The incidence of mistletoe (<Emphasis Type="Italic">Viscum album</Emphasis> ssp. <Emphasis Type="Italic">abietis</Emphasis>) on silver fir (<Emphasis Type="Italic">Abies alba</Emphasis>) in Croatia

The research on incidence of mistletoe (Viscum album ssp. abietis) on silver fir (Abies alba) was carried out in natural fir stands in Croatia. In the area of Gorski Kotar 32.8 % of the examined dominant fir trees were infected with mistletoe. The mistletoe incidence was presented according to the damage degrees of silver fir from 0 (healthy trees) to 4 (dead trees), rated by the crown defoliation and needle discoloration. With the increase of incidence, mistletoe spreads more onto more vital, i.e. less damaged trees. In the Dinaric Alps 28.6% of the examined fir trees were infected, this percentage amounting to 27.1% for the mountainous regions between the Sava and Drava rivers. The site and stand parameters (exposure, elevation, site quality, forest community and crown closure) were analysed in order to establish whether there was a correlation between these parameters and mistletoe incidence. There was a negative correlation between the elevation and mistletoe incidence. Among the compartments with a closed stands there were considerably less compartments with higher mistletoe incidence than among compartments with a sparsely closed and understocked stands. The other analysed site and stand parameters individually had no significant influence on mistletoe incidence. The correlation of silver fir mortality in 2004 and mistletoe incidence in 2002/03 was analysed, and their strong correlation was established. Mistletoe could be considered as a bioindicator of silver fir decline, and probably a significant contributor to that decline. In the areas where mistletoe incidence is great it can be presumed that silver fir is significantly damaged.     

Energy characteristics of the transport of monovalent cations in ascites tumor cells

The intensity of O2 adsorption by ascite tumour cells does not practically depend on the monovalent cation concentration gradient between the cells and the incubation medium, whereas the rate of glycolysis decreases simultaneously with the diminution of the concentration gradient. In synchronized cultures at the beginning of the mitotic cycle, the bulk of ATP resynthesized via glycolysis is utilized for the synthesis of biopolymers, whereas that at the end of the S-phase and in the G2-phase--for cation transport across plasma membranes. From 35 to 100% of the whole amount of ATP resynthesized via glycolysis is utilized for transport purposes. The experimental results and theoretical calculations suggest that in glucose-containing media Na+ transport increases from 0.75 to 1.78 pmol/hour on a per cell basis. The activation of Na+ transport is due to the exchange of protons formed via glucose conversion into lactate for Na+, i.e., to the stimulation of Na+/H+ antiport. The permeability of plasma membranes for K+ increases 2.75-fold, while the passive flux of Na+ diminishes. It is concluded that the observed increase in the Na+/K+ ratio in ascite tumour cells is connected with their enhanced ability to synthesize lactic acid. Presumably, glycolysis is one of regulatory mechanisms of intracellular ratios of monovalent cations.     

Chlorophyll mutations after low doses of chronic irradiation of barley

The chlorophyll mutation rate on a large number of plants after the dose rates 0·004–16·800 R/day during the whole vegetation cycle was examined. The mutation frequency increases as early as after the dose rate 4 mR/day. The dose rate of approximately 8 mR/day is necessary to double the mutation frequency.     

Hydrogen ion block of the sodium pore in squid giant axons

The block of squid axon sodium channels by H ions was studied using voltage-clamp and internal perfusion techniques. An increase in the concentration of internal permeant ions decreased the block produced by external H ions. The voltage dependence of the block was found to be nonmonotonic: it was reduced by both large positive and large negative potentials. The ability of internal ions to modify the block by external H+ is explained by a competition among these ions for a binding site within the pore. The nonmonotonic voltage dependence is consistent with this picture if the hydrogen ions are allowed to be permeant.     

Protoflavones: a class of unusual flavonoids as promising novel anticancer agents

Protoflavones represent a less widespread, unique class of natural flavonoids with a non-aromatic B-ring and a hydroxyl group at C-1′. Due to their recently discovered anticancer activity, these compounds have gotten into the focus of biomedical research during the past few years. The present review aims to give a brief summary on the available literature data on this special class of flavonoids, including their occurrence in plants and their bioactivity. A special emphasis is given on the anticancer potential of these compounds. Attempts for the development of certain synthetic/semi-synthetic protoflavone analogs as anticancer drugs, and structure–activity relationships are also discussed.