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L N Seravin

Publications and source records attributed to L N Seravin.

14 recordsLinked to original sources
PubMed1993

[The basic types and forms of the fine structure of mitochondrial cristae: the degree of their evolutionary stability (capacity for morphological transformations)].

The organellological analysis being made of the fine structure of mitochondria in different species of the kingdom Protista, and in different cells of representatives of the kingdoms Plantae and Animalia (Metazoa). On the base of this analysis the following classification of types and forms of the fine structure of mitochondrial cristae is proposed. The Ist type, with lamellar (flat) cristae includes four morphological forms: ribbon, sheet, bundle-like and rounded ones (discoidal and plate-like). The 2nd type, with vesicular cristae, includes bubble, ampule, and sac-like ones. The 3rd type with tubular cristae. Among the representatives of each kingdom (Protista, Plantae and Metazoa) all the three types of mitochondrial cristae have been observed. The majority of cells of higher plants and higher animals have lamellar mitochondrial cristae, but sometimes (in some tissues) there are cells with tubular or vesicular mitochondrial cristae. On the base of the above classification some other conclusions have been made. Among the eukaryotes the vesicular cristae are spread as widely as tubular and lamellar ones. Only in a few macrotaxa (superphyla and phyla) of Protista all the investigated organisms have mitochondria of similar cristal organization. For example, Ciliophora have only tubular, and Cryptophyta only lamellar mitochondrial cristae. In the majority of protistan macrotaxa a certain mitochondrial type of cristae may dominate, but there is the number of species with some different mitochondrial patterns (Euglenophyta, Chlorophyta, Chrysophyta, Mycetozoa, etc.). In some macrotaxa (Chrysophyta, Mycetozoa, etc.) such mitochondrial patterns as mentioned above, are characteristic of the lower organisms. Finally, in some macrotaxa of Protista mitochondrial cristae of two or three types may appear in different species, sometimes even within the same genus; for example--Sporozoa, Myxospora and Ascetospora. In the course of ontogenesis of the vertebrates and insects, cell mitochondria in some of their tissues can change their morphological type from lamellar to tubular or vesicular. Similar transformations of mitochondrial cristae were observed in the life cycles of some trypanosomes (Kinetoplastida) and in the flagellate Polytoma (Chlorophyta) due to modifications in the culture conditions. It is undoubtedly that the principle of morphological concervatism in the organization of mitochondrial cristae may be used for purposes of systematics and phylogeny, however only after a thorough comparative organellological analysis of the fine structure in numerous species of the examined taxon.

Animals↗
PubMed1992

[Eukaryotes devoid of the most important cellular organelles (flagella, Golgi apparatus, mitochondria) and the main task of organellology].

Comparative evidence on the lack of three important organelles (flagella, Golgi-complex, mitochondria) in cells and organisms at the cellular level of organization has been summarized for all the four eukaryotic kingdoms--Protista, Fungi, Plantae and Animalia (Metazoa). It is established that in the course of evolution these organelles may undergo the total reduction. There is no cellular organelle to be regarded as universal, indispensable. There are only three main obligatory cell components--the plasmalemma, nucleus and cytoplasm (with applied cytoskeleton, cytomembranes and ribosomes). The reduction of flagella (cilia) is occurring in different taxa independent of the transition of protists from the flagellate type of locomotion to the amoeboid, gliding of metabolizing ones, and in the number of metazoan cells. The members of Protista and Fungi, which line in microaerobic or anaerobic conditions, nearly inevitably lose their mitochondria. The tendency to lose Golgi-complex is demonstrated in protists with parasitic mode of life, especially in combination with anaerobiosis. There is so far no satisfied morphological criterium that could say with certainty whether the lacking of flagella, Golgi complex or mitochondria in the low eukaryotes may be primary or secondary (as the result of reduction). Data on the composition, structure and RNA nucleotide sequences cannot be either the straight evidence. A comparative analysis of these data shows that the ribosomes of the primary eukaryotes were, presumably, of a prokaryotic type. Their eukaryotization was carried out for a long time during the evolution of the low eukaryotes (Protista and Fungi), probably, independently in different phylogenetic lines. It is unknown at what steps and in what main phylogenetic lines the three above mentioned organelles may have appeared. It is proposed to single out a special division of cytology--organellology (organoidology)--as an individual science whose main purpose may be investigation of the origination, evolution and disappearance of organelles.

Animal Population Groups↗
PubMed1986

[The origin of the eukaryotic cell. II. A critical analysis of the symbiotic (exogenous) concept].

The exogenous (symbiotic) conception of the eukaryotic cell origin is unable to explain satisfactory the structure of mitochondria and chloroplasts. Either of these organelles possess its genome that can be compared with the viral one rather than with the bacterial one, judging by the dimensions and quantity of coding genes. The mitochondria resemble a little prokaryotes in the number of their proteins, chemical composition of their inner membrane and peculiarities of the protein-synthesizing apparatus. The primitive structure of mt DNA, the lesser quantity and greater unspecifity of the mitochondrial tRNA prove, additionally, the non-bacterial origin of this organelles. The deflexion of the genetic code from the universal one in the mitochondrial nucleoids also testify in favour of this point of view. The results of micropaleontological and paleobiochemical investigations evidence towards initial ability of the primary eukaryotes (primary protists) to photosynthesis. In this case, they did not need to acquire plastids from outside by symbiotic way. The autogenous origin of the flagellum of the primary protists was reported earlier (Seravin, 1985). The accumulated data permit us to consider that the cell organelles formed endogenously in the process of evolution of the cell.

Animals↗
PubMed1986

[The origin of the eukaryotic cell. I. Historical sources and current state of the concept of symbiotic and autogenic origins of the cell].

The exogenous (symbiotic) conception of the eukaryotic origin is now widely spread. It is based on the recognition of the principle of combination (addition or enclosing) of diverse prokaryotic organisms; so the complicated unicellular eukaryotic organism (eukaryotic cell) was resulted. the principle of combination takes its historical scientific sources from the ideas of Buffon. With reference to the cell this principle was claimed for the first time. In our time the exogenous conception is characterized as a "symbiotic boom", because it is widely used in attempts to explain the origin of all the main organelles of the cell (right up to the micro-bodies). The autogenetic (endogenous) conception is based on the principle of straight phyliation, on the recognition of a successive evolutionary transformation of prokaryotic forms into eukaryotic ones. In this way all the cell organelles may have an endogenous origin. This principle springing from Lamarck has got a contemporary meaning in the doctrine of Darwin. In the next papers the author will present his own analysis and generation of the present day relevant facts to find out which of these two conceptions based on quite different scientific methodological principles may be correct.

Animals↗
PubMed1986

[The origin of the eukaryotic cell. III. Principles of the morphofunctional organization of the eukaryotic cell].

The eukaryotic plasmalemma, eukaryotic cytoplasm with its usual cytomembranes, and eukaryotic nucleus are obligatory components of the eukaryotic cell. All other structural elements (organelles) are only derivates of the aforesaid cell components and they may be absent sometimes. There are protozoans having simultaneously no flagelles, mitochondria and chloroplasts (all the representatives of phylum Microspora, amoeba Pelomyxa palustris, and others). The following five general principles play the main role in the morphofunctional organization of the cell. The principle of hierarchy of block organization of living systems. Complex morphofunctional blocks (organelles) specific for the eukaryotic cell are formed. The compartmentalization principle. The main cell organelles (nuclei, flagellae, mitochondria, chloroplasts, etc.) undergo a relative morphological isolation from each other and other cell organelles by means of the total or partial surrounding by membranes; this may ensure the originality of their evolution and function. The principle of poly- and oligomerization of morphofunctional blocks. It permits the cell to enlarge its sizes and to raise the level of integration. The principle of heterochrony, including three subprinciples: conservatism of useful signs; a strong acceleration of evolutionary development of the separate blocks; simplification of the structure, reduction or total disappearance of some blocks. It explains a preservation of prokaryotic signs in the eukaryotic cell or in its organelles. The principle of independent origin of similar morphofunctional blocks in the process of evolution of living systems. The parallelism of the signs in unrelated groups of cells (or protists) arises due to this principle.

Animals↗
PubMed1986

[The origin of the eukaryotic cell. IV. The general hypothesis of the autogenous origin of eukaryotes].

The general hypothesis of autogenous (non-symbiotic) origin of the eukaryotic cell summarises some hypotheses explaining possible ways of the origin of main components and organelles of such a cell (the primary unicellular protist). Six hypothesises are suggested. Arising of the eukaryotic surface membrane of protist (cell) as a result of modification of its lipidoacidic composition, when most of synblocks and ensembles of eukaryotic enzymes sink into the cytoplasm (due to membrane vesiculation). Establishment of eukaryotic cytoplasm on the basis of successive formation of two locomotory-supporting apparates: the primary one (microtrabecular system), and the second one (cytoskeleton). Arising of the nucleus from a polyheteronomous nucleoid of proeukaryotes. A combinatorical hypothesis of mitosis formation. Polyheteronucleoid hypothesis of the origin of the mitochondria and chloroplasts. Arising of the flagellum from the contractile tentacle-like organelle, whose axoneme is made of single microtubules. A close interrelation and interaction in the process of evolution is noted between surface membranes, the cytoplasm and the nucleus. In accord a principles of block-construction and heterochrony (see: Seravin, 1986r), the author explains the preservation of prokaryotic signs of organization in some components (and organelles) of eukaryotic cell (and protists).

Aerobiosis↗
PubMedDate not supplied

[Amoeboid properties of cells during early morphogenesis and the nature of a possible protozoan ancestor of Metazoa].

Data analysis reveals that cells of most of the metazoans (especially from the phyla Spongia, Placozoa and Cnidaria) at the early stages of morphogenesis demonstrateas amoeboid properties i.e. ability to form pseudopodia, to move by means of pseudopodia and to phagocyte. In different degress these properties could be found at the late stages of embryogenesis and even in adult organisms. Moreover, during gastrulation and blastulation blastomeres is able to form flagellas and than loose them and return to amoeboid activity. These and other facts indicate that both amoeboid and flagellate types of cellular organization are programmed in the genome of metazoan cells, as well as their ability for mutual transformation. It leads to suggestion that ancestors of Metazoa were amoeboflagellates. Anarchic cleavage observed in some invertebrates evidences that separated blastomeres is able to aggregate into the unite embryo due to cytotaxis. Aggregation of artificially separated cells of sponges, trichoplax and cnidaria results in complete recovery of the organism by cytotaxis. Thus, there are reasons to suppose that ability of cell aggregation was inherited by the Metazoan genome from the amoeboflagellate ancestors. Thus amoeboflagellates may be considered as forerunners of Metazoa, i.e. Prometazoa.

Animals↗
PubMedDate not supplied

[Bacteria-cortical symbionts of Thichonympha turkestanica, a protozoan from the gut tract of the termite Hodotermes margabicus].

Intracellular symbiotic bacteria of the flagellate Trichonympha turkestanica located in the surface cortical part of the animal cell are described. The cell structure of the symbionts is typical of gramnegative bacteria, but contains also an additional outer membrane. The membrane is an element of the electron-dense structures which have contacts, at many points, with the kinetosomes or membranes surrounding flagella. A possible functional significance of symbiotic bacteria for the operation of flagella is discussed.

Animals↗