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Biomedical subjects

A H Lang

Publications and source records attributed to A H Lang.

At least 55 records · Page 3Linked to original sources
PubMed1978

Does transient blocking of axonal conduction occur in uraemic neuropathy?

In uraemic and other patients with neuropathies, motor unit spike intervals were analysed using a special computer program to detect prolonged intervals of twice the normal duration, so-called "double intervals." These may have different causes--trigger failure, double discharge, or a transient fall in the firing rate of coactive motor units. There was not sufficient evidence that transient conduction blockings will occur in the main axon in uraemic neuropathies.

Axons↗
PubMed1977

Statistical variation of nerve conduction velocity. An analysis in normal subjects and uraemic patients.

The maximal nerve conduction velocity (NCV) of 6 sensory nerves (N. radialis, suralis and peronaeus superficialis, bilaterally) was determined in 88 normals and 59 uraemic patients. When the effect upon nerve conduction velocity of age and temperature was removed through partial correlations, it became possible to verify the negative correlation between the height of the patient and NCV. This explained as much as 35% of the remaining variance in males. There were also other significant differences in the nerve functions between the sexes. A set of "statistical corrections" (grouping of NCV's according to the subject's sex, computing of the average NCV's of an individual, and height-, age- and temperature normalization of single or mean NCV values) substantially decreased the variability of NCV. At the same time, the sensitivity of NCV measurement in the early diagnosis of nerve dysfunction caused by uraemia was increased. It is suggested that the results of NCV measurements should not only be reported as rough, absolute data, but also as normative values, taking into account the known physiological determinants.

Age Factors↗
PubMed1977

Transient changes of sensory nerve functions in uraemia.

The neurophysiological parameters (conduction velocity, amplitude and rise time of the compound action potential) of two sensory nerves of the lower limb (N. suralis and peronaeus superficialis) were determined bilaterally in five patients. Measurements were carried out at least twice in each subject during a time of great metabolic change. Two patients were recovering from acute renal failure (a single haemodialysis had to be performed on one of them) and three were under chronic maintenance haemodialysis. In the case of the haemodialysis patients, measurements were performed on two successive days, before and after one haemodialysis session. All the neurophysiological parameters showed significant improvement in successive measurements. In one patient the follow-up after acute renal failure revealed a delayed deterioration of the nerve functions, but after one year the values were normal. From the results it seems probable that an acute metabolic disturbance may cause transient inhibition of nerve functions without morphological changes in the nerve fibres.

Action Potentials↗
PubMed1977

Carpal Tunnel syndrome in ovariectomized women.

Electrophysiological parameters were studied in 32 gynecological patients before and after major gynecological surgery. No changes in maximal nerve conduction velocity or simple reaction time could be found after either hysterectomy or ovariectomy. Of the 20 ovariectomized patients, 3 developed subjective symptoms and electrophysiological signs of the carpal tunnel syndrome within a few months after surgery. Thus the carpal tunnel syndrome, which is common in women of menopausal age, seems to be precipitated also by iatrogenic menopause. The present findings indicate that ovarian relaxin overproduction cannot be the basis of the carpal tunnel syndrome, but they are consistent with the view that the syndrome is a sign of hypothalamichypophyseal overactivity or imbalance.

Action Potentials↗
PubMed1976

"Satellite potentials" and the duration of motor unit potentials in normal, neuropathic and myopathic muscles.

Time-locked activity in the EMG was studied in normal, neuropathic and myopathic muscles, using the averaging technique. Normal and neuropathic muscles seemed in most cases not to differ with regard to the frequency nor the quality of "satellite signals", i.e. small and short potentials joining the main component of the MUP with a constant interval, up to 26 ms in duration. In normal muscles 10% of the MUPs and in neuropathic muscles 12% had a satellite, which, when studied, showed no signs of blocking. However, in 2 patients with an apparent old spinal affection both an increased number and an increased latency of satellite signals were found. In the different myopathies studied 45% of the MUPs recorded consecutively were preceded or followed by an often increased number of tiny satellites. Sometimes the satellites joining the myopathic MUP formed a long (up to 60 ms) "tail" after the triggering component. On the basis of our results we conclude that in myopathies the total duration of MUPs is in certain cases pathologically incrased rather than decreased.

Adolescent↗
PubMed1976

Diagnostic possibilities for the nuchal evoked potential.

As a response to stimulation of the arm nerves an evoked potential can be recorded in the posterior neck region in man. This nuchal evoked potential (NEP) was recorded in three selected patients with A) cervical rib, B) syringomyelia, and C) prolapse of cervical intervertebral disc. Patients A and C had low-amplitudic NEPs with increased latencies when the affected side was stimulated and "normal" NEPs when the unaffected side was stimulated. Patient B had grossly abnormal, polyphasic NEPs (regardless of the side stimulated) but the simultaneously recorded somatosensory evoked potential was "normal". No systematic differences in the parameters of the NEP due to different recording locations on the neck could be observed.

Adult↗
PubMedDate not supplied

Mismatch negativity and late discriminative negativity in investigating speech perception and learning in children and infants.

For decades, behavioral methods, such as the head-turning or sucking paradigms, have been the primary tools to investigate speech perception and learning of a language in infancy. Recently, however, new methods provided by event-related potentials have emerged. These are called mismatch negativity (MMN) and late discriminative negativity (LDN). MMN, the brain's automatic change-detection response in audition, has been intensively used in adults in both basic and clinical studies for longer than 20 years. LDN, on the other hand, was only recently discovered. There seem to be many differences between these two responses. MMN is developmentally quite stable and can be obtained even from preterm infants. LDN, however, can be obtained most reliably from young children, and its amplitude decreases as a function of age. New data suggest that both of these responses have a special role in language processing, although both of them can also be elicited by nonspeech stimuli.

Child↗