Effects of hydrogen peroxide on the content of major volatile halogenated compounds in the red alga <Emphasis Type="Italic">Asparagopsis taxiformis</Emphasis> (Bonnemaisoniaceae)

The genus Asparagopsis is a prolific source of halogenated metabolites. Due to its commercial applications, it has been intensively cultivated in southern Portugal. In the present study, we assess if the internal levels of the major halogenated metabolites (bromoform and dibromoacetic acid) in Asparagopsis taxiformis can be increased with hydrogen peroxide (H₂O₂) addition. Previous studies with red algae showed that the production/release of bromoform can be enhanced by exogenously supplying H₂O₂. However, no study has assessed if H₂O₂ supply enhances the content of secondary metabolites within the biomass. This detail is important as the objective of the proposed research is to enhance the content of these valuable metabolites in the produced biomass. Both the activity of the haloperoxidase enzyme and the metabolite content were assessed on short-term and long-term incubation periods to H₂O₂. To determine the susceptibility of A. taxiformis photosynthetic performance to the imposed oxidative stress, the in vivo fluorescence of photosystem II was monitored. A. taxiformis was shown to be physiologically vulnerable to H₂O₂, given the observed decrease of the maximum quantum yield of photosynthesis (F _v/F _m). Contrary to what was expected, the presence of H₂O₂ inhibited the activity of the iodoperoxidase enzyme. Nevertheless, the extracted halogenated metabolites were higher over the first hours of exposure to H₂O₂, decreasing after 48 h. These results are probably related to the prosthetic group of the halogenated enzyme in A. taxiformis and the long-term oxidative stress damage of H₂O₂ exposure. Considering the objective of the proposed research, addition of H₂O₂ to the cultures, prior (3 h) to biomass harvesting, increases the metabolite content.     

Human and mouse cementum proteins immunologically related to enamel proteins

SDS-polyacrylamide gel electrophoresis, immunoblot and amino acid composition analyses were applied to human and mouse acellular cementum proteins immunologically related to enamelins and amelogenins. In this analysis, anti-mouse amelogenin, anti-human enamelin and synthetic peptide (e.g., -LPPHPGHPGYIC-) antibodies were shown to cross-react with tooth crown-derived enamelin with a molecular mass of 72,000 Da (72 kDa), amelogenins (26 kDa), and also to four human cementum proteins (72, 58, 50 and 26 kDa) and two mouse cementum proteins (72 and 26 kDa). Each of the antibodies recognized tooth root-derived cementum polypeptides which share one or more epitopes with tooth crown-derived enamel proteins. The molecular mass and isoelectric points for crown-derived and root-derived enamel-related proteins were similar. Analysis of human and mouse cementum proteins revealed a characteristic amino acid composition enriched in glutamyl, serine, glycine, alanine, proline, valine and leucine residues; compared to the major enamel protein amelogenin, cementum proteins were low in proline, histidine and methionine. The human and mouse putative intermediate cementum proteins appear to represent a distinct class of enamel-related proteins. Moreover, these results support the hypothesis that epithelial root sheath epithelia express several cementum proteins immunologically related to canonical enamel proteins.     

Anti-inflammatory effect of l-cysteine (a semi-essential amino acid) on 5-FU-induced oral mucositis in hamsters

Oral mucositis is an inflammation of the oral mucosa mainly resulting from the cytotoxic effect of 5-fluorouracil (5-FU). The literature shows anti-inflammatory action of l-cysteine (l-cys) involving hydrogen sulfide (H₂S). In view of these properties, we investigate the effect of l-cys in oral mucositis induced by 5-FU in hamsters. The animals were divided into the following groups: saline 0.9%, mechanical trauma, 5-FU 60–40 mg/kg, l-cys 10/40 mg and NaHS 27 µg/kg. 5-FU was administered on days 1st to 2nd; 4th day excoriations were made on the mucosa; 5th–6th received l-cys and NaHS. For data analysis, histological analyses, mast cell count, inflammatory and antioxidants markers, and immunohistochemistry (cyclooxygenase-2(COX-2)/inducible nitric oxide synthase (iNOs)/H₂S) were performed. Results showed that l-cys decreased levels of inflammatory markers, mast cells, levels of COX-2, iNOS and increased levels of antioxidants markers and H₂S when compared to the group 5-FU (p < 0.005). It is suggested that l-cys increases the H₂S production with anti-inflammatory action in the 5-FU lesion.

     

Breeding biology of White‐rumped Tanagers in central Brazil

ABSTRACT White‐rumped Tanagers (Cypsnagra hirundinacea) are widely distributed in northern Brazil, Bolivia, and Paraguay, and are classified as vulnerable in the state of Paraná and as endangered in the state of São Paulo, Brazil. Little is currently known about their breeding biology. We studied the breeding behavior of White‐rumped Tanagers in the Cerrado (Neotropical savanna) in central Brazil from 2002 to 2007. The breeding period extended from mid‐August to mid‐December. Nests were cup‐shaped and located mainly in trees of the genus Kielmeyera at a mean height of 3.7 ± 0.3 m (SE). Clutch sizes varied from one to three eggs and the incubation period lasted an average of 16.0 ± 0.3 d. Incubation was by females only and started with the laying of the first egg. Mean nest attentiveness (percent time on nests by females) was 64 ± 0.08%. Nestlings were fed by males, females, and, when present, helpers. The mean rate of food delivery rate to nests was 5.2 ± 0.4 items/h, with rates similar for males (mean = 2.7 ± 0.3 items/h) and females (mean = 2.4 ± 0.3 items/h). The mean duration of the nestling period was 12.1 ± 0.5 d. Compared to many temperate species of tanagers, White‐rumped Tanagers in our study had relatively small clutches, low nest attentiveness, and long incubation periods. As with other tropical species, such characteristics might be due to food limitation or high rates of nest predation.     

Trehalose-6-phosphate-mediated phenotypic change in Acinetobacter baumannii

The stress protectant trehalose is synthesized in Acinetobacter baumannii from UPD-glucose and glucose-6-phosphase via the OtsA/OtsB pathway. Previous studies proved that deletion of otsB led to a decreased virulence, the inability to grow at 45°C and a slight reduction of growth at high salinities indicating that trehalose is the cause of these phenotypes. We have questioned this conclusion by producing ∆otsA and ∆otsBA mutants and studying their phenotypes. Only deletion of otsB, but not deletion of otsA or otsBA, led to growth impairments at high salt and high temperature. The intracellular concentrations of trehalose and trehalose-6-phosphate were measured by NMR or enzymatic assay. Interestingly, none of the mutants accumulated trehalose any more but the ∆otsB mutant with its defect in trehalose-6-phosphate phosphatase activity accumulated trehalose-6-phosphate. Moreover, expression of otsA in a ∆otsB background under conditions where trehalose synthesis is not induced led to growth inhibition and the accumulation of trehalose-6-phosphate. Our results demonstrate that trehalose-6-phosphate affects multiple physiological activities in A. baumannii ATCC 19606.     

Role of AIP56 disulphide bond and its reduction by cytosolic redox systems for efficient intoxication

Apoptosis‐inducing protein of 56 kDa (AIP56) is a major virulence factor of Photobacterium damselae subsp. piscicida, a gram‐negative pathogen that infects warm water fish species worldwide and causes serious economic losses in aquacultures. AIP56 is a single‐chain AB toxin composed by two domains connected by an unstructured linker peptide flanked by two cysteine residues that form a disulphide bond. The A domain comprises a zinc‐metalloprotease moiety that cleaves the NF‐kB p65, and the B domain is involved in binding and internalisation of the toxin into susceptible cells. Previous experiments suggested that disruption of AIP56 disulphide bond partially compromised toxicity, but conclusive evidences supporting the importance of that bond in intoxication were lacking. Here, we show that although the disulphide bond of AIP56 is dispensable for receptor recognition, endocytosis, and membrane interaction, it needs to be intact for efficient translocation of the toxin into the cytosol. We also show that the host cell thioredoxin reductase‐thioredoxin system is involved in AIP56 intoxication by reducing the disulphide bond of the toxin at the cytosol. The present study contributes to a better understanding of the molecular mechanisms operating during AIP56 intoxication and reveals common features shared with other AB toxins.     

Meningococcal disease: A paradigm of type‐IV pilus dependent pathogenesis

Neisseria meningitidis (meningococcus) is a Gram‐negative bacterium responsible for two devastating forms of invasive diseases: purpura fulminans and meningitis. Interaction with both peripheral and cerebral microvascular endothelial cells is at the heart of meningococcal pathogenesis. During the last two decades, an essential role for meningococcal type IV pili in vascular colonisation and disease progression has been unravelled. This review summarises 20 years of research on meningococcal type IV pilus‐dependent virulence mechanisms, up to the identification of promising anti‐virulence compounds that target type IV pili.