Protein synthesis: its control in erythropoiesis

Erythropoiesis in the fetal mouse provides a model to study several important aspects of the regulation of cell differentiation and differentiated protein synthesis. Changes in the patterns of hemoglobins formed during fetal and postfetal development are shown to be associated with the substitution of the liver erythroid cell line. In the course of differentiation of yolk sac erythroid cells there are at least two classes of proteins distinguishable with respect to dependence on continued RNA formatoin. The bulk of nuclear proteins, "nondifferentiated" proteins, appear to be dependent on relatively short-lived messenger RNA while synthesis of differentiated proteins, the hemoglobins, proceeds on relatively stable molecules of messenger RNA. Hemoglobin formation occurs in those cells which are actively synthesizing DNA and dividing. On the average, two to three cell divisions may occur after the formation and stabilization of the messenger RNA for globin. Yolk sac erythropoiesis, at least from day 10 of gestation, is unresponsive to erythropoietin. By comparison, in fetal liver erythropoiesis, the hormone, erythropoietin, acts selectively on the most immature erythroid cell precursor to induce differentiation, cell replication, and hemoglobin formation. The erythropoietin responsive cell in the liver is apparently differentiated from the progenitor, pluripotential stem cell and committed to erythroblast formation and hemoglobin synthesis on exposure to the hormone. The initial effects of erythropoietin on macromolecular synthesis are to stimulate RNA synthesis, which temporally is followed by cell replication and the increase in hemoglobin formation. During liver erythropoiesis, there appears to be a transition from hemoglobin synthesis dependent on RNA formation to hemoglobin synthesis directed by relatively stable messenger RNA.     

"Pure" human hematopoietic progenitors: permissive action of basic fibroblast growth factor

Methodology has been developed that enables virtually complete purification and abundant recovery of early hematopoietic progenitors from normal human adult peripheral blood. A fraction of the pure progenitors is multipotent (generates mixed colonies) and exhibits self-renewal capacity (gives rise to blast cell colonies). This methodology provides a fundamental tool for basic and clinical studies on hematopoiesis. Optimal in vitro cloning of virtually pure progenitors requires not only the stimulatory effect of interleukin-3, granulocyte-macrophage colony-stimulating factor, and erythropoietin, but also the permissive action of basic fibroblast growth factor. These findings suggest a regulatory role for this growth factor in early hematopoiesis.     

Est1p as a cell cycle-regulated activator of telomere-bound telomerase

In Saccharomyces cerevisiae, the telomerase components Est2p, TLC1 RNA, Est1p, and Est3p are thought to form a complex that acts late during chromosome replication (S phase) upon recruitment by Cdc13p, a telomeric DNA binding protein. Consistent with this model, we show that Est1p, Est2p, and Cdc13p are telomere-associated at this time. However, Est2p, but not Est1p, also binds telomeres before late S phase. The cdc13-2 allele has been proposed to be defective in recruitment, yet Est1p and Est2p telomere association persists in cdc13-2 cells. These findings suggest a model in which Est1p binds telomeres late in S phase and interacts with Cdc13p to convert inactive, telomere-bound Est2p to an active form.     

Renal lysosomes: role in biogenesis of erythropoietin

The "light" mitochondrial pellet obtained from the kidneys of rats previously treated with Triton WR-1339 and rendered hypoxic was separated into subcellular component fractions by sucrose density gradient centrifugation in a zonal rotor. Selected fractions were pooled, disrupted by osmotic lysis and repeated freeze-thawing, and incubated in the presence and absence of normal rat serum. The incubation mixtures were assayed for erythropoiesis-stimulating activity (erythropoietin). High specific activity was identified only in fractions rich in lysosomes. Biochemical analysis of reference enzymes for the identification of lysosomes and mitochondria, supplemented by electron microscopic examination of the various separated fractions, supports the observed requirement for lysosomal constituents in the formation of erythropoietin by the kidney.     

Use of Low Radioactive Rare—earth Waste for Sewage Treatment

1　Introduction　　 Our country has about 80 percent rare- earth reserve of the world.Since 1 980 ,great success has beenmade in exploitation and utilization of rare- earth resource〔1-3〕.Because there are many kinds of rare- earthin our country and the components are complex,a large amount of hazardous“three- wastes”are producedin the process of mineral production.Waste residues are the most among“three- wastes” and contain ra-dioactive elements Th,U and Re.Safety disposal of rare- ear…     

Activation of hemoglobin C synthesis in sheep marrow culture

Erythropoietin preferentially stimulates hemoglobin C synthesis in suspension cultures of marrow cells from sheep homozygous for hemoglobin A; the amount of synthesis is dependent on the dose of erythropoietin and is blocked by antiserum to erythropoietin. The results provide the first in vitro evidence that erythropoietin mediates the hemoglobin A --> C "switch" in sheep and indicate that bone marrow cultures may be used to investigate the mechanisms involved in the preferential gene activation characteristic of the hemoglobin A --> C system.     

Erythropoietin retards DNA breakdown and prevents programmed death in erythroid progenitor cells

The mechanism by which erythropoietin controls mammalian erythrocyte production is unknown. Labeling experiments in vitro with [3H]thymidine demonstrated DNA cleavage in erythroid progenitor cells that was accompanied by DNA repair and synthesis. Erythropoietin reduced DNA cleavage by a factor of 2.6. In the absence of erythropoietin, erythroid progenitor cells accumulated DNA cleavage fragments characteristic of those found in programmed cell death (apoptosis) by 2 to 4 hours and began dying by 16 hours. In the presence of erythropoietin, the progenitor cells survived and differentiated into reticulocytes. Thus, apoptosis is a major component of normal erythropoiesis, and erythropoietin controls erythrocyte production by retarding DNA breakdown and preventing apoptosis in erythroid progenitor cells.     

Interferon production and action in mouse, hamster and somatic hybrid mouse-hamster cells

A hybrid mouse-hamster cell line was developed from a mouse cell line which produces a high titer of interferon and is sensitive to its action, and a hamster cell line which produces little interferon and is relatively insensitive to its action. Parental cell lines demonstrated complete species specificity with respect to interferon production and action. The hybrid cells produced interferon (or interferons) effective when tested on the mouse cell line and primary hamster cells; the hybrids were sensitive to the action of both mouse and hamster interferons. Hybrid cells produced ten times more hamster interferon than the parent hamster cell line and were eight times more sensitive to hamster interferon than the parent hamster cell line.     

Platforms for collective action in multiple-use common-pool resources

Collective action processes in complex, multiple-use common-pool resources (CPRs) have only recently become a focus of study. When CPRs evolve into more complex systems, resource use by separate user groups becomes increasingly interdependent. This implies, amongst others, that the institutional framework governing resource use has to be re-negotiated to avoid adverse impacts associated with the increased access of any new stakeholders, such as overexploitation, alienation of traditional users, and inter-user conflicts. The establishment of platforms for resource use negotiation is a way of dealing with complex natural resource management problems. Platforms arise when stakeholders perceive the same resource management problem, realize their interdependence in solving it, and come together to agree on action strategies for solving the problem (Röling, 1994). This article sets the scene for a discussion in this Special Issue about the potential of nested platforms for resource use negotiation in facilitating collective action in the management of complex, multiple-use CPRs. The article has five objectives. First, we define collective action in the context of this paper. Second, we discuss the importance of collective action in multiple-use CPRs. Third, we introduce the concept of platforms to coordinate collective action by multiple users. Fourth, we address some issues that emerge from evidence in the field regarding the role and potential of nested platforms for managing complex CPRs. Finally, we raise five discussion statements. These will form the basis for the collection of articles in this special issue.     

野菊花提取物抑菌活性

利用琼脂扩散法和琼脂平板稀释法分别测定野菊花提取物对供试菌的抑菌活性和最小抑菌浓度MIC(Minimal inhibitory concentration)。通过测定不同培养时间后培养液的OD560值。活菌数和电导率研究野菊花提取物对金黄色葡萄球菌的生长曲线的影响。结果表明,野菊花提取物原液对金黄色葡萄球菌、大肠杆菌和沙门氏菌的抑菌活性分别为(27.02±0.45)mm、(20.56±0.43)mm、(17.82±0.36)mm,MIC分别为原液浓度的12.5%(v/v)、25%(v/v)、50%(v/v)。与对照组相比,野菊花提取物作用于金黄色葡萄球菌后,菌体的生长繁殖受到影响,细胞渗透性改变,而且作用方式与麦迪霉素对金黄色葡萄球菌的作用方式存在差异。     

ERYTHROID HOMEOSTASIS IN NORMAL AND GENETICALLY ANEMIC MICE: REACTION TO INDUCED POLYCYTHEMIA

After hypertransfusion, normal ww and anemic WW(T) mice show the same increase in red-cell volume, decrease in reticulocytes, and temporary cessation of blood formation. The time required for the red cell volume to return to the value observed before treatment is the same for both groucps of inice. The cell volume at which new erythrocytes are again released into the circulation depends upon the genotype of functioning blood-forming tissue. Injections of erythropoietin stimulate red cell formation in polycythemic ww mice, but have much less (if any) effect upon polycythemic WW(T) mice.     

耕层柽柳根生长分布和管花肉苁蓉接种的WINRHIZO扫描观察

为了研究耕层土壤中柽柳根和管花肉苁蓉的相互作用,明确管花肉苁蓉的接种时间、生长和药用成分动态,采用WINRHIZO根系扫描系统,定期检测柽柳根系生长和肉苁蓉接种;采用HPLC和分光光度法测定松果菊苷、毛蕊花糖苷和可溶性糖含量。结果表明:柽柳茎段在扦插后15d生根,根的生长遵循"S"曲线规律;首次观察到管花肉苁蓉与柽柳根建立稳定寄生关系的时间为扦插后60d,管花肉苁蓉的接种率动态变化遵循"S"曲线规律;管花肉苁蓉单株干重在接种后90d内增长缓慢,90d后快速增长,至150d单株干重达16g;生长150d的管花肉苁蓉含松果菊苷9.6%,毛蕊花糖苷1.7%,苯乙醇苷总量11.3%,可溶性糖0.19%。WINRHIZO扫描分析为确定耕层土壤中寄生植物和寄主的接种动态及影响因素研究提供了新方法。     

MITOMYCIN C: CHEMICAL AND BIOLOGICAL STUDIES ON ALKYLATION

The presence of an aziridine ring in mitomycin C suggests that the mechanism of action of the antibiotic is like that of the antitumor alkylating agents. However the compound is unexpectedly stable during aerobic incubation with rat liver homogenates although rapidly metabolized anaerobically. Mitomycin is not reactive with gamma-(4-nitrobenzyl) pyridine and reacts only slowly at acid p(H) with thiosulfate. It is proposed that mitomycin is activated in vivo, possibly by a reduction which "unmasks" the potential activity of the fused aziridine ring.     

小麦幼胚体细胞无性系及其继代过程的微观结构观察

利用扫描电子显微镜,观察了由小麦“千斤早”和“小偃22”幼胚离体培养产生的体细胞胚性无性系继代过程中微观结构的变化,以及胚性无性系和非胚性无性系的结构差异。结果发现,小麦“千斤早”和“小偃22”的幼胚体细胞胚性无性系的微观结构存在较大差异,主要表现在体细胞之间的组织形式上,胚性无性系发生能力强的小麦具有较好的细胞组织形式,胚性无性系发生能力弱的小麦其体细胞组织形式也较差。随着继代次数的增加,体细胞胚性无性系在组织结构上趋于无序化,且这种无序化的进程也受到小麦基因型的影响:对于耐离体培养小麦,在经历多次继代后,组织的有序化程度仍然保持着较高的水平;对于胚性无性系产生频率低的小麦,不仅其早期培养过程中胚性细胞所占的比例较低,且组织间的有序性很快在有限的继代过程中趋于崩溃。     

维生素C对β-伴大豆球蛋白诱导的仔猪肠上皮细胞炎性损伤的保护作用

为分析不同浓度维生素C(vitamin C,V_C)对β-伴大豆球蛋白(7S)诱导的仔猪肠上皮细胞(IPEC-J2)炎性损伤的保护作用,取对数生长期的IPEC-J2用于试验,随机分为对照组、7S模型组(5 mg·mL^-1 7S)和V_C(25、50、100、200、400、600、800、1 000 μmol·L^-1)保护组。细胞培养24 h后采用CCK-8法检测细胞存活率,倒置显微镜观察细胞形态学变化,ELISA法检测细胞上清液中LDH、ALP、DAO、IFABP1含量和IL-1β、IL-6、TNF-α、IL-4、IL-10的分泌水平,用qRT-PCR法检测IL-1β、IL-6、TNF-α、IL-4和IL-10 mRNA相对表达量。结果显示:7S可显著(P<0.01)降低IPEC-J2活力、破坏细胞膜完整性,上调细胞促炎性因子和下调抗炎因子的产生;与7S模型组相比,同时添加7S和V_C的试验组细胞活力增加,细胞上清液中LDH、ALP、DAO、IFABP1含量显著(P<0.01)降低,促炎因子IL-1β、IL-6、TNF-α分泌水平降低,抗炎因子IL-4和IL-10的分泌水平升高。因此,不同浓度V_C均可保护由7S诱导引起的仔猪肠上皮细胞损伤,100 μmol·L^-1 V_C的修复和保护作用最佳。     

Estrogen-receptor interaction

The interaction of estradiol with uterine cells involves the association of the hormone with an extranuclear receptor protein, followed by temperature dependent translocation of the resulting complex to the nucleus. During this process, the steroid binding unit of the protein undergoes an alteration, called "receptor transformation," that can be recognized by an increase in its sedimentation rate from 3.8S to 5.2S, and by its acquisition of the ability to bind to isolated uterine nuclei and to alleviate a tissue specific deficiency in the RNA synthesizing capacity of such nuclei. Receptor transformation can be effected in the absence of nuclei by warming uterine cytosol with estradiol. This preparation of transformed complex resembles that extracted from nuclei both in its sedimentation rate (5.3S) and in its ability to bind to uterine nuclei and augment RNA synthesis, properties that are not shown by the native complex. It is proposed that receptor transformation is an important step in estrogen action and that a principal role of the hormone is to induce conversion of the receptor protein to a biochemically functional form.     

Antibacterial activity of acyclic decapeptide analogs of gramicidin S

Three acyclic decapeptide analogs of gramicidin S, although found to possess antibacterial activity, apparently have modes of action which differ from that of the naturally occurring cyclic antibiotic. In contrast to the immediate action of gramicidin S, one of the decapeptides produced complete bacteriostasis only after several cell divisions had occurred. Furthermore, mixtures of gramicidin S with either of two of the acyclic peptides were synergistic. Some implications of these findings are discussed.     

Chalcocite Oxidation and Coupled Carbon Dioxide Fixation by Thiobacillus ferrooxidans

The reaction of cell suspensions of Thiobacillus ferrooxidans with pulverized chalcocite (Cu(2)S) in a Warburg manometric apparatus resulted in oxygen uptake accompanied by increased solubilization of copper and fixation of carbon dioxide. Since the only detectable oxidized products were cupric ions and the more oxidized form of the sulfide mineral, that is, digenite or covellite, the apparent source of energy for the carbon dioxide fixation was provided by the oxidation of the cuprous copper of the chalcocite.     

苹果在不同货架条件下的生理及品质变化

试验测定了不同方式贮藏后的红星、金冠、国光苹果在不同货架条件下呼吸强度、果肉硬度、失水率等指标的变化，并对保持货架品质的简易方法进行了研究。结果表明，贮藏方式对果实呼吸代谢的抑制在货架期间仍有后效作用；果实出库时的品质是决定能否保持良好货架品质的关键；在20℃的货架条件下，采用2．5或5kg容量的塑料薄膜小包装，对保持红星、金冠、国光苹果的果肉硬度及防止失水有良好作用。     

高淀粉玉米籽粒胚乳细胞增殖与淀粉积累的关系

本试验以大田种植的高淀粉玉米品种郑单18、费玉3号和普通玉米品种郑单958、农大108为试材,研究高淀粉玉米籽粒在不同生育期胚乳细胞增殖动态及其与淀粉积累的关系。结果表明:随着灌浆期的延长,不同品种玉米粒重逐渐增加,淀粉含量呈"S"形曲线增长,玉米籽粒胚乳细胞数在授粉后20 d基本稳定,细胞增殖动态可用Richards方程W=A(1+Be-kt)-1/n模拟,决定系数达极显著水平。胚乳细胞数与玉米粒重、籽粒淀粉含量、淀粉积累量呈显著正相关。籽粒胚乳细胞平均增殖速率(Gmean)的大小、最大增殖速率出现的日期(TmaxG)和最大增殖速率(Gmax)的大小等因素共同决定了粒重的大小。