Callosal transfer of impulses originating from superficial and deep nerves of the cat forelimb

1. Experiments were performed in 18 chloralose-anaesthetized, curarized cats in order to study the callosal transfer of somatic information originated in exteroceptive and proprioceptive receptors. Several cutaneous and deep nerves of the forelimb were prepared and stimulated with graded intensities, so as to activate selectively afferent fibres pertaining to the different groups of Lloyd's classification. Simultaneous records were taken (and averaged on-line by means of a multichannel analyzer) from the distal end of a cut dorsal rootlet (C7-C8), from the cerebral cortex (SI, SII or area 3a, according to the experiment) and from the somesthetic callosal region (SCR). 2. The low-threshold afferent fibres (Group II) of cutaneous origin were found to have a wide projection to the SCR, with the maximal density in its middle portion. Some of the fastest corticocallosal impulses are relayed monosynaptically at cortical level. Plots of the amplitude of cortical and callosal responses as a function of stimulus strength showed that both central responses have the same threshold and exhibit a parallel, sharply-rising amplitude increase, thus suggesting that the cortico-callosal re-transmission system for afferent impulses of cutaneous origin is very powerful in nature. Impulses elicited in afferent fibres of higher threshold (Group III) do not enhance the cortical and callosal positive waves provoked by Group II afferent volleys. 3. Afferent fibres of deep origin were also found to send a wide projection to the SCR, although less substantial than that of cutaneous fibres. Stimulation of the deep radial nerve elicited mass responses in the whole SCR, provided the strength of stimuli was high enough to engage the Group II fibres. Only in the central portion of the SCR were small potentials recorded in response to pure Group I volleys of DRN. Experiments performed with selective stimulation of pure muscular branches of forelimb deep nerves as well as of articular and mixed (muscular and articular) branches gave evidence making it possible to ascertain the origin of deep afferent fibres projecting to the SCR. Stimulation of the forelimb muscular branches with strength provoking full activation of Group I afferent and additional engagement of those of Group II, did not provoke mass responses in the whole extent of the SCR. In order to obtain callosal potentials upon stimulation of pure muscular nerves, it was necessary to increase the stimulus strength at or above the threshold for Group III fibres. On the contrary, the same callosal foci unresponsive to Group I and II muscular afferent volleys exhibited clear-cut responses to stimulation of the lowest-threshold Group I and/or Group II afferents of articular and mixed nerves. From the results it might be inferred that only proprioceptive information originating from articular receptors and from extrafusal muscular afferents has access to the callosal interhemispheric transfer.

[Surgical treatment of cardiospasm]

Results obtained with Heller's operation in the management of 27 cases of cardiospasm are presented. The probable causes of oesophageal achalasia leading to dilatation and elongation of the wall are examined. These, in association with nervous changes, form the most marked features of the syndrome. The soundness of the operation employed is confirmed by the results achieved. These are most satisfactory when the disease is at the initial stages and dilatation is not excessive.

[Our experience with peripheral arterial embolectomy]

34 cases of acute peripheral ischaemia examined in recent years at the University of Messina General Surgery Clinic are presented. 16 were subjected to embolectomy according to Fogarty. The remaining 18 received protracted medical therapy. Some successes were obtained. In other cases, gangrene necessitated amputation of the affected limb. Satisfactory results were observed in 70% of the operated series. Success was more marked when only a short interval was left between the embolic episode, with progressively poorer results as the penalty for delay. The long-term results of embolectomy are related to the nature of the underlying disease and the treatment given after surgery.