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Biomedical subjects

T Sakamoto

Publications and source records attributed to T Sakamoto.

At least 91 records · Page 5Linked to original sources
PubMed2001

Medication for hearing loss after fractionated stereotactic radiotherapy (SRT) for vestibular schwannoma.

PURPOSE: To investigate the effectiveness of corticosteroid treatments for patients showing decreases in hearing levels after stereotactic radiotherapy for vestibular schwannoma. METHODS AND MATERIALS: Twenty-one patients experienced a hearing loss in pure-tone average at greater than 20 dB or less than 10 dB within 1 year after irradiation administration of 44 Gy/22 fractions followed by a 4 Gy boost. Eight received oral prednisone at a daily dose of 30 mg, which was gradually decreased (medicated group), and 13 received none (nonmedicated group). The average observation period was 26.7 +/- 16.6 (range: 6--69) months. RESULTS: Hearing recovery was seen after initial onset of the hearing loss in all 8 patients in the medicated group and in 2 of 13 patients in the nonmedicated group (p = 0.001). The hearing recovery, that is, the change in pure-tone average (dB) at the last follow-up from the onset of hearing loss, was 9.8 +/- 6.9 dB (recovery) in the medicated group and -9.4 +/- 12.8 dB (further loss) in the nonmedicated group (p = 0.0013). The hearing recovery rate, normalizing to the degree of the hearing loss before medication, was also significantly higher in the medicated group than in the nonmedicated group (p = 0.0014). CONCLUSIONS: Corticosteroidal intake is suggested to be effective in improving hearing loss after stereotactic radiotherapy, at least in young patients having a useful pretreatment hearing level, if the treatment for hearing loss is administered immediately after the hearing loss is first detected.

Adult↗
PubMed2001

Acoustic priming lowers the threshold for electrically induced seizures in mice inferior colliculus, but not in the deep layers of superior colliculus.

Mice become highly susceptible to audiogenic seizures (AGS) after exposing them to an intense noise in their early life (priming). To elucidate the brain mechanisms for this priming effect of AGS, we compared the threshold current intensities inducing AGS syndromes between primed (n=88) and non-primed (n=84) mice by electrically stimulating the central nucleus and external cortex of the inferior colliculus (CIC and ECIC), and the deep layers of the superior colliculus (DLSC). The threshold for wild running was significantly lower for the primed mice than for the control mice in the case of the CIC and ECIC, but not the DLSC. The current intensity for inducing clonic seizure was lower for the primed mice than for the control mice in the case of the ECIC. These results show that the inferior colliculus (IC) plays an important role in the priming effect of AGS in mice, but that the DLSC does not.

Acoustic Stimulation↗
PubMed2001

Minimal functional structure of Escherichia coli 4.5 S RNA required for binding to elongation factor G.

Escherichia coli cells contain abundant amounts of metabolically stable 4.5 S RNA. Consisting of 114 nucleotides, 4.5 S RNA is structurally homologous to mammalian 7 S RNA, and it plays an essential role in targeting proteins containing signal peptide to the secretory apparatus by forming an signal recognition-like particle with Ffh protein. It also binds independently to protein elongation factor G (EF-G) and functions in the translation process. This RNA contains a phylogenetically conserved RNA domain, the predicted secondary structure of which consists of a hairpin motif with two bulges. We examined the binding activity of mutants with systematic deletions to define the minimal functional interaction domain of 4.5 S RNA that interacts with EF-G. This domain consisted of 35-nucleotides extending from 36 to 70 nucleotides of mature 4.5 S RNA and contained two conserved bulges in which mutations of A47, A60, G61, C62, A63, and A67 diminished binding to EF-G, whereas those at A39, C40, C41, A42, G48, and G49 did not affect binding. These data suggested that the 10 nucleotides in 4.5 S RNA, which are conserved between 4.5 S RNA and 23 S rRNA, have a key role for EF-G binding. Based on the NMR-derived structure of mutant A47U, we further verified that substituting U at A47 causes striking structural changes and the loss of the symmetrical bulge. These results indicate the mechanism by which EF-G interacts with 4.5 S RNA and the importance of the bulge structure for EF-G binding.

Base Sequence↗
PubMed2001

DYT1 mutation in Japanese patients with primary torsion dystonia.

A GAG deletion at position 946 in the DYT1 gene has been identified as one of the gene mutations responsible for autosomal dominant primary torsion dystonia. We examined 178 Japanese patients with various forms of dystonia, and found the mutation in six patients (3.4%) from three families. Five of them had early clinical onset (before age 12) with initial involvement of a limb. To our knowledge, this is the first report of the frequency and the clinical features of DYT1 mutation in oriental patients, and the clinical presentation of the mutation in these patients was similar to that of Jewish or non-Jewish Caucasian patients.

Adult↗
PubMed2001

KNOX homeodomain protein directly suppresses the expression of a gibberellin biosynthetic gene in the tobacco shoot apical meristem.

To identify genes targeted by the tobacco KNOX homeodomain protein, Nicotiana tabacum homeobox 15 (NTH15), we have generated an inducible system using the human glucocorticoid receptor. In this system, steroid treatment strictly induced NTH15 function and immediately suppressed the expression of a gibberellin (GA) biosynthetic gene encoding GA 20-oxidase (Ntc12) and also resulted in a decrease in bioactive GA levels. The repression of Ntc12 was observed even when indirect effects were blocked by cycloheximide. NTH15 mRNA was present in corpus cells of the shoot apical meristem (SAM), whereas Ntc12 mRNA was observed in leaf primordia and rib meristem but not in the corpus. Recombinant NTH15 protein strongly bound to a 5-bp dyadsymmetric sequence, GTGAC, in the first intron of Ntc12 in vitro. Mutation of this sequence in the Ntc12 gene abolished the NTH15-dependent suppression of Ntc12 in the corpus of the SAM. Our results indicate that NTH15 directly represses Ntc12 expression in the corpus of the wild-type SAM to maintain the indeterminate state of corpus cells. The suppression of NTH15 within cells at the flanks of the SAM permits GA biosynthesis, which promotes organized cell proliferation and consequently induces the determination of cell fate.

Cell Division↗
PubMed2001

Increase in plasma levels of oxidized low-density lipoproteins in patients with coronary spastic angina.

Oxidized low-density lipoproteins (LDL) impair endothelium-dependent dilation and constrict arteries. This study examined possible relation of the circulating plasma levels of Ox-LDL to coronary spastic angina (CSA). The plasma levels of Ox-LDL were measured by ELISA in 37 consecutive patients with CSA and normal coronary angiograms and in 79 consecutive control patients. The Ox-LDL levels in patients with CSA were significantly higher than those in controls. In multivariate analysis, higher levels of Ox-LDL were a risk factor for CSA independently of other traditional risk factors. The Ox-LDL levels had a significant and positive correlation with constrictor response of coronary arteries to the intracoronary acetylcholine infusion. Thus, Ox-LDL may play a possible role in pathogenesis of coronary spasm.

Acetylcholine↗
PubMed2001

The prognostic value of small-sized platelet aggregates in unstable angina: detection by a novel laser-light scattering method.

Platelet activation plays a pivotal role in the pathogenesis of acute coronary syndromes. This study was designed to evaluate the platelet aggregability in patients with unstable angina using a new aggregometer with laser-light scattering. We also examined whether there was a relationship between these platelet aggregabilities and unfavorable outcome during in-hospital stay. We measured platelet aggregability, in particular small-sized platelet aggregates in 31 patients with unstable angina, 31 patients with stable exertional angina, and 30 patients with chest pain syndrome. The patients with unstable angina were divided into two groups by their cardiac events during in-hospital stay, cardiac events (+)(n=11) group and cardiac events (-)(n=20) group. On admission, the number of small-sized platelet aggregates (V) was higher in patients with unstable angina (3.0+/-0.5x10(4)) than in those with stable exertional angina (1.4+/-0.3x10(4), P=.017) and chest pain syndrome (0.7+/-0.2x10(4), P=.0003). The number of small-sized platelet aggregates was higher in the cardiac events (+) group than in the cardiac events (-) group (5.5+/-0.9x10(4) vs. 1.6+/-0.4x10(4), P=.0001). A previous study elucidated that small-sized platelet aggregates ultimately developed into medium-sized and large-sized aggregates as platelet aggregation proceeds. Therefore, the production of small-sized platelet aggregates is more sensitive for hyperaggregability. Furthermore, the production of small-sized platelet aggregates increased significantly in patients with unstable angina than in those with stable exertional angina and chest pain syndrome. These findings suggest that a tendency toward thrombus formation increases markedly in patients with unstable angina and increased number of small-sized platelet aggregates on admission predicts poor prognosis during in-hospital stay in patients with unstable angina.

Adult↗
PubMed2001

A "green" route to perylene dyes: direct coupling reactions of 1,8-naphthalimide and related compounds under mild conditions using a "new" base complex reagent, t-BuOK/DBN.

The direct coupling reactions of 1,8-naphthalimide compounds efficiently occurred at 130 or 170 degrees C without the intervention of the leuco form dyes in the presence of base complex reagent, t-BuOK/1,5-diazabicyclo[4.3.0]non-5-ene (DBN), to give the corresponding perylene dyes in good yields with > 95% purities. A possible mechanistic speculation for these oxidative coupling reactions is briefly discussed.

Journal Article↗
PubMed2001

Mesityllithium as a reagent for chemoselective halogen-lithium exchange reaction.

[figure: see text] Mesityllithium was found to be an excellent selective lithiating agent to prepare aryllithium compounds having alkoxycarbonyl groups. To extend our studies on chemoselective lithiation, an important precursor for the synthesis of camptothecin was prepared using a halogen-lithium exchange reaction followed by an intramolecular 1,2-addition.

Camptothecin↗
PubMed2001

Aldosterone production is activated in failing ventricle in humans.

BACKGROUND: Recent reports have indicated that aldosterone is produced in extra-adrenal tissues in animals. The present study was designed to examine whether aldosterone is produced in human heart. METHODS AND RESULTS: Plasma levels of aldosterone, BNP, and angiotensin-converting enzyme were measured in anterior interventricular vein (AIV), coronary sinus (CS), and aortic root (Ao), respectively, in 20 patients with left ventricular systolic dysfunction (LVSD), 25 patients with LV diastolic dysfunction (LVDD), and 23 control subjects. Aldosterone levels were significantly higher in AIV and CS than Ao in LVSD (98+/-10 versus 72+/-9 pg/mL, P:<0.001, and 97+/-11 versus 72+/-9 pg/mL, P:<0.001, respectively) and LVDD (87+/-10 versus 71+/-9 pg/mL, P:<0.01, and 84+/-10 versus 71+/-9 pg/mL, P:<0.01, respectively) groups, but no differences were observed in levels for these sites in the control group. Levels of ACE activity and BNP also were higher in AIV than Ao in both LV dysfunction groups. The difference in aldosterone levels between AIV and Ao and those in BNP and angiotensin-converting enzyme had a significant positive correlation with LVEDP and a significant negative correlation with LV ejection fraction in the LVSD group. CONCLUSIONS: Production of aldosterone, angiotensin-converting enzyme, and BNP are activated in failing human ventricle in proportion to severity.

Adult↗
PubMed2001

Efficacy and safety of PTCA using brachial approach and low-dose heparin.

Percutaneous transluminal coronary angioplasty (PTCA) is routinely performed using the femoral approach. However, recent reports suggest the usefulness of the brachial approaches for patients for whom the femoral approach is impossible due to peripheral vessel disease or to shortened postoperative rest times. However, some reports have revealed that the incidence of vascular complications undergoing brachial-approach PTCA may be higher than those with the femoral approach, possibly due to relatively higher dose of heparin. Accordingly, in this study we evaluated the efficacy and safety of PTCA using the brachial approach and low-dose heparin, hypothesizing that lowering the heparin dose might result in reduced vascular complications. The study population of patients admitted for angina pectoris consisted of 217 subjects (221 lesions) who underwent brachial-approach PTCA and 102 subjects (115 lesions) who underwent PTCA via the femoral approach. Both groups were monitored for complications. There were no significant differences in patient or lesion characteristics between the groups. Incidence of vascular complications tended to be lower in the brachial group than in the femoral group (1.8% vs. 3.5%), although the difference did not reach statistical significance. Use of anodynes was also significantly lower in the brachial group (3.6% vs. 33%). PTCA from the brachial approach with low-dose heparin is as safe and effective a strategy as compared with the femoral approach with standard dose of heparin.

Aged↗
PubMed2001

Effects of melatonin on the proliferation and cis-diamminedichloroplatinum (CDDP) sensitivity of cultured human ovarian cancer cells.

OBJECTIVES: In this study, we investigated the antiproliferative effect and telomerase activity of melatonin with or without cis-diamminedichloroplatinum (CDDP) on CDDP-sensitive HTOA cells and CDDP-resistant OVCAR-3 cells of cultured human ovarian cancer. METHODS: HTOA cells and OVCAR-3 cells were cultured in RPMI-1640 at 37 degrees C with 5% CO(2) for 132 h. To examine the antiproliferative effect of melatonin, cells were cultured with or without melatonin (10(-12)-10(-6) M) and thereafter counted in a 96-well microplate using the alamarBlue assay. To examine the effect of melatonin and CDDP, cells were divided into group A (intermittent CDDP, 0.5 microg/ml), group B (intermittent CDDP + melatonin), and group C (sequential (12-h interval) CDDP/melatonin) and thereafter counted in a 96-well microplate using the alamarBlue assay. In different series, cells were cultured and treated with either ethanol, melatonin, CDDP, or CDDP + melatonin. After harvest, telomerase activity was semiquantified with a fluorescence-based telomeric repeat amplification protocol (F-TRAP). RESULTS: (1) Melatonin produced no antiproliferative effect on both types of ovarian cancer cells. (2) Melatonin 10(-6) M induced the antiproliferative effect in groups B and C compared with group A in the HTOA cell line. (3) Melatonin 10(-9) M produced the antiproliferative effect in groups B and C compared with group A in the OVCAR-3 cell line. (4) Telomerase activity in the HTOA cell line did not change but, in the OVCAR-3 cell line, was significantly lower in the CDDP + melatonin group compared with the ethanol and CDDP groups. CONCLUSIONS: Melatonin enhanced CDDP sensitivity in two ovarian cancer cell lines. Thus, melatonin may improve ovarian cancer chemotherapy.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2001

Use of win-stay and win-shift strategies in place and cue tasks by medial caudate putamen (MCPu) lesioned rats.

This study investigated the behavioral function of the medial caudate putamen (MCPu) in the solving of maze tasks. MCPu lesioned rats (n = 35) and control rats (n = 35) were trained for the place or cue task (the four baited arms and four unbaited arms task) in an eight-arm radial maze, which requires the win-stay or the win-shift strategy. In Experiment 1, in which the place task was used, MCPu lesioned rats could learn the task in the win-shift condition, but not in the win-stay condition. MCPu lesioned rats made a lot of unbaited errors in the win-stay condition, as they persistently chose adjacent arms. Control rats could learn the tasks in both conditions. In Experiment 2, in which the cue task was used, MCPu lesioned rats and control rats could learn the tasks in both the win-stay and the win-shift conditions. If anything, the performance of MCPu rats was a little better than that of control rats in the win-stay condition. The results of these two experiments revealed that the MCPu was involved in solving the win-stay place task, but not the win-shift place, win-stay cue, and win-shift cue tasks. These findings suggest that the MCPu plays an important role in utilizing both spatial information and switching foraging strategies flexibly and efficiently, that is, processing complicated visuospatial cognition.

Animals↗
PubMed2001

Endoscopic transanal decompression with a drainage tube for acute colonic obstruction: clinical aspects of preoperative treatment.

PURPOSE: The study was undertaken to evaluate the clinical usefulness of endoscopic transanal decompression with a newly developed drainage tube for the treatment of acute colonic obstruction. METHODS: Thirty-six patients ranging in age from 46 to 87 years (average age = 69 years) with acute colorectal obstruction secondary to carcinoma were treated by means of intubation with a flexible drainage tube using combined endoscopic and fluoroscopic guidance. After tube placement, the obstructed colon was aspirated, decompressed, and cleaned with a 50 ml syringe and saline solution. The drainage tube was kept inserted and the colon was irrigated two or three times per day using 500 to 1,000 ml of saline until there were no contents in the colon. The colon was almost empty at the time of operation. The success rate, benefits, and complications of this technique were evaluated. RESULTS: Placement of the drainage tube was successful in 34 (94.4 percent) of 36 patients. Immediately after aspiration and decompression, symptoms related to obstruction were relieved in 21 patients (61.8 percent), within one hour in 9 patients (26.5 percent) and within four hours in 4 patients (11.8 percent). All 34 patients had elective single-stage surgery without severe complications at the anastomotic site such as anastomotic leakage and postanastomotic stenosis that needed treatment a few days after placement of the drainage tube. In the two cases of unsuccessful placement of the drainage tube, emergent colostomy was performed. CONCLUSION: Decompression with a transanal drainage tube is an easy and safe technique to relieve colonic obstruction effectively without any excess burden to patients. Because the procedure permits single-stage surgery in most cases, it is also cost effective.

Acute Disease↗
PubMed2001

Use of an autologous cortical bone graft sandwiched between two intervertebral spacers in posterior lumbar interbody fusion.

Various intervertebral spacers with or without posterior instrumentation use pedicle screw fixation in posterior lumbar interbody fusion (PLIF). Recently we harvested an autologous cortical bone graft from a spinous process by en bloc resection and inserted it between two intervertebral spacers during PLIF surgery. Due to better balance, this procedure provides greater mechanical strength, larger contact area, and better bilateral restoration of disc height than PLIF using intervertebral spacers only, and there is no need to take a bone graft from the iliac crest. This technique appears to result in effective spinal fusion in PLIF surgery.

Adult↗
PubMed2001

Tissue factor increases in the aqueous humor of proliferative diabetic retinopathy.

BACKGROUND: Tissue factor (TF) is a cellular initiator of the coagulation cascade and is upregulated by the major factors of diabetic angiopathy, TF might thus be one of the key molecules in diabetic retinopathy (DR). PURPOSE: To measure TF in diabetic eyes and evaluate its possible role in DR. METHODS: TF concentration in the aqueous humor of the eyes in 44 patients with diabetes and 35 age-matched control patients was evaluated by ELISA. The concentration of TF in aqueous humor (AH) was compared with the grade of DR. The concentration of TF in AH was also compared with duration of diabetes, renal function, and blood glucose control. The serum TF concentration in each group was also compared. The correlation between the serum TF and aqueous TF in each patient was analyzed. The effect of vascular endothelial growth factor (VEGF) on the TF activity of cultured bovine retinal endothelial cells was evaluated. RESULTS: The mean TF concentration in AH was higher in patients with active proliferative DR (244.5 pg/ml) than in either those with non-proliferative DR (132.4 pg/ml, P<0.05) or the control patients (114.9 pg/ml, P<0.01). The serum TF concentration in active proliferative DR patients (348.3 pg/ml) was significantly higher than in either non-proliferative DR patients, (235.9 pg/ml, P<0.01) or in the controls (223.5 pg/ml, P<0.01). However, the TF concentration of AH was not significantly correlated to that of the serum in each patient. The TF concentration in AH closely correlated with the grade of DR and protein concentration. VEGF increased the biological activity of TF in vitro. CONCLUSION: The origin of TF in AH, however, is still not clearly understood. Nonetheless, TF in AH directly reflects the severity of ocular diabetic change, and the present results indicate that TF indeed plays some role in the progression of DR.

Adult↗