Further Studies on Microtubule Organizational Changes During Megagametogenesis in Rice Embryo Sac

Changes in the pattern of microtubule distribution and organization during megagametogenesis in the embryo sac of rice (Oryza sativa L. cv. IR36) were re-examined using a modified polyethylene glycol sectioning technique before immuno-fluorescence staining of microtubules. In the sectioned materials the pattern of distribution and structural organization of the microtubule cytoskeleton were quite well preserved. Fine details of the patterns of structural changes and re-organization of the microtubule cytoskeleton in the major stages of development during embryo sac megagametogenesis (viz. functional megaspore, uni-nucleate, 2-nucleate, 4-nucleate, 8-nucleate and mature stage) could be clearly observed and easily followed. Some new organizational patterns of microtubules associated with the probable movement and positioning of the polar nuclei were observed.     

心翼果一新的胚囊类型及其系统学意义

报道心翼果属 (Cardiopteris Wall. ex Royle)一种新的胚囊类型:胚珠无珠被、直生、薄珠心.成熟胚囊中,卵器位于合点端,反足细胞位于珠孔端.这样的胚囊在所有进行过胚胎学研究的被子植物中系首次发现.合子和胚胎也位于合点端.心翼果属的这一新特征无疑是特异性的,据此可认为单型科心翼果科在一定程度上是十分孤立的.     

Relationship of the maximum QRS vector with the left ventricular myocardial mass during the development of hypertrophy: Computer simulation and empirical data

A model of electrical activity of the heart has been used to demonstrate that, all other conditions remaining the same, the spatial vector of the heart changes, as a first approximation, proportionally to the increase in the surface area of the heart ventricles (rather than the myocardial mass) during proportional homothetic changes in the sizes of the heart and His-Purkinje system. In contrast, the electrocardiosignal (ECS) amplitude is determined, at any given moment, by the area of depolarized regions of the epicardium and endocardium, which agrees with the model of a double electrical layer on the surface of an electrically active myocardium.     

Expression of thiazide-sensitive Na+-Cl- cotransporter in the rat endolymphatic sac

The endolymphatic sac (ES) is a part of the membranous labyrinth and is believed to absorb endolymph. It has been well-established that the endolymph absorption is dependent on several ion transporters in a manner similar to that in the kidney, and the ES is regulated by hormones such as aldosterone and vasopressin that also affect on the kidney. The thiazide-sensitive Na⁺, Cl⁻ cotransporter (TSC) is an electroneutral cotransporter specific to the kidney that plays an important role in absorption of NaCl in renal tubules. In the inner ear, TSC expression has never been examined. The expression of TSC in the rat ES was examined by RT-PCR, in situ hybridization and immunohistochemistry. These analyses indicated that TSC genes and proteins were expressed in the rat ES. In contrast, it was not observed in the rat cochlea by RT-PCR. This is the first report confirming the expression of TSC in the ES.     

无籽八月桔胚囊及胚胎发育细胞学观察

运用酶解振荡压片技术和常规石蜡切片技术分别研究了无籽八月桔的胚囊育性及无籽八月桔自交和异交(无籽八月桔×台湾椪柑,无籽八月桔×有籽八月桔)的胚胎发育.结果表明:无籽八月桔胚囊可育,成熟胚囊具一个卵细胞、两个助细胞、三个反足细胞以及一个大的含二个极核的中央细胞;其自交和异交的胚胎发育均正常,授粉后2周出现球形胚和少量心形...     

Ovary signals for directional pollen tube growth

In angiosperms, the female gametophyte has a secluded life; it is protected by several concentric layers that envelop each other. The embryo sac is surrounded by the nucellus, which in turn is wrapped by the integuments forming the ovule, which is nested in the ovary. These wrappings are not hermetic, but contain little ”gates” the pollen tube must traverse on its way towards the embryo sac. Information is emerging that shows that the ovary and ovule provide signals orienting and directimng the pollen tube on the right course. There are three main bodies of evidence supporting this hypothesis. One relates to developmental changes in the female tissues and how they affect pollen tube growth. The second refers to defective ovule mutants, which induce defective pollen tube guidance. And the third relates to the possible molecules involved in this signalling. Here, information gathered along these three main lines of evidence is reviewed. All converge to the conclusion that different checkpoints exist all along the pollen tube pathway. These checkpoints provide active signalling that guides the pollen tube to its destination, the embryo sac. Received: 15 December 2000 / Accepted: 13 June 2001     

江西熊蛛幼蛛各龄期的形态特征

江西熊蛛的幼蛛共蜕皮５次,有６个龄期。对幼蛛各龄期和卵袋的特征作了较详尽的描述。     

琯溪蜜柚果实粒化症矫治研究

本文概述1995~1999年琯溪蜜柚果实汁胞粒化症矫治研究的主要进展,包括探讨各种内外因素对汁胞粒化指数的影响,以及提出矫治琯溪蜜柚果实粒化症的综合配套技术。     

暗纹东方鲀应激胀气行为功能形态学观察

该文以四齿鲀科(Tetraodontidae)的暗纹东方鲀(Takifugu obscurus)为对象,采用形态学解剖、X光透视和骨骼神经染色等方法,对其胀气行为的功能形态学进行研究。其结果发现,暗纹东方鲀腹部受到刺激后,口腔小幅高频将水或空气吞咽进入由食道腹壁特化成的气囊里,气囊与消化道的前后结合处由括约肌控制,腹壁肌呈束状,与此同时,高弹性的皮肤、脊柱和神经都会发生相应的位移变化,以保证胀气行为的快速完成。通过对暗纹东方鲀胀气行为及其吸、排水机制的深入了解,为进一步研究胀气行为的神经机理奠定基础,也将会丰富动物警戒逃避行为的理论。