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31.
The pollination biology and breeding systems ofKielmeyera coriacea andK. speciosa, two sympatric woody species common in the cerrado vegetation of C. Brazil, were studied. Both species have similar nectarless, polystemonous Papaver-type flowers which are visited by a similar spectrum of insects, though they bloom in different seasons and are thus phenologically isolated. Large carpenter bees seem to be the most important pollinators and these and other bees effect buzz pollen retrieval despite the fact that anthers are not poricidal. Both species ofKielmeyera possess strong xenogamous breeding systems. The presence of staminate flowers and andromonoecy inK. coriacea, as well as the longevity ofK. speciosa flowers are discussed as alternative strategies to improve pollination success and reproductive efficacy. 相似文献
32.
Enkephalin is liberated from metorphamide and dynorphin A1-8 by endo-oligopeptidase A, but not by metalloendopeptidase EC 3.4.24.15. 总被引:1,自引:0,他引:1 下载免费PDF全文
O Toffoletto K M Metters E B Oliveira A C Camargo J Rossier 《The Biochemical journal》1988,252(1):35-38
It has been previously reported that both the cysteinyl-endo-oligopeptidase A and the metalloendopeptidase EC 3.4.24.15 are able to generate enkephalin from a number of enkephalin-containing peptides, including dynorphin A1-8. The present study shows that only endo-oligopeptidase A is able to generate [Leu5]enkephalin and [Met5]enkephalin from dynorphin A1-8 and from metorphamide respectively. It is also shown that endo-oligopeptidase A neither hydrolyses the specific EC 3.4.24.15 substrate alpha-N-benzoyl-Gly-Ala-Ala-Phe p-aminobenzoate, nor is inhibited by the specific EC 3.4.24.15 inhibitor N-[1(RS)-carboxy-2-phenylethyl]-alpha-Ala-Ala-Phe p-aminobenzoate. 相似文献
33.
I. B. Kerr A. M. Mendes da Silva E. Drouhet P. de Oliveira S. C. G. da Costa 《Mycopathologia》1988,101(1):3-11
Congenitally athymic nude mice (nu/nu) and their phenotypically normal littermates (nu/+) were intraperitoneally infected with yeast cells of a strain of Paracoccidioides brasiliensis. The nude mice developed a severe and generalized infection with an intense parasitism of several organs, accompanied by a low-grade of tissue reaction. The lesions were characterized by abundant yeast-like cells of the fungus, and in some animals, numerous hyphal forms could be well visualized. In control animals, infection was moderate, almost exclusively restricted to the area of inoculation, and the lesions presented few parasites surrounded by an inflammatory response. Filamentous forms of the fungus were never encountered in these animals. 相似文献
34.
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
35.
R C de Oliveira D T Ribeiro R G Nigro P Di Mascio C F Menck 《Nucleic acids research》1992,20(16):4319-4323
In order to characterize the molecular nature of singlet oxygen (1O2) induced mutations in mammalian cells, a SV40-based shuttle vector (pi SVPC13) was treated with singlet oxygen arising from the thermal decomposition of the water-soluble endoperoxide of 3,3'-(1,4-naphthylidene) dipropionate (NDPO2). After the passage of damaged plasmid through monkey COS7 cells, the vector was shuffled into E. coli cells, allowing the screening of supF mutants. The mutation spectrum analysis shows that single and multiple base substitutions arose in 82.5% of the mutants, the others being rearrangements. The distribution of mutations within the supF gene is not random and some hotspots are evident. Most of the point mutations (98.4%) involve G:C base pairs and G:C to T:A transversion was the most frequent mutation (50.8%), followed by G:C to C:G transversion (32.8%). These results indicate that mutagenesis in mammalian cells, mediated by 1O2-induced DNA damage, is targeted selectively at guanine residues. 相似文献
36.
A simple and efficient method for the oligodeoxyribonucleotide-directed mutagenesis of double-stranded plasmid DNA. 总被引:4,自引:0,他引:4
A method for the oligodeoxyribonucleotide-directed mutagenesis of double-stranded DNA without the necessity for phenotypic selection is described. Plasmids denatured with alkali and purified by adsorption to and elution from nitrocellulose have single-stranded regions where primers can hybridize and serve as templates for a T7 DNA polymerase-catalyzed synthesis of complementary mutant DNA strands. When this procedure was carried out such that the original nonmutant strand contained uracil [method of Kunkel, Proc. Natl. Acad. Sci. USA 82(1985)488-492], mutation frequencies of between 30% and 40% were obtained. The technique has been used to generate mutant genes in plasmids of a wide variety of sizes. The largest plasmid manipulated and successfully mutagenized was 22 kb. The method is rapid and efficient and is not dependent upon either f1 phage vectors or the presence of restriction sites in the vicinity of the sequence targeted for mutation. 相似文献
37.
Paulo E. Oliveira Peter E. Gibbs Ana Angélica Barbosa Salvador Talavera 《Plant Systematics and Evolution》1992,179(3-4):207-219
The pollination biology and breeding systems ofEriotheca pubescens andE. gracilipes have been studied. These two species occur as trees in cerrado vegetation, the neotropical savannas of Central Brazil, with partially sympatric distributions. They have similar phenology and floral structure, although the flowers ofE. pubescens are larger. Both species have nectar flowers pollinated by largeAnthophoridae bees but the main pollinators of each species differ in size. The species have markedly different breeding systems: late-acting self-incompatibility inE. gracilipes and apomixis stimulated by pollination inE. pubescens. 相似文献
38.
Summary The obtention of embryogenic competence in Actinidia deliciosa var. deliciosa cv. Hayward is reported. Axillary buds from shoots submitted to cold (4°C) and starvation for 1.5 months, developed leaves with embryogenic competence. These leaves, cultured in darkness for 1.5 months on a medium containing zeatin as a sole growth regulator, originated compact structures from which embryos developed. The plating orientation and sectioning of leaves strongly affected the expression of the embryogenic potential. A selected fraction of the protoplasts isolated from these leaves was able to develop in an embryogenic way. The germination of the embryos is still only occasional.Abbreviations 2,4-D
2,4-dichlorophenoxyacetic acid
- 2-iP
6-dimethylallyl aminopurine
- IAA
indole-3-acetic acid
- NOA
naphthoxyacetic acid
- SEM
Scanning Electron Microscopy 相似文献
39.
Sertoli cells in culture produce two isoforms of proteoglycans which are found in the culture medium and associated with the cell membrane. The amount of both types of proteoglycans increased when Sertoli cells were plated on type I collagen-coated dishes as compared to uncoated dishes. The effect is due to an increase in the synthesis of proteoglycans rather than a diminished rate of degradation of these molecules. The collagen substrate also affects the distribution of these macromolecules; an increase in the amount of membrane-associated proteoglycans occurs at the expense of the proteoglycans released to the culture medium. 相似文献
40.
Chloramphenicol acetyl transferase (CAT) gene was used as a reporter gene to assess the conditions for polyethylene glycol (PEG)-mediated transfection of kiwifruit protoplasts. The effect of plasmid concentration and the presence of carrier DNA were each assessed by analysing CAT activity in transfected protoplasts using thin-layer chromatography (TLC) autoradiographic detection of acetylated chloramphenicol. A gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) non-radioactive method was developed for monitoring CAT gene activity. This method provides a high speed of analysis (30 min) and precise means of detecting acetylated products at the nanomolar level, enabling quantification at very low transfection rates. Using this method we optimized plasmid and PEG concentration and also assessed the effect of heat shock on transfection. The best CAT activity was obtained using 30% polyethylene glycol 4000 and by submitting protoplasts to heat shock (45 °C, 5 min) prior to transfection. 相似文献