[Fixation of metacentric chromosomes in populations of the common shrew Sorex araneus L. from populations of Eastern Europe]

In this review, we discuss the processes of fixation of Robertsonian chromosome fusions in populations of the common shrew Sorex araneus L. Various Robertsonian fusions, accumulating in populations, create an illusion of large chromosomal rearrangements, reciprocal translocations of complete chromosome arms. The use of these rearrangements for phylogenetic reconstructions results in false conclusions. Robertsonian fusions accumulate in populations at such stages of the species evolution, when large open or subdivided populations prevail (populations of warm periods of Pleistocene and many present-day populations) and are fixed in small isolated populations and glacial refugia. The formation of monomorphic chromosome races requires a long time, several glaciation epochs during the whole Pleistocene.

[On the taxonomic rank of ciscaucasicus and its relationships with the pygmy wood mouse Sylvaemus uralensis inferred from the mtDNA cytochrome b gene sequence]

To specify the taxonomic rank of form ciscaucasoides (independent species Sylvaemus ciscaucasoides, or intraspecific form of pygmy wood mouse, S. uralensis), a 402-bp the mtDNA cytochrome b gene fragment (402 bp) was examined in S. ciscaucasoides individuals from six geographic localities of the Caucasus and Ciscaucasus, (Krasnodar krai and Adygeya Republic) and 17 S. uralensis individuals from seven localities of the Russian Plai (Saratov oblast, Smolensk oblast, Voronezh oblast, Tula oblast, Moscow oblast, and Tver' oblast). For comparison, the cytochrome b gene was partly sequenced in the samples of yellow necked, S. flavicollis (n = 2, Samara oblast), and Caucasian, S. ponticus (n = 6, Krasnodar krai), wood mice. One Mus musculus specimen from Western Europe, whose nucleotide sequences were deposed in the GenBank, was used as intergeneric outgroup. Phylogenetic trees for the forms examined were constructed based on the mtDNA sequence variation and using the neighbor joining and maximum parsimony methods. The network of the cytochrome b haplotypes was also constructed. The level of genetic divergence was evaluated using Kimura's two-parameter algorithm. Based on the data on the sequence variation in a 402-bp mtDNA cytochrome b gene fragment, the hypothesis on the species status of the ciscaucasicus form was. The mean intergroup distances (d) between the geographic groups of S. uralensis varied from 0.0036 to 0.0152. At the same time, the distances between the pygmy wood mice and the group of S.flavicollis-S. ponticus varies in the range from 0.0860 to 0.0935, and the level of intergeneric genetic differentiation (Sylvaemus-Mus) is higher than the latter index (d = 0.142). Ciscaucasoides should be considered as geographic substitution form of S. uralensis. Furthermore, the Caucasian populations of S. uralensis (= ciscaucasoides) were characterized by a threefold lower value of intergroup genetic divergence (d = 0.0062) than the East European populations (d= 0.0179). This finding pointed to some isolation of Caucasian populations of pygmy wood mouse and depletion of their gene pool. However other molecular genetic data (similarity of nucleotide composition and consistence of the levels of intra- and intergroup distances) suggest the absence of geographic subdivision between Caucasian and East European populations ofS. uralensis relative to the molecular marker examined.

[Potentialities of multispiral computed tomography in the diagnostics of pathological alterations of the colon]

The work describes an experience with using different methods of multispiral computed tomography in the diagnosis and differential diagnostics of pathological changes in the colon of patients of colonoproctological profile. Methodical variations of the computed tomography investigations are described in patients with localization of tumors in different parts of the intestine.

[Using AELTIS-synchro-02 device in the therapy of chronic bacterial prostatitis]

The treatment of chronic bacterial prostatitis combined antibacterial drugs and physiotherapy (low-energy laser radiation, electrostimulation of the prostate). Treatment of chronic bacterial prostatitis with medication and complex two-channel bio-synchronized electrolaser therapy with application of the unit AELTIS-synchro-02 raises efficacy of treatment with chronic bacterial prostatitis due to combined effect of antibacterial drugs and bacteriostatic and immunomodulating actions of the physical factors applied. These normalize microcirculation in the region of the prostatic gland, improve a draining function of the prostatic ducts, allows achievement of good results in 88.2% patients.

[Genealogic analysis of hereditary components of a metapopulation of Przhevalsky horse]

The current condition of the megapopulation of the Przhevalsky horse was assessed using genetic indices of biological diversity of species and genealogical analysis and taking into account both nuclear and non-nuclear (mitochondrial), maternally inherited components of hereditary information.

[The use of monoclonal antibodies in studying the causative agents of viral hemorrhagic fevers]

The most promising trends of using monoclonal antibodies (Mabs) in virology research of the viral hemorrhagic-fevers' agents are related with studying viral antigen structure and with developing diagnostic preparations for indicating and identifying infectious agents of the mentioned pathologies. The methodological specificity of obtaining the Mabs to viral hemorrhagic-fevers' agents as well as data on its practical use are discussed.

Changes in the thermal unfolding of p-phenylenedimaleimide-modified myosin subfragment 1 induced by its 'weak' binding to F-actin

Differential scanning calorimetry (DSC) was used to analyze the thermal unfolding of myosin subfragment 1 (S1) with the SH1 (Cys-707) and SH2 (Cys-697) groups cross-linked by N,N'-p-phenylenedimaleimide (pPDM-S1). It has been shown that F-actin affects the thermal unfolding of pPDM-S1 only at very low ionic strength, when some part of pPDM-S1 binds weakly to F-actin, but not at higher ionic strength (200 mM KCl). The weak binding of pPDM-S1 to F-actin shifted the thermal transition of pPDM-S1 by about 5 degrees C to a higher temperature. This actin-induced increase in thermal stability of pPDM-S1 was similar to that observed with 'strong' binding of unmodified S1 to F-actin. Our results show that actin-induced structural changes revealed by DSC in the myosin head occur not only upon strong binding but also on weak binding of the head to F-actin, thus suggesting that these changes may occur before the power-stroke and play an important role in the motor function of the head.

Macroscopic aggregation of tobacco mosaic virus coat protein

The relationship between processes of thermal denaturation and heat-induced aggregation of tobacco mosaic virus (TMV) coat protein (CP) was studied. Judging from differential scanning calorimetry "melting" curves, TMV CP in the form of a trimer-pentamer mixture ("4S-protein") has very low thermal stability, with a transition temperature at about 40 degrees C. Thermally denatured TMV CP displayed high propensity for large (macroscopic) aggregate formation. TMV CP macroscopic aggregation was strongly dependent on the protein concentration and solution ionic strength. By varying phosphate buffer molarity, it was possible to merge or to separate the denaturation and aggregation processes. Using far-UV CD spectroscopy, it was found that on thermal denaturation TMV CP subunits are converted into an intermediate that retains about half of its initial alpha-helix content and possesses high heat stability. We suppose that this stable thermal denaturation intermediate is directly responsible for the formation of TMV CP macroscopic aggregates.

Dissociative mechanism of thermal denaturation of rabbit skeletal muscle glycogen phosphorylase b

The thermal stability of rabbit skeletal muscle glycogen phosphorylase b was characterized using enzymological inactivation studies, differential scanning calorimetry, and analytical ultracentrifugation. The results suggest that denaturation proceeds by the dissociative mechanism, i.e., it includes the step of reversible dissociation of the active dimer into inactive monomers and the following step of irreversible denaturation of the monomer. It was shown that glucose 1-phosphate (substrate), glucose (competitive inhibitor), AMP (allosteric activator), FMN, and glucose 6-phosphate (allosteric inhibitors) had a protective effect. Calorimetric study demonstrates that the cofactor of glycogen phosphorylase-pyridoxal 5'-phosphate-stabilizes the enzyme molecule. Partial reactivation of glycogen phosphorylase b preheated at 53 degrees C occurs after cooling of the enzyme solution to 30 degrees C. The fact that the rate of reactivation decreases with dilution of the enzyme solution indicates association of inactive monomers into active dimers during renaturation. The allosteric inhibitor FMN enhances the rate of phosphorylase b reactivation.

Complexes of smooth muscle tropomyosin with F-actin studied by differential scanning calorimetry

Differential scanning calorimetry (DSC) and light scattering were used to analyze the interaction of duck gizzard tropomyosin (tropomyosin) with rabbit skeletal-muscle F-actin. In the absence of F-actin, tropomyosin, represented mainly by heterodimers, unfolds at 41 degrees C with a sharp thermal transition. Interaction of tropomyosin heterodimers with F-actin causes a 2-6 degrees C shift in the tropomyosin thermal transition to higher temperature, depending on the tropomyosin/actin molar ratio and protein concentration. A pronounced shift of the tropomyosin thermal transition was observed only for tropomyosin heterodimers, and not for homodimers. The most pronounced effect was observed after complete saturation of F-actin with tropomyosin molecules, at tropomyosin/actin molar ratios > 1 : 7. Under these conditions, two well-separated peaks of tropomyosin were observed on the thermogram besides the peak of F-actin, the peak characteristic of free tropomyosin heterodimer, and the peak with a maximum at 45-47 degrees C corresponding to tropomyosin bound to F-actin. By measuring the temperature-dependence of light scattering, we found that thermal unfolding of tropomyosin is accompanied by its dissociation from F-actin. Thermal unfolding of tropomyosin is almost completely reversible, whereas F-actin denatures irreversibly. The addition of tropomyosin has no effect on thermal unfolding of F-actin, which denatures with a maximum at 64 degrees C in the absence and at 78 degrees C in the presence of a twofold molar excess of phalloidin. After the F-actin-tropomyosin complex had been heated to 90 degrees C and then cooled (i.e. after complete irreversible denaturation of F-actin), only the peak characteristic of free tropomyosin was observed on the thermogram during reheating, whereas the thermal transitions of F-actin and actin-bound tropomyosin completely disappeared. Therefore, the DSC method allows changes in thermal unfolding of tropomyosin resulting from its interaction with F-actin to be probed very precisely.

Two-state irreversible thermal denaturation of muscle creatine kinase

Thermal denaturation of creatine kinase from rabbit skeletal muscle has been studied by differential scanning calorimetry. The excess heat capacity vs. temperature profiles were independent of protein concentration, but strongly temperature scanning rate-dependent. It has been shown that thermal denaturation of creatine kinase satisfies the previously proposed validity criteria for the two-state irreversible model [Kurganov et al., Biophys. Chem.70 (1997) 125]. The energy activation value has been calculated to be 461.0 +/- 0.7 kJ/mol.

[Genetic differentiation of voles of the tribe Arvicolini (Cricetidae, Rodentia) using taxonprint analysis and polymerase chain reaction with random primers]

The variability of the genomes of ten vole species was analyzed by means of taxonomic DNA fingerprinting and polymerase chain reaction using random primers (RAPD-PCR). The dendrograms of genetic similarity between the representatives of the tribe Arvicolinae (Gray, 1821) were constructed, based on the data obtained by means of both methods. The topology of the genetic similarity dendrogram that is based on the RAPD-PCR data generally correlates with the genetic distances estimated from biochemical and karyological data. The results did not confirm the genus status of Terricola. On the other hand, the data from taxonprint analysis suggest the recognition of Lasiopodomys as a separate genus.

Thermally induced chain exchange of smooth muscle tropomyosin dimers studied by differential scanning calorimetry

The thermal unfolding of duck gizzard tropomyosin dimers, alphabeta, alphaalpha, and betabeta, and of a 1:1 mixture of alphaalpha and betabeta homodimers was studied by differential scanning calorimetry (DSC). Both alphaalpha and betabeta homodimers demonstrated a broad thermal transition with maxima at 37.4 degrees C and 44.6 degrees C, respectively. However, a sharp cooperative thermal transition at 41.5 degrees C characteristic for alphabeta heterodimer appeared on the thermogram of the mixture of homodimers. The appearance of this transition was prevented by disulfide cross-linking of polypeptide chains in the homodimers. Thus, DSC studies clearly demonstrate formation of tropomyosin heterodimers during heating of the mixture of homodimers and in agreement with earlier published reports indicate thermally induced chain exchange between tropomyosin dimers.

A comparative differential scanning calorimetric study of tobacco mosaic virus and of its coat protein ts mutant

The differential scanning calorimetry (DSC) 'melting curves' for virions and coat proteins (CP) of wild-type tobacco mosaic virus (strain U1) and for its CP ts mutant ts21-66 were measured. Strain U1 and ts21-66 mutant (two amino acid substitutions in CP: 121 --> T and D66 --> G) differ in the type of symptoms they induce on some host plants. It was observed that CP subunits of both U1 and ts21-66 at pH 8.0, in the form of small (3-4S) aggregates, possess much lower thermal stability than in the virions. Assembly into the virus particles resulted in a DSC melting temperature increase from 41 to 72 degrees C for U1 and from 38 to 72 degrees C for ts21-66 CP. In the RNA-free helical virus-like protein assemblies U1 and ts21-66 CP subunits had a thermal stability intermediate between those in 3-4S aggregates and in the virions. ts21-66 helical protein displayed a somewhat lower thermal stability than U1.

Irreversible thermal denaturation of uridine phosphorylase from Escherichia coli K-12

Thermal denaturation of uridine phosphorylase from Escherichia coli K-12 has been studied by differential scanning calorimetry. The excess heat capacity vs. temperature profiles were obtained at temperature scanning rates of 0.25, 0.5, and 1 K/min. These profiles were analysed using three models of irreversible denaturation which are approximations to the whole Lumry-Eyring model, namely, the one-step model of irreversible denaturation, the Lumry-Eyring model with the fast equilibrating first step, and the model involving two consecutive irreversible steps. In terms of statistics the latter model describes the kinetics of thermal denaturation of uridine phosphorylase more satisfactorily than the two other models. The values of energy activation for the first and second steps calculated for the model involving two consecutive irreversible steps are the following: Ea,1 = 609.3 +/- 1.8 kJ/mol and Ea,2 = 446.8 +/- 3.2 kJ/mol.

Differential scanning calorimetric studies on myosin and actin

This review is concerned with the application of the method of differential scanning calorimetry (DSC) to structural and functional studies of myosin and actin--the main two proteins of muscles and many other systems of biological motility. The domain organization of these proteins as revealed by DSC is considered. Data are presented on the conformational changes which occur in the myosin head and in F-actin due to the formation of the ternary complexes with ADP and Pi analogs (such as orthovanadate, beryllium fluoride, or aluminum fluoride). Recent data on the application of DSC to studies on the interaction of F-actin with myosin heads and with tropomyosin are also considered. It is concluded that DSC offers a new and promising approach to probe the structural changes which occur in the myosin head and in F-actin during ATP hydrolysis and due to interaction of these proteins with each other.