Estudio comparativo de la estructura de orden superior al interior del núcleo celular (NHOS) en dos especies cercanas de mamífero (rata y ratón)

En los metazoarios el DNA se organiza en bucles hiperenrollados que se estabilizan por su asociación a un compartimento o subestructura nuclear conocida como matriz nuclear (MN). Las interacciones entre el DNA y la MN son más estables que las interacciones entre proteínas de la cromatina y el DNA, y definen una estructura de orden superior al interior del núcleo celular (NHOS por sus siglas en inglés: Nuclear Higher Order Structure). El establecimiento de anclajes entre el DNA y la MN es una condición necesaria y fundamental que preserva la integridad y coherencia del genoma al interior del núcleo. Existe evidencia de que esta estructura es necesaria para la viabilidad de la célula y que tiene implicaciones relevantes para la apropiada fisiología nuclear. La evidencia disponible indica que limitantes de tipo estructural y termodinámico dirigen la actualización de las interacciones entre el DNA y la MN. Sin embargo, no se sabe si hay factores biológicos que también determinan esta organización estructural. Para responder esta pregunta se propuso estudiar a la NHOS desde una perspectiva evolutiva. La eventual conservación de la NHOS durante la evolución indica que factores biológicos están implicados en su establecimiento, ya que cualquier carácter funcional determinante para la supervivencia y/o adaptación de la especie es blanco de la selección natural. Siendo así, se realizó un estudio comparativo de las relaciones topológicas entre el DNA y la MN en hepatocitos primarios de dos especies cercanas de mamífero: la rata y el ratón. Para ello se determinó la posición relativa con respecto a la MN de ocho secuencias blanco que corresponden a regiones del genoma muy conservadas en ambas especies y que representan una muestra de diferentes territorios cromosómicos al interior del núcleo en interfase. Nuestros resultados mostraron que el patrón de relaciones topológicas entre el DNA y la MN no está conservado entre especies cercanas y sugieren que la NHOS es especie-específica. Esto indica que los factores de tipo biológico no son determinantes directos de las interacciones entre el DNA y la MN.ABSTRACT In metazoans, DNA is organized in supercoiled loops that are stabilized by their association with a nuclear compartment or substructure known as the nuclear matrix (NM). The interactions between DNA and the NM are more stable than those between DNA and chromatin proteins and define a nuclear higher order structure (NHOS). The establishment of anchorages between DNA and the NM is a necessary and fundamental condition in the organization of the genome, which preserves the integrity and coherence of such a massive genome within the nucleus. There is evidence that the NHOS is necessary for cell viability and that it has relevant implications for the appropriate nuclear physiology. Current evidence suggests that thermodynamic and structural constraints drive the actualization of the interactions between DNA and the 3 NM. To investigate whether functional factors may also determine the NHOS, we decided to study the NHOS from an evolutionary perspective, since in case that the NHOS is conserved during evolution, this would suggest that biological factors are involved in its establishment, since any functional factor that is determinant for the survival and/or adaptation of the species is a target of natural selection. We carried out a coarse-grained, comparative evaluation of the DNA-NM topological relationships in primary hepatocytes from two closely related mammals: rat and mouse, by determining the relative position to the NM of eight target sequences corresponding to highlyconserved genomic regions that also represent a sample of distinct chromosome territories within the interphase nucleus. Our results indicate that the pattern of topological relationships between DNA and NM is not conserved in two closely related species, suggesting that the NHOS is species-specific. This suggests that biological factors are not direct determinants of the interactions between DNA and the NM. In order to further investigate whether functional factors may participate in determining the NHOS, we compared the NHOS of neurons with that from hepatocytes and naïve B-lymphocytes in the rat. Neurons retain the capacity to replicate the genome under certain circumstances despite being postmitotic, and remain transcriptionally very active. Therefore, if the NHOS of neurons is similar to that of hepatocytes or naïve B-lymphocytes, this would suggest that functional factors (such as replication and/or transcription) have a role in determining this structure. Our results indicate that the NHOS of neurons is completely different from that one observed in hepatocytes or in naïve B-lymphocytes, suggesting that the NHOS is independent of functional factors. Therefore, now we know that NHOS is tissue-specific and species-specific, and that there is no obvious causal relationship between the functional processes of the nucleus (replication and transcription) and the NHOS; and this suggests that physical and thermodynamic factors are more important for establishing the NHOS. This structure represents a baseline level of organization on which the functional processes adapted to it unfold.CONACYT-México proyecto CB-17679

Safety and tolerability of subcutaneous trastuzumab for the adjuvant treatment of human epidermal growth factor receptor 2-positive early breast cancer: SafeHer phase III study's primary analysis of 2573 patients

Aim To assess the safety and tolerability of adjuvant subcutaneous trastuzumab (Herceptin® SC, H SC), delivered from an H SC Vial via hand-held syringe (Cohort A) or single-use injection device (Cohort B), with or without chemotherapy, for human epidermal growth factor receptor 2 (HER2)-positive stage I to IIIC early breast cancer (EBC) in the phase III SafeHer study (NCT01566721). Methods Patients received 600 mg fixed-dose H SC every 3 weeks for 18 cycles. The chemotherapy partner was at the investigators' discretion (H SC monotherapy was limited to ≤10% of the population). Data from the first H SC dose until 28 days (plus a 5-day window) after the last dose are presented. Results are descriptive. Results In the overall population, 2282/2573 patients (88.7%) experienced adverse events (AEs). Of the above, 128 (5.0%) patients experienced AEs leading to study drug discontinuation; 596 (23.2%) experienced grade ≥ 3 AEs and 326 (12.7%) experienced serious AEs. Grade ≥ 3 cardiac disorders were reported in 24 patients (0.9%), including congestive heart failure in eight (0.3%). As expected, the AE rates varied according to the timing of chemotherapy in both cohorts, with higher rates in concurrent versus sequential chemotherapy subgroups. In the concurrent chemotherapy subgroup, AEs were more common during the actual period of concurrent chemotherapy compared with the period when patients did not receive concurrent chemotherapy. Conclusion SafeHer confirms the safety and tolerability of the H SC 600 mg fixed dose for 1 year (every 3 weeks for 18 cycles) as adjuvant therapy with concurrent or sequential chemotherapy for HER2-positive EBC. These primary analysis results are consistent with the known safety profile for intravenous H and H SC

International Nosocomial Infection Control Consortiu (INICC) report, data summary of 43 countries for 2007-2012. Device-associated module

We report the results of an International Nosocomial Infection Control Consortium (INICC) surveillance study from January 2007-December 2012 in 503 intensive care units (ICUs) in Latin America, Asia, Africa, and Europe. During the 6-year study using the Centers for Disease Control and Prevention's (CDC) U.S. National Healthcare Safety Network (NHSN) definitions for device-associated health care–associated infection (DA-HAI), we collected prospective data from 605,310 patients hospitalized in the INICC's ICUs for an aggregate of 3,338,396 days. Although device utilization in the INICC's ICUs was similar to that reported from ICUs in the U.S. in the CDC's NHSN, rates of device-associated nosocomial infection were higher in the ICUs of the INICC hospitals: the pooled rate of central line–associated bloodstream infection in the INICC's ICUs, 4.9 per 1,000 central line days, is nearly 5-fold higher than the 0.9 per 1,000 central line days reported from comparable U.S. ICUs. The overall rate of ventilator-associated pneumonia was also higher (16.8 vs 1.1 per 1,000 ventilator days) as was the rate of catheter-associated urinary tract infection (5.5 vs 1.3 per 1,000 catheter days). Frequencies of resistance of Pseudomonas isolates to amikacin (42.8% vs 10%) and imipenem (42.4% vs 26.1%) and Klebsiella pneumoniae isolates to ceftazidime (71.2% vs 28.8%) and imipenem (19.6% vs 12.8%) were also higher in the INICC's ICUs compared with the ICUs of the CDC's NHSN