大鼠听神经单纤维的活动

本文以声压级(SP)的dB值为单位,用不同频率(从音频到超声)的声刺激,对大鼠听觉一级神经元325根单一纤维的活动进行了观察。结果表明:每一纤维都有自己的最佳频率和相应的最低阈值。测得最佳频率的最低值为0.58kHz,最高值为62.6kHz; 最低阈值为6dBSPL,其相应频率为27.49kHz;最敏感的频率范围在20—50kHz。频率-阈值曲线在比最佳频率高的一侧斜度陡峭,低的一侧倾斜缓慢。频率-阈值曲线的锐度若以Q值表示,它对最佳频率分布的回归曲线由最佳频率的低频向高频方向逐渐升高,且Q10,Q20,Q30,Q40,Q50,dB的回归曲线具有相似的倾斜度。绝大多数纤维都有自发放电。给最佳频率持续音作用时,随刺激强度的增强,放电速率增加,但到阈上30dB左右皆达饱和。由各频率的最低阈值绘成的听反应阈曲线与行为测听所得的听力曲线颇为近似。     

ENZYMES OF ENERGY-CONVERTING SYSTEMS IN INDIVIDUAL MAMMALIAN NERVE CELL BODIES1

Abstract— The activities of 7 enzymes (hexokinase, phosphofructokinase, glucose-6-P dehydrogenase, 6-P-gluconic dehydrogenase, NADP linked isocitric dehydrogenase, malic dehydrogenase and lactic dehydrogenase) were measured in individual nerve cell bodies of 8 different neuronal types: pyramidal cells from cerebral cortex and Amnion's horn, Purkinje cells, giant cells in the reticular formation, Deiters’nucleus cells, facial nucleus cells, anterior horn cells and dorsal root ganglion cells. Samples of similar size were analysed from the molecular layer of cerebellum. The cell bodies were dissected from frozen-dried tissue sections and weighed on quartz fibre balances. The weights ranged from 0–2 ng for the smallest pyramidal cells to 9 ng for the largest giant cells. The specific enzymatic reactions were carried out in small volumes (0–01–5 μl) under mineral oil (‘oil-well technique’). The NADPH₂ or NAD formed was amplified by‘enzymatic cycling’and measured fluorometrically. A new cycling method was used for measuring the NAD formed in three of the enzymatic methods. Double cycling was used to measure glucose-6-P and 6-P-gluconate dehydrogenases in the smallest cell bodies. Each type of neuron exhibited a unique enzyme pattern, but four general patterns could be distinguished. The most variable of the enzymes was glucose-6-P dehydrogenase which was nearly 10-fold higher in anterior horn cells than in pyramidal cells from the cerebral cortex. Malic dehydrogenase was the most constant, with a 3-fold range from the highest (Purkinje cells) to the lowest (dorsal root ganglion cells).     

THE FINE STRUCTURE OF NERVE CELL BODIES AND THEIR MYELIN SHEATHS IN THE EIGHTH NERVE GANGLION OF THE GOLDFISH

The eighth cranial nerve ganglion consists of bipolar nerve cell bodies each occupying part of an internodal segment. The perikaryal sheaths range from a single layer of Schwann cell cytoplasm on the smallest cells to typical thick compact myelin on the largest. On most perikarya, the sheath displays an intermediate form, consisting of multiple layers of Schwann cell cytoplasm (loose myelin), or of loose and compact myelin continuous with each other. Internodes beyond the one containing the cell body bear only compact myelin. In loose myelin the thickness of each layer of Schwann cell cytoplasm is about 100 A. It may be much greater (~ 3000 A) particularly in the outermost layers of the sheath, or the cytoplasm may thin and even disappear with formation of a major dense line. The cytoplasmic layers are separated from each other by a light zone, 40 to 200 A wide, which in its broader portions may contain an intermediate line. Desmosomes sometimes occur between lamellae. In addition to the usual organelles, the perikaryal cytoplasm contains granular and membranous inclusions. Large cells covered by compact myelin have a consistently higher concentration of neurofilaments, and some of the largest cells, in addition, show a reduced concentration of ribosomes. The functional significance and possible origins of perikaryal myelin sheaths are discussed.     

CHOLINE ACETYLTRANSFERASE, ACETYLCHOLINESTERASE AND AROMATIC l-AMINO ACID DECARBOXYLASE IN SINGLE IDENTIFIED NERVE CELL BODIES FROM SNAIL HELIX ASPERSA

—The distribution of choline acetyltransferase, aromatic l -amino acid decarboxylase and acetylcholinesterase in the nervous system of Helix aspersa has been studied using homogenates of whole ganglia, microdissection from freeze-dried sections and dissection of single neurons from fresh tissue. Choline acetyltransferase was found in both the cell body and neuropil layers of all the Helix ganglia. The enzyme was not specifically localized to any ganglion or region of ganglion. Between 10 and 30 per cent of the isolated single cell bodies contained the enzyme. The enzymic activity corresponded to 50–200 mmol ACh/1 cell bodies/h. Choline acetyltransferase is probably a specific marker for cholinergic cells in this species. Aromatic l -amino acid decarboxylase was more selectivity localized and its distribution corresponded well with that of monoamine containing cells as visualized by the fluorescence histochemical technique. A large proportion of cell bodies were localized in the boundary between the visceral and right parietal ganglia and in the pedal ganglion. The other ganglia contained few such cells. The activity of aromatic l -amino acid decarboxylase corresponded 10–50 mmol dopamine/1 cell bodies/h. A method was developed to measure the enzyme activity towards 5-hydroxytryptophan and DOPA in single cells simultaneously. The ratio between the activity towards both substrates did not vary significantly for the different cells. The enzyme is probably a specific marker for monoamine cells, but cannot be used to differentiate between the different monoamine cells. Acetylcholinesterase was uniformly distributed in the ganglia and was probably present in all nerve cells.     

兔腹部迷走神经、内脏大神经活动在孤束核中的相互作用

本实验在67只家兔身上分别观察了电解损毁孤束核(NTS)前后刺激腹迷走神经和内脏大神经中枢端对血压的影响,以及刺激这两种神经中枢端对 NTS 神经元放电活动的影响。结果表明:来自腹迷走神经和内脏大神经的感觉冲动不仅都可以投射至 NTS,而且这两种传入冲动在 NTS 还存在着会聚现象。一种传入神经的阈下刺激(背景刺激)可以削弱另一传入神经的血压效应,一种传入神经的(背景刺激)可以抑制另一种神经元引起的 NTS 神经元电活动。本文对这两种传入冲动之间存在的相互作用关系的可能机制及意义进行了讨论。     

THE LOCALIZATION OF ENZYME ACTIVITIES IN THE RAT BRAIN

Studies with rat brain illustrate the usefulness of formol-calcium-fixed tissue for studying both enzymatic "chemoarchitectonics" and intracellular organelles. Unembedded frozen sections and polyvinyl alcohol-embedded sections may be used to demonstrate the activities of DPNH-tetrazolium reductase localized in mitochondria and ergastoplasm, TPNH-tetrazolium reductase localized in mitochondria, ATPase (and/or apyrase or ADPase) in cell membranes, and acid phosphatase in lysosomes.¹ Among the observations recorded are: (1) the presence of lysosomes in all cells of the brain; (2) the presence of numerous large lysosomes near the nuclei of capillary endothelial cells; (3) a polarized arrangement of large lysosomes in epithelial cells of the ependyma and choroid plexus; (4) the presence of ATPase activity in the cell membranes of some neurons; (5) the presence of either an apyrase or combination of ATPase and ADPase in the cell membranes of neuroglia and capillaries; (6) the presence of both DPNH- and TPNH-tetrazolium reductase activities in neuroglia; (7) the presence of DPNH- and TPNH-tetrazolium reductase activities in mitochondria and of DPNH-tetrazolium reductase activity in Nissl substance. The possible functional significance of these localizations is briefly discussed, as is their relation to "quantitative histochemistry" data available in the literature.     

HISTOCHEMICAL LOCALIZATION OF ENZYME ACTIVITIES IN ROOT MERISTEM CELLS

Avers , Charlotte J. (Douglass Coll., Rutgers—The State University, New Brunswick, N. J.) Histochemical localization of enzyme activities in root meristem cells. Amer. Jour. Bot. 48(2): 137–143. Illus. 1961,—Particle counts were made in epidermal cells of the root meristem of 2 grasses after exposure of living seedlings to various substrates involved in dehydrogenation reactions. Hydrolytic enzyme activities also were recorded for 1 of these species. The mean number of particles stained with Janus green B was about 90 for each species, but significantly lower counts were obtained in all the dehydrogenase tests. With lactate, pyruvate, glutamate, citrate, and isocitrate as substrates, Phleum cells showed about 25% of the Janus green count, while Panicum cells were about 33% active. These substrates are known to be oxidized by DPN-linked enzymes. The succinic dehydrogenase counts were about 50% of the Janus green total, and 60–70% particle activity was recorded with hexose-phosphate substrates which are probably oxidized in TPN-mediated reactions. In Phleum, particulate activity occurred in the adenosine triphosphatase and aryl sulfatase tests, but a non-particulate distribution characterized 5-nucleotidase activity. The particle counts in the ATPase tests were not significantly different from the Janus green counts, but the 85% particle activity in the aryl sulfatase tests was significantly lower than the Janus green results. These intracellular distributions were compared with those obtained by various authors using biochemical and histochemical techniques and were found to be in close agreement. It was suggested that the evidence indicated intracellular differentiation of at least one kind of cellular organelle, which in all probability was mitochondria.     

RABBIT SCIATIC NERVE FASCICLE AND''ENDONEURIAL''PREPARATIONS FOR IN VITRO STUDIES OF PERIPHERAL NERVE GLUCOSE METABOLISM

Abstract— Suitable preparations for in vitro studies of the composite glucose and energy metabolism of peripheral nerve axons and Schwann cells have not been available. Methods are described for the preparation and incubation of a defined segment of a rabbit sciatic nerve fascicle, free of epineurial contamination, but with an intact perineurial membrane; removing the perineurium provides in addition an‘endoneurial’preparation. Conditions were selected for incubating each preparation with glucose that maintained stable P-creatine and ATP concentrations and a stable rate of O₂ uptake; under these conditions the preparations retained an unaltered EM appearance during a 2-h incubation. Glucose diffusion into the endoneurial compartment of the fascicle is restricted, possibly by the perineurial membrane, and a higher medium glucose concentration (20 mM) was required to maintain a steady state of energy metabolism in this preparation than in the‘endoneurial’preparation, which was incubated with 5 mwglucose. The‘endoneurial’preparation required 0.50 mm -myoinositol in the medium to prevent a decrease in tissue free myoinositol and a slow decrease in O₂ uptake, which occurred when it was omitted. Under the incubation conditions selected the glucose concentrations in the‘endoneurial’preparation and in the endoneurial compartment of the fascicle were reasonably similar, and the preparations had similar rates of respiration, similar estimated rates of glucose utilization, and similar relative rates of respiration and lactate production. The preparations derive the major fraction of their energy requirements from respiration. Their rates of O₂ uptake are 60% higher than the previous indirect estimate of O₂ uptake in whole rabbit tibial nerve in situ. Constant rates of incorporation of ¹⁴C from [U-¹⁴C]glucose into CO₂ and total lipid were observed in the‘endoneurial’preparation after a 15-min equilibration period. The preparations reported provide suitable tools for in vitro studies of peripheral nerve metabolism not previously available.     

A COMPARATIVE STUDY OF PINEAL ACETYL-CoA HYDROLASE AND N-ACETYLTRANSFERASE ACTIVITIES

pineal acetyl-CoA hydrolase is measurable at 4 days before birth. It increases rapidly to a maximum of 0.37 nmol/min/0.1 mg protein during the first week after birth, thereafter gradually decreasing and stabilizing at adult levels (0.27 nmol/min/0.1 mg protein) 3-4 weeks after birth. Unlike A/-acetyltransferase, the activity of acetyl-CoA hydrolase does not increase following treatment with isoproterenol, does not exhibit a circadian rhythm and is not inactivated on exposure of the animals to light at night. In addition, denervation of the pineal gland does not alter acetyl-CoA hydrolase activity.     

柱状田头菇生长发育中9种胞外酶活性的测定

柱状田头菇Agrocybe aegerita作为一种新开发的食用菌,越来越受到消费者的喜爱和研究者的关注,但在其栽培生产中遇到的产量相对较低的问题,一直未能得到很好的解决,致使柱状田头菇的栽培难以得到大规模的推广。本研究对不同来源的柱状田头菇在其6个不同生长发育阶段中,9种与培养料中主要组分分解相关的胞外酶活性的变化进行了测定,结果表明：柱状田头菇属褐腐菌,对非木质纤维素的利用能力最强,对纤维素的利用能力较强,对木质素的利用能力较差,但柱状田头菇具有漆酶活性。     

TYROSINE HYDROXYLASE ACTIVITY IN NORADRENERGIC NEURONS OF THE LOCUS COERULEUS AFTER RESERPINE ADMINISTRATION: SEQUENTIAL INCREASE IN CELL BODIES AND NERVE TERMINALS

The effect of a single systemic injection of reserpine on tyrosine hydroxylase activity in the locus coeruleus, cerebellum, hypothalamus, and hippocampus was examined. Increases in enzyme activity were seen in all four brain areas; the time-course of the changes, however, was different in each case. In the locus coeruleus the maximum change in enzyme activity was seen 3 days after drug administration; in the cerebellum, 7-11 days; in the hypothalamus, 8-11 days; and in the hippocampus, 21 days. Since tyrosine hydroxylase in the cerebellum and hippocampus is present in terminals of neurons whose cell bodies are located in the locus coeruleus, the delayed increase in enzyme activity in cerebellum and hippocampus probably depends upon the slow rate of transport of TH molecules in these neurons.     

AXONAL TRANSPORT OF LABELLED PROTEINS IN SENSORY FIBRES OF RABBIT VAGUS NERVE IN VITRO

—Rabbit vagus nerves and nodose ganglia were incubated in vitro for up to 24 h in two-compartment chambers. After the introduction of [³H]leucine or [³H]fucose to the ganglion compartments a rapid anterograde axonal transport of labelled proteins or glycoproteins occurred at rates of 330 ± 44 mm/day and 336 ± 30 mm/day respectively. Accumulation of [³H]leucine-labelled proteins proximal to a ligature on the nerve was unaffected by a delay of up to 6 h between removal of the nerve and labelling in vitro. Accumulation was prevented by inhibition of protein synthesis in the ganglion but not in the axon and was inhibited in a graded manner by colchicine.     

兔心迷走神经传出放电的活动特征

兔心迷走神经传出放电有三种类型:1.与后膈神经传出发放同步的节律性放电。这种节律性发放包含两个时相,第一时相大致与膈神经传出放电同时起止,第二时相在膈神经传出发放后期或发放终止时出现。2.持续性放电,出现在上述节律性放电的间歇期。3.偶然出现的高幅高频暴发放电。这种放电出现时,膈神经传出放电即受到明显的压抑。开放预先夹闭的颈总动脉使心迷走神经传出放电增强。窒息、静脉注射肾上腺素使心迷走神经传出放电增强,心率减慢;扩张肺、过度通气、吸入亚硝酸异戊酯使心迷走神经传出放电减少,心率增快。     

AXOPLASMIC TRANSPORT IN THE OPTIC NERVE AND TRACT OF THE RABBIT

The axonal transport of labelled proteins was studied in the optic system of adult rabbits after an intraocular injection of [³H]Ieucine. It was demonstrated that the precursor was incorporated into protein, which was transported along the axons of the retinal ganglion cells. Intraocularly injected puromycin inhibited protein synthesis in the retina and markedly inhibited the appearance of labelled protein in the optic nerve and tract. It was further demonstrated by intracisternal injection of [³H]leucine that an intraocular injection of puromycin did not affect the local protein synthesis in the optic nerve and tract. Cell fractionation studies of the optic nerve and tract showed that the rapidly migrating component, previously described as moving at an average rate of 110-150 mm/day, was largely associated with the microsomal fraction. About 40 per cent of the total protein-bound radioactivity in this component was found in the microsomal fraction and about 15 per cent was recovered in the soluble protein fraction. Most of the labelled material moving at a rate of 1-5-2 mm/day was soluble protein. The specific radioactivity of this component was about ten times greater than that of the fast one. In the slow component about 50 per cent of the radioactivity was found in the soluble protein fraction and about 10 per cent of the radioactivity was recovered in the microsomal fraction. Radioautography demonstrated incorporated label in the neuropil structures in the lateral geniculate body as early as 4-8 hr after intraocular injection. The labelling of the neuropil increased markedly during the first week, and could be observed after 3 weeks.     

THE CHARACTERIZATION OF HISTIDINE DECARBOXYLASE AND ITS DISTRIBUTION IN NERVES, GANGLIA AND IN SINGLE NEURONAL CELL BODIES FROM THE CNS OF APLYSIA CALIFORNICA

Histamine (HA) is present in substantial quantities in all ganglia of Aplysia californica. Within the cerebral ganglia this amine is known to be concentrated in at least two identified neurons designated C-2 neurons. In this study a combination of chemical and enzymatic analyses was employed to provide evidence for the existence of a biochemical pathway for HA synthesis in ganglia and individual neurons of this marine mollusk. Examination of extracts of individual neurons dissected from ganglia organ-cultured in the presence of [³H]histidine showed that every neuron accumulated labelled histidine, but only the HA-containing C-2 neurons synthesized and stored labelled HA suggesting that the formation of HA in Aplysia could be catalyzed by the enzyme histidine decarboxylase (HDC). HDC activity was studied with a new microradiometric assay. Many of the properties of the molluscan HDC studied were found to correspond to the vertebrate enzyme. Enzyme activity was inhibited by α-hydrazino-histidine but unaffected by concentrations of α-methyldopa or by 5-(3,4-dihydroxycinnamoyl) salicylic acid which produced nearly complete inhibition of aromatic amino acid decarboxylase activity. HDC was measurable in nervous but not other Aplysia tissues assayed. All 5 major ganglia contained HDC activity which spanned a 15-fold range between the least and most active ganglia. Only 4 of the 13 nerve trunks assayed yielded measurable enzymic activity; these active nerves were associated with the cerebral ganglia which has the highest HDC activity of all measured ganglia. Of the numerous individual neurons assayed for HDC, only the C-2 cells showed measurable enzyme activity, about 25 pmol/cell/h or 70 μmol/g protein/h. Since the activity of HDC in the HA-containing neurons was at least three orders of magnitude larger than all other neurons assayed in the cerebral and other ganglia, these data appear to provide a direct metabolic basis for the selective presence of HA in these cells, and they indicate that the cellular presence of HDC provides a useful biochemical marker for the location of HA-rich neurons in Aplysia.     

CHROMOSOME NUMBERS IN SINGLE CELL CLONES OF TOBACCO TISSUE

Two clones of tissue of single-cell origin isolated from crown gall callus of Nicotiana tabacum were examined cytologically. Both clones had been grown on the same medium under the same conditions for 8 years. Chromosome counts of 110 polar views of metaphase plates revealed chromosome numbers of 48, 96, and 192 in both clones, the majority having 48. The nucleus of the original cell from which each clone was grown must have possessed 48 chromosomes. The polyploidy which developed may be ascribed to wounding, to the constituents of the culture medium, and/or to abnormal mitoses.     

刺激家兔肾内感受器和肾传入神经的血流动力学效应

在39只麻醉家兔观察刺激肾脏机械和化学感受器以及电刺激肾传入神经的血流动力学效应。增加输尿管压8—22mmHg 及经输尿管向肾盂内逆向灌注 NaCl(1.0 mol/L)及 KCl(0.15mol/L)溶液时,引起平均动脉压(MAP)和心率(HR)下降;切断双侧缓冲神经后,MAP 降低更为显著。电刺激肾传入神经时,HR 减慢,MAP、肠系膜动脉和后肢动脉灌流压降低,左心室收缩压及其微分值下降,心输出量(CO)和总外周阻力(TPR)减小;切断双侧窦神经和减压神经后,除 HK、CO 和 TPR 外,其余各血流动力学指标的减弱更为显著。由此提示,动脉压力感受器反射对肾传入神经激活的心血管效应有缓冲作用。     

SLOW AXONAL TRANSPORT OF LABELLED PROTEINS IN SENSORY FIBRES OF RABBIT VAGUS NERVE

Both rapid (415 mm/day) and slow (24 mm/day) rates of axonal transport of proteins were found in sensory fibres of rabbit vagus nerve after injection of [³H]leucine into the nodose ganglion in vivo. The slow phase of transport was dependent on contact between the cell bodies and the nerve trunk, and did not continue under in vivro conditions. The results suggest some difference between the mechanisms of fast and slow transport.     

正常猫膈神经单纤维电活动特征

在麻醉猫和麻痹的切断迷走神经的清醒猫,观察了膈神经单纤维电活动特征。1.电活动类型:按膈神经单纤维放电与其总干放电的相位关系分为三种类型。(1)完全同步型,即单纤维放电与总干放电同时开始并同时停止,占76.9％。(2)部分同步型占15.4％,其中早期同步,即单纤维放电与总干放电同时开始,但提前终止,占1.9％,中期同步,即单纤维放电较总干放电开始晚,又提前终止,占5.8％,晚期同步,即单纤维放电较总干放电开始晚,但两者同时终止,占7.7％。(8)非同步型,即吸气相和呼气相都有放电,但呼气相时冲动频率较低,占7.7％。前两型为单纯的吸气性放电,共占92.3％。2.单纤维放电平均参数值:麻醉猫每次吸气发放11个冲动,其频率为21次/秒,清醒猫每次吸气发放18个冲动,其频率为34次/秒。结果表明:猫膈神经单纤维放电类型和文献上报导的直接记录膈神经运动神经元放电一致,即以单纯的吸气性放电为最多。