Human impact on vegetation at the Alpine tree-line ecotone during the last millennium: lessons from high temporal and palynological resolution

Three mires and a small lake in the Swiss and Austrian Alps were studied palynologically at high resolution, covering the last 1,000, 400, 50 and 1,200 years, respectively. Methodological lessons include: (1) Sub-decadal resolution in upper, little-decomposed peat layers reveals recurrent marked fluctuations in both percentages and influx of regional tree-pollen types, reflecting variations in pollen production rather than in plant-population sizes. (2) Intermittent, single-spectrum pollen maxima in samples of sub-decadal resolution indicate pollen transport in clumps. This type of pollen transport may remain unrecognized in sections with lower sampling resolution, which may then lead to inappropriate interpretation in terms of plant-population sizes. (3) The detection of short-lived phases of human impact in decomposed peat requires sampling intervals as close as 0.2 cm. (4) PAR (pollen influx) may reflect vegetation dynamics more faithfully than percentages. Reliable PAR, however, is difficult to achieve in Alpine mires due to past human impact on peat growth, even when complex depth–age modelling techniques are used. Critical comparison of PAR with percentages is therefore essential. (5) Careful consideration of spatial scales in pollen signals (local–regional and subdivisions) is essential for a realistic palaeo-ecological interpretation. Results in terms of past human impact on vegetation are summarized as follows: (1) Trends in pollen types reflecting regional human action are in general agreement with earlier findings for the western Swiss Alps, allowing for regional differences. (2) All mires in the Alps investigated here and in an earlier study experienced human impact during the last millennium. The studied small lake, lying in sub-alpine pasture, records forest dynamics at a lower elevation since a.d. 800.     

Biology, serology and biochemistry of leucemogenic viruses derived from a radiation-induced tumor of C57BL mice

Two distinct rat propagates of a radiation leukemia virus (RadLV-Rs) from the C57BL mouse respectively induced characteristic leukemogenic effects. These were found to be related with the infection titers of the isolates, but not with either their antigenic specificities or their viral and proviral genome sequences.     

Inhibition of cell wall synthesis and acylation of the penicillin binding proteins during prolonged exposure of growing Streptococcus pneumoniae to benzylpenicillin

Growing cultures of an autolysis-defective pneumococcal mutant were exposed to [3H]benzylpenicillin at various multiples of the minimal inhibitory concentration and incubated until the growth of the cultures was halted. During the process of growth inhibition, we determined the rates and degree of acylation of the five penicillin-binding proteins (PBPs) and the rates of peptidoglycan incorporation, protein synthesis, and turbidity increase. The time required for the onset of the inhibitory effects of benzylpenicillin was inversely related to the concentration of the antibiotic, and inhibition of peptidoglycan incorporation always preceded inhibition of protein synthesis and growth. When cultures first started to show the onset of growth inhibition, the same characteristic fraction of each PBP was in the acylated form in all cases, irrespective of the antibiotic concentration. Apparently, saturation of one or more PBPs with the antibiotic beyond these threshold levels is needed to bring about interference with normal peptidoglycan production and cellular growth. Although it was not possible to correlate the inhibition of cell wall synthesis or cell growth with the degree of acylation (percentage saturation) of any single PBP, there was a correlation between the amount of peptidoglycan synthesized and the actual amount of PBP 2b that was not acylated. In cultures exposed to benzylpenicillin concentrations greater than eight times the minimal inhibitory concentration, the rates of peptidoglycan incorporation underwent a rapid decline when bacterial growth stopped. However, in cultures exposed to lower concentrations of benzylpenicillin (one to six times the minimal inhibitory concentration) peptidoglycan synthesis continued at constant rate for prolonged periods, after the turbidity had ceased to increase. We conclude that inhibition of bacterial growth does not require a complete inhibition or even a major decline in the rate of peptidoglycan incorporation. Rather, inhibition of growth must be caused by an as yet undefined process that stops cell division when the rate of incorporation of peptidoglycan (or synthesis of protein) falls below a critical value.     

The effects of temperature and salinity on vital biological functions of the Antarctic crustacean Serolis polita

Effects of temperature rise (from 0 to +5°C) and salinity decline (from 34 to 30 psu) on vital biological functions of the Antarctic isopod Serolis polita were studied in laboratory experiments. Behavioural reactions to food odour, as well as righting responses and reburying in the sediments, were measured. Both temperature increase and salinity decline impaired the ability of S. polita to perform these biological functions critical for their long-term survival, by lowering the number of isopods able to right and rebury in the sediment, increasing time-to-right, reducing locomotory activity and weakening isopod reaction to food odour. Significant interactive effects between temperature and salinity on time-to-right and time spent swimming were observed, with isopods being more vulnerable to lower salinities when exposed to higher temperatures. Some biological functions (righting, reburying) were more sensitive to temperature and salinity changes than others (swimming). In conclusion, our findings strongly suggest that Antarctic isopods are vulnerable to environmental changes, and their ability to cope with them is limited.     

Induction of normal levels of genetic transformation in a class of endonuclease-defective mutants of Pneumococci.

Pneumococcal mutants were isolated that showed no zones of DNA hydrolysis around the bacterial colonies, even after prolonged incubation on the surface of agar plates containing DNA and methylgreen. Lysates of such mutants contained only very low levels of endonuclease activity; the mutants were also defective in genetic transformation even though they could still bind DNA to their surface. However, the same mutants could be made to undergo normal, high frequency genetic transformation by treatment with the activator protein, under appropriate conditions. The same treatment caused no detectable increase in the endonuclease level. Poor transformability of these mutants seems to be related to an inhibitory factor(s) released into the growth medium. Activation in the presence of this factor(s) leads to an abnormal (non-productive) DNA adsorption-both in mutant and in wild type pneumococci.     

Active polyphenolic compounds,nutrient contents and antioxidant capacity of extruded fish feed containing purple coneflower (Echinacea purpurea (L.) Moench.)

The growth of fish is directly dependent on feed composition and quality. Medicinal plants can be added to fish feed as adjuvant therapy for the prevention of fish diseases. The purple coneflower (Echinacea purpurea (L.) Moench.) has been reported to have multiple biological effects, including immunomodulatory and antioxidant activity. The most active compounds of E. purpurea are polyphenols - caffeic acid derivatives: caftaric acid, chlorogenic acid, cynarin, echinacoside and cichoric acid.Due to a relatively limited number of studies on the use of the purple coneflower as a nutritional supplement for fish feeding, extruded fish feed with addition of Echinacea roots was produced. In the feed total phenolic content, selected polyphenol contents, the energetic value, nutrient contents and antioxidant capacity were examined.The results indicate that fish feed with addition of the Echinacea has a great potential to be a good source of natural radical scavengers, for example polyphenols, and nutritive ingredients. Antioxidant properties of feed were well correlated with the coneflower content. The study findings confirmed that high-temperature extrusion-cooking process does not deactivate phenolic antioxidant compounds, which are present both in the Echinacea roots and in the final product. Fish feed with addition of E. purpurea can be used as a nutritional supplement in the prevention of fish diseases caused by oxidative stress.