Evolutionary relationships of endemic Draparnaldioides simplex C. Meyer et Skabitch. Green alga from Lake Baikal with non-Baikalian taxa of chaetophoraceae (Chlorophyta) family

The phylogenetic relationships between Baikalian endemic green alga Draparnaldioides simplex C. Meyer et Skabitch., 1976 and holarctic taxa of green algae have been studied using the 18S rDNA gene fragment and internal transcribed ITS1 and ITS2 spacers of nuclear DNA. The Baikalian genus Draparnaldioides was shown to be a separate taxon. The level of genetic difference between the studied species and non-Baikalian taxa of sister groups of green algae is insignificant, which indicates the young age of the genus Draparnaldioides and its recent radiation from the common ancestor with genera Draparnaldia and Chaetophora.     

Stress-induced changes in pigment and fatty acid content in the microalga Desmodesmus sp. Isolated from a White Sea hydroid

Effects of light intensity, nitrogen availability, and inoculum density on growth and the content of esterified fatty acids (FA), chlorophylls, and carotenoids in Desmodesmus sp. 3Dp86E-1 chlorophyte alga isolated from the White Sea hydroid Dynamena pumila L. were investigated. The growth of algae in the complete BG-11 medium was not limited by irradiances up to 480 μE/(m² s) PAR but depended on the inoculum density. Under nitrogen starvation conditions, high-intensity light retarded growth of the microalga; this effect was less pronounced in the cultures initiated at high inoculum densities. The highest FA percentage in biomass (30% at the 3rd day of cultivation) was detected in nitrogen-starving cultures grown under high light conditions; however, the highest volumetric FA content (0.25 g/L) was attained on a complete medium at 480 μE/(m² s). An increase in the content of oleic acid (18:1) on the background of a decrease in linolenic acid (18:3) was characteristic of the microalga under stress conditions. The microalga was found to be non-carotenogenic. Nitrogen starvation brought about a dramatic decrease in chlorophyll content on the background of relatively constant carotenoid content. On nitrogen-deplete medium, the high light did not trigger the adaptive response of the pigment apparatus. The changes in absorption spectra of Desmodesmus sp. 3Dp86E-1 cell suspensions reflected the increase in relative contribution of carotenoids to light absorption by the microalgal cells; these changes were tightly related with FA accumulation. The mechanisms of acclimation of Desmodesmus sp. 3Dp86E-1 to high light and nitrogen starvation are discussed in view of possible biotechnological applications of this alga.     

Acoustic thermometry of the patient brain with traumatic brain injury

Non-invasive deep brain acoustic thermometry is carried out for two patients at Burdenko Neurosurgery Institute. This method is based on the measurements of the own thermal acoustic radiation of the investigated object. These two patients have got the brain injury. Some of their skull bones are absent. Infrared thermometry was also used to measure the surface temperature of the forehead skin. On the basis of the experimental data the temperatures deep within the brain were reconstructed. The values for the two patients are equal to 37.3 ± 0.7 and 37.0 ± 0.3°C.     

In vivo study of fidelity of DNA double-strand break repair in bacteriophage T4

A method for in vivo studying the fidelity of DNA double-strand break (DSB) repair in bacteriophage T4 has been developed. The frequency of reversion of rII mutations to the wild phenotype was measured in i segC+ x i ets 1 segCDelta crosses, where ets 1 is an insertion in the initial part of the rII gene carrying a sequence recognized by SegC endonuclease; i designates a rIIB or rIIA mutation located at some distance from ets 1, and segCDelta is a deletion in the segC gene. In such cross, a DSB occurs in the site of ets 1. Their repair involves genetic recombination and DNA replication in the neighborhood of ets 1. In parallel, the frequency of reversion of the same i mutant in the absence of DSBs is measured in i x i self-crosses. Reversions of different types (base substitutions, deletions, insertions) can be studied with the use of structurally different i mutations located at varying distances from ets 1. The reversion frequencies were determined for three rIIB mutations and one rIIA mutation. The results obtained suggest that DSB repair in bacteriophage T4 is a process of high fidelity with the rate of errors that does not essentially exceed that in the case of usual phage multiplication.     

Use of the recombinant nonstructural 3A, 3B, and 3AB proteins of foot-and-mouth disease virus in indirect ELISA for differentiation of vaccinated and infected cattle

Recombinant foot-and-mouth disease virus (FMDV) proteins 3A, 3B, and 3AB were produced by expressing the corresponding genes in Escherichia coli and purified by metal-chelate affinity chromatography. The recombinant proteins were used as antigens in indirect enzyme-linked immunosorbent assay (ELISA) to differentiate between vaccinated and FMD-infected animals. The following parameters were determined: working concentrations of antigens and peroxidase conjugate of cattle anti-IgG, the optimum composition of blocking buffer, and the positive-negative threshold of the reaction. Tests performed with approximately 200 serum samples taken from animals of different immunity states showed that the protocol with protein 3A as the antigen (3A-ELISA) provided the most reliable differentiation. All the newly developed systems proved to outperform the commercial Chekit FMD-3ABC kit in sensitivity, and 3A-ELISA was no less specific.     

Differentiation between sources of mechanoluminescence and acoustic emission in impact‐loaded ZnSe and ZnS ceramics

Ductile semiconductor ceramics ZnSe and ZnS were damaged by a falling weight, and the time series of mechanoluminescence (ML) and acoustic emission (AE) pulses were recorded with the nanosecond resolution. The ML lighting appeared in the instance of shock but the AE generation emerged with a delay of 50–100 μsec; however, the maxima of the light and sound emissions coincided in time. This difference in temporal profiles was explained by the difference in prevailing sources of emissions of two types. The detected luminescence in A₂B₆ compounds was excited, mainly, by moving and multiplying dislocations, while the sound was generated by nucleating and growing cracks. The statistical analysis showed that at the stage of pre‐failure deformation, the ensemble of dislocations exhibited a trend to self‐organizing; the cracking was fully random. The effect of intergranular boundaries on the dislocation motion manifested itself in the statistics of mechanoluminescence generation.     

Genetic recombination: Formal implications of a crossed strand-exchange between two homologous DNA molecules

Formal genetic consequences of generation and break-up of a structure with cross connection have been studied on the basis of a simple quantitative model with a symmetric exchange of two strands between parental DNA molecules. In recombination analysis, this intermediate structure gives rise to a critical frequency R(ξ) (see Fig. 3), which corresponds to recombination between two markers separated by a distance equal to the mean genetic length ξ of the hybrid region at the time of scission of the cross connection. As concerns the routine mapping practice, a fundamental inference emerges: since genetic exchange has no invariable equivalent on molecular level it fails basically to serve as statistically independent elementary event in fine scale mapping. Instead of the number of exchanges between markers (or proportional metrics) the use of the number of the sites of initiation of hybrid regions (or proportional metrics) as a measure of map distance is suggested. Usage of the mean length of hybrid region ξ as a natural unit of map distance is shown to be of particular interest.In the case of bacteriophage T4 under the conditions of standard crosses, the structure with cross connection is characterized by the value R(ξ) equal to 3·0.10^?2, at the time of scission of the cross connection this structure acquiring either of the two alternative isomeric configurations with equal probability. About four percent of the total number of mismatches emerging as a result of formation of hybrid regions were repaired.     

Genetic Recombination in Bacteriophage T4: Single-Burst Analysis of Cosegregants and Evidence in Favor of a Splice/Patch Coupling Model

To reveal the structure of penultimate DNA intermediates in T4 bacteriophage recombination, resolution of which produces free recombinant molecules, a single-burst analysis of the recombinant progeny was made in multifactor crosses, enabling one to determine quantitatively the different recombinants generated by one or two exchanges within the same chromosome segment. It was found that double and single exchanges are highly correlated in T4 recombination. These results were interpreted as evidence for simultaneous formation of a splice/patch pair as the primary recombination products. A recombination model called here the "splice/patch coupling model" is presented according to which resolution of a single DNA intermediate results in two linear heterozygous molecules containing a patch and a splice, respectively, in homologous positions.