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BIOLOGICAL SCIENCES
Kotsyumbas G. I., Khalaniia M. R., Zolototska O.B.
Stepan Gzhytskyi National University of Veterinary Medicine and Biotechnologies Lviv
DOI: 10.24412/2520-6990-2021-996-4-8 MORPHOFUNCTIONAL FEATURES OF CHANGES IN THE PANCREAS IN WET AND DRY FORMS OF FELINE INFECTIOUS PERITONITIS
Abstract
The article presents the results of macroscopic, histological and histochemical studies of the pancreas of cats in wet and mixed forms of FIP. A pathological examination of 18 carcasses of cats aged from 3 months to 5.5 years, in which lifelong feline infectious peritonitis was diagnosed (based on history, clinical signs, morphological and biochemical analysis of blood, ultrasound, Rivalt test and rapid test). Samples of the pancreas were taken, which were fixed in 10% aqueous solution of neutral formalin, solutions of Carnois, Buena and 96 ° ethyl alcohol. Histoxylin and eosin-stained histoscripts were prepared according to McManus, Brachet, Van Gieson and examined under a microscope.
It was found that the most severe structural and functional changes in the pancreas of dead cats were developed in the stroma of the organ, in the arterio-venular system, receptors, excretory ducts, both in wet and dry forms of FIP. The development ofpancreatosis in the pancreas of cats in the wet form found, which was characterized by disorganization of connective tissue, the development of fibrinoid necrosis of the walls of arterioles, disseminated venous thrombosis, stasis in the capillaries, obstruction and obstruction of the excretory ducts. The detected morphological changes indicate the development of irreversible vascular-stromal dystrophies in the pancreas.
Productive pancreatitis has developed in the pancreas of cats in dry form, which in cats at a shorter course of the disease was characterized by round-cell infiltration ofthe stroma, dystrophicnecrobiotic processes ofparenchymal cells, obstruction of the interparticle ducts. Fibrosis progressed over a longer course in cats, which was expressed in the growth of interstitial connective tissue fibers, atrophy of the parenchymal lobes, productive ne-crotic vasculitis, and occlusion of the interparticle excretory ducts.
Keywords: cats, infectious peritonitis, FIP, pathomorphology, pancreas, exocrinocytes, vascular stromal dystrophies, pancreatosis, pancreatitis.
Introduction. Feline infectious peritonitis (FIP) is caused by an RNA genomic virus from the family Coronaviridae, genus Coronavirus. The disease, currently, still remains one of the incurable diseases of cats [1,2]. Infectious peritonitis affects domestic and wild cats, most often young animals under 3 years of age. The disease is characterized by a long incubation period, the absence of severe symptoms in the early stages of the disease, and the progression of pathological processes in the organs and tissues of patients with FIP in cats often leads to death.
Symptoms in ill cats, depending on the clinical and anatomical form varies widely. Cats with weak cellular immunity develop a wet (effusive) form, and in a moderate reaction - a dry (non-effusive) form of FIP. [3,4, 5]. The morphogenesis of changes in pathogenic processes by FIP in various organs and systems of cats is not yet fully understood.
There are relatively few publications in the available literature on the coverage of morphological changes of internal organs by FIP and there is little description of histological and histochemical changes in endocrine organs, in particular in the pancreas. It is important to determine the nature of the development of a pathological process in determining the morphological changes in the body, that underlies the development of various clinical and anatomical forms of the disease. Therefore, it is important to study morphohistochemi-cal changes in the pancreas of spontaneously infected
cats with infectious peritonitis. Thus, it will help to understand the morphogenesis of changes in wet and dry forms and to supplement the diagnosis of the disease.
The aim of the study was to investigate the pathological, histological and histochemical changes in the pancreas of cats in wet and dry forms of FIP.
Materials and methods of research.
Pathological examination of 18 corpses of cats aged from 3 months to 7 years, in which lifelong FIP was diagnosed (based on medical history, clinical signs, morphological and biochemical analysis of blood, ultrasound diagnosis, Rivalt test and rapid diagnosis). Selected samples of the pancreas were fixed in 10% aqueous solution of neutral formalin, Carnua solution, Buena. Then performed dehydration, filling the tissue with paraffin. Histocuts on a sled microtome MS-2 were made from paraffin blocks. Histographs were stained with hematoxylin and eosin, and a
McManus PAS reaction was performed to detect glycoproteins; methylene green and Brachet pyronine for nucleic acid detection [6,7]. The finished histoprep-arations were examined under a light microscope Leica DM-2500 (Switzerland), photographed with a Leica DFC450C camera with Leica Application Suite Version 4.4 software.
Results of the research
Macroscopic changes in the pancreas are inconspicuous in cats killed by infectious peritonitis. The or-
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gan is tape-shaped, pale pink in wet form, wet in section, the capsule is tense. In dry form, the pancreas is light purple, slightly compacted. The most striking changes were detected by microscopic examination, which differed significantly in the nature of the development of pathological processes in the wet form from those in the dry form.
Histologically, in the pancreas of cats at the wet form more pronounced changes were found in the stroma, in the structure of the arterio-venular system, receptors, excretory ducts. The stroma of the body is loose. The connective tissue fibers of the stroma, the walls of the excretory duct are impregnated with fuch-sinophilic compounds on preparations stained according to McManus. The lumen of small venous vessels is filled with adhesive forms of erythrocytes, disseminated thrombosis and stasis in capillaries were noted. The increase in the content of glycoproteins in the
stroma of the organ as well as in the walls of blood vessels indicated a deep disorganization of connective tissue fibers (Fig. 1). In the deformed, considerably thickened walls of arterioles all layers are retouched, homogeneous weight prevailed. The basement membrane of arterioles is impregnated with PAS-positive compounds, endothelial exfoliation was noted. The lumen of the arterioles is sharply narrowed, filled with plasma and desquamated endothelium. Destructive-necrobiotic processes in the smooth muscle and elastic fibers of the walls of the afferent arterioles have progressed. The violation of the structural organization of arterioles contributed to a sharp increase in the permeability and yield of plasma proteins and led to the development of fi-brinoid necrosis. The revealed structural changes in the arterio-venular system were functionally reflected by a sharp disturbance of blood supply, oxygenation, development of significant metabolic disorders of the organ tissue (Fig. 2).
Fig. 1. The pancreas of a cat in the wet form. Fuchsin-ophilicity of the stroma and walls of the duct and venous vessels. McManus. m.e.10, vol. 20
Fig. 2.
The cat's pancreas in the wet form. Fibrinoid necrosis of the arteriole wall. McManus. m.e. 10, vol. 20
The histological feature of the pancreas of cats is the presence in the interstitium of well-structured receptors of nerve fibers - Fater-Pacini bodies. The inner axon of the receptor is surrounded by perineural lamellae, in which the stratification of annular lamellae was noted, with the formation of vesicles and the accumulation of fuchsinophilic compounds in the lumens between them. The receptor is slightly enlarged due to the expansion of the lumen between the lamellae. Histostructural changes in the receptors were functionally reflected by a weakening of the sensitivity and neural conduction of the organ (Fig. 3).
The cytoplasm of the basal parts of the exocrine cells of the acinus is mainly pyroninophilic, nuclei with a high content of chromatin, which is a sign of the synthesis phase (Fig. 4) in the parenchyma of the organ of cats with the wet form, on preparations stained by Brache. A group of endocrine cells with an RNA-poor cytoplasm, the islets of Langenhars, stood out among the pyroninophilic exocrine cells of the acinuses. The dilated lumens of capillaries are well visible (Fig. 5) among the weakly stained endocritocytes surrounded by fibrous fibers.
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Fig. 3. The cat's pancreas in the wet form. Fater-Pacini's body. Fuchsinophilicity of the lumen and structures of perineural lamellae. McManus. m.e. 10, vol. 40
Fig. 4. Acinus of the cat's pancreas in the wet form. Interacinar lumens are expanded. The cytoplasm of pyrinophilic exocrino-cytes. Brachet. m.e.10, vol. 10
Fig. 5. The cat's pancreas in the wet form. Pyroninophilia of the cytoplasm of exocrine cells. The en-docrinocytes of the islet of Langen-hars are weakly stained. Brachet. m.e.10, vol. 40
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The intercinary stromal structures and the basement membrane of the intraparticle ducts are impregnated with glycoproteins on McManus-stained preparations. The lumen of the intraparticle ducts is markedly expanded, their epithelial lining is preserved, and the basement membrane is thickened (Fig. 6). It should be noted that the interparticle duct system of the pancreas underwent significant destructive changes. The basement membrane, connective tissue fibers are intensively impregnated with fuchsinophilic compounds, which indicates the disorganization of structures. The available magenta content is mixed with the desquamated epithelium in the lumen of the dilated, significantly deformed duct. (Fig. 7).
Fig. 6. The pancreas of a cat in the wet form. The aci- Fig. 7. The interparticle duct of the pancreas of a cat nus and intraparticle excretory duct are lined with cu- in the wet form. Fuchsinophilicity of the wall and the bic epithelium. McManus. m.e. 10, vol. 40 contents in the lumen of the duct. McManus. m.e. 10,
vol. 40
It should be noted, while analyzing the histochem-ical changes (Brachet) in the pancreas of the cat at the wet form, that in all lobes pyroninophilia of the cytoplasm of the basal exocrine glands was expressed, indicating the phase of synthesis and accumulation of secretion granules in cells and a sharp decrease in secretion in the duodenum. Prolonged decrease in secretion from cells causes metabolic disorders in them. However, stagnation of secretion with a high content of proteolytic enzymes in the interparticle parts of the excretory duct of the pancreas had a negative effect on the epithelial lining, as it caused the digestion of its own cells of the inner membrane.
In addition, it is necessary to focus on generalized damage to the vascular system. Structural changes in the arteriovenular system (hyperemia, disseminated thrombosis in venules, stasis in capillaries) were accompanied by increased vascular permeability with the release of not only water, electrolytes but also plasma proteins, which led to the development of irreversible
disorganization, destruction of connective tissue necrosis, fibril and was accompanied by a violation of the structure of the walls and patency of the interparticle excretory ducts of the gland.
In the pancreas of cats in a less long course of the dry form of the disease productive pancreatitis developed, which was characterized by round-cell infiltration of the stroma, especially in the perivascular and
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periductal areas. Brachet-stained preparations showed accumulations of lymphoid elements around the vessels, the interparticle duct and in the intercinary connective tissue (Fig. 8). Simultaneously, the histostruc-ture of arterioles, venules, capillaries is broken: the basal layer of membranes is loosened, in places homogenized. The endothelium of the vessel walls is
desquamated. The walls of venules and veins of average caliber underwent the most significant changes. The lumen of the veins is sharply dilated, without formed elements of blood, and in the lumen of the ven-ules - hypertrophied macrophages and single lymphocytes. The peculiar feature for macrophages was the presence of weakly pyroninophilic cytoplasmic inclusions (Fig. 9).
Fig. 8. The cat's pancreas in dry form. T lymphocytes in the stroma of the body. Brachet. m.e. 10, vol. 20
The ductal system of the pancreas underwent significant destructive changes as well. The intercinary and interparticle excretory ducts of the gland were involved in the inflammatory process. The contours of the connective tissue fibers of the interstitial duct wall are retouched, almost do not absorb pyronin, and single nuclei of fibers with low DNA content on Brachet-stained preparations. The lumen of the interparticle excretory duct is filled with secretion, which contains exfoliated epithelial fragments from the basement membrane. (Fig. 10 a). It is probable that due to the change in the structure of the ducts of the pancreas there was a thickening of the secretion from the formation of clots together with the desquamated epithelium and blockage of their lumen.
Fig. 9. The pancreas of a cat in dry form. The basement membrane of the venule is broken. Macrophage elements in the lumen of the venule. m.e. 10, vol. 100
Dystrophic-necrobiotic processes were developed in the parenchyma organ, and the clarity of the structure of acinuses and exocrinocytes was erased. Polygonal exocrine cells with altered outlines, cytoplasm was weakly stained with pyronine, nuclei enlarged with significantly reduced chromatin content. The contours of swollen, deformed exocrinocytes were blurred, some of them acquired a bubble shape, others lysed (Fig. 10 b). There are cells with vacuolated cytoplasm and lysed nuclei. The islets of Langenhars have undergone changes as well. The fibers surrounding the islands are lysed in places. The structure of most endocrinocytes is disturbed: the contours of the cells were not determined. The cytoplasm is swollen (Fig. 10 c).
Fig. 10 a. Obstruction of the lumen
of the interparticle duct by condensed secretion and exfoliated epithelium of the lining. m.e. 10, vol. 20
Fig. 10 b. Acinus. Exocrinocytes are weakly stained with pyronine, the nuclei are enlarged with reduced chromatin content. m.e. 10, vol. 100
Fig. 10 c. The islet of Langenhars. The fibers surrounding the islands are sometimes lysed. m.e. 10, vol. 100
Fig. 10. The pancreas of a cat in dry form. Brachet.
s
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The detected changes in the pancreas of cats in a shorter course of the dry form of the disease indicated the development of exocrine and endocrine insufficiency, which was expressed in a decrease in the production of digestive enzymes and insulin by the gland. The formation of clots of secretion with desquamated epithelium in the lumen of the excretory ducts has led to obstruction and impaired patency of the ducts.
In cats, atrophy of the lobes, significant thickening of the stroma due to intraparticle, interparticle, periduc-tal and perivascular growth of connective tissue fibers, among which cellular infiltrates of lymphocytes and histiocytic elements are clearly visible, were noted for a longer course. At the same time, exocrinocytes in the
acinuses were more often exposed to vacuolar dystrophy and atrophy (Fig. 11). The walls of the arterioles significantly thickened and deformed, and the lumen narrowed, productive-necrotic vasculitis progressed. A similar thickening due to intense roundcell infiltration occurred in the walls of the interparticle excretory ducts, which clearly led to a sharp narrowing and occlusion of their lumen.
Productive-necrotic processes in the arterio-venu-lar system, interstitium and interparticle excretory ducts of the pancreas in the dry form of infectious peritonitis of cats has led to the development of severe dys-trophic-necrobiotic changes, parenchymal atrophy, sclerosis of the stroma, which had an irreversible organ function.
Fig. 11.
The pancreas of a cat in a dry form. Particle atrophy. The growth of intraparticle and interparticle connective tissue. Hematoxylin and eosin. m.e. 10, vol. 40
Fig. 12. The pancreas of a cat in a dry form. Interpar-ticle growth of connective tissue. Hematoxylin and eosin. m.e. 10, vol. 20
Conclusions.
1. It was found the development of pancreatosis, which was characterized by disorganization of connective tissue, the development of fibrinoid necrosis of the walls of arterioles, disseminated venous thrombosis, stasis in capillaries, obstruction with impaired duct patency and functional hemorrhage tissue in the pancreas of cats in the wet form. Morphological changes have indicated the development of irreversible vascular-stro-mal dystrophies in the pancreas of cats in the wet form.
2. Productive pancreatitis developed in the pancreas of cats in dry form. Meanwhile in cats for a shorter course of the disease it was characterized by roundcell infiltration of the stroma, dystrophic-necrobi-otic processes of parenchymal cells, obstruction of the interparticle ducts. Fibrosis progressed over a longer course in cats, which was expressed in the growth of interstitial connective tissue fibers, atrophy of the parenchymal lobes, productive necrotic vasculitis, and occlusion of the interparticle excretory ducts.
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