[Morphofunctional parameters of nucleoli during development of the albumen gland polyploid cells in the snail Succinea lauta].
Ag-protein content, the total area and the number of nucleoli were estimated on AgNO3-methyl green stained squashed preparations of the albumen gland of Succinea lauta during polyploidization, differentiation and functioning of secretory cells. The investigation was made by means of morphometry and cytophotometry using the computer videoimage system. During the gland growth, the mean number of nucleoli increased from 1-2 in diploid (2c) nuclei to 3 in polyploid (16c-32c) nuclei, but commonly only one large nucleolus was formed in mature nuclei. As a whole, the area and Ag-protein content of nucleoli was changed proportionally to the gene dosage, but this dependence was not linear during several endocycles. Before 8c-level the coefficients of increase in each endocycle were more than 2 (2.7-4.0), and these decreased to 1.5-1.0 during the following endocycles (8c-16c-32c). The area of nucleoli increased more quickly than Ag-protein content in the course of endocycles of growing cells. On the contrary, a relative area of nucleoli decreased with the increase in ploidy levels in mature cells. This irregular dynamics reflects the influence of several factors of the nucleolar activity: endomitotic polyploidy (gene dosage effect), cell differentiation, inhibition of transcription, and its reactivation in mature cells. In addition, individual variations of nucleolar parameters in mature snails are associated with the rhythmical functioning of sexual system, and aging of animals.
Anisimova
A A
AA
Far East State University, Vladivostok. anis@bio.dvgu.ru
Anisimov
A P
AP
D000818:Animals; D002466:Cell Nucleolus / Q000235:genetics*; D005088:Exocrine Glands / Q000166:cytology / Q000378:metabolism / Q000648:ultrastructure; D011123:Polyploidy; D012908:Snails / Q000166:cytology / Q000502:physiology* / Q000648:ultrastructure