PubMed Health⌕ Search

Biomedical subjects

J R Patsch

Publications and source records attributed to J R Patsch.

At least 145 records · Page 8Linked to original sources
PubMed1979

Very low density lipoprotein. Removal of Apolipoproteins C-II and C-III-1 during lipolysis in vitro.

In this study we have investigated the effects of very low density lipoprotein (VLDL) lipolysis on the removal of radiolabeled apolipoprotein C-II and apolipoprotein C-III-1 from in vitro lipolyzed lipoproteins. Lipolysis was carried out in vitro using lipoprotein lipase purified from bovine milk, and mixtures with or without plasma. Lipoproteins were isolated by ultracentrifugation and by gel filtration. Labeled apo-C-II and apo-C-III-1 distributed among plasma lipoproteins, predominantly VLDL and high density lipoprotein (HDL). Lipolysis induced transfer of apo-C-II and apo-C-III-1 from VLDL to HDL. The transfer was proportional to the extent of triglyceride hydrolysis, and similar for the two apoproteins. The apo-C-II/apo-C-III-1 radioactivity ratio did not change in either VLDL or the fraction of d greater than 1.006 g/ml during the progression of the lipolytic process. Similar observations were recorded while using plasma-devoid lipolytic systems. Gel filtration of incubation mixtures, on 6% agarose, revealed that the removal of labeled apo-C molecules from VLDL is not a consequence of either centrifugation or high salt concentration. These results suggest that there is no preferential removal of apo-C-II or apo-C-III-1 from lipolyzed VLDL particles. They further indicate that the ratio of apo-C-II to apo-C-III-1 does not regulate the extent of lipolysis of different VLDL particles, at least in VLDL isolated from normolipidemic humans.

Animals↗
PubMed1979

Effects of nicotinic acid therapy on plasma high density lipoprotein subfraction distribution and composition and on apolipoprotein A metabolism.

This report describes the effects of pharmacologic doses (3 g/d) of nicotinic acid on the plasma distribution and chemical composition of the high density lipoprotein (HDL) subfractions HDL(2) and HDL(3) and examines the influence of the drug on the metabolism of the major HDL apoproteins, apolipoproteins A-I (ApoA-I) and A-II (Apo-II). The drug lowered plasma cholesterol (15%, P < 0.05) and triglyceride (27%, P < 0.01); the former effect a result of a fall in the amount of cholesterol associated with very low density lipoproteins (31%, P < 0.02) and low density lipoproteins (36%, P < 0.02). Conversely, it raised plasma HDL cholesterol (23%, P < 0.05) and increased (by 345%) the plasma HDL(2):HDL(3) ratio. The latter derived from an absolute increment (646%) in circulating HDL(2), coupled with a fall (47%) in HDL(3). This change was not associated with major alterations in the overall cholesterol (free and esterified), triglyceride, phospholipid, or protein content of the subfractions; however, it was accompanied by substantial changes in their protein composition. In particular, the molar ratio of ApoA-I:ApoA-II in HDL(3) declined from 2.7:1 to 2.1:1 during nicotinic acid treatment.Significant perturbations of ApoA-I and ApoA-II metabolism accompanied the drug-induced HDL subfraction redistribution. Specifically, the plasma concentration of ApoA-I rose by 7% (P < 0.05) because of a decrease in its fractional catabolic rate. Moreover, whereas before treatment 6 and 94% of the plasma ApoA-I circulated with HDL(2) and HDL(3), after commencement of nicotinic acid therapy this distribution became 49 and 51% in HDL(2) and HDL(3), respectively. ApoA-II was found mainly in HDL(3), both before and during nicotinic acid treatment. Administration of the drug caused a 14% reduction in its plasma concentration (P < 0.05), which derived principally from a fall (22%, P < 0.01) in its synthetic rate. These data suggest that the effects of nicotinic acid on the HDL subfraction distribution may be mediated via (a) net transfer of ApoA-I from HDL(3) to HDL(2) and (b) a reduction in ApoA-II synthesis. Our present understanding of the association between HDL and atherosclerosis indicates that such changes may have prophylactic value in the prevention of coronary artery disease.

Adult↗
PubMed1978

Isolation of subfractions of human very low density lipoproteins by zonal ultracentrifugation.

Very low density lipoproteins (VLDL) have been isolated and subfractionated on the basis of their differing flotation rates. The procedure consists of a single 45-min zonal ultracentrifugation step using a linear density gradient of d = 1.00 to 1.15 g/ml. Appropriate fractions of the zonal rotor effluent containing the entire VLDL spectrum were characterized by analytical ultracentrifugation, gel filtration chromatography, and complete chemical analysis. Flotation rates of VLDL subspecies from hypertriglyceridemic and normolipemic plasmas correlated directly with their Stokes radii and triglyceride content and inversely with their proportion of cholesterol, cholesteryl esters, phospholipids, and total protein. There was also an inverse correlation of flotation rate with the fraction of tetramethylurea-insoluble protein. This procedure provides a reliable methodology for a rapid isolation of VLDL subfractions and the accurate determination of their flotation rates.

Centrifugation, Zonal↗
PubMed1978

Formation of high density lipoprotein2-like particles during lipolysis of very low density lipoproteins in vitro.

The effects of lipolysis of human plasma very low density lipoprotein (VLDL) on the structure and composition of high density lipoproteins (HDL) have been investigated. Lipolysis was performed in a controlled system in vitro containing VLDL (d less than 1.006 g/ml) and HDL3 (d = 1.125-1.210 g/ml) from human plasma and lipoprotein lipase (EC 3.1.1.34) purified from bovine milk. Lipolysis of VLDL caused profound changes in HDL3. Protein, phospholipid, and cholesterol liberated from VLDL during its lipolysis were transferred to the HDL3 particles. As a consequence of this in vitro transfer, the chemical composition and biophysical properties of HDL3 were substantially altered. The newly formed particles exhibited a flotation rate (F01.20) of 6.7 and a hydrated density of 1.110 g/ml. The chemical composition closely resembled that of native HDL2, and their size was slightly larger than that of the precursor HDL3. When HDL3 and postlipolysis HDL2 were subjected to ultracentrifugation under flotation velocity and equilibrium conditions, both proved to be stable particles. These results, when extrapolated to in vivo conditions, suggest an important metabolic relationship between the levels of circulating VLDL and HDL2 in plasma. This relationship now permits a reasonable explanation for numerous in vivo observations in which the levels of VLDL and HDL2 change reciprocally.

Apolipoproteins↗
PubMed1978

Metabolism of apolipoproteins A-I and A-II and its influence on the high density lipoprotein subfraction distribution in males and females.

Rate zonal ultracentrifugation of plasma samples from ten healthy age-matched volunteers (five males, five females) indicated that the high density lipoprotein subfraction ratio (HDL2:HDL3) in females was significantly higher than in males. The cause of this phenomenon was investigated by simultaneous examination of the metabolism of the major HDL apoproteins (apoA-I and apoA-II) in both groups. The results show that there is no significant sex-related difference in the plasma pool size, fractional catabolic rate, or synthetic rate of either apoprotein. We conclude that the increased HDL2:HDL3 ratio in femalse versus males does not derive from measurable differences in the metabolic handling of either apoprotein.

Adult↗
PubMed1978

Control of 3-hydroxy-3-methylglutaryl-CoA reductase activity in cultured human fibroblasts by very low density lipoproteins of subjects with hypertriglyceridemia.

Very low density lipoproteins (VLDL) and low density lipoproteins (LDL) from human normolipemic plasma, and the VLDL, the intermediate density lipoprotein (IDL), and LDL from patients with Type III hyperlipoproteinemic plasma were tested for their abilities to suppress the activity of 3-hydroxy-3-methylglutaryl-Coenzyme A (HMG-CoA) reductase in cultured human fibroblasts from normal subjects and a Type III patient. Regulation of cholesterol synthesis in the fibroblasts of a patient with Type III hyperlipoproteinemia appears to be normal. VLDL from normal subjects, isolated by angle head ultracentrifugation (d < 1.006) or by gel filtration on BioGel A-5m, were about 5 times less effective than LDL in suppressing HMG-CoA reductase activity, based on protein content, in agreement with previous reports with normal fibroblasts. Zonal centrifugation of normal VLDL isolated by both methods showed that the VLDL contained IDL. Normal VLDL from the angle head rotor, refractionated by the zonal method, had little, if any, ability to suppress the HMG-CoA reductase activity in either normal or Type III fibroblasts. VLDL, IDL, and LDL fractionated by zonal ultracentrifugation from Type III plasma gave half-maximum inhibition at 0.2-0.5 mug of protein/ml, indistinguishable from the suppression caused by normal LDL. Type III VLDL did not suppress HMG-CoA reductase in mutant LDL receptor-negative fibroblasts. Zonally isolated VLDL obtained from one Type IV and one Type V patient gave half-maximal suppression at 5 and 0.5 mug of protein/ml, respectively. Molecular diameters and apoprotein compositions of the zonally isolated normal and Type III VLDL were similar; the major difference in composition was that Type III VLDL contained more cholesteryl esters and less triglyceride than did normal VLDL. The compositions and diameters of the Type IV and Type V VLDL were similar to normal VLDL. These findings show that the basic defect in Type III hyperlipoproteinemia is qualitatively different from the cellular defect found in familial hypercholesterolemia, since the regulation of HMG-CoA reductase activity is normal in Type III fibroblasts. The metabolic defect in hypertriglyceridemia is related to the triglyceriderich lipoproteins which, free of other lipoproteins, have an enhanced ability to interact with cultured fibroblasts to regulate HMG-CoA reductase activity. These studies suggest that, in hypertriglyceridemia, there is a mechanism for direct cellular catabolism of VLDL which is not functional for normal VLDL.

Adult↗
PubMed1978

Effects of dietary polyunsaturated and saturated fat on the properties of high density lipoproteins and the metabolism of apolipoprotein A-I.

In this study we have investigated, in four normal males the effects of dietary saturated and polyunsaturated fat on the chemical composition and thermotropic properties of human high density lipoproteins (HDL) and have measured the influence of the diets on the metabolism of that fraction of HDL apolipoprotein A-I (apoA-I) that undergoes exchange in vitro and accounts for approximately two-thirds of the lipoprotein's apoA-I complement. When compared with the saturated fat diet, the polyunsaturated diet reduced plasma cholesterol (24%, P < 0.01) by affecting the cholesterol content in the very low density lipoprotein ( downward arrow25%, P < 0.02), low density lipoprotein ( downward arrow20%, P < 0.01), and high density lipoprotein fractions ( downward arrow33%, P < 0.01). Plasma triglyceride was also lowered (by 13%, P < 0.01). Furthermore, polyunsaturated fat ingestion caused a significant fall in the palmitate and stearate content of HDL triglyceride (41 and 37%, respectively), cholesteryl esters (29 and 35%), and phospholipids (17 and 9%) with a concomitant increase in the linoleate content of these moieties (157, 28, and 29%, respectively). The polyunsaturated diet also produced reciprocal changes in the percentage protein ( downward arrow9%, P < 0.02) and phospholipid ( downward arrow11.5%, P < 0.01) in HDl. These compositional changes were associated with an increase in the microscopic fluidity of the polyunsaturated HDL, although both diets had little effect on the fluidity parameters of HDL at body temperature. Rate zonal ultracentrifugation indicated that the HDL(2)/HDL(3) ratio fell by 28% (P < 0.05) on the polyunsaturated fat diet. In addition to the above, this diet reduced plasma apoA-I by 21% (P < 0.01). No change was seen in the fractional catabolic rate or the distribution of the apoprotein between intravascular and extravascular compartments on the two diets. However, when compared with the saturated diet, the synthetic rate of apoA-I was reduced by 26% during polyunsaturated fat feeding. The results show that polyunsaturated fat alters the chemical composition, thermotropic properties, and subfraction distribution of HDL without changing the fractional rate of catabolism of their major protein, apoA-I.These findings deserve careful consideration in determining the applicability and efficacy of polyunsaturated fat diet therapy in the prevention of atherosclerosis in man.

Adult↗
PubMed1978

Dynamic properties of human high density lipoprotein apoproteins.

This study was designed to identify a method for the measurement of human high density lipoprotein subfraction (HDL2 and HDL3) metabolism. Apolipoproteins A-I, A-II, and C, the major HDL apoproteins, were radioiodinated and incorporated individually into HDL2 and HDL3 in vitro. Using a double label technique, the turnover of apoA-I in HDL2 and HDL3 was measured simultaneously in a normal male. The apoprotein exchanged rapidly between the two subfractions, evidenced by equilibration of their apoA-I specific activity. Radiolabeled apoA-II, incorporated into the subfractions, showed a similar exchange in vitro. Incubation of 131I-labeled very low density lipoproteins (VLDL) with HDL or its subfractions resulted in transfer of C proteins from VLDL to the HDL moiety. The extent of transfer was dependent on the HDL subfraction present; 50% of the VLDL apoC was transferred to HDL3, while the transfer to total HDL and HDL2 was 69% and 78%, respectively. ApoC also exchanged between HDL2 and HDL3, again showing a preference for the former and suggesting a primary metabolic relationship between VLDL and HDL2. Overall, the study indicates that apoA-I, apoA-II, and the C proteins exist in equilibrium between HDL2 and HDL3. This phenomenon precludes their use as probes for HDL subfraction metabolism in humans.

Apolipoproteins↗
PubMed1977

Synthesis and release of low density lipoproteins by the isolated perfused pig liver.

In previous studies, we have shown that a relatively large amount of low density lipoproteins is released into the perfusate during isolated pig liver perfusion. The present studies were done to determine the source of these lipoproteins. Breakdown of the very low density lipoproteins to low density lipoproteins by the perfusion apparatus or by hepatic catabolism was excluded by adding 125I very low density lipoproteins to the perfusate in the presence and absence of a liver and then measuring the radioactivity in the low density lipoprotein fraction after rate-zonal ultracentrifugation. Release of preformed low density, lipoproteins from the liver was investigated by injecting iodine-labeled low density lipoproteins in vivo several hours prior to perfusion of the liver and then measuring the release of labeled low density lipoproteins into the perfusate. It was shown that intact labeled low density lipoproteins were released by the perfused liver. De novo synthesis of the low density lipoproteins was established by measuring the incorporation of [1-14C]leucine into this lipoprotein fraction. The radioactivity in the low density lipoprotein fraction increased with time and accounted for 20 to 25% of the total radioactivity incorporated into all the lipoprotein fractions. The incorporation of [1-14C]leucine into the low density lipoproteins was confirmed by rate-zonal analysis. We conclude that the low density lipoproteins in the perfusate from pig liver perfusions were derived mainly from a preformed liver pool, but also partly from de novo synthesis by the liver.

Animals↗
PubMed1977

Evaluation of the classical methods for the diagnosis of type III hyperlipoproteinemia.

Familial type III hyperlipoproteinemia is characterized by the presence of elevated plasma levels of very low density lopoproteins (VLDL) which contain an increased amount of cholesterol and by the presence of a significant amount of lipoproteins with an intermediate density between that of VLDL and low density lipoproteins (LDL); the intermediate density lopoproteins, designated IDL or Lp III, have a slower electrophoretic migration rate than VLDL, and are found in the ultracentrifugal top fraction as a contaminant. Classically, the diagnosis of type III is based on the demonstration of beta-migrating lipoproteins in the ultracentrifugal top fraction (density less than 1.006), thus "floating beta-lipoprotein". More recently, it has been proposed that an elevated VLDL-cholesterol to triglyceride ratio is diagnostic of the disorder. In the present report, we have compared the two methods for their diagnostic value and have concluded that the chemical index definition is the more reliable method for the diagnosis of type III hyperlipoproteinemia.

Electrophoresis, Paper↗
PubMed1977

Isolation, chemical characterization, and biophysical properties of three different abnormal lipoproteins: LP-X1, LP-X2, and LP-X3.

Three different but related abnormal lipoprotein species, LP-X1, LP-X2, and LP-X3, have been isolated from cholestatic plasma by ethanol precipitation and zonal ultracentrifugation. All three populations are rich in phospholipids (64.9 to 67.5%) and cholesterol (23.0 to 26.8%) but poor in cholesteryl esters (0.4 to 1.9%), triglycerides (1.8 to 3.2%), and protein (3.2 to 6.7%) with differences in chemical composition which result in buoyant densities (1.038, 1.049, and 1.058, respectively) to allow their separation. LP-X1, LP-X2, and LP-X3 exhibited apparent flotation rates of 17.3, 9.7, and 3.2 Svedbergs and Stokes radii of 339, 343, and 294 A, respectively. As determined from circular dichroic measurements, the protein constituents of all three particles possessed a high degree of alpha helical structure (41 to 65%). Each LP-X particle exhibited abnormally low fluidity as evaluated by electron paramagnetic resonance. All of the particles contained human serum albumin and the C-proteins as major protein constituents, but only LP-X2 and LP-X3 contained apolipoprotein A-I and apolipoprotein E.

Apolipoproteins↗
PubMed1977

Lipoprotein-X: a substrate for lecithin: cholesterol acyltransferase.

The action of lecithin:cholesterol acyltransferase (LCAT) was studied on an abnormal lipoprotein (LP-X) rich in phosphatidylcholine and cholesterol from the plasma of patients with obstructive liver disease. 60 mg LP-X isolated free of other lipoproteins and subsequently labelled with 3H-cholesterol were incubated with 1 mg highly purified enzyme in the presence of albumin. After 45 h at 37 degrees C, the incubation mixture was subjected to zonal ultracentrifugation. 3H-cholesterol and 3H-cholesteryl esters were quantified in each fraction of the zonal gradient. More than 95% of the lipoproteins in this mixture banded in the density range of LP-X with no change in size distribution, but did contain 593 nmoles of newly formed cholesteryl esters. Agarose electrophoresis revealed an alpha-migrating band in addition to the original beta-band. Also on agar, the typically cathode migrating LP-X was changed to anode moving material. These studies indicate that LP-X can serve as a substrate for LCAT.

Acyltransferases↗
PubMed1977

[The effect of pindolol on carbohydrate and fat metabolism in diabetes mellitus].

Twenty-seven diabetic patients, nine treated with insulin, nine treated with tolbutamid, and nine placed on diet, were given either pindolol or placebo 5 mg, three times daily during a 6-week period. The following 6-week period those receiving pindolol in the first 6 weeks received placebo and vice versa. Pindolol had no influence on the concentration of blood glucose, free fatty acids, triglycerides, or total cholesterol. The effect of pindolol on carbohydrate and fat metabolism appears to be of no clinical relevance in diabetic patients receiving their usual therapy.

Adult↗
PubMed1976

[Electronmicroscopic characterisation of human plasma lipoproteins after isolation by zonal ultracentrifugation (author's transl)].

Human plasma proteins were isolated by zonal ultracentrifugation and the fractions obtained examined under the electron microscope. HDL2 had a high degree of uniformity in normal persons, characterised by numerous two-dimensional, hexagonal arrangements. Optical diffraction analysis of HDL2 gave a centre distance of 11.3 nm, individual HDL2 particles being spherical with a diameter of 9.8 nm. HDL3 represented a somewhat less uniform lipoprotein population with a particle diameter between 6.5 and 9.5 nm. LDL had a diameter of 20-25 nm. In patients with hyperlipoproteinaemia type III a third peak was isolated, in addition to the two normal lipoprotein peaks VLDL and LDL. It lies between them and has been called Lp III. VLDL from type III plasma consisted of spherical particles, diameter 31-81 nm, morphologically indistinguishable from normal VLDL. Lp III consisted of a relatively homogeneous spherical lipoprotein population with a diameter of 25-30 nm. LDL consisted of spherical particles whose size was highly homogeneous (18-23 nm diameter), indistinguishable from normal LDL.

Adult↗