Virtual planning in patients with frontal lobe lesions

The VIrtual Planning Test (VIP) was developed to investigate the planning and organisational abilities of 25 patients with frontal lobe neurosurgical lesions, comparing their performance with 25 matched control subjects. The task, presented in the form of a board game, simulates planning and execution of a set of target activities that have to take place over a four day period, involving those that are either preparatory for a fictional "trip" abroad, or those that relate to the subject's current environment (context). The frontal lobe patients were impaired overall, tending to select inappropriate activities associated with their current context and showing greater impairment on subtasks requiring only one, rather than two, preparatory acts. The findings are discussed in terms of the validity of the VIP test in identifying executive functioning impairment and the degree to which the pattern of deficits are consistent with neuropsychological models of executive function.     

Congenital fibrosis of the extraocular muscles type 2, an inherited exotropic strabismus fixus, maps to distal 11q13

The extraocular fibrosis syndromes are congenital ocular-motility disorders that arise from dysfunction of the oculomotor, trochlear, and abducens nerves and/or the muscles that they innervate. Each is marked by a specific form of restrictive paralytic ophthalmoplegia with or without ptosis. Individuals with the classic form of congenital fibrosis of the extraocular muscles (CFEOM1) are born with bilateral ptosis and a restrictive infraductive external ophthalmoplegia. We previously demonstrated that CFEOM1 is caused by an autosomal dominant locus on chromosome 12 and results from a developmental absence of the superior division of the oculomotor nerve. We now have mapped a variant of CFEOM, exotropic strabismus fixus ("CFEOM2"). Affected individuals are born with bilateral ptosis and restrictive ophthalmoplegia with the globes "frozen" in extreme abduction. This autosomal recessive disorder is present in members of three consanguineous Saudi Arabian families. Genetic analysis of 70 individuals (20 affected individuals) reveals linkage to markers on chromosome 11q13, with a combined LOD score of 12.3 at the single nonrecombinant marker, D11S1314. The 2.5-cM CFEOM2 critical region is flanked by D11S4196/D11S4162 and D11S4184/1369. Two of the three families share a common disease-associated haplotype, suggesting a founder effect for CFEOM2. We hypothesize that CFEOM2 results from an analogous developmental defect to CFEOM1, one that affects both the superior and inferior divisions of the oculomotor nerve and their corresponding alpha motoneurons and extraocular muscles.     

Binding and lysing of blood clots using MRX-408

RATIONALE AND OBJECTIVES: A thrombus-specific ultrasound contrast agent, MRX-408, has been developed recently. This agent consists of phospholipid-coated microbubbles with a ligand capable of targeting the GPIIb/IIIa receptor, thereby allowing the microbubbles to bind with thrombi rich in activated platelets. In vitro and in vivo animal experiments have been conducted to examine imaging enhancement and sonothrombolysis using this agent compared with a nontargeted agent. METHODS: For clot binding, blood-smeared slides were incubated with microbubbles and examined under a light microscope. Change in backscatter signals from the blood clots after binding was examined by both an ultrasound scanner and two single-element transducers arranged in a transmitter-receiver pair. For clot lysis, either 1-MHz or 20-KHz ultrasound was used to enhance the lysing effects of MRX-408 with or without urokinase. RESULTS: Evidence of binding was demonstrated under a microscope. In vitro experiments showed that the "acoustic signature", or properties, of blood clots changed after binding. Clots became more echogenic and nonlinear. In vivo fundamental ultrasound imaging confirmed that as a result of binding, blood clots were more visible, the area of detection was improved, and shadowing behind clots was more noticeable. Under 1-MHz ultrasound and 30 minutes of treatment, lysis efficiency reached 34% with MRX-408, whereas there was no visible clot lysis with saline. CONCLUSION: The results of these preliminary studies show that as a contrast agent, MRX-408 enhanced clots under ultrasound imaging and facilitated sonothrombolysis with or without thrombolytic drugs.     

Securing Wireless Mesh Networks

Now found in domestic, commercial, industrial, military, and healthcare applications, wireless networks are becoming ubiquitous. Wireless mesh networks (WMNs) combine the robustness and performance of conventional infrastructure networks with the large service area and self-organizing and self-healing properties of mobile ad hoc networks. In this article, the authors consider the problem of ensuring security in WMNs, introduce the IEEE 802.11s draft standard, and discuss the open security threats faced at the network and data-link layers.     

Experimental study of diffusion-based extraction from a cell suspension

A recently proposed application of microfluidics is the post-thaw processing of biological cells. Numerical simulations suggest that diffusion-based extraction of the cryoprotective agent dimethyl sulfoxide (DMSO) from blood cells is viable and more efficient than centrifugation, the conventional method of DMSO removal. In order to validate the theoretical model used in these simulations, a prototype was built and the flow of two parallel streams, a suspension of Jurkat cells containing DMSO and a wash stream that contained neither cells nor DMSO, was characterized experimentally. DMSO transport in a rectangular channel (depth 500 μm, width 25 mm and overall length 125 mm) was studied as a function of three dimensionless parameters: depth ratio of the streams, cell volume fraction in the cell solution, and the Peclet number (Pe) based on channel depth, average flow rate and the diffusion coefficient for DMSO in water. In our studies, values of Pe ranged from O(10³) to O(10⁴). Laminar flow was ensured by keeping the Reynolds number between O(1) and O(10). Experimental results based on visual and quantitative data demonstrate conclusively that a microfluidic device can effectively remove DMSO from liquid and cell laden streams without compromising cell recovery. Also, flow conditions in the microfluidic device appear to have no adverse effect on cell viability at the outlet. Further, the results demonstrate that we can predict the amount of DMSO removed from a given device with the theoretical model mentioned previously.     

Smooth muscle cell to elastic lamina connections in developing mouse aorta. Role in aortic medial organization

BACKGROUND: The structural and functional intigration of smooth muscle cells and elastic laminae in the aortic media is not well established. Detailed information concerning normal ultrastructural features of the aortic media will provide a better understanding of the medial changes that occur in vascular diseases such as hypertension and aortic aneurysms. EXPERIMENTAL DESIGN: The ultrastructural development and organization of connections between smooth muscle cells and elastic laminae in the mouse aortic media were studied by light and electron microscopy. RESULTS: Early in development, the smooth muscle cells become linked to the elastic laminae by bundles of microfibrils. These microfibrils become progressively infiltrated with elastin so as to form extensions of elastin from the elastic laminae in the adult media. Each elastin extension spans obliquely from the elastic lamina to the surface of the smooth muscle cell where it attaches in a region of membrane occupied by an intracellular membrane-associated dense plaque. On the cytoplasmic face of the plaque, a contractile filament bundle penetrates and anchors in an orientation similar to that of the extracellular elastin extension. The contractile filament bundle traverses the cell obliquely and anchors in a dense plaque on the opposite side of the cell that is in turn linked to the next elastic lamina by another elastin extension. The extracellular elastin extensions and the intracellular contractile filament bundles thus form a "contractile-elastic unit," a continuous line of structures that links adjacent elastic laminae. The oblique orientation of the contractile-elastic units reverses direction in successive smooth muscle cell layers in a herringbone-like pattern. Thus, tension transmitted to one elastic lamina by the smooth muscle cells on either side results in a uniform force exerted on the elastic lamina in one circumferential direction, that on the adjacent elastic laminae being in the opposite direction. CONCLUSIONS: Results from this study demonstrate the presence of smooth muscle cell to elastic lamina connections that form early in development as contractile-elastic units; basic units of aortic medial ultrastructure. The overall organization of the contractile-elastic units within the aortic media is proposed to provide a means for coordinating contractile and elastic tensions in response to mechanical stresses imposed on the vessel wall.     

Recasting Florida's insanity defense. Two modest proposals

Three states have established psychiatric security review boards mandated to primarily provide protection from the potentially destructive behavior of insanity acquitees. Each year in Florida there are 100 of these patients; 5% have been involved in capital offenses. These boards, as compared with the extant judiciary system, are more effective and parsimonious and serve the end of primary prevention. It is recommended that the plea, "not guilty by reason of insanity," be changed to "guilty but insane." The change is largely semantic but should result in greater prosecutorial and public acceptance of the insanity plea and be more in keeping with individual freedom for patients as provided under the Constitution.     

Optimization of vehicle accelerator-brake pedal foot travel time

This study was directed towards reducing the lag time between stimulus and incidence of braking. The effect of the relative vertical heights of the brake and accelerator pedals on foot travel time was the subject of the first part of the investigation. In the second part, two new pedal designs in which the accelerator was mounted directly on the brake pedal were evaluated. A significant reduction in foot travel time of approximately 12·5% was realised by locating the accelerator pedal 25–50 mm (1–2 in) higher than the brake pedal. Mounting of the accelerator pedal adjacent to or directly on the brake pedal allowed reductions in braking lag time of 46% to 74%.