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1.
Indirect evidence suggests that legumes can adjust rapidly theresistance of their root nodules to O2 diffusion. Here we describeexperiments using O2 specific micro-electrodes and dark fieldmicroscopy to study directly the operation of this diffusionbarrier. The O2 concentration sensed by the electrode decreasedsharply in the region of the inner cortex and was less than1.0 mmol m3 throughout the infected tissue in nodulesof both pea (Pisum sativum) and french bean (Phaseolus vulgaris).In a number of experiments the ambient O2 concentration wasincreased to 40% while the electrode tip was just inside theinner cortex. In 13 out of 21 cases the O2 concentration atthis position either remained low and unchanged or increasedirreversibly to near ambient values. In the remaining casesthe O2 concentration increased after 1 to 2.5 min and then decreasedto its former value. These results are ascribed to an increasein resistance of the barrier in response to increased O2 fluxinto the nodule. It was shown microscopically that air spacesboth at the boundary between the infected zone and the innercortex, and within the infected zone started to disappear 3min after nodules were exposed to high ambient O2 concentrationsand had disappeared completely after 8 min. These spaces werenot changed by exposure of the nodule for 10 min to either N2or air. Key words: Oxygen, root nodules, air spaces 相似文献
2.
Evolution of the 28S ribosomal RNA gene in anurans: regions of variability and their phylogenetic implications 总被引:1,自引:0,他引:1
Fifteen restriction sites were mapped to the 28S ribosomal RNA gene of
individuals representing 54 species of frogs, two species of salamanders, a
caecilian, and a lungfish. Eight of these sites were present in all species
examined, and two were found in all but one species. Alignment of these
conserved restriction sites revealed, among anuran 28S rRNA genes, five
regions of major length variation that correspond to four of 12 previously
identified divergent domains of this gene. One of the divergent domains
(DD8) consists of two regions of length variation separated by a short
segment that is conserved at least throughout tetrapods. Most of the
insertions, deletions, and restriction-site variations identified in the
28S gene will require sequence-level analysis for a detailed reconstruction
of their history. However, an insertion in DD9 that is coextensive with
frogs in the suborder Neobatrachia, a BstEII site that is limited to
representatives of two leptodactylid subfamilies, and a deletion in DD10
that is found only in three ranoid genera are probably synapomorphies.
相似文献
3.
Purification and characterization of microsomal glutathione S-transferase produced by Aspergillus ochraceus TS are reported. The isozymes are located in microsomes and were active against 1-chloro-2,4-dinitrobenzene, ethacrynic acid, 1,2-dichloro-4-nitrobenzene, trans-4- phenyl-3-buten-2-one,p-nitrobenzyl chloride and bromosulphophthalein. They were inhibited by N-ethylmaleimide and bromosulphophthalein. The GST isozymes produced by Aspergillus ochraceus TS are indistinguishable in respect of their molecular mass both in native and denatured state. The subunit of the purified protein had an apparent Mr of 11 kDa while molecular mass of the native protein is around 56 kDa. The substrate specificity and pl values of the isozymes were different. The GSTs produced by Aspergillus ochraceus TS fairly share functional properties with mammalian cytosolic isozymes. 相似文献
4.
We have expressed human tissue plasminogen activator (t-PA) gene at high levels in a mouse cell line. The t-PA cDNA with deletion of the long 3' untranslated region was inserted into a bovine papilloma virus (BPV) derived vector under the control of a mouse metallothionein promoter. The mouse metallothionein (mMT) gene also provided signals for splicing and polyadenylation. Mouse C127 cells transfected with this construct secreted t-PA at high levels into the cell culture medium. When an SV40 polyadenylation signal was inserted between the t-PA cDNA and the mMT splicing signals, the expression level increased by several fold. The expression levels did not increase further upon either introduction of Rous sarcoma virus LTR into the plasmid or mutation of the translation initiation context sequence to conform with the consensus one. Most of the plasmid appears to be integrated into the host chromosome. Cells producing high levels of t-PA tend to detach from the dish in a few days after passage. When grown on porous microcarriers, however, such cells can be maintained in culture for months and t-PA can be harvested continuously. 相似文献
5.
6.
Effects of exogenous 1,3-diaminopropane and spermidine on senescence of oat leaves : I. Inhibition of protease activity, ethylene production, and chlorophyll loss as related to polyamine content 总被引:3,自引:3,他引:0 下载免费PDF全文
Excision and dark incubation of oat (Avena sativa L., var. Victory) leaves cause a sharp increase in protease activity, which precedes Chl loss. Both these senescence processes are inhibited by exogenously applied 1,3-diaminopropane (Dap), which occurs naturally in leaf segments. The inhibition of protease activity is much greater in vivo than in vitro, suggesting inhibition of protease synthesis as well as protease action by Dap. Chl breakdown in leaves of radish and broccoli, which also senesce rapidly in the dark, is only slightly inhibited by DaP. These differences between cereal and dicotyledonous plants are correlated with the natural occurrence of Dap in cereals. In the light, Dap promotes, rather than retards, the loss of Chl in oat leaves. This resembles previously described effects of other polyamines. Addition of Mg2+ to the medium does not antagonize this effect. In the dark, the accumulated Dap also inhibits ethylene production and decreases titer of other polyamines. Addition of Ca2+ to the incubation medium containing Dap competitively reduces the effects of Dap. Thus, Dap, like other polyamines, seems to require an initial attachment to a membrane site shared with Ca2+ before exerting its antisenescence action. 相似文献
7.
The treatment of Ehrlich ascites tumor cells with mouse interferon increases the level of the latent enzyme (2'-5')(A)n synthetase. If activated by double-stranded RNA, this catalyzes the synthesis from ATP of a series of 2'-5'-oligoadenylates: (2'-5')(A)n where n extends from 2 to about 15. We isolated (2'-5')(A)n synthetase in a homogeneous state. In the presence of double-stranded RNA, the purified enzyme can convert the large majority (about 97%) of the ATP into (2'-5')(A)n and pyrophosphate, although it does not cleave the pyrophosphate. The stoichiometry of the reaction can be formulated as: (n + I) ATP leads to (2'-5') pppA(pA)n + n pyrophosphate. Added pyrophosphate does not inhibit the synthesis of (2'-5')(A)n. The extent of the reverse reaction, i.e. the pyrophosphorolysis of (2'-5')(A)n, was below the level of detection under our conditions. The affinity of the enzyme for ATP is low: the rate of the reaction increases by about 10% when the concentration of ATP is increased from 5 mM to 10 mM. The optimal concentration of double-stranded RNA increases with the concentration of the enzyme. As tested at 0.4, 2, and 10 micrograms/ml of enzyme concentrations, close to maximal (2'-5')(A)n synthesis can be obtained if reovirus double-stranded RNA or poly(I) . poly(C) are used at about half the concentration (in w/v) of the enzyme. The plot of the reaction rate versus enzyme concentration is sigmoidal. It remains to be seen if this reflects on a cooperative behavior of the enzyme. 相似文献
8.
Sushmita Sadangi Arpita Mohanty Mahismita Paichha Mrinal Samanta 《Journal of fish biology》2020,96(3):580-589
Mitogen-activated protein kinases (MAPKs) are crucial Ser/Thr protein kinases that play important roles in innate immunity by converting extracellular stimuli into a wide range of cellular responses, including the production of cytokines. In this study, two MAPK genes, jnk1 and erk1, were cloned and characterized in rohu (Labeo rohita), a commercially important freshwater fish species in the Indian subcontinent. In healthy rohu, both jnk1 and erk1 gene expressions were highest in the spleen as compared to gill, liver, blood and kidney tissues. In vitro stimulation of the L. rohita gill (LRG) cell line with γ-D-glutamyl-meso-diaminopimelic acid, muramyl dipeptide and polyinosinic: polycytidylic acid (poly I:C) resulted in significantly enhanced expressions of jnk1 and erk1 genes. In the in vivo experiments, jnk1 and erk1 gene expressions were also enhanced in lipopolysaccharides and poly I:C-treatment. Infection of rohu fingerlings with Aeromonas hydrophila and Bacillus subtilis revealed significantly enhanced expressions of the jnk1 and erk1 genes in all of the tested organs/tissues. Together these results imply the important role of jnk1 and erk1 genes in fish during pathogenic invasion and diseases. 相似文献
9.
Chakkiyath Madayi Roshith Ranjan Kumar Manna Vettath Raghavan Suresh Srikanta Samanta Raju Baitha Satish K. Koushlesh Sibina Mol Salim Lohith Kumar Shravan Kumar Sharma Ashis Roychowdhury Muttanahalli Eregowda Vijayakumar Rakesh Pal Basanta Kumar Das 《Zeitschrift fur angewandte Ichthyologie》2021,37(5):795-798
The present study estimated length–weight relationships (LWRs) for six indigenous fish species (Barilius gatensis, Salmostoma acinaces, S. boopis, Puntius amphibius, Hemibagrus punctatus and Ambassis miops) based on specimens collected from River Cauvery (including estuary) during July 2017–January 2020. The sampling surveys were carried out in three distinct sampling seasons, viz., the pre-monsoon (March–May), the monsoon (July–October) and the post-monsoon (November–February). Majority of the fish specimens dealt in the study were collected from multi-meshed monofilament gill nets (mesh sizes 18, 30, 45, 60, 90, 110, 120 and 150 mm) operated by local fishers. For those sites situated in the protected areas, sampling was carried out by cast nets with prior permission from the local administration and the collected fishes were released back into river after length–weight measurements. The length measurements were noted as total length (TL) measured to the nearest 0.1 cm by using a digital Vernier caliper. A digital balance was used for weight measurements with an accuracy of 0.01 g. The study recorded a new maximum length of 48 cm for H. punctatus. The LWR data generated from the present study are significant for proper assessment of the stock status and their management, if collected together with other essential biological and physical parameters. 相似文献
10.
Tumor infiltrating lymphocytes (TIL), especially T-cells, have both prognostic and therapeutic applications. The presence of CD8+ effector T-cells and the ratio of CD8+ cells to FOXP3+ regulatory T-cells have been used as biomarkers of disease prognosis to predict response to various immunotherapies. Blocking the interaction between inhibitory receptors on T-cells and their ligands with therapeutic antibodies including atezolizumab, nivolumab, pembrolizumab and tremelimumab increases the immune response against cancer cells and has shown significant improvement in clinical benefits and survival in several different tumor types. The improved clinical outcome is presumed to be associated with a higher tumor infiltration; therefore, it is thought that more accurate methods for measuring the amount of TIL could assist prognosis and predict treatment response. We have developed and validated quantitative immunohistochemistry (IHC) assays for CD3, CD8 and FOXP3 for immunophenotyping T-lymphocytes in tumor tissue. Various types of formalin fixed, paraffin embedded (FFPE) tumor tissues were immunolabeled with anti-CD3, anti-CD8 and anti-FOXP3 antibodies using an IHC autostainer. The tumor area of stained tissues, including the invasive margin of the tumor, was scored by a pathologist (visual scoring) and by computer-based quantitative image analysis. Two image analysis scores were obtained for the staining of each biomarker: the percent positive cells in the tumor area and positive cells/mm2 tumor area. Comparison of visual vs. image analysis scoring methods using regression analysis showed high correlation and indicated that quantitative image analysis can be used to score the number of positive cells in IHC stained slides. To demonstrate that the IHC assays produce consistent results in normal daily testing, we evaluated the specificity, sensitivity and reproducibility of the IHC assays using both visual and image analysis scoring methods. We found that CD3, CD8 and FOXP3 IHC assays met the fit-for-purpose analytical acceptance validation criteria and that they can be used to support clinical studies. 相似文献