Singlet oxygen formation and chlorophyll a triplet excited state deactivation in the cytochrome b6f complex from Bryopsis?corticulans

We have attempted to investigate the correlation between the detergent-perturbed structural integrity of the Cyt b ₆ f complex from the marine green alga Bryopsis corticulans and its photo-protective properties, for which the nonionic detergents n-octyl-β-d-glucopyranoside (β-OG) and n-dodecyl-β-d-maltoside (β-DM), respectively, were used for the preparation of Cyt b ₆ f, and the singlet oxygen (¹O₂*) production as well as the triplet excited-state chlorophyll a (³Chl a*) formation and deactivation were examined by spectroscopic means. Near-infrared luminescence of ¹O₂ * (~1,270 nm) on photo-irradiation was detected for the β-OG preparation where the complex is mainly in oligomeric state, but not for the β-DM one in which the complex exists in dimeric form. Under anaerobic condition, photo-excitation of Chl a in the β-DM preparation generated ³Chl a* with a lower quantum yield of Φ_T ~ 0.02 and a longer lifetime of ~600 μs with respect to those as in the case of β-OG preparation, Φ_T ~ 0.12 and 200–300 μs. These results prove that the enzymatically active and intact Cyt b ₆ f complex on photo-excitation tends to produce little ³Chl a* or ¹O₂ *, which implies that the pigment–protein assembly of Cyt b ₆ f complex per se is crucial for photo-protection. F. Ma and X.-B. Chen contributed equally to this work.     

Synthesis of p-nitrophenyl sulfated disaccharides with beta-D-(6-sulfo)-GlcNAc units using beta-N-acetylhexosaminidase from Aspergillus oryzae in a transglycosylation reaction

When α-d-GlcNAc-OC₆H₄NO₂ -p and β-d-(6-sulfo)-GlcNAc-OC₆H₄NO₂-p (2) were used as substrates, β-N-acetylhexosaminidase from Aspergillus oryzae transferred the β-d-(6-sulfo)-GlcNAc(unit from 2 to α-d-GlcNAc-OC₆H₄NO₂ -p to afford β-d-(6-sulfo)-GlcNAc-(1→4)-α-d-GlcNAc-OC₆H₄NO₂-p (3) in a yield of 94% based on the amount of donor, 2, added. β-d-(6-sulfo)-GlcNAc-(1→4)-α-d-Glc-OC₆H₄NO₂-p (4) was obtained with α-d-Glc-OC₆H₄NO₂ -p as acceptor in a similar manner. With a reaction mixture of 2 and β-d-GlcNAc-OC₆H₄NO₂-p (1) in a molar ratio of 6:1, the enzyme mediated the transfer of β-d-GlcNAc from 1 to 2, affording disaccharide β-d-GlcNAc-(1→4)-β-(6-sulfo)-d-GlcNAc-OC₆H₄NO₂-p (5) in a yield of 13% based on the amount of 1 added.     

The effects of detergents DDM and β-OG on the singlet excited state lifetime of the chlorophyll a in cytochrome b6f complex from spinach chloroplasts

The singlet excited state lifetime of the chlorophyll a (Chi a) in cytochrome b6f (Cyt b6f) complex was reported to be shorter than that of free Chl a in methanol, but the value was different for Cyt b6f complexes from different sources (～200 and ～600 ps are the two measured results). The present study demonstrated that the singiet excited state lifetime is associated with the detergents n-dodecyl-β-D-maltoside (DDM) and n-octyl-β-D-glucopyranoside (β-OG), but has nothing to do with the different sources of Cyt b6f complexes. Compared with the Cyt b6f dissolved in β-OG, the Cyt b6f in DDM had a lower fluorescence yield, a lower photodegradation rate of Chl a, and a shorter lifetime of Chl a excited state. In short, the singlet excited state lifetime, ～200 ps, of the Chl a in Cyt b6f complex in DDM is closer to the true in vivo.     

Microbial transformation of ginsenoside Rb<Subscript>1</Subscript> by <Emphasis Type="Italic">Acremonium strictum</Emphasis>

Preparative-scale fermentation of ginsenoside Rb₁ (1) with Acremonium strictum AS 3.2058 gave three new compounds, 12β-hydroxydammar-3-one-20 (S)-O-β-d-glucopyranoside (7), 12β, 25-dihydroxydammar-(E)-20(22)-ene-3-O-β-d-glucopyranosyl-(1→2)-β-d-glucopyranoside (8), and 12β, 20 (R), 25-trihydroxydammar-3-O-β-d-glucopyranosyl-(1→2)-β-d-glucopyranoside (9), along with five known compounds, ginsenoside Rd (2), gypenoside XVII (3), ginsenoside Rg₃ (4), ginsenoside F₂ (5), and compound K (6). The structural elucidation of these metabolites was based primarily on one- and two-dimensional nuclear magnetic resonance and high-resolution electron spray ionization mass spectra analyses. Among these compounds, 2–6 are also the metabolites of ginsenoside Rb₁ in mammals. This result demonstrated that microbial culture parallels mammalian metabolism; therefore, A. strictum might be a useful tool for generating mammalian metabolites of related analogs of ginsenosides for complete structural identification and for further use in pharmaceutical research in this series of compounds. In addition, the biotransformation kinetics was also investigated.     

Syntheses of dopa glycosides using glucosidases

Syntheses of l-dopa 1a glucoside 10a,b and dl-dopa 1b glycosides 10–18 with d-glucose 2, d-galactose 3, d-mannose 4, d-fructose 5, d-arabinose 6, lactose 7, d-sorbitol 8 and d-mannitol 9 were carried out using amyloglucosidase from Rhizopus mold, β-glucosidase isolated from sweet almond and immobilized β-glucosidase. Invariably, l-dopa and dl-dopa gave low to good yields of glycosides 10–18 at 12–49% range and only mono glycosylated products were detected through glycosylation/arylation at the third or fourth OH positions of l-dopa 1a and dl-dopa 1b. Amyloglucosidase showed selectivity with d-mannose 4 to give 4-O-C1β and d-sorbitol 8 to give 4-O-C6-O-arylated product. β-Glucosidase exhibited selectivity with d-mannose 4 to give 4-O-C1β and lactose 7 to give 4-O-C1β product. Immobilized β-glucosidase did not show any selectivity. Antioxidant and angiotensin converting enzyme inhibition (ACE) activities of the glycosides were evaluated glycosides, out of which l-3-hydroxy-4-O-(β-d-galactopyranosyl-(1′→4)β-d-glucopyranosyl) phenylalanine 16 at 0.9 ± 0.05 mM and dl-3-hydroxy-4-O-(β-d-glucopyranosyl) phenylalanine 11b,c at 0.98 ± 0.05 mM showed the best IC₅₀ values for antioxidant activity and dl-3-hydroxy-4-O-(6-d-sorbitol)phenylalanine 17 at 0.56 ± 0.03 mM, l-dopa-d-glucoside 10a,b at 1.1 ± 0.06 mM and dl-3-hydroxy-4-O-(d-glucopyranosyl)phenylalanine 11a-d at 1.2 ± 0.06 mM exhibited the best IC₅₀ values for ACE inhibition. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Adhesion forces in the self-recognition of oligosaccharide epitopes of the proteoglycan aggregation factor of the marine sponge <Emphasis Type="Italic">Microciona prolifera</Emphasis>

Cell aggregation in the marine sponge Microciona prolifera is mediated by a multimillion molecular-mass aggregation factor, termed MAF. Earlier investigations revealed that the cell aggregation activity of MAF depends on two functional domains: (i) a Ca²⁺-independent cell-binding domain and (ii) a Ca²⁺-dependent proteoglycan self-interaction domain. Structural analysis of involved carbohydrate fragments of the proteoglycan in the self-association established a sulfated disaccharide β-d-GlcpNAc3S-(1→3)-α-l-Fucp and a pyruvated trisaccharide β-d-Galp4,6(R)Pyr-(1→4)-β-d-GlcpNAc-(1→3)-α-l-Fucp. Recent UV, SPR, and TEM studies, using BSA conjugates and gold nanoparticles of the synthetic sulfated disaccharide, clearly demonstrated self-recognition on the disaccharide level in the presence of Ca²⁺-ions. To determine binding forces of the carbohydrate–carbohydrate interactions for both synthetic MAF oligosaccharides, atomic force microscopy (AFM) studies were carried out. It turned out that, in the presence of Ca²⁺-ions, the force required to separate the tip and sample coated with a self-assembling monolayer of thiol-spacer-containing β-d-GlcpNAc-(1→3)-α-l-Fucp-(1→O)(CH₂)₃S(CH₂)₆S- was found to be quantized in integer multiples of 30 ± 6 pN. No binding was observed between the two monolayers in the absence of Ca²⁺-ions. Cd²⁺-ions could partially induce the self-interaction. In contrast, similar AFM experiments with thiol-spacer-containing β-d-Galp4,6(R)Pyr-(1→4)-β-d-GlcpNAc-(1→3)-α-l-Fucp-(1→O)(CH₂)₃S(CH₂)₆S- did not show a binding in the presence of Ca²⁺-ions. Also TEM experiments of gold nanoparticles coated with the pyruvated trisaccharide could not make visible aggregation in the presence of Ca²⁺-ions. It is suggested that the self-interaction between the sulfated disaccharide fragments is stronger than that between the pyruvated trisaccharide.     

Aerobic electron transport in Propionibacterium shermanii effects of cyanide

Cyanide inhibited d- and l-lactate and NADH oxidase activities of membrane particles from Propionibacterium shermanii but only at relatively high concentrations. Inhibition occurred at two different sites in the electron transport pathway. One site, with a half-maximal inhibition concentration (I _0.5) of 2 to 3 mM KCN, is located at the terminal oxidase involved in cytochrome b oxidation; the evidence is consistent with cytochrome d being the major oxidase involved. At high concentrations, cyanide inhibited reduction of cytochrome b by d-lactate (I _0.5 value 20–25 mM cyanide). A proportion of the oxygen-uptake remained uninhibited even by 100 mM cyanide; this proportion was about 80% for succinate, 30% for l-lactate, 15% for d-lactate and 10% for NADH. The oxygen uptake per mol of substrate oxidised increased with increasing cyanide concentration and was accompanied by the formation of hydrogen peroxide as a product of a cyanide-insensitive oxidase system.Abbreviations PMS Phenazine methosulphate     

Site-directed mutagenesis of possible catalytic residues of cellobiose 2-epimerase from Ruminococcusalbus

The cellobiose 2-epimerase from Ruminococcus albus (RaCE) catalyzes the epimerization of cellobiose and lactose to 4-O-β-d-glucopyranosyl-d-mannose and 4-O-β-d-galactopyranosyl-d-mannose (epilactose). Based on the sequence alignment with N-acetyl-d-glucosamine 2-epimerases of known structure and on a homology-modeled structure of RaCE, we performed site-directed mutagenesis of possible catalytic residues in the enzyme, and the mutants were expressed in Escherichia coli cells. We found that R52, H243, E246, W249, W304, E308, and H374 were absolutely required for the activity of RaCE. F114 and W303 also contributed to catalysis. These residues protruded into the active-site cleft in the model (α/α)₆ core barrel structure.     

Why do traditional dispersion indices used for analysis of spatial distribution of plants tend to become obsolete?

It is common to characterize the spatial distribution of plant patterns as random, aggregate, or uniform. In this context, a major challenge for the researcher is the choice of the method to identify the spatial pattern correctly as well as the factors related to it. The vast literature on the subject is not recent, especially regarding the dispersion indices. The aim of this review was to conduct a critical and temporal analysis of these dispersion indices and test their effectiveness in determining the spatial distribution of Paepalanthus chiquitensis Herzog (Eriocaulaceae). This species is a meaningful model due to its occurrence in specific sites. The Lexis, Charlier, dispersion, relative variance, aggregation, Green, inverse of k of the negative binomial, Morisita, and standardized Morisita indices were limited to indicating that the individuals of the species are aggregate and did not provide information on neither spatial dimension (scale) where the aggregation occurs, nor the factors related to this aggregation. Although they have distinct magnitudes, the algebraic expressions of dispersion, relative variance, aggregation, Green, inverse of k, Morisita, and standardized Morisita indices exhibited a close relationship with each other and little progress from their precursors Lexis and Charlier. By disregarding the possibility of spatial dependence, these indices make it impossible to generate important hypotheses for the investigation of factors related to spatial structure. Therefore, they became obsolete and are falling into disuse. It should be noted that these measurements accomplished their role and contributed to science in times of limited technologies for spatial data.     

Rapid aggregation and assembly in aqueous solution of A<Emphasis Type="Italic">β</Emphasis> (25–35) peptide

The highly toxic Aβ(25–35) is a peculiar peptide that differs from all the other commonly studied β-amyloid peptides because of its extremely rapid aggregation properties and enhanced neurotoxicity. We investigated Aβ(25–35) aggregation in H₂O at pH 3.0 and at pH 7.4 by means of in-solution analyses. Adopting UV spectroscopy, Congo red spectrophotometry and thioflavin T fluorimetry, we were able to quantify, in water, the very fast assembling time necessary for Aβ(25–35) to form stable insoluble aggregates and their ability to seed or not seed fibril growth. Our quantitative results, which confirm a very rapid assembly leading to stable insoluble aggregates of Aβ(25–35) only when incubated at pH 7.4, might be helpful for designing novel aggregation inhibitors and to shed light on the in vivo environment in which fibril formation takes place.     

A role for arabinogalactan-proteins in root epidermal cell expansion

Arabinogalactan-proteins (AGPs) are abundant plant proteoglycans that react with (β-d-Glc)₃ but not (β-d-Man)₃ Yariv reagent. We report here that treatment with (β-d-Glc)₃ Yariv reagent caused inhibition of root growth of Arabidopsis thaliana (L.) Heynh. seedlings. Moreover, the treated roots exhibited numerous bulging epidermal cells. Treatment with (β-d-Man)₃ Yariv reagent did not have any such effects. These results indicate a role for AGPs in root growth and control of epidermal cell expansion. Because treatment with (β-d-Glc)₃ Yariv reagent phenocopies the reb1 (root epidermal cell bulging) mutant of Arabidopsis, AGPs were extracted from the reb1-1 mutant and compared with those of the wild type. The reb1-1 roots contained an approximately 30% lower level of AGPs than the wild type. More importantly, while the profile of AGPs from wild-type roots showed two major peaks upon crossed electrophoresis, the profile of AGPs from reb1-1 roots exhibited only one of the major peaks. Therefore, the reb1 phenotype appears to be a result of defective or missing root AGPs. Taken together, this pharmacological and genetic evidence strongly indicates a function of AGPs in the control of root epidermal cell expansion. Received: 13 February 1997 / Accepted: 1 April 1997     

Hydrogen peroxide-induced chlorophyll a bleaching in the cytochrome b 6 f complex: a simple and effective assay for stability of the complex in detergent solutions

The instability of cytochrome b ₆ f complex in detergent solutions is a well-known problem that has been studied extensively, but without finding a satisfactory solution. One of the important reasons can be short of the useful method to verify whether the complex suspended in different detergent is in an intact state or not. In this article, a simple and effective assay for stability of the complex was proposed based on the investigation on the different effects of the two detergents, n-octyl-β-d-glucopyranoside (OG) and dodecyl-β-d-maltoside (DDM), on the properties of the complex. DDM stabilizes the complex preparation more effectively whereas OG denatures the interactions of the heme groups and pigment molecules with the protein environment, leading to the bleaching of chlorophyll a induced by addition of hydrogen peroxide. The assay of the use of hydrogen peroxide to characterize the complex by studying the bleaching of chlorophyll induced by hydrogen peroxide and the peroxidase activity of the complex was discussed. This simple method will probably be useful to study the stability of the complex. Xiao-Bo Chen and Xiao-Hui Zhao contributed equally to this work.     

Linking stand-level self-thinning allometry to the tree-level leaf biomass allometry

Long-term experimental plots of Norway spruce and European beech are investigated for a link between stand-level self-thinning and tree-level leaf biomass allometry. Self-thinning refers to the finding of Reineke (1933), who postulated for unthinned forest stands that with β = −1.605; i.e. an increase of mean (quadratic) diameter d _q by 1% results in a decrease of tree number N by 1.605%. On the individual tree level, leaf biomass (w _L) can be related allometrically to the tree diameter d: w _L = ad ^α. If we assume that (a) the stands have reached the ceiling leaf area, (b) the specific leaf area (leaf area/leaf weight) is constant, and (c) differences resulting from the use of mean quadratic diameter or individual tree diameter are negligible, then the decrease in the stands’ leaf biomass due to the trees lost in self-thinning must be compensated by an equivalent increase in the remaining trees’ leaf biomass. This means, the absolute slope of the individual trees’ leaf biomass allometry α and the self-thinning allometry β would be equal and just have the opposite sign: α = −β. The analysis of the two long-term plots reveals that α is stronger than β, both for spruce (β = −1.744, α = 1.840) and especially for beech (β = −1.791, α = 2.181). The cause is traced back to a changing average specific leaf area during stand development [assumption (b) is wrong]. The results do not only bridge a gap between tree and stand allometry, but also emphasize an important effect for the understanding and modelling of the resource allocations in trees and forests.     

Canopy photosynthetic production in a Japanese larch stand. I. Seasonal and vertical changes of leaf characteristics along the light gradient in a canopy

In an 18 year old Japanese larch stand, leaf characteristics such as area, weight, gross photosynthetic rate and respiration rate were studied in order to obtain basic information on estimating canopy photosynthesis and respiration. The leaf growth courses in area and weight from bud opening were approximated by simple logistic curves. The growth coefficient for the area growth curve was 0.155–0.175 day⁻¹, while that for the weight growth was 0.112–0.117 day⁻¹. The larger growth coefficient in area growth caused the seasonal change in specific leaf area (SLA) that increased after bud opening to its peak early in May at almost 300 cm² g⁻¹ and then decreased until it leveled off at about 140 cm²g⁻¹. The change inSLA indicates the possibility that leaf area growth precedes leaf thickness growth. The relationship between the coefficientsa andb of the gross photosynthetic rate (p)-light flux density (1) curve (p=bI/(1+aI)) and the mean relative light flux density (I′/I ₀) at each canopy height were approximated by hyperbolic formulae:a=A/(I′/I ₀)+B andb=C/(I′/I ₀)+D. Leaf respiration rate was also increased with increasingI′/I ₀. Seasonal change of gross photosynthetic rate and leaf respiration rate were related to mean air temperature through linear regression on semilogarithmic co-ordinates.     

Purification and biochemical characterization of a transglucosilating β-glucosidase of <Emphasis Type="Italic">Stachybotrys</Emphasis> strain

The filamentous fungus Stachybotrys sp has been shown to possess a rich β-glucosidase system composed of five β-glucosidases. One of them was already purified to homogeneity and characterized. In this work, a second β-glucosidase was purified and characterized. The filamentous fungal A19 strain was fed-batch cultivated on cellulose, and its extracellular cellulases (mainly β-glucosidases) were analyzed. The purified enzyme is a monomeric protein of 78 kDa molecular weight and exhibits optimal activity at pH 6.0 and at 50°C. The kinetic parameters, K _m and V _max, on para-nitro-phenyl-β-d-glucopyranosid (p-NPG) as a substrate were, respectively, 1.846 ± 0.11 mM and 211 ± 0.08 μmol min⁻¹ ml⁻¹. One interesting feature of this enzyme is its high stability in a wide range of pH from 4 to 10. Besides its aryl β-glucosidase activity towards salicin, methylumbellypheryl-β-d-glucoside (MU-Glc), and p-NPG, it showed a true β-glucosidase activity because it splits cellobiose into two glucose monomers. This enzyme has the capacity to synthesize short oligosaccharides from cellobiose as the substrate concentration reaches 30% with a recovery of 40%. We give evidences for the involvement of a transglucosylation to synthesize cellotetraose by a sequential addition of glucose to cellotriose.     

Degradation of endosulfan during substrate preparation and cultivation of Pleurotus pulmonarius

Summary Endosulfan is an insecticide used on many vegetable crops. In mushroom cultivation, vegetable materials used as a growth substrate may contain residues of endosulfan that may accumulate in the final mushroom biomass. After preparing the substrate, it is subjected to pasteurization and/or composting and then inoculated with the desired fungus. The purpose of this research was to determine the rate and extent of endosulfan reduction from a grass substrate that was either composted or sterilized by autoclaving. In addition, the rate and extent of removal of endosulfan from substrate colonized with Pleurotus pulmonarius was determined. The degradation of 65 mg/kg endosulfan was analyzed on both, the substrate preparation and the culture of P. pulmonarius on the grass Digitaria decumbens. During composting in presence of Ca(OH)₂ for 120 h, the concentrations of α and β endosulfan were reduced by 61.4 and 49.5% respectively, significantly higher compared with the control (without Ca(OH)_2,) in which the reduction was 38.5%. After sterilization the concentration of α and β endosulfan was reduced by 84.8 and 87.5% respectively. After the colonization of substrate by P. pulmonarius (15 days after spawning) α and β endosulfan were reduced by 96% and at the end of cultivation (35 days after spawning) were reduced by 99%. When carpophores were analyzed, residues of α and β endosulfan were observed between 0.019–0.084 mg/kg. The results showed that α and β endosulfan were partially removed during the preparation of substrate and entirely eliminated during fungal colonization on the substrate.     

Adaptation of epiphytic bryophytes in the understorey attributing to the correlations and trade-offs between functional traits

This study explores adaptive strategies of epiphytic bryophytes in the understorey by investigating the photosynthetic characteristics, pigment concentrations and nutrient stoichiometry, as well as other functional traits of three trunk-dwelling bryophytes in a subtropical montane cloud forest in SW China. The results showed that their light-saturated net photosynthetic rate (A_nmax?L), light saturation point (I_sat), light compensation point (I_c) and dark respiration rate (R_d) were ca 0.55, 106.72, 4.17 and 0.25?μmol?m^?2?s^?1, respectively. Furthermore, the samples demonstrated photosynthetic down-regulation under high irradiance. These photosynthetic characteristics can be explained by higher total chlorophyll concentrations, specific leaf area, chlorophyll per unit leaf N (Chl/N), lower ratio of chlorophyll a to chlorophyll b (Chl a/b) and photosynthetic nitrogen-use efficiency. We suggest that the bryophytes adapted to the shaded understorey microhabitats through a series of correlations and trade-offs between functional traits.     

Excess irradiance causes early symptoms of senescence during leaf expansion in photoautotrophically <Emphasis Type="Italic">in vitro</Emphasis> grown tobacco plants

Photosynthetic parameters, growth, and pigment contents were determined during expansion of the fourth leaf of in vitro photoautotrophically cultured Nicotiana tabacum L. plants at three irradiances [photosynthetically active radiation (400–700 nm): low, LI 60 μmol m⁻² s⁻¹; middle, MI 180 μmol m⁻² s⁻¹; and high, HI 270 μmol m⁻² s⁻¹]. During leaf expansion, several symptoms usually accompanying leaf senescence appeared very early in HI and then in MI plants. Symptoms of senescence in developing leaves were: decreasing chlorophyll (Chl) a+b content and Chl a/b ratio, decreasing both maximum (F_V/F_M) and actual (Φ_PS2) photochemical efficiency of photosystem 2, and increasing non-photochemical quenching. Nevertheless, net photosynthetic oxygen evolution rate (P _N) did not decrease consistently with decrease in Chl content, but exhibited a typical ontogenetic course with gradual increase. P _N reached its maximum before full leaf expansion and then tended to decline. Thus excess irradiance during in vitro cultivation did not cause early start of leaf senescence, but impaired photosynthetic performance and Chl content in leaves and changed their typical ontogenetic course.     

Seasonal abundance and spatial distribution of larval and adult thrips (Thysanoptera) on weed host plants in mango orchards in Penang,Malaysia

The spatial distribution of larval and adult thrips (Thysanoptera) was studied on mango panicles, Mangifera indica L., on Penang Island, Malaysia, during two consecutive mango flowering seasons from December 2008 to March 2009 and from August to September 2009. Larval and adult thrips were sampled from mango panicles using the carbon dioxide (CO₂) collection technique weekly in treated and untreated orchards. Seasonal abundance and dispersion pattern of thrips were investigated on weed host plants in the treated orchard between June 2008 and March 2009. Spatiotemporal dynamics of larvae and adults was analyzed using Taylor’s Power Law (TPL), Lloyd’s Index (LI), and Green’s Index (GI). Thrips hawaiiensis (Morgan) was the dominant thrips species recovered from mango panicles and weeds in the treated orchard, whereas Scirtothrips dorsalis (Hood) was the most abundant species captured in the untreated orchard. Thrips adults and larvae analyzed via dispersion indices were found to be aggregated in mango panicles in both orchards. The value of the aggregation index (b) of TPL for the total number of adult thrips was significantly higher in the treated orchard than in the untreated orchard, whereas slopes of TPL for the total number of larval thrips did not differ significantly between treated and untreated orchards. All adult thrips species were distributed regularly on the weed plants; however, their larvae were aggregated. It is concluded that pesticide treatment caused adult thrips to become more aggregated on mango panicles, hiding in flower parts that were less exposed to the chemicals.     

Characterization of Recombinant Human Cardiac KCNQ1/KCNE1 Channels (I Ks) Stably Expressed in HEK 293 Cells

The present study was designed to characterize pharmacological, biophysical and electrophysiological properties of the recombinant human cardiac I _Ks (KCNQ1/KCNE1) channels at physiological temperature. Human cardiac KCNQ1 and KCNE1 genes were cotransfected into HEK 293 cells, and a cell clone stably expressing both genes was selected. Membrane currents were recorded using a perforated patch-clamp technique. The typical I _Ks was slowly activated upon depolarization voltages in HEK 293 cells stably expressing human cardiac KCNQ1 and KCNE1 genes, and the current was inhibited by I _Ks blockers HMR 1556 and chromanol 293B, with 50% inhibitory concentrations (IC₅₀s) of 83.8 nM and 9.2 μM, respectively. I _Ks showed a significant temperature-dependent increase in its magnitude upon elevating bath temperature to 36°C from room temperature (21°C). The current was upregulated by the β-adrenoceptor agonist isoproterenol, and the effect was reversed by H89. In addition, I _Ks was inhibited by Ba²⁺ in a concentration-dependent manner (IC₅₀ = 1.4 mM). Action potential clamp revealed a “bell-shaped” time course of I _Ks during the action potential, and maximal peak current was seen at the plateau of the action potential. A significant use- and frequency-dependent increase of I _Ks was observed during a train of action potential clamp. These results indicate that the recombinant human cardiac I _Ks stably expressed in HEK 293 cells is similar to native I _Ks in drug sensitivity and regulated by Ba²⁺ and β-adrenoceptor via the cyclic adenosine monophosphate/protein kinase A pathway. Importantly, the current exhibits significant temperature dependence, a bell-shaped time course during action potential and prominent use- or frequency-dependent accumulation during a train of action potentials.