Biomedical subjects

F R Sharp

Publications and source records attributed to F R Sharp.

At least 55 records · Page 3Linked to original sources

PubMed1996

FOS expression in the brainstem and cerebellum following phencyclidine and MK801.

The non-competitive N-methyl-D-aspartate (NMDA) receptor antagonists phencyclidine (PCP) and dizocilpine maleate (MK801) cause nystagmus, tremor, and cerebellar ataxia at toxic doses. We have shown that PCP but not MK801 is toxic to rat cerebellar Purkinje cells. To study the mechanism and pathways of PCP and MK801 action, Fos protein expression was examined in the cerebellum and functionally related nuclei of the brainstem. PCP, 1-50 mg/kg i.p., induced Fos immunostaining in neurons of the inferior olive, cerebellar granule cell layer, and deep cerebellar and vestibular nuclei. At higher doses, PCP, 25-50 mg/kg, induced dense Fos immunoreactivity throughout the inferior olive except for rostral parts of medial accessory olive and caudal parts of principal olive. At lower doses of PCP, 1-10 mg/kg, Fos positive cells in inferior olive were concentrated in the subnucleus beta. In the cerebellum Fos positive granule cells were arranged in patches distributed throughout the cerebellar cortex following PCP, 1-50 mg/kg. Rare Fos positive Purkinje cells were observed adjacent to these patches. At the highest dose of PCP tested (50 mg/kg), Fos was expressed in the fastigial, interpositus, and dentate nuclei, and in vestibular nuclei, most prominently in the medial vestibular nucleus. At lower doses, Fos was expressed mainly in medial cerebellar output nuclei and in vestibular nuclei. MK801, 0.2-10 mg/kg i.p., induced Fos expression in the same regions as PCP. However, MK801-induced Fos expression in inferior olive was localized primarily to subnucleus beta. No apparent differences in the number or distribution of Fos positive neurons were observed at MK801 doses of 0.2-10 mg/kg. MK801 also induced Fos expression in fastigial and vestibular nuclei, but not in lateral (interpositus and dentate) cerebellar nuclei. MK801, 0.2-10 mg/kg, induced patchy Fos expression in cerebellar granule cells that was similar to PCP. These results support our earlier observations that PCP and MK801 have different actions in the cerebellum, although they both cause ataxia and indistinguishable behavioral symptoms. That high doses of PCP induce substantially more Fos expression in inferior olive than MK801 suggests that its toxicity to Purkinje cells is at least partially the result of excessive activity of climbing fibers, the excitatory neural input that arises from the inferior olive and synapses on Purkinje cell dentrities.

Animals↗

PubMed1996

Astrocyte survival and HSP70 heat shock protein induction following heat shock and acidosis.

Although severe acidosis is an important mediator of brain infarction, recent evidence suggests that mild acidosis may protect ischemic cells. The HSP70 heat shock protein is induced by acidosis in cultured cells and in ischemic brain and protects cells against many types of injury. Therefore, this study determined whether induction of heat shock proteins protects cultured astrocytes against acidosis. Brief exposure of cultured cortical astrocytes to acid (pH 5.2 for 40 min) or heat shock (45 degrees C for 40 min) markedly induced hsp70 mRNA and HSP70 protein. HSP70 protein was detected with the C92 monoclonal antibody (Welch and Suhan: J Cell Biol 103:2035, 1986), which has been shown to recognize the protein product of the full-length rat hsp70 cDNA (Longo et al: J Neurosci Res 36:325, 1993). Heat shock of the cultured cortical astrocytes completely protected the astrocytes from an otherwise lethal heat exposure 24 h later (45 degrees C for 4 h). In contrast, heat pretreatment sensitized the astrocytes to injury from acidosis 24 h later. Acid pretreatment, which markedly induced the HSP70 protein without producing astrocytic cell death, similarly sensitized the cells to injury from acidosis 24 h later (60% survival following pH 5.2 for 3 h versus 90% survival in controls; P < 0.0001). Surprisingly, heat shock pretreatment protected astrocytes against exposure to acid 48 h later (P < 0.05, 1.5-3 h), whereas acid pretreatment had no effect on astrocyte survival 48 h later. Since heat shock did not protect against acidosis at 24 h when HSP70 induction was maximal but did protect at 48 h when HSP70 was markedly diminished, the protective effect of heat shock at 48 h may be related to stress proteins present at 48 h. It is concluded that induction of HSP70 and other heat shock proteins by heat shock protects astrocytes against subsequent lethal heat shock. However, heat shock and acid treatment increase the vulnerability of astrocytes to acidosis 24 h later in spite of the induction of HSP70 heat shock proteins. The finding that heat shock protected astrocytes against acidosis 2 days later may suggest that delayed induction of stress proteins partially protects the astrocytes against damage produced by high concentrations of hydrogen ions.

Acidosis↗

PubMed1996

Haloperidol prevents ketamine- and phencyclidine-induced HSP70 protein expression but not microglial activation.

Noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonists, inclu ding ketamine and phencyclidine (PCP), produce abnormal intracellular vacuoles in posterior cingulate and retrosplenial cortical neurons in the rat. Ketamine also induces 70-kDa heat shock protein (HSP70) expression in pyramidal neurons in the posterior cingulate and retrosplenial cortex and, as shown by this study, activates microglia in the retrosplenial cortex of the rat. Whereas HSP70 protein expression was induced with ketamine doses of 40 mg/kg (ip) and higher, doses of 80 mg/kg and higher were required to activate microglia. HSP70-positive neurons were observed in 30- to 90-day-old rats but not in younger, 10- to 20- day old animals following ketamine (80 mg/kg, ip). Pretreatment with the antipsychotic drug haloperidol at doses of 1.0 mg/kg and above abolished all HSP70 immunostaining produced by ketamine (80 mg/kg). However, a single dose of haloperidol (5 mg/kg, im) did not decrease the number of microglia activated in retrosplenial cortex by ketamine (80-140 mg/kg). Similarly, PCP (10 and 50 mg/kg, ip)-induced microglial activation in the posterior cingulate and retrosplenial cortex of adult rats was not blocked by haloperidol (10 mg/kg, im, 1 h prior to PCP). These results suggest that ketamine and PCP injure neurons in the posterior cingulate and retrosplenial cortex of adults rats. Though haloperidol may afford some protection against this injury since it inhibits induction of HSP70 expression, the failure to prevent microglial activation suggests that single doses of haloperidol do not completely protect neurons from NMDA antagonist toxicity.

Animals↗

PubMed1996

Heme oxygenase-1 (HO-1) protein induction in rat brain following focal ischemia.

The induction of the heme oxygenase-1 (HO-1) protein, also called HSP32, was compared to HSP70 heat shock protein induction following focal ischemia. Adult Sprague-Dawley male rats (n = 14) were subjected to either 30 min or 2 h of focal cerebral ischemia using the suture, middle-cerebral-artery (MCA) occlusion model. Controls (n = 4) had sham surgery. Following 24 h of reperfusion, subjects were killed and their brains stained immunocytochemically for HO-1 and the HSP70 heat shock proteins. One day following 30 min of ischemia, HO-1 and HSP70 staining in striatum occurred mainly in endothelial cells in infarcts and in glial cells surrounding the areas of infarction. Following the 30 min ischemia HO-1 was not induced in cortex whereas HSP70 was induced in cortical neurons in the MCA distribution. One day following 2 h of MCA ischemia, both HO-1 and HSP70 were induced in neurons in cortex in the MCA distribution. HO-1, however, was induced in glial cells throughout ipsilateral cortex, inside as well as outside the MCA distribution. This suggests that translation and/or transcription of the HO-1 and HSP70 genes are blocked in neurons and glia destined to die within infarcts, whereas translation of these stress genes continues in the endothelial cells. The duration of ischemia required to induce HSP70 in cortical neurons appears to be less than that required to induce HO-1 in cortical glia. Prolonged spreading depression and/or diffuse hemispheric ischemia may induce HO-1 in glia throughout the ipsilateral cortex via immediate early gene activation of the AP-1 site in the HO-1 promoter. Since HO-1 degrades heme, a pro-oxidant, to antioxidant molecules, the induction of HO-1 may augment oxidative defense mechanisms compromised by cerebral ischemia.

Animals↗

PubMed1996

Patient selection and treatment modalities for chronic anal fissure.

BACKGROUND: Incontinence of feces or flatus is a serious complication of lateral internal sphincterotomy with a incidence of 0-35%. Multiple cofactors may predispose to fecal incontinence. METHODS: Review of 27 reported series of internal sphincterotomy and analysis of 34 consecutive cases of fecal incontinence seen by the author were carried out. Reports of the effect of topical nitroglycerin or botulinum toxin on the anal sphincter are discussed and supplemented by the author's experience. RESULTS: Reported postoperative incidence of incontinence to feces or flatus is remarkably variable (0-35%). Multiple factors (eg, multiparity, age, constipation, and previous surgery) were identified in each of the author's cases of incontinence. Pharmacologic sphincterotomy reliably relieves sphincter spasm and may promote healing. CONCLUSIONS: Reappraisal of current standard treatment of anal fissure is warranted. Many preexisting, possibly predisposing, factors should be considered when deciding on treatment. Pharmacological sphincterotomy requires further clinical study. New nonsurgical modalities should be included in the treatment algorithm.

Adult↗

PubMed1996

Global ischemia induces apoptosis-associated genes in hippocampus.

Using in situ hybridization, Northern blotting and RT-PCR we studied the post-ischemic expression of bcl-2, bcl-x, bax and ICE. One day following 5 min or 10 min of global ischemia bcl-2 and bcl-x mRNAs were induced in CA1 hippocampal pyramidal neurons while bax was unchanged. By 72 h after ischemia the expression of bcl-2, bcl-x and bax mRNAs decreased in CA1. The large isoform of bcl-x (bcl-xL), detected using RT-PCR, decreased in whole hippocampus by 24-72 h after ischemia relative to the putative short (bcl-xS) and transmembrane deleted (bcl-x delta TM) forms. Oligonucleotides to interleukin-1 beta convertase (ICE), which detected the expected 2-kb transcript and two lesser 1.5- and 3-kb hybridizing species, demonstrated slight mRNA induction in the CA1 region at 72 h following ischemia. DNA nick end-labeling at 3 days following ischemia showed DNA fragmentation in neurons limited to the CA1 region of hippocampus following 5 min ischemia, while DNA fragmentation was detected in CA1, CA3, dentate gyrus and cortical neurons following 10 min ischemia. The data support the view that hippocampal neurons might undergo an apoptosis-like death after global ischemia. Since global ischemia decreases total protein synthesis especially in the CA1 region, the increases in bcl-2 mRNA levels may not necessarily lead to increased Bcl-2 protein levels. This may explain why the CA1 neurons die despite the prominent induction of the protective bcl-2 gene. The observed decrease by 24 h in the bcl-xL/bcl-xS ratio which preceded DNA fragmentation may participate in the cell death produced by ischemia. However, because of the ischemia-induced decrease in total protein synthesis, the decreased bcl-xL/bcl-xS ratio does not necessarily lead to a changed ratio in the amount of the appropriate proteins. Since ICE-like mRNA was induced at 72 h when the CA1 neurons were dead, the significance of this ICE-like mRNA induction remains unclear.

Animals↗

PubMed1996

Purkinje cell vulnerability to mild traumatic brain injury.

In this study we examined the cerebellar response to mild traumatic brain injury by assessing microglial activation and Purkinje cell loss. Activated microglia were identified using the antibodies OX-42 and ED-1 as well as isolectin B4. The anti-Purkinje cell antibody PEP-19 was used to evaluate Purkinje cell loss after injury. The mechanism of cell injury was examined using a monoclonal antibody to the inducible 72-kDa heat shock protein. A monoclonal antibody to the N-terminal sequence of Fos was used as a marker for neuronal activation. There was progressive activation of microglia in the cerebellar vermis within a few days after forebrain injury. In coronal sections the processes of activated microglia were oriented in "stripes" perpendicular to the cortical surface. In sagittal sections the activated microglia were in irregularly shaped clusters or in a fan-like distribution that radiated from the Purkinje cell layer toward the cortical surface. There was a significant loss of Purkinje cells 7 days postinjury as compared to the control group. There was no evidence of induction of heat shock protein in the cerebellum. In addition, there was no evidence of induction of c-Fos protein in either the cerebellar cortex or inferior olivary nuclei within the first 3 h after injury. These studies demonstrate that a fluid percussive impact to the forebrain results in cerebellar damage. The close anatomical association between activated microglia and Purkinje cells suggests that Purkinje cell injury is the cause of the microglial activation. The mechanism of Purkinje cell death, however, remains unclear.

Animals↗

PubMed1996

Global ischemia induces immediate-early genes encoding zinc finger transcription factors.

Ischemia induces immediate-early genes (IEGs) in brain. Since prolonged expression of some IEGs may precede neuronal death, some researchers have suggested that these IEGs mediate neuronal death. We therefore examined the effect of 5 and 10 min of global ischemia on the expression of the IEGs NGFI-A, NGFI-B, NGFI-C, egr-2, egr-3, and Nurr1 in gerbil brain. All of the IEGs were induced after 30 min of reperfusion in the hippocampus. Most of them were induced in several other regions as well, including cortex, hypothalamus, thalamus, and amygdala. The acute IEG induction decreased in most brain areas by 2-6 h. However, at 24 h following 5 min of ischemia NGFI-A continued to be expressed in the CA1 region and dentate gyrus. In the dentate gyrus, NGFI-C continued to be expressed for 24 h and egr-3 for as long as 72 h. In other brain areas, all of the IEGs returned to control levels by 72 h except in CA1, where most messenger RNA (mRNA) levels were decreased; this decrease correlated with marked neuronal loss. The persistent expression of NGFI-A in CA1 neurons destined to die and the persistent expression of NGFI-A, NGFI-C, and egr-3 genes in dentate granule cell neurons that survive may indicate that some transcription factors modulate cell death whereas others support cell survival when expressed for prolonged periods. The protein products of several transcription factors, including c-fos, are known to downregulate their own expression. The persistent expression of NGFI-A in the CA1 neurons destined to die could therefore be due to ischemia-induced transcriptional activation caused by, e.g., increased intracellular calcium levels plus a lack of negative feedback caused by the blockade of the translation of NGFI-A mRNA into protein.

Animals↗

PubMed1996

DNA fragmentation and HSP70 protein induction in hippocampus and cortex occurs in separate neurons following permanent middle cerebral artery occlusions.

DNA nick end-labeling (TUNEL) and heat shock protein (HSP)70 immunocytochemistry were performed on the same brain sections 1 (n = 6), 3 (n = 12), and 7 (n = 7) days following permanent middle cerebral artery (MCA) occlusions produced in adult rats using the endovascular carotid suture method. In the cortex at 1 and 3 days following MCA occlusions, HSP70 immunoreactive neurons were located outside areas of infarction and showed little evidence of DNA fragmentation. HSP70-stained cortical neurons were intermingled with TUNEL cells near the infarct, but extended for greater distances away from the infarct. DNA fragmentation occurred in CA1 hippocampal neurons in 39% of the animals at 1 and 3 days following ipsilateral MCA occlusion. Bilateral DNA fragmentation occurred in CA1 neurons in one subject. HSP70 protein was expressed in CA1 hippocampal neurons in nine of 18 (50%) animals at 1 and 3 days following MCA occlusions, including all animals that exhibited hippocampal DNA fragmentation. Three animals had bilateral expression of HSP70 in CA1 neurons. Cells that stained for either HSP70 protein or DNA fragmentation existed in close proximity to one another. Approximately 5-7% of HSP70-stained cells were TUNEL stained and 3% of TUNEL-positive cells also stained for HSP70. There was no HSP70 staining or DNA fragmentation in the brains of sham-operated controls (n = 4) or in the brains of animals 7 days following MCA occlusions. These data suggest that ischemic cells capable of translating HSP70 protein generally do not undergo DNA fragmentation. These data support the concept that most HSP70 protein-containing neurons in the cortical "penumbra" and hippocampus survive ischemic injury and are "reversibly injured." It is shown that CA1 hippocampal pyramidal neurons die or are reversibly injured in approximately 50% of animals following permanent MCA occlusions. Although the mechanism of this hippocampal injury is unknown, it could relate to transynaptic activation of N-methyl-D-aspartate (NMDA) receptors that mediate induction of early genes in hippocampus.

Animals↗

PubMed1996

Eliprodil prevents expression of the 70 kDa heat shock protein in MK801-injured neurones.

The present study examined whether eliprodil (SL 82.0715), an N-methyl-D-aspartate (NMDA) receptor antagonist acting on the polyamine sites induced expression of the 70 kDa heat shock protein (HSP70) in the rat brain. Whereas the NMDA channel blocker MK801 consistently induced HSP70 in posterior cingulate and retrosplenial cortices, eliprodil had no such effects even at the highest dose (50 mg/kg, intraperitoneally), supporting the idea that injury to the cerebrocortical neurones by NMDA receptor antagonists is probably related to specific sites of the receptor. Furthermore, eliprodil, given immediately after injection of MK801, blocked the effects of MK801 on HSP70. The result is discussed in terms of high affinity of eliprodil for the sigma receptor.

Animals↗

PubMed1996

MK-801 reduces uptake and stimulates efflux of excitatory amino acids via membrane depolarization.

MK-801 and related compounds reduce excitotoxic neuronal injury by blocking N-methyl-D-aspartate (NMDA) receptorgated ion channels. These agents also cause neuronal vacuolization and block glutamate-induced astrocyte swelling, effects that may be unrelated to actions at the NMDA receptor. In the present study, high concentrations of MK-801 (100-1,000 microM) caused uncompetitive inhibition of glutamate uptake in astrocyte and neuronal cultures and stimulated D-aspartate efflux from astrocytes. MK-801 (500 microM) reduced the maximal velocity for glutamate uptake in astrocytes from 31 to 17 nmol.mg protein-1.min-1, whereas competitive NMDA receptor antagonists did not affect glutamate uptake. MK-801 also inhibited uptake of gamma-aminobutyric acid (GABA). Because both GABA uptake and glutamate uptake are electrogenic, one mechanism by which MK-801 could inhibit uptake is by membrane depolarization. Whole cell patch-clamp recording confirmed that MK-801 in the range of 100-1,000 microM caused dose-dependent and reversible depolarization. These concentrations are far higher than necessary to block NMDA receptors, and the findings suggest that actions at sites other than NMDA receptors could contribute to the effects of high doses of MK-801 in some experimental and clinical settings.

Amino Acids↗

PubMed1996

Subarachnoid injections of lysed blood induce the hsp70 stress gene and produce DNA fragmentation in focal areas of the rat brain.

BACKGROUND AND PURPOSE: Most experimental studies of subarachnoid hemorrhage have demonstrated little histological evidence of injury. In the present study we examined both the expression of the hsp70 heat-shock gene, a molecular marker of reversible neuronal injury, and DNA fragmentation, a marker of irreversible cell injury and death. METHODS: Lysed blood, whole blood, oxyhemoglobin, bovine serum albumin, and saline were injected into the cisterna magna of adult rats. The induction of hsp70 mRNA and HSP70 heat-shock protein was assessed with the use of in situ hybridization and immunocytochemistry, respectively. Fragmentation of genomic DNA was studied by DNA nick end- labeling with the use of terminal deoxynucleotidyl transferase and biotinylated dATP. RESULTS: Expression of the hsp70 gene was not induced in the brains of rats injected with whole blood, oxyhemoglobin, bovine serum albumin, or saline. Lysed blood injections, however, induced hsp70 mRNA at 6 and 24 hours in the cerebellar hemispheres and in focal regions of the basal forebrain. HSP70 protein was induced by 24 hours and persisted for at least 4 days in the same regions. HSP70 protein was localized to patches of glial cells and occasional neurons in the forebrain. In the cerebellum HSP70 was localized to Bergmann glial cells, granule cells, molecular layer stellate cells, and occasional Purkinje cells. DNA nick end-labeling showed patches of labeled cells in the basal forebrain that occurred in the same regions that hsp70 mRNA was induced. CONCLUSIONS: The results demonstrate focal stress gene induction and DNA fragmentation after subarachnoid hemorrhage. It is hypothesized that the focal areas of hsp70 induction may reflect ischemic injury due to vasospasm produced by lysed blood and/or injury mediated by direct toxic effects of the lysed blood. The hsp70 induction and DNA nick end-labeling in the same regions suggests that lysed blood produces a spectrum of injury from HSP70 protein-labeled, reversibly injured cells to dead cells with fragmented DNA. Induction of the hsp70 stress gene and DNA nick end-labeling may be useful for evaluating the causes of injury, the spectrum of injury, and potential pharmacological therapies in experimental models of subarachnoid hemorrhage.

Animals↗

PubMed1996

Induction of HSP70 in rat brain following subarachnoid hemorrhage produced by endovascular perforation.

Current experimental research on subarachnoid hemorrhage (SAH) has been limited by the lack of a small-animal model that physiologically resembles SAH and consistently demonstrates acute and delayed cellular injury. Recently, a model for inducing SAH by endovascular perforation of the internal carotid artery has been developed in the rat. This model physiologically resembles SAH. However, little histological data detailing cellular injury after SAH are available in this or other models. Using immunocytochemistry, the authors investigated the induction of the 70-kD heat shock protein, HSP70, a sensitive marker for cellular stress or injury in the brain, 1 and 5 days following endovascular SAH. The authors also used the conventional histological techniques of cresyl violet and hematoxylin and eosin staining to investigate cellular damage 1 and 5 days after the endovascular SAH. One day following the SAH, HSP70 was induced in all six animals examined in multiple anatomical regions, including the basal forebrain, thalamus, neocortex, striatum, and hippocampus. This HSP70 induction was observed in multiple vascular distributions bilaterally. Immunostaining with HSP70 occurred primarily in neurons but also was observed in glia and endothelium. Five days after the SAH, a similar but more intense pattern of HSP70 immunostaining was observed in all eight animals examined. Specifically, HSP70 immunoreactivity was observed in at least one region of the hippocampus more often at 5 days (six of eight animals) than at 1 day (one of six animals, p < 0.05, one-tailed Fisher's exact test). No HSP70 immunostaining was observed in control animals at 1 day or at 5 days. Conventional histology demonstrated foci of ischemic neuronal damage and cellular necrosis; however, HSP70 immunocytochemistry detailed cellular injury far better than conventional histology in all animals tested at both 1 day and 5 days. Our results demonstrate that HSP70 is induced in multiple regions and cell types 1 day and 5 days following endovascular SAH. Because ischemia is a known inducer of stress genes, the authors propose that acute and delayed ischemia are the processes responsible for the induction of HSP70 that was observed at 1 day and 5 days, respectively. Investigation of HSP70 induction following endovascular SAH may also serve as the basis for a new, inexpensive animal model to assess potential therapeutic interventions.

Animals↗

PubMed1996

Focal hyperexpression of hemeoxygenase-1 protein and messenger RNA in rat brain caused by cellular stress following subarachnoid injections of lysed blood.

Induction of the hemeoxygenase-1 (ho-1) stress gene is of importance for rapid heme metabolism and protection against oxidative injury in vitro and in vivo. Although ho-1 expression is observed in glia following exposure to whole blood and oxyhemoglobin, expression is mild, and other stress genes are not induced simultaneously in this setting. Hemeoxygenase-1 can be induced by several other physiological stresses in addition to heme. In the brain, ho-1 induction has been observed in the penumbra following focal cerebral ischemia. Because lysed blood is a spasmogen, the authors studied focal hyperexpression of the ho-1 gene after injection of lysed blood, whole blood, or saline into the cisterna magna of adult rats. Immunocytochemical analysis of HO-1 was performed at 1, 2, 3, and 4 days after the injections. Because the 70-kD inducible heat shock protein (HSP70) is induced by cellular stress, alternate sections were immunostained for HSP70 to assess whether focal hyperexpression was a stress phenomenon. An oligonucleotide probe was also used for in situ hybridization to demonstrate that ho-1 messenger (m)RNA was present. Focal HO-1 immunostained areas were observed after lysed blood injection only and were located mainly in the basal cortex and cerebellar hemisphere, although focal hyperexpression was also found in many other regions. The intensity of staining and the number of regions were maximum at 1 day. Double-labeled immunofluorescence revealed that many HO-1-immunoreactive cells were microglia. The HSP70 immunostaining of adjacent sections from the same animals demonstrated focal regions of immunoreactivity whose topography corresponded exactly with the topography of the HO-1-immunostained areas. Conventional histology in regions of HO-1 hyperexpression was often normal. In situ hybridization using the same oligonucleotide demonstrated that ho-1 mRNA was induced in focal areas of forebrain and in large regions of cerebellum within 6 hours of injection. These results demonstrate that focal hyperexpression of the ho-1 stress gene occurs after lysed blood injection and appears to be an indicator of cellular stress and injury in regions in which infarction does not occur. These results also suggest that cellular injury that occurs after injection of lysed blood may go undetected using conventional histology. Although direct heme metabolism was not investigated, our results indicate that rapid metabolism of heme, both intracellular and extracellular, may prove to be beneficial after subarachnoid hemorrhage.

Animals↗

PubMed1996

The stress gene response in brain.

Changes in gene expression in the brain in response to adverse conditions, such as ischemia or excitotoxin exposure, may be part of the injury process or represent an adaptive response which may be protective during subsequent stressful events. In this review we have considered the regulation, functions and potential relationships to the pathophysiology of ischemia of several major groups of stress-induced genes, including those of the M(r) 27,000, 32,000 (heme oxygenase), 70,000 and 90,000 heat shock protein families, the glucose-regulated proteins, glucose transporters and ubiquitin. Patterns of gene expression in several injury models, including focal and global ischemia, excitotoxin/ seizure-related injury and hyperthermia are reviewed. In vitro expression studies and the phenomenon of ischemic tolerance are also discussed. It is concluded that stress gene expression provides a useful marker of cellular injury, and that disjunction of mRNA and protein expression may be indicative of imminent death in cells which survive the initial insult. Though other stress proteins may play a role, it seems unlikely that neuronal hsp70 expression is a major contributor to ischemic tolerance.

Animals↗

PubMed1995

Induction of HSP-70 after hyperosmotic opening of the blood-brain barrier in the rat.

The cellular response resulting from breakdown of the blood-brain barrier was evaluated 24 h after hyperosomotic infusion of mannitol into the internal carotid artery in the rat. Heat shock protein (HSP-70), a marker of cellular stress and/or injury, was induced in scattered patches of neurons and glia in regions of barrier breakdown. These findings suggest that osmotically induced breakdown of the blood-brain barrier may result in cell injury.

Animals↗

PubMed1995

HSP70 heat shock protein induction following global ischemia in the rat.

Stress proteins, including the 70 kD heat shock protein (HSP70), are induced in injured cells. The present study was designed to characterize the cells injured by global ischemia in rat brain. Adult rats were subjected to forebrain ischemia using bilateral carotid occlusion and systemic hypotension. HSP70 protein immunostaining of brain sections was performed using the C92 monoclonal antibody one day later. HSP70 immunoreactive cells were found in many brain regions including cortex. HSP70 positive neurons in cortex were found in certain laminae, especially layers 2 and 3. Acid fuchsin positive neurons, cells presumed to be dead, were located only in the layers of cortex where HSP70 immunoreactive neurons were found and were infrequent compared to the large number of HSP70 positive neurons. HSP70 immunoreactive glial cells were detected at the margins of ischemic areas, and were mostly OX42 immunoreactive microglia plus some GFAP immunoreactive astrocytes. In some animals HSP70 stained bipolar cells were detected in the striatum and in white matter which may be type 2 astrocytes. These findings confirm that global ischemia injures microglia and astrocytes, and that cells in a given ischemic region sustain varying degrees of injury--from the HSP70 stained neurons that likely survive the ischemia to acid fuchsin stained cells that die.

Animals↗

PubMed1995

Induction of heme oxygenase-1 (HO-1) after traumatic brain injury in the rat.

The induction of heme oxygenase-1 (HO-1), the 32 kDa heat shock protein, was examined in the traumatized rat brain. At 24 h after either mild or severe brain injury or sham surgery, HO-1 was immunolocalized in fixed sections of brain. After mild brain injury, hemorrhage was apparent in the subarachnoid space, external capsule and cerebellum. HO-1 was induced in similar areas in macrophages in the subarachnoid space and in glia in the cortex adjacent to the site of impact, the ipsilateral hippocampus, external capsule and cerebellum. After severe brain injury, extensive hemorrhage occurred in the external capsule, hippocampus and cerebellum. HO-1 was induced in glia in these areas of hemorrhage but was more extensive than that seen after mild injury and included the contralateral external capsule and hippocampus. These findings demonstrate remarkable induction of HO-1 in glia in the injured brain. Since heme is a potent inducer of HO-1, it is likely that the subarachnoid and/or intraparenchymal blood induced HO-1 in the glia where the heme was metabolized to biliverdin, iron, and carbon monoxide.

Animals↗