The Journal of physiology
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The Journal of physiology · Mar 1974
The effects of pentobarbitone anaesthesia on the volume and composition of the extracellular fluid of dogs.
1. The effects of pentobarbitone sodium (Nembutal) anaesthesia in dogs on extracellular fluid and plasma volumes, plasma protein concentration, haematocrit and extracellular fluid electrolyte composition were measured.2. ⋯ Extracellular fluid volume did not alter significantly during six hours of anaesthesia, but the haematocrit and extracellular fluid potassium concentration showed an increase towards control values.4. The relevance of these findings to the interpretation of experiments carried out under pentobarbitone anaesthesia is noted.
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The Journal of physiology · Feb 1974
The oxygen and carbon monoxide capacities of fetal and adult blood.
1. The oxygen capacities of foetal and adult blood have been compared by direct measurement of their oxygen and carbon monoxide combining power. Corrections have been applied to the capacities obtained from oxygen content determinations for the presence of carboxyhaemoglobin and methaemoglobin.2. ⋯ For neither carbon monoxide nor oxygen was there a significant difference (P > 0.05) of capacity between adult and foetal blood. There was, however, a significant difference (P < 0.05) on comparing the two methods of measurement on each form of blood and values from both methods were significantly different (P < 0.001) from the theoretical value of 1.39 ml. oxygen/g haemoglobin derived from the molecular weight of haemoglobin.4. These results suggest that the International Cyanmethaemoglobin Standard gives values of haemoglobin concentration which are approximately 6% higher than levels indicated by oxygen combining power.
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The Journal of physiology · Jan 1974
Mechanisms for differential block among single myelinated and non-myelinated axons by procaine.
1. The differential sensitivity of saphenous nerve fibres in the cat to block by procaine HCl was re-examined by recording identifiable unit action potentials from small nerve filaments.2. ⋯ Absolute differential block of non-myelinated and small myelinated axons was obtained by limiting the length of axons exposed to procaine to 2 mm.5. Differential rates of blocking among myelinated axons appear to depend on differences in the length of axons that must be exposed to blocking concentrations of procaine and to arise from the irregular distribution of such concentrations within an exposed nerve.
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The Journal of physiology · Aug 1973
Dorsal root potentials produced by afferent volleys in cutaneous group 3 fibers.
1. Dorsal root potentials (DRP) were recorded in the lumbosacral spinal cord of decerebrated unanaesthetized cats, following afferent volleys restricted to the thin myelinated (Group III) cutaneous afferents of the hind limb. The thick myelinated fibres (Group II) were blocked by a depolarizing current.2. ⋯ Both after transection of the spinal cord at various levels and after administration of pentobarbitone the III-DRP persisted at normal polarity. The duration of the DRPs was increased by these experimental procedures.5. The implications of these findings are discussed in relation to the prominent role postulated for the Group III fibres in the context of the gate control theory of pain.
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The Journal of physiology · Jun 1973
The effects of lung reflexes on laryngeal resistance and motoneurone discharge.
1. The reflex action of stimulation of alveolar J-receptors and of airway epithelial irritant receptors has been investigated on laryngeal resistance to airflow and on laryngeal motoneurone discharge in cats and rabbits.2. Resistance to airflow of the innervated larynx was measured (1) with the larynx isolated in situ with constant flow from the trachea to a pharyngeal opening; and (2) with the animal breathing through the larynx and the pharyngeal opening. ⋯ The laryngeal responses to histamine were more than halved by bilateral intrathoracic vagotomy.8. Phenyl diguanide and histamine increased the frequency of the discharge of inspiratory laryngeal motoneurones, but reduced the number of impulses per inspiratory phase. Laryngeal resistance in inspiration was usually increased.