PubMed · 4858259
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D A Carlson, E S Munson. Nerve-stimulator test unit.. https://pubmed.ncbi.nlm.nih.gov/4858259/
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Infection of percutaneous biomaterials implants, such as fixation frames used for the repair of complicated fractures in orthopedics, is a major complication that almost inevitably leads to replacement of the implant. As antibiotic therapy usually has little impact on biomaterial-associated infections, it is the aim of this article to examine whether implant-associated Staphylococcus epidermidis and Staphylococcus aureus strains could be stimulated to detach from a surgical stainless steel anode during application of an electric current. First, bacteria were allowed to adhere from a flowing suspension of physiological ionic strength in a parallel plate flow chamber to a stainless-steel surface, after which the suspension was replaced by a bacterium-free solution with a specified ionic strength (0.5-150-mM potassium phosphate). DC currents ranging from 15 to 125 microA were applied to induce bacterial detachment. Initial detachment decreased with increasing ionic strength at 100 microA. The percentage detachment achieved by application of an electric current after 2.5 h was highest (95%) in 1-mM potassium phosphate and decreased to 15% when the ionic strength exceeded 40 mM. The electric current did not significantly affect the percentage detachment, but initial detachment rates increased with increasing current from 1000 cm(-2) s(-1) at 15 microA to 7000 cm(-2) s(-1) at 125 microA. Although different isolates of S. epidermidis and S. aureus showed different patterns of current-induced detachment, all strains could be stimulated to detach. The results of this study define ionic-strength conditions and electric currents yielding staphylococcal detachment from surgical stainless steel and therewith point to a pathway for the treatment and prevention of percutaneous metal-implant infection.
BACKGROUND: Neuromuscular block is estimated by comparing the evoked peak twitch with a control value measured in the absence of neuromuscular block. In practice, this control value is often difficult to determine because repeated motor nerve stimulation enhances the evoked mechanical response of the corresponding muscle, resulting in an increased twitch response. This is known as twitch potentiation or the staircase phenomenon. It is probably the result of myosin light chain phosphorylation creating an increased twitch force for a given amount of Ca(2+) released at each action potential. Modelling of potentiation may improve studies of neuromuscular blocking agents using mechanomyography or accelerometry. METHODS: We used one- and two-exponential models to describe the degree of myosin light chain phosphorylation and associated twitch potentiation. These models were fitted to accelerographic twitch force measurements for various stimulation patterns and frequencies used in neuromuscular monitoring. RESULTS: Fitting a two-exponential model to twitch data for various stimulation rates and patterns provides better prediction than a one-exponential model. A one-exponential model performs poorly when the stimulation rate varies during measurement. CONCLUSIONS: We conclude that a two-exponential model can predict the degree of twitch potentiation for the stimulation patterns and frequencies tested more accurately than a one-exponential model. However, if only one stimulation frequency is used, a one-exponential model can provide good accuracy. We illustrate that such a potentiation model can improve the ability of pharmacodynamic-pharmacokinetic neuromuscular block models to predict twitch response in the presence of a neuromuscular blocking agent.
Interest in brain stimulation therapies has been rejuvenated over the last decade and brain stimulation therapy has become an alternative treatment for many neurological and psychiatric disorders, including Parkinson's disease (PD), dystonia, pain, epilepsy, depression, and schizophrenia. The effects of brain stimulation on PD are well described, and this treatment has been widely used for such conditions worldwide. Treatments for other conditions are still in experimental stages and large-scale, well controlled studies are needed to refine the treatment procedures. In the treatment of intractable brain disorders, brain stimulation, especially transcranial magnetic stimulation (TMS), is an attractive alternative to surgical lesioning as it is relatively safe, reversible, and flexible. Brain stimulation, delivered either via deeply implanted electrodes or from a surface-mounted transcranial magnetic device, can alter abnormal neural circuits underlying brain disorders. The neural mechanisms mediating the beneficial effects of brain stimulation, however, are poorly understood. Conflicting theories and experimental data have been presented. It seems that the action of stimulation on brain circuitry is not limited to simple excitation or inhibition. Alterations of neural firing patterns and long-term effects on neurotransmitter and receptor systems may also play important roles in the therapeutic effects of brain stimulation. Future research on both the basic and clinical fronts will deepen our understanding of how brain stimulation works. Real-time computation of neural activity allows for integration of brain stimulation signals into ongoing neural processing. In this way abnormal circuit activity can be adjusted by optimal therapeutic brain stimulation paradigms.