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21.
Abstract A method using membrane filters of appropriate pore size, to selectively isolate actinomycetes from a mixed population of soil microorganisms, is described.
The method is based on the ability of actinomycetes to propagate and pass through the pores of filters while bacteria and fungi are retained on the membrane surface. 相似文献
The method is based on the ability of actinomycetes to propagate and pass through the pores of filters while bacteria and fungi are retained on the membrane surface. 相似文献
22.
Fc gamma receptor III induces actin polymerization in human neutrophils and primes phagocytosis mediated by Fc gamma receptor II. 总被引:5,自引:0,他引:5
J E Salmon N L Brogle J C Edberg R P Kimberly 《Journal of immunology (Baltimore, Md. : 1950)》1991,146(3):997-1004
Human polymorphonuclear leukocytes (PMN) express two classes of Fc gamma R: Fc gamma RII the 42-kDa receptor with a traditional membrane spanning domain and cytoplasmic tail and Fc gamma RIIIPMN the 50- to 80-kDa receptor with a glycosyl-phatidylinositol membrane anchor expressed on PMN. To explore the capacity of Fc gamma RIIIPMN to generate intracellular signals, we have analyzed the ability of Fab and F(ab')2 anti-Fc gamma R mAb to induce actin filament assembly, a prerequisite for motile behaviors. Multivalent ligation of Fc gamma RIIIPMN, independent of Fc gamma RII, results in an increase in F-actin content that is [Ca2+]i dependent. Multivalent ligation of Fc gamma RII also initiates actin polymerization but uses a [Ca2+]i-independent initial pathway. In addition to providing a mechanism for Fc gamma RIIIPMN triggered effector functions, the increase in F-actin and [Ca2+]i generated by Fc gamma RIIIPMN ligation also serves as a "priming" signal to modify PMN responses to other stimuli. Experiments using erythrocytes specifically coated with anti-Fc gamma RII Fab demonstrate that cross-linking of Fc gamma RIIIPMN with anti-Fc gamma RIII F(ab')2 enhances phagocytosis mediated by Fc gamma RII. Thus, Fc gamma RIIIPMN, a glycosyl-phosphatidylinositol anchored protein, may contribute directly to an intracellular program of actin assembly that may trigger and prime neutrophil effector functions. 相似文献
23.
Wayne Chris Hawkes Calvin C. Willhite Kimberly A. Craig Stanley T. Omaye Douglas N. Cox Wai Nang Choy Andrew G. Hendrickx 《Biological trace element research》1992,35(3):281-297
Forty pregnant long-tailed macaques were treated daily for 30 d with 0, 25, 150 or 300 μg selenium as L-selenomethionine/kg
body weight. Erythrocyte and plasma selenium and glutathione peroxidase specific activities, hair and fecal selenium, and
urinary selenium excretion were increased by and were linearly related to L-selenomethionine dose. Hair selenium was most
sensitive to L-selenomethionine dose, with an 84-fold increase in the 300 μg selenium/(kg-d) group relative to controls (r=0.917). Daily urinary selenium excretion (80-fold,r=0.958), plasma selenium (22-fold,r=0.885), erythrocyte selenium (24-fold,r=0.920), and fecal selenium (18-fold,r=0.911) also responded strongly to L-selenomethionine. Erythrocyte and plasma glutathione peroxidase specific activities increased
154% and 69% over controls, respectively. Toxicity was associated with erythrocyte selenium >2.3 μg/mL, plasma selenium >2.8
μg/mL, and hair selenium >27 μg/g. Plasma, erythrocyte, and hair selenium concentrations may be useful for monitoring and
preventing the toxicity of L-selenomethionine administered to humans in cancer chemoprevention trials. 相似文献
24.
E. coli chromosomal DNA wastreated with various Pt co-ordiantion compounds and then used as donor DNA in E. coli transformation. Genetic analysis of transformants obtained with Pt-treated DNA showed effects of cis-diamminedichloroplatinum(II) (cis-Pt(II)) and cis-dimethyl-1,3-diaminopropane CL4 (cis-Pt(IV) (DMDAP) on the processing of DNA. With trans-diamminedichloroplatinum(II) (trans-Pt(II)) appllied in similar concentrations no effects were found.The effects of cis-Pt(II) and cis-Pt(IV) (DMDAP) on the genetic processing were different. The effects of cis-Pt(II) could be explained by assuming intra-strand crosslinks as an important lesion. 相似文献
25.
A. Mazza A. Casale P. Sassone-Corsi S. Bonotto 《Biochemical and biophysical research communications》1980,93(3):668-674
Data are presented which show that a population of covalently closed minicircles, 0.1 to 1.5 μm long, represent, on a DNA length basis, approximately 0.5% of the total chloroplast genome of .With a frequency of about 50% minicircles appear to undergo DNA replication following the rolling circle model.The significance of these findings is discussed. 相似文献
26.
Effect of 6-(p-hydroxyphenylazo)-uracil on the homologous and heterologous transduction processes in Bacillus subtilis. 下载免费PDF全文
We have studied the effect of 6-(p-hydroxyphenylazo)-uracil on the recombination processes that operate in the homologous and heterologous transduction mediated by PBS1 and SP10 phages of Bacillus subtilis. The results obtained demonstrate that the process of heterologous genetic exchange is sensitive to this compound, whereas the homologous process is not. The present data, along with those of our previous work (U. Canosi, A. G. Siccardi, A. Falaschi, and G. Mazza, J. Bacteriol. 126:108--121, 1976), suggest that the DNA polymerase III is involved in the recombination process that operates in transformation and heterologous transduction, whereas homologous transduction follows a partially independent pathway not involving this protein. 相似文献
27.
Carmen Attolini Giorgio Mazza Adriana Fortunato Giovanni Ciarrocchi Giorgio Mastromei Silvano Riva Arturo Falaschi 《Molecular & general genetics : MGG》1976,148(1):9-17
Summary The dnaP strains of Bacillus subtilis are altered in the initiation of DNA replication at high temperature (Riva et al., 1975). Fine mapping of the gene shows that it is located very close to the dnaF gene, described by Karamata and Gross (1970) and mapped by Love et al. (1976) in the polC region. The phenotype of both mutants is indistinguishable: the DNA synthesis stops at non permissive temperature after synthesizing an amount of DNA equivalent to the completion of the rounds of replication already initiated; at permissive temperature they are abnormally sensitive to MMS and are reduced in the ability to be transformed. Both mutants are to be considered as belonging to the dnaF locus.The dnaF gene is very close to the polC gene, which specifies the DNA polymerase III of B. subtilis. The DNA polymerase III of the dnaF mutants is not temperature sensitive in vitro, however, the level of this enzyme is lower by a factor of 4 or 5 in the dnaF mutants, at the permissive temperature. Following shift of dnaF cultures to the non permissive temperature, the level of DNA polymerase III activity specifically decreases further by a factor of at least 10 in the mutant, whereas the DNA polymerase I level is unaffected.The possible roles of the dnaF gene in the control of the cellular level of the DNA polymerase III, and the possibility of a regulatory role of DNA polymerase III in the initiation of DNA replication in bacteria are discussed.Abbreviations and symbols HPUra
6-(p-hydroxyphenylazo)-uracil; mic, minimum inhibitory concentration
- MMS
methyl-methanesufonate
- Pol I
Pol II and Pol III: DNA polymerase I, II and III respectively
- PCMB
parachloro-mercuri-benzoate 相似文献
28.
29.
Anya N. Metcalfe Jeffrey D. Muehlbauer Theodore A. Kennedy Charles B. Yackulic Kimberly L. Dibble Jane C. Marks 《Freshwater Biology》2021,66(1):89-101
- Most of the world's large rivers are dammed for the purposes of water storage, flood control, and power production. Damming rivers fundamentally alters water temperature and flows in tailwater ecosystems, which in turn affects the presence and abundance of downstream biota.
- We collaborated with more than 200 citizen scientists to collect 2,194 light trap samples across 2 years and more than 2,000 river km. Samples contained 16,222 net‐spinning caddisfly (Hydropsyche) individuals across six species. We used these data to model the distribution of Hydropsyche throughout the Colorado River Basin in the western U.S.A. to identify the roles of water temperature, flows, and species‐specific morphology in determining aquatic species distributions throughout a large arid watershed that has been heavily altered by damming.
- We predicted that water temperatures would determine Hydropsyche presence and abundance to a greater extent than diel variation in river stage associated with hydropower production. Among many species, adult female Hydropsychids are morphologically adapted to swim to deep‐water oviposition sites. We predicted that the presence of this ability would negate the otherwise deleterious effects of high stage change on caddisfly egg mortality.
- We found that distributions of the two most widespread species, Hydropsyche occidentalis and Hydropsyche oslari (92% of total Hydropsyche captured), were both predicted by water temperatures. However, we also found that the abundance of H. oslari decreased by as much as 10‐fold as diel stage change increased, despite the presence of female morphological adaptations for deep‐water oviposition. We found sexual dimorphism and evidence for deep‐water swimming adaptations in 5/6 species.
- Our results show that net‐spinning caddisflies have species‐specific responses to environmental variation and suggest that environmental flows designed to reduce diel stage change and destabilise water temperatures may improve habitat quality for these ubiquitous and important aquatic insects.
30.