Results of gal-knockout porcine thymokidney xenografts

Clinical transplantation for the treatment of end-stage organ disease is limited by a shortage of donor organs. Successful xenotransplantation could immediately overcome this limitation. The development of homozygous alpha1,3-galactosyltransferase knockout (GalT-KO) pigs removed hyperacute rejection as the major immunologic hurdle to xenotransplantation. Nevertheless, GalT-KO organs stimulate robust immunologic responses that are not prevented by immunosuppressive drugs. Murine studies show that recipient thymopoiesis in thymic xenografts induces xenotolerance. We transplanted life-supporting composite thymokidneys (composite thymus and kidneys) prepared in GalT-KO miniature swine to baboons in an attempt to induce tolerance in a preclinical xenotransplant model. Here, we report the results of seven xenogenic thymokidney transplants using a steroid-free immunosuppressive regimen that eliminated whole-body irradiation in all but one recipient. The regimen resulted in average recipient survival of over 50 days. This was associated with donor-specific unresponsiveness in vitro and early baboon thymopoiesis in the porcine thymus tissue of these grafts, suggesting the development of T-cell tolerance. The kidney grafts had no signs of cellular infiltration or deposition of IgG, and no grafts were lost due to rejection. These results show that xenogeneic thymus transplantation can support early primate thymopoiesis, which in turn may induce T-cell tolerance to solid organ xenografts.

Transgenic expression of human CD47 markedly increases engraftment in a murine model of pig-to-human hematopoietic cell transplantation

Mixed chimerism approaches for induction of tolerance of solid organ transplants have been applied successfully in animal models and in the clinic. However, in xenogeneic models (pig-to-primate), host macrophages participate in the rapid clearance of porcine hematopoietic progenitor cells, hindering the ability to achieve mixed chimerism. CD47 is a cell-surface molecule that interacts in a species-specific manner with SIRPα receptors on macrophages to inhibit phagocytosis and expression of human CD47 (hCD47) on porcine cells has been shown to inhibit phagocytosis by primate macrophages. We report here the generation of hCD47 transgenic GalT-KO miniature swine that express hCD47 in all blood cell lineages. The effect of hCD47 expression on xenogeneic hematopoietic engraftment was tested in an in vivo mouse model of human hematopoietic cell engraftment. High-level porcine chimerism was observed in the bone marrow of hCD47 progenitor cell recipients and smaller but readily measurable chimerism levels were observed in the peripheral blood of these recipients. In contrast, transplantation of WT progenitor cells resulted in little or no bone marrow engraftment and no detectable peripheral chimerism. These results demonstrate a substantial protective effect of hCD47 expression on engraftment and persistence of porcine cells in this model, presumably by modulation of macrophage phagocytosis.

Combining miR-10b-Targeted Nanotherapy with Low-Dose Doxorubicin Elicits Durable Regressions of Metastatic Breast Cancer

The therapeutic promise of microRNA (miRNA) in cancer has yet to be realized. In this study, we identified and therapeutically exploited a new role for miR-10b at the metastatic site, which links its overexpression to tumor cell viability and proliferation. In the protocol developed, we combined a miR-10b-inhibitory nanodrug with low-dose anthracycline to achieve complete durable regressions of metastatic disease in a murine model of metastatic breast cancer. Mechanistic investigations suggested a potent antiproliferative, proapoptotic effect of the nanodrug in the metastatic cells, potentiated by a cell-cycle arrest produced by administration of the low-dose anthracycline. miR-10b was overexpressed specifically in cells with high metastatic potential, suggesting a role for this miRNA as a metastasis-specific therapeutic target. Taken together, our results implied the existence of pathways that regulate the viability and proliferation of tumor cells only after they have acquired the ability to grow at distant metastatic sites. As illustrated by miR-10b targeting, such metastasis-dependent apoptotic pathways would offer attractive targets for further therapeutic exploration.

Dynamics of suspended sediment borne persistent organic pollutants in a large regulated Mediterranean river (Ebro, NE Spain)

Mediterranean rivers are characterized by highly variable hydrological regimes that are strongly dependent on the seasonal rainfall. Sediment transport is closely related to the occurrence of flash-floods capable to deliver enough kinetic energy to mobilize the bed and channel sediments. Contaminants accumulated in the sediments are likely to be mobilized as well during such events. However, whereas there are many studies characterizing contaminants in steady sediments, those devoted to the transport dynamics of suspended-sediment borne pollution are lacking. Here we examined the occurrence and transport of persistent organic microcontaminants present in the circulating suspended sediments during a controlled flushing flow in the low part of the River Ebro (NE Spain) 12 km downstream of a well-known contaminated hot-spot associated to a nearby chloro-alkali industry. Polycyclic aromatic hydrocarbons (PAHs) and semi-volatile organochlorine pollutants (DDT and related compounds, DDX; polychlorinated byphenils, PCBs; and other organochlorine compound, OCs) were measured in the particulate material by GC-MS and GC-MS/MS, using previously developed analytical methods. The concentration levels observed were compared to previously reported values in steady sediments in the same river and discussed on a regulatory perspective. Hydrographs and sedigraphs recorded showed a peak-flow of 1,300 m(3)s(-1) and a corresponding peak of suspended sediments of 315 mg L(-1). Combination of flow discharge, suspended sediments and pollutants' concentrations data allowed for quantifying the mass flows (mass per unit of time) and setting the load budgets (weight amount) of the different pollutants transported by the river during the monitored event. Mean mass-flows and total load values found were 20.2 mg s(-1) (400 g) for PAHs, 38 mg s(-1) (940 g) for DDX, 44 mg s(-1) (1,038 g) for PCBs and 8 mg s(-1) (200 g) for OCs. The dynamic pattern behavior of PAHs differs substantially to that of organochlorine pollutants, thus reflecting different pollution origins.

High incidence of xenogenic bone marrow engraftment in pig-to-baboon intra-bone bone marrow transplantation

Previous attempts of α-1,3-galactocyltransferase knockout (GalTKO) pig bone marrow (BM) transplantation (Tx) into baboons have demonstrated a loss of macro-chimerism within 24 h in most cases. In order to achieve improved engraftment with persistence of peripheral chimerism, we have developed a new strategy of intra-bone BM (IBBM) Tx. Six baboons received GalTKO BM cells, with one-half of the cells transplanted into the bilateral tibiae directly and the remaining cells injected intravenously (IBBM/BM-Tx) with a conditioning immunosuppressive regimen. In order to assess immune responses induced by the combined IBBM/BM-Tx, three recipients received donor SLA-matched GalTKO kidneys in the peri-operative period of IBBM/BM-Tx (Group 1), and the others received kidneys 2 months after IBBM/BM-Tx (Group 2). Peripheral macro-chimerism was continuously detectable for up to 13 days (mean 7.7 days; range 3-13) post-IBBM/BM-Tx and in three animals, macro-chimerism reappeared at days 10, 14 and 21. Pig CFUs, indicating porcine progenitor cell engraftment, were detected in the host BM in four of six recipients on days 14, 15, 19 and 28. In addition, anti-pig unresponsiveness was observed by in vitro assays. GalTKO/pCMV-kidneys survived for extended periods (47 and 60 days). This strategy may provide a potent adjunct for inducing xenogeneic tolerance through BM-Tx.

Competition between honeydew producers in an ant-hemipteran interaction may enhance biological control of an invasive pest

Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), is an invasive citrus pest in southern California, which secretes honeydew and has the potential to spread a lethal bacterial disease, huanglongbing, of citrus. In urban citrus, Argentine ant, Linepithema humile (Mayr) (Hymenoptera: Formicidae), also an invasive pest, tends honeydew-producing hemipterans. We used field data to determine whether the mutualistic relationship between L. humile and six established species of honeydew producers may hinder or favor the establishment of D. citri and its biological control with Tamarixia radiata (Waterston) (Hymenoptera: Eulophidae) in citrus via competition or mutualism for ants, respectively. In the field, L. humile and D. citri are engaged in a mutualistic relationship. Ants harvest solid honeydew secreted by psyllid nymphs and tended more than 55% of observed D. citri colonies. Linepithema humile displayed a preference hierarchy when tending honeydew producers infesting citrus. It responded equally or less intensively to D. citri than to other honeydew-producing species. Consequently, the mutualism between L. humile and D. citri was affected by the presence of other honeydew-producing species, and the percentage of D. citri colonies tended by L. humile. The number of ants per D. citri colony also decreased as the number of other honeydew producers increased. Diaphorina citri density was also affected by the presence of other honeydew producers. Both colony size and the number of D. citri nymphs counted per tree decreased as the number of other honeydew producers increased. Our results indicate that competition between honeydew producers for the mutualist ant L. humile may hinder the establishment of D. citri by possibly facilitating increased biological control.

Increased levels of anti-non-Gal IgG following pig-to-baboon bone marrow transplantation correlate with failure of engraftment

BACKGROUND

The development of genetically modified pigs, which lack the expression of alpha 1-3 galactosyl transferase, (GalT-KO pigs) has facilitated the xenogeneic transplantation of porcine organs and tissues into primates by avoiding hyperacute rejection due to pre-existing antibodies against the Gal epitope. However, antibodies against other antigens (anti-non-Gal antibodies), are found at varying levels in the pre-transplant sera of most primates. We have previously found that baboons with high levels of pre-transplant anti-non-Gal IgG, conditioned with a non-myeloablative conditioning regimen, failed to engraft following pig-to-baboon bone marrow transplantation (Xenotransplantation, 17, 2010 and 300). Two baboons with low levels of pre-transplant anti-non-Gal IgG, conditioned with the same regimen, showed porcine bone marrow progenitors at 28 days following transplantation, suggesting engraftment. These baboons also showed evidence of donor-specific hyporesponsiveness. This observation led us to investigate the hypothesis that selecting for baboon recipients with low pre-transplant anti-non-Gal IgG levels might improve engraftment levels following GalT-KO pig-to-baboon bone marrow transplantation.

METHODS

Five baboons, with low pre-transplant anti-non-Gal IgG levels, received transplantation of bone marrow cells (1-5 × 10(9) /kg of recipient weight) from GalT-KO pigs. They received a non-myeloablative conditioning regimen consisting of low-dose total body irradiation (TBI) (150 cGy), thymic irradiation (700 cGy), anti-thymocyte globulin (ATG), and tacrolimus. In addition, two baboons received Rituximab and Bortezomib (Velcade) treatment as well as extra-corporeal immunoadsorption using GalT-KO pig livers. Bone marrow engraftment was assessed by porcine-specific PCR on colony forming units (CFU) of day 28 bone marrow aspirates. Anti-non-Gal antibody levels were assessed by serum binding toward GalT-KO PBMC using flow cytometry (FACS). Peripheral macro-chimerism was measured by FACS using pig and baboon-specific antibodies and baboon anti-pig cellular responses were assessed by mixed lymphocyte reactions (MLR).

RESULTS

As previously reported, two of five baboons demonstrated detectable bone marrow engraftment at 4 weeks after transplantation. Engraftment was associated with lack of an increase in anti-non-Gal IgG levels as well as cellular hyporesponsiveness toward pig. Three subsequent baboons with similarly low levels of pre-existing anti-non-Gal IgG showed no engraftment and an increase in anti-non-Gal IgG antibody levels following transplantation. Peripheral macrochimerism was only seen for a few days following transplantation regardless of antibody development.

CONCLUSIONS

Selecting for baboon recipients with low levels of pre-transplant anti-non-Gal IgG did not ensure bone marrow engraftment. Failure to engraft was associated with an increase in anti-non-Gal IgG levels following transplantation. These results suggest that anti-non-Gal-IgG is likely involved in early bone marrow rejection and that successful strategies for combating anti-non-Gal IgG development may allow better engraftment. Since engraftment was only low and transient regardless of antibody development, innate immune, or species compatibility mechanisms will likely also need to be addressed to achieve long term engraftment.

Stem cells: Immunology and immunomodulation

Multipotent progenitor cells have the ability to differentiate in vitro into tissue-specific cells under the proper cellular signaling conditions. Because of this intrinsic property, pluripotent derived stem cells from embryonic tissues, induced from genetic reprogramming of somatic cells or from mesenchymal cells, have become the focus of many regenerative medicine studies directed toward application to clinical settings. Generation of retinal pigment epithelium derived from patient-specific, induced pluripotent stem cells may create the ability to recapitulate the disease state and screen new therapeutics, improving upon the limited treatment strategies currently available for afflicted patients. However, the method of delivery, cell culture differentiation, and immunological rejection are some of the limitations that continue to influence ongoing attempts for clinical applications. Understanding stem cell properties and the immune responses these cells elicit in vitro and in vivo will be of importance for designing successful protocols to overcome these immunological limitations. This chapter examines the immunological and immunomodulatory properties of multipotent stem cells in an attempt to provide insights for successful cellular transplantation.

Classical biological control of the African citrus psyllid Trioza erytreae, a major threat to the European citrus industry

Citrus greening or huanglongbing (HLB) is the main threat to the European citrus industry since one of its vectors, the African citrus psyllid, Trioza erytreae, has recently become established in mainland Europe. In this context, classical biological control programmes should be implemented to reduce the spread of the psyllid. The aims of this study were to: i) disentangle the parasitoid complex of T. erytreae combining morphological and molecular characterization; and ii) to study the biology of its main parasitoids in its area of origin in South Africa for their future importation into Europe. The main citrus producing areas of South Africa were surveyed during 2017. In contrast to previous studies, the parasitoid complex of T. erytreae included three species of primary parasitoids: Tamarixia dryi, Psyllaephagus pulvinatus and another parasitoid of the genus Tamarixia. Molecular analysis showed that it is a new species closely related to T. dryi. Tamarixia dryi was the most abundant parasitoid but its relative abundance varied among sampling sites. The sex ratio (males/females) of T. dryi and Tamarixia sp. decreased with T. erytreae size and became female biased when psyllid nymphs were larger than 0.6 and 1.2 mm², respectively. These parasitoids were attacked by three species of hyperparasitoids, Aphidencyrtus cassatus, Marietta javensis and a species of the genus Aphanogmus. Aphidencyrtus cassatus, the most abundant hyperparasitoid, tended to emerge from large nymphs, and adult females lived as long as those of T. dryi. The implications of these results are discussed within the framework of the introduction of T. dryi into Europe.

Reversal of age-related thymic involution by an LHRH agonist in miniature swine

BACKGROUND AND AIMS OF STUDY: We have previously demonstrated a requirement for the presence of a juvenile thymus for the induction of transplantation tolerance to renal allografts by a short-course of calcineurin inhibition in miniature swine. We have also shown that aged, involuted thymi can be rejuvenated when transplanted as vascularized thymic lobes into juvenile swine recipients. The present studies were aimed at elucidating the extrinsic factors facilitating this restoration of function in the aged thymus. In particular, we tested the impact of sex steroid blockade by Luteinizing Hormone-Releasing Hormone (LHRH).

MATERIALS AND METHODS

30 naive animals (25 males and 5 females) were used for measurement of serum testosterone levels. 3 mature male pigs (aged at 22, 22 and 29 months old) were used to test the effects of Lupron (LHRH analog) injection at 45 mg (per 70-80 kg body weight) as a 3-month depot on testosterone levels and thymic rejuvenation. Thymic rejuvenation was assessed by histology, flow cytometric analysis, morphometric analysis and TREC assays.

RESULTS

Hormonal alterations were induced by Lupron and resulted in macroscopic and histologic regeneration of the thymus of aged animals within 2 months, as evidenced by restoration of juvenile thymus architecture and increased cellularity. Two animals that were evaluated for TREC both showed increased levels in the periphery following Lupron treatment.

CONCLUSION

Treatment of aged animals with Lupron leads to thymic rejuventaion in adult miniature swine. This result could expand the applicability of thymus-dependent tolerance-inducing regimens to adult recipients.

Quantification of baboon thymopoiesis in porcine thymokidney xenografts by the signal-joining T-cell receptor excision circle assay

BACKGROUND

Transplantation of vascularized donor thymic tissue along with a kidney transplant has markedly improved graft survival across the discordant pig-to-baboon xenogeneic barrier. To quantify the production of baboon T cells by the porcine thymic tissue, we recently developed an assay to measure the excised DNA products of baboon T-cell receptor (TCR) gene rearrangement (signal-joining TCR excision circles, sjTREC).

METHODS

Initial polymerase chain reaction (PCR) analysis documented that TCR δREC-ψJα rearrangement occurs in baboons. Primers, specific to baboon sjTREC sequence were designed and used to quantify sjTREC molecules in peripheral blood mononuclear cells and thymic tissue using a quantitative PCR assay.

RESULTS

sjTREC levels were higher in phenotypically naïve (CD3CD45RA) T cells (650 copies/100,000 cells) than in phenotypically memory (CD3CD45RA) T cells, with sjTREC below the limit of detection (40 copies/100,000 cells). Surgical removal of the native thymus in two baboons led to a significant decrease of sjTREC in peripheral blood (from 1104 and 920 copies to 184 and 190 copies/100,000 cells, respectively), confirming the role of the thymus in maintaining the peripheral T-cell pool. In two thymectomized baboons that received porcine thymokidney xenografts, sjTREC levels remained low in the peripheral blood (<40 copies/100,000 cells), but increased to 52 and 192 copies/100,000 cells in thymic biopsies, implying that baboon thymopoiesis had begun to occur in the porcine thymic xenografts.

CONCLUSIONS

Baboon sjTREC can be quantified by quantitative PCR using primers specific to baboon sequence. Initial results suggest that baboon thymopoiesis occurs in vascularized porcine thymus xenografts.

Polymeric films based on blends of 6FDA–6FpDA polyimide plus several copolyfluorenes for CO2 separation

Three emitting copolyfluorenes, based on 2,7-(9,9-dihexyl)fluorene and different aryl groups were blended with a polyimide 6FDA–6FpDA to make gas separation membranes. Their intrinsic fluorescence correlates with their permselectivity.

Persistence of Indirect but Not Direct T Cell Xenoresponses in Baboon Recipients of Pig Cell and Organ Transplants

We investigated the contributions of direct and indirect T cell antigen recognition pathways to the immune response to porcine antigens in naïve baboons and baboon recipients of pig xenografts. In naïve baboons, in vitro culture of peripheral blood T cells with intact pig cells (direct xenorecognition pathway) or pig cell sonicates and baboon antigen-presenting cells (indirect xenorecognition pathway) induced the activation and expansion of xenoreactive T cells producing proinflammatory cytokines, interleukin-2 and interferon-γ. Primary indirect xenoresponses were mediated by preexisting memory T cells, whose presence is not typically observed in primary alloresponses. Next, baboons were conditioned with a nonmyeloablative regimen before short-term immunosuppression and transplantation of xenogeneic peripheral blood progenitor cells and a kidney, heart, or pancreatic islets from a miniature swine. All transplants were rejected acutely within 30 days after their placement. Posttransplantation, we observed an inhibition of the direct xenoresponse but a significant expansion of indirectly activated proinflammatory T cells. These results suggest that additional treatment to suppress indirect T cell immunity in primates may be required to achieve tolerance of pig xenografts through hematopoietic chimerism.

Effect of Mediterranean ants (Hymenoptera: Formicidae) on California red scale (Hemiptera: Diaspididae) populations in citrus orchards

We conducted an ant-exclusion experiment in a citrus orchard to evaluate the overall impact of three ant species native in the Mediterranean, Pheidole pallidula (Nylander), Plagiolepis schmitzii Forel, and Lasius grandis (Forel), on populations of Aonidiella aurantii Maskell (California red scale). The ant-exclusion was carried out in four experimental plots from March 2007 to November 2008. Another subset of four plots, adjacent to the ant-excluded plots, was used as control. We measured scale densities and percent parasitism on fruits at harvest in 2007 and 2008. Additionally, we sampled the seasonal trend of the scale on twigs and fruits in both treatments during 2008. California red scale densities in the ant-excluded treatment began to be significantly lower than in the ant-allowed control in May (1 mo after ant activity began), and this difference increased until November. Thus, the effect of the ants on California red scale density seems to be accumulative. At harvest, scale densities on fruits were significantly lower in the ant-excluded treatment. However, percent parasitism on fruits was similar between treatments. Finally, scale densities on the fruits of the ant-allowed plots were positively correlated with the number of ants that climbed to the citrus canopy. These results suggest that increases of scale densities induced by Mediterranean ants depend on the intensity of the ant-activity on citrus canopies.

Geomorphic status of regulated rivers in the Iberian Peninsula

River regulation by dams modifies flow regimes, interrupts the transfer of sediment through channel networks, and alters downstream bed dynamics, altogether affecting channel form and processes. So far, most studies on the geomorphic impacts of dams are restricted to single rivers, or even single river stretches. In this paper we analyse the geomorphic status of 74 river sites distributed across four large basins in the Iberian Peninsula (i.e. 47 sites located downstream of dams). For this purpose, we combine field data with hydrological data available from water agencies, and analyse historical (1970) and current aerial photographs. In particular, we have developed a Geomorphic Status (GS) index that allows us to assess the physical structure of a given channel reach and its change through time. The GS encompasses a determination of changes in sedimentary units, sediment availability, bar stability and channel flow capacity. Sites are statistically grouped in four clusters based on contrasted physical and climate characteristics. Results emphasise that regulation changes river's flow regime with a generalized reduction of the magnitude and frequency of floods (thus flow competence). This, in addition to the decrease downstream sediment supply, results in the loss of active bars as they are encroached by vegetation, to the point that only reaches with little or no regulation maintain exposed sedimentary deposits. The GS of regulated river reaches is negatively correlated with magnitude of the impoundment (regulation). Heavily impacted reaches present channel stabilization and, in contrast to the hydrological response, the distance and number of tributaries do not reverse the geomorphic impact of the dams. Stabilization limits river dynamics and may contribute to the environmental degradation of the fluvial ecosystem. Overall, results describe the degree of geomorphological alteration experienced by representative Iberian rivers mostly because of regulation, challenging the successful long-term implementation of river basin management programmes.

The rejuvenating effects of leuprolide acetate on the aged baboon's thymus

BACKGROUND

We have previously demonstrated that the juvenile thymus plays an essential role in tolerance induced by both renal transplantation and a short course of calcineurin inhibitors. Aged thymi have a decreased ability to induce tolerance. Luteinizing hormone-releasing hormone (LHRH) is known to pharmacologically rejuvenate the thymus in rodents. In order to develop a clinically applicable regimen of transplantation tolerance in adults, we sought to determine if thymic rejuvenation would occur with LHRH agonism in non-human primates.

METHODS AND RESULTS

Thymic rejuvenation was evaluated by magnetic resonance imaging (MRI), histology, as well as in-vitro cellular and molecular tests. Four aged male hamadryas baboons underwent subcutaneous injection of a 3-month depot of Lupron (11.25mg; LI) and were followed for 3 months. Thymi increased volumetrically by MRI. After LI, thymic cellularity markedly increased within the cortical and medullary thymus. Additionally, a significant increase in the CD4(+)/CD45RA(hi+) population in the peripheral blood occurred for 50 days after LI, and flow cytometry of thymic tissue revealed a large increase in the percentage of CD4(+)/CD8(+) cells. TREC assay corroborated enhancement in thymic function.

CONCLUSION

These data indicate that LI is associated with thymic rejuvenation in baboons, and further confirm that extrinsic factors play an important role in thymic rejuvenation in a non-human primate model.

Proposal for improved mixes to produce concrete masonry units with commonly used aggregates available in the Valley of Mexico

Proposal for improved mixes to produce concrete masonry units with commonly used aggregates available in the Valley of MexicoABSTRACTIn this paper, a proposal is done to update the masonry index compressive strength design value f*m for solid concrete masonry units for the masonry guidelines of Mexico´s Federal District Code (NTCM-2004). Solid units were made by taking into account the characteristics of the most commonly used raw materials available in the Valley of Mexico to fabricate such units in the Metropolitan Area of Mexico City. Different tests were conducted for both raw materials and the obtained concrete units. Based upon test results, it is illustrated why it is much better to design masonry structures based upon the experimental data of the units to be used at the construction site rather than using index values proposed in building codes.Keywords: masonry; concrete masonry units; compressive strength.Propuesta de mejora de mezclas para producir piezas de mampostería de concreto empleando materiales comúnmente disponibles en el Valle de MéxicoRESUMENSe presenta un estudio donde se hace una propuesta para actualizar los valores índices de la resistencia a la compresión de mamposterías (f*m) elaboradas con piezas de concreto especificados en las normas de mampostería vigentes en el Distrito Federal. Se realizó un estudio de mercado, donde se tomaron en cuenta las características de los materiales comúnmente utilizados en la actualidad en el Valle de México para la fabricación de piezas de concreto sólidas, incluyendo los resultados de distintas pruebas de laboratorio realizadas a la materia prima. Con base en estos resultados, se ilustran las ventajas de diseñar a la mampostería con base experimental en lugar de utilizar los valores indicativos que se ofrecen en las normas de mampostería.Palabras clave: mampostería; piezas de concreto; resistencia a la compresión. Proposta de melhoria de traços para produzir blocos de alvenaria de concreto utilizando materiais comumente disponíveis no Vale do México RESUMOApresenta-se um estudo onde se propõe uma atualização dos valores do índice de resistência à compressão da alvenaria (f*m) elaborados com blocos de concreto especificados nas normas de alvenaria em vigor no Distrito Federal. Foi realizado um estudo de mercado, que levou em conta as características dos materiais comumente utilizados atualmente no Vale do México para a fabricação de blocos de concreto sólidos, incluindo os resultados de vários testes de laboratório nas matérias-primas disponíveis. Com base nestes resultados, são apresentadas as vantagens de projetar a alvenaria com base experimental em lugar de usar os valores indicativos oferecidos nas normas de alvenaria.Palavras chave: alvenaria; blocos de concreto; resistência à compressão.

Aggregation Patterns, Sampling Plan, and Economic Injury Levels for the New Citrus Pest Delottococcus aberiae (Hemiptera: Pseudococcidae)

Delottococcus aberiae De Lotto (Hemiptera: Pseudococcidae) is the latest exotic mealybug species introduced in citrus in the Mediterranean basin. It causes severe distortion and size reduction on developing fruits. Due to its first interaction with citrus, D. aberiae economic thresholds are still unknown for this crop and the current Integrated Pest Management programs have been disrupted. The objectives of this study were to determine the aggregation patterns of D. aberiae in citrus, develop an efficient sampling plan to assess its population density, and calculate its Economic and Economic Environmental Injury Levels (EIL and EEIL, respectively). Twelve and 19 orchards were sampled in 2014 and 2015, respectively. At each orchard, population densities were monitored fortnightly in leaves, twigs, and fruit, and fruit damage was determined at harvest. Our results showed a clumped aggregation of D. aberiae in all organs with no significant differences between generations on fruit. Fruit damage at harvest was strongly correlated with fruit occupation in spring. Based on these results and using chlorpyrifos as the insecticide of reference, the EIL and EEIL were calculated as 7.1 and 12.1% of occupied fruit in spring, respectively. With all this, we recommend sampling 275 fruits using a binomial sampling method or alternatively, 140 fruits with an enumerative method bimonthly between petal fall and July.

Sediment transport in two mediterranean regulated rivers

Mediterranean climate is characterized by highly irregular rainfall patterns with marked differences between wet and dry seasons which lead to highly variable hydrological fluvial regimes. As a result, and in order to ensure water availability and reduce its temporal variability, a high number of large dams were built during the 20th century (more than 3500 located in Mediterranean rivers). Dams modify the flow regime but also interrupt the continuity of sediment transfer along the river network, thereby changing its functioning as an ecosystem. Within this context, the present paper aims to assess the suspended sediment loads and dynamics of two climatically contrasting Mediterranean regulated rivers (i.e. the Ésera and Siurana) during a 2-yr period. Key findings indicate that floods were responsible for 92% of the total suspended sediment load in the River Siurana, while this percentage falls to 70% for the Ésera, indicating the importance of baseflows on sediment transport in this river. This fact is related to the high sediment availability, with the Ésera acting as a non-supply-limited catchment due to the high productivity of the sources (i.e. badlands). In contrast, the Siurana can be considered a supply-limited system due to its low geomorphic activity and reduced sediment availability, with suspended sediment concentration remaining low even for high magnitude flood events. Reservoirs in both rivers reduce sediment load up to 90%, although total runoff is only reduced in the case of the River Ésera. A remarkable fact is the change of the hydrological character of the River Ésera downstream for the dam, shifting from a humid mountainous river regime to a quasi-invariable pattern, whereas the Siurana experiences the opposite effect, changing from a flashy Mediterranean river to a more constant flow regime below the dam.

Larval morphology of Metaphycus flavus and its role in host attachment and larval cannibalism

Metaphycus flavus (Howard) (Hymenoptera: Encyrtidae) is a facultatively gregarious endoparasitoid of soft scales (Hemiptera: Coccidae). When it develops in superparasitised hosts, the larvae often attack and consume brood mates six or more days post oviposition. Under our laboratory conditions (25±1°C and 14 hours of light followed by 18±1°C and ten hours of darkness in 50-70% R.H.), M. flavus eggs hatched three days after oviposition. Measurements of the mandibles and tentorium indicate there are four larval instars, and M. flavus reaches the fourth instar by day six post oviposition, and pupates on day eight. Thus, cannibalism among M. flavus larvae occurs during the fourth instar. During this instar, M. flavus larvae separate from their attachment to the scale cuticle, to which they were tethered by a respiratory structure during the previous three larval instars. Once detached, they are free to move within the scale, which increases the probability of larval encounters and aggressive behaviours. Moreover, the mandibles of the fourth instar are better adapted for fighting than are those of the first three larval instars, since they are larger and more sclerotized. The cranium and mouthparts of M. flavus have four different types of sensory organs, some of which are almost certainly olfactory, an unexpected function for a larva that presumably is surrounded by an aqueous medium where gustatory sensilla would seem to be more appropriate. The cranium also bears two pairs of what appear to be secretory pores.