The impact and specificity of nerve perturbation on novel vibrotactile sensory letter learning

The purposes of this study were to determine if induced radiating paresthesia interferes with (a) acquisition and/or (b) utilization of complex tactile information, and (c) identify whether interference reflects tactile masking or response competition. Radiating ulnar (experiment 1) and median (experiment 2) nerve paresthesia was quantified on ulnar innervated vibrotactile Morse code letter acquisition and recollection tasks. Induced paresthesia differentially impacted letter acquisition and recollection, but only when presented to the same anatomical spatial location.     

Axillary bud flowering after apical decapitation in Pharbitis in relation to photoinduction

The flowering response of axillary buds of seedlings of Pharbitis nil Choisy, cv. Violet, was examined in relation to the timing of apical bud removal (plumule including the first leaf or second leaf) before or after a flower-inductive 16-h dark period. When the apical bud was removed well before the dark period, flower buds formed on the axillary shoots that subsequently developed, but when removed just before, or after, the dark period, different results were observed depending on the timing of the apical bud removal and plant age. In the case of 8-day-old seedlings, fewer flower buds formed on the axillary shoots developing from the cotyledonary node when plumules were removed 20 to 0 h before the dark period. When the apical bud was removed after the dark period, no flower buds formed. Using 14-day-old seedlings a similar reduction of flowering response was observed on the axillary shoots developing from the first leaf node when the apical bud was removed just after the dark period. To further elucidate the relationship between apical dominance and flowering, kinetin or IAA was applied to axillary buds or the cut site where the apical bud was located. Both chemicals influenced flowering, probably by modulating apical dominance which normally forces axillary buds to be dormant.     

胡须信息在大鼠双侧初级体感皮层间的传递路径

大鼠的初级体感皮层(primary somatosensory cortex,SⅠ)虽然只接受来自对侧胡须的上行输入,但仍可以被同侧胡须刺激所激活.解剖学研究发现,在两侧SⅠ皮层之间有两条传递胡须信息胼胝体通路:一条是类颗粒区(perigranular zone,PGZ)通路;另一条是异颗粒区(dysgranular zone,DZ)通路.然而,哪一条通路在传递胡须刺激信息的过程中起主要作用还不清楚.本研究使用电压敏感染料(voltage-sensitive dye,VSD)成像技术来观察胡须刺激时整个SⅠ的神经元群体活动的空间分布和时间特性.实验发现,对侧胡须刺激首先激活barrel(颗粒区,granular zone,GZ),然后以兴奋波的形式传播到胡须感觉区(sub-barrel field cortex,BFC)外侧的DZ.而与首先激活BFC的对侧胡须刺激不同,同侧胡须刺激首先激活SⅠ的DZ.所激发的皮层兴奋以波的形式传播并扩散至BFC.失活另一侧皮层可以抑制这种同侧反应.电刺激另一侧半球皮层与刺激同侧胡须类似,也首先激活成像侧DZ.我们的实验结果显示,胡须刺激激活对侧SⅠ,在经过胼胝体传导后,另一侧半球的DZ(同侧于被刺激的胡须)被激活.连接双侧皮层DZ区的胼胝体连接在SⅠ对同侧胡须刺激的反应中起了主导作用.     

Cutaneous silent period evoked in human first dorsal interosseous muscle motor units by laser stimulation

Painful stimulation of the hand results in an inhibitory response in the hand muscles known as the cutaneous silent period (CSP). In this study, we employed probability- and frequency-based analysis methods to examine the CSP induced by laser stimuli. Subjects were asked to contract their first dorsal interosseous muscle so that selected motor units discharged at a rate of about 8 Hz. Laser pulses were delivered to the palm of the hand, and reflex responses were recorded. The stimuli generated CSP in all test subjects. We found that the latency of the CSP evoked using laser stimulation was longer than that the previously published latency values of the CSP evoked using electrical stimulation.Using only the presently generated laser induced CSP data, the CSP duration was longer when analyzed via peristimulus frequencygram method compared to the probability-based methods such as peristimulus time histogram and surface electromyogram.In the light of the current results, we suggest that laser stimulation could be used when studying pain pathways in human subjects and the frequency-based analysis methods can be preferred because they are previously shown to be more reliable for obtaining the synaptic activity profile. These results can be used to standardize the CSP methods in basic and clinical research.     

人脐带间充质干细胞于不同通电情况下在聚吡咯上生长情况的形态

目的观察人脐带间充质干细胞（human umbilical cord mesenchymal stem cell,hUC-MSC）与聚吡咯共培养后,在不同通电条件下形态学变化。方法体外分离培养hUC-MSC并进行鉴定。循环伏安法制备聚吡咯（polypyrrole,PPy）薄膜。选择第3～6代的hUC-MSC与PPy共培养,分别采用控制电压和控制电流的方法对细胞进行刺激,利用电镜及光镜观察细胞形态学变化。不通电组作为阴性对照。结果电刺激对细胞贴附、形态有较大影响,不同形式的电刺激对细胞形态影响的比较类似。结论电刺激结合生物导电材料对细胞的贴附和形态可造成显著改变,可作为调控细胞生长的手段之一,需要进一步研究其控制条件。     

The hatching stimulus for eggs of Aedes punctor (Diptera: Culicidae)

ABSTRACT.

• 1 Eggs of the British woodland mosquito, Aedes punctor (Kirby), were subjected to a variety of media in an attempt to determine the hatching stimulus.
• 2 It was found that continuous immersion in distilled water evoked almost no hatching (0.2%); intermittent removal from the water gave low hatching (8.9%).
• 3 Slow deoxygenation of the medium by either bacterial growth or the introduction of nitrogen produced the highest level of hatching (26.0–90.0%). Eggs of A.punctor were shown to hatch within a 4 h period of the oxygen concentration in the medium reaching zero.

     

Quantitative Studies of Stimulus Coding in First-Order Vibrissa Afferents of Rats. 1. Receptive Field Properties and Threshold Distributions

We examined stimulus-response relationships of vibrissa-activated mechanosensory neurons of the rat's fifth (trigeminal) ganglion. Single-unit activity was recorded with tungsten microelectrodes. The vibrissae were deflected with a variety of parametrically controlled stimulus waveforms.

We found that the receptive field of each vibrissa-activated neuron consisted of a single vibrissa. Few, if any, unambiguous examples of spontaneous activity were observed in these neurons. Even if true spontaneous activity was present, its observed incidence was low, as were the measured discharge rates.

Thresholds of individual neurons were usually quite discrete; often a 1-2% increase in pulse magnitude (angular displacement) above a level to which the neuron did not respond caused it to discharge on every trial. The distribution of thresholds for the sample was continuous with a median of about 1° and a range of over three orders of magnitude. The most sensitive neurons responded to deflections of less than 0.1°. Many neurons responded to a single suprathreshold pulse with more than one spike. We found no consistent relationships among the thresholds of the additional evoked discharges of an individual neuron other than that the total number of evoked spikes either increased or stayed the same, but never decreased, as stimulus magnitude increased.

About one-third of the neurons examined had velocity thresholds below 3°/sec. Above that value, thresholds were distributed continuously throughout a range of over three orders of magnitude. The median velocity threshold was about 100°/sec. The broad and continuous distributions of both magnitude and velocity thresholds suggest that a population of vibrissa-activated neurons can code stimulus strength smoothly and continuously over a wide range, even though individual neurons may be poorly suited to do so.     

Preparation of stimulus responsive multiple emulsions by membrane emulsification using con a as biochemical sensor

In this work, a novel strategy for the controlled fabrication of biomolecular stimulus responsive water-in-oil-in-water (W/O/W) multiple emulsion using the membrane emulsification process was investigated. The emulsions interface was functionalized with a biomolecule able to function as a receptor for a target compound. The interaction between the biomolecular receptor and target stimulus activated the release of bioactive molecules contained within the structured emulsion. A glucose sensitive emulsion was investigated as a model study case. Concanavalin A (Con A) was used as the biomolecular glucose sensor. Various physicochemical strategies for stimulus responsive materials formulation are available in literature, but the preparation of biomolecule-responsive emulsions has been explored for the first time in this paper. The development of novel drug delivery systems requires advanced and highly precise techniques to obtain their particular properties and targeting requirements. The present study has proven the flexibility and suitability of membrane emulsification for the preparation of stable and functional multiple emulsions containing Con A as interfacial biomolecular receptor able to activate the release of a bioactive molecule as a consequence of interaction with the glucose target molecule. The influence of emulsion interfacial composition and membrane emulsification operating conditions on droplets stability and functional properties have been investigated. The release of the bioactive molecule as a function of glucose stimulus and its concentration has been demonstrated.