Crystal structure of Pasteurella haemolytica ferric ion-binding protein A reveals a novel class of bacterial iron-binding proteins

Pasteurellosis caused by the Gram-negative pathogen Pasteurella haemolytica is a serious disease leading to death in cattle. To scavenge growth-limiting iron from the host, the pathogen utilizes the periplasmic ferric ion-binding protein A (PhFbpA) as a component of an ATP-binding cassette transport pathway. We report the 1.2-A structure of the iron-free (apo) form of PhFbpA, which is a member of the transferrin structural superfamily. The protein structure adopts a closed conformation, allowing us to reliably assign putative iron-coordinating residues. Based on our analysis, PhFbpA utilizes a unique constellation of binding site residues and anions to octahedrally coordinate an iron atom. A surprising finding in the structure is the presence of two formate anions on opposite sides of the iron-binding pocket. The formate ions tether the N- and C-terminal domains of the protein and stabilize the closed structure, also providing clues as to probable candidates for synergistic anions in the iron-loaded state. PhFbpA represents a new class of bacterial iron-binding proteins.     

Gibberellin and auxin contents and ethylene production in the hypocotyls of green and etiolated bean plants treated with chlorocholine chloride

The effect of CCC treatment on the GA and IAA contents of the hypocotyls of green and etiolated bean plants and on their distribution was studied. In the treated plants the GA content of the hypocotyls was higher than that of the control. On the application of CCC the distribution of the hormone content within the organ altered: in the basal part of the hypocotyls of the treated plants the hormone content increased. In the hypocotyls of the treated plants the IAA content was less than in the controls and it was accumulated in the basal part. The ethylene production of the aplcal and basal parts of the hypocotyls proved to be correlated with their IAA content. Presented at the International Symposium “Plant Growth Regulators” held on June 18–22, 1984 at Liblice, Czechoslovakia.     

Comparison of the effects of white light and the growth retardant paclobutrazol on the ethylene production in bean hypocotyls

At a concentration of 17 µmol·L^–1, paclobutrazol (PP), a triazole plant growth retardant, effectively reduced the elongation and increased the thickness of hypocotyls in 6-day-old Phaseolus vulgaris L. cv. Juliska seedlings, both in the light and in the dark. PP treatment did not increase the cell number in transverse sections of hypocotyls. The diameter of hypocotyls was uniform from the zone of intensive elongation along the whole hypocotyl in etiolated plants, but those grown in the light exhibited an additional lateral expansion at the base. Ethylene evolution was not reduced by PP in etiolated hypocotyls, and did not differ significantly in the elongating apical and fully grown basal zones. PP reduced the ethylene release by the growing zones in green hypocotyls, but not in the basal parts, which resulted in an increasing ethylene gradient towards the hypocotyl base. The level of 1-aminocyclopropane-1-carboxylic acid (ACC), the immediate precursor of ethylene, was much higher in retardant-treated hypocotyls than in the controls, which was due in part to the reduced malonylation. The swelling of the hypocotyl bases could be eliminated by inhibitors of ethylene biosynthesis or action, or could be induced by 10 µmol·L^–1ACC in control plants in the light. None of these treatments had a significant effect on the lateral expansion of hypocotyls in etiolated seedlings. PP treatment induced a similar effect to that of white light in etiolated seedlings, and amplified the effect of light in green plants with respect to the ACC distribution, and consequently, the ethylene production in the hypocotyls of 6-day-old bean seedlings. It can be concluded that the lateral expansion of hypocotyl bases in PP-treated green plants is controlled by ethylene.     

Limitations of the use of plant material grown in Petri dishes for physiological experiments

Roots of plants growing "aeroponically" (AP) on moistened filter paper in Petri dishes for a few days are fairly often used for physiological experiments (e.g. measurement of root growth), for ion or herbicide uptake tests, before the establishment of hydroponic or aseptic cultures although their hormonal status is markedly different from that of the hydroponic (HP) control. On the 4th day of germination the ethylene production of cucumber (Cucumis sativus L. cv. Budai csemege) roots growing in AP under controlled conditions increased considerably and exhibited a maximum curve, HP roots evolved ethylene much more constantly. The morphological changes in AP roots (e.g. inhibited elongation and swelling of primary roots, and increased formation of root hairs), resembling those caused by exogenously applied ethylene, can be prevented with 10(-5) M Ag+, an inhibitor of ethylene action. In roots of one-week-old AP seedlings, the amount of an acidic inhibitor, which as judged from the Rf values is likely to be abscisic acid (ABA), is about twice as high as in HP seedlings. An elevated ethylene or ABA level of AP roots may result in a reduced elongation of the primary roots. Counteraction of this inhibition by Ag+ suggests that the effect of ethylene is the primary event in the reduction of root length. When using plant material grown in Petri dishes the possibility of similar changes in hormonal status of the roots must be taken into consideration.     

Molecular interactions between a recombinant IgE antibody and the beta-lactoglobulin allergen

Allergies are caused by the immune reaction to commonly harmless proteins, allergens. This reaction is typified by immunoglobulin E (IgE) antibodies. We report the crystal structure of an IgE Fab fragment in complex with beta-lactoglobulin (BLG), one of the major allergens of bovine milk. The solved structure shows how two IgE/Fab molecules bind the dimeric BLG. The epitope of BLG consists of six different short fragments of the polypeptide chain, which are located especially in the beta strands, covering a flat area on the allergen surface. All six CDR (complementary-determining region) loops of the IgE Fab participate in the binding of BLG. The light chain CDR loops are responsible for the binding of the flat beta sheet region of BLG. The IgE epitope is different from common IgG epitopes that are normally located in the exposed loop regions of antigens and observed also in the two recently determined allergen-IgG complexes.     

The relationship of aerobic capacity,anaerobic peak power and experience to performance in CrossFit exercise

CrossFit is becoming increasingly popular as a method to increase fitness and as a competitive sport in both the Unites States and Europe. However, little research on this mode of exercise has been performed to date. The purpose of the present investigation involving experienced CrossFit athletes and naïve healthy young men was to investigate the relationship of aerobic capacity and anaerobic power to performance in two representative CrossFit workouts: the first workout was 12 minutes in duration, and the second was based on the total time to complete the prescribed exercise. The participants were 32 healthy adult males, who were either naïve to CrossFit exercise or had competed in CrossFit competitions. Linear regression was undertaken to predict performance on the first workout (time) with age, group (naïve or CrossFit athlete), VO₂max and anaerobic power, which were all significant predictors (p < 0.05) in the model. The second workout (repetitions), when examined similarly using regression, only resulted in CrossFit experience as a significant predictor (p < 0.05). The results of the study suggest that a history of participation in CrossFit competition is a key component of performance in CrossFit workouts which are representative of those performed in CrossFit, and that, in at least one these workouts, aerobic capacity and anaerobic power are associated with success.     

Effects of Cold Acclimation and Salicylic Acid on Changes in ACC and MACC Contents in Maize during Chilling

The effect of 0.5 mM salicylic acid (SA) pretreatment and of growing at hardening temperatures on chilling-induced changes in 1-aminocyclopropane-1-carboxylic acid (ACC) and malonyl 1-aminocyclopropane-1-carboxylic acid (MACC) was investigated in young maize (Zea mays L.) plants grown in hydroponic solution at 22/20 °C. Chilling at 5 °C caused an increase in ACC content;however, this increase was less pronounced in plants cold acclimated at 13/11 °C 4 d before the chilling treatment, and in those which were pretreated with SA for 1 d before the cold stress. Changes in MACC at low temperature showed no correlation with chilling tolerance in maize.     

A review of the Nearctic genus Prostoia (Ricker) (Plecoptera,Nemouridae), with the description of a new species and a surprising range extension for P. hallasi Kondratieff & Kirchner

The Nearctic genus Prostoia (Plecoptera: Nemouridae) is reviewed. Prostoia ozarkensis sp. n. is described from the male and female adult stages mainly from the Interior Highland region encompassing portions of Arkansas, Missouri, and Oklahoma. Prostoia ozarkensis sp. n. appears most closely related to two species, one distributed broadly across the western Nearctic region, P. besametsa (Ricker), and one found widely throughout the central and eastern Nearctic regions, P. completa (Walker). A surprising range extension is noted for P. hallasi Kondratieff & Kirchner, a species once known only from the Great Dismal Swamp, from small upland streams in southern Illinois. Additional new state records are documented for P. besametsa, P. completa, P. hallasi and P. similis (Hagen). Taxonomic keys to Prostoia males and females are provided, and scanning electron micrographs of adult genitalia of all species are given.     

Liposomes to Target Peripheral Neurons and Schwann Cells

While a wealth of literature for tissue-specific liposomes is emerging, optimal formulations to target the cells of the peripheral nervous system (PNS) are lacking. In this study, we asked whether a novel formulation of phospholipid-based liposomes could be optimized for preferential uptake by microvascular endothelia, peripheral neurons and Schwann cells. Here, we report a unique formulation consisting of a phospholipid, a polymer surfactant and cholesterol that result in enhanced uptake by targeted cells. Using fluorescently labeled liposomes, we followed particle internalization and trafficking through a distinct route from dextran and escape from degradative compartments, such as lysosomes. In cultures of non-myelinating Schwann cells, liposomes associate with the lipid raft marker Cholera toxin, and their internalization is inhibited by disruption of lipid rafts or actin polymerization. In contrast, pharmacological inhibition of clathrin-mediated endocytosis does not significantly impact liposome entry. To evaluate the efficacy of liposome targeting in tissues, we utilized myelinating explant cultures of dorsal root ganglia and isolated diaphragm preparations, both of which contain peripheral neurons and myelinating Schwann cells. In these models, we detected preferential liposome uptake into neurons and glial cells in comparison to surrounding muscle tissue. Furthermore, in vivo liposome administration by intramuscular or intravenous injection confirmed that the particles were delivered to myelinated peripheral nerves. Within the CNS, we detected the liposomes in choroid epithelium, but not in myelinated white matter regions or in brain parenchyma. The described nanoparticles represent a novel neurophilic delivery vehicle for targeting small therapeutic compounds, biological molecules, or imaging reagents into peripheral neurons and Schwann cells, and provide a major advancement toward developing effective therapies for peripheral neuropathies.