Showing papers by "David Burke published in 1986"

Reflex influences on muscle spindle activity in relaxed human leg muscles.

Abstract: The study was designed to determine whether low-threshold cutaneous and muscle afferents from the foot reflexly activate gamma-motoneurons innervating relaxed muscles of the leg. In 15 experiments multiunit recordings were made from 21 nerve fascicles innervating triceps surae or tibialis anterior. In a further nine experiments the activity of 19 identified single muscle spindle afferents was recorded, 13 from triceps surae, 5 from tibialis anterior, and 1 from extensor digitorum longus. Trains of electrical stimuli (5 stimuli, 300 Hz) were delivered to the sural nerve at the ankle (intensity, twice sensory threshold) and the posterior tibial nerve at the ankle (intensity, 1.1 times motor threshold for the small muscles of the foot). In addition, a tap on the appropriate tendon at varying times after the stimuli was used to assess the dynamic responsiveness of the afferents under study. The conditioning electrical stimuli did not change the discharge of single spindle afferents. Recordings of rectified and averaged multiunit activity also revealed no change in the overall level of background neural activity following the electrical stimuli. The afferent responses to tendon taps did not differ significantly whether or not they were preceded by stimulation of the sural or posterior tibial nerves. These results suggest that low-threshold afferents from the foot do not produce significant activation of fusimotor neurons in relaxed leg muscles, at least as judged by their ability to alter the discharge of muscle spindle afferents. As there may be no effective background activity in fusimotor neurons innervating relaxed human muscles, it is possible that these inputs from the foot could influence the fusimotor system during voluntary contractions when the fusimotor neurons have been brought to firing threshold. In one subject trains of stimuli were delivered to the posterior tibial nerve at painful levels (30 times motor threshold). They produced an acceleration of the discharge of a spindle in soleus at a latency of approximately 125 ms, in advance of detectable activity in skeletomotor neurons and before an increase in muscle length was noted. It presumably resulted from activation of gamma-motoneurons innervating soleus by small myelinated afferents (A-delta range).

An unusual infection after renal transplantation.

Abstract: Case report DR J. D. MACKIE: A 37-year-old white man was admitted for a renal transplant on August 21, 1984. He had developedinsulin-dependentdiabetes mellitus at the age of 14 years. In 1980, renal impairment was first documented and a renal biopsy at that time showeddiffuse nodular diabetic glomerulosclerosis. He also had retinopathy, smallvessel peripheral vascular disease and peripheral neuropathy. Haemodialysis was commenced on July 15, 1983 by means of an arteriovenous fistula in the left arm. In the month before transplantation his diabetic control had been poor in spite of the monitoring of blood-glucose levels at home and regular readjustment of his insulin dosage. Two weeks before admission to hospital he developedan upper respiratory tract infection that was followed by vomiting and diarrhoea. All symptoms had settled at the time of his admission to hospital. Examination revealed a healthy looking man with a pulse rate of 70 beats/min and a blood pressure of 105/80 mmHg; his temperature was 36.7 °C and his weight was 88 kg. A soft systolic ejection murmur was present at the cardiac apex and the apical impulse was palpable in the anterior axillary line; these abnormalities had been observed previously. There were no signs of fluid overload. The patient was blind in the right eye and tunnel vision was present in the left eye. A sensory peripheral neuropathy, in a glove-and-stocking distribution, was present in the lower limbs. Initial investigations showed: normal serum sodium level, 130 mmollL; normal serum potassium level, 4.0 mmollL; normal serum chloride level, 95 mmollL; normal serum bicarbonate level, 23 mmollL; blood urea level, 28 mmollL (normal, 2.8-7.8 mmoIlL); serum creatinine level, 930 IlmollL (normal, 65-115 IlmoIlL); and a normal serum albumin level, 37 giL. Total haemoglobin concentration was 68 gil (normochromic, normocytic picture; normal,