PubMed Health⌕ Search

Biomedical subjects

M Akashi

Publications and source records attributed to M Akashi.

At least 37 records · Page 2Linked to original sources
PubMed2001

Determination of radionuclides produced by neutrons in heavily exposed workers of the JCO criticality accident in Tokai-mura for estimating an individual's neutron fluence.

In the Tokai-mura criticality accident, three workers were heavily exposed. Biological materials, such as blood, urine, vomit and hair, were collected from the workers and analyzed for radioactivities, produced by the neutron irradiation. Activation products. such as 24Na, -K and 82Br, were found in these materials by gamma-ray spectrometry. The radionuclide of the highest activity observed in biological materials was 24Na, e.g. the concentrations of this nuclide in the blood samples from the three patients at the accident time were 169, 92 and 23 Bq/ml, respectively. The concentrations of stable sodium in the same samples were determined by ICP-AES to obtain specific activities of 24Na (concentration ratio between the produced 24Na and stable 23Na), which are essential for estimating the neutron fluences and radiation doses. The specific activities of 24Na obtained for the three patients through the blood analysis were 8.2 x 10(4),4.3 x 10(4) and 1.2 x 10(4) Bq24Na/g23Na. Based on these values, individual's neutron fluences were estimated to be 5.7 x 10(11), 3.0 x 10(-1) and 0.85 x 10(11) cm(-2), respectively.

Adult↗
PubMed2001

Bioassay for neutron-dose estimations of three patients in the JCO criticality accident in Tokai-mura by measuring beta-ray emitters.

The measurement of beta-emitters in biological samples (hair, urine and bone) from three patients in the JCO criticality accident was performed to assess the neutron dose to individuals. The result of the measurements of 32P in hair and urine collected immediately after the accident showed that sufficient 32P activities had been induced in the hair by fast neutrons and in the urine by thermal neutrons to know the severity of the exposure to the individuals and to the position. From the measurement of 32P and 45Ca in bone from various anatomical parts of two patients who died 82 and 210 days after the accident, it was suggested that the distribution of the induced beta-emitters activities could prove the position and posture of the patients at the moment of exposure.

Beta Particles↗
PubMed2001

Initial symptoms of acute radiation syndrome in the JCO criticality accident in Tokai-mura.

A criticality accident occurred on September 30, 1999, at the uranium conversion plant in Tokai-mura (Tokai-village), Ibaraki Prefecture, Japan. When the criticality occurred, three workers saw a "blue-white glow," and a radiation monitor alarm was sounded. They were severely exposed to neutron and gamma-ray irradiation, and subsequently developed acute radiation syndrome (ARS). One worker reported vomiting within minutes and loss of consciousness for 10-20 seconds. This worker also had diarrhea an hour after the exposure. The other worker started to vomit almost an hour after the exposure. The three workers, including their supervisor, who had no symptoms at the time, were brought to the National Mito Hospital by ambulance. Because of the detection of gamma-rays from their body surface by preliminary surveys and decreased numbers of lymphocytes in peripheral blood, they were transferred to the National Institute of Radiological Sciences (NIRS), which has been designated as a hospital responsible for radiation emergencies. Dose estimations for the three workers were performed by prodromal symptoms, serial changes of lymphocyte numbers, chromosomal analysis, and 24Na activity. The results obtained from these methods were fairly consistent. Most of the data, such as the dose rate of radiation, its distribution, and the quality needed to evaluate the average dose, were not available when the decision for hematopoitic stem cell transplantation had to be made. Therefore, prodromal symptoms may be important in making decisions for therapeutic strategies, such as stem-cell transplantation in heavily exposed victims.

Amylases↗
PubMed2000

Preparation and characterization of apatite deposited on silk fabric using an alternate soaking process.

Apatite-deposited silk fabric composite materials were developed using a new alternate soaking process. The characteristics of deposited apatite were studied using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectrophotometry (FTIR), and X-ray photoelectron spectroscopy (XPS). Apatite weight increased with alternating soaking in a calcium solution [200 mM aqueous calcium chloride solution buffered with tris(hydroxymethyl) aminomethane and HCl (pH 7.4)] and a phosphate solution (120 mM aqueous disodium hydrogenphosphate) changed every hour. SEM showed that apatite deposited after 21 or more repeated soakings was over 20 microm thick. XRD showed that with alternate soakings, the apatite crystals deposited on silk fabric elongated along the c axis. FTIR and XPS indicated the existence of carbonate, HPO(4)(2-), and Na(+) ions in addition to constituent ions of hydroxyapatite. A loss of HPO(4)(2-) and Na(+) ions in the deposit upon further soaking might be associated with an increasing apatite crystallinity. Apatite deposited on silk by the alternate soaking process was a deficient apatite containing carbonate, HPO(4)(2-), and Na(+) ions as in a natural bone tissue. Thus, this apatite-silk composite material might be potentially bioactive.

Animals↗
PubMed2000

Polymyxin B binds to anandamide and inhibits its cytotoxic effect.

Anandamide (ANA), an endogenous cannabinoid, can be generated by activated macrophages during endotoxin shock and is thought to be a paracrine contributor to hypotension. We discovered that ANA in saline/ethanol solution and in serum was efficiently adsorbed in a polymyxin B (PMB)-immobilized beads column and eluted with ethanol. We confirmed the direct binding of PMB to ANA by using surface plasmon resonance. The adsorption of ANA by PMB may abolish the diverse effects of ANA such as hypotension, immunosuppression, and cytotoxicity, and may suggest a new therapeutic strategy for endotoxin shock.

Adsorption↗
PubMed2000

Involvement of the MAP kinase cascade in resetting of the mammalian circadian clock.

Although the suprachiasmatic nucleus (SCN) is the major pacemaker in mammals, the peripheral cells or immortalized cells also contain a circadian clock. The SCN and the periphery may use different entraining signals-light and some humoral factors, respectively. We show that induction of the circadian oscillation of gene expression is triggered by TPA treatment of NIH-3T3 fibroblasts, which is inhibited by a MEK inhibitor, and that prolonged activation of the MAPK cascade is sufficient to trigger circadian gene expression. Therefore, such prolonged activation of MAPK by entraining cues may be involved in the resetting of the circadian clock.

3T3 Cells↗
PubMed2000

Role of TNFalpha in regulation of myeloperoxidase expression in irradiated HL60 promyelocytic cells.

Irradiation increases the generation of reactive oxygen intermediates, including hydrogen peroxide (H(2)O(2)). Myeloperoxidase (MPO), a heme-containing glycoprotein located in the primary granules of polymorphonuclear leukocytes and monocytes, reacts with H(2)O(2) and halide ion and produces a more potent microbicidal oxidant, hypochlorous acid (HOCl). Human HL60 promyelocytes constitutively had high levels of MPO protein and mRNA. Irradiation decreased the levels of MPO transcripts; the decrease in MPO transcripts by irradiation occurred in an almost dose-dependent manner. HL60 cells produce tumor necrosis factor alpha (TNFalpha), and irradiation markedly increased the TNFalpha production in these cells; in turn, TNFalpha decreased the levels of MPO transcripts in these cells. Furthermore, treatment of cells with anti-TNFalpha antibody blocked the reduction of MPO by irradiation. We also found that irradiation decreased the levels of the MPO mRNA with concomitant increased levels of TNFalpha mRNA in differentiation-induced HL60 cells and human THP-1 monocytic cells. Irradiation reduced the rate of MPO transcription but had only a slight effect on the half-life of MPO mRNA in HL60 cells. Our results suggest that irradiation reduces the steady-state levels of MPO mRNA mainly at transcriptional level and the endogenous production of TNFalpha is required for the reduction by irradiation in HL60 cells.

Cell Differentiation↗
PubMed2000

Study on complex formation between recombinant human thrombomodulin fragment and thrombin using surface plasmon resonance.

Human thrombomodulin (hTM) is a newly described endothelial cell associated protein that functions as a potent natural anticoagulant by converting thrombin from a procoagulant protease to an anticoagulant. The affinity constant of recombinant human soluble TM (rhs-TM) and a peptide containing active site of hTM fragment (f-hTM) with thrombin were determined using the surface plasmon resonance. The interaction of f-hTM with thrombin could be analyzed by a simple model, whereas the association and the dissociation steps of rhs-TM with thrombin consisted of at least two kinds of interaction phases. The dissociation constant for complex (K(D)) of f-hTM and thrombin was determined to be 205 nM, which was more than twice as high as that of rhs-TM (6.7 and 75 nM). The lower affinity of f-hTM was not due to the slow association rate but to the rapid dissociation rate. It comes clear that f-hTM interacts with thrombin rapidly.

Humans↗
PubMed2000

TNF-alpha induced p21(WAF1) but not Bax in colon cancer cells WiDr with mutated p53: important role of protein stabilization.

The p21(WAF1)induces cell cycle arrest at G(1)and its expression is regulated by the functional p53. TNF-alpha induced expression of p21(WAF1)at protein and mRNA levels in a dose-dependent fashion with an association with G(1)-arrest in human colon cancer cells WiDr that carry mutated p53 at codon 273 (His(273)). However, TNF-alpha did not affect the levels of the Bax protein, which also has p53-binding sites on its promoter and causes apoptosis. Further experiments suggested that cycloheximide (CHX), a protein synthesis inhibitor, increased the levels of p21(WAF1)mRNA and the induction of p21(WAF1)mRNA by TNF-alpha did not require new protein synthesis. Co-transfection of the p53 His(273)expression construct with a luciferase gene controlled by the p21(WAF1)promoter showed that the p53 His(273)was inactive, although TNF-alpha increased the transcriptional rate of p21(WAF1)in these cells. Further study found that TNF-alpha markedly stabilized the p21(WAF1)protein. These findings suggest that TNF-alpha induces expression of p21(WAF1)through a distinct pathway from Bax and that protein stabilization is an important mechanism in the expression of p21(WAF1)independent of p53.

Apoptosis↗
PubMed2000

Evaluation of biological responses to polymeric biomaterials by RT-PCR analysis IV: study of c-myc, c-fos and p53 mRNA expression.

In order to investigate how cells recognize biomaterials, mRNA that was expressed in attached human fibroblasts on various substrates was evaluated. The expressed oncogenes (c-fos and c-myc) and tumor suppressor gene (p53) mRNA were then isolated and detected using the RT-PCR method. As a result, c-fos and c-myc mRNA expression varied with respect to differences in the hydrophilicity-hydrophobicity of the substrates. Both c-fos and c-myc mRNA expression were low in the fibroblasts that had adhered to hydrophilic surfaces. The tendency of c-fos mRNA expression was similar to the adhesion curve of the cells. c-myc mRNA was largely induced in fibroblasts that had adhered to hydrophobic surfaces. p53 mRNA were largely induced in fibroblasts that had adhered to hydrophilic surfaces, while in the cells that had adhered to hydrophobic surfaces, p53 mRNA expression was low. We concluded that the expression of oncogenes and p53 mRNA is a powerful method for studying cell-polymer interactions or the evaluation of the carcinogenic activity of biomaterials.

Biocompatible Materials↗
PubMed2000

IL-1 induces expression of p21(WAF1) independently of p53 in high-passage human embryonic fibroblasts WI38.

We tested the effect of IL-1 on the expression of p21(WAF1) in human embryonic fibroblasts WI38. Exposure to IL-1 caused induction of p21(WAF1) protein in high-passage WI38 cells but not in early-passage cells. However, IL-1 did not stimulate the transcription of a CAT-reporter gene having two copies of the p53-responsive element on its promoter or the p53-binding capacity of nuclear extracts, although it increased transcriptional rate of p21(WAF1) in these high-passage cells. These results suggest that the induction of p21(WAF1) by IL-1 occurs at the transcriptional level, but p53 function is not required in these cells. Further studies found that IL-1 did not cause cell-cycle arrest, and the overexpression of p21(WAF1) resulted in only a slight delay of cell growth, while the level of p21(WAF1) coprecipitated with cyclin-dependent kinase-2 (Cdk2) was increased by IL-1. Moreover, a kinase assay of Cdk2 immunoprecipitates showed that IL-1 did not reduce the kinase activity, and IL-1 did not affect the status of phosphorylation of the retinoblastoma gene product (Rb). These findings imply that despite the induction of p21(WAF1), this cannot fully account for the growth arrest in high-passage WI38 cells. Thus, IL-1 mediates p21(WAF1) induction through a p53-independent pathway(s) in high-passage WI38 cells, but the cell cycle is regulated independently of p21(WAF1).

Cell Cycle↗
PubMed2000

Study of cellular responses to polymeric biomaterials using the differential display method.

In this study, we attempted to detect altered gene expressions in the cells that had adhered to various surfaces using the differential display method. Thioglycollate-elicited peritoneal exudate cells (PEC) and mouse fibroblast (L929) cells were cultured on the polymer films. After a predetermined time, the total RNA was isolated from cells and the differential mRNA expressions were evaluated by RT-PCR method. As a result, in the differential display of amplified cDNA from PEC, the different patterns of cDNA fragments among the samples were obtained. This indicates that there were many different mRNA expressions depending on the polymer surfaces. The use of differential method was proven to be useful for studying cell-polymer interaction.

Animals↗
PubMed1999

12-O-tetradecanoylphorbol-13-acetate-induced apoptosis is mediated by tumor necrosis factor alpha in human monocytic U937 cells.

12-O-tetradecanoylphorbol-13-acetate (TPA), a phorbol ester that is known as a tumor promoter, induces differentiation of myeloid cells and suppresses their proliferation. We studied the regulation of apoptosis by TPA in human monocytic cell line U937 cells that lack p53. Untreated U937 cells constitutively underwent apoptosis, and TPA enhanced apoptosis in these cells. Further studies showed that TPA increased production of tumor necrosis factor-alpha (TNFalpha) in U937 cells, and exogenously added TNFalpha induced apoptosis. Moreover, the induction of apoptosis by TPA was blocked by anti-TNFalpha antibody. Similar results were obtained in the myeloblastic cell line KY821 cells. We also found that the induction of apoptosis by TPA was increased in cells overexpressed with TNF receptor 1 but not in control cells. Furthermore, TPA failed to induce the production of TNFalpha and apoptosis in cells with either their protein kinase C or mitogen-activated protein kinase pathway blocked. Our results indicate that TPA induces apoptosis, at least in part, through a pathway that requires endogenous production of TNFalpha in U937 cells. Our data also suggest that the induction of apoptosis by TPA occurs through activation of protein kinase C and mitogen-activated protein kinase and TNFalpha is an autocrine-stimulating factor for the induction of apoptosis in these cells.

Apoptosis↗
PubMed1999

p21WAF1 expression by an activator of protein kinase C is regulated mainly at the post-transcriptional level in cells lacking p53: important role of RNA stabilization.

p21(WAF1) inhibits cyclin-cyclin-dependent kinase (Cdk) complexes, causing cell cycle arrest. p21(WAF1) contains p53-binding sites in its promoter and expression of p21(WAF1) is induced by functional p53. In the present work, we have studied the role of protein kinase C (PKC) in the induction of p21(WAF1) and show that induction of p21(WAF1) expression can occur by activation of PKC in cells having no p53. Human ovarian carcinoma cells, SKOV-3, lack p53 protein and PMA, a potent activator of PKC, did not induce p53. PMA increased the expression of p21(WAF1) mRNA both in these cells and in other cells which do not contain p53 (THP-1 and U937). Treatment of human embryonic fibroblasts, WI38, with PMA also induced the accumulation of p21(WAF1) without affecting p53 levels. However, PMA did not increase levels of p21(WAF1) mRNA in cells where either the PKC or the mitogen-activated protein kinase pathway was blocked. Furthermore, treatment of cells with various phorbol ester derivatives which activate PKC resulted in the induction of p21(WAF1) in SKOV-3 cells. In contrast, phorbol esters which do not activate PKC failed to induce p21(WAF1) expression. PMA increased the transcriptional rate of p21(WAF1) and activated the transcription of a luciferase reporter gene, controlled by the p21 promoter, in SKOV-3 cells with or without a p53 consensus-binding sequence. By contrast, PMA markedly stabilized p21(WAF1) mRNA; the half-life (t1/2) of p21(WAF1) in PMA-treated cells was >8 h compared with <1 h in untreated cells. These findings provide evidence that the PKC pathway induces expression of p21(WAF1) independently of p53. Our present study also suggests that the accumulation of p21(WAF1) transcripts by PMA occurs mainly at post-transcriptional level.

Calcium-Calmodulin-Dependent Protein Kinases↗
PubMed1999

Mucoadhesion of polystyrene nanoparticles having surface hydrophilic polymeric chains in the gastrointestinal tract.

The mucoadhesion of polystyrene nanoparticles having surface hydrophilic polymeric chains in the gastrointestinal (GI) tract was investigated in rats. Radiolabeled nanoparticles were synthesized by adding hydrophobic 3-(trifluoromethyl)-3-(m-[125I]iodophenyl)diazirine in the final process of nanoparticle preparation. The radioiodonated diazirine seemed to be incorporated in the hydrophobic polystyrene core of nanoparticles. The incorporation rate was less than 10%, irrespective of nanoparticle type. The diazirine incorporated in nanoparticles exhibited little leakage from them even though they were mixed with a solution corresponding to GI juice. The change in blood ionized calcium concentration after oral administration of salmon calcitonin (sCT) with nanoparticles showed that the in vivo enhancement of sCT absorption by radiolabeled nanoparticles was the same as that by non-labeled nanoparticles. The GI transit rates of nanoparticles having surface poly(N-isopropylacrylamide), poly(vinylamine) and poly(methacrylic acid) chains, which can improve sCT absorption, were slower than that of nanoparticles covered by poly(N-vinylacetamide), which does not enhance sCT absorption at all. These slow transit rates were probably the result of mucoadhesion of nanoparticles. The strength of mucoadhesion depended on the structure of the hydrophilic polymeric chains on the nanoparticle surface. The mucoadhesion of poly(N-isopropylacrylamide) nanoparticles, which most strongly enhanced sCT absorption, was stronger than that of ionic nanoparticles, and poly(N-vinylacetamide) nanoparticles probably did not adhere to the GI mucosa. These findings demonstrated that there is a good correlation between mucoadhesion and enhancement of sCT absorption.

Analgesics↗
PubMed1999

Molecular cloning and characterization of a novel member of the MAP kinase superfamily.

BACKGROUND: Members of the MAP kinase superfamily play important roles in a wide variety of signal transduction pathways, and several members have been identified. However, the diversity and complexity of cellular responses in mammalian systems may imply existence of hitherto unidentified members of the MAP kinase superfamily. RESULTS: We report the molecular cloning and characterization of a novel member of the MAP kinase superfamily. We isolated full-length mouse and human cDNAs that encode complete open reading frames of a novel protein kinase, termed MOK. MOK consists of 419 (human) and 420 (mouse) amino acids, with a calculated molecular weight of 48kDa. MOK contains all of the protein serine/threonine kinase consensus motifs and shows a modest similarity to members of the MAP kinase superfamily and MAK and MAK-related kinase (MRK). In addition, MOK possesses a Thr-Glu-Tyr (TEY) motif in the activation loop domain, as do classical MAP kinases. MOK is widely expressed in normal tissues and organs and localizes to the cytoplasm. MOK is able to phosphorylate several known MAP kinase substrates and to undergo autophosphorylation. A mutation in the TEY motif to AEF abolished the kinase activity of MOK, and the treatment of cells with a phosphatase inhibitor, okadaic acid, enhanced the kinase activity of MOK, suggesting the existence of an upstream kinase. Phorbol ester TPA was found to stimulate the kinase activity of MOK, whereas serum stimulation, osmotic shock, or anisomycin treatment did not significantly activate MOK. CONCLUSION: These results indicate that MOK is distantly related to members of known subfamilies of the MAP kinase superfamily and can therefore be classified as a novel member.

Amino Acid Sequence↗
PubMed1999

A study on hydroxyapatite formation on/in the hydroxyl groups-bearing nonionic hydrogels.

Using the biomimetic method, we formed a hydroxyapatite (HAp) layer on/in certain types of nonionic hydrogels that contain hydroxyl groups. The hydrogels used were poly(vinyl alcohol) (PVA), poly(2-hydroxyethyl methacrylate) (PHEMA), poly(glucosyloxyethyl methacrylate) (PGEMA), and agarose. Under an optical microscope, we observed a thin, continuous HAp layer on the top surface of the PVA, PHEMA, and PGEMA gels. On the other hand, we only observed an intermittent HAp layer on the surface of the agarose gel. The swelling ratio and the bound water content of these hydrogels were measured as an essential character in HAp formation. There was some relation among the HAp formation, the swelling ratios, and the bound water content.

Calcinosis↗