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K Sakamoto

Publications and source records attributed to K Sakamoto.

At least 73 records · Page 4Linked to original sources
PubMed2001

Promoter analysis for daily expression of Drosophila timeless gene.

Drosophila circadian clock gene timeless (tim) displays circadian oscillation in its mRNA level, and such oscillation is transcriptionally regulated. The promoter region up to -756 of tim is suggested to promote the circadian mRNA expression, however, the role of the sequence upstream of tim promoter region in the transcriptional regulation is still unrevealed. We novelly isolated and determined tim 5'-flanking sequence -2764 to -757, and found a putative cAMP-response element, six regions of the half site for PAR-basic leucine zipper transcription factors and six nonpalindromic E-boxes. Our in vivo reporter assay showed that 966 bp of tim promoter region, including a palindromic CACGTG E-box and a half site of PAR-basic leucine zipper transcription factors, was minimally required for its daily mRNA expression. While, the deletion of the 5'-flanking region -1970 to -967 caused a slight decrease in the reporter mRNA levels. These results indicate that the 5'-flanking sequence upstream of the promoter region have a role in the daily regulation of tim mRNA expression in Drosophila.

Animals↗
PubMed2001

Late preconditioning in rat retina: involvement of adenosine and ATP-sensitive K(+) channel.

To determine whether stimulation of adenosine receptors and opening of ATP-sensitive K(+) channels were involved in the protective effect of late preconditioning in the rat retina, rats were subjected to 60 min of retinal ischemia, and ischemic preconditioning was achieved by applying 5 min of ischemia 24 h before 60 min of ischemia. In non-preconditioned rats, cell loss in the ganglion cell layer and thinning of the inner plexiform and inner nuclear layer were observed 7 days after 60 min of ischemia. Ischemic preconditioning completely prevented the retinal tissue damage and 8-phenyltheophylline or 5-hydroxydecanoate reduced the protective effect of ischemic preconditioning. Therefore, stimulation of adenosine receptors and opening of ATP-sensitive K(+) channels might be involved in the mechanism of histological protection by late preconditioning in the retina.

Adenosine Triphosphate↗
PubMed2001

Involvement of platelet-derived growth factor and histocompatibility of DRB 1 in chronic renal allograft nephropathy.

BACKGROUND: The role of activated T cells in graft arteriosclerosis, which is observed in chronic renal allograft nephropathy, and the involvement of major histocompatibility complex (MHC) incompatibility remain to be determined. We examined the effect of T lymphocytes that were obtained from renal transplant patients undergoing chronic rejection treated with cyclosporine (CsA) on platelet-derived growth factor (PDGF)-induced proliferation of cultured human vascular smooth muscle cells (SMC) and compared the proliferation activity of T lymphocytes with MHC incompatibility, especially DRB 1 mismatch. METHODS: Renal transplant patients with continued allograft function, who survived more than 1 year after transplantation, were recruited. Chronic rejection was documented by graft-biopsy findings together with increasing serum creatinine levels (10-20% per year). After the incubation of supernatant (conditioning medium) of cultured T cells from CsA-treated renal transplant patients with chronic rejection (n=18) and with normal renal function (n=14) as control, normal subjects (n=11) and chronic hemodialysis (HD) patients (n=5) with cultured SMC in the presence or absence of PDGF, DNA synthesis (3H-thymidine uptake) of SMC was examined. The in vitro effects of CsA on DNA synthesis of cultured SMC were also evaluated. RESULTS: The supernatant of cultured T cells from renal transplant patients with chronic rejection stimulated PDGF-induced DNA synthesis of SMC in a dose-dependent manner, showing significant enhancement as compared with control transplant patients, normal subjects, and chronic HD patients. The supernatant itself did not significantly stimulate DNA synthesis of SMC. No significant in vitro stimulation of CsA on DNA synthesis was observed. The supernatant of T cells obtained from recipients undergoing chronic rejection with two DRB 1 mismatches showed significantly higher enhanced activity of PDGF-induced DNA synthesis than the supernatant from those recipients without mismatch of DRB 1. On the other hand, no significant correlation of the enhanced activity by T cell supernatant to HLA A and B mismatch numbers was observed. CONCLUSIONS: Growth factor-promoting factors(s) derived from activated T cells associated with MHC class II DR expression, which promotes PDGF-induced proliferation of SMC, exists in renal transplant patients with chronic renal allograft nephropathy, and is probably involved in arteriosclerosis of the graft kidney.

Adult↗
PubMed2001

Different potentiating effects of imidapril and enalapril on kaolin-induced writhing reaction in mice.

Effects of the angiotensin-converting enzyme (ACE) inhibitors, imidapril and enalapril, on kaolin-induced writhing reaction, which is believed to be caused by bradykinin (BK), were examined in mice. The number of writhes was increased significantly by 200 microg/kg of imidapril and by 100 and 200 microg/kg of enalapril. The intensity of writhing reaction was significantly suppressed by 1,000 nmol/kg of icatibant, a selective bradykinin B2 receptor antagonist, in the imidapril-, but not in the enalapril-treated groups. These results suggest that the potentiating effect of enalapril on kaolin-induced writhing reaction is greater than that of imidapril. This might depend on the difference of their inhibitory effects on BK degradation.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed2001

Thermal effect in unoccupied molecular orbitals of C60 molecules adsorbed on a Si(001)-(2 x 1) surface studied by NEXAFS.

We report here the temperature-dependent unoccupied molecular orbitals (MO's) of C60 molecules adsorbed on a Si(001)-(2 x 1) surface measured using near edge x-ray absorption fine structure (NEXAFS). At 300 K, the NEXAFS spectrum reveals that the interaction between a 1.0 monolayer (ML) C60 film and a Si(001) surface is mainly the van der Waals force. After annealing the samples at 500 K, we observe an increment in the full-width at half-maximum of unoccupied MO's, which indicates the change of the interaction. Moreover, the lowest unoccupied molecular orbital (LUMO) shifts to the higher photon energy side and the intensity of the LUMO+1 relative to that of the LUMO+3 decreases in the NEXAFS spectrum. These results suggest that the strong interaction induced at 500 K has a covalent character, to which the LUMO+1 contributes.

Journal Article↗
PubMed2001

Lipoxygenase-5 is overexpressed in prostate adenocarcinoma.

BACKGROUND: Epidemiologic studies suggest that populations that consume large amounts of dietary fat are at greater risk for prostate carcinoma. Arachidonic acid and its precursor, linoleic acid, are major ingredients of animal fats and many vegetable oils that are used in the regions where prostate carcinoma is prevalent. The metabolism of arachidonic acid by either the cyclooxygenase pathway or the lipoxygenase pathway generates eicosanoids, which have been implicated in the pathogenesis of a variety of human diseases, including cancer, and are now believed to play important roles in tumor promotion, progression, and metastasis. Studying these pathways in specimens from patients with prostate carcinoma, the authors recently demonstrated the overexpression of cyclooxygenase-2 in prostate adenocarcinoma. In the current study, the authors report the overexpression of lipoxygenase-5 (5-LO) in samples from patients with prostate adenocarcinoma. METHODS: Employing 22 pair-matched benign and malignant tissue samples that were obtained from the same patients with prostate carcinoma, the expression of 5-LO was determined using reverse transcriptase-polymerase chain reaction, immunoblotting, and immunohistochemistry and by measuring the levels of 5-hydroxyeicosatetraenoic acid (5-HETE) by radioimmunoassay. RESULTS: The mean level of 5-LO mRNA was six-fold greater (P < 0.001) in malignant tissue compared with benign tissue. The immunoblot analysis demonstrated that, compared with benign tissue, 5-LO protein was overexpressed in 16 of 22 samples examined and was 2.6 fold greater (P < 0.001) in malignant tissue. Immunohistochemical studies further verified 5-LO up-regulation in malignant tissue that was not present in benign tissue. The levels of 5-HETE, which is a metabolic product of arachidonic acid, was found to be 2.2-fold greater (P < 0.001) in malignant tumor tissue compared with benign tissue. CONCLUSIONS: To the authors' knowledge, this is the first in vivo study showing overexpression of 5-LO in patients with prostate carcinoma. This study suggests that inhibitors of arachidonic acid pathway in general and selective 5-LO inhibitors in particular may be useful for prevention or therapy in patients with prostate carcinoma.

Adenocarcinoma↗
PubMed2001

Altered quinone biosynthesis in the long-lived clk-1 mutants of Caenorhabditis elegans.

Mutations in the clk-1 gene of Caenorhabditis elegans result in an extended life span and an average slowing down of developmental and behavioral rates. However, it has not been possible to identify biochemical changes that might underlie the extension of life span observed in clk-1 mutants, and therefore the function of CLK-1 in C. elegans remains unknown. In this report, we analyzed the effect of clk-1 mutation on ubiquinone (UQ(9)) biosynthesis and show that clk-1 mutants mitochondria do not contain detectable levels of UQ(9). Instead, the UQ(9) biosynthesis intermediate, demethoxyubiquinone (DMQ(9)), is present at high levels. This result demonstrates that CLK-1 is absolutely required for the biosynthesis of UQ(9) in C. elegans. Interestingly, the activity levels of NADH-cytochrome c reductase and succinate-cytochrome c reductase in mutant mitochondria are very similar to those in the wild-type, suggesting that DMQ(9) can function as an electron carrier in the respiratory chain. To test this possibility, the short side chain derivative DMQ(2) was chemically synthesized. We find that DMQ(2) can act as an electron acceptor for both complex I and complex II in clk-1 mutant mitochondria, while another ubiquinone biosynthesis precursor, 3-hydroxy-UQ(2), cannot. The accumulation of DMQ(9) and its use in mutant mitochondria indicate, for the first time in any organism, a link between the alteration in the quinone species used in respiration and life span.

Animals↗
PubMed2001

Solution properties of amino acid-type new surfactant.

The solution properties of an amino acid-type new surfactant, N-[3-lauryloxy-2-hydroxypropyl]-L-arginine L-glutamate (C12HEA-Glu), were examined by means of pK(a), surface tension, light scattering and fluorescence measurements. The dissociation state of C12HEA-Glu was changed by varying pH of the aqueous solution. The critical micelle concentration (cmc) of aqueous solution of C12HEA-Glu was lowest at pH 5.6 and the cmc increased with decreasing pH. The aggregation number of C12HEA-Glu micelles was largest at pH 5.6 and decreased with decreasing pH. The surface tension-concentration curve for C12HEA-Glu in water (non-buffered solution) showed a minimum. This is considered to be due to the coexistence of a trace species and a main species of C12HEA-Glu with various dissociation states since the pH of aqueous solution of C12HEA-Glu changes with the concentration of C12HEA-Glu. The micropolarity in the micelles of C12HEA-Glu was almost independent of pH, while the microfluidity in the micelles increased with increasing pH.

Journal Article↗
PubMed2001

An anthelmintic compound, nafuredin, shows selective inhibition of complex I in helminth mitochondria.

Infections with parasitic helminths are important causes of morbidity and mortality worldwide. New drugs that are parasite specific and minimally toxic to the host are needed to counter these infections effectively. Here we report the finding of a previously unidentified compound, nafuredin, from Aspergillus niger. Nafuredin inhibits NADH-fumarate reductase (complexes I + II) activity, a unique anaerobic electron transport system in helminth mitochondria, at nM order. It competes for the quinone-binding site in complex I and shows high selective toxicity to the helminth enzyme. Moreover, nafuredin exerts anthelmintic activity against Haemonchus contortus in in vivo trials with sheep. Thus, our study indicates that mitochondrial complex I is a promising target for chemotherapy, and nafuredin is a potential lead compound as an anthelmintic isolated from microorganisms.

Administration, Oral↗
PubMed2001

Surgical repair of double-orifice of the mitral valve in cases with an atrioventricular canal defects.

OBJECTIVE: A Double-orifice in the mitral valve is an uncommon congenital cardiac lesion which occurs as an isolated anomaly or in association with other cardiac malformation. This report deals with our surgical experience of a double-orifice of the mitral valve in cases with an atrioventricular canal defect. PATIENTS AND METHODS: From 1991 through 1999, ten patients were diagnosed to have a double-orifice of the mitral valve at Shizuoka Children's Hospital. Each patient had associated major cardiac malformations, among which atrioventricular canal defect underwent surgical management, with five of these undergoing complete correction with or without previous pulmonary artery banding. Of these 10, the five cases were enrolled in this study. Two of these had a complete type, and the other three had a partial type. The cleft in the left-sided atrioventricular valve was closed partially in four and left untouched in one. Bridging tissue, when present, was left intact. There was no regurgitation from any accessory orifice and no repair for an accessory orifice was needed. RESULT: There was no late death and no replacement of the valve with prosthesis. During follow-up ranging from 1 to 4 years, none of the patients developed severe stenosis or progressive regurgitation in the left-sided atrioventricular valve. CONCLUSION: Meticulous surgical management of a double-orifice in the mitral valve in association with atrioventricular canal defect an achieve an acceptable midterm result without developing severe dysfunction in the left-sided atrioventricular valve.

Endocardial Cushion Defects↗
PubMed2001

Receiver operating characteristic (ROC) analysis of images reconstructed with iterative expectation maximization algorithms.

PURPOSE: The quality of images reconstructed by means of the maximum likelihood-expectation maximization (ML-EM) and ordered subset (OS)-EM algorithms, was examined with parameters such as the number of iterations and subsets, then compared with the quality of images reconstructed by the filtered back projection method. METHODS: Phantoms showing signals inside signals, which mimicked single-photon emission computed tomography (SPECT) images of cerebral blood flow and myocardial perfusion, and phantoms showing signals around the signals obtained by SPECT of bone and tumor were used for experiments. To determine signals for recognition, SPECT images in which the signals could be appropriately recognized with a combination of fewer iterations and subsets of different sizes and densities were evaluated by receiver operating characteristic (ROC) analysis. The results of ROC analysis were applied to myocardial phantom experiments and scintigraphy of myocardial perfusion. RESULTS: Taking the image processing time into consideration, good SPECT images were obtained by OS-EM at iteration No. 10 and subset 5. CONCLULSION: This study will be helpful for selection of parameters such as the number of iterations and subsets when using the ML-EM or OS-EM algorithms.

Algorithms↗
PubMed2001

Urinary bromide levels probably dependent to intake of foods such as sea algae.

The purpose of the present study is to examine if the bromide (Br) level in urine (Br-U) varies substantially among adult general populations of either sex or of different dietary habits. For this purpose, morning spot urine samples (about 50 per group) were collected from six groups of people, i.e., one group each of men and women in a city in Japan (thus two groups in Japan) and one group each of women in two urban and two rural areas in central and northeast China (four groups in China). The samples were analyzed for Br by ECD-gas chromatography after derivatization to methyl bromide. Br-U essentially followed a normal distribution. Whereas there was only a marginal difference in Br-U between men (7.7 +/- 2.5 mg/L as an arithmetic mean and arithmetic standard deviation) and women (8.1 +/- 2.9 mg/L) in Japan, and no difference between the urban (2.3 +/- 0.8 mg/L) and rural women (2.6 +/- 1.1 mg/L) in China, the difference between Japanese (8.1 +/- 2.9 mg/L) and Chinese women (2.3 +/- 0.8 mg/L for two cities and 2.6 +/- 1.1 mg/L for two villages) was substantial. A literature survey suggested variation in dietary habits, especially that in sea algae intake, is a possible factor affecting the observed difference in Br-U between the two ethnic groups. Contribution of Br in cereals after fumigation with, e.g., methyl bromide, was also thought to be possible. The implication of difference in background Br-U levels is discussed in relation to biological monitoring of exposure to Br-containing industrial chemicals, such as 1- and 2-bromopropane.

Adult↗
PubMed2001

Assessment of left ventricular diastolic function from quantitative electrocardiographic-gated 99mTc-tetrofosmin myocardial SPET.

We have developed new software which can evaluate left ventricular (LV) diastolic functional parameters from a quantitative gated SPET (QGS) program. To examine its accuracy, we compared these findings with the LV diastolic functional indices obtained from gated radionuclide ventriculography (RNV). Twenty-four patients were selected for this study. Gated SPET with technetium-99m tetrofosmin was performed and the QGS program was used with a temporal resolution of 32 frames per R-R interval. The LV volume of each frame was calculated and four harmonics of Fourier series were retained for the analysis of the LV volume curve. From this fitted curve and its first derivative curve, we derived LV systolic functional indices, e.g. ejection fraction (EF), peak ejection rate (PER) and time to PER (TPER), as well as LV diastolic functional variables, e.g. 1/3 filling fraction (1/3 FF), peak filling rate (PFR) and time to PFR (TPFR). Within 5+/-2 days, gated RNV was performed and diastolic functional parameters were determined by the same method. No significant difference was observed between the variables calculated by gated SPET and by gated RNV. There was a good correlation between EF, PER, TPER, 1/3 FF, PFR and TPFR determined by these two methods (EF: r=0.95, P<0.0001; PER: r=0.87, P<0.0001; TPER: r=0.84, P<0.0001; 1/3 FF: r=0.87, P<0.0001; PFR: r=0.92, P<0.0001; TPFR: r=0.89, P<0.0001). Bland-Altman plots did not reveal any significant degree of directional measurement bias in any of the comparisons of gated SPET data and RNV data. It is concluded that, in addition to the conventional LV systolic functional indices, our program accurately provides LV diastolic functional parameters from gated SPET. Also, this program will be useful for detecting LV diastolic dysfunction in various cardiac diseases before LV systolic dysfunction becomes evident.

Diastole↗
PubMed2001

The repeated bout effect of reduced-load eccentric exercise on elbow flexor muscle damage.

In this study we investigated the extent to which an initial eccentric exercise consisting of two (2ECC) or six maximal eccentric actions (6ECC) of the elbow flexors would produce a similar effect to 24 maximal eccentric actions (24ECC), on a second bout of 24ECC performed 2 weeks later. Male students (n = 34) were assigned to one of three groups, and with their non-dominant arm performed either 2ECC (n = 12), 6ECC (n = 10), or 24ECC (n = 12) as a first bout of exercise. Two weeks later all groups performed 24ECC. Maximal isometric strength, range of motion, upper arm circumference, muscle soreness, plasma creatine kinase activity and myoglobin concentration were assessed before, immediately after, and for 4 days after exercise. Changes in all variables were compared between the bouts and groups by a two-way repeated measures analysis of variance. All variables changed significantly (P< 0.05) after 2ECC, 6ECC, and 24ECC, but the amount of change after 2ECC and 6ECC was significantly smaller (P<0.05) than both 6ECC and 24ECC, and 24ECC, respectively. After the second bout, the 6ECC and 24ECC groups showed a profound repeated bout effect, and no significant differences were found between the groups. All variables except muscle soreness were significantly (P< 0.05) larger after the second bout for the 2ECC group, however the changes observed after 24ECC were significantly smaller (P < 0.01) than those observed after the first 24ECC of the 24ECC group. These results suggest that it is not necessary to conduct a high number of eccentric actions in the first bout to elicit a repeated bout effect in a subsequent bout performed some time later.

Adolescent↗
PubMed2001

Physiological tremor of the upper limb segments.

The acceleration signal produced by physiological tremor from four different upper limb segments (the finger, hand, forearm and upper limb) was measured by an acceleration sensor during holding posture and was analyzed by power spectrum analysis. Two prominent peaks appeared in the power spectrum, suggesting that the tremor in the four different limb segments was composed of two frequency components. The frequency of one peak at 8-12 Hz did not change between the different limb segments, while the frequency of the other peak decreased with the increase in the mass of the limb segment. A model with two reflex pathways was developed for the tremor in the four limb segments. The model includes two reflex pathways, a spinal pathway and a supraspinal pathway. The theoretical values of the frequency and the amplitude of the tremor predicted by the model were in good agreement with the experimental results. Analysis of the model revealed that one of the two frequency components of the tremor was of spinal origin and was dependent upon the mass of the limb segment, and the second was of supraspinal origin, corresponding to the frequency at 8-12 Hz. In the normal subject, it is possible that the tremor could be used to evaluate the change in neuromuscular function produced by prolonged work involving just part of a limb segments (e.g., typing). It may also be used to evaluate the neuromuscular function of patients suffering from neurological diseases such as muscular dystrophy and Parkinson's disease.

Adult↗
PubMed2001

Long-term outcomes of immunosuppressed renal transplant recipients with malignancies.

This study analyzes ten cases of malignancy in a cohort of 183 renal transplant recipients, examining surgical management, postoperative immunosuppressive therapy, and long-term outcome. One of these ten patients, who had malignant lymphoma of the jejunum, died of the neoplasm, but the other nine patients did not show any signs of tumor recurrence after removal. All of these nine patients, except for one who had transplant renal cell carcinoma (RCC), received the same dose of immunosuppressive agents after surgery for the malignant disease. Seven patients were still alive at the time of this report, six of whom had good transplant renal function. The findings of this study indicate that even if immunosuppressive agents predispose to the development of cancer, it is not necessary to reduce their dose after removal of the tumor.

Adult↗
PubMed2001

Successful surgical treatment of renal cell carcinoma in a transplanted kidney from a cadaveric donor: report of a case.

Posttransplant renal cell carcinoma (RCC) usually arises in the native kidneys of renal transplant recipients rather than in the transplanted kidney. This report describes a case of RCC that developed in the transplanted cadaveric kidney in a 37-year-old male recipient 9 months after transplantation. An en bloc radical transplant nephrectomy was performed, and he has subsequently remained stable on hemodialysis for 3 years without any sign of recurrence.

Adenocarcinoma↗