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Biomedical subjects

A Miyazaki

Publications and source records attributed to A Miyazaki.

At least 163 records · Page 9Linked to original sources
PubMed1994

Endocytic pathway of scavenger receptors via trans-Golgi system in bovine alveolar macrophages.

BACKGROUND: The scavenger receptors are trimeric membrane glycoproteins present on the surface membrane of macrophages and macrophage-derived foam cells and are implicated in the deposition of cholesterol in the arterial walls during atherogenesis. This receptor mediates endocytosis of a diverse alley of negatively charged macromolecules including modified low density lipoproteins. EXPERIMENTAL DESIGN: We tried biochemical and morphologic approaches to elucidate in more detail the endocytic and intracellular pathway of the scavenger receptors during endocytosis of acetylated low density lipoproteins (AcLDL) and oxidized LDL (OxLDL) by bovine alveolar macrophages. Biochemically, cell interaction and subsequent intracellular degradation of AcLDL and OxLDL were examined using [125I]AcLDL or [125I]OxLDL. At the ultramorphologic level, the scavenger receptors were detected by a mouse monoclonal antibody against bovine macrophages, D2, with colloidal gold particles (AcLDL-Au or OxLDL-Au particles) as tracer of ligands. RESULTS: The biochemical studies demonstrated that after binding of AcLDL and OxLDL to the cell surface, these ligands were internalized and degraded intracellularly. Immunoelectron microscopy revealed that after a 2-hour incubation at 4 degrees C AcLDL-Au or OxLDL-Au particles were bound to the scavenger receptors present on the cell surfaces. Upon a temperature shift from 4 to 37 degrees C, these particles were concentrated in coated pits and internalized in endosomes. After subsequent dissociation of the particles from the receptors within the endosomes, the ligands were transported to secondary lysosomes, the receptors were transported to a trans-Golgi system. In the Golgi complex, the receptors were packed in secretory vesicles and recycled to the cell surface membrane. The transport and recycling of the receptors via the trans-Golgi system were completely inhibited by incubation below 18 degrees C or pretreatment with monensin. CONCLUSIONS: These results suggest that during endocytosis of modified low density lipoprotein, the Golgi complex plays a crucial role in sorting and recycling of the scavenger receptors in macrophages.

Animals↗
PubMed1993

Chitin synthase-encoding gene(s) of the Zygomycete fungus Phycomyces blakesleeanus.

Using polymerase chain reaction (PCR) primers to two highly conserved sequences within fungal chitin synthase (CHS)-encoding genes, an approximately 750-bp DNA fragment was amplified from genomic DNA of Phycomyces blakesleeanus. The amino acid sequence deduced from the nucleotide sequence of this fragment best matches the motifs found in class-II CHS. The fragment includes an approximately 160-bp region that likely is an intron. Southern hybridization of restriction enzyme-digested genomic DNA, using the PCR-amplified DNA as the probe, suggests that P. blakesleeanus contains additional CHS-encoding genes (CHS). To our knowledge, this is the first report on the detection of a CHS gene in a Zygomycete fungus. These studies represent a major step toward exploring the molecular mechanisms of CHS regulation in Phycomyces. The prospects are exciting, since CHS is implicated to play a central role in the sensory responses of P. blakesleeanus involving growth modulations.

Amino Acid Sequence↗
PubMed1993

Two independent macrophage receptors for acetylated high-density lipoprotein.

We previously demonstrated that acetylated human high-density lipoprotein (acetyl-HDL) was recognized by a scavenger receptor of rat sinusoidal liver cells (Murakami, M., Horiuchi, S., Takata, K. and Morino, Y. (1987) J. Biochem. (Tokyo) 101, 729-741). The present study describes the interaction of acetyl-HDL with rat peritoneal macrophages in vitro. Acetylation of HDL enhanced its cell-association by 2-fold and cellular degradation by > 25-fold. The cell-association of [125I]acetyl-HDL was effectively inhibited by unlabeled acetyl-HDL (> 85%), whereas the inhibition by HDL or acetylated human low-density lipoprotein (acetyl-LDL) was partial (60% and 50%, respectively). However, when both HDL and acetyl-LDL were present, the cell-association of [125I]acetyl-HDL was effectively inhibited by > 80%, a level identical or closely similar to that by acetyl-HDL. The cellular degradation of [125I]acetyl-HDL was effectively suppressed by acetyl-LDL whereas the effect of HDL was much weaker. These findings indicate that acetyl-HDL is endocytosed by both the HDL receptor and the scavenger receptor for acetyl-LDL in which the ligands bound to the latter might be subjected to lysosomal degradation.

Acetylation↗
PubMed1993

Coronary arterial lesions due to Kawasaki disease: selective coronary angiography in five cases with difficult-to-detect localized stenosis.

We report five cases of localized stenosis in coronary arterial lesions due to Kawasaki disease which were difficult to demonstrate by routine selective coronary angiography. Of these cases, three had localized stenosis overlapping the aneurysm, one had localized stenosis overlapping another adjacent branch, and the fifth had localized stenosis at the proximal left main trunk of the coronary artery. The reasons for difficulty in demonstrating the stenoses by routine study include: the localized stenosis was often superimposed on the aneurysm and/or the other adjacent branches, and the catheter was pushed into the inlet of the aneurysm on the proximal left main trunk. For a precise demonstration of a localized stenosis by selective coronary angiography, many angiograms from different perspectives should be taken. In addition, when a large aneurysm exists in the left main coronary artery, selective coronary angiography should be taken without pushing the catheter into the inlet of the aneurysm, and each frame of the cine coronary angiography should be carefully examined. Care should also be taken to compare with the initial view of the projection.

Child↗
PubMed1993

Acetyl-low density lipoprotein receptors on rat mesangial cells.

To elucidate whether mesangial cells have any scavenger functions for modified lipoproteins, surface binding and cholesteryl ester (CE) formation by acetyl-low density lipoproteins (acetyl-LDL) have been studied in cultured rat renal mesangial cells. Specific binding kinetics for acetyl-LDL were observed with Kd = 28.3 micrograms/ml and Bmax = 1.1 ng/micrograms cell protein at 0 degrees C. The fluorescence microscopic finding demonstrated the enhanced uptake of DiI-acetyl-LDL in mesangial cells. Incorporation of [14C]oleate into CE was enhanced to 6-fold by loading 30 micrograms/ml of acetyl-LDL on 10 micrograms/ml of [14C]oleate-bovine serum albumin conjugate as compared with the control without lipoproteins (P < 0.05). The CE formation was completely inhibited by chloroquine. The light microscopic finding demonstrated the increased CE deposition by acetyl-LDL, resulting in foam cell formation. These results indicate biochemically and morphologically that the mesangial cells take up acetyl-LDL by receptor-mediated endocytosis, and that cholesterols in acetyl-LDL are converted to CE, resulting in an increased cellular cholesterol content. In conclusion, mesangial cells may have a scavenger function similar to macrophages.

Animals↗
PubMed1993

Characterization of [3H]staurosporine binding in protein kinase C-II purified from rat brain.

The type II protein kinase C (PKC-II) densely present in mammalian brain plays functional roles in CNS. We examined the characteristics of [3H]staurosporine binding to PKC-II purified from rat brain, compared to [3H]phorbol 12, 13-dibutyrate (PDBu) binding. In brief, [3H]staurosporine binding increased by phosphatidylserine (PtdSer) in a concentration-dependent manner and the binding was enhanced by Ca2+ and phorbol 12-myristate 13-acetate (PMA). In the presence of Ca2+, PMA and PtdSer, Bmax of these bindings markedly increased, but KD did not change. These characteristics of binding were similar to [3H]PDBu binding to PKC-II. Although [3H]PDBu binding was not affected by protein kinase inhibitors such as staurosporine, H-7, K-252a and K-252b, [3H]staurosporine binding was inhibited by these inhibitors. [3H]staurosporine binding was inhibited by several ATP analogues, but was not by guanine nucleotides. PtdSer-induced increase in [3H]PDBu binding was inhibited by Zn2+, but Zn2+ induced increase in [3H]staurosporine binding as well as PtdSer and/or Ca2+. Staurosporine would thus appear to bind to a domain different from phorbol ester-binding one in PKC, interactions between both domains may regulate kinase activity, and 1 mol staurosporine and 4 mol phorbol ester may bind to 1 mol PKC-II.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1993

Stimulatory effects of protein kinase C and calmodulin kinase II on N-methyl-D-aspartate receptor/channels in the postsynaptic density of rat brain.

To clarify the regulatory mechanism of the N-methyl-D-aspartate (NMDA) receptor/channel by several protein kinases, we examined the effects of purified type II of protein kinase C (PKC-II), endogenous Ca2+/calmodulin-dependent protein kinase II (CaMK-II), and purified cyclic AMP-dependent protein kinase on NMDA receptor/channel activity in the postsynaptic density (PSD) of rat brain. Purified PKC-II and endogenous CaMK-II catalyzed the phosphorylation of 80-200-kDa proteins in the PSD and L-glutamate- (or NMDA)-induced increase of (+)-5-[3H]methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imi ne maleate ([3H]MK-801; open channel blocker for NMDA receptor/channel) binding activity was significantly enhanced. However, the pretreatment of PKC-II- and CaMK-II-catalyzed phosphorylation did not change the binding activity of L-[3H]glutamate, cis-4-[3H](phosphonomethyl)piperidine-2-carboxylate ([3H]CGS-19755; competitive NMDA receptor antagonist), [3H]glycine, alpha-[3H]-amino-3-hydroxy-5-methyl-isoxazole-4-propionate, or [3H]-kainate in the PSD. Pretreatment with PKC-II- and CaMK-II-catalyzed phosphorylation enhanced L-glutamate-induced increase of [3H]MK-801 binding additionally, although purified cyclic AMP-dependent protein kinase did not change L-glutamate-induced [3H]MK-801 binding. From these results, it is suggested that PKC-II and/or CaMK-II appears to induce the phosphorylation of the channel domain of the NMDA receptor/channel in the PSD and then cause an enhancement of Ca2+ influx through the channel.

Animals↗
PubMed1993

Induction of murine macrophage growth by modified LDLs.

We previously reported that cell membrane components and lipoproteins were able to induce the growth of murine peritoneal macrophages. The aim of the present study was to examine whether macrophage growth could also be induced by chemically modified lipoproteins, such as acetylated low density lipoprotein (acetyl-LDL) or oxidized LDL, ligands known to be endocytosed by the macrophage scavenger receptors. When murine peritoneal exudate macrophages were cultured in vitro with 25-100 micrograms/mL acetyl-LDL or oxidized LDL, significant growth was induced. On comparing the dose-response curves of these LDLs, a more potent effect was seen with oxidized LDL than acetyl-LDL, especially on resident macrophages. On the other hand, growth of these cells was not stimulated by native (unmodified) LDL or high density lipoprotein. These in vitro data revealed a new function of chemically modified LDLs as effective inducers of macrophage cell growth. This aspect may be physiologically relevant to the growth of macrophage foam cells in situ in the development of atherosclerosis.

Animals↗
PubMed1993

Mononuclear cell infiltration and its relation to the expression of major histocompatibility complex antigens and adhesion molecules in pancreas biopsy specimens from newly diagnosed insulin-dependent diabetes mellitus patients.

We examined pancreas biopsy specimens from 18 newly diagnosed insulin-dependent diabetes mellitus (IDDM) patients to elucidate the mechanism underlying beta cell destruction. Pancreas islets were seen in all patients and insulitis in eight patients. Infiltrating mononuclear cells consisted of CD4+T, CD8+T, B lymphocytes, and macrophages. Among them, CD8+T lymphocytes were predominant and macrophages followed. The expression of MHC class I antigens was increased in islet and endothelial cells in nine patients. MHC class II expression was increased in endothelial cells of the same patients. The expression of intercellular adhesion molecule-1 was increased in endothelial cells in two of the nine patients with MHC hyperexpression; in one of them, lymphocyte function-associated antigen-3 expression was also increased. Out of the eight patients with insulitis, seven showed MHC class I hyper-expression, whereas 2 of the 10 patients without insulitis showed the phenomenon (P < 0.05). The relation between insulitis and the hyperexpression of adhesion molecules was not evident. In conclusion, we revealed the close relation between CD8+T lymphocyte-predominant insulitis and MHC class I hyperexpression in islet cells. This suggests that infiltrating CD8+T lymphocytes recognize islet autoantigens in association with increased MHC class I molecules and act as major effector cells in autoimmune response against islet cells in IDDM pancreases. The role of adhesion molecules in the pathogenesis of IDDM still remains to be elucidated.

Adolescent↗
PubMed1993

[Recent advances in lipoprotein metabolism].

Recent advances in lipoprotein metabolism were reviewed. The scavenger receptor for acetyl-LDL cloned by Kodama et al. was immunohistochemically demonstrated to exist in the human atherosclerotic lesions. LDL-receptor related protein (LRP) and VLDL receptor which would recognize apoE but not apoB have been recently cloned. Transgenic mice expressing high levels of apolipoproteins such as apoA-I and apoE or apolipoprotein deficient mice produced by gene targetting technique are providing important information on the function of apolipoproteins.

Animals↗
PubMed1993

[A case of primary cardiac amyloidosis with amyloid A protein].

A case of cardiac amyloidosis in a 46-year-old male is reported. He was admitted for dyspnea. Physical examination revealed third and forth heart sound and hepatomegaly. Radiographic heart-thoracic ratio was 53%. Electrocardiogram showed first degree A-V block, rS pattern in V1-V4 leads, and ambulatory electrocardiogram showed ventricular tachycardia. Echocardiogram revealed hypertrophy and highly refractile echoes of the left ventricular wall. Endomyocardial biopsy was performed and it demonstrated amyloid fibrils, which were characterized immunohistochemically as Amyloid A (AA) protein, which is generally a constituent in secondary amyloidosis. Urine protein electrophoresis showed lambda type Bence-Jones protein, but bone marrow biopsy was normal. There was no evidence of malignancy, chronic inflammatory disease, or collagen disease. This case was diagnosed as primary amyloidosis with AA protein. It is rare that, in spite of its being a case of primary amyloidosis, its constituent protein is AA protein.

Amyloidosis↗
PubMed1992

Cross-linking of apolipoproteins is involved in a loss of the ligand activity of high density lipoprotein upon Cu(2+)-mediated oxidation.

A recent study demonstrated that Cu(2+)-mediated oxidation of high density lipoprotein (HDL) resulted in a loss of the capacity to reduce cholesterol from macrophage foam cells [(1991) Proc. Natl. Acad. Sci. USA 88, 6457-6461]. In the present study we characterized the physicochemical properties of oxidized HDL and correlated them with the ligand activity toward the HDL receptor. Among them, the cross-linking of apolipoproteins and an increase in lipid peroxides were characteristic and closely similar to those of tetranitromethane-treated HDL, an abortive ligand for the HDL receptor. Cellular experiments with murine peritoneal macrophages revealed that both the cellular binding activity of HDL and its capacity to enhance cholesterol efflux from macrophage foam cells were markedly reduced upon oxidation. These results suggest that cross-linking of HDL apolipoproteins is involved in the loss of the ligand activity of oxidized HDL.

Animals↗
PubMed1992

Differential effect of subspecies of lipoprotein containing apolipoprotein A-I on cholesterol efflux from cholesterol-loaded macrophages: functional correlation with lecithin: cholesterol acyltransferase.

Two species of lipoprotein containing apoA-I, one containing only apoA-I (LpA-I), and the other containing apoA-I and apoA-II (LpA-I/A-II), were tested for their effects on macrophage foam cells. Rat macrophages were converted to foam cells by incubation with radiolabeled acetylated LDL. Incubation with LpA-I or LpA-I/A-II decreased the cellular cholesteryl esters (CE) mass. However, the free cholesterol (FC) mass was only reduced by LpA-I. All the radioactivity excreted into the medium was associated with LpA-I or LpA-I/A-II; 39% of the excreted radioactivity was esterified in LpA-I and 10% in LpA-I/A-II. Upon complete inactivation of lecithin: cholesterol acyltransferase (LCAT) activity with dithiobisnitrobenzoic acid, the cholesterol reducing capacity of LpA-I was weakened significantly. However, the CE mass reducing capacity of LpA-I/A-II was not affected. When LpA-I and LpA-I/A-II were combined, the cholesterol reducing capacity of the mixture was similar to that of LpA-I alone. However, LpA-I re-isolated from the medium showed a lower esterification rate than did the re-isolated LpA-I/A-II, thereby indicating that the cholesterol esterified in LpA-I was transferred to LpA-I/A-II. These results suggest that (i) the function of LpA-I is closely linked to the LCAT activity while that of LpA-I/A-II is not, and (ii) LpA-I in concert with LpA-I/A-II induces a series of extracellular events; LCAT-mediated esterification of excreted FC by LpA-I and a subsequent CE transfer to LpA-I/A-II. These mechanisms might be important for net cholesterol efflux from macrophage foam cells in physiological states.

Adolescent↗
PubMed1992

High density lipoprotein mediates selective reduction in cholesteryl esters from macrophage foam cells.

To elucidate an anti-atherogenic nature of high density lipoprotein (HDL) at cellular level, its in vitro effect on macrophage foam cells was examined. Rat peritoneal macrophages were converted to foam cells by incubation with [3H]cholesterol-labeled acetylated LDL. HDL addition to these foam cells resulted in a reduction in cellular radioactive cholesteryl esters (CE) as well as its CE mass. The radioactive free cholesterol (FC) was similarly reduced with time, whereas its FC mass level was unaltered. Other lipoproteins such as very low density lipoprotein and low density lipoprotein also reduced the radioactive FC. However, their CE-reducing capacity was negligibly weak. These results suggest that (i) CE reduction is selective to HDL, (ii) FC transfer from plasma membrane to lipoprotein (cholesterol efflux) expressed by reduction in radioactive FC is not selective to HDL but occurs to other lipoproteins, (iii) the CE-reducing capacity of HDL became weaker when cellular binding of HDL was reduced by chemical modification with tetranitromethane or a chemical cross-linker, dithiobis-succinimidylpropionate, suggesting an importance of the specific binding in the HDL-mediated CE reduction. These in vitro results gave an experimental support to a definite role of HDL as an anti-atherogenic lipoprotein in vivo.

Animals↗
PubMed1992

Effect of the beta-adrenoceptor antagonist, propranolol, on feeding induced by noradrenaline and muscimol in rats kept at high and temperate-ambient temperatures.

Both the gamma-aminobutyric acid (GABA) receptor agonist, muscimol, and noradrenaline stimulated the feeding behavior of rats in the two environments. When noradrenaline or muscimol was administered, however, the food intake at 26 degrees C was greater than that at 33 degrees C. In addition, the stimulatory effect of noradrenaline on food intake was significantly depressed by propranolol pretreatment at both temperatures. The stimulatory effect of muscimol on food intake was significantly depressed by the propranolol pretreatment at 33 degrees C but not at 26 degrees C. Some eating-stimulatory subsystems associated with feeding behavior induced by noradrenaline or muscimol might have been depressed in the hot environment, thus the food intake increased by these drugs in rats acclimated to the hot environment was less than that in rats acclimated to the temperate environment.

Animals↗