Genetic differences in milk proteins among laboratory rats (Rattus norvegicus)

Genetic differences in the electrophoretic pattern of milk proteins were observed among different inbred rat strains. The results of segregation analysis made on a limited number of females is consistent with the hypothesis of two codominant autosomal alleles system.     

Light-induced excitation quenching and structural transition in light-harvesting complex II

Light-induced fluorescence quenching of chlorophyll a in light-harvesting complex II (LHCII) incorporated into liposomes was examined. The rate of fluorescence quenching was found to depend on the incubation temperature. The effect was almost not observed at liquid nitrogen temperature, demonstrated a lag phase after onset of light at temperatures below 25 °C and was most distinctly pronounced at temperatures above 25 °C. Energetic uncoupling of accessory xanthophylls and chlorophyll a, and energetic uncoupling of chlorophyll b and chlorophyll a were observed as accompanying the excitation quenching. The observed changes were reversible during dark incubation. Similar energetic uncoupling was also observed in darkness, induced by the increase in temperature. Additionally, the temperature characteristics of fluorescence measurements displayed a pronounced transition in the region of 22–25 °C. The experiments carried out with the monomolecular layer technique in dicated a structural transition of LHC II in the same temperature region as demonstrated by an increase in the mean molecular area of LHC II at the argon-water interface. Alterations in surface topography induced by temperature changes could also be observed with scanning force microscopy of LHC II monolayers deposited as Langmuir-Blodgett films onto glass slides. The transition was found to be associated with the enhanced excitation energy consumption by the protein, monitored by calorimetric measurements. It is proposed that the observed transition efficiently protects LHC II against overexcitation-related damage and is therefore of physiological importance.     

Ensuring recovery of intact RNA from rat pancreas

The isolation of intact RNA from rat pancreas is compromised by autolysis and by the presence of endogenous ribonucleases. In order to ameliorate recovery we systematically investigated available RNA extraction methods and paid particular attention to the influence of frozen storage and ribonuclease inhibition strategies on overall yield and quality of RNA. Modifications to the basic procedure of Chomczynski and Sacchi (1987) are described which allow, reproducibly, to obtain rat pancreatic RNA suitable for Northern blot hybridization, RT-PCR, and differential display analysis.     

Is sampling subjectivity a distorting factor in surveys for vegetation diversity?

Sampling design has long been a key methodology issue of vegetation science. There are still unsolved problems, amongst which the influence of the positioning (spatial arrangement) of plots remains a basic one. Random sampling is considered the only statistically valid option, along with its amendment by stratifying. However, huge amounts of plot-sample data originated from using subjective plot positioning, involving a great deal of the author’s judgement, experience and bias. Field studies examining the role of subjectivity within a larger area (a landscape) are lacking. In the presented case-study, datasets sampled using computer-based geographically stratified random (R) and field-based subjective (S) designs are compared. In 1999–2000, 120 R and 244 S plots were spread across some 270 km². Their properties are compared regarding the differences in vegetation variability by ordination, and diversity by rarefaction. Although the differences are not conspicuous, both datasets partly contain different vegetation types and the S dataset contains at least some species-richer plots. The number of R plots had been clearly underrated while the expected species diversity values were nearly reached by the S. More R than S plots would probably be needed to reach the expected diversity maximum.     

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.     

Reactions to disturbances in the context of antipredatory behaviour in a solitary subterranean rodent

We investigated reactions of free-living silvery mole-rats (Heliophobius argenteocinereus) to anthropogenic disturbances. Mole-rats detected soil vibrations caused by man carefully walking at a distance of up to 6 m (proved by radio-telemetry). Occasionally, mole-rats encountered outside a nest retreated there after this type of disturbance. After having their burrows broken into, the mole-rats retreated into deep tunnels, separating themselves from the rest of the burrows by soil plugs. Trapping success of silvery mole-rats using live traps for subterranean rodents was low, which contrasts with data so far published on social bathyergids. Antipredatory function of examined behaviours is discussed.