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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
4.
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
5.
In the last twenty-five years, young inflorescences, floral buds and individual floral organs of a number of species have been cultured in vitro. There is considerable variability in the requirement of plant growth regulators and nutritional factors for flower development of different species. This variability is compounded by the fact that the hormonal and nutritional requirements are different at various stages of organ and floral development. Experimental studies on normal and mutant flowers in vitro have provided insights into some of the regulatory processes in floral organogenesis. The potential use of the in vitro technique in elucidating the various mechanisms in flower development is stressed. 相似文献
6.
The intracellular growth of pathogenic mycobacteria has been linked to the presence of an electron transparent zone (ETZ or capsule), which surrounds the phagocytized bacteria and prevents the diffusion of lysosomal enzymes in infected macrophages. Recently, it was suggested that this capsule may be a bacterial structures, even being present in test tube-grown pathogenic mycobacteria (FEMS Microbiol. Lett. 1988, 56, 225-230). In the present paper, we show that under special fixation and embedding conditions, this capsule was clearly observed among 7 strains of mycobacteria grown in axenic media and also in M. leprae extracted and purified from experimentally infected armadillo or nude mice. In the case of bacteria treated likewise but subject to a prior dehydration step, this capsular structure disappeared suggesting its lipidic nature. Ultrathin sections of M. intracellular after immunolabelling showed for the first time that this capsule obtained mycobacterial antigens confirming its mycobacterial origin. It is suggested that the mycobacterial capsule may be formed of inert lipids, in which surface antigens are embedded. 相似文献
7.
Raymond Hellio Dr. Claude Fréhel Jean-Yves Rauzier Nalin Rastogi 《Current microbiology》1988,17(4):235-242
Cytochemical characterization of mycobacterial surfaces was carried out on virulent (H37Rv) and avirulent (H37Ra) strains ofMycobacterium tuberculosis. The results were quantified and compared with those obtained with three colony types of the opportunistic pathogenMycobacterium avium. Mycobacterium aurum, a rapidly growing, nonpathogenic species, served as a model for the cytochemical methods. Concanavalin A (ConA) reacted with -d-mannose and -d-glucose residues, whereas negative charged residues were detected with either the ionized ferritin (CF) or the colloidal ferric hydroxide (CIH) method. Strongly acidic sulfate groups were detected by their selective blockage with alcian blue (AB) at pH 1 prior to the CIH labeling at pH 1.8. Weakly acidic groups were demonstrated by AB blockage at pH 2.5 prior to staining with CF stain. Except forM. aurum, all other strains showed a marked heterogeneity in regard to the abundance of their surface labeling. Accessible sulfate groups were present on the cell surface of the virulent H37Rv strain ofM. tuberculosis, but not on the avirulent strain H37Ra. Distribution of ConA receptors, on the other hand, was unrelated to the virulence or pathogenicity of the bacterial strain. 相似文献
8.
We tested the mutagenic effects of two commonly used fold colors, metanil yellow and orange II, in AHH-1 human lymphoblast cells. The cell line, which is competent for oxidative metabolism of various chemicals, was exposed to both compounds in high-dose x short-term (3 day) or high-dose x long-term (10-day) and low-dose x long-term (20-day) treatments. Concentrations of metanil yellow and orange II as low as 22 nM and 12 nM, respectively, were sufficient to induce mutation rates which were equal to twice the spontaneous mutation rate at the HPRT locus in AHH-1 cells. 相似文献
9.
R Rastogi S Sharma N Anand A Dutta N Fatma R K Chatterjee A B Sen 《Journal of helminthology》1984,58(3):251-254
The synthesis and filaricidal activity of 1-iso-butoxycarbonyl-4-methylpiperazine against Litomosoides carinii in Sigmodon hispidus and Dipetalonema viteae in Mastomys natalensis is reported. At an intraperitoneal or oral dose of 3 mg/kg given for 6 days, the compound removed 91% of the circulating microfilariae but had no effect on adult L. carinii. However, it killed all microfilariae and adults of D. viteae at a subcutaneous dose of 50 mg/kg given for 6 days. The compound also possessed chemoprophylactic activity against the larvae of L. carinii and D. viteae at a dose of 30 and 50 mg/kg respectively. 相似文献
10.
The processing and collaborative assay of a reference endotoxin 总被引:7,自引:0,他引:7
H D Hochstein D F Mills A S Outschoorn S C Rastogi 《Journal of biological standardization》1983,11(4):251-260
A preparation of Escherichia coli bacterial endotoxin, the latest of successive lots drawn from bulk material which has been studied in laboratory tests and in animals and humans for suitability as a reference endotoxin, has been filled and lyophilized in a large number of vials. Details of its characterization, including stability studies, are given. A collaborative assay was conducted by 14 laboratories using gelation end-points with Limulus amebocyte lysates. Approximate continuity of the unit of potency with the existing national unit was achieved. The lot was made from the single final bulk but had to be freeze-dried in five sublimators. An assessment was therefore made for possible heterogeneity. The results indicate that the lot can be used as a large homogeneous quantity. The advantages of using it widely as a standard for endotoxins are discussed. 相似文献