Oligogalacturonides stimulate pericycle cell wall thickening and cell divisions leading to stoma formation in tobacco leaf explants

Novel developmental events induced by micromolar concentrations of oligogalacturonides (OGs) in tobacco leaf explants cultured in vitro are described. Oligogalacturonides induced acceleration and synchronization of the mitotic activity of guard-cell precursors in the epidermis. In explants cultured for 24 h in the presence of OGs, the number of stomatal mitoses was higher than that observed in explants cultured in the absence of OGs; however, at the end of the culture period the density of mature stomata did not vary upon OG treatment. The OG-induced activation of stomatal mitosis was reduced by exogenously added indole-3-acetic acid (IAA). Oligogalacturonides also enhanced mean wall thickness, mainly due to cellulose deposition, of foliar pericycle cells, as well as the number of extra-thick-walled pericycle cells; the pericycle thus formed a sheath surrounding phloem and xylem. Indole-3-acetic acid decreased the number of extra-thick-walled cells forming in the presence of OGs but did not influence wall thickness. Moreover, OGs inhibited the stimulation of mitotic activity of phloem parenchyma cells (vascular mitoses) induced by auxin, leading to a nearly complete inhibition of IAA-induced formation of callus and of meristemoids of indirect origin. Instead, OGs did not influence mitotic activity occurring in the absence of auxin. All in all, our results provide further evidence of the pleiotropic role exerted on plant development by these oligosaccharins, and of the antagonism between auxin and OGs. Received: 4 March 1997 / Accepted: 15 July 1997     

Production of polysaccharides by Arthrobacter globiformis associated with Anabaena azollae in Azolla leaf cavity

Abstract The composition of the capsular polysaccharides (CPS) and exopolysaccharides (EPS) of three strains of Arthrobacter globiformis , isolated from the leaf cavities of Azolla caroliniana (strain B1), A. filiculoides (strains A3 and L1) and A. globiformis ATCC 8010 have been analysed by HPLC and enzymatic assays. Glucose and galactose were detected in the EPS of all the strains, while rhamnose was present only in the EPS of the strain L1 and uronic acids in B1 and ATCC 8010. Traces of fructose were detected by enzymatic assays in all the strains. The CPS contained glucose, galactose and rhamnose, while uronic acids were present only in strain B1. In all the strains the amount of EPS was higher than CPS. The reactivity to different dyes and lectins of the mucilagineous matrix of the algal packets extracted from the fern and of the bacterial mucilage were similar.     

Redox thermodynamics of mutant forms of the rubredoxin from Clostridium pasteurianum: identification of a stable FeIII(S-Cys)3(OH) centre in the C6S mutant

Redox thermodynamic data provide a detailed insight into control of the reduction potential E degrees' of the [Fe(S-Cys)4] site in rubredoxin. Mutant forms were studied in which specific structural changes were made in both the primary and secondary coordination spheres. Those changes have been probed by resonance Raman spectroscopy. The decrease of approximately 200 mV in E degrees' observed for the [Fe(S-Cys)3(O-Ser)]-/2- couples in the surface ligand mutants C9S and C42S is essentially enthalpic in origin and associated with the substitution of ligand thiolate by ligand olate. However, the pH dependence of the potentials below characteristic pKa(red) approximately equals 7 is an entropic contribution, plausibly associated with increased conformational flexibility induced by a longer Fe(II)-O(H)-Ser bond in the reduced form. The presence of a second surface Ser ligand in the new double mutant protein C9S/C42S affects the enthalpic term primarily for pH>pKa(red) > or = 9.3, but for pHpKa approximately 9: [Fe(III)(S-Cys)3(OH)]- + e- --> [Fe(II)(S-Cys)3(OH)]2-. pH [Fe(II)(S-Cys)3(OH2)]-.     

Echocardiographic alterations in a child with cow's milk allergy: a case report

ABSTRACT: INTRODUCTION: Cow's milk allergy is the most frequent food allergy in Europe and western countries and shows a wide spectrum of clinical features, including atopic dermatitis and gastrointestinal disease. To the best of our knowledge, this report is the first to describe Kawasaki disease-like clinical features and echocardiographic alterations which resolved after a cow's milk-free diet. CASE PRESENTATION: We report a case of a 9-month-old Caucasian girl with atopic dermatitis who developed clinical features commonly present in Kawasaki disease (erythematous skin rash, non-exudative conjunctivitis, fissured lips and neck lymph nodes), together with mild echocardiographic alterations (perivascular brightness, pericardial effusion) in the absence of fever. These features resolved within 2 weeks after the beginning of a cow's milk-free diet. CONCLUSION: Kawasaki disease has recently been considered a possible risk factor for subsequent allergic disease secondary to immune dysfunction. This case report suggests that the immune-related alterations which are commonly present in allergic patients could be similar to the antigen-related immune response in Kawasaki disease and thus could lead to similar clinical features.     

Induction of CAD gene amplification by restriction endonucleases in V79,B7 Chinese hamster cells

The restriction endonucleases PvuII, BamHI and EcoRI were tested for their ability to induce gene amplification in V79,B7 Chinese hamster cells. The results indicate that treatment with these enzymes efficiently increases the frequency of clones resistant to N-phosphonacetyl-L-aspartate, indicating induction of CAD gene amplification.     

Rainbow trout red cells in vitro

Washed rainbow trout erythrocytes incubated at 14 degrees C in Eagle's minimal essential medium and Cortland saline displayed sharp reductions in volume and water content, nucleoside triphosphate, K+ and Cl- concentrations. Mg2+ and, to a lesser extent, Na+ concentrations increased. Cellular to medium Cl- ratios were indicative of membrane hyperpolarization. Morphological irregularities were also observed. Oxygen consumption and hemoglobin system organization were not grossly affected. Supplementation with pyruvate stabilized nucleoside triphosphate concentrations for at least 24 hr, and reduced rates of volume and compositional change to some extent. Addition of norepinephrine at physiologically realistic levels led to stabilization of Cl- content and reductions in Mg2+ accumulation and water loss. Transient but modest increases in K+ and Ca2+ were coupled, under these circumstances, with some decrease in Na+ concentration. Factors which may contribute to the dysfunctional status of these cells in vitro are discussed.