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排序方式: 共有316条查询结果,搜索用时 31 毫秒
1.
2.
D Mourelatos C Petrou L Boutis A Papageorgiou P Catsoulacos J Dozi-Vassiliades 《Mutation research》1987,190(3):205-210
The effect of modified steroids, containing alkylating agents, on SCE rates and on cell kinetics in cultured human lymphocytes was studied. The homo-aza-steroidal ester of p-bis(2-chloroethyl)aminophenylacetic acid (ASE) was found to be the most effective in causing markedly increased SCE rates and cell division delays. The androsterone ester of p-bis(2-chloroethyl)aminophenylacetic acid (AE-CAPA) was found to be next in order of effectiveness with the lactone ester (LE-CAPA), chlorambucil ester 3 beta-hydroxy-13a-amino-13,17-seco-5a-androstan-17-oic-13,17-lactam (CBC-HAAL) and chlorambucil (CBC) following. p-Bis(2-chloroethyl)aminophenylacetic acid (CAPA) had only a small effect and 3 beta-hydroxy-13a-amino-13,17-seco-5a-androstan-17-oic-13,17-lactam (HAAL) had no effect at all. A correlation between potency for SCE induction, effectiveness in cell division delay and previously established antitumor activity of these drugs was observed. 相似文献
3.
Structural relatedness of lysis proteins from colicinogenic plasmids and icosahedral coliphages 总被引:4,自引:0,他引:4
The host-lysis-inducing functions of phi X174 protein E and MS2 protein L
were recently shown to reside on the N-terminal and C-terminal halves of
the two respective lysis proteins. In the present study it is shown that
the small lysis proteins encoded in various colicinogenic plasmids share
local sequence similarities and certain structural characteristics with the
essential peptides of their coliphage-coded counterparts. Despite their
dissimilar sizes and origins, it is suggested that the colicinogenic lysis
proteins are functionally analogous and evolutionarily related to those of
icosahedral single- stranded DNA and RNA phages.
相似文献
4.
Cecilia PC Soh Alastair SR Donald James Feeney Walter TJ Morgan Winifred M Watkins 《Glycoconjugate journal》1989,6(3):319-332
The tetrasaccharides GalNAcß1-4[NeuAc2-3]Galß1-4Glc and GalNAcß1-4[NeuAc2-3]Galß1-4GlcNAc were synthesised by enzymic transfer of GalNAc from UDP-GalNAc to 3-sialyllactose (NeuAc2-3Galß1-4Glc) and 3-sialyl-N-acetyllactosamine (NeuAc2-3Galß1-4GlcNAc). The structures of the products were established by methylation and1H-500 MHz NMR spectroscopy. In Sda serological tests the product formed with 3-sialyl-N-acetyllactosamine was highly active whereas that formed with 3-sialyllactose had only weak activity. 相似文献
5.
Davis G. M.; Coates A. L.; Papageorgiou A.; Bureau M. A. 《Journal of applied physiology》1988,65(3):1093-1098
The measurement of pulmonary mechanics has been developed extensively for adults, and these techniques have been applied directly to neonates and infants. However, the compliant chest wall of the infant frequently predisposes to chest wall distortion, especially when there is a low dynamic lung compliance (CL,dyn). We describe a technique of directly measuring the static chest wall compliance (Cw,st), developed initially in the newborn lamb and subsequently applied to the premature neonate with chest wall distortion. The mean CL,dyn in seven intubated newborn lambs in normoxia was 2.45 +/- 0.41 ml.cmH2O-1.kg-1, whereas Cw,st was 11.81 +/- 0.25 ml.cmH2O-1.kg-1. These values did not change significantly in seven animals breathing through a tight-fitting face mask or with hypercapnia-induced tachypnea. For the eight premature infants the mean CL,dyn was 1.35 +/- 0.36 ml.cmH2O-1.kg-1, whereas the mean Cw,st was 3.16 +/- 1.01 ml.cmH2O-1.kg-1. This study shows that, under relaxed conditions when measurements of static compliance are performed, the chest wall is more compliant than the lung. The measurement of Cw,st may thus be used to determine the contribution of the respiratory musculature in stabilizing the chest wall. 相似文献
6.
Light-Induced Changes in the Fluorescence Yield of Chlorophyll a In Vivo: II. Chlorella pyrenoidosa 总被引:2,自引:0,他引:2 下载免费PDF全文
The long-term fluorescence induction in Chlorella pyrenoidosa consists of a fast rise of the fluorescence yield from the level S (of the first wave transient) to a maximum M, followed by slower decay to a terminal stationary level T. The maximum M is attained within 40 seconds from the onset of illumination while the decay to the terminal level T lasts for several minutes. The fluorescence rise (S → M) coincides with an increase in the rate of oxygen evolution, which, however, remains constant during the fluorescence decay (M → T). Poisons of photosynthesis 3, (3,4-dichlorophenyl)-1,1 dimethylurea (DCMU, o-phenathroline) inhibit the fluorescence induction, while uncouplers of photophosphorylation affect the fluorescence time course only when they function at an early stage of the coupling sequence e.g., carbonyl cyanide p-trifluoremethoxy phenylhydrazone, (FCCP, atabrin). Phosphorylation inhibitors affecting only the terminal esterification step (phlorizin) have little effect on the fluorescence kinetics. These results suggest that the fluorescence induction requires the operation of a phosphorylating electron transport and that it is possibly related to the light-induced structural changes which accompany photophosphorylation. 相似文献
7.
Phillip A Patten Russell J Howard Willem PC Stemmer 《Current opinion in biotechnology》1997,8(6):724-733
DNA shuffling is a practical process for directed molecular evolution which uses recombination to dramatically accelerate the rate at which one can evolve genes. Single and multigene traits that require many mutations for improved phenotypes can be evolved rapidly. DNA shuffling technology has been significantly enhanced in the past year, extending its range of applications to small molecule pharmaceuticals, pharmaceutical proteins, gene therapy vehicles and transgenes, vaccines and evolved viruses for vaccines, and laboratory animal models. 相似文献
8.
Papageorgiou S 《Biophysical chemistry》1980,11(2):191-198
In a model for pattern regulation, use was made of local and global morphogens S and Sigma. Sigma is produced from the S-degradation and it is decomposed by first order kinetics while it diffuses along the field. We solve exactly the partial differential equation for the distribution of Sigma in one spatial dimension when its source S is monotonie (for simplicity, linear or generally a power function). Assuming that S and Sigma react reversibly with an allosteric protein P according to a sequential scheme, we derive the evolution in time of the field separation into compartments. At equilibrium the relative extent of each compartment is constant (for variable field size) and so pattern regulation is achieved. 相似文献
9.
We propose a model in which pattern formation is controlled by several concentration gradients of “morphogens” and by allosteric proteins which bind them. In this model, each protein can bind up to two molecules of each morphogen and has an “active state” when one molecule of each morphogen is bound. The concentration of the active state of such a “morphogen binding protein” varies with position in a way that depends on the values given the binding constants. In a contour map of the active state concentration, the contours can have a variety of simple shapes.Simply-shaped regions of cell differentiation can be defined directly by concentration contours of a morphogen binding protein using a threshold-sensing mechanism. More complex shapes may be generated using several proteins and a “winner-take-all” rule according to which each protein specifies some particular sort of cell differentiation and the differentiation of cells in any position is governed by the protein with the highest active state concentration.We present an application of our model to the vertebrate limb skeleton; we use the “winner-take-all” mechanism and thirteen morphogen binding proteins, eleven of which specify cartilage formation. In this model we use one morphogen binding protein to specify the shaft of a typical long bone and one for each epiphysis. Our model is reasonably successful in imitating the in vivo positions and orientations of developing bones and in generating simple, plausible-looking articular surfaces.In addition to the morphogen-binding model we propose a mechanism which could transform morphogen-binding patterns into high-amplitude patterns capable of controlling the activity of structural genes. This “amplifying mechanism” can account for two previously unexplained features of limb skeletal development: the early formation of the diffusely-bounded “scleroblastema” in the limb bud and the center-to-edge gradations in cartilage formation rate which are later seen within individual chondrification foci.A simple modification of the morphogen-binding model provides an explanation for the general anatomical phenomenon of metamerism: The model can account for the formation of inexactly repeating patterns (such as the pattern of the vertebral column) and suggests a mechanism by which such patterns could (1) evolve from exactly repeating patterns, and (2) acquire, in further evolution, a high degree of specialization of the individual repeating units.The most promising approach for testing the morphogen-binding model would appear to involve experiments in which cytoplasm is transferred between cells at various stages of pattern development. Support for the model could also come from the discovery of certain kinds of hereditary limb defects. 相似文献
10.
George C. Papageorgiou 《Biotechnology letters》1983,5(12):819-824
Summary Isolated higher plant chloroplasts with intact envelope membranes and bovine serum albumin were co-immobilized by treating the mixture with glutaraldehyde and then subjecting it to a freeze-thaw cycle. The immobilized chloroplasts are capable of photoinduced electron transport to lipophilic oxidants, but become compatible also with ionic oxidants after a transient hyposmotic shock.Abbreviations ASC
ascorbate
- Chl
chlorophyll
- DCIP
2,6-dichlorophenol indophenol
- DCMU
3-(3,4-dichlorophenyl)-1,1-dimethyl urea
- FeCN
K3 Fe(CN)6
- MV
methyl viologen
- PDox
FeCN-oxidized p-phenylene diamine 相似文献