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1.
High level of divergence of male-reproductive-tract proteins, between Drosophila melanogaster and its sibling species, D. simulans 总被引:1,自引:0,他引:1
We compared male-reproductive-tract polypeptides of Drosophila melanogaster
and D. simulans by using two-dimensional gel electrophoresis. Approximately
64% of male-reproductive-tract polypeptides were identical between two
randomly chosen isofemale lines from these two species, compared with 83%
identity for third-instar imaginal wing-disc polypeptides. Qualitatively
similar differences were found between reproductive tracts and imaginal
discs when D. sechellia was compared with D. melanogaster and with D.
simulans. When genic polymorphism was taken into account, approximately 10%
of male- reproductive-tract polypeptides were apparently fixed for
different alleles between D. melanogaster and D. simulans; this proportion
is the same as that found for soluble enzymes by one-dimensional gel
electrophoresis. Strikingly, approximately 20% of male-reproductive- tract
polypeptides of either D. melanogaster or D. simulans had no detectable
homologue in the other species. We propose that proteins of the Drosophila
male reproductive tract may have diverged more extensively between species
than have other types of proteins and that much of this divergence may
involve large changes in levels of polypeptide expression.
相似文献
2.
Isolation and characterization of the tubular organelles induced by fumarate reductase overproduction in Escherichia coli 总被引:5,自引:0,他引:5
Strains of Escherichia coli amplifying the intrinsic membrane enzyme fumarate reductase accommodate the overproduced enzyme by increasing the amount of membrane material, in the form of intracellular tubular structures. These tubules have been observed in strains harbouring multicopy frd plasmids and in ampicillin hyper-resistant strains. A procedure has been developed for isolation of tubules nearly free of cytoplasmic membrane. Using protein A-gold labelling and optical diffraction of electron micrographs, a model for tubule structure is proposed. The tubules have a lower lipid/protein ratio than the cytoplasmic membrane, with the enzyme accounting for greater than 90% of the protein in the tubules. Both cytoplasmic membranes and tubules from amplified strains are enriched in cardiolipin and have a more fluid fatty acid composition than wild-type strains. Mutants defective in cardiolipin synthesis produce tubules in response to excess fumarate reductase, but these tubules have an altered appearance, indicating that lipid-protein interactions may be important for tubule assembly. 相似文献
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Summary Field experiments were carried out using15N-labelled calcium nitrate, to investigate the relative uptake by barley of fertilizer-N and soil-N. On imperfectly drained till soils uptake of soil-N increased with increasing rate of fertilizer, but remained constant on a brown sand, possibly due to more efficient root exploration in the latter soil. In four out of five seasons, late uptake of soil-derived N was a major feature, and uptake from ploughed soil as compared with uptake from direct-drilled soil was correlated with seasonal rainfall patterns. Significantly higher quantities of both fertilizer- and soil-derived N were taken up by winter barley than by spring barley, reflecting the longer growth period and higher dry matter yield from the former crop. 相似文献
5.
RS Fisher 《The Journal of general physiology》1977,69(5):571-604
When the outer surface of short-circuited frog skin was penetrated with microelectrodes, stable negative potentials that averaged near -100 mV were recorded consistently, confirming the results of Nagel (W. Nagel. 1975. Abstracts of the 5th International Biophysics Congress, Copenhagen. P-147.). The appearance of these stable potentials, V(O), concurrent with the observations that (a) a high resistance outer barrier R(O) accounting for approximately 75 percent or more of the transcellular resistance of control skins had been penetrated and that (b) 10(-5) M amiloride and reduced [Na] outside caused the values of V(O) to increase towards means value near -130 mV while the values of percent R(O) increased to more than 90 percent. It was of relationships were the same as the values of E(1) observed in studies of the current-voltage relationships were the same as the values of E’(1) defined as the values of voltage at the inner barrier when the V(O) of the outer barrier was reduced to zero by voltage clamping of the skins. Accordingly, these data are interpreted to mean that the values of E(1), approximately 130 mV, represent the E(Na) of the sodium pump at the inner barrier. 2,4-DNP was observed to decrease the values of transepithelial voltage less than E(1) the V(O) was negative. These data can be interpreted with a simple electrical equivalent circuit of the active sodium transport pathway of the frog skin that includes the idea that the outer membrane behaves as an electrical rectifier for ion transport. 相似文献
6.
The quantity and quality of overwintered larvae in five species of Myrmica (Hymenoptera: Formicidae)
The numbers of queens, workers and larvae were recorded for a sample of hibernating colonies from five different species of Myrmica. The larvae were divided into three size classes. The frequencies and distribution of larvae within these size classes have been compared between species and between queened and queenless colonies. A sample of each larval class was reared to the pupal stage and the resulting castes were recorded. The Discussion compares all the species with Myrmica rubra and attempts to explain the differences observed for the different species. 相似文献
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Sebastian M. Marcuccio Bryan C. Elmes George Holan E. John Middleton 《Nucleosides, nucleotides & nucleic acids》2013,32(10):1695-1701
Abstract An economical two pot synthesis of 2′,3′-dideoxycytidine (2) from N4-acetyl-cytidine (4) has been developed. The key feature of this sequence is the in situ reductive elimination of a mixture of 1-(3-bromo-3-deoxy-2,5-di-O-acetyl-β-D-xylofuranosyl)-N4-acetylcytosine (5) and 1-(2-bromo-3-deoxy-3,5-di-O-acetyl-β-D-arabinofuranosyl)-N4-acetylcytosine (6) and subsequent hydrogenation of the resultant olefin over palladised charcoal. 相似文献