摘要:

AbstractIn the rat portal vein exogenous noradrenaline (NA) and the transmitter released during nerve activity seem to react with the same set of α‐receptors, located on muscle cells close to the nerve terminals. Very shortlasting, high transmitter concentration peaks have been calculated to occur at the receptors for each nerve impulse. In the present study an indirect approach was utilized to evaluate to what extent these peak concentrations, in view of their short duration, are effective in activating the smooth muscle. Electrical field stimulation of the adrenergic nerve supply of the rat portal vein was applied during fully developed responses to graded concentrations of exogenous NA. Transmural stimulation at 2–32 imp/s was found to increase the established responses to exogenous NA in concentrations up to 10‐5M. These effects were abolished by tetrodotoxin. The findings imply that the high, shortlasting NA concentrations, which occur at the α‐receptors for each nerve impulse, lead to high transient degrees of receptor occupancy during nerve activity. The effective transmitter concentrations, over a wide range of impulse frequencies, thus seem to approach the levels of NA which produce maximum responses when applied ex

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1972.tb05264.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractA mixture of14C‐4‐cholesterol and14C‐26‐cholesterol was injected into the invaginated yolks of newly hatched chicks which were then placed in metabolism chambers. By tracing the label in expired air, excreta (faeces+urine) and in their carcasses, the main pathways for the metabolism of the liver cholesterol could be estimated quantitatively. Over a period of 10 days about 26%of the administered chclesterol was catabolized to bile acids, about 19 % was eliminated from the body as neutral steroids in the excreta and at the end of the 10th day about 55%was retained in the carcasses. About 85 % of the bile acids synthesized was recovered in the excreta. As much as 45 % of the radioactivity derived from the14C‐4 cholesterol in the excreta was associated with the neutral steroids, while 55 % was found in the bile acid fraction. The rate of bile acid biosynthesis estimated from the14CO2‐production decreased from the fifth day after hatching. No estimation could be carried out during the days immediately following injection until isotopic equilibration had been reached. The faecal excretion of neutral steroids increased rapidly up to the fifth day, after which time it decreased. The body appears to treat part of the pre‐formed cholesterol from the yolk as a surplus which has to be eliminated. The specific activity of the cholesterol in the excreta collected on the 10th day was only about half of that of the intestinal content analyzed at the end of

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1972.tb05265.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractPrevious observations suggest that cholinergic secretory fibres reach the dog's parotid gland not only via the auriculo‐temporal nerve but also along the internal maxillary artery. 3–5 days after section of both these sets of nerves citric acid applied to the oral mucosa was found to evoke slow secretion only, or none at all. It has been reported, however, that the secretory response elicited reflexly after auriculo‐temporal nerve section gradually increases during the days following the operation. The auriculo‐temporal nerve was divided unilaterally in one group of dogs, and in another group this operation was combined with section of the nerves on the internal maxillary artery. During the following five weeks the dogs were examined repeatedly. Each time the secretory innervation was studied in two ways: by pouring citric acid into the mouth and by injecting esenne through the salivary duct into the gland. In addition the secretory responses to methacholine were estimated. The results indicate that postoperatively there was first a period in which there wag some increased release of acetylcholine in the gland (a “degeneration phenomenon”); supersensitivity then developed in the secretory cells. In spite of these complications both methods to study the secretory innervation could be used after the first week and onwards to demonstrate the difference in the effectiveness between the two denervation

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1972.tb05266.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractIn rabbit colon muscle there was a quantitative correlation and a co‐ordination in time between relaxation and an increase in cyclic AMP on stimulation of adrenergic β‐receptors. The cyclic AMP content had increased before the muscle had started to relax. There was an increase in the phosphorylaseaactivity and reduction of the ATP content. The adrenergic β‐receptor blocking agent sotalol inhibited the relaxation and the increase in cyclic AMP content. Reduction of the Ca++content of the muscle decreased the cyclic AMP content and the phosphorylaseaactivity. These effects were restored on addition of Ca++ions. In a Ca‐poor muscle adrenergic β‐receptor stimulation still produced an increase in cyclic AMP content and phosphorylaseaactivity but there was an increase in the ATP content instead. The reduction of cyclic AMP which followed an adrenergic a‐receptor stimulation was eliminated in the Ca‐poor muscle. The existence of a Ca++‐accumulating ATP‐utilizing mechanism, stimulated by cyclic AMP, might explain the relation between relaxation, cyclic AMP and Ca++and adrenergic β

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1972.tb05267.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractThe effect of sinus nerve stimulation on the blood pressure and heart rate was studied in dogs. Electrical stimulation of the sinus nerves of both sides was given both in the form of 2 types of intermittent impulse trains and as impulses of constant frequency. The intermittent impulse bursts, which were synchronized with the ECG, comprised 5–50 imp which coincided with systole (150 ms). Comparisons were made between stimulation with a constant frequency and the intermittent types, with the same number of impulses per cardiac cycle. It was found that the maximal blood pressure reduction was already reached at 5–10 imp per cardiac cycle. The difference between stimulation with a constant frequency and the intermittent types, with the same number of impulses per cardiac cycle, is negligible as regards blood pressure reduction but the intermittent type has a greater effect on the heart rate. Sinus nerve stimulation in massive haemorrhage and the influence of the amplitude of the stimulation signal were also stud

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1972.tb05268.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractA method has been developed which allows alterations in lung blood content and in extravascular lung water to be studied. The 2 upper lung lobes were removed separately from open‐chested cats. The first lobe was taken for control evaluations. The second one was removed when the circulatory situation had been changed. Labelled erythrocytes and plasma albumin had been injected beforehand. From the content of isotopes in the lung lobes, their blood volume could be calculated. Extravascular water was found by taking the difference between wet and dry weight of lung tissue, and correcting this difference for the blood content in that lobe. When total blood volume was reduced by a small bleeding, lung extravascular water content was reduced, and there was also a small reduction in lung blood volume. After a larger bleeding lung blood content was markedly reduced while the extravascular lung water content was then somewhat increased. Augmcntation of total blood volume by a blood transfusion led to an increase in lung blood volume, but to a decrease in extravascular lung water conten

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1972.tb05269.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractIn cats prolonged hemorrhagic hypotension had been shown to increase the pulmonary arterial pressure and vascular resistance. Pulmonary extravascular water volume and pulmonary blood volume have been evaluated early and late in such a period of post‐hemorrhagic hypotension.51Cr‐labelled erythrocytes and125I‐labelled albumin were injected intravascularly to animals with an opened chest and on positive pressure ventilation. One upper lung lobe was then suddenly clamped, removed and frozen. The lung lobe tissue and a simultaneously taken blood sample from a large vessel were measured for total w‐eight, dry weight and tracer content. The lobe's blood volume and extravascular water volume were then calculated per unit extravascular lung dry weight. A second lung lobe was removed and treated similarly at a later stage. 1 /2 h after the blood loss there was a marked reduction in lung blood volume and at the same time some increase in pulmonary extravascular water volume indicating constriction of postcapillary capacitance vessels. After 3 h of hypotension pulmonary extravascular water volume was found to be the same as before the hemorrhage although the pulmonary arterial pressure increased. This indicated that the increase in vascular resistance must predominantly be due to vasoconstriction at precapillary sites. The reduction in the lungs' blood volume remained at these late stages indicating that capacitance vessels were still constricted. When hyperinflations of the lungs were omitted in the experimental period, there was a tendency towards water accumulation in th

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1972.tb05270.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractOn instillation of 170 mM lactic acid (L or D) into unstimulated whole stomach pouches in cats the hydrogen ion concentration decreased more slowly than on instillation of 170 mM hydrochloric acid. When 700 mM lactic acid (L or D) was instilled the reverse was found. On instillation of 170 mM HCI subsequent to an instillation of 170 mM lactic acid (L or D) the changes in concentration of eleotrolytes as well as the net fluxes of electrolytes were of the same order of magnitude as during a preceding control instillation of HCI. On instillation of 170 mM HCI subsequent to an instillation of 700 mM lactic acid (L or D) the decrease in hydrogen ion concentration and the increase in sodium ion concentration were significantly larger than in the control instillation of HCI. The net influx of sodium ions was significantly increased but not the net efflux of hydrogen ions. After exposure of the gastric mucosa to 700 mM lactic acid (L or D) it produced a mucoid fluid that contained mainly sodium and chloride ions. This explained the results obtained when HCl was instilled subsequent to an instillation of 700 mM lactic acid. No morphological changes were found on examination in the scanning electron microscope of gastric mucosae exposed to 6 ml of 700 mM L lactic acid.

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1972.tb05271.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractMiddle ear muscle responses to tone bursts (0.5 to 12.0 kHz) were studied in nonanesthetized, unrestrained rabbits. The combined (total reflex) and the separate activity of the two muscles were recorded as changes of acoustic impedance in both ears simultaneously. The mean threshold of the ipsilateral total reflex, defined as the stimulus intensity eliciting 10 % of maximal response, was 98 dB SPL at 0.5 kHz and fell 12 dB/octave up to 2.0 kHz. Above 4.0 kHz it was about 70 dB SPL. The m. stapedius reflex was not found to differ from the total reflex, whereas the threshold of the m. tensor sympani reflex was about 10 dB higher at all frequencies. The crossed reflexes were significantly less sensitive than the ipsilateral reflexes. The stimulus‐response curves of the m. tensor tympani were less steep than those of the m. stapedius and reached their maxima at a higher sound level. The time course of the responses was interpreted to show nonlinear properties of the reflex system. The sensitivty to acoustic stimulation in the rabbit was found to be significantly higher than in man. The relationship between the activities of the two muscles as well as differences between species are discusse

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1972.tb05272.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractIn a previous investigation adrenergic nerve terminals were demonstrated in the hair follicles of cat vibrissae. The present study shows that electrical stimulation of the cervical sympathetic trunk produces small but repeatable changes in the dynamic responses of the slowly adapting mechanoreceptors of the vibrissae in that the number of impulses in each discharge is reduced and their latency increased. Changes in the static responses are very small. These effects were abolished by phentolamine. The receptor responses as well as effects of sympathetic stimulation remain unaffected by a brief carotid occlusion. It is concluded that the sympathetic modulation observed is a direct effect of locally released noradrenaline and is not attributable to circulatory changes or to pilomotor activity.

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1972.tb05273.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY