Cellular reactions to small cerebral stab wounds in the rat frontal lobe. An ultrastructural study

Ultrastructural Pathology of Oligodendroglial Cells in Traumatic and Hydrocephalic Human Brain Edema: A Review

Oligodendroglial cell changes in human traumatic brain injuries and hydrocephalus have been reviewed and compared with experimental brain edema. Resting unreactive oligodendrocytes, reactive oligodendrocytes, anoxic-ischemic oligodendrocytes, hyperthrophic phagocytic oligodendrocytes, and apoptotic oligodendrocytes are found. Anoxic-ischemic oligodendrocytes exhibit enlargement of endoplasmic reticulum, Golgi complex, and enlargement and disassembly of nuclear envelope. They appear in contact with degenerated myelinated axons. Hypertrophic phagocytic oligodendrocytes engulf degenerated myelinated axons exerting myelinolytic effects. A continuum oncotic and apoptotic cell death type leading to necrosis is observed. The vasogenic and cytotoxic components of brain edema are discussed in relation to oligodendroglial cell changes and reactivity.

Age determination of brain contusions

In 104 individuals who had sustained traumatic brain injury, the course of traumatically induced morphological changes was investigated immunohistochemically during the first 30 weeks after the trauma. Regarding the inflammatory cell reaction in human cortical contusions, CD15-labeled granulocytes were detectable within 10 minutes following brain injury, whereas significantly increased numbers of nuclear leukocytes occurred after a postinfliction interval of at least 1.1 days (leukocyte common antigen), 2 days (CD3), or 3.7 days (UCHL-1), respectively. A positive nuclear staining for the proliferation marker MIB-1 by cerebral macrophages could be observed as early as 3 days after the injury and regularly in cases with a survival between 7 and 11 days. Injury-induced glial staining reactions could be demonstrated, at the earliest, after a postinfliction interval of 3 hours for α1-antichymotrypsin, 22 hours for vimentin, 1 day for glial fibrillary acidic protein, and 7 days for tenascin. Regarding the vascular response to brain injury, a significantly increased immunoreactivity could be detected in cortical contusions with a wound age of at least 3 hours for factor VIII, 1.6 days for tenascin, and 6.8 days for thrombomodulin, whereas the immunostaining for laminin and type IV collagen was regularly whereas the immunostaining for laminin and type IV collagen was regularly positive even in the vascular endothelium of ininjured brain tissue.

Craniotomy: true sham for traumatic brain injury, or a sham of a sham?

Abstract Neurological dysfunction after traumatic brain injury (TBI) is caused by both the primary injury and a secondary cascade of biochemical and metabolic events. Since TBI can be caused by a variety of mechanisms, numerous models have been developed to facilitate its study. The most prevalent models are controlled cortical impact and fluid percussion injury. Both typically use "sham" (craniotomy alone) animals as controls. However, the sham operation is objectively damaging, and we hypothesized that the craniotomy itself may cause a unique brain injury distinct from the impact injury. To test this hypothesis, 38 adult female rats were assigned to one of three groups: control (anesthesia only); craniotomy performed by manual trephine; or craniotomy performed by electric dental drill. The rats were then subjected to behavioral testing, imaging analysis, and quantification of cortical concentrations of cytokines. Both craniotomy methods generate visible MRI lesions that persist for 14 days. The initial lesion generated by the drill technique is significantly larger than that generated by the trephine. Behavioral data mirrored lesion volume. For example, drill rats have significantly impaired sensory and motor responses compared to trephine or naïve rats. Finally, of the seven tested cytokines, KC-GRO and IFN-γ showed significant increases in both craniotomy models compared to naïve rats. We conclude that the traditional sham operation as a control confers profound proinflammatory, morphological, and behavioral damage, which confounds interpretation of conventional experimental brain injury models. Any experimental design incorporating "sham" procedures should distinguish among sham, experimentally injured, and healthy/naïve animals, to help reduce confounding factors.

Morphological and ultrastructural features of Iba1-immunolabeled microglial cells in the hippocampal dentate gyrus

Microglia are found throughout the central nervous system, respond rapidly to pathology and are involved in several components of the neuroinflammatory response. Iba1 is a marker for microglial cells and previous immunocytochemical studies have utilized this and other microglial-specific antibodies to demonstrate the morphological features of microglial cells at the light microscopic level. However, there is a paucity of studies that have used microglial-specific antibodies to describe the ultrastructural features of microglial cells and their processes. The goal of the present study is to use Iba1 immuno-electron microscopy to elucidate the fine structural features of microglial cells and their processes in the hilar region of the dentate gyrus of adult Sprague-Dawley rats. Iba1-labeled cell bodies were observed adjacent to neurons and capillaries, as well as dispersed in the neuropil. The nuclei of these cells had dense heterochromatin next to the nuclear envelope and lighter chromatin in their center. Iba1-immunolabeling was found within the thin shell of perikaryal cytoplasm that contained the usual organelles, including mitochondria, cisternae of endoplasmic reticulum and Golgi complexes. Iba1-labeled cell bodies also commonly displayed an inclusion body. Iba1-labeled cell bodies gave rise to processes that often had a small side branch arise within 5 mum of the microglial cell body. These data showing "resting" Iba-1 labeled microglial cells in the normal adult rat dentate gyrus provide a basis for comparison with the morphology of microglial cells in disease and injury models where they are activated or phagocytotic.

Neuroinflammatory responses after experimental diffuse traumatic brain injury

Little is known about microglial activation and macrophage localization after diffuse brain injury (DBI). DBI-mediated perisomatic traumatic axonal injury (TAI) was recently identified within the neocortex, hippocampus, and thalamus, providing an opportunity to characterize immune cell responses within diffusely injured brain loci uncomplicated by contusion. By using moderate midline/central fluid percussion injury, microglial/macrophage responses were examined with antibodies targeting immune cell phenotypes and amyloid precursor protein, a marker of TAI. Parallel assessments of blood-brain barrier alterations were also performed. Within 6 to 48 hours postinjury, microglial activation within injured loci was observed, whereas microglia within non-TAI-containing regions maintained a resting phenotype. Microglial activation shared a spatiotemporal relationship with TAI though no clear interactions were observed. By 7 to 28 days postinjury, activated microglia contained myelin debris, yet revealed limited aggregation. Immunophenotypic macrophages were also localized to injured loci. Select macrophages approximated somatic membranes of perisomatically axotomized neurons with evidence of bouton disruption. No causality was established between blood-brain barrier alterations and these inflammatory responses. These findings indicate rapid, yet initially nonspecific, and persistent microglial/macrophage responses to DBI. DBI-mediated inflammatory responses suggest further expansion of traumatic brain injury histopathologic evaluations to identify neuroinflammation indicative of diffuse pathology.

Prednisone induces cognitive dysfunction, neuronal degeneration, and reactive gliosis in rats

BACKGROUND

High glucocorticoid serum levels and prednisone (PDN) therapy have been associated with depression, posttraumatic stress disorder, and some types of cognitive dysfunction in humans.

OBJECTIVE

The aim of this study was to assess whether chronic (90 days) PDN administration produces disturbance in learning and memory retention associated with neuronal degeneration and cerebral glial changes.

METHODS

Male Wistar rats were studied. Controls received 0.1 ml distilled water vehicle orally. The PDN group was treated orally with 5 mg/kg/d PDN, which is equivalent to moderate doses used in clinical settings. Learning and memory retention were assessed with the Morris water maze. The index of degenerated neurons as well as the number and cytoplasmic transformation of astrocytes and microglia cells were evaluated in the prefrontal cortex and the CA1 hippocampus.

RESULTS

PDN-treated rats showed a significant delay of 20% in learning and memory retention as compared with controls. In addition, in the PDN group, the neuronal degeneration index was two times higher in the prefrontal cortex, and approximately 10 times higher in the CA1 hippocampus, than in control animals. The number and cytoplasmic transformation of astrocytes were also significantly higher in the PDN group than in control animals. In the PDN-treated group, isolectin-B4-labeled microglia cells were higher in the prefrontal cortex but not in the hippocampus.

CONCLUSION

These results suggest that chronic exposure to PDN produces learning and memory impairment, reduces neural viability, and increases glial reactivity in cerebral regions with these cognitive functions.

Intracerebral inflammatory response to experimental brain contusion

The inflammatory reaction following experimental brain contusion was studied by immunohistochemistry in 22 rats during the first 16 days after trauma. An inflammatory mononuclear cell response was evident on day 2, with a maximum on days 5-6 and signs remained still 16 days after the trauma. The time course of the cellular infiltration adjacent to the lesion correlated with blood brain barrier dysfunction in the contralateral side of the traumatized hemisphere. The cellular infiltrate comprised NK cells, T-helper cells and T-cytotoxic/suppressor cells as well as monocytes/macrophages. Most of the macrophages appeared to be activated by T-cells. Surprisingly, polymorphonuclear cells appeared less engaged than mononuclear cells in the inflammation. The demonstration of immunocompetent cells and the induction of MHC-1 and MHC-II antigen provides a substrate for inflammatory reactions similar to those that cause neurological damage in inflammatory diseases such as viral infections, multiple sclerosis and experimental allergic encephalitis. Our observations indicate that the role of the inflammatory reactions may have a role, hitherto neglected, in the pathogenesis of secondary traumatic brain injury.

Neutrophil accumulation after traumatic brain injury in rats: comparison of weight drop and controlled cortical impact models

Previous work in our laboratory and others using the weight drop (WD) model of traumatic brain injury (TBI) has shown that neutrophils accumulate in brain tissue during the initial 24 h posttrauma as measured by myeloperoxidase (MPO) activity and immunohistochemistry. This study compares the acute inflammatory response to TBI over time, as measured by MPO activity, in the WD and controlled cortical impact (CCI) models. Anesthetized adult Sprague-Dawley rats were traumatized using WD (10-g weight dropped 5 cm) or CCI (4 m/sec, 2.5 mm depth). At 2, 24, 48, or 168 h after trauma, rats (n = 4-5/group at each time) were anesthetized and killed, the brains were removed, and 6-mm coronal slices from traumatized and contralateral hemispheres were assayed for MPO activity. Nontraumatized rats (n = 4) served as controls. Three additional rats underwent a more severe CCI (3 mm depth) with MPO activity assayed at 24 h. A separate group of rats (n = 6) was subjected to WD trauma and killed at 2 weeks after injury for analysis of lesion volume. MPO activity in the traumatized hemisphere was demonstrated at 24 and 48 h in both the WD (0.3152 +/- 0.0472 and 0.3017 +/- 0.0228 U/g, respectively, p < 0.05 vs controls) and CCI (0.1866 +/- 0.0225 and 0.1937 +/- 0.0772 U/g, respectively, p < 0.05 vs controls) models. MPO activity was below the sensitivity of the assay in the control, 2 h, and 168 h groups in both models.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of neutropenia on edema, histology, and cerebral blood flow after traumatic brain injury in rats

Neutrophils accumulate during the acute inflammatory response to brain injury, but their role in the injury process remains controversial. We tested the hypothesis that neutrophils contribute to cerebral edema, tissue injury, and disturbed cerebral blood flow (CBF) (hyperemia or ischemia) during the first 24 h after traumatic brain injury. Wistar rats (n = 51) were injected with either vinblastine sulfate to induce neutropenia or the saline vehicle. Five days later, under halothane anesthesia, right hemispheric trauma was produced by weight drop (10 g x 5 cm) onto exposed dura. At 24 h after trauma, brain water (wet-dry weight), traumatic infarct size (percent of hemispheric section infarcted), or local CBF (lCBF, 14C-iodoantipyrine autoradiography) was assessed. Vinblastine treatment produced profound neutropenia on the day of trauma (absolute neutrophil count 0.024 +/- 0.008 x 10(9)/L vs 1.471 +/- 0.322 x 10(9)/L, p < 0.05 in neutropenic vs saline, respectively, mean +/- SEM). Neutropenia did not reduce the development of brain edema in the injured hemisphere (brain water 82.38 +/- 0.29% vs 82.73 +/- 0.37% in neutropenic and saline, respectively, mean +/- SEM) or traumatic infarct size (34.5 +/- 3.3% vs 33.2 +/- 2.1% in neutropenic vs saline respectively). In contrast, neutropenic rats exhibited 52%, 41%, and 57% reductions in lCBF in the frontal cortex, parietal cortex, and amygdala, respectively, of the injured hemisphere 24 h after trauma (all p < 0.05 vs nonneutropenic controls). These data suggest that neutrophils and the acute inflammatory process contribute to the level of CBF observed 24 h after trauma, but effects on edema or early posttraumatic infarct size could not be demonstrated.

Localization of basic fibroblast growth factor and its mRNA after CNS injury

Basic fibroblast growth factor (FGF) mRNA is increased 4 h after cortical brain injury. In situ hybridization reveals that the increased mRNA persists for at least 2 weeks and that, in areas adjacent and ipsilateral to the lesion, the expression of basic FGF mRNA is also modified. As an example, at three days distal from the lesion, mRNA can be detected in ependymal cells of the lateral ventricle and in selected cells of the hippocampus and cortex. Endothelial cells also synthesize basic FGF mRNA. The increase in basic FGF mRNA is paralleled by similar changes in the localization of the basic FGF protein. Both the intensity and number of cells which stain for basic FGF are increased when they are compared to staining in either the contralateral side or to comparable areas of unlesioned brains. The pattern of mRNA expression is similar from 4 hours to 14 days. Early in the response (4 h to 3 days) on the border of the lesion, the presence of basic FGF is most obvious within the MAC-1-immunopositive population (macrophages and/or microglia). From 7 days to 2 weeks, there has been extensive hypertrophy of the reactive astrocytes which stain intensely for anti-basic FGF(1-24). We conclude that there is increased basic FGF as a function of injury to the CNS. In view of the observation that it is an early and persistent response, the possibility that it plays multiple functions in the regenerative capacity of the CNS is discussed.

Early polymorphonuclear leukocyte accumulation correlates with the development of posttraumatic cerebral edema in rats

To evaluate the role of polymorphonuclear leukocytes (PMNs) in the development of posttraumatic cerebral edema, we quantitatively assessed the time course and magnitude of PMN accumulation and its relationship to cerebral edema formation after cerebral trauma in 78 rats. 111In-labeled PMN accumulation was measured in 26 rats in the first 8 h after right hemispheric percussive cerebral trauma or a sham control condition. 51Cr-labeled erythrocyte accumulation was measured simultaneously in 22 rats to assess the contribution of expansion of blood volume to early posttraumatic PMN accumulation. Edema formation [right-left (R-L) hemispheric difference in percent brain water], R-L hemispheric labeled-PMN accumulation, and blood volume index-adjusted PMN accumulation were measured between 0-2 h and 4-8 h posttrauma. PMN accumulation was elevated markedly in the first 2 h posttrauma compared with values in sham controls (13.45 +/- 2.53 vs -0.03 +/- 0.31, p less than 0.01) but not when adjusted for blood volume index (BVI), suggesting that PMN accumulation in the first 2 h posttrauma was due to expansion of blood volume. Between 4 and 8 h posttrauma, however, both total (2.56 +/- 0.82 vs -0.29 +/- 0.52) and BVI-adjusted (8.78 +/- 3.97 vs -0.48 +/- 0.79) PMN accumulation were elevated (p less than 0.05) compared with sham. Brain edema and total PMN accumulation were significantly correlated at both 2 h and 8 h posttrauma (r2 = 0.77, p less than 0.001, and r2 = 0.69, p less than 0.002, respectively), but a significant correlation between edema and BVI-adjusted PMN accumulation was observed only at 8 h posttrauma (r2 = 0.96, p less than 0.001). These data show that PMN accumulation after traumatic brain injury occurs with an initial phase explained by an increase in blood volume in the first 2 h posttrauma followed by a subsequent acute inflammatory phase. The significant correlation between PMN accumulation and the development of cerebral edema is the first quantitative relationship demonstrated between PMN accumulation and a relevant pathophysiological variable. A causal role for PMNs in the genesis of posttraumatic cerebral edema has yet to be proved.

Changes in CSF and brain soluble proteins following vigabatrin treatment in rats

1. Following the discovery of vacuoles in the white matter of the brain of small animals treated with vigabatrin (GVG) it was decided to investigate possible reasons for the occurrence of these vacuoles and to explore the possibility of finding CSF markers which could be applicable for monitoring toxicity in humans. 2. An animal model was developed to study the changes of protein synthesis and to assay soluble brain proteins by isoelectric focusing and two-dimensional electrophoretic techniques. 3. Five groups of rats were treated either with 300 mg kg-1 day-1 GVG, 50 mg kg-1 GVG every other day, 300 mg kg-1 day-1 sodium valproate, 100 mg kg-1 day-1 sodium valproate or sham treated. 4. All animals were given the drug in a liquid full nutrient diet. The dietary intake of the different groups was adjusted to the group which showed the smallest dietary intake, to compensate for possible differences between groups due to nutritional factors. 5. The rats on 300 mg kg-1 day-1 GVG had a 30% reduction of body weight and a 6% reduction of their brain weight, compared with the lower GVG dose group, the two valproate groups and the sham treated group. 6. The synthesis of soluble proteins in the cerebral cortex, hippocampus and cerebellum was decreased in rats given GVG at 300 mg kg-1 day-1 and was increased in rats given valproate at 300 mg kg-1 day-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Response of fetal and neonatal rat brain to injury

Previous observations have suggested that a reactive astrocytic response to damage does not occur in fetal brain. In this study the time course of the astrocytic response to injury in fetal and neonatal rat brains has been assessed using the immunoperoxidase technique for glial fibrillary acidic protein (GFAP). Cold lesions were induced in utero to the forebrain and brain stem of rat fetuses at 16-18 days of gestation. The inflammatory response and the presence of GFAP in the processes of reactive astrocytes were studied in the brains of animals killed from 4 days (20-22 days of fetal life) to 12 days (9 days of post natal life) after the injury. Reactive astrocytes containing GFAP were present at the site of injury in all fetal and neonatal rat brains. Astrocyte processes were thin and short but stained strongly for GFAP. There was a greater amount of astrocytic scar tissue in animals killed 12 days after injury than in those killed after 4 days. In contrast to adults, little mesenchymal component was observed in newly formed scar tissue on the meningeal surfaces of the fetal and newborn rat brain.

Deposition of scar tissue in the central nervous system

Standard parasagittal lesions were placed stereotactically in the cerebral hemispheres of neonatal and adult rats in order to compare scarring in the immature and mature animal. Lesions were examined by light and electron-microscopy and immunofluorescence to study the astrocyte reaction, collagen deposition, and the formation of the basement membrane of the glia limitans. Normal mature scarring characterized by the deposition of collagen, astrocyte end-feet alignment over a glia limitans, and the permanent presence of mesodermal cells (fibroblasts and macrophages) in the core of the lesion, does not occur in wounds before 8-10 days post-partum (dpp). Instead there is no deposition of collagen, and only a transitory astrocyte response occurs with the formation of an interrupted glia limitans. These latter features disappear with time so that the wound is ultimately obliterated by the growth of axons and dendrites through the lesion. Mature scarring is attained over 8-12 dpp when increasing amounts of collagen are deposited and a continuous permanent glia limitans is formed. The acquisition of the mature response to injury from 8-12 dpp may be correlated with the presence of increasing titres of a fibroblast growth factor (FGF), derived from autolytic digestion of injured brain tissue. We have investigated FGF activity using a 3 T 3 fibroblast tissue culture assay to detect mitogenic activity in brain extracts from rats lesioned at different ages and from leukodystrophic mice which have no myelin. Our results show that high titres of FGF are present in the developing brain long before myelination commences, and that normal levels of FGF are found in the brains of leukodystrophic mice which have no myelin. Scarring in brain lesions in these mutants is quite normal.

Increased blood-brain barrier dysfunction around cerebral stab wounds in rats immunized to brain antigens. A quantitative study on endogenous albumin and globulin

The extravasation of serum albumin and immunoglobulin G (IgG) was assayed by electroimmunoassay in cerebral cortex homogenates of rats subjected to stab wound injury either 2 weeks after immunisation to brain antigens or without prior immunisation. The amount of IgG in the brain was significantly higher in immunised than in non-immunised rats 3 and 24 h after injury. A significantly enhanced extravasation of albumin in immunised rats was found only after 24 h. It is concluded that immunisation to brain antigens enhances the vulnerability of the blood-brain barrier in rats subjected to stab wound injury.

Ultrastructural study of enzymes in reactive astrocytes: clarification of astrocytic activity

Enzymes in reactive of the cerebral cortex were examined at the ultrastructural level in an attempt to resolve some conflicting aspects of astrocytic activity. Correlations between morphological and enzyme changes after injury established that the apparent increase in oxidative enzyme activity was exclusively mitochondrial and not an artefactual reaction product resulting from anoxic cellular damage. Pronounced glucose-6-phosphatase activity within cisternae of an increased amount of the granular endoplasmic reticulum was related to increased glycogen. Further evidence from acid phosphatase activity indicated that astrocytes played a minimal role in phagocytosis.

Influence of ethanol and dexamethasone on blood-brain barrier dysfunction to albumin

Stab-wounded ethanol-intoxicated and non-intoxicated rats were studied with respect to the effect of postoperative dexamethasone treatment on blood-brain barrier dysfunction to bovine albumin. In ethanol-intoxicated rats, fluorescence microscopy revealed an increased area of extravasation of fluorescent tracer, compared to non-intoxicated ones. No significant effect of dexamethasone treatment was observed in non-intoxicated rats. In ethanol-intoxicated rats, dexamethasone treatment resulted in a decreased area of extravasation. Quantitative immuno-electrophoretic measurements of exogeneous bovine albumin confirmed a significant decrease of blood-brain barrier dysfunction to albumin after dexamethasone treatment in ethanol-intoxicated rats, while no significant effect was observed in non-intoxicated ones.