Biomedical subjects

Toshihiko Yajima

Publications and source records attributed to Toshihiko Yajima.

15 recordsLinked to original sources

PubMed2006

Operating behind Denonvilliers' fascia for reliable preservation of urogenital autonomic nerves in total mesorectal excision: a histologic study using cadaveric specimens, including a surgical experiment using fresh cadaveric models.

PURPOSE: Little is known about which urogenital nerves are liable to be injured along surgical planes in front of or behind Denonvilliers' fascia. METHODS AND RESULTS: Using semiserial histology for five fixed male pelves, we demonstrated that: 1) left/right communicating branches of bilateral pelvic plexuses run immediately in front of Denonvilliers' fascia; and 2) a lateral continuation of Denonvilliers' fascia separates the urogenital neurovascular bundle from the mesorectum. Notably, the mesorectum contains no or few extramural ganglion cells. At the level of the seminal vesicles, incision in front of Denonvilliers' fascia seems likely to injure superior parts of the pelvic plexus and the left/right communication. Moreover, at the prostate level, this incision misleads the surgical plane into the neurovascular bundle. Fresh cadaveric dissections of five unfixed male pelves confirmed that the surgical plane in front of Denonvilliers' fascia continues to a fascial space for the pelvic plexus containing ganglion cell clusters lateral and/or inferior to the seminal vesicles. CONCLUSIONS: To preserve all autonomic nerves for urogenital function, optimal total mesorectal excision for rectal cancer requires dissection behind Denonvilliers' fascia.

Aged↗

PubMed2005

Impaired alveolization in mice deficient in membrane-type matrix metalloproteinase 1 (MT1-MMP).

To clarify the involvement of membrane-type matrix metalloproteinase 1 (MT1-MMP) in lung organogenesis, we studied the lung morphology of 13-day-old MT1-MMP null mice. The lung architecture in MT1-MMP null mice was abnormal, and the airspace compartments were characterized by smooth walls and larger size. Most of the compartment wall consisted of one or two layers of cells and interstitial connective tissue that was thicker than that of normal alveoli. The wall frequently had capillaries on both sides of the interstitial connective tissue. These findings indicate that the lung in MT1-MMP null mice at 13 days of age is comparable to that of neonatal mice, i.e., it represents the stage before alveolization, suggesting that the generation of a large respiratory surface - the final process of lung development - is impaired in MT1-MMP null mice. Moreover, a zymography assay revealed decreased activity of matrix metalloproteinase 2 (MMP-2) in MT1-MMP null mice, suggesting that activation of pro-MMP-2 by MT1-MMP is critical in this process.

Animals↗

PubMed2005

Microfibril-associated glycoprotein-1 and fibrillin-2 are associated with tropoelastin deposition in vitro.

Elastic system fibers consist of microfibrils and tropoelastin. During development, microfibrils act as a template on which tropoelastin is deposited. Microfibril-associated glycoprotein-1 (MAGP-1) and fibrillin-2, the major components of microfibrils, provide the likely template for tropoelastin deposition. In this study, we used the RNA interference (RNAi) technique to establish MAGP-1 and fibrillin-2 gene-specific knock-downs individually in elastin-producing cells (human gingival fibroblasts). We then examined the extracellular deposition of tropoelastin by western blotting. These two genes were specifically suppressed to < 30% of the control level, and this was responsible for the diminution of tropoelastin deposition. An immunofluorescence study also confirmed that RNAi-mediated down-regulation of MAGP-1 or fibrillin-2 led to the loss of tropoelastin immunoreactivity. These results suggest that MAGP-1 and fibrillin-2 are, directly or indirectly, associated with the extracellular deposition of tropoelastin during elastic fiber formation in human gingival fibroblasts in vitro.

Cells, Cultured↗

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

Radiation-induced apoptosis is independent of caspase-8 but dependent on cytochrome c and the caspase-9 cascade in human leukemia HL60 cells.

We investigated the role of the caspase activation cascade in apoptosis induced by ionizing radiation or hydrogen peroxide (H(2)O(2)) in human leukemia HL60 cells. Electron paramagnetic resonance (EPR) spectra revealed that hydroxyl and hydrogen radicals were generated in the culture medium after exposure to radiation or H(2)O(2). Initial accumulation of DNA fragments at 2 h after exposure was delayed in irradiated cells compared with H(2)O(2)-treated cells, although formation of abasic sites immediately after exposure was significantly higher in irradiated cells and similar quantities of hydroxyl radicals were produced under both conditions. Activity assay of caspases revealed that caspase-3, -8 and -9 were activated 2 h after exposure to H(2)O(2), whereas in irradiated cells caspase-3 and -9 activation occurred 4 h after exposure but increased caspase-8 activation was not observed. Release of cytochrome c into cytosol was seen at 2 h after radiation and H(2)O(2) treatment. Radiation did not affect proapoptotic proteins (Bax and Bid), whereas H (2)O(2) increased accumulation of Bax in the mitochondrial membrane 2 h to 6 h after treatment, independently of the truncation of Bid by activated caspase-8. Moreover, treatment with the caspase-8 inhibitor Z-IETD-FMK increased cell survival and prevented accumulation of DNA fragments in H(2)O(2)-treated cells, but not in irradiated cells. These results suggest that, unlike the caspase cascade of H(2)O(2)-induced apoptosis, cytochrome c and caspase-9 are important for the intrinsic pathway of radiation-induced apoptosis, independent of caspase-8.

Apoptosis↗

PubMed2004

Induction of fibulin-5 gene is regulated by tropoelastin gene, and correlated with tropoelastin accumulation in vitro.

Fibulin-5 (also known as DANCE) is an elastin-binding protein that is thought to play a role in elastogenesis. We examined the relationship between the gene expression of fibulin-5 and the gene expression and accumulation of tropoelastin by comparing elastin-producing cells (human gingival fibroblasts) with non-elastin-producing cells (human periodontal ligament fibroblasts) by Northern blot analysis. Fibulin-5 gene induction was found only in elastin-producing cells. Induction of the fibulin-5 gene in elastin-producing cells occurred after induction of the tropoelastin gene, and the fibulin-5 level was reduced upon RNA interference-mediated down-regulation of tropoelastin. Fibulin-5 gene induction was also correlated with a rapid increase of tropoelastin accumulation within the cell layer. These results may suggest that the fibulin-5 gene induction is directly or indirectly regulated by tropoelastin gene expression and plays a role in the accumulation of elastic fibers within matrices.

Blotting, Northern↗

PubMed2003

Afferent and efferent lymph-collecting vessels of the submandibular nodes with special reference to the lymphatic route passing through the mylohyoid muscle.

BACKGROUND: Although metastasis of cancer in the oral region to the submandibular node is well described, there has been no anatomic representation of lymph vessels penetrating the oral floor and draining into the node. MATERIALS AND METHODS: Ninety specimens were obtained from formalin-fixed, donated cadavers. Histologic observations using serial sections followed the macroscopic observations. RESULTS: In 19 of 90 specimens, we found afferent collecting lymph vessels exiting from the mylohyoid surface and draining into the preglandular submandibular node. In 3 of the 19 specimens, collecting vessels passing through the narrow muscle gap with or without arteries, veins, and nerves were identified histologically. The postglandular submandibular node was not evident in the drainage route. CONCLUSIONS: Although it carries a low incidence, because of the direct lymphatic route or pathway between the oral region and preglandular submandibular node, the pathologically positive supraomohyoid node sometimes seems to be found even in elective neck dissection. However, we speculate that sentinel node investigation would reveal the much more critical role of the jugulodigastric node not only as the actual sentinel node but also as the common terminal node along the various drainage routes from the oral region.

Aged↗

PubMed2003

Osteoclast differentiation in ectopic bone formation induced by recombinant human bone morphogenetic protein 2 (rhBMP-2).

Osteoclast differentiation in the process of ectopic bone formation induced by recombinant human bone morphogenetic protein 2 (rhBMP-2) was examined to clarify the relationship between osteoclast development and rhBMP-2-induced bone formation. A combination of rhBMP-2 with a porous microsphere (PMS) and blood clot was implanted subcutaneously on the bilateral chest muscles of rats. Tartrate-resistant acid phosphatase (TRAPase) activity, cathepsin K (cath K), and calcitonin receptor (CTR), as markers of osteoclasts and their precursors, were examined using enzyme and immunohistochemical analysis up to 7 days after implantation. Mononuclear cells positive for TRAPase, cath K, and CTR first appeared on day 3 in connective tissue surrounding the PMS after implantation of rhBMP-2. Simultaneously, alkaline phosphatase activity became detectable in mesenchymal cells in the connective tissue. Electron microscopy demonstrated some mononuclear cells with abundant mitochondria and poorly developed rough endoplasmic reticulum in the proximity of mesenchymal cells. However, there was no evidence of cartilage or bone matrix formation on day 3. Osteoclasts in various stages of development, classified by the pattern of immunoreactivity for cath K, were observed by day 7. The polarized intracellular distribution of cath K was found only in osteoclasts attached to bone matrix. In conclusion, we have demonstrated for the first time the appearance of osteoclast precursors before bone matrix formation induced by rhBMP-2, suggesting that bone matrix is not a prerequisite for osteoclast precursor recruitment. Furthermore, we suggest that differentiation into polarized functional osteoclasts is accomplished when the osteoclasts attach to the bone matrix.

Animals↗

PubMed2003

Ultrastructural study of synovitis induced by trauma to the rat temporomandibular joint (TMJ).

BACKGROUND: Electron microscopy was used to examine the histologic effect of trauma on the rat temporomandibular joint synovial membrane. METHODS: Trauma to the TMJ in male Wister rats (100-200 g) was introduced through repeated forced condylar hypermobility. Ultrastructural observations were made 5 days and 6 weeks after the trauma. RESULTS: The early response of the synovial membrane was synovial hyperplasia, type A synovial cell loss, dilation of the r-ER in the type B synovial cells and fibrin deposition on the synovial surfaces. The late response included degeneration of synovial cells with swollen mitochondria and cell projections, and cell fragmentation. Large amount of fibrin deposition on opposing surface layers was also noticed. CONCLUSION: The type A cell loss and fibrin deposition followed by the occurrence of fibrinous materials at opposing surface layers of the synovial membrane suggest that traumatic synovitis causes synovial adhesions.

Animals↗

PubMed2003

Expression of bHLH transcription factors NSCL1 and NSCL2 in the mouse olfactory system.

We examined the expression of basic helix-loop-helix transcription factors NSCL1 and NSCL2 in the olfactory epithelium (OE) and the vomeronasal organ (VNO) during development. As detected by in situ hybridization, at embryonic day (E) 10 NSCL1 was weakly expressed in the entire olfactory placodes. From E12 to postnatal day (P) 3, NSCL1 was expressed in olfactory receptor neurons (ORNs) and receptor neurons of the VNO. The expression pattern of NSCL2 was similar to that of NSCL1. By Northern blot analysis, strong expression of NSCL1 was detected in the OE from E12 to P7, but the expression there was low in the adult (P35). NSCL2 mRNA was detected in the E12 and P1 OE, but its level was very low in the P7 and adult OE. The spatial pattern of expression suggests that NSCL1 and NSCL2 contribute to the maturation of ORNs (VNO receptor neurons) or maintenance of their differentiated state. Moreover, the temporal pattern of expression suggests that NSCL1 and NSCL2 may function during development rather than in the adult stage.

Animals↗

PubMed2003

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Journal Article↗

PubMed2002

Calcitonin gene-related peptide (CGRP)-containing nerve fibers in bone tissue and their involvement in bone remodeling.

Bone remodeling is a process of bone renewal accomplished by osteoclastic bone resorption and osteoblastic bone formation. These two activities are regulated by systemic hormones and by local cytokines and growth factors. Moreover, the nervous system and certain neuropeptides seem to be involved in regulation of bone remodeling. In this paper, we focus on the distribution of CGRP-containing nerve fibers and their dynamics, and discuss the role of these fibers as a possible mechanism for nervous system involvement in regulation of bone remodeling. CGRP-immunoreactive nerve fibers are widely distributed in bone tissue, such as periosteum and bone marrow, and show apparent regional distribution with different densities. They are often associated with blood vessels and show a beaded appearance. The wide distribution of CGRP-immunoreactive nerve fibers in bone tissue and the changes in distribution during bone development and regeneration suggest the involvement of these fibers in bone remodeling. The effect of CGRP on bone remodeling could partly be through its action on blood vessels, thereby regulating local blood flow. Moreover, in vitro biochemical data and the localization of CGRP-immunoreactive nerve fibers in the vicinity of bone cells suggest that they are directly involved in local regulation of bone remodeling by elevating the concentration of CGRP in the microenvironment around bone cells, especially during bone growth or repair.

Animals↗

PubMed2002

Evidence that zymogen granules do not function as an intracellular Ca2+ store for the generation of the Ca2+ signal in rat parotid acinar cells.

Rat parotid acinar cells lacking zymogen granules were obtained by inducing granule discharge with the beta-adrenoceptor agonist isoproterenol. To assess whether zymogen granules are involved in the regulation of Ca(2+) signalling as intracellular Ca(2+) stores, changes in cytosolic free Ca(2+) ion concentration ([Ca(2+)](i)) were studied with imaging microscopy in fura-2-loaded parotid acinar cells lacking zymogen granules. The increase in [Ca(2+)](i) induced by muscarinic receptor stimulation was initiated at the apical pole of the acinar cells, and rapidly spread as a Ca(2+) wave towards the basolateral region. The magnitude of the [Ca(2+)](i) response and the speed of the Ca(2+) wave were essentially similar to those in control acinar cells containing zymogen granules. Western blot analysis of the inositol 1,4,5-trisphosphate receptor (IP(3)R) was performed on zymogen granule membranes and microsomes using anti-IP(3)R antibodies. The immunoreactivity of all three IP(3)Rs was clearly observed in the microsomal preparations. Although a weak band of IP(3)R type-2 was detected in the zymogen granule membranes, this band probably resulted from contamination by the endoplasmic reticulum (ER), because calnexin, a marker protein of the ER, was also detected in the same preparation. Furthermore, Western blotting and reverse transcriptase-PCR analysis failed to provide evidence for the expression of ryanodine receptors in rat parotid acinar cells, whereas expression was clearly detectable in rat skeletal muscle, heart and brain. These results suggest that zymogen granules do not have a critical role in Ca(2+) signalling in rat parotid acinar cells.

Animals↗

PubMed2002

Expression of fibrillins and tropoelastin by human gingival and periodontal ligament fibroblasts in vitro.

The elastic system fibers consist of three different types, oxytalan, elaunin and elastic fibers, which differ in the relative content of microfibrils and elastin. In periodontal tissues, oxytalan fibers are known to be distributed in the periodontal ligament and gingiva, while elaunin and elastic fibers are present only in the gingiva. We examined the in vitro synthesis of microfibrils and elastin by human gingival fibroblasts (HGF) and periodontal ligament fibroblasts (HPLF). The two kinds of HGF and HPLF were cultured in MEM containing 10% newborn calf serum for 30 days. Since fibrillin-1 and fibrillin-2 are the major components of microfibrils involved in elastogenesis, we investigated the synthesis of fibrillins and tropoelastin in the conditioned medium of HGF and HPLF. Western blot analysis revealed fibrillin-1 and fibrillin-2 to occur in the HGF and HPLF culture medium, HGF exhibiting a higher level of synthesis than HPLF. Tropoelastin, on the other hand, was detected only in the medium of HGF after day 24. In addition, analysis of RNA extracted from HGF and HPLF on day 30 showed that only HGF expressed mRNA encoding tropoelastin. Immunohistochemically, accumulation of tropoelastin in the perinuclear area was found only in HGF. These results show that HGF expressed microfibrils and elastin, while HPLF expressed only microfibrils for the experimental period, and suggest a biochemical basis for the different distribution of elastic system fibers of the gingiva and periodontal ligament in vivo.

Blotting, Northern↗

PubMed2002

Apoptosis induced by generated OH radicals inside cells after irradiation.

OH radicals play a major role in radiation-induced DNA and cell membrane damage. These types of damage can also induce death by apoptosis through activation of a pro-apoptosis pathway. We attempted to detect OH radicals inside human promyelocytic leukemia (HL60) cells and estimate the relationship between radiation-induced apoptosis and OH radicals generated inside the cells. Electron spin resonance spectroscopy showed that OH radicals were generated by X-rays within irradiated cell pellets and the relative signal intensities of OH radicals increased with the radiation dose. Agarose gel electrophoresis revealed that the death of HL60 cells by apoptosis was accompanied by internucleosomal DNA fragmentation at 2 h after irradiation with 10-30 Gy. On ultrastructure evaluation by transmission electron microscopy, certain irradiated HL60 cells demonstrated condensed chromatin forms at the nuclear membrane and nuclear fragmentation. The frequency of apoptotic cells with condensation and fragmentation of nuclear chromatin increased with radiation dose in semithin sections. The increase of quantitative DNA fragmentation and percentage of non-living cells also correlated with radiation dose. These results suggest that OH radicals are generated inside cells before apoptosis occurs. The amount of OH radicals generated correlates with apoptotic cell death.

Apoptosis↗