Regulation of mitosis in Stentor coeruleus

When Stentor coeruleus was cut into anterior and posterior halves, the micronuclei in the posterior half underwent mitosis about 5 to 6 hours later, as shown in stained preparations. It is suggested that the division of the micronuclei was initiated by metabolic changes which resulted from the lack of adoral membranelles.     

Beta-catenin defines head versus tail identity during planarian regeneration and homeostasis

After amputation, freshwater planarians properly regenerate a head or tail from the resulting anterior or posterior wound. The mechanisms that differentiate anterior from posterior and direct the replacement of the appropriate missing body parts are unknown. We found that in the planarian Schmidtea mediterranea, RNA interference (RNAi) of beta-catenin or dishevelled causes the inappropriate regeneration of a head instead of a tail at posterior amputations. Conversely, RNAi of the beta-catenin antagonist adenomatous polyposis coli results in the regeneration of a tail at anterior wounds. In addition, the silencing of beta-catenin is sufficient to transform the tail of uncut adult animals into a head. We suggest that beta-catenin functions as a molecular switch to specify and maintain anteroposterior identity during regeneration and homeostasis in planarians.     

Fossil evidence for the origin of aquatic locomotion in archaeocete whales

Recent members of the order Cetacea (whales, dolphins, and porpoises) move in the water by vertical tail beats and cannot locomote on land. Their hindlimbs are not visible externally and the bones are reduced to one or a few splints that commonly lack joints. However, cetaceans originated from four-legged land mammals that used their limbs for locomotion and were probably apt runners. Because there are no relatively complete limbs for archaic archaeocete cetaceans, it is not known how the transition in locomotory organs from land to water occurred. Recovery of a skeleton of an early fossil cetacean from the Kuldana Formation, Pakistan, documents transitional modes of locomotion, and allows hypotheses concerning swimming in early cetaceans to be tested. The fossil indicates that archaic whales swam by undulating their vertebral column, thus forcing their feet up and down in a way similar to modern otters. Their movements on land probably resembled those of sea lions to some degree, and involved protraction and retraction of the abducted limbs.     

Effect of ribonuclease on retention of conditioned response in regenerated planarians

Conditioned planarians were transected and allowed to regenerate in a ribonuclease solution or in pond water. Heads which had regenerated in ribonuclease displayed a retention level equal to that of head and tail sections which had regenerated in pond water. However, tails regenerated in ribonuclease performed randomly although they could be retrained to criterion.     

Determination of anteroposterior polarity in Drosophila

The principles of pattern formation in embryogenesis can be studied in Drosophila by means of a powerful combination of genetic and transplantation experiments. The segmented pattern of the Drosophila embryo is organized by two activities localized at the anterior and posterior egg poles. Both activities exert inducing and polarizing effects on the pattern when transplanted to other egg regions. A small set of maternal genes have been identified that are required for these activities. Mutants in these genes lack either the anterior or posterior part of the segmented pattern. The unsegmented terminal embryonic regions require a third class of genes and form independently of the anterior and posterior centers.     

Hypoxic coordinate regulation of mitochondrial enzymes in mammalian cells

The effect of hypoxic exposure on various mitochondrial enzymes and on cell mitochondrial genomic content was studied in two types of mammalian cells. Hypoxia depressed the activity of six enzymes to the same degree. The kinetics of depression and of recovery during reexposure to normoxia were statistically similar for three marker enzymes. Despite the global and symmetrical decrease in enzyme activities, mitochondrial DNA remained constant. This suggests either symmetrical loss of mitochondrial enzymes from all mitochondria or complete loss of enzymes from a subpopulation of mitochondria with retention of an intact mitochondrial genome.     

一种数字图像空域加密新算法

针对数字图像的特点,在构造复合混沌系统的基础上提出一种加密算法:首先将4个高比特位和4个低比特位拆开形成2个新的图像,新图像中每个像素只有4比特；然后利用复合混沌系统分别置乱这2个新图像中像素的位置,并分别对它们进行替换和扩散；再后将高、低平面的数据对应组合形成8比特每像素的图像,并用混沌序列中后续的数值对8比特的像素进行代换和扩散.如此迭代2轮,最后得到密文图像.理论和实验结果表明该算法具有易于并行实现的特性,密钥空间大,敏感性强,符合密码学的混淆、扩散原则,安全性高.     

The brain connection: the corpus callosum is larger in left-handers

The size of the midsagittal area of the human corpus callosum obtained from postmortem measurement varied with tested hand preference. The corpus callosum, the main fiber tract connecting the two cerebral hemispheres, was larger by about 0.75 square centimeter, or 11 percent, in left-handed and ambidextrous people than in those with consistent right-hand preference. The difference was present in both the anterior and posterior halves, but not in the region of the splenium itself. This callosal morphology, which varied with hand preference, may also be related to individual differences in the pattern of hemispheric functional specialization. The greater bihemispheric representation of cognitive functions in left- and mixed-handers may be associated with greater anatomical connection between the hemispheres. The naturally occurring regressive events in neurogenesis, such as neuronal cell death and axonal elimination, may be factors in the individual differences in brain morphology and in functional lateralization. Specifically, right-handers may be those with more extensive early elimination of neural components.     

Transient regenerative potential of the neonatal mouse heart

Certain fish and amphibians retain a robust capacity for cardiac regeneration throughout life, but the same is not true of the adult mammalian heart. Whether the capacity for cardiac regeneration is absent in mammals or whether it exists and is switched off early after birth has been unclear. We found that the hearts of 1-day-old neonatal mice can regenerate after partial surgical resection, but this capacity is lost by 7 days of age. This regenerative response in 1-day-old mice was characterized by cardiomyocyte proliferation with minimal hypertrophy or fibrosis, thereby distinguishing it from repair processes. Genetic fate mapping indicated that the majority of cardiomyocytes within the regenerated tissue originated from preexisting cardiomyocytes. Echocardiography performed 2 months after surgery revealed that the regenerated ventricular apex had normal systolic function. Thus, for a brief period after birth, the mammalian heart appears to have the capacity to regenerate.     

水稻花培获得大群体健壮绿苗的研究

通过使用混合激素诱发籼稻871015、871109花粉愈伤形成胚性细胞;对籼稻花粉胚性细胞团和粳稻绿芽丛进行分割培养,快速繁育大群体绿苗获得成功。籼稻两个组合的8块胚性细胞团,在两个月内经3—5次切割培养获得绿苗12690株;粳稻花培绿芽丛仅经一次分割培养后的净增绿苗率127.2%,大幅度地提高了水稻花药培养再生绿苗率。分割培养的再生苗,健壮的形成特征:苗粗、浓绿、根多、洁白。良好的生理素质:发根力强,平均每棵试管苗多增根1.8条,根长度增长168.4%;平均每棵再生苗鲜重和干重分别增加0.29克和0.175毫克。     

糯玉米自交系茎尖诱导再生植株研究

以2个糯玉米自交系茎尖为外植体,在添加不同浓度6-BA和2,4-D的MS培养基上诱导丛生芽和胚状体,研究糯玉米茎尖诱导丛生芽和胚状体发生的适宜条件。结果表明:经丛生芽发生途径每个茎尖可再生3~4个植株,经胚状体发生途径每个茎尖可再生9~11个植株。该结果建立了糯玉米茎尖诱导再生体系,为基因工程改良糯玉米种质奠定了基础。     

乏情期奶山羊下丘脑催产素样神经元的分布

为了揭示不同生理期催产素(Oxytocin,OT)在下丘脑-垂体-性腺轴中的分布特点,采用链霉素抗生物素蛋白-过氧化物酶(Streptaridin-peroxidase,SP)法研究了OT免疫反应产物在乏情期奶山羊下丘脑中的分布。结果显示:OT样神经元存在于视上核、室旁核弓状核、室周核、穹隆周核、下丘脑前核、下丘脑后核、腹外侧核、背内侧核、下丘脑外侧区以及乳头体各核团等27个核区,分布区域呈前端尖、中部宽、后钝圆的梭形带。此外,在室旁核观察到大量的强阳性神经纤维,第三脑室附近的纤维伸向脑室内。说明OT在下丘脑广泛存在,且下丘脑OT经神经垂体、第三脑室、血管3条途径释放,经血液循环最终作用于靶细胞而发挥生理作用。     

稻飞虱捕捉器的创新与应用前景

稻飞虱捕捉器属于试验用仪器领域,广泛应用于稻飞虱的防治、测报、药效试验等植保工作中。创新性的稻飞虱捕捉器有两个对称的部件组成,包括了盆体、振动棒、操纵杆；其中操纵杆为空心圆柱,对称部件的操纵杆为实心圆柱,将实心圆柱操纵杆插入空心圆柱操纵杆,即可完成捕捉器的组装。创新性的捕捉器填补了稻飞虱捕捉器的空白,其具备构造简单、操作便捷的优点,能提高稻飞虱的捕捉效率,减轻农技人员劳动强度,具有广阔的应用前景。     

羔羊摆腰病心电图分析

对摆腰病羔羊心电图研究发现，主要改变为窦性心动过速、窦性心律不齐、Ａ－Ｂ导联ＱＳ波或Ｓ波加深，或显著加深。严重病例可见房颤伴室率频速（１５０～２００次／分）及双肢对称性冠状Ｔ波。心电图评定铜、硒制剂单独或联合应用的治疗反应，病羔多项指标均有改善。其中Ｃｕ剂组和Ｃｕ－Ｓｅ－Ｅ组疗效优于Ｓｅ－Ｅ组。     

Directionality of rewarding impulses within the medial forebrain bundle self-stimulation system of the rat

Self-stimulation performance of rats was tested with conditioning pulses to the anterior preoptic area of the medial forebrain bundle followed at various intervals by test pulses to the contralateral posterior hypothalamic area of this bundle. Alternatively, conditioning pulses were delivered through the posterior electrode and test pulses were sent through the anterior electrode. The animals' performance in these two test sequences was indicative of (i) synaptic facilitation and (ii) a posterior convergence site of "self-stimulation impulses" in the medial forebrain bundle.     

Asexual reproduction in a sipunculan worm

The sipunculan worm Aspidosiphon brocki reproduces asexually by transverse fision into two unequal parts, the smaller part comprising the posterior fifth of the animal. Prior to fission each part regenerates the structures essential to the formation of a new individual. The smaller posterior part (daughter) regenerates an anterior body, including introvert, anterior gut, retractor muscles, and nephridia, whereas the larger anterior part (parent) regenerates only the posterior body wall.     

Retrograde amnesia gradients: effects of direct cortical stimulation

Electrical stimulation was delivered bilaterally to either the anterior or posterior cortex in rats from 0.1 second to 4 hours after a single training trial on an inhibitory avoidance task. As indicated by a retention test given 24 hours later, the length of the retrograde amnesia gradients ranged from 5 seconds to 240 minutes, depending on the brain region stimulated and the intensity of the stimulating current. The stimulation intensity that was threshold for amnesia varied directly with the length of the interval between training and treatment.     

‘嘎啦’苹果花药培养种质创新

【目的】单倍体花药离体培养是农作物包括果树育种中种质资源创新的最有效方法之一,苹果是染色体高度杂合且自交不亲和树种之一。在当前苹果主栽品种中,‘嘎啦’具有早熟、丰产、稳产、多抗的优良性状,是苹果育种的重要种质资源之一。花药单倍体育种也是苹果新品种培育的重要手段。本研究通过‘嘎啦’苹果花药培养诱导胚状体并获得纯合再生植株,为创制新的纯合体种质资源,加速苹果新品种培育进程提供材料。【方法】采集‘嘎啦’苹果单核靠边期到双核早期的花药(未开放的花蕾),低温处理后进行离体培养,经胚状体诱导,分化培养形成再生苗,再经生根培养获得花药再生植株。之后利用FACS流式细胞仪对再生植株进行倍性分析。取再生植株叶片分离DNA,选用80个来源于苹果HIDRAS数据库的SSR标记对所有植株进行PCR扩增,经过凝胶电泳和荧光毛细管电泳鉴定再生植株纯合基因型。移栽成活后,对每个再生株系进行形态学特征观察及统计分析。【结果】过去3年中,共接种的74 200个‘嘎啦’花药,从未被污染的5万多个花药中成功诱导形成386个胚状体(胚状体诱导率0.7%),经分化培养获得64株再生苗(植株再生率16.6%),最终经生根培养、移栽获得30个成活再生株系。其中包括28个二倍体株系,1个单倍体株系和1个四倍体株系。SSR标记用于纯合性鉴定,PAGE结果表明再生株系均为花粉(小孢子)单倍体细胞来源。为了鉴定这些再生植株基因型,从80个SSR中筛选出17个SSR标记(其余SSR标记不具有多态性或带型杂乱)对所获得的30个再生株系进行基因型鉴定。17个SSR标记所对应的PCR扩增物能有效区分鉴定不同再生植株基因型。继代培养60 d后的形态学观察显示不同再生株系的株高、叶长、叶宽等特征差异明显。不同二倍体纯合植株的植物学特征也存在差异:Gala 5植株相对较高,叶基变宽,叶尖渐尖;Gala 7叶片变小、变厚,叶柄变短且基部宽大,叶色深且有很强的光泽度;Gala 18叶片较小,叶数较多。纯合二倍体再生植株长势弱于‘嘎啦’杂合供体,但强于单倍体和纯合四倍体。【结论】采用优化花药培养技术,成功获得了一批苹果纯合体再生植株种质并建立了SSR标记鉴定体系。这些新的种质很大程度丰富了苹果育种亲本种质资源,为挖掘‘嘎啦’苹果优良性状基因提供了重要材料,为后期的田间性状筛选,杂交育种奠定了基础。