摘要:

Summary.The respiratory dead space (physiological dead space) calculated from the Bohrformula on the basis of arterial pCO2has been determined on 4 young healthy subjects at rest and during light to heavy muscular work.It was found that the physiological dead space during work increased with the tidal volume from an average value of about 170 cc at rest to about 350 cc during work at a tidal volume of about 3.3 liters. The values were nearly the same when breathing atmospheric air and when breathing air with a low oxygen content (about 12.5% O2in inspired air).In muscular work with tidal volumes higher thait about 1.5 liters the arterial pCO2was found to be 2 to 3 mm Hghigherthan the alveolar pCO2calculated from the Bohrformula using a constant dead space at modum Kroghand Lindhard. The arterial pCO2was on the other hand in heavy work found to be about 3 mm Hglowerthan the alveolar pCO2determined by direct sampling (end‐normal expiration method). The alveolar pCO2determined by direct sampling was in heavy work found to be ahout 6 mm Hg lower than the alveolar pCO2calculated from Bohr'sforniula using the physiological dead space for CO2. The possible reasons for the differences are discussed in the tex

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1957.tb00169.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

Summary.1) A complete section through the forebrain through and just anterior to the orbital sulcus and directed well anterior to the caput of the caudate nucleus was not seen to primarily reduce the water intake of dogs or to cause any reduction in the amount of water drunk by the animals subsequent to the intravenous injection of a certain amount of hypertonic saline. The latter was temporarily the case in one animal where the lesion was extended in ventro‐caudal direction to involve the preoptic area on both sides.2) Amphetamine (1 mg per kg of body weight) completely inhibited the drinking of water after an intravenous injection of 20 cc of a 20 % NaCl solution in 4 of 5 normal dogs tested. This was no longer the case in 3 of these animals after “prefrontal lobotomy”.3) An incomplete section through the forebrain in 5 out of 8 dogs made that the dose of amphetamine necessary to inhibit, the food intake of the animals completely had to be increased by

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1957.tb00170.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

Summary.Previously it was found that the chloride as well as the sodium ions could be absorbed against a concentration gradient in the colon and the distal part of the small intestine of rats when pure sodium chloride solutions were infused. In this paper it is demonstrated that the chloride ion is still absorbed against a concentration gradient in the colon when sodium is replaced by potassium, calcium, magnesium or ammonium, and that sodium, too, is absorbed against a concentration gradient in the colon as well as the distal part of the small intestine when the chloride ion is replaced by acetate, nitrate, bicarbonate or sulphate ions.

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1957.tb00171.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

Summary.Tlie distensibility of the systematic resistance blood vessels has been quantitatively measured at known levels of a steady vascular tone. Their distensibility is, from a liaemodynamc point of view. considerable except at more intense vasoconstriction where the lnmen‐to‐wall ratio is decreased enough to minimize the dietending effect of the intravascular pressure.Often, however, vascular distension is more or less balanced by adaptive changes of smooth muscle tone. Therefore. a standard pressure‐flow relationship cannot be given. as this relationship varies, not only with the region studied, but also with the level of vascular tone and reactivity.Generally, a ‘critical closing pressure’, correlated with the prevailing tone, can only be recorded if the normally occurring, adaptive changes of smooth muscle tone are eliminated. The basis for this closing is discussed at length. Reasons are presented that it might simply be an extension of the well‐known intermittent closings of the praecapillary sphincter regions to include all parallel channels at this level. It is suggested that the complete closing of this section of the vascular tree is a consequence of a pronounced distensibility of the thin intima and muscle layers of these small vessels, where an outer limit for distension is set by a surrounding network of colla

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1957.tb00172.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

Summary.Intra‐axonal recording in Flechsig's fascieulus was used to study neurons which could be activated by electrical stimulation of group I muscle afferents. There were recorded simultaneously the mass discharge in the dissected Flechsig's fasciculus and sensory volleys with triphasic recording from dorsal roots for control of input in terms of Ia and Ib volleys. In addition adequate stimulation of stretch receptors in muscles was used in some experiments.Ib fibres reach the region of Clarke's column via the dorsal column as do the Ia fibres.Most of the mass discharge in the dissected Flechsig's fasciculus appears with a primary Ia volley but some increase occurs with Ib. Most neurons examined discharge on stimulation of Ia but some only when stimulation was raised to include part of Ib. In many neurons excited by Ia, a second post‐synaptic spike appeared with a Ib volley generated in the refractory period of the preceding Ia volley. Ia as well as Ib volleys were found to contribute inhibitory action to neurons excited by group I afferents from antagonist muscles.The discharge in secondary neurons, responding to a stretch of a muscle. was examined during contraction of the muscle (soleus. gastrocnemius or quadriceps). An acceleration was found in 36 per cent, demonstrating excitatory action by Golgi tendon organ afferents, and the remainder paused during rontraction. Occasionally results were obtained indicating convergence of excitatory action from Golgi tendon organ and muscle spindle afferents.It is concluded that some DSCT neurons subserve transmission of information from Golgi tendon organs and others from muscle spindles. The occurrence of convergence of excitatory action from muscle spindles and Golgi tendon organs is discussed.Convergence of excitatory and inhibitory actions mediated by group I afferents from the same muscle has been encountered in some cases. It is suggested that convergence of this type is exceptional and not representative for the general pattern of synaptic organizat

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1957.tb00173.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

Summary.Intra‐axonal recording in Flechsig's fasciculus was used for a further investigation of the functional organization of the dorsal spino‐cerebellar tract.After ipsilateral section of lumbar and sacral dorsal roots, many neurons identified as belonging to the dorsal spino‐cerebellar tract (neurons activated by group I muscle afferents) were found to have a resting discharge. In silent neurons a discharge could be made to appear after repetitive stimulation of dorsal roots. It is concluded that these neurons receive excitatory action from interneurons.Convergence of excitation and inhibition onto DSCT neurons from various muscles was studied with the use of electrical stimulation of muscle nerves as well as with adequate activation of stretch receptors.As evidenced by monosynaptic excitation on single shock stimulation of muscle nerves, convergence of excitatory action mediated by group I afferents was found to be rather limited. A number of neurons can only be fired from one muscle nerve but some from as many as three out of seven nerves (including non‐synergists).Convergence of inhibitory action mediated by group I afferents is extensive also from other muscles than the antagonist of the nerve supplying the main excitatory

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1957.tb00174.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY