The influence of β-cyclodextrin on the kinetics of progesterone transformation by Rhizopus nigricans

The process of progesterone 11α-hydroxylation by the pelleted growth form of the filamentous fungus Rhizopus nigricans has been described with a mathematical model, based on Michaelis-Menten enzyme kinetics and the rate of substrate dissolution. It was confirmed that the low water solubility of steroids is the limiting step of this process at high steroid concentrations. In order to overcome this problem, β-cyclodextrin, which is known to form inclusion complexes with these organic compounds, was added to the production medium. The phase solubility of the steroid-β-cyclodextrin system was investigated and the effect of β-cyclodextrin addition on progesterone biotransformation evaluated. Enhancement of steroid solubility was demonstrated and nearly two-fold increase in reaction rate was found in the presence of β-cyclodextrin.     

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.     

Developmental stability and morphological differences in Plantago major L. leaves under contrasting environmental conditions

Abstract

In the present study, an additional combination of end‐points was applied on the natural populations of the common plantain, previously estimated using morphometric assays. Here, besides measuring developmental instability (DI), by determining the level of fluctuating asymmetry (FA) and the total amount of phenotypic variability (PV), we tried to distinguish the three natural populations under contrasting environmental conditions using the morphological data. Results obtained using both FA indices were the same; higher asymmetry levels in the reference than in the polluted environments were detected for leaf width, vein distances within a leaf and lobe length. The one‐way analysis of variance results revealed that there were significant differences in PV values among populations analysed for each character. When all leaf traits were considered together, the PV median value was significantly higher in Crni Lug leaves compared with leaves from other sites. The multivariate analysis of variance results revealed the significant effect of environment on both FA₄ and PV values. The component scores of first factor (PC1) were significantly different between the Karaburma and Crni Lug populations. Besides, component scores of both PC1 and PC2 were significantly different between the Zemun and Crni Lug samples. The stepwise discriminant functional analysis results allowed us to identify a set of four variables, with a sufficient discriminating ability (75%).     

Comparison of allometric relationships and morphological differences in Tilia cordata Mill. outer leaves exposed to different environmental conditions

The study is based on four leaf parameters: leaf width (LW), lobe length (LL), leaf size (LS) and leaf shape which is calculated as LW to leaf length (LW/LL) ratio. Under different environmental conditions, LL is an isometric character, LW shows positive allometry, whereas LW/LL shows negative allometry. Regression analysis results indicated that there is no significant difference either in slopes or in regression coefficients between investigated sites. Thus, in this study, we found that allometric relationships between leaf parameters and LS are character specific and that they tended not to differ significantly between Tilia cordata Mill. outer leaves exposed to different environmental conditions. Also, there are no significant interpopulation differences for both principal component PC1 and PC2 scores. The stepwise discriminant functional analysis results allowed us to identify a set of two leaf parameters (LS and LL) with a moderate discriminating ability (59.8%). T. cordata outer leaves are significantly larger and broader in the reference area (R-leaves) than leaves from polluted (P-leaves) site. The data also indicated that there is a relatively larger petiole size in R-leaves than in P-leaves. We found that in P-leaves, LW increased faster with increasing LS than in R-leaves.     

Consequences of MnSOD interactions with nitric oxide: Nitric oxide dismutation and the generation of peroxynitrite and hydrogen peroxide

The present study demonstrates that manganese superoxide dismutase (MnSOD) (Escherichia coli), binds nitric oxide (^√NO) and stimulates its decay under both anaerobic and aerobic conditions. The results indicate that previously observed MnSOD-catalyzed ^√NO disproportionation (dismutation) into nitrosonium (NO⁺) and nitroxyl (NO^? ) species under anaerobic conditions is also operative in the presence of molecular oxygen. Upon sustained aerobic exposure to ^√NO, MnSOD-derived NO^? species initiate the formation of peroxynitrite (ONOO^? ) leading to enzyme tyrosine nitration, oxidation and (partial) inactivation. The results suggest that both ONOO^? decomposition and ONOO^? -dependent tyrosine residue nitration and oxidation are enhanced by metal centre-mediated catalysis. We show that the generation of ONOO^? is accompanied by the formation of substantial amounts of H₂O₂. MnSOD is a critical mitochondrial antioxidant enzyme, which has been found to undergo tyrosine nitration and inactivation in various pathologies associated with the overproduction of ^√NO. The results of the present study can account for the molecular specificity of MnSOD nitration in vivo. The interaction of ^√NO with MnSOD may represent a novel mechanism by which MnSOD protects the cell from deleterious effects associated with overproduction of ^√NO.     

Activity of the tick Ixodes ricinus monitored in a suburban park in Brno,Czech Republic,in association with the evaluation of selected repellents

The ever‐increasing number of Lyme borreliosis patients led us to consider more effective procedures for disease prevention. The aim of our study was to monitor the annual activity and infectivity of Ixodes ricinus ticks in the Pisárky region, City of Brno, CR, and to test the responses of the locally‐captured ticks to selected repellents. The result of regular one‐hour‐perweek monitoring in 2011 was the collection of ticks that directly reflected the highest number of Lyme disease patients (4,835) detected throughout the period of recording in the Czech Republic. The ticks were examined for spirochaetes by dark field microscopy. The positive samples were identified by PCR analysis, confirming that 76% of these were infected with Borrelia burgdorferi sensu lato. Ticks were most abundant in May and June, with August having the highest risk for spirochaetal infection. Tick activity was statistically correlated with temperature. The moving‐object‐bioassay was used to study repellent efficiency on the Ixodes ricinus nymphs captured in the above‐mentioned suburban park. Five selected commercial repellents based on DEET (N, N‐diethyl3methylbenzamide) showed statistically different effects on the non‐repellent control group.     

Hosts and distribution of Viscum album L. ssp. album in Croatia and Slovenia

Abstract

Viscum album L. ssp. album is semi-parasitic on deciduous trees and shrubs. In order to identify hosts and map the distribution of V. album ssp. album in Croatia and Slovenia, field research was carried out, and herbaria were surveyed. In Croatia and Slovenia, V. album ssp. album occurred on 59 taxa. In Croatia, there were 52 hosts (33 autochthonous and 15 allochthonous species, two cultivars and two hybrids). In Slovenia, there were 25 hosts (21 autochthonous and four allochthonous species). There were 18 hosts common to both countries, 34 hosts were found only in Croatia, and seven hosts only in Slovenia. The hosts belonged to 13 families. The majority of these (19 species) belong to the Rosaceae, followed by Salicaceae, Aceraceae, Betulaceae, Fagaceae, Juglandaceae, Tiliaceae, Hippocastanaceae, Ulmaceae, Oleaceae, Fabaceae, Moraceae and Viscaceae. All hosts have been previously recorded in the literature, except Alnus japonica (Thunb.) Steud., Amelanchier lamarckii F.G. Schroed. and Crataegus nigra Waldst. et Kit. The distribution of this mistletoe was scattered, due to the scattered distribution of hosts, local conditions, movement of bird-vectors, etc. A continuous distribution was found only in part of the distribution area of narrow-leaved ash (Fraxinus angustifolia Vahl).     

Leaflet morphometric variation of service tree (Sorbus domestica L.) in the Balkan Peninsula

Abstract

In most European countries, the service tree (Sorbus domestica L.) is a rare and threatened species and its conservation has been recognised as a priority. The aim of this study was to asses its morphologic variation in the western and central part of the Balkan Peninsula and in southern Central Europe. Three populations were analysed: one in Serbia, one in Bosnia and Herzegovina and one in Slovenia. In each population 30 trees were selected, and from each tree 30 leaves were collected for morphometric analysis based on nine leaflet morphological traits. Univariate (ANOVA) and multivariate (MANOVA) analysis of variance were used to estimate the variation within- and between populations and a discriminant analysis was performed to examine the structure of the between-population differences. The values of particular morphological traits found in our study did not differ considerably from the values reported elsewhere. The results revealed significant within- and between population variation. Variation within populations was highly significant for all the scored leaf morphological traits, while variation between populations was significant for all the studied traits except for the leaflet length. The discrimination between the three populations was significant. High percentages of correctly classified samples demonstrate good discriminating employability of the analysed leaf morphological traits and indicate differentiation of the analysed populations.     

Inhibition of Na+/K+-ATPase and Mg2+-ATPase by metal ions and prevention and recovery of inhibited activities by chelators

Kinetics and inhibition of Na⁺/K⁺-ATPase and Mg²⁺-ATPase activity from rat synaptic plasma membrane (SPM), by separate and simultaneous exposure to transition (Cu²⁺, Zn²⁺, Fe²⁺ and.Co²⁺) and heavy metals (Hg²⁺and Pb²⁺) ions were studied. All investigated metals produced a larger maximum inhibition of Na⁺/K⁺-ATPase than Mg²⁺-ATPase activity. The free concentrations of the key species (inhibitor, MgATP^{2 ?} , MeATP^{2 ?} ) in the medium assay were calculated and discussed. Simultaneous exposure to the combinations Cu²⁺/Fe²⁺ or Hg²⁺/Pb²⁺caused additive inhibition, while Cu²⁺/Zn²⁺ or Fe²⁺/Zn²⁺ inhibited Na⁺/K⁺-ATPase activity synergistically (i.e., greater than the sum metal-induced inhibition assayed separately). Simultaneous exposure to Cu²⁺/Fe²⁺ or Cu²⁺/Zn²⁺ inhibited Mg²⁺-ATPase activity synergistically, while Hg²⁺/Pb²⁺ or Fe²⁺/Zn²⁺ induced antagonistic inhibition of this enzyme. Kinetic analysis showed that all investigated metals inhibited Na⁺/K⁺-ATPase activity by reducing the maximum velocities (V_max) rather than the apparent affinity (K_m) for substrate MgATP^2-, implying the noncompetitive nature of the inhibition. The incomplete inhibition of Mg²⁺-ATPase activity by Zn²⁺, Fe²⁺ and Co²⁺ as well as kinetic analysis indicated two distinct Mg²⁺-ATPase subtypes activated in the presence of low and high MgATP^{2 ?} concentration. EDTA, L-cysteine and gluthathione (GSH) prevented metal ion-induced inhibition of Na⁺/K⁺-ATPase with various potencies. Furthermore, these ligands also reversed Na⁺/K⁺-ATPase activity inhibited by transition metals in a concentration-dependent manner, but a recovery effect by any ligand on Hg²⁺-induced inhibition was not obtained.     

New inhibitors of fungal 17β-hydroxysteroid dehydrogenase based on the [1,5]-benzodiazepine scaffold

The synthesis and activity of a new series of non-steroidal inhibitors of 17β-hydroxysteroid dehydrogenase that are based on a 1,5-benzodiazepine scaffold are presented. Their inhibitory potential was screened against 17β-hydroxysteroid dehydrogenase from the fungus Cochliobolus lunatus (17β-HSDcl), a model enzyme of the short-chain dehydrogenase/reductase superfamily. Some of these compounds are potent inhibitors of 17β-HSDcl activity, with IC₅₀ values in the low micromolar range and represent promising lead compounds that should be further developed and investigated as inhibitors of human 17β-HSD isoforms, which are the enzymes associated with the development of many hormone-dependent and neuronal diseases.