Repairing the injured spinal cord

Certain cell, molecular, and bioengineering strategies for repairing the injured spinal cord are showing encouraging results (either alone or in combination) in animal models, with limited recovery of mobility being reported in some cases.     

Induction of a neuronal proteoglycan by the NMDA receptor in the developing spinal cord

Activation of the N-methyl-D-aspartate (NMDA) subclass of glutamate receptors is a critical step in the selection of appropriate synaptic connections in the developing visual systems of cat and frog. Activity-dependent development of mammalian motor neurons was shown to be similarly mediated by activation of the NMDA receptor. The expression of the Cat-301 proteoglycan on motor neurons was developmentally regulated and could be specifically inhibited by blockade of the NMDA receptor at the spinal segmental level. In the adult, Cat-301 immunoreactivity on motor neurons was not diminished by NMDA receptor blockade. The NMDA receptor may regulate the expression of a class of neuronal proteins (of which Cat-301 is one example) that underlie the morphological and physiological features of activity-dependent development.     

Sympathetic outflows from cervical spinal cord in the dog

In some dogs there are preganglionic fibers leaving the cervical spinal cord through the ventral roots of the lower cervical nerves. When these fibers are stimulated electrically in the anesthetized dog with skeletal muscle paralysis (induced by decamethonium), the effects are vasoconstriction in the front footpad, cardiac acceleration and augmentation, and a rise in arterial blood pressure.     

C-fiber responses in the ventrolateral column of the cat spinal cord

Saphenous nerve C-fiber volleys generate, in the ventrolateral column of the cat spinal cord, a conducted postsynaptic response revealed by averaging the integrated temporally dispersed axonal discharges. This finding is compatible with the hypothesis that the feline ventrolateral column includes a major pathway related to nociception.     

颈部脊髓硬膜外电刺激治疗脑性瘫痪的临床观察

目的：观察颈部脊髓硬膜外电刺激治疗脑性瘫痪的临床疗效。方法：采用C2--C5脊髓硬膜外电刺激治疗脑性瘫痪病人18例，具体参数为：频率25—100ppm，强度3—15V，波宽0．3--0．4ms，时间6h／d。结果：18例病人中15例有效。结论：颈部脊髓硬膜外电刺激是一种治疗脑性瘫痪病人有效方法。     

5-Hydroxyindoleacetic acid in the lumbar fluid: a specific indicator of spinal cord injury

In cats, 19 days after the lower thoracic cord was injllred, the concentrations of 5-hydroxytryptamine and its metabolite 5-hydroxyindoleacetic acid in the lumbosacral cord and that of 5-hydroxyindoleacetic acid in the lumbar fluid decreased. At the same time the concentrations of these substances in the cord above the lesion and that of 5-hydroxyindoleacetic acid in the cisternal fluid was not significantly altered. Since high concentrations of 5-hydroxytryptamine and 5-hydroxyindoleacetic acid are present in the human lumbosacral cord, it appears that the concentration of 5-hydroxyincdoleacetic acid in the lumbar fluid of animals and man reflects the biochemical changes of 5-hydroxytryptamine in the spinal cord.     

Somatovisceral pathway: rapidly conducting fibers in the spinal cord

Fibers that respond to distension of hollow viscera and to mechanical stimulation of somatic structures were found primarily near the ventromedian fissure of the upper lumbar spinal cord. These fibers could be directly excited by electrical stimulation at C(1). The average conduction velocity for these fibers was 68.6 meters per second.     

Glycine in the spinal cord of cats with local tetanus rigidity

In cats, significant loss of glycine occurred in spinal grey matter on the side of local tetanus, whereas the gamma-aminobutyric acid concentration remained unaltered. These findings suggest that tetanus rigidity is due to the blocking of the spinal inhibitory transmission by decrease of inhibitory transmitter and that glycine is an effective inhibitory transmitter in cat spinal cord.     

山羊胚胎脊髓灰质的发育

对山羊胚胎脊髓灰质形成和发育的形态学变化进行了系统研究。结果表明 :山羊脊髓神经管闭合以后 ,其组织发生持续近 2 0 d才形成完整的 3层同心圆结构 ;山羊脊髓神经管的组织发生和脊髓灰质的形成在时间上有很大程度的重叠性 ;脊髓灰质各结构形成和发育的规律也不完全一致 ,有些结构发生早 ,而神经元分化较晚 ,如侧角、胶状质 ;有些结构发生虽然晚 ,但其中的神经元胞体分化和发育则较早 ,如 Clarke氏背核 ;有些结构发生早 ,神经元发育也早 ,如腹角运动神经元。     

Bioelectric activity in long-term cultures of spinal cord tissues

Fragments of embryonic spinal cord (human, rat, and chick) can regenerate and differentiate in tissue culture. Complex bioelectric activity evoked by electric stimuli indicates that nerve cells in cultures may maintain, for months in vitro, not only the capacity to propagate impulses along their neurites but also a remarkable degree of functional organization resembling the activity of synaptic networks of the central nervous system.     

Gamma-aminobutyric acid antagonism and presynaptic inhibition in the frog spinal cord

The convulsant alkaloid bicuculline blocked presynaptic inhibition, dorsal root potentials, primary afferent depolarization, and depolarizing effects of gamma-aminobutyric acid on dorsal root terminals of the amphibian spinal cord, but did not block effects of other putative amino acid transmitters. These actions of bicuculline suggest that gamma-aminobutyric acid may be the transmitter involved in spinal presynaptic inhibition.     

Gallamine (Flaxedil) and synaptic transmission in the spinal cord

A paralyzing dose of gallamine (Flaxedil) (1 to 2 milligrams per kilogram of body weight) has no effect on synaptic transmission in the cat's spinal cord. In spinal cats ventilated with oxygen, we stimulated a dorsal spinal root and recorded the compound ventral root potential. The reflex potential was not affected by 6.25 milligrams of gallamine per kilogram. Giving 12.5 milligrams of gallamine per kilogram had no significant effect on the monosynaptic spike height, but the polysynaptic response rose briefly to 12 percent above control. Increased magnitude of the polysynaptic response appeared related to a concomitant rise in blood pressure.     

Functional restoration of the traumatically injured spinal cord in cats by clonidine

The long-term, chronic, paralysis resulting from spinal cord injury in the cat has been reversed by the use of an alpha 2-adrenergic receptor agonist, clonidine. Administration of this drug resulted in "normalization" of sensory-motor and autonomic dysfunctions. Preliminary studies of the clonidine in humans with traumatically injured spinal cord indicate that autonomic dysreflexia can be controlled and spasticity minimized. The data suggest that biochemical and pharmacologic manipulation of receptors may ameliorate paralysis following traumatic injury to the spinal cord as well as to the brain and brainstem.     

Collagen synthesis in vitro by embryonic spinal cord epithelium

Isolated spinal cords from chick embryos (stages 12 to 15) were incubated in vitro with radioactive proline. The proteins synthesized were fractionated by coprecipitation with added carrier collagen, followed by molecularsieve and ion-exchange chromatography. A portion of the isotopically labeled proteins were found to be collagen molecules consisting only of alpha1 chains.     

A pericyte origin of spinal cord scar tissue

There is limited regeneration of lost tissue after central nervous system injury, and the lesion is sealed with a scar. The role of the scar, which often is referred to as the glial scar because of its abundance of astrocytes, is complex and has been discussed for more than a century. Here we show that a specific pericyte subtype gives rise to scar-forming stromal cells, which outnumber astrocytes, in the injured spinal cord. Blocking the generation of progeny by this pericyte subtype results in failure to seal the injured tissue. The formation of connective tissue is common to many injuries and pathologies, and here we demonstrate a cellular origin of fibrosis.     

Histochemical and functional correlations in anterior horn neurons of the cat spinal cord

The histochemical reaction for phosphorylase is completely lost from anterior horn neurons rich in phosphorylase within 72 hours after proximal or distal axonal section. Using this new type of axonal reaction as a marking technique in the anterior horn of the seventh lumbar spinal cord segment of the cat, we demonstrated that (i) alpha motor neurons of slow twitch motor units, like those of fast twitch motor units, are rich in phosphorylase and poor in succinate dehydrogenase, and (ii) interneurons and Renshaw neurons are rich in succinate dehydrogenase and poor in phosphorylase. Gamma motor neurons, because of their small size, are considered to be rich in succinate dehydrogenase and poor in phosphorylase. Thus, anterior horn neurons capable of higher firing frequencies (Renshaw neurons, interneurons, and gamma motor neurons) are richer in mitochondrial oxidative enzyme activity as marked by succinate dehydrogenase. Those firing at lower frequencies (both types of alpha motor neurons) are richer in phosphorylase activity and glycogen content and, thus, apparently better equipped for anaerobic glycolysis.     

Regeneration of functional synapses between individual recognizable neurons in the lamprey spinal cord

In 4- to 5-year-old sea lamprey larvae that had recovered from complete transection of the spinal cord, pairs of giant interneurons on opposite sides of the scar were impaled with microelectrodes. In 4 of 30 pairs, stimulation of the caudal cell elicited a monosynaptic electrochemical excitatory postsynaptic potential in the rostral cell. Fifty percent of such pairs were synaptically linked in control lampreys without transections. These results show regeneration of functional synaptic connections between individual neurons in a vertebrate central nervous system.     

From swimming to walking with a salamander robot driven by a spinal cord model

The transition from aquatic to terrestrial locomotion was a key development in vertebrate evolution. We present a spinal cord model and its implementation in an amphibious salamander robot that demonstrates how a primitive neural circuit for swimming can be extended by phylogenetically more recent limb oscillatory centers to explain the ability of salamanders to switch between swimming and walking. The model suggests neural mechanisms for modulation of velocity, direction, and type of gait that are relevant for all tetrapods. It predicts that limb oscillatory centers have lower intrinsic frequencies than body oscillatory centers, and we present biological data supporting this.     

Sensory and motor functions of spinal cord substance P

Low doses of D-Pro2-D-Phe7-D-Trp9-substance P, as specific substance P antagonist, depressed the scratching and biting behaviors elicited by intrathecal injections of substance P, and cutaneous application of algesic substances. Higher antagonist doses caused hindlimb paralysis. This suggests that substance P is a neurotransmitter for primary nociceptor afferents and may also have an important function in motor control.