to BDNF or neurotrophin-3. It is unlikely that BDNF is involved in an autocrine loop in sensory ganglia.

Animals↗
PubMed1997

Influence of rapid heating with infrared radiation on RF magnetron-sputtered calcium phosphate coatings.

This study evaluated the effect of rapid heating with infrared radiation on the physico-chemical and morphological properties of radio frequent (RF) magnetron-sputtered calcium phosphate (Ca-P) coatings. About 2.5 microm thick Ca-P coatings were deposited on titanium disks and cylinders. These specimens were left untreated or were heat treated by infrared radiation at 300, 400, 500, 600, and 700 degrees C for 4, 7, 11, 17, and 24 s. Subsequently, the specimens were immersed in simulated body fluid (SBF) for 1 day, 1 week, and 5 weeks. X-ray diffraction measurements showed that heating at 500 degrees C or higher resulted in an increase of coating crystallinity. In addition, FT-IR measurements revealed the appearance of OH peaks in the spectra of samples treated at 500-700 degrees C. Electron probe microanalysis showed that after 5 weeks of immersion about 40-50% of the coatings heat treated at 500 and 600 degrees C was maintained. The coatings heat treated at 700 degrees C showed no dissolution at all. On the other hand, as-coated and 300 degrees C treated films were dissolved within 1 day. Scanning electron microscopy of the samples showed that directly after heat treatment no apparent cracks were present in the coatings. On the basis of these findings, we conclude that rapid heating with infrared radiation around 600 degrees C is the best heat treatment for RF magnetron-sputtered coatings.

Biocompatible Materials↗
PubMed1997

Effects of N-methacryloyl-omega-amino acid primer pretreatment on the bond strength of the resin to acid-etched dentin.

To ascertain the adhesion mechanism of resins to etched dentin treated with hydrophilic primers such as N-methacryloyl-omega-amino acids (NM omega A), the effect of the application of NM omega A primers on the bond strength of the resin and also the characteristics of the "hybrid layer" were investigated. Here, the concept of "hybrid layer" has been proposed previously by Nakabayashi et al. When the demineralized dentin was treated with the NM omega A solution, the bond strength increased remarkably, thus indicating the formation of a hybrid layer. It can be construed that NM omega A primers allowed for diffusion of the bonding agent to the dentinal collageous layer that was exposed by acid etching, and thereby the creation of a hybrid layer. To obtain an understanding of how NM omega A primers improved bond strength at the interface between the resin and dentinal collagen, the 13C-NMR spectra of NM alpha A were observed in the absence and presence of demineralized dentin. The 13C peak intensities of all of the carbons of the NM alpha A species were dramatically reduced in the presence of the dentin. Specifically, the reduction of the carbon peak intensity of carboxylic acid in the NM alpha A species was reduced by 30%. This indicated that the unionized carboxylic acid in the NM alpha A primer interacted with the dentinal collagen. Thus, the composite resin can be considered to adhere to the dentinal collagen through the unionized NM alpha A that interacts with the dentinal collagen.

Amino Acids↗
PubMed1997

Solitary plasmacytomas of the occipital bone: a report of two cases.

The radiological appearances of two cases of solitary plasmacytoma in the occipital bone are described. One arose in the lateral part and the other in the squama. They showed characteristic radiological features on CT, MRI and angiography. Bone scintigraphy and gallium scintigraphy were also available. Solitary plasmacytoma of the skull is a rare condition and usually occurs in the calvarium. The skull base is an extremely rare site and only four cases have been reported. The literature of solitary plasmacytoma of the skull is reviewed.

Aged↗
PubMed1997

Molecular cloning and expression of a rat prostaglandin E2 receptor of the EP2 subtype.

Prostaglandin E2 (PGE2) is a potent local mediator of cell growth and differentiation in various tissues. The receptors for PGE2 have been classified into four pharmacological subtypes, EP1, EP2, EP3, and EP4, based on the responses to selective agonists and antagonists. We have cloned a functional cDNA for the rat EP2 receptor subtype from a rat lung cDNA library. The rat EP2 receptor cDNA encodes 357 amino acid residues having high homology with the human and mouse EP2 receptors and containing seven putative transmembrane domains. In COS-7 cells transfected with rat EP2 cDNA, specific [3H]PGE2 binding was found with a dissociation constant of 14.9 nM, and this binding was inhibited by unlabeled PGE2 and PGE2 alpha. PGE2 and butaprost, an EP2 selective agonist, were effective in increasing the cAMP level in the COS-7 cell transfectants. Northern blot and RT-PCR analysis showed widespread distribution of the EP2 receptor in various tissues. Higher EP2 expression was found in fetal long bones and calvariae than in adult by RT-PCR and in situ hybridization, suggesting a role for this receptor in rapidly growing skeletal tissue.

Alprostadil↗
PubMed1997

Immobilization stress reduced the expression of neurotrophins and their receptors in the rat brain.

Exposure to stressful events and elevated level of stress hormones are associated with impaired spatial memory and neuronal damage in the hippocampus. These neurons are considered to be maintained by neurotrophins such as nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3) and trk family of neurotrophin receptors. Male Wistar rats (6 weeks old) were exposed to immobilization stress for 8 h and their brains were processed for in situ hybridization histochemistry. Exposure to long-lasting immobilization stress reduced mRNA levels for neurotrophins and their high affinity receptors in the brain, especially in the hippocampus. Our results provide, some new information that may be relevant to the pathogenesis of stress-induced disturbances of memory and learning.

Animals↗