Relationship between Bitterness of Peptides and their Chemical Structures

Various peptides and derivatives of peptides and amino acids were synthesized and tasted, systematically, to elucidate the relationship between bitterness and chemical structures of peptides.

We have found that: 1. Peptides become more bitter than the original amino acids when their amino and carboxyl groups are blocked and when peptide bond is formed. 2. A peptide molecule with a high content of amino acids with hydrophobic side chains will develop bitter taste. 3. The amino acids in a peptide chain independently contribute to bitterness regardless of amino acid sequences and configuration.     

PROP1与联合垂体激素缺乏症

垂体特异性转录因子祖先蛋白(PROP l),是成对同源转录因子,在垂体腺中呈特异性表达,参与早期胚胎垂体的发育,因此,PROP1基因对于垂体前叶的发育是必需的。PROP1启动胚胎期垂体特异性转录因子(PIT-1)的起始表达并维持个体出生后的持续表达,且可直接促使PIT-1细胞系的前体分化为促性腺细胞系。其基因突变可使人、鼠患有联合垂体激素缺乏症(CPHD),表现为生长激素(GH)、促乳素(PRL)、促甲状腺素(TSH)以及促黄体激素(LH)、促卵泡激素(FSH)或促肾上腺皮质激素(ACTH)缺乏,垂体核磁共振成像显示垂体萎缩。在其它哺乳动物中PROP1突变也会引起垂体和性腺激素异常。就PROP1基因的结构与功能,以及与CPHD间的关系作一综述。     

比较L-精氨酸、肌苷对肾脏功能保护的实验研究

探讨L-精氨酸(L-Arg)的肾功能保护作用机制及与肌苷的疗效比较。模拟手术肾损伤模型,分别采用放射免疫法和硝酸还原酶法检测手术前后大鼠不同时期尿液β2-MG、血浆NO含量变化。结果表明L-Arg和肌苷均对肾功能损伤有明显保护作用,L-Arg比肌苷更快地促进肾功能的恢复。     

Effects of L-Arginine supplementation on bone metabolism

Recent experimental studies indicate that Nitric Oxide (NO) is an important regulator of bone turnover in humans by exerting an anabolic effect on bone cell activity. NO is synthesised from the nonessential amino acid L-Arginine. Therefore, a supplementation with oral L-Arginine might be highly potent to affect bone cell activity via NO synthesis from L-Arginine. In our study we examined the effect of a six months oral supplementation with L-Arginine-hydrochloride (18 g) on bone metabolism in 15 healthy postmenopausal women. We analysed nitrogen excretion, markers of bone turnover and calcium concentration. The results show neither a change in serum calcium concentration nor in bone turnover as shown by bone markers. In conclusion, L-Arginine-hydrochloride supplementation at that concentration seems to have no effect on bone cell activity in healthy postmenopausal women.     

生长期间的光强度对小麦光谱特性的影响

在强光(20 klx)下生长的小麦,其叶片和叶绿体的低温(77K)荧光发射强度明显高于在弱光(2 klx)下生长的小麦。同时,前者的PSⅡ的相对荧光产量与PSⅠ的相对荧光产量的比值也高,表明增加光强度有利于PSⅡ的发育。此外。在强光下生长的小麦具有更高的PSⅡ活性和原初光能转化效率。在等量叶绿素的情况下,生长在弱光下的小麦,其叶绿体在吸收光谱上的两个特异吸收带都有较高的吸收值,表明它们比在强光下生长的小麦叶绿体含有较多的光合膜,从而有更大截获光能的面积。     

厄他培南与人血清清蛋白体外相互作用的理化特性

研究新型碳青霉烯类抗菌素厄他培南（ertapenem, ERT）与人血清清蛋白（human serum albumin,HSA）的体外相互作用的物理化学特性。模拟生理条件下,计算机模拟技术结合荧光光谱和紫外光谱,研究ERT与HSA相互作用机制,荧光光谱实验中,Kq 值远大于2.0×1010 L·(mol·s)-1,ERT对HSA荧光猝灭的Stern-Volmer 曲线有良好的线性关系,表明ERT与HSA的相互作用表现为静态结合过程。HSA的最大发射波长发生轻微红移,说明HSA的微环境发生了改变。ERT与HSA的分子结合距离r值较小,说明发生能量转移现象。同步荧光技术解析出ERT对HSA的结构域微区构象产生影响,使色氨酸残基周围的微区构象及结合位域的疏水性发生改变。荧光相图技术解析出ERT与HSA相互反应呈线性,说明HSA构象型态的变迁为“二态”模型。HSA与ERT相互作用的热力学参数及分子模拟技术建立ERT-HSA结合模型,表明ERT与HSA的相互作用力主要是疏水作用力,兼有氢键作用力的存在。荧光偏振定量证明,HSA与ERT相互作用过程中生成了非共价复合物。光谱实验与计算机模拟结果基本一致,其结果可为研究ERT与HSA相互作用本质提供一定参考。     

A Direct Chemical Interaction between Dynorphin and Excitatory Amino Acids

The endogenous opioid peptide dynorphin A elicits non-opioid receptor-mediated neurotoxic effects. These effects are blocked by pretreatment with N-methyl-D-aspartate (NMDA) receptor antagonists. Herein, the mechanism for the non-opioid effects of dynorphin and related peptides was studied by matrix-assisted laser desorption ionization (MALDI) mass-spectrometry. We observed that both glutamate or aspartate bind non-covalently to dynorphin A and dynorphin 2-17. However, when dynorphin A or dynorphin 2-17 were added to an equimolar mixture of Glutamate and Aspartate, they both complexed preferentially with glutamate. These data may explain the non-opioid physiological effects of dynorphin A and related peptides and indicate that the direct chemical interaction between neurotransmitters should be monitored when studying interactions between different neurochemical systems.     

Dose-Dependent Adverse Effects of Salinomycin on Male Reproductive Organs and Fertility in Mice

Salinomycin is used as an antibiotic in animal husbandry. Its implication in cancer therapy has recently been proposed. Present study evaluated the toxic effects of Salinomycin on male reproductive system of mice. Doses of 1, 3 or 5 mg/kg of Salinomycin were administered daily for 28 days. Half of the mice were sacrificed after 24 h of the last treatment and other half were sacrificed 28 days after withdrawal of treatment. Effects of SAL on body and reproductive organ weights were studied. Histoarchitecture of testis and epididymis was evaluated along with ultrastructural changes in Leydig cells. Serum and testicular testosterone and luteinizing hormones were estimated. Superoxide dismutase, reduced glutathione, lipid peroxidation, catalase and lactate dehydrogenase activities were measured. Spermatozoa count, morphology, motility and fertility were evaluated. Expression patterns of steroidogenic acute regulatory protein (StAR) and cytochrome P450 side chain cleavage proteins (CYP11A1) were assessed by Western blotting. Salinomycin treatment was lethal to few mice and retarded body growth in others with decreased weight of testes and seminal vesicles in a dose dependent manner. Seminiferous tubules in testes were disrupted and the epithelium of epididymis showed frequent occurrence of vacuolization and necrosis. Leydig cells showed hypertrophied cytoplasm with shrunken nuclei, condensed mitochondria, proliferated endoplasmic reticulum and increased number of lipid droplets. Salinomycin decreased motility and spermatozoa count with increased number of abnormal spermatozoa leading to infertility. The testosterone and luteinizing hormone levels were decreased in testis but increased in serum at higher doses. Depletion of superoxide dismutase and reduced glutathione with increased lipid peroxidation in both testis and epididymis indicated generation of oxidative stress. Suppressed expression of StAR and CYP11A1 proteins indicates inhibition of steroidogenesis. Spermatogenesis was however observed in testis 28 days after Salinomycin withdrawal. The results indicate reversible dose-dependent adverse effects of Salinomycin on male reproductive system of mice.     

Mechanisms of Interaction between DNA and Chemical Analogues of Microbial Anabiosis Autoinducers

The alkylhydroxybenzene (AHB) autoregulatory factors d₁ (fd₁) of microorganisms have been found to directly interact with highly polymeric DNA. This circumstance results in changes, related to alterations in the topology of this macromolecule, in DNA physicochemical properties. The physicochemical properties of DNA in the presence of chemical analogues of microbial AHBs (methylresorcinol; hexylresorcinol; and 2-(4-hydroxyphenyl)ethane-1-ol, also known as tyrosol) were investigated using adsorption spectrophotometry, fluorometry, heat denaturation, viscosimetry, and electrophoresis in agarose gel. A number of concordant effects pointing to DNA-AHB interactions were revealed that manifest themselves in the hypochromic properties of the resulting complexes, an increase in their melting temperature and viscosity, a decrease in their electrophoretic mobility, and a change in the fluorescent properties of AHBs upon complexation with DNA. Such alterations were particularly significant in the presence of hexylresorcinol, which possessed the maximum alkyl radical length among the fd₁ analogues tested. Using atomic force microscopy, we visualized the micellelike DNA structures forming in the presence of AHBs. The results obtained provided the basis for developing a hypothetical model of the interaction between the biopolymer macromolecule and low-molecular-weight AHBs that takes into account the differences in the hydrophobicity of individual AHB homologues functioning as ligands. In terms of our model, we discuss AHB involvement in the stabilization of DNA and alteration of its topology, i.e., in the process related to intragenomic rearrangements, which account for the intrapopulational variability of bacteria, including dissociation processes.     

不同光照强度对马蹄金叶的特征及总黄酮含量的影响

以马蹄金叶为研究对象,利用遮荫网设置光照梯度(透光率分别为:对照100%、76.19%、59.27%、38.09%),对其形态特征及总黄酮含量进行测定和分析.结果表明:(1)随着光照强度的降低,马蹄金叶片的长度、宽度及厚度均表现出先增大后减小的趋势,在76.19%透光率下达到最大值;叶柄长度随着光强的减弱而增长,叶片的形态并未发生显著变化.(2)光照强度对马蹄金叶片总黄酮含量有影响,透光率为76.19%时,马蹄金叶中总黄酮含量最高.分析表明76.19%的透光率有利于马蹄金的生长并能提高马蹄金叶中总黄酮的含量.     

土壤水分和光强对景东翅子树幼苗生长及光合特性的影响

以1年生极小种群野生植物景东翅子树（Pterospermum kingtungense）实生苗为研究对象,通过双因子室内受控试验,设置6个土壤水分梯度（100％、90％、80％、60％、40％、30%田间持水量）和4个光强梯度（100%、75%、50％、25％自然光照）,研究土壤水分和光强对其幼苗生长（地上部分生物量、地下部分生物量、叶片数量和株高）及光合特性［净光合速率（P_n）、蒸腾速率（T_r）、气孔导度（G_s）、胞间二氧化碳摩尔分数（C_i）、气孔限制值（L_s）和瞬时水分利用效率（W_UE）］的影响。结果表明：①随着土壤水分的减少,景东翅子树幼苗的生长及光合指标呈现先升高后降低的趋势,一般会在田间持水能力W2（32.11%）或W3（28.54%）处理下达到峰值,W6（10.70%）条件下的生长状况最差。②随着光强的降低,除了L_s外,景东翅子树幼苗的4个生长指标及5个光合特性指标均表现出先增加后减少的趋势,且均在光强为L2（75%自然光照）或L3（50%自然光照）条件下表现最佳。③不同土壤水分和不同光强的综合评价得分显示,W2土壤水分和L2光强下的综合评价得分分别最高,证明适量的土壤水分环境和适度遮荫最适于景东翅子树幼苗的生长及其光合作用。④二元线性回归分析结果表明,土壤水分和光强这2个自变量分别对景东翅子树幼苗的生长和光合指标有较强的影响。研究结果可为景东翅子树的幼苗培育及其种群恢复与重建提供理论依据。     

The Dose-Dependent Antioxidant Effects of Physical Exercise in the Hippocampus of Mice

Exercise increases both the consumption of oxygen and the production of reactive species in biological tissues, and this is counterbalanced by antioxidant adaptations to regular physical training. When the intensity of exercise fluctuates between mild and moderate, it improves the status of reduction–oxidation balance in the brain and induces neuroplasticity. However, intense exercise can oxidize the brain and impair neurological function. The effect of the frequency of exercise, which is an important factor in physical training, is still unknown. The effect of periodic exercise on biomarkers of oxidative stress in the hippocampus of mice was evaluated in this study. Mice were made to run on a treadmill for 8 weeks, two, three, or five times per week, and their hippocampi and quadriceps femoris muscles were then dissected. Biomarkers of oxidative damage were negatively correlated with the frequency of exercise and mitochondrial muscular activity, while the sulfhydryl contents were positively correlated with exercise frequency. A logistic analysis revealed a dose-dependent effect of exercise on these biomarkers. In summary, these results suggested that manipulating the frequency of physical exercise could induce antioxidant-related adaptations in the hippocampi of adult mice.     

Effects of Light Quality on the Interaction between Cucumber Mosaic Virus and Nicotiana tabacum

Light is an important environment factor controlling plant growth, development, and nutritional quality and is also one of the most important factors inducing plant defence. In this study, we assayed the potential effects of light quality on the interaction between Nicotiana tabacum and cucumber mosaic virus (CMV). Our results indicated that white light‐treated N. tabacum plants displayed obvious symptoms at early stage postinoculation, while the symptoms were significantly inhibited under red light and blue light. Western blotting and quantitative real‐time PCR (qRT‐PCR) analyses showed that blue light and red light can effectively delay the replication of CMV compared with white light. The activities of various reactive oxygen species (ROS)‐scavenging enzymes and reducing substances [reduced glutathione (GSH) and ascorbic acid (ASA)] were increased under blue light and red light. In addition, hormone measurements and qRT‐PCR analyses revealed that salicylic acid (SA)‐mediated signalling pathway plays positive role in the related regulation, and cytokinin (CTK) may also participate in them. Furthermore, we found that the formation of dark green islands (DGIs) was significantly suppressed in plants under red light and blue light at 30 days postinoculation (Dpi). However, the accumulation of virus in plants under different light conditions had no notable differences at later stage of postinoculation. Taken together, these results indicated that red light and blue light could effectively delay symptom expression and replication of CMV on N. tabacum at the relatively earlier stage postinoculation.     

Interaction between Light Intensity and NaCl Salinity and Their Effects on Growth, CO(2) Assimilation, and Photosynthate Conversion in Young Broad Beans

Seedings of Vicia faba were grown for four weeks at two different light intensities (55 and 105 watts per square meter) in a saline (50 millimolar NaCl) and nonsaline nutrient solution. NaCl salinity depressed growth and restricted protein formation, CO₂ assimilation, and especially the incorporation of photosynthates into the lipid fraction. Conversion of photosynthates in leaves was much more affected by salinity than was photosynthate turnover in roots. The detrimental effect of NaCl salinity on growth, protein formation, and CO₂ assimilation was greater under low than under high light conditions. Plants of the high light intensity treatment were more capable of excluding Na⁺ and Cl⁻ and accumulating nutrient cation species (Ca²⁺, K⁺, Mg²⁺) than plants grown under low light intensity. It is suggested that the improved ionic status provided better conditions for protein synthesis, CO₂ assimilation, and especially for the conversion of photosynthates into lipids.     

Interaction between the Effects of Inside and Outside Na and K on Bullfrog Skin Potential

The composition of the solution bathing one border of the isolated frog skin affects the response of the potential across the skin to changes in the composition of the solution bathing the opposite border. Increasing the K concentration of the inside (corium) bathing solution decreased the sensitivity of the potential to a change in outside Na concentration. Decreasing the outside Na concentration decreased the sensitivity of the potential to a change in inside K concentration. Increasing the total ionic strength of the outside bathing solution or of both bathing solutions decreased the sensitivity of the potential to a change in outside Na concentration.     

光照强度对濒危植物毛瓣金花茶光合生理特性的影响

以盆栽3年生毛瓣金花茶实生苗为材料,采用人工遮荫方法研究不同光照强度(10％、25％、50％和100％自然光强)对其光合生理特性的影响,为其迁地保护和种群恢复提供科学依据.结果显示:(1)随着光照强度的升高,毛瓣金花茶叶片最大净光合速率(Pmmax)、表观量子效率(AQY)和光饱和点(LSP)降低,光补偿点(LCP)升高,其中P…和AQY在10％和25％光强下显著高于50％和100％光强处理.(2)叶片叶绿素总量(Chl)、叶绿素a(Chla)、叶绿素b(Chl b)、类胡萝卜素(Car)含量均随光强的升高而降低,Car/Chl含量随光强的升高而升高.(3)叶绿素荧光参数FmFv、Fv/Fm、Fv/F0均随光强的升高而降低,其中Fm、Fv、Fv/Fm在100％光强下显著低于其他3个遮荫处理,3个遮荫处理间则无显著差异.(4)叶片丙二醛(MDA)和脯氨酸(Pro)含量均随光强的升高而升高,在100％光强下,MDA和Pro含量显著高于其他3个遮荫处理,50％光强下的MDA含量显著高于10％和25％光强处理.(5)在25％光强下,毛瓣金花茶未发生明显光抑制,在50％光强下,其光抑制主要是由PSⅡ的可逆失活引起的,光合机构未遭到明显破坏,在100％光强下,其PSⅡ反应中心受到严重伤害,发生了光氧化.研究表明,毛瓣金花茶虽为阴生植物,却能忍受一定程度的强光(50％光强),在种群恢复过程中,可适当间伐上层乔木,增加林下透光率,提高毛瓣金花茶种群的开花结实率,促进其自然更新,在迁地保护时可选择相对开敞的遮荫环境.     

Intensity Characteristics of the Noctuid Acoustic Receptor

Spiking activity of the more sensitive acoustic receptor is described as a function of stimulus intensity. The form of the intensity characteristic depends strongly on stimulus duration. For very brief stimuli, the integral of stimulus power over stimulus duration determines the effectiveness. No response saturation is observed. With longer stimuli (50 msec), a steady firing rate is elicited. The response extends from the spontaneous rate of 20–40 spikes/sec to a saturated firing rate of nearly 700 spikes/sec. The characteristic is monotonic over more than 50 db in stimulus intensity. With very long stimuli (10 sec), the characteristics are nonmonotonic. Firing rates late in the stimulus decrease in response to an increase in stimulus intensity. The non-monotonic characteristics are attributed to intensity-related changes in response adaptation.