Chitosan as a Modifying Component of Artificial Scaffold for Human Skin Tissue Engineering.

We compared the structure and mechanical properties of scaffolds based on pure collagen, pure chitosan, and a mixture of these polymers. The role of the composition and structure of scaffolds in the maintenance of cell functions (proliferation, differentiation, and migration) was demonstrated in two experimental models: homogeneous tissue analogues (scaffold populated by fibroblasts) and complex skin equivalents (fibroblasts and keratinocytes). In contrast to collagen scaffolds, pure chitosan inhibited the growth of fibroblasts that did not form contacts with chitosan fibers, but formed specific cellular conglomerates, spheroids, and lose their ability to synthesize natural extracellular matrix. However, the use of chitosan as an additive stimulated proliferative activity of fibroblasts on collagen, which can be associated with improvement of mechanical properties of the collagen scaffolds. The effectiveness of chitosan as an additional cross-linking agent also manifested in its ability to improve significantly the resistance of collagen scaffolds to fibroblast contraction in comparison with glutaraldehyde treatment. Polymer scaffolds (without cells) accelerated complete healing of skin wounds in vivo irrespective of their composition healing, pure chitosan sponge being most effective. We concluded that the use of chitosan as the scaffold for skin equivalents populated with skin cells is impractical, whereas it can be an effective modifier of polymer scaffolds.

["Mode for mutation" in the natural population of Drosophila melanogaster from Umani is caused by distribution of a hobo-induced inversion in the regulatory region of the yellow gene]. / "Moda na mutatsiiu" v prirodnoi populiatsii Drosophila melanogaster Umani vyzvana rasprostraneniem indutsirovannoi homo-élementom nestabil'noi inversii reguliatornoi chasti gena yellow.

A mutation outburst of the yellow gene occurred in a Drosophila melanogaster population from the town of Uman' from 1982 to 1991 and was associated with the instability of several alleles. Molecular genetic analysis revealed a deletion variant of the hobo transposable element in the same site of the regulatory region of yellow in the mutant alleles and their derivatives. The outburst of the yellow-2 mutations was attributed to the spreading of the X chromosome, which contained an inversion of the yellow regulatory region, through the population. Reinversion resulted in the wild-type phenotype. Crossing lines carrying the inversion with laboratory line C(1)DX, ywf induced instability of the yellow alleles, which was associated with duplication or multiplication of a fragment of the yellow gene. Most derivative lines eventually became stable. The loss of instability was not associated with phenotypic changes; molecular genetic changes included a loss of the duplicated sequences or a deletion of the inverted regulatory region of the yellow gene.

hobo-induced rearrangements are responsible for mutation bursts at the yellow locus in a natural population of Drosophila melanogaster.

In 1981 recurrent local bursts of mutability of the yellow gene were observed in a natural population of Drosophila melanogaster from Uman' (Ukraine). A series of y2-like mutations in the yellow gene were recovered during the period 1982 to 1991. Most of the mutants display the y2-phenotype, i.e. mutant yellow color of wings and body cuticle. Ninety-nine y2 mutants were shown to be generated by an inversion that occurred between two hobo elements, one located 129 bp from the start site of yellow transcription, and the other in the distal telomere region. The y2 phenotype was caused by the separation of the body and wing enhancers from the transcription unit. Many of the y2-like alleles were highly unstable and reverted to y+, which again, gave rise to y2-like mutants. We found that the y2-->y+-->y2 transitions were generated by repeated inversions between the two hobo elements mentioned. The y2 and y+ alleles lost their instability after deletion of the hobo element present at the tip of the X chromosome.

[Lentiginous melanocytic dysplasia as a precursor of malignant melanoma]. / Lentiginoznaia melanotsitarnaia displaziia kak predshestvennik razvitiia zlokachestvennoi melanomy.

Precursors of malignant melanoma are special pigment spots characterized by proliferation of atypical melanocytes accompanied by reactive lymphoplasmocytic infiltration of the derma designated as lentiginous melanocytic dysplasia (LMD), a variant of Dubreuilh melanosis. The material of the study of 53 cases of LMD and the time course of its progress suggest LMD to be not a distinct nosological entity but the beginning of the development of malignant melanoma.

[Immunologic reactions in patients with soft tissue sarcomas after surgical treatment]. / Sostoianie immunologicheskikh reaktsii u bol'nykh sarkomami miagkikh tkanei pri khirurgicheskom lechenii.

Under examination was the possibility to reveal clinico-immunological features in patients with soft tissue sarcomas prior to and after surgery. Different immune responses were observed in patients with various forms of tumor progression. In case of a favourable course of the process surgery somewhat stimulates the cell immune response and reduces the titre of humoral antibodies. In patients with the tumor progression despite the employed treatment, a gradual fall of high cell immunity indices with a simultaneous increase of the humoral antibodies titre was noted. Wide metastases spread in the terminal phase is manifested by suppression of the immune response.

[Copper content and the ceruloplasmin activity in the blood in melanoma of the skin]. / Soderzhanie medi i aktivnost' tseruloplazmina v krovi bol'nykh melanomoi kozhi.

In comparative studies on the copper content and ceruloplasmin activity in blood of 212 patients with malignant melanoma, cancer and benign skin neoplasms, hypercupremia and an increased activity of the enzyme was revealed in 80% of patients with melanoma. Serum copper uptake in patients with non-pigmented melanoma was manifest to a greater extent. Some redistribution mechanisms are likely to underlie hypercupremia, that is especially indicated by the migration of copper from blood erythrocytes. Hypercupremia in patients with melanoma may be of a certain clinical interest as an accessory criterion for the differential diagnosis between malignant melanomas and benign skin neoplasms.

[Spontaneous regression of malignant melanoma]. / O spontannoi regressii zlokachestvennoi melanomy.

Malignant melanomas are known to be prone to undergo spontaneous regression (spontaneous resorption). The morphological picture of this process similar to that in spontaneous regressions of nevuses (halo-nevus), pigmentous spots (Dubreille melanosis) and superficially spreading melanoma is described. Six observations of spontaneously regressing melanomas are presented. Resorption of pigmented malignant tumors is similar to radiation resorption of malignant melanomas. It is noted that spontaneous resorption of malignant melanomas does not improve their prognosis.