THE OXYGEN CONSUMPTION OF FROG NERVE DURING STIMULATION

1. The resting rate of oxygen consumption of the excised sciatic nerve of the frog is 1.23 c.mm. of oxygen per gm. of nerve per minute. 2. During stimulation with an induction coil with 100 make and 100 break shocks per second there is an excess oxygen consumption amounting on the average to 0.32 c.mm. of oxygen per gm. of nerve per minute of stimulation, or a 26 per cent increase over the resting rate. 3. The magnitude of the excess oxygen consumption in stimulation, in agreement with the all-or-none law, is not markedly influenced by considerable variations in the intensity of stimulation. 4. Increasing the frequency of stimulation from 100 to 200 shocks per second increases the extra oxygen used only 1.12–1.18 times. The same change in frequency of stimulation increases the negative variation 1.15 times and the heat production about 1.25 times (Hill). 5. This parallelism between the excess oxygen and the negative variation argues definitely for some causal connection between the excess oxygen and the nerve impulse itself. 6. Calculation shows that the oxygen tension inside these nerves was not zero.     

EFFECTS OF ELECTRICAL STIMULATION OF CHORDA TYMPANI ON GLOSSOPHARYNGEAL NERVE RESPONSE TO THE FOLIATE PAPILLAE STIMULATION

The foliate papillae of the rat are dually innervated by thechorda tympani and the glossopharyngeal nerves. The effectsof electrical stimulation of the distal end of the cut chordatympani on the spontaneous discharges and the gustatory responsesof the glossopharyngeal nerve fibers were examined in the ratwhile gustatory stimuli were applied to the foliate papillae.Activities of 5 out of 35 taste units in the glossopharyngealnerve were influenced by this procedure. Three units showedan inhibitory effect, 1 unit showed an excitatory effect and1 unit changed its firing pattern. These facts may be derivedfrom alterations of the blood circulation in the vicinity ofthe taste receptor cells innervated by the glossopharyngealnerve fibers.     

EFFECTS OF ELECTRICAL STIMULATION OF THE NIGROSTRIATAL PATHWAY OF THE RAT ON DOPAMINE METABOLISM

Abstract— Electrical stimulation of the nigrostriatal dopaminergic pathway in rat brain elicited a frequency and current intensity-dependent increased in the formation of homovanillic acid in the basal ganglia. The accumulation of the acid in probenecid-treated animals was constant over 1 h, when maximally stimulated at 25 Hz and 300 μA. Dopamine levels remained unchanged during stimulation. When prior to stimulation the inhibitor of catecholamine synthesis α-methyl- p -tyrosine methyl ester was administered, dopamine levels declined biphasically. Tyrosine and nomifensine, a dopamine uptake inhibitor, and apomorphine had no major effect on the formation of homovanillic acid, whilst α-methyl- p -tyrosine prevented its formation. Our data suggest that dopamine in the striatum is compartmentalized and that the newly-synthesized amine is released and converted to homovanillic acid. Apomorphine decreases dopamine flux only when dopaminergic neurons are at rest. When depolarized neither access of the precursor nor reuptake seem to influence the conversion of dopamine to homovanillic acid.     

垂体在刺激脑内渗透压感受器引起的肾脏反应中的作用

实验在α氯醛糖和氨基甲酸乙酯混合麻醉的大鼠中进行。脑室内注射高张盐水(icv.HS)后,肾血浆流量、肾小球滤过率、尿量、尿钠排出量、尿钾排出量和渗透物质清除率均增加,游离水清除率下降。去除垂体后,icv.HS不再能引起上述肾脏反应。另外给大鼠静脉注射血管升压素(VP)拮抗剂(V_1和V_2受体拮抗剂),并不能削弱上述icv.HS引起的肾脏反应。脑室内注射高张盐水后,尿中多巴胺(DA)排出量无显著增多;给予多巴脱羧酶抑制剂苄丝肼也不能削弱icv.HS引起的肾脏反应。上述实验结果表明,在本实验条件下刺激脑内渗透压感受器引起的肾脏反应依赖于垂体的完整性,但看来并不依赖于外周的VP和DA,故垂体通过何种机制介导icv.HS引起上述肾脏反应,有待于进一步的研究。     

亚铁离子对水稻萌发后幼苗生长的促进作用

本文最新报道亚铁离子在远高于营养浓度的情况下（０．４４－７．１６ｍｍｏｌ／Ｌ）能显著促进水稻萌发后的幼苗生长,其效果与已报道的促进因子Ｃ２Ｈ４相当．在试验的１９种不同化合物中,发现只有ＦｅＳＯ４对萌发后水稻幼苗生长有显著的促进作用,并证明其有效成分为Ｆｅ（２＋）．这种促进作用在淹水的厌氧条件下和通气条件均能发生,但通气条件下促进程度稍低．水稻不同基因型对Ｆｅ（２＋）的反应无明显差异,可能这种促进作用是水稻适应水田厌氧环境的方式之一．高浓度乙烯（５０—１００ｐｐｍ）的促进作用与亚铁离子的效果相近．这一发现有助于提高水稻在淹水厌氧直播时的出苗率．－－ｓｉｇｎｉｆｉｃａｎｔａｔｌ％ｌｅｖｅｌ;＊－－ｓｉｇｎｉｆｉｃａｎｔａｔ５％ｌｅｖｅｌ;ｕｓ－－ｎｏｔｓｉｇｎｉｆｉｃａｎｔ．２．３ＥｆｆｅｃｔｏｆｖａｒｉｏｕｓＦｅ＋＋ｃｏｎｃｅｎｔｒａｈｏｎｓｏｎｔｈｅｓｅｅｄｌｉｎｇｇｒｏｗｔｈｏｆｒｉｃｅＴｗｏｇｅｎｏｔｙｐｅｓ,ｍｏｄｅｒｎＩＲ５０ａｎｄｔｒａｄｉｔｉｏｎａｌＡＳＤＩ,ｗｅｒｅｕｓｅｄｆｏｒｆｕｒｔｈｅｒｓｔｕｄｙ．Ｆｅ＋＋ｗｉｔｈｃｏｎｃｅｎｔｒａｔｉｏｎｓｆｒｏｍ０．４４ｔｏ７．１６ｍｍｏｌ／Ｌｗ     

THE EFFECTS OF MECHANICAL STIMULATION AND ETIOLATION ON THE COLLENCHYMA OF DATURA STRAMONIUM

Walker , Waldo S. (Grinnell College, Grinnell, Iowa.) The effects of mechanical stimulation and etiolation on the collenchyma of Datura stramonium. Amer. Jour. Bot. 47(9) : 717–724. Illus. 1960.–In an effort to determine the effect of mechanical stimulation on collenchyma tissue, plants of Datura stramonium L. were placed on a mechanical agitator and subjected to intensive shaking for 9 hr. per day for 40 days. Measurements indicated that such stimulation greatly increased the amount of wall thickening per cell, as observed in transverse section. Measurements also indicated that such stimulation may inhibit collenchyma cell elongation. A second group of Datura stramonium plants was placed in total darkness to determine the effect of such treatment on the quantity of wall thickening in the collenchyma tissue. Measurements indicated that when plants were placed in the dark for extended periods a great reduction of wall thickening resulted. It is suggested that reduction of wall material was due to its utilization as substrate for respiratory processes which occur in the plant under such extreme conditions. The composition and structure of the collenchyma cell walls are discussed.     

THE ALLEGED EFFECT OF ELECTRICAL STIMULATION ON THE METABOLISM OF RED CELL SUSPENSIONS

The apparent increase in the rate of O₂ consumption described when an alternating current, or induction coil current, is passed through a red cell suspension (in a buffered NaCl solution) is not a metabolic effect in any sense of the word. The passage of the current results in a permanent volume decrease in the system, and it is this which has been erroneously interpreted as an "increase in the rate of O₂ consumption." Its magnitude is about 1 part in 1000. The utilization of O₂ is not involved at all, and the same effect is obtained, on a somewhat smaller scale, when the current is passed through a solution of NaCl or of the other halogen salts. The effects occur only with shiny platinum electrodes, and disappear entirely when the electrodes are platinized. Passage of the current through serum, on the other hand, results in a permanent increase in the volume of the system, this effect also disappearing on platinization of the electrodes. The effects are apparently related to obscure electrode phenomena.     

THE RESPIRATORY QUOTIENT OF FROG NERVE DURING STIMULATION

1. By means of a differential volumeter the increased oxygen consumption and the increased carbon dioxide output of frog nerve during and after stimulation have been observed. 2. Measurements of the R.Q. of nerve by this method are complicated by the retention of carbon dioxide. Attempts were made to avoid this (a) by studying the nerves at high CO₂ tensions to make the retention small and (b) by calculating the amount of CO₂ retained from the carbon dioxide dissociation curve of nerve and applying this value as a correction. 3. The results of both those methods when averaged together give an R.Q. of the excess metabolism of 1.19 and an R.Q. of the resting nerve of 0.97. 4. Observations on the time course of the gas exchange during stimulation indicate a delay in the appearance of the extra carbon dioxide output relative to the oxygen intake. 5. Very similar time curves can be calculated from the diffusion coefficients and the solubilities of the oxygen and the carbon dioxide.     

延髓中线区在躯体传入冲动抑制刺激兔下丘脑诱发室性期前收缩中的作用

于兔延髓中线区闩部头端处微量注射5-HT 受体阻断剂肉桂硫胺(4μg溶于2μl中)可减弱躯体传入冲动对刺激下丘脑诱发的室性期前收缩(HVE)的抑制效应;微量注入阿片受体阻断剂纳洛酮(4μg溶于2μl中)则可完全消除此抑制效应。损毁延髓中线区后,中脑中央灰质微量注入5-HT 或吗啡均不再能抑制 HVE。上述现象提示,躯体传人冲动抑制 HVE 的效应依赖于延髓中线区内啡肽和5-HT 的活动,中脑中央灰质内5-HT 和内啡肽对 HVE 的抑制作用也可能主要是通过延髓中线区的活动而实现。文中还就躯体传入冲动抑制 HVE 的中枢机制进行了讨论。     

CYTOLOGICAL ALTERATIONS RELATED TO STIMULATION OF THE ZONA GLOMERULOSA OF THE ADRENAL GLAND

The structure of the zona glomerulosa of the rat adrenal gland stimulated by sodium restriction has been studied by light and electron microscopy. The major changes observed during the course of the experiment in stimulated glands involve cytoplasmic droplets, mitochondria, and the endoplasmic reticulum. There is a progressive decrease in the number of cytoplasmic droplets of low electron opacity. Numerous, greatly elongated mitochondria containing parallel arrays of tubules are noted. These tubules extend from within the mitochondria through gaps in the mitochondrial-limiting membranes into the cytoplasm. In addition, amorphous intramitochondrial deposits, possibly aldosterone precursors, are seen. Increased amounts of smooth-surfaced endoplasmic reticulum, often showing complex arrangements, are another feature of the stimulated zona glomerulosa. Other alterations include the presence of large numbers of dense bodies as well as cytoplasmic droplets of high electron opacity. These observations are discussed in relation to the biosynthesis of aldosterone.     

刺激脑内渗透压感受器能降低大鼠管球反馈的敏感性

在麻醉大鼠肾脏近曲小管和远曲小管分别进行微穿刺,采集小管液。测定单个肾单位肾小球滤过率(SNGFR)。由于微穿刺部位对管球反馈造成的影响,在同一肾单位,采集近曲小管末段小管液测出的SNGFR值(SNGFR_p)比在远曲小管起始段测出的SNGFR值(SNG-FR_d)高,故可将在这两个部位测得的SNGFR值的差(SNGFR_(p-d))用作衡量管球反馈(TGF)敏感性的间接指标。脑室内注射高张盐水(icv.HS)后,SNGFR_(p-d)减小,表明脑内渗透压感受器受刺激可使TGF的敏感性降低。静脉注射速尿后,icv.HS不再引起肾血浆流量和肾小球滤过率的增加,但仍能引起尿钠排出增多。上述结果表明,刺激脑内渗透压感受器可通过减弱TGF导致肾脏血流动力学的改变,而其增加尿钠排出的效应则是通过抑制肾小管的重吸收实现的。     

刺激脑内渗透压感受器对大鼠浅表肾单位功能的影响

我们先前已在麻醉大鼠中用锂清除率方法从全肾水平证实,脑室内注射高张盐水(icv.HS)引起的利尿和利尿钠反应是由于肾小球滤过率增加和近球小管重吸收能力降低。本实验用肾小管微穿刺方法从肾单位水平进一步观察icv.HS对浅表肾单位的单个肾单位肾小球滤过率以及近曲小管和髓袢的重吸收的影响。实验在麻醉大鼠中进行。icv.HS后,单个肾单位肾小球滤过率从39.6±1.9nl/min增加至48.8±2.0nl/min(P<0.001);近曲小管末段小管液流量从20.5±1.4nl/min增加至28.4±2.0nl/min(P<0.001);小管液菊糖浓度与血浆菊糖浓度的比值从1.98±0.98降低至1.69±0.05(P<0.01)。根据上述数据计算得到的近曲小管重吸收分数从49.2±2.2％下降至41.7±1.8％(P<0.001),而近曲小管的绝对重吸收无明显改变。这些结果与用锂清除率方法获得的结果相符合。icv.HS后,髓袢的绝对重吸收升高,而重吸收分数下降。上述结果表明刺激脑内渗透压感受器可增加浅表肾单位的肾小球滤过率,并降低近曲小管的重吸收能力,从而增加髓袢的负荷,使髓袢的绝对重吸收增加。本实验结果不能排除icv.HS对髓袢的重吸收过程具有直接影响的可能性。     

ON THE QUANTITY OF ELECTRICITY AND THE ENERGY IN ELECTRICAL STIMULATION

Weiss''s and Hoorweg''s laws are discussed with respect to the dynamics of the excitatory process. The former is shown to have a simple basis which is inadequate, however, because it implies a constant rate of subsidence of the state of excitation. Hoorweg''s law does not follow logically from the same basis so the two laws do not represent the same excitatory mechanism. Experimental data do not give minimal energies at 2 rheobases as predicted by each law. The experimental minima with direct currents are at 1.5 or more rheobases, while with condenser stimuli they are from 2.5 to 3.0 rheobases. These minima conform to the predictions of the writer''s equations which give the direct current minima as variable with a lower limit at 1.5 rheobases and the condenser minima as constant at e = 2.718 rheobases. The reasons for these differences are discussed and it is concluded that considerations of the quantity of electricity and the energy, per se, do not lead to any simple concepts with regard to the excitatory mechanism. The existing quantity and energy relations are, however, easily correlated in terms of the dynamics of the excitatory mechanism.     

THE PERMEABILITY OF CELLS FOR OXYGEN AND ITS SIGNIFICANCE FOR THE THEORY OF STIMULATION

It can be demonstrated by an indicator method that living cells are as freely permeable to oxygen as dead cells, and that sudden admission of oxygen to the cell cannot account for increased oxidation as a result of stimulation. Oxygen penetrates as readily as carbon dioxide among the acids and ammonia among the alkalies. Exposure of living plant cells to high oxygen pressures does not initiate certain oxidations (except after some hours), which proceed readily in dead plant cells in the air. In the light of the preceding statement, about the permeability of cells for oxygen, this is interpreted to mean that more oxygen enters the cell at high pressure, but that the reacting substances (chromogen and oxidase) are kept apart by some phase boundary as long as the cell is alive. Increased oxygen concentration eventually produces injury to the cell.