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Biomedical subjects

S Horiuchi

Publications and source records attributed to S Horiuchi.

At least 235 records · Page 13Linked to original sources
PubMed1993

Purification and characterization of two metalloproteinases from squid mantle muscle, myosinase I and myosinase II.

Metalloproteinases, myosinase I and myosinase II, that hydrolyze the heavy chain of myosin, were purified from squid mantle muscle. Myosinase I does not hydrolyze other muscle proteins, casein, haemoglobin, or MCA-substrates, while II hydrolyzes tropomyosin. Both myosinase I and myosinase II gave a single protein band on SDS-PAGE with a molecular mass of 16 and 20 kDa, respectively. Their activities were inhibited by EDTA and 1,10-phenanthroline, and II was also inhibited by EGTA. They could be reactivated with some divalent cations, I was especially reactivated with Co2+ and II especially with Zn2+. The optimum pH of both activities was 7.0; the optimum temperature for both was 40 degrees C. Myosinase I hydrolyzes myosin heavy chains to produce 130 and 90 kDa fragments. The N-terminal amino-acid sequence of the 90 kDa fragment indicates that myosinase I splits the myosin heavy chain between Ala-1161 and Thr-1162 in subfragment 2. Myosinase II hydrolyzes myosin heavy chain to produce 158 and 65 kDa fragments, and it splits between Glu-1381 and Thr-1382 in LMM. Myosinases I and II are most likely related to the metabolism of myosin in vivo.

Amino Acid Sequence↗
PubMed1993

cAMP stimulates human immunodeficiency virus (HIV-1) from latently infected cells of monocyte-macrophage lineage: synergism with TNF-alpha.

The present experiments were designed to study whether GTP binding protein activation and the resulting cAMP plays any role in HIV replication. The results showed that cholera toxin (CT) enhanced HIV replication dose dependently in myelo-monocytic cell lines latently infected with HIV-1, U1 and J22HL-60. Three- to 4-fold enhancement of virus production was observed in U1 cells and 4- to 11-fold enhancement in J22HL-60 cells 4 days after treatment with 100 ng/ml of CT. The increment of intracellular cAMP accumulation was parallel with HIV augmentation by CT in both cells. Even at the low concentration 0.1 ng/ml, TNF enhanced virus production to about an 80-fold higher level than the untreated U1 control cells as described previously (11). However, a synergistic effect (80- to 238-fold enhancement) was observed, when TNF-alpha and CT were added together to U1 cells. Similar synergism was seen in J22HL-60 cells. HIV antigen positive cells and gp120 expression were also increased to a similar degree. Phosphodiesterase inhibitor IBMX had no effect on HIV production alone, but potentiated HIV induction by CT and TNF. Adenylate cyclase activator, forskolin (FK), at 100 microM also significantly augmented HIV production (> 4-fold) and potentiated TNF induction in J22HL-60 and U1 cells. On the other hand, CT did not show any effect on HIV replication as well as TNF induction in HIV-1-infected T cell line. Northern blot experiment confirmed that this enhancement was mediated through the activation of HIV transcription. These data suggest that cAMP augments HIV replication and potentiates TNF induction in a particular monocyte-macrophage system.

1-Methyl-3-isobutylxanthine↗
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

Reduced susceptibilities of Shigella sonnei strains isolated from patients with dysentery to fluoroquinolones.

Seven clinical isolates of Shigella sonnei with reduced susceptibilities to fluoroquinolones (sparfloxacin, ciprofloxacin, and ofloxacin) were obtained. The MICs of fluoroquinolones against these S. sonnei strains were 16 to 32 times higher than those obtained against typical strains that are highly susceptible to these agents. The kinetics of [14C]ofloxacin accumulation in these clinical strains were not different from those in the fully susceptible strains. However, DNA synthesis was much less inhibited by ofloxacin in the strains with reduced susceptibility. Analysis of the in vitro activity of the partially purified DNA gyrase from these isolates showed that the decreased quinolone susceptibility of the S. sonnei strains was likely due to mutation of the DNA gyrase subunit A gene.

Anti-Infective Agents↗
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

beta 2-Microglobulin modified with advanced glycation end products is a major component of hemodialysis-associated amyloidosis.

beta 2-Microglobulin (beta 2M) is a major constituent of amyloid fibrils in hemodialysis-associated amyloidosis, a complication of long-term hemodialysis patients. Amyloid fibril proteins were isolated from connective tissues forming carpal tunnels in hemodialysis patients with carpal tunnel syndrome. Two-dimensional polyacrylamide gel electrophoresis and Western blotting demonstrated that most of the beta 2M forming amyloid fibrils exhibited a more acidic pI value than normal beta 2M. This acidic beta 2M was also found in a small fraction of beta 2M in sera and urine from these patients, whereas heterogeneity was not observed in healthy individuals. We purified acidic and normal beta 2M from the urine of long-term hemodialysis patients and compared their physicochemical and immunochemical properties. Acidic beta 2M, but not normal beta 2M, was brown in color and fluoresced, both of which are characteristics of advanced glycation end products (AGEs) of the Maillard reaction. Immunochemical studies showed that acidic beta 2M reacted with anti-AGE antibody and also with an antibody against an Amadori product, an early product of the Maillard reaction, but normal beta 2M did not react with either antibody. Incubating normal beta 2M with glucose in vitro resulted in a shift to a more acidic pI, generation of fluorescence, and immunoreactivity to the anti-AGE antibody. The beta 2M forming amyloid fibrils also reacted with anti-AGE antibody. These data provided evidence that AGE-modified beta 2M is a dominant constituent of the amyloid deposits in hemodialysis-associated amyloidosis.

Amyloidosis↗
PubMed1993

Establishment and characterization of a novel human monocytic leukemia cell line (KP-1) expressing scavenger receptor.

A new monocytic leukemia cell line (KP-1) was established from a 2-y-old Japanese girl with acute monocytic leukemia. The KP-1 cells were maintained in suspension culture with a doubling time of 96 h. The cells were positively stained with alpha-naphtyl butyrate esterase, but not with naphthol AS-D chloroacetate esterase, myeloperoxidase, and periodic acid-Schiff reagent. Cell surface marker analysis revealed that the cells were CD4, CD11a, CD11c, CD13, CD14, CD18, CD33, and HLA-DR positive. Karyotype analysis revealed near diploidy (47 XX) and a translocation t(11;19) was found. When treated with 12-o-tetradecanoylphorbol 13-acetate, KP-1 cells became tightly adherent, showed the enhanced reactivity for alpha-naphtyl butyrate esterase, and produced several monokines such as IL-1 beta, tumor necrosis factor-alpha, and macrophage colony-stimulating factor. Immunoelectron microscopy demonstrated that the human macrophage scavenger receptor was expressed after 12-o-tetradecanoylphorbol-13-acetate treatment, and the cells accumulated a large amount of cholesterol esters in the presence of acetylated LDL. Compared with another human monocytic leukemia cell line, THP-1, KP-1 expressed scavenger receptor and accumulated cholesterol ester more rapidly in the presence of 12-o-tetradecanoyl phorbol-13-acetate and acetylated LDL. Scatchard analysis using 125I-labeled acetylated LDL revealed a typical saturation curve with an apparent kd of 1.7 x 10(-7) M and 3400 binding sites per cell. KP-1 retained the characteristics of monocyte-macrophage lineage cells and will facilitate the in vitro studies of the pathologic and physiologic roles of scavenger receptors.

Antigens, Neoplasm↗
PubMed1993

[Benign hemorrhagic renal cyst mimicking cystic renal cell carcinoma].

We experienced four cases of benign hemorrhagic renal cyst which were indistinguishable from cystic renal cell carcinoma on ultrasonography, computer tomographic scanning, magnetic resonance imaging and angiography. Nephrectomy was performed in one case and enucleation of the mass in the other three. Pathological diagnoses were hemorrhagic septate cyst in two cases, cyst with inflammation containing old blood clots in one, and organized hemorrhagic cyst with calcification in one. Conservative surgeries should be considered when the definite diagnosis for renal hemorrhagic cysts is not made.

Adult↗
PubMed1993

[Role of oxygen radicals in the pathogenesis of acute gastric mucosal lesion under obstructive jaundice].

In this study we examined the role of oxygen-derived free radicals in the pathogenesis of acute gastric mucosal lesion induced by obstructive jaundice in rats. Rats were divided into 4 groups as follows: control (sham operation), jaundiced (ligation and dissection of bile duct), vagotomized (truncal vagotomy), and vagotomized with jaundice group. The water immersion restraint procedure was performed. The water immersion restraint procedure was performed. The results obtained are as follows: jaundiced group showed significant increase of ulcer index (UI) and significant decrease of gastric mucosal blood flow (GMBF) and gastric mucosal potential difference (PD). However, intragastric pH (pH) was unchanged compared to the control group. Oxygen radical generating system (gastric mucosal XOD activity and thiobarbiturate acid) and oxygen radical scavenging system (gastric mucosal SOD activity and GSH-px activity) were higher than those of control group. Vagotomized group showed significant increase of pH compared to the control group. Oxygen generating system and scavenging system were unchanged compared to the control group. Vagotomized with jaundice group showed depression of UI and improvement of oxygen radical generating system and scavenging system. However GMBF, PD nad pH were unchanged compared to the jaundiced group. These results suggest that oxygen radical play some role in the development of acute gastric mucosal lesion induced by obstructive jaundice.

Animals↗
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↗
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

Stagnation in the decline of the world population growth rate during the 1980s.

The world human population growth rate after World War II passed through three phases: the rise in the 1950s and 1960s, the fall (though still at a positive level) in the 1970s, and the plateau in the 1980s. The rise was produced by the global decline in death rates, the fall was mainly due to the reduction of fertility in a number of developing countries, and the stagnation of growth rate decline was attributable to three major factors. First, substantial fertility declines started around 1970 and stalled around 1980 in both China and India. Second, the age structure of population changed in favor of higher birth rates. Third, although fertility started to decline significantly around 1970 mainly in East Asia, Southeast Asia, and Latin America, few countries have begun fertility declines since then. Many countries in sub-Saharan Africa and South Asia have not started substantial fertility reductions, deepening the gap between developing countries that are moving to lower fertility levels and those that are left behind.

Age Factors↗
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

Immunochemical evidence for the presence of advanced glycation end products in human lens proteins and its positive correlation with aging.

Prolonged incubation of protein with reducing sugar proceeds through a series of reactions involving early stage products to the advanced glycation end products with fluorescence, brown color, and cross-linking. Known collectively as the Maillard reaction, these changes have been suggested as factors in diabetic complications and the aging process. The early stage products have been demonstrated in vivo, but evidence for the presence in vivo of the advanced glycation end products has been limited. We sought to provide immunochemical evidence by the preparation and use of polyclonal and monoclonal antibodies to these end products (Horiuchi, S., Araki, N., and Morino, Y. (1991) J. Biol. Chem. 266, 7329-7332) as probes to identify and quantitate such compounds in human lens crystallins. Neither of the antibodies reacted with extracts from infant lenses, but fractions from adult lenses showed a significant reactivity, correlating with lens age. Our findings provide the first immunochemical evidence that human lens crystallins contain advanced glycation end products and that these products increase with tissue age.

Adult↗
PubMed1992

Carrier-mediated uptake of pravastatin by rat hepatocytes in primary culture.

The transport mechanism of pravastatin, a new cholesterol-lowering drug, was compared in vitro with rat hepatocyte primary culture and mouse skin fibroblasts (L-cells). The uptake of 14C-labeled pravastatin by cultured hepatocytes was temperature- and dose-dependent. The temperature-dependent uptake as a function of [14C]pravastatin concentration showed saturation kinetics with Km = 32.2 microM and a maximal uptake rate of 68 pmol/mg protein/min. The uptake of pravastatin was inhibited significantly by metabolic inhibitors such as rotenone, oligomycin A, antimycin A, 2,4-dinitrophenol and KCN. Unlabeled pravastatin as well as R-416 and R-195, structural analogues of pravastatin, effectively competed for the hepatic uptake of [14C]pravastatin at 37 degrees. These results indicate that pravastatin is taken up by the liver by an active transport. In contrast, the transport of pravastatin by L-cells was temperature-independent and non-saturable, suggesting that the uptake of pravastatin by L-cells is mediated by passive diffusion. The marked difference in the uptake mechanism of pravastatin between hepatocytes and L-cells may account for a unique feature of this drug in that the uptake and inhibition of cholesterol biosynthesis occur selectively in the liver.

Animals↗
PubMed1992

Exposure of rat peritoneal macrophages to acetylated low density lipoprotein results in release of plasma membrane cholesterol. An efficient substrate for esterification by acyl-CoA:cholesterol acyltransferase.

In J774 macrophages and murine macrophages stimulated with acetylated low density lipoprotein (acetyl-LDL), the plasma membrane free cholesterol (FC) became accessible to acyl-CoA:cholesterol acyltransferase (ACAT) as substrate, the result being an accumulation of cholesteryl esters (CE) (Tabas, I., Rosoff, W. J., and Boykow, G. C (1988) J. Biol. Chem. 263, 1266-1272). As the route of delivery of FC to ACAT was not well characterized, we examined this route in the present study. In foam cells derived from rat peritoneal macrophages by preincubation with acetyl-LDL, esterification of the exogenously labeled [3H]FC was low (1.3% of total labeled cholesterol). In contrast, when cells were first labeled with exogenous [3H]FC and then chased with acetyl-LDL, the esterification was more extensive (9.2% of the total labeled cholesterol). During this experiment a significant portion of cellular [3H]FC was released into the medium (up to 33.4% of the total labeled cholesterol). In experiments using a two-compartment chamber in which cells in the lower and upper chambers were separated by filter paper yet the cells in both compartments could communicate without direct contact, [3H]FC released into the medium was biologically active and could serve as an efficient substrate for ACAT. Thus, when acetyl-LDL is not included in culture medium, FC delivery from the macrophage plasma membrane to ACAT is not enhanced, whereas in the presence of acetyl-LDL, plasma membrane FC released and bound to acetyl-LDL may re-enter the cells, possibly through the scavenger receptor. This would provide a significant route for CE synthesis in macrophages.

Animals↗