The functional reanimation of paralyzed limbs.

The functional reanimation of paralyzed limbs has been a longstanding goal of neural prosthetic research, but clinically successful applications have been elusive. Natural voluntary limb movement requires four major elements: actuators (i.e., motor units), sensors (i.e., somatosensory afferents), commands (i.e., cerebral cortical activity), and control (i.e., integration of the previous three elements at various levels of the neuraxis). Prosthetic equivalents of each of these elements are, as yet, primitive and often cumbersome to deploy, but new technologies promise substantial improvements for all. This article focuses on one such technology, bionic neuon (BION) modular microimplants, and its relationship to alternative and complementary technologies. The challenge remains to select and integrate them into systems that can be tailored efficiently to the widely disparate needs of patients with various patterns of weakness and paralysis.     

Effects of muscle immobilization at different lengths on tetrodotoxin-induced disuse atrophy

Previous studies have shown that immobilization causes muscle atrophy and that the rate of atrophy depends on the length at which the muscle is immobilized. However, most studies have been carried out in neurologically intact animals that were capable of generating at least some voluntary muscle activation. In this study, terrodotoxin was applied chronically to the rat sciatic nerve to produce complete paralysis of distal muscles for seven days, and the ankle was immobilized to hold the muscles at long or short lengths. Paralysis without immobilization resulted in relative weight losses of 36% for soleus, 19% for tibialis anterior (TA), and 17% for lateral gastrocnemius (LG) muscles. Casting the ankle in plantarflexion stretched TA and reduced its weight loss to 10%. Soleus and LG were shortened by this intervention and had increased losses of 43% and 28%, respectively. Fixing the limb in dorsiflexion resulted in a posture similar to that adopted by the unrestrained rats and had no significant effect on the amount of muscle atrophy compared to that in unrestrained paralyzed animals.     

Value of early variables as predictors of short-term outcome in patients with acute focal cerebral ischemia

The pathogenesis of essential thrombocythemia as a clonal myeloproliferative disorder has been clearly established. However, there continues to be considerable controversy concerning the management of this disease, particularly because its natural history is consistent with a nearly normal life expectancy. Therapeutic decisions have been complicated by a reliance on largely anecdotal, retrospective experience in the medical literature and, until very recently, an absence of prospective, controlled clinical trials. A recent study of patients with essential thrombocythemia at high risk of thrombosis because of advanced age or previous history of thrombotic complications demonstrated that platelet cytoreduction with hydroxyurea is effective in reducing thrombotic complications. Other cytoreducing agents that have been used in this disease include alkylating agents, recombinant interferon alpha, and anagrelide. The use of antiplatelet therapy is also controversial, and is most highly effective in patients with digital or cerebrovascular ischemic problems.     

Soil removal as a rate process

The rate of soil removal during multiple cycle washing has been studied for three artificially soiled cotton test cloths. Results are considered in relation to a soil removal rate concept proposed some years ago by Vaughn, Vittone, and Smith. It is shown that the rate of removal for these soils, when washed in the Terg-O-Tometer with a built, anionic, synthetic detergent, does not correspond to a simple first order rate process as proposed by Vaughn et al. Rather, it was found that under a variety of washing situations the percentage soil removal increased linearly with the log of cumulative wash time. Further, it was shown that for those experiments involving detergent concentration or level of mechanical action, the slopes of these log time relationships, which reflect the rate of soil removal, vary in the expected manner.     

Effects of regional stimulation using a miniature stimulator implanted in feline posterior biceps femoris

The effects of placement of a miniature implantable stimulator on motor unit recruitment were examined in the posterior head of cat biceps femoris. The implantable stimulator (13-mm long x 2-mm diameter) was injected either proximally near the main nerve branch, or distally near the muscle insertion, through a 12-gauge hypodermic needle. Glycogen-depletion methods were used to map the distribution of fibers activated by electrical stimulation. Muscle fibers were found to be depleted at most or all proximodistal levels of the muscle, but the density of depleted fibers varied transversely according to the stimulus strength and proximity of the device to the nerve-entry site. Thus, muscle cross sections often had a "patchy" appearance produced because different proportions of depleted fibers intermingled with undepleted fibers in different parts of the cross section. In other preparations, the force of muscle contraction was measured when stimuli of varying strengths were delivered by the stimulator positioned at the same proximal or distal sites within the muscle. Devices placed close to the nerve-entry site produced the greatest forces. Those placed more distally produced less force. As stimulus current and/or pulse width increased, muscle force increased, often in steps, until a maximum was reached, which was usually limited by the compliance voltage of the device to less than the force produced by whole nerve stimulation.     

BCI Meeting 2005--workshop on signals and recording methods.

This paper describes the highlights of presentations and discussions during the Third International BCI Meeting in a workshop that evaluated potential brain-computer interface (BCI) signals and currently available recording methods. It defined the main potential user populations and their needs, addressed the relative advantages and disadvantages of noninvasive and implanted (i.e., invasive) methodologies, considered ethical issues, and focused on the challenges involved in translating BCI systems from the laboratory to widespread clinical use. The workshop stressed the critical importance of developing useful applications that establish the practical value of BCI technology.     

Applying reticular synthesis to the design of Cu-based MOFs with mechanically interlocked linkers

The concept of“robust dynamics”describes the incorporation of mechanically interlocked molecules(MIMs)into metal-organic framework(MOF)materials such that large amplitude motions(e.g.,rotation or translation of a macrocycle)can occur inside the free volume pore of the MOF.To aid in the preparation of such materials,reticular synthesis was used herein to design rigid molecular building blocks with predetermined ordered structures starting from the well-known MOF NOTT-101.New linkers were synthesized that have a T-shape,based on a triphenylene tetra-carboxylate strut,and their incorporation into Cu(II)-based MOFs was investigated.The single-crystal structures of three new MOFs,UWCM-12(fof),β-UWCM-13(loz),UWCM-14(lil),with naked T-shaped linkers were determined;β-UWCM-13 is the first reported example of the loz topology.A fourth MOF,UWDM-14(lil)is analogous to UWCM-14(lil)but contains a[2]rotaxane linker.Variable-temperature,²H solid-state NMR was used to probe the dynamics of a 24-membered macrocycle threaded onto the MOF skeleton.