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Biomedical subjects

D C Woolley

Publications and source records attributed to D C Woolley.

7 recordsLinked to original sources

Geriatric psychiatry in primary care. A focus on ambulatory settings.

Considering how tightly interwoven are the strands of mental and physical health in the fabric of late life, it would be unwise for psychiatrists and primary care physicians to continue to insist on separately tracing and mending frayed old threads, each in mostly one direction, occasionally irritated by the shortcomings in the others work, and only occasionally seeking or offering assistance. As reflected in their help-seeking behavior and their characterization of suffering, the elderly often do not see, or do not choose to recognize, the theoretical and professional distinctions we hold so dear. Acknowledging the impact of the unmet needs of elderly patients, and respecting the wisdom of their choices, primary care physicians and psychiatrists have an obligation to work together more effectively. Improved mental health in our geriatric patients will require major efforts in the areas of research, public education, health care funding, and community resource development, as well as in individual patient care. Medical disciplines working in isolation or in opposition will not attenuate these obstacles effectively.

Aged↗

The effect of supranodose vagotomy on the hexamethonium-resistant bradycardia in the anaesthetized rabbit.

Previous studies from this laboratory have established that electrical stimulation of non-myelinated axons in the rabbit vagus nerve produces a bradycardia which is unaffected by the nicotinic ganglion blocker hexamethonium. The present study was undertaken to determine whether this effect is mediated by afferent or efferent axons. A unilateral supranodose vagotomy was performed on four New Zealand White rabbits, one further animal served as a sham-operated control. Fourteen days later the effects of vagal nerve stimulation (10 Hz, 20 s) were assessed. On the operated side, where the supranodose vagotomy would have led to the degeneration of efferent axons, vagal stimulation had no effect on heart rate. The integrity of afferent axons was demonstrated by recording both electrically evoked volleys and characteristically normal patterns of afferent activity from the nerve. On the unoperated side the bradycardia produced by vagal stimulation was consistent with previous studies. It is concluded that the hexamethonium-resistant bradycardia evoked by stimulation of the rabbit vagus is mediated by non-myelinated preganglionic efferent axons.

Action Potentials↗

The actions of myelinated and non-myelinated vagal fibres on atrial contraction in the rabbit.

The bradycardia and reduction in atrial contraction on electrical stimulation of the peripheral cut end of the vagus nerve in the cat have been attributed solely to the action of myelinated fibres. In the rabbit however, recruitment of non-myelinated fibres produces an additional prolonged bradycardia. The objective of this investigation was to examine the relative contributions of myelinated and non-myelinated fibres to the vagal action on atrial contraction in the rabbit. In 5 rabbits stimulation of myelinated fibres at 10 Hz for 20 s reduced developed atrial tension of the paced heart by 17.1 +/- 2.6%. After stimulation, atrial tension returned rapidly to the control value in 6.5 +/- 0.5 s. Recruitment of non-myelinated fibres resulted in a reduction in developed atrial tension of 29.1 +/- 2.8%. This larger fall in atrial tension outlasted the period of stimulation by 34.1 +/- 4.8 s. Hexamethonium blocked the reduction in atrial contraction due to myelinated fibres but not that due to non-myelinated fibres. Atropine abolished all effects of vagal stimulation on atrial contraction. We conclude that the recruitment of non-myelinated fibres produces an additional prolonged reduction in atrial contraction which is resistant to hexamethonium but blocked by atropine.

Animals↗

The effect of selective electrical stimulation of non-myelinated vagal fibres on heart rate in the rabbit.

The bradycardia evoked by electrical stimulation of the peripheral cut end of the rabbit vagus nerve is mediated by both myelinated and non-myelinated fibres. The purpose of this study was to assess the effects of non-myelinated fibres on heart rate in the rabbit using selective electrical stimulation techniques. In 8 rabbits selective activation of non-myelinated fibres using reversed polarity triangular shaped pulses (10 Hz, 20 s), resulted in a slowly developing fall in heart rate of 24.1 +/- 1.1 beats/min which outlasted the period of stimulation by 58.4 +/- 4.2 s. In 4 rabbits stimulation of myelinated fibres at 10 Hz for 20 s resulted in a fall in heart rate of 24.5 +/- 2.6 beats/min. On stimulation of both myelinated and non-myelinated fibres heart rate fell by 39.9 +/- 3.2 beats/min. Heart rate returned rapidly to control value following stimulation of myelinated fibres (5.6 +/- 0.5 s) but only slowly after stimulation of both myelinated and non-myelinated fibres (56.7 +/- 4.9 s). Atropine (5 mg/kg, i.v.) abolished all effects of vagal stimulation on heart rate. Hexamethonium (15 mg/kg, i.v.) abolished the effect of myelinated fibres on heart rate but did not affect the fall in heart rate produced by non-myelinated fibres. We suggest that the prolonged effects on stimulation of non-myelinated fibres may reflect the persistent action of a non-cholinergic excitatory transmitter at the cardiac parasympathetic ganglia.

Animals↗