[Light- and electron-microscopic study of pelobiont Pelomyxa secunda (Gruber, 1884) comb. nov. (Archamoebae, Pelobiontida)].

Morphology of a pelobiont Pelomyxa secunda (Gruber, 1884) comb. nov. was investigated at light- and electron-microscopical levels. Locomotive forms are elongated or cigar-shaped. The size of active forms varies from 200 to 300 µm. Larger individuals (up to 400 µm) are not able to directed movement. Organism can produce short, usually finger-shaped hyaline pseudopodia at the frontal side or laterally. The cell coat is represented by amorphous glycocalix, up to 300 nm in thickness. A thin periphery cytoplasmic zone is deprived of any organelles, vacuoles, endocytobionts and other inclusions and separated from main cytoplasm by a layer of arranged microfilaments. P. secunda is multinucleate organism; nuclei are of granular type. The nucleolar material is represented by two forms of discrete structures differing in size and electron density. Two or three layers of short microtubules organized in the parallel arrangement are associated with outer side of the nuclear envelop. P. secunda possess two types of obligate prokaryotic endocytobionts lying in individual symbiontophoric vacuoles. Undulipodia, kinetosomes and root microtubular derivatives are not observed in P. secunda cells as well as any developed cytoplasmic microtubular cytoskeleton.

[Reisolation and redescription of pelobiont Pelomyxa paradoxa Penard, 1902 (Archamoebae, Pelobiontida)].

Morphology of a pelobiont Pelomyxa paradoxa Penard, 1902 was investigated at light- and electron-microscopical levels. Locomoting cells are cigar-shaped. The cells produce many hyaline pseudopodia of digital and conical form at lateral sides of the body. The organism has a pronounced hyaline bulbous uroid with broad peripheral zone of hyaloplasm and many conical hyaline villi. There is a thin layer of amorphous glycocalix at the cell surface. "Structure" and food vacuoles of different size are very abundant in the endoplasm. Two different species of prokaryote endocytobionts are peculiar for P. paradoxa. Uninucleate stage dominates in the life cycle of P. paradoxa. Usually there are no more than 10-12 nuclei in multinucleate forms of P. paradoxa. Pelomyxae nuclei are closely surrounded by thick multilaminar layer and additionally by one more layer, which is formed by small vesicles with electron-dense content. Several irregular-shaped nucleoli are situated at the nucleus periphery. Inside the nucleoli, and sometimes directly in nucleoplasm the small round bodies are revealed, these bodies being formed by tightly packed electron-dense fibrils. Many non-motile flagellae are located mainly in the uroidal zone of the cell. Pronounced lateral root and 50-60 radial microtubules originate from the electrone-dense muft around the kinetosome. All elements of the rootlet system of flagella are limited by peripheral layers of cytoplasm. P. paradoxa occupy an intermediate position between two groups of species of Pelomyxa genus--P. gruberi + P. prima and P. palustris + P. stagnalis + P. belewski, which differ greatly by the organization of their flagella basal apparatus.

[Comparative morphology of the subphilum Conosa Cavalier-Smith 1998].

Comparative analysis of archamoebae and slime molds morphology revealed that this organisms have a marked similarity in organization of locomotive forms, structure of glycocalix and also in organization of nuclear and flagellar apparatus. A possible scheme of formation the modern diversity of Conosa group was proposed.

[Morphology of Mastigamoeba aspera Schulze, 1875 (Archamoebae, Pelobiontida)].

The morphology of Mastigamoeba aspera, a type species of the genus Mastigamoeba Schulze, 1875, has been investigated at the light- and electron-microscopical level. Motile individuals are oval or peach-shaped. Motile flagella is situated at the anterior end of uninucleate cells. During locomotion, the surface of mastigamoebes forms many conical or finger-shaped hyaline pseudopodia, wereas bulbous uroid is often formed at the posterior end of the cell. Micropopulations of M. aspera consist of uninucleate flagellate forms as well as multinucleate aflagellate ones. There is a thick layer ofglycocalix on the cell surface where many rod-shaped bacterial ectobionts live. The nucleus is vesicular with spherical central nucleolus. The flagellar apparatus of M. aspera is connected with nucleus to form so called kariomastigont. A single kinetosome is associated with many radial microtubules and a lateral root. A distinct microtubule organization centre (MTOC) is situated at the basal part of the kinetosome. Microtubules of the nuclear cone are connected with the MTOC. This microtubules take part in the formation of kariomastigont. The axoneme has a standart set of microtubules 9(2)+2. Digestive vacuoles are the main component of the cytoplasm of M. aspera. Beside, many light-difracted granules and glycogen bodies were found in the cells. Mitochondria, dictyosomes of the Golgi apparatus and microbodies were not revealed in the cytoplasm of M. aspera.

[Light- and electron-microscopical study of Pelomyxa flava sp. n. (archamoebae, pelobiontida)].

Using light and electron microscopy, the morphology of a new species of pelobionts Pelomyxa flava was studied. The coverings of P. flava are represented by plasma membrane bearing the thick layer of weakly structured glycocalyx on its outer surface. Numerous flagella are often located on the tops of short conical pseudopodia. Kinetosomes of flagella reach a length of 0.9 microm and are hollow with a pronounced central filament. Rootlet system is represented by three groups of microtubules: the radial, basal and microtubules of lateral root. The transition zone is short and does not exceed the level of cell surface; the axoneme is characterized by an unstable set of microtubules. Trophic stages of P. flava life cycle are presented by binuclear cells; plasmotomy is performed at the tetranuclear stage. Nuclei have a granular structure. Fibrillar nuclear bodies were revealed in karyoplasm. The nuclei shell has a complex organization. On its surface, the outer membrane has a layer of electron-dense material which contacts with short microtubules, located in a row at the surface of the nuclear envelope. The bubbles and cisterns of endoplasmic reticulum, which are the derivatives of the nuclear envelope, are located outward from the microtubules. The presence of structural and digestive vacuoles and grains of glycogen was noticed in P. flava endoplasm. Three types of prokaryotic cytobionts were revealed. Large multi-membranous organelles reaching 5 pm in diameter were described for the first time. We discuss morphology and biology features of P. flava in comparison with the previously studied Pelomyxa species.

[Light- and electron-microscopical study of Pelomyxa stagnalis Sp. n. (Archamoebae, Pelobiontida)].

The structure of a new pelomyxa species was investigated with the use of light- and electron-microscope technique. Motile individuals reach 800 microm in length. There is a thin layer of amorphous glycocalix on the cell surface. Many non-motile flagellae are found mainly in the uroidal zone. The axoneme has a non-stable set of microtubules. There are no any special elements in the transition zone. A short kinetosome is about 150 nm long. A bundle of 15-20 microtubules starts from the one side of kinetosome and pass below the cell surface. Structure vacuoles are one of the main cytoplasm components of Pelomyxa stagnalis. Glycogen bodies are surrounded with flattened reticulum cisterns often containing electron-dense material. Two morphological distinct species if prokaryote endobionts were found in the cells of P. stagnalis. The number of nuclei in the cells of P. stagnalis reaches 50 or more. The nuclei are rounded by a two-layer envelope including a multilaminar layer and outer layer, which is formed by small vesicles often containing electron-dense material. One nucleolus is situated at the center of a nucleus. In the nuclei, often in connection with the nucleolus, there are bodies formed by electron-dense threads.

[The morphological study of the cysts Pelomyxa palustris Greeff, 1874].

Pelomyxa palustris Greeff, 1874, is the only species of pelomixoid amoebas with the rest cysts in its life cycle. The morphology of the P. palustris has been studied by the light and electronic microscopy. Encystation of P. palustris under climatic conditions of North-West of Russia occurs within August-September. Rest cysts have a complex, trilaminar wall. Two inner lamina are the dense endocyst and the laminated mesocyst, thickness of each layer runs up to 0.6-0.7 microm. Thickness of the electron-dense ectocyst usually does not exceed 0.1-0.2 microm. The encystated cell of P. palustris has the unique structure. About 60 % of the cell volume are occupied by a huge vacuole placed in the center and filled up with the prokaryotic cytobionts. Different vacuoles, small vesicles of various nature, autophagosomes and lipid drops could be found inside that huge vacuole. The amoebae cytoplasm occupies the space in between endocyst's inner surface and the central vacuole. No any inclusions, prokaryotic cytobionts and most of cell organelles are absent in the cytoplasm. There are 4 large nuclei filled with relatively homogeneous karyoplasm lying in the cytoplasm. Nuclear envelope forms a lot of long tubular channels, running through the cytoplasm and lining the membrane of the central vacuole. Encysted pelomixoid stay in this state up until the beginning of excystation. Excystation of P. palustris in the studied region occurs in spring, during the latter half of April and the beginning of May. Cysts undergo complex morphofunctional changes, related to the reorganization of the wall and formation of young multinucleate amoebas. Only one wall lamina of the 3 initial ones is left up to the moment of excystation. The central vacuole endures ruination and its content penetrates into the cytoplasm. Pelomixoid nuclei divide twice. Prokaryotic cytobionts are localized in cytoplasm and in the perinuclear area. Young multinuclear species of P. palustris coming out of the cysts do not differ in their structure from the adult forms.

[The use of endobiotic ciliates from old collections in transmission electron microscopic investigations].

The opportunity of the use of formalin-fixed endobiotic ciliates from old collections in transmission electron microscopic investigations (TEM) has been studied. Ciliates from the following species were examined: Ditoxum funinucleum Gassovsky, 1919 from the hindgut of Equus hemionus kulan Groves et Mazak, 1967 preserved in a collection during 19 years, Blepharoprosthium pireum Bundle, 1895 and Cochliatoxum periachtum Gassovsky, 1919 from the hindgut of the Yakut horse Equus caballus L. stored during 1.5 years, and Triplumaria heterofasciculata Timoshenko et Imai, 1995 from faeces of the Asian elephant Elephas maximus L. stored during 2.5 years. It is shown, that the main taxonomically important characters of the cortex ultrastructure, ciliature, and internal fibril structure of the cell of Trichostomatia keep well during a long-term storage in formalin.

[Light and electron microscopic investigation of Pelomyxa prima (Gruber, 1884) (Peloflagellatea, Pelobiontida)].

Cell organization of a multinuclear pelobiont Pelomyxa prima has been studied at the light and electron microscopic levels. Motile individuals demonstrate a characteristic drop-like or pyriform shape and reach 550 microkm in length. The cell cover is represented by a well-developed, morphologically differentiated glycocalyx 80-100 nm thick. The cytoplasm contains many structural vacuoles. The nuclei are of vertical type, numbering up to several nuclei in large individuals. Numerous cytoplasmic microtubules are associated with the external membrane of the nuclear envelope. Separate non-motile flagella are distributed throughout the cell surface, being more numerous in the posterior body end and uroidal zone of the protist. Basal bodies of the flagella are extremely long, being deeply immersed into the cytoplasm. These bodies are surrounded by a muff of electron-dense material, with numerous microtubules radiating from it. A compact bundle of microtubules starts from the base of a basal body axially into the cytoplasm. Besides, a band-like lateral microtubular rootlet is present. The number of microtubules in the axoneme of undulipodia is unstable. Neither mitochondria, nor Golgi complex were found. Two species of bacterial endocytobionts are present in the cytoplasm in considerable numbers.

[A case of Axenfeld's syndrome]. / Sluchai sindroma Aksenfel'da.

This syndrome has occurred in three generations of one family. It involves congenital aniridia, lens opacity, congenital glaucoma because of anterior chamber angle dysgenesis. The authors emphasize a high risk of inheriting this condition and recommend the subjects suffering from it consult medical geneticists if they wish to marry and have children.