Octopamine: presence in single neurons of Aplysia suggests neurotransmitter function

Octopamine has been identified and measured in individual neurons from Aplysia californica. Neither dopamine nor norepinephrine was detected in these cells. Thus, in Aplysia there may be separate populations of catecholaminergic and monophenolaminergic cells. Octopamine may have functions of its own in the central nervous system of mollusks.     

Target-dependent structural changes accompanying long-term synaptic facilitation in Aplysia neurons

The mechanisms underlying structural changes that accompany learning and memory have been difficult to investigate in the intact nervous system. In order to make these changes more accessible for experimental analysis, dissociated cell culture and low-light-level video microscopy were used to examine Aplysia sensory neurons in the presence or absence of their target cells. Repeated applications of serotonin, a facilitating transmitter important in behavioral dishabituation and sensitization, produced growth of the sensory neurons that paralleled the long-term enhancement of synaptic strength. This growth required the presence of the postsynaptic motor neuron. Thus, both the structural changes and the synaptic facilitation of Aplysia sensorimotor synapses accompanying long-term behavioral sensitization can be produced in vitro by applying a single facilitating transmitter repeatedly. These structural changes depend on an interaction of the presynaptic neuron with an appropriate postsynaptic target.     

Differential classical conditioning of a defensive withdrawal reflex in Aplysia californica

The defensive siphon and gill withdrawal reflex of Aplysia is a simple reflex mediated by a well-defined neural circuit. This reflex exhibits classical conditioning when a weak tactile stimulus to the siphon is used as a conditioned stimulus and a strong shock to the tail is used as an unconditioned stimulus. The siphon withdrawal component of this reflex can be differentially conditioned when stimuli applied to two different sites on the mantle skin (the mantle shelf and the siphon) are used as discriminative stimuli. The differential conditioning can be acquired in a single trial, is retained for more than 24 hours, and increases in strength with increased trials. Differential conditioning can also be produced within the field of innervation of a single cluster of sensory neurons (the LE cluster) since two separate sites on the siphon skin can serve as discriminative stimuli. The finding that two independent afferent inputs that activate a common set of interneurons and motor neurons can be differentially conditioned restricts the possible cellular loci involved in the associative learning.     

Optical imaging of neuronal populations during decision-making

We investigated decision-making in the leech nervous system by stimulating identical sensory inputs that sometimes elicit crawling and other times swimming. Neuronal populations were monitored with voltage-sensitive dyes after each stimulus. By quantifying the discrimination time of each neuron, we found single neurons that discriminate before the two behaviors are evident. We used principal component analysis and linear discriminant analysis to find populations of neurons that discriminated earlier than any single neuron. The analysis highlighted the neuron cell 208. Hyperpolarizing cell 208 during a stimulus biases the leech to swim; depolarizing it biases the leech to crawl or to delay swimming.     

汉中人工流水和仿生态养殖大鲵肌肉营养成分研究

本研究分别提取4育龄汉中人工流水养殖和仿生态养殖大鲵肌肉,测定其营养元素、氨基酸含量及矿物质含量。结果表明,仿生态养殖大鲵较人工流水饲养大鲵肌肉更具开发价值。仿生态养殖大鲵肌肉的平均粗蛋白含量高于人工流水饲养大鲵3.85%；仿生态养殖大鲵肌肉含有大量优质蛋白,EAA/TAA较人工流水饲养大鲵高11.37%,且矿物质含量丰富。由此看出,4育龄仿生态养殖大鲵具有更重要的市场价值,具有高蛋白及脂肪的特点,口味鲜美,应对其进行重点开发和利用。     

育成巨胚稻与其亲本的γ-氨基丁酸和氨基酸含量的比较分析

比较了育成的3种巨胚稻与其亲本糙米中GABA、氨基酸的含量。结果表明:育成巨胚稻糙米的GABA含量约为常规非巨胚稻的4倍,且高于其巨胚稻亲本的GABA含量;与常规非巨胚稻相比,巨胚稻糙米中绝大多数氨基酸的含量有不同程度的提高,其中赖氨酸、必需氨基酸总量和氨基酸总量的平均增幅分别达51.85%、26.24%和23.75%;育成巨胚稻与其巨胚稻亲本间的氨基酸含量没有显著差异。     

Intracellular injection of cAMP induces a long-term reduction of neuronal K+ currents

Intracellular signals that trigger long-term (24-hour) changes in membrane currents in identified neurons of Aplysia have been examined in order to understand the cellular mechanisms underlying long-term sensitization. Adenosine 3',5'-monophosphate (cAMP) was directly injected into individual sensory neurons to mimic the effects of sensitization training at the single cell level. Potassium currents of these cells were reduced 24 hours after injection of cAMP; these currents were similar to those reduced 24 hours after behavioral sensitization. These results suggest that cAMP is part of the intracellular signal that induces long-term sensitization in Aplysia.     

A critical period for macromolecular synthesis in long-term heterosynaptic facilitation in Aplysia

Both long-term and short-term sensitization of the gill and siphon withdrawal reflex in Aplysia involve facilitation of the monosynaptic connections between the sensory and motor neurons. To analyze the relationship between these two forms of synaptic facilitation at the cellular and molecular level, this monosynaptic sensorimotor component of the gill-withdrawal reflex of Aplysia can be reconstituted in dissociated cell culture. Whereas one brief application of 1 microM serotonin produced short-term facilitation in the sensorimotor connection that lasted minutes, five applications over 1.5 hours resulted in long-term facilitation that lasted more than 24 hours. Inhibitors of protein synthesis or RNA synthesis selectively blocked long-term facilitation, but not short-term facilitation, indicating that long-term facilitation requires the expression of gene products not essential for short-term facilitation. Moreover, the inhibitors only blocked long-term facilitation when given during the serotonin applications; the inhibitors did not block the facilitation when given either before or after serotonin application. These results parallel those for behavioral performance in vertebrates and indicate that the critical time window characteristic of the requirement for macromolecular synthesis in long-term heterosynaptic facilitation is not a property of complex circuitry, but an intrinsic characteristic of specific nerve cells and synaptic connections involved in the long-term storage of information.     

Identification of a peptide specific for Aplysia sensory neurons by PCR-based differential screening.

In order to identify genes specific for the sensory neurons of Aplysia, a miniaturized differential screening method based on the polymerase chain reaction and applicable to small amounts of tissue was used. One messenger RNA was isolated that is expressed in every mechanoreceptor sensory cluster of the Aplysia central nervous system. This messenger RNA encodes a peptide that seems to function as an inhibitory cotransmitter. The peptide selectively inhibits certain postsynaptic cells but not others and thereby allows the sensory neurons to achieve target-specific synaptic actions.     

环境因素对大豆化学品质及产量影响研究 IV常规肥料对大豆化学品质及产量的影响

不同的施肥水平对大豆产量及品质影响较大,各肥料组合处理对产量、脂肪和蛋白质的影响都达到显著水平;蛋脂总量相对稳定,不同施肥水平间差异不显著。研究表明,氮肥对蛋白质的影响较大,磷钾肥对脂肪影响较大,但是每种肥料的影响作用都不是单独作用,而是与其它两种肥料的共同作用。此外,每种肥料都有一个最佳施用量。蛋白质含量最高的施肥组合为:尿素80kg 磷酸二铵180kg 氯化钾20kg/hm2;脂肪含量最高的处理为:尿素60kg 磷酸二铵180kg 氯化钾50kg/hm2;蛋脂总量最高的处理为:尿素60kg 磷酸二铵120kg 氯化钾50kg/hm2;产量最高的处理为:尿素60kg 磷酸二铵120kg 氯化钾50kg/hm2。     

沼肥不同用量对小麦光合特性和产量的影响

在大田条件下用沼肥作基肥,通过6个不同施用量观测其对小麦不同时期叶片光合特性和产量的影响,结果表明:施用沼肥,能有效地提高小麦叶片的叶绿素含量(Chl)、光合速率(Pn)、叶片水分利用效率(WUE)和产量;在22500 kg/hm2施肥水平下,小区产量、单位面积穗数、千粒重最高;在30000 kg/hm2施肥水平下的光合速率、蒸腾速率、拔节期叶绿素含量最高。在37500 kg/hm2施肥水平下的株高、穗下节长、穗粒数明显高于对照;基肥施用沼肥的各处理小麦产量比对照提高了12.4%~26.14%,沼肥施用量在0~30000 kg/hm2范围内叶绿素含量、叶片光合速率、产量随着施肥量的增加而提高,但过量的施用沼肥会抑制叶绿素的合成、降低光合速率。沼肥在麦田作基肥的最佳施肥量应在22500~30000 kg/hm2左右。     

Active transport of potassium and chloride in an identifiable molluscan neuron

Direct measurements of intracellular K(+) and Cl(-)activities before and after blockage of cellular metabolic processes indicate that K(+) is actively transported inwardly and Cl(-)is actively transported outwardly from the giant cell of the abdominal ganglion of Aplysia. The rewarming of cells that have been cooled to 1 degrees +/- 1 degrees C causes K(+) to be taken up and Cl(-) to be extruded against electrochemical gradients.     

长期施肥对菜地土壤氮磷钾养分积累的影响

以皖北地区菜地土壤为供试土壤,以其相邻粮田为对照,研究了菜地土壤氮磷钾含量变化及其分布特征,结果表明:经过长时间种植蔬菜,菜地土壤氮磷钾养分发生了不同变化,与一般粮田相比,菜地土壤铵态氮含量没有发生明显变化,而菜地土壤硝态氮含量明显增加,菜地土壤0￣60cm土层中硝态氮含量一般为相邻粮田土壤的3￣20倍;菜地土壤磷素积累特别明显,主要积累于0￣40cm土层中,菜地土壤全磷积累量为粮田的1￣5倍,有效磷积累量为粮田的7￣20倍;菜地耕层土壤速效钾含量也明显高于粮田土壤,为粮田土壤的0.6￣4倍左右。种植蔬菜时间越长,土壤养分积累量越高。     

Enzymatic amplification of beta-globin genomic sequences and restriction site analysis for diagnosis of sickle cell anemia

Two new methods were used to establish a rapid and highly sensitive prenatal diagnostic test for sickle cell anemia. The first involves the primer-mediated enzymatic amplification of specific beta-globin target sequences in genomic DNA, resulting in the exponential increase (220,000 times) of target DNA copies. In the second technique, the presence of the beta A and beta S alleles is determined by restriction endonuclease digestion of an end-labeled oligonucleotide probe hybridized in solution to the amplified beta-globin sequences. The beta-globin genotype can be determined in less than 1 day on samples containing significantly less than 1 microgram of genomic DNA.     

Ribonucleic acid metabolism of a single neuron: correlation with electrical activity

The giant neuron of the abdominal ganglion of Aplysia californica incorporates tritiated uridine into RNA at a constant rate at rest. This rate incrceases under synaptic stimulation, the increase being directly proportional to the number of action potentials produced by the neuron. Multineuronal samples from stimulated ganglia faiiled to show an increase in incorporation.     

转基因鲤鲫杂交(F1)回交三倍体子代红细胞大小与DNA含量测定

通过细胞遗传学方法对转基因鲤鲫杂交(F1)回交三倍体子代鱼进行了红细胞及其核大小的测量和DNA含量的测定,结果为：采用血涂片法测量鲤鲫杂交回交子代红细胞面积和体积分别是二倍体红鲫鱼的1．43倍和1．57倍,接近三倍体的理论预期值1．5倍;通过流式细胞仪对鲤鲫杂交子代细胞和二倍体细胞进行相对DNA含量测定,结果为：在所测的12尾鱼中,有9尾鲤鲫杂交回交子代鱼的DNA含量是对照鱼的1．5倍。占总鱼数的75％,在2～3倍体之间非常接近三倍体(非整倍三倍体)的鱼有3尾,占总鱼数的25％,本结果与其细胞染色体核型分析结果基本一致。     

提取桑天牛成虫肠道微生物基因组DNA的2种方法比较

比较了改良CTAB法和改良SDS法两种提取桑天牛成虫肠道微生物基因组DNA的方法,结果表明：改良SDS法提取的DNA杂质较多,并且有部分降解;改良CTAB法提取的DNA纯度较高,适用于后续试验研究.     

精液中猪细小病毒DNA三种提取方法效果比较

猪精液中含有高浓度的蛋白质,因此提取高纯度DNA较为困难;试验分别用水煮法、异硫氰酸胍法和Trizol法三种方法对连续稀释梯度猪精液提取猪细小病毒DNA,应用Taqman荧光定量PCR技术评价提取效果并加以对比。结果发现Trizol法可以提取出高纯度的DNA,但因Trizol试剂价格昂贵,不适用临床检测;比较另外两种方法,水煮法较异硫氰酸胍抽提法更为有效,是一种迅速、简便、经济、高效的DNA提取方法,适合于临床大量样品的检测。     

Cretaceous extinctions: evidence for wildfires and search for meteoritic material

Clay samples from three Cretaceous-Tertiary boundary sites contain 0.36 to 0.58 percent graphitic carbon, mainly as fluffy aggregates of 0.1 to 0.5 micrometers-apparently a worldwide layer of soot. It may have been produced by wildfires triggered by a giant meteorite. This carbon, corresponding to a global abundance of 0.021 +/- 0.006 gram per square centimeter, could have greatly enhanced the darkening and cooling of the earth by rock dust, which has been suggested as a cause of the extinctions. The surprisingly large amount of soot (10 percent of the present biomass of the earth) implies either that much of the earth's vegetation burned down or that substantial amounts of fossil fuels were ignited also. The particle-size distribution of the soot is similar to that assumed for the smoke cloud of "nuclear winter," but the global distribution is more uniform and the amounts are much greater, suggesting that soot production by large wildfires is about 10 times more efficient that has been assumed for a nuclear winter. Thus cooling would be more pervasive and lasting. No trace of meteoritic noble gases and no meteoritic spinel were found in these carbon fractions. Accordingly, limits can be set on the mass fraction of the meteorite that escaped degassing (相似文献