An ultrastructural study of reproduction in the parthenogenetic metacercariae of Cercaria margaritensis Ching, 1982 (Digenea: Gymnophallidae).

The parthenogenetic metacercarial stages of the gymnophallid trematode Cercaria margaritensis are found in the extrapallial cavity of the subtidal prosobranch mollusc Margarites helicinus. The primary metacercariae (M1) produce second-generation metacercariae (M2) which become independent and give rise to M3 metacercariae which are infective to the definitive host, the common eider (Somateria mollissima). This study used transmission electron microscopy to follow the development of M2 inside M1 organisms and M3 inside M2 organisms. The process is similar in both cases with embryos developing from individual cells from the parent body walls. In each case the brood sac was divided into brood chambers by multilaminated cells and both M2 and M3 embryos developed inside embryonic membranes that originated from specialized blastomeres. The tegument of M2 and M3 embryos developed in a similar manner underneath the embryonic membrane. Both the multilaminated cells and the embryonic membranes possessed features that indicated that they are involved in transport of nutrients. It is suggested that the continuous nature of M2 and M3 embryo development may well be similar to that postulated for ancestral digeneans.

The structure and formation of metacercarial cysts in the trematode family Microphallidae travassos 1920.

This study deals with the formation of the metacercarial cysts of four microphallid trematodes, Maritrema subdolum, M. arenaria, Levinseniella brachysoma and Microphallus claviformis. The first observable cyst was present around Maritrema arenaria 18 h p.i. (post-infection). The other species had not developed a cyst by day 8 p.i. but their cysts were apparent by day 16 p.i. These were bi-layered and that of M. subdolum was thicker than those of L. brachysoma and Microphallus claviformis of the same age. The structure of older cysts varied substantially between the four species. Microphallus claviformis and Maritrema subdolum cysts were fully formed at 30 days p.i. Like those of M. arenaria they were bi-layered, the outer layer (up to 3 microm thick) being electron-dense and the inner one (up to 7 microm thick) being less electron-dense. The cysts of fully formed L. brachysoma metacercariae were much more complex, composed of four layers, one of which was divisible into three sub-layers. It was concluded that the outer cyst layer was the product of secretory granules which were previously identified in cercarial tegument. The inner, thicker layer was derived from several sources. These included small tegument vesicles produced over the entire surface of the metacercariae, larger fragments of tegument released from the anterio-ventral region and material liberated from the metacercarial excretory bladder. This heterogeneous material accumulated in the cyst lumen for some time before becoming polymerized to form the thick inner layer or layers of the metacercarial cysts.

[The prospects for using the genetically engineered surface antigen of the hepatitis B virus (HBsAg) expressed by recombinant poxvirus strains as the basis for vaccines against hepatitis B]. / Perspektivy ispol'zovaniia genno-inzhenernogo poverkhnostnogo antigena virusa gepatitia B (HBsAg), ekspressiruemogo rekombinantnymi shtammami poksvirusov, v kachestve osnovy vaktsin protiv gepatita B.

The use of a recombinant poxvirus (RPV) strain, expressing HBsAg in the process of reproduction in different bioreactor systems under stationary and bioreactor conditions of cultivation, made it possible to obtain highly purified HBsAg. The identity and purity of HBsAg was confirmed by the analysis of its amino acid composition, SDS electrophoresis in polyacrylamide gel, electron microscopy and high-performance liquid chromatography. Good prospects of the use of RPV-expressed gene engineering HBsAg as the basis vaccines against hepatitis B was demonstrated in 10 experimental batches of vaccine. All batches of the preparation had pronounced immunogenicity and were safe and nontoxic in animal experiments. The ID50 of experimental batches did not exceed 211 ng/ml, which, according to the data of comparative experiments, was lower than, or equal to, corresponding values of analogous foreign commercial preparations, based on plasma or yeast HBsAg.

The glands of trematode cercariae of the family Microphallidae Travassos, 1920.

The ultrastructure of the glands of microphallid cercariae is described. The fully-formed cercariae possess only penetration glands opening onto the surface of the tegument. Cercarial embryos have tegumental glands transferring their secretion in the tegument. In all studied species two anterior pairs of penetration glands produce identical granules while two posterior pairs produce heterogeneous granules of various shapes and sizes. Tegument cells are divided into mucoid and two other types of tegument glands (TG1 and TG2). The mucoid glands of Microphallinae cercariae produce large fibrous granules, while those of Maritrematinae cercariae produce osmiophil ones. TG1 cells of Maritrema subdolum produce large rod-shaped granules and TG1 cells of Levinseniella brachysoma, Microphallus sp. and M. claviformis produce two types of osmiophil granules. TG2 produce small rod-shaped granules. The association of gland ultrastructure with their function and features of the microphallid life-history are discussed.

[The structure of the cercarian tegument of microphallid trematodes]. / Stroenie tegumenta tserkarii mikrofallidnykh trematod.

The tegument of mature cercariae of Microphallus sp. Podlipajev, 1979, M. claviformis, Levinseniella brachysoma and Maritrema subdolum consists of the outer syncytial layer filled with several types of secretory inclusions. Cytons and subtegumental cell ducts are absent. Covers of Microphallus cercariae have structure typical of larvae of trematodes. The tegument surface of L. brachysoma cercariae carries lamelli, spines are divided into two parts: short massive body sharpened at fore end and long thin stalk connected with basal membrane. The tegument surface of M. subdolum larvae forms tongue-like protrusions, modified spines serve as their frame. The development of tegument of the above species during cercaria morphogenesis has been traced. It is shown that at first in embryos syncytial lamina of the tegument is formed. Within it rudiments of spines have been detected as narrow transversal columns of mediate electron density. Henceforward syncytial layer has thickened, provisional spines have become conical, their matrix has become fibrous. Then the joining of protrusions of subtegumental glandular cells to outer syncytium has begun. These cells have been arranged into three types depending on the character of secret produced. The spines have acquired the species-specific structure. In members of the genus Microphallus they have become massive, and both in L. brachysoma and M. subdolum they have lengthened and subdivided into body and stalk. Spines of M. subdolum have flattened appreciably, their bodies have been found within tegumental tongue-like protrusions.

[Ultrastructure of the tail appendage in microphallid cercariae (Trematoda, Microphallidae)]. / Ul'trastruktura khvostovogo pridatka mikrofallidnykh tserkarui (Trematoda, Microphallidae).

The tail structure of larvae of Maritrema subdolum and Microphallus claviformes is similar in essence. Its wall is made by the tegument and underlying layers of muscles. The syncytial anucleated tegumental lamina with the only type of secretory inclusions forms regular circular folds along the tail. The outer muscle layer is formed by the smooth muscular cells. It is underlaid by the longitudinal cross-striated muscles with the strongly pronounced sarcomere organization. The nucleus-containing bodies of the muscle cells occupy the axial part of the tail excepting the central cavity. The functional joining of tail and body musculatures is provided by thick muscle bundles in the caudal department of the larval body.

[Autoradiographic research on the dark and light Purkinje cells in the cerebellum of rats]. / Avtoradiograficheskoe issledovanie temnykh i svetlykh kletok Purkin'e mozzhechka krys.

Intensity of the 3H-sodium acetate and 3H-leucine incorporation into dark and light Purkinje cells of the rat cerebellum was studied. The intensity of incorporation into light Purkinje cells was found to be 1.5 times higher than into the dark ones.