Effects of glyphosate on phenolic metabolism in yellow nutsedge leaves

The action of the herbicide glyphosate [N-(phosphonomethyl)-glycine] on phenolic metabolism and phenylalanine ammonia lyase (PAL; EC 4.3.1.5) activity was investigated in yellow nutsedge (Cyperus esculentus L.). Glyphosate caused significant increases in the amount of total soluble hydroxyphenolics in the three fractions studied (neutral, acid and residual). Qualitative and quantitative differences in relation to these fractions and the amount of applied glyphosate were observed. Most of the phenolic compounds which increased after glyphosate treatment were benzoic acids (gentisic. p -OH-benzoic, salicylic and vanillic). Gentisic acid showed the greatest increase in neutral and acid fractions, being twenty- and four-fold, respectively, of the amount found in the control. PAL activity was not affected by the lowest doses of glyphosate (10−⁴and 10−³ M) , but a dramatic decrease in PAL activity was observed after 10−² M treatment. These findings, together with the low levels of cinnamic acids measured in treated yellow nutsedge plants, suggest that PAL activity is only marginally involved in glyphosate action. Since the herbicidal action probably takes place at 5-enol-pyruvylshikimate-3-P synthase (EC 2.5.1.19), an alternative pathway to PAL in phenolic biosynthesis should be activated yielding benzoic acids.     

Cultivar and Rhizobium strain effect on nitrogen fixation and transport inPhaseolus vulgaris L.

The effects of Rhizobium strain and its interaction with plant cultivar were examined in glasshouse-grownPhaseolus vulgaris in two experiments where the physiological attributes defining the symbiotic efficiency were determined. Strains of Rhizobium significantly affected nodulation, rates of N accumulation, partitioning of N within the mature shoot and remobilizaton of the N stored in the vegetative organs to the seeds. The most efficient symbiosis (strain CO5 with Negro Argel), in comparison with the least efficient symbiosis (strain 127 K-17 with Venezuela-350) showed higher rates of C₂H₂ reduction from flowering to mid pod fill stage, evolved less hydrogen from nodules and showed higher rates of N transport as well as higher percentages of ureide-N in the xylem sap. At maturity, the best cultivar/strain association exceeded the total N accumulated in the seed and the harvest index of the poorest symbiosis in 88% and 20%, respectively. The other symbiotic combinations were intermediate in all characteristics. Nitrogen accumulation in plant shoot showed highly significant correlation with acetylene reduction rates, nodule relative efficiency, total N transport in the xylem sap and percentage of N transported as ureides.     

The accessibility of DNA to dimethylsulfate in complexes with recA protein.

recA protein coats DNA co-operatively to form filaments approximately 100 A thick, which in the presence of ATP, and more stably so in the presence of the non-hydrolyzable analog ATP gamma S, have a helical appearance with a deep cleft in the protein coat. This protein helix follows the DNA helix, to which it imparts a new helicity of 18.5 bp per turn of 97 A pitch. Here we test the accessibility of the DNA in the complex to modification by dimethylsulfate, and find that the complexed DNA is approximately 2-fold more reactive on the major groove side than it was in B-DNA (methylation of guanine N7), while it is protected approximately 2-fold on the minor groove side (methylation of adenine N3), suggesting that the protein coats the DNA along the minor groove. Furthermore, N3 of cytosine, a residue involved in base pairing, is found exposed in complexes with single strands as it is in naked single-stranded DNA, while it remains inaccessible in complexes with double strands, suggesting that the latter is not melted at this stage of the strand exchange reaction.     

Effect of cytochalasins on cytosolic-free calcium concentration and phosphoinositide metabolism in leukocytes

Cytochalasins are routinely used to stimulate a variety of functions in eukaryotic cells even though their precise mode of action remains to be elucidated. In the present work we used the fluorescent Ca2+ indicator quin2 to study the effect of various cytochalasins, cytochalasins A, B, C, D, E (CA, CB, CC, CD, CE) and dihydrocytochalasin B (dhCB) on the intracellular Ca2+ concentration ([Ca2+]i) in various types of leukocytes, viz, neutrophils and lymphocytes. In human neutrophils, cytochalasins increase [Ca2+]i mainly by releasing Ca2+ from membrane-bound, intracellular stores. Thus, in order to readily appreciate the effect of cytochalasins on [Ca2+ )i, these cells must be loaded with low intracellular quin2 concentrations. On the other hand, in peripheral blood lymphocytes, splenocytes and thymocytes, the increase in [Ca2+]i is predominantly due to an increased Ca2+ influx from the extracellular medium. In addition, we found that in neutrophils these drugs prolong the increase in [Ca2+]i induced by chemotactic peptides, probably by increasing the cell permeability to Ca2+. Finally, in thymocytes, cytochalasins potentiate the production of inositol phosphates induced by the polyclonal mitogen concanavalin A (conA).     

Differentiation-related changes of cytokeratin expression in cultured keratinocytes and in fetal, newborn, and adult epidermis

Cytokeratin expression in differentiating cultured foreskin keratinocytes was studied using chain-specific anti-cytokeratin monoclonal antibodies directed against cytokeratins 4, 8, 10, 13, 18, and 19, respectively. Keratinocytes were cultured at low Ca2+ concentration (0.06 mM) to repress differentiation. At confluency, the cells were switched to high Ca2+ concentration (1.6 mM) to induce differentiation. Cells were harvested 0, 3, 8, 16, 24, 48, and 72 h after the switch. Keratinocytes cultured throughout at high Ca2+ concentration were also harvested. Immunoblots of cytokeratin preparations isolated from these cultures showed that cytokeratins 4, 13, and 19 were not present in nondifferentiating keratinocytes but could be detected from about 16 h after the Ca2+ switch. Immunohistochemical studies were performed on frozen sections of cell sheets incubated with anti-cytokeratin and anti-vimentin. Expression of cytokeratins 4, 13, and 19 was seen in superficial cells. Cytokeratin 10 was locally present in suprabasal and superficial cells. Vimentin was present in 40-70% of the basal cells and in only a few differentiating keratinocytes. Expression of cytokeratins 8 and 18 could not be detected. The same antibodies were also used to stain sections from fetal (15, 20, and 29 weeks), newborn (40 weeks), and mature (5 and 75 years) epidermis. In the 15-week-old epidermis, basal cells were positive for cytokeratins 8 and 19 and locally for cytokeratin 4; intermediate cells expressed cytokeratins 4, 10, 13, and 19; and the periderm contained cytokeratins 4, 8, 13, 18, and 19. In the 20-week-old epidermis, cytokeratin 4 had disappeared from the basal cell layer and cytokeratin 19 was present only locally; in the intermediate cell layer, cytokeratins 4 and 19 had disappeared; and in the periderm, the expression of the cytokeratins studied was the same as that in the 15-week-old epidermis. The basal cells of the 29-week-old fetal epidermis, the newborn epidermis, and the mature epidermis are negative with all antibodies tested, except for some scattered cells in the fetal and newborn skin, presumably Merkel cells, that were positive for cytokeratins 8, 18, and 19. Suprabasal cells in all specimens were positive only for cytokeratin 10. With respect to the cytokeratins studied, our results show that cultured differentiating keratinocytes resemble the suprabasal cells of early fetal epidermis. Basal cells of cultured keratinocytes resemble the basal cells of late fetal, newborn, and adult epidermis and therefore support previous observations.     

Effects of retinoids on differentiation, lipid metabolism, epidermal growth factor, and low-density lipoprotein binding in squamous carcinoma cells

The relationship among keratinocyte differentiation capacity, lipid synthesis, low-density lipoprotein (LDL) metabolism, plasma membrane composition, and epidermal growth factor (EGF) binding has been studied in SCC-12F2 cells. The differentiation capacity of the cells, i.e., ionophore-induced cornified envelope formation, was inhibited by various retinoids and stimulated by hydrocortisone. Retinoids that caused a significant reduction of cornified envelope formation, i.e., retinoic acid and 13-cis-retinoic acid, caused only minor changes in lipid synthesis and plasma membrane composition. Arotinoid ethylsulfone, having a minor effect on cornified envelope formation, caused a drastic inhibition of cholesterol synthesis, resulting in changes in the plasma membrane composition. Hydrocortisone stimulated cornified envelope formation but had only minor effects on lipid synthesis and plasma membrane composition. Of all retinoids tested, only arotinoid ethylsulfone caused a drastic increase in EGF binding, while hydrocortisone had no effect. Retinoic acid, arotinoid ethylsulfone, and hydrocortisone had no effects on LDL binding and only minor effects on LDL degradation. These results clearly demonstrate that the plasma membrane composition is not related to keratinocyte differentiation capacity, but most likely does determine EGF binding. Furthermore, EGF binding does not determine keratinocyte differentiation capacity.     

Copepods of the Juréia ecological reserve,state of São Paulo,Brazil. II. The genera Hesperocyclops,Muscocyclops, and Bryocyclops (Cyclopoida,Cyclopidae)

Cyclopid copepods collected mainly in aquatic microcosms and semiterrestrial habitats in the Juréia Ecological Reserve are studied. Hesperocyclops herbsti and Bryocyclops campaneri are described as new species and their taxonomical relationships discussed. Females of Muscocyclops operculatus (Chappuis) are redescribed and the males described for the first time. An emended diagnosis for Muscocyclops is proposed.     

Purification and characterization of glutathione transferase of human thyroid

An anionic (pI 4.6) isoenzyme of glutathione transferase was purified to homogeneity from human thyroid by affinity chromatography followed by isoelectric focusing. The content of enzyme was calculated to constitute about 0.2% of soluble proteins. The enzyme is formed by two identical subunits of 23,000 daltons approximately. The thyroid transferase did not catalyze the reduction of peroxides. Physical, catalytic and immunological analyses demonstrated extensive similarities between the thyroid transferase and the transferase from placenta, erythrocytes and breast. On the other hand, the thyroid transferase appears catalytically different from transferase 7-7, even if both cross-react with the antibodies raised against human placenta transferase.     

Kinetics of binding of macrolides, lincosamides, and synergimycins to ribosomes

The synergistic effect of type A (virginiamycin M (VM)) and type B (virginiamycin S (VS)) synergimycins and their antagonistic effect against erythromycin (a 14-membered macrolide) for binding to the large ribosomal subunit (50 S) have been related. This investigation has now been extended to 16-membered macrolides (leucomycin A3 and spiramycin) and to lincosamides (lincomycin). A dissociation of VS-ribosome complexes was induced as well by 16-membered macrolides as by lincosamides. The observed dissociation rate constant of VS-ribosome complexes was identified with the kappa-vs in the case of 16-membered macrolides, but linearly related to lincomycin concentration, suggesting a direct binding of the latter antibiotic to VS-ribosome complexes and the triggering of a conformational change of particles entailing VS release. Two different mechanisms were also involved in the VM-promoted reassociation to ribosomes of VS previously displaced by either macrolides or lincosamides. By binding to lincosamide-ribosome complexes, VM induced a conformational change of ribosomes resulting in higher affinity for VS and lower affinity for lincosamides. On the contrary, an incompatibility for a simultaneous binding of VM and 16-membered macrolides to ribosomes was observed. These results have been interpreted by postulating specific (nonoverlapping) and aspecific (overlapping) antibiotic binding sites at the peptidyltransferase domain. All the kinetic constants of five antibiotic families (type A and B synergimycins, 14- and 16-membered macrolides, and lincosamides) and a topological model of peptidyltransferase are presently available.