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1.
Mui Keng Tan 《Plant molecular biology》1991,17(2):221-227
A total of 864 bases from 5 regions interspersed in the 18S and 26S rRNA molecules from various clones of Pteridium covering the general geographical distribution of the genus was analysed using a rapid rRNA sequencing technique. No base difference has been detected amongst the three major lineages, two of which apparently separated before the breakup of the ancient supercontinent, Pangaea. These regions of the rRNA sequences have thus been conserved for at least 160 million years and are here compared with other eukaryotic, especially plant rRNAs. 相似文献
2.
3β, 7α, 26-Triacetoxy-5α-cholestane was prepared from 25R-3β, 26-diacetoxy-5α-cholestan-7α-ol, and partially hydrolyzed with potassium carbonate in methanol-benzene. The three acetylated products thus obtained were characterized by thin layer and gas liquid chromatography, and mass spectrometry. By oxidation and alkaline hydrolysis, 3β, 7α-diacetoxy-5α-cholestan-26-ol was converted to 3β, 7α-dihydroxy-5α-cholestanoic acid. 7α, 26-Diacetoxy-5α-cholestan-3β-ol was characterized as indicated. The third product, 7α-acetoxy-5α-cholestane-3β, 26-diol was oxidized to 3-oxo-7α-acetoxy-5α-cholestanoic acid which was reduced catalytically and hydrolyzed to provide 3α, 7α-dihydroxy-5α-cholestanoic acids and its 3β-isomer. By comparison of the specific rotation of this sample of 3α, 7α-dihydroxy-5α-cholestanoic acid derived from 25R-kryptogenin with a similar product derived from arihydro-5α-cyprinol obtained from carp bile, the latter derivative appears to be primarily the 25S material. 相似文献
3.
Interleukin-3 stimulates the tyrosine phosphorylation of the 140-kilodalton interleukin-3 receptor 总被引:9,自引:0,他引:9
Murine interleukin-3 (mIL-3) stimulates the rapid and transient tyrosine phosphorylation of a number of proteins in mIL-3-dependent B6SUtA1 cells. Two of these proteins, p68 and p140, are maximally phosphorylated at tyrosine residues within 2 min of addition of mIL-3. Because 125I-mIL-3 can be cross-linked to both 70- and 140-kDa proteins on intact B6SUtA1 cells, we investigated whether the tyrosine phosphorylated p68 and p140 were these two mIL-3 receptor proteins. Addition of antiphosphotyrosine antibodies (alpha PTyr Abs) to cell lysates from B6SUtA1 cells, to which 125I-mIL-3 had been disuccinimidyl suberate-cross-linked, resulted in the immunoprecipitation of 125I-mIL-3 complexed to both 70- and 140-kDa proteins. To determine if the observed immunoprecipitation pattern was due to the direct interaction of alpha-PTyr Abs with these two mIL-3 receptor proteins or with tyrosine-phosphorylated proteins that were associated with the receptor proteins, cell lysates were treated with 2% sodium dodecyl sulfate, 5% 2-mercaptoethanol, and boiled for 1 min. After removal of sodium dodecyl sulfate and 2-mercaptoethanol, alpha PTyr Abs immunoprecipitated 125I-mIL-3 cross-linked to only the 140-kDa protein. To confirm this finding, 32P-labeled B6SUtA1 cells were treated with biotinylated or fluoresceinated mIL-3. Addition of immobilized streptavidin or antifluorescein antibodies, respectively, to cell lysates from these cells resulted in the enrichment of only a 140-kDa tyrosine phosphorylated protein. Taken together, these results strongly suggest that only the 140-kDa receptor protein is tyrosine phosphorylated upon mIL-3 binding. 相似文献
4.
The ATP-binding-cassette transmembrane transporters (ABC transporters)
known from vertebrates belong to four major subfamilies: (1) the P-
glycoproteins (Pgp); (2) the cystic fibrosis transmembrane conductance
regulators (CFTR); (3) the Tap proteins encoded with the major
histocompatibility complex of mammals; and (4) the peroxisomal membrane
proteins. Both Pgp and CFTR have a structure suggesting a past internal
gene duplication; a phylogenetic analysis indicated that these duplications
occurred independently, while an independent tandem gene duplication
occurred in the case of the Tap family. Both the Pgp and Tap proteins show
evidence of relationship to bacterial ABC transporters lacking internal
duplication, and both are significantly more closely related to the HlyB
and MsbA families of transporters from purple bacteria than they are to ABC
transporters from nonpurple bacteria. The simplest hypothesis to explain
this observation is that eukaryotic Pgp and Tap genes are descended from a
mitochondrial gene or genes that were subsequently translocated to the
nuclear genome. The Pgp genes of eukaryotes are characterized by a
remarkable degree of convergent evolution between the ATP-binding cassettes
of their N- terminal and C-terminal halves, whereas no such convergence is
seen between the two halves of CFTR genes or between the duplicated Tap
genes. Exon 13 of the CFTR gene, which encodes a putative regulatory domain
not found in other ABC transporters apart from CFTR, showed high levels of
both synonymous and nonsynonymous difference in comparisons among different
mammalian species, suggesting that this region is a mutational hot spot.
相似文献
5.
6.
X Xiao G Hintermann AL Demanin J Piret 《Journal of industrial microbiology & biotechnology》1996,16(4):261-262
Streptomyces glaucescens is shown to possess -lactamase activity which is inhibitable by clavulanate. This is important in regard to its use as a cloning host for enzymes of \-lactam biosynthesis. 相似文献
7.
Donald J. Brasch Hi Mui Chang Chaw T. Chuah Laurence D. Melton 《Carbohydrate research》1981,97(1):113-125
A galactan sulfate has been isolated from the seaweed Porphyra columbina, and its structure established by a combination of methylation, methanolysis, treatment with alkali followed by methylation, and 13C-n.m.r. spectroscopy. The polysaccharide belongs to the porphyran class, and consists of 3-linked β-d-galactosyl residues and 4-linked α-l-galactosyl residues. 3,6-Anhydro-l-galactose and l-galactose 6-sulfate residues total approximately half of the sugar units, the other half being made up of d-galactose and 6-O-methyl-d-galactose residues. Some evidence is presented that suggests that the galactan sulfate does not have a completely alternating structure. 相似文献
8.
ERIC S. BONO PATRICK SMOLINSKI AL CASAGRANDA JUNDE XU 《Computer methods in biomechanics and biomedical engineering》2013,16(2):125-131
The Shear-slip Mesh Update Method (SSMUM) is being used in flow simulations involving large but regular displacements of one or more boundaries of the computational domain. We follow up the earlier discussion of the method with notes on practical implementation aspects. In order to establish a benchmark problem for this class of flow problems, we define and report results from a two-dimensional viscous flow around a rotating stirrer in a square chamber. The application potential of the method is demonstrated in the context of biomedical design problem, as we perform an analysis of blood flow in a centrifugal left ventricular assist device, or blood pump, which involves a rotating impeller in a non-axisymmetric housing. 相似文献
9.
Objective
To study the attitudes among general practitioners towards pneumococcal vaccination for middle-aged (50–64) and elderly population (over 65) in Hong Kong and the factors affecting their decision to advise pneumococcal vaccination for those age groups.Design
Cross-sectional study of general practitioners in private practice in Hong Kong.Participants
Members of Hong Kong Medical Association delivering general practice services in private sector.Measuring Tool
Self-administered questionnaire.Main Outcome Measures
Intention to recommend pneumococcal vaccination, barriers against pneumococcal vaccination.Results
53.4% of the respondents would actively recommend pneumococcal vaccination to elderly patients but only 18.8% would recommend for middle-aged patients. Consultation not related to pneumococcal vaccine was the main reason for not recommending pneumococcal vaccine (43.6%). Rarity of pneumonia in their daily practice was another reason with 68.4% of respondents attending five or less patients with pneumonia each year. In multivariate analysis, factors such as respondents would get vaccination when reaching age 50 (ORm 10.1), and attending 6 pneumonia cases or more per year (ORm 2.28) were found to be associated with increasing likelihood for recommending vaccination to the middle-aged. While concerns of marketing a product (ORm 0.41), consultation not related to vaccination (ORm 0.45) and limited time (ORm 0.38) were factors that reduced the likelihood.Conclusion
Public policy is needed to increase the awareness of impact of pneumococcal pneumonia and the availability of preventive measures. 相似文献10.
Enrique Palomo Atance M. José Ballester Herrera Patricio Giralt Muiña Rafael Ruiz Cano Alberto León Martín Juan Giralt Muiña 《Endocrinología y nutrición》2013,60(7):379-385
ObjectiveTo assess the estimated glucose disposal rate (eGDR), insulin dose, and lipoprotein profile in children with type 1 diabetes mellitus (T1DM) and overweight or obesity as compared to children with T1DM and normal weight.MethodsA total of 115 patients (aged 5-16 years) with T1DM on intensive insulin therapy were recruited. The following parameters were measured: weight, height, body mass index, waist and hip circumference, insulin dose, eGDR, glycosylated hemoglobin, blood pressure, and lipoprotein profile. Results were stratified by sex and age.ResultsNo significant differences were found in eGDR between children with normal weight, overweight, and obesity. However, obese children older than 11 years had lower eGDR values (9.3 ± 1.3 vs 10.1 ± 0.8 mg kg-1min-1; p < 0.01). Insulin dose was higher in overweight and obese children, especially in IU/m2/day (37.7 vs 36.1 vs 29.4 respectively; p < 0.01). Obese children had higher low-density lipoprotein cholesterol levels than children with overweight and normal weight (106.5 vs 91.7 vs 91.5 mg/dL respectively; p < 0.01). No correlation was found between waist circumference and the different markers of insulin resistance.ConclusionsValues of eGDR values were lower in obese children with T1DM older than 11 years, and this may therefore be considered a marker of insulin resistance. Insulin dose was higher in diabetic patients with overweight or obesity, specially in IU/m2/day. Obese children with T1DM had a lipoprotein profile of cardiovascular risk. 相似文献