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931.
Evidence for nonclassical alpha adrenoceptor blockade by prazosin in isolated rabbit blood vessels 总被引:6,自引:0,他引:6
In isolated rabbit ear artery, prazosin shifted the concentration-response curve for norepinephrine (NE) to the right and increased the slope of the curve in the ED50 region. Prazosin caused a smaller shift to the right of the concentration-response curve for NE in rabbit small saphenous vein and had no effect on the slope in the ED50 region. The prazosin-induced increase in the slope of the NE concentration-response curve did not occur in the ear artery when neuronal and extraneuronal uptake were inhibited by desipramine (DMI) and deoxycorticosterone acetate (DOCA). Prazosin concentration ratios were significantly larger in the ear artery than in the small saphenous vein at all prazosin concentrations in the presence or absence of DMI and DOCA. Significant differences were found between prazosin dissociation constants (KB) determined at three concentrations of prazosin in ear artery. No such differences were found between phentolamine dissociation constants determined in this vessel. Prazosin dissociation constants determined in small saphenous vein were higher than those determined in ear artery. These findings suggest that prazosin behaves as a noncompetitive antagonist in ear artery and that there are differences between the alpha adrenoceptors of the ear artery and those of the small saphenous vein. 相似文献
932.
Transposition of the kanamycin-resistance transposon Tn903 总被引:6,自引:0,他引:6
Ry Young Dana Smith Grillo Ralph Isberg Jeffrey Way Michael Syvanen 《Molecular & general genetics : MGG》1980,178(3):681-689
Summary The insertion of the kanamycin-resistance transposon, Tn903, into the Escherichia coli chromosome was studied. Tn903 is similar in structure to the well known transposons Tn5 and Tn10 in that it has a unique central sequence flanked by inverted repeat sequences extending more than a thousand base pairs. However, the central region of Tn903 has enough single-frame coding capacity only for the drug modifying enzyme, whereas Tn5 and Tn10 carry multigenic unique sequences. In this paper we demonstrate that two different classes of insertion event occur: (1) the first class is a complex event in which all or part of the genome of the bacteriophage lambda vector is co-inserted near the purE locus on the E. coli chromosome (11.7 min); (2) the second class appears to be a simple transposition event in which the transposon alone is inserted at relatively nonspecific sites in the chromosome, as has been described for Tn5 and Tn10. Furthermore both classes show dependency on homology-requiring recombination systems. We suggest that Tn903 transposes infrequently because it must utilize a recA-controlled host function, whereas Tn5 and Tn10 are recA-independent and encode similar but more active functions on the transposon DNA. 相似文献
933.
Simultaneous kinetic analysis of ribulose 1,5-bisphosphate carboxylase/oxygenase activities 总被引:4,自引:4,他引:0 下载免费PDF全文
An assay was developed for simultaneous kinetic analysis of the activities of the bifunctional plant enzyme ribulose 1,5-bisphosphate carboxylase/oxygenase [EC 4.1.1.39]. [1-14C,5-3H]Ribulose 1,5-bisphosphate (RuBP) was used as the labeled substrate. Tritium enrichment of the doubly labeled 3-phosphoglycerate (3-PGA) product, common to both enzyme activities, may be used to calculate Vc/Vo ratios from the expression A/(B-A) where A and B represent the 3H/14C isotope ratios of doubly labeled RuBP and 3-PGA, and Vc and Vo represent the activities of carboxylase and oxygenase, respectively. Doubly labeled substrate was synthesized from [2-14C]glucose and [6-3H]glucose using the enzymes of the pentose phosphate pathway coupled with phosphoribulokinase. 相似文献
934.
Terrance O. Kurtz Drew J. Winston William J. Martin Lowell S. Young William L. Hewitt 《Current microbiology》1980,4(1):21-26
Moxalactam (LY127935), a novel beta-lactam antibiotic, was compared with semisynthetic penicillins, cephalosporins, and aminoglycosides
by the agar dilution method against 5,317 recent clinical isolates of facultative and anaerobic bactria. At 0.5 μg/ml, moxalactam
inhibited 90% of all Gram-negative bacilli tested except forPseudomonas aeruginosa (81% inhibited by 32 μg/ml) andAcinetobacter calcoaceticus (88% inhibited by 32 μg/ml). More than 90% ofBacteroides fragilis andStaphylococcus aureus were inhibited by 4 μg/ml and 8 μg/ml, respectively. Moxalactam was at least 16-fold more active by weight than cephalothin,
cefamandole, and cefoxitin forEscherichia coli, Klebsiella pneumoniae, andEnterobacter species, and 2- to 4-fold more active than cefoxitin forB. fragilis. Moxalactam was 4-fold less active than cefamandole and cephalothin forS. aureus and 2- to 4-fold less active than piperacillin forP. aeruginosa. Moxalactam was as active or more active than the aminoglycosides for all facultative Gram-negative bacilli except forP. aeruginosa. Moxalactam was inhibitory (minimal inhibitory concentration <16 μg/ml) for 20/27 gentamicin-resistant isolates and 8/13
amikacin-resistant organisms. Moxalactam’s in vitro activity against Gram-negative bacilli is markedly superior to presently
available cephalosporins and, except forP. aeruginosa, is comparable to the aminoglycosides. 相似文献
935.
Expression of thymidylate synthetase activity in Bacillus subtilis upon integration of a cloned gene from Escherichia coli 总被引:6,自引:0,他引:6
The gene from Escherichia coli encoding thymidylate synthetase was cloned in the plasmid pBR322. The resulting chimeric plasmid, pER2, was effective in transforming both E. coli and Bacillus subtilis to thymine prototrophy. Uncloned linear E. coli chromosomal DNA was unable to transform thymine-requiring strains of B. subtilis to thymine independence. Linearization of the chimeric plasmid, pER2, with restriction enzymes markedly diminished its ability to transform B. subtilis auxotrophs. The Thy+ transformants derived from the transformation of B. subtilis with pER2 DNA did not contain detectable extrachromosomal DNA as demonstrated by Southern hybridization patterns and centrifugation in CsCl gradients of DNA isolated from B. subtilis colonies transformed with the chimeric plasmid. We conclude that the DNA from the chimeric plasmid was integrated into the chromosome of B. subtilis, demonstrating that extensive homology is not required for the integration of foreign DNA. This is the first reported case of a gene from a Gram-negative bacterium functioning in a Gram-positive organism. 相似文献
936.
937.
938.
Delano V. Young Michael C. Dean Peter Heit Stewart D. Chipman 《In vitro cellular & developmental biology. Plant》1980,16(11):949-957
Summary Simian virus 40-transformed 3T3 cells are dependent on serum for survival and growth. This growth activity can be separated
on a pH 2 Sephadex G100 column into two fractions: a high molecular weight activity and a low molecular weight substance that
has recently been characterized as containing as its major agent, biotin.
To replace the remainder of the serum requirement, hormones and other growth factors were tested. Both insulin at high, nonphysiological
concentrations (200 to 500 ng/ml) and transferrin (5×10−8
M) stimulate the growth rate in low serum medium (0.3% v/v bovine calf serum DME) individually and, when added together, are
nearly as growth enhancing as 10% serum.
The need for the residual serum in this medium can be eliminated by the use of crystalline trypsin during trypsinization.
Under these serum-free conditions, biotin and transferrin supplementation provide for moderately good growth (20 to 30 hr
population doubling time, 1×106 cells/3.2-cm dish final cell density). Insulin addition further stimulates the growth rate (16 to 20 hr) and the final density
(1.5×106 cells). Although the protein growth factors, EGF (0.5 to 1.0 ng/ml) and FGF (4 to 10 ng/ml), also appear to enhance growth
individually and additively, their effects are slight and very variable. Nevertheless, the complete serum-free medium (DME
supplemented with biotin, transferrin, insulin, EGF and FGF) yields growth comparable but still inferior to 10% serum supplementation
(14-versus 12-hr population doubling time, 1 to 2×106 versus 2 to 3×106 cells final cell density).
This work was supported by NIH Grant CA 20040. 相似文献
939.
940.
Allan Young 《Culture, medicine and psychiatry》1982,6(1):57-71
The previous issue of Culture, Medicine and Psychiatry (Vol. 5, N. 4) included my article When Rational Men Fall Sick: An Inquiry into Some Assumptions Made by Medical Anthropologists together with a series of comments. This paper consists of my replies to some of the commentators and a case study illustrating my points.My collaborators in this research were two physicians, Dr. Robert Like, of the Department of Family Practice of Case Western Reserve University and Dr. Rivka Plotkin of the Ben-Gurion University of the Negev (Israel). Also, I want to thank Avraham Blidstein for his invaluable assistance. 相似文献