Ethylene-Insensitive Arabidopsis Mutants etr1-1 and ein2-1 Have a Decreased Freezing Tolerance.

The freezing tolerance of Arabidopsis thaliana (L.) Heynh. was studied in relation to functioning of the ethylene signaling pathway. Constitutive freezing tolerance was compared in wild-type plants (ecotype Col-0) and ethylene-insensitive mutants etr1-1 and ein2-1. For the first time it was established that the ethylene-insensitive mutants had a 25-30% lower net photosynthesis rate, a decreased content of soluble sugars, and, as a result, a lower freezing tolerance. Our work provides evidence that the perception and transduction of ethylene signal are necessary for constitutive tolerance of Arabidopsis to low temperature.

[Ability of winter wheat plants to become hardened against frost related to peculiarities of carbon dioxide exchange, biomass synthesis, and various forms of water-soluble carbohydrates].

The donor-acceptor relation (DAR) in a plant under cold exposure to frost was studied in the plants of winter wheat (Triticum aestivum L.) Mironovskaya 808 cultivar and its allocytoplasmatic hybrid containing alien cytoplasm of goat grass (Aegilops ovata L.) and grown in a water culture until phenophase, from two leaves until branching. The alteration of DAR was processed by treatment of plant with solutions of diuron and paraquat the photosynthesis inhibitors, keeping plants in the dark, changing from mixotrophic to autotrophic nutrient, and also through the exchange of nutrient solution to distillate water. Determination of frost-resistance on the basis of survival percentage among frozen plants is more significant (R = 0.701-0.999) and related to the frost-resistance of leaves, the correlation P/Rd between speeds of true photosynthesis at light saturation (P) and plant dark respiration (Rd), the approximate speed of dry plant biomass alteration, the total content of water-soluble sugars, and the ratio of di- and monosaccharides (sucrose, glucose + fructose) in leaves. The importance of all the indexes mentioned above for acquiring resistance to low temperatures in plants is discussed in the present article.

[Specific features of source-sink relations in alloplasmic hybrid of winter wheat with alien cytoplasm of goatgrass with emphasis on resistance to low temperature stress].

We studied the influence of alien cytoplasm of spring goatgrass Aegilops ovata L. on some physiological parameters in winter wheat (Triticum aestivum L.), Mironovskaya 808, under normal conditions and in the case of modified source-sink relations. Measurements of relative rates of plant dry matter growth and its distribution among organs, CO2 exchange (photosynthesis upon light saturation and dark respiration), content of sugars (sucrose + glucose + fructose) and their ratio in leaves, frost hardiness, and indices of membrane stability and damage of leaves by frost have shown that, on average, alloplasmic hybrid differed from the initial cultivar by almost all parameters. Reduced frost hardiness, increased index of leaf damage by frost, lowered leaf content of sugars, and reduced sucrose/(glucose + fructose) ratio in the alloplasmic hybrid were combined with higher roots/leaves ratio, relative rate of dry matter growth, and photosynthesis and respiration rates. The alloplasmic hybrid was more tolerant to decreased source strength in source-sink relations as compared to the initial cultivar.

[Role of NO-mediated mechanisms in post-irradiation changes of neurohormonal regulation of the heart function]. / Rol' NO-oposredovannykh mekhanizmov v postradiatsionnykh izmeneniiakh neirogormonal'noi reguliatsii funktsii serdtsa.

Investigations on isolated Langendorff-perfused rat heart have shown that after the impact of ionizing radiation in 1 Gy dose the myocardial contractility and relaxation are decreased. The inhibition of NO synthesis attenuates chrono- and inotropic responses of the heart and reaction of coronary vessels to norepinephrine (NE), increases negative inotropic and vasoconstrictor effects of carbamylcholine (CCh). In the irradiated animals the reaction of isolated heart to NE and CCh is decreased. The post-irradiation changes in adreno- and cholinoreactivity caused not only by changes in receptor sensitivity and density, but also by impairment of NO-mediated regulation of coronary flow and biomechanical heart function.

[The pathogenesis of Q fever in the intratracheal infection of guinea pigs]. / Patogenez Ku-likhoradki pri intratrakheal'nom infitsirovanii morskikh svinok.

The intratracheal introduction of R. burnetii is the method of infection, highly similar to aerogenic infection, the most widespread route of R. burnetii infection in humans under natural conditions. This suggests that the study of the pathogenesis of Q fever resulting from the intratracheal infection of guinea pigs is highly topical. The authors have established that after the penetration of the infective agent generalized infection develops in the animals with rickettsiae accumulating mostly in the lungs and the organs of the reticuloendothelial system being affected; this infection is commonly more pronounced than that developing after the intraperitoneal inoculation of rickettsiae.

[A comparative study of Coxiella burnetii strains differing in virulence in the intratracheal infection of guinea pigs]. / Sravnitel'noe izuchenie razlichaiushchikhsia po virulentnosti shtammov Coxiella burnetii pri intratrakheal'nom infitsirovanii morskikh svinok.

As found out in earlier investigations, after the intratracheal infection of guinea pigs with C. burnetii (the method of infection, most similar to aerogenic infection which is characteristic of Coxiella under natural conditions) the maximum amount of the infective agent is accumulated in the lungs of the animals, damaging the organs of the reticuloendothelial system. The present investigation has revealed that this method of infection makes it possible differentiate C. burnetii virulent strains, differing in the level of the accumulation of the infective agent in the lungs of guinea pigs.

[An experimental study of the immunogenic and protective properties of Coxiella burnetii strain M-44 and a live enteral vaccine against Q fever]. / Eksperimental'noe izuchenie immunogennykh i protektivnykh svoistv shtamma M-44 Coxiella burnetii i zhivoi énteral'noi vaktsiny protiv likhorodki Ku.

High effectiveness of C.burnetii strain M-44 was confirmed in experimental studies on subcutaneously immunized guinea pigs ¿correction of pig] after their intratracheal infection with the virulent culture of the infective agent. The study revealed that the dose necessary for the enteral immunization of guinea pigs and monkeys was 10(4.8) -- 10(5.0) times less than that needed for the oral immunization of the animals. Live enteral vaccine obtained on the basis of this strain possessed sufficiently pronounced immunogenic and protective properties, protecting 75% of immunized monkeys from subcutaneous infection with C.burnetii virulent culture.