Fatty Degeneration

FATTY DEGENERATION (fatty degeneration, degenerative obesity), arises like all other degenerative processes, as a consequence of a disturbance of normal metabolism in the tissues. The term F. d. came into use since Virchow, who understood by this name such damage to the cell, at which 1) pre-existing in it fat particles, which were until then in connection with the protein components of the protoplasm and nucleus, are freed from this connection due to chemical destruction of the cell and therefore become visible, and 2) new fat molecules are formed from proteins and carbohydrates. Among modern authors (Aschoff) the first of these processes is known under the name of fatty decomposition, the second - fatty transformation. Virchow did not admit the perception of fat by the cell from outside (from blood and tissue plasma) for pathologically altered cellular elements; he opposed this latter kind of process (as purely physiological) under the name of fatty infiltration to the two first (fatty decomposition and transformation), which he united in the concept of F. d. Morphologically, for fatty infiltration, according to Virchow, the appearance in the cell of one, gradually increasing and reaching large sizes drop (large-drop obesity) is characteristic; for F. d., on the contrary - the formation of many small drops, penetrating the cell body (small-drop obesity). At present, these processes are viewed somewhat differently. In the first years of the 20th century it was clarified that in all kinds of obesity - both physiological and pathological - the predominant role is played by the perception of fat (or its components) by the cell from outside, i.e. the process of fatty infiltration. As for fatty decomposition and transformation, at present the first is recognized as established, although rarely encountered, the second, although theoretically considered admissible, has in fact never been proved by anyone under any conditions. Thus, the origin of fat in the cell, under whatever conditions it is found there, is almost always the same, i.e. infiltrative. However, the causes of its appearance can be extremely different, and it is these that are laid at the basis of the modern classification of disorders of fat metabolism. If the vital activity of the cells that have deposited fat in themselves is essentially not disturbed, in other words, if the appearance of fat is not connected with serious damage to the fat-containing cellular elements themselves, but is caused by causes, mainly lying outside these cells (e.g. general disturbance of fat metabolism in the organism due to excessive introduction of fats or their slowed combustion), then such forms of cellular obesity belong to the category of simple obesity. In these cases, it is a matter of only a quantitative change in normal fat metabolism. On the contrary, damage to the cell, depriving it of the possibility to assimilate the perceived fat even in the volume necessary to maintain its own normal structure and vital activity, gives those pictures of obesity which are designated as degenerative obesity or F. d. The latter is accessible to reverse development only in mild degrees; with significant intensity and duration, however, it always leads to the disintegration and death of the cell. As for the chemical structure of the fats revealed at F. d., here, apparently, the appearance of almost all known to us in the animal organism fat substances is possible both in pure form and in various combinations. However, neutral fats, cholesterol with its compounds (cholesterol esters) and phosphatides are encountered most often. Regarding the morphological signs of F. d., first of all it must be noted that they do not always give the opportunity to orient oneself as to what kind of obesity is dealt with. The characteristic of small-drop obesity, established for F. d. by Virchow, is justified only in most cases and cannot serve as a decisive sign. Much greater significance have: 1) topography of fat inclusions; simple obesity is characteristic only of cells capable of depositing fat in the order of function, e.g. connective tissue cells, liver cells [see separate table, (to the article Stagnant nipple), fig. 6], adrenal cortex cells; F. d. as an elementary disturbance of fat metabolism is possible in all cells of the organism; 2) the state of the cell and its nucleus [at F. d. other signs of necrobiosis are very frequent, such as nuclear pyknosis, pallor or disappearance of it, loss of normal structure by the cell, e.g. transverse striation and so on. (see separate table, article 103-104, fig. 4)] and 3) the chemistry of the fat in connection with the general character of pathological changes in the organism. In the case of clearly expressed F. d., already at external examination of the organ one can note a more or less distinct yellow or yellowish-gray color of it and a flabby consistency. The causes of F. d. are: 1. Insufficiency of blood supply of a given section or of the whole organism (local and general anemias of various kinds, especially chronic), the acting agent here apparently being cellular oxygen starvation. This includes, for example, F. d. of individual sections of the heart muscle due to arteriosclerotic narrowing of the lumen of the corresponding branches of the coronary artery, widespread F. d. of many organs in pernicious anemia, etc. 2. Various toxic influences (phosphorus, arsenic, chloroform, typhoid, cholera, scarlet fever, diphtheria toxins, etc.). 3. Influence of high t° (prolonged high fever). Especially often one has to observe F. d. together with cloudy swelling in severe cases of various acute infectious diseases. The term F. d. is applied not only in relation to cells, but also to intercellular substances. In the latter case, it is a matter of the appearance of fat deposits, consisting mainly of cholesterol esters, first of all in the so-called basic (gluing) substance between elastic and collagen fibers. The further process of obesity goes here simultaneously with hyaline transformation of fibers and F. d. of the cellular elements enclosed between them, at the end of which the entire corresponding section can turn into fatty disintegration. The indicated changes are very often observed in the walls of blood vessels (primarily arteries), representing the most essential and basic component of the atherosclerotic process, as well as in the valves of the heart, tendons, in the connective tissue of the papillae of the kidney, cartilages, cornea, etc.