Rapid growth and large body size in annual fish populations are compromised by density-dependent regulation

We tested the effect of population density on maximum body size in three sympatric species of annual killifishes Nothobranchius spp. from African ephemeral pools. We found a clear negative effect of population density on body size, limiting their capacity for extremely fast development and rapid growth. This suggests that density-dependent population regulation and the ephemeral character of their habitat impose contrasting selective pressures on the life history of annual killifishes.     

Incidence of nontuberculous mycobacteria in four hot water systems using various types of disinfection

The objective of this study was to determine the incidence of nontuberculous mycobacteria (NTM) in hot water systems of 4 selected hospital settings. The hospitals provided the following types of disinfection for their hot water systems: hydrogen peroxide and silver, thermal disinfection, chlorine dioxide, and no treatment (control). In each building, 6 samples were collected from 5 sites during a 3 month period. NTM were detected in 56 (46.7%) of 120 samples; the CFU counts ranged from 10 to 1625 CFU/L. The detected NTM species were the pathogens Mycobacterium kansasii, Mycobacterium xenopi, and Mycobacterium fortuitum and the saprophyte Mycobacterium gordonae. The most common to be isolated was M. xenopi, which was present in 51 samples. The hot water systems differed significantly in the incidence of NTM. NTM were not detected in the system treated by thermal disinfection, and a relatively low incidence (20% positive samples) was found in the system disinfected with chlorine dioxide. However, a high incidence was found in the control system with no additional disinfection (70% positives) and in the system using hydrogen peroxide and silver (97% positives). Water temperatures above 50 degrees C significantly limited the occurrence of NTM.     

Role of mitogen-activated protein kinases in aryl hydrocarbon receptor signaling

Human populations are increasingly exposed to a number of environmental pollutants such as polycyclic aromatic hydrocarbons, polychlorinated biphenyls and dioxins. These compounds are activators of the aryl hydrocarbon receptor (AhR) that controls the expression of many genes including those for detoxification enzymes. The regulatory mechanisms of AhR are multi-factorial and include phosphorylation by various protein kinases. Significant progress in the research of mitogen-activated protein kinases (MAPKs) has been achieved in the last decade. Isolated reports have been published on the role of MAPKs in AhR functions and vice versa, with activation of MAPKs by AhR ligands. This mini-review summarizes current knowledge on the mutual interactions between MAPKs and AhR. The majority of studies has been done on cancer-derived cell lines that have impaired cell cycle regulation and lacks the complete detoxification apparatus. We emphasize the importance of the future studies that should be done on non-transformed cells to distinguish the role of MAPKs in cancer and normal cells. Primary cultures of human or rodent hepatocytes that are equipped with a fully functional biotransformation battery or xenobiotics-metabolizing extra-hepatic tissues should be the models of choice, as the results in our experiments confirm.     

Identification and Quantification of Several Mammalian Steroid Hormones in Plants by UPLC-MS/MS

We have developed an effective method for the isolation, identification, and quantification of several mammalian steroid hormones and their metabolites in different plant tissues. The purification protocol was based on solid-phase extraction (SPE) combined with immunoaffinity chromatography (IAC) using immobilized generic polyclonal anti-Δ⁴-3-keto-steroid antibodies covalently bound to Affi-Gel 10 sorbent. The antibodies were characterized by means of enzyme-linked immunosorbent assay (ELISA). The detection limit of the ELISA was 6.0 × 10⁻¹⁰ mol L⁻¹ and cross-reactivity with most Δ⁴-3-keto-steroids was very high as predicted (68–122%). The IAC allowed fast, single-step purification of different plant extracts prior to analysis by ultra-performance liquid chromatography-electrospray tandem mass spectrometry [UPLC-ESI(+)-MS/MS]. In multiple-reaction-monitoring (MRM) mode, the detection limit of the method for most of the steroids analyzed was close to 10 fmol and the response was linear up to 50 pmol injected. The analytical accuracy was validated using tobacco leaf samples spiked with known amounts of authentic and deuterium-labeled standards. The newly developed method was capable of detecting and quantifying at least 12 specified steroid compounds in plant extracts. In the analyzed extracts from three plant species, that is, common foxglove (Digitalis purpurea L.), tobacco (Nicotiana tabacum L.), and elecampane inula (Inula helenium L.), four endogenous steroids were detected, identified, and quantified. Progesterone was found in all three plants at concentrations comparable to those reported in previous studies. Three other steroids, androstendione, 17α-hydroxyprogesterone, and 16-dehydroprogesterone, were identified for the first time in plant extracts. 17α-Hydroxyprogesterone and 16-dehydroprogesterone occurred at significant concentrations in D. purpurea, whereas androstendione was found in N. tabacum and I. helenium but not in D. purpurea.     

Comparison of vascular plant diversity and species composition of coppice and high beech forest in the Banat region,Romania

Abandonment of coppicing is one of the main reasons of diversity decline in European temperate forests. To reverse this trend, coppicing has been reintroduced in several forests, especially in areas of high conservation value. However, empirical information on the effects of coppicing on plant diversity and composition is still scarce. By comparing vegetation data from active coppices and beech-dominated high forests in the Banat region in Romania, we tested the hypothesis that coppices have a higher plant diversity and different plant species composition than high forests. Data were collected in 60 randomly placed phytosociological relevés and were analysed using linear models and multivariate methods. As expected, we found differences in understorey plant composition. Herb species with various environmental demands–sciophytes-(hemi)-heliophytes and grassland species–were more frequent in coppices whereas high forests had more vernal species and sciophytes. Coppices also had slightly greater plant diversity but did not differ in herb species richness. Our results demonstrate that coppicing has a small positive effect on plant diversity but a large effect on species composition. Coppice restoration may be especially beneficial for populations of thermophilous and non-forest species.     

Variation in canopy openness among main structural types of woody vegetation in a traditionally managed landscape

The decrease in canopy openness after the abandonment of traditional coppicing in the twentieth century has been previously identified as the main reason behind changes in species composition and diversity in lowland woodlands in Europe. However, little is known about the role of other traditional practices in shaping woody vegetation and canopy cover in the past. In a traditionally managed landscape of the Banat region, western Romania, where long-established activities, such as human-induced burning, coppicing and grazing of woody vegetation are still being practised, we studied woody vegetation structure and canopy openness in 70 plots. Using a set of structural traits, we classified woody vegetation into four groups: active coppices, scrubs, abandoned coppices and high forests. Surprisingly, the lowest canopy openness was found in active coppices, probably due to high canopy recovery rate and selection coppice system. Scrubs, in which grazing and browsing were the most common activities in the past, were the most open type of woody vegetation. Our results emphasize the role of other traditional management practices in addition to coppicing in keeping canopy openness relatively high and spatially heterogeneous.     

Patterns of functional diversity of two trophic groups after canopy thinning in an abandoned coppice

Coppice abandonment had negative consequences for the biodiversity of forest vegetation and several groups of invertebrates. Most coppicing restoration studies have focused only on a single trophic level despite the fact that ecosystems are characterized by interactions between trophic levels represented by various groups of organisms. To address the patterns of functional diversity in the perspective of coppicing restoration, we studied the short-term effects of conservation-motivated tree canopy thinning in an abandoned coppice with standards in Central Europe, a region where such attempts have been rare so far. The functional diversity of vascular plants and spiders, chosen as two model trophic groups within the forest ecosystem, was compared between thinned and control forest patches. To characterize functional patterns, we examined several functional traits. These traits were assigned to two contrasting categories: response traits reflecting a change of environment (for both vascular plants and spiders) and effect traits influencing the ecosystem properties (only for vascular plants). Functional diversity was analysed by CCA using two measures: community-weighted means (CWM) and Rao’s quadratic diversity (RaoQ). CCA models revealed that the canopy thinning had a positive effect on the diversity of the response traits of both trophic groups and negatively influenced the diversity of effect traits. In addition, we found distinct seasonal dynamics in functional diversity of the spider communities, which was probably linked to leaf phenology of deciduous trees. We conclude that canopy thinning affected functional diversity across trophic groups during the initial phase of coppicing restoration. With necessary precautions, careful canopy thinning can be effectively applied in the restoration of functional diversity in abandoned coppices.     

Regulation of Rac1 activation by the low density lipoprotein receptor-related protein

The low density lipoprotein receptor-related protein (LRP-1) binds and mediates the endocytosis of multiple ligands, transports the urokinase-type plasminogen activator receptor (uPAR) and other membrane proteins into endosomes, and binds intracellular adaptor proteins involved in cell signaling. In this paper, we show that in murine embryonic fibroblasts (MEFs) and L929 cells, LRP-1 functions as a major regulator of Rac1 activation, and that this activity depends on uPAR. LRP-1-deficient MEFs demonstrated increased Rac1 activation compared with LRP-1-expressing MEFs, and this property was reversed by expressing the VLDL receptor, a member of the same gene family as LRP-1, with overlapping ligand-binding specificity. Neutralizing the activity of LRP-1 with receptor-associated protein (RAP) increased Rac1 activation and cell migration in MEFs and L929 cells. The same parameters were unaffected by RAP in uPAR-/- MEFs, prepared from uPAR gene knockout embryos, and in uPAR-deficient LM-TK- cells. Untreated uPAR+/+ MEFs demonstrated substantially increased Rac1 activation compared with uPAR-/- MEFs. In addition to Rac1, LRP-1 suppressed activation of extracellular signal-regulated kinase (ERK) in MEFs; however, it was Rac1 (and not ERK) that was responsible for the effects of LRP-1 on MEF migration. Thus, LRP-1 regulates two signaling proteins in the same cell (Rac1 and ERK), both of which may impact on cell migration. In uPAR-negative cells, LRP-1 neutralization does not affect Rac1 activation, and other mechanisms by which LRP-1 may regulate cell migration are not unmasked.