Transformation of clay minerals caused by an alkaliphilic cyanobacterial community

Transformation of clay minerals (smectite-zeolite, illite, kaolinite, and bentonite) and admixtures of iron oxides (hydroxides) under the action of an alkaline cyanobacterial community was studied. The results demonstrate that the processes of transformation of clay minerals such as intensification of removal of exchange bases and dissolution of silicates and iron oxides occurred in the presence of the alkaliphilic cyanobacterial community. The main factor that determines resistance of a mineral to biochemical weathering is its composition. Transformations of clay minerals in the course of active cyanobacterial photosynthesis (up to 14 days) and at decomposition of organic matter (OM) (28–60 days) are different. For smectite-zeolite and illite, these processes are dissolution of silicates and oxides (removal of Si and Fe) and removal of exchange bases (K), which were observed at both the of biomass production and OM destruction stages. For two other clays, the processes of neosynthesis are more typical: formation of carbonates (most probably siderite for bentonite clay and Mg-calcite for kaolin clay) and transformation of ferrihydrite into the more thermodynamically stable goethite.     

The effect of radioprotective preparations on the system of active transport. Mitochondrial ATPase

The effects in vivo and in vitro of the radioprotective agents (MEA, AET, serotonin, dopamine, and histamine) on mitochondrial ATPase activity of rat brain and liver have been investigated. The enzyme activity has been found to be inhibited for the most. Possible mechanisms of the effects observed are discussed.     

Carbonic Anhydrase of the Alkaliphilic Cyanobacterium Microcoleus chthonoplastes

The activity of carbonic anhydrase (CA) was studied in different cell fractions of the alkaliphilic cyanobacterium Microcoleus chthonoplastes. The activity of this enzyme was found in the soluble and membrane protein fractions, as well as in intact cells and in a thick glycocalyx layer enclosing the cyanobacterium cells. The localization of CA in glycocalyx of M. chthonoplastes was shown by western blot analysis and by immunoelectron microscopy studies with antibodies to the thylakoid CA from Chlamydomonas reinhardtii (Cah3). At least one of the CA forms occurring in M. chthonoplastes CA was shown to be an -type enzyme. A possible mechanism of the involvement of the glycocalyx CA in calcification of cyanobacteria is discussed.     

A new method for the activation of the locomotor circuitry in humans

We examined the possibility of initiation of involuntary stepping movements by spinal electromagnetic stimulation (SEMS) during leg suspension. The subject’s legs were supported by a special apparatus in a gravity neutral position that to provide horizontal rotation in the hip, knee and ankle. SEMS (3 Hz and 1.56 Tesla) over the T11–T12 vertebrae induced involuntary locomotor_like movements in the legs. The latency period from the initiation of stimulation to the first EMG burst was 0.68 1.0 s. Increasing the frequency of SEMS from 3 Hz to 20 Hz resulted in shortening of the latency period. Thus, SEMS is able to initiate involuntary stepping in humans.     

Heterologous expression of a Rauvolfia cDNA encoding strictosidine glucosidase, a biosynthetic key to over 2000 monoterpenoid indole alkaloids.

Strictosidine glucosidase (SG) is an enzyme that catalyses the second step in the biosynthesis of various classes of monoterpenoid indole alkaloids. Based on the comparison of cDNA sequences of SG from Catharanthus roseus and raucaffricine glucosidase (RG) from Rauvolfia serpentina, primers for RT-PCR were designed and the cDNA encoding SG was cloned from R. serpentina cell suspension cultures. The active enzyme was expressed in Escherichia coli and purified to homogeneity. Analysis of its deduced amino-acid sequence assigned the SG from R. serpentina to family 1 of glycosyl hydrolases. In contrast to the SG from C. roseus, the enzyme from R. serpentina is predicted to lack an uncleavable N-terminal signal sequence, which is believed to direct proteins to the endoplasmic reticulum. The temperature and pH optimum, enzyme kinetic parameters and substrate specificity of the heterologously expressed SG were studied and compared to those of the C. roseus enzyme, revealing some differences between the two glucosidases. In vitro deglucosylation of strictosidine by R. serpentina SG proceeds by the same mechanism as has been shown for the C. roseus enzyme preparation. The reaction gives rise to the end product cathenamine and involves 4,21-dehydrocorynantheine aldehyde as an intermediate. The enzymatic hydrolysis of dolichantoside (Nbeta-methylstrictosidine) leads to several products. One of them was identified as a new compound, 3-isocorreantine A. From the data it can be concluded that the divergence of the biosynthetic pathways leading to different classes of indole alkaloids formed in R. serpentina and C. roseus cell suspension cultures occurs at a later stage than strictosidine deglucosylation.     

Membrane repair: Ca(2+)-elicited lysosomal exocytosis.

Cells in exposed positions are subject to injury and therefore need membrane repair mechanisms. Ca(2+) entry inevitably follows membrane rupture and recent studies indicate that this elicits repair via Ca(2+)-activated exocytosis of lysosomes, regulated by lysosomal synaptotagmin VII.     

A radioimmunoprecipitation method in the serodiagnosis of HIV infection: the development of the optimal conditions for its performance and the evaluation of the possibilities for its use

The optimum conditions for using the method of radioimmunoprecipitation (RIP) for the detection of human immunodeficiency virus (HIV) in serum samples have been established. Out of several available cell lines persistently infected with HIV, specially selected line 17 has been chosen. The characteristic feature of this is the high and stable (under the conditions of prolonged cultivation) accumulation of virus-specific proteins in infected cells. The optimum conditions for making the test and its evaluation have also been established. The data of literature on the advantages of the method of RIP over such traditional methods as the enzyme immunoassay and immunoblotting have been confirmed. Thus, the presence of specific antibodies in several serum samples registered as false negative has been established. The intertypical reactivity of two serotypes of the virus, HIV-1 and HIV-2, has been studied. Cross reactivity of antibodies with respect to the HIV gene gag, but not with respect to viral glycoproteids, has been established. Ideas on the expediency and prospects of using RIP for the serological control of HIV infection are presented.     

The role of cyanobacteria in crystallization of magnesium calcites

Laboratory experiments showed the effect of the cyanobacterium Microcoleus chthonoplastes on the formation of magnesium calcites, using model solutions (2.14M MgCl₂-0.05M CaCl₂-0.6M NaCl-0.18M NaHCO₃). The conditions of existence of cyanobacteria in such solutions in light or darkness significantly alter the structure of the sediment and the shape and size of the carbonate crystals. Cyanobacteria slow down crystallization due to the formation of exometabolites with a chelating effect, which leads to the precipitation of high-magnesium calcites. In the photosynthetic environment the presence of huntite (CaMg₃(CO₃)₄), possible forerunner of dolomite, is prominent.     

Biological effectiveness of helium ions and relativistic-energy protons

It was shown that RBE coefficients of protons (9 GeV) and accelerated helium ions (4 GeV/nucleon) are within the range from 1.0 to 11.6 and 1.0 to 7.2, respectively, depending on the object under study, the criterium of estimation, the registration time, and the dose value.     

Nonuniformity of calcium efflux from pancreatic acinar cells and its analysis by mathematical model of calcium diffusion and buffering in extracellular solution

We studied spatial and temporal patterns of Ca²⁺ extrusion from pancreatic acinar cells evoked by acetylcholine(ACh)-induced activation of plasma membrane calcium pumps. Using a modification of an earlier developed model, we estimated the time course of extracellular calcium concentration changes near the basal pole of a cell in the case, when calcium ions are released from the same site on the cell surface, and in the case when they are extruded from the apical pole and diffuse to the basal one. It is concluded that at the first stage of ACh-induced Ca²⁺ extrusion the appearance of Ca²⁺ elevation near the basal pole of the cells cannot be explained as a result of diffusion, but is mainly determined by Ca²⁺ efflux from this pole. The results also show that there are plasma membrane calcium pumps in both apical and basal parts of pancreatic acinar cells, but the activity of the pumps is substantially higher in the apical region.