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。     

霸王的原生质体培养的研究

目的：为利用原生质体融合技术转移霸王抗旱基因。方法：采用酶解法分离霸王原生质体,比较了霸王子叶和愈伤组织游离原生质体的产量和活力,不同渗透压和起始密度对原生质体分裂频率的影响。结果：愈伤组织游离的原生质体产量和活力均高于子叶,原生质体产率可达2.4×106个/g.FW,活力达89%。采用液体浅层培养,在附加2,4-D（2mg/L）、6-BA（1.0mg/L）、2%蔗糖和甘露醇（0.4mol/L）的DPD培养基中,原生质体分裂频率最高,达68.6%。转移到附加2-iP（3mg/L）、KT（1.0mg/L）、6-BA（1.0mg/L）的分化培养基上,获得2个再生苗。结论：采用酶解法游离霸王愈伤组织,可获得高活力和高分裂频率的霸王原生质体。     

EFFECTS OF CORTICOSTEROIDS ON THE BIOCHEMICAL MATURATION OF RAT BRAIN: POSTNATAL CELL FORMATION

(1) Treatment with cortisol acetate (0.2 mg daily during the first 4 days after birth) reduced the rate of growth in the rat: at 35 days of age the body weight was reduced by 50 per cent and the brain weight, depending on the region, by up to 30 per cent. (2) In the brain the normal increase in cell number was severely inhibited during the period of cortisol treatment; this resulted in a final deficit in cell number of about 20 per cent in the cerebrum and 30 per cent in the cerebellum. (3) To determine whether cortisol affected primarily cell formation or cell destruction the labelling of brain DNA was studied 1 h after a subcutaneous injection of 20 Ci/100 g [2-¹⁴C]thymidine. In the controls the amount of labelled DNA increased by a factor of two in the cerebrum and seven in the cerebellum during the period 2-13 days, and it decreased to 40 and 27 per cent of the peak values in the cerebrum and cerebellum respectively in the following 7 days. The results indicated that mitotic activity is higher in the cerebellum than in the cerebrum in the 2nd week of life. It would appear that in the cerebrum appreciable cell death accompanies new cell formation, especially during the period 13-35 days of age. (4) Cortisol treatment affected cell division rather than cell destruction in the brain since it strongly inhibited the incorporation of [2-¹⁴C]thymidine into DNA. The inhibition was severe during the period of treatment but it did not result in a lasting fall in mitotic activity. At the age of 13 days the amount of labelled DNA formed approached the normal level and it was twice that in controls at 20 days, indicating a tendency for compensating cell deficit by an accelerated mitotic activity. Nevertheless, massive cell proliferation ceased at about the same age as in normals; the labelling of DNA decreased markedly between 13 and 20 days after birth, and the DNA content did not increase after the age of 20 days. (5) In contrast to the marked effect on cell number, cortisol treatment did not influence significantly the maturational changes related to average cell size (DNA concentration) or the chemical composition of cells (RNA/DNA and protein/DNA).     

EFFECT OF UNDERNUTRITION ON CELL FORMATION IN THE RAT BRAIN

Abstract— Rats were undernourished by approximately halving the normal food given from the 6th day of gestation throughout lactation. Growth of the foetuses was nearly normal, in marked contrast to the severe retardation caused by undernutrition during the suckling period. In comparison with controls the size and the DNA content of the brain were permanently reduced by undernutrition during the suckling period: this effect was relatively small, approx. 15 per cent decrease at 21 and 35 days. The rate of ¹⁴C incorporation into brain DNA at 30 min after administration of [2-¹⁴C] thymidine was taken as an index of mitotic activity; compared with controls there was severe reduction in mitotic activity (maximal decrease by about 80 per cent at 6 days in the cerebrum and by 70 per cent at 10 days in the cerebellum). The rate of acquisition of cells was calculated from the slopes of the logistic curves fitted to the estimated DNA contents. In normal animals the maximal slope was attained at 2·7 days and at 12·8 days after birth in cerebrum and cerebellum respectively; the daily acquisition of cells at these times was 4·8 × 10⁶ and 18 × 10⁶ cells respectively. The fractional increase in cell number at the maximum was 5·4 percent per day in the cerebrum and 15·2 per cent per day in the cerebellum. The rate of acquisition of cells relative to the rate of mitotic activity was higher in the brains of undernourished animals than in controls. One of the compensatory mechanisms for the severe depression of mitotic activity in the brain of undernourished animals Seems to involve a reduction in the normal rate of cell loss.     

广东省烟草花叶病病原病毒的鉴定

烟草花叶病是广东省产烟区的主要病害之一。我们在南雄等八个县进行调查,1983年至1984年的一般发病率为2～20％。根据血清学反应、病毒粒体形态、鉴别寄主反应及寄主范围、媒介昆虫种类、物理性质、交互保护反应等各项检验结果,鉴定广东省烟草花叶病病原是:三个黄瓜花叶病毒可能株系(普通株系CMV-C,烟草坏死株系CMV-TN,烟草黄色坏死株系(CMV-TYN),烟草花叶病毒(TMV),马铃薯病毒Y(PVY),烟草脉带花叶病毒(TVBMV)和烟草褪绿斑驳病毒(TCMV)(暂定)。     

320例腹泻患者病原菌分离及流行病学分析

目的了解广州市2009年至2010年肠道门诊就诊的细菌性腹泻患者病原谱的分布情况,为制定针对重点人群肠道传染病防治策略提供依据。方法收集2009年5月至2010年5月暨南大学附属第一医院腹泻患者的粪便标本,使用卡-布运送培养基,增菌培养后,采用生化反应和氧化酶试验进行菌株鉴定,并用梅里埃API生化板条进行验证,用病原菌诊断血清进行细菌分型。结果从320份粪便标本中分离到38株菌株,其中沙门菌15株,产毒大肠埃希菌12株,致病大肠埃希菌6株,志贺菌2株,出血性大肠埃希菌、霍乱弧菌、气单胞菌各1株。0—20岁年龄段高发,以1岁以内婴幼儿为主;7—10月为发病高峰期。结论来该院肠道门诊就诊的细菌性腹泻患者,其病原体以沙门菌为主,其次为产毒大肠埃希菌。因此．广州地区细菌件腹泻的预防．廊右针对件的面向雷占人群和重占病厢莴．     

COMPARTMENTATION AND LABELLING OF AMINO ACIDS IN THE DEVELOPING RAT BRAIN AFTER INJECTION OF [U-14C]RIBOSE

Abstract— [U-¹⁴C]Ribose was given by subcutaneous injection to young rats aged 2–56 days. During the first week after birth ¹⁴C in the brain was found mainly combined in glucose, fructose and sedoheptulose which contained 46–57 per cent of the ¹⁴C in the acid soluble metabolites in the rat brain. In contrast, during the critical period (10–15 days after birth) the ¹⁴C in the free sugars decreased from 24 to 3 per cent, while the ¹⁴C content of amino acids in the brain increased from 11 to 44 per cent of the total perchloric acid-soluble ¹⁴C. The increase in labelling of amino acids during the critical period was attributed to increased glycolysis and increased oxidation of pyruvate. The relative specific radioactivity of y -aminobutyrate and aspartate in the rat brain at 28 days after birth was equal to or greater than the relative specific radioactivity of glutamate. Assuming that the increase in amino acid content following the cessation of cell proliferation in the brain is located mainly in cell processes (cytoplasm of axons, dendrites, glial processes and nerve terminals), tentative values were estimated for the pool sizes of glutamate, glutamine, aspartate and y -amino butyrate.     

THE PREPARATION AND USE OF TOBACCO MOSAIC VIRUS CONTAINING RADIOACTIVE PHOSPHORUS

Normal and tobacco mosaic-diseased Turkish tobacco plants were grown in sand for a period of several weeks, during which they were fed daily a complete nutrient solution to which had been added disodium phosphate containing radioactive phosphorus. Determinations were made of the distribution of radioactive phosphorus in different fractions such as the wash from the sand and roots, the press cake obtained on pressing the juice from the plants, the protein and protein-free portions of the supernatant liquids obtained on ultracentrifugation of the juices, and the purified tobacco mosaic virus isolated from the diseased plants. Chemical analyses as well as radiographs of the normal and diseased leaves indicated that they contained the same amount of phosphorus. Approximately 30 per cent of the radioactive phosphorus absorbed by the diseased plants was found to be combined with the purified tobacco mosaic virus that was isolated from these plants. Following the inoculation of purified tobacco mosaic virus possessing high radioactivity to normal Turkish tobacco plants, most of the radioactivity was found to be associated with non-virus components of which about 40 per cent was in the inoculated and 60 per cent in the uninoculated portions of the plants. Although a small amount of radioactive virus was isolated from the uninoculated portions of the plants, it was impossible, because of a number of complicating factors which have been discussed, to draw from the results any reliable conclusions regarding the mode of reproduction of tobacco mosaic virus.     

EFFECTS OF SPREADING CORTICAL DEPRESSION ON THE INCORPORATION OF [14C]LEUCINE INTO PROTEINS OF RAT BRAIN

Abstract— Incorporation of dl -[1-¹⁴C]leucine into proteins of the cerebral cortex of the rat was measured during spreading cortical depression (CSD) evoked by a single topical application of 25% (w/v) KCI. Maximal inhibition (42 per cent) of the rate of incorporation occurred 1 hr after application of KCI. Spreading depression of 2–3 hr duration was associated with 22 per cent and 13 per cent decreases, respectively, of incorporation of labelled leucine. Specific activity of the free pool leucine was not decreased during CSD but appeared to be higher than controls at 20 min after initiation of CSD. The specific activity of the total free pool amino acids was also increased at 10, 20, 60 and 120 min after application of KCI.
The inhibitory effect of CSD on incorporation of leucine into proteins was uniformly distributed among the crude mitochondrial, microsomal and soluble subcellular fractions from brains of adult animals, while in fractions from 25-day old animals there appeared to be relatively more inhibition in the crude mitochondrial fraction.     

AXONAL TRANSPORT OF RADIOACTIVITY IN THE GOLDFISH OPTIC SYSTEM FOLLOWING INTRAOCULAR INJECTION OF LABELLED RNA PRECURSORS

After injection of the tritiated RNA precursors [³H]guanosine, [³H]uridine or [³H]orotic acid into the eye of goldfish, labelled TCA-soluble material and RNA appeared to be axonally transported to the contralateral optic tectum. From the time courses of arrival in the tectum,‘average’rates of transport of 6 mm/day for the soluble material and 1·7 mm/day for the RNA were calculated. If the optic nerve was cut after the transported material had arrived in the tectum, about 60 per cent of the TCA-soluble material disappeared by 7 days after the cut, but almost none of the RNA. After a further 8- to 13-day period, the TCA-soluble material had declined by a further 50 per cent from the 7-day value, but the RNA by only 20 per cent. Thus, relatively little RNA was lost when the optic axons degenerated, an observation which suggested that the RNA might be extra-axonal. However, if the optic nerve was crushed before the arrival of the transported material, RNA did not appear in the tectum until the regenerating optic nerve fibres arrived. Therefore, the presence of RNA must be dependent on intact nerve fibres. Moreover, in the earliest stages of regeneration the proportion of transported RNA to TCA-soluble material was considerably higher than normal, suggesting that the regenerating fibres arrived in the tectum already carrying RNA. This implies that the RNA itself was transported in the optic fibres.     

BIOCHEMICAL EFFECTS OF THYROID DEFICIENCY ON THE DEVELOPING BRAIN

Abstract— The effects of neonatal thyroidectomy on some constituents of the cerebrum, cerebellum and liver of the rat have been studied during the first 7 weeks of life. In the normal rat between the 6th and 14th post-natal days the RNA content per unit of DNA in the brain increased by 70 per cent. Although the brain continued to grow from the 14th to the 35th day, the amount of RNA relative to DNA decreased by about 20 per cent. The ratio of protein to DNA increased during the whole period studied and in the cerebral cortex it was more than trebled between the age of 6 and 35 days. The growth of the cerebellum extended over a longer period than that of the cerebrum, its weight increasing by 88 per cent between the ages of 14 and 35 days as compared with a cerebral increase of 34 per cent. The DNA content showed a 50 per cent increase during this period. Qualitatively these maturational changes were not affected by neonatal thyroidectomy. Quantitative changes, which applied equally to the cerebral cortex and brain as a whole, were observed. At the age of 35 days, the weights of the cerebral hemispheres and cerebellum were reduced by thyroidectomy by 20 per cent; the overall DNA content per organ did not change, but the amounts of protein and RNA relative to DNA decreased significantly. It is therefore inferred that thyroid deficiency affects the size of the cells in brain and cerebellum rather than their total number. Conversely, the cell population of the liver was only a quarter of that in the control. There was a small but significant decrease in the hepatic protein and RNA content in the hypothyroid animal. The activities of the following enzymes which served as markers for subcellular fractions in homogenates of cerebral cortex were determined: lactate dehydrogenase for the supernatant, glutamate dehydrogenase for the mitochondrial and glutamate decarboxylase for the synaptosomal fractions. When the activities were expressed on a fresh weight basis a significant decrease by comparison with the control values was observed only in the case of glutamate decarboxylase (—15 per cent at the age of 17–32 days); when the activities were based on DNA content all values were reduced, probably as a result of the general decrease in cell size. Pyrimidine metabolism of brain and liver, studied after the administration of [6-¹⁴C]-orotic acid, was not affected in either tissue by neonatal thyroidectomy. A small but significant reduction in the incorporation of labelled pyrimidine nucleotides in liver RNA was observed, but no significant decrease in the incorporation in cerebral RNA was found in the hypothyroid rats.