Functionally different states of the "hydrophobic pocket" of the myosin ATPase center]

The influence of an increased temperature (39 degrees C) on a denaturation of 50 kDa-fragment of myosin subfragment 1 was studied in the presence of different nucleoside triphosphates (NTP) and nucleoside diphosphates (NDP). The degree of the denaturation was appreciated evaluated from its trypsinolysis depth. According to their protective influence NTP and NDP were shown to arrange in lines ATP greater than or equal to CTP greater than UTP greater than GTP and ADP greater than GDP greater than CDP greater than UDP, correspondingly. The results received and the literature data allow to suggest that there are at least two states of ATPase site hydrophobic pocket, one of which in responsible for sharp ATPase reaction slowing-down on the stage of macroergic bonding splitting.     

Interaction of annexin VI with actin

Actin polymerization was investigated using fluorescence probe N-(1-pyrenyl)iodoacetamide, which was bound covalently to reactive sulfhydryl group, Cys-373. Labeled actin in the bulk was 0.5 to 1% of total actin concentration. Actin polymerization at concentration 12 mM was started by addition of 20 mM KCl and 2 mM MgCl2. The label fluorescence was excited at 365 nm and registered at 386 nm. Under actin polymerization the label fluorescence increased almost 10 times. Two main phases may be distinguished in the process of actin polymerization: 1) monomer activation and nucleus (trimer) formation, 2) growth of actin filaments on the nuclei. In our experimental conditions, both for pure actin and for that with added annexin VI, the 1st phase continued for about 3 min and after that the 2nd phase was perfectly approximated by exponential dependence. An analysis of the exponential curves showed that actin monomer lifetime increased from 327 s, at annexin absence, to about 373 s at 0.7 microM annexin and more. Calculation of rate constants at two ends of growing actin filament suggests that annexin VI binds with pointed ("slow") end so that at sufficient annexin concentration the filament grows only on barbed ("fast") end. Our results, together with data of other researchers showing that annexin VI binds with the inner membrane surface of smooth muscle cell through Ca2+, may indicate that, at Ca2+ entering the cell, this annexin binds actin filament pointed ends to cell surface making it ready for the act of contraction.     

Influence of Low-Intensity Electromagnetic Field on Some Biological Parameters of Freshwater Crustaceans <Emphasis Type="Italic">Daphnia magna</Emphasis> Straus

We have studied the effects of a low-intensity electromagnetic field (EMF) with a frequency of 30 MHz in continuous-wave and amplitude-modulation modes on Daphnia magna in a laboratory culture. The exposure range is from 10 to 10000 s. We examine the parental generation (irradiated) and three subsequent (F₁–F₃) generations (nonirradiated). It is found that irradiation does not affect the total fertility of any specimen in four generations (P–F₃), except for continuous EMF exposure for 10000 s, which increases the total fertility in generations F₂ and F₃ by 23 and 43%, respectively. Electromagnetic radiation has a significant impact on offspring quality and causes fetal abnormalities in the offspring of all generations.     

Spectrofluorimetric detection of two states during melting of ribonuclease T1

The melting temperature of ribonuclease T1 was studied by the fluorescent method. It was shown that in the melting region the tryptophanyl fluorescence spectrum of the protein containing a single tryptophanyl is the sum of two simple spectra typical for tryptophanyl located in the hydrophobic environment and for tryptophanyl completely accessible to aqueous solvent, correspondingly. This implies the evidence of two forms of the protein, i.e. native (folded) and denatured (unfolded), in the transition region. No intermediate states were found in measured quantities. Therefore, ribonuclease T1 melting process corresponds to the two states model. The free energy of native structure stabilization of the protein at room temperature is delta G approximately equal to 37 kJ/mol.     

Genetic polymorphism of Russian,European, and Asian chicken breeds as revealed with DNA and protein markers

The variation in polymorphic DNA (RAPD and minisatellite) and protein markers was compared for nine Russian chicken breeds differing in morphological and productivity types and in origin, three European egg breeds, and three broiler breeds of the Asian origin. Genetic diversity indices were calculated for each breed group and each marker type and were used to construct dendrograms of genetic similarity. In all breed groups, minisatellites and RAPD markers revealed higher genetic diversity as compared with protein markers. With any type of markers, genetic diversity of the Russian and Asian broiler breeds proved to be significantly higher than that of the European egg breeds. The differentiating potentialities of molecular and genetic biochemical markers at the breed level and the origin of the Russian chicken breeds are discussed.     

Plasmid mediated expression of human growth hormone increases splenocytes proliferative response in vivo

As far as a physiological state of immune system cells is of great importance, for the investigation of the growth hormone influence on spleen T-lymphocytes ability to divide, we utilised plasmid-mediated gene transfer of hGH cDNA regulated by a powerful human cytomegalovirus immediate-early (CMV-IE) enhancer-promoter. The femur muscles of mice were injected with 50 mg of the plasmid DNA and then electrostimulated. 7 days later muscle tissues were harvested, and hGH DNA and RNA presence were proved by Southern and Northern blot analysis, respectively. Splenocytic proliferative response after ConA stimulation was shown to be increased by 6.8 times in experimental mice comparing to controls. Besides that in mice treated with plasmid vector increased cellularity of spleen. These results demonstrate that gene transfer of hGH is one of possible methods to increase immunity in aging organisms.     

The lifespan of the cladoceran Ceriodaphnia affinis Lilljeborg in a laboratory culture

The lifespan of the cladoceran Ceriodaphnia affinis Lilljeborg in a laboratory culture has been determined. The lifespan decreases in June and from November to December and it increases from February to March and from August to September. Minor changes in temperature over the year (21±3°C) have no direct effect on the lifespan of the animals. The average lifespan proves to be a more variable parameter than the maximum lifespan.     

Stimulation of life processes in Ceriodaphnia affinis Lilljeborg (Crustacea,Anomopoda) at low concentrations of potentially toxic substances

The effects of ethanol, potassium chloride, and potassium dichromate on the lifespan and fecundity of cladoceran Ceriodaphnia affinis have been studied experimentally. The average lifespan and female fecundity increase at ethanol concentrations of 0.002 mg/L and 0.02 mg/L and at a potassium chloride concentration of 0.1 mg/L. Only a concentration of 0.0001 mg Cr/L increased the lifespan of the cladocerans by 108% in comparison with the control condition within a wide spectrum of tested concentrations of this agent. The reason for such a phenomenon is discussed, as is its ecological role.     

Effect of heavy metals on samples and model population of rotifers <Emphasis Type="Italic">Brachionus plicatilis</Emphasis> muller at different salinity

Effect of Cu²⁺ and Cr⁶⁺ on samples and on model populations of rotifers Brachionus plicatilis Muller in chronic conditions at different salinity was investigated. The LC₅₀ (48 h) at salinities 10, 20, and 30‰ were 53.9, 0.25, and 0.1 mg Cr/l, respectively. The concentrations of 0.3 mg Cu/l and more led to the death of 100% of rotifers in 48 h in salinities 10 and 20‰, but at 30‰ the concentration 0.1 mg Cu/l was lethal. LC₅₀ (48 h) at salinities 10, 20, and 30‰ were 7.06, 0.07, and 0.01 mg Cu/l, respectively. The toxicity of Cr and Cu for samples became higher with increasing salinity. For the model populations, the salinity influenced toxicity only at high concentrations of Cr (20 mg/l). The effect of Cr was higher on samples than on model populations.