摘要:

Summary.Action potentials were recorded inside and outside isolated frog muscle fibres in Ringer's solution and in moist air in order to correlate the different potentials and to study volume conductionTheextracellular action potentialrecorded from isolated frog muscle fibres in Ringer's solution was diphasic with a first positive and a second negative phase.The duration of the potential measured at a distance of 30 μ from the surface of the fibre was 2.67 ± 0.14 msec (21.2° C). It increased slightly with increasing fibre circumference from 2.5 msec in a fibre of 150 μ circumference to 3.2 msec in a fibre of 350 μ, circumference.The amplitude increased proportionally to the square of the fibre circumference. The peak to peak amplitude was 0.8 to 2.9 m V 30 μ from the surface of the fibre. Near the fibre the amplitude decreased linearly with the logarithm of the distance from the axis of the fibre. At distances (d) exceeding 0.15 mm from the axis of the fibre the amplitude decreased as d‐1,3.The peak of theintracellularlymeasured potential coincided with the negative peak of the extracellular potential with the fibre in Ringer's solution. This indicates that the extracellular action potential can be accounted for by means of the second derivative of the intracellular potential. A third positive phase of the volume conducted potential which is present in nerve disappears within the noise level for the muscle fibre in Ringer's solution because of the more protracted course of repolarization.The spread of the action potential along the fibre determined from the intracellularly recorded action potential was 8.8 ±0.9 mm (conduction velocity × duration of the potential from 50 per cent rise to 50 per cent fall).From the action potentials recorded at different distances from the fibre equipotential lines of the travelling potential field were constructed. By means of this field the charge passing the membrane during depolarization was determined to 1.4× 10‐6coulomb per cm2.The surface action potential from a fibre surrounded by a moist gas mixture had an amplitude of the same order of magnitude as the intracellularly measured action potential with the fibre surrounded by Ringer's solution. The time for rise from 20 to 100 per cent of crest was about half the rise time of the intracellularly recorded potential. The duration of the reconstructed monophasic potential from 50 per cent rise to 50 per cent full was slightly shorter than the intracellular action potential.The conduction velocity of the potential with the fibre in air was half that measured in Ringer's solution (2.41 ± 0.12 m per sec in Ringer's solution; 1.05 ± 0.05 m per sec in air at 21° C). From this difference in propagation velocity the impedance of the Ringer's film surrounding the fibre in air was estimated to 12 megohms per cm. The thickness of the Ringer's layer

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1957.tb01430.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

Summary.1  The effects of subcutaneous injections of histamine on the rectal temperature of guinea‐pigs were potentiated by amino‐guanidine and 2‐methyl‐4‐amino‐5‐methylaminopyrimidine, two histaminase inhibitors.2 The histaminase inhibitors did not increase the response of the rectal temperature to two “histamine analogues”, which have pharmacological effects resembling those of histamine. The “histamine analogues” used are resistant to histaminase in vitro.I am grateful to dr. H. O. Schildfor advice on the statistical treatment of the data. The technical assistance given by Miss M.‐B. Johanssonwas highly appreciated.This investigation was aided by a grant from the Medical

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1957.tb01431.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

Summary.1 The lymphopenic response to emotional stimulation and to injections of ACTH, histamine and adrenaline was investigated in unanaesthetized normal, hypophysectomized and demedullated rabbits.2 Intravenous injection of histamine, 50 μg per kilogram body weight, causes a significant lymphopenic response of the same type as the response following the injection of ACTH.3 After hypophysectomy histamine fails to give distinct lymphopenic responses.4 The histamine antagonist mepyramine did not abolish the lymphopenic response to histamine.5 Adrenaline, liberated from the adrenal medulla, is not essential in the lymphopenic response to histamine or to emotional stimulation.6 It is suggested that “physiological” quantities of histamine, when appearing in the general circulation, constitute an effective stimulus to increased secretion of ACTH from the

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1957.tb01432.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

Summary.The electrical potential gradients through the frog skin bathed in sulphate Ringer's were studied with microelectrodes inserted through the skin from its outer surface.The total skin potentials ranged between 73 and 145 mV, the inside positive with reference to ground. In most instances the total skin potential was reached in two, rarely three, distinct potential jumps. Comparison with measurements of the frog skin thickness indicated that the site of the first jump is in the epidermis while the second potential jump may correspond to the junction between epidermis and corium.

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1957.tb01433.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

Summary.1 The effect of increasingly large doses of adrenaline, nor‐adrenaline, and acetylcholine on the electrocardiogram of the isolated, perfused guinea‐pig heart was studied before and after administration of dibenamine and atropine, respectively.2 The threshold value for nor‐adrenaline to cause electrocardiographic changes was lower than that for adrenaline. The chronotropic effect seemed to be the same for the two substances at low doses, while at higher doses nor‐adrenaline seemed to be the more effective positive chronotropic agent. Cardiac arrhythmias were observed in about one‐third of the experiments and nor‐adrenaline appeared to be as potent as adrenaline in developing conduction disturbances and evoking ectopic discharges. Adrenaline increased the amplitude of the P wave, while nor‐adrenaline had no effect on the amplitude. There was no difference between the two substances as to the changes in the P—R interval, Q—T duration, S—T segment, or on the T waves. At lower doses the P—R interval was shortened; a prolongation was seen at high doses. The Q—T duration was first prolonged, but 30 to 60 secs later a shortening appeared. The T waves showed reduction in amplitude, so that a previously positive or negative T wave became less positive or less negative, respectively. In some hearts the opposite results were seen. At high doses a previously positive T wave could become negative and vice versa.3  After dibenaminization, slightly higher threshold values of adrenaline and nor‐adrenaline were necessary in order to produce electrocardiographic changes. At higher doses of the two substances, dibenamine could not abolish or decrease the chronotropic effect or electrocardiographic contour changes.4  At lower doses acetylcholine produced decreased auricular rate, with increasing doses heart block occurred, partial or complete. A propensity to evoke auricular fibrillation was evident. Ectopic auricular or ventricular discharges occurred. The P wave often became notched, its amplitude and duration decreased. In some experiments the Q—T duration was shortened and was followed by a lengthening. The T wave amplitude increased so that a previously positive or negative T wave became more positive or more negative, respectively.5 The inhibitory effect of acetylcholine was abolished by atropine. High doses of acetylcholine caused acceleration of

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1957.tb01434.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

Summary.1 The action of histaminase and amine oxidase preparations on seven histamine‐like substances was examined. The enzyme preparations were obtained from pig and cat kidney and from guinea‐pig and rabbit liver.2 Some of the substances studied were found to be oxidized by amine oxidase preparations but not by histaminase.3 1‐methyl‐4βaminoethyl imidazole was found to be a good substrate of histaminase. It was also oxidized by amine oxida

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1957.tb01435.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY