Adapting molecular inversion probe (MIP) technology for allele quantification in childhood leukemia

9530

Background: Leukemia accounts for ∼40% of newly diagnosed pediatric malignancies, and relapsed leukemia is the leading cause of death in childhood cancer. Genomic instability events contribute to neoplastic development and have been used to classify and risk stratify non-leukemic adult and pediatric tumors. Analyzing leukemic blasts for gene copy changes with advanced molecular techniques could prove useful in further risk stratifying and developing new treatment strategies for pediatric leukemia. Methods: Molecular Inversion Probes (MIPs) analyze genetic target sequences in parallel with high specificity and sensitivity at the highest genomic resolution, and were originally designed for single nucleotide genotyping. The MIP assay was adapted to analyze both gene copy number and loss of heterozygosity (LOH) events in pediatric leukemia samples (pre-B ALL, T-ALL, AML). DNA was extracted (100 ng) from paired bone marrow (diagnosis) and peripheral blood (remission) samples (n = 40). The MIP assay was run with a customized Affymetrix 20K Cancer Panel (representing oncogenes, tumor suppressor, DNA repair, cell growth, and metabolism genes). Gene copy number changes were identified by comparing probe signal intensity between leukemia samples and normal cell-lines. LOH events were determined by identifying genotype changes between matched leukemic and remission samples. Results: Each sample had unique patterns of multiple gene copy changes and LOH events distributed across all chromosomes. Additionally, samples were found to have overlapping copy number changes and LOH regardless of leukemia type. AML samples had fewer LOH events and could be separated by unsupervised clustering from the other leukemia samples. Conclusions: MIPs represent novel genotyping technology that can be adapted for gene copy analysis of childhood leukemia. Unique and distinguishing signatures of allelic imbalance can be determined between ALL and AML clinical samples using MIP technology. The unexpected overlap of LOH and deleted genes may represent a common molecular mechanism that requires further investigation.

No significant financial relationships to disclose.

Inhibitors of blood coagulation factors Xa and IIa synergize to reduce thrombus weight and thrombin generation in vivo and in vitro

BACKGROUND

Many compounds currently in development for treatment of thrombotic disorders demonstrate high specificity for single targets of blood coagulation such as factor Xa (FXa) or thrombin.

AIM

The aim of this study is to determine if inhibition of both FXa and thrombin by simultaneous administration of PD0313052 and argatroban, respectively, synergistically increases the effect of either drug alone in vivo and in vitro.

METHODS AND RESULTS

Analyses of thrombin generation from combined inhibition in human plasma using statistical methods of Bliss independence identified a synergistic reduction in thrombin production 30% lower than predicted by simple additivity. The greatest synergy occurred at concentrations of each compound below their individual IC50 values. In a rabbit arterio-venous shunt model (RAV) of thrombosis, co-administration of PD0313052 and argatroban reduced thrombus weight (TW) to a much greater degree than expected by additivity alone producing a synergistic decrease of 45% over the level predicted by additivity. Analyses of thrombin generation in plasma samples from the RAV also demonstrated 38% synergy ex vivo. Furthermore, at plasma concentrations with the greatest synergistic effect, no increase in bleeding or appreciable change in prothrombin time, activated partial thromboplastin time, or activated clotting time was observed, but thrombus weight reduction was greater than twofold higher than that expected from simple additivity.

CONCLUSIONS

These results demonstrate a significant synergistic antithrombotic effect of combining low doses of PD0313052 and argatroban and support the hypothesis that simultaneous targeting of multiple coagulation enzymes may offer an improved therapeutic index in the prevention and treatment of thrombosis.

Lack of clinical significance of early ischemic changes on computed tomography in acute stroke

CONTEXT

The prevalence and clinical significance of early ischemic changes (EICs) on baseline computed tomography (CT) scan of the head obtained within 3 hours of ischemic stroke are not established.

OBJECTIVE

To determine the frequency and significance of EIC on baseline head CT scans in the National Institute of Neurological Disorders and Stroke (NINDS) rt-PA (recombinant tissue plasminogen activator) Stroke Trial.

DESIGN AND SETTING

The original study, a randomized controlled trial, took place from January 1991 through October 1994 at 43 sites, during which CT images were obtained within 3 hours of symptom onset and prior to the initiation of rt-PA or placebo. For the current analysis, detailed reevaluation was undertaken after October 1994 of all baseline head CT scans with clinical data available pretreatment (blinded to treatment arm).

PATIENTS

Of 624 patients enrolled in the trial, baseline CT scans were retrieved and reviewed for 616 (99%).

MAIN OUTCOME MEASURES

Frequency of EICs on baseline CT scans; association of EIC with other baseline variables; effect of EICs on deterioration at 24 hours (>/=4 points increase from the baseline National Institutes of Health Stroke Scale [NIHSS] score); clinical outcome (measured by 4 clinical scales) at 3 months, CT lesion volume at 3 months, death at 90 days; and symptomatic intracranial hemorrhage (ICH) within 36 hours of treatment.

RESULTS

The prevalence of EIC on baseline CT in the combined rt-PA and placebo groups was 31% (n = 194). The EIC was significantly associated with baseline NIHSS score (rho = 0.23; P<.001) and time from stroke onset to baseline CT scan (rho = 0.11; P =.007). After adjusting for baseline variables, there was no EIC x treatment interaction detected for any clinical outcome, including deterioration at 24 hours, 4 clinical scales, lesion volume, and death at 90 days (P>/=.25), implying that EIC is unlikely to affect response to rt-PA treatment. After adjusting for NIHSS score (an independent predictor of ICH), no EIC association with symptomatic ICH at 36 hours was detected in the group treated with rt-PA (P>/=.22).

CONCLUSIONS

Our analysis suggests that EICs are prevalent within 3 hours of stroke onset and correlate with stroke severity. However, EICs are not independently associated with increased risk of adverse outcome after rt-PA treatment. Patients treated with rt-PA did better whether or not they had EICs, suggesting that EICs on CT scan are not critical to the decision to treat otherwise eligible patients with rt-PA within 3 hours of stroke onset.

Magnetoencephalographic fields from patients with spontaneous and induced migraine aura

We investigate and characterize the magnetoencephalographic waveforms from patients during spontaneous and visually induced migraine aura. Direct current neuromagnetic fields were measured during spontaneous onset of migraine auras in 4 migraine patients, and compared with recordings from 8 migraine-with-aura patients and 6 normal controls during visual stimulation of the occipital cortex. Complex direct current magnetoencephalographic shifts, similar in waveform, were observed in spontaneous and visually induced migraine patients, but not in controls. Two-dimensional inverse imaging showed multiple cortical areas activated in spontaneous and visually induced migraine aura patients. In normal subjects, activation was only observed in the primary visual cortex. Results support a spreading, depression-like neuroelectric event occurring during migraine aura that can arise spontaneously or be visually triggered in widespread regions of hyperexcitable occipital cortex.

Periaqueductal gray matter dysfunction in migraine: cause or the burden of illness?

OBJECTIVE

The periaqueductal gray matter (PAG) is at the center of a powerful descending antinociceptive neuronal network. We studied iron homeostasis in the PAG as an indicator of function in patients with episodic migraine (EM) between attacks and patients with chronic daily headache (CDH) during headache. High-resolution magnetic resonance techniques were used to map the transverse relaxation rates R2, R2*, and R2' in the PAG, red nucleus (RN), and substantia nigra (SN). R2' is a measure of non-heme iron in tissues.

METHODS

Seventeen patients diagnosed with EM with and without aura, 17 patients diagnosed with CDH and medication overuse, and 17 normal adults (N) were imaged with a 3.0-tesla magnetic resonance imaging system. For each subject, mean values of the relaxation rates, R2 (1/T2), R2* (1/T2*), and R2' (R2* - R2) were obtained for the PAG, RN, and SN. R2, R2*, and R2' values of the EM, CDH, and N groups were compared using analysis of variance, Student t test, and correlation analysis.

RESULTS

In the PAG, there was a significant increase in mean R2' and R2* values in both the EM and CDH groups (P<.05) compared with the N group, but no significant difference in these values was demonstrated between the EM and CDH groups, or between those with migraine with or without aura in the EM group. Positive correlations were found for duration of illness with R2' in the EM and CDH groups. A decrease in mean R2' and R2* values also was observed in the RN and SN of the CDH group compared with the N and EM groups (P<.05), explained best by flow activation due to head pain.

CONCLUSIONS

Iron homeostasis in the PAG was selectively, persistently, and progressively impaired in the EM and CDH groups, possibly caused by repeated migraine attacks. These results support and emphasize the role of the PAG as a possible "generator" of migraine attacks, potentially by dysfunctional control of the trigeminovascular nociceptive system.

Automated three-dimensional signature model for assessing brain injury in emergent stroke

This presentation will focus on the value of established and newer MR methods that can be applied to the diagnosis and management of ischemic stroke with emphasis on future applications of MR to provide previously unmet needs of the treating clinician and clinical trials. Time alone is an inadequate indicator of the therapeutic window, especially when the time of stroke onset is uncertain. Thus, there is a need to predict the evolution of stroke in a way that more precisely and with greater resolution identifies the progression of cellular damage at the moment of investigation. This also would be of value for thrombolysis when knowledge of the degree and extent of tissue necrosis and the consequent potential for brain hemorrhage is of the utmost importance. To provide this, we perform postprocessing of diffusion-, T(1)- and T(2)-weighted images to produce the apparent diffusion coefficient of water, and T(1) and T(2) maps that are then further processed to provide maps and quantitation of the tissue signatures of ischemic histopathology. By these means, we can accomplish objective volumetric analysis of infarct size and of the proportions of potentially viable and salvageable tissue. We will show how this has the potential to predict long-term stroke outcome and facilitate decision-making in terms of safety of reperfusion strategies and the appropriateness of cytoprotective treatment. The value of our approach is to replace time as the therapeutic window and extend the opportunity of treatment to those patients presenting beyond the stringent time limits employed in current investigative clinical trials. Further, used as a surrogate marker of clinical outcome, this form of stroke analysis may speed proof of principle clinical trials in small numbers of stroke patients.

Clinical deterioration following improvement in the NINDS rt-PA Stroke Trial

BACKGROUND AND PURPOSE

Little is known in regard to cerebral arterial reocclusion after successful thrombolysis. In the absence of arteriographic information, the National Institute of Neurological Disorders and Stroke (NINDS) rt-PA Stroke Trial investigators prospectively identified clinical deterioration following improvement (DFI) as a possible surrogate marker of cerebral arterial reocclusion after rt-PA-induced recanalization. Also, we identified any significant clinical deterioration (CD) even if not preceded by improvement. This observational analysis was designed to determine the incidence of DFI and CD in each treatment group, to identify baseline or posttreatment variables predictive of DFI or CD, and to determine any relationship between DFI, CD, and clinical outcome.

METHODS

DFI was defined as any 2-point deterioration on the NIH Stroke Scale after an initial 2-point improvement after treatment. CD was defined as any 4-point worsening after treatment compared with baseline. All data were collected prospectively by investigators blinded to treatment allocation. A noncontrast brain CT was mandated when a 2-point deterioration occurred. All cases were validated by a central review committee.

RESULTS

DFI was identified in 81 of the 624 patients (13%); 44 were treated with rt-PA and 37 were treated with placebo (P:=0.48). DFI occurred more often in patients with a higher baseline NIH Stroke Scale score. CD within the first 24 hours occurred in 98 patients (16% of all patients); 43 were given rt-PA and 55 were given placebo (P:=0.19). Baseline variables associated with CD included a less frequent use of prestroke aspirin and a higher incidence of early CT changes of edema or mass effect or dense middle cerebral artery sign. Patients with CD had higher rates of increased serum glucose and fibrin degradation products, and they also had higher rates of symptomatic intracranial hemorrhage and death. Patients who experienced either DFI or CD were less likely to have a 3-month favorable outcome.

CONCLUSIONS

We found no association between DFI, CD, and rt-PA treatment, and no clinical evidence to suggest reocclusion. Deterioration was strongly associated with stroke severity and poor outcome and was less frequent in patients whose stroke occurred while they were on aspirin.

Headache types and panic disorder: directionality and specificity

OBJECTIVE

To examine the relationship of migraine and other severe headaches with panic disorder.

METHODS

Representative samples of persons with migraine, non-migrainous severe headaches, and controls with no history of severe headaches, identified by a telephone survey, were interviewed in person, using a standardized psychiatric interview. Cox proportional hazards models with time-dependent covariates were used to examine the relationship of headaches with first-onset panic disorder and vice versa.

RESULTS

Lifetime prevalence of panic disorder was significantly higher in persons with migraine and in persons with other severe headaches, compared with controls. Migraine and other severe headaches were associated with an increased risk for first onset of panic disorder (hazards ratios = 3.55 and 5.75). Panic disorder was associated with an increased risk for first onset of migraine and for first onset of other severe headaches, although the influences in this direction were lower (hazards ratios = 2.10 and 1.85).

CONCLUSIONS

Comorbidity of panic disorder is not specific to migraine and applies also to other severe headaches. The influence is primarily from headaches to panic disorders, with a weaker influence in the reverse direction. The bidirectional associations, despite the difference in the strength of the associations, suggest that shared environmental or genetic factors might be involved in the comorbidity of panic disorder with migraine and other severe headaches.

The endothelin-A-receptor antagonist PD 180988 (CI-1034) selectively reverses the pulmonary vasoconstrictor response to hypoxia in the lamb

Endothelin-1 (ET-1) is assigned a mediator role in the constrictor response of the pulmonary vasculature to hypoxia. Accordingly, a recently developed endothelin-A (ETA) antagonist, PD180988, was tested in the chronically instrumented newborn lamb to verify this possibility and, at the same time, to study a potential new treatment for pulmonary hypertension (PH). PD180988, given by infusion after a priming bolus, had an insignificant effect on the pulmonary circulation under normoxia, while it reversed the sustained pulmonary constriction caused by hypoxia. No appreciable change was noted under either experimental condition in the systemic circulation and cardiac contractility. We conclude that PD180988 is a selective inhibitor of hypoxic pulmonary vasoconstriction and lends itself to therapeutic use in infants.

Tolerability of sumatriptan: clinical trials and post-marketing experience

Through December 1998, sumatriptan had been used to treat more than 236 million migraine attacks world-wide. In clinical trials alone, more than 88000 migraine patients had treated more than 300000 migraine attacks with sumatriptan, and 2000 normal healthy volunteers had been exposed to the drug. This paper describes the safety and tolerability profile of sumatriptan in three sections: adverse events reported in clinical trials, special issues, and spontaneous post-marketing reports of adverse reactions. Data from the extensive clinical trials programme coupled with information from nearly 10 years of experience in clinical practice demonstrate that sumatriptan is generally well-tolerated, with an acceptable benefit-risk ratio when used properly. Significant cardiovascular and cerebrovascular events are rare but have been observed. This fact highlights the need for careful patient selection and vigilant adherence to the prescribing recommendations for sumatriptan. The wealth of clinical trials and post-marketing information for sumatriptan may be useful in guiding prescribing decisions for members of this class of drugs.

Magnetic resonance assessment of acute and chronic stroke

This article describes the important role of magnetic resonance imaging (MRI) in noninvasively assessing human focal ischemic stroke. Conventional MRI, diffusion-weighted and/or perfusion-weighted imaging have been used to facilitate both the qualitative and quantitative evaluation of heterogeneity of ischemic brain tissue. Further, by combining 2 or more magnetic resonance parameters, tissue-signature models have been developed that may be used as surrogate markers of tissue histopathology to characterize ischemic tissue as salvageable, necrotic, or tissue in transition to necrosis. Magnetic resonance tissue-signature models and results are presented. Dynamic changes in the evolution of ischemic tissue to infarction are also discussed. Recovery from acute stroke was studied with blood oxygenation level-dependent functional MRI to investigate the neural mechanisms for recovery from aphasia after stroke.

Language hemispheric dominance in patients with congenital lesions of eloquent brain

OBJECTIVE

In 90% of normal subjects, the left hemisphere is dominant for language function. We investigated whether congenital lesions of the left perisylvian regions altered cortical language representation in right-handed individuals.

METHODS

Using functional magnetic resonance imaging, we studied language hemispheric dominance in five right-handed adult patients with congenitally acquired arteriovenous malformations (AVMs) originating from left hemispheric cortical language regions. The AVMs had not caused neurological symptoms during early development, but patients presented as adults with migraine, seizure, or minor hemorrhage. Results obtained from the AVM patients were contrasted to those from right-handed brain-injured stroke patients recovering from aphasia and to those from right-handed normal subjects.

RESULTS

During silent picture naming and verb generation tasks, cortical language networks lateralized primarily to the right hemisphere in the AVM group, compared with the left hemisphere in the normal group. This right hemisphere-shifted language network in the AVM group exceeded the shifts toward right hemispheric dominance found in the stroke group.

CONCLUSION

Patients with AVMs affecting the left perisylvian regions recruited the right hemisphere into language processing networks during early development, presumably in response to congenitally aberrant circulation. This early right hemisphere recruitment in the AVM patients exceeded the similar process in the brains of stroke patients whose left cortical language networks were damaged in adulthood. Our data provide evidence of effective plasticity in the developing human brain compared with the mature brain response to injury. Knowledge of cortical language representation should assist presurgical planning in patients with developmental anomalies affecting apparently language-dominant brain regions.

Migraine: imaging the aura

We currently conceive of a migraine attack as originating in the brain. Triggers of an attack initiate a depolarizing neuroelectric and metabolic event likened to the spreading depression of Leao. This event activates the headache and associated features of the attack by mechanisms that remain to be determined, but appear to involve either peripheral trigeminovascular or brainstem pathways, or both. The excitability of cell membranes, perhaps partly genetically determined, is the brain's susceptibility to attacks. Factors that increase or decrease neuronal excitability constitute the threshold for triggering attacks. Using a model of visual stress-induced migraine or by studying spontaneous attacks and applying advanced imaging and neurophysiological methods, results have been obtained that support spreading neuronal inhibition as the basis of aura. This neuroelectric event is accompanied by hyperoxia of the brain, possibly associated with vasodilation. Evidence has also been obtained that the spreading cortical event can activate the subcortical centers possibly involved in nociception and associated symptoms of the migraine attack. Susceptibility to migraine attacks appears to be related to brain hyperexcitability. These newer techniques of functional neuroimaging have confirmed the primary neural basis of the migraine attack with secondary vascular changes, reconciling previous theories into a neurovascular mechanism.

Effects of the anti-migraine drug sumatriptan on muscle energy metabolism: relationship to side-effects

Sumatriptan succinate (Imitrex) is a 5-HT (5-hydroxytryptamine) agonist used for relief of migraine symptoms. Some individuals experience short-lived side-effects, including heaviness of the limbs, chest heaviness and muscle aches and pains. The effects of this drug on skeletal muscle energy metabolism were studied during short submaximal isometric exercises. We studied ATP flux from anaerobic glycolysis (An Gly), the creatine kinase reaction (CK) and oxidative phosphorylation (Ox Phos) using 31P nuclear magnetic resonance spectroscopy (31P MRS) kinetic data collected during exercise. It was found that side-effects induced acutely by injection of 6 mg sumatriptan succinate s.c. were associated with reduced oxygen storage in peripheral skeletal muscle 5-20 min after injection as demonstrated by a transient reduction in mitochondrial function at end-exercise. These results suggest that mild vasoconstriction in peripheral skeletal muscle is associated with the action of sumatriptan and is likely to be the source of the side-effects experienced by some users. Migraine with aura patients were more susceptible to this effect than migraine without aura patients.

Headache and major depression: is the association specific to migraine?

OBJECTIVE

To examine the relationship between migraine and major depression, by estimating the risk for first-onset major depression associated with prior migraine and the risk for first migraine associated with prior major depression. We also examined the extent to which comorbidity with major depression is specific to migraine or is observed in other severe headaches.

METHODS

Representative samples of persons 25 to 55 years of age with migraine or other severe headaches (i.e., disabling headaches without migraine features) and controls with no history of severe headaches were identified by a telephone survey and later interviewed in person to ascertain history of common psychiatric disorders.

RESULTS

Lifetime prevalence of major depression was approximately three times higher in persons with migraine and in persons with severe headaches compared with controls. Significant bidirectional relationships were observed between major depression and migraine, with migraine predicting first-onset depression and depression predicting first-onset migraine. In contrast, persons with severe headaches had a higher incidence of first-onset major depression (hazard ratio = 3.6), but major depression did not predict a significantly increased incidence of other severe headaches (hazard ratio = 1.6).

CONCLUSIONS

The contrasting results regarding the relationship of major depression with migraine versus other severe headaches suggest that different causes may underlie the co-occurrence of major depression in persons with migraine compared with persons with other severe headaches.

Cortical language activation in stroke patients recovering from aphasia with functional MRI

BACKGROUND AND PURPOSE

Two mechanisms for recovery from aphasia, repair of damaged language networks and activation of compensatory areas, have been proposed. In this study, we investigated whether both mechanisms or one instead of the other take place in the brain of recovered aphasic patients.

METHODS

Using blood oxygenation level-dependent functional MRI (fMRI), we studied cortical language networks during lexical-semantic processing tasks in 7 right-handed aphasic patients at least 5 months after the onset of left-hemisphere stroke and had regained substantial language functions since then.

RESULTS

We found that in the recovered aphasic patient group, functional language activity significantly increased in the right hemisphere and nonsignificantly decreased in the left hemisphere compared with that in the normal group. Bilateral language networks resulted from partial restitution of damaged functions in the left hemisphere and activation of compensated (or recruited) areas in the right hemisphere. Failure to restore any language function in the left hemisphere led to predominantly right hemispheric networks in some individuals. However, better language recovery, at least for lexical-semantic processing, was observed in individuals who had bilateral rather than right hemisphere-predominant networks.

CONCLUSIONS

The results indicate that the restoration of left-hemisphere language networks is associated with better recovery and inversely related to activity in the compensated or recruited areas of the right hemisphere.

Analysis of MEG signals of spreading cortical depression with propagation constrained to a rectangular cortical strip. I. Lissencephalic rabbit model

Magnetic fields arising from the rabbit cortex during spreading cortical depression (SCD) were measured in order to study the currents in the neocortex during SCD. SCD was constrained to propagate in a rectangular cortical strip perpendicular to the midline. This simplified in vivo cortical preparation enabled us to correlate magnetoencephalographic (MEG) signals to their underlying currents within the cortical strip. The propagation of SCD was monitored with an array of electrodes placed along the strip. The propagation speed for SCD in the lissencephalic rabbit brain was 3. 5+/-0.3 mm/min (mean+/-S.E.M., n=14). Slow, quasi-dc, MEG signals were observed as the SCD entered into the longitudinal fissure. The currents giving rise to the MEG signals were perpendicular to the cortical surface and directed from the surface to deeper layers of the cortex. A distributed dipolar source model was used to relate the data to the underlying cortical current. The moment of the single equivalent current dipole source was 38+/-9 nA-m (n=17). This study clarified the nature of the cortical currents during SCD in a lissencephalic in vivo preparation.

Analysis of MEG signals of spreading cortical depression with propagation constrained to a rectangular cortical strip. II. Gyrencephalic swine model

Currents produced during spreading cortical depression (SCD) in a gyrencephalic species (swine) were studied with magnetoencephalography (MEG) and electrocorticography (ECoG). SCD, initiated using electrical stimulation of the cortex, was constrained to propagate within a rectangular cortical strip in order to simplify the interpretation of the underlying currents. The ECoG signals monitored along the strip revealed that SCD propagated from an initiation site on the gyrus at a rate of 7.9+/-3.2 mm/min (n=23), entered the deep coronal sulcus and in most cases emerged from the other side of the sulcus, continuing to propagate across the next gyrus at a rate of 5.9+/-2.7 mm/min (n=22). The apparent propagation velocity within the sulcus was reduced to 1.7+/-0.8 mm/min (n=21). Strong MEG signals were observed as SCD entered the sulcus. The direction of magnetic field was opposite for SCD's on opposite banks of the sulcus. The currents were directed from a superficial layer to deeper layers of the cortex. The characteristics of SCD and associated MEG patterns from a gyrencephalic species may be similar to those in human patients during migraine aura.

The cortical silent period is shortened in migraine with aura

OBJECTIVES

Central neuronal hyperexcitability may be the physiological disturbance that predisposes subjects to migraine attacks. To test this hypothesis, we studied the cortical stimulation silent period (CSSP) elicited by transcranial magnetic stimulation (TMS), which is in part a measure of central inhibition of motor pathways in migraine with aura (MwA) patients and normal controls.

METHODS

In nine MwA patients (mean age 35.9 +/- 7) and 9 controls (mean age 37.6 +/- 7), we carried out transcranial stimulation using a 95 mm circular coil and Caldwell MES 10 stimulator to determine resting motor threshold (MT) for bilateral FDI muscles. All subjects performed isometric voluntary contraction of bilateral FDI maintained at 20% of maximal effort, during which we measured bilateral CSSP at (i) the stimulus intensity (SI) determined for the MT and (ii) an SI of 1.5 x MT.

RESULTS

Although the mean MT was higher in MwA compared with controls (63.1 +/- 14.4 vs 58.1 +/- 8.9), the difference was not significant. At an SI of 1.5 x MT the mean CSSP did not differ between the groups (MwA 141.7 +/- 31.9 vs controls 162.4 +/- 36.6). At the SI of the MT, however, the CSSP was shorter in MwA patients than in controls (62.9 +/- 27.3 vs 106.3 +/- 19.6, p = 0.001). There was an inverse correlation between the duration of CSSP and an increased frequency of headache (p = 0.02).

CONCLUSIONS

The shortened CSSP that we measured in MWA patients compared to normal with low intensity magnetic stimulation suggests reduced central inhibition resulting in increased excitability of cortical neurons in migraine subjects. The association of CSSP reduction with increased frequency of migraine is further suggestive that brain excitability is the basis of susceptibility to migraine attacks.

Scientific basis of migraine: speculation on the relationship to cyclic vomiting

The pathogenesis of migraine is reviewed. Migraine is a brain disorder that is activated by various triggers working on a susceptibility to attacks, in part genetically determined. The frequency of attacks is determined by triggers working on a threshold that determines excitability of brain. The mechanisms of the attack may involve both cortical and brain-stem structures and their dysfunction. It remains to be determined if cortical or brain-stem centers "generate the attack." Because migraine involves severe nausea and vomiting, this review contains speculations on similarities in the mechanisms of migraine and cyclic vomiting.

The occipital cortex is hyperexcitable in migraine: experimental evidence

OBJECTIVES

Threshold for generation of magnetophosphenes has been reported to be lower in migraine. We compared the threshold for eliciting phosphenes by transcranial magnetic stimulation and the ability to visually trigger headache in a select group of individuals with migraine with and without aura to normal controls.

METHODS

Transcranial magnetic stimulation was performed using the Cadwell MES-10 stimulator. A circular coil, 9.5 cm in diameter, was applied to the occipital scalp (7 cm above the inion). Stimulator intensity was increased in 10% increments until subjects reported visual phenomena or 100% intensity was reached. Stimulator intensity was then fine-tuned to determine the threshold at which phosphenes were seen. In the same subjects, visual stimulation was given in 3.0 T MRI and if a headache occurred the response was recorded.

RESULTS

Fifteen subjects with migraine were compared to 8 controls. A significant proportion of the migraineurs (86.7%) developed phosphenes compared to the controls (25%) (P = .006). The probability of triggering a headache was also higher in the migraineurs (53%); no headache was triggered in the controls (P = .019). A significant correlation was found between the threshold for phosphenes on transcranial magnetic stimulation and visually triggered headache (P = .002). When only migraine was considered, there was again a significant trend (P = .084).

CONCLUSIONS

There is a difference in threshold for excitability of occipital cortex in migraineurs and controls. The hyperexcitable visual cortex in migraine is predisposed to visually triggered headache.

Butenolide endothelin antagonists with improved aqueous solubility

Continued development around our ETA-selective endothelin (ET) antagonist 1 (CI-1020) has led to the synthesis of analogues with improved aqueous solubility profiles. Poor solubility characteristics displayed by 1 required a complex buffered formulation in order to conduct iv studies. To overcome the use of specific iv formulations for preclinical studies on additional drug candidates, analogues with improved aqueous solubility were desired. Several analogues were synthesized with substitution patterns that allowed for the formation of either acid or base addition salts. These derivatives had dramatically improved aqueous solubility. In addition, these analogues retained equivalent or improved ETA receptor selectivity and antagonist potency, versus 1, both in vitro and in vivo. Compound 29, which contains as a substituent the sodium salt of a sulfonic acid, has an ETA IC50 = 0.38 nM, ETA selectivity of 4200-fold, and ETA functional activity of KB = 7.8, all of which are similar or superior to those of 1. Compound 29 also has vastly superior aqueous solubility and solubility duration, compared to 1. Furthermore, 29 after iv infusion displays improved activity to 1 in preventing acute hypoxia-induced pulmonary hypertension in rats with an ED50 = 0.3 microg/kg/h.

31P MRS studies of exercising human muscle at high temporal resolution

Methods for measuring mitochondrial activity from 31P magnetic resonance spectroscopy data collected during and after exercise were compared in controls, weight lifters, and peripheral vascular occlusive disease (PVOD) patients. There were trends toward increasing mitochondrial activity during exercise in order from PVOD patients, moderately active controls, highly active controls, to weight lifters. Results from PVOD patients show divergence of some measures due to 1) the non-exponential nature of phosphocreatine recovery, and 2) potential breakdown of [ADP] control of the mitochondria due to lack of oxygen (for Qmax calculation). These results demonstrate the utility of obtaining and directly analyzing high time resolution data rather than assuming monoexponential behavior of metabolite recovery.

Functional MRI-BOLD of visually triggered headache in patients with migraine

BACKGROUND

Spreading depression of Leao has been hypothesized as the basis for the visual aura of the migraine attack, supported by cerebral blood flow measurements of spreading hypoperfusion. The early depolarizing or activation phase of experimental spreading depression, however, is associated with a transient but pronounced cerebral blood flow increase that precedes spreading hypoperfusion.

OBJECTIVE

To study this early phase of the migraine attack, we investigated visually triggered attacks of headache and visual symptoms using a red-green checkerboard stimulus in patients with migraine.

INTERVENTIONS

We studied occipital cortex activation during visual stimulation by measuring occipital cortex perfusion with functional magnetic resonance imaging-blood oxygenation level-dependent contrast in 10 patients with migraine with aura and 2 patients with migraine without aura and 6 healthy subjects.

RESULTS

In 6 patients with migraine with aura and 2 patients with migraine without aura, their typical headache with (n = 2) or without visual change was visually triggered at 7.3 minutes (mean time) after visual stimulation began. In 5 of these patients, the onset of headache or visual change, or both, was preceded by suppression of initial activation (mean onset time, 4.3 minutes; P<.001) The suppression slowly propagated into contiguous occipital cortex at a rate ranging from 3 to 6 mm/ min. This neuronal suppression was accompanied by baseline contrast intensity increases that indicated vasodilatation and tissue hyperoxygenation.

CONCLUSIONS

We conclude that visually triggered headache and visual change in patients with migraine is accompanied by spreading suppression of initial neuronal activation and increased occipital cortex oxygenation. We postulate that this spreading suppression may be associated with initial activation of a migraine attack, independent of whether there are associated aura symptoms. We further postulate that there may be an association between vasodilation accompanying the initial stage of suppression and the induction of headache.

Magnesium and pH imaging of the human brain at 3.0 Tesla

Multislice, two-dimensional phosphorus 31 spectroscopic imaging (SI) of human brain was performed in 15 normal volunteers on a 3-Tesla magnetic resonance system. Images of free magnesium concentrations and pH as well as phosphoesters, inorganic phosphate, phosphocreatine, and adenosine triphosphate (ATP), were calculated from the SI data. By using the equations of Golding and Golding (Magn. Reson. Med. 1995;33: 467-474), average [Mg2+] for all brain regions studied was 0.42+/-0.05 mM, whereas average brain pH was found to be 7.07+/-0.03, with no significant regional variations. Phosphorus metabolite concentrations (relative to ATP, assumed to be 3.0 mM/kg wet weight)were 5.39+/-1.88, 1.30+/-0.39, 5.97+/-3.17, and 4.33+/-1.45 mM/kg wet weight for phosphomonoesters, inorganic phosphate, phosphodiesters, and phosphocreatine (PCr), respectively. These values are in good general agreement with those reported previously. Typical signal-to-noise ratios of 15:1 were obtained for PCr in spectra from nominal 31.5 cc voxel sizes with a 34-min scan time. Limits on spatial resolution and the likely error of the magnesium and pH values are discussed.

MRI of the occipital cortex, red nucleus, and substantia nigra during visual aura of migraine

The authors report a patient with migraine in whom they measured brain oxygenation indirectly during a visual aura by means of T2-weighted MRI. An aura of left homonomous quadrantanopia was accompanied by increased T2-weighted contrast intensity of bilateral regions in the occipital cortex, and the red nucleus and substantia nigra bilaterally. The mechanisms of these changes remain to be determined, but in this patient the migraine aura was associated with probable hyperoxia and not cerebral ischemia.

Endothelin receptor antagonists: synthesis and structure-activity relationships of substituted benzothiazine-1,1-dioxides

The development of benzothiazine-1,1-dioxide derivatives as a new structural class of potent endothelin receptor antagonists is described. Structure-activity relationships (SAR) revealed that PD164800 (1) is a potent antagonist of the ETA receptor subtype.

Time course of ADCw changes in ischemic stroke: beyond the human eye!

BACKGROUND AND PURPOSE

Using newly developed computerized image analysis, we studied the heterogeneity of apparent diffusion coefficient of water (ADCw) values in human ischemic stroke within 10 hours of onset.

METHODS

Echo-planar trace diffusion-weighted images from 9 patients with focal cortical ischemic stroke were obtained within 10 hours of symptom onset. An Iterative Self-Organizing Data Analysis (ISODATA) clustering algorithm was implemented to segment different tissue types with a series of DW images. ADCw maps were calculated from 4 DW images on a pixel-by-pixel basis. The segmented zones within the lesion were characterized as low, pseudonormal, or high, expressed as a ratio of the mean+/-SD of ADCw of contralateral noninvolved tissue.

RESULTS

The average ADCW in the ischemic stroke region within 10 hours of onset was significantly depressed compared with homologous contralateral tissue (626.6+/-76.8 versus 842.9+/-60.4x10(-6) mm2/s; P<0.0001). Nevertheless, ISODATA segmentation yielded multiple zones within the stroke region that were characterized as low, pseudonormal, and high. The mean proportion of low:pseudonormal:high was 72%:20%:8%.

CONCLUSIONS

Despite low average ADCW, computer-assisted segmentation of DW MRI detected heterogeneous zones within ischemic lesions corresponding to low, pseudonormal, and high ADCw not visible to the human eye. This supports acute elevation of ADCw in human ischemic stroke and, accordingly, different temporal rates of tissue evolution toward infarction.

Endothelin B receptors on human endothelial and smooth-muscle cells show equivalent binding pharmacology

We have described the pharmacologic profiles of endothelin B receptors in human endothelial cells and vascular and nonvascular smooth-muscle cells. First, by amplifying endothelin B receptor numbers through the use of phosphoramidon and intact cell-binding techniques, we demonstrated the presence of these receptors in human umbilical vein endothelial cells (100% endothelin B receptors), human aortic smooth-muscle cells (22% endothelin B, 78% endothelin A receptors), and human bronchial smooth-muscle cells (55% endothelin B, 45% endothelin A receptors) by using [125I]-endothelin-1 radioligand binding. The typical binding profiles of the endothelin B receptors were established through competition binding curve analysis with endothelin-1, endothelin-3, sarafotoxin 6c, and the endothelin A receptor-selective antagonist BQ-123. In the presence of BQ-123, a diverse group of antagonists, including PD 142893, BQ-788, SB 209670, and Ro 47-0203, were used to probe for binding differences indicative of multiple endothelin B-receptor subtypes. The results indicate a rank order of potency for the antagonists of BQ-788 > SB 209670 > PD 142893 > Ro 47-0203 for each cell line, and that between any of these human cell lines, measurements of [125I]-endothelin-1-binding antagonism for each of the four test compounds differed by less than twofold. Although this study cannot discount the possibility of more than one endothelin B-receptor subtype in humans, it does indicate that these tissues express receptors that show equivalent binding pharmacology.

Brain excitability in migraine: evidence from transcranial magnetic stimulation studies

Central neuronal hyperexcitability is proposed to be the putative basis for the physiologic disturbances in migraine. Because there are no structural disturbances in migraine, only physiologic studies can provide insight into the underlying mechanisms. Recently, transcranial magnetic stimulation has been developed as a valuable research tool and can be used to study brain function noninvasively. This article is a review of the studies done in migraine using transcranial magnetic stimulation.

Assessment of endothelin receptor subtype-mediated increases of [Ca2+]i in distinct rat cell types using fluorimetric imaging

Activation of endothelin (ET) receptor subtypes by various agonists causes an increase in [Ca2+]i in different cell types. This effect can be readily monitored in a 96-well plate format by detecting 1-s fluorescence changes of cell-permeant, Ca(2+)-sensitive dyes (e.g., Calcium Green-1 AM) using a fluorimetric imaging plate reader. This device was used to assess the ET receptor subtypes in primary cultures of rat mixed neocortical neuronal/glial cells and aortic smooth-muscle cells. Pharmacologic experiments with several ET receptor agonists and antagonists indicated that the ETA receptor subtype was functionally responsive in the smooth-muscle cells and that the ETB receptor subtype had a similar role in the mixed neuronal/glial cells.

Preliminary clinical-radiological assessment of a MR tissue signature model in human stroke

We evaluated the ability of an MR signature model (SM) of cerebral ischemic injury to stage the evolution of cellular damage in human stroke. In 19 patients with ischemic stroke of presumed embolic or non-embolic cause we carried out diffusion-weighted and T2-weighted MR imaging within 48 h of onset, and obtained apparent diffusion coefficient of water (ADCw), and T2 weighted images. We used the signatures obtained from these ADCw/T2 maps to formulate two patterns of damage signifying accelerated or non-accelerated progression of cellular death after stroke onset. Those patients with the accelerated pattern corresponded to those with the neuroradiological (NRC) and clinical diagnosis (TOAST.1 and TOAST.2) of presumed embolic stroke, with clinical diagnosis performed blinded both to NRC and to SM. Agreement between the SM and NRC was substantial (kappa=0.62), moderate (0.60<kappa<0.40) between the SM or NRC and TOAST.2, and fair (0.40<kappa<0.20) among the SM or NRC and TOAST.1. We believe these results constitute a preliminary validation of the MR tissue signature modeling in clinical stroke assessment.

Transcranial magnetic stimulation confirms hyperexcitability of occipital cortex in migraine

OBJECTIVES

We hypothesized that the hyperexcitability of occipital cortex neurons may predispose migraine subjects to develop spreading depression, the putative basis of migraine with aura (MwA). To date there is no direct physiologic correlate confirming this in patients. Accordingly, we evaluated the differences in the threshold of occipital cortex excitation between MwA patients and normal controls (C) using transcranial magnetic stimulation (TMS).

METHODS

TMS was performed using the Cadwell MES 10 stimulator. A circular coil 9.5 cm in diameter was applied to the occipital scalp (7 cm above the inion). Stimulator intensity was increased in 10% increments until subjects reported visual phenomena or 100% intensity was reached. Stimulation intensity was then fine-tuned to determine the threshold at which phosphenes were just visualized.

RESULTS

Eleven MwA patients, mean age 37 +/- 7 years, were compared with 11 C, mean age 37.7 +/- 7 years. The difference in the proportion of subjects with phosphene generation between MwA patients and C was significant (MwA patients 100% versus C 27.3%, p = 0.001). The mean threshold level for MwA patients was 44.2 +/- 8.6 versus 68.7 +/- 3.1 for C (p = 0.0001). All threshold levels for MwA patients were lower than the lowest threshold for C; the MwA patient with the lowest threshold had an aura after stimulation.

CONCLUSIONS

The threshold for excitability of occipital cortex is lower in MwA patients compared with C. This is a direct neurophysiologic correlate for clinical observations that have indicated hyperexcitability of the occipital cortex in migraineurs.

Pathogenesis of migraine

Prevailing hypotheses for the mechanisms of migraine are reviewed. Models of aura mechanisms include transient cerebral ischemia and spreading depression. Models of headache involve trigeminovascular and brainstem mechanisms. The ability to trigger an attack may depend on a threshold of brain excitability. Mitochondrial disorder, magnesium deficiency, and abnormality of presynaptic calcium channels may be responsible for neuronal hyperexcitability between attacks. It remains to be determined whether cortical or brainstem centers generate the attack.

Pilot study of functional MRI to assess cerebral activation of motor function after poststroke hemiparesis

BACKGROUND AND PURPOSE

Studies of cerebral activation of motor function after ischemic stroke may enhance our understanding of the underlying mechanisms of motor functional recovery, including the role of the noninfarcted hemisphere.

METHODS

Eight right-handed recovering hemiparetic or hemiplegic patients were studied using functional MRI. Results were evaluated for each patient to consider individual variability in original functional organization, neuroanatomy, infarct size and extent, treatment, age, and sex. The results were also pooled as a group for comparison with a control group of eight right-handed normal subjects.

RESULTS

In six of eight stroke patients, extended activation in ipsilateral sensorimotor cortex was observed during paretic hand movements. Bilateral activation of the primary sensorimotor cortex was recorded in three of these six patients; ipsilateral activation alone was recorded in the remaining three patients. Only two patients had mild synkinesia. Furthermore, in two male patients, the paretic hand movements activated extended areas of ipsilateral premotor and dorsolateral prefrontal cortex, when compared with normal subjects. In two patients with left frontal infarction, profound activation in the right supramarginal gyrus and in the right premotor cortex was observed during the ipsilateral paretic hand movements.

CONCLUSIONS

Synkinesia alone cannot explain the extent of ipsilateral activation in primary sensorimotor cortex. The explanation offered for our findings is that preexisting uncrossed motor neural pathways may be accessed or recruited to compensate for damage to the crossed motor pathways after ischemic stroke.

Prediction of impending hemorrhagic transformation in ischemic stroke using magnetic resonance imaging in rats

BACKGROUND AND PURPOSE

Hemorrhagic transformation (HT) of ischemic brain tissue may occur in stroke patients either spontaneously or after thrombolysis. A method to assess the risk of HT in ischemic tissue after stroke would improve the safety of thrombolytic therapy. As a means of predicting HT, we investigated the role of contrast-enhanced MRI at acute time points in a rat middle cerebral artery occlusion model with reperfusion.

METHODS

Intraluminal suture occlusion of the middle cerebral artery was used to produce transient ischemia in male Wistar rats (n=11). Reperfusion was performed by withdrawal of the occluding filament after 2 (n=4), 3 (n=6), or 4 (n=1) hours. MRI studies were performed before and after reperfusion with the use of conventional T1-weighted imaging, with and without gadolinium (Gd-DTPA) contrast agent, and T2-weighted imaging. Follow-up MRI and histological studies were obtained at 24 hours.

RESULTS

Petechial hemorrhage occurred by 24 hours in 9 of 11 animals. All animals showed brain swelling and cellular death throughout the ischemic region at 24 hours. A hyperintense region in the preoptic area became visible after Gd-DTPA injection within minutes after reperfusion in animals with subsequent HT. All animals showing acute Gd-DTPA enhancement subsequently developed petechial hemorrhage (or died) by 24 hours. In these animals, statistically significant differences in signal intensity (P=.0005) between the ipsilateral enhancing region and a homologous contralateral region were detected on post-Gd-DTPA T1-weighted imaging. There was also a statistically significant correlation (P=.01) between the rate of Gd-DTPA uptake and the size of the enhancing area. Two animals did not enhance with Gd-DTPA and did not exhibit hemorrhage on histological examination or MRI at 24 hours. No abnormalities were seen on precontrast T1-weighted images before and shortly after reperfusion or postcontrast T1-weighted images before reperfusion.

CONCLUSIONS

The primary finding of this study was the detection of early Gd-DTPA parenchymal enhancement in 82% of the animals after reperfusion. Enhancement was seen before any detectable hemorrhage, suggesting that early endothelial ischemic damage occurs before gross brain infarction and hemorrhage. Thus, we suggest that acute Gd-DTPA enhancement may provide an early prediction of petechial hemorrhage.

Migraine and ovarian steroid hormones

This chapter reviews clinical and epidemiological data that support a role for ovarian steroid hormones in the migraine syndrome. Changes in the clinical presentation of migraine are discussed on the basis of current knowledge of biochemistry and pharmacology of ovarian steroids. Finally, special treatment considerations of ovarian hormone-sensitive migraine are discussed.

Total quality improvement method for reduction of delays between emergency department admission and treatment of acute ischemic stroke. The National Institute of Neurological Disorders and Stroke rt-PA Stroke Study Group

OBJECTIVE

To develop an approach for reducing time between emergency department (ED) admission and treatment in patients with acute ischemic stroke to meet the challenge of providing tissue plasminogen activator treatment within 180 minutes.

DESIGN

An observational study.

SETTING

Forty trial-affiliated hospitals, including 30 community hospitals.

PARTICIPANTS

A total of 17,324 consecutive patients admitted to trial-affiliated hospital EDs within 24 hours of possible stroke, from January 1991 through October 1994.

INTERVENTION

Appraisal of the process of triage, evaluation, diagnosis, and treatment by means of total quality improvement techniques in each hospital. Staff participating in the process identified sources of variation and modifications by flow charting the process.

MAIN OUTCOME MEASURE

Time between ED admission and treatment with study medication.

RESULTS

Total quality improvement methods identified hospital-specific process improvements. Many improvements were administrative, requiring no additional resources. More than 50% of screened patients arrived too late to be treated. Only 1268 patients were admitted between 0 and 125 minutes from stroke onset with no other trial exclusion criteria; 48% were treated. Of 243 patients admitted between 126 and 170 minutes from stroke onset with no exclusion criteria, 4% were treated. Mean time from ED admission to treatment was similar in teaching and community hospitals.

CONCLUSIONS

Total quality improvement methods identified ED-specific sources of process variability and reduced time between ED admission and treatment. Therefore, these methods should be considered in developing and monitoring emergent stroke treatment protocols.

Cerebral blood flow in chronic posttraumatic headache

BACKGROUND AND PURPOSE

Headache is the most common neurologic symptom following minor closed head injury. There is often a lack of objective evidence supporting an organic basis of cerebral pathology in these cases. This pilot study considers the possibility of alterations in cerebral blood flow, indicating evidence of an organic disorder in posttraumatic headache.

METHODS

Regional cerebral blood flow studies of 35 patients with chronic posttraumatic headache (PTH) (International Headache Society criteria), identified retrospectively from our cerebral blood flow data base, were compared with those of 49 nonheadache controls and 92 migraineurs (Ad Hoc Committee criteria). Regional cerebral blood flow (initial slope index method) was measured using the xenon Xe 133 inhalation technique.

RESULTS

Compared to migraineurs and controls, and after adjusting for differences (analysis of covariance) in baseline variables such as blood pressure, hematocrit, and PCO2, patients with PTH had: (1) significantly lower mean initial slope indices (P < 0.001, P = 0.002, respectively); (2) regional interhemispheric flow differences (rIFD), with higher distribution of regional asymmetrical probe pairs (rIFD > or = 7%: P[PTH versus control] = 0.006, P[PTH versus migraine] = 0.016: rIFD > or = 10%; P[PTH versus control] = 0.011, P[PTH versus migraine] = 0.003); and (3) more hemispheric asymmetries (P[PTH versus control] = 0.023, P[PTH versus migraine] = 0.57). Lower mean initial slope indices and hemispheric asymmetry (mean interhemispheric flow difference > or = 3.2%) predicted PTH over control (P = 0.023 and 0.002, respectively). Lower mean initial slope indices predicted PTH over migraine (P = 0.002).

CONCLUSIONS

Patients with PTH have reduced regional cerebral blood flow, and regional and hemispheric asymmetries. These cerebral hemodynamic alterations support an organic basis to chronic posttraumatic headache.