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51.
52.
Myriam Gazeau Florence Delort Philippe Dessen Sylvain Blanquet Pierre Plateau 《FEBS letters》1992,300(3):254-258
Using random Tn10 insertion mutagenesis, we isolated an Escherichia coli mutant strain affected in the regulation of lysU, the gene encoding the inducible form of lysyl-tRNA synthetase. The transposon giving rise to the altered expression of lysU was found inserted within lrp. The latter gene codes for the leucine-responsive regulatory protein (Lrp) which mediates a global response of the bacterium to leucine. An involvement of Lrp in the regulation of lysU was searched for by using a lysU-lacZ operon fusion. The following conclusions were reached: (i) inactivation of lrp causes an increased activity of the lysU promoter, whatever the growth conditions assayed, (ii) insertion of a wild-type lrp gene into a multi-copy plasmid significantly reduces lysU expression, and (iii) sensitivity of the lysU promoter to the presence of leucine in the growth medium is abolished in the lrp context. 相似文献
53.
Jose A.L. Arruda Harry Lubansky Sandra Sabatini George Dytko C.Tyler Burt 《Biochemical and biophysical research communications》1981,100(4):1459-1463
The urinary bladder of the fresh water turtle is capable of acidification and Na transport, in vitro, and it has been extensively used as a model of distal nephron of the kidney. In the course of measuring intracellular pH of stripped turtle bladder mucosa with phosphorus nuclear magnetic resonance, we observed the consistent presence of two inorganic phosphorus resonances under aerobic conditions, indicating the existence of a pH gradient possibly between cytosol and mitochondrion. This pH gradient was collapsed by addition of N2 and could be restored by reintroduction of oxygen. These observations demonstrate the existence of a spontaneous pH gradient between cytosol and mitochondria of turtle bladder epithelial cells. 相似文献
54.
Summary
Urastoma cyprinae (Graff) is a microturbellarian which has been recorded both as a free-living organism by Westblad (1955) and Marcus (1951) and as a commensal in various lamellibranch molluscs (see Burt & Drinnan 1968). The material used in this study came from oysters, Crassostroea virginica, collected off the coast of Prince Edward Island, in which hosts it occurs in large numbers especially during the summer months when the oysters are spawning (Fleming et al. 1981). When U. cyprinae is exposed to light as happens, for example, when an oyster is opened, it shows a marked negative phototactic response.Preliminary work on the fine structure of the photoreceptors in U. cyprinae shows that the two eyes each consists of: (1) a single cup cell full of relatively large, electron-dense pigment granules; (2) a tripartite conical lens system; and (3) what appear to be two photosensitive rhabdomes. The pigment cup cell has a single, well defined nucleus situated basally and close to the membrane of the pigment cell furthest away from the rhabdomeres. The lens system consists of a cone made up of three, separate but equal, parts. Each part has two, flat inner surfaces which join at an angle of 120°, an outer rounded surface, and a rounded upper surface. When these three parts fit together, the cone-shaped lens is formed with the apex of the lens within the cup of the pigment cell and the rounded, convex, broad end of the cone lying more or less at the same level as the top of the pigment cup and below the epidermis layer. The rhabdomeres lie between the electron dense lenses and the inside of the pigment cup. They show connections to the visual cells which are bipolar: one extension joining the rhabdomeres; the other constituting the axon which extends into the centrally situated brain or into the longitudinal, lateral nerves. The axons that enter the brain, form connections with other axons from the other eye. The axons that extend posteriorly in a lateral position, presumably play a role in facilitating the avoidance reaction.The chemical nature of the unusual lens has not yet been determined. This is presently under investigation and will be reported later at which time our work will be discussed in relation to other types of rhabdomeric eyes in the Turbellaria. 相似文献
55.
On some commensal Turbellaria of the Canadian East Coast 总被引:2,自引:1,他引:1
The brachyurans Chionoecetes opilio and Hyas araneus collected from the east coast of Canada harbour two species of commensal turbellarians. Ectocotyla hirudo (Levinsen) and E. multitesticulata Fleming & Burt are found on the gills and branchial chambers of male and female crabs. The molluscs Crassostrea virginica and Mytilus edulis collected from several locations where they are cultured along the Northumberland strait carry two commensal eulecithophoran turbellarians, both on the gills, viz., Urasloma cyprinae (Graff) and Paravortex gemellipara (Linton), the latter being a new host record. Aspects of the biology and life-history of these turbellarians are discussed, especially in relationship to the biology of their hosts.Abbreviations in the figures A
Atrium
- An
Antrum
- C
Capsule
- CO
Common Oviduct
- E
Embryo
- Ep
Egg-laying pore
- GP
Genital Pore
- I
Intestine
- O
Ovary
- Od
Oviduct
- Og
Ora-genital Pore
- Ph
Pharynx
- Sp
Sperm
- SV
Seminal Vesicle
- T
Testes
- Va
Vagina
- Y
Yolk 相似文献
56.
Harry J. Lubansky Akira Omachi C.Tyler Burt 《Biochemical and biophysical research communications》1980,97(3):1170-1175
The reciprocals of the spin-lattice relaxation times (T1s) of the 2-P and 3-P nuclei of 2,3-diphosphoglycerate (DPG) increased linearly as percent DPG bound was raised in model hemoglobin solutions. The 2-P T1 was slightly greater in intact erythrocytes than in model solutions under similar experimental conditions. The change in the 3-P T1 with cellular deoxygenation was anomalous indicating that this nucleus should not be used to estimate DPG binding inside intact erythrocytes. 相似文献
57.
Hugh D. Campbell David A. Dionysius Dianne T. Keough Bruce E. Wilson John de Jersey Burt Zerner 《Biochemical and biophysical research communications》1978,85(2):615-622
The iron-containing violet acid phosphatases from beef spleen and pig allantoic fluid have been purified to homogeneity. Molecular weight determinations by zonal gel filtration, SDS-gel electrophoresis, and ultracentrifugation support values close to 40,000 for both enzymes, necessitating reappraisal of literature values. Similarly, the equivalent weight for iron is close to 20,000 for both enzymes, indicating the presence of two iron atoms per molecule of enzyme. The enzymes also have very similar ultraviolet and visible spectra, with λmax values close to 550 nm, and ?550 values(in terms of iron) of 2.04 × 103 and 2.00 × 103 for the beef spleen and pig allantoic fluid enzymes respectively. 相似文献
58.
3H-Dopamine and 3H-haloperidol bind with high affinity and selectivity to synaptic dopamine receptors in membrane preparations of the calf caudate. Binding of both ligands shows marked regional variations with greatest density in caudate, putamen, globus pallidus, nucleus accumbens and olfactory tubercle, areas rich in dopamine nerve terminals. The rank-order of phenothiazines and related agents as well as catecholamines in displacing both dopamine and haloperidol binding closely parallels their pharmacological potencies and affinities for the dopamine-sensitive adenylate cyclase. Dopamine's affinity for specific 3H-dopamine binding sites is 100 times its apparent affinity for the dopamine sensitive adenylate cyclase. Agonists have about 50 times more affinity for dopamine than haloperidol sites, whereas antagonists display about 100 times greater affinity for haloperidol than dopamine sites. 相似文献
59.
60.
Florence S. Steinberg James J. Cereghino Chris C. Plato 《American journal of physical anthropology》1975,42(2):183-193
Digital and palmar dermatoglyphics of 184 male and 224 female normal American Negroes were evaluated for digital patterns, digital ridge counts, palmar patterns, palmar main line terminations, accessory triradii and palmar creases. All subjects were seven year olds examined and found free of chronic or other genetic diseases. The results were presented for the left and right hand for the most part comparable to those of the African and other American Negro groups reported earlier. The distributions of the various dermatoglyphic features among the Negroes taken as a group were compared to those of the other racial groups and their differences were discussed. 相似文献