ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1973.tb05427.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

AbstractThe time course of polysynaptic reflex responses is known to exhibit two prominent non‐linearities, one dependent on the amplitude of the stimulus and the other dependent on the direction of change of the stimulus. Both nonlinearities were demonstrated in the open‐loop responses of the acoustic middle ear reflex and simulated in a piecewise linear model. Their significance for stability of the closed‐loop feed‐back system was investigated. In this model the source of nonlinearity was a pool of “reflex units” with various thresholds and time constants. The mode! responses were studied in the time domain and the frequency domain. The amplitude dependent nonlinearity could be simulated when low threshold reflex units were made slow and tonic and high threshold units fast and tonic or when some of the high threshold units were phasic. A decrease in transport delay at increased input step amplitude was seen under these conditions but also when all units mere made equal. Both types of nonlinearities were found to improve the stability of the model system without decreasing its bandwidth (a measure of the speed of action). The nonlinearities were suggested to be important in systems with high values of tran

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1973.tb05362.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

AbstractNine healthy boys, mean age 11.7 years (11.0–13.0), height 150.4 cm and weight 45.1 kg, were examined with determinations of maximal oxygen uptake (1.85 1×min‐1), heart volume (499 ml) and total hemoglobin (391 g). Cardiac output was determined at rest and during exercise, including maximal exercise, using the dye‐dilution technique and i.a. pressures were recorded. Cardiac output was approximately 2 1×min‐1lower and the systemic a‐v oxygen difference (AVD) was correspondingly higher than for young adult men at the same sub‐maximal oxygen uptake. At maximal exercise cardiac output was 12.5 1×min‐1, stroke volume 67 ml, AVD 14.2 ml × 100 ml‐1, systolic, diastolic and mean blood pressure 160, 71 and 105 mm Hg respectively and total peripheral resistance 8.6 mm Hg×1–1×min. After a training period of 4 months a normal increase in height was found in all boys, but body weight was unchanged. Maximal oxygen uptake increased to 2.21 1×min‐1(p<0.01), almost entirely due to increased stroke volume (80 ml), resulting in a maximal cardiac output of 14.6 1×min‐1. No significant increase in AVD was found. Mean blood pressure at maximal exercise increased significantly, total peripheral resistance was unchanged. Both heart volume and total hemoglobin showed minor increases, but the changes found were not significantly larger than expected from body growth. The hemoglobin concentration was normal (13 g%) for the a

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1973.tb05363.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

AbstractRepetitive impulse firing was elicited in neurone models by steady stimulating currents of abrupt onset. The neurone models were based on the Frankenhaeuser—Huxley equations (1964) for voltage clamp data from the amphibian peripheral nerve. A frequency‐current curve (‘f‐I curve’), initial adaptation, and minimum firing rate similar to those of cat spinal motoneurones were obtained in the Frankenhaeuser—Huxley model if it were provided with (i) a long‐lasting after‐hyperpolarization due to potassium permeability changes, and (ii) a decreased subthreshold sodium inactivation. For detailed comparisons to the repetitive impulse firing of spinal motoneurones, model versions were used in which the subthreshold sodium inactivation was very slight, and the passive membrane properties as well as the afterpotentials resembled those of spinal motoneurones. In their repetitive behaviour, these models were quantitatively similar to spinal motoneurones. In the motoneurone‐like model versions, initial adaptation was due to a kind of ‘summation’ of the potassium permeability changes underlying the after‐hyperpolarizations of consecutive spikes. The slope of the f‐I curve was markedly affected by modifications of the size or time course of the potassium permeability changes responsible for th

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1973.tb05364.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

AbstractA new methodological approach to the fluorescence microscopical visualization of biogenic monoamines, based on condensation with gaseous glyoxylic acid, is presented. Glyoxylic acid treatment seems both to be more sensitive for the well‐known biogenic catecholamines and indolamines, and to allow the detection of other biogenic amines—such as melatonin—which are not demonstrable with available techn

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1973.tb05365.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

AbstractThe spectral sensitivity of the compound eye in a moth (Manduca sexta) was tested electrophysiologically by extracellular recordings in the wavelength region 310 to 650 nm, a) during dark‐adaptation, and b) during exposure to violet (408 nm) and red (680 nm) light. Sensitivity maxima were found at 370 to 390 nm, 450 to 470 nm, and 530 to 550 nm. During exposure to violet light a larger decrease in sensitivity was found for the maxima at 370 to 390 nm and 450 to 470 nm compared to that at 530 to 550 nm. During exposure to red light a larger decrease in sensitivity was found for the latter maximum. The results are interpreted as evidence for at least two photoreceptor types with different spectral sensitivity maxima. Intracellular recordings from single photoreceptors showed maxima in the same wavelength regions as those found extracellularly. The spectral sensitivities obtained were approximately similar. The homogeneity of the intracellular recordings is suggested to be due to interreceptor couplin

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1973.tb05366.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

AbstractIn order to study if bilateral ligation of the carotid arteries, either alone or combined with moderate arterial hypotension is accompanied by a macroscopically uneven brain perfusion, the regional cerebral blood flow (rCBF) was measured using the antipyrine‐14C method with direct counting of the radioactivity in the tissue. Ligation of the carotid arteries at normal blood pressure decreased blood flow in the frontal‐parietal regions by about 50 % in both hemispheres. At a mean blood pressure of 100 mm Hg, the ligation caused a further reduction in flow but the results were variable and gross differences often occurred between the hemispheres. At 70 mm Hg in blood pressure carotid occlusion drastically reduced the frontal‐parietal rCBF but flow in the occipital and basal temporal regions was usually better upheld. It is concluded that in the rat, combined carotid artery ligation and moderate hypotension gives rise to a macroscopically inhomogenous reduction in rCBF, and that regions of nonperfusion may coexist with adequately perfused

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1973.tb05367.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

AbstractCholine aecetyltransferase has been demonstrated in the duct and parenchyma of the pancreatic: gland of the cat. Potentiation of the effect of acetylcholine on the contractility of ductal segments has been observed after eserinization, indicating the presence of cholinesterase in the duct. These findings are considered to indicate that the pancreatic duct of the cat is cholinergically innervated.

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1973.tb05368.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

AbstractIn bovine mesenteric artery catecholamines stimulated simultaneously adrenergic α‐and β‐receptors. The relaxation induced by a specific adrenergic β‐receptor stimulation was associated with an increased content of cyclic AMP, a phosphorylaseaactivation and a decrease of the content of ATP and creatinephosphate (CrP). No effect on the high energy phosphate compounds was present in the Ca++‐poor artery, but the effect on cyclic AMP and phosphorylase was still evident. Sotalol blocked all the actions induced by adrenergic β‐receptor stimulation. The contracting action induced by selective adrenergic α‐receptor stimulation was initially associated with a decrease of the cyclic AMP content, but when the tension was maximally developed, after 120 s, the cyclic AMP content was increased and the phosphodiesterase activity reduced. In Ca++‐poor artery a cyclic AMP decreasing effect was still present after 120 s and there was no reduction of the phosphodiesterase activity. The mechanical and metabolic effects induced by α‐receptor stimulation were blocked by dibenamine. Histamine, which increased the artery tension, significantly reduced the cyclic AMP content after 15 s, but after 5 min the level of cyclic AMP had increased and phosphorylaseawas activated. The mechanical and metabolic effects of histamine were blocked by promethazine, an antihistaminic drug. The role of cyclic AMP in relaxation and contraction of vascular smoot

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1973.tb05369.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

AbstractElectrocortial synchronization, associated behaviourally with light sleep, was induced by low‐frequency stimulation of the subcallosal region and the orbital gyrus of the frontal lobe in unanesthetized cats. The effect was weaker than that obtained with basal forebrain stimulation. The above cortical areas have previously been shown to exert strong inhibitory influences on a variety of somatomotor and autonomic activities. High‐frequency stimulation of the same areas produces electrocortical desynchronization and behavioural arousal. It is suggested that the subcallosal and orbital portions of the frontal cortex give origin to.a descending system capable of modulating the excitatory state of sleep‐producing mechanisms in the brain stem or diencep

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1973.tb05370.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY