Xp38gamma/SAPK3 promotes meiotic G(2)/M transition in Xenopus oocytes and activates Cdc25C

We have studied the role of p38 mitogen-activated protein kinases (MAPKs) in the meiotic maturation of Xenopus oocytes. Overexpression of a constitutively active mutant of the p38 activator MKK6 accelerates progesterone-induced maturation. Immunoprecipit ation experiments indicate that p38gamma/SAPK3 is the major p38 activated by MKK6 in the oocytes. We have cloned Xenopus p38gamma (Xp38gamma) and show that co-expression of active MKK6 with Xp38gamma induces oocyte maturation in the absence of progesterone. The maturation induced by Xp38gamma requires neither protein synthesis nor activation of the p42 MAPK-p90Rsk pathway, but it is blocked by cAMP-dependent protein kinase. A role for the endogenous Xp38gamma in progesterone-induced maturation is supported by the inhibitory effect of kinase-dead mutants of MKK6 and Xp38gamma. Furthermore, MKK6 can rescue the inhibition of oocyte maturation by anthrax lethal factor, a protease that inactivates MAPK kinases. We also show that Xp38gamma can activate the phosphatase XCdc25C, and we identified Ser205 of XCdc25C as a major phosphorylation site for Xp38gamma. Our results indicate that phosphorylation of XCdc25C by Xp38gamma/SAPK3 is important for the meiotic G(2)/M progression of Xenopus oocytes.     

Entamoeba histolytica: mechanism of decrease of virulence of axenic cultures maintained for prolonged periods

Intraportal injection of non-virulent E. histolytica (derived from prolonged axenic culture of virulent E. histolytica) strain HM1-IMSS in normal hamsters results in no liver lesions and disappearance of the parasites 48-72 h after injection. Viability of non-virulent E. histolytica after 2 h of in vitro incubation in either fresh or decomplemented hamster serum is the same as control virulent E. histolytica (50-90%). In hamsters made leukopenic, or both leukopenic+hypocomplementemic, or hypocomplementemic+sephadex microspheres (to produce focal liver ischemia) intraportally injected non-virulent E. histolytica cause no lesions and disappear after 24 h. In addition, neither hypocomplementemia nor immunosuppression with cyclosporin A prolonged the survival of non-virulent E. histolytica. Methyl prednisolone treatment of hamsters resulted in survival of large numbers of non-virulent E. histolytica in the liver, with little inflammation and minimal tissue damage, for up to 7 days. Inflammatory cells (macrophages) would appear to be chiefly responsible for elimination of non-virulent E. histolytica. Parallel experiments with E. dispar suggest a different mechanism for its non-pathogenicity.     

Entamoeba histolytica: apoptosis induced in vitro by nitric oxide species

Apoptosis has been described in some parasites like Leishmania, Trypanosoma, and Trichomonas. This phenomenon has not been observed yet in Entamoeba histolytica. This work analyzed the in vitro effect of sodium nitroprusside, sodium nitrite and sodium nitrate (NOs) on E. histolytica apoptosis. Parasites incubated for 1h with NOs revealed apoptosis 6h later (95% viability), demonstrated by YOPRO-1, TUNEL, DNA fragmentation and low ATP levels. The caspase inhibitor Z-VAD-FMK inhibited total intracellular cysteine protease activity (CPA) but had no effect on apoptosis. When treated with NOs some amebic functions like complement resistance and hemolytic activity decreased but CPA and erythrophagocytosis remained unchanged. After treatment in vitro with NOs, parasite death was almost complete at 24h; but when injected into hamster livers they disappeared in less than 6h. These results show that apoptosis is induced in vitro by NOs in E. histolytica and renders them incapable of surviving in hamster's livers.     

Does Cataract Surgery Alleviate Poverty? Evidence from a Multi-Centre Intervention Study Conducted in Kenya,the Philippines and Bangladesh

Background

Poverty and blindness are believed to be intimately linked, but empirical data supporting this purported relationship are sparse. The objective of this study is to assess whether there is a reduction in poverty after cataract surgery among visually impaired cases.

Methodology/Principal Findings

A multi-centre intervention study was conducted in three countries (Kenya, Philippines, Bangladesh). Poverty data (household per capita expenditure – PCE, asset ownership and self-rated wealth) were collected from cases aged ≥50 years who were visually impaired due to cataract (visual acuity<6/24 in the better eye) and age-sex matched controls with normal vision. Cases were offered free/subsidised cataract surgery. Approximately one year later participants were re-interviewed about poverty. 466 cases and 436 controls were examined at both baseline and follow-up (Follow up rate: 78% for cases, 81% for controls), of which 263 cases had undergone cataract surgery (“operated cases”). At baseline, operated cases were poorer compared to controls in terms of PCE (Kenya: $22 versus £35 p = 0.02, Bangladesh: $16 vs $24 p = 0.004, Philippines: $24 vs 32 p = 0.0007), assets and self-rated wealth. By follow-up PCE had increased significantly among operated cases in each of the three settings to the level of controls (Kenya: $30 versus £36 p = 0.49, Bangladesh: $23 vs $23 p = 0.20, Philippines: $45 vs $36 p = 0.68). There were smaller increases in self-rated wealth and no changes in assets. Changes in PCE were apparent in different socio-demographic and ocular groups. The largest PCE increases were apparent among the cases that were poorest at baseline.

Conclusions/Significance

This study showed that cataract surgery can contribute to poverty alleviation, particularly among the most vulnerable members of society. This study highlights the need for increased provision of cataract surgery to poor people and shows that a focus on blindness may help to alleviate poverty and achieve the Millennium Development Goals.     

Titles of related papers in other sections

The effect of hypoglycemic drugs chlorpropamide and phenformin has been tested on isolated liver plasma membranes as to their microviscosity parameters. Results reported suggest that both drugs are able to increase in vitro plasma membrane microviscosity in a dose-dependent way.     

Molecular intraspecific characterization of Photobacterium damselae ssp. damselae strains affecting cultured marine fish

Aims: The aim of this study was to analyse the intraspecific variability of Photobacterium damselae ssp. damselae strains isolated from different cultured marine fish species using molecular typing methods. Methods and Results: Twenty P. damselae ssp. damselae strains isolated from marine fish species were used in this study. Phenotypic characterization of the strains was carried out using standard microbiological methods. Genetic characterization was conducted using three PCR‐based methods [random amplified polymorphic DNA (RAPD), enterobacterial repetitive intergenic consensus‐PCR (ERIC‐PCR) and repetitive extragenic palindromic‐PCR (REP‐PCR)]. Dice coefficient and the unweighted pair group method with average linkage were used for numerical analyses of banding patterns. At phenotypic level, the strains analysed showed seven different profiles, which could not be related to the host fish species, geographic area or outbreak of disease. Isolates were grouped into nine and eight clusters using the RAPD technique with primers 5 and 4, respectively. In both cases, the main cluster grouped 45% of strains. The techniques ERIC‐PCR and REP‐PCR were more discriminatory, both resulting in 14 different clusters, which grouped 15–20% of the isolates. Conclusions: In this study, the techniques tested are confirmed as good tools for molecular typing, because they allow discrimination between P. damselae ssp. damselae strains isolated within the same outbreak. In addition, ERIC‐PCR and REP‐PCR methods were more adequate for rapid typing of P. damselae ssp. damselae than RAPD, allowing the discrimination at strain level. Significance and Impact of the Study: The results, in agreement with previous studies, confirmed the high intraspecific variability among isolated P. damselae ssp. damselae strains at both phenotypic and genetic levels. This suggests the existence of different clonal lineages that coexist in the same geographic area, within a short period of time (2–3 years). The discrimination at strain level can be useful to study the traceability of infections.     

Diversity of Cacao Trees in Waslala,Nicaragua: Associations between Genotype Spectra,Product Quality and Yield Potential

The sensory quality and the contents of quality-determining chemical compounds in unfermented and fermented cocoa from 100 cacao trees (individual genotypes) representing groups of nine genotype spectra (GG), grown at smallholder plantings in the municipality of Waslala, Nicaragua, were evaluated for two successive harvest periods. Cocoa samples were fermented using a technique mimicking recommended on-farm practices. The sensory cocoa quality was assessed by experienced tasters, and seven major chemical taste compounds were quantified by near infrared spectrometry (NIRS). The association of the nine, partially admixed, genotype spectra with the analytical and sensory quality parameters was tested. The individual parameters were analyzed as a function of the factors GG and harvest (including the date of fermentation), individual trees within a single GG were used as replications. In fermented cocoa, significant GG-specific differences were observed for methylxanthines, theobromine-to-caffeine (T/C) ratio, total fat, procyanidin B5 and epicatechin, as well as the sensory attributes global score, astringency, and dry fruit aroma, but differences related to harvest were also apparent. The potential cocoa yield was also highly determined by the individual GG, although there was significant tree-to-tree variation within every single GG. Non-fermented samples showed large harvest-to-harvest variation of their chemical composition, while differences between GG were insignificant. These results suggest that selection by the genetic background, represented here by groups of partially admixed genotype spectra, would be a useful strategy toward enhancing quality and yield of cocoa in Nicaragua. Selection by the GG within the local, genetically segregating populations of seed-propagated cacao, followed by clonal propagation of best-performing individuals of the selected GG could be a viable alternative to traditional propagation of cacao by seed from open pollination. Fast and gentle air-drying of the fermented beans and their permanent dry storage were an efficient and comparatively easy precondition for high cocoa quality.