Thomas R. Dirksen

Quantitative Determination of Some Constituent Lipids in Human Dentin

Abstract : A method is described for the extraction of dentin lipids and the separation of these lipids into six components (cholesterol esters, free cholesterol, triglycerides, diglycerides, monoglycerides, and phospholipids). Essentially, the method requires the decalcification of dentin using EDTA and subsequent extraction with diethyl ether, ethanol, and chloroform. The lipid extract is separated into six components by a small silicic acid column and the effluents are quantitated colorimetrically.

Lipid metabolism in bone and bone cells I. The in vitro incorporation of [14C]glycerol and [14C]glucose into lipids of bone and bone cell cultures

Abstract 1. 1. To study lipid synthesis in mineralizing tissues, calvaria of new-born rats were incubated in buffer containing radioactive glycerol or glucose. The effects of non-labeled ATP, CTP, and glucose on lipid synthesis were investigated. Lipid synthesis by bone cells grown in primary cell culture was also studied. 2. 2. Calvaria and bone cells were found to contain cholesterol, cholesterol esters, mono-, di- and triglycerides, free fatty acids, and various phospholipids. The phospholipids included lecithin, lysolecithin, phosphatidyl ethanolamine, lysophosphatidyl ethanolamine, phosphatidyl serine, phosphatidyl inositol, cardiolipin, sphingomyelin, and various unidentified components. Appreciable quantities of phosphatidyl serine were not extractable from calvaria until after demineralization with EDTA. 3. 3. The incubation of calvaria or bone cell cultures with [14C]glycerol and [14C]glucose gave rise to lipids labeled in the glycerol moiety of the various glycerides. Triglycerides and lecithin were the two most heavily labeled lipids. Phosphatidyl serine, cholesterol, sphingomyelin, and fatty acids were not labeled with these two labeled precursors. ATP generally stimulated neutral lipid synthesis but retarded phosphohpid synthesis from [14C]glycerol in a medium containing a low level of unlabeled glucose. An elevated glucose level generally decreased labeling of lipids from [14C]glycerol, probably by increasing intracellular glycerol phosphate concentrations. At higher levels of ATP and non-radioactive glucose, varied results were obtained which suggest that critical levels of both substances are required for optimal lipogenesis. CTP stimulated the synthesis of diglycerides, triglycerides, and lecithin, but inhibited the labeling of phosphatidyl ethanolamine. The synthesis of lipid from [14C]glucose was generally inhibited by ATP, but the simple effect of ATP on phosphofructokinase does not totally account for this inhibition.

Lipid metabolism in bone and bone cells. II. The in vitro incorporation of [32P] orthophosphate and [14C] serine into lipids of bone and bone cell cultures.

Abstract 1. 1. Calvaria of new-born rats or bone cell cultures were incubated with buffer containing [ 32 P]orthophosphate or [ 14 C]serine to study lipid synthesis in mineralizing tissues. 2. 2. [ 32 P]Orthophosphate was readily incorporated into phospholipids by calvaria and bone cell cultures. As with [ 14 C]glucose or [ 14 C]glycerol (ref. 1), lecithin was more heavily labeled than the other phospholipids. The labeling of sphingomyelin and phosphatidyl serine could not be demonstrated from radioactive phosphate. ATP decreased the incorporation of this isotope into lipids. 3. 3. [ 14 C]Serine gave rise to a variety of radioactive lipids. The synthesis of phosphatidyl serine was enhanced by the addition of both CTP and ATP whereas the labeling of sphingomyelin and phosphatidyl ethanolamine was little affected by these two co-factors.

Lipid Constituents of Whole and Parotid Saliva

The importance of serum lipid determinations in the diagnosis of systemic disease is well established. Whether or not salivary lipid concentrations reflect the levels in other body fluids has not been ascertained. Lipid methodology has been a limiting factor, but Marinetti1 and Marinetti and Stotz2 have recently introduced procedures by which lipid classes may be separated by paper chromatography and identified through chemical tests. The present study was designed to apply these methods to human saliva, in an effort to establish physiologic base lines for lipid components.