Assessment of the mechanical activity of cardiac isomyosins V1 and V3 by the in vitro motility assay with regulated thin filament

The dependences of thin filament sliding velocity on the calcium concentration in solution (pCa 5 to 8) for rabbit cardiac myosin isoforms V1 and V3 were determined in a set of experiments using an in vitro motility assay with a reconstructed thin filament. The constructed pCa-versus-velocity curves had a sigmoid shape. It was demonstrated that the sliding velocity of regulated thin filament at the saturating calcium concentration (pCa 5) did not differ from the actin sliding velocity for each isoform. The determined values of Hill’s cooperativity coefficient for isomyosins V1 and V3 were 1.04 and 0.75, respectively. It was demonstrated that isomyosin V3 was more sensitive to calcium as compared with isomyosin V1. Using the same assay, the dependence of thin filament sliding velocity on the concentration of the actin-binding protein α-actinin (analog of a force-velocity dependence) was determined at the saturating calcium concentration for each myosin isoform (V1 and V3). The results suggest that the calcium regulation of V1 and V3 contractile activity follows different mechanisms.     

Laccase and Lectin Activities of Intracellular Proteins Produced in a Submerged Culture of the Xylotrophic Basidiomycete Lentinus edodes

The white-rot fungus Lentinus edodes produced D: -melibiose-specific lectins and two laccase forms in a lignin-containing medium. The maxima of laccase and lectin activities coincided, falling within the period of active mycelial growth. The enzymes and lectins were isolated and purified by gel filtration followed by anion-exchange chromatography. The L. edodes lectins were found to be able to stabilize the activity of the fungus's own laccases. Lectin activity during the formation of lectin-enzyme complexes remained unchanged.     

Human Microsatellites: Mutation and Evolution

Microsatellites (MSs) are short tandem DNA repeats with the repetitive motif of two to six nucleotides, forming tracts up to hundreds of nucleotides long. Notwithstanding the active use of MSs in genetic studies of various biological problems, the reasons for their wide occurrence in the genome, their possible functions, and mutational behavior are still unclear. The mutation rate in MS repeats is on average several orders of magnitude higher than in the remaining DNA, which allows for direct estimation of evolutionary transformation rate in nucleotide sequences of the genome. Mutation process in MSs is highly heterogeneous, with distinct differences between species; furthermore, within a species it differs among loci with different repeat size, among alleles of one locus, and among individuals of different sex and age. Most MS mutations are caused by DNA slippage during replication but the probability of this event depends on the locus. In this review, a number of models of MS evolution are discussed, which account for the relationship between mutation rate and allele size, different mutation direction in alleles of different size, and the appearance of point mutations within repeat tracts restricting allele size. The MS evolution is considered mainly in the context of selective neutrality, although there is evidence showing functional significance of some variants of tandem repeats and thus their possible selective value.     

Activity of <Emphasis Type="Italic">Lentinus edodes</Emphasis> intracellular lectins at various developmental stages of the fungus

We studied changes of the hemagglutinating activity of intracellular lectins of the basidiomycete Lentinus edodes (shiitake) at various stages of its morphogenetic development depending on erythrocyte type, growth medium, and lectin purification degree. Under certain experimental conditions, the specific lectin activity at the brown mycelium film stage exceeded the corresponding value for nonpigmented mycelium. The sensitivity of the lectins towards trypsin-treated rabbit erythrocytes was no less than a hundredfold higher than towards any other erythrocyte type studied. The general regularities of specific activity change did not depend on nutrient medium composition. With purification of intracellular shiitake lectins, their sensitivity to human erythrocytes decreased seventyfold or more, whereas their sensitivity to rabbit erythrocytes increased by the same factor.     

Distribution and Physiological State of Microorganisms in Petrochemical Oily Sludge

The occurrence, vertical distribution, and physiological state of microorganisms in a petrochemical oily sludge deposit were studied. The total number and the number of viable microbial cells at depths of 0.2 and 3 m were about 10¹⁰ and 10⁸ cells/g dry wt sludge. Most microbial cells taken from the middle (1 m deep) and the bottom (3 m deep) sludge horizons showed a delayed colony-forming ability, which suggested that the cells occurred in a hypometabolic state. The relative number of microaerobic denitrifying microorganisms steeply increased with depth. The amount of microorganisms tolerant to 3, 5, and 10% NaCl and capable of growing at 7 and 40°C varied from 10² to 10⁸ CFU/g dry wt sludge. Petrochemical oily sludge was found to maintain the growth of heterotrophs, among which the degraders of oily sludge and ten different individual polycyclic aromatic hydrocarbons were detected. The occurrence of highly adaptable microorganisms with an adequate metabolic potential in the petrochemical oily sludge deposit implies that its bioremediation is possible without introducing special microorganisms.     

Detection of Aneuploidy in Spontaneous Abortions Using Comparative Genomic Hybridization

Comparative genomic hybridization (CGH) technique was used to examine a set of ten spontaneous abortions whose cell cultures were characterized by the lack of proliferation in vitro, and thereby, were not available for the analysis by means of routine cytogenetic methods. Five abortions (50%) had aneuploidy of autosomes, including trisomy 10, 14, 18, and 21, and monosomy 22. The latter variant of unbalanced chromosomal abnormalities is rarely detected in spontaneous abortions by use of conventional cytogenetic methods. The results were validated by using fluorescent in situ hybridization (FISH) analysis with centromere-specific DNA probes. Embryos with trisomy 10 and monosomy 22 displayed mosaicism with the frequencies of abnormal cell clones constituting 68 and 33% respectively. The advantages and limitations of the applying of CGH technique for detection of genomic abnormalities in both nonmosaic and mosaic forms are discussed.     

The action of serotonin and its analogs on the in vitro maturation of amphibian oocytes

Indolylalkylamines (5-HT, 5-chlorotryptamine, 5-ethyltryptamine) suppress or block the progesterone-induced oocyte maturation in Bufo viridis and Xenopus laevis and disturb cytoskeletal rearrangements associated with oocytes involved, together with the other transmitter systems, in modulation of progesterone effect.