Pollination and embryo development in Brassica rapa L. in microgravity

Plant reproduction under spaceflight conditions has been problematic in the past. In order to determine what aspect of reproductive development is affected by microgravity, we studied pollination and embryo development in Brassica rapa L. during 16 d in microgravity on the space shuttle (STS-87). Brassica is self-incompatible and requires mechanical transfer of pollen. Short-duration access to microgravity during parabolic flights on the KC-135A aircraft was used initially to confirm that equal numbers of pollen grains could be collected and transferred in the absence of gravity. Brassica was grown in the Plant Growth Facility flight hardware as follows. Three chambers each contained six plants that were 13 d old at launch. As these plants flowered, thin colored tape was used to indicate the date of hand pollination, resulting in silique populations aged 8-15 d postpollination at the end of the 16-d mission. The remaining three chambers contained dry seeds that germinated on orbit to produce 14-d-old plants just beginning to flower at the time of landing. Pollen produced by these plants had comparable viability (93%) with that produced in the 2-d-delayed ground control. Matched-age siliques yielded embryos of equivalent developmental stage in the spaceflight and ground control treatments. Carbohydrate and protein storage reserves in the embryos, assessed by cytochemical localization, were also comparable. In the spaceflight material, growth and development by embryos rescued from siliques 15 d after pollination lagged behind the ground controls by 12 d; however, in the subsequent generation, no differences between the two treatments were found. The results demonstrate that while no stage of reproductive development in Brassica is absolutely dependent upon gravity, lower embryo quality may result following development in microgravity.     

A comparison of the immune response induced by DNA or by an inactivated vaccine against tick-borne encephalitis

BALB/c mice were immunized with recombinant plasmid DNA pSVK3-ENS1 and pcDNAI-NS3 containing, respectively, genes E-NS1 and NS3 of tick-borne encephalitis (TBE) virus. Antibodies to TBE virus proteins were detected in the blood sera of the immunized animals by the method of the enzyme immunoassay. Though the titers of virus-specific antibodies in the sera of mice immunized with protein vaccines exceeded those registered after immunization with DNA vaccines, essential protective immunity was observed after the use of both vaccines.     

Factor of salinity and adaptive capacity of recombinant strains of Escherichia coli and Bacillus subtilis

Effect of different concentrations of salts on natural and recombinant strains of Bacillus subtilis and Escherichia coli was studied. The recombinant strain of B. subtilis was found to be more osmotolerant than the wild-type strain of this bacterium, whereas the opposite situation was observed for the recombinant and wild-type strains of E. coli. Some salts exerted a bacteriostatic effect on E. coli and B. subtilis. The adaptive capacity of recombinant strains depended on the number of plasmid copies in the cells. The introduction of recombinant bacteria into model ecosystems resulted in the generation of their variants with increased osmotolerance.     

The study of heterogeneity of plasmid-bearing and plasmid-f ree populations of Bacillus subtilis under different environmental conditions

The population heterogeneity of recombinant and plasmid-free Bacillus subtilis strains introduced into aquatic microcosms was studied. After introduction, the population of the plasmid-free strain B. subtilis 2335 in microcosms has long been represented by both vegetative cells and spores, whereas, already ten days after introduction, the population of the recombinant strain B. subtilis 2335/105 (Km[symbol: see text]nf+) was represented only by spores. The number of plasmid copies in the spore isolates of the recombinant strain was the same as before introduction, but the plasmid abundance in the vegetative isolates of this strain decreased. The isolates of B. subtilis 2335/105 obtained from microcosms and the variants of this strain obtained by ten successive subcultures on M9 and 0.1 x M9 media with and without kanamycin (Km) differed in the number of plasmid copies, Km resistance, and maximum biomass yield during batch cultivation. Irrespective of the presence of Km, more than 50% of the variants subcultured on M9 medium showed reduced plasmid abundance. At the same time, about 70% of the variants subcultured on 0.1 x M9 medium with Km and 90% of the variants subcultured on the same medium without Km retained the initial number of plasmid copies. The variants subcultured on media with Km retained the initial biomass level. In more than 70% of the variants isolated from media without Km, the biomass yield increased.     

Fumaric acid is a competitive inhibitor of wheat germ lipoxygenase

Fumaric acid is shown to be a competitive inhibitor of wheat germ lipoxygenase.     

Distribution, biomass and primary production of an Ahnfeltia tobuchiensis (Ahnfeltiales, Rhodophyta) population in the Bay of Izmena, Kunashir Island

Regularities of distribution and primary production of an Ahnfeltia tobuchiensis (Kanno et Matsubara) Mak. population, an agar-containing red alga, were studied in the Bay ot Izmena. Experiments were conducted in a flow-through system under conditions similar to algal habitats. The population of A. tobuchiensis unattached to the ground may be from a few centimeters to as much as 1 m thick. It has been shown that only the upper part of a stratum 15–20 cm thick receives a sufficient amount ot light to realize its production potential. While 15–20% of photosynthetically active radiation (PAR) of that falling on the water surface reaches the stratum surface, only 0.1% of PAR from that falling on the water surface penetrates through stratum 15 cm thick. It has been shown for A. tobuchiensis that its photosynthetic rate curve during the daytime mainly follows the PAR intensity curve. The highest values of photosynthetic rate have been measured in the afternoon when PAR reaches its maximum. It is noted that a stratum 15–20 cm thick has peak values ot net primary production (NPP) which averages 3.2 g C m^?2 day^?1. The total area of A. tobuchiensis population was 23.4 km², and its biomass was 125 000 tons in this area. On average, the NPP of the A. tobuchiensis population made up in summer and in autumn was 46.8 and 25.0% of its biomass, respectively.     

Enzymes of SPZ7 phage: Isolation and properties

Bacteriophage enzyme preparations exolysin and endolysin were studied. Exolysin (a phage-associated enzyme) was obtained from tail fraction and endolysin from phage-free cytoplasmic fraction of disintegrated Salmonella enteritidis cells. A new method for purification of these enzymes was developed, and their molecular masses were determined. The main catalytic properties of the studied enzymes (pH optimum and specificity to bacterial substrates) were found to be similar. Both enzymes lyse Escherichia coli cells like chicken egg lysozyme, but more efficiently lyse S. enteritidis cells and cannot lyse Micrococcus luteus, a good substrate for chicken egg lysozyme. Similar properties of exolysin and endolysin suggest that these enzymes are structurally similar or even identical.     

Induction of permeability of the inner membrane of yeast mitochondria

The current view on apoptosis is given, with a special emphasis placed on apoptosis in yeasts. Induction of a non-specific permeability transition pore (mPTP) in mammalian and yeast mitochondria is described, particularly in mitochon-dria from Yarrowia lipolytica and Dipodascus (Endomyces) magnusii yeasts, which are aerobes possessing the fully competent respiratory chain with all three points of energy conservation and well-structured mitochondria. They were examined for their ability to induce an elevated permeability transition of the inner mitochondrial membrane, being subjected to virtually all conditions known to induce the mPTP in animal mitochondria. Yeast mitochondria do not form Ca²⁺-dependent pores, neither the classical Ca²⁺/P_i-dependent, cyclosporin A-sensitive pore even under deenergization of mitochondria or depletion of the intramitochondrial nucleotide pools, nor a pore induced in mammalian mitochondria upon concerted action of moderate Ca²⁺ concentrations (in the presence of the Ca²⁺ ionophore ETH129) and saturated fatty acids. No pore formation was found in yeast mitochondria in the presence of elevated phosphate concentrations at acidic pH values. It is concluded that the permeability transition in yeast mitochondria is not coupled with Ca²⁺ uptake and is differently regulated compared to the mPTP of animal mitochondria.     

Effects of chronic imipramine treatment on behavior in mice of congenic strains AKR and AKR.CBA-D13Mit76 differing in the distal fragment of chromosome 13

Congenic mouse strain AKR.CBA-D13Mit76 carries the 59-70 cM fragment of chromosome 13 transferred from genome of cataleptic CBA/Lac strain to genome of AKR/J none-cataleptic strain. This fragment contains the major gene of predisposition to pinch-induced catalepsy. We investigated contribution of the fragment to regulation of sensitivity of catalepsy, sexual motivation and social investigation to classical tricyclic antidepressant imipramine. The sexual motivation was higher in AKR.CBA-D13Mit76 than in AKR mice. Chronic imipramine treatment (25 mg/kg) reduced it in AKR.CBA-D13Mit76 mice and had no effect on weakly expressed sexual motivation of AKR males. No significant effects of genotype or chronic imipramine treatment on characteristics of social interest were observed. Imipramine failed to alter catalepsy expression in AKR.CBA-DI3Mit76 mice. Possible molecular genetic mechanisms underlying difference in behavioral responses to antidepressant administration are discussed.