Intracellular calcium in the fertilization and development of mammalian eggs

1. Mammalian eggs are arrested at metaphase of their second meiotic division when ovulated and remain arrested until fertilized. The sperm delivers into the egg phospholipase C (PLC) zeta, which triggers a series of Ca(2+) spikes lasting several hours. The Ca(2+) spikes provide the necessary and sufficient trigger for all the events of fertilization, including exit from metaphase II arrest and extrusion of cortical granules that block the entry of other sperm. 2. The oscillatory Ca(2+) signal switches on calmodulin-dependent protein kinase II (CaMKII), which phosphorylates the egg-specific protein Emi2, earmarking it for degradation. To remain metaphase II arrested, eggs must maintain high levels of maturation-promoting factor (MPF) activity, a heterodimer of CDK1 and cyclin B1. Emi2 prevents loss of MPF by blocking cyclin B1 degradation, a process that is achieved by inhibiting the activity of the anaphase-promoting complex/cyclosome. However, CaMKII is not the primary initiator in the extrusion of cortical granules. 3. Ca(2+) spiking is also observed in mitosis of one-cell embryos, probably because PLCzeta contains a nuclear localization signal and so is released into the cytoplasm following nuclear envelope breakdown. The function of these mitotic Ca(2+) spikes remains obscure, although they are not absolutely required for passage through mitosis. 4. Intriguingly, the pattern of Ca(2+) spikes observed at fertilization has an effect on both pre- and postimplantation development in a manner that is independent of their ability to activate eggs. This suggests that the Ca(2+) spikes set in train at fertilization are having effects on processes initiated in the newly fertilized egg but whose influences are only observed several cell divisions later. The nature of the signals remains little explored, but their importance is clear and so warrants further investigation.     

禽蛋中抗菌药物残留状况研究

摘要：畜禽养殖中抗菌药物的使用,导致其在畜禽体内残留带来食品安全问题。禽蛋是人类获取动物蛋白的重要来源之 一,禽蛋中蓄积的抗菌药物经食物链进入人体,威胁人类健康。目前,禽蛋中抗菌药物的残留状况未见有综合性、系统性的归 纳总结。本文总结了2001-2019年国内外文献及2018-2019年我国市场监督管理总局网站中报道的禽蛋抗菌药物残留情况总 结。分析了分药物类别对禽蛋中残留的抗菌药物阳性率及残留量现状,为抗菌药物的监管及食品安全的保障提供参考。     

Quantitative analysis of cellular glutathione in early preimplantation mouse embryos developing in vivo and in vitro.

The relative levels of reduced glutathione (GSH) have been measured fluorimetrically in individual eggs and early embryos from two mouse strains, one of which shows developmental arrest in vitro. GSH levels fell by approximately 20-25% at fertilization and by approximately 45% by the late 2-cell and early 4-cell stages. No differences were observed between strains or between embryos cultured in vitro or in vivo. Addition of exogenous H2O2 or diethylmaleate depleted GSH. GSH levels were not affected significantly after inhibition of GSH-peroxidase by mercaptosuccinate nor of catalase by aminotriazole. Mercaptosuccinate did not inhibit development but catalase inhibition caused arrest at the 2-cell stage. Addition of exogenous GSH or thioredoxin did not promote development of 'blocking' embryos through the 2-cell block. It is concluded that early embryos lack a mercaptosuccinate sensitive peroxidase activity for removing H2O2, which may be removed by catalase or the glutathione-S-transferase system. It is suggested that GSH may have a role in detoxifying peroxidated lipids. The results are consistent with a role for reactive oxygen species in the 2-cell block.     

25%灭幼脲胶悬剂对家蝇和致乏库蚊幼虫灭效观察

本文报道了25％灭幼脲胶悬剂对家蝇和致乏库蚊幼虫的灭效。当灭幼脲浓度在20ppm时,对家蝇Ⅱ龄幼虫的死亡率为54％,阻碍羽化率为100％,对家蝇卵孵出的幼虫5天死亡率为100％。对致乏库蚊Ⅱ龄幼虫,当浓度0.6ppm时,阻碍羽化率为100％。     

黔、川、浙选点调查农村土壤蛔虫卵及其他寄生虫的污染情况

目的 :进一步了解中国长江以南农户蛔虫卵污染情况。方法 :选择 3个试点县 ,贵州省都匀、四川省南川和浙江省余姚农户各 2 0户 ,每户查家庭内外共 7处 ,及中、小学各 1所和菜场、肉场各 2处。虫卵用5 % Na OH分离 ,用饱和硫酸镁离心漂浮后镜检。结果 :以贵州省都匀农户的土壤标本蛔虫卵数最多 (1 6 2 2.5 /1 0 g) ,四川南川次之 (1 0 99.2 /1 0 g) ,浙江余姚最少 (2 49.0 /1 0 g)。农户的 7处中以厕所土壤污染最严重 ,占蛔虫卵总数的 6 4.3% ,依次为牲畜棚 (9.3% )、庭院 (7.3% )、厨房 (7.2 % )、门槛 (6 .5 % )、客堂 (3.1 % )和卧室 (2 .2 % )。此外尚见鞭虫卵、肝毛细线虫卵、犬弓蛔虫卵、类圆线虫卵、微小膜壳绦虫卵、蛲虫卵、贾第虫包囊和艾美尔球虫卵囊等。结论 :结果表明所查地区农村土壤受蛔虫卵等污染严重。     

蔬菜、瓜果、土壤等携带蛔虫卵情况的调查

本文报告了10种蔬菜、12种瓜果及6类土壤等携带蛔虫卵的情况。蛔虫卵的检出率蔬菜为12.6％,瓜果5.5％,土壤28.4％,鞋底土为6％。小学生的手在洗手前检查能查到蛔虫卵者占10％,洗手后未检出虫卵。     

我国5种按蚊卵表面细微结构的形态观察

扫描电镜下观察比较了须荫按蚊(Anopheles arbumbrosus)、须喙按蚊(An. arbirostris)、克氏按蚊(An. crawfordi)、带足按蚊(An. peditaeniatus)及菲律宾按蚊(An. philippinensis)5种蚊卵的表面细微结构,分析了卵表面结构变化的一般规律,探讨其对按蚊近似种鉴别的意义。     

Multiple activation currents can be evoked inXenopus laevis eggs when cortical granule exocytosis is inhibited by weak bases

The fertilization potential inXenopus eggs under normal circumstances is considered to be a unique event. It is associated with a concomitantly occurring cortical granule exocytosis. If eggs were exposed to weak bases, exocytosis was inhibited but the fertilization potential could still be evoked. After recovery from this first transient increase in membrane conductance, a second could be elicited by a further stimulus. A fertilization potential could be triggered either before or after the egg had undergone an electrically induced activation potential. This suggests that sperm receptors and sperm activated ionic channels in the egg membrane remain functional following the conductance change, at least when the exocytotic event was prevented.A transient conductance increase could only be induced by NH ₄ ⁺ (pH 9.0) in unactivated eggs that had not undergone cortical granule exocytosis.Tremendous variation was noticed between successive activation currents elicited in the same egg. Under voltageclamp at 0 mV holding potential, the current often changed from inward to outward. Although cortical granule exocytosis may only play a minor role in the transient conductance change triggered at fertilization, it may well be involved in subsequent modifications of membrane conductance.     

Pregnancies from Fallopian replacement of immature eggs with delayed intrauterine insemination

Gamete intrafallopian transfer requires that a woman shouldnot only have patent tubes but should also have had mature eggscollected for replacement. Eggs must be collected as close toovulation as possible, to give them a good chance of fertilizingupon replacing them directly into the tubes with the spermatozoa.Preliminary results from the three patients who received Fallopianreplacement of immature eggs followed by delayed intrauterineinsemination indicate that maturation of eggs can occur in vivoin the Fallopian tubes. Intrauterine insemination at a latertime when the eggs were judged to be mature has given rise totwo pregnancies from the three patients with whom this procedurewas adopted     

Chromosome anomalies in mouse zygotes treated by growth hormone-releasing factor.

The incidence of chromosome anomalies was studied in fertilized oocytes in two groups of hybrid mice in which superovulation was induced by gonadotrophins and growth hormone-releasing factor (GRF) supplementation or gonadotrophins alone (controls). The rate of fertilization was significantly higher among GRF-treated females than among controls (74.1 versus 84.7%; P < 0.013). Cytogenetic data were obtained in 262 fertilized oocytes (89 from control females and 173 from GRF-treated females). The frequency of aneuploidy, calculated as twice the frequency of hyperhaploidy was 2.31% in GRF-treated females and 2.24% in controls (NS). The use of GRF to treat female mice did not adversely affect the maturation process of oocytes nor did it induce an increased frequency of aneuploidy.