小黄皮叶挥发油的化学成分

利用水蒸气蒸馏法提取小黄皮叶挥发油,运用毛细管气相色谱-质谱联用法对挥发油进行了分析,分离出40个峰,鉴定了其中的37种成分,所鉴定成分占挥发油总量的99.87%,其主要化学成分为单萜及倍半萜类化合物。     

Tissue transglutaminase modulates alpha-synuclein oligomerization

We have studied the interaction of the enzyme tissue transglutaminase (tTG), catalyzing cross-link formation between protein-bound glutamine residues and primary amines, with Parkinson's disease-associated α-synuclein protein variants at physiologically relevant concentrations. We have, for the first time, determined binding affinities of tTG for wild-type and mutant α-synucleins using surface plasmon resonance approaches, revealing high-affinity nanomolar equilibrium dissociation constants. Nanomolar tTG concentrations were sufficient for complete inhibition of fibrillization by effective α-synuclein cross-linking, resulting predominantly in intramolecularly cross-linked monomers accompanied by an oligomeric fraction. Since oligomeric species have a pathophysiological relevance we further investigated the properties of the tTG/α-synuclein oligomers. Atomic force microscopy revealed morphologically similar structures for oligomers from all α-synuclein variants; the extent of oligomer formation was found to correlate with tTG concentration. Unlike normal α-synuclein oligomers the resultant structures were extremely stable and resistant to GdnHCl and SDS. In contrast to normal β-sheet-containing oligomers, the tTG/α-synuclein oligomers appear to be unstructured and are unable to disrupt phospholipid vesicles. These data suggest that tTG binds equally effective to wild-type and disease mutant α-synuclein variants. We propose that tTG cross-linking imposes structural constraints on α-synuclein, preventing the assembly of structured oligomers required for disruption of membranes and for progression into fibrils. In general, cross-linking of amyloid forming proteins by tTG may prevent the progression into pathogenic species.     

ACTH,cyclic nucleotides,and brain protein phosphorylation in vitro

Endogenous phosphorylation of proteins from rat brain synaptosomal plasma membranes was studied in vitro. Cyclic AMP (cAMP) markedly stimulated³²P incorporation in three protein bands with molecular weights of 75,000, 57,000, and 54,000, respectively. The effect of the behaviorally active peptide ACTH_1–24 on this endogenous phosphorylation in vitro was studied using peptide concentrations from 10^–10 to 10^–4 M. In a number of protein bands, a biphasic effect of ACTH_1–24 was observed: in concentrations of 10^–4–10^–5 M, a reduced amount of³²P was found; in concentrations of 10^–6–10^–7 M, hardly any effect could be detected, whereas consistently at concentrations around 10^–8 M, a significant decrease was again observed. The phosphoprotein bands affected by in vitro addition of ACTH_1–24 were of a smaller molecular weight than those affected by in vitro addition of cAMP.     

Dynamic testosterone responses to near-physiological LH pulses are determined by the time pattern of prior intravenous LH infusion

The long-lived glycoprotein hormone, human chorionic gonadotropin (hCG), downregulates testosterone (T) biosynthesis in vitro and in vivo in animals and humans. The degree to which short-lived pulses of pituitary luteinizing hormone (LH) do so, particularly at physiological concentrations, is not known. We test the hypothesis that continuous LH infusion compared with bolus injections of LH every 1 h or every 2 h overnight downregulates T secretory responses to a subsequent fixed template of three consecutive intravenous pulses of a physiological amount of recombinant human (rh) LH (triple stimulus). Nineteen healthy men ages 18-49 yr each underwent four separate randomly ordered overnight gonadotropin-releasing hormone-receptor antagonist treatments with superimposed intravenous infusions of saline or rhLH (1-h pulses, 2-h pulses, or continuously). Each 12-h infusion protocol was followed by the triple rhLH-pulse stimulus the next morning. During the triple stimulus, basal (nonpulsatile) as well as total (basal plus pulsatile) T secretion was higher after overnight 2- and 1-h rhLH pulses than after continuous rhLH or saline delivery. Approximate entropy, a probabilistic measure of feedforward-induced irregularity of T concentration time series, was higher after 1-h rhLH pulses than after continuous rhLH. Analytical estimation of pulsatile rhLH-T dose-response measures revealed higher T secretory sensitivity and greater rhLH potency (lower EC(50)) after exposure to 1-h than 2-h rhLH pulses. Collectively, these data indicate that in vivo dynamics of LH-stimulated T secretion under standardized conditions in men depend on the prior time mode of LH delivery in the bloodstream.     

A role for somatomedin C as a differentiating hormone and amplifier of hormone action on ovarian cells: studies with synthetically pure human somatomedin C and swine granulosa cells

Isolated swine granulosa cells incubated in chemically defined medium in vitro responded to synthetically pure human somatomedin C/IGF-I in a dose and time-dependent fashion with increased pregnenolone, progesterone and estradiol biosynthesis. These stimulatory actions were not mimicked by growth hormone, proinsulin, desoctapeptide insulin, epidermal growth factor, or fibroblast growth factor. Moreover, somatomedin C/IGF-I augmented the steroidogenic response of granulosa cells to exogenously supplied sterol substrate in the form of low-density lipoprotein, and amplified the stimulatory actions of the classical ovarian effector hormones, estradiol and follicle-stimulating hormone, in a synergistic fashion. The ability of somatomedin C/IGF-I to stimulate estradiol production on the one hand, and to act synergistically with estradiol to stimulate progesterone biosynthesis on the other hand, suggests a unique intrafollicular mechanism for amplifying progestin biosynthetic capacity in granulosa cells.     

益生菌对调节脑梗死后大鼠运动功能的机制研究

探讨在脑梗死后康复期使用益生菌治疗促进大鼠运动功能恢复的机制。

成年雄性SPF级7～8周龄Wistar大鼠,体重200～250 g,共35只。25只大鼠颅内注射内皮素制作脑缺血模型,模型制作后5只大鼠死亡,剩余20只大鼠按照随机数表法分为缺血组（ISC组）和缺血+益生菌组（ISC+PB组）,每组10只。另外10只大鼠作为假手术组（SHAM组）。SHAM组大鼠仅使用生理盐水按照上述造模流程进行。各组均喂食普通大鼠饲料。ISC+PB组大鼠第7天开始使用益生菌VSL#3溶液进行灌胃,0.25 mL/(只•d)。采用原位末端转移酶标记（TdT-mediated dUTP nick-end labeling,TUNEL）凋亡试剂盒检测凋亡细胞。采用蛋白质免疫印迹法检测各组大鼠海马与梗死周边皮层脑源性神经营养因子（brain derived neurotrophic factor,BDNF）的蛋白水平变化。使用梯形平衡木测试大鼠的肢体运动功能。

ISC组大鼠TUNEL阳性细胞数量较SHAM组显著增多（t=3.278,P=0.016）,ISC+PB组大鼠的TUNEL阳性细胞数量低于ISC组（t=2.721,P=0.037）。ISC组大鼠海马与梗死周边BDNF蛋白表达水平高于SHAM组（t=2.012,P=0.032）,ISC+PB组大鼠海马与梗死周边皮层BDNF水平较ISC组进一步提高（t=1.892,P=0.021）。梯形平衡木行走实验显示ISC组大鼠产生明显的运动功能损伤（t=3.425,P=0.041）,而ISC+PB组错误率低于ISC组（t=4.131,P=0.024）。

脑梗死后益生菌通过调控BDNF水平,抑制细胞凋亡,改善运动功能。

     

5-HT_(1A)受体参与学习记忆的分子机制研究进展

5-HT(五羟色胺)能神经元是起源最早的神经元之一,在传统的神经元形成前,成长中的轴突就可释放5-HT,并且通过5-HT的各种亚型受体来实现不同的功能。近年来,随着5-HT、5-HTRs(五羟色胺受体)的基因克隆及5-HT受体选择性激动剂和拮抗剂的研究发展,5-HT系统在学习记忆中的作用越发明确,许多研究结果表明:5-HT系统在记忆的巩固、短时程记忆(STM)及长时程记忆(LTM)中起重要作用,5-HT1A受体更是在非脊椎动物及哺乳动物的脑中都高度表达,并通过相似的信号转导途径参与学习与记忆的形成和巩固。本文将介绍5-HT1A受体、5-HT1A受体激动剂、5-HT1A受体拮抗剂及其与学习记忆的联系,重点综述5-HT1A受体参与学习记忆的信号转导途径研究进展,讨论5-HT1A受体参与学习记忆的可能性分子神经生物学机制。     

PHOTOSYNTHESIS AND CALCIFICATION BY EMILIANIA HUXLEYI (PRYMNESIOPHYCEAE) AS A FUNCTION OF INORGANIC CARBON SPECIES

To test the possibility of inorganic carbon limitation of the marine unicellular alga Emiliania huxleyi (Lohmann) Hay and Mohler, its carbon acquisition was measured as a function of the different chemical species of inorganic carbon present in the medium. Because these different species are interdependent and covary in any experiment in which the speciation is changed, a set of experiments was performed to produce a multidimensional carbon uptake scheme for photosynthesis and calcification. This scheme shows that CO₂ that is used for photosynthesis comes from two sources. The CO₂ in seawater supports a modest rate of photosynthesis. The HCO is the major substrate for photosynthesis by intracellular production of CO₂ (HCO+ H⁺→ CO₂+ H₂O → CH₂O + O₂). This use of HCO is possible because of the simultaneous calcification using a second HCO, which provides the required proton (HCO+ Ca²⁺→ CaCO₃+ H⁺). The HCO is the only substrate for calcification. By distinguishing the two sources of CO₂ used in photosynthesis, it was shown that E. huxleyi has a K_½ for external CO₂ of “only” 1.9 ± 0.5 μM (and a V_max of 2.4 ± 0.1 pmol·cell⁻¹·d⁻¹). Thus, in seawater that is in equilibrium with the atmosphere ([CO₂]= 14 μM, [HCO]= 1920 μM, at fCO₂= 360 μatm, pH = 8, T = 15° C), photosynthesis is 90% saturated with external CO₂. Under the same conditions, the rate of photosynthesis is doubled by the calcification route of CO₂ supply (from 2.1 to 4.5 pmol·cell⁻¹·d⁻¹). However, photosynthesis is not fully saturated, as calcification has a K_½ for HCO of 3256 ± 1402 μM and a V_max of 6.4 ± 1.8 pmol·cell⁻¹·d⁻¹. The H⁺ that is produced during calcification is used with an efficiency of 0.97 ± 0.08, leading to the conclusion that it is used intracellularly. A maximum efficiency of 0.88 can be expected, as NO uptake generates a H⁺ sink (OH⁻ source) for the cell. The success of E. huxleyi as a coccolithophorid may be related to the efficient coupling between H⁺ generation in calcification and CO₂ fixation in photosynthesis.     

Growth characteristics of flagellated cells of Phaeocystis pouchetii revealed by diel changes in cellular DNA content

The present study reports on effects of different light:dark periods, light intensities, N:P ratios and temperature on the specific growth rate of flagellated cells of Phaeocystis pouchetii in culture. The specific growth rate was estimated by diel changes in cellular DNA content. The cellular DNA content and cell cycle of flagellated cells of P. pouchetii are shown, and the importance of light:dark period in cell division is demonstrated. Diel patterns of the cellular DNA content showed that cell division was confined to the dark period. The cells dealt with more than one division per day by rapid divisions shortly after each other.The specific growth rates (μ_DNA) based on the DNA cell cycle model were in close agreement with specific growth rates (μ_Cell) determined from cell counts. The temperature affected the specific growth rates (multiple regression, p < 0.01) and were higher at 5 °C (μ ≤ 2.2 d⁻¹) than at 10 °C (μ ≤1.6 d⁻¹). Increasing the light:dark period from 12:12 h to 20:4 h affected the specific growth rate of P. pouchetii at the lower temperature tested (5 °C) (multiple regression, p < 0.01), resulting in higher specific growth rates than at 10 °C. At 10 °C, the effect of light:dark period was severely reduced. Neither light nor nutrients could compensate the reduction in specific growth rates caused by elevated temperature. The specific growth rates was not affected by the N:P ratios tested (multiple regression, p = 0.21). The experiments strongly suggest that the flagellated cells have a great growth potential and could play a dominating role in northern areas at increased day length.