Biomedical subjects

R J Traystman

Publications and source records attributed to R J Traystman.

At least 73 records · Page 4Linked to original sources

PubMed1999

Quantitative EEG during early recovery from hypoxic-ischemic injury in immature piglets: burst occurrence and duration.

This study examined the course of EEG recovery in an animal model of hypoxic-ischemic injury. The model used periods of hypoxia, room air and asphyxia to induce cardiac arrest. One-week-old piglets (n = 16) were exposed to a period of hypoxia, room air and complete asphyxia for 7 minutes. After cardiac arrest and resuscitation, two EEG features were evaluated as prognostic indicators of behavioral outcome as assessed by a neuroscore at 24 hours after insult. A prominent EEG feature was the number and duration of bursts evident during recovery. Episodes of bursting were detected through the thresholds on sustained periods of elevated power. After the animal was resuscitated, the EEG was monitored continuously for 4 hours. To assess outcome in the recovering animal, a behavioral testing scale was used to test the animal's neurological capabilities. Trends of EEG burst counts were measured through thresholds on sustained power changes. Bursts are energy transients in the EEG record. High degrees of bursting were characteristic of animals having good neurological condition whereas piglets having low burst counts had poor 24 hr neuroscores. At 100 min the average burst rate of the good neuroscore outcome group was more than 8 per min and was significantly different from the poor outcome group's level of 2.7 (p < or = 0.05). When these counts were weighted by their total duration, differences between groups increased (p < or = 0.02). This study showed that the QEEG measure of burst counts and duration together provided a strong prognostic indication of the 24 hour outcome after asphyxic injury in a neonatal animal model. The critical determinant of the bursting character was the time when bursting occurred. Bursting occurring early in recovery was a good gauge of outcome. We conclude that quantitative EEG analysis and interpretation can be an important tool for the outcome determination during recovery from cerebral injury states.

Animals↗

PubMed1999

Heme oxygenase-2 is neuroprotective in cerebral ischemia.

Heme oxygenase (HO) is believed to be a potent antioxidant enzyme in the nervous system; it degrades heme from heme-containing proteins, giving rise to carbon monoxide, iron, and biliverdin, which is rapidly reduced to bilirubin. The first identified isoform of the enzyme, HO1, is an inducible heat-shock protein expressed in high levels in peripheral organs and barely detectable under normal conditions in the brain, whereas HO2 is constitutive and most highly concentrated in the brain. Interestingly, although HO2 is constitutively expressed, its activity can be modulated by phosphorylation. We demonstrated that bilirubin, formed from HO2, is neuroprotectant, as neurotoxicity is augmented in neuronal cultures from mice with targeted deletion of HO2 (HO2(-/-)) and reversed by low concentrations of bilirubin. We now show that neural damage following middle cerebral artery occlusion (MCAO) and reperfusion, a model of focal ischemia of vascular stroke, is substantially worsened in HO2(-/-) animals. By contrast, stroke damage is not significantly altered in HO1(-/-) mice, despite their greater debility. Neural damage following intracranial injections of N-methyl-d-aspartate (NMDA) is also accentuated in HO2(-/-) animals. These findings establish HO2 as an endogenous neuroprotective system in the brain whose pharmacologic manipulation may have therapeutic relevance.

Animals↗

PubMed1998

Nerve growth factor rapidly suppresses basal, NMDA-evoked, and AMPA-evoked nitric oxide synthase activity in rat hippocampus in vivo.

In adult forebrain, nerve growth factor (NGF) influences neuronal maintenance and axon sprouting and is neuroprotective in several injury models through mechanisms that are incompletely understood. Most NGF signaling is thought to occur after internalization and retrograde transport of trkA receptor and be mediated through the nucleus. However, NGF expression in hippocampus is rapidly and sensitively regulated by synaptic activity, suggesting that NGF exerts local effects more dynamically than possible through signaling requiring retrograde transport to distant afferent neurons. Interactions have been reported between NGF and nitric oxide (NO). Because NO affects both neural plasticity and degeneration, and trk receptors can mediate signaling within minutes, we hypothesized that NGF might rapidly modulate NO production. Using in vivo microdialysis we measured conversion of L-[14C]arginine to L-[14C]citrulline as an accurate reflection of NO synthase (NOS) activity in adult rat hippocampus. NGF significantly reduced NOS activity to 61% of basal levels within 20 min of onset of delivery and maintained NOS activity at less than 50% of baseline throughout 3 hr of delivery. This effect did not occur with control protein (cytochrome c) and was not mediated by an effect of NGF on glutamate levels. In addition, simultaneous delivery of NGF prevented significant increases in NOS activity triggered by the glutamate receptor agonists N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA). Rapid suppression by NGF of basal and glutamate-stimulated NOS activity may regulate neuromodulatory functions of NO or protect neurons from NO toxicity and suggests a novel mechanism for rapidly mediating functions of NGF and other neurotrophins.

Animals↗

PubMed1998

Regional and cellular expression of glial (GLT1) and neuronal (EAAC1) glutamate transporter proteins in ovine fetal brain.

Glutamate transport is a primary mechanism for regulating extracellular levels of glutamate which can have either neurotrophic or neurotoxic effects in the developing brain, depending on its concentration. Using immunoblotting and immunocytochemistry, we tested the hypotheses that expression of neuronal and glial glutamate transporter proteins was regionally and temporally regulated in the developing ovine brain and that expression of the glial isoform early in development was not cell-type specific. Immunoblots for the neuronal glutamate transporter EAAC1 revealed a major band of immunoreactivity at 69,000 nmol. wt, whereas glial glutamate transporter-1 (GLT1) immunoreactivity was observed as 73,000 and 146,000 mol. wt proteins. EAAC1 and GLT1 are regulated differently during development, with EAAC1 immunoreactivity being most abundant at 60 and 71 days completed gestation (term=145 days) and dissipating thereafter, while GLT1 immunoreactivity was most abundant at 136 days gestation. By immunocytochemistry EAAC1 expression is neuronal throughout gestation with intense labelling of dendrites within the telencephalon evident at 60 days. Neuropil, neuronal cell bodies and processes are EAAC1-immunoreactive throughout gestation with no evidence of astrocytic or oligodendroglial immunoreactivity. In contrast, GLT1 is expressed by neuronal and non-neuronal cell types during midgestation with astrocyte selectivity developing by 136 days. During midgestation, GLT1 is transiently expressed in neurons of the subplate, cranial nerve nuclei, basal ganglia, and cerebellar cortex. The major finding of this study, that GLT1 is transiently expressed in various neuronal populations at midgestation demonstrates that the cell-type specificity of the GLT1 phenotype is developmentally regulated and depends on brain maturity.

ATP-Binding Cassette Transporters↗

PubMed1998

Quantitative assessment of blood flow, blood volume and blood oxygenation effects in functional magnetic resonance imaging.

The ability to measure the effects of local alterations in blood flow, blood volume and oxygenation by nuclear magnetic resonance has stimulated a surge of activity in functional MRI of many organs, particularly in its application to cognitive neuroscience. However, the exact description of these effects in terms of the interrelations between the MRI signal changes and the basic physiological parameters has remained an elusive goal. We here present this fundamental theory for spin-echo signal changes in perfused tissue and validate it in vivo in the cat brain by using the physiological alteration of hypoxic hypoxia. These experiments show that high-resolution absolute blood volume images can be obtained by using hemoglobin as a natural intravascular contrast agent. The theory also correctly predicts the magnitude of spin-echo MRI signal intensity changes on brain activation and thereby provides a sound physiological basis for these types of studies.

Animals↗

PubMed1998

Neuroprotection from focal ischemia by 4-phenyl-1-(4-phenylbutyl) piperidine (PPBP) is dependent on treatment duration in rats.

UNLABELLED: The IV administration of the potent sigma1-receptor ligand 4-phenyl-1-(4-phenylbutyl)piperidine (PPBP) provides neuroprotection against focal cerebral ischemia. We tested the hypothesis that prolonged, continuous administration of PPBP would provide further neuroprotection in a rat model of transient focal ischemia and reperfusion. Under controlled conditions of normoxia, normocarbia, and normothermia, halothane-anesthetized male Wistar rats were subjected to 2 h of middle cerebral artery occlusion by the intraluminal occlusion technique. Sixty minutes after the onset of ischemia, rats were randomly assigned to six treatment groups to receive a continuous IV infusion of PPBP (1 micromol . kg(-1). h(-1) for 1, 2, 3, or 4 days or saline for 1 or 4 days. The infarction volume was assessed by triphenyltetrazolium chloride (TFC) staining on Day 4 after ischemia in all rats. The TTC-determined infarction volume of the ipsilateral cerebral cortex was smaller in rats treated with PPBP for 1 day (42+/-13 mm3; 10%+/-3% of ipsilateral hemisphere; P < 0.05) (mean+/-SEM) compared with that in corresponding 1-day control rats (124+/-22 mm; 29%+/-5% of ipsilateral hemisphere; P < 0.05) or 4-day control rats (112+/-10 mm; 26%+/-2% of ipsilateral hemisphere; P < 0.05). Cortical infarction volumes in 2-, 3-, and 4-day PPBP-treated rats were not different compared with 1- and 4-day saline-treated controls. These data demonstrate that the sigma1(-receptor ligand PPBP attenuates ischemic injury when administration is initiated 60 min after the onset of focal ischemia but that prolonged continuous treatment with PPBP beyond 24 h provides no neuroprotection. IMPLICATIONS: sigma-Ligands decrease infarction size in various animal models when given after the onset of stroke. Prolonged treatment with a potent sigma-ligand is associated with loss of therapeutic efficacy for this compound.

Animals↗

PubMed1998

Noninvasive detection of cerebral hypoperfusion and reversible ischemia from reductions in the magnetic resonance imaging relaxation time, T2.

The hypothesis was tested that hypoperfused brain regions, such as the ischemic penumbra, are detectable by reductions in absolute transverse relaxation time constant (T2) using magnetic resonance imaging (MRI). To accomplish this, temporal evolution of T2 was measured in several models of hypoperfusion and focal cerebral ischemia in the rat at 9.4 T. Occurrence of acute ischemia was determined through the absolute diffusion constant D(av) = 1/3 TraceD, while perfusion was assessed by dynamic contrast imaging. Three types of regions at risk of infarction could be distinguished: (1) areas with reduced T2 (4% to 15%, all figures relative to contralateral hemisphere) and normal D(av), corresponding to hypoperfusion without ischemia; (2) areas with both reduced T2 (4% to 12%) and D(av) (22% to 49%), corresponding to early hypoperfusion with ischemia; (3) areas with increased T2 (2% to 9%) and reduced D(av) (28% to 45%), corresponding to irreversible ischemia. In the first two groups, perfusion-deficient regions detected by bolus tracking were similar to those with initially reduced T2. In the third group, bolus tracking showed barely detectable arrival of the tracer in the region where D(av) was reduced. We conclude that T2 reduction in acute ischemia can unambiguously identify regions at risk and potentially discriminate between reversible and irreversible hypoperfusion and ischemia.

Animals↗

PubMed1998

Estrogen increases cGMP in selected brain regions and in cerebral microvessels.

We have previously reported that exogenous and endogenous estrogen can amplify residual cerebral blood flow during experimental cerebral ischemia. Because estrogen has been linked to nitric oxide and cyclic guanosine monophosphate (cGMP) signaling in noncerebral tissue, we tested the hypothesis that long-term 17beta-estradiol treatment increases basal cGMP in brain homogenates and cerebral microvessels in female rabbits. We also determined whether there are important baseline gender-specific differences in regional cGMP. Adult female rabbits were implanted with 17beta-estradiol pellets, 10 mg (F10, n = 10) or 50 mg (F50, n = 13), and compared with untreated females (F, n = 19) and males with negligible estrogen (M, n = 19) (plasma 17beta-estradiol levels of 4+/-4 pg/mL in M, 7+/-5 pg/mL in F, 141+/-74 pg/mL in F10, and 289 +/-10 pg/mL in F50). Cyclic GMP was determined by radioimmunoassay in cerebellum, hypothalamus, caudate nucleus, hippocampus, and cortex. Cerebral microvessels were harvested from additional cohorts of untreated males and females or estradiol-implanted females (n = 6 per group). Basal cGMP was higher in F versus M only in cerebellum. Estrogen-induced increases in regional cGMP were prominent in hippocampus at all doses (M = 43+/-26, F = 43+/-21, F10 = 84+/-24, F50 = 117+/-55 fmol/mg protein) and in cortex at the high dose (M = 78+/-55, F = 88+/-51, F10 = 69+/-34, F50 = 143+/-52 fmol/mg protein). Similarly, microvascular cGMP increased only in females treated with the 50 mg dose (M = 77+/-13, F = 86+/-25, F10O = 106+/-35, F50 = 192+/-88 fmol/mg protein). Therefore, 17beta-estradiol increases cGMP content in parenchymal regions that are known physiologic targets for reproductive steroids but are also areas of selective vulnerability to ischemic insult. Further, high doses of estrogenic steroids could amplify cGMP signaling within the cerebral microvasculature.

Animals↗

PubMed1998

Intravenous basic fibroblast growth factor does not ameliorate brain injury resulting from transient focal ischemia in cats.

This study sought to test the hypothesis that intravenous basic fibroblast growth factor (bFGF) inhibits the development of brain injury during transient focal ischemia. Halothane-anesthetized cats (n=39) underwent left middle cerebral artery occlusion for 60 minutes. After the onset of reperfusion, wounds were closed and the cats were allowed to emerge from anesthesia. Experimental cats were treated with intravenous bFGF at a dose of either 2 or 5 microg/kg per hour, beginning 45 minutes after initiation of ischemia and continuing until 24 hours of reperfusion, when neurologic function and infarction volume were evaluated. The cats in the control group received diluent. Three of thirteen cats treated with bFGF 2 microg/kg/hour and six of sixteen cats treated with bFGF 5 microg/kg/hour died during the 24 hour reperfusion period. There was no difference in injury volume or neurologic evaluation score in the control group (n=10; hemisphere injury, 1301+/-306 mm3, mean+/-SE; score 53+/-3), and cats treated with either 2 microg/kg/hour (n=10; hemisphere injury, 1170+/-292 mm3; score 50+/-3) or 5 microg/kg/hour bFGF (n=10; hemisphere injury, 1343+/-374 mm3; score 50+/-2). The data collected do not support the hypothesis that intravenous bFGF is neuroprotective in a cat model of transient focal ischemia.

Analysis of Variance↗

PubMed1998

Incomplete global cerebral ischemia alters platelet biology in neonatal and adult sheep.

Platelets are implicated as etiologic agents in cerebral ischemia and as modulators of neural injury following an ischemic insult. We examined the effects of severe, transient global ischemia on platelet aggregation during 45-min ischemia and 30-, 60-, and 120-min reperfusion in adult and neonatal lambs. We also examined postischemic platelet deposition in brain and other tissues (120-min reperfusion) using indium-111-labeled platelets. Ischemic cerebral blood flow fell to 5 +/- 1 and 5 +/- 2 ml.min-1.100 g-1 in lambs and sheep, respectively. During ischemia, platelet counts fell to 47.5 +/- 5.1% of control (P < 0.05) in lambs and 59 +/- 4.9% of control in sheep (P < 0.05). Ischemia depressed platelet aggregation response (P < 0.01) to 4 micrograms collagen in lambs and sheep (20.4 +/- 29.2 and 26 +/- 44.7% of control, respectively). Marked platelet deposition occurred in brain and spleen in sheep, whereas significant platelet entrapment occurred only in brain in lambs. Our findings suggest that ischemia causes platelet activation and deposition in brain and noncerebral tissues.

Aging↗

PubMed1998

Tyrosine confounds oxidative electrochemical detection of nitric oxide.

We report evidence that a porphyrinic microsensor for detection of nitric oxide (NO) also detects biologically relevant concentrations of tyrosine (Tyr) in dog brain. Tyr is oxidized by this sensor at the same potential as NO, and the sensitivity for NO and Tyr are of the same order of magnitude. The interference from Tyr is of importance because 1) Tyr is abundant and 2) there is a concentration gradient of Tyr across the blood-brain barrier that can lead to unpredictable results if disturbed by ischemia or hypoxia. The knowledge of this interference is important for the interpretation of results obtained with this sensor and for the design of future studies.

Animals↗

PubMed1998

Cerebral blood flow during hypoxic hypoxia with plasma-based hemoglobin at reduced hematocrit.

We determined whether cerebral blood flow (CBF) remained related to arterial O2 content (CaO2) during hypoxic hypoxia when hematocrit and hemoglobin concentration were independently varied with cell-free, tetramerically stabilized hemoglobin transfusion. Three groups of pentobarbital sodium-anesthetized cats were studied with graded reductions in arterial O2 saturation to 50%: 1) a control group with a hematocrit of 31 +/- 1% (mean +/- SE; n = 7); 2) an anemia group with a hematocrit of 21 +/- 1% that underwent an isovolumic exchange transfusion with an albumin solution (n = 8); and 3) a group transfused with an intramolecularly cross-linked hemoglobin solution to decrease hematocrit to 21 +/- 1% (n = 10). Total arterial hemoglobin concentration (g/dl) after hemoglobin transfusion (8.8 +/- 0.2) was intermediate between that of the control (10.3 +/- 0.3) and albumin (7.2 +/- 0.4) groups. Forebrain CBF increased after albumin and hemoglobin transfusion at normoxic O2 tensions to levels attained at equivalent reductions in CaO2 in the control group during graded hypoxia. Over a wide range of arterial O2 saturation and sagittal sinus PO2, CBF remained greater in the albumin group. When CBF was plotted against CaO2 for all three groups, a single relationship was formed. Cerebral O2 transport, O2 consumption, and fractional O2 extraction were constant during hypoxia and equivalent among groups. We conclude that CBF remains related to CaO2 during hypoxemia when hematocrit is reduced with and without proportional reductions in O2-carrying capacity. Thus O2 transport to the brain is well regulated at a constant level independently of alterations in hematocrit, hemoglobin concentration, and O2 saturation.

Adjuvants, Anesthesia↗

PubMed1998

Effect of cross-linked hemoglobin transfusion on endothelial-dependent dilation in cat pial arterioles.

We determined whether addition of hemoglobin to the plasma would inhibit endothelial-dependent dilation in brain where tight endothelial junctions limit hemoglobin extravasation. Pial arteriolar diameter was measured by intravital microscopy through closed cranial windows in anesthetized cats either without transfusion (hematocrit = 32%) or after exchange transfusion with an albumin or sebacyl-cross-linked human hemoglobin solution (hematocrit = 18%). Dilation of small, medium, and large arterioles to acetylcholine and ADP was not significantly altered by hemoglobin transfusion. The dilatory responses were inhibited by the nitric oxide synthase inhibitor NG-nitro-L-arginine, although significant dilation to 30 microM acetylcholine persisted in small arterioles in the control and albumin-transfused group but not in the hemoglobin-transfused group. The dilatory response to the nitric oxide donor 3-morpholinosydnonimine was unaffected by albumin or hemoglobin transfusion, but the response to nitroprusside was reduced by one-third after hemoglobin transfusion. When cross-linked hemoglobin was superfused through the cranial window, the acetylcholine response became inhibited at a hemoglobin concentration of 0.1 microM and was completely blocked at 10 microM. Because this concentration is substantially less than the 500 microM hemoglobin concentration in plasma after transfusion when there was no inhibition of the acetylcholine response, hemoglobin permeation of the blood-brain barrier was considered negligible. We conclude that exchange of red cell-based hemoglobin with plasma-based hemoglobin does not produce a more effective sink for endothelial-derived nitric oxide evoked by agonist receptor-mediated activation. Furthermore, decreased hematocrit does not affect agonist-evoked endothelial-dependent dilation.

Acetylcholine↗

PubMed1998

Gender-linked brain injury in experimental stroke.

BACKGROUND AND PURPOSE: Premenopausal women are at lower risk than men for stroke, but the comparative vulnerability to tissue injury once a cerebrovascular incident occurs is unknown. We hypothesized that female rats sustain less brain damage than males during experimental focal ischemia and that the gender difference in ischemic outcome can be eliminated by ovariectomy. METHODS: Age-matched male (M), intact female (F), and ovariectomized female (O; plasma estradiol: 4.1+/-1.6 pg/mL compared with 7.4+/-1.5 in F and 4.0+/-1.1 in M) rats from two different strains, normotensive Wistar and stroke-prone spontaneously hypertensive rats, were subjected to 2 hours of intraluminal middle cerebral artery occlusion, followed by 22 hours of reperfusion. Cerebral blood flow (CBF) was monitored throughout the ischemic period by laser-Doppler flowmetry. Infarction volume in the cerebral cortex (Ctx) and caudoputamen (CP) was determined by 2,3,5-triphenyltetrazolium chloride staining. In a separate cohort of M, F, and O Wistar rats, absolute rates of regional CBF were measured at the end of the ischemic period by quantitative autoradiography using [14C]iodoantipyrine. RESULTS: F rats of either strain had a smaller infarct size in Ctx and CP and a higher laser-Doppler flow during ischemia compared with respective M and O rats. Mean end-ischemic CBF was higher in F compared with M and O rats in CP, but not in Ctx. Cerebrocortical tissue volume with end-ischemic CBF < 10 mL/100 g/min was smaller in F than M rats, but not different from O rats. CONCLUSIONS: We conclude that endogenous estrogen improves stroke outcome during vascular occlusion by exerting both neuroprotective and flow-preserving effects.

Animals↗

PubMed1998

Effect of the no-flow interval and hypothermia on cerebral blood flow and metabolism during cardiopulmonary resuscitation in dogs.

BACKGROUND AND PURPOSE: We sought (1) to determine the effect of brief periods of no flow on the subsequent forebrain blood flow during cardiopulmonary resuscitation (CPR) and (2) to test the hypothesis that hypothermia prevents the impact of the no-flow duration on cerebral blood flow (CBF) during CPR. METHODS: No-flow intervals of 1.5, 3, and 6 minutes before CPR at brain temperatures of 28 degreesC and 38 degreesC were compared in 6 groups of anesthetized dogs. Microsphere-determined CBF and metabolism were measured before and during vest CPR adjusted to maintain cerebral perfusion pressure at 25 mm Hg. RESULTS: Increasing the no-flow interval from 1.5 to 6 minutes at 38 degreesC decreased the CBF (18. 6+/-3.6 to 6.1+/-1.7 mL/100 g per minute) and the cerebral metabolic rate (2.1+/-0.3 to 0.7+/-0.2 mL/100 g per minute) during CPR. Cooling to 28 degreesC before and during the arrest eliminated the detrimental effects of increasing the no-flow interval on CBF (16. 8+/-1.0 to 14.8+/-1.9 mL/100 g per minute) and cerebral metabolic rate (1.1+/-0.1 to 1.3+/-0.1 mL/100 g per minute). Unlike the forebrain, 6 minutes of preceding cardiac arrest did not affect brain stem blood flow during CPR. CONCLUSIONS: Increasing the no-flow interval to 6 minutes in normothermic animals decreases the supratentorial blood flow and cerebral metabolic rate during CPR at a cerebral perfusion pressure of 25 mm Hg. Cooling to 28 degreesC eliminates the detrimental impact of the 6-minute no-flow interval on the reflow produced during CPR. The brain-protective effects of hypothermia include improving reflow during CPR after cardiac arrest. The effect of hypothermia and the impact of short durations of no flow on reperfusion indicate that increasing viscosity and reflex vasoconstriction are unlikely causes of the "no-reflow" phenomenon.

Animals↗

PubMed1998

Low molecular weight iron in cerebral ischemic acidosis in vivo.

BACKGROUND AND PURPOSE: Iron-catalyzed radical generation is a potentially significant mechanism by which extensive tissue acidosis exacerbates brain injury during ischemia/reperfusion. We hypothesized that levels of low-molecular-weight (LMW) iron increase during in vivo global cerebral ischemia in a pH-dependent manner, potentially catalyzing oxidant injury. The present study quantified regional differences in LMW iron during global cerebral incomplete ischemia and determined whether augmenting the fall in ischemic tissue pH with hyperglycemia also amplifies free iron availability. METHODS: Dogs anesthetized with pentobarbital-fentanyl were treated with 30 minutes of global incomplete cerebral ischemia produced by intracranial pressure elevation. Cerebral energy metabolites (ATP, phosphocreatine) and intracellular pH (pHi) were measured by 31P magnetic resonance spectroscopy. Preischemic plasma glucose level was manipulated to titrate end-ischemic pHi. After ischemia, brains were perfused with cold phosphate-buffered saline solution; then 16 different brain areas were sampled, filtered to separate the LMW fraction (<30000 D), and assayed by rapid colorimetric assay for tissue iron. Total iron, LMW iron, and protein in each sample were measured in sham-operated (no ischemia, n=8), normoglycemic ischemia (ISCH [glucose 7+/-4 mmol/L], n=7), and hyperglycemic (GLU-ISCH [glucose 31+/-3 mmol/L], n=9) groups. RESULTS: High-energy phosphates fell to near zero values in both ISCH and GLU-ISCH groups by 30 minutes but remained unchanged in the sham-operated group. As expected, pHi decreased during ischemia but to a greater extent in GLU-ISCH (6.20+/-0.05 in ISCH, 6.08+/-0.04 in GLU-ISCH, P<.05). Iron could be detected in all areas of the brain in sham-operated animals, with the highest amounts obtained from subcortical areas such as the hippocampus, pons, midbrain, and medulla. Total iron was higher in ISCH relative to sham-operated animals and higher in cortex and pons relative to GLU-ISCH. Regional LMW (as a percentage of total iron; LMW/total iron) was elevated in numerous brain areas in ISCH, including cortical gray matter, cerebellum, hippocampus, caudate, and midbrain. LMW/total iron was higher in GLU-ISCH versus ISCH in cortical gray matter only. In other brain areas, ischemic LMW/total iron was equivalent in glucose-treated or normoglycemic animals (white matter, thalamus, pons, medulla) or lower in the glucose-treated group (cerebellum, hippocampus, caudate, midbrain). CONCLUSIONS: These data demonstrate that levels of total and LMW iron increase with global cerebral ischemia in the majority of cortical and subcortical regions of normoglycemic brain. However, exacerbation of ischemic acidosis via glucose administration does not increase tissue iron and produces a greater increase in the LMW fraction in cortical gray matter only. In other brain regions, total and LMW iron availability is similar to that of nonischemic animals.

Acidosis↗

PubMed1998

Treatment with the competitive NMDA antagonist GPI 3000 does not improve outcome after cardiac arrest in dogs.

BACKGROUND AND PURPOSE: We previously showed that treatment with a competitive N-methyl-D-aspartate (NMDA) receptor antagonist GPI-3000 (GPI) improved short-term physiological recovery after incomplete global cerebral ischemia complicated by dense acidosis. We tested the hypothesis that GPI administered after resuscitation from cardiac arrest would improve a more long-term recovery as measured by neurobehavioral assessment and neuropathology 4 days after resuscitation. METHODS: Anesthetized dogs were subjected to 7 minutes of cardiac arrest followed by vest cardiopulmonary resuscitation. Neurobehavioral outcomes were scored daily on a score ranging from 0 (normal) to 500 (worst). On the fourth day, the animals were killed, and neuropathology was evaluated in a blinded manner in the hippocampus and the neocortex by hematoxylin and eosin staining and by determination of percentage of injured neurons. Three groups of animals were treated in a randomized, blinded protocol with either saline (SAL), low-dose GPI (5 mg/kg followed by 1 mg/kg per hour for 2 hours), or high-dose GPI (25 mg/kg, followed by 5 mg/kg per hour for 2 hours). RESULTS: The mortality rate was higher in animals receiving GPI than in saline-treated control animals (4 of 15 deaths in SAL, 6 of 15 in the low-dose GPI group, and 9 of 18 in the high-dose GPI group). Neurobehavioral scores were depressed in GPI-treated animals compared with saline-treated control animals in a dose-dependent manner, with 96-hour scores of essentially normal (9+/-2) in saline-treated animals compared with those animals with significant impairment (181+/-47) treated with high-dose GPI. Neuropathological damage in the neocortex was most severe in GPI-treated animals, with the percentage of injured neurons dependent on the dose: 8.3%+/-2.7% SAL, 13.2%+/-6.4% low-dose GPI, and 39.4%+/-10.1%, high-dose GPI. CA1 neuronal damage was severe regardless of treatment. CONCLUSIONS: Contrary to results seen in experimental global and focal cerebral ischemia, in which NMDA receptor antagonism may improve responses to injury, receptor antagonism with GPI does not improve brain outcome after cardiac arrest and resuscitation in the dog. Behavioral and histological outcomes both were worsened by GPI treatment at two doses, and mortality was higher relative to saline control treatment. We speculate that systemic drug effects, as well as potential neurotoxicity of the drug under ischemic conditions, may be responsible for the deleterious outcomes observed in our cardiac arrest model.

Amino Acids↗

PubMed1998

Protein kinase C expression and activity after global incomplete cerebral ischemia in dogs.

BACKGROUND AND PURPOSE: Studies suggest that protein kinase C (PKC) activation during ischemia plays an important role in glutamate neurotoxicity and that PKC inhibition may be neuroprotective. We tested the hypothesis that elevations in the biochemical activity and protein expression of Ca2+-dependent PKC isoforms occur in hippocampus and cerebellum during the period of delayed neurodegeneration after mild brain ischemia. METHODS: We used a dog model of 20 minutes of global incomplete ischemia followed by either 6 hours, 1 day, or 7 days of recovery. Changes in PKC expression (Western blotting and immunocytochemistry) and biochemical activity were compared with neuropathology (percent ischemically damaged neurons) by means of hematoxylin and eosin staining. RESULTS: The percentage of ischemically damaged neurons increased from 13+/-4% to 52+/-10% in CA1 and 24+/-11% to 69+/-6% in cerebellar Purkinje cells from 1 to 7 days, respectively. The occurrence of neuronal injury was accompanied by sustained increases in PKC activity (240% and 211% of control in hippocampus and cerebellum, respectively) and increased protein phosphorylation as detected by proteins containing phosphoserine residues. By Western blotting, the membrane-enriched fraction showed postischemic changes in protein expression with increases of 146+/-64% of control in hippocampal PKCalpha and increases of 138+/-38% of control in cerebellar PKCalpha, but no changes in PKCbeta and PKCgamma were observed. By immunocytochemistry, the neuropil of CA1 and CA4 in hippocampus and the radial glia in the molecular layer of cerebellum showed increased PKCalpha expression after ischemia. CONCLUSIONS: This study shows that during the period of progressive ischemic neurodegeneration there are regionally specific increases in PKC activity, isoform-specific increases in membrane-associated PKC, and elevated protein phosphorylation at serine sites.

Animals↗