Hymenolepis diminuta: experimental studies on the antioxidant system with short and long term infection periods in the rats

Many helminths cause long-lasting infections, living for several years in mammalian hosts reflecting a well balanced coexistence between host and parasite. There are many possible explanations as to how they can survive for lengthy periods. One possibility is their antioxidant systems, which can serve as defence mechanisms against host-generated oxygen radicals. Therefore, the aim of this experimental study was to examine the antioxidant system in Hymenolepisdiminuta during short (1.5 months young tapeworms) and long (1.5 years old tapeworms) term infection in the rat small intestine.The strobilae of H. diminuta tapeworms (14 young and three old) were divided into three pieces: the anterior part, containing the genital primordiae in the immature segments; the medial part, containing the early uterus in the mature, hermaphroditic proglottids and the terminal part with the mature gravid uterus in the gravid segments. Supernatants of these fragments were used for determination of markers of oxidative stress: concentration of thiobarbiturate reactive substances (TBARS) and of reduced glutathione (GSH), and the activity of antioxidant enzymes: superoxide dismutase (SOD1 and SOD2), catalase (CAT), glutathione peroxidases (GSHPxs), glutathione transferase (GST) and glutathione reductase (GSHR).The results indicated changes in levels of oxidative stress markers and antioxidant enzyme activity in both the young and old forms of H. diminuta. Relatively high activity of SOD (particularly in the anterior part of young tapeworms) was observed, as was increased activity of total GSHPx and a relatively high concentration of GSH in all parts of the tapeworms. These are caused by exposure to increased amount of ROS, which are produced during the inflammatory state. Due to the high activity of antioxidant enzymes, the anterior section of young and old tapeworms is equipped with a very effective antioxidant system. Old organisms also effectively resist oxidative stress due to reduced levels of lipid peroxidation and the high activity of GST, all of which suggest good adaptation to the hostile environment in the host’s intestine.     

A two-parameter model of the effective elastic tensor for cortical bone

Multiscale models of cortical bone elasticity require a large number of parameters to describe the organization and composition of the tissue. We hypothesize that the macro-scale anisotropic elastic properties of different bones can be modeled retaining only two variable parameters, and setting the others to universal values identical for all bones. Cortical bone is regarded as a two-phase composite material: a dense mineralized matrix (ultrastructure) and a soft phase (pores). The ultrastructure is assumed to be a homogeneous and transversely isotropic tissue whose elastic properties in different directions are mutually dependent and can be scaled with a single parameter driving the overall rigidity. This parameter is taken to be the volume fraction of mineral f(ha). The pore network is modeled as an ensemble of water-filled cylinders and described only by the porosity p. The effective macroscopic elasticity tensor C(ij)(f(ha),p) is calculated with a multiscale micromechanics approach starting from existing models. The modeled stiffness coefficients compare favorably to four literature datasets which were chosen because they provide the full stiffness tensors of groups of human samples. Since the physical counterparts of f(ha) and p were unknown for the datasets, their values which allow the best fit of experimental tensors by the modeled ones were determined by optimization. Optimum values of f(ha) and p are found to be unique and realistic. These results suggest that a two-parameter model may be sufficient to model the elasticity of different samples of human femora and tibiae. Such a model would in particular be useful in large-scale parametric studies of bone mechanical response.     

Upregulation of cardiac NO/NOS system during short-term hypoxia and the subsequent reoxygenation period

Hypoxia/reoxygenation (H/R) reportedly influences nitric oxide (NO) production and NO synthase (NOS) expression in the heart. Nonetheless, a number of works have shown controversial results regarding the changes that the cardiac NO/NOS system undergoes under such situations. Therefore, this study aims to clarify the behaviour of this system in the hypoxic heart by investigating seven different reoxygenation times. Wistar rats were submitted to H/R (hypoxia for 30 min; reoxygenation of 0, 2, 12, 24, 48, 72 h, and 5 days) in a novel approach to address the events provoked by assaults under such circumstances. Endothelial and inducible NOS (eNOS and iNOS) mRNA and protein expression, as well as enzymatic activity and enzyme location were determined. NO levels were indirectly quantified as nitrate/nitrite, and other S-nitroso compounds (NOx), which would act as NO-storage molecules. The results showed a significant increase in eNOS mRNA, protein and activity, as well as in NOx levels immediately after hypoxia, while iNOS protein and activity were induced throughout the reoxygenation period. These findings indicate that, not only short-term hypoxia, but also the subsequent reoxygenation period upregulate cardiac NO/NOS system until at least 5 days after the hypoxic stimulus, implying major involvement of this system in the changes occurring in the heart in response to H/R.     

Loss-of-function of Constitutive Expresser of Pathogenesis Related Genes5 affects potassium homeostasis in Arabidopsis thaliana

Here, we demonstrate that the reduction in leaf K(+) observed in a mutant previously identified in an ionomic screen of fast neutron mutagenized Arabidopsis thaliana is caused by a loss-of-function allele of CPR5, which we name cpr5-3. This observation establishes low leaf K(+) as a new phenotype for loss-of-function alleles of CPR5. We investigate the factors affecting this low leaf K(+) in cpr5 using double mutants defective in salicylic acid (SA) and jasmonic acid (JA) signalling, and by gene expression analysis of various channels and transporters. Reciprocal grafting between cpr5 and Col-0 was used to determine the relative importance of the shoot and root in causing the low leaf K(+) phenotype of cpr5. Our data show that loss-of-function of CPR5 in shoots primarily determines the low leaf K(+) phenotype of cpr5, though the roots also contribute to a lesser degree. The low leaf K(+) phenotype of cpr5 is independent of the elevated SA and JA known to occur in cpr5. In cpr5 expression of genes encoding various Cyclic Nucleotide Gated Channels (CNGCs) are uniquely elevated in leaves. Further, expression of HAK5, encoding the high affinity K(+) uptake transporter, is reduced in roots of cpr5 grown with high or low K(+) supply. We suggest a model in which low leaf K(+) in cpr5 is driven primarily by enhanced shoot-to-root K(+) export caused by a constitutive activation of the expression of various CNGCs. This activation may enhance K(+) efflux, either indirectly via enhanced cytosolic Ca(2+) and/or directly by increased K(+) transport activity. Enhanced shoot-to-root K(+) export may also cause the reduced expression of HAK5 observed in roots of cpr5, leading to a reduction in uptake of K(+). All ionomic data presented is publically available at www.ionomicshub.org.     

IL-21 promotes lupus-like disease in chronic graft-versus-host disease through both CD4 T cell- and B cell-intrinsic mechanisms

T cell-driven B cell hyperactivity plays an essential role in driving autoimmune disease development in systemic lupus erythematosus. IL-21 is a member of the type I cytokine family with pleiotropic activities. It regulates B cell differentiation and function, promotes T follicular helper (T(FH)) cell and Th17 cell differentiation, and downregulates the induction of T regulatory cells. Although IL-21 has been implicated in systemic lupus erythematosus, the relative importance of IL-21R signaling in CD4(+) T cells versus B cells is not clear. To address this question, we took advantage of two induced models of lupus-like chronic graft-versus-host disease by using wild-type or IL-21R(-/-) mice as donors in the parent-into-F1 model and as hosts in the Bm12→B6 model. We show that IL-21R expression on donor CD4(+) T cells is essential for sustaining T(FH) cell number and subsequent help for B cells, resulting in autoantibody production and more severe lupus-like renal disease, but it does not alter the balance of Th17 cells and regulatory T cells. In contrast, IL-21R signaling on B cells is critical for the induction and maintenance of germinal centers, plasma cell differentiation, autoantibody production, and the development of renal disease. These results demonstrate that IL-21 promotes autoimmunity in chronic graft-versus-host disease through both CD4(+) T cell- and B cell-intrinsic mechanisms and suggest that IL-21 blockade may attenuate B cell hyperactivity, as well as the aberrant T(FH) cell pathway that contributes to lupus pathogenesis.     

Habitat distribution modelling,under the present climatic scenario,of the threatened endemic Iberian Delphinium fissum subsp. sordidum (Ranunculaceae) and implications for its conservation

We modelled the potential habitat of a threatened species D. fissum subsp. sordidum, an endemic hemicryptophyte with a disjunct distribution in the Iberian Peninsula. Maxent was used to predict the subspecies habitat suitability by relating field sample-based distributional information with environmental and topographic variables. Our results suggest that the model performed well, predicting with high accuracy the current distribution of the species. The variables that most contributed to the model were Mean Temperature of Wettest Quarter (MTWtQ), Precipitation of Warmest Quarter (PWmQ), Temperature Annual Range (TAR) and Slope (Slo). These variables are biological significant for the taxon, as they have decisive influence in the critical stages of germination and fruiting. The current and potential distributional areas identified by the model fall mainly in regions with some degree of environmental protection, with some exceptions. A recovery plan for the species should be considered. Species Distribution Modelling cannot substitute long-term monitoring programmes, yet it is a useful tool for identifying appropriate areas of taxon occurrence, and thus allow for efficient use of the economic and human resources.     

Comparison of cadmium biosorption by Gram-positive and Gram-negative bacteria from activated sludge

Summary Gram-positive and Gram-negative bacteria were isolated from activated sludge and used to evaluate differences in cadmium biosorption. Gram-positive bacteria exhibited approximately 20% more cadmium biosorption at 30°C and pH 6.6 than Gram-negatives. Biosorption was largely passive in both cases, although metabolic uptake appeared to occur to a higher extent with Gram-positive bacteria.     

The Caspase-8 Homolog Dredd Cleaves Imd and Relish but Is Not Inhibited by p35

In Drosophila, the Imd pathway is activated by diaminopimelic acid-type peptidoglycan and triggers the humoral innate immune response, including the robust induction of antimicrobial peptide gene expression. Imd and Relish, two essential components of this pathway, are both endoproteolytically cleaved upon immune stimulation. Genetic analyses have shown that these cleavage events are dependent on the caspase-8 like Dredd, suggesting that Imd and Relish are direct substrates of Dredd. Among the seven Drosophila caspases, we find that Dredd uniquely promotes Imd and Relish processing, and purified recombinant Dredd cleaves Imd and Relish in vitro. In addition, interdomain cleavage of Dredd is not required for Imd or Relish processing and is not observed during immune stimulation. Baculovirus p35, a suicide substrate of executioner caspases, is not cleaved by purified Dredd in vitro. Consistent with this biochemistry but contrary to earlier reports, p35 does not interfere with Imd signaling in S2* cells or in vivo.