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991.
D A Klaerke P L J?rgensen 《Comparative biochemistry and physiology. A, Comparative physiology》1988,90(4):757-765
1. Reabsorption of NaCl in the thick ascending limb of Henle's loop involves the integrated function of the Na+,K+,Cl- -cotransport system and a Ca2+-activated K+ channel in the luminal membrane with the Na+,K+-pump and a net Cl- conductance in the basolateral membrane. 2. Assay of K+ channel activity after reconstitution into phospholipid vesicles shows that the K+ channel is stimulated by Ca2+ in physiological concentrations and that its activity is regulated by calmodulin and phosphorylation from cAMP dependent protein kinase. 3. For purification luminal plasma membrane vesicles are isolated and solubilized in CHAPS. K+ channel protein is isolated by affinity chromatography on calmodulin columns. The purified protein has high Ca2+-activated K+ channel activity after reconstitution into vesicles. 4. The purified K+ channel consists of two proteins of 51 and 36 kDa. Phosphorylation from cAMP dependent protein kinase stimulates K+ channel activity and labels the 51 kDa band. The 36 kDa band is rapidly cleaved by trypsin and may be involved in Ca2+ stimulation. 5. Opening of the K+ channel by Ca2+ in physiological concentrations and regulation by calmodulin and phosphorylation by protein kinase may mediate kinetic and hormonal regulation of NaCl transport across the tubule cells in TAL. 相似文献
992.
C. M. Calkins J. D. Scasta T. Smith M. M. Stayton S. L. Lake 《Medical and veterinary entomology》2019,33(4):546-551
The horn fly Haematobia irritans (Diptera: Muscidae) is a blood obligate ectoparasite of bovids that causes annual losses to the U.S. beef cattle industry of over US$1.75 billion. Climate warming, the anthropogenic dispersion of bovids and the cross‐breeding of beef cattle with other bovid species may facilitate novel horn fly–host interactions. In particular, hybridizing yaks [Bos grunniens (Artiodactyla: Bovidae)] with beef cows (Bos taurus) for heterosis and carcass improvements may increase the exposure of yak × beef hybrids to horn flies. The present paper reports on the collection of digital images of commingled beef heifers (n = 12) and F1 yak × beef hybrid bovids (heifers, n = 7; steers, n = 5) near Laramie, Wyoming (~ 2200 m a.s.l.) in 2018. The total numbers of horn flies on beef heifers and F1 yak × beef heifers [mean ± standard error (SE): 88 ± 13 and 70 ± 17, respectively] did not differ significantly; however, F1 yak × beef steers had greater total horn fly abundance (mean ± SE: 159 ± 39) than female bovids. The present report of this experiment is the first such report in the literature and suggests that F1 yak × beef bovids are as susceptible as cattle to horn fly parasitism. Therefore, similar monitoring and treatment practices should be adopted by veterinarians, entomologists and producers. 相似文献
993.
994.
995.
Mice were immunized with dengue type 2 virus (DEN 2) under a schedule favoring the production of IgE antibody. The antibody obtained could sensitize peritoneal resident mast cells both in vitro and in vivo so that the sensitized cells were degranulated and released histamine on challenge with the DEN 2 antigen. It was also demonstrated that the antibody was cytophilic and heat-labile. The above observations suggest that the present experimental system can be used to detect anti-DEN 2 IgE antibody in mice. 相似文献
996.
Summary The intercellular contacts of the migrating edge of chick and quail blastoderms during gastrulation were studied by transmission electron microscopy of thin sections and of freeze-fracture replicas. Tight junctions and gap junctions as well as desmosomes were found. Tight junctions were organized as single junctional strands or as a complex of numerous junctional strands interposed between the lamellae and the bodies of the cells building up the margin of overgrowth. The function of these intercellular junctions is considered in relation to the locomotion of the margin of overgrowth cells. 相似文献
997.
S L Mukomolov V A Anan'ev L I Shliakhtenko V V Nechaev T V Evdokimova 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1984,(12):76-80
The occurrence of HBsAg carriership in Leningrad has been found to be 1.4% according to the results of countercurrent immunoelectroosmophoresis (CIEO) and 2.1% according to the results of the passive hemagglutination (PHA) test. In children HBsAg occurs with higher frequency: 1.9% according to the results of CIEO and 3.4% according to the results of the PHA test. The latter test reveals HBsAg carriers more completely, especially in women who have usually less pronounced antigenemia than men. Most of chronic HBsAg carriers are patients with chronic forms of hepatitis B (chronic active hepatitis and chronic persistent hepatitis); frequently they become the source of infection among their relatives under the conditions of family contacts. A complex of antiepidemic measures is necessary in the foci of chronic HBsAg carriership. 相似文献
998.
M. I. Jsselstijn J. Kaiser F. L. van Delft H. E. Schoemaker F. P. J. T. Rutjes 《Amino acids》2003,24(3):263-266
Summary. Novel synthetic procedures for the modification of non-proteinogenic acetylene-containing amino acids have been developed.
The functionalization either proceeds via zinc/copper-mediated introduction of alkyl substituents, or via tungsten-catalyzed
ring-closing alkyne metathesis reactions.
Received March 28, 2002 Accepted October 3, 2002 Published online December 18, 2002
Acknowledgements These investigations are supported (in part) by the Netherlands Research Council for Chemical Sciences (CW) with financial
aid from the Netherlands Technology Foundation (STW).
Authors' address: Floris P. J. T. Rutjes, Prof. Dr., Department of Organic Chemistry, University of Nijmegen, Toernooiveld 1, NL-6525 ED Nijmegen,
The Netherlands, E-mail: rutjes@sci.kun.nl
2, selected data: 1H NMR (300 MHz, CDCl3) δ 5.32 (d, J = 7.7 Hz, 1H), 4.44–4.40 (m, 1H), 3.76 (s, 3H), 2.75–2.73 (d, J = 5.0 Hz, 2H), 1.44 (s, 9H); 13C NMR (75 MHz, CDCl3) δ 171.0, 155.0, 80.3, 74.6, 52.6, 51.9, 41.7, 28.3, 24.0; mp = 55°C.
Typical procedure for 5: zinc dust (116 mg, 1.408 mmol) was weighed into a 20 mL flask, which was repeatedly evacuated (with heating using a heat
gun) and flushed with argon. Dry DMF (0.5 mL, distilled from CaH2) and 1,2-dibromoethane (9.2 μL, 0.106 mmol) were added and the flask was heated at 80°C for 40 min. The reaction mixture was allowed to cool to room temperature,
trimethylsilyl chloride (4 μL, 0.035 mmol) was added and the resulting mixture was stirred vigorously for a further 30 min under argon. Iodocyclohexane
(69 μl, 0.528 mmol) was added and stirred at room temperature for 3 h more after which stirring was ceased to settle the zinc.
CuCN (41 mg, 0.458 mmol) and LiCl (40 mg, 0.915 mmol) were heated to 150°C for 2 h and cooled to room temperature. Addition
of DMF (1 mL) formed a soluble CuCN·2LiCl complex within 5 min. After cooling the Cu-complex to −15°C, the organozinc reagent
was added dropwise followed by the bromoacetylene 2 (116 mg, 0.352 mmol). The mixture was allowed to stir overnight at room temperature. Water was added and the suspension was
extracted using heptane, washed with brine, dried (MgSO4) and concentrated. Purification using flash column chromatography (10% EtOAc in heptane) yielded 5 (100 mg, 81%) as a colorless oil. 5: IR ν 3355, 2929, 2852, 2359, 2337, 1749, 1717, 1498, 1447, 1365, 1251, 1181, 1060; 1H NMR (300 MHz, CDCl3) δ 5.28 (d, J = 7.7 Hz, 1H), 4.43–4.38 (m, 1H), 3.73 (s, 3H), 2.69–2.63 (m, 2H), 2.13 (m, 1H), 1.73–1.22 (m, 10H), 1.43 (s, 9H); 13C NMR (75 MHz, CDCl3) δ 171.4, 155.0, 88.1, 79.9, 73.8, 52.3, 32.7, 32.7, 28.8, 28.2, 25.8, 24.6, 23.1; HRMS (EI): calculated for C17H27NO4 309.1940, found 309.1937.
A solution of the tungsten catalyst (7 mg, 10 mol%) in C6H5Cl (2 mL) was treated with a solution of 14 (49.0 mg, 0.120 mmol) in C6H5Cl (5.0 mL) under an argon atmosphere and the resulting mixture was heated at 80°C for 3 h. Evaporation followed by flash
column chromatography (80% EtOAc in heptane) afforded 15 (21.0 mg, 50%; 64% after correction for starting material) and 14 (16 mg, 33%) as colorless oils. 15: [α]D =–14.6 (c = 1, CH2Cl2); IR ν 3313, 2931, 2865, 2249, 1744, 1667, 1520, 1366, 1170; 1H NMR (400 MHz, CDCl3) δ 7.14 (d, J = 8.7 Hz, 1H), 6.08 (d, J = 8.3 Hz, 1H), 4.78 (q, J = 6.8 Hz, 1H), 4.27 (q, J = 7.9 Hz, 1H), 3.73 (s, 3H), 2.17–2.15 (m, 4H), 2.07–1.96 (m, 2H), 1.79–1.52 (m, 4H), 1.45 (s, 9H), 0.89–0.83 (m, 2H); 13C NMR (100 MHz, CDCl3) δ 173.2, 171.8, 155.8, 80.4, 80.2, 79.3, 53.8, 52.5, 51.2, 32.8 (2×), 28.1, 24.6, 24.2, 18.3 (2×); HRMS (EI): calculated for
C18H28N2O5 相似文献
999.
Depurination-induced infidelity of deoxyribonucleic acid synthesis with purified deoxyribonucleic acid replication proteins in vitro 总被引:18,自引:0,他引:18
Removal of purine bases from phi X174 single-stranded DNA leads to increased reversion frequency of amber mutations when this DNA is copied in vitro with purified DNA polymerases. This depurination-induced mutagenesis is observed at three different genetic loci and with several different purified enzymes, including Escherichia coli DNA polymerases I and III, avian myeloblastosis virus DNA polymerase, and eukaryotic DNA polymerases alpha, beta, and gamma. The extent of mutagenesis correlates with the estimated frequency of bypass of the lesion and is greatest with inherently inaccurate DNA polymerases which lack proofreading capacity. With E. coli DNA polymerase I, conditions which diminish proofreading result in a 3-5-fold increase in depurination-induced mutagenesis, suggesting a role for proofreading in determining the frequency of bypass of apurinic sites. The addition of E. coli single-stranded DNA-binding protein to polymerase I catalyzed reactions with depurinated DNA had no effect on the extent of mutagenesis. Analysis of wild-type revertants produced during in vitro DNA synthesis by polymerase I or avian myeloblastosis virus DNA polymerase on depurinated phi X174 amber 3 DNA indicates a preference for insertion of dAMP opposite the putative apurinic site at position 587. These results are discussed in relation both to the mutagenic potential of apurinic sites in higher organisms and to studies on error-prone DNA synthesis. 相似文献
1000.