Novel insights into mitotic chromosome condensation

The fidelity of mitosis is essential for life, and successful completion of this process relies on drastic changes in chromosome organization at the onset of nuclear division. The mechanisms that govern chromosome compaction at every cell division cycle are still far from full comprehension, yet recent studies provide novel insights into this problem, challenging classical views on mitotic chromosome assembly. Here, we briefly introduce various models for chromosome assembly and known factors involved in the condensation process (e.g. condensin complexes and topoisomerase II). We will then focus on a few selected studies that have recently brought novel insights into the mysterious way chromosomes are condensed during nuclear division.The author(s) declared that no grants were involved in supporting this work

Cohesin cleavage is insufficient for centriole disengagement in Drosophila

Medical Research Council; Wellcome Trust; European Research Council

Compromised mitotic fidelity in human pluripotent stem cells

Human pluripotent stem cells (PSCs), which include both embryonic and induced pluripotent stem cells, are widely used in fundamental and applied biomedical research. They have been instrumental for better understanding development and cell differentiation processes, disease origin and progression and can aid in the discovery of new drugs. PSCs also hold great potential in regenerative medicine to treat or diminish the effects of certain debilitating diseases, such as degenerative disorders. However, some concerns have recently been raised over their safety for use in regenerative medicine. One of the major concerns is the fact that PSCs are prone to errors in passing the correct number of chromosomes to daughter cells, resulting in aneuploid cells. Aneuploidy, characterised by an imbalance in chromosome number, elicits the upregulation of different stress pathways that are deleterious to cell homeostasis, impair proper embryo development and potentiate cancer development. In this review, we will summarize known molecular mechanisms recently revealed to impair mitotic fidelity in human PSCs and the consequences of the decreased mitotic fidelity of these cells. We will finish with speculative views on how the physiological characteristics of PSCs can affect the mitotic machinery and how their suboptimal mitotic fidelity may be circumvented.info:eu-repo/semantics/publishedVersio

Metaphase chromosome structure is dynamically maintained by condensin I-directed DNA (de)catenation

This deposit is composed by the main article and the supplementary materials are present in the publisher's page in the following link: https://elifesciences.org/articles/26120/figures.Mitotic chromosome assembly remains a big mystery in biology. Condensin complexes are pivotal for chromosome architecture yet how they shape mitotic chromatin remains unknown. Using acute inactivation approaches and live-cell imaging in Drosophila embryos, we dissect the role of condensin I in the maintenance of mitotic chromosome structure with unprecedented temporal resolution. Removal of condensin I from pre-established chromosomes results in rapid disassembly of centromeric regions while most chromatin mass undergoes hyper-compaction. This is accompanied by drastic changes in the degree of sister chromatid intertwines. While wild-type metaphase chromosomes display residual levels of catenations, upon timely removal of condensin I, chromosomes present high levels of de novo Topoisomerase II (TopoII)-dependent re-entanglements, and complete failure in chromosome segregation. TopoII is thus capable of re-intertwining previously separated DNA molecules and condensin I continuously required to counteract this erroneous activity. We propose that maintenance of chromosome resolution is a highly dynamic bidirectional process.Fundação para a Ciência e a Tecnologia grants: (SRFH/BD/52172/2013, IF/0085½012/CP0185/CT0004 WP1); European Commission grants: (MCCIG321883/CCC, ERC-2014-STG-638917-ChromoCellDev); European Molecular Biology Organization grant: (IG2778).info:eu-repo/semantics/publishedVersio

Evaluation of applicants' satisfaction index in engineering courses in Portugal during pre- and Post-Bologna period

In this work we describe and characterize students’ allocation satisfaction in the Portuguese public higher education system, through the students' own point of view, namely in academic engineering programs, extending previous studies by the author's team. We compare the ratio provided by the Portuguese Ministry of Education with the institutions' point of view, the demand satisfaction index with the ratio proposed, and the applicants’ satisfaction index for the Pre- and Post-Bologna period. The dataset used in this paper was provided by the Portuguese Education Institute and covers the results of the national contest from 1997 to 2015. Non-parametric tests were performed in order to assess whether there are significant differences between the ratios and to allow a better understanding of the applicants’ satisfaction index in engineering courses during Pre- and Post-Bologna period.This work is financed by FEDER funds through the Competitivity Factors Operational Programme - COMPETE and by national funds through FCT – Foundation for Science and Technology within the scope of the project POCI-01-0145-FEDER-007136 and the Project PEstOE/MAT/ UI0013/2017

A negative binomial model for student allocation to higher education in Portugal during the Post-Bologna process

The primary goal of this paper is to model the student allocation in the Portuguese public higher education system, namely in academic engineering programs for the Post-Bologna period. This work follows the results obtained for the Pre-Bologna period. The data used refer to the years 2007 to 2015 and most of them are available online, provided by the Portuguese Ministry of Education. By estimating student allocation through the negative binomial regression model, we have concluded that the results are similar to the results already obtained for the Pre-Bologna period. That is, the model had a satisfactory performance for the data in study.A. Manuela Goncalves and Raquel Oliveira were supported by the Research Centre of Mathematics of the University of Minho with the Portuguese Funds from the "FCT-Fundacao para a Ciencia e a Tecnologia", through the Project PEstOE/MAT/UI0013/2014. This research was financed by Portuguese.Rosa M. Vasconcelos was supported by the Foundation through FCT - Fundacao para a Ciencia e Tecnologia, within the Project UID/MAT/00013/2013, by FEDER funds through the Compctitivity Factors Operational Programme - COMPET and by national funds through FCT within the scope of the project POCI-01-0145-FEDER-007136

Pain, anxiety and patient satisfaction in office hysteroscopy, is there a link? Are patient satisfaction questionnaires reliable?

Background: Office hysteroscopy is becoming increasingly popular leading to examinations and operations without anesthesia.  Anxiety is always present before an aversive medical intervention and may play a role in pain perception. The objectives of the study were to determine if pain perception is linked to anxiety and how well patient satisfaction questionnaires correlate with pain.Methods: Prospective observational study enrolled one hundred and four women. One hundred cases were included and analyzed. Patients scheduled for office hysteroscopy, who accepted to participate and were able to answer questionnaires.Results: A ten centimeter visual analogue scale was used for pain evaluation and the State anxiety-trait inventory for adults questionnaires for anxiety assessment. Three other satisfaction questionnaires, each consisting of three answers, were also administered and investigated. Analysis was performed using SPSS 22.0 IBM for windows software tools.Conclusions: Correlation between anxiety and pain reporting showed no influence with anxiety trait (p value = 0.4170) and a mild correlation with anxiety state (p value = 0.146). Classification of pain into “no pain”, “mild pain”, “moderate pain” and “severe pain”, should be revised in office hysteroscopy: for visual analogue scale, scores of 2.5 to 3 cm correspond to the lower boundary of moderate pain and scores above limit 6.5 cm should define pain as severe. Satisfaction questionnaires significantly correlated to discomfort (p value <0.001) and may be a practical option to assess tolerance of medical procedures with excellent sensibility and specificity

Dynamical Scenarios for Chromosome Bi-orientation

AbstractChromosome bi-orientation at the metaphase spindle is essential for precise segregation of the genetic material. The process is error-prone, and error-correction mechanisms exist to switch misaligned chromosomes to the correct, bi-oriented configuration. Here, we analyze several possible dynamical scenarios to explore how cells might achieve correct bi-orientation in an efficient and robust manner. We first illustrate that tension-mediated feedback between the sister kinetochores can give rise to a bistable switch, which allows robust distinction between a loose attachment with low tension and a strong attachment with high tension. However, this mechanism has difficulties in explaining how bi-orientation is initiated starting from unattached kinetochores. We propose four possible mechanisms to overcome this problem (exploiting molecular noise; allowing an efficient attachment of kinetochores already in the absence of tension; a trial-and-error oscillation; and a stochastic bistable switch), and assess their impact on the bi-orientation process. Based on our results and supported by experimental data, we put forward a trial-and-error oscillation and a stochastic bistable switch as two elegant mechanisms with the potential to promote bi-orientation both efficiently and robustly

An Image-Based Real-Time Georeferencing Scheme for a UAV Based on a New Angular Parametrization

Simultaneous localization and mapping (SLAM) of a monocular projective camera installed on an unmanned aerial vehicle (UAV) is a challenging task in photogrammetry, computer vision, and robotics. This paper presents a novel real-time monocular SLAM solution for UAV applications. It is based on two steps: consecutive construction of the UAV path, and adjacent strip connection. Consecutive construction rapidly estimates the UAV path by sequentially connecting incoming images to a network of connected images. A multilevel pyramid matching is proposed for this step that contains a sub-window matching using high-resolution images. The sub-window matching increases the frequency of tie points by propagating locations of matched sub-windows that leads to a list of high-frequency tie points while keeping the execution time relatively low. A sparse bundle block adjustment (BBA) is employed to optimize the initial path by considering nuisance parameters. System calibration parameters with respect to global navigation satellite system (GNSS) and inertial navigation system (INS) are optionally considered in the BBA model for direct georeferencing. Ground control points and checkpoints are optionally included in the model for georeferencing and quality control. Adjacent strip connection is enabled by an overlap analysis to further improve connectivity of local networks. A novel angular parametrization based on spherical rotation coordinate system is presented to address the gimbal lock singularity of BBA. Our results suggest that the proposed scheme is a precise real-time monocular SLAM solution for a UAV.Peer reviewe