温度对神经元网络活动的影响

利用多通道微电极阵列上培养的海马神经元网络,通过分析28～41℃范围内不同温度时网络自发放电频率．幅度和相邻峰电位时间间隔(interspike interval,ISI)的变化,探讨了温度对网络活动的影响。发现温度升高过程中放电频率、幅度呈不同程度增大的趋势,峰电位数目的变化程度随其间隔的增大呈减小趋势。结果表明体外培养的胎鼠海马神经元的网络活动具有温度敏感性。     

刺激丘脑体感觉核引起的皮层诱发电位和胼胝体电位的相互作用

用刺激兔丘脑后腹核引起的皮层诱发电位作为制约反应,胼胝体电位作为测验反应,可见到后者发生先抑制后易化的改变。易化过程表现为测验反应慢成分幅度的增大和其后发放活动的增强,而快成分却只受到抑制。如制约反应具有后发放活动,则测验反应幅度将伴有相应的周期性波动。如果,被后腹核刺激引起的诱发电位作用而增大的胼胝体电位,反过来再作用于后腹核刺激引起的诱发电位,则可见到其有强大的胼胝体易化作用,同时胼胝体电位慢成分幅度愈大,其胼胝体易化作用也愈强,两者有正比关系。     

刺激隐神经中C类纤维诱发的小脑浦肯野细胞简单锋电位反应

用玻璃微电极记录了猫小脑浦肯野细胞的简单锋电位(PC-SS)。在标准化互协方差函数图中,PC-SS自发放电无明显波峰;弱刺激隐神经只引起A类纤维传入时,PC-SS出现A类诱发放电反应(A-CED),它包括潜伏期为16.7±0.9ms的早反应和270.8±12.8ms的晚反应。用极化电流选择性阻滞A类纤维传导后,强刺激只引起C类纤维单独传入时,出现潜伏期为142.4±4.3ms的C类诱发反应(C-CED)。强刺激同时引起A类和C类纤维传入时,只出现A-CED而不出现C-CED。按标准化功率谱密度函数分析,PC-SS自发放电可分为两种类型。一类为高峰型,最大能量峰值平均为15.7±4.7×10~(-3),峰频为4.07±1.67Hz;刺激A类纤维使峰值增大,而刺激C类纤维却使峰值减小。另一类为低峰型,峰值为8.4±1.4×10~(-3),峰频为3.67±2.90Hz。刺激A类和C类纤维均使峰值增大,前者增大更多,但峰频均无显著性变化。上述结果表明,C类纤维传入可以到达小脑浦肯野细胞,引起特异的PC-SS放电反应。     

基于复杂性度量的心率变异信号非线性分析

假设心率变异信号是累积－发放模型（Ｉｎｔｅｇｒａｔｅ－ｆｉｒｅ）与非线性动力学系统耦合产生的峰电位链（ＳｐｉｋｅＴｒａｉｎ）。以符号动力学为基础,提出利用峰电位间隔（ｉｎｔｅｒｓｐｉｋｅｉｎｔｅｒｖａｌ,ＩＳＩ）及其随机替代数据的Ｃ１、Ｃ２复杂度来定量刻划非线性动力学系统特性。结果表明：确定性驱动产生的峰电位间隔序列可以与随机性驱动产生的峰电位间隔序列区分开。因此,在噪声干扰较强的生理信号中,尤其是在不清楚非线性动力系统变量和峰电位间隔序列之间是否存在微分同胚的情况下,以复杂性度量来代替以Ｔａｋｅｎｓ嵌入定理为基础的关联维数、Ｌｙａｐｎｏｖ指数等描述动力系统特征的方法是合适的。最后通过２类共３７个个体,每个个体的心电数据为１０００个Ｒ－Ｒ间期的微分序列检验心率变异信号的非线性结构。     

大鼠脊髓诱发电位与脊髓损伤的关系——Ⅱ、皮肤、椎板和硬膜上诱发电位的比较

从大鼠的背侧皮肤表面和椎板分别记录刺激坐骨神经诱发的脊髓电位,并与硬膜上电位进行了比较。结果表明:皮肤表面电位与硬膜上直接记录具有相同的节段性特征。从硬膜上经椎板至皮肤表面、反应潜伏时延长、电位幅度递减。各波峰潜伏时也相应增加。电位的波形、幅度与记录方式有关,但反应潜伏时不受影响。     

猫下丘脑腹内侧核与旁中央中脑区神经联系的电生理学观察

用电脉冲刺激戊巴比妥钠麻醉和三碘季铵酚麻痹的31只猫的下丘脑腹內侧核(HVM),记录旁中央中脑区的平均诱发电位(AEP)。HVM 刺激点46个,旁中央中脑区引导点1046个,其中阳性反应点103个,快波反应151个,大多数为“峰电位式”快波。用逐渐增强的电脉冲刺激 HVM 可得等级式和“全或无”式两类反应。用不同频率的双刺激(PST)测试了111个 AEP 的反应性,其中有38个能跟随500Hz 以上的 PST,27个能跟随200—499Hz 的PST,46个仅能跟随199Hz 以下的 PST。给予短串刺激时,得到跟随500Hz 以上及500Hz以下的两类反应。这些结果提示 HVM 与旁中央中脑区之间既有经突触的投射又有直接的纤维连接。据计算,这些直接纤维的传导速度约为0.29—4.1m/s,相当于细有髓鞘和无髓鞘两类纤维。另外还描述了可能属于中枢轴突的某些传导特性。反映直接纤维连接的 HVM 刺激点与中脑中央灰质反应点的位置关系提示两者之间可能具有背腹侧方向的对应关系。     

大鼠脊髓诱发电位与脊髓损伤的关系——Ⅲ.脊髓局部损毁后电位的变化及电位来源分析

本文描述了大鼠脊髓L_1节段后柱、后索、侧索和前角的诱发电位及其损伤后的变化,并观察了切断L_4、L_5脊神经背、腹根与横断高位颈髓对电位的影响,以进行行电位来源分析。结果可见,上述四个区域的诱发电位基本由早反应三相波和晚反应组成。分别电解损毁这些部位后,电位波幅均普遍降低,晚期反应较早反应降低明显。后柱或后索受损对电位影响最大。局部损毁后可见L_1及T_(13)水平的硬膜上电位改变明显,尤其晚反应减弱、波峰平坦。反应时值与潜伏时未见明显改变。切断L_4脊神经背、腹根后、电位基本消失。去大脑对电位未见明显影响。结果表明,刺激坐骨神经诱发的脊髓电位起源于低位腰段传入神经和脊髓内多通路的兴奋传导,在一定程度上受腹根逆行活动的影响,与大脑及脊髓下行传导束活动无直接联系。脊髓诱发电位的幅度与波形改变可作为脊髓损伤的判断指标之一。     

一种心肌细胞电参数微机实时分析系统

本文介绍了一种分析心肌细胞膜电位参数的微机系统。该系统能用两种采样间隔(50μs和1ms)自动地把动作电位的0至4相转换为数字量,并测量和打印出静息电位、最大上升速率、振幅、时程以及波形面积。同时,还能转换并测量心肌收缩张力信号。该系统配备有心肌细胞膜电位的概率密度函数分析软件以及基于 FFT 的功率谱分析软件。     

瞳孔控制系统非线性的频率特性与固有频率

本文用实验方法从时域和频域上揭示了瞳孔对光反应的非线性特性.在亮度以正弦变化的光刺激下,瞳孔反应波形呈同步倍频现象;描述函数的频率-振幅特性曲线呈多峰的锯齿形;具有1.2Hz左右的系统固有频率和极限环现象.     

视网膜电图振荡电位参数的稳定性

用系列强度１１档刺激闪光记录２０例３０只眼的视网膜电图（ＥＲＧ）振荡电位（ＯＰ）,研究ＯＰ的光强特性和参数稳定性。结果表明,ＯＰ各子波峰时和刺激光强呈指数曲线相关,相关性很高;而振幅和光强的函数关系的变异很大,相关性较低,不同对象间ＯＰ各子波振幅的变异系数较大,而峰时的变异系数较小,ＯＰ的峰时改变比振幅改变更为稳定。     

Assessment of the Reliability of Amplitude Histograms for Inhibitory Synaptic Currents in Rat Cortex Culture

We analyzed in detail the quantum parameters of evoked inhibitory postsynaptic currents (eIPSC) recorded from synaptically connected cultured cortex neurons using a whole-cell patch-clamp technique. The IPSC were evoked using minimum extracellular stimulation of a presynaptic unit with a frequency of 0.2 sec^-1 at the holding potential of -80 mV. Amplitude histograms for eIPSC demonstrated clearly detectable equally spaced peaks. For each histogram, we used a method based on autocorrelation analysis and Monte Carlo simulation to determine whether peaks in the amplitude histograms can result due to finite sampling from the sum of the Gaussian distributions. The autocorrelation function allowed us to measure the peak spacing (and, hence, the mean quantum size) for each histogram; this parameter was found to be 10 pA.     

Influence of the Latency Fluctuations and the Quantal Process of Transmitter Release on the End-Plate Potentials' Amplitude Distribution

Spontaneous synaptic potentials and their relation to the end-plate potential (e.p.p.) are studied. It has been suggested earlier that the e.p.p. at a single nerve-muscle junction is built up statistically of small all-or-none units which are identical in size with the spontaneous miniature end-plate potentials (m.e.p.p.'s). In this paper, a more general theory is developed which takes into account latency fluctuations of the unit components. A general equation for e.p.p. amplitude probability distribution is derived. This probability distribution is a function of the latency distribution, m.e.p.p.'s pulse shape, m.e.p.p.'s amplitude distribution, and the mean quantal content. The time course of transmitter release, or latency distribution, is derived from a histogram of synaptic delays in a frog muscle, but obtained equations can be used for other distribution functions as well.     

An automated method for counting and sizing fish eggs

This paper describes an automated method for counting and sizing fish eggs in the diameter range 200–2500 μm. Eggs, suspended in water, are pumped at a controlled rate through an electronic sensor which produces a voltage pulse which is proportional in amplitude to particle size. The sensor is connected to a HIAC Criterion PC-320 particle analyser which is in turn connected to a Tracor Northern pulse height analyser. This equipment separates the voltage pulses into 398 recording channels. An ACT 1 Sirius microcomputer is used to store the data, transform it to egg size and then produce a histogram of egg size distribution in 20-μm class intervals.
The method has a counting accuracy of 99.5 ± 0.5%. It has been compared with two manual methods of estimating egg numbers.     

Maturational changes in opioidergic control of luteinizing hormone and follicle-stimulating hormone in ram lambs

Stimulation by naloxone, an opioid antagonist, of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion was examined in spring-born crossbred ram lambs raised under natural photoperiod. Vehicle (n = 6) or 1 mg naloxone/kg vehicle (n = 6) was injected (i.m.) 3 times at 2-h intervals at 5, 10 and 15 weeks of age and 4 times at 2-h intervals at 20, 25, 30 and 35 weeks of age. Blood samples were taken every 12 min for 6 h at 5, 10 and 15 weeks of age and for 8 h at 20, 25, 30 and 35 weeks of age. Naloxone had no effect on age at sexual maturity (controls 239 +/- 23 days; naloxone 232 +/- 33 days). The only significant (P less than 0.05) effect of naloxone on FSH was a greater pulse amplitude in 10-week-old treated lambs than in control lambs. Naloxone treatment resulted in greater LH pulse amplitude at 5 and 10 weeks of age (P less than 0.05), lower basal serum concentration of LH at 10 weeks of age (P less than 0.05), greater LH pulse frequency at 25 weeks of age (P less than 0.05), and greater mean serum concentrations of LH, basal LH and LH pulse amplitude at 35 weeks of age (P less than 0.01) than in the controls. In both groups of lambs, mean and basal FSH, and LH and FSH pulse amplitude were highest at 5 weeks of age and fell with age. LH pulse amplitude was lowest at 35 weeks of age (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Discriminative control of the vaginal vasomotor response

With use of a discriminative control procedure and operant techniques, women significantly increased their vaginal pulse amplitude (produced vaginal vasodilation) but did not significantly decrease vaginal pulse amplitude (produce vaginal vasoconstriction). Acquisition of vaginal pulse amplitude control was rapid with no significant improvement over trials or the 5 experimental days. Specificity of vaginal pulse amplitude control occurred in relation to the other vasomotor responses, including vaginal blood volume and digital pulse amplitude. Vagnial pulse amplitude changes were not related to somatic-muscular, respiratory, or heart-rate changes. Women who used oral contraceptives were better able to control vaginal pulse amplitude than women who used other forms of birth control. Although the sexual behavior of these two groups and did not differ, women in the latter group tended to be more clitorally oriented.     

Discriminative control of the vaginal vasomotor response

With use of a discriminative control procedure and operant techniques, women significantly increased their vaginal pulse amplitude (produced vaginal vasodilation) but did not significantly decrease vaginal pulse amplitude (produce vaginal vasoconstriction). Acquisition of vaginal pulse amplitude control was rapid with no significant improvement over trials or the 5 experimental days. Specificity of vaginal pulse amplitude control occurred in relation to the other vasomotor responses, including vaginal blood volume and digital pulse amplitude. Vaginal pulse amplitude changes were not related to somatic-muscular, respiratory, or heart-rate changes. Women who used oral contraceptives were better able to control vaginal pulse amplitude than women who used other forms of birth control. Although the sexual behavior of these two groups did not differ, women in the latter group tended to be more clitorally oriented.This work was supported in part by NIH grant MH 27098 awarded to C.A.S.     

LH secretion around the time of the preovulatory gonadotrophin surge in the ewe

Blood samples were taken once an hour from 17 ewes starting on Day 15 of a natural oestrous cycle and continuing for 4 days or until 36 h after the onset of oestrus. On Days 12, 16, 17 and 18 of the cycle, blood samples were also taken every 5 min for 6 h, between 09:00 and 15:00 h. LH pulse frequency rose and amplitude fell between the luteal and follicular phase of the oestrous cycle ( ). In the period from 48 h before to 40 h past the peak of the preovulatory LH surge, LH pulse frequency did not change. LH pulse amplitude was similar prior to and following the LH surge. During the preovulatory LH surge, LH pulse amplitude rose markedly ( ), with the visible, discrete components of pulses ranging from twice to 20 times those seen prior to or following the surge. The amplitude of LH pulses on the downslope of the LH surge was greater than that on the upslope of the surge (P < 0.05). We conclude that the preovulatory LH surge may consist of an amalgamation of high frequency, high amplitude pulses of LH secretion.     

Intraspecific agonistic interactions in freely swimming mormyrid fish, Marcusenius macrolepidotus (South African form)

South African bulldogs (Marcusenius macrolepidotus, Mormyridae) generate brief (less than 1 ms) electric organ discharges (EODs), separated by much longer and highly variable inter-discharge intervals (IDIs). The diurnal and nocturnal overt behaviour and electrical activity were studied under various conditions: in isolated fish, in pairs of fish, and in a group of four fish that were kept in a "natural" large aquarium. EODs from up to four individuals were recorded simultaneously and identified. While resting during the day, isolated fish showed a broad inter-individual variability of IDI patterns, with distribution histogram modes ranging from 85.7 ms to 325.8 ms. When foraging during the day, IDI modes were shorter and less variable (36.3–48.3 ms). Behaviour patterns displayed during nocturnal agonistic encounters were retreating, parallel swimming, anti-parallel display, attack, and fleeing/chasing. High-discharge-rate (HD) displays were observed at several stages of these encounters, for example, during anti-parallel display (a period of low overt motor activity), or following attacks. IDI durations as short as 11 ms occurred during HD displays, which followed low-rate inter-HD activity almost without transition. IDI distribution histogram modes when fish showed anti-parallel display were 15.4 ms and 24.8 ms, and 30.0 ms during nocturnal non-agonistic interactions. No overt fighting was observed once a dominance relationship was established. In a large aquarium, an approaching dominant male evoked a simultaneous discharge arrest in a group of three subdominant males. Electronic Publication     

Modulation of luteinizing hormone pulse amplitude by the frequency of luteinizing hormone-releasing hormone stimulation and by testosterone in castrated, hypothalamic-lesioned male rats

The frequency of spontaneous luteinizing hormone (LH) pulses is thought to be a direct result of the frequency of luteinizing hormone-releasing hormone (LHRH) pulses from the hypothalamus. By contrast, the amplitude of spontaneous LH pulses may be controlled by several factors other than the amplitude of LHRH pulses. We tested two hypotheses: 1) that LH pulse amplitude is determined in part by the frequency of LHRH pulses of constant magnitude, and 2) that testosterone (T) exerts a direct feedback effect on the pituitary gland to regulate LH pulse amplitude. Gonadal feedback was eliminated by castrating adult male rats (n = 20). Endogenous LHRH secretion was eliminated by lesioning the medial basal hypothalamus. Serum LH levels (0.19 +/- 0.04 ng/ml RP-2, mean +/- SEM) and T levels (0.15 +/- 0.02 ng/ml), measured several weeks after hypothalamic lesioning, confirmed the hypogonadotropic hypogonadal state of the animals. During a 8-h period, unanesthetized, unrestrained animals were injected with 40-ng pulses of LHRH via catheters into the jugular vein, and blood samples for LH measurement were drawn at 10-min intervals. The LHRH pulse interval was 20 min during the first 4 h in all animals. The pulse interval was doubled to 40 min in half of the animals (n = 10) during the next 4 hours; in the other 10 animals, the pulse interval was maintained constant at 20 min throughout the study. Within both of these groups, one-half of the animals (n = 5) were infused with T to achieve a physiological level of T in serum (2.46 +/- 0.36 ng/ml at 4 h), while the other half received vehicle.(ABSTRACT TRUNCATED AT 250 WORDS)     

Velocity distributions of the streaming protoplasm in Nitella flexilis.

Laser light is Doppler-shifted in frequency by the streaming endoplasm of living cells of Nitella flexilis. The frequency spectrum of the scattered light can be interpreted as the histogram of velocities within the organism, with the exception of the intense low-frequency portion of the spectrum. We demonstrate that the lowest-frequency component is the result of amplitude modulation of the scattered light by the array of chloroplasts in the cell. Measurement of the streaming endoplasm in a photobleached "window" region allows correction of the frequency distribution for the modulation component. The complete velocity histogram for the streaming endoplasm is calculated directly from the corrected frequency distribution. Measurements of vacuolar and endoplasmic motions show that the tonoplast, the membrane separating the vacuole and the endoplasm, seems to be flowing along with the endoplasm and vacuolar sap. Placing the cell in medium containing ATP in concentrations greater than 10(-3) M greatly increases the contribution of low velocities to the velocity histogram. Cytochalasin B at high dosages (10-50 mug/ml) does not noticably change the shape of the velocity histogram, while at low dosages (1 mug/ml) there is an increase in the contribution of low velocities to the velocity histogram. Colchicine in high concentrations (1%) has no observable effect on the velocity histogram.