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排序方式: 共有358条查询结果,搜索用时 890 毫秒
1.
E R Boersma 《BMJ (Clinical research ed.)》1979,1(6167):850-853
Changes in the fatty-acid composition of human adipose tissue before birth and during infancy and childhood were studied in Tanzania and compared with data for British and Dutch infants in relation to their diet. From the 32nd to the 37th week of gestation in Tanzania the proportion in the body fat of the unsaturated fatty acid linoleic acid tended to rise, suggesting an adequate supply of this essential fatty acid from the mother to the fetus. At term 2.5% of the total fatty acids of the body fat was linoleic acid, which corresponded with values in Dutch newborn infants but was significantly higher than those in British infants. During infancy in Tanzania the composition of the fat showed a dramatic increase in the proportions of the saturated fatty acids lauric acid and myristic acid, which did not occur in Dutch and British infants. The proportion of linoleic acid increased to 8%. These changes were a reflection of the fatty-acid composition of the fat in the human milk that the infants received. During weaning (1-2 years of age) the fatty-acid composition changed only slightly. The specific fatty-acid composition of the fat in Tanzanian breast milk may have a beneficial influence on the extent of intestinal absorption in the newborn child. 相似文献
2.
D Tetaert V Gomes G Huet-Duvillier D Demeyer M Hublart A Boersma P Degand 《Biochemical and biophysical research communications》1987,144(3):1222-1228
High performance liquid chromatography (HPLC) procedures have been used to analyze a preparation of the variant surface glycoprotein AnTat 1.1A of Trypanosoma brucei. The native preparation gives several peaks with a high reproducibility both by reverse-phase (RP-) and gel permeation (GP-) HPLC. Under RP-HPLC conditions, nine fractions are fully resolved. The RP-HPLC fractions migrate with the same molecular weight VSG band on polyacrylamide slab gel electrophoresis and no significant differences are observed in amino acid composition among these fractions. The RP-HPLC resolution is found to be related to the ability of the VSG to polymerize as shown using GP-HPLC. These results suggest the existence of a microheterogeneity of the AnTat 1.1A VSG preparation in relation to post-translational modification of the VSG molecule. 相似文献
3.
G Huet-Duvillier V Gomes D Tetaert P Mathon A Boersma P Degand 《Experimental parasitology》1988,67(1):31-38
In our isolation procedure, the surface antigens of the variants AnTat 1.1 and 1.10 (Trypanosoma brucei brucei) are essentially obtained as a disulfide-linked dimer while the AnTat 1.8 surface antigen is found as a mixture of monomer and disulfide-linked dimer. This observation may be related to the localization of the cysteine residues in the protein sequences. In the purification procedure using concanavalin-A Sepharose chromatography, besides the VSG elution by methyl-alpha-D-mannopyranoside, a quantitative elution of still bound VSG may be obtained by the addition of beta-mercaptoethanol to methyl-alpha-D-mannopyrannoside in the elution buffer. The surface antigen of the variant AnTat 1.1 was examined for molecular form at several different times during the release procedure. The disulfide-linked dimer could be observed within 30 min of the surface coat release, indicating its presence within the parasite. 相似文献
4.
Genetic interpretation of enzyme variation in sexual and agamospermous taxa of Taraxacum sections Vulgaria and Mongolica 总被引:1,自引:0,他引:1
The inheritance of 15 enzymes, comprising at least 22 genetic loci, was investigated in crosses between sexual diploid individuals of Taraxacum sections Vulgaria and Mongolica. Patterns were consistent with simple Mendelian segregation. From the inheritance information isozyme phenotypes in agamospermous plants from natural populations were inferred. In some crosses part or all of the progeny originated from self-fertilization, sofar a very rare phenomenon in the sections Vulgaria and Mongolica. It is possible that the probability of self-fertilization increases after pollination by triploid pollen, affecting the cohabitation dynamics of the various ploidy components in mixed natural stands. 相似文献
5.
Use of the pressure vessel to measure concentrations of solutes in apoplastic and membrane-filtered symplastic sap in sunflower leaves 总被引:7,自引:0,他引:7
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A simple, repeatable, and accurate method is described for the collection of apoplastic and membrane-filtered symplastic sap fractions, and for the determination of the origin of these fractions within the leaf. The apoplastic distribution patterns of the naturally occurring apoplastic leaf solutes, and the apoplastic dye PTS (trisodium 3-hydroxy-5, 8, 10-pyrenetrisulfonate) were compared. Aliquots of sap were expressed from detached sunflower leaves in a pressure chamber over intervals of 0.02 to 0.04 megapascal. Three distinct fractions were detected in the expressed sap volume. These were successively released and identified as a petiole-midrib fraction, a minor vein-cell wall fraction, and a mixed fraction consisting of a contribution from the minor vein-cell wall with an increasing proportion of membrane-filtered cell sap. 相似文献
6.
The phylogeny of the hominoid primates: a statistical analysis of the DNA-DNA hybridization data 总被引:1,自引:0,他引:1
Sibley and Ahlquist compared the single-copy nuclear DNA sequences of the
hominoid primates using DNA-DNA hybridization. From this data set they
estimated a phylogeny that clusters man and chimpanzees using a distance
Wagner procedure. However, no assessment of statistical confidence in this
estimated phylogeny was made, despite the fact that their data set contains
internal inconsistencies concerning the correct branching order. This paper
presents a modification of Pielou's Q- statistic that allows one to make
nonparametric tests of phylogenetic relationship from distance data. The
results of this analysis indicate that the estimated phylogeny of Sibley
and Ahlquist is without statistical significance owing to the internal
inconsistencies of the data set. A survey and additional analyses of other
types of molecular data indicate that the phylogeny that clusters
chimpanzees and gorillas and has the human lineage splitting off earlier is
statistically consistent with all the molecular data (including the DNA-DNA
hybridization data), whereas the phylogeny estimated by Sibley and Ahlquist
can be rejected at the 5% level using the data on restriction- endonuclease
sites in the mitochondrial genome.
相似文献
7.
G Lamblin A Boersma A Klein P Roussel H van Halbeek J F Vliegenthart 《The Journal of biological chemistry》1984,259(14):9051-9058
The structure of sialylated carbohydrate units of bronchial mucins obtained from cystic fibrosis patients was investigated by 500-MHz 1H NMR spectroscopy in conjunction with sugar analysis. After subjecting the mucins to alkaline borohydride degradation, sialylated oligosaccharide-alditols were isolated by anion-exchange chromatography and fractionated by high performance liquid chromatography. Five compounds could be obtained in a rather pure state; their structures were established as the following: A-1, NeuAc alpha(2----3)Gal beta(1----4) [Fuc alpha(1----3)]GlcNAc beta(1----3)Gal-NAc-ol; A-2, NeuAc alpha(2----3)Gal beta(1----4)GlcNAc beta(1----6)-[GlcNAc beta (1----3)]GalNAc-o1; A-3, NeuAc alpha(2----3)Gal beta-(1----4)[Fuc alpha(1----3)]GlcNAc beta(1----3)Gal beta(1----3) GalNAc-o1; A-4, NeuAc alpha(2----3)Gal beta(1----4)[Fuc alpha(1----3)]Glc-NAc NAc beta(1----6)[GlcNAc beta(1----3)]GalNAc-o1; A-6,NeuAc alpha-(2----3) Gal beta(1----4)[Fuc alpha(1----3)]GlcNAc beta(1----6)[Gal beta-(1----4) GlcNAc beta(1----3)]GalNAc-o1. The simultaneous presence of sialic acid in alpha(2----3)-linkage to Gal and fucose in alpha(1----3)-linkage to GlcNAc of the same N-acetyllactosamine unit could be adequately proved by high resolution 1H NMR spectroscopy. This sequence constitutes a novel structural element for mucins. 相似文献
8.
Separation of spleen colony-forming units and prothymocytes by use of a monoclonal antibody detecting an H-2K determinant 总被引:1,自引:0,他引:1
A H Mulder J G Bauman J W Visser W J Boersma G J van den Engh 《Cellular immunology》1984,88(2):401-410
The density of H-2K antigens was determined on both the mouse hemopoietic stem cell, using an assay for spleen colony-forming units (CFU-S), and the prothymocyte, using a thymus repopulation assay. This was done by light-activated cell sorting of bone marrow cells labeled first with a biotinylated antibody against H-2Kk and then with avidin-fluorescein isothiocyanate. Almost all CFU-S were found to be present among the 4% bone marrow cells with high forward light scatter (FLS), low perpendicular light scatter (PLS), and bright immunofluorescence. Thymus regeneration by this brightly fluorescent fraction was delayed 3 days compared to thymus regeneration by unsorted cells, although the same number of CFU-S was present in each cell suspension. This delay indicates that differentiation from CFU-S to prothymocytes takes 3 days. The fraction of cells in the FLS/PLS window with dull anti-H-2Kk fluorescence contained few CFU-S and gave rise to a transient thymus regeneration. These findings indicate that the prothymocyte carries fewer H-2K antigens than does the CFU-S. The H-2K antigen is a marker with which CFU-S and prothymocytes can be separated. Therefore, during early T-cell differentiation, the number of H-2K molecules on the cell surface decreases (CFU-S----prothymocyte----cortical thymocyte). During maturation of T cells, a reexpression of H-2K molecules occurs, since lymph node cells and spleen cells were shown to be brightly positive for H-2K antigen. 相似文献
9.
Photosynthesis and transpiration of monterey pine seedlings as a function of soil water suction and soil temperature 总被引:4,自引:0,他引:4
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Rates of photosynthesis, respiration, and transpiration of Monterey pine (Pinus radiata D. Don) were measured under controlled conditions of soil water suction and soil temperature. Air temperature, relative humidity, light intensity, and air movement were maintained constant. Rates of net photosynthesis, respiration, and transpiration decreased with increasing soil water suction. The decrease in the rates of net photosynthesis and transpiration as a function of the soil temperature at low soil water suctions may be attributed to changes in the viscosity of water. At soil water suctions larger than 0.70 bars rates of transpiration and net photosynthesis may be affected in the same proportion by changes in stomatal apertures. 相似文献
10.
Dr AR Holmes RD Cannon HF Jenkinson 《Journal of industrial microbiology & biotechnology》1995,15(3):208-213
The yeastCandida albicans coaggregates with a variety of streptococcal species, an interaction that may promote oral colonization by yeast cells.C. albicans andCandida tropicalis are the yeasts most frequently isolated from the human oral cavity and our data demonstrate that both these species bind toStreptococcus gordonii NCTC 7869 while two otherCandida species (Candida krusei andCandida kefyr) do not. Adherence ofC. albicans was greatest when the yeast had been grown at 30° C to mid-exponential growth phase. For 21 strains ofC. albicans there was a positive correlation between the ability to adhere toS. gordonii and adherence to experimental salivary pellicle. Whole saliva either stimulated or slightly inhibited adherence ofC. albicans toS. gordonii depending on the streptococcal growth conditions. The results suggest that the major salivary adhesins and coaggregation adhesins ofC. albicans are co-expressed. 相似文献