Crh1p and Crh2p are required for the cross-linking of chitin to beta(1-6)glucan in the Saccharomyces cerevisiae cell wall

In budding yeast, chitin is found in three locations: at the primary septum, largely in free form, at the mother-bud neck, partially linked to beta(1-3)glucan, and in the lateral wall, attached in part to beta(1-6)glucan. By using a recently developed strategy for the study of cell wall cross-links, we have found that chitin linked to beta(1-6)glucan is diminished in mutants of the CRH1 or the CRH2/UTR2 gene and completely absent in a double mutant. This indicates that Crh1p and Crh2p, homologues of glycosyltransferases, ferry chitin chains from chitin synthase III to beta(1-6)glucan. Deletion of CRH1 and/or CRH2 aggravated the defects of fks1Delta and gas1Delta mutants, which are impaired in cell wall synthesis. A temperature shift from 30 degrees C to 38 degrees C increased the proportion of chitin attached to beta(1-6)glucan. The expression of CRH1, but not that of CRH2, was also higher at 38 degrees C in a manner dependent on the cell integrity pathway. Furthermore, the localization of both Crh1p and Crh2p at the cell cortex, the area where the chitin-beta(1-6)glucan complex is found, was greatly enhanced at 38 degrees C. Crh1p and Crh2p are the first proteins directly implicated in the formation of cross-links between cell wall components in fungi.     

A multicentre randomized controlled trial of the efficacy and safety of single-dose praziquantel at 40 mg/kg vs. 60 mg/kg for treating intestinal schistosomiasis in the Philippines, Mauritania, Tanzania and Brazil

Background

Praziquantel at 40 mg/kg in a single dose is the WHO recommended treatment for all forms of schistosomiasis, but 60 mg/kg is also deployed nationally.

Methodology/Principal Findings

Four trial sites in the Philippines, Mauritania, Tanzania and Brazil enrolled 856 patients using a common protocol, who were randomised to receive praziquantel 40 mg/kg (n = 428) or 60 mg/kg (n = 428). While the sites differed for transmission and infection intensities (highest in Tanzania and lowest in Mauritania), no bias or heterogeneity across sites was detected for the main efficacy outcomes. The primary efficacy analysis was the comparison of cure rates on Day 21 in the intent-to-treat population for the pooled data using a logistic model to calculate Odd Ratios allowing for baseline characteristics and study site. Both doses were highly effective: the Day 21 cure rates were 91.7% (86.6%–98% at individual sites) with 40 mg/kg and 92.8% (88%–97%) with 60 mg/kg. Secondary parameters were eggs reduction rates (ERR), change in intensity of infection and reinfection rates at 6 and 12 months. On Day 21 the pooled estimate of the ERR was 91% in both arms. The Hazard Ratio for reinfections was only significant in Brazil, and in favour of 60 mg/kg on the pooled estimate (40 mg/kg: 34.3%, 60 mg/kg: 23.9%, HR = 0.78, 95%CI = [0.63;0.96]). Analysis of safety could not distinguish between disease- and drug-related events. 666 patients (78%) reported 1327 adverse events (AE) 4 h post-dosing. The risk of having at least one AE was higher in the 60 than in the 40 mg/kg group (83% vs. 73%, p<0.001). At 24 h post-dosing, 456 patients (54%) had 918 AEs with no difference between arms. The most frequent AE was abdominal pain at both 4 h and 24 h (40% and 24%).

Conclusion

A higher dose of 60 mg/kg of praziquantel offers no significant efficacy advantage over standard 40 mg/kg for treating intestinal schistosomiasis caused by either S. mansoni or S. japonicum. The results of this study support WHO recommendation and should be used to inform policy decisions in the countries.

Trial Registration

Controlled-Trials.com ISRCTN29273316 ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT00403611","term_id":"NCT00403611"}}NCT00403611     

A genetic code Boolean structure. I. The meaning of Boolean deductions

This paper proposes a genetic code Boolean structure derived from hydrogen bond numbers and chemical types of bases, purines and pyrimidines. It shows that in such Boolean structure, deductions comprise physico-chemical meaning. In particular, codons with adenine as a second base coding to hydrophilic amino acids are not deductible from codons with uracil in the same position, which code to hydrophobic amino acids. Boolean deductions could help us describe the gene evolution process. For instance, most of the reported mutations that confer drug resistance to the HIV protease gene correspond to deductions. What is more, in the human beta-globin gene a similar situation appears where most of the single codon mutations correspond to Boolean deductions from the respective wild-type codon.     

Epidermal fatty acid-binding protein is increased in rat lungs following in vivo treatment with keratinocyte growth factor

Exogenous application of keratinocyte growth factor protects the lung against a variety of injurious stimuli. KGF-treatment leads to pronounced hyperplasia of alveolar epithelial type II cells and to stabilization of surfactant homeostasis after lung injury. Epidermal fatty acid-binding protein is involved in the synthesis of surfactant phospholipids and acts as an antioxidant scavenging reactive lipids. We treated adult rats with recombinant human keratinocyte growth factor (Palifermin) via intratracheal instillation and analyzed the expression of epidermal fatty acid-binding protein mRNA and protein by quantitative RT-PCR, immunoblotting as well as immunohistochemistry. Keratinocyte growth factor-treatment in vivo leads to an increased expression of epidermal fatty acid-binding protein mRNA and protein in the total lung. Epidermal fatty acid-binding protein mRNA expression per alveolar epithelial type II cell remains constant as shown in isolated type II cells. Epidermal fatty acid-binding protein immunoreactivity is seen in most if not all hyperplastic alveolar epithelial type II cells, and is mainly localized to the cytoplasm. The increase in epidermal fatty acid-binding protein gene expression associated with type II cell hyperplasia might contribute to the molecular mechanisms mediating lung protection by keratinocyte growth factor.     

Current perspectives on the mechanism of action of artemisinins

Artemisinin derivatives are the most recent single drugs approved and introduced for public antimalarial treatment. Although their recommended use is for treatment of Plasmodium falciparum infection, these drugs also act against other parasites, as well as against tumor cells. The mechanisms of action attributed to artemisinin include interference with parasite transport proteins, disruption of parasite mitochondrial function, modulation of host immune function and inhibition of angiogenesis. Artemisinin combination therapies are currently the preferred treatment for malaria. These combinations may prevent the induction of parasite drug resistance. However, in view of the multiple mechanisms involved, especially when additional drugs are used, the combined therapy should be carefully examined for antagonistic effects. It is now a general theory that the crucial mechanism is interference with plasmodial SERCA. Therefore, future development of resistance may be associated with overproduction or mutations of this transporter. However, a general mechanism, such as alterations in general drug transport pathways, is feasible. In this article, we review the evidence for each mechanism of action suggested.     

Cerebral malaria: role of microparticles and platelets in alterations of the blood-brain barrier

Brain lesions of cerebral malaria (CM) are characterised by a sequestration of Plasmodium falciparum-parasitised red blood cells (PRBC), leucocytes and platelets within brain microvessels, by an excessive release of pro-inflammatory cytokines as well as by disruption of the blood-brain barrier (BBB). We evaluated the possibility that PRBC and platelets interact and induce functional alterations in brain endothelium. Using an in vitro model of endothelial lesion, we showed that platelets can act as bridges between PRBC and endothelial cells (EC) allowing the binding of PRBC to endothelium devoid of cytoadherence receptors. Furthermore, platelets potentiated the cytotoxicity of PRBC for brain EC by inducing an alteration of the integrity of their monolayer and increasing their apoptosis. These findings provide insights into the mechanisms by which platelets can be deleterious to the brain endothelium during CM. Another aspect of inflammatory and infectious diseases is that they often lead to activation of vascular and blood cells. Such activation results in an enhanced vesiculation, i.e. the release of circulating microparticles (MP). We thus explored plasma levels of endothelial MP in Malawian children with malaria. Plasma MP numbers were markedly increased on admission only in patients with severe malaria complicated with coma. Using the experimental mouse model of CM, we evaluated the pathogenic implications of MP using genetically deficient mice in which the capacity to vesiculate is impaired. Such mice, lacking the ABCA-1 gene, upon infection by Plasmodium berghei ANKA, showed complete resistance to CM. When purified from infected susceptible animals, MP were able to reduce normal plasma clotting time and to significantly enhance tumour necrosis factor release from na?ve macrophages. Altogether these data provide a novel insight into the pathogenic mechanisms leading to the neurological syndrome. The finding that ABCA-1 gene deletion confers complete protection against cerebral pathology, linked to an impaired MP production, provides new potential targets for therapeutic amelioration of severe malaria.