Publisher Summary This chapter describes the general aspects of the regulation of protein metabolism by diet and by hormones. There is a complex interrelationship between the diet and homeostatic mechanisms within the body. The chapter presents an integrated picture of dietary and hormonal factors that influence the course of protein metabolism in different organs. It also presents the evidence for the existence and nature of labile protein components of the body. Certain tissues protein increase or diminish rapidly in response to variations in dietary protein intake and could, thus, function as sensitive regulators in protein metabolism. Dietary factors other than protein intake can influence the protein content of tissues, and the next section, therefore, describes the influence exerted by dietary carbohydrate and fat on the course of protein metabolism and particularly on labile tissue proteins. The chapter also discusses the modifying action of hormones on protein distribution within the body, and the interaction between diet and hormones in this process.

General Aspects of the Regulation of Protein Metabolism by Diet and by Hormones

"Interstitial and depot fat is by far the most variable constituent of the body and the one most clearly related to nutrition" (148). Fatty tissue can amount to half or more of the live weight of the animal (173, 269, 304) or can be so reduced as to be undissectible; this feature of it so impressed the 18th century anatomist John Hunter that he regarded fat as "not animal substance" because "the animal is the same with as without it" [kited in (214)]. It is now universally accepted that much (but not all) body fat serves as an energy reserve, but its other "functions" and the consequences of its presence on the anatomy and physiology of the whole animal have not been the subject of critical review since the work of Shattock (247) and Auerbach (10). As long ago as 1940, Wells (294) described the anatomy of adipose tissue as a "neglected subject" in humans and in other animals. Statements made in elementary texts (78, 201, 248, 288) are extremely brief; they stress aspects that are in fact of minor importance in many species-e.g. the role of fat in thermoregulation. Indeed, 20th Century opinion on the subject is well summarized by Langebartel (157), who devoted one of the 510 pages of his standard textbook of veterinary anatomy to adipose tissue and concluded that "little more seems necessary to be said about the subject." Comparative anatomists have long treated the subject with suspicion; the most recent systematic attempt to apply the concept of homology to fat masses across classes and orders of vertebrates was that of Butler (49). Many anatomy texts do not mention the subject at all (103, 135, 137); others dismiss the subject very briefly (201, 214) or refer only to biochemical aspects of the tissue (78, 248).

Morphological Aspects and the Ecological and Mechanical Consequences of Fat Deposition in Wild Vertebrates

2,3,7,8-Tetrachlorodibenzo-p-dioxin tissue distribution, excretion, and effects on clinical chemical parameters in guinea pigs.

Publisher Summary The techniques of tissue preparation and the techniques of solvent extraction are so interrelated that it is extremely difficult to discuss them separately. Consequently, in this chapter, thirteen procedures are given whereby lipids may be separated from tissues. Lipid extraction by homogenizing tubes is useful when it is desired to obtain all the lipids from relatively small amounts of tissue and quantitatively to study certain constituents in the residue remaining. In lipid extraction by centrifuge tubes. The tissue is placed in a 50-ml. round-bottomed centrifuge tube, finely divided with a tissue disintegrator le in the presence of alcoholether, and all the lipids are extracted. In lipid extraction by chloroform, the sodium sulfate is used to dehydrate the tissue in order that the chloroform may then dissolve the lipids. The Waring blendor and similar apparatus offer a convenient means of reducing tissue to a fine state of subdivision after which lipids can be removed. Similarly lipid extraction is performed with different solvents, such as alcohol-ether, chloroform, alcohol-ether, then ether (soxhlet), and methanol-chloroform. The choice of one procedure over another is very greatly dependent on the equipment present in the laboratory, the experimental design, and the nature of the determination to be made on the extracts obtained. From the variety of procedures presented it should not be difficult to select one which meets most requirements.

[55] General procedures for separating lipid components of tissue

Chylomicron fat labelled with glyceryl tri(l-14C)palmitate is removed rapidly from the blood stream when introduced in the form of homologous chyle (Havel & Fredrickson, 1956; French & Morris, 1957). Some of the fat leaves the blood stream in the form of intact chylomicrons (Courtice & Morris, 1955; Morris & Courtice, 1956), but some may first undergo intravascular hydrolysis by a reaction analogous to the heparin clearing reaction (Robinson, Jeffries & French, 1954). The intravenous injection of heparin induces intravascular hydrolysis and increases the rate of removal of chylomicron fat from the blood stream, while protamine and Triton WR-1339 inhibit this hydrolytic reaction induced by heparin and slow down removal (Bragdon & Havel, 1954; French & Morris, 1957). The experiments described in this paper were carried out to determine the distribution in the body of 14C-labelled chylomicron fat and the extent to which it undergoes oxidation to C02 following its removal from the blood stream. The tissue distribution and oxidation of chylomicron fat have also been studied following the intravenous injection of heparin, protamine sulphate or Triton WR-1339 in an attempt to obtain further information on the significance of intravascular lipolysis in fat transport and metabolism.

The tissue distribution and oxidation of 14C-labelled chylomicron fat injected intravenously in rats.

Factors influencing the distribution and character of adipose tissue in the rat

Since 1926, when Depisch1in Germany and Barborka2in America described the disappearance of fat from the subcutaneous tissues of several diabetic patients at the site of insulin injections, a number of reports have been made of this condition and many speculations have arisen as to its cause. Priesel and Wagner3believed the preservative tricresol, at that time used in some insulin preparations, was responsible for the phenomenon because of its fat splitting properties. Carmichael and Graham4suggested that minute amounts of lipase in the insulin could cause this disappearance of fat. Rabinowitch,5however, was unable to demonstrate the presence of lipase in the large amount of a particular lot of insulin which he concentrated at low temperature and pressure, thereby confirming the claims of three American manufacturers of insulin6that their product was lipase free. Avery7observed that development of the atrophic

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Lucille L. Reed

Papers

Factors influencing the distribution and character of adipose tissue in the rat

Lipodystrophy from insulin injections