Phytosiderophore release in relation to micronutrient metal deficiencies in barley

Phytosiderophore release occurs under both iron and zinc deficiencies in representative Poaceae and has been speculated to be a general adaptive response to enhance the acquisition of micronutrient metals. To test this hypothesis, phytosiderophore (PS) release rates from barley (Hordeum vulgare cv. CM72) subjected to deficiencies of Fe, Zn, Mn, and Cu were compared using chelator-buffered nutrient solutions. PS release rates were determined at two day intervals during onset and development of deficiency symptoms. Plant dry matter yields and nutrient concentrations, measured at three time points were used to construct growth curves for calculation of PS release per unit root mass and estimation of critical internal nutrient levels associated with PS release. In comparison to trace metal-sufficient control plants, dry matter production was markedly reduced in the Zn, Mn, and Cu deficiency treatments, with final relative yields of 49, 61, and 34%, respectively. Relative yields for Fe-deficient plants grown at three suboptimal Fe levels ranged from 95 to 33% of control, and provided a basis for comparison of PS release rates by Zn-, Mn-, and Cu-deficient plants at similar levels of growth inhibition. Under Fe deficiency, PS release increased with severity of the deficiency as measured by foliar Fe concentration, yield reduction, and chlorosis. Changes in PS release rates over time suggested a cyclical pattern that may be regulated by Fe concentration in the plant shoot. The highest rate of PS release (35 mol g^–1 root dw 2 h^–1) was measured after 10 days of growth at pFe 19, whereas control plants adapted for growth at pFe 17 released only 2 to 3 mol g^–1 root dw 2 h^–1. In a second experiment, maximum PS release rates for barley subjected to Zn, Mn, and Cu deficiencies were only 2.6, 2.5 and 1 mol g^–1 2 h^–1, respectively and were only slightly elevated over those of the control plants (ca. 1 mol g^–1 root dw 2 h^–1) grown at pFe 16.5. Moreover, enhanced PS release under Zn deficiency occurred much later, after the deficiency had already caused severely reduced growth. The results suggest that phytosiderophore release in this barley cultivar is a specific response to Fe deficiency and is not significantly induced in response to deficiencies of other trace metals.     

Simian varicella virus antibody response in experimental infection of African green monkeys

Abstract: The humoral immune response to simian varicella virus (SVV) was investigated following primary and secondary experimental infection of African green monkeys. Neutralization and immunoprecipitation assays were used to determine antibody titers to SVV throughout the course of infection. The immune response to specific viral polypeptides was analyzed by immunoprecipitation analysis. The results demonstrate that the simian varicella model offers a useful approach to investigate immune mechanisms in human varicella zoster virus (VZV) infections.     

The Endothelin ETA Receptor Exists in the Caudal Solitary Tract Nucleus of the Rat Brain

1. The receptor autoradiographic method done on the rat lower brain stem and cerebellum plus ¹²⁵I-endothelin-1, BQ-123, an antagonist for the endothelin ET_A receptor, and sarafotoxin S6c, an agonist for the ET_B receptor, revealed minute amounts of the ET_A receptor coexisting with the ET_B receptor in the caudal solitary tract nucleus of the rat lower brain stem.2. The ET_B receptor is present predominantly in other parts of the lower brain stem.3. Knowledge of the heterogeneous distribution of the central endothelin receptor subtypes aids in understanding the neurophysiology of endothelins.     

Evidence for male- and juvenile-specific contact pheromones of the common bed bug Cimex lectularius

Males and females of the common bed bug, Cimex lectularius L. (Heteroptera: Cimicidae), have been shown to produce and respond to an aggregation pheromone. We tested whether juvenile C. lectularius also produce and respond to aggregation pheromone, and whether the pheromone is perceived by contact chemoreception. In dual‐choice laboratory experiments, juveniles, but not males or females, preferred juvenile‐exposed paper discs to control discs. Unlike juveniles, males and females preferred male‐exposed paper discs to control discs. Neither juveniles, males, nor females preferred female‐exposed discs to control discs. When test stimuli were inaccessible, C. lectularius failed to show any preference. Male‐ and juvenile‐specific contact pheromones may have contrasting functions of marking shelters as safe refugia for development and growth (juveniles) or mate encounter (adults), but result in the same phenomenon, the aggregation of conspecifics.     

Alternative entry receptors for herpes simplex virus and their roles in disease

Either herpesvirus entry mediator (HVEM, TNFRSF14) or nectin-1 (PVRL1) is sufficient for herpes simplex virus (HSV) infection of cultured cells. The contribution of individual receptors to infection in vivo and to disease is less clear. To assess this, Tnfrsf14(-/-) and/or Pvrl1(-/-) mice were challenged intravaginally with HSV-2. Infection of the vaginal epithelium occurred in the absence of either HVEM or nectin-1 but was virtually undetectable when both receptors were absent, indicating that either HVEM or nectin-1 was necessary. Absence of nectin-1 (but not HVEM) reduced efficiency of infection of the vaginal epithelium and viral spread to the nervous system, attenuating neurological disease and preventing external lesion development. While nectin-1 proved not to be essential for infection of the nervous system, it is required for the full manifestations of disease. This study illustrates the value of mutant mice for understanding receptor contributions to disease caused by a human virus.     

ATP binding site mutagenesis reveals different subunit stoichiometry of functional P2X2/3 and P2X2/6 receptors

The aim of the present experiments was to clarify the subunit stoichiometry of P2X2/3 and P2X2/6 receptors, where the same subunit (P2X2) forms a receptor with two different partners (P2X3 or P2X6). For this purpose, four non-functional Ala mutants of the P2X2, P2X3, and P2X6 subunits were generated by replacing single, homologous amino acids particularly important for agonist binding. Co-expression of these mutants in HEK293 cells to yield the P2X2 WT/P2X3 mutant or P2X2 mutant/P2X3 WT receptors resulted in a selective blockade of agonist responses in the former combination only. In contrast, of the P2X2 WT/P2X6 mutant and P2X2 mutant/P2X6 WT receptors, only the latter combination failed to respond to agonists. The effects of α,β-methylene-ATP and 2-methylthio-ATP were determined by measuring transmembrane currents by the patch clamp technique and intracellular Ca(2+) transients by the Ca(2+)-imaging method. Protein labeling, purification, and PAGE confirmed the assembly and surface trafficking of the investigated WT and WT/mutant combinations in Xenopus laevis oocytes. In conclusion, both electrophysiological and biochemical investigations uniformly indicate that one subunit of P2X2 and two subunits of P2X3 form P2X2/3 heteromeric receptors, whereas two subunits of P2X2 and one subunit of P2X6 constitute P2X2/6 receptors. Further, it was shown that already two binding sites of the three possible ones are sufficient to allow these receptors to react with their agonists.