谷子胚和胚乳的发育

合子的第一次分裂为斜的横分裂,胚发育至棒状原胚后,胚顶端一侧的细胞加速分裂形成一团分生组织细胞,由这团分生组织分化盾片、胚芽鞘、胚芽生长点和胚根。胚体的其它部分参与部分盾片和胚根鞘的构成。胚柄不参与胚的组成,胚无外胚叶,胚胎发育属禾本型。核型胚乳。从胚囊壁产生的自由生长壁把胚乳游离核隔开形成一层胚乳细胞。然后这层细胞平周分裂使胚乳细胞变成二层,以后的胚乳细胞增殖以细胞有丝分裂方式进行。胚乳的最外层     

掌叶大黄胚胎学研究

掌叶大黄(Rheum palmatum L.)的花药4室,单或复孢原。药壁发育为单子叶型。腺质绒毡层发育后期出现双核。小孢子四分体为四面体型,胞质分裂为同时型。成熟花粉为3细胞,表面具3条沟。子房1室,单胚珠,直生,两层珠被,由内珠被形成珠孔,厚珠心。单孢原,位于珠心表皮下。直线形或T形大孢子四分体。合点端的大孢子发育为蓼型胚囊。2个极核在受精前合并为次生核。3个反足细胞宿存。胚乳发育为核型,在球形胚末期开始形成细胞。合点端的胚乳核一直不形成细胞,而为游离核的胚乳吸器。在胚乳吸器和其它部位都发现胚乳核融合现象。胚的发育属于紫菀型。胚具小胚柄。成熟胚囊时期出现承珠盘,且存留时间很长,成熟胚期尚存痕迹。     

刺五加胚和胚乳发育的研究

刺五加Eleutherococcus senticosus(Rupr .et Maxim．)Maxim的胚胎发生类型为茄型。其卵细胞受精后,合子经历15天左右的休眠期才进行第一次分裂。合子分裂通常发生在胚乳细胞化之后,经棒形胚、球形胚、至果实成熟时发育到心形胚。棒形胚后期至心形胚初期,胚柄最为发达。刺五加的胚乳发育类型为核型。其初生胚乳核的休眠期为1天左右。当胚乳游离核数目增加到200至300时,胚乳以自由生长细胞壁的方式细胞化,胚乳细胞以典型的有丝分裂方式进一步增殖,增加细胞数目。球形胚时期,胚乳细胞内开始贮藏营养物质。少数种子的胚乳里存在巨大细胞核的异型胚乳细胞。在胚乳游离核为32至64个时,分化出珠被绒毡层;球形胚时期,珠被绒毡层解体。珠被绒毡层解体后,胚乳表层细胞分化为分泌层。球形胚至心形胚阶段,约有5％的种子里,胚与胚乳组织发生弥散样降解。成熟果实中,含有大量的瘪粒种子和虫咬种子;饱满种子率为40％左右。饱满种子中,胚乳组织占据种子体积的绝大部分,胚所占比率很小。讨论了不同发育时期胚和胚乳的营养供应。     

黄花油点草胚胎发育研究

利用石蜡切片技术对百合科植物黄花油点草[Tricyrtis maculata(D.Don)Machride]双受精、胚及胚乳发育进行了研究,以明确其胚胎发育的特征,为百合科植物的系统研究提供生殖生物学资料。结果表明:(1)黄花油点草为珠孔受精;进入胚囊的2枚精子分别与卵细胞和中央细胞进行正常的双受精,其受精作用属有丝分裂前型。(2)受精后的初生胚乳核立即分裂,其发育方式为核型胚乳;早期的游离胚乳核沿胚囊的边缘分布,胚囊中央部位主要为胚乳细胞质,随着游离胚乳核数量的增加,胚乳核慢慢充满整个胚囊;当发育至球形胚早期阶段,在各胚乳核周围产生胚乳细胞壁,形成完整的胚乳细胞。(3)合子有较长的休眠时间,胚的发育方式为茄型;合子第一次有丝分裂为横裂,分裂后形成基细胞和顶细胞;基细胞经过3次横裂,形成一列胚柄细胞;顶细胞经过分裂形成胚体,依次形成球形胚、棒状胚和盾形胚。(4)种子成熟时胚无器官分化;成熟种子由种皮、胚和胚乳三部分组成。     

刺梨胚及胚乳的发育

本研究对单瓣刺梨胚及胚乳的发育过程进行了观察,获得如下主要结果:1.刺梨胚的发育属于紫菀型的一种变异类型。原胚发育早期,在胚体顶端具有明显的胚芽原细胞。成熟胚为典型的双子叶植物胚的形态,在子叶中贮藏大量的蛋白质粒。2.刺梨的胚乳属核型。经游离核时期以后形成胚乳细胞。紧邻胚囊周界壁的表层胚乳细胞可以进行平周分裂,产生层叠状的胚乳周缘层。此种后形成的胚乳,我们称之为次生胚乳。当次生胚乳形成时,其余的胚乳细胞逐渐解体,最后几乎完全消失。次生胚乳只在合点处解体,其余保留至种子成熟。3.发现了开花后一些胚珠中无胚或胚和胚乳在发育早期退化的现象,可认为是刺梨种子不育的一个重要原因。     

白桦雌花发育、大孢子发生及胚胎发育的解剖学观察

白桦雌花从开花到雌性器官的成熟需经历1个月左右的时间,解剖学观察表明：四月下旬越冬的雌蕊原基开始了活跃的分裂和分化。子房和柱头开始生长。四月末开花,五月初授粉。此后胚珠开始长大。五月中旬即分化形成珠被,珠心,珠被为单层珠被,胚珠为厚珠心胚珠,胚珠倒生,五月中下旬,珠心内产生大孢子母细胞,一周左右发育为成熟胚囊-七细胞八核胚囊,五月末完成双受精,白桦胚胎发育经过合子,原胚,球形胚,心形胚和鱼雷形胚等时期最后发育成熟,胚乳发育与胚胎同步,即受精的极核进行几次分裂后形成核型胚乳,胚乳核不断增多,在形成心形胚后胚乳细胞形成细胞壁。     

大葱胚和胚乳的发育

观察了“章丘大葱”胚珠、胚囊的结构,胚及胚乳的发育。胚发育属紫菀型,经历球胚前的原胚、球胚、椭形胚、凹形胚、长棒形胚及弯形成熟胚等各期。宿存助细胞生存到球形胚期。胚乳发育属核型。球胚晚期,在胚褒珠孔端及合点端,胚乳开始细胞化。由于游离核之间出现了垂周壁,由一层胚乳游离核形成了一层无内切向壁的“开放细胞”。“开放细胞”行平周分裂而形成两层细胞,外层为完整细胞,内层为新的“开放细胞”。如此多次分裂,向心增生胚乳细胞,最后将中央细胞填满。初始的垂周壁来自于间期游离核之间的细胞板,非“自由生长壁”但又未见明显的成膜体。初始的平周壁是正常有丝分裂的胞质分裂的结果,与成膜体,细胞板有关。在球胚晚期,胚乳细胞化后,在中央液泡内观察到游离细胞。     

西瓜胚和胚乳的发育

应用显微技术对西瓜胚和胚乳的发育过程进行了观察并分析了西瓜胚珠败育的原因。西瓜胚发育属紫菀型。合子第一次分裂为不均等分裂 ,形成的基细胞体积明显较顶细胞大 ,两细胞均含有多个液泡。原胚发育过程中没有明显的胚柄。最外层的原胚细胞 ,与胚乳细胞相邻的壁上被胼胝质物质包围 ,且无外连丝存在 ;与胚囊壁相接的壁上无壁内突结构。胚的子叶体积增长的同时 ,子叶细胞内积累蛋白质和脂类物质 ,多糖物质的含量下降。胚乳发育属核型 ,在球形胚期开始自珠孔端向合点端细胞化 ,胚子叶分化出后开始自珠孔端向合点端退化。胚乳合点端在球形胚早期形成发达的胚乳吸器 ,开始呈游离核状态 ,后细胞化 ,在心型胚期之后退化。     

不同倍性香石竹杂交受精过程及胚胎发育研究

采用石蜡切片法对以四倍体香石竹品种‘紫蝴蝶’(2n=4x=60)为母本,单瓣中间材料‘NH6’(2n=2x=30)为父本杂交后受精过程及胚胎发育进行研究。结果表明:(1)授粉后17h,花粉管进入助细胞并释放内容物,精核进入极核细胞内,与二极核细胞融合形成初生胚乳核;授粉后1d,精核向卵核方向移动,贴伏于卵核核膜上;授粉后2d,形成合子及游离的胚乳核;随后,胚发育经过原胚、球形胚、心形胚、鱼雷形胚阶段。(2)杂交障碍发生在受精过程及胚胎发育的各个时期,表现为:精子与卵细胞不相融合或精子与二极核不相融合、合子未分裂或初生胚乳核未分裂及胚胎的败育。(3)胚败育虽能发生在原胚、球形胚、棒状形胚、三角形胚、心形胚、鱼雷形胚及子叶形胚阶段,但主要发生在球形胚阶段。     

花椒球心胚及胚乳的发生和发育

对花椒珠心胚及胚乳的发生和发育过程进行了详细的细胞学及细胞学研究。主要研究结果如下;珠心胚发生前,有性胚囊发育过程中从大孢子发生到胚囊形成的各个阶段均可发生退化,退化频率５０％,未退化的胚囊发育成熟,成熟胚囊仅含卵器和两个极核。卵器最终退化,极核不经受精自发形成胚肥。当胚乳游离核达到１５或３２个时,最早的珠心胚原始细胞由靠近胚囊球孔端的珠心细胞分化形成。随着子房生长,多个原始细胞持续不断地从珠孔端     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

Comparative morphology of the carpel in the Liliaceae: Hewardieae, Petrosavieae, and Tricyrteae

The young pistils in the melanthioid tribes, Hewardieae, Petrosavieae and Tricyrteae, are uniformly tricarpellate and syncarpous. They lack raphide idioblasts. All are multiovulate, with bitegmic ovules. The Petrosavieae are marked by the presence of septal glands and incomplete syncarpy. Tepals and stamens adhere to the ovary in the Hewardieae and the Petrosavieae but not in the Tricyrteae. Two vascular bundles occur in the stamens of the Hewartlieae and Tricyrtis latifolia. Ventral bundles in the upper part of the ovary of the Hewardieae are continuous with compound septal bundles and placental bundles in the lower part. Putative ventral bundles occur in the alternate position in the Tricyrteae and putative placental bundles in the opposite. position in the Petrosavieae. The dichtomously branched stigma in each carpel of the Tricyrteae is supplied by a bifurcated dorsal bundle.     

Enterovirus 71 3C proteolytically processes the histone H3 N-terminal tail during infection

Highlights
1. The N-terminal tail of histone H3 is specifically cleaved during EV71 infection.
2. Viral protease 3C is identified as a protease responsible for proteolytically processing the N-terminal H3 tail.
3. Our finding reveals a new epigenetic regulatory mechanism for Enterovirus 71 in virus-host interactions.     

Detection of EBV and HHV6 in the Brain Tissue of Patients with Rasmussen’s Encephalitis

Rasmussen’s encephalitis (RE) is a rare pediatric neurological disorder, and the exact etiology is not clear. Viral infection may be involved in the pathogenesis of RE, but conflicting results have reported. In this study, we evaluated the expression of both Epstein-Barr virus (EBV) and human herpes virus (HHV) 6 antigens in brain sections from 30 patients with RE and 16 control individuals by immunohistochemistry. In the RE group, EBV and HHV6 antigens were detected in 56.7% (17/30) and 50% (15/30) of individuals, respectively. In contrast, no detectable EBV and HHV6 antigen expression was found in brain tissues of the control group. The co-expression of EBV and HHV6 was detected in 20.0% (6/30) of individuals. In particular, a 4-year-old boy had a typical clinical course, including a medical history of viral encephalitis, intractable epilepsy, and hemispheric atrophy. The co-expression of EBV and HHV6 was detected in neurons and astrocytes in the brain tissue, accompanied by a high frequency of CD8⁺ T cells. Our results suggest that EBV and HHV6 infection and the activation of CD8⁺ T cells are involved in the pathogenesis of RE.     

Perinatal Vertical Transmission of Chikungunya Virus in Ruili,a Town on the Border between China and Myanmar

正Dear Editor,Chikungunya virus (CHIKV), an arbovirus in the family of Togaviridae, genus Alphavirus, is transmitted by the A.aegyptii or A. albopictus mosquito, and causes disease in humans characterized by fever, rash, and arthralgia (Silva and Dermody 2017; Suhrbier 2019). It was first reported in 1953 in Tanzania, and caused only a few outbreaks and sporadic cases in Africa and Asia in last century. However, in the epidemic in 2004, CHIKV acquired mutations that conferred enhanced transmission by the A. albopictus mosquito(Schuffenecker et al. 2006). Since then, it has successively caused outbreaks in Africa, the Indian Ocean, South East Asia, the South America, and Europe (Zeller et al. 2016).     

Development of a Novel Reverse Transcription Loop-Mediated Isothermal Amplification Method for Rapid Detection of SARS-CoV-2

In conclusion, the novel visual RT-LAMP assay is a simple, rapid, and sensitive approach for detection of SARS-CoV-2, and it is ready for application in primary care and community hospitals or health care centers, and even patients' own houses in response to the current SARS-CoV-2 epidemic because the assay does not require sophisticated equipment and skilled personnel. Furthermore, it is also ready to be used in fields for screening samples from wild animals and environments to facilitate the identification of potential intermediate hosts that mediate the cross-species transmission of SARS-CoV-2 from bats to humans.