Biomedical subjects

Megumi Nakamura

Publications and source records attributed to Megumi Nakamura.

6 recordsLinked to original sources

PubMed2005

Expression of versican and ADAMTS1, 4, and 5 during bone development in the rat mandible and hind limb.

Extracellular matrix (ECM) remodeling is achieved by both production and degradation of ECM molecules during bone development. ADAMTS (a disintegrin and metalloprotease with thrombospondin type 1 motifs) constitutes a family of extracellular proteases which are implicated in cleaving the protein versican. The present study was designed to investigate the expression of versican and ADAMTS1, 4, and 5 mRNA during bone development in rat mandibles and hind limbs by RT-PCR and in situ hybridization. Versican was localized by immunohistochemistry. The process of bone development from day 14 postcoitum through week 6 postnatum was divided into the beginning of osteogenesis, woven bone, and lamellar bone stages. Versican protein was abundant in the woven bone matrix, but decreased in the lamellar bone matrix. Versican mRNA was prominent in some osteoblasts with corresponding localization of the cognate protein. The temporal and spatial mRNA expression pattern of ADAMTS1, 4, and 5 was comparable to that of versican. These results suggest that woven bone rich in versican alters into lamellar bone containing little versican during bone development in both mandibles and hind limbs, where some osteoblasts may be involved in production as well as degradation of versican by secreting ADAMTS1, 4, and 5.

ADAM Proteins↗

PubMed2005

Expression of caveolin-1 and its correlation with cisplatin sensitivity in oral squamous cell carcinoma.

PURPOSE: Cisplatin (CDDP) is widely used for chemotherapy of oral squamous cell carcinoma (OSCC). However, the mechanism of resistance to CDDP is unclear. Recently, caveolin-1 was identified as being associated with both metastasis and multidrug resistance. In the present study, we showed that caveolin-1 expression is significantly related to chemosensitivity in OSCC. METHODS: We established a CDDP-resistant cell line, H-1R, from the parental OSCC cell line, H-1. Caveolin-1 expression was determined by reverse transcriptase-polymerase chain reaction (RT-PCR) in both cell lines. We analyzed expression of caveolin-1 in 30 OSCC biopsy specimens and investigated the relationship between expression of caveolin-1 and patients' clinicopathological parameters and chemotherapeutic responses. RESULTS: The 3-(3,4-dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay indicated that H-1R has a ten-times greater resistance to CDDP than H-1 has. The level of caveolin-1 expression in H-1R was significantly decreased in comparison with that in H-1 by real-time RT-PCR analysis. Positive caveolin-1 immunostaining correlated positively with a complete response (16/20, 80.0%). However, negative immunostaining was found in 6/7 (85.7%) cases with no response. Positive immunohistochemical staining of caveolin-1 correlated positively with chemosensitivity to CDDP-based combination chemotherapy (P=0.02). CONCLUSIONS: These results suggest that overexpression of the caveolin-1 gene may provide novel diagnostic markers associated with CDDP sensitivity in OSCC.

Aged↗

PubMed2005

Proteomic analysis on insulin signaling in human hematopoietic cells: identification of CLIC1 and SRp20 as novel downstream effectors of insulin.

Insulin/IGF-I-dependent signals play important roles for the regulation of proliferation, differentiation, metabolism, and autophagy in various cells, including hematopoietic cells. Although the early protein kinase activation cascade has been intensively studied, the whole picture of intracellular signaling events has not yet been clarified. To identify novel downstream effectors of insulin-dependent signals in relatively early phases, we performed high-resolution two-dimensional electrophoresis (2-DE)-based proteomic analysis using human hematopoietic cells 1 h after insulin stimulation. We identified SRp20, a splicing factor, and CLIC1, an intracellular chloride ion channel, as novel downstream effectors besides previously reported effectors of Rho-guanine nucleotide dissociation inhibitor 2 and glutathione S-transferase-pi. Reduction in SRp20 was confirmed by one-dimensional Western blotting. Moreover, MG-132, a proteasome inhibitor, prevented this reduction. By contrast, upregulation of CLIC1 was not observed in one-dimensional Western blotting, unlike the 2-DE results. As hydrophilic proteins were predominantly recovered in 2-DE, the discrepancy between the 1-DE and 2-DE results may indicate a certain qualitative change of the protein. Indeed, the nuclear localization pattern of CLIC1 was remarkably changed by insulin stimulation. Thus insulin induces the proteasome-dependent degradation of SRp20 as well as the subnuclear relocalization of CLIC1.

Amino Acid Sequence↗

PubMed2005

Thoracoscopic removal of neurogenic mediastinal tumors in children.

PURPOSE: The aim of this study was to evaluate the feasibility and advantages of thoracoscopic removal of neurogenic mediastinal tumors (NMTs) in children. METHODS: From January 1998 to December 2001, 6 patients, ages 1.1 to 6.8 years (mean, 3.5 years), underwent thoracoscopic removal of NMT. A retrospective study was done to assess the type of anesthesia, conversions to standard thoracotomy, operative time, complications, and the current status of each patient. RESULTS: General anesthesia using a Fogarty catheter as an ipsilateral bronchial blocker was utilized. Four 5-mm ports were placed in all patients. All NMTs were successfully removed without a need to convert to standard thoracotomy. The tumor was captured in an extraction bag, fragmented, and then removed through the trocar site, which had been enlarged up to 2.0-2.5 cm in each case. Pathologic diagnosis was neuroblastoma in 1 patient, ganglioneuroblastoma in 2, and ganglioneuroma in 3 patients. The mean operative time was 230 minutes. There was no need for transfusion and no serious complication related to this approach. All patients are alive at the time of writing, without any evidence of tumor recurrence. CONCLUSION: All tumors were successfully removed. Thoracoscopic surgery is a feasible, safe, and effective technique in the treatment for children with NMT.

Child↗

PubMed2005

Establishment and gene analysis of a cisplatin-resistant cell line, Sa-3R, derived from oral squamous cell carcinoma.

Cisplatin (CDDP) is widely used for chemotherapy of many malignancies, especially of oral squamous cell carcinoma (SCC). However, because the mechanism of resistance to CDDP is unclear, we established a CDDP-resistant cell line, Sa-3R, from a CDDP-sensitive cell line, Sa-3, which was derived from moderately differentiated SCC of the lower gingiva. The 3-(3,4-dimethyl-thiazol-2-yl) 2,5-diphenyltetrazolium bromide assay indicated that Sa-3R has 7.5-fold greater resistance to CDDP than Sa-3. Comparing gene expression levels in the cell lines using an in-house cDNA microarray, which represented 2,201 oral disease origin genes, many differentially expressed genes were identified. The ATP-binding cassette transporter genes (MDR-1, MRP-1, and MRP-2), and FANCONI, GRP58, FLJ12089, and SPINT-2 were up-regulated, whereas FOSL1, MRPS27, and PGK-1 were down-regulated. These results were confirmed by semiquantitative reverse transcriptase-polymerase chain reaction. The Sa-3/Sa-3R cell lines could be useful to identify the candidates responsible for the mechanism of CDDP-resistance and the up- or down-regulated genes identified by the gene expression profiles in the Sa-3R cell line may be, in part, associated with the mechanism.

Biopsy↗

PubMed2003

Cellular aging-dependent decrease in cholesterol in membrane microdomains of human diploid fibroblasts.

Recently it has been shown that cholesterol plays indispensable roles in the function of cholesterol-rich microdomains (rafts), such as in ligand-mediated signal transduction. Using a perfringolysin O derivative (BCtheta) that binds selectively to cholesterol in rafts without causing membrane damage (Proc. Natl. Acad. Sci. USA 98 (2001) 4926), we have investigated the effect of in vitro replicative aging of human diploid fibroblasts, TIG-1, on the distribution of plasma membrane cholesterol. The amount of BCtheta-labeled membrane cholesterol decreased during replicative aging of TIG-1 cells, whereas total cholesterol increased somewhat. The relationship was confirmed by double staining with BCtheta and senescence-associated-beta-galactosidase, a biomarker of senescent cells. Cell fractionation experiments revealed decreases in both cholesterol in rafts and a raft marker, flotillin, during replicative aging. In addition, hydroxyurea-induced prematurely senescent cells also showed a lower level of BCtheta-labeled cholesterol than untreated cells, despite maintaining the total amount of cholesterol. When TIG-1 cells were cultured in cholesterol-deficient medium, BCtheta labeling was first diminished and then premature senescence was induced. Taken together with the reduced signaling capacity of aged cells, these results suggest that plasma membrane cholesterol in raft microdomains is more sensitive to senescence than total cholesterol and is a primary target in aging.

Apoptosis↗