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Biomedical subjects

H Masuno

Publications and source records attributed to H Masuno.

14 recordsLinked to original sources
PubMed1992

Glycosylation of lipoprotein lipase in human subcutaneous and omental adipose tissues.

Human adipose tissues from the abdomen (subcutaneous), thigh (subcutaneous) and omentum were incubated for 2 h with [35S]methionine. Then glycosylation of lipoprotein lipase (LPL) was analyzed by sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of endoglycosidase H (endo H)-digested subunits of the 35S-labeled lipase. Adipose tissues from the abdomen, thigh, and omentum all synthesized LPL subunits with Mr = 57,000 composed of two types of subunits. One type was partially endo H-sensitive yielding a product with Mr = 55,000, indicating that it had one endo H-resistant and one endo H-sensitive oligosaccharide chain. The other type of subunit was totally endo H-sensitive yielding a product with Mr = 52,000. Subcutaneous adipose tissues contained nearly equal amounts of partially and totally endo H-sensitive subunits of LPL, whereas omental adipose tissues contained mainly partially endo H-sensitive subunits of LPL.

Adipose Tissue↗
PubMed1992

Anorexia induced by toxohormone-L isolated from ascites fluid of patients with hepatoma.

To ascertain anorexigenic effect of toxohormone-L, a polypeptide extracted and purified from ascites of patients with hepatoma were infused into the rat third cerebroventricle. Food intake decreased on the first day after infusion of an optimum dose of 10.0 micrograms (p less than 0.05). The suppressive effect on feeding was linearly dose dependent (p less than 0.05). Meal size and latency to the first meal decreased in the 12-h dark period, and the first and the second 4-h cumulative blocks after infusion of a 10.0 micrograms dose (p less than 0.01 for each). The suppressive effects on total food intake and meal size were completely recovered within 24 h after infusion. Neither postprandial intermeal interval nor eating speed was affected. Periprandial drinking, a ratio of water intake to food intake, was not affected after infusion of 5.0 and 10.0 micrograms toxohormone-L. Infusion of a 10.0 micrograms dose showed no effect on ambulation. These findings suggest that anorexia and cachexia produced in cancer patients may essentially be due to the suppressive effect of toxohormone-L on food intake.

Animals↗
PubMed1992

Retention of glucose by N-linked oligosaccharide chains impedes expression of lipoprotein lipase activity: effect of castanospermine.

The effect of castanospermine (CSTP), an inhibitor of glucosidase I, on processing, activity, and secretion of lipoprotein lipase was studied in 3T3-L1 adipocytes. Processing was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of endoglycosidase H (endo H)-digested subunits of lipoprotein lipase from cells incubated 1-2 h with [35S]methionine. Lipoprotein lipase in untreated cells consisted of two groups of subunits, M(r) = 55,000-58,000 and M(r) = 53,000-55,000. The heavier subunits were endo H-resistant, whereas the others were either totally or partially endo H-sensitive. The lipase secreted by untreated cells contained primarily endo H-resistant subunits. Immunofluorescent studies showed that lipoprotein lipase accumulated in Golgi in untreated cells. CSTP, 100 micrograms/ml for 18 h, decreased intracellular lipase activity by 80% and decreased secretion of lipase activity by 91%. Most of the lipase subunits in CSTP-treated cells were totally endo H-sensitive with M(r) = 57,000, some were partially endo H-sensitive, and a trace was endo-H resistant. Totally endo H-sensitive subunits in CSTP-treated cells had a M(r) 2,000-4,000 larger than that in untreated cells, indicating impaired trimming of sugar residues from oligosaccharide chains of the lipase in CSTP-treated cells. The small amount of lipase secreted by CSTP-treated cells consisted primarily of partially endo H-sensitive subunits, with one sensitive and one resistant chain per subunit. Immunofluorescent studies showed that lipoprotein lipase was excluded from Golgi in CSTP-treated cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1991

Glycosylation, activity and secretion of lipoprotein lipase in cultured brown adipocytes of newborn mice. Effect of tunicamycin, monensin, 1-deoxymannojirimycin and swainsonine.

The effect of inhibitors on the glycosylation, activity and secretion of lipoprotein lipase was studied in brown adipocytes cultured from newborn mice. Such cells synthesized and secreted active lipoprotein lipase. It is generally accepted that active lipoprotein lipase is a homodimer. Glycosylation of lipoprotein lipase was analysed by PAGE of endoglycosidase H (endo H)-digested subunits of lipoprotein lipase immunoprecipitated from cells incubated for 1-2 h with [35S]methionine. The most prevalent 35S-labelled lipase subunit (Mr 57,000-58,000) in these cells contained endo H-resistant oligosaccharide chains, the next most prevalent contained totally endo H-sensitive chains, and the least prevalent subunit contained partially endo H-sensitive chains. Complete blocking of the glycosylation of lipoprotein lipase with tunicamycin (1 microgram/ml) for 24 h resulted in synthesis of an inactive non-secretable form of lipase with a smaller subunit (Mr 51,000-52,000). Immunofluorescent studies showed that unglycosylated lipase in tunicamycin-treated cells was retained in the endoplasmic reticulum. Cells treated with 1 microM-monensin, an intra-Golgi transport inhibitor, synthesized an active form of lipase which was not secreted, but was retained in the Golgi. The lipase in monensin-treated cells contained only partially or totally endo H-sensitive chains. Blocking either Golgi mannosidase I with 4 mM-1-deoxymannojirimycin or Golgi mannosidase II with 10 microM-swainsonine resulted in production of a form of lipoprotein lipase which was active and secreted, and which contained only endo H-sensitive chains. Our findings demonstrate that core glycosylation of lipoprotein lipase in the endoplasmic reticulum is required for lipase activity and transport from the reticulum, whereas processing of the oligosaccharide chains to endo H-resistant (complex) type chains in the Golgi is not required for either the activity or the secretion of lipoprotein lipase.

1-Deoxynojirimycin↗
PubMed1990

Synthesis of inactive nonsecretable high mannose-type lipoprotein lipase by cultured brown adipocytes of combined lipase-deficient cld/cld mice.

Combined lipase deficiency (cld) is a recessive mutation which causes a severe deficiency of lipoprotein lipase and hepatic lipase activities and lethal hypertriacylglycerolemia within 3 days in newborn mice. The effect of this genetic defect on lipoprotein lipase was studied in primary cultures of brown adipocytes derived from tissue of newborn mice. Cells cultured from cld/cld mice replicated, accumulated triacylglycerol, and differentiated into adipocytes at normal rates. Lipoprotein lipase activity in unaffected cells was detectable on Day 0 of confluence and increased to 1.3 units/mg DNA by Day 6, while that in cld/cld cells was less than 4% of that in unaffected cells on Days 4-6. Unaffected cells released 1.2% of their lipase activity in 30 min in the absence of heparin, and 11% in 10 min in the presence of heparin, whereas cld/cld cells released no lipase activity. cld/cld cells contained 2-3 times as much lipoprotein lipase protein as unaffected cells, and released no lipase protein to the medium. Immunofluorescent lipoprotein lipase was not detectable in unaffected adipocytes unless lipase secretion was blocked with monesin, causing retention of the lipase in Golgi. cld/cld adipocytes, in contrast, contained immunofluorescent lipoprotein lipase distributed in a diffuse reticular pattern, indicating retention of lipase in endoplasmic reticulum. Lipoprotein lipase immunoprecipitated from cells incubated 1-3 h with [35S]methionine was digested with or without endoglycosidase H (endo H) or F, and resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Lipoprotein lipase in unaffected cells (Mr = 56,000-58,000) consisted of three glycosylated forms, of which the most prevalent was endo H-resistant, the next was totally endo H-sensitive, and the least was partially endo H-sensitive. In contrast, lipoprotein lipase in cld/cld cells (Mr = 56,000) consisted of a single, totally endo H-sensitive form. Lipoprotein lipase in both groups of cells contained two oligosaccharide chains. Chromatography studies with heparin-Sepharose indicated that at least some of the lipoprotein lipase in cld/cld cells was dimerized. The findings demonstrate that brown adipocytes cultured from cld/cld mice synthesize lipoprotein lipase with two high mannose oligosaccharide chains, but it is inactive and retained in endoplasmic reticulum. Whether the cld mutation affects primarily processing of oligosaccharide chains of lipoprotein lipase in endoplasmic reticulum, transport of the lipase from the reticulum, or some other process, is to be resolved.

Adipose Tissue, Brown↗
PubMed1990

Relation between blood pressure, left ventricular mass and pulsed Doppler parameters in healthy school children.

We analyzed the relations between blood pressure in sitting and supine positions, left ventricular mass (LVM) and Doppler aortic, pulmonary and mitral flow velocity measurements in 163 healthy school children. Systolic blood pressure in a supine position correlated significantly with aortic acceleration (ATc) and ejection time (ETc), corrected by the square of R-R interval, pulmonary AT and peak flow velocities. Moreover, the systolic blood pressure in a sitting position correlated with pulmonary AT and LVM. LVM correlated with pulmonary ATc, the ratio of AT to ET and average acceleration, and aortic ETc and peak flow velocity. These data suggest the following: (1) the posture influences the relation between blood pressure and flow velocity, (2) pulmonary hemodynamics are influenced by systemic blood pressure in healthy children and (3) the development of LVM may be dependent not only on blood pressure but also on cardiac work in childhood.

Aorta↗
PubMed1989

Expression of lipoprotein lipase gene in combined lipase deficiency.

The expression of the gene for lipoprotein lipase (LPL) was studied in brown adipose tissue and the liver of combined lipase deficient (cld/cld) and unaffected mice. The mRNA specific for LPL was detected in both animals. Although the size of LPL mRNA in cld mice was similar to that of unaffected mice, the mRNA concentration in affected animals was higher than in unaffected animals. We also studied the LPL gene mutation in cld mice by Southern blot analysis. No restriction fragment length polymorphisms were observed after digestion with 16 endonucleases. These data indicate that there is no gene insertion or deletion, but do not exclude the possibility of point mutation in the LPL structural gene. However, the present results agree with the hypothesis that the genetic defect in cld is not due to a mutation in the LPL structural gene, but instead involves the defective post-translational processing of LPL or defective cellular function affecting transport and secretion of this enzyme group.

Animals↗
PubMed1989

Lipoprotein lipase in myocytes and capillary endothelium of heart: immunocytochemical study.

Lipoprotein lipase was immunolocalized by electron microscopy in hearts of young mice; 78% of lipoprotein lipase was in myocytes, 3-6% in extracellular space, and 18% in capillary endothelium. Lipoprotein lipase in myocytes was located primarily in sarcoplasmic reticulum, Golgi sacs, and transport vesicles and also in secretory vesicles at the cell periphery. Lipoprotein lipase in extracellular space was present near the orifice of secretory vesicles of myocytes and in narrow zones spanning the space between myocytes and capillary endothelium. The lowest concentration of lipase associated with endothelial cells was at the basal plasma membrane, whereas the highest concentration was at the surface of luminal projections. Lipoprotein lipase was associated with chylomicrons at the capillary surface but not with chylomicron remnants. Fasting mice for 48 h increased, in heart, lipoprotein lipase activity by 120% and immunolocalized lipase by 270%. The greatest increase (5-fold) occurred at the surface of intraluminal endothelial projections. The findings indicate that lipoprotein lipase in heart is synthesized by myocytes, transferred across extracellular space along cell surfaces and across endothelial cells via vesicles or intracellular channels, and concentrated at the surface of luminal projections of endothelium where the enzyme hydrolyzes triacylglycerol of chylomicrons and very low-density lipoproteins.

Animals↗
PubMed1986

Hepatic triacylglycerol lipase in circulating blood of normal and tumor-bearing mice and its hydrolysis of very-low-density lipoprotein and synthetic acylglycerols.

A large amount of triacylglycerol lipase activity was present in the circulating blood of normal mice, and this activity decreased with development of Sarcoma 180 inoculated intraperitoneally. Triacylglycerol lipase in plasma of both normal and tumor-bearing mice was retained on the heparin-Sepharose columns and over 90% of the activity was eluted with 0.75 M NaCl. This enzyme had similar properties to hepatic triacylglycerol lipase and hydrolyzed very-low-density lipoprotein (VLDL)-triacylglycerol. Hepatic triacylglycerol lipase in plasma of normal mice hydrolyzed tricaprin and trilaurin most readily and better than 1-monoacylglycerols with the same acyl chain length. The hydrolyzing activities decreased with increase in the acyl chain length. The activity toward triolein was also higher than that toward 1-monoolein. 1-Monomyristin was hydrolyzed better than trimyristin. In contrast, hepatic triacylglycerol lipase in plasma of mice on day 4 after tumor inoculation hydrolyzed 1-monoacylglycerols better than triacylglycerols with the same acyl chain length. Hydrolysis of triolein by hepatic triacylglycerol lipase in plasma of both normal and tumor-bearing mice was reduced in the presence of 1-monoacylglycerols in the reaction mixture. The orders of their inhibitory effects coincided with the orders of the hydrolyzing activities toward 1-monoacylglycerols.

Animals↗
PubMed1985

Decrease in alkaline triglyceride lipase in primary cultured hepatocytes from mice with sarcoma 180.

Primary cultured hepatocytes from normal mice and mice with Sarcoma 180 were characterized. The viability of freshly isolated hepatocytes from both sources was over 90% and the cells had a relatively stable population of DNA for a minimum of three days. After incubation with (3H)leucine, the syntheses and secretions of (3H)labeled trichloracetic acid-insoluble materials by hepatocytes from both normal and tumor-bearing mice increased similarly. However, the alkaline triglyceride lipase activity of a homogenate of freshly isolated hepatocytes from tumor-bearing mice was one-third that of cells from normal mice. The activity of hepatocytes from tumor-bearing mice increased less during culture than did the activity of cells isolated from normal mice.

Animals↗
PubMed1985

Demonstration of hepatic triglyceride lipase-like activity in ascites fluid of mice with sarcoma 180.

The contents of apolipoproteins of plasma and ascites fluid of mice with Sarcoma 180 were measured. The apolipoprotein A-I contents of plasma decreased with development of the tumor. The apolipoprotein C-II and C-III contents of plasma reached a maximum on day 7 after tumor inoculation and then decreased. The apolipoprotein A-I content of the ascites fluid was lower than that of normal mouse plasma. In contrast, the apolipoprotein C-II and C-III contents of the ascites fluid were higher than those of normal mouse plasma. The ascites fluid of mice with Sarcoma 180 was found to contain at least two lipases. One had a pH optimum of 5.5-7.0 and was strongly inhibited by chlorpromazine. The other had an alkaline pH optimum and was inhibited only slightly by chlorpromazine. When the ascites fluid was applied to a heparin-Sepharose column 40-45% of the applied triglyceride lipase activity was retained on the column, which was eluted with 0.75 M NaCl. This fraction was inhibited by heat-inactivated (56 degrees C, 10 min) human serum, and was relatively resistant to l M NaCl. These results suggest that one of the lipolytic enzymes present in the ascites fluid of mice with Sarcoma 180 is hepatic triglyceride lipase.

Animals↗
PubMed1985

Hepatic triglyceride lipase and lipoprotein lipase activities in post-heparin plasma of patients with various cancers.

The total post-heparin lipolytic activity (PHLA) and hepatic triglyceride lipase (HTGL) and lipoprotein lipase (LPL) activities in post-heparin plasma of patients with various cancers were measured. In patients with cancers, PHLA was similar to that of controls, but the HTGL activity was decreased and the LPL activity was increased. Thus, in cancer patients the ratios of HTGL to PHLA were lower, and the ratios of LPL to PHLA were higher than in controls. No correlation was found between the plasma lipid level and HTGL or LPL activity.

Aged↗