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At least 685 records · Page 38Linked to original sources
PubMed1995

Rhizobial lipo-oligosaccharide nodulation factors: multidimensional chromatographic analysis of symbiotic signals involved in the development of legume root nodules.

Nod factors are a group of biologically active oligosaccharide signals that are secreted by symbiotically competent bacteria of the family Rhizobiaceae. Their biosynthesis is determined by rhizobial nodulation (nod) genes, and is specifically induced in response to flavonoids secreted from the roots of host leguminous plants. The biological activity of Nod factors on these host legumes dramatically mimics the early developmental symptoms of the Rhizobium-legume symbiosis including, amongst other effects, root hair deformations and nodule initiation. Structurally, all Nod factors are short oligomers of beta-1,4-linked N-acetylglucosamine residues [usually degree of polymerization (dp) 4 or 5] that are N-acylated on the distal glucosamine. This common 'core' structure may be modified by a number of species-specific substituents on the distal or reducing sugars. These modifications are governed by rhizobial host specificity nod genes. The biological activity of purified Nod factors mirrors this host specificity, indicating that the symbiotic host range of individual Rhizobium species is, at least partially, determined by the variety of Nod factors they are able to produce. Here we describe techniques that are universally applicable to the extraction, chromatographic separation and identification of Nod factors. We have applied these techniques to Nod factors from the broad-host-range species Rhizobium fredii USDA257 and Rhizobium spp. NGR234, and the more narrow-host-range Bradyrhizobium japonicum USDA110, and have identified a group of novel, relatively hydrophilic Nod factors from the NGR234 species that may have implications for Nod factor biosynthesis.

Antigens, Bacterial↗
PubMed2001

Ultrastructural studies on nodules induced by pyrimidine auxotrophs of Sinorhizobium meliloti.

Twenty three pyrimidine auxotrophs of Sinorhizobium meliloti Rmd201 were generated by random mutagenesis with transposon Tn5. On the basis of biochemical characters these auxotrophic mutants were classified into car, pyrC and pyrE/pyrF categories. All auxotrophs induced white nodules which were ineffective in nitrogen fixation. Light and electron microscopic studies revealed that the nodules induced by pyrC mutants were more developed than the nodules of car mutants. Similarly the nodules induced by pyrE/pyrF mutants had more advanced structural features than the nodules of pyrC mutants. The nodule development in case of pyrE/pyrF mutants was not to the extent observed in the parental strain. These results indicated that some of the intermediates and/or enzymes of pyrimidine biosynthetic pathway of S. meliloti play a key role in bacteroidal transformation and nodule development.

Medicago sativa↗
PubMed1997

Sequential functioning of Sym-13 and Sym-31, two genes affecting symbiosome development in root nodules of pea (Pisum sativum L.).

Two Fix- mutants of pea (Pisum sativum L.) which are unable to fix molecular nitrogen, E135f (sym-13) and Sprint-2Fix- (sym-31), were crossed to create the doubly homozygous recessive line, named RBT (sym-13, sym-31). The ultrastructural organization of nodules of the RBT line was compared with that of each of the two parental mutant lines and with the original wild-type genotypes of the cultivars Sparkle and Sprint-2. It was shown that the RBT line is similar to the mutant line Sprint-2Fix- in having abnormal symbiosome composition and bacteroids with relatively undifferentiated morphology. Because the phenotypic manifestation of the sym-31 mutant allele suppresses the phenotypic manifestation of the sym-13 mutant allele, it is concluded that the function of the gene Sym-31 (which is mutated in the Sprint-2Fix- line) is necessary at an earlier stage of symbiosome development than the gene Sym-13 (which is mutant in the E135f line).

Genes, Plant↗
PubMedDate not supplied

New tactile sensor techniques for localization of pulmonary nodules.

We developed a new method for thoracoscopically localizing pulmonary nodules using a tactile sensor. This sensor was originally designed to probe the hardness of an object, which is represented by changes in resonance frequency of the sensor (delta f: Hz). By moving over the lung surface, the sensor probe, introduced through a 10 mm trocar, was able to search for nodules within the pulmonary parenchyma thoracoscopically. When the sensor probe passed just above a nodule, which was harder than the adjacent tissue, a sudden sharp increase in the curve was observed. We have successfully utilized this method in 16 cases since August 1994. A representative case is that of a 68-year-old male who was admitted with an indeterminate nodule, demonstrated preoperatively in the left lung by chest computed tomography, which was localized with this technique and resected under thoracoscopic surgery.

Aged↗
PubMed2000

Development of mineralized nodules in fetal rat mandibular osteogenic precursor cells: requirement for dexamethasone but not for beta-glycerophosphate.

We have reported that a cell population obtained from fetal rat mandible with neutral protease (Pro I) has a unique differentiation sequence in which the elevation of alkaline phosphatase (ALPase), calcium accumulation, and collagen synthesis occurs simultaneously. In this report, we further characterized Pro I-released population of cells by studying the effect of dexamethasone (Dex) or beta-glycerophosphate (beta-GP) on the formation of bone nodules. The formation of bone nodules in Pro I-released population of cells (ProIRPC) was augmented by the addition of Dex (10(-7) M) from days 3 to 14, suggesting that Pro IRPC contained osteoprogenitor (OP) cells. A 24-hour pulse treatment of ProIRPC released population of cells with Dex on days 9 and 12 resulted in an increase in the number of nodules but treatment on days 3, 6, or 15 did not. The number of bone nodules formed in Pro IRPC pulse treated with Dex on day 9 was comparable with that in Pro IRPC treated with Dex from days 3 to 14. Dex caused an earlier elevation of ALPase, in which maximal expression was observed on day 10. beta-GP caused a prolonged elevation of ALPase, but did not affect the formation of bone nodules. Unlike Pro I-released population of cells, rat calvarial cells did not form mineralized nodules without beta-GP, and showed that a Dex-responsive period on bone nodule formation in rat calvarial cells was at preconfluency (days 0 and 1). Thus, it appeared that the Dex-induced differentiation of early OP cells in Pro IRPCs occurred during the limited period from day 9 to day 12. Pro IRPC was found to have an unique characteristic that bone nodule formation was not affected by beta-GP.

Alkaline Phosphatase↗
PubMed2000

The injection of nodules of Dupuytren's disease with triamcinolone acetonide.

Over a 4-year period 63 patients (75 hands) with Dupuytren's nodules were treated with a series of injections with the steroid triamcinolone acetonide directly into the area of disease. The purpose of this study was to determine whether intralesional injections of triamcinolone acetonide could produce softening and flattening in nodules of Dupuytren's disease as seen in the intralesional injections of hypertrophic scars and keloids. After an average of 3.2 injections per nodule 97% of the hands showed regression of disease as exhibited by a softening or flattening of the nodule(s). Although some patients had complete resolution of the nodules, most experienced definite but incomplete resolution of the nodules in the range of 60% to 80%. Although a few patients did not experience recurrence or reactivation of the disease in the injected nodules or development of new nodules, 50% of patients did experience reactivation of disease in the nodules 1 to 3 years after the last injection, necessitating 1 or more injections. The findings of this study indicate that the intralesional injection of nodules of Dupuytren's disease with triamcinolone acetonide may modify the progression of the disease.

Chronic Disease↗
PubMed1980

Changes in the outer cell wall of Rhizobium during development of root nodule symbiosis in soybean.

Treatment of soybean root nodule tissue with a nonionic detergent. Nonidet P-40, after aldehyde fixation, results in a selective solubilization of membranes. The cell wall membrane of bacteroids and of free-living Rhizobium is resistant to this treatment. Fragments of "extra" membrane present inside the membrane envelope enclosing the bacteroids are also resistant to the detergent and are morphologically similar to the outer membrane of the cell wall of Rhizobium grown in broth culture. These observations, along with electrophoretic profiles of detergent resistant membranes from nodules, free-living Rhizobium, and isolated nodule bacteroids, suggest that the Rhizobium cell wall membrane undergoes significant changes during establishment of the root nodule symbiosis.

Cell Membrane↗
PubMed2004

Development of ectopic roots from abortive nodule primordia.

The symbiotic phenotype of five Tn5-induced mutants of Rhizobium etli affected in different anabolic pathways (namely, gluconeogenesis and biosynthesis of lysine, purine, or pyrimidine) was analyzed. These mutants induced, on the root of Phaseolus vulgaris, a normal early sequence of morphogenetics events, including root hair deformation and development of nodule primordia. Later on, however, from the resulting root outgrowths, instead of nodules, one or more ectopic roots (spaced closely related and agravitropic) emerged. Therefore, this group of mutant was collectively called "root inducer" (RIND). It was observed that the RIND-induced infection threads aborted early inside the invaded root hair, and that the resulting abortive nodules lack induction of late nodulin genes. Moreover, experiments performed using a conditional mutant (a methionine-requiring invader) revealed that bacterial invasion plays a key role in the maintenance of the program of nodule development and, in particular, in the differentiation of the most specific symbiotic tissue of globose nodules, the central tissue. These data indicate that, in P. vulgaris, the nodule primordium is a root-specified pro-meristematic tissue.

Base Sequence↗
PubMedDate not supplied

Lisch nodules after trabeculectomy.

The development of Lisch nodules in an eye that had undergone trabeculectomy with mitomycin C is described. Complete ophthalmologic examinations and genetic testing of a 12-year-old boy were performed. Lisch nodules can develop after trabeculectomy without the systemic manifestations of neurofibromatosis type 1.

Child↗