Ciliary Beating Compartmentalizes Cerebrospinal Fluid Flow in the Brain and Regulates Ventricular Development

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Discrete character of the development of the photosynthetic apparatus in greening barley leaves

Biogenesis of the photosynthetic apparatus in greening etiolated leaves of barley (Hordeum vulgare L) was investigated by an approach permitting investigation of this process under conditions that minimize differences in plastid development. Distributions of barley leaves greening for 24 h as to chlorophyll content and of chloroplast grana as to number of thylakoids were shown to be of a multimodal character. The shape of time-course curves of chlorophyll accumulation in local sites of greening etiolated leaves was of a stepped or (at the end of greening) undulated character. The stepwise accumulation of chlorophyll was accompanied by wave-like changes in chlorophyll b/a ratio, intensity of low-temperature chlorophyll fluorescence and photosynthetic activity with minima at the time points of transition to accelerated chlorophyll accumulation. It is assumed that (1) development of the photosynthetic apparatus in local sites of greening etiolated leaves occurs stepwise, from one steady level to another, but not as gradually as is generally accepted, and (2) every separate step in development of the photosynthetic apparatus seems to begin with formation of photosystem cores and to end with the synthesis of light-harvesting complexes. This revised version was published online in June 2006 with corrections to the Cover Date.     

高温对温室草莓光合生理特性的影响及胁迫等级构建

以草莓品种"红颜"为材料,采用人工控制试验对草莓苗进行动态高温(32℃/22℃,35 ℃/25℃,38 ℃/28 ℃和41℃/31℃;日最高温/日最低温)胁迫(2、5、8和11 d)处理,以28℃/18℃为对照(CK),测定各处理下草莓叶片的光合生理参数.通过主成分分析提取关键参数,并以此计算高温胁迫指数(Z),划分高...     

溶氧量与谷氨酸棒杆菌代谢

正自从1957年Kinoshita等首次描述谷氨酸棒杆菌(Corynebacterium glutamicum)为谷氨酸产生菌[1]以来,其已成为用于氨基酸生产的主要菌株。目前,全世界每年利用谷氨酸棒杆菌生产约100万t L-谷氨酸用于食品调味剂和约45万t L-赖氨酸用作食品添加剂[2]。通过谷氨酸棒状杆菌发酵获得谷氨酸的发酵水平已较高,通过进一步优化工艺来提高产量具有较大困难[3]。     

Effects of enhanced solar irradiation on chlorophyll fluorescence and photosynthetic oxygen production of five species of phytoplankton

Abstract The effects of solar irradiation on chlorophyll a fluorescence and photosynthetic oxygen production of three Cryptomonas species, Euglena gracilis and Scenedesmus cf. quadricauda were investigated in comparative field studies in Erlangen (280 m above sea level) and at Zugspitze (2957 m above sea level). The experiments showed that the decrease of fluorescence and the inhibition of photosynthetic oxygen production occurred after shorter times of exposure to solar radiation at Zugspitze compared to Erlangen in all tested organisms. Cryptomonas maculata was more sensitive towards radiation than the other organisms: fluorescence decreased earlier, while Scenedesmus cf. quadricauda seemed to be much less sensitive since fluorescence and photosynthetic oxygen production decreased later and to a smaller extent compared to the other organisms. The results of the present study indicate that increased solar radiation (with an increased level of UV-B radiation) at higher geographical altitudes may have significant effects on phytoplankton populations.     

干旱胁迫对杨树幼苗生长、光合特性及活性氧代谢的影响

2011年4-10月在山东省林业科学研究院试验苗圃,选取欧美I-107杨扦插苗为试材,采用盆栽控水试验,研究了不同水分处理(正常水分、轻度干旱、中度干旱和重度干旱)对杨树幼苗生长和气体交换、叶绿素荧光特性、活性氧代谢的影响.结果表明: 与正常水分处理相比,轻度、中度和重度干旱胁迫下的地径生长量分别下降12.8%、44.5%和65.6%,苗高生长量分别下降12.2%、43.1%和57.2%;随着胁迫强度的增加和胁迫时间的延长,杨树幼苗叶片的PSⅡ光能转化效率、实际量子产量、光化学猝灭系数、净光合速率和气孔导度在轻度胁迫下缓慢下降,而在中度和重度胁迫下迅速下降;非光化学猝灭系数在轻度胁迫下显著升高,而在中度和重度胁迫下先升高后降低;叶片超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性均先升高后降低,但对干旱胁迫和活性氧的响应存在一定差异;叶片相对电导率、丙二醛含量显著增加,质膜受损,大量离子外渗,且重度胁迫下质膜的损害最严重.轻度干旱胁迫下,I-107杨树幼苗具有较高的光合效率和较强的抗氧化保护酶系统;而中度和重度干旱下,其光合效率显著下降,抗氧化保护酶系统明显遭到破坏.     

A hydrogen-atom abstraction model for the function of YZ in photosynthetic oxygen evolution

Recent magnetic-resonance work on Y suggests that this species exhibits considerable motional flexibility in its functional site and that its phenol oxygen is not involved in a well-ordered hydrogen-bond interaction (Tang et al., submitted; Tommos et al., in press). Both of these observations are inconsistent with a simple electron-transfer function for this radical in photosynthetic water oxidation. By considering the roles of catalytically active amino acid radicals in other enzymes and recent data on the water-oxidation process in Photosystem II, we rationalize these observations by suggesting that Y functions to abstract hydrogen atoms from aquo- and hydroxy-bound managanese ions in the (Mn)₄ cluster on each S-state transition. The hydrogen-atom abstraction process may occur either by sequential or concerted kinetic pathways. Within this model, the (Mn)₄/Y_Z center forms a single catalytic center that comprises the Oxygen Evolving Complex in Photosystem II.     

Reactive oxygen species (ROS) production in human peripheral blood neutrophils exposed in vitro to static magnetic field

The aim of this study was to determine the effect of gradient static magnetic field (SMF) on reactive oxygen species (ROS) production in human neutrophils in peripheral blood in vitro. Blood samples collected from healthy individuals were incubated in an inhomogeneous SMF (in a south or north pole of the field) for 15, 30 or 45 minutes. The maximum value of induction (B _max) amounted to ≈ 60 mT. To determine the strength of the ROS production, dihydrorhodamine (123DHR) as fluorophore and phorbol 12-myristate 13-acetate (PMA) as respiratory burst stimulator were used. 123DHR oxidation by ROS was measured by flow cytometry. The exposure of blood samples to SMF induced statistically significant changes in ROS production in unstimulated and PMA-stimulated neutrophils. The observed effects were highly correlated with the exposure time and depended on the orientation of the field. Although intracellular mechanisms underlying such interactions are not thoroughly understood, it could be presumed that SMF affects ROS metabolic oscillations and their formation and inactivation. This study emphasizes the importance of proper adjustment of exposure time to SMF for any potential therapeutic applications.     

An inducible release of reactive oxygen radicals in four species of gorgonian corals

The capability for physical injury or heat stress to elicit the production of reactive oxygen species was examined in four species of gorgonian corals. The sea plumes Pseudopterogorgia elisabethae, Pseudopterogorgia americana, the sea rod Eunicea fusca and the azooxanthellate red branching gorgonian Lophogorgia chilensis were physically injured using sonic sound cavitations and heat shocked by incubation in 33°C sea water. The pharmacological probe, diphenylene iodonium chloride (DPI), an inhibitor of NAD(P)H oxidase and peroxidases was used to identify an enzymatic surrogate of the oxidative burst. Both injury and heat stress were capable of inducing the release of reactive oxygen species (ROS) in all gorgonians tested, yet the kinetics and amplitude of ROS release varied among genera. In both the treatments, P. americana demonstrated the largest oxidative burst among the other corals tested.     

The relationship between CO2 assimilation, photosynthetic electron transport and water–water cycle in chill-exposed cucumber leaves under low light and subsequent recovery

The effects of chilling under low light (9/7 °C, 100 µmol m^?2 s^?1) on the photosynthetic and antioxidant capacities and subsequent recovery were examined in two (one tolerant and one sensitive) cucumber genotypes. Chilling resulted in an irreversible inhibition of net CO₂ assimilation and growth for the sensitive genotype, which was accompanied by decreases in the maximum velocity of RuBP carboxylation by Rubisco (V_cmax), the capacity for ribulose‐1,5‐bisphosphate regeneration (J_max), Rubisco content and activity, and the quantum efficiency of photosystem II, in the absence of any stomatal limitation of CO₂ supply or inorganic phosphate limitation. In contrast, CO₂ assimilation for the tolerant genotype fully recovered after chill. The chill‐induced decrease in the proportion of electron flux for photosynthetic carbon reduction was mostly compensated by an O₂‐dependent alternative electron flux driven by the water–water cycle, especially in the sensitive genotype. Compared with the tolerant genotype, the sensitive genotype after chill showed reduced capacity for scavenging reactive oxygen species and increased accumulation of reactive oxygen species. The balance between O₂‐dependent alternative electron flux and the capacity for scavenging reactive oxygen species in response to chill plays a major role in determining the tolerance of cucumber leaves to this stress factor. It is concluded that the water–water cycle operates at high rates when CO₂ assimilation is restricted in cucumber leaves subjected to chill and low light conditions.     

Determining the limitations and regulation of photosynthetic energy transduction in leaves

The light-dependent production of ATP and reductants by the photosynthetic apparatus in vivo involves a series of electron and proton transfers. Consideration is given as to how electron fluxes through photosystem I (PSI), using absorption spectroscopy, and through photosystem II (PSII), using chlorophyll fluorescence analyses, can be estimated in vivo. Measurements of light-induced electrochromic shifts using absorption spectroscopy provide a means of analyzing the proton fluxes across the thylakoid membranes in vivo. Regulation of these electron and proton fluxes is required for the thylakoids to meet the fluctuating metabolic demands of the cell. Chloroplasts exhibit a wide and flexible range of mechanisms to regulate electron and proton fluxes that enable chloroplasts to match light use for ATP and reductant production with the prevailing metabolic requirements. Non-invasive probing of electron fluxes through PSI and PSII, and proton fluxes across the thylakoid membranes can provide insights into the operation of such regulatory processes in vivo.     

Light-harvesting mutants show differential gene expression upon shift to high light as a consequence of photosynthetic redox and reactive oxygen species metabolism

The amount of light energy that is harvested and directed to the photosynthetic machinery is regulated in order to control the production of reactive oxygen species (ROS) in leaf tissues. ROS have important roles as signalling factors that instigate and mediate a range of cellular responses, suggesting that the mechanisms regulating light-harvesting and photosynthetic energy transduction also affect cell signalling. In this study, we exposed wild-type (WT) Arabidopsis and mutants impaired in the regulation of photosynthetic light-harvesting (stn7, tap38 and npq4) to transient high light (HL) stress in order to study the role of these mechanisms for up- and downregulation of gene expression under HL stress. The mutants, all of which have disturbed regulation of excitation energy transfer and distribution, responded to transient HL treatment with surprising similarity to the WT in terms of general ‘abiotic stress-regulated’ genes associated with hydrogen peroxide and 12-oxo-phytodienoic acid signalling. However, we identified distinct expression profiles in each genotype with respect to induction of singlet oxygen and jasmonic acid-dependent responses. The results of this study suggest that the control of excitation energy transfer interacts with hormonal regulation. Furthermore, the photosynthetic pigment–protein complexes appear to operate as receptors that sense the energetic balance between the photosynthetic light reactions and downstream metabolism.     

Effect of abscisic acid on the photosynthetic oxygen evolution in barley chloroplasts

In vivo effect of abscisic acid (ABA) on photosynthetic oxygen evolution was investigated in barley chloroplasts. The most important kinetic parameters of O₂-producing reactions were changed. The results show inhibition of the O₂-flash yields at ABA concentrations of 10 mol/l and 100 mol/l and an increase in the degree of damping of the oscillations. ABA has a marked effect on the distribution of the oxygenevolving centers in S₀ and S₁ states and on sum of the centers (S₀+S₁) estimated according to the Kok model. In addition, the amplitude and the shape of the initial oxygen burst under continuous illumination are also significantly altered. At a concentration of 100 mol/l, ABA strongly inhibits Hill reaction activity measured by DCPIP reduction. The results cannot be explained by the hypothesis of socalled stomata effect. On the other hand, no effects were observed on the investigated parameters in experiments involving ABA applied in vitro to isolated chloroplasts. It is hypothesized that ABA disrupts the granal chloroplasts structure and raises the degree of participation of the cooperative mechanism of O₂-evolution connected with the functioning of PS II centers in the stroma situated thylakoids.Abbreviations DCPIP 2,6-Dichlorophenolindophenol - DCMU 3-(3,4-dichlorophenil)-1,1-dimethylurea - HEPES N-2-Hydroxyethylpiperazine-N-2-ethane sulfonic acid - PSII photosystem II - RubisCO Ribulose-1,5-bis-phosphate carboxylase-oxygenase     

An inducible release of reactive oxygen radicals in four species of gorgonian corals

The capability for physical injury or heat stress to elicit the production of reactive oxygen species was examined in four species of gorgonian corals. The sea plumes Pseudopterogorgia elisabethae, Pseudopterogorgia americana, the sea rod Eunicea fusca and the azooxanthellate red branching gorgonian Lophogorgia chilensis were physically injured using sonic sound cavitations and heat shocked by incubation in 33°C sea water. The pharmacological probe, diphenylene iodonium chloride (DPI), an inhibitor of NAD(P)H oxidase and peroxidases was used to identify an enzymatic surrogate of the oxidative burst. Both injury and heat stress were capable of inducing the release of reactive oxygen species (ROS) in all gorgonians tested, yet the kinetics and amplitude of ROS release varied among genera. In both the treatments, P. americana demonstrated the largest oxidative burst among the other corals tested.     

EPR detection of a cryogenically photogenerated intermediate in photosynthetic oxygen evolution

In Photosystem II preparations at low temperature we were able to generate and trap an intermediate state between the S₁ and S₂ states of the Kok scheme for photosynthetic oxygen evolution. Illumination of dark-adapted, oxygen-evolving Photosystem II preparations at 140 K produces a 320-G-wide EPR signal centered near g = 4.1 when observed at 10 K. This signal is superimposed on a 5-fold larger and somewhat narrower background signal; hence, it is best observed in difference spectra. Warming of illuminated samples to 190 K in the dark results in the disappearance of the light-induced g = 4.1 feature and the appearance of the multiline EPR signal associated with the S₂ state. Low-temperature illumination of samples prepared in the S₂ state does not produce the g = 4.1 signal. Inhibition of oxygen evolution by incubation of PS II preparations in 0.8 M NaCl buffer or by the addition of 400 μM NH₂OH prevents the formation of the g = 4.1 signal. Samples in which oxygen evolution is inhibited by replacement of Cl^? with F^? exhibit the g = 4.1 signal when illuminated at 140 K, but subsequent warming to 190 K neither depletes the amplitude of this signal nor produces the multiline signal. The broad signal at g = 4.1 is typical for a $\text{S =}\text{5}\text{2}$ spin system in a rhombic environment, suggesting the involvement of non-heme Fe in photosynthetic oxygen evolution.     

Influence of chlorophyll concentrations on the reliability of measurements with an oxygen electrode when studying photosynthetic efficiency in bioassays using microalgae

Euglena gracilis and Chlamydomonas reinhardtii were used as model organisms to establish the best conditions for studying photosynthetic efficiency using the Light Pipette – experimental system, which enables sensitive detection of changes in oxygen evolution/consumption and an easy collection and digitalisation of data. Chlorophyll concentrations of 0.005, 0.025, 0.050 and 0.075 mgmL^-1 were investigated using different light regimes. Cultures of E. gracilis at the same chlorophyll concentration absorbed more light(measured at 580 μmol m^-2 s^-1) than those of C. reinhardtii. Cell density had a considerable effect on the reliability of measurements. Chlorophyll concentrations between 0.025 mg_Chl ml^-1 and 0.050 mg_Chlml^-1 can be recommended when applying the Light Pipette system in bioassays using microalgae. This revised version was published online in August 2006 with corrections to the Cover Date.     

高氧条件下灵芝子实体活性氧含量及其代谢相关酶活性

灵芝Ganoderma lingzhi是最著名的药用真菌之一。本文研究了60%高氧条件下灵芝子实体呼吸速率、灵芝酸（ganoderic acid,GA）含量、总酚含量、活性氧（reactive oxygen species,ROS）含量、丙二醛（malondialdehyde,MDA）含量、抗氧化酶活性、黄嘌呤氧化酶（xanthineoxidase,XOD）活性、琥珀酸脱氢酶（succinic dehydrogenase,SDH）活性、H ⁺-ATP酶活性、Ca ²⁺-ATP酶活性的变化。结果显示,高氧抑制灵芝子实体的呼吸速率;处理前期（第1天）,灵芝子实体内过氧化氢（H₂O₂）和超氧阴离子自由基（O₂ ^-?）含量高于对照组,但随着处理的进行,ROS含量显著减少,MDA积累减少,超氧化物歧化酶（superoxide dismutase,SOD）、过氧化氢酶（catalase,CAT）和SDH活性提高,GA和总酚含量增加。表明一定的环境胁迫压力可以激发灵芝启动自身的抗氧化系统,保护机体免受氧化损伤,并促进相关次生代谢产物的合成。     

Temporal dynamics of dissolved oxygen in a floating–leaved macrophyte bed

1. Oxygen concentrations in shallow vegetated areas of aquatic systems can be extremely dynamic. In these waters, characterizing the average oxygen content or frequency of low oxygen events (hypoxia) may require high frequency measurements that span seasons and even years. In this study, moored sondes were used to collect 15‐min interval dissolved oxygen (DO) readings in an embayment of the tidal Hudson River with dense coverage by an invasive floating leaved plant (Trapa natans) and in adjacent open waters. Measurements were made from late spring to summer over a 2‐year period (2005, 2006). 2. Oxygen concentrations were far more dynamic in the vegetated embayment than in the adjacent open waters and while hypoxic conditions never occurred in the open waters, they occurred frequently in the vegetated site. Overall the vegetated site was hypoxic (DO < 2.5 mg L^?1) 30% of the time and had an average oxygen concentration of 5.1 mg L^?1. Oxygen concentration was significantly (P < 0.0001, anova ) related to season, year and tide. Low tide periods during summer of 2006 had the lowest average oxygen concentration and the highest frequency of hypoxia. 3. The greater hypoxia in summer than spring is related to changes in plant morphology. In the spring and early summer when plants are submersed hypoxia occurs at lower frequency and duration than in the summer when dense floating vegetation covers the water. The tidal pattern in oxygen is related to hydrologic exchange with the non‐vegetated open waters. Year‐to‐year variation may be related to relatively small changes in plant biomass between years. 4. Oxygen concentrations in aquatic systems can be critical to habitat quality and can have cascading impacts on redox sensitive nutrient and metal cycling. For some systems with dynamic oxygen patterns neither weekly spot sampling nor short‐duration, high‐frequency measurements may be sufficient to characterize oxygen conditions of the system.     

Molecular dynamics simulations of energy accommodation coefficients for gas flows in nano-channels

The energy accommodation coefficient (EAC) used in thermal boundary condition in micro- and nano-gas flows is reported to be always less than unity and greatly influenced by wall characteristics, for example, the wall temperature. A statistical EAC definition was described to calculate the EAC for thermal conduction in argon gas between two smooth platinum plates from two-dimensional non-equilibrium molecular dynamics simulations. The non-equilibrium EAC at the upper wall was calculated for different upper wall temperatures and a fixed bottom wall temperature. The equilibrium EAC at each temperature can then be extrapolated from a series of non-equilibrium EACs as the temperature difference between the two walls approaches zero. The analyses of the effects of wall temperature for various Knudsen number on non-equilibrium and equilibrium EACs show that, for a given lower bottom wall temperature, the non-equilibrium EAC at a high temperature wall increases with an increase in the wall temperature. For a given wall temperature difference, the non-equilibrium EAC increases with the increase in the wall temperatures. The equilibrium EAC also becomes larger at higher temperatures.     

Comparative squamation of the lateral line canal pores in sharks

The current study collected the first quantitative data on lateral line pore squamation patterns in sharks and assessed whether divergent squamation patterns are similar to experimental models that cause reduction in boundary layer turbulence. In addition, the hypothesis that divergent orientation angles are exclusively found in fast‐swimming shark species was tested. The posterior lateral line and supraorbital lateral line pore squamation of the fast‐swimming pelagic shortfin mako shark Isurus oxyrinchus and the slow‐swimming epi‐benthic spiny dogfish shark Squalus acanthias was examined. Pore scale morphology and pore coverage were qualitatively analysed and compared. In addition, pore squamation orientation patterns were quantified for four regions along the posterior lateral line and compared for both species. Isurus oxyrinchus possessed consistent pore scale coverage among sampled regions and had a divergent squamation pattern with multiple scale rows directed dorsally and ventrally away from the anterior margin of the pore with an average divergent angle of 13° for the first row of scales. Squalus acanthias possessed variable amounts of scale coverage among the sampled regions and had a divergent squamation pattern with multiple scale rows directed ventrally away from the anterior margin of the pore with an average angle of 19° for the first row of scales. Overall, the squamation pattern measured in I. oxyrinchus fell within the parameters used in the fluid flow analysis, which suggests that this pattern may reduce boundary layer turbulence and affect lateral line sensitivity. The exclusively ventral oriented scale pattern seen in S. acanthias possessed a high degree of divergence but the pattern did not match that of the fluid flow models. Given current knowledge, it is unclear how this would affect boundary layer flow. By studying the relationship between squamation patterns and the lateral line, new insights are provided into sensory biology that warrant future investigation due to the implications for the ecology, morphology and sensory evolution of sharks.