Search PubMed⌕ Search

Biomedical subjects

A Trzebski

Publications and source records attributed to A Trzebski.

At least 73 records · Page 4Linked to original sources
PubMed1975

Bulbo-spinal neurons activated by baroreceptor afferents and their possible role in inhibition of preganglionic sympathetic neurons.

In paralyzed cats under chloralose-urethane anaesthesia the medulla oblongata was searched with dye-filled microelectrodes for neurons responding to electrical stimulation of the carotid sinus nerve (CSN) and distension of the isolated carotid sinus (CS). 89 cells localized in the solitary tract nucleus and in the reticular formation ventrally and ventrolaterally to the nucleus exhibited mainly an excitatory input from the CSN. 16 could be also antidromically excited from the cervical spinal cord at C4 level. 11 of these were shown to be excited by a pressure rise in the CS. The latencies of the antidromically driven units ranged from 1.2-2.8 msec and the calculated conduction velocity of the descending fibres was 29 plus or minus 5.2 m/sec. The possibility of involvement of these bulbo-spinal neurons in the inhibition of the preganglionic sympathetic neurons at the spinal cord level is discussed.

Animals↗
PubMedDate not supplied

Split medulla preparation in the cat: arterial chemoreceptor reflex and respiratory modulation of the renal sympathetic nerve activity.

The study was undertaken in order to assess the changes in sympathetic output in a split medulla preparation of the cat which, as shown earlier, has impaired respiratory rhythm generation. The effects of medullary midsagittal sections on renal sympathetic nerve firing were investigated in chloralose anesthetized, paralyzed and artificially ventilated cats. Recordings of phrenic and recurrent laryngeal nerve activity served as indices of central respiratory rhythm generation. Sections, 5 mm deep from the dorsal medullary surface and extending 6 mm rostrally and 3 mm caudally to the obex, did not produce any significant changes in heart rate, blood pressure or tonic renal sympathetic nerve firing levels. They decreased or abolished, however, the respiratory rhythmicity in renal sympathetic nerve which paralleled the reduction of inspiratory discharges in phrenic and recurrent laryngeal nerves, and abolished the carotid body chemoreceptor-sympathetic reflex. The inspiratory activity remaining after the sections could still be enhanced by chemoreceptor stimulation. The inhibitory baroreceptor and pulmonary stretch receptor sympathetic reflexes, and the central excitatory effect of CO2 on renal sympathetic nerve firing were not altered. The effects of electrical stimulation within the midsagittal plane of the medulla have shown that descending pathways from the medullary inspiratory neurons (or their medullary collaterals) do not participate in the facilitation of spinal preganglionic neurons during inspiration and in relaying the pulmonary stretch receptor inhibitory sympathetic reflex. A region located close to the obex was identified from which excitatory responses in renal sympathetic nerves, compatible with the response obtained by carotid sinus nerve stimulation, could be evoked. It is concluded that a lesion in the midline of the lower medulla at the level of the obex selectively destroys cells or pathways which relay the carotid body chemoreceptor-sympathetic reflex.

Animals↗
PubMedDate not supplied

The effect of acute rise in intracranial pressure on the sympathetic cardiac, vertebral and phrenic nerve activities.

A transient rise of intracranial pressure in cats under chloralose-urethane anaesthesia increased the activity of the sympathetic vertebral nerve, cardiac nerve and in the first phase phrenic nerve. If the vagus nerves were intact this rise in sympathetic activity was associated with bradycardia. These effects developed with a delay, as a rule after abatement of the transient intracranial pressure rise. The authors suggest that Cushing's reaction is caused by medullary ischaemia and development of local metabolic acidosis activating simultaneously the sympathetic and parasympathetic neurons in the medulla oblongata.

Animals↗
PubMedDate not supplied

Increased resistance to acute anoxia of the respiratory and cardiac function in spontaneously hypertensive rats.

In spontaneously hypertensive rats NIbn (SHR) and in normotensive Wistar rats (NCR) 12-16 weeks old, anaesthetized with urethane, anoxia was produced by nitrogen administration through a tracheal cannula. Ventilation was measured by tetrapolar impedance rheography. NCR responded to anoxia with a marked increase in TV and in respiratory rate (f.), whereas in SHR a depression of TV and increase in f. was observed. In NCR respiratory arrests and alternating with spontaneous restorations of respiration were observed during anoxia. This pattern of response to anoxia never appeared in SHR. After the glossopharyngeal nerves had been cut anoxia caused a depression of TV and increase of f. in NCR. In contrast, chemodenervation in SHR did not qualitatively change the respiratory response to anoxia. Periods of spontaneous respiration under anoxic conditions were significantly longer in SHR than in NCR. Also left ventricular contractions and ECG activity were maintained for a longer time in SHR than in NCR during anoxia. EEG activity disappeared in both groups of animals at about the same time after the onset of acute anoxia. The above data point to: 1) reduced responsiveness of the arterial chemoreflex in SHR, and 2) markedly increased tolerance to anoxic conditions in SHR.

Animals↗
PubMedDate not supplied

Augmented chemoreceptor reflex tonic drive in early human hypertension and in normotensive subjects with family background of hypertension.

The study was carried out in 30 subjects with mild primary hypertension and in 82 normotensive age-matched volunteers, 18-20 years of age. Hyperoxia test was used to withdraw the tonic chemoreceptor reflex drive. The following circulatory and respiratory effects of short lasting hyperoxia were observed in the hypertensive group and in most of the normotensive subjects yet with a family background of hypertension: a decrease in the mean arterial pressure, in total peripheral vascular resistance, and in forearm vascular resistance, and a significantly greater reduction of the resting ventilation as compared to the normotensive group. Our results suggest that the augmented arterial chemoreceptor drive is one of the mechanisms responsible for the elevated arterial blood pressure and total peripheral resistance in early human hypertension. The positive response to hyperoxia test in healthy subjects with a family background of hypertension suggests a familial occurrence of the hyperactivity of the arterial chemoreceptors.

Adolescent↗