Rapid tau protein dephosphorylation and differential rephosphorylation during cardiac arrest-induced cerebral ischemia and reperfusion

The effects of cerebral ischemia/reperfusion on phosphorylation of microtubule-associated tau proteins were assessed in a canine model of cardiac arrest. As tau proteins are phosphorylated by kinases involved in different transduction signal pathways, their phosphorylation state is an excellent marker of neuronal homeostasis and microtubule dynamics. Canine brain tau proteins were characterized by immunoblotting using phosphorylation-dependent antibodies and antisera raised against different amino- and carboxy-terminal tau sequences. The present study reports a complete dephosphorylation of tau proteins during ischemia, which is shown by a higher electrophoretic mobility and the almost (if not total) disappearance of phosphorylation-dependent monoclonal antibody labeling. After 2-hour restoration of spontaneous circulation, a decrease in the electrophoretic mobility was observed, and after 24 hours of reperfusion, a full restoration of the phosphorylation was visualized using phosphorylation-dependent monoclonal antibodies directed against Ser/Thr-Pro sites. However, one particular phosphorylation site involved in tau binding to microtubules, located on Ser262/356, was never fully significantly rephosphorylated, suggesting that microtubule metabolism was still affected after 24 hours of reperfusion. Thus, the sequential and differential recovery of tau phosphorylation after ischemia followed by reperfusion is a useful marker with which to monitor neuronal integrity after brain ischemia.

Neuronal subclass-selective loss of pyruvate dehydrogenase immunoreactivity following canine cardiac arrest and resuscitation

Chronic impairment of aerobic energy metabolism accompanies global cerebral ischemia and reperfusion and likely contributes to delayed neuronal cell death. Reperfusion-dependent inhibition of pyruvate dehydrogenase complex (PDHC) enzyme activity has been described and proposed to be at least partially responsible for this metabolic abnormality. This study tested the hypothesis that global cerebral ischemia and reperfusion results in the loss of pyruvate dehydrogenase immunoreactivity and that such loss is associated with selective neuronal vulnerability to transient ischemia. Following 10 min canine cardiac arrest, resuscitation, and 2 or 24 h of restoration of spontaneous circulation, brains were either perfusion fixed for immunohistochemical analyses or biopsy samples were removed for Western immunoblot analyses of PDHC immunoreactivity. A significant decrease in immunoreactivity was observed in frontal cortex homogenates from both 2 and 24 h reperfused animals compared to samples from nonischemic control animals. These results were supported by confocal microscopic immunohistochemical determinations of pyruvate dehydrogenase immunoreactivity in the neuronal cell bodies located within different layers of the frontal cortex. Loss of immunoreactivity was greatest for pyramidal neurons located in layer V compared to neurons in layers IIIc/IV, which correlates with a greater vulnerability of layer V neurons to delayed death caused by transient global cerebral ischemia.

Release of caspase-9 from mitochondria during neuronal apoptosis and cerebral ischemia

Caspase-9 is critical for cytochrome c (cyto-c)-dependent apoptosis and normal brain development. We determined that this apical protease in the cyto-c pathway for apoptosis resides inside mitochondria in several types of cells, including cardiomyocytes and many neurons. Caspase-9 is released from isolated mitochondria on treatment with Ca2+ or Bax, stimuli implicated in ischemic neuronal cell death that are known to induce cyto-c release from mitochondria. In neuronal cell culture models, apoptosis-inducing agents trigger translocation of caspase-9 from mitochondria to the nucleus, which is inhibitable by Bcl-2. Similarly, in an animal model of transient global cerebral ischemia, caspase-9 release from mitochondria and accumulation in nuclei was observed in hippocampal and other vulnerable neurons exhibiting early postischemic changes preceding apoptosis. Loss of mitochondrial barrier function during neuronal damage from ischemia or other insults therefore may play an important role in making certain caspases available to participate in apoptosis.

Lack of a neuroprotective effect from N-acetylcysteine after cardiac arrest and resuscitation in a canine model

OBJECTIVE

Oxygen free radicals cause brain injury following resuscitation from cardiac arrest. In preclinical trials, some free radical scavenging drugs reduce oxidative neuronal damage after ischemia and reperfusion, but these drugs are generally not yet available for clinical testing or use. N-Acetylcysteine (NAC), a commonly used antidote in acetaminophen poisoning, is also a potent free radical scavenger that can ameliorate oxidative injury following ischemia and reperfusion in neuronal cell culture. We hypothesized that treatment with NAC would improve neurological outcome after cardiac arrest and resuscitation.

METHODS

In 16 adult female beagles, 10 min of ventricular fibrillation was followed by 3 min of open-chest CPR, and defibrillation. Immediately following return of spontaneous circulation, animals randomly received either 150 mg/kg NAC (3% solution) (n = 8) or an equivalent volume of normal saline (n = 8). Twenty-three hours later, neurological deficit was scored (0 = normal, 100 = brain death).

RESULTS

All animals were successfully resuscitated, and there were no apparent adverse effects to the administration of NAC in post resuscitative animals. There was, however, no significant difference in neurological deficit in the animals receiving NAC (40 +/- 12.9, mean +/- SD) compared to control animals (44 +/- 6.5, P = 0.73).

CONCLUSION

No neuroprotective effect was found from the administration of NAC at currently used clinical dosages, to dogs subjected to 10 min of global cerebral ischemia from cardiac arrest and resuscitation.

Normoxic ventilation after cardiac arrest reduces oxidation of brain lipids and improves neurological outcome

BACKGROUND AND PURPOSE

Increasing evidence that oxidative stress contributes to delayed neuronal death after global cerebral ischemia has led to reconsideration of the prolonged use of 100% ventilatory O2 following resuscitation from cardiac arrest. This study determined the temporal course of oxidation of brain fatty acyl groups in a clinically relevant canine model of cardiac arrest and resuscitation and tested the hypothesis that postischemic ventilation with 21% inspired O2, rather than 100% O2, results in reduced levels of oxidized brain lipids and decreased neurological impairment.

METHODS

Neurological deficit scoring and high performance liquid chromatography measurement of fatty acyl lipid oxidation were used in an established canine model using 10 minutes of cardiac arrest followed by resuscitation with different ventilatory oxygenation protocols and restoration of spontaneous circulation for 30 minutes to 24 hours.

RESULTS

Significant increases in frontal cortex lipid oxidation occurred after 10 minutes of cardiac arrest alone with no reperfusion and after reperfusion for 30 minutes, 2 hours, and 24 hours (relative total 235-nm absorbing peak areas=7.1+/-0.7 SE, 17.3+/-2.7, 14.2+/-3.2, 16.1+/-1.0, and 14.0+/-0.8, respectively; n=4, P<0.05). The predominant oxidized lipids were identified by gas chromatography/mass spectrometry as 13- and 9-hydroxyoctadecadienoic acids (13- and 9-HODE). Animals ventilated on 21% to 30% O2 versus 100% O2 for the first hour after resuscitation exhibited significantly lower levels of total and specific oxidized lipids in the frontal cortex (1.7+/-0.1 versus 3.12+/-0.78 microg 13-HODE/g wet wt cortex., n=4 to 6, P<0.05) and lower neurological deficit scores (45.1+/-3.6 versus 58.3+/-3.8, n=9, P<0.05).

CONCLUSIONS

With a clinically relevant canine model of 10 minutes of cardiac arrest, resuscitation with 21% versus 100% inspired O2 resulted in lower levels of oxidized brain lipids and improved neurological outcome measured after 24 hours of reperfusion. This study casts further doubt on the appropriateness of present guidelines that recommend the indiscriminate use of 100% ventilatory O2 for undefined periods during and after resuscitation from cardiac arrest.

Neuroprotective effects of acetyl-L-carnitine after stroke in rats

STUDY OBJECTIVE

To test the hypothesis that acetyl-L-carnitine (ALCAR) promotes neurologic recovery from experimental focal cerebral ischemia (stroke) in rats.

METHODS

We conducted a prospective, randomized, blinded study in which adult male Sprague-Dawley rats were subjected to coagulative occlusion of the distal right middle cerebral artery (MCA) and temporary occlusion of both common carotid arteries (CCAs) for 60 minutes. After the onset of ischemia each rat was given ALCAR (200 mg/kg) or a similar volume of drug vehicle. Neurologic evaluation was performed on postoperative days 1, 2, 3, and 7. Postoperative weight loss was measured at day 7. Infarct volume was measured in separate groups of rats at 24 hours.

RESULTS

Neurologic outcomes, as assessed with an 11-point neurologic deficit scoring system, were significantly improved in ALCAR-treated rats on days 1, 2, and 3 (P < .05). Improvement approached significance on day 7. Rats treated with ALCAR also demonstrated significantly less weight loss on day 7 compared with the vehicle-treated controls. We detected no differences, however, in infarct volumes measured between treatment groups.

CONCLUSION

Although we noted no differences in infarct volume, postischemic treatment with ALCAR did improve early clinical recovery and prevented significant weight loss in this rat model of focal cerebral ischemia.

Global cerebral ischemia and reperfusion alters NMDA receptor binding in canine brain

We employed a canine model to test whether binding to the N-methyl-D-aspartate (NMDA) class of glutamate receptor channels is altered by global cerebral ischemia and/or reperfusion. Ischemia was induced by 10-min cardiac arrest, followed by restoration of spontaneous circulation for periods of 0, 0.5, 2, 4, and 24 h. In vitro autoradiography was performed on frozen brain sections with three radioligands: [3H]glutamate (under conditions to label the NMDA site), [3H]glycine, and [3H]MK-801. Modest decreases in [3H]glutamate and [3H]MK-801 binding were seen in several regions of hippocampus, and parietal and temporal cortex at early times after reperfusion, with values returning toward control by 24 h. In the striatum, a different pattern was seen: [3H]glutamate and [3H]MK-801 binding increased 50-200% at 0.5-4 h after the start of reperfusion, returning toward control levels by 24 h. These increases correlate with findings of increased sensitivity to NMDA-stimulated release of dopamine from striatal tissue in the same model (Werling et al., 1993), and suggest that changes in tissue receptors may contribute to the selective vulnerability to ischemic damage during the first hours following reperfusion.

Non-NMDA glutamate receptor binding in canine brain after global cerebral ischemia and reperfusion

We employed a canine model to test the effects of global cerebral ischemia and reperfusion on binding to alpha-amino-3-hydroxy-5-methyl- 4-isoxazole proprionate (AMPA), kainate (KA), and metabotropic glutamate receptors. Ischemia was induced by 10 min of cardiac arrest, followed by restoration of spontaneous circulation for periods of 0, 0.5, 2, 4, and 24 h. Frozen sections were prepared from parietal and temporal cortex, hippocampus, and striatum, and in vitro autoradiography was performed with one of three radioligands: [3H]AMPA, [3H]KA, or [3H] glutamate (using conditions allowing specific labeling of the metabotropic binding site). In striatum, metabotropic binding was unchanged, whereas AMPA and KA binding decreased by 20-30% at 30 min postischemia, remaining depressed through 24 h. In cortex, AMPA and metabotropic binding were decreased at several time-points after ischemia and recirculation, particularly in parietal cortex, whereas KA binding was unaffected in this tissue. Binding to hippocampal regions was largely unchanged, except for a decrease in KA binding at 2 and 4 h postischemia. These findings contrast with results from parallel studies showing increased striatal binding to NMDA receptors following ischemia. Decreased binding to non-NMDA glutamate receptors in striatum and parietal cortex may serve to protect against damage mediated through these receptors.

Distribution of neuronal populations containing neurofilament protein and calcium-binding proteins in the canine neocortex: regional analysis and cell typology

Neurophysiological experiments in carnivores have revealed the existence of a large number of cortical regions and an organization of sensory systems quite similar to that found in primates. However, the cyto- and chemoarchitecture of the cerebral cortex is relatively poorly known in carnivores. We analyzed the distribution and typology of classes of neurons containing neurofilament protein or the calcium-binding proteins parvalbumin, calbindin, and calretinin in six neocortical regions of the dog. In all these areas, neurofilament protein was present in a subpopulation of medium-to-large size pyramidal neurons predominantly distributed in layers III and V. Parvalbumin was present in a large population of morphologically diverse interneurons. Small ovoid and multipolar neurons were observed throughout the cortical layers, but predominated in layers II and IV. Layers III and V-VI were characterized by the presence of larger and intensely immunoreactive neurons with bitufted or multipolar morphology, and layers V-VI also contained large multipolar neurons. Calbindin was observed in small round and multipolar interneurons in layer II, and typical double bouquet cells in layer III. Layers IV-VI contained isolated double bouquet cells and large multipolar neurons. A few calbindin-immunoreactive pyramidal neurons were also observed in layer V. Calretinin was localized in bipolar and double bouquet cells in layers II and upper III. The lower part of layer III and layers IV-VI contained rare calretinin-immunoreactive neurons. In some areas, layer III displayed a few large isolated multipolar neurons and pyramidal neurons containing calretinin. In addition, the results show that there is a substantial degree of variability in the distribution of these proteins among cortical regions, and that although they are found in morphologically comparable neuronal types in dog, monkeys, and humans, many differences exist in their regional distribution patterns between carnivores and primates.

Distribution of neurofilament protein and calcium-binding proteins parvalbumin, calbindin, and calretinin in the canine hippocampus

Neurofilament protein and calcium-binding proteins parvalbumin, calbindin, and calretinin are present in morphologically distinct neuronal subpopulations in the mammalian cerebral cortex. Immunohistochemical studies of the hippocampal formation and neocortex have demonstrated that while neurofilament protein and calbindin are localized in subsets of pyramidal neurons, the three calcium-binding proteins are useful markers to differentiate non-overlapping populations of interneurons. To date, most studies have been performed in rodents and primates. In the present analysis, we analyzed the distribution of these proteins in the canine hippocampus. Neurofilament protein was present in large multipolar neurons in the hilus and in pyramidal neurons in the CA3 field, whereas pyramidal neurons in the CA1 field and subiculum were less intensely immunoreactive. Parvalbumin immunoreactivity was observed in large multipolar neurons in the hilus and throughout the CA3-CA1 fields, in a few pyramidal-shaped neurons in the CA1 field and subiculum, and had a distinct neuropil staining pattern in the granule cell layer and stratum pyramidale of the Ammon's horn. Calbindin immunoreactivity displayed a strong labeling of the granule cells and mossy fibers and was also observed in a population of moderately immunoreactive neurons in the CA1 field and subiculum. Calretinin immunoreactivity was relatively weaker overall. The inner molecular layer in the dentate gyrus had a distinct band of labeling, the stratum lacunosum/moleculare contained a punctate neuropil staining, and there were a few small multipolar neurons in the hilus, CA3-CA1 fields, and subiculum. Comparison of the staining patterns observed in the dog hippocampus with those in human, macaque monkeys and rats revealed that although there are some subregional differences among these taxa, the dog may constitute a valuable large animal model for the study of certain neurological conditions that affect humans, in spite of the phylogenetic distance between carnivores and primates.

Distribution of glutamate receptor subunit proteins GluR2(4), GluR5/6/7, and NMDAR1 in the canine and primate cerebral cortex: a comparative immunohistochemical analysis

The distribution of the AMPA, kainate and NMDA glutamate receptor subunit proteins GluR2(4), GluR5/6/7 and NMDAR1, respectively, were analyzed in the dog hippocampus and neocortex and compared to macaque monkeys and humans. In the dog hippocampus, these glutamate receptor classes exhibited a comparable distribution with few differences in densities of labeled of neurons in the CA1-CA3 fields and in neuropil staining patterns in the dentate gyrus. In particular, the GluR5/6/7 subunit proteins were characterized by a more restricted cellular distribution in the CA1-CA3 fields. In the dog neocortex, the GluR2(4) subunit was found in a higher number of neurons in layers III and V compared to the GluR5/6/7 or NMDAR1 subunits, which were found predominantly in a population of medium-to-large layer V pyramidal neurons. Layers II and VI were consistently densely labeled with all three receptor classes, especially in the case of the GluR5/6/7 and NMDAR1 subunits. All three antibodies used thus far showed an intense labeling of the perikaryon and dendritic segments in the dog cerebral cortex. Apical dendrites could be followed through several layers in some cases, and formed well-stained plexuses in all of the neocortical layers. These patterns were very similar to those observed in the hippocampus and neocortex of both monkey and human, although GluR2(4) and NMDAR1 immunoreactivity was visualized in more heterogeneous populations of cortical neurons in the primates than in dogs. Glutamate is the principal excitatory neurotransmitter in the brain and is involved in the excitotoxic mechanisms occurring in pathologic conditions such as epilepsy and cerebral ischemia. The dog has been shown to represent a reliable large animal model for several neurologic disorders and is used particularly in investigations of the cerebral repercussions of cardiac arrest. The overall similarity of the staining patterns in dogs and primates observed in the present study suggest that the dog model may be highly valuable for the characterization of potential cellular and synaptic shifts in the distribution and expression of specific glutamate receptor subunits, in the context of other biochemical and morphologic effects of global brain ischemia and reperfusion following cardiac arrest.

The role of L-type voltage dependent calcium channels in stimulated [3H]norepinephrine release from canine hippocampal slices following global cerebral ischemia and reperfusion

The hippocampus is among those brain regions which are selectively vulnerable to ischemic damage. Hippocampal damage due to transient cerebral ischemia is mainly of the delayed, non-necrotic type which may arise after disruption or activation of specific cellular systems, including transmitter release through excitatory amino acid receptors. We investigated the contribution of L-type voltage dependent calcium channels (VDCCs) to glycine (GLY) potentiated N-methyl-D-aspartate (NMDA) receptor- and potassium-stimulated [3H]norepinephrine (NE) release in a canine model of global cerebral ischemia and reperfusion. Tissue was collected from four experimental groups: non-arrested controls (NA), global cerebral ischemia induced by 10 minute cardiac arrest (CA), and CA followed by 30 min or 24 hours reperfusion after restoration of spontaneous circulation. Brain slices prepared from all groups accumulated approximately equivalent amounts of [3H]NE. The sensitivity of [3H]NE release to stimulation by NMDA/GLY or elevated potassium was unchanged after ischemia and reperfusion. About 30% of release stimulated by the addition of 20 mM potassium was inhibited by the NMDA receptor-operated channel antagonist MK801 in all groups except CA in which only 4% of release was inhibited by MK801. The ability of 1 microM nitrendipine (NTP) to block stimulated release indicated that the contribution of the L-type VDCC to potassium or NMDA/GLY-stimulated release was significant only in NA and 24 hour reperfused animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Autoradiographic analysis of L- and N-type voltage-dependent calcium channel binding in canine brain after global cerebral ischemia/reperfusion

Binding of antagonists to L- and N-type voltage-dependent calcium channels (VDCC) was measured in canine brain following global ischemia and reperfusion. Ischemia was induced by 10 min cardiac arrest, followed by restoration of spontaneous circulation for periods of up to 24 h. Binding of [3H]PN200-110 and [125I]omega-conotoxin GVIA to frozen sections from hippocampus, striatum, parietal cortex and temporal cortex was analyzed using quantitative receptor autoradiography. The binding patterns of the two radioligands were similar in cortex and striatum, but differed in hippocampus. In the latter tissue, [125I]omega-conotoxin GVIA binding was dense over synaptic regions, especially the presynaptic polymorph layer of the dentate gyrus, but was virtually absent over cell body layers. In contrast, [3H]PN200-110 binding was more homogenously distributed, with highest binding in the molecular layer of the dentate gyrus. The binding of [125I]omega-conotoxin GVIA was not different from sham controls at any time point following cardiac arrest. [3H]PN200-110 binding was decreased in each region immediately following ischemia, recovering within 30 min of recirculation. These findings are in contrast to earlier findings of rapid increases in L-type VDCC binding to membrane fractions obtained from cortex and striatum in this model, and suggest that the previously detected increases may be due to a redistribution of channels from subcellular compartments to the plasma membrane during ischemia.

Increased activation of L-type voltage-dependent calcium channels is associated with glycine enhancement of N-methyl-D-aspartate-stimulated dopamine release in global cerebral ischemia/reperfusion

We investigated the relationships among N-methyl-D-aspartate, glycine, L-type voltage-dependent calcium channels, and [3H]dopamine release in a canine model of global cerebral ischemia/reperfusion. The binding of [3H]PN200-110 ([3H]isradipine) to L-type voltage-dependent calcium channels, that open as a consequence of N-methyl-D-aspartate-induced changes in membrane potential, was approximately doubled in striatal membranes prepared from ischemic animals relative to controls, and remained significantly elevated at 30 min and 2 h of reperfusion. These changes coincided temporally with changes in the ability of the voltage-sensitive calcium channel blocker nitrendipine to inhibit glycine enhancement of N-methyl-D-aspartate-stimulated [3H]dopamine release in striatal slices prepared from the same animals. Compared with nonischemic controls, N-methyl-D-aspartate-stimulated [3H]dopamine release was increased in ischemic animals and remained increased throughout reperfusion up to at least 24 h. Glycine enhanced N-methyl-D-aspartate-stimulated release in all treatment groups. The enhancement of N-methyl-D-aspartate-stimulated dopamine release by glycine was reduced by the inclusion of nitrendipine in striatal slices from ischemic and 30-min reperfused animals. These data suggest that glycine may facilitate opening of the voltage-dependent calcium channels activated by N-methyl-D-aspartate and that this facilitation is blocked by the antagonist nitrendipine.

Effectiveness of transnasal butorphanol for the treatment of musculoskeletal pain

A prospective, open-label study of the effectiveness of transnasal butorphanol in the treatment of pain resulting from musculoskeletal injuries. Twenty-eight patients with strains (n = 20), fractures (n = 6), contusions (n = 1), and stab wounds (n = 1) were included. All patients were examined by an attending level emergency medicine physician and deemed to have pain severe enough to warrant parenteral narcotic analgesia. All patients received an initial 1-mg dose of transnasal butorphanol. Subsequent dosing was flexible depending on response to the initial dose. All patients received pain relief from transnasal butorphanol, and only one requested alternative analgesic medication. Fifty-seven percent (n = 16) of patients noticed at least a little relief of pain within 5 minutes of administration and 93% (n = 26) received at least a little relief within 15 minutes. Seventy-one percent of the patients received a 50% reduction of pain within 60 minutes. No serious side effects were noted, but drowsiness occurred in 82% (n = 23) and dizziness in 54% (n = 15) of the patients. One patient discontinued participation in the study because of nausea. In this limited trial transnasal butorphanol proved to be a rapidly effective opioid analgesic. Further controlled studies comparing transnasal butorphanol with standard parenteral narcotics are needed.

Postischemic inhibition of cerebral cortex pyruvate dehydrogenase

Postischemic, mitochondrial respiratory impairment can contribute to prolonged intracellular lactic acidosis, secondary tissue deenergization, and neuronal cell death. Specifically, reperfusion-dependent inhibition of pyruvate dehydrogenase (PDH) may determine the degree to which glucose is metabolized aerobically vs. anaerobically. In this study, the maximal activities of pyruvate and lactate dehydrogenase (LDH) from homogenates of canine frontal cortex were measured following 10 min of cardiac arrest and systemic reperfusion from 30 min to 24 h. Although no change in PDH activity occurred following ischemia alone, a 72% reduction in activity was observed following only 30 min of reperfusion and a 65% inhibition persisted following 24 h of reperfusion. In contrast, no significant alteration in LDH activity was observed in any experimental group relative to nonarrested control animals. A trend toward reversal of PDH inhibition was observed in tissue from animals treated following ischemia with acetyl-L-carnitine, a drug previously reported to inhibit brain protein oxidation, and lower postischemic cortical lactate levels and improve neurological outcome. In vitro experiments indicate that PDH is more sensitive than LDH to enzyme inactivation by oxygen dependent free radical-mediated protein oxidation. This form of inhibition is potentiated by either elevated Ca2+ concentrations or substrate/cofactor depletion. These results suggest that site-specific protein oxidation may be involved in reperfusion-dependent inhibition of brain PDH activity.

Inhibition of postcardiac arrest brain protein oxidation by acetyl-L-carnitine

Free radical mediated, site-specific protein oxidation has been implicated in the pathophysiology of ischemia/reperfusion brain injury. The purpose of this study was to determine whether this form of molecular damage could be detected in a clinically relevant model employing 10-min cardiac arrest in dogs followed by restoration of spontaneous circulation for up to 24 h. The effects of postischemic acetyl-L-carnitine administration on protein oxidation were also tested due to its previously reported improvement of brain energy metabolism and neurological outcome in this model. Following the experimental period, soluble proteins were extracted from a sample of frontal cortex and reacted with dinitrophenylhydrazine for spectrophotometric measurement of protein carbonyl groups. The most important results of this study were that brain protein carbonyl groups were significantly elevated following 2 and 24 h of reperfusion compared to nonischemic controls, and that postischemic IV administration of acetyl-L-carnitine eliminated the increase in carbonyl groups observed at the 24-h period. These results indicate that brain protein oxidation does occur in a clinically relevant model of complete global cerebral ischemia and reperfusion, and that oxidation is inhibited under treatment conditions that improve neurological outcome.

Dopamine release from canine striatum following global cerebral ischemia/reperfusion

The elevation of extracellular dopamine (DA) levels in the striatum of experimental animals subjected to ischemic insult has been well documented. The contribution of excessive DA to neuronal damage can be inferred from the ability of DA antagonists, as well as selective destruction of dopaminergic tracts, to confer neuroprotection in models of ischemia. In the current study, we report an enhanced releasability of preloaded [3H]DA in response to either elevated potassium or N-methyl-D-aspartate (NMDA) from striatal slices of beagles that had experienced 10 min of ischemia induced by cardiac arrest. The elevation in sensitivity to potassium stimulation was transient, approaching control levels after 30 min of reperfusion. In contrast, release stimulated by NMDA was elevated immediately after cardiac arrest and remained elevated for as long as 24 h of reperfusion. Release stimulated by NMDA was enhanced by glycine (Gly) and inhibited by MK801, consistent with mediation through the NMDA receptor/channel complex. The increased sensitivity of DA release, coupled with the high levels of excitatory amino acids (EAAs), including glutamate (Glu), aspartate (Asp) and Gly in ischemic brain, probably contribute to the extensive neuronal cell damage.

MR imaging of hepatocellular carcinoma at 1.5 Tesla

The authors investigated the magnetic resonance appearance of hepatocellular carcinoma using a 1.5-Tesla magnet. Twenty-four patients with pathologically proven hepatocellular carcinoma had magnetic resonance imaging (MRI) studies, which were retrospectively reviewed. All patients were imaged with at least two of the following techniques: (1) T1-weighted (T1W), (2) T1-weighted with Gd-DTPA enhancement (T1W-E), (3) T2-weighted (T2W), (4) proton density (PD), and (5) gradient-recalled echoes (GRE). T1W images were equal to T2W images for tumor detection using a grading system. T1W images were slightly better than T2W images for the total number of lesions detected. The other pulsing techniques (PD, T1W-E, and GRE) detected fewer lesions. Eight cases of hepatocellular carcinoma (33%) had nonhomogeneous increased signal intensity on both T1W and T2W images. The authors conclude that T1W images are equal to T2W images for detection of hepatocellular carcinoma. The authors also conclude that 33% of hepatocellular carcinomas have an imaging pattern with increased signal intensity on both T1W and T2W images. This pattern is atypical for most other hepatic masses and hence can be used to suggest the mass is hepatocellular carcinoma.

Prevention of postischemic canine neurological injury through potentiation of brain energy metabolism by acetyl-L-carnitine

BACKGROUND AND PURPOSE

Mechanisms of ischemia/reperfusion brain injury include altered patterns of energy metabolism that may be amenable to pharmacological manipulation. The purpose of this study was to test the effectiveness of postischemic acetyl-L-carnitine administration on potentiation of metabolic recovery and prevention of neurological morbidity in a clinically relevant model of complete, global cerebral ischemia and reperfusion.

METHODS

Neurological deficit scoring as well as spectrophotometric and fluorescent assays of frontal cortex lactate and pyruvate levels were used in a canine model employing 10 minutes of cardiac arrest followed by restoration of spontaneous circulation for 2 or 24 hours.

RESULTS

Dogs treated with acetyl-L-carnitine exhibited significantly lower neurological deficit scores (p = 0.0037) and more normal cerebral cortex lactate/pyruvate ratios than did vehicle-treated control animals.

CONCLUSIONS

Postischemic administration of acetyl-L-carnitine potentiates normalization of brain energy metabolites and substantially improves neurological outcome in a clinically relevant model of global cerebral ischemia and reperfusion.

Alteration of voltage-dependent calcium channels in canine brain during global ischemia and reperfusion

Elevated intracellular calcium (iCa2+) plays an important role in the pathophysiology of ischemic brain damage. The mechanisms by which iCa2+ increases are uncertain. Recent evidence implicates the voltage-dependent calcium channel (VDCC) as a likely site for the alteration in Ca2+ homeostasis during ischemia. The purpose of this study was to determine whether VDCCs are altered by global ischemia and reperfusion in a canine cardiac arrest, resuscitation model. We employed the radioligand, [3H]PN200-110, to quantitate the equilibrium binding characteristics of the VDCCs in the cerebral cortex. Twenty-five adult beagles were separated into four experimental groups: (a) nonischemic controls, (b) those undergoing 10-min ventricular fibrillation and apnea, (c) those undergoing 10-min ventricular fibrillation and apnea followed by spontaneous circulation and controlled respiration for 2 and (d) 24 h. Brain cortex samples were taken prior to killing of the animal, frozen immediately in liquid nitrogen, and crude synaptosomal membranes isolated by differential centrifugation/filtration. After 10 min of ischemia the maximal binding (Bmax) of [3H]PN200-110 increased to greater than 250% of control values (control Bmax 11.16 +/- 0.98; ischemic 28.35 +/- 2.78 fmol/mg protein; p less than 0.05). Bmax returned to near control values after 2 h of reperfusion but remained significantly greater than the control at 24 h. Although the affinity constant (Kd) (control = 0.12 +/- 0.03 nM) appeared to increase with ischemia and normalize with reperfusion, the changes were not statistically significant. We conclude that the binding of [3H]PN200-110 to L-type VDCCs is increased after 10 min of global ischemia/anoxia produced by ventricular fibrillation and apnea in the dog.(ABSTRACT TRUNCATED AT 250 WORDS)

Prevention of post-ischemic brain lipid conjugated diene production and neurological injury by hydroxyethyl starch-conjugated deferoxamine

Hydroxyethyl starch conjugated deferoxamine (DFO) was administered to rats following resuscitation from 6.5 min cardiac arrest (CA) in an attempt to prevent the iron-catalyzed production of oxygen free radicals which may lead to neurologic injury and ultimately death following restoration of spontaneous circulation (ROSC). Brain conjugated dienes were analyzed spectrophotometrically 4 and 24 hr following ROSC, and were found to be significantly elevated when compared to non-ischemic controls. Hydroxyethyl starch-DFO treated rats demonstrated no increased conjugated diene production at either period. Neurologic injury was significantly less in drug treated rats surviving 24 or 72 hours when compared to controls. While mortality was similar in drug treated or control rats for the first 24 hours following ROSC, delayed mortality (days 1-10) was significantly less in drug treated animals, presumably as a result of neurologic protection afforded by post-ischemic drug administration. Administration of DFO conjugated to hydroxyethyl starch appears to modulate the neurologic injury which occurs during brain ischemia and reperfusion.

Diagnostic value of gadopentetate dimeglumine for 1.5-T MR imaging of musculoskeletal masses: comparison with unenhanced T1- and T2-weighted imaging

Three magnetic resonance (MR) imaging techniques (T1-weighted, T2-weighted, and T1-weighted gadopentetate dimeglumine--enhanced) were compared in 32 consecutive MR imaging studies of 26 patients with suspected musculoskeletal masses. T2-weighted images were superior to T1-weighted enhanced images with respect to detection and definition of lesions in 12% of cases (n = 4) and were equal in 88% of cases (n = 28). T2-weighted images were also superior to T1-weighted images in 38% of cases (n = 12). In no cases were T1-weighted enhanced images superior to T2-weighted images. In two cases, T1-weighted images were superior to both T1-weighted enhanced and T2-weighted images. The authors conclude that gadopentetate dimeglumine did not provide much value in lesion detection above that obtained with T2-weighted images. They also conclude that T1-weighted images were occasionally superior to T1-weighted enhanced images and T2-weighted images because of loss of definition between fat and lesion on the latter.

Office evaluation and management of acute orthopedic trauma

Virtually any injury that can be treated as an outpatient can be treated in a properly equipped and staffed orthopaedist's office, provided that it is accurately identified and evaluated initially. Anesthetic blocks, closed manipulations, some suturing, and immobilizations can all be done in the acute setting. Children and elderly patients are particularly suited to office treatment. Close follow-up is essential, and early rehabilitation can begin in the office setting.

The emergency department as part of a successful strategy for increasing adult immunization

To evaluate acceptance of the emergency department as a setting for vaccine delivery, we interviewed and offered pneumococcal vaccine to 338 high-risk ED patients presenting with unrelated complaints. Only 27 (8%) had previously been immunized with pneumococcal vaccine. Of the unimmunized, 187 (60%) initially indicated that they would accept vaccine during their current ED visit, and 51 (37%) of those without immediate medical contraindications were immunized. Willingness to take pneumococcal vaccine in the ED was independent of whether the patient had a primary medical provider (P = .77). Our immunization strategy complements other vaccination schemes that target those at high risk for pneumococcal disease and may in particular serve those patients who use the ED as their primary source of health care.

Cerebral ischemia and reperfusion: prevention of brain mitochondrial injury by lidoflazine

Mitochondrial degradation is implicated in the irreversible cell damage that can occur during cerebral ischemia and reperfusion. In this study, the effects of 10 min of ventricular fibrillation and 100 min of spontaneous circulation on brain mitochondrial function was studied in dogs in the absence and presence of pretreatment with the Ca2+ antagonist lidoflazine. Twenty-three beagles were separated into four experimental groups: (i) nonischemic controls (ii) those undergoing 10-min ventricular fibrillation, (iii) those undergoing 10-min ventricular fibrillation pretreated with 1 mg/kg lidoflazine i.v., and (iv) those undergoing 10-min ventricular fibrillation followed by spontaneous circulation for 100 min. Brain mitochondria were isolated and tested for their ability to respire and accumulate calcium in a physiological test medium. There was a 35% decrease in the rate of phosphorylating respiration (ATP production) following 10 min of complete cerebral ischemia. Those animals pretreated with lidoflazine showed significantly less decline in phosphorylating respiration (16%) when compared with nontreated dogs. Resting and uncoupled respiration also declined following 10 min of fibrillatory arrest. One hundred minutes of spontaneous circulation following 10 min of ventricular fibrillation and 3 min of open-chest cardiac massage provided complete recovery of normal mitochondrial respiration. Energy-dependent Ca2+ accumulation by isolated brain mitochondria was unimpaired by 10 min of complete cerebral ischemia. However, by 100 min after resuscitation, there was a small, but significant rise in the capacity for mitochondrial Ca2+ sequestration when compared to either control or fibrillated groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiopulmonary resuscitation. Historical and future perspectives

Although cardiopulmonary resuscitation (CPR) has been practiced for over a century, further study into methods for reviving victims of cardiac arrest is obviously needed. We now know that standard external CPR has numerous drawbacks, and modifications must be tested in a careful, randomized fashion. Three alternatives to standard external CPR (simultaneous compression-ventilation, interposed abdominal compression, and open-chest CPR) are currently being investigated. Of these procedures, open-chest CPR appears to show the most promise. Reproducible animal data must demonstrate the advantages of any method before widespread human studies are begun, however. If techniques seem promising in animals, well-controlled multicenter studies will be needed to verify applicability to humans. Major changes in CPR techniques should be made only after careful study, not on the basis of a limited number of reports from a single source. Resuscitation research must also extend beyond the study of techniques of cardiac massage. Although CPR is effective in some cases, clearly a person's chance of survival is directly linked to the speed of definitive care, that is, defibrillation. Research must continue into ways of providing rapid advanced cardiac care, such as home defibrillators or rapid prehospital response to the victims of cardiac arrest by those trained in advanced cardiac life support (ACLS). In addition, to counteract the problem of neurologic demise after prolonged anoxia, study of postresuscitative care must continue. Only through the combination of these measures will survival rates after cardiac arrest improve.

Stab wounds to the abdomen: failure of blunt probing to predict peritoneal penetration

A study was conducted to examine the usefulness of blunt probing for evaluation of penetrating abdominal trauma. Ten anesthetized adult beagles weighing 8 to 17 kg were sacrificed by ventricular fibrillation following a standardized resuscitation protocol. Immediately thereafter, the abdomen was shaved and ten stab wounds were placed in the abdomen of each dog with #11 blade. A separate individual probed the wounds sequentially with a cotton swab and predicted on the basis of this examination whether the wound penetrated the parietal peritoneum (deep) or not (superficial). The abdomen then was opened and reflected, by a midline incision, and peritoneal penetration was verified visually by two observers. Statistical analysis of data was performed using the z test for binomial proportions. Fifty-nine of the 100 wounds were found to penetrate the parietal peritoneum. Examiners predicted 35 correctly, but called 24 of 59 superficial. Thirty-eight of 41 superficial wounds were identified correctly; three were incorrectly called deep. Sensitivity was .59 (z = 1.432, P greater than .5); specificity was .93 (z = 5.466, P less than .001). Blunt probing may be a useful technique if peritoneal penetration is determined, but it is inaccurate in predicting peritoneal nonpenetration. If violation of the peritoneum is not determined with this technique, other methods must be used.

Truncal seizures: an unusual presentation of cerebral cysticercosis

We present the case of a 24-year-old woman who developed repetitive partial simple seizures confined to her right rib cage. Computed tomography scan of the head was consistent with the diagnosis of cerebral cysticercosis. The patient was started on a regimen of anticonvulsants, steroids, and praziquantel with full resolution of symptoms.

Lead intoxication 18 months after a gunshot wound

Lead poisoning can result from a retained intra-articular bullet. A 30-year-old man who was shot with a .38-caliber pistol illustrates the symptoms, signs, and differential diagnosis of lead intoxication.

Emergency department evaluation of musculoskeletal injuries

The author discusses the recognition and initial management of fractures, including open and pathologic fractures; wounds, including gunshot wounds; dislocations and fracture-dislocations; peripheral nerve and vascular injuries; sprains and ligament injuries; and musculoskeletal injuries in the multiply injured patient.

Combined skeletal and vascular injuries of the lower extremities

In order to determine the long-term results of surgical treatment in patients with significant combined skeletal and arterial injuries, the authors reviewed the records of those patients treated for this injury between 1970 and 1981, at their institutions. These cases were confined to fractures and/or dislocations of the femur, knee, and tibia which were associated with vascular injuries. Thirty-one patients with 32 injured extremities fit these criteria for our review. The distribution of the orthopedic injuries were as follows: femoral fractures, 16; tibial fractures, 20; and knee dislocations, four. Fifty percent of the injuries had neurologic deficit; significant soft tissue injury was present in 22 extremities; and all but 4 had attempted arterial revascularization. Vascular procedures included saphenous vein by-pass, saphenous vein interposition, end-to-end anastomosis and lateral arteriorrhaphy. Orthopedic repairs were generally accomplished by external means with only five cases treated by immediate internal fixation. Long-term results were categorized as excellent, fair, or poor. Amputations were classified as primary and secondary. Excellent results were found in only five of the reconstructed extremities. Thirty-five percent of the extremities were classified as having a fair result. Two extremities had a poor result. Four extremities were primarily amputated, and secondary amputation was performed on seven extremities. Associated nerve deficits and/or significant soft tissue injuries were found to be the major factors determining the eventual success or failure of reconstructive efforts.

Osteomyelitis of the symphysis pubis: a separate disease from osteitis pubis. Report of three cases and review of the literature

We reviewed the case of three of our own patients who had osteomyelitis of the symphysis pubis, as well as those of twenty-five patients described in the literature. The early symptoms of osteomyelitis of the symphysis mimic those of osteitis pubis. Osteomyelitis almost invariably is preceded by urological or gynecological surgery (often when a technical complication has occurred), and does not respond to shortterm antibiotic treatment. Characteristic radiographic findings develop. Osteomyelitis of the symphysis pubis should be treated by debridement and curettage, together with long-term treatment with an appropriately high dose of antibiotics.

Bilateral total hip replacement in a diastrophic dwarf

This article reports a case of bilateral total hip replacement in a diastrophic dwarf. We were unable to find reports of any similar cases in the world literature, although we do know that Hungerford performed a total hip replacement in a diastrophic dwarf in 1974 (personal communication). In addition to the case report, this article reviews some of the salient characteristics that set diastrophic dwarfism apart from other chondrodystrophies.

Unstable fracture-dislocations of the thoracolumbar spine: results of surgical treatment

In a review of 22 patients with unstable fractures or fracture-dislocations of the thoracolumbar spine, treated by Harrington rod instrumentation and spinal arthrodesis, all arthrodeses became solid. All patients with incomplete neurologic lesions regained some function. No patient was made neurologically worse by the procedure. Solid arthrodesis was achieved whether laminectomy was performed or not. Harrington rods offer a method of reduction of compression fractures, offer partial stability to the spine, and serve as an adjunct to spine arthrodesis.

Unstable ankle fractures: comparison of closed versus open treatment

To determine what factors were important in final clinical results, we evaluated 145 patients admitted to Vanderbilt University Hospital with ankle fractures between January 1971 and December 1976. There was a strong correlation between anatomic results of reduction and final clinical results. Talar displacement of more than 5 mm before reduction, a posterior malleolus fracture involving more than 25% of the articular surface, an anterior tibial plafond fracture involving more than 25% of the articular surface, and talus fractures involving the articular surface were four variables which significantly affected results. Open reduction, torn deltoid ligaments, open fractures, type of fracture, type of internal fixation devices used, sex, and age did not signficantly affect results. Other injuries in association with ankle fractures, especially after automobile accidents, frequently prolonged hospitalization.