Pollenfertility and seed formation in theOrnithogalum umbellatum/angustifolium complex (Liliaceae/Scilloideae)

The pollen fertility and seed formation of six species of theOrnithogalum umbellatum/angustifolium complex and of seven related species were studied. Four types of pollen grains could be recognized. The pollen fertility varied greatly in this complex and is not related to the ploidy level. The seed formation ofO. umbellatum showed an adaptation to a subcontinental-Mediterranean climate, that ofO. angustifolium to an Atlantic climate. In both cases raindrops seem to be important for pollination, in view of the absence of insect pollinators. After open pollination 113 seedlings were obtained in four species. Their chromosome numbers were determined. Nearly all the cultivated seedlings were aneuploid, which points to a positive selection of euploids in nature, because aneuploid individuals are rare in the wild.Biosystematic Studies on theOrnithogalum umbellatum/angustifolium Complex III.—Previous parts of this series are Part I: Taxonomy. Proceeding Kon. Ned. Acad. Wet. series C,85 (4), 563–574 (1982) andvan Raamsdonk (1984).     

Mechanism of inhibition of net ion transport across frog corneal epithelium by calcium channel antagonists

Summary In the isolated bullfrog cornea, three calcium channel antagonists had dose-dependent inhibitory effects on the Cl-originated short-circuit current (SCC). Their order of decreasing potency was bepridil, verapamil and diltiazem. One millimolar diltiazem inhibited the SCC by 98% and subsequent incubation with the calcium ionophore A23187 had no restorative effect. Increasing the bathing solution Ca concentration from 0.05 to 15mm, however, decreased diltiazem's inhibitory efficacy. This antagonist depolarized the intracellular potential differenceV _m from –54 to –18 mV (tear: reference) and the voltage divider ratioFR ₀ decreased from 0.58 to 0.30, suggesting an increase in basolateral membrane electrical resistance. Additional indication of a basolateral membrane effect by the drug was that preincubation with 10⁵ m amphotericin B in Cl-free Ringer's did not eliminate the inhibitory effect of the drug on the Na- and K-elicited SCC. In the absence of amphotericin B in Cl-free Ringer's (SCC=0), 1 ×10³ m diltiazem depolarized theV _m from –78 to –9 mV suggesting that the increase in basolateral membrane resistance was due to K channel blockade. Diltiazem (1×10³ m) significantly decreased cyclic AMP content; however, isoproterenol in the presence of the drug increased cyclic AMP fourfold without having any restorative effect on the inhibited SCC. Therefore, the inhibition of the Cl-originated SCC resulting from an increase in basolateral membrane K resistance is not caused by a decline in cyclic AMP content. In plasma membrane-enriched fractions prepared from broken cell preparations of bovine corneal epithelium, 1×10³ m diltiazem had no inhibitory effects on either Na,K-ATPase or Ca,Mg-ATPase activities. These latter effects further point to the selectivity of diltiazem as an inhibitor of K-channel activity, but do not preclude a Ca-channel blocker effect by the drug in the micromolar range.     

Salinity tolerance of Kosteletzkya virginica. II. Root growth, lipid content, ion and water relations

Abstract. Kosteletzkya virginica (L.) Presl., a dicot halophyte native to brackish tidal marshes, was grown on nutrient solution containing 0. 85, 170 or 255 mol m ³ NaCl, and the effects of external salinity on root growth, ion and water levels, and lipid content were examined in successive harvests. Root growth paralleled shoot growth trends, with some enhancement observed at 85 mol m ³ NaCl and a reduction noted at the higher salinities. Root Na⁺ content increased with increasing external NaCl, but remained constant with time for each treatment. K⁺ content, although lower in salt-grown plants after 14 d salinization, subsequently increased to levels comparable to unsalinized plants. A strong K⁺ affinity was reflected in the increased K⁺/Na⁺ selectivity of salt-grown plants and by their low Na⁺/K⁺ ratios. Cl levels rose in salinized plants and values were double or more those for Na⁺, indicating the possibility of a sodium-excluding mechanism in roots. Root phospholipids and sterols, principal membrane constituents, were maintained or elevated and the free sterol/phospholipids ratio increased in salinized K. virginica plants, suggesting retention of overall membrane structure and decreased permeability. This response, considered in light of root calcium maintenance and high potassium levels, suggests that salinity-induced changes in membrane lipid composition may be important in preventing K⁺ leakage from cells.     

A Historical Perspective for the Catalytic Reaction Mechanism of Glycosidase; So As to Bring about Breakthrough in Confusing Situation

Various catalytic reaction models have been proposed as the reaction mechanisms of glycosidases, but a reasonable and unitary model capable of interpreting both “inverting” and “retaining” glycosidase reactions remains to be established. As for the models proposed to date, the nucleophilic displacement mechanism and the oxocarbenium ion intermediate mechanism are widely known, but recently the former is widely accepted, and so the general tendency of world opinion appears to favor it. This reaction model, however, is considered to comprise some inconsistencies that cannot be neglected from the viewpoint of reactivity in organic chemistry. While the nucleophilic displacement mechanism is often applied to reactions of glycosidases, it appears unlikely that such reactions actually occur. This review argues that the oxocarbenium ion intermediate reaction mechanism is more rational than the nucleophilic displacement reaction mechanism, as the action mode of glycosidases and related enzymes.     

Thermally Durable Lithium‐Ion Capacitors with High Energy Density from All Hydroxyapatite Nanowire‐Enabled Fire‐Resistant Electrodes and Separators

The reliability and durability of lithium‐ion capacitors (LICs) are severely hindered by the kinetic imbalance between capacitive and Faradaic electrodes. Efficient charge storage in LICs is still a huge challenge, particularly for thick electrodes with high mass loading, fast charge delivery, and harsh working conditions. Here, a unique thermally durable, stable LIC with high energy density from all‐inorganic hydroxyapatite nanowire (HAP NW)‐enabled electrodes and separators is reported. Namely, the LIC device is designed and constructed with the electron/ion dual highly conductive and fire‐resistant composite Li₄Ti₅O₁₂‐based anode and activated carbon‐based cathode, together with a thermal‐tolerant HAP NW separator. Despite the thick‐electrode configuration, the as‐fabricated all HAP NW‐enabled LIC exhibits much enhanced electrochemical kinetics and performance, especially at high current rates and temperatures. Long cycling lifetime and state‐of‐the‐art areal energy density (1.58 mWh cm^?2) at a high mass loading of 30 mg cm^?2 are achieved. Benefiting from the excellent fire resistance of HAP NWs, such an unusual LIC exhibits high thermal durability and can work over a wide range of temperatures from room temperature to 150 °C. Taking full advantage of synergistic configuration design, this work sets the stage for designing advanced LICs beyond the research of active materials.     

New preparation techniques for molecular and in‐situ analysis of ancient organic micro‐ and nanostructures

Organic microfossils preserved in three dimensions in transparent mineral matrices such as cherts/quartzites, phosphates, or carbonates are best studied in petrographic thin sections. Moreover, microscale mass spectrometry techniques commonly require flat, polished surfaces to minimize analytical bias. However, contamination by epoxy resin in traditional petrographic sections is problematic for the geochemical study of the kerogen in these microfossils and more generally for the in situ analysis of fossil organic matter. Here, we show that epoxy contamination has a molecular signature that is difficult to distinguish from kerogen with time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS). This contamination appears pervasive in organic microstructures embedded in micro‐ to nano‐crystalline carbonate. To solve this problem, a new semi‐thin section preparation protocol without resin medium was developed for micro‐ to nanoscale in situ investigation of insoluble organic matter. We show that these sections are suited for microscopic observation of Proterozoic microfossils in cherts. ToF‐SIMS reveals that these sections are free of pollution after final removal of a <10 nm layer of contamination using low‐dose ion sputtering. ToF‐SIMS maps of fragments from aliphatic and aromatic molecules and organic sulfur are correlated with the spatial distribution of organic microlaminae in a Jurassic stromatolite. Hydrocarbon‐derived ions also appeared correlated with kerogenous microstructures in Archean cherts. These developments in analytical procedures should help future investigations of organic matter and in particular, microfossils, by allowing the spatial correlation of microscopy, spectroscopy, precise isotopic microanalyses, and novel molecular microanalyses such as ToF‐SIMS.     

House dust mite extract activates apical Cl− channels through protease‐activated receptor 2 in human airway epithelia

Adequate fluid secretion from airway mucosa is essential for maintaining mucociliary clearance, and fluid hypersecretion is a prominent feature of inflammatory airway diseases such as allergic rhinitis. House dust mite extract (HDM) has been reported to activate protease‐activated receptors (PARs), which play various roles in airway epithelia. However, the role of HDM in regulating ion transporters and fluid secretion has not been investigated. We examined the effect of HDM on ion transport in human primary nasal epithelial cells. The Ca²⁺‐sensitive dye Fura2‐AM was used to determine intracellular Ca²⁺ concentration ([Ca²⁺]_i) by means of spectrofluorometry in human normal nasal epithelial cells (NHNE). Short‐circuit current (Isc) was measured using Ussing chambers. Fluid secretion from porcine airway mucosa was observed by optical measurement. HDM extract (10 µg/Ml) effectively cleaved the PAR‐2 peptide and induced an increase of [Ca²⁺]_i that was abolished by desensitization with trypsin, but not with thrombin. Apical application of HDM‐induced Isc sensitive to both a cystic fibrosis transmembrane conductance regulator (CFTR) inhibitor and a Ca²⁺‐activated Cl^? channel (CaCC) inhibitor. HDM extract also stimulated fluid secretion from porcine airway mucosa. HDM extract activated PAR‐2 and apical Cl^? secretion via CaCC and CFTR, and HDM‐induced fluid secretion in porcine airway mucosa. Our results suggest a role for PAR‐2 in mucociliary clearance and fluid hypersecretion of airway mucosa in response to air‐borne allergens such as HDM. J. Cell. Biochem. 109: 1254–1263, 2010. © 2010 Wiley‐Liss, Inc.     

NaHCO3胁迫下3种灌木Na+、K+、Ca2+的吸收及转运

通过盆栽试验,采用原子吸收分光光度法和非损伤微测技术,研究了NaHCO₃胁迫(300 mmol·L^-1)对大洋洲滨藜、四翅滨藜和宁夏枸杞3种灌木离子吸收及运转的影响.结果表明: 随着NaHCO₃浓度升高,两种滨藜和宁夏枸杞叶片中Na⁺含量升高,300 mmol·L^-1NaHCO₃胁迫下,宁夏枸杞叶肉细胞Na⁺的外排增加,两种滨藜净Na⁺外排降低;随着胁迫时间的延长,大洋洲滨藜和宁夏枸杞叶片的K⁺含量下降,Na⁺/K⁺升高,四翅滨藜叶片K⁺含量升高,Na⁺/K⁺降低;随着浓度的升高,宁夏枸杞叶片积累Ca²⁺减少,Na⁺/Ca²⁺高于对照,叶肉细胞Ca²⁺外排;两种滨藜叶Ca²⁺含量总体呈升高趋势,叶肉细胞Ca²⁺表现为内流.在NaHCO₃胁迫下,3种灌木通过不同的策略来消除Na⁺毒害.宁夏枸杞叶片Na⁺的积累抑制了对Ca²⁺的吸收;两种滨藜Ca²⁺的内流促使细胞质中游离Ca²⁺增加,增加的细胞质\[Ca²⁺\]cyt防治质膜H⁺ ATPase去极化,限制K⁺的外排,从而维持细胞内Na⁺/K⁺的平衡,其中四翅滨藜调控Na⁺/K⁺平衡的能力较强.     

Measurement of Greenhouse Gas Flux from Agricultural Soils Using Static Chambers

Measurement of greenhouse gas (GHG) fluxes between the soil and the atmosphere, in both managed and unmanaged ecosystems, is critical to understanding the biogeochemical drivers of climate change and to the development and evaluation of GHG mitigation strategies based on modulation of landscape management practices. The static chamber-based method described here is based on trapping gases emitted from the soil surface within a chamber and collecting samples from the chamber headspace at regular intervals for analysis by gas chromatography. Change in gas concentration over time is used to calculate flux. This method can be utilized to measure landscape-based flux of carbon dioxide, nitrous oxide, and methane, and to estimate differences between treatments or explore system dynamics over seasons or years. Infrastructure requirements are modest, but a comprehensive experimental design is essential. This method is easily deployed in the field, conforms to established guidelines, and produces data suitable to large-scale GHG emissions studies.     

Membrane permeable local anesthetics modulate NaV1.5 mechanosensitivity

Voltage-gated sodium selective ion channel Na_V1.5 is expressed in the heart and the gastrointestinal tract, which are mechanically active organs. Na_V1.5 is mechanosensitive at stimuli that gate other mechanosensitive ion channels. Local anesthetic and antiarrhythmic drugs act upon Na_V1.5 to modulate activity by multiple mechanisms. This study examined whether Na_V1.5 mechanosensitivity is modulated by local anesthetics. Na_V1.5 channels wereexpressed in HEK-293 cells, and mechanosensitivity was tested in cell-attached and excised inside-out configurations. Using a novel protocol with paired voltage ladders and short pressure pulses, negative patch pressure (-30 mmHg) in both configurations produced a hyperpolarizing shift in the half-point of the voltage-dependence of activation (V_1/2a) and inactivation (V_1/2i) by about -10 mV. Lidocaine (50 µM) inhibited the pressure-induced shift of V_1/2a but not V_1/2i. Lidocaine inhibited the tonic increase in pressure-induced peak current in a use-dependence protocol, but it did not otherwise affect use-dependent block. The local anesthetic benzocaine, which does not show use-dependent block, also effectively blocked a pressure-induced shift in V_1/2a. Lidocaine inhibited mechanosensitivity in Na_V1.5 at the local anesthetic binding site mutated (F1760A). However, a membrane impermeable lidocaine analog QX-314 did not affect mechanosensitivity of F1760A Na_V1.5 when applied from either side of the membrane. These data suggest that the mechanism of lidocaine inhibition of the pressure-induced shift in the half-point of voltage-dependence of activation is separate from the mechanisms of use-dependent block. Modulation of Na_V1.5 mechanosensitivity by the membrane permeable local anesthetics may require hydrophobic access and may involve membrane-protein interactions.