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1.
Surface haemagglutinating activity of Pseudomonas aeruginosa 总被引:2,自引:0,他引:2
Intact cells of several strains of Pseudomonas aeruginosa agglutinate papain-treated human erythrocytes. The agglutinating activity appears to reside in the surface layers of the bacterium-Pseudomonas surface haemagglutinin. This activity does not correlate with the existence of the internal PA-I and PA-II lectins, the presence of fimbriae or adherence to human buccal epithelial cells. Disruption of the bacterial cells by sonication abolishes their haemagglutinating activity. The intact cells of P. aeruginosa are also able to agglutinate rabbit, chicken, dog, guinea pig and sheep erythrocytes. This activity is generally higher with papain-treated erythrocytes, except those of rabbit in which lower haemagglutinating activity is observed after papain treatment. Optimal conditions for the haemagglutination are 37 degrees C and pH 6-7. Simple sugars do not inhibit, while fetuin and hydrophobic amino acids inhibit this activity. Exposure of the bacterial cells to proteolytic enzymes, EDTA or denaturating conditions abolish the haemagglutinating activity. These results indicate that the surface haemagglutinin is a protein which agglutinates red blood cells via hydrophobic interactions. 相似文献
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Direct sequencing of the mitochondrial displacement loop (D-loop) of shrews
(genus Sorex) for the region between the tRNA(Pro) and the conserved
sequence block-F revealed variable numbers of 79-bp tandem repeats. These
repeats were found in all 19 individuals sequenced, representing three
subspecies and one closely related species of the masked shrew group (Sorex
cinereus cinereus, S. c. miscix, S. c. acadicus, and S. haydeni) and an
outgroup, the pygmy shrew (S. hoyi). Each specimen also possessed an
adjacent 76-bp imperfect copy of the tandem repeats. One individual was
heteroplasmic for length variants consisting of five and seven copies of
the 79-bp tandem repeat. The sequence of the repeats is conducive to the
formation of secondary structure. A termination-associated sequence is
present in each of the repeats and in a unique sequence region 5' to the
tandem array as well. Mean genetic distance between the masked shrew taxa
and the pygmy shrew was calculated separately for the unique sequence
region, one of the tandem repeats, the imperfect repeat, and these three
regions combined. The unique sequence region evolved more rapidly than the
tandem repeats or the imperfect repeat. The small genetic distance between
pairs of tandem repeats within an individual is consistent with a model of
concerted evolution. Repeats are apparently duplicated and lost at a high
rate, which tends to homogenize the tandem array. The rate of D- loop
sequence divergence between the masked and pygmy shrews is estimated to be
15%-20%/Myr, the highest rate observed in D-loops of mammals. Rapid
sequence evolution in shrews may be due either to their high metabolic rate
and short generation time or to the presence of variable numbers of tandem
repeats.
相似文献
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大鼠胼胝体内神经肽Y免疫反应阳性纤维的发育 总被引:1,自引:0,他引:1
本实验用免疫组织化学ABC法研究了大鼠胼胝体内神经肽Y免疫反应阳性(NPY-IR)纤维的生后发育。结果发现,许多NPY-IR纤维在大鼠出生时便存在于胼胝体内。NPY-IR胼胝体纤维的密度在生后1周内继续逐渐增高,在第2周内达到最高峰。之后,NPY-IR胼胝体纤维的密度逐渐下降,至第3周末时接近成年时的水平,即仅有少量NPY-IR纤维存在于胼胝体内。这些结果提示在大鼠早期生后发育过程中许多NPY-IR胼胝体纤维是暂时性的,其作用可能与大脑皮质的机能发育有关。 相似文献
6.
A spectrin-like protein from mouse brain membranes: phosphorylation of the 235,000-dalton subunit 总被引:2,自引:0,他引:2
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Margaret R. Clark John C. Guatelli Anthony T. White Stephen B. Shohet 《生物化学与生物物理学报:生物膜》1981,646(3):422-432
Using the antibiotic Nystatin, we have developed a systematic method for the preparation of red blood cells with independently selected levels of intracellular Na+ concentrations and water content. Such cells provided an experimental model to study the effect of Na+/K+ pump stimulation on red cell water content. Even in initially dehydrated cells, stimulation of the Na+/K+ pump by elevated intracellular Na+ caused subsequent further loss of cell water. Cell water loss was reflected in decreased monovalent cation content per unit mass of hemoglobin and by a shift in the density distribution of the cell populations to higher densities on discontinuous Stractan gradients. We conclude that the 3 Naout+ : 2 Kin+ stoichiometry of the Na+/K+ pump results in a net desalting effect with increased pump activity. Under the conditions of these experiments, the cell appears to have no effective mechanism to compensate for a net loss of ions and water. 相似文献
9.
The temperature and cell volume dependence of the NMR water proton line-width, spin-lattice, and spin-spin relaxation times have been studied for normal and sickle erythrocytes as well as hemoglobin A and hemoglobin S solutions. Upon deoxygenation, the spin-spin relaxation time (T2) decreases by a factor of 2 for sickle cells and hemoglobin S solutions but remains relatively constant for normal cells and hemoglobin A solutions. The spin-lattice relaxation time (T1) shows no significant change upon deoxygenation for normal or sickle packed red cells. Studies of the change in the NMR linewidth, T1 and T2 as the cell hydration is changed indicate that these parameters are affected only slightly by a 10-20% cell dehydration. This result suggests that the reported 10% cell dehydration observed with sickling is not important in the altered NMR properties. Low temperature studies of the linewidth and T1 for oxy and deoxy hemoglobin A and hemoglobin S solutions suggest that the "bound" water possesses similar properties for all four species. The low temperature linewidth ranges from about 250 Hz at -15 degrees C to 500 Hz at -36 degrees C and analysis of the NMR curves yield hydration values near 0.4 g water/g hemoglobin for all four species. The low temperature T1 data go through a minimum at -35 degrees C for measurements at 44.4 MHz and -50 degrees C for measurements at 17.1 MHz and are similar for oxy and deoxy hemoglobin A and hemoglobin S. These similarities in the low temperature NMR data for oxy and deoxy hemoglobin A and hemoglobin S suggest a hydrophobically driven sickling mechanism. The room temperature and low temperature relaxation time data for normal and sickle cells are interpreted in terms of a three-state model for intracellular water. In the context of this model the relaxation time data imply that type III, or irrotationally bound water, is altered during the sickling process. 相似文献
10.