Neuronal apoptosis and necrosis following spinal cord ischemia in the rat

Delayed cell death signaling in traumatized central nervous system: hypoxia

There are two different ways for cells to die: necrosis and apoptosis. Cell death has traditionally been described as necrotic or apoptotic based on morphological criteria. There are controversy about the respective roles of apoptosis and necrosis in cell death resulting from trauma to the central nervous system (CNS). An evaluation of work published since 1997 in which electron microscopy was applied to ascertain the role of apoptosis and necrosis in: spinal cord injury, stroke, and hypoxia/ischemia (H/I) showed evidence for necrosis and apoptosis based on DNA degradation, presence of histones in cytoplasm, and morphological evidence in spinal cord. In the aftermath of stroke, many of the biochemical markers for apoptosis were present but the morphological determinations suggested that necrosis is the major source of post-traumatic cell death. This was not the case in H/I where both biochemical assays and the morphological studies gave more consistent results in a manner similar to the spinal cord injury studies. After H/I, major factors affecting cell death outcomes are DNA damage and repair processes, expression of bcl-like gene products and inflammation-triggered cytokine production.

Differential effects of ischemia and reperfusion on c-Jun N-terminal kinase isoform protein and activity

Activation of the c-Jun N-terminal (JNK) or stress-activated protein kinases (SAPK) is associated with a wide range of disparate cellular responses to extracellular stimuli, including either induction of or protection from apoptosis. This study investigates the effect of ischemia and reperfusion on JNK isoform activities using a reversible rabbit spinal cord ischemia model. High basal JNK activity, attributed to the p46 JNK1 isoform, was expressed in the CNS of untreated rabbits. JNK activity decreased in the lumbar spinal cord of rabbits occluded for 15-60 min. During reperfusion animals occluded for 15 min recovered neurological function and JNK activity returned to normal levels. In contrast animals occluded for 60 min remained permanently paraplegic and JNK activity was half the control activity after 18 h of reperfusion. In these animals proteolytic fragments of JNK1 and JNK3 were observed and protein levels, but not activity, of JNK isoforms increased in a detergent-insoluble fraction. Two novel c-Jun (and ATF-2) kinase activities increased during reperfusion of animals occluded for 60 min. An activity designated p46(slow) was similar in M(r) to a JNK2 isoform induced in these animals. A second 30-kDa activity associated with the detergent-insoluble fraction co-migrated with a JNK3 N-terminal fragment. The results show that JNK1 is active in the normal CNS and increased activity is not associated with durations of ischemia and reperfusion that induce cell death. However, specific JNK isoform activation may participate in the cell death pathways as increased activity of novel c-Jun (ATF-2) kinase activities was observed in paraplegic animals.

Fluororuby as a marker for detection of acute axonal injury in rat spinal cord

Axonal damage is a common pathological consequence of spinal cord injury. Previous studies have detected axonal injury with silver stains for degeneration or immunohistochemistry for alterations in components such as beta-amyloid precursor protein, neurofilament or ubiquitin. Fluororuby has recently been introduced as a neuronal tracer in studies of spinal cord injury and regeneration. Our study was carried out to determine whether Fluororuby can be used to identify injured axons and monitor the time course of axonal damage. Adult rats underwent needle puncture injury to the white matter in the midline and lateral spinal cord at T11. At the same time, 0.05 microl of Fluororuby was injected into the cord at the same sites. After survival times ranging from 6 h to 3 weeks, spinal cords were cut into longitudinal frozen sections and examined with confocal microscopy. Fluororuby was found to label key features of axonal injury including axonal swelling, retraction balls and disrupted axons. Damaged axons close to the injury site were consistently labeled within 6 h, with indications of swollen and disconnected axons spreading further from the site during the first week. Fewer injured axons were labeled after 1 week survival, but the marker revealed longer distances of degenerating axons both distal and rostral to the injury site. Our findings indicate that Fluororuby is a quick, sensitive, reliable and technically simple fluorescent marker for early stages of acute axonal injury and degeneration.

Temporal and spatial profile of caspase 8 expression and proteolysis after experimental traumatic brain injury

Recent studies have demonstrated that the downstream caspases, such as caspase 3, act as executors of the apoptotic cascade after traumatic brain injury (TBI) in vivo. However, little is known about the involvement of caspases in the initiation phase of apoptosis, and the interaction between these initiator caspases (e.g. caspase 8) and executor caspases after experimental brain injuries in vitro and in vivo. This study investigated the temporal expression and cell subtype distribution of procaspase 8 and cleaved caspase 8 p20 from 1 h to 14 days after cortical impact-induced TBI in rats. Caspase 8 messenger RNA levels, estimated by semiquantitaive RT-PCR, were elevated from 1 h to 72 h in the traumatized cortex. Western blotting revealed increased immunoreactivity for procaspase 8 and the proteolytically active subunit of caspase 8, p20, in the ipsilateral cortex from 6 to 72 h after injury, with a peak at 24 h after TBI. Similar to our previous studies, immunoreactivity for the p18 fragment of activated caspase 3 also increased in the current study from 6 to 72 h after TBI, but peaked at a later timepoint (48 h) as compared with proteolyzed caspase 8 p20. Immunohistologic examinations revealed increased expression of caspase 8 in neurons, astrocytes and oligodendrocytes. Assessment of DNA damage using TUNEL identified caspase 8- and caspase 3-immunopositive cells with apoptotic-like morphology in the cortex ipsilateral to the injury site, and immunohistochemical investigations of caspase 8 and activated caspase 3 revealed expression of both proteases in cortical layers 2-5 after TBI. Quantitative analysis revealed that the number of caspase 8 positive cells exceeds the number of caspase 3 expressing cells up to 24 h after impact injury. In contrast, no evidence of caspase 8 and caspase 3 activation was seen in the ipsilateral hippocampus, contralateral cortex and hippocampus up to 14 days after the impact. Our results provide the first evidence of caspase 8 activation after experimental TBI and suggest that this may occur in neurons, astrocytes and oligodendrocytes. Our findings also suggest a contributory role of caspase 8 activation to caspase 3 mediated apoptotic cell death after experimental TBI in vivo.

Electron microscopy of oligodendroglia in severe mental illness

Qualitative electron microscopy was performed to verify whether brain pathology in schizophrenia and bipolar disorder is associated with alterations of oligodendroglial cells and myelinated fibers. Ultrastructural signs of apoptosis and necrosis of oligodendroglial cells were found in the prefrontal area 10 and the caudate nucleus in both schizophrenia and bipolar disorder. Damage of myelin sheath lamellae, with the formation of concentric lamellar bodies, were detected in both brain structures in schizophrenia. There was also a significant decrease in the area of the nucleus and the volume density of mitochondria in oligodendrogliocytes in the caudate nucleus and in the prefrontal cortex in schizophrenia, as compared to normal controls. Volume density of heterochromatin was significantly increased (+14%) in the caudate nucleus in schizophrenia. The density of concentric lamellar bodies (as an indicator of damage of myelinated fibers) was dramatically increased (4.5-fold) in the caudate nucleus in schizophrenia, as compared to controls, and was positively correlated with volume density of heterochromatin. Multiple regression analysis and analysis of covariance demonstrated that these changes could not be explained by the effects of postmortem delay, age, neuroleptic medication, or gender. Pathology of oligodendroglia might be an essential feature of severe mental disorders.

Temporal-spatial pattern of acute neuronal and glial loss after spinal cord contusion

The secondary loss of neurons and glia over the first 24 h after spinal cord injury (SCI) contributes to the permanent functional deficits that are the unfortunate consequence of SCI. The progression of this acute secondary cell death in specific neuronal and glial populations has not previously been investigated in a quantitative manner. We used a well-characterized model of SCI to analyze the loss of ventral motoneurons (VMN) and ventral funicular astrocytes and oligodendrocytes at 15 min and 4, 8, and 24 h after an incomplete midthoracic contusion injury in the rat. We found that both the length of lesion and the length of spinal cord devoid of VMN increased in a time-dependent manner. The extent of VMN loss at specified distances rostral and caudal to the injury epicenter progressed symmetrically with time. Neuronal loss was accompanied by a loss of glial cells in ventral white matter that was significant at the epicenter by 4 h after injury. Oligodendrocyte loss followed the same temporal pattern as that of VMN while astrocyte loss was delayed. This information on the temporal-spatial pattern of cell loss can be used to investigate mechanisms involved in secondary injury of neurons and glia after SCI.

A new model for diffuse brain injury by rotational acceleration: II. Effects on extracellular glutamate, intracranial pressure, and neuronal apoptosis

The aim of this study is to monitor excitatory amino acids (EAAs) in the extracellular fluids of the brain and to characterize regional neuronal damage in a new experimental model for brain injury, in which rabbits were exposed to 180-260 krad/s2 rotational head acceleration. This loading causes extensive subarachnoid hemorrhage, focal tissue bleeding, reactive astrocytosis, and axonal damage. Animals were monitored for intracranial pressure (ICP) and for amino acids in the extracellular fluids. Immunohistochemistry was used to study expression of the gene c-Jun and apoptosis with the terminal deoxynucleotidyl transferase nick-end labeling (TUNEL) technique. Extracellular glutamate, glycine, and taurine increased significantly in the hippocampus within a few hours and remained high after 24 h. Neuronal nuclei in the granule layers of the hippocampus and cerebellum were positive for c-Jun after 24 h. Little immunoreactivity was detected in the cerebral cortex. c-Jun-positive neuronal perikarya and processes were found in granule and pyramidal CA4 layers of the hippocampus and among the Purkinje cells of the cerebellum. Also some microglial cells stained positively for c-Jun. TUNEL reactivity was most intense at 10 days after trauma and was extensive in neurons of the cerebral cortex, hippocampus, and cerebellum. The initial response of the brain after rotational head injury involves brain edema after 24 h and an excitotoxic neuronal microenvironment in the first hour, which leads to extensive delayed neuronal cell death by apoptosis necrosis in the cerebral cortex, hippocampus and cerebellum.

The effect of riluzole treatment in rats on the survival of injured adult and grafted embryonic motoneurons

The effect of riluzole on the survival of injured motoneurons was studied. The L4 ventral root was avulsed and reimplanted into the spinal cord. Immediately after the operation, 4 animals were treated with riluzole for 3 weeks while another 4 animals received no treatment after the operation. Three months later the fluorescent dyes, Fast Blue and Diamidino Yellow, were applied to the cut ventral ramus of the L4 spinal nerve, for retrograde labelling of neurons. Three days later, the spinal cords were processed to reveal the retrograde-labelled cells. In untreated animals, there were 20 +/- 2.1 labelled neurons (+/- SEM), while in animals treated with riluzole there were 723 +/- 26. Thus, treatment with riluzole dramatically enhanced the survival of injured motoneurons. In another series of experiments, after avulsion of the L4 ventral root and its reinsertion, embryonic spinal cord pieces were grafted into the host cord. Five animals received riluzole treatment and 4 were left untreated. In the untreated animals, 125 +/- 5.1 retrograde-labelled cells of both graft and host origin were detected. In rats treated with riluzole, 645 +/- 35.7 retrograde-labelled cells were seen and almost all of these were of host origin. Thus, treatment with riluzole enhanced the survival of injured host motoneurons, and by doing so, (i) reduced the ability of grafted neurons to extend their axons into the reimplanted L4 ventral root, and (ii) reduced the survival of the grafted cells.

Hyperthermic preconditioning protects against spinal cord ischemic injury

BACKGROUND

Paraplegia can result from operations requiring transient occlusion of the descending thoracic aorta. The present study tested whether inducing hyperthermia in rats before aortic ischemia would be neuroprotective.

METHODS

Rats were randomly assigned to hyperthermic preconditioning (n = 27) or control (n = 32) groups. Eighteen hours before ischemia, the hyperthermic preconditioned rats were heated at 41 degrees C for 15 minutes. Ten minutes of spinal ischemia were produced by balloon occlusion of the thoracic aorta. Neurologic performance scores were evaluated daily to 7 days after ischemia. The lumbar region of the spinal cord was removed for histologic grading.

RESULTS

The hyperthermic preconditioned animals had less permanent spinal cord injury compared with controls (29.6% versus 59.4%, p = 0.02), and the incidence of immediate paraplegia in the hyperthermic preconditioned group was significantly less than that in the control group (3.7% versus 28.1%, p = 0.03). Histologic scores correlated with the neurologic outcome at the time of sacrifice in rats with permanent spinal cord injury but not in those walking normally.

CONCLUSIONS

We used a rat model of spinal cord ischemia and found that hyperthermic preconditioning before spinal cord ischemia resulted in improved clinical outcome.

White matter injury in spinal cord ischemia: protection by AMPA/kainate glutamate receptor antagonism

BACKGROUND AND PURPOSE

Spinal cord ischemia is a serious complication of surgery of the aorta. NMDA receptor activation secondary to ischemia-induced release of glutamate is a major mechanism of neuronal death in gray matter. White matter injury after ischemia results in long-tract dysfunction and disability. The AMPA/kainate receptor mechanism has recently been implicated in white matter injury.

METHODS

We studied the effects of AMPA/kainate receptor blockade on ischemic white matter injury in a rat model of spinal cord ischemia.

RESULTS

Intrathecal administration of an AMPA/kainate antagonist, 6-nitro-7-sulfamoyl-(f)-quinoxaline-2, 3-dione (NBQX), 1 hour before ischemia reduced locomotor deficit, based on the Basso-Beattie-Bresnahan scale (0=total paralysis; 21=normal) (sham: 21+/-0, n=3; saline: 3.7+/-4.5, n=7; NBQX: 12. 7+/-7.0, n=7, P<0.05) 6 weeks after ischemia. Gray matter damage and neuronal loss in the ventral horn were evident after ischemia, but no difference was noted between the saline and NBQX groups. The extent of white matter injury was quantitatively assessed, based on axonal counts, and was significantly less in the NBQX as compared with the saline group in the ventral (sham: 1063+/-44/200x200 microm, n=3; saline: 556+/-104, n=7; NBQX: 883+/-103, n=7), ventrolateral (sham: 1060+/-135, n=3; saline: 411+/-66, n=7; NBQX: 676+/-122, n=7), and corticospinal tract (sham: 3391+/-219, n=3; saline: 318+/-23, n=7; NBQX: 588+/-103, n=7) in the white matter on day 42.

CONCLUSIONS

Results indicate severe white matter injury in the spinal cord after transient ischemia. NBQX, an AMPA/kainate receptor antagonist, reduced ischemia-induced white matter injury and improved locomotor function.

Basic fibroblast growth factor (bFGF) enhances functional recovery following severe spinal cord injury to the rat

We have recently demonstrated that following a moderate contusion spinal cord injury (SCI) to rats, subsequent administration of basic fibroblast growth factor (bFGF) significantly enhances functional recovery and tissue sparing. To further characterize the effects of bFGF, we evaluated its efficacy after a more severe contusion injury at T(10) using the NYU impactor. Immediately after SCI, osmotic minipumps were implanted into the lateral ventricle and lumbar thecal sac to deliver bFGF at 3 or 6 microg per day versus control vehicle for 1 week. Animals were behaviorally tested for 6 weeks before histological assessment of tissue sparing through the injured segment and glial reactivity distal to the lesion. Compared to moderate SCI, all rats had more prolonged and sustained functional deficits 6 weeks after severe contusion. Subjects treated with bFGF had pronounced recovery of hindlimb movements from 2 to 6 weeks compared to controls, manifested in significantly higher behavioral scores. Only marginal tissue sparing was seen rostral to the injury in bFGF-treated spinal cords versus controls. Optical density measurements of astrocyte and microglial cell immunoreactivity in bFGF-treated spinal cords showed that after 6 weeks they approximated controls, although astrocyte immunoreactivity remained higher in controls rostrally. In summary, intrathecal infusion of bFGF following severe SCI significantly restores gross hindlimb motor function that is not correlated with significant tissue sparing. In light of previous evidence that pharmacological intervention with bFGF after moderate SCI enhances tissue preservation, the current findings indicate that yet undefined mechanisms contribute to the enhanced functional recovery following bFGF treatment.

Advances in secondary spinal cord injury: role of apoptosis

The outcome of spinal cord injury depends on the extent of secondary damage produced by a series of cellular and molecular events initiated by the primary trauma. This article reviews the evidence that secondary spinal cord injury involves the apoptotic as well as necrotic death of neurons and glial cells. Also discussed are the major factors that can contribute to cell death, such as glutamatergic excitotoxicity, free radical damage, cytokines, and inflammation. The development of innovative therapeutic strategies to reduce secondary spinal cord injury depends on an increased understanding of secondary injury mechanisms at the molecular and biochemical level. Such therapeutic interventions may include the use of antiapoptotic drugs, free radical scavengers, and anti-inflammatory agents. These could be targeted to block key reactions on cellular and molecular injury cascades, thus reducing secondary tissue damage, minimizing side effects, and improving functional recovery.

Granule neuron DNA damage following deafferentation in adult rats cerebellar cortex: a lesion model

Neuronal programmed cell death is regulated by a neurotrophic supply from targets and afferent inputs. The relative contribution of each component varies according to neuronal type and age. We have previously reported that primary cultures of cerebellar granule cells undergo apoptosis when deprived of depolarising KCl concentrations, suggesting a significant role of afferent inputs in the control of cerebellar granule cells survival. This issue was investigated by setting up various in vivo lesional paradigms in order to obtain partial or total deafferentation of the cerebellar granule layer in adult rats. At different times after surgery, cerebellar sections were subjected to TUNEL staining in order to detect possible DNA damage. One week after unilateral pedunculotomy, few scattered groups of apoptotic granule neurons were observed in the homolateral hemisphere. On the contrary, total deafferentation obtained by a new experimental paradigm based on an "L-cut" lesion induced massive and widespread apoptotic death in the granule layer of the deafferentated area. The time window of DNA fragmentation in granule layer was one to seven days after the "L-cut". Selective Purkinje cell deafferentation obtained by 3-acetylpyridine injection did not result in TUNEL staining in the cerebellar cortex. The current finding that mossy fiber axotomy induces granule cell apoptotic death points out for the first time the crucial role of afferent inputs in mature granule cell survival. Moreover, the in vivo lesional model described here may prove to be an useful tool for investigating cellular and molecular mechanisms of neuronal death triggered by deafferentation.

DNA strand breaks in Alzheimer's disease

The goal of this study was to investigate the presence of DNA damage in Alzheimer's disease (AD) utilizing independent assays for three different types of DNA strand breaks. Sections from hippocampi of AD brains, brains with Alzheimer neurofibrillary changes (Ch) from non-demented individuals, and controls (C) were labeled with (1) the TUNEL assay to identify blunt-ended and 3' protruding termini of breaks in double-stranded DNA, (2) the Klenow assay to detect single-stranded and double-stranded breaks with protruding 5' termini, and (3) the Apostain assay which utilizes a monoclonal antibody to single-stranded DNA and is based on the decreased stability of apoptotic DNA to thermal denaturation caused by DNA breaks. The highest incidence of nuclei positive for either molecular form of DNA strand breaks was detected in AD, followed by Ch, and controls (C). In either AD and Ch, the incidence of TUNEL- or Klenow-positive nuclei did not differ significantly, but was higher than the incidence of Apostain-positive nuclei. With all three assays, the highest incidence of positive nuclei was in the molecular layer of CA1. In the majority of nuclei positive for either the Klenow or the Apostain assay, the product of the labeling reaction was localized either to the periphery of the nucleus or to distinct clumps of chromatin (or both). With the TUNEL assay, the majority of positive nuclei were diffusely labeled. In both AD and Ch, the individual positive nuclei were labeled with both the Klenow and the TUNEL assays. The results indicate high incidence of nuclei with either double-stranded or single-stranded DNA breaks in AD, which, for the forms detectable with the Klenow or TUNEL assays, were colocalized.

A specific inhibitor of apoptosis decreases tissue injury after intestinal ischemia-reperfusion in mice

PURPOSE

Apoptosis is a stereotypical pathway of cell death that is orchestrated by a family of cysteine endoproteases called caspases. This study examined the effect of apoptosis inhibition with a specific caspase inhibitor on murine intestinal viability after ischemia-reperfusion (IR).

METHODS

C57Bl6 X SV129 mice underwent segmental small bowel ischemia by vascular isolation of 10 cm of terminal ileum. In separate experiments, the ischemic time was varied from 30 to 130 minutes with a reperfusion interval of 6 hours. The degree of small bowel injury was quantified from 1 to 5 (increasing severity) by standardized, blinded histologic grading. The degree of apoptosis was assessed with a specific assay (terminal deoxyamcleotydil transferase-mediated deoxyuridine triphosphate nick end labeling [TUNEL]) and quantified by calculating the apoptotic index (apoptotic cells/10 high-power fields). To evaluate for activation of interleukin-1beta converting enzyme we measured tissue mature interleukin-1beta levels using a specific enzyme-linked immunosorbent assay. To evaluate the effect of apoptosis inhibition on intestinal viability after IR, mice received 3.0 mg of the caspase inhibitor ZVAD (N-benzyloxycarbonyl Val-Ala-Asp-Ome-fluoromethylketone) subcutaneously before and after IR in five divided doses (n = 11), the same dose of ZFA (N-benzyloxycarbonyl Phe-Ala fluoromethylketone), a structurally similar molecule with no anticaspase activity (n = 9), or sham operation (n = 6).

RESULTS

A linear relationship existed between ischemic interval and histologic grade (r = 0.69, P <.006). Increasing the ischemic interval from 0 to 50 minutes was associated with a fivefold increase in apoptotic index (P =.05). Ischemic bowel was measured to have an average of 57.3 +/- 7.8 pg/mL whereas normal bowel had an average of 1.8 +/- 0.5 pg/mL of mature interleukin-1beta present. Mice tolerated multiple injections of ZVAD and ZFA without signs of toxicity. Animals treated with ZVAD (apoptosis inhibitor) had little injury after 50 minutes of ischemia and 6 hours of reperfusion (injury grade 1.8) compared with sham controls (injury grade 1.2, P =.7) and had significantly less injury than mice treated with ZFA (placebo) (injury grade 3.0, P <.006).

CONCLUSIONS

Increasing ischemic interval in a segmental small bowel murine IR model is associated with increased histologic injury and augmented apoptosis as evidenced by increased TUNEL staining and interleukin-1beta converting enzyme activation. Inhibition of apoptosis with a specific caspase inhibitor significantly diminishes the degree of small bowel injury.

Ischemic cell death in brain neurons

This review is directed at understanding how neuronal death occurs in two distinct insults, global ischemia and focal ischemia. These are the two principal rodent models for human disease. Cell death occurs by a necrotic pathway characterized by either ischemic/homogenizing cell change or edematous cell change. Death also occurs via an apoptotic-like pathway that is characterized, minimally, by DNA laddering and a dependence on caspase activity and, optimally, by those properties, additional characteristic protein and phospholipid changes, and morphological attributes of apoptosis. Death may also occur by autophagocytosis. The cell death process has four major stages. The first, the induction stage, includes several changes initiated by ischemia and reperfusion that are very likely to play major roles in cell death. These include inhibition (and subsequent reactivation) of electron transport, decreased ATP, decreased pH, increased cell Ca(2+), release of glutamate, increased arachidonic acid, and also gene activation leading to cytokine synthesis, synthesis of enzymes involved in free radical production, and accumulation of leukocytes. These changes lead to the activation of five damaging events, termed perpetrators. These are the damaging actions of free radicals and their product peroxynitrite, the actions of the Ca(2+)-dependent protease calpain, the activity of phospholipases, the activity of poly-ADPribose polymerase (PARP), and the activation of the apoptotic pathway. The second stage of cell death involves the long-term changes in macromolecules or key metabolites that are caused by the perpetrators. The third stage of cell death involves long-term damaging effects of these macromolecular and metabolite changes, and of some of the induction processes, on critical cell functions and structures that lead to the defined end stages of cell damage. These targeted functions and structures include the plasmalemma, the mitochondria, the cytoskeleton, protein synthesis, and kinase activities. The fourth stage is the progression to the morphological and biochemical end stages of cell death. Of these four stages, the last two are the least well understood. Quite little is known of how the perpetrators affect the structures and functions and whether and how each of these changes contribute to cell death. According to this description, the key step in ischemic cell death is adequate activation of the perpetrators, and thus a major unifying thread of the review is a consideration of how the changes occurring during and after ischemia, including gene activation and synthesis of new proteins, conspire to produce damaging levels of free radicals and peroxynitrite, to activate calpain and other Ca(2+)-driven processes that are damaging, and to initiate the apoptotic process. Although it is not fully established for all cases, the major driving force for the necrotic cell death process, and very possibly the other processes, appears to be the generation of free radicals and peroxynitrite. Effects of a large number of damaging changes can be explained on the basis of their ability to generate free radicals in early or late stages of damage. Several important issues are defined for future study. These include determining the triggers for apoptosis and autophagocytosis and establishing greater confidence in most of the cellular changes that are hypothesized to be involved in cell death. A very important outstanding issue is identifying the critical functional and structural changes caused by the perpetrators of cell death. These changes are responsible for cell death, and their identity and mechanisms of action are almost completely unknown.

Basic fibroblast growth factor (bFGF) enhances tissue sparing and functional recovery following moderate spinal cord injury

The rapid increase in basic fibroblast growth factor (bFGF) production following spinal cord injury (SCI) in rats is thought to serve a role in the cellular processes responsible for the functional recovery often observed. In this study, bFGF was intrathecally administered continuously for 1 week beginning 30 min after a moderate (12.5 mm) spinal cord contusion in adult rats using the New York University impactor device. Osmotic minipumps were implanted into the lateral ventricle and lumbar thecal sac to deliver bFGF at a rate of 3 microg or 6 microg per day versus control vehicle. Animals were behaviorally tested for 6 weeks using the Basso, Beattie, Bresnahan locomotor rating scale and histologically assessed for both tissue sparing and glial reactivity rostral and caudal to the lesion. Rats treated with bFGF regained coordinated hindlimb movements earlier than controls and demonstrated consistent coordination from 4 to 6 weeks. Vehicle-treated rats showed only modest improvements in hindlimb function. The amount of spared tissue was significantly higher in bFGF-treated rats than in controls. Astrocyte and microglial reactivity was more pronounced in bFGF-treated animals versus controls. In summary, intrathecal infusion of exogenous bFGF following SCI significantly reduces tissue damage and enhances functional recovery. Early pharmacological intervention with bFGF following SCI may serve a neuroprotective role and/or create a proregenerative environment, possibly by modulating the neuroglial response.

Temporal profile of apoptotic-like changes in neurons and astrocytes following controlled cortical impact injury in the rat

Apoptotic cell death has been observed in both neurodegenerative diseases and acute neurological traumas such as ischemia, spinal cord injury, and traumatic brain injury (TBI). Recent studies employing different models of TBI have described morphological and biochemical changes characteristic of apoptosis following injury. However, no study has examined the temporal profile of apoptosis following controlled cortical impact (CCI) injury in the rat. In addition, the relative frequency of apoptotic profiles in different cell types (neurons versus glia) following CCI has yet to be investigated. In the present experiments, injured cortex was subjected to DNA electrophoresis, and serial sections from the contusion area were stained with hematoxylin and eosin or Hoechst 33258 or double-labeled with TUNEL and neuronal or glial markers. The results of the present study indicate that CCI produces a substantial amount of DNA damage associated with both apoptotic-like and necrotic-like cell death phenotypes primarily at the site of cortical impact and focal contusion. DNA damage, as measured by TUNEL and DNA electrophoresis, was most apparent 1 day following injury and absent by 14 days post-TBI. However, quantitative analysis showed that the majority of TUNEL-positive cells failed to exhibit apoptotic-like morphology and were probably undergoing necrosis. In addition, apoptotic-like morphology was predominantly observed in neurons compared to astrocytes. The present study provides further evidence that apoptosis is involved in the pathology of TBI and could contribute to some of the ensuing cell death following injury.

Changes in expression of the DNA repair protein complex DNA-dependent protein kinase after ischemia and reperfusion

Reperfusion of ischemic tissue causes an immediate increase in DNA damage, including base lesions and strand breaks. Damage is reversible in surviving regions indicating that repair mechanisms are operable. DNA strand breaks are repaired by nonhomologous end joining in mammalian cells. This process requires DNA-dependent protein kinase (DNA-PK), composed of heterodimeric Ku antigen and a 460,000 Da catalytic subunit (DNA-PKcs). In this study, a rabbit spinal cord model of reversible ischemia was used to demonstrate the effect of acute CNS injury on the activity and expression of DNA-dependent protein kinase. The DNA-binding activity of Ku antigen, analyzed by an electrophoretic mobility shift assay, increased during reperfusion after a short ischemic insult (15 min of occlusion), from which the animals recover neurological function. After severe ischemic injury (60 min of occlusion) and reperfusion that results in permanent paraplegia, Ku DNA binding was reduced. Protein levels of the DNA-PK components-Ku70, Ku80, and DNA-PKcs-were monitored by immunoblotting. After 60 min of occlusion, the amount of DNA-PKcs and the enzyme poly(ADP-ribose) polymerase (PARP) decreased with the same time course during reperfusion. Concurrently 150 and 120 kDa fragments were immunostained by an anti-DNA-PKcs monoclonal antibody. This antibody was shown to cross-react with alpha-fodrin breakdown products. The 120 kDa fodrin peptide is associated with caspase-3 activation during apoptosis. Both DNA-PKcs and PARP are also substrates for caspase-3-like activities. The results are consistent with a model in which after a short ischemic insult, DNA repair proteins such as DNA-PK are activated. After severe ischemic injury, DNA damage overwhelms repair capabilities, and cell death programs are initiated.

A review of the pathophysiology of cervical spondylotic myelopathy with insights for potential novel mechanisms drawn from traumatic spinal cord injury

Cervical spondylotic myelopathy (CSM) is the most common cause of spinal cord dysfunction. Despite advances in diagnosis and surgical treatment, many patients still have severe permanent neurologic deficits caused by this condition. An improved understanding of the pathophysiology of cervical spondylotic myelopathy, particularly at a cellular and molecular level, may allow improved treatments in the future. A detailed review of articles in the literature pertaining to cervical spondylotic myelopathy was supplemented by an analysis of relevant mechanisms of spinal cord injury. The pathologic course of cervical spondylotic myelopathy is characterized by early involvement of the corticospinal tracts and later destruction of anterior horn cells, demyelination of lateral and dorsolateral tracts, and relative preservation of anterior columns. Static and mechanical factors and ischemia are critical to the development of cervical spondylotic myelopathy. Free radical-and cation-mediated cell injury, glutamatergic toxicity, and apoptosis may be of relevance to the pathophysiology of cervical spondylotic myelopathy. To date, research in cervical spondylotic myelopathy has focused exclusively on the role of mechanical factors and ischemia. Fundamental research at a cellular and molecular level, particularly in the areas of glutamatergic toxicity and apoptosis may result in clinically relevant treatments for this condition.

The long-term effects of prostatic infarction in the rat

OBJECTIVE

To evaluate the long-term effects of infarction, which usually induces organ atrophy, on the prostate by examining the changes occurring in rat ventral prostate after infarction.

MATERIALS AND METHODS

The unilateral arteriolar branches to the ventral prostate were electrocauterized under an operative microscope in 10 adult rats. The gross and histological changes of the treated lobes of the ventral prostate were compared with those of untreated control lobes in the same rats 12 weeks later.

RESULTS

The size and mean (SD) weight of the treated lobes decreased markedly, to 148 (34) mg, compared with those of the controls, at 698 (62) mg (P<0.01). The treated lobes were composed of both normal and atrophic glandular tissue.

CONCLUSION

Prostatic atrophy can be induced by infarction in the rat; prostatic infarction might have potential as a new therapeutic strategy in the treatment of benign prostatic hyperplasia.