A gating mutation at the internal mouth of the Kir6.2 pore is associated with DEND syndrome

Inwardly rectifying potassium (Kir) channels control cell membrane K+ fluxes and electrical signalling in diverse cell types. Heterozygous mutations in the human Kir6.2 gene (KCNJ11), the pore-forming subunit of the ATP-sensitive (K(ATP)) channel, cause permanent neonatal diabetes mellitus. However, the I296L mutation also results in developmental delay, muscle weakness and epilepsy. We investigated the functional effects of the I296L mutation by expressing wild-type or mutant Kir6.2/SUR1 channels in Xenopus oocytes. The mutation caused a marked increase in resting whole-cell K(ATP) currents by reducing channel inhibition by ATP, in both homomeric and simulated heterozygous states. Kinetic analysis showed that the mutation impaired ATP sensitivity indirectly, by stabilizing the open state of the channel and possibly also by means of an allosteric effect on ATP binding and/or transduction. The results implicate a new region in Kir-channel gating and suggest that disease severity is correlated with the extent of reduction in ATP sensitivity.     

"Harshlighting" small blemishes on microarrays

Background  

Microscopists are familiar with many blemishes that fluorescence images can have due to dust and debris, glass flaws, uneven distribution of fluids or surface coatings, etc. Microarray scans show similar artefacts, which affect the analysis, particularly when one tries to detect subtle changes. However, most blemishes are hard to find by the unaided eye, particularly in high-density oligonucleotide arrays (HDONAs).     

The influence of plasma membrane ion permeability modulators on superoxide formation and bioelectrical characteristics of wheat root cells

Changes in superoxide radical formation and bioelectrical characteristics of excised wheat root cells under modification of plasma membrane ion permeability were studied. It was shown that a 2 h treatment of excised roots with valinomycin (Val, 20 microM), N, N'-dicyclohexylcarbodimide (DCCD, 100 microM), gramicidin S (Gr, 20 microM), chlorpromazine (CPZ, 100 microM) caused an increased loss of potassium by cells, lowering of membrane potential (MP) and electrical input resistance (Rin) of the cells. The superoxide formation by excised root cells diminished (under DCCD) or remained at the control level (under Val), which was accompanied by a minor decrease of MP and Rin of the cells, a small increase in potassium loss by excised roots, and in no change of pH of incubation medium. Significant depolarization of plasma membrane, dropping of Rin and essential loss of potassium ions by the cells correlated with a rise in the medium alkalinization and superoxide formation by excised roots (in the presence of Gr, CPZ). Ion channel blocker gadolinium (Gd3+, 200 microM) caused an increase of MP and Rin reduction of potassium loss by cells, and a decrease of pH of the incubation medium, and also enhancement of superoxide formation by excised root cells. It is suggested that upon plasma membrane ion permeability modification the activity of superoxide generating systems depends on the specificity and mechanisms of action of modulators, and is determined by their influence on redox state of plasma membrane as well as by peculiarities of ion transport disturbance.     

Emotionality and spatio-temporal organization of momentary EEG potentials

With the aim to reveal features of the neocortical spatiotemporal organization of potentials characteristic of different genetically predetermined emotional levels, momentary values of EEG potentials were analyzed in inbred rats of MR and MNRA strains. A topogram was described by a basic parameter such as its general level (the mean of momentary values of potentials derived from 24 symmetrical electrodes bilaterally implanted into the brain cortex) and a similarity coefficient (correlation between the set of its momentary values and that of a standard topogram). The general level and similarity coefficient values were calculated for a series of successive topograms individually for the right and left hemisphere. Also, right- and left-side power spectra of these series were calculated. In rats of MR strain, significant (p < 0.05) peaks in the general level and similarity coefficient spectra were observed in the delta (2.0 Hz), teta (6.5 Hz) and alpha (9 Hz) frequency bands. In this strain, the general level power was higher at the right side, and the similarity coefficient power displayed the left-side dominance. In rats of MNRA strain, peaks in the delta(2.0 Hz) band coinsided in the general level and similarity coefficient spectra, whereas, independently, the general level spectra had peaks in the theta band (7.0 Hz), and similarity coefficient had peaks at frequencies 3.0, 4.5, and 6.0 Hz. The left-side general level spectral power was higher than the right-side general level spectral power in the delta and lower in the high-frequency theta bands. The similarity coefficient power displayed the left-side dominance for the peaks in the delta (2.0 Hz) and theta (3.0 Hz) bands, and it displayed the right-side dominance for the peaks in the theta (4.5 Hz) band. The specific features of the cortical spatiotemporal organization of potentials revealed in rats of MR and MNRA strains suggest different modes of functioning of at least two systems, reticulo-thalamo-corticaland hippocampo-cortical.     

Influence of chronic melipramine administration abolition on locomotion and defensive conditioned reflexes in passive and active avoidance in rats

The chronic (21 days duration) administration of tricyclic antidepressant melipramine of Wistar rats strain (15 mg/kg daily, intraperitoneally) evoked weight loss of animals. The 7 days after melipramine abolition its sedative effect was observed in the "open field" test by decrease of locomotion and the number of boles. The 7 and 14 days after melipramine abolition the difference between control and melipramine treated animals in passive and active avoidance learning and memory not found. The experimental results comparison with the literature data show, that chronic melipramine administration of intact animals evokes a sedative state. This conclusion does not contradict to idea of punishment function of brain serotoninergic system.     

Energy metabolism in wheat root cells under modification of plasma membrane permeability by antibiotic nystatin

This paper reports changes in ion transport and energy metabolism of plant cells during short- and long-term expositions, resp., to antibiotic nystatin, which is known to specifically bind with plasma membrane sterols to form channels. The excised roots of 5 days old wheat seedlings were used as a model system in this research. It has been shown that treatment of excised roots with nystatin leads to activation of energy metabolism expressed as an increase of respiration and heat production by root cells. Furthermore, in the presence of nystatin increased pH of incubation medium, plasma membrane depolarization and a significant loss of potassium ions were observed. Nystatin-induced stimulation of respiration was prevented by malonate, an inhibitor of succinate dehydrogenase, electron acceptor dichlorophenolindophenol, and AgNO3, an inhibitor of H(+)-ATPase. Based on the data obtained it can be suggested that nystatin-induced stimulation of respiration is related to electron transport activation via mitochondrial respiratory chain, and is connected with activation of plasmalemma proton pump. Moreover, nystatin-induced increase of oxygen consumption was prevented by cerulenin, an inhibitor of fatty acid and sterol synthesis. This indicates that additional sterols and phospholipids may be synthesized in root cells to "heal" nystatin-caused damage of plasma membrane. A supposed chain of events of cell response to nystatin action may by as following: formation of nystatin channels-influx of protons--depolarization of plasmalemma-efflux of potassium ions-disturbance of ion homeostasis--activation of H(+)-ATPase work-increase in energy "requests" for H(+)-ATPase function--increase in the rate of oxygen consumption and heat production. The increased energy production under the action of nystatin, may provide the work of proton pump and synthesis of sterols and phospholipids, which are necessary for membrane regeneration.     

Primary Structure of NM.<Emphasis Type="Italic">Bst</Emphasis>SEI Operon from <Emphasis Type="Italic">Bacillus stearothermophilus</Emphasis>, the Producer of N.<Emphasis Type="Italic">Bst</Emphasis>SEI Site-Specific Nicking Endonuclease

The nucleotide sequence of Bacillus stearothermophilus SE-589 DNA fragment including an operon for the site-specific nicking-modification (NM) system with a gene for BstSEI nicking endonuclease (nickase) has been determined. An analysis of the regions adjacent to the nickase gene has revealed two genes encoding DNA methyltransferases belonging to different classes. Three genes that form the system operon are separated by short open reading frames (ORFs). An analysis of these ORFs has shown that the polypeptides they encode are homologous to different parts of BstSEI nickase, NatB protein, and arginase. A difference in the GC content of the beginning and ending regions of the cloned DNA fragment and the presence of short ORFs similar to genes for known proteins indicate that the NM.BstSEI system operon has probably evolved by horizontal DNA transfer.     

Photoinhibition in vivo of Photosystem II reactions during developmentof the photosystems of wheat seedlings

Photoinhibition of O₂ evolution and reactions leading to millisecond-delayed light emission (ms-DLE) of chlorophyll by illumination of leaves with excess white light were investigated in wheat seedlings greened for different times in a special chamber with constant conditions (20°C; CO₂ and humidity). A sharp reduction in initial and steady state rates of O₂ evolution and in the intensity of different components of ms-DLE under excess light on the stage of lag-phase of chlorophyll biosynthesis (4–6h of greening) were observed. An increasing stability of the oxygen-evolving process and ms-DLE of chlorophyll during formation of the thylakoid membrane photosystems (12–24 h of greening) was shown. Rifampicin did not influence the stability of oxygen evolution whereas cycloheximide led to the intensification of photoinhibition of the initial and steady-state rates of oxygen evolution under the inhibitory light action. The early stages of photosystems formation during short time of greening of etiolated seedlings were more sensitive to the action of inhibitory light, possibly due to a weak interaction of the oxygen-evolving system components and connection with reaction centers of Photosystem II.