The effect of light conditions on herbs, bryophytes and seedlings of temperate mixed forests in ?rség, Western Hungary

A vegetation survey was carried out in a relatively intact Atlantic blanket bog in Southwest Ireland to study the vegetation patterns in relation to environmental variation, and to quantify the effect of artificial and natural borders on compositional variation. The data were analysed using canonical correspondence analysis. In terms of both vegetation and water chemistry, the study site can be categorized as typical of Atlantic blanket bogs in the maritime regions of North-western Europe. The distribution of plant species was explained mainly by depth of the water table. The distribution of bryophytes was secondarily explained by the pH of the bog water, while the distribution of vascular plants was secondarily explained by concentrations of ammonia. The vegetation distribution exhibited little variation between the central sector of the peatland and its disturbed edges (hill-grazing and restoration areas), but a substantial variation was observed between the area along a natural edge (stream) and the areas close to the other peatland borders or centre. Similarly, the internal variation within each sector (centre, hill-grazing edge and restoration area edge) was small, but substantial vegetation variation was observed within the area located along the stream. The area along the stream was associated with relatively deep water table, shallow peat depth, high water colour, pH and NH₄ ⁺ concentrations, and low Cl⁻ concentrations in the bog water. Our results suggest the existence of strong centre-natural margin gradients, as in raised bogs, and indicate that human or animal disturbance do not give rise to the marked transition zones that often characterize natural margins of mire systems. This indicates that even small areas and remnants of Atlantic blanket bogs are worthy of conservation and that their conservation value would benefit from the inclusion of sectors close to the natural peatland borders, which would increase the plant biodiversity of the conserved area.     

Differential regulation of the human versus the mouse apolipoprotein AV gene by PPARalpha: Implications for the study of pharmaceutical modifiers of hypertriglyceridemia in mice

Mice have been used widely to define the mechanism of action of fibric acid derivatives. The fibrates are pharmacological agonists of the peroxisome proliferator-activated receptor α (PPARα), whose activation in human subjects promotes potent reduction in plasma levels of triglycerides (TG) with concomitant increase in those of HDL-cholesterol. The impact of PPARα agonists on gene expression in humans and rodents is however distinct; such distinctions include differential regulation of key genes of lipid metabolism. We evaluated the question as to whether the human and murine genes encoding apolipoprotein apoAV, a regulator of plasma concentrations of TG-rich lipoproteins, might be differentially regulated in response to fibrates. Fenofibrate, a classic PPARα agonist, repressed expression of mouse Apoa5 in vivo in a mouse model transgenic for the human APOA5 gene; by contrast, expression of the human ortholog was up-regulated. Our findings are consistent with the presence of a functional PPAR-binding element in the promoter of the human APOA5 gene; this element is however degenerate and non-functional in the corresponding mouse Apoa5 sequence, as demonstrated by reporter assays and gel shift analyses. These data further highlights the distinct mechanisms which are implicated in the metabolism of TG-rich lipoproteins in mice as compared to man. They equally emphasize the importance of the choice of a mouse model for investigation of the impact of pharmaceutical modifiers on hypertriglyceridemia.     

Crown structure and wood properties: Influence on tree sway and response to high winds

Wind can alter plant growth and cause extensive, irreversible damage in forested areas. To better understand how to mitigate the effects of wind action, we investigated the sensitivity of tree aerodynamic behavior to the material and geometrical factors characterizing the aerial system. The mechanical response of a 35-yr-old maritime pine (Pinus pinaster, Pinaceae) submitted to static and dynamic wind loads is simulated with a finite element model. The branching structure is represented in three dimensions. Factor effects are evaluated using a fractional experimental design. Results show that material properties play only a limited role in tree dynamics. In contrast, small morphological variations can produce extreme behaviors such as either very little or nearly critical dissipation of stem oscillations. Slender trees are shown to be relatively more vulnerable to stem breakage than uprooting. Dynamic loading leads to deflections and forces up to 20% higher near the base of the tree than those calculated for a static loading of similar magnitude. Effects of branch geometry on dynamic amplification are substantial yet not linear. The flexibility of the aerial system is found to be critical to reducing the resistance to the airflow and thus to minimizing the risk of failure.     

Multiple reprobing of Western blots after inactivation of peroxidase activity by its substrate, hydrogen peroxide

Sequential detections of different proteins on Western blot save time and precious samples. The main problem concerning reprobing is that stripping buffers can unbind both the antibody and the tested antigen. An original reprobing method has been set up based on horseradish peroxidase (HRP) inhibition after enhanced chemiluminescence detection. Instead of removing previously fixed antibodies as common stripping buffers do, the HRP activity linked to the secondary antibody is irreversibly inhibited by excess of hydrogen peroxide. A 15-min incubation allows one to perform at least five different sequential detections without losing significant amounts of blotted proteins.     

A potential species-specific molecular marker suggests interspecific hybridization between sibling species Littorina arcana and L. saxatilis (Mollusca, Caenogastropoda) in natural populations

Three sister species of rough periwinkles, viz. Littorina saxatilis (Olivi 1792), L. arcana (Hannaford Ellis 1978) and L. compressa (Jeffreys 1865) from the Barents Sea (Russia), the White Sea (Russia) and the Norwegian Sea (Norway) were studied. The identification of two sibling species L. saxatilis and L. arcana is often difficult as both species have extremely similar shell morphology and reproductive systems. Only mature females can be unambiguously distinguished, with a jelly gland present in female L. arcana, but which is replaced by a brood pouch containing developing embryos in L. saxatilis. No clear-cut diagnostic features have been found to discriminate between males or juveniles of the two species. The very first diagnostic DNA marker (DNA fragment A2.8, 271 bp length) for L. arcana and L. saxatilis separation was developed. The marker was derived from apparently species-specific L. arcana DNA fragments obtained via Random Amplified Polymorphic DNA (RAPD) analysis. This fragment was cloned and sequenced, whereupon specific primers were designed and the amplification was surveyed in a large number of morphologically well-identified females of both species. Subsequently, the specific DNA marker was used for the identification of male L. arcana and partners in copulating pairs. In this way, we obtained evidence of possible interspecific hybridization between the sibling species L. arcana and L. saxatilis living in sympatry in natural populations: the presence of A2.8 fragment in 12% of morphologically well identified L. saxatilis females and its absence in 14% of morphologically well identified L. arcana females. The A2.8 fragment never amplified in L. saxatilis from sites without L. arcana. The A2.8 fragment did not amplify in L. compressa, not even in microsympatric populations, and we did not observe interspecific copulations between L. arcana and L. compressa.     

Structural Characterization of Mouse Neutrophil Serine Proteases and Identification of Their Substrate Specificities: RELEVANCE TO MOUSE MODELS OF HUMAN INFLAMMATORY DISEASES*

It is widely accepted that neutrophil serine proteases (NSPs) play a critical role in neutrophil-associated lung inflammatory and tissue-destructive diseases. To investigate NSP pathogenic role(s), various mouse experimental models have been developed that mimic acutely or chronically injured human lungs. We and others are using mouse exposure to cigarette smoke as a model for chronic obstructive pulmonary disease with or without exacerbation. However, the relative contribution of NSPs to lung disease processes as well as their underlying mechanisms remains still poorly understood. And the lack of purified mouse NSPs and their specific substrates have hampered advances in these studies. In this work, we compared mouse and human NSPs and generated three-dimensional models of murine NSPs based on three-dimensional structures of their human homologs. Analyses of these models provided compelling evidence that peptide substrate specificities of human and mouse NSPs are different despite their conserved cleft and close structural resemblance. These studies allowed us to synthesize for the first time novel sensitive fluorescence resonance energy transfer substrates for individual mouse NSPs. Our findings and the newly identified substrates should better our understanding about the role of NSPs in the pathogenesis of cigarette-associated chronic obstructive pulmonary disease as well as other neutrophils-associated inflammatory diseases.     

Prediction of Pharmacokinetic Profile of Valsartan in Humans Based on in vitro Uptake‐Transport Data

The aim of this study was to evaluate a physiologically based pharmacokinetic (PBPK) model for predicting PK profiles in humans based on a model refined in rats and humans in vitro uptake‐transport data using valsartan as a probe substrate. Valsartan is eliminated unchanged, mostly through biliary excretion, both in humans and rats. It was, therefore, chosen as model compound to predict in vivo elimination based on in vitro hepatic uptake‐transport data using a fully mechanistic PBPK model. Plated rat and human hepatocytes, and cell lines overexpressing human OATP1B1 and OATP1B3 were used for in vitro uptake experiments. A mechanistic two‐compartment model was used to derive the active and passive transport parameters, namely uptake Michaelis–Menten parameters (V_max and K_m,u) together with passive diffusion (P_dif). These transport parameters were then used as input in a whole body physiologically based pharmacokinetic (PBPK) model. The uptake rate of valsartan was higher for rat hepatocytes (K_m,u=28.4±3.7 μM , V_max=1320±180 pmol/mg/min, and P_dif =1.21±0.42 μl/mg/min) compared to human hepatocytes (K_m,u=44.4±14.6 μM , V_max=304±85 pmol/mg/min, and P_dif=0.724±0.271 μl/mg/min). OATP1B1 and ‐1B3 parameters were correlated to human hepatocyte data, using experimentally established relative activity factors (RAF). Resulting PBPK simulations were compared for plasma‐ (humans and rats) and bile‐ (rats) concentration–time profiles following iv bolus administration of valsartan. Plasma clearances (CL_P) for rats and humans were predicted within twofold relative to predictions based on respective in vitro data. The simulations were extended to simulate the impact of either OATP1B1 or ‐1B3 inhibition on plasma profile. The limited data set indicates that the mechanistic model allowed for accurate evaluation of in vitro transport data; and the resulting hepatic uptake transport kinetic parameters enabled the prediction of in vivo PK profiles and plasma clearances, using PBPK modelling. Moreover, the interspecies difference in elimination rate observed in vivo was correctly reflected in the transport parameters determined in vitro.     

Role of Varp,a Rab21 exchange factor and TI‐VAMP/VAMP7 partner,in neurite growth

The vesicular soluble N‐ethylmaleimide‐sensitive factor attachment protein receptor (SNARE) tetanus neurotoxin‐insensitive vesicle‐associated membrane protein (TI‐VAMP/VAMP7) was previously shown to mediate an exocytic pathway involved in neurite growth, but its regulation is still largely unknown. Here we show that TI‐VAMP interacts with the Vps9 domain and ankyrin‐repeat‐containing protein (Varp), a guanine nucleotide exchange factor (GEF) of the small GTPase Rab21, through a specific domain herein called the interacting domain (ID). Varp, TI‐VAMP and Rab21 co‐localize in the perinuclear region of differentiating hippocampal neurons and transiently in transport vesicles in the shaft of neurites. Silencing the expression of Varp by RNA interference or expressing ID or a form of Varp deprived of its Vps9 domain impairs neurite growth. Furthermore, the mutant form of Rab21, defective in GTP hydrolysis, enhances neurite growth. We conclude that Varp is a positive regulator of neurite growth through both its GEF activity and its interaction with TI‐VAMP.