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Biomedical subjects

E Bystrzycka

Publications and source records attributed to E Bystrzycka.

At least 19 recordsLinked to original sources
PubMed1977

Inhibition of cuneate neurones: its afferent source and influence on dynamically sensitive "tactile" neurones.

1. Responses were recorded in decereberate, unanaesthetized cats from individual cuneate neurones in order to determine firstly, the afferent sources of inhibition on cuneate neurones and secondly, the influence of afferent-induced inhibition on those response features of dynamically sensitive tactile neurones which determine their capacity to code information about parameters of tactile stimuli.2. For all cuneate neurones which displayed afferent-induced inhibition from areas surrounding or within their excitatory receptive field (71% of the sample) it was consistently found that 300 Hz vibration at low amplitudes (< 25-50 mum) which selectively engages Pacinian corpuscles was an effective source of inhibition. In contrast, steady indentation which activates slowly adapting tactile afferents was quite ineffective, as was low frequency vibration (30 Hz) at amplitudes of < 50-100 mum. The latter stimulus can be used to engage rapidly adapting receptors either within glabrous skin (presumed to be Meissners corpuscles) or in association with hair follicles. It is concluded that afferents from Pacinian corpuscles are the dominant or exclusive source of afferent-induced inhibition of cuneate neurones.3. For dynamically sensitive neurones responsive to low frequency cutaneous vibration (30 Hz) there was a reduction in the slope of stimulus-response relations with afferent-induced inhibition, but no expansion of the range of stimulus amplitudes over which the neurone responded.4. The influence of afferent-induced inhibition on the phase-locking of impulse activity to a cutaneous vibratory wave form was examined by constructing post-stimulus time histograms and cycle histograms. Measures of dispersion of impulse activity around the preferred point of firing in the vibratory waveform indicated that the capacity of individual cuneate neurones to code information about the frequency of the cutaneous vibration was not systematically changed in the presence of afferent-induced inhibition.

Adaptation, Physiological↗
PubMed1975

Central and peripheral neural respiratory activity in the mature sheep foetus and newborn lamb.

Activity from respiratory neurones in the medulla, the phrenic and intercostal nerves was recorded in 25 foetal sheep, exteriorized a few days before term from ewes given a spinal anaesthetic, and from nine newborn lambs, anaesthetized with an allobarbitone-urethane mixture. In 12 foetuses, there was little or no sustained respiratory activity, central activity consisting of tonically discharging expiratory and other neurones and silent inspiratory neurones. In the remaining 13 foetuses, respiratory activity was periodic or continuous and it was possible to confirm that the motor component of the respiratory reflex was mature, that apnoea was not due to medullary depression, that foetal respiration was unaffected by chemoreceptor stimulation, by noise, by light, by electrical stimulation of the sciatic nerve and only slightly by inflation or deflation of the lungs. All these stimuli were effective shortly after birth. Occlusion of the umbilical cord caused poorly sustained gasps in the "non-breathing" foetuses and in the "breathing" foetuses, abolition of inspiratory and expiratory activity in the medulla and the onset of gasps and flattening of the electro-corticogram. Rhythmic respiration resumed after release of the cord with a latency which varied with the duration and severity of the asphyxia. This type of respiratory depression was not reflex but due to a direct, central action of hypoxia. The sequence of respiratory events at birth is discussed.

Animals↗
PubMed1973

Studies of the pulmonary vagal control of central respiratory rhythm in the absence of breathing movements.

1. Breuer's hypothesis that the vagus nerves exert a tonic control of respiratory rhythm, in addition to the phasic control, was examined.2. Closed-chest cardiopulmonary bypass was instituted in dogs weighing 20-30 kg anaesthetized with chloralose. Respiratory rhythm was recorded from a phrenic electroneurogram.3. Complete muscular paralysis induced with gallamine triethiodide produced an increase in the duration of inspiration and an increase in the amplitude of the integrated phrenic electroneurogram. There was no consistent effect on expiratory duration. Gallamine produced no effect when given after vagotomy.4. In the paralysed state, an increase in lung volume of 25-100 ml. for 30-60 sec produced a sustained increase in the duration of expiration and a decrease of respiratory rate: there was little effect on inspiratory duration, or the amplitude of the integrated phrenic electroneurogram.5. A decrease in lung volume of the same order of magnitude for the same period produced a sustained decrease in the duration of expiration and an increase of respiratory rate: there was little effect on inspiratory duration or the amplitude of the integrated phrenic electroneurogram.6. The phenomena described in (5) and (6) constitute a high gain respiratory frequency controller. They did not occur after bilateral cervical vagotomy.7. Bilateral cervical vagotomy during complete muscular paralysis produced a further increase in the duration of inspiration and in the amplitude of the integrated phrenic electroneurogram; there was no consistent effect on expiratory duration.8. The results confirmed Breuer's hypothesis and showed that inspiratory duration and expiratory duration are controlled independently.

Animals↗
PubMed1973

Studies on the central effects of Hering-Breuer reflexes.

In our previous experiments performed with rabbits, it was found out that the strength of both inflation and deflation Hering-Breuer reflexes depends on the level of anaesthesia and ventilation as correlative factors in spontaneously and artificially ventilated animals, though this dependence was quantitatively and qualitatively different in these two groups. On the basis of the recent evidence pointing to the rapidly conducting fibres and thus indirectly the pulmonary stretch receptors as the pathway along which both Hering-Breuer reflexes are transmitted, an attempt has been made to show how both parameters of ventilation are centrally controlled in response to afferent information concerning such mechanical factors as resistance and compliance of the respiratory system. The results presented seem to allow the following conclusions: (i) An important role may be ascribed to the pulmonary stretch receptors in transmission of both Hering-Breuer reflexes. (ii) In quiet breathing the central mechanisms of the Hering-Breuer inflation reflex are set to regulate tidal volume on the basis of analysis of the compliance of the respiratory apparatus at the given moment. Their role to the control of the respiratory frequency is of minor importance. (iii) The contribution of the pulmonary stretch receptors to the control of respiratory frequency is based on information about the resistance of the airways. This parameter influences the ratio of duration of the activity phase to silent phase in discharges of pulmonary stretch receptors.

Anesthesia↗