Biomedical subjects

Yasuhiro Takeuchi

Publications and source records attributed to Yasuhiro Takeuchi.

72 records · Page 4Linked to original sources

PubMed2003

[Treatment with vitamin D metabolites for rickets/osteomalacia].

Rickets and osteomalacia is a metabolic bone disease due to a mineralization defect as principal pathophysiology. Since a variety of disorders cause insufficient mineralization of bone, treatment specific to each disorder should be applied to a patient with rickets/osteomalacia. Clinical consensus for medical treatment for rickets/osteomalacia is overviewed in this manuscript. Vitamin D as an anti-rachitic factor and its metabolites play a pivotal role for treatment of patients with rickets/osteomaracia.

English Abstract↗

PubMed2002

Interleukin-11 as a stimulatory factor for bone formation prevents bone loss with advancing age in mice.

Cytokines in interleukin (IL)-11 subfamily participate in the regulation of bone cell proliferation and differentiation. We report here positive effects of IL-11 on osteoblasts and bone formation. Overexpression of human IL-11 gene in transgenic mice resulted in the stimulation of bone formation to increase cortical thickness and strength of long bones, and in the prevention of cortical bone loss with advancing age. Bone resorption and osteoclastogenesis were not affected in IL-11 transgenic mice. In experiments in vitro, IL-11 stimulated transcription of the target gene for bone morphogenetic protein (BMP) via STAT3, leading to osteoblastic differentiation in the presence of BMP-2, but inhibited adipogenesis in bone marrow stromal cells. These results indicate that IL-11 is a stimulatory factor for osteoblastogenesis and bone formation to conserve cortical bone, possibly by enhancing BMP actions in bone. IL-11 may be a new therapeutic target for senile osteoporosis.

Aging↗

PubMed2002

Association between activating mutations of calcium-sensing receptor and Bartter's syndrome.

Bartter's syndrome is a heterogeneous disorder characterised by deficient renal reabsorption of sodium and chloride, and hypokalaemic metabolic alkalosis with hyper-reninaemia and hyperaldosteronaemia. Mutations in several ion transporters and channels have been associated with the pathogenesis of Bartter's syndrome. We describe two hypocalcaemic patients with deficient parathyroid hormone secretion who also showed characteristics of Bartter's syndrome. We found activating mutations of the gene for the calcium-sensing receptor (CASR) in both patients. Activation of this calcium-sensing receptor inhibits the activity of a renal outer-medullary potassium channel that is mutated in type 2 Bartter's syndrome. We therefore suggest that some activating mutations of CASR could provide new mechanisms for the development of Bartter's syndrome.

Adult↗

PubMed2002

Restriction of lentivirus in monkeys.

Retroviruses are able to cross species barriers and have done so many times throughout evolution. Perhaps as a consequence, dominant mechanisms have arisen to block infection by murine retroviruses in mice (restriction factor Fv1) and humans (restriction factor Ref1), as well as in other mammals. Here we describe a block to HIV and simian immunodeficiency virus in monkeys. Like previously described restrictions the block is saturable and gives rise to multiple-hit infection kinetics. Furthermore, like restriction of murine leukemia virus in humans, the block is before reverse transcription. Intriguingly, African green monkey cells are able to block both HIV and simian immunodeficiency virus, and each virus is able to saturate and abrogate the restriction of the other, suggesting that a common factor is responsible.

Animals↗

PubMed2002

Biochemical changes in the central nervous system of rats exposed to 1-bromopropane for seven days.

1-Bromopropane is used widely as an alternative to ozone-depleting solvents. The neurotoxic effects of this agent have been described in humans and experimental animals. Here we investigated the underlying mechanisms of the neurotoxic effects of 1-bromopropane by examining the initial biochemical changes in the central nervous system. Four groups of 9 Wistar male rats each were exposed to 200, 400, or 800 ppm 1-bromopropane or only fresh air, 8 h per day for 7 days. At the end of the experiment, the cerebrum, cerebellum, brain stem and lumbar enlargement of the spinal cord were dissected out from each rat (n = 8) for biochemical analyses. Morphological examinations of the nervous system were performed in the remaining rat of each group. 1-Bromopropane dose-dependently decreased neurospecific gamma-enolase, total glutathione, and nonprotein sulfhydryl groups in the cerebrum and cerebellum. Creatine kinase activity decreased dose-dependently in the brain and spinal cord. Histopathological examination showed swelling of preterminal axons in gracile nucleus and degeneration of myelin in peripheral nerves. Our results of low levels of gamma-enolase suggested that 1-bromopropane might primarily cause functional or cellular loss of neurons in the cerebrum and cerebellum. Glutathione depletion or modification to functional proteins containing a sulfhydryl base as a critical site might be the underlying mechanism of 1-bromopropane neurotoxicity.

Animals↗

PubMed2002

PCR-based cloning and immunocytological titration of infectious porcine endogenous retrovirus subgroup A and B.

Two pig endogenous retroviruses (PERV), PERV-A and -B, productively infect human cells and are therefore considered to constitute a potential risk in pig-to-human xenotransplantation. A PCR-based cloning technique to isolate infectious PERV proviruses was established. Overlapping 3' half and 5' halves of PERV proviral genomes were amplified using DNA extracted from human 293 cells infected with PERV-A or -B. These clones were fused at a unique restriction site in the overlapping region and tested for their infectivity. Representative constructs possessed the same infectious properties as their parent isolates. We also developed a polyclonal anti-PERV serum by using recombinant PERV capsid protein derived from one of the infectious constructs as immunogen and established an immunocytological method for detection and titration of PERV infection. This detection method proved to be more sensitive than the current method of choice (transfer of MLV-lacZ vectors) for infectivity assessment of PERV. These findings should be considered for future characterization of PERV isolates.

Animals↗

PubMed2002

Heparin binds to murine leukemia virus and inhibits Env-independent attachment and infection.

Certain glycosaminoglycans (GAGs), including heparin, inhibit infection by murine leukemia virus (MLV). We now show that this is due to inhibition of virus attachment independent of the interaction between viral envelope proteins (Env) and their cellular receptors. Heparin blocked the binding of both Env-deficient and amphotropic MLV (MLV-A) particles to NIH 3T3 fibroblasts, CHO cells which lack the amphotropic retroviral receptor Pit-2, and CHO cells transfected with Pit-2 (CHO-Pit-2). Heparin also inhibited the transduction of NIH 3T3 cells by MLV-A over a similar concentration range. This effect was observed within 15 min of exposure to retrovirus. Preloading target cells with heparin had no effect on transduction and both MLV-A and Env-deficient retrovirus bound efficiently to heparin-coated agarose beads, suggesting that heparin interacts with the virus rather than the target cell. This requires both a strong negative charge and a specific structure since GAGs with different charge and carbohydrate composition inhibited virus infection variably. The specificity of GAG-virus interaction also depends on the producer cells, since virus packaged by murine GP+EnvAM12 cells was 1,000-fold more sensitive to inhibition by chondroitin sulfate A than was virus packaged by human FLYA13 packaging cells. No evidence for an interaction between MLV and cell surface proteoglycans was found, however, since the attachment of MLV-A and envelope-defective virus to proteoglycan-deficient CHOpgsA-745 cells was similar to that seen with both wild-type and CHO-Pit-2 cells. Although the molecular mechanism is unclear, this study presents evidence that Env receptor-independent attachment is an important step in MLV infection.

3T3 Cells↗

PubMed2002

Abrogation of Ref1 retrovirus restriction in human cells.

We have previously described postentry restriction of murine leukemia virus in mammals. Here we characterize the block in human cells. Restricted infection kinetics are multiple hit at high virus dose, and restriction is abrogated by preexposure to restricted virus. We hypothesize that restricted capsid can titrate out the restriction factor.

Animals↗

PubMed2002

Mutant FGF-23 responsible for autosomal dominant hypophosphatemic rickets is resistant to proteolytic cleavage and causes hypophosphatemia in vivo.

FGF-23 is involved in the pathogenesis of two similar hypophosphatemic diseases, autosomal dominant hypophosphatemic rickets/osteomalacia (ADHR) and tumor-induced osteomalacia (TIO). We have shown that the overproduction of FGF-23 by tumors causes TIO. In contrast, ADHR derives from missense mutations in FGF-23 gene. However, it has been unclear how those mutations affect phosphate metabolism. Therefore, we produced mutant as well as wild-type FGF-23 proteins and examined their biological activity. Western blot analysis using site-specific antibodies showed that wild-type FGF-23 secreted into conditioned media was partially cleaved between Arg(179) and Ser(180). In addition, further processing of the cleaved N-terminal portion was observed. In constrast, mutant FGF-23 proteins found in ADHR were resistant to the cleavage. In order to clarify which molecule has the biological activity to induce hypophosphatemia, we separated full-length protein, the N-terminal and C-terminal fragments of wild-type FGF-23. When the activity of each fraction was examined in vivo, only the full-length FGF-23 decreased serum phosphate. Mutant FGF-23 protein that was resistant to the cleavage also retained the activity to induce hypophosphatemia. The extent of hypophosphatemia induced by the single administration of either wild-type or the mutant full-length FGF-23 protein was similar. In addition, implantation of CHO cells expressing the mutant FGF-23 protein caused hypophosphatemia and the decrease of bone mineral content. We conclude that ADHR is caused by hypophosphatemic action of mutant full-length FGF-23 proteins that are resistant to the cleavage between Arg(179) and Ser(180).

Amino Acid Sequence↗

PubMed2002

Increased circulatory level of biologically active full-length FGF-23 in patients with hypophosphatemic rickets/osteomalacia.

Hypophosphatemic rickets/osteomalacia with inappropriately low serum 1,25-dihidroxyvitamin D level is commonly observed in X-linked hypophosphatemic rickets/osteomalacia, autosomal dominant hypophosphatemic rickets/osteomalacia and tumor-induced osteomalacia. Although the involvement of a newly identified factor, FGF-23, in the pathogenesis of ADHR and TIO has been suggested, clinical evidence indicating the role of FGF-23 has been lacking. We have previously shown that FGF-23 is cleaved between Arg(179) and Ser(180), and this processing abolished biological activity of FGF-23 to induce hypophosphatemia. Therefore, sandwich ELISA for biologically active intact human FGF-23 was developed using two kinds of monoclonal antibodies that requires the simultaneous presence of both the N-terminal and C-terminal portion of FGF-23. The serum levels of FGF-23 in healthy adults were measurable and ranged from 8.2 to 54.3 ng/L. In contrast, those in a patient with TIO were over 200 ng/L. After the resection of the responsible tumor, the elevated FGF-23 level returned to normal level within 1 h. The increase of serum concentrations of 1,25-dihidroxyvitamin D and phosphate, and the decrease of serum 24,25-dihydroxyvitamin D followed the change of FGF-23. In addition, the elevated serum FGF-23 levels were demonstrated in most patients with XLH. It is likely that increased serum levels of FGF-23 contributes to the development of hypophosphatemia not only in TIO but also in XLH.

Adult↗

PubMed2002

Stimulation of Smad1 transcriptional activity by Ras-extracellular signal-regulated kinase pathway: a possible mechanism for collagen-dependent osteoblastic differentiation.

Signals from bone morphogenetic protein receptors (BMPRs) and cell adhesion to type I collagen are both important for osteoblastic differentiation and functions. BMP signals are mediated mostly by Smad and collagen signals are transduced by integrins to activate focal adhesion kinase (FAK) and its downstream molecules. This study was undertaken to clarify how extracellular matrix collagen signals converge with BMP actions. We show that integrin activation by collagen was involved in BMP signals because disruption of either collagen synthesis or collagen-alpha2beta1-integrin binding inhibited the stimulatory effect of BMP-2 on osteoblastic MC3T3-E1 cells. Downstream signals of collagen-integrin might be FAK-Ras-extracellular signal-regulated kinase (ERK) in osteoblastic cells. We further show that Ras-ERK signals enhanced the transcriptional activity of Smad1 in response to BMP in these cells transiently transfected with expression plasmids for a constitutively active mutant RasV12, a dominant negative mutant RasN17, and an ERK phosphatase CL100. Ras-ERK signals did not augment the transcriptional activity of Smad3 in response to transforming growth factor beta (TGF-beta) receptor activation but that of Smad1 in response to BMPR activation as examined in COS-1 cells. These observations suggest that the Ras-ERK pathway downstream of integrin-FAK is involved in Smad1 signals activated by BMP and provide a possible mechanism for cooperation between intracellular signals activated by integrin and BMPRs in osteoblastic cells.

Activin Receptors, Type I↗

PubMed2002

Parathyroid hormone-related protein induced coupled increases in bone formation and resorption markers for 7 years in a patient with malignant islet cell tumors.

Parathyroid hormone-related protein (PTHrP) and PTH share the common PTH/PTHrP receptor. Although an elevated level of circulating PTHrP in patients with malignancies causes hypercalcemia as does PTH, chronic and systemic effects of PTHrP on bone metabolism in humans are not well understood because tumor-burden patients showing hypercalcemia usually have a poor prognosis. We investigated bone and calcium metabolism in a patient with malignant islet cell tumors showing hypercalcemia due to the elevated plasma PTHrP level for 7 years. Hypercalcemia and hypercalciuria continued throughout the clinical course in spite of frequent infusions of bisphosphonates. Bone resorption markers and a bone formation marker were consistently elevated as seen in primary hyperparathyroidism, a disease caused by an autonomous hypersecretion of PTH. Based on biochemical measurements including bone markers and serum 1,25-dihydroxyvitamin D, the clinical features of this case essentially are the same as those of primary hyperparathyroidism except for the elevated level of plasma PTHrP with suppressed intact PTH level. Therefore, it is suggested that chronic and systemic effects of PTHrP on bone as well as calcium metabolism are indistinguishable from those of PTH in human.

Adult↗

PubMed2002

Clonal endothelial cells produce humoral factors that inhibit osteoclast-like cell formation in vitro.

Angiogenesis and bone remodeling are closely associated, and vascular endothelial cells may have potential roles for osteoclastic bone resorption. We examined whether clonal endothelial cells established from bone, aorta and brain of Balb/c mice influenced osteoclast-like cell formation in vitro. As low as 1% conditioned media of those endothelial cells inhibited osteoclast-like cell formation in bone marrow cultures induced by 1,25-dihydroxyvitamin D3, and did so in spleen cell cultures in the presence of soluble receptor activator of nuclear factor-kappaB ligand (RANKL), M-CSF and prostaglandin E2. The level of osteoprotegerin (OPG), a decoy receptor for RANKL, secreted by endothelial cells was not high enough to inhibit osteoclastogenesis. These observations suggest that endothelial cells derived from various tissues secrete factor(s) that inhibits precursors to differentiate into osteoclasts even in the presence of optimal stimulators for osteoclastogenesis. Hence, endothelial cells in bone may inhibit recruitment of fresh osteoclasts, and those in tissues other than bone may be involved in prohibiting ectopic osteoclastogenesis.

Animals↗

PubMed2002

[Stevens-Johnson syndrome accompanied by acute hepatitis in workers exposed to trichloroethylene or tetrachloroethylene].

Since the late 1980s, there has been an increasing tendency in the number of case reports on Stevens-Johnson syndrome accompanied by acute hepatitis in workers exposed to trichloroethylene from Asian countries. Recently, mass outbreaks of it have been disclosed in the Philippines and China. Besides trichloroethylene, although the number is small, a similar health disorder has also occurred in workers using tetrachloroethylene. Since the above-mentioned facts are not yet well recognized in the occupational health community, this review is aimed at making clear (1) the clinical features of the health disorder, (2) details of patients' jobs, working environments, and exposure to hazardous chemicals, and (3) the relationship between exposure to trichloroethylene or tetrachloroethylene and the health disorder. Based on a critical review of articles, the following were pointed out. First, it is important to carefully observe the health status of workers exposed to trichloroethylene or tetrachloroethylene and to take countermeasures to reduce exposure. Secondly, circumstantial evidence suggests a cause-effect relationship between the two chemicals and the health disorder; but at the present time it is impossible to rule out the participation of unelucidated factors promoting the occurrence of the health disorder or the existence of a hidden genuine causative substance. Therefore further investigation to trace such a case is needed. Thirdly, the mechanism of the health disorder and the reason why there seems to be a large inter-individual difference in sensitivity to the causative agent should be clarified.

Acute Disease↗

PubMed2002

Involvement of caspase 3 mediated apoptosis in hematopoietic cytotoxicity of metabolites of ethylene glycol monomethyl ether.

The hematopoietic toxicity of ethylene glycol monomethyl ether (EGME) and its metabolites, methoxy acetaldehyde (MALD) and methoxyacetic acid (MAA), was analyzed using human bone marrow cells from a lymphoma patient without bone marrow involvement and a human leukemia cell line, HL60. After 24-hour incubation, the concentrations of 50 percent inhibition (IC50) of human hematopoietic progenitor cells with MALD or MAA were 3 mM and 3.9 mM, respectively, and EGME (10 mM or more) did not show any cytotoxicity. IC50 (after 48-hour exposure) of MALD and MAA on HL60 cells were 2.45 mM and 5.6 mM, respectively, suggesting that both hematopoietic progenitor cells and HL60 have a similar sensitivity. DNA ladder formation, a characteristics of apoptosis, was observed in MALD- or MAA-treated HL60 cells, but not in EGME-treated samples. Caspase-3 enzyme activity, the effector of the apoptotic process, was greatly enhanced with MALD treatment. The inhibitor of caspase-3 repressed cell death induced with MALD as well as MAA.

Acetaldehyde↗

PubMed2002

[Cell adhesion molecule in osteobrast biology].

Investigation of integrins among cell adhesion molecules has revealed that bone matrix proteins including type I collagen play a pivotal role in the regulation of osteoblastic differentiation via their binding to integrins on osteoblasts. It is now suggested that cell-matrix interactions are critically involved in bone formation by osteoblasts. Cell-cell interactions among osteoblasts and hematopoietic cells are also mediated by cell adhesion molecules including integrins. Recently, it is reported that adhesion of osteoclast precursors to osteoblasts via cell adhesion molecules supports the formation of bone resorbing osteoclasts. These observations indicate that cell adhesion molecules on osteoblasts are functionally involved in bone metabolism.

English Abstract↗

PubMedDate not supplied

Xenotransplantation and pig endogenous retroviruses.

Xenotransplantation, in particular transplantation of pig cells, tissues and organs into human patients, may alleviate the current shortage of suitable allografts available for human transplantation. This overview addresses the physiological, immunological and virological factors considered with regard to xenotransplantation. Among the issues reviewed are the merits of using pigs as xenograft source species, the compatibility of pig and human organ physiology and the immunological hindrances with regard to the various types of rejection and attempts at abrogating rejection. Advances in the prevention of pig organ rejection by creating genetically modified pigs that are more suited to the human microenvironment are also discussed. Finally, with regard to virology, possible zoonotic infections emanating from pigs are reviewed, with special emphasis on the pig endogenous retrovirus (PERV). An in depth account of PERV studies, comprising their discovery as well as recent knowledge of the virus, is given. To date, all retrospective studies on patients with pig xenografts have shown no evidence of PERV transmission, however, many factors make us interpret these results with caution. Although the lack of PERV infection in xenograft recipients up to now is encouraging, more basic research and controlled animal studies that mimic the pig to human xenotransplantation setting more closely are required for safety assessment.

Animals↗

PubMedDate not supplied

Asbestos exposures during reprocessing of automobile brakes and clutches.

Asbestos exposures of workers in three small factories reprocessing automobile brakes and clutches in Japan were investigated. Airborne asbestos was collected on a membrane filter using an air sampler. From 1982 to 1989, asbestos counting was performed on 295 samples (198 personal and 97 stationary), using phase contrast microscopy. Only chrysotile asbestos was detected. Workers who reprocessed automobile brakes and clutches were exposed to asbestos concentrations of 0.025-76.4 fibers/cm3. Geometric mean asbestos concentrations during attaching linings to brake shoes and attaching facings to clutch disks were 0.859 fibers/cm3 and 0.780 fibers/cm3, respectively. Concentrations during stripping worn brake linings and clutch facings were 0.484 fibers/cm3 and 0.382 fibers/cm3, respectively. Machine grinding and leveling of new brake-lining surfaces represent potential sources of heavy asbestos exposures, unless enclosures and local ventilation are efficient.

Asbestos, Serpentine↗