Hyalinous Transformation

HYALINOUS TRANSFORMATION. In pathology, hyalin (from the Greek hyalinos—transparent, glassy) is the name given to any homogeneous, semi-transparent (glassy), dense protein substance appearing in tissues, regardless of its origin and detailed chemical structure. Thus, this name unites a whole group of formations, from which amyloid (see Amyloidous transformation) is distinguished in chemical terms, having a somewhat more definite chemical composition and giving certain specific reactions. The most characteristic properties of hyalin are its morphological structurelessness, resistance to chemical reagents, and ability to stain well with acidic aniline dyes (eosin, acid fuchsin, picric acid, etc.). As for the origin of hyalin, in addition to living tissues, many dead protein substances inside the body can serve as its source; for this reason, hyalinous transformation (hyalinosis) of living parts is distinguished from hyalinous transformation (hyalinization) of dead substances. The first process represents one of the types of so-called protein transformation (see) and can occur both in cells (epithelium of the kidneys, liver, plasma cells, eosinophilic leukocytes) and in intercellular formations (fibrous, reticular connective tissue, membrana propria of glands), the latter localization being encountered most often and being the most typical for hyalinous transformation. Morphologically, the process is expressed by the appearance of a homogeneous protein mass between bundles of connective tissue, accompanied by swelling of the bundles themselves, loss of their fibrillarity, and gradual fusion of these formations into a completely homogeneous substance, which, depending on the histological structure of the given place, either completely occupies more or less significant areas of tissue or forms in it globules, strands, and crossbars [see separate table (to article Hypernephroma, vol. VII), fig. 6]. Cellular elements are preserved for some time among hyalin masses, but are then compressed and disappear. Very often hyalinosis affects the walls of blood vessels, in which case it may be a question either of hyalinous transformation of proliferated intima or of a change in the entire wall, with the beginning of deposition of hyalin substance under the endothelium and gradual spread of it to the middle and outer coats. Since the hyalin mass always occupies a much larger volume than the part of the tissue at the place of its formation, the walls of the vessel in all these cases are sharply thickened, while the lumen is correspondingly narrowed, sometimes to complete disappearance. This has as a consequence atrophic changes in the parenchyma of the corresponding organs, sclerosis of them, disturbance of function, etc. When capillaries are affected, hyalin appears on the outer surface of the endothelial membrane in the form of more or less thick sheaths, enveloping the vessel and compressing its lumen. The endothelium in this case can remain intact for quite a long time. Hyalinosis of reticular tissue is observed predominantly in lymphatic glands and leads to the transformation of the delicate, even microscopically indistinguishable crossbars of this network into thick, worm-like interwoven homogeneous strands, among which cellular elements gradually die off. The same change can affect the membrana propria of glands (seminiferous tubules, seminal vesicles and ducts of the mammary gland, urinary tubules, Bowman's capsule, etc.), as a result of which it becomes clearly visible on histological preparations as a coarse homogeneous stripe bordering on various glandular formations. Naturally, this entails a disturbance of metabolism in epithelial cells, their compression, and atrophy. The immediate causes of the described forms of hyalinosis are difficult to determine; as for the conditions of their occurrence, one most often encounters: 1) in atrophic states of organs and in the reverse development of various parts of them (hyalinosis of membrana propria of seminiferous tubules in senile atrophy of the testicle, hyalinosis of vessels of the ovary in the postmenopausal period, formation of hyalin masses at the place of atretic follicles or at the place of a corpus luteum that has undergone reverse development), 2) in connection with various chronic inflammatory processes of both specific and non-specific character (especially the scar tissue developed as a result of inflammation readily undergoes hyalinosis) and 3) in various tumors (hyalinosis of stroma, vessels). In addition, cases of so-called local hyalinosis of unknown origin are occasionally observed, in which in people, mostly of advanced age, in various organs (in the endocardium, cornea of the eye, conjunctiva of the eyelids, respiratory organs) development of hyalin nodules occurs, sometimes extremely numerous. With the naked eye, hyalinous transformation is indeterminate. With very significant spread of the process, one can only assume its presence by the increased density and peculiar semi-translucent appearance of the affected parts. As for intracellular formation of hyalin, the most known forms are hyalin-capillary transformation of epithelium and the so-called Russell bodies. Hyalin-capillary transformation arises in the epithelium of convoluted tubules of the kidney and occasionally in liver cells under the influence of the same harmful factors that cause the so-called parenchymatous, or granular, transformation (see Cloudy swelling). Both these processes, in terms of changes, apparently stand close to each other, but in the first of them the destruction of protoplasm is revealed much more sharply. Here it is a question of an increase in the volume of cells and the appearance in them of numerous shiny, brightly staining eosin formations having the appearance of droplets of very diverse and mostly quite significant size (often exceeding the size of the cell nucleus), which seem to gradually disintegrate the entire cell body. In the initial stage, the process, apparently, is capable of reverse development, but in the future leads to necrosis. The so-called Russell (after the author who first described them), or fuchsinophilic (due to their sharp staining with carbolfuchsin) bodies, having the same appearance as the hyalin droplets just described, appear mainly in plasma cells in many pathological processes (infectious granulomas, polyps of mucous membranes, tumors, infiltrates in chronic inflammations), but especially often in granulation tissue rich in plasma cells in rhinoscleroma (see). Often these bodies, as a result of cell disintegration, turn out to lie freely among tissue elements. In other cases, cells, swelling, are completely transformed into glassy rounded formations, which, due to their larger size, are called hyalin spheres. By the majority of authors, intracellular hyalin also includes the colloid secreted by the epithelium of the thyroid gland and the appendage of the brain. However, in pathology it is customary to separate disorders of secretion of this kind into a separate category under the name of colloid transformation (see). Hyalinous transformation of dead organic material is most often observed on fibrin, if it remains lying in the place of its formation (in thrombi, exudates) for a long time without undergoing dissolution or organization. In this case, its fibers swell and fuse with each other into a homogeneous hyalin-like mass. In thrombi, masses of such a nature can involve, together with fibrin, coagulated blood plates. A similar transformation is undergone by red blood cells in the development of so-called hyalin thrombi. The unclear position in the category of phenomena under consideration is occupied by so-called hyalin cylinders (see Urine), appearing in the urinary tubules of the kidney in various pathological states. According to one view, hyalin cylinders arise due to the peculiar delicate coagulation of protein fluid filtering from the Malpighian bodies (TranssudatcyUnder). Others consider that the basis of their formation lies in the secretion by epithelial cells of protein hyalin spheres and droplets (Sekretionscylinder) or in the disintegration of cells into such droplets (as a result of hyalin-capillary transformation) with subsequent fusion of them in the lumen of the tubule. In the first case one can speak of hyalinous transformation of dead masses, in the second case of intracellular formation of hyalin. It is very probable that, depending on various conditions, processes of both kinds can take place.