Simulation of spontaneous action potentials of cardiomyocytes in pulmonary veins of rabbits

Atrial fibrillation is the most prevalent arrhythmia, but the mechanisms by which it develops are not clear. Recently, over 90% of paroxysmal atrial fibrillation was found to be located inside the main pulmonary veins (PVs). We found that single cardiac myocytes isolated from the main PVs of rabbits generate spontaneous action potentials (SAP). We therefore assayed the electrical characteristics of these cardiomyocytes. Among the diverse ionic currents identified were I_Na, I_Ca,L, I_K1, I_Kr, I_Ks, I_to, I_Ksus, I_ncx, I_pump, I_KH and I_Cl,Ca. In contrast, I_K1 was minimal, I_Ks could be detected only in the presence of 10 μM forskolin, and we were unable to detect I_f and I_Ca,T, the most important currents for pacemaking activity in sinoatrial node cells. To identify the main cause of SAP, we developed a model that can explain the electrical properties of these cardiomyocytes. After reconstructing the ionic currents based on experimental observations, we were able to use our model to successfully reconstruct the characteristics of the SAP of PV cardiomyocytes. The simulation showed that the major currents contributing to pacemaking depolarization were I_CaL, I_Kr, a background current and Na⁺–K⁺ pump current. Deactivation kinetics of I_Kr was one of the major determinants of the rate of pacemaking depolarization. The steady state inactivation of I_to was shifted to the negative voltage and the activity of I_to was minimal in the range of the SAP. The major currents for the repolarization were I_Kr and I_pump. The amplitude of most currents in these cardiac myocytes was small and no currents did not exceed 30 pA during the SAP, indicating that slight activation of other inward or outward currents will have profound effects on the SAP. To our knowledge, this report is the first to show the simulation of SAP of PV cardiomyocytes. This model may help to study on the electrophysiological basis of paroxysmal atrial fibrillation originating from PVs.     

荒漠草原猪毛蒿种群繁殖特征的土壤驱动因子分析

繁殖是植物生命活动的重要环节, 了解植物的繁殖特征是解释植物生态适应性和制定有效管理措施的重要依据。该研究以荒漠草原猪毛蒿(Artemisia scoparia)种群为研究对象, 通过测定不同土壤类型的理化性质和猪毛蒿的繁殖特征, 以期探讨影响其繁殖特征的主要土壤驱动因子。结果表明: 灰钙土、风沙土和基岩风化残积土的水溶性碳含量、全氮含量、全磷含量、全盐含量、土壤水分含量、土壤硬度存在显著差异。猪毛蒿平均个体大小、单株头状花序的平均质量和数量均以灰钙土生境下最大, 基岩风化残积土最小。繁殖分配在不同土壤类型下无显著差异, 但与单个头状花序质量、单株头状花序数量和质量间呈极显著正相关关系。单株头状花序数量与单个头状花序质量间呈负相关关系。在风沙土生境下, 单株头状花序质量主要受到土壤水溶性碳含量、土壤水分含量以及pH值的共同影响; 单株头状花序数量受全盐含量的影响最大; 繁殖分配和单个头状花序质量主要受全碳含量的影响。灰钙土生境下, 单株头状花序质量与土壤水溶性碳含量、土壤水分含量和有机碳含量呈正相关关系; 速效氮含量显著影响着单株头状花序数量。而基岩风化残积土生境下, 繁殖特征的变异主要受到土壤水溶性碳含量、土壤硬度、土壤水分含量、全磷和速效磷含量的影响。综合分析发现, 土壤因子对猪毛蒿繁殖特征的影响程度不同, 其中单株头状花序数量和质量极显著地受到土壤水溶性碳含量和土壤水分含量的影响, 繁殖分配和单个头状花序质量与土壤水溶性碳含量、土壤水分含量呈负相关关系。因此, 土壤水溶性碳含量和土壤水分是荒漠草原地区影响猪毛蒿种群繁殖特征的主要土壤因子。     

Effect of different species of endophytes on fungal disease resistance of Achnatherum sibiricum

AimsAchnatherum sibiricum, a native grass species, is widely distributed in the steppe of Nei Mongol, China. In this study, three endophytic fungi, i.e., Neotyphodium sibiricum, N. gansuensis and Epichloë gansuensis, were isolated from A. sibiricum and examined the effect of the endophytes on the resistance of A. sibiricum to fungal disease.
Methods Three fungi: Curvularia lunata, Bipolaris sorokiniana and Cladosporium sp. were chosen as the target pathogens. Three experiments were carried out to evaluate the effects of endophytic inoculation of A. sibiricum on its pathogen resistance: 1) endophye in vitro, 2) inoculated detached leaves and 3) intact plants. They were infected with the three pathogens above mentioned, separately. Seven days later, inhibition rates, the number of lesions, lesion length and concentration of spores were measured.
Important findings The results showed that all endophytes significantly reduced the growth of pathogens fungi in vitro, and N. sibiricums had the strongest effect: its bacteriostasis rate to Curvularia lunata, B. sorokiniana and Cladosporium sp. were 47.8%, 40.1% and 39.4%, respectively. Culture filtration of three endophytes also effectively reduced pathogen spore germination, in which N. gansuensis showed the strongest impact. The germination rates of Curvularia lunata, B. sorokiniana and Cladosporium sp. were only 9.8%, 8.7% and 8.5%, respectively. Neotyphodium sibiricum and N. gansuensis could reduce lesion number and spore concentration of detached host leaves after the pathogens inoculation. Epichloë gansuensis reduced lesion number of detached leaves after inoculation with Curvularia lunata and Cladosporium sp., and decreased spore concentration of the pathogens fungi of Cladosporium sp. In the intact leaves, three endophytes reduced lesion number, lesion length and spore concentration as well after inoculation of the pathogens with those infected with N. sibiricum showing the strongest resistance, while with Epichloë gansuensis, the weakest resistance.     

Specific sequence of motifs of mitochondrial uncoupling proteins

We have searched for the exclusivity of common sequence motifs of the mitochondrial uncoupling proteins (UCP1, UCP2, UCP3, UCP4, BMCP1, and plant UCP [PUMP]) within the gene family of mitochondrial anion carrier proteins. The UCP-specific sequences, "UCP signatures", were found in the first, second, and fourth alpha-helices. First: Ala/Ser-Cys/Thr/n-n/Phe-Ala/Gly-[negatively charged residue]-n/Phe-n/Cys-Thr-Phe/n; second: Gly/Ala-Ile/Leu-Gln/X-[positively charged residue]-NH-n/Cys-Ser/nphi/X-n/Ser-OH/Gly-n-[positively charged residue]-Ile/Met-Gly/Val-n/Thr; fourth: Pro-Asn/ Thr-n-X-[positively charged residue]-Asn/Ser/Ala-n-n-Ile/Leu-n-Asn/Val-Cys/n-n/Thr-[negatively charged residue]-n-n/Thr/Pro-OH/Val (n, nonpolar; phi, aromatic; (positively charged residue/negatively charged residue, charged residue). The second and part of the third signature are also present in the yeast dicarboxylate transporter. The UCP signature excluding BMCP1 was also found in the second matrix segment: [positively charged residue]-(Pro/ del-Leu/del)-[positively charged residue]-phi-X-Gly/Ser-Thr/n-X-NH/[negatively charged residue]-Ala-phi. These UCP signatures are thought to be involved in fatty acid anion binding and translocation.     

Regulation of DOPA Decarboxylase Activity in Brain of Living Rat

Abstract: To test the hypothesis that l -DOPA decarboxylase (DDC) is a regulated enzyme in the synthesis of dopamine (DA), we developed a model of the cerebral uptake and metabolism of [³H]DOPA. The unidirectional blood-brain clearance of [³H]DOPA ( K ^D₁) was 0.049 ml g⁻¹ min⁻¹. The relative DDC activity ( k ^D₃) was 0.26 min⁻¹ in striatum, 0.04 min⁻¹ in hypothalamus, and 0.02 min⁻¹ in hippocampus. In striatum, 3,4-[³H]dihydroxyphenylacetic acid ([³H]DOPAC) was formed from [³H]DA with a rate constant of 0.013 min⁻¹, [³H]homovanillic acid ([³H]HVA) was formed from [³H]DOPAC at a rate constant of 0.020 min⁻¹, and [³H]HVA was eliminated from brain at a rate constant of 0.037 min⁻¹. Together, these rate constants predicted the ratios of endogenous DOPAC and HVA to DA in rat striatum. Pargyline, an inhibitor of DA catabolism, substantially reduced the contrast between striatum and cortex, in comparison with the contrast seen in autoradiograms of control rats. At 30 min and at 4 h after pargyline, k ^D₃ was reduced by 50% in striatum and olfactory tubercle but was unaffected in hypothalamus, indicating that DDC activity is reduced in specific brain regions after monoamine oxidase inhibition. Thus, DDC activity may be a regulated step in the synthesis of DA.     

The effect of variation of thermal processing on the microbial spoilage of chub-packed luncheon meat

Process pasteurization values for reference temperature 70°C (P₇₀) were calculated from the temperature profiles of 250 g luncheon meat chubs cooked under experimental conditions. A simple equation relating Process P₇₀-value and the time and temperature of cooking was derived. With minimal cooking (P₇₀= 40) the surviving microflora (10³/g) was dominated by species of Lactobacillus, Brochothrix and Micrococcus. These organisms were destroyed by more intensive cooking (P₇₀= 105), leaving a flora (10²/g) composed of Bacillus and Micrococcus species. The spoilage that developed after 14 d storage at 25°C reflected the severity of the heat treatment received by each chub: with P₇₀ between 40 and 90, a Streptococcus spoilage sequence occurred; with P₇₀ between 105 and 120, a Bacillus/Streptococcus spoilage sequence occurred; with P₇₀ of 135 and above, a Bacillus spoilage sequence occurred. Cooking to a P₇₀= 75 was adequate to reduce the surviving microflora to the 10²/g level associated with current good manufacturing practice.     

丝兰属6种植物叶绿体基因组特征分析

为了理清丝兰属（Yucca）叶绿体基因组特征和序列变异情况,进行丝兰属植物叶绿体比较基因组学分析,并构建基于叶绿体基因组的系统发育树。利用高通量测序技术获得无刺龙舌兰（Y. treculeana）叶绿体基因组序列,结合丝兰属现已发表的叶绿体基因组,使用生物信息学方法对6种丝兰属植物叶绿体全基因组进行基本结构、重复序列、边界收缩与扩张以及序列变异分析等在内的比较基因组学研究,并进行系统发育分析。结果表明：6种丝兰属植物叶绿体基因组大小、基因的类型及数目相近,种间基因组结构比较保守;从丝兰属植物叶绿体基因组中检测到多条重复序列,其中SSR位点多是由单核苷酸、双核苷酸和四核苷酸组成,且偏好使用A、T碱基;根据核酸多态性指数π≥0.008,在6种丝兰属植物叶绿体基因组中筛选出了psbK-psbl-trnS-GCU、rpl20-rps12和ccsA-ndhD 3个高变异区域;基于叶绿体全基因组和LSC+SSC区序列构建的系统发育关系基本一致,确定了6种丝兰属植物间的系统发育关系,其中无刺龙舌兰与克雷塔罗丝兰（Y. queretaroensis）的亲缘关系最近。本研究测序获得了无刺龙舌兰叶绿体基因组,揭示了6种丝兰属植物叶绿体基因组特征和序列变异情况,明确了各物种间的亲缘关系,研究结果可为后续丝兰属植物分子标记开发及系统发育研究提供参考。     

Hydrodynamics of cryogelation

Cryogel, prevalent in the plasma of rheumatoid arthritis patients, is a plasma fibronectin (pFN)-extra domain A containing FN [EDA(+)FN]-fibrinogen (Fbg) aggregate formed by the addition of heparin (Hep) at low temperature. Although EDA(+)FN is not usually present in normal plasma, its prevalence in rheumatic patients induces cryogelation. In this study, we determined the hydrodynamic radius (R_h) ratio (R_h/R_h30) of the cryogel component by dynamic light scattering in vitro. R_h/R_h30 was normalized to R_h at 30 °C (R_h30) at several temperatures. The R_h/R_h30 of Fbg was found to increase only by self-aggregation, whereas the R_h/R_h30 of FNs does not increase in response to temperature changes. The R_h/R_h30 of the Fbg/FN aggregate is increased by the addition of Hep, and the R_h/R_h30 (12.5) of the Hep-induced EDA(+)FN/Fbg aggregate is greater than that (2.5) of the pFN/Fbg aggregate. These results suggest that cryogelation requires Fbg self-aggregation and the interaction between EDA(+)FN and Hep.     

Effect of modification of storage atmosphere on phospholipids and ultrastructure of cauliflower mitochondria

Differences in mitochondrial membrane composition and ultrastructure were studied after storage of cauliflower ( Brassica oleracea , L., Botrytis group) for 5 days at 25°C in air or under controlled atmospheres: 3% O₂, 21% O₂+ 15% CO₂ or 3% O₂+ 15% CO₂. In air, postharvest senescence involved a 20% decrease in mitochondrial phospholipid content. A large reduction in the relative abundance of phosphati-dylcholine (PC) and in the degree of unsaturation of PC and phosphatidyl ethanolamine (PE) was observed. However, the degree of unsaturation increased in cardiolipin (CL). Storage under 3% O₂ did not prevent phospholipid breakdown. Low O₂ prevented the relative decrease in PC observed during storage in air and the loss of linoleic acid from PC, but not from PE. This relative protection offered by the low O₂ atmosphere was lost under 3% O₂+ 15% CO₂. The high CO₂ atmospheres caused twice as much loss in phospholipids as that observed during storage in air. Extensive loss of mitochondrial protein, a marked decrease in phospholipid to protein ratio, and electron micrograph observations suggest structural alterations in the presence of high CO₂.     

Physiological relevance of successive hydroxylations of toluene by toluene para-monooxygenase of Ralstonia pickettii PKO1

We have recently found that toluene para-monooxygenase (TpMO) of Ralstonia pickettii PKO1 (encoded by tbuA1UBVA2C) performs successive hydroxylations of benzene (Appl. Environ. Microbiol. 70: 3814, 2004) as well as hydroxylates toluene to a mixture of 90% p-cresol and 10% m-cresol which are then further oxidized to 100% 4-methylcatechol (J. Bacteriol. 186: 3117, 2004) whereas it was thought previously that TpMO forms 100% m-cresol and is not capable of successive hydroxylations. Here we propose a modification of the degradation pathway originally described by Olsen et al. (J. Bacteriol. 176: 3749, 1994) that now relies primarily on TpMO for conversion of toluene to 4-methylcatechol (instead of m-cresol) since both m-cresol and p-cresol are shown here to be good substrates for Escherichia coli expressing TpMO (V_max/K_m=0.046, 0.036, and 0.055 mL min^-1 mg^-1 protein for the oxidation of toluene, m-cresol, and p-cresol, respectively). In light of the broader activity of TpMO, phenol hydroxylase (encoded by tbuD) appears to facilitate conversion of any m-cresol or p-cresol formed from toluene oxidation by TpMO to 4-methylcatechol; hence, the cell has a redundant method for making this important intermediate 4-methylcatechol. Further, it is suggested that the physiological relevance of the 10% m-cresol formed from toluene oxidation by TpMO is needed for induction of the meta cleavage operon tbuWEFGKIHJ to enable full metabolism of toluene since p-cresol (and o-cresol) do not induce the meta-cleavage pathway. Therefore both the successive hydroxylation of toluene by TpMO and the product distribution are of physiological relevance to the cell.     

Simultaneous Measurement of Nitrite and Nitrate Levels as Indices of Nitric Oxide Release in the Cerebellum of Conscious Rats

Abstract: We examined the modulation of nitric oxide production in vivo by measuring levels of nitrite (NO₂⁻) and nitrate (NO₃⁻) in the dialysate of the cerebellum in conscious rats, by using an in vivo brain microdialysis technique. The levels of both NO₂⁻ and NO₃⁻ were decreased by the intraperitoneal injection of N ^G-nitro- l -arginine methyl ester, an inhibitor of nitric oxide synthase, whereas N ^G-nitro- d -arginine methyl ester had no effect. l -Arginine by itself increased NO₂⁻ and NO₃⁻ levels and diminished the reduction of their levels caused by N ^G-nitro- l -arginine methyl ester. Direct infusion of l -glutamate, N -methyl- d -aspartate, or KCl into the cerebellum through a dialysis probe resulted in an increase in NO₂⁻ and/or NO₃⁻ levels. The effects of N -methyl- d -aspartate and KCl were dependent on extracellular calcium. Furthermore, the stimulatory effects of l -glutamate and N -methyl- d -aspartate were inhibited by N ^G-nitro- l -arginine methyl ester and (±)-3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid (CPP), an N -methyl- d -aspartate receptor antagonist. These results suggest that NO₂⁻ and NO₃⁻ levels may be related to nitric oxide production in vivo.     

三种桑黄属真菌人工栽培子实体营养、药效成分及抗氧化活性分析评价

本研究通过测定人工段木栽培3年生杨树桑黄Sanghuangporus vaninii、鲍姆桑黄S. baumii、桑树桑黄S. sanghuang及野生桑树桑黄子实体的粗蛋白质、粗脂肪、粗纤维、氨基酸、多糖、三萜、总黄酮、总酚含量和抗氧化活性（ABTS和FRAP）,探究此3种栽培桑黄及野生桑树桑黄子实体的营养、药效成分及抗氧化活性差异。结果表明,供试材料在营养、药效成分及抗氧化活性上差异较大。其中,栽培鲍姆桑黄子实体粗纤维含量最低,多糖含量较高,总黄酮、总酚含量和ABTS、FRAP活性最高;栽培杨树桑黄粗纤维含量较低,粗脂肪含量最低,总黄酮、总酚、三萜含量较高,多糖含量最高;野生桑树桑黄粗蛋白、粗脂肪、总氨基酸含量最高,多糖含量较高,三萜含量最高,总黄酮、总酚含量和ABTS、FRAP活性最低;栽培桑树桑黄粗纤维含量较高,多糖、总黄酮、总酚、三萜含量和ABTS、FRAP均较低。栽培杨树桑黄、鲍姆桑黄和野生桑树桑黄在药效成分含量上各有所长。筛选到可结实、药效成分含量高的桑树桑黄菌株是可能的。桑黄优良品种选育是今后的工作重点。本研究为桑黄真菌资源开发利用提供了参考。     

不同CO2浓度升高水平对粳稻叶片荧光特性的影响

为研究不同CO₂浓度升高水平对水稻叶片荧光特性的影响,利用开顶式气室组成CO₂浓度自动调控平台开展田间试验,使用便携式植物效率分析仪测定剑叶快速叶绿素荧光诱导动力学曲线,分析不同CO₂浓度(CK:背景大气CO₂浓度;T₁:比CK的CO₂浓度高80 μmol·mol^-1;T₂:比CK的CO₂浓度高200 μmol·mol^-1)下水稻主要生育期剑叶快速叶绿素荧光诱导动力学参数的变化特征.结果表明:CO₂浓度升高80 μmol·mol^-1,用于电子传递的量子产额(φ_Eo)、最大光化学效率(F_v/F_m)、性能指数(PI_ABS)在扬花期、乳熟期、蜡熟期和完熟期均显著升高,用于热耗散的量子比率(φ_Do)显著降低,其中φ_Eo显著升高了7.3%～23.3%,F_v/F_m极显著升高了3.1%～7.1%,PI_ABS极显著升高了46.2%～93.0%,φ_Do则显著降低了10.3%～20.5%.CO₂浓度升高200 μmol·mol^-1,在拔节期,φ_Eo、F_v/F_m、PI_ABS分别极显著降低了68.7%、41.4%和93.4%,φ_Do则极显著升高了78.4%;在扬花期、乳熟期、蜡熟期,T₂使φ_Eo显著升高了11.6%～19.8%,F_v/F_m显著升高了4.8%～6.8%,PI_ABS显著升高了53.0%～72.6%,φ_Do则显著降低了7.7%～19.4%.表明CO₂浓度升高(80、200 μmol·mol^-1)对水稻剑叶光系统Ⅱ的光合电子传递具有促进作用.     

Effects of Surfactant Protein-A on the Interaction of Pneumocystis murina with its Host at Different Stages of the Infection in Mice

ABSTRACT. We examined the effects of surfactant protein A (SP-A), a collectin, on the interaction of Pneumocystis murina with its host at the beginning, early to middle, and late stages of infection. Pneumocystis murina from SP-A wild-type (WT) mice inoculated intractracheally into WT mice (WT_S-WT_R) adhered well to alveolar macrophages, whereas organisms from SP-A knockout (KO) mice inoculated into KO mice (KO_S-KO_R) did not. Substitution of WT mice as the source of organisms (WT_S-KO_R) or recipient host macrophages (KO_S-WT_R) restored adherence to that found with WT_S-WT_R mice. In contrast, when immunosuppressed KO and WT mice were inoculated with P. murina from a homologous source (KO_S-KO_R, WT_S-WT_R) or heterologous source (WT_S-KO_R, KO_S-WT_R) and followed sequentially, WT_S-KO_R mice had the highest levels of infection at weeks 3 and 4; these mice also had the highest levels of the chemokine macrophage inflammatory protein-2 and neutrophils in lavage fluid at week 3. Surfactant protein-A administered to immunosuppressed KO_S-KO_R mice with Pneumocystis pneumonia for 8 wk as a therapeutic agent failed to lower the organism burden. We conclude that SP-A can correct the host immune defect in the beginning of P. murina infection, but not in the middle or late stages of the infection.     

Inhibitory effect of sodium bicarbonate on the motility of sperm of Japanese eel

Sperm motility of Japanese eel Anguilla japonica was depressed from 59.1 to 1.1% when NaHCO₃ concentration increased from 0 to 150 mM. In 25 mM NaHCO₃, when pH of the medium was 6.2, 7.2, 8.2, 9.2 and 10.2, relative sperm motility was 0, 0, 55.8, 93.7 and 136.6%, respectively to that of the control (0 mM NaHCO₃). The remarkable effect in acid or neutral condition indicates that free-CO₂ (liberated CO₂ and H₂CO₃) is a key factor for the motility inhibiting effect of NaHCO₃.     

内生真菌对羽茅抗病性的影响

为探讨不同种类内生真菌对宿主植物羽茅(Achnatherum sibiricum)抗病性的影响, 以感染不同内生真菌的天然禾草羽茅为实验材料, 进行了体外纯培养的内生真菌、感染内生真菌的离体叶片和在体叶片对3种植物病原真菌的抑菌实验。结果表明: 体外纯培养条件下, 分离自羽茅的内生真菌Neotyphodium sibiricum、Neotyphodium gansuensis和Epichloë gansuensis对新月弯孢霉(Curvularia lunata)、根腐离蠕孢(Bipolaris sorokiniana)和枝孢霉(Cladosporium sp.)等3种病原真菌都具有抑制作用, 其中N. sibiricum的抑制作用最强, 对新月弯孢霉、根腐离蠕孢和枝孢霉的抑菌率分别为47.8%、40.1%、39.4%; 内生真菌培养滤液也可以有效抑制这3种病原真菌的孢子萌发, 其中N. gansuensis的抑制作用最强, 新月弯孢、根腐离蠕孢和枝孢霉的孢子萌发率分别为9.8%、8.7%、8.5%。对于离体叶片, N. sibiricum和N. gansuensis感染可以有效降低叶片受3种病原真菌侵染后的病斑数和孢子浓度, 其中N. sibiricum对根腐离蠕孢的抑制作用显著高于N. gansuensis, 而E. gansuensis只降低新月弯孢和枝孢霉侵染的病斑数以及枝孢霉侵染的孢子浓度。在体条件下, 内生真菌均可以显著降低病原真菌侵染羽茅后的病斑数、病斑长度和孢子浓度, 其中E. gansuensis的抑菌作用趋于最弱, 而N. sibiricum的抑菌作用趋于最强。     

根虫瘟霉和相关种的分类地位研究及其ITS核苷酸序列分析

根虫瘟霉是最常见的一种虫霉,寄主广泛,世界广布。目前有学者认为该种是个复合种。本研究对世界不同地区和不同寄主的根虫瘟霉及其近缘类群总计19个菌株,进行3个靶位点（ITS、LSU rDNA、RPB2）的分子系统发育学分析。结果显示,根虫瘟霉ITS长度较为保守性,介于1 321-1 324bp之间,而所研究的虫霉亚门的其他类群的长度范围较大,为556-1 654bp。本研究确认根虫瘟霉是单系种,同时西虫瘟霉、矛孢虫瘟霉和英吉利虫瘟霉具有明确种的分类地位。鬼笔状虫瘟霉种应该被视为西虫瘟霉的异名。