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91.
The kinetics of asymbiotic nitrogenase activity in three strains of the actinomycete Frankia were studied. Decay rates for enzyme activity were determined by adding chloramphenicol to active acetylene-reducing cells and measuring the time required for all activity to cease. Synthesis rates were measured by bubbling oxygen through actively-reducing cells (which totally destroyed all activity) and then measuring the time required for activity to return to normal. Decay rates (t
1/2) for these three strains were approximately 30 to 40 min. Synthesis rates were slower and initial nitrogenase activities were recorded about 110 min (DDB 011610) or 210 min (DDB 020210 and WgCc1.17) after return to air-equilibrated cultures. Frankia strain WgCc1.17 showed a greater sensitivity to oxygen and nitrogenase activity was totally lost when cells were bubbled only with atmospheric concentrations of oxygen. The results presented here indicate that nitrogenase activity turnover time is relatively rapid, on the order of minutes rather than hours or days. However, regulation of nitrogenase activity will differ from one strain to another and asmmbiotic characterization will be useful for understanding nitrogenase regulation in the bacterial-plant symbiosis.Contribution no. 879 from the Battelle-Kettering Laboratory 相似文献
92.
C Manwell C M Baker 《Comparative biochemistry and physiology. B, Comparative biochemistry》1986,84(4):601-605
Electrophoretic resolution of the heterogeneity of sheep serum "leucine aminopeptidase" is greatly improved by the use of gradients of acrylamide polymer, together with enzyme localisation involving L-alanyl beta-naphthylamide and cobaltous ion. The improved resolution contradicts an earlier claim of the existence of only two patterns of individual variation in the heterogeneity of sheep serum "leucine aminopeptidase", with one pattern completely dominant to the other. While the sheep enzyme is unusual among mammalian serum "leucine aminopeptidases" in its complex heterogeneity, it does conform to the typical mammalian pattern of codominant individual variation. The complexity of sheep serum "leucine aminopeptidase" is useful in the study of sheep evolution. 相似文献
93.
Diane S. Herson Balkumar Marthi Mary Anne Payer Dr. Katherine H. Baker 《Current microbiology》1986,13(2):77-80
Direct microscopic enumeration ofEnterobacter cloacae with the acridine orange 2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyl tetrazolium chloride technique (AOINT) was compared with spread plate counts on nonselective media to establish the usefulness of the former technique in the enumeration of chlorine-stressed cells. Results indicate that the techniques are comparable when the organisms are not stressed. However, AOINT is more sensitive than are plate counts in the detection of chlorine-stressed cells. 相似文献
94.
Amino acid sequence homology between rat prostatic steroid binding protein and rabbit uteroglobin 总被引:2,自引:0,他引:2
M E Baker 《Biochemical and biophysical research communications》1983,114(1):325-330
Using a computer program designed to detect evolutionary relationships between proteins, I find that the polypeptide chain of rabbit uteroglobin has amino acid sequence homology with the C1 and C2 polypeptide chains of rat prostatic steroid binding protein. Using this finding I suggest several interesting approaches for studying the biology of these proteins. 相似文献
95.
Cowpea-type Rhizobium sp. strain 32H1 and Rhizobium japonicum USDA 26 and 110 grown on a glutamate-mannitol-gluconate agar medium showed increases in the number of pleomorphic cells coincident with their acetylene-reducing activity. Pleomorphs appeared to be inhibited in growth nonuniformly, because acetylene-reducing cultures were mixtures of rod, branched (V, Y, and T), and other irregularly shaped cells. In contrast, strain USDA 10 consistently failed to reduce acetylene, even though it also could grow and yield pleomorphic cells under various conditions. With minimal inhibitory supplements (5 micrograms per ml of medium) of nalidixic acid and novobiocin as cell division inhibitors, an increase in pleomorphic cells was observed, but the inhibited cultures displayed lower acetylene-reducing activity. A study of pleomorphic cells derived in different ways indicated that not all pleomorphs reduce acetylene. 相似文献
96.
Paul E. Baker Anita Hagemo Kenneth Knoblock J.P. Dubey 《Experimental parasitology》1983,55(3):320-330
Using a sensitive, economical, and reproducible microassay, the relationship of toxoplasma inhibiting factor to interleukin 2 has been examined. The assay developed took advantage of the observation that (1) Toxoplasma gondii tachyzoites replicated efficiently in the murine monocytic cell line, RAW 264; (2) treatment of RAW 264 cells with toxoplasma inhibiting factor prevented intracellular replication of the parasite to an extent similar to that observed with identical treatment of freshly isolated murine peritoneal exudate cells; and (3) [3H]uracil incorporation was an efficacious means to quantify replication (or inhibition of replication) of tachyzoites within the cell line. Although toxoplasma inhibiting factor and interleukin 2 were both present in the same lectin -and antigen-stimulated splenocyte supernatant fluids, results from microassays strongly suggested that the molecules were two distinct entities. 相似文献
97.
Longevity of Salmonella typhimurium in Tilapia aurea and water from pools fertilized with swine waste. 总被引:1,自引:1,他引:0 下载免费PDF全文
Salmonella typhimurium declined rapidly when inoculated into Tilapia aurea culture pools fertilized with fresh swine waste. Within the water column, a 95% decline of viable cells occurred during the first 6 h. Isolation of viable salmonellae was possible at 16 days post-inoculation, but not at 32 days. Similarly, salmonellae could be detected in the viscera and epithelium of T. aurea at 16 days, although not at 32 days. Salmonellae were not isolated from the fish flesh, nor was there evidence of septicemic infection. 相似文献
98.
Bacterial Activity Associated with the Decomposition of Woody Substrates in a Stream Sediment 下载免费PDF全文
Ground bark and heartwood from Alnus rubra and Pseudotsuga menziesii were added to a muddy sediment from a small Oregon stream and incubated in situ. Carbon dioxide and methane production rates were increased by all amendments, the biggest increase being shown with A. rubra wood. Except for sediment amended with A. rubra wood, nitrogen fixation rates from all treatments (including the control) were approximately 0.1 nmol/g per h throughout the 6-month study period. Contrary to expectations, neither bark had a noticeable adverse effect on microbial activity, but the A. rubra wood promoted nitrogen fixation. These results help to explain the faster rate of decomposition of A. rubra wood in water compared with that of P. menziesii described in the literature. The uptake kinetics of glucose (Vmax) did not follow the same pattern as gas evolution. 相似文献
99.
Identification of a monoclonal antibody that specifically recognizes corneal and skeletal keratan sulfate. Monoclonal antibodies to cartilage proteoglycan 总被引:25,自引:0,他引:25
Monoclonal antibodies were raised against proteoglycan core protein isolated after chondroitinase ABC digestion of human articular cartilage proteoglycan monomer. Characterization of one of the monoclonal antibodies (1/20/5-D-4) indicated that it specifically recognized an antigenic determinant in the polysaccharide structure of both corneal and skeletal keratan sulfate. Enzyme immunoassay analyses indicated that the mouse monoclonal IgG1 recognized keratan sulfate in native proteoglycan aggregate and proteoglycan monomer preparations isolated from hyaline cartilages of a wide variety of animal species (human, monkey, cow, sheep, chicken, and shark cartilage). The 1/20/5-D-4 monoclonal antibody did not recognize antigenic determinants on proteoglycan isolated from Swarm rat chondrosarcoma. This finding is consistent with several biochemical analyses showing the absence of keratan sulfate in proteoglycan synthesised by this tissue. A variety of substructures isolated after selective cleavage of bovine nasal cartilage proteoglycan (Heineg?rd, D., and Axelsson, J. (1977) J. Biol. Chem. 252, 1971-1979) were used as competing antigens in radioimmunoassays to characterize the specificity of the 1/20/5-D-4 immunoglobulin. Substructures derived from the keratan sulfate attachment region of the proteoglycan (keratan sulfate peptides) showed the strongest inhibition. Both corneal and skeletal keratan sulfate peptides as competing antigens in radioimmunoassays showed similar inhibition when compared on the basis of their glucosamine content. Therefore, the 1/20/5-D-4 monoclonal antibody appears to recognize a common determinant in their polysaccharide moieties. Chemical desulfation of the keratan sulfate reduced the antigenicity of the glycosaminoglycan. The antibody did not recognize determinants present in dermatan sulfate, heparin, heparin sulfate, or hyaluronic acid. 相似文献
100.
Heritable fragile sites on human chromosomes. X. New folate-sensitive fragile sites: 6p23, 9p21, 9q32, and 11q23 总被引:3,自引:1,他引:2 下载免费PDF全文
Four new folate-sensitive fragile sites are documented at 6p23, 9p21, 9q32, and 11q23. These have all been shown to be heritable except for the one at 9p21, which has been seen only in a single individual. As with the other autosomal fragile sites, these appear to be innocuous in heterozygotes. 相似文献