Chrysonila sitophila (TFB-27441): A hyperlignolytic strain

Summary C. sitophila strain TFB-27441 showed 2–3 times higher lignolytic activity thanPhanerochaete chrysosporium (BKM-F-1767 strain). Lignin had a marked effect on the ligninase activity indicating that some induction or activation mechanism is involved in lignin degradation byC. sitophila.     

Disparity between expression of transferrin receptor ligand binding and non-ligand binding domains on human lymphocytes

We compared transferrin receptor (TfR) expression on human peripheral blood lymphocytes (PBL) activated by phorbol myristate acetate (PMA) or L-phytohemagglutinin (LPHA) using two techniques: (1) 125I-iron-saturated transferrin (FeTf) binding, (2) reactivity with monoclonal anti-TfR antibodies--OKT9 and B3/25. These monoclonal antibodies do not block FeTf binding, and therefore bind to TfR domains separate from the ligand binding site. Unstimulated PBL bound fewer than 1,000 molecules of 125I-FeTf per cell, and less than 5% of cells expressed TfR antigens detected by OKT9 or B3/25. 125I-FeTf binding and antibody binding increased in parallel on LPHA-activated PBL. After exposure to LPHA for 72 hr, 125I-FeTf binding increased 100-fold to 10(5) molecules per cell and greater than 50% of cells expressed TfR antigens. By contrast, PMA activation of PBL markedly increased binding of OKT9 and B3/25 but not the binding of 125I-FeTf. Cell surface expression of TfR antigens seen by OKT9 and B3/25 did not differ between LPHA- and PMA-activated PBL. However, after 72 hr with PMA, 125I-FeTf binding increased only 6-fold and consistently remained at less than 10(4) molecules per cell. Therefore, PMA induced a disparity between expression of TfR ligand binding domains and immunological domains at the cell surface. Cell proliferation assessed by fluorescent DNA analysis was similar in cultures stimulated by LPHA or PMA. These data indicate that lymphoid cells may possess a mechanism for modulating TfR expression in which down-regulation of FeTf binding occurs without receptor internalization. Alternatively, it is possible that this observation may reflect a membrane perturbation effect of PMA.     

Genetic studies on the acidification capacity of sunflower roots induced under iron stress

Under stress of iron deficiency roots of sunflower (Helianthus annuus L.) increase proton efflux which acidifies the root medium, increase the ferric reducing capacity and the exudation of phenolic compounds. Differences have been found previously among sunflower inbred lines in the capacity of their roots to lower pH and it was also found that this character is under genetic control.This work presents the results of an inheritance study made by crossing two genotypes, one (CMS HA 89) without acidification capacity and another (RHA 271) with it. Plants were grown individually in 75 mL vessels with an aerated solution low in iron. After 4 days, solutions were changed to one without iron and the pH of the medium was measured during the following days. Results from F₁, F₂, and backcross generations can be explained with two pairs of alleles controlling the character, being the relation between alleles of complete dominance at both gene pairs, but either gene, when dominant is epistatic to the other.     

Arachidonic acid inhibits glycine transport in cultured glial cells.

The effects of arachidonic acid on glycine uptake, exchange and efflux in C6 glioma cells were investigated. Arachidonic acid produced a dose-dependent inhibition of high-affinity glycine uptake. This effect was not due to a simple detergent-like action on membranes, as the inhibition of glycine transport was most pronounced with cis-unsaturated long-chain fatty acids, whereas saturated and trans-unsaturated fatty acids had relatively little or no effect. Endogenous unsaturated non-esterified fatty acids may exert a similar inhibitory effect on the transport of glycine. The mechanism for this inhibitory effect has been examined in a plasma membrane vesicle preparation derived from C6 cells, which avoids metabolic or compartmentation interferences. The results suggest that part of the selective inhibition of glycine transport by arachidonic acid could be due to the effects of the arachidonic acid on the lipid domain surrounding the carrier.     

Gyrodactylus gemini n. sp. (Monogenea: Gyrodactylidae), a parasite of Semaprochilodus taeniurus (Steindachner) from the Venezuelan Amazon

Gyrodactylus gemini n. sp. (Monogenea, Gyrodactylidae) is described from the surface of the body and fins of the fish Semaprochilodus taeniurus (Steindachner) imported into Britain from the Venezuelan Amazon. The new species differs from other species of the genus, including those described from South and Central America, by having: (i) stout hamuli with straight shafts and diverging roots; (ii) marginal hooks with the sickle length larger than the width; (iii) a dorsal bar without a medial constriction; (iv) a rectangular ventral bar with short processes; (v) a triangular ventral bar membrane; and, most obviously, (vi) at least two generations which can develop two embryos simultaneously. This is the first known species of the genus Gyrodactylus from the Venezuelan Amazon and the first record of the subgenus Gyrodactylus (Gyrodactylus) from South America.     

Iron-Deficiency Stress Responses in Cucumber (Cucumis sativus L.) Roots (A Possible Role for Ethylene?)

Most dicotyledonous species respond to Fe deficiency by developing several mechanisms known as Fe-deficiency stress responses. To study the regulation of these responses, young cucumber plants (Cucumis sativus L. cv Ashley) were grown in nutrient solution for 11 d, being deprived of Fe during the last 4 or 5 d. Inhibitors of ethylene synthesis (2 or 10 [mu]M aminoethoxyvinylglycine; 10 or 20 [mu]M aminooxyacetic acid; 1, 2, 5, or 10 [mu]M Co2+ as CoCl2) or action (50, 200, or 800 [mu]M Ag+ as silver thiosulfate) were added to the nutrient solution at different times during this period of growth with no Fe. After this period, the reduction of Fe3+ ethylenedi-aminetetraacetate by the roots of entire plants was measured with ferrozine by reading the absorbance at 562 nm after 2 h. The presence of the ethylene inhibitors in the nutrient solution inhibited the Fe-deficiency stress responses ferric-reducing capacity and subapical root swelling. In another experiment, the addition of 1 [mu]M 1-aminocyclopropane-1-carboxylic acid (ACC), a precursor of ethylene synthesis, to the nutrient solution of plants having low ferric-reducing activity increased notably the ferric-reducing capacity and subapical root swelling. Here we show evidence that ethylene plays a role in the development of Fe-deficiency stress responses, since when ethylene synthesis or action was inhibited, the responses were also inhibited, and when a precursor of ethylene (ACC) was added, the responses were increased.     

Trypanosoma cruzi: Role of macrophage membrane components in the phagocytosis of bloodstream forms

The phagocytosis of Trypanosoma cruzi bloodstream forms is mediated by macrophage Pronase-sensitive membrane components. Trypsin and chymotrypsin treatment of macrophages, which prevents the uptake of T. cruzi culture forms, does not inhibit the phagocytosis of bloodstream parasites. The phagocytosis activity of the macrophages was recovered within 6–8 hr after the removal of Pronase. Inhibition of protein synthesis after Pronase treatment prevents the recovery of the endocytic activity of the macrophages. Fc and C3b receptors are not apparently essential for the phagocytosis of T. cruzi bloodstream forms. The described membrane components may help to explain the tropism of some T. cruzi strains for cells of the mononuclear phagocytic system in the living host.     

Purification and characterization of an exon 2-deleted human beta-tropomyosin constructed by the polymerase chain reaction.

We deleted exon 2 in human skeletal beta-tropomyosin (h beta-SK tropomyosin) using an improved adaptation of polymerase chain reaction (PCR) technology. The first PCR product was used to prime the full-length cDNA, leading to an exon 2-deleted h beta-SK tropomyosin. This new protein, des-(39-80)-tropomyosin, could then be expressed in Escherichia coli and purified to homogeneity. At the nucleotide level, the junction between exons 1 and 3 has been precisely made in the PCR product. The mutated protein was purified using high-performance liquid chromatography. Des-(39-80)-tropomyosin revealed new immunological properties but was still recognized by certain antitropomyosin antibodies. Furthermore, the structural characteristics of the mutated tropomyosin fit those of the full-length tropomyosin. This new adaptation of PCR technology appears to be suitable for every kind of mutation inside a cloned DNA molecule, and one mutation primer per mutation is sufficient.