A solvent system for delipidation of plasma or serum without protein precipitation

The effect of delipidated high density lipoprotein on human leukocyte sterol synthesis

Sterol synthesis is increased when whole human serum is added to leukocytes in buffer. Addition to the buffer of an equivalent amount of serum from which lipid has been extracted by organic solvent leads to a greater increase in synthesis. The addition of whole high density lipoprotein to buffer has little effect on sterol synthesis whereas addition of delipidated high density lipoprotein stimulates sterol synthesis. Delipidated high density lipoprotein may be responsible for the stimulation of sterol synthesis by delipidated serum.

A novel chromatographic method for the preparation of high density lipoproteins

High density lipoproteins (HDL) were isolated by a procedure employing polyanion precipitation and column chromatography. The product polyanion precipitation and column chromatography. The product was free of low denisty lipoproteins (LDL) but serum albumin (HSA) was still present. The remaining HSA was removed by an immunoadsorbent column. The HDL isolated by our method was compared to another HDL preparation isolated from the same plasma sample by the combination of ultracentrifugation and gel chromatgraphy. It was found to have approximately the same lipid and protein composition as the HDL isolated by conventional techniques. Minor differences included a higher phospholipid and apoprotein E content and lower triglyceride and ApoC II content of the HDL isolated by column chromatography. The method described here is considerably less tedious than earlier techniques, can be scaled up without substantial increase in labor and results in an approximately 30% higher yield than the method described by Rudel et al.

Fluorescence polarization of DPH-labeled cells adsorbing viruses and its diagnostic potential

Mammalian or avian cells were labeled with a fluorescent probe DPH (1,6-diphenyl-1,3,5-hexatriene). Within a few minutes after adsorption of various naked and enveloped viruses, the degree of fluorescence polarization (P) of the DPH embedded in the adsorbing cells as measured at 37 degrees C, was reduced, a finding indicating a decrease in the microviscosity of the lipids in the cell membrane. This change of fluidity was proportional to the concentration of the adsorbing virus and could be abolished or inhibited by homologous specific antiviral sera, but not by heterologous sera. Potential use of fluorescence polarization tests is described for titration of virus concentration, as well as for serological identification of a virus.

Regulation of cholesterol synthesis in skin fibroblasts derived from old people

Sterol synthesis from radioactive acetate and the suppression of this synthesis by human low density lipoprotein (LDL) have been investigated in skin fibroblast strains derived from infant donors and from donors over the age of 70 years. The activity of the enzyme hydroxymethylglutaryl-CoA reductase and its repression by LDL has also been investigated in these fibroblast strains and in senescent cells of the foetal lung cell strain MRC-5. No age-related differences could be detected either in repression of [3H]acetate incorporation by LDL, or in repression of HMG-CoA reductase activity.

The relation of temperature and lipid composition to cell adhesion

We have examined as a function of temperature the effect of changes in the composition of the fatty acid chains of membrane phospholipids on the rate of cell to cell adhesion in the neuronal cell line B103. The rate of cell to cell adhesion in this cell line is highly temperature dependent but is not influenced by changes in the fatty acid composition of the plasma membrane generated by growing the cells either in the presence of oleic acid or elaidic acid. In contrast the temperature dependence of the rate of cell to cell adhesion, measured in a monolayer adhesion assay, is highly dependent on the shear force used during the assay. A two-step model of cell to cell adhesion involving multiple adhesion ligands is presented which can be used to explain these observations.

Purification of retinol-binding protein from serum and urine by affinity chromatography

A new method for the purification of retinol-binding protein from urine and serum is described. The method is based on the reversible binding of retinol-binding protein to retinoic acid linked to Sepharose and prealbumin linked to Sepharose. The yield is comparable to conventional methods using ion exchange and gel filtration and the product is an apo retinol-binding protein of high purity. The product has the same electrophoretic mobility and molecular weight and the same ability to interact with retinoic acid and prealbumin as retinol-binding protein prepared by conventional methods.

Cholesteryl ester exchange protein in human plasma isolation and characterization

A protein catalyzing the exchange of cholesteryl esters among the lipoproteins was found in human plasma. A rapid method for assaying this activity was developed based on the transfer of radioactive cholesteryl esters from low density lipoprotein with MnCl2 in the presence of phosphate. Fractionation of plasma through a combination of ammonium sulfate precipitation, ultracentrifugation at p = 1.25, and chromatography on Phenyl-Sepharose, CM-cellulose, and concanavalin A-Sepharose, yielded a preparation purified 3500-fold compared to the starting plasma. The exchange protein was found to be a glycoprotein with an isoelectric point of 5 and apparent molecular weight of 80 000. On the basis of these properties and its immunological characteristics the exchange protein was judged to be distinct from any of the known apolipoproteins. This protein could also be separated from plasma phosphatidylcholine cholesterol acyl-transferase on DEAE-cellulose. The exchange protein did not appear to influence cholesterol esterification in lipoproteins by phosphatidylcholine cholesterol acyl-transferase, and the latter had no effect on the transfer of low density lipoprotein cholesteryl esters to high density lipoprotein. The exchange protein did not esterify cholesterol or hydrolyze cholesteryl esters in lipoproteins.

HDL-cholesterol, apolipoproteins A1 and B. Age and index body weight

Some data of previous literature have emphasized a negative correlation between plasma apo A1, HDL cholesterol and coronary heart disease. The present paper stresses a high negative correlation existing both in females and males between values of index body weight (IBW) and plasma levels of HDL cholesterol and apo A1. No correlation has been found between age and, respectively, HDL cholesterol, apo A1 and apo B.

Variations in apolipoproteins B and A1 during the course of myocardial infarction

The plasma apolipoproteins B and A1, and plasma lipids and lipoproteins, were studied in fifteen patients with acute myocardial infarction. In the days immediately after acute infarction there was a decrease in total cholesterol, low density lipoprotein-cholesterol, total apolipoprotein-B, low density lipoprotein apolipoprotein-B and high density lipoprotein apolipoprotein A1. High density lipoprotein-cholesterol remained unchanged. In the same period the total triglycerides, very low density lipoprotein-protein, very low density lipoprotein-cholesterol, very low density lipoprotein apolipoprotein-B and very low density lipoprotein apolipoprotein A1 were increased. A reduction of the apolipoprotein ratio CII/CIII occurred after the acute phase. After 25--30 days all these values regained their baseline values.

Importance of apolipoproteins in lipid metabolism

Lipids, which serve as a source of energy and are an important constituent of cell membrane structure, are readily stored in the body. By definition they are insoluble in water. Specific proteins called apolipoproteins interact with lipids to form soluble lipid-protein complexes called lipoproteins. It is in this form that the major lipids--cholesterol, triglyceride and phospholipid--circulate in plasma. Unesterified fatty acids, another major lipid group, are bound to albumin in the circulation. The plasma lipoproteins are complex macromolecules composed of lipids, apolipoproteins and carbohydrates. The relative proportions of these components differ markedly between lipoprotein classes. Hyperlipidemia is a term used for increased concentrations of plasma cholesterol and/or triglycerides. Any one plasma lipid is present in several types of lipoproteins. Thus, hyperlipidemia implies the presence of hyperlipoproteinemia. The latter has important therapeutic implications. Most of the recent attempts at classification have been directed at the lipoprotein level of plasma lipid organization. Decreased concentrations of lipids in plasma can be achieved by altering the rates of metabolism of lipoproteins. Decrease in lipoprotein synthesis, increased catabolism or impaired release from cells into the blood stream may all result in a decrease of plasma lipids. Drugs which affect one or more of these factors are used to treat hyperlipoproteinemia. In order to elucidate the mechanism of action of hypolipidemic drugs it is necessary to understand the lipoprotein defect at the molecular level. This requires a more detailed knowledge of lipoprotein metabolism than is presently available for most of the hyperlipoproteinemias. This paper will review some of the generally accepted properties of the plasma lipoproteins, describe some difficulties which hamper the understanding of lipoprotein metabolism, and identify possible mechanisms by which drugs may affect lipoprotein metabolism.

The properties and clinical significance of some electrophoretically slow forms of alkaline phosphatase

Sera from 8 patients with a marked slow-moving alkaline phosphatase band on electrophoresis were investigated. Inhibitor studies and treatment with neuraminidase showed that all the patients had slow bands with alkaline phosphatase properties resembling those of the liver or bone isoenzyme. In no case did the slow band resemble the intestinal isoenzyme. Immunoelectrophoretic and molecular weight studies indicated that the slow band consisted of an IgG-alkaline phosphatase complex of molecular weight 540 000. Serum from a patient with the slow band was able to bind liver or bone, but not intestinal, alkaline phosphatase from other patients to form the slow band. Serum from patients with the slow band probably contains an abnormal IgG molecule which can bind alkaline phosphatase in the ratio 2:1. No clinical condition was common to all 8 patients although most of them had either intestinal or lung disease.

Modulation of macrophage tumoricidal capability by components of normal serum: a central role for lipid

The tumoricidal capabilities of macrophages can be reversibly inhibited by a lipoprotein of high molecular weight, and the inhibition appears to be reproduced by enrichment of macrophage plasma membranes with cholesterol. A second serum component of lower molecular weight enhances macrophage cytotoxicity. The presence of these components in normal serums suggests a physiological role for such factors in the regulation of macrophage function.

Rapid cell surface-related stimulation of alkaline phosphatase in HeLa cells by dimethyl DL-2,3-distearoylotypropyl-2'-hydroxyethylammonium acetate (Rosenthal's inhibitor)

Cultures of HeLa cells, strains S3G (HeLa65) and S3K (HeLa71) were grown in plastic dishes until firmly attached and were then treated with sonic dispersions of Rosenthal's phospholipase inhibitor. A rapid increase in alkaline phosphatase activity occurred following this treatment in the S3G strain (low inducible alkaline phosphatase) but not in the S3K strain (high constitutive alkaline phosphatase). The stimulatory effect was dependent on the presence of bovine serum in the medium. No stimulation of alkaline phosphatase was observed in a variety of soluble preparations of this enzyme.

Quantitative determination of human apolipoprotein D by electroimmunoassay and radial immunodiffusion

1. An electroimmunoassay and a radial immunodiffusion procedure are described for the quantitative determination of human serum apolipoprotein D. Purified apolipoprotein D and antisera to both lipoprotein D and apolipoprotein D were used to standardize the assays. The assays are applicable to measurement of apolipoprotein D in serum and density classes. The electroimmunoassay is more sensitive (50 ng apolipoprotein D quantitatively detectable), rapid (time required for completion of assay is 5 h) and precise (the within- and between-assay coefficients of variation are 4 and 7%, respectively) than radial immunodiffusion. However, comparable results were obtained by both methods (r = 0.85). 2. Serum apolipoprotein D levels of normal subjects and hyperlipoproteinemic phenotypes IIa, IIb, III, IV and V were in the same range (10 to 12 mg/dl). In contrast, patients with hyperchylomicronemia (type I) had decreased apolipoprotein D levels (5 mg/dl; P less than 0.001). The apolipoprotein D in serum of normolipidemic subjects was detectable in all density classes but measurable only in HDL2 (21%), HDL3 (43%) and VHDL (36%). 3. Rocket electrophoresis is also a valuable tool for assessing the structural relationships among apolipoproteins or their constituent polypeptides. Interaction between serum and a mixture of antibodies to A-I, A-II and apolipoprotein D resulted in the formation of separate lipoprotein A and lipoprotein D rockets indicating that apolipoprotein D is not a constituent polypeptide of apolipoprotein A. This observation confirms the existence of lipoproteins A and D as separate lipoprotein families.

Rapid delipidation of and particulate removal from human serum by membrane filtration in a tangential flow system

Approximately 50% of the total lipids and virtually all of the colloids and particulates which impart turbidity to human serum are removed by filtration through 0.1 micrometer-poresize membrane filters in a high-volume tangential flow device. The advantages of the method over solvent extraction are: (a) no organic solvent(s) is added to the serum at any time, (b) filtrations can be performed rapidly at room temperature, (c) unstable lipoproteins and particulates are removed in 1 step, (d) scaleup from hundreds of ml to hundreds of liters is readily achievable, and(e) process time is markedly reduced.

Isolation and characterization of proteins associated with the lung surfactant system

Rabbit lung washings and purified lung surfactant were delipidated without precipitation or loss of protein. This enabled effective study of the proteins by electrophoretic and immunoelectrophoretic techniques. The lung washings contained secretory immunoglobulin A and several serum proteins. The protein composition of purified lung surfactant was the same as the unfractionated lung washings confirming our previous study which indicated that there is no specific protein associated with surfactant phospholipids obtained by alveolar lavage with isotonic saline.