Search PubMed⌕ Search

Biomedical subjects

S Sakakibara

Publications and source records attributed to S Sakakibara.

At least 37 records · Page 2Linked to original sources
PubMed2000

Molecular design, synthesis, and hypoglycemic activity of a series of thiazolidine-2,4-diones.

A series of imidazopyridine thiazolidine-2,4-diones were designed and synthesized from their corresponding pyridines. These compounds represent conformationally restricted analogues of the novel hypoglycemic compound rosiglitazone (5). The series was evaluated for its effect on insulin-induced 3T3-L1 adipocyte differentiation in vitro and its hypoglycemic activity in the genetically diabetic KK mouse in vivo. The structure-activity relationships are discussed. On the basis of the in vivo potency, 5-[4-(5-methoxy-3-methyl-3H-imidazo[4, 5-b]pyridin-2-ylmethoxy)benzyl]thiazolidine-2,4-dione (19a) was selected as the candidate for further studies in a clinical setting.

3T3 Cells↗
PubMed2000

Energy confinement time and heat transport in initial neutral beam heated plasmas on the large helical device

The confinement characteristics of large net-current-free plasmas heated by neutral-beam injection have been investigated in the Large Helical Device (LHD). A systematic enhancement in energy-confinement times from the scaling derived from the medium-sized heliotron/torsatron experiments have been observed, which is attributed to the edge pedestal. The core confinement is scaled with the Bohm term divided by the square root of the gyro radii. The comparative analysis using a dimensionally similar discharge in the Compact Helical System indicates gyro-Bohm dependence in the core and transport improvement in the edge region of LHD plasmas.

Journal Article↗
PubMed2000

Structural basis for the biological activity of dendrotoxin-I, a potent potassium channel blocker.

A topochemical model to explain the biological activity of dendrotoxin-I (DTX-I), a potent blocker for potassium channels, was developed by searching common spatial arrangements of functionally important residues between DTX-I, alpha-dendrotoxin, dendrotoxin-K, BgK, ShK, and charybdotoxin. The first three are structurally and functionally related to one another, and specifically target to Kv1 type potassium channels. The last three are structurally unrelated to the first three but have the ability to displace (125)I-labeled dendrotoxins on the same types of potassium channels. In order to obtain the correct electronic surface potential, thought to be crucial for the DTX-I function, we determined the three-dimensional solution structure of DTX-I by nmr spectroscopy using its correct amino acid sequence recently determined by our group. The most interesting characteristic of our model is that DTX-I has two binding sites to potassium channels: one is the cationic domain made up of Lys residues at positions 5 in the 3(10)-helix, 28 and 29 in the beta-turn, and the other is the Lys19/Tyr17/Trp37 triad located in the antiprotease domain. The cationic domain and the triad are located at the opposite sides of the molecular structure and are separated by about 25 A between Lys29 Calpha and Tyr17 Calpha. The functional triad is characterized by three distances, d(1) approximately 7.5 A (Lys19 Calpha-the center of the Tyr17 aromatic ring), d(2) approximately 8.1 A (Lys19 Calpha-the center of the 6-membered ring of the Trp37 indole group), and d(3) approximately 7. 3 A (the center of the Tyr17 aromatic ring-the center of the 6-membered ring of the Trp37 indole group). This model should aid in the pharmaceutical design of peptide and nonpeptide drugs with potassium channel blocking potencies, as well as in understanding of the physiology, pharmacology, biochemistry, and structure-function analysis of potassium channels.

Amino Acid Sequence↗
PubMed2000

Differences in electroencephalogram power densities between genuine narcolepsy and secondary narcolepsy.

Diagnosing narcolepsy is not always simple. Some patients secondarily show narcoleptic tetrad through irregular sleep patterns or psychotic diseases. The power densities of daytime electroencephalograms in genuine narcolepsy and secondary narcolepsy were analysed and compared. Electroencephalogram power densities for a 6.5-h period after waking in genuine narcoleptic patients were lower than those of secondary narcoleptic patients in the 11.0-12.5 Hz bands. Arousal levels may be lower in genuine narcoleptic patients than in secondary narcoleptic patients. Spectral analysis may be useful in clarifying differences between the two groups.

Adolescent↗
PubMed2000

Autonomic nervous function after evening bright light therapy: spectral analysis of heart rate variability.

In order to investigate the effects of 5000 lx evening bright light on autonomic nervous function, a spectral analysis was used to assess heart rate variability in consecutive 5-min epochs just after 60 min of bright light therapy was given to 12 young women (range: 20-21 years of age). The study revealed that a low frequency band (LF) increased in bright light conditions (BL) in comparison with controlled conditions (CL). High frequency band (HF), LF:HF ratio and the coefficient of variance (CV R-R) were not significantly different between the two conditions. These results indicate that 5000 lx evening bright light may affect sympathetic nervous system activity in healthy women.

Adult↗
PubMed2000

Effect of short duration morning bright light in elderly men: sleep structure.

Sleep structure was measured in five healthy elderly men in their homes. The subjects were exposed to bright light (6000 lx) for 30 min in the morning or instructed to sit in front of a desktop lighting device without light. Relative to the control conditions, bright light exposure significantly decreased time in bed and the number of awakenings. Rapid eye movement sleep was significantly fragmented by stage 1 sleep in the control condition compared with the bright light condition. These findings indicate that a short duration of morning bright light changes sleep structure and is effective in maintaining sleep.

Aged↗
PubMed2000

Transcriptional regulation of the Kaposi's sarcoma-associated herpesvirus viral interferon regulatory factor gene.

The Kaposi's sarcoma-associated herpesvirus (KSHV), or human herpesvirus 8, open reading frame (ORF) K9 encodes a viral interferon regulatory factor (vIRF) that functions as a repressor for interferon-mediated signal transduction. Consequently, this gene is thought to play an important role in the tumorigenicity of KSHV. To understand the molecular mechanisms underlying vIRF expression, we studied the transcriptional regulation of this gene. Experiments using 5' rapid amplification of cDNA ends and primer extension revealed that vIRF had different transcriptional patterns during the latent and lytic phases. The promoter region of the minor transcript, which was mainly expressed in uninduced BCBL-1 cells, did not contain a canonical TATA box, but a cap-like element and an initiator element flanked the transcription start site. The promoter of the major transcript, which was mainly expressed in tetradecanoyl phorbol acetate-induced BCBL-1 cells, contained a canonical TATA box. A luciferase reporter assay using a deletion mutant of the vIRF promoter and a mutation in the TATA box showed that the TATA box was critical for the lytic activity of vIRF. The promoter activity in the latent phase was eight times stronger than that of the empty vector but was less than 10% of the activity in the lytic phase. Therefore, KSHV may use different functional promoter elements to regulate the expression of vIRF and to antagonize the cell's interferon-mediated antiviral activity. We have also identified a functional domain in the ORF 50 protein, an immediate-early gene product that is mainly encoded by ORF 50. The ORF 50 protein transactivated the vIRF and DNA polymerase promoters in BCBL-1, 293T, and CV-1 cells. Deleting one of its two putative nuclear localization signals (NLSs) resulted in failure of the ORF 50 protein to localize to the nucleus and consequently abrogated its transactivating activity. We further confirmed that the N-terminal region of the ORF 50 protein included an NLS domain. We found that this domain was sufficient to translocate beta-galactosidase to the nucleus. Analysis of deletions within the vIRF promoter suggested that two sequence domains were important for its transactivation by the ORF 50 protein, both of which included putative SP-1 and AP-1 binding sites. Competition gel shift assays demonstrated that SP-1 bound to these two domains, suggesting that the SP-1 binding sites in the vIRF promoter are involved in its transactivation by ORF 50.

Base Sequence↗
PubMed2000

Musashi1: an evolutionally conserved marker for CNS progenitor cells including neural stem cells.

In situ detection of neural progenitor cells including stem-like cells is essential for studying the basic mechanisms of the generation of cellular diversity in the CNS, upon which therapeutic treatments for CNS injuries, degenerative diseases, and brain tumors may be based. We have generated rat monoclonal antibodies (Mab 14H1 and 14B8) that recognize an RNA-binding protein Musashi1, but not a Musashi1-related protein, Musashi2. The amino acid sequences at the epitope sites of these anti-Musashi1 Mabs are remarkably conserved among the human, mouse, and Xenopus proteins. Spatiotemporal patterns of Musashi1 immunoreactivity in the developing and/or adult CNS tissues of frogs, birds, rodents, and humans indicated that our anti-Musashi1 Mabs reacted with undifferentiated, proliferative cells in the CNS of all the vertebrates tested. Double or triple immunostaining of embryonic mouse brain cells in monolayer cultures demonstrated strong Musashi1 expression in Nestin(+)/RC2(+) cells. The relative number of Musashi1(+)/Nestin(+)/RC2(+) cells increased fivefold when embryonic forebrain cells were cultured to form 'neurospheres' in which stem-like cells are known to be enriched through their self-renewing mode of growth. Nestin(+)/RC2(-) cells, which included Talpha1-GFP(+) neuronal progenitor cells and GLAST(+) astroglial precursor cells, were also Musashi1(+), as were GFAP(+) astrocytes. Young neurons showed a trace of Musashi1 expression. Cells committed to the oligodendroglial lineage were Musashi(-). Musashi1 was localized to the perikarya of CNS stem-like cells and non-oligodendroglial progenitor cells without shifting to cell processes or endfeet, and is therefore advantageous for identifying each cell and counting cells in situ.

Amino Acid Sequence↗
PubMed1999

Mammalian ELAV-like neuronal RNA-binding proteins HuB and HuC promote neuronal development in both the central and the peripheral nervous systems.

Hu proteins are mammalian embryonic lethal abnormal visual system (ELAV)-like neuronal RNA-binding proteins that contain three RNA recognition motifs. Although Drosophila ELAV is required for the correct differentiation and survival of neurons, the roles played by the Hu genes in the mammalian nervous system remain largely unknown. To explore the in vivo functions of mouse Hu proteins, we overexpressed them in rat pheochromocytoma PC12 cells, where they induced neuronal phenotype in the absence of nerve growth factor. We have characterized the functions of various forms of mHuB and mHuC bearing point mutations or deletions. Mutants of mHuC that had amino acid exchanges in the RNP1 domain of the first or second RNA recognition motifs (RRMs) lost biologic activity as well as RNA-binding activity. In addition, the mutants containing only the third RRM failed to induce the neuronal phenotype in PC12 cells and inhibited the biologic activity of cotransfected wild-type mHuB and mHuC, thus acting as a dominant-negative form. However, these mutants could not suppress the nerve growth factor-induced differentiation of PC12 cells. Further, we misexpressed wild-type and dominant-negative Hu in E9.5 mouse embryos, by using electroporation into the neural tube at the level of the rhombencephalon. mHuB and mHuC induced the ectopic expression of neuronal markers, whereas the dominant-negative forms of mHuB and mHuC suppressed the differentiation of central nervous system motor neurons. From these results, we suggest that Hu proteins are required for neuronal differentiation in the mammalian nervous system.

Animals↗
PubMed1999

Structure, backbone dynamics and interactions with RNA of the C-terminal RNA-binding domain of a mouse neural RNA-binding protein, Musashi1.

Musashi1 is an RNA-binding protein abundantly expressed in the developing mouse central nervous system. Its restricted expression in neural precursor cells suggests that it is involved in the regulation of asymmetric cell division. Musashi1 contains two ribonucleoprotein (RNP)-type RNA-binding domains (RBDs), RBD1 and RBD2. Our previous studies showed that RBD1 alone binds to RNA, while the binding of RBD2 is not detected under the same conditions. Joining of RBD2 to RBD1, however, increases the affinity to greater than that of RBD1 alone, indicating that RBD2 contributes to RNA-binding. We have determined the three-dimensional solution structure of the C-terminal RBD (RBD2) of Musashi1 by NMR. It folds into a compact alpha beta structure comprising a four-stranded antiparallel beta-sheet packed against two alpha-helices, which is characteristic of RNP-type RBDs. Special structural features of RBD2 include a beta-bulge in beta2 and a shallow twist of the beta-sheet. The smaller 1H-15N nuclear Overhauser enhancement values for the residues of loop 3 between beta2 and beta3 suggest that this loop is flexible in the time-scale of nano- to picosecond order. The smaller 15N T2 values for the residues around the border between alpha2 and the following loop (loop 5) suggest this region undergoes conformational exchange in the milli- to microsecond time-scale. Chemical shift perturbation analysis indicated that RBD2 binds to an RNA oligomer obtained by in vitro selection under the conditions for NMR measurements, and thus the nature of the weak RNA-binding of RBD2 was successfully characterized by NMR, which is otherwise difficult to assess. Mainly the residues of the surface composed of the four-stranded beta-sheet, loops and C-terminal region are involved in the interaction. The appearance of side-chain NH proton resonances of arginine residues of loop 3 and imino proton resonances of RNA bases upon complex formation suggests the formation of intermolecular hydrogen bonds. The structural arrangement of the rings of the conserved aromatic residues of beta2 and beta3 is suitable for stacking interaction with RNA bases, known to be one of the major protein-RNA interactions, but a survey of the perturbation data suggested that the stacking interaction is not ideally achieved in the complex, which may be related to the weaker RNA-binding of RBD2.

Amino Acid Sequence↗
PubMed1999

Chemical synthesis of proteins in solution.

Development of a novel strategy suitable for the solution synthesis of proteins is described, wherein the entire molecule is assembled from fully protected segments in the size range of about 10 residues. Each segment is designed so as to have a common structure of Boc-peptide-OPac (Pac: phenacyl) and all of the side-chain functional groups are protected by Bzl-based groups. New types of solvent systems are described for dissolving fully protected segments in which the segment condensation reactions in solution can be carried out smoothly. After removal of the Boc or Pac group, the segments are coupled together to obtain the entire sequence using the 1-ethyl-3-(3'-dimethylaminopropyl)-carbodiimide/3, 4-dihydro-3-hydroxy-4-oxo-1,2,3-benzotriazine method. The side-chain protecting groups are then removed by HF and the liberated peptide is subjected to folding reactions to obtain the native conformation. Applying the strategy, the 123-residue human angiogenin, the 121-residue human midkine, the 136-residue human pleiotrophin, and the 238-residue Aequoria green fluorescent protein were synthesized successfully.

Amino Acid Sequence↗
PubMed1999

Effects of morning bright light in healthy elderly women: effects on wrist activity.

To investigate the effects of 8000 lux morning bright light in the elderly, home-based motor activity on sleep was monitored for 5 days in 10 healthy women (mean age: 59.7 years old, range: 50-69 years old). The activity level and movement index on night 4 were significantly lower in bright light conditions, compared with the controlled condition. The activity level during the day was not significantly different between the two conditions. These results indicate that 8000 lux morning bright light improves sleep quality in healthy elderly women.

Aged↗
PubMed1999

Effects of morning bright light on sleep in healthy elderly women.

Subjective sleep feeling and polysomnography were measured in 10 elderly women to investigate the effects of 8000 lux morning bright light (BL) exposure. The profile of sleep feeling in the BL condition was better than in the control condition. The proportion of awakening time in the first one-third of night sleep decreased, and the amount of awakening time in the last one-third increased in BL condition. Daytime napping reduced in BL condition. These findings suggested the effectiveness of exposure to bright light on the improvement of sleep quality and daytime vigilance of healthy elderly women.

Aged↗
PubMed1999

Analysis of rapid eye movement periodicity in narcoleptics based on maximum entropy method.

We examined REM sleep periodicity in typical narcoleptics and patients who had shown signs of a narcoleptic tetrad without HLA-DRB1*1501/DQB1*0602 or DR2 antigens, using spectral analysis based on the maximum entropy method. The REM sleep period of typical narcoleptics showed two peaks, one at 70-90 min and one at 110-130 min at night, and a single peak at around 70-90 min during the daytime. The nocturnal REM sleep period of typical narcoleptics may be composed of several different periods, one of which corresponds to that of their daytime REM sleep.

Adult↗
PubMed1999

Gender difference of slow wave sleep in middle aged and elderly subjects.

Sleep EEG of eight healthy males and eight females aged 54-72 years were recorded at their homes. The electroencephalograms were visually scored and analyzed by spectral analysis using the FFT method. There were no significant differences in sleep parameters except for a higher percentage of stage 3+4 in females. The spectral power of the delta band EEG was classified into two frequencies: 0.5-2 Hz and 2-4 Hz. The total amount of the delta band spectral power through the night was significantly larger in females. Periodic fluctuation of delta band power was observed in females along with non-rapid eye movement-rapid eye movement cycles.

Aged↗
PubMed1999

Effects of moderately bright light on subjective evaluations in healthy elderly women.

Eight healthy elderly women aged 56-72 years (mean age: 67.4 years) participated in this study. They were exposed to moderately bright light (1000 lux) for 1h in the morning every 6 days in their homes. Moderately bright light improved self evaluations for alertness, mood, motivation, happiness, refreshment, concentration and appetite after the second exposure to the light. Sleep maintenance, anxiety and integrated sleep feeling also improved after the fourth exposure to the light. The phase of rectal temperature rhythm did not change in a moderately bright light condition. These results suggest that bright light influences sleep quality and self evaluations without changing the biological rhythm phase.

Adaptation, Psychological↗