Oocyte activation and phospholipase C zeta (PLCζ): diagnostic and therapeutic implications for assisted reproductive technology

ABSTRACT: Infertility affects one in seven couples globally and has recently been classified as a disease by the World Health Organisation (WHO). While in-vitro fertilisation (IVF) offers effective treatment for many infertile couples, cases exhibiting severe male infertility (19-57%) often remain difficult, if not impossible to treat. In such cases, intracytoplasmic sperm injection (ICSI), a technique in which a single sperm is microinjected into the oocyte, is implemented. However, 1-5% of ICSI cycles still fail to fertilise, affecting over 1000 couples per year in the UK alone. Pregnancy and delivery rates for IVF and ICSI rarely exceed 30% and 23% respectively. It is therefore imperative that Assisted Reproductive Technology (ART) protocols are constantly modified by associated research programmes, in order to provide patients with the best chances of conception. Prior to fertilisation, mature oocytes are arrested in the metaphase stage of the second meiotic division (MII), which must be alleviated to allow the cell cycle, and subsequent embryogenesis, to proceed. Alleviation occurs through a series of concurrent events, collectively termed 'oocyte activation'. In mammals, oocytes are activated by a series of intracellular calcium (Ca2+) oscillations following gamete fusion. Recent evidence implicates a sperm-specific phospholipase C, PLCzeta (PLCζ), introduced into the oocyte following membrane fusion as the factor responsible. This review summarises our current understanding of oocyte activation failure in human males, and describes recent advances in our knowledge linking certain cases of male infertility with defects in PLCζ expression and activity. Systematic literature searches were performed using PubMed and the ISI-Web of Knowledge. Databases compiled by the United Nations and World Health Organisation databases (UNWHO), and the Human Fertilization and Embryology Authority (HFEA) were also scrutinised. It is clear that PLCζ plays a fundamental role in the activation of mammalian oocytes, and that genetic, molecular, or biochemical perturbation of this key enzyme is strongly linked to human infertility where oocyte activation is deficient. Consequently, there is significant scope for our understanding of PLCζ to be translated to the ART clinic, both as a novel therapeutic agent with which to rescue oocyte activation deficiency (OAD), or as a prognostic/diagnostic biomarker of oocyte activation ability in target sperm samples.     

Receptor Interactions of β-N-Oxalyl-L-α,β-Diaminopropionic Acid,the Lathyrus sativus Putative Excitotoxin,with Synaptic Membranes

Direct evidence for the excitotoxicity of -N-oxalyl-L-,-diaminopropionic acid (ODAP), the Lathyrus sativus neurotoxin has been studied by examining the binding of chemically synthesized [2,3 ³H]ODAP ([³H]ODAP) to synaptic membranes. [³H]ODAP binding to membranes was mostly nonspecific, with only a very low specific binding (15–20% of the total binding) and was also not saturable. The low specific binding of [³H]ODAP remained unaltered under a variety of assay conditions. A low B_max of 3.2 ± 0.4 pmol/mg and K_d 0.2 ± 0.08 M could be discerned for the high affinity interactions under conditions wherein more than 80–90% of the binding was nonspecific. While ODAP could inhibit the binding of [³H]glutamate to chick synaptic membranes with a K_i of 10 ± 0.9 M, even L-DAP, a non neurotoxic amino acid was also equally effective in inhibiting the binding of [³H]glutamate. The very low specific binding of [³H]ODAP to synaptic membranes thus does not warrant considering its interactions at glutamate receptors as a significant event. The results thus suggest that the reported in vitro excitotoxic potential of ODAP may not reflect its true mechanism of neurotoxicity.     

Characterization of gut bacterial flora of Apis mellifera from north-west Pakistan

Gut microbiota has been recognized to play a beneficial role in honey bees (Apis mellifera). Present study was designed to characterize the gut bacterial flora of honey bees in north-west Pakistan. Total 150 aerobic and facultative anaerobic bacteria from guts of 45 worker bees were characterized using biochemical assays and 16S rDNA sequencing followed by bioinformatics analysis. The gut isolates were classified into three bacterial phyla of Firmicutes (60%), Proteobacteria (26%) and Actinobacteria (14%). Most of the isolates belonged to genera and families of Staphylococcus, Bacillus, Enterococcus, Ochrobactrum, Sphingomonas, Ralstonia, Enterobacteriaceae, Corynebacterium and Micrococcineae. Many of these bacteria were tolerant to acidic environments and fermented sugars, hence considered beneficial gut inhabitants and involved the maintenance of a healthy microbiota. However, several opportunistic commensals that proliferate in the hive environment including members Staphylococcus haemolyticus group and Sphingomonas paucimobilis were also identified. This is the first report on bee gut microbiota from north-west Pakistan geographically situated at the crossroads of Indian subcontinent and central Asia.     

祁连山大野口流域青海云杉种群数量动态

种群数量动态揭示了种群的结构特征及其潜在的驱动机制,有助于预测种群未来的动态,进而为森林生态系统的保护与恢复提供理论依据。本研究基于10.2 hm²青海云杉动态监测样地数据,以种群径级结构代替年龄结构,编制静态生命表,绘制径级结构图、存活曲线、死亡率曲线、消失率曲线和4个生存分析函数曲线,分析青海云杉种群数量特征,并利用种群数量动态变化指数和时间序列模型对种群数量动态进行预测。结果表明：（1）青海云杉种群的年龄结构近似于倒"J"型,幼苗和小树储量丰富;（2）种群存活曲线趋近于Deevey-Ⅱ型,为稳定型种群,死亡率曲线和消失率曲线变化趋势基本一致,均在第2、8龄级出现高峰期;（3）生存率曲线呈下降趋势,累计死亡率曲线呈上升趋势,死亡密度曲线缓慢下降,而危险率曲线逐渐上升,该种群具有：前期减少、中期稳定、后期衰退的生长特点;（4）种群数量变化动态指数V_pi>0,表明该种群属于增长型种群,V_pi''>0且趋近于0,则表明该种群趋近于稳定型;（5）时间序列预测分析表明,在未来2、4、6、8个龄级时间后,种群呈稳定增长趋势。研究显示,祁连山大野口流域青海云杉种群为稳定增长型种群,只要未来不遭受强烈干扰,种群数量会保持逐渐增长。针对该种群幼龄个体在前期的更新过程死亡率较高情况,建议在今后的经营管理中应重点加强对第1、2龄级植株生存环境的保护和改善,提高幼苗和小树的存活率。     

基于红外相机技术分析鼬獾的活动节律

鼬獾(Melogale moschata)是食肉目鼬科鼬獾属动物,在我国分布广泛、种群数量丰富,但有关鼬獾的生态研究报导比较少.为掌握鼬獾的活动节律及其影响因素,2017年2月至2019年2月,利用红外相机技术对江西省桃红岭梅花鹿国家级自然保护区、九岭山国家级自然保护区和齐云山国家级自然保护区的鼬獾进行了监测,每个保护...     

Eukaryotic genes in Mycobacterium tuberculosis could have a role in pathogenesis and immunomodulation.

Acquisition of new genetic material through horizontal gene transfer has been an important feature in the evolution of many pathogenic bacteria. Here, we report the presence of 19 genes of eukaryotic origin in the genome of Mycobacterium tuberculosis, some of which are unique to the M. tuberculosis complex. These genes, having been retained in the genome through selective advantage, most probably have key functions in the organism and in mammalian tuberculosis. We explore the role these genes might have in manipulation of the host immune system by altering the balance of steroid hormones.     

Regulation of TGFbeta1-mediated collagen formation by LOX-1: studies based on forced overexpression of TGFbeta1 in wild-type and lox-1 knock-out mouse cardiac fibroblasts

Transforming growth factor beta(1) (TGFbeta(1)) activation leads to tissue fibrosis. Here, we report on the role of LOX-1, a lectin-like 52-kDa receptor for oxidized low density lipoprotein, in TGFbeta(1)-mediated collagen expression and underlying signaling in mouse cardiac fibroblasts. TGFbeta(1) was overexpressed in wild-type (WT) and LOX-1 knock-out mouse cardiac fibroblasts by transfection with adeno-associated virus type 2 vector carrying the active TGFbeta(1) moiety (AAV/TGFbeta (ACT)(1)). Transfection of WT mouse cardiac fibroblasts with AAV/TGFbeta (ACT)(1) markedly enhanced the expression of NADPH oxidases (p22(phox), p47(phox), and gp91(phox) subunits) and LOX-1, formation of reactive oxygen species, and collagen synthesis, concomitant with an increase in the activation of p38 and p44/42 mitogen-activated protein kinases (MAPK). The TGFbeta(1)-mediated increase in collagen synthesis was markedly attenuated in the LOX-1 knock-out mouse cardiac fibroblasts as well as in WT mouse cardiac fibroblasts treated with a specific anti-LOX-1 antibody. Treatment with anti-LOX-1 antibody also reduced NADPH oxidase expression and MAPK activation. The NADPH oxidase inhibitors and gp91phox small interfering RNA reduced LOX-1 expression, MAPK activation, and collagen formation. The p38 MAPK inhibitors as well as the p44/42 MAPK inhibitors reduced collagen formation without affecting LOX-1 expression in cardiac fibroblasts. These observations suggest that collagen synthesis in cardiac fibroblasts involves a facilitative interaction between TGFbeta(1)-NADPH oxidase and LOX-1. Further, the activation of MAPK pathway appears to be downstream of TGFbeta(1)-reactive oxygen species-LOX-1 cascade.