Central synaptic inputs to identified leech neurons determined by peripheral targets

Developing Retzius (Rz) neurons in different segments of the central nervous system of the medicinal leech have different peripheral targets: Rz cells in standard segments innervate the body wall, whereas Rz cells in the reproductive segments innervate reproductive tissue. Early removal of reproductive tissue primordia causes reproductive Rz cells to develop morphologically like their standard segmental homologs, suggesting that Rz cells depend on peripheral targets for signals that determine their central and peripheral morphology. Furthermore, after removal of reproductive tissue, reproductive Rz cells also receive synaptic inputs normally appropriate for standard Rz cells. These results suggest that the functional identity of these neurons is specified by the target they contact during embryogenesis.     

Locally resonant sonic materials

We have fabricated sonic crystals, based on the idea of localized resonant structures, that exhibit spectral gaps with a lattice constant two orders of magnitude smaller than the relevant wavelength. Disordered composites made from such localized resonant structures behave as a material with effective negative elastic constants and a total wave reflector within certain tunable sonic frequency ranges. A 2-centimeter slab of this composite material is shown to break the conventional mass-density law of sound transmission by one or more orders of magnitude at 400 hertz.     

Long-term synaptic potentiation

Long-term synaptic potentiation (LTP) is a leading candidate for a synaptic mechanism of rapid learning in mammals. LTP is a persistent increase in synaptic efficacy that can be quickly induced. The biophysical process that controls one type of LTP is formally similar to a synaptic memory mechanism postulated decades ago by the psychologist Donald Hebb. A key aspect of the modification process involves the N-methyl-D-aspartate (NMDA) receptor-ionophore complex. This ionophore allows calcium influx only if the endogenous ligand glutamate binds to the NMDA receptor and if the voltage across the associated channel is also sufficiently depolarized to relieve a magnesium block. According to one popular hypothesis, the resulting increase in the intracellular calcium concentration activates protein kinases that enhance the postsynaptic conductance. Further biophysical and molecular understanding of the modification process should facilitate detailed explorations of the mnemonic functions of LTP.     

Hemodynamic signals correlate tightly with synchronized gamma oscillations

Functional imaging methods monitor neural activity by measuring hemodynamic signals. These are more closely related to local field potentials (LFPs) than to action potentials. We simultaneously recorded electrical and hemodynamic responses in the cat visual cortex. Increasing stimulus strength enhanced spiking activity, high-frequency LFP oscillations, and hemodynamic responses. With constant stimulus intensity, the hemodynamic response fluctuated; these fluctuations were only loosely related to action potential frequency but tightly correlated to the power of LFP oscillations in the gamma range. These oscillations increase with the synchrony of synaptic events, which suggests a close correlation between hemodynamic responses and neuronal synchronization.     

关于局部S-闭空间的另一注记

讨论了局部S-闭空间的遗传性及其与其他空间的联系,得到：1）局部S-闭空间是半正则遗传的;2）每一个局部S-闭空间（X,T）,存在T′T,使（X,T′）是拟H-闭空间.     

山羊胚胎移植受体同期发情优化程序研究

用国产炔诺酮阴道栓、促卵泡素(FSH)和氯前列烯醇(PG)组成3种诱导山羊同期发情的处理程序,分别对579、889和673只四川本地山羊进行同期发情处理.结果表明,设计的3种同期发情处理程序都有较好的同期发情效果,同期发情有效率分别为88.9 %(515/ 579)、91.9 %(817/ 889)和96.4 %(649/ 673),处理羊同期发情后正常排卵并形成功能黄体的比率分别为67.6 %(348/ 515)、66.1 %(540/ 817)和70.9 %(460/ 649).处理程序结束后,从撤除炔诺酮阴道栓到母羊开始发情的间隔时间分别为47.3±16.4、47.0±18.7和42.7±16.4 h,各组发情羊发情持续时间分别为43.9±16.5、41.5±17.9和44.1±16.4 h.总的来看,使用PG-炔诺酮阴道栓-FSH-PG处理法,同期发情总有效率最好.     

加大科技投入推动云南马铃薯产业升级

云南马铃薯经过10多年的快速发展,近年来种植面积达到33.33万hm2,每公顷产量达18 t。马铃薯在云南已发展成为重要的粮食、蔬菜、饲料和加工原料兼备的多用途作     

Nutritional outputs and energy inputs in seafoods

Energy used by U.S. ships in harvesting seafoods can vary by a factor of more than 100 when the seafoods are compared on the basis of their content of edible protein or line weight. This energy difference bears no relationship to the nutritive value in the food. When protein yield is compared, the energy to harvest some seafoods is in the same range as that needed to grow field crops. There is a large increase in energy consumption after processing, partly because of the small percent of the live weight used for human food.     

Cyclic changes in enzyme activity in synchronized mammalian cell cultures

Activity of the enzymes glucose-6-phosphate dehydrogenase and lactate dehydrogenase increases intermittently in synchronized cultures of Chinese hamster cells. During G(1) phase (3 hours after mitosis), midway through S phase (7 hours after mitosis) and again in late S phase (10 hours after mitosis), rapid increases in activity were observed and correlated with a net increase in cell size and total protein. The evidence suggests that this is a general phenomenon which affects a whole population of proteins and may be the expression of an endogenous cellular rhythm.     

森林生态系统服务功能市县联动核算与精度控制

  目的  探讨以市县联动核算体系为手段进行森林生态系统服务功能物质量精度控制的应用方法。  方法  选取浙江省湖州市为研究地,通过设定1个市级总体和5个县级副总体,并依托森林资源连续清查和森林资源规划设计调查体系建立样地核算和小班核算2个体系,形成由同步核算机制、相容机制和修正机制构成的市县联动核算机制,完成森林生态系统水源涵养、土壤保育、固碳、林木养分固持和提供负离子5项指标的物质量核算和精度控制。  结果  在显著性水平a=0.05下,市级总体各指标物质量的样地核算结果估计精度均超过90%;除提供负离子,其他指标物质量的小班核算结果均落入样地核算置信区间。县级副总体中,除长兴县和安吉县的提供负离子,其他指标的小班核算结果均落入样地核算置信区间。采用修正机制,对提供负离子结果予以修正,最后得到2018年湖州市森林生态系统5项服务功能物质量与精度。  结论  市县联动核算体系能够对各层级森林生态系统功能物质量核算结果进行精度控制,可根据小班核算结果是否落入样地核算置信区间来确定区域森林生态系统服务功能物质量最终结果。图1表5参28     

Visual and auditory inputs into the cuneate nucleus

Sound clicks or light flashes modify somatic sensory activity in the cuneate nucleus of the cat. The techniques of gross potential recording in the cuneate nucleus or medial lemniscal tract, of single unit recording in the cuneate nucleus, and of excitability testing of cuneate terminals demonstrate this heterosensory interactionsensory interaction.     

Molecular biology of synaptic receptors

A special proteolipid (a hydrophobic protein) has been extracted and purified from nerve-ending membranes and total particulate matter of gray areas of the central nervous system. Such a proteolipid shows a high affinity for binding d-tubocurarine, serotonin, and atropine and has been called receptor proteolipid. The interaction of this proteolipid with atropine sulfate was studied with light scattering and polarization of fluorescence. The changes observed, which follow a cooperative type of curve, were attributed to the aggregation of the proteolipid macromolecules. Such a phenomenon was then observed under the electron microscope. A receptor proteolipid having a high affinity for binding acetylcholine, hexamethonium, and other cholinergic drugs was isolated and purified from electric tissue of fishes and from electroplax membranes. Such a proteolipid was also extracted from membranes from which acetylcholinesterase had been removed, and it was concluded that this enzyme and the receptor proteolipid are two different macromolecules. A high affinity binding site with a dissociation constant of K1 equal to 10(-7) and about ten sites with K2 equal to 10(-5) were recognized in the receptor proteolipid. Under the electron microscope the receptor proteolipid of brain appears as a rod-shaped macromolecule which may assume paracrystalline arrays with 10(-8) molar atropine sulfate. Similarly the receptor proteolipid from electric tissue and from skeletal muscle may form paracrystalline arrays under the action of acetylcholine and hexamethonium. A model of the cholinergic receptor based on the properties of the proteolipid is presented. Preliminary work indicates the possibility of obtaining a biophysical response to acetylcholine when the receptor proteolipid is embedded in artificial bilayered lipid membrance.     

Neural and immunological synaptic relations

A synapse is a stable adhesive junction between two cells across which information is relayed by directed secretion. The nervous system and immune system utilize these specialized cell surface contacts to directly convey and transduce highly controlled secretory signals between their constituent cell populations. Each of these synaptic types is built around a microdomain structure comprising central active zones of exocytosis and endocytosis encircled by adhesion domains. Surface molecules that may be incorporated into and around the active zones contribute to modulation of the functional state of the synapse.     

Cell biology of synaptic plasticity

The nervous system of mammals retains throughout the animals' life-span the ability to modify the number, nature, and level of activity of its synapses. Synaptic plasticity is most evident after injury to the nervous system, and the cellular and molecular mechanisms that make it possible are beginning to be understood. Transplantation of brain tissue provides a powerful approach for studying mechanisms of synaptic plasticity. In turn, understanding the response of the central nervous system to injury can be used to optimize transplant survival and integration with the host brain.     

Slow synaptic excitation in sympathetic ganglion cells: evidence for synaptic inactivation of potassium conductance

The slow excitatory postsynaptic potential (EPSP) was investigated in frog sympathetic ganglion cells. In contrast to the increased conductance associated with other known EPSP's, during the slow EPSP resting membrane conductance was decreased. Electrical depolarization of the membrane potentiated the slow EPSP, whereas progressive hyperpolarization decreased its size and then reversed it to a hyperpolarizing potential (the opposite of the effect of membrane polarization on other EPSP's). The reversal potential of the slow EPSP was close to the potassium equilibrium potential. We propose that the slow EPSP, in contrast to classical EPSP's, is generated by an inactivation of resting potassium conductance.     

Complex synaptic configurations in planarian brain

Complex synaptic configurations which appear to have especial evolutionary and functional significance are shown in the neuropil of the brain of the planarian Dugesia dorotocephala. Some of the endings in these synaptic attachments contain dense core vesicles, suggesting that nonadrenaline or serotonin or both are neurotransmitters at a more primitive phyletic level than reported hitherto. The spatial proximity and connectivity of the synapses suggest modes of action permitting greater functional complexity to the planarian brain than previously supposed. Closely adjacent cellular processes which contain polysomal ribosomes, unusual in the neuropil, suggest synaptic transmission-protein synthesis coupling and a possible role in memory.     

Alzheimer's disease is a synaptic failure

In its earliest clinical phase, Alzheimer's disease characteristically produces a remarkably pure impairment of memory. Mounting evidence suggests that this syndrome begins with subtle alterations of hippocampal synaptic efficacy prior to frank neuronal degeneration, and that the synaptic dysfunction is caused by diffusible oligomeric assemblies of the amyloid beta protein.