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Using steady-state relaxation spectrophotometric technique a P700 component () has been detected which was sensitized by low concentration (10?7M) DCMU in isolated broken chloroplasts of pea. The relative quantum yield of electron flux through DCMU-sensitized P700 was similar to that with methyl viologen or NADP as terminal electron acceptor and water as electron donor. Kinetic analysis showed that a small fraction (10%) of the total P700 reaction centers was sensitized by low DCMU. 相似文献
44.
Mycobacillin non-producers, whether sporogenous or asporogenous, possess less exoprotease, but effective exoprotease producers are not always good mycobacillin yielders. There might exist a minimum level of exoprotease formation for elaboration of mycobacillin. 相似文献
45.
Splenic lymphocytes from chickens infected with reticuloendotheliosis virus (REV) are cytostatically impaired in their ability to undergo mitogen-induced blastogenesis ([3H]TdR uptake and proliferation), but are fully capable of eliciting cytotoxic reactions against allogeneic, 51Chromium-labeled chicken erythrocytes. Spleen cells from birds with reticuloendotheliosis (REs) are able to suppress DNA synthesis of normal splenic lymphocytes (Ns), but are unable to inhibit 1[3H]TdR uptake by chick embryo fibroblasts. The suppression of the Ns mitogenic response is not restricted by major histocompatibility (B-locus) differences between populations of REs suppressor and Ns target cells. Moreover, infection of birds with an attenuated form of REV, which replicates in the host but does not cause tumorigenesis, also leads to suppression of phytohemagglutinin-induced, [3H]TdR uptake by host lymphocytes. These results are discussed in terms of the interaction between viral-infected/transformed cells and host defense mechanisms. 相似文献
46.
The polypeptides of reticuloendotheliosis virus (REV) were separated by gel filtration in the presence of guanidine hydrochloride. The eight peaks obtained by gel filtration were then analyzed by polyacrylamide gel electrophoresis and four appeared to contain single polypeptides. The material identified as p29 was used to prepare antiserum. This protein constitutes the major internal non-glycosylated polypeptide in the virion. Double immunodiffusion indicated that the antiserum was specific for p29. Using this antiserum, cross-reactivity was demonstrated between REV, chick syncytial virus, duck infectious anemia virus, and spleen necrosis virus. Antiserum to p29 failed to cross-react with Rous sarcoma virus. This indicates that p29 is a group-specific antigen shared by the viruses of the REV complex. A microcomplement fixation test was developed with this antiserum that will be useful in the quantitation of REV and the identification of other members of this newly defined group. 相似文献
47.
Apparent dispensability of the carbohydrate moiety of human interferon for antiviral activity. 总被引:1,自引:0,他引:1
S Bose D Gurari-Rotman U T Ruegg L Corley C B Anfinsen 《The Journal of biological chemistry》1976,251(6):1659-1662
Human leukocyte and tritium-labeled fibroblast interferons, prepared by induction with Sendai virus and with double-stranded polyinosinic acid.polycytidylic acid respectively, have been studied in relation to the carbohydrate moieties attached to them. These interferons were partially purified by immunoabsorbance and by gel filtration. On treatment with glycosidases, about 80% of the 3H-labeled sugar moieties in this glycoprotein-containing fraction was removed without detectable alteration of the antiviral activity or antibody-binding properties characteristic of interferon. The molecular weight of leukocyte interferon was reduced by about 4000. As others have reported, the heterogeneous character of interferon revealed by isoelectric focusing was greatly reduced by the enzyme treatment. 相似文献
48.
Arun K. Bose Arthur Gessler Andreas Bolte Alessandra Bottero Allan Buras Maxime Cailleret J. Julio Camarero Matthias Haeni Ana‐Maria Here Andrea Hevia Mathieu Lvesque Juan C. Linares Jordi Martinez‐Vilalta Luis Matías Annette Menzel Raúl Snchez‐Salguero Matthias Saurer Michel Vennetier Daniel Ziche Andreas Rigling 《Global Change Biology》2020,26(8):4521-4537
Global climate change is expected to further raise the frequency and severity of extreme events, such as droughts. The effects of extreme droughts on trees are difficult to disentangle given the inherent complexity of drought events (frequency, severity, duration, and timing during the growing season). Besides, drought effects might be modulated by trees’ phenotypic variability, which is, in turn, affected by long‐term local selective pressures and management legacies. Here we investigated the magnitude and the temporal changes of tree‐level resilience (i.e., resistance, recovery, and resilience) to extreme droughts. Moreover, we assessed the tree‐, site‐, and drought‐related factors and their interactions driving the tree‐level resilience to extreme droughts. We used a tree‐ring network of the widely distributed Scots pine (Pinus sylvestris) along a 2,800 km latitudinal gradient from southern Spain to northern Germany. We found that the resilience to extreme drought decreased in mid‐elevation and low productivity sites from 1980–1999 to 2000–2011 likely due to more frequent and severe droughts in the later period. Our study showed that the impact of drought on tree‐level resilience was not dependent on its latitudinal location, but rather on the type of sites trees were growing at and on their growth performances (i.e., magnitude and variability of growth) during the predrought period. We found significant interactive effects between drought duration and tree growth prior to drought, suggesting that Scots pine trees with higher magnitude and variability of growth in the long term are more vulnerable to long and severe droughts. Moreover, our results indicate that Scots pine trees that experienced more frequent droughts over the long‐term were less resistant to extreme droughts. We, therefore, conclude that the physiological resilience to extreme droughts might be constrained by their growth prior to drought, and that more frequent and longer drought periods may overstrain their potential for acclimation. 相似文献
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50.
Ishan Agarwal Sayantan Biswas Aaron M. Bauer Eli Greenbaum Todd R. Jackman Anslem De Silva 《分类学与生物多样性》2013,11(5):427-439
We evaluated the status of 16 of 22 recognized Sri Lankan Cnemaspis Strauch species, and flagged overlooked diversity with two mitochondrial (cyt b & ND2) and two nuclear markers (RAG1 & PDC) totalling 2829 base pairs. A fossil-calibrated timetree and sampling of other South Asian Cnemaspis provide insights into the diversification of the genus in peninsular India and Sri Lanka. Phylogenetic analyses consistently inferred two broad clades within South Asian Cnemaspis, with Sri Lankan species in two clades, which we call the podihuna and kandiana clades. Each Sri Lankan clade as a whole is sister to Indian taxa and nested within Indian lineages. Cnemaspis modigliani Das from Indonesia is a member of the kandiana clade. This suggests a minimum of two dispersal events between India and Sri Lanka and one between Sri Lanka/India and South-east Asia. South Asian Cnemaspis date back to at least the Eocene, in Sri Lanka to the early Miocene, with late Miocene diversification in the kandiana clade. All but one of the named species we sampled is likely to be valid, and 10 divergent unnamed lineages may warrant specific recognition. A resolution of Sri Lankan Cnemaspis taxonomy will require thorough sampling and the use of both morphological and molecular data. 相似文献