Changes in regional energy metabolism after closed head injury in the rat.

We examined in the present investigation regional ATP, glucose, and lactate content in the cortical and subcortical structures, in a rat model of closed head injury (CHI). In serial tissue sections bioluminescence imaging of ATP, glucose, and lactate was performed at 4 h, 12 h and 24 h (n = 4/5 per time point with) after the induction of CHI or sham surgery. Bioluminescence images were analyzed by computer-assisted densitometry, at the lesion site, in remote cortical areas, and in the subcortical structures (thalamus and caudate nucleus). ATP content was significantly decreased at the lesion site after 4 h and in the remote cortex at 12 h post-injury. At 12 h, the ATP content reached baseline levels on the ipsilateral side and at 24 h also at remote lateral parietal sites. In the contralateral cortex, ATP increased transiently above the baseline at 12 h. No significant changes in ATP were found in the thalamus and caudate nucleus. Cortical glucose and lactate contents could not be discerned over time. Following CHI there is an acute and progressive, yet transient, ischemic cortical profile, which is not reflected in subcortical areas.

Changes in ornithine decarboxylase activity and putrescine concentrations after spinal cord compression injury in the rat.

Traumatic spinal cord injury results in direct physical damage to structures and the generation of local factors contributing to secondary pathogenesis. In the present study, we investigated changes in polyamine metabolism after spinal cord compression injury in the rat. This is a stress induced metabolic pathway, of which an activation may indicate both, secondary pathogenesis or induction of neuroprotective response. Ornithine decarboxylase (ODC) activity, the rate limiting step of polyamine synthesis, and levels of the diamine putrescine, the product of ornithine decarboxylase reaction, were analyzed in control (non-laminectomized) animals and at 2 and 4 h after laminectomy or compression injury at the L4 segmental level. ODC activity was significantly increased 4 h after laminectomy in L4 and in adjacent L3 and L5 segments and compression to L4 produced a further increase 4 h after injury as compared with the intact control group. Putrescine levels were likewise significantly elevated to the same extend in the laminectomized and injured cord as compared with the intact control group. These findings demonstrate increased ODC and putrescine levels in the laminectomized and traumatized spinal cord and suggest that laminectomy may be an important 'priming event' that contributes to secondary injury after spinal cord compression injury.

Ultrastructural characteristics of glutamatergic and GABAergic terminals in cat lamina IX before and after spinal cord injury.

The present study was designed to: 1) morphologically characterize cat glutamate and GABAergic synaptic terminals in lamina IX in the intact spinal cord at the electron microscopic level using postembedding immunochemical techniques and .2), begin an analysis of how the synaptic architecture of glutamate and GABAergic terminals changes after an ipsilateral spinal cord hemisection. The present study shows that glutamate immunoreactive terminals are characterized by a wide synaptic cleft, asymmetric synaptic membrane densities and spherical synaptic vesicles. Most of the glutamatergic terminals are presynaptic to small or medium size dendrites. In contrast, GABAergic terminals display typical pleomorphic synaptic vesicles, a narrow synaptic cleft and a symmetrical membrane density. Qualitative analysis indicated that 13-17 months after hemisection, the length of the synaptic active zones in both glutamatergic and GABAergic terminals ipsilateral to hemisection is longer than those observed in the terminals contralateral to hemisection orfin normal control cats. Furthermore, the perimeters of both dendrites and either glutamate or GABA immunoreactive terminals are longer on the hemisected side compared with those observed in the nonhemisected side of the spinal cord. The results are important for complete understanding of the mechanisms which underlie locomotor recovery in mammals following spinal cord injury.

B-50 (GAP-43) in the spinal cord caudal to hemisection: indication for lack of intraspinal sprouting in dorsal root axons.

Sprouting of dorsal root axons has been suggested to occur in the mature cat spinal cord caudal to a hemisection at a low thoracic level sparing the dorsal columns. The lesion interrupts supraspinal descending projections, while leaving ascending collaterals of dorsal root axons intact. This hypothesis was re-evaluated by comparing the light and electron microscopic immunoreactivity of B-50 (GAP-43) on both sides of the postulated target regions for sprouting, the intermediate gray and the dorsal horn. The neural-specific phosphoprotein B-50 is involved in regenerative and developmental axonal outgrowth and synaptic plasticity. The light microscopic distribution pattern and density of B-50 immunostaining, measured by quantitative densitometry, were bilaterally symmetrical in all segments below the hemisection 3.5, 8, 14, 21, and 56 days postoperatively, as they were in the intact animal. Ultrastructurally, growth cone-like profiles were not detectable during putative periods of sprouting in regions of interest. After removal of degenerated axon terminals, vacated postsynaptic places appeared to be covered by astrocytic processes. These results indicate that, under the present experimental conditions, sprouting of primary afferents in adult cats is unlikely to be involved in functional plasticity after removal of descending pathways.

B-50 (GAP-43) in Onuf's nucleus of the adult cat.

The nucleus of Onuf in the sacral spinal cord contains motoneurons that innervate the pelvic floor muscles and possess somatic and autonomic characteristics. We show in this study that in the intact adult cat, the immunocytochemical labelling of the nervous tissue-specific growth-associated protein, B-50 (GAP-43), which persists in Onuf's nucleus, differs markedly from that in the remaining 'purely somatic' motor nuclei of the sacral spinal cord. At the light microscopic level, an intense B-50 (GAP-43) immunoreactivity (B-50-IR) in the neuropil of Onuf's nucleus contrasts with a faint staining in the other spinal motor nuclei. Ultrastructurally, B-50-IR is found in Onuf's nucleus within some unmyelinated small diameter nerve fibres and numerous axon terminals on dendritic and somatic surfaces. Conversely, in all other motor nuclei only a few of these structures are stained. No other cellular profiles show B-50-IR in the tissue examined. According to the proposed functions of B-50 (GAP-43), its persistence in mature spinal axon terminals may indicate a latent capability of functional and structural remodeling, as well as an involvement in long-term enhancement in synaptic transmission. If so, these properties would be considerably more pronounced in Onuf's nucleus as compared to purely somatic motor nuclei.

Immunocytochemistry of B-50 (GAP-43) in the spinal cord and in dorsal root ganglia of the adult cat.

The distribution of the neural-specific growth associated protein B-50 (GAP-43), which persists in the mature spinal cord and dorsal root ganglia, has been studied by light and electron microscopic immunohistochemistry in the cat. Throughout the spinal cord, B-50 immunoreactivity was seen confined to the neuropil, whereas neuronal cell bodies were unreactive. The most conspicuous immunostaining was observed in the dorsal horn, where it gradually decreased from superficial laminae (I-II) toward more ventral laminae (III-V), and in the central portion of the intermediate gray (mainly lamina X). In these regions, the labelling was localized within unmyelinated, small diameter nerve fibres and axon terminals. In the rest of the intermediate zone (laminae VI-VIII), B-50 immunoreactivity was virtually absent. The intermediolateral nucleus in the thoracic and cranial lumbar cord showed a circumscribed intense B-50 immunoreactivity brought about by the labelling of many axon terminals on preganglionic sympathetic neurons. In motor nuclei of the ventral horn (lamina IX), low levels of B-50 immunoreactivity were present in a few axon terminals on dendritic and somal profiles of motoneurons. In dorsal root ganglia, B-50 immunoreactivity was mainly localized in the cell bodies of small and medium-sized sensory neurons. The selective distribution of persisting B-50 immunoreactivity in the mature cat throughout sensory, motor, and autonomic areas of the spinal cord and in dorsal root ganglia suggests that B-50-positive systems retain in adult life the capacity for structural and functional plasticity.

Cytochemistry of 5'-nucleotidase in the superior cervical ganglion of cat and guinea pig.

The localization of 5'-nucleotidase, an adenosine-producing ectoenzyme, was studied by a cytochemical method in the superior cervical ganglion of the adult cat and guinea pig. The following subcellular sites of enzymatic activity were detected: (1) the surface of Schwann and satellite cells including the extracellular space between these cells and neuronal profiles; (2) the plasmalemma and pinocytotic vesicles of capillary endothelial cells; and (3) the synaptic clefts between cholinergic preganglionic axon terminals and sympathetic neurons. The simultaneous presence of 5'-nucleotidase at both glial elements and synapses within the adult peripheral nervous system (PNS) constitutes a novel distribution pattern for this enzyme which does not apply to the mature central nervous system (CNS), but which is rather typical for the developing CNS. These distributions of 5'-nucleotidase activity may reflect specific cellular requirements for nucleosides involved in parenchymal metabolism, in vascular transport processes and, possibly, in synaptic plasticity.

Age-dependent changes of short-latency somatosensory evoked potentials in healthy adults.

Age-dependent changes of short-latency somatosensory evoked potentials following median nerve stimulation in humans were investigated in two groups of healthy adults aged 20-30 and 50-60 years. Normative values for both age groups are given. Compared to the younger group, in the older one P27 latency and N20-P27 interpeak latency were about 2 ms longer, and P27-N35 and P27-P45 interpeak latencies were significantly decreased. These findings suggest that N20 and P27 are generated by different structures and that the subsequent components do not depend on P27.

Structural alterations in the spinal cord during progressive communicating syringomyelia. An experimental study in the cat.

A hydrocephalic-hydromyelic condition was induced in adult cats by causing the closure of the lateral apertures with intracisternal injections of kaolin. After displaying the symptoms characteristic of increased intracranial pressure, which lasted about 10-14 days but varied somewhat in intensity from animal to animal, the cats recovered. From approximately the 2nd post-operative week onward, a distended central canal was revealed by ventriculography; subsequently cavities developed in the tissue of the cord that communicated with the canal. Most cavities were located dorsal to the canal. The surfaces of the distended canal and the cavities showed that in ventral areas the ependyma streched but remained intact, whereas in dorsal areas it ruptured, exposing the nerve fibers to the cerebrospinal fluid (CSF). In cats which had been hydrocephalic for up to 2 years the walls of the cavities were covered by gliotic scar tissue; the nerve fibers were no longer exposed directly to the CSF.

Acute effects of dexamethasone on normal and on posttraumatic spinal cord polysynaptic reflex activity and axonal conduction.

The effects of a single intravenous injection of a high dose of dexamethasone (4 mg/kg) on polysynaptic reflex activity and axonal conduction were measured for 5 hours in the intact and in the compression-injured L-7 spinal cord segment of high spinal cats. The segment was injured by a transient compression of preset degree and duration. In the uninjured preparation, dexamethasone administration significantly reduced polysynaptic reflex size for 2 hours. Axonal conduction was unaltered. One group of injured animals was given dexamethasone 30 minutes after trauma, whereas another was not treated. The acute posttraumatic changes in both parameters did not differ significantly in treated and untreated animals. Histopathologically, differences in the amount of segmental edema and hemorrhage between untreated and treated animals were not significant.

Increased functional vulnerability to acute compression injury of a spinal cord segment under barbiturate anesthesia.

Posttraumatic changes in polysynaptic reflex activity and axonal long-tract conduction were measured after transient compression of the L-7 spinal cord segment of cats, either made high spinal and unanesthetized or left intact under pentobarbital anesthesia. The severity of acute post-injury changes increased significantly in the anesthetized animals. Partial recovery and stabilization of functional deficits were observed in the spinal cat, but not in the anesthetized one. These findings suggest that, at least in the acute postinjury stage, pentobarbital anesthesia may enhance functional damages after experimental spinal cord compression.

Acute changes in somatosensory evoked potentials following graded experimental spinal cord compression.

Amplitude and latency of cortical somatosensory potentials evoked in cats by peripheral nerve stimulation were measured before, during, and for 5 hours after injury of spinal cord segment L-7 by a predetermined degree and duration of compression. An amplitude decrease, slight and transitory, was first observed after compression reduced the segmental cross section by 60%. After an 80% compression, amplitude reduction was initially larger and lasted longer, but recovered 2.5 hours after injury to a level that did not differ statistically from control values. After total (100%) compression, evoked responses disappeared abruptly and did not recover significantly. Latency was unaltered at all degrees of compression. Structural damage increased with the degree of compression. In this model, evoked potential changes neither reflect nor predict the magnitude of acute incomplete spinal cord injury.

Reflex activity and axonal conduction in the L-7 spinal cord segment following experimental compression trauma.

In cats in which the spinal cord was transected at C-1, the exposed L-7 spinal cord segment was compressed with an electromagnetically driven rod applied to the dorsal surface of the segment. With the magnitude of compression constant at 3 mm, the cord was compressed for durations of 50 msec, 0.5 sec, or 1.0 sec. Polysynaptic reflex discharges integrated in the injured segment and action potentials conducted in dorsal column axons traversing the same region were electrophysiologically measured before, during, and for 41/2 hours after trauma. Structural changes were evaluated on frozen serial sections obtained both from compressed segments and from tissue adjacent to the injury. At a compression duration of 50 msec, the amplitude of evoked reflex activity decreased abruptly, and dorsal column axonal conduction was blocked for 1 minute following compression. This early-phase response was followed by partial recovery of both functions which persisted until the end of the experiment. Prolonging compression to 0.5 sec brought about a further decrease of polysynaptic reflex activity. Axonal conduction was also decreased, but not significantly. With compression lasting 1.0 sec, no significant changes in reflex discharges and axonal conduction occurred compared with those measured at 0.5 sec. Neither function was abolished, even after the longest compression time. Prolongation of compression significantly increased both the intensity and the spread of edema, whereas changes in hemorrhage were not significant. Thus, a plateau rather than a progressive increase in severity of functional and structural posttraumatic changes was reached by increasing the duration of compression. This injury model reduces the sources of variability found in other experimental compression trauma models and permits the quantitative assessment of basic spinal cord mechanisms and correlated histopathological changes in the same preparation following trauma.

The ependyma of the cat central canal, with particular reference to its mitochondria-containing bulbs.

The ultrastructure of the ependyma in the central canal of adult cats was examined in both the scanning and the transmission electron microscopes (SEM and TEM). The same morphological details were seen in the ependyma of the central canal as have so frequently been described in the ependyma of the brain ventricular system, for example bundles of cilia, single cilia, microvilli and occasional small cytoplasmic protrusions. The supraependymal cells and supraependymal nerve fibers found in the central canal also resembled those seen in the ventricular system. The most striking feature of the canal ependyma were the large, spherical bodies containing numerous mitochondria. They are therefore called mitochondria-containing bulbs. In sections the bulbs were seen to be connected by long, slender stalks to neurons in subependymal position. In some respects the mitochondria-containing bulbs resemble the processes of cerebrospinal fluid-contacting neurons.