A Toxoplasma type 2C serine-threonine phosphatase is involved in parasite growth in the mammalian host cell

Toxoplasma gondii is a human protozoan parasite that belongs to the phylum of Apicomplexa and causes toxoplasmosis. As the other members of this phylum, T. gondii obligatory multiplies within a host cell by a peculiar type of mitosis that leads to daughter cell assembly within a mother cell. Although parasite growth and virulence have been linked for years, few molecules controlling mitosis have been yet identified and they include a couple of kinases but not the counteracting phosphatases. Here, we report that in contrast to other animal cells, type 2C is by far the major type of serine threonine phosphatase activity both in extracellular and in intracellular dividing parasites. Using wild type and transgenic parasites, we characterized the 37 kDa TgPP2C molecule as an abundant cytoplasmic and nuclear enzyme with activity being under tight regulation. In addition, we showed that the increase in TgPP2C activity significantly affected parasite growth by impairing cytokinesis while nuclear division still occurred. This study supports for the first time that type 2C protein phosphatase is an important regulator of cell growth in T. gondii.     

Genotype-specific interactions and the trade-off between host and parasite fitness

Background  

Evolution of parasite traits is inextricably linked to their hosts. For instance one common definition of parasite virulence is the reduction in host fitness due to infection. Thus, traits of infection must be viewed in both protagonists and may be under shared genetic and physiological control. We investigated these questions on the oomycete Hyaloperonospora arabidopsis (= parasitica), a natural pathogen of the Brassicaceae Arabidopsis thaliana.     

RGD Surface Functionalization of the Hydrophilic Acrylic Intraocular Lens Material to Control Posterior Capsular Opacification

Posterior Capsular Opacification (PCO) is the capsule fibrosis developed on implanted IntraOcular Lens (IOL) by the de-differentiation of Lens Epithelial Cells (LECs) undergoing Epithelial Mesenchymal Transition (EMT). Literature has shown that the incidence of PCO is multifactorial including the patient''s age or disease, surgical technique, and IOL design and material. Reports comparing hydrophilic and hydrophobic acrylic IOLs have shown that the former has more severe PCO. On the other hand, we have previously demonstrated that the adhesion of LECs is favored on hydrophobic compared to hydrophilic materials. By combining these two facts and contemporary knowledge in PCO development via the EMT pathway, we propose a biomimetically inspired strategy to promote LEC adhesion without de-differentiation to reduce the risk of PCO development. By surface grafting of a cell adhesion molecule (RGD peptide) onto the conventional hydrophilic acrylic IOL material, the surface-functionalized IOL can be used to reconstitute a capsule-LEC-IOL sandwich structure, which has been considered to prevent PCO formation in literature. Our results show that the innovative biomaterial improves LEC adhesion, while also exhibiting similar optical (light transmittance, optical bench) and mechanical (haptic compression force, IOL injection force) properties compared to the starting material. In addition, compared to the hydrophobic IOL material, our bioactive biomaterial exhibits similar abilities in LEC adhesion, morphology maintenance, and EMT biomarker expression, which is the crucial pathway to induce PCO. The in vitro assays suggest that this biomaterial has the potential to reduce the risk factor of PCO development.     

Ornithologische Notizen aus dem Ebrodelta

Zusammenfassung Im Ebrodelta ist, abgesehen von einigen Seen und Sümpfen, nur noch ein schmaler Küstenstreifen landwirtschaftlich ungenutzt. Hier hat sich ein Teil ursprünglichen Vogelreichtums erhalten, und hier wurde seit einigen Jahren eine Reihe faunistischer Erhebungen durchgeführt.Diese erbrachten mehrere erste Brutnachweise für Spanien oder die spanische Mittelmeerküste:Larus ridibundus, Sterna dougallii, St. sandvicensis, Haematopus ostralegus, Limosa limosa, Asio flammeus, Acrocephalus palustris. Als Rast- und Überwinterungsgebiet ist das Delta von großer Bedeutung, z. B. fürEgretta garzetta undPhoenicopterus ruber. Enge Beziehungen zur Camargue sind vielfach erkennbar, vielleicht sogar hinsichtlich der Ausbreitung vonLarus ridibundus undHaematopus ostralegus. Regelmäßige Wintervorkommen vonMarmaronetta angustirostris sind erwähnenswert.Es wird mit einigen bisher unbekannten Brutplätzen von Laro-Limicolen bekanntgemacht, von denen eine Kolonie vonSterna albifrons mit 300–400 Paaren besonders vermerkt sei. Für weitere Arten können Bestandsangaben gemacht werden.Dieses einzige, bedeutende Brut- und Rastgebiet zwischen Camargue und Coto Doñana ist in höchster Gefahr, durch intensivere landwirtschaftliche Nutzung und touristische Erschließung vernichtet zu werden.

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Resumen Datos ornitologicos sobre el Delta del Ebro. — Sin contar con charcas y marismas, el Delta del Ebro es una franja costera aun no explotada por la agricultura. Gracias a esto una numerosa variedad de aves ha podido mantenerse aprovechando las todavia persistentes condiciones orginarias del medio ambiente. Sobre estas aves se han venido acumulando en los ultimos años un buen acopio de observaciones.Se pudo constatar como nidificantes por primera vez en España o costas mediterranes a las siguientes especies:Larus ridibundus, Sterna dougalli, St. sandvicensis, Haematopus ostralegus, Limosa limosa, Asio flammeus, Acrocephalus palustris. Como lugar de invernada o refugio durante el paso el Delta del Ebro tiene un especial interes, por ejemplo paraEgretta garzetta yPhoenicopterus ruber. Se establecen algunas relaciones con la Camarga principalmente en cuanto a la expansión deLarus ridibundus yHaematopus ostralegus. Se mencionan invernadas regulares deMarmaronetta angustirostris. Se señalan algunos nuevos lugares de cria para Laro-Limicolas, merece destacarse el hallazgo de una colonia deSterna albifrons compuesta por unos 300–400 pares. Para otras especies se dan datos numerieos estimativos.El Delta del Ebro es un lugar unico y de gran importancia, situado entre la Camarga y el Coto de Doñana, que está hoy en peligro de desaparición debido a la colonización intensiva de la agricultura y a la creciente afluencia turistica.

     

Rat liver mitochondria contain two immunologically distinct dihydrolipoamide dehydrogenases

We have raised antisera against dihydrolipoamide dehydrogenase. One antigen was isolated from purified bovine kidney pyruvate dehydrogenase complex (PDC). The other antigen was a commercial preparation of porcine heart dihydrolipoamide dehydrogenase (E3) which did not first involve purification of the alpha-keto acid dehydrogenase complex(es). Both antibody preparations cross-reacted with the E3 components of PDC, alpha-ketoglutarate dehydrogenase complex, and branched-chain keto acid dehydrogenase complex. This demonstrates the immunological identity of the E3 components. These sera totally precipitated E3 activity from the purified complexes, from purified preparations of E3, and from extracts of rat heart and kidney mitochondria. The two sera vary in their reaction with rat liver mitochondrial extracts: the anti PDC-E3 serum left residual E3 activity (approximately 50% of the original) that was precipitable by the anti-E3 anti-serum. This indicates that liver contains two immunologically distinct forms of E3. Metabolic assays measuring the differential effects of the two sera on the glycine decarboxylation reaction suggest that the form which is immunologically nonreactive with the anti-PDC-E3 serum could represent the E3 involved in the glycine cleavage system.     

Trivalent behavior during prophase I in male mice heterozygous for three Robertsonian translocations: an electron-microscopic study

A synaptonemal complex (SC) analysis was carried out in male mice heterozygous (CHT/+) for three Robertsonian translocations. All pachytene preparations studied showed the presence of three trivalents. At early pachytene, the nonhomologous centromeric regions of the acrocentric chromosomes were unpaired. Heterosynapsis subsequently took place with complete pairing of the trivalents. Association between one of the three trivalents and the sex vesicle was observed in 30.4% of the nuclei. Association between the unpaired regions of two trivalents was present in 14.4% of the cells, suggesting that the relationship between unpaired regions of structural rearrangements and the X-Y bivalent may simply reflect the tendency of unpaired regions to establish end-to-end associations or heterosynapses among them, which are usually resolved during the pachytene stage of prophase I. Since the sex bivalent always has unpaired regions, these associations often affect the sex chromosomes.     

Standardized method for evaluation of hand disinfection by surgical scrub formulations

A standardized protocol for the evaluation of hand disinfection by surgical scrub formulations was applied to volunteers in a multicenter trial. Povidone iodine (PVI), chlorhexidine (CHX), and a nonmedicated soap (NMS) were tested. The scrubbing procedure involved three daily hand washings for five consecutive days; surviving bacteria were counted daily after being collected in a suitable neutralizing solution. Immediate efficacy (IE), cumulative efficacy (CE), and remanent effect (RE) were calculated by reference to the control hand. Statistical analyses of IE, CE, and RE showed significant differences among the three scrub formulations. IEs of PVI and CHX were equivalent and different from IE of NMS; CE and RE of CHX were higher than those of PVI and NMS. On the basis of the statistical analysis, the population size required for further studies aimed at detecting significant differences between surgical scrub formulations could be estimated.     

Antigenic probes locate binding sites for the glycolytic enzymes glyceraldehyde-3-phosphate dehydrogenase, aldolase and phosphofructokinase on the actin monomer in microfilaments.

The topology of the interfaces between actin monomers in microfilaments and three glycolytic enzymes (glyceraldehyde-3-phosphate dehydrogenase, aldolase and phosphofructokinase) was investigated using several specific antibodies directed against precisely located sequences in actin. A major contact area for glyceraldehyde-3-phosphate dehydrogenase was characterized in a region near residue 103. This interaction altered, by long-range conformational changes, the reactivity of antigenic epitopes in the C-terminal part of actin. The interface between actin and aldolase appeared to involve a sequence around residue 299 in the C-terminal region of actin. The interaction of phosphofructokinase, in contrast, modified the reactivity of all antibodies tested. Finally, the phosphagen kinases arginine kinase and creatine kinase showed no interaction with the microfilament.     

A new cellular model of response to estrogens: a bioluminescent test to characterize (anti) estrogen molecules

With the aim of quickly and easily characterizing new estrogen or anti-estrogen molecules, we developed a cellular model in which estrogenic action can be detected by bioluminescence. This model is based on MCF-7 cells stably transfected with a receptor gene which allows expression of the firefly luciferase enzyme under control of the estrogen regulatory element of the Xenopus vitellogenin A2 gene. A stably transfected cell line (cultured for more than eight months without loss of the chimeric estrogenic response) was established by cotransfection of a neomycin resistance gene and cloning under selective pressure. Subcloning luminescent clones was accomplished by using a single-photon detecting camera. This cellular model allowed the study of an estrogenic activity either in whole-cell or in cell-free experiments by detection of the induced luciferase. Estradiol induced the luciferase activity in a dose-dependent manner at subnanomolar concentrations. The induced luciferase activity reached a maximum level as early as 24 hours after the cells were incubated with estradiol. The antiestrogen 4-hydroxy-tamoxifen inhibited the luciferase activity induced by estradiol. The cross-reactivity of ligands, such as dexamethasone, progesterone, testosterone, aldosterone, calcitriol, oxysterol and retinoic acid, were also studied, showing an estradiol specificity for a 24-hour incubation time.