Enhancement of YD spin relaxation by the CaMn4 cluster in photosystem II detected at room temperature: A new probe for the S-cycle

The long-lived, light-induced radical Y_D^• of the Tyr161 residue in the D2 protein of Photosystem II (PSII) is known to magnetically interact with the CaMn₄ cluster, situated ∼ 30 Å away. In this study we report a transient step-change increase in Y_D^• EPR intensity upon the application of a single laser flash to S₁ state-synchronised PSII-enriched membranes from spinach. This transient effect was observed at room temperature and high applied microwave power (100 mW) in samples containing PpBQ, as well as those containing DCMU. The subsequent decay lifetimes were found to differ depending on the additive used. We propose that this flash-induced signal increase was caused by enhanced spin relaxation of Y_D^• by the OEC in the S₂ state, as a consequence of the single laser flash turnover. The post-flash decay reflected S₂ → S₁ back-turnover, as confirmed by their correlations with independent measurements of S₂ multiline EPR signal and flash-induced variable fluorescence decay kinetics under corresponding experimental conditions. This flash-induced effect opens up the possibility to study the kinetic behaviour of S-state transitions at room temperature using Y_D^• as a probe.     

Asymmetric reduction of prochiral ketones to chiral alcohols catalyzed by plants tissue

As an important organic compound, chiral alcohols are the key chiral building blocks to many single enantiomer pharmaceuticals. Asymmetric reduction of the corresponding prochiral ketones to produce the chiral alcohols by biocatalysis is one of the most promising routes. Asymmetric reduction of different kinds of non-natural prochiral ketones catalyzed by various plants tissue was studied in this work. Acetophenone, 4'-chloroacetophenone and ethyl 4-chloroacetoacetate were chosen as the model substrates for simple ketone, halogen-containing aromatic ketone and beta-ketoesters, respectively. Apple (Malus pumila), carrot (Daucus carota), cucumber (Cucumis sativus), onion (Allium cepa), potato (Soanum tuberosum), radish (Raphanus sativus) and sweet potato (Ipomoea batatas) were chosen as the biocatalysts. It was found that these kinds of prochiral ketoness could be reduced by these plants tissue with high enantioselectivity. Both R- and S-form configuration chiral alcohols could be obtained. The e.e. and chemical yield could reach about 98 and 80% respectively for acetophenone and 4'-chloroacetophenone reduction reaction with favorable plant tissue. And the e.e. and yield for ethyl 4-chloroacetoacetate reduction reaction was about 91 and 45% respectively.     

Soft–part preservation in heteromorph ammonites from the Cenomanian–Turonian Boundary Event (OAE 2) in north–west Germany

Abstract: From thinly laminated marlstones of the Hesseltal Formation, representing the Late Cenomanian Oceanic Anoxic Event (OAE) 2, at Lengerich in the Teutoburger Wald (Westfalen, north‐west Germany), 17 sediment‐compacted baculitid ammonites with carbonised and partially phosphatised soft parts are recorded. Some preserve remains of the buccal mass, including jaws (occasionally articulated) and radulae, as well as of the cephalic cartilage, such as eye capsules. Such have not yet been recorded previously for the order Ammonoidea. In addition, originally unmineralised parts found preserved in these specimens include extensive portions of the digestive tract, the siphonal tube, false colour patterns (megastriae), as well as traces of what would appear to be the oviduct. At the same levels, patches with numerous isolated horny upper and rarer lower jaws as well as radulae occur; these may represent regurgitates or faeces of larger predators. The cephalopod remains described were deposited in an epicontinental setting, possibly at palaeodepths between 200 and 600 m. In this particular Late Cretaceous fossil Lagerstätte, upper jaws and anaptychi of ammonites rank among the commonest fossils.     

Intraspecific variation for CO2 compensation point and differential growth among variants in a C3−C4 intermediate plant

CO₂ compenstation point (), the concentration of CO₂ at which photosynthesis and respiration are at equilibrium, is a commonly used diagnostic for the C₄ photosynthetic pathway, since it reflects the reduced photorespiration that is a property of C₄ photosynthesis. Geographic variation for was examined within Flaveria linearis, a C₃–C₄ intermediate species. Collections from four widely separated Floridian populations were propagated in a greenhouse and measured for . Little differentiation among populations was found, but significant within-population variation was present. Temperature is a hypothesized selective agent for the C₄ photosynthetic pathway. To test this hypothesis, plants exhibiting a range of were cloned and placed in growth chambers at 25°C and 40°C. After 7 weeks, valves were remeasured and plants were harvested and weighed. There was a poor correlation between initial and final measures of for a given genotype (r=0.38, P>0.1). Broad sense heritability for was computed to be 0.10. At 25°C, there was no relationship between final size and . At 40°C, more C₄-like plants, as indicated by their low , had grown larger. Differences in relative growth rate were attributable more to differences in net assimilation rate than in leaf area ratio. Taken together, these results demonstrate that although significant plasticity exists in the amount of photorespiration in this C₃–C₄ species, high temperature appears to be an effective selective agent for the reduction of photorespiration and the enhancement of C₄-like traits.     

The first potassium channel toxin from the venom of the Iranian scorpion Odonthobuthus doriae

The very first member of K(+) channels toxins from the venom of the Iranian scorpion Odonthobuthus doriae (OdK1) was purified, sequenced and characterized physiologically. OdK1 has 29 amino acids, six conserved cysteines and a pI value of 4.95. Based on multiple sequence alignments, OdK1 was classified as alpha-KTx 8.5. The pharmacological effects of OdK1 were studied on six different cloned K(+) channels (vertebrate Kv1.1-Kv1.5 and Shaker IR) expressed in Xenopus laevis oocytes. Interestingly, OdK1 selectively inhibited the currents through Kv1.2 channels with an IC50 value of 183+/-3 nM but did not affect any of the other channels.     

细胞生物活性肽-蛋氨酸脑啡肽对小鼠CD4~+T细胞mRNA的影响

从基因水平探讨蛋氨酸脑啡肽对小鼠CD4'T细胞mRNA转录的影响。6～8周龄BALB/c雌性小鼠体内、外不同浓度MEK刺激。采用RT-PCR技术检测mRNA,所得不同浓度MEK刺激的CD4+T细胞mRNA和β-actin条带密度比值作为相对表达强度,所得数据采用SPSS11.5软件进行统计分析。4mg/mLMEK体内刺激及10-9～10-12mol/mL的MEK体外刺激促进小鼠CD4'T细胞mRNA转录;10-1～10-8mol/mL的MEK抑制小鼠CD4+T细胞mRNA的转录。10-13～10-14mol/mL的MEK对小鼠CD4'T细胞mRNA的转录无明显变化。适量浓度的MEK体内、外刺激能促进小鼠CD4+T细胞mRNA转录的高效表达。     

Mitochondrial Oxidative Phosphorylation Regulates the Fate Decision between Pathogenic Th17 and Regulatory T Cells

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Dimebon attenuates methamphetamine, but not MPTP, striatal dopamine depletion

Dimebon is an anti-histamine with central nervous system activity. In this report the effects of dimebon as a neuroprotectant in animal models of Parkinson's disease were tested as assessed in methamphetamine- and MPTP-induced striatal dopaminergic toxicity. Dimebon (1mg/kg) administered at 30 min prior to methamphetamine (40mg/kg) significantly reduced the amount of striatal dopamine depletion in mice, without altering the initial methamphetamine-induced increase in body temperature. In contrast, dimebon at either 1 or 25mg/kg administered at 30 min prior to MPTP (35 mg/kg) was unable to prevent MPTP-induced striatal dopamine loss as determined at 7 days post-methamphetamine/MPTP. These data suggest that dimebon may be exerting a neurotoxin specific neuroprotective effect upon the striatal dopaminergic system and may serve as an important tool for discriminating the mechanistic basis of these two dopaminergic neurotoxins.     

Neurotrophins,but not depolarization,regulate substance P expression in the developing optic tectum

Neurotransmitter expression can be regulated by both activity and neurotrophins in a number of in vitro systems. We examined whether either of these factors was likely to play a role in the in vivo optic nerve‐dependent regulation of a substance P‐like immunoreactive (SP‐ir) population of cells in the developing optic tectum of the frog. In contrast to our previous results with the adult system, blocking tectal cell responses to glutamate release by retinal ganglion cells with 6‐cyano‐7‐nitroquinoxaline‐2,3 dione (CNQX) did not affect the percent of SP‐ir cells in the developing tectum. Treatment with d‐(‐)‐2‐amino‐5‐phosphonovaleric acid (d‐AP‐5) was also ineffective in this regard, although both it and CNQX treatment disrupted visual map topography. Chronic treatment with brain‐derived neurotrophic factor (BDNF) and neurotrophin‐4/5 (NT‐4/5) produced increases in SP‐ir cells in the treated lobes of normal animals, which were significant in the case of NT‐4/5. Both substances also prevented the decrease of SP cells that would otherwise occur in the deafferented lobe of unilaterally optic nerve‐transected tadpoles. These changes in the percent of SP‐ir cells occurred without any detectable changes in the overall number of tectal cells. NGF had no effect on SP expression. Nor did it affect topographic map formation, which was disrupted by treatment with either BDNF or NT‐4/5. Our results demonstrate that different mechanisms regulate SP expression in the developing and adult tectum. They indicate that neurotrophin levels in the developing optic tectum may selectively regulate a specific neuropeptide‐expressing population of cells. © 2001 John Wiley & Sons, Inc. J Neurobiol 48: 131–149, 2001     

Retinoic acid receptor signalling directly regulates osteoblast and adipocyte differentiation from mesenchymal progenitor cells

Low and high serum retinol levels are associated with increased fracture risk and poor bone health. We recently showed retinoic acid receptors (RARs) are negative regulators of osteoclastogenesis. Here we show RARs are also negative regulators of osteoblast and adipocyte differentiation. The pan-RAR agonist, all-trans retinoic acid (ATRA), directly inhibited differentiation and mineralisation of early osteoprogenitors and impaired the differentiation of more mature osteoblast populations. In contrast, the pan-RAR antagonist, IRX4310, accelerated differentiation of early osteoprogenitors. These effects predominantly occurred via RARγ and were further enhanced by an RARα agonist or antagonist, respectively. RAR agonists similarly impaired adipogenesis in osteogenic cultures. RAR agonist treatment resulted in significant upregulation of the Wnt antagonist, Sfrp4. This accompanied reduced nuclear and cytosolic β-catenin protein and reduced expression of the Wnt target gene Axin2, suggesting impaired Wnt/β-catenin signalling. To determine the effect of RAR inhibition in post-natal mice, IRX4310 was administered to male mice for 10 days and bones were assessed by µCT. No change to trabecular bone volume was observed, however, radial bone growth was impaired. These studies show RARs directly influence osteoblast and adipocyte formation from mesenchymal cells, and inhibition of RAR signalling in vivo impairs radial bone growth in post-natal mice.