Biomedical subjects
Publications and source records attributed to M Fukuda.
The two-neutron removal cross section (sigma(-2n)) and the longitudinal momentum distribution of 15B fragments from the breakup of 17B on 9Be were measured at 70A MeV. The distribution in the projectile rest frame is characterized by a FWHM of 80+/-10 MeV/c for 15B. The sigma(-2n) is found to be 0.22+/-0.05 b. A Glauber-type analysis of the data provides clear evidence of a two-neutron halo structure in 17B.
Electron beams with the lowest, normalized transverse emittance recorded so far were produced and confirmed in single-bunch-mode operation of the Accelerator Test Facility at KEK. We established a tuning method of the damping ring which achieves a small vertical dispersion and small x-y orbit coupling. The vertical emittance was less than 1% of the horizontal emittance. At the zero-intensity limit, the vertical normalized emittance was less than 2.8 x 10(-8) rad m at beam energy 1.3 GeV. At high intensity, strong effects of intrabeam scattering were observed, which had been expected in view of the extremely high particle density due to the small transverse emittance.
We conducted a phase I study of irinotecan (CPT-11) and cisplatin with concurrent split-course radiotherapy in limited-disease small-cell lung cancer (LD-SCLC). This study aimed to determine the maximum tolerated dose (MTD) and dose-limiting toxicity (DLT) of this therapy. Four chemotherapy cycles of CPT-11 (days 1, 8 and 15) and cisplatin (day 1) were repeated every 28 days. Radiotherapy of 2 Gy/day commenced on day 2 of each chemotherapy cycle with 20 Gy administered from the first to the third cycles (a total of 60 Gy). 17 patients were enrolled at three dose levels (CPT-11/cisplatin: 40/60, 50/60 and 60/60 mg/m(2)), and 16 were evaluable for toxicity and outcome. 2 of 4 patients at 60/60 mg/m(2) refused continuation of therapy because of general fatigue, and the relative dose intensity of CPT-11 at 50/60 mg/m(2) was approximately 50%. These levels were considered as the MTD. Tumour responses included four complete responses (CR), 11 partial responses (PR) and one no change (NC), and the overall response rate was 93.8% (95% confidence interval: (CI) 71.7-98.9%). This combined modality is tolerable, and CPT-11/cisplatin of 40/60 mg/m(2) in this modality is recommended for phase II study.
We conducted a phase I study of paclitaxel and irinotecan (CPT-11) in advanced non-small cell lung cancer (NSCLC). This study aimed to determine the maximum tolerated doses (MTD). The pharmacokinetics of CPT-11 and its major active metabolite, SN-38, were also analysed. Patients received paclitaxel (day 1) followed by CPT-11 (days 1, 8 and 15), in a 4-week cycle, and paclitaxel and CPT-11 were escalated from 120 and 40 mg/m(2), respectively. 28 patients were enrolled, who were evaluated for toxicity. 2 of 6 patients at 210 mg/m(2) paclitaxel and 50 mg/m(2) CPT-11, and 2 of 4 at 180 and 60 mg/m(2) developed dose-limiting toxicity (DLT) (neutropenia, fever, neurotoxicity and diarrhoea). The area under the plasma concentration-time curve (AUC) of CPT-11 on day 1 was significantly higher than that on days 8 or 15 at each dose level (P=0.002). The AUC of SN-38 on day 1 was significantly increased using paclitaxel doses >or=150 mg/m(2). A preceding paclitaxel administration changed the pharmacokinetics of CPT-11 and SN-38. However, the toxicity was tolerable. Paclitaxel 180 mg/m(2) and CPT-11 50 mg/m(2) were the recommended doses for further phase II study of this combination.
To investigate further the pharmacological mechanism of an anti-migraine drug, sumatriptan, a 5-HT1B/1D receptor agonist, we studied its effect on the cerebral circulation in seven anaesthetized rats, particularly during hypercapnia. After injection of 0.6 or 6.0 microg/kg sumatriptan succinate, no significant change in cerebral blood flow (CBF) was observed either in the striatum or in the parietal cortex. The increase in CBF both in the parietal cortex and the striatum during 5% CO2 inhalation was significantly less when sumatriptan succinate 6.0 microg/kg was injected. Sumatriptan appeared to have a vasoconstrictor effect on the relaxed vessels by CO2 inhalation. This mechanism might be attributable to vasoconstriction through activation of 5-HT1B receptors located in the vascular smooth muscle rather than 5-HT1B receptors in the vascular adventitia.
This study examined the characteristics and outcome of patients undergoing partial inferior turbinectomy during secondary alveolar bone grafting. Thirty-three of 55 patients with cleft lip and palate or cleft lip and alveolus who underwent secondary alveolar bone grafting concurrently received partial inferior turbinectomy to ensure that the height of the nasal floor was similar on the cleft side and non-affected side. At the time of surgery, patients who underwent turbinectomy were significantly older than those who did not undergo the procedure. The proportion of patients who underwent turbinectomy was significantly higher among patients with cleft lip and palate than among those with cleft lip and alveolus. These differences apparently reflected the developmental stage of the inferior turbinate and the relative severity of alveolar and palatal defects. In most patients who underwent partial inferior turbinectomy, postoperative X-ray films revealed excellent bone formation at the graft site. Our findings suggest that partial inferior turbinectomy during secondary alveolar bone grafting is a very useful procedure that facilitates dissection to the height of the nasal floor, reconstruction of the mucosal nasal floor, and formation of a sufficient bone bridge. It also promotes alveolar cleft closure, especially in patients with wide bone defects.
In this report, we describe a novel concept of extramembrane control of channel peptide assembly and the eventual channel current modulation. Alamethicin is a peptide antibiotic, which usually forms ion channels in various association states. By introducing an extramembrane leucine zipper segment (Alm-LeuZ), the association number of alamethicin was effectively controlled to produce a single predominant channel open state. The assembly was estimated to be a tetramer, by comparison of the channel conductance with that of the template-assembled Alm-LeuZ tetramer, which was prepared by the conjugation of a maleimide-functionalized peptide template with cysteine-derivatized Alm-LeuZ segments. Employment of an extramembrane segment of a random conformation provided higher levels of channel conductance. The result exemplified the possibility of channel current control by a conformational switch of the extramembrane segments.
OBJECTIVE: To assess the effects of levodopa on resting-state brain metabolism in PD. BACKGROUND: In previous studies the authors used [18F] fluorodeoxyglucose (FDG) and PET to quantify regional metabolic abnormalities in PD. They found that this disease is characterized reproducibly by a specific abnormal PD-related pattern (PDRP). In this study the authors used IV levodopa infusion to quantify the effects of dopamine replacement on regional metabolism and PDRP network activity. They tested the hypothesis that clinical response to dopaminergic therapy correlates with these metabolic changes. METHODS: The authors used FDG/PET to measure resting-state regional brain metabolism in seven patients with PD (age, 59.4 +/- 4.2 years; Hoehn and Yahr stage, 1.9 +/- 0.7, mean +/- SD); subjects were scanned both off levodopa and during an individually titrated constant-rate IV levodopa infusion. The authors used statistical parametric mapping to identify significant changes in regional brain metabolism that occurred with this intervention. They also quantified levodopa-induced changes in PDRP expression. Metabolic changes with levodopa correlated with clinical improvement as measured by changes in Unified PD Rating Scale (UPDRS) motor scores. RESULTS: Levodopa infusion improved UPDRS motor ratings (30.6% +/- 12.0%, p < 0.002) and significantly decreased regional glucose metabolism in the left putamen, right thalamus, bilateral cerebellum, and left primary motor cortex (p < 0.001). Changes in pallidal metabolism correlated significantly with clinical improvement in UPDRS motor ratings (p < 0.01). Levodopa infusion also resulted in a significant (p = 0.01) decline in PDRP expression. The changes in PDRP activity mediated by levodopa correlated significantly with clinical improvement in UPDRS motor ratings (r = -0.78, p < 0.04). CONCLUSION: Levodopa reduces brain metabolism in the putamen, thalamus, and cerebellum in patients with PD. Additionally, levodopa reduces PD-related pattern activity, and the degree of network suppression correlates with clinical improvement. The response to dopaminergic therapy in Patients with PD may be determined by the modulation of cortico-striato-pallido-thalamocortical pathways.
B/K protein belongs to a family of C-terminal-type (C-type) tandem C2 proteins that contain two C2 Ca(2+)-binding motifs at the C-terminus. Although other C-type tandem C2 proteins have been found to have a unique N-terminal domain that is involved in membrane anchoring (e.g. synaptotagmin) or specific ligand binding (e.g. rabphilin-3A and Doc2), no research has been conducted on the function of the N-terminal domain of B/K protein. In this study we showed that despite lacking a transmembrane domain, both native and recombinant B/K proteins are tightly bound to the membrane fraction, which was completely resistant to 0.1 M Na(2)CO(3), pH 11, or 1 M NaCl treatment. Deletion and mutation analyses indicated that the cysteine cluster at the N-terminal domain (consisting of seven cysteine residues, Cys-19, Cys-23, Cys-26, Cys-27, Cys-30, Cys-35 and Cys-36) is essential for the membrane localization of B/K protein. When wild-type B/K was expressed in PC12 cells, B/K proteins were localized mainly in the perinuclear region (trans-Golgi network), whereas mutant B/K proteins carrying Cys-to-Ala substitutions were present in the cytosol. Based on our findings, we propose that the N-terminal domain of B/K protein contains a novel cysteine-based protein motif that may allow B/K protein to localize in the trans-Golgi network.
A recent report based on the results of 2 epidemiological studies, the Etude Cas-Temoin de l'Infarctus Myocarde (ECTIM) and the Glasgow Heart Scan Study, revealed that a G/T polymorphism with an amino acid substitution (Lys-->Asn) at codon 198 in exon 5 of the endothelin-1 gene (ET-1) is associated with blood pressure in overweight people. They suggested that G/T polymorphism of ET-1 strongly interacted with body mass index (BMI) in the determination of BP levels. To examine interaction among G/T polymorphism of ET-1, BMI, and BP, we performed an association study in a general Japanese population. Subjects (n=1250) were recruited from Ohasama, a cohort in a rural community of northern Japan. DNA was extracted from buffy coat of participants, and G/T polymorphism of ET-1 was determined by the TaqMan probe polymerase chain reaction method, a powerful tool for semiautomatic genotype determination of a large number of samples. Frequency of T (Asn 198) allele in Japanese (27%) was slightly but significantly higher than in whites (24%). Baseline characteristics (age, BMI, systolic and diastolic BP, and antihypertensive treatment) of all subjects were not significantly different according to the genotype of G/T polymorphism. However, in obese subjects (> or =25 kg/m(2)) diastolic BPs were significantly associated with G/T polymorphism of ET-1. After adjustment for confounding factors, significant association remained; for overweight subjects, diastolic BP level in those with T allele (GT + TT) was 1.8 mm Hg (P=0.04) higher than in those with GG genotype. That similar results were obtained from subjects of different races suggests that the Lys198Asn polymorphism of ET-1 is involved in determination of BP levels in obese subjects.
The recent development of endothelin-1 (ET-1) antagonists and their potential use in the treatment of human disease raises questions as to the role of ET-1 in the pathophysiology of such cardiovascular ailments as hypertension, heart failure, renal failure and atherosclerosis. It is still unclear, for example, whether activation of an endogenous ET-1 system is itself the primary cause of any of these ailments. In that context, the phenotypic manifestations of chronic ET-1 overproduction may provide clues about the tissues and systems affected by ET-1. We therefore established two lines of transgenic mice overexpressing the ET-1 gene under the direction of its own promoter. These mice exhibited low body weight, diminished fur density and two- to fourfold increases in the ET-1 levels measured in plasma, heart, kidney and aorta. There were no apparent histological abnormalities in the visceral organs of young (8 weeks old) transgenic mice, nor was their blood pressure elevated. In aged (12 months old) transgenic mice, however, renal manifestations, including prominent interstitial fibrosis, renal cysts, glomerulosclerosis and narrowing of arterioles, were detected. These pathological changes were accompanied by decreased creatinine clearance, elevated urinary protein excretion and salt-dependent hypertension. It thus appears that mild, chronic overproduction of ET-1 does not primarily cause hypertension but triggers damaging changes in the kidney which lead to the susceptibility to salt-induced hypertension.
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We examined the fine structure of the type I signal-anchor sequence of synaptotagmin II, which has a 60-residue N-terminal domain followed by a hydrophobic region (H-region), focusing on the hinge region between the N-terminal and the H-regions. It was found that the charged or highly polar residues support the translocation of the N-terminal domain through the endoplasmic reticulum membrane at specific positions in the hinge. The residue requirement correlated with the turn propensity scale for transmembranes. It is suggested that a certain conformation, likely helical hairpin, in the hinge is critical for N-terminal domain translocation.
A series of lactosaminylated oligosaccharides found in mucin type O-glycans was synthesized using a generalized block strategy. The synthesis involved the addition of a protected lactosamine donor to a partially protected T-disaccharide derivative. The nonreducing galactose residues of the deblocked oligosaccharide products could be removed by beta-galactosidase from jack bean to produce the corresponding GlcNAc terminated compounds. A series of tri- to hexasaccharides was thus efficiently produced.
GAP1, one of the Ras GTPase-activating protein families, includes four distinct genes (GAP1(m), GAP1(IP4BP), MRASAL (murine Ras GTPase-activating-like), and KIAA0538). It contains an amino-terminal tandem C2 domain, a GAP-related domain, and a carboxyl-terminal pleckstrin homology (PH) domain. Although the PH domains of GAP1(m) and GAP1(IP4BP) have been shown to be essential for membrane targeting via binding of specific phospholipids, little is known about the functions of the PH domains of MRASAL and KIAA0538. Herein, we show that the PH domain of MRASAL has binding activity toward PI(4,5)P(2) and PI(3,4,5)P(3), while the PH domain of KIAA0538 does not bind these phospholipids due to an amino acid substitution at position 592 (Leu-592). Mutation of the corresponding position of MRASAL (Arg-to-Leu substitution at position 591) resulted in loss of the phospholipid binding activity. MRASAL proteins were localized at the plasma membrane in NIH3T3 cells, and this plasma membrane association was unchanged even after cytochalasin B or wortmannin treatment. By contrast, KIAA0538 and MRASAL (R591L) proteins were present in the cytosol. Our data indicate that the distinct phosphoinositide binding specificity of the PH domain is attributable to the distinct subcellular localization of the GAP1 family.
BACKGROUND: Adrenomedullin (AM) is a vasodilating peptide involved in the regulation of circulatory homeostasis and in the pathophysiology of certain cardiovascular diseases. Levels of AM are markedly increased in the fetoplacental circulation during pregnancy, although its function there remains unknown. To clarify the physiological functions of AM, we chose a gene-targeting strategy in mice. METHODS AND RESULTS: Targeted null mutation of the AM gene is lethal in utero: the mortality rate among AM(-/-) embryos was >80% at E13.5. The most apparent abnormality in surviving AM(-/-) embryos at E13.5 to E14.0 was severe hemorrhage, readily observable under the skin and in visceral organs. Hemorrhage was not detectable at E12.5 to E13.0, although the yolk sac lacked well-developed vessels. Electron microscopic examination showed endothelial cells to be partially detached from the basement structure at E12.5 in vitelline vessels and hepatic capillaries, which allowed efflux of protoerythrocytes through the disrupted barrier. The basement membrane was not clearly recognizable in the aorta and cervical artery, and the endothelial cells stood out from the wall of the lumen, only partially adhering to the basement structure. AM(+/-) mice survived to adulthood but exhibited elevated blood pressures with diminished nitric oxide production. CONCLUSIONS: AM is indispensable for the vascular morphogenesis during embryonic development and for postnatal regulation of blood pressure by stimulating nitric oxide production.
Polysialic acid (PSA), which is abundantly expressed in the embryonic brain, plays important roles in neural development and plasticity. PSA is also expressed in tumors of neural crest origin such as neuroblastoma. However, the biologic significance of PSA in these tumors has not been elucidated. In this study, we examined the expression of PSA as well as 2 polysialyltransferases, PST and STX, in various tumor cell lines. PST and STX were simultaneously expressed in all the tumor cells positive for PSA. However, even in the tumor cells negative for PSA, they expressed PSA after transfection of neural cell adhesion molecule (NCAM) cDNA when these cells expressed PST, suggesting that the presence of NCAM was critical for PSA expression. To determine the role of PSA in tumor growth and development, we established tumor sublines expressing or lacking PSA from PC-14 or NCI-H146 cells. Although significant differences of growth rates between the PSA-positive and -negative tumor cells were not detected in vitro, the PSA-positive tumor cells hardly produced detectable tumors when injected into nude mice subcutaneously or intravenously. In addition, the PSA-positive tumor cells adhered less to a basement membrane matrix Matrigel than did the PSA-negative tumor cells. These results altogether suggested that PSA significantly reduced tumor formation in the transplanted xenografts through attenuation of cell-cell or cell-matrix interactions by its large, negatively charged glycans in this particular animal model system.
Poly-alpha2,8-sialic acid (PSA) has been implicated in numerous normal and pathological processes, including development, neuronal plasticity, and tumor metastasis. We report that cell surface PSA expression can be reversibly inhibited by a small molecule, N-butanoylmannosamine (ManBut). Inhibition occurs through a metabolic mechanism in which ManBut is converted to unnatural sialic acid derivatives that effectively act as chain terminators during cellular PSA biosynthesis. N-Propanoylmannosamine (ManProp), which differs from ManBut by a single methylene group, did not inhibit PSA biosynthesis. Modulation of PSA expression by chemical means has a role complementary to genetic and biochemical approaches in the study of complex PSA-mediated events.