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1.
Thiobacillus thiooxidans DSM 504 was shown to grow with adenine, hypoxanthine, xanthine and uric acid as sole sources of nitrogen. Growth with these compounds was observed after lag periods of varying lengths, unless the cells had been previously grown with the same purine base. The disappearance of adenine was accompanied by a temporary accumulation of hypoxanthine in the medium. The utilization of purines was inhibited by ammonia (1 mM). Guanine, pyrimidines and some other organic compounds were not utilized.Non-standard abbreviation U-14C
uniformly labeled by 14C 相似文献
2.
Plasmodium falciparum: assessment of in vitro growth by [3H]hypoxanthine incorporation 总被引:6,自引:0,他引:6
To evaluate rapidly Plasmodium falciparum growth in Vitro, [3H]hypoxanthine was added to parasite microcultures and radioisotope incorporation was measured. When culture parameters were carefully controlled, [3H]hypoxanthine incorporation was proportional to the number of parasitized erythrocytes present. Factors affecting [3H]hypoxanthine incorporation included initial parasitemia, duration of culture, duration of radioisotope pulse, parasite stage, concentration of uninfected erythrocytes, the use of serum or plasma to supplement growth, and the concentration of a variety of purines in the culture medium. The method described can be used to measure inhibition of P. falciparum growth by immune serum and has previously been used to study antimalarial drug activity in vitro. 相似文献
3.
B. Edwin Blaisdell 《Journal of molecular evolution》1983,19(2):122-133
Summary Coding sequences of eucaryotic nuclear DNA were characterized by an excess of short runs and a deficit of long runs of weak
and of strong hydrogen bonding bases; non-coding sequences by a deficit of short runs and an excess of long runs, in the same
of purines and of pyrimidines. The conservation of these attributes across DNA sequences coding for proteins of widely different
function, across widely different eucaryotic species for the same protein and across related genes that diverged a long time
ago and that now show large differences in base and, if coding, amino acid sequence suggested that these attributes have survival
value. It was concluded that these attributes constitute probalistic constraints on th primary structure (base sequence) of
both coding and non-coding DNA. 相似文献
4.
R. Pérez-Vicente M. I. Burón J. A. González-Reyes J. Cárdenas M. Pineda 《Protoplasma》1995,186(1-2):93-98
Summary Utilization of xanthine as the sole nitrogen source for growth byChlamydomonas reinhardtii cells involved the formation of a transient, intracellular pool of xanthine. Up to 20% of the total xanthine supplied to the medium was not assimilated after uptake but stored in the cells at concentrations that exceeded xanthine solubility in water. At the subcellular level, a massive accumulation of starch grains in the chloroplast and the appearance of many vacuoles in the cytoplasm distinguished xanthine-grown from ammonium-grown cells. Starch accumulation, but not development of vacuoles, was also observed in N-starved cells. Uptake experiments with radio-labelled xanthine showed that this accumulates only in the cytoplasm, most probably inside vacuoles. The electron-dense material observed in vacuoles of xanthine-grown cells suggests that the intracellular xanthine is in part solid xanthine. 相似文献
5.
Heng T. Duong Zhan-Guo Gao Kenneth A. Jacobson 《Nucleosides, nucleotides & nucleic acids》2013,32(10-12):1507-1517
Residues of the second extracellular loop are believed to be important for ligand recognition in adenosine receptors. Molecular modeling studies have suggested that one such residue, Gln 167 of the human A 3 receptor, is in proximity to the C2 moiety of some adenosine analogs when bound. Here this putative interaction was systematically explored using a neoceptor strategy, i.e., by site-directed mutagenesis and examination of the affinities of nucleosides modified to have complementary functionality. Gln 167 was mutated to Ala, Glu, and Arg, while the 2-position of several adenosine analogs was substituted with amine or carboxylic acid groups. All compounds tested lost affinity to the mutant receptors in comparison to the wild type. However, comparing affinities among the mutant receptors, several compounds bearing charge at the 2-position demonstrated preferential affinity for the mutant receptor bearing a residue of complementary charge. 13, with a positively-charged C2 moiety, displayed an 8.5-fold increase in affinity at the Q167E mutant receptor versus the Q167R mutant receptor. Preferential affinity for specific mutant receptors was also observed for 8 and 12. The data suggests that a direct contact is made between the C2 substituent of some charged ligands and the mutant receptor bearing the opposite charge at position 167. 相似文献
6.
ABSTRACTIn June, 2015, the Purine and Pyrimidine Society organized the 16th biennial symposium on Purine and Pyrimidine metabolism at the Faculty House of Columbia University, New York City. This exciting meeting focused on these important molecules, new developments in inborn errors of metabolism; therapeutic analogs. In addition, the biochemistry of mammalian and non-mammalian systems were discussed. Due to significant advances in molecular medicine, the boundaries between clinical and basic sciences have merged into exciting translational research, of which a small portion was highlighted in the presymposium. 相似文献
7.
Ticks are ectoparasites of vertebrates and utilize a variety ofinfochemicals for host finding and acceptance as well as for intraspecificaggregation and mating responses. Individual male and female Ixodesricinus, the vector of Lyme disease in Europe, readily arrest onfilter paper strips contaminated with their own faeces. I.ricinus also responds, but to a lesser degree, tofaeces-contaminatedpapers enclosed in metal mesh envelopes, i.e. without directly contacting thefaeces, suggesting a role for volatiles in the arrestment response. The faecalconstituents guanine, xanthine, uric acid and 8-azaguanine (a bacterialbreakdown product of guanine) also caused arrestment of individual I.ricinus males and females. However, mixtures of these productsinduced arrestment of I. ricinus at doses one hundred foldlower than the lowest active dose of any of them tested singly. Saline extractsof faeces activated receptor cells in terminal pore sensilla on the first legtarsi of I. ricinus. One cell in these sensilla respondedin a similar dose dependent manner to guanine and 8-azaguanine, whereas asecondcell was more sensitive to lower doses of 8-azaguanine. The response thresholdapproached 100 fM for both cells. These findings suggest thatfaeces and faecal breakdown products are implicated in aggregation responses ofI. ricinus. This may account for the clumped distributionof this ectoparasite on the ground and contribute to the high proportion ofmated individuals recorded prior to host colonization. 相似文献
8.
In order to elucidate the mechanisms of purinergic transmission of calcium (Ca2 + ) waves between microglial cells, we have employed micro-photolithographic methods to form discrete patterns of microglia
that allow quantitative measurements of Ca2 + wave propagation. Microglia were confined to lanes 20–100 wide and Ca2 + waves propagated from a point of mechanical stimulation, with a diminution in amplitude, for about 120 . The number of cells participating in propagation also decreased over this distance. Ca2 + waves could propagate across a cell-free lane from one microglia lane to another if this distance of separation was less
than about 60 , indicating that propagation involved diffusion of a chemical transmitter. This transmitter was identified as ATP since all
Ca2 + wave propagation was blocked by the purinoceptor antagonist suramin, which blocks P2Y2 and P2Y12 at relatively low concentrations. Antibodies to P2Y12 showed these at very high density compared with P2Y2, indicating a role for P2Y12 receptors. These observations were quantitatively accounted for by a model in which the main determinants are the diffusion
of ATP released from a stimulated microglial cell and differences in the dissociation constant of the purinoceptors on the
microglial cells. 相似文献
9.
《Bioorganic & medicinal chemistry letters》2014,24(15):3302-3306
2-Arylethynyl-(N)-methanocarba adenosine 5′-methyluronamides containing rigid N6-(trans-2-phenylcyclopropyl) and 2-phenylethynyl groups were synthesized as agonists for probing structural features of the A3 adenosine receptor (AR). Radioligand binding confirmed A3AR selectivity and N6-1S,2R stereoselectivity for one diastereomeric pair. The environment of receptor-bound, conformationally constrained N6 groups was explored by docking to an A3AR homology model, indicating specific hydrophobic interactions with the second extracellular loop able to modulate the affinity profile. 2-Pyridylethynyl derivative 18 was administered orally in mice to reduce chronic neuropathic pain in the chronic constriction injury model. 相似文献
10.
Leandro S. Silva Gustavo C. Prado Paula G. Quintana Norton Heise Kildare R. Miranda Eduardo J.L. Torres Pedro M. Persechini Ana Acacia de Sá Pinheiro Julieta Schachter 《Microbes and infection / Institut Pasteur》2018,20(3):205-211
Purine nucleotide synthesis in protozoa takes place exclusively via the purine salvage pathway and S-adenosyl-l-homocysteine hydrolase (SAHH) is an important enzyme in the Plasmodium salvage pathway which is not present in erythrocytes. Here, we describe the antimalarial effect of 2′3′-dialdehyde adenosine or oxidized adenosine (oADO), inhibitor of SAHH, on in vitro infection of human erythrocytes by P. falciparum. Treatment of infected erythrocytes with oADO inhibits parasite development and reinvasion of new cells. Erythrocytes pre-treated with oADO have a reduced susceptibility to invasion. Our results suggest that oADO interferes with one or more parasitic enzymes of the purine salvage pathway. 相似文献