Pacemaker synchronization

A method using the standard radio-frequency receiver was developed to telemeter biopotentials across the intact body Wall; it can be employed to program a stimulus to the heart at any phase of the cardiac cycle. The small variations of potential across the electrodes of the implanted cardiac pacemaker change the natural resonant frequency of the receiver in direct relation to the electrical activity of the heart.     

仿刺参体壁的组织学和组织化学

用组织学和组织化学方法对仿刺参Apostichopus japonicus体壁的结构和成分进行了研究。组织学研究结果表明:仿刺参体壁自外向内由上皮层、结缔组织层、肌肉层和体腔上皮层组成。上皮层主要包括一层薄的角质层和2~3层上皮细胞,结缔组织层内含丰富的胶原纤维,肌肉层主要是平滑肌,体腔上皮层由单层扁平上皮组成。组织化学研究结果表明:仿刺参体壁各层(除体腔上皮层外)均富含糖类和蛋白质,不含脂类;碱性磷酸酶和酸性磷酸酶在体壁中存在酶活性的部位相同,主要在结缔组织层的空洞状结构处以及结缔组织层与肌肉层交联处。     

Ammonium and chloride extrusion: hyperpolarizing synaptic inhibition in spinal motoneurons

The reversal potential of postsynaptic inhibition shifts toward resting membrane potentials in cat spinal motoneurons after intravenous infusion of ammonium salts(1 to 3 millimoles per kilogram of body weight). Simultaneously, the depolarizing action of intracellularly injected chloride ions on the inhibitory membrane is enhanced and recovery therefrom is prolonged. Passive membrane properties remain unaltered. The results indicate a blocking of active extrusion of chloride which normally maintains a high ionic gradient for hyperpolarizing inhibition.     

Electrical output of a receptor membrane

The electrical output of the receptor membrane of the nonmyelinated ending of Pacinian corpuscles is a function of the electrical gradients across the receptor membrane. The generator potential of the receptor membrane in response to equal mechanical stimuli varies linearly with the intensity of polarizing currents passed through the membrane. The production of a generator potential leaves a refractory state in the receptor membrane which is independent of the amount of charge transferred across the membrane but is dependent on a factor related to the strength of the stimulus which produced the response.     

Reversal response elicited in nonbeating cilia of paramecium by membrane depolarizatin

Ciliary reversal occurs in response to electrical and chemical stimuli in specimens of Paramecium caudatum in which ciliary beat has been completely inhibited by external application of nickel ions. The mechanism underlying ciliary reversal appears, therefore, to differ from that of ciliary beat. The cessation of ciliary beat has no effect on the intracellular potential of Paramecium. However, depolarizing action potentials are associated with ciliary reversals in paramecia, treated with nickel, without ciliary beat. Thus, membrane depolarization in this species seems specifically concerned with the ciliary reversal, and not with ciliary beat.     

Crayfish muscle fiber: spike electrogenesis in fibers with long sarcomeres

Most of the muscle fibers in the walking legs of the crayfish Procambarus clarkii generate only graded electrical responses. However, some fibers in extensor muscles of the carpopodite have long sarcomeres, about 10 micrometers in length, and generate overshooting spikes that have conduction velocities of 0.3 meter per second. The spikes induce twitch contractions.     

Olfactory epithelium: unitary responses in the tortoise

In the tortoise, Gopherus polyphemus, single unit spikes in the olfactory epithelium in response to amyl acetate were positive relative to the slow potential. The number of spikes in a response train was 4 to 15, the duration 3 to 4 msec, the height 0.5 to 2 mv. The height of successive spikes in a train decreased. The decrement in height, the number, and the frequency of spikes changed with the strength of the odor.     

瑞香狼毒毒性物质的提取及对小鼠的致病作用

[目的]探究瑞香狼毒的致病作用。[方法]采用乙醇提取法从瑞香狼毒根中提取瑞香狼毒粗提物,并测定了其对进小鼠的毒性。[结果]小白鼠灌胃LD50为2 083.33 mg/kg,灌胃后表现为:身体无力,全身蜷缩,皮毛无光泽,抽搐、挣扎甚至死亡。剖检症状为:肺呈红色;肝、脾呈暗紫色;胃壁浆膜下有出血斑,胃黏膜广泛出血,内容物色红。病理变化为:心肌变性,横纹消失,血管扩张充血、出血;肝细胞颗粒变性、脂肪变性,中央静脉扩张,瘀血;肾小球毛细血管扩张充血,肾小管上皮细胞颗粒变性,肾间质血管扩张充血;脾窦高度扩张,含有大量红细胞,脾小梁结构不完整,断裂肺血管及肺泡壁毛细血管扩张充血,有出血,肺泡壁增厚,有中性白细胞浸润,部分肺泡腔扩张,肺泡壁断裂,细支气管扩张,管腔中有浆液性渗出和脱落的上皮细胞;肠黏膜血管扩张充血,黏膜层上皮细胞溶解,呈网状。[结论]为今后瑞香狼毒的开发利用提供了理论依据。     

Synchronous bursts of action potentials in ganglion cells of the developing mammalian retina

The development of orderly connections in the mammalian visual system depends on action potentials in the optic nerve fibers, even before the retina receives visual input. In particular, it has been suggested that correlated firing of retinal ganglion cells in the same eye directs the segregation of their synaptic terminals into eye-specific layers within the lateral geniculate nucleus. Such correlations in electrical activity were found by simultaneous recording of the extracellular action potentials of up to 100 ganglion cells in the isolated retina of the newborn ferret and the fetal cat. These neurons fired spikes in nearly synchronous bursts lasting a few seconds and separated by 1 to 2 minutes of silence. Individual bursts consisted of a wave of excitation, several hundred micrometers wide, sweeping across the retina at about 100 micrometers per second. These concerted firing patterns have the appropriate spatial and temporal properties to guide the refinement of connections between the retina and the lateral geniculate nucleus.     

The role of chloride transport in postsynaptic inhibition of hippocampal neurons

Hippocampal inhibitory postsynaptic potentials are depolarizing in granule cells but hyperpolarizing in CA3 neurons because the reversal potentials and membrane potentials of these cells differ. Here the hippocampal slice preparation was used to investigate the role of chloride transport in these inhibitory responses. In both cell types, increasing the intracellular chloride concentration by injection shifted the reversal potential of these responses in a positive direction, and blocking the outward transport of chloride with furosemide slowed their recovery from the injection. In addition, hyperpolarizing and depolarizing inhibitory responses and the hyperpolarizing and depolarizing responses to the inhibitory neurotransmitter gamma-aminobutyric acid decreased in the presence of furosemide. These effects of furosemide suggest that the internal chloride activity of an individual hippocampal neuron is regulated by two transport processes, one that accumulates chloride and one that extrudes chloride.     

大穗型与多穗型小麦单株生产潜力研究

为了解大穗型与多穗型小麦基因型的单株生产潜力,以5个大穗型基因型和5个多穗型基因型为试验材料,在株距14cm、8cm和2cm 3种种植密度条件下对单株产量及产量因素进行试验研究。结果表明：两种穗型的基因型都有较高的单株产量潜力,在株距14cm密度处理中单株产量最高,均达到20 g;多穗型基因型单株产量在株距14cm和2cm的密度处理中分别比大穗型基因型多0.8g和0.5g,差异显著,在株距为8cm的密度处理中后者显著高于前者,表明大穗型基因型对生存环境反映敏感,适应范围窄,而多穗型基因型则具有更好的适应能力;多穗型基因型在株距14cm和2cm密度处理条件下穗数高出幅度大于穗粒重高出的幅度,说明穗数是影响其单株产量在这两个密度处理条件下高于大穗型基因型的主要原因。     

水稻抛秧除草专用肥应用试验初报

除草专用肥、丁苄对旱育抛秧田化除效果及产量效应试验表明 :除草专用肥对大田早期莎草及阔叶杂草的防效较好 ;大田中后期防效有所下降。应用除草专用肥可提高成穗率7.6%,增加有效穗数 ,提高结实率 ,实现穗大粒多 ,集除草、追肥于一体 ,省时省工 ,具有广阔的应用前景     

大穗型小麦增穗措施

针对大穗型小麦分蘖成穗困难的问题,进行了连续多年的田间试验。结合大穗型小麦的生长发育特点和试验结果,总结出＂高肥力、早播种、窄行距、适播量、控旺长＂的组合增穗措施。     

Inferior olive of the cat: intracellular recording

The action potential evoked from inferior olivary neurons of the cat by orthodromic, antidromic, or intracellular stimulation has a large prolonged depolarization, frequently with several superimposed smaller spikes. The all-or-nothing unitary response appears to be a property of the cell, and the later spikes are not secondary to synaptic excitation by recurrent axon collaterals.     

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.     

Resistance spikes at transitions between quantum hall ferromagnets

We report a manifestation of first-order magnetic transitions in two-dimensional electron systems. This phenomenon occurs in aluminum arsenide quantum wells with sufficiently low carrier densities and appears as a set of hysteretic spikes in the resistance of a sample placed in crossed parallel and perpendicular magnetic fields, each spike occurring at the transition between states with different partial magnetizations. Our experiments thus indicate that the presence of magnetic domains at the transition starkly increases dissipation, an effect also suspected in other ferromagnetic materials. Analysis of the positions of the transition spikes allows us to deduce the change in exchange-correlation energy across the magnetic transition, which in turn will help improve our understanding of metallic ferromagnetism.     

Piezoelectric nanogenerators based on zinc oxide nanowire arrays

We have converted nanoscale mechanical energy into electrical energy by means of piezoelectric zinc oxide nanowire (NW) arrays. The aligned NWs are deflected with a conductive atomic force microscope tip in contact mode. The coupling of piezoelectric and semiconducting properties in zinc oxide creates a strain field and charge separation across the NW as a result of its bending. The rectifying characteristic of the Schottky barrier formed between the metal tip and the NW leads to electrical current generation. The efficiency of the NW-based piezoelectric power generator is estimated to be 17 to 30%. This approach has the potential of converting mechanical, vibrational, and/or hydraulic energy into electricity for powering nanodevices.     

Active transport of 5,5-dimethyl-2,4-oxazolidinedione

5,5-Dimethyl-2,4-oxazolidinedinedione, a substance commonly used to estimate intracellular pH, moves against both a concentration gradient and a hydrogen-ion gradient in the everted gut sac. Furthermore, the value of the flux ratio for this substance under conditions of zero electrochemical potential across the bowel wall unequivocally demonstrates active transport.     

Changes of simple and complex spike activity of cerebellar purkinje cells with sleep and waking

Action potentials of cerebellar Purkinje cells were observed in intact monkeys during sleep and waking. Purkinje cells exhibit two sorts of action potentials, called simple and complex spikes, and these two sorts of spikes were differently affected by sleep. Simple-spike activity (generated by the parallel fiber inputs to the Purkinje cell) was highest during sleep with rapid eye movements as compared with both waking and sleep with electroencephalographic slow waves. In contrast, complex-spike activity (generated by the climbing fiber inputs to the Purkinje cell) was lowest during sleep with rapid eye movements. The complex action potential of the Purkinje cell consists of an initial large spike followed by one or more smaller secondary spikes, and the number of these secondary spikes was found to be independent of the background discharge frequency of the simple spike. This independence suggests a possible role of presynaptic factors rather than the excitability level of the Purkinje cell itself in determining the number of secondary discharges occurring in the complex spike.     

Self-assembled hexa-peri-hexabenzocoronene graphitic nanotube

An amphiphilic hexa-peri-hexabenzocoronene self-assembles to form a pi-electronic, discrete nanotubular object. The object is characterized by an aspect ratio greater than 1000 and has a uniform, 14-nanometer-wide, open-ended hollow space, which is an order of magnitude larger than those of carbon nanotubes. The wall is 3 nanometers thick and consists of helical arrays of the pi-stacked graphene molecule, whose exterior and interior surfaces are covered by hydrophilic triethylene glycol chains. The graphitic nanotube is redox active, and a single piece of the nanotube across 180-nanometer-gap electrodes shows, upon oxidation, an electrical resistance of 2.5 megohms at 285 kelvin [corrected]. This family of molecularly engineered graphite with a one-dimensional tubular shape and a chemically accessible surface constitutes an important step toward molecular electronics.