Biomedical subjects

M Kobayashi

Publications and source records attributed to M Kobayashi.

At least 469 records · Page 26Linked to original sources

PubMed2000

Long-term changes of hydroxyapatite-coated dental implants.

There are many controversies about the long-term prognosis of hydroxyapatite (HA)-coated implants. Failure may be related to compositional and structural changes of the coating occurring during implantation. Two retrieved and two unused HA-coated blade-type implants were examined by stereomicroscopy, secondary electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and electron probe microanalysis. The objective was to investigate the HA morphology, composition, and structure, and to characterize the changes that occurred in the retrieved implant coatings. Retrieved implants presented partial loss of the coating, especially at the apical and mesiodistal edges. Remaining HA was thick and flattened in the cervical and central areas and gradually thinner and rougher towards the apical and mesiodistal edges. Increase of Cl and Mg, decrease of OH, and X-ray diffraction peak broadening were found in the retrieved implant coatings, in comparison with the unused implants. Morphological changes of the retrieved implants seem to depend on stress values in the surrounding bone and on implant mobility. Compositional changes and increased amount of lattice imperfections appeared in the retrieved implant coatings, as a result of ion substitutions in the apatite lattice. However, the present study could not confirm the influence of these changes on implant failure.

Coated Materials, Biocompatible↗

PubMed2000

Ultrastructure of the interface between alumina bead composite and bone.

We developed a composite (ABC) consisting of alumina bead powder as an inorganic filler and bisphenol-a-glycidyl dimethacrylate (Bis-GMA)-based resin as an organic matrix. Alumina bead powder was manufactured by fusing crushed alpha-alumina powder and quenching it. The beads took a spherical form 3 microm in average diameter. The proportion of filler in the composites was 70% w/w. The composite was implanted into rat tibiae and cured in situ. Specimens were prepared 1, 2, 4, and 8 weeks after the operation and observed by transmission electron microscopy. The results were compared with those of a bone composite made of alpha-alumina powder (alpha-ALC). In ABC-implanted tibiae, the uncured surface layer of Bis-GMA-based resin was completely filled with newly formed bonelike tissue 2 weeks after implantation. The alumina bead fillers were surrounded by and in contact with bonelike tissue. No intervening soft tissue was seen. In alpha-ALC-implanted tibiae, a gap was always observed between the alpha-ALC and the bonelike tissue. These results indicate that the ABC has osteoconductivity, although the precise mechanism is still unclear.

Aluminum Oxide↗

PubMed2000

Bioactive polymethyl methacrylate-based bone cement: comparison of glass beads, apatite- and wollastonite-containing glass-ceramic, and hydroxyapatite fillers on mechanical and biological properties.

A new bioactive bone cement (designated GBC) consisting of polymethyl methacrylate (PMMA) as an organic matrix and bioactive glass beads as an inorganic filler has been developed. The bioactive beads, consisting of MgO-CaO-SiO(2)-P(2)O(5)-CaF(2) glass, have been newly designed, and a novel PMMA powder was selected. The purpose of the present study was to compare this new bone cement GBC's mechanical properties in vitro and its osteoconductivity in vivo with cements consisting of the same matrix as GBC and either apatite- and wollastonite-containing glass-ceramic (AW-GC) powder (designated AWC) or sintered hydroxyapatite (HA) powder (HAC). Each filler added to the cements amounted to 70 wt %. The bending strength of GBC was significantly higher than that of AWC and HAC (p < 0.0001). Cements were packed into intramedullar canals of rat tibiae in order to evaluate osteoconductivity as determined by an affinity index. Rats were sacrificed at 2, 4, and 8 weeks after operation. An affinity index, which equaled the length of bone in direct contact with the cement expressed as a percentage of the total length of the cement surface, was calculated for each cement. At each time interval studied, GBC showed a significantly higher affinity index than AWC or HAC up to 8 weeks after implantation (p < 0.03). The value for GBC increased significantly with time up to 8 weeks (p < 0.006). The handling property of GBC was comparable with that of PMMA bone cement. Our study revealed that the higher osteoconductivity of GBC was due to the higher bioactivity of the bioactive glass beads at the cement surface and the lower solubility of the new PMMA powder to MMA monomer. In addition, it was found that the smaller spherical shape and glassy phase of the glass beads gave GBC strong enough mechanical properties to be useful under weight-bearing conditions. GBC shows promise as an alternative with improved properties to the conventionally used PMMA bone cement.

Animals↗

PubMed2000

Down's syndrome with myelodysplastic syndrome showing t(7;11)(p13;p14).

We report a boy with Down's syndrome (DS) who developed myelodysplastic syndrome (MDS) after spontaneous remission of transient myeloproliferative disorder (TMD) at birth. Chromosomal analysis of the blasts in the MDS phase demonstrated t(7;11)(p13;p14) which had not been detected in the TMD phase. NUP98-HOXA9 chimera mRNA, which is known to be involved in t(7;11)(p15;p15) translocation in acute myeloid leukemia (AML), was not detected by reverse transcriptase-polymerase chain reaction, and NUP98 rearrangement was not detected by Southern blot analysis of the blasts in the MDS phase. Reciprocal translocation is very rare in AML/MDS in DS, and the t(7;11)(p13;p14) found in our patient was different from the recurrent translocation t(7;11)(p15;p15) previously reported.

Blotting, Southern↗

PubMed2000

Glycyrrhizin improves the resistance of MAIDS mice to opportunistic infection of Candida albicans through the modulation of MAIDS-associated type 2 T cell responses.

Compared with normal mice, MAIDS mice (mice infected with LP-BM5 murine leukemia virus) exhibited an increase up to 100 times greater in susceptibility to infection with Candida albicans. The impaired resistance of MAIDS mice to the infection was recovered to levels observed in normal mice by the administration of glycyrrhizin (GR), an active component of licorice roots. MAIDS mice inoculated with CD4(+) T cells from GR-treated mice were also resistant to C. albicans infection. Normal mice inoculated with CD4(+) T helper type 2 cells (Th2 cells) from MAIDS mice were susceptible to C. albicans infection at the same levels shown in MAIDS mice. The susceptibility of normal mice inoculated with type 2 T cells was reversible by (i) administration of GR and (ii) inoculation of CD4(+) T cells from GR-treated mice and injection of a mixture of mAbs targeted against type 2 cytokines (IL-4 and IL-10). Type 2 cytokines were not detected in sera of MAIDS mice inoculated with CD4(+) T cells from GR-treated mice, while they were present in sera of MAIDS mice treated with saline. These results suggest that, by inducing CD4(+) T cells which suppress type 2 cytokine production by MAIDS-associated Th2 cells, GR improves the resistance of MAIDS mice to C. albicans infection.

AIDS-Related Opportunistic Infections↗

PubMed2000

Interferon-gamma and interleukin 4 inhibit interleukin 1beta-induced delayed prostaglandin E(2)generation through suppression of cyclooxygenase-2 expression in human fibroblasts.

Interleukin (IL-)1 stimulates prostaglandin E(2)(PGE(2)) generation in fibroblasts, and preferential couplings between particular phospholipase A(2)(PLA(2)) and cyclooxygenase (COX) isozymes are implicated with IL-1-induced delayed PGE(2)generation. The regulatory effects of interferon (IFN)-gamma and IL-4 on IL-1beta-induced COX, PLA(2)isoforms expression and terminal delayed PGE(2)generation were examined in three types of human fibroblasts. These human fibroblasts constitutively expressed cytosolic PLA(2)(cPLA(2)) and COX-1 enzymes, and exhibited delayed PGE(2)generation in response to IL-1beta. IL-1beta also stimulated expression of cPLA(2)and COX-2 only, while constitutive and IL-1beta-induced type IIA and type V secretory PLA(2)s (sPLA(2)s) expression could not be detected. A COX-2 inhibitor and cPLA(2)inhibitor markedly suppressed the IL-1beta-induced delayed PGE(2)generation, while a type IIA sPLA(2)inhibitor failed to affect it. IFN-gamma and IL-4 dramatically inhibited the IL-1beta-induced delayed PGE(2)generation; these cytokines apparently suppressed IL-1beta-stimulated COX-2 expression and only weakly suppressed cPLA(2)expression in response to IL-1beta. These results indicate that IL-1beta-induced delayed PGE(2)generation in these human fibroblasts mainly depends on de novo induction of COX-2 and cPLA(2), irrespective of the constitutive presence of COX-1, and that IFN-gamma and IL-4 inhibit IL-1beta-induced delayed PGE(2)generation by suppressing, predominantly, COX-2 expression.

Adult↗

PubMed2000

Phylogenetic relationships, character evolution, and biogeography of the subfamily Lygosominae (Reptilia: Scincidae) inferred from mitochondrial DNA sequences.

Phylogenetic relationships among the lygosomine skinks were inferred from 1249 base positions of mitochondrial DNA sequences of 12S and 16S rRNA genes. The monophyly of this subfamily was confirmed and the presence of five distinct infrasubfamilial lineages detected. Of these, the Sphenomorphus group appears to have diverged first, followed by the Lygosoma and Egernia groups in order, leaving the Eugongylus and Mabuya groups as sister groups. Our results did not support monophyly of the Mabuya group sensu lato (i.e., an assemblage of the Lygosoma, Egernia, and Mabuya groups), for which a number of morphological and karyological studies demonstrated a considerable similarity. Our results also contradict the previous hypothesis, formulated on the basis of morphological and immunological data, which argued for the sister relationship between the Egernia and the Eugongylus groups. Morphological and karyological characters used to define the Mabuya group (sensu lato) may actually represent plesiomorphic states. The phylogenetic diversity of lygosomine skinks in the Australian region appears to have increased through multiple colonizations from Southeast Asia.

Animals↗

PubMed2000

Immunohistochemical study of tight junction-related protein in neovasculature in astrocytic tumor.

To clarify whether the neovasculature of brain tumors preserves blood-brain barrier (BBB) functions, we studied the expression of a tight junction-related protein, Zo-1, using immunohistochemistry. Twenty-six astrocytic tumors were examined using an anti-Zo-1 Mab, and Zo-1 expression was compared with the expression of vasicular endothelial growth factor (VEGF), vascular endothelial growth factor receptor (VEGFR) (fit-1), and antiproliferative cell nuclear antigen (PCNA). A positive reaction for Zo-1 was seen in the endothelial cells in micro-blood vessels in all astrocytic tumors. The reactions for Zo-1 in the endothelial cells forming glomeruloid proliferations in newly formed micro-blood vessels in high-grade tumors were weaker than those in the endothelial cells of normal cerebral capillaries. Although there is a negative correlation between positive immunoreactions for BBB-related proteins and the expression of VEGF of the endothelial cells in micro-blood vessels, the proliferative activity of tumor cells, and histological grades, the present findings suggest that the endothelial cells of the neovasculature of high-grade tumors preserve partial BBB function at the cellular level. Because of the ease of immunohistochemical procedures compared with electron microscopic examination, the immunohistochemical detection of Zo-1 should provide a useful marker for tight junctions.

Adolescent↗

PubMed2000

Malignant proliferating trichilemmal tumor in the skin over the breast: a case report.

A proliferating trichilemmal tumor is relatively uncommon. It is composed of multiple cysts consisting of squamous epithelium with trichilemmal keratinization without granular layer interposition. This lesion usually occurs in the scalp of elderly women. We describe a 67-year-old woman with a malignant proliferating trichilemmal tumor in the skin over the breast. We first misdiagnosed the disease as a primary squamous cell carcinoma of the breast with a metastatic lymph node in the axilla because of the disease site and our unfamiliarity with the disease. The patient underwent radical mastectomy with axillary dissection. Eight months postoperatively, a tumor appeared in her right axilla and progressively enlarged. We subsequently excised the tumor. She is healthy as of 8 months postoperatively. To the best of our knowledge, only one case of a proliferating trichilemmal tumor occurring in the skin over the breast has been reported.

Aged↗

PubMed2000

Skin reactions after breast-conserving therapy and prediction of late complications using physiological functions.

BACKGROUND: The temperature of the skin remains elevated long after breast-conserving treatment with irradiation, perhaps because evaporative cooling is impaired. We investigated physiological changes of the irradiated skin and reevaluated the radiosensitivity of sweat glands on a functional basis to determine whether severe complications can be predicted. METHODS: Breast and axillary skin temperatures were measured with thermography and sweat production in response to local thermal stimuli was measured on the basis of changes in electrical skin resistance with a bridge circuit in 45 women before, during, and after breast irradiation for breast cancer. RESULTS: Breast and axillary skin temperatures were significantly increased after irradiation. In response to cutaneous thermal stimuli, the electric skin resistance of nonirradiated areas decreased significantly because of sweating, but that of irradiated areas was unchanged. CONCLUSION: Impairment of sweating may play an important role in skin damage after irradiation. Although glandular tissue is not usually radiosensitive, the results of our functional assessment suggest that sweat glands are more radiosensitive than expected.

Adult↗

PubMed2000

Gastric seromuscular and omental pedicle flap for bronchopleural fistula after pneumonectomy.

We report a case of postpneumonectomy bronchopleural fistula treated using a gastric seromuscular and omental pedicle flap and maintaining good postoperative respiratory function. A 76-year-old man underwent right pneumonectomy with regional lymph node dissection for squamous cell carcimoma of the lung. Five weeks later, a bronchopleural fistula occurred. Empyema with the bronchopleural fistula was diagnosed and chest tube drainage implemented immediately. Despite the drainage, signs of inflammation persisted and the patient's nutrition did not improve leading to surgery, on August 18, 1997. The bronchopleural fistula was closed by horizontal suture proximal to the stapling sutured line. A gastric seromuscular and omental pedicle flap was sutured as a cover over the bronchial stump. Postoperative analysis of respiratory function and arterial blood gas showed good results.

Aged↗

PubMed2000

Indole-inducible proteins in bacteria suggest membrane and oxidant toxicity.

Oxidant toxicity of indole was demonstrated by the induction of alkylhydroperoxide reductase subunit C (AhpC) in Escherichia coli K12 and by the constitutive overproduction of AhpC in a variant of E. coli JM109 with enhanced resistance to indole. Oxidant toxicity was also indicated in an indole-adapted variant of Brevibacterium flavum by the indole-inducible overproduction of a novel 36-kDa protein with N-terminal sequence similarity to proteins involved in superoxide and singlet oxygen resistance. It is proposed that indole dissolved in membrane lipids, which caused membrane derangement and enabled direct interaction of redox-cycling isoprenoid quinones and dioxygen, resulting in the generation of superoxide. A direct indication of membrane derangement in E. coli may be the indole-inducible overproduction of spheroplast protein y (Spy).

Amino Acid Sequence↗

PubMed2000

Effects of phencyclidine on behavior and extracellular levels of dopamine and its metabolites in neonatal ventral hippocampal damaged rats.

RATIONALE: The use of neonatal hippocampal lesioned rats is well established in animal models of schizophrenia. Moreover, the dysfunction of N-methyl-D-aspartate (NMDA) neurotransmission may play a crucial role in the pathophysiology of schizophrenia. OBJECTIVE: To examine the role of NMDA neurotransmission in the neonatal ventral hippocampal damaged rat. METHODS: In initial experiments, we compared the effects of mild environmental stress (HAB) and the injection of saline and methamphetamine (MAP, 1.5 mg/kg, IP) in lesioned and sham-operated rats. We also examined the effects of a single injection of phencyclidine (PCP, 10 mg/kg, IP) on locomotor activity and extracellular levels of dopamine (DA) and its metabolites in the nucleus accumbens (NAc) of lesioned and sham-operated rats using an in vivo brain microdialysis method. RESULTS: Compared with sham-operated controls, the lesioned rats showed increased locomotor activity at postnatal day 56 (PD56) but not at PD35 after HAB and MAP administration. Similarly, the lesioned rats showed increased locomotor activity at PD56 but not at PD35 after PCP administration. Unexpectedly, the increase in DA levels was significantly greater in the sham-operated rats than in the lesioned rats. CONCLUSIONS: The results suggest that neonatal hippocampal lesioned rats are accompanied by the dysfunction of NMDA neurotransmission. They also suggest that hyperresponsiveness to PCP following neonatal hippocampal lesions does not depend on the extracellular DA concentration in the NAc.

Animals↗

PubMed2000

In vivo antioxidant role of astaxanthin under oxidative stress in the green alga Haematococcus pluvialis.

Intracellular production of active oxygen in the green alga Haematococcus pluvialis was studied by measuring the capacity for in vivo conversion of 2',7'-dichlorohydrofluorescein diacetate to the fluorescent dye dichlorofluorescein in different algal cell types (i.e., vegetative, immature cyst and mature cyst cells). The increase in formation of dichlorofluorescein by methyl viologen (superoxide anion radical generator) was linear for 2 h in immature cyst cells (low astaxanthin) in a methyl viologen-concentration-dependent manner, while no production was detected in mature (high astaxanthin) cysts. Compared to cyst cells, formation of dichlorofluorescein in vegetative cells (no astaxanthin) was markedly increased by methyl viologen. The formation of dichlorofluorescein in cyst cells was decreased with higher astaxanthin content under excessive oxidative stress. All of the active oxygen species tested (singlet oxygen, superoxide anion radical, hydrogen peroxide and peroxy radical) at 10(-3) M increased the intracellular dichlorofluorescein formation in immature cysts, but did not increase the dichlorofluorescein content of mature cysts. Therefore, astaxanthin in cyst cells appeared to function as an antioxidant agent against oxidative stress.

Antioxidants↗

PubMed2000

Nonoxidative protein glycation is implicated in familial amyotrophic lateral sclerosis with superoxide dismutase-1 mutation.

To assess a role for oxidative stress in the pathogenesis of amyotrophic lateral sclerosis (ALS), we analyzed the immunohistochemical localization of 8-hydroxy2'-deoxyguanosine (OHdG) as a nucleic acid oxidation product, acrolein-protein adduct and 4-hydroxy-2-nonenal (HNE)-protein adduct as lipid peroxidation products, Nepsiloncarboxymethyl-lysine (CML) as a lipid peroxidation or protein glycoxidation product, pentosidine as a protein glycoxidation product, and imidazolone and pyrraline as nonoxidative protein glycation products in the spinal cord of three familial ALS patients with superoxide dismutase(SOD 1) A4V mutation, six sporadic ALS patients, and six age-matched control individuals. The spinal cord sections of the control cases did not show any distinct immunoreactivities for these examined products. In the familial ALS cases, intense immunoreactivities for pyrraline and CML were confined to the characteristic Lewy body-like hyaline inclusions, and imidazolone immunoreactivity was located in the cytoplasm of the residual motor neurons. No significant immunoreactivities for other examined products were detected in the familial ALS spinal cords. In the sporadic ALS cases, intense immunoreactivities for pentosidine, CML and HNE-protein adduct were seen in the cytoplasm of the degenerated motor neurons, and OHdG immunoreactivity was located in the cell nuclei of the residual neurons and glial cells. The present results indicate that oxidative reactions are involved in the disease processes of sporadic ALS, while there is no evidence for increased oxidative damage except for CML deposition in the familial ALS spinal cords. Furthermore, it is likely that the accumulation of pyrraline and imidazolone supports a nonoxidative mechanism in SOD1-related motor neuron degeneration.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed2000

Onset of rigor mortis is earlier in red muscle than in white muscle.

Rigor mortis is thought to be related to falling ATP levels in muscles postmortem. We measured rigor mortis as tension determined isometrically in three rat leg muscles in liquid paraffin kept at 37 degrees C or 25 degrees C--two red muscles, red gastrocnemius (RG) and soleus (SO) and one white muscle, white gastrocnemius (WG). Onset, half and full rigor mortis occurred earlier in RG and SO than in WG both at 37 degrees C and at 25 degrees C even though RG and WG were portions of the same muscle. This suggests that rigor mortis directly reflects the postmortem intramuscular ATP level, which decreases more rapidly in red muscle than in white muscle after death. Rigor mortis was more retarded at 25 degrees C than at 37 degrees C in each type of muscle.

Adenosine Triphosphate↗

PubMed2000

Effect of nifedipine administration (10 mg) on esophageal acid exposure time.

The effect of nifedipine administration (10 mg) on esophageal acid exposure time was investigated in 11 non-reflux esophagitis (non-RE) patients and 11 grade C (Los Angeles classification) reflux esophagitis (RE) patients. In each subject, esophageal pH monitoring was performed, with the subject in the supine position, preprandially (1 h) and 3-h postprandially after oral administration of a placebo in the morning and oral administration of nifedipine (10 mg) in the afternoon on the same day. In the non-RE patients, there was no difference in the esophageal acid exposure time between administration of the placebo and that of nifedipine. In patients with RE, the esophageal acid exposure time after the administration of nifedipine was significantly (P<0.05) longer than that after the placebo. In patients with severe RE, the severity of RE may worsen with nifedipine administration.

Aged↗

PubMed2000

Fluctuation patterns of HCV-RNA serum level in patients with chronic hepatitis C.

The serum level of hepatitis C virus (HCV)-RNA is clinically important as a predictor of the response to interferon (IFN) therapy in patients with chronic hepatitis C. If serum HCV-RNA levels fluctuate during follow-up, and IFN therapy is begun at the time of a low HCV-RNA level, the IFN therapy may be more effective. We evaluated the fluctuation of HCV-RNA serum levels for 2 years in 212 patients with chronic hepatitis C, untreated with IFN who had HCV genotype 1b and an HCV-RNA level of 10 Meq/ml or more at first consultation. The HCV-RNA level was measured monthly for 2 years with an HCV branched DNA probe assay (b DNA probe assay). We classified HCV-RNA patterns into three types by the ratio of maximum HCV-RNA level (a) to minimum HCV-RNA level (b). In pattern 1 (constant type, 151 patients; 71.2%) the a/ b ratio was 1-5. In pattern 2 (slight fluctuation type, 46 patients; 21.7%) the a/b ratio was 5-10. In pattern 3 (severe fluctuation type, 15 patients; 7.1%), the a/b ratio was 10 or more. Next, we evaluated the factors associated with the three patterns. Acute exacerbation of chronic hepatitis was regarded as an increase in serum alanine aminotransferase (ALT) level to more than 250 IU/l. The incidence of acute exacerbation for a 2-year follow-up was 13.9% (21/151) in pattern 1, 19.6% (9/46) in pattern 2, and 53.3% (8/15) in pattern 3. Multivariate analysis showed that acute exacerbation was the most important factor in the manifestation pattern 3. In conclusion, we found that: (1) about 70% of patients had a constant HCV-RNA levels for 2 years. (2) A few patients had severe fluctuation of serum HCV-RNA level after acute exacerbation of chronic hepatitis.

Adult↗