Structural and functional characterization of cyst cells in Sarcocystis sp. (Sporozoa, Apicomplexa)

By means of light and electron microscopy, the structural pattern of muscle cysts (sarcocysts) was examined for the four species of the genus Sarcocystis: S. muris (from murine skeletal muscles), Sarcocystis sp. and S. fusiformis (from, respectively, heart and skeletal muscles of buffalo), and S. ovifelis (from ovine tong muscles). The orderly fashion of the interior of the cyst is attained by partitition of its space into numerous compartments with the involvement of the intermediate filaments. These, in their turn, are bound to each other by thin filaments to make eventually a common filamentous net. The net limits separate groups of cells referred to as cyst zoites. The common net of filaments and microtubules (when present) may be regarded not only as the organizer of the cyst interior cytoskeleton, but also as the main mechanism of substance transportation in various directions: from the host cell to the sarcocyst, and within or outside the cyst. The role of dedifferentiation, proliferation and differentiation processes is suggested in the establishment of the fixed sequence of events throughout the unidirectional development of cyst cells and their interaction, from precystic meronts to cyst merozoites (gamonts). Special attention is paid to metrocyte morphogenesis and functioning. In the present work, metrocytes subjected to apoptosis were recognized. It is suggested that phenomenon of programmed cell death in metrocytes may be associated with the control of cell number in mature and ageing sarcocysts.     

Protein synthesis-dependent reactivation of environmental conditioned reflex in terrestrial snails

We investigated influence of anisomycine injection on reconsolidation of contextual memory after development of environmental conditioned reflex in terrestrial snail Helix. Testing the amplitude of behavioral reactions (tentacle withdrawal) in response to standard tactile stimulation of the skin in two contexts: a) when the snail was fixed by the shell and was moving on the surface of the ball floating in water, or b) was moving on the flat surface of glass terrarium, has shown no difference in response amplitudes. After a session of electric shocks (5 days) in one context only (ball) the associative learning was clearly observed as the significant difference of response amplitudes in two contexts. On the other day following testing was performed a session of "reminding", immediately after which the snails were injected by anisomycine (control snails were injected by saline solution). Testing has shown that injection of anisomycine led to impairment of the context conditioning. Results suggest that the mechanisms of consolidation of new memory and memory reconsolidation after retrieval are not identical.     

Macroevolution: macrogenesis and typogenesis

One can distinguish two levels (and stages) of macroevolutionary processes: the lower (macrogenesis) and higher (typogenesis) ones. The macrogenesis represents macroevolutionary alterations of separate structures; the typogenesis is the forming of general Bauplan (type of organization) of a new macrotaxon on a base of initial macrogenesis. Discrete (or quantum) character of many macroevolutionary transformations is caused by various mechanisms, which are based on properties of integrated organismic systems and are characterized by threshold effect of their action. Initial macrogenesis can be resulted from the morphofunctional preadaptations; the pattern (or regime) transformations of morphofunctional organismic systems; emerging of dichotomy of morphogenetic programs and their following switching; the ontogenetic heterochronies (in particular, paedomorphosis); the allometric structural changes (and possibly some other mechanisms). The initial macrogenesis forms a base for qualitatively new adaptation and essentially influences on other systems in whole organism. That changes the selection vectors significantly. All these alterations trigger the typogenesis. The latter represents a complex of organismic systems transformations, integrated by selection and interconnections of various systems in whole organism. The important role in typogenesis belongs to the key alterations of some limiting organismic system that trigger and direct evolutionary changes of depended organismic systems. In course of typogenesis evolution, new macrotaxon occupies new adaptive zone.     

Transport dependence of leaf evolution in dicots

The diversity of tissue and cell organization in the leaves of dicots is explained as the mutual effect of light and water fluxes distribution. Equally with certain data about the role of light distribution, the same influence of water flux distribution on the leaf structure is recognized. Dorsiventral leaves of woody plants have an adequate to structure dorsiventral ring of water circulation. Rising flux from the xylem allocates via leaf apoplast with intermediate accumulation in upper epiderma. Descending flux starts and returns to bundle moving from cell to cell along the symplast (ER) of spongy parenchyma, bundle sheath and terminal complexes of the phloem. Isolateral leaves of herbs have a concentric pathway of solute circulation corresponding to the structure. Xylem flux allocates via symplast with water and nitrogen accumulation in paraveinal parenchyma. Water returns to phloem by transit via the apoplast in parallels with phloem exudate formation. Structural features correlated with the model of water circulation in the leaf are described. Numerous lines of leaf evolution well-known for dicots collect to two main topics which are typical for woody and herbaceous forms of dicots. The mechanisms of cell and tissue differentiation under the control of transport fluxes are discussed with special attention to ontogenetic and phylogenetic trends.     

Epigenetic and synergistic types of inheritance of the reproductive characters in angiosperms

The author considers three types of hereditary memory (structural, cell and signal), that are realized on different levels of biological organization. These three types of hereditary memory correspond to three types of reproduction: self-replication, cell division and reproduction s. str. Reproductive characters are exemplified with three essential characters in angiosperm plants: dimorphism in population by flower sex; mono-, di- and trystyly of flowers; uni- and biparental mode of seed reproduction. All these characters are considered as "supercharacters" that are controlled by gene ensembles. The correspondence between three types of reproduction and three types of hereditary memory are discussed. The authors reviews also the role of polyploidy (auto- and endoploidy) in the inheritance of reproductive condition. From the information theory point the increase in cell ploidy causes the growth of uncertainty in expression of genes and gene ensembles thus creating new type of variability--epigenetic variation. The change of reproductive strategy in plants is regulated by state of gene and gene ensembles and does not demand structural changes in genome. The reproductive characters of plants in spite its complex structure are inherited in number of generations as a discrete Mendel characters by mono-, di-, ot trihybrid schemas.     

An ACTH-like peptide immunocortin: effect on the activity of cells from the rat adrenal cortex

The effect of immunocortin, an ACTH-like decapeptide VKKPGSSVKV corresponding to the 11-20 sequence of the variable part of the human IgG1 heavy chain on the content of 11-hydroxycorticosteroids (CS) in rat adrenal glands and blood serum in vivo was studied. An intramuscular injection of immunocortin at a dose of 10 microg/kg was found in an hour to induce a twofold decrease in CS content in the adrenal glands and a 1.8-fold increase in the blood serum CS content. At the same time, an immunocortin dose of 100 microg/kg exerted practically no effect on the CS content and its dose of 1000 microg/kg increased the CS content both in adrenal glands and in blood serum by 1.6 and 2.2 times, respectively. Four hours after the injection of any of the three doses of immunocortin, the CS content in adrenal glands did not differ from the control value, and after 24 h the content decreased threefold. Immunocortin was shown to be bound by the ACTH receptors in the membranes of the rat adrenal cortex with a high affinity and specificity (inhibiting the specific binding of 125I-labeled ACTH-(11-24) peptide with Ki of 1.2 nM).     

The influence of local changes in the temperature-dependent conformational mobility of thioredoxins on their thermostability

For the development of a method for the prediction of single point mutations substantially affecting protein thermostability, we studied the effect of the E85R and R82E mutations on the thermostability of thioredoxins from Escherichia coli (Trx) and Bacillus acidocaldarius (BacTrx), respectively. The basic method of investigation was the molecular dynamics simulation of 3D protein models in a particular solvent at different temperatures (300 and 373 K). Some thermolabile regions in Trx, BacTrx, and their mutants were revealed by analyzing the temperature effect on the molecular dynamics of the protein molecule. The effect of single point mutations on the temperature changes of the protein conformation mobility in several thermolabile regions was found. The results of the calculations are in accord with the experimental data indicating that the mutation E85R increases Trx thermostability, whereas the mutation R82E decreases BacTrx thermostability. The thermostability of these proteins was revealed to depend on ionic interactions between the thermolabile regions. The single point mutations change the parameters of these interactions and make them more favorable in the E85R-Trx mutant and less favorable in the R82E-BacTrx mutant. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2004, vol. 30, no. 5; see also http: // www.maik.ru.