Cytophotometric and biochemical research on the amount of DNA in the nuclei of loach embryos injected with low-molecular RNA

The cell cycle structure in the cells of loach embryos at the early blastula stage (5 h of development at 21 degrees) is markedly altered under the influence of injection of homologous low molecular weight nuclear RNA and, as a result, the number of cells in G2-phase. The DNA amount in the embryo increases by 20%. At the midblastula stage (7 h) no increase in the number of cells in G2-phase was found.     

Geophytes–herbivore interactions: reproduction and population dynamics of <Emphasis Type="Italic">Anemone coronaria</Emphasis> L.

Anemone coronaria, an attractive Mediterranean geophyte, seems to disappear from grazing-protected areas in Israel. We experimentally examined the ecological mechanism driving the decline of this geophyte. Ten plot-pairs were established, half we fenced as grazing exclosures and half were grazed by beef cattle. Grazing clearly reduced herbaceous biomass, increased relative solar photosynthetic active radiation (PAR) at ground level, but had almost no effect on soil properties. Grazing did not affect the number of flowers and young fruits produced by A. coronaria, nor the percentage fruit-set at the plot scale, indicating no effect on flowering, pollination, or on resource allocation to reproduction. Five years after grazing exclusion, Anemone seedling and adult plant densities were higher in grazed than in ungrazed plots. We propose a model explaining our results that can be applied also to other similar ecosystems: excluding grazing increased biomass and height of the herbaceous community and reduced relative PAR at ground level. Consequently, seedling, adult plant and flowering Anemone plant densities were lower in ungrazed plots. We recommend adding seasonal grazing as a management tool when vegetation outcompete light demanding geophytes that we wish to conserve.     

Testing the efficacy of antimicrobial peptides in the topical treatment of induced osteomyelitis in rats

Joint replacement infections and osteomyelitis are among the most serious complications in orthopaedics and traumatology. The risk factors for these infections are often bacterial resistance to antimicrobials. One of the few solutions available to control bacterial resistance involves antimicrobials, which have a different mechanism of action from traditional antibiotics. Antimicrobial peptides (AMP) appear to be highly promising candidates in the treatment of resistant infections. We have identified several AMP in the venom of various wild bees and designed analogues that show potent antimicrobial activity and low toxicity against eukaryotic cells. The aim of the present study was to test the efficacy of one of those synthetic peptide analogues for the treatment of acute osteomyelitis invoked in laboratory rats. Femoral cavities of 20 laboratory Wistar rats were infected with Staphylococcus aureus. After 1 week, eight rats received an injectable calcium phosphate carrier alone, another eight rats were treated with a calcium phosphate mixed with AMP, and four rats were left without any further treatment. After another week, all rats were euthanized and radiographs were made of both the operated and healthy limbs. The animals with the carrier alone exhibited more severe acute osteomyelitis on radiographs in comparison to the recipients of the calcium phosphate carrier loaded AMP and untreated infected individuals. Based on the results of the above mentioned experiment, it was concluded that when injected directly into the site of femoral acute osteomyelitis, the calcium phosphate carrier mixed with AMP reduced osteomyelitis signs visible on radiographs.     

Optimization of the exposure of normal and transformed cell populations to phase-specific agents

Dynamic behavior of stem cells population of the "critical" tissue (normal population) and tumor cell population under periodic treatment with a phase-specific cytotoxic agent was considered. The results were used for optimization of anticancer chemotherapy. The schedules of treatment were found which provide a maximum rate of tumor-cell elimination for any given rate of the normal population size decrease. If the mean generation times of normal and tumor populations differ (which was stated for many tumors), usage of the optimal period markedly increases the selectivity of therapy, while application of other periods can result in selective elimination of the normal population. Problems concerned with practical realization of the proposed regimes are discussed.     

Genetic transformation of alfalfa somatic embryos and their clonal propagation through repetitive somatic embryogenesis

Genetically transformed alfalfa (Medicago sativa L., cv. Zajearska 83) plantlets were obtained by inoculating somatic embryos with Agrobacterium tumefaciens strains A281/pGA472 and LBA4404/pBI121. Single somatic embryos, 5–7 mm long, were released from a repetitively embryogenic culture, wounded, and cocultivated with the bacteria. The agar-solidified culture medium contained mineral salts, vitamins, 40 g l^–1 sucrose, 1 g l^–1 yeast extract and 0.05 mg l^–1 BA. Five clones, transformed with A281/pGA472, and 4 clones transformed with LBA4404/pBI121, were selected for proliferation by repetitive somatic embryogenesis, on media containing 100 mg l^–1 of kanamycin. The transformation of kanamycin-resistant clones was confirmed by assaying the activity of neomycin phosphotransferase II and/or -glucuronidase enzymes, and by the Southern blot analysis. It is suggested that the transformation/regeneration system based on somatic embryogenesis may be suitable for establishing transgenic alfalfa lines. The relatively low frequency of embryo transformation is compensated for by abundant proliferation in secondary somatic embryogenesis.Abbreviations BA 6-benzyladenine - GUS -glucuronidase - Km kanamycin - NPTII neomycin phosphotransferase II - X-gluc 5-bromo-4-chloro-3-indolyl--glucuronic acid - BM basal medium