Complete transection of the midthoracic spinal cord was performed on adult female dogs. Development of reflexes and locomotive movements in the hindlimbs after spinal transection was investigated over several months. In the earlier stages after the surgery, dogs showed flaccid paralysis of the hindlimbs. Within several weeks, muscle tone of the hindlimbs was gradually increased accompanied by development of flexion reflex with after-discharge in addition to monosynaptic reflexes. Alternating stepping movement also began to develop. Afterward, extensor thrust and crossed extension reflex were observed. Standing behavior of the hindlimbs was found after enough development of the extensor thrust and correct placement of the pads of the toes. Steady development of stepping and standing caused forward locomotion using fore-and hindlimbs. This walking behavior of the hindlimbs was never inhibited by additional spinal cord transection. These findings indicate that the isolated spinal cord caudal to the transected site is responsible for the locomotive behavior of the hindlimbs in adult spinal dogs. Spinal automatism and development of responses induced by afferent inflow from outside the cord may help to explain such functional recovery of the paralyzed hindlimbs.

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The G protein-coupled inward rectifier K + channel (GIRK) is activated by direct interaction with the heterotrimeric GTP-binding protein L LQ Q subunits (GL LQ Q). However, the precise role of GL L and GQ Q in GIRK activation remains to be elucidated. Using transient expression of GIRK1, GIRK2, GL L1, and GQ Q2 in human embryonic kidney 293 cells, we show that C-terminal mutants of GL L1, which do not bind to GQ Q2, are still able to associate with GIRK, but these mutants are unable to induce activation of GIRK channels. In contrast, other C-terminal mutants of GL L1 that bind to GQ Q2, are capable of activating the GIRK channel. These results suggest that GQ Q plays a more important role than that of an anchoring device for the GL LQ Qinduced GIRK activation.z 1999 Federation of European Biochemical Societies.

Perikaryal myelin sheaths on statoacoustic ganglion cells in 3-day-old chicks were studied by electron microscopy. The fixation method with a high-concentrated warm fixative helped in successful demonstrations of perikaryal myelin structures. The sheaths were composed of loose and compact myelin mixed by various arrangements. Twenty-seven percent of perikarya were entirely encircled by compact myelin, 71% were partly wrapped by compact myelin, and 2% were wrapped by just loose myelin. The perikaryal myelin was composed of 3 to 16 layers of loose and compact lamellae, whereas the axonal myelin of 10 to 28 of compact lamellae. Since no unmyelinated perikarya, which are covered by a single layer of Schwann cell cytoplasm, were detected, it is suggested that the perikarya myelination on all the ganglion cells has started before 3 days after hatching.

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