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Biomedical subjects

T Akaike

Publications and source records attributed to T Akaike.

At least 217 records · Page 12Linked to original sources
PubMed1992

The tectorecipient zone in the inferior olivary nucleus in the rat.

Tecto-olivary and olivocerebellar projections in the rat were investigated in order to identify the tectorecipient zone in the inferior olivary nucleus and to determine whether inferior olivary neurons projecting to the cerebellar tecto-olivo-recipient zones (lobule VII, crus II, lobulus simplex, and paramedian lobule) originate in the different regions within the tectorecipient zone. An electrophysiological method and an axonal transport technique of wheat-germ agglutinin-conjugated horseradish peroxidase were used. The tectorecipient zone was identified in the caudomedial region of the medial accessory olive. Neurons projecting to lobule VII originated in the caudomedial region of the tectorecipient zone, but those to crus II, lobulus simplex, and paramedian lobule originated in its rostrolateral region. These observations suggest that there are two independent tecto-olivo-cerebellar systems: 1) superior colliculus--the medial region of the tectorecipient zone--lobule VII--the caudomedial region of the fastigial nucleus; and 2) superior colliculus--the rostralateral region of the tectorecipient region--crus II, lobulus simplex, and paramedian lobule--the dorsolateral protuberance of the fastigial nucleus.

Animals↗
PubMed1992

Receptor-mediated formation of multilayer aggregates of primary cultured adult rat hepatocytes on lactose-substituted polystyrene.

We used a lactose-substituted polystyrene, poly-N-p-vinylbenzyl-D-lactonamide (PVLA), as a substratum for adult rat hepatocytes in primary culture. Spherical-shaped hepatocytes attached on PVLA substratum formed stable multilayer aggregates anchored on substratum through the stimulation of epidermal growth factor (EGF). The cells required calcium ion essentially to form the aggregates. The formation of multilayer aggregates was inhibited by colchicine, but not by cytochalasin B. The inhibition was also observed by added PVLA molecules in the culture medium and by treating surfaces of PVLA-coated dishes with allo A lectin. It was suggested that adult rat hepatocytes attached on PVLA substratum required the specific interaction between asialoglycoprotein receptors on the cell surface and PVLA substratum to form anchored multilayer aggregates.

Animals↗
PubMed1992

Hydroxyl radical generation by red tide algae.

The unicellular marine phytoplankton Chattonella marina is known to have toxic effects against various living marine organisms, especially fishes. However, details of the mechanism of the toxicity of this plankton remain obscure. Here we demonstrate the generation of superoxide and hydroxyl radicals from a red tide unicellular organism, C. marina, by using ESR spectroscopy with the spin traps 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) and N-t-butyl-alpha-phenylnitrone (PBN), and by using the luminol-enhanced chemiluminescence response. The spin-trapping assay revealed productions of spin adduct of superoxide anion (O2-) (DMPO-OOH) and that of hydroxyl radical (.OH) (DMPO-OH) in the algal suspension, which was not observed in the ultrasonic-ruptured suspension. The addition of superoxide dismutase (500 U/ml) almost completely inhibited the formation of both DMPO-OOH and DMPO-OH, and carbon-centered radicals were generated with the disappearance of DMPO-OH after addition of 5% dimethyl sulfoxide (Me2SO) and 5% ethanol. Furthermore, the generation of methyl and methoxyl radicals, which are thought to be produced by the reaction of hydroxyl radical and Me2SO under aerobic condition, was identified using spin trapping with a combination of PBN and Me2SO. Luminol-enhanced chemiluminescence assay also supported the above observations. These results clearly indicate that C. marina generates and releases the superoxide radical followed by the production of hydroxyl radical to the surrounding environment. The velocity of superoxide generation by C. marina was about 100 times faster than that by mammalian phagocytes per cell basis. The generation of oxygen radical is suggested to be a pathogenic principle in the toxication of red tide to susceptible aquaculture fishes and may be directly correlated with the coastal pollution by red tide.

Cyclic N-Oxides↗
PubMed1992

Bactericidal activity of alkyl peroxyl radicals generated by heme-iron-catalyzed decomposition of organic peroxides.

To clarify the nature of cytocidal molecular species among the radicals generated in the iron-catalyzed reactions of peroxides (ROOH), we examined the cytocidal effects of these radicals against gram-positive and gram-negative bacteria in the presence or absence of various radical scavengers. Three organic peroxides, t-butyl hydroperoxide (t-BuOOH), methyl ethyl ketone peroxide (MEKOOH), and cumene hydroperoxide, were used. Each radical generated from these peroxides was identified and quantitated by electron spin resonance (ESR) spin trapping with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). The major cytotoxic radical species generated in the mixtures of various peroxides and heme iron, especially methemoglobin, metmyoglobin, or hemin, was the alkyl peroxyl radical (ROO.). Strong bactericidal action against gram-positive bacteria was observed in the peroxide-heme iron system, especially in the case of t-BuOOH and MEKOOH. Killing curves for gram-positive bacteria showed an initial lag period, which may indicate the multihit/multitarget kinetics of cell killing. When the diethylenetriamine pentaacetic acid (DTPA)-Fe2+ complex was used as a catalyst for decomposition of various peroxides, alkyl, alkoxyl, and alkyl peroxyl radicals were identified by spin-trapping analysis. However, study of the time course of alkyl peroxyl radical production in the DTPA-Fe2+ complex system revealed that radical species generated in this system were very short lived: a maximal level was achieved within 1 min and then declined sharply, and no bactericidal activity was observed after 10 min. In contrast, the alkyl peroxyl radical level generated by the organic peroxide-heme iron system remained high for 30 min or longer. The generation of alkyl peroxyl radicals quantified by ESR correlated quite well with the bactericidal effect of the system of peroxide plus iron. In addition, bactericidal activity was completely inhibited by the addition of the spin trap DMPO, as well as of other various radical scavengers (alpha-tocopherol and L-ascorbic acid), into the peroxide-heme iron system, but this effect was not observed with superoxide dismutase, beta-carotene, dimethyl sulfoxide, diphenylamine, or butylated hydroxyltoluene. In view of these results, it is assumed that alkyl peroxyl radicals are the potent molecular species that are cytotoxic against bacteria, whereas alkoxyl radicals (RO.) generated in this system do not affect bacterial viability.

Benzene Derivatives↗
PubMed1992

High correlation between lipid peroxide radical and tumor-promoter effect: suppression of tumor promotion in the Epstein-Barr virus/B-lymphocyte system and scavenging of alkyl peroxide radicals by various vegetable extracts.

We examined the ability of hot-water extracts of 66 vegetables and plants to suppress tumor promotion, as well as to scavenge lipid peroxide radicals in vitro. To assess the effect against tumor promotion (transformation) in vitro, we used the phorbol myristate acetate/Epstein-Barr virus/B-lymphocyte system. To assess the lipid radical-scavenging effect, the luminol-enhanced chemiluminescence method using the tert-butyl hydroperoxide/heme system was used, which generates more alkyl peroxide radical (ROO.) than alkyl (R.) and alkoxyl (RO.) radicals. The results showed a significant correlation between the anti-tumor-promoting effect and the lipid radical-scavenging effect (r = 0.82). We found that boiled extracts of green leaves of carrot, crucifers, and beans (black bean, red bean, mung bean, and soybean) had the greatest anti-tumor-promoter and radical-scavenging activities. Cold-water extracts of vegetables generally exhibited only about 10% or less of the activity of the hot-water extracts.

Antigens, Viral↗
PubMed1992

Evidence of direct generation of oxygen free radicals from heterocyclic amines by NADPH/cytochrome P-450 reductase in vitro.

Highly purified cytochrome P-450 reductase (also called cytochrome c reductase; EC 1.6.2.4.) and NADPH were used to generate superoxide radical (O2.-) from 11 different heterocyclic amines (HCAs) as identified by electron spin resonance spectroscopy using the spin trapping method with 5,5-dimethyl-1-pyrroline N-oxide (DMPO). The signal intensity of DMPO-OOH(-O2-) (i.e., the DMPO spin adduct of O2.-) was strongest for 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ). The O2.- generation with HCAs decreased in the following order: 2-amino-3,8-dimethyl-imidazo[4,5-f]quinoxaline (MeIQx) = 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) > 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (diMeIQx) > or = other HCAs; O2.- generation was lowest with 2-amino-3-methyl-9H-pyrido[2,3-b]indole .CH3COOH (MeA alpha C). By using Lineweaver-Burk plots, Km values of cytochrome P-450 reductase for mitomycin C, IQ, and MeIQ were determined to be 1.60 x 10(-6) M, 1.97 x 10(-5) M, and 2.83 x 10(-6) M, respectively. The present findings have important implications for carcinogenesis because of the known effect of oxygen radicals on cell proliferation.

Amines↗
PubMed1992

Tissue reconstruction in primary cultured rat hepatocytes on asialoglycoprotein model polymer.

Adult rat hepatocytes attached on an asialoglycoprotein model polymer, poly-N-p-vinylbenzyl-D-lactonamide (PVLA), formed anchored multilayer aggregates that had stable three-dimensional structure when epidermal growth factor (EGF) and insulin were added to the culture medium. The formation of multilayer aggregates depended on the concentrations of EGF and insulin added. Furthermore, the formation was synergistically accelerated by the presence of both hormones. Cells in the aggregates expressed a higher level of albumin secretion and lower proliferative ability than those in monolayer cultures on collagen. It seemed likely that the cells in multilayer aggregates experienced stable differentiated states resembling those in vivo through the formation of multilayer aggregates. The culture system described here has potential use for the study of the process of liver regeneration and the development of hepatic module systems such as a bioreactor and a hybrid artificial liver.

Albumins↗
PubMed1992

Regulation of differentiation and proliferation of rat hepatocytes by lactose-carrying polystyrene.

We noticed that hepatocytes recognize the structure of oligosaccharides via asialoglycoprotein receptors and synthesized lactose-carrying styrene polymer (PVLA) as an asialoglycoprotein model. We found that the regulation of differentiated function and proliferation of hepatocytes that were cultured on polystyrene dishes can be achieved by varying the amount of PVLA coated on the dishes. The 3H-thymidine uptake of cultured hepatocytes is low for cells cultured on dishes coated with high amounts of PVLA in which the hepatocytes are round and is highest for those cultured on dishes with a low PVLA coating level in which the hepatocytes are spread in shape. Moreover, bile acid release as a typical differentiated function of hepatocytes was maintained at higher levels in hepatocytes attached on dishes coated with a high level of PVLA. Our results indicated that regulation of differentiated function and proliferation in hepatocytes could be achieved by specific ligand-mediated recognition of microscopic surface structure. Thus, it may be possible to regulate proliferation and differentiation of hepatocytes by design of the culturing substrata.

Animals↗
PubMed1992

Control of adhesion and detachment of parenchymal liver cells using lactose-carrying polystyrene as substratum.

Adhesion of hepatocytes on culture dishes whose surface was coated with a lactose-carrying styrene homopolymer (PVLA) was investigated. Hepatocytes maintained their round shape on PVLA substratum, which is in contrast to the usual spread shape characteristic of those cultured on collagen and fibronectin substrata. Calcium ion was indispensable for hepatocyte adhesion in PVLA substratum, and hence the hepatocytes on PVLA were easily detached when the culture was treated with ethylenediamine tetraacetic acid (EDTA). The recovered hepatocytes readheres to PVLA. The adhesion of hepatocytes to PVLA was not inhibited by cytochalasin B but by colchicine. Hepatocytes recognize the galactose moieties on the surface of asialoglycoproteins and removes these proteins from the blood stream by receptor mediated endocytosis. The mechanism of adhesion of hepatocytes on PVLA substratum which contains a high density of galactose residues was distinct from the attachment on collagen and fibronectin substrata, and showed great similarity to the receptor and ligand interactions which occurs in the clearance of asialoglycoproteins by hepatocytes.

Animals↗
PubMed1992

[Intracellular killing mechanisms of alveolar macrophages against Mycobacterium avium complex].

To clarify the intracellular killing mechanisms of alveolar macrophages against Mycobacterium avium complex, effects of cytokines on O2- and NO2- production from normal and BCG-induced alveolar macrophages were studied. Intracellular growth of M. avium complex was inhibited in the alveolar macrophages stimulated by TNF, but not IFN. Enhancement of O2- production by normal alveolar macrophages stimulated by cytokines, was associated with the inhibition of intracellular growth of M. avium complex. However, when NO2- production by the alveolar macrophages was enhanced by the stimulating of IFN or IFN+TNF, in the presence L-arginine in the culture medium, their defense activity against M. avium complex decreased.

Animals↗
PubMed1991

Enhancement by IL-1 beta and IFN-gamma of platelet activation: adhesion to leukocytes via GMP-140/PADGEM protein (CD62).

We have examined the effect of inflammatory cytokines on the platelet activation. IL-1 beta and IFN-gamma were found to enhance the adhesion of thrombin-treated platelets to monocytic leukemia cells (U937), when the adhesion was assayed by platelet-mediated cell agglutination. The agglutination was inhibited by a monoclonal anti-GMP140 antibody or EDTA, suggesting that the enhanced platelet adhesion to the leukemic cells was mediated by GMP140. In addition, these cytokines also increased the release of 5-HT from platelets in the presence of a low concentration of thrombin. These data suggest that platelet functions are regulated by the cytokines and that activated platelets participate in inflammatory process.

Blood Platelets↗
PubMed1991

Triggering of the vascular permeability reaction by activation of the Hageman factor-prekallikrein system by house dust mite proteinase.

A 30-kilodalton (kDa) proteinase from the house dust mite Dermatophagoides farinae (Df-proteinase) was recently purified (Takahashi et al. (1990) Int. Arch. Allergy Appl. Immunol. 91, 80-85). In this paper we detailed the biological activities of the Df-proteinase. The activation of the kinin cascade by Df-proteinase was examined in vitro by using purified guinea pig Hageman factor (HF), prekallikrein (PK) and high-molecular-weight kininogen (HMWK) and the effect of this proteinase on endogenous human plasma proteinase inhibitors (serpins) and alpha 2-macroglobulin was tested. In addition, enhancement of the vascular permeability reaction in guinea pig skin by Df-proteinase was examined in vivo. These experiments showed that Df-proteinase could activate all the steps of the kinin-generating cascade, i.e., HF, PK and HMWK, and that Df-proteinase retained proteolytic activity even in the presence of an excess amount of endogenous proteinase inhibitors in plasma. We also found that the marked enhancement of the vascular permeability reaction was induced by Df-proteinase via the activation of the kinin-generating cascade without the release of histamine. From these results, we conclude that the proteinase of the house dust mite, Df-proteinase, has the potential to generate bradykinin and that the presence of this proteinase in biological systems would exacerbate inflammatory reactions in some pathological conditions.

Animals↗
PubMed1991

Oxygen free radicals as pathogenic molecules in viral diseases.

Oxygen free radicals such as superoxide anion (O2-) were generated markedly in influenza virus-infected mouse lung, and these molecular species were identified as the potent pathogenic agents. This finding has many important implications for understanding viral pathogenesis: namely, the direct viral cytotoxicity (referred cytopathic effect) is only a fraction of several types of events induced by virus infection. The toxicity and reactivity of oxygen radicals, which are presumably generated in excessive amounts by the overreaction of the host's immune response against the organs or tissues in which viruses are replicating, may explain the mechanism of tissue injuries observed not only in influenza virus infection in mice, but also in other types of viral diseases in which immunological interactions are usually involved.

Animals↗
PubMed1991

[A preview of the practical application of hybrid artificial liver].

In order to replace the liver function, the development of the system where natural hepatocytes are immobilized in a matrix polymer might be considered as the best way. Each hepatocyte has a number of specific receptors for several ligards. We noticed that the hepatocyte recognizes the structure of oligosaccharides via asialoglycoprotein receptors and synthesizes lactose-carrying styrene polymer (PVLA) as a asialoglycoprotein model. On PVLA-coated dish, the specific functions as well as attachment of hepatocyte were successfully maintained. Moreover, cultured hepatocytes on PVLA substratum started gradual movement, and then remarkably formed multilayer aggregations which had long-term survival. Hepatocytes in the aggregation exhibited better maintenance of specific hepatocyte-functions such as the synthesis of albumin and secretion of bile acid, and retained mitochondrial enzyme activity than those in the monolayer culture on collagen and fibronectin. Furthermore, we found that DNA synthesis in cultured hepatocytes was correlated to the cell-shape which could be controlled by the concentration of PVLA substratum. These results also suggested that the PVLA could potentiate the regulation of the differentiation and proliferation of hepatocytes.

Artificial Organs↗
PubMed1990

Selective removal of anti-acetylcholine receptor antibodies and IgG in vitro with an immunoadsorbent containing immobilized sulfathiazole.

Adsorption therapy, which treats the autoimmune disease by the selective removal of pathogenic substances from the blood, is an active subject. In this therapy, bioactive molecules such as antigen, antibodies and protein A are usually used as affinity-ligands. The disadvantages of using these substances as affinity-ligands are the availability, sterilizability, and ability to cause antigenic reactions. After surveying hundreds of synthetic compounds, it was found that polyacrylic beads [Eupergit C (EC)] immobilized covalently with sulfathiazole (ST) are an ideal biomimetic ligand for the selective adsorption of IgG (24.3 +/- 0.4 mg IgG/g wet beads). In an in vitro study, this adsorbent selectively removed the antiacetylcholine (AChR) receptor antibody of myasthenia gravis (MG) patients. Further experiments demonstrated that the Fab fragment was adsorbed three times more efficiently than the Fc fragment of IgG.

Animals↗