Stability of currently used cytometers facilitates the identification of pipetting errors and their volumetric operation: "time" can tell all.
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CD4 Lymphocyte Count↗
Biomedical subjects
M Bergeron
Publications and source records attributed to M Bergeron.
Selection of lymphocyte gating protocol has an impact on the level of reliability of T-cell subsets in aging specimens.
BACKGROUND: In the past decade, human immunodeficiency virus (HIV) lymphocyte immunophenotyping has evolved significantly. New fluorochromes, new multicolor reagents, enhanced instruments, and the capacity to provide absolute cell counts using the single-platform technique have all contributed to the reliability of T-cell subset measurements. In this study, four gating protocols were evaluated to select the most robust method for T-cell subset enumeration. METHODS: Peripheral blood specimens from 21 HIV(+) and 20 HIV(-) individuals were monitored up to 96 h. Aliquots of specimens were stored at room temperature and analyzed at 6 (baseline), 48, 72, and 96 h. Aliquots were stained with CD45-fluorescein isothiocyanate (FITC)/CD3PC5/CD4RD1/CD8ECD. Data analysis was performed with all four gating protocols. RESULTS: Only with fresh blood did all protocols provide similar results. From samples that were 48 h old, the choice of gating strategy had a dramatic impact on immunophenotyping results. The largest deviations from baseline values occurred at 96 h and gating protocols that included dual light scatter gates provided the greatest shift of T-cell subset values over time. The gating protocols that were based exclusively on cell lineage-specific gates gave the most robust T-cell values up to 96 h. CONCLUSION: By selecting the appropriate gating protocol, the temporal integrity of specimens can be extended up to 4 days.
Acquired Immunodeficiency Syndrome↗
Hypoxia-inducible factor in brain.
HIF-1 is composed of HIF-1alpha and HIF-1beta protein subunits. HIF-1 is induced by hypoxia and binds to promoter/enhancer elements and stimulates the transcription of hypoxia-inducible target genes. Because HIF-1 activation might promote cell survival in hypoxic tissues, we studied the effect of stroke on the expression of HIF-1alpha, HIF-1beta and several HIF-1 target genes in adult rat brain. After focal cerebral ischemia, mRNAs encoding HIF-1alpha, glucose transporter-1 and several glycolytic enzymes including lactate dehydrogenase were up-regulated in the areas around the infarction. HIF and its target genes were induced by 7.5 hours after the onset of ischemia and increased further at 19 and 24 hours. Since hypoxia induces HIF in other tissues, systemic hypoxia (6% O2 for 4.5 h) was also shown to increase HIF-1alpha protein expression in the adult rat brain. It is proposed that decreased blood flow to the penumbra decreases the supply of oxygen and that this induces HIF-1 and its target genes. Because HIF-1 activation may promote cell survival in hypoxic tissues, we studied the effect of hypoxic preconditioning on HIF-1 expression in neonatal rat brain. Hypoxic preconditioning (8% O2/3 hrs), a treatment known to protect the newborn rat brain against hypoxic-ischemic injury, markedly increased HIF-1alpha and HIF-1beta expression. We also studied the effect of two other known HIF-1 inducers, cobalt chloride (CoCl2) and desferrioxamine (DFX), on HIF-1 expression and neuroprotection in newborn brain. HIF-1alpha and HIF-1beta protein levels were markedly increased after i.p. injection of CoCl2 and DFX. Preconditioning with CoCl2 or DFX 24 hours before the stroke decreased infarction by 75% and 56% respectively, compared with vehicle-injected, littermate controls. Thus, HIF-1 activation could contribute to protective brain preconditioning.
Animals↗
Cellular localization of BM88 mRNA in paraffin-embedded rat brain sections by combined immunohistochemistry and non-radioactive in situ hybridization.
With the advent of gene cloning and sequencing, it has become increasingly common to identify novel genes for which no antibody is available. The best approach to study the expression and the distribution of these new genes is by in situ hybridization. One of the challenges with this method is to define the exact cellular subtype where the gene of interest is expressed. Conventional isotopic in situ hybridization methods lack precision for cellular identification because radioactive probes often result in a scattered signal. To identify the exact cellular subtype expressing BM88, we established a rapid colocalization method using non-isotopic in situ hybridization followed by chromogenic immunohistochemistry on the same tissue section. We demonstrated that BM88, which was identified from subtractive hybridization experiments between normal and ischemic tolerant brain tissue, was expressed exclusively in neurons in normal adult rat brain. Paraffin-embedded tissue was used as it resulted in better preservation of tissue and cellular morphology, thus allowing for more accurate histological localization of gene expression. It also allowed for retrospective studies on a number of archived tissue samples.
Animals↗
Hypoxic preconditioning induces changes in HIF-1 target genes in neonatal rat brain.
Hypoxic preconditioning induces tolerance to hypoxic-ischemic injury in neonatal rat brain and is associated with changes in gene expression. Hypoxia-inducible factor-1 (HIF-1) is a transcription factor that is strongly induced by hypoxia or the hypoxia-mimetic compound cobalt chloride (CoCl(2)). Hypoxia-inducible factor-1 modulates the expression of several target genes including the glycolytic enzymes, glucose transporter-1 (GLUT-1), and erythropoietin. Recently, HIF-1 expression was shown to increase after hypoxic and CoCl(2) preconditioning in newborn rat brain. To study the involvement of HIF-1 target genes in neonatal hypoxia-induced ischemic tolerance, the authors examined the brains of newborn rats after exposure to hypoxia (8% O(2) for 3 hours) or injection of CoCl(2) (60 mg/kg). Preconditioning with hypoxia or CoCl(2) 24 hours before hypoxia-ischemia afforded a 96% and 76% brain protection, respectively, compared with littermate control animals. Hypoxic preconditioning increased the expression of GLUT-1 mRNA and protein, and of aldolase, phosphofructokinase, and lactate dehydrogenase proteins but not mRNA. This suggests that the modulation of glucose transport and glycolysis by hypoxia may contribute to the development of hypoxia-induced tolerance. In contrast, preconditioning with CoCl(2) did not produce any change in HIF-1 target gene expression suggesting that different molecular mechanisms may be involved in the induction of tolerance by hypoxia and CoCl(2) in newborn brain.
Animals↗
Overview and application of suspension array technology.
A cell-based solid-phase immunoassay usually is called immunophenotyping when performed on a flow cytometer. Using the same principles, there is a new flow cytometric application available with the suspension array technology. The significant difference is that the immunologic reaction does not occur on the surface of leukocytes, but rather on the surface of plastic fluorospheres. This is a multiplexed solid-phase flow cytometry-based technology with some clinically relevant potential.
Enzyme-Linked Immunosorbent Assay↗
Sustained induction of heme oxygenase-1 in the traumatized spinal cord.
Oxidative stress contributes to secondary injury after spinal cord trauma. Among the consequences of oxidative stress is the induction of heme oxygenase-1 (HO-1), an inducible isozyme that metabolizes heme to iron, biliverdin, and carbon monoxide. Here we examine the induction of HO-1 in the hemisected spinal cord, a model that results in reproducible degeneration in the ipsilateral white matter. HO-1 was induced in microglia and macrophages from 24 h to at least 42 days after injury. Within the first week after injury, HO-1 was induced in both the gray and the white matter. Thereafter, HO-1 expression was limited to degenerating fiber tracts. HSP70, a heat shock protein induced mainly by the presence of denatured proteins, was consistently colocalized with HO-1 in the microglia and macrophages. This study to demonstrates long-term induction of HO-1 and HSP70 in microglia and macrophages after traumatic injury and an association between induction of HO-1 and Wallerian degeneration. White matter degeneration is characterized by phagocytosis of cellular debris and remodeling of surviving tissue. This results in the metabolism, synthesis, and turnover of heme and heme proteins. Thus, sustained induction of HO-1 and HSP70 in microglia and macrophages suggests that tissue degeneration is an ongoing process, lasting 6 weeks and perhaps even longer.
Animals↗
Role of hypoxia-inducible factor-1 in hypoxia-induced ischemic tolerance in neonatal rat brain.
Hypoxia-inducible factor-1 (HIF-1) is a heterodimer composed of HIF-1alpha and HIF-1beta protein subunits. This transcription factor is essential for the activation of hypoxia-inducible genes like erythropoietin, some glucose transporters, the glycolytic enzymes, and vascular endothelial growth factor. Because HIF-1 activation may promote cell survival in hypoxic tissues, we studied the effect of hypoxic preconditioning on HIF-1 expression in neonatal rat brain. Hypoxic preconditioning (8% O2 for 3 hours), a treatment known to protect the newborn rat brain against hypoxic-ischemic injury, markedly increased HIF-1alpha and HIF-1beta expression. To support the role of HIF-1 in protective preconditioning, we also studied the effect of two other known HIF-1 inducers, cobalt chloride (CoCl2) and desferrioxamine (DFX), on HIF-1 expression and neuroprotection in newborn brain. HIF-1alpha and HIF-1beta protein levels were markedly increased after intraperitoneal injection of CoCl2 (60 mg/kg) and moderately increased after intraperitoneal injection of DFX (200 mg/kg) 1 to 3 hours after the injections. Preconditioning with CoCl2 or DFX 24 hours before hypoxia-ischemia afforded 75 and 56% brain protection, respectively, compared with that in vehicle-injected littermate controls. Thus, HIF-1 activation could contribute to protective brain preconditioning, which could be used in high-risk deliveries and other clinical situations.
Animals↗
Norms of subjective frequency of use and imagery for a sample of 1,916 French nouns.
Norms of rated subjective frequency of use and imagery on seven-point scales are reported for 1,916 French nouns. Subjective frequency was defined as the rated frequency of occurrence of words in spoken French, and imagery was defined as the rated case with which a word aroused a mental image. The mean, standard deviation, and percentile rank of the frequency and imagery ratings for each item are presented in the Appendix together with their objective frequency of occurrence in Baudot's (1992) dictionary. Interjudge reliability was assessed by calculating the correlation between the mean ratings of items repeated in the booklet, between the mean ratings obtained from odd-numbered and even-numbered respondents, and by computing the Cronbach alpha statistic for each page of the booklet. These reliability estimates were equal to or greater than .92 for frequency and for imagery, confirming the high level of interjudge consistency. Although the estimates provided by female and male participants were highly correlated (r = .97), the former gave a slightly higher frequency rating to the word sample but a slightly lower imagery rating than the latter did. Moreover, female respondents gave slightly more extreme ratings on the frequency and imagery scales. An analysis of the absolute difference between female and male ratings revealed a discrepancy of one half point or more on 20% of the word sample for frequency and 13% for imagery. On both scales, the mean absolute difference between male and female ratings was larger than that obtained by chance alone. This finding highlights the possibility that some words may not be equally familiar to women and men or may not evoke imagery with the same ease in these groups. Validity estimates for the frequency and imagery ratings were derived from correlations with scale values drawn from other normative studies. These correlation coefficients were equal to or greater than .78 for frequency and .86 for imagery, confirming the high level of consistency between this and other studies. An analysis of the relationship between subjective frequency and imagery ratings indicated that these variables are generally uncorrelated but exceptions occur. In the present study the coefficient of the correlation between subjective frequency and imagery was .24. However, when items with extreme mean frequency were excluded from the calculation, the correlation coefficient dropped to .04 and was no longer significant. Imagery ratings from five independent studies were all positively and significantly correlated with Vikis-Freibergs's (1974) frequency estimates, which were obtained from a free-association task. This finding suggests that word association, as a form of cued recall, may be influenced by several stimulus attributes including prior frequency of association and imagery-evoking value. The pattern of correlation between imagery ratings and text-based frequency estimates is not coherent. It reveals significant correlations only in select cases and no consistent polarity of linear relationship. The main contribution of this research is to provide reliable estimates of subjective frequency and imagery value for a word sample that is larger than those included in previous studies. A close examination of the linear relationship among the various sources of frequency and imagery data underscores the risk of confounding these variables in the selection of lexical stimuli for research.
Adolescent↗
Two different schedules for integrating filgrastim as adjuvant therapy in the treatment of patients with advanced stage Hodgkin's lymphoma receiving MOPP/ABV hybrid chemotherapy.
PURPOSE: Management of advanced-stage Hodgkin's disease with a MOPP/ABV hybrid regimen (mechlorethamine, vincristine, procarbazine, prednisone, Adriamycin, bleomycin and vinblastine) has yielded a high complete response rate (75-85%). However, myelosuppression can limit delivery of treatment. Filgrastim has been shown to reduce chemotherapy-related neutropenia and allow for on-time administration of planned doses of chemotherapeutic agents. The objective of this study was to find the best way to integrate filgrastim with the MOPP/ABV hybrid regimen. METHODS: Enrolled in this study were 24 patients (aged 18-52 years) with newly diagnosed, histologically documented Hodgkin's disease. In schedule I, patients received filgrastim (5 microg/kg s.c. daily) beginning on day 9, 24 h after administration of ABV. In schedule II, patients received filgrastim concomitantly with procarbazine on days 2-7 (starting 24 h after day-1 MOPP administration and stopping 24 h before ABV administration) as well as after ABV beginning on day 9. Filgrastim after ABV administration was administered until two consecutive ANC readings of 10 x 10(9)/l were achieved. RESULTS: All patients were able to complete all six cycles of therapy. There was a trend to fewer dose reductions in schedule II (0.76%) as compared to schedule I (4.2%) with a P-value of 0.077 (chi-squared test). Specifically, 11.6% of MOPP courses and 5.5% of ABV courses were dose-reduced in schedule I versus 1.7% and 1.4%, respectively, in schedule II. CONCLUSION: In conclusion, filgrastim was effective in supporting the delivery of the MOPP/ABV chemotherapy. Concomitant administration of filgrastim with procarbazine (days 2-7) appears to be safe and allows the maximum dose intensity of this therapy.
Adolescent↗
Detection of hypoxic cells with the 2-nitroimidazole, EF5, correlates with early redox changes in rat brain after perinatal hypoxia-ischemia.
The hypoxia-dependent activation of nitroheterocyclic drugs by cellular nitroreductases leads to the formation of intracellular adducts between the drugs and cellular macromolecules. Because this covalent binding is maximal in the absence of oxygen, detection of bound adducts provides an assay for estimating the degree of cellular hypoxia in vivo. Using a pentafluorintated derivative of etanidazole called EF5, we studied the distribution of EF5 adducts in seven-day-old rats subjected to different treatments which decrease the level of oxygen in the brain. EF5 solution was administered intraperitoneally 30 min prior to each treatment. The effect of acute and chronic hypoxia on EF5 adduct formation (binding) was studied in the brain of newborn rats exposed to global hypoxia (8% O2 for 30, 90 or 150 min) and in the brain of chronically hypoxic rat pups with congenital cardiac defects (Wistar Kyoto). The effect of combined hypoxia-ischemia was investigated in rat pups subjected to right carotid coagulation and concurrent exposure to 8% O2 for 30, 90 or 150 min. Brains were frozen immediately at the end of each treatment. Using a Cy3-conjugated monoclonal mouse antibody (ELK3-51) raised against EF5 adducts, hypoxic cells within brain regions were visualized by fluorescence immunocytochemistry. Brains from controls or vehicle-injected animals showed no EF5 binding. Notably, brains from animals which were chronically hypoxemic as a result of congenital cardiac defects also showed no EF5 binding. A short exposure (30 min) to hypoxia or to combined hypoxia-ischemia resulted in increased background stain and few scattered cells with low-intensity immunostaining. Acute hypoxia exposure of at least 90-150 min, which in this age animal does not result in frank cellular damage, produced patchy areas of low- to moderate-intensity fluorescence scattered throughout the brain. In contrast, 90-150 min of hypoxia-ischemia was associated with intense immunofluorescence in the hemisphere ipsilateral to the carotid occlusion, with a pattern similar to that reported previously for the histological damage seen in this model. This study provides a sensitive method for the evaluation of the level of oxygen depletion in brain tissue after neonatal hypoxia-ischemia at times much earlier than any method demonstrates apoptotic or necrotic cell death Since the level of in vivo formation of macromolecular adducts of EF5 depends on the degree of oxygen depletion in a tissue, intracellular EF5 binding may serve as a useful marker of regional cellular vulnerability and redox state after brain injury resulting from hypoxia-ischemia.
Acute Disease↗
Induction of hypoxia-inducible factor-1 (HIF-1) and its target genes following focal ischaemia in rat brain.
HIF-1 is a heterodimeric transcription factor, induced by hypoxia, that is composed of HIF-1alpha and HIF-1beta protein subunits. It binds to promoter/enhancer elements and stimulates the transcription of hypoxia-inducible target genes, including glucose transporter-1 and the glycolytic enzymes. Because HIF-1 activation might promote cell survival in hypoxic tissues, we studied the effect of permanent middle cerebral artery occlusion on the expression of HIF-1alpha, HIF-1beta and several HIF-1 target genes in adult rat brain. After focal ischaemia, mRNAs encoding HIF-1alpha, glucose transporter-1 and several glycolytic enzymes were up-regulated in the peri-infarct penumbra. This was observed by 7.5 h after the onset of ischaemia and increased further at 19 and 24 h. Regional cerebral blood flow was moderately decreased at 1 and 24 h after the ischaemia in areas of HIF-1 and HIF-1 target gene induction. Because hypoxia induces HIF-1 in other tissues, systemic hypoxia (6% O2 for 4.5 h) was also shown to increase HIF-1alpha protein expression in the adult rat brain. It is proposed that decreased blood flow to the penumbra decreases the supply of oxygen and that this induces HIF-1 and its target genes. This is the first study to show induction of HIF-1 after focal ischaemia in brain. Increased expression of HIF-1 target genes as a result of HIF-1 activation by hypoxia may contribute to tissue viability in the hypoxic/ischaemic penumbra by increasing glucose transport and glycolysis.
Animals↗
A randomized controlled trial of nonpharmacologic approaches for relief of low back pain during labor.
BACKGROUND: Low back pain is common during labor. Our randomized controlled trial compared the effectiveness of 3 nonpharmacologic approaches for relief of back pain. METHODS: A total of 34 women suffering from low back pain during labor were randomly assigned to receive 1 of 3 treatments: (1) intracutaneous sterile water injections (ISW); (2) transcutaneous electrical nerve stimulation (TENS); and (3) standard care, including back massage, whirlpool bath, and liberal mobilization. Women self-evaluated both intensity and affective dimensions of pain using visual analog scales. Their evaluations of control and satisfaction were assessed using adapted versions of the Labour Agentry Scale and the Labor and Delivery Satisfaction Index. RESULTS: Women in the ISW group rated the intensity and unpleasantness of pain during the experimental period significantly lower than women in the standard care group or the TENS group, (P = .001 and P = .003, respectively). Similar results were observed for intensity (P = .01) and unpleasantness (P = .03) of pain assessed just before delivery or request for an epidural. Mean pain intensity at 15 and 60 minutes after randomization was significantly reduced in the ISW group compared with the 2 other groups. There was no significant difference in the 3 groups in the level of control and satisfaction with labor and delivery, but less women in the ISW group indicated that they would like to receive the same treatment for back pain during another delivery. CONCLUSIONS: Intracutaneous sterile water injections are more effective than standard care (back massage, bath, and mobilization) or transcutaneous electrical nerve stimulation for relieving low back pain during labor.
Analgesia, Obstetrical↗
Impact of unified procedures as implemented in the Canadian Quality Assurance Program for T lymphocyte subset enumeration. Participating Flow Cytometry Laboratories of the Canadian Clinical Trials Network for HIV/AIDS Therapies.
The objective of the Canadian Quality Assurance Program (CQAP) is to provide the most reproducible and accurate T-cell subset enumeration for individuals living with HIV who are enrolled in the Canadian Clinical Trial Network for Human Immunodeficiency Virus (HIV) and Acquired Immune Deficiency Syndrome (AIDS) Therapies (abbreviated as CTN). The Canadian National Laboratory for Analytical Cytology, within the Laboratory Centre for Disease Control, is part of the Health Protection Branch of Health Canada. For the past eight years, the Laboratory for Analytical Cytology has been responsible for delivering a bilingual quality assurance program for CD4 T-cell enumeration. This federal program, which integrates biotechnology transfer with quality assessment, was achieved through the organization of workshops focused on technology transfer and essential skill-building techniques. Two training sessions were conducted for the CTN flow cytometer operators. The first introduced the concept of window of analysis, to demonstrate the practical benefits of unified quantitative fluorescent measurement. As a follow-up to the first workshop, participants performed a series of quantitative assays that monitored the expression of CD69, an early activation marker. This quantitative fluorescence protocol was performed with acceptable inter-laboratory variation using modified commercial kits. The second workshop focused on a absolute count method based on a single platform. Four preserved whole-blood preparations were tested with this approach. The combined effort reduced inter-laboratory variation. The direct impact was monitored as related to the frequency of participation. Over the years, the standard deviation of average accumulated variation decreased dramatically with increased frequency of participation, from 10% to <4%.
Canada↗
Induction of heme oxygenase-1 (HO-1) in the contused spinal cord of the rat.
The induction of heme oxygenase-1 (HO-1) was studied in intact spinal cords and injured spinal cords after a moderate, thoracic contusion injury. HO-1 was immunolocalized in the normal cord and along the axis of the cord at 1, 2, 3 and 4 days after contusion. Induction of this enzyme in astrocytes and microglia/macrophages was evaluated using immunofluorescent double labeling with monoclonal antibodies to HO-1 and either glial fibrillary acidic protein or the complement C3bi receptor. HO-1 was expressed in neurons in the normal spinal cord. After contusion, HO-1 was induced in both gray and white matter at the impact site. In segments of cord that were 1 cm proximal or distal to the injury, HO-1 was primarily induced in the dorsal columns and occasionally in the lateral white matter. This pattern of induction was noted at all time points. The HO-1 was induced primarily in microglia/macrophages. The distribution of the HO-1 positive cells closely correlated with the pattern of intraparenchymal hemorrhage. These findings demonstrate acute induction of HO-1 in non-neuronal cells in the injured spinal cord. Induction of HO-1 in glia may be a consequence of multiple factors including exposure to heme proteins, hypoxia and oxidative stress.
Animals↗
Developmental expression of heme oxygenase-1 (HSP32) in rat brain: an immunocytochemical study.
Heme oxygenase (HO) is a microsomal enzyme that oxidatively cleaves heme molecules to produce bile pigments, iron and carbon monoxide. In normal adult rat brain, HO-2 is the most abundant isozyme whereas HO-1 is present at very low levels except in select cell populations. Because its promoter region has NF-kB and AP-1 sites, heat-shock and heme-responsive elements, the HO-1 isozyme can be induced by a variety of stimuli. Since the expression and activity of several transcription factors such as NF-kB, Fos/Jun, and CREB show specific changes during development, we postulated that HO-1 expression may show similar developmental regulation. Using immunocytochemistry and Western blotting, this study demonstrates the development changes of HO-1 protein expression in normal brain from rats at postnatal day 7 (P7), P14, P21, and adult. Brain HO-1 immunoreactivity was highest at P7 in most brain regions including the white matter in areas of myelinogenesis, cerebral cortex, hippocampus, thalamus and hypothalamus and, in the blood vessel endothelial cells throughout the brain. In most regions, the adult pattern was reached by P21 with HO-1 protein localized almost exclusively to the dentate regions of hippocampus, some thalamic and hypothalamic nuclei, with little or no staining of endothelium, white matter and cortex. In a few select areas such as the substantia nigra, globus pallidus, ventromedial hypothalamic nucleus and the lateral preoptic nuclei area, little or no cellular HO-1 staining was observed at P7 whereas increased staining was found with maturation and adulthood. These results show that HO-1 protein expression is regulated in different cell types of specific regions of the rat brain during development.
Animals↗
Induction of heme oxygenase-1 after hyperosmotic opening of the blood-brain barrier.
The induction of the stress protein heme oxygenase-1 (HO-1) was studied in the rat brain after intracarotid administration of hyperosmolar mannitol. HO-1 was immunolocalized in fixed sections of brain 24 h to 7 days after injection. Immunoglobulin G (IgG) was immunolocalized in adjacent sections to demonstrate areas of breakdown of the blood-brain barrier. Induction of HO-1 was also evaluated by Western immunoblots, performed at 24 h after the insult. Immunofluorescent double labelling with monoclonal antibodies to HO-1 and either glial fibrillary acidic protein or the complement C3bi receptor was used to determine if glia/macrophages expressed HO-1. There was pronounced, widespread induction of HO-1 in the ipsilateral hemisphere and cerebellum by 24 h both by immunocytochemistry and by Western blots. This induction was markedly attenuated at later times. HO-1 was induced in astrocytes and microglia/macrophages in the ipsilateral hemisphere. In addition, the protein was induced in Bergmann glia and scattered microglia/macrophages in the cerebellum. The mechanism of induction of HO-1 in glia after opening of the blood-brain barrier could include exposure to heme proteins, denatured proteins and other plasma constituents known to induce HO-1. This glial induction may reflect a protective response of these cells.
Animals↗
Heme oxygenase-1 is induced in glia throughout brain by subarachnoid hemoglobin.
The heme oxygenase-1 gene, HO-1, induced by heme, ischemia, and heat shock, metabolizes heme to biliverdin, free iron, and carbon monoxide. Though the distribution of HO-1 has been described in normal rat brain, little is known about how extracellular heme proteins in the subarachnoid space distribute in brain. To address this issue, hemoglobin was injected into the cisterna magna of adult rats. Expression of HO-1 in these animals was compared with saline-injected, BSA-injected, and uninjected controls. Western blot analysis showed that 24 hours after injection oxyhemoglobin increased HO-1 levels approximately four- to fivefold in all brain regions studied compared with saline-injected and BSA-injected controls. In the brain, HO-1 immunoreactivity was evident at 4 hours and peaked at 24 hours after oxyhemoglobin injections, returning to control levels by 4 to 8 days. This HO-1 induction was detected mainly in cells with small, rounded somas bearing two to four truncated processes, a morphology consistent with that of microglia. These cells were double-stained with the microglial marker, OX42, in every brain region examined. It is proposed that subarachnoid hemoglobin may be taken up into microglia wherein heme induces HO-1.
Animals↗