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Journal of Ichthyology - Gonadal structure, cytological condition of oocytes, ultrastructure of egg envelope, and spermatozoa morphology are studied in the individuals of Inimicus sinensis... 相似文献
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Victor N. Mikheev Dmitry S. Pavlov Daria Pakulska 《Environmental Biology of Fishes》1992,35(4):351-360
Synopsis Swimming speed and swimming path of goldfish and tetra larvae were studied in aquaria containing food patches composed of decapsulated cysts and immobilized nauplii of Artemia salina or sparsely distributed prey. The mean swimming speed of starved larvae in the medium without food was about four times higher than the speed of larvae feeding in a patch. Satiated larvae swam about 1.5 times slower than hungry fish. Consumption of single prey items by starved larvae caused the following sequence of swimming responses: handling pause (cessation of swimming), slow swimming in a restricted area, and fast swimming (approximately twice as fast as hungry larvae before encountering food) accompanied by a widening of the area searched (area increased searching). Mean swimming speed was constant over a broad range (101–103 ind·1–1 of food density, although at extreme (high or low) values of food density it depended on swimming responses of the predator. Frequency of visits to the different parts of the aquarium strongly depended on encounters of hungry fish with food particles or patches. 相似文献
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Production of phosphomonoesterases by Nicotiana tabacum 1507 in an aqueous two-phase system 总被引:1,自引:0,他引:1
Ilieva MP Bakalova A Mihneva M Pavlov A Dolapchiev L 《Biotechnology and bioengineering》1996,51(4):488-493
Studies were conducted on Nicotiana tabacum 1507 cultivation in an aqueous two-phase system (PD(5)) formed by adding 4% PEG (MW 20,000) and 7.5% dextran (MW 70,000) to the medium. The time course of growth and changes in the phase volumes of the PD(5) system, as well as the biosynthesis, secretion, and partitioning of phosphomonoesterases during 11 days of cultivation, were followed. In comparison with N. tabacum 1507 cultivation as a free suspension, on day 8 of cultivation in the PD(5) system the yields of acid and alkaline extracellular phosphomonoesterases were 18 and 10 times higher, respectively. Partitioning took place mainly in the bottom phase with specific activity being 4.5 and 3.5 times higher, respectively. (c) 1996 John Wiley & Sons, Inc. 相似文献
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The fidelity of the human leading and lagging strand DNA replication apparatus with 8-oxodeoxyguanosine triphosphate. 下载免费PDF全文
A product of oxidative metabolism, 8-oxodeoxyguanosine triphosphate (8-O-dGTP), readily pairs with adenine during DNA replication, ultimately causing A.T-->C.G transversions. This study utilized 8-O-dGTP as a probe to examine the fidelity of the leading and lagging strand replication apparatus in extracts of HeLa cells. Simian virus (SV) 40 T antigen-dependent DNA replication reactions were performed with two M13mp2 vectors with the SV40 origin located on opposite sides of the lacZ alpha sequence used to score replication errors. The presence of 8-O-dGTP at equimolar concentration with each of the 4 normal dNTPs resulted in a > 46-fold increase in error rate for A.T-->C.G transversion over that observed in the absence of 8-O-dGTP. A similar average error rate was observed on the (+) and (-) strands in both vectors, suggesting that the fidelity of replication by leading and lagging strand replication proteins is similar for the dA.8-O-dGMP mispair. Replication fidelity in the presence of 8-O-dGTP was reduced on both strands when an inhibitor of exonucleolytic proofreading (dGMP) was added to the reaction. These data suggest that the majority of dA.8-O-dGMP mispairs are proofread by both leading and lagging strand replication proteins. 相似文献
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Georges M. Pavlov Evguenija V. Korneeva Natalia P. Yevlampieva 《International journal of biological macromolecules》1994,16(6):318-323
The hydrodynamic characteristics of the polysaccharide pullulan (polymaltotriose) in water have been investigated and its molecular characteristics have been determined. Experimental values varied over the following ranges: velocity sedimentation coefficient (S): 0.9 < S < 11.2, translational diffusion coefficient (107 cm2 s−1): 1.1 < D < 14.7 and intrinsic viscosity (cm3 g−1): 6.7 < [η] < 164, which corresponds to a change in molecular weight (× 103) in the range 3.9 < MSD < 644. On the basis of analysis of the literature and our experimental data, excluded volume effects have been shown to have a prevailing influence on the chain length of these polysaccharides. The equilibrium rigidity and hydrodynamic chain diameter of pullulan were evaluated on the basis of the theory of hydrodynamic properties of a wormlike necklace, taking into account excluded volume effects. At low M (< 30 × 103) the translation friction data (in contrast to viscometric data) cannot be described in the framework of the theory of linear molecules. 相似文献
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Fluctuation in levels of endogenous free IAA has been followed in the SD plant Chenopodium rubrum under photoperiodic conditions inductive or not inductive of flowering. Endogenous IAA was measured fluorimetrically as -pyrone. The level of IAA shows little fluctuation under continuous illumination. An endogenous rhythm of IAA fluctuation was found in plants transferred from light to continuous darkness, with a natural period of 30 hrs. The troughs of minimum IAA level within the endogenous rhythm coincided with the peaks in the endogenous rhythm of flowering response, which possessed the same period length. The concentration of IAA in the shoot always decreased at the end of cycles of dark period that induce flowering. The results are discussed in relation to the role of IAA in flowering of SD plants. 相似文献
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A method has been developed for selective fragmentation of T7 DNA at AT-rich regions. The molecules have been subjected to complete digestion with single-strand-specific SI endonuclease after fixation of DNA AT-rich regions in the denatured state by glyoxal. The treatment resulted in three fragments having molecular weights of 13.6 +/- 0.4, 8.2 +/- 0.4 and 3.5 +/- 0.16 megadaltons as determined by electron microscopy. The position of these fragments along the T7 DNA molecule has been determined by means of analysis of the intermediates during SI-cleavage. 相似文献