Respiratory allergy to Blomia tropicalis: Immune response in four syngeneic mouse strains and assessment of a low allergen-dose,short-term experimental model

Background

The dust mite Blomia tropicalis is an important source of aeroallergens in tropical areas. Although a mouse model for B. tropicalis extract (BtE)-induced asthma has been described, no study comparing different mouse strains in this asthma model has been reported. The relevance and reproducibility of experimental animal models of allergy depends on the genetic background of the animal, the molecular composition of the allergen and the experimental protocol.

Objectives

This work had two objectives. The first was to study the anti-B. tropicalis allergic responses in different mouse strains using a short-term model of respiratory allergy to BtE. This study included the comparison of the allergic responses elicited by BtE with those elicited by ovalbumin in mice of the strain that responded better to BtE sensitization. The second objective was to investigate whether the best responder mouse strain could be used in an experimental model of allergy employing relatively low BtE doses.

Methods

Groups of mice of four different syngeneic strains were sensitized subcutaneously with 100 μg of BtE on days 0 and 7 and challenged four times intranasally, at days 8, 10, 12, and 14, with 10 μg of BtE. A/J mice, that were the best responders to BtE sensitization, were used to compare the B. tropicalis-specific asthma experimental model with the conventional experimental model of ovalbumin (OVA)-specific asthma. A/J mice were also sensitized with a lower dose of BtE.

Results

Mice of all strains had lung inflammatory-cell infiltration and increased levels of anti-BtE IgE antibodies, but these responses were significantly more intense in A/J mice than in CBA/J, BALB/c or C57BL/6J mice. Immunization of A/J mice with BtE induced a more intense airway eosinophil influx, higher levels of total IgE, similar airway hyperreactivity to methacholine but less intense mucous production, and lower levels of specific IgE, IgG1 and IgG2 antibodies than sensitization with OVA. Finally, immunization with a relatively low BtE dose (10 μg per subcutaneous injection per mouse) was able to sensitize A/J mice, which were the best responders to high-dose BtE immunization, for the development of allergy-associated immune and lung inflammatory responses.

Conclusions

The described short-term model of BtE-induced allergic lung disease is reproducible in different syngeneic mouse strains, and mice of the A/J strain was the most responsive to it. In addition, it was shown that OVA and BtE induce quantitatively different immune responses in A/J mice and that the experimental model can be set up with low amounts of BtE.     

Plant phenylacetaldehyde synthase is a bifunctional homotetrameric enzyme that catalyzes phenylalanine decarboxylation and oxidation

We have isolated and characterized Petunia hybrida cv. Mitchell phenylacetaldehyde synthase (PAAS), which catalyzes the formation of phenylacetaldehyde, a constituent of floral scent. PAAS is a cytosolic homotetrameric enzyme that belongs to group II pyridoxal 5'-phosphate-dependent amino-acid decarboxylases and shares extensive amino acid identity (approximately 65%) with plant L-tyrosine/3,4-dihydroxy-L-phenylalanine and L-tryptophan decarboxylases. It displays a strict specificity for phenylalanine with an apparent Km of 1.2 mM. PAAS is a bifunctional enzyme that catalyzes the unprecedented efficient coupling of phenylalanine decarboxylation to oxidation, generating phenylacetaldehyde, CO2, ammonia, and hydrogen peroxide in stoichiometric amounts.     

Interference between Streptococcus pneumoniae and Staphylococcus aureus: In vitro hydrogen peroxide-mediated killing by Streptococcus pneumoniae

The bactericidal activity of Streptococcus pneumoniae toward Staphylococcus aureus is mediated by hydrogen peroxide. Catalase eliminated this activity. Pneumococci grown anaerobically or genetically lacking pyruvate oxidase (SpxB) were not bactericidal, nor were nonpneumococcal streptococci. These results provide a possible mechanistic explanation for the interspecies interference observed in epidemiologic studies.     

The phage‐driven microbial loop in petroleum bioremediation

During the drilling process and transport of crude oil, water mixes with the petroleum. At oil terminals, the water settles to the bottom of storage tanks. This drainage water is contaminated with emulsified oil and water-soluble hydrocarbons and must be treated before it can be released into the environment. In this study, we tested the efficiency of a continuous flow, two-stage bioreactor for treating drainage water from an Israeli oil terminal. The bioreactor removed all of the ammonia, 93% of the sulfide and converted 90% of the total organic carbon (TOC) into carbon dioxide. SYBR Gold staining indicated that reactor 1 contained 1.7 × 10⁸ bacteria and 3.7 × 10⁸ phages per millilitre, and reactor 2 contained 1.3 × 10⁸ bacteria and 1.7 × 10⁹ phages per millilitre. The unexpectedly high mineralization of TOC and high concentration of phage in reactor 2 support the concept of a phage-driven microbial loop in the bioremediation of the drainage water. In general, application of this concept in bioremediation of contaminated water has the potential to increase the efficiency of processes.     

Development and fecundity of Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae) on different soybean cultivars

The life history of Spodoptera exigua was studied under laboratory conditions at temperature of 25°C ± 1°C, relative humidity (RH) of 60% ± 5% and a photoperiod of 16:8 h (Light:Dark) on nine soybean (Glycine max L.) cultivars: 032, 033, Hill, M4, M7, M9, M11, TMS and Zan. Larval and pupal development times were longest on M7 cultivar (14.09 ± 0.078 and 7.78 ± 0.090 days) and shortest on 033 cultivar (11.98 ± 0.054 and 7.033 ± 0.090 days). The longest and shortest female and male longevities were observed on Hill and Zan cultivars, respectively. The results showed that the whole life span varied from 32.80 ± 0.89 to 37 ± 0.98 days for females and from 33.3 ± 0.66 to 38.74 ± 0.95 days for males. The highest daily fecundity was obtained on M9 (102. 38 eggs), and the lowest on Hill (75.87 eggs). Mean total fecundity per female during adult life was highest on 033 (1156.20 eggs) and lowest on M7 cultivars (841.68 eggs). Clustering analysis of the biological parameters of S. exigua confirmed that 033 and Hill cultivars were the susceptible and the resistant cultivars, respectively.     

Feeding ecology and trophic impact of the hydroid Obelia dichotoma in the Kongsfjorden (Spitsbergen, Arctic)

Obelia dichotoma is a thecate hydroid with a worldwide distribution, occurring mainly on shallow water hard substrates. Since the trophic ecology of hydroids in polar waters is badly understood, the aim of the present work was to study qualitatively and quantitatively the diet of these organisms in an Arctic environment and to determine their trophic significance. For this purpose, the density of the hydroid population was documented, and simultaneously, zooplankton was sampled in two different years (1997 and 1998). Prey capture rates were estimated by analysing the gastrovascular content of the polyps in a diurnal cycle. Additionally, the digestion time of O. dichotoma was measured by laboratory feeding experiments using diatoms as food items. The analyses of the gastrovascular cavities of the polyps sampled during the diurnal cycles showed that O. dichotoma fed mainly on faecal pellets, organic matter and microalgae. Zooplankton prey was also observed, but gastrovascular contents and zooplankton abundance did not show any correlation in both years. The consumption rates of the hydroid populations differed between the 2 years. It was almost double (8.9 mg Carbon m^?2) in 1998 compared to 1997 (5.5 mg Carbon m^?2). The significance of the environmental variability in the feeding ecology and population dynamics of hydroids under Arctic conditions is discussed.     

Culturing of stoneworts and submersed angiosperms with phosphate uptake exclusively from an artificial sediment

1. We aimed to demonstrate reproducible nutrition and growth of macrophytes in non‐axenic laboratory cultures preventing growth of phytoplankton and epiphytes. 2. Macrophyte shoot segments were planted in a mixture of commercial acid‐washed silica sand with crystalline tricalcium phosphate, and this artificial sediment was covered with a layer of pure silica sand. The liquid mineral media used did not contain phosphorus but were rich in all other nutrient elements. A CO₂ reservoir provided sustainable CO₂ supply to macrophyte cultures by gas diffusion through a polyethylene membrane. 3. Chara hispida, Chara tomentosa, Chara baltica, Elodea canadensis, Potamogeton pectinatus and Zanichellia palustris could be cultivated for long term without medium exchange and aeration. Microalgae growth was prevented by the absence of phosphate in the water column. Mobilisation of tricalcium phosphate and phosphate uptake by the rhizoids of C. hispida enabled sustainable rapid shoot growth and increased the concentration of inorganic phosphate in the shoot dry weight by five to six times in comparison with plants cultivated on pure silica sand. A significant growth support from tricalcium phosphate was also observed for E. canadensis, but the rate of phosphate uptake by the roots was not sufficient to maintain a storage pool of inorganic phosphate (P_i) in the growing shoots of this plant. 4. Membrane‐controlled CO₂ supply from a reservoir and artificial sediments like the one described provide attractive options for the laboratory culture of macrophytes.     

Development and characterization of high affinity leptins and leptin antagonists

Leptin is a pleiotropic hormone acting both centrally and peripherally. It participates in a variety of biological processes, including energy metabolism, reproduction, and modulation of the immune response. So far, structural elements affecting leptin binding to its receptor remain unknown. We employed random mutagenesis of leptin, followed by selection of high affinity mutants by yeast surface display and discovered that replacing residue Asp-23 with a non-negatively charged amino acid leads to dramatically enhanced affinity of leptin for its soluble receptor. Rational mutagenesis of Asp-23 revealed the D23L substitution to be most effective. Coupling the Asp-23 mutation with alanine mutagenesis of three amino acids (L39A/D40A/F41A) previously reported to convert leptin into antagonist resulted in potent antagonistic activity. These novel superactive mouse and human leptin antagonists (D23L/L39A/D40A/F41A), termed SMLA and SHLA, respectively, exhibited over 60-fold increased binding to leptin receptor and 14-fold higher antagonistic activity in vitro relative to the L39A/D40A/F41A mutants. To prolong and enhance in vivo activity, SMLA and SHLA were monopegylated mainly at the N terminus. Administration of the pegylated SMLA to mice resulted in a remarkably rapid, significant, and reversible 27-fold more potent increase in body weight (as compared with pegylated mouse leptin antagonist), because of increased food consumption. Thus, recognition and mutagenesis of Asp-23 enabled construction of novel compounds that induce potent and reversible central and peripheral leptin deficiency. In addition to enhancing our understanding of leptin interactions with its receptor, these antagonists enable in vivo study of the role of leptin in metabolic and immune processes and hold potential for future therapeutic use in disease pathologies involving leptin.     

Biochemical characteristics of surface sediments on the eastern Weddell Sea continental shelf, Antarctica: is there any evidence of seasonal patterns?

Biochemical characteristics of seafloor sediment off Austasen in the southeastern Weddell Sea were assayed in samples recovered in the early autumn and late spring of 2000 and 2003, respectively. Sediment was separated in the grain-size fractions >200 μm and <200 μm to distinguish biochemical characteristics in the fraction available for benthic suspension feeders (<200 μm). In the bulk sediment, the lipid (LPD) and carbohydrate (CHO) contents were significantly different between seasons with higher LPD content in the early autumn and higher CHO content in the late spring. In the grain-size fractions <200 μm, the LPD and protein (PRT) contents were significantly higher in the early autumn meaning that in this season the fraction available for benthic suspension feeders presented higher nutritive value. The relatively higher CHO concentrations observed in each fraction in the late spring were attributed to refractory matter, whereas the higher PRT and LPD concentrations found during the early autumn were associated with planktonic material settled after the summer phytoplankton bloom. Our results suggest that there is seasonal variation in the composition of organic matter in the sediment, with better nutritive quality in the early autumn, especially in the grain-size fraction available for benthic suspension feeders. These variations also suggest that the benthic community exploits the fresh organic matter accumulated after the summer throughout the Antarctic dark months leaving the sediment almost exhaust of LPD and with higher CHO contents, presumably of refractory nature, at the onset of the seasonal phytoplankton bloom of the following year.