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1.
A dimeric hemoglobin was purified from nitrogen-fixing root nodules formed by association of Rhizobium with a nonleguminous plant, Parasponia. The oxygen dissociation rate constant is probably sufficiently high to allow Parasponia hemoglobin to function in a fashion similar to that of leghemoglobin, by oxygen buffering and transport during symbiotic nitrogen fixation. The identification of hemoglobin in a nonlegume raises important questions about the evolution of plant hemoglobin genes. 相似文献
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Twenty micromolar hemin causes no change in the rate of division of K562 cells but results in accumulation of 11 to 14 picograms of embryonic and fetal hemoglobins per cell. This effect is reversible, and hemoglobin induction in response to hemin, and loss of hemoglobin upon removal of hemin, can be cyclically repeated. The cells can be indefinitely subcultured in the presence of the inducer. Thus, the control of hemoglobin levels in K562 cells does not depend on irreversible differentiation. 相似文献
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COLLINS RE 《Science (New York, N.Y.)》1961,133(3464):1593-1594
A mathematical theory is developed to explain the observed enhancement of oxygen transport through solutions by hemoglobin. At high partial pressures of oxygen, ordinary diffusion through the solvent accounts for all transport of oxygen, but at low partial pressures the transport may be increased many fold by the presence of hemoglobin. This phenomenon is explained and the possible role of this phenomenon in living organisms is discussed. The theory also indicates a new method of determining dissociation curves from diffusion experiments. 相似文献
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云南家禽十项生理常值的测定 总被引：6，自引：0，他引：6
我们进行了云南武定鸡、火鸡、云南鸭、番鸭(瘤头鸭)、云南鸽和鹌鹑等七种家禽的体温、心率、呼吸频率、红细胞沉降速度(血沉)、血红蛋白、红细胞计数、白细胞计数、嗜酸性白细胞计数、血小板计数、白细胞分类计数等十项生理常值的测定。结果表明:云南武定鸡的呼吸频率(28.84次/min)和血红蛋白(102.4g/L)比广东三黄鸡的(19.4次/min)和(74.09g/L)快(高):火鸡的血红蛋白(136.6g/L)比文献报道的值(88～134g/L)高;云南鹅的心率(109.47次/min)和白细胞分类计数中的假嗜酸性白细胞(异嗜性粒细胞)的比例(36.23%)比文献报道的值(300次/min)和(50%)低:云南鸭的心率(102.34次/min)呼吸频率(19.59次/min)和血红蛋白(110.3g/L)比文献报道的值(178次/min)、(42次/min)和(127g/L)低,云南鸽的呼吸频率(56.64次/min)比文献报道的值(30次/min)高,而白细胞数(38.9×109/L)比文献报道的值(13.0×109/L)高。 相似文献
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Injection of two 25-microgram-per-gram doses of the hemolytic agent phenylhydrazine reduced the hemoglobin level and the erythrocyte count to less than 1 percent of normal tadpole and young blullfrog blood. These anemic animals survive for weeks with little change in overall metabolism. A slow recovery of hemoglobin levels was observed. The implications of this observation for comparative biochemistry are considered. 相似文献
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Polymorphism of sickle cell hemoglobin aggregates: structural basis for limited radial growth 总被引：2，自引：0，他引：2
Fibers composed of molecules of deoxygenated sickle cell hemoglobin are the basic cause of pathology in sickle cell disease. The hemoglobin molecules in these fibers are arranged in double strands that twist around one another with a long axial repeat. These fibrous aggregates exhibit a pattern of polymorphism in which the ratio of their helical pitch to their radius is approximately constant. The observed ratio agrees with an estimate of its value calculated from the geometric properties of helical assemblies and the degree of distortion that a protein-protein interface can undergo. This agreement indicates that the radius of an aggregate is limited by the maximum possible stretching of double strands. The geometric properties limiting the radial extent of sickle hemoglobin fibers are fundamental to all cables of protein filaments and could contribute to the control of diameter in other biological fibers such as collagen or fibrin. 相似文献
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在饲料中添加0(对照组),0.025,0.050,0.100,0.200,0.400,0.800 mg/kg的维生素B12,研究不同含量维生素B12对草鱼幼鱼生长性能、饲料系数、机体营养组分、造血机能的影响,以确定草鱼幼鱼饲料中适宜维生素B12需要量。试验结果表明:维生素B12添加量为0.100 mg/kg时特定生长率和增重率最大,0.050 mg/kg时饲料系数最低,并与对照组有显著性差异(P<0.05);维生素B12的添加对试验鱼的存活率和肥满度无显著影响;血小板计数和血红蛋白含量分别在0.100 mg/kg和0.200 mg/kg时最高,并与对照组有显著性差异,维生素B12的添加对红细胞计数无显著影响;维生素B12对草鱼全鱼水分、粗蛋白、粗脂肪和粗灰分无显著影响。草鱼特定生长率与饲料中维生素B12添加量回归方程表明,草鱼幼鱼饲料中维生素B12适宜添加量为0.094 mg/kg。 相似文献
10.
Urea is maintained at moderately high concentrations in the blood and tissues of marine elasmobranchs. Functional properties of the hemoglobins fromn several elasmobranch species are unaffected by urea concentrations as high as 5 molar. This in. sensitivity to urea, which is not observed with human hemoglobin, is accompanied by an increased sensitivity to sodium chloride. 相似文献
11.
F Abdel-Hameed 《Science (New York, N.Y.)》1972,178(63):864-865
Of 19 adult intersex chickens examined, 17 were triploid animals with ZZW sex chromosomes. Triploid erythrocytes were about 1.5 times the size of diploid erythrocytes, and were present in amounts that were about two-thirds the number of diploid erythrocytes. Both diploid and triploid animals had similar hematocrits and hemoglobin concentrations. Triploidy is reflected in a relative increase in RNA, as well as in DNA, per erythrocyte. This, in addition to the trisomic mode of inheritance observed in several genetically distinct loci determining isoantigens, indicates that all three sets of chromosomes in the triploid animals are genetically active. Apparently, there is a homeostatic mechanism maintaining the concentration of hemoglobin for the species in spite of triploidy and its effect on erythrocyte size. 相似文献
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Hyperbaric nitrogen at a pressure of 100 atmospheres increases significantly the affinity of erythrocytic hemoglobin for oxygen. This results in oxygen dissociation curves which are shifted to lower than normal oxygen partial pressures. The pressure effect is completely reversible and can therefore be observed only during exposure of the blood cells to the hyperbaric gas. 相似文献
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Delay time of hemoglobin S polymerization prevents most cells from sickling in vivo 总被引：10，自引：0，他引：10
A laser photolysis technique has been developed to assess the quantitative significance of the delay time of hemoglobin S gelation to the pathophysiology of sickle cell disease. Changes in the saturation of hemoglobin S with carbon monoxide produced by varying the intensity of a photolytic laser beam were used to simulate changes in the saturation of oxyhemoglobin S produced by variations in oxygen pressure. The presence of polymer at steady-state saturation with carbon monoxide was determined by measurement of the kinetics of gelation after complete photodissociation. The kinetics are a very sensitive probe for polymer since small amounts of polymerized hemoglobin increase the rate of nucleation sufficiently to eliminate the delay period. First, the equilibrium gelation properties of partially photodissociated carbonmonoxyhemoglobin S were shown to be the same as partially oxygenated hemoglobin S, and the method was then used to determine the effect of saturation on the formation and disappearance of polymers in individual sickle cells. The saturation at which polymers first formed upon deoxygenation was much lower than the saturation at which polymers disappeared upon reoxygenation. The results indicate that at venous saturations with oxygen, gelation takes place in most cells at equilibrium, but is prevented from occurring in vivo because the delay times are sufficiently long that most cells return to the lungs and are reoxygenated before polymerization has begun. 相似文献
14.
Structure, dynamics, and reactivity in hemoglobin 总被引：10，自引：0，他引：10
J M Friedman 《Science (New York, N.Y.)》1985,228(4705):1273-1280
The static structure of hemoglobin and its functional properties are very well characterized. It is still not known how energy is stored and used within the structure of the protein to promote function and functional diversity. An essential part of this question is understanding the mechanism through which the overall protein structure (quaternary structure) couples to the local environment about the oxygen binding sites. Time-resolved resonance Raman spectroscopy has been used to probe the vibrational degrees of the freedom of the binding site as a function of protein structure. Comparison of the spectra from both equilibrium and transient forms of deoxy hemoglobin from a variety of mammalian, reptilian, and fish hemoglobins reveals that for each quaternary structure there exist two tertiary states stabilized by the presence or absence of an iron-bound ligand. Pulse-probe Raman experiments show that for photodissociated, ligated hemoglobins the local tertiary structure relaxes at a solution-dependent rate extending from tens of nanoseconds to microseconds. In this local environment, the linkage between the iron and the proximal histidine proves to be the single observed structural feature that responds in a systematic and substantial manner to structural changes in the protein. The additional finding of a correlation between the frequency of the iron-proximal histidine stretching motion (nu Fe-His) and various parameters of ligand reactivity, including geminate recombination, implicates the associated localized structural element in the mechanism of protein control of ligand binding. On the basis of these and related finds, a model is presented to account for both coarse and fine control of ligand binding by the protein structure. 相似文献
15.
Rate theories and puzzles of hemeprotein kinetics 总被引：11，自引：0，他引：11
The binding of dioxygen and carbon monoxide to heme proteins such as myoglobin and hemoglobin has been studied with flash photolysis. At temperatures below 200 K, binding occurs from within the heme pocket and, contrary to expectation, with nearly equal rates for both ligands. This observation has led to a reexamination of the theory of the association reaction taking into account friction, protein structure, and the nature of electronic transitions. The rate coefficients for the limiting cases of large and small friction are found with simple arguments that use characteristic lengths and times. The arguments indicate how transition state theory as well as calculations based on nonadiabatic perturbation theory, which is called the Golden Rule, may fail. For ligand-binding reactions the data suggest the existence of intermediate states not directly observed so far. The general considerations may also apply to other biomolecular processes such as electron transport. 相似文献
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[目的]研究红花苷对K562白血病细胞的抑制增殖和诱导分化作用。[方法]以培养的K562白血病细胞为试验对象,通过XTT试验、集落形成试验、血红蛋白联苯胺染色试验以及形态学试验,考察红花苷对白血病细胞抑制增殖和诱导分化作用。[结果]红花苷剂量依赖性地抑制了K562白血病细胞的活性及集落形成(P0.05),形态学观察及联苯胺染色试验也证实了红花苷剂量依赖性地诱导K562白血病细胞向产生血红蛋白的终末细胞分化。[结论]红花苷对K562白血病细胞具有明显的抑制增殖和诱导分化作用。 相似文献
17.
Erythrocytes: pits and vacuoles as seen with transmission and scanning electron microscopy 总被引：3，自引：0，他引：3
Vacuoles containing inclusions were observed by transmission electron microscopy in erythrocytes of a splenectomized patient with hemoglobin Ann Arbor. The membranes of these vacuoles became fused with the surface membrane of the red cell, thus opening the vacuoles and exposing their contents to the outside. These vacuoles when they have become thus attached to the cell membrane of the erythrocyte are responsible for the pits observed with scanning electron microscopy. 相似文献
18.
The glycosylation of hemoglobin: relevance to diabetes mellitus 总被引：34，自引：0，他引：34
Glucose reacts nonenzymatically with the NH2-terminal amino acid of the beta chain of human hemoglobin by way of a ketoamine linkage, resulting in the formation of hemoglobin AIc. Other minor components appear to be adducts of glucose 6-phosphate and fructose 1,6-diphosphate. These hemoglobins are formed slowly and continuously throughout the 120-day life-span of the red cell. There is a two- to threefold increase in hemoglobin AIc in the red cells of patients with diabetes mellitus. By providing an integrated measurement of blood glucose, hemoglobin AIc is useful in assessing the degree of diabetic control. Furthermore, this hemoglobin is a useful model of nonenzymatic glycosylation of other proteins that may be involved in the long-term complications of the disease. 相似文献
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Two genetic sources of variation influence the percentage of sickle cell hemoglobin found in heterozygotes. One factor is strongly related to the percentage of hemoglobin S in the carrier parent and appears to be determined by sickle hemoglobin isoalleles, whereas the other is related to racial background and may well be polygenic. 相似文献
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Activation of hemoglobin C synthesis in sheep marrow culture 总被引：6，自引：0，他引：6
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. 相似文献