Morphologic changes in the rat's thymus in case of intrapulmonic development of the experimental solid ovarian tumor

It is known that the thymus is an organ regulating immunomorphologic processes in the organism. Reactive changes in the thymus occur in case of oncological diseases. Information that we discovered in the available literature concerns mainly structural changes in thymus in case of spontaneous and chemically induced tumors. We tried to determine structural changes in the rat's thymus in case of intrapulmonic development of the experimental solid ovarian tumor.

Actuality. It is known that the thymus is an organ regulating immunomorphologic processes in the organism. Reactive changes in the thymus occur in case of oncological diseases. Information that we discovered in the available literature concerns mainly structural changes in thymus in case of spontaneous and chemically induced tumors. We tried to determine structural changes in the rat's thymus in case of intrapulmonic development of the experimental solid ovarian tumor.

Methods. For our investigation we used two groups (number one and number two) of laboratory rat's males at the age of two and a half months. Each of the groups included ten animals. Rats of the group number one (control) were intact. Rats of the group number two were subjected to the intravenous transplantation of fifty thousand tumor cells. The number of the tumor cells was determined with the help of Gorjaev's count chamber.

On the twentieth day of the experiment all the animals were killed. The thymus was extracted and fixed in solution of formalin. Paraffin sections were stained with haematoxylin-eosin. Histologic specimens were observed under light microscope.

Discussion. Microscopically it was estimated that on the outside the thymus of the control rats (animals of the group number one) is surrounded by connective tissue capsule that consists of numerous cells, and thin wavy fibres lying parallel to the sirface of the organ. The connective tissue cells contain rounded and oval nuclei that are pooly stained, and are characterized by presence of distinct karyolemma and masses of chromatin. Within some zones of the capsule its structural elements are loosely arranged, and among them there are lymphoid cells. Thickness of the capsule is 19,03Ã0,62 micrometers.

Trabeculae arising from the capsule extend deeply into the substance of the thymus and partially separate lobules from each other. The trabeculae are penetrated by thin-walled vessels filled with formed elements of blood. Inner surfaces of the blood vessels are lined by thin endotheliocytes containing elongated poorly stained nuclei.

Each thymic lobule has an outer cortex and an inner medulla that differ from one another by density of the lymphoid cell arrangement. The medulla of the adjoining lobules is continuous.

Thickness of the cortex is 213,33Ã10,04 micrometers. The lymphoid cells in it are very densely arranged, their boundaries are not prominent. Rounded and oval nuclei of the cells are densely stained and are 3,86Ã0,14 micrometers in diameter.

The epithelial reticular cells are sometimes found between the cortical thymocytes. The epithelial reticular cells contain rounded and oval poorly stained nuclei that have distinct karyolemma and masses of chromatin. The nuclei are 5,62Ã0,21 micrometers in diameter. The thymic cortex is penetrated by thin-walled vessels filled with formed elements of blood.

Thymic medulla is 260,0Ã7,6 micrometers in thickness. It is penetrated by numerous small blood vessels. Thymocytes of the medulla are arranged looser, and their nuclei are bigger in size than those of the cortex, the diameter of the nuclei is 4,45Ã0,14 micrometers.

Epithelial reticular cells of the medulla are found more often, and some of them are arranged in groups including two to twelve cells. Nuclei of the cells are 6,9Ã0,3 micrometers in diameter. Among the medullary epithelial reticular cells there are degenerative ones, this fact obviously is the result of the beginning of formation of Hassall's corpuscles.

Completely formed Hassall's corpuscles are found in the cortex of the lobules. The corpuscles are rounded or irregular in shape, they are composed of concentrically arranged epithelial cells. Some of them contain centrally located cavities. Average diameter of the Hassall's corpuscles is 10,3Ã0,4 micrometers.

In different parts of the thymus of the control rats there are singly present large oval cells (11,4Ã0,2 micrometers in diameter). Their cytoplasm is eosiniphilic, and their nuclei are centrally situated and densely stained. Those cells resemble plasma cells.

In the rats of the group number two the thymus is surrounded by connective tissue capsule infiltrated by lymphoid cells. Capsular vessels are dilated and filled with formed elements of blood.

Within the lobules of the thymic parenchyma the structural difference between cortex and medulla isn't conspicuous: in all zones the lymphoid cells are arranged very densely. Boundaries of the thymocytes are not prominent.

In some zones of the lobules the nuclei of the lymphoid cells are densely stained; the diameter of the nuclei is 3,67Ã0,16 micrometers. In other zones the thymocytes contain poorly stained nuclei that are 4,56Ã0,1micrometers in diameter; within those zones there are small cavities that remain in places of the entirely destroyed lymphoid cells. Some zones are made up of homogeneous eosinophilic substance containing fragments of thymocytes.

Thymus of the rats of the group number two is penetrated by numerous dilated blood vessels filled with the formed elements of blood. Hassall's corpuscles are not found. The subcapsular zone of the thymic lobules contains large clusters of cells that resemble the tumor cells. Such clusters of cells are penetrated by numerous dilated thin-walled vessels filled with formed elements of blood. Rounded and oval nuclei of the cells are 8,77Ã0,22 micrometers in diameter. They have distinct karyolemma, nucleoli, and masses of chromatin.

Conclusions. Intrapulmonic development of the experimental solid ovarian tumor causes structural changes in thymus. Within the lobules of the thymic parenchyma the structural difference between cortex and medulla isn't conspicuous. Hassall's corpuscles are not found. The subcapsular zone of the thymic lobules contains large clusters of cells that resemble the tumor cells.

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