Transmission pathways in the rat superior cervical ganglion

On isolated preparations of the superior cervical ganglion (SCG, n = 8) taken from 21-day-old rats, we studied the intraganglion pathways and mechanisms underlying generation of synaptic responses of SCG neurons to antidromic stimulation. One of the three nerves connected with the SCG was stimulated, and compound action potentials were recorded simultaneously from the other two nerves; then, the order of stimulated and recorded nerves was changed. Orthodromic stimulation of the cervical sympathetic nerve (CSN) evoked responses in the internal carotid nerve (ICN), which could be completely blocked by hexamethonium, and responses in the external carotid nerve (ECN), which contained a component that was not blocked by this of the ECN caused responses in the CSN, which were not blocked by hexamethonium. Effects of superfusion of the SCG with a Ca²⁺-free solution allowed us to conclude that the hexamethonium-insensitive component of the responses in the CSN and ECN and ECN-CSN conduction can be explained by the presence of direct fibers going from the CSN to the ECN with no synaptic relay. Possible mechanisms underlying antidromic stimulation-induced synaptic responses in SCG neurons are discussed. Neirofiziologiya/Neurophysiology, Vol. 39, Nos. 4/5, pp. 396–399, July–October, 2007.     

家兔减压神经颈部变异的几种新类型

用解剖学方法结合电生理学方法鉴别减压神经形态上的变异。在35只纯种青紫蓝家兔中,减压神经颈部有形态变异者达23只(占65.71％)20种,观察到减压神经变异的三种新类型:减压神经三分支型、“无”减压神经型和减压迷走交感干型;至于减压神经的起点,以起于喉前神经者居多。     

Power-frequency electric fields averaged over the body surfaces of grounded humans and animals

Calculated electric-field strengths averaged over the body surfaces of grounded humans, swine, rats, horses, and cattle exposed to vertical, uniform, power-frequency electric fields are presented. To produce the same average fields over the body surfaces of grounded animals, as that experienced by a grounded man exposed to an unperturbed vertical field of 10 kV/m, the following unperturbed fields are required: swine, 19 kV/m; rat, 37 kV/m; horse, 18 kV/m; cow, 18 kV/m.     

Responses of Mature and Aged Sympathetic Neurons to Laminin and NGF: An in Vitro Study

Whilst the potent effects of NGF and laminin on developing neurons are well documented, relatively little is known about the effects of, or altered availability of or altered responsiveness to, these substances on the growth of adult neurons. We have therefore examined this question using explant cultures of sympathetic neurons from the superior cervical ganglion (SCG) of mature and aged rats. Explants were grown on substrata containing different doses of laminin, either with or without added NGF in culture medium containing FCS. Individually, laminin and NGF had relatively small effects on neurite outgrowth and length, which tended to be reduced in old neurons. In contrast, laminin in the presence of exogenous NGF exerted a powerful effect on nerve growth which was substantially greater than the sum of the effects of the individual factors. This synergy was evident in all experimental groups and was greatest in old explants at high doses of laminin, where growth was comparable to that of mature neurons. The dose-response curve of old neurons to laminin in the presence of added NGF indicated reduced responsiveness. These results suggest that variations in the availability of laminin and/or exogenous NGF, together with altered patterns of neuronal responsiveness, may contribute to impaired neuronal plasticity in old age.     

Biological effects of a 765-kV transmission line: Exposures and thresholds in honeybee colonies

Honeybee colonies exposed under a 765-kV, 60-Hz transmission line at 7 kV/m show the following sequence of effects: 1) increased motor activity with transient increase in hive temperature; 2) abnormal propolization; 3) impaired hive weight gain; 4) queen loss and abnormal production of queen cells; 5) decreased sealed brood; and 6) poor winter survival. When colonies were exposed at 5 different E fields (7, 5.5, 4.1, 1.8, and 0.65–0.85 kV/m) at incremental distances from the line, different thresholds for biologic effects were obtained. Hive net weights showed significant dose-related lags at the following exposures: 7 kV/m, one week; 5.5 kV/m, 2 weeks; and 4.1 kV/m, 11 weeks. The two lowest exposure groups had normal weight after 25 weeks. Abnormal propolization of hive entrances did not occur below 4.1 kV/m. Queen loss occurred in 6 of 7 colonies at 7 kV/m and 1 of 7 at 5.5 kV/m, but not below. Foraging rates were significantly lower only at 7 and 5.5 kV/m. Hive weight impairment and abnormal propolization occur at lower E-field intensity than other effects and limit the “biological effects corridor” of the transmission line to approximately 23 m beyond a ground line projection of each outer phase wire. Intrahive E fields of 15–100 kV/m were measured with a displacement current sensor. Step-potential-induced currents up to 0.5 μA were measured in an electrically equivalent bee model placed on the honeycomb in a hive exposed at 7 kV/m. At 1.8 kV/m body currents were a few nanoamperes, or two orders of magnitude lower, and these colonies showed no effects. E-field versus electric shock mechanisms are discussed.     

Characterization of cholecystokinin receptors in bullfrog (Rana catesbeiana) brain and pancreas

The binding of biologically active 125I-Bolton-Hunter-CCK-33 to bullfrog brain and pancreatic membrane particles was characterized. Both tissues exhibited time-dependent, saturable, reversible, and high affinity binding without evidence for cooperative interaction. Both bullfrog CCK receptors resembled their mammalian counterparts in having acidic pH optima for tracer binding and a Kd of about 0.5 nM. However, the receptors differed from their mammalian counterparts in that (1) the bullfrog brain membranes bound more tracer per mg protein than did the pancreatic membranes, (2) both bullfrog CCK receptors were relatively insensitive to dibutyryl cGMP, and (3) both bullfrog brain and pancreatic CCK receptors exhibited the same general specificity toward a variety of CCK and gastrin peptides. For both tissues, the relative order of receptor binding potency was CCK-8 greater than caerulein = CCK-33 greater than gastrin-17-II greater than CCK-8-ns = gastrin-17-I greater than caerulein-ns greater than gastrin-4 with the sulfated CCK peptides being 1000-fold more potent than their nonsulfated analogs. Sulfated gastrin was also relatively potent, being only 10-fold weaker than CCK-8. Gastrin-4 was 20 000-fold weaker than CCK-8 in interacting with the brain CCK receptor. The latter finding is in sharp contrast to the mammalian brain CCK receptor. We conclude that the bullfrog brain and pancreas contain similar CCK receptors of probable physiological significance and may represent an ancestral condition from which the two distinct CCK receptors present in mammalian brain and pancreas have evolved.     

Short-circuit currents,surface electric fields,and axial current densities for guinea pigs exposed to ELF electric fields.

Short-circuit currents, surface electric fields, and axial current densities were measured in electrically grounded guinea pigs exposed to a uniform, vertical, ELF electric field. These data are 70–110% of corresponding values obtained in grounded rats exposed to the same electric field.     

Variable spatial magnetic field influences peripheral nerves regeneration in rats

Generator of spatial magnetic field is one of most recent achievements among the magnetostimulators. This apparatus allows to obtain the rotating magnetic field. This new method may be more effective than other widely used techniques of magnetostimulation and magnetotherapy. We investigated the influence of alternating, spatial magnetic field on the regeneration of the crushed rat sciatic nerves. Functional and morphological evaluations were used. After crush injury of the right sciatic nerve, Wistar C rats (n?=?80) were randomly divided into four groups (control and three experimental). The experimental groups (A, B, C) were exposed (20?min/day, 5?d/week, 4 weeks) to alternating spatial magnetic field of three different intensities. Sciatic Functional Index (SFI) and tensometric assessments were performed every week after nerve crush. Forty-eight hours before the sacrificing of animals, DiI (1,1’-di-octadecyl-3,3,3’,3’-tetramethyloindocarbocyanine perchlorate) was applied 5?mm distally to the crush site. Collected nerves and dorsal root ganglia (DRG) were subjected to histological and immunohistochemical staining. The survival rate of DRG neurons was estimated. Regrowth and myelination of the nerves was examined. The results of SFI and tensometric assessment showed improvement in all experimental groups as compared to control, with best outcome observed in group C, exposed to the strongest magnetic field. In addition, DRG survival rate and nerve regeneration intensity were significantly higher in the C group. Above results indicate that strong spatial alternating magnetic field exerts positive effect on peripheral nerve regeneration and its application could be taken under consideration in the therapy of injured peripheral nerves.     

Perinatal exposure to 60-Hz electric fields: Effects on the development of the visual-evoked response in rats

Two independent series of experiments were performed on 114 male Sprague-Dawley derived, albino rat pups, which represented 61 litters in experimental series I and 53 litters in experimental series II. Animals were exposed for 20 h/day from conception to testing (postnatal days 11–20) to a vertical, 65-kV/m, 60-Hz electric field or sham-exposed. Recordings of the visual-evoked response (VER) were obtained using a small silver ball electrode placed epidurally over the visual cortex. Visual stimuli consisted of 10-μS light flashes delivered at 0.2 Hz. Computer-averaged VERs were obtained and power spectral analyses (fast Fourier transform) were performed on the tapered (split cosine-bell window), averaged VERs. The expected age-related changes were clearly evident; however, a detailed analysis of VER component latencies, peak-to-peak amplitude, and power spectra failed to reveal any consistent, statistically significant effect of exposure to 60-Hz electric fields.     

不同日龄大鼠颈上交感神经节神经元电转染方法

目的 建立一种高效电转染不同日龄大鼠颈上交感神经节(superior cervical sympathetic ganglion,SCG)神经元细胞的方法.提高转染后细胞的成活率、转染效率和干扰效率.方法 用传统的及经改良的神经元培养液分别培养电转染后的7日龄、14日龄和40日龄SD大鼠SCG细胞,24 h后用台盼蓝染色方法观察并计算细胞成活率;通过改变质粒DNA和siRNA与转染液比例,优化转染条件,于转染24h后在共聚焦显微镜下观察并计算转染效率或干扰效率.结果 改良培养液可使14日龄以上SD大鼠SCG细胞转染后成活率达到75％以上,明显高于传统培养液转染后的成活率(P＜0.01),且结果稳定,细胞状态良好,能够满足后续实验研究的要求;优化转染条件后,DNA 的转染率及siRNA的干扰率显著提高,当DNA与转染液比例为1∶100(μg∶μL)时,细胞转染率最高;当siRNA与转染液比例为1∶50(μg∶ μL)时干扰率最高.结论 通过改良神经元培养液及优化转染条件,成功提高了电转染后细胞的成活率、转染效率和干扰效率,利用电转染方法可成功转染不同日龄SD大鼠SCG神经元.     

Influence of 50 Hz electric and magnetic fields on the human heart

This investigation studied the effect of 50 Hz electric and magnetic fields on the human heart. The electrocardiograms of 27 transmission-line workers and 26 male volunteers were recorded with a Holter recorder both in and outside the fields. The measurements took from half an hour to a few hours. The electric field strength varied from 0.14 to 10.21 kV/m and the magnetic flux density from 1.02 to 15.43 μT. Analysis of the ECG recordings showed that extrasystoles or arrhythmias were as frequent outside the field as in the field. In some cases a small decrease in heart rate was observed after field exposure. © 1993 Wiley-Liss, Inc.