DEGENERATIONS AND CERTAIN INFILTRATIONS
Adiposity or Interstitial Fatty Infiltration
In science under biology, microbiology or pathology, adiposity, which is commonly associated with generalized obesity, means an abnormal or excessive accumulation of adipose tissue or adult fat cells between parenchymal cells of an organ. The increase in adult fat cells is believed to result from the transformation of interstitial connective tissue cells after the deposition of lipid within them. The heart and pancreas are the two organs principally affected.
In the heart, as seen using specially designed microscopes, the adipose tissue appears between myocardial fibers and frequently is continuous with the overlying epicardial fat, which usually is increased in amount. Atrophy of muscle fibers may occur. Only rarely will myocardial adiposity produce clinical manifestations as observed in microscopy. In the pancreas, as observed using the specially designed microscope, there is an accumulation of adipose tissue in the interlobular septa that may affect also the interacinar stroma within the lobules. Usually, fatty infiltration of the pancreas produces no functional disturbance of the acinar tissue or islets. Areas of necrosis or atrophy in an organ or tissue may be replaced by adipose tissue, the so called fatty replacement.
Hyaline Degeneration and Extracellular Hyalins
In science mainly in microbiology or pathology, the term hyaline is a descriptive adjective used to qualify any translucent, homogeneous, structureless material that stains with eosin. Under the microscopes, there are a variety of intracellular or extracellular hyaline substances or hyalins, which are mainly of a protein nature. To speak of a substance as a hyalin does not disclose its specific chemical nature or its localization. Certain types of hyalin, such as amyloid, have distinctive characteristics or staining reactions and hence are separable from the general group and are better viewed using the different microscopes that are available nowadays such as light microscopes, electron microscopes, scanning electron microscopes, forensic microscopes and stereo microscopes.
As seen through microscopy, after injury to certain cells, a hyaline change of varying degree may take place in the cytoplasm, which is termed hyaline degeneration. Nonetheless, not all intracellular hyaline changes, even though commonly termed hyaline degeneration, represent a true degenerative process. The following sentences are examples of intracellular hyaline change. Hyaline droplet degeneration of renal tubular epithelium, particularly in proximal convoluted tubules, is characterized by numerous, closely grouped, minute, hyaline droplets within the cytoplasm as observed under the microscopes. The droplets were thought to result from coagulation of the intracellular protein, but now it is believed that they represent protein that has passed through injured and abnormally permeable glomeruli and has been reabsorbed into tubular cells perhaps by pinocytosis. Mallory bodies, which are hyaline, masses within degenerating liver cells in active nutritional or alcoholic cirrhosis as monitored using the microscopes. The Councilman bodies are hyaline masses in liver cells in yellow fever as shown using the microscopes. Acidophilic bodies are hyaline rounded masses in liver cells in viral hepatitis, in primary cancer of the liver, and in other hepatic lesions as presented under the microscopes. Crookes hyaline change is in basophils of the pituitary gland in Cushings disease as examined under the microscopes. Russell Fuchs bodies are rounded hyaline masses that contain gamma globulin formed apparently in response to antigenic stimuli, thus not a true degenerative process as found out through microscopy. Zenkers or waxy degeneration is a hyaline change voluntary muscle originally described by Zenker in cases of typhoid fever but also seen in other severe infections as evident by microscopy. The alteration is not caused by the localization of the infection in the muscle but rather by the toxins or excess accumulation of lactic acid as proved through microscopy. Under the microscopes, the lesion is best seen in the rectus abdominis and diaphragmatic muscles. As pictured using a microscope, the involved muscle is very pale and friable, so that rupture of the fibers and small hemorrhages are frequent. Under the microscope, the affected fibers are swollen, they lose their striations, and they have a hyaline appearance. When advanced, the lesion progresses to necrosis as monitored using a microscope.
In microscopy, of the three types of hepatocellular hyaline change mentioned, the Mallory body is the most distinctive. It is a protein complex consisting of hyaline clumps about the nucleus as seen under the microscopes. Although it was initially considered to be derived from degenerated mitochondria, later electron microscopic studies suggested an origin from altered ergastoplasm. The Councilman body of yellow fever, as observed under the microscopes, is a condensation of the cytoplasm, affecting first a part of the cell and later the entire cell, after which the latter becomes contracted and distorted, since by that time death of the cell already has occurred. Councilman bodies do not contain virus particles and thus are not to be confused with true viral inclusions as evident by microscopy. The acidophilic body is somewhat like a Councilman body, consisting of condensed cytoplasm. When a cell is totally involved, it may become reduced in size and separated from neighboring cells and may be found free in tissue spaces or even in the sinusoids as viewed under the microscopes.
Extracellular Hyalins
These include connective tissue hyalin, fibrinoid, vascular hyalin, and amyloid. Hyaline change in connective tissue is common, occurring in old scars, in thickened serosae or pleura after chronic inflammation, in a thickened capsule of the spleen, in the intima of arteries or atherosclerosis, in the stroma of tumors such as leiomyomas, and in other sites. The change actually is a physical alteration of the collagen fibers, which become fused to form a homogeneous, acellular area, but the collagen retains its usual staining quality as observed under the microscopes. This change is sometimes referred to as hyaline degeneration of connective tissue, but it is better called hyalinization.
In science, fibrinoid represents altered collagen that appears homogeneous and stains deeply eosinophilic so that it resembles fibrin. Fibrinoid change often called fibrinoid degeneration or fibrinoid necrosis is a characteristic lesion in many of the generalized collagen diseases associated with hypersensitivity such as polyarteritis nodosa, rheumatic fever or systemic lupus erythematosus among others. It also is present in the arteriolar walls in malignant hypertension. Studies using microscopy have shown that fibrinoid consists of a mixture of substances including fragments of collagen, acid mucopolysaccharide, fibrin, and, in certain situations, also gamma globulin.
As observed under the microscopes, vascular hyalin occurs in the walls of arterioles in the hyaline form of arteriolosclerosis. Despite several thorough electron microscopy of vascular hyaline, the origin of this substance is still not settled. Some investigators who used microscopes in order to examine the case believe that the hyaline deposits are derived from plasma proteins that filter through the endothelium and are deposited predominantly within intimal spaces. As proved in microscopy, when the deposits are larger, they infiltrate the adjacent elastic tissue and smooth muscle of the media. Others claim that the hyaline is essentially an excessive elaboration of endothelial and smooth muscle cell basement membrane material, which is followed by atrophy and disappearance of smooth muscle.
It should be mentioned that certain substances of a different nature may have a hyaline appearance such as protein casts in the lumen of renal tubules, colloid in thyroid acini, clumped masses of fibrin, inspissated secretions in glandular ducts, and thrombi in small blood vessels as in thrombotic thrombocytopenic purpura as studied under the microscopes.
Amyloid Deposition or Amyloidosis
In science under microbiology or pathology through microscopy, amyloid is a hyaline material characterized by deposition intercellularly, rather than in cells, and by specific staining reactions with iodine, methyl violet, Congo red, silver, and thioflavine T. Amyloid stains orange red in light microscopy and shows a green birefringence in polarization microscopy when stained with Congo red. It stains purple red methyl or crystal violet such as metachromatic stain, mahogany brown with iodine, and dark brown to black with silver stains. Thioflavine T causes a yellow fluorescence of amyloid in ultraviolet light as seen under the microscope. The Congo red test to determine amount of absorption of the dye from the serum after its injection into the circulation is seldom used today for the diagnosis of amyloidosis. More usual diagnostic tests, which use microscopes, include biopsy of the rectal mucosa or of the gingiva and needle biopsy of organs as in liver or kidney.
