PubMed Health⌕ Search

Biomedical subjects

N A Zarenkov

Publications and source records attributed to N A Zarenkov.

6 recordsLinked to original sources
PubMedDate not supplied

[Symmetries and homologies of Geomerida].

The symmetry of Earths life cover (Geomerida) was described generally by L.A. Zenkevich (1948). It coincides with the symmetry of geographic cover. Its symmetry elements are equatorial plane and three meridonal planes corresponded to oceans and continents. The hypsographic curve with point of inflection (symmetry element) on 3 km depth line should be added to these elements. The plankton and benthos communities as well as fauna of taxons are distributed symmetrically according these symmetry elements. Zenkevich model was successfully extrapolated to plankton by K.V. Beklemishev (1967, 1969) and to abyssal benthos by Sokolova M.N. (1986). The plankton communities inhabiting symmetrically located macrocirculations are considered as homologous. The character of circulation determines the trophic structure of plankton and benthos. In the case of high productivity of plankton, benthic grazing animals feed on sedimented particles have bilateral symmetric mouthpart. Otherwise they have to acquire food from water column and use cyclomeric mouthpart. Thus, the symmetry of macrocirculations determines the symmetry distribution of benthic animals with two major symmetries of mouthparts. The peculiarities of organisms' symmetry are discussed in the context of Pierre Curie principle and the ideas of K.V. Beklemishev concerning evolution of morphological axes.

Animals↗
PubMedDate not supplied

[A noneuclidean Volvox, or why it is better not to teach Volvox in the course on zoology].

Empty "spheroid" of Volvox is compared with biomorph "thread", "disk" and solid "sphere" using such characteristics as topological dimensionality, average distance between cells, mutual remoteness of inner and surface cells, contiguity of cells. It is usually supposed that these parameters are significant for physiological gradients that determine cell specialization. One-dimensional "thread" has the longest physiological communications between cells and the average degree of contiguity about 2 (each cell contacts two neighbors). Biological morph "disk" has a degree about 6, two-side frontal physiological gradient inside the cell, and less expressed inter-cell gradient. Biomorph designated as 3-dimensional solid "sphere" has a degree of contiguity about 12-24, strong radial inter-cell gradient (non-equal conditions for surface and inner layers) and short distances between cells. These parameters favor cell specialization and their integration in multicellular organism. The "sphere" corresponds to hypothetical ancestor of Metazoa - "Metschnikoff's Phagocytella", while the "disk" - to "Placula of Bütschli". Biomorph "spheroid" of Volvox has a degree of contiguity about 6 and continuous tangential inter-cell gradient on noneuclidean surface. Radial gradient is absent here. Due to noneuclidean nature of "spheroid" the distances between cells are longer here than in case of "disc" and "sphere". All cells are under the same conditions for specialization and multiple primary integration. The secondary integration in higher Volvocales (differentiation in somatic and generative hemispheres) was probably caused by directed movement of the whole colony. Specialization of cells in lower invertebrates develops in a way which is characteristic for biomorph "sphere" on the basis of 3-dimensionality. The differentiation of animal and vegetal poles is connected with gastrulation (but not with directed movement as in case of Volvox). Gastrulation through invagination does not comparable with inversion of plate-like embryo of Volvox into "spheroid". Invagination is the transformation of a "bent of sphere", whereas the inversion is the "bent of plate". Independently of particular mechanism gastrulation results in 3-dimensionality (as in case of "sphere"). However the integration of cells in Volvox is explained by special peculiarities of 2-dimensional noneuclidean surface. That's why Volvox cannot be considered as model of ancestor of Metazoa.

Volvox↗
PubMedDate not supplied

[Topology of cleavage in light of the Pierre Curie principle].

The stages of radial, spiral, and bilateral cleavage, including blastula, are considered as polyhedrons and projections of polyhedrons onto a plane: Wenn, Schlegel, and Euler projections. The blastula spatial organization is characterized by face numerals and Euler characteristics, as well by symmetry groups. The classes of equivalence of polyhedrons have been considered: duality and eqicomposition. The correspondence between different types of cleavage has been established by shift transformation on Schlegel projections and turn on a spherical noneuclidean surface. Determination of the prospective significance of blastomeres during cleavage was compared with the dichotomous division of the general notion in logic. This in view, the Wenn diagram of four figures has been reflected onto the sphere surface. Blastula faceting is interpreted as a reflection of hereditary information about the prospective significance of blastomeres onto a spherical surface. Topologically, the reflection represents a transformation of the linear orderliness of information contained in the genome into a two-dimensional orderliness of prospective properties on the blastula noneuclidean surface. Therefore, the elements of blastula symmetry can be considered as self in the sense of Pierre Curie principle.

Blastocyst↗