[Connexin 43 expression in human brain glial tumors]. / Ékspressiia konneksina 43 v glial'nykh opukholiakh golovnogo mozga cheloveka.

AIM: Тo conduct an immunohistochemical (IHC) study of the expression of connexin 43 in the samples of glial tumors of various grades: gemistocytic astrocytomas (Grade 2), oligodendrogliomas (Grade 2) and glioblastomas (Grade 4). MATERIAL AND METHODS: The material investigated was fragments of human brain glial tumors (grade 2 gemistocytic astrocytomas (n=2), grade 2 oligodendrogliomas (n=2), and grade 4 glioblastomas (n=14) and those of tumor-surrounding tissue (n=4). The material was fixed in 10% buffered formalin, dehydrated, and embedded in paraffin according to the standard technique. IHC studies of the slices applied primary rabbit polyclonal antibodies against connexin 43 ('Spring Bioscience', USA) and the Dako EnVision + Peroxidase (DAB) visualization system ('Dako', Denmark). After the immunohistochemical reaction, the cell nuclei were stained with Mayer's hematoxylin. RESULTS: Immunohistochemistry showed the changing pattern of connexin 43 expression as compared with intact tissue in the glial tumors. Instead of the fine-granular expression in the thin cellular processes in the neuropil, the tumors mainly displayed a coarse-grained cytoplasmic and even nuclear reaction. The morphology and localization of positive structures depended on the variant of an examined tumor. In addition, the most malignant brain gliomas generally exhibited a reduction in the expression of connexin 43, i.e. its quantity is inversely proportional to the degree of malignancy of the tumor. CONCLUSION: The low connexin 43 expression levels may reflect both a reduction in astroglial functional gap junctions and semicanals and a decrease in the amount of the protein itself that has independently antioncogenic properties. The observed cytoplasmic and nuclear expression of connexin 43 is most likely to be associated with the aberrant activity of a number of kinases, such as proto-oncogene tyrosine-kinase Src or protein kinase C (PKC).

[Ultrastructural characteristics of gap junctions in human glial brain tumors]. / Ul'trastrukturnaya identifikatsiya shchelevykh kontaktov v glial'nykh opukholyakh golovnogo mozga cheloveka.

AIM: to conduct an electron microscopic study of intercellular communication in the samples of gemistocytic astrocytoma, oligodendroglioma, and glioblastoma. MATERIAL AND METHODS: Surgically resected tumor tissue fragments were fixed in 2.5% glutaraldehyde solution, afterfixed in 1% OsO4 solution, dehydrated, and embedded in epoxy resin. Ultrathin sections were examined using a Jem 1011 electron microscope (Jeol, Japan). RESULTS: Solitary and closely spaced gap junctions (GJs) formed by the thin processes that have the ultrastructure of an astroglial processes were identified in the astrocytoma samples. In this case, chemical synapses were noted to be completely absent in gemistocytic astrocytoma and glioblastoma. The identified GJs had a small length and deformed nexuses. The oligodendroglioma samples exhibited intact astroglial processes around the chemical synapses; however, interglial GJs were not found. CONCLUSION: The investigation showed the presence of intercellular GJs with some ultrastructural differences in the samples of low- and high-grade astroglial tumors. According to current data, astrocytomic GJs are able to create a stable self-sustaining network that promotes tumor progression and provides resistance to a therapeutic intervention. At the same time, the noticeable reduction in the number of GJs, which is most pronounced in the oligodendroglioma sample, can accelerate tumor cell migration into the surrounding parenchyma. The investigation of GJs should be, of course, continued using a group of a larger number of glial tumors to confirm the intercellular communication features revealed in this study.