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.     

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.     

Getting Your Sea Legs

Sea travel mandates changes in the control of the body. The process by which we adapt bodily control to life at sea is known as getting one''s sea legs. We conducted the first experimental study of bodily control as maritime novices adapted to motion of a ship at sea. We evaluated postural activity (stance width, stance angle, and the kinematics of body sway) before and during a sea voyage. In addition, we evaluated the role of the visible horizon in the control of body sway. Finally, we related data on postural activity to two subjective experiences that are associated with sea travel; seasickness, and mal de debarquement. Our results revealed rapid changes in postural activity among novices at sea. Before the beginning of the voyage, the temporal dynamics of body sway differed among participants as a function of their (subsequent) severity of seasickness. Body sway measured at sea differed among participants as a function of their (subsequent) experience of mal de debarquement. We discuss implications of these results for general theories of the perception and control of bodily orientation, for the etiology of motion sickness, and for general phenomena of perceptual-motor adaptation and learning.     

Characterisation of the effects of leaf galls of Clusiamyia nitida (Cecidomyiidae) on Clusia lanceolata Cambess. (Clusiaceae): Anatomical aspects and chemical analysis of essential oil

Galls develop in different plant organs and are induced by the activity of various organisms. Some studies have investigated the ecological interactions between species of Clusia and gall-inducing insects. The goal of our study is to characterise changes in leaf anatomy caused by the activity of gall insects in Clusia lanceolata. Additionally, we also investigated the chemical composition of volatile compounds of normal leaves and those with galls to detect possible effects on the host plants. For anatomical studies, we used botanical material fixed in FAA₅₀. Transversal sections of the leaf blade were obtained from samples of leaves located on the third and fourth nodes from both male and female individuals. Material was studied from both sexes both with unaffected leaves and leaves containing galls. Fresh leaves of C. lanceolata were used for the extraction of volatile compounds, which were submitted to stem distillation using a modified Clevenger apparatus determining the oil yields subsequently (w/w). The unaffected leaves of female and male individuals of C. lanceolata exhibit similar anatomical structures. However, galls on leaves of both sexes show anatomical differences. The activity of the gall insect Clusiamyia nitida induces several changes in the foliar anatomy and the distribution of metabolic compounds in new tissues during gall development. However, the larvae are not able to induce significant changes in the volatile compounds of inflected leaves from male and female individuals.     

Comparative binding of Cry1Ab and Cry1F Bacillus thuringiensis toxins to brush border membrane proteins from Ostrinia nubilalis, Ostrinia furnacalis and Diatraea saccharalis (Lepidoptera: Crambidae) midgut tissue

The European (Ostrinia nubilalis Hübner) and Asian corn borers (Ostrinia furnacalis Guenée) are closely related and display similar sensitivity to Cry1 toxins. In this study, we compared the binding patterns of Cry1Ab and Cry1F toxins between both Ostrinia spp., as well as the expression of putative cadherin- and aminopeptidase-N (APN)-like protein receptors. Additionally, cDNA sequences of these putative toxin receptors from both Ostrinia species were compared. Ligand blots for both species indicated a similar binding pattern for Cry1Ab with the strongest immunoreactive band at 260 kDa in both species. In addition, similar expression of the putative cadherin- and APN-like protein receptors were observed at 260 and 135 kDa, respectively. A high degree of similarity (98% amino acid sequence identity) of cDNA sequences for both putative receptor sequences was observed. The Cry1F ligand blot revealed that O. furnacalis and O. nubilalis BBMV exhibited slightly different binding patterns, with strong binding to putative proteins at 150 and 140 kDa, respectively. Both proteins appeared to also bind Cry1Ab, although the signal intensity was much reduced with Cry1Ab. O. furnacalis showed an additional but weaker band at 210 kDa relative to the 150 kDa band. Diatraea saccharalis (Fabricius), which was used as an outgroup species, exhibited different binding patterns than either Ostrinia species, with both Cry1Ab and Cry1F toxins binding to a 210 kDa protein. These results support the previous experiments indicating that O. nubilalis and O. furnacalis share similar patterns of susceptibility to Cry toxins.     

Potentiation of high hydrostatic pressure inactivation of Mycobacterium by combination with physical and chemical conditions

Mycobacterium abscessus is an important hospital-acquired pathogen involved in infections associated with medical, surgical, and biopharmaceutical materials. In this work, we investigated the pressure-induced inactivation of two strains [2544 and American Type Culture Collection (ATCC) 19977] of M. abscessus in combination with different temperatures and pH conditions. For strain 2544, exposure to 250 MPa for 90 min did not significantly inactivate the bacteria at 20 °C, whereas at ?15 °C, there was complete inactivation. Exposure to 250 MPa at ≥60 °C caused rapid inactivation, with no viable bacteria after 45 min. With 45 min of exposure, there were no viable bacteria at any temperature when a higher pressure (350 MPa) was used. Extremes of pH (4 or 9) also markedly enhanced the pressure-induced inactivation of bacteria at 250 MPa, with complete inactivation after 45 min. In comparison, exposure of this strain to the disinfecting agent glutaraldehyde (0.5 %) resulted in total inactivation within 5 min. Strain 19977 was more sensitive to high pressure but less sensitive to glutaraldehyde than strain 2544. These results indicate that high hydrostatic pressure in combination with other physical parameters may be useful in reducing the mycobacterial contamination of medical materials and pharmaceuticals that are sensitive to autoclaving.