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1.
Relationship between a 47-kDa cytoplasmic membrane polypeptide and nitrate transport in Anacystis nidulans 总被引:2,自引:0,他引:2
M N Sivak C Lara J M Romero R Rodríguez M G Guerrero 《Biochemical and biophysical research communications》1989,158(1):257-262
The polypeptide composition of cytoplasmic membranes of the cyanobacterium Anacystis nidulans changes in response to variations in the nitrogen source available to the cells, differing specifically in the amount of a polypeptide of 47-kDa molecular mass. Synthesis of the polypeptide and expression of nitrate transport activity are repressed by ammonium. Transfer of ammonium-grown cells to a medium containing nitrate as the sole nitrogen source results in parallel development of the 47-kDa polypeptide and nitrate transport activity of the cells. These results suggest the involvement of the 47-kDa cytoplasmic membrane polypeptide in nitrate transport by A. nidulans. 相似文献
2.
Summary The properties of agglutination by plant lectins, along with chromosome patterns, were examined in a variety of mammalian
cell types. Untransformed adult and embryonic cells in culture, direct mouse spleen cell preparations, SV40-transformed 3T3
cells, and trypsinized 3T3 cells were all highly agglutinable with concanavalin A and with wheat germ agglutinin. In contrast,
untreated cells of the contact-inhibited 3T3 line were alone among the cells tested in their low agglutinability. Chromosome
analysis of the cultured cells showed that karyotypic variation from the diploid to an aneuploid state in mouse and rat embryo
cultures was not accompanied by a change in agglutinability. Adult rat lung, adult monkey kidney, and embryonic human lung
cells, which were all highly agglutinable, showed the normal diploid pattern. Thus, agglutination of cells by plant lectins
appears to be a cellular property often associated with non-neo-plastic cells.
This investigation was supported by Grants CA-12503 and ES-00260 from the National Institutes of Health, United States Public
Health Service. 相似文献
3.
Purification and characterization of two transcribed repetitive DNA fractions from the pigeon genome
Two fractions of the repeats belonging to intermediate frequency repetitive DNA were isolated from the total pigeon nuclear DNA fragmented to about 450 nucleotides. One fraction was designated as rare repeats (repetition frequency about 35 per haploid genome) and another termed as moderate repeats (repetition frequency about 2500 per haploid genome). The rare repeats, which constitute about 7% of the total DNA, include at least 75% of the repetitive DNA sequences transcribed into the high molecular fraction (>45S) of HnRNA in erythroid cells. These repeats have properties compatible with the characteristics of the class of low frequency interspersed DNA found in genomes of many other Metazoan species. The moderate repeats contribute only about 10–20% of the total repetitive DNA copies present in >45S HnRNA and differ from the rare repeats in some other properties. — The possible role of the rare repeats in the genome is discussed. 相似文献
4.
J. G. Sivak 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1982,146(3):345-349
Summary The winter flounder,Pseudopleuronectes americanus, is mildly hyperopic. However, chromatic aberration exists in significant amounts and therefore the eye may be emmetropic (zero refractive error) in natural conditions when light is restricted to shorter wavelengths. Large accommodative lens motion was observed along the direction of the pupil axis. This direction is rare among the teleosts and is the result of the unusual split origin of the retractor lentis muscle. While the lens is spherical, as in other teleosts, the retina is not uniformly distant from the lens. Rather, a vertical asymmetry exists such that dorsal and ventral portions of the retina are further from the lens than the central retina. In view of the existing large accommodative ability, this distortion of the globe is not likely to have an optical function but is probably due to the shape of the cartilagenous scleral cup supporting the eye in its extraorbital location. Further, the lens is overcorrected for spherical aberration so that rays passing through the periphery of the lens are focused further away. The value of a lens of this type is unclear. 相似文献
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J. G. Sivak W. R. Bobier B. Levy 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1978,125(4):335-339
Summary Previous authors have suggested that in certain aquatic birds a transparent nictitating membrane of high refractive index could compensate for the refractive loss of the cornea in water. Measurements of refractive indices, refractive state and curvature carried out on a number of aquatic birds indicate that the nictitating membrane does not have a refractive function; the refractive indices of the cornea and nictitating membrane are very similar (approximately 1.37), the nictitating membrane does not alter the refractive state of the eye, and its curvature, when it is in place in front of the globe, is virtually the same as that of the cornea.This research was supported by grants from the National Research Council of Canada and the Canadian National Sportsmen's Fund. The assistance of Mote Marine Laboratory, The Mount Desert Island Biological Laboratory, the Niska Wildlife Foundation and the Felicadades Wildlife Foundation is gratefully acknowledged. The herring gulls and black guillemots were provided by Dr. W.B. Kinter. In addition, the authors are grateful for the assistance provided by Drs. J.L. Lincer and D. Peakall and Mr. R. Orleib. 相似文献
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Richard B Sherley Robert JM Crawford Bruce M Dyer Jessica Kemper Azwianewi B Makhado Makhudu Masotla 《Ostrich》2019,90(4):335-346
The Cape Gannet Morus capensis is one of several seabird species endemic to the Benguela upwelling ecosystem (BUS) but whose population has recently decreased, leading to an unfavourable IUCN Red List assessment. Application of ‘JARA’ (‘Just Another Red-List Assessment,’ a Bayesian state-space tool used for IUCN Red List assessments) to updated information on the areas occupied by Cape Gannets and the nest densities of breeding birds at their six colonies, suggested that the species should be classified as Vulnerable. However, the rate of decrease of Cape Gannets in their most-recent generation exceeded that of the previous generation, primarily as a result of large decreases at Bird Island, Lambert’s Bay, and Malgas Island, off South Africa’s west coast (the western part of their range). Since the 1960s, there has been an ongoing redistribution of the species from northwest to southeast around southern Africa, and ~70% of the population now occurs on the south coast of South Africa, at Bird Island in Algoa Bay, on the eastern border of the BUS. Recruitment rather than adult survival may be limiting the present population; however, information on the seabird’s demographic parameters and mortality in fisheries is lacking for colonies in the northern part of the BUS. Presently, major threats to Cape Gannet include: substantially decreased availability of their preferred prey in the west; heavy mortalities of eggs, chicks and fledglings at and around colonies, inflicted by Cape Fur Seals Arctocephalus pusillus and other seabirds; substantial disturbance at colonies caused by Cape Fur Seals attacking adult gannets ashore; oiling; and disease. 相似文献
10.
The signal produced by fluorescence in situ hybridization (FISH) often is inconsistent among cells and sensitivity is low. Small DNA targets on the chromatin are difficult to detect. We report here an improved nick translation procedure for Texas red and Alexa Fluor 488 direct labeling of FISH probes. Brighter probes can be obtained by adding excess DNA polymerase I. Using such probes, a 30 kb yeast transgene, and the rp1, rp3 and zein multigene clusters were clearly detected. 相似文献