No abstract

Over the past two decades, there have been many publications dealing with the further development of an urgent issue on the immune system of the mucous membranes of the digestive tract, called mucoseassociated lymphoid tissue (MALT), which includes spheres of innate (non-specific) and adaptive (specific) immunity. Most structured formations and indicators of adaptive immunity in the intestinal mucosa are lymphoepithelial formation (Peyer's patches). The data on the formation of the peripheral part of the immune system are carried through the epithelium, mechanisms of interaction between pathogenic intestinal microflora and immunocompetent cells, thereby initiating the development of immune responses in the mucous membranes. A concept has long been established in the literature, according to which a leading role in mediating these reactions belongs to a special type of enterocytes, called M-cells. Before the concept of the initial role of these cells in the development of immune responses in the mucous membranes of the intestinal tract they were known as caveolated cells. The purpose of this study was to determine the shape and topological relations of M-cells with other types of enterocytes, and also with lymphoid elements Peyer's patches of the small intestine. 30 mature albino male rats weighted 200,0±20,0 g were involved into the study. After vivisection, which was carried out by an overdose of thiopental anesthesia (75 mg / kg of animal body weight intramuscularly in the upper third of the thigh of the hind paw) [1] in compliance with the requirements for dissection of the abdominal cavity, the entire complex of the gastrointestinal tract was removed, which was preserved in 10 % formalin solution. Subsequently, short sections of the small intestine, containing Peyer’s patches, were selectively excised. Finding the latter was not difficult due to their clear visualization on the external (nonmesenteric) surface of the small intestine in the form of whitish spots. The specimens, after washing from formalin and dehydration in alcohol of increasing concentration, were embedded into paraffin blocks, from which serial sections of 4 µm thick (Microm HM 325) were obtained with subsequent staining with hematoxylin-eosin and Van Gieson. Their study and documentation was carried out using the “Konus” light microscope equipped with the Sigeta DCM-900 9.0MP digital microphoto attachment and the Biorex 3 program (serial number 5604) adapted for these studies. In the study of many series of paraffin sections stained with hematoxylin-eosin, it was found that while maintaining the general shape of the structure, lymphoid nodules are susceptible to plastic variability, which depends on situationally changing factors of antigenic effect, i.e., functional polymorphism is characteristic of them. This is especially true of their lymphoidassociated epithelium, which appears in a rather diverse form, which depends not only on the section angle, but also, probably, on its reactive state. Thus, in some cases it is a relatively even monolayer of intestinal epithelium, consisting mainly of absorbing enterocytes, among which the most distinct are goblet cells. At the same time, it draws attention to itself that in the apical sections of some of them there are clear signs of rupture of the plasmolemma and the presence in the cytoplasm of basophilic granular fibrous material of an unknown nature. Along with this picture, other histological sections of large lymphoid nodules of Peyer's patches of the small intestine demonstrate a different configurational character of lymphoid-associated epithelium, in which the cluster principle of cell distribution in the form of limited portioned sets is clearly noted. While maintaining the general structural shape, Peyer's patches were found to be subjected to plastic variability, which depends on situationally changing factors of antigenic exposure, i.e., functional polymorphism is characteristic of them. This is especially true of their lymphoid-associated epithelium. Identification of M-cells using only traditional histological methods in practice is complicated. And yet, in the process of a focused study of serial paraffin sections, it was possible to detect some morphological signs indicating their location.

To date, there is a theory that increased resistance to caries is observed in the teeth, which for any reason underwent destructive changes in the pulp. That is why there is a need to study the impact of pulp vitality on the development of the carious process. The aim of the research was to study the microscopic structure of epoxy sections of intact and carious third molars. We studied 4 intact and 6 carious third molars. For this purpose, specimens were made taking into account the free penetration of the fixative solution into the pulp. To this end, immediately after the tooth was removed, we cut off its roots almost near the crown, preserving the integrity of the latter. The method relied on the impregnation of specimens with epoxy resin, according to the method of epoxy plastination of tooth specimens, developed at the Department of Human Anatomy of Ukrainian Medical Stomatological Academy. The epoxy blocks were cut with a disk into two halves until the hard tissues of the tooth crown were exposed together with the pulp. We found that the hard tissues (dentin and enamel coating) of intact third molars did not have any structural defects. However, their pulp chamber contained mainly an amorphous substance, devoid of any typical pulp tissue structures. That is, the pulp was in a state of complete devolution. Quite the opposite presentation was observed in specimens of carious teeth. We found that their pulp chamber contained quite noticeable tissue structures typical of the dental pulp. It is interesting that in the subodontoblastic layer, in front of the carious alteration of the enamel, there was compaction of the pulp, which may be due to infiltration of perivascular connective tissue by immunocompetent cells. It was found that on the border with carious destruction of enamel, there was a compacted spot of altered dentin, whose matrix was intensely pigmented in brown colour, due to the accumulation of melanin on the dentino-enamel junction. Its excessive formation is associated with the destruction of protein-carbohydrate complexes of organic matter in the deep layers of dentin. We found that the pulp compaction and the focus of carious alteration of the enamel are projectively connected by a radial cord of altered dentin, known in the literature as “dead tracts”. Hence, there is reason to believe that the identified changes indicate a latent form of caries, with a pulpogenic mechanism of development. Thus, it can be argued that the teeth, which for any reason underwent degenerative changes in the pulp, are not prone to carious lesions, whereas in carious teeth, the pulp is active and involved in the pathogenesis of the carious process.