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     

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。     

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。     

正红菇的化学成分的研究

采用ＧＣ、ＨＰＬＣ、ＧＣ／ＭＳ．凝胶过滤层析等方法对正红菇（Ｒｕｓｓｕｌａ ｖｉｎｏｓａ）的某些成分的分析结果表明：正红菇其色素由红紫色素和黄色素两个组分的组成,其中红紫色素对酸稳定,对碱及高温不稳定,而黄色素对它们则表现一定的稳定性。其多糖含量２．７４％,含有五种多糖组分。在脂肪酸组成上,主要是油酸和亚油酸,并有可能 存在ＥＰＡ和ＤＨＡ。全氨基酸分析表明含有十六种氨基酸,必需氨基酸占总氨基酸的５     

百合花粉母细胞腺苷三磷酸酶反应产物的X-射线微区分析

百合早前期花粉母细胞经腺苷三磷酸酶反应处理后,一部分经过锇酸后固定和铀染色,一部分不经锇酸后固定和铀染色,其余的经锇酸固定,但不经铀染色,在此三种情况下,细胞质膜和染色质中都出现有致密的,电子不通透的沉淀。进一步的X-射线微区分析表明这些沉淀物中含有一定量的铅。X-射线微区分析结果也表明核膜和胞间连丝通道内部的酶反应沉淀中也含有铅,并且质膜、染色质和胞间连丝通道中酶反应沉淀中的铅较为丰富,细胞融合期染色质酶反应沉淀物中的铅含量较高,进入粗线期后,酶反应沉淀物中铅的含量下降。本研究结果表明百合早前期花粉母细胞的质膜、染色质、核膜及胞间连丝通道内部的确具有ATP酶活性;ATP酶在细胞融合过程中可能起重要作用。     

Nature, significance, and cytological consequences of cytomixis

Cytomixis is a widespread natural process of intercellular interaction, which is common for vegetative and generative tissues in both normal and pathological conditions. The origin, significance, and genetic control of cytomixis still remain partially unclear. The widespread point of view regarding the pathological nature of cytomixis is based on its singularity for plants with genetic instability and impaired homeostasis. Meiotic genes responsible for the segregation and organization of chromosomes, the activity of which is modified by environmental factors through the signal transduction system, seem to be involved in the genetic control of cytomixis. It is assumed that, via cytomoxis, on the one hand, an information contact can be reached as well as meiosis and gametogenesis are synchronized and, on the other hand, the genetic variety and heterozygosis of microsporocytes increase. The activity of cytomoxis varies within a wide interval. Mutagenesis, hybridization, induction, and polyploidy have the greatest influence on this activity. In this context, cytomixis may have a function of cell selection, which is activated by exceeding the threshold level of microsporocytes damage (or genetic disbalance).     

Intra- and intertissular cytomictic interactions in the microsporogenesis of mono- and dicotyledonous plants

Comparative cytological analysis of intra- and intertissular cytomictic interactions in the microsporogenesis of mono- and dicotyledonous plants has been performed for two cellular systems: the microsporocytes and the tapetum. Cytomixis was shown to be more common for intratissular interactions, and cytomixis in the tapetum exhibited taxon-specific features, both structural and temporal. Nuclear migration in the microsporocytes mostly occurred during the zygotene–pachytene and exhibited certain synchrony with cytomixis in the tapetum. Intertissular cytomictic interactions (between the tapetum and the microsporocytes) were detected only in monocotyledonous plant anthers. Intertissular interactions may reflect more intense competition for space between the tapetum and the microsporocytes during the differentiation of anther tissues. The polyploid nuclei of the tapetum and the syncytia are powerful acceptors that can compete with the microsporocytes and attract the chromatin during translocation of the latter. The absence of intertissular interactions in dicotyledonous plants may be indicative of a better balance between the processes of differentiation of somatic and generative tissues of the microsporangium as compared to monocotyledonous plants.     

Cytomixis, its nature, significance and the cytological consequences

Cytomixis is the widespread natural process of intercellular interaction which is characteristic for vegetative and generative tissues in both normal and pathological conditions. The origin significance and genetic control cytomixis still remain not completely clear. The popularity of view of the pathological nature of cytomixis based on its peculiar plants with genetic instability and impaired homeostasis. In the genetic control of cytomixis seem to be involved meiotic genes which are responsible for segregation and organization of chromosomes. Their activity is modified by environmental factors through signal transduction. It is assumed via cytomixis, from one side, the informational contact can be reached and meiosis and gametogenesis are synchronized, with another, increase of the genetic variety and level of the heterozygosis of microsporocytes. The activity of cytomixis varies over wide limits. The greatest influence on its activity have mutagenesis hybridization and polyploidy. In this context cytomixis can fulfill the function of cell selection which is activated by exceeding of the threshold level of the microsporocyte damages (or genetical disbalance).     

New insights into cytomixis: specific cellular features and prevalence in higher plants

The phenomenon of intercellular migration of nuclei in plant tissues (cytomixis) was discovered over a century ago, which has been followed by numerous attempts to clarify the essence of this process as well as to determine its causes and consequences. Most attention of researchers has been paid to cytomixis in microsporogenesis, since the transfer of part of genetic material between microsporocytes may influence the ploidy level of the produced pollen and, presumably, have an evolutionary significance. This review compiles the data on cytological pattern of cytomixis and proposes a scheme as to how cytomictic channels are formed and function in angiosperms. The prevalence of cytomixis in different plant taxa is analyzed using the published data. The causes, mechanisms, and consequences of the nuclear migration between cells in plant tissues are discussed.     

Efficiency of the induction of cytomixis in the microsporogenesis of dicotyledonous (<Emphasis Type="Italic">N. tabacum</Emphasis> L.) and monocotyledonous (<Emphasis Type="Italic">H. distichum</Emphasis> L.) plants by thermal stress

The efficiencies of the induction of cytomixis in microsporogenesis by thermal stress are compared in tobacco (N. tabacum L.) and barley (H. distichum L.) It has been shown that different thermal treatment schedules (budding tobacco plants at 50°C and air-dried barley grains at 48°C) produce similar results in the species: the frequency of cytomixis increases, and its maximum shifts to later stages of meiosis. However, the species show differences in response. The cytomixis frequency increase in tobacco is more pronounced, and its maximum shifts from the zygotene–pachytene stages of meiotic prophase I to prometaphase–metaphase I. Later in the meiosis, aberrations in chromosome structure and meiotic apparatus formation typical of cytomixis are noted, as well as cytomixis activation in tapetum cells. Thermal stress disturbs the integration of callose-bearing vesicles into the callose wall. Cold treatment at 7°C does not affect cytomixis frequency in tobacco microsporogenesis. Incubation of barley seeds at 48°C activates cytomixis in comparison to the control, shifts its maximum from the premeiotic interphase to zygotene, and changes the habit of cytomictic interactions from pairwise contacts to the formation of multicellular clusters. Thermal treatment induces cytomictic interactions within the tapetum and between microsporocytes and the tapetum. However, later meiotic phases show no adverse consequences of active cytomixis in barley. It is conjectured that heat stress affects callose metabolism and integration into the forming callose wall, thereby causing incomplete closure of cytomictic channels and favoring intercellular chromosome migration at advanced meiotic stages.     

高等植物花粉母细胞内肌动蛋白的聚丙烯酰胺凝胶电泳分析

采用聚丙烯酰胺凝胶电泳技术分析了黑麦、蚕豆和百合花粉母细胞内肌动蛋白的存在与动态,结果表明高等植物的花粉母细胞在细胞融合期内的确存在一定量的肌动蛋白,并且,这种蛋白在早偶线期时出现,到四分体时期后消失。文章讨论了肌动蛋白的存在及其与细胞融合现象的联系。     

Cytomixis in shoot apex of Norway spruce [<Emphasis Type="Italic">Picea abies</Emphasis> (L.) Karst.]

Atypical cell walls and nuclei were observed in the apex of Norway spruce shoots from late April to early May on the material collected from a few grafts of a clone of Norway spruce growing on an experimental area. Images of ultrastructure attest to cytomixis. The phenomenon of cytomixis has previously been described in various plant material, both in the meiotic and mitotic cells, but this is the first report of cytomixis in gymnosperms.     

Methomyl,imbraclaobrid and clethodim induced cytomixis and syncytes behaviors in PMCs of Pisum sativum L: Causes and outcomes

Cytomixis is a common phenomenon observed in meiotic cells such as anther which is influenced by various factors. Use of pesticides is a common practice in agriculture. However, it is not known whether pesticides can induce cytomixis in plant cells and induce genetic variation. To understand this, the present study was planned to assess the cytomixis and syncytes behaviors in PMCs of Pisum sativum L. Seeds of P. sativum (Family: Fabaceae) were treated with different concentrations of commonly used pesticides methomyl (ME), imbraclaobrid (IM) and clethodim (CL). Seeds were treated with various concentrations (0.1, 0.2, 0.3, 0.4 and 0.5% of ME, IM and CL prepared in water) for 1 and 3 h. Effect of pesticides on pollen fertility, frequency of cytomixis, and kind of cytomixis cells was assessed. In the cytomixis cells, the cytomictic channel (CC) and direct fusion (DF), and various stages of meiosis (PI, MI, AI and TI) with cytomixis cells were observed. In addition, frequency of syncytes cell and their various stages of meiosis I (PI, MI, AI and TI) in pollen mother cells (PMCs) was assessed. During the microsporogenesis in P. sativum, the occurrence of cytomixis and syncytes at various stages of meiosis I were seen. The formation of cytoplasmic channels and direct fusing of pollen mother cells (PMCs) were both seen to cause cytomixis, with the former being more common than the latter. The percentage of PMCs with cytomixis and syncytes cells increased with increase in the concentration of pesticides. The result of the present investigation indicates that commonly used pesticides ME, IM, and CL have a significant effect on pollen fertility, frequency of cytomixis, and kind of cytomixis cells, the cytomictic channel (CC) and direct fusion (DF), in addition, frequency of syncytes cell and their various stages of meiosis I (PI, MI, AI and TI) in pollen mother cells (PMCs) on P. sativum.     

Polyacrylamide Gel Electro rhoresis Analysis of Actin in Pollen Mother Cells of Higher Plants

The existence and change of actin in the pollen mother cells of Secale cereale L., Vicia faba L., and Lilium davidii var willmottiae were identified by the application of the polyacrylamide gel electronphoresis. It was proved that the pollen mother cells of the three plants contained certain amount of actin at cytomixis stage and that this protein began to appear at early zygotene stage and to disappear after tetrad stage. Finally, the relation between the actin and cytomixis was discussed.