PubMed · 7098270
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Iu Iu Bredikis, A D Drogaĭtsev. 1982. [Controlled permanent electrocardiostimulation].. https://pubmed.ncbi.nlm.nih.gov/7098270/
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The photosynthetic reaction center is one of the most complicated molecular complexes. Transducing photon energy to a transmembrane electrochemical potential difference for protons, it is the direct or indirect energy source for virtually all life. We show here that it operates in a simple, battery-like manner, with a maximum potential of 0.20 V. Intriguingly this is only one fifth of the energy of the absorbed photon.
Electrical stimulation of human upper limb muscle tendons produces a reflex inhibition (I(1)) in the same muscles. This inhibition is reduced in Parkinson's disease (PD), prompting a similar study of essential tremor (ET). In essential tremor, two of eight subjects had no discernible inhibition, even following supramaximal stimulation (< 80 mA) of the tendons from extensor digitorum communis and extensor pollicis brevis. In the remaining six subjects, the mean thresholds for I(1) in these muscles were increased by 270 and 320%, respectively, relative to controls. The maximal amplitude of the inhibition was significantly reduced in the ET group, as was the following excitation (E(1)). The latency and duration of I(1) were not different in ET subjects and controls. The maximal duration of I(1) was correlated with tremor frequency in individuals, and tendon stimulation was effective in initiating ongoing tremor cycles. These results disclose a peripheral reflex abnormality in ET that is mediated by tendon afferents and can be linked to the coexistent tremor. The response in ET was distinguished from that in PD by its different time-course and by failure of the response to appear in the antagonist muscle. The abnormality may prove a useful marker for ET, which currently lacks a definitive pathological or neurophysiological marker to support objective clinical diagnosis.
F-wave generation, axon conduction velocities, and contractile properties were compared in 44 healthy individual human thenar motor units. Force and muscle action potentials were recorded when single motor axons were stimulated intraneurally about 10 cm proximal to the elbow. Each stimulus usually evoked only one electromyographic (EMG) potential. However, in seven units (16%), a single stimulus elicited an F wave in response to 1.7 +/- 1.6% (mean +/- SD) of the stimuli applied. Axon conduction velocity proximal to the site of stimulation was faster than distal conduction velocity (72.7 +/- 8.0 m/s versus 64.2 +/- 10.5 m/s). Distal conduction velocities, twitch forces, and contraction times were similar for units that did and did not generate F waves. Thus, no obvious subset of thenar motor units generated F waves. These results provide valuable baseline information on F waves that can be used to assess changes in axon conduction, motor unit contractile properties, and motoneuron excitability in disease.