scholarly journals Glycogen depletion elicited in tenuissimus intrafusal muscle fibres by stimulation of static gamma-axons in the cat.

1984 ◽  
Vol 346 (1) ◽  
pp. 341-352 ◽  
Author(s):  
L Decorte ◽  
F Emonet-Dénand ◽  
D W Harker ◽  
L Jami ◽  
Y Laporte

It was shown in an earlier paper (7) that if maximal stimulation of either of two different afferent nerves can reflexly excite fractions of a given flexor muscle, there are generally, within the aggregate of neurones which innervate that muscle, motoneurones which can be caused to discharge by either afferent (i. e., motoneurones common to both fractions). The relationship which two such afferents bear to a common motoneurone was shown, by the isometric method of recording contraction, to be such that the activation of one afferent, at a speed sufficient to cause a maximal motor tetanus when trans­mitted to the muscle fibres, caused exclusion of any added mechanical effect when the other afferent was excited concurrently. This default in mechanical effect was called “occlusion.” Occlusion may conceivably be due to total exclusion of the effect of one afferent pathway on the common motoneurone by the activity of the other; but facilitation of the effect of one path by the activation of the other when the stimuli were minimal suggests that, in some circumstances at least, the effect of each could augment and summate with th at of the other at the place of convergence of two afferent pathways. Further investigation, using the action currents of the muscle as indication of the nerve impulses discharged by the motoneurone units, has now given some information regarding the effect of impulses arriving at the locus of convergence by one afferent path when the unit common to both is already discharging in response to impulses arriving by the other afferent path. Our method has been to excite both afferent nerves in overlapping sequence by series of break shocks at a rapid rate and to examine the action currents of the resulting reflex for evidence of the appearance of the rhythm of the second series in the discharge caused by the first when the two series are both reaching the motoneurone.


In the study of the phenomena of anaphylaxis there are certain points on which some measure of agreement seems to have been attained. In the case of anaphylaxis to soluble proteins, with which alone we are directly concerned in this paper, the majority of investigators probably accept the view that the condition is due to the formation of an antibody of the precipitin type. Concerning the method, however, by which the presence of this antibody causes the specific sensitiveness, the means by which its interaction with the antibody produces the anaphylactic shock, there is a wide divergence of conception. Two main currents of speculation can be discerned. One view, historically rather the earlier, and first put forward by Besredka (1) attributes the anaphylactic condition to the location of the antibody in the body cells. There is not complete unanimity among adherents of this view as to the nature of the antibody concerned, or as to the class of cells containing it which are primarily affected in the anaphylactic shock. Besredka (2) himself has apparently not accepted the identification of the anaphylactic antibody with a precipitin, but regards it as belonging to a special class (sensibilisine). He also regards the cells of the central nervous system as those primarily involved in the anaphylactic shock in the guinea-pig. Others, including one of us (3), have found no adequate reason for rejecting the strong evidence in favour of the precipitin nature of the anaphylactic antibody, produced by Doerr and Russ (4), Weil (5), and others, and have accepted and confirmed the description of the rapid anaphylactic death in the guinea-pig as due to a direct stimulation of the plain-muscle fibres surrounding the bronchioles, causing valve-like obstruction of the lumen, and leading to asphyxia, with the characteristic fixed distension of the lungs, as first described by Auer and Lewis (6), and almost simultaneously by Biedl and Kraus (7). But the fundamental conception of anaphylaxis as due to cellular location of an antibody, and of the reaction as due to the union of antigen and antibody taking place in the protoplasm, is common to a number of workers who thus differ on details.


1989 ◽  
Vol 66 (1) ◽  
pp. 61-71 ◽  
Author(s):  
C. G. Hammond ◽  
D. C. Gordon ◽  
J. T. Fisher ◽  
F. J. Richmond

Recent studies have demonstrated that, under certain circumstances, the diaphragm does not contract as a homogeneous unit. These observations suggest that motor units may not be randomly distributed throughout the muscle but confined to localized subvolumes. In the present study, electromyographic (EMG) and glycogen depletion methods were combined to investigate the organization of motor units supplied by the primary branches of the phrenic nerve in the cat. Four primary branches are generally present, one branch to the crus and three branches to the sternocostal region. The gross motor-unit territory of each of the four phrenic primary branches was determined by stimulating each nerve separately, while recording from nine EMG electrodes distributed over the hemidiaphragm. Stimulation of the crural branch evoked activity in the ipsilateral crus, whereas stimulation of each of the remaining branches evoked activity in discrete but overlapping areas of the sternocostal diaphragm. A more precise analysis of the distribution and borders of the motor territories was obtained by mapping regions depleted of muscle glycogen due to stimulation of each primary branch for 90 min. Glycogen depletion results closely matched the EMG findings of a localized distribution of motor units served by single primary branches. Stimulation of the crural branch typically caused depletion of the ipsilateral crus, whereas the sternocostal branches each served a striplike compartment. In the majority of cases, the borders of the sternocostal compartments were relatively abrupt and consisted of a 1- to 2-mm transition zone of depleted and nondepleted fibers. These studies demonstrate that motor unit territories of the primary branches of the phrenic nerve are highly delineated. This compartmentalization provides the central nervous system with the potential for a more precise regional motor control of costal and crural diaphragm than previously suspected.


2003 ◽  
Vol 550 (1) ◽  
pp. 263-278 ◽  
Author(s):  
R. Durbaba ◽  
A. Taylor ◽  
P. H. Ellaway ◽  
S. Rawlinson

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