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Hiroaki Nakamura

Publications and source records attributed to Hiroaki Nakamura.

At least 19 recordsLinked to original sources
PubMed2006

New 19-nor-(20S)-1alpha,25-dihydroxyvitamin D3 analogs strongly stimulate osteoclast formation both in vivo and in vitro.

2-Methylene-19-nor-(20S)-1alpha,25-dihydroxyvitamin D3 (2MD), an analog of 1alpha,25-dihydroxyvitamin D3 [1alpha,25(OH)2D3], has been shown to strongly induce bone formation both in vitro and in vivo. We have synthesized four substituents at carbon 2 of 2MD (2MD analogs), four stereoisomers at carbon 20 of the respective 2MD analogs (2MD analog-C20 isomers) and four 2MD analogs with an oxygen atom at carbon 22 (2MD-22-oxa analogs) and examined their ability to stimulate osteoclastogenesis and induce hypercalcemia. 2MD analogs were 100 times as potent as 1alpha,25(OH)2D3 in stimulating the formation of osteoclasts in vitro and in inducing the expression of receptor activator of NF-kappaB ligand (RANKL) and 25-hydroxyvitamin D3-24 hydroxylase mRNAs in osteoblasts. The osteoclast-inducing activities of 2MD analog-C20 isomers and 2MD 22-oxa analogs were much weaker than those of 2MD analogs. In addition, the activity of a 2MD analog in inducing dentine resorption was much stronger than that of 1alpha,25(OH)2D3 in the pit formation assay. Affinities to the vitamin D receptor and transcriptional activities of these compounds did not always correlate with their osteoclastogenic activities. Osteoprotegerin-deficient (OPG-/-) mice provide a suitable model for investigating in vivo effects of 2MD analogs because they exhibit extremely high concentrations of serum RANKL. The same amounts of 2MD analogs and 1alpha,25(OH)2D3 were administered daily to OPG-/- mice for 2 days. The elevation in serum concentrations of RANKL and calcium was much greater in 2MD analog-treated OPG-/- mice than in 1alpha,25(OH)2D3-treated ones. A 2MD analog was much more potent than 1alpha,25(OH)2D3 in causing hypercalcemia and in increasing soluble RANKL with enhanced osteoclastogenesis even in wild-type mice. In contrast, the administration of the 2MD analog to c-fos-deficient mice failed to induce osteoclastogenesis and hypercalcemia. These results suggest that new substituents at carbon 2 of 2MD strongly stimulate osteoclast formation in vitro and in vivo, and that osteoclastic bone resorption is indispensable for their hypercalcemic action of 2MD analogs in vivo.

Animals↗
PubMed2006

Increase of bone volume by a nanosecond pulsed laser irradiation is caused by a decreased osteoclast number and an activated osteoblasts.

The biostimulatory effects of laser irradiation focus not only in the field of soft tissue but also bone formation. Studies have shown that the light of a nanosecond pulsed laser which has a high peak power can produce stress waves in tissue. We have hypothesized that nanosecond pulsed laser irradiation stimulates bone formation. Our aim was to clarify the mechanism of increased bone volume by nanosecond pulsed laser irradiation. Rat femur was irradiated with a Q-switched Nd:YAG laser, which has a wavelength of 1064 nm. The quantification of trabecular architecture using three-dimensional morphometric analysis and measurement of bone mineral density (BMD) using pQCT was performed on day 1, day 3, day 5, and day 7 after laser irradiation. The laser effects on bone cells were also investigated using histological and immunohistochemical analysis. On day 1 after laser irradiation, bone volume (BV/TV), trabecular thickness (Tb.Th), and other parameters of the irradiated group did not significantly differ from the non-irradiation group (control). However, the mean BV/TV, Tb.Th, mineral apposition rate, and BMD of the laser group on day 7 after laser irradiation were significantly greater than those of the control. On histological analysis, the number of TRAP-positive osteoclasts was lower on day 3 after laser irradiation. Osteoblasts with activated clearance were seen in the laser irradiated group on day 1 and day 3. These data reveal that the increased bone volume by nanosecond pulsed laser irradiation causes an increase in osteoblast activity and a decrease in osteoclast number.

Acid Phosphatase↗
PubMed2006

Immunohistochemical localization of alpha-Smooth muscle actin during rat molar tooth development.

The dental follicle contains mesenchymal cells that differentiate into osteoblasts, cementoblasts, and fibroblasts. However, the characteristics of these mesenchymal cells are still unknown. alpha-Smooth muscle actin (alpha-SMA) is known to localize in stem cells and precursor cells of various tissues. In the present study, to characterize the undifferentiated cells in the dental follicle, immunohistochemical localization of alpha-SMA was examined during rat molar tooth development. Rat mandibles were collected at embryonic days (E) 15-20 and postnatal days (P) 7-28. Immunohistochemical stainings for alpha-SMA, periostin, Runt-related transcription factor-2 (Runx2), tissue nonspecific alkaline phosphatase (TNAP), and bone sialoprotein (BSP) were carried out using paraffin-embedded sections. alpha-SMA localization was hardly detected in the bud and cap stages. At the early bell stage, alpha-SMA-positive cells were visible in the dental follicle around the cervical loop. At the late bell to early root formation stage (P14), these cells were detected throughout the dental follicle, but they were confined to the apical root area at P28. Double immunostaining for alpha-SMA and periostin demonstrated that alpha-SMA-positive cells localized to the outer side of periostin-positive area. Runx2-positive cells were visible in the alpha-SMA-positive region. TNAP-positive cells in the dental follicle localized nearer to alveolar bone than Runx2-positive cells. BSP was detected in osteoblasts as well as in alveolar bone matrix. These results demonstrate that alpha-SMA-positive cells localize on the alveolar bone side of the dental follicle and may play a role in alveolar bone formation.

Actins↗
PubMed2006

Lumbar juxta-facet cyst after trauma.

We report a post-traumatic lumbar facet cyst in which results of magnetic resonance imaging (MRI) performed at the time of injury were available. The patient was a 59-year-old man who presented with severe low back and right leg pain immediately after injury of his sacroiliac region in a traffic accident. MRI at the time of injury revealed high intensity signal change in the right facet joint at L4/5. Re-examination 5 months after the injury with MRI revealed a cyst, which was continuous with the facet joint. Surgical resection of the cyst yielded satisfactory results. We describe detailed MRI findings for this case and review the literature on traumatic juxta-facet cyst in the lumbar spine.

Cysts↗
PubMed2006

Localization of perlecan and heparanase in Hertwig's epithelial root sheath during root formation in mouse molars.

During cementogenesis, dental follicular cells penetrate the ruptured Hertwig's epithelial root sheath (HERS) and differentiate into cementoblasts. Mechanisms involved in basement membrane degradation during this process have not been clarified. Perlecan, a heparan sulfate (HS) proteoglycan, is a component of all basement membranes. Degradation of HS of perlecan by heparanase cleavage affects a variety of biological processes. We elucidated immunolocalization of perlecan and heparanase in developing murine molars to clarify their roles in cementoblast differentiation. At the initial stage of root formation, perlecan immunoreactivity was detected on the basement membrane of HERS. Weak heparanase immunoreactivity was detected in HERS cells. HERS showed intense staining for heparanase as root formation progressed. In contrast, labeling for perlecan disappeared from the basement membrane facing the dental follicle, and weak immunoreactivity for perlecan was detected on the inner side of the basement membrane of HERS. These findings suggest that perlecan removal is an important step for root and periodontal tissue formation. Heparanase secreted by the cells of HERS may contribute to root formation by degrading perlecan in the dental basement membrane.

Animals↗
PubMed2006

The structure and diversity of alpha1-acid glycoprotein/orosomucoid gene in Africans.

Human orosomucoid (ORM), or alpha(1)-acid glycoprotein, is known to be controlled by duplicated and triplicated genes on chromosome 9, encoding ORM1 and ORM2 proteins. In this study, the structure and diversity of the ORM gene were investigated in 16 Sub-Saharan Africans, who originated from widely dispersed locations in Africa. The duplicated ORM1-ORM2 gene was observed in all 16 samples. ORM1*S1(2), characterized by an ORM2 gene-specific sequence in intron 5, was common in Africans. Three Africans showed the duplication of the ORM1 gene. The organization of the triplicated ORM1A-ORM1B-ORM2 gene was established in two Africans. The recombination breakpoints resulting in the ORM1 duplication lay within a small genomic interval around exon 1 of the ORM1B gene. The duplication of the ORM2 gene reported previously was not detected in this population sample. Several single-nucleotide polymorphisms were observed in the ORM2 gene. The rearrangement of the ORM gene is likely to occur often in Africans.

Alu Elements↗
PubMed2006

Endometrial thickness in Japanese women with hypertension or/and type 2 diabetes mellitus.

OBJECTIVES: The purpose of this study was: (a) to examine whether the endometrium of postmenopausal women with hypertension (HT) and/or type 2 diabetes mellitus (DM) was thicker than that of healthy controls (HC) and (b) whether endometrial thickness (ET) was associated with endometrial cancer risk factors. STUDY DESIGN: A total of 242 postmenopausal women were included in this study. Thirty women with type 2 DM, 49 women with HT, 23 women with DM and HT and 140 HCs were studied. Clinical evaluation of all women was done using TVS and endometrial cytology. RESULTS: In the 140 HCs, the mean ET of nulliparous women was larger than multiparous women (3.0 mm versus 1.6 mm, p = 0.017). However, there was no significant relationship between ET and other clinical parameters such as a history of sterility or BMI. There was no significant difference in ET amongst the four groups. The relationship between ET, age, pregnancy history, menopause age, BMI and presence of DM or HT were analyzed using stepwise multivariate analysis. There was no significant relationship between these risk factors and ET (p = 0.063). CONCLUSIONS: The risk factors such as age, pregnancy history, menopause age, BMI and presence of DM or HT were not related to ET in Japanese women.

Adult↗
PubMed2006

Endoscopic vertebroplasty for the treatment of chronic vertebral compression fracture. Technical note.

The authors describe a new vertebroplasty technique for the treatment of chronic painful vertebral compression fractures (VCFs). A urinary balloon catheter is introduced into the vertebral body (VB) via a bilateral transpedicular approach and inflated with contrast medium to obtain sufficient space for endoscopic observation. The granulation tissue occupying the VB is then removed using a punch or curette inserted through one pedicle, with the guidance of an endoscope introduced through the contralateral pedicle. After endoscopic resection of granulation tissue in the fractured VB, vertebroplasty is performed by injecting calcium phosphate cement (CPC) into the VB. Fourteen patients in whom chronic painful VCFs were diagnosed underwent surgery involving the aforementioned technique. In all cases, intractable pain and ambulatory function improved after surgery, and there were no significant systemic complications. On radiological evaluation in eight cases in which the follow-up period exceeded 1 year, the mean height of the fractured VB improved from 38% of that of adjacent intact VBs to 85%. Although a slight loss of correction was routinely observed at 1 month postoperatively, an additional loss of VB height was not noted up to 1 year later. Bone formation was commonly seen along the anterior wall of the involved vertebrae in all cases. Vertebroplasty involving the endoscopic removal of granulation tissue proved to be an efficacious procedure for the treatment of chronic painful VCFs. The osteoconductive capacity of CPC facilitated callus formation and ultimately restoration of vertebral bone structure.

Aged↗
PubMed2006

[Vertebroplasty for osteoporotic vertebral fracture].

Vertebroplasty for osteoporotic vertebral fracture has been published to enhance fractured vertebra and to reduce severe pain after the fracture. Bone cement such as Polymethylmethacrylate or calcium phosphate cement has been used for this procedure. However, serious neurological complication and pulmonary embolism might occur following the leakage of the cement. In order to avoid these serious complications, it seems to be important to make an enough space in the vertebral body before injecting bone cement. For this purpose, we utilized balloon inflation and endoscopic resection of connective tissue for pseudoarthrosis following osteoporotic vertebral fracture. With this procedure, severe pain after the fracture improved dramatically. So far, we did not have any serious systemic complications.

Bone Cements↗
PubMed2005

Transvaginal ultrasonography of the endometrium in postmenopausal Japanese women.

AIMS: To determine the cut-off level of endometrial thickness for detecting endometrial disease on a large scale of screening and to examine the usefulness of transvaginal ultrasonography (TVS) for endometrial disease screening in asymptomatic postmenopausal Japanese women. METHODS: The study involved 1,400 postmenopausal women in whom endometrial thickness was measured with TVS, and then compared with the histopathological diagnosis of endometrial specimens. RESULTS: The prevalence of endometrial disease in asymptomatic and symptomatic cases was 2.3 and 21%. In symptomatic cases, at a cut-off limit of 3 mm for endometrial thickness, the sensitivity for detecting endometrial disease was 94%, specificity 70% and positive predictive value 46%. With an endometrial thickness < or = 3 mm, the probability that endometrial disease would be overlooked was 0.025. In asymptomatic cases, the corresponding figures at a cut-off limit of 3 mm were 90, 84, 12% and 0.003. CONCLUSIONS: TVS does not appear to be an effective screening method in asymptomatic postmenopausal Japanese women because of the low prevalence of endometrial disease in this population. We recommend a normal cut-off level for endometrial thickness of 4 mm in symptomatic postmenopausal Japanese women.

Adult↗
PubMed2005

Transcytosis of calcium from bone by osteoclast-like cells evidenced by direct visualization of calcium in cells.

'Transcytosis' of calcium (Ca) from bone by osteoclasts was identified by using a newly developed method that uses fixed or living osteoclast-like cells previously differentiated in vitro, a Ca-specific cell-membrane-impermeable fluorescent dye, and confocal laser scanning microscopy. This method, called the cell-membrane-impermeable dye method, revealed that in fixed osteoclast-like cells, a large quantity of Ca was confined within vacuoles and transported toward the apical cell membrane in the cells. These Ca-confined vacuoles were co-localized with marker proteins of both ruffled border and lysosome. The vacuoles were disrupted when treated with an inhibitor of ruffled border ATPase. In living osteoclast-like cells, Ca-confined vacuoles were again preferentially located at the central region and near the apical cell membrane. These results suggest actual transcytosis of Ca from bone by osteoclasts, and are the first direct evidence of the significant role of osteoclasts in the entire process of Ca metabolism in bone.

Adenosine Triphosphatases↗
PubMed2005

Experimental spinal fusion with recombinant human bone morphogenetic protein-2 delivered by a synthetic polymer and beta-tricalcium phosphate in a rabbit model.

STUDY DESIGN: An experimental animal study to achieve posterolateral intertransverse process spine fusion with recombinant bone morphogenetic protein in combination with a new delivery system. OBJECTIVE: To evaluate the efficacy of a new synthetic biodegradable bone-inducing material containing recombinant human bone morphogenetic protein-2 (rhBMP-2) as a bone-graft substitute for posterolateral intertransverse process fusion in a rabbit model. SUMMARY OF BACKGROUND DATA: rhBMP-2, a powerful bone-inducing cytokine, has been used as a bone graft substitute in combination with animal-derived collagen to achieve spinal fusion in animal models. However, the minimum dose of rhBMP-2 required to obtain solid posterolateral intertransverse process fusion was high on the basis of previous reports (>100 microg in rabbit models). To improve the efficacy, performance of rhBMP-2, and the safety of the delivery system for this protein, a more sophisticated system is required. METHODS: To fabricate one implant for one-side L4-L5 intertransverse process fusion, beta-tricalcium phosphate (beta-TCP) powder (300 microg), a polymer gel (PLA-DX-PEG block copolymer; 300 microg) and rhBMP-2 (7.5, 15, or 30 microg) were mixed and manually shaped to resemble a rod. Through a posterolateral approach, two implants were placed on both sides (1 per side) by surgery so as to bridge the transverse processes of adult New Zealand white rabbits (n = 27). In control animals, implants without rhBMP or autogenous cortico-cancellous bone chips from the iliaccrest were placed in a similar location. The lumbar vertebrae were recovered 6 weeks after surgery. The posterolateral fusion was examined by manual palpation, radiography, biomechanical testing, and histology. RESULTS: Rabbits that received 15 or 30 microg of rhBMP-2 showed consistent fusion. However, solid fusion was seen in 2 of 5 rabbits with autografting and rabbits that received 7.5 microg of rhBMP-2. Fusion was not observed in the rabbits that did not receive rhBMP-2. CONCLUSIONS: Consistent spinal fusion was obtained by implanting a biodegradable bone-inducing implant composed of beta-TCP, PLA-DX-PEG, and rhBMP-2 within a period of 6 weeks. The rhBMP-2 doses required for the spinal fusion were significantly lower than those reported previously.

Animals↗
PubMed2005

Objective assessment of reduced invasiveness in MED. Compared with conventional one-level laminotomy.

Microendoscopic discectomy (MED) has been accepted as a minimally invasive procedure for lumbar discectomy because of the small skin incision and short hospital stay required for this surgery. However, there are few objective laboratory data to confirm the reduced systemic responses in the early phase after this procedure. In order to substantiate the reduced invasiveness of MED compared to microdiscectomy (MD) or procedures involved in one-level unilateral laminotomy, the invasiveness of each surgical procedure was evaluated by measuring serum levels of biochemical parameters reflective of a post-operative inflammatory reaction and damage to the paravertebral muscles. Thirty-three patients who underwent lumbar discectomy or one-level unilateral laminotomy (MED in 15 cases, MD in 11 cases and one-level unilateral laminotomy in 7 cases with lumbar spinal canal stenosis) were included in this study. The serum levels of C-reactive protein (CRP) and creatine phosphokinase (CPK) were measured at 24 h after operation. Interleukin-6 (IL-6) and Interleukin-10 (IL-10) were measured at 2, 4, 8 and -24 h following the surgery to monitor the inflammatory response to the respective surgery. The post-operative serum CRP levels from both the MD and MED groups were significantly lower than those from the open laminotomy group. However, there was no significant difference in these serum levels between the MED and MD groups. The levels of IL-6 and IL-10 in the MED group during the first post-operative day were also significantly lower than those in the laminotomy group. When the MED and MD groups were compared, the IL-6 levels in the MED group were lower than in MD group at 2, 4 and 8 h after surgery, but the differences were not statistically significant. However, the level was significantly lower in the MED group at 24 h after surgery. In terms of IL-10, no significant difference was noted between the MED and MD groups over the study period. The changes in serum levels of post-operative inflammatory: markers (CRP, IL-6 and IL-10) in the early phase indicated reduced inflammatory reactions in MED as well as in MD when compared with classical open unilateral laminotomy. These data draw a direct link between the lower level of the inflammatory response and reduced invasiveness of MED. However, an indicator for muscle damage (CPK) appeared not to be affected by the type of surgical procedure used to correct disc herniation.

Adult↗
PubMed2005

Pharmacological and pharmacokinetic study of olmesartan medoxomil in animal diabetic retinopathy models.

A close relationship between the renin-angiotensin system and the pathophysiology of diabetic retinopathy has been suggested, several angiotensin II type 1 receptor (angiotensin AT1 receptor) antagonists being effective in animal models. Therefore, we examined the efficacy of an angiotensin AT1 receptor antagonist, olmesartan medoxomil (CS-866), in animal retinopathy models. In diabetic stroke-prone spontaneously hypertensive (SHRSP) rats, 4-week treatment with CS-866 prevented the elongation of oscillatory potential peaks dose-dependently which almost normalized at 3 mg/kg/day. Next, in oxygen-induced retinopathy mice, CS-866 at 1 mg/kg significantly prevented the retinal neovascularization. In these animal models, plasma concentrations of CS-866 were comparable to the in vitro IC50 value of the angiotensin AT1 receptor. In summary, our data demonstrated that CS-866 was effective in early and late stage retinopathy models through the inhibition of the angiotensin AT1 receptor. These findings suggest the possibility of CS-866 as a therapeutic agent for diabetic retinopathy.

Angiotensin II Type 1 Receptor Blockers↗
PubMed2005

Ultrastructural and immunohistochemical studies of medullary bone calcification, with special reference to sulphated glycosaminoglycans.

Histochemical, immunohistochemical and electron energy-loss spectroscopic studies were performed to examine the relationship between sulphated glycosaminoglycans and medullary bone calcification using oestrogen-injected male Japanese quail. Sulphated glycosaminoglycans, detected by high iron diamine (HID) or HID-thiocarbohydrazide-silver protein (HID-TCH-SP) methods, were distributed throughout the matrix of medullary bone, some periphery and extending tips of the trabeculae stained weakly, and the globular structures at osteoid areas were exclusively positive for HID-TCH-SP stain. Immunohistochemistry identified keratan sulphate located in the globular structures at osteoid areas and calcified matrix, but chondroitin-4 sulphate and chondroitin-6 sulphate were not detected in the matrix. Using electron spectroscopic imaging, sulphur was determined to be localized in the globular structures. These results demonstrate that medullary bone matrix accumulates keratan sulphate in the globular structures, which are the foci for calcification, and eventually in the calcified areas. This suggests that keratan sulphate containing sulphur is maintained in the calcified matrix. These results indicate a unique process of calcification exists in medullary bone.

Animals↗
PubMed2005

Immunolocalization of receptor activator of nuclear factor-kappaB ligand (RANKL) and osteoprotegerin (OPG) in Meckel's cartilage compared with developing endochondral bones in mice.

We examined the immunolocalization of receptor activator of nuclear factor-kappaB ligand (RANKL) and osteoprotegerin (OPG) in areas of resorption caused by osteoclasts/chondroclasts on embryonic days 14-16 (E14-16) in Meckel's cartilage, and compared the results with those in endochondral bones in mice. Intense RANKL and OPG immunoreactivity was detected in the chondrocytes in Meckel's cartilage. On E15, when the incisor teeth were closest to the middle portion of Meckel's cartilage, tartrate-resistant acid phosphatase (TRAP)-positive cells appeared on the lateral side of the cartilage. Furthermore, the dental follicle showed moderate immunoreactivity for RANKL and OPG, whereas osteoblasts derived from perichondral cells were immunonegative for RANKL and OPG in that area. On E16, cartilage resorption by TRAP-positive cells had progressed at the differential position, and intensely immunoreactive products of RANKL were overlapped on and found to exist next to TRAP-positive cells in the resorption area. In developing metatarsal tissue, OPG immunoreactivity was intense in periosteal osteoblasts, whereas RANKL was only faintly seen in some of the periosteal cells. In epiphyseal chondrocytes of the developing femur, RANKL immunoreactivity was moderate, and OPG scarcely detected. These results indicate a peculiarity of RANKL and OPG immunolocalization in resorption of Meckel's cartilage. Growth of the incisor teeth may be involved in the time- and position-specific resorption of Meckel's cartilage through local regulation of the RANKL/OPG system in dental follicular cells and periosteal osteoblasts, whereas RANKL and OPG in chondrocytes seem to contribute to resorption through regulation of the chondroclast function.

Animals↗
PubMed2005

Localization of CD44 (hyaluronan receptor) and hyaluronan in rat mandibular condyle.

CD44 is a multifunctional adhesion molecule that binds to hyaluronan (HA), type I collagen, and fibronectin. We investigated localization of CD44 and HA in mandibular condylar cartilage compared with the growth plate and the articular cartilage, to clarify the characteristics of chondrocytes. We also performed Western blotting using a lysate of mandibular condyle. In mandibular condyle, CD44-positive cells were seen in the surface region of the fibrous cell layer and in the proliferative cell layer. Western blotting revealed that the molecular weight of CD44 in condyle was 78 to 86 kD. Intense reactivity for HA was detected on the surface of the condyle and the lacunae of the hypertrophic cell layer. Moderate labeling was seen in cartilage matrix of the proliferative and maturative layer. Weak labeling was also seen in the fibrous cell layer. In growth plate and articular cartilage, HA was detected in all cell layers. However, chondrocytes of these cartilages did not exhibit reactivity for CD44. These results suggest that chondrocytes in the mandibular condylar cartilage differ in expression of CD44 from those in tibial growth plate and articular cartilage. Cell-matrix interaction between CD44 and HA may play an important role in the proliferation of chondrocytes in the mandibular condyle.

Animals↗