Combined effects of selenium and drought on photosynthesis and mitochondrial respiration in potato.

The possible effects of selenium (Se) foliar spraying and drought were studied for 3 months in potato (Solanum tuberosum L.) cultivar Desiree in Ljubljana, Slovenia. Four combinations of treatments were conducted: well-watered plants with and without Se foliar spraying, and drought exposed plants with and without Se foliar spraying. The following parameters were monitored 2 and 4 weeks after treatments: net photosynthesis, transpiration rate, quantum yield of photosystem II (PSII), and respiratory potential measured by electron transport system activity. After 3 months of treatments, leaf water potential and tuber yield were determined. The content of Se in tubers was measured after harvesting time. Several effects of drought and Se foliar spraying and their combinations were found. Net photosynthesis and respiratory potential were lower in drought exposed plants 4 weeks after treatments. Se induced higher respiratory potential in the leaves 4 weeks after treatments. Higher efficiency of energy conversion in PSII, expressed by a higher effective quantum yield, was observed in Se treated plants 2 weeks after treatments. Foliarly applied Se was efficiently absorbed by plant leaves and transported to the tubers.     

Endocytotic activity of bladder superficial urothelial cells is inversely related to their differentiation stage

The composition of the apical plasma membrane of bladder superficial urothelial cells is dramatically modified during cell differentiation, which is accompanied by the change in the dynamics of endocytosis. We studied the expression of urothelial differentiation-related proteins uroplakins and consequently the apical plasma membrane molecular composition in relation to the membrane-bound and fluid-phase endocytosis in bladder superficial urothelial cells. By using primary urothelial cultures in the environment without mechanical stimuli, we studied the constitutive endocytosis. Four new findings emerge from our study. First, in highly differentiated superficial urothelial cells with strong uroplakin expression, the endocytosis of fluid-phase endocytotic markers was 43% lower and the endocytosis of membrane-bound markers was 86% lower compared to partially differentiated cells with weak uroplakin expression. Second, superficial urothelial cells have 5–15-times lower endocytotic activity than MDCK cells. Third, in superficial urothelial cells the membrane-bound markers are delivered to lysosomes, while fluid-phase markers are seen only in early endocytotic compartments, suggesting their kiss-and-run recycling. Finally, we provide the first evidence that in highly differentiated cells the uroplakin-positive membrane regions are excluded from internalization, suggesting that uroplakins hinder endocytosis from the apical plasma membrane in superficial urothelial cells and thus maintain optimal permeability barrier function.     

Long-Range Correlations in Rectal Temperature Fluctuations of Healthy Infants during Maturation

Background

Control of breathing, heart rate, and body temperature are interdependent in infants, where instabilities in thermoregulation can contribute to apneas or even life-threatening events. Identifying abnormalities in thermoregulation is particularly important in the first 6 months of life, where autonomic regulation undergoes critical development. Fluctuations in body temperature have been shown to be sensitive to maturational stage as well as system failure in critically ill patients. We thus aimed to investigate the existence of fractal-like long-range correlations, indicative of temperature control, in night time rectal temperature (T_rec) patterns in maturing infants.

Methodology/Principal Findings

We measured T_rec fluctuations in infants every 4 weeks from 4 to 20 weeks of age and before and after immunization. Long-range correlations in the temperature series were quantified by the correlation exponent, α using detrended fluctuation analysis. The effects of maturation, room temperature, and immunization on the strength of correlation were investigated. We found that T_rec fluctuations exhibit fractal long-range correlations with a mean (SD) α of 1.51 (0.11), indicating that T_rec is regulated in a highly correlated and hence deterministic manner. A significant increase in α with age from 1.42 (0.07) at 4 weeks to 1.58 (0.04) at 20 weeks reflects a change in long-range correlation behavior with maturation towards a smoother and more deterministic temperature regulation, potentially due to the decrease in surface area to body weight ratio in the maturing infant. α was not associated with mean room temperature or influenced by immunization

Conclusions

This study shows that the quantification of long-range correlations using α derived from detrended fluctuation analysis is an observer-independent tool which can distinguish developmental stages of night time T_rec pattern in young infants, reflective of maturation of the autonomic system. Detrended fluctuation analysis may prove useful for characterizing thermoregulation in premature and other infants at risk for life-threatening events.     

The dimerization mechanism of LIS1 and its implication for proteins containing the LisH motif

Miller-Dieker lissencephaly, or "smooth-brain" is a debilitating genetic developmental syndrome of the cerebral cortex, and is linked to mutations in the Lis1 gene. The LIS1 protein contains a so-called LisH motif at the N terminus, followed by a coiled-coil region and a seven WD-40 repeat forming beta-propeller structure. In vivo and in vitro, LIS1 is a dimer, and the dimerization is mediated by the N-terminal fragment and is essential for the protein's biological function. The recently determined crystal structure of the murine LIS1 N-terminal fragment encompassing residues 1-86 (N-LIS1) revealed that the LisH motif forms a tightly associated homodimer with a four-helix antiparallel bundle core, while the parallel coiled-coil situated downstream is stabilized by three canonical heptad repeats. This homodimer is uniquely asymmetric because of a distinct kink in one of the helices. Because the LisH motif is widespread among many proteins, some of which are implicated in human diseases, we investigated in detail the mechanism of N-LIS1 dimerization. We found that dimerization is dependent on both the LisH motif and the residues downstream of it, including the first few turns of the helix. We also have found that the coiled-coil does not contribute to dimerization, but instead is very labile and can adopt both supercoiled and helical conformations. These observations suggest that the presence of the LisH motif alone is not sufficient for high-affinity homodimerization and that other structural elements are likely to play an important role in this large family of proteins. The observed lability of the coiled-coil fragment in LIS1 is most likely of functional importance.     

Spatial pattern of native species Myriophyllum spicatum and invasive alien species Elodea nuttallii after introduction of the latter one into the Drava River (Slovenia)

Invasive alien species Elodea nuttallii was introduced into the Drava River (Slovenia) in 2007. The spatial distribution of native macrophyte species Myriophyllum spicatum and the invasive alien species E. nuttallii was studied in two impoundments, HPP Vuhred and HPP Mariborski otok in the years 2009, 2010 and 2011. The very heterogeneous environment of the Drava River had resulted in dynamic and non-uniform distributions of E. nuttalli and M. spicatum in both impoundments. The distribution of E. nuttalli was shown to be suppressed in river stretches exposed to great turbulence. It had, however, successfully invaded areas with gentle slope of littoral, low exposition to main water flow and muddy sediment and prevailed against the native species M. spicatum. The latter was more abundant than E. nuttallii in stretches exposed to higher flow velocity. Thus, the competitive success of M. spicatum and E. nuttallii depended on environmental conditions. Our results lead to the prediction that E. nuttallii will increase further in the river Drava, causing serious economic problems.     

Lipids of a citric-acid-producing Aspergillus niger strain grown in copper- and in manganese-supplemented media

A citric-acid-producing Aspergillus niger strain was cultivated in conditions favouring citric acid biosynthesis and in conditions hindering it. During both extreme processes, the mycelia were analysed for their lipid content, individual lipid classes, the content of sterols and free fatty acids. Since phospholipids, especially phosphatidylcholine and sterols, play an essential role in membrane permeability one can conclude that the differences observed substantially contribute to citric acid excretion into fermentation media. The difference in sterol composition was the most pronounced. Citric-acid-excreting mycelia contained lower quantities of sterols and ergosterol was the only component. A. niger mycelia grown in conditions hindering citric acid accumulation contained higher amounts of sterols with ergosterol as the main component and six other sterol components representing a minor amount.Offprint requests to: K. Jernejc     

Taxanes inhibit human TLR4 signaling by binding to MD-2

LPS is the primary ligand of Toll-like receptor 4, activating it through binding to its accessory protein MD-2. Murine but not human cells expressing MD-2/TLR4 are also activated by paclitaxel. Paclitaxel binds to human MD-2. The binding site of paclitaxel overlaps with the binding site of bis-ANS and LPS, which results in the ability of taxanes to inhibit LPS signaling in the system with human receptors. Circular dichroic spectra of human MD-2 indicated differences in the chemical environment in the presence of paclitaxel and docetaxel. Molecular docking identified the interacting residues of MD-2 and suggests that hydrophobic interactions govern the binding, while the C-3′N group where the paclitaxel and docetaxel differ is exposed on the surface of MD-2.     

Clinical features and virologic characteristics of primary and early HIV-1 infection in Slovenian patients

Analysis of time trends in newly diagnosed HIV-1 infected patients in Slovenia over a 10-year period (1996-2005) showed an increase in the number of newly diagnosed HIV-1 infected patients in 2004 and 2005 as well as increase in the number of newly diagnosed patients with primary/early HIV-1 infection. A retrospective analysis was performed in order to evaluate the clinical, epidemiological, laboratory and virological parameters of primary/early HIV-1 infection presenting with or without acute retroviral syndrome (ARS). Primary/early HIV-1 infection was diagnosed in 33 (19.5%) out of 169 newly diagnosed HIV-1 infected patients during the 10-year period. Most patients experienced ARS, the most commonly reported symptoms being fever, malaise and pharyngitis, followed by rash and lymphadenopathy. Median CD4 cell count was 415 cells/mm3, median CD8 cell count was 865 cells/mm3 and median HIV-1 viral load at the time of diagnosis was 5.1 loglo copies/mL. The increase in the number of newly diagnosed HIV-1 infected patients may be in part due to increased awareness among clinicians of the possibility of ARS, and the possibility of increased awareness of symptoms of ARS among persons at high risk of infection.     

Selective binding of lectins to normal and neoplastic urothelium in rat and mouse bladder carcinogenesis models

Bladder cancer adjuvant intravesical therapy could be optimized by more selective targeting of neoplastic tissue via specific binding of lectins to plasma membrane carbohydrates. Our aim was to establish rat and mouse models of bladder carcinogenesis to investigate in vivo and ex vivo binding of selected lectins to the luminal surface of normal and neoplastic urothelium. Male rats and mice were treated with 0.05 % N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) in drinking water and used for ex vivo and in vivo lectin binding experiments. Urinary bladder samples were also used for paraffin embedding, scanning electron microscopy and immunofluorescence labelling of uroplakins. During carcinogenesis, the structure of the urinary bladder luminal surface changed from microridges to microvilli and ropy ridges and the expression of urothelial-specific glycoproteins uroplakins was decreased. Ex vivo and in vivo lectin binding experiments gave comparable results. Jacalin (lectin from Artocarpus integrifolia) exhibited the highest selectivity for neoplastic compared to normal urothelium of rats and mice. The binding of lectin from Amaranthus caudatus decreased in rat model and increased in mouse carcinogenesis model, indicating interspecies variations of plasma membrane glycosylation. Lectin from Datura stramonium showed higher affinity for neoplastic urothelium compared to the normal in rat and mouse model. The BBN-induced animal models of bladder carcinogenesis offer a promising approach for lectin binding experiments and further lectin-mediated targeted drug delivery research. Moreover, in vivo lectin binding experiments are comparable to ex vivo experiments, which should be considered when planning and optimizing future research.     

Purification and characterization of an inverting stereo- and enantioselective sec-alkylsulfatase from the gram-positive bacterium Rhodococcus ruber DSM 44541

Whole cells of Rhodococcus ruber DSM 44541 were found to hydrolyze (+/-)-2-octyl sulfate in a stereo- and enantiospecific fashion. When growing on a complex medium, the cells produced two sec-alkylsulfatases and (at least) one prim-alkylsulfatase in the absence of an inducer, such as a sec-alkyl sulfate or a sec-alcohol. From the crude cell-free lysate, two proteins responsible for sulfate ester hydrolysis (designated RS1 and RS2) were separated from each other based on their different hydrophobicities and were subjected to further chromatographic purification. In contrast to sulfatase RS1, enzyme RS2 proved to be reasonably stable and thus could be purified to homogeneity. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed a single band at a molecular mass of 43 kDa. Maximal enzyme activity was observed at 30 degrees C and at pH 7.5. Sulfatase RS2 showed a clear preference for the hydrolysis of linear secondary alkyl sulfates, such as 2-, 3-, or 4-octyl sulfate, with remarkable enantioselectivity (an enantiomeric ratio of up to 21 [23]). Enzymatic hydrolysis of (R)-2-octyl sulfate furnished (S)-2-octanol without racemization, which revealed that the enzymatic hydrolysis proceeded through inversion of the configuration at the stereogenic carbon atom. Screening of a broad palette of potential substrates showed that the enzyme exhibited limited substrate tolerance; while simple linear sec-alkyl sulfates (C(7) to C(10)) were freely accepted, no activity was found with branched and mixed aryl-alkyl sec-sulfates. Due to the fact that prim-sulfates were not accepted, the enzyme was classified as sec-alkylsulfatase (EC 3.1.6.X).