不同条件下乳铁蛋白对铁溶解度的影响

文章通过不同条件下乳铁蛋白对铁溶解度影响的测定,结果表明,随着加热温度升高和时间延长,乳铁蛋白对铁吸收逐渐降低,加热温度在75℃以下时,对铁溶解度影响不明显,加热温度75℃以上时,铁溶解度明显下降;当溶液pH11或pH3时都会影响乳铁蛋白对铁结合能力,随时间延长,铁溶解度逐渐降低,中性条件下有利于铁结合。试验表明,在中性条件下,巴氏杀菌对乳铁蛋白吸收铁影响最小。     

Altered dihydrofolate reductase associated with drug-resistance transfer between rodent plasmodia

Resistance to pyrimethamine in strains of Plasmodium vinckei and of Plasmodium berghei is attributed to changes in amounts and properties of the dihydrofolate reductases. The resistant strain of Plasmodium berghei was isolated from an experimentally induced mixed infection of drug-resistant Plasmodium vinckei and drug-sensitive Plasmodium berghei, through biological filtration in hamsters. The drug resistance in Plasmodium berghei appears to have been acquired through transfer of part of the gene or genes coding for dihydrofolate reductase from the resistant Plasmodium vinckei to the sensitive Plasmodium berghei.     

Inhibition of protein synthesis: a mechanism for the production of impaired iron absorption

Treatment of rats with cycloheximide results in a defect in intestinal iron transport. A similar defect occurs after the parenteral administration of iron. Under both conditions there is impaired uptake of iron into the mucosal cells as well as defective transfer from the intestinal mucosa. It is suggested that the interference in iron transport may be due to a deficiency of an unidenti-fild carrier Substance.     

高剂量铜、锌、铁日粮对断奶仔猪生产性能及血红蛋白的影响

铜、锌、铁微量元素与畜禽体内许多代谢活动密切相关。高铜能引起猪条件性缺锌、缺铁以及贫血和生长停滞 ,而补锌、铁既能弥补不足又能提高铜的促生长效应 ,提高猪的生长能力。试验对不同水平铜、锌、铁仔猪全价日粮的生产性能及血红蛋白的水平进行了研究 ,旨在探讨断奶仔猪日粮中铜、锌、铁的适宜添加量。1　材料与方法1.1　仔猪的选择与分组试验于 2 0 0 1年 9月 2 2日在信阳市政府农场富民猪场进行。选择母猪胎次、窝产仔数、仔猪个体重相近 ,产仔时间集中在 5日内的 4窝 4 0头仔猪 ,随机分为Ａ、Ｂ、Ｃ、Ｄ、Ｅ 5组 ,每组 8头 ,其中Ｅ组…     

磷酸根和碳酸氢根浓度对樟树幼苗铁吸收的影响

砂培条件下对不同磷酸根和碳酸氢根浓度对樟树幼苗吸收铁的影响进行了研究.由樟树幼苗地上部和根部的鲜重、干重、含水量和含铁量及鲜基和干基的根冠比分析可知,樟树幼苗最适宜生长的磷酸根浓度为0.1 mmol/L,适宜磷酸根浓度为0.1～1.0 mmol/L;当磷酸根浓度大于1.0 mmol/L,对樟树幼苗生长产生一定程度的抑制作用;当浓度达到10 mmol/L,这种抑制作用已相当明显.当碳酸氢根浓度为10 mmol/L,对樟树幼苗生长基本不受影响;当碳酸氢根浓度为20 mmol/L,可产生一定程度的抑制作用;当浓度达到30 mmol/L,这种抑制作用已相当明显.     

不同铁肥及其施用方法对水稻籽粒镉吸收的影响

针对四川省稻田生态系统中镉(Cd)污染突出的问题,以轻度Cd超标稻田治理为目标,开展阻控稻米积累Cd的施肥技术研究。通过大田试验采用裂区设计,研究不同铁肥种类及施用方法对水稻籽粒Cd吸收的影响。结果表明,不同铁肥处理均增加了四个不同类型水稻品种的产量,其中硫酸亚铁追肥喷施显著增加了Y两优的产量(6.67%,P0.05),EDDHA-Fe底肥土施及追肥喷施显著增加了德粳1号的产量(13.33%～14.32%,P0.05)。不同铁肥施用方式中,EDDHA-Fe喷施处理对四个水稻品种的稻米Cd含量降低幅度最大(20.87%,P0.05)。不同时期喷施铁肥结果来看,以孕穗期、扬花期和灌浆期各喷施一次EDDHA-Fe处理的稻米Cd含量最低。四个水稻品种的秸秆Fe含量与稻米Cd含量呈直线性负相关。扬花期喷施铁肥稻米中Fe含量增加最多,稻米/秸秆Fe含量比值远高于稻米/秸秆Cd含量比值,这表明水稻中Fe由植株向稻米转移的速率远高于Cd。水稻稻米Fe含量与稻米Cd含量呈二元函数关系(P0.05),在较低含量时,水稻籽粒中Cd的含量随着Fe含量的上升而上升,当到达一定程度时,水稻籽粒中Cd的含量随着Fe含量的上升而下降。研究表明,水稻籽粒中的Cd受秸秆中Cd和铁肥施用方式和类型的影响,通过合理施用铁肥可以降低镉轻度污染土壤中稻米Cd含量。     

Effects of long-term application of different green manures on ferric iron reduction in a red paddy soil in Southern China

Dissimiiatory Fe(Ⅲ) reduction is an important process in the geochemicai cycle of iron in anoxic environment.As the main products of dissimiiatory iron reduction,the Fe(Ⅱ) species accumulation could indicate the reduction ability.The effects of different green manures on Fe(Ⅲ) reduction in paddy soil were explored based on a 31-year rice-rice-winter green manure cropping experiment.Four treatments were involved,i.e.,rice-rice-milk vetch(RRV),rice-rice-rape(RRP),rice-rice-ryegrass(RRG) and rice-rice-winter fallow(RRF).Soils were sampled at flowering stage of milk vetch and rape(S1),before transplantation(S2),at tillering(S3),jointing(S4),and mature(S5) stages of the early rice,and after the harvest of the late rice(S6).The contents of TFe_(HCI)(HCI-extractable total Fe),Fe(Ⅱ)_(HCI)(HCI-extractable Fe(ll) species) and Fe(Ⅲ)_(HCI)(HCIextractable Fe(Ⅲ) species) were measured.The correlations among those Fe species with selected soil environmental factors and the dynamic characteristics of Fe(Ⅱ)_(HCI) accumulation were investigated.The results showed that TFe_(HCI) in RRF was significantly higher than those in the green manure treatments at most of the sampling stages.Fe(Ⅱ)_(HCI) increased rapidly after the incorporation of green manures in all treatments and kept rising with the growth of early rice.Fe(Ⅱ)_(HCI) in RRG was quite different from those in other treatments,i.e.,it reached the highest at the S2 stage,then increased slowly and became the lowest one atthe S4 and S5 stages.Fe(Ⅲ)_(HCI) showed oppositely,and Fe(Ⅱ)_(HCI)/Fe(Ⅲ)_(HCI) performed similarly to Fe(Ⅱ)_(HCI).The maximum accumulation potential of Fe(Ⅱ)_(HCI) was significantly higher in RRF,while the highest maximum reaction rate of Fe(Ⅱ)_(HCI) accumulation appeared in RRG.Significant correlations were found between the indexes of Fe(Ⅱ)_(HCI)accumulation and soil pH,oxidation-reduction potential(Eh) and total organic acids,respectively.In together,we found that long-term application of green manures decreased the TFe_(HCI) in red paddy soils,but promoted the ability of Fe(Ⅲ)reduction,especially the ryegrass;Fe(Ⅱ)_(HCI) increased along with the growth of rice and was affected by soil conditions and environmental factors,especially the water and redox ability.     

An x-ray nebula associated with the millisecond pulsar B1957+20

We have detected an x-ray nebula around the binary millisecond pulsar B1957+20. A narrow tail, corresponding to the shocked pulsar wind, is seen interior to the known Halpha bow shock and proves the long-held assumption that the rotational energy of millisecond pulsars is dissipated through relativistic winds. Unresolved x-ray emission likely represents the shock where the winds of the pulsar and its companion collide. This emission indicates that the efficiency with which relativistic particles are accelerated in the postshock flow is similar to that for young pulsars, despite the shock proximity and much weaker surface magnetic field of this millisecond pulsar.     

An octahedral coordination complex of iron(VI)

The hexavalent state, considered to be the highest oxidation level accessible for iron, has previously been found only in the tetrahedral ferrate dianion, FeO4(2-). We report the photochemical synthesis of another Fe(VI) compound, an octahedrally coordinated dication bearing a terminal nitrido ligand. M?ssbauer and x-ray absorption spectra, supported by density functional theory, are consistent with the octahedral structure having an FeN triple bond of 1.57 angstroms and a singlet d2(xy) ground electronic configuration. The compound is stable at 77 kelvin and yields a high-spin Fe(III) species upon warming.     

周龄,饲粮锌水平和锌背景对肉鸡锌吸收利用的影响

进行３个试验观察半纯合饲粮锌水平、锌背景及周龄和锌的鸡锌吸收利用的影响。采用氨基酸利用率测定方法测定鸡排污物中锌浓度、锌的吸收和锌的真利用率。试验结果表明，排泄物中锌浓度随着饲粮锌水平的提高而呈线性增加，ｙ＝６１．７３＋７．６２ｘ（４＝０．９８）。锌的真利用率随饲粮锌水平的提高而显著降低，表明多食入的锌水平的提高而增加。     

Autoradiography with tritiated methotrexate and the cellular distribution of folate reductase

Bound methotrexate has been revealed by an autoradiographic procedure, presumed to introduce a method for cytochemical study of folate reductase. Preferential localization is seen in kidney proximal tubules, intestinal epithelium, and nuclei of parenchymal liver cells in mice. The extremely firm binding and prolonged retention of this drug should render it suitable as an inert label for the autoradiographic study of cell migrations and lifetimes.     

亚铁胁迫影响不同基因型水稻地上部养分吸收的研究

溶液培养试验表明：连续４周对水稻ＤＨ群体（Ａｚｕｃｅｎａ×ＩＲ６４）进行高铁胁迫，该群体在铁的抗性上出现高度分离，筛选出极抗铁毒基因型．铁毒极敏感基因型和中间型ｌｉｎｅｓ．养分测定表明：不同基因型水稻本身养分含量存在差异．高铁胁迫抑制了Ｃａ、Ｍｇ、Ｚｎ、Ｍｎ、Ｐ的吸收，促进了Ｃｕ的吸收．高铁胁迫破坏了养分吸收的一些相关关系     

不同油菜品种对土壤镉的吸收试验初探

通过对川油Ⅱ-10、花油5号、油研7号、史力丰、川中油18号等油菜品种对土壤镉的吸收进行盆栽试验,结果表明,不同品种油菜对土壤镉均有一定的吸收累积作用,川油Ⅱ-10的平均单株吸收镉量最高,达52.31μg;油菜吸收累积镉的主要部位是根系和茎,其中根系所吸收累积的镉所占比例最高,为整个油菜植株所吸收累积的镉总量的50%-70%,茎次之,所占比例为30%-40%;叶所吸收累积的镉所占比例很少,约为1%-2%。     

有机酸与根表铁膜对茶树吸收和富集氟的影响

采用溶液培养法,研究了Fe2+质量浓度、Fe2+诱导时间、pH值、外源有机酸(草酸、苹果酸、柠檬酸)对根表铁膜形成及茶树吸收、富集氟的影响。结果表明:茶树根表铁膜主要集中在离根尖0.2～0.5 cm区域;茶树根表铁膜含量随Fe2+诱导时间的延长呈现先升高后降低的趋势,随Fe2+质量浓度的增加显著升高,与溶液pH、有机酸浓度呈负相关。当铁膜含量为2.40～13.60 mg.g-1,根表铁膜含量与茶树吸收、富集氟的能力呈正相关。与根表无铁膜的茶树单加氟处理的对照(CK1)相比,加Fe2+诱导形成铁膜后,茶树体内氟的含量增加了42.3%～103.7%;有机酸与Fe2+共同作用时,茶树体内氟含量显著增加了101.7%～243.0%。     

土地利用多功能性研究进展与展望

目的分析土地利用多功能性空间差异及影响因素,更全面、深入地探究土地利用多功能驱动机制。方法综合评价法、空间自相关法和地理加权回归模型。结果(1)甘肃省土地利用多功能性水平空间特征显著,呈现空间集聚状态。土地利用总功能整体为西北高、东南低的空间格局,土地利用各功能总体为“点—片”结构特征。(2)全局自相关莫兰指数表明：除了经济功能,其余功能均表现为较大的空间正相关性。局部自相关莫兰指数和LISA图显示HH区和LL区整体为对称分布。(3)影响因素具有显著的空间集聚性,自然、社会经济因素和土地利用总功能均呈正相关关系。自然因素分布与甘肃省复杂地貌形态密切相关,而社会经济因素分布与人类要素投入偏好密切相关。结论甘肃省土地利用多功能水平主要取决于社会经济要素投入数量分布,甘肃省各市州应充分识别不同要素对土地利用多功能性的作用强度,因地制宜地加大要素投入,从而有效率地提高土地利用多功能性。     

根系硝酸还原酶对小白菜硝酸盐吸收和代谢的影响

采用溶液培养方法,选取上海青、兔子腿矮脚黄、上海青×兔子腿矮脚黄F1代为材料,筛选出对根系硝酸还原酶(NRA)抑制效果最佳的硝酸还原酶抑制剂Na2WO4的浓度为0.8 mmol/L。研究结果表明,根系NRA受抑的情况下根系对NO3-吸收速率显著下降,而地上部的硝酸盐含量并无显著差异。同时,根系NRA受抑条件下,其根系可溶性糖浓度提高,而地上部可溶性糖浓度则相对降低。     

麦麸膳食纤维面包制作工艺研究

对麦麸纤维面包的制作工艺进行了研究，并对膳食纤维的添加量及其对面包质量的影响进行了探讨。随着膳食纤维添加量的增加，面包的外观和内在质量均有降低的趋势。膳食纤维加入量对面包的生产工艺条件有明显的影响。     

Fumarate reductase in the control of heme biosynthesis

A drug-induced stimulation of heme biosynthesis in mouse liver was accompanied by altered fumarate metabolism. In liver homogenate, fumarate 1,4-C(14) was incorporated, via succinate and succinyl coenzyme A, into heme at an accelerated rate. This pathway of fumarate utilization was inhibited by acetoacetate but not by beta-hydroxybutyrate. Fumarate reduction to succinate required reduced nicotinamide adenine dinucleotide. The enzyme fumarate reductase is suggested as a link between terminal oxidation and cellular control of the heme biosynthetic pathway.     

黑白两种糯米米糠可溶性膳食纤维的特性及对淀粉体外消化吸收的影响

以黑糯米米糠和白糯米米糠2种米糠为原料,从中提取可溶性膳食纤维(soluble dietary fiber,SDF),比较两者的理化性质和生物活性,通过模拟葡萄糖体外消化和吸收试验,探讨SDF降低餐后血糖水平的作用机制。结果表明,黑糯米米糠和白糯米米糠的红外和紫外光谱特征显示两者均具有多糖的典型特征;黑糯米米糠SDF的酚含量、粘度、相对分子质量、聚集颗粒的组装、表面孔隙率和孔径、抗氧化性等均有利于其对葡萄糖的吸附和抑制葡萄糖的扩散,效果优于白糯米米糠SDF;而白糯米米糠SDF的溶解度、抑制淀粉的消化和α-淀粉酶活力的能力却大于黑糯米米糠SDF。上述结果说明,黑糯米米糠SDF具备更好的营养价值和生物活性。