Biomedical subjects

N Konishi

Publications and source records attributed to N Konishi.

At least 73 records · Page 4Linked to original sources

PubMed1999

Influence of filler content and gap dimension on wear resistance of resin composite luting cements around a CAD/CAM ceramic inlay restoration.

We investigated the influence of filler content and gap dimension on the wear resistance of composite luting cement around CAD/CAM ceramic inlay restorations. Experimental hybrid dual-cured composite luting cements containing 60, 70, 72, 74 and 80 wt% of silanated barium-silica fillers were used for cementing CAD/CAM ceramic inlay into the cavity. The specimens involving inlay-cement-tooth interfaces were subjected to a three-body wear test. The relation between the interfacial gap dimension and wear loss was also investigated using 60, 70 and 80 wt% filled cements. The cements containing more than 70 wt% filler presented significantly higher wear resistance than 60 wt% filled cement. There was a positive linear relationship between gap dimension and wear loss, and the inclination of the regression line decreased with increasing filler content. These results indicated that the higher filler content of the cement increased the wear resistance and this desirable influence appeared more remarkably in the wider horizontal gap dimension.

Analysis of Variance↗

PubMed1999

Artificial caries removal and inhibition of artificial secondary caries by pulsed CO2 laser irradiation.

PURPOSE: To investigate the inhibition of artifical secondary caries around restorations placed after removal of artificial caries by pulsed CO2 laser irradiation and by mechanical means. MATERIALS & METHODS: Beveled cavities were prepared mechanically on the facial surfaces of extracted human molars. Each cavity was subsequently exposed to an artificial caries (demineralizing) solution (pH 5.0) for 7 d to generate a demineralized zone approximately 100-200 microns thick on the cavity surface. The artificial carious/demineralized zones of the cavities were removed by a pulsed CO2 laser operating at a wavelength of 9.3 microns with pulse duration of 100 microseconds and an irradiation intensity of 5 J/cm2. Artificial control caries were removed mechanically with a carbide bur in a slow speed handpiece. The cavities were slightly undercut and restored with a resin-based composite without etching and bonding and the restored teeth were subjected to pH cycling solutions for 10 d as follows: Demineralization solution, pH 4.5 for 6 hrs, followed by remineralization solution, pH 7.0 for 18 hrs. Cycled teeth were sectioned through the restorations and the resulting lesions were analyzed in thin section using polarized light and Knoop microhardness. RESULTS: Mean microhardness delta Z values, indicating mineral loss were: 549 (SD 191) for control, and 140 (SD 127) N = 11. This difference is significant with t = 5.543 and P = 0.000 (Paired t-test). Caries penetration: Control side--231 microns (SD 71), Laser treated side: 123 microns (SD 79) N = 6. This difference is significant with t = 5.198 and P = 0.003 (Paired t-test). The results show that the laser treatment not only removed artificial caries, but also inhibited decalcification of the cavity wall in a subsequent artificial caries challenge by as much as 81% compared to control samples. No etching and bonding was used in this pilot study, which might have influenced the results. Future studies should address the inhibition effect of the laser treatment as compared to adhesive techniques, fluoride treatments and fluoride release restorative materials. CONCLUSION: Caries removal by a pulsed lambda = 9.3 microns CO2 laser produces a cavity surface morphology with marked resistance to artificial secondary caries as compared to mechanical removal.

Carbon Dioxide↗

PubMed1998

Different ras gene mutational frequencies in thyroid papillary carcinomas in Japan and Thailand.

The incidence and pattern of ras oncogene mutations in human malignancies demonstrate geographic and racial differences. For example, specificity of alterations is found in cholangiocellular carcinomas in Thai patients with a different etiology from those in Japanese patients. In the present study, a comparison of ras gene mutations in thyroid papillary carcinomas from Japanese and Thai patients was performed using single-strand conformation polymorphism and direct sequencing analyses. The incidence of ras mutation differed markedly in Japanese (two of 24 carcinomas, 8.3%) and Thai (five of 10 carcinomas, 50%) patients. In addition, all but one ras mutation occurred at codon 12 of the K-ras gene in the Thai cases. These results suggest that thyroid cancers in Thailand may be due to specific genetic and/or environmental factors.

Adult↗

PubMed1998

Formation of 8-hydroxydeoxyguanosine in rat kidney DNA after administration of N-ethyl-N-hydroxyethylnitrosamine.

N-Ethyl-N-hydroxyethylnitrosamine (EHEN) is known to induce renal and liver tumors in rodents. Recent reports have indicated the formation of 8-hydroxydeoxyguanosine (8-OHdG), an oxidative DNA product, induced by various carcinogens. In the present study, to examine whether oxygen radicals are involved in tumorigenesis induced by EHEN, we investigated the formation and localization of 8-OHdG in kidney, liver and lung of rats. The effects of reduced glutathione (GSH) and diethylmaleate on these responses were also studied. Multiple doses of EHEN administrations (250, 500 or 750 mg/kg, i.p.) resulted in a significant elevation of the 8-OHdG level in kidney DNA in a dose-dependent manner and the formation of 8-OHdG reached the maximal level at 1-2 h after EHEN injection and recovered to the control level at 4 h. On the other hand, no increase in the 8-OHdG level was observed in the DNA of liver and lung. Combined pre- and post-treatment of rats with 2 x 800 mg/kg of GSH i.p. inhibited the elevation of the 8-OHdG level induced by EHEN. Pre-treatment with 0.3 ml/kg of diethylmaleate i.p. increased the formation of 8-OHdG. In the immunohistochemical examinations of rats treated with EHEN (750 mg/kg, i.p.), nuclear expression of 8-OHdG was detected in the epithelial cells of renal cortex, while no induction was observed in liver and lung. These findings suggest that the formation of 8-OHdG by active oxygen species may be an important factor in the initiation of EHEN-induced kidney carcinogenesis.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed1998

Genomic aberrations in early stage human hepatocellular carcinomas.

BACKGROUND: Primary liver cancer, which most often takes the form of hepatocellular carcinoma (HCC), is among the 10 most common cancers in humans worldwide. In hepatocarcinogenesis, evidence of a multistep process is supported by the marked increase of HCC incidence with age; most HCCs are diagnosed in the second half of life, generally after a long period of chronic liver disease and in frequent association with cirrhosis. This long process may be correlated with the development of multiple genetic lesions, the origin of which currently remain largely unknown. In a previous study, the authors collected data on genomic DNA aberrations in primary HCC by restriction landmark genomic scanning (RLGS), a powerful screening method for the human genome. METHODS: The authors examined the genomic aberrations that occurred in early stage HCCs by means of RLGS of NotI-cleaved and 32P-end-labeled genomic DNA resolved by electrophoresis in a two-dimensional gel. More than 2000 radioactive spots originating from NotI cleavage sites were compared among six small HCC nodules and their normal counterparts. RESULTS: The intensities of five spots were consistently higher in the small HCCs, and the same effect was observed in large HCCs. In addition, the intensities of 22 spots were consistently half those of normal tissue, suggesting the loss of one allele. CONCLUSIONS: The occurrence of certain genomic alterations in early stage HCCs, as reflected by an increase or decrease in spot intensity, seems to reflect early events that occur during HCC development.

Adult↗

PubMed1998

Frequent alterations of cell-cycle regulators in astrocytic tumors as detected by molecular genetic and immunohistochemical analyses.

Alterations of CDKN2A, RB, and cyclin D1 genes and expression of their products in astrocytic tumors were studied using a combination of molecular genetic and immunohistochemical assays. In addition, the association of gene status with clinical outcome was evaluated. Alterations of CDKN2A and RB gene in 30 lesions were analyzed by single-strand conformation polymorphism of polymerase chain reaction (PCR-SSCP), direct sequencing, and Western blotting. Methylation of the CDKN2A promoter was detected by methylation-specific PCR. Immunohistochemistry was applied to determine the expression of gene products in tumors from 94 patients for whom clinical outcome was also evaluated. Analyses of the CDKN2A gene revealed 12 homozygous or hemizygous deletions, one mutation in exon 1, and three methylations in the promoter. Expression of p 16 protein was not detected in 18 of 30 cases. RB mutations leading to loss of expression of the pRb were found in four (13%) cases, and six were immunohistochemically negative for this protein. Overexpression of cyclin D1 was obtained in 51 (54%) of 94 cases. Patients with pRb-negative tumors had a significantly greater risk of earlier death than those with p16 and cyclin D1 alterations, Both p16 and pRb immunohistochemistry provides useful complementary information and may provide valuable predictive information in screening. The biological consequences of deregulating individual components along cell control pathways are unequal, perhaps reflecting their hierarchical roles in the G1 checkpoint.

Adolescent↗

PubMed1998

Genetic variations in recurrent astrocytic tumors detected by restriction landmark genomic scanning.

The genetic mechanisms associated with recurrence of advanced astrocytic tumors are poorly understood. We therefore analyzed 24 biopsy specimens from 12 patients with a recurrent astrocytic tumor by a two-dimensional gel electrophoresis method, termed restriction landmark genomic scanning (RLGS). Four spot changes were commonly present in the primary astrocytomas, indicating that the corresponding gene alterations were early events in the development of this tumor type. Altered spots were more frequent and of different distribution in recurrent tumors than in the primary astrocytomas. In particular, specifically increased intensity for spots on chromosomes 9-12 and 18 were observed in the secondary tumors, suggesting a relation with recurrence. The same spot changes observed in primary tumors were also found in the respective secondary lesions but with strikingly different densities in some cases, suggesting increased genetic instability. The altered segments provide important candidate regions for the search for genes involved in events leading to progression and more malignant recurrent tumors.

Astrocytoma↗

PubMed1998

A germline mutation abolishing the original stop codon of the human adenine phosphoribosyltransferase (APRT) gene leads to complete loss of the enzyme protein.

Adenine phosphoribosyltransferase (APRT) is a purine metabolic enzyme and a homozygous deficiency in this enzyme causes 2,8-dihydroxyadenine urolithiasis. Various germline abnormalities have been described, but we report here a unique type of germline mutation in a homozygous individual (SY) who had excreted 2,8-dihydroxyadenine crystals. In SY, TCA was substituted for the physiological stop codon TGA. This base substitution generates a new HinfI restriction site, and, using the polymerase chain reaction and subsequent digestion by this enzyme, it was confirmed that SY is homozygous for the base substitution. This base change is unique in that it generates an open reading frame that extends to the poly(A) addition site. The amount of mRNA in transformed B cells from SY was approximately a quarter of that in control subjects and no APRT proteins were detected. In eukaryotes, unlike in prokaryotes, no rescue systems for defective polypeptide termination caused by a missing stop codon have been found. Therefore, the outcome of the defect of SY is unclear from present knowledge about termination of polypeptide synthesis. Investigations into the mechanisms of the absence of protein in the cells of SY may lead to a better understanding of the physiological and nonphysiological termination of polypeptide synthesis in eukaryotic cells.

Adenine Phosphoribosyltransferase↗

PubMed1998

Electrophysiologic evaluation of denervated muscles in incomplete paraplegia using macro electromyography.

OBJECTIVE: To evaluate denervated muscles in persons with incomplete paraplegia due to thoracolumbar spinal injury (TLSI) using macro electromyography in determining indications for functional electrical stimulation (FES). DESIGN: A randomized clinical trial and a criterion standard. SETTING: A department of orthopedic surgery in a university hospital. PATIENTS AND OTHER PARTICIPANTS: Eighteen patients with incomplete paraplegia, including 11 with TSLI, and 50 healthy adults. INTERVENTION: Area and amplitude of macro motor unit potential (macro MUP) were measured at the tibialis anterior, the vastus lateralis, and the vastus medialis. The normal limits of macro MUP parameters were defined based on values from healthy subjects. Abnormal denervated muscles were detected by macro EMG and conventional EMG in paralytic patients. The correlation between macro MUP parameter values and muscle forces of the tibialis anterior and quadriceps femoris induced by electrical stimulation was analyzed. MAIN OUTCOME MEASURES: The number of abnormal muscles, parameter values, and muscle force induced by electrical stimulation. RESULTS: Abnormal muscles were found only in the TLSI patients and 13 abnormal muscles were detected by macro EMG only. The abnormal muscles defined by macro EMG showed insufficient contraction induced by electrical stimulation. The increase of parameter value negatively correlated with the muscle force (tibialis anterior area r=-.797, amplitude r=-.866; quadriceps area r=-.866, amplitude r=-.893; p < .001). CONCLUSIONS: These results suggest that macro EMG is useful in detecting denervated muscles, in determining indications for FES, and in predicting FES effects before implantation of electrodes.

Adolescent↗

PubMed1998

Genomic aberrations in renal cell carcinomas detected by restriction landmark genomic scanning.

In order to reveal and characterise genetic events occurring in renal tumorigenesis, samples of sporadic renal cell carcinomas (RCCs) were examined using restriction landmark genomic scanning (RLGS), an electrophoretic separation technique which detects gene amplification and deletion. We were able to find two fragments frequently amplified and 10 others commonly showing reduced signal intensity within the 16 tumour samples analysed. These altered spots were located on chromosomes 2, 3, 9-12, 16, 17 and 18 according to chromosomal assigned RLGS. A subset of reduced fragments appeared to be correlated to tumour type and were located within a new chromosomal region, suggesting genetic specificity within the process of renal carcinogenesis.

Aged↗

PubMed1998

Genomic alterations in oral squamous cell carcinoma cell lines detected by two-dimensional gel analysis.

To initially analyze the genomic abnormalities in human oral squamous cell carcinoma, DNA extracted from each of four oral carcinoma cell lines (Ca9-22, HO-1-u-1, HSC-2, KB) was examined using restriction landmark genomic scanning (RLGS), a method especially conducive to detection of amplifications and rearrangements of genomic DNA. Isolated cell line and normal oral epithial DNAs were sequentially cleaved with specific restriction enzymes, radiolabelled and separated in two-dimensional gel electrophoreses. Thirteen distinct fragments were commonly amplified in the oral cancer cell lines, six of which were evident in all samples. These results suggest genetic alterations characteristic of oral squamous cell carcinogenesis.

Carcinoma, Squamous Cell↗

PubMed1998

Drug resistance and apoptosis in ENU-induced rat brain tumors treated with anti-cancer drugs.

To cast light on the mechanisms of drug-resistance, experimental brain tumors were immunohistochemically evaluated for expression of glutathione S-transferase (GST)-alpha, mu, pi, p-glycoprotein and apoptosis-related factors, such as bcl-2 and p53, as well as by the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labelling (TUNEL) method. Rat brain tumors induced by means of prenatal exposure to ethylnitrosourea (ENU) were treated with 1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3-(2-chloroethyl)-3-nitrosourea hydrochloride (ACNU) and/or vincristine. Tumors more than 2 mm in size were considered to be drug resistant. The expression of GST-mu was strongly positive in ACNU-treated brain tumors, while p-glycoprotein was overexpressed in vincristine-treated brain tumors. Neither p53 nor bcl-2 expression directly correlated with apoptosis identified by TUNEL method, but tumors lacking apoptotic cells always demonstrated the expression of either GST-mu or p-glycoprotein. These results indicate that tumors resistant to chemotherapy might not be susceptible to induction of apoptosis, and therefore that mechanisms of drug resistance are related to programmed cell death in brain tumors.

Animals↗

PubMed1998

Effect of preinduction of heat-shock proteins on acetic acid-induced small intestinal lesions in rats.

Bowel dysfunction such as irritable bowel syndrome caused by stress is well described. Previous reports suggest that stress is known to cause the release of endogenous substances such as catecholamine, beta-endorphine, 5-hydroxytryptamine, corticotropin-releasing factor, and thyrotropin-releasing hormone (TRH). However, the role played by these neurohormonal mediators in bowel dysfunction under stress conditions is not well known. We investigated the influence of water-immersion stress or TRH administration on the expression of 60-kDa, 72-kDa, and 90-kDa heat-shock proteins (HSP60, HSP72, and HSP90, respectively) in rat small intestinal mucosa by Western blot and immunohistochemical analyses. The cytoprotective function of preinduced HSPs on experimentally induced mucosal damage also was studied. In order to investigate the influence of preinduction of HSP60 on small intestinal damage, the small intestinal lumen was perfused with 1.5% acetic acid 1 ml/min for 15 min with or without pretreatment with water-immersion stress or TRH administration. Expression of HSP60 was significantly increased by water-immersion stress or TRH administration in the small intestinal mucosa, whereas HSP72 and HSP90 did not increase. Interestingly, expression of this protein showed the biphasic peak pattern after water-immersion stress or TRH administration. Each peak was observed 3-6 hr and 21-24 hr after the initiation of water-immersion stress or TRH administration. Immunohistochemical study also showed a significant increment of HSP60 in both the cytoplasm and nuclei of the small intestinal mucosal cells. No histopathologic alteration was observed in rat small intestinal mucosa after each treatment. Small intestinal damage caused by 1.5% acetic acid perfusion was not influenced by preinduction of HSP60. We demonstrated that water-immersion stress or TRH administration specifically induced HSP60, although preinduction of this protein did not show a cytoprotective function in the small intestinal mucosa.

Acetic Acid↗

PubMed1998

Expression of KAI1 in paraffin-embedded normal, hyperplastic and neoplastic prostate and prostate carcinoma cell lines.

Expression of KAI1, a tumor metastasis suppressor gene, was studied with different fixatives in frozen and paraffin-embedded sections of human and rat prostate carcinoma cell lines and human prostate lesions by immunohistochemistry. Immunoreactivity of the membrane antigen in cell lines was associated with known expression levels in these lines and the fixative used. Formalin and paraformaldehyde helped maintain the immunoreactivity of cells. In human prostate, frozen sections revealed diffuse reactivity of the antigen in normal and neoplastic tissues while paraffin-embedded tissues usually showed focal reactivity, although more than 50% of cases with normal epithelium and adenocarcinomas were reactive. In some cases, pretreatment with trypsin enhanced immunoreactivity. Benign prostatic hyperplasia (BPH) showed the most intense diffuse immunoreactivity, which suggested enhanced expression. Prostatic intraepithelial neoplasia (PIN) also often expressed high levels of KAI1. Three of five metastases were reactive but two primaries and their metastases were not. Lymphocytes in primary carcinomas and lymphocytes and germinal center cells in lymph nodes were immunoreactive, while adjacent primary or metastatic prostate adenocarcinoma epithelium was not immunoreactive. Although paraffin-embedded human tissues were not optimal for determining levels of expression of KAI1, they did show immunoreactivity that could have prognostic value and showed the specific cytoplasmic localization of the protein in cells.

Adenocarcinoma↗

PubMed1998

Coronary risk factors in acute Kawasaki disease: correlation of serum immunoglobulin levels with coronary complications.

BACKGROUND: To determine the usefulness of the IgG z-score (age and sex-standardized serum IgG level) before intravenous gamma globulin therapy (IVGG) in predicting the occurrence or severity of coronary complications in Kawasaki disease (KD). METHODS: A case-control study of clinical and laboratory findings with 88 children in the early stage of acute KD who received IVGG (100 or 200 mg/kg for 2-5 days) therapy. Of these, 20 cases had persistent coronary arterial lesions (small aneurysm, moderate aneurysm or large aneurysm persisting more than 1 month). The controls comprised 68 children with no coronary aneurysms or transient small aneurysm only observed within 1 month after the onset of KD. The association between serum levels of immunoglobulin G (IgG). IgM, IgA as well as other coronary risk factors previously reported and the occurrence of the coronary arterial lesions was evaluated using logistic regression analysis. RESULTS: After adjustment for age, gender, total IVGG dose before the 9th illness day and other traditional coronary risk factors, the odds ratio for the persistent coronary aneurysm associated with lower serum IgG z-score (< -0.7485 vs > or = -0.7485), was 30.3 (95% confidence interval, 3.8-243.2). Furthermore, the serum IgG z-score was inversely correlated with the severity of the coronary arterial lesion. CONCLUSIONS: The IgG z-score before IVGG therapy in the early stage of KD provides useful information on the risk factors for persistent coronary aneurysm and is a novel, additional indicator for therapy to prevent the coronary complications in acute KD.

Case-Control Studies↗

PubMed1998

Studies on anti-inflammatory agents. VI. Synthesis and pharmacological properties of 2,3-diarylthiophenes.

A series of novel 5-substituted-2,3-diarylthiophenes has been synthesized and found to be active in the rat adjuvant arthritis (AA) model and/or in the yeast-induced hyperalgesia (Randall-Selitto) assay. Among the compounds synthesized herein, 2-(4-fluorophenyl)-3-[4-(methylsulfonyl)phenyl]-5-(trifluoromethyl)thiop hene (6a) exhibited the most potent activities on AA, collagen-induced arthritis (CIA) and the delayed-type hypersensitivity response to type II collagen. 5-Bromo-2-[4-(methylamino)phenyl]-3-[4-(methylsulfinyl)phenyl]thiophene (38) is also a potent inhibitor of AA, CIA, hyperalgesia and in vitro tumor necrosis factor-alpha production.

Adjuvants, Immunologic↗

PubMed1998

Purification and characterization of recombinant human granulocyte colony-stimulating factor (rhG-CSF) derivatives: KW-2228 and other derivatives.

Various derivatives of recombinant human granulocyte colony-stimulating factor (rhG-CSF) have been overproduced in Escherichia coli with the strong, inducible trp promoter. A derivative designated as KW-2228 in which the amino acids were replaced at five positions showed more potent granulopoietic activity and stability than those of wild-type both in vitro and in vivo. The purification involved a sequential renaturation process and three-step chromatography. Refolding succeeded in very high yield using a urea system. The purity of KW-2228 was greater than 99% as measured by SDS-PAGE and HPLC analysis. According to circular dichroism and nuclear magnetic resonance spectroscopy, rhG-CSF and KW-2228 have very similar conformations. This suggests that the substitution of five amino acids does not appreciably change the conformation of hG-CSF. KW-2228 ([Ala1, Thr3, Tyr4, Arg5, and Ser17]-hG-CSF) and derivative A ([Ala1, Thr3, Tyr4, Arg5]-hG-CSF) are easily crystallized and they show similar in vitro activity. On the other hand, neither rhG-CSF nor derivative B ([Ser17]-hG-CSF) are crystallized under the same conditions. Thus, the four amino acid substitution (Ala1, Thr3, Tyr4, Arg5) of the N-terminal sequence may facilitate crystallization. The change of Cys17 to Ser may not influence the stability and activity of hG-CSF.

Amino Acids↗

PubMed1998

Effect on the femur of a new hip fracture preventive system using dropped-weight impact testing.

To reduce hip fractures during falls, we devised a new hip fracture preventive system to attenuate impact on the greater trochanteric region and studied the effects of the system on the femur. Twelve coupled, embalmed, cadaveric femora were used. Right femora were fractured without protection as a control and compared with left femora covered by the protection system, which consisted of a silicone gel pad or the silicone gel pad combined with a resin cover. The impact of a fall was simulated by mounting a femur in the horizontal plane and dropping an 8.4 kg mass on its greater trochanteric region. The impact load and time were measured using a load cell within the mass. The maximum strain during impact at the inferior side of the femoral neck was determined from an attached strain gauge. Trochanteric fractures were produced in 18 of the 24 femora (75%). The mean impact load for a drop height of 25 cm was reduced from 3117 N to 2176 N by silicone gel (p < 0.01) and to 1681 N by the addition of the resin cover (p < 0.01). The mean maximum strain was similarly reduced from 2276 microvarepsilon to 1872 microvarepsilon (p = 0.15) and to a mean 1559 microvarepsilon (p < 0. 05). The mean impact time was prolonged from 13 ms to 20 ms (p < 0. 01) and 22 ms (p < 0.01), respectively. The effect of the cover became more conspicuous as height increased. We concluded that the silicone gel pad provided effective impact attenuation, and the addition of the rigid cover was even more effective for impact reduction. This system was thought to be clinically useful in preventing hip fractures.

Absorptiometry, Photon↗