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排序方式: 共有120条查询结果,搜索用时 15 毫秒
1.
Within the past year, it has become apparent, in connection with its use on automatic flow cytometers, that the quality of commercially available Alcian Blue has significantly declined. A homologous series of alkylated (C1-C7) Astra Blue quaternary ammonium halides was prepared, characterized, and evaluated for the detection of basophils in whole blood. On the Technicon H6000 flow cytometer, the resolution of the basophil cluster from the main population of unstained white blood cells was found to depend on the chain length of the quaternizing alkyl group. Optimal basophil resolution was observed for the n-propyl derivative. Correlation of the new method vs Alcian Blue as the reference on the H6000 was expressed as follows: %Baso (Astra Blue) = 0.89% Baso (Alcian Blue) + 0.12% for 180 fresh whole blood samples. Within-run precision at a basophil differential count of 0.73% was characterized by SD = 0.11, identical to that obtained for Alcian Blue. Aqueous solutions of n-propyl Astra Blue iodide, in contrast to Alcian Blue, are thermally stable. Heating the reagent for 1 h at 100 degrees C did not alter solubility or cytochemical behavior. In contrast, parallel treatment of Alcian Blue yielded insoluble material by hydrolysis of the isothiouronium groups. The reagent for basophil detection comprises n-propyl Astra Blue iodide, lanthanum chloride, sodium chloride, Tween 20, and cetylpyridinium chloride. The Astra Blue derivatives were characterized by uv-vis, ir, percentage halide, paper chromatography, and 13C NMR. 相似文献
2.
Donal A. Hickey Bernhard F. Benkel Poppo H. Boer Yves Genest Sumaia Abukashawa Gerard Ben-David 《Journal of molecular evolution》1987,26(3):252-256
Summary We constructed a cDNA library for the beetle,Tribolium castaneum. This library was screened using a cloned amylase gene fromDrosophila melanogaster as a molecular probe. Beetle amylase cDNA clones were isolated from this bank, and the nucleotide sequence was obtained for a cDNA clone with a coding capacity for 228 amino acids. Both the nucleotide sequence and predicted amino acid sequence were compared to our recent results forD. melanogaster alpha-amylases, along with published sequences for other alpha-amylases. The results show that animal alpha-amylases are highly conserved over their entire length. A borader comparison, which includes plant and microbial alpha-amylase sequences, indicates that parts of the gene are conserved between prokaryotes, plants, and animals. We discuss the potential importance of this and other enzyme-coding genes for the construction of molecular phylogenies and for the study of the general question of molecular clocks in evolution. 相似文献
3.
A mammalian protein kinase with potential for serine/threonine and tyrosine phosphorylation is related to cell cycle regulators. 总被引:25,自引:4,他引:21
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In a screen of mouse erythroleukemia cDNA expression libraries with anti-phosphotyrosine antibodies, designed to isolate tyrosine kinase coding sequences, we identified several cDNAs encoding proteins identical or very similar to known protein-tyrosine kinases. However, two frequently isolated cDNAs, clk and nek, encode proteins which are most closely related to protein kinases involved in regulating progression through the cell cycle, and contain motifs generally considered diagnostic of protein-serine/threonine kinases. The clk gene product contains a C-terminal cdc2-like kinase domain, most similar to the FUS3 catalytic domain. The Clk protein, expressed in bacteria, becomes efficiently phosphorylated in vitro on tyrosine as well as serine/threonine, and phosphorylates the exogenous substrate poly(glu, tyr) on tyrosine. Direct biochemical evidence indicates that both protein-tyrosine and protein-serine/threonine kinase activities are intrinsic to the Clk catalytic domain. These results suggest the existence of a novel class of protein kinases, with an unusual substrate specificity, which may be involved in cell cycle control. 相似文献
4.
A simplification of the enzymatic isotopic assay for serotonin is described, Serotonin is converted to [3H]melatonin by a two-step reaction: N-acetylation of serotonin using acetic anhydride, followed by O-methylation with the enzyme hydroxyindole O-methyltransferase (EC 2.1,1.4) and S-adenosyl-
-[methyl-3H]methionine as methyl donor. The present assay avoids the use of unstable acetylating enzyme, rat liver N-acetyltransferase (EC2.3,1.5). Blank values are lowered considerably and the sensitivity is doubly increased. Two-tenths micromole of serotonin per 30 μl of sample in tissue homogenates can be measured. 相似文献
5.
Annual and seasonal changes in diets of martens: evidence from stable isotope analysis 总被引:18,自引:0,他引:18
Theory predicts that generalist predators will switch to alternative prey when preferred foods are not readily available.
Studies on the feeding ecology of the American marten (Martes americana) throughout North America suggest that this mustelid is a generalist predator feeding largely on voles (Microtus sp.; Clethrionomys sp.). We investigated seasonal and annual changes in diets of martens in response to the changing abundance of small rodents
(Peromyscus keeni, and Microtus longicaudus) on Chichagof Island, Southeast Alaska, using stable isotope analysis. We hypothesized that martens would feed primarily
on small rodents during years with high abundance of these prey species, whereas during years of low abundance of prey, martens
would switch to feed primarily on the seasonally available carcasses of salmon. We also hypothesized that home-range location
on the landscape (i.e., access to salmon streams) would determine the type of food consumed by martens, and martens feeding
on preferred prey would exhibit better body condition than those feeding on other foods. We live-captured 75 martens repeatedly,
from mid-February to mid-December 1992–1994. We also obtained marten carcasses from trappers during late autumn 1991 and 1992,
from which we randomly sub-sampled 165 individuals. Using stable isotope ratios and a multiple-source mixing model, we inferred
that salmon carcasses composed a large portion of the diet of martens in autumn during years of low abundance of rodents (1991
and 1992). When small rodents were available in high numbers (1993 and 1994), they composed the bulk of the diet of martens
in autumn, despite salmon carcasses being equally available in all years. Selection for small rodents occurred only in seasons
in which abundance of small rodents was low. Logistic regression revealed that individuals with access to salmon streams were
more likely to incorporate salmon carcasses in their diet during years of low abundance of small rodents. Using stable isotope
analysis on repeated samples from the same individuals, we explored some of the factors underlying feeding habits of individuals
under variable ecological conditions. We were unable to demonstrate that body weights of live-captured male and female martens
differed significantly between individuals feeding on marine-derived or terrestrial diets. Therefore, martens, as true generalist
predators, switched to alternative prey when their principal food was not readily available on a seasonal or annual basis.
Although salmon carcasses were not a preferred food for martens, they provided a suitable alternative to maintain body condition
during years when small rodents were not readily available.
Received: 1 May 1996 / Accepted: 24 February 1997 相似文献
6.
7.
Itzhak Zander Ester Shmidov Shira Roth Yossi Ben-David Irit Shoval Sivan Shoshani Amos Danielli Ehud Banin 《Environmental microbiology》2020,22(12):5048-5057
Toxin–antitoxin (TA) systems are small genetic modules usually consisting of two elements—a toxin and an antitoxin. The abundance of TA systems among various bacterial strains may indicate an important evolutionary role. Pseudomonas aeruginosa, which can be found in a variety of niches in nature, is an opportunistic pathogen for various hosts. While P. aeruginosa strains are very versatile and diverse, only a few TA systems were characterized in this species. Here, we describe a newly characterized TA system in P. aeruginosa that is encoded within the filamentous Pf4 prophage. This system, named PfiT/PfiA, is a homologue of the ParE/YefM TA system. It is a type II TA system, in which the antitoxin is a protein that binds the toxic protein and eliminates the toxic effect. PfiT/PfiA carries several typical type II characteristics. Specifically, it constitutes two small genes expressed in a single operon, PfiT inhibits growth and PfiA eliminates this effect, PfiA binds PfiT, and PfiT expression results in elongated cells. Finally, we assigned a novel function to this TA system, where an imbalance between PfiT and PfiA, favouring the toxin, resulted in cell elongation and an increase in virion production. 相似文献
8.
Biomechanics and Modeling in Mechanobiology - We show that cell-applied, normal mechanical stresses are required for cells to penetrate into soft substrates, matching experimental observations in... 相似文献
9.
Granek Leeat Nakash Ora Ariad Samuel Shapira Shahar Ben-David Merav A. 《Culture, medicine and psychiatry》2020,44(2):214-229
Culture, Medicine, and Psychiatry - To explore the role of culture in communicating with cancer patients about mental health distress and suicidality. The Grounded Theory method of data collection... 相似文献
10.