Biomedical subjects

H Saito

Publications and source records attributed to H Saito.

At least 127 records · Page 7Linked to original sources

PubMed2001

Allylstannylation of carbon-carbon and carbon-oxygen unsaturated bonds via a radical chain process.

In the presence of a radical initiator, allyltributylstannanes bearing an electron-withdrawing group at the beta-position smoothly reacted with electron-deficient terminal alkenes to give allylstannylated products in good yields. The stannyl group was introduced into the terminal carbon with high regioselectivity. The allylstannylation of homochiral 8-phenylmenthyl acrylate proceeded with moderate to good diastereoselectivity. Terminal and electron-deficient internal alkynes as well efficiently underwent the radical-initiated allylstannylation in an anti addition mode. The reaction of terminal alkynes showed the same regioselectivity as that of terminal alkenes. The present radical reaction was applicable to allylation of aromatic aldehydes and ketones.

Journal Article↗

PubMed2001

Histone acetylation induced by granulocyte colony-stimulating factor in a map kinase-dependent manner.

Histone acetylation has been shown to affect chromatin structure and gene expression. The mitogen-activated protein (MAP) kinase pathway is activated by a number of cytokines and plays critical roles in hematopoietic cell survival, proliferation, and differentiation. We focused on the part of the MAP kinase cascade and granulocyte colony-stimulating factor (G-CSF)in histone acetylation at one of the critical myeloid differentiation-associated genes, myeloperoxidase (MPO). G-CSF caused rapid acetylation of histone H3 and H4 at the promoter of MPO as revealed by chromatin immunoprecipitation. In addition, CBP and p300 were recruited to the promoter in response to G-CSF. Furthermore, we showed that rapid histone acetylation induced by G-CSF is MAP kinase-dependent. These results illustrate how myeloid-differentiating signals via G-CSF may be coupled with histone acetylation during the process of gene expression.

Acetylation↗

PubMed2001

Expression of p-glycoprotein is associated with that of multidrug resistance protein 1 (MRP1) in the vestibular labyrinth and endolymphatic sac of the guinea pig.

Expression of p-glycoprotein (p-gp) and multidrug resistance protein 1 (MRP1) was detected in the vestibular labyrinth and endolymphatic sac (ES) of the guinea pig by immunohistochemical staining using anti-p-gp monoclonal antibody (mAb) C219 and anti-MRP mAb MRPr1. P-gp was detected in capillary endothelial cells of the crista ampullaris, utricle, saccule and ES. MRP1 was detected in the epithelial lining of the crista ampullaris, utricle, saccule, and epithelial cells of the ES. Since p-gp and MRP1 act as extrusion pumps, they may coordinate with each other in vestibular organs and ES and play an important role in the blood-labyrinth barrier.

ATP Binding Cassette Transporter, Subfamily B↗

PubMed2001

Activating mutation of D835 within the activation loop of FLT3 in human hematologic malignancies.

Mutations of receptor tyrosine kinases are implicated in the constitutive activation and development of human malignancy. An internal tandem duplication (ITD) of the juxtamembrane (JM) domain-coding sequence of the FLT3 gene (FLT3/ITD) is found in 20% of patients with acute myeloid leukemia (AML) and is strongly associated with leukocytosis and a poor prognosis. On the other hand, mutations of the c-KIT gene, which have been found in mast cell leukemia and AML, are clustered in 2 distinct regions, the JM domain and D816 within the activation loop. This study was designed to analyze the mutation of D835 of FLT3, which corresponds to D816 of c-KIT, in a large series of human hematologic malignancies. Several kinds of missense mutations were found in 30 of the 429 (7.0%) AML cases, 1 of the 29 (3.4%) myelodysplastic syndrome (MDS) cases, and 1 of the 36 (2.8%) acute lymphocytic leukemia patients. The D835Y mutation was most frequently found (22 of the 32 D835 mutations), followed by the D835V (5), and D835H (1), D835E (1), and D835N (1) mutations. Of note is that D835 mutations occurred independently of FLT3/ITD. An analysis in the 201 patients newly diagnosed with AML (excluding M3) revealed that, in contrast to the FLT3/ITD mutation (n = 46), D835 mutations (n = 8) were not significantly related to the leukocytosis, but tended to worsen disease-free survival. All D835-mutant FLT3 were constitutively tyrosine-phosphorylated and transformed 32D cells, suggesting these mutations were constitutively active. These results demonstrate that the FLT3 gene is the target most frequently mutated to become constitutively active in AML.

Acute Disease↗

PubMed2001

An in vitro evolved precursor tRNA with aminoacylation activity.

A set of catalysts for aminoacyl-tRNA synthesis is an essential component for translation. The RNA world hypothesis postulates that RNA catalysts could have played this role. Here we show an in vitro evolved precursor tRNA consisting of two domains, a catalytic 5'-leader sequence and an aminoacyl-acceptor tRNA. The 5'-leader sequence domain selectively self-charges phenylalanine on the 3'-terminus of the tRNA domain. This cis-acting ribozyme is susceptible to RNase P RNA, generating the corresponding 5'-leader segment and the mature tRNA. Moreover, the 5'-leader segment is able to aminoacylate the mature tRNA in trans. Mutational studies have revealed that C(74) and C(75) at the tRNA aminoacyl-acceptor end form base pairs with G71 and G70 of the trans-acting ribozyme. Such Watson-Crick base pairing with tRNA has been observed in RNase P RNA and 23S rRNA, suggesting that all three ribozymes use a similar mechanism for the recognition of the aminoacyl-acceptor end. Our demonstrations indicate that catalytic precursor tRNAs could have provided the foundations for the genetic coding system in the proto-translation system.

Acylation↗

PubMed2001

Acidic environment modifies heat- or radiation-induced apoptosis in human maxillary cancer cells.

PURPOSE: The effects of hyperthermia or irradiation on cell killing and induction of apoptosis were evaluated using human maxillary carcinoma IMC-3 cells and low pH (pH 6.8) adapted cells (IMC-3-pH). METHODS AND MATERIALS: Cellular heat-sensitivity or radiosensitivity was determined using the clonogenic assay. Apoptosis was assessed on the basis of a flow cytometric determination of the DNA content, DNA fragmentation, and poly(ADP-ribose)polymerase cleavage. RESULTS: When IMC-3 cells or IMC-3-pH cells were exposed to heat at 44 degrees C in pH 6.8 medium, an increase in thermosensitivity was observed compared with when the IMC-3 cells were exposed to heat at 44 degrees C in pH 7.4 medium. However, the selective reduction in survival was not observed after irradiation. In IMC-3 cells, apoptosis after heating at 44 degrees C for 60 min in pH 7.4 medium occurred earlier than that after 8 Gy irradiation, although both thermal and irradiated doses decreased the cell count to 10%. The degree of apoptosis after heating at pH 6.8 in IMC-3 cells or IMC-3-pH cells was greater than that at pH 7.4 in IMC-3 cells. However, the degree of apoptosis after 8 Gy irradiation at pH 6.8 in IMC-3 cells or IMC-3-pH cells was smaller than that at pH 7.4 in IMC-3 cells. CONCLUSION: Hyperthermia treatment is more effective at inducing apoptosis than radiation is in tumors that contain a population of low pH adapted cells.

Apoptosis↗

PubMed2001

(S)-preferential detoxification of 4-hydroxy-2(E)-nonenal enantiomers by hepatic glutathione S-transferase isoforms in guinea-pigs and rats.

In guinea-pig liver cytosol, racemic 4-hydroxy-2(E)-nonenal (HNE), a reactive and highly toxic product released from biomembranes by lipid peroxidation, was detoxified (S)-preferentially by GSH conjugation mediated by glutathione S-transferases (GSTs) and (R)-preferentially by NAD(+)-dependent oxidation mediated by aldehyde dehydrogenase (ALDH). The GST-mediated detoxification of the HNE enantiomers proceeded at much higher rates than that mediated by ALDH in guinea-pig liver cytosol. All the major guinea-pig GSTs, A1-1, M1-1, M1-2 and M1-3*, isolated from guinea-pig liver cytosol also catalysed the (S)-preferential conjugation of the HNE enantiomers. The liver and other major tissues of guinea-pigs had no immunologically detectable level of a putative GSTA4-4 orthologue, which exists as a minor GST protein in rat, mouse and human livers and exhibits extremely high catalytic activity towards HNE. All the hepatic rat GSTs, A1-1(2), A1-3, A4-4, M1-1, M1-2 and M2-2, also catalysed the (S)-preferential conjugation of HNE enantiomers.

Aldehydes↗

PubMed2001

Expression of multidrug resistance protein 1 (MRP1) in the rat cochlea with special reference to the blood-inner ear barrier.

Expression of multidrug resistance protein 1 (MRP1) was detected in the rat cochlea by RT-PCR and immunohistochemistry using anti-MRP monoclonal antibody MRPr1. Use of primers specific for rat mrp1 gene resulted in the amplification of an expected 394 bp fragment prepared from brain and cochlear tissues. Immunohistochemically, MRP was found in the choroid plexus, stria vascularis, spiral ligament, spiral prominence and cochlear nerve in the modiolus. From these results, it was suggested that MRP in the rat cochlea might function as an extrusion pump and play an important role in the blood-inner ear barrier.

ATP Binding Cassette Transporter, Subfamily B↗

PubMed2001

Enhancement of ATP release in hindlimb sympathetic perivascular nerve of the golden hamster during hibernation.

The present study investigated the effects of hibernation and hibernating body temperature (10 degrees C) on the relative changes that may occur in adrenergic and purinergic perivascular neurotransmission of the golden hamster. The hindlimb resistance vessels and the tibial artery of age-matched controls, cold exposed controls and hibernated hamsters were examined by pharmacological and electrophysiological techniques. At 34 degrees C, electrical field stimulation (EFS; supramaximal voltage, 0.5 ms; for 10 s) in all three groups evoked only twitch responses at 1-5 Hz, which were inhibited by piridoxal phosphate-6-azophenyl-2',4'-disulphonic acid (PPADS), a 2PX receptor antagonist. At 10-50 Hz the twitch responses were followed by sustained contractile responses, which were inhibited by prazosin, an alpha1-adrenoceptor antagonist. These responses were markedly enhanced at higher frequencies in hibernated tissues. At 10 degrees C, EFS evoked only the PPADS-sensitive transient responses in all the three groups, and this was markedly enhanced in hibernated tissues. At 34 degrees C, a single stimulus evoked a PPADS-sensitive excitatory junction potential (EJP) in all three groups but a train of pulses (e.g. approximately 0.5) evoked EJPs and prazosin-sensitive sustained depolarizations. These responses were markedly enhanced in hibernated cells. At 10 degrees C, either a single stimulus or a train of stimuli evoked only transient PPADS-sensitive EJPs, which were markedly enhanced in hibernated cells. The contractile responses and electrical membrane responses to exogenous ATP (1-1000 microM) and noradrenaline (0.1-100 microM) were unchanged in the three groups at 34 and at 10 degrees C. These results suggest that during hibernation enhancement of ATP release from the sympathetic perivascular nerves may occur, leading to an efficient means for maintenance of vascular tone and peripheral resistance.

Adenosine Triphosphate↗

PubMed2001

Endogenous serotonin contributes to a developmental decrease in long-term potentiation in the rat visual cortex.

The primary visual cortex shows synaptic plasticity during a postnatal "critical period," and its plasticity declines with development. Indeed, we found a developmental decrease in the induction of long-term potentiation (LTP) in the rat visual cortex. In visual cortex slices obtained from 2- to 3-week-old rats, tetanic stimulation (100 Hz for 1 sec, twice at an interval of 30 sec) of the white matter reproducibly induced LTP of field potentials in layer II/III. However, in slices from 5-week-old rats, the same tetanic stimulation failed to induce LTP. We hypothesized that endogenous serotonin (5-HT) is responsible for the developmental decrease in visual cortex LTP, because the induction of visual cortex LTP was suppressed by the addition of exogenous 5-HT (10 microm) and because the amount of 5-HT in the visual cortex increased during development. To test this hypothesis, we investigated the effect of methysergide, a 5-HT receptor antagonist, on the induction of visual cortex LTP. When visual cortex slices from 5-week-old rats were perfused with 50 microm methysergide, tetanic stimulation of the white matter induced robust LTP in layer II/III. Furthermore, serotonergic neurons were lesioned by intracerebroventricular injection of 5,7-dihydroxytryptamine (5,7-DHT). LTP was induced in visual cortex slices from 5,7-DHT-treated, 5-week-old rats. These results suggest that the induction of visual cortex LTP in 5-week-old rats is suppressed by endogenous 5-HT. 5-HT may be a factor that determines a critical period for synaptic plasticity in the rat visual cortex.

5,7-Dihydroxytryptamine↗

PubMed2001

Intermittent implosion and pattern formation of trapped Bose-Einstein condensates with an attractive interaction.

The collapsing dynamics of a trapped Bose-Einstein condensate with attractive interaction are revealed to exhibit two previously unknown phenomena. During the collapse, the condensate undergoes a series of rapid implosions that occur intermittently within a very small region. When the sign of the interaction is suddenly switched from repulsive to attractive, e.g., by the Feshbach resonance, density fluctuations grow to form various patterns such as a shell structure.

Journal Article↗

PubMed2001

Selective down-regulation of high-affinity IgE receptor (FcepsilonRI) alpha-chain messenger RNA among transcriptome in cord blood-derived versus adult peripheral blood-derived cultured human mast cells.

Substantial numbers of human mast cells (MCs) were generated from umbilical cord blood (CB) and from adult peripheral blood (PB). A single CB progenitor produced 15 436 MCs, whereas a single PB progenitor produced 807 MCs on average. However, PB-derived MCs were far more active than CB-derived MCs in terms of high-affinity IgE receptor (FcepsilonRI)-mediated reactions. One million sensitized PB-derived MCs released 3.6 microg histamine, 215 pg IL-5, and 14 ng granulocyte macrophage-colony-stimulating factor (GM-CSF), whereas 10(6) sensitized CB-derived MCs released only 0.8 microg histamine, 31 pg IL-5, and 0.58 ng GM-CSF on anti-IgE challenge. However, ionophore A23 187 released similar levels of histamine from the 2 MC types. PB-derived MCs highly expressed surface FcepsilonRI alpha chain, and CB-derived MCs almost lacked it in the absence of IgE. PB-derived MCs expressed approximately 5 times higher levels of messenger RNA (mRNA) for FcepsilonRI alpha chain than CB-derived MCs, but mRNAs for beta and gamma chains of the receptors were equally expressed. Among the approximately 5600 kinds of full-length human genes examined by using the high-density oligonucleotide probe-array system, FcepsilonRIalpha was ranked the fifth most increased transcript in PB-derived MCs. The 4 other increased transcripts were unrelated to MC function. These results suggest that IgE-mediated reactions may be restricted during early infancy through the selective inhibition of FcepsilonRIalpha transcription, which is probably committed at progenitor stages and is, at least in part, cytokine-insensitive.

Adult↗

PubMed2001

Constitutive kinase activation of the TEL-Syk fusion gene in myelodysplastic syndrome with t(9;12)(q22;p12).

The TEL gene on 12p12-13 is a target for a number of translocations associated with various hematological malignancies. The fusion of the TEL gene to the Syk gene in a patient with myelodysplastic syndrome (MDS) with t(9;12)(q22;p12) is reported. Southern blot analysis of patient bone marrow cells with TEL and Syk gene probes detected rearranged fragments. Anchored polymerase chain reaction identified the Syk gene, a nonreceptor tyrosine kinase, on 9q22 fused downstream of TEL exon 5. The TEL gene was fused in-frame to Syk and produced a fusion protein that was constitutively phosphorylated in tyrosine with dimerization that was mediated by the helix-loop-helix domain of TEL. A TEL-Syk fusion product transformed the murine hematopoietic cell line BaF3 to interleukin-3 growth factor independence. TEL-Syk is a novel transforming protein and leads to the transformation of hematopoietic cells. These data implicate that the rearranged Syk gene is involved in the pathogenesis of hematopoietic malignancies.

Amino Acid Sequence↗

PubMed2001

Mutations in the NMMHC-A gene cause autosomal dominant macrothrombocytopenia with leukocyte inclusions (May-Hegglin anomaly/Sebastian syndrome).

Macrothrombocytopenia with leukocyte inclusions is a rare autosomal dominant platelet disorder characterized by a triad of giant platelets, thrombocytopenia, and characteristic Döhle body-like leukocyte inclusions. A previous study mapped a locus for the disease on chromosome 22q12.3-q13.2 by genome-wide linkage analysis. In addition, the complete DNA sequence of human chromosome 22 allowed a positional candidate approach, and results here indicate that the gene encoding nonmuscle myosin heavy chain-A, NMMHC-A, is mutated in this disorder. Mutations were found in 6 of 7 Japanese families studied: 3 missense mutations, a nonsense mutation, and a one-base deletion resulting in a premature termination. Immunofluorescence studies revealed that NMMHC-A distribution in neutrophils appeared to mimic the inclusion bodies. These results provide evidence for the involvement of abnormal NMMHC-A in the formation of leukocyte inclusions and also in platelet morphogenesis.

Amino Acid Sequence↗

PubMed2001

The ERBB2/HER2 receptor differentially interacts with ERBIN and PICK1 PSD-95/DLG/ZO-1 domain proteins.

Identification of protein complexes associated with the ERBB2/HER2 receptor may help unravel the mechanisms of its activation and regulation in normal and pathological situations. Interactions between ERBB2/HER2 and Src homology 2 or phosphotyrosine binding domain signaling proteins have been extensively studied. We have identified ERBIN and PICK1 as new binding partners for ERBB2/HER2 that associate with its carboxyl-terminal sequence through a PDZ (PSD-95/DLG/ZO-1) domain. This peptide sequence acts as a dominant retention or targeting basolateral signal for receptors in epithelial cells. ERBIN belongs to the newly described LAP (LRR and PDZ) protein family, whose function is crucial in non vertebrates for epithelial homeostasis. Whereas ERBIN appears to locate ERBB2/HER2 to the basolateral epithelium, PICK1 is thought to be involved in the clustering of receptors. We show here that ERBIN and PICK1 bind to ERBB2/HER2 with different mechanisms, and we propose that these interactions are regulated in cells. Since ERBIN and PICK1 tend to oligomerize, further complexity of protein networks may participate in ERBB2/HER2 functions and specificity.

Adaptor Proteins, Signal Transducing↗

PubMed2001

Blue biliprotein as an effective factor for cryptic colouration in Rhodinia fugax larvae.

The fifth instar larva of the saturniid silkworm, Rhodinia fugax, is light yellowish-green on its dorsal surface and dark green on the ventral surface with a lateral demarcation between the two colours. The larva of R. fugax closely resembles the leaves of the host plant, Quercus serrata, in colour and shape. The spectral reflectance of the larval integument of R. fugax corresponds to that of the Q. serrata leaf. In the larval integument, there is more blue biliproteins (BPs) on the ventral surface than on the dorsal surface. Light intensity influences larval colouration. The larval integuments are green under light conditions (1000 lux), whereas larvae kept in dark conditions (10 lux) turn yellow. The BP-I content of the haemolymph is also affected by light intensity. The quantities of BP-I and its blue chromophore are higher under light conditions than under dark conditions. In contrast, there is little difference in the yellow chromophore content between the two light intensities. When larvae are kept in the light, the BP-I content in the cuticle is higher than under dark conditions in both the ventral and dorsal surfaces, and its chromophore content parallels the BP content. However, the amounts of BP-II and its chromophore in the epidermis show no change with the light intensity. Moreover, the quantity of yellow chromophore in the integument is also not affected by light intensity. Therefore, light stimulates the accumulation of BP-I and its chromophore in the haemolymph and cuticle, whereas the accumulation of BP-II and its chromophore in the epidermis are not influenced by light intensity. These results suggest that BPs and their chromophores determine the larval colouration and may play an important role in the cryptic colouration of R. fugax larvae.

Journal Article↗

PubMed2001

Molecular analysis of the mitotic checkpoint genes BUB1, BUBR1 and BUB3 in human lung cancers.

Our previous studies showed that mitotic checkpoint impairment is present in about 40% of human lung cancer cell lines but that mutations in the MAD mitotic checkpoint genes are infrequent. In the present study, we examined 44 lung cancer cases for the potential involvement of the other gene family involved in the mitotic checkpoint, i.e. BUB. We found that the BUB gene family members including BUB1, BUBR1 and BUB3 are not frequent targets for mitotic checkpoint defects in lung cancers, if present at all. Further studies are thus warranted to elucidate the molecular basis for the acquisition of mitotic checkpoint defects in order to better understand the molecular pathogenesis of lung cancers.

Cell Cycle Proteins↗

PubMed2001

Localization of human interleukin 13 receptor in non-haematopoietic cells.

Although the functional roles of interleukin (IL-)13 in haematopoietic cells are well investigated, those in non-haematopoietic cells remain to be addressed. IL-13 exerts its actions by binding to the IL-13 receptor (IL-13R) on target cells, which is composed of IL-13Ralpha1 and the IL-4 receptor alpha chain (IL-4Ralpha). However, there has been no study of localization of IL-13R in each tissue. To address this question, we generated monoclonal anti-IL-13Ralpha1 antibody, and performed immunohistochemistry using this antibody and anti-IL-4Ralpha antibody. Distribution of these two components was the same in all examined tissues. Staining was positive in keratinocytes, hair follicles, and sebaceous and sweat glands in skin; in ciliated respiratory epithelial cells in nasal tissue; in heart muscle cells; in foveola cells, gastric glands, and the smooth muscle layer in stomach; and in hepatocytes in liver. However, staining was undetectable in brain and bone marrow. Fibroblasts and endothelial cells were stained in some tissues. These results provide clues to elucidate the known pathological roles of IL-13 in atopic dermatitis and allergic rhinitis, as well as its unknown physiological roles.

Animals↗