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Biomedical subjects

Toshiaki Tanaka

Publications and source records attributed to Toshiaki Tanaka.

At least 19 recordsLinked to original sources
PubMed2006

Asymmetric total synthesis of (+)-K01-0509 B: determination of absolute configuration.

K01-0509 B is a novel natural product which contains a carbamoylated cyclic guanidine. Our asymmetric total synthesis features a Sharpless asymmetric epoxidation and a stereocontrolled construction of the cyclic guanidine via an asymmetric nitroaldol reaction, followed by intramolecular SN2 cyclization. These reactions allowed the cyclic guanidine and the adjacent hydroxy group to be assembled, facilitating the asymmetric total synthesis and determination of the absolute stereochemistry of K01-0509 B. [reaction: see text].

Anti-Bacterial Agents↗
PubMed2006

Distal colorectal cancers with microsatellite instability (MSI) display distinct gene expression profiles that are different from proximal MSI cancers.

Promoter methylation of the mismatch repair gene plays a key role in sporadic microsatellite instability (MSI) colorectal cancers. However, promoter methylation often occurs in proximal colon cancers, and molecular phenotypes underlying MSI cancers in distal colon have not been fully clarified. Our goal was to clarify the difference between MSI and microsatellite stability (MSS) cancers and, furthermore, to determine distinct characteristics of proximal and distal MSI cancers. By DNA microarray analysis of 84 cancers (33 MSI and 51 MSS), we identified discriminating genes (177 probe sets), which predicted MSI status with a high accuracy rate (97.6%). These genes were related to phenotypic characteristics of MSI cancers. Next, we identified 24 probe sets that were differentially expressed in proximal and distal MSI cancers. These genes included promoter methylation-mediated genes, whose expression was significantly down-regulated in proximal MSI cancers. Among discriminating genes between MSI and MSS, nine methylation-mediated genes showed down-regulation in MSI cancers. Of these, 7 (77.8%) showed down-regulation in proximal MSI cancers. Furthermore, methylation-specific PCR confirmed that frequency of hMLH1 promoter methylation was significantly higher in proximal MSI cancers (P = 0.0317). These results suggested that there is a difference between proximal and distal MSI cancers in methylation-mediated influence on gene silencing. In conclusion, using DNA microarray, we could distinguish MSI and MSS cancers. We also showed distinct characteristics of proximal and distal MSI cancers. The inactivation form of hMLH, per se, differed between proximal and distal MSI cancers. These results suggested that distal MSI cancers constitute a distinct subgroup of sporadic MSI cancers.

Adaptor Proteins, Signal Transducing↗
PubMed2006

Inhibitory effect of c-Met mutants on the formation of branching tubules by a porcine aortic endothelial cell line.

The association of hepatocyte growth factor (HGF) with its high-affinity receptor (c-Met) has been shown to induce mitogenesis, motogenesis and morphogenesis in a variety of cell types. Various point mutations in c-Met have been identified in hereditary and sporadic papillary renal carcinomas as well as in other carcinomas. In the present study, we examined the effects of c-Met point mutations on the morphology of a porcine aortic endothelial (PAE) cell line. When cultured in three-dimensional collagen gel, PAE cells formed branching tubule structures, and HGF treatment caused breakdown of the structures and induced a scattered morphology. The exogenous expression of c-Met point mutants inhibited the formation of tubules. HGF treatment induced the formation of tubules by PAE cells expressing some c-Met mutants, but it induced the scattering of PAE cells expressing other c-Met mutants. The presence of a low concentration of a mitogen-activated protein kinase/extracellular signal-regulated kinase kinase (MEK) inhibitor cancelled the inhibitory effect of the c-Met point mutations on the formation of tubules. These results suggest that c-Met point mutations affect the extracellular signal-regulated kinase (ERK) signaling required for the formation of tubules by PAE cells, and HGF binding changes the conformation of c-Met mutants, leading to the different signals required for formation of tubules and cell scattering.

Animals↗
PubMed2006

Growth hormone (GH) effects on central fat accumulation in adult Japanese GH deficient patients: 6-month fixed-dose effects persist during second 6-month individualized-dose phase.

Both Japanese and Caucasian adults with GH deficiency (GHD) have pronounced abdominal obesity, which is associated with increased risk of cardiovascular complications. We investigated the effects of GH treatment in 27 adult Japanese GHD patients, 15 with adult onset (AO) and 12 with childhood onset (CO) GHD. Patients initially received GH titrated to 0.012 mg/kg/day for 24 weeks in a double-blind design and the dose was then individualized for each patient according to IGF-I for a further 24 weeks. Dual-energy x-ray absorptiometry (DXA) data were evaluated for percentages of trunk fat, total body fat and lean body mass. Serum IGF-I and lipid concentrations were determined at a central laboratory. There were 25 patients who completed 48 weeks of treatment, with 7, 6 and 12 patients then receiving GH at 0.003, 0.006 and 0.012 mg/kg/day, respectively. With the reductions in dose when individualized between weeks 24 and 48, mean serum IGF-I level was reduced and excessively high values, observed in AO patients on the fixed GH dose, were no longer seen. The decrease from baseline in trunk fat was similar at week 24 (-3.8 +/- 3.3%, p<0.001) and week 48 (-3.1 +/- 3.7%, p<0.001), and the difference between changes was not significant. Total cholesterol was decreased from baseline by -24 +/- 28 mg/dl (p<0.001) at week 24 and -17 +/- 28 mg/dl (p = 0.007) at week 48. Two patients had elevated HbA1c levels: one continued GH treatment after a dose reduction and the other discontinued due to persistent impaired glucose tolerance. Therefore, excessively high IGF-I levels can be avoided by individualized dosing during long-term GH treatment. Individualized dosing maintains the decrease in abdominal fat in adult Japanese GHD patients and should reduce the cardiovascular risk.

Abdominal Fat↗
PubMed2006

Low-dose growth hormone treatment (0.175 mg/kg/week) for short stature in patients with Turner Syndrome: data from KIGS Japan.

Turner syndrome is a common sex chromosome anomaly. Human growth hormone (hGH) is effective for treating short stature, which is a major characteristic of the disease. In this report, we analyzed the results of low-dose GH treatment for short stature in 212 Turner syndrome patients with growth hormone deficiency. These patients were enrolled in KIGS Japan. After 5 years of treatment, change in height was more than the mean growth curve in many patients, and the standard deviation (SD) for stature improved by +1.22 SDS. As the treatment progressed, the weight-for-height index (WHI) decreased in patients aged 8.1 years or older but not more than 14.8 years at the commencement of the treatment.

Adolescent↗
PubMed2006

Determination of specific activities and kinetic constants of biotinidase and lipoamidase in LEW rat and Lactobacillus casei (Shirota).

Enzyme kinetic parameters, such as K(m), V(max) (or V), k(cat)/K(m), and K(i) (by biotin or lipoic acid) for biotinidase and lipoamidase were determined in Lewis (LEW) rat and Lactobacillus casei (Shirota) using fluorimetric high-performance liquid chromatography (HPLC). It was found that the final protein concentration below 0.1mg/ml is sufficient to obtain linear hydrolytic reaction and to determine the Michaelis-Menten type kinetic parameters (K(m), V, K(i)). We applied this HPLC enzyme assay method onto the rat and some bacteria. The highest specific activities (Vs) for biotinidase were found in Lactobacillus casei (Shirota) and rat kidney. It was also found that the largest K(i) by product for biotinidase and lipoamidase were present in the Lactobacillus casei (Shirota). There has been found specie (between rat and mouse) differences and tissue (organ) differences, together with tissue region differences and sex differences in some tissues. Summary of the distributions of both enzymes in LEW rat was also presented. Therefore, this HPLC determination method for the enzyme kinetic parameters in tissues is expected to be an indispensable tool for the investigation of the various diseases in humans.

Amidohydrolases↗
PubMed2006

Modified and bilateral retroperitoneal lymph node dissection for testicular cancer: peri- and postoperative complications and therapeutic outcome.

OBJECTIVE: To characterize surgical invasiveness and morbidity and to verify therapeutic efficacy, we reviewed perioperative and postoperative courses and therapeutic outcomes of patients who underwent retroperitoneal lymph node dissection (RPLND) for testicular germ cell cancers. METHODS: The study included 31 patients who underwent retroperitoneal lymph node dissection. A modified template was used if retroperitoneal metastasis was limited to the areas below the level of the renal hilus and above the level of the inferior mesenteric artery (IMA). Perioperative and postoperative courses and complications were reviewed as well as therapeutic outcomes. RESULTS: Overall, 27 perioperative and postoperative complications were observed in 15 patients (48.4%). Superficial surgical site infection and paralytic ileus were seen most frequently. All of them were resolved without special additional treatments; however, patients who underwent retrocrural dissection had a tendency to have severe symptomatic complications such as chylothorax, phrenic nerve palsy and orthostatic hypotension. Antegrade ejaculation was preserved in 94.1% of patients with modified template dissection, whereas no patients with additional dissection below the level of the IMA had the function preserved. One patient (3.2%) developed a postoperative recurrent disease in the retroperitoneum, which was outside the dissection field, as well as in the mediastinum. CONCLUSIONS: Although RLND had high morbidity, most peri- and postoperative complications were manageable conservatively. Modified template dissection enabled patients to preserve antegrade ejaculation without compromising its therapeutic efficacy, if the disease extension allowed us to use the template.

Adolescent↗
PubMed2006

Replacement of alanine with asparagic acid at position 203 in human steroidogenic acute regulatory protein impairs the ability to enhance steroidogenesis in vitro.

Steroidogenic acute regulatory protein (StAR) is a 30-kDa phosphorylated protein that rapidly appears in mitochondria of steroidogenic cells following tropic stimulation, and is required in the acute regulation of steroidogenesis. It was reported that mutations in the STAR gene encoding StAR cause congenital lipoid adrenal hyperplasia (CLAH), an autosomal recessive disorder characterized by impaired synthesis of all adrenal and gonadal steroid hormones. We previously reported a D203A polymorphism in the STAR gene in Japanese patients with CLAH as well as in normal Japanese subjects. In the present study, we analyzed the ability of the A203 StAR and D203 StAR to stimulate steroidogenesis using the in vitro functional expression system. The A203 StAR caused a twelve-fold increase in pregnenolone secretion over COS-1 cells transfected with an NH2-cholesterol side-chain cleavage enzyme (P450scc)-adrenodoxin reductase-adrenodoxin-COOH fusion protein expressing plasmid (F2) and an empty vector, whereas the D203 StAR increased pregnenolone production no more than threefold. Western blot analysis detected mainly two species of StAR consisting of the 37-kDa precursor and the 30-kDa mature form. Together, these results indicate that the alanine at position 203 in human StAR is functionally important and that the D203 StAR is extremely unlikely to be a polymorphism.

Alanine↗
PubMed2006

Prediction of sensitivity of rectal cancer cells in response to preoperative radiotherapy by DNA microarray analysis of gene expression profiles.

Preoperative radiotherapy has been widely used to improve local control of disease and to improve survival in the treatment of rectal cancer. However, the response to radiotherapy differs among individual tumors. Our objective here was to identify a set of discriminating genes that can be used for characterization and prediction of response to radiotherapy in rectal cancer. Fifty-two rectal cancer patients who underwent preoperative radiotherapy were studied. Biopsy specimens were obtained from rectal cancer before preoperative radiotherapy. Response to radiotherapy was determined by histopathologic examination of surgically resected specimens and classified as responders or nonresponders. By determining gene expression profiles using human U95Av2 Gene Chip, we identified 33 novel discriminating genes of which the expression differed significantly between responders and nonresponders. Using this gene set, we were able to establish a new model to predict response to radiotherapy in rectal cancer with an accuracy of 82.4%. The list of discriminating genes included growth factor, apoptosis, cell proliferation, signal transduction, or cell adhesion-related genes. Among 33 discriminating genes, apoptosis inducers (lumican, thrombospondin 2, and galectin-1) showed higher expression in responders whereas apoptosis inhibitors (cyclophilin 40 and glutathione peroxidase) showed higher expression in nonresponders. The present study suggested the possibility that gene expression profiling may be useful in predicting response to radiotherapy to establish an individualized tailored therapy for rectal cancer. Global expression profiles of responders and nonresponders may provide insights into the development of novel therapeutic targets.

Combined Modality Therapy↗
PubMed2006

Long-term survival after three-field lymph-adenectomy for an adenocarcinoma in Barrett's esophagus with metastasis to Virchow's node.

Here, we report a case of long-term survival after resection of an adenocarcinoma in Barrett's esophagus with metastasis to Virchow's node. A 71-year-old woman was referred to our hospital with a tumor in the lower third of the thoracic esophagus, located just beneath the tracheal bifurcation because of an hiatal hernia. On admission, she had a palpable lymph node in Virchow's node. The esophageal tumor and this lymph node were biopsied. They were pathologically found to be an adenocarcinoma in the esophagus which had metastasised to the lymph node. She underwent transthoracic esophagectomy with three-field lymph node dissection. The pathological diagnosis was adenocarcinoma in Barrett's esophagus with the UICC stage classification of pT1, pN1, pM1-LYM, Stage IVB. She received postoperative chemotherapy of cisplatin combined with 5-fluorouracil. The patient is well without recurrence at 14 years to date after surgery. We recommend thoracoabdominal esophagectomy with three-field lymphadenectomy for an advanced carcinoma in the upper and middle thoracic esophagus regardless of histological types.

Abdomen↗
PubMed2006

Hearing loss in Turner syndrome.

OBJECTIVE: To address the characteristics of hearing loss in patients with Turner syndrome (TS), we evaluated hearing levels of patients with TS and analyzed causative factors. STUDY DESIGN: Thirty-three patients with TS (8 to 40 years of age) were studied through the use of audiological measurements, and causative factors were explored. RESULTS: Twenty cases (35 of 66 ears tested) showed high-frequency (8 kHz) sensory neural hearing loss (HFQ-SNHL). Fifteen cases (26 ears) and 15 cases (24 ears) of the impaired 20 cases were unresponsive to distortion-product otoacoustic emissions and transient-evoked otoacoustic emissions, respectively. HFQ-SNHL showed little relation to the history of middle ear infection and puberty, although middle ear infections were seen in 11 of the 20 cases. The hearing thresholds at high frequencies were correlated with age and body height (P < .001). The age-dependent increase in hearing thresholds in the high frequencies was more apparent in patients with TS with monosomic 45, X than in those with the mosaic type (P < .05). CONCLUSIONS: More than 60% of patients with TS had HFQ-SNHL. Because the increase in hearing threshold at high frequencies was shown to depend on karyotype and aging, regular otological examination is important for the determination of proper treatment.

Acoustic Impedance Tests↗