The vibration of an artery-like tube conveying pulsatile fluid flow.

A hybrid method for investigating pulsatile fluid flow in a long, thin, artery-like tube subjected to external excitations is presented. The non-linear partial differential equations governing the motion of the system, which incorporate the influence of circumferential strains, are solved by a combination of a finite element method, a finite difference method and a method of characteristics with interpolation. An initially axially stretched elastic tube conveying pulsating fluid, simply supported at both ends, is modelled to assess the effect of external harmonic excitation on the dynamic responses of the tube and the fluid flow. The results agree well with new experimental data. Comparison of the predicted results with those of a decoupled model demonstrates that it is necessary to consider the mechanism of fluid-structure interaction fully in the study of initially stretched cylindrical tubes conveying pulsatile fluid flow. An analysis of these coupling effects is presented for Womersley numbers alpha = 2.81 and 3.97 and a mean flow Reynolds number Re = 875.

Hypersexuality and hemiballism due to subthalamic infarction.

OBJECTIVE: A 70-year-old right-handed man presented with a subthalamic infarction followed by persistent hypersexuality and hemiballism. A lacunar infarction 1 cm in diameter was observed on magnetic resonance imaging. We hypothesized that metabolic abnormalities would be detected in cortical areas related to his neurobehavioral symptoms. BACKGROUND: Statistical validation of the regional metabolic changes that may relate to neuropsychiatric symptoms has been elusive. Relating metabolic changes to neuropsychiatric symptoms is especially important in unique neurobehavioral cases. METHOD: Quantitative fluorodeoxyglucose positron emission tomography was obtained for a single-subject comparison with scans from 60 healthy subjects. RESULTS: Substantial glucose hypometabolism (p <0.001, uncorrected; [df = 56]) was identified in the subthalamic nucleus at the site of the lacunar infarction. Hypermetabolism (p <0.01) was identified within the basal forebrain and temporal lobes, anterior cingulate and medial prefrontal cortices (areas previously associated with hypersexuality), and striatum (p <0.001) ipsilateral to the stroke (areas known to relate to hemiballism). CONCLUSIONS: Single-subject statistical parametric mapping may improve our understanding of unique neurobehavioral cases.

Fluid shear stress induction of the tissue factor promoter in vitro and in vivo is mediated by Egr-1.

Hemodynamic forces such as fluid shear stress have been shown to modulate the activity of an expanding family of genes involved in vessel wall homeostasis and the pathogenesis of vascular disease. We have investigated the effect of shear stress on tissue factor (TF) gene expression in human endothelial cells (ECs) and in a rat arterial model of occlusion. As measured by reverse transcriptase polymerase chain reaction, exposure of ECs to 1.5 N/m2 shear stress resulted in a time-dependent induction of endogenous TF transcripts of over 5-fold. Transient transfection of TF promoter mutants into cultured ECs suggests the involvement of the transcription factor Egr-1 in mediating the response of the TF promoter to shear stress. To address the importance of flow induction of Egr-1 in vivo, we have established a flow-restricted rat arterial model and determined the level of expressed Egr-1 and TF at the site of restricted flow using immunohistochemistry. We report an increase in the level of Egr-1 and TF protein in ECs expressed at the site of restricted flow. Elevated expression of Egr-1 and TF is restricted to a highly localized area, as evidenced by the fact that no significant increase in level can be detected at arterial sites distal to the site of occlusion. These findings suggest a direct role for Egr-1 in flow-mediated induction of TF and further substantiate the importance of shear stress as a modulator of vascular endothelial gene function in vivo.

A split-shank prefabricated post system: a critical multidisciplinary review.

A multidisciplinary panel of senior academics and practitioners has evaluated a system of prefabricated threaded split-shank posts (Flexi-Post/Flexi-Flange) from published research and their own clinical use. These posts have been compared with requirements of an ideal post system in relation to clinical use, stress effects, stress distribution, retention, loosening and displacement, provision for cores, and biocompatibility. The purpose was to provide this critical review to allow interested clinicians to compare this novel design to other available post systems.

Physostigmine ameliorates the delusions of Alzheimer's disease.

Alzheimer's disease (AD) patients frequently manifest delusions, and the cholinergic deficiency of AD may contribute to this aspect of the psychopathology of the disorder. In a double-blind, crossover study involving two patients, we compared the antidelusional efficacy of physostigmine, an acetylcholinesterase inhibitor, with haloperidol, a widely used neuroleptic agent. Physostigmine ameliorated the delusions and produced fewer side effects. These preliminary observations suggest that the cholinergic deficiency contributes to the occurrence of delusions in AD and cholinergic therapy may have a role in the treatment of the delusional symptoms.

Neurobehavioral presentations of the antiphospholipid antibody syndrome.

Antiphospholipid antibodies, including lupus anticoagulant and anticardiolipin antibodies, are increasingly recognized as a cause of neurological morbidity. They may occur with or without evidence of systemic lupus erythematosus and have been associated with stroke, migraine, and confusional states. Their role as etiologic or contributing factors in neurobehavioral and neuropsychiatric syndromes of obscure etiology has not been emphasized. The cases of 7 patients who were referred for evaluation of behavior abnormalities and had antiphospholipid antibodies are presented, and the potential relationships of the antiphospholipid antibody syndrome to behavioral alterations are discussed.

Neurosurgical treatment of refractory status epilepticus.

Refractory status epilepticus (RSE) is defined as status epilepticus that continues despite aggressive treatment. A 9.8-year-old boy with a past history of daily left focal motor seizures was transferred to University of California at Los Angeles (UCLA) Hospital in pentobarbital coma after 4 days in RSE. The RSE was treated with very high doses of all appropriate antiepileptic drugs (AEDs), alone and in combination. The pentobarbital was titrated to burst suppression on EEG, but whenever pentobarbital was decreased, the seizures recurred. An ictal positron tomography scan of glucose metabolism demonstrated a right frontal area of hypermetabolism corresponding to an epileptic focus on EEG and magnetic resonance lesion. Eight days after the boy was admitted to UCLA, the right frontal focus was surgically removed, with immediate control of the status epilepticus. Whereas before onset of RSE, he had daily focal seizures, the boy has been seizure-free postoperatively for greater than 1 year. Operative treatment should be considered in patients with RSE in whom a focus of seizure onset can be demonstrated and who are reasonably considered surgical candidates.

Hypersexuality following septal injury.

Hypersexuality is an uncommon consequence of brain injury. We report two cases of markedly increased sexual activity following septal damage sustained in the course of placement of ventriculoperitoneal shunts. These two cases, observations in animal experiments, and descriptions of altered behavior in humans with localized brain dysfunction indicate that a circuit involving the septal nuclei has an important role in the mediation of sexual behavior.

Organic delusional syndrome.

Delusions may be the most prominent manifestations of brain dysfunction, and a host of medical and neurologic conditions can present with or produce delusions. Recognition of the underlying disorder frequently aids in successful treatment. Comparison of organic delusional syndromes with schizophrenia suggests that limbic system abnormality and dopamine dysfunction are common underlying factors shared by different causes of delusions.