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Biomedical subjects

J Yamada

Publications and source records attributed to J Yamada.

At least 19 recordsLinked to original sources
PubMed2001

p53 regulates ceramide formation by neutral sphingomyelinase through reactive oxygen species in human glioma cells.

The present study was designed to elucidate the relationship between p53 and ceramide, both of which are involved in apoptotic signaling. Treatment of human glioma cells with etoposide caused apoptosis only in cells expressing functional p53. p53 activation was followed by the formation of reactive oxygen species (ROS), superoxide anion (O2-*) measured by hydroethidium oxidation into ethidium and hydrogen peroxide (H2O2) measured by oxidation of 2',7'-dichlorofluorescin (DCFH) into 2',7'-dichlorofluorescein (DCF), which was accompanied with ceramide generation through the activation of neutral, but not acid, sphingomyelinase. Superoxide dismutase (SOD), a selective antioxidant for O2-*, had no effects on p53 expression but inhibited ceramide generation and apoptotic cell death caused by etoposide. However, catalase, a specific antioxidant for H2O2, only weakly inhibited and sodium formate, a hydroxyl radical (* OH) scavenger, unaffected etoposide-induced apoptosis. Like etoposide-induced cell death, treatment of glioma cells with the O2-*-releasing agent, pyrogallol, induced typical apoptosis and ceramide generation even in the presence of catalase. In contrast, human glioma cells lacking functional p53, either due to mutation or the expression of E6 protein of human papillomavirus, were highly resistant to etoposide and exhibited no significant change in the ceramide level. Moreover, expression of functional p53 protein in glioma cells expressing mutant p53 using a temperature-sensitive human p53(Val138) induced ceramide accumulation by the activation of neutral sphingomyelinase which was dependent on the generation of O2-*. Taken together, these results suggest that p53 may modulate ceramide generation by activation of neutral sphingomyelinase through the formation of O2-*, but not its downstream compounds H2O2 or * OH.

Apoptosis↗
PubMed2001

Role of phasic dynamism of p38 mitogen-activated protein kinase activation in ischemic preconditioning of the canine heart.

Although ischemic stress, including ischemic preconditioning (IP), activates p38 mitogen-activated protein kinase (MAPK), the relationship between p38 MAPK activation and the underlying cellular mechanisms of cardioprotection by IP is not verified in vivo. We examined the effects of the selective p38 MAPK inhibition on the cardioprotective effect of IP in the open-chest dogs. The coronary artery was occluded 4 times for 5 minutes, separated by 5 minutes of reperfusion (IP) followed by 90 minutes of occlusion and 6 hours of reperfusion. We infused SB203580 into the coronary artery during IP and 1 hour of reperfusion, during IP alone, and during sustained ischemia in the IP group. p38 MAPK activity markedly increased during IP but did not additionally increase at the onset of ischemia and was even attenuated at 15 minutes of sustained ischemia, and heat-shock protein (HSP) 27 was phosphorylated and translocated from cytosol to myofibril or nucleus without affecting total protein level at the onset of ischemia compared with the control group. SB203580 treatment (1 micromol/L) only during IP blunted the infarct size limitation by IP (37.3+/-6.3% versus 7.4+/-2.1% in the IP group, P:<0.01) and attenuated either phosphorylation or translocation of HSP27 during IP. Although the SB203580 treatment throughout the preischemic and postischemic periods had no significant effect on infarct size (33.3+/-9.4%) in this model, treatment with SB203580 only during ischemia partially mimicked the infarct size limitation by IP (26.8+/-3.5%). Thus, transient p38 MAPK activation during ischemic preconditioning mainly mediates the cardioprotection followed by HSP27 phosphorylation and translocation in vivo in the canine heart.

Animals↗
PubMed2001

Enhancement of Rho/Rho-kinase system in regulation of vascular smooth muscle contraction in tachycardia-induced heart failure.

OBJECTIVE: The Rho/Rho-kinase system regulates Ca(2+) sensitivity in vascular smooth muscle. A new drug, Y-27632, specifically inhibits Rho-kinase and hence decreases the phosphorylation of myosin light chain, thus reducing contraction. Here, we compare the effects of Y-27632 and nifedipine on the vasoconstrictor response of the femoral artery in heart failure. METHODS: Heart failure (HF) was produced by chronic rapid RV pacing (250 bpm, 28 days, six dogs). Indo1-AM was loaded into endothelium-denuded femoral artery segments for measuring intracellular [Ca(2+)]. Tension and changes in intracellular [Ca(2+)] [the change in the ratio (418 nm/468 nm) of Indo1 fluorescence (F(ratio))] were simultaneously measured in Krebs-Ringer solution. RESULTS: In HF: (i) norepinephrine (10 microM) produced greater tension (784+/-52 g/cm(2)) than in control (502+/-64 g/cm(2)) despite a similar increase in F(ratio), indicating increased Ca(2+) sensitivity in vascular smooth muscle; (ii) nifedipine attenuated this enhanced response by only a maximum of 27% at 1 micromol/l with a 56% reduction in F(ratio); (iii) Y-27632 attenuated it by a maximum of 80% at 100 micromol/l without a significant change in F(ratio); (iv) RhoA protein and mRNA expression levels in the femoral artery were up-regulated by +110% and +56%, respectively, while those of Rho-kinase were unchanged. CONCLUSIONS: The Ca(2+)-sensitizing mechanism involving the Rho/Rho-kinase system may be deeply involved in the enhanced arterial vasoconstriction seen in HF. Since Y-27632 attenuated this response in small arteries, it shows potential as a novel, potent vasodilator for the treatment of HF.

Amides↗
PubMed2001

Improved beta-thujaplicin production in Cupressus lusitanica suspension cultures by fungal elicitor and methyl jasmonate.

Production of a novel antimicrobial tropolone, beta-thujaplicin, in Cupressus lusitanica suspension cultures was studied by using a variety of chemicals and fungal elicitors. Sodium alginate, chitin, and methyl jasmonate resulted in 2-, 2.5-, and 3-fold higher beta-thujaplicin production, respectively, than in the control. Significantly improved beta-thujaplicin production (187 mg l(-1)) was obtained using a high cell density (180-200 g l(-1)) and fungal elicitor treatment [10 mg (g fresh cells)(-1)] in a production medium with a high ferrous ion concentration (0.3 mM). This improved volumetric productivity was 3- to 4-fold higher than obtained under standard conditions. A synergistic effect of fungal elicitor and ferrous ion on beta-thujaplicin production was also suggested by our study. Plant cell culture technology is a promising alternative for producing a large variety of secondary metabolites that are widely used as food additives, pharmaceuticals, and dairy products (Verpoorte et al. 1999). Thus, beta-thujaplicin production by plant cell cultures was developed with the goal of commercial application (Berlin and Witte 1988; Itose and Sakai 1997; Ono et al. 1998). However, the production of beta-thujaplicin by plant cell cultures is still not competitive for use in industrial applications. In this study, we assessed the effects of methyl jasmonate, alginate, chitin, and fungal elicitor on beta-thujaplicin production; we obtained a significantly elevated beta-thujaplicin production by using an improved culture strategy.

Acetates↗
PubMed2001

Cytoarchitectonic subdivisions of the parabrachial nucleus in the Japanese monkey (Macacus fuscatus) with special reference to spinoparabrachial fiber terminals.

The cytoarchitectonic subnuclear organization of the parabrachial nucleus (PB) surrounding the brachium conjunctivum (BC) in the monkey was examined using the Nissl method and the anterograde axonal flow method. PB of the monkey could be divided into the following subnuclei: the dorsal area (DPBM) along the medial surface of the medial three-fourths of BC in the caudal half of medial PB (PBM), the ventral area (VPBM) along the medial surface of the lateral one-fourth of BC in the rostral two-thirds of PB, the ventrolateral part of lateral PB (PBL) lateral to BC throughout PB (EL), the ventral part of the rostral half of PBL ventral to EL (EXL), the medial part of middle PBL along the dorsal surface of BC (VL), the dorsal and lateral marginal part of PBL in the rostral two-thirds of PB (DL), the cell cluster in the dorsomedial part of the rostral half of PBL between VL and DL (CL), the dorsocentral part appearing at the level of root exit of the trochlear nerve between DL and CL and extending to the rostral end of PBL (IL), the area between DL and IL in the rostral one-seventh of PBL (SL), and Kölliker-Fuse nucleus (KF) ventral to EL and BC in the middle one-third of PB and lateral to the lateral pontine tegmentum. After the injection of biotinylated dextran amine into the upper cervical segments, labeled fibers terminated in each subdivision of PB with different densities; most heavily in IL, more heavily in DL and KF, moderately in EL and VPBM, and scarcely in the rest of PB. The present study demonstrated for the first time the subdivisions of PB in the monkey, which were essentially common to those of the rat based on the cytoarchictecture of PB and spinal fiber terminals in it.

Animals↗
PubMed2001

Immunohistochemical study of the distribution of endocrine cells in the gastrointestinal tract of the camel (Camelus bactrianus).

The regional distribution and relative frequency of endocrine cells in the gastrointestinal tract of the camel, Camelus bactrianus, were investigated using immunohistochemical methods. Ten types of immunoreactive (IR) endocrine cells were identified in this study. Among these cell types, only serotonin- and somatostatin-IR cells were detected in almost all regions of the gastrointestinal tract. Most of the cell types showed peak density in the pyloric gland region. The others showed restricted distribution: gastrin, cholecystokinin (CCK), motilin, bovine pancreatic polypeptide (BPP), and (gastric) substance P in the stomach; gastrin, CCK, BPP, gastric inhibitory polypeptide (GIP), glucagon, peptide tyrosine tyrosine (PYY) and substance P in the small intestine; and CCK, motilin, BPP, and PYY in the large intestine. Fundamentally the distribution pattern of endocrine cells in the gastrointestinal tract of the camel is similar to that of cattle. The distribution and frequency of endocrine cells in the glandular sac region are the same as those of the cardiac gland.

Animals↗
PubMed2001

Immunolocalization of gastrin-releasing peptide in the bovine uterus and placenta.

Gastrin-releasing peptide (GRP), a mammalian homologue of amphibian bombesin, has been suggested to be a novel regulatory peptide in the reproductive tract during pregnancy. In this study, the localization of GRP in the bovine uterus and placenta was demonstrated by immunohistochemistry. Uterine and placental samples were collected from nonpregnant and pregnant specimens, respectively. Tissue sampling was done from the caruncle and intercaruncle of the uterus, and from the placentome (caruncle and cotyledon) and intercotyledon of the placenta. In all the tissues examined, GRP was detected although its immunoreactivity was observed at various degrees. In the uterus, moderate immunoreactivity for GRP was observed in the uterine gland epithelial cells. In the placenta, strong immunoreactivity for GRP was demonstrated in the uterine gland epithelial cells; moderate in superficial epithelial cells; and weak in the trophoblasts, trophoblastic giant cells and cryptal epithelial hybrid cells. In both nonpregnant and pregnant animals, GRP was immunolocalized in the uterine gland secretions and was found predominantly in the supranuclear region of the uterine gland epithelial cells. These findings may suggest that GRP is secreted into the uterine lumen and regulates the intrauterine environment of both the nonpregnant and pregnant bovine by exocrine, autocrine and/or paracrine manner.

Animals↗
PubMed2001

Cytotoxic T cells play no essential role in acute rejection of orthotopic corneal allografts in mice.

PURPOSE: To determine whether cytotoxic T cells of the direct alloreactive type are activated and responsible for early, acute failure of orthotopic corneal allografts observed in eyes of C57BL/6 but not of BALB/c mice. METHODS: Corneas from BALB/c and BALB.B mice were placed orthotopically in eyes of C57BL/6 and beta-2 microglobulin knockout mice (deficient in CD8(+) cytotoxic T cells). Graft fates were assessed clinically, and the T lymphocytes of recipients were assayed for the capacity to lyse target cells bearing donor major (MHC) and/or minor histocompatibility (minor H) antigens (direct and indirect pathways, respectively). RESULTS. Similar to BALB/c recipients, C57BL/6 mice with rejected cornea allografts acquired donor minor H-specific T cells. Unlike BALB/c recipients, C57BL/6 mice-both rejectors and acceptors-acquired donor MHC-specific T cells. beta-2 Microglobulin knockout mice showed rejection of corneal allografts in a manner indistinguishable from C57BL/6 mice, including early, acute rejection, yet T cells from beta-2 microglobulin knockout recipients of corneal allografts displayed no cytotoxic T cells specific for either donor MHC or minor H alloantigens. CONCLUSIONS: Although C57BL/6 mice acquired donor MHC-specific cytotoxic T cells (direct alloreactive cells), neither these cells nor donor minor H-specific cytotoxic T cells (indirect alloreactive cells) play any essential role in corneal allograft rejection, including the early acute failure uniquely observed in C57BL/6 eyes.

Acute Disease↗
PubMed2000

Increased phospholipase D2 activity during hypoxia-induced death of PC12 cells: its possible anti-apoptotic role.

During hypoxic incubation (1% O2) of PC12 cells, the PLD activity was transiently increased within 12h, followed by a gradual decrease. In the in vitro assay, the increased PLD activity was independent of GTPgammaS required for PLD1 or of oleic acid for PLD(OA), suggesting the activation of PLD2. The level of PLD2 protein showed no change up to 12h but a gradual decrease after 24 h. Pretreatment of cells with S. chromofuscus PLD resulted in inhibition of hypoxia-induced apoptotic cell death. In contrast, 1-butanol, but not 2-butanol, potentiated cell death. Moreover, the number of apoptotic cells significantly reduced in PC12 cells over-expressing PLD2. These results raise the possibility that PLD2 activation may play an anti-apoptotic role in hypoxia-induced cell death.

1-Butanol↗
PubMed2000

Serum leptin levels after central and systemic injection of a serotonin precursor, 5-hydroxytryptophan, in mice.

Effects of peripheral and central injections of a serotonin (5-hydroxytryptamine, 5-HT) precursor, 5-hydroxytryptophan (5-HTP), on serum leptin levels were studied in mice. Intracerebroventricular (i.c.v.) injection of 5-HTP or 5-HT did not increase serum leptin levels, although the peripheral injection of 5-HTP elicited an apparent hyperleptinemia. The elevation of serum leptin levels in mice induced by the peripheral injection of 5-HTP was inhibited by pretreatment with the peripheral aromatic amino acid decarboxylase inhibitor, benserazide. Furthermore, the peripheral injection of 5-HT increased serum leptin levels. These results suggest that the hyperleptinemia following systemic injection of 5-HTP is elicited by 5-HT formed in the peripheral system.

5-Hydroxytryptophan↗
PubMed2000

The 5-HT(2C/2B) receptor agonist, m-chlorophenylpiperazine, increases plasma glucagon levels in rats.

Effects of the 5-HT(2C/2B) receptor agonist m-chlorophenylpiperazine (mCPP) on plasma glucagon levels were investigated in rats. mCPP dose dependently increased plasma glucagon levels. Hyperglucagonemia elicited by mCPP was prevented by the 5-HT(2A/2B/2C) receptor antagonist, ritanserin, while the 5-HT(2A) receptor antagonist, ketanserin, did not show any effect. Increases in glucagon levels induced by mCPP were inhibited by prior adrenodemedullation. These results indicate that increases in plasma glucagon levels induced by mCPP are mediated by the 5-HT(2C/2B) receptor which in turn facilitates adrenaline release.

Adrenal Medulla↗
PubMed2000

Involvement of the 5-HT(2) receptor in hyperthermia induced by p-chloroamphetamine, a serotonin-releasing drug in mice.

The effects of a serotonin (5-hydroxytryptamine, 5-HT)-releasing drug, p-chloroamphetamine (PCA), on body temperature were investigated in mice. PCA induced hyperthermia in mice. PCA-induced hyperthermia was inhibited by the 5-HT(2A/2B/2C) receptor antagonist, 4-isopropyl-7-methyl-9-(2-hydroxy-1-methyl-propoxycarbonyl)-4,6A,7 , 8,9,10,10A-octahydro-indolo[4,3-FG]quinolone maleate (LY53857). The 5-HT(2A) receptor antagonist, ketanserin, reduced the PCA-induced hyperthermia, while the 5-HT(2B/2C) receptor antagonist, N-3-pyridinyl-3,5-dihydro-5-methyl-benzo[1,2-b:4, 5-b']dipyrrole-1(2H)-carboxamide (SB 206553), enhanced it. LY 53857, ketanserin and SB 206553 did not affect hyperactivity in mice treated with PCA. These results suggest that PCA-induced hyperthermia in mice is mediated by 5-HT(2A) receptors and is not related to changes in locomotor activity.

Animals↗
PubMed2000

A nitric oxide synthase inhibitor reduces hyperphagia induced in rats by the 5-HT(1A) receptor agonist, 8-OH-DPAT, independently of hypothalamic serotonin metabolism.

In rats, a nitric oxide (NO) synthase inhibitor, N(G)-nitro-L-arginine methyl ester (L-NAME) inhibited the hyperphagia induced by the 5-hydroxytryptamine (5-HT)(1A) autoreceptor agonist, 8-hydroxy-2-di-n-(propylamino)tetralin (8-OH-DPAT). 8-OH-DPAT reduced 5-HT metabolism in the hypothalamus, and this was not blocked by pretreatment with L-NAME. L-NAME also did not affect basal hypothalamic 5-HT metabolism or reverse the decreases in 5-HT synthesis in hypothalamus. These results suggest that the hypophagic effects of L-NAME, which inhibits NO formation, are independent of 5-HT metabolism in the hypothalamus.

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

ICAM-1 deficiency suppresses host allosensitization and rejection of MHC-disparate corneal transplants.

BACKGROUND: We used a murine model of orthotopic corneal transplantation to determine whether host deficiency in ICAM-1 promotes survival of corneal grafts with different degrees of allodisparity. METHODS: ICAM-1-/- and wild-type C57BL/6 (ICAM-1+/+) received corneal grafts from the following strains of mice: BALB/c (fully mismatched), BALB.b (mismatched at multiple minor H only), or B10.D2 [including major histocompatibility complex (MHC) mismatch]. Graft rejection, induction of allospecific delayed-type hypersensitivity (DTH) responses, and leukocytic infiltration of grafts were measured. RESULTS: There were no differences in long-term survival of allografts that were either fully mismatched or had only minor H disparity in ICAM-1+/+ vs. ICAM-1-/-hosts. However, whereas B10.D2 grafts were accepted in only 58% of the ICAM-1+/+ hosts, graft survival in ICAM-1-/- recipients was 100% (P=0.006). Moreover, none of the ICAM-1-/- mice receiving B10.D2 grafts developed allospecific DTH. CONCLUSIONS: Prolonged survival seen in MHC-mismatched grafts in ICAM-1-/- mice, along with a suppressed DTH response to donor alloantigens after transplantation, suggest that ICAM-1 is associated with recipient sensitization to MHC alloantigens.

Animals↗
PubMed2000

Immunobiology of xenogeneic cornea grafts in mouse eyes. I. Fate of xenogeneic cornea tissue grafts implanted in anterior chamber of mouse eyes.

BACKGROUND: The cornea is an immune privileged tissue that, when grafted orthotopically, forms the anterior surface of the immune privileged anterior chamber. We have recently reported that allogeneic cornea fragments implanted in the anterior chamber of mouse eyes resist immune rejection, although such graft fragments are rejected outside the eye. We wished to determine the extent to which xenogeneic cornea fragments placed in the eyes of normal mice are vulnerable to immune rejection. METHODS: Guinea pig corneas, deprived surgically of epithelium, were cut into fragments and inserted into the anterior chamber of eyes of BALB/c and severe combined immune deficient (SCID) mice, adjacent to the central cornea of the recipient. The fate of the grafts was assessed clinically by biomicroscopy and histologically for 8 weeks postimplantation. RESULTS: The majority of guinea pig cornea fragments devoid of epithelium came to rest with the raw stroma adjacent to recipient endothelium. These fragments remained clear for the 8-week observation interval in both BALB/c and severe combined immune deficient mice. Clear grafts displayed viable guinea pig keratocytes and endothelial cell layers for 4 weeks. The endothelium was then replaced by murine cells by 8 weeks. A minority of guinea pig cornea fragments were oriented with donor endothelium adjacent to recipient endothelium. Although these grafts in severe combined immune deficient eyes eventually acquired an endothelial layer that faces the anterior chamber and remained clear, similar fragments in BALB/c eyes became opaque, failed to acquire a proper lining of endothelium that faces the anterior chamber, and incited an inflammatory reaction in adjacent recipient cornea. CONCLUSIONS: Immune privilege is afforded to xenografts of guinea pig cornea placed as stromal: endothelial cell fragments in the anterior chamber of mouse eyes, but only if the surface of the fragments that faces the anterior chamber is promptly covered with corneal endothelium. The possible roles of corneal endothelium in promoting immune privilege of corneal xenografts are discussed.

Animals↗
PubMed2000

Involvement of adrenaline in diazepam-induced hyperglycemia in mice.

Diazepam-elicited hyperglycemia in mice was inhibited by adrenalectomy and the catecholamine synthesis inhibitor alpha-methyl-p-tyrosine, although it was unaffected by pretreatment with the corticosterone synthesis inhibitor dexamethasone. Diazepam-induced hyperglycemia was prevented by the alpha2 adrenoceptor antagonist idazoxan, while the beta1 and beta2 adrenoceptor antagonists, metoprolol and ICI 118 551, did not affect it. Furthermore, diazepam increased plasma adrenaline levels in mice. These results suggest that diazepam-induced hyperglycemia is closely related to adrenaline release from the adrenal gland.

Adrenergic beta-Antagonists↗
PubMed2000

Biosynthesis of sterols and ecdysteroids in Ajuga hairy roots.

Hairy roots of Ajuga reptans var. atropurpurea produce clerosterol, 22-dehydroclerosterol, and cholesterol as sterol constituents, and 20-hydroxyecdysone, cyasterone, isocyasterone, and 29-norcyasterone as ecdysteroid constituents. To better understand the biosynthesis of these steroidal compounds, we carried out feeding studies of variously 2H- and 13C-labeled sterol substrates with Ajuga hairy roots. In this article, we review our studies in this field. Feeding of labeled desmosterols, 24-methylenecholesterol, and 13C2-acetate established the mechanism of the biosynthesis of the two C29-sterols and a newly accumulated codisterol, including the metabolic correlation of C-26 and C-27 methyl groups. In Ajuga hairy roots, 3alpha-, 4alpha-, and 4beta-hydrogens of cholesterol were all retained at their original positions after conversion into 20-hydroxyecdysone, in contrast to the observations in a fern and an insect. Furthermore, the origin of 5beta-H of 20-hydroxyecdysone was found to be C-6 hydrogen of cholesterol exclusively, which is inconsistent with the results in the fern and the insect. These data strongly support the intermediacy of 7-dehydrocholesterol 5alpha,6alpha-epoxide. Moreover, 7-dehydrocholesterol, 3beta-hydroxy-5beta-cholest-7-en-6-one (5beta-ketol), and 3beta,14alpha-dihydroxy-5beta-cholest-7-en-6-one (5beta-ketodiol) were converted into 20-hydroxyecdysone. Thus, the pathway cholesterol-->7-dehydrocholesterol-->7-dehydrocholesterol 5alpha,6alpha-epoxide-->5beta-ketol-->5beta-k etodiol is proposed for the early stages of 20-hydroxyecdysone biosynthesis. 3beta-Hydroxy-5beta-cholestan-6-one was also incorporated into 20-hydroxyecdysone, suggesting that the introduction of a 7-ene function is not necessarily next to cholesterol. C-25 Hydroxylation during 20-hydroxyecdysone biosynthesis was found to proceed with ca. 70% retention and 30% inversion. Finally, clerosterol was shown to be a precursor of cyasterone and isocyasterone.

Carbon Isotopes↗