DNA double strand breaks but not interstrand crosslinks prevent progress through meiosis in fully grown mouse oocytes

There is some interest in how mammalian oocytes respond to different types of DNA damage because of the increasing expectation of fertility preservation in women undergoing chemotherapy. Double strand breaks (DSBs) induced by ionizing radiation and agents such as neocarzinostatin (NCS), and interstrand crosslinks (ICLs) induced by alkylating agents such as mitomycin C (MMC), are toxic DNA lesions that need to be repaired for cell survival. Here we examined the effects of NCS and MMC treatment on oocytes collected from antral follicles in mice, because potentially such oocytes are readily collected from ovaries and do not need to be in vitro grown to achieve meiotic competency. We found that oocytes were sensitive to NCS, such that this ionizing radiation mimetic blocked meiosis I and caused fragmented DNA. In contrast, MMC had no impact on the completion of either meiosis I or II, even at extremely high doses. However, oocytes treated with MMC did show ?-H2AX foci and following their in vitro maturation and parthenogenetic activation the development of the subsequent embryos was severely compromised. Addition of MMC to 1-cell embryos caused a similarly poor level of development, demonstrating oocytes have eventual sensitivity to this ICL-inducing agent but this does not occur during their meiotic division. In oocytes, the association of Fanconi Anemia protein, FANCD2, with sites of ICL lesions was not apparent until entry into the embryonic cell cycle. In conclusion, meiotic maturation of oocytes is sensitive to DSBs but not ICLs. The ability of oocytes to tolerate severe ICL damage and yet complete meiosis, means that this type of DNA lesion goes unrepaired in oocytes but impacts on subsequent embryo quality

An investigation of the effectiveness of human resource management in the Hong Kong police

In the literature, there is the increasing trend to link human resource planning with strategic planning giving greater importance to, and greater involvement of, human resource management in organization strategy. Also the Hong Kong Police is a manpower oriented discipline force and the human resource management functions play a critical role in the effective management of these human resources. Therefore, the critical nature of the human resource management of the Hong Kong Police justifies a management report orientation where the focus is on the production of positive and practical recommendations. The objectives of the report are to evaluate the effectiveness of the existing human resource management system of the Hong Kong Police and also if and where appropriate to make recommendations designed to enhance the present system. In order to achieve the objectives, four aspects were evaluated. The first aspect is the human resource management goals of the Hong Kong Police. It was evaluated against the criteria of the extent to which it is consistent with the ii Vision, Statement of the Common Purposes and Values of the Police. The second aspect is its policies and practices of the each of the functions, which include 1. human resource planning (HRP), 2. recruitment and selection, 3. training and career development, 4. compensation and benefits management, 5. performance evaluation, 6. employee and labor relations, 7. counseling and 8. termination of the existing human resource management. It was evaluated through the comparison between the policies and practices of the each of the functions mentioned above and the corresponding theoretical functional goals. The third aspect is outcomes of human resource management, including complaints from the public, and opinions to it from the general public. It was evaluated against the overall goals of human resource management of the Hong Kong Police. The last but not the least, others, which are the things other than the above, factors viewed as relevant including what it has done during 1996 to 1999. Peters and Waterman Model was used as a framework for evaluating how well the Police was doing during this period. After considering all the aspects, we concluded that the Hong Kong Police did well in the planning process of the human resource management, as theoretically, the effectiveness of the human resource management was achieved. However, further improvement is needed in certain areas concerning the actual performance during the implementation, which may imply there are some problems that may affect the effectiveness of the human resource management of the Hong Kong Police. Based on the evaluation, we suggest that Competency Assessment Methods can be used as a framework for the Hong Kong Police to develop a set of competency for evaluating the performance of the employees. Also, a number of ways were suggested to improve the existing promotion mechanism. The supervisor’s recommendation involved in it can be improved by giving guidelines to the supervisors and having a group of supervisors to evaluate the performance of the employee. Also the recommendations should base on credible information. Moreover, feedback channels should be given to the employees to raise their opinions towards the decision in the promotion mechanism. In order to improve the competency of the supervisors, training should be given to strengthen their accountability for handling their work. Also a flexible and cafeteria benefits package was recommended to increase the flexibility of the existing benefits package iv for motivating the employees by giving autonomy to choose the benefits they need

Mindfulness-based cognitive therapy v. group psychoeducation for people with generalised anxiety disorder: randomised controlled trial

Background: Research suggests that an 8-week mindfulness-based cognitive therapy (MBCT) course may be effective for generalised anxiety disorder (GAD). Aims: To compare changes in anxiety levels among participants with GAD randomly assigned to MBCT, cognitive–behavioural therapy-based psychoeducation and usual care. Method: In total, 182 participants with GAD were recruited (trial registration number: CUHK_CCT00267) and assigned to the three groups and followed for 5 months after baseline assessment with the two intervention groups followed for an additional 6 months. Primary outcomes were anxiety and worry levels. Results: Linear mixed models demonstrated significant group × time interaction (F(4,148) = 5.10, P = 0.001) effects for decreased anxiety for both the intervention groups relative to usual care. Significant group × time interaction effects were observed for worry and depressive symptoms and mental health-related quality of life for the psychoeducation group only. Conclusions: These results suggest that both of the interventions appear to be superior to usual care for the reduction of anxiety symptoms

A global role for KLF1 in erythropoiesis revealed by ChIP-seq in primary erythroid cells

KLF1 regulates a diverse suite of genes to direct erythroid cell differentiation from bipotent progenitors. To determine the local cis-regulatory contexts and transcription factor networks in which KLF1 operates, we performed KLF1 ChIP-seq in the mouse. We found at least 945 sites in the genome of E14.5 fetal liver erythroid cells which are occupied by endogenous KLF1. Many of these recovered sites reside in erythroid gene promoters such as Hbb-bl, but the majority are distant to any known gene. Our data suggests KLF1 directly regulates most aspects of terminal erythroid differentiation including production of alpha- and beta-globin protein chains, heme biosynthesis, coordination of proliferation and anti-apoptotic pathways, and construction of the red cell membrane and cytoskeleton by functioning primarily as a transcriptional activator. Additionally, we suggest new mechanisms for KLF1 cooperation with other transcription factors, in particular the erythroid transcription factor GATA1, to maintain homeostasis in the erythroid compartment

Cyclin A2 modulates kinetochore–microtubule attachment in meiosis II

Cyclin A2 is a crucial mitotic Cdk regulatory partner that coordinates entry into mitosis and is then destroyed in prometaphase within minutes of nuclear envelope breakdown. The role of cyclin A2 in female meiosis and its dynamics during the transition from meiosis I (MI) to meiosis II (MII) remain unclear. We found that cyclin A2 decreases in prometaphase I but recovers after the first meiotic division and persists, uniquely for metaphase, in MII-arrested oocytes. Conditional deletion of cyclin A2 from mouse oocytes has no discernible effect on MI but leads to disrupted MII spindles and increased merotelic attachments. On stimulation of exit from MII, there is a dramatic increase in lagging chromosomes and an inhibition of cytokinesis. These defects are associated with an increase in microtubule stability in MII spindles, suggesting that cyclin A2 mediates the fidelity of MII by maintaining microtubule dynamics during the rapid formation of the MII spindle

The photometric observation of the quasi-simultaneous mutual eclipse and occultation between Europa and Ganymede on 22 August 2021

Mutual events (MEs) are eclipses and occultations among planetary natural satellites. Most of the time, eclipses and occultations occur separately. However, the same satellite pair will exhibit an eclipse and an occultation quasi-simultaneously under particular orbital configurations. This kind of rare event is termed as a quasi-simultaneous mutual event (QSME). During the 2021 campaign of mutual events of jovian satellites, we observed a QSME between Europa and Ganymede. The present study aims to describe and study the event in detail. We observed the QSME with a CCD camera attached to a 300-mm telescope at the Hong Kong Space Museum Sai Kung iObservatory. We obtained the combined flux of Europa and Ganymede from aperture photometry. A geometric model was developed to explain the light curve observed. Our results are compared with theoretical predictions (O-C). We found that our simple geometric model can explain the QSME fairly accurately, and the QSME light curve is a superposition of the light curves of an eclipse and an occultation. Notably, the observed flux drops are within 2.6% of the theoretical predictions. The size of the event central time O-Cs ranges from -14.4 to 43.2 s. Both O-Cs of flux drop and timing are comparable to other studies adopting more complicated models. Given the event rarity, model simplicity and accuracy, we encourage more observations and analysis on QSMEs to improve Solar System ephemerides.Comment: 23 pages, 5 appendixes, 16 figures, 7 table

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

DNA repair and the Fanconi Anemia pathway: insights into female meiosis and mitosis

Research Doctorate - Doctor of Philosophy (PhD)There are numerous intrinsic and extrinsic factors that cause DNA damage. Without proper DNA repair, such damage would cause genomic instability, premature aging and cancer. The Fanconi Anemia (FA) pathway is important for the repair and resolution of interstrand crosslinks. The key events of this pathway are the ubiquitination of a FA protein, FANCD2, and its localisation onto sites of DNA damage as nuclear foci. Of interest, Gametogenetin (GGN) has been found previously to interact directly with the FA protein responsible for this ubiquitination. In this thesis, using siRNA knockdown, I examined first the role of GGN1 in HeLa cell growth and survival. The phenotypic similarities of GGN1 depleted cells and FA-deficient fibroblasts led me to investigate the role of GGN1 in the FA pathway. It was found that GGN1 was important for the localisation but not the ubiquitination of FANCD2. In addition, an automated method for FANCD2 foci quantification and analysis was developed. In comparison to mitotic cells, oocytes spend the majority of their life arrested in prophase I and this would make them vulnerable to DNA damage. This could in turn lead to female infertility and embryo abnormalities. However, there is little known about the DNA repair capacity of oocytes to respond to such damages. It was discovered, in this thesis, that oocytes have a high tolerance for interstrand crosslinks (ICLs) as compared to double stranded breaks. In combination with the expression of FA transcripts and proteins, this suggested that oocytes might have an active ICL repair. It was determined in this thesis that although oocytes had the ability to detect DNA damage, the FA pathway was found to be inactive during meiosis and only initiated upon embryo formation. The data presented in this thesis also suggest that FANCD2 might have a separate role in meiosis