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S Yokota

Publications and source records attributed to S Yokota.

At least 55 records · Page 3Linked to original sources
PubMed2001

Autophagosome requires specific early Sec proteins for its formation and NSF/SNARE for vacuolar fusion.

Double membrane structure, autophagosome, is formed de novo in the process of autophagy in the yeast Saccharomyces cerevisiae, and many Apg proteins participate in this process. To further understand autophagy, we analyzed the involvement of factors engaged in the secretory pathway. First, we showed that Sec18p (N-ethylmaleimide-sensitive fusion protein, NSF) and Vti1p (soluble N-ethylmaleimide-sensitive fusion protein attachment protein, SNARE), and soluble N-ethylmaleimide-sensitive fusion protein receptor are required for fusion of the autophagosome to the vacuole but are not involved in autophagosome formation. Second, Sec12p was shown to be essential for autophagy but not for the cytoplasm to vacuole-targeting (Cvt) (pathway, which shares mostly the same machinery with autophagy. Subcellular fractionation and electron microscopic analyses showed that Cvt vesicles, but not autophagosomes, can be formed in sec12 cells. Three other coatmer protein (COPII) mutants, sec16, sec23, and sec24, were also defective in autophagy. The blockage of autophagy in these mutants was not dependent on transport from endoplasmic reticulum-to-Golgi, because mutations in two other COPII genes, SEC13 and SEC31, did not affect autophagy. These results demonstrate the requirement for subgroup of COPII proteins in autophagy. This evidence demonstrating the involvement of Sec proteins in the mechanism of autophagosome formation is crucial for understanding membrane flow during the process.

Adenosine Triphosphatases↗
PubMed2001

[Clinical study of 33 children with systemic pneumococcal infections].

We retrospectively analyzed 33 cases of children with systemic pneumococcal infections, 22 bacteremia and 11 meningitis, diagnosed and treated in Asahi General Hospital between 1985 and 1999. The median age at diagnosis was 15 months old and the incidence peaked in infants between 7 and 24 months of age (57.6%). Two cases showed low serum IgG2 levels. Fever was a common symptom in all cases and 13 (39.4%) presented convulsions. Meningitis [median age: 10 months] tended to occur, if not significant, in younger children than bacteremia [16 months]. All cases of meningitis were diagnosed 12 hours or later after the onset of fever, though 54.5% of the cases of bacteremia were diagnosed within 12 hours. The cases of meningitis showed statistically lower white blood cell counts [median: 9,700/mm3] and higher CRP levels [median: 25.6 mg/dl] than those of bacteremia [23,900/mm3 and 4.2 mg/dl, respectively] at diagnosis. Although all cases of bacteremia were cured without any sequelae by antibiotic treatment, 3 cases (27.3%) of meningitis died and 4 (36.4%) developed severe neurological sequelae. Our findings suggest that the putative pathogenesis by which pneumococcal meningitis results from bacteremia and, taking in the account of the poor outcome of meningitis, may justify the early antibiotic intervention against pneumococcal bacteremia.

Bacteremia↗
PubMed2001

Clinical evaluation of anti-tuberculous glycolipid immunoglobulin G antibody assay for rapid serodiagnosis of pulmonary tuberculosis.

Previously we reported the development of a highly sensitive enzyme-linked immunosorbent assay specific for anti-tuberculous glycolipid (anti-TBGL) for the rapid serodiagnosis of tuberculosis. In this study, the usefulness of an anti-TBGL antibody assay kit for rapid serodiagnosis was evaluated in a controlled multicenter study. Antibody titers in sera from 318 patients with active pulmonary tuberculosis (216 positive for Mycobacterium tuberculosis in smear and/or culture tests and 102 smear and culture negative and clinically diagnosed), 58 patients with old tuberculosis, 177 patients with other respiratory diseases, 156 patients with nonrespiratory diseases, and 454 healthy subjects were examined. Sera from 256 younger healthy subjects from among the 454 healthy subjects were examined as a control. When the cutoff point of anti-TBGL antibody titer was determined as 2.0 U/ml, the sensitivity for active tuberculosis patients was 81.1% and the specificity was 95.7%. Sensitivity in patients with smear-negative and culture-negative active pulmonary tuberculosis was 73.5%. Even in patients with noncavitary minimally advanced lesions, the positivity rate (60.0%) and the antibody titer (4.6 +/- 9.4 U/ml) were significantly higher than those in the healthy group. These results indicate that this assay using anti-TBGL antibody is useful for the rapid serodiagnosis of active pulmonary tuberculosis.

Antibodies, Bacterial↗
PubMed2001

Morphological changes and cellular dynamics of oligodendrocyte lineage cells in the developing vertebrate central nervous system.

Oligodendrocyte precursor cells (OPCs) originate in multiple restricted regions of the developing central nervous system (CNS). Here, we focus on morphological changes of oligodendrocyte lineage cells and their cellular dynamics including cell motility and proliferation. Morphological studies with molecular markers for OPCs suggest distinct spatiotemporal patterns of OPC migration in vivo, which are directly demonstrated by application of exogenous fluorescent markers to OPCs. Extensive proliferation of OPCs in the CNS parenchyma is also demonstrated by pulse labeling of the cells with bromodeoxyuridine. The results strongly suggest that oligodendrocyte lineage cells are highly motile and actively proliferate with an elongated morphology. These data provide insights into the potential molecular mechanisms of OPC dispersal throughout the CNS.

Animals↗
PubMed2001

The role of 15-lipoxygenase in disruption of the peroxisomal membrane and in programmed degradation of peroxisomes in normal rat liver.

Our earlier electron microscopic observations revealed that prolonged exposure of glutaraldehyde-fixed rat liver sections to buffer solutions induced focal membrane disruptions of peroxisomes with catalase diffusion as shown cytochemically. Recently, it was suggested that 15-lipoxygenase (15-LOX) might be involved in natural degradation of membrane-bound organelles in reticulocytes by integrating into and permeabilizing the organelle membranes, leading to the release of matrix proteins. We have now investigated the localization of 15-LOX and its role in degradation of peroxisomal membranes in rat liver. Aldehyde-fixed liver slices were incubated in a medium that conserved the 15-LOX activity, consisting of 50 mM HEPES-KOH buffer (pH 7.4), 5 mM mercaptoethanol, 1 mM MgCl(2), 15 mM NaN(3), and 0.2 M sucrose, in presence or absence of 0.5-0.05 mM propyl gallate or esculetin, two inhibitors of 15-LOX. The exposure of aldehyde-fixed liver sections to this medium induced focal disruptions of peroxisome membranes and catalase diffusion around some but not all peroxisomes. This was significantly reduced by both 15-LOX inhibitors, propyl gallate and esculetin, with the latter being more effective. Double immunofluorescent staining for 15-LOX and catalase revealed that 15-LOX was co-localized with catalase in some but not all peroxisomes in rat hepatocytes. By postembedding immunoelectron microscopy, gold labeling was localized on membranes of some peroxisomes. These observations suggest that 15-LOX is involved in degradation of peroxisomal membranes and might have a physiological role in programmed degradation and turnover of peroxisomes in hepatocytes. (J Histochem Cytochem 49:613-621, 2001)

Animals↗
PubMed2001

Localization of cytosolic NADP-dependent isocitrate dehydrogenase in the peroxisomes of rat liver cells: biochemical and immunocytochemical studies.

Two types of NADP-dependent isocitrate dehydrogenases (ICDs) have been reported: mitochondrial (ICD1) and cytosolic (ICD2). The C-terminal amino acid sequence of ICD2 has a tripeptide peroxisome targeting signal 1 sequence (PTS1). After differential centrifugation of the postnuclear fraction of rat liver homogenate, approximately 75% of ICD activity was found in the cytosolic fraction. To elucidate the true localization of ICD2 in rat hepatocytes, we analyzed the distribution of ICD activity and immunoreactivity in fractions isolated by Nycodenz gradient centrifugation and immunocytochemical localization of ICD2 antigenic sites in the cells. On Nycodenz gradient centrifugation of the light mitochondrial fraction, ICD2 activity was distributed in the fractions in which activity of catalase, a peroxisomal marker, was also detected, but a low level of activity was also detected in the fractions containing activity for succinate cytochrome C reductase (a mitochondrial marker) and acid phosphatase (a lysosomal marker). We have purified ICD2 from rat liver homogenate and raised a specific antibody to the enzyme. On SDS-PAGE, a single band with a molecular mass of 47 kD was observed, and on immunoblotting analysis of rat liver homogenate a single signal was detected. Double staining of catalase and ICD2 in rat liver revealed co-localization of both enzymes in the same cytoplasmic granules. Immunoelectron microscopy revealed gold particles with antigenic sites of ICD2 present mainly in peroxisomes. The results clearly indicated that ICD2 is a peroxisomal enzyme in rat hepatocytes. ICD2 has been regarded as a cytosolic enzyme, probably because the enzyme easily leaks out of peroxisomes during homogenization. (J Histochem Cytochem 49:1123-1131, 2001)

Animals↗
PubMed2001

Physical and inflammatory stressors elevate circadian clock gene mPer1 mRNA levels in the paraventricular nucleus of the mouse.

Stress induces secretion of corticosterone through activation of the hypothalamic-pituitary-adrenal axis. This corticosterone secretion is thought to be controlled by a circadian clock in the suprachiasmatic nucleus (SCN). The hypothalamic paraventricular nucleus (PVN) receives convergent information from both stress and the circadian clock. Recent reports demonstrate that mammalian orthologs (Per1, Per2, and Per3) of the Drosophila clock gene Period are expressed in the SCN, PVN, and peripheral tissues. In this experiment, we examined the effect of physical and inflammatory stressors on mPer gene expression in the SCN, PVN, and liver. Forced swimming, immobilization, and lipopolysaccharide injection elevated mPer1 gene expression in the PVN but not in the SCN or liver. A stress-induced increase in mPer1 expression was observed in the corticotropin-releasing factor-positive cells of the PVN; however, the stressors used in this study did not affect mPer2 expression in the PVN, SCN, or liver. The present study suggests that a stress-induced disturbance of circadian corticosterone secretion may be associated with the stress-induced expression of mPer1 mRNA in the PVN.

Animals↗
PubMed2001

Increased expression of cytosolic chaperonin CCT in human hepatocellular and colonic carcinoma.

The chaperonin-containing t-complex polypeptide 1 (CCT) is a hetero-oligomeric molecular chaperone that assists in the folding of actin, tubulin, and other cytosolic proteins. We recently reported that the expression level of CCT is closely correlated with growth rates of mammalian cultured cells. Here we examine the levels of CCT subunits and other molecular chaperones in tumor tissues of patients with hepatocelluar and colonic carcinoma, and compare them with nontumor tissues in the same patients. Expression levels of CCTbeta in tumor tissues was significantly higher than in nontumor tissues in all patients with hepatocellular carcinoma (n = 15) and 83% of patients with colonic carcinoma (n = 17). The increased level of CCT expression in colonic cancer cells was confirmed by immunohistochemistry with anti-CCTbeta antibody. The levels of CCTbeta were highly correlated (r = 0.606) with those of the proliferating cell nuclear antigen (PCNA), which was used as an indicator of cell growth. CCTalpha gave similar results, although the correlation with PCNA levels was weaker. Other cytosolic and endoplasmic reticulum chaperones also showed higher expression in significant numbers of tumor tissues but less frequently than that observed with CCT. These results suggest that CCT is up-regulated in rapidly proliferating tumor cells in vivo to effectively produce proteins required for growth, and may serve as a useful tumor marker because it is widely distributed in the cytosol.

Carcinoma↗
PubMed2001

Regulation of the ion-transporting mitochondrion-rich cell during adaptation of teleost fishes to different salinities.

The mitochondrion-rich cells (MRCs) in teleost gill and equivalent tissues are important osmoregulatory sites in maintaining ionic balance. These cells express a variety of ion pumps, transporters, and channels, which play central roles in ionic regulation. Recently, two types of MRCs have been identified in euryhaline fishes: seawater (SW)-type MRCs extrude Na and Cl ions in SW conditions; freshwater (FW)-type MRCs take up at least Cl-. Long-term development/differentiation of the two types of MRCs during adaptation to different salinities appears to be regulated mainly by endocrine factors. Osmolality, Ca2+, neurotransmitters, and fast-acting hormones rapidly regulate the SW MRCs. Recent information is assembled in this review and suggests the functional plasticity of highly specialized MRCs.

Adaptation, Physiological↗
PubMed2001

The effects of KNK437, a novel inhibitor of heat shock protein synthesis, on the acquisition of thermotolerance in a murine transplantable tumor in vivo.

A newly synthesized reagent, KNK437, has been found specifically to inhibit the synthesis of heat shock proteins in vitro. In this study, we investigated the effects of KNK437 on the synthesis of heat shock proteins and the induction of thermotolerance in transplantable tumors in vivo. SCC VII cells were grown in vivo and transplanted into C3H/He mice. The concentrations of KNK437 in the tumors and the sera of the mice were examined by high-performance liquid chromatography. Hsp72 synthesis was examined by Western immunoblot analysis. The response to hyperthermia was evaluated in terms of the delay in tumor growth. KNK437 had low toxicity in vivo. The concentration of KNK437 in the tumors gradually increased and reached a peak 6 h after i.p. injection. Hsp72 were synthesized 8 h after hyperthermia at 44 degrees C for 10 min, and their synthesis was inhibited by administration of KNK437 6 h before hyperthermia. At a concentration of 200 mg/kg, KNK437 alone showed no antitumor effects and did not increase the thermosensitivity of nontolerant tumors. The same dose of KNK437 enhanced the antitumor effects of fractionated heat treatment at 44 degrees C in a synergistic manner. This study strongly suggests the inhibition of thermotolerance via the inhibition of HSP72 in vivo. The inhibition of thermotolerance by KNK437 may help to improve the efficacy of clinical fractionated hyperthermia.

Animals↗
PubMed2001

[The minimal residual disease (MRD) in hematological malignancies].

Molecular genetic and cytoimmunological markers have been applied for the detection of minimal residual disease (MRD) in hematological malignancies. These markers include surface markers or rearranged T-cell receptor and immunoglobulin genes in the lymphoid malignancies and fused genes associated with chromosomal translocations such as BCR-ABL in t(9;22) or PML-RAR alpha in t(15;17) in myeloid malignancies. The expression of the WT1 gene is recognized as the universal tumor marker for a wide variety of hematological malignancies. Using these sensitive markers, a tumor cell in 10,000 to 1,000,000 normal cells can be detected. By examining a large number of patients, it has been shown that the MRD in the early phase of chemotherapy has a correlation with the prognosis of childhood ALL. Based on these observations, a new strategy of chemotherapy in which the post-remission therapy is modified based on the MRD results has begun. The amount of tumor cells contaminated in the autologous stem cell grafts in ALL patients might be related to the prognosis. The diagnosis of MRD will be used as an important routine examination in chemotherapy for leukemia/lymphoma patients.

Adult↗
PubMed2001

[Small lymphocytic lymphoma/chronic lymphocytic leukemia with t(11;14)].

A 83-year-old woman was referred to our hospital because of swollen lymph nodes, marked splenomegaly, and bone marrow abnormality. Histological examination of the lymph nodes revealed characteristic findings for small lymphocytic lymphoma/chronic lymphocytic leukemia (SLL/CLL). The immunophenotype of the tumor cells was CD5+, 10-, 19+, 20+, 23-, IgM+D+. Interphase fluorescent in situ hybridization (FISH) detected t(11;14), and immunohistochemical studies demonstrated cyclin D1 expression. In both SLL/CLL and mantle cell lymphoma (MCL), the normal counterpart of the tumor cells is thought to be CD5-positive B1 cells. The present case may therefore have been borderline between SLL/CLL and MCL.

Aged↗
PubMed2000

Proteasome-dependent degradation of cytosolic chaperonin CCT.

The chaperonin containing t-complex polypeptide 1 (CCT) is a heterooligomeric molecular chaperone that assists in the folding of actin, tubulin, and other cytosolic proteins. We show here that degradation of CCT in mammalian cells is inhibited by a proteasome-specific inhibitor, lactacystin. When CCT synthesis was inhibited by growth arrest of cells, the decrease in CCT levels was much slower in the presence of lactacystin than in its absence. Pulse-chase experiments indicated that degradation of CCT is inhibited 2- to 2.5-fold by addition of lactacystin. In addition, CCT degradation rate in ts85 cells that produce thermolabile ubiquitin-activating enzyme E1 was reduced 3-fold at the nonpermissive temperature compared to the degradation at the permissive temperature. These results indicate that the ubiquitin-proteasome system is involved in CCT degradation.

Acetylcysteine↗
PubMed2000

Transcriptional regulation of the mouse cytosolic chaperonin subunit gene Ccta/t-complex polypeptide 1 by selenocysteine tRNA gene transcription activating factor family zinc finger proteins.

The chaperonin containing t-complex polypeptide 1 (CCT) is a molecular chaperone assisting in the folding of proteins in eukaryotic cytosol, and the Ccta (encoding the alpha subunit of CCT)/t-complex polypeptide 1 gene encodes the alpha subunit of CCT. We show here that transcription of the mouse Ccta gene is regulated by selenocysteine tRNA gene transcription activating factor (Staf) family zinc-finger transcription factors ZNF143 and ZNF76. Reporter gene assay using HeLa cells indicated that the Ccta gene promoter contains two 18-base pair-long cis-acting elements with similar sequences at -70 and -20 base pairs (designated CCT alpha subunit gene transcription activating element 1 (CAE1) and CAE2, respectively). By yeast one-hybrid screening of CAE1-binding factors, we isolated human ZNF143, which is known to activate transcription of selenocysteine tRNA and small nuclear RNA genes. DNA binding domains of ZNF143 and ZNF76 produced in E. coli recognized CAE1 and CAE2 elements in electrophoretic mobility shift assay. HeLa cell nuclear extract contained a protein that specifically binds to CAE1 and CAE2 and recognized by anti-ZNF143 antibody. Transcription from a minimal Ccta promoter containing CAE2 element in HeLa cells was enhanced by overexpression of full-length ZNF143 and ZNF76 but inhibited by that of their DNA binding domains alone. These results demonstrate that the Staf family proteins control transcription of at least one of the chaperone-encoding genes besides that of tRNA and small nuclear RNA genes. These RNA and chaperone genes are suggested to be coregulated to facilitate synthesis of mature proteins during active cell growth.

Animals↗
PubMed2000

Nonphotic entrainment by 5-HT1A/7 receptor agonists accompanied by reduced Per1 and Per2 mRNA levels in the suprachiasmatic nuclei.

In mammals, the environmental light/dark cycle strongly synchronizes the circadian clock within the suprachiasmatic nuclei (SCN) to 24 hr. It is well known that not only photic but also nonphotic stimuli can entrain the SCN clock. Actually, many studies have shown that a daytime injection of 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH DPAT), a serotonin 1A/7 receptor agonist, as a nonphotic stimulus induces phase advances in hamster behavioral circadian rhythms in vivo, as well as the neuron activity rhythm of the SCN in vitro. Recent reports suggest that mammalian homologs of the Drosophila clock gene, Period (Per), are involved in photic entrainment. Therefore, we examined whether phase advances elicited by 8-OH DPAT were associated with a change of Period mRNA levels in the SCN. In this experiment, we cloned partial cDNAs encoding hamster Per1, Per2, and Per3 and observed both circadian oscillation and the light responsiveness of Period. Furthermore, we found that the inhibitory effect of 8-OH DPAT on hamster Per1 and Per2 mRNA levels in the SCN occurred only during the hamster's mid-subjective day, but not during the early subjective day or subjective night. The present findings demonstrate that the acute and circadian time-dependent reduction of Per1 and/or Per2 mRNA in the hamster SCN by 8-OH DPAT is strongly correlated with the phase resetting in response to 8-OH DPAT.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed2000

Morphological evidence for a vestibulo-thalamo-striatal pathway via the parafascicular nucleus in the rat.

We observed by anterograde and retrograde tracing techniques that projection fibers originating from the medial vestibular nucleus (MVe) of the rat terminated in the dorsal two-thirds of the lateral part of the parafascicular thalamic nucleus (PF), where neurons sending their axons to the dorsolateral part of the striatum existed. It was further revealed that the vestibular fibers made asymmetrical synaptic contacts mainly with dendrites and additionally with soma of the striatum-projecting PF neurons. These data suggest that output signals from the MVe may be transmitted disynaptically to the striatal neurons via the PF neurons.

Animals↗
PubMed2000

Benzylidene lactam compound, KNK437, a novel inhibitor of acquisition of thermotolerance and heat shock protein induction in human colon carcinoma cells.

Cells exposed to heat or other types of stressors transiently synthesize a group of proteins known as heat shock proteins (HSPs). A nonlethal heat treatment can elicit in the cells an ability to resist subsequent lethal heat treatments. We report here that a novel benzylidene lactam compound, KNK437, dose-dependently inhibited the acquisition of thermotolerance and the induction of various HSPs including HSP105, HSP70, and HSP40 in COLO 320DM (human colon carcinoma) cells. The induction of heat-inducible HSP70, which is reported to be involved in the development of thermotolerance, was inhibited at mRNA levels by treatment with KNK437. This compound also inhibited the acquisition of thermotolerance as developed by sodium arsenite. However, it did not increase thermosensitivity in nontolerant cells. The effect of KNK437 was much greater than that of quercetin, a bioflavonoid that was previously reported to inhibit the acquisition of thermotolerance as well as the induction of HSPs. We conclude that this drug is a novel inhibitor of the acquisition of thermotolerance caused by the induction of HSPs.

Arsenites↗