Julian B. Marsh

Bio: Julian B. Marsh is an academic researcher from Drexel University. The author has contributed to research in topics: Very low-density lipoprotein & Lipoprotein. The author has an hindex of 37, co-authored 90 publications receiving 4427 citations. Previous affiliations of Julian B. Marsh include United States Department of Agriculture & University of Pennsylvania.

Hepatic Secretion of Lipoproteins in the Rat and the Effect of Experimental Nephrosis

Abstract: Livers from normal and nephrotic rats were perfused by the nonrecirculating technique Nephrosis was studied on the 7th d after the injection of puromycin animonucleoside Amino acid-labeled lipoproteins (d < 121) were isolated from the perfusion medium by agarose column chromatography or by sequential density ultracentrifugation In both groups of animals, in addition to very low density lipoproteins and nascent high density lipoproteins, column chromatography revealed the presence of a peak of 2-3 × 106 daltons This peak contained lipoproteins of densities corresponding to <1006, 1006 < d < 102, and 102 < d < 106, which indicated that rat liver secretes a heterogeneous mixture of triglyceride-rich lipoproteins The amount of these lipoprotein density classes was measured and their lipid and apoprotein composition and their apoprotein specific activity were determined In both groups of rats there was a progressive rise in phospholipid and decrease in triglyceride content as the isolation density increased from 1006 and 106 The lipoproteins from the nephrotics had higher amounts of cholesterol The livers from the nephrotic rats secreted two to three times as much lipoprotein as controls in all density classes in the first 20 min, but during the next 40 min only the 102 < d < 106 and nascent high density lipoproteins remained at this high level compared to controls A larger total liver pool of apolipoproteins in nephrotic livers was inferred from their lower specific activities during the first 20 min The apoprotein composition of liver perfusate lipoproteins from nephrotics differed from controls There was a 40% decrease in the amount of low molecular weight apoproteins in all density classes, with corresponding increases in apo B and apo E in the triglyceride-rich fractions The apo A-1 content of nascent HDL was increased from 16% in controls to 52% in nephrotics, with corresponding decreases in apo C and apo E When these results were combined with specific activity measurements of the individual apoproteins and the net secretion rate of total protein in each lipoprotein class, it was possible to estimate the total amount of each apoprotein secreted and the total incorporation of labeled amino acids into each The incorporation of label gave results similar to those obtained by direct measurement of the amounts of apoproteins Apo E secretion was increased by a factor of 18, apo B by 28, and apo A-1 by 84, whereas the secretion of apo C was not significantly altered We explain these results by postulating that the primary stimulus to hepatic plasma protein synthesis in response to proteinuria is general and that subsequent negative feedback regulation affects individual apolipoprotein synthesis rates A corollary of this hypothesis is that the biosynthesis and secretion of an apoprotein may be regulated independently of the lipoprotein density class in which it is found

Effects of eicosapentaenoic and docosahexaenoic acids on apoprotein B mRNA and secretion of very low density lipoprotein in HepG2 cells.

Abstract: Oleic acid (18:1n-9, OA), docosahexaenoic acid (22:6n-3, DHA), or eicosapentaenoic acid (20:5n-3, EPA) was added to HepG2 cells at a concentration of 1 mM in a 5:1 or 2:1 molar complex with bovine serum albumin (BSA), and this was incubated for 3 hours. The incorporation of 3H-glycerol into cellular and medium triglyceride (TG), and the mass of TG were measured. The effects of these fatty acids on the secretion of very low density lipoprotein (VLDL) apolipoprotein B (apo B) were estimated from the incorporation of 3H-leucine into the medium apo B in comparison to cells incubated with fatty acid-poor albumin. The secretion of human albumin by the cells was also estimated by immunochemical precipitation of the labeled albumin. In addition, the intracellular levels of apo B messenger ribonucleic acid (mRNA) were measured by the dot-blot hybridization technique. Relative to control cells incubated with BSA, OA (complexed to BSA at a 5:1 molar ratio) stimulated TG synthesis and secretion sevenfold. Compared to OA, EPA was 24% less effective for both processes, whereas DHA inhibited only the secretion of TG (-43%). The secretion of VLDL apo B was not affected by OA, but was decreased 31% by EPA and 54% by DHA. When the molar ratio of fatty acid complexed to albumin was changed to 2:1, similar results were obtained with respect to TG production. The levels of apo B mRNA relative to actin mRNA were not significantly altered by any of the fatty acids.(ABSTRACT TRUNCATED AT 250 WORDS)

Microalgae for oil: strain selection, induction of lipid synthesis and outdoor mass cultivation in a low-cost photobioreactor.

Abstract: Thirty microalgal strains were screened in the laboratory for their biomass productivity and lipid content. Four strains (two marine and two freshwater), selected because robust, highly productive and with a relatively high lipid content, were cultivated under nitrogen deprivation in 0.6-L bubbled tubes. Only the two marine microalgae accumulated lipid under such conditions. One of them, the eustigmatophyte Nannochloropsis sp. FM102: 100–112. © 2008 Wiley Periodicals, Inc.

Fat Transport in Lipoproteins — An Integrated Approach to Mechanisms and Disorders

Abstract: Type II Hyperlipoproteinemia159, 192 193 194 195 196 General Definitions By the Type II lipoprotein pattern we mean an increase in the concentration of lipoproteins that have discrete β mobility b

Glycosphingolipids in Cellular Interaction, Differentiation, and Oncogenesis

Abstract: The idea that glycosphingolipids (or, briefly, glycolipids) are ubiquitous components of plasma membrane and display cell type-specific patterns perhaps stemmed from the classical studies on glycolipids of erythrocyte membranes.(1,2) Subsequently, plasma membranes of various animal cells were successfully isolated and analyzed; all were characterized by their much higher content of glycolipid than was found in intracellular membranes.(3–8) It is generally assumed that glycolipids are present at the outer leaflet of the plasma membrane bilayer, although this assumption is based only on experiments with surface-labeling by galactose oxidase-NaB[3H]4 of intact and lysed erythrocyte membranes and inside-out vesicles.(9,10) Obviously, further extensive studies of the organization of glycolipid in other eukaryotic cell membranes are necessary. Interestingly, the majority of neutral glycolipids present in plasma membranes are cryptic (see Section 4.2.1).

A multiubiquitin chain is confined to specific lysine in a targeted short-lived protein.

Abstract: The ubiquitin-dependent degradation of a test protein beta-galactosidase (beta gal) is preceded by ubiquitination of beta gal. The many (from 1 to more than 20) ubiquitin moieties attached to a molecule of beta gal occur as an ordered chain of branched ubiquitin-ubiquitin conjugates in which the carboxyl-terminal Gly76 of one ubiquitin is jointed to the internal Lys48 of an adjacent ubiquitin. This multiubiquitin chain is linked to one of two specific Lys residues in beta gal. These same Lys residues have been identified by molecular genetic analysis as components of the aminoterminal degradation signal in beta gal. The experiments with ubiquitin mutated at its Lys48 residue indicate that the multiubiquitin chain in a targeted protein is essential for the degradation of the protein.