Effects-based chemical category approach for prioritization of low affinity estrogenic chemicals.

Regulatory agencies are charged with addressing the endocrine disrupting potential of large numbers of chemicals for which there is often little or no data on which to make decisions. Prioritizing the chemicals of greatest concern for further screening for potential hazard to humans and wildlife is an initial step in the process. This paper presents the collection of in vitro data using assays optimized to detect low affinity estrogen receptor (ER) binding chemicals and the use of that data to build effects-based chemical categories following QSAR approaches and principles pioneered by Gilman Veith and colleagues for application to environmental regulatory challenges. Effects-based chemical categories were built using these QSAR principles focused on the types of chemicals in the specific regulatory domain of concern, i.e. non-steroidal industrial chemicals, and based upon a mechanistic hypothesis of how these non-steroidal chemicals of seemingly dissimilar structure to 17ß-estradiol (E2) could interact with the ER via two distinct binding types. Chemicals were also tested to solubility thereby minimizing false negatives and providing confidence in determination of chemicals as inactive. The high-quality data collected in this manner were used to build an ER expert system for chemical prioritization described in a companion article in this journal.

The impact of pregnancy and childbirth on the metabolism of lamotrigine.

This study was performed to clarify alterations in lamotrigine (LTG) clearance during pregnancy and childbirth. Fourteen women on LTG monotherapy had LTG concentration samples obtained before conception and monthly. LTG apparent clearance, weight-adjusted relative clearance, and percentages of baseline clearance significantly differed between preconception baseline and each trimester and between trimesters. LTG clearance progressively increased until 32 weeks' gestational age, reaching a peak of >330% of baseline, and then began to decline.

Proteomics in zebrafish exposed to endocrine disrupting chemicals.

Embryonic zebrafish were examined for changes in protein expression following exposure to sublethal concentrations of 17beta-estradiol (E2) and the estrogen mimic 4-nonylphenol (4-NP). Protein Expression Signatures were derived from embryo homogenates by two-dimensional electrophoresis and digital imaging. In both experiments approximately 30% of the proteins sampled were specific to either E2 or 4-NP and about 33% were common to the control, 4-NP and E2. However, of the proteins induced by either E2 or 4-NP, 28% were common to both chemicals at 1 ppm but only 7% were common to both at 0.1 ppm. While there are many proteins that respond specifically to each chemical, relatively few are common to the two chemicals suggesting that the response pathways of the two chemicals are distinct.

Remission of intractable partial epilepsy following implantation of intracranial electrodes.

Six patients with medically intractable partial epilepsy (IPE) underwent seizure localization with intracranial EEG using intracerebral or subdural electrodes. No surgical resection was performed, but all had seizure remission ranging from 11 months to 15 years. Invasive monitoring may rarely produce remission of IPE, possibly through interruption of seizure propagation pathways.

Relative potencies of polychlorinated dibenzo-p-dioxin, dibenzofuran, and biphenyl congeners to induce cytochrome P4501A mRNA in a zebrafish liver cell line.

Induction of cytochrome P4501A (CYP1A) mRNA by polychlorinated dibenzo-p-dioxin (PCDD), polychlorinated dibenzofuran (PCDF), and polychlorinated biphenyl (PCB) congeners was measured in a zebrafish liver (ZF-L) cell line. The ZF-L cells were far less sensitive to PCDD, PCDF, and PCB congeners than were other fish cell lines. The 2,3,7,8-PCDDs, 2,3,7,8-PCDFs, and PCB 126 caused dose-related induction. All other PCBs tested, including other coplanar as well as ortho-substituted congeners, were ineffective at inducing CYP1A. The potency of each congener that gave a response, relative to 2,3,7,8-tetrachlorodibenzo-p-dioxin, was determined. The ZF-L cell-derived relative potency values (REPs) are similar to other in vitro REPs in that the ZF-L cell-derived REPs are generally higher than those derived from in vivo models. Furthermore, the ZF-L cell-derived REPs are generally within fivefold of REPs determined in a variety of rainbow trout systems when the same endpoint in the same tissue are compared. Analysis of these data indicates that REPs based on molecular and biochemical responses in sensitive and insensitive species are similar, but overestimate relative in vivo toxicity in the rainbow trout. The ZF-L cell-derived REPs expand the database of REPs, providing additional information that will be useful in quantifying the uncertainty associated with applying consensus fish-specific toxic equivalency factors in ecological risk assessment.

Repetitive transcranial magnetic stimulation does not replicate the Wada test.

The authors compared inferior frontal speech arrest from repetitive transcranial magnetic stimulation (rTMS) with bilateral Wada tests in 17 epilepsy surgery candidates. Although rTMS lateralization correlated with the Wada test in most subjects, rTMS also favored the right hemisphere at a rate significantly greater than the Wada test. Postoperative language deficits were more consistent with Wada results. Available methods for inducing speech arrest with rTMS do not replicate the results of Wada tests.

Ictal spiking patterns recorded from temporal depth electrodes predict good outcome after anterior temporal lobectomy.

PURPOSE: Investigators have shown that the presence of ictal spiking (IS) recorded from temporal depth electrodes is associated with mesial temporal sclerosis (MTS). We investigated the relation of IS to seizure control and pathology after anterior temporal lobectomy (ATL). METHODS: All patients undergoing intracranial ictal monitoring from a single institution since 1989 were identified. Those who did not undergo ATL or had postoperative follow-up of <1 year were excluded. All received at a minimum bilateral temporal depth electrodes. Ictal recordings were reviewed for the presence of IS, and the proportion of seizures with IS was determined for each patient. Outcome was determined by using Engel's classification. Surgical specimens were reviewed for pathology. Statistics used were chi2, Fisher exact test, and Wilcoxon rank sum. RESULTS: Forty patients with 571 seizures were reviewed. In 292 seizures from 32 patients, IS was seen. Outcomes were 24 class I (22 with IS), five class II (four with IS), three class III (one with IS), seven class IV (four with IS), and one lost to follow-up (with IS). Pathologic review revealed 25 with MTS, 22 of whom had IS. The presence of IS was associated with class I outcomes (p = 0.04), but not MTS (p = 0.06). Patients with class I outcomes had a significantly greater proportion of seizures with IS (mean, 0.58 +/- 0.3) compared with other outcomes (mean, 0.30 +/- 0.3, p = 0.02). CONCLUSIONS: The presence of IS and higher proportion of seizures with IS correlated with good seizure outcome after ATL. This information may be used in preoperative counseling.

Increased secondary generalization of partial seizures after temporal lobectomy.

OBJECTIVE: This study tests the primary hypothesis that secondary generalization of partial seizures is more likely after anterior temporal lobectomy (ATL) than before ATL, and the secondary hypothesis that antiepileptic drug withdrawal accounts for increased generalization of seizures postoperatively. BACKGROUND: The authors observed that some patients had generalized tonic-clonic (GTC) seizures after but not before ATL, by using a new classification of outcome that compares preoperative and postoperative seizure frequencies by seizure type. METHODS: Twenty patients with refractory temporal lobe epilepsy had postoperative GTC seizures or nongeneralizing complex partial (CP) seizures in a consecutive ATL series. All had reduced seizure frequency postoperatively and more than 2 years of follow-up on antiepileptic drugs. The authors calculated a generalization fraction, as (number of GTC seizures)/(number of CP and GTC seizures), for 2 years before and 2 years after surgery. RESULTS: Postoperative generalization fractions were greater than preoperative generalization fractions (Wilcoxon signed-rank test, p < 0.01). Most postoperative GTC seizures were not associated with antiepileptic drug withdrawal, and postoperative GTC seizures were not more associated with drug withdrawal than were postoperative CP seizures. Patients with more than two GTC seizures per year preoperatively were more likely than other patients to have postoperative GTC seizures. CONCLUSIONS: Patients with reduced seizure frequency after ATL have a greater tendency for partial seizures to secondarily generalize postoperatively. This phenomenon is not explained by antiepileptic drug withdrawal.

Indications and outcome of ictal recording with intracerebral and subdural electrodes in refractory complex partial seizures.

Intracranial electrophysiologic recording has often been used to localize ictal onset zones in presurgical evaluation of refractory complex partial seizures. Specific indications for intracranial ictal monitoring have not been analyzed in detail, however. The authors designed this study to test the utility of intracranial monitoring in specific indications and considered six specific indications for intracranial monitoring. They compared prospectively determined indications and outcomes of chronic intracerebral and subdural electrophysiologic recording in 50 consecutive patients whose ictal onset zones had been inadequately localized with interictal and ictal EEG using extracranial electrodes, magnetic resonance imaging, interictal[18F]fluorodeoxyglucose positron emission tomography, and neuropsychological testing. In 47 patients ictal onset zones were localized with intracranial recordings, leading to resections in 38 patients. Each indication for intracranial monitoring selected a group in which the majority went on to have efficacious epilepsy surgery (5-year follow-up). Definitive diagnosis of bilateral independent ictal onset zones in temporal lobe epilepsy required intracranial ictal EEG. Intracranial EEG localization supported efficacious resection in most patients, despite contradictory or nonlocalizing extracranial ictal EEG and neuroimaging abnormalities. Critical analysis of these specific indications for intracranial monitoring may be useful in multicenter evaluation of these techniques.

A confrontational naming task produces congruent increases and decreases in PET and fMRI.

This work uses the well-established (by PET) confrontation naming task to compare PET and fMRI in a cognitive activation experiment. The signal changes from this task are much less than the changes caused by visual or motor activation tasks used in previous comparisons. ANOVA methods adjusted for multiple comparisons were used to determine significant changes in signal between confrontation naming and figure size discrimination tasks. All 17 significantly increased regions (confrontation naming signal greater) seen on one modality were increased on both modalities. Ten of 13 regions that were significantly decreased on one modality were decreased on the other. Three mismatched regions showed a significant decrease on one modality and a nonsignificant increase on the other. This study could not detect a consistent difference in activation site location between PET and fMRI.

Butanol is superior to water for performing positron emission tomography activation studies.

[15(O)]Butanol has been shown to be superior to [15(O)]water for measuring cerebral blood flow with positron emission tomography. This work demonstrates that it is also superior for performing activation studies. Data were collected under three conditions: a visual confrontation animal-naming task, nonsense figure size discrimination, and a nonvisual darkroom control task. Time-activity curves (TAC) were obtained for regions known to be activated by the confrontation naming task to compare absolute uptake and the different kinetics of the two tracers. Also, t statistic maps were calculated from the data of 10 subjects for both tracers and compared for magnitude of change and size of activated regions. Peak uptake in the whole-brain TAC were similar for the two tracers. For all regions and conditions, the washout rate of [15(O)]butanol was 41% greater than that of [15(O)]water. At a threshold of 0, the [15(O)]water and [15(O)]butanol percent difference (nonnormalized) and t statistic (global normalization) images are nearly identical, indicating that the same property is being measured with both tracers. The [15(O)]butanol parametric images displayed at a threshold of /t/ = 5 look similar to the [15(O)]water parametric maps displayed at a threshold of /t/ = 4, which is consistent with the observation that t statistic values in [15(O)]butanol images are generally greater. The t statistic values were equal when the [15(O)]butanol parametric map was created from any subset of 6 subjects and the [15(O)]water parametric map was created from all 10 subjects. Fewer subjects need to be studied with [15(O)]butanol to reach the same statistical power as an [15(O)]water-based study.

Value of inpatient diagnostic CCTV-EEG monitoring in the elderly.

PURPOSE: To examine the outcome of inpatient diagnostic closed circuit TV-EEG (CCTV-EEG) monitoring in a consecutive series of elderly patients admitted to an adult epilepsy-monitoring unit (EMU) over a continuous 6-year period. METHODS: Retrospective review of all admissions to a university hospital adult EMU. Those older than 60 years were identified. Patients who were monitored for status epilepticus were excluded. Data on duration of events, frequency of events, physical examination, medications, preadmission EEG, brain imaging, length of stay, and interictal and ictal EEG were obtained. RESULTS: Of the 18 patients admitted for monitoring only, mean age was 69.5 years (range, 60-90 years). Mean length of stay was 4.3 days (range, 2-9 days). Five patients had complex partial seizures recorded. Three patients, all treated with anti-epileptic drugs (AEDs), had no spells recorded, and no additional diagnostic information was gained from the admission. The other 10 patients, eight of whom had been treated with AEDs, were symptomatic during their admission, leading to a variety of neurologic but not epileptic, psychiatric, or other medical disorders, and allowing tapering of AEDs. CONCLUSIONS: In elderly patients with suspected epilepsy, CCTV-EEG is a very useful diagnostic tool. In this series of 18, 10 patients were diagnosed with potentially treatable medical illnesses not responsive to AEDs.

Acute blood flow changes and efficacy of vagus nerve stimulation in partial epilepsy.

OBJECTIVE: To determine possible sites of therapeutic action of vagus nerve stimulation (VNS), by correlating acute VNS-induced regional cerebral blood flow (rCBF) alterations and chronic therapeutic responses. BACKGROUND: We previously found that VNS acutely induces rCBF alterations at sites that receive vagal afferents and higher-order projections, including dorsal medulla, somatosensory cortex (contralateral to stimulation), thalamus and cerebellum bilaterally, and several limbic structures (including hippocampus and amygdala bilaterally). METHODS: VNS-induced rCBF changes were measured by subtracting resting rCBF from rCBF during VNS, using [O-15]water and PET, immediately before ongoing VNS began, in 11 partial epilepsy patients. T-statistical mapping established relative rCBF increases and decreases for each patient. Percent changes in frequency of complex partial seizures (with or without secondary generalization) during three months of VNS compared with pre-VNS baseline, and T-thresholded rCBF changes (for each of the 25 regions of previously observed significant CBF change), were rank ordered across patients. Spearman rank correlation coefficients assessed associations of seizure-frequency change and t-thresholded rCBF change. RESULTS: Seizure-frequency changes ranged from 71% decrease to 12% increase during VNS. Only the right and left thalami showed significant associations of rCBF change with seizure-frequency change. Increased right and left thalamic CBF correlated with decreased seizures (p < 0.001). CONCLUSIONS: Increased thalamic synaptic activities probably mediate some antiseizure effects of VNS. Future studies should examine neurotransmitter-receptor alterations in reticular and specific thalamic nuclei during VNS.

Muscarinic receptor loss and preservation of presynaptic cholinergic terminals in hippocampal sclerosis.

PURPOSE: Prior single-photon emission tomography studies showed losses of muscarinic acetylcholine receptor (MAChR) binding in patients with refractory mesial temporal lobe epilepsy. Experimental animal studies demonstrated transient losses of MAChR due to electrically induced seizures originating in the amygdala. However, the relations between cholinergic synaptic markers, seizures, and underlying neuropathology in human temporal lobe epilepsy are unknown. We tested the hypotheses that human brain MAChR changes are attributable to hippocampal sclerosis (HS), and that HS resembles axon-sparing lesions in experimental animal models. METHODS: We measured MAChR binding-site density, an intrinsic neuronal marker, within the hippocampal formation (HF) in anterior temporal lobectomy specimens from 10 patients with HS and in 10 autopsy controls. Binding-site density of the presynaptic vesicular acetylcholine transporter (VAChT) was measured as a marker of extrinsic cholinergic afferent integrity. MAChR and VAChT results were compared with neuronal cell counts to assess their relations to local neuronal losses. RESULTS: Reduced MAChR binding-site density was demonstrated throughout the HF in the epilepsy specimens compared with autopsy controls and correlated in severity with reductions in cell counts in several HF regions. In contrast to MAChR, VAChT binding-site density was unchanged in the epilepsy specimens compared with autopsy controls. CONCLUSIONS: Reduction in MAChR binding in HS is attributable to intrinsic neuronal losses. Sparing of afferent septal cholinergic terminals is consistent with the hypothesis that an excitotoxic mechanism may contribute to the development of HS and refractory partial epilepsy in humans.

Discordance between traditional pathologic and energy metabolic changes in very early Alzheimer's disease. Pathophysiological implications.

These results suggest that neither the loss of entorhinal efferents nor cholinergic deficit explains all the metabolic features seen in very early AD. Given recent immunohistological evidence of massive glutamatergic synaptic alteration in early AD cortex and insights into neuronal and glial mechanisms of glucose metabolism, very early metabolic changes in AD probably reflect a significant impairment of glycolytic activities in the cortico-cortical glutamatergic systems in a preclinical stage of the disease. However, the exact mechanisms of such impairment in these neurons are yet to be determined.

Nonconvulsive status epilepticus in the critically ill elderly.

PURPOSE: To describe the electrographic and clinical features of nonconvulsive status epilepticus (NCSE) in the critically ill elderly and to identify potential predictors of outcome. METHODS: We prospectively identified 25 episodes of altered mentation and NCSE in 24 critically ill elderly patients associated with generalized, focal, or bihemispheric epileptiform EEG patterns. Patients with anoxic encephalopathy were excluded. RESULTS: Of 25 hospitalizations, 13 (52%) resulted in death, and 12 (48%) patients survived to discharge. Death was associated with the number of acute, life-threatening medical problems on presentation (survivors, 1.8; fatalities, 2.8; p = 0.013) and with generalized EEG pattern (p = 0.017). Higher doses or greater number of antiepileptic drugs (AEDs) did not improve outcome. Treatment with intravenous benzodiazepines was associated with increased risk of death (p = 0.033). Ten patients with advance directives were managed outside the intensive care unit (ICU). Mean hospitalization was 39 days in the ICU group and 22 for those with advance directives (p = 0.017). CONCLUSIONS: Severity of illness correlates with mortality in critically ill elderly patients with NCSE. Treatment with intravenous benzodiazepines may increase their risk of death. Aggressive ICU management may prolong hospitalization at considerable cost, without improving outcome. It is unclear whether NCSE affects outcome in the critically ill elderly or is merely a marker for severity of disease in predisposed patients. The benefits of aggressive therapy are unclear. Carefully controlled, prospective trials will be necessary to determine the best therapies for NCSE in the critically ill elderly and the appropriate role of the ICU in their management.

Alumina gel injections into the temporal lobe of rhesus monkeys cause complex partial seizures and morphological changes found in human temporal lobe epilepsy.

The goal of the present study was to determine whether alumina gel injections into temporal lobe structures cause complex partial seizures (CPS) and pathological changes observed in human temporal lobe epilepsy. Rhesus monkeys with alumina gel injections in the amygdala, perirhinal and entorhinal cortices, or Ammon's horn and dentate gyrus all initially displayed focal pathological electroencephalographic (EEG) slowing limited to the site of injection. After clinical seizures developed, they also displayed widespread pathological EEG slowing over both hemispheres, interictal and ictal epileptiform EEG abnormalities limited to the mesial-inferior temporal lobe on the side of injection, and different degrees of spread to other ipsilateral and contralateral structures. Noninjected control and nonepileptic monkeys with injections into the middle and inferior temporal gyri displayed no hippocampal neuronal loss or mossy fiber sprouting. When alumina gel was injected into the amygdala, CPS began within 3-6 weeks and degeneration of neurons and gliosis occurred in the perirhinal cortex or the hippocampus, with consequent sprouting of mossy fibers in the dentate gyrus. Dispersion of the granule cell layer was also observed. Other monkeys with alumina gel in the perirhinal and entorhinal cortices developed CPS within 2-3 weeks after the injections and displayed mossy fiber sprouting only after 4 weeks after the injections. Alumina gel in Ammon's horn and the dentate gyrus also induced CPS, but mossy fiber sprouting was limited to sites immediately adjacent to the injection, probably because none survived more than 4 weeks after the injections. This nonhuman primate model of CPS displayed similar anatomical, behavioral, and EEG features as observed in human temporal lobe epilepsy and provides opportunities to analyze the chronological sequence of epileptogenesis and to test potential therapies.