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Biomedical subjects

Akira Yamaguchi

Publications and source records attributed to Akira Yamaguchi.

At least 55 records · Page 3Linked to original sources
PubMed2004

Self-assembly of a silica-surfactant nanocomposite in a porous alumina membrane.

A mesoporous membrane composed of nanochannels with a uniform diameter has a potential use for precise size-exclusive separation of molecules. Here, we report a novel method to form a hybrid membrane composed of silica-surfactant nanocomposite and a porous alumina membrane, by which size-selective transport of molecules across the membrane becomes possible. The nanocomposite formed inside each columnar alumina pore was an assembly of surfactant-templated silica-nanochannels with a channel diameter of 3.4 nm; the channel direction being predominantly oriented along the wall of the columnar alumina pore. Molecules could be transported across the membrane including the silica-surfactant nanocomposite with a capability of nanometre-order size-exclusive separation. Our proposed membrane system has a potential use not only for separation science, but also catalysis and chip technologies.

Aluminum Oxide↗
PubMed2004

RETRACTED: A human chondrogenic cell line retains multi-potency that differentiates into osteoblasts and adipocytes.

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the author, Dr. Kimihito Yagami. Dr. Yagami's collaborators Yohei Uyama, Yasumasa Yoshizawa, Saburo Kakuta, Akira Yamaguchi, Masao Nagumo were not involved in the RT-PCR experiments and figure preparation The editor, Sundeep Khosla, was notified by an independent group that specific bands in Figure 3 of the paper appear to be duplicated. This was brought to the attention of the authors. Due to the long interval from the original publication of the paper, the raw data was not available; however, the authors subsequently chose to retract the entire manuscript, and the editor agreed.

Adipocytes↗
PubMed2004

Evaluation of 9.4-T MR microimaging in assessing normal and defective fetal bone development: comparison of MR imaging and histological findings.

We evaluated 9.4-T magnetic resonance (MR) microimaging in assessing normal and defective bone development in mouse embryos. For this purpose, we performed 9.4-T MR microimaging on developing bones in normal embryos, and also in Runx2/Cbfa1-/- embryos with severely defective bone development. MR images were compared with the histological and histochemical features of these fetal bones. MR microimaging delineate successfully the normal long bone development in embryos. The T1- and T2-weighted MR microimaging demonstrated chondrocyte maturation in different regions of growing cartilage, such as epiphysis, physis, hypertrophic cartilage, and zone of provisional calcification. These developmental changes were detectable in as early as E14.5 embryos. The MR microimaging clearly demonstrated defective bone development in Runx2/Cbfa1-/- embryos. The femur from E18.5 homozygous Runx2/Cbfa1-/- embryos lacked MR signal intensity patterns including the hypertrophic cartilage, which are characteristic of the bone from the age-matched Runx2/Cbfa1+/+ embryos. Interestingly, however, the tibia from the same mutants was associated with MR signal patterns indicative of hypertrophic cartilage but not of the primary spongiosa and ossifying perichondrium, suggesting that bone development is differently regulated in these two long bones. On the other hand, the bones from heterozygous Runx2/Cbfa1+/- embryos exhibited an MR phenotype intermediate between the Runx2/Cbfa1+/+ and Runx2/Cbfa1-/- embryos; the primary spongiosa and ossifying perichondrium formation occurred normally even in the absence of preceding organized maturation of chondrocytes, a phenotype that was not detected by histological examinations. We concluded that MR microimaging is useful in assessing the bone development.

Animals↗
PubMed2004

Nrf2 deficiency causes tooth decolourization due to iron transport disorder in enamel organ.

Rodents have brownish-yellow incisors whose colour represents their iron content. Iron is deposited into the mature enamel by ameloblasts that outline enamel surface of the teeth. Nrf2 is a basic region-leucine zipper type transcription factor that regulates expression of a range of cytoprotective genes in response to oxidative and xenobiotic stresses. We found that genetically engineered Nrf2-deficient mice show decolourization of the incisors. While incisors of wild-type mice were brownish yellow, incisors of Nrf2-deficient mice were greyish white in colour. Micro X-ray imaging analysis revealed that the iron content in Nrf2-deficient mouse incisors were significantly decreased compared to that of wild-type mice. We found that iron was aberrantly deposited in the papillary layer cells of enamel organ in Nrf2-deficient mouse, suggesting that the iron transport from blood vessels to ameloblasts was disturbed. We also found that ameloblasts of Nrf2-null mouse show degenerative atrophy at the late maturation stage, which gives rise to the loss of iron deposition to the surface of mature enamel. Our results thus demonstrate that the enamel organ of Nrf2-deficient mouse has a reduced iron transport capacity, which results in both the enamel cell degeneration and disturbance of iron deposition on to the enamel surface.

Animals↗
PubMed2004

Alpha-blocker test: alternative to pressure-flow study of bladder outlet obstruction and detrusor contractility in patients without an enlarged prostate.

OBJECTIVES: We investigated whether the cause of urinary disturbance in men with a prostate volume < or =20 mL can be determined by analyzing the efficacy of alpha1-adrenoceptor antagonist (alpha-blocker) treatment. METHODS: Thirty-five men who were >50 years of age, with an International Prostate Symptom Score (IPSS) > or =8 points, a quality of life (QOL) index > or =2 points and a prostate volume </=20 mL were enrolled in the non-enlarged prostate group. Twenty-six men who met the above conditions but who had a prostate volume >20 mL served as controls. The alpha1-adrenoceptor antagonist tamsulosin was administered at a dose of 0.2 mg/day for 4 weeks. Results for the IPSS, QOL index, free flowmetry and pressure-flow studies were obtained before and after tamsulosin administration. RESULTS: In both groups, tamsulosin improved the IPSS and QOL index and the bladder outlet obstruction index (BOOI) was lowered without reducing the bladder contractility index (BCI). No parameter showed a significant difference in treatment efficacy between the two groups. In the non-enlarged prostate group, both the pretreatment BOOI and BCI correlated with the efficacy of treatment in improving maximum flow rate (Qmax). In the enlarged prostate group, BOOI and BCI did not correlate with Qmax. When Qmax was improved by > or =3.5 mL/s, the positive predictive value for both pretreatment BOOI >40 and BCI >100 was 100% in the non-enlarged prostate group. CONCLUSIONS: The alpha-blocker test is one method to assess the presence of bladder outlet obstruction and the state of detrusor contractility in men without an enlarged prostate.

Adrenergic alpha-Antagonists↗
PubMed2004

Possible role of autoantibodies in the pathophysiology of GM2 gangliosidoses.

Mice containing a disruption of the Hexb gene have provided a useful model system for the study of the human lysosomal storage disorder known as Sandhoff disease (SD). Hexb(-/-) mice rapidly develop a progressive neurologic disease of ganglioside GM2 and GA2 storage. Our study revealed that the disease states in this model are associated with the appearance of antiganglioside autoantibodies. Both elevation of serum antiganglioside autoantibodies and IgG deposition to CNS neurons were found in the advanced stages of the disease in Hexb(-/-) mice; serum transfer from these mice showed IgG binding to neurons. To determine the role of these autoantibodies, the Fc receptor gamma gene (FcR gamma) was additionally disrupted in Hexb(-/-) mice, as it plays a key role in immune complex-mediated autoimmune diseases. Clinical symptoms were improved and life spans were extended in the Hexb(-/-)FcR gamma(-/-) mice; the number of apoptotic cells was also decreased. The level of ganglioside accumulation, however, did not change. IgG deposition was also confirmed in the brain of an autopsied SD patient. Taken together, these findings suggest that the production of autoantibodies plays an important role in the pathogenesis of neuropathy in SD and therefore provides a target for novel therapies.

Animals↗
PubMed2004

Adsorption behavior of lauric acid at heptane/water interface as studied by second harmonic generation spectroscopy and interfacial tensiometry.

Interfacial tensiometry and second harmonic generation (SHG) spectroscopy were applied to examine the adsorption behavior of lauric acid (LA) at a heptane/water interface. From interfacial tensiometry measurements, the adsorption kinetics of LA was revealed to be diffusion-controlled, and the adsorption constant of LA was estimated to be 9.6 x 10(4) M(-1). The adsorption isotherms obtained by SHG measurements were analyzed by taking account of both the molecular orientation of LA at the interface and a surface electric field generated by the adsorbed LA layer. It was confirmed that the carboxylic groups of adsorbed LA molecules were well ordered at the heptane/water interface and the orientation of the carboxylate group was invariant during the adsorption process.

Journal Article↗
PubMed2004

Early stage of Epstein-Barr virus lytic infection leading to the "starry sky" pattern formation in endemic Burkitt lymphoma.

CONTEXT: Burkitt lymphoma (BL) is histologically characterized by a "starry sky" appearance, representing scattered macrophages that have phagocytosed cell debris among proliferating lymphoma cells. As is well known, almost all the neoplastic cells of endemic BL are infected with Epstein-Barr virus (EBV). Previous studies have indicated that most of the EBV in B cells is latent, and few virus particles enter the lytic cycle. OBJECTIVE: To examine the histologic relationship between EBV infection stages and the formation of the starry sky pattern in African endemic BL tissues. DESIGN: Tissue samples from 44 patients with African endemic BL were examined with immunohistochemistry and in situ hybridization. We used EBV-encoded small RNA (EBER) as a marker of latent infection, and BamHI H left frame 1 (BHLF1) and BamHI Z EBV replication activator (ZEBRA) as lytic cycle markers. RESULTS: In all cases, signals for EBER were found in most neoplastic lymphocytes, and in 73% of cases, signals for BHLF1 and/or ZEBRA were recognized in the lymphoma cells within and around the lacunae in starry sky figures. The mean number of lacunae per unit area in cases positive for lytic cycle markers was significantly higher than that in negative cases (P <.001). CONCLUSIONS: Our findings suggest that EBV-infected lymphoma cells in the lytic cycle, which eventually lapse into cell death, are phagocytosed prior to their rupture by macrophages that have migrated into the parenchyma. We emphasize that transition of EBV-infected lymphoma cells to the lytic cycle is one of the histomorphogenetic factors influencing the formation of starry sky pattern in endemic BL.

Adolescent↗
PubMed2003

Recombinant motor domain constructs of Chara corallina myosin display fast motility and high ATPase activity.

The mechanism and structural features that are responsible for the fast motility of Chara corallina myosin (CCM) have not been elucidated, so far. The low yields of native CCM that can be purified to homogeneity were the major reason for this. Here, we describe the expression of recombinant CCM motor domains, which support the fast movement of actin filaments in an in vitro motility assay. A CCM motor domain without light chain binding site moved actin filaments at a velocity of 8.8 microm/s at 30 degrees C and a CCM motor domain with an artificial lever arm consisting of two alpha-actinin repeats moved actin filaments at 16.2 microm/s. Both constructs displayed high actin-activated ATPase activities ( approximately 500 Pi/s/head), which is indicative of a very fast hydrolysis step. Our results provide an excellent system to dissect the specific structural and functional features that distinguish the myosin responsible for fast cytoplasmic streaming.

Adenosine Triphosphatases↗
PubMed2003

Osteogenic differentiation of the mesenchymal progenitor cells, Kusa is suppressed by Notch signaling.

Notch receptor plays a crucial role in proliferation and differentiation of many cell types. To elucidate the function of Notch signaling in osteogenesis, we transfected the constitutively active Notch1 (Notch intracellular domain, NICD) into two different osteoblastic mesenchymal cell lines, KusaA and KusaO, and examined the changes of their osteogenic potentials. In NICD stable transformants (KusaA(NICD) and KusaO(NICD)), osteogenic properties including alkaline phosphatase activity, expression of osteocalcin and type I collagen, and in vitro calcification were suppressed. Transient transfection of NICD attenuated the promoter activities of Cbfa1 and Ose2 element. KusaA was capable of forming trabecular bone-like tissues when injected into mouse abdomen, but this in vivo bone forming activity was significantly suppressed in KusaA(NICD). Osteoclasts were induced in the KusaA-derived bone-like tissues, but lacked in the KusaA(NICD)-derived tissues. These results suggest that Notch signaling suppresses the osteoblastic differentiation of mesenchymal progenitor cells.

Animals↗
PubMed2003

Neuronal accumulation of alpha- and beta-synucleins in the brain of a GM2 gangliosidosis mouse model.

Sandhoff disease (SD) is a heritable lysosomal storage disease resulting from impaired degradation of GM2 ganglioside. The hallmark pathology of the SD model mouse brain is GM2 ganglioside accumulation in neurons. In the present study, we immunohistochemically investigated the neuronal pathology in SD mouse brains, and demonstrated neuronal accumulation of alpha- and beta-synucleins in addition to GM2 ganglioside. Synuclein-positive neurons were extensively observed throughout SD mouse brains, although the distribution of beta-synuclein was less extensive than that of alpha-synuclein. Synuclein-positive neurons were negative to ubiquitin and PHF-tau. These findings suggest that neuronal synucleins may accumulate secondarily to GM2 ganglioside in SD mouse brains, and that neuronal accumulation of synucleins may be more critical than that of GM2 ganglioside for SD mice.

Animals↗
PubMed2003

Plasmid-based gene transfer ameliorates visceral storage in a mouse model of Sandhoff disease.

Sandhoff disease is a severe neurodegenerative disorder with visceral involvement caused by mutations in the HEXB gene coding for the beta subunit of the lysosomal hexosaminidases A and B. HEXB mutations result in the accumulation of undegraded substrates such as GM2 and GA2 in lysosomes. We evaluated the efficacy of cationic liposome-mediated plasmid gene therapy using the Sandhoff disease mouse, an animal model of a human lysosomal storage disease. The mice received a single intravenous injection of two plasmids, encoding the human alpha and beta subunits of hexosaminidase cDNAs. As a result, 10-35% of normal levels of hexosaminidase expression, theoretically therapeutic levels, were achieved in most visceral organs, but not in the brain, 3 days after injection with decreased levels by day 7. Histochemical staining confirmed widespread enzyme activity in visceral organs. Both GA2 and GM2 were reduced by almost 10% and 50%, respectively, on day 3, and by 60% and 70% on day 7 compared with untreated age-matched Sandhoff disease mice. Consistent with the biochemical results, a reduction in GM2 was observed in liver cells histologically as well. These initial findings support further development of the plasmid gene therapy against lysosomal diseases with visceral pathology.

Animals↗
PubMed2003

Use of isolated mature osteoblasts in abundance acts as desired-shaped bone regeneration in combination with a modified poly-DL-lactic-co-glycolic acid (PLGA)-collagen sponge.

Controlled regeneration of bone or cartilage has recently begun to facilitate a host of novel clinical treatments. An osteoblast line, which we isolated is able to form new bone matrix in vivo within 2 days and exhibits a mature osteoblast phenotype both in vitro and in vivo. Using these cells, we show that cuboidal bones can be generated into a predesigned shaped-bone with high-density bone trabeculae when used in combination with a modified poly-DL-lactic-co-glycolic acid (PLGA)-collagen sponge. PLGA coated with collagen gel serves as a good scaffold for osteoblasts. These results indicate that mature osteoblasts, in combination with a scaffold such as PLGA-collagen sponge, show promise for use in a custom-shaped bone regeneration tool for both basic research into osteogenesis and for development of therapeutic applications.

Absorbable Implants↗
PubMed2003

Usefulness of measuring plasma cytokines in oral and maxillofacial surgery.

We determined the intra- and postoperative plasma concentrations of cytokines (tumor necrosis factor [TNF]-Alpha, interleukin [IL]-1Beta, IL-6, and IL-8) in oral surgery patients with procedures ranging in duration from 20 to 375 min and investigated their relationship to the intensity of the surgical stress over time. No significant differences from baseline levels were observed in the levels of TNF-Alpha, IL-1Beta, and IL-8. By contrast, increased IL-6 levels were noted only on the first postoperative day, when they reached 1500% of the baseline level, after which they decreased to preoperative levels by the third postoperative day and tended to reflect the intensity of surgical stress.

Adult↗
PubMed2003

Sternocleidomastoid myocutaneous flap for intraoral reconstruction after resection of oral squamous cell carcinoma.

PURPOSE: The sternocleidomastoid (SCM) myocutaneous flap remains an important tool in head and neck reconstruction. This article retrospectively reviews 40 consecutive SCM myocutaneous flaps used for the reconstruction after resection of oral squamous cell carcinoma with respect to reliability and complications. PATIENTS: From 1987 to 1997, 40 patients underwent SCM myocutaneous flap reconstruction of the oral cavity. The age and gender of the patients, site of primary tumor TNM stage, type of associated operation, and clinical course were analyzed. RESULTS: In 8 cases, partial epithelial loss over the skin paddle occurred with survival of the muscle and at least some of the dermis. Unilateral supraomohyoid neck dissection (SND) was performed in 11 cases, and unilateral functional neck dissection, which preserves SCM and/or internal jugular vein and/or accessory nerve, in 16 cases. Pathologically positive nodes were recognized in 14 of these 27 neck dissection cases; in 11 of these 14 cases, the neck lesion was controlled. CONCLUSION: The SCM myocutaneous flap appears to be simple to use and useful for reconstruction of the defect after resection of oral carcinoma, and the indications for this flap will be extended in accordance with the recent increases in the number of supraomohyoid and functional neck dissection cases.

Aged↗
PubMed2003

Effect of intermittent parathyroid hormone (1-34) treatment on the bone response after placement of titanium implants into the tibia of ovariectomized rats.

PURPOSE: This study investigated the effect of parathyroid hormone (1-34) [PTH(1-34)] on bone reactions after tibial placement of titanium screw implants into ovariectomized rats. MATERIALS AND METHODS: Twelve-week-old female Wistar rats were divided into 3 groups of 24. The first group (Sham group) was sham-operated; the second group (OVX group) was ovariectomized only; and the third group (PTH group) was subcutaneously administered 30 microg/kg PTH in the dorsal region 3 days per week starting the fourth week after ovariectomy until the end of the experiment. Titanium screw implants were placed in the proximal metaphysis of the tibia of all 3 groups at 168 days after surgery. The animals were killed 7, 14, 28, and 56 days after implantation. Undecalcified sections were prepared and evaluated by light microscopy. Histomorphometric measurements were obtained using a computer-based image analyzer to quantify the unit bone mass around the implant and the rate of implant-bone contact. RESULTS: When PTH administration was started 21 days after ovariectomy, the volume density of bone around implants in the PTH group was almost the same as that of the Sham group throughout the entire observation period. This finding suggests that not only can intermittent human PTH(1-34) administration prevent resorption of newly generated trabeculae around an implant but also it can aid in the recovery of bone volume lost due to ovariectomy. CONCLUSION: When dental implants are applied to jaw bone showing trabecular bone loss, it may be possible to increase bone density around an implant by intermittent human PTH(1-34) administration and thereby improve clinical results.

Animals↗