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排序方式: 共有627条查询结果,搜索用时 625 毫秒
11.
ZHU JINGDE 《Cell research》1995,(1)
INTanDUCTI0NMyeloidcelldifferentiati0n,inwhichmultip0tentialprogenitorcellsarec0nvertedint00neofthesixmaturedifferentiatedcells,i.e.,erythr0cytes,platelets(megakary-ocytes),macr0phages,neutr0phils,e0sinophilsandbas0phils,involvestemporalre-gulati0nofexpression0fanumberoflineage-anddifferentiationstage-specificgenes.Understandingthedevel0pmentalspecificationoflineageaJswellasmaturationstageassociatedpatterns0fgeneexpressioninmyel0idcelldifferentiationrequiresanin-sightintothecontrol0findivid… 相似文献
12.
David W. Ow 《In vitro cellular & developmental biology. Plant》1993,29(4):213-219
Summary Plants and certain fungi respond to heavy metal toxicity with the induced synthesis of metal-binding peptides known as phytochelatins
(PCs). With cadmium, PCs can bind the metal to form a low molecular weight PC-Cd complex and a high molecular weight PC-Cd-S2− complex. The sulfide ions enhance the stability and Cd-binding capacity of the metal chelate, and formation of this sulfide-containing
complex is associated with enhanced tolerance to cadmium. Molecular analyses of two fission yeast mutants that fail to produce
a wild type level of the PC-Cd-S2− complex have determined that a vacuolar membrane transporter and several enzymes of the purine biosynthesis pathway are necessary
in vivo for formation of the PC- Cd-S2− complex. A model based on vacuolar sequestration of the PC-Cd complex by an ATP-binding cassette-type transporter and its
subsequent maturation into the stable PC-Cd-S2− complex via the actions of two purine biosynthetic enzymes is described.
Presented in the Session-in-Depth Bioremediation through Biotechnological Means at the 1993 Congress on Cell and Tissue Culture,
San Diego, CA, June 5–9, 1993. 相似文献
13.
Chlamydomonas reinhardtü Dangeard, adenine or guanine can be used as the sole nitrogen source for growth by means of an inducible system which is repressed by ammonia. Cells grown on either adenine or guanine were able to take up both purines, although the adenine uptake rate was always about 40% of the guanine uptake rate. Both adenine and guanine were taken up by an inducible system(s) exhibiting hyperbolic kinetics with identical apparent A, values of 3-2 mmol m?3 for adenine and 3-2mmol m?3 for guanine. Adenine and guanine utilization depended on pH, with similar optimal pH values of 7·3 and 7·4, respectively. Adenine and guanine each acted as a competitive inhibitor of the other's uptake, and their utilization was also inhibited by hypoxanthine, xanthine and urate. Inhibition of adenine uptake by guanine and hypoxanthine was competitive, with A′, values of 5·5 and 1. 6 mmol m?3 respectively. Guanine uptake was also inhibited competitively by adenine (K1= 1·3mmol m?3) and hypoxanthine (K1= 3. 3 mmol m?3). Utilization of both adenine and guanine was inhibited by cyanide, azide, 3-(3,4-dichlorophenyl)-1,1-dimethyl urea, 2,4-dinitrophenol and carbonylcyanide m-chlorophenylhydrazone, and was also sensitive to p-hydroxymercuribenzoate and N-ethyl-maleimide. On the basis of these results, taken together, the possibility that adenine and guanine are translocated into Chlamydomonas by a common system is discussed. 相似文献
14.
R. Vagnozzi G. Lazzarino B. Tavazzi D. Di Pierro P. Siragusa R. Giuffré B. Giardina 《Biological trace element research》1995,47(1-3):241-246
Short-term incomplete cerebral ischemia was induced in the rat by bilaterally clamping for 5 min the common carotid arteries;
subsequent reperfusion of 10 min was obtained by removing carotid occlusion. At the end of ischemia or reperfusion, animals
were sacrificed by decapitation. A control group was represented by sham-operated rats. Peripheral venous blood samples were
withdrawn from the femoral vein from rats subjected to cerebral reperfusion 5 min before ischemia, at the end of ischemia,
and 10 min after reperfusion. A highly sensitive HPLC method for the direct determination of malondialdehyde, oxypurines,
and nucleosides was used on 200 μL of brain tissue and plasma extracts. Incomplete cerebral ischemia induced the, appearance
of a significant amout of tissue malondialdehyde (undetectable in control animals) and a decrease of ascorbic acid. A further
6.6-fold increase of malondialdehyde and a 18.5% decrease of ascorbic acid occurred after 10 min of reperfusion. Plasma malondialdehyde,
which was present in minimal amount before ischemia, significantly increased after 5 min of ischemia, being strikingly augmented
after 10 min of reperfusion. A similar trend was observed for oxypurines and nucleosides. From these data, it can be affirmed
that tissue concentrations of malondialdehyde and ascorbic acid, and plasma levels of malondialdehyde, oxypurines, and nucleosides,
reflect both the oxygen radical-mediated tissue injury and the depression of energy metabolism thus representing early biochemical
markers of short-term incomplete brain ischemia, and reperfusion in the rat. 相似文献
15.
Frank W. Crow Kenneth B. Tomer Michael L. Gross James A. McCloskey Donald E. Bergstrom 《Analytical biochemistry》1984,139(1):243-262
The positive and negative ion fast atom bombardment (FAB) mass spectra and fast atom bombardment collisionally activated decomposition (CAD) spectra of a series of nucleosides and two dinucleotides are reported. The nucleosides studied are substituted forms of guanosine, adenosine, nebularine, tubercidin, uridine, and related pyrimidines. The FAB and CAD data both contain similar information. The CAD spectra are found to provide some structural information not found in the FAB mass spectra. Tandem mass spectrometry also allows emphasis to be put on weak fragments which are either not observed in the FAB mass spectrum or are lost in the matrix ion signals. 相似文献
16.
Summary We have studied the reactions between adenosine 5-phosphorimidazolide and 9-(2-amino-2-deoxyxylofuranosyl) adenine (I) or 3-methylamino-3-deoxyadenosine (II), both with and without a poly (U) template. We find that both amino compounds react much more rapidly than does adenosine, in the absence of a template. The rate of reaction is greatly enhanced by a poly (U) template in the case of I, but the enhancement is slight in the case of II.Abbreviations A
adenosine
- xylo ANH2
9-(2-amino-2-deoxy--D-xylofuranosyl) adenine
- ANHMe
3-methylamino-3-deoxyadenosine
- ImpA
adenosine 5-phosphorimidazolide
- A3 pA
adenylyl-[35]-adenosine
- A2 pA
adenylyl-[25]-adenosine
- UNPA
adenylyl-[52]-2-amino-2-deoxyuridine
- xylo ANPA
9-[adenylyl-(52)-2-amino-2-deoxy--D-xylofuranosyl]adenine
- A(NMe)pA
adenylyl-[53]-3-methylamino-3-deoxyadenosine
- pA
adenosine 5phosphate
- AppA
P1, P2-diadenosine 5pyrophosphate
- (pA)n
n = 2, 3 [2-5]-linked oligomers of pA
- A2 pA2 pA
[2-5]-linked trinucleoside diphosphate of A
- poly (U)
polyuridylic acid 相似文献
17.
Summary Vesicles of inner mitochondrial membrane, mitoplasts, from rat brown adipose tissue were prepared by osmotic swelling and studied using the patch-clamp technique. Current events of a 107.8±8.7 pS (n=16, 21°C) channel were recorded in the mitoplast-attached mode. This channel was selective for anions and its kinetics resembled those of channels previously found in liver and heart mitochondria of mouse and ox. In whole-mitoplast mode each of five purine nucleotides (20 m) blocked the channel. This is the first demonstration of pharmacological blockade of this type of channel. Although a similar anion channel in mouse and ox mitochondria was suggested to be the uncoupling protein (UCP) associated with nonshivering thermogenesis, we present several arguments against this possibility. Thus we describe a high-conductance, purine-nucleotide-binding, anion selective mitochondrial channel, that is not the UCP. 相似文献
18.
6-(2,3,4-trihydroxy-3-methylbutylamino) purine (trihydroxyzeatin) applied to soybean callus is metabolised slowly. After 48 h only one peak of biological activity which co-eluted with the applied cytokinin was detected. When the callus was incubated on a medium which contained 10–5 M trihydroxyzeatin, spiked with 8 {14C} trihydroxyzeatin, for 28 days, three peaks of biological activity and three peaks of radioactivity were detected. One of the biologically active and radioactive peaks co-eluted with zeatin. Another of the radioactive peaks co-eluted with N-(purin-6-yl) glycine. From the data obtained it apears that trihydroxyzeatin can be both oxidized and reduced by soybean callus. The potential to be converted to zeatin may explain why trihydroxyzeatin and its parent compound, which is usually rapidly metabolised by living material, are equally active in the soybean callus bioassay. From the radioactive data obtained it appears that trihydroxyzeatin is susceptible to oxidation to form N-(purin-6-yl) glycine. 相似文献
19.
Two new adenosine analogs, 2-(2-bromoethyl) adenosine monophosphate and 3-(2-bromoethyl) adenosine monophosphate, were synthesized, purified by semipreparative high-pressure liquid chromatography, and completely characterized. A new synthesis of 5-(2-bromoethyl) adenosine monophosphate is presented which facilitates the preparation of radioactive reagent with label either in the ethyl group or the purine ring of the nucleotide derivative. The reactive moiety of these derivatives, a bromoalkyl group, has the ability to react with the nucleophilic side chains of several amino acids. The second-order, pH-independent rate constants for reaction with the side chains of the amino acids cysteine, lysine, histidine, and tyrosine were determined as 3×10–4, 6×10–6, 3×10–7, and <1×10–7 M–1 sec–1, respectively. These data could be use in estimating the rate enhancement observed in modification of a protein by these affinity-labeling reagents. 5-(S-(2-hydroxyethyl)cysteine) adenosine monophosphate, the derivative expected from exhaustive digestion of protein in which a cysteinyl residue is modified by 5-(2-bromoethyl) adenosine monophosphate, and S-2-hydroxyethyl)cysteine, the derivative anticipated upon acid hydrolysis of such a modified protein, were synthesized, characterized, and their elution positions from an amino acid analyzer determined. These bromoethyl AMP derivatives are potential affinity labels for enzymes that bind 2-, 3-, or 5-nucleotides such as TPN, coenzyme A, or ADP, respectively. 相似文献
20.
Cloning and restriction map of the E. coli apt gene 总被引:2,自引:0,他引:2
The apt gene coding for Escherichia coli adenine phosphoribosyl transferase has been cloned in pBR322. The restriction map of a 1.6-kb fragment containing the apt gene is presented. 相似文献