Strychnine: its action on spinal motoneurons of cats

In cats strychnine does not alter measurably the potential, threshold, after potentials, or refractoriness of the membrane of the spinal motoneurons. Increased reflexes probably result from increase of excitatory impingement upon motoneurons. Spikes recorded during a rapid succession of nerve impulses produced by strychnine ("strychnine burst") suggest that soma membrane resistance is appreciable during stimulation.     

Rapid neural coding in the retina with relative spike latencies

Natural vision is a highly dynamic process. Frequent body, head, and eye movements constantly bring new images onto the retina for brief periods, challenging our understanding of the neural code for vision. We report that certain retinal ganglion cells encode the spatial structure of a briefly presented image in the relative timing of their first spikes. This code is found to be largely invariant to stimulus contrast and robust to noisy fluctuations in response latencies. Mechanistically, the observed response characteristics result from different kinetics in two retinal pathways ("ON" and "OFF") that converge onto ganglion cells. This mechanism allows the retina to rapidly and reliably transmit new spatial information with the very first spikes emitted by a neural population.     

瓶插液对储藏后牡丹“洛阳红”切花瓶插品质的影响

以经过储藏12d、24d、36d的牡丹品种“洛阳红”为试材,通过测定切花瓶插期间的瓶插寿命、花径变化、鲜重变化率、水分平衡值和乙烯释放率等指标,研究了瓶插液(3%蔗糖 0.2g/LHQS 2mmolSTS)对“洛阳红”切花瓶插品质的影响。结果表明:瓶插液(3%蔗糖 0.2g/LHQS 2mmolSTS)可以显著延长“洛阳红”切花的瓶插寿命、提高其水分平衡值和花径、降低其鲜重损失和乙烯释放,提高‘洛阳红’切花的瓶插观赏品质。     

甘蔗种质资源的研究

对 2 64个国内外栽培甘蔗品种及福建省内野生甘蔗“割手密”的特征特性等进行了研究 ,结果表明 :“割手密”的体细胞染色体数有 2n =72、80、84、88、92、96、1 0 2等 7种类型 ,酯酶同工酶有 1 9种类型 ;印度培育的甘蔗品种产量高 ,澳大利亚培育的甘蔗品种锤度高 ;从国外引进的品种中筛选出 3个生长特快的高产品种 (“C1 55-76”、“My5462”和“My5770”)和 2个高纤维含量的高产品种 (“FCP86-2 61”和“FCP86-2 63”)。对上述甘蔗种质资源进行了创新利用 ,已初步选育出特高糖品种“闽糖 91 -2 2 1”及高生物量品系“闽糖 92 -1 1 7”和“闽糖 92 -2 2 5”等     

Discovery of till deposition at the grounding line of Whillans Ice Stream

We report on the discovery of a grounding-line sedimentary wedge ("till delta") deposited by Whillans Ice Stream, West Antarctica. Our observation is that grounding-line deposition serves to thicken the ice and stabilize the position of the grounding line. The ice thickness at the grounding line is greater than that of floating ice in hydrostatic equilibrium. Thus, the grounding line will tend to remain in the same location despite changes in sea level (until sea level rises enough to overcome the excess thickness that is due to the wedge). Further, our observation demonstrates the occurrence of rapid subglacial erosion, sediment transport by distributed subglacial till deformation, and grounding-line sedimentation, which have important implications for ice dynamics, numerical modeling of ice flow, and interpretation of the sedimentation record.     

Anatomical connections between medial and lateral regions of the hypothalamus concerned with food intake

No anatomical connections have yet been demonstrated from the ventromedial ("satiety") to the lateral ("feeding") areas of the hypothalamus. Lesions were induced with goldthioglucose in mice in the ventromedial region, including the arcuate and ventromedial nuclei. With the Fink-Heimer stain for degenerating axons, fiber connections between these two areas were demonstrated.     

新复方中药制剂“沙大净”对鸡红细胞免疫功能的影响

为了解研究新复方中药制剂(“沙大净”口服液)对蛋鸡红细胞免疫功能的影响,试验选用35周龄的海兰白蛋鸡80只,随机分成4组,1%“沙大净”组、0.5%“沙大净”组、0.25%“沙大净”组和对照组,每组20只。结果表明:1%“沙大净”组、0.5%“沙大净”组的RBC-C3bRR、RFER都极显著(P<0.01)高于对照组,而RBC-ICR显著低于(P<0.05)对照组。因此,“沙大净”对鸡红细胞的免疫功能有较明显的促进作用。     

Receptive fields of opponent color units in the optic nerve of the ground squirrel

When mapped with white light, each receptive field consisted either of an excitatory ("on") center and a concentric inhibitory ("off") surround, or of the reverse arrangement. Monochromatic stimuli revealed that each receptive field was composed of two mutually antagonistic components (one excitatory, one inhibitory) which had different spectral sensitivities and different spatial distributions. For some units the two chromatic components had identical spatial distributions.     

Interstellar carbon in meteorites

The Murchison and Allende chondrites contain up to 5 parts per million carbon that is enriched in carbon-13 by up to + 1100 per mil (the ratio of carbon-12 to carbon-13 is approximately 42, compared to 88 to 93 for terrestrial carbon). This "heavy" carbon is associated with neon-22 and with anomalous krypton and xenon showing the signature of the s-process (neutron capture on a slow time scale). It apparently represents interstellar grains ejected from late-type stars. A second anomalous xenon component ("CCFXe") is associated with a distinctive, light carbon (depleted in carbon-13 by 38 per mil), which, however, falls within the terrestrial range and hence may be of either local or exotic origin.     

Acetylcholine noise: analysis after chemical modification of receptor

The elementary voltage pulses ("shot effects") produced by the action of acetylcholine molecules on the receptor were studied by analyzing the membrane voltage fluctuations ("noise") after acetylcholine application at the frog neuromuscular junction. The amplitude of these pulses was decreased after treatment with a disulfide-bond reducing agent. The shot effect may thus depend on the structure or conformation of the receptor molecule.     

明前中期延绥镇长城沿线屯垦的兴衰

通过研究明朝前、中期延绥镇长城沿线屯垦,得出其发展的时间特征:洪武时期缓慢恢复—永乐至宣德时期部分地段初步垦殖—正统至成化初期缓慢发展—成化中至弘治中兴盛—正德至隆庆中荒废;空间特征是:屯垦的北界由腹里州县—界石—"二边"长城—"大边"长城逐步北移。影响明朝前、中期延绥镇长城沿线屯垦发展的主要因素是地理条件和战争破坏,其中前者是根本原因,后者是重要影响因素。明代延绥镇长城沿线屯垦对毛乌素沙地南侵的影响不大,自然原因可能是根本原因。     

夏秋反季节花椰菜营养吸收规律探讨

通过2年的试验表明:夏秋反季节花椰菜的整个生长过程中干物质积累呈“S”型变化趋势,主要表现在移栽后的60 d生长相对缓慢,移栽后60~75 d干物质积累变化迅速,干物质日积累量达到6.9 g。氮磷钾的吸收规律表现为:氮的吸收最高峰出现在移栽后的第75 d左右,吸收强度达到176.2 mg/d;磷钾的吸收最高峰出现在移栽后的第75 d左右,吸收强度分别达到49.5 mg/d和195.3 mg/d。花椰菜对氮肥和钾肥的吸收都表现出较大的需求量,磷在移栽第75 d左右表现出较大的需求量。     

Shocked quartz at the triassic-jurassic boundary in Italy

Quartz grains that appear to have been shock-metamorphosed occur within three closely spaced shale beds from the uppermost Triassic ("Rhaetian") Calcare a Rhaetavicula in the Northern Apennines of Italy. The upper shale coincides with the abrupt termination of the distinctive, uppermost Triassic Rhaetavicula fauna and is overlain by the Hettangian (Lower Jurassic) Calcare Massiccio; no extinctions appear to be associated with the two lower layers, which occur 1.2 and 2.4 meters below the boundary shale. Approximately 5 to 10% of the quartz grains within these layers exhibit one or more sets of planar deformational features whose orientations cluster around the rational crystallographic planes (basal, omega, and pi) most commonly observed in shocked quartz. Textural and stratigraphic observations support an interpretation of at least three closely spaced impacts at the end of the Triassic.     

越橘果实及新梢生长发育的动态变化

以早、中和晓熟品种“都克”(Duke)、“蓝丰”(Bluecrop)和“埃利奥特”(Elliot)为试材,对不同成熟期的越橘品种在同一生态条件下果实及枝条的各项指标进行测定,研究其果实及枝条在年周期中的变化规律.结果表明:越橘果实的生长变化规律基本一致,总体呈“快速增长-缓慢增长-迅速增长”的趋势;越橘延长枝春梢生长发育动态变化总体呈“快速增长-缓慢增长-停止生长”的趋势;基生枝生长发育动态不同.“都克”与“埃利奥特”基生枝的生长动态一致,呈现“平缓增长-快速增长-缓慢增长”的趋势;“蓝丰”基生枝的生长分为春梢和秋梢2个时期,分别呈现“平缓增长”和“快速增长”趋势.     

The ant odometer: stepping on stilts and stumps

Desert ants, Cataglyphis, navigate in their vast desert habitat by path integration. They continuously integrate directions steered (as determined by their celestial compass) and distances traveled, gauged by as-yet-unknown mechanisms. Here we test the hypothesis that navigating ants measure distances traveled by using some kind of step integrator, or "step counter." We manipulated the lengths of the legs and, hence, the stride lengths, in freely walking ants. Animals with elongated ("stilts") or shortened legs ("stumps") take larger or shorter strides, respectively, and concomitantly misgauge travel distance. Travel distance is overestimated by experimental animals walking on stilts and underestimated by animals walking on stumps.     

Building neural representations of habits

Memories for habits and skills ("implicit or procedural memory") and memories for facts ("explicit or episodic memory") are built up in different brain systems and are vulnerable to different neurodegenerative disorders in humans. So that the striatum-based mechanisms underlying habit formation could be studied, chronic recordings from ensembles of striatal neurons were made with multiple tetrodes as rats learned a T-maze procedural task. Large and widely distributed changes in the neuronal activity patterns occurred in the sensorimotor striatum during behavioral acquisition, culminating in task-related activity emphasizing the beginning and end of the automatized procedure. The new ensemble patterns remained stable during weeks of subsequent performance of the same task. These results suggest that the encoding of action in the sensorimotor striatum undergoes dynamic reorganization as habit learning proceeds.     

散叶莴苣幼苗高温胁迫下生理生化变化的研究

以3个耐热品种(“意大利全能生菜”、“耐抽薹生菜”和“辛普森-精英”)和3个不耐热品种(“生菜王”、“大速生”和“嫩绿奶油生菜”)为试验材料,研究散叶莴苣在人工模拟高温胁迫下的热害情况、细胞膜透性、保护酶相对活性变化以及丙二醛相对含量的变化。结果表明,幼苗热害指数是鉴定散叶莴苣的耐热性的理想指标,高温导致相对电导率和丙二醛含量升高,过氧化物酶、超氧化物歧化酶活性下降,过氧化氢酶活性升高。     

A functional dosage compensation complex required for male killing in Drosophila

Bacteria that selectively kill males ("male-killers") were first characterized more than 50 years ago in Drosophila and have proved to be common in insects. However, the mechanism by which sex specificity of virulence is achieved has remained unknown. We tested the ability of Spiroplasma poulsonii to kill Drosophila melanogaster males carrying mutations in genes that encode the dosage compensation complex. The bacterium failed to kill males lacking any of the five protein components of the complex.     

Energetics of hydrogen bond network rearrangements in liquid water

A strong temperature dependence of oxygen K-edge x-ray absorption fine structure features was observed for supercooled and normal liquid water droplets prepared from the breakup of a liquid microjet. Analysis of the data over the temperature range 251 to 288 kelvin (-22 degrees to +15 degrees C) yields a value of 1.5 +/- 0.5 kilocalories per mole for the average thermal energy required to effect an observable rearrangement between the fully coordinated ("ice-like") and distorted ("broken-donor") local hydrogen-bonding configurations responsible for the pre-edge and post-edge features, respectively. This energy equals the latent heat of melting of ice with hexagonal symmetry (ice Ih) and is consistent with the distribution of hydrogen bond strengths obtained for the "overstructured" ST2 model of water.     

Evidence for addiction-like behavior in the rat

Although the voluntary intake of drugs of abuse is a behavior largely preserved throughout phylogeny, it is currently unclear whether pathological drug use ("addiction") can be observed in species other than humans. Here, we report that behaviors that resemble three of the essential diagnostic criteria for addiction appear over time in rats trained to self-administer cocaine. As in humans, this addiction-like behavior is present only in a small proportion of subjects using cocaine and is highly predictive of relapse after withdrawal. These findings provide a new basis for developing a true understanding and treatment of addiction.