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Biomedical subjects

K Reiners

Publications and source records attributed to K Reiners.

90 records · Page 5Linked to original sources
PubMed1989

The blood-nerve barrier in Wallerian degeneration: a sequential long-term study.

The blood-nerve barrier (BNB) for serum proteins was studied after a crush lesion of the murine sciatic nerve or after transsection with persistent Wallerian degeneration. Using single intraperitoneal injections of biotinylated human albumin, transferrin, IgG, and complement components as tracers, the integrity of the BNB during degeneration and regeneration was determined over time. In Wallerian degeneration induced by crush the BNB became increasingly leaky, with a maximum in the distal stump 8 days after crush (i.e., during early regeneration). When regeneration potentials could first be elicited from the small foot muscles and when thinly myelinated nerve fibers were present, the BNB gradually regained its barrier function and was nearly intact on day 30 after crush. After transsection breakdown of the BNB persisted beyond 30 days. The BNB leakage may foster repair by allowing exchange of trophic factors of large molecular size during nerve regeneration.

Animals↗
PubMed1989

Altered mechanisms of muscular force generation in lower motor neuron disease.

Recruitment and firing rate modulation (FRM) of single motor units (MUs) were evaluated in the first dorsal interosseus muscle in patients with chronic lower motor neuron disorders of primarily neuroaxonal or demyelinating pathology. Residual muscle function was estimated by maximal voluntary force, twitch tension, and compound muscle action potential. The recruitment range of MUs was expanded toward higher relative force levels in all patients. Changes in firing rates per unit force increment were larger in patients with more pronounced muscle atrophy. When this effect was accounted for by calculating FRM for increments of 10% of residual maximal force, patients with subnormal motor nerve conduction velocities showed selective impairment of rate modulation. This was not due to intermittent conduction failure. We conclude that the two force-generating mechanisms, recruitment and FRM, show unspecific compensatory changes related to the loss of MUs and also alterations that are specifically related to the neuroaxonal or demyelinating nature of the neuropathy.

Action Potentials↗
PubMed1989

Good recovery after sublethal ethylene glycol intoxication: serial EEG and CT findings.

The case of a young man with sublethal ethylene glycol poisoning is reported. Complete recovery occurred after 12 days of deep coma and a prolonged flaccid tetraplegia. The lesions of gross degree in the CNS, demonstrated by serial CT, resolved and electrophysiological testing as well as neuromuscular signs improved. The recovery, clinically and radiographically, over 35 days was dramatic. Ethylene glycol intoxication should always be considered in the differential diagnosis of acute severe encephalopathy because complete recovery is possible with correct therapy.

Adult↗
PubMed1987

Stability of frequency during long-term recordings of hand tremor.

During recording of physiological postural hand tremor over a period of 60 min tremor peak frequency (PF) did not change in 14 normal subjects as long as the mechanical conditions were not changed. In contrast, tremor amplitude and synchronization of the corresponding EMG varied considerably. Any alteration in hand mechanics such as changing hand position or adding masses led to changes of PF according to the alteration in mechanical resonant properties. The results show that PF of physiological postural hand tremor is mainly determined by mechanical factors. There is no evidence for a systematic decrease of PF (Stiles et al. 1976) or for the emergence of a formerly described (Lippold 1981) 4-6 Hz tremor component with prolonged maintenance of posture. In the pathological tremor forms of Parkinson's disease or essential tremor PF also remained unchanged during prolonged maintenance of posture.

Adolescent↗
PubMed1987

Regeneration following tibial nerve crush in the rabbit: the effect of proximal constriction.

In order to test the regenerative capacity of atrophic axons, a constricting ligature was placed around the proximal tibial nerve of the rabbit, and the nerve crushed at the ankle one week later. Axonal atrophy with altered g ratios was subsequently confirmed in fibres distal to the site of ligature and proximal to the site of crush. In nerves with tight proximal ligatures the reinnervation of plantar muscles and the subsequent recovery of distal motor latency were delayed, indicating impaired regeneration. This result may be relevant to the "double-crush" theory of nerve damage.

Action Potentials↗
PubMed1987

Differential effects of changes in mechanical limb properties on physiological and pathological tremor.

The effect of changes in mechanical limb properties on the peak frequency of different tremor forms was analysed. Wrist tremor was recorded by an accelerometer fixed to the dorsum of the hand and demodulated surface EMG was recorded from the wrist extensors, while the extended hand was loaded with successively heavier weights. Physiological tremor was characterised by flat EMG spectra and a gradual decrease in tremor peak frequency with increasing load, as would be expected from the properties of a passive spring-mass-system. Also the peak frequency of activated physiological tremor characterised by increased synchronisation between motor units decreased in frequency with increasing loads. EMG spectra showed clear peaks of activity at the various mechanically determined tremor frequencies. In contrast, in two pathological tremor forms, the postural tremor in Parkinsonian patients and essential tremor, peak frequency tended to remain stable irrespective of changes in load. The method therefore allows a simple distinction between physiological and these two pathological tremors.

Adolescent↗
PubMed1986

Normal myelination of regenerating peripheral nerve sprouts despite circulating antibodies to galactocerebroside in rabbits.

Rabbits were immunized with galactocerebroside and a crush lesion was created in the tibial nerve before the onset of experimental allergic neuritis. Normal regeneration and myelination of distal peripheral nerve sprouts occurred and was identical to that of controls, although circulating antigalactocerebroside antibodies were present and nerve roots showed typical signs of beginning experimental allergic neuritis.

Animals↗
PubMed1986

The muscle activity spectrum: spectral analysis of muscle force as an estimator of overall motor unit activity.

Starting from the observation that the part above 6 Hz of the power spectrum of force tremor during isometric contractions can be related to the unfused twitches of motor units firing asynchronously, an attempt was made to study the usefulness of force tremor spectral analysis as a global descriptor of motoneurone pool activity. To compensate for the mechanical low-pass filter characteristic of skeletal muscle which leads to increased damping of mechanical ripples at higher frequencies, a numerical compensation rule was derived from data obtained by electrical microstimulation of small ensembles of motor units (MUs). Hidden line plots of consecutive partially overlapping spectra allowed visualization of changes in spectral composition during ongoing muscle activity. The resulting muscle activity spectra (MAS) showed broad peaks according to the range of onset firing rates in normal subjects. These tended to shift to higher frequencies with increasing force. Under conditions with increased synchronization of the MUs these broad peaks were replaced by sharp peaks corresponding to the burst repetition rate. Patients with different motor dysfunctions were selected to illustrate how alterations of MU activity are reflected in the MAS. Decreased or increased firing rates were observed as well as abnormal states of synchronization. It is concluded that the MAS provides useful information about some aspects of the discharge characteristics of ensembles of MUs and therefore represents a method to monitor some qualitative 'image' of the MU activities within a muscle.

Adolescent↗
PubMed1986

[Dependence of the action potential amplitude of motor units on the recruitment threshold: implications for electromyography].

The relationship between the action potential amplitude and the threshold force of recruitment of 275 motor units (MU) recorded from the first dorsal interosseus muscle of 15 healthy subjects was analysed. The number of newly recruited MU decreased exponentially with increasing muscular force. Action potential amplitudes showed a highly significant positive linear correlation with threshold force of recruitment. This relationship is in accordance with the size principle of MU recruitment. Applying the rank correlation method, 88.6 +/- 2.0% (mean +/- standard deviation) of paired comparisons between all MU of one subject followed the normal activation sequence of MU with an increasing action potential amplitude. It is shown that small variations of the distance between the leading-off surface of the electrode and the MU recorded do not affect these findings. These results demonstrate that the force at which a MU is recruited is the most important factor influencing MU action potential amplitude in normal subjects. So far this fact has not been adequately appreciated in clinical electromyography although it is of significance for the assessment of pathological conditions.

Action Potentials↗
PubMed1984

Demyelination following diphtheria toxin in the presence of axonal atrophy.

In 23 guinea-pigs a constricting ligature was placed on the tibial nerve in the thigh on one side, in order to produce axonal atrophy in the distal part of the nerve. Either before or after ligature, 10 of the guinea-pigs received subcutaneous diphtheria toxin into the abdominal wall, in a dose insufficient to cause generalised paralysis or reduced motor conduction velocity (MCV). In 7 of the 10 animals, MCV distal to the ligature fell below the range seen after ligature alone. In animals which had received toxin histological studies revealed paranodal and segmental demyelination in the distal tibial nerve, which was more extensive on the side of the ligature than in the opposite leg. Occasional paranodal but no segmental demyelination was seen distal to ligature alone. These results indicate that a small dose of systemic diphtheria toxin is more likely to produce peripheral nerve demyelination if an axonal abnormality is also present.

Action Potentials↗
PubMed1975

[Isolation of intact liver parenchymal cells by a modified enzymatic method].

An enzymatic method is described for isolating intact parenchymal cells from rat livers. 3--4 g cells (wet weight) could be isolated from livers of rats weighing 180--230 g. After an in vitro preperfusion of 15 minutes with a Ca-free buffer, collagenase (200 mg/1) and calcium chloride (5.2 mmol/1) were added. Perfusion was continued for another 15 minutes at 37 degrees C. Micromorphological integrity of cell membranes was demonstrated by scanning electron microscopy. With regard to rates of gluconeogenesis and protein synthesis, parenchymal cells isolated according to our method were found to be superior to liver slices and cells isolated by other methods. Ratios of ATP/ADP (5.69) and of lactate/pyruvate (8.64) as parameters of the energetic situation and the redox state resp. were found within the physiological range. Integrity of cell surface receptors was proved by their sensitivity to epinephrine, glucagon and insulin. Glucagon (0.3 mumol/1) and epinephrine (1 mumol/1) and reduced glycogen deposition in hepatocytes of fasted rats by 84.9 % and 95.9 % resp. Both hormones stimulated glycogenolysis in parenchymal cells of fed rats to a similar extent. Urea synthesis was stimulated 29.5 % by glucagon (1 mumol/1), and inhibited 28.0 % by insulin (10 nmol/1). The stimulatory effect of glucagon (1 mumol/1) was abolished by insulin (10 nmol/1).

Adenosine Diphosphate↗
PubMedDate not supplied

Plasma exchange in chronic inflammatory polyneuropathy: evidence suggestive of a pathogenic humoral factor.

Chronic progressive of relapsing inflammatory polyneuropathy (CRIP) can be treated effectively with immunosuppressive drugs and/or plasma exchange (PE). This report describes a patient who responded dramatically and reproducibly to PE during four successive relapses and remained in remission while on medical immunosuppression with azathioprine and corticosteroids. The clinical course was closely correlated with electrophysiologic parameters such as compound muscle action potential amplitudes and distal latencies. The purified IgG fraction of PE filtrate bound to rat and human sciatic nerve on immunohistochemistry. Furthermore, a similar staining pattern was achieved by purified Fab fragments, which was absent in all control preparations. These findings support the hypothesis that circulating plasma factors may play a role in CRIP and that one of these factors may be an IgG antibody to peripheral nerve components.

Adolescent↗
PubMedDate not supplied

Diagnostic value of in situ muscle fiber conduction velocity measurements in myopathies.

In situ studies on muscle fiber conduction velocity (MFCV) were performed in 54 patients with histologically and biochemically defined myopathies. MFCV was measured over a 10 cm segment of the rectus femoris muscle by intramuscular stimulation and recording. Muscle disorders included muscular dystrophies, myotonic dystrophy, inflammatory myopathies, metabolic myopathies, endocrine myopathies, and congenital myopathies with structural abnormalities. Ten healthy volunteers served as controls. MFCV was significantly reduced in all patients except those with a defect in glycolysis and those that had recovered from acute myositis. MFCV did not vary with either sex. age or the duration of the disease. This shows that MFCV slowing is an unspecific finding in most myopathies. However, in some patients with normal needle electromyography, MFCV provided additional information in diagnosing muscle disease.

Adolescent↗
PubMedDate not supplied

A simple method for the routine assessment of heart-rate variation in autonomic neuropathy.

A simple method is described for the rapid assessment of respiratory heart-rate variation (HRV) by making use of an EMG machine to record the RR-interval of the electrocardiogram. The built-in software for single-fibre EMG usually incorporated in modern EMG equipment is sufficient for a rapid data analysis based on the difference between the shortest and longest RR-intervals recorded over a period of 60 to 100 s. Measurements of HRV obtained by our new method correlate well with those obtained by the more tedious conventional manual measurement of an ECG recording (r = 0.88).

Adolescent↗