The effect of lake restoration measures on the physical,chemical and phytoplankton variables of Lake Bled

Monthly changes of physical, chemical and biological variables due a combination of artificial inflow of clean water, removal of hypolimnetic water, and diversion of sewage were studied in Lake Bled from December 1980 to December 1982.During the winter period 1981/82 the species composition of the phytoplankton changed. New species replaced those observed in previous years. We conclude that the combined effect of these three lake restoration measures was responsible for the sudden disappearance ofOscillatoria rubescens D.C. A marked decrease in some nutrients and an increase in temperature and oxygen concentration also occurred.     

Thermodynamics of denaturation of α-chymotrypsinogen A in aqueous urea and alkylurea solutions

The effects of pH, urea, and alkylureas on the thermal stability ofα-chymotrypsinogen A (α-ctg A) have been investigated by differential scanning calorimetry (DSC) and UV spectroscopy. Heat capacity changes and enthalpies of transition ofα-ctg A in the presence of urea and alkylureas were measured at the transition temperature. Using these data, the corresponding Gibbs free energies, enthalpies, and entropies of denaturation at 25°C were calculated. Comparison of these values shows that at 25°C denaturation with urea is characterized by a significantly smaller enthalpy and entropy of denaturation. At all denaturant concentrations the enthalpy term slightly dominates the entropy term in the Gibbs free energy function. The most obvious effect of alkylureas was lowering of the temperature of transition, which was increasing with alkylurea concentration and the size of alkyl chain. Destabilization of the folded protein in the presence of alkylureas appears to be primarily the result of the weakening of hydrophobic interactions due to diminished solvent ordering around the protein molecules. At pH lower than 2.0,α-ctg A still exists in a very stable form, probably the acid-denatured form (A-form).     

Effect of spatial and temporal patterns of stress and disturbance intensities in a sub-Mediterranean grassland

Abstract

The present study examined a sub-Mediterranean pastoral system in the central Apennines (Italy) with a long history of grazing, where winter cold stress is alternated with summer drought stress. The research goals were to ascertain whether different floristic structures correspond to different stress conditions (xeric and semimesic), and whether peculiar functional plant traits (such as avoidance and tolerance mechanisms) respond to stress/disturbance intensities, and understand how vegetation reacts to changeable livestock pressure (through floristic and plant trait variations). Cluster analysis indicated that separate communities develop under different stress intensities. Other analyses highlighted how avoidance strategies predominate within the pastoral system. Observations of grazed and ungrazed patches conducted in 10-m transects revealed spiny cushion formation in semimesic grassland, where a brief period of overgrazing occurs in late summer, causing variations in plant community structure. All these results confirm the importance of historical grazing and current land use, showing how small disturbances and stress variations cause ecosystem responses. Best practices for management were identified. In xeric conditions, it is advisable that the intensity of disturbance be lessened, while in semimesic grassland overgrazing should be forbidden during the dry period, because it could facilitate the development of spiny patches, and subsequent spread of Brachypodium rupestre.     

Sex influences the taxanes content in Taxus baccata

Like other species of the genus Taxus, European yew trees contain taxanes, including paclitaxel (T) and its precursor 10-deacetylbaccatin III (10-DAB). Taxanes are one of the most effective anticancer drugs. This study was undertaken to describe the levels and patterns of taxane variation in the Sudetian region (SW Poland). Paclitaxel (T) and 10-deacetylbaccatin III (10-DAB) concentrations were analysed in five populations. Needles and twigs were analysed from 60 individuals (30 males and 30 females) in each population. In addition, morphometric measurements were taken in the populations to obtain light intensity coefficients (specific leaf area, SLA). High variability in the taxane contents at both intra and interpopulational levels was found. Nevertheless, females had a significantly higher taxane content compared to males. Because taxanes are carbon-based secondary metabolites, females have higher rate of gas exchange of females compared to males. This was probably an adaptation to greater reproductive effort incurred by females. In this regard, female individuals seem to be better for selecting elite cultivars with a higher taxane production. The relationship between light intensity and taxane content was not significant. Shading, important for optimizing crop production, should not reduce the concentration of taxanes.     

Palomena prasina (Hemiptera: Pentatomidae) vibratory signals and their tuning with plant substrates

Palomena prasina is interesting for the study of vibrational communication within the Pentatomid subfamily Pentatominae, because its host range is limited to woody plants, unlike the better known Nezara viridula, whose vibrational communication is commonly used as a model for the whole family. The vibrational repertoire of P. prasina was described several decades ago and is redescribed in this paper using modern methods for non-contact vibration recording. Additionally, we hypothesized that this species has retained the capacity for signal frequency variation necessary for tuning to resonance properties of various host plants of Pentatominae, but if the signals are emited in the absence of mechanical feedback, they are tuned more specifically to their native acoustic environment — woody plants. By recording live bugs signalling on different substrates and comparing spectral properties of their signals among substrates, we found that there is a match between the signals emitted on a woody branch and those emitted on a non-resonant surface, while spectral properties of signals emitted on herbaceous plants differ. Our findings provide evidence in support of the signal tuning hypothesis and shed further light on the crucial role of substrate in vibrational communication of insects.     

Upgrading the efficiency of dissimilatory sulfate reduction by Desulfovibrio desulfuricans via adjustment of the COD/SO4 ratio

The potential for upgrading the microbiological reduction of sulfates and for decreasing the organic pollution levels in industrial waste-water by the adjustment of the COD/SO4 ratio was investigated. The experiments involved waste-water samples coming from industrial pig farming, baker's yeast production and organic dye manufacture. The results show that in the presence of Desulfovibrio desulfuricans both the objectives can be achieved by abating the disproportion between the content of sulfates and that of organic substances.     

The SARS-CoV S glycoprotein: expression and functional characterization

We have cloned, expressed, and characterized the full-length and various soluble fragments of the SARS-CoV (Tor2 isolate) S glycoprotein. Cells expressing S fused with receptor-expressing cells at neutral pH suggesting that the recombinant glycoprotein is functional, its membrane fusogenic activity does not require other viral proteins, and that low pH is not required for triggering membrane fusion; fusion was not observed at low receptor concentrations. S and its soluble ectodomain, S(e), were not cleaved to any significant degree. They ran at about 180-200kDa in SDS gels suggesting post-translational modifications as predicted by previous computer analysis and observed for other coronaviruses. Fragments containing the N-terminal amino acid residues 17-537 and 272-537 but not 17-276 bound specifically to Vero E6 cells and purified soluble receptor, ACE2, recently identified by M. Farzan and co-workers [Nature 426 (2003) 450-454]. Together with data for inhibition of binding by antibodies developed against peptides from S, these findings suggest that the receptor-binding domain is located between amino acid residues 303 and 537. These results also confirm that ACE2 is a functional receptor for the SARS virus and may help in the elucidation of the mechanisms of SARS-CoV entry and in the development of vaccine immunogens and entry inhibitors.     

Unravelling the genetic diversity of ruminal bacteria belonging to the CFB phylum

Molecular biology approaches were employed to examine the genetic diversity of bacteria from the Cytophaga/Flexibacter/Bacteroides (CFB) phylum in the rumen of cattle. By this means we were able to identify cultured strains that represent some of the larger CFB clusters previously identified only by PCR amplification and sequencing. Complete 16S rDNA sequences were obtained for 16 previously isolated rumen strains, including the type strains of Prevotella ruminicola, P. bryantii, P. brevis and P. albensis to represent a wide range of diversity. Phylogenetic analysis of cultured strains revealed the existence of three clusters of ruminal CFB: (i) a cluster of Prevotella strains, which have been found only in the rumen, including the two type strains, P. brevis GA33(T) and P. ruminicola 23(T); (ii) Prevotella spp. that cluster with prevotellas from other ecological niches such as the oral cavity and which include the type strains, P. bryantii B(1)4(T) and P. albensis M384(T); (iii) two Bacteroides spp. strains clustering with B. forsythus of oral origin. In order to establish whether the cultivated isolates cover the whole range of ruminal CFB genetic diversity, 16S rRNA gene sequences were amplified and cloned from DNA extracted from the same rumen samples (one cow in Slovenia, one in Scotland and three in Japan). Sequencing and phylogenetic analysis of 16S rRNA genes confirmed the existence of two superclusters of ruminal Prevotella, one exclusively ruminal and the other including non-ruminal species. In the case of ruminal Bacteroides spp., however, phylogenetic analysis revealed the existence of three new superclusters, one of which has as yet no cultivable counterpart. Interestingly, these Bacteroides clusters were represented almost exclusively by clone libraries from the Japanese cattle and only three sequences were from the European cattle. This study agrees with previous analyses in showing that rumen Prevotella/Bacteroides strains exhibit a remarkable degree of genetic diversity and suggests that different strain groupings may differ greatly in their recovery by cultural methods. The most important conclusion, however, is that cultured strains can be identified that represent some of the larger clusters previously identified only by PCR amplification and sequencing.     

The effect of intracerebroventricular administration of substance P fragment and met-enkephalin on the transmission of nervous impulses between the midbrain reticular formation and two generators of the hippocampal theta rhythm in rabbits

The effect of intracerebroventricular administration of Substance P fragment and met-enkephalin on the excitability of two generators of hippocampal theta rhythm was investigated in the experiments performed on chronic rabbits. Substance P had a strong facilitatory effect on the threshold of the generator of the hippocampal theta rhythm of the frequency 4-7 c/s and an inhibitory effect on the threshold of the generator of the 7-12 c/s frequency evoked by stimulation of the midbrain reticular formation. These effects were dose dependent. The effects of met-enkephalin were opposite. They increased the threshold of the 4-7 c/s hippocampal generator and decreased the threshold of the other generator. The effect of these two compounds was evaluated according to the energy of electrical trains of pulses maintaining the continuous arousal pattern in the hippocampus.     

A comparison of the effectiveness, tolerability and safety of high and low carbohydrate diets in women with gestational diabetes

INTRODUCTION: Nutrition therapy is an integral part of the management of gestational diabetes mellitus (GDM). Most women with GDM are treated by nutritional management alone. The goal of our study was to compare low and high carbohydrate diets in their effectiveness, safety and tolerability in women with GDM. MATERIAL AND METHODS: The study group consisted of 30 Caucasian women newly diagnosed with GDM, with a mean age of 28.7 +/- 3.7 years and pregnancy duration of 29.2 +/- 5.4 weeks. The patients were randomised into two groups: those on a low and those on a high carbohydrate diet (45% vs. 65% respectively of energy supply coming from carbohydrates). The presence of urine ketones was controlled every day. After two weeks daily glucose profiles and compliance with the recommended diets were analysed. RESULTS: Glucose concentration before implementation of the diet regimen did not differ between groups. No changes in fasting blood glucose were noticed in the group that had followed a low carbohydrate diet, although a significant decrease in glucose concentration was observed after breakfast (102 +/- 16 vs. 94 +/- 11 mg/dl), lunch (105 +/- 12 vs. 99 +/- 9 mg/dl) and dinner (112 +/- 16 vs. 103 +/- 13 mg/dl) (p < 0.05). In the high carbohydrate diet group fasting and after-breakfast glucose concentration did not change. A significant decrease in glycaemia was noticed after lunch (106 +/- 15 vs. 96 +/- 7 mg/dl) and dinner (107 +/- 12 vs. 97 +/- 7 mg/dl) (p < 0.05). Ketonuria was not observed in either group. Obstetrical outcomes did not differ between groups. CONCLUSIONS: Both high and low carbohydrate diets are effective and safe. A diet with carbohydrate limitation should be recommended to women who experience the highest glycaemia levels after breakfast.