Single-motor-unit and gross electromyograms (EMG) were recorded from the soleus muscle in six unrestrained rats. The median firing frequencies of nine motor units were in the 16-25 Hz range, in agreement with previous studies. One additional motor unit had a median firing frequency of 47 Hz. This unit and one of the lower-frequency units regularly fired doublets. Motor-unit firing frequency was...

Rabbits and rhesus monkeys were injected with 3 X 10(5) units of human gamma interferon (IFN) prepared in human leukocyte suspensions. Circulating IFN was detected up to 4 h after intravenous administration. Intramuscular injection maintained a relatively stable serum IFN level of about 50 units/ml for 7 to 9 h. The results in both species were similar. Little or no circulating IFN was detected...

Proteins are complex adaptive systems. Their functional and structural units, termed domains, are conserved and recombined during evolution. Domains are thermodynamically stable and fold independently within the context of the whole protein, and can arguably be seen as stable units of evolution. New domain functions evolve within the constraints of maintaining thermodynamic stability and autono...

The use of chronic intracortical multielectrode arrays has become increasingly prevalent in neurophysiological experiments. However, it is not obvious whether neuronal signals obtained over multiple recording sessions come from the same or different neurons. Here, we develop a criterion to assess single-unit stability by measuring the similarity of 1) average spike waveforms and 2) interspike i...

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...

Two delayed coupled excitable systems with internal delays are studied. For different parametric values each of the isolated units displays excitable, bi-stable or oscillatory dynamics. Bifurcational relations among coupling time-lag and coupling constant for different values of the internal time-lags are obtained. Possible types of synchronization between the units in typical dynamical regimes...