STUDIES ON THE SYNTHESIS OF PLASMA GLYCOLIPOPROTEIN AND HEPATIC SUB-CELLULAR GLYCOPROTEIN IN EARLY CHOLINE DEFICIENCY

1967 ◽  
Vol 45 (6) ◽  
pp. 825-838 ◽  
Author(s):  
Sailen Mookerjea ◽  
David Jeng ◽  
Judith Black
Keyword(s):  
Liver Microsome ◽  
Specific Radioactivity ◽  
Plasma Lipoproteins ◽  
Residual Fraction ◽  
Choline Deficiency ◽  
Glycoprotein Synthesis ◽  
Limiting Step ◽  
Residual Protein ◽  
Lipoprotein Synthesis ◽  
Smooth Membrane

Impairment of glycoprotein synthesis in trichloroacetic acid insoluble and in residual protein (d > 1.21) fractions of plasma in early choline deficiency has been confirmed. Plasma lipoproteins of d < 1.006, 1.006–1.063, and 1.063–1.21 are also rapidly labelled after intraperitoneal injection of glucosamine-1-14C. In general, there was no difference in specific radioactivity of plasma glycolipoproteins between choline-supplemented rats and rats deprived of choline for 2 days during 180 min of incorporation.Incorporation of glucosamine-1-14C into microsomal glycoprotein is significantly impaired in early choline deficiency. Further sub-microsomal fractionation produced evidence that the site of impairment of glycoprotein synthesis is in the smooth microsome portion. These studies suggest that a decreased synthesis of glycoprotein(s) in liver-microsome smooth membrane and in the plasma residual fraction (d > 1.21) may represent an impairment of 'lipoprotein precursor protein' synthesis in early choline deficiency. An inhibition of this limiting step would possibly impair the rate of plasma lipoprotein synthesis, leading to the development of fatty liver in choline deficiency.

scholarly journals Phosphatidylcholine–cholesterol acyltransferase in the ultracentrifugal residual protein fraction of rat plasma

1971 ◽  
Vol 122 (4) ◽  
pp. 469-475 ◽  
Author(s):  
Michihiro Sugano
Keyword(s):  
Protein Fraction ◽  
Cholesterol Acyltransferase ◽  
Initial Step ◽  
Rat Plasma ◽  
Plasma Lipoproteins ◽  
Residual Fraction ◽  
Cholesterol Esters ◽  
General Properties ◽  
Residual Protein ◽  
Cholesteryl Linoleate

1. The phosphatidylcholine–cholesterol acyltransferase of rat plasma was dissociated from the plasma lipoproteins by ultracentrifugation and shown to be present in the plasma residual-protein fraction of density >1.210. 2. The general properties of the acyltransferase were substantially unchanged in the residual fraction as judged from the effects of differences in the substrates and of overnight starvation on the formation of different cholesterol esters. 3. The enzyme from rats starved overnight, by comparison with the enzyme from fed rats, preferentially formed cholesteryl arachidonate at the expense of cholesteryl linoleate. 4. The results suggest that ultracentrifugal separation of the plasma residual fraction may be used as an initial step for the purification of the acyltransferase.

Impairment of plasma glycoprotein synthesis in choline deficiency compared with effects of carbon tetrachloride intoxication

1968 ◽  
Vol 46 (3) ◽  
pp. 499-505 ◽  
Author(s):  
Sailen Mookerjea
Keyword(s):  
Carbon Tetrachloride ◽  
Plasma Proteins ◽  
Specific Radioactivity ◽  
Starch Gel Electrophoresis ◽  
Choline Deficiency ◽  
Deficient Diet ◽  
Glycoprotein Synthesis ◽  
Carbon Tetrachloride Intoxication ◽  
Starch Gel ◽  
Plasma Glycoprotein

The incorporation of glucosamine-1-14C into plasma proteins is impaired in rats within 2 days when they are fed a choline-deficient diet. Separation of plasma proteins by starch-gel electrophoresis, and autoradiography of the dried gels, showed four labelled areas (glycoproteins). In choline deficiency there was visual evidence of depletion of radioactivity in the fast α-globulin area, a finding confirmed by the specific radioactivity of proteins eluted from electrophoretic zones of the starch gel. Within 4 h after ingestion of carbon tetrachloride, the synthesis of plasma glycoprotein was reduced by 90% and labelling of all four glycoprotein areas on dried starch gel autoradiograms virtually ceased. The results suggest that the defect in glycoprotein synthesis in carbon tetrachloride intoxication is nonspecific, whereas in choline deficiency the impairment is specific and localized in the fast α-globulin fraction. The results suggest a limiting role of a glycoprotein in the pathway of plasma lipoprotein synthesis.

scholarly journals Exogenous cholesterol transport in rabbit plasma lipoproteins

1973 ◽  
Vol 134 (2) ◽  
pp. 531-537 ◽  
Author(s):  
L. L. Rudel ◽  
J. M. Felts ◽  
M. D. Morris
Keyword(s):  
Free Cholesterol ◽  
Specific Radioactivity ◽  
Plasma Lipoproteins ◽  
Cholesterol Transport ◽  
Low Density ◽  
Cholesteryl Esters ◽  
Exogenous Cholesterol ◽  
Rate Of Increase ◽  
Chylomicron Metabolism

1. The appearance of exogenous cholesterol in free cholesterol and ester cholesterol of plasma chylomicra, very-low-density (VLD), low-density (LD) and high-density (HD) lipoproteins was studied in unanaesthetized rabbits after ingestion of a meal containing 5% fat and 0.08% [3H]cholesterol. 2. The specific radioactivity of ester cholesterol of VLD lipoproteins reached the highest value of any lipoprotein fraction and for each lipoprotein it increased at a faster rate and reached a higher maximum than that of free cholesterol; the maximum in VLD lipoproteins occurred later than in chylomicra. 3. The pattern of appearance of exogenous cholesterol in chylomicra and VLD lipoproteins of plasma was similar to the pattern previously observed in lymph. The specific radioactivity of ester cholesterol in plasma VLD lipoproteins was higher than that in chylomicra in spite of a larger pool size and dilution of cholesteryl esters from VLD lipoproteins produced by the liver. These results support the concept that during absorption the major portion of exogenous cholesterol is transported in VLD lipoproteins as ester cholesterol. 4. The specific radioactivity of ester cholesterol of chylomicra and VLD lipoproteins increased at a faster rate than that of LD and HD lipoproteins. However, the rate of increase and the absolute values of the specific radioactivity in LD and HD lipoproteins were identical. Since cholesteryl esters are thought not to exchange between lipoproteins, this observation supports the hypothesis that a result of VLD lipoprotein and chylomicron metabolism is the formation of LD and HD lipoproteins. 5. Results in vivo showed that the free cholesterol of individual plasma lipoproteins does not equilibrate within a period of 24h.

scholarly journals Serum glycoprotein synthesis after partial hepatectomy in the rat

1976 ◽  
Vol 158 (1) ◽  
pp. 153-155 ◽  
Author(s):  
F Serafini-Cessi
Keyword(s):  
Partial Hepatectomy ◽  
Specific Radioactivity ◽  
Glycoprotein Synthesis ◽  
Early Stages ◽  
Serum Glycoprotein

The incorporation in vivo of D-[1-14C]glucosamine into serum glycoproteins and proteins of liver microsomal fractions shows a decrease in the early stages (24h) after partial hepatectomy compared with sham-operated animals; 72h after partial hepatectomy the specific radioactivity of hexosamines bound to liver microsomal fractions reaches the same value as for sham-operated animals.

scholarly journals Transmembrane migration (‘flip-flop’) of cholesterol in erythrocyte membranes

1977 ◽  
Vol 168 (3) ◽  
pp. 575-577 ◽  
Author(s):  
C J Kirby ◽  
C Green
Keyword(s):  
Bile Salt ◽  
Erythrocyte Membrane ◽  
Specific Radioactivity ◽  
Plasma Lipoproteins ◽  
Erythrocyte Membranes ◽  
Half Time ◽  
Salt Solutions ◽  
Flip Flop ◽  
Two Sides

After exchange with [14C]cholesterol-labelled plasma lipoproteins for 0.5-4h, erythrocytes were extracted with bile-salt solutions. The extracted cholesterol (mainly from the outside of the erythrocyte membrane) had the same specific radioactivity as the residual sterol. Thus cholesterol equilibrates rapidly (half-time less than 1 h) between the two sides of the membrane.

Studies on the plasma glycolipoprotein synthesis by the isolated perfused liver: effect of early choline deficiency

1969 ◽  
Vol 47 (2) ◽  
pp. 125-133 ◽  
Author(s):  
Sailen Mookerjea
Keyword(s):  
Trichloroacetic Acid ◽  
Liver Perfusion ◽  
Dietary Treatment ◽  
Plasma Lipoproteins ◽  
High Density Lipoproteins ◽  
Low Density ◽  
Choline Deficiency ◽  
Significant Impairment ◽  
Isolated Liver ◽  
Insoluble Protein Fraction

Isolated liver perfusion preparations have been used to study the incorporation of glucosamine-1-14C into plasma glycoproteins and glycolipoproteins. The livers obtained from 2-day-choline-deficient rats and perfused with blood obtained from rats on similar dietary treatment showed, compared to controls, an impairment of incorporation of radioactive glucosamine into the trichloroacetic-acid-insoluble protein fraction of plasma during the progress of perfusion. The rate of disappearance of radioactivity in the trichloroacetic-acid-soluble fraction of plasma during perfusion was not affected by choline deficiency. Synthesis of plasma glycolipoproteins as judged by the progressively increased incorporation of radioactivity showed a very significant impairment of synthesis of very low-density (d < 1.006) and low-density (d > 1.006–1.063) glycolipoproteins in early choline deficiency. A similar inhibition of synthesis of plasma proteins of d > 1.21 ("lipid acceptor protein") was observed, whereas the synthesis of high-density lipoproteins (d < 1.063–1.21) was not affected in choline deficiency.The fatty liver in choline deficiency appears to result from an impairment of plasma low-density glycolipoprotein synthesis. A postulation has been made on the stepwise biosynthesis of plasma lipoproteins on the basis of these and earlier studies.

Reduction in VLDL, but not HDL, in plasma of rats deficient in choline

1990 ◽  
Vol 68 (2) ◽  
pp. 552-558 ◽  
Author(s):  
Zemin Yao ◽  
Dennis E. Vance
Keyword(s):  
Gel Electrophoresis ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
High Density ◽  
Plasma Lipoproteins ◽  
Male Rats ◽  
High Density Lipoproteins ◽  
Choline Deficiency ◽  
Deficient Diet ◽  
Apo B

We have analyzed plasma lipoprotein levels in young male rats fed a choline-deficient diet for 3 days. We confirmed previous studies that choline deficiency promotes 6.5-fold accumulation of triacylgycerol in the liver (23.9 ± 6.0 versus 3.69 ± 0.92 μmol/g liver) and reduction of triacylglycerol concentration in plasma by 60% (0.17 ± 0.04 versus 0.46 ± 0.10μmol/mL plasma). Agarose gel electrophoresis showed that the plasma very low density lipoprotein (VLDL) levels were reduced in choline-deficient rats, but the concentration of plasma high density lipoproteins (HDL) was not affected. Sodium dodecyl sulfate – polyacrylamide gel electrophoresis of fractionated plasma lipoproteins revealed that the concentrations of apolipoproteins (apo) BH, BL, and E in VLDL from choline-deficient rats were 37.1, 11.0, and 37.2% of normal levels, respectively. In contrast, the amount of apo A-I, the major one in HDL, was almost unchanged. Correspondingly, there were decreased lipid (mainly phosphatidylcholine and triacylglycerol) levels in VLDL from choline-deficient rats, but no change in the levels of phosphatidylcholine, cholesterol, and cholesterol ester in HDL. There were similar levels of apo B and E (components of VLDL) in homogenates of livers from normal and choline-deficient rats, as determined by immunoblotting. These results support the hypothesis that choline deficiency causes reduction of VLDL, but not HDL, levels in plasma as a consequence of impaired hepatic VLDL secretion.Key words: choline deficiency, very low and high density lipoproteins, apolipoproteins, rat plasma.

Studies on Acute Phase Proteins of Rat Serum. III. Site of Synthesis of Albumin and α1-Acid Glycoprotein and the Contents of These Proteins in Liver Microsome Fractions from Rats Suffering from Induced Inflammation

1973 ◽  
Vol 51 (7) ◽  
pp. 1034-1045 ◽  
Author(s):  
J. C. Jamieson ◽  
F. E. Ashton
Keyword(s):  
Liver Microsome ◽  
Acute Phase Proteins ◽  
Specific Radioactivity ◽  
Rat Serum ◽  
Experimental Animals ◽  
Acid Glycoprotein ◽  
Inflammatory Agent ◽  
Microsome Fraction ◽  
Rapid Stimulation ◽  
Short Times

Following injection of L-ieucine-3H or D-glucosamine-14C to normal rats or rats suffering from inflammation for 12 h there was a delay of 10–15 min before label appeared in albumin and α1-acid glycoprotein in serum; thereafter, there were rapid increases in specific radioactivities. The specific radioactivity of L-leucine-3H in albumin in serum from normal and experimental animals was not significantly different; however, there was a more rapid increase in specific radioactivities of both labelled compounds in α1-acid glycoprotein isolated from serum from experimental animals. Immunological techniques coupled with radioautography indicated that the microsome fraction of liver was the subcellular site of synthesis of albumin and of carbohydrate and polypeptide moieties of α1-acid glycoprotein in normal and experimental animals. The contents of albumin and α1-acid glycoprotein in liver microsome fractions from normal and experimental animals were determined by application of the quantitative precipitin technique to Lubrol-W extracts of microsome material. Little change in content of albumin associated with microsome material was found as a result of inflammation; however, there was a significant increase in the content of α1-acid glycoprotein in microsome material from experimental animals, reaching a maximum at 8–12 h after inflammation. On the basis of these latter results, it is suggested (1) that there is a fairly rapid stimulation of synthesis of α1-acid glycoprotein by liver in response to inflammation and (2) that the increased content of α1-acid glycoprotein associated with microsome material at short times of exposure to inflammatory agent is responsible for the increased content of this protein found in serum at longer times of exposure to inflammatory agent.

Changes in Plasma Lipoprotein Lipids in Hypercholesterolaemic Patients Treated with the Bile Acid-Sequestering Resin, Colestipol

1974 ◽  
Vol 47 (6) ◽  
pp. 547-557 ◽  
Author(s):  
P. Clifton-Bligh ◽  
N. E. Miller ◽  
P. J. Nestel
Keyword(s):  
Bile Acid ◽  
Plasma Concentration ◽  
Plasma Cholesterol ◽  
Low Density Lipoprotein ◽  
Specific Radioactivity ◽  
Early Period ◽  
Density Lipoprotein ◽  
Plasma Lipoproteins ◽  
Low Density ◽  
The Individual

1. Seven patients with type II hyperlipoproteinaemia were treated with the bile acid-sequestering resin, colestipol (5 g three times daily), after a prolonged period of taking placebo. 2. After 8–9 weeks of treatment, the plasma concentration of the non-esterified cholesterol of very-low-density lipoprotein (VLDL) had risen by a mean of 0.09 mmol/l (43% increase, P < 0.001), that of the esterified cholesterol of VLDL had risen by a mean of 0.11 mmol/l (38% increase, P < 0.01), and that of the triglyceride of VLDL had risen by a mean of 0.40 mmol/l (53% increase, P<0.001). During the same period, the plasma concentration of the non-esterified cholesterol of low-density lipoprotein (LDL) decreased by a mean of 0.44 mmol/l (26% decrease, P < 0.01), that of the esterified cholesterol of LDL decreased by a mean of 1.28 mmol/l (30% decrease, P< 0.001), and that of the triglyceride of LDL decreased by a mean of 0.04 mmol/l (8% decrease, P < 0.01). No significant changes occurred in the plasma concentration of either the cholesterol or triglyceride of high-density lipoprotein (HDL) during treatment. 3. During the early period of treatment with colestipol, changes took place in the specific radioactivity of plasma cholesterol (labelled by intravenous injection of [3H]cholesterol), which, together with the changes in the mass of cholesterol within the individual plasma lipoproteins, were consistent with an increased influx into plasma of non-esterified cholesterol within VLDL, and an increased efflux of cholesterol from plasma within LDL.

scholarly journals An alternative procedure for incorporating radiolabelled cholesteryl ester into human plasma lipoproteins in vitro

1985 ◽  
Vol 226 (1) ◽  
pp. 319-322 ◽  
Author(s):  
D C K Roberts ◽  
N E Miller ◽  
S G L Price ◽  
D Crook ◽  
C Cortese ◽  
...  
Keyword(s):  
Cholesteryl Ester ◽  
Human Plasma ◽  
Specific Radioactivity ◽  
Density Lipoprotein ◽  
Plasma Lipoproteins ◽  
Cholesteryl Esters ◽  
Simple Method ◽  
High Specific Radioactivity

A simple method has been developed for labelling human plasma lipoproteins to high specific radioactivity with radioactive cholesteryl esters in vitro. After isolation by preparative ultracentrifugation, the selected lipoprotein was incubated for 30 min at 4 degrees C in human serum (d greater than 1.215) that had been prelabelled with [4-14C]cholesteryl oleate or [1,2-3H]cholesteryl linoleate, and was then re-isolated by ultracentrifugation. All major lipoprotein classes were labelled by the procedure. Specific radioactivities of up to 18 d.p.m. pmol-1 (46 d.p.m. ng-1) were achieved. When radiolabelled high-density lipoprotein was infused intravenously, the radioactive cholesteryl ester behaved in vivo indistinguishably from endogenous cholesteryl esters produced by the lecithin (phosphatidylcholine): cholesterol acyltransferase reaction.

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