Heme oxygenase-1 induction by nitric oxide in RAW 264.7 macrophages is upregulated by a cyclo-oxygenase-2 inhibitor

Unstimulated RAW 264.7 macrophages express negligible heme oxygenase-1 (HO-1) protein but incubation with the nitric oxide (NO) donor spermine nonoate (SPNO) induced HO-1 and weakly cyclo-oxygenase-2 (COX-2) protein. This effect was potentiated by coincubation with the COX-2 selective inhibitor, SC58125. Cells incubated with SPNO showed a strong increase in HO-1 mRNA levels after 4 h with a significant potentiation in the presence of SC58125, which did not modify HO-1 mRNA stability. The induction of HO-1 by NO and its potentiation by anti-inflammatory agents may play a role in inflammatory and immune responses.     

On two nematodes from Brazilian birds and description of a new species (Acuarioidea, Schistorophinae) parasitizing Laterallus viridis (Müller, 1776) (Gruiformes, Rallidae)

The present paper reports acuarioid nematodes recovered from avian hosts. A new species of the genus Schistorophus Railliet, 1916 is proposed based mainly on findings referring to ptilina, spicules and vagina. Ancyracanthopsis coronata (Molin, 1860) Chabaud & Petter, 1959 is referred again in Brazil since its proposition in 1860, from specimens recovered from a Brazilian bird. A revised key to the species of the genus Schistorophus is also presented.     

Revised structures for the bejarols from Santolina oblongifolia

The ¹³C NMR spectra of the bejarols isolated from Santolina oblongifolia suggest they are nerolidol derivatives with a 2,6-dialkyldihydropyranose structure.     

Nest size and hatchling sex ratio in chinstrap penguins

Variation in the sex ratio at hatching in the chinstrap penguin Pygoscelis antarctica was investigated, using molecular sexing to test predictions of sex allocation theory. The sex ratio was slightly male-biased (0.54) but did not differ significantly from parity. The proportion of males increased with nest size, an estimator of parental quality in chinstrap penguins. High-quality parents were able to produce and rear a higher proportion of male offspring, the more costly sex in this slightly sexually dimorphic species. Our results may be in agreement with Trivers and Willards (1973) argument on biases in the offspring sex ratio being contingent on parental condition or quality.     

Repression of the RcsC-YojN-RcsB phosphorelay by the IgaA protein is a requisite for Salmonella virulence

Bacterial pathogenesis relies on regulators that activate virulence genes. Some of them act, in addition, as repressors of specific genes. Intracellular-growth-attenuator-A (IgaA) is a Salmonella enterica membrane protein that prevents overactivation of the RcsC-YojN-RcsB regulatory system. This negative control is critical for growth because disruption of the igaA gene is only possible in rcsC, yojN or rcsB strains. In this work, we examined the contribution of this regulatory circuit to virulence. Viable igaA point mutant alleles were isolated and characterized. These alleles encode IgaA variants leading to different levels of activation of the RcsC-YojN-RcsB system. IgaA-mediated repression of the RcsB-YojN-RcsC system occurred at the post-translational level, as shown by chromosomal epitope tagging of the rcsC, yojN and rcsB genes. The activity of the RcsC-YojN-RcsB system, monitored with the product of a tagged gmd-3xFLAG gene (positively regulated by RcsC-YojN-RcsB), was totally abolished by wild-type bacteria in mouse target organs. Such tight repression occurred only in vivo and was mediated by IgaA. Shutdown of the RcsC-YojN-RcsB system is a requisite for Salmonella virulence since all igaA point mutant strains were highly attenuated. The degree of attenuation correlated to that of the activation status of RcsC-YojN-RcsB. In some cases, the attenuation recorded was unprecedented, with competitive index (CI) values as low as 10(-6). Strikingly, IgaA is a protein absolutely dispensable for virulence in mutant strains having a non-functional RcsC-YojN-RcsB system. To our knowledge, IgaA exemplifies the first protein that contributes to virulence by exclusively acting as a negative regulator upon host colonization.     

Cytochemical location of urease in the cell wall of two different lichen phycobionts

The enzyme urease has been located in the cell wall of recently isolated phycobionts from Evernia prunastri and Xanthoria parietina lichens. Cytochemical detection is achieved by producing a black, electron-dense precipitate of cobalt sulfide proceeding from CO(2) evolved from urea in the presence of cobalt chloride. Cellular fractionation reveals that about 80% of total urease activity was associated to the cell wall on both phycobionts whereas only 20% was recovered as soluble protein.     

Cross talk between 2,4-diacetylphloroglucinol-producing biocontrol pseudomonads on wheat roots

The performance of Pseudomonas biocontrol agents may be improved by applying mixtures of strains which are complementary in their capacity to suppress plant diseases. Here, we have chosen the combination of Pseudomonas fluorescens CHA0 with another well-characterized biocontrol agent, P. fluorescens Q2-87, as a model to study how these strains affect each other's expression of a biocontrol trait. In both strains, production of the antimicrobial compound 2,4-diacetylphloroglucinol (DAPG) is a crucial factor contributing to the suppression of root diseases. DAPG acts as a signaling compound inducing the expression of its own biosynthetic genes. Experimental setups were developed to investigate whether, when combining strains CHA0 and Q2-87, DAPG excreted by one strain may influence expression of DAPG-biosynthetic genes in the other strain in vitro and on the roots of wheat. DAPG production was monitored by observing the expression of lacZ fused to the biosynthetic gene phlA of the respective strain. Dual-culture assays in which the two strains were grown in liquid medium physically separated by a membrane revealed that Q2-87 but not its DAPG-negative mutant Q2-87::Tn5-1 strongly induced phlA expression in a DeltaphlA mutant of strain CHA0. In the same way, phlA expression in a Q2-87 background was induced by DAPG produced by CHA0. When coinoculated onto the roots of wheat seedlings grown under gnotobiotic conditions, strains Q2-87 and CHA0, but not their respective DAPG-negative mutants, were able to enhance phlA expression in each other. In summary, we have established that two nonrelated pseudomonads may stimulate each other in the expression of an antimicrobial compound important for biocontrol. This interpopulation communication occurs in the rhizosphere, i.e., at the site of pathogen inhibition, and is mediated by the antimicrobial compound itself acting as a signal exchanged between the two pseudomonads.     

Analysis of the S-locus structure in Prunus armeniaca L. Identification of S-haplotype specific S-RNase and F-box genes

The gametophytic self-incompatibility (GSI) system in Rosaceae has been proposed to be controlled by two genes located in the S-locusan S-RNase and a recently described pollen expressed S-haplotype specific F-box gene (SFB). However, in apricot (Prunus armeniaca L.) these genes had not been identified yet. We have sequenced 21kb in total of the S-locus region in 3 different apricot S-haplotypes. These fragments contain genes homologous to the S-RNase and F-box genes found in other Prunusspecies, preserving their basic gene structure features and defined amino acid domains. The physical distance between the F-boxand the S-RNase genes was determined exactly in the S ₂-haplotype (2.9kb) and inferred approximately in the S ₁-haplotype (< 49kb) confirming that these genes are linked. Sequence analysis of the 5 flanking regions indicates the presence of a conserved region upstream of the putative TATA box in the S-RNase gene. The three identified S-RNase alleles (S ₁, S ₂ and S ₄) had a high allelic sequence diversity (75.3 amino acid identity), and the apricot F-box allelic variants (SFB₁, SFB₂ and SFB₄) were also highly haplotype-specific (79.4 amino acid identity). Organ specific-expression was also studied, revealing that S ₁- and S ₂-RNases are expressed in style tissues, but not in pollen or leaves. In contrast, SFB ₁ and SFB ₂ are only expressed in pollen, but not in styles or leaves. Taken together, these results support these genes as candidates for the pistil and pollen S-determinants of GSI in apricot.     

Key differences between lateral and apical branching in hyphae of Neurospora crassa

We examined in fine detail growth kinetics and intracellular events during lateral and apical branching in hyphae of Neurospora crassa. By high-resolution video-enhanced light microscopy, we found remarkable differences in the events preceding lateral vs apical branching. While apical branching involved a significant disturbance in the apical growth of the parental hypha, lateral branching occurred without any detectable alterations in the growth of the parental hypha. Prior to the emergence of a lateral branch, an incipient Spitzenk?rper was formed about 12-29 microm behind the apex. Lateral branch formation did not interfere with the elongation rate of the primary hypha, the shape of its apex or the behavior of its Spitzenk?rper. In sharp contrast, apical branching was preceded by marked changes in physiology and morphology of the parental hypha and by a sharp drop in elongation rate. The sequence involved a cytoplasmic contraction, followed by a retraction, dislocation, and disappearance of the Spitzenk?rper; hyphal elongation decreased sharply and a transient phase of isotropic growth caused the hyphal apex to round up. Growth resumed with the formation of two or more apical branches, each one with a Spitzenk?rper formed by gradual condensation of phase-dark material (vesicles) around an invisible nucleation site. The observed dissimilarities between lateral and apical branching suggest that these morphogenetic pathways are triggered differently. Whereas apical branching may be traced to a sudden discrete disruption in cytoplasmic organization (cytoplasmic contraction), the trigger of lateral branching probably stems from the subapical accumulation of wall precursors (presumably vesicles) reaching a critical concentration.