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Selected AbstractsAnisotropic contraction in forisomes: Simple models won't fitCYTOSKELETON, Issue 5 2008Winfried S. Peters Abstract Forisomes are ATP-independent, Ca2+ -driven contractile protein bodies acting as reversible valves in the phloem of plants of the legume family. Forisome contraction is anisotropic, as shrinkage in length is associated with radial expansion and vice versa. To test the hypothesis that changes in length and width are causally related, we monitored Ca2+ - and pH-dependent deformations in the exceptionally large forisomes of Canavalia gladiata by high-speed photography, and computed time-courses of derived geometric parameters (including volume and surface area). Soybean forisomes, which in the resting state resemble those of Canavalia geometrically but have less than 2% of the volume, were also studied to identify size effects. Calcium induced sixfold volume increases in forisomes of both species; in soybean, responses were completed in 0.15 s, compared to about 0.5 s required for a rapid response in Canavalia followed by slow swelling for several minutes. This size-dependent behavior supports the idea that forisome contractility might rest on similar mechanisms as those of polyelectrolyte gels, a class of artificial "smart" materials. In both species, time-courses of forisome length and diameter were variable and lacked correlation, arguing against a simple causal relationship between changes in length and width. Moreover, changes in the geometry of soybean forisomes differed qualitatively between Ca2+ - and pH-responses, suggesting that divalent cations and protons target different sites on the forisome proteins. Cell Motil. Cytoskeleton 2008. © 2008 Wiley-Liss, Inc. [source] Improved Detection Limit and Stability of Amperometric Carbon Nanotube-Based Immunosensors by Crosslinking Antibodies with PolylysineELECTROANALYSIS, Issue 2 2008Vito Cataldo Abstract Amperometric immunosensor configurations featuring covalently bound anti-biotin antibodies (Ab) embedded into a polylysine (PLL)-single walled carbon nanotube (SWCNT) composite layer were evaluated. Assemblies were made by first oxidizing pyrolytic graphite (PG) electrodes to form surface carboxylic acid groups, to which PLL, SWCNTs and anti-biotin were covalently linked. Incorporating SWCNT into PLL-antibody assemblies improved the amperometric detection limit for biotin (Ag) labeled with horseradish peroxidase to 10,fmol mL,1. Anti-biotin embedded into the PLL matrix had improved thermal stability and retained its binding ability for biotin after exposure to temperatures of 42,°C for up to 3 hours, while the noncrosslinked antibody was inactivated at this temperature in several minutes. [source] Temperature-Responsive Substrates: Adhesion and Mechanical Properties of PNIPAM Microgel Films and Their Potential Use as Switchable Cell Culture Substrates (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 19 2010Mater. Abstract Thermoresponsive poly(N -isopropylacrylamide) (PNIPAM) microgel films are shown to allow controlled detachment of adsorbed cells via temperature stimuli. Cell response occurs on the timescale of several minutes, is reversible, and allows for harvesting of cells in a mild fashion. The fact that microgels are attached non-covalently allows using them on a broad variety of (charged) surfaces and is a major advantage as compared to approaches relying on covalent attachment of active films. In the following, the microgels' physico-chemical parameters in the adsorbed state and their changes upon temperature variation are studied in order to gain a deeper understanding of the involved phenomena. By means of atomic force microscopy (AFM), the water content, mechanical properties, and adhesion forces of the microgel films are studied as a function of temperature. The analysis shows that these properties change drastically when crossing the critical temperature of the polymer film, which is the basis of the fast cell response upon temperature changes. Furthermore, nanoscale mechanical analysis shows that the films posses a nanoscopic gradient in mechanical properties. [source] Adhesion and Mechanical Properties of PNIPAM Microgel Films and Their Potential Use as Switchable Cell Culture SubstratesADVANCED FUNCTIONAL MATERIALS, Issue 19 2010Stephan Schmidt Abstract Thermoresponsive poly(N -isopropylacrylamide) (PNIPAM) microgel films are shown to allow controlled detachment of adsorbed cells via temperature stimuli. Cell response occurs on the timescale of several minutes, is reversible, and allows for harvesting of cells in a mild fashion. The fact that microgels are attached non-covalently allows using them on a broad variety of (charged) surfaces and is a major advantage as compared to approaches relying on covalent attachment of active films. In the following, the microgels' physico-chemical parameters in the adsorbed state and their changes upon temperature variation are studied in order to gain a deeper understanding of the involved phenomena. By means of atomic force microscopy (AFM), the water content, mechanical properties, and adhesion forces of the microgel films are studied as a function of temperature. The analysis shows that these properties change drastically when crossing the critical temperature of the polymer film, which is the basis of the fast cell response upon temperature changes. Furthermore, nanoscale mechanical analysis shows that the films posses a nanoscopic gradient in mechanical properties. [source] Electrical Stimulation of Sphenopalatine Ganglion for Acute Treatment of Cluster HeadachesHEADACHE, Issue 7 2010Mehdi Ansarinia MD (Headache 2010;50:1164-1174) Introduction., Cluster headaches (CH) are primary headaches marked by repeated short-lasting attacks of severe, unilateral head pain and associated autonomic symptoms. Despite aggressive management with medications, oxygen therapy, nerve blocks, as well as various lesioning and neurostimulation therapies, a number of patients are incapacitated and suffering. The sphenopalatine ganglion (SPG) has been implicated in the pathophysiology of CH and has been a target for blocks, lesioning, and other surgical approaches. For this reason, it was selected as a target for an acute neurostimulation study. Methods., Six patients with refractory chronic CH were treated with short-term (up to 1 hour) electrical stimulation of the SPG during an acute CH. Headaches were spontaneously present at the time of stimulation or were triggered with agents known to trigger clusters headache in each patient. A standard percutaneous infrazygomatic approach was used to place a needle at the ipsilateral SPG in the pterygopalatine fossa under fluoroscopic guidance. Electrical stimulation was performed using a temporary stimulating electrode. Stimulation was performed at various settings during maximal headache intensity. Results., Five patients had CH during the initial evaluation. Three returned 3 months later for a second evaluation. There were 18 acute and distinct CH attacks with clinically maximal visual analog scale (VAS) intensity of 8 (out of 10) and above. SPG stimulation resulted in complete resolution of the headache in 11 attacks, partial resolution (>50% VAS reduction) in 3, and minimal to no relief in 4 attacks. Associated autonomic features of CH were resolved in each responder. Pain relief was noted within several minutes of stimulation. Conclusion., Sphenopalatine ganglion stimulation can be effective in relieving acute severe CH pain and associated autonomic features. Chronic long-term outcome studies are needed to determine the utility of SPG stimulation for management and prevention of CH. [source] Effects of hippocampal lesions on the monkey's ability to learn large sets of object-place associations,HIPPOCAMPUS, Issue 4 2006Annabelle M. Belcher Abstract Earlier studies found that recognition memory for object-place associations was impaired in patients with relatively selective hippocampal damage (Vargha-Khadem et al., Science 1997; 277:376,380), but was unaffected after selective hippocampal lesions in monkeys (Malkova and Mishkin, J Neurosci 2003; 23:1956,1965). A potentially important methodological difference between the two studies is that the patients were required to remember a set of 20 object-place associations for several minutes, whereas the monkeys had to remember only two such associations at a time, and only for a few seconds. To approximate more closely the task given to the patients, we trained monkeys on several successive sets of 10 object-place pairs each, with each set requiring learning across days. Despite the increased associative memory demands, monkeys given hippocampal lesions were unimpaired relative to their unoperated controls, suggesting that differences other than set size and memory duration underlie the different outcomes in the human and animal studies. © 2005 Wiley-Liss, Inc. [source] Characterizing user-perceived impairment events using end-to-end measurementsINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 10 2005Soshant Bali Abstract Measures of quality of service (QoS) must correlate to end-user experience. For multimedia services, these metrics should focus on the phenomena that are observable by the end-user. Metrics such as delay and loss may have little direct meaning to the end-user because knowledge of specific coding and/or adaptive techniques is required to translate delay and loss to the user-perceived performance. Impairment events, as defined in this paper, are observable by the end-users independent of coding, adaptive playout or packet loss concealment techniques employed by their multimedia applications. Time between impairments and duration of impairments are metrics that are easily understandable by a network user. Methods to detect these impairment events using end-to-end measurements are developed here. In addition, techniques to identify Layer 2 route changes and congestion events using end-to-end measurements are also developed. These are useful in determining what caused the impairments. End-to-end measurements were conducted for about 26 days on 9 different node pairs to evaluate the developed techniques. Impairments occurred at a high rate on the two paths on which congestion events were detected. On these two paths, congestion occurred for 6,8 hours during the day on weekdays. Impairments caused by route changes were rare but lasted for several minutes. Copyright © 2005 John Wiley & Sons, Ltd. [source] Persistence effects in flavour release from liquids in the mouthINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 3 2003Kevin M. Wright Summary The flavour of drinks, creams and liquid-like food consumed without chewing is an important quality factor for consumers and manufacturers alike, so reliable predictive models of flavour release from liquids in the mouth are highly desirable. In this paper we show how the breath-by-breath concentration of aroma in the headspace after swallowing an aliquot of liquid can be modelled using basic principles of interfacial mass transfer. This mechanistic model is used to fit the experimental data for dilute aqueous solutions of five aroma compounds consumed by trained panellists. It is shown that many aroma compounds give detectable concentrations in the exhaled breath several minutes after swallowing and after ten or more exhalations. The influence of liquid composition on this aroma persistence effect is discussed. [source] A Selective and Benign Synthesis of Functionalized Benzalacetones via Mizoroki,Heck Reaction Using Aryldiazonium SaltsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2010Therese Stern Abstract Palladium-catalyzed Mizoroki,Heck reactions were carried out in the presence of calcium carbonate in alcoholic solvents. Under these conditions an efficient preparation of functionalized benzalacetones was developed. The reactions were carried out at room temperature and aerobic conditions, giving the products within several minutes in up to 95% isolated yields. Furthermore, some kinetic investigations, mechanistic insights and considerations are presented. [source] Independent Autonomic Modulation of Sinus Node and Ventricular Myocardium in Healthy Young Men During SleepJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 10 2000PETER KOWALLIK M.D. Autonomic Modulation of Sinus Node and Ventricle. Introduction. The aim of this study was to investigate whether autonomic modulation of ventricular repolarization may spontaneousiy differ from that of the sinoatrial node. Methods and Results. Onset of P waves. QRS complexes, and the apex and end of T waves were detected heat to heat in high-resolution ECGs from nine healthy young men during the night. There were time-dependent fluctuations in the QT/RR slopes of consecutive 5-minute segments that could not he explained by the mean RR cycle length of the respective segment. Because the variahility found in QT intervals could not be explained hy either possible effects of rate dependence or hysteresis, autonomic effects were obvious. Power speetral analysis was performed for consecutive 5-minute segments of PP and QT techograms. In a given subject. trends in the time course of low-frequency (LF) and high-frequency (HF) power in PP and QT often were similar, but they were quite different at other times. The mean LF/HF ratio for QTend (0.75 ± 0.1) was different from that of PP (1.8 ± 0.2; P = 0.002), indicating differences in sympathovagal balance at the different anatomic sites. Furthermore, at a given mean heart rate, averaged QT intervals were different on a time scale of several minutes to hours. The QT/RR slope of 5-minute segments correlated significantly with the HF power of QT variability but not with that of PP variability, indicating effects of the autonomic nervous system on ventricular action potential restitution. Conclusion. These differences demonstrate that changes in sinus node automaticity are not necessarily indicative of the autonomic control of ventricular myocardium. (J Cardiavasc Electrophysiol, Vol. II, pp. 1063-1070. October 2000) [source] Variations of sperm release in three batches of zebrafishJOURNAL OF FISH BIOLOGY, Issue 2 2004J. R. Kemadjou Njiwa By collecting and counting the number of sperm released during separate matings in three batches of zebrafish Danio rerio, aged 3,4, 4,5 and 5,6 months, males were observed to release sperm before the female started laying their eggs. After the female left the nest, the number and motility of sperm and life span of sperm of younger fish were higher than those of older fish in water samples collected under the nest and at the surface of the tank. Sperm were released in the form of sperm trails laid on the nest surface, subsequently active spermatozoa left the trails and moved in the water for several minutes. Sperm trails consisted of bands of viscous material in which the sperm were embedded. In most cases eggs were not laid directly over the sperm trail, suggesting that sperm may contact the eggs after the latter are released into the water. In all the three tested groups there was no significant difference (P > 0·05) between the number of sperm collected on some portions of the acetate sheets which lined the nest ceiling. This result demonstrated that the greater activity of younger fish accelerated the sperm dispersal in water. Male sperm duct glands, seminal vesicles, known to secrete mucosubstances are probably involved in the production of sperm trails. The possible influence of insemination on the mating style of zebrafish is discussed. [source] Chemical-looping combustion process: Kinetics and mathematical modelingAICHE JOURNAL, Issue 4 2010Ion Iliuta Abstract Chemical Looping Combustion technology involves circulating a metal oxide between a fuel zone where methane reacts under anaerobic conditions to produce a concentrated stream of CO2 and water and an oxygen rich environment where the metal is reoxidized. Although the needs for electrical power generation drive the process to high temperatures, lower temperatures (600,800°C) are sufficient for industrial processes such as refineries. In this paper, we investigate the transient kinetics of NiO carriers in the temperature range of 600 to 900°C in both a fixed bed microreactor (WHSV = 2-4 g CH4/h/g oxygen carrier) and a fluid bed reactor (WHSV = 0.014-0.14 g CH4/h per g oxygen carrier). Complete methane conversion is achieved in the fluid bed for several minutes. In the microreactor, the methane conversion reaches a maximum after an initial induction period of less than 10 s. Both CO2 and H2O yields are highest during this induction period. As the oxygen is consumed, methane conversion drops and both CO and H2 yields increase, whereas the CO2 and H2O concentrations decrease. The kinetics parameter of the gas,solids reactions (reduction of NiO with CH4, H2, and CO) together with catalytic reactions (methane reforming, methanation, shift, and gasification) were estimated using experimental data obtained on the fixed bed microreactor. Then, the kinetic expressions were combined with a detailed hydrodynamic model to successfully simulate the comportment of the fluidized bed reactor. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source] Three-photon microscopy shows that somatic release can be a quantitatively significant component of serotonergic neurotransmission in the mammalian brainJOURNAL OF NEUROSCIENCE RESEARCH, Issue 15 2008S.K. Kaushalya Abstract Recent experiments on monoaminergic neurons have shown that neurotransmission can originate from somatic release. However, little is known about the quantity of monoamine available to be released through this extrasynaptic pathway or about the intracellular dynamics that mediate such release. Using three-photon microscopy, we directly imaged serotonin autofluorescence and investigated the total serotonin content, release competence, and release kinetics of somatic serotonergic vesicles in the dorsal raphe neurons of the rat. We found that the somata of primary cultured neurons contain a large number of serotonin-filled vesicles arranged in a perinuclear fashion. A similar distribution is also observed in fresh tissue slice preparations obtained from the rat dorsal raphe. We estimate that the soma of a cultured neuron on an average contains about 9 fmoles of serotonin in about 450 vesicles (or vesicle clusters) of ,370 nm average diameter. A substantial fraction (>30%) of this serotonin is released with a time scale of several minutes by K+ -induced depolarization or by para-chloroamphetamine treatment. The amount of releasable serotonin stored in the somatic vesicles is comparable to the total serotonin content of all the synaptic vesicles in a raphe neuron, indicating that somatic release can potentially play a major role in serotonergic neurotransmission in the mammalian brain. © 2008 Wiley-Liss, Inc. [source] Topographic electroencephalogram in children during mask induction of anaesthesia with sevofluraneACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 1 2009E. SONKAJÄRVI Background: Epileptiform patterns, spikes, polyspikes and periodic epileptiform discharges (PED) have been reported in electroencephalograms (EEGs) during anaesthesia induction with sevoflurane in healthy adults and children. Published recordings have been performed with a limited number of channels, and therefore the topographic distributions of these patterns are not known. Methods: Twenty ASA I children aged 4,10 years undergoing routine operations were anaesthetized with 8% sevoflurane in 50%/50% oxygen and nitrous oxide using mask induction with controlled normoventilation. An EEG was recorded with a full 10,20 electrode system including orbitofrontal and ear electrodes, and a recording band of 0.016,70 Hz. Beat-to-beat heart rate (HR) was calculated off-line. Results: Nineteen out of 20 children developed multifocal spikes and polyspikes with a maximum over the frontal lobes. Four patients developed suppression, which was almost continuous and lasted several minutes, and thereafter a continuous EEG resumed, a few spikes were seen and then a nonepileptiform pattern. In three children a couple of PED waves were seen at the onset of a continuous EEG. HR increased maximally before the onset of spikes. No motor phenomena were seen. Conclusion: These recordings confirm the epileptogenic property of sevoflurane in mask induction. The spikes and polyspikes had frontal multifocal maxima and may be missed in recordings from frontopolar electrodes used by depth-of-anaesthesia monitors. PED and burst suppression were synchronous over the whole cortex. Epileptiform activity was indiscernible from epileptiform waveforms without anaesthesia, such as the patterns seen in status epilepticus. [source] Chemical Agent Simulant Release from Clothing Following Vapor ExposureACADEMIC EMERGENCY MEDICINE, Issue 2 2010Robert J. Feldman MD ACADEMIC EMERGENCY MEDICINE 2010; 17:1,4 © 2010 by the Society for Academic Emergency Medicine Abstract Objectives:, Most ambulatory victims of a terrorist chemical attack will have exposure to vapor only. The study objective was to measure the duration of chemical vapor release from various types of clothing. Methods:, A chemical agent was simulated using methyl salicylate (MeS), which has similar physical properties to sulfur mustard and was the agent used in the U.S. Army's Man-In-Simulant Test (MIST). Vapor concentration was measured with a Smiths Detection Advanced Portable Detector (APD)-2000 unit. The clothing items were exposed to vapor for 1 hour in a sealed cabinet; vapor concentration was measured at the start and end of each exposure. Clothing was then removed and assessed every 5 minutes with the APD-2000, using a uniform sweep pattern, until readings remained 0. Results:, Concentration and duration of vapor release from clothing varied with clothing composition and construction. Lightweight cotton shirts and jeans had the least trapped vapor; down outerwear, the most. Vapor concentration near the clothing often increased for several minutes after the clothing was removed from the contaminated environment. Compression of thick outerwear released additional vapor. Mean times to reach 0 ranged from 7 minutes for jeans to 42 minutes for down jackets. Conclusions:, This simulation model of chemical vapor release demonstrates persistent presence of simulant vapor over time. This implies that chemical vapor may be released from the victims' clothing after they are evacuated from the site of exposure, resulting in additional exposure of victims and emergency responders. Insulated outerwear can release additional vapor when handled. If a patient has just moved to a vapor screening point, immediate assessment before additional vapor can be released from the clothing can lead to a false-negative assessment of contamination. [source] RAPID AMMONIUM- AND NITRATE-INDUCED PERTURBATIONS TO CHL a FLUORESCENCE IN NITROGEN-STRESSED DUNALIELLA TERTIOLECTA (CHLOROPHYTA),JOURNAL OF PHYCOLOGY, Issue 2 2003Erica B. Young When NH4+ or NO3, was supplied to NO3, -stressed cells of the microalga Dunaliella tertiolecta Butcher, immediate transient changes in chl a fluorescence were observed over several minutes that were not seen in N-replete cells. These changes were predominantly due to nonphotochemical fluorescence quenching. Fluorescence changes were accompanied by changes in photosynthetic oxygen evolution, indicating interactions between photosynthesis and N assimilation. The magnitude of the fluorescence change showed a Michaelis-Menten relationship with half-saturation concentration of 0.5 ,M for NO3, and 10 ,M for NH4+. Changes in fluorescence responses were characterized in D. tertiolecta both over 5 days of N starvation and in cells cultured at a range of NO3, -limited growth rates. Variation in responses was more marked in starved than in limited cells. During N starvation, the timing and onset of the fluorescence responses were different for NO3, versus NH4+ and were correlated with changes in maximum N uptake rate during N starvation. In severely N-starved cells, the major fluorescence response to NO3, disappeared, whereas the response to NH4+ persisted. N-starved cells previously grown with NH4+ alone showed fluorescence responses with NH4+ but not NO3, additions. The distinct responses to NO3, and NH4+ may be due to the differences between regulation of the uptake mechanisms for the two N sources during N starvation. This method offers potential for assessing the importance of NO3, or NH4+ as an N source to phytoplankton populations and as a diagnostic tool for N limitation. [source] Control of Induced Chirality in Optically Active Poly(N-propargylcarbamate) Films by Solvent VaporMACROMOLECULAR RAPID COMMUNICATIONS, Issue 15 2009Toshiyuki Fukushima Abstract Chiral polyethyne derivatives with lyotropic liquid-crystalline properties are found to be able to self-assemble, forming two chiral organizations with opposite handedness in solid thin films by selection of the casting solvent and its concentration. After the film preparation, chiral organization could also be induced by simple exposure to an appropriate organic solvent's vapor for several minutes without thermal treatment. Furthermore, irreversible inversion of the handedness of the chiral organization in the film could be achieved by exposure to solvent vapor. [source] Vergence adaptation and the clinical AC/A ratioOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 3 2000Mark Rosenfield Summary The accuracy of the gradient technique for measuring the clinical accommodative convergence to accommodation (AC/A) ratio is dependent upon obtaining veridical heterophoria measurements. However, previous studies have demonstrated that the sustained output of slow fusional vergence, which may take several minutes or even hours to decay, can bias heterophoria assessment. In the clinical setting, it is usual to estimate the AC/A ratio after just a few seconds of dissociation. This study investigated whether the slow fusional vergence response alters this crosslink ratio by comparing values of AC/A measured both before and immediately after a 1-hr period of continuous monocular occlusion. Sustained occlusion produced a significant change in near heterophoria in 10 out of the 21 subjects examined, but no significant change in AC/A was observed in either the adapting or non-adapting subgroups. Accordingly, while the sustained output of slow fusional vergence will influence clinical measurements of heterophoria, its presence does not alter the stimulus AC/A ratio significantly. [source] Delayed Restoration of Atrioventricular Synchrony with Beat-to-Beat Mode SwitchPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 8 2001FRANK BODE BODE, F., et al.: Delayed Restoration of Atrioventricular Synchrony with Beat-to-Beat Mode Switch. This case report describes a patient with complete AV block and a VDD pacemaker who experienced repetitive episodes of symptomatic bradycardia. Episodes occurred due to activation of an automatic beat-to-beat mode switch algorithm. After mode switch to VDI operation, the pacemaker failed to immediately switch back to AV synchronous pacing when regular sinus rhythm (, 100 beats per minute) resumed despite adequate P wave sensing. Dizziness was felt for up to several minutes of asynchronous pacing at the lower rate limit until VDD mode was restored. Episodes were completely eliminated by programming the mode switch function from an automatic beat-to-beat algorithm to a fixed rate algorithm. [source] Efficient on-chip proteolysis system based on functionalized magnetic silica microspheresPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 14 2007Yan Li Abstract An easily replaceable enzymatic microreactor has been fabricated based on the glass microchip with trypsin-immobilized magnetic silica microspheres (MS microspheres). Magnetic microspheres with small size (,300,nm in diameter) and high magnetic responsivity to magnetic field (68.2,emu/g) were synthesized and modified with tetraethyl orthosilicate (TEOS). Aminopropyltriethoxysilane (APTES) and glutaraldehyde (GA) were then introduced to functionalize the MS microspheres for enzyme immobilization. Trypsin was stably immobilized onto the MS microspheres through the reaction of primary amines of the proteins with aldehyde groups on the MS microspheres. The trypsin-immobilized MS microspheres were then locally packed into the microchannel by the application of a strong field magnet to form an on-chip enzymatic microreactor. The digestion efficiency and reproducibility of the microreactor were demonstrated by using cytochrome c (Cyt-C) as a model protein. When compared with an incubation time of 12,h by free trypsin in the conventional digestion approach, proteins can be digested by the on-chip microreactor in several minutes. This microreactor was also successfully applied to the analysis of an RPLC fraction of the rat liver extract. This opens a route for its further application in top-down proteomic analysis. [source] Isomer differentiation by combining gas chromatography, selective self-ion/molecule reactions and tandem mass spectrometry in an ion trap mass spectrometerRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 10 2003Hui-Fen Wu This study presents a novel, simple and rapid procedure for isomer differentiation by combining gas chromatography (GC), a selective self-ion/molecule reaction (SSIMR) and tandem mass spectrometry (MS/MS) in an ion trap mass spectrometer (ITMS). SSIMR product ions were produced from four isomers. For aniline, SSIMR induces the formation of the molecular ion, [M+H]+, [M+CH]+, adduct ions of fragments ([M+F]+, where F represents fragment ions) and [2MH]+. 2 and 3-Picoline produce [M+H]+, [2MH]+ and [M+F]+, while 5-hexynenitrile produces [M+H]+, [M+F]+ and [2M+H]+ ions. The proposed method provides a relatively easy, rapid and efficient means of isomer differentiation via a SSIMR in the ITMS. Typically, isomer differentiation can be achieved within several minutes. The superiority of the SSIMR technique for isomer differentiation over electronic ionization (EI) is also demonstrated. Copyright © 2003 John Wiley & Sons, Ltd. [source] Heat stress activates phospholipase D and triggers PIP2 accumulation at the plasma membrane and nucleusTHE PLANT JOURNAL, Issue 1 2009Michael Mishkind Summary Heat stress induces an array of physiological adjustments that facilitate continued homeostasis and survival during periods of elevated temperatures. Here, we report that within minutes of a sudden temperature increase, plants deploy specific phospholipids to specific intracellular locations: phospholipase D (PLD) and a phosphatidylinositolphosphate kinase (PIPK) are activated, and phosphatidic acid (PA) and phosphatidylinositol 4,5-bisphosphate (PIP2) rapidly accumulate, with the heat-induced PIP2 localized to the plasma membrane, nuclear envelope, nucleolus and punctate cytoplasmic structures. Increases in the steady-state levels of PA and PIP2 occur within several minutes of temperature increases from ambient levels of 20,25°C to 35°C and above. Similar patterns were observed in heat-stressed Arabidopsis seedlings and rice leaves. The PA that accumulates in response to temperature increases results in large part from the activation of PLD rather than the sequential action of phospholipase C and diacylglycerol kinase, the alternative pathway used to produce this lipid. Pulse-labelling analysis revealed that the PIP2 response is due to the activation of a PIPK rather than inhibition of a lipase or a PIP2 phosphatase. Inhibitor experiments suggest that the PIP2 response requires signalling through a G-protein, as aluminium fluoride blocks heat-induced PIP2 increases. These results are discussed in the context of the diverse cellular roles played by PIP2 and PA, including regulation of ion channels and the cytoskeleton. [source] Cytological studies on induced meiogynogenesis in Japanese flounder Paralichthys olivaceus (Temminck et Schlegel)AQUACULTURE RESEARCH, Issue 6 2009Jilun Hou Abstract The cytological process of induced gynogenetic development and subsequent chromosome duplication by a cold shock treatment was observed in Japanese flounder Paralichthys olivaceus (Temminck et Schlegel). Mature eggs were at the metaphase of the second meiosis when inseminated with ultraviolet (UV)-irradiated sperm of red sea bream Pagrus major. After the beginning of cold shock treatment, the previously visible spindle became invisible, probably due to the side effect caused by cold shock treatment. The chromosomes at the centre of the metaphase plate were condensed. This condition continued during the duration of the cold shock treatment and several minutes after it. The release of the second polar body was blocked and it developed into a female-like pronucleus. Then, it fused with the female pronucleus to generate a diploid zygotic nucleus, and the egg exhibited the first mitosis. Consequently, the haploid female chromosome set of the egg was doubled by the inhibition of the second polar body release. There was a significant delay in developmental time in the gynogenetic eggs when compared with that in the normal eggs. From the time of insemination to early cleavage, the UV-irradiated heterospecific sperm nucleus remained condensed. [source] Fractional contribution of major ions to the membrane potential of Drosophila melanogaster oocytesARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 4 2009Susan M. Munley Abstract In ovarian follicles of Drosophila melanogaster, ion substitution experiments revealed that K+ is the greatest contributor (68%) in setting oocyte steady-state potential (Em), while Mg2+ and a metabolic component account for the rest. Because of the intense use made of Drosophila ovarian follicles in many lines of research, it is important to know how changes in the surrounding medium, particularly in major diffusible ions, may affect the physiology of the cells. The contributions made to the Drosophila oocyte membrane potential (Em) by [Na+]o, [K+]o, [Mg2+]o, [Ca2+]o, [Cl,]o, and pH (protons) were determined by substitutions made to the composition of the incubation medium. Only K+ and Mg2+ were found to participate in setting the level of Em. In follicles subjected to changes in external pH from the normal 7.3 to either pH 6 or pH 8, Em changed rapidly by about 6,mV, but within 8,min had returned to the original Em. Approximately half of all follicles exposed to reduced [Cl,]o showed no change in Em, and these all had input resistances of 330,k, or greater. The remaining follicles had smaller input resistances, and these first depolarized by about 5,mV. Over several minutes, their input resistances increased and they repolarized to a value more electronegative than their value prior to reduction in [Cl,]o. Together, K+ and Mg2+ accounted for up to 87% of measured steady-state potential. Treatment with sodium azide, ammonium vanadate, or chilling revealed a metabolically driven component that could account for the remaining 13%. © 2009 Wiley Periodicals, Inc. [source] Rapid media transition: An experimental approach for steady state analysis of metabolic pathwaysBIOTECHNOLOGY PROGRESS, Issue 1 2010Hannes Link Abstract Commonly steady state analysis of microbial metabolism is performed under well defined physiological conditions in continuous cultures with fixed external rates. However, most industrial bioprocesses are operated in fed-batch mode under non-stationary conditions, which cannot be realized in chemostat cultures. A novel experimental setup,rapid media transition,enables steady state perturbation of metabolism on a time scale of several minutes in parallel to operating bioprocesses. For this purpose, cells are separated from the production process and transferred into a lab-scale stirred-tank reactor with modified environmental conditions. This new approach was evaluated experimentally in four rapid media transition experiments with Escherichia coli from a fed-batch process. We tested the reaction to different carbon sources entering at various points of central metabolism. In all cases, the applied substrates (glucose, succinate, acetate, and pyruvate) were immediately utilized by the cells. Extracellular rates and metabolome data indicate a metabolic steady state during the short-term cultivation. Stoichiometric analysis revealed distribution of intracellular fluxes, which differs drastically subject to the applied carbon source. For some reactions, the variation of flux could be correlated to changes of metabolite concentrations. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010 [source] Controllable Synthesis of Nickel Hydroxide and Porous Nickel Oxide Nanostructures with Different MorphologiesCHEMISTRY - A EUROPEAN JOURNAL, Issue 16 2008Lihong Dong Dr. Abstract ,-Ni(OH)2 nanobelts, nanowires, short nanowires, and ,-Ni(OH)2 nanoplates have been successfully prepared in high yields and purities by a convenient hydrothermal method under mild conditions from very simple systems composed only of NaOH, NiSO4, and water. It has been found that the ratio of NaOH to NiSO4 not only affects the morphology of the Ni(OH)2 nanostructures, but also determines whether the product is of the ,- or ,-crystal phase. A notable finding is that porous NiO nanobelts were produced after exposure of the Ni(OH)2 products to an electron beam for several minutes during transmission electron microscopy (TEM) observations. Another unusual feature is that rectangular nanoplates with many gaps were obtained. Furthermore, porous NiO nanobelts, nanowires, and nanoplates could also be obtained by annealing the as-prepared Ni(OH)2 products. A sequence of dissolution, recrystallization, and oriented attachment-assisted self-assembly of nanowires into nanobelts is proposed as a plausible mechanistic interpretation for the formation of the observed structures. The method presented here possesses several advantages, including high yields, high purities, low cost, and environmental benignity. It might feasibly be scaled-up for industrial mass production. [source] Laser Microbeams and Optical Tweezers in Ageing ResearchCHEMPHYSCHEM, Issue 1 2009Paulius Grigaravi Abstract We show how a technique developed within the framework of physics and physical chemistry,in a true interdisciplinary approach,can answer questions in life sciences that are not solvable by using other techniques. Herein, we focus on blood-pressure regulation and DNA repair in ageing studies. Laser microbeams and optical tweezers are now established tools in many fields of science, particularly in the life sciences. A short glimpse is given on the wide field of non-age-research applications in life sciences. Then, optical tweezers are used to show that exerting a vertical pressure on cells representing the inner lining of blood vessels results in bursts of NO liberation concomitant with large changes in cell morphology. Repeated treatment of such human umbilical vein endothelial cells (HUVEC) results in stiffening, a hallmark of manifest high blood pressure, a disease primarily of the elderly. As a second application in ageing research, a laser microbeam is used to induce, with high spatial and temporal resolution, DNA damages in the nuclei of U2OS human osteosarcoma cells. A pairwise study of the recruitment kinetics of different DNA repair proteins reveals that DNA repair starts with non-homologous end joining (NHEJ), a repair pathway, and may only after several minutes switch to the error-free homologous recombination repair (HRR) pathway. Since DNA damages,when incorrectly repaired,accumulate with time, laser microbeams are becoming well-used tools in ageing research. [source] | ||||||||||||||||||||||