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191.
A membrane-bound phosphatidylinositol (PtdIns) kinase has been purified approximately 9500-fold to apparent homogeneity from sheep brains. The purification procedure involves: solubilisation of the membrane fraction with Triton X-100, ammonium sulphate fractionation and a number of ion-exchange and gel-filtration chromatography steps. The purified enzyme exhibited a final specific activity of 1149 nmol.min-1.mg-1. The molecular mass of the enzyme was estimated to be 55 kDa by SDS/PAGE and 150 +/- 10 kDa by HPLC gel filtration in the presence of Triton X-100. Kinetic measurements have shown that the apparent Km value of PtdIns kinase for the utilisation of PtdIns is 22 microM and for ATP 67 microM. Mg2+ was the most effective divalent cation activator of PtdIns kinase, with maximal enzymatic activity reached at a concentration of 10 mM Mg2+. In addition to adenosine and ADP, the 2'(3')-O-(2,4,6-trinitrophenyl) derivative of ATP was found to be a strong competitive inhibitor of the enzyme, with a Ki of 32 microM. Enzymatic activity was found to be stimulated by Triton X-100 but inhibited by deoxycholate. 相似文献
192.
This is a report of the concentrations of DA, DOPAC, HVA, 5-HT, and 5-HIAA in the brain ofspontaneously diabetic male Wistar rats. These rats showed a marked increase in blood and urine glucose, polydipsia, polyuria, and weight loss that had an onset 11–23 days earlier. Controls were litter mates with no hyperglycemia, glucosuria or weight reduction. Thespontaneously diabetic rats showed a significant reduction of DOPAC in the striatum, and DOPAC, HVA, and 5HIAA in the olfactory tubercles (to 69, 61, 62, and 65% of their respective controls). No changes were found in the concentrations of DA or 5-HT. Thus thespontaneously diabetic rats showed a marked reduction in striatal and mesolimbic DA and mesolimbic 5-HT metabolism. This reduction in metabolism could be the consequence of a reduction in the formation of DA and 5-HT. 相似文献
193.
Significance of nucleotide sequence alignments: a method for random sequence permutation that preserves dinucleotide and codon usage 总被引:10,自引:0,他引:10
The similarity of two nucleotide sequences is often expressed in terms of
evolutionary distance, a measure of the amount of change needed to
transform one sequence into the other. Given two sequences with a small
distance between them, can their similarity be explained by their base
composition alone? The nucleotide order of these sequences contributes to
their similarity if the distance is much smaller than their average
permutation distance, which is obtained by calculating the distances for
many random permutations of these sequences. To determine whether their
similarity can be explained by their dinucleotide and codon usage, random
sequences must be chosen from the set of permuted sequences that preserve
dinucleotide and codon usage. The problem of choosing random dinucleotide
and codon-preserving permutations can be expressed in the language of graph
theory as the problem of generating random Eulerian walks on a directed
multigraph. An efficient algorithm for generating such walks is described.
This algorithm can be used to choose random sequence permutations that
preserve (1) dinucleotide usage, (2) dinucleotide and trinucleotide usage,
or (3) dinucleotide and codon usage. For example, the similarity of two
60-nucleotide DNA segments from the human beta-1 interferon gene
(nucleotides 196-255 and 499-558) is not just the result of their nonrandom
dinucleotide and codon usage.
相似文献
194.
Hypoglycemic Effects of a Polysaccharide from Tetrastigma hemsleyanum Diels & Gilg in Alloxan‐Induced Diabetic Mice
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Yi Ru Xiao Chen Jie Xu Lihong Huang Miaoshan Jiang Longhua Guo Zhenyu Lin Bin Qiu Kwok‐Yin Wong 《化学与生物多样性》2018,15(8)
Tetrastigma hemsleyanum Diels & Gilg , a well‐known traditional Chinese medicine, possesses antitumor and anti‐inflammatory activity, etc. However, the anti‐diabetic effect has not been determined. In our present study, a water‐soluble polysaccharide, named THP with molecular weight of 93 307 Da, was isolated from T. hemsleyanum by DEAE‐52 ion‐exchange and Sephadex G‐100 chromatography. It contains rhamnose, arabinose, mannose, glucose, and galactose in the molar ratio of 0.07:0.14:0.38:0.21:0.31. Then anti‐diabetic effects of THP were examined by treating alloxan‐induced diabetic mice with different doses (100, 200, and 300 mg/kg) of THP orally. The results showed that THP could decrease the blood glucose, TC, TG, LDL‐C levels, increase the body weight, HDL‐C, insulin levels, and enhance the activities of antioxidant enzyme system in alloxan‐induced diabetic mice. Furthermore, the histopathological examination of pancreas, liver, and kidney indicated that THP could protect and reverse β‐cells in diabetic mice with low damage to liver and kidney, which suggests that THP may stimulate pancreatic release of insulin and can be an effectively potential candidate for diabetes mellitus. 相似文献
195.
Solange Oliveira Juliana Aizawa Herbert Sousa Soares Daniela Pontes Chiebao Márcio Botelho de Castro Aline S. Hora Marcos Gomes Lopes Gereon Schares Mark C. Jenkins Oliver C.H. Kwok Ricardo Augusto Dias Solange Maria Gennari Jitender P. Dubey Hilda Fátima Jesus Pena 《International journal for parasitology》2018,48(2):117-123
The importance of birds in the biological cycle of Neospora caninum is not clear. We report unsuccessful Neospora infection in chickens (Gallus gallus domesticus) using two isolates of N. caninum. In experiment #1, 30 White Leghorn chickens were orally inoculated with viable N. caninum oocysts (NC-SP1 isolate, 200 oocysts per bird) via the crop at 21 days of age. Groups of three birds were euthanised at intervals of 7 days (a total of 9 weeks) and one group was challenged with the same oocyst dose at 37 days p.i. and observed for 11 weeks. Blood samples were collected weekly, and sera were tested using IFAT. Chicken tissues were collected for PCR, quantitative PCR and immunohistochemistry. Two dogs approximately 45 days of age were fed with tissues from chickens euthanised at 138 and 159 days p.i. The results indicated that the chickens were resistant to neosporosis as revealed by failure to seroconvert, to detect parasite DNA or N. caninum antigen by immunohistochemistry in inoculated bird tissues, and by no oocyst excretion by the dogs fed avian tissues. Similar results were obtained in experiment #2, in which 34 1-week-old chickens were each s.c. inoculated with 100,000 tachyzoites of the NcWTDMn1 isolate of N. caninum. The chickens were euthanised on days 7, 15, 22, 28, 36 and 60 p.i. At necropsy, all tissues and serum from each bird were collected. All chickens remained asymptomatic, and N. caninum antigen was not detected by immunohistochemistry. Seven chickens euthanised at day 60 p.i. demonstrated low (1:25 dilution) levels of antibodies by using the Neospora agglutination test. Two 12-week-old dogs fed tissues pooled from 10 inoculated chickens euthanised at day 60 p.i. did not excrete N. caninum oocysts. This investigation indicates that chickens are resistant to experimental infection by N. caninum. 相似文献
196.
Reduced blood‐brain barrier expression of fatty acid‐binding protein 5 is associated with increased vulnerability of APP/PS1 mice to cognitive deficits from low omega‐3 fatty acid diets
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Yijun Pan Kwok H. C. Choy Philip J. Marriott Siew Y. Chai Martin J. Scanlon Christopher J. H. Porter Jennifer L. Short Joseph A. Nicolazzo 《Journal of neurochemistry》2018,144(1):81-92
197.
Diane?M.?ThomsonEmail authorView authors OrcID profile Jonas?W.?Kwok Emily?L.?Schultz 《Plant Ecology》2018,219(6):705-717
Climate change will not only alter mean conditions, but increase the frequency and intensity of extreme events such as severe droughts. Yet the consequences of extreme drought for plant demography are poorly understood. We compared phenology, demographic rates and effects of competition with exotic grasses for the California annual forb Phacelia distans between a year with slightly below average precipitation (2011–2012) and one in extreme drought (2012–2013). We also contrasted these demographic responses with changes in seedling emergence rates and cover in the annual plant community. Early Phacelia mortality actually fell in the extreme drought year, as low October rainfall shifted germination to cooler conditions in November. Survival from mid December to flowering did not change between years. In contrast to expectations, competition with early-emerging exotic annual grasses did not reduce Phacelia spring survival in 2012–2013. A shorter window for fall germination that reduced priority effects may explain this result. Yet the 2012–2013 growing season ended a month earlier than in 2011–2012, significantly reducing Phacelia size at flowering and inflorescence production. Community seedling emergence and cover changed only weakly between the 2 years. Our results demonstrate the importance of within season precipitation patterns in determining whether a climatically extreme year will lead to extreme ecological outcomes. This work also illustrates how annual plant drought responses depend critically on germination behavior and phenology. An important future question is whether seed banks can sustain native forb population persistence through an extended drought with multiple years of low or failed reproduction. 相似文献
198.
Summary We have studied the effects of agar and agarose on Vent DNA polymerase and Taq DNA polymerase. Agar strongly inhibited Vent DNA polymerase but only moderately inhibited Taq DNA polymerase. Such a difference may be due to the fact that the two polymerases belong to different structural families. When Vent DNA polymerase is used to amplify DNA from lambda plaques, agarose rather than agar is the solid medium of choice. 相似文献
199.
Ben J. Lang Rebecca J. Gorrell Mona Tafreshi Masanori Hatakeyama Terry Kwok John T. Price 《Cell stress & chaperones》2016,21(3):523-533
Bacterial infections typically elicit a strong Heat Shock Response (HSR) in host cells. However, the gastric pathogen Helicobacter pylori has the unique ability to repress this response, the mechanism of which has yet to be elucidated. This study sought to characterize the underlying mechanisms by which H. pylori down-modulates host HSP expression upon infection. Examination of isogenic mutant strains of H. pylori defective in components of the type IV secretion system (T4SS), identified the secretion substrate, CagA, to be essential for down-modulation of the HSPs HSPH1 (HSP105), HSPA1A (HSP72), and HSPD1 (HSP60) upon infection of the AGS gastric adenocarcinoma cell line. Ectopic expression of CagA by transient transfection was insufficient to repress HSP expression in AGS or HEK293T cells, suggesting that additional H. pylori factors are required for HSP repression. RT-qPCR analysis of HSP gene expression in AGS cells infected with wild-type H. pylori or isogenic cagA-deletion mutant found no significant change to account for reduced HSP levels. In summary, this study identified CagA to be an essential bacterial factor for H. pylori-mediated suppression of host HSP expression. The novel finding that HSPH1 is down-modulated by H. pylori further highlights the unique ability of H. pylori to repress the HSR within host cells. Elucidation of the mechanism by which H. pylori achieves HSP repression may prove to be beneficial in the identification of novel mechanisms to inhibit the HSR pathway and provide further insight into the interactions between H. pylori and the host gastric epithelium. 相似文献
200.