Experimental testing of hypotheses for temperature- and pH-based niche specialization of ammonia oxidizing archaea and bacteria.

Investigation of niche specialization in microbial communities is important in assessing consequences of environmental change for ecosystem processes. Ammonia oxidizing bacteria (AOB) and archaea (AOA) present a convenient model for studying niche specialization. They coexist in most soils and effects of soil characteristics on their relative abundances have been studied extensively. This study integrated published information on the influence of temperature and pH on AOB and AOA into several hypotheses, generating predictions that were tested in soil microcosms. The influence of perturbations in temperature was determined in pH 4.5, 6 and 7.5 soils and perturbations in pH were investigated at 15°C, 25°C and 35°C. AO activities were determined by analysing changes in amoA gene and transcript abundances, stable isotope probing and nitrate production. Experimental data supported major predictions of the effects of temperature and pH, but with several significant discrepancies, some of which may have resulted from experimental limitations. The study also provided evidence for unpredicted activity of AOB in pH 4.5 soil. Other discrepancies highlighted important deficiencies in current knowledge, particularly lack of consideration of niche overlap and the need to consider combinations of factors when assessing the influence of environmental change on microbial communities and their activities.

The impact of flow PRA on outcome in pediatric heart recipients in modern era: An analysis of the Pediatric Heart Transplant Study database.

Data from patients in the Pediatric Heart Transplant Study (PHTS) registry transplanted between 2010 and 2014 were analyzed to determine the association between HLA antibody (PRA) determined by SPA using Luminex or flow cytometry with a positive retrospective cross-match and the post-transplant outcomes of acute rejection and graft survival. A total of 1459 of 1596 (91%) recipients had a PRA reported pretransplant; 26% had a PRA > 20%. Patients with a PRA > 20% were more likely to have CHD, prior cardiac surgery, ECMO support at listing, and waited longer for transplantation than patients with a PRA <20%. Patients with higher PRA% determined by SPA were predictive of a positive retrospective cross-match determined by flow cytometric method (P < .001). A PRA > 50% determined by SPA was independently associated with worse overall graft survival after first month of transplant in both unadjusted and adjusted for all other risk factors. In this large multicenter series of pediatric heart transplant recipients, an elevated PRA determined by SPA remains a significant risk factor in the modern era.

Relación de la expresión del factor inducido por hipoxia-2alfa (HIF-2alfa) y sVEGF-R1/sFlt-1: implicación en la fisiopatología de preeclampsia / Relationship between hypoxiainducible factor-2alpha (HIF-2alpha ) and soluble vascular endothelial growth factor receptor-1 (sVEGF-R1)/sFlt-1: role in the physiopathology of preeclampsia

La invasión trofoblástica es crítica para el establecimiento de la circulación uteroplacentaria. La fase inicial de este proceso se realiza en ambientes hipóxicos que patológicamente durante la preeclampsia permanecen sostenidos. Por tanto, es importante entender el comportamiento de las células placentarias frente a estos estímulos. En el presente trabajo se utilizan cultivos primarios de células trofoblásticas (CT), fibroblastos de las vellosidades y células endoteliales de cordón umbilical, aisladas de placentas pretérmino y a término (con y sin preeclampsia), para explorar el efecto de la presión de oxígeno en la expresión y síntesis de VEGF, sVEGFR-1, HIF-1a y 2a. Nuestros resultados muestran que la presión reducida de oxígeno resultó en un incremento significativo del ARNm y la proteína del receptor sVEGF-R1 de manera selectiva en las CT. La expresión y síntesis de VEGF se encontraron elevadas en los 3 tipos celulares, pero la proteína libre (no unida al sVEGF-R1) se encontró disminuida en las CT. Por otro lado, no hubo diferencias significativas en la expresión del ARNm de HIF-1a o 2a, pero sí en la proteína de HIF-2a. Para evaluar la relación de HIF-2a y el incremento del receptor sVEGFR-1, se utilizó siARN-HIF2a. En respuesta a la inhibición, la expresión del receptor sVEGF-R1 disminuyó dramáticamente. El bloqueo de HIF-2a no alteró la expresión de VEGF. Nuestros resultados son los primeros en proponer que el factor de transcripción HIF-2a es un regulador de la expresión selectiva del receptor sVEGF-R1 por CT en hipoxia (AU)

Trophoblast invasion is critical for the establishment of uteroplacental circulation. At the early phases of this process, local oxygen pressure in the placenta is lower, which pathologically remains constant in preeclampsia. Consequently, understanding the response of placental cells to these stimuli is important. In the present study, we used primary cultures of trophoblast cells (TCs), fibroblasts from villous cells, and human umbilical endothelial cells isolated from preterm and term placentas (with and without preeclampsia) to explore the effect of oxygen pressure on the expression and synthesis of VEGF, sVEGFR-1/sFlt-1, and HIF-1a and-2a. Our results show that low oxygen pressure led to a significant selective increase in mRNA and the sVEGF-R1 receptor protein in TCs. VEGF expression and synthesis was elevated in three cell types, but free protein (not bound to sVEGF-R1) was decreased in TCs. Expression of HIF-1a or -2a mRNA in cells was similar in all the types of placentas, but the increase in HIF-2a protein was greater in the TCs of preeclamptic placentas. To evaluate the relationship between HIF-2a and the increase in the sVEGFR-1 receptor, we used siRNA-HIF2a. In response to inhibition, expression of the sVEGF-R1 receptor diminished dramatically. HIF-2a blockade did not alter VEGF expression. Our data are the first to indicate that the HIF-2a transcription factor protein is one of the molecules involved in the selective expression of the sVEGF-R1 receptor in TCs during hypoxia (AU)