Water permeability differs between growing and non-growing barley leaf tissues

A pressure probe technique and an osmotic swelling assay were used to compare water transport properties between growing and non-growing tissues of leaf three of barley. The epidermis was analysed in planta by pressure probe, whereas (predominantly) mesophyll protoplasts were analysed by osmotic swelling. Hydraulic conductivity (Lp) and, by implication, water permeability (Pf) of epidermal cells was 31% higher in the leaf elongation zone (Lp=0.5+/-0.2 microm s-1 MPa-1; Pf=65+/-25 microm s-1; means+/-SD of n=17 cells) than in the, non-growing, emerged leaf zone (Lp=0.4+/-0.1 microm s-1 MPa-1; Pf=50+/-15 microm s-1; n=24; P<0.05). Similarly, water permeability of mesophyll protoplasts was by 55% higher in the elongation compared with emerged leaf zone (Pf=13+/-1 microm s-1 compared with 8+/-1 microm s-1; n=57 and 36 protoplasts, respectively; P<0.01). Within the leaf elongation zone, a small population of larger-sized protoplasts could be distinguished. These protoplasts, which originated most likely from parenchymateous bundle sheath or midrib parenchyma cells, had a three-fold higher water permeability (P<0.001) as mesophyll protoplasts. The effect on Lp and Pf of known aquaporin inhibitors was tested with the pressure probe (Au+, Ag+, Hg2+, phloretin) and the osmotic swelling assay (phloretin). Only phloretin, when applied to protoplasts in the swelling assay caused an average decrease in Pf, but the effect varied between isolations. Technical approaches and cell-type and growth-specific differences in water transport properties are discussed.     

Functional connections between auditory cortical fields in humans revealed by Granger causality analysis of intra-cranial evoked potentials to sounds: comparison of two methods

Knowledge of neural interactions amongst cortical sites is important for understanding higher brain function. We studied such interactions using Granger causality (GC) to analyze auditory event-related potentials (ERPs) recorded directly and simultaneously from two physiologically identified and functionally interconnected auditory areas of cerebral cortex in human neurosurgical patients. Two methods of GC analysis were used and the results compared. Both approaches involved adaptive autoregressive modeling but differed from each other in other ways. Results obtained by using the two methods also differed. Fewer false-positive results were obtained using the method that suppressed the ERP non-stationarity and that expressed the GC as the sum of model coefficients, which suggests that this is the more appropriate approach for analyzing ERPs recorded directly from the human cortex.     

Synthesis, structure, spectroscopic properties, and electrochemical behavior of mixed ligand bis(β-ketoesterato)zirconium (IV) and -hafnium (IV) phthalocyaninates

The synthesis of new zirconium and hafnium mixed ligand phthalocyanine complexes PcM(β-ketoester)₂, where M-Zr (IV), Hf (IV); Pc - the dianion of phthalocyanine, and β-ketoester - the out planed ligand, is reported. The obtained complexes are characterized by ¹H NMR, IR, UV-Vis spectroscopy and cyclic voltammetry. ¹H NMR and elemental analysis confirm the substitution of two Cl atoms for two β-ketoester fragments to the central atom of the macrocycle. The data of ¹H NMR, UV-Vis spectroscopy have allowed us to conclude that two β-ketoester ligands are in the cis geometry to the phthalocyanine plane. X-ray crystallography for bis(isopropyl 3-oxobutanoato)hafnium(IV)phthalocyanine confirms this conclusion. The central macrocycle of the phthalocyanine ligand is not exactly planar (deviations from the least-square plane exceed 0.15 Å) and has the conformation of an essentially flattened crown. The Hf(1) atom is 1.349(3) above this least-square plane. Cyclic voltammetry investigation shows that the introduction of two β-ketoester ligands to the central atom of phthalocyanine complex leads to both chemical and electrochemical stabilization of the whole Pc system.     

In vivo functions of mitogen-activated protein kinases: conclusions from knock-in and knock-out mice

Multicellular organisms achieve intercellular communication by means of signalling molecules whose effect on the target cell is mediated by signal transduction pathways. Such pathways relay, amplify and integrate signals to elicit appropriate biological responses. Protein kinases form crucial intermediate components of numerous signalling pathways. One group of protein kinases, the mitogen-activated protein kinases (MAP kinases) are kinases involved in signalling pathways that respond primarily to mitogens and stress stimuli. In vitro studies revealed that the MAP kinases are implicated in several cellular processes, including cell division, differentiation, cell survival/apoptosis, gene expression, motility and metabolism. As such, dysfunction of specific MAP kinases is associated with diseases such as cancer and immunological disorders. However, the genuine in vivo functions of many MAP kinases remain elusive. Genetically modified mouse models deficient in a specific MAP kinase or expressing a constitutive active or a dominant negative variant of a particular MAP kinase offer valuable tools for elucidating the biological role of these protein kinases. In this review, we focus on the current status of MAP kinase knock-in and knock-out mouse models and their phenotypes. Moreover, examples of the application of MAP kinase transgenic mice for validating therapeutic properties of specific MAP kinase inhibitors, and for investigating the role of MAP kinase in pathogen-host interactions will be discussed.     

Wide dynamic range phase-sensitive surface plasmon resonance biosensor based on measuring the modulation harmonics

In this study, a novel phase-sensitive surface plasmon resonance (SPR) setup, based on temporal modulation of a pumping beam by a photoelastic modulator, and subsequent extraction of phase information at the second and the third harmonics of the modulation frequency, has been developed to study biomolecular interactions on SPR-supporting gold. We demonstrated that the design setup provides ultra-high phase sensitivity, together with a wide dynamic range of measurements. In particular, the proposed scheme was used to study real-time interaction of biotin-protein and streptavidin-BSA complexes. We have found that the proposed technique has a detection limit as high as 2.89 x 10(-7) in terms of refractive index units (RIU). In terms of biosensing performance, a detection sensitivity of 1.3 nM from the streptavidin-maleimide/thiolated BSA complex binding reaction has also been demonstrated.     

An electronic analog of synthetic genetic networks

An electronic analog of a synthetic genetic network known as the repressilator is proposed. The repressilator is a synthetic biological clock consisting of a cyclic inhibitory network of three negative regulatory genes which produces oscillations in the expressed protein concentrations. Compared to previous circuit analogs of the repressilator, the circuit here takes into account more accurately the kinetics of gene expression, inhibition, and protein degradation. A good agreement between circuit measurements and numerical prediction is observed. The circuit allows for easy control of the kinetic parameters thereby aiding investigations of large varieties of potential dynamics.