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Biomedical subjects

J Hannerz

Publications and source records attributed to J Hannerz.

65 records · Page 4Linked to original sources
PubMed1973

Recruitment order of motor units in man: significance of pre-existing state of facilitation.

It has been shown in previous investigations that the recruitment order of motor units is different in tonic and in phasic voluntary activity. The significance of the pre-existing state of facilitation in the motoneurone pool for the recruitment of units is studied, using the phasic flexion reflex in the anterior tibial muscle as test reflex. It is shown that the recruitment order of units in a series of reflexes (1) is unstable if the subject does not expect the stimulus; (2) is stable and identical with that in tonic activity if the subject subliminally facilitates the motoneurone pool before the reflex activation; (3) is stable and almost identical with that in tonic activity if the subject expects the stimulus and therefore involuntarily influences the motoneurone pool; (4) is stable and similar to that in phasic voluntary activity if the subject inhibits the motoneurone pool before the activation and the stimulus strength thus consequentially is increased; and (5) is influenced by blockade of the proprioceptive afferent impulses from the muscle. It is concluded that normal man can select in advance the recruitment order of motor units most appropriate for the work intended.

Action Potentials↗
PubMed1970

Differences in recruitment order of motor units in phasic and tonic flexion reflex in "spinal man".

The recruitment order of motoneurones in muscle contractions has been held to be largely constant and determined by the size of the cell. However, as shown in a previous investigation using electromyographic techniques, the order in which different motor units are activated during voluntary muscle contractions changes in normal human subjects on shifts from phasic to tonic contraction. In order to investigate these two types of activity also in cases in which the cerebral influence on the motoneurone pool is blocked, an analysis was made of the recruitment order in phasic and tonic flexion reflexes in 10 patients with total interruption of the spinal cord. The following four principles were found to apply and presumed to be generally valid for the isolated human spinal cord: (1) in the phasic exteroceptive reflex, the order of recruitment varies despite application of a standardized stimulus; (2) in the tonic reflex, the first unit to be recruited is usually the same even with widely different types of stimuli; (3) a shift from phasic to tonic reflex activation may result in considerable changes in recruitment order; (4) after facilitation by a subliminal long-lasting stimulus, the first unit to be recruited in the phasic reflex is also the first to be recruited in the tonic reflex. It is suggested that a tonic influence on the motoneurone pool is required for the presupposed constancy of the recruitment order.

Action Potentials↗
PubMedDate not supplied

The afferent influence on the voluntary firing range of individual motor units in man.

The firing ranges of 50 normal anterior tibial or short toe extensor motor units in sustained isometric voluntary contraction were studied in electromyographic recordings. The afferent inflow was decreased by compression of the sciatic nerve, thereby blocking large afferents before alpha efferents. Motor units with low minimum and low maximum rates before blockade had higher minimum and maximum rates before blockade had a lower minimum but an unchanged maximum rate on blockade. The firing range recorded for both types of motor unit on blockade was also recorded for all tonically firing motor units during early reinnervation after traumatic lesion to the muscle nerve in 14 patients. It is concluded that both facilitating and inhibiting proprioceptive afferent activity is involved in the differentiation of motor unit firing ranges in sustained isometric voluntary contraction.

Electromyography↗
PubMedDate not supplied

Motor neuron firing range, axonal conduction velocity, and muscle fiber histochemistry in neuromuscular diseases.

The voluntary discharge properties and axonal conduction velocity of single motor units were studied in patients with neuromuscular diseases with retained differentiation of the muscle fibers into type 1 and type 2, and in patients with late-onset hereditary distal myopathy in which muscle fibers have only intermediate histochemical properties. In the patients with muscle fiber differentiation, the findings were similar to those in normal subjects; that is, there was a continuum between motor units which fired tonically at low rates and had a low axonal conduction velocity, and motor units which fired phasically at high rates and had a high axonal conduction velocity. In the patients without muscle fiber differentiation, all motor units had intermediate firing properties and a low axonal conduction velocity. It is suggested that in chronic pathologic states, the differentiation of the muscle fiber histochemistry remains only as long as the differentiation of the motor neurons remains.

Adenosine Triphosphatases↗
PubMedDate not supplied

Postlumbar puncture headache and its relation to chronic tension-type headache.

One hundred consecutive patients, the majority suffering from bilateral chronic tension-type headache, investigated with lumbar puncture, were studied as to age, sex, body mass index, diagnosis, lumbar cerebrospinal fluid pressure, and signs of inflammation in the serum in relation to postlumbar puncture headache. Patients younger than 40 years of age were significantly more prone to develop postlumbar puncture headache than patients older than 40 years of age (P = 0.01). Sex, body mass index, cerebrospinal fluid pressure, and signs of inflammation in the serum were not related to the frequency of postlumbar puncture headache in the present study. Postlumbar puncture headache occurred significantly more often in patients with bilateral chronic tension-type headache than in patients with unilateral headache (P = 0.02) and in patients without headache (P < 0.01). In a regression analysis with age, sex, and chronic tension-type headaches, only bilateral headache contributed significantly to the prediction of postlumbar puncture headache (P < 0.01). Age did not contribute apart from the common variance with chronic tension-type headache/no chronic tension-type headache. The results may indicate that postlumbar puncture headache and chronic tension-type headache have etiologic mechanisms in common, mechanisms presumably localized intracranially rather than extracranially.

Adolescent↗
PubMedDate not supplied

Chronic bilateral headache responding to indomethacin.

Three patients with bilateral chronic tension-type headache (meeting IHS diagnostic criteria) responded with complete control of the headache during the more than 2 years they were treated with indomethacin. The headache recurred within 12 to 26 hours after indomethacin was stopped. Fifty milligrams of intravenous indomethacin resulted in complete relief of headache for 6.5 to 25 hours, similar to results found earlier in patients with hemicrania continua. It is concluded that there may be a subgroup of patients with bilateral chronic headache who respond to indomethacin in the group of patients otherwise diagnosed as having chronic tension-type headache.

Administration, Oral↗
PubMedDate not supplied

Computed tomography of the brain in cases with venous vasculitis compared with an age-matched reference group.

Patients with a particular, steroid-sensitive headache and often characteristic pathology at orbital phlebography, have been suggested to suffer from venous vasculitis. Fifty such patients were examined with computed tomography (CT) of the brain. The findings were compared with those of an age-matched reference group selected at random to represent normal subjects. The CT examinations were analyzed with respect to size of lateral ventricles and signs of atrophy. In both groups, there was a significant increase of atrophy with age. There was also a significantly higher degree of atrophy in the patient group as compared with the reference group. The findings indicate that the supposedly underlying venous vasculitis is related to early aging and atrophy of the brain.

Adult↗
PubMedDate not supplied

Orbital phlebography for differentiation between multiple sclerosis and venous vasculitis in subacute blindness.

Thirteen consecutive patients with subacute unilateral loss of vision and periorbital pain but without pathology of the fundus or increased erythrocyte sedimentation rate, were investigated with visual evoked response, electrophoresis of serum and cerebrospinal fluid, and orbital phlebography. Seven of these patients were found to suffer from multiple sclerosis. The remaining 6 were considered to have venous vasculitis. There was a spontaneous recovery from visual impairment in all patients with multiple sclerosis, but not in patients with venous vasculitis. Of the latter patients, only two, who were treated with steroids within the first four days after onset of symptoms, regained vision. It appears that orbital phlebography is the diagnostic procedure of choice for proper management of patients with subacute loss of vision.

Adult↗