Neutral lipids facilitate transfer of bone morphogenetic proteins and other noncollagenous proteins.

In the process of separation of bone morphogenetic proteins from bone matrix, lipids were found in unexpected amounts closely associated with noncollagenous proteins soluble in guanidine hydrochloride. Lipids representing 33.7-49.9% by weight were recovered with various solvents. Composites of noncollagenous proteins and lipids soluble in either chloroform- methanol or acetone implanted in the hindquarter muscles of mice induced the formation of large deposits of heterotopic bone. The protein-lipid aggregates formed microspherules which were stained by Sudan Black B. Implants of bone morphogenetic proteins and noncollagenous proteins-lipid microspherules stained with Sudan Black B induced bone development in the same manner as unstained delipidized bone morphogenetic proteins associated with noncollagenous proteins. Lipid-free osteocalcein, osteonectin, albumin and other bone matrix proteins did not induce bone formation or bind Sudan Black B. The more highly purified the noncollagenous proteins, with or without activity of bone morphogenetic proteins, the lower the level of binding with Sudan Black B. Acetone-soluble bone matrix lipids consisted chiefly of triglycerides, cholesterol and saturated short chain fatty acids, and included little or no phospholipids or monounsaturated fatty acids. Composites of recombinant bone morphogenetic proteins-2 and acetone-soluble lipids induced larger deposits of bone than implants of recombinant bone morphogenetic proteins-2 without acetone-soluble lipids. The hypothesis that an association of bone lipids with protein facilitates the local transport of bone morphogenetic proteins warrants further investigation.

The gill lipids of spawning Pacific salmon.

The gill phospholipids of 2 Pacific salmon species, Oncorhynchus keta and O gorbuscha, were composed of 38-43% phosphatidylcholine (PC) and 19-22% phosphatidylethanolamine (PE). Ether phosphoglycerides constituted 4-8% of the total PC fraction and 37-51% of the PE fraction. No significant changes in gill phospholipids were observed between those of pre-spawning fish in sea water and those of spawned salmon in the river. Cholesterol, however, was higher in the latter (0.59% vs 0.38%).

Plasmalogens in the gill lipids of aquatic animals.

Lipids constituted 0.6-2.2% wet wt of the gills of 11 species of aquatic animals (4 bivalves, a crustacean and 6 fishes). Phospholipids, largely phosphatidylcholine (PC) and phosphatidylethanolamine (PE), are major components of all species. The plasmalogen contents of these lipids were 47-291 mumol/g, with the highest values found for bivalve gill total lipids and the catfish phospholipid fraction.

Specificity of digestive lipases in hydrolysis of wax esters and triglycerides studied in anchovy and other selected fish.

The physiological specificity of fat digestion in several species of marine fish was studied by incubating a variety of synthetic and natural lipid substrates in fish intestinal fluid. Wax ester and triglyceride hydrolyses were studied in vivo and in vitro. In vivo feeding studies showed triglyceride hydrolysis and reesterification in the gut occurred 4 times faster than wax ester metabolism. In vitro comparisons of wax and triglyceride lipolysis always showed triglycerides to be hydrolyzed faster than wax esters; however, wide variation in the ratio occurred among different batches of intestinal juice. Ca. 50% of the 2 monoglycerides formed in the lipolytic sequence were hydrolyzed. Esters of lipase resistent fatty acids (20:4 and 20:5) were cleaved faster than normal fatty acid esters (18:2 and 18:3). Two of the species studied, the northern anchovy, Engraulis mordax and the jack mackerel, Trachurus symmetricus, empty lipase(s) into their gall bladders and produce-phospholipid free bile.

The metabolism of wax ters and other lipids by the marine copepod, Calanus helgolandicus.

The polyunsaturated wax esters which occur in an oil droplet in Calanus helgolandicus apparently serve as a short term reserve metabolic fuel. The lipids of the copepods were labeled by feeding them (14)C-labeled diatoms, Skeletonema costatum, after which starvation and turnover experiments were carried out. During starvation both wax esters and triglycerides are largely depleted within 72 hr, whereas cholesterol and phospholipid decreased at much slower rates.

Wax esters in marine copepods.

Two pelagic copepods, Calanus helgolandicus and Gaussia princeps, contained wax esters with 28 to 44 carbon atoms as major lipid constituents. In laboratory cultures of the former species, changes in nutrition (amount or species of diatoms fed) affected both the amount of total lipid and the composition of the wax esters. Thus, the wax esters serve as a reserve energy store in this organism.

Lipids of the living coelacanth, Latimeria chalumnae.

The muscle of Latimeria chalumnae contains 30 to 71 percent (dry weight) of lipid deposited extracellularly. Wax esters constituted 90 percent or more of the lipids from muscle and fat storage tissues. These esters, by gaschromatographic analysis, consisted of C(30) to C(40) homologs with one or two double bonds.