动物的的变态

变态是动物学中一个较重要的专用名词,有关内容在中学课本也多处涉及到。现择要介绍一点动物变态的知识,供动物学教学参考。何谓动物的变态动物由于外在和内在的原因,个体形态发生变化,这叫变态。但动物学所讲的变态,是狭义地从发生学角度理解,即胚胎不直接转变为成体,而是在后期发育过程中,先形成形态、生理、生态方面特殊的幼体,行独立生活和生长,以后在某阶段发生急剧变化,转变为成体。青     

活的不可培养的细菌的研究进展

活的不可培养微生物(VBNC)即一些微生物明显地丧失了可培养的特性,但是保留了自身原有的代谢活力,并且在一定条件下,又可以回复到可培养的状态。从VBNC细菌的诱导条件、生物学特性和检测方法3个方面对VBNC细菌研究进展做一综述。     

高频率的波动对于种子的萌发和植物的发育的影响

本文主要是以理论和试验来说明音波对植物的生长发育和种子萌发所起的影响。在农业实践上音波所起的作用,据现在所知:有缩短植物成熟期,加速萌芽和增强植物的生长发育等。这一些非但具有理论和实践上的意义,同时在今後把物理科学应用到农业科学中开辟了极广阔的前程。     

真核细胞的基因的组织

一、真核细胞基因的基本结构 1.转录单位: 从已知的数十种基因的顺序,可得出一个具有功能的基因的共同规律,在基因5’端—25至—75区,有CCAAT和TATAAA区(后者又称ATA box或Hogness box),相当于促进子区(Promotor),为体外转录所必需。     

由吸附的缩氨酸诱导的细胞膜的形变

研究了由一系列相互平行的吸附在细胞膜上的缩氨酸引起的膜的弹性形变，以及膜对缩氨酸的包裹行为，得到膜的平衡方程，用它可以来处理大尺度的形变，弯曲能量、吸附能量和弹性形变的相互竞争导致膜对缩氨酸发生从不吸附到部分吸附乃至完全包裹的结构转变．在膜的形变很小的时候，可以得到系统能量的解析解。     

远古的人们是怎样认识自己的起源的

人是从那里来的? 回答这个问题,你也许会说这有什么困难——人是从古猿变来的;甚至你还会进一步说,在这个从猿到人的转变过程中,劳动起着决定性的作用。然而这个现在看来比较明了的道理,恰是经历了多么漫长的认识过程才达到的呵!现在让我们首先来谈谈,远古的人们是怎样认识自己的起源的。最初的原始人可能还想不到自己的起源在人类诞生的最早时期,“最初的、从动物界分离出来的人,在一切本质方面是和动物本身一样不自由的”(恩格斯:《反杜林论》),这些最初的原始人为艰苦     

分离的蚕豆细胞核的RNA聚合酶活力的研究

利用Triton X-100对叶绿体膜的作用,可快速地从蚕豆幼叶制备较纯净的细胞核,它具有较高的RNA聚合酶活力。比较了两种分离核的方法,证明利用匀浆法制备的核具有较高的活力。核活力与发育时期有关系,茎端和第1对幼叶的核活力显著高于第2和第3对叶片的核活力。此外,核活力明显地受反应液内锰离子的抑制。     

敲除pckA基因的结核杆菌引起的免疫反应的研究

研究结核杆菌pckA基因编码的磷酸烯醇型丙酮酸羧激酶(PEPCK)诱导机体产生的保护性免疫反应。用敲除pckA基因的牛结核杆菌BCG和野生型BCG分别感染小鼠,取肝、肺、脾进行病理分析,并进行脾细胞培养,检测CD4 、CD4 /CD8 、细胞因子IFNI-γI、L-12和TNF等。用敲除pckA基因的BCG感染的小鼠比野生型BCG感染的小鼠体内产生的结核结节少且不典型,炎性程度低。野生型BCG感染的小鼠脾脏内的CD4 T细胞和CD4 /CD8 、细胞因子IFN-γ、IL-12、TNF均明显高于敲除pckA基因BCG感染的小鼠。pckA基因为结核杆菌生长所必需,其编码产物PEPCK能够刺激机体产生免疫反应,是一种很好的疫苗候选分子。     

观赏用的红肉苹果的组织培养

1植物名称红肉苹果[Malus pumila var.niedzwet- zkyana(Dieck)Schneid]。2材料类别春梢幼嫩茎段。3培养条件MS为基本培养基,(1)芽诱导培养基:MS 6-BA 0.2mg·L~(-1)(单位下同) NAA 0.2;(2)芽增殖培养基:MS 6-BA 0.5 NAA 0.5:(3)生根培养基:1/2MS IBA 0.1 NAA 0.1。以上培养基中均加入5.5 g·L~(-1)琼脂粉和30g·L~(-1)蔗糖,pH 5.8;     

金鱼精巢支持细胞间连接和血睾屏障

Freeze-fracture and etching technique combined with thin sectioning and lanthanum impregnation has been used for the study of Sertoli cell junctions and the blood-testis barrier formation in goldfish testis with lobular organization. Some observations and results are first given in this paper. The results of experiments can be summarized as the following: 1). Sertoli cell junctions are compound junctions of tight junctions, desmosomes and gap junctions. Tight junctions usually appear as parallel or network like ridges on the P face and fine grooves on the E face at the freeze-etching replicas. Desmosomes and gap junctions often are located between or nearby the ridges of tight junctions. In addition, endoplasmic reticulum cristae near the junction area can also be observed. 2). The number, area and density of each individual junction vary with the development and differentiation stages of germinal cells in the cyst. 3). Tight junctions can be observed at any stage during germinal cell differentiation through the period of spermatogenesis and spermiogenesis. However, they appear morphologically different as type I and type II. 4). Lanthanum can partially penetrate into the intercellular spaces of spermatogonium and early primary spermatocyte but can't penetrate after the stage of late primary spermatocyte. 5). The blood-testis barrier formation starts at the stage of pachytene spermatocytes. The formation of the blood-testis barrier is the result of the development of the tight junction from type I to type II.     

Nuclear envelope remodeling during mouse spermiogenesis: postmeiotic expression and redistribution of germline lamin B3

Lamins are members of a multigene family of structural nuclear envelope (NE) proteins. Differentiated mammalian somatic cells express lamins A, C, B1, and B2. The composition and organization of the nuclear lamina of mammalian spermatogenic cells differ significantly from that of somatic cells as they express lamin B1 as well as two short germ line-specific isoforms, namely lamins B3 and C2. Here we describe in detail the expression pattern and localization of lamin B3 during mouse spermatogenesis. By combining RT-PCR, immunoblotting, and immunofluorescence microscopy, we show that lamin B3 is selectively expressed during spermiogenesis (i.e., postmeiotic stages of spermatogenesis). In round spermatids, lamin B3 is distributed in the nuclear periphery and, notably, also in the nucleoplasm. In the course of spermiogenesis, lamin B3 becomes redistributed as it concentrates progressively to the posterior pole of spermatid nuclei. Our results show that during mammalian spermiogenesis the nuclear lamina is composed of B-type isoforms only, namely the ubiquitous lamin B1 and the germline-specific lamin B3. Lamin B3 is the first example of a mammalian lamin that is selectively expressed during postmeiotic stages of spermatogenesis.     

Cellular content of ubiquitin and formation of ubiquitin conjugates during chicken spermatogenesis.

Ubiquitin was purified from chicken testis and its content, biosynthesis and formation of conjugates was determined in germinal cells at successive stages of spermatogenesis. Free ubiquitin increased markedly during spermatogenesis, reaching its maximum level in early spermatids. High levels of ubiquitin were still present in late spermatids but were not detectable in mature spermatozoa. Biosynthesis of ubiquitin occurred in vitro in a fraction containing meiotic and pre-meiotic cells, and during spermiogenesis, in early and late spermatids. The cellular content of free ubiquitin increased after ATP depletion, especially in early spermatids. Lysates of chicken testis cells, particularly those obtained from spermatids, were able to form nuclear (24 and 27 kDa) and extranuclear (55-90 kDa) ubiquitin conjugates in vitro. The presence of increasing levels of ubiquitin and ubiquitin conjugates in chicken spermatids may suggest a possible involvement of this protein in the marked changes of protein turnover, chromatin structure and cell-cell interactions that spermatids undergo during spermiogenesis.     

Aspects of germinal cyst and sperm development in Poecilia latipinna (Teleostei: Poeciliidae).

The structure of the testis of Poecilia latipinna is described with particular reference to Sertoli cell-germ cell relationships during development and maturation of the germinal cyst. The cyst develops when primary spermatocytes become surrounded by a single layer of Sertoli cells at the testis periphery. As spermatogenesis and then spermiogenesis proceed, the cyst moves centrally in the testis toward the ducts comprising the vasa efferentia. In addition to being a structural part of the germinal cyst, the Sertoli cells phagocytize residual bodies cast off by developing spermatids and form an association with mature bodies cast off by developing spermatids and form an association with mature sperm, which resembles that observed in mammals, before the sperm are released into the vasa efferentia as a spermatozeugmata. The results of this investigation are discussed in view of what is known concerning testis structure in other teleosts and similarities between cell functions in teleosts and mammals. It is concluded that teleost Sertoli cells, teleost lobule boundary cells and mammalian Sertoli cells are homologous.     

Annual changes in germinal epithelium determine male reproductive classes of the cobia

Five reproductive classes of cobia Rachycentron canadum , caught along the Gulf of Mexico and the south-east Atlantic coast of the U.S.A., are described during the annual reproductive cycle. These are based upon changes in the testicular germinal epithelium and the stages of germ cells that are present: early maturation, mid maturation, late maturation, regression and regressed. During early maturation, the germinal epithelium is continuous from the testicular ducts to the periphery of the testis and active spermatogenesis occurs throughout the testis. In mid maturation, the germinal epithelium near the ducts becomes discontinuous, but it remains continuous distally. In late maturation, a discontinuous germinal epithelium extends all along the lobules to the testicular periphery; lobules are swollen with sperm and there is minimal spermatogenesis. The regression class is characterized by a discontinuous epithelium throughout the testis, sperm storage and widely scattered spermatocysts. Spermatogonial proliferation also occurs along the lobule walls and at the periphery of the testis. In regressed testes, spermatogonia exist only in a continuous or discontinuous germinal epithelium, although residual sperm are nearly always present in the lobules and ducts. The presence or absence of sperm is not an accurate indicator of reproductive classes. At the periphery of the testis in the regression and regressed classes, the distal portions of lobules elongate as cords of cells containing spermatogonia and Sertoli cells. All reproductive classes can be identified in paraffin sections, although plastic sections provide better resolution. Using maturation classes defined by changes in the germinal epithelium to describe testicular development and spermatogenesis gives a more accurate picture than does using the traditional terminology.     

Ultrastructure and histochemistry of the testicular efferent duct system and spermiogenesis in Opistognathus whitehurstii (Teleostei, Trachinoidei)

 Testis organization and spermatogenesis, with the emphasis on spermiogenesis, in Opistognathus whitehurstii are described by ultrastructural and histochemical methods. The germinal epithelium is extremely reduced and restricted to the periphery of the testis, while most of the organ is occupied by a highly developed system of testicular efferent ducts. A semicystic type of spermatogenesis is observed and in the germinal epithelium spermatogenesis occurs only until the spermatidal stage. Young spermatids are released into the lumen of the testicular lobules and mature to sperm within the efferent duct system. The epithelial cells of these ducts are involved in protein and glycogen secretion and in phagocytosis of degenerating germ cells and residual bodies cast off by developing spermatids. On the basis of these functions, the testicular efferent duct system cells are considered to be homologous to the Sertoli cells. A correlation between a highly developed testicular efferent duct system and semicystic spermatogenesis is examined and a possible functional meaning of this apparently unusual mode of sperm production is proposed. Accepted: 18 March 1997     

Cytological evaluation of spermatogenesis within the germinal epithelium of the male European wall lizard, Podarcis muralis

The annual cytological changes to the male germinal epithelium were investigated in an introduced population of European wall lizards (Podarcis muralis). Testicular tissues were collected, embedded, sectioned by an ultramicrotome, and stained with the PAS procedure followed by a toluidine counterstain. Spermatogenesis in the lizard is divided into the proliferative, meiotic, and maturational phases. Wall lizards have a prenuptial pattern of spermatogenesis, where sperm development begins immediately prior to and continues through the months of breeding (April-June). The testis then involutes, undergoes a short period of quiescence, and recrudescence commences in mid-July. Germ cells undergo proliferation, meiosis, and the early stages of spermiogenesis (maturation) from late July through December. However, the late stages of spermiogenesis are retarded from December through February. Spermiogenesis continues at an accelerated pace from March through May, leading to a single massive spermiation event through the month of June. Although spatial relationships are seen between germ cells within the seminiferous epithelium, accumulation of spermatids during winter and acceleration of elongation in spring prevents determination of consistent cellular associations between early and late developing germ cells within the wall lizard testis. This temporal germ cell development is different from the consistent spatial development seen within seasonally breeding birds and mammals and may represent an evolutionary intermediate in terms of amniotic germ cell development.     

Changes in mRNA length accompany translational regulation of the somatic and testis-specific cytochrome c genes during spermatogenesis in the mouse

The mouse testis contains two isotypes of cytochrome c, which differ in 14 of 104 amino acids: cytochrome cs is present in all somatic tissues and cytochrome cT is testis specific. The regulation of cytochrome cS and cytochrome cT gene expression during spermatogenesis was examined by Northern blot analysis using specific cDNA probes. Total RNA was isolated from adult tissues, enriched germinal cell populations and polysomal gradients of total testis and isolated germinal cells. Three cytochrome cS mRNAs were detected averaging 1.3 kb, 1.1 kb and 0.7 kb in all tissues examined; an additional 1.7 kb mRNA was observed in testis. Isolated germinal cells through prepuberal pachytene spermatocytes contained only the three smaller mRNAs; the 1.7 kb mRNA was enriched in round spermatids. All three smaller cytochrome cS mRNAs were present on polysomes; the 1.7 kb mRNA was non-polysomal. Cytochrome cT mRNA of 0.6-0.9 kb was detected in testis; mRNA levels were low in early spermatogonia and peaked in prepuberal pachytene spermatocytes. In adult pachytene spermatocytes, a subset of the cytochrome cT mRNAs, 0.7-0.9 kb, was present on polysomes; a shortened size class, 0.6-0.75 kb, was non-polysomal. A distinct, primarily non-polysomal, cytochrome cT 0.7 kb mRNA was present in round spermatids. These results indicate that (1) both cytochrome cS and cytochrome cT mRNAs are present in early meiotic cells, (2) a 1.7 kb cytochrome cS mRNA is post-meiotically expressed and non-polysomal and (3) cytochrome cS and cytochrome cT mRNAs are each developmentally and translationally regulated during spermatogenesis.