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T Agui

Publications and source records attributed to T Agui.

At least 55 records · Page 3Linked to original sources
PubMed1993

Reduced efficiency of copper transport from cytosolic to noncytosolic fractions in LEC mutant rat.

Long-Evans Cinnamon (LEC) mutant rat, which spontaneously develops a necrotizing hepatic injury at 4-5 months of age, exhibits an excess hepatic copper accumulation. Neonatal LEC rat showed higher ratio of cytosolic to noncytosolic copper contents than neonatal normal rat, suggesting that the efficiency of copper transportation into noncytosolic compartment is primarily inherently reduced in LEC rat. Additionally using northern blot analysis with neonates we suggested that the elevated metallothionein levels observed in adult LEC rat are probably secondary to elevated copper levels.

Animals↗
PubMed1993

Low response of DNA synthesis upon growth stimulation in LEC mutant rat.

Long-Evans Cinnamon (LEC) mutant rat, which spontaneously develops a chronically necrotizing hepatic injury at 4 months of age, exhibits an excess hepatic copper accumulation. DNA synthesis upon growth stimulation in LEC rat primary-cultured hepatocytes markedly decreased when compared to that of normal rat hepatocyte culture. Low response of DNA synthesis seems to be associated with nuclear disorganization induced by copper toxicity. However, LEC rat electrophoretic profile and content of each histone component responsible for DNA stability were indistinguishable from those of normal rat. These results suggest that copper-generated damage of substrates other than histones causes nuclear damage in LEC rat.

Animals↗
PubMed1992

Elevation of metallothionein gene expression associated with hepatic copper accumulation in Long-Evans Cinnamon mutant rat.

The mechanism of the metallothionein (MT) gene expression was investigated in a mutant rat, LEC, which exhibits an abnormal accumulation of copper in hepatocytes. The levels of MT mRNA were extremely high and correlated with the hepatic copper concentrations in LEC rat liver. Gel retardation assays in nuclear extracts from LEC rat liver showed an increase in the copper-dependent binding proteins, which bind to the metal responsive element (MRE) of the MT gene. These results suggest that the high intracellular copper accumulation results in the elevation of the MT gene expression through increasing a putative trans-activating factor in LEC rat.

Aging↗
PubMed1992

Expression of receptors for atrial natriuretic peptide on the murine bone marrow-derived stromal cells.

Atrial natriuretic peptide (ANP) receptors were identified on both murine bone marrow-derived stromal cell lines A-3 and ALC and primary cultured cells using [125I]ANP binding assays and Northern blot analyses. The binding of [125I] ANP to the stromal cells was rapid, saturable, and of high affinity. The dissociation constants between ANP and its receptors on these cells showed no difference among cell types, while maximal binding capacity values were different among cell types. Competitive inhibition of [125I]ANP binding with C-atrial natriuretic factor, specific for ANP clearance receptor (ANPR-C), revealed that most of [125I]ANP-binding sites corresponded to ANPR-C. Northern blotting data corroborated that bone marrow-derived stromal cells expressed ANPR-C. However, in ALC cells, ANP biological receptors (either ANPR-A or ANPR-B), the mol wt of which is approximately 130K, were detected, and cGMP was accumulated after stimulation with ANP. On the other hand, in another stromal cell clone, A-3 cells, the expression of biological receptor was not detected in the affinity cross-linking and competitive inhibition experiments using [125I]ANP. However, A-3 cells accumulated cGMP by responding to ANPR-B-specific ligand, C-type natriuretic peptide. These results suggest that ALC cells equally express ANPR-A and ANPR-B, while A-3 cells express ANPR-B dominantly. Although the physiological roles of these receptors in the bone marrow is still not resolved, ANP is expected to play a role in the regulation of stromal cell functions in bone marrow.

Animals↗
PubMed1992

A new restriction fragment length polymorphism of the ceruloplasmin gene in rat.

Using a cDNA probe of the ceruloplasmin (CP) gene, a new restriction fragment length polymorphism (RFLP) was detected in inbred strains of rat with the restriction enzyme KpnI. The RFLP behaved as a codominant trait on a single autosomal locus. Two alleles of the CP gene, which were tentatively designated as CP-A and CP-B, were almost equally distributed in 10 inbred strains. These indicate that the RFLP of the CP gene is a useful marker locus of the rat. We utilized this CP gene polymorphism for the investigation of the pathogenesis of the aberrant hepatic copper metabolism in LEC mutant rat, since CP has a pivotal role in copper metabolism in the liver. Using backcross progenies originating from LEC and BN rats, we found that the CP gene is not associated with the excess hepatic copper accumulation and the deficiency in serum CP activity, both of which are congenital abnormal phenotypes exhibited in LEC mutant rat.

Alleles↗
PubMed1992

Identification of the number of genes encoding rat liver glutathione S-transferase Yc, and their close location on the genome.

We have tried to determine the number of genes for the rat liver glutathione S-transferase Yc, using specific probes prepared by polymerase chain reaction. DNA blot hybridization with specific probes and analysis in isolated genomic clones indicated that two copies of the Yc gene exist on the rat genome. Furthermore, DNA blot hybridization after clamped homogenous electric field gel electrophoresis indicated that the two copies of Yc gene family are closely located on the genome.

Animals↗
PubMed1992

Elevation of the level of lipid peroxidation associated with hepatic injury in LEC mutant rat.

Long-Evans Cinnamon (LEC) mutant rat, which spontaneously develops a chronically necrotizing hepatic injury at 4-5 months of age, exhibits an excess hepatic copper accumulation. The hepatic injury was completely correlated to the excess hepatic copper accumulation in backcross progenies, supporting the previous hypothesis that the copper cytotoxicity causes the hepatic injury in LEC rat liver. The levels of the lipid peroxidation in symptomatic LEC rats at 4 months of age were significantly higher than those of age-matched asymptomatic LEC and normal rats. These results suggest that excessively accumulated copper provokes hepatic injury through initiating the lipid peroxidation.

Animals↗
PubMed1992

Correlation between a hepatic copper accumulation and an altered expression of glutathione S-transferase Ya/Yc subunits in LEC mutant rat.

Long-Evans Cinnamon (LEC) rat, an animal model of Wilson's disease, that develops a necrotizing hepatic injury with an abnormally high hepatic copper accumulation exhibits an altered expression of glutathione S-transferase (GST) subunits, that is, a low percentage of the Ya and a high percentage of the Yc subunit expression in males. The altered expression of GST subunits and the abnormal copper accumulation in liver were found to be completely correlated in male LEC mutant rat liver, suggesting that the copper toxicity caused by the anomaly of copper metabolism in LEC rat liver leads to the altered expression of GST subunits.

Animals↗
PubMed1991

Bone marrow-derived progenitor T cells convey the origin of maturational arrest from CD4+CD8+ to CD4-CD8+ thymocytes in LEC mutant rats.

A mutant strain of rats, LEC, shows a novel arrest of T cell maturation from CD4+CD8+ to CD4+CD8- but not to CD4-CD8+ cells in the thymus. Transplantation of LEC rat fetal thymuses into the subcapsule of the kidney of athymic nude rats resulted in a normal maturation of thymocytes in the thymus graft. Furthermore, both single-positive thymocytes and peripheral lymph node T cells expressed T cell receptor alpha/beta antigen, and lymph node T cells acquired the ability to produce interleukin 2 upon mitogen stimulation. Transplantation of fetal thymuses from LEA rats, which express the same major histocompatibility complex haplotype as LEC rats, into LEC rat kidney subcapsule resulted in the maturational arrest from CD4+CD8+ to CD4+CD8- cells in the thymus graft. These data strongly suggest that bone marrow-derived progenitor T cells carry the cause of maturational arrest and that the thymic stroma of LEC rats has a normal potential to nurse thymocytes.

Animals↗
PubMed1991

Ontogeny of T cell maturation in LEC mutant rats which bear a congenital arrest of maturation from CD4+CD8+ to CD4+CD8- thymocytes.

LEC rats bear a congenital deficiency in CD4+CD8- thymocytes and peripheral CD4+ T cells, and consequently a deficiency in Th cell functions. Ontogeny of T cell maturation in normal and LEC mutant rats was, therefore, investigated. Prenatal development of thymocytes in normal rat strains, with respect to the expression of CD4/CD8 and TcR antigens, was similar to that of mice except that its kinetics was delayed by approximately 24 h. The kinetics of T cell maturation in LEC rats was comparable with that of normal rats up to day 19 of gestation, at which stage double-negative thymocytes (CD4-CD8-) developed into double positives (CD4+CD8+) through immature CD4-CD8+ subset. At day 19 of gestation in LEC as well as normal rats, double positives occupied approximately 80% of the total thymocytes, half of which were TcR-dull positive, indicating that TcR was normally rearranged and then expressed in LEC rat thymocytes. These data indicate that double negatives normally mature into at least double positives in LEC rats. Both single positives appeared after day 19 of gestation in normal rats, while in LEC rats CD4+CD8- cells did not appear, suggesting that the deficiency in CD4+CD8- cells is due to a congenital arrest of maturation from CD4+CD8+ to CD4+CD8- cells, but not due to a postnatal deletion.

Age Factors↗
PubMed1990

Maturational arrest from CD4+8+ to CD4+8- thymocytes in a mutant strain (LEC) of rat.

A mutant strain (LEC) of rats was found to have a novel defect in T cell maturation, that is, arrest of differentiation from CD4+8+ to CD4+8- but not to CD4-8+ thymocytes. FACS analyses demonstrated a deficiency in the CD4+8- T cell subset in the thymus and a marked decrease in CD4+ T cells in peripheral lymphoid organs. Expression of the T cell receptor (TCR)/CD3 complex in CD4+8+ and CD4-8+ thymocytes of LEC rats was normal. Expression of class II major histocompatibility complex (MHC) in the thymus of LEC rats was also the same as that of normal rats. These results indicate that maturational arrest occurs only in the transition pathway from CD4+8+ to CD4+8- thymocytes, and that this mutation can not be attributed to the default of expression of either TCR/CD3, CD4, or class II MHC antigen. Consequently, dysfunction of helper T cells was observed in LEC rats, while killer T cells and B cells functioned normally. Although the complete identification of the origin of this mutation requires further studies, it is hoped that such investigations will throw light on the mechanism of positive selection.

Animals↗
PubMed1990

Ecto-ATPase activity in cytolytic T-lymphocytes. Protection from the cytolytic effects of extracellular ATP.

Addition of ATP or ATP analog to the incubation media is shown to result in cell death in experiments with different cultured cell lines as evidenced by the results of several independent assays, both in the absence or presence of extracellular Ca2+. Cytolytic T-lymphocyte (CTL) clone itself was not only resistant to cytolytic effects of ATP, but was able to "rescue" antigen-nonbearing 51Cr-labeled cells from lytic effects of extracellular ATP (but not from lytic effects of adenosine 5'-thiotriphosphate) when present during assay. To test whether the resistance of CTL to ATP is due to a high activity of ecto-ATPase, four independent assays of ATPase activity were utilized to demonstrate the presence and relatively high activity of the ecto-ATPase(s) on CTL surface. Studies of substrate specificity of CTL ecto-ATPase suggest that there is more than one nucleoside 5'-triphosphatase on the surface of CTL. The enzyme(s) activity is Ca2+- and Mg2+-dependent and in this respect is similar to recently described hepatic cells ecto-ATPase. We tested effects of known ATP-binding site-specific reagents fluorescein 5'-isothiocyanate (FITC) and 5'-fluorosulfonylbenzoyladenosine (FSBA) to find covalent modification procedures to be used in studies of functional role of ecto-ATPase. FSBA, but not FITC, inhibits lymphocyte ecto-ATPase but addition of ATP together with FSBA protects ecto-ATPase activity. Inactivation of CTL ecto-ATPase by pretreatment with FSBA makes CTL susceptible to lytic effects of extracellular ATP, as was hypothesized for the functional role of this enzyme in CTL.

Adenosine↗
PubMed1989

Multiple types of receptors for atrial natriuretic peptide.

The binding of atrial natriuretic peptide (ANP) to olfactory bulb, pituitary anterior lobe and thymus gland membranes was examined. [125I]ANP (rat, 99-126) bound specifically to the three types of membranes. However, the affinity for ANP receptor in olfactory bulb was much higher than those in either pituitary or thymus gland. Competitive inhibition of cold ANP (rat, 99-126) with [125I]ANP binding sites on olfactory bulb membranes gave a value of 796 +/- 80 pM (mean +/- S.E.M., n = 4) as a dissociation constant (Kd) of cold ANP (rat, 99-126), while on pituitary and thymus membranes, the competitive curve gave a value of 9.3 +/- 0.4 nM (mean +/- S.E.M., n = 3) and 25.5 +/- 2.2 nM (mean +/- S.E.M., n = 6) as a Kd of cold ANP (rat, 99-126), respectively. Furthermore, a truncated ANP fragment (rat, 111-126) did not inhibit the [125I]ANP binding in olfactory bulb, while this peptide fragment inhibited the [125I]ANP binding in either pituitary or thymus gland with affinities only 2- to 4-fold less potent than ANP (rat, 99-126). These data indicate the possibility of the existence of multiple types of ANP receptors. We propose alpha-receptor in olfactory bulb and beta-receptor in either pituitary anterior lobe or thymus gland.

Animals↗
PubMed1989

Chronic estrogen treatment promotes a functional uncoupling of the D2 dopamine receptor in rat anterior pituitary gland.

The effect of chronic estrogen treatment on the anterior pituitary D2 dopamine receptor was studied by treating rats with diethylstilbestrol (DES) over a 6-week period. DES treatment resulted in an increase in anterior pituitary weight and PRL content and serum PRL levels compared to those in sham-treated controls. The status of the anterior pituitary D2 dopamine receptor was evaluated using both radioligand binding and adenylate cyclase assays. [125I]N-(p-aminophenethyl)spiroperidol [( 125I]NAPS), a derivative of the D2-selective antagonist spiperone, was used to quantitate D2 receptors. Saturation analysis of [125I]NAPS binding indicated that DES treatment had no effect on the affinity or maximum binding capacity of the radioligand for the D2 receptor. Competition analysis with unlabeled D2 antagonists for [125I]NAPS binding also indicated that DES treatment did not affect antagonist interactions with the receptor. In contrast, the interactions of agonists with the D2 receptors from DES-treated rats were modified, as assessed through [125I]NAPS competition analysis. Using control tissue, agonist competition curves revealed both high and low affinity agonist binding states of the receptor. In the presence of guanine nucleotides, the high affinity agonist binding state is abolished, reflecting coupling of the receptor with a guanine nucleotide regulatory (G) protein. In DES-treated tissue, agonist competition curves indicated the presence of only low affinity agonist binding, with minimal effects of guanine nucleotides, suggesting uncoupling of receptor-G-protein interactions. The functionality of the D2 receptor was further assessed by examining dopaminergic inhibition of vasoactive intestinal peptide-stimulated adenylate cyclase activity. Although DES treatment resulted in a reduction of vasoactive intestinal peptide-stimulated enzyme activity itself, the ability of dopaminergic agonists to inhibit this activity was reduced by about 50%. These results suggest that estrogen is capable of attenuating the functional coupling of the D2 receptor with its biochemical effector system in the anterior pituitary gland.

Adenylyl Cyclases↗
PubMed1988

Identification of D1-dopamine receptor in chicken embryo retina with [125I]SCH 23982.

The D1-dopamine receptor in chicken embryo retina was identified with the D1-dopamine receptor specific ligand, [125I]SCH 23982. Binding of [125I]SCH 23982 to both pre-hatched and post-hatched chicken retina was rapid, saturable and of high affinity. The dissociation constant and maximal binding capacity were 795 +/- 25 pM (mean +/- S.E.M., n = 3) and 32.2 +/- 3.8 fmol/mg protein (mean +/- S.E.M., n = 3), respectively for 13-day-old chicken embryo retina, and 785 +/- 58 pM (mean +/- S.E.M., n = 3) and 96.9 +/- 4.1 fmol/mg protein (mean +/- S.E.M., n = 3), respectively for 1-day-old post-hatched chicken retina. The binding properties of the D1-dopamine receptor in chicken retina were similar to those in rat striatum. The maximal binding capacity of the D1-dopamine receptor for [125I]SCH 23982 was increased concomitant with embryonic development, but without any changes in either affinity or pharmacological properties. Dopamine-stimulated adenylate cyclase activity in the retinal homogenates increased concomitant with embryonic development, diminished in the presence of 1 microM SCH 23390 (a D1-dopaminergic antagonist) but remained unaffected by 1 microM YM-09151-2 (a D2-dopaminergic antagonist).

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1988

Agonist-induced desensitization of the D-2 dopamine receptor in the intermediate lobe of the rat pituitary gland.

The mechanism of agonist-induced desensitization of the D-2 dopamine receptor in the intermediate lobe (IL) of the rat pituitary gland was investigated. Exposure of neurointermediate lobe to 60 microM (-)apomorphine (APO) for 60 min altered the binding of [125I]-N-(p-aminophenethyl)spiperone (NAPS), a D-2 receptor-specific ligand. The capacity of the tissue to bind the ligand (Bmax) was not significantly altered by the exposure to (-)APO but the affinity for [125I]NAPS was decreased 3.6-fold in (-)APO-exposed tissue. The molar potency of YM-09151-2, a D-2 receptor-specific antagonist, showed a minimal difference between in control and (-)-APO-exposed tissue. However, the molar potency of (-)APO towards the D-2 receptor was diminished. The loss of [125I]NAPS binding in (-)APO-exposed tissue was reversed by the addition of guanyl nucleotide. These data suggest that exposure to agonist causes a persistent occupancy of the high affinity state of the receptor. Exposure to (-)APO had no effect on either basal or forskolin-activated adenylate cyclase activity of the intermediate lobe. However, the inhibitory effect of (-)APO upon adenylate cyclase activity of IL homogenates was diminished when the tissue was exposed to (-)APO before homogenization. Furthermore, the ability of GTP but not 5'-guanylyl imidodiphosphate [Gpp(NH)p] to inhibit enzyme activity diminished in the (-)APO-exposed tissue. These data suggest that an agonist-induced desensitization of D-2 receptor in rat IL is thought to occur by uncoupling the receptor from the inhibitory guanyl nucleotide binding protein (Gi) or potentiating the hydrolysis of GTP by Gi.

Adenylyl Cyclases↗