Endothelin-like immunoreactivity in hippocampus following transient global cerebral ischemia. I. Neuronal and glial cells

The effect of transient, global ischemia on endothelin (ET) localization in CA1 area of hippocampus of the rats was investigated using post-embedding immunogold method. This paper provides immunocytochemical evidence that cerebral ischemia is accompanied by the increase of production of endothelin in CA1 area of the rat. This study focuses on the analysis ET-like immunoreactive neurons and glial cells in hippocampal CA1 area after long-term survival after ischemia: 1 week-12 months. One and two weeks after ischemia appearance of shrunken neurons and significant increase in ET-like immunoreactivity in astroglial cells as well as their proliferation was observed. Six and twelve months--marked immunoreactivity of endothelin in shrunken neurons and in perineuronal microglial macrophages was observed. The data suggest the possibility that the increased intracellular content of endothelin has a role in the development of neuronal death even following a long-term period after ischemia.     

Cold-injury of the cerebral cortex: immunolocalization of cellular proteins and blood-brain barrier permeability studies

The occurrence of blood-brain barrier (BBB) permeability alterations and neovascularization are well documented in the cerebral cortical cold-injury model. This model was used to determine whether the glucose transporter (glutI) protein was present in endothelium of cerebral vessels with breakdown of BBB to protein and when regenerating endothelial cells become immunoreactive for glutI protein. Secondly, the protein products of c-fos and c-jun were localized to determine whether these early immediate genes are activated in this model. Observations were made over a period of 12 hours to 14 days after the cold-injury. Blood-brain barrier permeability was assessed using horseradish peroxidase (HRP) as a tracer. Since HRP may not be able to enter thrombosed vessels within the cold lesion, immunohistochemistry was used to detect extravasation of endogenous serum proteins using antisera to rat serum proteins. The proteins-glut1, GFAP, c-fos and c-jun-were localized by immunohistochemistry. Endothelium of vessels which were permeable to protein, whether in the cold-injury site or in the perilesional area, all contained glut1 protein; hence, the presence of glut1 did not appear to correlate with an intact BBB to protein. An interesting point is that in the process of neovascularization, regenerating endothelial cells become immunoreactive for glut1 at 5 days and this coincides with the presence of tight junctions in these cells. Immunoreactivity for c-fos was observed in regenerating endothelium within the lesion site, in astrocytes, and to a lesser extent in endothelial cells and neurons in the perilesional area. Few astrocytes showed immunoreactivity for c-jun at 4 and 5 days. Possibly, the growth factors generated to promote angiogenesis and repair led to activation of the c-fos gene with deposition of c-fos protein. The results suggest that during nervous system development or endothelial regeneration, the presence of glut1 in cerebral endothelium coincides with the presence of an intact BBB to protein and protein tracers. However, in pathological states presence of glut1 in cerebral endothelium does not appear to correlate with an intact BBB to protein. This model lends itself to the study of angiogenesis and repair processes in the cerebral cortex in an environment unaffected by ischemia and thus the findings may be relevant to traumatic injuries of the human cerebral cortex.     

An experimental model of closed head injury in mice: pathophysiology, histopathology, and cognitive deficits

The present study describes the characterization of an experimental model of closed head injury (CHI) in the mouse. This model is a modification of a setup described and used previously in the rat. The weight-drop device was modified and adapted to the size and weight of the mouse and the typical parameters that define the severity of the injury and its outcome were evaluated. The posttraumatic accumulation of water, i.e., cerebral edema, the disruption of the blood-brain barrier (BBB), histopathology, motor and cognitive functions were studied up to 30 days following CHI. Increases in cerebral water content and of BBB permeability were observed in the injured hemisphere at 4 h (p < 0.05) and 24 h (p < 0.01) postinjury, respectively. By 7 days, edema disappeared, while the BBB remained open for up to 30 days. The motor function was evaluated by a set of criteria termed neurological severity score (NSS). NSS was severely impaired immediately after CHI and later showed a spontaneous progressive recovery, although some residual deficits, mainly of beam-walk and balance, were still present at 30 days. Mice trained in the Morris water maze before the injury demonstrated highly significant deficits in memory retention up to at least 11 days postinjury (p < 0.01). Histopathological analysis revealed significant neuronal cell death in CA1, CA2, and CA3 regions of the left hippocampus following CHI. However, in the right hippocampus, overt neuronal cell death was observed only in area CA3 at 7 days after CHI. These results suggest that the modified model of CHI in mice can reproduce the posttraumatic sequelae observed in rats and show that some of the data obtained in this model are essentially similar to those observed in human head injury. The experimental model of CHI in mice may be a useful tool for studies in animals that carry specific genetic alterations, aimed at manipulating neurochemical pathways involved in the pathophysiology of brain damage.     

Brain uptake of mannitol and sucrose after cerebral ischemia: effect of hyperglycemia

The effect of 10 min cerebral ischemia on blood-brain barrier permeability to mannitol and sucrose was evaluated in normo- and hyperglycemic rats. In the period immediately after ischemia (1-4 min) the PS (permeability-surface area product) for mannitol was 159% +/- 75 of control (0.17 +/- 0.02 mg/100 g min) in the hyperglycemic rats (plasma glucose 8 mM) and 204% +/- 30 of control (0.09 +/- 0.02 mg/100 g min) in the hyperglycemic rats (plasma glucose 28 mM). Two hours after ischemia, PS for mannitol returned to the control levels in the normoglycemic rats and remained elevated in hyperglycemic animals. The mannitol/sucrose ratios-2.3 +/- 0.4 in normoglycemic rats and 2.6 +/- 0.1 in hyperglycemic rats-remained unchanged after ischemia. As there was no significant difference in the effects of ischemia on normo- and hyperglycemic rats, it was concluded that the deleterious effect of hyperglycemic on clinical recovery after cerebral ischemia in rats (Siemkowicz & Hansen 1978) is not related to enhancement of BBB damage.     

Hemodynamic rounds series II: pulmonic balloon valvuloplasty

We studied changes in expression of F3/contactin (F3), a neuron-specific adhesion molecule, in the gerbil hippocampus after transient forebrain ischemia for 5 min. By immunohistochemical techniques using F3 antibody, we found a biphasic change in immunoreactivity for F3 in the CA1 area after ischemia. Western blotting of F3 protein showed a similar biphasic change. F3 immunoblots decreased to 67% of the control at 1 week, but then they increased and attained 159% at 3 weeks and 152% at 5 weeks after ischemia. Immunoreactivity of a neurofilament (NF145) showed a similar biphasic change to F3 but to a lesser extent. In contrast, microtubule-associated protein 2 (MAP2) immunoreactivity uniformly decreased after ischemia. In situ hybridization revealed that F3 messenger RNA (mRNA) hybridization signals in CA1 area were greatly reduced 1 week after ischemia, while the signals in the CA3 area were unchanged and even increased 3 weeks after ischemia. Damage to CA3 neurons by hyperthermic ischemia blocked the F3 increase in area CA1. Our results suggest that the initial decrease in F3 following ischemia reflects loss of CA1 neurons and the late increase in F3, which shows that a similar time course with neurofilaments may be caused by neurite sprouting.     

Effect of naftidrofuryl (LS129) on axonal growth

Wistar rats, eight days old, were subjected to permanent bilateral forebrain ischemia, followed by hypoxia for 15 minutes. A cerebral infarct, mainly involving the cerebral neocortex, hippocampus, amygdala, striatum and subcortical white matter was produced. Neurons and glia showing punctate chromatin condensation and karyorrhectic cells were observed 12 hours after hypoxia-ischemia. Their number increased during the first two days and recruitment of cells with degenerating nuclei occurred until day five. In situ labeling of nuclear DNA fragmentation stained many normal-appearing nuclei, as well as punctate chromatin condensations and nuclear fragments in karyorrhectic cells. Delayed neuronal death in the CA1 area of the hippocampus was observed after 20 minutes of transient forebrain ischemia in the adult gerbil. In situ labeling of nuclear DNA fragmentation demonstrated stained punctate chromatin condensation in a few degenerating cells at 48 hours post-ischemia. Substantial labeling of CA1 neurons occurred in the fourth day. Agarose gel electrophoresis of extracted brain DNA from ischemic infant rats and adult gerbils showed a ladder-type pattern which is typical of nuclear DNA fragmentation into oligonucleosomal fragments (internucleosomal cleavage). These findings suggest that endonuclease(s) activation may play a role in cell death induced by different forms of hypoxia-ischemia.     

Amelioration by cyclosporin A of brain damage in transient forebrain ischemia in the rat

The immunosuppressant drug cyclosporin A (CsA) is considered to be inherently protective in conditions of ischemia, e.g. in hepatic and cardiac tissue. However, investigations of effects of CsA on neuronal tissue have been contradictory, probably because the blood-brain barrier (BBB) is virtually impermeable to CsA. In the present study, we exploited the finding that the insertion of a syringe needle into brain parenchyma obviously disrupts the BBB and allows influx of CsA, and explored whether CsA, given as intraperitoneal injections daily for 1 week before and 1 week after forebrain ischemia of 7 or 10 min duration, ameliorates the damage incurred to the hippocampal CA 1 sector. In other experiments, the needle insertion and the first i.p. injection of CsA were made 30 min after the start of recirculation, with continued daily administration of CsA during the postinsult week. In animals which were injected with CsA in daily doses of 10 mg kg-1, but in which no needle was inserted, the drug failed to ameliorate CA1 damage, whether the ischemia had a duration of 7 or 10 min. Likewise, needle insertion had no effect on CA1 damage if CsA was not administered. In contrast, when CsA was given to animals with a needle insertion, CA1 damage was dramatically ameliorated, whether treatment was initiated 1 week before ischemia, or 30 min after the start of recirculation. The effect of CsA seemed larger than that of any other drug proposed to have an anti-ischemic effect in forebrain/global ischemia. Injection of tritiated CsA in one animal with BBB disruption lead to detectable radioactivity throughout the ventricular system, suggesting a generalised increase of the entry of CsA across the BBB. The results demonstrate that immunosuppressants of the type represented by CsA markedly ameliorate delayed neuronal damage after transient forebrain ischemia, provided that they can pass the BBB. It is discussed whether the effect of the drug is one involving calcineurin, a protein phosphatase, or if CsA counteracts a permeability transition of the inner mitochondrial membrane, assumed to occur in response to adverse conditions, e.g. gradual accumulation of Ca2+ in the mitochondria in the postischemic period.     

Two proto-oncogenes that play dual roles in embryonal cell growth and differentiation

BACKGROUND AND PURPOSE: Clinical and experimental data indicate that hyperglycemia can aggravate the consequences of stroke and cerebral ischemia. The purpose of this study was to examine the effects of moderate hyperglycemia on the response of the blood-brain barrier to normothermic (37 degrees C) and hypothermic (30 degrees C) global forebrain ischemia. METHODS: Sixteen rats underwent 20 minutes of four-vessel occlusion followed by 30 minutes of postischemic recirculation. We used the protein tracer horseradish peroxidase as an indicator of increased vascular permeability, and rats were perfusion-fixed for microscopic analysis. To produce moderate hyperglycemia, we gave an intraperitoneal injection of 50% dextrose 15 minutes before the ischemic insult. RESULTS: After normothermic brain ischemia, normoglycemic rats (plasma glucose level, 115 +/- 3 mg/dl) demonstrated extravasated horseradish peroxidase mainly restricted to the cerebral cortex. In contrast, more severe and widespread protein extravasation was documented throughout the neuraxis of hyperglycemic (plasma glucose level, 342 +/- 27) rats. Sites of protein leakage included the cerebral cortex, striatum, hippocampus, thalamus, and cerebellum. Foci of protein extravasation were associated with pial and large penetrating vessels. Intraischemic hypothermia significantly attenuated the blood-brain barrier consequences of hyperglycemic brain ischemia. CONCLUSIONS: Under normothermic ischemic conditions, hyperglycemia significantly worsens the degree of acute blood-brain barrier breakdown compared with normoglycemia. Postischemic blood-brain barrier disruption may play an important role in the pathogenesis of increased brain damage associated with systemic hyperglycemia.     

Efflux of taurocholic acid across the blood-brain barrier: interaction with cyclic peptides

The mechanism for the efflux of taurocholic acid (TC) across the blood-brain barrier (BBB) was studied by examining the elimination of [3H]TC after microinjection into the cerebral cortex. The efflux of [3H]TC from the brain was saturable with a Vmax of 15.0 pmol/min/g brain and a Km value of 0.396 nmol/0.2 microl injectate. Efflux was inhibited by cholic acid (CA), a cationic cyclic octapeptide (octreotide; a somatostatin analogue) and an anionic cyclic pentapeptide (BQ-123; an endothelin receptor antagonist), with an IC50 value of 1.09 nmol/0.2 microl injectate, 1.12 nmol/0.2 microl injectate and 0.12 nmol/0.2 microl injectate, respectively. Probenecid (20 nmol/0.2 microl injectate), but not p-aminohippuric acid (10 nmol/0.2 microl injectate), inhibited the brain efflux of [3H]TC. In addition, elimination of [3H]BQ-123 after microinjection was saturable with a Vmax of 20.8 pmol/min/g brain and a Km of 2.92 nmol/0.2 microl injectate; it was also inhibited by TC with an IC50 value of 0.074 nmol/0.2 microl injectate. In contrast, no significant efflux of [14C]octreotide from the brain was observed until 60 min after microinjection. These results suggest that both TC and BQ-123 are transported from the brain to the circulating blood across the blood-brain barrier via specific mechanisms. Although mutual inhibition was observed between TC and BQ-123, kinetic analysis suggested that the two transport systems differ.     

Degradation of cytokeratin intermediate filaments by calcium-activated proteases (calpains) in vitro: implications for formation of Mallory bodies

A replication defective adenoviral vector containing the E. coli lacZ gene (AdCMVnLacZ) was directly injected into right hippocampus and lateral ventricle immediately after 5 min of transient global ischemia in gerbils. The relations between the lacZ gene expression and DNA fragmentation or heat shock protein 72 (HSP72) immunoreactivity were examined up to 21 days post ischemia. The lacZ gene was transiently expressed at 1 day in the hippocampus except around the CA1 region, while a large number of the periventricular cells strongly expressed the lacZ gene from 8 h to 7 days. In CA1 layer, terminal deoxynucleotidyl dUTP nick end labeling (TUNEL) positive cells, which were present only adjacent to the needle track at 8 h to 1 day, became more extensive in the whole CA1 layer at 3 to 7 days. TUNEL-positive cells were also detected around the DG at 1 day, around the needle track at 8 h to 3 days, and in the choroid plexus cells at 7 days. HSP72 staining was detected in the subiculum at 1 to 3 days, the dentate granule cells at 8 h to 1 day, and in the CA3 or CA4 pyramidal cells at 1 to 3 days. Some lacZ expressing cells were double-positive with HSP72 in DG, while the majority of those were distinguished from the TUNEL-positive cells. Pyramidal neurons were almost completely lost in the CA1 sector at 7 days after the ischemia. The present study demonstrates the successful LacZ gene transfer into the hippocampus and ventricle of postischemic gerbil brain except in the vulnerable CA1 layer by adenoviral vector injection. However, adenovirus-mediated gene transfer may induce indirect apoptotic cell death in the DG and ventricle, in addition to direct traumatic injury around the needle track.     

Influences of chronic tobacco smoke inhalation on aging and oxidant-antioxidant balance in the senescence-accelerated mouse (SAM)-P/2

Our previous investigations demonstrated that neurons in the area between the subiculum and the medial CA1 region and another area between the lateral CA1 and the CA3 region of the hippocampus are very vulnerable to cerebral ischemia in gerbils, where irreversible damages have been observed occur as early as 4-5 min after unilateral or bilateral common carotid artery occlusion. The present study was aimed to characterize these areas anatomically by using the immunohistochemical and zinc histochemical as well as Golgi silver impregnation methods. Our results indicated that these two areas which are topographically apart on the coronal section actually had a common origin in the rostral part of the hippocampus and that they were separated by insertion of the Ca1 neurons between them in the more caudal part of the hippocampus. The distribution pattern of mossy fibers indicated that these areas belonged to the CA2 region. The double immunohistochemical and zinc histochemical procedure confirmed that these areas developed ischemic lesions promptly even without reperfusion but that the CA1 region did not develop similar lesions until after reperfusion for 12-24 h if the ischemic period was brief. While the reason for the observed susceptibility of the CA2 region is not certain at the present time, it is important to distinguish the ischemic lesions in the CA2 region from those in the CA1 and CA3 regions.     

Reduction in brain-derived neurotrophic factor protein level in the hippocampal CA1 dendritic field precedes the delayed neuronal damage in the rat brain

Utilizing a specific polyclonal antibody against a peptide unique for brain-derived neurotrophic factor (BDNF), we investigated the regional and temporal profiles of immunoreactivity of the BDNF protein in the rat hippocampus after transient forebrain ischemia. The pattern of immunoreactivity for the BDNF receptor (TrkB) was also examined and compared with that for BDNF. In the early phase after ischemia, we observed a distinct regional difference in immunoreactivity between the pyramidal cell layer and the stratum radiatum of the CA1 subfield. In the pyramidal cell layer, there was a rapid and transient increase in the positive immunostaining for both BDNF and TrkB. By contrast, in the stratum radiatum there was a marked decrease in BDNF immunoreactivity, but not one in that of TrkB. One week after ischemia, high immunoreactivity for both BDNF and TrkB was observed in the reactive astrocytes in the dendritic field of the CA1 subfield. These findings suggest that a transport of BDNF from the neuronal soma to the dendrites of the stratum radiatum might be ceased after the ischemic insult. Thus, a dysfunctional autocrine mechanism of BDNF within the CA1 neuron may be involved in the pathogenesis of selective neuronal damage after ischemia.     

Cell density-dependent mitogenic effect and -independent cellular handling of epidermal growth factor in primary cultured rat hepatocytes

Brain swelling is a serious complication associated with focal ischemia in stroke and severe head injury. Experimentally, reperfusion following focal cerebral ischemia exacerbates the level of brain swelling. In this study, the permeability of the blood-brain barrier has been investigated as a possible cause of reperfusion-related acute brain swelling. Blood-brain barrier disruption was investigated using Evans Blue dye and [14C]aminoisobutyric acid autoradiography in a rodent model of reversible middle cerebral artery (MCA) occlusion. Acute brain swelling and cerebral blood flow (CBF) during ischemia and reperfusion were analyzed from double-label CBF autoradiograms after application of the potent vasoconstrictor peptide endothelin-1 to the MCA. Ischemia was apparent within ipsilateral MCA territory, 5 min after endothelin-1 application to the exposed artery. Reperfusion, examined at 30 min and 1, 2, and 4 h, was gradual but incomplete within this time frame in the core of middle cerebral artery territory and associated with significant brain swelling. Ipsilateral hemispheric swelling increased over time to a maximum (>5%) at 1-2 h after endothelin-1 but was not associated with a significant increase in the ipsilateral transfer constant for [14C]aminoisobutyric acid over this time frame. These results indicate that endothelin-1 induced focal cerebral ischemia is associated with an acute but reversible hemispheric swelling during the early phase of reperfusion which is not associated with a disruption of the blood-brain barrier.     

Induction of caspase-3-like protease may mediate delayed neuronal death in the hippocampus after transient cerebral ischemia

Delayed neuronal death after transient cerebral ischemia may be mediated, in part, by the induction of apoptosis-regulatory gene products. Caspase-3 is a newly characterized mammalian cysteine protease that promotes cell death during brain development, in neuronal cultures, and in other cell types under many different conditions. To determine whether caspase-3 serves to regulate neuronal death after cerebral ischemia, we have (1) cloned a cDNA encoding the rat brain caspase-3; (2) examined caspase-3 mRNA and protein expression in the brain using in situ hybridization, Northern and Western blot analyses, and double-labeled immunohistochemistry; (3) determined caspase-3-like activity in brain cell extracts; and (4) studied the effect of caspase-3 inhibition on cell survival and DNA fragmentation in the hippocampus in a rat model of transient global ischemia. At 8-72 hr after ischemia, caspase-3 mRNA and protein were induced in the hippocampus and caudate-putamen (CPu), accompanied by increased caspase-3-like protease activity. In the hippocampus, caspase-3 mRNA and protein were predominantly increased in degenerating CA1 pyramidal neurons. Proteolytic activation of the caspase-3 precursor was detected in hippocampus and CPu but not in cortex at 4-72 hr after ischemia. Double-label experiments detected DNA fragmentation in the majority of CA1 neurons and selective CPu neurons that overexpressed caspase-3. Furthermore, ventricular infusion of Z-DEVD-FMK, a caspase-3 inhibitor, decreased caspase-3 activity in the hippocampus and significantly reduced cell death and DNA fragmentation in the CA1 sector up to 7 d after ischemia. These data strongly suggest that caspase-3 activity contributes to delayed neuronal death after transient ischemia.     

A study of the ethical duty of physicians to disclose errors

A quantitative immunocytochemical procedure was used for evaluation of the blood-brain barrier (BBB) to endogenous albumin in plaque-forming (PF) and non-plaque-forming (NPF) groups of scrapie-infected mice at the clinical stage of disease. Ultrathin sections of brain samples (cerebral cortex, hippocampus and cerebellum) embedded in resin (Lowicryl K4M) were exposed to anti-mouse albumin antiserum followed by protein A-gold. Using morphometry, the density of immunosignals (gold particles per microns2) was recorded over four compartments: vascular lumen, endothelium, subendothelial space, and brain parenchyma (neuropil). Morphometric and statistical analyses did not reveal significant differences in the barrier function of the microvasculature of the cerebral cortex and hippocampus in either group of mice, although a slight increase in the number of leaking vessels in the PF group was noted. In contrast, in the cerebellum, the permeability of the microvessels to albumin was significantly higher in the PF than in the NPF mouse group, and this was paralleled by the infiltration of the walls of numerous vascular profiles with amyloid deposits (amyloid angiopathy). These data also indicate the existence of distinct regional differences in BBB function in the brain of scrapie-infected mice. The vascular amyloid deposits and the amyloid plaques present in the cerebral cortex of PF mice were labeled with numerous immunosignals suggesting the affinity of extravasated albumin to these deposits. In conclusion, no convincing evidence was obtained indicating that impairment of the BBB, manifested by increased permeability of vascular segments, is directly related to the deposition of amyloid in the vascular wall and in plaques. Segmental impairment of the barrier function seems to be rather the result of disturbed structural integrity of the components of the vascular wall.     

Flow threshold for reduction of cyclic AMP binding in the hippocampus CA1 and other brain regions during stroke development in gerbils

The flow threshold for alterations of the in vitro [3H]cyclic AMP (cAMP) binding, an indicator of the total amount of particulate cAMP-dependent protein kinase, was evaluated in the gerbil brain after 30 min, 2 h, and 6 h of unilateral common carotid artery occlusion, respectively. The autoradiographic method developed in our laboratory enabled us to measure the [3H]cAMP binding and local CBF in each region of the same brain. The ischemic flow thresholds for reduction of the cAMP binding in the hippocampus CA1 were 18, 34, and 49 ml 100 g-1 min-1 after 30-min, 2-h, and 6-h ischemia, respectively. These values were higher than those in other regions such as the hippocampus CA, and temporal cerebral cortex in each duration of ischemia. These findings indicate that (a) the ischemic flow threshold for perturbation of the cAMP system may be higher in the hippocampus CA1 than in other brain regions, suggesting that the hippocampus CA1 could be especially vulnerable to acute ischemic stress; and (b) the level of the aforementioned threshold may increase progressively during the time course of ischemia in particular regions such as the hippocampus CA1 and CA3, suggesting that the duration of ischemia exerts a definite influence on the viability of the ischemic neuronal cells in these regions.     

The EMG development of the longissimus and multifidus muscles after plugging the horizontal semicircular canals

The intercellular adhesion molecule-1 (ICAM-1) expressed by endothelial cells is crucial in promoting adhesion and transmigration of circulating leukocytes across the blood-brain barrier (BBB). Migrated immunocompetent cells, in turn, release mediators that stimulate glial and endothelial cells to express ICAM-1 and release cytokines, possibly sustaining cerebral damage. Following activation, proteolytic cleavage of membrane-anchored ICAM-1 results in measurable levels of a soluble form, sICAM-1. The aims of this study were to investigate the changes of sICAM-1 levels in ventricular CSF and serum and to elucidate the influence of structural brain damage as estimated by computerized tomography (CT) as well as the extent of BBB dysfunction as calculated by the CSF/serum albumin ratio (QA) in patients with severe traumatic brain injury (TBI). All investigated parameters revealed two subgroups. Patients belonging to group A had sICAM-1 levels in CSF above normal range, presented marked cerebral damage and a disturbance of the BBB (range 0.6-24.7 ng/ml, n = 8). In contrast, patients belonging to group B had no elevation of sICAM-1 values in CSF (range 0.3-3.9 ng/ml, n = 5; p < 0.017) and showed minor cerebral damage with an intact BBB in most cases. In addition, overall analysis showed that sICAM-1 in CSF correlated with the extent of BBB damage as indicated by the QA (r = 0.76; p < 0.001). These results suggest that increased sICAM-1 levels in CSF might depict ongoing immunologic activation and that sICAM-1 correlates with the extent of tissue and BBB damage. The origin of soluble ICAM-1 in CSF and its pathophysiologic role after TBI remains to be clarified.     

Mild traumatic brain injury does not modify the cerebral blood flow profile of secondary forebrain ischemia in Wistar rats

The rat hippocampus is hypersensitive to secondary cerebral ischemia after mild traumatic brain injury (TBI). An unconfirmed assumption in previous studies of mild TBI followed by forebrain ischemia has been that antecedent TBI did not alter cerebral blood flow (CBF) dynamics in response to secondary ischemia. Using laser Doppler flowmetry (LDF), relative changes in regional hippocampal CA1 blood flow (hCBF) were recorded continuously to quantitatively characterize hCBF before, during, and after 6 min of forebrain ischemia in either normal or mildly traumatized rats. Two experimental groups of fasted male Wistar rats were compared. Group 1 (n = 6) rats were given 6 minutes of transient forebrain ischemia using bilateral carotid clamping and hemorrhagic hypotension. Group 2 (n = 6) rats were subjected to mild (0.8 atm) fluid percussion TBI followed 1 h after trauma by 6 min of transient forebrain ischemia. The laser Doppler flow probe was inserted stereotactically to measure CA1 blood flow. The electroencephalogram (EEG) was continuously recorded. During the forebrain ischemic insult there were no intergroup differences in the magnitude or duration of the decrease in CBF in CA1. In both groups, CBF returned to preischemic values within one minute of reperfusion but traumatized rats had no initial hyperemia. There were no intergroup differences in the CBF threshold when the EEG became isoelectric. These data suggest that the ischemic insult was comparable either with or without antecedent TBI in this model. This confirms that this model of TBI followed by forebrain ischemia is well suited for evaluating changes in the sensitivity of CA1 neurons to cerebral ischemia rather than assessing differences in relative ischemia.     

Gangliosides prevent reduction in exploratory activity and delayed neuronal death in gerbils subjected to transitory cerebral ischemia

INTRODUCTION: The ganglioside GM1 has been shown to be effective in the treatment of experimental cerebral ischemia. Gangliosides from bovine brain have not been used in the treatment of ischemic cerebral accidents. There is evidence suggesting that they may also be effective. RESULTS: Ten minutes of bilateral occlusion of the carotid arteries of Mongolian gerbils leads a week later to reduced spontaneous exploratory activity, assessed by counting the number of times they stood up in an open field over a period of three minutes, and retarded neuronal death in the pyramidal stratum of the CA1 sector of the hippocampus, evaluated on the density of normal neurons in this region of both hemispheres. Treatment with 30 mg/kg of intra-peritoneal bovine cerebral gangliosides during the first six days following occlusion of the carotid arteries, leads to conservation of both exploratory activity and density of pyramidal neurons observed in the control animals. CONCLUSIONS: Bovine cerebral gangliosides have a short term cytoprotector effect on neurons sensitive to the ischemia-reperfusion phenomenon. This effect may be due to more than one mechanism, in which other gangliosides (together with GM1) may be present due to transient permeability of the blood-brain barrier.