摘要:

AbstractThe synaptic transmission through the cuneate nucleus was studied during local cooling of the dorsal column region. Field potentials, recorded from the surface as well as inside the nucleus, were greatly increased during moderate cooling (to 30–25oC) but diminished rapidly if the cuneate temperature fell below about 20oC. The increase was most evident for the afferent fibre volley potentials, but large changes of synaptic potentials (N‐wave) were regularly seen as well. The increase (up to several hundred per cent) was partly rate‐dependent since fast cooling gave larger increases than slower cooling did. In spite of the greatly increased N‐wave, the transmission through the nucleus was always reduced. This was tested in various ways: measurement of the latency and probability of firing of single units, “killed end”–recording from lemniscal fibres as a measure of number of discharging cuneate neurones, and measurement of the size of thalamic and cortical field potential produced by impulses relayed through the cuneate nucleus. The reduced transmission was most likely due to a greatly increased synaptic delay, with slowing of conduction along the terminal branches of the afferent fibres as a contributing factor. On severe cooling blocking of conduction in these branches occurred. During moderate cooling the probability of firing of most relay cells remained st

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1972.tb05194.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractInhibitory mechanisms in the dorsal column nuclei have been studied during local cooling. The inhibition of transmission of a cutaneous volley across the cuneate nucleus caused by a preceding volley to the same or a neighbouring cutaneous nerve was prolonged and slightly increased by a moderate (25–30oC) reduction of the cuneate temperature. The excitability of presynaptic fibres and of the postsynaptic cell membrane both decreased progressively with decreasing temperature. Presynaptic depolarization increased during moderate cooling (25–30oC) but disappeared when the temperature was reduced to about 20oC.One type of interneurone in the cuneate nucleus showed a progressive disruption of the normal pattern of firing with a gradual increase in the initial latency. An other type showed an increase of the rate and duration of the discharges to a single afferent volley on cooling. The latter type was susceptible to stimulation at 10 per s or higher. The behaviour of the latter interneurones matched the increased and prolonged presynaptic depolarization. These cells may be interneurones in a presynaptic inhibitory pathway. The prolonged and moderately increased inhibition caused by local cooling is probably due to activation of such cells causing increased presynaptic depolarizat

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1972.tb05195.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractRat brain cortex was homogenized in 0.25 M or 0.32 M sucrose and sedimented at 10,000Xgfor 20 min. The supernatant was further separated into two subtractions by density gradient centrifugation in Cs+‐containing sucrose. Electron microscopy, RNA/protein and phospholipid/ protein indices showed that one of the subfractions was similar to the rough‐surfaced (R) and the other to the smooth‐surfaced (S) microsomal fractions separated from liver tissue by Dallner (1963). Cholinesterase (ChE) activity was studied by titration. Only 8–13 % of the total ChE activity was recovered in the 10,000 × g supernatant and about 3–6 % in the subfractions. Both the R and S microsomal subfractions displayed ChE activity; however, the S sub‐fraction had about three times as much activity per mg protein as the R subfraction. Activity due to nonspecific cholinesterase was 13 % of the total ChE activity in the R fraction and 7 % in the S fraction when the homogenate was prepared by homogenization with a clearance of 250 urn at 840 rpm. More vigorous homogenization increased the activities. Histochemical staining for AChE and ns. ChE activities revealed reaction product adjacent to both R an

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1972.tb05196.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractThe effects of plasma hypertonicity on blood viscosity have been examinedin vitroas well as in avascular bed.NaCl was added to ox‐blood to produce plasma osmolalities up to about 1000 mosm/kg. The isolated rabbit ear was perfused at 70 and 30 mm Hg. Apparent viscosities of blood relative to plasma were calculated from the corresponding flow ratios (‘in vivo’viscosity). Relative viscositiesin vitroof the perfusates were determined by means of a cone‐plate viscometer. Blood viscosity measured‘in vivo’as well asin vitrowas significantly increased by increasing osmolality. Maximal increments (almost 100 per cent) were observed between 700 and 900 mosm/kg. Plasma viscosity and vascular resistance was not influenced by hypertonicity. Viscosities‘in vivo’were generally lower thanin vitro–the discrepancy was more pronounced at 70 than at 30 mm Hg and was greater in isotonic than in hypertonic blood. The effect of hypertonicity on blood viscosity is explained mainly by a reduced deformability of the hypertonically crenated red cells. It seems likely to explain the inverse relationship between renal medullary blood flow and medullary hypertonicity (Thurauet al.1960) as caused partly by passive mechanisms involving blood viscosity changes with v

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1972.tb05197.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractThe oxygen affinity of normal human blood was measured at two different pH values and three different pCO2values over the whole saturation range. From these data, and from data on the interaction of 2,3‐diphosphoglycerate with hemoglobin, values were calculated for the proton‐linked oxygen affinity at different pCO2values and for the carbamino‐linked oxygen affinity at different pH values. Both the proton‐linked and the carbamino‐linked oxygen affinity were found to be markedly dependent on the degree of oxygen saturation. The relative contribution of the three ligands,i.e.protons, carbon dioxide and 2,3‐diphosphoglycerate, to the classical Bohr effect was estimated and found to be dependant on the oxygen saturation level. The values for the proton‐linked oxygen affinity and the carbamino‐linked oxygen affinity were found, by applications of Wyman's reciprocal relations and 2,3‐diphosphoglycerate binding data, to give good estimates of the oxygen‐linked proton binding and the oxygen‐linked carbamino binding. The data show that the oxygen‐linked carbamino reaction takes place mainly during the binding of the first 2 oxygen molecules with a value of about 0.25 mol per mol of oxygen. The proton release accompanying this reaction was estimated to

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1972.tb05198.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractIt has earlier been established that in a number of motor nuclei la inhibition can be evoked from several muscles. It has now been investigated if this convergence takes place already at the interneuronal level or if the la inhibition from the different muscles is exerted through separate interneuronal pools which then converge at motoneuronal level. With intracellular recording from motoneurones and utilizing the technique of spatial facilitation it has been demonstrated that when activity in la afferents from several muscles can evoke inhibition in a given motoneurone a convergence of these la afferents does occur onto common interneurones.

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1972.tb05199.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractRats denervated by excision of the superior cervical sympathetic ganglion and given reserpine at the time of operation were used. The width of the palpebral aperture, which reflects the tone of the sympathetically innervated periorbital smooth muscle, was measured in the conscious rats after differenti.p.doses of 1‐noradrenaline. The sensitivity of the muscle to exogenous noradrenaline was thus tested during 3 periods of 3 h duration each between 13 and 30 h after denervation. Bretylium, which is known to delay the degeneration contraction of the muscle,i.e.the degeneration transmitter release, postponed the development of denervation supersensitivity. Hence, bretylium seems to preserve temporarily both the amine storage mechanisms and the axonal amine pump in the degenerating adrenergic nerve terminal

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1972.tb05200.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractThe contractile response of the guinea pig seminal vesicle to postganglionic nerve stimulation is inhibited by prostaglandin Ei and E2 in low doses and potentiated by high doses. Prostaglandin Ei and E2 consistently increase the contractile response to exogenous noradrenaline. The potentiation by high doses of prostaglandin Ei of the effector response to nerye stimulation is antagonized by SC 19220, inhibitor of prostaglandin action. The effect of prostaglandin Ei and E2 on the neuroeffector system of the seminal vesicle may be explained by a dual action, inhibition of noradrenaline release from the nerve terminals and potentiation of the effector response to the noradrenaline released. An endogenous prostaglandin‐mediated regulation of the smooth muscle response to nerve activity is suggeste

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1972.tb05201.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractNewborn litters of spontaneously hypertensive rats (SHR) and normotensive control rats (NCR) were identically treated with sympathetic nerve growth factor antiserum (Wellcome) which markedly interferes with adrenergic cardiovascular control (Zaimis 1967). Blood pressure, measured intermittently during 8 months, was in treated SHR (SHRis) about 25 % higher than in NCRis, their respective pressures being about 40 % and 25 % lower than those of sham‐treated SHR and NCR.–The hindquarters of one SHRis, or NCRis, were then perfused at constant flow in parallel with those of ordinary NCR. Starting from maximal vasodilatation, resistance increases were induced by graded noradrenaline (NA) infusions, from “threshold” to maximal pressor responses. Compared to NCRis, SHRisshowed an increased resistance at maximal dilatation, an increased slope of the NA dose‐response curve and an increased maximal pressor response, while their NA “thresholds” did not differ significantly. Thus, the structurally determined hemodynamic differences between ordinary SHR and NCR (Folkowet al.1970 b) characterize also SHRisand NCRis, though to a reduced extent. Even when comparing SHRiswith ordinary‐ NCR, which exhibited similar “resting” pressures, these differences partly remain, suggesting that the SHR resistance vessels might, for genetic reasons, be more prone to adapt structurally to pressure load

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1972.tb05202.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractHomogenates of the liver, the kidneys and the brain of the hedgehog,Erinaceus europaeus,.have been tested for monoamine oxidase activity. The enzyme was present in all 3 tissues, and the enzyme was found to act on all the substrates known to be oxidised by other mammalian sources of the enzyme. When the rates of oxidation of tyramine and /?‐phenylethylamine were compared, it was found that the relative rate of the latter amine in liver was about 3 times that found for kidneys. In the brain the position seems to be intermediat

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1972.tb05203.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY