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Biomedical subjects

H Sasaki

Publications and source records attributed to H Sasaki.

At least 109 records · Page 6Linked to original sources
PubMed2001

Controlled release and ocular absorption of tilisolol utilizing ophthalmic insert-incorporated lipophilic prodrugs.

To control ocular drug delivery, the O-butyryl ester prodrug of tilisolol (BUTL) and the O-palmitoyl ester prodrug of tilisolol (PalTL) were incorporated into an ophthalmic insert. The released TL from BUTL inserts and PalTL inserts in pH 7.4 phosphate-buffered saline until 5 h were approximately 25% and 3% of that from TL inserts, respectively. In addition, BUTL was also released from BUTL inserts. However, PalTL was not released from the PalTL insert. The release of drugs from TL inserts and BUTL inserts was little affected by the addition of bovine serum albumin (BSA) in pH 7.4 phosphate-buffered saline. In contrast, the release of drugs from PalTL inserts were enhanced by the addition of BSA. After application of TL, BUTL, and PalTL inserts to the rabbit eye, the aqueous humor concentration of TL was prolonged compared with TL instillation, and the plasma concentration of TL was much lower than that of TL instillation. The ratios of the area under the TL concentration-time curve (AUC) in the aqueous humor to AUC in the plasma (AUC(aqueous)/AUC(plasma)) after application of BUTL until 8 h were 3.1-fold and 3.8-fold higher than those of the TL insert and PalTL insert, respectively.

Absorption↗
PubMed2001

Effect of chronic stress on cholinergic transmission in rat hippocampus.

We previously demonstrated that chronic stress impaired prefrontal cortex-sensitive working memory, but not reference memory. Since the hippocampal cholinergic system is also involved in these memories, we examined the effects of chronic stress on cholinergic transmission in the rat hippocampus. A microdialysis study revealed that the stress did not affect the basal acetylcholine release, but enhanced the KCl-evoked response. These results suggest that cholinergic transmission in the chronically stressed hippocampus does not contribute to working memory impairment, but it may be involved in maintenance of reference memory.

Acetylcholine↗
PubMed2001

Tumor location and growth pattern correlate with genetic signature in oligodendroglial neoplasms.

Molecular genetic subsets of anaplastic oligodendroglioma behave in biologically distinct ways, in both their rates of growth and their responses to standard therapies. In a series of 64 cases, we evaluated whether allelic loss of chromosomal arms 1p and 19q, an early molecular event in the genesis of chemosensitive oligodendrogliomas, is related to tumor location and extent of tumor spread in the brain. We observed that tumor genotype was closely associated with tumor location (P < 0.001). Anaplastic oligodendrogliomas located in the frontal, parietal, and occipital lobes were significantly more likely to harbor allelic loss of chromosomal arms 1p and 19q than histologically indistinguishable tumors arising in the temporal lobe, insula, and diencephalon (P < 0.001). In addition, loss of heterozygosity for 1p and 19q was significantly associated with a bilateral pattern of growth (P = 0.037); all seven bilaterally distributed anaplastic oligodendrogliomas had 1p and 19q allelic loss. We conclude, therefore, that molecular subtypes of oligodendrogliomas may arise preferentially in certain lobes of the brain and have differential patterns of growth, with tumors having allelic loss of chromosomes 1p and 19q occurring most frequently in the frontal lobes and having a tendency for widespread growth across the midline. These findings encourage inquiries into the biological basis of such marked differences and already have implications for the current management of these neoplasms.

Adolescent↗
PubMed2001

Enzymatic properties of de novo-type mouse DNA (cytosine-5) methyltransferases.

We have purified GST-fused recombinant mouse Dnmt3a and three isoforms of mouse Dnmt3b to near homogeneity. Dnmt3b3, an isoform of Dnmt3b, did not have DNA methylation activity. Dnmt3a, Dnmt3b1 or Dnmt3b2 showed similar activity toward poly(dG-dC)-poly(dG-dC) for measuring de novo methylation activity, and toward poly(dI-dC)-poly(dI-dC) for measuring total activity. This indicates that the enzymes are de novo-type DNA methyltransferases. The enzyme activity was inhibited by NaCl or KCl at concentrations >100 mM. The kinetic parameter, K(m)(AdoMet), for Dnmt3a, Dnmt3b1 and Dnmt3b2 was 0.4, 1.2 and 0.9 microM when poly(dI-dC)-poly(dI-dC) was used, and 0.3, 1.2 and 0.8 microM when poly(dG-dC)-poly(dG-dC) was used, respectively. The K(m)(DNA) values for Dnmt3a, Dnmt3b1 and Dnmt3b2 were 2.7, 1.3 and 1.5 microM when poly(dI-dC)-poly(dI-dC) was used, and 3.5, 1.0 and 0.9 microM when poly(dG-dC)-poly(dG-dC) was used, respectively. For the methylation specificity, Dnmt3a significantly methylated CpG >> CpA. On the other hand, Dnmt3b1 methylated CpG > CpT >/= CpA. Immuno-purified Dnmt3a, Myc-tagged and overexpressed in HEK 293T cells, methylated CpG >> CpA > CpT. Neither Dnmt3a nor Dnmt3b1 methylated the first cytosine of CpC.

Binding Sites↗
PubMed2001

Genetic polymorphisms of IL-1beta and IL-1 receptor antagonist in association with multiple sclerosis in Japanese patients.

In the present study, we have investigated the association of specific polymorphisms of the interleukin (IL)-1beta and IL-1 receptor antagonist (ra) gene with both the susceptibility to and the clinical characteristics of multiple sclerosis (MS) in Japanese patients. We collected and analyzed DNA from 98 MS patients and 104 healthy controls for distribution of IL-1beta or IL-1ra polymorphisms. Our results show no significant differences in the distribution of the polymorphisms between MS patients and controls. Furthermore, no association was observed between IL-1beta or IL-1ra polymorphisms and clinical characteristics, such as age at disease onset, clinical course and severity. Together, our findings suggest that IL-1beta or IL-1ra gene polymorphisms may not be relevant in the susceptibility to MS or the clinical characteristics of Japanese patients with MS.

Adult↗
PubMed2001

Serum level of the periostin, a homologue of an insect cell adhesion molecule, as a prognostic marker in nonsmall cell lung carcinomas.

BACKGROUND: Periostin protein shares structural and sequence homology with fasciclin I, which is an insect adhesion molecule. Periostin has a typical signal peptide at the N-terminal end, which suggests that it is a secreted protein. Recently, the authors developed a novel sandwich chemiluminescence assay to determine serum concentrations of periostin. METHODS: The authors investigated the serum periostin level in lung carcinoma patients and attempted to determine the influence of serum periostin level on clinical outcome for patients with nonsmall cell lung carcinoma (NSCLC) who had undergone surgery between January 1994 and July 1996. Expression of periostin messenger RNA was also examined by in situ RNA hybridization for lung carcinomas. RESULTS: The periostin gene was shown to be highly expressed at the tumor periphery of lung carcinoma tissue but not within the tumor by in situ RNA hybridization. Serum periostin levels were not significantly different between the NSCLC patients (1142.1 +/- 89.2 ng/mL) and the normal control (962.0 +/- 118.6 ng/mL) (P = 0.2985). There was no relation between serum periostin level and gender, stage, bone metastasis, N status, or T status. However, the serum periostin levels of NSCLC patients had decreased significantly by 4 weeks after the resection of the tumor. The NSCLC patients with high periostin level (> 962 ng/mL) had significantly poorer survival than the patients with normal periostin level (P = 0.0406). Using the Cox proportional hazards regression model, the authors found that stage (P < 0.0001) and serum periostin level (P = 0.0226) were independent prognostic factors. CONCLUSIONS: The in situ RNA hybridization data from the current study suggested that expression of periostin may be involved in tumor invasionand that the serum periostin level may serve as a prognostic marker for NSCLC.

Adult↗
PubMed2001

Junctional adhesion molecule (JAM) binds to PAR-3: a possible mechanism for the recruitment of PAR-3 to tight junctions.

At tight junctions (TJs), claudins with four transmembrane domains are incorporated into TJ strands. Junctional adhesion molecule (JAM), which belongs to the immunoglobulin superfamily, is also localized at TJs, but it remains unclear how JAM is integrated into TJs. Immunoreplica electron microscopy revealed that JAM showed an intimate spatial relationship with TJ strands in epithelial cells. In L fibroblasts expressing exogenous JAM, JAM was concentrated at cell-cell adhesion sites, where there were no strand-like structures, but rather characteristic membrane domains free of intramembranous particles were detected. These domains were specifically labeled with anti-JAM polyclonal antibody, suggesting that JAM forms planar aggregates through their lateral self-association. Immunofluorescence microscopy and in vitro binding assays revealed that ZO-1 directly binds to the COOH termini of claudins and JAM at its PDZ1 and PDZ3 domains, respectively. Furthermore, another PDZ-containing polarity-related protein, PAR-3, was directly bound to the COOH terminus of JAM, but not to that of claudins. These findings led to a molecular architectural model for TJs: small aggregates of JAM are tethered to claudin-based strands through ZO-1, and these JAM aggregates recruit PAR-3 to TJs. We also discuss the importance of this model from the perspective of the general molecular mechanisms behind the recruitment of PAR proteins to plasma membranes.

Animals↗
PubMed2001

Structural conversion between open and closed forms of radixin: low-angle shadowing electron microscopy.

The function of ERM (ezrin/radixin/moesin) proteins as general cross-linkers between actin filaments and plasma membranes is regulated downstream of Rho, through the transition between active and inactive forms. To directly examine the conformational change between the active and inactive forms of ERM proteins, we applied low-angle rotary-shadowing electron microscopy to the radixin molecules, wild-type, T564A-non-phosphorylated-type, and T564E-phosphorylated-type, since most of the active forms are reportedly stabilized in cells by the C-terminal threonine phosphorylation. As a result, the T564A- and wild-type radixin molecules yielded the globular closed forms, approximately 8-14 nm in diameter, with some striations on their surfaces. In contrast, the T564E-radixin molecules tended to take elongated open forms, in which two globular structures measuring approximately 8 nm and approximately 5 nm in diameter were associated with both ends of the filamentous structures. The filamentous structure took either a approximately 20-25 nm-long straight course or a folded course. Taken together with the biochemical and the crystal structural results obtained to date, the closed and open forms represent the inactive and active forms of radixin as cross-linkers between actin filaments and plasma membranes.

Amino Acid Substitution↗
PubMed2001

Expression of the prothymosin alpha mRNA correlated with that of N-myc in neuroblastoma.

Neuroblastoma is the most common malignant solid cancers in early childhood. Overexpression of the proto-oncogene, N-myc, has been reported to be correlated with more malignant course of the disease. Prothymosin alpha, a cellular proliferation-associated gene, is reported to be a target of myc and elevated in several malignant cells and tissues. Expression of prothymosin alpha and N-myc messenger RNAs were evaluated by real-time reverse transcription polymerase chain reaction (RT-PCR) assay in 18 tumor samples from neuroblastoma using LightCycler. The data was analyzed in reference to clinicopathological factors. There was a tendency that higher prothymosin alpha transcripts levels in the tumor samples from younger patients (<1year.) when compared to the older group (>1 year.) (P=0.0845). There was no relationship between prothymosin alpha gene expression and gender (P=0.3029), mass screening case or not (P=0.3007), or stage. The prothymosin alpha mRNA expression levels were correlated with N-myc mRNA levels (P=0.006). Thus we suggest that prothymosin alpha plays an active role as a target of N-myc in neuroblastoma.

Age Factors↗
PubMed2001

p53 Pseudogene dating: identification of the origin of laboratory mice.

Mutations were accumulated with a wide variety in the p53 pseudogene of various wild mouse species and subspecies captured at different localities, as extensively observed in the exon 4 - exon 5 region. The rate of mutation accumulation in the mouse p53 pseudogene was estimated to be 1.4-2.1x10(-8) mutations/bp/year, which is 20-30 times faster than that of the functional p53 and makes the dating possible for the time range of 10(6) years or more. From comparison of the mutation spectrum, the origin of laboratory mice was identified to one of two M. m. domesticus groups.

Animals↗
PubMed2001

Hormone-specific combinations of isoforms of adenylyl cyclase and phosphodiesterase in the rat liver.

Since many isoforms of adenylyl cyclase and adenosine 3', 5'-monophosphate (cAMP) phosphodiesterase have been cloned, it is likely that receptors of each hormone have a specific combination of these isoforms. Types I, III and VIII adenylyl cyclases are reported to be stimulated by Ca(2+)-calmodulin, type I phosphodiesterase by Ca(2+)-calmodulin, but types IV and VII (cAMP-specific) phosphodiesterases by Co2+. In the present study, we examined different effects of Ca2+ and Co2+ on hormone-induced cAMP response in the isolated perfused rat liver.The removal of Ca2+ from the perfusion medium (0 mM CaCl(2 ) + 0.5 mM EGTA) did not affect glucagon (0.1 nM)-responsive cAMP but reduced secretin (1 nM)-, vasoactive intestinal polypeptide (VIP, 1-10 nM)- and forskolin (1 microM)-responsive cAMP considerably. The addition of 1 mM CoCl2 reduced glucagon- and secretin-responsive cAMP considerably, forskolin-responsive cAMP partly, did not affect 1 nM VIP-responsive cAMP, but enhanced 10 nM VIP-responsive cAMP. Forskolin- and VIP-responsive cAMP was greater in the combination (0 mM CaCl(2) + 0.5 mM EGTA + 3 mM CoCl2) than in the Ca(2+)-free perfusion alone. These results suggest that secretin, VIP1 and VIP2 receptors are linked to Ca(2+)-calmodulin-sensitive adenylyl cyclase; glucagon receptor to Ca(2+)-calmodulin-insensitive adenylyl cyclase; VIP1 receptor to Ca(2+)-calmodulin-dependent phosphodiesterase; glucagon, secretin and VIP2 receptors to cAMP-specific phosphodiesterase, respectively, in the rat liver.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2001

Conversion of zonulae occludentes from tight to leaky strand type by introducing claudin-2 into Madin-Darby canine kidney I cells.

There are two strains of MDCK cells, MDCK I and II. MDCK I cells show much higher transepithelial electric resistance (TER) than MDCK II cells, although they bear similar numbers of tight junction (TJ) strands. We examined the expression pattern of claudins, the major components of TJ strands, in these cells: claudin-1 and -4 were expressed both in MDCK I and II cells, whereas the expression of claudin-2 was restricted to MDCK II cells. The dog claudin-2 cDNA was then introduced into MDCK I cells to mimic the claudin expression pattern of MDCK II cells. Interestingly, the TER values of MDCK I clones stably expressing claudin-2 (dCL2-MDCK I) fell to the levels of MDCK II cells (>20-fold decrease). In contrast, when dog claudin-3 was introduced into MDCK I cells, no change was detected in their TER. Similar results were obtained in mouse epithelial cells, Eph4. Morphometric analyses identified no significant differences in the density of TJs or in the number of TJ strands between dCL2-MDCK I and control MDCK I cells. These findings indicated that the addition of claudin-2 markedly decreased the tightness of individual claudin-1/4-based TJ strands, leading to the speculation that the combination and mixing ratios of claudin species determine the barrier properties of individual TJ strands.

Amino Acid Sequence↗
PubMed2001

Combined effects of working environmental conditions in VDT work.

The combined effects of city noise and luminance of the computer display were evaluated from the changes in lymphocytes and mental activities of participants. Healthy male students were tested under the following four experimental conditions: (1) a calculating task on a video display terminal (VDT) with luminance of 90 cd m(-2) without city noise; (2) a calculating task on a VDT with luminance of 20 cd m(-2) without city noise; (3) a calculating task on a VDT with luminance of 90 cd m(-2) with city noise of 70 dB(A); and (4) a calculating task on a VDT with luminance of 20 cd m(-2) with city noise of 70 dB(A). A visual reaction test (VRT) was performed, and critical flicker fusion frequency (CFF), heart rate (HR), numbers of circulating white blood cells (WBCs), lymphocyte subsets and subjective symptoms of fatigue were measured (1) before; (2) just after; and (3) 30 min after each 60 min test. Subjective symptoms of fatigue significantly increased just after experiments conducted under the two noisy conditions. VRT and CFF showed significant changes in the case of the high-luminance display with noise. WBCs and neutrophils showed significant increases in the two quiet conditions. These results suggested that high luminance with noise had the most effect on subjective fatigue and mental activities.

Adult↗
PubMed2001

Feedback inhibition of amidophosphoribosyltransferase regulates the rate of cell growth via purine nucleotide, DNA, and protein syntheses.

To clarify the contributions of amidophosphoribosyltransferase (ATase) and its feedback regulation to the rates of purine de novo synthesis, DNA synthesis, protein synthesis, and cell growth, mutated human ATase (mhATase) resistant to feedback inhibition by purine ribonucleotides was engineered by site-directed mutagenesis and expressed in CHO ade (-)A cells (an ATase-deficient cell line of Chinese hamster ovary fibroblasts) and in transgenic mice (mhATase-Tg mice). In Chinese hamster ovary transfectants with mhATase, the following parameters were examined: ATase activity and its subunit structure, the metabolic rates of de novo and salvage pathways, DNA and protein synthesis rates, and the rate of cell growth. In mhATase-Tg mice, ATase activity in the liver and spleen, the metabolic rate of the de novo pathway in the liver, serum uric acid concentration, urinary excretion of purine derivatives, and T lymphocyte proliferation by phytohemagglutinin were examined. We concluded the following. 1) ATase and its feedback inhibition regulate not only the rate of purine de novo synthesis but also DNA and protein synthesis rates and the rate of cell growth in cultured fibroblasts. 2) Suppression of the de novo pathway by the salvage pathway is mainly due to the feedback inhibition of ATase by purine ribonucleotides produced via the salvage pathway, whereas the suppression of the salvage pathway by the de novo pathway is due to consumption of 5-phosphoribosyl 1-pyrophosphate by the de novo pathway. 3) The feedback inhibition of ATase is more important for the regulation of the de novo pathway than that of 5-phosphoribosyl 1-pyrophosphate synthetase. 4) ATase superactivity leads to hyperuricemia and an increased bromodeoxyuridine incorporation in T lymphocytes stimulated by phytohemagglutinin.

Adenosine Monophosphate↗