Cell-specific caspase expression by different neuronal phenotypes in transient retinal ischemia

Emerging evidence supports an important role for caspases in neuronal death following ischemia-reperfusion injury. This study assessed whether cell specific caspases participate in neuronal degeneration and whether caspase inhibition provides neuroprotection following transient retinal ischemia. We utilized a model of transient global retinal ischemia. The spatial and temporal pattern of the active forms of caspase 1, 2 and 3 expression was determined in retinal neurons following ischemic injury. Double-labeling with cell-specific markers identified which cells were expressing different caspases. In separate experiments, animals received various caspase inhibitors before the induction of ischemia. Sixty minutes of ischemia resulted in a delayed, selective neuronal death of the inner retinal layers at 7 days. Expression of caspase 1 was not detected at any time point. Maximal expression of caspase 2 was found at 24 h primarily in the inner nuclear and ganglion cell layers of the retina and localized to ganglion and amacrine neurons. Caspase 3 also peaked at 24 h in both the inner nuclear and outer nuclear layers and was predominantly expressed in photoreceptor cells and to a lesser extent in amacrine neurons. The pan caspase inhibitor, Boc-aspartyl fmk, or an antisense oligonucleotide inhibitor of caspase 2 led to significant histopathologic and functional improvement (electroretinogram) at 7 days. No protection was found with the caspase 1 selective inhibitor, Y-vad fmk. These observations suggest that ischemia-reperfusion injury activates different caspases depending on the neuronal phenotype in the retina and caspase inhibition leads to both histologic preservation and functional improvement. Caspases 2 and 3 may act in parallel in amacrine neurons following ischemia-reperfusion. These results in the retina may shed light on differential caspase specificity in global cerebral ischemia.

Functional and morphologic comparison of two methods to produce transient retinal ischemia in the rat

OBJECTIVES

Much of our knowledge of the pathophysiology of retinal ischemic injury is from a multitude of studies that use in vitro or in vivo animal models of retinal ischemia followed by reperfusion. The objective of this study was to compare histopathologic and electrophysiologic (electroretinography) parameters using two different models of transient retinal ischemia: high intraocular pressure (HIOP) and suture ligation of the optic nerve (SL).

METHODS

Transient retinal ischemia was induced using the HIOP model or the SL model in the Sprague-Dawley rat for either 30 or 60 minutes. Histopathologic outcome was determined at 1 and 7 days after ischemia. In addition, electroretinography (ERG) was performed at 2 hours, I day, 3 days, and 7 days after ischemia.

RESULTS

At 1 and 7 days after 30 minutes of ischemia, there were no significant histopathologic abnormalities in the retina with either model, except for a slight decrease of the cell count in the ganglion cell layer (GCL) with the SL method. After 60 minutes of ischemia, there was significant thinning of the inner retina. There was a significant early dropout of cells at 1 day in the inner nuclear layer (INL) in the HIOP method compared to the SL method where the dropout was delayed and gradually progressive. Dropout of cells in the GCL was early (I day) and gradually progressive in both models but more severe in HIOP than SL. There was a significant decrease in the ERG b-wave amplitudes as early as 2 hours after both 30 and 60 minutes of ischemia compared to preischemic baselines.

CONCLUSIONS

The degree of retinal injury after transient retinal ischemia was more severe at 1 day after reperfusion in the HIOP method compared to the SL method but was similar at 7 days in both models. Furthermore, our data suggests that functional assessment of ischemic damage by electroretinography may be a more sensitive parameter than conventional histopathologic quantification. The timing of either measurement relative to the ischemic stimulus is critical because histologic measurements performed too early after ischemia may underestimate the degree of injury.

Antithrombotic and thrombolytic therapy for ischemic stroke

Antithrombotic and thrombolytic agents form the cornerstone of stroke prevention and treatment. Large, randomized trials have also highlighted the effectiveness and safety of early and continuous antiplatelet therapy in reducing atherothrombotic stroke recurrence. Aspirin is the antiplatelet treatment standard against which several other antiplatelet agents (ticlopidine, clopidogrel, aspirin-dipyridamole) have been shown to be more effective. The prevention of cardioembolic stroke is best accomplished with oral anticoagulation, barring any contraindications. The thrombolytic agent, rt-PA, improves outcome in ischemic stroke patients treated within 3 hours of onset. The risk-benefit ratio is narrow because of an increased risk for bleeding but studies do not support a higher risk in the geriatric population.

Fas (CD95/APO-1) plays a role in the pathophysiology of focal cerebral ischemia

The purpose of this study was to investigate the role of fas antigen, a member of the TNF receptor family, in cell death after focal cerebral ischemia. Focal ischemia was induced in the Sprague-Dawley rat. Evidence for apoptosis was determined by morphology as well as the presence of DNA fragmentation by the end labeling technique (TUNEL). Immunohistochemistry was performed to detect expression of both fas and fas ligand (fasL). In a separate set of experiments, two groups of mice were studied: lpr (that have a loss of function mutation for fas) and wild type. Infarct volume was measured at 24 hr as well as evidence for apoptosis. Twenty-four hours after ischemia, there was evidence for apoptosis based on morphological criteria as well as the TUNEL technique in the rat. Immunohistochemistry demonstrated increased expression of both fas and fasL in the ischemic region, with maximal staining occurring between 24-48 hr for both. Twenty-four hours after ischemia in the mice, there was evidence of apoptosis in both groups, however, the mutant mice (lpr) had significantly smaller infarcts as compared to the wild type. There was no difference in the cerebrovasculature of the two groups of mice. These data support the hypothesis that apoptosis plays a role in the pathophysiology of focal cerebral ischemia. Furthermore, these data suggest that fas-mediated apoptosis contributes to this process.

The novel beta-blocker, carvedilol, provides neuroprotection in transient focal stroke

Increasing evidence supports a role for oxidative stress, proinflammatory cytokines, and apoptosis in the pathophysiology of focal ischemic stroke. Previous studies have found that the multi-action drug, carvedilol, is a mixed adrenergic antagonist, and that it behaves as an antioxidant and inhibits apoptosis. In the current study, the authors investigated whether carvedilol provides protection in focal cerebral ischemia and whether this protection is associated with reduced apoptosis and the downregulation of the inflammatory cytokines, tumor necrosis factor-alpha (TNF-alpha) and interleukin- 1beta (IL-1beta). Male Sprague-Dawley rats were subjected to transient middle cerebral artery occlusion (MCAO) by an intraluminal filament technique. Carvedilol (1, 3, and 10 mg/kg) was injected daily subcutaneously 2 or 4 days before the induction of ischemia. Neurologic scores, infarct volumes, TUNEL staining, and mRNA levels of TNF-alpha and IL-1beta were assessed at 24 hours reperfusion. The effect of carvedilol on microvascular cortical perfusion was studied with continuous laser-Doppler flowmetry. Twenty-four hours after MCAO, carvedilol at all three doses reduced infarct volumes by at least 40% and reduced neurologic deficits on average by 40% compared with vehicle-treated controls when given 2 or 4 days before the induction of ischemia. This protection was not mediated by changes in temperature or blood flow. Treatment with all three dose regimens resulted in fewer TUNEL positive cells compared with controls. At 24 hours reperfusion, carvedilol decreased TNF-alpha and IL-1beta expression by 40% to 50% in the ipsilateral ischemic cortex compared with the contralateral controls. The results of the current study indicate that carvedilol is neuroprotective in focal cerebral ischemia and may protect the ischemic brain by inhibiting apoptosis and attenuating the expression of TNF-alpha and IL-1beta.

Signal transduction mechanisms involved in ischemic preconditioning in the rat retina in vivo

Ischemic preconditioning (IPC) protects the rat retina against the injury that ordinarily follows severe ischemia. We showed previously that release of adenosine and de novo protein synthesis were required for IPC protection. The mechanisms of IPC were studied in the rat retina by examining the signal transduction mediators responsible, in particular, those theorized to be downstream of adenosine receptors. In addition, we examined the hypothesis that nitric oxide and hydroxyl radicals were involved in the IPC protective phenomenon. Retinal ischemia was produced for 60 min in ketamine/xylazine-anesthetized Sprague-Dawley rats, and recovery was measured using electroretinography. We tested the effects on the protective effect of IPC resulting from antagonism of protein kinase C, potassium ATP channels, nitric oxide synthase, or hydroxyl radicals. The effects of the inhibition of de novo protein synthesis or of protein kinase C, and blockade of potassium ATP channels on the mimicking of IPC by adenosine receptor agonists was examined.IPC protection was strongly attenuated by inhibition of protein kinase C and by blockade of potassium ATP channels, but unaffected by the inhibition of hydroxyl radicals. Blockade of nitric oxide synthase produced a trend toward enhancement of IPC protection. Mimicking of IPC protection by adenosine receptor agonists was inhibited by blockade of protein synthesis or of protein kinase C, as well as by potassium ATP channel antagonism. These results demonstrate that protein kinase C and potassium ATP channels are mediators of the protective effect produced by IPC. In addition, the results show that stimulation of adenosine receptor subtypes A1 and A2a is responsible for IPC protection via downstream stimulation of protein kinase C, the opening of potassium ATP channels, and de novo protein synthesis.

The role of the p53 protein in the selective vulnerability of the inner retina to transient ischemia

PURPOSE

To determine whether the p53 protein plays a role in the selective vulnerability of the inner retina to transient ischemia.

METHODS

Transient retinal ischemia was induced using a high intraocular pressure (HIOP) model in the Sprague-Dawley rat for 60 minutes. Histopathologic outcome was determined 7 days after ischemia. In addition, analysis for evidence for apoptosis (TdT-dUTP terminal nick-end label [TUNEL] staining) and p53 protein expression (immunohistochemistry) was performed at several points during the reperfusion period. In a separate set of experiments, wild-type mice and two groups of transgenic mice, one homozygous and the other heterozygous for the p53 null gene, were also subjected to HIOP for 60 minutes, and histopathology was performed 7 days later.

RESULTS

At 7 days subsequent to 60 minutes of ischemia in the rat, there was marked thinning of the inner retinal layers. There were scattered TUNEL-positive cells within the inner retina, peaking at 24 to 48 hours and persisting for at least 7 days. p53 immunochemistry demonstrated elevated protein levels within the inner retina; this finding peaked at 24 to 48 hours but was no longer present at 4 days after ischemia. TUNEL staining of the inner retina of the mouse was most prominent 24 hours subsequent to ischemia but persisted at 48 hours. Seven days subsequent to 60 minutes of ischemia in the wild-type and transgenic mice, histopathologic evaluation demonstrated preservation of the retinal histoarchitecture in the heterozygous group compared with the wild-type or homozygous animals.

CONCLUSIONS

These data further support the hypothesis that the delayed cell death that occurs after transient retinal ischemia is, in part, apoptotic. In addition, they suggest a role for the p53 protein in the selective vulnerability of the inner retina to transient ischemia. p53 protein may be a target for future therapeutic agents in the treatment of disorders of the retina where ischemia plays a pathogenetic role.

Aurintricarboxylic acid prevents GLUR2 mRNA down-regulation and delayed neurodegeneration in hippocampal CA1 neurons of gerbil after global ischemia

Aurintricarboxylic acid (ATA), an inhibitor of endonuclease activity and other protein-nucleic acid interactions, blocks apoptosis in several cell types and prevents delayed death of hippocampal pyramidal CA1 neurons induced by transient global ischemia. Global ischemia in rats and gerbils induces down-regulation of GluR2 mRNA and increased alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-induced Ca2+ influx in CA1 before neurodegeneration. This result and neuroprotection by antagonists of AMPA receptors suggests that formation of AMPA receptors lacking GluR2, and therefore Ca2+ permeable, leads to excessive Ca2+ influx in response to endogenous glutamate; the resulting delayed neuronal death in CA1 exhibits many characteristics of apoptosis. In this study, we examined the effects of ATA on expression of mRNAs encoding glutamate receptor subunits in gerbil hippocampus after global ischemia. Administration of ATA by injection into the right cerebral ventricle 1 h before (but not 6 h after) bilateral carotid occlusion prevented the ischemia-induced decrease in GluR2 mRNA expression and the delayed neurodegeneration. These findings suggest that ATA is neuroprotective in ischemia by blocking the transcriptional changes leading to down-regulation of GluR2, rather than by simply blocking endonucleases, which presumably act later after Ca2+ influx initiates apoptosis. Maintaining formation of Ca2+ impermeable, GluR2 containing AMPA receptors could prevent delayed death of CA1 neurons after transient global ischemia, and block of GluR2 down-regulation may provide a further strategy for neuroprotection.

Pretreatment with intraventricular aurintricarboxylic acid decreases infarct size by inhibiting apoptosis following transient global ischemia in gerbils

The goal of this study was to determine whether aurintricarboxylic acid (ATA), an endonuclease inhibitor known to inhibit apoptosis, could ameliorate cell damage in a gerbil model of transient ischemia. Transient ischemia was induced in gerbils by bilateral carotid artery occlusion for a period of 5 minutes. Four micrograms of ATA was administered intraventricularly 1 hour before ischemia, and the brains were assessed histologically 1 week later to quantitate cell loss in the vulnerable CA-1 subsector of the hippocampus. In a separate set of experiments, 4 microg of ATA was administered intraventricularly 1 hour before ischemia and the brains were assessed for evidence of DNA fragmentation by the TUNEL method. There was only a 16% cell loss compared with nonischemic controls in animals pretreated with ATA that was significantly less (p < 0.05) than the 48% cell loss in animals pretreated with saline alone. TUNEL-positive cells were first evident at 3 days and were still present at 7 days subsequent to ischemia. Maximal staining occurred at 4 days. Pretreatment with ATA virtually eliminated TUNEL staining at 4 days. These results support the hypothesis that the delayed cell death secondary to transient ischemia is, in part, apoptotic. Furthermore, ATA afforded significant neuronal protection and prevented DNA fragmentation.

Apoptosis in neurological disease

Enormous interest in cell death in the past several years has moved apoptosis to the forefront of scientific research. Apoptosis has been found to mediate cell deletion in tissue homeostasis, embryological development, and immunological functioning. It also occurs in pathological conditions, including cancer and acquired immunodeficiency syndrome, and is implicated in neurodegenerative diseases. Claims of neuronal apoptosis induced by various agents and conditions are published regularly, but in many instances the data are questionable because they are incomplete. This review presents a brief history of apoptosis and describes the evidence required before claims of apoptosis are made. Summaries and critiques of important investigations concerning the genetic and biochemical regulation of neuronal apoptosis are presented, as are other studies describing connections between apoptosis and neuronal cell death in physiological and pathological situations. There is a realization that apoptosis can be programmed and is distinguishable from necrotic cell death. Combining apoptosis with programmed cell death produces misleading terminology and confusion over these two forms of cell degeneration. Further investigations into neuronal apoptosis should focus on all of the criteria that the original investigators outlined 25 years ago, to clarify whether apoptosis and/or another form of cell death mediates neuronal degeneration in physiological settings and in neurological diseases such as Alzheimer's disease, Parkinson's disease, epilepsy, and ischemia/stroke.

Retinal ischemia leads to apoptosis which is ameliorated by aurintricarboxylic acid

Transient retinal ischemia results in a delayed cell death of the inner retinal layers. This study demonstrates that this ischemic cell death occurs, at least in part, through apoptosis. The general endonuclease inhibitor, aurintricarboxylic acid, protected rat retinal cells from ischemic cell damage when administered before the onset of ischemia and, more importantly, when administered 6 hr after the insult. Thus, the demonstration that transient retinal ischemia results in cell damage as a result of apoptosis opens new therapeutic strategies aimed at lessening retinal damage as a result of this process.

Apoptosis in the retina

An enormous interest in cell death over the past several years has catapulted apoptosis to the forefront of scientific research. Apoptosis has been found to mediate cell deletion in tissue homeostasis, embryological development and immunologic function. It also occurs in pathological situations including cancer and AIDS, and is implicated in a variety of ocular diseases. This review presents a brief history of apoptosis and the proper evidence needed in order to claim that apoptosis is taking place. A summary and critique of important investigations concerning the genetic and biochemical regulation of apoptosis is presented, as well as a focus on other studies drawing a connection between apoptosis and cell death in physiological and pathological situations.

Global ischemia induces downregulation of Glur2 mRNA and increases AMPA receptor-mediated Ca2+ influx in hippocampal CA1 neurons of gerbil

Transient, severe forebrain or global ischemia leads to delayed cell death of pyramidal neurons in the hippocampal CA1. The precise molecular mechanisms underlying neuronal cell death after global ischemia are as yet unknown. Glutamate receptor-mediated Ca2+ influx is thought to play a critical role in this cell death. In situ hybridization revealed that the expression of mRNA encoding GluR2 (the subunit that limits Ca2+ permeability of AMPA-type glutamate receptors) was markedly and specifically reduced in gerbil CA1 pyramidal neurons after global ischemia but before the onset of neurodegeneration. To determine whether the change in GluR2 expression is functionally significant, we examined the AMPA receptor-mediated rise in cytoplasmic free Ca2+ level ([Ca2+]i) in individual CA1 pyramidal neurons by optical imaging with the Ca2+ indicator dye fura-2 and by intracellular recording. Seventy-two hours after ischemia, CA1 neurons that retained the ability to fire action potentials exhibited a greatly enhanced AMPA-elicited rise in [Ca2+]i. Basal [Ca2+]i in these neurons was unchanged. These findings provide evidence for Ca2+ entry directly through AMPA receptors in pyramidal neurons destined to die. Downregulation of GluR2 gene expression and an increase in Ca2+ influx through AMPA receptors in response to endogenous glutamate are likely to contribute to the delayed neuronal death after global ischemia.

Fracture of the cuboid in children. A source of leg symptoms

We report eight cases of fracture of the cuboid in seven children under four years of age, collected during a two-year period. There was no history of trauma in five of the patients. This fracture is rarely diagnosed and has probably been under-reported. Small children are poor historians and difficult to examine, and early radiographs may be normal or have only subtle abnormalities. Cuboid fracture should be considered in the differential diagnosis of limping toddlers, and a bone scan may be needed to confirm the diagnosis earlier than radiography. These fractures heal completely, without sequelae. Treatment in a short-leg walking cast is recommended, primarily for reasons of comfort.

Safety, tolerability, and pharmacokinetics of the N-methyl-D-aspartate antagonist dextrorphan in patients with acute stroke. Dextrorphan Study Group

BACKGROUND AND PURPOSE

Dextrorphan hydrochloride is a noncompetitive N-methyl-D-aspartate antagonist that is neuroprotective in experimental models of focal brain ischemia. The purpose of this study was to determine the maximum loading dose and maintenance infusion of dextrorphan hydrochloride that are well tolerated in patients with an acute stroke.

METHODS

An intravenous infusion of dextrorphan or placebo was begun within 48 hours of onset of a mild-to-moderate hemispheric stroke. Initially, patients were treated with either placebo (n = 15) or dextrorphan (n = 22) using a 1-hour loading dose (60 to 150 mg) followed by a 23-hour ascending-dose maintenance infusion (maximum total dose, 3310 mg). Subsequently, 29 patients were treated with dextrorphan in an open trial using a 1-hour loading dose (145 to 260 mg) followed by an 11-hour constant rate (30 to 70 mg/h) infusion.

RESULTS

Transient and reversible adverse effects, including nystagmus, nausea, vomiting, somnolence, hallucinations, and agitation, commonly occurred in dextrorphan-treated patients. Loading-dose escalation was stopped because of rapid-onset, reversible, symptomatic hypotension in 7 of 21 patients treated with doses of 200 to 260 mg/h. At the highest rates of maintenance infusion (> 90 mg/h), 3 patients developed deep stupor or apnea. The maximum tolerated loading dose was 180 mg/h, and the maximum tolerated maintenance infusion was 70 mg/h. Maximum plasma levels of 750 to 1000 ng/mL were obtained in 9 patients. There was no difference in neurological outcome at 48 hours between the dextrorphan-treated and placebo-treated patients.

CONCLUSIONS

The highest doses of dextrorphan administered were associated with serious adverse experiences in some patients. Lower doses (loading doses of 145 to 180 mg, maintenance infusions of 50 to 70 mg/h) were better tolerated and rapidly produced potentially neuroprotective plasma concentrations of dextrorphan. These doses were associated with well-defined pharmacological effects compatible with N-methyl-D-aspartate receptor antagonism.

Fracture of the cuboid in children. A source of leg symptoms

We report eight cases of fracture of the cuboid in seven children under four years of age, collected during a two-year period. There was no history of trauma in five of the patients. This fracture is rarely diagnosed and has probably been under-reported. Small children are poor historians and difficult to examine, and early radiographs may be normal or have only subtle abnormalities. Cuboid fracture should be considered in the differential diagnosis of limping toddlers, and a bone scan may be needed to confirm the diagnosis earlier than radiography. These fractures heal completely, without sequelae. Treatment in a short-leg walking cast is recommended, primarily for reasons of comfort.

Evidence for hypoxia-induced, programmed cell death of cultured neurons

Apoptosis, a form of cell death ("programmed" cell death) in which the nucleus and cytoplasm shrink and often fragment, serves to eliminate excessive or unwanted cells during remodeling of embryonic tissues, during organ involution, and in tumor regression. In acute pathological states, such as ischemia, the cells tend to swell and lyse--a process called necrosis. We hypothesize that the delayed neural death clinically associated with hypoxia may, in part, represent apoptosis. A tissue culture model of 24 hours of hypoxia was employed using sympathetic neurons. Pretreatment with an endonuclease inhibitor (aurintricarboxylic acid) decreased cell death by 53%, depolarizing conditions (55 mM potassium chloride) decreased cell death by 33%, and an RNA synthesis inhibitor (actinomycin D) by 26% (all have been shown to prevent apoptosis). Pretreatment with antisense c-myc had no effect. Fluorescent staining with propidium iodide (a DNA marker) demonstrated chromatin condensation and agarose gel electrophoresis demonstrated a DNA "ladder." These data suggest that apoptosis may play a role in hypoxic cell death and that in this paradigm, expression of c-myc is unnecessary. This would suggest a new approach to our understanding of hypoxia and open new strategies to lessen neuronal damage secondary to this process.

Superoxide dismutase ameliorates neuronal death from hypoxia in culture

BACKGROUND AND PURPOSE

Studies showing efficacy with free radical scavengers have been conflicting, and when protection was demonstrated it was attributed to action at the level of the vascular endothelium. The purpose of this study was to test the hypotheses that neuronal free radical formation plays a role in the ischemic cascade and occurs intracellularly and that free radical scavengers, if taken up intracellularly, will protect against hypoxic damage.

METHODS

A tissue culture model of hypoxia followed by restoration of oxygen was employed, using both superior cervical ganglia and hippocampal neurons. Cells were exposed to an anoxic atmosphere of 95% N2 and 5% CO2 and examined 2 to 24 hours later after restoration of oxygen. Determination of survival was measured by trypan blue exclusion. Nitroblue tetrazolium stain was used to assess free radical formation.

RESULTS

Pretreatment with free superoxide dismutase did not decrease cell death after hypoxia as measured by trypan blue exclusion. However, when superoxide dismutase was taken up intracellularly under depolarizing conditions (55 mmol/L KCl in the medium), cell death was decreased significantly compared with hypoxic controls (28.7 +/- 4.34 versus 40.3 +/- 4.33; P < .03). During hypoxia neurons reduced nitroblue tetrazolium to form the blue precipitate formazan, and the color change was blocked in neurons pretreated with superoxide dismutase in depolarizing medium. Similar findings occurred in both superior cervical ganglia and hippocampal neurons.

CONCLUSIONS

These findings provide evidence to support the role of neuronal free radical formation in cell death secondary to hypoxia. In addition, free radical scavengers, if taken up intracellularly, may partially ameliorate their deleterious effect.

Sonographic diagnosis of intestinal malrotation in infants: importance of the relative positions of the superior mesenteric vein and artery

OBJECTIVE

An abnormal relative position of the superior mesenteric vein and artery can be present in patients with intestinal malrotation. We undertook this retrospective study to see how often we could determine the relative position of these vessels on abdominal sonograms in infants and how often abnormal position of the vessels was associated with malrotation.

MATERIALS AND METHODS

We reviewed the radiology files and medical records of 337 infants with vomiting who were referred for sonography because of possible pyloric stenosis. We used sonograms and written reports to determine the position of the superior mesenteric vessels. The position was considered normal when the superior mesenteric vein was to the right of the superior mesenteric artery on transverse sonograms. The position was considered abnormal when the vein was directly ventral to the artery or when the vein was to the left of the artery. Sonographic findings were compared with results of upper gastrointestinal series when possible and with clinical outcome.

RESULTS

The relative positions of the superior mesenteric vein and artery were evident in 249 (74%) of the 337 patients. Abnormal orientation of the mesenteric vessels was detected in nine patients. In five patients, the superior mesenteric vein was located to the left of the artery, and all five had intestinal malrotation. In four patients, the superior mesenteric vein was directly ventral to the artery, and one of these had malrotation.

CONCLUSION

Sonographic assessment of the relative positions of the mesenteric artery and vein is an important adjunct in the examination of infants with suspected pyloric stenosis. Patients in whom sonograms show an abnormal position of the vessels should have further examination to detect malrotation.

Pilot study of nicardipine for acute ischemic stroke

The author performed a pilot study of nicardipine (NC), a Ca(+)+ channel blocker, to study its dosing, toxicity, and possible efficacy for hemispheric cerebral infarction within 12 hours (mean 6.9 hr) of onset to determine the advisability of proceeding with a multi-centered controlled trial. NC was administered IV (3 to 7 mg/hr) X 72 hours by titrating dose to mean arterial blood pressure (MABP not less than 10% of baseline), then orally X 30 days. Forty-three patients have been entered; mean age 63 (range 34-89), 25 male and 18 female. Only 3 had CT evidence of infarct on entry. Results have shown improvement in a 100-point (pt) graded exam (40 pts at entry, 68 pts at 3 months). Of 20 patients completing 3 months' evaluation, 17 improved and none worsened. Sixteen out of 20 were at home and 8 had minimal or no impairment. Mean Barthel's index was 72. Mean maximal serum NC level was 75 ng/mL. MABP decreased from 103 (entry) to 83 (72 hours). A larger controlled study is warranted to determine the efficacy of NC for acute cerebral infarct.

Renal involvement in children with lymphoma: comparison of CT with sonography

In order to determine whether real-time sonography or contrast-enhanced CT was better for detecting renal involvement by lymphoma in children, we retrospectively studied 44 patients (6 months to 19 years of age) in whom lymphoma was diagnosed at our hospital during a 5-year period. In no patient was there any clinical evidence of renal disease at the time of presentation. In 39 patients, sonographic and CT findings were similar (normal in 36 patients and showing extrinsic mass effects on the kidneys in three patients). In five patients with non-Hodgkin lymphoma whose contrast-enhanced CT scans showed low-attenuation renal nodules, renal sonography was normal in two, showed renal enlargement in two, and showed a solitary hypoechoic nodule in one patient with multiple, bilateral nodules on CT. Tissue diagnosis of the renal lesions was not obtained, but in the four patients who had follow-up CT, the renal abnormalities resolved after chemotherapy. Our findings suggest that contrast-enhanced CT is superior to sonography for detection of renal lymphoma in children.

Baclofen does not protect against cerebral ischemia in rats

Presynaptic release of glutamate into the extracellular compartment and activation of receptor-operated calcium channels may contribute to ischemic neuronal damage. We evaluated the effect of baclofen, a selective inhibitor of presynaptic glutamate release, on mortality, working memory, and light microscopic hippocampal and cortical damage in the four-vessel occlusion model of cerebral ischemia using 64 male Wistar rats. Baclofen (10 mg/kg i.p.) given 1 hour before and 30-60 minutes after 20 minutes of global ischemia did not lessen mortality, prevent ischemic cellular damage, or significantly improve working memory compared with no treatment. We conclude that preischemic and postischemic administration of baclofen does not protect neurons from ischemic injury.

Apraxia of eyelid opening secondary to right hemisphere infarction

A variety of eyelid movement abnormalities have been attributed to lesions of the central nervous system. Apraxia of lid movements, and especially of lid opening, has received the least attention. We present 2 cases of lid opening apraxia and propose that this abnormality may be due to right hemisphere dysfunction.

Sonographic diagnosis of hypertrophic pyloric stenosis

In many pediatric centers, sonography has become the primary imaging method for the diagnosis of hypertrophic pyloric stenosis, but investigators have disagreed about which dimension of the gastric outlet is most useful and accurate. We analyzed 326 consecutive sonograms in 319 infants who presented with vomiting in order to further evaluate the sonographic criteria for the diagnosis of hypertrophic pyloric stenosis. Four observers retrospectively measured three parameters: (1) the thickness of the muscle in the wall of the gastric outlet, (2) the length of that muscle, and (3) the length of the pyloric channel. In the patients with hypertrophic pyloric stenosis, muscle thickness was 4.8 +/- 0.6 mm, muscle length was 2.1 +/- 0.3 cm, and channel length was 1.8 +/- 0.3 cm. In the patients without hypertrophic pyloric stenosis, muscle thickness was 1.8 +/- 0.4 mm, muscle length was 1.3 +/- 0.3 cm, and channel length was 1.1 +/- 0.3 cm. The mean measurement for each parameter was significantly larger in patients who had hypertrophic pyloric stenosis than in those who did not (p less than .01). However, histograms of the three parameters show significant overlap in the measurements of muscle length and channel length between the patients with and those without hypertrophic pyloric stenosis. The thickness of the muscle is the most discriminating and accurate criterion for hypertrophic pyloric stenosis.

Atlantooccipital instability in Down syndrome

Atlantooccipital instability is an uncommon and usually lethal result of major trauma. Nontraumatic cases of instability at this site are rare. We report the findings in two children with Down syndrome who have striking atlantooccipital subluxation demonstrated on flexion and extension radiographs. Since there is increasing radiologic evaluation of cervical spine stability in patients with Down syndrome who wish to participate in athletic activities, the status of the atlantooccipital joint needs careful assessment, especially after cervical fusion for C1-C2 instability.

Acute epiphyseal osteomyelitis in children

Nine children over 20 months of age had acute osteomyelitis of the epiphysis of a long bone. The clinical features varied, but all of the patients had pain at the infected site and an elevated erythrocyte sedimentation rate. The distal femur was involved in seven cases, the proximal tibia in two, and the proximal humerus in one. In two patients there was a contiguous metaphyseal lesion, while the other seven patients (eight sites) had lesions limited to the epiphysis. Bone scintigraphy clearly identified the infected sites in all seven patients in whom it was performed, and allowed an early diagnosis in four cases. Radiographs showed a lytic lesion of the epiphysis that corresponded to the scintigraphic findings in all cases. The vascular supply to the epiphysis and the microscopic structure of the epiphyseal venous sinusoids provide locations that favor lodgement of blood-borne organisms. The epiphysis of the child should be recognized as another site of hematogenous osteomyelitis.

Empyema in children: clinical course and long-term follow-up

Sixteen patients, aged 1 month to 15 years, were studied to determine the clinical course and long-term outcome of empyema in previously healthy children. The pathogens responsible were Haemophilus influenzae type b (seven patients), Staphylococcus aureus (five patients), Streptococcus pneumoniae (three patients), and viridans group Streptococcus (one patient). All patients had loculated fluid showing on chest roentgenographs. Chest tube drainage yielded 20 to 1,495 mL (mean 293 mL) during the first three days, accounting for 83% of total drainage. Chest tubes were removed after three to 17 days (mean ten days). Only slight roentgenographic improvement showed during chest tube drainage. Three patients required an open thoracotomy because of an unsatisfactory clinical response. Hospitalization ranged from eight to 77 days (mean 25 days). All patients had residual pleural thickening shown on chest roentgenographs taken at discharge. Thirteen patients were seen 5 to 140 months (mean 66 months) after discharge. Findings from physical examination were normal in 12 of the 13 patients. Pulmonary function tests in ten of the 13 patients revealed (mean percent predicted +/- 1 SD): vital capacity 92 +/- 12, residual volume 85 +/- 31, total lung capacity 92 +/- 13, peak flow rate 96 +/- 17, forced expiratory volume in 1 second 90 +/- 13, and maximal mid-expiratory flow rate 93 +/- 25. In all but one patient, findings on chest roentgenograms were normal or showed slight pleural thickening. Children with loculated empyema can be treated successfully with antibiotics and chest tube drainage. Few patients require open drainage, and further surgery is rarely required. The long-term outcome is excellent.

Excretion of contrast media by the immature rabbit. Comparison of Renografin and Iopamidol

The excretion of iodinated contrast media was studied in 13 immature rabbits after the intravenous injection of 2 ml/kg (approximately 600 mg I/kg) of radio-labelled Renografin-60, a high osmolality agent (1510 mOsm/kg), or Iopamidol-300, a new agent with a much lower osmolality (616 mOsm/kg). Renografin, but not Iopamidol, induced an immediate but transient 40% fall in blood pressure, a marked diuresis that was 3.4 times greater at its maximum than for Iopamidol, and a much lower urinary iodine concentration at the time of maximum diuresis (Renografin: 90.3 +/- 9.2 microgram/ml; Iopamidol: 213 +/- 32.9 microgram/ml). No difference between the two contrast media was found for plasma iodine concentration, renal clearance from the plasma, urinary iodine excretion rate or volume of distribution. In five additional rabbit pups, formal clearance studies made using a constant IV infusion of the agents and timed collections of urine and plasma showed that Iopamidol and Renografin were cleared at the same rate by the kidneys (P greater than 0.9).

Sonographic assessment of renal length in normal children

Renal length was measured from normal real-time sonograms of 203 pediatric patients and graphed to provide a "growth chart" of normal renal size vs. age. Mean renal lengths are reported for each year of age. For children older than 1 year, the regression equation is: renal length (cm) = 6.79 + 0.22 X age (years). For babies younger than 1 year, the equation is: renal length (cm) = 4.98 + 0.155 X age (months).

Ultrasonographic findings in mesenchymal hamartoma of the liver

The ultrasonographic appearance of mesenchymal hepatic hamartoma in two infants is described. In both cases the echo patterns were predominantly anechoic, but showed evidence of trabeculation. The differential diagnosis of mesenchymal hepatic hamartoma is discussed.