Mathematical analysis of the oncornavirus maturation process (virion RNA conversion and morphological condensation)

The rate of the maturation process of avian myeloblastosis virus experimentally estimated on the basis of genomic viral RNA conversion and morphological transition of virions was mathematically analysed. Three mathematical models were suggested and fitted to experimental data. It was found that: (a) model of simple kinetics (Model 1) does not agree with experimental data. Therefore, two hypotheses were considered in further mathematical modelling: (b) virions are identical in time of budding: maturation is dependent on the presence of a virion component which is degraded with time (Model 2). This model agrees with experimental data in all stages of the maturation process. (c) Virions are released from cells at different stages of assembly (Model 3). This model differs from experimental data especially in early stages of maturation. The hypothesis used for the construction of Model 2 seems to be the most plausible to explain the maturation process and is in agreement with data of murine leukemia virus maturation which was found to be accomplished by cleavage of p70 precursor protein.     

Evaluation of potential deer browsing impact on sunflower (<Emphasis Type="Italic">Helianthus annus</Emphasis>)

Large herbivores are the key species for game management in the Central Europe. Analyses of factors affecting the feeding behaviour of herbivores and consequences of their browsing are therefore highly important both for farmers and for game managers as the protective measurements should be focused on the most threatened fields. The influence of fallow (Dama dama) and roe deer (Capreolus capreolus) browsing during vegetation period on sunflower production was studied. The experiment was carried out in 2006 on a field located near a forest complex. We marked out pairs of paired permanent plots and monitored deer impact regularly from the emergence of plants until the harvest. Herbivores damaged the sunflower intensively immediately after the emergence at the height of 1 to 2 cm above the ground. When the plants had reached approximately 15-40 cm in height, deer browsed the top shoots and as the plants grew higher the browsing was restricted to leaves or to substitute stems of the previously browsed plants. Sunflower ceased to attract big herbivores in flowering stage. Browsing significantly affected the yield of seeds. Approximately one half of the plants that had been damaged in early stage died as well as 12.5% of plants that had been damaged at second term; the rest produced substitute stems. Almost 33% of the substitute stems did not form disc florets; the second third of them formed disc florets with a diameter of 6-8 cm, and the last third set disc florets with a diameter of 8-10 cm.