Training on motor and visual spatial learning tasks in early adulthood produces large changes in dendritic organization of prefrontal cortex and nucleus accumbens in rats given nicotine prenatally.

Experience-dependent plasticity is an ongoing process that can be observed and measured at multiple levels. The first goal of this study was to examine the effects of prenatal nicotine on the performance of rats in three behavioral tasks (elevated plus maze (EPM), Morris water task (MWT), and Whishaw tray reaching). The second goal of this experiment sought to examine changes in dendritic organization following exposure to the behavioral training paradigm and/or low doses of prenatal nicotine. Female Long-Evans rats were administered daily injections of nicotine for the duration of pregnancy and their pups underwent a regimen of behavioral training in early adulthood (EPM, MWT, and Whishaw tray reaching). All offspring exposed to nicotine prenatally exhibited substantial increases in anxiety. Male offspring also showed increased efficiency in the Whishaw tray-reaching task and performed differently than the other groups in the probe trial of the MWT. Using Golgi-Cox staining we examined the dendritic organization of the medial and orbital prefrontal cortex as well as the nucleus accumbens. Participation in the behavioral training paradigm was associated with dramatic reorganization of dendritic morphology and spine density in all brain regions examined. Although both treatments (behavior training and prenatal nicotine exposure) markedly altered dendritic organization, the effects of the behavioral experience were much larger than those of the prenatal drug exposure, and in some cases interacted with the drug effects.

Apneic seizures in infants: role of continuous EEG monitoring.

Respiratory compromise is not uncommon in epileptic seizures. However, pure apneic seizures are rare. In this study, we report 10 children who presented with pure apneic seizures. All the children were admitted because of apneic events. Seizures were also considered in the differential diagnosis. Six patients had nonspecific findings consisting of multifocal interictal epileptiform activity with no event correlation. Continuous 24-72 hours electroencephalogram (EEG) was performed in all patients to rule out apneic seizures. Ictal EEG showed high correlation with the apneic episodes, confirming the diagnosis of apneic seizures. Our study suggests that continuous EEG monitoring is essential in the diagnosis and treatment of apneic seizures.

Vagus nerve stimulation treatment for Lennox-Gastaut syndrome.

Lennox-Gastaut syndrome is a severe age-specific epilepsy syndrome that presents with medication-resistant seizures in childhood. Antiepileptic drugs are the mainstay of treatment. Nonpharmacologic treatments include corpus callosum section and the ketogenic diet. However, no single treatment is safe and effective. We treated 13 patients with Lennox-Gastaut syndrome between the ages of 4 and 44 years (mean, 16.7 years) with vagus nerve stimulation. During the first 6 months of treatment, vagus nerve stimulation produced a median seizure rate reduction of 52% (range, 0% to 93%; P = .04). At 6 months of follow-up, three patients had a greater than 90% reduction in seizures, two had a greater than 75% reduction, one had a greater than 50% reduction, and six had at least a 25% reduction. One patient did not improve. No patient worsened after initial improvement. Side effects, including hoarseness, coughing, and pain in the throat, were transient and tolerable. No patient discontinued vagus nerve stimulation. Our results suggest that vagus nerve stimulation could be an effective and safe adjunct therapy for the treatment of Lennox-Gastaut syndrome.

Localization of urokinase-type plasminogen activator, its receptor, and inhibitors in mouse forebrain during postnatal development.

Proteolytic enzymes are postulated to play a role in cell migration and synapse organization during brain development. Among these, urokinase-type plasminogen activator (uPA) has been studied in neoplastic and cultured brain cells extensively. We hypothesized that uPA, its receptor, and its inhibitors would be expressed in immature glial and neuronal cells in postnatal mouse forebrain. Immature cortical neurons were immunoreactive for uPA, its receptor, and its substrate plasminogen peaking at the end of postnatal week two, consistent with the postulated role in synaptogenesis. Immunoreactivity for uPA receptor was also observed on astroglial cells in vitro. Neither it nor uPA were convincingly detected in subventricular zone precursor cells, immature white matter or pre-labeled immature cells that had been transplanted into brain. Plasminogen activator inhibitor type 1 immunoreactivity was observed on endothelia up to 12 days age, and type 2 was observed to surround immature cells. We conclude, based on the spatial and temporal distribution of immunoreactivity, that uPA and its receptor may be relatively more important for synaptogenesis, remodeling, and reactive processes than for cell migration in developing mouse brain.

The synergistic effect of sympathectomy and hyperbaric oxygen exposure on transcutaneous PO2 in healthy volunteers.

UNLABELLED: The benefit of hyperbaric oxygen (HBO2) exposure is dependent on the oxygen delivery. Such benefit may be limited by the fact that hyperoxia causes vasoconstriction and decreases blood flow. The aim of this study was to determine whether regional sympathectomy attenuates this vasoconstriction response and thus improves oxygen delivery. In a double-blinded manner, healthy volunteers were subjected to HBO2 in a monoplace chamber on two occasions separated by at least 1 wk. Transcutaneous oxygen (tcPO2) and carbon dioxide (tcPCO2) on the forearm were monitored continuously, and blood flow in the axillary artery was measured using angiodynography before and after exposure to HBO2. During one visit, each volunteer received a sympathetic block to the upper extremity by an injection of lidocaine into the brachial plexus at the axilla. During a second visit, the volunteer received a placebo injection of isotonic sodium chloride solution into the brachial plexus of the same side. Skin temperature was recorded on the back of the hand. All subjects exhibited a small but significant increase in skin temperature (2.5%) and in upper limb blood flow (23%) (P < 0.05%) after sympathectomy, but not after isotonic sodium chloride solution injection. Sympathectomy increased tcPO2 marginally while in room air. However, during HBO2, tcPO2 was substantially and significantly higher (409.8+/-98.8 mm Hg) after sympathectomy compared with that after isotonic sodium chloride solution injection (171.3+/-38.1 mm Hg). tcPCO2 did not change significantly after sympathectomy or during HBO2. Thus, sympathectomy presumably improved oxygen delivery by preventing vasoconstriction during hyperoxia. The results suggest that sympathectomy may be a useful adjunct to HBO2 therapy in patients in whom vascular resistance is increased because of sympathetic tone or hyperoxia. IMPLICATIONS: Sympathetic nerve block of the extremities markedly enhances tissue oxygen delivery during hyperbaric oxygen treatment. Sympathectomy may be a beneficial adjunct treatment to hyperbaric oxygen in peripheral vascular insufficiency.

Concordance between functional magnetic resonance imaging and intraoperative language mapping.

Although the correspondence between functional-magnetic resonance imaging (fMRI) representations of the sensorimotor cortex and intraoperative electrophysiology (including somatosensory evoked potential, SSEP, recordings and direct cortical stimulation) has been reported, a similar correspondence between fMRI and intraoperative localization of the language-sensitive cortex is not as well established. The aim of the present study was to evaluate the concordance between fMRI and intraoperative electrophysiology with respect to the localization of the language-sensitive and sensorimotor cortices. We present the results of 21 patients who underwent language and sensorimotor mapping by fMRI and intraoperative electrophysiology including SSEP recordings (n = 21), direct cortical stimulation of motor cortex (n = 15) and direct cortical stimulation of Broca's and Wernicke's area (n = 5). When responses were obtained with both methods, localization of function concurred in all cases. These observations suggest that fMRI represents a reliable preoperative tool for the identification of language-sensitive areas.

Effects of nitrous oxide on electrocorticography during epilepsy surgery.

Interictal spikes on intraoperative electrocorticography during epilepsy are used to tailor resections. There have been a few systematic quantitative studies of anesthetic effects on these interictal discharges, and none on the effects of nitrous oxide (N2O). We calculated spike rates on ECoG on and off N2O in 18 epilepsy surgery patients with subdural strips and grids, analyzing the most active recording contract. In a blinded analyses ten patients had fewer spikes on N2O, while eight patients had more spikes on N2O. The mean spike rates did not differ (41/min on N2O and 40/min off N2O). Spike rate on and off N2O were compared using the non-parametric Wilcoxon matched pairs test. These rates were not significantly different. Our study indicates that N2O in doses employed dose not effect interictal spikes and this agent may be used during epilepsy surgery without concerns about suppression of epileptiform activity.

Focal suppression-burst on electrocorticography after temporal lobectomy.

Of 40 patients with cortical resections for epilepsy, three had focal suppression-burst (S-B) on postresection intraoperative electrocorticography (ECoG). Eighteen to 24 months later, two patients were seizure-free and one had rare seizures. Follow-up neuropsychological testing and MRI did not reveal unexpected postoperative abnormalities. Follow-up scalp surface EEGs did not show S-B. Although S-B on postresection ECoG suggests severe localized cortical damage, this pattern near anterior temporal lobectomy resection margins was not associated with postoperative deficits.

Diagnoses of neuronal ceroid-lipofuscinosis by immunochemical methods.

The neuronal ceroid-lipofuscinoses (NCL), also known as Batten disease, are a not uncommon group of disorders affecting infants, children, and young adults. The abnormal ultrastructural profiles seen in NCL are used for standard diagnosis; however, they can be missed, and are also found in other neurodegenerative conditions. Furthermore, there is an overlap between the types of inclusion profiles among the different forms of NCL. Therefore, a more specific and biochemically-based marker is necessary to confirm the diagnosis of NCL. Antibodies raised against the storage material from the ovine form of NCL (mitochondrial ATP synthase subunit c) were utilized to determine whether NCL could be distinguished from other metabolic-neurodegenerative disorders. By immunoblotting and immunohistochemistry, several brain samples of well-evaluated NCL cases confirmed increased accumulations in all NCL cases except in the brain of an infantile-onset NCL patient. The immunoblot studies of skin fibroblasts and brain were sensitive but not highly specific to NCL, due to the recognition of this material in normal controls as well as in other neurogenetic diseases. Immunocytochemistry of skin fibroblasts clearly distinguished LINCL and JNCL cases from controls, and with further refinement has the potential for becoming a diagnostic tool.

Use of a calcium channel blocker (nicardipine HCl) in the treatment of childhood moyamoya disease.

Moyamoya disease is a cerebrovascular disease characterized radiologically by progressive narrowing and occlusion of the arteries contributing to the circle of Willis and its branches. There is formation of an exuberant collateral network of blood vessels at the base of the brain, which is thought to arise in response to chronic ischemia. Clinically, the course is variable, with patients having repeated transient ischemic attacks, strokes, migraine, and seizures. Effective treatment is not available. The etiology and pathophysiology of moyamoya disease are largely unknown. Two patients with arteriographically proven moyamoya disease were identified. Both patients were symptomatic before age 5 years. Despite successful encephaloduroarteriosynangiosis revascularization procedures, they continued to experience an inexorable downhill course. A calcium channel blocker (nicardipine HCl) was introduced in order to prevent further symptoms. After the introduction of nicardipine, no further strokes occurred in either patient. There were no further episodes of transient ischemic attacks, seizures, or headache in one patient and decreased frequency in the other. In patients with moyamoya disease, nicardipine may have a beneficial effect on cerebral hemodynamics and may prevent ischemic sequelae by optimizing existing collateral circulation.

Attenuation characteristics of single-mode metal-clad graded-index waveguides with a dielectric buffer: a simple and accurate numerical method.

We present a simple and accurate numerical method for the determination of the complex propagation constants of metal-clad graded-index planar waveguides with arbitrary refractive-index profiles. Numerical results for practically important profiles such as exponential and Gaussian are presented and compared with the homogeneous core waveguides. The analysis should find application in the design of high-differential-attenuation metal-clad polarizers, in reducing losses in integrated-optic modulators using metal electrodes, and in other devices using metal overlays.

Splice-loss evaluation for single-mode graded-index fibers.

In this paper we present highly accurate and simple methods for the evaluation of splice loss in single-mode graded-index fibers. These are based on accurate approximations of the modal field of such fibers which we have recently developed. Splice losses for angular and transverse offsets have been expressed in analytical forms which are quite easy to evaluate. A comparison of our results with those obtained using the Gaussian approximation is also presented which shows that our method is much more accurate than the latter.