Reiniciación de la transcripción en el ciclo celular: Nucleologénesis

The transition from a telophase to the G1 of a new cell cycle includes the nucleologenesis process o nucleolar reorganization. In it, specific chromosomal regions of the karyitype, the nucleolar organizer regions (NORs) are involved in the development of the new nucleoli responsible for the synthesis of ribosomal RNAs in the cell. Synthesis of both RNA and proteins are cancelled or very low in the central stages of mitosis. They re-start or increase again by telophase completion, when many small prenucleolar bodies appear on the surface of chromosomes. To assess how the reinitiation of RNA and protein synthesis at the beginning of the new cycle affect the nucleologenesis process, three premises were used: a) synchronous telophases become binucleate cells in eartly G1 if blocking their cytokinesis by caffeine; b) the whole nucleologenesis takes place in a time window that represent only 7.4% of the whole cell cycle duration, RNA or protein synthesis at different times of the nucleologenesis process. They were used for the kinematic study of the process. It was shown, for the first time, that the prenucleolar bodies were not product of nay concurrent RNA synthesis taking place after metaphase. Moreover, their appearance was also independent from the reinitiation of the mature nucleoli were growing, the advancement in the completion of the nucleologenesis when the simultaneous protein synthesis was prevented, and their inhibition when the re-start of rDNA synthesis was prevented, allowed to design a model integrating the different factors involved in nucleolar formation. Lastly, it is a long standing fact that the presence of a NOR does not always ensure the development of a nucleolus on it. Thus, a NOR could result active (dominant) in developing a nucleolus versus okther interspecific, independent from the normal fusion of nucleoli formed in different NORs. Nucleolar dominance or amphiplastia can be achieved by selective hypomethylation of cytosines in certain NORs. The factors involved in such process has been determined.La transición de telofase al periodo G1 interfásico incluye el proceso de nucleologénesis o reorganización nucelolar en la que específicas regiones (NOR) de determinados cromosomas en cada cariotipo se encuentran involucradas en la formación de los nuevos nucleolos. Los estudios realizados en células que efectúan esta transición muestran que tanto la síntesis de proteínas como la de RNA, que son inexistentes en las etapas medias de la mitosis, aumentan su intensidad al final de la telofase, precisamente durante el periodo de reorganización nucleolar, justamente cuando son observados los llamados cuerpos prenucleolares en la superficie de los cromosomas. Para abordar de qué manera podrían influir la biosíntesis de proteínas y del RNA en la nucleologénesis se partió de varios hechos: a) El marcado citocinesis por inhibición mediante cafeína; b) el conocimiento de que la nucleologénesis abarca a un 7,4% de la duración del ciclo celular y se sitúa entre telofase y G1 temprano; c) la aplicación de inhibidores de síntesis de proteínas o de RNA antes, durante y posteriormente al marcado binucleado y su análisis sobre la reorganización celular. Experimentalmente se demostró que los cuerpos prenucleolares no eran productos inmediatos de la actividad transcripcional de los cromosomas postmetafásicos, apareciendo independientemente de una simultánea síntesis de proteínas. La correlación cronológica perfecta entre la desaparición de los cuerpos prenucleolares y la nucleologénesis completa, así como su adelantamiento mediante inhibición de síntesis de proteínas o su bloqueo por inhibición de la síntesis de RNA, mostraron concluyentemente qué factores se encontraban en el proceso de nucleologénesis.La existencia del NOR no siempre asegura la reorganización de un nucleolo. Puede existir dominancia de unos NORs sobre otros, tanto inter- como intra-específicos, formándose un número de nucleolos inferior al número de NORs, debiéndose a proteínas de unión al DNA condicionadas por el nivel de metilación de sus citosinas. Esta dominancia en la nucleologénesis es detallada en sus diferentes fases

PIASγ Is Required for Faithful Chromosome Segregation in Human Cells

BACKGROUND: The precision of the metaphase-anaphase transition ensures stable genetic inheritance. The spindle checkpoint blocks anaphase onset until the last chromosome biorients at metaphase plate, then the bonds between sister chromatids are removed and disjoined chromatids segregate to the spindle poles. But, how sister separation is triggered is not fully understood. PRINCIPAL FINDINGS: We identify PIASγ as a human E3 sumo ligase required for timely and efficient sister chromatid separation. In cells lacking PIASγ, normal metaphase plates form, but the spindle checkpoint is activated, leading to a prolonged metaphase block. Sister chromatids remain cohered even if cohesin is removed by depletion of hSgo1, because DNA catenations persist at centromeres. PIASγ-depleted cells cannot properly localize Topoisomerase II at centromeres or in the cores of mitotic chromosomes, providing a functional link between PIASγ and Topoisomerase II. CONCLUSIONS: PIASγ directs Topoisomerase II to specific chromosome regions that require efficient removal of DNA catenations prior to anaphase. The lack of this activity activates the spindle checkpoint, protecting cells from non-disjunction. Because DNA catenations persist without PIASγ in the absence of cohesin, removal of catenations and cohesin rings must be regulated in parallel

Psychometric characteristics of the Spanish version of instruments to measure neck pain disability

[EN] Background. The NDI, COM and NPQ are evaluation instruments for disability due to NP. There was no Spanish version of NDI or COM for which psychometric characteristics were known. The objectives of this study were to translate and culturally adapt the Spanish version of the Neck Disability Index Questionnaire (NDI), and the Core Outcome Measure (COM), to validate its use in Spanish speaking patients with non-specific neck pain (NP), and to compare their psychometric characteristics with those of the Spanish version of the Northwick Pain Questionnaire (NPQ). Methods. Translation/re-translation of the English versions of the NDI and the COM was done blindly and independently by a multidisciplinary team. The study was done in 9 primary care Centers and 12 specialty services from 9 regions in Spain, with 221 acute, subacute and chronic patients who visited their physician for NP: 54 in the pilot phase and 167 in the validation phase. Neck pain (VAS), referred pain (VAS), disability (NDI, COM and NPQ), catastrophizing (CSQ) and quality of life (SF-12) were measured on their first visit and 14 days later. Patients' self-assessment was used as the external criterion for pain and disability. In the pilot phase, patients' understanding of each item in the NDI and COM was assessed, and on day 1 test-retest reliability was estimated by giving a second NDI and COM in which the name of the questionnaires and the order of the items had been changed. Results. Comprehensibility of NDI and COM were good. Minutes needed to fill out the questionnaires [median, (P25, P75)]: NDI. 4 (2.2, 10.0), COM: 2.1 (1.0, 4.9). Reliability: [ICC, (95%CI)]: NDI: 0.88 (0.80, 0.93). COM: 0.85 (0.75,0.91). Sensitivity to change: Effect size for patients having worsened, not changed and improved between days 1 and 15, according to the external criterion for disability: NDI: -0.24, 0.15, 0.66; NPQ: -0.14, 0.06, 0.67; COM: 0.05, 0.19, 0.92. Validity: Results of NDI, NPQ and COM were consistent with the external criterion for disability, whereas only those from NDI were consistent with the one for pain. Correlations with VAS, CSQ and SF-12 were similar for NDI and NPQ (absolute values between 0.36 and 0.50 on day 1, between 0.38 and 0.70 on day 15), and slightly lower for COM (between 0.36 and 0.48 on day 1, and between 0.33 and 0.61 on day 15). Correlation between NDI and NPQ: r = 0.84 on day 1, r = 0.91 on day 15. Correlation between COM and NPQ: r = 0.63 on day 1, r = 0.71 on day 15. Conclusion. Although most psychometric characteristics of NDI, NPQ and COM are similar, those from the latter one are worse and its use may lead to patients' evolution seeming more positive than it actually is. NDI seems to be the best instrument for measuring NP-related disability, since its results are the most consistent with patient's assessment of their own clinical status and evolution. It takes two more minutes to answer the NDI than to answer the COM, but it can be reliably filled out by the patient without assistanceS

Psychometric characteristics of the Spanish version of instruments to measure neck pain disability

Background: The NDI, COM and NPQ are evaluation instruments for disability due to NP. There was no Spanish version of NDI or COM for which psychometric characteristics were known. The objectives of this study were to translate and culturally adapt the Spanish version of the Neck Disability Index Questionnaire (NDI), and the Core Outcome Measure (COM), to validate its use in Spanish speaking patients with non-specific neck pain (NP), and to compare their psychometric characteristics with those of the Spanish version of the Northwick Pain Questionnaire (NPQ). Methods: Translation/re-translation of the English versions of the NDI and the COM was done blindly and independently by a multidisciplinary team. The study was done in 9 primary care Centers and 12 specialty services from 9 regions in Spain, with 221 acute, subacute and chronic patients who visited their physician for NP: 54 in the pilot phase and 167 in the validation phase. Neck pain (VAS), referred pain (VAS), disability (NDI, COM and NPQ), catastrophizing (CSQ) and quality of life (SF-12) were measured on their first visit and 14 days later. Patients' self-assessment was used as the external criterion for pain and disability. In the pilot phase, patients' understanding of each item in the NDI and COM was assessed, and on day 1 test-retest reliability was estimated by giving a second NDI and COM in which the name of the questionnaires and the order of the items had been changed. Results: Comprehensibility of NDI and COM were good. Minutes needed to fill out the questionnaires [median, (P25, P75)]: NDI. 4 (2.2, 10.0), COM: 2.1 (1.0, 4.9). Reliability: [ICC, (95%CI)]: NDI: 0.88 (0.80, 0.93). COM: 0.85 (0.75,0.91). Sensitivity to change: Effect size for patients having worsened, not changed and improved between days 1 and 15, according to the external criterion for disability: NDI: -0.24, 0.15, 0.66; NPQ: -0.14, 0.06, 0.67; COM: 0.05, 0.19, 0.92. Validity: Results of NDI, NPQ and COM were consistent with the external criterion for disability, whereas only those from NDI were consistent with the one for pain. Correlations with VAS, CSQ and SF-12 were similar for NDI and NPQ (absolute values between 0.36 and 0.50 on day 1, between 0.38 and 0.70 on day 15), and slightly lower for COM (between 0.36 and 0.48 on day 1, and between 0.33 and 0.61 on day 15). Correlation between NDI and NPQ: r = 0.84 on day 1, r = 0.91 on day 15. Correlation between COM and NPQ: r = 0.63 on day 1, r = 0.71 on day 15. Conclusion: Although most psychometric characteristics of NDI, NPQ and COM are similar, those from the latter one are worse and its use may lead to patients' evolution seeming more positive than it actually is. NDI seems to be the best instrument for measuring NP-related disability, since its results are the most consistent with patient's assessment of their own clinical status and evolution. It takes two more minutes to answer the NDI than to answer the COM, but it can be reliably filled out by the patient without assistance

Treatment with tocilizumab or corticosteroids for COVID-19 patients with hyperinflammatory state: a multicentre cohort study (SAM-COVID-19)

Objectives: The objective of this study was to estimate the association between tocilizumab or corticosteroids and the risk of intubation or death in patients with coronavirus disease 19 (COVID-19) with a hyperinflammatory state according to clinical and laboratory parameters. Methods: A cohort study was performed in 60 Spanish hospitals including 778 patients with COVID-19 and clinical and laboratory data indicative of a hyperinflammatory state. Treatment was mainly with tocilizumab, an intermediate-high dose of corticosteroids (IHDC), a pulse dose of corticosteroids (PDC), combination therapy, or no treatment. Primary outcome was intubation or death; follow-up was 21 days. Propensity score-adjusted estimations using Cox regression (logistic regression if needed) were calculated. Propensity scores were used as confounders, matching variables and for the inverse probability of treatment weights (IPTWs). Results: In all, 88, 117, 78 and 151 patients treated with tocilizumab, IHDC, PDC, and combination therapy, respectively, were compared with 344 untreated patients. The primary endpoint occurred in 10 (11.4%), 27 (23.1%), 12 (15.4%), 40 (25.6%) and 69 (21.1%), respectively. The IPTW-based hazard ratios (odds ratio for combination therapy) for the primary endpoint were 0.32 (95%CI 0.22-0.47; p < 0.001) for tocilizumab, 0.82 (0.71-1.30; p 0.82) for IHDC, 0.61 (0.43-0.86; p 0.006) for PDC, and 1.17 (0.86-1.58; p 0.30) for combination therapy. Other applications of the propensity score provided similar results, but were not significant for PDC. Tocilizumab was also associated with lower hazard of death alone in IPTW analysis (0.07; 0.02-0.17; p < 0.001). Conclusions: Tocilizumab might be useful in COVID-19 patients with a hyperinflammatory state and should be prioritized for randomized trials in this situatio

Nurses' perceptions of aids and obstacles to the provision of optimal end of life care in ICU

Contains fulltext : 172380.pdf (publisher's version ) (Open Access

Synaptonemal-like complexes in Allium cepa Microspores

10 p.-4 fig.The paper describes the synaptonemal-like complexes found in the course of microsporogenesis in Allium cepa, during the young microspore stage. In longitudinal sections these structures are morphologically more or less like the synaptonemal complexes, which appear during the pachytene stage of meiosis, and consist of two regions resembling the lateral elements, separated from one another by a space measuring about 1000 Å, in which a central element is occasionally observed. When observed in transverse or oblique sections, their shape indicates that they are tubular structures with a central axis; they are generally observed as independent units inside the nucleus, sometimes associated with the chromatin masses. By using the uranyl-EDTA-lead staining method, which picks out the RNA the synaptonemal-like complexes, show up at the level of their lateral elements and a similar result can be achieved by using the alcoholic PTA technique, which is believed to be a selective staining method for histones. We suppose that the synaptonemal-like complexes consist, at least partially, of RNP material.This work was partially supported by a grant from the III Plan de Desarrollo, Spain.Peer reviewe

Cytochemical aspects of the nucleolar organizer in Allium cepa microspores

11 p.-4 fig.In Allium cepa mierospores, the nucleolar organizing region appears as an area of low density situated between two nucleolar masses. It consists of a series of zones with a density similar to that of the chromatin surrounded by areas of lower density. The dense zones are sometimes arranged in an orderly pattern of 2–4 rows. The organizing region consists of filaments, about 100 Å in diameter, which are seen to be concentrated in the dense areas, and more scattered in the rest of the region. — The alcoholic PTA staining technique reveals the presence of an appreciable quantity of arginine-Iysine rich histones in the organizing region, as well as a similarity between the dense areas of this region and the rest of the chromatin: a similarity which is also brought out by the thallium alcoholate technique, used for DNA staining. By means of uranyl-BDTA-lead RNP material can be shown to be predominantly located in the low-density areas of the organizing region in the form of fibres of about 80 Å in diameter, presumably representing the newly synthetized r-RNA (45 S RNA). A pattern is suggested for the organizing region, in which areas of functional chromatin (euchromatin) would appear alternating with areas of non-functional chromatin (heterochromatin).This work was partially supported by a grant from the III Plan de Desarrollo, Spain.Peer reviewe

Nucleolar Organizer ultrastructure in Allium cepa

The Nuoleolar Organizer Region (NOR) was studied in Allium cepa. The cells analyzed were: meristematic root tip cells, cells from the layers of the anther (exothecium, intermediate layer cells, endothecium and tapetum) and meiocytes from preleptotene to diptotene. Conventional electron microscope techniques and serial section were used in the study. Ultracytochemical tests, using preferential techniques for nucleic acids were also applied. The results show that: a) Although the NOR may have a very variable form in the different cells analyzed, in each case its fine structure is similar, being constituted of chromatin differentiated in high and low density zones. b) In each case, its cytochemical characteristics are similar; highly positively to EDTA (preferential stain for RNP) being observed in the low density zones. As scattered chromatin these would constitute the active regions of the NOR. c) In certain cases a clear relationship is seen between NOR volume and the size of the nucleolus. d) The chromatin associated to the NOR always appears as very dense zones. e) The NOR-Nucleolus relationships are established exclusively with the latter's fibrillar pars. f) The nucleolar segregation phenomenon takes place sometimes as a result of a NOR contraction and in other cases depends on the position of the NOR in relation to the nucleolus. g) In preleptotene, the NOR shows its characteristic morphology and is positive to EDTA, while from zygotene to diplotene the structure of the NOR presents no differences from the rest of the chromatin and only the lateral elements of the synaptonemal complex or its remnants are positive to EDTA. h) The synaptonemal complex runs through the NOR with no differentiation and on occasions its lateral elements show associations with the nucleolus.. This work has been supported by Tercer Plan de Desarrollo and by a Rodrlguez-Pascual's grant.Peer reviewe