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Biomedical subjects

K Hamasaki

Publications and source records attributed to K Hamasaki.

At least 19 recordsLinked to original sources
PubMed2005

Clonally expanded T-cell populations in atomic bomb survivors do not show excess levels of chromosome instability.

Radiation-induced genomic instability has been studied primarily in cultured cells, while in vivo studies have been limited. One major obstacle for in vivo studies is the lack of reliable biomarkers that are capable of distinguishing genetic alterations induced by delayed radiation effects from those that are induced immediately after a radiation exposure. Here we describe a method to estimate cytogenetic instability in vivo using chromosomally marked clonal T-cell populations in atomic bomb survivors. The basic idea is that clonal translocations are derived from single progenitor cells that acquired an aberration, most likely after a radiation exposure, and then multiplied extensively in vivo, resulting in a large number of progeny cells that eventually comprise several percent of the total lymphocyte population. Therefore, if chromosome instability began to operate soon after a radiation exposure, an elevated frequency of additional but solitary chromosome aberrations in clonal cell populations would be expected. In the present study, six additional translocations were found among 936 clonal cells examined with the G-band method (0.6%); the corresponding value with multicolor FISH analysis was 1.2% (4/333). Since these frequencies were no higher than 1.2% (219/17,878 cells), the mean translocation frequency observed in control subjects using the G-band method, it is concluded that chromosome instabilities that could give rise to an increased frequency of persisting, exchange-type aberrations were not commonly generated by radiation exposure.

Breast Neoplasms↗
PubMed2004

Bone marrow engraftment in a rodent model of chemical carcinogenesis but no role in the histogenesis of hepatocellular carcinoma.

BACKGROUND AND AIM: Recent studies indicated that hepatic stem cells in the bone marrow could differentiate into mature hepatocytes, suggesting that bone marrow cells could be used for replacement of damaged hepatocytes in a variety of liver diseases. Hepatocellular carcinoma (HCC) is thought to arise from hepatic stem cells. In this study, we investigated the malignant potential of hepatic stem cells derived from the bone marrow in a mouse model of chemical hepatocarcinogenesis. METHODS: Bone marrow cells were obtained from the male beta-galactosidase (beta-gal) transgenic mouse and transplanted into female recipient mice. Hepatocarcinogenesis was induced by a year of treatment with diethylnitrosamine and phenobarbital (NDEA/PB). One year later, the liver was removed from each treated mouse and evaluated by x-gal staining, immunohistochemistry, and fluorescence in situ hybridisation (FISH). RESULTS: Forty per cent of recipient mice survived and developed multiple HCC. Clusters of beta-gal positive mature hepatocytes were detected sporadically in the entire liver of NDEA/PB treated mice who underwent bone marrow transplantation (BMT) with while no such hepatocytes were identified in the liver of BMT mice that were not treated with NDEA/PB. The Y chromosome was detected with the same frequency as the donor male liver in clusters of beta-gal positive mature hepatocytes by FISH. However, no HCC was positive for beta-gal or the Y chromosome. Immunohistochemically, beta-gal positive mature hepatocytes did not express CD34 or alpha-fetoprotein. CONCLUSIONS: Our results suggest that hepatic stem cells derived from the bone marrow have low malignant potential, at least in our model.

Animals↗
PubMed2003

Systemic lupus erythematosus and thrombotic thrombocytopenic purpura: a case report and literature review.

We describe a patient with systemic lupus erythematosus (SLE) who developed severe and acute thrombotic thrombocytopenic purpura (TTP). Detection of the fragmentation of peripheral red blood cells (RBC) helped the early diagnosis of TTP and the patient was rescued by extensive plasma exchange started promptly after the diagnosis. Because manifestations of TTP are similar to those in SLE, it is sometimes difficult to make an accurate diagnosis of TTP in SLE patients. We emphasise here the significance of the early diagnosis of TTP by the observation of fragmented RBC and the intensive therapy, including plasma exchange, for this very severe condition.

Adult↗
PubMed2002

Full-length sequence and functional analysis of hepatitis B virus genome in a virus carrier: a case report suggesting the impact of pre-S and core promoter mutations on the progression of the disease.

In chronic hepatitis B virus (HBV) infection, the quiescent immunotolerant phase evolves into the immunoactive phase. The aim of the present study was to clarify the virological alterations relevant to progression. Serial serum samples obtained from a patient with HBV during long-term follow-up were analysed by sequencing of the full-length HBV-DNA using polymerase chain reaction (PCR). In addition, PCR products of HBV genome from each serum sample were transfected into HuH-7 human hepatoma cells for the functional analysis of the transfected viral genomes. Based on the HBV-DNA sequence analysis, the patient had the genotype C virus, and the mutant HBV with common core promoter mutations (T(1762)A(1764)) and deletion of the pre-S region responsible for large surface protein transcription emerged before the onset of hepatitis. When the vigorous host immune response developed (indicated by the flare-up of hepatitis), the mutant HBV containing common core promoter mutations and another pre-S deletion causing lack of the surface protein promoter became predominant. The HBV-DNA sequences, other than pre-S and core promoter regions were identical to the wild-type sequence throughout the study. Transfection of PCR products containing the mutant HBV sequences resulted in increased amounts of intracellular replicative intermediates but the decreased secretion of HBsAg and HBeAg into culture media, suggesting accumulation of nonenveloped viral core particles within the cells. These results indicate that pre-S deletion and core promoter mutations may participate cooperatively in progression of the disease.

Adult↗
PubMed2001

Immobilized fluorescent cyclodextrin on a cellulose membrane as a chemosensor for molecule detection.

Dansylglycine-modified cyclodextrin (DnsC4-beta-CD) was prepared as a fluorescent host that is capable of being immobilized on a cellulose membrane (DnsC4-beta-CD membrane). DnsC4-beta-CD immobilized on the cellulose membrane decreased its fluorescence intensity with increasing concentration of guest molecules, indicating that the host changes the location of the dansyl group from inside to outside the cyclodextrin cavity upon guest accommodation, which is similar to DnsC4-beta-CD in solution; thereby, the DnsC4-beta-CD membrane is useful as a novel chemosensor for detecting molecules. This result demonstrates that the cellulose membrane is useful as a practical supporting material for various chromophore-modified cyclodextrins.

Journal Article↗
PubMed2001

HIV Rev peptides conjugated with peptide nucleic acids and their efficient binding to RRE RNA.

HIV Rev peptides conjugated with peptide nucleic acids (PNAs) were designed and synthesized to develop a designing approach for a novel RNA-binding molecule. The binding affinities of PNA-peptides with the Rev responsive element (RRE) RNA were determined by the competition assay using a rhodamine-labeled Rev. The peptide conjugated with an antisense PNA (TGCGC) bound RRE RNA more efficiently than the molecule without the PNA or the peptide sequence.

Amino Acid Sequence↗
PubMed2001

Fluorescent cyclodextrin immobilized on a cellulose membrane as a chemosensor system for detecting molecules.

Dansyl glutamate-modified cyclodextrin (DnsGlu-beta-CD) was prepared as a fluorescent host, which is capable of being immobilized on a cellulose membrane (DnsGlu-beta-CD-membrane). The fluorescence intensity of DnsGlu-beta-CD decreased with increasing concentration of guest molecules, indicating that the host changes the location of the dansyl group from inside to outside the cyclodextrin cavity upon guest accommodation. Similar guest-induced decrease in the fluorescence intensity was observed for DnsGlu-beta-CD immobilized to a cellulose membrane. This result demonstrates that the cellulose membrane may be used as a practical supporting material of various chromophore-modified cyclodextrins and that DnsGlu-beta-CD-membrane is useful as a novel disposable chemosensor for molecules.

Journal Article↗
PubMed2001

Aminoglycoside antibiotics, neamine and its derivatives as potent inhibitors for the RNA-protein interactions derived from HIV-1 activators.

Neamine derivatives which have an arginine (RN), a pyrene (PCN) and both pyrene and arginine (PRN) have been prepared and their binding toward the RNA fragments derived from HIV-1 activator region, TAR and RRE RNA were examined. Among them, PRN bound either TAR RNA or RRE RNA with equivalent binding affinities as Tat and Rev peptide, respectively.

Amino Acid Sequence↗
PubMed2001

Geranylgeranylacetone induces antiviral gene expression in human hepatoma cells.

Geranylgeranylacetone (GGA), an isoprenoid compound, is used clinically as an anti-ulcer drug. Since some isoprenoids including retinoids have anti-tumor and anti-viral activities in a variety of cell types, we investigated whether GGA could induce anti-viral proteins in human hepatoma cells. The HuH-7 and HepG2 cells were treated with GGA, and expression of anti-viral proteins such as 2'5'-oligoadenylate synthetase (2'5'-OAS) and double-stranded RNA-dependent protein kinase (PKR) in these cells was analyzed. GGA stimulated 2'5'-OAS and PKR gene expression at the transcriptional level through the formation of interferon-stimulated gene factor 3 (ISGF3), which regulates both gene transcription. By Western blotting, GGA induced expression of signal transducers and activators of transcription 1, 2 (STAT1, STAT2) and p48 proteins, components of ISGF3, together with the phosphorylation of STAT1. These results suggest that GGA acts as a potent inducer of anti-viral gene expression by stimulating the ISGF3 formation in human hepatoma cells.

2',5'-Oligoadenylate Synthetase↗
PubMed2001

The sympathetic nervous system promotes carbon tetrachloride-induced liver cirrhosis in rats by suppressing apoptosis and enhancing the growth kinetics of regenerating hepatocytes.

Norepinephrine is considered to possess potent anti-apoptotic action in regenerating hepatocytes. To clarify the role of the sympathetic nervous system in apoptosis that occurs in chronic liver damage and following the promotion of liver cirrhosis, we studied a carbon tetrachloride (CCl4)-induced liver injury model, using spontaneously hypertensive rats (SHR), Wistar-Kyoto rats (WKY), and chemically sympathectomized WKY. At 24 h after CCl4 administration. acute damage, characterized by vacuolated hepatocytes in the centrilobular zone, was greater in SHR than in WKY. This vacuolated change in WKY hepatocytes was significantly reduced by chemical sympathectomy with 6-hydroxydopamine (6-OHDA). After 48 h, the acute damage was dramatically improved in each animal, without significant differences between the three groups. In chronic damage after weekly repetition of CCl4 treatment for 4 weeks, fibrosis was evident in SHR, while in the other groups there was only scant fibrosis in the centrilobular zone. After 8 weeks' repetition of CCl4, liver cirrhosis was seen only in SHR. The incidence of apoptotic cells in areas of both acute and chronic damage in WKY, detected by terminal deoxynucleotidyl transferase-dUTP nick end labeling, was significantly increased in comparison with that in SHR, and was further increased by 6-OHDA pretreatment. In contrast, there was significantly greater enhancement of the growth of hepatocytes in SHR than in WKY in both acute and chronic damage. Moreover. hepatocyte growth kinetics in WKY was significantly inhibited after sympathectomy in acute injury, as evidenced by immunohistochemistry for proliferating cell nuclear antigen (PCNA). In vitro, the amount of hepatocellular apoptosis induced by transforming growth factor-beta1 was significantly decreased by incubation with norepinephrine. These findings suggest that the anti-apoptotic effect of the sympathetic nervous system increases cell growth kinetics and promotes liver cirrhosis in this animal model.

Animals↗
PubMed2001

Construction of peptides with nucleobase amino acids: design and synthesis of the nucleobase-conjugated peptides derived from HIV-1 Rev and their binding properties to HIV-1 RRE RNA.

In order to develop a novel molecule that recognizes a specific structure of RNA, we have attempted to design peptides having L-alpha-amino acids with a nucleobase at the side chain (nucleobase amino acid (NBA)), expecting that the function of a nucleobase which can specifically recognize a base in RNA is regulated in a peptide conformation. In this study, to demonstrate the applicability of the NBA units in the peptide to RNA recognition, we designed and synthesized a variety of NBA-conjugated peptides, derived from HIV-1 Rev. Circular dichroism study revealed that the conjugation of the Rev peptide with an NBA unit did not disturb the peptide conformation. RNA-binding affinities of the designed peptides with RRE IIB RNA were dependent on the structure of the nucleobase moieties in the peptides. The peptide having the cytosine NBA at the position of the Asn40 site in the Rev showed a higher binding ability for RRE IIB RNA, despite the diminishing the Asn40 function. Furthermore, the peptide having the guanine NBA at the position of the Arg44 site, which is the most important residue for the RNA binding in the Rev, bound to RRE IIB RNA in an ability similar to Rev34-50 with native sequence. These results demonstrate that an appropriate NBA unit in the peptide plays an important role in the RNA binding with a specific contact such as hydrogen bonding, and the interaction between the nucleobase in the peptide and the base in the RNA can enhance the RNA-binding affinity and specificity.

Amino Acids↗
PubMed2001

A long-term follow-up analysis of serial core promoter and precore sequences in Japanese patients chronically infected by hepatitis B virus.

To investigate the association of hepatitis B virus (HBV) with core promoter mutation (T1762A1764) or precore mutation (A1896) with the clinical course of illness, we analyzed serial core promoter and precore sequences in 22 patients with HBV-associated chronic liver disease who were followed for 12+/-4 years (mean +/- SD). Sixteen of 22 patients were positive for HBeAg at baseline, and 15 of the 16 patients seroconverted to anti-HBe during the observation period. T1762A1764 mutation was detected in 16 of 22 patients, including 11 patients positive for HBeAg, at baseline. During the follow-up period, A1896 mutation emerged in 7 of 16 patients who had the wild-type HBV or only the T1762A1764 mutation at baseline. Sustained remission of hepatitis correlated with the low level of viremia, but did not with type of mutations. These results indicate that HBV with T1762A1764 mutation tends to precede A1896 mutation during the course of infection in Japanese patients with chronic liver disease.

Adult↗
PubMed2001

Influence of various hemodialysis membranes on the plasma (1-->3)-beta-D-glucan level.

BACKGROUND: Recently, invasive fungal infections have increased significantly because of the growing number of immunocompromised hosts. The measurement of plasma (1-->3)-beta-D-glucan has been proposed as a useful diagnostic tool for deep mycosis. In this study, we analyzed the alteration of the plasma (1-->3)-beta-D-glucan concentration by using different kinds of hemodialysis (HD) membranes in end-stage renal disease (ESRD) patients and estimated its half-life. METHODS: Twenty-seven patients with ESRD without known fungal infections (with a median age of 66 years old) were enrolled in this study. Cellulose triacetate (CTA) membrane, cellulose (Cu) membrane, and polymethyl methacrylate (PMMA) membrane were used in three consecutive initiations of HD and plasma (1-->3)-beta-D-glucan concentration was measured before and after each HD session. RESULTS: The level did not change between before and after HD when CTA and PMMA membranes were used. In contrast, the plasma (1-->3)-beta-D-glucan level increased greatly after HD using the Cu membrane (from 9.4 to 332 pg/mL in median). Hypothesizing that the plasma (1-->3)-beta-D-glucan level declines exponentially, its median half-life is estimated at 20 hours, which is not affected by hepatic or renal function. CONCLUSIONS: Because the plasma (1-->3)-beta-D-glucan level increases dramatically after HD using the Cu membrane, dialyzers with Cu membrane should be avoided for HD in patients with suspected deep mycosis. The measurement of plasma (1-->3)-beta-D-glucan is also useful for the patients with hepatic or renal failure.

Adult↗
PubMed2001

Immunocytochemistry of glutathione S-transferase in taste bud cells of rat circumvallate and foliate papillae.

Immunocytochemistry was used to investigate the distribution of cells reacting with specific antibodies against glutathione S-transferase (GST) mu and pi in rat circumvallate and foliate taste buds; the findings were confirmed by Western blotting. Double immunofluorescence staining for protein gene product (PGP) 9.5 and GST subunits allowed the classification of taste bud cells of both papillae into: (i) cells immunoreactive to either PGP 9.5 or GST subunit antibody; (ii) cells immunoreactive to both antibodies; and (iii) cells that did not react with either of these antibodies. Immunoelectron microscopy revealed that most GST subunit-immunoreactive cells seemed to be either type II or type III cells based on their ultrastructure. Since PGP 9.5 is now widely used as a marker for type III cells in mammalian taste buds, it seems reasonable to believe that most GST subunit-immunoreactive cells are type II cells. Whether cells immunoreactive for both PGP 9.5 and GST subunits constitute a small subpopulation of type III cells or whether they are intermediate forms between type II and III cells is under investigation. No type I cells reacted with antibodies against GST subunits in the present study. GST subunits in taste bud cells may participate in xenobiotic metabolism of certain substances exposed to taste pits, as already shown for olfactory epithelium.

Animals↗
PubMed2001

Geranylgeraniol, an intermediate product in mevalonate pathway, induces apoptotic cell death in human hepatoma cells: death receptor-independent activation of caspase-8 with down-regulation of Bcl-xL expression.

Geranylgeraniol (GGOH), an intermediate of mevalonate metabolism, is known to induce apoptosis in various lines of cancer cells. The present study was undertaken to clarify the signaling pathways of apoptosis induced by GGOH in human hepatoma cells. HuH-7 human hepatoma cells were incubated in the absence or presence of GGOH. Activation of caspase-8 /-9 /-3 in HuH-7 cells was found after 8 h treatment with GGOH, at which time DNA fragmentation and loss of mitochondrial transmembrane potential (Deltaphim) occurred. HuH-7 cells do not express Bcl-2; however, down-regulation of Bcl-xL expression preceded activation of the caspase cascade in GGOH-treated HuH-7 cells, while Bax expression was not changed by GGOH treatment. Addition of caspase inhibitors restored the decreased cell viability of HuH-7 cells by GGOH, including Deltaphim, to the baseline level, which indicated that caspase triggers mitochondria-dependent apoptotic pathways in GGOH-treated HuH-7 cells. Similarly, GGOH-mediated apoptosis of HuH-7 cells was clearly prevented by coadministration of ursodeoxycholic acid (UDCA), which led to restoration of the level of Bcl-xL expression. Activation of caspase-8 /-9 /-3, as well as Deltaphim, by GGOH treatment was suppressed by addition of UDCA. Our results indicate that activation of the caspase cascade initiating from caspase-8, which could be accelerated by down-regulation of Bcl-xL expression, plays a key role in an apoptotic process induced by GGOH in human hepatoma cells.

Apoptosis↗
PubMed2000

A high-throughput screening utilizing intramolecular fluorescence resonance energy transfer for the discovery of the molecules that bind HIV-1 TAR RNA specifically.

A 16-residue peptide, including the Tat(49-57) sequence was labeled with a fluorescein and a tetramethylrhodamine at its N- and C-terminus, respectively. This double dye-labeled peptide was prepared as a tracer for high-throughput screening utilizing intramolecular fluorescence resonance energy transfer (FRET). The binding of the competitor molecules for HIV-1 TAR RNA were monitored and dissociation constants of those molecule were determined by using this tracer. This novel screening system might be useful to discover the drug for HIV-1 TAR RNA.

Drug Evaluation, Preclinical↗